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

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.

1 . 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 μg/g.    
   
   
       2 . A method of producing the electroconductive fine particle according to  claim 1 , 
 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.    
   
   
       3 . An anisotropic electroconductive material, 
 which comprises the electroconductive fine particle according to  claim 1  dispersed in a resin binder.