CN116075380A - Silver-coated flake copper powder and method for producing same - Google Patents

Silver-coated flake copper powder and method for producing same Download PDF

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Publication number
CN116075380A
CN116075380A CN202180058151.0A CN202180058151A CN116075380A CN 116075380 A CN116075380 A CN 116075380A CN 202180058151 A CN202180058151 A CN 202180058151A CN 116075380 A CN116075380 A CN 116075380A
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silver
copper
coated
volume
powder
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藤本卓
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Mitsui Mining and Smelting Co Ltd
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Mitsui Mining and Smelting Co Ltd
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    • CCHEMISTRY; METALLURGY
    • C23COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23CCOATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/54Contact plating, i.e. electroless electrochemical plating
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22FWORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/06Metallic powder characterised by the shape of the particles
    • B22F1/068Flake-like particles
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22FWORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/14Treatment of metallic powder
    • B22F1/145Chemical treatment, e.g. passivation or decarburisation
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22FWORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/17Metallic particles coated with metal
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22FWORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00Making metallic powder or suspensions thereof
    • B22F9/02Making metallic powder or suspensions thereof using physical processes
    • B22F9/04Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C1/00Making non-ferrous alloys
    • C22C1/04Making non-ferrous alloys by powder metallurgy
    • C22C1/0425Copper-based alloys
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C1/00Making non-ferrous alloys
    • C22C1/04Making non-ferrous alloys by powder metallurgy
    • C22C1/0466Alloys based on noble metals
    • CCHEMISTRY; METALLURGY
    • C23COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23CCOATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C23C18/31Coating with metals
    • CCHEMISTRY; METALLURGY
    • C23COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23CCOATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C23C18/31Coating with metals
    • C23C18/42Coating with noble metals
    • CCHEMISTRY; METALLURGY
    • C25ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25CPROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C1/00Electrolytic production, recovery or refining of metals by electrolysis of solutions
    • C25C1/12Electrolytic production, recovery or refining of metals by electrolysis of solutions of copper
    • CCHEMISTRY; METALLURGY
    • C25ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25CPROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C5/00Electrolytic production, recovery or refining of metal powders or porous metal masses
    • C25C5/02Electrolytic production, recovery or refining of metal powders or porous metal masses from solutions
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01BCABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B5/00Non-insulated conductors or conductive bodies characterised by their form
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22FWORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2301/00Metallic composition of the powder or its coating
    • B22F2301/10Copper
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22FWORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2999/00Aspects linked to processes or compositions used in powder metallurgy
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22FWORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00Making metallic powder or suspensions thereof
    • B22F9/16Making metallic powder or suspensions thereof using chemical processes
    • B22F9/18Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
    • B22F9/24Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from liquid metal compounds, e.g. solutions
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C5/00Alloys based on noble metals
    • C22C5/06Alloys based on silver
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C9/00Alloys based on copper

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Abstract

The volume cumulative particle diameter of the silver-coated flake copper powder of the present invention when 90% by volume of the cumulative volume by the laser diffraction scattering particle size distribution measurement method is set as D 90 (μm) the volume cumulative particle diameter at a cumulative volume of 10% by volume was set to D 10 At (μm), luminance L is relative to D 90 /D 10 The value of the degree of dispersion is defined to be 13 or more. Silver-coated flake copper powder was produced by the following method: treating a dispersion liquid containing copper mother powder and a 1 st complexing agent by a medium stirring mill device to deform copper mother particles forming the copper mother powder into a sheet shape; subjecting the copper master powder comprising the copper master particles deformed into flakes to an aqueous liquid comprising silver ions and a2 nd complexing agentAnd (3) carrying out a line treatment to precipitate silver on the surface of the copper master particles.

Description

Silver-coated flake copper powder and method for producing same
Technical Field
The present invention relates to silver-coated copper flake powder and a method for producing the same.
Background
The flake copper particles have a large specific surface area due to their shape, and the particles are easily contacted with each other, so that the addition of the flake copper particles to a resin makes it easy to impart conductivity to the resin. However, copper is easily oxidized, and as a result, there is a disadvantage that the resistance of copper particles is easily increased. In order to overcome this disadvantage, various techniques have been proposed in which the surface of copper particles is covered with silver, which is a metal having a lower electrical resistance than copper, to thereby suppress an increase in the electrical resistance of the particles.
For example, patent documents 1 to 3 propose a silver-coated flake copper powder comprising: silver-coated sheet-like copper particles having silver on the surface and subjected to flattening treatment.
Prior art literature
Patent literature
Patent document 1: japanese patent laid-open No. 2010-275638
Patent document 2: japanese patent application laid-open No. 2015-71818
Patent document 3: japanese patent laid-open publication 2016-35098
Disclosure of Invention
According to the techniques described in patent documents 1 to 3, electrolytic copper powder is flattened by using a pulverizing device such as a grinder, and then the surface of the copper powder is covered with silver by displacement plating. However, the silver-coated flake copper powder obtained by this method has the following problems: the silver coating is uneven, and a part of the surface of the copper powder is exposed. This problem is particularly remarkable when the thickness of the electrolytic copper powder after flattening is thin. When the silver-coated copper powder in such a coated state is mixed with a resin, copper is likely to be eluted into the resin, and the resin is likely to deteriorate with time due to this.
Accordingly, an object of the present invention is to provide silver-coated copper flake powder and a method for producing the same, which can solve the various drawbacks of the prior art.
The present invention solves the above-described problems by providing a silver-coated flake copper powder,
comprising silver-coated flaky copper particles having silver at least on the surface,
the volume cumulative particle diameter at 90% by volume of the cumulative volume of the silver-coated flake copper powder by the laser diffraction scattering particle size distribution measurement method was set as D 90 (μm) the volume cumulative particle diameter at a cumulative volume of 10% by volume was set to D 10 When the particle size is (mu m),
the brightness L of the silver-coated flake copper powder is equal to D 90 /D 10 The value of the degree of dispersion is defined to be 13 or more.
The present invention also provides a method for producing silver-coated copper flake powder,
treating the dispersion liquid containing the copper mother powder and the 1 st complexing agent by a medium stirring mill device to deform copper mother particles forming the copper mother powder into a sheet shape,
the copper master batch containing the copper master batch deformed into a sheet shape is treated with an aqueous liquid containing silver ions and a2 nd complexing agent to precipitate silver on the surface of the copper master batch.
Detailed Description
The present invention will be described below based on preferred embodiments.
The present invention relates to a silver-coated copper powder, which is an aggregate of silver-coated copper particles having silver at least on the surfaces of copper particles as a base material. One of the characteristics of the silver-coated copper particles is its shape. In detail, the silver-coated copper particles have a sheet-like shape. Therefore, in the following description, the silver-coated copper particles are also referred to as "silver-coated flaky copper particles", and the silver-coated copper powder is referred to as "silver-coated flaky copper powder".
The term "flake" as used herein is synonymous with "flat" and "flake" and means that the particles have a platelet-like shape. The platelet particles are defined by their aspect ratio. The aspect ratio is a value of D/T, which is a ratio of the long diameter D of the plate surface to the thickness T of the sheet-like particles when the sheet-like particles are viewed from above. The long diameter D of the plate surface is the length of the longest line segment among the line segments crossing the plate surface. In the present invention, the aspect ratio of the silver-coated sheet copper particles is preferably 5 or more and 160 or less, more preferably 10 or more and 160 or less, still more preferably 10 or more and 140 or less, still more preferably 15 or more and 140 or less, still more preferably 20 or more and 140 or less, particularly preferably 30 or more and 120 or less, and most preferably 30 or more and 80 or less, from the viewpoint that high conductivity can be imparted when the silver-coated sheet copper powder is added to the resin.
The aspect ratio takes the following values: the operation of measuring the long diameter D and the thickness T of 1 particle was performed on 50 or more particles, and the value of D/T was calculated, and the arithmetic average of the values of D/T thus obtained was taken.
The measurement methods of the major axis D and the thickness T are as follows.
Long diameter D: after a sample was photographed at an arbitrary magnification by an electron microscope, the major diameter was measured using image analysis particle size distribution measuring software (mount co., ltd. Mac-View).
Thickness T: the sample was resin-embedded, and the cross section was processed by a cross section polisher. Then, after photographing at an arbitrary magnification using an electron microscope, measurement was performed in the same manner as the long diameter D.
The shape of the silver-coated sheet-like copper particles in plan view, that is, the shape of the plate surface is not particularly limited, and for example, a shape such as a substantially circular shape, a substantially oval shape, a substantially elliptical shape, or an irregular shape may be used. Of these shapes, a substantially circular shape is preferable from the viewpoint that high conductivity can be imparted when the silver-coated flake copper powder is added to the resin.
When the shape of the plate surface of the silver-coated sheet-like copper particles is substantially circular, the degree of circularity of the plate surface is preferably 0.60 or more and 0.95 or less, more preferably 0.65 or more and 0.90 or less, and still more preferably 0.65 or more and 0.85 or less. When the area of the plate surface is S and the perimeter of the plate surface is L, 4pi S/L is used 2 To define circularity. The circularity is an arithmetic average of values measured for 50 or more particles.
The specific measurement method of the circularity is as follows.
The particle size distribution was measured using image analysis particle size distribution measuring software (mount co., ltd. Mac-View). The software was used to draw the outline of 50 or more samples and determine the area within the outline. The circle equivalent diameter is calculated from the area and averaged.
In the silver-coated sheet copper particles, when a part of the surface of the sheet copper particles as a base material is exposed, that is, when the coating of silver is uneven, when the silver-coated sheet copper powder is mixed with a resin, the resin may be modified by contact of copper with the resin. Therefore, the silver-coated flaky copper particles are preferably silver-coated on the surface of the flaky copper particles as a base material with excellent uniformity. In particular, from the viewpoint of economy, it is preferable to uniformly coat the surface of the flake-like copper particles with as small an amount of silver as possible.
The state of coating of silver in the silver-coated platelet-shaped copper particles can be evaluated by the value of the brightness L of the silver-coated platelet-shaped copper powder. The reason for this is as follows: the brightness of silver itself is higher than that of copper itself. In particular, the results of the studies by the present inventors indicate that: even if the surface of the flake copper particles is covered with silver in a large thickness, it is economically disadvantageous that the brightness is improved, and the dispersibility of the silver-coated flake copper powder in the resin is reduced. Therefore, it cannot be said that the silver-coated flake copper powder is preferable only because the value of the brightness L of the silver-coated flake copper powder is high.
The present inventors have conducted intensive studies from the viewpoint of preventing modification of a resin at the time of mixing with the resin and improving dispersibility in the resin, and as a result, found that: d adopting silver to coat flake copper powder 90 /D 10 It is advantageous to use as an index the ratio of the value of (c) to the value of luminance L. D (D) 90 Refers to the volume cumulative particle diameter (μm) at 90% by volume of the cumulative volume based on the laser diffraction scattering particle size distribution measurement method, D 10 Refers to the volume cumulative particle diameter (μm) at 10% by volume based on the cumulative volume of the same assay. In addition, D 90 /D 10 The value of (2) is a value that is an index of the particle size distribution of the powder, and is generally referred to as the dispersity. The smaller the value of the dispersity, the lower the aggregation degree of the particles of the powder, and the sharp the particle size distribution. Thus, a larger value of L x/dispersity indicates a more uniform silver-based coating and a lower aggregation of the silver-coated platelet-shaped copper powder.
In the silver-coated flake copper powder of the present invention, the value of L/dispersity is preferably 13 or more, more preferably 14 or more, and even more preferably 15 or more. The larger the value of L/dispersity is, the more preferable, but if the value is as large as about 25, the effect expected by the present invention can be fully exerted.
The value of L/dispersivity is preferably 70 or more, more preferably 73 or more, and even more preferably 76 or more from the viewpoint of uniform coating with silver. The silver-coated copper flake having such an L value can be produced by a method described below. The upper limit value of L is not particularly limited, and the closer to 100, the more preferable, but the effect expected by the present invention can be fully exerted as long as the value of L is about 86. The value of L is measured using a diffuse illumination vertical light receiving system described in JIS Z8722 (based on the geometric condition c/including specular reflection light), for example, a color colorimeter (CR-400) manufactured by konikamada corporation.
On the other hand, from the viewpoint of improving the dispersibility of the silver-coated copper flake powder in the resin, the value of the dispersibility is preferably 5.3 or less, particularly preferably 5.0 or less, and particularly preferably 4.5 or less. The silver-coated flake copper powder having such a dispersity can be produced by a method described later. The lower limit of the dispersity is not particularly limited, and the closer to 1, the more preferable, but the effect expected by the present invention can be sufficiently exhibited as long as the value of the dispersity is as small as about 3.0.
The value of the dispersity can be calculated by the following method, for example. A small amount of silver-coated copper flake powder was taken in a beaker, 2 and 3 drops of 3 mass% Triton (Triton) X solution (manufactured by Kanto chemical Co., ltd.) were added, and after mixing with the powder, 50mL of 0.1 mass% SN dispersont 41 solution (manufactured by Sanremo Co., ltd.) was added. Next, a sample for measurement was prepared by performing a dispersion treatment using an ultrasonic disperser TIP.phi.20 (OUTPUT: 8, TUNING:5, manufactured by Japanese finisher, inc.) for 2 minutes. The particle size distribution of the measurement sample was measured by using a laser diffraction/scattering particle size distribution measuring apparatus MT3300 (manufactured by microtracB EL Corp.), to obtain D 90 And D 10 Is a value of (2). The degree of dispersion was calculated from these values.
The research result of the inventor shows that: from the viewpoint of preventing modification of the resin at the time of mixing with the resin and improving dispersibility in the resinIn view, the thickness T (μm) of the flaky copper particles coated with silver was measured with respect to D 50 The ratio of (μm) is also advantageous as an index. D (D) 50 Refers to the volume cumulative particle diameter (μm) at 50% by volume of the cumulative volume based on the laser diffraction scattering particle size distribution measurement. In the present invention, T/D 50 The value of (2) is preferably 0.04 or less, more preferably 0.03 or less. On the other hand, T/D 50 The value of (2) is preferably 0.005 or more, more preferably 0.01 or more, still more preferably 0.01 or more and 0.02 or less. With respect to T/D 50 At a fixed particle diameter D 50 When considered, it is expressed relative to particle size D 50 The silver-coated flaky copper particles have a small thickness T. When the thickness is too small, the surface area of the particles becomes too large, and the reactivity with the resin becomes strong. When the silver-coated flake copper powder is mixed with a resin, it is effective for preventing the modification of the resin and for improving the dispersibility in the resin. In general, in order to reduce the thickness T, external force is applied to the copper master batch as a raw material for a long time to sufficiently deform it to be flat, but the application of external force for a long time causes aggregation of the copper master batch, thereby giving D 50 An increasing tendency. Namely, the thickness T and D are reduced 50 In an contradictory relationship. However, in the present invention, the copper master powder is flaked by a method described later, whereby D can be suppressed 50 Is increased and decreased by a thickness T.
The thinner the thickness T, the more preferable, specifically, the less than 0.5 μm, and among them, the less than 0.3 μm is preferable, the less than 0.25 μm is particularly preferable, and the less than 0.20 μm is very preferable. The lower limit of the thickness T is not particularly limited, but the effect expected by the present invention can be sufficiently exhibited as long as the thickness T is as small as about 0.10 μm.
On the other hand, from the viewpoint of improving the dispersibility of the silver-coated flake copper powder in the resin, D 50 The value of (2) is preferably 7 μm or more and 17 μm or less, more preferably 8 μm or more and 16 μm or less, still more preferably 9 μm or more and 15 μm or less. D (D) 50 The value of (2) can be measured by the same method as the measurement of the degree of dispersion described above.
As described above, the silver-coated copper flake powder of the present invention has a low degree of aggregation, i.e., the above-mentioned dispersionDegree (D) 90 /D 10 ) Is small. Thus, in the silver-coated flake copper powder of the present invention, D 90 And D 10 The value of (2) is preferably the distance D 50 A value that is not far away. From this point of view, D 90 The value of (2) is preferably 15 μm or more and 35 μm or less, more preferably 16 μm or more and 31 μm or less, still more preferably 17 μm or more and 30.5 μm or less. On the other hand, D 10 The value of (2) is preferably 3.0 μm or more and 8.0 μm or less, more preferably 3.9 μm or more and 7.0 μm or less, still more preferably 5.0 μm or more and 6.2 μm or less.
As described above, the silver-coated copper flake particles constituting the silver-coated copper flake powder of the present invention have a small thickness and have a low aggregation level. For this reason, the silver-coated flake copper powder of the present invention has a low tap density. Specifically, the tap density of the silver-coated flake copper powder of the present invention is preferably 0.5g/cm 3 Above and 2.5g/cm 3 Hereinafter, more preferably 0.5g/cm 3 Above and 2.0g/cm 3 Hereinafter, it is more preferably 0.7g/cm 3 Above and 2.0g/cm 3 Hereinafter, it is more preferably 0.7g/cm 3 Above and 1.8g/cm 3 Hereinafter, it is more preferably 0.7g/cm 3 Above and 1.5g/cm 3 Hereinafter, it is particularly preferably 0.8g/cm 3 Above and 1.3g/cm 3 The following is given. Tap density was measured in accordance with JIS Z2512.
In the silver-coated copper flake powder of the present invention, the surface of the copper flake particles as the base material is desirably coated with silver as thinly and uniformly as possible. Therefore, it is not desirable to increase the proportion of silver in the silver-coated copper flake powder of the present invention. Specifically, the silver-coated copper flake powder according to the present invention has a silver content of 5 mass% or more and 20 mass% or less, more preferably 7 mass% or more and 16 mass% or less, still more preferably 9 mass% or more and 14 mass% or less. The proportion of silver in the silver-coated flake copper powder can be determined by ICP emission spectrometry.
Next, a suitable method for producing the silver-coated copper flake according to the present invention will be described. The production method of the present invention is roughly classified into a flaking step of copper particles as a base material and a coating step of silver on the flaked copper particles.
In the flaking step, a dispersion liquid containing the copper master batch and the 1 st complexing agent is treated by a medium stirring mill device, and copper master batch particles constituting the copper master batch are deformed into flakes.
In the silver coating step, copper master powder containing copper master particles deformed into a sheet shape is treated with an aqueous liquid containing silver ions and a2 nd complexing agent to precipitate silver on the surface of the copper master particles.
Hereinafter, each step will be described.
In the flaking step of the copper master powder, an external force is applied to the copper master powder having a shape other than a flake shape, and the copper master powder is deformed into a flat shape. Examples of the copper master powder include spherical copper master powder produced by a wet reduction method, electrolytic copper master powder obtained by electrolyzing an electrolyte containing copper ions, spherical copper master powder produced by an atomization method, and the like. Among these copper master powders, it is preferable to flake the dendrite-like copper master powder produced by the electrolytic method, in view of being able to smoothly produce flake-like copper powder having a small thickness.
When dendritic copper particles produced by an electrolytic method are used as a mother powder, it is preferable to crush the dendritic copper particles before flaking, in order to smoothly produce copper flakes having a small thickness. The method of pulverization is not particularly limited, and examples thereof include pulverizing methods based on a disk type, a roll type, a cylinder type, an impact type, a jet type, and a high-speed rotation type. In addition, both dry pulverization and wet pulverization may be used. From the viewpoint of reliably separating the branch portions and the trunk portions in the dendrite copper particles, dry pulverization is preferable. The dry grinding is preferably performed by, for example, a jet mill of an impact plate type or a jet mill of an impact type for causing particles to collide with each other.
From the viewpoint of obtaining flaky copper particles having a desired particle diameter and thickness, the particle diameter D of the pulverized copper particles 50 Preferably 2 μm or more and 8 μm or less, more preferably 3 μm or more and 7 μm or less, and still more preferably 4 μm or more and 6 μm or less.
Next, the copper particles as the base material were flaked. The flaking may be carried out by using a medium stirring mill such as a bead mill, a ball mill, or an attritor.
Copper particles were dispersed in a liquid solvent to prepare a dispersion before flaking by using a medium stirring mill. Examples of the liquid solvent used for preparing the dispersion include water and an organic solvent. A mixed solvent of water and an organic solvent may also be used. As the organic solvent, 2 or more kinds of the following organic solvents may be used singly or in combination: lower monohydric alcohols having 1 to 4 carbon atoms such as methanol and ethanol; lower polyols having 1 to 4 carbon atoms such as ethylene glycol; lower carboxylic acids having 1 to 4 carbon atoms; lower amines having 1 to 4 carbon atoms, and the like. Among these liquid solvents, an organic solvent is preferably used in view of improving dispersibility of copper particles in the dispersion and improving stability of quality in the treatment with a medium stirring mill. In particular, from the viewpoint of easy volatilization of the medium and difficulty in residue of the medium in the target flaky copper particles, a lower alcohol such as methanol is preferably used.
The concentration of copper particles in the dispersion is preferably 10 mass% or more and 60 mass% or less, and preferably 20 mass% or more and 50 mass% or less, from the viewpoint of productivity and prevention of generation of coarse particles.
To prepare the dispersion, only the copper particles and the liquid solvent are mixed. According to circumstances, a dispersion liquid may be prepared by using a stirring dispersion device. Examples of such a device include a fluid mill, t.k.fillmix (registered trademark) manufactured by PRIMIX Corporation, and the like.
In the present production method, the 1 st complexing agent is preferably contained in the dispersion in advance. By the action of the 1 st complexing agent, aggregation of copper particles during the progress of flaking is effectively suppressed. In addition, the oxide existing on the surface of the copper particles is removed by the 1 st complexing agent, so that silver can be coated on the surface of the flaky copper particles in a thin and uniform manner. From this viewpoint, the concentration of the 1 st complexing agent contained in the dispersion is preferably 0.1 mass% or more and 40 mass% or less, more preferably 0.5 mass% or more and 20 mass% or less, still more preferably 1 mass% or more and 10 mass% or less, provided that the concentration of the copper particles in the dispersion is within the above-described range.
Conventionally, when a copper master powder is flaked by a medium stirring mill, a dispersion liquid containing the copper master powder often contains a fatty acid to suppress aggregation of copper particles constituting the copper master powder. However, when a fatty acid is used, the fatty acid remains on the surface of the copper particles after flaking, and therefore, in order to coat the silver on the surface of the copper particles after flaking, the fatty acid needs to be removed before this. In order to remove fatty acids, a degreasing step is required, and there are inconvenience in that the step is increased and inconvenience in that the degreasing step causes oxidation of the surface of copper particles. In contrast, the present production method, in which the fatty acid is not contained in the dispersion liquid but the 1 st complexing agent is contained instead, does not cause such inconvenience.
The 1 st complexing agent can be single-tooth or multi-tooth such as two-tooth, three-tooth, four-tooth and the like. From the viewpoint of strength of complexation with copper, examples of the 1 st complexing agent include citric acid, ascorbic acid, ethylenediamine tetraacetate, and the like. These complexing agents may be used alone in an amount of 1 or in an amount of 2 or more. Among these complexing agents, ethylenediamine tetraacetate is preferably used from the viewpoint of effectively suppressing aggregation of copper particles in the flaking step.
In the flaking step, the dispersion liquid and the grinding medium are put into a medium stirring mill to be mixed and stirred.
The diameter of the pulverization medium is preferably 0.1mm or more and 1mm or less. The material of the grinding medium is usually zirconia or alumina.
The running time, the rotating speed, the passing times and the like of the medium stirring mill device are properly regulated in a mode of obtaining the target flaky copper powder.
After the copper master particles constituting the copper master powder are deformed into a sheet shape in this way, a silver coating step is performed. In the silver coating step, as described above, the copper master batch including the copper master batch particles deformed into a flake shape is treated with the aqueous liquid including the silver ions and the 2 nd complexing agent. The treatment preferably includes the following treatments 1 and 2.
[ Process 1]
The silver ions and the flaky copper particles are brought into contact with each other in water to perform displacement plating, and silver is precipitated on the surfaces of the flaky copper particles. Precursor particles are obtained by this precipitation.
[ treatment 2]
The precursor particles obtained in the treatment 1, silver ions and a reducing agent for silver ions are brought into contact with water to further precipitate silver on the surfaces of the precursor particles.
The silver ions used in the treatments 1 and 2 are generated from a silver compound as a silver source. As the silver compound, a water-soluble silver compound such as silver nitrate can be used. The concentration of silver ions in water is preferably set to 0.01 to 10mol/L, particularly preferably 0.04 to 2.0mol/L, from the viewpoint of being able to deposit a desired amount of silver on the surface of the sheet-like copper particles.
In the treatment 1, the amount of the flaky copper particles in water is preferably 1 to 1000g/L, and particularly preferably 50 to 500g/L, from the viewpoint that a desired amount of silver can be deposited on the surfaces of the flaky copper particles.
In the process 1, the order of addition of the flaky copper particles and silver ions is not particularly limited. For example, the flaky copper particles and silver ions may be added to water at the same time. From the viewpoint of ease of controlling precipitation of silver by displacement plating, it is preferable to prepare a dispersion by dispersing flaky copper particles in water in advance, and to add a silver compound as a silver source to the dispersion. In this case, the dispersion may be at normal temperature or may be in a temperature range of 0 to 80 ℃.
Preferably, the 2 nd complexing agent is added to the dispersion in advance of the addition of the silver compound to control the reduction of silver. Examples of the 2 nd complexing agent include ethylenediamine tetraacetate, triethylenediamine, iminodiacetic acid and salts thereof, citric acid and salts thereof, tartaric acid and salts thereof, and the like.
The 1 st complexing agent and the 2 nd complexing agent described above may be the same species or may be different species, and from the viewpoint of fitting the stability constants of the complexes, the 1 st complexing agent and the 2 nd complexing agent are preferably the same species. In particular, from the viewpoint of effectively suppressing aggregation of copper particles in the flaking step and from the viewpoint of making silver thin and uniformly coated in the silver coating step, it is preferable that both the 1 st complexing agent and the 2 nd complexing agent are ethylenediamine tetraacetate.
The addition of the silver compound in process 1 is preferably performed in the form of an aqueous solution. The aqueous solution may be added to the dispersion liquid at one time, or may be added continuously or discontinuously over a predetermined period of time. From the viewpoint of easy control of the reaction of displacement plating, an aqueous solution of a silver compound is preferably added to the dispersion over a predetermined period of time.
In the treatment 1, the dispersion is preferably irradiated with ultrasonic waves before or simultaneously with the addition of the silver compound to the dispersion. By irradiation with ultrasonic waves, the dispersion of the flaky copper particles in the dispersion is promoted, and the silver-based uniform coating of the flaky copper particles is easily performed. The frequency of the ultrasonic wave is particularly preferably 200kHz or less, more preferably 45kHz or less, as long as the irradiation has a certain effect. The lower limit is 10 kHz.
In the treatment 1, silver is precipitated on the surface of the sheet-like copper particles by the displacement plating described above, to obtain precursor particles. In view of the possibility of forming a thin and uniform coating of silver, the amount of silver deposited in the precursor particles is preferably 0.1 to 50 mass%, particularly preferably 1 to 10 mass%, of the amount of silver in the finally obtained silver-coated sheet copper powder.
Next, the process 2 will be described. In the process 2, silver ions and a reducing agent for silver ions are added to the dispersion liquid containing the precursor particles obtained in the process 1. In this case, the precursor particles obtained in the treatment 1 may be temporarily subjected to solid-liquid separation and then dispersed in water to prepare a dispersion, or the dispersion of the precursor particles obtained in the treatment 1 may be directly supplied to the treatment 2. In the latter case, silver ions added in the treatment 1 may remain in the dispersion, or may not remain.
The silver ions added in the treatment 2 are generated from a water-soluble silver compound as in the treatment 1. The silver compound is preferably added to the dispersion in the form of an aqueous solution. The concentration of silver ions in the aqueous solution is preferably 0.01 to 10mol/L, more preferably 0.1 to 2.0mol/L. From the viewpoint of enabling the formation of a thin and uniform coating of silver, an aqueous solution of silver ions having a concentration in this range is preferably added in an amount of 0.1 to 55 parts by mass, particularly preferably 1 to 25 parts by mass, relative to 100 parts by mass of precursor particles in the aforementioned dispersion containing 1 to 1000g/L, particularly 50 to 500g/L, of the precursor particles.
As the reducing agent added in the treatment 2, a reducing agent having a reducing power of such a degree that the substitution plating and the reduction plating of silver can be performed simultaneously is used. By using such a reducing agent, a thin and uniform coating of silver can be smoothly formed. When a reducing agent having a high reducing property is used, the reduction plating is unilaterally performed, and the silver coating having the target structure is not easily formed. On the other hand, when a reducing agent having a weak reducing property is used, the reduction plating of silver ions is difficult to be performed, and the silver coating having the target structure is still difficult to be formed due to this. From the above viewpoints, an organic reducing agent which exhibits acidity when dissolved in water is preferably used as the reducing agent. Concretely, formic acid, oxalic acid, L-ascorbic acid, isoascorbic acid, formaldehyde and the like are mentioned. These organic reducing agents may be used alone or in combination of 1 or more than 2. Among them, L-ascorbic acid is preferably used. The term "acidic" as used herein means that an aqueous solution of 0.1 mol of an organic reducing agent dissolved in 1000g of water exhibits a pH of 1 to 6 at 25 ℃.
The amount of the reducing agent to be added is preferably 0.5 to 5.0 equivalents, particularly preferably 1.0 to 2.0 equivalents, to silver ions in the aqueous solution to be added, in view of easiness in simultaneous replacement plating and reduction plating of silver.
The order of adding the reducing agent and silver ions to the dispersion liquid containing the precursor particles is not particularly limited. From the viewpoint of controlling the reduction of silver ions and forming a thin and uniform coating of silver, it is preferable to add a reducing agent to the dispersion and then add silver ions. The silver compound as the silver source may be added to the dispersion liquid at one time, or may be added continuously or discontinuously over a predetermined period of time. In view of easy control of the reduction of silver ions, the silver compound is preferably added to the dispersion in the state of an aqueous solution thereof for a predetermined period of time.
In the treatment 2, when the substitution plating and the reduction plating of silver are performed simultaneously, the dispersion may be set in advance to a normal temperature state, or may be heated in advance at a temperature range of 0 to 80 ℃.
In the same manner as in the case of the treatment 1, in the treatment 2, it is preferable to irradiate the dispersion with ultrasonic waves before or simultaneously with the addition of the reducing agent to the dispersion. By irradiation with ultrasonic waves, dispersion of the precursor particles in the dispersion is promoted, and uniform coating of the precursor particles by silver is easily performed. The frequency of the ultrasonic wave is particularly preferably 200kHz or less, more preferably 45kHz or less, as long as the irradiation has a certain effect. The lower limit is 10 kHz.
The silver-coated sheet copper powder thus obtained can be suitably used in the form of a conductive composition containing the copper powder and a resin. For example, the silver-coated copper flake powder may be mixed with a resin, an organic solvent, glass frit, or the like to prepare a conductive paste. Alternatively, the silver-coated flake copper powder may be mixed with an organic solvent or the like to prepare a conductive ink. By applying the conductive paste or the conductive ink thus obtained to the surface of the application object, a conductive film having a desired pattern can be obtained.
In the silver-coated flake copper powder of the present invention, the coating of silver is thin and uniform, and therefore, the silver-coated flake copper powder can effectively suppress elution of copper in the conductive composition. As a result, the modification of the resin contained in the conductive composition is suppressed.
Further, the silver-coated copper flake powder of the present invention has a low aggregation level, and therefore, has good dispersibility in the conductive composition. Therefore, the conductive film obtained from the conductive composition has high conductivity.
Examples
The present invention will be described in further detail with reference to examples. However, the scope of the present invention is not limited to these examples. Unless otherwise specified, "%" and "parts" mean "% by mass" and "parts by mass", respectively.
[ example 1]
(1) Electrolytic copper powder production
In the size of 2.5m×1.1m×1.5m (about 4m 3 ) Is formed by the distance between the electrodes9 cathode plates and insoluble anode plates (DSE (manufactured by permelec electrode ltd.)) were individually suspended to a size of 5cm (1.0mX1.0 m). The copper sulfate solution as the electrolyte was circulated at 20L/min in the electrolytic tank. The anode and the cathode are immersed in the electrolytic solution, and direct current is applied thereto to electrolyze the solution, thereby precipitating powdered copper on the surface of the cathode.
The concentration of copper ions in the circulating electrolyte was adjusted to 5g/L, sulfuric acid (H) 2 SO 4 ) Is adjusted to 100g/L and the current density is adjusted to 100A/m 2 Electrolysis was performed for 40 minutes.
Mechanically scraping and recovering copper precipitated on the surface of the cathode, and then cleaning to obtain the aqueous copper powder cake. The cake was dispersed in 3L of water, stirred for 10 minutes, filtered through a Buchner funnel, washed, and then dried under reduced pressure (1X 10) -3 Pa) was dried at 80℃for 6 hours to obtain electrolytic copper powder.
(2) Comminution of electrolytic copper powder
By impact plate type jet mill (IDS type jet mill manufactured by Nippon Pneumatic Mfg. Co., ltd., IDS-5) to crush pressure of 6kgf/cm 2 The electrolytic copper powder was pulverized under the conditions of a feed rate of 6.7 kg/hr. Particle diameter D of pulverized copper powder 50 4.5 μm.
(3) Flaking
3kg of the crushed electrolytic copper powder, 9kg of methanol, and 1kg of disodium ethylenediamine tetraacetate (hereinafter also referred to as "EDTA2 Na") were mixed to prepare a methanol dispersion of copper powder. 12kg of this dispersion was added to a StirMill (registered trademark) LMZ of a bead mill manufactured by Ashizawa Finetech Ltd. And 4.85kg of zirconia microbeads having a diameter of 0.2mm were further added. The bead mill was run for 180 minutes to effect flaking of the copper powder. After that, the dispersion and the microbeads were separated by filtration, and the dispersion was left to stand to precipitate the flaky copper particles. Removing the supernatant, filtering, and extracting the flaky copper particles. Then, the sheet-like copper particles were washed with water, followed by repeated 2 times of washing with methanol.
(4) Silver coating
100g of flaky copper particles were poured into 500mL of pure water heated to 40℃to prepare a dispersion. While stirring the dispersion, 4.3g of EDTA2Na was added to dissolve the dispersion. Further, 48mL of a silver nitrate aqueous solution (0.44 mol/L) was continuously added to the dispersion over 6 minutes, and displacement plating was performed to deposit silver on the surfaces of the sheet-like copper particles, thereby obtaining precursor particles. At this time, ultrasonic waves (100W, 28 kHz) were irradiated to the dispersion.
Then, L-ascorbic acid as a reducing agent was added to the dispersion to dissolve the L-ascorbic acid. Further, 192mL of a silver nitrate aqueous solution of 0.44mol/L was continuously added to the dispersion over 24 minutes. Thus, the reduction plating and the displacement plating were performed simultaneously, and silver was further deposited on the surface of the precursor particles, thereby obtaining the target silver-coated sheet copper powder. The irradiation of ultrasonic waves is continued during this period.
Examples 2 to 8
Silver-coated flake copper powder was produced in the same manner as in example 1, except that the conditions shown in table 1 below were used.
Comparative example 1
EDTA2Na was not used in the flaking step in example 1, and the flaking time was set to 20 minutes. In addition, the ultrasonic irradiation was not performed in the silver coating step. Except for these, silver-coated flake copper powder was produced in the same manner as in example 1.
TABLE 1
Figure BDA0004113532970000141
[ evaluation 1]
The silver-coated copper flake powder obtained in examples and comparative examples was measured for particle size distribution, brightness, circularity of the surface of the particle, thickness of the particle, tap density, and silver content ratio by the methods described above. The results are shown in table 2 below.
[ evaluation 2]
The silver-coated flake copper powder obtained in examples and comparative examples was used to prepare a conductive composition.
The mass ratio is 35:65 epoxy resin (EPICLON 850, manufactured by DIC Co., ltd.) and butyl carbitol were mixed, and silver-coated copper flake powder was added thereto so as to have a concentration of 70%, to prepare a paste-like conductive composition.
The conductive composition was coated on one side of a polyethylene terephthalate (PET) film using a bar coater. The coating width was set to 200mm. The gap of the bar coater was set at 30. Mu.m.
The formed coating film was dried in a vacuum dryer at 90℃for 60 minutes. Thereafter, the PET film having the coating film formed thereon was sandwiched between sheets, and vacuum-pressed at 160℃and 20 kN. The thickness of the conductive film was measured on the thus obtained sample using a micrometer (Digimicro MF-501 manufactured by Nikon). In addition, the resistance value of the conductive film was measured. The resistance value was measured by a four-probe method using a resistivity meter (Mitsubishi chemical MCP-T600). The results are shown in Table 2.
[ evaluation 3 ]
The amount of copper ions eluted was measured for the silver-coated flake copper powder obtained in examples and comparative examples.
A dispersion was prepared by mixing 0.2g of silver-coated copper flake powder, 10mL of 15% hydrochloric acid, and 2mL of methanol. The dispersion was allowed to stand at 25℃for 10 minutes. Thereafter, the dispersion was filtered, and the concentration of copper ions contained in the filtrate was measured by ICP emission spectrometry. The results are shown in Table 2.
TABLE 2
Figure BDA0004113532970000161
As is clear from the results shown in table 2, the conductive film formed using the silver-coated flake copper powder obtained in each example had higher conductivity than the conductive film formed using the silver-coated flake copper powder obtained in the comparative example.
Further, it was found that the elution of copper ions from the silver-coated flake copper powder obtained in each example was suppressed as compared with the silver-coated flake copper powder obtained in the comparative example.
Industrial applicability
The present invention provides a silver-coated copper flake powder which has good dispersibility in a resin when mixed with the resin, and in which deterioration of the resin is suppressed, and further, which can reduce the electric resistance of a film formed from the resin, and a method for producing the same.

Claims (16)

1. A silver-coated flake copper powder comprising silver-coated flake copper particles having silver at least on the surface thereof,
the volume cumulative particle diameter at 90% by volume of the cumulative volume by the laser diffraction scattering particle size distribution measurement method for the silver-coated flake copper powder was set as D 90 (μm) the volume cumulative particle diameter at a cumulative volume of 10% by volume was set to D 10 When the particle size is (mu m),
the brightness L of the silver-coated flake copper powder is equal to D 90 /D 10 The value of the degree of dispersion is defined to be 13 or more.
2. A silver-coated flake copper powder comprising silver-coated flake copper particles having silver at least on the surface thereof,
the volume cumulative particle diameter at 50% by volume of the cumulative volume by the laser diffraction scattering particle size distribution measurement method for the silver-coated flake copper powder was set as D 50 (μm) when the thickness of the silver-coated flaky copper particles is T (μm),
thickness T relative to particle size D 50 The value of (2) is 0.04 or less.
3. The silver-coated flake copper powder according to claim 1 or 2, wherein the thickness T of the silver-coated flake copper particles is 0.1 μm or more and 0.5 μm or less.
4. A silver-coated flake copper powder according to claim 3, wherein the silver-coated flake copper particles have a thickness T of 0.1 μm or more and 0.3 μm or less.
5. The silver-coated flake copper powder according to any one of claims 1 to 4, having a tap density of 0.5g/cm 3 Above and 2.5g/cm 3 The following is given.
6. The silver-coated flake copper powder according to any one of claims 1 to 5, wherein the proportion of silver is 5 mass% or more and 20 mass% or less.
7. The silver-coated flake copper powder according to any one of claims 1 to 6, wherein the circularity of the silver-coated flake copper particles is 0.60 or more and 0.95 or less.
8. A silver-coated flake copper powder according to any one of claims 1 to 7, having a brightness L of 70 or more and 86 or less.
9. The silver-coated sheet-like copper powder according to any one of claims 1 to 8, wherein the volume cumulative particle diameter D at 90% by volume of the cumulative volume of the silver-coated sheet-like copper powder based on a laser diffraction scattering particle size distribution measurement method 90 15 μm or more and 35 μm or less.
10. The silver-coated sheet-like copper powder according to any one of claims 1 to 9, wherein the volume cumulative particle diameter D at 10% by volume of the cumulative volume of the silver-coated sheet-like copper powder based on a laser diffraction scattering particle size distribution measurement method 10 Is 3 μm or more and 8 μm or less.
11. The silver-coated copper flake powder of claim 10, wherein D 90 /D 10 The degree of dispersion is 3.0 to 5.3.
12. The silver-coated sheet-like copper powder according to any one of claims 1 to 11, wherein the volume cumulative particle diameter D at 50% by volume of the cumulative volume of the silver-coated sheet-like copper powder based on a laser diffraction scattering particle size distribution measurement method 50 Is 7 μm or more and 17 μm or less.
13. A method for producing silver-coated copper flake powder, wherein,
treating the dispersion liquid containing the copper mother powder and the 1 st complexing agent by a medium stirring mill device to deform copper mother particles forming the copper mother powder into a sheet shape,
treating the copper master powder containing the copper master particles deformed into a sheet shape with an aqueous liquid containing silver ions and a2 nd complexing agent to precipitate silver on the surface of the copper master particles.
14. The production method according to claim 13, wherein the 1 st complexing agent and the 2 nd complexing agent are the same kind of substance or different kinds of substances.
15. The method of claim 14, wherein the 1 st complexing agent and the 2 nd complexing agent are each ethylenediamine tetraacetate.
16. The production method according to any one of claims 13 to 15, wherein the copper master powder is electrolytic copper powder obtained by electrolyzing an electrolytic solution containing copper ions.
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