Investigation on Isolated Failure Mechanisms in Active Power Cycle Testing

In the last decades, considerable effort has been invested to predict the operational lifetime of classical IGBT power modules. Most of these investigations were based on end-oflife active power cycling tests. Two dominant failure modes were hereby identified: solder fatigue and Al wire bond failure. However, the lifetime models derived from these accelerated tests could not discriminate between these failure modes. Recently, more reliable interconnection technologies were developed, and both failure modes can now be studied independently. The experimental results presented in this paper show that the failure modes cannot be described within one common lifetime model, as both the dependence on the temperature swing deltaTj and the influence of the absolute mean temperature Tjm differ significantly for both failures. As a consequence, the extrapolation of accelerated test results might lead to erroneous lifetime expectations.