PURPOSE: To reduce cost of heat sink and improve the radiating efficiency by applying metallic plating on at least one side of the cooling fin or the main of heat sink and connecting it by melting by heat.

CONSTITUTION: Metallic plating of less than 30μ of thickness, for example 10μ of silver plating, is applied on the surface of cooling fin 6. Main unit 1 and fin 6 are assembled and, then, joined by heating and melting the plated layer in a hydrogen furnace. The layer of plating is so thin that a gap may be temporarily made when melting. but it is completely filled by the surface tension. Therefore, the heat radiating efficiency is increased and a heat sink of low production cost can be obtained. Furthermore, if all parts to be joined are plated, highly accurate manufacturing method can be obtained.