Failure precursors for insulated gate bipolar transistors (IGBTs)

Failure precursors indicate changes in a measured variable that can be associated with impending failure. By identifying precursors to failure and by monitoring them, system failures can be predicted and actions can be taken to mitigate their effects. In this study, three potential failure precursor candidates, threshold voltage, transconductance, and collector-emitter ON voltage, are evaluated for insulated gate bipolar transistors (IGBTs). Based on the failure causes determined by the failure modes, mechanisms and effects analysis (FMMEA), IGBTs are aged using electrical-thermal stresses. The three failure precursor candidates of aged IGBTs are compared with new IGBTs under a temperature range of 25-200°C. The trends in the three electrical parameters with changes in temperature are correlated to device degradation. A methodology is presented for validating these precursors for IGBT'prognostics using a hybrid approach.