Development of Material and Processing Technology for High Thermal Conductive Multilayer Module

We have developed a multilayer substrate that is formed from a high thermal conductive resin including ceramic fillers at high density in order to realize a module that is more miniaturized and has lower thermal resistance. First, we realized a resin with a very high filler filling rate of 75% by mixing two kinds of spherical fillers different in particle size. The thermal conductivity of the insulation resin films we developed is 4.4 W/mK. And we were able to make resin films with a thickness from 35 mum-120 mum. Additionally, with the improvement of adhesion between Cu and resin affected by control of the resin fluidity and filler diameter, a high thermal conductive multilayer substrate could be realized. The reliability of the high thermal conductive multilayer substrate formed from the developed resin was then investigated. Even after 1000 cycles of HC test (heat cycle test: 233 K-398 K, 30 minutes at each temperature), the resistance of the daisy chain pattern did not change. The THB test results (temperature, humidity, and bias test: 358 K, 85% RH, 50 V), showed that an insulation layer of more than 60 mum thickness gives enough dielectric reliability. Finally, we made a high voltage (350 V) drive inverter power supply circuit module for automobile applications including the high thermal conductive multilayer substrate we developed. Applying a multilayer substrate enabled the inverter module to be downsized to 85% of the one with a conventional monolayer substrate. Further, the thermal resistance of the miniaturized module was the same as the conventional module. In addition, the results of HC test and THB test indicated that the reliability of the developed module is sufficient for automobile applications.