JP6722679B2 - Conductive paste - Google Patents

Description

The present invention relates to a conductive paste which can be suitably used for joining a chip-type electronic component to a printed wiring board, for example.

For a long time, solder has been used as a bonding material for surface-mounting electronic components on a substrate.

In recent years, a technique for joining objects to be joined by interposing an electrically conductive paste containing fine particles of a metal such as silver between the objects to be joined and sintering the metal in the joining material instead of soldering Is being developed.

When a large void is present in the joint portion formed by the joint material, cracks may be generated in the joint portion from the void and the reliability of the joint may be deteriorated when repeatedly subjected to a thermal cycle.

Patent Document 1 discloses, as a bonding material capable of suppressing the occurrence of voids, silver fine particles having an average primary particle diameter of 1 to 50 nm and coated with an organic compound having 8 or less carbon atoms, such as hexanoic acid, and an organic material such as oleic acid. Compound-coated silver particles having an average primary particle diameter of 0.5 to 4 μm, a solvent consisting of 3 to 7% by mass of alcohol and 0.3 to 1% by mass of triol, and 0.5 to 2% by mass. Silver containing a dispersant comprising an acid dispersant and 0.01 to 0.1% by mass of a phosphate ester dispersant, and 0.01 to 0.1% by mass of a sintering aid such as diglycolic acid. In a bonding material made of a paste, the content of silver fine particles is 5 to 30% by mass, the content of silver particles is 60 to 90% by mass, and the total content of silver fine particles and silver particles is 90% by mass or more. Agents are disclosed.

Patent Document 2 discloses a conductive material containing a micro or sub-micro size silver flake having a tap density of 4.6 g/cc or more and a solvent that dissolves any fatty acid lubricant or surfactant present on the silver surface. A composition is disclosed. The challenge in this document is to provide enhanced conductivity of high power devices as a replacement for solder in conventional semiconductor assembly, with typical conductive adhesive compositions containing conventional silver flakes and adhesive resins and pressure. To provide an alternative to compositions containing only nanosilver that need to be sintered.

Patent Document 3 discloses a paste containing metal particles having a coating containing at least one compound selected from the group consisting of fatty acids, fatty acid salts and fatty acid esters, and at least one aliphatic hydrocarbon compound. It Said at least one coating compound comprises saturated fatty acids having 8 to 28 carbon atoms, salts of saturated fatty acids having 8 to 28 carbon atoms, esters of saturated fatty acids having 8 to 28 carbon atoms, and these Can be selected from the group consisting of mixtures of The problem in this document is to provide a sintering process that allows electronic components to be stably bonded to a substrate, the process temperature being below 250° C., and a paste that can be used for this process. is there.

JP, 2005-004105, A Japanese Patent Publication No. 2014-512634 JP, 2012-084514, A

According to the study by the present inventor, when a relatively small chip having a chip size of about 2 mm or less is bonded to a substrate with a conventional silver paste, it is possible to suppress the generation of a large void at the bonding portion. When bonding a relatively large chip having a size of about 10 mm, it may be difficult to suppress the generation of a large void in the bonded portion with the conventional silver paste.

An object of the present invention is to provide a conductive paste capable of suppressing the generation of large voids in a bonded portion even when bonding a relatively large chip to a substrate.

According to one aspect of the invention,
Metal powder having an average particle size of 0.5 μm or more and 10 μm or less,
Metal particles,
A coating agent coating the surface of the metal fine particles,
A solvent in which the metal powder and the metal fine particles are dispersed,
A conductive paste containing
The average particle diameter of the metal fine particles including the coating agent adhered to the surface of the metal fine particles is 1 nm or more and 50 nm or less,
The coating material is a compound having 6 to 20 carbon atoms and a carboxyl structure,
The solvent is Ri compound der having at least one member selected from the group consisting of hydroxyl structure, ester structure and ether structure,
The metal powder includes spherical metal powder and flaky metal powder,
The mass ratio of the spherical metal powder and the flake-shaped metal powder (spherical metal powder:flake-shaped metal powder) is in the range of 90:10 to 15:85,
A conductive paste is provided.

According to another aspect of the present invention, there is provided a substrate having a layer made of a sintered body of the conductive paste.

According to the present invention, there is provided a conductive paste capable of suppressing the generation of large voids in a bonded portion even when a relatively large chip is bonded to a substrate.

The conductive paste according to the present invention,
Metal powder having an average particle size of 0.5 μm or more and 10 μm or less,
Metal particles,
A coating agent coating the surface of the metal fine particles,
A solvent in which the metal powder and the metal fine particles are dispersed,
including.

The average particle size of the metal fine particles including the coating agent attached to the surface of the metal fine particles is 1 nm or more and 50 nm or less.

In addition, in the present invention, when referring to the amount (mass or content) of the metal fine particles, it means the amount of only the metal fine particles (hence not including the coating agent) unless otherwise specified. On the other hand, when referring to the particle size of the metal fine particles, unless otherwise specified, it means the particle size including the coating agent adhered to the surface of the metal fine particles. Further, the average particle diameter means a median diameter whose cumulative value of the volume-based existence ratio is 50%.

[Metal component]
As the metal component in the conductive paste, metal powder having an average particle size of 0.5 μm or more and 10 μm or less and metal fine particles having an average particle size of 1 nm or more and 50 nm or less are used. The average particle size of the metal powder is preferably 0.5 to 2 μm. The average particle size of the metal fine particles is preferably 1 to 30 nm. By using such metal powder and metal fine particles, it is possible to suppress the generation of large voids in the joint portion formed of the sintered body of the conductive paste.

From the viewpoint of conductivity and availability, the metal powder preferably comprises at least one selected from the group consisting of silver, copper, aluminum and nickel.

The shape of the metal powder can be appropriately selected, but the metal powder preferably contains spherical metal powder and flake-shaped metal powder. The metal powder may be composed of spherical metal powder and flake-shaped metal powder. The mass ratio of the spherical metal powder to the flake-shaped metal powder (spherical metal powder:flake-shaped metal powder) is preferably in the range of 90:10 to 15:85. Using spherical metal powder and flake-shaped metal powder, more preferably by using in the above ratio, the organic components that volatilize during firing become easy to escape, it is possible to more reliably suppress the occurrence of large voids in the joint. You can

The spherical shape and flake shape of the metal powder are defined based on the aspect ratio. The spherical shape of the metal powder means that the aspect ratio is less than 1.1, and the metal powder has the flake shape. "Yes" means that the aspect ratio is 1.1 or more. The aspect ratio is calculated by [average long diameter (μm)]/[average thickness (μm)] of the metal powder. The average major axis and average thickness of the spherical metal powder are obtained by observing an observation image with an appropriate magnification (around 2000 times) with a scanning electron microscope, and measuring the major axis and thickness of 30 or more particles in the observation image. It is possible to directly observe and use the value obtained as the average value. On the other hand, the average major axis and the average thickness of the flake-shaped metal powder are determined by first manufacturing a sample in which flake silver powder is hardened with an epoxy resin, and then observing the cross section of the sample directly with a scanning electron microscope (magnification: 10,000 times). It can be determined by dividing the total of 30 or more major axes and thicknesses of silver particles in the visual field by the number of flaky metal powders.

From the viewpoint of conductivity, the metal fine particles are preferably composed of at least one selected from the group consisting of silver, copper, palladium and nickel.

The metal forming the metal powder and the metal forming the metal fine particles may be the same or different.

[Coating agent]
The metal fine particles are coated with a coating agent for the purpose of suppressing aggregation of the metal fine particles. This coating agent is a compound having 6 to 20 carbon atoms and a carboxyl structure, particularly an organic compound. This compound is capable of strongly adhering to the surface of metal fine particles and is decomposed in the temperature range of 200°C to 400°C where the conductive paste is used, while it is sufficiently stable at room temperature (separated from metal fine particles).・It is hard to volatilize). The preferred carbon number is 6 or more and 18 or less. Further, as the coating agent, it is preferable to use a carboxylic acid having 6 to 8 carbon atoms and a carboxylic acid having 16 to 18 carbon atoms in combination.

The coating agent may include only one carboxyl group in the molecular structure, or may include two or more carboxyl groups. Further, the coating agent may contain, in the molecular structure, one or more groups selected from the group consisting of an ester group, an ether group and a hydroxyl group, in addition to the carboxyl group. As the coating agent, monoethyl maleate or ricinoleic acid is preferable. As the coating agent, these compounds may be used alone or in combination of two or more kinds.

The compound having a carboxyl group used as a coating agent may have one or more unsaturated bonds in the structure, or may not have an unsaturated bond.

〔solvent〕
A solvent is used to disperse the metal powder and the metal fine particles. The solvent is a compound having at least one selected from the group consisting of a hydroxyl structure, an ester structure and an ether structure, particularly an organic compound.

The solvent preferably contains one or more hydroxyl groups in the molecular structure, and may contain an ester group and/or an ether group in addition to the hydroxyl group.

When the boiling point of the solvent (at 1 atm) is preferably in the range of 200 to 400° C., more preferably in the range of 220 to 320° C., the generation of large voids at the time of firing is maintained while maintaining the stability of the conductive paste. It can be surely suppressed.

As the solvent, diethylene glycol monobutyl ether (boiling point 230° C.), diethylene glycol monohexyl ether (boiling point 258° C.), diethylene glycol monooctyl ether (boiling point 286° C.), 2-ethyl-1,3-hexanediol (boiling point 244° C.), diethylene glycol Monobutyl ether acetate (boiling point 247°C), 2,2,4-trimethyl-1,3-pentanediol (boiling point 255°C) and the like are preferable. These solvents may be used alone or in combination of two or more.

〔composition〕
The content of the metal component in the conductive paste (the total content of the metal powder and the metal fine particles) is preferably more than 87% by mass and less than 98% by mass, more preferably 88% by mass or more and 97% by mass or less. More preferably, it is 90% by mass or more and 96% by mass or less. This is because it is possible to reduce the amount of organic components to be volatilized during firing, and it is possible to more reliably suppress the generation of large voids at the joint. Further, the content of the metal component in the conductive paste is also related to the viscosity of the conductive paste, which will be described in detail later, and the upper limit of the above range also takes the viscosity into consideration.

The ratio of the amount of the coating material to the total amount of the metal fine particles and the coating material is preferably more than 4% by mass and less than 13% by mass, more preferably 5% by mass or more and 12% by mass or less. More preferably, it is 5% by mass or more and 9% by mass or less. This is because it is possible to reduce the amount of organic components to be volatilized during firing, and it is possible to more reliably suppress the generation of large voids at the joint.

The conductive paste may consist of metal powder, fine metal particles, a coating agent and a solvent. Alternatively, the conductive paste may include other components other than these.

The preferable mass ratio of the metal powder and the metal fine particles is 97:3 to 80:20, more preferably 93:7 to 87:13.

From the viewpoint of preventing the resistivity of the sintered body of the conductive paste from increasing due to the organic components remaining inside the fired film, the conductive paste is a thermosetting resin formed by polymerization. It is preferable not to contain a resin component.

[Viscosity of conductive paste]
The viscosity of the conductive paste (value measured with an E-type viscometer at 10 rpm and 25° C.) is preferably 3 Pa·s or more and 150 Pa·s or less, more preferably 10 Pa·s or more and 100 Pa·s or less. is there. This makes it possible to obtain a paste suitable for metal mask printing and dispense printing.

[Use of conductive paste]
It is possible to sinter the conductive paste by applying the conductive paste onto a substrate, particularly by a printing method such as metal mask printing or dispenser printing, and then firing it appropriately. As the method, a conventionally known method in the field of conductive paste can be used. The layer made of the sintered body thus formed on the substrate can be used as a wiring or an electrode. In addition, the conductive paste can be used as a bonding material by applying the conductive paste to the substrate by the same method as described above, placing an object such as an electronic component in contact with the coating film, and baking the applied material. Since the resin component (organic component) does not remain inside the fired film, the conductive paste containing no resin can be fired at a relatively low temperature. As the substrate, for example, an electronic circuit substrate, especially a printed circuit board can be appropriately used.

As described in detail below, after silver fine particles were prepared, a conductive paste was prepared using the silver fine particles.

[Example 1]
<Preparation of fine silver particles>
・Process 1a
To a 2 L beaker, 54.25 g of powdered silver oxide (manufactured by Toyo Chemical Industry, special grade of silver oxide, particle size distribution of 30 μm or less, average particle size of 6 μm) and 225 g of methylcyclohexane (a non-polar hydrocarbon solvent having a boiling point of 101° C.) were added and stirred. After that, 22.8 g of formic acid was added over 30 seconds and the mixture was stirred.

・Process 1b
When the heat generated by the generation of silver formate subsided and the liquid temperature reached 30°C, 4.35 g of oleylamine (primary amine, molecular weight 267.49), dibutylamine (secondary amine, molecular weight 129.24) 64 g, methylcyclohexane 40 g was added at the same time to carry out a decomposing reduction reaction. The liquid temperature rose to 58°C. The stirring was stopped when the liquid temperature reached 40°C or lower.

・Process 1c
The obtained dark blue dispersion liquid was transferred to a 1 L eggplant type flask, and methylcyclohexane as a reaction solvent was distilled off under the conditions of 40° C. and 50 hPa using an evaporator (trade name: N-1100S, manufactured by Tokyo Scientific Instruments). did. A slurry-like residue containing silver particles was obtained.

・Process 1d
200 g of methanol was added to the residue after demethylcyclohexane, and the mixture was stirred for 3 minutes. Aggregation of silver fine particles occurred when methanol was added, and silver fine particles coated with primary amine and secondary amine were precipitated without being dispersed in methanol. A considerable amount of excess components such as formic acid and amine, or salts containing them are dissolved in methanol. Then, the supernatant layer was removed by decantation (first washing). Next, similarly, 125 g of methanol was added and stirred for 3 minutes, and the supernatant layer was removed by decantation (second washing). Similarly, 10 g of methanol was added and stirred for 3 minutes, and the supernatant layer was removed by decantation (3rd washing), and the washing step was completed.

・Process 1e
To the residue obtained by washing with methanol obtained in step 1d, 125 g of methanol and 3.0 g of ricinoleic acid (organic acid used as a protective agent having an affinity for a polar solvent, that is, a coating agent) were added and the mixture was added at 40° C. for 15 minutes. Stirring was performed. At this stage, the silver fine particles are not completely dispersed in methanol but are precipitated in methanol. After removing the methanol by decantation, 75 g of methanol was added and washing was performed by stirring for 3 minutes, and the methanol was removed by decantation. To the obtained residue, 25 g of methanol and 5 g of monoethyl maleate (organic acid used as a protective agent having an affinity for a polar solvent, that is, a coating agent) were added, and the mixture was stirred at 40° C. for 15 minutes.

・Process 1f
100 g of hexane was added to the obtained mixture of silver fine particles and methanol, and the mixture was stirred for 3 minutes. Since these fine particles have an affinity for polar solvents, they are aggregated and precipitated by adding hexane, which is a hydrocarbon solvent. The fine particles were washed by removing the mixed layer of methanol and hexane by decantation (first washing). After removing the mixed layer of methanol and hexane by decantation, 100 g of hexane was added and stirred for 3 minutes, and hexane was removed by decantation to wash the fine particles (second washing). To the obtained residue, 100 g of acetone was added and stirred for 3 minutes, and acetone was removed by decantation (third washing). 50 g of hexane was added to the obtained residue, the mixture was stirred for 3 minutes, and the hexane was removed by decantation (fourth washing) to complete the washing. A part of the residue after cleaning, which was obtained by removing the cleaning solvent (silver fine particles+coating agent), was subjected to thermal analysis. As a result, the ratio of silver fine particles to the total of the silver fine particles and the coating agent was 93.0% by mass.

・Process 1g
125 g of isopropanol (IPA) was added to the obtained silver fine particles (residue obtained from step 1f) to obtain an IPA dispersion liquid (dispersion liquid in which silver fine particles coated with a coating agent were dispersed in IPA). A small amount of methanol, hexane, and acetone used in the washing step are mixed in this IPA dispersion liquid. Those solvents were selectively removed using a difference in vapor pressure under the conditions of 40° C. and 120 hPa using an evaporator. The IPA dispersion liquid was filtered through a 0.5 μm glass filter (manufactured by Advantech) to remove a small amount of aggregates contained in the dispersion liquid. The concentration of silver contained in the IPA dispersion liquid (175.1 g) (mass ratio of silver fine particles to the entire dispersion liquid) was 27.4% by mass (silver yield: 95% by mass).

・Process 1h
Of 175.1 g of the obtained IPA dispersion of fine silver particles (dispersion obtained from step 1 g), 73 g was placed in a 300 ml eggplant flask, and 5.0 g of diethylene glycol monobutyl ether (KH Neochem) was added to the evaporator. Was used to remove IPA under the conditions of 60° C. and 30 hPa. As a result, a dispersion of silver fine particles in diethylene glycol monobutyl ether (25.0 g) was obtained, and the silver concentration was measured to be 80.0% by mass. The average particle size of the silver fine particles was 15 nm.

<Creating conductive paste>
・Process 1i
Of 25.0 g of the silver particle dispersion obtained in step 1h, 11.63 g (corresponding to the total amount of the silver particles and the coating agent contained in the conductive paste and a part of the solvent contained in the conductive paste) ) Was placed in a polypropylene container. 4.67 g of diethylene glycol monobutyl ether (manufactured by KH Neochem) was added thereto (since the silver fine particle dispersion obtained in step 1h contains 1.63 g of solvent, the total amount of the solvent contained in the conductive paste is 1.67 g. A small amount (63 g) was added, and the mixture was mixed for 30 seconds with a stirring and defoaming device (Kurabo Co., Ltd., trade name: KK-V300, rotation: 720 rpm, revolution: 935 rpm). There, spherical silver powder (manufactured by DOWA Electronics Co., Ltd., trade name: Ag-2-1C, average particle size 1.0 μm), flake-shaped silver powder: (manufactured by Tokoriki Head Office, trade name: TC-506C, average particle size 3. 6 μm) and 41.85 g each were added and mixed for 60 seconds with a stirring and defoaming device to obtain a conductive silver paste. The silver concentration of the obtained conductive silver paste was measured and found to be 93.2% by mass.

The average particle size of the silver fine particles was measured by a Nanotrac particle size analyzer (manufactured by Nikkiso, trade name: UPA-EX 1.50) using a dynamic light scattering method.

<Evaluation of conductive paste>
The following evaluation was performed about the said electroconductive paste.

-Evaluation of voids 100 mg of the conductive paste was dispense-printed on a silver-plated copper substrate, and a silicon chip (with gold plating, 10 mm□) was mounted so that the paste film thickness was 100 μm. Then, firing was performed under the following temperature conditions using a firing furnace (manufactured by ESPEC, trade name: PHH-101M).

Temperature conditions:
The temperature is raised from room temperature to 120° C. at a temperature rising rate of 10° C./minute, and held at 120° C. for 30 minutes, then to 250° C. at a temperature rising rate of 10° C./minute, and held at 250° C. for 60 minutes.

After cutting and polishing the central portion of the fired 10 mm□ chip bonded sample, voids were evaluated using SEM (Hitachi High-Technologies Corporation, trade name: S3400N scanning electron microscope).

Of the voids observed on the cut surface of the bonded sample, the length of the largest void in the major axis direction is shown in Table 1 as the void size (μm). When the length of the largest void in the major axis direction was less than 20 μm, “−” was shown in the column of void size in Table 1.

-Viscosity measurement Using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd., trade name: TV-25), viscosity was measured at a rotation speed of 10 rpm and 20°C.

Table 1 shows these evaluation results together with the manufacturing conditions of the conductive paste.

Examples 2 to 10 will be described below, but the amount of the coating agent is changed in these examples. Table 1 also shows manufacturing conditions and evaluation results of the conductive pastes of Examples 2 to 10.

[Example 2]
In step 1i, the amount of diethylene glycol monobutyl ether to be blended was changed to 3.99 g, and following addition of diethylene glycol monobutyl ether, 0.34 g of ricinoleic acid and 0.34 g of monoethyl maleate were further blended, followed by degassing with stirring. A conductive silver paste was produced and evaluated in the same manner as in Example 1 except that the paste was mixed in the apparatus.

[Example 3]
In step 1i, the amount of diethylene glycol monobutyl ether to be blended was changed to 4.10 g, and following addition of diethylene glycol monobutyl ether, 0.285 g of ricinoleic acid and 0.285 g of monoethyl maleate were further blended, followed by degassing with stirring. A conductive silver paste was produced and evaluated in the same manner as in Example 1 except that the paste was mixed in the apparatus.

[Example 4]
In step 1i, the amount of diethylene glycol monobutyl ether to be blended was changed to 4.22 g, and following addition of diethylene glycol monobutyl ether, 0.225 g of ricinoleic acid and 0.225 g of monoethyl maleate were further blended, followed by degassing with stirring. A conductive silver paste was produced and evaluated in the same manner as in Example 1 except that the paste was mixed in the apparatus.

[Example 5]
In step 1i, the amount of diethylene glycol monobutyl ether to be blended was changed to 4.34 g, and following addition of diethylene glycol monobutyl ether, 0.165 g of ricinoleic acid and 0.165 g of monoethyl maleate were further blended and then degassed by stirring. A conductive silver paste was produced and evaluated in the same manner as in Example 1 except that the paste was mixed in the apparatus.

[Example 6]
In step 1i, the amount of diethylene glycol monobutyl ether to be blended was changed to 4.45 g, and following addition of diethylene glycol monobutyl ether, 0.11 g of ricinoleic acid and 0.11 g of monoethyl maleate were further blended, followed by degassing with stirring. A conductive silver paste was produced and evaluated in the same manner as in Example 1 except that the paste was mixed in the apparatus.

[Example 7]
In step 1i, the amount of diethylene glycol monobutyl ether to be blended was changed to 4.56 g, and following addition of diethylene glycol monobutyl ether, 0.055 g of ricinoleic acid and 0.055 g of monoethyl maleate were further blended and stirred for defoaming. A conductive silver paste was produced and evaluated in the same manner as in Example 1 except that the paste was mixed in the apparatus.

[Example 8]
In this example, a conductive silver paste was produced and evaluated in the same manner as in Example 1 except for the points described below.

-Change of Step 1f To the residue obtained by the fourth washing of Step 1f, 100 g of acetone was further added and stirred for 3 minutes, and acetone was removed by decantation (fifth washing). 50 g of hexane was added to the obtained residue, the mixture was stirred for 3 minutes, and hexane was removed by decantation (sixth washing) to complete the washing. When the residue obtained by removing the washing solvent from the residue after washing (silver fine particles+coating agent) was subjected to thermal analysis, the ratio of silver fine particles to the total of the silver fine particles and the coating agent was 96.0% by mass.

-Modification of Step 1i In Step 1i, the amount of diethylene glycol monobutyl ether blended was changed to 4.45 g, and 0.11 g of ricinoleic acid and 0.11 g of monoethyl maleate were further blended following the addition of ethylene glycol monobutyl ether. Then, the mixture was mixed with a stirring defoaming device.

The concentration of silver contained in the IPA dispersion liquid (175.1 g) obtained in step 1 g (mass ratio of silver fine particles to the entire dispersion liquid) was 27.4% by mass (silver yield: 95% by mass). )Met. In addition, IPA was removed from the silver particle dispersion liquid obtained in step 1g to obtain silver particles. As a result of thermal analysis of this, the ratio of the silver solid content in the silver particles (including the coating agent) (the ratio of the silver particles to the total amount of the silver particles and the coating agent) was 96.0% by mass.

The silver concentration in the diethylene glycol monobutyl ether dispersion liquid (25.0 g) of the silver fine particles obtained in step 1h was measured and found to be 80.0% by mass. The average particle size of the silver fine particles was 15 nm.

[Example 9]
Up to Step 1h, a diethylene glycol monobutyl ether dispersion liquid (25.0 g) of fine silver particles was obtained in the same manner as in Example 8, the amount of diethylene glycol monobutyl ether blended in Step 1i was changed to 4.56 g, and In 1i, the conductive silver was added in the same manner as in Example 1 except that 0.055 g of ricinoleic acid and 0.055 g of monoethyl maleate were further added after the addition of diethylene glycol monobutyl ether and mixed in a stirring defoaming apparatus. A paste was produced and evaluated.

[Example 10]
Other than obtaining diethylene glycol monobutyl ether dispersion liquid (25.0 g) of fine silver particles in the same manner as in Example 8 up to step 1 h, and changing the amount of diethylene glycol monobutyl ether blended in step 1 i to 4.67 g. A conductive silver paste was produced and evaluated in the same manner as in Example 1.

Examples 11 to 16 will be described below, but in these examples, the ratio of spherical silver powder to flake silver powder is changed. Table 2 shows the manufacturing conditions and the evaluation results of the conductive pastes of these Examples, and the data of Example 1 are also shown for convenience.

[Example 11]
A conductive silver paste was produced and evaluated in the same manner as in Example 1 except that the amount of spherical silver powder blended in step 1i was 83.70 g and the flake silver powder was not blended.

[Example 12]
A conductive silver paste was produced and evaluated in the same manner as in Example 1 except that the spherical silver powder blended in step 1i was 79.52 g and the flake silver powder was 4.19 g.

[Example 13]
A conductive silver paste was produced and evaluated in the same manner as in Example 1 except that the spherical silver powder blended in step 1i was 75.33 g and the flake silver powder was 8.37 g.

[Example 14]
A conductive silver paste was produced and evaluated in the same manner as in Example 1 except that the spherical silver powder blended in step 1i was 16.74 g and the flake silver powder was 66.96 g.

[Example 15]
A conductive silver paste was produced and evaluated in the same manner as in Example 1 except that the spherical silver powder blended in step 1i was 12.56 g and the flake silver powder was 71.14 g.

Example 16
A conductive silver paste was produced and evaluated in the same manner as in Example 1 except that the spherical silver powder blended in step 1i was 8.37 g and the flake silver powder was 75.33 g.

Hereinafter, Examples 17 to 22 will be described, but in these examples, the amount of the metal component is changed. Table 3 shows the manufacturing conditions and the evaluation results of the conductive pastes of these examples, and the data of Example 7 is reprinted for convenience.

Example 17
In this example, a conductive silver paste was produced and evaluated in the same manner as in Example 1 except for the points described below.

-Change of Step 1h IPA was removed in the same manner as in Step 1h of Example 1 except that the amount of diethylene glycol monobutyl ether (manufactured by KH Neochem) was changed to 2.0 g in Step 1h. As a result, a diethylene glycol monobutyl ether dispersion liquid (23.5 g) of silver fine particles was obtained, and the silver concentration was measured and found to be 85.0% by mass. The average particle size of the silver fine particles was 15 nm.

-Modification of step 1i Of the diethylene glycol monobutyl ether dispersion liquid of the silver fine particles obtained above, 11.53 g is set aside in a polypropylene container, and diethylene glycol monobutyl ether (KH Neochem) 0.26 g, ricinoleic acid 0.02 g, After blending 0.02 g of monoethyl maleate, the mixture was mixed by a stirring and defoaming apparatus in the same manner as in Step 1i of Example 1. Furthermore, the amount of spherical silver powder added was 44.1 g, and the amount of flake silver powder added was 44.1 g.

[Example 18]
In this example, a conductive silver paste was produced and evaluated in the same manner as in Example 1 except for the points described below.

-Change of Step 1i 12.125 g of the diethylene glycol monobutyl ether dispersion of silver fine particles obtained in Step 1h was set aside in a polypropylene container, 0.545 g of diethylene glycol monobutyl ether (KH Neochem), 0.015 g of ricinoleic acid, and maleic acid. After blending 0.015 g of monoethyl, the mixture was mixed by a stirring and degassing apparatus in the same manner as in Step 1i of Example 1. Further, the amount of spherical silver powder added was 43.65 g, and the amount of flake silver powder added was 43.65 g.

Example 19
In this example, a conductive silver paste was produced and evaluated in the same manner as in Example 1 except for the points described below.

-Change of step 1i 11.25 g of the diethylene glycol monobutyl ether dispersion of silver fine particles obtained in step 1h was set aside in a polypropylene container, and diethylene glycol monobutyl ether (KH Neochem) was 7.64 g, ricinoleic acid 0.055 g, and maleic acid. After blending 0.055 g of monoethyl, the mixture was mixed by a stirring and defoaming apparatus in the same manner as in Step 1i of Example 1. Further, the amount of spherical silver powder added was 40.50 g, and the amount of flake silver powder added was 40.50 g.

Example 20
In this example, a conductive silver paste was produced and evaluated in the same manner as in Example 1 except for the points described below.

-Change of Step 1i 11.25 g of the diethylene glycol monobutyl ether dispersion of silver fine particles obtained in Step 1h was set aside in a polypropylene container, 8.67 g of diethylene glycol monobutyl ether (KH Neochem), 0.055 g of ricinoleic acid, and maleic acid. After blending 0.055 g of monoethyl, the mixture was mixed by a stirring and defoaming apparatus in the same manner as in Step 1i of Example 1. Furthermore, the amount of spherical silver powder added was 40.05 g, and the amount of flake silver powder added was 40.05 g.

Example 21
In this example, a conductive silver paste was produced and evaluated in the same manner as in Example 1 except for the points described below.

-Modification of step 1i 12.13 g of the diethylene glycol monobutyl ether dispersion of silver fine particles obtained in step 1h was set aside in a polypropylene container, and 9.69 g of diethylene glycol monobutyl ether, 0.055 g of ricinoleic acid and 0.055 g of monoethyl maleate were added. After compounding, the mixture was mixed by a stirring and defoaming device in the same manner as in Step 1i of Example 1. Further, the amount of spherical silver powder added was 39.60 g, and the amount of flake silver powder added was 39.60 g.

Example 22
In this example, a conductive silver paste was produced and evaluated in the same manner as in Example 1 except for the points described below.

-Change of Step 1i 12.13 g of the diethylene glycol monobutyl ether dispersion of silver fine particles obtained in Step 1h was set aside in a polypropylene container, and 10.72 g of diethylene glycol monobutyl ether, 0.055 g of ricinoleic acid, and 0.055 g of monoethyl maleate were added. After compounding, the mixture was mixed by a stirring and defoaming device in the same manner as in Step 1i of Example 1. Further, the amount of spherical silver powder added was 39.15 g, and the amount of flake silver powder added was 39.15 g.

Example 23 will be described below, but the type of solvent was changed in this example.

[Example 23]
A conductive silver paste was produced and evaluated in the same manner as in Example 1 except that the type of solvent used in steps 1h and 1i was changed from diethylene glycol monobutyl ether to 2-ethyl-1,3-hexanediol.

Table 4 shows the manufacturing conditions and evaluation results of the conductive paste of this example. For the sake of convenience, the data according to Example 1 are shown in Table 4 again.

Examples 24 and 25 will be described below, but in these examples, only one of ricinoleic acid and monoethyl maleate is used as a coating agent.

Example 24
In this example, only ricinoleic acid was used as the coating agent. Specifically, a conductive silver paste was produced and evaluated in the same manner as in Example 1 except for the following points.

-In step 1e, 5 g of ricinoleic acid was used instead of 5 g of monoethyl maleate.

-The following operation was performed instead of steps 1g, 1h, and 1i.
The solvent in the silver fine particles (residue) obtained from step 1f was removed under the conditions of 40° C. and 120 hPa using an evaporator to obtain paste-like silver fine particles (53.30 g). When the silver concentration contained in it was measured, it was 90.0 mass% (silver yield: 95 mass %). The average particle size of the silver fine particles was 15 nm.

Out of 53.30 g of the obtained silver fine particles, 10.33 g (corresponding to the total amount of the silver fine particles contained in the conductive paste and the coating agent) was placed in a polypropylene container, and diethylene glycol monobutyl ether (made by KH Neochem was added thereto. 5.97 g) was added and mixed for 30 seconds with a stirring and defoaming device (Kurabo Co., Ltd., trade name: KK-V300, rotation: 720 rpm, revolution: 935 rpm). 41.85 g of the same spherical silver powder and flaky silver powder as in Example 1 were added thereto and mixed for 60 seconds with a stirring and defoaming device to obtain a conductive silver paste. When the silver concentration of the obtained conductive silver paste was measured, it was 93.1% by mass.

Table 5 shows the manufacturing conditions and evaluation results of this example. Table 5 also shows the manufacturing conditions and the evaluation results of the conductive paste of Example 25.

Example 25
In Example 26, only monoethyl maleate was used as the coating agent. Specifically, a conductive silver paste was produced and evaluated in the same manner as in Example 1 except for the following points.

-In step 1e, 3 g of monoethyl maleate was used instead of 3 g of ricinoleic acid.

-The following operation was performed instead of steps 1g, 1h, and 1i.
The solvent in the obtained silver fine particle liquid was removed using an evaporator under the conditions of 40° C. and 120 hPa to obtain paste silver fine particles (58.51 g). The concentration of silver contained therein was measured and found to be 82.0% by mass (silver yield: 95% by mass). The average particle size of the silver fine particles was 16 nm.

Out of 58.51 g of the obtained silver fine particles, 11.34 g (corresponding to the total amount of the silver fine particles and the coating agent contained in the conductive paste) was placed in a polypropylene container, and diethylene glycol monobutyl ether (made by KH Neochem was added thereto. ) Was added for 30 seconds with a stirring and defoaming device (Kurabo Co., trade name: KK-V300, rotation: 720 rpm, revolution: 935 rpm). 41.85 g of the same spherical silver powder and flaky silver powder as in Example 1 were added thereto and mixed for 60 seconds with a stirring and defoaming device to obtain a conductive silver paste. The silver concentration of the obtained conductive silver paste was measured and found to be 93.0% by mass.

[Comparative Example 1]
<Preparation of fine silver particles>
・Process 2a
54.25 g of powdered silver oxide (manufactured by Toyo Chemical Industry, special grade of silver oxide, particle size distribution 30 μm or less, average particle size 6 μm) in a 1000 ml beaker, Swaclean 150 (trade name, manufactured by Maruzen Petrochemical, boiling point 150° C., non-polar carbonization) (Hydrogen solvent) 100.3 g, tributylamine 76 g (made by KH Neochem), NAA-35 (trade name, oleic acid, made by NOF) 4.75 g are added, and the internal temperature becomes 75° C. for 1 hour while heating. It was stirred. After the internal temperature reached 75° C., stirring was continued for 1 hour while maintaining the temperature.

・Process 2b
After stirring for 1 hour, 5.4 g of dibutylaminopropylamine (manufactured by KH Neochem) was added, and stirring was continued. When it was confirmed that the internal temperature had risen from 75°C, heating was stopped and stirring was continued. It was confirmed that the internal temperature reached 125° C. by the decomposable reduction reaction of silver oleate, and further cooled with stirring until the internal temperature reached 50° C.

・Process 2c
180 g of methanol and 1.8 g of water were added to the obtained dark blue dispersion liquid, and after stirring, the supernatant layer was removed by decantation. 180 g of methanol was added for the second time and 100 g for the third time, respectively, and the particles were washed in the same manner to obtain a slurry-like residue. To the obtained residue, 80 g of heptane and 7.5 g of dibutylaminopropylamine were added and stirred. After standing, the upper methanol layer was removed by decantation. Further, 50 g of methanol was added and after stirring, the supernatant layer was removed. Further, 50 g of methanol and 0.5 g of distilled water were added and stirred, and then the supernatant layer was removed.

・Process 2d
The heptane dispersion obtained from step 2c was heated until the internal temperature reached 60°C to remove methanol and water.

・Process 2e
The heptane dispersion obtained in step 2d was filtered through a 0.2 μm PTFE filter (manufactured by Advantech) to remove a small amount of aggregates contained in the dispersion. A part of the heptane dispersion was sampled, and after removing heptane, the amount of organic matter in the silver fine particles (silver fine particles coated with the coating agent) was measured by thermal analysis. As a result, the amount of organic matter was 14.0% by mass. The ratio of the silver solid content (metal component) in the heptane dispersion (94.0 g) was 52.1% by mass.

・Process 2f
Of 94.0 g of the obtained heptane dispersion of fine silver particles (dispersion obtained from step 2f), 50 g was placed in a 300 ml eggplant flask, 6.5 g of tetradecane was added thereto, and the temperature was adjusted to 60° C. using an evaporator. Heptane was removed under the condition of 30 hPa. As a result, a tetradecane dispersion liquid (32.55 g) of fine silver particles was obtained, and the silver concentration was measured and found to be 80.0% by mass.

<Creating conductive paste>
・Process 2g
11.63 g (corresponding to the total amount of the silver particles and the coating agent contained in the conductive paste and a part of the solvent contained in the conductive paste) of 32.55 g of the silver fine particle dispersion obtained in step 2f Was placed in a polypropylene container, and 4.69 g of tetradecane was added thereto (since 0.81 g of the solvent was contained in the silver fine particle dispersion obtained in step 2f, 0% of the total amount of solvent contained in the conductive paste was 0.81 g less amount), and the mixture was mixed for 30 seconds with a stirring and defoaming device (Kurabo Co., trade name: KK-V300, rotation: 720 rpm, revolution: 935 rpm). 41.85 g of the same spherical silver powder and flaky silver powder as in Example 1 were added thereto and mixed for 60 seconds with a stirring and defoaming device to obtain a conductive silver paste. The silver concentration of the obtained conductive silver paste was measured and found to be 93.0% by mass.

The conductive paste thus obtained was evaluated in the same manner as in Example 1. Table 6 shows the manufacturing conditions and evaluation results of this example. In addition, Table 6 also shows manufacturing conditions and evaluation results of the conductive pastes of Comparative Examples 2 to 4.

[Comparative Example 2]
A conductive silver paste was produced and evaluated in the same manner as in Comparative Example 1 except that in Step 2g, the amount of the silver fine particle dispersion liquid to be blended was changed to 10.88 g and the amount of tetradecane to be blended was changed to 10.82 g.

[Comparative Example 3]
In Step 2g, a conductive silver paste was produced and evaluated in the same manner as in Comparative Example 1 except that the spherical silver powder to be blended was 83.7 g and the flaky silver powder was not blended.

[Comparative Example 4]
In step 2g, the amount of the silver fine particle dispersion to be blended was changed to 10.88 g, the amount of tetradecane to be blended was changed to 10.82 g, the spherical silver powder to be blended was 78.3 g, and the flaky silver powder was not blended. A conductive silver paste was produced and evaluated in the same manner as in Example 1.

Claims (8)

Metal powder having an average particle size of 0.5 μm or more and 10 μm or less,
Metal particles,
A coating agent coating the surface of the metal fine particles,
A solvent in which the metal powder and the metal fine particles are dispersed,
A conductive paste containing
The average particle diameter of the metal fine particles including the coating agent adhered to the surface of the metal fine particles is 1 nm or more and 50 nm or less,
The coating material is a compound having 6 to 20 carbon atoms and a carboxyl structure,
The solvent is Ri compound der having at least one member selected from the group consisting of hydroxyl structure, ester structure and ether structure,
The metal powder includes spherical metal powder and flaky metal powder,
The mass ratio of the spherical metal powder and the flake-shaped metal powder (spherical metal powder:flake-shaped metal powder) is in the range of 90:10 to 15:85,
Conductive paste. The ratio of the amount of the coating material to the total amount of the metal fine particles and the coating material is more than 4% by mass and less than 13% by mass.
The conductive paste according to claim 1. The total content of the metal powder and the metal fine particles is more than 87% by mass and less than 98% by mass.
The conductive paste according to claim 1. The boiling point of the solvent is in the range of 200 ℃ or more and 400 ℃ or less,
Claims 1-3 in any one of the description of the conductive paste. The metal powder is at least one selected from the group consisting of silver, copper, aluminum and nickel,
The metal fine particles, at least one selected from the group consisting of silver, copper, palladium and nickel,
Claims 1-4 for any one in the conductive paste according. The viscosity (10 rpm, 25° C.) of the conductive paste is in the range of 3 Pa·s or more and 150 Pa·s or less,
Claim 1-5 any one of the description of the conductive paste. The coating agent comprises a carboxylic acid having 6 to 8 carbon atoms and a carboxylic acid having 16 to 18 carbon atoms,
The conductive paste according to any one of claims 1 to 7 . A layer comprising a sintered body of the conductive paste according to any one of claims 1 to 7 ,
substrate.