Investigation of gate voltage oscillations in an IGBT module after partial bond wires lift-off

The identification of precursor parameters is crucial in evaluating degradation of an insulated gate bipolar transistor (IGBT) module. In this paper, the theoretic background of oscillations in the gate voltage contributed by parasitic parameters of the IGBT module is investigated. Those parasitic parameters are extracted, and a detailed equivalent gate circuit is constructed to examine the changes of gate voltage oscillations before and after partial bond wires lift off. In addition, the electromagnetic coupling between the gate circuit and the power circuit is also analyzed. A confirmatory experiment is carried out, in which a special open sample is adopted. Partial bond wires of the sample are cut off manually on purpose to simulate the bond wires lift-off commonly encountered in power-cycling tests or in field usage. The results of these analysis and experiment show that the observed considerable deviation of the gate voltage can be used as a potential precursor parameter to detect chip-level failure and improve the development of a prognostic approach for the IGBT module.