Power Cycling Lifetime Investigation under Low Temperature Swings and 50 Hz Load with Experiment and Simulation

Inhalt:
This paper focuses on the high cycle fatigue zone with low temperature swings for power modules, which is a new field in experimental testing. An advanced power cycling test concept, which can provide switching and conduction losses, was used. This combination allows accelerated testing with a load frequency of 50 Hz while avoiding to overstress devices with a current beyond specification. A design of experiments was developed and carried out with several million power cycling swings. Unexpectedly, the results can be fitted with standard models up to temperature swings of DeltaT = 25 K. A wide range of simulations has been performed to further investigate the temperature distribution and the mechanical background. The mechanical simulation underlined the failure analysis which exposes solder layer degradation as a main failure mode for low temperature swings.