Preparation of anisotropic conductive fine particles by electroless nickel plating

Mechanical solderless chip packaging with small gold bumps(1) has increased in electronic devices. The preparation of conductive particles (5 similar to 7 mu m diameter) by electroless nickel plating has now been investigated. Generally, batch type electroless plating is applied to provide conductivity on nonconductors. Since the surface areas of particles are much larger than the bulk substrate, accordingly the electroless plating bath becomes unstable. The continuous dropping method has therefore been applied, in the preparation of conductive particles. Uniform coverage of deposited nickel on the particles was obtained by using ammonium acetate as a complexing agent, and surface coverage was further improved without coagulation of particles by treatment with a surface active agent before their introduction to the plating bath.