First power cycling results of improved packaging technologies for hybrid electrical vehicle applications

For cooling the power electronics in hybrid electrical vehicles nowadays a separate cooling loop is needed, which has lower temperature in comparison to cooling loop of combustion engine. For omission of second coolant loop power electronics with improved reliability is needed, especially power cycling capability must be higher. In this application with coolant temperature until 125°C, power electronics with high power density is exposed up to 200°C junction temperature. Weak points in power modules at high temperatures at power cycling load are wire bonds and joint between chip and substrate. These two interconnections were improved during ongoing research project EfA (=electronics for active gear). Power cycling tests were conducted with test power modules. The results show significant higher power cycling capability when as well bond wires as chip-substrate joints are improved.