PURPOSE: To enable production of spherical solder particles having uniform sphericity and particle size by forming solder on the surface of spherical copper particles having a uniform particle size by substitution plating method.

CONSTITUTION: Copper particles 2 of about 30-50μm particle diameter are first dipped in an etching liquid, washed with water and dried. Then, these particles are dipped in an active treatment agent, washed with water, and dipped in an electroless substitution plating liquid at about 50°C for ten minutes, washed with water and dried. Thereby, a solder layer 3 of about 1-2μm thickness is formed on the surface of the copper particle 2.