PURPOSE: To prevent the melting of the end face of an aluminum core in the middle of production process thereby extending the life of a plating solution and simplifying the working process by applying powder coating to the peripheral end face of an aluminum substrate for semiconductor substrate or printed board after drilling but before plating treatment process.

CONSTITUTION: After drilling, an aluminum material is masked with heat- resisting tape in the central portion by leaving a strip 10mm wide along the periphery of the aluminum material. Then, powder coating 4 about 100μm thick is applied to the aluminum material by using polyester powder resin. Then, the masking is removed and an aluminum core 1 with the powder coat 4 formed on the peripheral end face is obtained. An insulation layer 2 made of epoxy polyimide and glass cloth is formed and further a copper foil 3 is formed on the insulation layer 2. Thereafter, pattern etching is performed on the copper foil 3, secondary drilling is performed and then gold plating treatment is given.