JP6577316B2 - Copper powder for conductive paste and method for producing the same - Google Patents

Description

  The present invention relates to a copper powder for conductive paste and a method for manufacturing the same, and more particularly to a copper powder used for a conductive paste for forming a conductive film for forming an electrode or wiring of an electronic component and a method for manufacturing the same.

  Conventionally, in order to form electrodes and wiring of electronic parts by printing methods, etc., conductive paste prepared by blending solvent, resin, dispersant, etc. with conductive metal powder such as silver powder and copper powder has been used. Yes.

  However, although silver powder has a very small volume resistivity and is a good conductive material, it is a noble metal powder, and thus costs are high. On the other hand, copper powder has a low volume resistivity and is a good conductive material. However, since it is easily oxidized, it has poor storage stability (reliability) compared to silver powder.

  In order to solve these problems, silver-coated copper powder in which the surface of the copper powder is coated with silver has been proposed as the metal powder used for the conductive paste (see, for example, Patent Documents 1 to 4).

  In addition, the conductive film that forms the electrode and wiring of the electronic component is often repeatedly bent depending on the use environment, such as the conductive film that forms the antenna for an IC tag for wireless communication. It is desired that the electrical resistance of the conductive film is little increased.

JP 2010-174411 A (paragraph number 0003) JP 2010-077745 (paragraph number 0006) JP 2012-153967 A (paragraph number 0010) Japanese Patent Laying-Open No. 2015-71818 (paragraph number 0008)

  However, when the conventional silver-coated copper powder is used for forming a conductive film, the conductive film is repeatedly bent even if the electrical resistance of the conductive film is high or the initial electrical resistance is low. There was a problem that the electrical resistance increased greatly.

  Therefore, in view of such conventional problems, the present invention has a low electrical resistance of the conductive film when used for the formation of the conductive film, and even when it is repeatedly bent, the electrical resistance of the conductive film is small. It aims at providing the copper powder for electrically conductive paste, and its manufacturing method.

  As a result of intensive studies to solve the above problems, the present inventors have found that dendritic silver-coated copper powder coated with a dendritic copper powder and a flaky copper powder coated with a silver-containing layer. When mixed with flaky silver-coated copper powder, the conductive paste has a low electrical resistance when it is used to form a conductive film, and the electrical resistance of the conductive film does not increase even when it is repeatedly bent. The present inventors have found that copper powder for manufacturing can be produced and have completed the present invention.

  That is, the copper powder for conductive paste according to the present invention includes a dendritic silver-coated copper powder in which a dendritic copper powder is coated with a silver-containing layer, and a flaky silver-coated copper in which a flaky copper powder is coated with a silver-containing layer. It consists of powder mixed with powder.

In the copper powder for conductive paste, the mass ratio of the dendritic silver-coated copper powder and the flaky silver-coated copper powder is preferably 5:95 to 85:15. Moreover, it is preferable that the coating amount of a silver content layer is 1-20 mass% with respect to mixed powder, and it is preferable that a silver content layer is a layer which consists of silver or a silver compound. Moreover, it is preferable that the volume-based cumulative 50% particle diameter (D ₅₀ ) measured by a laser diffraction particle size distribution device of the mixed powder is 3 to ²⁰ μm, and the BET specific surface area is 0.1 to ³ m ² / g. The tap density is preferably 0.5 to 5 g / cc.

  In addition, the method for producing copper powder for conductive paste according to the present invention includes adding a silver ion-containing solution to a copper powder dispersion in which dendritic copper powder and flaky copper powder are dispersed, and dendritic copper powder and flaky copper. A powder mixture of dendritic silver-coated copper powder and flaky silver-coated copper powder is produced by coating the surface of the powder with a silver-containing layer.

  In the method for producing copper powder for conductive paste, the silver ion-containing solution is preferably a silver complex salt solution. Moreover, it is preferable that the mass ratio of the dendritic copper powder and the flaky copper powder in the copper powder dispersion is 5:95 to 85:15. Moreover, it is preferable that the coating amount of a silver content layer is 1-20 mass% with respect to mixed powder, and it is preferable that a silver content layer is a layer which consists of silver or a silver compound.

  According to the present invention, when used for forming a conductive film, a copper powder for conductive paste is produced which has a low electrical resistance of the conductive film and does not increase in electrical resistance of the conductive film even when it is repeatedly bent. Can do.

It is a scanning electron microscope (SEM) photograph (5000 times) of the dendritic copper powder used for the copper powder for electrically conductive pastes by this invention. It is a SEM photograph (5000 times) of the flaky copper powder used for the copper powder for electrically conductive pastes by this invention. It is a SEM photograph (5000 times) of the silver covering copper mixed powder of Example 1. It is a SEM photograph (5000 times) of the silver covering copper mixed powder of Example 2. It is a SEM photograph (5000 times) of the silver covering copper mixed powder of Example 3.

  Embodiments of the copper powder for conductive paste according to the present invention include dendritic silver-coated copper powder in which dendritic copper powder is coated with a silver-containing layer, and flaky silver in which flaky copper powder is coated with a silver-containing layer. It consists of mixed powder with coated copper powder. Thus, when the mixed powder of dendritic silver-coated copper powder and flaky silver-coated copper powder is used in the conductive paste, the number of contacts between the particles of the silver-coated copper powder can be increased, and it has excellent conductivity. A conductive film can be formed.

In this copper powder for conductive paste, the mass ratio of the dendritic silver-coated copper powder and the flaky silver-coated copper powder is preferably 5:95 to 85:15, and is 10:90 to 80:20. Is more preferable. The silver-containing layer is preferably a layer made of silver or a silver compound, and the coating amount of the silver-containing layer is preferably 1 to 20% by mass, and 2 to 15% by mass with respect to the mixed powder. Is more preferable. The volume-based cumulative 50% particle diameter (D ₅₀ ) measured by a laser diffraction particle size distribution device (by the Helos method) of the mixed powder is preferably 3 to 20 μm, and more preferably 5 to 15 μm. BET specific surface area of the mixed powder is preferably from 0.1~3m ² / g, and even more preferably 0.3~1m ² / g. The tap density of the mixed powder is preferably 0.5 to 5 g / cc, more preferably 1 to 3 g / cc.

  Moreover, in embodiment of the manufacturing method of the copper powder for electrically conductive pastes by this invention, dendritic copper powder (as shown in FIG. 1) (dendritic copper powder) and flake-like copper (as shown in FIG. 2) By adding a silver ion-containing solution to the copper powder dispersion in which the powder is dispersed and coating the surface of the dendritic copper powder and flaky copper powder with a silver-containing layer, the dendritic silver-coated copper powder and flaky silver coating A mixed powder of copper powder is produced.

  Since the dendritic copper powder and the flaky copper powder have different specific surface areas, when the silver-coated copper powder is prepared by separately coating with a silver-containing layer, the silver-containing layer becomes thin in the copper powder having a large specific surface area. In copper powder with a small surface area, the silver-containing layer becomes thick, the thickness of each silver-containing layer is easily different, and when the dendritic silver-coated copper powder and flaky silver-coated copper powder after coating with the silver-containing layer are mixed, Each thickness is different, and when used to form a conductive film, the conductivity tends to vary. Moreover, when the dried dendritic copper powder and the flaky copper powder are mixed, energy concentrates on a part of the copper powder, and the shapes of the dendritic copper powder and the flaky copper powder are easily destroyed. Therefore, in the embodiment of the method for producing copper powder for conductive paste according to the present invention, a silver ion-containing solution is added to a copper powder dispersion in which dendritic copper powder and flaky copper powder are dispersed, and dendritic copper powder is added. And coating the surface of the flaky copper powder with a silver-containing layer makes it difficult for the thickness of the silver-containing layer to vary, and maintains the shape of the dendritic copper powder and the flaky copper powder while maintaining the shape of the dendritic copper powder. The surface of the powder and the flaky copper powder can be covered with a silver-containing layer.

  In this method for producing copper powder for conductive paste, the mass ratio of dendritic copper powder and flaky copper powder in the copper powder dispersion is preferably 5:95 to 85:15, and 10:90 to 80. : 20 is more preferable. The silver-containing layer is preferably a layer made of silver or a silver compound, and the coating amount of the silver-containing layer is preferably 1 to 20% by mass, and 2 to 15% by mass with respect to the mixed powder. Is more preferable.

  As a method of coating the surface of dendritic copper powder and flaky copper powder with a silver-containing layer (a coating layer made of silver or a silver compound), a substitution method using a copper-silver substitution reaction or a reduction method using a reducing agent Can be used to deposit silver or a silver compound on the surface of the copper powder, for example, silver or silver compound on the surface of the copper powder while stirring a solution containing the copper powder and the silver or silver compound in a solvent. Or a method of precipitating silver or a silver compound on the surface of a copper powder while mixing and stirring a solution containing silver or a silver compound and an organic substance in a solvent. Etc. can be used.

  As a solvent for the copper powder dispersion and the silver ion-containing solution, water, an organic solvent, or a solvent obtained by mixing these can be used. When using a mixed solvent of water and organic solvent, it is necessary to use an organic solvent that becomes liquid at room temperature (20 to 30 ° C.). The mixing ratio of water and organic solvent depends on the organic solvent used. It can be adjusted appropriately. In addition, as water used as a solvent, distilled water, ion-exchanged water, industrial water, or the like can be used as long as there is no fear that impurities are mixed therein.

  As a raw material for a silver-containing layer (a coating layer made of silver or a silver compound), it is preferable to use silver nitrate having high solubility in water and many organic solvents because silver ions need to be present in the solution. . In order to perform the silver coating reaction as uniformly as possible, it is preferable to use a silver nitrate solution in which silver nitrate is dissolved in a solvent (water, an organic solvent or a mixed solvent thereof) instead of solid silver nitrate. The amount of the silver nitrate solution to be used, the concentration of silver nitrate in the silver nitrate solution, and the amount of the organic solvent can be determined according to the amount of the target silver-containing layer (a coating layer made of silver or a silver compound).

  In order to form a silver-containing layer (a coating layer made of silver or a silver compound) more uniformly, a chelating agent may be added to the solution. As the chelating agent, it is preferable to use a chelating agent having a high complex stability constant with respect to copper ions or the like so that copper ions or the like by-produced by substitution reaction between silver ions and metallic copper do not reprecipitate. . In particular, since copper powder is used as the core of the silver-coated copper powder, it is preferable to select a chelating agent while paying attention to the complex stability constant with copper. Specifically, a chelating agent selected from the group consisting of ethylenediaminetetraacetic acid (EDTA), iminodiacetic acid, diethylenetriamine, triethylenediamine, and salts thereof can be used as the chelating agent.

  In order to perform the silver coating reaction stably and safely, a pH buffer may be added to the solution. As this pH buffering agent, ammonium carbonate, ammonium hydrogen carbonate, aqueous ammonia, sodium hydrogen carbonate, or the like can be used.

  During the silver coating reaction, before adding the silver ion-containing solution, the dendritic copper powder and the flaky copper powder are put in the solution and stirred, and the dendritic copper powder and the flaky copper powder are sufficiently in the solution. It is preferable to add a silver ion-containing solution in a dispersed state. The reaction temperature in the silver coating reaction may be a temperature at which the reaction solution is solidified or evaporated, but is preferably in the range of 10 to 80 ° C, more preferably 15 to 75 ° C, and most preferably 20 to 70 ° C. Set. Moreover, although reaction time changes with the coating amount of silver or a silver compound, and reaction temperature, it can set in the range of 1 minute-5 hours.

  Hereinafter, the Example of the copper powder for electrically conductive paste by this invention and its manufacturing method is described in detail.

[Example 1]
Electrolytic copper powder (# 52-C manufactured by JX Nippon Mining & Metals Co., Ltd.) 306.5 g as dendritic copper powder, 177.6 g of industrial alcohol (Solmix AP-7 manufactured by Nippon Alcohol Sales Co., Ltd.), 1858.1 g of SUS balls with a diameter of 1.6 mm were put into a sand grinder (capacity 1 L), and the SUS balls were separated from the slurry obtained by stirring for 120 minutes at a stirring blade speed of 652 rpm, and then filtered. The wet cake was vacuum-dried at 70 ° C. and passed through a sieve having an opening of 32 μm to obtain a flaky (flattened) copper powder (flaked copper powder).

A solution prepared by dissolving 157.5 g of ammonium carbonate and 315.0 g of ethylenediaminetetraacetic acid disodium salt (EDTA · 2H · 2Na · 2H ₂ O) in 1254.6 g of pure water was adjusted to a liquid temperature of 25 ° C. A silver complex solution mixed with an aqueous silver nitrate solution containing 33.3 g of silver was prepared. In addition, electrolytic copper powder (GGP) was used as a dendritic copper powder in a solution obtained by dissolving 142.8 g of ammonium carbonate and 142.8 g of ethylenediaminetetraacetic acid disodium salt (EDTA · 2H · 2Na · 2H ₂ O) in 1662.0 g of pure water. A copper powder dispersion was prepared by adding 240.0 g of Cu CH-L5 UF-d50 (10 μm) manufactured by Metalpowder AG and 60.0 g of the above flaky copper powder.

  Next, in a dry nitrogen gas atmosphere, the copper powder dispersion is adjusted to a liquid temperature of 25 ° C., and the silver complex salt solution is added to the copper powder dispersion and held for 30 minutes with stirring. 4.9 g of stearic acid emulsion containing 15% by mass of stearic acid was added, and the mixture was further stirred for 5 minutes to surface-treat the dendritic copper powder and flaky copper powder, followed by ion exchange of the wet cake obtained by filtration It was washed with water, dried at 120 ° C. in a nitrogen atmosphere, passed through a sieve having an opening of 32 μm, and dendritic copper powder coated with silver (silver-coated dendritic copper powder) and flaky copper powder coated with silver ( A mixed powder (silver-coated copper mixed powder) of silver-coated flaky copper powder was obtained. In addition, the compounding ratio of the silver-coated dendritic copper powder and the silver-coated flaky copper powder in the silver-coated copper mixed powder is 80:20 (= 240 g: 60 g). An SEM photograph (5,000 times) of this silver-coated copper mixed powder is shown in FIG.

The BET specific surface area, tap density, oxygen content, carbon content, silver content, particle size distribution, green compact resistance, color difference (L ^* , a ^* , b ^* ) of the silver-coated copper mixed powder thus obtained ^. ) And the heat resistance (high temperature stability) of the silver-coated copper mixed powder was evaluated.

The BET specific surface area of the silver-coated copper mixed powder was determined by the BET method using a BET specific surface area measuring apparatus (4 Sorb US manufactured by Yours IONICS Inc.). As a result, the BET specific surface area of the silver-coated copper mixed powder was 0.45 m ² / g.

The tap density of the silver-coated copper mixed powder is obtained by filling the silver-coated copper mixed powder into a bottomed cylindrical container having an inner diameter of 6 mm in the same manner as in the method described in JP-A-2007-263860. After forming a layer and applying a pressure of 0.16 N / m ² to the silver-coated copper mixed powder layer from the top, the height of the silver-coated copper mixed powder layer is measured, and the height of the silver-coated copper mixed powder layer is measured. From the measured value of the thickness and the weight of the filled silver-coated copper mixed powder, the density of the silver-coated copper mixed powder was determined and used as the tap density of the silver-coated copper mixed powder. As a result, the tap density of the silver-coated copper mixed powder was 2.24 g / cc.

  The oxygen content in the silver-coated copper mixed powder was measured with an oxygen / nitrogen analyzer (TC-436 type manufactured by LECO). As a result, the oxygen content in the silver-coated copper mixed powder was 0.14% by mass.

  The carbon content in the silver-coated copper mixed powder was measured by a carbon / sulfur analyzer (EMIA-220V manufactured by Horiba, Ltd.). As a result, the carbon content in the silver-coated copper mixed powder was 0.23% by mass.

  The silver content (silver coating amount) in the silver-coated copper mixed powder was measured by drying the silver chloride (AgCl) precipitate generated by adding hydrochloric acid after dissolving the silver-coated copper mixed powder with nitric acid. Was determined by That is, 2 g of silver-coated copper mixed powder was weighed and transferred to a beaker while washing with pure water, then 10 mL of nitric acid was added, dissolved by heating, allowed to cool, then the solution was filtered to float organic matter The components were removed, 100 mL of pure water was added to the obtained filtrate, 6 mL of hydrochloric acid was added and stirred sufficiently, hydrochloric acid was further added, and hydrochloric acid was added until no new silver chloride precipitated. After aging by heating until transparent, the silver chloride precipitate recovered by filtration through a glass fiber filter (with a weight of W1 (g)) was dried at 110 ° C. for 3 hours with a dryer, allowed to cool, The weight W2 (g) of silver chloride is measured together with the glass fiber filter, and from Ag (mass%) = {(W2-W1) × 0.7526 × 100} / (weight of silver-coated copper mixed powder used for measurement) Asked. As a result, the silver content (silver coating amount) in the silver-coated copper mixed powder was 10.4% by mass.

As the particle size distribution of the silver-coated copper mixed powder, a volume-based cumulative 10% particle size (D ₁₀ ) and cumulative 50% particle measured by a laser diffraction particle size distribution device (Hellos particle size distribution measuring device (HELOS & RODOS) manufactured by SYMPATEC) The diameter (D ₅₀ ), the cumulative 90% particle diameter (D ₉₀ ), and the cumulative 99% particle diameter (D ₉₉ ) were determined. As a result, the volume-based cumulative 10% particle diameter (D ₁₀ ) of the silver-coated copper mixed powder is 2.4 μm, the cumulative 50% particle diameter (D ₅₀ ) is 9.2 μm, and the cumulative 90% particle diameter (D ₉₀ ) is The particle size (D ₉₉ ) of 28.4 μm and cumulative 99% was 54.6 μm.

  As the green compact resistance of the silver-coated copper mixed powder, 6.5 g of the silver-coated copper mixed powder is packed in a measurement container of the powder resistance measurement system (MCP-PD51 type manufactured by Mitsubishi Chemical Analytech Co., Ltd.) and then pressurized. The volume resistivity (of the green compact) at the time when a load of 20 kN was applied was measured. As a result, the volume resistivity of the green compact of the silver-coated copper mixed powder was 22 μΩ · cm.

The color difference of the silver-coated copper mixed powder was measured by weighing 5 g of the silver-coated copper mixed powder as a measurement sample, putting it in a round cell with a diameter of 30 mm, tapping 10 times, and flattening the surface. Spectro Color Meter SQ2000). As a result, the color differences L ^* , a ^* and b ^* of the silver-coated copper mixed powder were 68.5, 9.0 and 13.1, respectively.

  Regarding the high temperature stability of the silver-coated copper mixed powder, the silver-coated copper mixed powder was raised from room temperature (25 ° C.) in the atmosphere using a differential thermothermal gravimetric simultaneous measurement apparatus (EXATERTTG / DTA6300 manufactured by SII Nanotechnology Co., Ltd.). The difference between the weight measured by heating up to 300 ° C. at a temperature rate of 5 ° C./min and the weight of the silver-coated copper mixed powder before heating (the weight increased by heating) with respect to the weight of the silver-coated copper mixed powder before heating From the rate of increase (%), all the weight increased by heating was regarded as the weight increased by oxidation of the silver-coated copper mixed powder, and the high-temperature stability (against oxidation) of the silver-coated copper mixed powder was evaluated. . As a result, the rate of increase in the weight of the silver-coated copper mixed powder was 2.94%.

  Further, 33.3 parts by weight of the obtained silver-coated copper mixed powder, 12 parts by weight of a polyester resin (Byron 200 manufactured by Toyobo Co., Ltd.), and 54.7 parts by weight of methyl ethyl ketone (manufactured by Wako Pure Chemical Industries, Ltd.) as a solvent. The mixture was mixed and rotated at 1400 rpm for 60 seconds using a self-revolving vacuum stirring defoaming mixer (V-mini300 manufactured by EME Co., Ltd.) to obtain a conductive paste by kneading and defoaming.

  The conductive paste thus obtained was printed on a PET film (S10 Lumirror manufactured by Toray Industries, Inc.) with a 77.7 μm bar coater, and then heated at 100 ° C. for 5 minutes with an air circulation dryer. A conductive film was prepared.

  The film with the conductive film thus obtained was placed on a metal plate, and a release film, a Si chip (size of 12.5 mm × 12.5 mm), a PTEF sheet, and a metal plate were placed in this order. After applying a pressure of 2 MPa at 150 ° C. and hot pressing for 10 minutes, the FTEF sheet, the metal plate, the Si chip, the release film and the metal plate were separated to obtain a hot pressed film with a conductive film.

  This hot-pressed film with a conductive film was cut into a size of 12.5 mm × 12.5 mm, and a 4-probe using a PSP probe of a surface resistance meter (Loresta GP manufactured by Mitsubishi Chemical Analytech Co., Ltd.) When the surface resistance of the conductive film was measured by this method, it was 23 mΩ / □.

  Further, the film with the conductive film after the hot pressing is fixed with a cellophane tape to a fixed film for bending test (S10 Lumirror made by Toray Industries, Inc.) with the conductive film side down, and one end of the fixed film for bending test. A load of 900 g is applied to the side, and a fixed, rotatable cylinder with a diameter of 20 mm is used as an axis, and the other end side of the fixed film is pulled to bend the entire conductive film on the cylinder, and this bending is continuously 10,000. After conducting a bendability test that is repeated several times, using a PSP probe of a surface resistance meter (Loresta GP, manufactured by Mitsubishi Chemical Analytech Co., Ltd.), conducting by a four-probe method so that the measurement direction is parallel to the bending axis. The surface resistance of the film was measured. As a result, the surface resistance of the conductive film after the flexibility test was 132 mΩ / □, and the change in the surface resistance of the conductive film by the flexibility test was 574%.

[Example 2]
The amount of dendritic copper powder and flaky copper powder in the copper powder dispersion is adjusted so that the compounding ratio of silver-coated dendritic copper powder and silver-coated flaky copper powder in the silver-coated copper mixed powder is 70:30. A silver-coated copper mixed powder was obtained in the same manner as in Example 1 except that the amount was 210.0 g and 90 g, respectively. An SEM photograph (5,000 times) of this silver-coated copper mixed powder is shown in FIG.

For the silver-coated copper mixed powder thus obtained, the same method as in Example 1, BET specific surface area, tap density, oxygen content, carbon content, silver content, particle size distribution, green compact resistance, Color differences L ^* , a ^* , b ^* ) were determined, heat resistance (high temperature stability) was evaluated, a conductive film was prepared, its surface resistance was measured, and a flexibility test was performed.

As a result, the BET specific surface area of the silver-coated copper mixed powder was 0.45 m ² / g, the tap density was 2.16 g / cc, the oxygen content was 0.16% by mass, the carbon content was 0.24% by mass, silver The content (silver coating amount) was 10.4% by mass. Further, the volume-based cumulative 10% particle diameter (D ₁₀ ) of the silver-coated copper mixed powder is 2.9 μm, the cumulative 50% particle diameter (D ₅₀ ) is 11.1 μm, and the cumulative 90% particle diameter (D ₉₀ ) is 31. The particle size (D ₉₉ ) was 65.9 μm and the cumulative 99% particle diameter (D ₉₉ ) was 55.9 μm. Moreover, the volume resistivity of the green compact of the silver-coated copper mixed powder is 24 μΩ · cm, and the color differences L ^* , a ^* and b ^* of the silver-coated copper mixed powder are 71.4, 7.9 and 12.4, respectively. The weight increase rate of the silver-coated copper mixed powder was 2.79%. The initial surface resistance of the conductive film was 19 mΩ / □, the surface resistance of the conductive film after the flexibility test was 86.1 mΩ / □, and the change in the surface resistance of the conductive film by the flexibility test was 453%. .

[Example 3]
The amount of dendritic copper powder and flaky copper powder in the copper powder dispersion is adjusted so that the compounding ratio of silver-coated dendritic copper powder and silver-coated flaky copper powder in the silver-coated copper mixed powder is 50:50. A silver-coated copper mixed powder was obtained in the same manner as in Example 1 except that the amount was 150.0 g. The SEM photograph (5000 times) of this silver covering copper mixed powder is shown in FIG.

For the silver-coated copper mixed powder thus obtained, the same method as in Example 1, BET specific surface area, tap density, oxygen content, carbon content, silver content, particle size distribution, green compact resistance, A color difference (L ^* , a ^* and b ^* ) was determined, heat resistance (high temperature stability) was evaluated, a conductive film was prepared, its surface resistance was measured, and a flexibility test was performed.

As a result, the BET specific surface area of the silver-coated copper mixed powder was 0.47 m ² / g, the tap density was 2.22 g / cc, the oxygen content was 0.14 mass%, the carbon content was 0.23 mass%, silver The content (silver coating amount) was 10.4% by mass. Further, the volume-based cumulative 10% particle diameter (D ₁₀ ) of the silver-coated copper mixed powder is 3.4 μm, the cumulative 50% particle diameter (D ₅₀ ) is 13.2 μm, and the cumulative 90% particle diameter (D ₉₀ ) is 34. 0.1 μm, cumulative 99% particle size (D ₉₉ ) was 58.1 μm. The volume resistivity of the green-coated copper mixed powder compact is 28 μΩ · cm, and the color differences L ^* , a ^* and b ^* of the silver-coated copper mixed powder are 75.1, 6.2 and 10.9, respectively. The weight increase rate of the silver-coated copper mixed powder was 2.81%. The initial surface resistance of the conductive film was 14 mΩ / □, the surface resistance of the conductive film after the flexibility test was 54.4 mΩ / □, and the change in the surface resistance of the conductive film by the flexibility test was 388%. .

[Example 4]
The amount of dendritic copper powder and flaky copper powder in the copper powder dispersion is adjusted so that the compounding ratio of silver-coated dendritic copper powder and silver-coated flaky copper powder in the silver-coated copper mixed powder is 30:70. A silver-coated copper mixed powder was obtained in the same manner as in Example 1 except that the amount was 90.0 g and 210.0 g, respectively.

For the silver-coated copper mixed powder thus obtained, the same method as in Example 1, BET specific surface area, tap density, oxygen content, carbon content, silver content, particle size distribution, green compact resistance, The color difference (L ^* , a ^* , b ^* ) was determined, heat resistance (high temperature stability) was evaluated, a conductive film was prepared, its surface resistance was measured, and a flexibility test was performed.

As a result, the BET specific surface area of the silver-coated copper mixed powder was 0.44 m ² / g, the tap density was 2.46 g / cc, the oxygen content was 0.13 mass%, the carbon content was 0.22 mass%, The silver content (silver coating amount) was 10.5% by mass. Further, the volume-based cumulative 10% particle diameter (D ₁₀ ) of the silver-coated copper mixed powder is 4.3 μm, the cumulative 50% particle diameter (D ₅₀ ) is 14.7 μm, and the cumulative 90% particle diameter (D ₉₀ ) is 34. The particle size (D ₉₉ ) was 0.01 μm and the cumulative 99% particle size (D ₉₉ ) was 56.1 μm. The volume resistivity of the green-coated copper mixed powder compact is 24 μΩ · cm, and the color differences L ^* , a ^* and b ^* of the silver-coated copper mixed powder are 79.4, 4.7 and 10.1, respectively. The weight increase rate of the silver-coated copper mixed powder was 2.66%. The initial surface resistance of the conductive film was 9.6 mΩ / □, the surface resistance of the conductive film after the flexibility test was 37.5 mΩ / □, and the change in the surface resistance of the conductive film by the flexibility test was 391%. there were.

[Example 5]
The amount of dendritic copper powder and flaky copper powder in the copper powder dispersion is adjusted so that the compounding ratio of silver-coated dendritic copper powder and silver-coated flaky copper powder in the silver-coated copper mixed powder is 10:90. A silver-coated copper mixed powder was obtained in the same manner as in Example 3 except that the amounts were 30.0 g and 270.0 g, respectively.

For the silver-coated copper mixed powder thus obtained, the same method as in Example 1, BET specific surface area, tap density, oxygen content, carbon content, silver content, particle size distribution, green compact resistance, The color difference (L ^* , a ^* , b ^* ) was determined, heat resistance (high temperature stability) was evaluated, a conductive film was prepared, its surface resistance was measured, and a flexibility test was performed.

As a result, the BET specific surface area of the silver-coated copper mixed powder was 0.33 m ² / g, the tap density was 2.67 g / cc, the oxygen content was 0.12% by mass, the carbon content was 0.20% by mass, silver The content (silver coating amount) was 10.2% by mass. Further, the volume-based cumulative 10% particle diameter (D ₁₀ ) of the silver-coated copper mixed powder is 5.8 μm, the cumulative 50% particle diameter (D ₅₀ ) is 17.2 μm, and the cumulative 90% particle diameter (D ₉₀ ) is 38. 0.1 μm, cumulative 99% particle size (D ₉₉ ) was 63.0 μm. The volume resistivity of the green-coated copper mixed powder compact is 22 μΩ · cm, and the color differences L ^* , a ^* and b ^* of the silver-coated copper mixed powder are 82.1, 4.3 and 9.8, respectively. The weight increase rate of the silver-coated copper mixed powder was 2.19%. The initial surface resistance of the conductive film was 12 mΩ / □, the surface resistance of the conductive film after the flexibility test was 71.7 mΩ / □, and the change in the surface resistance of the conductive film by the flexibility test was 598%. .

[Example 6]
A silver-coated copper mixed powder was obtained in the same manner as in Example 2 except that electrolytic copper powder (CE-20 manufactured by Fukuda Metal Foil Powder Co., Ltd.) was used as the dendritic copper powder.

For the silver-coated copper mixed powder thus obtained, the same method as in Example 1, BET specific surface area, tap density, oxygen content, carbon content, silver content, particle size distribution, green compact resistance, Color differences (L ^* , a ^* , b ^* ) were determined, heat resistance (high-temperature stability) was evaluated, and a conductive film was prepared and its surface resistance was measured.

As a result, the BET specific surface area of the silver-coated copper mixed powder was 0.46 m ² / g, the tap density was 2.26 g / cc, the oxygen content was 0.13 mass%, the carbon content was 0.23 mass%, silver The content (silver coating amount) was 10.4% by mass. Further, the volume-based cumulative 10% particle diameter (D ₁₀ ) of the silver-coated copper mixed powder is 2.6 μm, the cumulative 50% particle diameter (D ₅₀ ) is 11.3 μm, and the cumulative 90% particle diameter (D ₉₀ ) is 33. The particle size (D ₉₉ ) was 26.3 μm and the cumulative 99% particle size (D ₉₉ ) was 56.3 μm. The volume resistivity of the green-coated copper mixed powder compact is 24 μΩ · cm, and the color differences L ^* , a ^*, and b ^* of the silver-coated copper mixed powder are 70.8, 7.5, and 11.9, respectively. The rate of increase in the weight of the silver-coated copper mixed powder was 2.92%. The initial surface resistance of the conductive film was 20 mΩ / □.

[Example 7]
A silver-coated copper mixed powder was obtained in the same manner as in Example 3 except that electrolytic copper powder (CE-20 manufactured by Fukuda Metal Foil Powder Co., Ltd.) was used as the dendritic copper powder.

For the silver-coated copper mixed powder thus obtained, the same method as in Example 1, BET specific surface area, tap density, oxygen content, carbon content, silver content, particle size distribution, green compact resistance, Color differences (L ^* , a ^* , b ^* ) were determined, heat resistance (high-temperature stability) was evaluated, and a conductive film was prepared and its surface resistance was measured.

As a result, the BET specific surface area of the silver-coated copper mixed powder was 0.42 m ² / g, the tap density was 2.34 g / cc, the oxygen content was 0.12% by mass, the carbon content was 0.22% by mass, silver The content (silver coating amount) was 10.4% by mass. Further, the volume-based cumulative 10% particle diameter (D ₁₀ ) of the silver-coated copper mixed powder is 3.4 μm, the cumulative 50% particle diameter (D ₅₀ ) is 14.8 μm, and the cumulative 90% particle diameter (D ₉₀ ) is 36. The particle size (D ₉₉ ) of 0.0 μm and cumulative 99% was 59.0 μm. The volume resistivity of the green-coated copper mixed powder compact is 25 μΩ · cm, and the color differences L ^* , a ^* and b ^* of the silver-coated copper mixed powder are 74.6, 5.8 and 10.7, respectively. The weight increase rate of the silver-coated copper mixed powder was 3.05%. The initial surface resistance of the conductive film was 15 mΩ / □.

[Comparative Example 1]
Flakes with an amount of dendritic copper powder in the copper powder dispersion of 300.0 g so that the compounding ratio of silver-coated dendritic copper powder and silver-coated flaky copper powder in the silver-coated copper mixed powder is 100: 0. A silver-coated copper mixed powder was obtained in the same manner as in Example 1 except that the copper powder was not added.

For the silver-coated copper mixed powder thus obtained, the same method as in Example 1, BET specific surface area, tap density, oxygen content, carbon content, silver content, particle size distribution, green compact resistance, The color difference (L ^* , a ^* , b ^* ) was determined, heat resistance (high temperature stability) was evaluated, a conductive film was prepared, its surface resistance was measured, and a flexibility test was performed.

As a result, the BET specific surface area of the silver-coated copper mixed powder was 0.45 m ² / g, the tap density was 2.29 g / cc, the oxygen content was 0.13 mass%, the carbon content was 0.22 mass%, silver The content (silver coating amount) was 10.4% by mass. Further, the volume-based cumulative 10% particle diameter (D ₁₀ ) of the silver-coated copper mixed powder is 1.9 μm, the cumulative 50% particle diameter (D ₅₀ ) is 7.0 μm, and the cumulative 90% particle diameter (D ₉₀ ) is 19. The particle size (D ₉₉ ) was 82.1 μm and the cumulative 99% particle size (D ₉₉ ) was 42.1 μm. The volume resistivity of the green-coated copper mixed powder compact is 19 μΩ · cm, and the color differences L ^* , a ^*, and b ^* of the silver-coated copper mixed powder are 61.9, 11.7, and 16.1, respectively. The weight increase rate of the silver-coated copper mixed powder was 2.65%. The initial surface resistance of the conductive film was 28 mΩ / □, the surface resistance of the conductive film after the flexibility test was 88.9 mΩ / □, and the change in the surface resistance of the conductive film by the flexibility test was 318%. .

[Comparative Example 2]
The amounts of electrolytic copper powder and flaky copper powder in the copper powder dispersion were respectively adjusted so that the blending ratio of silver-coated dendritic copper powder and silver-coated flaky copper powder in the silver-coated copper mixed powder was 95: 5. A silver-coated copper mixed powder was obtained in the same manner as in Example 3 except that the amount was 285.0 g and 15.0 g.

For the silver-coated copper mixed powder thus obtained, the same method as in Example 1, BET specific surface area, tap density, oxygen content, carbon content, silver content, particle size distribution, green compact resistance, The color difference (L ^* , a ^* , b ^* ) was determined, heat resistance (high temperature stability) was evaluated, a conductive film was prepared, its surface resistance was measured, and a flexibility test was performed.

As a result, the BET specific surface area of the silver-coated copper mixed powder was 0.48 m ² / g, the tap density was 2.15 g / cc, the oxygen content was 0.13 mass%, the carbon content was 0.23 mass%, silver The content (silver coating amount) was 10.3% by mass. Further, the volume-based cumulative 10% particle diameter (D ₁₀ ) of the silver-coated copper mixed powder is 2.1 μm, the cumulative 50% particle diameter (D ₅₀ ) is 7.6 μm, and the cumulative 90% particle diameter (D ₉₀ ) is 24. The particle diameter (D ₉₉ ) of 0.0 μm and the cumulative 99% was 50.2 μm. The volume resistivity of the green-coated copper mixed powder compact is 14 μΩ · cm, and the color differences L ^* , a ^* and b ^* of the silver-coated copper mixed powder are 61.6, 11.5 and 14.9, respectively. The weight increase rate of the silver-coated copper mixed powder was 3.05%. The initial surface resistance of the conductive film was 32 mΩ / □, the surface resistance of the conductive film after the flexibility test was 118 mΩ / □, and the change in the surface resistance of the conductive film by the flexibility test was 369%.

[Comparative Example 3]
The amounts of the electrolytic copper powder and the flaky copper powder in the copper powder dispersion are respectively adjusted so that the blending ratio of the silver-coated dendritic copper powder and the silver-coated flaky copper powder in the silver-coated copper mixed powder is 90:10. A silver-coated copper mixed powder was obtained in the same manner as in Example 3 except that 270.0 g and 30.0 g were used.

For the silver-coated copper mixed powder thus obtained, the same method as in Example 1, BET specific surface area, tap density, oxygen content, carbon content, silver content, particle size distribution, green compact resistance, The color difference (L ^* , a ^* , b ^* ) was determined, heat resistance (high temperature stability) was evaluated, a conductive film was prepared, its surface resistance was measured, and a flexibility test was performed.

As a result, the BET specific surface area of the silver-coated copper mixed powder was 0.47 m ² / g, the tap density was 2.23 g / cc, the oxygen content was 0.14% by mass, the carbon content was 0.22% by mass, silver The content (silver coating amount) was 10.4% by mass. Further, the volume-based cumulative 10% particle diameter (D ₁₀ ) of the silver-coated copper mixed powder is 2.2 μm, the cumulative 50% particle diameter (D ₅₀ ) is 8.2 μm, and the cumulative 90% particle diameter (D ₉₀ ) is 26. The particle diameter (D ₉₉ ) of 0.0 μm and the cumulative 99% was 54.1 μm. The volume resistivity of the green-coated copper mixed powder compact is 19 μΩ · cm, and the color differences L ^* , a ^* and b ^* of the silver-coated copper mixed powder are 65.5, 10.8 and 14.4, respectively. The weight increase rate of the silver-coated copper mixed powder was 2.98%. The initial surface resistance of the conductive film was 38 mΩ / □, the surface resistance of the conductive film after the flexibility test was 116 mΩ / □, and the change in the surface resistance of the conductive film by the flexibility test was 305%.

[Comparative Example 4]
The amount of the flaky copper powder in the copper powder dispersion is 300.0 g so that the blending ratio of the silver-coated dendritic copper powder and the silver-coated flaky copper powder in the silver-coated copper mixed powder is 0: 100. A silver-coated copper mixed powder was obtained in the same manner as in Example 3 except that the copper powder was not added.

For the silver-coated copper mixed powder thus obtained, the same method as in Example 1, BET specific surface area, tap density, oxygen content, carbon content, silver content, particle size distribution, green compact resistance, The color difference (L ^* , a ^* , b ^* ) was determined, heat resistance (high temperature stability) was evaluated, a conductive film was prepared, its surface resistance was measured, and a flexibility test was performed.

As a result, the BET specific surface area of the silver-coated copper mixed powder was 0.32 m ² / g, the tap density was 3.16 g / cc, the oxygen content in the silver-coated copper mixed powder was 0.10% by mass, and the carbon content was 0.17 mass% and silver content (silver coating amount) were 10.3 mass%. Further, the volume-based cumulative 10% particle diameter (D ₁₀ ) of the silver-coated copper mixed powder is 6.0 μm, the cumulative 50% particle diameter (D ₅₀ ) is 17.1 μm, and the cumulative 90% particle diameter (D ₉₀ ) is 36. The cumulative 99% particle diameter (D ₉₉ ) was 59.3 μm. The volume resistivity of the green-coated copper mixed powder compact is 20 μΩ · cm, and the color differences L ^* , a ^* and b ^* of the silver-coated copper mixed powder are 82.3, 3.4 and 8.7, respectively. The weight increase rate of the silver-coated copper mixed powder was 2.12%. The initial surface resistance of the conductive film was 16 mΩ / □, the surface resistance of the conductive film after the flexibility test was 144 mΩ / □, and the change in the surface resistance of the conductive film by the flexibility test was 713%.

  Tables 1 to 4 show the production conditions and characteristics of the copper powder for conductive pastes of these Examples and Comparative Examples, and the characteristics of the conductive films prepared using the conductive paste.

Claims (4)

By adding a silver ion-containing solution to a copper powder dispersion in which dendritic copper powder and flaky copper powder are dispersed, the surface of the dendritic copper powder and flaky copper powder is coated with a silver-containing layer, thereby dendritic silver. In the method for producing a copper powder for conductive paste for producing a mixed powder of coated copper powder and flaky silver-coated copper powder, the mass ratio of dendritic copper powder and flaky copper powder in the copper powder dispersion is 5:95. It is -85: 15, The manufacturing method of the copper powder for electrically conductive paste characterized by the above-mentioned. The method for producing copper powder for conductive paste according to claim 1 , wherein the silver ion-containing solution is a silver complex salt solution. The method for producing a copper powder for conductive paste according to claim 1 or 2 , wherein a coating amount of the silver-containing layer is 1 to 20 mass% with respect to the mixed powder. The method for producing copper powder for conductive paste according to any one of claims 1 to 3 , wherein the silver-containing layer is a layer made of silver or a silver compound.

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