PURPOSE: To obtain efficiently composite metallic micro-balls having a uniform grain size by placing cores of the metallic micro-balls having a prescribed grain size on a plate consisting of graphite, etc., dropping a mixture composed of a single metallic substance having a very small grain size and an org. binder thereon to form a film on each ball then heating and holding the balls in a non-oxidative atmosphere kept at the temp. slightly higher than the temp. of said metal and cooling the balls.

CONSTITUTION: A metallic micro-ball (e.g.; iron ball) of 0.1W3mm dia. grain size to be used as a core is placed on a graphite plate or ceramic plate having low wettability with a metal. A mixture composed of a single metallic substance having ≤44μ dia. grain size or mixed powder and an alloy powder (e.g.; mixed powder composed or reduced silver powder and electrolytic copper powder) and 1W50% by weight thereof an org. binder is dropped onto such metallic micro-ball by a constant rate feeder in a way that the prescribed film thickness is attained. A mixture composed of, for example, an acrylic acid, EG and epoxy resin is used for the above- described org. binder. The ball is then heated and held in a non-oxidative atmosphere kept at the temp. higher by 0W100°C than the m.p. of the metal in the above-described mixture and thereafter the ball is cooled. As a result, the composite metallic micro-balls having a uniform grain size over a wide grain size range are obtd. without being limited by the kind of the metllic ball to be formed on the outside surface of the metallic micro-balls.