Formation of High Efficient Heat-Transfer Surfaces with Brazed Porous Structure.

Heat-transfer surfaces for cooling system of high power semiconductor such as G.T.O (Gate Turn Off Thyrister) is developed. The surface which has high efficient heat-transfer rate is consisted with porous structures formed by brazing.Ball like particles in diameter of about 0.4 mm with Ni-P prepared by plating on the surfaces are accum ulated on substrates with a few layers. Then the substrates with porous structure are obtained by heating under the brazing conditions of at 1223 K for 600 s in the 10-1 Pa atmosphere.Efficiency of heat transfer rate of the brazed porous structure is about twice as high as the one of coarse surfaces by conventional shot-blast process.