JP5980574B2 - Material for forming conductive metal thick film and method for forming conductive metal thick film - Google Patents

Description

  The present invention relates to a conductive metal thick film forming material and a method of forming a conductive metal thick film using the conductive metal thick film forming material. In particular, the present invention relates to a conductive metal paste type conductive metal thick film forming material capable of being fired using microwave plasma in a reducing atmosphere, and the conductive metal thick film forming material. The present invention relates to a method of forming a “bulk conductive metal thick film” by a firing process using microwave plasma in a reducing atmosphere.

  As a conductive copper paste that can be used to form a conductor layer, a conductive copper paste that can reduce the heating temperature in the baking process to 300 ° C. or lower by using low-temperature baking of copper nanoparticles has already been proposed. ing.

  For example, using a dispersion containing copper nanoparticles having a copper oxide coating layer on the surface, the average particle diameter being selected in the range of 1 to 100 nm, and drawing the coating layer of the dispersion on the substrate In the coating layer, the copper nanoparticles having a copper oxide coating layer on the surface are subjected to a treatment for reducing the copper oxide on the surface, and further, the copper nanoparticles subjected to the reduction treatment are fired. A method for forming a sintered body layer has been proposed. At that time, the reduction treatment and the baking treatment carried out in the same process are included in the coating layer in the plasma atmosphere generated in the presence of the reducing gas by selecting a heating temperature of 300 ° C. or lower. It is a technical feature that is performed by exposing copper nanoparticles (see Patent Document 1). An example is disclosed in which a copper sintered body film having an average film thickness of 3 μm and a resistivity of 3.2 μΩ · cm was produced by applying a copper nanoparticle firing method having a copper oxide coating layer on the surface.

  Similarly, using a dispersion liquid containing copper nanoparticles having a copper oxide coating layer on the surface, the average particle diameter being selected in the range of 1 to 100 nm, the coating layer of the dispersion liquid is drawn on the transfer sheet. After that, the copper nanoparticles having a copper oxide coating layer on the surface, which is included in the coating layer, are subjected to a treatment for reducing the copper oxide on the surface, and further, the copper nanoparticles subjected to the reduction treatment are fired. A method for forming a sintered body layer has been proposed. At that time, the reduction treatment and the baking treatment carried out in the same process are included in the coating layer in the plasma atmosphere generated in the presence of the reducing gas by selecting a heating temperature of 300 ° C. or lower. It is a technical feature that is performed by exposing copper nanoparticles (see Patent Document 2). An example is disclosed in which a copper sintered body film having an average film thickness of 2 μm and a resistivity of 4.9 μΩ · cm was produced by applying the copper nanoparticle firing method.

  In addition, when conducting conductive bonding between two metal layers, metal nanoparticles dispersed with a surface oxide film layer are used to produce a conductive bonding layer composed of metal nanoparticles used for the conductive bonding. By applying the liquid and drying the coated layer in a high-frequency plasma atmosphere containing hydrogen at a heating temperature of 150 ° C. or lower, the reduction of the surface oxide film layer and the sintering of the metal nanoparticles are performed. A method for producing a conductive bonding layer has also been proposed. Note that argon plasma generated by applying a high frequency (frequency: 13.56 MHz) to argon is used as the high-frequency plasma (see Patent Document 3).

In addition, as conductive copper paste that can be used for the production of copper thick films, copper powder, fine copper powder, copper nanoparticles, and coating molecules used on the surface of copper nanoparticles (dialkylamino) alkylamine, A conductive copper paste containing an organic solvent has been proposed. In particular,
A conductive copper paste not containing a 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 dispersed in (dialkylamino) alkylamine, to form a mixed solution,
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 (WCu-powder + WCu-fine-powder) to the weight of the third organic solvent (Wdispersion-medium), (WCu-powder + WCu-fine-powder): Wdispersion-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 (WCu-powder + WCu-fine-powder) to the total weight of the copper nanoparticles (WCu-nano-particle), (WCu-powder + WCu-fine-powder): (WCu-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 (VCu-nano-particle) to the volume of (dialkylamino) alkylamine (Vdispersion-medium). VCu-nano-particle): Vamine is selected in the range of 10:50 to 10: 100;
There has been proposed a conductive copper paste characterized in that the conductive copper paste can be fired by heating to a temperature of 300 ° C. or higher and 400 ° C. or lower (see Patent Document 4). In a reducing atmosphere containing hydrogen gas with respect to the coating film of the conductive copper paste, a temperature of 300 ° C. to 400 ° C., for example, an atmosphere containing 1 to 4% by volume of hydrogen gas in an inert gas Thus, it is described that a sintered body film can be produced by heating to a temperature selected in the range of 350 ° C. to 400 ° C. It is also described that the thickness of the sintered body film to be produced can be selected in the range of 20 μm to 100 μm, and in that case, a conductive thick film having a resistivity of 15 μΩ · cm or less can be produced. At least the narrow gaps near the contact areas between the copper powders are filled with copper nanoparticles and sintered at a low temperature. As a result, the effective contact area of the contact areas between the copper powders is expanded, It is also shown that the resistivity of the entire sintered body layer is further reduced. However, in the case disclosed in the examples, the ratio of the “voids” remaining in the 55 μm-thick sintered body film (copper thick film) is 20% by volume or more.

In addition, a conductive copper paste containing aluminum powder, metal nanoparticles, (dialkylamino) alkylamine, and an organic solvent has been proposed as a conductive aluminum paste that can be used for producing an aluminum sintered body film. In particular,
A conductive aluminum paste that does not contain glass frit,
The conductive aluminum paste is
Including aluminum powder, metal nanoparticles, organic dispersion solvent,
The aluminum powder and the metal nanoparticles are a paste-like composition dispersed in an organic dispersion solvent,
The average particle size of the aluminum powder is selected in the range of 1 μm to 5 μm,
The average particle size of the metal nanoparticles is selected in the range of 5 nm to 50 nm,
The surface of the metal nanoparticles is coated with a coating molecule,
The compound having an affinity for the organic dispersion solvent, wherein the coating agent molecule is selected from the group consisting of an aliphatic monocarboxylic acid having 10 to 18 carbon atoms and an aliphatic monoamine or diamine having 8 to 14 carbon atoms. And
The organic dispersion solvent is a nonpolar organic solvent having a boiling point in the range of 150 ° C to 350 ° C,
Per 100 parts by weight of the aluminum powder,
The content of the metal nanoparticles is selected in the range of 100 parts by mass to 230 parts by mass,
The content of the organic dispersion solvent is selected in the range of 15 to 35 parts by mass,
The content of the coating molecule covering the surface of the metal nanoparticles is
It is selected in the range of 8 to 15 parts by mass per 100 parts by mass of the metal nanoparticles,
There has been proposed a conductive aluminum paste characterized in that the conductive aluminum paste can be fired by heating to a temperature of 350 ° C. or higher and 500 ° C. or lower (see Patent Document 5). As a preferred form of the conductive aluminum paste,
In addition to the aluminum powder and metal nanoparticles,
Including fine metal powder having an average particle size of submicron,
The average particle size of the metal fine powder is selected in the range of 0.1 μm to 1 μm,
Per 100 parts by weight of the aluminum powder,
A conductive aluminum paste is proposed in which the total content of the metal fine powder is selected in the range of 5 to 50 parts by mass. It has been verified that the conductive aluminum paste can be used for producing an aluminum sintered body film having a thickness of about 15 μm. At that time, metal nanoparticles are filled in gaps around the contact sites between the aluminum powders, and the resulting sintered metal nanoparticles function as an adhesive layer that improves the adhesion between the aluminum powders. As a result, it is specified that the effective contact area at the contact area between the aluminum powders is increased, and the contact resistance at the contact area is reduced. However, in the examples disclosed in the examples, the ratio of the “void” remaining in the sintered body film (aluminum thick film) having a film thickness of about 10 μm is 8.5% by volume or more. It has become.

In addition, a conductive metal paste containing metal powder and metal nanoparticles and blending a resin component is also proposed, which is suitable for the production of a thick film conductor layer. In particular,
A conductive metal paste,
The conductive metal paste comprises a varnish-like resin composition, a metal filler uniformly dispersed therein, and metal ultrafine particles having a fine average particle diameter,
The metal filler is selected in the range of an average particle size of 0.5 to 20 μm,
The metal ultrafine particles having a fine average particle diameter are selected so that the average particle diameter is in the range of 1 to 100 nm,
The ultrafine metal particle surface contains nitrogen, oxygen, or sulfur atoms as groups capable of coordinative bonding with the metal elements contained in the ultrafine metal particles, and coordinated bonds by lone electron pairs of these atoms. Covered with one or more compounds having a group capable of
The total amount of one or more compounds having a group containing nitrogen, oxygen, or sulfur atoms with respect to 100 parts by mass of the ultrafine metal particles, 0.1 to 60 parts by mass,
The varnish-like resin composition is a group containing a nitrogen, oxygen, or sulfur atom when heated with respect to a resin component that functions as an organic binder, and a compound having a group containing nitrogen, oxygen, or sulfur atoms. A compound component having reactivity with, and at least one organic solvent,
A conductive metal paste comprising 5 to 100 parts by mass of the varnish-like resin composition per 100 parts by mass of the total of the metal filler and ultrafine metal particles having a fine average particle diameter is proposed. (See Patent Document 6). A “resin component” that functions as an organic binder, for example, a thermosetting resin, has a function of improving adhesion to a substrate. Further, in the conductive layer produced using the conductive metal paste, there is no “void” inside as a result of the “resin” densely filling the gap between the sintered body of the metal filler and the metal ultrafine particles. It is in a state.

JP 2004-119686 A JP 2004-247572 A JP 2007-083288 A JP 2012-28243 A JP 2011-119340 A International Publication No. 2002/035554 Pamphlet

  It can be fired by heat treatment at a temperature of 300 ° C. or higher and 400 ° C. or lower in a reducing atmosphere, for example, at 350 ° C. in a reducing atmosphere for at least 10 minutes. Available conductive copper pastes have already been proposed. However, due to the heat treatment, the “copper thick film” produced by adopting the already proposed conductive copper paste has a “porosity” of 20% by volume in the fired film, or More than that, that is, there are “voids” inside, and cannot be said to be “bulk copper thick film”.

  In other words, the development of a “copper thick film forming material” of the conductive copper paste type that can be used for the production of “bulk copper thick film” in which “void” does not substantially exist inside is desired. Yes.

  For example, instead of heating at a temperature of 300 ° C. or higher and 400 ° C. or lower for 10 minutes or longer, at least the preheating temperature of the substrate is selected to be 200 ° C. or lower, and then the heating time required for the firing treatment is 10 minutes or shorter. However, there is a demand for the development of a conductive copper paste that can be used for the production of “bulk copper thick film” that can be satisfactorily sintered and has substantially no “void” inside. .

  Furthermore, instead of heating at a temperature of 300 ° C. or higher and 400 ° C. or lower for 10 minutes or longer, the substrate preheating temperature is selected to be at least 200 ° C. or lower and the substrate is heated to 200 ° C. or lower. Good firing is possible by irradiating the plasma under a reducing atmosphere for 10 minutes or less, preferably 5 minutes or less at a temperature, and there are substantially "voids" inside. There is a demand for the development of a conductive copper paste that can be used to produce a “bulk copper thick film”.

  In addition to the production of copper thick film, conductive silver that can be used for production of “bulk-shaped silver thick film” in which “void” does not substantially exist in the production of silver thick film. Development of a paste-type “material for forming a silver thick film” is desired.

  For example, instead of heating at a temperature of 300 ° C. or higher and 400 ° C. or lower for 10 minutes or longer, the substrate preheating temperature is selected to be at least 200 ° C. or lower, and the heating temperature of the substrate is selected to be 200 ° C. or lower. Lower, 10 minutes or less, desirably 5 minutes or less, plasma can be irradiated in a reducing atmosphere for good firing, and there is substantially no “void” inside. Development of a conductive silver paste that can be used for the production of a “bulk-shaped silver thick film” is desired.

  The present invention solves the above problems. The goal of the present invention is, for example, that it can be fired satisfactorily by irradiating plasma in a reducing atmosphere, and can be used for the production of a “bulk conductive metal thick film” having a film thickness of 1 μm or more. Using a new configuration, the conductive metal paste type “conductive metal thick film forming material” and the conductive metal paste type “conductive metal thick film forming material” An object of the present invention is to provide a method for forming a “bulk conductive metal thick film” of 1 μm or more.

  Specifically, one of the goals of the present invention is to produce a “bulk copper thick film” having a film thickness of 1 μm or more by irradiating plasma in a reducing atmosphere, which enables good firing. Utilizing a new structure that can be used, conductive copper paste type “copper thick film forming material”, and the conductive copper paste type “copper thick film forming material” An object of the present invention is to provide a method of forming a “bulk copper thick film” of 1 μm or more.

  Another goal of the present invention is that it can be fired satisfactorily by irradiating plasma in a reducing atmosphere, and can be used for the production of a “bulk-shaped silver thick film” having a film thickness of 1 μm or more. A conductive silver paste type “silver thick film forming material” and a “silver thick film forming material” of the conductive silver paste type adopting a novel configuration, and having a film thickness of 1 μm or more The object is to provide a method of forming a “bulk-shaped silver thick film”.

  The “preferable target” of the present invention is, for example, that the preheating temperature of the substrate is selected to be at least 200 ° C. or less, and the heating temperature of the substrate is selected to be 200 ° C. or less. A novel conductive copper paste that can be fired by irradiating plasma in a reducing atmosphere for a period of 5 minutes or less and that can be used to produce a “bulk copper thick film” with a thickness of 10 μm or more To provide a novel copper thick film forming material and a novel conductive silver paste type silver thick film forming material that can be used for the production of a “bulk-shaped silver thick film” having a thickness of 10 μm or more is there.

  The present applicant has already proposed the following two types of conductive metal pastes and applied for patents as conductive metal pastes applicable to the formation of a “conductive metal thick film”.

One of the already proposed “conductive metal pastes” (Japanese Patent Application No. 2010-265991) has the following configuration.
"A conductive metal paste containing no binder resin component,
The conductive metal paste is a dispersion obtained by uniformly dispersing fine metal powder, metal nanoparticles having a coating molecular layer on the surface thereof in a dispersion solvent,
The conductive metal paste can be subjected to a sintering treatment at a temperature selected in the range of 150 ° C. to 250 ° C., thereby forming a conductor layer composed of a sintered body of the metal fine powder and metal nanoparticles. ;
The metal fine powder, the metal species constituting the metal fine powder is selected from the group consisting of gold, silver, copper, platinum, palladium, nickel, one type of metal fine powder, two or more types of metal Either a mixture of fine metal powders consisting of seeds or a fine metal powder consisting of an alloy consisting of two or more metal species;
The metal nanoparticle is a metal nanoparticle composed of one kind of metal selected from the group consisting of gold, silver, copper, platinum, palladium, nickel, and two or more kinds of metals. Either a mixture of metal nanoparticles consisting of seeds or metal nanoparticles consisting of an alloy consisting of two or more metal species;
The average particle diameter dmetal-particle of the metal fine powder is (1/3 · tconductive-layer) ≧ dmetal-particle ≧ (1/100 · tconductive-layer) with respect to the thickness tconductive-layer of the conductive layer to be produced. ) Selected in the range;
The average particle diameter dmetal-particle of the metal nanoparticle itself is (1/10 · dmetal-particle) ≧ dnano-particle ≧ (1/100 · dmetal-) relative to the average particle diameter dmetal-particle of the fine metal powder. particle) range;
The volume ratio of the metal fine powder contained in the conductive metal paste is Vmetal-particle, the volume ratio of the metal nanoparticles is Vnano-particle, and the volume of the coating molecule used to form the coating molecule layer. If the ratio is Vcoating-molecule and the volume ratio of the dispersion solvent is Vsolvent,
The sum of the volume ratio Vmetal-particle of the metal fine powder and the volume ratio Vnano-particle of the metal nanoparticles (Vmetal-particle + Vnano-particle) is selected in the range of 30 volume% to 55 volume%;
The ratio Vmetal-particle: (Vnano-particle + Vcoating-molecule + Vsolvent) is selected in the range of 1: 1 to 1: 4.6;
Ratio (Vnano-particle + Vcoating-molecule): Vsolvent is selected in the range of 1: 0.7 to 1: 3;
The ratio (Vmetal-particle: Vnano-particle) is selected in the range of 90: 10-60: 40;
The dispersion solvent is selected from the group consisting of a hydrocarbon solvent having a boiling point in the range of 150 ° C. to 300 ° C., or an alcohol solvent having a boiling point in the range of 150 ° C. to 300 ° C .;
The coating molecule used for forming the coating molecular layer has an amino group or a carboxyl group as an atomic group used for forming an intermolecular bond non-covalently with the surface of the metal nanoparticle. An organic compound composed of a hydrocarbon group having an affinity for a hydrocarbon group in the hydrocarbon solvent or alcohol solvent, and the amino group or carboxyl group, the boiling point of which is in the range of 130 ° C to 250 ° C. Conductive metal paste characterized by being selected from the group consisting of organic compounds having amino groups or carboxyl groups of
When using the “conductive metal paste” having the above-described configuration, for example, “conductive silver paste”, when the sintering process is performed at a temperature selected in the range of 150 ° C. to 250 ° C., the average film thickness is 33.5 μm. It is verified that the ratio of the “void” remaining in the “produced silver thick film” reaches 6.4% by volume when applied to the production of a thick silver film.

Another one of the “conductive metal paste” that has already been proposed (Japanese Patent Application No. 2011-140609) has the following configuration, for example.
"A conductive paste that does not contain a binder resin component,
The conductive paste is a dispersion obtained by uniformly dispersing metal nanoparticles and metal nanoparticles having a coating molecular layer on the surface thereof in a dispersion solvent.
The conductive paste is applied to the substrate surface to form a coating film,
The coating film is allowed to stand, metal microparticles contained in the coating film are allowed to settle, and an accumulation layer of metal microparticles is formed on the surface of the substrate.
Thereafter, by performing heat treatment at a temperature Theating selected in the range of 150 ° C. to 300 ° C., low-temperature sintering of the metal nanoparticles proceeds, and a lower layer portion derived from the metal microparticle accumulation layer and an upper portion thereof It is possible to form a conductive structure having a gradient composition comprising a surface layer derived from a low-temperature sintered body of the metal nanoparticles;
The metal microparticle is a kind of metal selected from the group consisting of gold, silver, copper, platinum, palladium, indium, bismuth, titanium, tin, nickel, and aluminum. Metal microparticles, a mixture of metal microparticles composed of two or more metal species, or metal microparticles composed of an alloy composed of two or more metal species;
The metal nanoparticle is a kind of metal selected from the group consisting of gold, silver, copper, platinum, palladium, indium, bismuth, titanium, tin, nickel, and aluminum. A metal nanoparticle, a mixture of metal nanoparticles composed of two or more metal species, or a metal nanoparticle composed of an alloy composed of two or more metal species;
The average particle diameter dmetal-particle of the metal microparticle is selected in the range of 1 μm to 10 μm;
The average particle diameter dnano-particle of the metal nanoparticles themselves is selected in the range of 1 nm to 100 nm;
The coating molecule used for forming the coating molecule layer has a boiling point Tcoating-molecule-bp,
Selected from the group consisting of alkylamines ranging from 150 ° C to 250 ° C;
The dispersion solvent is selected from the group consisting of hydrocarbon solvents, the boiling point Tsolvent-bp of which ranges from 150 ° C to 350 ° C;
The volume ratio of the metal microparticles contained in the conductive paste is Vmetal-particle, the volume ratio of the metal nanoparticles is Vnano-particle, and the volume ratio of the coating molecules used to form the coating molecule layer. Is Vcoating-molecule and the volume ratio of the dispersion solvent is Vsolvent.
The sum of the volume ratio Vmetal-particle of the metal microparticles and the volume ratio Vnano-particle of the metal nanoparticles (Vmetal-particle + Vnano-particle) is selected in the range of 40 vol% to 60 vol%,
The ratio Vmetal-particle: Vnano-particle is selected in the range of 90: 10-60: 40,
The volume ratio Vmetal-particle of the metal microparticle is selected in the range of 20 vol% to 50 vol%,
The ratio Vnano-particle: Vcoating-molecule is selected in the range of 1: 1 to 1: 2.
The ratio Vnano-particle: (Vnano-particle + Vcoating-molecule + Vsolvent) is selected in the range of 10: 100 to 30: 100.
When using the “conductive paste” having the above-described configuration, for example, “conductive copper paste”, when the sintering process is performed at a temperature selected in the range of 150 ° C. to 300 ° C., the copper thickness with an average film thickness of 55 μm When applied to the production of a film, it has been verified that the ratio of “voids” remaining in the “produced copper thick film” reaches 22.7% by volume.

  The present inventors have a configuration different from the above-described two types of conductive metal pastes (Japanese Patent Application Nos. 2010-265991 and 2011-140609), and have a “bulk-like conductive type having a thickness of 1 μm or more. We have developed a conductive metal paste type “conductive metal thick film forming material” that can be used for the production of “conductive metal thick film”.

  The present inventors reduced the copper nanoparticles having a copper oxide coating layer on the surface by selecting a heating temperature of 300 ° C. or less and exposing them to a generated plasma atmosphere in the presence of a reducing gas. It paid attention to the point which can carry out processing and baking processing in parallel. Moreover, when producing a copper thick film, copper powder, fine copper powder, and copper nanoparticles are used in combination to form a laminated structure composed of copper powder and fine copper powder, forming the laminated structure, copper powder, The inventors also paid attention to the fact that a copper thick film exhibiting good conductivity can be obtained by filling a contact portion of fine copper powder with a sintered body of copper nanoparticles.

  Utilizing the above two elemental technologies, copper nanoparticles are densely filled in the gaps in the laminated structure consisting of copper powder and fine copper powder, and in addition, the laminated structure consisting of copper powder and fine copper powder When the structure of embedding the unevenness of the upper surface with copper nanoparticles is achieved, a “bulk” having a film thickness of 1 μm or more is formed on the upper surface of the resulting thick copper film, in which no “void” is generated due to a gap between the copper powder and the fine copper powder. It has been found that it is possible to form a “thick copper film”.

  Furthermore, the silver nanoparticles having a silver oxide coating layer on the surface are subjected to a reduction treatment and a firing treatment by selecting a heating temperature of 300 ° C. or less and exposing them to a generated plasma atmosphere in the presence of a reducing gas. We focused on the fact that it can be implemented in parallel. Moreover, when producing a silver thick film, by using silver powder and silver nanoparticles in combination, a laminated structure made of silver powder is formed, and a sintered body of silver nanoparticles is formed at the contact portion of the silver powder to form the laminated structure. It also paid attention to the fact that a thick silver film showing good conductivity can be obtained by filling.

  Utilizing the above two elemental technologies, a structure in which silver nanoparticles are densely filled in gaps in a laminated structure made of silver powder, and in addition, the irregularities on the upper surface of the laminated structure made of silver powder are embedded with silver nanoparticles As a result, it has been found that a “bulk-shaped thick silver film” can be formed on the upper surface of the resulting thick silver film without causing “voids” due to gaps between silver powders.

  At that time, the “conductive metal paste” type conductive metal thick film forming material used, for example, the “conductive copper paste” type copper thick film forming material, the “conductive silver paste” type silver thickness The film forming materials use copper nanoparticles and silver nanoparticles, respectively, but when using metal nanoparticles selected from the group consisting of copper nanoparticles, silver nanoparticles, and gold nanoparticles, the film thickness It has been found that a “bulk-shaped copper thick film” having a thickness of 1 μm or more and a “bulk-shaped silver thick film” having a thickness of 1 μm or more can be formed.

  The present invention has been completed based on the above findings.

"Conductive metal thick film forming material" according to the present invention,
A conductive metal thick film forming material used for forming a conductive metal thick film,
The conductive metal thick film forming material includes metal particles and metal nanoparticles used for forming the conductive metal thick film, and an organic substance, and is a material that exhibits fluidity that can be applied.
After applying a conductive metal thick film forming material on the substrate and forming a conductive metal thick film forming material coating film,
By applying a firing process by irradiating microwave plasma in a reducing atmosphere,
A conductive metal thick film forming material characterized in that a bulk conductive metal thick film can be formed from metal particles and metal nanoparticles contained in a coating film.

  In the “conductive metal thick film forming material” according to the present invention, the following preferred embodiments can be adopted.

  The metal particles are preferably selected from the group consisting of copper particles, silver particles, and aluminum particles.

  The metal nanoparticles are preferably selected from copper nanoparticles, silver nanoparticles, and gold nanoparticles.

The metal nanoparticles are
A coating molecule layer comprising at least one compound having an amino group (—NH 2) or a carboxyl group (—COOH) as an atomic group that can be used for forming a non-covalent intermolecular bond with a metal on the surface. Is preferably formed.

The metal nanoparticles are
The average particle diameter is desirably selected in the range of 1 nm to 200 nm, preferably in the range of 5 nm to 100 nm, more preferably in the range of 10 nm to 100 nm.

The metal particles are
It is desirable that the outer shape is a metal particle having a substantially spherical shape and / or a scale shape.

The metal particles are
It is desirable that the average particle diameter is selected in the range of 0.2 μm to 30 μm, preferably in the range of 0.3 μm to 20 μm, more preferably in the range of 0.4 μm to 10 μm.

As the compound having an amino group, used for forming the coating agent molecular layer,
It is preferable to select one or more amine compounds having one or more terminal amino groups.

  One or more amine compounds having one or more terminal amino groups preferably contain an alkylamine.

  It is preferable that the one or more compounds having a carboxyl group used for forming the coating agent molecular layer include an aliphatic carboxylic acid having 8 to 20 carbon atoms.

For 100 volume% of the metal particles,
The content of the metal nanoparticles is desirably selected in the range of 5% by volume to 90% by volume, preferably in the range of 7% by volume to 80% by volume.

  It is desirable that the total sum of the metal particles and the metal nanoparticles is selected in the range of 30% by volume to 80% by volume, preferably in the range of 40% by volume to 70% by volume.

The material showing the fluidity that can be applied is
In order to adjust the viscosity of the mixture of metal particles and metal nanoparticles to a viscosity suitable for printing, it is preferable to add a solvent.

The material showing the fluidity that can be applied is
It is preferable that a resin is added to the mixture of the metal particles and the metal nanoparticles in order to improve the adhesion to the base material or to impart fluidity after curing.

When irradiating with microwave plasma,
The frequency of the microwave used to generate the microwave plasma is
It is desirable that the frequency is selected in the range of 300 MHz to 300 GHz, preferably in the range of 3 GHz to 100 GHz.

When irradiating with microwave plasma,
The output of the microwave used for generating the microwave plasma is preferably selected in the range of 300 W to 3 kW.

When irradiating with microwave plasma,
The microwave plasma irradiation time is preferably selected in the range of 30 seconds to 30 minutes, preferably in the range of 1 minute to 15 minutes.

Upon irradiation with microwave plasma in a reducing atmosphere,
The reducing atmosphere is preferably hydrogen or a mixture of hydrogen and an inert gas such as nitrogen, helium, or argon.

After applying a conductive metal thick film forming material on the substrate and forming a conductive metal thick film forming material coating film,
The process of firing by irradiating microwave plasma in a reducing atmosphere,
After the step of applying the conductive metal thick film forming material on the substrate,
Drying the coating film of the conductive metal thick film forming material to remove the solvent,
Removing the remaining organic matter under reduced pressure;
It is desirable to have a step of firing by irradiating microwave plasma in a reducing atmosphere.

The “method for forming a conductive metal thick film” according to the present invention includes:
A method of forming a conductive metal thick film using a conductive metal thick film forming material,
The conductive metal thick film forming material is:
It contains metal particles and metal nanoparticles used to form a conductive metal thick film, and organic matter, and exhibits applicable fluidity.
After applying a conductive metal thick film forming material on the substrate and forming a conductive metal thick film forming material coating film,
By applying a firing process by irradiating microwave plasma in a reducing atmosphere,
It is a material that can form a bulk conductive metal thick film from metal particles and metal nanoparticles contained in the coating film,
The method for forming the conductive metal thick film is as follows:
After applying a conductive metal thick film forming material on the substrate and forming a conductive metal thick film forming material coating film,
By applying a firing process by irradiating microwave plasma in a reducing atmosphere,
Comprising a process of forming a bulk conductive metal thick film from metal particles and metal nanoparticles contained in a coating film,
This is a method for forming a conductive metal thick film.

  In the “method for forming a conductive metal thick film” according to the present invention, for example, the following preferred embodiments can be adopted for the “conductive metal thick film forming material” used.

  The metal particles are preferably selected from the group consisting of copper particles, silver particles, and aluminum particles.

  The metal nanoparticles are preferably selected from copper nanoparticles, silver nanoparticles, and gold nanoparticles.

The metal nanoparticles are
A coating molecule layer comprising at least one compound having an amino group (—NH 2) or a carboxyl group (—COOH) as an atomic group that can be used for forming a non-covalent intermolecular bond with a metal on the surface. Is preferably formed.

The metal nanoparticles are
The average particle diameter is desirably selected in the range of 1 nm to 200 nm, preferably in the range of 5 nm to 100 nm, more preferably in the range of 10 nm to 100 nm.

The metal particles are
It is desirable that the outer shape is a metal particle having a substantially spherical shape and / or a scale shape.

The metal particles are
It is desirable that the average particle diameter is selected in the range of 0.2 μm to 30 μm, preferably in the range of 0.3 μm to 20 μm, more preferably in the range of 0.4 μm to 10 μm.

As the compound having an amino group, used for forming the coating agent molecular layer,
It is preferable to select one or more amine compounds having one or more terminal amino groups.

  One or more amine compounds having one or more terminal amino groups preferably contain an alkylamine.

  It is preferable that the one or more compounds having a carboxyl group used for forming the coating agent molecular layer include an aliphatic carboxylic acid having 8 to 20 carbon atoms.

For 100 volume% of the metal particles,
The content of the metal nanoparticles is desirably selected in the range of 5% by volume to 90% by volume, preferably in the range of 7% by volume to 80% by volume.

  It is desirable that the total sum of the metal particles and the metal nanoparticles is selected in the range of 30% by volume to 80% by volume, preferably in the range of 40% by volume to 70% by volume.

The material showing the fluidity that can be applied is
In order to adjust the viscosity of the mixture of metal particles and metal nanoparticles to a viscosity suitable for printing, it is preferable to add a solvent.

The material showing the fluidity that can be applied is
It is preferable that a resin is added to the mixture of the metal particles and the metal nanoparticles in order to improve the adhesion to the base material or to impart fluidity after curing.

When irradiating with microwave plasma,
The frequency of the microwave used to generate the microwave plasma is
It is desirable that the frequency is selected in the range of 300 MHz to 300 GHz, preferably in the range of 3 GHz to 100 GHz.

When irradiating with microwave plasma,
The output of the microwave used for generating the microwave plasma is preferably selected in the range of 300 W to 3 kW.

When irradiating with microwave plasma,
The microwave plasma irradiation time is preferably selected in the range of 30 seconds to 30 minutes, preferably in the range of 1 minute to 15 minutes.

Upon irradiation with microwave plasma in a reducing atmosphere,
The reducing atmosphere is preferably hydrogen or a mixture of hydrogen and an inert gas such as nitrogen, helium, or argon.

After applying a conductive metal thick film forming material on the substrate and forming a conductive metal thick film forming material coating film,
The process of firing by irradiating microwave plasma in a reducing atmosphere,
After the step of applying the conductive metal thick film forming material on the substrate,
Drying the coating film of the conductive metal thick film forming material to remove the solvent,
Removing the remaining organic matter under reduced pressure;
It is desirable to have a step of firing by irradiating microwave plasma in a reducing atmosphere.

  By using the “conductive metal thick film forming material” according to the present invention, the conductive metal thick film forming material was applied onto the substrate to form a coating film of the conductive metal thick film forming material. After that, a “bulk conductive metal thick film” is formed from the metal particles and metal nanoparticles contained in the coating film by performing a firing process by irradiating with microwave plasma in a reducing atmosphere. be able to.

  For example, by using the “copper thick film forming material” of the conductive copper paste type according to the present invention, instead of heating at a temperature of 300 ° C. or more and 400 ° C. or less for 10 minutes or more, the substrate preheating temperature At least at a temperature of 180 ° C. or less, and at a heating temperature of the substrate selected to be 200 ° C. or less, for example, by irradiating plasma in a reducing atmosphere for a time of 10 minutes or less. It becomes possible to easily produce a “bulk copper thick film” having conductivity.

  Further, by using the conductive silver paste type “material for forming a thick silver film” according to the present invention, the heating temperature of the base material is changed to a preheating temperature of the base material in place of heating at a temperature of 300 ° C. or higher and 400 ° C. or lower for 10 minutes or longer. At least at a temperature of 180 ° C. or less, and at a heating temperature of the substrate selected to be 200 ° C. or less, for example, by irradiating plasma in a reducing atmosphere for a time of 10 minutes or less. It is possible to easily produce a “bulk-shaped silver thick film” having conductivity.

  Furthermore, by using the conductive aluminum paste type “aluminum thick film forming material” according to the present invention, the substrate is preheated at a temperature of 300 ° C. to 400 ° C. for 10 minutes or more. The temperature is selected to be at least 180 ° C. or lower, and the substrate is selected to be 200 ° C. or lower. For example, the plasma is irradiated in a reducing atmosphere for 10 minutes or less in a reducing atmosphere. It is possible to easily produce a “bulk-like thick aluminum film” having excellent conductivity.

The result of SEM observation of the microscopic structure of the produced “copper thick film” is shown. The left is in a reducing atmosphere, when microwave plasma irradiation is used (Example 1), and the left is in a reducing atmosphere. The surfaces of the “copper thick film” in the case of using infrared irradiation (infrared heating) (Comparative Example 1) are respectively shown. Immediately after application in the step of applying the conductive metal paste type “conductive metal thick film forming material” according to the present invention to the surface of the substrate, the step of subjecting the coating film to a preheating drying treatment, and the step of subjecting it to a reduced pressure drying treatment Of metal microparticles in the coating film of metal, and then formation of a microparticle accumulation layer (metal powder laminate structure) by sedimentation of metal microparticles, a nanoparticle accumulation layer (metal nanoparticle laminate structure) accompanying evaporation of the solvent FIG. 6 is a diagram schematically illustrating an example of a formation process.

  The “conductive metal thick film forming material” and the “conductive metal thick film forming method” according to the present invention will be described in more detail with reference to typical embodiments thereof.

  The “conductive metal thick film forming material” according to the present invention contains at least metal particles and metal nanoparticles used for forming the conductive metal thick film. Generally, based on the use of the “conductive metal thick film” to be produced, the metal species used for forming the conductive metal thick film and the metal species of the metal nanoparticles are selected. Usually, “metal powder” which is “metal microparticles” having an average particle diameter of 1 μm or more is used as the metal particles. In general, the metal species constituting the “metal powder” are, for example. It is selected from the group consisting of gold, silver, copper, platinum, palladium, indium, bismuth, titanium, tin, nickel, and aluminum. At that time, the metal species constituting the “metal nanoparticles” can also be selected from the group consisting of gold, silver, copper, platinum, palladium, indium, bismuth, titanium, tin, nickel, and aluminum. Therefore, the “material for forming a conductive metal thick film” according to the present invention includes at least various metal species used for forming the conductive metal thick film and various combinations of metal species of the metal nanoparticles. According to the form, that is, the selection of the metal species constituting the “metal powder”, the “metal thick film forming material” of the metal species is obtained.

As an example of a representative form of the “conductive metal thick film forming material” according to the present invention,
As the metal particles used for forming the conductive metal thick film, at least “copper powder” which is “copper microparticles” having an average particle diameter of 1 μm or more is adopted, and as the metal nanoparticles, “copper nanoparticles”, “silver” “Nanoparticles”, “gold nanoparticles”, in particular, a form of selecting “copper nanoparticles”, “copper thick film forming material”;
As the metal particles used for forming the conductive metal thick film, at least “silver powder” which is “silver microparticles” having an average particle diameter of 1 μm or more is adopted, and “copper nanoparticles”, “silver” are used as metal nanoparticles. “Nanoparticles”, “gold nanoparticles”, in particular, “silver nanoparticles” in a selected form, “silver thick film forming material”;
As the metal particles used for forming the conductive metal thick film, at least “silver powder” which is “aluminum microparticles” having an average particle diameter of 1 μm or more is adopted, and as the metal nanoparticles, “copper nanoparticles”, “silver” “Nanoparticles”, “gold nanoparticles”, in particular, “silver nanoparticles” in a selected form, “aluminum thick film forming material”;
The following three forms can be mentioned.

  The “conductive metal thick film forming material” according to the present invention is the following “copper thick film forming material”, “silver thick film forming material”, or “aluminum thick film forming material”. It is desirable to implement in.

  Hereinafter, the “copper thick film forming material”, the “copper thick film forming method”, and the “aluminum thick film forming material” according to the present invention will be described in more detail.

  First, in the “copper thick film forming material” according to the present invention, the average film thickness tCu-sintered layer of the “copper thick film” to be formed is at least 1 μm or more (tCu-sintered layer ≧ 1 μm), usually The range is 10 μm to 100 μm (100 μm ≧ tCu-sintered layer ≧ 10 μm), preferably 15 μm to 60 μm (60 μm ≧ tCu-sintered layer ≧ 15 μm).

  In order to achieve the target “thick copper film” average film thickness tCu-sintered layer, a fired film having a main structure of a laminated structure of copper powder in which copper powder is densely laminated is formed. Therefore, the average particle diameter dCu-particle of the copper powder used for the structure of the laminated structure of the copper powder is at least within a range not exceeding the target average film thickness tCu-sintered layer of the “copper thick film” (tCu-sintered layer). layer> dCu-particle). Since the particle diameter of the copper powder shows a distribution centering on the average particle diameter dCu-particle, copper powder having a particle diameter larger than the average particle diameter dCu-particle is included. Considering the particle size distribution, the average particle size dCu-particle of the copper powder used is usually 1/2 · (tCu-sintered layer) ≧ dCu-particle ≧ 1/20 · (tCu-sintered layer) Preferably, the range of 1/3 · (tCu-sintered layer) ≧ dCu-particle ≧ 1/10 · (tCu-sintered layer) is selected.

  In order to effectively reduce the contact resistance rcontact-Cu-particle at the contact area between “copper powder”, which constitutes the laminated structure of copper powder, in the narrow gap near the contact area between “copper powder” The copper nanoparticles are filled to form a low-temperature sintered body of copper nanoparticles.

  In addition, since there is a “gap” between the “copper powder” constituting the laminated structure of the copper powder, it exists between the “copper powder” in the “laminated structure of the copper powder”. There are “voids” due to “clearances”.

  The tap density ρCu-particle-tap of the “copper powder” used is smaller than the density ρCu-bulk of metallic copper (bulk). The sum (Σvspace + Σvparticle) of the volume (vspace) of the “void” existing in the “copper powder laminate structure” and the sum of the volume (vparticle) of the “copper powder” (vparticle) in the “copper powder laminate structure” This corresponds to the bulk volume of the “laminated structure of copper powder”.

  Assuming that the “copper powder” in the “copper powder laminate structure” is laminated in the “close-packed” state, the total volume (vparticle) of the “copper powder” in the “copper powder laminate structure” The ratio of Σvparticle to the bulk volume (Σvspace + Σvparticle) of the “copper powder laminated structure”, {Σvparticle / (Σvspace + Σvparticle)}, is estimated as (ρCu-particle-tap / ρCu-bulk). Therefore, the ratio {Σvspace / (Σvspace + Σvparticle)} of the total volume Σvspace of the “voids” existing in the “copper powder laminate structure” and the bulk volume (Σvspace + Σvparticle) of the “copper powder laminate structure” is , {1- (ρCu-particle-tap / ρCu-bulk)}.

In the “copper thick film forming material” according to the present invention, preferably, a copper fine powder is added, and the “copper fine powder” is taken into “interstices” existing between the “copper powder”. It is assumed that a “copper fine powder” is filled in a substantial portion of “voids” existing in the “laminated structure of powder”.
The average particle diameter dCu-fine-particle of the “copper fine powder” filled in the “gap” existing between the “copper powder” is usually based on the average particle diameter dCu-particle of the “copper powder”. 1/3 · (dCu-particle) ≧ dCu-fine-particle ≧ 1/15 · (dCu-particle), preferably 1/4 · (dCu-particle) ≧ dCu-fine-particle ≧ 1/10・ Select within the range of (dCu-particle).

  The tap density ρCu-fine-particle-tap of “copper fine powder” is smaller than the density ρCu-bulk of metallic copper (bulk).

  The “copper fine powder” taken into the “gap” existing between the “copper powder” is rarely taken into the “gap” in the “close-packed” state. Since the “copper powder” itself has a particle size distribution, the individual sizes of the “gap” existing between the “copper powder” also have a distribution. As a result, the “copper fine powder” is virtually never taken into the “gap” in the “close-packed” state.

  The sum total of the bulk volume of the “copper fine powder” taken into the “gap” is somewhat smaller than the total Σvspace of the volume (vspace) of “voids” existing in the “laminated structure of copper powder”. The sum of the bulk volume of the “copper fine powder” taken into the “gap” is {(ρCu-bulk / ρCu-fine] with respect to the total Σvfine-particle of the volume (vfine-particle) of the taken “copper fine powder”. -particle-tap) · Σvfine-particle}.

  Therefore, {(ρCu-bulk / ρCu-fine-particle-tap) · Σvfine-particle} is at least relative to the total Σvspace of the volume (vspace) of “voids” present in the “copper powder laminate structure”. , Σvspace> {(ρCu-bulk / ρCu-fine-particle-tap) · Σvfine-particle}. When adding “copper fine powder”, usually in the range of 5/6 · Σvspace ≧ {(ρCu-bulk / ρCu-fine-particle-tap) · Σvfine-particle} ≧ 2/6 · Σvspace, preferably 4 / 5 · Σvspace ≧ {(ρCu-bulk / ρCu-fine-particle-tap) · Σvfine-particle} ≧ 2/5 · the volume of “copper fine powder” to be in the range of Σvspace (vfine-particle It is desirable to adjust the total Σvfine-particle).

Σvspace is based on the total Σvparticle of the volume (vparticle) of “copper powder”.
(Σvspace / Σvparticle)
= {1- (ρCu-particle-tap / ρCu-bulk)} / (ρCu-particle-tap / ρCu-bulk)
= {(ΡCu-bulk / ρCu-particle-tap) -1}.

The ratio (Σvfine-particle / Σvparticle) of the total volume (vfine-particle) of the added “copper fine powder” Σvfine-particle and the total volume (vparticle) of the “copper powder” (Σvfine-particle / Σvparticle)
Usually, 5/6 · {(ρCu-bulk / ρCu-particle-tap) -1} / (ρCu-bulk / ρCu-fine-particle-tap) ≧ (Σvfine-particle / Σvparticle) ≧ 2/6 · {( ρCu-bulk / ρCu-particle-tap) -1} / (ρCu-bulk / ρCu-fine-particle-tap),
Preferably, 4/5 · {(ρCu-bulk / ρCu-particle-tap) -1} / (ρCu-bulk / ρCu-fine-particle-tap) ≧ (Σvfine-particle / Σvparticle) ≧ 2/5 · { It is desirable to adjust to the range of (ρCu-bulk / ρCu-particle-tap) -1} / (ρCu-bulk / ρCu-fine-particle-tap).

  In a form in which “copper fine powder” is filled with a substantial portion of “voids” present in “laminated structure of copper powder”, “copper powder” and “copper” are filled even after filling with “copper fine powder”. A narrow gap remains between the “fine powder” and the “copper fine powder”. The total volume of the narrow gaps, that is, the total volume of the “remaining voids” present in the “copper powder laminate structure” is added from the total Σvspace of the volume (vspace) of the “voids”. This corresponds to a value obtained by subtracting the total Σvfine-particle (Σvspace-Σvfine-particle) of the volume of powder ”(vfine-particle).

  In addition to “copper powder” and “copper fine powder”, the “copper thick film forming material” according to the present invention includes “copper nanoparticles” and “coating agent molecules that coat the surfaces of the“ copper nanoparticles ”. “Coating molecule” used for forming the “layer” and “organic solvent” used as a dispersion solvent are contained.

  Part of the “coating agent molecule” is dissolved in the “organic solvent”, and the “coating agent molecule” dissolved in the “organic solvent” and the “coating agent molecular layer” on the surface of the “copper nanoparticles” The “coating molecule” constituting “is achieving a dissociation equilibrium. That is, the “coating molecule molecule” forming the “coating agent molecular layer” on the “copper nanoparticle” surface, and the “coating agent molecule” dissolved in the “organic solvent”. The dissociation equilibrium is achieved between the concentration of Ccoating-molecule-liquid-phase.

  The “coating agent molecule” can also form a “coating agent molecule layer” having a surface density Ccoating-molecule-surface on the surfaces of “copper powder” and “copper fine powder”. However, the total surface area of “copper nanoparticles” ΣSCu-nanoparticle, the total surface area of “copper fine powder” ΣSCu-fine-particle, the total surface area of “copper powder” ΣSCu-particle is ΣSCu-nanoparticle >> ΣSCu-fine -particle >> ΣSCu-particle, and the amount of “coating molecules” covering the surface of “copper fine powder” and “copper powder” is the same as “coating agent” covering the surface of “copper nanoparticles” It is a negligible range for the amount of “molecule”.

  Therefore, the amount Mcoating-molecule-surface of the “coating molecule” covering the surface of the “copper nanoparticle” and the amount Mcoating-molecule-liquid-phase of the “coating agent molecule” dissolved in the “solvent”. The total can be regarded as the total amount Mcoating-molecule of “coating agent molecules” contained in the “copper thick film forming material” (Mcoating-molecule = Mcoating-molecule-surface + Mcoating-molecule-liquid-phase).

  The “copper nanoparticles” that form the “coating agent molecular layer” on the surface are uniformly dispersed in the “organic solvent” in which the “coating agent molecule” is dissolved to form a “liquid phase”. Yes.

  This “liquid phase” fills the “residual voids” present in the “copper powder laminated structure”, and the excess “liquid phase” immerses the upper surface of the “copper powder laminated structure”.

  Sum of volume (vnano-particle) of “copper nanoparticles” Σvnano-particle, volume of “coating agent molecule” (vcoating-molecule), sum of volume of “organic solvent” (vsolvent), {Σvnano-particle + vcoating-molecule + vsolvent} Is at least larger than the total volume (Σvspace−Σvfine-particle) of “residual voids” existing in the “copper powder laminated structure” ({Σvnano-particle + vcoating-molecule + vsolvent}> (Σvspace−Σvfine-particle) ).

  Note that the total volume (vnano-particle) of “copper nanoparticles” Σvnano-particle is based on the total volume of “residual voids” (Σvspace−Σvfine-particle) present in the “laminated structure of copper powder”. In general, (Σvspace−Σvfine-particle) ≧ Σvnano-particle ≧ 1/2 · (Σvspace−Σvfine-particle) can be selected.

  The “copper nanoparticles” need to be able to be fired at a low temperature, and at least the average particle diameter dCu-nanoparticle of the “copper nanoparticles” itself is selected within a range not exceeding 100 nm (100 nm ≧ dCu-nanoparticle) To do.

  In the “liquid phase”, a “coating agent molecular layer” is formed on the surface of the “copper nanoparticle”, and the “coating agent layer” includes the thickness tcoating-molecule of the “coating agent molecular layer”. The average particle diameter of the “copper nanoparticles” forming the “molecular layer” is (dCu-nanoparticle + 2 tcoating-molecule).

  “Copper powder” is a narrow gap near the contact area between each other, “narrow gap between“ copper powder ”and“ copper fine powder ”, and“ narrow gap between “copper fine powder” ” It is necessary to enter and be filled in the “copper nanoparticles” forming the “layer”.

  In order to enter and fill the narrow gaps between the “copper fine powders” in the form of “copper nanoparticles” forming a “coating agent molecular layer” on the surface, the average particle diameter (dCu− The nanoparticle + 2tcoating-molecule) is usually in the range of 1/5 · dCu-fine-particle> (dCu-nanoparticle + 2tcoating-molecule), preferably 1 based on the average particle diameter dCu-fine-particle of “copper fine powder”. / 10 · dCu-fine-particle> (dCu-nanoparticle + 2tcoating-molecule)> 1/40 · dCu-fine-particle is preferably selected.

  As the average particle diameter (dCu-nanoparticle + 2 tcoating-molecule) becomes smaller, the volume (vnano-particle) of the “copper nanoparticles” itself in the “copper nanoparticles” forming the “coating agent molecular layer” on the surface, The ratio (vcoating-molecule-surface / vnano-particle) of the “coating molecule layer” formed on the surface is proportional to (2tcoating-molecule / dCu-nanoparticle). Increase. In general, (2tcoating-molecule / dCu-nanoparticle) is selected in the range 1/5> (2tcoating-molecule / dCu-nanoparticle), preferably 1/10> (2tcoating-molecule / dCu-nanoparticle). It is desirable.

  The average particle diameter dCu-nanoparticle of the “copper nanoparticles” itself is usually selected in the range of 1 nm to 100 nm, preferably in the range of 5 nm to 100 nm, more preferably in the range of 10 nm to 100 nm. In order to keep (2tcoating-molecule / dCu-nanoparticle) within the above range, the average particle diameter dCu-nanoparticle of the “copper nanoparticle” itself can be selected in the range of 20 nm to 100 nm.

  In the “liquid phase”, the total volume (vnano-particle + vcoating-molecule-surface) of “copper nanoparticles” having “coating agent molecular layer” on the surface (vnano-particle + vcoating-molecule-surface) and “organic solvent” The ratio of {volume (vsolvent)}, {Σ (vnano-particle + vcoating-molecule-surface) / vsolvent} is at least 1> {Σ (vnano-particle + vcoating-molecule-surface) / vsolvent}, usually 4 / 5> {Σ (vnano-particle + vcoating-molecule-surface) / vsolvent}, preferably 2/3> {Σ (vnano-particle + vcoating-molecule-surface) / vsolvent}.

  As a “coating agent molecule” used in the “coating agent molecular layer” formed on the surface of the “copper nanoparticle”, an amino group (as an atomic group that can be used for forming a non-covalent intermolecular bond with copper) It is desirable to use a compound having —NH 2) or a compound having a carboxyl group (—COOH).

  The boiling point of the compound having an amino group (—NH 2) or the compound having a carboxyl group (—COOH) used as a “coating agent molecule” is in the range of 150 ° C. to 400 ° C., preferably under atmospheric pressure. Is preferably in the range of 180 ° C to 370 ° C. The boiling point under reduced pressure, for example, 200 Pa, is preferably in the range of 10 ° C to 200 ° C, and preferably in the range of 40 ° C to 170 ° C.

  Examples of the compound having an amino group (—NH 2) that can be used as the “coating agent molecule” include amine compounds having one or more terminal amino groups, such as alkylamines. The number of carbon atoms in the alkyl chain constituting the alkylamine is desirably selected in the range of 8-20, preferably in the range of 10-18.

  As an amine compound having one or more terminal amino groups, (alkyloxy) alkylamine such as 2-ethylhexyloxypropylamine (boiling point 235 ° C.), carbon number 8-20 such as oleylamine (melting point 21 ° C., boiling point 364 ° C.) Linear aliphatic amines can also be used.

  As a compound having a carboxyl group (—COOH) that can be used as a “coating agent molecule”, an aliphatic carboxylic acid having 8 to 20 carbon atoms, preferably an aliphatic monocarboxylic acid having 8 to 20 carbon atoms, such as carbon The alkanoic acid of several 8-20 can be illustrated.

  The “organic solvent” to be used is used as a dispersion solvent when the “copper nanoparticles” are uniformly dispersed using the “coating agent molecular layer” formed on the surface. It must also be able to dissolve the “coating molecule”.

  The solubility of the “coating agent molecule” is not less than a predetermined level, and when forming a thick coating film of the “copper thick film forming material” of the present invention, the transpiration does not proceed rapidly and has a high boiling point. It is desirable to use “organic solvents”. For example, when preheating from room temperature to 120 ° C. or higher, “coating agent molecules” constituting “coating agent molecular layer” formed on the surface of “copper nanoparticles” can be eluted. It is possible to use a “high boiling organic solvent” having a solubility of “molecule”, for example, a “high boiling nonpolar organic solvent” or a “high boiling low polar organic solvent”.

  When using a compound having an amino group (—NH 2) as a “coating agent molecule”, for example, tripropylene glycol (molecular weight 192, boiling point 268 ° C.) can be used as the “organic solvent”.

  The “organic solvent” is selected so that the boiling point Tbp-solvent of the “organic solvent” to be used is in the range of 150 ° C. to 300 ° C., preferably in the range of 180 ° C. to 280 ° C.

  The “coating agent molecule” should be selected such that the boiling point Tbp-coating-molecule of the “coating agent molecule” used is in the range of 130 ° C. to 300 ° C., preferably in the range of 150 ° C. to 270 ° C. You can also.

  When forming a thick coating film of the “copper thick film forming material” of the present invention, it is necessary to maintain the thickness of the coating film of the “copper thick film forming material” and the planar pattern shape, It is at least 30 Pa · s (spiral rotational viscometer 10 rpm 25 ° C.) or more, preferably 50 Pa · s to 200 Pa · s. For example, when the thickness of the coating film is selected in the range of 20 μm to 200 μm, the liquid viscosity is desirably adjusted to at least the range of 50 Pa · s to 200 Pa · s.

  In addition, in the “material for forming a copper thick film” according to the present invention, “in order to improve adhesion with a base material or to have fluidity after curing”, a form in which “resin” is added. It is also possible to do.

  As the “resin” to be added, a thermosetting resin such as an epoxy resin can be used for the purpose of “improving adhesion with the substrate”. As the “resin” to be added, a thermoplastic resin such as an acrylic resin can be used for the purpose of “giving fluidity after curing”.

The amount of “resin” added to the “copper thick film forming material” according to the present invention is the volume ratio VCu-particle of “copper powder” contained in the copper thick film forming material, “copper fine powder”. "VCu-fine-particle", "Cu nanoparticle" volume ratio VCu-nanoparticle, "Coating molecule" volume ratio Vcoating-molecule, "Organic solvent" volume ratio Vsolvent total {VCu-particle + VCu-fine -particle + VCu-nanoparticle + Vcoating-molecule + Vsolvent}, the volume ratio Vresin of “resin” is
0.25 ≧ {Vresin / (VCu-particle + VCu-fine-particle + VCu-nanoparticle + Vcoating-molecule + Vsolvent)} range,
Preferably, it is desirable to select 0.25 ≧ {Vresin / (VCu-particle + VCu-fine-particle + VCu-nanoparticle + Vcoating-molecule + Vsolvent)} ≧ 0.05.

  Usually, the added “resin” is mixed with an “organic solvent” to constitute a “liquid phase”. In this case, the volume ratio (Vresin / Vsolvent) of “resin” to “organic solvent” is usually in the range of 0.65 ≧ (Vresin / Vsolvent) ≧ 0.35, preferably 0.60 ≧ (Vresin /Vsolvent)≧0.40 is preferable.

  When “thermosetting resin” is adopted as the “resin”, the curing temperature Tcure of the “thermosetting resin” is usually in the range of 120 ° C. to 250 ° C., preferably in the range of 150 ° C. to 220 ° C. It is desirable to be. In particular, during the “preheating drying step” and the “vacuum drying step” performed at a preheating temperature Tpreheating selected at a temperature of 180 ° C. or lower during the manufacturing process described later, the heat of the “thermosetting resin” It is desirable that the curing temperature Tcure of the “thermosetting resin” be within a range where curing does not proceed. That is, when the curing temperature Tcure of the “thermosetting resin” is higher than the preheating temperature Tpreheating employed in the “preheating drying step” and the “vacuum drying step”, the “preheating drying step” and the “vacuum drying step” Sometimes, the thermosetting of the “thermosetting resin” does not proceed, and the thermosetting treatment of the “thermosetting resin” is performed in the “baking step by microwave plasma irradiation” during the manufacturing process described later. This is carried out in parallel with the firing.

  When adopting “thermoplastic resin” as “resin”, glass transition temperature Tg of “thermoplastic resin” is usually in the range of −20 ° C. to 200 ° C., preferably in the range of −10 ° C. to 150 ° C. It is desirable that Accordingly, during the manufacturing process described later, glass transition of the added “thermoplastic resin” also occurs in the “firing step by microwave plasma irradiation” in parallel with the firing of “copper nanoparticles”. In particular, the “solvent” is removed at the time when the “preheating drying step” and the “reduced pressure drying step” performed at the preheating temperature Tpreheating selected at a temperature of 180 ° C. or lower are completed during the manufacturing process described later. It is preferable that at least the “thermoplastic resin” contained is in a state of glass transition. Accordingly, the glass transition temperature Tg of the “thermoplastic resin” is preferably lower than the preheating temperature Tpreheating selected to be a temperature of 180 ° C. or lower.

  The amount of “resin” in the formed “copper thick film” may be appropriately determined within a range not impairing the effects of the present invention.

  On the other hand, the method of forming the “copper thick film” using the “copper thick film forming material” of the present invention includes the following steps.

Applying a copper thick film forming material on a substrate, applying a copper thick film forming material,
A preheat drying step of heating and drying the resulting coating film at a preheating temperature selected at a temperature of 180 ° C. or lower, and precipitating the contained copper powder and copper fine powder,
A vacuum drying process that removes the remaining solvent and organic matter by evaporation under reduced pressure while heating to the preheating temperature,
Firing process by microwave plasma irradiation, heating to preheating temperature and irradiating with microwave plasma in reducing atmosphere "Coating process of copper thick film forming material"
When applying the copper thick film forming material on the base material, the average thickness tpaste of the coating film is selected on the basis of the target average thickness tCu-sintered layer of the copper thick film.

  Specifically, the volume ratio VCu-particle of “copper powder”, the volume ratio VCu-fine-particle of “copper fine powder”, and the volume ratio of “copper nanoparticles” contained in the copper thick film forming material VCu-nanoparticle, “coating agent molecule” volume ratio Vcoating-molecule, “organic solvent” volume ratio Vsolvent total {VCu-particle + VCu-fine-particle + VCu-nanoparticle + Vcoating-molecule + Vsolvent} = 100% by volume In the copper thick film, the volume ratio VCu-particle of “copper powder”, the volume ratio VCu-fine-particle of “copper fine powder”, and the volume ratio VCu-nanoparticle of “copper nanoparticles” {VCu-particle + VCu- A volume of metallic copper atoms corresponding to fine-particle + VCu-nanoparticle} is included.

Taking into account the ratio of the remaining “void” to the bulk volume of the “copper thick film” to be produced and the target of “void ratio” Vvoid, the average thickness tpaste of the coating film is set so as to satisfy the following relationship: select.
(TCu-sintered layer / tpaste) · (1-Vvoid) =
= {VCu-particle + VCu-fine-particle + VCu-nanoparticle} / {VCu-particle + VCu-fine-particle + VCu-nanoparticle + Vcoating-molecule + Vsolvent}
As a means for applying the “copper thick film forming material”, screen printing can be suitably used.

"Preheating drying process"
When the “organic solvent” contained in the obtained coating film is heated to a preheating temperature Tpreheating selected to a temperature of 180 ° C. or less, the coating film evaporates from the surface of the coating film, and drying of the coating film proceeds. When drying is completed, a “dried coating film” from which “organic solvent” has been removed is obtained. The average film thickness tdried-paste of the “dried coating film” is approximately tpaste · {VCu-particle + VCu-fine-particle + VCu-nanoparticle + Vcoating-molecule} / {VCu-particle + VCu− Fine-particle + VCu-nanoparticle + Vcoating-molecule + Vsolvent}.

  In the “preheating drying step”, in order to selectively remove only the “organic solvent”, the “coating agent molecule” dissolved in the “organic solvent” does not evaporate in the “liquid phase”. It is necessary to select the conditions for transpiration of the “organic solvent”.

  At room temperature, “copper powder” and “copper fine powder” and “copper nanoparticles” contained in the coating film of “copper thick film forming material” are dispersed in “organic solvent”. Yes. At that time, the “copper nanoparticles” are dispersed in the “organic solvent” in a state in which the “coating agent molecular layer” is formed on the surface thereof. In addition, the “coating agent molecules” are bonded in a non-conjugated manner to the metal copper atoms exposed in the surfaces of “copper powder” and “copper fine powder” dispersed in the “organic solvent”. Yes (chemical adsorption).

  At that time, the specific gravity of the entire “copper nanoparticles” having the “coating agent molecular layer” on the surface is more than the specific gravity of the “copper powder” or “copper fine powder” on which the “coating agent molecules” are chemically adsorbed on the surface. Of course, the particle size is extremely small, and of course, the particle size is extremely small. Therefore, the dispersibility of “copper nanoparticles” having a “coating molecule layer” on the surface is more than the dispersibility of “copper powder” or “copper fine powder” on which “coating agent molecules” are chemically adsorbed on the surface. , Is superior in orders of magnitude.

  When heated to a preheating temperature Tpreheating selected at a temperature of 180 ° C. or less, the “coating agent molecules” chemically adsorbed on the surfaces of “copper powder” and “copper fine powder” are thermally desorbed, It is eluted in the “solvent”. In addition, the viscosity of the “organic solvent” significantly decreases with heating. As a result, dispersibility of “copper powder” and “copper fine powder” is lost when heated to a preheating temperature Tpreheating selected to be a temperature of 180 ° C. or less.

  For example, the average particle diameter dCu-particle of “copper powder”, the average particle diameter dCu-fine-particle of “copper fine powder”, and the average particle diameter dCu-nanoparticle of “copper nanoparticle” itself are dCu-particle> dCu- In the case of fine-particle >> dCu-nanoparticle, even if the dispersibility of “copper powder” and “copper fine powder” is lost, “copper nanoparticle” having “coating agent molecular layer” on the surface is “organic solvent” It is possible to keep the state dispersed in.

  During heating at a preheating temperature Tpreheating selected to be a temperature of 180 ° C. or lower, precipitation of “copper powder” and “copper fine powder” contained in the coating film proceeds. When the “copper powder” and the “copper fine powder” are settled, the “copper powder” is densely laminated to form a laminated structure of the “copper powder”. The “copper fine powder” that settles at the same time is taken into the laminated structure of the “copper powder”. Specifically, in the laminated structure of “copper powder”, there is a gap between “copper powder”, but “copper fine powder” fills the gap between these “copper powder”. Incorporated into the laminated structure of “copper powder”. In the laminated structure of the “copper powder” formed, the “copper fine powder” closely fills the gaps between the “copper powder”, but between the “copper powder” and the “copper fine powder” There are fine gaps between “copper fine powder”. On the other hand, “copper nanoparticles” are uniformly dispersed in an “organic solvent” to constitute a “liquid phase”. This “liquid phase” infiltrates narrow gaps in the laminated structure of the “copper powder” to be formed. In addition, an upper layer made of a “liquid phase” exists on the upper surface of the laminated structure of “copper powder” to be formed.

  In FIG. 2, when dCu-particle> dCu-fine-particle >> dCu-nanoparticle, the “copper powder” laminated structure (microparticle accumulation layer) formed in the coating film and the upper surface thereof are present. An example of the separated state is schematically shown in the upper layer composed of “liquid phase” (nanoparticle / solvent).

  Upon completion of the evaporation of the “organic solvent” contained in the upper layer composed of the “liquid phase” (nanoparticles / solvent) during the “preheating drying process”, the upper layer composed of the “liquid phase” (nanoparticles / solvent) The “copper nanoparticles” included in the structure constitute a “copper nanoparticle multilayer structure” (nanoparticle aggregate layer) covering the upper surface of the “copper powder” multilayer structure (microparticle multilayer layer). Therefore, it becomes a “dried coating film” composed of two layers of a “copper powder” laminated structure (microparticle integrated layer) and a “copper nanoparticle laminated structure” (nanoparticle integrated layer).

  In the two-layer structure shown in FIG. 2, the film thickness tCu-particle-stacked-layer of the “copper powder” laminated structure (microparticle accumulation layer) is tpaste · {VCu based on the average thickness tpaste of the coating film. -particle / 100 vol%) · (ρCu-bulk / ρCu-particle-tap).

  In a state where all of the “copper fine powder” is accommodated in the “void” in the laminated structure of the “copper powder”, the remaining “remaining void” Vunoccupied space is VCu-particle · (ρCu-bulk / ρCu- particle-tap) · {1- (ρCu-particle-tap / ρCu-bulk)} − VCu-fine-particle. When this “residual void” Vunoccupied space is densely filled with “copper nanoparticles”, the total volume of the filled “copper nanoparticles” vCu-nanoparticle-occupied-tap ΣvCu-nanoparticle-occupied-tap is ΣvCu -nanoparticle-occupied-tap = Estimated as Vunoccupied space.

  On the other hand, the total ΣvCu-nanoparticle-tap of the bulk volume vCu-nanoparticle-tap of all “copper nanoparticles” contained in the “liquid phase” (nanoparticle / solvent) is ΣvCu-nanoparticle-tap = VCu-nanoparticle · (ΡCu-bulk / ρCu-nanoparticle-tap) is estimated.

  Since ΣvCu-nanoparticle-tap> ΣvCu-nanoparticle-occupied-tap, at least the bulk part of (ΣvCu-nanoparticle-tap-ΣvCu-nanoparticle-occupied-tap) has a laminated structure of “copper powder” (micro A “stacked structure of copper nanoparticles” (nanoparticle accumulation layer) covering the upper surface of the particle accumulation layer) is formed.

  In the state where this “residual void” Vunoccupied space is densely filled with “copper nanoparticles”, the “copper powder” stack structure (microparticle stack layer) and the “copper nanoparticle stack structure” (nanoparticle stack layer) The sum of the apparent volumes of the two layers is estimated as {VCu-particle + VCu-fine-particle} + VCu-nanoparticle · (ρCu-bulk / ρCu-nanoparticle-tap). Therefore, the film thickness tCu-particle-stacked-lower-layer of the lower layer “copper powder” (microparticle accumulation layer) and the film thickness of the upper layer “stacked structure of copper nanoparticles” (nanoparticle accumulation layer) The total thickness of two layers of tCu-nanoparticle-stacked-upper-layer {tCu-particle-stacked-lower-layer + tCu-nanoparticle-stacked-upper-layer} is based on the average thickness tpaste of the coating film. -[{VCu-particle + VCu-fine-particle} + VCu-nanoparticle · (ρCu-bulk / ρCu-nanoparticle-tap)] / 100% by volume.

  Therefore, the film thickness tCu-nanoparticle-stacked-upper-layer of the upper layer “stacked structure of copper nanoparticles” (nanoparticle accumulation layer) is {tCu-particle-stacked-lower-layer + tCu-nanoparticle-stacked-upper-layer } -TCu-particle-stacked-layer.

That is, when the “organic solvent” and the “coating agent molecule” are removed, the “copper powder”, the “copper fine powder”, and the “copper nanoparticle” are laminated in a close-packed state. The total thickness of the two layers of the “powder” laminate structure (microparticle accumulation layer) and the “copper nanoparticle accumulation structure” (nanoparticle accumulation layer) is minimized, and the average thickness tpaste of the coating film is used as a reference. tpaste · [{VCu-particle + VCu-fine-particle} + VCu-nanoparticle · (ρCu-bulk / ρCu-nanoparticle-tap)] / 100% by volume.

In the present invention, by combining the “preheating drying step” and the “reduced pressure drying step” described later, the “organic solvent” and the “coating agent molecule” are substantially removed at the stage where “copper powder”, The "copper fine powder" and the "copper nanoparticles" are all stacked in a close-packed state.

  In addition, as for the preheating temperature Tpreheating at the time of a "preheating drying process", it is desirable to select in the range of 120 to 180 degreeC.

"Decompression drying process"
When only the “organic solvent” is selectively removed in the “preheating drying step”, the “coating agent molecules” remain in the “dried coating film”.

  The remaining “coating agent molecules” are evaporated and removed by heat treatment under reduced pressure at a temperature of 180 ° C. or lower (Tpreheating).

  In the “reduced pressure” condition in the “remaining organic matter removing step”, the pressure is maintained in the range of 1 Pa to 200 Pa, preferably in the range of 5 Pa to 100 Pa.

  Therefore, at the time when removal of the “coating agent molecules” is completed, only “copper powder”, “copper fine powder”, and “copper nanoparticles” remain in the “dried coating film”.

  The “dried coating film” is usually composed of two layers of a “copper powder” laminated structure (microparticle integrated layer) and a “copper nanoparticle laminated structure” (nanoparticle integrated layer). At that time, in the “copper powder” laminated structure (microparticle accumulation layer), the contact area between “copper powder”, the contact area between “copper powder” and “copper fine powder”, and the mutual contact between “copper fine powder” A narrow gap existing at the contact site is filled with “copper nanoparticles”.

  The “liquid phase” infiltrating the laminated structure (microparticle accumulation layer) of “copper powder” gradually evaporates when the vacuum drying process proceeds. In contact with each other, a contact portion between “copper powder” and “copper fine powder”, and a contact portion between “copper fine powder”. As a result, the “copper nanoparticles” contained in the “liquid phase” are the contact sites between the “copper powder”, the contact site between the “copper powder” and the “copper fine powder”, and the “copper fine powder”. Accumulated in narrow gaps that exist at mutual contact sites, the narrow gaps are filled with “copper nanoparticles”.

  The “coating agent molecule” can be evaporated by performing a heat treatment at a temperature of 180 ° C. or less (Tpreheating) under the above-mentioned “reduced pressure” condition. For example, the boiling point Tbp-coating in a reduced pressure state of 200 Pa. -molecule (P = 200 Pa) is at least 180 ° C.> Tbp-coating-molecule (P = 200 Pa), preferably 120 ° C.> Tbp-coating-molecule (P = 200 Pa).

  The heating temperature (stage temperature) at the “reduced pressure drying step” is usually preferably equal to the preheating temperature Tpreheating at the “preheating drying step”. Therefore, it is desirable to select the heating temperature in the “vacuum drying step” in the range of 120 ° C. to 180 ° C.

"Baking process by microwave plasma irradiation"
In the “firing process by microwave plasma irradiation”, as a result of performing the “preheating drying process” and the “reduced pressure drying process”, the “organic solvent” and the “coating agent molecule” are removed, and the “dried coating film” In the inside, only “copper powder”, “copper fine powder”, and “copper nanoparticles” remain, and the reducing property is reduced while heating the substrate at a temperature of 180 ° C. or less (Tpreheating) under reduced pressure. In the atmosphere, microwave plasma is irradiated to bak the “copper nanoparticles”.

  In the “microwave plasma irradiation (plasma firing) step”, an inert gas containing hydrogen is introduced into the plasma firing furnace in a state where the stage temperature is maintained at a temperature (Tpreheating) of 180 ° C. or less. After the internal pressure is controlled to a predetermined pressure (depressurized state), microwaves are supplied to generate microwave plasma in an inert gas containing hydrogen. A plasma baking process is performed by holding for a predetermined processing time while being irradiated with the generated microwave plasma.

The frequency of the microwave used to generate the microwave plasma is
The range is selected from 300 MHz to 300 GHz, preferably from 3 GHz to 100 GHz.

  At the time of generating the microwave plasma, the pressure in the plasma baking furnace is maintained in the range of 1 Pa to 200 Pa, preferably in the range of 5 Pa to 100 Pa. As the inert gas containing hydrogen, a mixed gas obtained by adding hydrogen in an amount of 1 to 5% by volume to an inert gas selected from He gas, Ar gas, and nitrogen gas can be used. It is one of the technical features of the present invention that microwave plasma can be generated using “nitrogen gas” containing hydrogen and irradiation by the microwave plasma can be used.

  The processing time for maintaining the state irradiated with the microwave plasma depends on the plasma density of the irradiated microwave plasma and also depends on the stage temperature at which the heating is performed in parallel.

  The stage temperature (Tpreheating) is preferably selected in the range of 120 ° C to 180 ° C.

  For example, in a plasma firing furnace used in the examples described later, “Nissin plasma firing furnace”, a microwave (frequency 2.4 GHz) is supplied from a high frequency power source (frequency 2.4 GHz) with a high frequency power of 1.5 kW, Microwave plasma can be generated in helium-3% hydrogen gas at a reduced pressure of 10 Pa. When helium-3% hydrogen gas having the same frequency and reduced pressure is used, the output (electric power) of the supplied microwave can be selected in the range of 300 W to 3 kW.

  The output (electric power) of the microwave used for generating the microwave plasma depends on the scale of the apparatus used, and also depends on the plasma generation conditions (pressure, type of gas used).

  By maintaining the state irradiated by the generated microwave plasma, the plasma baking process proceeds from the upper surface side to the bottom surface of the “dried coating film”. Therefore, when the processing time is short, the upper surface side of the “dried coating film” is sufficiently plasma-baked, but the bottom surface side of the “dried coating film” is sufficiently plasma-baked. Not in a state.

Therefore, depending on the thickness of the “dried coating film”, upon microwave plasma irradiation,
The irradiation time of the microwave plasma is desirably selected in the range of 30 seconds to 30 minutes, preferably in the range of 1 minute to 15 minutes.

  The “copper thick film forming material” according to the present invention usually employs “copper nanoparticles”, but uses “silver nanoparticles” or “gold nanoparticles” instead of “copper nanoparticles”. It can also be. At that time, except for the change of “copper nanoparticles” to “silver nanoparticles” or “gold nanoparticles”, the other configurations can be selected to be essentially the same as the configurations described above.

On the other hand, a method of forming a “copper thick film” using the “copper thick film forming material” of the present invention in accordance with the change of “copper nanoparticles” to “silver nanoparticles” or “gold nanoparticles”. Then
When adopting `` silver nanoparticles ''
The preheating temperature Tpreheating at the “preheating drying step” and the heating temperature (stage temperature) at the “reduced pressure drying step” are preferably selected in the range of 100 ° C. to 150 ° C.
When adopting “gold nanoparticles”
The preheating temperature Tpreheating at the “preheating drying step” and the heating temperature (stage temperature) at the “reduced pressure drying step” are preferably selected in the range of 120 ° C. to 180 ° C.

  That is, when performing the “preheating drying step” and the “reduced pressure drying step”, the above temperature range is selected in order to avoid the progress of low-temperature sintering between the “silver nanoparticles” in the “liquid phase”. It is desirable. When performing the “preheating drying process” and “reduced pressure drying process”, the above temperature range can be selected in order to avoid the progress of low temperature sintering between the “gold nanoparticles” in the “liquid phase”. desirable.

  Hereinafter, the “material for forming a silver thick film” and the “method for forming a silver thick film” according to the present invention will be described in more detail.

  The “silver thick film forming material” according to the present invention corresponds to the “copper” of the metal material used in the “copper thick film forming material” according to the present invention described above replaced with “silver”. ing. Except for replacing “copper” of the metal material with “silver”, the configuration of the “silver thick film forming material” according to the present invention is the same as the configuration of the “copper thick film forming material” according to the present invention. It is essentially the same.

On the other hand, instead of “copper nanoparticles”, using “silver nanoparticles”, the method of forming “silver thick film” using the “material for forming silver thick film” of the present invention,
The preheating temperature Tpreheating at the “preheating drying step” and the heating temperature (stage temperature) at the “reduced pressure drying step” are preferably selected in the range of 100 ° C. to 150 ° C.

  The “material for forming a silver thick film” according to the present invention usually employs “silver nanoparticles”, but uses “copper nanoparticles” or “gold nanoparticles” instead of “silver nanoparticles”. It can also be. In that case, except for the change from “silver nanoparticles” to “copper nanoparticles” or “gold nanoparticles”, the other configurations can be selected to be essentially the same as the configurations described above.

On the other hand, a method of forming a “silver thick film” using the “material for forming a silver thick film” of the present invention in accordance with the change of the “silver nanoparticles” to “copper nanoparticles” or “gold nanoparticles” Then
When adopting `` copper nanoparticles ''
The preheating temperature Tpreheating at the “preheating drying step” and the heating temperature (stage temperature) at the “reduced pressure drying step” are preferably selected in the range of 120 ° C. to 180 ° C.
When adopting “gold nanoparticles”
The preheating temperature Tpreheating at the “preheating drying step” and the heating temperature (stage temperature) at the “reduced pressure drying step” are preferably selected in the range of 120 ° C. to 180 ° C.

  That is, when performing the “preheating drying process” and the “reduced pressure drying process”, the above temperature range is selected in order to avoid the progress of low-temperature sintering between the “copper nanoparticles” in the “liquid phase”. It is desirable. When performing the “preheating drying process” and “reduced pressure drying process”, the above temperature range can be selected in order to avoid the progress of low temperature sintering between the “gold nanoparticles” in the “liquid phase”. desirable.

  Hereinafter, the “aluminum thick film forming material” and the “aluminum thick film forming method” according to the present invention will be described in more detail.

  The “aluminum thick film forming material” according to the present invention is the “copper fine powder” used in the above “copper thick film forming material” according to the present invention. Is replaced with “aluminum”. The configuration of the “aluminum thick film forming material” according to the present invention is the same as that described above except that “copper” in the metal material used for the “fine metal powder” is replaced with “aluminum” every time “metal powder” is used. This is essentially the same as the configuration of the “copper thick film forming material” according to the invention.

On the other hand, instead of “copper nanoparticles”, using “silver nanoparticles”, the “aluminum thick film forming material” of the present invention is used to form an “aluminum thick film”.
The preheating temperature Tpreheating at the “preheating drying step” and the heating temperature (stage temperature) at the “reduced pressure drying step” are preferably selected in the range of 100 ° C. to 150 ° C.

  The “aluminum thick film forming material” according to the present invention usually employs “aluminum nanoparticles”, but uses “copper nanoparticles” or “gold nanoparticles” instead of “silver nanoparticles”. It can also be. In that case, except for the change from “silver nanoparticles” to “copper nanoparticles” or “gold nanoparticles”, the other configurations can be selected to be essentially the same as the configurations described above.

On the other hand, a method of forming an “aluminum thick film” using the “aluminum thick film forming material” of the present invention in accordance with the change from “silver nanoparticles” to “copper nanoparticles” or “gold nanoparticles” Then
When adopting `` copper nanoparticles ''
The preheating temperature Tpreheating at the “preheating drying step” and the heating temperature (stage temperature) at the “reduced pressure drying step” are preferably selected in the range of 120 ° C. to 180 ° C.
When adopting “gold nanoparticles”
The preheating temperature Tpreheating at the “preheating drying step” and the heating temperature (stage temperature) at the “reduced pressure drying step” are preferably selected in the range of 120 ° C. to 180 ° C.

  That is, when performing the “preheating drying process” and the “reduced pressure drying process”, the above temperature range is selected in order to avoid the progress of low-temperature sintering between the “copper nanoparticles” in the “liquid phase”. It is desirable. When performing the “preheating drying process” and “reduced pressure drying process”, the above temperature range can be selected in order to avoid the progress of low temperature sintering between the “gold nanoparticles” in the “liquid phase”. desirable.

  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.

"Copper thick film forming material"
Example 1
The material for forming a copper thick film of Example 1 is prepared in the shape of “conductive copper paste” using the following raw materials.

  As the copper microparticles, 1400YM (average particle diameter dCu-particle 4 μm: tap density ρCu-particle-tap 5.5 g / cm 3) manufactured by Mitsui Kinzoku Co., Ltd., which is a copper powder produced by a wet method, is used. 1050Y manufactured by Mitsui Kinzoku Co., Ltd. (average particle diameter dCu-fine-particle 0.8 μm: tap density ρCu-fine-particle-tap 4.3 g / copper fine powder produced by a wet method as copper submicron particles cm3) is used.

  As “copper nanoparticle dispersion liquid”, Harima Kasei copper nanoparticle NPC is used. The Harima Kasei copper nanoparticle NPC is composed of copper nanoparticles and “coating agent molecular amine”. 99 parts by mass of copper nanoparticles and 1 part by mass of “coating agent molecular amine” are contained per 100 parts by mass of “copper nanoparticle NPC”. The average particle diameter dCu-nanoparticle of the copper nanoparticles contained in the “copper nanoparticle NPC” is 80 nm. A surface coating molecular layer of “coating agent molecular amine” is formed on the surface of the copper nanoparticles. In the copper nanoparticle NPC, 2-ethylhexyloxypropylamine (boiling point 235 ° C., density ρcoating-molecule 0.85 g / cm 3) is used as the “coating agent molecular amine”. Therefore, the volume ratio of “copper nanoparticles” and “coating agent molecular amine” contained in the “copper nanoparticle NPC” is “copper nanoparticle”: “coating agent molecular amine” = (33. 0 / 8.94) :( 0.3 / 0.85) = 3.69: 0.353 = 91.3% by volume: 8.7% by volume. When the “copper nanoparticles” contained in the copper nanoparticle NPC are stacked in a close-packed state, the bulk density (tap density) is the density of metallic copper (bulk) ρCu-bulk = 8.94 g / cm 3. On the other hand, it is estimated to be about 2/3. That is, the bulk density (tap density) ρCu-nanoparticle of the “copper nanoparticles” contained in the copper nanoparticle NPC is estimated to be about 6.0 g / cm 3.

  As a “high-boiling nonpolar organic solvent”, tripropylene glycol (molecular weight 192, boiling point 268 ° C., density ρsolvent 1.02 g / cm 3) manufactured by Nippon Emulsifier is used.

  33.3 parts by mass of “Copper Nanoparticles NPC” manufactured by Harima Chemicals (33.0 parts by mass of copper nanoparticles and 0.3 parts by mass of “coating agent molecular amine”), 10.8YM by Mitsui Kinzoku Co., Ltd., 50.8 parts by mass, Mitsui Metal Co., Ltd. 1050Y11.1 mass part and Japanese emulsifier tripropylene glycol 4.8 mass part are mixed uniformly. The mixture is stirred with a stirring deaerator to uniformly disperse copper powder, copper fine powder, and copper nanoparticles in a dispersion solvent to prepare a “conductive copper paste”.

  The volume ratio VCu-particle of the copper powder, the volume ratio VCu-fine-particle of the copper fine powder, and the volume ratio VCu-nanoparticle of the copper nanoparticle contained in the prepared “conductive copper paste” are VCu-particle = VCu-fine-particle = 7.92% by volume; VCu-nanoparticle = 23.55% by volume. The sum of the volume ratio Vcoating-molecule of the “coating agent amine” and the volume ratio Vsolvent of the “solvent” is {Vcoating-molecule + Vsolvent} = 32.3 vol%.

The ratio of the volume ratio VCu-particle of copper powder and the volume ratio VCu-fine-particle of copper fine powder (VCu-particle + VCu-fine-particle) and the volume ratio of copper nanoparticles VCu-nanoparticle is (VCu -particle + VCu-fine-particle): VCu-nanoparticle = 100: 53.3.
{VCu-particle + VCu-fine-particle + VCu-nanoparticle} / {Vcoating-molecule + Vsolvent} = {(50.8 + 11.1 + 33.0) /8.94} / {0.3 / 0.85 + 4.8 / 1.02} = 10.615 / (0.353 + 4.706) = 10.615 / 5.059 = 67.72: 32.28
In the “conductive copper paste”, the copper nanoparticles are uniformly dispersed in the “solvent” tripropylene glycol by forming a coating molecular layer composed of “coating molecular amine” on the surface thereof. At that time, the “coating agent molecular amine” is dissolved in the “solvent” tripropylene glycol. Surface density Ccoating-molecule-surface of “Coating molecular amine” forming a coating molecular layer on the surface of copper nanoparticles and concentration of “Coating molecular amine” dissolved in “solvent” Ccoating-molecule Dissociation equilibrium is achieved with -liquid-phase.

  The “coating agent molecular amine” contained in the “conductive copper paste” is coordinated to the copper atom exposed on the surface of the copper nanoparticle by utilizing the lone pair of the amino group. In addition, when copper atoms are exposed on the surfaces of copper powder and copper fine powder, the “coating agent molecular amine” is also distributed to the copper atoms by utilizing the lone pair of the amino group. Coordinate bonding is possible. However, the total surface area of copper nanoparticles ΣSCu-nanoparticle, the total surface area of copper fine powder ΣSCu-fine-particle, and the total surface area of copper powder ΣSCu-particle is ΣSCu-nanoparticle >> ΣSCu-fine-particle >> ΣSCu-particle The amount of “coating agent molecular amine” covering the surface of copper fine powder and the surface of copper powder is negligible with respect to the amount of “coating agent molecular amine” covering the surface of copper nanoparticles. It is a range.

  Therefore, the amount Mcoating-molecule-surface of the “coating molecule amine” coating the surface of the copper nanoparticles and the amount Mcoating-molecule-liquid-phase of the “coating agent molecular amine” dissolved in the “solvent”. The total can be regarded as the total amount Mcoating-molecule of “coating agent molecular amine” contained in “conductive copper paste” (Mcoating-molecule = Mcoating-molecule-surface + Mcoating-molecule-liquid-phase).

  The liquid viscosity of the prepared “conductive copper paste” was 150 Pa · s (spiral rotational viscometer 10 rpm 25 ° C.).

  The prepared “conductive copper paste” was applied in a 10 mm × 50 mm pattern on a slide glass. The average thickness tpaste of the paste coating film was tpaste = 40 μm.

  Using a Nissin plasma baking furnace, the paste coating film was subjected to the following procedures according to the following procedures: “preheating drying (solvent removal) step”, “vacuum drying (organic matter removal) step”, “microwave plasma irradiation ( Plasma firing) step ”was performed, and the copper powder, copper fine powder and copper nanoparticles contained in the paste coating film were fired.

  As a “preheating drying (solvent removal) step”, preheating is performed for 30 seconds at a stage temperature of 150 ° C. under atmospheric pressure in a Nissin plasma baking furnace. As a “reduced pressure drying (organic matter removal) step”, “evacuation” is performed for 60 seconds while maintaining the stage temperature at 150 ° C., and the inside of the plasma firing furnace is maintained in a reduced pressure state. The pressure in the plasma baking furnace in the reduced pressure state is maintained at 10 Pa or less.

  In the “microwave plasma irradiation (plasma firing) step”, first, helium-3% hydrogen is introduced into the plasma firing furnace at a flow rate of 25 sccm for 30 seconds while the stage temperature is maintained at 150 ° C. After controlling the pressure in the plasma firing furnace to 10 Pa, a microwave (frequency 2.4 GHz) is supplied from a high frequency power source (frequency 2.4 GHz) at a high frequency power of 1.5 kW, and helium-3% hydrogen gas is micronized. Generate wave plasma. In a state where the stage temperature is maintained at 150 ° C., microwave plasma irradiation is continued for 90 seconds to perform a plasma baking process. The copper powder, the copper fine powder and the copper nanoparticles contained in the paste coating film are fired by irradiation of the generated microwave plasma in a reducing atmosphere composed of the helium-3% hydrogen gas.

  The average film thickness tCu-sintered layer of the fired product was tCu-sintered layer = 30 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 3.0 μΩ · cm.

  Assuming that the resulting fired product is a “bulk metal copper thick film”, the film thickness tCu-bulk layer of the “bulk metal copper thick film” is tCu-bulk layer = tpaste · {VCu-particle + VCu-fine-particle + VCu -nanoparticle} / 100% by volume. The average film thickness tCu-sintered layer of the fired product actually obtained is thicker than the film thickness tCu-bulk layer of the “bulk metal copper thick film”, and the ratio tCu-bulk layer / tCu-sintered layer is 90.3 / 100. It has become. In other words, the “porosity” in the obtained fired product is estimated to be Vvoid = 9.7% by volume.

  The volume resistivity of 3.0 μΩ · cm of the obtained fired product is 1.8 times that of the resistivity of metallic copper of 1.673 μΩ · cm (30 ° C.).

  The “copper powder” used in the “conductive copper paste” of Example 1 has a bulk density (tap density ρCu-particle-tap) of 5.5 g / cm 3 when laminated in a close-packed state. is there. Since the density ρCu-bulk of metallic copper (bulk) is 8.94 g / cm 3, the ratio of “voids” existing in the laminated structure is {(1 / ρCu− particle-tap) − (1 / ρCu-bulk)} · (1 / ρCu-particle-tap) = {1− (ρCu-particle-tap / ρCu-bulk)}. For the volume ratio VCu-particle of the copper powder contained in the “conductive copper paste” of Example 1, the “void” is VCu-particle · (ρCu-bulk / ρCu-particle-tap) · { 1- (ρCu-particle-tap / ρCu-bulk)}. The tap density ρCu-fine-particle-tap of “copper fine powder” contained in the “conductive copper paste” of Example 1 is 4.3 g / cm 3. Therefore, when the “copper fine powder” is gathered in a close-packed state, the volume is VCu-fine-particle · (ρCu-bulk / ρCu-fine with respect to the volume ratio VCu-fine-particle of the copper fine powder. -particle). “Void” in the laminated structure of “copper powder”: VCu-particle · (ρCu-bulk / ρCu-particle-tap) · {1- (ρCu-particle-tap / ρCu-bulk)} "Bulk" when assembled in the close-packed state: If it exceeds VCu-fine-particle (ρCu-bulk / ρCu-fine-particle), "void" in the laminated structure of "copper powder" A state in which all of the “copper fine powder” is housed can be achieved.

  In a state where all of the “copper fine powder” is stored in the “void” in the laminated structure of “copper powder”, the remaining “remaining void” is VCu-particle · (ρCu-bulk / ρCu-particle- tap) · {1- (ρCu-particle-tap / ρCu-bulk)} − VCu-fine-particle.

  “Residual voids” remaining in the laminated structure of “copper powder”: VCu-particle · (ρCu-bulk / ρCu-particle-tap) · {1- (ρCu-particle-tap / ρCu-bulk)} − VCu When the volume ratio VCu-nanoparticle of the “copper nanoparticles” included in the “conductive copper paste” of Example 1 exceeds -fine-particles, a part of the “copper nanoparticles” The remaining “copper nanoparticles” are filled in the “powder” laminate structure, but the remaining “copper nanoparticles” are assumed to form a “copper nanoparticle” laminate on the upper surface of the “copper powder” laminate structure. The

  Specifically, the tap density ρCu-nanoparticle of the “copper nanoparticles” contained in the “conductive copper paste” of Example 1 is about 6.0 g / cm 3. Therefore, when the “copper nanoparticles” are aggregated in the close-packed state, the volume is VCu-nanoparticle · (ρCu-bulk / ρCu-nanoparticle) with respect to the volume ratio VCu-nanoparticle of the copper fine powder. When the “preheated drying (solvent removal) step” is performed to form the “dried coating film”, the bulk when the “copper nanoparticles” aggregate in the closest packing state: VCu-nanoparticle · (ρCu-bulk / ρCu-nanoparticle) remains in the laminated structure of “copper powder”: VCu-particle ・ (ρCu-bulk / ρCu-particle-tap) ・ {1- (ρCu-particle-tap / ρCu -bulk)}-When exceeding VCu-fine-particle, some of the "copper nanoparticles" fill the "residual voids" remaining in the "copper powder" laminate structure, but the remaining "copper" “Nanoparticles” are assumed to form a stack of “copper nanoparticles” on the top surface of the “copper powder” stack structure.

  At the time when the “preheating drying (solvent removal) step” is completed, the surface of the “copper nanoparticles” is in a state of being coated with the “coating agent molecular layer”. The “copper nanoparticles” having the “coating molecule layer” on the surface fill the “remaining voids” remaining in the laminated structure of the “copper powder”. The remaining “copper nanoparticles” are assumed to form a stack of “copper nanoparticles” having a “covering agent molecular layer” on the upper surface of the stack structure of “copper powder”.

  In the case of the “conductive copper paste” used in Example 1, the average thickness tCu-particle-layer of the laminated structure of “copper powder” included in the paste coating film having the average thickness tpaste is tCu−. It is estimated that particle-layer = {[tpaste · {VCu-particle} / 100 volume%]} · (ρCu-bulk / ρCu-particle-tap). {[Tpaste · {VCu-particle} / 100 vol%]} · (ρCu-bulk / ρCu-particle-tap) = {[40 μm · {36.25 vol%} / 100 vol%]} · (8.94 /5.5)=2.57 μm. The average film thickness tCu-sintered layer of the obtained fired product is much thicker than the average thickness tCu-particle-layer of the estimated laminated structure of “copper powder”.

  At that time, “void” in the laminated structure of “copper powder”: VCu-particle · (ρCu-bulk / ρCu-particle-tap) · {1- (ρCu-particle-tap / ρCu-bulk)} is VCu -particle · (ρCu-bulk / ρCu-particle-tap) · {1- (ρCu-particle-tap / ρCu-bulk)} = 36.25% by volume · (8.94 / 5.5) · {1- It is estimated that (5.5 / 8.94)} = 22.41% by volume. "Bulk" when "copper fine powder" is assembled in the close-packed state: VCu-fine-particle (ρCu-bulk / ρCu-fine-particle) is VCu-fine-particle (ρCu-bulk / ρCu -fine-particle) = 7.92 vol% · (8.94 / 4.3) = 16.47 vol%. Accordingly, it is assumed that “copper fine powder” is filled in “voids” in the laminated structure of “copper powder”.

(Example 2)
The material for forming a copper thick film of Example 2 is prepared in the form of “conductive copper paste” using the following raw materials.

  As the copper microparticles, 1400YM manufactured by Mitsui Kinzoku Co., Ltd., which is a copper powder produced by a wet method, is used. As the copper submicron particles, 1050Y manufactured by Mitsui Kinzoku Co., Ltd., which is a fine copper powder produced by a wet method, is used.

  As the “copper nanoparticle dispersion”, Harima Kasei copper nanoparticle NPC-J2 is used. The Harima Kasei copper nanoparticles NPC-J2 are composed of copper nanoparticles and a “coating agent molecular amine”. 90.7 parts by mass of copper nanoparticles and 9.3 parts by mass of “coating agent molecular amine” are contained per 100 parts by mass of “copper nanoparticles NPC-J2”. The average particle diameter dCu-nanoparticle of the copper nanoparticles contained in the “copper nanoparticles NPC-J2” is 20 nm. A surface coating molecular layer of “coating agent molecular amine” is formed on the surface of the copper nanoparticles. In Example 2, oleylamine (melting point 21 ° C., boiling point 364 ° C., density ρcoating-molecule 0.813 g / cm 3) is used as the “coating agent molecular amine”. Therefore, the volume ratio of “copper nanoparticles” and “coating agent molecular amine” contained in the “copper nanoparticles NPC-J2” is “copper nanoparticle”: “coating agent molecular amine” = 46.94 volume. %: Estimated as 53.06% by volume. When “copper nanoparticles” contained in “copper nanoparticles NPC-J2” are also stacked in a close-packed state, the bulk density (tap density) is the density of metallic copper (bulk) ρCu-bulk = 8 It is estimated to be about 2/3 for .94g / cm3. That is, the bulk density (tap density) ρCu-nanoparticle of the “copper nanoparticles” contained in the “copper nanoparticles NPC-J2” is also estimated to be about 6.0 g / cm 3.

  As a “high-boiling nonpolar organic solvent”, tripropylene glycol manufactured by Nippon Emulsifier is used.

  35.4 parts by mass of “Copper Nanoparticles NPC-J2” (32.1 parts by mass of copper nanoparticles and 3.3 parts by mass of “Coating Molecular Amine”) manufactured by Harima Kasei Co., Ltd., 1400 YM 49.2 parts by mass of Mitsui Metals , 10.7 parts by mass of Mitsui Kinzoku Co., Ltd. and 4.7 parts by mass of tripropylene glycol made by Nippon Emulsifier are mixed uniformly. The mixture is stirred with a stirring deaerator to uniformly disperse copper powder, copper fine powder, and copper nanoparticles in a dispersion solvent to prepare a “conductive copper paste”.

  The volume ratio VCu-particle of the copper powder, the volume ratio VCu-fine-particle of the copper fine powder, and the volume ratio VCu-nanoparticle of the copper nanoparticle contained in the prepared “conductive copper paste” are VCu-particle = 30.67% by volume; VCu-fine-particle = 6.67% by volume; VCu-nanoparticle = 20.01% by volume. The sum of the volume ratio Vcoating-molecule of the “coating agent amine” and the volume ratio Vsolvent of the “solvent” is {Vcoating-molecule + Vsolvent} = 42.64% by volume.

The ratio of the volume ratio VCu-particle of copper powder and the volume ratio VCu-fine-particle of copper fine powder (VCu-particle + VCu-fine-particle) and the volume ratio of copper nanoparticles VCu-nanoparticle is (VCu -particle + VCu-fine-particle): VCu-nanoparticle = 100: 53.6.
{VCu-particle + VCu-fine-particle + VCu-nanoparticle} / {Vcoating-molecule + Vsolvent} = 57.36: 42.64
In the “conductive copper paste”, the copper nanoparticles are uniformly dispersed in the “solvent” tripropylene glycol by forming a coating molecular layer composed of “coating molecular amine” on the surface thereof. At that time, the “coating agent molecular amine” is dissolved in the “solvent” tripropylene glycol. Surface density Ccoating-molecule-surface of “Coating molecular amine” forming a coating molecular layer on the surface of copper nanoparticles and concentration of “Coating molecular amine” dissolved in “solvent” Ccoating-molecule Dissociation equilibrium is achieved with -liquid-phase.

  Also in the “conductive copper paste” of Example 2, the relationship is ΣSCu-nanoparticle >> ΣSCu-fine-particle >> ΣSCu-particle.

  Therefore, the amount Mcoating-molecule-surface of the “coating molecule amine” coating the surface of the copper nanoparticles and the amount Mcoating-molecule-liquid-phase of the “coating agent molecular amine” dissolved in the “solvent”. The total can be regarded as the total amount Mcoating-molecule of “coating agent molecular amine” contained in “conductive copper paste” (Mcoating-molecule = Mcoating-molecule-surface + Mcoating-molecule-liquid-phase).

  At that time, the total surface area ΣSCu-nanoparticle of the copper nanoparticles in the “conductive copper paste” of Example 2 is the total surface area ΣSCu-nanoparticle of the copper nanoparticles in the “conductive copper paste” of Example 1. It is about 62 times that. The total amount Mcoating-molecule of “coating agent molecular amine” contained in “conductive copper paste” of Example 2 is the total amount Mcoating of “coating agent molecular amine” contained in “conductive copper paste” of Example 1. It is only 11 times the -molecule.

  That is, in the “conductive copper paste” of Example 2, the surface density Ccoating-molecule-surface of the “coating agent molecular amine” on the surface of the copper nanoparticles and the “coating agent molecular amine” dissolved in the “solvent” Concentration Ccoating-molecule-liquid-phase is dissolved in “Coating-molecule-surface” and “Solvent” of “Coating molecule amine” on the surface of copper nanoparticles in “Conductive copper paste” of Example 1. Compared with the concentration Ccoating-molecule-liquid-phase of the “coating agent molecular amine”, it is estimated that it is considerably lower and at least ½ or less.

  The liquid viscosity of the prepared “conductive copper paste” was 145 Pa · s (spiral rotational viscometer 10 rpm 25 ° C.).

  The prepared “conductive copper paste” was applied in a 10 mm × 50 mm pattern on a slide glass. The average thickness tpaste of the paste coating film was tpaste = 40 μm.

  For the paste coating film, using a Nissin plasma baking furnace, the procedure described in Example 1 was followed by a “preheating drying (solvent removal) step”, “reduced pressure drying (organic matter removal) step”, “micro A wave plasma irradiation (plasma firing) step "was performed, and the copper powder, copper fine powder and copper nanoparticles contained in the paste coating film were fired.

  The average film thickness tCu-sintered layer of the fired product was tCu-sintered layer = 30 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 3.7 μΩ · cm.

  Assuming that the resulting fired product is a “bulk metal copper thick film”, the film thickness tCu-bulk layer of the “bulk metal copper thick film” is tCu-bulk layer = tpaste · {VCu-particle + VCu-fine-particle + VCu -nanoparticle} / 100% by volume. The average film thickness tCu-sintered layer of the fired product actually obtained is thicker than the film thickness tCu-bulk layer of the “bulk metal copper thick film”, and the ratio tCu-bulk layer / tCu-sintered layer is 76.47 / 100. It has become. In other words, the “porosity” in the obtained fired product is estimated to be Vvoid = 23.53 volume%.

  The volume resistivity of 3.7 μΩ · cm of the obtained fired product is 2.1 times that of the resistivity of metallic copper of 1.673 μΩ · cm (30 ° C.).

  The “copper powder” used in the “conductive copper paste” of Example 2 has a bulk density (tap density ρCu-particle-tap) of 5.5 g / cm 3 when laminated in a close-packed state. is there. Since the density ρCu-bulk of metallic copper (bulk) is 8.94 g / cm 3, the ratio of “voids” existing in the laminated structure is {(1 / ρCu− particle-tap) − (1 / ρCu-bulk)} · (1 / ρCu-particle-tap) = {1− (ρCu-particle-tap / ρCu-bulk)}. With respect to the volume ratio VCu-particle of the copper powder contained in the “conductive copper paste” of Example 2, the “void” is VCu-particle · (ρCu-bulk / ρCu-particle-tap) · { 1- (ρCu-particle-tap / ρCu-bulk)}. The tap density ρCu-fine-particle-tap of “copper fine powder” contained in the “conductive copper paste” of Example 1 is 4.3 g / cm 3. Therefore, when the “copper fine powder” is gathered in a close-packed state, the volume is VCu-fine-particle · (ρCu-bulk / ρCu-fine with respect to the volume ratio VCu-fine-particle of the copper fine powder. -particle). “Void” in the laminated structure of “copper powder”: VCu-particle · (ρCu-bulk / ρCu-particle-tap) · {1- (ρCu-particle-tap / ρCu-bulk)} "Bulk" when assembled in the close-packed state: If it exceeds VCu-fine-particle (ρCu-bulk / ρCu-fine-particle), "void" in the laminated structure of "copper powder" A state in which all of the “copper fine powder” is housed can be achieved.

  In a state where all of the “copper fine powder” is stored in the “void” in the laminated structure of “copper powder”, the remaining “remaining void” is VCu-particle · (ρCu-bulk / ρCu-particle- tap) · {1- (ρCu-particle-tap / ρCu-bulk)} − VCu-fine-particle.

  “Residual voids” remaining in the laminated structure of “copper powder”: VCu-particle · (ρCu-bulk / ρCu-particle-tap) · {1- (ρCu-particle-tap / ρCu-bulk)} − VCu When the volume ratio VCu-nanoparticle of the “copper nanoparticles” included in the “conductive copper paste” of Example 1 exceeds -fine-particles, a part of the “copper nanoparticles” The remaining “copper nanoparticles” are filled in the “powder” laminate structure, but the remaining “copper nanoparticles” are assumed to form a “copper nanoparticle” laminate on the upper surface of the “copper powder” laminate structure. The

  Specifically, the tap density ρCu-nanoparticle of the “copper nanoparticles” contained in the “conductive copper paste” of Example 2 is about 6.0 g / cm 3. Therefore, when the “copper nanoparticles” are aggregated in the close-packed state, the volume is VCu-nanoparticle · (ρCu-bulk / ρCu-nanoparticle) with respect to the volume ratio VCu-nanoparticle of the copper fine powder. When the “preheated drying (solvent removal) step” is performed to form the “dried coating film”, the bulk when the “copper nanoparticles” aggregate in the closest packing state: VCu-nanoparticle · (ρCu-bulk / ρCu-nanoparticle) remains in the laminated structure of “copper powder”: VCu-particle ・ (ρCu-bulk / ρCu-particle-tap) ・ {1- (ρCu-particle-tap / ρCu -bulk)}-When exceeding VCu-fine-particle, some of the "copper nanoparticles" fill the "residual voids" remaining in the "copper powder" laminate structure, but the remaining "copper" “Nanoparticles” are assumed to form a stack of “copper nanoparticles” on the top surface of the “copper powder” stack structure.

  At the time when the “preheating drying (solvent removal) step” is completed, the surface of the “copper nanoparticles” is in a state of being coated with the “coating agent molecular layer”. The “copper nanoparticles” having the “coating molecule layer” on the surface fill the “remaining voids” remaining in the laminated structure of the “copper powder”. The remaining “copper nanoparticles” are assumed to form a stack of “copper nanoparticles” having a “covering agent molecular layer” on the upper surface of the stack structure of “copper powder”.

  The average particle diameter dCu-nanoparticle of the copper nanoparticles contained in the “copper nanoparticles NPC-J2” used in Example 2 is 20 nm. In the “copper nanoparticles NPC” used in Example 1 Is 1/4 of 80 nm of the average particle diameter dCu-nanoparticle of the copper nanoparticles. Assuming that the thickness of the “coating agent molecular layer” on the surface is the same, the “copper molecular layer” on the surface fills the “remaining voids” remaining in the laminated structure of the “copper powder”. The total volume of the “copper nanoparticles” themselves in the “nanoparticles” is considerably reduced as compared with Example 1. As a result, the total volume of the “copper nanoparticles” themselves, which forms a laminate of “copper nanoparticles” having a “coating agent molecular layer” on the surface on the upper surface of the “copper powder” laminate structure, Compared with, it increases considerably.

  In the case of the “conductive copper paste” used in Example 2, the average thickness tCu-particle-layer of the laminated structure of “copper powder” contained in the paste coating film having the average thickness tpaste is tCu- It is estimated that particle-layer = {[tpaste · {VCu-particle} / 100 volume%]} · (ρCu-bulk / ρCu-particle-tap). {[Tpaste · {VCu-particle} / 100 vol%]} · (ρCu-bulk / ρCu-particle-tap) = {[40 μm · {30.67 vol%} / 100 vol%]} · (8.94 /5.5)=1.94 μm. The average film thickness tCu-sintered layer of the obtained fired product is much thicker than the average thickness tCu-particle-layer of the estimated laminated structure of “copper powder”.

  At that time, “void” in the laminated structure of “copper powder”: VCu-particle · (ρCu-bulk / ρCu-particle-tap) · {1- (ρCu-particle-tap / ρCu-bulk)} is VCu -particle · (ρCu-bulk / ρCu-particle-tap) · {1- (ρCu-particle-tap / ρCu-bulk)} = 30.67% by volume · (8.94 / 5.5) · {1- It is estimated that (5.5 / 8.94)} = 19.18% by volume. "Bulk" when "copper fine powder" is assembled in the close-packed state: VCu-fine-particle (ρCu-bulk / ρCu-fine-particle) is VCu-fine-particle (ρCu-bulk / ρCu -fine-particle) = 6.67 vol% · (8.94 / 4.3) = 13.87 vol%. Accordingly, it is assumed that “copper fine powder” is filled in “voids” in the laminated structure of “copper powder”.

(Example 3)
The material for forming a copper thick film of Example 3 is prepared in the shape of “conductive copper paste” using the following raw materials.

  As the copper microparticles, 1400YM manufactured by Mitsui Kinzoku Co., Ltd., which is a copper powder produced by a wet method, is used. As the copper submicron particles, 1050Y manufactured by Mitsui Kinzoku Co., Ltd., which is a fine copper powder produced by a wet method, is used.

  As the “copper nanoparticle dispersion”, Harima Kasei copper nanoparticle NPC-J1 is used. The Harima Kasei copper nanoparticles NPC-J1 are composed of copper nanoparticles, a “coating agent molecular amine”, and a solvent (tripropylene glycol). Contains 72.2 parts by mass of copper nanoparticles, 10.6 parts by mass of “coating agent molecular amine” and 17.2 parts by mass of “solvent (tripropylene glycol)” per 100 parts by mass of “copper nanoparticles NPC-J1” It is. The average particle diameter dCu-nanoparticle of the copper nanoparticles contained in the “copper nanoparticle NPC” is 5 nm. A surface coating molecular layer of “coating agent molecular amine” is formed on the surface of the copper nanoparticles. As in Example 2, in this Example 3, oleylamine is used as the “coating agent molecular amine”. Therefore, the volume ratio of “copper nanoparticles”, “coating agent molecular amine”, and “solvent (tripropylene glycol)” contained in the “copper nanoparticles NPC-J1” is “copper nanoparticles”. : "Coating molecular amine": "Solvent" = 21.29% by volume: 34.32% by volume: 44.38% by volume. When “copper nanoparticles” contained in “copper nanoparticles NPC-J2” are also stacked in a close-packed state, the bulk density (tap density) is the density of metallic copper (bulk) ρCu-bulk = 8 It is estimated to be about 2/3 for .94g / cm3. That is, the bulk density (tap density) ρCu-nanoparticle of the “copper nanoparticles” contained in the “copper nanoparticles NPC-J2” is also estimated to be about 6.0 g / cm 3.

  42.5 parts by mass of Harima Chemical Co., Ltd. “copper nanoparticles NPC-J1” (30.7 parts by mass of copper nanoparticles, 4.5 parts by mass of “coating agent molecular amine”, 7.3 parts by mass of “solvent (tripropylene glycol)” Part) is uniformly mixed with 47.2 parts by mass of Mitsui Kinzoku Co., Ltd. 1400YM and 1050Y10.3 parts by mass of Mitsui Kinzoku Co., Ltd. The mixture is stirred with a stirring deaerator to uniformly disperse copper powder, copper fine powder, and copper nanoparticles in a dispersion solvent to prepare a “conductive copper paste”.

  The volume ratio VCu-particle of the copper powder, the volume ratio VCu-fine-particle of the copper fine powder, and the volume ratio VCu-nanoparticle of the copper nanoparticle contained in the prepared “conductive copper paste” are VCu-particle = VCu-fine-particle = 5.11% by volume; VCu-nanoparticle = 15.22% by volume. The sum of the volume ratio Vcoating-molecule of the “coating agent molecular amine” and the volume ratio Vsolvent of the “solvent” is {Vcoating-molecule + Vsolvent} = 56.24% by volume.

The ratio of the volume ratio VCu-particle of copper powder and the volume ratio VCu-fine-particle of copper fine powder (VCu-particle + VCu-fine-particle) and the volume ratio of copper nanoparticles VCu-nanoparticle is (VCu -particle + VCu-fine-particle): VCu-nanoparticle = 100: 53.4.
{VCu-particle + VCu-fine-particle + VCu-nanoparticle} / {Vcoating-molecule + Vsolvent} = 43.74 / 56.24
In the “conductive copper paste”, the copper nanoparticles are uniformly dispersed in the “solvent” tripropylene glycol by forming a coating molecular layer composed of “coating molecular amine” on the surface thereof. At that time, the “coating agent molecular amine” is dissolved in the “solvent” tripropylene glycol. Surface density Ccoating-molecule-surface of “Coating molecular amine” forming a coating molecular layer on the surface of copper nanoparticles and concentration of “Coating molecular amine” dissolved in “solvent” Ccoating-molecule Dissociation equilibrium is achieved with -liquid-phase.

  The “conductive copper paste” in Example 3 also has a relationship of ΣSCu-nanoparticle >> ΣSCu-fine-particle >> ΣSCu-particle.

  Therefore, the amount Mcoating-molecule-surface of the “coating molecule amine” coating the surface of the copper nanoparticles and the amount Mcoating-molecule-liquid-phase of the “coating agent molecular amine” dissolved in the “solvent”. The total can be regarded as the total amount Mcoating-molecule of “coating agent molecular amine” contained in “conductive copper paste” (Mcoating-molecule = Mcoating-molecule-surface + Mcoating-molecule-liquid-phase).

  At that time, the total surface area ΣSCu-nanoparticle of the copper nanoparticles in the “conductive copper paste” of Example 3 is the total surface area ΣSCu-nanoparticle of the copper nanoparticles in the “conductive copper paste” of Example 1. It is about 238 times. The total amount Mcoating-molecule of the “coating agent molecular amine” contained in the “conductive copper paste” of Example 3 is the total amount Mcoating of the “coating agent molecular amine” contained in the “conductive copper paste” of Example 1. It is only 15 times the -molecule.

  That is, in the “conductive copper paste” of Example 3, the surface density Ccoating-molecule-surface of the “coating agent molecular amine” on the surface of the copper nanoparticles and the “coating agent molecular amine” dissolved in the “solvent” Concentration Ccoating-molecule-liquid-phase is dissolved in “Coating-molecule-surface” and “Solvent” of “Coating molecule amine” on the surface of copper nanoparticles in “Conductive copper paste” of Example 1. Compared with the concentration Ccoating-molecule-liquid-phase of the “coating agent molecular amine”, it is assumed that the concentration is considerably lower and at least 1/5 or less.

  The liquid viscosity of the prepared “conductive copper paste” was 135 Pa · s (spiral rotational viscometer 10 rpm 25 ° C.).

  The prepared “conductive copper paste” was applied in a 10 mm × 50 mm pattern on a slide glass. The average thickness tpaste of the paste coating film was tpaste = 40 μm.

  For the paste coating film, using a Nissin plasma baking furnace, the procedure described in Example 1 was followed by a “preheating drying (solvent removal) step”, “reduced pressure drying (organic matter removal) step”, “micro A wave plasma irradiation (plasma firing) step "was performed, and the copper powder, copper fine powder and copper nanoparticles contained in the paste coating film were fired.

  The average film thickness tCu-sintered layer of the fired product was tCu-sintered layer = 30 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 4.9 μΩ · cm.

  Assuming that the resulting fired product is a “bulk metal copper thick film”, the film thickness tCu-bulk layer of the “bulk metal copper thick film” is tCu-bulk layer = tpaste · {VCu-particle + VCu-fine-particle + VCu -nanoparticle} / 100% by volume. The average film thickness tCu-sintered layer of the fired product actually obtained is thicker than the film thickness tCu-bulk layer of the “bulk metal copper thick film”, and the ratio tCu-bulk layer / tCu-sintered layer is 58.32 / 100. It has become. In other words, the “porosity” in the obtained fired product is estimated as Vvoid = 41.68% by volume.

  The volume specific resistivity 4.9 μΩ · cm of the obtained fired product is 2.93 times the resistivity of metallic copper 1.673 μΩ · cm (30 ° C.).

  The “copper powder” used in the “conductive copper paste” of Example 3 has a bulk density (tap density ρCu-particle-tap) of 5.5 g / cm 3 when laminated in a close-packed state. is there. Since the density ρCu-bulk of metallic copper (bulk) is 8.94 g / cm 3, the ratio of “voids” existing in the laminated structure is {(1 / ρCu− particle-tap) − (1 / ρCu-bulk)} · (1 / ρCu-particle-tap) = {1− (ρCu-particle-tap / ρCu-bulk)}. With respect to the volume ratio VCu-particle of the copper powder contained in the “conductive copper paste” of Example 3, the “void” is VCu-particle · (ρCu-bulk / ρCu-particle-tap) · { 1- (ρCu-particle-tap / ρCu-bulk)}. The tap density ρCu-fine-particle-tap of “copper fine powder” contained in the “conductive copper paste” of Example 1 is 4.3 g / cm 3. Therefore, when the “copper fine powder” is gathered in a close-packed state, the volume is VCu-fine-particle · (ρCu-bulk / ρCu-fine with respect to the volume ratio VCu-fine-particle of the copper fine powder. -particle). “Void” in the laminated structure of “copper powder”: VCu-particle · (ρCu-bulk / ρCu-particle-tap) · {1- (ρCu-particle-tap / ρCu-bulk)} "Bulk" when assembled in the close-packed state: If it exceeds VCu-fine-particle (ρCu-bulk / ρCu-fine-particle), "void" in the laminated structure of "copper powder" A state in which all of the “copper fine powder” is housed can be achieved.

  In a state where all of the “copper fine powder” is stored in the “void” in the laminated structure of “copper powder”, the remaining “remaining void” is VCu-particle · (ρCu-bulk / ρCu-particle- tap) · {1- (ρCu-particle-tap / ρCu-bulk)} − VCu-fine-particle.

  “Residual voids” remaining in the laminated structure of “copper powder”: VCu-particle · (ρCu-bulk / ρCu-particle-tap) · {1- (ρCu-particle-tap / ρCu-bulk)} − VCu When the volume ratio VCu-nanoparticle of the “copper nanoparticles” included in the “conductive copper paste” of Example 1 exceeds -fine-particles, a part of the “copper nanoparticles” The remaining “copper nanoparticles” are filled in the “powder” laminate structure, but the remaining “copper nanoparticles” are assumed to form a “copper nanoparticle” laminate on the upper surface of the “copper powder” laminate structure. The

  Specifically, the tap density ρCu-nanoparticle of the “copper nanoparticles” contained in the “conductive copper paste” of Example 3 is about 6.0 g / cm 3. Therefore, when the “copper nanoparticles” are aggregated in the close-packed state, the volume is VCu-nanoparticle · (ρCu-bulk / ρCu-nanoparticle) with respect to the volume ratio VCu-nanoparticle of the copper fine powder. When the “preheated drying (solvent removal) step” is performed to form the “dried coating film”, the bulk when the “copper nanoparticles” aggregate in the closest packing state: VCu-nanoparticle · (ρCu-bulk / ρCu-nanoparticle) remains in the laminated structure of “copper powder”: VCu-particle ・ (ρCu-bulk / ρCu-particle-tap) ・ {1- (ρCu-particle-tap / ρCu -bulk)}-When exceeding VCu-fine-particle, some of the "copper nanoparticles" fill the "residual voids" remaining in the "copper powder" laminate structure, but the remaining "copper" “Nanoparticles” are assumed to form a stack of “copper nanoparticles” on the top surface of the “copper powder” stack structure.

  At the time when the “preheating drying (solvent removal) step” is completed, the surface of the “copper nanoparticles” is in a state of being coated with the “coating agent molecular layer”. The “copper nanoparticles” having the “coating molecule layer” on the surface fill the “remaining voids” remaining in the laminated structure of the “copper powder”. The remaining “copper nanoparticles” are assumed to form a stack of “copper nanoparticles” having a “covering agent molecular layer” on the upper surface of the stack structure of “copper powder”.

  The average particle diameter dCu-nanoparticle of the copper nanoparticles contained in the “copper nanoparticles NPC-J1” used in Example 3 is 5 nm, and in the “copper nanoparticles NPC” used in Example 1 Is 1/16 of 80 nm of the average particle diameter dCu-nanoparticle of the copper nanoparticles. Assuming that the thickness of the “coating agent molecular layer” on the surface is the same, the “copper molecular layer” on the surface fills the “remaining voids” remaining in the laminated structure of the “copper powder”. The total volume of the “copper nanoparticles” in the “nanoparticles” is significantly reduced as compared with Example 1. As a result, the total volume of the “copper nanoparticles” themselves, which forms a laminate of “copper nanoparticles” having a “coating agent molecular layer” on the surface on the upper surface of the “copper powder” laminate structure, Compared with, it increases significantly.

  In the case of the “conductive copper paste” used in Example 3, the average thickness tCu-particle-layer of the laminated structure of “copper powder” included in the paste coating film having the average thickness tpaste is tCu- It is estimated that particle-layer = {[tpaste · {VCu-particle} / 100 volume%]} · (ρCu-bulk / ρCu-particle-tap). {[Tpaste · {VCu-particle} / 100 vol%]} · (ρCu-bulk / ρCu-particle-tap) = {[40 μm · {23.41 vol%} / 100 vol%]} · (8.94 /5.5)=15.22 μm. The average film thickness tCu-sintered layer of the obtained fired product is much thicker than the average thickness tCu-particle-layer of the estimated laminated structure of “copper powder”.

  At that time, “void” in the laminated structure of “copper powder”: VCu-particle · (ρCu-bulk / ρCu-particle-tap) · {1- (ρCu-particle-tap / ρCu-bulk)} is VCu -particle · (ρCu-bulk / ρCu-particle-tap) · {1- (ρCu-particle-tap / ρCu-bulk)} = 23.41% by volume · (8.94 / 5.5) · {1- It is estimated that (5.5 / 8.94)} = 14.64% by volume. "Bulk" when "copper fine powder" is assembled in the close-packed state: VCu-fine-particle (ρCu-bulk / ρCu-fine-particle) is VCu-fine-particle (ρCu-bulk / ρCu -fine-particle) = 5.11% by volume · (8.94 / 4.3) = 10.62% by volume. Accordingly, it is assumed that “copper fine powder” is filled in “voids” in the laminated structure of “copper powder”.

Example 4
The copper thick film forming material of Example 4 is prepared in the shape of “conductive copper paste” using the raw materials described in Example 1 and changing the blending ratio.

  Harima Chemical Co., Ltd. “copper nanoparticles NPC” 22.2 parts by mass (copper nanoparticles 22.0 parts by mass and “coating agent molecular amine” 0.2 parts by mass), Mitsui Metals Co., Ltd. 1400YM 59.9 parts by mass, Mitsui Metal Co., Ltd. 1050Y13.1 mass part and Japanese emulsifier tripropylene glycol 4.8 mass part are mixed uniformly. The mixture is stirred with a stirring deaerator to uniformly disperse copper powder, copper fine powder, and copper nanoparticles in a dispersion solvent to prepare a “conductive copper paste”.

  The volume ratio VCu-particle of the copper powder, the volume ratio VCu-fine-particle of the copper fine powder, and the volume ratio VCu-nanoparticle of the copper nanoparticle contained in the prepared “conductive copper paste” are VCu-particle = VCu-fine-particle = 9.41% by volume; VCu-nanoparticle = 15.81% by volume. The sum of the volume ratio Vcoating-molecule of the “coating agent amine” and the volume ratio Vsolvent of the “solvent” is {Vcoating-molecule + Vsolvent} = 31.74% by volume.

The ratio of the volume ratio VCu-particle of copper powder and the volume ratio VCu-fine-particle of copper fine powder (VCu-particle + VCu-fine-particle) and the volume ratio of copper nanoparticles VCu-nanoparticle is (VCu -particle + VCu-fine-particle): VCu-nanoparticle = 100: 30.1.
{VCu-particle + VCu-fine-particle + VCu-nanoparticle} / {Vcoating-molecule + Vsolvent} = 68.26 / 31.74
In the “conductive copper paste”, the copper nanoparticles are uniformly dispersed in the “solvent” tripropylene glycol by forming a coating molecular layer composed of “coating molecular amine” on the surface thereof. At that time, the “coating agent molecular amine” is dissolved in the “solvent” tripropylene glycol. Surface density Ccoating-molecule-surface of “Coating molecular amine” forming a coating molecular layer on the surface of copper nanoparticles and concentration of “Coating molecular amine” dissolved in “solvent” Ccoating-molecule Dissociation equilibrium is achieved with -liquid-phase.

  Also in the “conductive copper paste” of Example 4, the relationship is ΣSCu-nanoparticle >> ΣSCu-fine-particle >> ΣSCu-particle.

  Therefore, the amount Mcoating-molecule-surface of the “coating molecule amine” coating the surface of the copper nanoparticles and the amount Mcoating-molecule-liquid-phase of the “coating agent molecular amine” dissolved in the “solvent”. The total can be regarded as the total amount Mcoating-molecule of “coating agent molecular amine” contained in “conductive copper paste” (Mcoating-molecule = Mcoating-molecule-surface + Mcoating-molecule-liquid-phase).

  At that time, the total surface area ΣSCu-nanoparticle of the copper nanoparticles in the “conductive copper paste” of Example 4 is the total surface area ΣSCu-nanoparticle of the copper nanoparticles in the “conductive copper paste” of Example 1. It is 2/3 times. The total amount Mcoating-molecule of the “coating agent molecular amine” contained in the “conductive copper paste” of Example 4 is the total amount Mcoating of the “coating agent molecular amine” contained in the “conductive copper paste” of Example 1. -2/3 times the molecule.

  That is, in the “conductive copper paste” of Example 4, the surface density of the “coating agent molecular amine” on the surface of the copper nanoparticles Ccoating-molecule-surface and the “coating agent molecular amine” dissolved in the “solvent” Concentration Ccoating-molecule-liquid-phase is dissolved in “Coating-molecule-surface” and “Solvent” of “Coating molecule amine” on the surface of copper nanoparticles in “Conductive copper paste” of Example 1. The concentration of the “coating molecule amine” is estimated to be slightly lower than the concentration Ccoating-molecule-liquid-phase.

  The liquid viscosity of the prepared “conductive copper paste” was 160 Pa · s (spiral rotational viscometer 10 rpm 25 ° C.).

  The prepared “conductive copper paste” was applied in a 10 mm × 50 mm pattern on a slide glass. The average thickness tpaste of the paste coating film was tpaste = 40 μm.

  For the paste coating film, using a Nissin plasma baking furnace, the procedure described in Example 1 was followed by a “preheating drying (solvent removal) step”, “reduced pressure drying (organic matter removal) step”, “micro A wave plasma irradiation (plasma firing) step "was performed, and the copper powder, copper fine powder and copper nanoparticles contained in the paste coating film were fired.

  The average film thickness tCu-sintered layer of the fired product was tCu-sintered layer = 30 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 3.2 μΩ · cm.

  Assuming that the resulting fired product is a “bulk metal copper thick film”, the film thickness tCu-bulk layer of the “bulk metal copper thick film” is tCu-bulk layer = tpaste · {VCu-particle + VCu-fine-particle + VCu -nanoparticle} / 100% by volume. The average film thickness tCu-sintered layer of the fired product actually obtained is thicker than the film thickness tCu-bulk layer of the “bulk metal copper thick film”, and the ratio tCu-bulk layer / tCu-sintered layer is 91.0 / 100. It has become. In other words, the “void ratio” in the obtained fired product is estimated to be Vvoid = 9.0% by volume.

  The volume specific resistivity 3.2 μΩ · cm of the obtained fired product is 1.91 times that of the metallic copper resistivity 1.673 μΩ · cm (30 ° C.).

  The “copper powder” used in the “conductive copper paste” of Example 4 has a bulk density (tap density ρCu-particle-tap) of 5.5 g / cm 3 when laminated in a close-packed state. is there. Since the density ρCu-bulk of metallic copper (bulk) is 8.94 g / cm 3, the ratio of “voids” existing in the laminated structure is {(1 / ρCu− particle-tap) − (1 / ρCu-bulk)} · (1 / ρCu-particle-tap) = {1− (ρCu-particle-tap / ρCu-bulk)}. With respect to the volume ratio VCu-particle of the copper powder contained in the “conductive copper paste” of Example 4, the “void” is VCu-particle · (ρCu-bulk / ρCu-particle-tap) · { 1- (ρCu-particle-tap / ρCu-bulk)}. The tap density ρCu-fine-particle-tap of “copper fine powder” contained in the “conductive copper paste” of Example 1 is 4.3 g / cm 3. Therefore, when the “copper fine powder” is gathered in a close-packed state, the volume is VCu-fine-particle · (ρCu-bulk / ρCu-fine with respect to the volume ratio VCu-fine-particle of the copper fine powder. -particle). “Void” in the laminated structure of “copper powder”: VCu-particle · (ρCu-bulk / ρCu-particle-tap) · {1- (ρCu-particle-tap / ρCu-bulk)} "Bulk" when assembled in the close-packed state: If it exceeds VCu-fine-particle (ρCu-bulk / ρCu-fine-particle), "void" in the laminated structure of "copper powder" A state in which all of the “copper fine powder” is housed can be achieved.

  In a state where all of the “copper fine powder” is stored in the “void” in the laminated structure of “copper powder”, the remaining “remaining void” is VCu-particle · (ρCu-bulk / ρCu-particle- tap) · {1- (ρCu-particle-tap / ρCu-bulk)} − VCu-fine-particle.

  “Residual voids” remaining in the laminated structure of “copper powder”: VCu-particle · (ρCu-bulk / ρCu-particle-tap) · {1- (ρCu-particle-tap / ρCu-bulk)} − VCu When the volume ratio VCu-nanoparticle of the “copper nanoparticles” included in the “conductive copper paste” of Example 1 is less than the fine particle, the “copper nanoparticles” is a laminated structure of “copper powder” It is assumed that the “residual void” remaining inside is filled.

  Specifically, the tap density ρCu-nanoparticle of the “copper nanoparticles” contained in the “conductive copper paste” of Example 4 is about 6.0 g / cm 3. Therefore, when the “copper nanoparticles” are aggregated in the close-packed state, the volume is VCu-nanoparticle · (ρCu-bulk / ρCu-nanoparticle) with respect to the volume ratio VCu-nanoparticle of the copper fine powder. When the “preheated drying (solvent removal) step” is performed to form the “dried coating film”, the bulk when the “copper nanoparticles” aggregate in the closest packing state: VCu-nanoparticle · (ρCu-bulk / ρCu-nanoparticle) remains in the laminated structure of “copper powder”: VCu-particle ・ (ρCu-bulk / ρCu-particle-tap) ・ {1- (ρCu-particle-tap / ρCu -bulk)}-VCu-fine-particles, the “copper nanoparticles” are assumed to fill the “residual voids” remaining in the “copper powder” laminate structure.

  In the case of the “conductive copper paste” used in Example 4, the average thickness tCu-particle-layer of the laminated structure of “copper powder” included in the paste coating film having the average thickness tpaste is tCu−. It is estimated that particle-layer = {[tpaste · {VCu-particle} / 100 volume%]} · (ρCu-bulk / ρCu-particle-tap). {[Tpaste · {VCu-particle} / 100 vol%]} · (ρCu-bulk / ρCu-particle-tap) = {[40 μm · {43.04 vol%} / 100 vol%]} · (8.94 /4.55)=27.98 μm. The average film thickness tCu-sintered layer of the obtained fired product is slightly thicker than the estimated average thickness tCu-particle-layer of the laminated structure of “copper powder”.

  At that time, “void” in the laminated structure of “copper powder”: VCu-particle · (ρCu-bulk / ρCu-particle-tap) · {1- (ρCu-particle-tap / ρCu-bulk)} is VCu -particle · (ρCu-bulk / ρCu-particle-tap) · {1- (ρCu-particle-tap / ρCu-bulk)} = 43.04% by volume · (8.94 / 5.5) · {1- It is estimated that (5.5 / 8.94)} = 26.92% by volume. "Bulk" when "copper fine powder" is assembled in the close-packed state: VCu-fine-particle (ρCu-bulk / ρCu-fine-particle) is VCu-fine-particle (ρCu-bulk / ρCu -fine-particle) = 9.41% by volume · (8.94 / 4.3) = 19.56% by volume. Accordingly, it is assumed that “copper fine powder” is filled in “voids” in the laminated structure of “copper powder”.

(Example 5)
The material for forming a copper thick film of Example 5 is prepared in the shape of “conductive copper paste” using the raw materials described in Example 1 and changing the blending ratio.

  44.4 parts by mass of “Copper nanoparticles NPC” (44.0 parts by mass of copper nanoparticles and 0.4 parts by mass of “coating agent molecular amine”), 1400YM 41.7 parts by mass of Mitsui Kinzoku Co., Ltd., Mitsui Metal Co., Ltd. 1050Y9.1 mass part and Japanese emulsifier tripropylene glycol 4.8 mass part are mixed uniformly. The mixture is stirred with a stirring deaerator to uniformly disperse copper powder, copper fine powder, and copper nanoparticles in a dispersion solvent to prepare a “conductive copper paste”.

  The volume ratio VCu-particle of the copper powder, the volume ratio VCu-fine-particle of the copper fine powder, and the volume ratio VCu-nanoparticle of the copper nanoparticle contained in the prepared “conductive copper paste” are VCu-particle = VCu-fine-particle = 6.45% by volume; VCu-nanoparticle = 31.19% by volume. The sum of the volume ratio Vcoating-molecule of “coating agent molecular amine” and the volume ratio Vsolvent of “solvent” is {Vcoating-molecule + Vsolvent} = 32.80 vol%.

The ratio of the volume ratio VCu-particle of copper powder and the volume ratio VCu-fine-particle of copper fine powder (VCu-particle + VCu-fine-particle) and the volume ratio of copper nanoparticles VCu-nanoparticle is (VCu -particle + VCu-fine-particle): VCu-nanoparticle = 100: 86.6.
{VCu-particle + VCu-fine-particle + VCu-nanoparticle} / {Vcoating-molecule + Vsolvent} = 67.20 / 32.80
In the “conductive copper paste”, the copper nanoparticles are uniformly dispersed in the “solvent” tripropylene glycol by forming a coating molecular layer composed of “coating molecular amine” on the surface thereof. At that time, the “coating agent molecular amine” is dissolved in the “solvent” tripropylene glycol. Surface density Ccoating-molecule-surface of “Coating molecular amine” forming a coating molecular layer on the surface of copper nanoparticles and concentration of “Coating molecular amine” dissolved in “solvent” Ccoating-molecule Dissociation equilibrium is achieved with -liquid-phase.

  Also in the “conductive copper paste” of Example 5, the relationship is ΣSCu-nanoparticle >> ΣSCu-fine-particle >> ΣSCu-particle.

  Therefore, the amount Mcoating-molecule-surface of the “coating molecule amine” coating the surface of the copper nanoparticles and the amount Mcoating-molecule-liquid-phase of the “coating agent molecular amine” dissolved in the “solvent”. The total can be regarded as the total amount Mcoating-molecule of “coating agent molecular amine” contained in “conductive copper paste” (Mcoating-molecule = Mcoating-molecule-surface + Mcoating-molecule-liquid-phase).

  At that time, the total surface area ΣSCu-nanoparticle of the copper nanoparticles in the “conductive copper paste” of Example 5 is the total surface area ΣSCu-nanoparticle of the copper nanoparticles in the “conductive copper paste” of Example 1. It is 4/3 times. The total amount Mcoating-molecule of the “coating agent molecular amine” contained in the “conductive copper paste” of Example 5 is the total amount Mcoating of the “coating agent molecular amine” contained in the “conductive copper paste” of Example 1. -4/3 times -molecule.

  That is, in the “conductive copper paste” of Example 5, the surface density Ccoating-molecule-surface of the “coating agent molecular amine” on the surface of the copper nanoparticles and the “coating agent molecular amine” dissolved in the “solvent” Concentration Ccoating-molecule-liquid-phase is dissolved in “Coating-molecule-surface” and “Solvent” of “Coating molecule amine” on the surface of copper nanoparticles in “Conductive copper paste” of Example 1. It is estimated that the concentration of the “coating molecule amine” is slightly higher than the concentration Ccoating-molecule-liquid-phase.

  The liquid viscosity of the prepared “conductive copper paste” was 148 Pa · s (spiral rotational viscometer 10 rpm 25 ° C.).

  The prepared “conductive copper paste” was applied in a 10 mm × 50 mm pattern on a slide glass. The average thickness tpaste of the paste coating film was tpaste = 40 μm.

  For the paste coating film, using a Nissin plasma baking furnace, the procedure described in Example 1 was followed by a “preheating drying (solvent removal) step”, “reduced pressure drying (organic matter removal) step”, “micro A wave plasma irradiation (plasma firing) step "was performed, and the copper powder, copper fine powder and copper nanoparticles contained in the paste coating film were fired.

  The average film thickness tCu-sintered layer of the fired product was tCu-sintered layer = 30 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 3.8 μΩ · cm.

  Assuming that the resulting fired product is a “bulk metal copper thick film”, the film thickness tCu-bulk layer of the “bulk metal copper thick film” is tCu-bulk layer = tpaste · {VCu-particle + VCu-fine-particle + VCu -nanoparticle} / 100% by volume. The average film thickness tCu-sintered layer of the fired product actually obtained is thicker than the film thickness tCu-bulk layer of the “bulk metal copper thick film”, and the ratio tCu-bulk layer / tCu-sintered layer is 89.6 / 100. It has become. In other words, the “void ratio” in the obtained fired product is estimated to be Vvoid = 10.4% by volume.

  The volume specific resistivity 3.8 μΩ · cm of the obtained fired product is 2.27 times that of the metal copper resistivity 1.673 μΩ · cm (30 ° C.).

  The “copper powder” used in the “conductive copper paste” of Example 5 has a bulk density (tap density ρCu-particle-tap) of 5.5 g / cm 3 when laminated in a close-packed state. is there. Since the density ρCu-bulk of metallic copper (bulk) is 8.94 g / cm 3, the ratio of “voids” existing in the laminated structure is {(1 / ρCu− particle-tap) − (1 / ρCu-bulk)} · (1 / ρCu-particle-tap) = {1− (ρCu-particle-tap / ρCu-bulk)}. With respect to the volume ratio VCu-particle of the copper powder contained in the “conductive copper paste” of Example 5, the “void” is VCu-particle · (ρCu-bulk / ρCu-particle-tap) · { 1- (ρCu-particle-tap / ρCu-bulk)}. The tap density ρCu-fine-particle-tap of “copper fine powder” contained in the “conductive copper paste” of Example 1 is 4.3 g / cm 3. Therefore, when the “copper fine powder” is gathered in a close-packed state, the volume is VCu-fine-particle · (ρCu-bulk / ρCu-fine with respect to the volume ratio VCu-fine-particle of the copper fine powder. -particle). “Void” in the laminated structure of “copper powder”: VCu-particle · (ρCu-bulk / ρCu-particle-tap) · {1- (ρCu-particle-tap / ρCu-bulk)} "Bulk" when assembled in the close-packed state: If it exceeds VCu-fine-particle (ρCu-bulk / ρCu-fine-particle), "void" in the laminated structure of "copper powder" A state in which all of the “copper fine powder” is housed can be achieved.

  In a state where all of the “copper fine powder” is stored in the “void” in the laminated structure of “copper powder”, the remaining “remaining void” is VCu-particle · (ρCu-bulk / ρCu-particle- tap) · {1- (ρCu-particle-tap / ρCu-bulk)} − VCu-fine-particle.

  “Residual voids” remaining in the laminated structure of “copper powder”: VCu-particle · (ρCu-bulk / ρCu-particle-tap) · {1- (ρCu-particle-tap / ρCu-bulk)} − VCu When the volume ratio VCu-nanoparticle of the “copper nanoparticles” included in the “conductive copper paste” of Example 1 exceeds -fine-particles, a part of the “copper nanoparticles” The remaining “copper nanoparticles” are filled in the “powder” laminate structure, but the remaining “copper nanoparticles” are assumed to form a “copper nanoparticle” laminate on the upper surface of the “copper powder” laminate structure. The

  Specifically, the tap density ρCu-nanoparticle of the “copper nanoparticles” contained in the “conductive copper paste” of Example 5 is about 6.0 g / cm 3. Therefore, when the “copper nanoparticles” are aggregated in the close-packed state, the volume is VCu-nanoparticle · (ρCu-bulk / ρCu-nanoparticle) with respect to the volume ratio VCu-nanoparticle of the copper fine powder. When the “preheated drying (solvent removal) step” is performed to form the “dried coating film”, the bulk when the “copper nanoparticles” aggregate in the closest packing state: VCu-nanoparticle · (ρCu-bulk / ρCu-nanoparticle) remains in the laminated structure of “copper powder”: VCu-particle ・ (ρCu-bulk / ρCu-particle-tap) ・ {1- (ρCu-particle-tap / ρCu -bulk)}-When exceeding VCu-fine-particle, some of the "copper nanoparticles" fill the "residual voids" remaining in the "copper powder" laminate structure, but the remaining "copper" “Nanoparticles” are assumed to form a stack of “copper nanoparticles” on the top surface of the “copper powder” stack structure.

  At the time when the “preheating drying (solvent removal) step” is completed, the surface of the “copper nanoparticles” is in a state of being coated with the “coating agent molecular layer”. The “copper nanoparticles” having the “coating molecule layer” on the surface fill the “remaining voids” remaining in the laminated structure of the “copper powder”. The remaining “copper nanoparticles” are assumed to form a stack of “copper nanoparticles” having a “covering agent molecular layer” on the upper surface of the stack structure of “copper powder”.

  The volume ratio VCu-particle of the copper powder contained in the “conductive copper paste” used in Example 5 is the copper powder contained in the “conductive copper paste” used in Example 1. The volume ratio of VCu-particle is about 4/5. The volume ratio VCu-nanoparticle of “copper nanoparticles” contained in the “conductive copper paste” used in Example 5 is contained in the “conductive copper paste” used in Example 1. The volume ratio VCu-nanoparticle of “copper nanoparticles” is 4/3. Assuming that the thickness of the “coating agent molecular layer” on the surface is the same, the “copper molecular layer” on the surface fills the “remaining voids” remaining in the laminated structure of the “copper powder”. The total volume of the “copper nanoparticles” in the “nanoparticles” is significantly reduced as compared with Example 1. As a result, the total volume of the “copper nanoparticles” themselves, which forms a laminate of “copper nanoparticles” having a “coating agent molecular layer” on the surface on the upper surface of the “copper powder” laminate structure, Compared with, it increases significantly.

  In the case of the “conductive copper paste” used in Example 5, the average thickness tCu-particle-layer of the laminated structure of “copper powder” included in the paste coating film having the average thickness tpaste is tCu−. It is estimated that particle-layer = {[tpaste · {VCu-particle} / 100 volume%]} · (ρCu-bulk / ρCu-particle-tap). {[Tpaste · {VCu-particle} / 100 vol%]} · (ρCu-bulk / ρCu-particle-tap) = {[40 μm · {29.56 vol%} / 100 vol%]} · (8.94 /5.5)=19.22 μm. The average film thickness tCu-sintered layer of the obtained fired product is much thicker than the average thickness tCu-particle-layer of the estimated laminated structure of “copper powder”.

  At that time, “void” in the laminated structure of “copper powder”: VCu-particle · (ρCu-bulk / ρCu-particle-tap) · {1- (ρCu-particle-tap / ρCu-bulk)} is VCu -particle · (ρCu-bulk / ρCu-particle-tap) · {1- (ρCu-particle-tap / ρCu-bulk)} = 29.56% by volume · (8.94 / 5.5) · {1- It is estimated that (5.5 / 8.94)} = 18.49% by volume. "Bulk" when "copper fine powder" is assembled in the close-packed state: VCu-fine-particle (ρCu-bulk / ρCu-fine-particle) is VCu-fine-particle (ρCu-bulk / ρCu -fine-particle) = 6.45 vol% · (8.94 / 4.3) = 13.41 vol%. Accordingly, it is assumed that “copper fine powder” is filled in “voids” in the laminated structure of “copper powder”.

(Example 6)
The material for forming a copper thick film of Example 6 is prepared in the form of “conductive copper paste” using the following raw materials.

  As copper microparticles, MA-C025K (average particle diameter dCu-particle 2.5 μm: tap density ρCu-particle-tap 4.55 g / cm3) manufactured by Mitsui Kinzoku Co., Ltd., which is a copper powder produced by the atomization method, is used. To do. 1050Y manufactured by Mitsui Kinzoku Co., Ltd. (average particle diameter dCu-fine-particle 0.8 μm: tap density ρCu-fine-particle-tap 4.3 g / copper fine powder produced by a wet method as copper submicron particles cm3) is used.

  As “copper nanoparticle dispersion liquid”, Harima Kasei copper nanoparticle NPC is used. The volume ratio of “copper nanoparticles” and “coating agent molecular amine” contained in the “copper nanoparticle NPC” is “copper nanoparticles”: “coating agent molecular amine” = 91.3 vol% : Estimated to be 8.7% by volume.

  As a “high-boiling nonpolar organic solvent”, tripropylene glycol manufactured by Nippon Emulsifier is used.

  Harima Chemical Co., Ltd. “Copper Nanoparticles NPC” 33.3 parts by mass (copper nanoparticles 33.0 parts by mass and “Coating Molecular Amine” 0.3 parts by mass), Mitsui Metals Co., Ltd. MA-C025K 50.8 parts by mass Part, Mitsui Kinzoku Co., Ltd. product 1050Y11.1 mass part, Japanese emulsifier tripropylene glycol 4.8 mass part is mixed uniformly. The mixture is stirred with a stirring deaerator to uniformly disperse copper powder, copper fine powder, and copper nanoparticles in a dispersion solvent to prepare a “conductive copper paste”.

  The volume ratio VCu-particle of the copper powder, the volume ratio VCu-fine-particle of the copper fine powder, and the volume ratio VCu-nanoparticle of the copper nanoparticle contained in the prepared “conductive copper paste” are VCu-particle = VCu-fine-particle = 7.92% by volume; VCu-nanoparticle = 23.55% by volume. The sum of the volume ratio Vcoating-molecule of the “coating agent amine” and the volume ratio Vsolvent of the “solvent” is {Vcoating-molecule + Vsolvent} = 32.3 vol%.

The ratio of the volume ratio VCu-particle of copper powder and the volume ratio VCu-fine-particle of copper fine powder (VCu-particle + VCu-fine-particle) and the volume ratio of copper nanoparticles VCu-nanoparticle is (VCu -particle + VCu-fine-particle): VCu-nanoparticle = 100: 53.3.
{VCu-particle + VCu-fine-particle + VCu-nanoparticle} / {Vcoating-molecule + Vsolvent} = 67.72: 32.28
The liquid viscosity of the prepared “conductive copper paste” was 136 Pa · s (spiral rotational viscometer 10 rpm 25 ° C.).

  The prepared “conductive copper paste” was applied in a 10 mm × 50 mm pattern on a slide glass. The average thickness tpaste of the paste coating film was tpaste = 40 μm.

  For the paste coating film, using a Nissin plasma baking furnace, the procedure described in Example 1 was followed by a “preheating drying (solvent removal) step”, “reduced pressure drying (organic matter removal) step”, “micro A wave plasma irradiation (plasma firing) step "was performed, and the copper powder, copper fine powder and copper nanoparticles contained in the paste coating film were fired.

  The average film thickness tCu-sintered layer of the fired product was tCu-sintered layer = 30 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 3.5 μΩ · cm.

  Assuming that the resulting fired product is a “bulk metal copper thick film”, the film thickness tCu-bulk layer of the “bulk metal copper thick film” is tCu-bulk layer = tpaste · {VCu-particle + VCu-fine-particle + VCu -nanoparticle} / 100% by volume. The average film thickness tCu-sintered layer of the fired product actually obtained is thicker than the film thickness tCu-bulk layer of the “bulk metal copper thick film”, and the ratio tCu-bulk layer / tCu-sintered layer is 90.3 / 100. It has become. In other words, the “porosity” in the obtained fired product is estimated to be Vvoid = 9.7% by volume.

  The volume resistivity of 3.5 μΩ · cm of the obtained fired product is 2.09 times that of the metal copper resistivity of 1.673 μΩ · cm (30 ° C.).

  The “copper powder” used in the “conductive copper paste” of Example 6 has a bulk density (tap density ρCu-particle-tap) of 4.55 g / cm 3 when laminated in a close-packed state. is there. Since the density ρCu-bulk of metallic copper (bulk) is 8.94 g / cm 3, the ratio of “voids” existing in the laminated structure is {(1 / ρCu− particle-tap) − (1 / ρCu-bulk)} · (1 / ρCu-particle-tap) = {1− (ρCu-particle-tap / ρCu-bulk)}. With respect to the volume ratio VCu-particle of the copper powder contained in the “conductive copper paste” of Example 6, the “void” is VCu-particle · (ρCu-bulk / ρCu-particle-tap) · { 1- (ρCu-particle-tap / ρCu-bulk)}. The tap density ρCu-fine-particle-tap of “copper fine powder” contained in the “conductive copper paste” of Example 1 is 4.3 g / cm 3. Therefore, when the “copper fine powder” is gathered in a close-packed state, the volume is VCu-fine-particle · (ρCu-bulk / ρCu-fine with respect to the volume ratio VCu-fine-particle of the copper fine powder. -particle). “Void” in the laminated structure of “copper powder”: VCu-particle · (ρCu-bulk / ρCu-particle-tap) · {1- (ρCu-particle-tap / ρCu-bulk)} "Bulk" when assembled in the close-packed state: If it exceeds VCu-fine-particle (ρCu-bulk / ρCu-fine-particle), "void" in the laminated structure of "copper powder" A state in which all of the “copper fine powder” is housed can be achieved.

  In a state where all of the “copper fine powder” is stored in the “void” in the laminated structure of “copper powder”, the remaining “remaining void” is VCu-particle · (ρCu-bulk / ρCu-particle- tap) · {1- (ρCu-particle-tap / ρCu-bulk)} − VCu-fine-particle.

  “Residual voids” remaining in the laminated structure of “copper powder”: VCu-particle · (ρCu-bulk / ρCu-particle-tap) · {1- (ρCu-particle-tap / ρCu-bulk)} − VCu When the volume ratio VCu-nanoparticle of the “copper nanoparticles” included in the “conductive copper paste” of Example 1 exceeds -fine-particles, a part of the “copper nanoparticles” The remaining “copper nanoparticles” are filled in the “powder” laminate structure, but the remaining “copper nanoparticles” are assumed to form a “copper nanoparticle” laminate on the upper surface of the “copper powder” laminate structure. The

  Specifically, the tap density ρCu-nanoparticle of the “copper nanoparticles” contained in the “conductive copper paste” of Example 6 is about 6.0 g / cm 3. Therefore, when the “copper nanoparticles” are aggregated in the close-packed state, the volume is VCu-nanoparticle · (ρCu-bulk / ρCu-nanoparticle) with respect to the volume ratio VCu-nanoparticle of the copper fine powder. When the “preheated drying (solvent removal) step” is performed to form the “dried coating film”, the bulk when the “copper nanoparticles” aggregate in the closest packing state: VCu-nanoparticle · (ρCu-bulk / ρCu-nanoparticle) remains in the laminated structure of “copper powder”: VCu-particle ・ (ρCu-bulk / ρCu-particle-tap) ・ {1- (ρCu-particle-tap / ρCu -bulk)}-When exceeding VCu-fine-particle, some of the "copper nanoparticles" fill the "residual voids" remaining in the "copper powder" laminate structure, but the remaining "copper" “Nanoparticles” are assumed to form a stack of “copper nanoparticles” on the top surface of the “copper powder” stack structure.

  At the time when the “preheating drying (solvent removal) step” is completed, the surface of the “copper nanoparticles” is in a state of being coated with the “coating agent molecular layer”. The “copper nanoparticles” having the “coating molecule layer” on the surface fill the “remaining voids” remaining in the laminated structure of the “copper powder”. The remaining “copper nanoparticles” are assumed to form a stack of “copper nanoparticles” having a “covering agent molecular layer” on the upper surface of the stack structure of “copper powder”.

  The bulk density (tap density ρCu-particle-tap) of 4.55 g / cm 3 contained in the “conductive copper paste” used in Example 6 is “conductive copper paste” used in Example 1. Compared with the bulk density (tap density ρCu-particle-tap) of 5.5 g / cm 3 of the copper powder contained in the “paste”, it is about 4/5. “Fine powder atomized copper powder” has a wider “particle size distribution” than “wet copper powder”. Accordingly, the total volume of the “copper nanoparticles” themselves, which forms a laminate of “copper nanoparticles” having a “coating agent molecular layer” on the surface on the upper surface of the “copper powder” laminate structure, is shown in Example 1. It is estimated that there is a slight increase compared to.

  In the case of the “conductive copper paste” used in Example 6, the average thickness tCu-particle-layer of the laminated structure of “copper powder” contained in the paste coating film having the average thickness tpaste is tCu− It is estimated that particle-layer = {[tpaste · {VCu-particle} / 100 volume%]} · (ρCu-bulk / ρCu-particle-tap). {[Tpaste · {VCu-particle} / 100 vol%]} · (ρCu-bulk / ρCu-particle-tap) = {[40 μm · {36.25 vol%} / 100 vol%]} · (8.94 /4.55)=28.49 μm. The average film thickness tCu-sintered layer of the obtained fired product is slightly thicker than the estimated average thickness tCu-particle-layer of the laminated structure of “copper powder”.

  At that time, “void” in the laminated structure of “copper powder”: VCu-particle · (ρCu-bulk / ρCu-particle-tap) · {1- (ρCu-particle-tap / ρCu-bulk)} is VCu -particle · (ρCu-bulk / ρCu-particle-tap) · {1- (ρCu-particle-tap / ρCu-bulk)} = 36.25% by volume · (8.94 / 4.55) · {1- It is estimated that (4.55 / 8.94)} = 34.98% by volume. "Bulk" when "copper fine powder" is assembled in the close-packed state: VCu-fine-particle (ρCu-bulk / ρCu-fine-particle) is VCu-fine-particle (ρCu-bulk / ρCu -fine-particle) = 7.92 vol% · (8.94 / 4.3) = 16.47 vol%. Accordingly, it is assumed that “copper fine powder” is filled in “voids” in the laminated structure of “copper powder”.

(Example 7)
The material for forming a copper thick film of Example 7 is prepared in the shape of “conductive copper paste” using the following raw materials.

  MFD2 manufactured by Mitsui Kinzoku Co., Ltd. (particle size distribution maximum 10 μm-20 μm), which is a copper powder prepared by subjecting a dendritic copper powder produced by an electrolytic method to mechanical pulverization treatment as copper microparticles. A tap density of 4.87 g / cm3) is used. As the copper submicron particles, 1050Y (average particle diameter 0.8 μm: tap density 4.3 g / cm 3) manufactured by Mitsui Kinzoku Co., Ltd., which is a copper fine powder produced by a wet method, is used.

  As “copper nanoparticle dispersion liquid”, Harima Kasei copper nanoparticle NPC is used. The volume ratio of “copper nanoparticles” and “coating agent molecular amine” contained in “copper nanoparticle NPC” is “copper nanoparticle”: “coating agent molecular amine” = 91.3 vol%: Estimated at 8.7% by volume.

  As a “high-boiling nonpolar organic solvent”, tripropylene glycol manufactured by Nippon Emulsifier is used.

  33.3 parts by mass of “Copper nanoparticles NPC” manufactured by Harima Kasei Co., Ltd. (33.0 parts by mass of copper nanoparticles and 0.3 parts by mass of “covering agent molecular amine”), 45.2 parts by mass of MFD2 manufactured by Mitsui Kinzoku Co., Ltd. 16.7 parts by mass of Mitsui Kinzoku 1050Y and 4.8 parts by mass of tripropylene glycol manufactured by Nippon Emulsifier are mixed uniformly. The mixture is stirred with a stirring deaerator to uniformly disperse copper powder, copper fine powder, and copper nanoparticles in a dispersion solvent to prepare a “conductive copper paste”.

  The volume ratio VCu-particle of the copper powder, the volume ratio VCu-fine-particle of the copper fine powder, and the volume ratio VCu-nanoparticle of the copper nanoparticle contained in the prepared “conductive copper paste” are VCu-particle = VCu-fine-particle = 11.92% by volume; VCu-nanoparticle = 23.55% by volume. The sum of the volume ratio Vcoating-molecule of the “coating agent molecular amine” and the volume ratio Vsolvent of the “solvent” is {Vcoating-molecule + Vsolvent} = 32.28% by volume.

The ratio of the volume ratio VCu-particle of copper powder and the volume ratio VCu-fine-particle of copper fine powder (VCu-particle + VCu-fine-particle) and the volume ratio of copper nanoparticles VCu-nanoparticle is (VCu -particle + VCu-fine-particle): VCu-nanoparticle = 100: 53.3.
{VCu-particle + VCu-fine-particle + VCu-nanoparticle} / {Vcoating-molecule + Vsolvent} = 67.72: 32.28
The liquid viscosity of the prepared “conductive copper paste” was 160 Pa · s (spiral rotational viscometer 10 rpm 25 ° C.).

  The prepared “conductive copper paste” was applied in a 10 mm × 50 mm pattern on a slide glass. The average thickness tpaste of the paste coating film was tpaste = 40 μm.

  For the paste coating film, using a Nissin plasma baking furnace, the procedure described in Example 1 was followed by a “preheating drying (solvent removal) step”, “reduced pressure drying (organic matter removal) step”, “micro A wave plasma irradiation (plasma firing) step "was performed, and the copper powder, copper fine powder and copper nanoparticles contained in the paste coating film were fired.

  The average film thickness tCu-sintered layer of the fired product was tCu-sintered layer = 30 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 4.0 μΩ · cm.

  Assuming that the resulting fired product is a “bulk metal copper thick film”, the film thickness tCu-bulk layer of the “bulk metal copper thick film” is tCu-bulk layer = tpaste · {VCu-particle + VCu-fine-particle + VCu -nanoparticle} / 100% by volume. The average film thickness tCu-sintered layer of the fired product actually obtained is thicker than the film thickness tCu-bulk layer of the “bulk metal copper thick film”, and the ratio tCu-bulk layer / tCu-sintered layer is 90.3 / 100. It has become. In other words, the “porosity” in the obtained fired product is estimated to be Vvoid = 9.7% by volume.

  The volume specific resistivity 4.0 μΩ · cm of the obtained fired product is 2.39 times that of the metallic copper resistivity 1.673 μΩ · cm (30 ° C.).

  The “copper powder” used in the “conductive copper paste” of Example 7 has a bulk density (tap density ρCu-particle-tap) of 4.87 g / cm 3 when laminated in a close-packed state. is there. Since the density ρCu-bulk of metallic copper (bulk) is 8.94 g / cm 3, the ratio of “voids” existing in the laminated structure is {(1 / ρCu− particle-tap) − (1 / ρCu-bulk)} · (1 / ρCu-particle-tap) = {1− (ρCu-particle-tap / ρCu-bulk)}. With respect to the volume ratio VCu-particle of the copper powder contained in the “conductive copper paste” of Example 7, the “void” is VCu-particle · (ρCu-bulk / ρCu-particle-tap) · { 1- (ρCu-particle-tap / ρCu-bulk)}. The tap density ρCu-fine-particle-tap of “copper fine powder” contained in the “conductive copper paste” of Example 1 is 4.3 g / cm 3. Therefore, when the “copper fine powder” is gathered in a close-packed state, the volume is VCu-fine-particle · (ρCu-bulk / ρCu-fine with respect to the volume ratio VCu-fine-particle of the copper fine powder. -particle). “Void” in the laminated structure of “copper powder”: VCu-particle · (ρCu-bulk / ρCu-particle-tap) · {1- (ρCu-particle-tap / ρCu-bulk)} "Bulk" when assembled in the close-packed state: If it exceeds VCu-fine-particle (ρCu-bulk / ρCu-fine-particle), "void" in the laminated structure of "copper powder" A state in which all of the “copper fine powder” is housed can be achieved.

  In a state where all of the “copper fine powder” is stored in the “void” in the laminated structure of “copper powder”, the remaining “remaining void” is VCu-particle · (ρCu-bulk / ρCu-particle- tap) · {1- (ρCu-particle-tap / ρCu-bulk)} − VCu-fine-particle.

  “Residual voids” remaining in the laminated structure of “copper powder”: VCu-particle · (ρCu-bulk / ρCu-particle-tap) · {1- (ρCu-particle-tap / ρCu-bulk)} − VCu When the volume ratio VCu-nanoparticle of the “copper nanoparticles” included in the “conductive copper paste” of Example 1 exceeds -fine-particles, a part of the “copper nanoparticles” The remaining “copper nanoparticles” are filled in the “powder” laminate structure, but the remaining “copper nanoparticles” are assumed to form a “copper nanoparticle” laminate on the upper surface of the “copper powder” laminate structure. The

  Specifically, the tap density ρCu-nanoparticle of the “copper nanoparticles” contained in the “conductive copper paste” of Example 7 is about 6.0 g / cm 3. Therefore, when the “copper nanoparticles” are aggregated in the close-packed state, the volume is VCu-nanoparticle · (ρCu-bulk / ρCu-nanoparticle) with respect to the volume ratio VCu-nanoparticle of the copper fine powder. When the “preheated drying (solvent removal) step” is performed to form the “dried coating film”, the bulk when the “copper nanoparticles” aggregate in the closest packing state: VCu-nanoparticle · (ρCu-bulk / ρCu-nanoparticle) remains in the laminated structure of “copper powder”: VCu-particle ・ (ρCu-bulk / ρCu-particle-tap) ・ {1- (ρCu-particle-tap / ρCu -bulk)}-When exceeding VCu-fine-particle, some of the "copper nanoparticles" fill the "residual voids" remaining in the "copper powder" laminate structure, but the remaining "copper" “Nanoparticles” are assumed to form a stack of “copper nanoparticles” on the top surface of the “copper powder” stack structure.

  At the time when the “preheating drying (solvent removal) step” is completed, the surface of the “copper nanoparticles” is in a state of being coated with the “coating agent molecular layer”. The “copper nanoparticles” having the “coating molecule layer” on the surface fill the “remaining voids” remaining in the laminated structure of the “copper powder”. The remaining “copper nanoparticles” are assumed to form a stack of “copper nanoparticles” having a “covering agent molecular layer” on the upper surface of the stack structure of “copper powder”.

  In the “conductive copper paste” of Example 7, the ratio of the volume ratio VCu-fine-particle of “copper fine powder” to the volume ratio VCu-particle of “copper powder” (VCu-fine-particle: VCu-particle ) Is significantly higher than the “conductive copper paste” of Example 1. As a result, the total volume of the “copper nanoparticles” themselves in the “copper nanoparticles” that fill the “remaining voids” remaining in the laminated structure of the “copper powder” and have the “coating agent molecular layer” on the surface. Is significantly reduced as compared with Example 1. As a result, the total volume of the “copper nanoparticles” themselves, which forms a laminate of “copper nanoparticles” having a “coating agent molecular layer” on the surface on the upper surface of the “copper powder” laminate structure, Compared with, it increases significantly.

  In the case of the “conductive copper paste” used in Example 7, the average thickness tCu-particle-layer of the laminated structure of “copper powder” contained in the paste coating film having the average thickness tpaste is tCu− It is estimated that particle-layer = {[tpaste · {VCu-particle} / 100 volume%]} · (ρCu-bulk / ρCu-particle-tap). {[Tpaste · {VCu-particle} / 100 vol%]} · (ρCu-bulk / ρCu-particle-tap) = {[40 μm · {32.26 vol%} / 100 vol%]} · (8.94 /4.87)=23.69 μm. The average film thickness tCu-sintered layer of the obtained fired product is much thicker than the average thickness tCu-particle-layer of the estimated laminated structure of “copper powder”.

  At that time, “void” in the laminated structure of “copper powder”: VCu-particle · (ρCu-bulk / ρCu-particle-tap) · {1- (ρCu-particle-tap / ρCu-bulk)} is VCu -particle · (ρCu-bulk / ρCu-particle-tap) · {1- (ρCu-particle-tap / ρCu-bulk)} = 32.26% by volume · (8.94 / 4.87) · {1- It is estimated that (4.87 / 8.94)} = 26.96% by volume. "Bulk" when "copper fine powder" is assembled in the close-packed state: VCu-fine-particle (ρCu-bulk / ρCu-fine-particle) is VCu-fine-particle (ρCu-bulk / ρCu -fine-particle) = 11.92% by volume · (8.94 / 4.3) = 24.78% by volume. Accordingly, it is assumed that “copper fine powder” is filled in “voids” in the laminated structure of “copper powder”.

(Example 8)
The material for forming a copper thick film of Example 8 is prepared in the form of “conductive copper paste” using the following raw materials.

  As the copper microparticles, 1400YM (average particle diameter 4 μm: tap density 5.5 g / cm 3) manufactured by Mitsui Kinzoku Co., Ltd., which is a copper powder produced by a wet method, is used. As the copper submicron particles, 1050Y (average particle diameter 0.8 μm: tap density 4.3 g / cm 3) manufactured by Mitsui Kinzoku Co., Ltd., which is a copper fine powder produced by a wet method, is used.

  As “copper nanoparticle dispersion liquid”, Harima Kasei copper nanoparticle NPC is used. The volume ratio of “copper nanoparticles” and “coating agent molecular amine” contained in “copper nanoparticle NPC” is “copper nanoparticle”: “coating agent molecular amine” = 91.3 vol%: Estimated at 8.7% by volume.

  As a “high boiling nonpolar organic solvent”, terpineol (molecular weight 154.25, melting point 31-35 ° C., boiling point 217-218 ° C., density ρsolvent 0.94 g / cm 3) is used. Usually, terpineol is a mixture of four isomers: α, β, γ, δ-terpineol, and the main component in the mixture is α-terpineol (melting point 18 ° C., boiling point 218 ° C., 81- 82 ° C./4.5 mmHg, density ρsolvent 0.9338 g / cm 3).

  33.3 parts by mass of “Copper Nanoparticles NPC” manufactured by Harima Chemicals (33.0 parts by mass of copper nanoparticles and 0.3 parts by mass of “coating agent molecular amine”), 10.8YM by Mitsui Kinzoku Co., Ltd., 50.8 parts by mass, Mitsui Metal Co., Ltd. 1050Y11.1 mass part and terpineol 4.8 mass part are mixed uniformly. The mixture is stirred with a stirring deaerator to uniformly disperse copper powder, copper fine powder, and copper nanoparticles in a dispersion solvent to prepare a “conductive copper paste”.

  The volume ratio VCu-particle of the copper powder, the volume ratio VCu-fine-particle of the copper fine powder, and the volume ratio VCu-nanoparticle of the copper nanoparticle contained in the prepared “conductive copper paste” are VCu-particle = 35.27% by volume; VCu-fine-particle = 7.71% by volume; VCu-nanoparticle = 22.92% by volume. The sum of the volume ratio Vcoating-molecule of the “coating agent molecular amine” and the volume ratio Vsolvent of the “solvent” is {Vcoating-molecule + Vsolvent} = 34.10 vol%.

The ratio of the volume ratio VCu-particle of copper powder and the volume ratio VCu-fine-particle of copper fine powder (VCu-particle + VCu-fine-particle) and the volume ratio of copper nanoparticles VCu-nanoparticle is (VCu -particle + VCu-fine-particle): VCu-nanoparticle = 100: 53.3.
{VCu-particle + VCu-fine-particle + VCu-nanoparticle} / {Vcoating-molecule + Vsolvent} = 65.90: 34.10
The liquid viscosity of the prepared “conductive copper paste” was 144 Pa · s (spiral rotational viscometer 10 rpm 25 ° C.).

  The prepared “conductive copper paste” was applied in a 10 mm × 50 mm pattern on a slide glass. The average thickness tpaste of the paste coating film was tpaste = 40 μm.

  For the paste coating film, using a Nissin plasma baking furnace, the procedure described in Example 1 was followed by a “preheating drying (solvent removal) step”, “reduced pressure drying (organic matter removal) step”, “micro A wave plasma irradiation (plasma firing) step "was performed, and the copper powder, copper fine powder and copper nanoparticles contained in the paste coating film were fired.

  The average film thickness tCu-sintered layer of the fired product was tCu-sintered layer = 30 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 3.1 μΩ · cm.

  Assuming that the resulting fired product is a “bulk metal copper thick film”, the film thickness tCu-bulk layer of the “bulk metal copper thick film” is tCu-bulk layer = tpaste · {VCu-particle + VCu-fine-particle + VCu -nanoparticle} / 100% by volume. The average film thickness tCu-sintered layer of the fired product actually obtained is thicker than the film thickness tCu-bulk layer of the “bulk metal copper thick film”, and the ratio tCu-bulk layer / tCu-sintered layer is 87.87 / 100. It has become. In other words, the “porosity” in the obtained fired product is estimated to be Vvoid = 12.13% by volume.

  The volume specific resistivity 3.1 μΩ · cm of the obtained fired product is 1.85 times that of the metal copper resistivity 1.673 μΩ · cm (30 ° C.).

  In the case of the “conductive copper paste” used in Example 8, the average thickness tCu-particle-layer of the laminated structure of “copper powder” included in the paste coating film having the average thickness tpaste is tCu−. It is estimated that particle-layer = {[tpaste · {VCu-particle} / 100 volume%]} · (ρCu-bulk / ρCu-particle-tap). {[Tpaste · {VCu-particle} / 100 vol%]} · (ρCu-bulk / ρCu-particle-tap) = {[40 μm · {35.27 vol%} / 100 vol%]} · (8.94 /5.5)=2.93 μm. The average film thickness tCu-sintered layer of the obtained fired product is much thicker than the average thickness tCu-particle-layer of the estimated laminated structure of “copper powder”.

  At that time, “void” in the laminated structure of “copper powder”: VCu-particle · (ρCu-bulk / ρCu-particle-tap) · {1- (ρCu-particle-tap / ρCu-bulk)} is VCu -particle · (ρCu-bulk / ρCu-particle-tap) · {1- (ρCu-particle-tap / ρCu-bulk)} = 35.27% by volume · (8.94 / 5.5) · {1- It is estimated that (5.5 / 8.94)} = 22.06% by volume. "Bulk" when "copper fine powder" is assembled in the close-packed state: VCu-fine-particle (ρCu-bulk / ρCu-fine-particle) is VCu-fine-particle (ρCu-bulk / ρCu -fine-particle) = 7.71% by volume · (8.94 / 4.3) = 16.03% by volume. Accordingly, it is assumed that “copper fine powder” is filled in “voids” in the laminated structure of “copper powder”.

Example 9
In Example 9, the “conductive copper paste” prepared in Example 1 was used, and conditions different from those described in Example 1 were used to form a thick copper film.

  The “conductive copper paste” prepared in Example 1 was applied on a slide glass in a 10 mm × 50 mm pattern. The average thickness tpaste of the paste coating film was tpaste = 40 μm.

  Using a Nissin plasma baking furnace, the paste coating film was subjected to the following procedures according to the following procedures: “preheating drying (solvent removal) step”, “vacuum drying (organic matter removal) step”, “microwave plasma irradiation ( Plasma firing) step ”was performed, and the copper powder, copper fine powder and copper nanoparticles contained in the paste coating film were fired.

  The “preheating drying (solvent removal) step” and the “reduced pressure drying (organic matter removal) step” employ the same conditions as described in Example 1.

  In the “microwave plasma irradiation (plasma firing) step”, first, microwave plasma is generated in helium-3% hydrogen gas under the same conditions as described in Example 1. In a state where the stage temperature is maintained at 150 ° C., microwave plasma irradiation is continued for 60 seconds to perform a plasma baking process. The copper powder, the copper fine powder and the copper nanoparticles contained in the paste coating film are fired by irradiation of the generated microwave plasma in a reducing atmosphere composed of the helium-3% hydrogen gas.

  The average film thickness tCu-sintered layer of the fired product was tCu-sintered layer = 30 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 3.3 μΩ · cm.

  Assuming that the resulting fired product is a “bulk metal copper thick film”, the film thickness tCu-bulk layer of the “bulk metal copper thick film” is tCu-bulk layer = tpaste · {VCu-particle + VCu-fine-particle + VCu -nanoparticle} / 100% by volume. The average film thickness tCu-sintered layer of the fired product actually obtained is thicker than the film thickness tCu-bulk layer of the “bulk metal copper thick film”, and the ratio tCu-bulk layer / tCu-sintered layer is 90.3 / 100. It has become. In other words, the “porosity” in the obtained fired product is estimated to be Vvoid = 9.7% by volume.

  The volume specific resistivity 3.3 μΩ · cm of the obtained fired product is 1.97 times that of the metal copper resistivity 1.673 μΩ · cm (30 ° C.).

(Example 10)
In Example 10, the “conductive copper paste” prepared in Example 1 is used, and conditions different from those described in Example 1 are adopted to form a thick copper film.

The “conductive copper paste” prepared in Example 1 was applied on a slide glass in a 10 mm × 50 mm pattern. The average thickness tpaste of the paste coating film was tpaste = 40 μm.

  Using a Nissin plasma baking furnace, the paste coating film was subjected to the following procedures according to the following procedures: “preheating drying (solvent removal) step”, “vacuum drying (organic matter removal) step”, “microwave plasma irradiation ( Plasma firing) step ”was performed, and the copper powder, copper fine powder and copper nanoparticles contained in the paste coating film were fired.

  The “preheating drying (solvent removal) step” and the “reduced pressure drying (organic matter removal) step” employ the same conditions as described in Example 1.

  In the “microwave plasma irradiation (plasma firing) step”, first, microwave plasma is generated in helium-3% hydrogen gas under the same conditions as described in Example 1. In a state where the stage temperature is maintained at 150 ° C., microwave plasma irradiation is continued for 120 seconds to perform plasma baking. The copper powder, the copper fine powder and the copper nanoparticles contained in the paste coating film are fired by irradiation of the generated microwave plasma in a reducing atmosphere composed of the helium-3% hydrogen gas.

  The average film thickness tCu-sintered layer of the fired product was tCu-sintered layer = 30 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 2.9 μΩ · cm.

  Assuming that the resulting fired product is a “bulk metal copper thick film”, the film thickness tCu-bulk layer of the “bulk metal copper thick film” is tCu-bulk layer = tpaste · {VCu-particle + VCu-fine-particle + VCu -nanoparticle} / 100% by volume. The average film thickness tCu-sintered layer of the fired product actually obtained is thicker than the film thickness tCu-bulk layer of the “bulk metal copper thick film”, and the ratio tCu-bulk layer / tCu-sintered layer is 90.3 / 100. It has become. In other words, the “porosity” in the obtained fired product is estimated to be Vvoid = 9.7% by volume.

  The volume specific resistivity 2.9 μΩ · cm of the obtained fired product is 1.73 times that of the metal copper resistivity 1.673 μΩ · cm (30 ° C.).

(Example 11)
In Example 11, the “conductive copper paste” prepared in Example 1 is used, and a condition different from the condition described in Example 1 is adopted to form a thick copper film.

  The “conductive copper paste” prepared in Example 1 was applied on a slide glass in a 10 mm × 50 mm pattern. The average thickness tpaste of the paste coating film was tpaste = 40 μm.

  Using a Nissin plasma baking furnace, the paste coating film was subjected to the following procedures according to the following procedures: “preheating drying (solvent removal) step”, “vacuum drying (organic matter removal) step”, “microwave plasma irradiation ( Plasma firing) step ”was performed, and the copper powder, copper fine powder and copper nanoparticles contained in the paste coating film were fired.

  As a “preheating drying (solvent removal) step”, preheating is performed for 30 seconds at a stage temperature of 120 ° C. under atmospheric pressure in a Nissin plasma baking furnace. As a “reduced pressure drying (organic matter removal) step”, “evacuation” is performed for 60 seconds while maintaining the stage temperature at 120 ° C., and the inside of the plasma firing furnace is maintained in a reduced pressure state. The pressure in the plasma baking furnace in the reduced pressure state is maintained at 10 Pa or less.

  In the “microwave plasma irradiation (plasma firing) step”, first, helium-3% hydrogen is introduced into the plasma firing furnace at a flow rate of 25 sccm for 30 seconds while the stage temperature is maintained at 120 ° C. After controlling the pressure in the plasma firing furnace to 10 Pa, a microwave (frequency 2.4 GHz) is supplied from a high frequency power source (frequency 2.4 GHz) at a high frequency power of 1.5 kW, and helium-3% hydrogen gas is micronized. Generate wave plasma. In a state where the stage temperature is maintained at 120 ° C., microwave plasma irradiation is continued for 90 seconds to perform a plasma baking process. The copper powder, the copper fine powder and the copper nanoparticles contained in the paste coating film are fired by irradiation of the generated microwave plasma in a reducing atmosphere composed of the helium-3% hydrogen gas.

  The average film thickness tCu-sintered layer of the fired product was tCu-sintered layer = 30 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 3.6 μΩ · cm.

  Assuming that the resulting fired product is a “bulk metal copper thick film”, the film thickness tCu-bulk layer of the “bulk metal copper thick film” is tCu-bulk layer = tpaste · {VCu-particle + VCu-fine-particle + VCu -nanoparticle} / 100% by volume. The average film thickness tCu-sintered layer of the fired product actually obtained is thicker than the film thickness tCu-bulk layer of the “bulk metal copper thick film”, and the ratio tCu-bulk layer / tCu-sintered layer is 90.3 / 100. It has become. In other words, the “porosity” in the obtained fired product is estimated to be Vvoid = 9.7% by volume.

  The volume specific resistivity 3.6 μΩ · cm of the obtained fired product is 2.15 times that of the metal copper resistivity 1.673 μΩ · cm (30 ° C.).

(Example 12)
In the present Example 12, the “conductive copper paste” prepared in Example 1 is used, and conditions different from those described in Example 1 are employed to form a thick copper film.

  The “conductive copper paste” prepared in Example 1 was applied on a slide glass in a 10 mm × 50 mm pattern. The average thickness tpaste of the paste coating film was tpaste = 40 μm.

  Using a Nissin plasma baking furnace, the paste coating film was subjected to the following procedures according to the following procedures: “preheating drying (solvent removal) step”, “vacuum drying (organic matter removal) step”, “microwave plasma irradiation ( Plasma firing) step ”was performed, and the copper powder, copper fine powder and copper nanoparticles contained in the paste coating film were fired.

  As a “preheating drying (solvent removal) step”, preheating is performed for 30 seconds at a stage temperature of 180 ° C. under atmospheric pressure in a Nissin plasma baking furnace. As a “reduced pressure drying (organic matter removal) step”, “evacuation” is performed for 60 seconds while maintaining the stage temperature at 180 ° C., and the inside of the plasma firing furnace is maintained in a reduced pressure state. The pressure in the plasma baking furnace in the reduced pressure state is maintained at 10 Pa or less.

  In the “microwave plasma irradiation (plasma firing) step”, helium-3% hydrogen is first introduced into the plasma firing furnace at a flow rate of 25 sccm for 30 seconds while the stage temperature is maintained at 180 ° C. After controlling the pressure in the plasma firing furnace to 10 Pa, a microwave (frequency 2.4 GHz) is supplied from a high frequency power source (frequency 2.4 GHz) at a high frequency power of 1.5 kW, and helium-3% hydrogen gas is micronized. Generate wave plasma. In a state where the stage temperature is maintained at 120 ° C., microwave plasma irradiation is continued for 90 seconds to perform a plasma baking process. The copper powder, the copper fine powder and the copper nanoparticles contained in the paste coating film are fired by irradiation of the generated microwave plasma in a reducing atmosphere composed of the helium-3% hydrogen gas.

  The average film thickness tCu-sintered layer of the fired product was tCu-sintered layer = 30 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 2.8 μΩ · cm.

  Assuming that the resulting fired product is a “bulk metal copper thick film”, the film thickness tCu-bulk layer of the “bulk metal copper thick film” is tCu-bulk layer = tpaste · {VCu-particle + VCu-fine-particle + VCu -nanoparticle} / 100% by volume. The average film thickness tCu-sintered layer of the fired product actually obtained is thicker than the film thickness tCu-bulk layer of the “bulk metal copper thick film”, and the ratio tCu-bulk layer / tCu-sintered layer is 90.3 / 100. It has become. In other words, the “porosity” in the obtained fired product is estimated to be Vvoid = 9.7% by volume.

  The volume specific resistivity 2.8 μΩ · cm of the obtained fired product is 1.67 times the resistivity of metallic copper 1.673 μΩ · cm (30 ° C.).

(Example 13)
In this Example 13, the “conductive copper paste” prepared in Example 1 was used, and the same plasma baking conditions as those described in Example 9 were adopted. A thick copper film is formed.

  The “conductive copper paste” prepared in Example 1 was applied on a slide glass in a 10 mm × 50 mm pattern. The average thickness tpaste of the paste coating film was tpaste = 20 μm.

  For the paste coating film, using a Nissin plasma baking furnace, the procedure described in Example 9 was followed by a “preheating drying (solvent removal) step”, “reduced pressure drying (organic matter removal) step”, “micro A wave plasma irradiation (plasma firing) step "was performed, and the copper powder, copper fine powder and copper nanoparticles contained in the paste coating film were fired.

  The average film thickness tCu-sintered layer of the fired product was tCu-sintered layer = 15 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 3.1 μΩ · cm.

  Assuming that the resulting fired product is a “bulk metal copper thick film”, the film thickness tCu-bulk layer of the “bulk metal copper thick film” is tCu-bulk layer = tpaste · {VCu-particle + VCu-fine-particle + VCu -nanoparticle} / 100% by volume. The average film thickness tCu-sintered layer of the fired product actually obtained is thicker than the film thickness tCu-bulk layer of the “bulk metal copper thick film”, and the ratio tCu-bulk layer / tCu-sintered layer is 90.3 / 100. It has become. In other words, the “porosity” in the obtained fired product is estimated to be Vvoid = 9.7% by volume.

  The volume specific resistivity 3.1 μΩ · cm of the obtained fired product is 1.85 times that of the metal copper resistivity 1.673 μΩ · cm (30 ° C.).

  In the case of Example 13, the average thickness tCu-particle-layer of the “copper powder” laminated structure included in the paste coating film having an average thickness tpaste is tCu-particle-layer = {[tpaste · {VCu-particle} / 100% by volume]} · (ρCu-bulk / ρCu-particle-tap). {[Tpaste · {VCu-particle} / 100 vol%]} · (ρCu-bulk / ρCu-particle-tap) = {[20 μm · {36.25 vol%} / 100 vol%]} · (8.94 /5.5)=11.78 μm. The average film thickness tCu-sintered layer of the obtained fired product is much thicker than the average thickness tCu-particle-layer of the estimated laminated structure of “copper powder”.

(Example 14)
In this Example 14, the “conductive copper paste” prepared in Example 1 was used, and the same plasma baking condition as the plasma baking condition described in Example 9 was adopted. A thick copper film is formed.

  The “conductive copper paste” prepared in Example 1 was applied on a slide glass in a 10 mm × 50 mm pattern. The average thickness tpaste of the paste coating film was tpaste = 80 μm.

  For the paste coating film, using a Nissin plasma baking furnace, the procedure described in Example 9 was followed by a “preheating drying (solvent removal) step”, “reduced pressure drying (organic matter removal) step”, “micro A wave plasma irradiation (plasma firing) step "was performed, and the copper powder, copper fine powder and copper nanoparticles contained in the paste coating film were fired.

  The average film thickness tCu-sintered layer of the fired product was tCu-sintered layer = 60 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 3.8 μΩ · cm.

  Assuming that the resulting fired product is a “bulk metal copper thick film”, the film thickness tCu-bulk layer of the “bulk metal copper thick film” is tCu-bulk layer = tpaste · {VCu-particle + VCu-fine-particle + VCu -nanoparticle} / 100% by volume. The average film thickness tCu-sintered layer of the fired product actually obtained is thicker than the film thickness tCu-bulk layer of the “bulk metal copper thick film”, and the ratio tCu-bulk layer / tCu-sintered layer is 90.3 / 100. It has become. In other words, the “porosity” in the obtained fired product is estimated to be Vvoid = 9.7% by volume.

  The volume specific resistivity 3.8 μΩ · cm of the obtained fired product is 2.27 times that of the metal copper resistivity 1.673 μΩ · cm (30 ° C.).

  In the case of Example 14, the average thickness tCu-particle-layer of the laminated structure of “copper powder” included in the paste coating film having an average thickness tpaste is tCu-particle-layer = {[tpaste · {VCu-particle} / 100% by volume]} · (ρCu-bulk / ρCu-particle-tap). {[Tpaste · {VCu-particle} / 100 vol%]} · (ρCu-bulk / ρCu-particle-tap) = {[80 μm · {36.25 vol%} / 100 vol%]} · (8.94 /5.5)=47.14 μm. The average film thickness tCu-sintered layer of the obtained fired product is much thicker than the average thickness tCu-particle-layer of the estimated laminated structure of “copper powder”.

(Comparative Example 1)
In Comparative Example 1, the “conductive copper paste” prepared in Example 1 is used, and a thick copper film is formed by performing heat treatment in a reducing atmosphere.

  The “conductive copper paste” prepared in Example 1 was applied on a slide glass in a 10 mm × 50 mm pattern. The average thickness tpaste of the paste coating film was tpaste = 40 μm.

  The paste coating film was subjected to a heat treatment at 300 ° C. for 15 minutes in a reducing atmosphere of nitrogen-3% hydrogen using an infrared furnace manufactured by Yonekura Seisakusho, in the following procedure. The copper powder, copper fine powder, and copper nanoparticles contained in were fired.

  In an infrared furnace manufactured by Yonekura Seisakusho, the temperature is raised from room temperature (25 ° C.) to 300 ° C. at a heating rate of 1600 ° C./hour in a reducing atmosphere of nitrogen—3% (1 atm). The time required for the temperature raising process is about 10.3 minutes. After the temperature rise, heat treatment is performed at 300 ° C. for 15 minutes in a reducing atmosphere of nitrogen-3% (1 atm).

  Since the temperature of 300 ° C. during the heat treatment is significantly higher than the boiling point of 268 ° C. of tripropylene glycol, when the temperature reaches 268 ° C. during the temperature rising process, it is assumed that the evaporation of tripropylene glycol is completed. The

  The average film thickness tCu-sintered layer of the fired product was tCu-sintered layer = 30 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 4.5 μΩ · cm.

  Assuming that the resulting fired product is a “bulk metal copper thick film”, the film thickness tCu-bulk layer of the “bulk metal copper thick film” is tCu-bulk layer = tpaste · {VCu-particle + VCu-fine-particle + VCu -nanoparticle} / 100% by volume. The average film thickness tCu-sintered layer of the fired product actually obtained is thicker than the film thickness tCu-bulk layer of the “bulk metal copper thick film”, and the ratio tCu-bulk layer / tCu-sintered layer is 90.3 / 100. It has become. In other words, the “porosity” in the obtained fired product is estimated to be Vvoid = 9.7% by volume.

  The volume resistivity of 4.5 μΩ · cm of the obtained fired product is 2.7 times the resistivity of metallic copper, 1.673 μΩ · cm (30 ° C.).

  Also in Comparative Example 1, when the “pre-heating drying (solvent removal) step” was performed on the coating film of “conductive paste” prepared in Example 1 and the solvent was evaporated, the “copper powder” was dense. Thus, a “dried coating film” having a shape laminated on the substrate is obtained. It is presumed that the “copper powder” constituting the “dried coating film” is laminated with the same denseness when the “tap density” is measured.

  The tap density of “copper powder” is ρCu-particle-tap = 5.5 g / cm 3, whereas the density of metallic copper (bulk) ρCu-bulk = 8.94 g / cm 3. Therefore, the average film thickness tCu-particle-layer of the “copper powder” laminate structure is estimated as {[tpaste · {VCu-particle} / 100% by volume]} · (ρCu-bulk / ρCu-particle-tap). Can do. {[Tpaste · {VCu-particle} / 100 vol%]} · (ρCu-bulk / ρCu-particle-tap) = {[40 μm · {36.25 vol%} / 100 vol%]} · (8.94 /5.5)=2.56 μm. The average film thickness tCu-sintered layer of the obtained fired product is much thicker than the average film thickness tCu-particle-layer of the estimated “copper powder” laminate structure.

  In the “dried coating film”, “copper fine powder” and “copper nanoparticles” fill a “gap” of a structure in which “copper powder” is densely laminated.

The density of metallic copper (bulk) ρCu-bulk = 8.94 g / cm 3, whereas the tap density of “copper powder” is ρCu-particle-tap = 5.5 g / cm 3, so the layers are densely stacked. “Gap” existing in “copper powder” is estimated as {1- (ρCu-particle-tap / ρCu-bulk)} · {VCu-particle} · (ρCu-bulk / ρCu-particle-tap) volume%. Is possible. In order to accommodate “copper fine powder” and “copper nanoparticles” with tap density ρCu-fine-particle-tap = 4.3 g / cm 3 in this “gap”, the volume ratio VCu of “copper fine powder” -Fine-particle and "copper nanoparticle" volume ratio VCu-nanoparticle must satisfy the following conditions. {1- (ρCu-particle-tap / ρCu-bulk)}, {VCu-particle}, (ρCu-particle-tap / ρCu-bulk) volume%> {VCu-fine-particle, (ρCu-bulk / ρCu- fine-particle-tap) volume% + VCu-nanoparticle volume%}
In the case of Comparative Example 1, the “gap” existing in the densely laminated “copper powder” is {1- (ρCu-particle-tap / ρCu-bulk)} · {VCu-particle} · (ρCu− bulk / ρCu-particle-tap) volume% = {1- (5.5 / 8.94)} · {36.25} · (8.94 / 5.5) volume% = 22.67 volume% It is possible. The bulk volume ratio of “copper fine powder” with a tap density of ρCu-fine-particle-tap = 4.3 g / cm3 is {VCu-fine-particle · (ρCu-bulk / ρCu-fine-particle-tap) volume% = It can be estimated that {7.92 · (8.94 / 4.3) volume% = 16.47 volume%. Therefore, all of the “copper fine powder” having a tap density ρCu-fine-particle-tap = 4.3 g / cm 3 can be accommodated in the “gap” existing in the “copper powder” densely laminated. Is possible. At that time, the volume ratio of the “residual voids” still remaining in the state where all of the “copper fine powder” is accommodated in the “interstices” existing in the “copper powder” densely laminated is VCu− It is estimated that particle · (ρCu-bulk / ρCu-particle-tap) · {1- (ρCu-particle-tap / ρCu-bulk)}-VCu-fine-particle. VCu-particle · (ρCu-bulk / ρCu-particle-tap) · {1- (ρCu-particle-tap / ρCu-bulk)} − VCu-fine-particle = 22.67 vol% −7.92 vol% = It is estimated to be 14.75% by volume. The volume ratio VCu-nanoparticle of the copper nanoparticles is VCu-nanoparticle = 23.55% by volume, which is larger than the volume ratio of the “residual voids” still remaining. Therefore, a part of the copper nanoparticles can be stored in the remaining “remaining void”, but a corresponding part cannot be stored.

The “conductive copper paste” prepared in Example 1 is selected by selecting the conditions described in Comparative Example 1.
The average thickness tCu-sintered layer of the fired product can be a “copper thick film” that satisfies the relationship of tCu-sintered layer = (3/4) · tpaste with respect to the coating film thickness tpaste. Visa results have been obtained.

In addition, the “conductive copper paste” prepared in Example 1 is the conditions described in Example 1 and Examples 9 to 14,
That is, the coating film thickness tpaste is at least in the range of 80 μm ≧ tpaste ≧ 20 μm,
The stage temperature Tstage-heating in the “preheating drying (solvent removal) step”, “reduced pressure drying (organic matter removal) step”, and “microwave plasma irradiation (plasma firing) step” is at least 180 ° C. ≧ Tstage-heating ≧ In the range of 120 ° C,
In the “microwave plasma irradiation (plasma firing) step”, a microwave (frequency 2.4 GHz) is supplied from a high frequency power source (frequency 2.4 GHz) with a high frequency power of 1.5 kW, and microwave plasma is applied to helium-3% hydrogen gas. And the time tplasma-treating to irradiate the microwave plasma is selected to be at least 120 seconds ≧ tplasma-treating ≧ 60 seconds.
The average film thickness tCu-sintered layer of the fired product is suitable for the production of a “copper thick film” that satisfies the relationship of tCu-sintered layer = (3/4) · tpaste with respect to the film thickness tpaste of the coating film. Visa results have been obtained.

  When using the “conductive copper paste” prepared in Example 1, at least when the coating film thickness tpaste is tpaste = 40 μm, the “preheating drying (solvent removal) step” is performed, and the solvent is removed. When evaporated, a “dried coating film” having a shape in which “copper powder” is densely laminated is obtained. The average film thickness tdried-paste of the “dried coating film” is the same average film thickness tdried-paste in the case of Example 1, Examples 9 to 12 and Comparative Example 1. It is guessed. Accordingly, in the case of Example 1 and Examples 9 to 12, as in the case of Comparative Example 1, the average film thickness tdried-paste of the “dried coating film” is a laminated structure portion of “copper powder”. Thickness {[tpaste · {VCu-particle} / 100% by volume]} · (ρCu-bulk / ρCu-particle-tap) and the thickness of the layered structure of “copper nanoparticles” formed on the top surface Can be estimated as the sum of The average film thickness tCu-sintered layer of the fired product obtained is estimated to be approximately equal to the average film thickness tdried-paste of the “dried coating film”.

  When using the “conductive copper paste” prepared in Example 1, the average film of “copper thick film” formed in Example 13, Example 9, and Example 14 adopting the same firing conditions The thickness tCu-sintered layer is proportional to the film thickness tpaste of the coating film. The average film thickness tdried-paste of the “dried coating film” is also the thickness {[tpaste · {VCu-particle} / 100 vol%]} · (ρCu-bulk / ρCu- particle-tap) and the thickness of the laminated structure of “copper nanoparticles” formed on the upper surface thereof can be estimated. Accordingly, the average film thickness tCu-sintered layer of the obtained fired product is substantially equal to the average film thickness tdried-paste of the “dried coating film”. As a result, the average film thickness tCu-sintered layer of the “copper thick film” is It is understood that it is proportional to the film thickness tpaste of the coating film.

  Furthermore, by adopting the same firing conditions, the average film thickness tCu-sintered layer formed in Example 13 is 15 μm “copper thick film”, and the average film thickness tCu-sintered layer formed in Example 9 is 30 μm. Between the “copper thick film” and the “copper thick film” having an average film thickness tCu-sintered layer of 60 μm formed in Example 14, its “volume resistivity”: ρ15 μm-plasma-treating, ρ30 μm-plasma- Treating, ρ60 μm-plasma-treating increases as the average film thickness tCu-sintered layer increases, but the “thick copper film” of the “copper thick film” formed in Comparative Example 1 has an average film thickness tCu-sintered layer of 30 μm. Compared with “volume resistivity” ρ30 μm-thermal-heating, the value is significantly lower.

  In Example 13, Example 9, and Example 14, the film thickness tpaste of the coating film is increased to 20 μm, 40 μm, and 80 μm, and among the average film thickness tdried-paste of the “dried coating film”, “copper” The thickness of the laminated structure portion of “copper nanoparticles” formed on the upper surface of the laminated structure portion of “powder” is thick. Since the processing time in the “microwave plasma irradiation (plasma firing) step” is equal, when the thickness of the laminated structure of “copper nanoparticles” formed on the upper surface increases, the “copper powder” present in the lower layer increases. The progress level of firing of the laminated structure portion is lowered. The firing of the laminated structure portion of “copper nanoparticles” formed on the upper surface proceeds, but the progress level of the firing of the laminated structure portion of “copper powder” existing in the lower layer is such that the film thickness tpaste of the coating film is thicker. It decreases with becoming. As a result, “Volume Specific Resistivity” in Examples 13, 9, and 14: ρ15 μm-plasma-treating, ρ30 μm-plasma-treating, and ρ60 μm-plasma-treating increase the film thickness tpaste of the coating film. , Is judged to be increasing.

  Between Example 9, Example 1, and Example 10, when the processing time in the “microwave plasma irradiation (plasma firing) step” increases, the average film thickness tCu-sintered layer of the “copper thick film” is the same. However, the “volume resistivity” of the “copper thick film” gradually decreases. When the processing time in the “microwave plasma irradiation (plasma firing) process” increases, in addition to firing the laminated structure of the “copper nanoparticles” formed on the upper surface, the “copper powder” layer that exists in the lower layer The progress level of the firing of the structure portion also increases. As a result, between Example 9, Example 1, and Example 10, as the processing time in the “microwave plasma irradiation (plasma firing) step” increases, the “volume resistivity” of the “copper thick film” is It is judged to gradually decrease.

  Between Example 11, Example 1, and Example 12, the stages in the “preheating drying (solvent removal) step”, “reduced pressure drying (organic matter removal) step”, and “microwave plasma irradiation (plasma firing) step” As the temperature Tstage-heating increases to 120 ° C, 150 ° C, and 180 ° C, the average film thickness tCu-sintered layer of the "copper thick film" is the same, but the "volume resistivity" of the "copper thick film" is , Is gradually falling. As the stage temperature Tstage-heating increases in the “preheating drying (solvent removal) step”, “reduced pressure drying (organic matter removal) step”, and “microwave plasma irradiation (plasma firing) step”, “ In addition to firing the laminated structure portion of “copper nanoparticles”, the progress level of firing of the laminated structure portion of “copper powder” existing in the lower layer is also increased. As a result, between Example 11, Example 1, and Example 12, the “preheating drying (solvent removal) step”, “reduced pressure drying (organic matter removal) step”, and “microwave plasma irradiation (plasma firing) step”. It is determined that the “volume resistivity” of the “copper thick film” gradually decreases as the stage temperature Tstage-heating increases.

  The average "porosity" when using a firing process that uses "microwave plasma irradiation" in a reducing atmosphere and when using a firing process that uses "heat treatment" in a reducing atmosphere Are the same, but there is a clear difference when, for example, comparing the microscopic shape of the surface of the fired “copper thick film”. In FIG. 1, when the firing step using “microwave plasma irradiation” is employed under a reducing atmosphere and when the firing step utilizing “heat treatment” is employed under a reducing atmosphere, The SEM observation result of the microscopic structure of “copper thick film” is shown in comparison.

  For example, in the manufacturing process described in Example 1, at the time when the “dried coating film” is formed, the “copper powder” laminated structure portion existing in the lower layer and the “copper nanoparticles” formed on the upper surface thereof are formed. The “two-layer” structure of the laminated structure portion is already formed. After that, by performing a firing process using “microwave plasma irradiation” in a reducing atmosphere from the laminated structure of “copper nanoparticles” formed on the upper surface, only “copper nanoparticles” are present on the upper surface. A “copper nanoparticle sintered body layer” is formed. The upper surface of the lower “copper thick film” base formed by firing the laminated structure of “copper powder” is covered with a “copper nanoparticle sintered body layer” consisting only of “copper nanoparticles”. As a result, “copper powder” and “copper fine powder” are essentially not exposed on the upper surface of the produced “copper thick film”. Accordingly, the “void” reflecting the “gap” between the “copper powder” and the “copper fine powder” is essentially not formed in the “copper nanoparticle sintered body layer” on the upper surface.

  On the other hand, in the manufacturing process described in Comparative Example 1, in the process of raising the temperature after finishing “coating”, “copper powder” and “copper fine powder” are settled. A laminated structure portion of “copper powder” filled with “copper fine powder” is formed. The “solvent” gradually evaporates in a state where the dispersion liquid of “copper nanoparticles” is infiltrated into the gap between the laminated structures of the “copper powder”. As a result, on the upper surface of the laminated structure portion of “copper powder”, a surface layer portion composed of “copper fine powder” and “copper nanoparticles” is present. Accordingly, the “copper fine powder” is exposed on the upper surface of the produced “copper thick film”, and “voids” reflecting the “gap” between the “copper fine powder” are generated.

(Comparative Example 2)
In this comparative example 2, a “paste” -like dispersion liquid containing copper powder and copper fine powder is prepared using the following raw materials.

  As the copper microparticles, 1400YM (average particle diameter 4 μm: tap density 5.5 g / cm 3) manufactured by Mitsui Kinzoku Co., Ltd., which is a copper powder produced by a wet method, is used. As the copper submicron particles, 1050Y (average particle diameter 0.8 μm: tap density 4.3 g / cm 3) manufactured by Mitsui Kinzoku Co., Ltd., which is a copper fine powder produced by a wet method, is used.

  As a “high-boiling nonpolar organic solvent”, tripropylene glycol manufactured by Nippon Emulsifier is used.

  1400YM 78.1 parts by mass of Mitsui Kinzoku Co., Ltd., 1050Y17.1 parts by mass of Mitsui Kinzoku Co., Ltd., and 4.8 parts by mass of tripropylene glycol manufactured by Nippon Emulsifier Co., Ltd. are uniformly mixed. The mixture is stirred with a stirring deaerator to uniformly disperse the copper powder and the fine copper powder in the dispersion solvent to prepare a “pasty dispersion”.

Since the density of metallic copper (bulk) is ρCu-bulk = 8.94 g / cm 3, the volume ratio VCu-particle of copper powder and the volume ratio of copper fine powder contained in the prepared “pasted dispersion” VCu-fine-particle is VCu-particle = 56.84% by volume; VCu-fine-particle = 12.46% by volume. The volume ratio Vsolvent of “solvent” is Vsolvent = 30.65% by volume.
{VCu-particle + VCu-fine-particle} / {Vsolvent} = 69.35: 30.65
The liquid viscosity of the prepared “pasty dispersion liquid” was 166 Pa · s (spiral rotational viscometer 10 rpm 25 ° C.).

  The prepared “pasty dispersion” was applied in a 10 mm × 50 mm pattern on a slide glass. The average thickness tpaste of the paste coating film was tpaste = 40 μm.

  For the paste coating film, using a Nissin plasma baking furnace, the procedure described in Example 1 was followed by a “preheating drying (solvent removal) step”, “reduced pressure drying (organic matter removal) step”, “micro A wave plasma irradiation (plasma firing) step "was performed, and the copper powder and the copper fine powder contained in the paste coating film were fired.

  The average film thickness tCu-sintered layer of the fired product was tCu-sintered layer = 32 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 800 μΩ · cm.

  Assuming that the resulting fired product is a “bulk metal copper thick film”, the film thickness tCu-bulk layer of the “bulk metal copper thick film” is tCu-bulk layer = tpaste · {VCu-particle + VCu-fine-particle } / 100% by volume. The average film thickness tCu-sintered layer of the fired product actually obtained is thicker than the film thickness tCu-bulk layer of the “bulk metal copper thick film”, and the ratio tCu-bulk layer / tCu-sintered layer is 86.7 / 100. It has become. In other words, the “void ratio” in the obtained fired product is estimated to be Vvoid = 13.3 volume%.

  The volume specific resistivity 800 μΩ · cm of the obtained fired product is 478 times that of the metal copper resistivity 1.673 μΩ · cm (30 ° C.).

  When the surface shape of the fired product produced using the “paste-like dispersion liquid” of Comparative Example 2 was observed by SEM, it was an aggregate of “copper powder and copper fine powder”, but the “void” structure was Observed at high density.

  Since “copper nanoparticles” are not contained in the “paste-like dispersion liquid” of Comparative Example 2, in the aggregate of “copper powder and copper fine powder”, “copper powder” is in contact with each other, “ A low-temperature sintered body of “copper nanoparticles” is formed at a portion where “copper powder and copper fine powder” are in contact with each other, and at a portion where “copper fine powder” is in contact with each other. -particle-contact, contact resistance rCu-particle / Cu-fine-particle-contact where "copper powder and copper fine powder" contact, and contact resistance rCu-fine-particle where "copper fine powder" contact each other There is no effect to reduce -contact. Therefore, it is determined that the volume resistivity of the fired product formed in Comparative Example 2 is two orders of magnitude higher than the volume resistivity of the fired product formed in Comparative Example 1. The

  Therefore, the fired product formed in Comparative Example 2 was subjected to a treatment of irradiating microwave plasma under a stage temperature of 150 ° C. and a reducing atmosphere, and “copper powder”, “copper powder and copper fine powder”, It is verified that the calcination does not proceed substantially between the “copper fine powders”.

  When a “preheating drying (solvent removal) step” is performed on the coating film of the “paste-like dispersion liquid” in Comparative Example 2 to evaporate the solvent, a “drying treatment” in which the copper powder is densely laminated. Finished coating film ". It is presumed that the copper powder constituting the “dried coating film” is laminated with the same denseness when the “tap density” is measured.

  At that time, “gap” in the laminated structure of “copper powder”: VCu-particle · (ρCu-bulk / ρCu-particle-tap) · {1- (ρCu-particle-tap / ρCu-bulk)} is VCu -particle · (ρCu-bulk / ρCu-particle-tap) · {1- (ρCu-particle-tap / ρCu-bulk)} = 56.84% by volume · (8.94 / 5.5) · {1- It is estimated that (5.5 / 8.94)} = 35.55% by volume. "Bulk" when "copper fine powder" is assembled in the close-packed state: VCu-fine-particle (ρCu-bulk / ρCu-fine-particle) is VCu-fine-particle (ρCu-bulk / ρCu -fine-particle) = 12.46 vol% · (8.94 / 4.3) = 25.91 vol%. Therefore, the condition that the “gap” in the laminated structure of “copper powder” is larger than the “bulk” when the “copper fine powder” is assembled in the closest packing state: {1- (ρCu-particle-tap / ρCu-bulk)} ・ {VCu-particle} ・ (ρCu-bulk / ρCu-particle-tap) volume%> VCu-fine-particle (ρCu-bulk / ρCu-fine-particle-tap) Yes. That is, it is inferred that “copper fine powder” is filled in “clearance” in the laminated structure of “copper powder”.

  Therefore, it is presumed that in the “dried coating film”, the “copper fine powder” fills the “gap” of the structure in which the “copper powder” is densely laminated.

(Comparative Example 3)
In Comparative Example 3, a “paste” -like dispersion liquid containing copper fine powder is prepared using the following raw materials.

  As a copper submicron particle, 1050Y (average particle diameter 0.8 μm: tap density ρCu-fine-particle-tap = 4.3 g / cm 3) manufactured by Mitsui Kinzoku Co., Ltd., which is a copper fine powder produced by a wet method. use.

  As a “high-boiling nonpolar organic solvent”, tripropylene glycol manufactured by Nippon Emulsifier is used.

  1050Y95.2 parts by mass manufactured by Mitsui Kinzoku Co., Ltd. and 4.8 parts by mass of tripropylene glycol manufactured by Nippon Emulsifier Co. The mixture is stirred with a stirring deaerator to uniformly disperse the copper fine powder in the dispersion solvent, thereby preparing a “pasty dispersion”.

  Since the density of metallic copper (bulk) is ρCu-bulk = 8.94 g / cm 3, the volume ratio VCu-fine-particle of the copper fine powder contained in the prepared “pasty dispersion” is VCu− fine-particle = 69.35% by volume. The volume ratio Vsolvent of “solvent” is Vsolvent = 30.65% by volume.

  The liquid viscosity of the prepared “pasty dispersion liquid” was 132 Pa · s (spiral rotational viscometer 10 rpm 25 ° C.).

  The prepared “pasty dispersion” was applied in a 10 mm × 50 mm pattern on a slide glass. The average thickness tpaste of the paste coating film was tpaste = 40 μm.

  For the paste coating film, using a Nissin plasma baking furnace, the procedure described in Example 1 was followed by a “preheating drying (solvent removal) step”, “reduced pressure drying (organic matter removal) step”, “micro A wave plasma irradiation (plasma firing) step "was performed, and the copper powder and the copper fine powder contained in the paste coating film were fired.

  The average film thickness tCu-sintered layer of the fired product was tCu-sintered layer = 32 μm. For the fired product, an attempt was made to measure the sheet resistance value, but it was found that it exceeded the measurable range. That is, since the “volume resistivity” far exceeds 1000 μΩ · cm, it has been found that it is difficult to measure the sheet resistance value.

  Assuming that the resulting fired product is a “bulk metal copper thick film”, the film thickness tCu-bulk layer of the “bulk metal copper thick film” is tCu-bulk layer = tpaste · {VCu-fine-particle} / Estimated to be 100% by volume. The average film thickness tCu-sintered layer of the fired product actually obtained is thicker than the film thickness tCu-bulk layer of the “bulk metal copper thick film”, and the ratio tCu-bulk layer / tCu-sintered layer is 86.7 / 100. It has become. In other words, the “void ratio” in the obtained fired product is estimated to be Vvoid = 13.3 volume%.

  When the surface shape of the fired product produced using the “paste-like dispersion liquid” of Comparative Example 3 was observed by SEM, it was an aggregate of “copper fine powder”, but the “void” structure had a high density. Observed.

  When the “preliminary drying (solvent removal) step” is performed on the coating film of the “paste-like dispersion liquid” of Comparative Example 3 and the solvent is evaporated, the “drying” of the shape in which the copper fine powder is densely laminated is performed. A “treated coating film” is obtained. It is presumed that the copper fine powder constituting the “dried coating film” is laminated with the same denseness when measuring the “tap density”.

  The density of metallic copper (bulk) ρCu-bulk = 8.94g / cm3, whereas the tap density of “copper fine powder” is ρCu-fine-particle-tap = 4.3g / cm3. "Void fraction" existing in "copper fine powder": Vempty-space volume% can be estimated as {1- (ρCu-fine-particle-tap / ρCu-bulk)} · 100 volume% is there. Actually, {1- (ρCu-fine-particle-tap / ρCu-bulk)} · 100 volume% = {1- (4.3 g / cm 3 /8.94 g / cm 3)} · 100 volume% = 51.9 Estimated as volume%.

  The volume ratio Vsolvent of the “solvent” contained in the “pasty dispersion” is Vsolvent = 30.65% by volume, and the “porosity” present in the densely laminated “copper fine powder”: Much smaller than Vempty-space volume%.

"Material for forming silver thick film"
(Example 15)
The material for forming a silver thick film of Example 15 is prepared in the shape of “conductive silver paste” using the following raw materials.

  AG-5-7F (average particle diameter dAg-particle 3 μm, tap density ρAg-particle-tap 5.9 g / cm 3) manufactured by DOWA Electronics Co., Ltd., which is a fine silver powder produced by a wet method, as silver microparticles use.

  Harima Kasei silver nanoparticles are used as the silver nanoparticle dispersion. The average particle diameter dAg-nanoparticle of the silver nanoparticles dispersed in the dispersion is 62 nm. On the surface of the silver nanoparticles, a surface coating molecular layer of coating molecules (2-ethylhexanoic acid and dodecylamine) is formed. As "coating agent molecules", 2-ethylhexanoic acid (molecular weight 144.21, boiling point 228 ° C, density ρcoating-molecule-acid 0.90 g / cm3) and dodecylamine (molecular weight 185.34, boiling point 247 ° C, density ρcoating -molecule-amine 0.7841 g / cm3 (40 ° C.)). The content ratio of 2-ethylhexanoic acid and dodecylamine is (2-ethylhexanoic acid: dodecylamine) = (0.28 parts by mass: 0.36 parts by mass). Dodecylamine = 1 mol: 1 mol is selected.

  When “silver nanoparticles” contained in the “silver nanoparticle dispersion liquid” are also laminated in a close-packed state, the bulk density (tap density) is the density of metallic silver (bulk) ρAg-bulk = 10. It is estimated to be about 2/3 for 49 g / cm3. That is, the bulk density (tap density) ρAg-nanoparticle of the “silver nanoparticles” contained in the “silver nanoparticle dispersion liquid” is estimated to be about 7.0 g / cm 3.

  1-decanol (melting point 6.4 ° C., boiling point 232.9 ° C., density ρsolvent 0.829 g / cm 3) is used as the high boiling point solvent.

  AG-5-7F8 parts by mass of DOWA Electronics Co., Ltd., 2 parts by mass of Harima Kasei silver nanoparticles, 0.1 parts by mass of the coating molecule, and 1.6 parts by mass of 1-decanol are mixed uniformly. Stir with a stirring deaerator to disperse the silver powder uniformly to obtain a conductive silver paste.

  The volume ratio VAg-particle of silver powder and the volume ratio VAg-nanoparticle of silver nanoparticles contained in the prepared “conductive silver paste” are VAg-particle = 25.39 vol%; VAg-nanoparticle = 6. 35% by volume. The sum of the volume ratio Vcoating-molecule of “coating agent molecule” and the volume ratio Vsolvent of “solvent” is {Vcoating-molecule + Vsolvent} = (4.01 + 64.25) volume% = 68.26 volume%.

The ratio of the volume ratio VAg-particle of silver powder to the volume ratio VAg-nanoparticle of silver nanoparticles is calculated as VAg-particle: VAg-nanoparticle = 100: 25.0.
{VAg-particle + VAg-nanoparticle} / {Vcoating-molecule + Vsolvent} = 31.74: 68.26.

  The liquid viscosity of the prepared “conductive silver paste” was 60 Pa · s (spiral rotational viscometer 10 rpm 25 ° C.).

  In the “conductive silver paste”, the silver nanoparticles are uniformly dispersed in 1-decanol of “solvent” by forming a coating molecule layer composed of “coating molecule” on the surface thereof. At that time, “coating agent molecule” is dissolved in 1-decanol of “solvent”. Surface density Ccoating-molecule-surface of “coating molecule” forming coating molecule layer on silver nanoparticle surface and concentration of “coating molecule” dissolved in “solvent” Ccoating-molecule-liquid A dissociation equilibrium is achieved with -phase.

  The “conductive silver paste” of Example 16 also has a relationship of ΣSAg-nanoparticle >> ΣSAg-particle.

  Therefore, the sum of the amount “coating molecule” covering the surface of the silver nanoparticles Mcoating-molecule-surface and the amount “coating molecule” dissolved in the “solvent” Mcoating-molecule-liquid-phase is The total amount of “coating agent molecules” contained in the “conductive silver paste” Mcoating-molecule (Mcoating-molecule = Mcoating-molecule-surface + Mcoating-molecule-liquid-phase).

  The prepared “conductive silver paste” was applied on a slide glass in a pattern of 10 mm × 50 mm. The average thickness tpaste of the paste coating film was tpaste = 30 μm.

  Using a Nissin plasma baking furnace, the paste coating film was subjected to the following procedures according to the following procedures: “preheating drying (solvent removal) step”, “vacuum drying (organic matter removal) step”, “microwave plasma irradiation ( Plasma firing) step ”was performed, and the silver powder and silver nanoparticles contained in the paste coating film were fired.

  As a “preheating drying (solvent removal) step”, preheating is performed for 180 seconds at a stage temperature of 100 ° C. under atmospheric pressure in a Nissin plasma baking furnace. As the “reduced pressure drying (organic matter removal) step”, “evacuation” is performed for 60 seconds while maintaining the stage temperature at 100 ° C., and the inside of the plasma firing furnace is maintained in a reduced pressure state. The pressure in the plasma baking furnace in the reduced pressure state is maintained at 10 Pa or less.

  In the “microwave plasma irradiation (plasma firing) step”, helium-3% hydrogen is first introduced into the plasma firing furnace at a flow rate of 50 sccm for 30 seconds while the stage temperature is maintained at 100 ° C. After controlling the pressure in the plasma firing furnace to 10 Pa, a microwave (frequency 2.4 GHz) is supplied from a high frequency power source (frequency 2.4 GHz) at a high frequency power of 1.5 kW, and helium-3% hydrogen gas is micronized. Generate wave plasma. In a state where the stage temperature is maintained at 100 ° C., microwave plasma irradiation is continued for 120 seconds to perform plasma baking. The silver powder and silver nanoparticles contained in the paste coating film are fired by irradiation of the generated microwave plasma in a reducing atmosphere made of the helium-3% hydrogen gas.

  The average film thickness tAg-sintered layer of the obtained fired product was tAg-sintered layer = 15 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 3.8 μΩ · cm.

  Assuming that the resulting fired product is a “bulk metal silver thick film”, the film thickness tAg-bulk layer of the “bulk metal silver thick film” is tAg-bulk layer = tpaste · {VAg-particle + VAg-nanoparticle} / Estimated to be 100% by volume. The average film thickness tAg-sintered layer of the fired product actually obtained is thicker than the film thickness tAg-bulk layer of the “bulk metal silver thick film”, and the ratio tAg-bulk layer / tAg-sintered layer is 63.48 / 100. It has become. In other words, the “porosity” in the obtained fired product is estimated to be Vvoid = 36.52% by volume.

  The volume specific resistivity 3.8 μΩ · cm of the obtained fired product is 2.4 times that of the resistivity of metallic silver 1.587 μΩ · cm (20 ° C.).

  When the “silver powder” contained in the coating film of the “conductive silver paste” forms a dense laminated structure having a bulk density (tap density) ρAg-particle-tap of 5.9 g / cm 3, the “silver powder” The average thickness tAg-particle-layer of the laminated structure of “powder” is estimated as tAg-particle-layer = tpaste · (VAg-particle / 100 volume) · (ρAg-bulk / ρAg-particle-tap). tAg-particle-layer = tpaste · (VAg-particle / 100 volume) (ρAg-bulk / ρAg-particle-tap) = 30 μm · (25.39% by volume / 100 volume) · (10.49 / 5.9) = 13.54 μm.

  The “gap” existing in the laminated structure of the “silver powder” is {1- (ρAg-particle-tap / ρAg-bulk)} · {VAg-particle} · (ρAg-bulk / ρAg-particle- tap) volume% can be estimated. {1- (ρAg-particle-tap / ρAg-bulk)} · {VAg-particle} · (ρAg-bulk / ρAg-particle-tap) = {1- (5.9 / 10.49)} · {25 .39% by volume} · (10.49 / 5.9) = 19.75% by volume. “Bulk” when “silver nanoparticles” are assembled in a close-packed state: VAg-nanoparticle (ρAg-bulk / ρAg-nanoparticle-tap) is VAg-nanoparticle (ρAg-bulk / ρAg-nanoparticle-tap) ) = 6.35% by volume · (10.49 / 7.0) = 9.52% by volume. Further, the sum of the volume ratio Vag-nanoparticle of silver nanoparticles and the volume ratio Vcoating-molecule of the “coating agent molecule” (VAg-nanoparticle + Vcoating-molecule) is (VAg-nanoparticle + Vcoating-molecule) = (6.35 + 4.01) = 10.36 vol%. The sum (VAg-nanoparticle + Vcoating-molecule) is smaller than the volume ratio of “gap” existing in the estimated laminated structure of “silver powder”.

  On the other hand, the average film thickness tAg-sintered layer of the fired product is thicker than the average thickness tAg-particle-layer of the “silver powder” laminated structure. Of course, the average film thickness tdried-paste of the “dried coating film” is predicted to be approximately the same as the average film thickness tAg-sintered layer of the obtained fired product. Therefore, the “dried coating film” has a lower layer corresponding to the average thickness tAg-particle-layer of the laminated structure of “silver powder” and an upper layer made of a laminated structure of “silver nanoparticles” on the upper surface. It is presumed that it constitutes a “two-layer structure”. The average thickness tAg-nanoparticle-upper-layer of the layered structure of “silver nanoparticles” is (tdried-paste-tAg-particle-layer) = (tAg-sintered layer-tAg-particle-layer) = 1 It is estimated to be about .46 μm.

(Example 16)
In this Example 16, the “conductive silver paste” prepared in Example 15 was used, and the same plasma baking condition as the plasma baking condition described in Example 16 was adopted. A thick silver film is formed.

  The average thickness tpaste of the paste coating film was selected to be tpaste = 60 μm, and the silver powder and silver nanoparticles contained in the paste coating film were fired under the same conditions as in Example 15.

  The average film thickness tAg-sintered layer of the obtained fired product was tAg-sintered layer = 32 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 5.5 μΩ · cm.

  Assuming that the resulting fired product is a “bulk metal silver thick film”, the film thickness tAg-bulk layer of the “bulk metal silver thick film” is tAg-bulk layer = tpaste · {VAg-particle + VAg-nanoparticle} / Estimated to be 100% by volume. The average film thickness tAg-sintered layer of the fired product actually obtained is thicker than the film thickness tAg-bulk layer of the “bulk metal silver thick film”, and the ratio tAg-bulk layer / tAg-sintered layer is 59.51 / 100. It has become. In other words, the “porosity” in the obtained fired product is estimated to be Vvoid = 40.49% by volume.

  The volume resistivity of 5.5 μΩ · cm of the obtained fired product is 3.46 times that of the resistivity of metallic silver of 1.587 μΩ · cm (20 ° C.).

  When the “silver powder” contained in the coating film of the “conductive silver paste” forms a dense laminated structure having a bulk density (tap density) ρAg-particle-tap of 5.9 g / cm 3, the “silver powder” The average thickness tAg-particle-layer of the laminated structure of “powder” is estimated as tAg-particle-layer = tpaste · (VAg-particle / 100 volume) · (ρAg-bulk / ρAg-particle-tap). tAg-particle-layer = tpaste · (VAg-particle / 100 volume) (ρAg-bulk / ρAg-particle-tap) = 60 μm · (25.39% by volume / 100 volume) · (10.49 / 5.9) = 27.09 μm.

  The “gap” existing in the laminated structure of the “silver powder” is {1- (ρAg-particle-tap / ρAg-bulk)} · {VAg-particle} · (ρAg-bulk / ρAg-particle- tap) volume% can be estimated. {1- (ρAg-particle-tap / ρAg-bulk)} · {VAg-particle} · (ρAg-bulk / ρAg-particle-tap) = {1- (5.9 / 10.49)} · {25 .39% by volume} · (10.49 / 5.9) = 19.75% by volume. “Bulk” when “silver nanoparticles” are assembled in a close-packed state: VAg-nanoparticle (ρAg-bulk / ρAg-nanoparticle-tap) is VAg-nanoparticle ) = 6.35% by volume · (10.49 / 7.0) = 9.52% by volume. Further, the sum of the volume ratio Vag-nanoparticle of silver nanoparticles and the volume ratio Vcoating-molecule of the “coating agent molecule” (VAg-nanoparticle + Vcoating-molecule) is (VAg-nanoparticle + Vcoating-molecule) = (6.35 + 4.01) = 10.36 vol%. The sum (VAg-nanoparticle + Vcoating-molecule) is smaller than the volume ratio of “gap” existing in the estimated laminated structure of “silver powder”.

  The average film thickness tAg-sintered layer of the fired product obtained is much thicker than the average thickness tAg-particle-layer of the laminated structure of “silver powder”. At that time, the average film thickness tdried-paste of the “dried coating film” is predicted to be about the same as the average film thickness tAg-sintered layer of the obtained fired product. Therefore, the “dried coating film” has a lower layer corresponding to the average thickness tAg-particle-layer of the laminated structure of “silver powder” and an upper layer made of a laminated structure of “silver nanoparticles” on the upper surface. It is presumed that it constitutes a “two-layer structure”. The average thickness tAg-nanoparticle-upper-layer of the laminated layer of “silver nanoparticles” is (tdried-paste-tAg-particle-layer) = (tAg-sintered layer-tAg-particle-layer) = 4 It is estimated to be about 91 μm.

(Comparative Example 4)
In Comparative Example 4, “Harima Kasei Silver Nanoparticles” used in the preparation of “Conductive Silver Paste” of Example 16 was adopted, and the silver nanoparticles were not contained and the silver nanoparticles had a high boiling point. A “silver nanoparticle dispersion liquid” dispersed in a solvent is prepared.

  The average particle diameter dAg-nanoparticle of the silver nanoparticles dispersed in the “silver nanoparticle dispersion liquid” of Comparative Example 4 is 62 nm. On the surface of the silver nanoparticles, a surface coating molecular layer of coating molecules (2-ethylhexanoic acid and dodecylamine) is formed. 2-Ethylhexanoic acid and dodecylamine are used as “coating agent molecules”. The content ratio of 2-ethylhexanoic acid and dodecylamine is selected as a molar ratio of 2-ethylhexanoic acid: dodecylamine = 1 mol: 1 mol.

  1-decanol is used as the high boiling point solvent.

  The “silver nanoparticle dispersion liquid” of Comparative Example 4 contains 0.1 part by mass of the coating agent molecule and 0.3 part by mass of 1-decanol per 2 parts by mass of Harima Kasei silver nanoparticles.

The volume ratio VAg-nanoparticle of “silver nanoparticles” contained in the “silver nanoparticle dispersion liquid” is VAg-nanoparticle = 28.33% by volume; the volume ratio Vcoating-molecule of “coating agent molecule” is Vcoating -molecule = 18.02% by volume; The volume ratio Vsolvent of “solvent” is Vsolvent = 53.65% by volume. Therefore, the sum of the volume ratio Vcoating-molecule of the “coating agent molecule” and the volume ratio Vsolvent of the “solvent” is {Vcoating-molecule + Vsolvent} = 71.67 volume%.
{VAg-nanoparticle} / {Vcoating-molecule + Vsolvent} = 28.33: 71.67.

  The liquid viscosity of the “silver nanoparticle dispersion liquid” in Comparative Example 4 was 55 Pa · s (spiral rotational viscometer 10 rpm 25 ° C.).

  In the “silver nanoparticle dispersion liquid” of Comparative Example 4, the silver nanoparticles are uniformly dispersed in 1-decanol of “solvent” by forming a coating molecule layer composed of “coating molecule” on the surface thereof. ing. At that time, “coating agent molecule” is dissolved in 1-decanol of “solvent”. Surface density Ccoating-molecule-surface of “coating molecule” forming coating molecule layer on silver nanoparticle surface and concentration of “coating molecule” dissolved in “solvent” Ccoating-molecule-liquid A dissociation equilibrium is achieved with -phase.

  In the “conductive silver paste” of Example 15, the content ratio of “covering agent molecule” / “solvent” is 0.1 parts by mass / 1.6 parts by mass. In the “dispersion”, the content ratio of “coating agent molecule” / “solvent” is 0.1 part by mass / 0.3 part by mass. Accordingly, the concentration Ccoating-molecule-liquid-phase of the “coating agent molecule” dissolved in the “solvent” in the “conductive silver paste” of Example 16 is the “silver nanoparticle dispersion liquid of Comparative Example 4”. ”Is estimated to be the same as the concentration Ccoating-molecule-liquid-phase of the“ coating molecule ”dissolved in the“ solvent ”. At that time, the amount Mcoating-molecule-liquid-phase of the “coating agent molecule” dissolved in the “solvent” in the “silver nanoparticle dispersion liquid” of Comparative Example 4 was the “conductive silver paste of Example 15”. The amount of the “coating agent molecule” dissolved in the “solvent” is determined to be considerably less than the Mcoating-molecule-liquid-phase. In other words, in the “silver nanoparticle dispersion” of Comparative Example 4, the amount “coating molecule” included in the “coating molecule layer” formed on the surface of the “silver nanoparticle” Mcoating-molecule-surface is In the “conductive silver paste” of Example 15, the amount of “coating molecule” contained in the “coating molecule layer” formed on the surface of “silver nanoparticles”, compared to the Mcoating-molecule-surface, It is judged that there are many. Compared to the film thickness tcoating-molecule of the “coating agent molecular layer” formed on the surface of “silver nanoparticles” in the “conductive silver paste” of Example 15, “silver nanoparticle dispersion liquid” of Comparative Example 4 The film thickness tcoating-molecule of the “coating molecule layer” formed on the surface of the “silver nanoparticles” is determined to be considerably thick.

  The prepared paste-like “silver nanoparticle dispersion liquid” was applied on a slide glass in a pattern of 10 mm × 50 mm. The average thickness tpaste of the paste coating film was tpaste = 30 μm.

  For the “silver nanoparticle dispersion” coating film, using a Nissin plasma firing furnace, the following procedure is followed: “preheating drying (solvent removal) step”, “vacuum drying (organic matter removal) step”, The “microwave plasma irradiation (plasma firing) step” was performed, and the silver nanoparticles contained in the “silver nanoparticle dispersion liquid” coating film were fired.

  As a “preheating drying (solvent removal) step”, preheating is performed for 180 seconds at a stage temperature of 100 ° C. under atmospheric pressure in a Nissin plasma baking furnace. As the “reduced pressure drying (organic matter removal) step”, “evacuation” is performed for 60 seconds while maintaining the stage temperature at 100 ° C., and the inside of the plasma firing furnace is maintained in a reduced pressure state. The pressure in the plasma baking furnace in the reduced pressure state is maintained at 10 Pa or less.

  In the “microwave plasma irradiation (plasma firing) step”, helium-3% hydrogen is first introduced into the plasma firing furnace at a flow rate of 50 sccm for 30 seconds while the stage temperature is maintained at 100 ° C. After controlling the pressure in the plasma firing furnace to 10 Pa, a microwave (frequency 2.4 GHz) is supplied from a high frequency power source (frequency 2.4 GHz) at a high frequency power of 1.5 kW, and helium-3% hydrogen gas is micronized. Generate wave plasma. In a state where the stage temperature is maintained at 100 ° C., microwave plasma irradiation is continued for 120 seconds to perform plasma baking. The silver nanoparticles contained in the “silver nanoparticle dispersion liquid” coating film are fired by irradiation of the generated microwave plasma made of the helium-3% hydrogen gas in a reducing atmosphere.

  The average film thickness tAg-sintered layer of the obtained fired product was tAg-sintered layer = 10 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 8.5 μΩ · cm.

  Assuming that the obtained fired product is a “bulk metal silver thick film”, the film thickness tAg-bulk layer of the “bulk metal silver thick film” is tAg-bulk layer = tpaste · VAg-nanoparticle / 100 vol%. Estimated. The average film thickness tAg-sintered layer of the fired product actually obtained is thicker than the film thickness tAg-bulk layer of the “bulk metal silver thick film”, and the ratio tAg-bulk layer / tAg-sintered layer is 84.99 / 100. It has become. In other words, the “void ratio” in the obtained fired product is estimated to be Vvoid = 15.01% by volume.

  The “silver nanoparticles” contained in the “silver nanoparticle dispersion” coating film having an average thickness tpaste has a dense laminated structure with a bulk density (tap density) ρAg-nanoparticle = 7.0 g / cm 3. When formed, the average thickness tAg-nanoparticle-layer of the laminated structure of the “silver nanoparticles” is estimated as tAg-nanoparticle-layer = tAg-bulk layer · (ρAg-bulk / ρAg-nanoparticle). tAg-nanoparticle-layer = tAg-bulk layer · (ρAg-bulk / ρAg-nanoparticle) = 30 μm · (28.33 vol% / 100 vol%) · (10.49 / 7.0) = 12.74 μm It is. On the other hand, the sum of the volume ratios (VAg-nanoparticle + Vcoating-molecule) of “silver nanoparticles” and “coating agent molecules” contained in the “silver nanoparticle dispersion” coating film having an average thickness tpaste is 46.35. % By volume. When the “solvent” evaporates and the “silver nanoparticles” and “coating agent molecules” form a laminated structure, the film thickness tpredried-layer is tpredried-layer = tpaste · (VAg-nanoparticle + Vcoating-molecule) / 100 volume. % = 30 μm · (46.35% by volume / 100% by volume) = 13.90 μm.

  The average film thickness tAg-sintered layer of the fired product actually obtained is thinner than the average thickness tAg-nanoparticle-layer of the laminated structure of the “silver nanoparticles”. Moreover, the average film thickness tAg-sintered layer of the fired product actually obtained is thinner than the film thickness tpredried-layer. Accordingly, the average film thickness tAg-sintered layer of the fired product actually obtained by removing the “solvent” and “coating agent molecule” and firing the “silver nanoparticles” is the laminated structure of “silver nanoparticles”. It is thinner than the average thickness of tAg-nanoparticle-layer.

  The volume resistivity of 8.5 μΩ · cm of the obtained fired product is 5.3 times that of the resistivity of metallic silver of 1.587 μΩ · cm (20 ° C.).

(Comparative Example 5)
In Comparative Example 5, the “silver nanoparticle dispersion” prepared in Comparative Example 4 was used, and the same plasma baking conditions as those described in Comparative Example 4 were adopted. An attempt is made to form a thick conductive silver film.

  Silver nanoparticles contained in the “silver nanoparticle dispersion” coating film under the same conditions as in Comparative Example 4 with the average thickness tpaste of the “silver nanoparticle dispersion liquid” coating film being selected as tpaste = 60 μm. Was fired.

  The average thickness tAg-sintered layer of the obtained fired product was tAg-sintered layer = 28 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 2.0 Ω · cm = 2.0 × 10 6 μΩ · cm.

  Assuming that the obtained fired product is a “bulk metal silver thick film”, the film thickness tAg-bulk layer of the “bulk metal silver thick film” is tAg-bulk layer = tpaste · VAg-nanoparticle / 100 vol%. Estimated. The average film thickness tAg-sintered layer of the fired product actually obtained is thicker than the film thickness tAg-bulk layer of the “bulk metal silver thick film”, and the ratio tAg-bulk layer / tAg-sintered layer is 60.70 / 100. It has become. In other words, the “porosity” in the obtained fired product is estimated to be Vvoid = 39.30% by volume.

  The “silver nanoparticles” contained in the “silver nanoparticle dispersion” coating film having an average thickness tpaste has a dense laminated structure with a bulk density (tap density) ρAg-nanoparticle = 7.0 g / cm 3. When formed, the average thickness tAg-nanoparticle-layer of the laminated structure of the “silver nanoparticles” is estimated as tAg-nanoparticle-layer = tAg-bulk layer · (ρAg-bulk / ρAg-nanoparticle). tAg-nanoparticle-layer = tAg-bulk layer · (ρAg-bulk / ρAg-nanoparticle) = 60 μm · (28.33% by volume / 100% by volume) · (10.49 / 7.0) = 25.47 μm It is. When the “solvent” evaporates and the “silver nanoparticles” and “coating agent molecules” form a laminated structure, the film thickness tpredried-layer is tpredried-layer = tpaste · (VAg-nanoparticle + Vcoating-molecule) / 100 volume. % = 60 μm · (46.35% by volume / 100% by volume) = 27.81 μm. The average thickness tAg-sintered layer of the fired product actually obtained is thicker than the average thickness tAg-nanoparticle-layer of the laminated structure of the “silver nanoparticles” and is substantially equal to the thickness tpredried-layer.

  The resistivity of metallic silver is 1.587 μΩ · cm (20 ° C.), and the volume resistivity of the obtained fired product is 2.0Ω · cm = 2.0 × 106 μΩ · cm is 1.26 × 106 times. It has become. That is, the obtained fired product cannot be regarded as a “conductive silver thick film”. Specifically, in a fired product having an average film thickness tAg-sintered layer = 28 μm, a very thin portion of the surface is a “baked product” that exhibits “conductivity” due to the mutual sintering of “silver nanoparticles”. However, most of the parts are aggregates of “silver nanoparticles”, but it is judged that the sintering of “silver nanoparticles” does not proceed.

  When the “silver nanoparticle dispersion liquid” of Comparative Example 4 is used, when the average thickness tpaste of the coating film is doubled, the “coating molecule” contained in the coating film of the “silver nanoparticle dispersion liquid” The total amount Mcoating-molecule and the total amount Msolvent of “solvent” are doubled.

  On the other hand, in the “preheating drying (solvent removal) step” and “reduced pressure drying (organic matter removal) step”, the evaporation of the “solvent” and the evaporation of the “coating agent molecule” proceed mainly from the surface of the coating film. When the processing conditions and the processing time of the “preheating drying (solvent removal) step” and “reduced pressure drying (organic matter removal) step” are equal, the amount of “coating molecule” ΔMcoating-molecule removed during The amount ΔMsolvent is not essentially different between Comparative Example 4 and Comparative Example 5.

  Therefore, when the “preheating drying (solvent removal) step” and the “reduced pressure drying (organic matter removal) step” are completed, the remaining amount of “coating agent molecules” remaining in the coating film of Comparative Example 4 { Mcoating-molecule-ΔMcoating-molecule} and the residual amount of “solvent” {Msolvent-ΔMsolvent}, in the coating film of Comparative Example 5, the residual amount of “coating agent molecule” is {2Mcoating-molecule-ΔMcoating-molecule } The remaining amount of “solvent” is {2Msolvent−ΔMsolvent}.

  Therefore, in the coating film of Comparative Example 4, when the “preheating drying (solvent removal) step” and the “vacuum drying (organic matter removal) step” are completed, the contained “silver nanoparticles” form a laminated structure. However, most of the “silver nanoparticles” constituting the laminated structure are in a state where the “coating agent molecular layer” on the surface is removed. However, it is inferred that the “coating agent molecular layer” remains on the surface of the “silver nanoparticles” at the bottom of the laminated structure. In the “microwave plasma irradiation (plasma firing) process”, sintering of “silver nanoparticles” in a state where the “coating agent molecular layer” on the surface has been removed proceeds, It is presumed that the sintering of “silver nanoparticles” in which the “coating molecular layer” remains does not proceed.

  On the other hand, in the coating film of Comparative Example 5, at the time when the “preheating drying (solvent removal) step” and the “vacuum drying (organic matter removal) step” were completed, most of the contained “silver nanoparticles” The “covering agent molecular layer” remains on the surface. That is, a laminated structure composed of “silver nanoparticles” having a “coating agent molecular layer” on the surface is formed. However, it is presumed that the “coating agent molecular layer” on the surface of the “silver nanoparticles” is removed from the upper surface portion of the laminated structure. In the “microwave plasma irradiation (plasma firing) process”, sintering of “silver nanoparticles” in a state where the “coating agent molecular layer” on the surface is removed proceeds on the upper surface portion of the laminated structure. It is presumed that the sintering of “silver nanoparticles” in which the “coating agent molecular layer” remains on the surface does not proceed.

"Material for forming aluminum thick film"
(Example 17)
The material for forming an aluminum thick film of Example 17 is prepared in the form of “conductive aluminum paste” using the following raw materials.

  As aluminum microparticles, Minalco's # 900F (atomized powder, average particle diameter dAl-particle 2.4 μm, bulk density (tap density) ρAl-particle-tape 1.0 g / cm3) is used. The density ρAl-bulk of metallic aluminum (bulk) is 2.699 g / cm 3 (20 ° C.).

  Harima Kasei silver nanoparticles are used as the metal nanoparticle dispersion. The average particle diameter dAg-nanoparticle of the silver nanoparticles dispersed in the dispersion is 10 nm. On the surface of the silver nanoparticles, a surface coating molecular layer of a coating molecule dodecylamine is formed. As the “coating agent molecule”, dodecylamine (molecular weight: 185.34, boiling point: 247 ° C., density ρcoating-molecule-amine 0.7841 g / cm 3 (40 ° C.)) is used. When “silver nanoparticles” contained in the “silver nanoparticle dispersion liquid” are also laminated in a close-packed state, the bulk density (tap density) is the density of metallic silver (bulk) ρAg-bulk = 10. It is estimated to be about 2/3 for 49 g / cm3. That is, the bulk density (tap density) ρAg-nanoparticle of the “silver nanoparticles” contained in the “silver nanoparticle dispersion liquid” is estimated to be about 7.0 g / cm 3.

  As a non-polar organic solvent having a high boiling point, a petroleum non-aromatic hydrocarbon solvent, No. AF5 solvent manufactured by JX Nippon Oil & Energy (boiling point: 275-306 ° C; pour point: -30 ° C; density ρsolvent 0.815 g / cm 3 ( 15 ° C)).

  Minalco Co., Ltd. # 900F7 parts by mass, Harima Kasei silver nanoparticles 2 parts by mass, coating agent molecules 0.1 parts by mass, JX Nippon Oil & Energy's AF5 Solvent 5 parts by mass are mixed uniformly. The mixture is stirred with a stirring deaerator to uniformly disperse the aluminum powder, thereby obtaining a conductive aluminum paste.

  The volume ratio VAl-particle of the aluminum powder and the volume ratio VAg-nanoparticle of the silver nanoparticles contained in the prepared “conductive aluminum paste” are VA-particle = 28.67% by volume; VAg-nanoparticle = 2. 11% by volume. The sum of the volume ratio Vcoating-molecule of “coating agent molecule” and the volume ratio Vsolvent of “solvent” is {Vcoating-molecule + Vsolvent} = (1.41 + 67.81) volume% = 69.22 volume%.

The ratio of the volume ratio VAl-particle of the aluminum powder and the volume ratio VAg-nanoparticle of the silver nanoparticles is calculated as VA1-particle: VAg-nanoparticle = 100: 7.36.
{VAl-particle + VAg-nanoparticle} / {Vcoating-molecule + Vsolvent} = 30.78: 69.22.

  The liquid viscosity of the prepared “conductive aluminum paste” was 105 Pa · s (spiral rotational viscometer 10 rpm 25 ° C.).

  In the “conductive aluminum paste”, the silver nanoparticles are uniformly dispersed in the “solvent” AF No. 5 solvent by forming a coating agent molecular layer composed of “coating agent molecules” on the surface thereof. At that time, “coating agent molecules” are dissolved in the AF5 solvent of “solvent”. Surface density Ccoating-molecule-surface of “coating molecule” forming coating molecule layer on silver nanoparticle surface and concentration of “coating molecule” dissolved in “solvent” Ccoating-molecule-liquid A dissociation equilibrium is achieved with -phase.

  Therefore, the sum of the amount “coating molecule” covering the surface of the silver nanoparticles Mcoating-molecule-surface and the amount “coating molecule” dissolved in the “solvent” Mcoating-molecule-liquid-phase is The total amount of “coating agent molecules” contained in “conductive aluminum paste” Mcoating-molecule (Mcoating-molecule = Mcoating-molecule-surface + Mcoating-molecule-liquid-phase).

  The prepared “conductive aluminum paste” was applied in a 10 mm × 50 mm pattern on a slide glass. The average thickness tpaste of the paste coating film was tpaste = 30 μm.

  When the “aluminum powder” contained in the paste coating film forms a dense laminated structure with a bulk density (tap density) ρAl-particle-tap of 1.0 g / cm 3, the laminated structure of the “aluminum powder” The average thickness tAl-particle-layer is estimated as tAl-particle-layer = tpaste · (VAl-particle / 100 volume) · (ρAl-bulk / ρAl-particle-tap). tAl-particle-layer = tpaste · (VAl-particle / 100 volume) (ρAl-bulk / ρAl-particle-tap) = 30 μm · (28.67 vol% / 100 volume) · (2.699 / 1.0) = 23.21 μm.

  At this time, the “gap” existing in the laminated structure of the “aluminum powder” is {1- (ρAl-particle-tap / ρAl-bulk)} · {VAl-particle} · (ρAl-bulk / ρAl-particle). -tap) volume% can be estimated. {1- (ρAl-particle-tap / ρAl-bulk)} · {VAl-particle} · (ρAl-bulk / ρAl-particle-tap) = {1- (1.0 / 2.699)} · {28 .67% by volume} · (2.699 / 1.0) = 48.71% by volume. “Bulk” when “silver nanoparticles” are assembled in a close-packed state: VAg-nanoparticle (ρAg-bulk / ρAg-nanoparticle-tap) is VAg-nanoparticle (ρAg-bulk / ρAg-nanoparticle-tap) ) = 2.11 volume% · (10.49 / 7.0) = 3.16 volume%. Further, the sum of the volume ratio Vag-nanoparticle of silver nanoparticles and the volume ratio Vcoating-molecule of “coating agent molecule” (VAg-nanoparticle + Vcoating-molecule) is (VAg-nanoparticle + Vcoating-molecule) = (2.11 + 1.41) = 3.52% by volume. The sum (VAg-nanoparticle + Vcoating-molecule) is smaller than the volume ratio of the “gap” existing in the estimated laminated structure of “aluminum powder”.

  As will be described later, the average film thickness tAl-sintered layer of the fired product actually obtained is substantially equal to the estimated average thickness tAg-particle-layer of the laminated structure of “aluminum powder”.

  Using a Nissin plasma baking furnace, the paste coating film was subjected to the following procedures according to the following procedures: “preheating drying (solvent removal) step”, “vacuum drying (organic matter removal) step”, “microwave plasma irradiation ( Plasma firing) step ”was performed, and the silver powder and silver nanoparticles contained in the paste coating film were fired.

  As a “preheating drying (solvent removal) step”, preheating is performed for 180 seconds at a stage temperature of 100 ° C. under atmospheric pressure in a Nissin plasma baking furnace. As the “reduced pressure drying (organic matter removal) step”, “evacuation” is performed for 60 seconds while maintaining the stage temperature at 100 ° C., and the inside of the plasma firing furnace is maintained in a reduced pressure state. The pressure in the plasma baking furnace in the reduced pressure state is maintained at 10 Pa or less.

  In the “microwave plasma irradiation (plasma firing) step”, helium-3% hydrogen is first introduced into the plasma firing furnace at a flow rate of 50 sccm for 30 seconds while the stage temperature is maintained at 100 ° C. After controlling the pressure in the plasma firing furnace to 10 Pa, a microwave (frequency 2.4 GHz) is supplied from a high frequency power source (frequency 2.4 GHz) at a high frequency power of 1.5 kW, and helium-3% hydrogen gas is micronized. Generate wave plasma. In a state where the stage temperature is maintained at 100 ° C., microwave plasma irradiation is continued for 120 seconds to perform plasma baking. The aluminum powder and silver nanoparticles contained in the paste coating film are fired by irradiation with the generated microwave plasma in a reducing atmosphere composed of the helium-3% hydrogen gas.

  The average film thickness tAl-sintered layer of the fired product was tAl-sintered layer = 23 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 4.8 μΩ · cm.

  The resistivity 4.8 μΩ · cm of the obtained fired product is 1.81 times that of the metal aluminum (bulk) resistivity of 2.655 μΩ · cm (20 ° C.).

  The conductive metal thick film as the fired product was clearly different from the conventional product in that it was bulky compared to the conventional product.

  The “conductive metal thick film forming material” of the present invention, for example, the copper thick film forming material according to the present invention can be suitably used for forming a copper thick film without voids, and voids are formed inside the fired film. Therefore, the bulk copper thick film contributes to the improvement of reliability as a conductive material or a bonding material. Further, the material for forming a silver thick film according to the present invention can be suitably used for forming a silver thick film without voids, no voids remain in the fired film, and the bulk silver thick film is Contributes to improving the reliability of conductive materials and bonding materials.

Claims (25)

A conductive metal thick film forming material used for forming a conductive metal thick film,
The conductive metal thick film forming material includes metal particles and metal nanoparticles used for forming a conductive metal thick film, and an organic substance, and is a material exhibiting an applicable fluidity,
The metal particles contained in the conductive metal thick film forming material exhibiting the flowability that can be applied are selected from the group consisting of copper particles, silver particles, and aluminum particles,
The outer shape of the metal particles is substantially spherical and / or scaly,
The average particle size of the metal particles is selected in the range of 0.3 μm to 20 μm;
The metal nanoparticles contained in the conductive metal thick film-forming material exhibiting the flowability that can be applied are selected from copper nanoparticles, silver nanoparticles, and gold nanoparticles,
The average particle diameter of the metal nanoparticles is selected in a range of 1 nm or more and not exceeding 100 nm,
A compound having an amino group (—NH ₂ ) or a compound having a carboxyl group (—COOH) as an atomic group that can be used for forming a non-covalent intermolecular bond with the metal on the surface of the metal nanoparticles. A coating molecular layer is formed,
Provided that the compound having an amino group (—NH ₂ ) is different from (dialkylamino) alkylamine;
The organic substance contained in the conductive metal thick film forming material exhibiting the flowability that can be applied is added to the mixture of the metal particles and the metal nanoparticles to adjust the viscosity to be suitable for printing. Including organic solvents,
As the organic solvent, a high-polarity nonpolar organic solvent having a boiling point Tbp-solvent in the range of 150 ° C. to 300 ° C. is adopted;
The total volume (content) of the metal particles and the metal nanoparticles contained in the conductive metal thick film forming material exhibiting the fluidity that can be applied is the conductive metal exhibiting the fluidity that can be applied. Selected in the range of 30 vol% to 80 vol% of the total thickness of the thick film forming material;
The ratio (volume) of the sum of the volume (content) of the metal particles and the volume (content) of the metal nanoparticles contained in the conductive metal thick film forming material exhibiting fluidity that can be applied % Ratio); the total volume (content) of the metal particles: the total volume (content) of the metal nanoparticles is:
The total volume (content) of the metal nanoparticles is selected in the range of 5 to 90 with respect to the total volume (content) of the metal particles: 100;
The liquid viscosity at 25 ° C. of the conductive metal thick film-forming material exhibiting fluidity that can be applied is selected at least in the range of 50 Pa · s to 200 Pa · s;
The conductive metal thick film forming material exhibiting the flowability that can be applied,
In the formation of the following conductive metal thick film, it can be used for forming the conductive metal thick film by the method using the conductive metal thick film forming material;
In the formation of the conductive metal thick film, the method of using the conductive metal thick film forming material,
After applying the conductive metal thick film forming material on a substrate and forming a coating film of the conductive metal thick film forming material,
By subjecting the coating film to a firing process by irradiating microwave plasma in a reducing atmosphere,
A conductive metal thick film forming material comprising a step of forming a bulk conductive metal thick film from metal particles and metal nanoparticles contained in the coating film. The metal particles are copper particles,
The material according to claim 1, wherein the metal nanoparticles are copper nanoparticles. The metal particles are silver particles,
The material according to claim 1, wherein the metal nanoparticles are silver nanoparticles. The metal particles are aluminum particles,
The material according to claim 1, wherein the metal nanoparticles are silver nanoparticles. The metal nanoparticles are
The material according to any one of claims 1 to 4, wherein the average particle size is selected in the range of 5 nm to 100 nm. The metal nanoparticles are
The material according to any one of claims 1 to 5, wherein the average particle size is selected in the range of 10 nm to 100 nm. The metal particles are
The material according to any one of claims 1 to 6, wherein the average particle size is selected in the range of 0.4 µm to 10 µm. As the compound having an amino group, used for forming the coating agent molecular layer,
The material according to claim 1, wherein one or more amine compounds having one or more terminal amino groups are selected. 9. The material according to claim 8, wherein the one or more amine compounds having one or more terminal amino groups contain an alkylamine. 8. The compound according to claim 1, wherein the one or more compounds having a carboxyl group used for forming the coating agent molecular layer include an aliphatic carboxylic acid having 8 to 20 carbon atoms. The materials described. The ratio (volume) of the sum of the volume (content) of the metal particles and the volume (content) of the metal nanoparticles contained in the conductive metal thick film forming material exhibiting fluidity that can be applied % Ratio); the total volume (content) of the metal particles: the total volume (content) of the metal nanoparticles is:
The total volume (content) of the metal nanoparticles is selected in a range of 7 to 80 with respect to the total volume (content) of the metal particles: 100. The material as described in any one of -10. The total volume (content) of the metal particles and the metal nanoparticles contained in the conductive metal thick film forming material exhibiting the fluidity that can be applied is the conductive metal exhibiting the fluidity that can be applied. The material according to any one of claims 1 to 11, wherein the material is selected in a range of 40% by volume to 70% by volume of the total volume forming material. The organic solvent added to the material for forming a conductive metal thick film exhibiting fluidity that can be applied is a high-boiling nonpolar organic solvent having a boiling point Tbp-solvent of 180 ° C. to 280 ° C. The material according to claim 1, wherein the material is a material. In the conductive metal thick film forming material showing fluidity that can be applied,
14. The resin according to any one of claims 1 to 13, wherein a resin is added in order to improve adhesion with a base material or to impart fluidity after curing. material. The volume ratio of the resin to the organic solvent added in the conductive metal thick film forming material exhibiting fluidity that can be applied: (Vresin / Vsolvent) is 0.65 ≧ (Vresin / Vsolvent) ≧ 0 The material according to claim 14, characterized in that it is selected in the range of. The organic solvent added to the conductive metal thick film-forming material exhibiting the flowability that can be applied is tripropylene glycol, according to any one of claims 1 to 15. Materials described in. A method for forming a conductive metal thick film using the conductive metal thick film forming material according to claim 1,
The method for forming the conductive metal thick film is as follows:
In the formation of the following conductive metal thick film is a method of forming a conductive metal thick film by a method using a conductive metal thick film forming material,
In the formation of the conductive metal thick film, the method of using the conductive metal thick film forming material,
After applying the conductive metal thick film forming material on a substrate and forming a coating film of the conductive metal thick film forming material,
By subjecting the coating film to a firing process by irradiating microwave plasma in a reducing atmosphere,
A method for forming a conductive metal thick film, comprising the step of forming a bulk conductive metal thick film from metal particles and metal nanoparticles contained in a coating film. The conductive metal forming the thick film material is characterized by a conductive metal thick film forming material of any one of claims 2 to 16, a conductive metal thickness of Claim 17 Method for forming a film. In the method of using the conductive metal thick film forming material in the formation of the conductive metal thick film,
When the coating film is subjected to a process of firing by irradiating microwave plasma in a reducing atmosphere,
The frequency of the microwave used to generate the microwave plasma is
The method according to claim 17 or 18 , characterized in that it is selected in the range of 300 MHz to 300 GHz. The frequency of the microwave used to generate the microwave plasma is
The method according to claim 19 , characterized in that it is selected in the range of 3 GHz to 100 GHz. In the method of using the conductive metal thick film forming material in the formation of the conductive metal thick film,
When the coating film is subjected to a process of firing by irradiating microwave plasma in a reducing atmosphere,
21. The method according to claim 19 or 20 , wherein the microwave output used for generating the microwave plasma is selected in the range of 300W to 3kW. In the method of using the conductive metal thick film forming material in the formation of the conductive metal thick film,
When the coating film is subjected to a process of firing by irradiating microwave plasma in a reducing atmosphere,
The method according to any one of claims 17 to 21 , wherein the irradiation time of the microwave plasma is selected in a range of 30 seconds to 30 minutes. The method according to claim 22 , wherein the microwave plasma irradiation time is selected in a range of 1 minute to 15 minutes. In the method of using the conductive metal thick film forming material in the formation of the conductive metal thick film,
When the coating film is subjected to a process of firing by irradiating microwave plasma in a reducing atmosphere,
The method according to any one of claims 19 to 23 , wherein the reducing atmosphere is hydrogen or a mixture of hydrogen and an inert gas selected from nitrogen, helium, and argon. In the method of using the conductive metal thick film forming material in the formation of the conductive metal thick film,
After applying a conductive metal thick film forming material on the substrate and forming a conductive metal thick film forming material coating film,
The process of subjecting the coating film to a firing process by irradiating microwave plasma in a reducing atmosphere,
After the step of applying the conductive metal thick film forming material on the substrate,
Drying the coating film of the conductive metal thick film forming material to remove the organic solvent,
Removing the remaining organic matter under reduced pressure;
The method according to any one of claims 17 to 24 , comprising a step of firing by irradiating microwave plasma in a reducing atmosphere.