Failure Mechanisms in IGBT Modules Under AC Repetitive Stresses at the Converter Level

Failure mechanism analysis of insulated gate bipolar transistor (IGBT) modules is essential for the reliability assessment in AC converters. Standard DC power cycling tests (PCT) fail to fully replicate the stress conditions encountered in actual AC converters. To address this issue, this article investigates failure mechanisms in IGBT modules under AC repetitive stresses at the converter level and compares the failure difference under DC and AC PCTs. Under the same junction-temperature fluctuation and maximum junction temperature, experiments reveal that DC PCTs shorten cycling lifetime with severe bond-wire cracking and solder degradation, while AC PCTs show fewer cracks with metallic spherical particles. An electro-thermal-mechanical multiphysics model incorporating creep/viscoplasticity clarifies that longer high-temperature dwell and higher temperature change in DC PCTs accelerate strain accumulation, driving faster degradation. Consequently, in a practical converter, IGBT degradation under AC repetitive stresses should be paid more attention to obtain a more realistic degradation trajectory.