Oliver Schilling

Power cycling testing and FE modelling focussed on Al wire bond fatigue in high power IGBT modules

Abstract Aging of Al wire bonds of IGBT modules is studied in power cycling tests and FEM simulations. For a clearer distinction of bond wire fatigue from solder delamination a die attach with high melting temperature is chosen to reduce the influence of chip solder aging. Test conditions cover a broad range of cycle amplitude Δ T j . The FEM model for bond wire fatigue achieves a good reproduction of the measured dependence of cycle numbers on Δ T j . A low impact of absolute temperature on N cyc is confirmed both by experiment and theory.

End of life and acceleration modelling for power diodes under high temperature reverse bias stress

This work is motivated by the growing importance of lifetime modelling in power electronics. Strongly accelerated High Temperature Reverse Bias (HTRB) testing of power diodes at different stress conditions is performed until alterations and fatigue mechanisms become evident. Two categories of effects can be separated: Drifting breakdown voltage and hard failures with complete loss of blocking capability. Nevertheless the overall stress duration needed to provoke destructive failures is very high with test durations > 2500 h even at almost 230 °C and 100% rated voltage. For both mechanisms the temperature and voltage acceleration is evaluated. Especially temperature acceleration is significant in the regime of testing between 200 °C and 230 °C and an activation energy Ea in the regime > 1 eV can be deduced which is higher compared to values commonly reported in the literature. Failure analysis shows that both package and also chip related effects could contribute to the observed hard failures in HTRB stress under extreme conditions.

Realistic climatic profiles and their effect on condensation in encapsulated test structures representing power modules

Abstract During the last years applications for power modules with harsh environmental conditions have gained increasing importance. Extreme combinations of environmental conditions especially at weak load conditions have to be understood to avoid risks induced by humidity condensation. The present work investigates the influence of different cycling profiles on condensation phenomena. The phase within the cycling profile that is liable for condensation can be identified and the risk for long term build-up of humidity inside a package is studied in outdoor measurements.