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Electroconductive fine particle, method of producing electroconductive fine particle, and anisotropic electroconductive material

Inactive Publication Date: 2007-03-15
SEKISUI CHEM CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0028] When the amount of dissolved nickel in the dissolution test of the electroconductive fine particles of the present invention with nitric acid is 30 to 100 μg / g, the resulting electroconductive fine particles are almost free of pinholes in a gold coating formed by electroless gold plating, attributable to dissolution of the nickel undercoating. Accordingly, the resulting electroconductive fine particles have excellent electrical conductivity because of fewer pinholes in the gold coating.
[0078] According to the present invention, there can be provided electroconductive fine particles having excellent electrical conductivity with fewer pinholes in a gold coating, a method of producing the electroconductive fine particles, which are cyan-free type with a plating bath excellent in stability, and an anisotropic electroconductive material using the electroconductive fine particles.

Problems solved by technology

Conventionally, metal particles such as gold, silver and nickel have been used as electroconductive fine particles, but they are often not uniformly dispersed in a binder resin because of their high specific gravity and uneven shape, to cause uneven electrical conductivity in an anisotropic electroconductive material.
However, the substitution-type electroless gold plating is a deposition method utilizing a difference in ionization tendency between undercoating nickel and gold, and its plating bath composition is relatively simple and easily controlled, but there is a problem that because the reaction is terminated once undercoating nickel is coated with gold, the thickness of the deposited coating is thin with many pinholes attributable to dissolution of the undercoating.
However, the method of using these plating solutions is very sensitive to contaminants such as nickel, thus suffering from a problem that the plating bath is lacking in stability.
In gold plating, a cyan bath using gold cyanide or the like is usually employed because this plating bath is excellent in stability, but the cyan bath is used in a strongly alkaline state, and thus has a problem of strong corrosion of core particles etc. and a problem of being harmful to the environment, so there has been demand for cyan-free type electroless gold plating.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

[0061] Divinyl benzene type polymer resin particles having a particle diameter of 4 μm (manufactured by Sekisui Chemical Co., Ltd.) were treated for 5 minutes with 10 wt% ion adsorbent, then treated for 5 minutes with 0.01 wt% aqueous palladium sulfate, further subjected to reduction treatment by adding dimethyl amine borane, filtered, washed, and reacted by dipping in a nickel plating solution to obtain fine particles plated with nickel.

[0062] Then, a solution containing 10 g of sodium chloroaurate and 1000 mL of deionized water was prepared, and 10 g of the resulting fine particles plated with nickel was mixed with the solution to prepare an aqueous suspension. 30 g of ammonium thiosulfate, 80 g of ammonium sulfite and 40 g of ammonium hydrogen phosphate were introduced into the resulting aqueous suspension to prepare a plating solution. 10 g of hydroxyl amine was introduced into the resulting plating solution which was then adjusted to pH 10 with ammonia, and the mixture was rea...

example 2

[0064] For the nickel-plated fine particles obtained in Example 1, a solution containing 16 g of chloroauric acid and 1000 mL of deionized water was prepared and then mixed with 10 g of the nickel-plated fine particles to prepare an aqueous suspension. 30 g of ammonium thiosulfate, 80 g of ammonium sulfite, and 40 g of ammonium hydrogen phosphate were introduced into the resulting aqueous suspension to prepare a plating solution. 5 g of aminopyridine was introduced into the resulting plating solution which was then adjusted to pH 7 with ammonia, and the mixture was reacted for about 15 to 20 minutes at a bath temperature kept at 60° C., whereby electroconductive fine particles having a gold coating formed thereon was obtained.

[0065] The resulting electroconductive fine particles were dipped for 15 minutes in 1 wt% nitric acid solution, and the amount of dissolved nickel was measured by neutralization titration. As a result of this dissolution test using nitric acid, the amount of d...

example 3

[0070] The electroconductive fine particles obtained in Example 1 were added to 100 parts of epoxy resin (Epicoat 828, manufactured by Yuka-Shell Epoxy Co., Ltd.) as resin of the resin binder, 2 parts of tris-dimethylaminoethyl phenol and 100 parts of toluene, then sufficiently mixed by a sun-and-planet stirrer, and applied onto a release film such that the resulting coating after drying became 7 μm, and then the toluene was evaporated, whereby an adhesive film containing the electroconductive fine particles was obtained. The amount of the electroconductive fine particles incorporated into the film was 50,000 particles / cm2.

[0071] Thereafter, the adhesive film containing the electroconductive fine particles was stuck at ordinary temperatures onto an adhesive film obtained without incorporating the electroconductive fine particles, to obtain an anisotropic electroconductive film of 2-layer structure having a thickness of 17 μm.

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Abstract

The present invention aims to provide electroconductive fine particles having excellent electrical conductivity with fewer pinholes in a gold coating, a method of producing the electroconductive fine particles, which are cyan-free type with a plating bath excellent in stability, and an anisotropic electroconductive material using the electroconductive fine particles. The present invention is an electroconductive fine particle, which has a gold coating formed by electroless gold plating on the surface of a nickel undercoating, the amount of nickel dissolved in a dissolution test of the electroconductive fine particle with nitric acid being 30 to 100 μ / g; a method of producing the electroconductive fine particle, wherein the method allows a reducing agent, causing oxidation reaction on the surface of a nickel undercoating but not causing oxidation reaction on the surface of gold as deposited metal, to be present on the surface of the nickel undercoating thereby reduces a gold salt to deposit gold; and an anisotropic electroconductive material, which comprises the electroconductive fine particle dispersed in a resin binder.

Description

TECHNICAL FIELD [0001] The present invention relates to an electroconductive fine particle, a method of producing electroconductive fine particle, and an anisotropic electroconductive material, and in particular, to an electroconductive fine particle having excellent electrical conductivity with fewer pinholes in a gold coating, a method of producing the electroconductive fine particle, and an anisotropic electroconductive material using the electroconductive fine particle. BACKGROUND ART [0002] Conventionally, metal particles such as gold, silver and nickel have been used as electroconductive fine particles, but they are often not uniformly dispersed in a binder resin because of their high specific gravity and uneven shape, to cause uneven electrical conductivity in an anisotropic electroconductive material. [0003] To cope with this problem, electroconductive fine particles having a metallic coating such as nickel or nickel-gold formed by electroless plating on the surfaces of non-...

Claims

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Application Information

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IPC IPC(8): B22F9/16B22F1/10B22F1/18
CPCB22F1/0059B22F1/025C23C18/1651H05K3/323C23C18/44H01B1/22H01R13/03C23C18/42B22F1/10B22F1/18H01B5/00
Inventor KUBOTA, TAKASHI
Owner SEKISUI CHEM CO LTD
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