High heat dissipation and high heat durability technologies for transfer-molded power modules with insulating sheets

Investigations of high heat dissipation and high heat durability technologies were carried out for the transfer-molded power module (T-PM) with insulating sheets. The thermal conductivity of the insulating sheet with an agglomerated BN filler as the thermal conductive material was improved drastically, and was three times larger than the conventional insulating sheet. The advanced insulating sheet reduced the thermal resistance of the first T-PM by 15 %. On the other hand, the electrical resistivity of the advanced insulating sheet at high temperature was enhanced three digits by improving the curing system of the epoxy resin. Furthermore, as a result of the molding resin being improved, the glass transition temperature of the resin increased by 13 deg C, and the elastic modulus and the linear expansion coefficient of the resin was reduced remarkably. Consequently the durability of the T-PM in a high temperature bias test (DC1kV bias @ 200 deg C) has been greatly improved using the developed insulating sheet and the molding resin. In addition, a power cycle test at high temperature (Tj-max = 200 deg C, DeltaTj = 80 deg C) showed stable operation even over 100K cycles.