Impact of Current Density on Wire Bond Lifetime – Power Cycle Testing with Clamped VCE for Realistic Current Stress

Abstract:
Power cycle testing is the established method to assess IGBT modules’ lifetime. In a highly accelerated test, the end-of-life failure modes are provoked by repetitive DC current pulses. However, in real-life inverter operation a big portion of the power losses is produced by switching events and much smaller current densities are present in the module. Especially the wire bond lifetime depends on the current density and exaggerated test load currents can lead to early wire bond lift-off. This article presents experimental results on the impact of current density on wire bond lifetime and introduces a novel power cycling test method that allows for testing with moderate currents.