JP5506042B2 - Conductive copper paste - Google Patents

Description

  The present invention relates to a conductive copper paste, and more particularly to a conductive copper paste that does not contain a thermosetting resin component or glass frit, which provides adhesion to an underlayer.

  Conventionally, a conductive metal paste has been used for the purpose of forming a wiring layer and an electrode layer on the substrate surface of an inorganic material substrate.

For example, in a solar cell manufactured using a p-type silicon substrate, an n ⁺ type semiconductor layer is formed on the substrate surface serving as a light receiving surface, and a grid-shaped n-side electrode is formed on the n ⁺ type semiconductor layer. Is produced. On the other hand, an aluminum electrode is produced as a p-side electrode on the back surface of the p-type silicon substrate. A conductive aluminum paste is used to produce the aluminum electrode on the back surface of the p-type silicon substrate. In addition, a conductive silver paste or a conductive copper paste is used for producing the grid-shaped n-side electrode.

  An antireflection film is formed on the surface of the substrate that serves as the light receiving surface of the solar cell. A grid-like opening is provided in the antireflection film, and a grid-like n-side electrode is formed in the opening. For example, in conjunction with the grid-shaped openings, a conductive copper paste is applied using screen printing to form a coating film layer of the conductive copper paste having a grid pattern. Next, the conductive film is formed by subjecting the coating film layer of the conductive copper paste to a baking treatment.

  Conventional conductive copper pastes used for forming conductive films can be broadly classified into two types: thermosetting conductive copper pastes and conductive copper pastes for firing.

  The thermosetting type conductive copper paste contains the copper powder of the conductive filler and the thermosetting resin component, and in the conductor layer, the copper powder of the conductive filler is kept in contact with each other. A cured resin is used. The cured product of the thermosetting resin also has an organic adhesive function that maintains the adhesion between the formed conductor layer and the underlying layer. The electrical contact between the copper powders of the conductive filler and the electrical contact between the copper powder and the base layer are held by the cured product of the thermosetting resin.

  The conductive copper paste for baking generally contains copper powder of a conductive filler and glass frit. By conducting the baking treatment at a high temperature, the copper powder of the conductive filler constitutes a sintered body, and at that time, the melting of the glass frit proceeds and infiltrates the entire sintered body layer of the copper powder. Maintains adhesion to the formation. That is, the glass / frit component that solidifies after melting functions as an inorganic adhesive that maintains the adhesion between the entire sintered powder layer of the copper powder and the underlying layer. The formed conductor layer is composed of a copper powder sintered body layer and a molten and solidified product of glass frit infiltrated in the layer. The electrical contact between the copper powder sintered body layer and the underlying layer is maintained by the molten and solidified product of the glass frit.

  The grid-shaped n-side electrode formed on the surface of the substrate serving as the light-receiving surface of the solar cell should have a narrow electrode width and a relatively thick electrode thickness in order to increase the light-receiving area. Therefore, an increase in wiring resistance is suppressed. In general, the resistivity of a conductor layer produced using a thermosetting conductive copper paste is higher than the resistivity of a conductor layer produced using a conductive copper paste for firing. Become. Therefore, in many cases, a conductive copper paste for firing is used for forming the grid-shaped n-side electrode.

  A conventional conductive copper paste, that is, a thermosetting conductive copper paste and a conductive copper paste for baking, are formed on a substrate surface that becomes a light receiving surface of a solar cell, and a grid-shaped n-side electrode is formed. However, there is still room for improvement in the following points.

  The conductor layer formed using a thermosetting conductive copper paste is essentially composed of a cured product of thermosetting resin and copper powder of conductive filler, so it is not suitable for solder bonding. It has various problems.

  In addition, in the conductor layer formed using conductive copper paste for firing, the surface of the copper powder sintered body layer is covered with a glass / frit melt. It has an essential problem of becoming an unsuitable shape.

  The above problems are caused by the fact that the thermosetting conductive copper paste has a thermosetting resin component as an essential component, and that the conductive copper paste for firing has a glass frit as an essential component. ing.

  Considering this point, a conductive material with a novel configuration that can maintain adhesion to the underlying layer and electrical contact with the underlying layer without the addition of a thermosetting resin component or glass frit. Development of copper paste is required. In particular, when it is used for forming a grid-like n-side electrode formed on the surface of a substrate serving as a light-receiving surface of a solar cell, a thermosetting resin component suitable for the production of a thick conductor layer, or glass It is necessary to develop a conductive copper paste to which no frit is added. Furthermore, when the conductive layer is formed using the conductive copper paste, the conductive layer capable of forming a conductive layer exhibiting good conductivity can be formed by selecting the temperature of the heat treatment at about 400 ° C. A copper paste is desirable.

  The present invention solves the above-mentioned problems. The object of the present invention is to maintain a thermosetting resin component or a glass frit in order to maintain adhesion to the underlayer and electrical contact with the underlayer. It is another object of the present invention to provide a conductive copper paste having a novel structure that is suitable for the production of a thick conductor layer.

  In order to solve the above-mentioned problems, the present inventors have provided means for forming a sintered body of conductive filler copper powders in a state where no thermosetting resin component or glass frit is added. It was investigated.

  First, since the surface oxide film slightly exists on the surface of the copper powder of the conductive filler, it was found that the surface oxide film needs to be reduced. An organic compound having a hydroxyl group that can be converted to an oxo group (═O) or a formyl group (—CHO) by oxidation, specifically, in a reducing atmosphere containing hydrogen gas in the presence of an aliphatic polyhydric alcohol. It was found that a slight surface oxide film present on the surface of the copper powder can be reduced by performing a heat treatment at a temperature of at least 250 ° C. Furthermore, after finishing the reduction of the surface oxide film, when the heat treatment is continued in a reducing atmosphere containing hydrogen gas at a temperature of 300 ° C. or more in a state where the copper powders are in contact with each other, a sintered body of the copper powders is obtained. Has been found to be possible to form.

  The sintered body of copper powder formed under the above conditions exhibits conductivity through the contact part between the copper powders, but the contact area of the contact part between the copper powders is small, so the contact resistance is large. It was found that the resistivity of the entire sintered powder layer between the copper powders was considerably high.

  As a copper powder used as a conductive filler, a micron-size copper powder with an average particle size of 2 μm to 10 μm and a sub-micron size with an average particle size of 0.2 μm to 1.0 μm are selected. It was found that the density of contact portions between copper powders was remarkably increased when the micron-sized copper powders were filled with the submicron-sized fine copper powders. As a result of the marked increase in the density of contact areas between copper powders, the contact area between the contact areas of individual copper powders is narrow, but a network of high-density electrical conduction paths is formed. It has been found that the resistivity of the entire combined layer can be greatly reduced.

  Furthermore, in addition to micron-sized copper powder and sub-micron-sized fine copper powder, when copper nanoparticles having an average particle size selected in the range of 10 nm to 100 nm are added, the copper nanoparticles are brought into contact with each other. It was found to fill a narrow gap near the site. At that time, when heat treatment is performed at a temperature of 300 ° C. or higher in a reducing atmosphere containing hydrogen gas, the copper nanoparticles are fused to the surface of the copper powder, and the fusion of the copper nanoparticles also proceeds. As a result, the effective contact area of each copper powder mutual contact site was expanded, and it discovered that the resistivity of the whole sintered compact layer of copper powder mutual was further reduced.

  Further, the copper nanoparticles fill the narrow gap even at the site where the surface of the underlayer and the copper powder are in contact. At that time, when heat treatment is performed at a temperature of 300 ° C. or higher in a reducing atmosphere containing hydrogen gas, the copper nanoparticles are fused to the surface of the copper powder, and the fusion of the copper nanoparticles also proceeds. As a result, a fusion film between the copper nanoparticles is formed with the site where the surface of the base layer and the copper powder contact each other as a nucleus. As a result, a state in which the copper powder is fixed to the surface of the underlayer through the fusion film of the copper nanoparticles is achieved, and adhesion to the surface of the underlayer is given, and the underlayer It has been found that electrical contact with is maintained.

On the other hand, instead of adding copper nanoparticles that select an average particle size in the range of 10 nm to 100 nm, a copper salt of an aliphatic monocarboxylic acid ((R—COO) ₂ Cu (II)) is replaced with a (dialkylamino) alkylamine. The solution of the aliphatic monocarboxylic acid is subjected to heat treatment at a temperature of at least 250 ° C. in a reducing atmosphere containing hydrogen gas in the presence of an aliphatic polyhydric alcohol. When the copper cation (Cu ²⁺ ) contained in ((R—COO) ₂ Cu (II)) is reduced to form a metal copper atom (Cu), the metal copper atom (Cu) It has been found that it is selectively accumulated in a very narrow gap portion of the contact site. That is, as a result of the accumulation of the copper metal atoms (Cu) so as to fill a very narrow gap between the contact portions of the copper powders, the effective contact area of the contact portions of the copper powders is expanded. It was found that the resistivity of the entire sintered powder layer between the copper powders was further reduced.

  Furthermore, the metal copper atoms (Cu) are accumulated so as to fill the narrow gaps even at the site where the surface of the underlayer and the copper powder come into contact. At that time, when heat treatment is performed at a temperature of 300 ° C. or higher in a reducing atmosphere containing hydrogen gas, the accumulated metal copper atom (Cu) layer is fused to the surface of the copper powder, and the underlayer A copper film made of accumulated copper metal atoms (Cu) is formed using a site where the surface and the copper powder contact each other as a nucleus. As a result, a state in which the copper powder is fixed to the surface of the underlayer through the copper film is achieved, and the adhesion to the surface of the underlayer and the electrical contact with the underlayer are maintained. I found out that

In particular, when a silanol structure (Si—OH) is present on the surface of the underlayer, the copper atom (Cu) derived from a copper salt of an aliphatic monocarboxylic acid ((R—COO) ₂ Cu (II)) The structure (Si—OH) part is fixed in the form of Si—O—Cu. Furthermore, on the surface of the underlayer, a copper metal film layer that covers the underlayer surface is grown using copper atoms immobilized in the form of Si—O—Cu as nuclei. Therefore, the metal copper film layer covering the surface of the base layer exhibits excellent adhesion. In addition, at the part where the copper powder contacts the surface of the underlayer, the metal copper film layer is also partially formed on the surface of the copper powder, and there is a bond between metal atoms between the two. In addition to this contribution, high adhesion characteristics due to the interposition of the metal copper film layer are imparted between the surface of the base layer having a silanol structure (Si—OH) and the copper powder.

  Based on the above series of findings, the present inventors have completed the present invention.

That is, the conductive copper paste according to the first aspect of the present invention is
A conductive copper paste containing no thermosetting resin component or glass frit,
The conductive copper paste is
Including copper powder, fine copper powder, copper salt of aliphatic monocarboxylic acid, (dialkylamino) alkylamine, first organic solvent,
The first organic solvent is a liquid at room temperature, has a boiling point of 200 ° C. or higher, but does not exceed 400 ° C., and does not contain any reactive functional groups other than hydroxyl groups. An organic solvent having a group;
The copper salt of the aliphatic monocarboxylic acid is mixed with the first organic solvent as a solution obtained by dissolving in a (dialkylamino) alkylamine, to obtain a mixed solution,
The copper powder and the fine copper powder are a paste-like composition dispersed in the mixed solution;
The average particle diameter of the copper powder is selected in the range of 2 μm to 10 μm,
The average particle diameter of the fine copper powder is selected in the range of 0.2 μm to 1.0 μm,
The copper salt of the aliphatic monocarboxylic acid has a boiling point of 230 ° C. or higher, but is derived from an aliphatic monocarboxylic acid (R—COOH) that does not exceed 400 ° C. Copper salt,
The (dialkylamino) alkylamine is a liquid at room temperature and has a boiling point of 230 ° C. or higher but not exceeding 300 ° C.
The content ratio of the copper powder and fine copper powder, (copper powder content): (fine copper powder content) is selected in the range of 80 parts by mass: 20 parts by mass to 60 parts by mass: 40 parts by mass,
Ratio of the total weight of copper atoms (W _{Cu-carboxylate} ) contained in the copper salt of aliphatic monocarboxylic acid to the total weight (W _Cu-powder + W _{Cu-fine-powder} ) of the copper powder and fine copper powder , (W _Cu-powder + W _{Cu-fine-powder} ): (W _{Cu-carboxylate} ) is selected in the range of 100 parts by mass: 0.15 parts by mass to 100 parts by mass: 0.7 parts by mass,
The ratio of the total weight of the copper powder and fine copper powder (W _Cu-powder + W _{Cu-fine-powder} ) to the weight of the first organic solvent (W _{dispersion-medium} ), (W _Cu-powder + W _{Cu-fine -powder} ): W _{dispersion-medium} is selected in the range of 100 parts by mass: 2 parts by mass to 100 parts by mass: 10 parts by mass,
The content ratio of the copper salt of the aliphatic monocarboxylic acid and the (dialkylamino) alkylamine is such that (dialkylamino) alkylamine is 2.2 to 8 molecules per molecule of the copper salt of the aliphatic monocarboxylic acid. Chosen to be a ratio;
The conductive copper paste is a conductive copper paste that can be fired by heating to a temperature of 300 ° C. or higher and 400 ° C. or lower.

that time,
The first organic solvent is
An alkanol having 9 to 14 carbon atoms that is liquid at room temperature and has a boiling point of 200 ° C. or higher but not exceeding 400 ° C .;
An alkanediol having 4 to 9 carbon atoms that is liquid at room temperature and has a boiling point of 200 ° C. or higher but not exceeding 400 ° C.,
A polyalkylene glycol having a molecular weight of 4000 or less, which is liquid at room temperature and has a boiling point of 200 ° C. or higher but not exceeding 400 ° C.,
A polyhydric alcohol monoalkyl ether that is liquid at room temperature and has a boiling point of 200 ° C. or higher but not exceeding 400 ° C .;
It can be selected from the group consisting of glycerin, 1,2,3-butanetriol, 1,2,4-butanetriol, 1,2,5-pentanetriol, 1,2,6-hexanetriol.

In addition, one aspect of the conductive copper paste according to the first aspect of the present invention is
A conductive copper paste containing no thermosetting resin component or glass frit,
The conductive copper paste is
Including copper powder, fine copper powder, copper salt of aliphatic monocarboxylic acid, (dialkylamino) alkylamine, second organic solvent,
The second organic solvent is an aliphatic polyhydric alcohol that is liquid at room temperature and has a boiling point of 230 ° C. or higher but not exceeding 400 ° C .;
The copper salt of the aliphatic monocarboxylic acid is mixed with the second organic solvent as a solution obtained by dissolving in a (dialkylamino) alkylamine, to obtain a mixed solution,
The copper powder and the fine copper powder are a paste-like composition dispersed in the mixed solution;
The average particle diameter of the copper powder is selected in the range of 2 μm to 10 μm,
The average particle diameter of the fine copper powder is selected in the range of 0.2 μm to 1.0 μm,
The copper salt of the aliphatic monocarboxylic acid has a boiling point of 230 ° C. or higher, but is derived from an aliphatic monocarboxylic acid (R—COOH) that does not exceed 400 ° C. Copper salt,
The (dialkylamino) alkylamine is a liquid at room temperature and has a boiling point of 230 ° C. or higher but not exceeding 300 ° C.
The content ratio of the copper powder and fine copper powder, (copper powder content): (fine copper powder content) is selected in the range of 80 parts by mass: 20 parts by mass to 60 parts by mass: 40 parts by mass,
Ratio of the total weight of copper atoms (W _{Cu-carboxylate} ) contained in the copper salt of aliphatic monocarboxylic acid to the total weight (W _Cu-powder + W _{Cu-fine-powder} ) of the copper powder and fine copper powder , (W _Cu-powder + W _{Cu-fine-powder} ): (W _{Cu-carboxylate} ) is selected in the range of 100 parts by mass: 0.15 parts by mass to 100 parts by mass: 0.7 parts by mass,
The ratio of the total weight of the copper powder and fine copper powder (W _Cu-powder + W _{Cu-fine-powder} ) to the weight of the second organic solvent (W _{dispersion-medium} ), (W _Cu-powder + W _{Cu-fine -powder} ): W _{dispersion-medium} is selected in the range of 100 parts by mass: 2 parts by mass to 100 parts by mass: 10 parts by mass,
The content ratio of the copper salt of the aliphatic monocarboxylic acid and the (dialkylamino) alkylamine is such that (dialkylamino) alkylamine is 2.2 to 8 molecules per molecule of the copper salt of the aliphatic monocarboxylic acid. Chosen to be a ratio;
The conductive copper paste is a conductive copper paste that can be fired by heating to a temperature of 300 ° C. or higher and 400 ° C. or lower.

that time,
The second organic solvent is
It is liquid at room temperature and has a boiling point of 230 ° C. or higher, but is an alkanediol having 4 to 9 carbon atoms in a range not exceeding 400 ° C. It is liquid at room temperature and its boiling point is 230 ° C. or higher, but 400 ° C. A polyalkylene glycol having a molecular weight of 4000 or less and a glycerin, 1,2,3-butanetriol, 1,2,4-butanetriol, 1,2,5-pentanetriol, 1,2,6 -It can be selected from the group consisting of hexanetriol.

In the conductive copper paste according to the first embodiment of the present invention,
The average particle size of the copper powder is selected in the range of 3 μm to 8 μm,
The average particle size of the fine copper powder is more preferably selected in the range of 0.3 μm to 0.8 μm.

  In particular, the content ratio of the copper powder and fine copper powder, (copper powder content): (fine copper powder content) is in the range of 75 parts by mass to 25 parts by mass to 35 parts by mass. It is desirable that it is selected.

Also, the total weight of copper atoms (W _{Cu-carboxylate} ) contained in the copper salt of the aliphatic monocarboxylic acid with respect to the total weight of the copper powder and fine copper powder (W _Cu-powder + W _{Cu-fine-powder} ) The ratio of (W _Cu-powder + W _{Cu-fine-powder} ) :( W _{Cu-carboxylate} ) can be selected in the range of 100 parts by mass: 0.3 part by mass to 100 parts by mass: 0.5 part by mass. Preferred Ratio of the total weight of the copper powder and fine copper powder (W _Cu-powder + W _{Cu-fine-powder} ) and the weight of the first organic solvent (W _{dispersion-medium} ), (W _Cu-powder + W _{Cu- fine-powder} ): W _{dispersion-medium} is preferably selected in the range of 100 parts by mass: 3 parts by mass to 100 parts by mass: 4.5 parts by mass.

In particular, in one embodiment of the conductive copper paste according to the first aspect of the present invention, an aliphatic polyhydric alcohol is used as the second organic solvent.
The ratio of the total weight of the copper powder and fine copper powder (W _Cu-powder + W _{Cu-fine-powder} ) to the weight of the second organic solvent (W _{dispersion-medium} ), (W _Cu-powder + W _{Cu-fine -powder} ): W _{dispersion-medium} is preferably selected in the range of 100 parts by mass: 3 parts by mass to 100 parts by mass: 4.5 parts by mass.

As the aliphatic monocarboxylic acid anion having a boiling point of 230 ° C. or higher, which does not exceed 400 ° C., constituting the aliphatic monocarboxylic acid copper salt ((R—COO) ₂ Cu (II)),
It is preferable to select an anion derived from an aliphatic monocarboxylic acid having 10 to 20 carbon atoms.

The (dialkylamino) alkylamine is
(Dialkylamino) propylamine (R ′ ₂ N—CH ₂ CH ₂ CH ₂ —NH) having a total carbon number of 9 to 13 which is liquid at room temperature and has a boiling point of 230 ° C. or higher but not exceeding 300 ° C. ₂ ) is preferably selected from the group consisting of:

  The viscosity of the conductive copper paste is preferably selected in the range of 2 Pa · s to 50 Pa · s (25 ° C.).

  In the conductive copper paste according to the first aspect of the present invention, a sintering aid can be further added.

For example, as a sintering aid, a carboxylic acid metal salt or a metal carboxylic acid complex that is a metal cation species other than copper and a carboxylic acid anion species is added,
The metal cation species other than copper is selected from the group consisting of bismuth and tin, or one or a plurality of types of metal cation species,
The carboxylic acid anion species is a carboxylic acid anion species selected from the group consisting of aliphatic monocarboxylic acids having 6 to 20 carbon atoms,
Volume of metal atoms generated by reducing the carboxylic acid metal salt or metal carboxylic acid complex V _low-mp-metal and volume of metal atoms generated by reducing the copper salt of the aliphatic monocarboxylic acid The ratio of the total V _Cu-metal , V _low-mp-metal : V _Cu-metal may be selected in a range not exceeding 2: 1.

In addition, as a sintering aid, a carboxylic acid metal salt or metal carboxylic acid complex, which is a metal cation species other than copper and a carboxylic acid anion species,
The metal cation species other than copper is a mixed metal cation species formed by mixing a cation species of the first metal group and a cation species of the second metal group,
The cation species of the first metal group is selected from the group consisting of bismuth and tin, or one or more metal cation species,
The cation species of the second metal group is selected from the group consisting of zinc, aluminum, indium, silver, cobalt, titanium, nickel, manganese, or a cation species of one or more metals.
In the mixed metal cation species, the total number of metal atoms of the cation species of the second metal group is selected within a range of less than 10% with respect to the total number of metal atoms of the cation species of the first metal group. And
The carboxylic acid anion species is a carboxylic acid anion species selected from the group consisting of aliphatic monocarboxylic acids having 6 to 20 carbon atoms,
A volume sum V _low-mp-metal of metal atoms of the first metal group formed by reducing a carboxylic acid metal salt or metal carboxylic acid complex, which is a cation species of the first metal group and a carboxylic acid anion species; , Ratio of the total volume of metal atoms V _Cu-metal generated by reducing the copper salt of the aliphatic monocarboxylic acid, V _low-mp-metal : V _Cu-metal does not exceed 2: 1 It can be set as the aspect currently selected.

In addition, the conductive copper paste according to the second embodiment of the present invention,
A conductive copper paste containing no thermosetting resin component or glass frit,
The conductive copper paste is
Including copper powder, fine copper powder, copper nanoparticles, (dialkylamino) alkylamine, a third organic solvent,
The third organic solvent is a liquid at room temperature, has a boiling point of 200 ° C. or higher, but does not exceed 400 ° C., and has no reactive functional groups other than hydroxyl groups. An organic solvent having a group;
The copper nanoparticles are mixed with the third organic solvent as a dispersion liquid dispersed in (dialkylamino) alkylamine, to obtain a mixed liquid,
The copper powder and the fine copper powder are a paste-like composition dispersed in the mixed solution;
The average particle size of the copper powder is selected in the range of 2 to 10 μm,
The average particle diameter of the fine copper powder is selected in the range of 0.2 to 1.0 μm,
The average particle diameter of the copper nanoparticles is selected in the range of 10 nm to 100 nm,
The (dialkylamino) alkylamine is a liquid at room temperature and has a boiling point of 230 ° C. or higher but not exceeding 300 ° C.
The content ratio of the copper powder and fine copper powder, (copper powder content): (fine copper powder content) is selected in the range of 80 parts by mass: 20 parts by mass to 60 parts by mass: 40 parts by mass,
The ratio of the total weight of the copper powder and fine copper powder (W _Cu-powder + W _{Cu-fine-powder} ) to the weight of the third organic solvent (W _{dispersion-medium} ), (W _Cu-powder + W _{Cu-fine -powder} ): W _{dispersion-medium} is selected in the range of 100 parts by mass: 3 parts by mass to 100 parts by mass: 10 parts by mass,
The ratio of the total weight of the copper powder and fine copper powder (W _Cu-powder + W _{Cu-fine-powder} ) and the total weight of the copper nanoparticles (W _{Cu-nano-particle} ), (W _Cu-powder + W _{Cu-fine-powder} ) :( W _{Cu-nano-particle} ) is selected in the range of 100 parts by mass: 3 parts by mass to 100 parts by mass: 15 parts by mass,
The content ratio of the copper nanoparticles and (dialkylamino) alkylamine is the ratio of the total volume of the copper nanoparticles (V _{Cu-nano-particle} ) to the volume of (dialkylamino) alkylamine (V _{dispersion-medium} ). , (V _{Cu-nano-particle} ): V _amine is selected in the range of 10:50 to 10: 100;
The conductive copper paste is a conductive copper paste that can be fired by heating to a temperature of 300 ° C. or higher and 400 ° C. or lower.

that time,
The third organic solvent is
An alkanol having 9 to 14 carbon atoms that is liquid at room temperature and has a boiling point of 200 ° C. or higher but not exceeding 400 ° C .;
An alkanediol having 4 to 9 carbon atoms that is liquid at room temperature and has a boiling point of 200 ° C. or higher but not exceeding 400 ° C.,
A polyalkylene glycol having a molecular weight of 4000 or less, which is liquid at room temperature and has a boiling point of 200 ° C. or higher but not exceeding 400 ° C.
A polyhydric alcohol monoalkyl ether that is liquid at room temperature and has a boiling point of 200 ° C. or higher but not exceeding 400 ° C .;
It can be selected from the group consisting of glycerin, 1,2,3-butanetriol, 1,2,4-butanetriol, 1,2,5-pentanetriol, 1,2,6-hexanetriol.

In addition, one aspect of the conductive copper paste according to the second aspect of the present invention is
A conductive copper paste containing no thermosetting resin component or glass frit,
The conductive copper paste is
Including copper powder, fine copper powder, copper nanoparticles, (dialkylamino) alkylamine, a fourth organic solvent,
The fourth organic solvent is an aliphatic polyhydric alcohol that is liquid at room temperature and has a boiling point of 230 ° C. or higher but not exceeding 400 ° C .;
The copper nanoparticles are mixed with the fourth organic solvent as a dispersion liquid dispersed in (dialkylamino) alkylamine, to form a mixed liquid,
The copper powder and the fine copper powder are a paste-like composition dispersed in the mixed solution;
The average particle diameter of the copper powder is selected in the range of 2 μm to 10 μm,
The average particle diameter of the fine copper powder is selected in the range of 0.2 μm to 1.0 μm,
The average particle diameter of the copper nanoparticles is selected in the range of 10 nm to 100 nm,
The (dialkylamino) alkylamine is a liquid at room temperature and has a boiling point of 230 ° C. or higher but not exceeding 300 ° C.
The content ratio of the copper powder and fine copper powder, (copper powder content): (fine copper powder content) is selected in the range of 80 parts by mass: 20 parts by mass to 60 parts by mass: 40 parts by mass,
The ratio of the total weight of copper atoms (W _{Cu-nano-particle} ) in the copper nanoparticles to the total weight of the copper powder and fine copper powder (W _Cu-powder + W _{Cu-fine-powder} ), ( W _Cu-powder + W _{Cu-fine-powder} ): (W _{Cu-nano-particle} ) is selected in the range of 100 parts by mass: 3 parts by mass to 100 parts by mass: 15 parts by mass,
The ratio of the total weight of the copper powder and fine copper powder (W _Cu-powder + W _{Cu-fine-powder} ) to the weight of the fourth organic solvent (W _{dispersion-medium} ), (W _Cu-powder + W _{Cu-fine -powder} ): W _{dispersion-medium} is selected in the range of 100 parts by mass: 3 parts by mass to 100 parts by mass: 10 parts by mass,
The content ratio of the copper nanoparticles and (dialkylamino) alkylamine is the ratio of the total volume of the copper nanoparticles (V _{Cu-nano-particle} ) to the volume of (dialkylamino) alkylamine (V _{dispersion-medium} ). , (V _{Cu-nano-particle} ): V _amine is selected in the range of 10:50 to 10: 100;
The conductive copper paste is a conductive copper paste that can be fired by heating to a temperature of 300 ° C. or higher and 400 ° C. or lower.

that time,
The fourth organic solvent is
It is liquid at room temperature and has a boiling point of 230 ° C. or higher, but is an alkanediol having 4 to 9 carbon atoms in a range not exceeding 400 ° C. It is liquid at room temperature and has a boiling point of 230 ° C. or higher, but 400 ° C. A polyalkylene glycol having a molecular weight of 4000 or less, and glycerin, 1,2,3-butanetriol, 1,2,4-butanetriol, 1,2,5-pentanetriol, 1,2, It is preferable to select from the group consisting of 6-hexanetriol.

In the conductive copper paste according to the second aspect of the present invention,
The average particle size of the copper powder is selected in the range of 3 μm to 8 μm,
The average particle size of the fine copper powder is more preferably selected in the range of 0.3 μm to 0.8 μm.

  The content ratio of the copper powder and fine copper powder, (copper powder content): (fine copper powder content) is selected in the range of 75 parts by mass: 25 parts by mass to 65 parts by mass: 35 parts by mass. Preferably it is.

Also, the ratio of the total weight of copper atoms (W _{Cu-nano-particle} ) in the copper nanoparticles to the total weight of the copper powder and fine copper powder (W _Cu-powder + W _{Cu-fine-powder} ) , (W _Cu-powder + W _{Cu-fine-powder} ) :( W _{Cu-nano-particle} ) is more preferably selected in the range of 100 parts by mass: 3 parts by mass to 100 parts by mass: 8 parts by mass. .

On the other hand, the ratio of the total weight of the copper powder and fine copper powder (W _Cu-powder + W _{Cu-fine-powder} ) to the weight of the third organic solvent (W _{dispersion-medium} ), (W _Cu-powder + W _{Cu-fine-powder} ): W _{dispersion-medium} is preferably selected in the range of 100 parts by mass: 3.5 parts by mass to 100 parts by mass: 5.0 parts by mass.

In particular, in one aspect of the conductive copper paste according to the second aspect of the present invention, an aliphatic polyhydric alcohol is used as the fourth organic solvent.
The ratio of the total weight of the copper powder and fine copper powder (W _Cu-powder + W _{Cu-fine-powder} ) to the weight of the fourth organic solvent (W _{dispersion-medium} ), (W _Cu-powder + W _{Cu-fine -powder} ): W _{dispersion-medium} is preferably selected in the range of 100 parts by mass: 3.5 parts by mass to 100 parts by mass: 5.0 parts by mass.

The (dialkylamino) alkylamine is
(Dialkylamino) propylamine (R ′ ₂ N—CH ₂ CH ₂ CH ₂ —NH) having a total carbon number of 9 to 13 which is liquid at room temperature and has a boiling point of 230 ° C. or higher but not exceeding 300 ° C. ₂ ) is preferably selected from the group consisting of:

  The viscosity of the conductive copper paste is preferably selected in the range of 2 Pa · s to 50 Pa · s (25 ° C.).

  In the conductive copper paste according to the second embodiment of the present invention, a copper salt of an aliphatic monocarboxylic acid and a sintering aid can be further added.

For example, the conductive copper paste further includes a copper salt of an aliphatic monocarboxylic acid and a sintering aid,
The copper salt of the aliphatic monocarboxylic acid has a boiling point of 230 ° C. or higher, but is derived from an aliphatic monocarboxylic acid (R—COOH) that does not exceed 400 ° C. Copper salt,
The copper salt of the aliphatic monocarboxylic acid is added as a solution formed by dissolving in the (dialkylamino) alkylamine,
In the (dialkylamino) alkylamine solution of the aliphatic monocarboxylic acid copper salt, the content ratio of the aliphatic monocarboxylic acid copper salt to the (dialkylamino) alkylamine is determined as follows. Per molecule, (dialkylamino) alkylamine is selected in a ratio ranging from 2.2 to 8 molecules,
The sintering aid is a carboxylic acid metal salt or a metal carboxylic acid complex, which is a metal cation species other than copper and a carboxylic acid anion species,
The metal cation species other than copper is selected from the group consisting of bismuth and tin, or one or a plurality of types of metal cation species,
The carboxylic acid anion species is a carboxylic acid anion species selected from the group consisting of aliphatic monocarboxylic acids having 6 to 20 carbon atoms,
Ratio of the total weight of copper atoms (W _{Cu-carboxylate} ) contained in the copper salt of aliphatic monocarboxylic acid to the total weight (W _Cu-powder + W _{Cu-fine-powder} ) of the copper powder and fine copper powder , (W _Cu-powder + W _{Cu-fine-powder} ): (W _{Cu-carboxylate} ) is selected in the range of 100 parts by mass: 0.15 parts by mass to 100 parts by mass: 0.7 parts by mass,
Volume of metal atoms generated by reducing the carboxylic acid metal salt or metal carboxylic acid complex V _low-mp-metal and volume of metal atoms generated by reducing the copper salt of the aliphatic monocarboxylic acid The ratio of the total V _Cu-metal , V _low-mp-metal : V _Cu-metal may be selected in a range not exceeding 2: 1.

Further, the conductive copper paste further includes a copper salt of an aliphatic monocarboxylic acid and a sintering aid,
The copper salt of the aliphatic monocarboxylic acid has a boiling point of 230 ° C. or higher, but is derived from an aliphatic monocarboxylic acid (R—COOH) that does not exceed 400 ° C. Copper salt,
The copper salt of the aliphatic monocarboxylic acid is added as a solution formed by dissolving in (dialkylamino) alkylamine,
In the (dialkylamino) alkylamine solution of the aliphatic monocarboxylic acid copper salt, the content ratio of the aliphatic monocarboxylic acid copper salt to the (dialkylamino) alkylamine is determined as follows. Per molecule, (dialkylamino) alkylamine is selected in a ratio ranging from 2.2 to 8 molecules,
The sintering aid is a carboxylic acid metal salt or a metal carboxylic acid complex, which is a metal cation species other than copper and a carboxylic acid anion species,
The metal cation species other than copper is a mixed metal cation species formed by mixing a cation species of the first metal group and a cation species of the second metal group,
The cation species of the first metal group is selected from the group consisting of bismuth and tin, or one or more metal cation species,
The cation species of the second metal group is selected from the group consisting of zinc, aluminum, indium, silver, cobalt, titanium, nickel, manganese, or a cation species of one or more metals.
In the mixed metal cation species, the total number of metal atoms of the cation species of the second metal group is selected within a range of less than 10% with respect to the total number of metal atoms of the cation species of the first metal group. And
The carboxylic acid anion species is a carboxylic acid anion species selected from the group consisting of aliphatic monocarboxylic acids having 6 to 20 carbon atoms,
Ratio of the total weight of copper atoms (W _{Cu-carboxylate} ) contained in the copper salt of aliphatic monocarboxylic acid to the total weight (W _Cu-powder + W _{Cu-fine-powder} ) of the copper powder and fine copper powder , (W _Cu-powder + W _{Cu-fine-powder} ): (W _{Cu-carboxylate} ) is selected in the range of 100 parts by mass: 0.15 parts by mass to 100 parts by mass: 0.7 parts by mass,
A volume sum V _low-mp-metal of metal atoms of the first metal group formed by reducing a carboxylic acid metal salt or metal carboxylic acid complex, which is a cation species of the first metal group and a carboxylic acid anion species; , Ratio of the total volume of metal atoms V _Cu-metal generated by reducing the copper salt of the aliphatic monocarboxylic acid, V _low-mp-metal : V _Cu-metal does not exceed 2: 1 It can be set as the aspect currently selected.

In the conductive copper paste according to the second embodiment of the present invention described above, in the aspect of further adding a copper salt of an aliphatic monocarboxylic acid and a sintering aid,
As the aliphatic monocarboxylic acid anion having a boiling point of 230 ° C. or higher, which does not exceed 400 ° C., constituting the aliphatic monocarboxylic acid copper salt ((R—COO) ₂ Cu (II)),
It is desirable to select an anion derived from an aliphatic monocarboxylic acid having 10 to 20 carbon atoms.

  In addition, the present invention also applies the conductive copper paste according to the first aspect of the present invention described above and the method of using the conductive copper paste according to the second aspect of the present invention.

That is, the method of using the conductive copper paste according to the present invention is as follows.
A conductive copper paste selected from the group consisting of the conductive copper paste according to the first embodiment of the present invention having the above-described configuration and the conductive copper paste according to the second embodiment of the present invention, and a sintered body film. A method used to produce
Using the conductive copper paste, the step of producing a sintered body film is as follows:
Forming a coating film of the conductive copper paste on an underlayer;
In a reducing atmosphere containing hydrogen gas, the step of baking the conductive copper paste by heating the coating film of the conductive copper paste to a temperature of 300 ° C. or higher and 400 ° C. or lower,
The reducing atmosphere containing hydrogen gas contains hydrogen gas in an amount of 1 to 4% by volume in an inert gas,
The heating time is selected in the range of 5 minutes to 60 minutes,
The sintered body film to be produced is a conductive film having a resistivity in the range of 15 μΩ · cm or less,
The method of using a conductive copper paste is characterized in that the thickness of the sintered body film is selected in the range of 20 μm to 100 μm.

  In that case, it is desirable that the thickness of the sintered body film is selected in the range of 30 μm to 80 μm.

  The sintered body film to be produced is preferably a conductive film having a resistivity in the range of 5 μΩ · cm to 15 μΩ · cm.

  Furthermore, in the conductive copper paste according to the first aspect of the present invention and the conductive copper paste according to the second aspect of the present invention, when the above-mentioned sintering aid is added, the sintering is selected. The addition amount of the auxiliary agent can be selected within the following range on the basis of the above-mentioned “sum of the surface area of the copper powder and the surface area of the fine copper powder”.

That is, in one aspect of the conductive copper paste to which the sintering aid is further added,
As a sintering aid, when adding a carboxylic acid metal salt or metal carboxylic acid complex, which becomes a metal cation species other than copper and a carboxylic acid anion species,
The total number of metal atoms of the metal cation species contained in the metal carboxylate or metal carboxylate complex is 100 μmol / m ² or less with respect to the sum of the surface area of the copper powder and the surface area of the fine copper powder. It is desirable to select a range.

Moreover, in another aspect of the conductive copper paste to which the sintering aid is further added,
Carboxylic acid metal salt or metal carboxylic acid complex comprising a mixed metal cation species and a carboxylic acid anion species obtained by mixing the cation species of the first metal group and the cation species of the second metal group as a sintering aid When adding
The total number of metal atoms of the metal cation species contained in the metal carboxylate or metal carboxylate complex is 100 μmol / m ² or less with respect to the sum of the surface area of the copper powder and the surface area of the fine copper powder. It is desirable to select a range.

  When using the conductive copper paste according to the present invention, in the reducing atmosphere containing hydrogen gas, used as the first organic solvent, the second organic solvent, the third organic solvent, the fourth organic solvent, By heat treatment in the presence of an organic solvent having an alcoholic hydroxyl group, for example, an aliphatic polyhydric alcohol, at a temperature of 300 ° C. to 400 ° C., for example, a temperature selected in the range of 350 ° C. to 400 ° C. Copper powder selected from a mixture of copper powder selected as a conductive filler and having an average particle diameter of 2 μm to 10 μm, and a fine copper powder selected as an average particle diameter of 0.2 μm to 1.0 μm. The sintered body layer is formed and can be used as a highly conductive conductor layer.

In particular, in the conductive copper paste according to the first aspect of the present invention, the copper cation (Cu ² ) contained in the mixed aliphatic monocarboxylic acid copper salt ((R—COO) ₂ Cu (II)). ⁺ ) Is reduced with heat treatment, and metal copper atoms (Cu) are deposited, and the metal copper atoms (Cu) deposited at the contact points between the copper powders and at the contact points between the underlying layer and the copper powders Is accumulated. As a result, the effective contact area of the contact portions between the copper powders is expanded, and the resistivity of the entire sintered powder layer between the copper powders is further reduced. In addition, adhesion to the surface of the underlayer and electrical contact with the underlayer are maintained.

  Further, in the conductive copper paste according to the second aspect of the present invention, the mixed copper nanoparticles are in contact with the copper powder in the narrow gap near the contact portion between the copper powder and the surface of the base layer. Fill a narrow gap near the site. As a result, the effective contact area of the contact portions between the copper powders is expanded, and the resistivity of the entire sintered powder layer between the copper powders is further reduced. In addition, adhesion to the surface of the underlayer and electrical contact with the underlayer are maintained.

  Further, since the conductive copper paste according to the present invention does not contain a thermosetting resin component or glass frit, the conductive layer composed of the sintered powder of the copper powder of the conductive filler is soldered. It will be suitable for joining. Moreover, the sintered compact layer of copper powder mutually consists of the mixture of the copper powder selected in the range whose average particle diameter is 2 micrometers-10 micrometers, and the average particle diameter is selected in the range of 0.2 micrometer-1.0 micrometer. It is formed and is suitable for the production of a thick conductor layer.

  Hereinafter, the conductive copper paste according to the present invention will be described in more detail.

  The conductive copper paste according to the present invention is characterized in that it does not contain a glass frit and a thermosetting resin component that are widely used in conventional conductive copper pastes. Furthermore, the conductive copper paste according to the present invention is obtained by heat-treating the conductive filler contained at a temperature of 300 ° C. or more and 400 ° C. or less, for example, a temperature selected in the range of 350 ° C. to 400 ° C. Sintering is possible, and the resistivity (volume resistivity) of the obtained sintered body is less than 10 times that of metallic copper with a resistivity of 1.673 μΩ · cm (30 ° C.). It is characterized by having the advantage of becoming a body.

In the conductor layer produced by using the conductive copper paste according to the first embodiment of the present invention, it is possible to use glass frit and thermosetting resin in order to improve the adhesion with the surface of the underlayer. Instead, the copper cation (Cu ²⁺ ) contained in the mixed copper salt of aliphatic monocarboxylic acid ((R—COO) ₂ Cu (II)) is reduced to form a metallic copper atom (Cu) The metal copper film layer which consists of is utilized. Moreover, the copper powder selected in the range whose average particle diameter is 2 micrometers-10 micrometers and the fine copper powder selected in the range whose average particle diameter is 0.2 micrometers-1.0 micrometer are used together, Furthermore, each copper powder mutual By accumulating metal copper atoms (Cu) generated in a narrow gap near the contact site and expanding the effective contact area of the contact sites between the copper powders, The resistivity is reduced.

  In the conductor layer produced by using the conductive copper paste according to the second embodiment of the present invention, it is possible to use glass frit and thermosetting resin in order to improve the adhesion with the surface of the underlying layer. Instead, copper nanoparticles that are blended and that have an average particle diameter of 10 nm to 100 nm are used. Moreover, the copper powder selected in the range whose average particle diameter is 2 micrometers-10 micrometers and the fine copper powder selected in the range whose average particle diameter is 0.2 micrometers-1.0 micrometer are used together, Furthermore, each copper powder mutual Copper nanoparticles are accumulated in a narrow gap near the contact area, and the effective contact area of each copper powder contact area is expanded to reduce the resistivity of the entire sintered body layer of copper powder. I am trying.

  In addition, in the conductive copper paste according to the present invention, an organic compound having a hydroxyl group that can be converted into an oxo group (═O) or a formyl group (—CHO) by oxidation as a dispersion solvent, for example, an aliphatic polyhydric acid. A monohydric alcohol or a monoalkyl ether of an aliphatic polyhydric alcohol is used. When forming a conductor layer using a conductive copper paste, hydrogen gas is included in the presence of an organic compound having a hydroxyl group, for example, an aliphatic polyhydric alcohol or a monoalkyl ether of an aliphatic polyhydric alcohol. By performing heat treatment at least at a temperature of 250 ° C. or higher in a reducing atmosphere, the surface oxide film slightly present on the surfaces of the copper powder and fine copper powder is reduced. As a result, the metal copper surfaces come into contact with each other at the contact portions between the copper powders, and the contact resistance at the contact portions between the copper powders can be reduced.

  In the conductive copper paste according to the second aspect of the present invention, a coated molecular layer was formed on the surface of the copper nanoparticles whose average particle diameter was selected in the range of 10 nm to 100 nm using (dialkylamino) alkylamine. Above, the form which disperse | distributes the copper nanoparticle in which this coating molecular layer is formed in the surface in an aliphatic polyhydric alcohol is employ | adopted.

In the conductive copper paste according to the first aspect of the present invention, an aliphatic monocarboxylic acid copper salt ((R—COO) ₂ Cu (II)) is once dissolved in (dialkylamino) alkylamine, and then aliphatic. A form in which an amine complex of a copper salt of monocarboxylic acid ((R—COO) ₂ Cu (II)) is formed and an amine solution of the complex is mixed into an aliphatic polyhydric alcohol is employed.

Therefore, the conductive copper paste according to the first embodiment of the present invention has, as an essential component, a copper powder having an average particle size selected in the range of 2 to 10 μm and an average particle size in the range of 0.2 μm to 1.0 μm. Fine copper powder selected from the following: copper salt of aliphatic monocarboxylic acid ((R—COO) ₂ Cu (II)), (dialkylamino) alkylamine used for dissolving the copper salt, used as a dispersion solvent, First organic solvent or second organic solvent, for example, an aliphatic polyvalent organic solvent having an alcoholic hydroxyl group that can be converted to an oxo group (═O) or a formyl group (—CHO) by oxidation. It is made into the form of the paste-form composition which contains alcohol and the said copper powder and fine copper powder are uniformly disperse | distributed in this dispersion solvent.

  The conductive copper paste according to the second embodiment of the present invention is selected as an essential component, copper powder having an average particle diameter of 2 to 10 μm, and an average particle diameter of 0.2 to 1.0 μm. Fine copper powder to be used, copper nanoparticles with an average particle size selected in the range of 10 nm to 100 nm, (dialkylamino) alkylamine used for forming a coating molecular layer on the surface of the copper nanoparticles, used as a dispersion solvent, Third or fourth organic solvent, for example, an aliphatic polyvalent organic solvent having an alcoholic hydroxyl group that can be converted to an oxo group (═O) or a formyl group (—CHO) by oxidation. It is made into the form of the paste-form composition which contains alcohol and the said copper powder, fine copper powder, and copper nanoparticle are uniformly disperse | distributed in this dispersion solvent.

  First, the copper powder selected in the range whose average particle diameter is 2-10 micrometers used for preparation of the electroconductive copper paste which concerns on the 1st form of this invention and a 2nd form, and an average particle diameter are 0.00. The fine copper powder selected in the range of 2 μm to 1.0 μm, the first organic solvent or the second organic solvent, and the third organic solvent or the fourth organic solvent will be described below. Also, an organic solvent having an alcoholic hydroxyl group, such as an aliphatic polyhydric alcohol, used as the first organic solvent or the second organic solvent, and the third organic solvent or the fourth organic solvent, or Specific examples of monoalkyl ethers of aliphatic polyhydric alcohols will be shown, and their roles in the sintering process will be described below.

The conductor layer produced using the conductive copper paste of the present invention is used for producing a thick copper wiring layer or an n-side electrode layer provided on the light-receiving surface side of the solar cell. In the above-mentioned use, the thickness t _layer of the produced conductor _layer is usually selected in the range of 30 μm to 80 μm. This electric conductor layer is comprised by the sintered compact layer of fine copper powder and copper powder formed by heating and baking the copper powder and fine copper powder which are contained in electroconductive copper paste. At that time, the thickness of the conductor layer corresponds to the thickness of the sintered body layer in which the laminated copper powder and fine copper powder are sintered. The thickness variation of the sintered body layer in which the laminated copper powder and the fine copper powder are sintered, and the unevenness of the surface are the average particle diameter d _Cu-powder of the copper powder used and the average particle of the fine copper powder. It depends on the diameter d _{Cu-fine-powder} and the content ratio of copper powder and fine copper powder.

When copper powder and fine copper powder are uniformly dispersed, a laminated structure of copper powder and fine copper powder is formed in a form in which the gap between the copper powders is filled with fine copper powder. At that time, the thickness variation Δt _layer of the sintered powder layers (conductor layers) between the copper powders formed is at most about 1/2 of the average particle diameter d _Cu-powder of the copper powder used, Further, the surface unevenness δt _layer is at most about ¼ of the average particle diameter d _Cu-powder of the copper powder used.

The thickness variation Δt _layer is usually (Δt _layer / t _layer ) <1/4 at most with respect to the thickness t _{layer of the} conductor layer to be manufactured, and more preferably (Δt _layer / t _layer ) ≦ 1/10 is desirable. At that time, considering the _{Δt layer ≦ 1/2 · d} Cu-powder, (1/2 · d Cu-powder / t layer) <1/4, more _{preferably, (1/2 · d Cu-powder} / It is desirable to select the average particle diameter d _Al-powder of the aluminum powder so that t _layer ) ≦ 1/10. Therefore, the average particle diameter d _Cu-powder of the _{copper powder} is (d _Cu-powder / t _layer ) <1/2, more preferably (d _Cu ) with respect to the thickness t _{layer of the} conductor layer to be produced. _-powder / t _layer ) is preferably selected to be in the range of 1/5.

Considering this point, when the thickness t _{layer of the} conductor layer to be produced is in the range of 20 μm to 100 μm, preferably in the range of 30 μm to 80 μm, it is contained in the conductive copper paste according to the present invention. The average particle diameter d _CU-powder of the copper _powder is preferably selected in the range of 2 μm to 10 μm, more preferably in the range of 3 μm to 8 μm.

On the other hand, in forming a laminated structure of copper powder and fine copper powder in a form filled with fine copper powder, the average particle diameter d of fine copper powder is defined as the gap between the copper powders of average particle diameter d _Cu-powder. the _{Cu-fine-powder,} the average particle diameter d _Cu-powder of less than 1/4 of copper powder, and more preferably, it is desirable to select 1/10 following range of the average particle diameter d _Cu-powder of copper powder . Therefore, the average particle diameter d _Cu-powder is in the range of 2 to 10 [mu] m, for example, when using a copper powder is selected in the range of 3Myuemu～8myuemu, average particle diameter d _{Cu-fine-powder} of fine copper powder, It is desirable to select in the range of 0.2 μm to 1.0 μm, more preferably in the range of 0.2 μm to 0.8 μm.

  Moreover, the shape of the copper powder used is selected from the group consisting of flaky copper powder, granular copper powder, and irregular-shaped copper powder. In general, it is desirable to use granular copper powder for the purpose of suppressing variations in the thickness of the conductor layer to be formed and surface irregularities. The shape of the fine copper powder can also be selected from the group consisting of flaky fine copper powder, granular fine copper powder, and irregular-shaped fine copper powder. In general, it is desirable to use granular fine copper powder for the purpose of filling gaps between copper powders with fine copper powder.

  In the present invention, by filling the gap between the copper powder with the fine copper powder, in addition to the contact area between the copper powder, the contact area between the copper powder and the fine copper powder filling the gap between the copper powder By using this, the electrical connection path between the copper powders is remarkably increased. In achieving this object, the content ratio of copper powder and fine copper powder, (copper powder content): (fine copper powder content) is 80 parts by mass: 20 parts by mass to 60 parts by mass: 40 parts by mass. It is desirable to select within the range of 75 parts by mass, more preferably within the range of 75 parts by mass to 65 parts by mass: 35 parts by mass. By selecting the content ratio of the copper powder and the fine copper powder, the gap space is reduced as the entire laminated structure of the copper powder and the fine copper powder, and the electrical connection path between the copper powders is remarkably increased.

  On the other hand, the surface of the copper powder and the fine copper powder used for the preparation of the conductive copper paste according to the present invention usually has a slight surface oxide film. When forming a sintered body layer from the laminated structure of copper powder and fine copper powder, the surface oxide film present on the surface of the copper powder and fine copper powder is reduced. Organic solvents having an alcoholic hydroxyl group, especially organic compounds having an alcoholic hydroxyl group (—OH) which can be converted to an oxo group (═O) or a formyl group (—CHO) by oxidation, for example, aliphatic In the presence of a polyhydric alcohol or a monoalkyl ether of an aliphatic polyhydric alcohol, heat treatment is performed at a temperature of at least 250 ° C. in a reducing atmosphere containing hydrogen gas. A slight surface oxide film existing in the substrate is reduced.

When selecting the content ratio of the copper powder and fine copper powder, the ratio of the average particle diameter d _{Cu-fine-powder of the fine} copper powder and the average particle diameter d _Cu-powder of the copper powder, When the total surface area of the fine copper powder is compared, (total surface area of the fine copper powder) >> (total surface area of the copper powder).

  The surface oxide film partially present on the surfaces of the copper powder and fine copper powder is composed of a copper oxide corresponding to copper oxide (CuO). In the conductive copper paste, an organic solvent having an alcoholic hydroxyl group used as a dispersion solvent, for example, an aliphatic polyhydric alcohol or a monoalkyl ether of an aliphatic polyhydric alcohol is a surface of copper powder or fine copper powder. Is solvated (adsorbed). For a copper oxide corresponding to copper oxide (CuO), an organic solvent having an alcoholic hydroxyl group, for example, an aliphatic polyhydric alcohol, or a monoalkyl ether of an aliphatic polyhydric alcohol has a hydroxyl group (> CH -OH) is used to form hydrogen-bonded intermolecular bonds with oxygen atoms (Cu-O-Cu) in the copper oxide. At that time, it is presumed that the reduction of the surface oxide film proceeds via the following two elementary processes.

When a heat treatment is performed in a reducing atmosphere containing hydrogen gas (H ₂ ), an organic solvent having an alcoholic hydroxyl group that can be converted into an oxo group (═O) by oxidation, such as an aliphatic polyhydric alcohol, Alternatively, a monoalkyl ether of an aliphatic polyhydric alcohol reacts with the copper oxide to cause the following oxidation / reduction reaction.

CuO + (> CH—OH) → Cu + (> C═O) + H ₂ O ↑

The organic solvent having an alcoholic hydroxyl group, for example, a monoalkyl ether of an aliphatic polyhydric alcohol or a reaction product derived from an aliphatic polyhydric alcohol (> C═O) is exposed on the surface of fine copper powder or copper powder. Coordination can be carried out on the copper metal atom by using the π electron of the oxo group (> C═O). In a reducing atmosphere containing hydrogen gas, a hydrogen molecule (H ₂ ) is added to an oxo group (> C═O) coordinated on the metal copper atom, whereby the original hydroxyl group ( > CH—OH).

(> C = O) + H ₂ → (> CH—OH)

  An organic solvent having an alcoholic hydroxyl group in which the original hydroxyl group (> CH—OH) has been regenerated, for example, an aliphatic polyhydric alcohol molecule, or a monoalkyl ether molecule of an aliphatic polyhydric alcohol, is again made of copper. It can be solvated (adsorbed) on the surface of the powder and fine copper powder.

Apparently, reduction of the surface oxide film proceeds using hydrogen molecules (H ₂ ) supplied from a reducing atmosphere containing hydrogen gas.

Therefore, in the conductive copper paste according to the present invention, an organic solvent having an alcoholic hydroxyl group, for example, an aliphatic polyhydric alcohol, used as a dispersion solvent, is oxidized by an oxo group (= O) or a formyl group (- Having a hydroxyl group (—OH) convertible to CHO), and utilizing the hydroxyl group (> CH—OH), the oxygen atom (Cu—O—Cu) in the copper oxide and the hydrogen bond type Must be capable of intermolecular bonding. Further, in a reducing atmosphere containing hydrogen gas in the presence of an organic solvent having an alcoholic hydroxyl group, for example, an aliphatic polyhydric alcohol or a monoalkyl ether of an aliphatic polyhydric alcohol, at a temperature of at least 250 ° C. In performing the heat treatment, the organic solvent having the alcoholic hydroxyl group, for example, an aliphatic polyhydric alcohol, or a monoalkyl ether of an aliphatic polyhydric alcohol, has the alcoholic hydroxyl group ( > CH—OH) is required to solvate (adsorb) on the surface oxide film on the surface of copper powder and fine copper powder. That is, it is preferable to use an organic compound having an alcoholic hydroxyl group (—OH) in which the hydroxyl group (—OH) is present in the form of> CH—OH or —CH ₂ —OH.

  In the conductive copper paste according to the first aspect of the present invention and the conductive copper paste according to the second aspect, the first organic solvent or the second organic solvent, and the third organic solvent or the fourth organic solvent. As the solvent, an organic solvent that satisfies the above conditions is employed. Specifically, the first organic solvent and the third organic solvent are liquid at room temperature, and the boiling point is 200 ° C. or higher, but does not exceed 400 ° C., and preferably does not exceed 300 ° C. An organic solvent having an alcoholic hydroxyl group that does not have any reactive functional group other than the hydroxyl group is used. In addition, the second organic solvent and the fourth organic solvent are liquid at room temperature and have a boiling point of 230 ° C. or higher but not exceeding 400 ° C., preferably not exceeding 300 ° C. Use polyhydric alcohol.

  On the other hand, after the reduction of the surface oxide film on the surface of the copper powder and fine copper powder is completed, at the stage where the sintering of the copper powder and fine copper powder proceeds, the copper powder and the fine copper powder are solvated on the metal copper surface. It is desirable not to remain in the (adsorbed) state. Therefore, it is liquid at room temperature and has a boiling point of 230 ° C. or higher, but does not exceed 400 ° C., preferably does not exceed 300 ° C., or a monoalkyl of an aliphatic polyhydric alcohol. It is preferable to use ether. In general, it is liquid at room temperature and has a boiling point of 230 ° C. or higher, but it is more preferable to use an aliphatic polyhydric alcohol in a range not exceeding 400 ° C., preferably not exceeding 300 ° C.

  For example, one aspect of the conductive copper paste according to the first aspect of the present invention described above, one aspect of the conductive copper paste according to the second aspect of the present invention, a second organic solvent that satisfies the above conditions, As the fourth organic solvent, an aliphatic polyhydric alcohol that is liquid at room temperature and has a boiling point of 230 ° C. or higher but not exceeding 400 ° C., preferably not exceeding 300 ° C. is used.

  On the other hand, after the reduction of the surface oxide film on the surface of the copper powder and fine copper powder is completed, at the stage where the sintering of the copper powder and fine copper powder proceeds, the copper powder and the fine copper powder are solvated on the metal copper surface. It is desirable not to remain in the (adsorbed) state. Therefore, it is a liquid at room temperature and has a boiling point of 230 ° C. or higher but not exceeding 300 ° C., preferably not exceeding 300 ° C., or a monoalkyl of an aliphatic polyhydric alcohol. It is preferable to use ether. More preferably, it is a liquid at room temperature and has a boiling point of 230 ° C. or higher, but it is desirable to use an aliphatic polyhydric alcohol in a range not exceeding 280 ° C., or a monoalkyl ether of an aliphatic polyhydric alcohol.

In the conductive copper paste according to the first aspect of the present invention and the conductive copper paste according to the second aspect of the present invention, it can be used as the first organic solvent and the third organic solvent, and is liquid at room temperature. Yes, the boiling point is 200 ° C. or higher, but does not exceed 400 ° C., and the organic compound having an alcoholic hydroxyl group (—OH) does not contain any reactive functional group other than the hydroxyl group, An organic compound having an alcoholic hydroxyl group (—OH) that can be converted into an oxo group (═O) or a formyl group (—CHO) by oxidation is formed on the surface oxide film on the surface of the copper powder or fine copper powder. It is preferably used for reduction removal. An alcoholic hydroxyl group (--convertible to an oxo group (= O) or formyl group (-CHO) by oxidation, which can be suitably used for reduction and removal of the surface oxide film on the surface of the copper powder and fine copper powder. As the organic compound having OH), the following compounds can be exemplified.
1-nonanol (melting point −5.5 ° C., boiling point 213.5 ° C.), 1-dodecanol (melting point 23.5 ° C., boiling point 259 ° C.), which are linear saturated aliphatic primary alcohols having 9 to 12 carbon atoms. )Such;
Oleyl alcohol (melting point: 5.5 to 7.5 ° C., boiling point: 345 to 355 ° C.), which is an unsaturated aliphatic primary alcohol having 18 carbon atoms;
Isodecyl alcohol (melting point 7 ° C., boiling point 220 ° C.), isostearyl alcohol (boiling point 265 to 275 ° C.), hexyldecanol (melting point −21 to −−), which are saturated aliphatic primary alcohols having 10 to 24 carbon atoms. 15 ° C, boiling point 300-310 ° C), 2-octyl-1-dodecanol (melting point -20 ° C, boiling point 340-360 ° C), 2-decyl-1-tetradecanol (melting point 19-20 ° C, boiling point 280-290) ° C) etc .;
2-decanol (melting point −6 to −4 ° C., boiling point 211 ° C.), 2-dodecanol (melting point 19 ° C., boiling point 250 ° C.) and the like, which are aliphatic secondary alcohols having 10 to 12 carbon atoms;
2,5-hexanediol (boiling point 216 ° C.), 2-ethyl-1,3-hexanediol (boiling point 243 ° C.), 3-methyl-1,3-butanediol (alkanediol having 4 to 9 carbon atoms) Boiling point 203 ° C.), 3-methyl-1,5-pentanediol (boiling point 250 ° C.), 2-methyl-1,8-octanediol (boiling point 290-300 ° C.), 1,2-pentanediol (boiling point 206 ° C.) 1,2-hexanediol (boiling point 223 ° C.), 1,3-nonanediol (boiling point 271 ° C.), etc .;
Polyalkylene glycols having a molecular weight in the range of 4000 or less, for example, polyalkylene glycols having a total carbon number in the range of 4 to 9, particularly polyethylene glycols such as diethylene glycol (boiling point 244 ° C.), triethylene glycol (boiling point 287 ° C. ), Polypropylene glycols such as dipropylene glycol (boiling point 232 ° C.), tripropylene glycol (boiling point 268 ° C.), etc .;
Glycerin (melting point: 17.8 ° C., boiling point: 298 ° C.), 1,2,3-butanetriol (boiling point: 290-300 ° C.), 1,2,4-butanetriol (boiling point), which are alkanetriols having 3 to 6 carbon atoms. 320-330 ° C), 1,2,5-pentanetriol (boiling point 325-335 ° C), 1,2,6-hexanetriol (melting point 25 ° C, boiling point 340-350 ° C), etc .;
Alkylene glycol monoalkyl ether, polyalkylene glycol monoalkyl ether type polyhydric alcohol monoalkyl ether, ethylene glycol monohexyl ether (boiling point 208 ° C), ethylene glycol monooctyl ether (boiling point 229 ° C), diethylene glycol monobutyl ether (boiling point) 231 ° C.), diethylene glycol monohexyl ether (boiling point 259 ° C.), diethylene glycol monooctyl ether (boiling point 272 ° C.), triethylene glycol monomethyl ether (boiling point 249 ° C.), triethylene glycol monobutyl ether (boiling point 271 ° C.), dipropylene glycol mono Propyl ether (bp 212 ° C), dipropylene glycol monobutyl ether (bp 229 ° C), tripropylene glycol Glycol monomethyl ether (boiling point 242 ° C.), such as tripropylene glycol monobutyl ether (boiling point 274 ° C.);
In the conductive copper paste according to the first aspect of the present invention, as the first organic solvent used as a dispersion solvent,
An alkanol having 9 to 14 carbon atoms that is liquid at room temperature and has a boiling point of 200 ° C. or higher but not exceeding 400 ° C .;
An alkanediol having 4 to 9 carbon atoms that is liquid at room temperature and has a boiling point of 200 ° C. or higher but not exceeding 400 ° C.,
A polyalkylene glycol having a molecular weight of 4000 or less, which is liquid at room temperature and has a boiling point of 200 ° C. or higher but not exceeding 400 ° C.,
A polyhydric alcohol monoalkyl ether that is liquid at room temperature and has a boiling point of 200 ° C. or higher but not exceeding 400 ° C.,
An oxo group by oxidation selected from the group consisting of glycerin, 1,2,3-butanetriol, 1,2,4-butanetriol, 1,2,5-pentanetriol, 1,2,6-hexanetriol; An organic solvent having an alcoholic hydroxyl group (—OH) that can be converted into (═O) or a formyl group (—CHO) can be suitably used.

In the polyhydric alcohol monoalkyl ether that is liquid at room temperature and has a boiling point of 200 ° C. or higher but not exceeding 400 ° C., preferably not exceeding 300 ° C., the polyhydric alcohol moiety is: What is alkane polyol can use suitably. For example, among the alkane polyol monoalkyl ethers, ethylene glycol monooctyl ether (melting point: −60 or less, boiling point: 229 ° C.) can be exemplified as satisfying the above requirements. Furthermore, in the polyhydric alcohol monoalkyl ether which is liquid at room temperature and has a boiling point of 200 ° C. or higher but not exceeding 400 ° C., preferably not exceeding 300 ° C., the polyhydric alcohol A moiety that is a polyalkylene glycol (HO— (C _n H _2n —O) _m —C _n H _2n —OH) can also be used. Among the polyalkylene glycol monoalkyl ethers, triethylene glycol monobutyl ether (melting point: −48 ° C., boiling point: 271 ° C.) can be exemplified as one that satisfies the above requirements.

  Furthermore, in one aspect of the conductive copper paste according to the first aspect of the present invention described above, the aliphatic polyhydric alcohol used as the second organic solvent is a liquid at room temperature and has a boiling point of 230. It is an aliphatic polyhydric alcohol having a temperature not lower than 400 ° C. but not exceeding 400 ° C., preferably not exceeding 300 ° C. For example, the aliphatic polyhydric alcohol is a liquid at room temperature and has a boiling point of 230 ° C. or higher, but does not exceed 400 ° C., and preferably does not exceed 300 ° C. Diol, for example, one of alkanediols having 6 to 8 carbon atoms, 2-ethyl-1,3-hexanediol (melting point: −40 ° C., boiling point: 245 ° C.), or boiling point is 230 ° C. or higher , A polyalkylene glycol having a molecular weight of 4000 or less, for example, a dialkylene glycol having a total carbon number of 4 to 9 in a range not exceeding 400 ° C., preferably not exceeding 300 ° C. Melting point: −40 ° C., boiling point: 232 ° C.), tripropylene glycol (molecular weight 192, boiling point 268 ° C.), etc., and glycerin, 1,2,3- Phytantriol, 1,2,4-butanetriol, 1,2,5-pentane triol, 1,2,6-hexane triol can be suitably used. Specifically, one of the alcoholic hydroxyl groups (—OH) present in the aliphatic polyhydric alcohol is oxidized to (> CH—OH) → (> C═O) and an oxo group (═O). For example, 2-ethyl-1,3-hexanediol (melting point: −40 ° C., boiling point: 245 ° C.), glycerin and the like can be suitably used.

  The aliphatic polyhydric alcohol used as the second organic solvent is preferably used also as the fourth organic solvent in one embodiment of the conductive copper paste according to the second aspect of the present invention described above. Can do.

In the conductive copper paste according to the second aspect of the present invention, copper powder, fine copper is used in the organic solvent having the above alcoholic hydroxyl group, for example, an aliphatic polyhydric alcohol, which is used as the third organic solvent. Powder and copper nanoparticles are dispersed. Therefore, the volume of the third organic solvent (V _{dispersion-medium} ) relative to the total volume of copper powder, fine copper powder, and copper nanoparticles (V _Cu-powder + V _{Cu-fine-powder} + V _{Cu-nano-particle} ) ) Ratio, (V _Cu-powder + V _{Cu-fine-powder} + V _{Cu-nano-particle} ): V _{dispersion-medium} is in the range of 20: 6 to 20:10, preferably 20: 7 to 20: 9 It is desirable to select a range.

The organic solvent having the above-mentioned alcoholic hydroxyl group, for example, an aliphatic polyhydric alcohol, used as the third organic solvent, is used when reducing the surface oxide film on the surface of copper powder or fine copper powder. Is done. Considering this point, the ratio of the total weight of copper powder and fine copper powder (W _Cu-powder + W _{Cu-fine-powder} ) to the weight of the third organic solvent (W _{dispersion-medium} ), (W _{Cu- powder} + W _{Cu-fine-powder} ): W _{dispersion-medium} is in the range of 100 parts by mass: 2 parts by mass to 100 parts by mass: 10 parts by mass, preferably 100 parts by mass: 3 parts by mass to 100 parts by mass: 7 parts by mass. It is desirable to select within the range of 100 parts by mass: 3.5 parts by mass to 100 parts by mass: 5.0 parts by mass.

On the other hand, in the conductive copper paste according to the first aspect of the present invention, the liquid phase includes the first organic solvent described above and a copper salt of an aliphatic monocarboxylic acid ((R—COO) ₂ Cu (II)). A solution obtained by mixing a (dialkylamino) alkylamine solution. Copper powder and fine copper powder are dispersed in this mixed solution. Therefore, the ratio of the volume of the first organic solvent (V _{dispersion-medium} ) to the total volume of copper powder and fine copper powder (V _Cu-powder + V _{Cu-fine-powder} ), (V _Cu-powder + V _{Cu- Fine-powder} ): V _{dispersion-medium} is selected in the range of 20: 5 to 20: 9, preferably in the range of 20: 6 to 20: 8.

The organic solvent having the above-mentioned alcoholic hydroxyl group, for example, an aliphatic polyhydric alcohol, used as the first organic solvent, is used for reducing the surface oxide film on the surface of copper powder or fine copper powder. Is done. Considering this point, the ratio of the total weight of copper powder and fine copper powder (W _Cu-powder + W _{Cu-fine-powder} ) to the weight of the first organic solvent (W _{dispersion-medium} ), (W _{Cu- powder} + W _{Cu-fine-powder} ): W _{dispersion-medium} is in the range of 100 parts by mass: 2 parts by mass to 100 parts by mass: 10 parts by mass, preferably 100 parts by mass: 3 parts by mass to 100 parts by mass: 5 parts by mass. It is desirable to select a range of parts, for example, a range of 100 parts by mass: 3 parts by mass to 100 parts by mass: 4.5 parts by mass.

In the conductive copper paste according to the first aspect of the present invention, after once preparing a (dialkylamino) alkylamine solution of an aliphatic monocarboxylic acid copper salt ((R—COO) ₂ Cu (II)), Mixed with the first organic solvent.

The copper salt of the aliphatic monocarboxylic acid ((R—COO) ₂ Cu (II)) in the (dialkylamino) alkylamine solution is obtained from the copper salt of the aliphatic monocarboxylic acid ((R—COO) ₂ Cu (II). ) A composition in which (dialkylamino) alkylamine is in the range of 2.2 to 8 molecules per molecule, preferably in the range of 3 to 8 molecules, more preferably in the range of 4 to 7 molecules. It is desirable that the composition be such that

The copper salt of an aliphatic monocarboxylic acid ((R—COO) ₂ Cu (II)) generally forms a dimer having a Cu: Cu bond. When dissolved in the solvent (dialkylamino) alkylamine, the copper cation (Cu ²⁺ ) of the aliphatic monocarboxylic acid copper salt ((R—COO) ₂ Cu (II)) is converted into two molecules of (dialkylamino) Alkylamine (R ′ ₂ N—C _m H _2m —NH ₂ ) is a copper salt of an aliphatic monocarboxylic acid coordinated by utilizing a lone pair of its amino group (—NH ₂ ) (( R-COO) ₂ Cu (II)) amine complex ((R—COO) ₂ Cu (II)): 2 (R ′ ₂ N—C _m H _2m —NH ₂ )). Thereafter, when a (dialkylamino) alkylamine solution of a copper salt of an aliphatic monocarboxylic acid ((R—COO) ₂ Cu (II)) and an aliphatic polyhydric alcohol as a dispersion solvent are mixed, the aliphatic monocarboxylic acid The amine complex of copper salt ((R—COO) ₂ Cu (II)) is dissolved in a mixed liquid of (dialkylamino) alkylamine and aliphatic polyhydric alcohol. Most of them are the first with respect to C═O of the aliphatic monocarboxylic acid anion (R—COO ⁻ ) of the amine complex of the aliphatic monocarboxylic acid copper salt ((R—COO) ₂ Cu (II)). The organic solvent having the above-mentioned alcoholic hydroxyl group, for example, the hydroxyl group (> CH—OH) of the aliphatic polyhydric alcohol of the second organic solvent is used as an organic solvent for the hydrogen bonding type intermolecular bond. Formed and solvated.

When heat treatment is performed in a reducing atmosphere containing hydrogen gas (H ₂ ), the organic solvent having the above-mentioned alcoholic hydroxyl group represented by the following reaction formula, for example, the hydroxyl group of an aliphatic polyhydric alcohol ( > CH—OH) to an oxo group (> C═O) and a reduction reaction of the amine complex of the aliphatic monocarboxylic acid copper proceeds.

_{(R-COO) 2 Cu (} II): 2 (R '2 NC m H 2m -NH 2) + (> CH-OH)
→ 2R-COOH + (Cu ( 0): 2 (R '2 NC m H 2m -NH 2)) + (> C = O)

In addition, the above-mentioned organic solvent having an alcoholic hydroxyl group, for example, a reaction product derived from an aliphatic polyhydric alcohol (> C═O) is a fine copper powder, on the metal copper atom exposed on the surface of the copper powder, Coordination can be performed using the π electron of the oxo group (> C═O). In a reducing atmosphere containing hydrogen gas, a hydrogen molecule (H ₂ ) is added to an oxo group (> C═O) coordinated on the metal copper atom, whereby the original hydroxyl group ( > CH—OH).

(> C = O) + H ₂ → (> CH—OH)

On the other hand, the metal copper atom produced | generated by the reduction | restoration of the amine complex of this aliphatic monocarboxylic acid copper becomes a shape which (dialkylamino) alkylamine coordinated two molecules initially. When (dialkylamino) alkylamine functions as a bidentate ligand, a metal copper atom (Cu (0): 2) coordinated with two (dialkylamino) alkylamine molecules of the bidentate ligand (R ′ ₂ NC _m H _2m —NH ₂ ) can be dispersed in a dispersion solvent, while (dialkylamino) alkylamine is present in the periphery when functioning as a monodentate ligand ( Dialkylamino) alkylamine or an aliphatic polyhydric alcohol in a dispersion solvent is further coordinated, for example, a metal copper atom (Cu (0)) coordinated with 4 molecules of a monodentate (dialkylamino) alkylamine : Disperse in a dispersion solvent as 4 (R ′ ₂ NC _m H _2m —NH ₂ ).

In the state where the concentration of (dialkylamino) alkylamine dissolved in the liquid phase is sufficiently high, even when (dialkylamino) alkylamine functioning as a bidentate ligand is used, bidentate metallic copper atoms (dialkylamino) alkylamine 2 molecule ligand is coordinated (Cu (0): 2 ( R '2 NC m H 2m -NH 2) are corresponding parts, (dialkylamino) alkyl It is converted into a metal copper atom (Cu (0): 4 (R ′ ₂ NC _m H _2m —NH ₂ ) coordinated with four amine molecules.

On the other hand, (dialkylamino) alkylamine is coordinated to fine copper powder and metal copper atoms exposed on the surface of copper powder by utilizing the lone pair of amino group (—NH ₂ ). Make a realistic bond.

On the other hand, when heat treatment is performed in a reducing atmosphere containing hydrogen gas (H ₂ ), the reduction of the surface oxide film on the surface of the copper powder and fine copper powder proceeds, and the generated metal copper atoms (dialkylamino) ) As a result of the coordination (adsorption) of the alkylamine, the amount of (dialkylamino) alkylamine dissolved in the liquid phase is reduced. The metal copper atoms (dialkylamino) alkylamine 4 molecule is coordinated (Cu (0): If _{4 (R '2 NC m H} 2m -NH 2) generation of advances, dissolved in the liquid phase The amount of (dialkylamino) alkylamine is reduced.

  In addition, when the boiling point of the (dialkylamino) alkylamine is lower than the boiling point of the organic solvent having the above-mentioned alcoholic hydroxyl group of the first organic solvent, for example, the aliphatic polyhydric alcohol of the second organic solvent, In particular, the transpiration rate of (dialkylamino) alkylamine is excellent. The concentration of (dialkylamino) alkylamine dissolved in the liquid phase decreases.

  (Dialkylamino) alkylamine, which is coordinated (adsorbed) to metal copper atoms exposed on the surface of copper powder and fine copper powder, and (dialkylamino) alkylamine dissolved in the liquid phase Is in a dissociation equilibrium state. Therefore, when the concentration of (dialkylamino) alkylamine dissolved in the liquid phase falls below a certain level, a coordinated bond (adsorption) is formed on the copper metal atoms exposed on the surfaces of the copper powder and fine copper powder. The dissociation of (dialkylamino) alkylamine proceeds.

  Further, the metal copper atom coordinated by four molecules of (dialkylamino) alkylamine is also dissolved in the liquid phase with (dialkylamino) alkylamine coordinated to the metal copper atom (dialkylamino). ) Alkylamine is in dissociation equilibrium. Therefore, when the concentration of (dialkylamino) alkylamine dissolved in the liquid phase is below a certain level, dissociation of (dialkylamino) alkylamine coordinated to the metal copper atom proceeds.

For example, coordinated (dialkylamino) alkylamine is reduced to 2 molecules, metallic copper atom (Cu (0): 2 ( R '2 NC m H 2m -NH 2) is copper powder, fine copper powder When the metal copper atoms exposed on the surface of the metal are in contact with each other, a metal bond is formed between the metal copper atoms, and the metal copper atoms are fixed. metallic copper atoms derived from monocarboxylic copper (Cu (0): 2 ( R '2 NC m H 2m -NH 2) occurs sticking, then coordinated to the fixed metal copper atoms (dialkyl When the amino) alkylamine is released, the metal copper atom (Cu (0): 2 (R ' ₂ NC _m H _2m -NH ₂ ) derived from the aliphatic monocarboxylic acid copper is further fixed. Aggregates of metallic copper atoms derived from aliphatic monocarboxylic acid copper are formed using metallic copper atoms exposed on the surface of the copper powder as nuclei.

  The above phenomenon is remarkably promoted as the dispersion density of metal copper atoms coordinated by four (dialkylamino) alkylamine molecules dispersed in the liquid phase increases. In other words, the transpiration of the organic solvent having the above-mentioned alcoholic hydroxyl group of the (dialkylamino) alkylamine and the first organic solvent constituting the liquid phase, for example, the aliphatic polyhydric alcohol of the second organic solvent As the process proceeds, the above phenomenon is significantly promoted.

  As transpiration progresses and the volume of the liquid phase decreases (concentration progresses), the liquid phase is in contact with the fine copper powder, the narrow gap around the contact area of the copper powder, the contact between the underlayer and the fine copper powder, copper powder. The liquid phase is agglomerated in a narrow gap around the site. Therefore, as the liquid phase is concentrated, the dispersion concentration of metallic copper atoms coordinated with (dialkylamino) alkylamine is increased, and as a result, fine copper powder, a narrow gap around the contact area between the copper powder, Aggregation of metal copper atoms preferentially proceeds in a narrow gap around the contact area between the underlayer, the fine copper powder, and the copper powder.

  Therefore, the narrow gap around the contact area between the fine copper powder and the copper powder, the narrow gap around the contact area between the underlayer and the fine copper powder, and the copper powder are embedded with the aggregate of the metal copper atoms. Become. Then, when firing proceeds, the fine copper powder, around the copper powder contact area, around the base layer and the fine copper powder, around the copper powder contact area, the aggregate of metal copper atoms, fine copper powder, copper Integration with the powder proceeds. As a result, the contact area is increased in the contact area between the fine copper powder, the contact area between the copper powders, and the contact area between the ground layer and the fine copper powder and the copper powder.

  In addition, when a silanol structure (Si—OH) is present on the surface of the underlayer, the copper atom (Cu) derived from the aliphatic monocarboxylic acid copper is converted into the silanol structure (Si—OH) during the heat treatment. It is fixed to the part in the shape of Si—O—Cu. Formation of aggregates of metallic copper atoms derived from copper aliphatic monocarboxylate also proceeds with copper atoms immobilized in the form of Si—O—Cu on the surface of the underlayer as nuclei. When the silanol structure (Si-OH) is present at a high density on the surface of the underlayer, when the aggregates of the formed metal copper atoms come into contact with each other and are integrated by surface diffusion, the metal copper film layer covering the surface Growth is made. This phenomenon is possible for the first time when the evaporation of (dialkylamino) alkylamine and the aliphatic polyhydric alcohol as a dispersion solvent has progressed. That is, the above phenomenon preferentially proceeds in a narrow gap around the contact portion between the underlayer and the fine copper powder or copper powder.

  Of course, the metal copper film layer covering the surface of the underlayer exhibits excellent adhesion. In particular, in the part where the copper powder contacts the surface of the underlayer, metal copper atom aggregates are also partially formed on the surface of the copper powder, and integration between both metal copper atom aggregates is also possible. As it proceeds, bonds between metal atoms are formed. In addition to this contribution, high adhesion characteristics due to the interposition of the metal copper film layer are imparted between the surface of the base layer having a silanol structure (Si—OH) and the copper powder.

  In the conductive copper paste according to the first aspect of the present invention, by utilizing the above phenomenon, in the sintered body between the fine copper powder and the copper powder, the contact at the contact area between the fine copper powder and the copper powder, The area has been expanded. Moreover, the effective contact area is expanded also in the contact part of a base layer, fine copper powder, and copper powder.

Considering the mechanism, the sum of the volume of copper powder and fine copper powder for _{(V Cu-powder + V Cu} -fine-powder), the total volume of the metallic copper atoms derived from an aliphatic monocarboxylic acid copper (V _Cu- The ratio of ( _metal ), (V _Cu-powder + V _{Cu-fine-powder} ) :( V _Cu-metal ) is in the range of 100: 0.15 to 100: 0.7, more preferably 100: 0.3 to A range of 100: 0.5 is desirable. In other words, the total number of copper atoms contained in aliphatic monocarboxylic acid copper (M _{Cu-carboxylate} ) relative to the sum of metal copper atoms in copper powder and fine copper powder (M _Cu-powder + M _{Cu-fine-powder} ) The ratio, (M _Cu-powder + M _{Cu-fine-powder} ) :( M _{Cu-carboxylate} ), is in the range of 100: 0.15 to 100: 0.7, more preferably 100: 0.3 to 100: 0. Desirably, the range is .5. That is, the total weight of copper atoms contained in aliphatic monocarboxylic acid copper (W _{Cu-carboxylate} ) with respect to the total weight of copper metal and fine copper powder (W _Cu-powder + W _{Cu-fine-powder} ) The ratio of (W _Cu-powder + W _{Cu-fine-powder} ) :( W _{Cu-carboxylate} ) is in the range of 100 parts by mass: 0.15 parts by mass to 100 parts by mass: 0.7 parts by mass, more preferably It is desirable to set it as the range of 100 mass parts: 0.3 mass part-100 mass parts: 0.5 mass part.

On the other hand, (dialkylamino) alkylamine used for dissolving copper aliphatic monocarboxylate is subjected to heat treatment in a reducing atmosphere containing hydrogen gas (H ₂ ), similarly to the aliphatic polyhydric alcohol of the dispersion solvent. When applied, it is necessary to evaporate. Therefore, it is preferable to use a (dialkylamino) alkylamine that is liquid at room temperature and has a boiling point of 230 ° C. or higher but does not exceed 300 ° C. More preferably, it is desirable to use (dialkylamino) alkylamine which is liquid at room temperature and has a boiling point of 230 ° C. or higher but not exceeding 280 ° C.

  Further, the boiling point of the (dialkylamino) alkylamine is lower than the boiling point of the organic solvent having an alcoholic hydroxyl group of the first organic solvent, for example, the aliphatic polyhydric alcohol of the second organic solvent. In addition, it is desirable to select an organic solvent having an alcoholic hydroxyl group as the first organic solvent, for example, a combination of an aliphatic polyhydric alcohol and a (dialkylamino) alkylamine as the second organic solvent. More preferably, the boiling point of the (dialkylamino) alkylamine is lower than the boiling point of the organic solvent having an alcoholic hydroxyl group of the first organic solvent, for example, the aliphatic polyhydric alcohol of the second organic solvent. It is desirable to select a combination of the first organic solvent (or the second organic solvent) and the (dialkylamino) alkylamine so that the difference is at least within 30 ° C., preferably within 20 ° C.

In addition, in the organic solvent having an alcoholic hydroxyl group of the first organic solvent, for example, the aliphatic polyhydric alcohol of the second organic solvent, the (dialkylamino) alkylamine is derived from an aliphatic monocarboxylic acid copper when coordinated to the metal of copper atoms, by using the lone pairs of the amino (-NH _2), can be formed a coordinative bond, in particular, its amino group (-NH ₂₎ It is desirable to function as a bidentate ligand using a dialkylamino group (—NR ′ ₂ ).

In the conductive copper paste according to the first aspect of the present invention, (dialkylamino) alkylamine (R ′ ₂ N—C _m H _2m —NH ₂ ) used for dissolving aliphatic monocarboxylic acid copper is used at room temperature. It is preferable to use a (dialkylamino) alkylamine having 9 to 13 carbon atoms, which is a liquid. In particular, using the amino group (—NH ₂ ) and the dialkylamino group (—NR ′ ₂ ), the (dialkylamino) propylamine (R ' ₂ N—CH ₂ CH ₂ CH ₂ —NH ₂ ), for example, dibutylaminopropylamine (melting point: −50 ° C., boiling point: 238 ° C.) can be suitably used.

  As a combination of an organic solvent having an alcoholic hydroxyl group of the first organic solvent, for example, an aliphatic polyhydric alcohol of the second organic solvent and a (dialkylamino) alkylamine, 2-ethyl-1,3-hexanediol ( Melting point: −40 ° C., boiling point: 245 ° C.) and dibutylaminopropylamine (melting point: −50 ° C., boiling point: 238 ° C.), or dipropylene glycol (melting point: −40 ° C., boiling point: 232 ° C.) and dibutyl A combination of aminopropylamine and the like can be suitably selected.

On the other hand, an amine complex of a copper salt of an aliphatic monocarboxylic acid ((R—COO) ₂ Cu (II)) is an organic solvent having an alcoholic hydroxyl group as a first organic solvent, for example, a second organic solvent. In heat treatment in an aliphatic polyhydric alcohol, the (dialkylamino) alkylamine of the ligand is released and, instead, an organic solvent having an alcoholic hydroxyl group of the first organic solvent, for example, a second It is necessary that the organic solvent aliphatic polyhydric alcohol is not converted into a coordinated form. For example, when an aliphatic polyhydric alcohol has a structure (—CH (OH) —CH (OH) —) in which a hydroxyl group (—OH) is present on an adjacent carbon atom, the structure is bidentately coordinated. It functions as a child and can replace two (dialkylamino) alkylamine molecules of the ligand. In other words, the organic solvent having the alcoholic hydroxyl group of the first organic solvent, for example, the aliphatic polyhydric alcohol of the second organic solvent has a structure in which a hydroxyl group (—OH) is present on an adjacent carbon atom ( Those not containing -CH (OH) -CH (OH)-) do not function as a bidentate ligand, and thus are easily eliminated. For example, when an alkanediol having a 1,3-diol structure such as 2-ethyl-1,3-hexanediol is employed as the aliphatic polyhydric alcohol of the dispersion solvent, the above-described advantages can be obtained.

In addition, the reduction of the amine complex of the aliphatic monocarboxylic acid copper salt ((R—COO) ₂ Cu (II)) is performed by using an organic solvent having the above alcoholic hydroxyl group as the first organic solvent, for example, the second Since the mechanism using the aliphatic polyhydric alcohol of the organic solvent is used, the amine complex of the aliphatic monocarboxylic acid copper salt ((R—COO) ₂ Cu (II)) is the alcohol of the first organic solvent. It is desirable not to carry out the autolytic degradation reaction in an organic solvent having a functional hydroxyl group, for example, an aliphatic polyhydric alcohol as the second organic solvent. In the autolytic reduction reaction, generation of CO ₂ originating from the aliphatic monocarboxylate anion occurs, and foaming due to the generated CO ₂ occurs, which is not desirable in the present invention.

When the heat treatment is performed in a reducing atmosphere containing hydrogen gas (H ₂ ) in the presence of an organic solvent having an alcoholic hydroxyl group as the first organic solvent, for example, an aliphatic polyhydric alcohol as the second organic solvent. It is desirable that the reduction reaction using the organic solvent having the above-mentioned alcoholic hydroxyl group, for example, an aliphatic polyhydric alcohol, proceeds preferentially over the autolytic reduction reaction. In general, the autodegradative reduction of an aliphatic monocarboxylic acid copper salt ((R—COO) ₂ Cu (II)) increases the carbon number of the aliphatic monocarboxylic acid anion and increases the reaction initiation temperature. To do. Therefore, in the conductive copper paste according to the first aspect of the present invention, the aliphatic monocarboxylic acid anion constituting the aliphatic monocarboxylic acid copper salt ((R—COO) ₂ Cu (II)) has carbon number. It is desirable to select anions derived from 10-20 aliphatic monocarboxylic acids.

On the other hand, in the mechanism described above, aliphatic monocarboxylic acid (R—COOH) is by-produced with the reduction of the amine complex of the copper salt of aliphatic monocarboxylic acid ((R—COO) ₂ Cu (II)). The It is desirable that the aliphatic monocarboxylic acid (R—COOH) is evaporated during the heat treatment in a reducing atmosphere containing hydrogen gas (H ₂ ). Accordingly, the boiling point of the aliphatic monocarboxylic acid (R—COOH) is 230 ° C. or higher, but does not exceed 400 ° C., preferably 230 ° C. or higher, but does not exceed 300 ° C. Is desirable. Therefore, the boiling point is 230 ° C. or higher, but does not exceed 400 ° C., preferably 230 ° C. or higher, but is derived from an aliphatic monocarboxylic acid (R—COOH) whose range does not exceed 300 ° C. It is desirable to employ a copper salt of an aliphatic monocarboxylic acid ((R—COO) ₂ Cu (II)).

  For example, among aliphatic monocarboxylic acids having 10 to 20 carbon atoms, decanoic acid having 10 carbon atoms (boiling point: 268.4 ° C.), undecanoic acid having 11 carbon atoms (boiling point: 284 ° C.), lauric acid having 12 carbon atoms (Dodecanoic acid, boiling point: 298.9 ° C.) and the like, corresponding to those having a boiling point of 300 ° C. or lower. Among aliphatic monocarboxylic acids having 10 to 20 carbon atoms, the boiling point is 230 ° C. or higher, but those not exceeding 400 ° C. include oleic acid (boiling point: 286 ° C./100 mmHg), elaidic acid ( Boiling point: 234 ° C./15 mmHg) can be suitably used.

Specifically, as a copper salt of aliphatic monocarboxylic acid ((R—COO) ₂ Cu (II)), for example, oleic acid copper (boiling point: 286 ° C./100 mmHg), elaidic acid ( Boiling point: 234 ° C./15 mmHg), a linear aliphatic monocarboxylic acid (R −) in which the boiling point of the carboxylic acid, such as copper elaidate, is 230 ° C. or more but not exceeding 400 ° C. It is desirable to employ an aliphatic monocarboxylic acid copper salt ((R—COO) ₂ Cu (II)) derived from (COOH).

  In the conductive copper paste according to the second aspect of the present invention, the copper nanoparticle having an average particle diameter selected in the range of 10 nm to 100 nm has a coating molecular layer made of dialkylaminoalkylamine formed on the surface thereof. In this state, it is dispersed in the above-mentioned third organic solvent. When stored at room temperature, the dialkylaminoalkylamine is dissolved in the above-mentioned third organic solvent in order to prevent dissociation of the coating agent molecular layer composed of dialkylaminoalkylamine.

That is, the dialkylaminoalkylamine is coordinated to the metallic copper atom exposed on the surface of the copper nanoparticle by utilizing a lone pair of the amino group (—NH ₂ ). . Specifically, a dispersion liquid obtained by dispersing the copper nanoparticles in dialkylaminoalkylamine is once prepared, and the amine dispersion liquid of the copper nanoparticles is mixed in a third organic solvent.

The copper nanoparticle amine dispersion is a ratio of the total volume of copper nanoparticles (V _{Cu-nano-particle} ) to the volume of the solvent dialkylaminoalkylamine (V _{dispersion-medium} ), (V _{Cu-nano -particle} ): V _amine is selected in the range of _{10:50 to} 10: 100, preferably in the range of _{10:50 to 10:80} .

Even in the conductive copper paste according to the second embodiment of the present invention, the dialkylaminoalkylamine is a lone electron of its amino group (—NH ₂ ) with respect to the metal copper atom exposed on the surface of the copper powder or fine copper powder. The pair is used for coordinate binding (adsorption).

On the other hand, when heat treatment is performed in a reducing atmosphere containing hydrogen gas (H ₂ ), the reduction of the surface oxide film on the surface of the copper powder and fine copper powder proceeds, and the generated metal copper atoms (dialkylamino) ) As a result of the coordination (adsorption) of the alkylamine, the amount of (dialkylamino) alkylamine dissolved in the liquid phase is reduced.

  In addition, an organic solvent having an alcoholic hydroxyl group of the third organic solvent, for example, when the boiling point of (dialkylamino) alkylamine is lower than the boiling point of the aliphatic polyhydric alcohol of the fourth organic solvent, Because the transpiration rate of (dialkylamino) alkylamine is excellent. The concentration of (dialkylamino) alkylamine dissolved in the liquid phase decreases.

  (Dialkylamino) alkylamine, which is coordinated (adsorbed) to metal copper atoms exposed on the surface of copper powder and fine copper powder, and (dialkylamino) alkylamine dissolved in the liquid phase Is in a dissociation equilibrium state. Therefore, when the concentration of (dialkylamino) alkylamine dissolved in the liquid phase falls below a certain level, a coordinated bond (adsorption) is formed on the copper metal atoms exposed on the surfaces of the copper powder and fine copper powder. The dissociation of (dialkylamino) alkylamine proceeds.

  Also, in the coating agent molecular layer on the surface of the copper nanoparticles, the (dialkylamino) alkylamine coordinated to the metal copper atom and the (dialkylamino) alkylamine dissolved in the liquid phase are in a dissociation equilibrium. It is in a state. Therefore, when the concentration of (dialkylamino) alkylamine dissolved in the liquid phase is below a certain level, dissociation of (dialkylamino) alkylamine coordinated to the metal copper atom proceeds.

  For example, when copper nanoparticles with a substantial part of the coating molecular layer are separated from the copper metal exposed on the surface of the copper powder or fine copper powder, a metal bond is formed between the metal copper atoms. And stick. That is, with copper metal exposed on the surface of copper powder and fine copper powder as a nucleus, copper nanoparticles are fixed, and then (dialkylamino) alkylamine is further detached from the surface of the fixed copper nanoparticles. The copper nanoparticles are further fixed. Therefore, an integrated layer (aggregate) composed of a plurality of copper nanoparticles is formed using metal copper atoms exposed on the surfaces of copper powder and fine copper powder as nuclei.

  The above phenomenon is significantly promoted as the dispersion density of the copper nanoparticles dispersed in the liquid phase increases. In other words, the transpiration of the (dialkylamino) alkylamine constituting the liquid phase and the organic solvent having an alcoholic hydroxyl group of the third organic solvent, for example, the aliphatic polyhydric alcohol of the fourth organic solvent As the process proceeds, the above phenomenon is significantly promoted.

  As transpiration progresses and the volume of the liquid phase decreases (concentration progresses), the liquid phase is in contact with the fine copper powder, the narrow gap around the contact area of the copper powder, the contact between the underlayer and the fine copper powder, copper powder. The liquid phase is agglomerated in a narrow gap around the site. Therefore, as the liquid phase is concentrated, the dispersion concentration of the copper nanoparticles increases, and as a result, the narrow gap around the contact area between the fine copper powder and the copper powder, the contact area between the underlayer and the fine copper powder, and the copper powder. Formation of an accumulation layer (aggregate) of copper nanoparticles preferentially proceeds in a narrow gap around the.

  Therefore, the narrow gap around the contact area between the fine copper powder and the copper powder, the narrow gap around the contact area between the underlayer and the fine copper powder, and the copper powder are filled with the accumulation layer (aggregate) of the copper nanoparticles. It will be in the state. After that, when firing proceeds, the fine copper powder, around the contact area between the copper powder, around the base layer and the fine copper powder, around the contact area between the copper powder, Integration with copper powder and copper powder proceeds. As a result, the contact area is increased in the contact area between the fine copper powder, the contact area between the copper powders, and the contact area between the ground layer and the fine copper powder and the copper powder.

  In addition, when a silanol structure (Si—OH) is present on the surface of the underlayer, the copper atoms (Cu) on the surface of the copper nanoparticles are applied to the silanol structure (Si—OH) portion during the heat treatment. Then, it is fixed in the shape of Si—O—Cu. The formation of an aggregate (integrated layer) of copper nanoparticles also proceeds with the copper nanoparticles immobilized in the form of Si—O—Cu on the surface of the underlayer as a nucleus. When a silanol structure (Si-OH) is present at a high density on the surface of the underlayer, when the immobilized copper nanoparticles come into contact with each other and are integrated by surface diffusion, growth of a metallic copper coating layer covering the surface Is made. This phenomenon is caused by transpiration of (dialkylamino) alkylamine constituting the liquid phase and an organic solvent having an alcoholic hydroxyl group of the third organic solvent, for example, an aliphatic polyhydric alcohol of the fourth organic solvent. It will be possible for the first time at the stage when That is, the above phenomenon preferentially proceeds in a narrow gap around the contact portion between the underlayer and the fine copper powder or copper powder.

  Of course, the metal copper film layer covering the surface of the underlayer exhibits excellent adhesion. In particular, at the part where the copper powder contacts the surface of the underlayer, an aggregate (aggregation layer) of copper nanoparticles is also partially formed on the surface of the copper powder, and even between the aggregates of both copper nanoparticles As the integration proceeds, bonds between metal atoms are formed. In addition to this contribution, high adhesion characteristics due to the interposition of the metal copper film layer are imparted between the surface of the base layer having a silanol structure (Si—OH) and the copper powder.

Considering this mechanism, the ratio of the total volume of copper nanoparticles (V _{Cu-nano-particle} ) to the total volume of copper powder and fine copper powder (V _Cu-powder + V _{Cu-fine-powder} ), (V _Cu-powder + V _{Cu-fine-powder} ) :( V _{Cu-nano-particle} ) is in the range of 100: 3 to 100: 15, preferably in the range of 100: 3 to 100: 8, more preferably 100: A range of 3 to 100: 5 is desirable. In other words, the ratio of the total number of copper atoms contained in copper nanoparticles (M _{Cu-nano-particle} ) to the sum of metal copper atoms in copper powder and fine copper powder (M _Cu-powder + M _{Cu-fine-powder} ) , (M _Cu-powder + M _{Cu-fine-powder} ) :( M _{Cu-nano-particle} ) is in the range of 100: 3 to 100: 15, preferably in the range of 100: 3 to 100: 8, more preferably , 100: 3 to 100: 5 is desirable. That is, the total weight of copper atoms (W _{Cu-nano-particle} ) in the copper nanoparticles relative to the total weight of copper and fine copper powder (W _Cu-powder + W _{Cu-fine-powder} ) The ratio (W _Cu-powder + W _{Cu-fine-powder} ) :( W _{Cu-nano-particle} ) is in the range of 100 parts by mass: 3 parts by mass to 100 parts by mass: 15 parts by mass, preferably 100 parts by mass: It is desirable to set it as the range of 3 mass parts-100 mass parts: 8 mass parts, More preferably, it is the range of 100 mass parts: 3 mass parts-100 mass parts: 5 mass parts.

On the other hand, (dialkylamino) alkylamine used for the preparation of copper nanoparticle amine dispersion is an organic solvent having an alcoholic hydroxyl group of a third organic solvent, for example, an aliphatic polyvalent of a fourth organic solvent. Similar to alcohol, it is necessary to evaporate when heat treatment is performed in a reducing atmosphere containing hydrogen gas (H ₂ ). Therefore, it is preferable to use a (dialkylamino) alkylamine that is liquid at room temperature and has a boiling point of 230 ° C. or higher but does not exceed 300 ° C. More preferably, it is desirable to use (dialkylamino) alkylamine which is liquid at room temperature and has a boiling point of 230 ° C. or higher but not exceeding 280 ° C.

  Furthermore, the boiling point of the (dialkylamino) alkylamine is lower than the boiling point of the organic solvent having an alcoholic hydroxyl group of the third organic solvent, for example, the aliphatic polyhydric alcohol of the fourth organic solvent. In addition, it is desirable to select a combination of an organic solvent having an alcoholic hydroxyl group as the third organic solvent, for example, an aliphatic polyhydric alcohol as the fourth organic solvent and a (dialkylamino) alkylamine. More preferably, the boiling point of the (dialkylamino) alkylamine is lower than the boiling point of the organic solvent having an alcoholic hydroxyl group of the third organic solvent, for example, the aliphatic polyhydric alcohol of the fourth organic solvent. The organic solvent having an alcoholic hydroxyl group of the third organic solvent, for example, the aliphatic polyhydric alcohol of the fourth organic solvent, so that the difference is at least within 30 ° C., preferably within 20 ° C. And a combination of (dialkylamino) alkylamines.

In addition, in the organic solvent having an alcoholic hydroxyl group of the third organic solvent, for example, the aliphatic polyhydric alcohol of the fourth organic solvent, the (dialkylamino) alkylamine is derived from the aliphatic monocarboxylic acid copper when coordinated to the metal of copper atoms, by using the lone pairs of the amino (-NH _2), can be formed a coordinative bond, in particular, its amino group (-NH ₂₎ A dialkylamino group (—NR ′ ₂ ) can be used to function as a bidentate ligand, but it is desirable.

In the conductive copper paste according to the second aspect of the present invention, (dialkylamino) alkylamine (R ′ ₂ N—C _m H _2m —NH ₂ ) used for dispersion of copper nanoparticles is liquid at room temperature. It is preferable to use a (dialkylamino) alkylamine having a total carbon number of 9 to 13. In particular, using the amino group (—NH ₂ ) and the dialkylamino group (—NR ′ ₂ ), the (dialkylamino) propylamine (R ' ₂ N—CH ₂ CH ₂ CH ₂ —NH ₂ ), for example, dibutylaminopropylamine (melting point: −50 ° C., boiling point: 238 ° C.) can be suitably used.

  As a combination of an organic solvent having an alcoholic hydroxyl group as a third organic solvent, for example, an aliphatic polyhydric alcohol as a fourth organic solvent and a (dialkylamino) alkylamine, 2-ethyl-1,3-hexanediol (Melting point: −40 ° C., boiling point: 245 ° C.) and dibutylaminopropylamine (melting point: −50 ° C., boiling point: 238 ° C.) or dipropylene glycol (melting point: −40 ° C., boiling point: 232 ° C.) and dibutylamino A combination of propylamine and the like can be suitably selected.

  In addition, in the conductive copper paste according to the first aspect of the present invention, in addition to the copper salt of the aliphatic monocarboxylic acid, it is also possible to make a conductive copper paste to which the following sintering aid is added. It is.

That is, when the reduction is performed by performing a heat treatment in a reducing atmosphere containing hydrogen gas (H ₂ ) in the presence of an organic solvent having an alcoholic hydroxyl group as the first organic solvent, for example, an aliphatic polyhydric alcohol. A sintering aid can be further added to a metal carboxylate or metal carboxylate complex that can form a metal atom and become a metal cation species other than copper and a carboxylate anion species.

In one aspect of the conductive copper paste in which the sintering aid is further added in addition to the copper salt of the aliphatic monocarboxylic acid,
In the carboxylic acid metal salt or metal carboxylic acid complex, which is added as a sintering aid and becomes a metal cation species other than copper and a carboxylic acid anion species,
The metal cation species other than copper is selected from the group consisting of bismuth and tin, or one or a plurality of types of metal cation species,
The carboxylic acid anion species is an anionic species of carboxylic acid selected from the group consisting of aliphatic monocarboxylic acids having 6 to 20 carbon atoms.

  By reducing the carboxylic acid metal salt or metal carboxylic acid complex, the metal atoms produced are the copper atoms produced by the reduction of the aliphatic monocarboxylic acid copper salt, and the contact sites between the fine copper powder and the copper powder. A narrow gap around the contact area between the base layer and the fine copper powder or copper powder is filled.

  By reducing the carboxylic acid metal salt or metal carboxylic acid complex, the melting point of the metal produced is 271.4 ° C. for bismuth and 232 ° C. for tin, and at least a temperature of 350 ° C. or higher is in a molten state. . Aggregates composed of these low-melting-point metal atoms generated by reducing the carboxylic acid metal salt or metal carboxylic acid complex and metal copper atoms generated by reduction of the copper salt of an aliphatic monocarboxylic acid, Alloying occurs at temperatures above the melting point of the melting point metal.

  By reducing the metal carboxylate or metal carboxylate complex, the resistivity of the metal produced is 120 μΩ · cm (20 ° C.) for bismuth and 11 μΩ · cm (20 ° C.) for tin, and the resistance of metal copper Compared with the rate of 1.673 μΩ · cm (30 ° C.), it is an order of magnitude higher value. Therefore, the alloy composed of these low melting point metals and copper has a sudden increase in resistivity as the content ratio of the low melting point metals increases. Even in a range where the content ratio of the low melting point metal is low, the resistivity of the alloy composed of the low melting point metal and copper is much higher than the resistivity of metallic copper due to the so-called alloy scattering.

  An alloy formed from an aggregate of these low melting point metal atoms generated by reducing the carboxylic acid metal salt or metal carboxylic acid complex and metal copper atoms formed by reduction of the copper salt of an aliphatic monocarboxylic acid is In order to fill a narrow gap around the contact area between the fine copper powder and the copper powder, the content ratio of the low melting point metal is increased and the contact area at the contact area between the fine copper powder and the copper powder is increased. On the other hand, as the content ratio of the low melting point metal increases, the resistivity of the formed alloy itself increases rapidly from the resistivity of metallic copper. The effect of the “increase in resistivity caused by alloying” becomes more prominent as the resistivity of the low melting point metal is higher.

  Accordingly, when the content ratio of the low melting point metal exceeds a certain level, the effect of “expansion of contact area” is offset by the effect of “increase in resistivity caused by alloying”.

In other words, it is generated by reducing the volume sum V _{low-mp-metal of} these low melting point metal atoms and the copper salt of an aliphatic monocarboxylic acid, which are generated by reducing the carboxylic acid metal salt or metal carboxylic acid complex. The ratio of the volume total V _Cu-metal of metal copper atoms, V _low-mp-metal : V _Cu-metal needs to be selected in a range not exceeding a certain level according to the type of low melting point metal. Typically, the ratio, V _low-mp-metal : V _Cu-metal, is selected at least in a range not exceeding 4: 1, usually not exceeding 2: 1, preferably not exceeding 1: 1. It is desirable to do.

In the conductive copper paste according to the first aspect of the present invention, the total number of metal atoms of the metal cation species contained in the carboxylic acid metal salt or metal carboxylic acid complex is the surface area of the copper powder and the fine copper powder. against the sum of the surface area, 100 [mu] mol / m ² or less, preferably in the range of from, 80μmol / m ² or less, more preferably in the range, 50 [mu] mol / m ² or less of the range, particularly preferably, 30 [mu] mol / m ² or less of It is desirable to select a range.

Furthermore, in another aspect of the conductive copper paste to which the sintering aid is further added,
In the carboxylic acid metal salt or metal carboxylic acid complex, which is added as a sintering aid and becomes a metal cation species other than copper and a carboxylic acid anion species,
The metal cation species other than copper is a mixed metal cation species formed by mixing a cation species of the first metal group and a cation species of the second metal group,
The cation species of the first metal group is selected from the group consisting of bismuth and tin, or one or more metal cation species,
The cation species of the second metal group is selected from the group consisting of zinc, aluminum, indium, silver, cobalt, titanium, nickel, manganese, or a cation species of one or more metals.
In the mixed metal cation species, the total number of metal atoms of the cation species of the second metal group is selected within a range of less than 10% with respect to the total number of metal atoms of the cation species of the first metal group. And
The carboxylic acid anion species is an anionic species of carboxylic acid selected from the group consisting of aliphatic monocarboxylic acids having 6 to 20 carbon atoms.

  By reducing the carboxylic acid metal salt or metal carboxylic acid complex, the metal atom of the first metal group and the metal atom of the second metal group are produced by reduction of a copper salt of an aliphatic monocarboxylic acid. Along with the copper atoms, the fine copper powder, a narrow gap around the contact area between the copper powder, and a narrow gap around the contact area between the underlayer and the fine copper powder, the copper powder are filled.

  By reducing the metal carboxylate or metal carboxylate complex, the melting point of the metal of the first metal group produced is 271.4 ° C. for bismuth and 232 ° C. for tin, and at least at a temperature of 350 ° C. or higher. It will be in a molten state. In addition, the melting point of the metal of the second metal group to be generated is 419.5 ° C. for zinc, 660.36 ° C. for aluminum, 156.6 ° C. for indium, 961 ° C. for silver, 1495 ° C. for cobalt, 1667 ° C. for titanium, Nickel is 1456 ° C and manganese is 1244 ° C.

  Metal formed by reducing the metal atom of the first metal group, the metal atom of the second metal group, and the copper salt of an aliphatic monocarboxylic acid, which is generated by reducing the metal carboxylate or metal carboxylate complex Aggregates composed of copper atoms cause alloying at a temperature exceeding the melting point of the metal of the first metal group. The metals of the first metal group are all low melting point metals, and the metal of the first metal group melts to promote alloying of the aggregates.

  In general, the alloying process becomes difficult as the content of the refractory metal increases.

  The metals of the second metal group have a melting point of 400 ° C. or higher except for indium. When alloying from an aggregate composed of metal atoms of the first metal group, metal atoms of the second metal group, and copper nanoparticles, the total number of metal atoms of the cation species of the second metal group is By keeping the total number of metal atoms of the cation species of the first metal group within less than 10%, it is guaranteed that alloying proceeds in the range of 300 ° C to 400 ° C.

  By reducing the carboxylic acid metal salt or metal carboxylic acid complex, the resistivity of the metal of the first metal group produced is 120 μΩ · cm (20 ° C.) for bismuth and 11 μΩ · cm (20 ° C.) for tin. Compared with the resistivity of metallic copper, 1.673 μΩ · cm (30 ° C.), it is an order of magnitude higher value. Moreover, the resistivity of the metal of the 2nd metal group to produce | generate is 5.8 microhm * cm (20 degreeC) for zinc, 2.655 microohm * cm (20 degreeC) for aluminum, and 8.37 microohm * cm (20 degreeC) for indium. Silver is 1.59 μΩ · cm (20 ° C.), cobalt is 6.24 μΩ · cm (20 ° C.), titanium is 42.0 μΩ · cm (20 ° C.), nickel is 6.84 μΩ · cm (20 ° C.), manganese Is 185 μΩ · cm (20 ° C.). Except for silver, the resistivity of the metal of the second metal group is also higher than the resistivity of metallic copper, 1.673 μΩ · cm (30 ° C.).

  Accordingly, the alloy of the metal of the first metal group, the metal of the metal of the second metal group and copper increases in resistivity as the content ratio of the metal of the first metal group increases. Further, even in a range where the metal content ratio of the first metal group is low, the resistivity of the alloy of the metal of the first metal group, the metal of the second metal group and copper due to the influence of so-called alloy scattering, The resistivity is much higher than that of metallic copper.

  Metal formed by reducing the metal atom of the first metal group, the metal atom of the second metal group, and the copper salt of an aliphatic monocarboxylic acid, which is generated by reducing the metal carboxylate or metal carboxylate complex The alloy formed from the aggregate of copper atoms fills a narrow gap around the contact area between the fine copper powder and the copper powder, so that the content ratio of the metal of the first metal group and the metal of the second metal group is As it increases, the contact area at the contact site between the fine copper powder and the copper powder is increased. On the other hand, as the metal content ratio of the first metal group increases, the resistivity of the formed alloy itself rapidly increases from the resistivity of metallic copper. The effect of this “increase in resistivity caused by alloying” becomes more prominent as the resistivity of the metal of the first metal group is higher.

  Therefore, when the metal content ratio of the first metal group exceeds a certain level, the effect of “expansion of contact area” is offset by the effect of “increased resistivity caused by alloying”.

In other words, the total volume V _low-mp-metal of the metal atoms of the first metal group which is a low melting point metal produced by reducing the carboxylic acid metal salt or metal carboxylic acid complex, and an aliphatic monocarboxylic acid The total volume of copper atoms generated by the reduction of the copper salt V _Cu-metal ratio, V _low-mp-metal : V _Cu-metal , depending on the type of metal in the first metal group (low melting point metal) Therefore, it is necessary to select a range that does not exceed a certain level. Typically, the ratio, V _low-mp-metal : V _Cu-metal, is selected at least in a range not exceeding 4: 1, usually not exceeding 2: 1, preferably not exceeding 1: 1. It is desirable to do.

In the conductive copper paste according to the first aspect of the present invention, the cation species of the first metal group and the cation species of the second metal group contained in the carboxylic acid metal salt or metal carboxylic acid complex are mixed. The total number of metal atoms of the mixed metal cation species is 100 μmol / m ² or less, preferably 80 μmol / m ² or less, based on the sum of the surface area of the copper powder and the surface area of the fine copper powder. more preferably, 50 [mu] mol / m ² or less of the range, particularly preferably, it is desirable to select the range of 30 [mu] mol / m ² or less.

  In addition, in the conductive copper paste according to the second embodiment of the present invention, in addition to the copper nanoparticles, the conductive copper paste further includes a copper salt of an aliphatic monocarboxylic acid and the following sintering aid. It is also possible.

That is, the copper salt of the aliphatic monocarboxylic acid used in the first aspect of the present invention and an organic solvent having an alcoholic hydroxyl group as a third organic solvent as a sintering aid, for example, the fourth Metal cation species other than copper and carboxylic acids that can generate metal atoms when reduced by heat treatment in a reducing atmosphere containing hydrogen gas (H ₂ ) in the presence of an aliphatic polyhydric alcohol as an organic solvent Carboxylic acid metal salts or metal carboxylic acid complexes that become anionic species can be further added.

In one embodiment of the conductive copper paste in which the sintering aid is further added in addition to the aliphatic monocarboxylic acid copper salt,
In the carboxylic acid metal salt or metal carboxylic acid complex, which is added as a sintering aid and becomes a metal cation species other than copper and a carboxylic acid anion species,
The metal cation species other than copper is selected from the group consisting of bismuth and tin, or one or a plurality of types of metal cation species,
The carboxylic acid anion species is an anionic species of carboxylic acid selected from the group consisting of aliphatic monocarboxylic acids having 6 to 20 carbon atoms.

  By reducing the carboxylic acid metal salt or metal carboxylic acid complex, the metal atom produced is a fine copper atom together with the metal copper atom produced by reducing the copper salt of the aliphatic monocarboxylic acid, and the copper nanoparticles. Narrow gaps around the contact area between the powder and copper powder, and a narrow gap around the contact area between the ground layer and the fine copper powder and copper powder are filled.

  By reducing the carboxylic acid metal salt or metal carboxylic acid complex, the melting point of the metal produced is 271.4 ° C. for bismuth and 232 ° C. for tin, and at least a temperature of 350 ° C. or higher is in a molten state. . Aggregates composed of these low-melting-point metal atoms generated by reducing the carboxylic acid metal salt or metal carboxylic acid complex, and metal copper atoms generated by reducing the copper salt of an aliphatic monocarboxylic acid Causes alloying at temperatures above the melting point of the low melting point metal. Along with the agglomerates of the low-melting metal atoms and metal copper atoms and the copper nanoparticles, a narrow gap around the contact area between the fine copper powder and the copper powder, the contact area between the underlayer and the fine copper powder, and the copper powder. It is filled in a narrow gap around.

  By reducing the metal carboxylate or metal carboxylate complex, the resistivity of the metal produced is 120 μΩ · cm (20 ° C.) for bismuth and 11 μΩ · cm (20 ° C.) for tin, and the resistance of metal copper Compared with the rate of 1.673 μΩ · cm (30 ° C.), it is an order of magnitude higher value. Therefore, in the alloy composed of these low melting point metal atoms and metallic copper atoms, the resistivity rapidly increases as the content ratio of the low melting point metal increases. Even in a range where the content ratio of the low melting point metal is low, the resistivity of the alloy composed of the low melting point metal and copper is much higher than the resistivity of metallic copper due to the so-called alloy scattering.

  From an aggregate composed of these low melting point metal atoms generated by reducing the metal carboxylate or metal carboxylate complex and metal copper atoms generated by reducing the copper salt of an aliphatic monocarboxylic acid The formed alloy fills a narrow gap around the contact area between the fine copper powder and the copper powder, so the content ratio of the low melting point metal increases and the contact area at the contact area between the fine copper powder and the copper powder increases. Enlargement is made. On the other hand, as the content ratio of the low melting point metal increases, the resistivity of the formed alloy itself increases rapidly from the resistivity of metallic copper. The effect of the “increase in resistivity caused by alloying” becomes more prominent as the resistivity of the low melting point metal is higher.

  Accordingly, when the content ratio of the low melting point metal exceeds a certain level, the effect of “expansion of contact area” is offset by the effect of “increase in resistivity caused by alloying”.

In other words, the metal produced by the reduction of the total volume V _{low-mp-metal of} low melting point metal atoms and the copper salt of an aliphatic monocarboxylic acid produced by reducing the carboxylic acid metal salt or metal carboxylic acid complex. The ratio of the total volume of copper atoms V _Cu-metal , V _low-mp-metal : V _Cu-metal needs to be selected in a range not exceeding a certain level according to the type of low melting point metal. Usually, the ratio, V _low-mp-metal : V _Cu-metal is selected in a range not exceeding 4: 1, preferably not exceeding 2: 1, more preferably not exceeding 1: 1. It is desirable to do.

In the conductive copper paste according to the second aspect of the present invention, the total number of metal atoms of the metal cation species contained in the carboxylic acid metal salt or metal carboxylic acid complex is the surface area of the copper powder and the fine copper powder. against the sum of the surface area, 100 [mu] mol / m ² or less, preferably in the range of from, 80μmol / m ² or less, more preferably in the range, 50 [mu] mol / m ² or less of the range, particularly preferably, 30 [mu] mol / m ² or less of It is desirable to select a range.

In addition, in another aspect of the conductive copper paste in which the copper salt of an aliphatic monocarboxylic acid and the sintering aid are further added,
In the carboxylic acid metal salt or metal carboxylic acid complex, which is added as the sintering aid and becomes a metal cation species other than copper and a carboxylic acid anion species,
The metal cation species other than copper is a mixed metal cation species formed by mixing a cation species of the first metal group and a cation species of the second metal group,
The cation species of the first metal group is selected from the group consisting of bismuth and tin, or one or more metal cation species,
The cation species of the second metal group is selected from the group consisting of zinc, aluminum, indium, silver, cobalt, titanium, nickel, manganese, or a cation species of one or more metals.
In the mixed metal cation species, the total number of metal atoms of the cation species of the second metal group is selected within a range of less than 10% with respect to the total number of metal atoms of the cation species of the first metal group. And
The carboxylic acid anion species is an anionic species of carboxylic acid selected from the group consisting of aliphatic monocarboxylic acids having 6 to 20 carbon atoms.

  By reducing the carboxylic acid metal salt or metal carboxylic acid complex, the metal atom of the first metal group and the metal atom of the second metal group are produced by reduction of a copper salt of an aliphatic monocarboxylic acid. Along with copper atoms and copper nanoparticles, the fine copper powder, a narrow gap around the contact area between the copper powder, and a narrow gap around the contact area between the underlayer and the fine copper powder, the copper powder are filled.

  By reducing the metal carboxylate or metal carboxylate complex, the melting point of the metal of the first metal group produced is 271.4 ° C. for bismuth and 232 ° C. for tin, and at least at a temperature of 350 ° C. or higher. It will be in a molten state. In addition, the melting point of the metal of the second metal group to be generated is 419.5 ° C. for zinc, 660.36 ° C. for aluminum, 156.6 ° C. for indium, 961 ° C. for silver, 1495 ° C. for cobalt, 1667 ° C. for titanium, Nickel is 1456 ° C and manganese is 1244 ° C.

  The aggregate composed of the metal atom of the first metal group, the metal atom of the second metal group, and the copper nanoparticles produced by reducing the metal carboxylate or metal carboxylate complex, Alloying occurs at temperatures above the melting point of a single metal group. The metals of the first metal group are all low melting point metals, and the metal of the first metal group melts to promote alloying of the aggregates.

  In general, the alloying process becomes difficult as the content of the refractory metal increases.

  The metals of the second metal group have a melting point of 400 ° C. or higher except for indium. When alloying from an aggregate composed of a metal atom of the first metal group, a metal atom of the second metal group, and a metal copper atom formed by reduction of a copper salt of an aliphatic monocarboxylic acid, By keeping the sum of the number of metal atoms of the cation species of the metal group within a range of less than 10% with respect to the sum of the number of metal atoms of the cation species of the first metal group, It is guaranteed that alloying will proceed.

  By reducing the carboxylic acid metal salt or metal carboxylic acid complex, the resistivity of the metal of the first metal group produced is 120 μΩ · cm (20 ° C.) for bismuth and 11 μΩ · cm (20 ° C.) for tin. Compared with the resistivity of metallic copper, 1.673 μΩ · cm (30 ° C.), it is an order of magnitude higher value. Moreover, the resistivity of the metal of the 2nd metal group to produce | generate is 5.8 microhm * cm (20 degreeC) for zinc, 2.655 microohm * cm (20 degreeC) for aluminum, and 8.37 microohm * cm (20 degreeC) for indium. Silver is 1.59 μΩ · cm (20 ° C.), cobalt is 6.24 μΩ · cm (20 ° C.), titanium is 42.0 μΩ · cm (20 ° C.), nickel is 6.84 μΩ · cm (20 ° C.), manganese Is 185 μΩ · cm (20 ° C.). Except for silver, the resistivity of the metal of the second metal group is also higher than the resistivity of metallic copper, 1.673 μΩ · cm (30 ° C.).

  Therefore, the alloy of the metal of the first metal group, the metal of the second metal group and copper has a resistivity rapidly as the content ratio of the metal of the first metal group and the metal of the second metal group increases. To rise. In addition, even in a range where the content ratio of the metal of the first metal group and the metal of the second metal group is low, the so-called alloy scattering affects the metal of the first metal group, the metal of the second metal group, and copper. The resistivity of the resulting alloy is much higher than that of metallic copper.

  Metal formed by reducing the metal atom of the first metal group, the metal atom of the second metal group, and the copper salt of an aliphatic monocarboxylic acid, which is generated by reducing the metal carboxylate or metal carboxylate complex The alloy formed from the aggregate composed of copper atoms fills a narrow gap around the contact area between the fine copper powder and the copper powder, so that the metal of the first metal group and the metal of the second metal group As the content ratio increases, the contact area at the contact portion between the fine copper powder and the copper powder is increased. On the other hand, as the content ratio of the metal of the first metal group and the metal of the second metal group increases, the resistivity of the formed alloy itself increases rapidly from the resistivity of metallic copper. The effect of the “increase in resistivity caused by alloying” becomes more prominent as the resistivity of the metal of the first metal group and the metal of the second metal group is higher.

  Therefore, when the content ratio of the metal of the first metal group and the metal of the second metal group exceeds a certain level, the effect of “expansion of contact area” is influenced by the effect of “increase in resistivity due to alloying”. cancel.

In other words, the total volume V _low-mp-metal of the metal atoms of the first metal group, which is a low melting point metal, which is generated by reducing the carboxylic acid metal salt or metal carboxylic acid complex, and the second metal group The ratio of the total volume V of the metal atoms V _{second-metal to} the total volume V _Cu-metal of the copper metal atoms generated by the reduction of the copper salt of the aliphatic monocarboxylic acid, (V _low-mp-metal + V _second-metal ): V _Cu-metal needs to be selected in a range not exceeding a certain level according to the type of metal (low melting point metal) of the first metal group and the type of metal of the second metal group.

The sum of the number of metal atoms of the cation species of the second metal group is kept within a range of less than 10% with respect to the sum of the number of metal atoms of the cation species of the first metal group. V _low-mp-metal + V _second-metal ): In place of the conditions for V _Cu-metal , the total volume V _{low-mp-metal of} the first metal group which is a low melting point _metal and an aliphatic monocarboxylic Volume ratio of copper metal atoms generated by reduction of copper salt of acid V _Cu-metal ratio, V _low-mp-metal : V _Cu-metal is the first metal group metal (low melting point metal) Accordingly, it is possible to adopt a condition of selecting a range that does not exceed a certain level. Usually, the ratio, V _low-mp-metal : V _Cu-metal is selected in a range not exceeding 4: 1, preferably not exceeding 2: 1, more preferably not exceeding 1: 1. It is desirable to do. Therefore, (V _low-mp-metal + V _second-metal ): V _Cu-metal also does not exceed 4: 1, preferably does not exceed 2: 1, more preferably does not exceed 1: 1. It is desirable to select a range.

In the conductive copper paste according to the second aspect of the present invention, the cation species of the first metal group and the cation species of the second metal group contained in the carboxylic acid metal salt or metal carboxylic acid complex are mixed. The total number of metal atoms of the mixed metal cation species is 100 μmol / m ² or less, preferably 80 μmol / m ² or less, based on the sum of the surface area of the copper powder and the surface area of the fine copper powder. more preferably, 50 [mu] mol / m ² or less of the range, particularly preferably, it is desirable to select the range of 30 [mu] mol / m ² or less.

  In addition, in any of the conductive copper paste according to the first aspect of the present invention and the conductive copper paste according to the second aspect of the present invention, a metal cation species other than copper, which is added as the sintering aid, The carboxylic acid metal salt or metal carboxylic acid complex, which becomes the carboxylic acid anion species, is used as the first organic solvent or the third organic solvent, and is an organic solvent having the above-mentioned alcoholic hydroxyl group, for example, an aliphatic polyvalent group. In a monohydric alcohol, it is dissolved in the form of an amine complex of the carboxylic acid metal salt or metal carboxylic acid complex.

Specifically, (dialkylamino) alkylamine (R ′ ₂ N—C _m H _2m —NH ₂ ) is contained in the liquid phase of the conductive copper paste. Carboxylic acid metal salts or metal carboxylic acid complexes, such as divalent metal cation species (M ²⁺ ) and carboxylic acid anions (R ″ -COO ⁻ ), which become metal cation species other than copper and carboxylate anion species Coordination of (dialkylamino) alkylamine as a monodentate ligand to the metal cation species (M ²⁺ ) in (R ″ —COO ⁻ ) ₂ (M ²⁺ ) comprising ((R "-COO) ₂ M (II)): 2 (R ' ₂ NC _m H _2m -NH ₂ )) is thus formed, which becomes a metal cation species other than copper and a carboxylate anion species. The carboxylic acid metal salt or metal carboxylic acid complex is an amine complex, for example, in the form of ((R "-COO) ₂ M (II)): 2 (R ' ₂ NC _m H _2m -NH ₂ )) Used as a third organic solvent, an organic solvent having an alcoholic hydroxyl group, for example, an aliphatic polyhydric alcohol. It is.

An amine complex of a carboxylic acid metal salt or metal carboxylic acid complex, which becomes a metal cation species other than copper and a carboxylic acid anion species, for example, ((R "-COO) ₂ M (II)): 2 (R ' ₂ NC The amine complex in the form of _m H _2m -NH ₂ ) is an amine complex of a copper salt of an aliphatic monocarboxylic acid ((R-COO) ₂ Cu (II)): 2 (R ' ₂ NC _m H _2m It is reduced by the same reaction mechanism as that for —NH ₂ )).

Also, amine complexes of carboxylic acid metal salts or metal carboxylic acid complexes, for example, amine complexes in the form of ((R "-COO) ₂ M (II)): 2 (R ' ₂ NC _m H _2m -NH ₂ )) The metal atom M (0) produced by the reduction of is initially in the form of coordination of two molecules of (dialkylamino) alkylamine.When (dialkylamino) alkylamine functions as a bidentate ligand, , Disperse in a dispersion solvent as a metal atom (M (0): 2 (R ′ ₂ NC _m H _2m —NH ₂ )) coordinated by two (dialkylamino) alkylamine molecules of the bidentate ligand be able to.

Carboxylic acid derived from carboxylate anion (R ″ -COO ⁻ ) (R ″ -COO ⁻ ) with reduction of carboxylate metal salt or amine complex of metal carboxylate complex which becomes metal cation species other than copper and carboxylate anion species -COOH) is by-produced.

  The carboxylic acid anion species is an anionic species of carboxylic acid selected from the group consisting of aliphatic monocarboxylic acids having 6 to 20 carbon atoms (R ″ —COOH).

In this case, a carboxylic acid metal salt that becomes a carboxylic acid anion (R ″ —COO ⁻ ) derived from the aliphatic monocarboxylic acid (R ″ —COOH) having 6 to 20 carbon atoms and a metal cation species other than copper, or The metal carboxylic acid complex is a reduction containing hydrogen gas (H ₂ ) in the presence of an organic solvent having an alcoholic hydroxyl group, for example, an aliphatic polyhydric alcohol, used as a first organic solvent or a third organic solvent. When the heat treatment is performed in a neutral atmosphere, it is desirable that the reduction reaction using the organic solvent having the above-mentioned alcoholic hydroxyl group, for example, an aliphatic polyhydric alcohol, proceeds preferentially over the self-decomposing reduction reaction. . In general, the autolytic decomposition reaction of a metal salt of an aliphatic monocarboxylic acid ((R ″ —COO) ₂ M (II)) increases the carbon number of the aliphatic monocarboxylic acid anion, and the reaction initiation temperature is Therefore, in the conductive copper paste according to the first aspect of the present invention, the aliphatic monocarboxylic acid anion constituting the metal salt of aliphatic monocarboxylic acid ((R ″ —COO) ₂ M (II)). It is desirable to select an anion derived from an aliphatic monocarboxylic acid having 6 to 20 carbon atoms.

On the other hand, in the above-described mechanism, aliphatic monocarboxylic acid (R ″ —COOH) is by-produced along with the reduction of the carboxylic acid metal salt or the amine complex of the metal carboxylic acid complex. Hydrogen gas (H ₂ ) is included. It is desirable that the aliphatic monocarboxylic acid (R ″ —COOH) be evaporated during the heat treatment in a reducing atmosphere. Accordingly, the boiling point of the aliphatic monocarboxylic acid (R ″ —COOH) is 230 ° C. or higher, but does not exceed 400 ° C., preferably 230 ° C. or higher, but does not exceed 300 ° C. Accordingly, an aliphatic monocarboxylic acid (R ″ −) having a boiling point of 230 ° C. or higher but not exceeding 400 ° C., preferably 230 ° C. or higher but not exceeding 300 ° C. It is desirable to employ a metal salt of an aliphatic monocarboxylic acid ((R ″ —COO) ₂ M (II)) derived from (COOH).

  In addition, the linear alkanoic acid in the range of C7 heptanoic acid (boiling point 223.0 ° C) to C12 lauric acid (dodecanoic acid, boiling point 298.9 ° C) does not exceed 300 ° C. It can be used as an aliphatic monocarboxylic acid.

When a conductive layer such as a copper wiring layer or an electrode layer is formed on a base layer using the conductive copper paste according to the present invention, a coating film of the conductive copper paste is formed in a desired coating shape. To do. The film thickness t _drawing of the conductive copper paste coating film is selected according to the thickness t _layer of the conductor layer to be produced.

When the conductive copper paste according to the first aspect of the present invention is used, the ratio of the thickness t layer of the produced conductor _layer to the film thickness t _drawing of the coating film, t _layer / t _drawing is Depends on the total volume ratio of the copper powder and fine copper powder contained in the conductive copper paste.

  The total volume ratio of the copper powder and fine copper powder contained in the conductive copper paste according to the first embodiment of the present invention is in the range of 30% by volume to 60% by volume, preferably 40% by volume to It is desirable to be selected in the range of 55% by volume.

  Further, when forming the coating film of the conductive copper paste in a desired coating shape, for example, when a screen printing method is applied, the liquid viscosity of the conductive copper paste needs to be a viscosity suitable for the screen printing method. There is. When the screen printing method is applied, the liquid viscosity of the conductive copper paste is in the range of 2 Pa · s to 50 Pa · s (25 ° C.), more preferably in the range of 2 Pa · s to 40 Pa · s (25 ° C.). Preferably it is selected.

When using a second conductive copper paste according to the embodiment of the present invention, the ratio of the thickness t _drawing of the thickness t _layer conductor layer made coating film, t _layer / t _drawing, the conductive Depends on the total volume ratio of the copper powder, fine copper powder, and copper nanoparticles contained in the conductive copper paste.

  The total of the volume ratio of the copper powder, fine copper powder, and copper nanoparticles contained in the conductive copper paste according to the second embodiment of the present invention is in the range of 30% by volume to 70% by volume, preferably It is desirable that it is selected in the range of 30% to 55% by volume, more preferably in the range of 40% to 55% by volume.

  Further, when forming the coating film of the conductive copper paste in a desired coating shape, for example, when a screen printing method is applied, the liquid viscosity of the conductive copper paste needs to be a viscosity suitable for the screen printing method. There is. When the screen printing method is applied, the liquid viscosity of the conductive copper paste is in the range of 2 Pa · s to 50 Pa · s (25 ° C.), more preferably in the range of 2 Pa · s to 40 Pa · s (25 ° C.). Preferably it is selected.

When a conductor layer is produced on an underlayer using the conductive copper paste according to the first aspect of the present invention, the adhesion of the conductor layer to the surface of the underlayer is improved by an aliphatic monolayer. To expand the effective contact area between the underlying layer and the sintered body layer by utilizing metallic copper atoms generated by reduction of the carboxylic acid copper salt ((R—COO) ₂ Cu (II)) Has been achieved.

  When the conductive copper paste according to the first aspect of the present invention is used to produce a conductor layer on the base layer, the adhesion of the conductor layer to the surface of the base layer is improved by copper nanoparticles. This is achieved by expanding the effective contact area between the base layer and the sintered body layer by utilizing the metal copper film formed from the above.

  Therefore, the conductive copper paste according to the present invention does not contain a thermosetting resin component or glass frit.

  Since the conductive copper paste according to the present invention does not contain glass frit, it is not necessary to heat the glass frit to a temperature at which the glass frit is melted in the baking treatment.

  When a conductive layer is produced on an underlayer using the conductive copper paste according to the present invention, it is contained in a reducing atmosphere containing hydrogen gas with respect to the coating film of the conductive copper paste. , (Dialkylamino) alkylamine and the organic solvent having the above-mentioned alcoholic hydroxyl group, for example, aliphatic polyhydric alcohol transpiration, and heat treatment is performed at a temperature at which the firing of copper powder and fine copper powder proceeds. Specifically, firing can be performed by heating to a temperature of 300 ° C. to 400 ° C., preferably 350 ° C. to 400 ° C.

As the reducing atmosphere containing hydrogen gas, for example, a mixed gas containing hydrogen gas in an inert gas at a concentration of 1% to 4% can be used.

In that case, it is preferable to use the layer which has a silanol structure (Si-OH) on the surface as a base layer. The situation where the silanol structure (Si—OH) is present on the surface of the underlayer corresponds to, for example, the case where a very thin surface oxide layer is present on the surface of a glass substrate or the like or the surface of silicon.

Therefore, when the conductive copper paste according to the first embodiment of the present invention and the conductive copper paste according to the second embodiment of the present invention are used for producing a sintered body film, the conductive copper paste is used. The process of using and producing a sintered body film is as follows:
Forming a coating film of the conductive copper paste on an underlayer;
In a reducing atmosphere containing hydrogen gas, the conductive copper paste coating film is heated to a temperature of 300 ° C. or higher and 400 ° C. or lower, preferably 350 ° C. or higher and 400 ° C. or lower. A step of baking the paste. At that time, the reducing atmosphere containing the hydrogen gas contains 1 to 4% by volume of hydrogen gas in the inert gas, and depending on the heating temperature selected in the range of 300 ° C. or more and 400 ° C. or less, The heating time can be selected in the range of 5 minutes to 60 minutes. Specifically, when the heating temperature is selected to be 350 ° C. or higher and 400 ° C. or lower, the heating time can be selected in the range of 5 minutes to 20 minutes.

  As shown in the specific examples described later, the resistivity of the sintered body film to be produced is 9 times or less of the resistivity of metallic copper of 1.673 μΩ · cm (30 ° C.), specifically 15 μΩ · It is possible to make it the range below cm. That is, the resistivity of the sintered body film to be produced can be in the range of 3 to 9 times that of metallic copper, specifically in the range of 5 μΩ · cm to 15 μΩ · cm.

  Hereinafter, the present invention will be described more specifically with reference to examples. These examples are examples of the best mode according to the present invention, but the present invention is not limited by these examples.

Example 1
The conductive copper paste of Example 1 is prepared using the following raw materials.

Assuming that the average particle size is selected in the range of 2 to 10 μm, Mitsui Metals' spherical copper powder MA-C08JM (average particle size of 7 μm) is selected as the average particle size in the range of 0.2 μm to 1.0 μm. As copper powder, Mitsui Metals fine copper powder 1020Y (average particle size 0.4 μm) is used. The ratio of the average particle diameter d _{Cu-fine-powder of the fine} copper powder and the average particle diameter d _Cu-powder of the spherical copper powder (d _{Cu-fine-powder} / d _Cu-powder ) is selected to be _4/70 Has been.

As a copper salt of aliphatic monocarboxylic acid ((R—COO) ₂ Cu (II)), copper oleate ((CH ₃ (CH ₂ ) ₇ CH═CH (CH ₂ ) ₇ COO) ₂ Cu (II): Oleic acid, having a molecular weight of 626.54), previously dissolved in dibutylaminopropylamine ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ , melting point: −50 ° C., boiling point: 238 ° C.) A copper amine complex is formed. The solid copper oleate itself forms a dimer having a Cu: Cu bond. The amine complex of copper oleate formed is composed of dibutylaminopropylamine (one molecule of copper oleate ((CH ₃ (CH ₂ ) ₇ CH═CH (CH ₂ ) ₇ COO) ₂ Cu (II))). It can be presumed that (C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ) 2 molecules coordinate to the copper cation (Cu ²⁺ ). As a result, the dimer type copper oleate is converted into an amine complex of two molecules of copper oleate and is dissolved in the solvent dibutylaminopropylamine. In Example 1, 3.3 parts by mass of copper oleate is dissolved in 6.6 parts by mass of dibutylaminopropylamine, and an amine solution of an amine complex of copper oleate is prepared in advance. The composition of the amine solution of the copper oleate amine complex is selected to be 7 molecules of dibutylaminopropylamine per molecule of copper oleate.

  The aliphatic polyhydric alcohol used as the first organic solvent is 2-ethyl-1,3-hexanediol (molecular weight: 146.2, melting point: −40 ° C., boiling point: 245 ° C.).

  Mitsui Metals spherical copper powder MA-C08JM (average particle size 7 μm) 70 parts by mass, Mitsui Metals fine copper powder 1020Y (average particle size 0.4 μm) 30 parts by mass, copper oleate 3.3 parts by mass dibutylamino A solution dissolved in 6.6 parts by mass of propylamine is mixed with 3 parts by mass of 2-ethyl-1,3-hexanediol. Thereafter, the mixture is stirred with a stirring deaerator to prepare a copper paste in which the copper powder and the fine copper powder are uniformly dispersed in the liquid phase.

  Sum of the number of metallic copper atoms in the spherical copper powder and fine copper powder and the ratio of the number of copper atoms in the copper oleate, (sum of the number of metallic copper atoms in the spherical copper powder and fine copper powder): (oleic acid The number of atoms with copper in the copper) is 100: 0.335. Further, 0.013 mol of 2-ethyl-1,3-hexanediol is contained per 1 mol of metallic copper of the spherical copper powder and fine copper powder.

When the density of metallic copper is 8.95 g / cm ³ (20 ° C.) and the density of 2-ethyl-1,3-hexanediol is 0.942 g / cm ³ (25 ° C.), the volume of the spherical copper powder and fine copper powder Of the total volume (V _Cu-powder + V _{Cu-fine-powder} ) and the volume of the first organic solvent 2-ethyl-1,3-hexanediol (V _{dispersion-medium} ), (V _Cu-powder + V _{Cu -fine-powder} ): V _{dispersion-medium} is calculated as 20: 5.7.

The density of oleic acid copper ^{0.95g / cm 3 (20 ℃)} , since the density 0.826 g / cm ³ of dibutylaminopropylamine (20 ° C.), the oleic acid copper amine complex of the amine solution 10g The volume can be estimated as 11.6 cm ³ .

  Therefore, the volume ratio of the spherical copper powder to the fine copper powder in the prepared copper paste is 23% by volume.

  Moreover, when all the copper in 3.3 mass parts copper oleate is reduce | restored to a metal copper atom, the sum total of the metal copper atom originating in a copper oleate will be 0.335 mass part. Accordingly, the total volume of metallic copper atoms, spherical copper powder and fine copper powder derived from copper oleate with respect to 100 parts by volume of the prepared copper paste is 23 parts by volume.

  The liquid viscosity of the prepared copper paste was 3 Pa · s (spiral rotational viscometer 10 rpm 25 ° C.).

First, the surface of spherical copper powder and fine copper powder dispersed in the copper paste is solvated with dibutylaminopropylamine or 2-ethyl-1,3-hexanediol contained in the liquid phase. (Adsorption). Dibutylaminopropylamine is coordinated to the metallic copper exposed on the surface by utilizing the lone electron pair of the amino group (—NH ₂ ). On the other hand, a surface oxide film partially exists on the surfaces of the spherical copper powder and the fine copper powder. With respect to the copper oxide corresponding to copper oxide (CuO) constituting the surface oxide film, 2-ethyl-1,3-hexanediol uses the hydroxyl group (> CH—OH), Hydrogen-bonded intermolecular bonding is performed with oxygen atoms (Cu—O—Cu) in the copper oxide. At that time, it is presumed that the reduction of the surface oxide film proceeds via the following two elementary processes.

  When heat treatment is performed in a reducing atmosphere containing hydrogen gas, the hydroxyl group (> CH—OH) of 2-ethyl-1,3-hexanediol reacts with the copper oxide, and the following oxidation / reduction reaction Wake up.

CuO + (> CH—OH) → Cu + (> C═O) + H ₂ O ↑

The reaction product (> C═O) derived from 2-ethyl-1,3-hexanediol is a fine copper powder, a metal copper atom (Cu) exposed on the surface of the copper powder, and its oxo group (> C═O). Coordination can be performed using the π electrons of O). In a reducing atmosphere containing hydrogen gas, a hydrogen molecule (H ₂ ) is added to the oxo group (> C═O) coordinated on the metal copper atom (Cu), so that the original It is possible to convert to a hydroxyl group (> CH—OH).

(> C = O) + H ₂ → (> CH—OH)

  The 2-hydroxy-1,3-hexanediol, in which the original hydroxyl group (> CH—OH) has been regenerated, again becomes an oxygen atom (Cu—O—Cu) in the copper oxide constituting the surface oxide film. ) Can be solvated (adsorbed).

Apparently, the reduction of the surface oxide film proceeds using hydrogen molecules (H ₂ ) supplied from a reducing atmosphere containing hydrogen gas.

On the other hand, in the copper paste, an amine complex of copper oleate ((CH ₃ (CH ₂ ) ₇ CH═CH (CH ₂ ) ₇ COO) ₂ Cu (II): 2 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ )) is dissolved in a mixture of dibutylaminopropylamine and 2-ethyl-1,3-hexanediol. When heat treatment is performed in an N ₂ /3% H ₂ atmosphere in the presence of 2-ethyl-1,3-hexanediol, 2-ethyl-1,3-hexanediol represented by the following reaction formula: Conversion of a hydroxyl group (> CH—OH) to an oxo group (> C═O) and a reduction reaction of the amine complex of copper oleate proceed.

(CH ₃ (CH ₂ ) ₇ CH = CH (CH ₂ ) ₇ COO) ₂ Cu (II): 2 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ) + (> CH-OH)
_{→ 2CH 3 (CH 2) 7} CH = CH (CH 2) 7 COOH + (Cu (0): 2 ((C 4 H 9) 2 N (CH 2) 3 NH 2) + (> C = O)

The reaction product derived from 2-ethyl-1,3-hexanediol (> C═O) is a fine copper powder, and the oxo group (> C═O) on the metal copper atom exposed on the surface of the copper powder. ) Electrons can be coordinated. In a reducing atmosphere containing hydrogen gas, a hydrogen molecule (H ₂ ) is added to an oxo group (> C═O) coordinated on the metal copper atom, whereby the original hydroxyl group ( > CH—OH).

(> C = O) + H ₂ → (> CH—OH)

On the other hand, the metal copper atom generated by the reduction of the amine complex of copper oleate has a shape in which two molecules are coordinated with dibutylaminopropylamine as a bidentate ligand. Thereafter, when two molecules of dibutylaminopropylamine are further coordinated, a metal copper atom coordinated by a total of four molecules of dibutylaminopropylamine (Cu (0): 4 ((C ₄ H ₉ ) ₂ N ( CH ₂ ) ₃ NH ₂ ) (Cu (0): 4 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ) and (Cu (0): 2 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ) finally forms an aggregate of metallic copper atoms with metallic copper atoms on the surface of copper powder and fine copper powder as nuclei.

Dibutylaminopropylamine and 2-ethyl-1,3-hexanediol evaporate during the heat treatment in an N ₂ /3% H ₂ atmosphere. As a result, when the volume of the liquid phase decreases (concentration progresses), the liquid phase becomes a narrow gap around the contact area between the fine copper powder and the copper powder, the contact area between the underlayer and the fine copper powder, and the copper powder. The liquid phase is agglomerated in a narrow gap around the periphery. Therefore, along with the concentration of the liquid phase, the metal copper atom (Cu (0): 4 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ )) coordinated with a total of 4 molecules of dibutylaminopropylamine is Aggregates of metallic copper atoms are preferentially formed in a narrow gap around the contact area between the fine copper powder and the copper powder, and a narrow gap around the contact area between the underlayer and the fine copper powder and the copper powder. The narrow gap around the contact area between the fine copper powder and the copper powder, the narrow gap around the contact area between the underlayer and the fine copper powder, and the copper powder are embedded with the aggregate of the metal copper atoms. Then, when the firing proceeds, the fine copper powder, around the copper powder contact area, around the base layer and the fine copper powder, around the copper powder contact area, the aggregate of the metal copper atoms, the fine copper powder, As a result, the contact area of the fine copper powder, the contact area between the copper powders, the contact area between the underlayer and the fine copper powder, and the copper powder is increased. Is expanded.

The oleic acid (boiling point: 286 ° C.) produced as a by-product with the reduction of the amine complex of copper oleate is once dissolved in 2-ethyl-1,3-hexanediol as a dispersion solvent. Thereafter, when heat treatment is performed in an N ₂ /3% H ₂ atmosphere, oleic acid is gradually evaporated in the same manner as 2-ethyl-1,3-hexanediol as the first organic solvent.

In addition, dibutylaminopropylamine is initially coordinated to the copper metal exposed on the surfaces of copper powder and fine copper powder by utilizing the lone pair of amino groups (—NH ₂ ). Have a strong bond. Since the boiling point of dibutylaminopropylamine is lower than the boiling point of 2-ethyl-1,3-hexanediol as the first organic solvent, the evaporation rate of dibutylaminopropylamine is relatively fast. As a result, the concentration of dibutylaminopropylamine in the liquid phase is reduced, and the coordinative bonding of dibutylaminopropylamine with metal copper exposed on the surface of copper powder and fine copper powder is reduced. The withdrawal is promoted. Finally, when the copper metal exposed to the surface comes into direct contact with the fine copper powder and the copper powder, the sintering proceeds.

  In addition, since the silanol structure (Si—OH) exists on the surface of the slide glass, the copper atom (Cu) derived from the copper oleate has Si— with respect to the silanol structure (Si—OH) part. Immobilized in the form of O-Cu. Further, on the surface of the slide glass, a copper metal film layer covering the surface is grown with copper atoms immobilized in the form of Si—O—Cu as nuclei. Therefore, the metal copper film layer covering the surface of the slide glass exhibits excellent adhesion. In particular, at the part where the copper powder contacts the surface of the slide glass, the metal copper film layer is also partially formed on the surface of the copper powder, and there is a bond between metal atoms between the two. In addition to this contribution, high adhesion characteristics resulting from the interposition of the metal copper film layer are imparted between the slide glass surface having a silanol structure (Si—OH) and the copper powder.

The prepared copper paste was applied on a slide glass in a pattern of 5 mm × 20 mm. The average thickness of the copper paste coating film was 58 μm. The copper paste coating film was baked by heat treatment at 400 ° C. for 10 minutes in an N ₂ /3% H ₂ atmosphere.

  The average film thickness of the obtained fired product was 49 μm. The volume resistivity was calculated from the measured sheet resistance value, assuming that the fired product was a conductor having a uniform average film thickness. The calculated volume resistivity was 9 μΩ · cm.

  The volume specific resistivity 9 μΩ · cm of the obtained fired product is 5.4 times the resistivity of metallic copper 1.673 μΩ · cm (30 ° C.).

(Example 2)
The conductive copper paste of Example 2 is prepared using the following raw materials.

As the copper powder selected in the range of 2 to 10 μm in average particle size, Mitsui Metals' spherical copper powder MA-C08JM (average particle size of 7 μm) was selected in the range of 0.2 μm to 1.0 μm in average particle size. As the fine copper powder, Mitsui Metals fine copper powder 1020Y (average particle size 0.4 μm) is used. The ratio of the average particle diameter d _{Cu-fine-powder of the fine} copper powder and the average particle diameter d _Cu-powder of the spherical copper powder (d _{Cu-fine-powder} / d _Cu-powder ) is selected to be _4/70 Has been.

As a copper nanoparticle which selects an average particle diameter in the range of 10 nm-100 nm, a copper nanoparticle with an average particle diameter of 70 nm is used. The surface of the copper nanoparticles is in a state where a coating molecular layer made of dibutylaminopropylamine is formed. At that time, the metal copper atoms exposed on the surface of the copper nanoparticles, dibutyl aminopropyl amine, using a lone pair of the amino (-NH _2), and a coordinative bond Yes. Specifically, a dispersion obtained by dispersing copper nanoparticles having an average particle diameter of 70 nm having a coating molecular layer of dibutylaminopropylamine in ethanol is used. The composition of the ethanol dispersion of copper nanoparticles having an average particle diameter of 70 nm is a composition containing 0.15 parts by mass of dibutylaminopropylamine and 5 parts by mass of ethanol as a dispersion solvent per 5 parts by mass of copper nanoparticles having an average diameter of 70 nm. Is selected.

  The aliphatic polyhydric alcohol used as the third organic solvent is 2-ethyl-1,3-hexanediol (melting point: −40 ° C., boiling point: 245 ° C.).

  65 parts by mass of Mitsui Metals spherical copper powder MA-C08JM (average particle size 7 μm), 35 parts by mass of Mitsui Metals fine copper powder 1020Y (average particle size 0.4 μm), 5 parts by mass of copper nanoparticles having an average diameter of 70 nm A dispersion liquid dispersed in 5 parts by mass of ethanol is mixed with 5 parts by mass of 2-ethyl-1,3-hexanediol. Next, ethanol in the mixed solution is removed by an evaporator. Thereafter, the mixture is stirred with a stirring deaerator to prepare a copper paste in which the copper nanoparticles and the copper powder and fine copper powder are uniformly dispersed in the liquid phase.

  The sum of the metallic copper weight of the spherical copper powder and the fine copper powder, the weight of the copper nanoparticles, (the sum of the metallic copper weight of the spherical copper powder and the fine copper powder): (the weight of the copper nanoparticles) is 100: 5. It has become. Moreover, 0.021 mol of 2-ethyl-1,3-hexanediol is contained per 1 mol of metallic copper of the spherical copper powder and fine copper powder.

When the density of metallic copper is 8.95 g / cm ³ (20 ° C.) and the density of 2-ethyl-1,3-hexanediol is 0.942 g / cm ³ (25 ° C.), the volume of the spherical copper powder and fine copper powder Of the total volume (V _Cu-powder + V _{Cu-fine-powder} ) and the volume of the third organic solvent 2-ethyl-1,3-hexanediol (V _{dispersion-medium} ), (V _Cu-powder + V _{Cu -fine-powder} ): V _{dispersion-medium} is calculated as 21: 9.5.

  Therefore, the ratio of the total volume of the spherical copper powder, fine copper powder, and copper nanoparticles in the prepared copper paste is 70% by volume.

  The liquid viscosity of the prepared copper paste was 20 Pa · s (spiral rotational viscometer 10 rpm 25 ° C.).

First, dibutylaminopropylamine utilizes a lone electron pair of its amino group (—NH ₂ ) for metallic copper that is dispersed in the copper paste and exposed on the surface of the copper nanoparticles. And have coordinate bonds. On the other hand, 2-ethyl-1,3-hexanediol contained in the liquid phase is solvated (adsorbed) on the surfaces of the spherical copper powder and fine copper powder. Usually, surface oxide films are present on the surfaces of the spherical copper powder and the fine copper powder. With respect to the copper oxide corresponding to copper oxide (CuO) constituting the surface oxide film, 2-ethyl-1,3-hexanediol uses the hydroxyl group (> CH—OH), Hydrogen-bonded intermolecular bonding is performed with oxygen atoms (Cu—O—Cu) in the copper oxide. At that time, it is presumed that the reduction of the surface oxide film proceeds via the following two elementary processes.

  When heat treatment is performed in a reducing atmosphere containing hydrogen gas, the hydroxyl group (> CH—OH) of 2-ethyl-1,3-hexanediol reacts with the copper oxide, and the following oxidation / reduction reaction Wake up.

CuO + (> CH—OH) → Cu + (> C═O) + H ₂ O ↑

The reaction product (> C═O) derived from 2-ethyl-1,3-hexanediol is a fine copper powder, a metal copper atom (Cu) exposed on the surface of the copper powder, and its oxo group (> C═O). Coordination can be performed using the π electrons of O). In a reducing atmosphere containing hydrogen gas, a hydrogen molecule (H ₂ ) is added to the oxo group (> C═O) coordinated on the metal copper atom (Cu), so that the original It is possible to convert to a hydroxyl group (> CH—OH).

(> C = O) + H ₂ → (> CH—OH)

  The 2-hydroxy-1,3-hexanediol, in which the original hydroxyl group (> CH—OH) has been regenerated, again becomes an oxygen atom (Cu—O—Cu) in the copper oxide constituting the surface oxide film. ) Can be solvated (adsorbed).

Apparently, the reduction of the surface oxide film proceeds using hydrogen molecules (H ₂ ) supplied from a reducing atmosphere containing hydrogen gas.

Initially, for metallic copper exposed on the surface of copper nanoparticles, dibutylaminopropylamine is coordinated using the lone pair of its amino group (—NH ₂ ). Yes. Since the boiling point of dibutylaminopropylamine is lower than that of the dispersion solvent 2-ethyl-1,3-hexanediol, the evaporation rate of dibutylaminopropylamine is relatively fast. As a result, when the heat treatment is applied, the concentration of dibutylaminopropylamine in the liquid phase decreases, and dibutylamino which has a coordinate bond to the metallic copper exposed on the surface of the copper nanoparticles. The release of propylamine is promoted.

  Finally, at the contact area between the fine copper powder and copper powder after the reduction of the surface oxide film, the metallic copper exposed on the surface between the fine copper powder, copper powder, and copper nanoparticles When it comes into direct contact, sintering proceeds.

Specifically, transpiration of dibutylaminopropylamine and 2-ethyl-1,3-hexanediol proceeds during the heat treatment in an N ₂ /3% H ₂ atmosphere. As a result, when the volume of the liquid phase decreases (concentration progresses), the liquid phase becomes a narrow gap around the contact area between the fine copper powder and the copper powder, the contact area between the underlayer and the fine copper powder, and the copper powder. The liquid phase is agglomerated in a narrow gap around the periphery. Therefore, with the concentration of the liquid phase, the dispersed copper nanoparticles are fine copper powder, narrow gap around the contact area between the copper powder, narrow gap around the contact area between the underlayer and the fine copper powder, copper powder. Is accumulated. Therefore, the narrow gap around the contact area between the fine copper powder and the copper powder, and the narrow gap around the contact area between the underlayer and the fine copper powder and the copper powder are embedded with the copper nanoparticles. Then, when firing proceeds, the copper nanoparticles, the copper powder, and the copper powder are contacted between the fine copper powder, the copper powder contact area, the base layer and the fine copper powder, and the copper powder contact area. Integration proceeds. As a result, the contact area is increased in the contact area between the fine copper powder, the contact area between the copper powders, and the contact area between the ground layer and the fine copper powder and the copper powder.

The prepared copper paste was applied on a slide glass in a pattern of 5 mm × 20 mm. The average thickness of the copper paste coating film was 63 μm. The copper paste coating film was baked by heat treatment at 400 ° C. for 10 minutes in an N ₂ /3% H ₂ atmosphere.

  The average film thickness of the obtained fired product was 55 μm. The volume resistivity was calculated from the measured sheet resistance value, assuming that the fired product was a conductor having a uniform average film thickness. The calculated volume resistivity was 8 μΩ · cm.

  The volume specific resistivity 8 μΩ · cm of the obtained fired product is 4.8 times the resistivity of metallic copper 1.673 μΩ · cm (30 ° C.).

(Example 3-1) to (Example 3-8)
The conductive copper pastes of Example 3-1 to Example 3-8 are prepared using the following raw materials.

As the copper powder selected in the range of the average particle diameter of ^{2 to} 10 μm, Mitsui Metals' spherical copper powder 1400YM (average particle diameter of 4 μm, BET specific surface area of 1600 cm ² / g) and average particle diameter of 0.2 μm to 1. As the fine copper powder selected in the range of 0 μm, Mitsui Metals fine copper powder 1020Y (average particle diameter 0.4 μm, BET specific surface area 26000 cm ² / g) is used. The ratio of the average particle diameter d _{Cu-fine-powder of the fine} copper powder to the average particle diameter d _Cu-powder of the spherical copper powder (d _{Cu-fine-powder} / d _Cu-powder ) is selected to be 1/10 Has been.

Copper salt of aliphatic monocarboxylic acid ((R—COO) ₂ Cu (II)), copper oleate ((CH ₃ (CH ₂ ) ₇ CH═CH (CH ₂ ) ₇ COO) ₂ Cu (II)) And dissolved in advance in dibutylaminopropylamine ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ , melting point: −50 ° C., boiling point: 238 ° C.), and an amine complex of copper oleate is dissolved. It is formed. The solid copper oleate itself forms a dimer having a Cu: Cu bond. The amine complex of copper oleate formed is composed of dibutylaminopropylamine (one molecule of copper oleate ((CH ₃ (CH ₂ ) ₇ CH═CH (CH ₂ ) ₇ COO) ₂ Cu (II))). It can be presumed that (C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ) 2 molecules coordinate to the copper cation (Cu ²⁺ ). As a result, the dimer type copper oleate is converted into an amine complex of two molecules of copper oleate and is dissolved in the solvent dibutylaminopropylamine. In Example 3-1 to Example 3-8, 3.3 parts by mass of copper oleate was dissolved in 6.6 parts by mass of dibutylaminopropylamine, and an amine solution of an amine complex of copper oleate was prepared in advance. Yes. The composition of the amine solution of the copper oleate amine complex is selected to be 7 molecules of dibutylaminopropylamine per molecule of copper oleate.

  The aliphatic polyhydric alcohol used as the first organic solvent is 2-ethyl-1,3-hexanediol (molecular weight: 146.23, melting point: −40 ° C., boiling point: 245 ° C.).

  In the conductive copper pastes of Example 3-1 to Example 3-7, a sintering aid is added.

  The carboxylic acid metal salt used as a sintering aid is bismuth (III) 2-ethylhexanoate. Specifically, bismuth (III) 2-ethylhexanoate / 2-ethylhexanoic acid solution (manufactured by Wako Pure Chemical Industries, bismuth content 25% by mass) is used, and a predetermined amount of bismuth 2-ethylhexanoate (III ) Is added.

  In the conductive copper pastes of Examples 3-1 to 3-7, 80 parts by mass of Mitsui Metals spherical copper powder 1400YM, 20 parts by mass of Mitsui Metals fine copper powder 1020Y, 3.3 parts by mass of copper oleate are added to dibutylamino. A solution dissolved in 6.6 parts by mass of propylamine, a predetermined amount of bismuth (III) 2-ethylhexanoate / 2-ethylhexanoic acid solution, and 3 parts by mass of 2-ethyl-1,3-hexanediol are mixed. To do. Thereafter, the mixture is stirred with a stirring deaerator to prepare a copper paste in which the copper powder and the fine copper powder are uniformly dispersed in the liquid phase.

  On the other hand, in the conductive copper paste of Example 3-8, no sintering aid is added.

  In the conductive copper paste of Example 3-8, Mitsui Metals spherical copper powder 1400YM 80 parts by mass, Mitsui Metals fine copper powder 1020Y 20 parts by mass, 3.3 parts by mass of copper oleate 6.6 parts by mass of dibutylaminopropylamine The solution dissolved in the part and 3 parts by mass of 2-ethyl-1,3-hexanediol are mixed. Thereafter, the mixture is stirred with a stirring deaerator to prepare a copper paste in which the copper powder and the fine copper powder are uniformly dispersed in the liquid phase.

  Sum of the number of metallic copper atoms in the spherical copper powder and fine copper powder and the ratio of the number of copper atoms in the copper oleate, (sum of the number of metallic copper atoms in the spherical copper powder and fine copper powder): (oleic acid The number of atoms with copper in the copper is 299: 1 (100: 0.334). Further, 0.013 mol of 2-ethyl-1,3-hexanediol is contained per 1 mol of metallic copper of the spherical copper powder and fine copper powder.

The total surface area of the spherical copper powder and fine copper powder is [(80 × 1600 + 20 × 26000) / 10000] m ² .

The density of oleic acid copper ^{0.95g / cm 3 (20 ℃)} , since the density 0.826 g / cm ³ of dibutylaminopropylamine (20 ° C.), the oleic acid copper amine complex of the amine solution 10g The volume can be estimated as 11.6 cm ³ .

Further, since the density of the bismuth (III) 2-ethylhexanoate / 2-ethylhexanoic acid solution is 1.17 g / cm ³ (25 ° C.), the bismuth (III) 2-ethylhexanoate / 2-ethylhexanoic acid solution A volume of 10 g can be estimated as 8.5 cm ³ .

The prepared copper paste was applied on a slide glass in a pattern of 5 mm × 20 mm. The copper paste coating film was baked by heat treatment at 400 ° C. for 10 minutes in an N ₂ /3% H ₂ atmosphere. The specific volume resistivity was calculated from the measured sheet resistance value assuming that the fired product was a conductor having a uniform average film thickness.

  Tables 1-1 to 1-2 below show the compositions of the conductive copper pastes of Example 3-1 to Example 3-8. The average film thickness of the copper paste coating film, the average film thickness of the fired product, and the calculated volume specific resistivity are also shown.

  In the conductive copper pastes of Example 3-1 to Example 3-7, the following reaction proceeds with heating.

First, the surfaces of spherical copper powder and fine copper powder dispersed in the copper paste are 2-ethylhexanoic acid, dibutylaminopropylamine, or 2-ethyl-1,3- In contact with hexanediol. Dibutylaminopropylamine is coordinated to the metallic copper exposed on the surface by utilizing the lone electron pair of the amino group (—NH ₂ ). On the other hand, a surface oxide film partially exists on the surfaces of the spherical copper powder and the fine copper powder. When 2-ethylhexanoic acid acts on a copper oxide corresponding to copper oxide (CuO) constituting the surface oxide film, it is estimated that the following reaction proceeds with the copper oxide.
_{CuO + CH 3 (CH 2)} 4 CH (C 2 H 5) COOH) → [CH 3 (CH 2) 4 CH (C 2 H 5) COO -: Cu 2+ (- OH)];
_{[CH 3 (CH 2) 4} CH (C 2 H 5) COO -: Cu 2+ (- OH)] + CH 3 (CH 2) 4 CH (C 2 H 5) COOH)
→ (CH ₃ (CH ₂ ) ₄ CH (C ₂ H ₅ ) COO) ₂ Cu (II) + H ₂ O;

The produced copper (II) 2-ethylhexanoate is presumed to be dissolved in a mixed liquid of dibutylaminopropylamine and 2-ethyl-1,3-hexanediol. That is, an amine complex ((CH ₃ (CH ₂ ) ₄ CH (C ₂ H ₅ ) COO) of copper (II) 2-ethylhexanoate in which dibutylaminopropylamine is coordinated to copper (II) 2-ethylhexanoate. ) ₂ Cu (II): 2 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ )) is presumed to be formed. When heat treatment is performed in an N ₂ /3% H ₂ atmosphere in the presence of 2-ethyl-1,3-hexanediol, 2-ethyl-1,3-hexanediol represented by the following reaction formula: It is presumed that the conversion of the hydroxyl group (> CH—OH) to the oxo group (> C═O) and the reduction reaction of the amine complex of copper (II) 2-ethylhexanoate proceed.

(CH ₃ (CH ₂ ) ₄ CH (C ₂ H ₅ ) COO) ₂ Cu (II): 2 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ) + (> CH-OH)
_{→ 2CH 3 (CH 2) 4} CH (C 2 H 5) COOH + (Cu (0): 2 ((C 4 H 9) 2 N (CH 2) 3 NH 2) + (> C = O)

  In addition, when the part which does not react with 2-ethylhexanoic acid remains among the copper oxides which correspond to copper oxide (CuO) which comprises this surface oxide film, with respect to this remaining copper oxide, 2-ethyl -1,3-hexanediol uses its hydroxyl group (> CH—OH) to form hydrogen-bonded intermolecular bonds with oxygen atoms (Cu—O—Cu) in the copper oxide. . At that time, it is presumed that the reduction of the surface oxide film proceeds via the following two elementary processes.

  When heat treatment is performed in a reducing atmosphere containing hydrogen gas, the hydroxyl group (> CH—OH) of 2-ethyl-1,3-hexanediol reacts with the copper oxide, and the following oxidation / reduction reaction Wake up.

CuO + (> CH—OH) → Cu + (> C═O) + H ₂ O ↑

The reaction product (> C═O) derived from 2-ethyl-1,3-hexanediol is a fine copper powder, a metal copper atom (Cu) exposed on the surface of the copper powder, and its oxo group (> C═O). Coordination can be performed using the π electrons of O). In a reducing atmosphere containing hydrogen gas, a hydrogen molecule (H ₂ ) is added to the oxo group (> C═O) coordinated on the metal copper atom (Cu), so that the original It is possible to convert to a hydroxyl group (> CH—OH).

(> C = O) + H ₂ → (> CH—OH)
The 2-hydroxy-1,3-hexanediol, in which the original hydroxyl group (> CH—OH) has been regenerated, again becomes an oxygen atom (Cu—O—Cu) in the copper oxide constituting the surface oxide film. ) Can be solvated (adsorbed).

Apparently, the reduction of the surface oxide film proceeds using hydrogen molecules (H ₂ ) supplied from a reducing atmosphere containing hydrogen gas.

Further, in the copper paste, bismuth (III) 2-ethylhexanoate added as a solution of 2-ethylhexanoic acid, bismuth (III) 2-ethylhexanoate is dibutylaminopropylamine and 2-ethyl-1, Dissolved in a mixture of 3-hexanediol. As a result, amine complex ((CH ₃ (CH ₂ ) ₄ CH (C ₂ H ₅ ) of bismuth 2-ethylhexanoate) in which dibutylaminopropylamine was coordinated to bismuth (III) 2-ethylhexanoate COO) ₃ Bi (III): ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ )) is presumed to be formed. When heat treatment is performed in an N ₂ /3% H ₂ atmosphere in the presence of 2-ethyl-1,3-hexanediol, 2-ethyl-1,3-hexanediol represented by the following reaction formula: It is presumed that the conversion of the hydroxyl group (> CH—OH) to the oxo group (> C═O) and the reduction reaction of the amine complex of bismuth (III) 2-ethylhexanoate proceed.

(CH ₃ (CH ₂ ) ₄ CH (C ₂ H ₅ ) COO) ₃ Bi (III): ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ) + (> CH—OH)
→ 3CH ₃ (CH ₂ ) ₄ CH (C ₂ H ₅ ) COOH + [(Bi (0) :( C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ )] + (> C═O)
[(Bi (0) :( C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ )] + (C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂
→ (Bi (0): 2 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ )

The reaction product derived from 2-ethyl-1,3-hexanediol (> C═O) is a fine copper powder, and the oxo group (> C═O) on the metal copper atom exposed on the surface of the copper powder. ) Electrons can be coordinated. In a reducing atmosphere containing hydrogen gas, a hydrogen molecule (H ₂ ) is added to an oxo group (> C═O) coordinated on the metal copper atom, whereby the original hydroxyl group ( > CH—OH).

(> C = O) + H ₂ → (> CH—OH)

  That is, the metal bismuth atom formed by the reduction of the amine complex of bismuth (III) 2-ethylhexanoate has a shape in which two molecules are coordinated with dibutylaminopropylamine as a bidentate ligand.

In the conductive copper pastes of Example 3-1 to Example 3-5, 4 dibutylaminopropylamines are present per metal atom (Cu and Bi) contained in the total of copper oleate and bismuth 2-ethylhexanoate. Contains more than molecules. Therefore, metal copper atoms (Cu (0): 2 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ) and metal bismuth atoms (Bi (0): 2 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ) is further coordinated by two molecules of dibutylaminopropylamine, each coordinated by four molecules of dibutylaminopropylamine, (Cu (0): 4 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ) and (Bi (0): 4 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ). Finally, copper powder, fine copper powder Aggregates composed of metal copper atoms and metal bismuth atoms are formed using metal copper atoms on the surface of the metal as nuclei.

In the conductive copper pastes of Examples 3-6 and 3-7, 2 dibutylaminopropylamines are present per one metal atom (Cu and Bi) contained in the total of copper oleate and bismuth 2-ethylhexanoate. More than 4 molecules are included. Therefore, metal copper atoms (Cu (0): 2 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ) and metal bismuth atoms (Bi (0): 2 ((C ₄ H ₉ ) ₂ N A part of (CH ₂ ) ₃ NH ₂ ) is further coordinated by two molecules of dibutylaminopropylamine, each coordinated by four molecules of dibutylaminopropylamine, (Cu (0): 4 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ) and (Bi (0): 4 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ). Then, an aggregate composed of metallic copper atoms and metallic bismuth atoms is formed using metallic copper atoms on the surface of the fine copper powder as nuclei.

In the conductive copper paste of Example 3-8, seven molecules of dibutylaminopropylamine are contained per one metal atom (Cu and Bi) contained in copper oleate. Therefore, the metal copper atom (Cu (0): 2 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ) is further coordinated by two molecules of dibutylaminopropylamine, each of which is dibutylaminopropylamine. It is converted into (Cu (0): 4 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ) coordinated by 4 molecules. Finally, the metal on the surface of copper powder and fine copper powder Aggregates composed of metallic copper atoms are formed with copper atoms as nuclei.

In the conductive copper pastes of Example 3-1 to Example 3-5, dibutylaminopropylamine and 2-ethyl-1,3- were used during the heat treatment in an N ₂ /3% H ₂ atmosphere. The transpiration of hexanediol also proceeds. As a result, when the volume of the liquid phase decreases (concentration progresses), the liquid phase becomes a narrow gap around the contact area between the fine copper powder and the copper powder, the contact area between the underlayer and the fine copper powder, and the copper powder. The liquid phase is agglomerated in a narrow gap around the periphery. Therefore, as the liquid phase is concentrated, metallic copper atoms (Cu (0): 4 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ) and metallic bismuth atoms (Bi ( 0): 4 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ) is a narrow gap around the contact area between fine copper powder and copper powder, contact between the underlayer and fine copper powder, copper powder Aggregates consisting of metallic copper atoms and metallic bismuth atoms preferentially form in narrow gaps around the site, so fine copper powder, narrow gaps around the contact area between the copper powder, underlayer and fine copper powder The narrow gap around the contact area of the copper powder is filled with an aggregate composed of the metal copper atom and the metal bismuth atom.After the firing, the contact area between the fine copper powder and the copper powder Around the contact area between the underlayer and the fine copper powder and copper powder, alloying of the aggregate composed of the metal copper atoms and metal bismuth atoms and integration of the fine copper powder and copper powder There progresses. Consequently, fine copper powder, copper powder mutual contact portions, underlayer and fine copper powder, at the site of contact of the copper powder, the expansion of the contact area is made.

Even in the conductive copper pastes of Example 3-6 and Example 3-7, during the heat treatment in the N ₂ /3% H ₂ atmosphere, dibutylaminopropylamine and 2-ethyl-1,3- The transpiration of hexanediol also proceeds. As a result, when the volume of the liquid phase decreases (concentration progresses), the liquid phase becomes a narrow gap around the contact area between the fine copper powder and the copper powder, the contact area between the underlayer and the fine copper powder, and the copper powder. The liquid phase is agglomerated in a narrow gap around the periphery. Therefore, as the liquid phase is concentrated, metallic copper atoms (Cu (0): 2 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ), metallic bismuth atoms (Bi ( 0): 4 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ), copper metal atoms (Cu (0): 4 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ) and Metal bismuth atoms (Bi (0): 4 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ) are fine copper powder, narrow gaps around the contact area of copper powder, underlayer and fine copper In the narrow gap around the contact area of the powder and copper powder, an aggregate composed of metal copper atoms and metal bismuth atoms is formed preferentially, so the narrow gap around the contact area between the fine copper powder and the copper powder, A narrow gap around the contact area between the base layer and the fine copper powder and the copper powder is filled with an aggregate composed of the metal copper atom and the metal bismuth atom. Around the contact area between copper powder, around the contact area between the underlayer and fine copper powder, copper powder In the box, alloying of the aggregates composed of the metal copper atoms and metal bismuth atoms and integration with the fine copper powder and the copper powder proceed, resulting in the contact area between the fine copper powder and the copper powder, The contact area is enlarged at the contact area between the formation and the fine copper powder or copper powder.

Even in the conductive copper paste of Example 3-8, transpiration of dibutylaminopropylamine and 2-ethyl-1,3-hexanediol progresses during the heat treatment in an N ₂ /3% H ₂ atmosphere. . As a result, when the volume of the liquid phase decreases (concentration progresses), the liquid phase becomes a narrow gap around the contact area between the fine copper powder and the copper powder, the contact area between the underlayer and the fine copper powder, and the copper powder. The liquid phase is agglomerated in a narrow gap around the periphery. Therefore, as the liquid phase is concentrated, the metal copper atoms (Cu (0): 4 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ )) dispersed in the liquid phase are fine copper powder, copper Aggregates composed of metal copper atoms and metal bismuth atoms are preferentially formed in narrow gaps around the contact area between the powders, narrow gaps around the contact area between the base layer and the fine copper powder, and the copper powder. The narrow gap around the contact area between the fine copper powder and the copper powder, the narrow gap around the contact area between the underlayer and the fine copper powder, and the copper powder are embedded with aggregates composed of the metal copper atoms. Thereafter, when the firing proceeds, in the vicinity of the contact area between the fine copper powder and the copper powder, the contact area between the underlayer and the fine copper powder, and the copper powder, the agglomerates composed of the metal copper atoms are alloyed. As a result, integration with fine copper powder and copper powder proceeds as a result of contact between the fine copper powder and the copper powder, the contact area between the underlayer and the fine copper powder, and copper powder. The contact area is enlarged.

  Compared with Example 1 and Example 2, in Example 3-8, the average particle diameter of the spherical copper powder used is small, and the blending ratio of the spherical copper powder and fine copper powder is 80:20, The ratio of spherical copper powder is increasing. Therefore, compared with Example 1 and Example 2, in Example 3-8, the density of the contact part between spherical copper powders has increased significantly. In other words, compared with Example 1 and Example 2, in Example 3-8, the sum total of the contact resistance in the contact part of spherical copper powder mutually increases significantly. As a result, when using the copper paste of Example 3-8, the volume resistivity of the obtained fired product is significantly higher than when using the copper paste of Example 1 and Example 2. ing.

  On the other hand, in the conductive copper pastes of Example 3-1 to Example 3-7, bismuth (III) 2-ethylhexanoate as a sintering aid is added. Therefore, the contact resistance at the contact site between the spherical copper powders depends on the volume and resistivity of the alloy layer due to alloying of aggregates composed of metal copper atoms and metal bismuth atoms.

Compared to the resistivity ρ _{Cu of} 1.673 μΩ · cm (30 ° C.) of metallic copper, the resistivity ρ _{Bi of} 120 μΩ · cm (20 ° C.) of metal bismuth is orders of magnitude greater. However, the change in contact resistance at the contact site due to the addition of bismuth (III) 2-ethylhexanoate is due to “expansion of the contact area” and “alloying metal copper atoms and metal bismuth atoms at the contact sites. Depends on the balance of the two factors of "increased resistivity".

In the conductive copper paste of Example 3-1, the ratio V _Cu-metal : V _Bi-metal was 1: 0.32, and the “contact area of the bismuth (III) 2-ethylhexanoate” The contribution of “expansion” is relatively large, and the effect of reducing contact resistance is obtained as compared with the conductive copper paste of Example 3-8.

In the conductive copper paste of Example 3-2, the ratio V _Cu-metal : V _Bi-metal is 1: 0.16, which is due to the addition of bismuth (III) 2-ethylhexanoate. The contribution of “expansion” is relatively large, and the effect of reducing contact resistance is obtained as compared with the conductive copper paste of Example 3-8.

In the conductive copper paste of Example 3-3, the ratio V _Cu-metal : V _Bi-metal is 1: 0.70, which is due to the addition of bismuth (III) 2-ethylhexanoate. The contribution of “expansion” is relatively large, and the effect of reducing contact resistance is obtained as compared with the conductive copper paste of Example 3-8.

In the conductive copper paste of Example 3-4, the ratio V _Cu-metal : V _Bi-metal is 1: 1.03, which is due to the addition of bismuth (III) 2-ethylhexanoate due to alloying. Although the influence of “increase in resistivity” is increasing, the contribution of “expansion of contact area” is relatively large, and the effect of reducing contact resistance is obtained when compared with the conductive copper paste of Example 3-8. ing.

In the conductive copper paste of Example 3-5, the ratio V _Cu-metal : V _Bi-metal is 1: 1.73, which is due to the addition of bismuth (III) 2-ethylhexanoate due to alloying. Although the influence of “increased resistivity” is increasing, the contribution of “expansion of contact area” is relatively large, and the effect of reducing contact resistance is obtained as compared with the conductive copper paste of Example 3-8. It has been.

In the conductive copper paste of Example 3-6, the ratio V _Cu-metal : V _Bi-metal is 1: 2.76, which results from the addition of bismuth (III) 2-ethylhexanoate due to alloying. Although the influence of “increased resistivity” is further increased, the contribution of “expansion of contact area” is relatively large, and compared with the conductive copper paste of Example 3-8, the effect of reducing contact resistance is obtained. It has been.

In the conductive copper paste of Example 3-7, the ratio V _Cu-metal : V _Bi-metal is 1: 3.46, which results from the addition of bismuth (III) 2-ethylhexanoate due to alloying. Since the influence of “increase in resistivity” is further increased, the effect of reduction in contact resistance is not obtained as a result of offsetting the contribution of “expansion of contact area” as compared with Example 3-8.

(Example 3B-1) to (Example 3B-4)
The conductive copper pastes of Example 3B-1 to Example 3B-4 are prepared using the following raw materials.

As the copper powder selected in the range of the average particle diameter of ^{2 to} 10 μm, Mitsui Metals' spherical copper powder 1400YM (average particle diameter of 4 μm, BET specific surface area of 1600 cm ² / g) and average particle diameter of 0.2 μm to 1. As the fine copper powder selected in the range of 0 μm, Mitsui Metals fine copper powder 1020Y (average particle diameter 0.4 μm, BET specific surface area 26000 cm ² / g) is used. The ratio of the average particle diameter d _{Cu-fine-powder of the fine} copper powder to the average particle diameter d _Cu-powder of the spherical copper powder (d _{Cu-fine-powder} / d _Cu-powder ) is selected to be 1/10 Has been.

As a copper nanoparticle which selects an average particle diameter in the range of 10 nm-100 nm, a copper nanoparticle with an average particle diameter of 70 nm is used. The surface of the copper nanoparticles is in a state where a coating molecular layer made of dibutylaminopropylamine is formed. At that time, the metal copper atoms exposed on the surface of the copper nanoparticles, dibutyl aminopropyl amine, using a lone pair of the amino (-NH _2), and a coordinative bond Yes. Specifically, a dispersion obtained by dispersing copper nanoparticles having an average particle diameter of 70 nm having a coating molecular layer of dibutylaminopropylamine in ethanol is used. The composition of the ethanol dispersion of copper nanoparticles having an average particle diameter of 70 nm is a composition containing 0.15 parts by mass of dibutylaminopropylamine and 5 parts by mass of ethanol as a dispersion solvent per 5 parts by mass of copper nanoparticles having an average diameter of 70 nm. Is selected.

Copper salt of aliphatic monocarboxylic acid ((R—COO) ₂ Cu (II)), copper oleate ((CH ₃ (CH ₂ ) ₇ CH═CH (CH ₂ ) ₇ COO) ₂ Cu (II)) And dissolved in advance in dibutylaminopropylamine ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ , melting point: −50 ° C., boiling point: 238 ° C.), and an amine complex of copper oleate is dissolved. It is formed. The solid copper oleate itself forms a dimer having a Cu: Cu bond. The amine complex of copper oleate formed is composed of dibutylaminopropylamine (one molecule of copper oleate ((CH ₃ (CH ₂ ) ₇ CH═CH (CH ₂ ) ₇ COO) ₂ Cu (II))). It can be presumed that (C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ) 2 molecules coordinate to the copper cation (Cu ²⁺ ). As a result, the dimer type copper oleate is converted into an amine complex of two molecules of copper oleate and is dissolved in the solvent dibutylaminopropylamine.

  In Example 3B-1, 1.0 part by mass of copper oleate is dissolved in 2.0 parts by mass of dibutylaminopropylamine, and an amine solution of an amine complex of copper oleate is prepared in advance. In Example 3B-2 to Example 3B-4, 3.3 parts by mass of copper oleate was dissolved in 6.6 parts by mass of dibutylaminopropylamine, and an amine solution of an amine complex of copper oleate was prepared in advance. Yes. The composition of the amine solution of the copper oleate amine complex is selected to be 6.7 molecules of dibutylaminopropylamine per molecule of copper oleate.

  The aliphatic polyhydric alcohol used as the third organic solvent is 2-ethyl-1,3-hexanediol (molecular weight: 146.23, melting point: -40 ° C, boiling point: 245 ° C).

  The carboxylic acid metal salt used as a sintering aid is bismuth (III) 2-ethylhexanoate. Specifically, bismuth (III) 2-ethylhexanoate / 2-ethylhexanoic acid solution (manufactured by Wako Pure Chemical Industries, bismuth content 25% by mass) is used, and a predetermined amount of bismuth 2-ethylhexanoate (III ) Is added.

  In the conductive copper pastes of Example 3B-1 to Example 3B-4, copper nanoparticles with an average diameter of 70 nm are contained in ethanol in Mitsui Metals spherical copper powder 1400YM 80 parts by mass, Mitsui Metals fine copper powder 1020Y20 parts in mass. A predetermined amount of the dispersed dispersion, a predetermined amount of a solution of copper oleate dissolved in dibutylaminopropylamine, a predetermined amount of bismuth (III) 2-ethylhexanoate / 2-ethylhexanoic acid solution, A predetermined amount of 2-ethyl-1,3-hexanediol is mixed. Next, ethanol in the mixed solution is removed by an evaporator. Thereafter, the mixture is stirred with a stirring deaerator to prepare a copper paste in which the copper powder and the fine copper powder are uniformly dispersed in the liquid phase.

  Sum of the number of metallic copper atoms in the spherical copper powder and fine copper powder and the ratio of the number of copper atoms in the copper oleate, (sum of the number of metallic copper atoms in the spherical copper powder and fine copper powder): (oleic acid The number of atoms with copper in copper is 986: 1 in Example 3B-1 and 299: 1 (100: 0.334) in Examples 3B-2 to 3B-4.

The total surface area of the spherical copper powder and fine copper powder is [(80 × 1600 + 20 × 26000) / 10000] m ² .

The prepared copper paste was applied on a slide glass in a pattern of 5 mm × 20 mm. The copper paste coating film was baked by heat treatment at 400 ° C. for 10 minutes in an N ₂ /3% H ₂ atmosphere. The specific volume resistivity was calculated from the measured sheet resistance value assuming that the fired product was a conductor having a uniform average film thickness.

  Table 2 below shows the compositions of the conductive copper pastes of Example 3B-1 to Example 3B-4. The average film thickness of the copper paste coating film, the average film thickness of the fired product, and the calculated volume specific resistivity are also shown.

  Compared with Example 1 and Example 2, in Example 3B-1, Example 3-4, and Example 3-8, the average particle diameter of the spherical copper powder to be used is small, and the spherical copper powder and the fine particle are fine. The blending ratio of the copper powder is 80:20, and the ratio of the spherical copper powder is increasing. Therefore, compared with Example 1 and Example 2, in Example 3B-1, Example 3-4, and Example 3-8, the density of contact portions between the spherical copper powders is significantly increased. .

In Example 3B-1 and Example 3-4, the volume ratio of the metal bismuth atom derived from bismuth 2-ethylhexanoate (III) and the metal copper atom derived from copper oleate is about 1: 1. In Example 3-4, the volume total (V _Cu-metal + V _Bi-metal ) of metal bismuth atoms derived from bismuth (III) 2-ethylhexanoate and copper oleate and the spherical copper The total volume of powder and fine copper powder (V _Cu-powder + V _{Cu-fine-powder} ) and ratio is (V _Cu-metal + V _Bi-metal ): (V _Cu-powder + V _{Cu-fine-powder} ) In Example 3B-1, (V _Cu-metal + V _Bi-metal ) :( V _Cu-powder + V _{Cu-fine-powder} ) is about 1: 500 in Example 3B-1. Therefore, the “reduction effect of contact resistance” by the “metal copper atom and metal bismuth atom alloy” filled in the contact portion between the spherical copper powders is higher than that of the copper paste of Example 3-4. -1 copper paste is not superior. Therefore, in the copper paste of Example 3B-1, the “contact resistance reduction effect” by the “copper nanoparticles” filled in the contact portions between the spherical copper powders has a major contribution, and the mutual contact between the spherical copper powders. It is judged that the “contact resistance reducing effect” by the “metal alloy of metal copper atoms and metal bismuth atoms” filled in the contact site has only a secondary contribution.

  Compared with Example 1 and Example 2, in Example 3B-2, Example 3-1, and Example 3-8, the average particle diameter of the spherical copper powder used is small, and the spherical copper powder and finer The blending ratio of the copper powder is 80:20, and the ratio of the spherical copper powder is increasing. Therefore, compared with Example 1 and Example 2, in Example 3B-2, Example 3-1, and Example 3-8, the density of the contact part between spherical copper powders has increased significantly.

In Example 3B-2 and Example 3-1, the volume ratio of the metal bismuth atom derived from bismuth 2-ethylhexanoate (III) and the metal copper atom derived from copper oleate is about 0.32: 1. is there. In Example 3-1, the volume total (V _Cu-metal + V _Bi-metal ) of metal bismuth atoms derived from bismuth (III) 2-ethylhexanoate and copper oleate (V _Cu-metal + V _Bi-metal ), and the spherical copper The total volume of powder and fine copper powder (V _Cu-powder + V _{Cu-fine-powder} ) and ratio is (V _Cu-metal + V _Bi-metal ): (V _Cu-powder + V _{Cu-fine-powder} ) In Example 3B-2, (V _Cu-metal + V _Bi-metal ) :( V _Cu-powder + V _{Cu-fine-powder} ) is about 1: 228. Accordingly, the “effect of reducing contact resistance” by the “metal copper atom and metal bismuth atom alloy” filled in the contact area between the spherical copper powders is higher than that of the copper paste of Example 3-1. -2 copper paste is not superior. Therefore, in the copper paste of Example 3B-2, the “contact resistance reducing effect” by the “copper nanoparticles” filled in the contact sites between the spherical copper powders and the contact sites between the spherical copper powders are filled. It is judged that the “reduction effect of contact resistance” by the “metal copper atom and metal bismuth atom alloy” has an equivalent contribution.

  Compared with Example 1 and Example 2, in Example 3B-3, Example 3-1, and Example 3-8, the average particle size of the spherical copper powder used is small, and the spherical copper powder and finer The blending ratio of the copper powder is 80:20, and the ratio of the spherical copper powder is increasing. Therefore, compared with Example 1 and Example 2, in Example 3B-3, Example 3-1, and Example 3-8, the density of the contact part between spherical copper powders has increased significantly.

In Example 3B-3 and Example 3-1, the volume ratio of the metal bismuth atom derived from bismuth (III) 2-ethylhexanoate and the copper metal atom derived from copper oleate is about 0.32: 1. is there. In Example 3-1, the volume total (V _Cu-metal + V _Bi-metal ) of metal bismuth atoms derived from bismuth (III) 2-ethylhexanoate and copper oleate (V _Cu-metal + V _Bi-metal ), and the spherical copper The total volume of powder and fine copper powder (V _Cu-powder + V _{Cu-fine-powder} ) and ratio is (V _Cu-metal + V _Bi-metal ): (V _Cu-powder + V _{Cu-fine-powder} ) In Example 3B-3, (V _Cu-metal + V _Bi-metal ) :( V _Cu-powder + V _{Cu-fine-powder} ) is about 1: 228. Therefore, the “effect of reducing contact resistance” by the “metal copper atom and metal bismuth atom alloy” filled in the contact area between the spherical copper powders is greater than that of the copper paste of Example 3-1. The 3B-3 copper paste is not superior. Therefore, in the copper paste of Example 3B-3, the “contact resistance reduction effect” by the “copper nanoparticles” filled in the contact sites between the spherical copper powders and the contact sites between the spherical copper powders are filled. It is judged that the “reduction effect of contact resistance” by the “metal copper atom and metal bismuth atom alloy” has an equivalent contribution.

  Compared with Example 1 and Example 2, in Example 3B-4, Example 3-1, and Example 3-8, the average particle diameter of the spherical copper powder used is small, and the spherical copper powder and finer The blending ratio of the copper powder is 80:20, and the ratio of the spherical copper powder is increasing. Therefore, compared with Example 1 and Example 2, in Example 3B-4, Example 3-1, and Example 3-8, the density of the contact part between spherical copper powders has increased significantly.

In Example 3B-4 and Example 3-1, the volume ratio of the metal bismuth atom derived from bismuth (III) 2-ethylhexanoate and the copper metal atom derived from copper oleate is about 0.32: 1. is there. In Example 3-1, the volume total (V _Cu-metal + V _Bi-metal ) of metal bismuth atoms derived from bismuth (III) 2-ethylhexanoate and copper oleate (V _Cu-metal + V _Bi-metal ), and the spherical copper The total volume of powder and fine copper powder (V _Cu-powder + V _{Cu-fine-powder} ) and ratio is (V _Cu-metal + V _Bi-metal ): (V _Cu-powder + V _{Cu-fine-powder} ) In Example 3B-4, (V _Cu-metal + V _Bi-metal ) :( V _Cu-powder + V _{Cu-fine-powder} ) is about 1: 228. Accordingly, the “effect of reducing contact resistance” by the “metal copper atom and metal bismuth atom alloy” filled in the contact area between the spherical copper powders is higher than that of the copper paste of Example 3-1. -4 copper paste is not superior. Therefore, in the copper paste of Example 3B-4, the “contact resistance reduction effect” by the “copper nanoparticles” filled in the contact sites between the spherical copper powders and the contact sites between the spherical copper powders are filled. It is judged that the “reduction effect of contact resistance” by the “metal copper atom and metal bismuth atom alloy” has an equivalent contribution.

  When the copper paste of Example 3B-2 to Example 3B-4 and the copper paste of Example 3B-1 are compared, 2-ethyl used for reducing the surface oxide film of spherical copper powder and fine copper powder. There is a significant difference in the content ratio of -1,3-hexanediol. In addition, since 2-ethyl-1,3-hexanediol is slightly evaporated when ethanol is distilled off under reduced pressure, it is contained in the copper pastes of Examples 3B-2 to 3B-4. -The content ratio of ethyl-1,3-hexanediol is further decreased. In particular, in the copper paste of Example 3B-4, the reduction in the content ratio of 2-ethyl-1,3-hexanediol is increased, resulting in partial reduction of the surface oxide film of spherical copper powder and fine copper powder. Concomitantly, compared with the copper paste of Example 3B-1, the “reduction effect of contact resistance” by “copper nanoparticles” filled in the contact sites between the spherical copper powders is equivalent. However, it is presumed that the “contact resistance reduction effect” by the “metal copper atom and metal bismuth atom alloy” filled in the contact area between the spherical copper powders is not sufficiently exhibited.

(Example 3C-1), (Example 3D-1)
The conductive copper pastes of Example 3C-1 and Example 3D-1 are prepared using the following raw materials.

As the copper powder selected in the range of the average particle diameter of ^{2 to} 10 μm, Mitsui Metals' spherical copper powder 1400YM (average particle diameter of 4 μm, BET specific surface area of 1600 cm ² / g) and average particle diameter of 0.2 μm to 1. As the fine copper powder selected in the range of 0 μm, Mitsui Metals fine copper powder 1020Y (average particle diameter 0.4 μm, BET specific surface area 26000 cm ² / g) is used. The ratio of the average particle diameter d _{Cu-fine-powder of the fine} copper powder to the average particle diameter d _Cu-powder of the spherical copper powder (d _{Cu-fine-powder} / d _Cu-powder ) is selected to be 1/10 Has been.

As a copper nanoparticle which selects an average particle diameter in the range of 10 nm-100 nm, a copper nanoparticle with an average particle diameter of 70 nm is used. The surface of the copper nanoparticles is in a state where a coating molecular layer made of dibutylaminopropylamine is formed. At that time, the metal copper atoms exposed on the surface of the copper nanoparticles, dibutyl aminopropyl amine, using a lone pair of the amino (-NH _2), and a coordinative bond Yes. Specifically, a dispersion obtained by dispersing copper nanoparticles having an average particle diameter of 70 nm having a coating molecular layer of dibutylaminopropylamine in ethanol is used. The composition of the ethanol dispersion of copper nanoparticles having an average particle diameter of 70 nm is a composition containing 0.15 parts by mass of dibutylaminopropylamine and 5 parts by mass of ethanol as a dispersion solvent per 5 parts by mass of copper nanoparticles having an average diameter of 70 nm. Is selected.

Copper salt of aliphatic monocarboxylic acid ((R—COO) ₂ Cu (II)), copper oleate ((CH ₃ (CH ₂ ) ₇ CH═CH (CH ₂ ) ₇ COO) ₂ Cu (II)) And dissolved in advance in dibutylaminopropylamine ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ , melting point: −50 ° C., boiling point: 238 ° C.), and an amine complex of copper oleate is dissolved. It is formed. The solid copper oleate itself forms a dimer having a Cu: Cu bond. The amine complex of copper oleate formed is composed of dibutylaminopropylamine (one molecule of copper oleate ((CH ₃ (CH ₂ ) ₇ CH═CH (CH ₂ ) ₇ COO) ₂ Cu (II))). It can be presumed that (C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ) 2 molecules coordinate to the copper cation (Cu ²⁺ ). As a result, the dimer type copper oleate is converted into an amine complex of two molecules of copper oleate and is dissolved in the solvent dibutylaminopropylamine.

  In Example 3C-1, 3.3 parts by mass of copper oleate is dissolved in 2.6 parts by mass of dibutylaminopropylamine to prepare an amine solution of an amine complex of copper oleate in advance. The composition of the amine solution of the amine complex of copper oleate is selected to be 2.65 molecules of dibutylaminopropylamine per molecule of copper oleate.

  In Example 3D-1, an amine solution of an amine complex of copper oleate was not added.

  The aliphatic polyhydric alcohol used as the third organic solvent is 2-ethyl-1,3-hexanediol (molecular weight: 146.23, melting point: -40 ° C, boiling point: 245 ° C).

  The carboxylic acid metal salt used as a sintering aid is bismuth (III) 2-ethylhexanoate. Specifically, bismuth (III) 2-ethylhexanoate / 2-ethylhexanoic acid solution (manufactured by Wako Pure Chemical Industries, bismuth content 25% by mass) is used, and a predetermined amount of bismuth 2-ethylhexanoate (III ) Is added.

  A predetermined amount of a dispersion in which copper nanoparticles having an average diameter of 70 nm are dispersed in ethanol in 80 parts by mass of Mitsui Metals spherical copper powder 1400YM and 20 parts by mass of Mitsui Metals fine copper powder 1020Y, and dibutylaminopropyl copper oleate A predetermined amount of a solution dissolved in an amine, 0.48 parts by mass of bismuth (III) 2-ethylhexanoate / 2-ethylhexanoic acid solution, and a predetermined amount of 2-ethyl-1,3-hexanediol are mixed. . Next, ethanol in the mixed solution is removed by an evaporator. Thereafter, the mixture is stirred with a stirring deaerator to prepare a copper paste in which the copper powder and the fine copper powder are uniformly dispersed in the liquid phase.

The addition ratio of bismuth atoms to the total surface area of the spherical copper powder and fine copper powder is 0.48 × 0.25 / 209 / [(80 × 1600 + 20 × 26000) / 10000] ≈8.88 μmol / m ² . .

The prepared copper paste was applied on a slide glass in a pattern of 5 mm × 20 mm. The copper paste coating film was baked by heat treatment at 400 ° C. for 10 minutes in an N ₂ /3% H ₂ atmosphere. The specific volume resistivity was calculated from the measured sheet resistance value assuming that the fired product was a conductor having a uniform average film thickness.

  Table 3 below shows the compositions of the conductive copper pastes of Example 3C-1 and Example 3D-1. The average film thickness of the copper paste coating film, the average film thickness of the fired product, and the calculated volume specific resistivity are also shown.

  Compared with Example 1 and Example 2, in Example 3C-1, Example 3B-2, Example 3-1, and Example 3-8, the average particle diameter of the spherical copper powder used is small, The blending ratio of spherical copper powder and fine copper powder is 80:20, and the ratio of spherical copper powder is increased. Therefore, compared with Example 1 and Example 2, in Example 3C-1, Example 3B-2, Example 3-1, and Example 3-8, the density of the contact part between spherical copper powders is significant. Has increased.

In Example 3C-1, Example 3B-2 and Example 3-1, the volume ratio of the metal bismuth atom derived from bismuth 2-ethylhexanoate (III) and the metal copper atom derived from copper oleate is about 0.32: 1. In Example 3-1, the volume total (V _Cu-metal + V _Bi-metal ) of metal bismuth atoms derived from bismuth (III) 2-ethylhexanoate and copper oleate (V _Cu-metal + V _Bi-metal ), and the spherical copper The total volume of powder and fine copper powder (V _Cu-powder + V _{Cu-fine-powder} ) and ratio is (V _Cu-metal + V _Bi-metal ): (V _Cu-powder + V _{Cu-fine-powder} ) In Example 3C-1 and Example 3B-2, (V _Cu-metal + V _Bi-metal ) :( V _Cu-powder + V _{Cu-fine-powder} ) is about 1: 228. is there. Accordingly, the “effect of reducing contact resistance” by the “metal copper atom and metal bismuth atom alloy” filled in the contact area between the spherical copper powders is higher than that of the copper paste of Example 3-1. -1 and the copper paste of Example 3B-2 are not superior. Therefore, in the copper pastes of Example 3C-1 and Example 3B-2, the “reduction effect of contact resistance” by the “copper nanoparticles” filled in the contact portion between the spherical copper powders and the mutual contact between the spherical copper powders. It is judged that the “contact resistance reduction effect” by the “metal alloy of copper metal atoms and metal bismuth atoms” filled in the contact portion of the metal has the same contribution.

  Compared with Example 1 and Example 2, in Example 3D-1, Example 3B-3, Example 3-1, and Example 3-8, the average particle size of the spherical copper powder used is small, The blending ratio of spherical copper powder and fine copper powder is 80:20, and the ratio of spherical copper powder is increased. Therefore, compared with Example 1 and Example 2, in Example 3D-1, Example 3B-3, Example 3-1, and Example 3-8, the density of the contact part between spherical copper powders is significant. Has increased.

In Example 3B-3 and Example 3-1, the volume ratio of the metal bismuth atom derived from bismuth (III) 2-ethylhexanoate and the copper metal atom derived from copper oleate is about 0.32: 1. However, in Example 3D-1, there are no metallic copper atoms derived from copper oleate. In Example 3B-3, the volume total (V _Cu-metal + V _Bi-metal ) of metal bismuth atoms derived from bismuth (III) 2-ethylhexanoate and copper oleate and the spherical copper The total volume of powder and fine copper powder (V _Cu-powder + V _{Cu-fine-powder} ) and ratio is (V _Cu-metal + V _Bi-metal ): (V _Cu-powder + V _{Cu-fine-powder} ) In this example 3D-1, (V _Bi-metal ) :( V _Cu-powder + V _{Cu-fine-powder} ) is about 1: 912. Therefore, in the copper paste of Example 3D-3, the “effect of reducing contact resistance” by the “metal bismuth atoms” filled in the contact portions between the spherical copper powders is spherical in the copper paste of Example 3B-1. There is no advantage over the “reduction effect of contact resistance” by the “metal copper atom and metal bismuth atom alloy” filled in the contact area between the copper powders. Therefore, in the copper paste of Example 3D-1, the “contact resistance reduction effect” by the “copper nanoparticles” filled in the contact sites between the spherical copper powders and the contact sites between the spherical copper powders are filled. It is judged that “the effect of reducing contact resistance” by “metal bismuth atoms” has an equivalent contribution.

(Example 3E-1, Example 3E-2)
(Example 3F-1, Example 3F-2)
The conductive copper pastes of Example 3E-1, Example 3E-2, Example 3F-1, and Example 3F-2 are prepared using the following raw materials.

As the copper powder selected in the range of the average particle diameter of ^{2 to} 10 μm, Mitsui Metals' spherical copper powder 1400YM (average particle diameter of 4 μm, BET specific surface area of 1600 cm ² / g) and average particle diameter of 0.2 μm to 1. As the fine copper powder selected in the range of 0 μm, Mitsui Metals fine copper powder 1020Y (average particle diameter 0.4 μm, BET specific surface area 26000 cm ² / g) is used. The ratio of the average particle diameter d _{Cu-fine-powder of the fine} copper powder to the average particle diameter d _Cu-powder of the spherical copper powder (d _{Cu-fine-powder} / d _Cu-powder ) is selected to be 1/10 Has been.

Copper salt of aliphatic monocarboxylic acid ((R—COO) ₂ Cu (II)), copper oleate ((CH ₃ (CH ₂ ) ₇ CH═CH (CH ₂ ) ₇ COO) ₂ Cu (II)) And dissolved in advance in dibutylaminopropylamine ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ , melting point: −50 ° C., boiling point: 238 ° C.), and an amine complex of copper oleate is dissolved. It is formed. The solid copper oleate itself forms a dimer having a Cu: Cu bond. The amine complex of copper oleate formed is composed of dibutylaminopropylamine (one molecule of copper oleate ((CH ₃ (CH ₂ ) ₇ CH═CH (CH ₂ ) ₇ COO) ₂ Cu (II))). It can be presumed that (C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ) 2 molecules coordinate to the copper cation (Cu ²⁺ ). As a result, the dimer type copper oleate is converted into an amine complex of two molecules of copper oleate and is dissolved in the solvent dibutylaminopropylamine.

  In Example 3E-1, 6.6 parts by mass of copper oleate is dissolved in 6.6 parts by mass of dibutylaminopropylamine to prepare an amine solution of an amine complex of copper oleate in advance. The composition of the amine solution of the copper oleate amine complex is selected to be 3.36 molecules of dibutylaminopropylamine per molecule of copper oleate.

  In Example 3E-1, 1.0 part by mass of copper oleate is dissolved in 2.0 parts by mass of dibutylaminopropylamine, and an amine solution of an amine complex of copper oleate is prepared in advance. The composition of the amine solution of the copper oleate amine complex is selected to be 3.36 molecules of dibutylaminopropylamine per molecule of copper oleate.

  The aliphatic polyhydric alcohol used as the first organic solvent is 2-ethyl-1,3-hexanediol (molecular weight: 146.23, melting point: −40 ° C., boiling point: 245 ° C.).

  In Example 3E-1 and Example 3E-2, a sintering aid is added.

  The carboxylic acid metal salt used as a sintering aid is bismuth (III) 2-ethylhexanoate. Specifically, bismuth (III) 2-ethylhexanoate / 2-ethylhexanoic acid solution (manufactured by Wako Pure Chemical Industries, bismuth content 25% by mass) is used, and a predetermined amount of bismuth 2-ethylhexanoate (III ) Is added.

  A predetermined amount of a solution obtained by dissolving copper oleate in dibutylaminopropylamine in 80 parts by mass of Mitsui Metals spherical copper powder 1400YM and 20 parts by mass of Mitsui Metals fine copper powder 1020Y, and bismuth 2-ethylhexanoate (III) / 2 -0.48 part by mass of ethylhexanoic acid solution and a predetermined amount of 2-ethyl-1,3-hexanediol are mixed. Thereafter, the mixture is stirred with a stirring deaerator to prepare a copper paste in which the copper powder and the fine copper powder are uniformly dispersed in the liquid phase.

The addition ratio of bismuth atoms to the total surface area of the spherical copper powder and fine copper powder is 0.48 × 0.25 / 209 / [(80 × 1600 + 20 × 26000) / 10000] ≈8.88 μmol / m ² . .

  In Example 3F-1 and Example 3F-2, no sintering aid is added.

  A predetermined amount of a solution obtained by dissolving copper oleate in dibutylaminopropylamine in 80 parts by mass of Mitsui Metals spherical copper powder 1400YM and 20 parts by mass of Mitsui Metals fine copper powder 1020Y, and 2-ethyl-1,3-hexanediol Mix a predetermined amount. Thereafter, the mixture is stirred with a stirring deaerator to prepare a copper paste in which the copper powder and the fine copper powder are uniformly dispersed in the liquid phase.

The prepared copper paste was applied on a slide glass in a pattern of 5 mm × 20 mm. The copper paste coating film was baked by heat treatment at 400 ° C. for 10 minutes in an N ₂ /3% H ₂ atmosphere. The specific volume resistivity was calculated from the measured sheet resistance value assuming that the fired product was a conductor having a uniform average film thickness.

  Table 4 below shows the compositions of the conductive copper pastes of Example 3E-1, Example 3E-2, Example 3F-1, and Example 3F-2. The average film thickness of the copper paste coating film, the average film thickness of the fired product, and the calculated volume specific resistivity are also shown.

  In Example 3E-1, the content ratio of dibutylaminopropylamine with respect to copper oleate and one molecule of bismuth (III) 2-ethylhexanoate is greatly reduced as compared with Example 3-1 described above. Two or more molecules of dibutylaminopropylamine are contained per molecule of copper oleate or bismuth (III) 2-ethylhexanoate. Therefore, similarly to Example 3-1, also in Example 3E-1, similarly to the amine complex of copper oleate, bismuth (III) 2-ethylhexanoate forms an amine complex, and then its reduction proceeds. It is presumed that

Compared with said Example 3-1, in Example 3E-1, the volume of the metal copper atom derived from copper oleate is doubled. Accordingly, V _Cu-metal : V _Bi-metal = 1: 0.32 in Example 3-1, but in this Example 3E-1, V _Cu-metal : V _Bi-metal = 1: 0. It is 16. Further, V _Cu-metal : V _Bi-metal = 1: 0.16 in Example 3E-1 is substantially equal to V _Cu-metal : V _Bi-metal = 1: 0.15 in Example 3-2. equal.

  Compared to the resistivity of metallic copper, 1.673 μΩ · cm (30 ° C.), the resistivity of metallic bismuth, 120 μΩ · cm (20 ° C.), is much larger. However, the change in contact resistance at the contact site due to the addition of bismuth (III) 2-ethylhexanoate is due to “expansion of the contact area” and “alloying metal copper atoms and metal bismuth atoms at the contact sites. Depends on the balance of the two factors of "increased resistivity". Similar to Example 3-2, also in Example 3E-1, the contribution of “expansion of contact area” due to the addition of bismuth (III) 2-ethylhexanoate is relatively large. Compared with -8, the effect of reducing the contact resistance is obtained.

  Even in Example 3E-2, the content ratio of dibutylaminopropylamine with respect to one molecule of copper oleate and bismuth (III) 2-ethylhexanoate is significantly lower than that of Example 3-1 described above. Two or more molecules of dibutylaminopropylamine are contained per molecule of copper oleate or bismuth (III) 2-ethylhexanoate. Therefore, as in Example 3-1, in Example 3E-2, as in the case of the copper oleate complex, bismuth (III) 2-ethylhexanoate forms an amine complex, and then its reduction proceeds. It is presumed that

  Compared to the resistivity of metallic copper, 1.673 μΩ · cm (30 ° C.), the resistivity of metallic bismuth, 120 μΩ · cm (20 ° C.), is much larger. However, the change in contact resistance at the contact site due to the addition of bismuth (III) 2-ethylhexanoate is due to “expansion of the contact area” and “alloying metal copper atoms and metal bismuth atoms at the contact sites. Depends on the balance of the two factors of "increased resistivity". Similar to Example 3-4, also in Example 3E-2, the contribution of “expansion of contact area” due to the addition of bismuth (III) 2-ethylhexanoate was relatively large. Compared with -8, the effect of reducing the contact resistance is obtained.

  In Example 3-8, 6.7 molecules of dibutylaminopropylamine is added per copper oleate molecule, but in Example 3F-1, dibutylaminopropylamine 2. Only 7 molecules are added. As a result, in Example 3-8, 4 molecules of dibutylaminopropylamine are coordinated to the copper atom generated from copper oleate, but in Example 3F-1, it is generated from copper oleate. Only a state where two molecules of dibutylaminopropylamine are coordinated to a copper atom can be achieved. Therefore, in Example 3F-1, a considerable portion of copper atoms generated from copper oleate aggregates in the liquid to form an aggregate, and adheres to the surface of copper powder or fine copper powder. As described above, it is estimated that the amount of copper atoms filled in the narrow gap between the copper powders and the narrow gap between the copper powder and the fine copper powder is significantly reduced as compared with the case of Example 3-8. As a result, in Example 3F-1, it is determined that the effect of reducing contact resistance is rather inferior to that of Example 3-8 described above.

  In Example 3-8, 6.7 molecules of dibutylaminopropylamine are added per 1 molecule of copper oleate, but in Example 3F-1, 6.2 of dibutylaminopropylamine per 1 molecule of copper oleate. Five molecules are added. As a result, in Example 3-8, 4 molecules of dibutylaminopropylamine are coordinated to the copper atom generated from copper oleate, but Example 3F-1 also generates from copper oleate. A state in which four molecules of dibutylaminopropylamine are coordinated to a copper atom is achieved. Therefore, in Example 3F-2, the amount of copper atoms filled in the narrow gap between the copper powders and the narrow gap between the copper powder and the fine copper powder is about ½ of that in Example 3-8. It is estimated that As a result, in Example 3F-2, the effect of reducing contact resistance is low compared to Example 3-8 described above, but the effect of reducing contact resistance is superior compared to Example 3F-1. It is judged that

(Example 4-1)
The conductive copper paste of Example 4-1 is prepared using the following raw materials.

As the copper powder selected in the range of the average particle diameter of ^{2 to} 10 μm, Mitsui Metals' spherical copper powder 1400YM (average particle diameter of 4 μm, BET specific surface area of 1600 cm ² / g) and average particle diameter of 0.2 μm to 1. As the fine copper powder selected in the range of 0 μm, Mitsui Metals fine copper powder 1020Y (average particle diameter 0.4 μm, BET specific surface area 26000 cm ² / g) is used. The ratio of the average particle diameter d _{Cu-fine-powder of the fine} copper powder to the average particle diameter d _Cu-powder of the spherical copper powder (d _{Cu-fine-powder} / d _Cu-powder ) is selected to be 1/10 Has been.

Copper salt of aliphatic monocarboxylic acid ((R—COO) ₂ Cu (II)), copper oleate ((CH ₃ (CH ₂ ) ₇ CH═CH (CH ₂ ) ₇ COO) ₂ Cu (II)) And dissolved in advance in dibutylaminopropylamine ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ , melting point: −50 ° C., boiling point: 238 ° C.), and an amine complex of copper oleate is dissolved. It is formed. The solid copper oleate itself forms a dimer having a Cu: Cu bond. The amine complex of copper oleate formed is composed of dibutylaminopropylamine (one molecule of copper oleate ((CH ₃ (CH ₂ ) ₇ CH═CH (CH ₂ ) ₇ COO) ₂ Cu (II))). It can be presumed that (C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ) 2 molecules coordinate to the copper cation (Cu ²⁺ ). As a result, the dimer type copper oleate is converted into an amine complex of two molecules of copper oleate and is dissolved in the solvent dibutylaminopropylamine. In this Example 4-1, 3.3 parts by mass of copper oleate is dissolved in 6.6 parts by mass of dibutylaminopropylamine, and an amine solution of an amine complex of copper oleate is prepared in advance. The composition of the amine solution of the copper oleate amine complex is selected to be 7 molecules of dibutylaminopropylamine per molecule of copper oleate.

  The aliphatic polyhydric alcohol used as the first organic solvent is 2-ethyl-1,3-hexanediol (molecular weight: 146.23, melting point: −40 ° C., boiling point: 245 ° C.).

  The carboxylic acid metal salt used as a sintering aid is tin (II) 2-ethylhexanoate (manufactured by Wako Pure Chemical Industries, Ltd., molecular weight 405.12).

  A solution prepared by dissolving 3.3 parts by mass of copper oleate in 6.6 parts by mass of dibutylaminopropylamine in 80 parts by mass of Mitsui Metals spherical copper powder 1400YM, 20 parts by mass of Mitsui Metals fine copper powder 1020Y, and 2-ethylhexane 0.23 parts by mass of tin (II) acid and 3 parts by mass of 2-ethyl-1,3-hexanediol are mixed. Thereafter, the mixture is stirred with a stirring deaerator to prepare a copper paste in which the copper powder and the fine copper powder are uniformly dispersed in the liquid phase.

The addition ratio of tin atoms to the total surface area of the spherical copper powder and fine copper powder is 0.23 × 405.12 / [(80 × 1600 + 20 × 26000) / 10000] ≈9 μmol / m ² . Assuming that all the added tin (II) 2-ethylhexanoate is reduced to form metallic tin, the density of metallic copper is 8.95 g / cm ³ (20 ° C.) and the density of metallic tin is 7.265 g / cm. ³ (20 ° C.), the volume V _Sn-metal of metallic tin produced by the reduction of tin (II) 2-ethylhexanoate and the total volume of the spherical copper powder and fine copper powder (V _Cu-powder + V _{(Cu-fine-powder} ) ratio, (V _Cu-powder + V _{Cu-fine-powder} ): V _Sn-metal is calculated as 1210: 1.

In addition, an amine complex of copper oleate ((CH ₃ (CH ₂ ) ₇ CH═CH (CH ₂ ) ₇ COO) ₂ Cu (II)) and tin (II) 2-ethylhexanoate ((CH ₃ (CH _{2) 4} addition ratio between _{CH (C 2 H 5) COO} ) 2 Sn (II)) is an amine complex of oleic acid copper: tin 2-ethylhexanoate (II) is one molecule: and 0.12 molecules Calculated. In the copper paste, 3.75 molecules of 2-ethyl-1,3-hexanediol and 6.25 molecules of dibutylaminopropylamine are present per molecule of copper oleate or tin (II) 2-ethylhexanoate. doing.

  Sum of the number of metallic copper atoms in the spherical copper powder and fine copper powder and the ratio of the number of copper atoms in the copper oleate, (sum of the number of metallic copper atoms in the spherical copper powder and fine copper powder): (oleic acid The number of atoms with copper in the copper is 299: 1 (100: 0.334). Further, 0.013 mol of 2-ethyl-1,3-hexanediol is contained per 1 mol of metallic copper of the spherical copper powder and fine copper powder.

The density 0 · 95g / cm ³ of oleic acid copper (20 ° C.), since the density 0.826 g / cm ³ of dibutylaminopropylamine (20 ° C.), the oleic acid copper amine complex of the amine solution 10g The volume can be estimated as 11.6 cm ³ .

The density of tin (II) 2-ethylhexanoate is 1.251 g / cm ³ (20 ° C.).

  The volume ratio of the said spherical copper powder and fine copper powder in the prepared copper paste is 42.96 volume%.

  Moreover, when all the copper in 3.3 mass parts copper oleate is reduce | restored to a metal copper atom, the sum total of the metal copper atom originating in a copper oleate will be 0.334 mass part. When all the tin in 0.23 parts by mass of tin (2-ethylhexanoate) is reduced to metal tin atoms, the total number of metal tin atoms derived from tin (2-ethylhexanoate) is 0. 0.067 parts by mass. Therefore, the total volume of the metal tin atom derived from tin (II) 2-ethylhexanoate, the metal copper atom derived from copper oleate, the spherical copper powder and the fine copper powder with respect to 100 parts by volume of the copper paste is 43. 14 capacity parts.

  The liquid viscosity of the prepared copper paste was 3 Pa · s (spiral rotational viscometer 10 rpm 25 ° C.).

First, the surface of spherical copper powder and fine copper powder dispersed in the copper paste is solvated with dibutylaminopropylamine or 2-ethyl-1,3-hexanediol contained in the liquid phase. (Adsorption). Dibutylaminopropylamine is coordinated to the metallic copper exposed on the surface by utilizing the lone electron pair of the amino group (—NH ₂ ). On the other hand, a surface oxide film partially exists on the surfaces of the spherical copper powder and the fine copper powder. With respect to the copper oxide corresponding to copper oxide (CuO) constituting the surface oxide film, 2-ethyl-1,3-hexanediol uses the hydroxyl group (> CH—OH), Hydrogen-bonded intermolecular bonding is performed with oxygen atoms (Cu—O—Cu) in the copper oxide. At that time, it is presumed that the reduction of the surface oxide film proceeds via the following two elementary processes.

  When heat treatment is performed in a reducing atmosphere containing hydrogen gas, the hydroxyl group (> CH—OH) of 2-ethyl-1,3-hexanediol reacts with the copper oxide, and the following oxidation / reduction reaction Wake up.

CuO + (> CH—OH) → Cu + (> C═O) + H ₂ O ↑

The reaction product (> C═O) derived from 2-ethyl-1,3-hexanediol is a fine copper powder, a metal copper atom (Cu) exposed on the surface of the copper powder, and its oxo group (> C═O). Coordination can be performed using the π electrons of O). In a reducing atmosphere containing hydrogen gas, a hydrogen molecule (H ₂ ) is added to the oxo group (> C═O) coordinated on the metal copper atom (Cu), so that the original It is possible to convert to a hydroxyl group (> CH—OH).

(> C = O) + H ₂ → (> CH—OH)

  The 2-hydroxy-1,3-hexanediol, in which the original hydroxyl group (> CH—OH) has been regenerated, again becomes an oxygen atom (Cu—O—Cu) in the copper oxide constituting the surface oxide film. ) Can be solvated (adsorbed).

Apparently, the reduction of the surface oxide film proceeds using hydrogen molecules (H ₂ ) supplied from a reducing atmosphere containing hydrogen gas.

On the other hand, in the copper paste, an amine complex of copper oleate ((CH ₃ (CH ₂ ) ₇ CH═CH (CH ₂ ) ₇ COO) ₂ Cu (II): 2 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ )) is dissolved in a mixture of dibutylaminopropylamine and 2-ethyl-1,3-hexanediol. When heat treatment is performed in an N ₂ /3% H ₂ atmosphere in the presence of 2-ethyl-1,3-hexanediol, 2-ethyl-1,3-hexanediol represented by the following reaction formula: Conversion of a hydroxyl group (> CH—OH) to an oxo group (> C═O) and a reduction reaction of the amine complex of copper oleate proceed.

(CH ₃ (CH ₂ ) ₇ CH = CH (CH ₂ ) ₇ COO) ₂ Cu (II): 2 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ) + (> CH-OH)
_{→ 2CH 3 (CH 2) 7} CH = CH (CH 2) 7 COOH + (Cu (0): 2 ((C 4 H 9) 2 N (CH 2) 3 NH 2) + (> C = O)

Further, in the copper paste, tin (II) 2-ethylhexanoate is dissolved in a mixed solution of dibutylaminopropylamine and 2-ethyl-1,3-hexanediol. Therefore, an amine complex ((CH ₃ (CH ₂ ) ₄ CH (C ₂ H ₅ ) COO) of tin (II) 2-ethylhexanoate in which dibutylaminopropylamine is coordinated to tin (II) 2-ethylhexanoate ) ₂ Sn (II): 2 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ )) is presumed to be formed. When heat treatment is performed in an N ₂ /3% H ₂ atmosphere in the presence of 2-ethyl-1,3-hexanediol, 2-ethyl-1,3-hexanediol represented by the following reaction formula: It is presumed that the conversion of the hydroxyl group (> CH—OH) to the oxo group (> C═O) and the reduction reaction of the amine complex of 2-ethylhexanoic acid tin (II) proceed.

(CH ₃ (CH ₂ ) ₄ CH (C ₂ H ₅ ) COO) ₂ Sn (II): 2 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ) + (> CH—OH)
→ 2CH ₃ (CH ₂ ) ₄ CH (C ₂ H ₅ ) COOH + (Sn (0): 2 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ) + (> C═O)

That is, the metal copper atom generated by the reduction of the amine complex of copper oleate has a shape in which two molecules are coordinated with dibutylaminopropylamine as a bidentate ligand. The metal tin atom produced by the reduction of the amine complex of tin (II) 2-ethylhexanoate has a shape in which two molecules are coordinated with dibutylaminopropylamine as a bidentate ligand. Metal copper atom (Cu (0): 2 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ) and metal tin atom (Sn (0): 2 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ) finally forms an aggregate composed of metallic copper atoms and metallic tin atoms with the metallic copper atoms on the surface of the copper powder and fine copper powder as nuclei.

Dibutylaminopropylamine and 2-ethyl-1,3-hexanediol evaporate during the heat treatment in an N ₂ /3% H ₂ atmosphere. As a result, when the volume of the liquid phase decreases (concentration progresses), the liquid phase becomes a narrow gap around the contact area between the fine copper powder and the copper powder, the contact area between the underlayer and the fine copper powder, and the copper powder. The liquid phase is agglomerated in a narrow gap around the periphery. Therefore, as the liquid phase is concentrated, metallic copper atoms (Cu (0): 2 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ) and metallic tin atoms (Sn (0): 2 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ) is a narrow gap around the contact area between the fine copper powder and copper powder, and a narrow gap around the contact area between the underlayer and the fine copper powder, copper powder. Aggregates composed of metallic copper atoms and metallic tin atoms are formed preferentially, so a narrow gap around the contact area between the fine copper powder and the copper powder, around the contact area between the underlayer and the fine copper powder, and the copper powder. The narrow gap is filled with an aggregate composed of the metal copper atoms and metal tin atoms.After the firing, fine copper powder, the periphery of the contact area between the copper powder, the underlayer and the fine copper In the vicinity of the contact area of the powder and copper powder, the aggregation of the metal copper atom and the metal tin atom, and the fine copper powder and copper powder proceed to be integrated. Contact area, ground Fine copper powder, the contact sites of the copper powder, the expansion of the contact area is made.

In addition, by the reduction | restoration of the amine complex of the oleic acid (boiling point: 286 degreeC) and 2-ethylhexanoic acid tin (II) byproduced by the reduction | restoration of the amine complex of copper oleate, 2 byproduced -Ethylhexanoic acid (boiling point: 228 ° C) is once dissolved in the dispersion solvent 2-ethyl-1,3-hexanediol. Thereafter, when heat treatment is performed in an N ₂ /3% H ₂ atmosphere, oleic acid and 2-ethylhexanoic acid are gradually evaporated in the same manner as the dispersion solvent 2-ethyl-1,3-hexanediol. .

In addition, dibutylaminopropylamine is initially coordinated to the copper metal exposed on the surfaces of copper powder and fine copper powder by utilizing the lone pair of amino groups (—NH ₂ ). Have a strong bond. Since the boiling point of dibutylaminopropylamine is lower than that of the dispersion solvent 2-ethyl-1,3-hexanediol, the evaporation rate of dibutylaminopropylamine is relatively fast. As a result, the concentration of dibutylaminopropylamine in the liquid phase is reduced, and the coordinative bonding of dibutylaminopropylamine with metal copper exposed on the surface of copper powder and fine copper powder is reduced. The withdrawal is promoted. Finally, in the contact area between the fine copper powder and the copper powder, when the metal copper exposed on the surface is in direct contact, the sintering proceeds.
The prepared copper paste was applied on a slide glass in a pattern of 5 mm × 20 mm. The average thickness of the copper paste coating film was 55 μm. The copper paste coating film was baked by heat treatment at 400 ° C. for 10 minutes in an N ₂ /3% H ₂ atmosphere.

  The average film thickness of the obtained fired product was 43 μm. The volume resistivity was calculated from the measured sheet resistance value, assuming that the fired product was a conductor having a uniform average film thickness. The calculated volume resistivity was 11 μΩ · cm.

  The volume specific resistivity 11 μΩ · cm of the obtained fired product is 5.8 times that of the resistivity of metallic copper 1.673 μΩ · cm (30 ° C.).

  Compared to the resistivity of metallic copper, 1.673 μΩ · cm (30 ° C.), the resistivity of metallic tin, 11 μΩ · cm (20 ° C.), is about seven times larger, but the resistivity of metal bismuth is 120 μΩ · cm (20 ° C. ) And about 1/10. The change in contact resistance at the contact site caused by the addition of tin (II) 2-ethylhexanoate is “expansion of contact area” and “resistivity due to alloying of metal copper atoms and metal tin atoms at the contact sites”. Depends on the balance of the two factors. In Example 4-1, the contribution of “expansion of contact area” due to the addition of tin (II) 2-ethylhexanoate is relatively large, and compared with Example 3-8 described above, the contact resistance Reduction effect is obtained.

(Example 5-1) to (Example 5-10)
The conductive copper pastes of Example 5-1 to Example 5-10 are prepared using the following raw materials.

As the copper powder selected in the range of the average particle diameter of ^{2 to} 10 μm, Mitsui Metals' spherical copper powder 1400YM (average particle diameter of 4 μm, BET specific surface area of 1600 cm ² / g) and average particle diameter of 0.2 μm to 1. As the fine copper powder selected in the range of 0 μm, Mitsui Metals fine copper powder 1020Y (average particle diameter 0.4 μm, BET specific surface area 26000 cm ² / g) is used. The ratio of the average particle diameter d _{Cu-fine-powder of the fine} copper powder to the average particle diameter d _Cu-powder of the spherical copper powder (d _{Cu-fine-powder} / d _Cu-powder ) is selected to be 1/10 Has been.

Copper salt of aliphatic monocarboxylic acid ((R—COO) ₂ Cu (II)), copper oleate ((CH ₃ (CH ₂ ) ₇ CH═CH (CH ₂ ) ₇ COO) ₂ Cu (II)) And dissolved in advance in dibutylaminopropylamine ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ , melting point: −50 ° C., boiling point: 238 ° C.), and an amine complex of copper oleate is dissolved. It is formed. The solid copper oleate itself forms a dimer having a Cu: Cu bond. The amine complex of copper oleate formed is composed of dibutylaminopropylamine (one molecule of copper oleate ((CH ₃ (CH ₂ ) ₇ CH═CH (CH ₂ ) ₇ COO) ₂ Cu (II))). It can be presumed that (C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ) 2 molecules coordinate to the copper cation (Cu ²⁺ ). As a result, the dimer type copper oleate is converted into an amine complex of two molecules of copper oleate and is dissolved in the solvent dibutylaminopropylamine. In Example 5-1 to Example 5-10, 3.3 parts by mass of copper oleate was dissolved in 6.6 parts by mass of dibutylaminopropylamine, and an amine solution of an amine complex of copper oleate was prepared in advance. Yes. The composition of the amine solution of the copper oleate amine complex is selected to be 7 molecules of dibutylaminopropylamine per molecule of copper oleate.

As the first organic solvent, instead of 2-ethyl-1,3-hexanediol (molecular weight: 146.23, melting point: -40 ° C, boiling point: 245 ° C), a solvent having the following alcoholic hydroxyl group is used. doing.
(Example 5-1)
1,2-hexanediol (molecular weight 118.17, melting point: -25 ° C, boiling point 223 ° C),
(Example 5-2)
1,3-butanediol (molecular weight 90.12, melting point: <-50 ° C, boiling point 208 ° C),
(Example 5-3)
1,4-butanediol (molecular weight 90.12, melting point: 20.1 ° C., boiling point 235 ° C.),
(Example 5-4)
1-decanol (molecular weight 158.3, melting point: 6.4 ° C., boiling point 232.9 ° C.),
(Example 5-5)
Triethylene glycol monobutyl ether (TEGBE, molecular weight 206.08, melting point -48 ° C, boiling point 271 ° C)
(Example 5-6)
Glycerin (1,2,3-propanetriol, molecular weight 92.10, melting point 18.07 ° C., boiling point 290.5 ° C.),
(Example 5-7)
1,2,6-hexanetriol (molecular weight 134.17, melting point 25 ° C., boiling point 220 ° C.),
(Example 5-8)
Dipropylene glycol monobutyl ether (molecular weight 190.29, boiling point 231 ° C.)
(Example 5-9)
Tripropylene glycol (molecular weight 192, boiling point 268 ° C)
(Example 5-10)
Tripropylene glycol monomethyl ether (molecular weight 206.3, boiling point 242 ° C)
No sintering aid is added.

  A solution prepared by dissolving 3.3 parts by mass of copper oleate in 6.6 parts by mass of dibutylaminopropylamine in 80 parts by mass of Mitsui Metals spherical copper powder 1400YM, 20 parts by mass of Mitsui Metals fine copper powder 1020Y, and the above various solvents Mix 3 parts by weight. Thereafter, the mixture is stirred with a stirring deaerator to prepare a copper paste in which the copper powder and the fine copper powder are uniformly dispersed in the liquid phase.

  Sum of the number of metallic copper atoms in the spherical copper powder and fine copper powder and the ratio of the number of copper atoms in the copper oleate, (sum of the number of metallic copper atoms in the spherical copper powder and fine copper powder): (oleic acid The number of atoms with copper in the copper is 299: 1 (100: 0.334).

The prepared copper paste was applied on a slide glass in a pattern of 5 mm × 20 mm. The copper paste coating film was baked by heat treatment at 400 ° C. for 10 minutes in an N ₂ /3% H ₂ atmosphere. The specific volume resistivity was calculated from the measured sheet resistance value assuming that the fired product was a conductor having a uniform average film thickness.

  Tables 5-1 to 5-3 below show the compositions of the conductive copper pastes of Examples 5-1 to 5-10. The average film thickness of the copper paste coating film, the average film thickness of the fired product, and the calculated volume specific resistivity are also shown.

In Example 5-1, transpiration of dibutylaminopropylamine and 1,2-hexanediol also proceeds during heat treatment in an N ₂ /3% H ₂ atmosphere. As a result, when the volume of the liquid phase decreases (concentration progresses), the liquid phase becomes a narrow gap around the contact area between the fine copper powder and the copper powder, the contact area between the underlayer and the fine copper powder, and the copper powder. The liquid phase is agglomerated in a narrow gap around the periphery. Therefore, along with the concentration of the liquid phase, the metal copper atom (Cu (0): 4 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ )) coordinated with a total of 4 molecules of dibutylaminopropylamine is Aggregates of metallic copper atoms are preferentially formed in a narrow gap around the contact area between the fine copper powder and the copper powder, and a narrow gap around the contact area between the underlayer and the fine copper powder and the copper powder. The narrow gap around the contact area between the fine copper powder and the copper powder, the narrow gap around the contact area between the underlayer and the fine copper powder, and the copper powder are embedded with the aggregate of the metal copper atoms. Then, when the firing proceeds, the fine copper powder, around the copper powder contact area, around the base layer and the fine copper powder, around the copper powder contact area, the aggregate of the metal copper atoms, the fine copper powder, As a result, the contact area of the fine copper powder, the contact area between the copper powders, the contact area between the underlayer and the fine copper powder, and the copper powder is increased. Is expanded.

As the copper oleate amine complex is reduced, oleic acid (boiling point: 286 ° C.) produced as a by-product is once dissolved in 1,2-hexanediol as the first organic solvent. Thereafter, when heat treatment is performed in an N ₂ /3% H ₂ atmosphere, the oleic acid is gradually evaporated in the same manner as the first organic solvent 1,2-hexanediol.

In addition, dibutylaminopropylamine is initially coordinated to the copper metal exposed on the surfaces of copper powder and fine copper powder by utilizing the lone pair of amino groups (—NH ₂ ). Have a strong bond. The boiling point (238 ° C.) of dibutylaminopropylamine is slightly higher than the boiling point (223 ° C.) of 1,2-hexanediol as a dispersion solvent. Since the difference in boiling point is slight, there is no significant difference in the evaporation rate between dibutylaminopropylamine and 1,2-hexanediol. Therefore, dibutylaminopropylamine, which is coordinated to the copper metal exposed on the surface of copper powder and fine copper powder, elutes into the liquid phase and evaporates, so that it can be detached. Made. Finally, when the copper metal exposed to the surface comes into direct contact with the fine copper powder and the copper powder, the sintering proceeds.

In Example 5-2, transpiration of dibutylaminopropylamine and 1,3-butanediol also proceeds during the heat treatment in an N ₂ /3% H ₂ atmosphere. As a result, when the volume of the liquid phase decreases (concentration progresses), the liquid phase becomes a narrow gap around the contact area between the fine copper powder and the copper powder, the contact area between the underlayer and the fine copper powder, and the copper powder. The liquid phase is agglomerated in a narrow gap around the periphery. Therefore, along with the concentration of the liquid phase, the metal copper atom (Cu (0): 4 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ )) coordinated with a total of 4 molecules of dibutylaminopropylamine is Aggregates of metallic copper atoms are preferentially formed in a narrow gap around the contact area between the fine copper powder and the copper powder, and a narrow gap around the contact area between the underlayer and the fine copper powder and the copper powder. The narrow gap around the contact area between the fine copper powder and the copper powder, the narrow gap around the contact area between the underlayer and the fine copper powder, and the copper powder are embedded with the aggregate of the metal copper atoms. Then, when the firing proceeds, the fine copper powder, around the copper powder contact area, around the base layer and the fine copper powder, around the copper powder contact area, the aggregate of the metal copper atoms, the fine copper powder, As a result, the contact area of the fine copper powder, the contact area between the copper powders, the contact area between the underlayer and the fine copper powder, and the copper powder is increased. Is expanded.

The oleic acid (boiling point: 286 ° C.) produced as a by-product with the reduction of the amine complex of copper oleate is once dissolved in 1,3-butanediol as the first organic solvent. Thereafter, when heat treatment is performed in an N ₂ /3% H ₂ atmosphere, the oleic acid is gradually evaporated in the same manner as the first organic solvent 1,3-butanediol.

In addition, dibutylaminopropylamine is initially coordinated to the copper metal exposed on the surfaces of copper powder and fine copper powder by utilizing the lone pair of amino groups (—NH ₂ ). Have a strong bond. The boiling point (238 ° C.) of dibutylaminopropylamine is higher than the boiling point (208 ° C.) of 1,3-butanediol as the first organic solvent. Since the difference in boiling point is not so large, there is no significant difference in the evaporation rate between dibutylaminopropylamine and 1,3-butanediol. Therefore, dibutylaminopropylamine, which is coordinated to the copper metal exposed on the surface of copper powder and fine copper powder, elutes into the liquid phase and evaporates, so that it can be detached. Made. Finally, when the copper metal exposed to the surface comes into direct contact with the fine copper powder and the copper powder, the sintering proceeds.

In Example 5-3, transpiration of dibutylaminopropylamine and 1,4-butanediol also proceeds during heat treatment in an N ₂ /3% H ₂ atmosphere. As a result, when the volume of the liquid phase decreases (concentration progresses), the liquid phase becomes a narrow gap around the contact area between the fine copper powder and the copper powder, the contact area between the underlayer and the fine copper powder, and the copper powder. The liquid phase is agglomerated in a narrow gap around the periphery. Therefore, along with the concentration of the liquid phase, the metal copper atom (Cu (0): 4 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ )) coordinated with a total of 4 molecules of dibutylaminopropylamine is Aggregates of metallic copper atoms are preferentially formed in a narrow gap around the contact area between the fine copper powder and the copper powder, and a narrow gap around the contact area between the underlayer and the fine copper powder and the copper powder. The narrow gap around the contact area between the fine copper powder and the copper powder, the narrow gap around the contact area between the underlayer and the fine copper powder, and the copper powder are embedded with the aggregate of the metal copper atoms. Then, when the firing proceeds, the fine copper powder, around the copper powder contact area, around the base layer and the fine copper powder, around the copper powder contact area, the aggregate of the metal copper atoms, the fine copper powder, As a result, the contact area of the fine copper powder, the contact area between the copper powders, the contact area between the underlayer and the fine copper powder, and the copper powder is increased. Is expanded.

The oleic acid (boiling point: 286 ° C.) produced as a by-product with the reduction of the copper oleate complex is once dissolved in 1,4-butanediol as the first organic solvent. Thereafter, when heat treatment is performed in an N ₂ /3% H ₂ atmosphere, oleic acid is gradually evaporated in the same manner as 1,4-butanediol as the first organic solvent.

In addition, dibutylaminopropylamine is initially coordinated to the copper metal exposed on the surfaces of copper powder and fine copper powder by utilizing the lone pair of amino groups (—NH ₂ ). Have a strong bond. The boiling point of dibutylaminopropylamine (238 ° C.) is slightly higher than the boiling point of 1,4-butanediol (235 ° C.) of the first organic solvent. Since the difference in boiling point is small, there is no significant difference in the transpiration rate between dibutylaminopropylamine and 1,4-butanediol. Therefore, dibutylaminopropylamine, which is coordinated to the copper metal exposed on the surface of copper powder and fine copper powder, elutes into the liquid phase and evaporates, so that it can be detached. Made. Finally, when the copper metal exposed to the surface comes into direct contact with the fine copper powder and the copper powder, the sintering proceeds.

In Example 5-4, transpiration of dibutylaminopropylamine and 1-decanol also proceeds during heat treatment in an N ₂ /3% H ₂ atmosphere. As a result, when the volume of the liquid phase decreases (concentration progresses), the liquid phase becomes a narrow gap around the contact area between the fine copper powder and the copper powder, the contact area between the underlayer and the fine copper powder, and the copper powder. The liquid phase is agglomerated in a narrow gap around the periphery. Therefore, along with the concentration of the liquid phase, the metal copper atom (Cu (0): 4 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ )) coordinated with a total of 4 molecules of dibutylaminopropylamine is Aggregates of metallic copper atoms are preferentially formed in a narrow gap around the contact area between the fine copper powder and the copper powder, and a narrow gap around the contact area between the underlayer and the fine copper powder and the copper powder. The narrow gap around the contact area between the fine copper powder and the copper powder, the narrow gap around the contact area between the underlayer and the fine copper powder, and the copper powder are embedded with the aggregate of the metal copper atoms. Then, when the firing proceeds, the fine copper powder, around the copper powder contact area, around the base layer and the fine copper powder, around the copper powder contact area, the aggregate of the metal copper atoms, the fine copper powder, As a result, the contact area of the fine copper powder, the contact area between the copper powders, the contact area between the underlayer and the fine copper powder, and the copper powder is increased. Is expanded.

In addition, with the reduction | restoration of the amine complex of copper oleate, the oleic acid (boiling point: 286 degreeC) byproduced once melt | dissolves in 1-decanol of a 1st organic solvent. Thereafter, when heat treatment is performed in an N ₂ /3% H ₂ atmosphere, oleic acid is gradually evaporated in the same manner as 1-decanol as the first organic solvent.

In addition, dibutylaminopropylamine is initially coordinated to the copper metal exposed on the surfaces of copper powder and fine copper powder by utilizing the lone pair of amino groups (—NH ₂ ). Have a strong bond. The boiling point of dibutylaminopropylamine (238 ° C.) is slightly higher than the boiling point of 1-decanol (232.9 ° C.) of the first organic solvent. Since the difference in boiling point is not large, there is no significant difference in the transpiration rate between dibutylaminopropylamine and 1-decanol. Therefore, dibutylaminopropylamine, which is coordinated to the copper metal exposed on the surface of copper powder and fine copper powder, elutes into the liquid phase and evaporates, so that it can be detached. Made. Finally, when the copper metal exposed to the surface comes into direct contact with the fine copper powder and the copper powder, the sintering proceeds.

In Example 5-5, transpiration of dibutylaminopropylamine and TEGBE proceeds during the heat treatment in an N ₂ /3% H ₂ atmosphere. As a result, when the volume of the liquid phase decreases (concentration progresses), the liquid phase becomes a narrow gap around the contact area between the fine copper powder and the copper powder, the contact area between the underlayer and the fine copper powder, and the copper powder. The liquid phase is agglomerated in a narrow gap around the periphery. Therefore, along with the concentration of the liquid phase, the metal copper atom (Cu (0): 4 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ )) coordinated with a total of 4 molecules of dibutylaminopropylamine is Aggregates of metallic copper atoms are preferentially formed in a narrow gap around the contact area between the fine copper powder and the copper powder, and a narrow gap around the contact area between the underlayer and the fine copper powder and the copper powder. The narrow gap around the contact area between the fine copper powder and the copper powder, the narrow gap around the contact area between the underlayer and the fine copper powder, and the copper powder are embedded with the aggregate of the metal copper atoms. Then, when the firing proceeds, the fine copper powder, around the copper powder contact area, around the base layer and the fine copper powder, around the copper powder contact area, the aggregate of the metal copper atoms, the fine copper powder, As a result, the contact area of the fine copper powder, the contact area between the copper powders, the contact area between the underlayer and the fine copper powder, and the copper powder is increased. Is expanded.

The oleic acid (boiling point: 286 ° C.) produced as a by-product with the reduction of the amine complex of copper oleate is once dissolved in TEGBE as the first organic solvent. Thereafter, when heat treatment is performed in an N ₂ /3% H ₂ atmosphere, the oleic acid is gradually evaporated in the same manner as the first organic solvent TEGBE.

In addition, dibutylaminopropylamine is initially coordinated to the copper metal exposed on the surfaces of copper powder and fine copper powder by utilizing the lone pair of amino groups (—NH ₂ ). Have a strong bond. Since the boiling point of dibutylaminopropylamine (238 ° C.) is significantly lower than that of the first organic solvent TEGBE (271 ° C.), the evaporation rate of dibutylaminopropylamine is relatively fast. As a result, the concentration of dibutylaminopropylamine in the liquid phase is reduced, and the coordinative bonding of dibutylaminopropylamine with metal copper exposed on the surface of copper powder and fine copper powder is reduced. The withdrawal is promoted. Finally, when the copper metal exposed to the surface comes into direct contact with the fine copper powder and the copper powder, the sintering proceeds.

In Example 5-6, transpiration of dibutylaminopropylamine and glycerin also proceeds during heat treatment in an N ₂ /3% H ₂ atmosphere. As a result, when the volume of the liquid phase decreases (concentration progresses), the liquid phase becomes a narrow gap around the contact area between the fine copper powder and the copper powder, the contact area between the underlayer and the fine copper powder, and the copper powder. The liquid phase is agglomerated in a narrow gap around the periphery. Therefore, along with the concentration of the liquid phase, the metal copper atom (Cu (0): 4 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ )) coordinated with a total of 4 molecules of dibutylaminopropylamine is Aggregates of metallic copper atoms are preferentially formed in a narrow gap around the contact area between the fine copper powder and the copper powder, and a narrow gap around the contact area between the underlayer and the fine copper powder and the copper powder. The narrow gap around the contact area between the fine copper powder and the copper powder, the narrow gap around the contact area between the underlayer and the fine copper powder, and the copper powder are embedded with the aggregate of the metal copper atoms. Then, when the firing proceeds, the fine copper powder, around the copper powder contact area, around the base layer and the fine copper powder, around the copper powder contact area, the aggregate of the metal copper atoms, the fine copper powder, As a result, the contact area of the fine copper powder, the contact area between the copper powders, the contact area between the underlayer and the fine copper powder, and the copper powder is increased. Is expanded.

The oleic acid (boiling point: 286 ° C.) produced as a by-product with the reduction of the amine complex of copper oleate is once dissolved in glycerin as the first organic solvent. Thereafter, when the heat treatment is performed in an N ₂ /3% H ₂ atmosphere, the oleic acid is gradually evaporated like the first organic solvent glycerin.

In addition, dibutylaminopropylamine is initially coordinated to the copper metal exposed on the surfaces of copper powder and fine copper powder by utilizing the lone pair of amino groups (—NH ₂ ). Have a strong bond. Since the boiling point of dibutylaminopropylamine (238 ° C.) is significantly lower than that of the first organic solvent glycerol (290.5 ° C.), the evaporation rate of dibutylaminopropylamine is relatively fast. As a result, the concentration of dibutylaminopropylamine in the liquid phase is reduced, and the coordinative bonding of dibutylaminopropylamine with metal copper exposed on the surface of copper powder and fine copper powder is reduced. The withdrawal is promoted. Finally, when the copper metal exposed to the surface comes into direct contact with the fine copper powder and the copper powder, the sintering proceeds.

In Example 5-7, transpiration of dibutylaminopropylamine and 1,2,6-hexanetriol also proceeds during the heat treatment in an N ₂ /3% H ₂ atmosphere. As a result, when the volume of the liquid phase decreases (concentration progresses), the liquid phase becomes a narrow gap around the contact area between the fine copper powder and the copper powder, the contact area between the underlayer and the fine copper powder, and the copper powder. The liquid phase is agglomerated in a narrow gap around the periphery. Therefore, along with the concentration of the liquid phase, the metal copper atom (Cu (0): 4 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ )) coordinated with a total of 4 molecules of dibutylaminopropylamine is Aggregates of metallic copper atoms are preferentially formed in a narrow gap around the contact area between the fine copper powder and the copper powder, and a narrow gap around the contact area between the underlayer and the fine copper powder and the copper powder. The narrow gap around the contact area between the fine copper powder and the copper powder, the narrow gap around the contact area between the underlayer and the fine copper powder, and the copper powder are embedded with the aggregate of the metal copper atoms. Then, when the firing proceeds, the fine copper powder, around the copper powder contact area, around the base layer and the fine copper powder, around the copper powder contact area, the aggregate of the metal copper atoms, the fine copper powder, As a result, the contact area of the fine copper powder, the contact area between the copper powders, the contact area between the underlayer and the fine copper powder, and the copper powder is increased. Is expanded.

The oleic acid (boiling point: 286 ° C.) produced as a by-product with the reduction of the copper oleate complex is once dissolved in the first organic solvent 1,2,6-hexanetriol. Thereafter, when heat treatment is performed in an N ₂ /3% H ₂ atmosphere, oleic acid is gradually evaporated in the same manner as the first organic solvent dispersion solvent 1,2,6-hexanetriol.

In addition, dibutylaminopropylamine is initially coordinated to the copper metal exposed on the surfaces of copper powder and fine copper powder by utilizing the lone pair of amino groups (—NH ₂ ). Have a strong bond. The boiling point (238 ° C.) of dibutylaminopropylamine is slightly higher than the boiling point (220 ° C.) of 1,2,6-hexanetriol as the first organic solvent. Since the difference in boiling point is not so large, there is no significant difference in the evaporation rate between dibutylaminopropylamine and 1,2,6-hexanetriol. Therefore, dibutylaminopropylamine, which is coordinated to the copper metal exposed on the surface of copper powder and fine copper powder, elutes into the liquid phase and evaporates, so that it can be detached. Made. Finally, when the copper metal exposed to the surface comes into direct contact with the fine copper powder and the copper powder, the sintering proceeds.

In Example 5-8, transpiration of dibutylaminopropylamine and dipropylene glycol monobutyl ether also proceeds during heat treatment in an N ₂ /3% H ₂ atmosphere. As a result, when the volume of the liquid phase decreases (concentration progresses), the liquid phase becomes a narrow gap around the contact area between the fine copper powder and the copper powder, the contact area between the underlayer and the fine copper powder, and the copper powder. The liquid phase is agglomerated in a narrow gap around the periphery. Therefore, as the liquid phase is concentrated, the metal copper atom (Cu (0): 4 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ )) coordinated with 4 molecules of dibutylaminopropylamine is Aggregates of copper metal atoms are preferentially formed in the narrow gaps around the contact areas between the fine copper powder and the copper powder, and the narrow gaps around the contact areas between the underlayer and the fine copper powder and the copper powder. A narrow gap around the contact area between the fine copper powder and the copper powder, and a narrow gap around the contact area between the underlayer and the fine copper powder and the copper powder are filled with the aggregate of the metal copper atoms. Then, when firing proceeds, the fine copper powder, around the copper powder contact area, around the base layer and the fine copper powder, around the copper powder contact area, the aggregate of metal copper atoms, fine copper powder, copper As a result, the contact area between the fine copper powder and the contact area between the copper powder and the contact area between the ground layer and the fine copper powder and the copper powder is increased. Big is done.

The oleic acid (boiling point: 286 ° C.) produced as a by-product with the reduction of the copper oleate complex is once dissolved in dipropylene glycol monobutyl ether as the first organic solvent. Thereafter, when heat treatment is performed in an N ₂ /3% H ₂ atmosphere, oleic acid is gradually evaporated in the same manner as the first organic solvent dipropylene glycol monobutyl ether.

In addition, dibutylaminopropylamine is initially coordinated to the copper metal exposed on the surfaces of copper powder and fine copper powder by utilizing the lone pair of amino groups (—NH ₂ ). Have a strong bond. Since the boiling point (238 ° C.) of dibutylaminopropylamine is about the same as the boiling point (231 ° C.) of dipropylene glycol monobutyl ether as the first organic solvent, the evaporation rate of dibutylaminopropylamine is also about the same. As a result, the concentration of dibutylaminopropylamine in the liquid phase is reduced, and the coordinative bonding of dibutylaminopropylamine with metal copper exposed on the surface of copper powder and fine copper powder is reduced. The withdrawal is promoted. Finally, when the copper metal exposed to the surface comes into direct contact with the fine copper powder and the copper powder, the sintering proceeds.

In Example 5-9, transpiration of dibutylaminopropylamine and tripropylene glycol also proceeds during the heat treatment in an N ₂ /3% H ₂ atmosphere. As a result, when the volume of the liquid phase decreases (concentration progresses), the liquid phase becomes a narrow gap around the contact area between the fine copper powder and the copper powder, the contact area between the underlayer and the fine copper powder, and the copper powder. The liquid phase is agglomerated in a narrow gap around the periphery. Therefore, as the liquid phase is concentrated, the metal copper atom (Cu (0): 4 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ )) coordinated with 4 molecules of dibutylaminopropylamine is Aggregates of copper metal atoms are preferentially formed in the narrow gaps around the contact areas between the fine copper powder and the copper powder, and the narrow gaps around the contact areas between the underlayer and the fine copper powder and the copper powder. A narrow gap around the contact area between the fine copper powder and the copper powder, and a narrow gap around the contact area between the underlayer and the fine copper powder and the copper powder are filled with the aggregate of the metal copper atoms. Then, when firing proceeds, the fine copper powder, around the copper powder contact area, around the base layer and the fine copper powder, around the copper powder contact area, the aggregate of metal copper atoms, fine copper powder, copper As a result, the contact area between the fine copper powder and the contact area between the copper powder and the contact area between the ground layer and the fine copper powder and the copper powder is increased. Big is done.

The oleic acid (boiling point: 286 ° C.) produced as a by-product with the reduction of the copper oleate complex is once dissolved in tripropylene glycol as the first organic solvent. Thereafter, when the heat treatment is performed in an N ₂ /3% H ₂ atmosphere, the oleic acid is gradually evaporated in the same manner as the first organic solvent tripropylene glycol.

In addition, dibutylaminopropylamine is initially coordinated to the copper metal exposed on the surfaces of copper powder and fine copper powder by utilizing the lone pair of amino groups (—NH ₂ ). Have a strong bond. Since the boiling point of dibutylaminopropylamine (238 ° C.) is significantly lower than that of the first organic solvent tripropylene glycol (268 ° C.), the evaporation rate of dibutylaminopropylamine is relatively fast. As a result, the concentration of dibutylaminopropylamine in the liquid phase is reduced, and the coordinative bonding of dibutylaminopropylamine with metal copper exposed on the surface of copper powder and fine copper powder is reduced. The withdrawal is promoted. Finally, when the copper metal exposed to the surface comes into direct contact with the fine copper powder and the copper powder, the sintering proceeds.

In Example 5-10, transpiration of dibutylaminopropylamine and tripropylene glycol monomethyl ether also proceeds during heat treatment in an N ₂ /3% H ₂ atmosphere. As a result, when the volume of the liquid phase decreases (concentration progresses), the liquid phase becomes a narrow gap around the contact area between the fine copper powder and the copper powder, the contact area between the underlayer and the fine copper powder, and the copper powder. The liquid phase is agglomerated in a narrow gap around the periphery. Therefore, as the liquid phase is concentrated, the metal copper atom (Cu (0): 4 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ )) coordinated with 4 molecules of dibutylaminopropylamine is Aggregates of copper metal atoms are preferentially formed in the narrow gaps around the contact areas between the fine copper powder and the copper powder, and the narrow gaps around the contact areas between the underlayer and the fine copper powder and the copper powder. A narrow gap around the contact area between the fine copper powder and the copper powder, and a narrow gap around the contact area between the underlayer and the fine copper powder and the copper powder are filled with the aggregate of the metal copper atoms. Then, when firing proceeds, the fine copper powder, around the copper powder contact area, around the base layer and the fine copper powder, around the copper powder contact area, the aggregate of metal copper atoms, fine copper powder, copper As a result, the contact area between the fine copper powder and the contact area between the copper powder and the contact area between the ground layer and the fine copper powder and the copper powder is increased. Big is done.

In addition, oleic acid (boiling point: 286 ° C.) produced as a by-product with the reduction of the amine complex of copper oleate is once dissolved in tripropylene glycol monomethyl ether as the first organic solvent. Thereafter, when heat treatment is performed in an N ₂ /3% H ₂ atmosphere, oleic acid is gradually evaporated in the same manner as the first organic solvent tripropylene glycol monomethyl ether.

In addition, dibutylaminopropylamine is initially coordinated to the copper metal exposed on the surfaces of copper powder and fine copper powder by utilizing the lone pair of amino groups (—NH ₂ ). Have a strong bond. Since the boiling point (238 ° C.) of dibutylaminopropylamine is about the same as the boiling point (242 ° C.) of tripropylene glycol monomethyl ether as the first organic solvent, the evaporation rate of dibutylaminopropylamine is also about the same. As a result, the concentration of dibutylaminopropylamine in the liquid phase is reduced, and the coordinative bonding of dibutylaminopropylamine with metal copper exposed on the surface of copper powder and fine copper powder is reduced. The withdrawal is promoted. Finally, when the copper metal exposed to the surface comes into direct contact with the fine copper powder and the copper powder, the sintering proceeds.

(Reference Example 1)
The conductive copper paste of Reference Example 1 is prepared using the following raw materials.

As the copper powder selected in the range of the average particle diameter of ^{2 to} 10 μm, Mitsui Metals' spherical copper powder 1400YM (average particle diameter of 4 μm, BET specific surface area of 1600 cm ² / g) and average particle diameter of 0.2 μm to 1. As the fine copper powder selected in the range of 0 μm, Mitsui Metals fine copper powder 1020Y (average particle diameter 0.4 μm, BET specific surface area 26000 cm ² / g) is used. The ratio of the average particle diameter d _{Cu-fine-powder of the fine} copper powder to the average particle diameter d _Cu-powder of the spherical copper powder (d _{Cu-fine-powder} / d _Cu-powder ) is selected to be 1/10 Has been.

Copper salt of aliphatic monocarboxylic acid ((R—COO) ₂ Cu (II)), copper oleate ((CH ₃ (CH ₂ ) ₇ CH═CH (CH ₂ ) ₇ COO) ₂ Cu (II)) And dissolved in advance in dibutylaminopropylamine ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ , melting point: −50 ° C., boiling point: 238 ° C.), and an amine complex of copper oleate is dissolved. It is formed. The solid copper oleate itself forms a dimer having a Cu: Cu bond. The amine complex of copper oleate formed is composed of dibutylaminopropylamine (one molecule of copper oleate ((CH ₃ (CH ₂ ) ₇ CH═CH (CH ₂ ) ₇ COO) ₂ Cu (II))). It can be presumed that (C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ) 2 molecules coordinate to the copper cation (Cu ²⁺ ). As a result, the dimer type copper oleate is converted into an amine complex of two molecules of copper oleate and is dissolved in the solvent dibutylaminopropylamine. In Reference Example 1, 3.3 parts by mass of copper oleate is dissolved in 6.6 parts by mass of dibutylaminopropylamine, and an amine solution of an amine complex of copper oleate is prepared in advance. The composition of the amine solution of the copper oleate amine complex is selected to be 7 molecules of dibutylaminopropylamine per molecule of copper oleate.

  The aliphatic polyhydric alcohol used as a dispersion solvent is 1,2-butanediol (molecular weight 90.12, melting point: −50 ° C., boiling point 195 to 196.9 ° C.).

  No sintering aid is added.

  A solution prepared by dissolving 3.3 parts by mass of copper oleate in 6.6 parts by mass of dibutylaminopropylamine in 80 parts by mass of Mitsui Metals spherical copper powder 1400YM, 20 parts by mass of Mitsui Metals fine copper powder 1020Y; 3 parts by weight of butanediol are mixed. Thereafter, the mixture is stirred with a stirring deaerator to prepare a copper paste in which the copper powder and the fine copper powder are uniformly dispersed in the liquid phase.

  Sum of the number of metallic copper atoms in the spherical copper powder and fine copper powder and the ratio of the number of copper atoms in the copper oleate, (sum of the number of metallic copper atoms in the spherical copper powder and fine copper powder): (oleic acid The number of atoms with copper in the copper is 299: 1 (100: 0.334). Moreover, 0.021 mol of 1,2-butanediol is contained per 1 mol of metallic copper of spherical copper powder and fine copper powder.

  The volume ratio of the spherical copper powder to the fine copper powder in the prepared copper paste is 43.61% by volume.

  Moreover, when all the copper in 3.3 mass parts copper oleate is reduce | restored to a metal copper atom, the sum total of the metal copper atom originating in a copper oleate will be 0.34 mass part. Accordingly, the total volume of metallic copper atoms, spherical copper powder and fine copper powder derived from copper oleate with respect to 100 parts by volume of the prepared copper paste is 43.76 parts by volume.

  The liquid viscosity of the prepared copper paste was 3 Pa · s (spiral rotational viscometer 10 rpm 25 ° C.).

First, the surface of spherical copper powder and fine copper powder dispersed in the copper paste is solvated (adsorbed) with dibutylaminopropylamine or 1,2-butanediol contained in the liquid phase. ing. Dibutylaminopropylamine is coordinated to the metallic copper exposed on the surface by utilizing the lone electron pair of the amino group (—NH ₂ ). On the other hand, a surface oxide film partially exists on the surfaces of the spherical copper powder and the fine copper powder. With respect to the copper oxide corresponding to copper oxide (CuO) constituting the surface oxide film, 1,2-butanediol utilizes its hydroxyl group (> CH—OH), The hydrogen bond type intermolecular bond is performed with the oxygen atom (Cu—O—Cu). At that time, it is presumed that the reduction of the surface oxide film proceeds via the following two elementary processes.

  When heat treatment is performed in a reducing atmosphere containing hydrogen gas, the hydroxyl group (> CH—OH) of 1,2-butanediol reacts with the copper oxide to cause the following oxidation / reduction reaction.

CuO + (> CH—OH) → Cu + (> C═O) + H ₂ O ↑

The reaction product derived from 1,2-butanediol (> C═O) is a fine copper powder, a metal copper atom (Cu) exposed on the surface of the copper powder, π of its oxo group (> C═O) Coordination can be performed using electrons. In a reducing atmosphere containing hydrogen gas, a hydrogen molecule (H ₂ ) is added to the oxo group (> C═O) coordinated on the metal copper atom (Cu), so that the original It is possible to convert to a hydroxyl group (> CH—OH).

(> C = O) + H ₂ → (> CH—OH)

On the other hand, in the copper paste, the amine complex of copper oleate is dissolved in a mixed liquid of dibutylaminopropylamine and 1,2-butanediol. When heat treatment is performed in an N ₂ /3% H ₂ atmosphere in the presence of 1,2-butanediol, the hydroxyl group of 1,2-butanediol (> CH—OH) represented by the following reaction formula: Conversion to an oxo group (> C = O) and a reduction reaction of the amine complex of copper oleate proceed.

(CH ₃ (CH ₂ ) ₇ CH = CH (CH ₂ ) ₇ COO) ₂ Cu (II): 2 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ) + (> CH-OH)
_{→ 2CH 3 (CH 2) 7} CH = CH (CH 2) 7 COOH + (Cu (0): 2 ((C 4 H 9) 2 N (CH 2) 3 NH 2) + (> C = O)

On the other hand, the metal copper atom generated by the reduction of the amine complex of copper oleate has a shape in which two molecules are coordinated with dibutylaminopropylamine as a bidentate ligand. The metal copper atom coordinated by two molecules of dibutylaminopropylamine (Cu (0): 2 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ )) Aggregates of metal copper atoms are formed using metal copper atoms on the surface of the copper powder as nuclei.

Dibutylaminopropylamine and 1,2-butanediol evaporate during the heat treatment in an N ₂ /3% H ₂ atmosphere. As a result, when the volume of the liquid phase decreases (concentration progresses), the liquid phase becomes a narrow gap around the contact area between the fine copper powder and the copper powder, the contact area between the underlayer and the fine copper powder, and the copper powder. The liquid phase is agglomerated in a narrow gap around the periphery. Therefore, as the liquid phase is concentrated, the metal copper atom (Cu (0): 2 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ )) coordinated with two molecules of dibutylaminopropylamine is Aggregates of copper metal atoms are preferentially formed in the narrow gaps around the contact areas between the fine copper powder and the copper powder, and the narrow gaps around the contact areas between the underlayer and the fine copper powder and the copper powder. A narrow gap around the contact area between the fine copper powder and the copper powder, and a narrow gap around the contact area between the underlayer and the fine copper powder and the copper powder are filled with the aggregate of the metal copper atoms. Then, when firing proceeds, the fine copper powder, around the copper powder contact area, around the base layer and the fine copper powder, around the copper powder contact area, the aggregate of metal copper atoms, fine copper powder, copper As a result, the contact area between the fine copper powder and the contact area between the copper powder and the contact area between the ground layer and the fine copper powder and the copper powder is increased. Big is done.

The oleic acid (boiling point: 286 ° C.) produced as a by-product with the reduction of the amine complex of copper oleate is once dissolved in 1,2-butanediol as a dispersion solvent. Thereafter, when heat treatment is performed in an N ₂ /3% H ₂ atmosphere, oleic acid is gradually evaporated in the same manner as the dispersion solvent 1,2-butanediol.

In addition, dibutylaminopropylamine is initially coordinated to the copper metal exposed on the surfaces of copper powder and fine copper powder by utilizing the lone pair of amino groups (—NH ₂ ). Have a strong bond. The boiling point of dibutylaminopropylamine (238 ° C.) is significantly higher than the boiling point of 1,2-butanediol (195-196.9 ° C.) as a dispersion solvent. Since the difference in boiling point is quite large, there is a considerable difference in the evaporation rate between dibutylaminopropylamine and 1,2-butanediol. Dibutylaminopropylamine, which is coordinated to the copper metal exposed on the surface of copper powder and fine copper powder, elutes once in the liquid phase, but 1,2-butanediol As transpiration proceeds, dibutylaminopropylamine is concentrated in the liquid phase. At that time, the liquid phase containing concentrated dibutylaminopropylamine is aggregated in the gap between the contact portions of the copper powder and the fine copper powder. Eventually, dibutylaminopropylamine is evaporated, but the process of reaching the state where the aggregates of metal copper atoms are embedded around the contact area between the fine copper powder and the copper powder is partially inhibited. As a result, the effect of expanding the contact area due to the progress of the integration of the aggregate of the metal copper atoms, the fine copper powder, and the copper powder is limited.

The prepared copper paste was applied on a slide glass in a pattern of 5 mm × 20 mm. The average thickness of the copper paste coating film was 55 μm. The copper paste coating film was baked by heat treatment at 400 ° C. for 10 minutes in an N ₂ /3% H ₂ atmosphere.

  The average film thickness of the obtained fired product was 44 μm. The volume resistivity was calculated from the measured sheet resistance value, assuming that the fired product was a conductor having a uniform average film thickness. The calculated volume resistivity was 18 μΩ · cm.

  The volume specific resistivity 18 μΩ · cm of the obtained fired product is 10.7 times that of the metal copper resistivity 1.673 μΩ · cm (30 ° C.).

(Reference Example 2)
The conductive copper paste of Reference Example 2 is prepared using the following raw materials.

As the copper powder selected in the range of the average particle diameter of ^{2 to} 10 μm, Mitsui Metals' spherical copper powder 1400YM (average particle diameter of 4 μm, BET specific surface area of 1600 cm ² / g) and average particle diameter of 0.2 μm to 1. As the fine copper powder selected in the range of 0 μm, Mitsui Metals fine copper powder 1020Y (average particle diameter 0.4 μm, BET specific surface area 26000 cm ² / g) is used. The ratio of the average particle diameter d _{Cu-fine-powder of the fine} copper powder to the average particle diameter d _Cu-powder of the spherical copper powder (d _{Cu-fine-powder} / d _Cu-powder ) is selected to be 1/10 Has been.

Copper salt of aliphatic monocarboxylic acid ((R—COO) ₂ Cu (II)), copper oleate ((CH ₃ (CH ₂ ) ₇ CH═CH (CH ₂ ) ₇ COO) ₂ Cu (II)) And dissolved in advance in dibutylaminopropylamine ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ , melting point: −50 ° C., boiling point: 238 ° C.), and an amine complex of copper oleate is dissolved. It is formed. The solid copper oleate itself forms a dimer having a Cu: Cu bond. The amine complex of copper oleate formed is composed of dibutylaminopropylamine (one molecule of copper oleate ((CH ₃ (CH ₂ ) ₇ CH═CH (CH ₂ ) ₇ COO) ₂ Cu (II))). It can be presumed that (C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ) 2 molecules coordinate to the copper cation (Cu ²⁺ ). As a result, the dimer type copper oleate is converted into an amine complex of two molecules of copper oleate and is dissolved in the solvent dibutylaminopropylamine. In Reference Example 2, 3.3 parts by mass of copper oleate is dissolved in 6.6 parts by mass of dibutylaminopropylamine, and an amine solution of an amine complex of copper oleate is prepared in advance. The composition of the amine solution of the copper oleate amine complex is selected to be 7 molecules of dibutylaminopropylamine per molecule of copper oleate.

  As a dispersion solvent, α-terpineol (molecular weight: 154.25, melting point: 31-35 ° C., boiling point: 217-218 ° C.) is used.

  No sintering aid is added.

  A solution prepared by dissolving 3.3 parts by mass of copper oleate in 6.6 parts by mass of dibutylaminopropylamine in 80 parts by mass of Mitsui Metals spherical copper powder 1400YM, 20 parts by mass of Mitsui Metals fine copper powder 1020Y, and α-terpineol 3 Mix parts by weight. Thereafter, the mixture is stirred with a stirring deaerator to prepare a copper paste in which the copper powder and the fine copper powder are uniformly dispersed in the liquid phase.

  Sum of the number of metallic copper atoms in the spherical copper powder and fine copper powder and the ratio of the number of copper atoms in the copper oleate, (sum of the number of metallic copper atoms in the spherical copper powder and fine copper powder): (oleic acid The number of atoms with copper in the copper is 299: 1 (100: 0.334). Further, 0.012 mol of α-terpineol is contained per 1 mol of metallic copper of the spherical copper powder and fine copper powder.

  The volume ratio of the spherical copper powder and fine copper powder in the prepared copper paste is 42.88% by volume.

  Moreover, when all the copper in 3.3 mass parts copper oleate is reduce | restored to a metal copper atom, the sum total of the metal copper atom originating in a copper oleate will be 0.34 mass part. Accordingly, the total volume of metallic copper atoms, spherical copper powder and fine copper powder derived from copper oleate with respect to 100 parts by volume of the prepared copper paste is 43.22 parts by volume.

  The liquid viscosity of the prepared copper paste was 3 Pa · s (spiral rotational viscometer 10 rpm 25 ° C.).

First, dibutylaminopropylamine or α-terpineol contained in the liquid phase is solvated (adsorbed) on the surfaces of the spherical copper powder and fine copper powder dispersed in the copper paste. Dibutylaminopropylamine is coordinated to the metallic copper exposed on the surface by utilizing the lone electron pair of the amino group (—NH ₂ ). On the other hand, a surface oxide film partially exists on the surfaces of the spherical copper powder and the fine copper powder. With respect to the copper oxide corresponding to copper oxide (CuO) that constitutes the surface oxide film, α-terpineol utilizes the hydroxyl group (—OH) and oxygen atoms (Cu in the copper oxide). -O-Cu) and hydrogen-bonded intermolecular bonds.

  The hydroxyl group (—OH) of α-terpineol cannot be converted to an oxo group (> C═O) by oxidation.

  On the other hand, it is estimated that the reduction of the surface oxide film proceeds via the following two elementary processes.

When heat treatment is performed in a reducing atmosphere containing hydrogen gas, α-terpineol undergoes an oxidative dehydrogenation reaction with copper oxide (CuO), while copper oxide (CuO) contains metallic copper and water molecules. Presumed to be converted to (H ₂ O).

CuO + (—CH ₂ —CH <) → Cu + (—CH═C <) + H ₂ O ↑

The reaction product (-CH = C <) derived from α-terpineol is a fine copper powder, a metal copper atom (Cu) exposed on the surface of the copper powder, π of C = C bond (-CH = C <) Coordination can be performed using electrons. In a reducing atmosphere containing hydrogen gas, hydrogen molecules (H) are formed by reductive hydrogenation reaction on C═C bonds (—CH═C <) coordinated on the metal copper atoms (Cu). ₂ ) is added, it is possible to convert to a C—C bond (—CH ₂ —CH <).

(-CH = C <) + H 2 → (-CH 2 -CH <)

On the other hand, in the copper paste, the amine complex of copper oleate is dissolved in a mixed solution of dibutylaminopropylamine and α-terpineol. When heat treatment is performed in an N ₂ /3% H ₂ atmosphere in the presence of α-terpineol, the C—C bond (—CH ₂ —CH <) of α-terpineol represented by the following reaction formula is expressed. Conversion to a C═C bond (—CH═C <) and a reduction reaction of the copper oleate amine complex proceed.

(CH ₃ (CH ₂ ) ₇ CH = CH (CH ₂ ) ₇ COO) ₂ Cu (II): 2 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ) + (− CH ₂ −CH < )
_{→ 2CH 3 (CH 2) 7} CH = CH (CH 2) 7 COOH + (Cu (0): 2 ((C 4 H 9) 2 N (CH 2) 3 NH 2) + (- CH = C <)

On the other hand, the metal copper atom generated by the reduction of the amine complex of copper oleate has a shape in which two molecules are coordinated with dibutylaminopropylamine as a bidentate ligand. The metal copper atom coordinated by two molecules of dibutylaminopropylamine (Cu (0): 2 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ )) Aggregates of metal copper atoms are formed using metal copper atoms on the surface of the copper powder as nuclei.

During the heat treatment in the N ₂ /3% H ₂ atmosphere, the evaporation of dibutylaminopropylamine and α-terpineol also proceeds. As a result, when the volume of the liquid phase decreases (concentration progresses), the liquid phase becomes a narrow gap around the contact area between the fine copper powder and the copper powder, the contact area between the underlayer and the fine copper powder, and the copper powder. The liquid phase is agglomerated in a narrow gap around the periphery. Therefore, as the liquid phase is concentrated, the metal copper atom (Cu (0): 2 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ )) coordinated with two molecules of dibutylaminopropylamine is Aggregates of copper metal atoms are preferentially formed in the narrow gaps around the contact areas between the fine copper powder and the copper powder, and the narrow gaps around the contact areas between the underlayer and the fine copper powder and the copper powder. A narrow gap around the contact area between the fine copper powder and the copper powder, and a narrow gap around the contact area between the underlayer and the fine copper powder and the copper powder are filled with the aggregate of the metal copper atoms. Then, when firing proceeds, the fine copper powder, around the copper powder contact area, around the base layer and the fine copper powder, around the copper powder contact area, the aggregate of metal copper atoms, fine copper powder, copper As a result, the contact area between the fine copper powder and the contact area between the copper powder and the contact area between the ground layer and the fine copper powder and the copper powder is increased. Big is done.

The oleic acid (boiling point: 286 ° C.) produced as a by-product with the reduction of the amine complex of copper oleate is once dissolved in α-terpineol as a dispersion solvent. Thereafter, when heat treatment is performed in an N ₂ /3% H ₂ atmosphere, the oleic acid is gradually evaporated in the same manner as the dispersion solvent α-terpineol.

In addition, dibutylaminopropylamine is initially coordinated to the copper metal exposed on the surfaces of copper powder and fine copper powder by utilizing the lone pair of amino groups (—NH ₂ ). Have a strong bond. The boiling point of dibutylaminopropylamine (238 ° C.) is slightly higher than that of α-terpineol (217-218 ° C.) as a dispersion solvent. Since the difference in boiling point is not large, there is no significant difference between dibutylaminopropylamine and α-terpineol transpiration rate. Therefore, dibutylaminopropylamine, which is coordinated to the copper metal exposed on the surface of copper powder and fine copper powder, elutes into the liquid phase and evaporates, so that it can be detached. Made. Finally, when the copper metal exposed to the surface comes into direct contact with the fine copper powder and the copper powder, the sintering proceeds.

The prepared copper paste was applied on a slide glass in a pattern of 5 mm × 20 mm. The average thickness of the copper paste coating film was 58 μm. The copper paste coating film was baked by heat treatment at 400 ° C. for 10 minutes in an N ₂ /3% H ₂ atmosphere.

  The average film thickness of the obtained fired product was 46 μm. The volume resistivity was calculated from the measured sheet resistance value, assuming that the fired product was a conductor having a uniform average film thickness. The calculated volume resistivity was 18 μΩ · cm.

  The volume resistivity of 18 μΩ · cm of the obtained fired product is 10.76 times that of metal copper having a resistivity of 1.673 μΩ · cm (30 ° C.).

(Reference Example 3)
The conductive copper paste of Reference Example 3 is prepared using the following raw materials.

As the copper powder selected in the range of the average particle diameter of ^{2 to} 10 μm, Mitsui Metals' spherical copper powder 1400YM (average particle diameter of 4 μm, BET specific surface area of 1600 cm ² / g) and average particle diameter of 0.2 μm to 1. As the fine copper powder selected in the range of 0 μm, Mitsui Metals fine copper powder 1020Y (average particle diameter 0.4 μm, BET specific surface area 26000 cm ² / g) is used. The ratio of the average particle diameter d _{Cu-fine-powder of the fine} copper powder to the average particle diameter d _Cu-powder of the spherical copper powder (d _{Cu-fine-powder} / d _Cu-powder ) is selected to be 1/10 Has been.

Copper salt of aliphatic monocarboxylic acid ((R—COO) ₂ Cu (II)), copper oleate ((CH ₃ (CH ₂ ) ₇ CH═CH (CH ₂ ) ₇ COO) ₂ Cu (II)) And dissolved in advance in dibutylaminopropylamine ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ , melting point: −50 ° C., boiling point: 238 ° C.), and an amine complex of copper oleate is dissolved. It is formed. The solid copper oleate itself forms a dimer having a Cu: Cu bond. The amine complex of copper oleate formed is composed of dibutylaminopropylamine (one molecule of copper oleate ((CH ₃ (CH ₂ ) ₇ CH═CH (CH ₂ ) ₇ COO) ₂ Cu (II))). It can be presumed that (C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ) 2 molecules coordinate to the copper cation (Cu ²⁺ ). As a result, the dimer type copper oleate is converted into an amine complex of two molecules of copper oleate and is dissolved in the solvent dibutylaminopropylamine. In this Reference Example 3, 3.3 parts by mass of copper oleate is dissolved in 6.6 parts by mass of dibutylaminopropylamine, and an amine solution of an amine complex of copper oleate is prepared in advance. The composition of the amine solution of the copper oleate amine complex is selected to be 7 molecules of dibutylaminopropylamine per molecule of copper oleate.

  As a dispersion solvent, diethylene glycol di-n-butyl ether (DEGDBE, molecular weight 218.33, melting point −60 ° C., boiling point 250 ° C.) is used.

  No sintering aid is added.

  A solution prepared by dissolving 3.3 parts by mass of copper oleate in 6.6 parts by mass of dibutylaminopropylamine and 80 parts by mass of Mitsui Metals spherical copper powder 1400YM, 20 parts by mass of Mitsui Metals fine copper powder 1020Y, and 3 parts by mass of DEGDBE Mix. Thereafter, the mixture is stirred with a stirring deaerator to prepare a copper paste in which the copper powder and the fine copper powder are uniformly dispersed in the liquid phase.

  Sum of the number of metallic copper atoms in the spherical copper powder and fine copper powder and the ratio of the number of copper atoms in copper oleate, (sum of the number of metallic copper atoms in the spherical copper powder and fine copper powder): (oleic acid The number of atoms with copper in the copper is 299: 1 (100: 0.334). Moreover, DEGDBE0.009 mol is contained per 1 mol of metallic copper of spherical copper powder and fine copper powder.

  The volume ratio of the spherical copper powder and fine copper powder in the prepared copper paste is 42.92% by volume.

  Moreover, when all the copper in 3.3 mass parts copper oleate is reduce | restored to a metal copper atom, the sum total of the metal copper atom originating in a copper oleate will be 0.34 mass part. Therefore, the sum total of the volume of the metal copper atom derived from copper oleate, spherical copper powder, and fine copper powder with respect to 100 volume parts of the prepared copper paste is 43.07 volume parts.

  The liquid viscosity of the prepared copper paste was 2 Pa · s (spiral rotational viscometer 10 rpm 25 ° C.).

First, dibutylaminopropylamine or DEGDBE contained in the liquid phase is solvated (adsorbed) on the surfaces of the spherical copper powder and fine copper powder dispersed in the copper paste. Dibutylaminopropylamine is coordinated to the metallic copper exposed on the surface by utilizing the lone electron pair of the amino group (—NH ₂ ).

  DEGDBE does not have a hydroxyl group (> CH—OH) that can be converted to an oxo group (> C═O) by oxidation.

  On the other hand, it is estimated that the reduction of the surface oxide film proceeds via the following two elementary processes.

When heat treatment is performed in a reducing atmosphere containing hydrogen gas, DEGDBE undergoes an oxidative dehydrogenation reaction with copper oxide (CuO), while copper oxide (CuO) contains metallic copper and water molecules (H ₂ O) is estimated to be converted.

CuO + (—CH ₂ —CH ₂ —) → Cu + (—CH═CH —) + H ₂ O ↑

The reaction product (-CH = CH-) derived from DEGDBE is a fine copper powder, on the metal copper atom (Cu) exposed on the surface of the copper powder, π electrons of C = C bond (-CH = CH-) You can use it to coordinate. In a reducing atmosphere containing hydrogen gas, hydrogen molecules (H) are formed by reductive hydrogenation reaction on the C═C bond (—CH═CH—) coordinated on the metal copper atom (Cu). _By adding ₂ ), it is possible to convert to a C—C bond (—CH ₂ —CH ₂ —).

_{(-CH = CH-) + H 2} → (-CH 2 -CH 2)
On the other hand, in the copper paste, the amine complex of copper oleate is dissolved in a mixed solution of dibutylaminopropylamine and DEGDBE. When heat treatment is performed in an N ₂ /3% H ₂ atmosphere in the presence of DEGDBE, C═C of a C—C bond (—CH ₂ —CH ₂ —) in DEGDBE represented by the following reaction formula: Conversion to a bond (—CH═CH—) and a reduction reaction of the copper oleate amine complex proceed.

(CH ₃ (CH ₂ ) ₇ CH = CH (CH ₂ ) ₇ COO) ₂ Cu (II): 2 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ ) + (− CH ₂ −CH ₂ −)
_{→ 2CH 3 (CH 2) 7} CH = CH (CH 2) 7 COOH + (Cu (0): 2 ((C 4 H 9) 2 N (CH 2) 3 NH 2) + (- CH = CH-)

On the other hand, the metal copper atom generated by the reduction of the amine complex of copper oleate has a shape in which two molecules are coordinated with dibutylaminopropylamine as a bidentate ligand. The metal copper atom coordinated by two molecules of dibutylaminopropylamine (Cu (0): 2 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ )) Aggregates of metal copper atoms are formed using metal copper atoms on the surface of the copper powder as nuclei.

During the heat treatment in the N ₂ /3% H ₂ atmosphere, transpiration of dibutylaminopropylamine and DEGDBE proceeds. As a result, when the volume of the liquid phase decreases (concentration progresses), the liquid phase becomes a narrow gap around the contact area between the fine copper powder and the copper powder, the contact area between the underlayer and the fine copper powder, and the copper powder. The liquid phase is agglomerated in a narrow gap around the periphery. Therefore, as the liquid phase is concentrated, the metal copper atom (Cu (0): 2 ((C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ NH ₂ )) coordinated with two molecules of dibutylaminopropylamine is Aggregates of copper metal atoms are preferentially formed in the narrow gaps around the contact areas between the fine copper powder and the copper powder, and the narrow gaps around the contact areas between the underlayer and the fine copper powder and the copper powder. A narrow gap around the contact area between the fine copper powder and the copper powder, and a narrow gap around the contact area between the underlayer and the fine copper powder and the copper powder are filled with the aggregate of the metal copper atoms. Then, when firing proceeds, the fine copper powder, around the copper powder contact area, around the base layer and the fine copper powder, around the copper powder contact area, the aggregate of metal copper atoms, fine copper powder, copper As a result, the contact area between the fine copper powder and the contact area between the copper powder and the contact area between the ground layer and the fine copper powder and the copper powder is increased. Big is done.

The oleic acid (boiling point: 286 ° C.) produced as a by-product with the reduction of the amine complex of copper oleate is once dissolved in DEGDBE as a dispersion solvent. Thereafter, when the heat treatment is performed in an N ₂ /3% H ₂ atmosphere, the oleic acid is gradually evaporated like the dispersion solvent DEGDBE.

In addition, dibutylaminopropylamine is initially coordinated to the copper metal exposed on the surfaces of copper powder and fine copper powder by utilizing the lone pair of amino groups (—NH ₂ ). Have a strong bond. Since the boiling point of dibutylaminopropylamine (238 ° C) is lower than that of the dispersion solvent DEGDBE (250 ° C), the evaporation rate of dibutylaminopropylamine is relatively fast. As a result, the concentration of dibutylaminopropylamine in the liquid phase is reduced, and the coordinative bonding of dibutylaminopropylamine with metal copper exposed on the surface of copper powder and fine copper powder is reduced. The withdrawal is promoted. Finally, when the copper metal exposed to the surface comes into direct contact with the fine copper powder and the copper powder, the sintering proceeds.

The prepared copper paste was applied on a slide glass in a pattern of 5 mm × 20 mm. The average thickness of the copper paste coating film was 52 μm. The copper paste coating film was baked by heat treatment at 400 ° C. for 10 minutes in an N ₂ /3% H ₂ atmosphere.

  The average film thickness of the obtained fired product was 40 μm. The volume resistivity was calculated from the measured sheet resistance value, assuming that the fired product was a conductor having a uniform average film thickness. The calculated volume resistivity was 18 μΩ · cm.

  The volume specific resistivity 18 μΩ · cm of the obtained fired product is 10.7 times that of the metal copper resistivity 1.673 μΩ · cm (30 ° C.).

  Table 6 below shows the compositions of the conductive copper pastes of Reference Examples 1 to 3. The average film thickness of the copper paste coating film, the average film thickness of the fired product, and the calculated volume specific resistivity are also shown.

  The conductive copper paste according to the present invention can be used for forming a conductor layer in which a conductive copper paste containing a conventional glass frit or a conductive copper paste containing a thermosetting resin component is used. . Specifically, the conductor layer formed using the conductive copper paste according to the present invention exhibits good conductive properties, and has a base layer having a silanol structure (Si-OH) on the surface, for example, Since it exhibits good adhesion to glass, silicon wafers, etc., it can be suitably used as a material for wiring formation and electrode formation for solar cells.

Claims (30)

A conductive copper paste containing no thermosetting resin component or glass frit,
The conductive copper paste is
Including copper powder, fine copper powder, copper salt of aliphatic monocarboxylic acid, (dialkylamino) alkylamine, first organic solvent,
The first organic solvent is a liquid at room temperature, has a boiling point of 200 ° C. or higher, but does not exceed 400 ° C., and does not contain any reactive functional groups other than hydroxyl groups. An organic solvent having a group;
The copper salt of the aliphatic monocarboxylic acid is mixed with the first organic solvent as a solution obtained by dissolving in a (dialkylamino) alkylamine, to obtain a mixed solution,
The copper powder and the fine copper powder are a paste-like composition dispersed in the mixed solution;
The average particle diameter of the copper powder is selected in the range of 2 μm to 10 μm,
The average particle diameter of the fine copper powder is selected in the range of 0.2 μm to 1.0 μm,
The copper salt of the aliphatic monocarboxylic acid has a boiling point of 230 ° C. or higher, but is derived from an aliphatic monocarboxylic acid (R—COOH) that does not exceed 400 ° C. Copper salt,
The (dialkylamino) alkylamine is a liquid at room temperature and has a boiling point of 230 ° C. or higher but not exceeding 300 ° C.
The content ratio of the copper powder and fine copper powder, (copper powder content): (fine copper powder content) is selected in the range of 80 parts by mass: 20 parts by mass to 60 parts by mass: 40 parts by mass,
Ratio of the total weight of copper atoms (W _{Cu-carboxylate} ) contained in the copper salt of aliphatic monocarboxylic acid to the total weight (W _Cu-powder + W _{Cu-fine-powder} ) of the copper powder and fine copper powder , (W _Cu-powder + W _{Cu-fine-powder} ): (W _{Cu-carboxylate} ) is selected in the range of 100 parts by mass: 0.15 parts by mass to 100 parts by mass: 0.7 parts by mass,
The ratio of the total weight of the copper powder and fine copper powder (W _Cu-powder + W _{Cu-fine-powder} ) to the weight of the first organic solvent (W _{dispersion-medium} ), (W _Cu-powder + W _{Cu-fine -powder} ): W _{dispersion-medium} is selected in the range of 100 parts by mass: 2 parts by mass to 100 parts by mass: 10 parts by mass,
The content ratio of the copper salt of the aliphatic monocarboxylic acid and the (dialkylamino) alkylamine is such that (dialkylamino) alkylamine is 2.2 to 8 molecules per molecule of the copper salt of the aliphatic monocarboxylic acid. Chosen to be a ratio;
The conductive copper paste can be fired by heating to a temperature of 300 ° C. or higher and 400 ° C. or lower. The first organic solvent is
An alkanol having 9 to 14 carbon atoms that is liquid at room temperature and has a boiling point of 200 ° C. or higher but not exceeding 400 ° C .;
An alkanediol having 4 to 9 carbon atoms that is liquid at room temperature and has a boiling point of 200 ° C. or higher but not exceeding 400 ° C.,
A polyalkylene glycol having a molecular weight of 4000 or less, which is liquid at room temperature and has a boiling point of 200 ° C. or higher but not exceeding 400 ° C.,
A polyhydric alcohol monoalkyl ether that is liquid at room temperature and has a boiling point of 200 ° C. or higher but not exceeding 400 ° C .;
The glycerin, 1,2,3-butanetriol, 1,2,4-butanetriol, 1,2,5-pentanetriol, 1,2,6-hexanetriol are selected. Item 2. The conductive copper paste according to Item 1. A conductive copper paste containing no thermosetting resin component or glass frit,
The conductive copper paste is
Including copper powder, fine copper powder, copper salt of aliphatic monocarboxylic acid, (dialkylamino) alkylamine, second organic solvent,
The second organic solvent is an aliphatic polyhydric alcohol that is liquid at room temperature and has a boiling point of 230 ° C. or higher but not exceeding 400 ° C .;
The copper salt of the aliphatic monocarboxylic acid is mixed with the second organic solvent as a solution obtained by dissolving in a (dialkylamino) alkylamine, to obtain a mixed solution,
The copper powder and the fine copper powder are a paste-like composition dispersed in the mixed solution;
The average particle diameter of the copper powder is selected in the range of 2 μm to 10 μm,
The average particle diameter of the fine copper powder is selected in the range of 0.2 μm to 1.0 μm,
The copper salt of the aliphatic monocarboxylic acid has a boiling point of 230 ° C. or higher, but is derived from an aliphatic monocarboxylic acid (R—COOH) that does not exceed 400 ° C. Copper salt,
The (dialkylamino) alkylamine is a liquid at room temperature and has a boiling point of 230 ° C. or higher but not exceeding 300 ° C.
The content ratio of the copper powder and fine copper powder, (copper powder content): (fine copper powder content) is selected in the range of 80 parts by mass: 20 parts by mass to 60 parts by mass: 40 parts by mass,
Ratio of the total weight of copper atoms (W _{Cu-carboxylate} ) contained in the copper salt of aliphatic monocarboxylic acid to the total weight (W _Cu-powder + W _{Cu-fine-powder} ) of the copper powder and fine copper powder , (W _Cu-powder + W _{Cu-fine-powder} ): (W _{Cu-carboxylate} ) is selected in the range of 100 parts by mass: 0.15 parts by mass to 100 parts by mass: 0.7 parts by mass,
The ratio of the total weight of the copper powder and fine copper powder (W _Cu-powder + W _{Cu-fine-powder} ) to the weight of the second organic solvent (W _{dispersion-medium} ), (W _Cu-powder + W _{Cu-fine -powder} ): W _{dispersion-medium} is selected in the range of 100 parts by mass: 2 parts by mass to 100 parts by mass: 10 parts by mass,
The content ratio of the copper salt of the aliphatic monocarboxylic acid and the (dialkylamino) alkylamine is such that (dialkylamino) alkylamine is 2.2 to 8 molecules per molecule of the copper salt of the aliphatic monocarboxylic acid. Chosen to be a ratio;
The conductive copper paste can be fired by heating to a temperature of 300 ° C. or higher and 400 ° C. or lower. The second organic solvent is
It is liquid at room temperature and has a boiling point of 230 ° C. or higher, but is an alkanediol having 4 to 9 carbon atoms in a range not exceeding 400 ° C. It is liquid at room temperature and has a boiling point of 230 ° C. or higher, but 400 ° C. A polyalkylene glycol having a molecular weight of 4000 or less, and glycerin, 1,2,3-butanetriol, 1,2,4-butanetriol, 1,2,5-pentanetriol, 1,2, The conductive copper paste according to claim 3, wherein the conductive copper paste is selected from the group consisting of 6-hexanetriol. The average particle size of the copper powder is selected in the range of 3 μm to 8 μm,
5. The conductive copper paste according to claim 1, wherein an average particle diameter of the fine copper powder is selected in a range of 0.3 μm to 0.8 μm. Ratio of the total weight of copper atoms (W _{Cu-carboxylate} ) contained in the copper salt of aliphatic monocarboxylic acid to the total weight (W _Cu-powder + W _{Cu-fine-powder} ) of the copper powder and fine copper powder , (W _Cu-powder + W _{Cu-fine-powder} ): (W _{Cu-carboxylate} ) is selected in the range of 100 parts by mass: 0.3 part by mass to 100 parts by mass: 0.5 part by mass. The electroconductive copper paste as described in any one of Claims 1-5 characterized by the above-mentioned. The ratio of the total weight of the copper powder and fine copper powder (W _Cu-powder + W _{Cu-fine-powder} ) to the weight of the first organic solvent (W _{dispersion-medium} ), (W _Cu-powder + W _{Cu-fine -powder} ): W _{dispersion-medium} is selected in the range of 100 parts by mass: 3 parts by mass to 100 parts by mass: 4.5 parts by mass, The conductive copper according to claim 1 or 2, paste. The ratio of the total weight of the copper powder and fine copper powder (W _Cu-powder + W _{Cu-fine-powder} ) to the weight of the second organic solvent (W _{dispersion-medium} ), (W _Cu-powder + W _{Cu-fine -powder} ): W _{dispersion-medium} is selected in the range of 100 parts by mass: 3 parts by mass to 100 parts by mass: 4.5 parts by mass, The conductive copper according to claim 3 or 4 paste. The content ratio of the copper powder and fine copper powder, (copper powder content): (fine copper powder content) is selected in the range of 75 parts by mass: 25 parts by mass to 65 parts by mass: 35 parts by mass. The conductive copper paste according to any one of claims 1 to 8, wherein As the aliphatic monocarboxylic acid anion having a boiling point of 230 ° C. or higher, which does not exceed 400 ° C., constituting the aliphatic monocarboxylic acid copper salt ((R—COO) ₂ Cu (II)),
The conductive copper paste according to any one of claims 1 to 8, wherein an anion derived from an aliphatic monocarboxylic acid having 10 to 20 carbon atoms is selected. The (dialkylamino) alkylamine is
(Dialkylamino) propylamine (R ′ ₂ N—CH ₂ CH ₂ CH ₂ —NH) having a total carbon number of 9 to 13 which is liquid at room temperature and has a boiling point of 230 ° C. or higher but not exceeding 300 ° C. The conductive copper paste according to any one of claims 1 to 10, wherein the conductive copper paste is selected from the group consisting of ₂ ). The conductive copper paste according to any one of claims 1 to 11, wherein the viscosity of the conductive copper paste is selected in a range of 2 Pa · s to 50 Pa · s (25 ° C). A conductive copper paste containing no thermosetting resin component or glass frit,
The conductive copper paste is
Including copper powder, fine copper powder, copper nanoparticles, (dialkylamino) alkylamine, a third organic solvent,
The third organic solvent is a liquid at room temperature, has a boiling point of 200 ° C. or higher, but does not exceed 400 ° C., and has no reactive functional groups other than hydroxyl groups. An organic solvent having a group;
The copper nanoparticles are mixed with the third organic solvent as a dispersion liquid dispersed in (dialkylamino) alkylamine, to obtain a mixed liquid,
The copper powder and the fine copper powder are a paste-like composition dispersed in the mixed solution;
The average particle size of the copper powder is selected in the range of 2 to 10 μm,
The average particle diameter of the fine copper powder is selected in the range of 0.2 to 1.0 μm,
The average particle diameter of the copper nanoparticles is selected in the range of 10 nm to 100 nm,
The (dialkylamino) alkylamine is a liquid at room temperature and has a boiling point of 230 ° C. or higher but not exceeding 300 ° C.
The content ratio of the copper powder and fine copper powder, (copper powder content): (fine copper powder content) is selected in the range of 80 parts by mass: 20 parts by mass to 60 parts by mass: 40 parts by mass,
The ratio of the total weight of the copper powder and fine copper powder (W _Cu-powder + W _{Cu-fine-powder} ) to the weight of the third organic solvent (W _{dispersion-medium} ), (W _Cu-powder + W _{Cu-fine -powder} ): W _{dispersion-medium} is selected in the range of 100 parts by mass: 3 parts by mass to 100 parts by mass: 10 parts by mass,
The ratio of the total weight of the copper powder and fine copper powder (W _Cu-powder + W _{Cu-fine-powder} ) and the total weight of the copper nanoparticles (W _{Cu-nano-particle} ), (W _Cu-powder + W _{Cu-fine-powder} ) :( W _{Cu-nano-particle} ) is selected in the range of 100 parts by mass: 3 parts by mass to 100 parts by mass: 15 parts by mass,
The content ratio of the copper nanoparticles and (dialkylamino) alkylamine is the ratio of the total volume of the copper nanoparticles (V _{Cu-nano-particle} ) to the volume of (dialkylamino) alkylamine (V _{dispersion-medium} ). , (V _{Cu-nano-particle} ): V _amine is selected in the range of 10:50 to 10: 100;
The conductive copper paste can be fired by heating to a temperature of 300 ° C. or higher and 400 ° C. or lower. The third organic solvent is
An alkanol having 9 to 14 carbon atoms that is liquid at room temperature and has a boiling point of 200 ° C. or higher but not exceeding 400 ° C .;
An alkanediol having 4 to 9 carbon atoms that is liquid at room temperature and has a boiling point of 200 ° C. or higher but not exceeding 400 ° C.,
A polyalkylene glycol having a molecular weight of 4000 or less, which is liquid at room temperature and has a boiling point of 200 ° C. or higher but not exceeding 400 ° C.,
A polyhydric alcohol monoalkyl ether that is liquid at room temperature and has a boiling point of 200 ° C. or higher but not exceeding 400 ° C .;
The glycerin, 1,2,3-butanetriol, 1,2,4-butanetriol, 1,2,5-pentanetriol, 1,2,6-hexanetriol are selected. Item 14. A conductive copper paste according to Item 13. A conductive copper paste containing no thermosetting resin component or glass frit,
The conductive copper paste is
Including copper powder, fine copper powder, copper nanoparticles, (dialkylamino) alkylamine, a fourth organic solvent,
The fourth organic solvent is an aliphatic polyhydric alcohol that is liquid at room temperature and has a boiling point of 230 ° C. or higher but not exceeding 400 ° C .;
The copper nanoparticles are mixed with the fourth organic solvent as a dispersion liquid dispersed in (dialkylamino) alkylamine, to form a mixed liquid,
The copper powder and the fine copper powder are a paste-like composition dispersed in the mixed solution;
The average particle diameter of the copper powder is selected in the range of 2 μm to 10 μm,
The average particle diameter of the fine copper powder is selected in the range of 0.2 μm to 1.0 μm,
The average particle diameter of the copper nanoparticles is selected in the range of 10 nm to 100 nm,
The (dialkylamino) alkylamine is a liquid at room temperature and has a boiling point of 230 ° C. or higher but not exceeding 300 ° C.
The content ratio of the copper powder and fine copper powder, (copper powder content): (fine copper powder content) is selected in the range of 80 parts by mass: 20 parts by mass to 60 parts by mass: 40 parts by mass,
The ratio of the total weight of copper atoms (W _{Cu-nano-particle} ) in the copper nanoparticles to the total weight of the copper powder and fine copper powder (W _Cu-powder + W _{Cu-fine-powder} ), ( W _Cu-powder + W _{Cu-fine-powder} ): (W _{Cu-nano-particle} ) is selected in the range of 100 parts by mass: 3 parts by mass to 100 parts by mass: 15 parts by mass,
The ratio of the total weight of the copper powder and fine copper powder (W _Cu-powder + W _{Cu-fine-powder} ) to the weight of the fourth organic solvent (W _{dispersion-medium} ), (W _Cu-powder + W _{Cu-fine -powder} ): W _{dispersion-medium} is selected in the range of 100 parts by mass: 3 parts by mass to 100 parts by mass: 10 parts by mass,
The content ratio of the copper nanoparticles and (dialkylamino) alkylamine is the ratio of the total volume of the copper nanoparticles (V _{Cu-nano-particle} ) to the volume of (dialkylamino) alkylamine (V _{dispersion-medium} ). , (V _{Cu-nano-particle} ): V _amine is selected in the range of 10:50 to 10: 100;
The conductive copper paste can be fired by heating to a temperature of 300 ° C. or higher and 400 ° C. or lower. The fourth organic solvent is
It is liquid at room temperature and has a boiling point of 230 ° C. or higher, but is an alkanediol having 4 to 9 carbon atoms in a range not exceeding 400 ° C. It is liquid at room temperature, and its boiling point is 230 ° C. or higher, A polyalkylene glycol having a molecular weight of 4000 or less, and glycerin, 1,2,3-butanetriol, 1,2,4-butanetriol, 1,2,5-pentanetriol, 1,2, The conductive copper paste according to claim 15, wherein the conductive copper paste is selected from the group consisting of 6-hexanetriol. The average particle size of the copper powder is selected in the range of 3 μm to 8 μm,
The average particle diameter of the said fine copper powder is selected in the range of 0.3 micrometer-0.8 micrometer, The conductive copper paste as described in any one of Claims 13-16 characterized by the above-mentioned. The ratio of the total weight of copper atoms (W _{Cu-nano-particle} ) in the copper nanoparticles to the total weight of the copper powder and fine copper powder (W _Cu-powder + W _{Cu-fine-powder} ), ( W _Cu-powder + W _{Cu-fine-powder} ) :( W _{Cu-nano-particle} ) is selected in the range of 100 parts by mass: 3 parts by mass to 100 parts by mass: 8 parts by mass Item 18. The conductive copper paste according to any one of Items 13 to 17. The ratio of the total weight of the copper powder and fine copper powder (W _Cu-powder + W _{Cu-fine-powder} ) to the weight of the third organic solvent (W _{dispersion-medium} ), (W _Cu-powder + W _{Cu- The fine-powder} ): W _{dispersion-medium} is selected in the range of 100 parts by mass: 3.5 parts by mass to 100 parts by mass: 5.0 parts by mass. Conductive copper paste. The ratio of the total weight of the copper powder and fine copper powder (W _Cu-powder + W _{Cu-fine-powder} ) to the weight of the fourth organic solvent (W _{dispersion-medium} ), (W _Cu-powder + W _{Cu-fine -powder} ): W _{dispersion-medium} is selected in the range of 100 parts by mass: 3.5 parts by mass to 100 parts by mass: 5.0 parts by mass. Copper paste. The content ratio of the copper powder and fine copper powder, (copper powder content): (fine copper powder content) is selected in the range of 75 parts by mass: 25 parts by mass to 65 parts by mass: 35 parts by mass. The conductive copper paste according to any one of claims 13 to 20, wherein The (dialkylamino) alkylamine is
(Dialkylamino) propylamine (R ′ ₂ N—CH ₂ CH ₂ CH ₂ —NH) having a total carbon number of 9 to 13 which is liquid at room temperature and has a boiling point of 230 ° C. or higher but not exceeding 300 ° C. The conductive copper paste according to any one of claims 13 to 21, wherein the conductive copper paste is selected from the group consisting of ₂ ). The conductive copper paste according to any one of claims 13 to 22, wherein a viscosity of the conductive copper paste is selected in a range of 2 Pa · s to 50 Pa · s (25 ° C). As a sintering aid, a carboxylic acid metal salt or metal carboxylic acid complex, which becomes a metal cation species other than copper and a carboxylic acid anion species, is added,
The metal cation species other than copper is selected from the group consisting of bismuth and tin, or one or a plurality of types of metal cation species,
The carboxylic acid anion species is a carboxylic acid anion species selected from the group consisting of aliphatic monocarboxylic acids having 6 to 20 carbon atoms,
Volume of metal atoms generated by reducing the carboxylic acid metal salt or metal carboxylic acid complex V _low-mp-metal and volume of metal atoms generated by reducing the copper salt of the aliphatic monocarboxylic acid The ratio to the total V _Cu-metal , V _low-mp-metal : V _Cu-metal, is selected in a range not exceeding 2: 1. The conductive copper paste as described. As a sintering aid, a carboxylic acid metal salt or metal carboxylic acid complex, which becomes a metal cation species other than copper and a carboxylic acid anion species, is added,
The metal cation species other than copper is a mixed metal cation species formed by mixing a cation species of the first metal group and a cation species of the second metal group,
The cation species of the first metal group is selected from the group consisting of bismuth and tin, or one or more metal cation species,
The cation species of the second metal group is selected from the group consisting of zinc, aluminum, indium, silver, cobalt, titanium, nickel, manganese, or a cation species of one or more metals.
In the mixed metal cation species, the total number of metal atoms of the cation species of the second metal group is selected within a range of less than 10% with respect to the total number of metal atoms of the cation species of the first metal group. And
The carboxylic acid anion species is a carboxylic acid anion species selected from the group consisting of aliphatic monocarboxylic acids having 6 to 20 carbon atoms,
A volume sum V _low-mp-metal of metal atoms of the first metal group formed by reducing a carboxylic acid metal salt or metal carboxylic acid complex, which is a cation species of the first metal group and a carboxylic acid anion species; , Ratio of the total volume of metal atoms V _Cu-metal generated by reducing the copper salt of the aliphatic monocarboxylic acid, V _low-mp-metal : V _Cu-metal does not exceed 2: 1 The conductive copper paste according to claim 1, wherein the conductive copper paste is selected. The conductive copper paste further includes a copper salt of an aliphatic monocarboxylic acid and a sintering aid,
The copper salt of the aliphatic monocarboxylic acid has a boiling point of 230 ° C. or higher, but is derived from an aliphatic monocarboxylic acid (R—COOH) that does not exceed 400 ° C. Copper salt,
The copper salt of the aliphatic monocarboxylic acid is added as a solution formed by dissolving in the (dialkylamino) alkylamine,
In the (dialkylamino) alkylamine solution of the aliphatic monocarboxylic acid copper salt, the content ratio of the aliphatic monocarboxylic acid copper salt to the (dialkylamino) alkylamine is determined as follows. Per molecule, (dialkylamino) alkylamine is selected in a ratio ranging from 2.2 to 8 molecules,
The sintering aid is a carboxylic acid metal salt or a metal carboxylic acid complex, which is a metal cation species other than copper and a carboxylic acid anion species,
The metal cation species other than copper is selected from the group consisting of bismuth and tin, or one or a plurality of types of metal cation species,
The carboxylic acid anion species is a carboxylic acid anion species selected from the group consisting of aliphatic monocarboxylic acids having 6 to 20 carbon atoms,
Ratio of the total weight of copper atoms (W _{Cu-carboxylate} ) contained in the copper salt of aliphatic monocarboxylic acid to the total weight (W _Cu-powder + W _{Cu-fine-powder} ) of the copper powder and fine copper powder , (W _Cu-powder + W _{Cu-fine-powder} ): (W _{Cu-carboxylate} ) is selected in the range of 100 parts by mass: 0.15 parts by mass to 100 parts by mass: 0.7 parts by mass,
Volume of metal atoms generated by reducing the carboxylic acid metal salt or metal carboxylic acid complex V _low-mp-metal and volume of metal atoms generated by reducing the copper salt of the aliphatic monocarboxylic acid _23. The ratio to the total V _Cu-metal , V _low-mp-metal : V _Cu-metal, is selected in a range not exceeding 2: 1. The conductive copper paste as described. The conductive copper paste further includes a copper salt of an aliphatic monocarboxylic acid and a sintering aid,
The copper salt of the aliphatic monocarboxylic acid has a boiling point of 230 ° C. or higher, but is derived from an aliphatic monocarboxylic acid (R—COOH) that does not exceed 400 ° C. Copper salt,
The copper salt of the aliphatic monocarboxylic acid is added as a solution formed by dissolving in (dialkylamino) alkylamine,
In the (dialkylamino) alkylamine solution of the aliphatic monocarboxylic acid copper salt, the content ratio of the aliphatic monocarboxylic acid copper salt to the (dialkylamino) alkylamine is determined as follows. Per molecule, (dialkylamino) alkylamine is selected in a ratio ranging from 2.2 to 8 molecules,
The sintering aid is a carboxylic acid metal salt or a metal carboxylic acid complex, which is a metal cation species other than copper and a carboxylic acid anion species,
The metal cation species other than copper is a mixed metal cation species formed by mixing a cation species of the first metal group and a cation species of the second metal group,
The cation species of the first metal group is selected from the group consisting of bismuth and tin, or one or more metal cation species,
The cation species of the second metal group is selected from the group consisting of zinc, aluminum, indium, silver, cobalt, titanium, nickel, manganese, or a cation species of one or more metals.
In the mixed metal cation species, the total number of metal atoms of the cation species of the second metal group is selected within a range of less than 10% with respect to the total number of metal atoms of the cation species of the first metal group. And
The carboxylic acid anion species is a carboxylic acid anion species selected from the group consisting of aliphatic monocarboxylic acids having 6 to 20 carbon atoms,
Ratio of the total weight of copper atoms (W _{Cu-carboxylate} ) contained in the copper salt of aliphatic monocarboxylic acid to the total weight (W _Cu-powder + W _{Cu-fine-powder} ) of the copper powder and fine copper powder , (W _Cu-powder + W _{Cu-fine-powder} ): (W _{Cu-carboxylate} ) is selected in the range of 100 parts by mass: 0.15 parts by mass to 100 parts by mass: 0.7 parts by mass,
A volume sum V _low-mp-metal of metal atoms of the first metal group formed by reducing a carboxylic acid metal salt or metal carboxylic acid complex, which is a cation species of the first metal group and a carboxylic acid anion species; , Ratio of the total volume of metal atoms V _Cu-metal generated by reducing the copper salt of the aliphatic monocarboxylic acid, V _low-mp-metal : V _Cu-metal does not exceed 2: 1 The conductive copper paste according to any one of claims 12 to 22, wherein the conductive copper paste is selected. As the aliphatic monocarboxylic acid anion having a boiling point of 230 ° C. or higher, which does not exceed 400 ° C., constituting the aliphatic monocarboxylic acid copper salt ((R—COO) ₂ Cu (II)),
The conductive copper paste according to claim 26 or 27, wherein an anion derived from an aliphatic monocarboxylic acid having 10 to 20 carbon atoms is selected. A method of using the conductive copper paste according to any one of claims 1 to 28 for producing a sintered body film,
Using the conductive copper paste, the step of producing a sintered body film is as follows:
Forming a coating film of the conductive copper paste on an underlayer;
In a reducing atmosphere containing hydrogen gas, the step of baking the conductive copper paste by heating the coating film of the conductive copper paste to a temperature of 300 ° C. or higher and 400 ° C. or lower,
The reducing atmosphere containing hydrogen gas contains hydrogen gas in an amount of 1 to 4% by volume in an inert gas,
The heating time is selected in the range of 5 minutes to 60 minutes,
The sintered body film to be produced is a conductive film having a resistivity in the range of 15 μΩ · cm or less,
The method of using a conductive copper paste, wherein the thickness of the sintered body film is selected in the range of 20 μm to 100 μm. 30. The method of using a conductive copper paste according to claim 29, wherein the thickness of the sintered body film is selected in a range of 30 [mu] m to 80 [mu] m.