Conductive fine particles and anisotropic conductive material

Abstract

The invention provides conductive fine particles with a satisfactory monodisperse property, low cost, resistance to migration and excellent conductivity. Conductive fine particles having core particle surfaces coated with a metal-plated coating film layer containing nickel and phosphorus and a multilayer conductive layer comprising a palladium layer as the outer surface, wherein the phosphorus content in region A of the metal-plated coating film layer, at a distance of no greater than 20% of the thickness of the entire metal-plated coating film layer from the surface of the core particle, is 7-15 wt % of the entire region A, the phosphorus content in region B of the metal-plated coating film layer, at a distance of no greater than 10% of the thickness of the entire metal-plated coating film layer from the surface of the metal-plated coating film layer on the palladium layer side, is 0.1-3 wt % of the entire region B, and the phosphorus content of the entire metal-plated coating film layer is 7 wt % or greater.

1 . Conductive fine particle,
 having core particle surface coated with a metal-plated coating film layer containing nickel and phosphorus and a multilayer conductive layer comprising a palladium layer as the outer surface,   wherein the phosphorus content in region A of the metal-plated coating film layer, at a distance of no greater than 20% of the thickness of the entire metal-plated coating film layer from the surface of the core particle, is 7-15 wt % of the entire region A,   the phosphorus content in region B of the metal-plated coating film layer, at a distance of no greater than 10% of the thickness of the entire metal-plated coating film layer from the surface of the metal-plated coating film layer on the palladium layer side, is 0.1-3 wt % of the entire region B, and   the phosphorus content of the entire metal-plated coating film layer is 7 wt % or greater.   
     
     
         2 . Conductive fine particle according to  claim 1 ,
 comprising insulating fine particles situated on the surface of the palladium layer and   the insulating fine particles having a particle size of 20-500 nm.   
     
     
         3 . Conductive fine particle according to  claim 1 ,
 wherein the palladium layer on the outer surface is dense and continuous with no exposure of the underlying nickel, and   no more than 10 of the conductive fine particles have 5 or more pinholes on the surface of the palladium layer, when the surface of the palladium layer of each of 100 arbitrarily selected particles of the conductive fine particles is observed using SEM, with an observation range of a concentric circle of the conductive fine particle radius, and an observation magnification of 30,000.   
     
     
         4 . Conductive fine particle according to  claim 1 , wherein the thickness of the metal-plated coating film layer is 40-150 nm. 
     
     
         5 . Conductive fine particle according to  claim 1 , wherein at least a part of the palladium layer is a palladium layer formed by reduction plating. 
     
     
         6 . Conductive fine particle according to  claim 1 , wherein the thickness of the palladium layer is 10-50 nm. 
     
     
         7 . An anisotropic conductive material comprising conductive fine particles according to  claim 1  dispersed or situated in a binder resin.