Investigations on power cycling induced fatigue failure of IGBTs with silver sinterea interconnects

Because of the need for electronics use at temperatures beyond 150°C, new high temperature interconnection technologies emerge, like silver sintering and copper wire bonding. In the project PROPOWER inverter modules with IGBTs and diodes mounted on DBC substrates were investigated as a prototype. Analyses were made to study the effects of the new interconnect technologies on fatigue failure. It is one basic question for the replacement of solders by sinter silver to what extend the failure behaviour depends on the kind of loading, that means passive thermal cycling versus active thermal cycling, and how it relates to solder fatigue failure. These questions were addressed by passive thermal cycling and in particular by different kinds of power cycling. Failure modes different from those observed with traditional interconnection technologies were detected. Finite element (FE-) analyses were made to understand the thermo-mechanical stresses, which cause these failures. To simulate the power cycle loading most realistic, coupled electro-thermal-mechanical analyses were carried out which are in the focus of this paper. The simulation results are compared to failures found by testing.