JP4583164B2 - Silver-copper composite powder and method for producing silver-copper composite powder - Google Patents

Description

  The present invention is a silver-copper composite powder and a product that is capable of uniform diffusion of silver and copper when obtaining the silver-copper composite powder, has good powder characteristics, and is atomized and uniformized The present invention relates to a manufacturing method for obtaining

  Conventionally, silver powder has been widely used as a filler material used for conductive pastes and the like because of its excellent oxidation resistance and specific resistance. However, copper powder is used in applications that dislike silver migration, but copper has a weak point of being easily oxidized. Therefore, the use of silver-copper composite powder is also seen as a filler having characteristics that compensate for both weaknesses of silver migration and copper oxidation.

  As an industrial method for producing silver-copper composite powder, an atomizing method is generally used as described in the examples of Patent Document 1 (Japanese Patent Laid-Open No. 2000-144203). In this atomizing method, powder particles are generated by spray cooling a molten metal heated to a temperature higher than the melting point. Therefore, it is relatively easy to generate a mixture of two or more metals or alloy particles. Generally, there is a limit to atomization and equalization due to the characteristics of Specifically, the powder itself after spraying usually has a wide particle size distribution of about 1 to several tens of μm. If a fine powder having a center particle diameter of 5 μm or less is to be obtained, classification is performed. It was necessary to sort out the fine particles by operation.

  On the other hand, as a production method suitable for the production of fine powder, there is a conventional wet reduction method. However, in principle, the reaction conditions are determined by the electrochemical characteristics unique to the metal element. It is difficult to deposit.

  In addition, as silver-copper composite fine particles, for example, as disclosed in Patent Document 2 (Japanese Patent Laid-Open No. 1-1119602), there is conventionally silver-coated copper powder by a wet reduction method, but the distribution of the surface layer is almost silver only. Therefore, when used as a conductive filler, there is a problem that it is difficult to obtain a composite characteristic of both silver and copper at the contact point on the particle surface.

JP 2000-144203 A JP-A-1-119602

  As described above, the silver-copper composite powder is used for the purpose of eliminating the respective disadvantages of the silver powder and the copper powder. However, the silver-copper composite powder is used to efficiently obtain the finely divided and uniform silver-copper composite powder. A manufacturing method has not been established.

  Accordingly, an object of the present invention is to provide a silver-copper composite powder in which silver and copper are uniformly dispersed, and have good powder characteristics, and are atomized and uniformed. An object of the present invention is to provide a production method with excellent productivity for supplying powder to the market at a low cost.

  Therefore, as a result of studies to solve the above problems, the present inventors have obtained silver-copper composite powder that achieves the above objects by performing wet heat treatment after preparing silver-coated copper fine particles by a wet reduction method. I came up with it.

<Silver copper composite powder according to the present invention>
Silver copper composite powder according to the present invention is a silver copper composite powder containing silver and copper, the silver-coated layer formed by a wet process particulate surface of the copper powder, the silver-coated copper powder 50 ° C. ~ It is obtained by heating in a solution at a temperature of 200 ° C. for 30 minutes to 120 minutes and thermally interdiffusing silver and copper, and the silver content is 20 wt% to 55 wt%, the remaining copper and inevitable impurities, CIE1976L ^* a ^* b ^* provided with a color tone of L ^* value = 56 to 78, a ^* value = −0.5 to −0.1, b ^* value = 10.0 to 12.0 obtained in the color system It is characterized by that.

  In addition, among the silver-copper composite powders according to the present invention, the silver-copper composite powder composed of substantially spherical particles is as follows. ~ C. It is preferable to have the following powder characteristics.

A. Cumulative volume-average particle size _{D 50} by laser diffraction scattering particle size distribution measuring method 0.3Myuemu～6.0Myuemu.
B. The volume cumulative maximum particle size D _max by laser diffraction scattering type particle size distribution measurement method is 20.0 μm or less.
C. Specific surface area is 0.2 m ² / g or more.

  Furthermore, among the silver-copper composite powder according to the present invention, the silver-copper composite powder composed of flaky powder particles has the following a. ~ C. It is preferable to have the following powder characteristics.

a. Cumulative volume-average particle size _{D 50} by laser diffraction scattering particle size distribution measuring method 1.0Myuemu～10.0Myuemu.
b. The volume cumulative maximum particle size D _max by the laser diffraction / scattering particle size distribution measurement method is 40.0 μm or less.
c. The aspect ratio (thickness / [D ₅₀ ]) of the powder is 0.02 to 0.5.

<Method for producing silver-copper composite powder according to the present invention>
In the method for producing a silver-copper composite powder according to the present invention , a silver-containing solution is added to and reacted with a dispersion obtained by adding a chelating agent to an aqueous solution to which copper powder is added, and further filtered to obtain copper. a silver-coated copper powder particulate surface to form a silver coating layer on the powder, in the silver-coated copper powder 50 ° C. to 200 DEG at a temperature of ° C. solution of silver by wet heat treatment for heat treatment for 30 minutes to 120 minutes The copper is thermally interdiffused and then filtered, washed with alcohol, and dried.

  And in the manufacturing method of the silver copper composite powder which concerns on this invention, when the copper powder weight in a dispersion liquid is 100 weight part, the silver containing solution containing 20 weight part-95 weight part as silver is said dispersion liquid. It is preferable to add to.

  Moreover, in the manufacturing method of the silver-copper composite powder which concerns on this invention, the powder particle shape can use the substantially spherical shape or flake-shaped copper powder.

  Moreover, it is preferable to use ethylenediaminetetraacetate as the chelating agent.

  The silver-copper composite powder according to the present invention is a silver-copper composite powder that has good powder characteristics and is atomized and uniform. And since the said silver-copper composite powder has the favorable distribution state of silver and copper, it can suppress a silver migration phenomenon and can utilize the characteristic as an electrical good conductor which silver has effectively. In addition, by the production method of the present invention, a finely divided and uniform silver-copper composite powder having good powder characteristics can be obtained. And this silver copper composite powder has the favorable distribution state of silver and copper in the surface of a granular material, and makes mass production of the silver copper composite powder with the favorable characteristic which silver and copper compounded easy.

  Hereinafter, the best mode for carrying out the silver-copper composite powder and the method for producing the same according to the present invention will be described.

<Silver copper composite powder according to the present invention>
The silver-copper composite powder according to the present invention forms a silver coat layer on the surface of copper powder particles by a wet method, and the silver-coated copper powder is in a solution at a temperature of 50 ° C. to 200 ° C. for 30 minutes to 120 minutes. L ^* obtained by heating and thermal interdiffusion of silver and copper, silver content of 20 wt% to 55 wt%, balance copper and inevitable impurities, and obtained in CIE 1976 L ^* a ^* b ^* color system It has a color tone of value = 56 to 78, a ^* value = −0.5 to −0.1, b ^* value = 10.0 to 12.0. As a result, it has different characteristics compared with the silver-copper composite powder obtained by the conventional atomization method.

Here, the formation of the silver coat layer on the surface of the copper powder is preferably a silver layer formed by an electrochemical technique. The electrochemical method is intended for displacement deposition and electroless plating. In other words, compared to the case where the copper powder and silver powder are mixed by stirring and formed by a mechanochemical method such as fixing silver to the surface of the copper powder particles, mutual diffusion is easy by wet heat treatment described later. is there.

  And the silver-copper composite powder which concerns on this invention is set as the composition whose silver content is 20 wt%-55 wt%, remainder copper and an unavoidable impurity. Here, when the silver content is less than 20 wt%, the conductor resistance of the conductor formed by processing the product silver-copper composite powder into a conductive paste or the like cannot be improved, and the significance of containing silver is lost. On the other hand, if the silver content exceeds 55 wt%, the silver layer becomes too thick, the diffusion of copper and silver becomes insufficient, the effect of preventing migration cannot be obtained, and the component-uneven silver copper A composite powder is easily obtained and is not preferable because it is economically expensive.

  Furthermore, the silver-copper composite powder according to the present invention has a silver content of 60 wt% or less and the remaining copper (however, including certain inevitable impurities) as the amount of silver and copper in the surface layer portion of the particle. preferable. It is difficult to measure the amount of components of silver and copper in the surface layer of such a powder using a chemical analysis technique. Therefore, the present inventors decided to adopt a simple quantitative analysis in the particle surface layer portion using the energy dispersive EPMA, the acceleration voltage of the electron beam at this time is 15 keV, the observation magnification is 5000 times or more, It is the result of simple quantitative analysis. As a result, when the silver content in the surface layer portion of the powder particles exceeds 60 wt%, silver migration tends to occur, and expensive silver is wasted. And if silver content is not more than 10 wt%, the favorable electroconductivity of silver cannot be utilized. Therefore, in the simple quantitative analysis in the particle surface layer portion using energy dispersive EPMA, the silver content is preferably in the range of 10 wt% to 60 wt%.

In addition, the silver-copper composite powder according to the present invention is characterized by a color tone when viewed as a powder. Silver copper composite powder according to the present invention, CIE1976L ^* a ^* b ^* obtained by the color system ^{L *} value = 56 to 78, ^{a *} value = -0.5~-0.1, ^{b *} value = 10. It has a color tone represented as 0 to 12.0.

Here, the CIE 1976 L ^* a ^* b ^* color system is a color difference that is most commonly used, and it is considered that the description thereof is not particularly necessary. It should be noted that the L ^* value is a value obtained by digitizing light and dark, and the larger the value, the brighter the color tone. “a ^* value =” represents a hue and saturation in the CIE 1976 L ^* a ^* b ^* color system, and is a coordinate value indicating the position of the red-green transition line. The b * value represents a hue and saturation in the CIE 1976 L ^* a ^* b ^* color system, and is a coordinate value indicating the position of the yellow-blue transition line.

The L ^* value of the silver-copper composite powder according to the present invention falls within the range of 56 to 78. Therefore, visually, it is perceived as a rather dark tone. Color means that an object receives light and the light reflected from the object is captured by human vision and recognized as light and dark, and color tone. Then, light is irregularly reflected on the surface of the object, and if the reflected light is reduced, it is recognized as a dark and black object. Therefore, it is considered that the surface of the silver-copper composite powder according to the present invention has certain irregularities and the specific surface area as a powder is widened. When the specific surface area of the silver-copper composite powder according to the present invention is actually measured and compared with a product having an equivalent particle size obtained by the atomization method, the specific surface area is surely increased. This will be specifically mentioned through Examples and Comparative Examples. When the L ^* value is smaller than 56 and darker, the oxidation progresses by wet heat treatment, which will be described later, becomes significant, and the resulting silver-copper composite powder is processed into a conductive paste or the like to form a conductor. Resistance tends to increase. When the L ^* value is greater than 78 and the color tone becomes brighter, mutual diffusion between the silver coat layer and copper as the core material is insufficient, and uniform dispersion of silver and copper does not proceed.

The a ^* value of the silver-copper composite powder according to the present invention falls within the range of -0.5 to -0.1, which means that it has a hue and saturation stronger than green than red. Furthermore, the b ^* value of the silver-copper composite powder according to the present invention falls within the range of 10.0 to 12.0, and has a hue and saturation that are stronger than yellow than blue. From these, it can be seen that the hue and saturation of the silver-copper composite powder according to the present invention have a dark yellow-green color tone. At this stage, it is not clear how the a ^* value and b ^* value of the silver-copper composite powder according to the present invention are related to the product quality, but the silver content in the surface layer region of the silver-copper composite powder There seems to be a certain relationship with quantity.

The L ^* value, a ^* value, and b ^* value obtained by the CIE 1976 L ^* a ^* b ^* color system of the silver-copper composite powder described above are an estimate of the dispersion level of silver and copper in the silver-copper composite powder. Therefore, it is effective to use the L ^* value as an indicator of product quality in process management.

  The silver-copper composite powder that has been described above is not particularly limited in the shape of the powder as the copper powder used for the core material. Accordingly, copper particles having a substantially spherical shape or flake shape can be used. Therefore, the silver-copper composite powder according to the present invention is an unprecedented product with fine particles and excellent particle size distribution.

  Among the silver-copper composite powders according to the present invention, the silver-copper composite powder composed of substantially spherical particles is as follows. ~ C. The powder characteristics can be provided.

Powder characteristics Has a volume cumulative average particle diameter D ₅₀ of 0.3 μm to 6.0 μm as measured by a laser diffraction / scattering particle size distribution measurement method. The volume cumulative particle size determined by the laser diffraction / scattering particle size distribution measurement method is regarded as one particle even if it is an aggregated particle. Thus, powder particles that constitute the silver copper composite powder according to the present invention, even primary particles are caused aggregation at a constant level, keep the volume accumulated average particle diameter D ₅₀ in the range of 0.3μm~6.0μm I can do things. In fact, silver copper composite powder having a volume cumulative mean particle diameter D ₅₀ 0.3Myuemu～6.0Myuemu, using a scanning electron microscope, the average primary particle diameter was measured primary particle size from that observed image 0. It can be observed as 2 μm to 4.0 μm. Therefore, there is no problem in the filling property into the via hole having a diameter of 100 μm or less used for obtaining the interlayer conduction of the printed wiring board.

In addition, although not included in the powder characteristics in specifying the silver-copper composite powder according to the present invention, the volume cumulative particle size D ₉₀ by the laser diffraction scattering type particle size distribution measuring method is also the particle size distribution as the powder. It is an element in estimating the goodness of the. As described above, the volume cumulative particle size D ₉₀ of the silver-copper composite powder having a volume cumulative average particle size D ₅₀ of 0.3 μm to 6.0 μm is in the range of 0.5 μm to 10.0 μm.

Powder characteristics Has a volume cumulative maximum particle size D _max of 20.0 μm or less by a laser diffraction / scattering particle size distribution measurement method. Here, the lower limit is not particularly defined, but if it is intentionally defined, it is 1.0 μm as an industrially stable range. From this powder characteristic, it is possible to read the maximum particle diameter including the aggregation state of the powder grains. With such a level of coarse particles, there is no problem in the filling property of via holes having a diameter of 100 μm or less used for obtaining interlayer conduction of the printed wiring board.

Powder characteristics C.I. The specific surface area of the silver-copper composite powder according to the present invention is 0.2 m ² / g or more. This specific surface area represents the uneven state of the powder surface, and the higher the specific surface area, the higher the viscosity when processed into a paste, making it difficult to handle. On the other hand, the higher the specific surface area, the easier the powder particles to sinter. And is related to the property that enables low-temperature sintering. Therefore, the specific surface area of the silver copper composite powder according to the present invention obtained in ^reality, it become in the range of 0.2m ² /g~3.0m 2 / g is generally, at the present, It has not been possible to specify the limit of the upper limit. The specific surface area of the silver copper composite powder according to the present invention, when considered prima facie within a range of 0.2m ² /g~3.0m ² / ^g, also cause significant viscosity increase when processed into a conductive paste In other words, it can be said that good sintering characteristics of the powder can be achieved. Moreover, since this specific surface area represents the state of the particle surface of the silver-copper composite powder and affects the above-mentioned color tone, it correlates with the color tone of the silver-copper composite powder when the production method described later is adopted. There seems to be a relationship.

Furthermore, there are identifiable powder characteristics of the silver-copper composite powder composed of substantially spherical particles. Is a tap bulk density, in the case of flaky silver-copper composite powder comprising the powder characteristics ^is a range of ^{1.0g / cm 3 ~5.0g / cm 3} .

  And among the silver-copper composite powder which concerns on this invention, the silver-copper composite powder which consists of a flaky powder particle is the following a. ~ C. The powder characteristics can be provided. Since this flaky silver-copper composite powder has a flat shape, it is a conductor formed by processing into a conductive paste or the like by using the flaky powder alone or a mixture of the flaky powder and a substantially spherical portion. It can be used for the purpose of lowering the electrical resistance of the conductor.

Powder characteristics a. The volume accumulated average particle diameter _{D 50} by laser diffraction scattering particle size distribution measuring method is 1.0Myuemu～10.0Myuemu. As described above, the volume cumulative particle diameter determined by the laser diffraction / scattering particle size distribution measurement method is regarded as one particle even if it is an aggregated particle. Therefore, the flake-like powder particles constituting the silver-copper composite powder according to the present invention have a volume cumulative average particle diameter D ₅₀ even if they are aggregated considering that the primary particles are aggregated at a certain level. In the above range, it can be said that it is a fine flake powder. In fact, silver copper composite powder having a volume cumulative mean particle diameter D ₅₀ is in the above range, using a scanning electron microscope, an average primary particle diameter of 1.0μm was measured primary particle diameter (major axis) from the observation image It can be observed as ˜7.0 μm. Therefore, there is no problem in the filling property into the via hole having a diameter of 100 μm or less used for obtaining the interlayer conduction of the printed wiring board.

In addition, when specifying the silver-copper composite powder composed of flaky powder particles according to the present invention, it is not included in the powder characteristics, but here also the volume cumulative particle size D by the laser diffraction scattering particle size distribution measurement method ₉₀ is an element in estimating the good particle size distribution as a powder. As described above, the volume cumulative particle size D ₉₀ of the flaky silver-copper composite powder having a volume cumulative average particle size D ₅₀ of 1.0 μm to 10.0 μm is in the range of 3.0 μm to 20.0 μm. In a normal flake product obtained by physically processing a spherical powder produced using the atomization method, the value between the value of the volume cumulative particle size D _{90 and} the value of the volume cumulative average particle size D ₅₀ is 3 times. In general, there is a coarse particle exceeding the value, and there is no large difference between the value of the volume cumulative particle size D _{90 and} the value of the volume cumulative average particle size D ₅₀ , and the particle size distribution becomes extremely sharp. I can imagine that.

Powder characteristics b. Has a volume cumulative maximum particle diameter D _max of 40.0 μm or less as measured by a laser diffraction / scattering particle size distribution measurement method. From this powder characteristic, it is possible to read the maximum particle diameter including the aggregation state of the powder grains. Again cumulative volume maximum particle diameter D _max is the perspective in relation to the values of the cumulative volume-average particle diameter D ₅₀ of the above-described cumulative volume particle diameter D _90, it would indicate a sense outliers. However, in a normal flake product obtained by physically processing a spherical powder produced using the atomizing method, the volume cumulative maximum particle size _Dmax is 80 μm or more, and in some cases it may exceed 100 μm. Considering this, the volume cumulative maximum particle diameter _{Dmax in} the case of the flaky silver-copper composite powder according to the present invention is 40.0 μm or less, and at this level, the diameter used to obtain the interlayer conduction of the printed wiring board is 100 μm. There is no major problem with the filling property in the following via hole.

Powder characteristics c. The aspect ratio (thickness / [D ₅₀ ]) of the powder particles is 0.02 to 0.5. As for the aspect ratio here, the value of the aspect ratio ([thickness] / [D ₅₀ ]) represented by the thickness of the powder particles constituting the flaky powder and the volume cumulative average particle diameter D50 is 0.02 to 0.02. 0.5. This aspect ratio can be said to represent the degree of processing of the flake powder. Therefore, when the aspect ratio value is less than 0.02, the thickness of the powder grain becomes too thin, the dislocation density inside the powder grain and the refinement of crystal grains begin to occur rapidly, and the resistance increases. As well as causing the occurrence of coarse grains. On the other hand, if the aspect ratio exceeds 0.5, the degree of processing is low and the flatness is low, so that the sufficient contact interface area between the powder particles cannot be improved, and the resistance of the formed conductor may be lowered. It will not be possible.

  Regarding the powder characteristics described above, it is thought that it depends on the basic powder characteristics of the copper powder as the core material used in the manufacturing method described below. If particle agglomeration occurs, the powder characteristics deteriorate, and it is a product that can be produced for the first time by finding a production method that can avoid particle agglomeration as much as possible in the production process.

<Method for producing silver-copper composite powder according to the present invention>
As described above, the production method according to the present invention is as follows. “To a dispersion obtained by adding a chelating agent to an aqueous solution to which copper powder has been added, a silver-containing solution is added and reacted, and further filtered. a silver-coated copper powder in granular surface of the copper powder to form a silver coating layer, the silver-coated copper powder in temperature solution of 50 ° C. to 200 DEG ° C., silver by wet heat treatment for heat treatment for 30 minutes to 120 minutes And a method of producing a silver-copper composite powder, wherein the copper and copper are thermally interdiffused, followed by filtration, alcohol washing, and drying.

Copper powder as a core material: The copper powder used here is a copper powder obtained from a usual electrolytic method, reduction method, atomization method, mechanical pulverization method, etc., and there is no particular limitation on its shape, A spherical shape or a flake shape is preferably used. The copper powder is preferably pretreated, and examples of the pretreatment include classification, washing with dilute sulfuric acid, and degreasing with an alkaline solution. For example, pretreated copper powder obtained by adding copper powder to sulfuric acid-washed pure water, stirring, dilute sulfuric acid, stirring, and performing repulp washing is preferably used.

  In particular, among the silver-copper composite powder according to the present invention, it is a silver-copper composite powder composed of substantially spherical powder particles, and the A. ~ C. In the case of manufacturing a product having the following powder characteristics, A ′. ~ C '. It is preferable to use a substantially spherical copper powder having the following powder characteristics as a core material.

Powder characteristics of copper powder as a core material A ′. Has a volume cumulative average particle diameter D ₅₀ of 0.2 μm to 5.0 μm as measured by a laser diffraction / scattering particle size distribution measurement method. If it is not this range, the volume accumulation average as a powder characteristic of the silver copper composite powder after manufacturing the silver coat copper powder of the range used as the silver content (20 wt%-55 wt%) mentioned above, and also wet-heat-treating. It becomes difficult to keep the particle size D ₅₀ in the range of 0.3 μm to 6.0 μm.

Powder characteristics of copper powder as a core material B ′. Has a volume cumulative maximum particle diameter D _max of 15.0 μm or less as measured by a laser diffraction / scattering particle size distribution measurement method. If this range is not satisfied, the volume cumulative maximum as the powder characteristics of the silver-copper composite powder after producing the silver-coated copper powder in the range of the silver content (20 wt% to 55 wt%) described above and further wet-treating it. It becomes difficult to keep the particle size D _max in the range of 20.0 μm or less.

And the powder characteristic C '. Has a specific surface area of 0.1 m ² / g or more. If it is not this range, the specific surface area as a powder characteristic of the silver copper composite powder after manufacturing the silver coat copper powder of the range used as the silver content (20 wt%-55 wt%) mentioned above, and also wet-heat-treating. 0.2 m ² / g or more cannot be achieved. In addition, when the specific surface area of the copper powder as the core material is less than 0.1 m ² / g, the precipitation of the silver coat layer in the case of producing the silver coat copper powder tends to be non-uniform, and wet-heat-treated It tends to be difficult to obtain a uniform dispersed structure of silver and copper on the surface of the subsequent powder grains.

  Moreover, among the silver-copper composite powders according to the present invention, a silver-copper composite powder comprising flaky powder particles, the a. ~ C. In the case of manufacturing a product having the following powder characteristics, the following a '. ~ C '. It is preferable to use flaky copper powder having the following powder characteristics as a core material.

Powder characteristics of copper powder as a core material a ′. The volume accumulated average particle diameter _{D 50} by laser diffraction scattering particle size distribution measuring method is 1.0Myuemu～8.0Myuemu. If it is not this range, the volume accumulation average as a powder characteristic of the silver copper composite powder after manufacturing the silver coat copper powder of the range used as the silver content (20 wt%-55 wt%) mentioned above, and also wet-heat-treating. It becomes difficult to keep the particle size D ₅₀ in the range of 1.0 μm to 10.0 μm.

Powder characteristics of copper powder as a core material b '. Has a volume cumulative maximum particle size D _max of 30.0 μm or less by a laser diffraction / scattering particle size distribution measurement method. If this range is not satisfied, the volume cumulative maximum as the powder characteristics of the silver-copper composite powder after producing the silver-coated copper powder in the range of the silver content (20 wt% to 55 wt%) described above and further wet-treating it. It becomes difficult to keep the particle size D _max in the range of 40.0 μm or less.

And the powder characteristic of copper powder as a core material c '. The aspect ratio (thickness / [D ₅₀ ]) of the powder particles is 0.02 to 0.5. If it is not this range, the silver coating copper powder of the range used as the silver content (20 wt%-55 wt%) mentioned above is manufactured, and also as a powder characteristic of the silver copper composite powder after carrying out wet heat processing, The aspect ratio (thickness / [D ₅₀ ]) cannot be 0.02 to 0.5. In addition, if the aspect ratio of the copper powder particles as the core material is made relatively thin in relation to the particle size of less than 0.02, it is not preferable because coarse production tends to occur due to large variations in production. It is.

  In order to stably produce the flake copper powder as described above, a substantially spherical copper powder obtained by a method such as a wet method represented by a conventional hydrazine reduction method or a dry method represented by an atomization method, It is not possible to obtain a flake shape by directly deforming and flattening the powder particles by pulverizing the copper powder particles with balls or beads, which are media, by directly applying to a pulverizer such as a ball mill or a bead mill. . Even if it is compressed and deformed without eliminating the agglomerated state of the particles, it is subjected to compression deformation while maintaining the agglomerated state of the particles, and flake copper powder in the agglomerated state is obtained. This is because the powder particles are not dispersed.

  Accordingly, the inventors of the present invention first adopt a method of breaking the agglomerated state of the substantially spherical copper powder, performing a pulverization treatment to disperse the agglomerated particles, and then compressing and deforming the powder particles into flakes. It is preferable. For example, copper powder composed of substantially spherical powder particles is blown up to form a circular trajectory using a wind circulator using centrifugal force to dry copper powder in an agglomerated state, and its range The agglomerated powder particles collide with each other. In addition, the copper powder slurry containing copper powder in an agglomerated state is flowed at high speed to draw a circular orbit using a fluid mill using centrifugal force, and the centrifugal force generated at this time The powder particles agglomerated by the above are collided with each other in a solvent, and the pulverization operation is performed. And it is preferable to employ | adopt the method of carrying out the compression deformation of the powder particle | grains of copper powder by processing the substantially spherical copper powder which this pulverization process complete | finished using a high energy ball mill, and making it flake copper powder. The high energy ball mill referred to here is a powder of copper powder using a medium regardless of whether it is performed in a dried state of copper powder or in a state of copper powder slurry, such as a bead mill or an attritor. It is used as a general term for devices that can be compressed and plastically deformed.

Production of silver-coated copper powder: Silver-coated copper powder is produced by using the copper powder as described above as a core material. The silver-coated copper powder used in the production method according to the present invention is produced by a wet method. It is preferable to use it. Strictly speaking, when a silver coat layer is formed on the surface of copper powder by a wet method, the silver coat layer tends not to be a pure silver layer, but to have a composition containing a copper component eluted from copper powder as a core material. It is in. And by forming such a silver coat layer containing a copper component, mutual diffusion in a low temperature region between silver and copper by a wet heat treatment described later is facilitated.

  When silver-coated copper powder is produced by a wet method, a chelating agent is added to an aqueous solution to which copper powder has been added to form a dispersion, to which a silver-containing solution is added and reacted, and further filtered to obtain a copper powder. It is preferable to use one having a silver coat layer formed on the surface of the powder particles. This is because the thickness of the silver coat layer can be easily controlled and a uniform film thickness can be formed.

  The chelating agent used here forms a stable complex with copper ions, and preferably does not react with silver ions. Such chelating agents include ethylenediaminetetraacetate, triethylenediamine, diethylenetriaminepentaacetic acid, N, N, N ′, N′-tetraethylethylenediamine, diethylenediamine, phenanthroline, ethylenedioxybis (ethylamine) -N, N , N ′, N′-tetraacetic acid, nitrilotriacetic acid, picolinic acid and combinations thereof are used. Of these, ethylenediaminetetraacetate (EDTA) is preferably used because it is excellent in terms of the stability of the copper chelate complex, the inexpensiveness of the reagent, and the workability.

  The amount of the chelating agent added to the copper powder is 1 part by weight to 50 parts by weight, preferably 5 parts by weight to 40 parts by weight, and more preferably 10 parts by weight to 35 parts by weight with respect to 100 parts by weight of the copper powder. Part. In the range of the above addition amount, the copper hydroxide or oxide on the copper powder surface can be changed to a copper chelate complex, and silver coating on the copper powder surface can be performed quickly and efficiently. Therefore, when the amount of the chelating agent added is less than 1 part by weight, the subsequent silver coating cannot be performed satisfactorily. On the other hand, even if the addition amount of the chelating agent exceeds 50 parts by weight, the silver coating speed on the surface of the copper powder does not increase, and industrial profitability when cost is considered cannot be ensured. The more preferable range is a range of results in consideration of process stability in consideration of mass productivity.

  Moreover, in the manufacturing method which concerns on this invention, in addition to a chelating agent, various additives can also be added as needed. Examples of such additives include brighteners and dispersants such as lead chloride, potassium ferrocyanide and lauric acid for improving spreadability.

  In the production method according to the present invention, a silver-containing solution is added and reacted with a dispersion obtained by adding and stirring a chelating agent to an aqueous solution to which copper powder has been added. Although there is no limitation in the silver containing solution used here, when the copper powder weight in a dispersion liquid is 100 weight part, it is preferable to add so that 20 weight part-95 weight part may be contained as silver. If the silver content relative to the copper powder weight is less than 20 parts by weight, the silver coating amount on the copper powder particle surface is insufficient, and the minimum silver content required for the silver-copper composite powder according to the present invention is reduced. Cannot be achieved. On the other hand, when the silver content with respect to the copper powder weight exceeds 95 parts by weight, the silver coating amount on the surface of the copper powder particles is within the range of the silver content required for the silver-copper composite powder according to the present invention. In addition, the thickness of the silver coat layer on the surface of the copper powder particles tends to be non-uniform.

  As the silver-containing solution, the silver nitrate solution is most excellent in process stability. Here, the concentration in the case of using a silver nitrate solution is adjusted to, for example, 10 g / l to 300 g / l. The silver nitrate solution is preferably adjusted to 20 to 60 ° C. and added over 10 to 60 minutes. Moreover, it is preferable to add about 30 to 150 parts by weight of silver nitrate with respect to 100 parts by weight of copper powder. If it is out of the above range, it tends to be out of the above range of silver content.

  By adding a silver-containing solution to the dispersion, a substitution reaction starts immediately, and silver is deposited on the surface of the copper powder. The reaction is further promoted by stirring the dispersion during and after the addition of the silver-containing solution, and at the same time, non-uniform reaction in the reaction layer is prevented.

  Thereafter, a silver-coated copper powder is prepared by filtering and washing the mixed solution of the stirred dispersion and the silver ion solution.

Wet heat treatment (production of silver-copper composite powder): In the production method according to the present invention, the silver-coated copper powder obtained as described above is added to pure water, and then wet heat treatment is performed. The wet heat treatment is performed by stirring at a temperature of 50 ° C. to 200 ° C. for 30 minutes to 120 minutes. By performing the wet heat treatment in this way, the silver of the silver coat layer diffuses into the copper, and the silver and copper are uniformly dispersed. Strictly speaking, it is considered that there is a gradient of silver concentration from the surface of the powder grain toward the central portion, and the silver concentration is changed from a high silver concentration to a low silver concentration. Usually, in order to cause mutual diffusion between different kinds of metals, heating at a higher temperature is required. However, a metal layer deposited by an electrochemical reduction reaction or the like is in an activated state and has a crystal structure that is likely to cause rearrangement of crystal structure dislocations by heating at a low temperature. Furthermore, since a certain amount of copper is contained in the silver coat layer from the beginning, it is considered that interdiffusion at a low temperature can be easily performed. The reason why such heating is performed in a solvent is to prevent contact with the atmosphere as much as possible and to prevent unnecessary oxidation and contamination of the powder particle surface.

  After the wet heat treatment, the resultant is filtered, then washed with alcohol, and dried to produce a silver-copper composite powder. The alcohol cleaning at this time is not particularly essential. This is because it is used to facilitate the evaporation of moisture. For alcohol cleaning, methanol and ethanol are generally used.

  The silver-copper composite powder obtained by the production method according to the present invention can be used in various applications, for example, as a conductive filler for conductive paste, conductive ink, conductive paint, conductive resin, etc. Can do. Hereinafter, the present invention will be specifically described based on Examples and Comparative Examples.

<Sulfuric acid washing of copper powder as core material>
To 1.33 liters of pure water, 200 g of copper powder composed of substantially spherical particles having a volume cumulative average particle diameter D ₅₀ of 1.0 μm was added, stirred for 5 minutes, and then added with 50 g of 20% sulfuric acid solution for 20 minutes. The mixture was stirred and repulped with 1 liter of pure water three times to obtain a pretreated copper powder.

<Preparation of silver-coated copper powder>
200 g of the pretreated copper powder was added to 1 liter of pure water, and after stirring, 26.6 g of EDTA was added and stirred for 5 minutes to obtain a dispersion. Next, a silver nitrate solution in which 94.4 g of silver nitrate was dissolved in 900 ml of pure water was maintained at 40 ° C., and added to the dispersion over 30 minutes with stirring to perform a substitution reaction. Further, after stirring for 5 minutes, filtration and washing were performed to prepare silver-coated copper powder.

<Manufacture of silver-copper composite powder>
The above silver-coated copper powder is added to 1.3 liters of pure water, stirred at a liquid temperature of 80 ° C. for 60 minutes, subjected to wet heat treatment, filtered, then washed with methanol and dried, and then a silver-copper composite powder. Manufactured.

Table 1 shows the results of chemical analysis and the like indicating the particle size distribution (D ₅₀ , D ₉₀ , D _max ), specific surface area, and tap packing density of the silver-copper composite powder produced as described above and the composition of the tap filling density. In Table 1, the powder characteristics (D ₅₀ , D ₉₀ , D _max , specific surface area (SSA), tap filling density (TD)), chemical quantitative analysis using ICP analyzer after dissolving the powder particles Results (displayed as “content by chemical analysis” in the table), simple quantitative analysis results at the particle surface layer using energy-dispersed EPMA (displayed as “component amount of surface layer by EDX” in the table), color difference as silver It showed so that the state which changed from the coat copper powder to the silver copper composite powder might be understood.

As can be seen from Table 1, even when the silver-coated copper powder is wet-heat-treated to form a silver-copper composite powder, there is not much change in the powder characteristics among D ₅₀ , D ₉₀ , D _max and tap filling density (TD). No. However, the value of the specific surface area (SSA) is changing, and the specific surface area of the wet-heat treated silver-copper composite powder is larger than that of the silver-coated copper powder.

  And it turns out that it does not change with wet heat processing about the chemical-quantitative-analysis result of each content of silver and copper of the silver coat copper powder and silver copper composite powder before and after performing wet heat processing. On the other hand, when the simple quantitative analysis result in the particle surface part using the energy dispersive EPMA is seen, the amount of silver in the surface layer as the silver coated copper powder is 55.8 wt%, but after the wet heat treatment In the silver-copper composite powder, the amount of silver in the surface layer was as low as 33.9 wt%, and it can be understood that the silver powder was surely diffused into the copper powder as the core material.

For the measurement of particle size distribution, 0.1 g of silver-copper composite powder was mixed with a 0.1% aqueous solution of SN Dispersant 5468 (manufactured by San Nopco) and dispersed with an ultrasonic homogenizer (US-300T, manufactured by Nippon Seiki Seisakusho) for 5 minutes. Thereafter, the measurement was performed using a laser diffraction / scattering particle size distribution analyzer, Micro Trac HRA 9320-X100 (Leeds + Northrup). The average particle diameter D ₅₀ was particle size ([mu] m) at the time the cumulative volume is 50% as determined by a laser diffraction scattering method, D ₉₀ is the particle diameter at the time the cumulative volume of 90% as determined by a laser diffraction scattering method ( μm), and the maximum particle size D _max is the particle size (μm) having the maximum cumulative volume determined by the laser diffraction scattering method. The specific surface area is a value determined by a transmission method using a Shimadzu specific surface area measuring device SS-10. The tap filling density was obtained by accurately weighing 200 g of silver-copper composite powder, putting it in a 150 cm ³ graduated cylinder, repeatedly tapping 1000 drops at a stroke of 40 mm, and then obtaining the volume of the silver-copper alloy powder. It is. In addition, the color difference is measured by preparing silver-coated copper powder or silver-copper composite powder into a tablet shape at a press pressure of 10 kg / mm ² in a dry state, and preparing it as a color difference measurement sample. The measurement was performed using a SM color computer SM-4 manufactured by company.

In view of the color difference that can be used as an alternative index of the dispersion level and surface roughness of silver and copper, L ^* value = 60.22, a ^* value = −1 in the silver-coated copper powder before wet heat treatment .35, b ^* value = 9.31, and it can be seen from the a ^* value and b ^* value that red and blue tend to be stronger than the silver-copper composite powder according to the present invention. On the other hand, in the silver-copper composite powder after the wet heat treatment, L ^* value = 63.53, a ^* value = −0.22, b ^* value = 10.21, and the L ^* value that is appropriate in the present invention = It was confirmed that it was in the range of 56 to 78, a ^* value = −0.5 to −0.1, b ^* value = 10.0 to 12.0.

  To 1 liter of pure water, 200 g of pretreated copper powder similar to that used in Example 1 was added, and after stirring, 44.4 g of EDTA was added and stirred for 5 minutes to obtain a dispersion. Next, a silver nitrate solution in which 157.4 g of silver nitrate was dissolved in 900 ml of pure water was kept at 40 ° C., and added to the dispersion under stirring for 30 minutes to carry out a substitution reaction. Further, after stirring for 5 minutes, filtration and washing were performed to prepare silver-coated copper fine particles.

  The obtained silver-coated copper fine particles were subjected to wet heat treatment, filtration, methanol washing and drying in the same manner as in Example 1 to produce silver-copper composite powder.

Measurement of the particle size distribution (D ₅₀ , D ₉₀ , D _max ), specific surface area and tap packing density and chemical analysis of the silver-copper composite powder produced in this manner were performed in the same manner as in Example 1, and the results are shown in Table 1. It is shown in 2.

As can be seen from Table 2, even when the silver-coated copper powder is wet-heat treated to form a silver-copper composite powder, there is not much change in D ₅₀ , D ₉₀ , D _max and tap filling density among the powder characteristics. However, the value of the specific surface area (SSA) is changing, and the specific surface area of the wet-heat treated silver-copper composite powder is larger than the specific surface area of the silver-coated copper powder.

  And it turns out that it does not change with wet heat processing about the chemical-quantitative-analysis result of each content of silver and copper of the silver coat copper powder and silver copper composite powder before and after performing wet heat processing. On the other hand, when the simple quantitative analysis result in the particle surface part using the energy dispersion type EPMA is seen, the amount of silver in the surface layer as the silver-coated copper powder is 59.4 wt%, but after the wet heat treatment In the silver-copper composite powder, the amount of silver in the surface layer is as small as 47.0 wt%, and it can be understood that the silver powder was surely diffused into the copper powder as the core material.

The color difference of the silver-coated copper powder before the wet heat treatment is L ^* value = 59.65, a ^* value = −1.49, b ^* value = 9.19. From the a ^* value and the b ^* value, the present invention It can be seen that red and blue tend to be stronger than the silver-copper composite powder according to. On the other hand, in the silver-copper composite powder after the wet heat treatment, L ^* value = 58.26, a ^* value = −0.29, b ^* value = 10.16, and L ^* value that is appropriate in the present invention = It was confirmed that it was in the range of 56 to 78, a ^* value = −0.5 to −0.1, b ^* value = 10.0 to 12.0.

  To 1 liter of pure water, 200 g of the pretreated copper powder similar to that used in Example 1 was added, and after stirring, 62.2 g of EDTA was added and stirred for 5 minutes to obtain a dispersion. Next, a silver nitrate solution obtained by dissolving 220.4 g of silver nitrate in 900 ml of pure water was kept at 40 ° C., and added to the dispersion over 30 minutes with stirring to perform a substitution reaction. Further, after stirring for 5 minutes, filtration and washing were performed to prepare silver-coated copper fine particles.

  The obtained silver-coated copper fine particles were subjected to wet heat treatment, filtration, methanol washing and drying in the same manner as in Example 1 to produce silver-copper composite powder.

Measurement of the particle size distribution (D ₅₀ , D ₉₀ , D _max ), specific surface area and tap packing density and chemical analysis of the silver-copper composite powder produced in this manner were performed in the same manner as in Example 1, and the results are shown in Table 1. 3 shows.

As can be seen from Table 3, even when the silver-coated copper powder is wet-heat treated to form a silver-copper composite powder, there is not much change in D ₅₀ , D ₉₀ , D _max and tap filling density among the powder characteristics. However, the value of the specific surface area (SSA) is changing, and the specific surface area of the wet-heat treated silver-copper composite powder is larger than the specific surface area of the silver-coated copper powder.

  And it turns out that it does not change with wet heat processing about the chemical-quantitative-analysis result of each content of silver and copper of the silver coat copper powder and silver copper composite powder before and after performing wet heat processing. On the other hand, when the simple quantitative analysis result in the particle surface part using the energy dispersive EPMA is seen, the amount of silver in the surface layer as the silver coated copper powder is 69.3 wt%, but after the wet heat treatment In the silver-copper composite powder, the amount of silver in the surface layer is as small as 51.6 wt%, and it can be understood that the silver powder was surely diffused into the copper powder as the core material.

The color difference of the silver-coated copper powder before the wet heat treatment is L ^* value = 61.89, a ^* value = −1.69, b ^* value = 9.57. From the a ^* value and the b ^* value, the present invention It can be seen that red and blue tend to be stronger than the silver-copper composite powder according to. On the other hand, in the silver-copper composite powder after the wet heat treatment, L ^* value = 60.23, a ^* value = −0.38, b ^* value = 10.35, and L ^* value that is appropriate in the present invention = It was confirmed that it was in the range of 56 to 78, a ^* value = −0.5 to −0.1, b ^* value = 10.0 to 12.0.

Cumulative volume-average particle size D ₅₀ as the raw material of copper powder 3.2 .mu.m, except that the aspect ratio using the flaky copper powder of 0.1 in the same manner as in Example 1, a wet heat treatment, filtration, washed with methanol, and dried To produce a flaky silver-copper composite powder.

Measurement of the particle size distribution (D ₅₀ , D ₉₀ , D _max ) and specific surface area of the flaky silver-copper composite powder produced in this way, chemical analysis, etc. were carried out in the same manner as in Example 1, and the results are shown in Table 4. Shown in

As can be seen from Table 4, even when the silver-coated copper powder is wet-heat-treated to form a silver-copper composite powder, there is not much change in D ₅₀ , D ₉₀ , D _max and tap filling density among the powder characteristics. However, the value of the specific surface area (SSA) is changing, and the specific surface area of the wet-heat treated silver-copper composite powder is larger than the specific surface area of the silver-coated copper powder.

  And it turns out that it does not change with wet heat processing about the chemical-quantitative-analysis result of each content of silver and copper of the silver coat copper powder and silver copper composite powder before and after performing wet heat processing. On the other hand, when the simple quantitative analysis result in the particle surface layer part using energy dispersion type EPMA is seen, the amount of silver in the surface layer as a silver coat copper powder is 55.1 wt%, but after wet heat treatment In the silver-copper composite powder, the amount of silver in the surface layer is as small as 34.5 wt%, and it can be understood that the silver powder was surely diffused into the copper powder as the core material.

The color difference of the silver-coated copper powder before the wet heat treatment is L ^* value = 70.52, a ^* value = −1.33, b ^* value = 9.01, and from the a ^* value and the b ^* value, the present invention It can be seen that red and blue tend to be stronger than the silver-copper composite powder according to. On the other hand, in the silver-copper composite powder after the wet heat treatment, L ^* value = 73.12, a ^* value = −0.25, b ^* value = 10.01, and L ^* value that is appropriate in the present invention = It was confirmed that it was in the range of 56 to 78, a ^* value = −0.5 to −0.1, b ^* value = 10.0 to 12.0.

  Except that the flaky copper powder used in Example 4 was used as the raw material copper powder, wet heat treatment, filtration, methanol washing and drying were performed in the same manner as in Example 2 to produce a flaky silver-copper composite powder.

Measurement of the particle size distribution (D ₅₀ , D ₉₀ , D _max ) and specific surface area of the flaky silver-copper composite powder produced in this way, chemical analysis, etc. were carried out in the same manner as in Example 1, and the results are shown in Table 5. Shown in

As can be seen from Table 5, even when the silver-coated copper powder is wet-heat-treated to form a silver-copper composite powder, there is not much change in D ₅₀ , D ₉₀ , D _max and tap filling density among the powder characteristics. However, the value of the specific surface area (SSA) is changing, and the specific surface area of the wet-heat treated silver-copper composite powder is larger than the specific surface area of the silver-coated copper powder.

  And it turns out that it does not change with wet heat processing about the chemical-quantitative-analysis result of each content of silver and copper of the silver coat copper powder and silver copper composite powder before and after performing wet heat processing. On the other hand, when the simple quantitative analysis result in the particle surface layer part using energy dispersion type EPMA is seen, the amount of silver in the surface layer as the silver coat copper powder is 57.8 wt%, but after the wet heat treatment In the silver-copper composite powder, the amount of silver in the surface layer was as small as 48.0 wt%, and it can be understood that the silver powder was surely diffused into the copper powder as the core material.

The color difference of the silver-coated copper powder before the wet heat treatment is L ^* value = 73.23, a ^* value = −1.52, b ^* value = 9.23. From the a ^* value and the b ^* value, the present invention It can be seen that red and blue tend to be stronger than the silver-copper composite powder according to. On the other hand, in the silver-copper composite powder after the wet heat treatment, L ^* value = 72.15, a ^* value = −0.32, b ^* value = 10.12, and L ^* value that is appropriate in the present invention = It was confirmed that it was in the range of 56 to 78, a ^* value = −0.5 to −0.1, b ^* value = 10.0 to 12.0.

  Except that the flaky copper powder used in Example 4 was used as the raw material copper powder, wet heat treatment, filtration, methanol washing and drying were performed in the same manner as in Example 3 to produce a flaky silver-copper composite powder.

Measurement of the particle size distribution (D ₅₀ , D ₉₀ , D _max ) and specific surface area, chemical analysis, etc. of the flaky silver-copper composite powder produced in this manner was carried out in the same manner as in Example 1, and the results are shown in Table 6. Shown in

As can be seen from Table 6, even when the silver-coated copper powder is wet-heat-treated to obtain a silver-copper composite powder, there is not much change in D ₅₀ , D ₉₀ , D _max and tap filling density among the powder characteristics. However, the value of the specific surface area (SSA) is changing, and the specific surface area of the wet-heat treated silver-copper composite powder is larger than that of the silver-coated copper powder.

  And it turns out that it does not change with wet heat processing about the chemical-quantitative-analysis result of each content of silver and copper of the silver coat copper powder and silver copper composite powder before and after performing wet heat processing. On the other hand, when the simple quantitative analysis result in the particle surface layer part using energy dispersion type EPMA is seen, the amount of silver in the surface layer as a silver coat copper powder is 66.3 wt%, but after wet heat treatment In the silver-copper composite powder, the amount of silver in the surface layer was as small as 52.5 wt%, and it can be understood that the silver powder was surely diffused into the copper powder as the core material.

The color difference of the silver-coated copper powder before the wet heat treatment is L ^* value = 74.24, a ^* value = −1.75, b ^* value = 9.52, and the present invention is based on the a ^* value and the b ^* value. It can be seen that red and blue tend to be stronger than the silver-copper composite powder according to. On the other hand, in the silver-copper composite powder after the wet heat treatment, L ^* value = 74.31, a ^* value = −0.42, b ^* value = 10.33, and L ^* value that is appropriate in the present invention = It was confirmed that it was in the range of 56 to 78, a ^* value = −0.5 to −0.1, b ^* value = 10.0 to 12.0.

Comparative example

(Comparative Example 1)
Using a silver-copper alloy melt, spherical silver-copper composite powder was produced by the atomizing method. Measurement of particle size distribution (D ₅₀ , D ₉₀ , D _max ), specific surface area and tap packing density, chemical analysis, and the like of this silver-copper composite powder were performed in the same manner as in Example 1, and the results are shown in Table 7.

As can be seen from Table 7, when the powder characteristics of the silver-copper composite powder obtained by the atomization method are compared with the silver-copper composite powder according to the above examples, among the powder characteristics, D ₅₀ , D ₉₀ , D _max There is not much change in tap packing density. However, it can be understood that the value of the specific surface area (SSA) is small, and the powder particle surface is smooth.

  However, regarding the chemical quantitative analysis results of the silver and copper contents of the silver-copper composite powder obtained by the atomization method, the silver content is as high as 72.1 wt%. This is because it is difficult to produce a uniform molten metal as a silver-copper alloy unless the silver content is increased. And when the simple quantitative analysis result in the particle surface layer part using energy dispersion type EPMA is seen, the amount of silver in a surface layer is as high as 63.9 wt%, and if it is this surface layer silver amount, silver and copper and It can be understood that it is not a silver-copper composite powder that has the advantages of both.

(Comparative Example 2)
Using a silver-copper alloy melt, a silver-copper composite powder obtained by the atomizing method was used to physically plastically deform the powder particles by a conventional method to produce a flaky silver-copper composite powder. Measurement of the particle size distribution (D ₅₀ , D ₉₀ , D _max ), specific surface area and tap packing density of this silver-copper composite powder, chemical analysis, etc. were carried out in the same manner as in Example 1, and the results are shown in Table 8. Show. In addition, the aspect ratio of this flake powder is 0.1.

As can be seen from Table 7, when the powder characteristics of the silver-copper composite powder obtained by the atomization method are compared with the silver-copper composite powder according to the above examples, among the powder characteristics, D ₅₀ , D ₉₀ , D _max There is not much change in tap packing density. However, it can be understood that the value of the specific surface area (SSA) is small, and the powder particle surface is smooth.

  However, regarding the chemical quantitative analysis results of the silver and copper contents of the silver-copper composite powder obtained by the atomization method, the silver content is as high as 71.8 wt%. This is because it is difficult to produce a uniform molten metal as a silver-copper alloy unless the silver content is increased. And when the simple quantitative analysis result in the particle surface layer part using energy dispersion type EPMA is seen, the amount of silver in the surface layer is as high as 62.1 wt%. It can be understood that it is not a silver-copper composite powder that has the advantages of both.

<Contrast between Example and Comparative Example>
First, Examples 1 to 3 and Comparative Example 1 are compared with respect to the silver-copper composite powder composed of substantially spherical particles. It can be seen that the silver-copper composite powder obtained in each of Examples 1 to 3 has all the powder characteristics required for the silver-copper alloy according to the present invention. . From the viewpoint of powder characteristics, it can be said that Examples 1 to 3 are finer and more uniform than Comparative Example 1 and have the same tap filling density. Accordingly, Comparative Example 1 cannot satisfy the powder characteristics required for the silver-copper composite powder according to the present invention, and Comparative Example 1 has larger particles and a specific surface area than Examples 1 to 3. I understand that it is small.

  Moreover, Example 3-Example 6 and the comparative example 2 are contrasted regarding the silver-copper composite powder which consists of flake-like powder particles. It can be seen that the silver-copper composite powder obtained in each of Examples 3 to 6 has all the powder characteristics required for the silver-copper composite powder according to the present invention. . From the viewpoint of powder characteristics, Examples 3 to 4 are finer and more uniform than Comparative Example 2. Therefore, Comparative Example 2 cannot satisfy the powder characteristics required for the silver-copper composite powder according to the present invention, and Comparative Example 2 has larger particles and a specific surface area than Examples 3 to 6. I understand that it is small.

  The silver-copper composite powder according to the present invention is a silver-copper composite powder that has good powder characteristics not found in conventional silver-copper composite powder and is atomized and uniform. And since the silver-copper composite powder has a good dispersion state of silver and copper, the silver migration phenomenon can be suppressed, and the characteristics of silver as an electrical good conductor can be effectively utilized. It can be suitably used as a conductive filler such as ink, conductive paint, conductive resin.

  Moreover, the said silver-copper composite powder which has favorable powder characteristics, and was atomized and equalized by the manufacturing method which concerns on this invention is obtained. And this silver-copper composite powder has good dispersion of silver and copper on the surface of the grain, but it does not require new production equipment, it is a composite of silver and copper using conventional equipment. This facilitates mass production of silver-copper composite powder having good characteristics. Therefore, inexpensive and high-quality silver-copper composite powder can be provided to the market.

Claims (6)

A silver-copper composite powder containing silver and copper,
A silver coat layer is formed on the surface of the copper powder particles by a wet method, and the silver-coated copper powder is heated in a solution at a temperature of 50 ° C. to 200 ° C. for 30 minutes to 120 minutes to thermally convert silver and copper. Obtained by interdiffusion,
The silver content is 20 wt% to 55 wt%, the remaining copper and inevitable impurities,
CIE1976L ^* a ^* b ^* provided with a color tone of L ^* value = 56 to 78, a ^* value = −0.5 to −0.1, b ^* value = 10.0 to 12.0 obtained in the color system A silver-copper composite powder characterized by that. The silver-copper composite powder according to claim 1, wherein: ~ C. A silver-copper composite powder comprising substantially spherical powder particles having the following powder characteristics.
A. Cumulative volume-average particle size _{D 50} by laser diffraction scattering particle size distribution measuring method 0.3Myuemu～6.0Myuemu.
B. The volume cumulative maximum particle size D _max by laser diffraction scattering type particle size distribution measurement method is 20.0 μm or less.
C. Specific surface area is 0.2 m ² / g or more. The silver-copper composite powder according to claim 1, wherein the following a. ~ C. A silver-copper composite powder composed of flaky particles having the following powder characteristics.
a. Cumulative volume-average particle size _{D 50} by laser diffraction scattering particle size distribution measuring method 1.0Myuemu～10.0Myuemu.
b. The volume cumulative maximum particle size D _max by the laser diffraction / scattering particle size distribution measurement method is 40.0 μm or less.
c. The aspect ratio (thickness / [D ₅₀ ]) of the powder is 0.02 to 0.5. A method for producing a silver-copper composite powder according to any one of claims 1 to 3,
Silver with a silver coating layer formed on the surface of copper powder particles by adding a silver-containing solution to the dispersion obtained by adding a chelating agent to an aqueous solution containing copper powder and reacting. Using coated copper powder,
After a temperature of the solution in the silver-coated copper powder 50 ° C. to 200 DEG ° C., silver and copper thermally by interdiffusion by a wet heat treatment for heat treatment for 30 minutes to 120 minutes, filtered, washed with alcohol, A method for producing a silver-copper composite powder, which comprises drying. The silver according to claim 4 , wherein a silver-containing solution is added to the dispersion so as to contain 20 parts by weight to 95 parts by weight as silver when the weight of the copper powder in the dispersion is 100 parts by weight. A method for producing a copper composite powder. The method for producing a silver-copper composite powder according to claim 4 or 5 , wherein the chelating agent is ethylenediaminetetraacetate.