JP3454796B2 - Method for producing conductive fine particles - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention provides a conductive fine particle having a plating layer having a very uniform thickness, which is free from agglomeration of fine particles to be plated in a plating solution and has few scratches and bipolar. The present invention relates to a method for producing conductive fine particles.

[0002]

2. Description of the Related Art As a conductive material such as a conductive paste, a conductive adhesive or an anisotropic conductive film, a conductive composition composed of conductive fine particles and a resin is used. As the conductive fine particles, metal fine powder, carbon powder, or fine particles having a metal plating layer on the surface are generally used.

A method for producing conductive fine particles having a metal plating layer on such a surface is described, for example, in Japanese Patent Laid-Open No. 52-
147797, JP 61-277104, JP 61-277105, JP 62-1
85749, JP-A-63-190204,
Japanese Patent Application Laid-Open Nos. 1-225776 and 1-24750
The methods disclosed in Japanese Patent Laid-Open No. 1-147475 and Japanese Patent Laid-Open No. 4-147513 can be used.

In the above known technique, the particle size is 5000 μ
When plating fine particles of m or less, a barrel plating apparatus is generally used. This barrel plating device puts an object to be plated in a rotatable polygonal barrel-shaped barrel immersed in a plating solution, and while rotating the barrel, the cathode and the object to be plated are brought into contact with each other to generate electricity. Plating is performed.

However, with a conventional barrel plating apparatus, the grain size is 5
When fine particles of less than 000 μm are plated, they are plated in the plating solution while they are still agglomerated, and when they cannot be obtained as single particles, or when all the particles are not agglomerated, all the particles are not evenly plated. The thickness is uneven, or plating is not performed at all, so-called bipolar state is likely to occur.

Further, in the method using the barrel plating apparatus, when a plated object having a small specific gravity, such as a thin conductive layer formed on the surface of synthetic resin, is plated, the plated object in the barrel floats. There was a problem that it became a bipolar that plating was not performed at all.

The bipolar phenomenon is a case where the contact force between the object to be plated and the cathode is weak, or when a large number of objects to be plated in the barrel are present as a single lump and float in the barrel. Is a phenomenon in which the floating object to be plated is polarized and the film is dissolved from the positively charged portion.

In particular, a bipolar phenomenon occurs in fine particles imparted with conductivity by forming an angstrom-order conductive underlayer on the surface of non-conductive fine particles such as organic resin fine particles and inorganic fine particles by an electroless plating method or the like. Then, since the conductive underlayer is dissolved, the conductivity of the particle surface is lost, and electroplating cannot be performed.

[0009]

DISCLOSURE OF THE INVENTION In view of the above, the present invention has the advantage that fine particles do not aggregate in a plating solution.
To provide a method for producing conductive fine particles that can obtain conductive fine particles having a plating layer with an extremely uniform thickness in a simple process, and for all fine particles without a bipolar phenomenon. It is an object of the present invention to provide a method for producing conductive fine particles capable of forming a uniform plating layer.

[0010]

The present invention is a method for producing conductive fine particles in which a plating layer is formed on the surface of fine particles to be plated using a barrel plating apparatus having a rotatable barrel in a plating tank. Te, the difference in specific gravity between the plating solution and the plating fine particles is from 0.04 to 22.00, the object to be plated fine particles Ri particle size 0.5~5000μm der,且
At least a part of the conductive fine particles is made of synthetic resin.
It is a manufacturing method for conductive fine particles, characterized by comprising.
The present invention is described in detail below.

[0011] One embodiment of a plating apparatus used in the present invention shown in FIG. 1, 2. 1 is a front view of the plating apparatus, and FIG.
Is a diagram showing fine particle rotary stirring means. In the plating apparatus used in the present invention, the plating tank 1 is fixed on the apparatus pedestal 3 ,
Motor 7 for fine particles rotary stirring means is provided.

In the fine particle rotary stirring means shown in FIG. 2 , a fine particle storage container (barrel) 9 is fixed to a rotary shaft 8, and a motor 7 is provided via the rotary shaft 8 for the fine particle storage container (barrel).
Rotate 9. Particle storage container (barrel) 9 is filter at least a portion is formed, further, negative electrode is formed. By storing the fine particles to be plated in the fine particle storage container (barrel) 9 and rotating the fine particle storage container (barrel) 9, the fine particles to be plated come into contact with the cathode placed in the container while being stirred, and the fine particles to be plated are plated. A plating layer is formed on the surface of the. The shape of the fine particle storage container (barrel) 9 shown in FIG. 2 is a polygonal column, but is not particularly limited, and may be, for example, a column or a sphere.

By the manufacturing method of the present invention, it is possible to obtain conductive fine particles having a plating layer formed on the surface of fine particles to be plated. The fine particles to be plated are not particularly limited, and examples thereof include organic compounds such as synthetic resins; and inorganic compounds such as silica, alumina, metals, and carbon, which have appropriate elasticity, flexibility, and recoverability. A synthetic resin is preferable because it is easy to obtain a spherical shape.

In the method for producing conductive fine particles of the present invention, the difference in specific gravity between the fine particles to be plated and the plating solution is 0.04 to 2
2.00, and the particle size of the fine particles to be plated is 0.5 to 5
000μm der is, and the conductive fine particles is less when the
Is partly made of synthetic resin . In this case, the conductive fine particles are produced by forming a plating layer on the surface of the fine particles to be plated using a barrel plating device having a rotatable barrel in the plating tank.

In the present invention, the difference in specific gravity between the fine particles to be plated and the plating solution is 0.04 to 22.00. When the difference in specific gravity is less than 0.04, it takes time for the fine particles to settle in the barrel, and the fine particles fly up due to the rotation or vibration of the barrel, which makes it impossible to contact the cathode, resulting in a bipolar phenomenon. In order to suppress the soaring of fine particles, it is necessary to reduce the rotation speed and the vibration level. However, if the rotation speed is lowered, the stirring effect in the barrel is also lowered, and thus the uniformity of the plating film thickness is also lowered. If the specific gravity difference is less than 0.04, it is not possible to suppress the rising of the particles unless it is made almost stationary, it is necessary to reduce the number of rotations, and agglomeration occurs and plating becomes impossible.

On the other hand, the specific gravity of a generally known solid substance is about 0.5 to 23. In the production method according to the present invention, the larger the specific gravity difference from the fine particles, the more the particles in the barrel. Sedimentation is fast and particles do not rise even if the number of rotations of the barrel is increased, so the stirring effect is high and effective. That is, the range of specific gravity that can be plated is 0.0
It can be said that it is 4 to 22.00. Preferably 0.08
˜1.00, more preferably 0.08 to 0.2.

Further, the higher the rotation speed of the barrel, the higher the stirring effect and the more effective the uniformity of the plating film thickness and the prevention of aggregation, but as the difference in specific gravity between the object to be plated and the plating solution becomes smaller. The particles are more likely to fly up and the rotation speed cannot be increased. Therefore, if the difference in specific gravity between the object to be plated and the plating solution is small, set the number of rotations at the start of plating to a low number of rotations so that particles do not rise, and the specific gravity of the object to be plated increases with the deposition of the plating film. Therefore, it is more effective if the number of rotations is increased according to the difference in specific gravity from the plating solution.

Generally, the specific gravity of the plating solution is 1.02 to 1.3.
However, as the difference in specific gravity from the fine particles to be plated becomes smaller, plating becomes more difficult, but even if the specific gravity of the object to be plated is small, good plating fine particles can be obtained without the bipolar phenomenon even if the specific gravity of the object to be plated is small. be able to. Therefore, in the production method of the present invention, the specific gravity of the plated object is 0.
It can be used particularly preferably when it is from 5 to 3.0. It is more preferably 0.5 to 1.5.

When the specific gravity of the fine particles to be plated becomes 1.0 or less, the specific gravity difference of 0.04 or more is secured by increasing the specific gravity of the plating solution, and the fine particles to be plated are suspended in the barrel. Plating is performed in this condition. Since the specific gravity of the fine particles to be plated gradually increases with the formation of the plating film,
There is a possibility that a specific gravity difference of 0.04 or more cannot be secured.
In this case, change or dilute the plating solution,
Good plating can be obtained by reducing the specific gravity of the plating solution and ensuring a specific gravity difference of 0.04 or more with the fine particles to be plated.

If the current density at the time of plating can be set high, the plating time can be shortened and the productivity can be improved. However, when the difference in specific gravity between the fine particles to be plated and the plating solution becomes small, Since the contact force between the fine particles to be plated and the cathode that have settled at 1 becomes weak, increasing the current density may cause a sharp decrease in current efficiency and hydrogen gas generation, resulting in defective plating.

Therefore, it is important to keep the current density as low as possible, especially when the difference in specific gravity between the fine particles to be plated and the plating solution is in the range of 0.04 to 0.2.
It becomes more important in the range of 04 to 0.12. Since the specific gravity difference increases as the plating film thickness increases, the plating time can be shortened by increasing the current density as the specific gravity difference increases.

For example, in the case of plating with a copper sulfate bath, the difference in specific gravity between the fine particles to be plated and the plating solution is 0.04 to
In the range of 0.12, the current density is preferably 0.5 A / dm ² , more preferably 0.25 A / dm ² or less, still more preferably 0.1 A / dm ² or less. If the specific gravity difference is 0.12 or more, the current density is 1 A / dm.
^It is preferably ² or less, more preferably 0.5 A / dm ² or less, and further preferably 0.25 A / dm ² or less.

The plating apparatus used in the method for producing conductive fine particles of the present invention has, as a stirring means, a container (barrel) capable of accommodating and storing fine particles to be plated, at least a part of which comprises a filter. The above-mentioned filter is not particularly limited as long as it does not hinder the circulation of the plating solution inside and outside the container for containing fine particles to be plated, and the opening is smaller than the fine particles to be plated, for example, a slit,
Examples include various meshes such as mesh, non-woven fabric, filter, and nylon mesh.

The fine particles to be plated used in the present invention are not particularly limited, and examples thereof include chip capacitors, chip resistors and other chip parts, BGA fine particles, powders, fibers and the like. Moreover, examples of the fine particles used in the present invention include metal fine particles, organic resin fine particles, and inorganic fine particles. When the above-mentioned organic resin fine particles or inorganic fine particles are used, those having a conductive underlayer formed on the surface are preferably used. The conductive underlayer can be preferably formed, for example, by an electroless plating method, but can also be formed by another known method for imparting conductivity.

The metal fine particles are not particularly limited,
Examples thereof include iron, copper, silver, gold, tin, lead, platinum, nickel, titanium, cobalt, chromium, aluminum, zinc, tungsten, and alloys thereof.

The above-mentioned organic resin fine particles are not particularly limited, and examples thereof include fine particles made of a linear polymer, fine particles made of a network polymer, fine particles made of a thermosetting resin, and fine particles made of an elastic body.

Examples of the linear polymer which constitutes the fine particles of the linear polymer include nylon, polyethylene, polypropylene, methylpentene polymer, polystyrene, polymethylmethacrylate, polyvinyl chloride, polyvinyl fluoride, poly Tetrafluoroethylene,
Examples thereof include polyethylene terephthalate, polybutylene terephthalate, polysulfone, polycarbonate, polyacrylonitrile, polyacetal and polyamide.

Examples of the network polymer constituting the fine particles of the network polymer include divinylbenzene,
Hexatriene, divinyl ether, divinyl sulfone, diallyl carbinol, alkylene diacrylate, oligo or poly (alkylene glycol) diacrylate, oligo or poly (alkylene glycol)
Homopolymers of cross-linking reactive monomers such as dimethacrylate, alkylene triacrylate, alkylene trimethacrylate, alkylene tetraacrylate, alkylene tetramethacrylate, alkylene bis acrylamide and alkylene bis methacrylamide, or these cross-linking reactive monomers and other polymerizable Examples thereof include copolymers obtained by copolymerizing with a monomer.

Particularly suitable polymerizable monomers include divinylbenzene, hexatriene, divinyl ester, divinyl sulfone, alkylene triacrylate, alkylene tetraacrylate and the like. Examples of the thermosetting resin forming the thermosetting resin fine particles include phenol-formaldehyde resin, melamine-formaldehyde resin, penzoguanamine-formaldehyde resin, urea-formaldehyde resin, and epoxy resin. Can be mentioned. Examples of the elastic body forming the fine particles of the elastic body include natural rubber and synthetic rubber.

The material of the inorganic fine particles is not particularly limited, and examples thereof include silica, titanium oxide, iron oxide, cobalt oxide, zinc oxide, nickel oxide, manganese oxide, aluminum oxide and the like. The method for synthesizing the crosslinked resin is not particularly limited, and for example, a known synthesis method such as a suspension polymerization method, an emulsion polymerization method, a seed polymerization method, and a dispersion polymerization method may be appropriately selected and used.

In the manufacturing method of the present invention, the particle size of the fine particles to be plated is preferably 0.5 to 5000 μm. The thickness is more preferably 1 to 2000 μm, still more preferably 3 to 1000 μm.

The coefficient of variation of the fine particles is preferably 50% or less. It is more preferably 35% or less, further preferably 20% or less, and most preferably 10% or less. The coefficient of variation is a standard deviation expressed as a percentage of the average value of particle diameters, and is expressed by the following equation. Coefficient of variation = (standard deviation of particle size / average value of particle size) × 100 (%)

In the method for producing conductive fine particles of the present invention, a plating layer is formed on the fine particles to be plated. Examples of the material of the plating layer include gold, silver, copper, platinum, zinc,
Examples include metals such as iron, lead, tin, aluminum, cobalt, indium, nickel, chromium, titanium, antimony, bismuth, germanium, cadmium, and silicon. These may be used alone or in combination of two or more. Among these metals, nickel, copper, gold, silver, so-called solder alloys (including those not containing lead), and the like are preferable in terms of conductivity, availability, cost, and the like.

The plating layer preferably has a multi-layer structure made of different metals. When the plating layer has a two-layer structure, preferable metal combinations include, for example, nickel (first layer) and copper (second layer), nickel (first layer), copper (second layer) and solder alloy. (Third layer), nickel (first layer) and gold (second layer), nickel (first layer) and silver (second layer), nickel (first layer), copper (second layer) and nickel ( Third layer) and solder alloy (fourth layer). Here, the first layer, the second layer, and the like are counted from the inner layer side, but the layers may be laminated in the reverse order.

The production method of the present invention has a particle size of 0.5 to 50.
It can be applied to the conductive fine particles having a particle size variation coefficient of 100 μm and a particle size variation coefficient of 50% or less. Particle size is 0.
5 to 5000 μm, and the variation coefficient of particle size is 50
If the conductive fine particles of less than 100% are plated by a conventional barrel plating device, the fine particles cannot be obtained as a single particle because they are agglomerated in the plating solution, and all the fine particles to be plated are uniformly plated. However, the thickness of the plating layer tends to be non-uniform or bipolar, but by conducting the plating according to the production method of the present invention, conductive fine particles can be obtained as single particles in which all fine particles are uniformly plated.

Here, the particle diameter is more preferably 1 to 2000 μm, and more preferably 3 to 1000 μm. Also,
The variation coefficient of particle size is more preferably 0.1 to 15
%, More preferably 0.1 to 5% for the conductive fine particles. The method of obtaining the coefficient of variation is as described above.

The production method of the present invention can it to apply the conductive fine particles at least partially made of synthetic resin.
When at least a part of the conductive fine particles is a synthetic resin, since the synthetic resin often has a low specific gravity, the fine particles may float on the liquid surface in the container or adhere to the wall surface of the container, so that the particles are evenly distributed. It was sometimes difficult to obtain as plated single particles. However, according to the manufacturing method of the present invention, it is possible to ensure a uniform plating state, and therefore it is possible to perform suitable plating even if the conductive fine particles are at least partially made of synthetic resin.

The embodiment in which at least a part of the conductive fine particles is made of synthetic resin is not particularly limited. For example, the conductive fine particle core is made of synthetic resin, and the conductive fine particle surface is partially made of synthetic resin. Examples include modified products. Examples of the synthetic resin include the same ones as described above.

The production method of the present invention can be particularly preferably used when the specific gravity of the synthetic resin is 1.5 or less. When the specific gravity of the synthetic resin exceeds 1.5, it is difficult for the synthetic resin to float in the plating solution, and it is difficult to obtain a sufficient effect. However, even if the specific gravity is 1.5 to 10, good plating can be performed by the manufacturing method of the present invention.

[0040]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

Example 1 A nickel plating layer was formed as a conductive underlayer on the synthetic resin fine particles obtained by copolymerizing styrene and divinylbenzene, and the average particle diameter was 230.6 μm and the standard deviation was 12.2 μ.
m, a coefficient of variation of 5.3%, and a specific gravity of 1.245 were obtained. The obtained nickel-plated fine particles 200
take g, was nickel plated on its surface using a plating apparatus shown in FIG. The plating bath has a liquid specific gravity of 1.200.
I used a Watt bath. At this time, the difference in specific gravity between the fine particles to be plated and the plating solution is 0.045. The container for the fine particles to be plated is a regular hexagon with a diameter of 100 mm and a length of 16
5 mm, with a hole diameter of 0.125 mm on the longitudinal side surface
The mesh that was filtered was used. The storage container was rotated about the axis passing through the centers of the substantially regular hexagons at a rotation speed such that the peripheral speed of the inner surface of the storage container was 0.01 m / s, and electricity was supplied for 3 hours.

When the nickel-plated resin fine particles whose outermost grains were nickel-plated layers were observed by an optical microscope, all the particles were single particles without any aggregation, and the underlying layer was formed by the bipolar phenomenon. No dissolved particles were found at all. The average particle size of the 300 nickel-plated resin particles is 244.2 μm.
m, and the thickness of the copper plating layer was measured to be 6.8 μm. The variation coefficient of grain size was 6.1%, and it was proved that the thickness of the nickel plating layer was extremely uniform.

[0043] except that the specific gravity of the nickel plating bath and 1.225 in (Comparative Example 1) Example 1 and exactly the same particles were plated with in Example 1 under the same conditions. The difference in specific gravity between the fine particles to be plated and the plating solution was as small as 0.02, the sedimentation speed of the particles was slow, and the particles rose sharply due to the rotation of the barrel, and a bipolar phenomenon occurred, and the conductive underlayer of almost all particles was dissolved. .

(Example 2 ) Nickel plating was formed as a conductive underlayer on the synthetic resin fine particles obtained by copolymerizing styrene and dipinylbenzene, and the average particle size was 749.8 μm and the standard deviation was 36.0 μm.
m, the coefficient of variation was 4.8%, and the specific gravity of 1.207 was obtained. Obtained nickel plating fine particles 250
take g, was subjected to copper plating on its surface using a plating apparatus shown in FIG. As the plating bath, a copper sulfate bath having a liquid specific gravity of 1.091 was used. At this time, the difference in specific gravity between the fine particles to be plated and the plating solution was 0.116.

The container for the fine particles to be plated has a diameter of 150 m.
m is a regular hexagon, the length is 165 mm, and the side surface in the longitudinal direction provided with a filter which is a mesh having a hole diameter of 0.3 mm was used. The peripheral speed of the inner surface of the storage container is 0.0 with respect to the axis passing through the centers of the substantially regular hexagons.
It is rotated at a rotation speed of 3 m / s and the current density is 0.5 A.
/ Dm ^{2 and} was energized for 0.5 hours.

The nickel-plated resin fine particles whose outermost grain thus obtained was a copper-plated layer were observed by an optical microscope. As a result, all particles are single particles without any aggregation, and the underlying layer is formed by the bipolar phenomenon. Although 13 particles out of 100 were found to be melted or scratched, the average particle diameter of 300 copper-plated resin particles was 75.
The thickness of the copper plating layer was 6.6 μm and the thickness of the copper plating layer was 3.4 μm. The coefficient of variation of grain size was 5.15%, which proved that the thickness of the Cu plating layer was extremely uniform.

(Comparative Example 2 ) The specific gravity of the copper plating bath was 1.17 for the same particles as in Example 2.
Plating was performed under the same conditions as in Example 2 except that the number was 7. The difference in specific gravity between the fine particles to be plated and the plating solution was as small as 0.03, the sedimentation speed of the particles was slow, and the particles rose sharply due to the rotation of the barrel, causing a bipolar phenomenon and melting the conductive underlayer of almost all particles. .

Example 3 The same nickel plating fine particles as in Example 2 were applied with a current density of 0.
Example except that 25 A / dm ² and energization time were 1 hour
Plating was performed exactly as in 2 . The nickel-plated resin fine particles having the Cu plating layer as the outermost shell thus obtained were observed by an optical microscope. As a result, all the particles were single particles without any aggregation, but the underlying layer was dissolved due to the bipolar phenomenon. The number of particles and scratched particles was reduced to 4 out of 100.

The Cu-plated resin fine particles 3
The average particle size of 00 pieces was measured to be 757.0 μm, and the thickness of the copper plating layer was measured to be 3.6 μm. Coefficient of variation of particle size is 4.62
%, It was proved that the uniformity of the thickness of the Cu plating layer was improved.

Example 4 The same nickel plating fine particles as in Example 2 were applied with a current density of 0.
The plating was performed in exactly the same manner as in Example 2 except that the current was applied for 1 A / dm ² and the energization time was 2.5 hours. When the nickel-plated resin fine particles whose outermost shell is the Cu-plated layer thus obtained are observed by an optical microscope, all the particles are present as single particles without any aggregation, and the underlying layer is formed by the bipolar phenomenon. No dissolved or scratched particles were found.

The Cu-plated resin fine particles 3
The average particle diameter of 00 pieces was measured to be 756.8 μm and the thickness of the copper plating layer was measured to be 3.5 μm. Coefficient of variation of particle size is 4.0%
Thus, it was proved that the thickness uniformity of the Cu plating layer was improved.

(Example 5 ) The same nickel plating particles as in Example 2 were plated at exactly the same time as in Example 4 at the start of plating, and when the plating film thickness increased and the difference in specific gravity from the plating solution increased. The rotation speed was increased to 0.07 m / s. The energization time was 2.5 hours. Specifically, the rotation speed was increased when the plating film thickness increased and the particle specific gravity reached 1.24.

When the nickel-plated resin fine particles whose outermost shell is the Cu-plated layer were observed with an optical microscope, there was no aggregation at all, and all the particles were present as single particles. Neither particles in which the underlayer was dissolved nor particles with scratches were found. Also,
The average particle diameter of 300 Cu-plated resin fine particles was measured to be 757.4 μm, and the thickness of the copper plating layer was measured to be 3.8 μm. The coefficient of variation of the particle diameter was 2.0%, and the number of times the particles were agitated increased with an increase in the number of rotations, which proved that the uniformity of the thickness of the Cu plating layer was further improved.

Example 6 The same nickel-plated fine particles as in Example 2 were plated in exactly the same manner as in Example 5 , except that the current density was also increased to 0.25 A / dm ² when the rotation speed was increased. When the nickel-plated resin fine particles whose outermost shell is the Cu-plated layer thus obtained are observed by an optical microscope, all the particles are present as single particles without any aggregation, and the underlying layer is formed by the bipolar phenomenon. No dissolved or scratched particles were found.

The Cu-plated resin fine particles 3
The average particle size of 00 pieces was measured to be 757.0 μm, and the thickness of the copper plating layer was measured to be 3.6 μm. Coefficient of variation of particle size is 2.1%
Then, it was proved that the uniformity of the thickness of the Cu plating layer was improved as in Example 5 . Furthermore, the energization time is 1.
2 hours, which is less than half that of Example 5 , and productivity was improved.

[0056]

According to the present invention, for example, a particle size of 5000
Even when using fine particles with a small particle size of less than μm, especially fine particles mainly made of synthetic resin with a low specific gravity, the fine particles agglomerate in the plating solution or the fine particles float on the liquid surface in the container. Or to adhere to the wall surface of the container and not be plated, and the thickness of the plating layer will not be uneven, and using a simple device, obtain conductive fine particles having a plating layer of extremely uniform thickness. be able to. Further, according to the present invention, even in the case of fine particles centering on a synthetic resin having a particularly low specific gravity, a uniform plating layer can be efficiently formed on all the fine particles without causing the underlying layer to be dissolved by the bipolar phenomenon. can do.

[Brief description of drawings]

FIG. 1 is a front view showing an aspect of a plating apparatus used in the present invention.

FIG. 2 is a fine particle cycle of one embodiment of the plating apparatus used in the present invention .
It is a figure which shows a roll stirring means.

[Explanation of symbols]

1 plating tank 3 device supports stand 7 motor 8 rotating shaft 9 microparticles container (barrel)

─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP 2001-271189 (JP, A) JP 59-74300 (JP, A) JP 59-67397 (JP, A) JP 11-253782 (JP, A) JP 10-43569 (JP, A) JP 9-137289 (JP, A) JP 8-239799 (JP, A) JP 7-118896 (JP, A) Kaihei 6-312124 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C25D 7/00 C25D 5/56

Claims (5)

(57) [Claims] 1. A method for producing conductive fine particles, which comprises forming a plating layer on the surface of fine particles to be plated by using a barrel plating apparatus having a rotatable barrel in a plating tank, wherein the fine particles to be plated and plating are provided. Specific gravity difference with liquid is 0.04 ~
22.00, and the fine particles to be plated have a particle size of 0.
5 to 5000 μm, and at least a part of the conductive fine particles is made of synthetic resin. 2. The plated fine particles have a particle size variation coefficient of 5
It is 0% or less, The manufacturing method of the electroconductive fine particle of Claim 1 characterized by the above-mentioned. 3. The plating layer comprises gold, silver, copper, platinum, zinc,
2. At least one metal selected from the group consisting of iron, lead, tin, aluminum, cobalt, indium, nickel, chromium, titanium, antimony, bismuth, germanium, cadmium, and silicon. Or the method for producing the conductive fine particles according to 2. 4. The method for producing conductive fine particles according to claim 1, 2 or 3, wherein the plating layer has a multilayer structure made of different metals. 5. The method for producing electrically conductive fine particles according to claim 1, 2, 3 or 4, wherein the synthetic resin has a specific gravity of 1.5 or less.