The effects of the stray elements on the failure of parallel connected IGBTs during Turn-Off

The very good performances of IGBT modules in terms of current robustness and thermal overstress can be used on power converters in order to obtain cost and weight reduction. Moreover, in order to develop higher performance devices, it is very important to discover and understand instable failure mechanisms that can occur during IGBT operations. The paper presents an experimental characterization aimed to understand the effects of the stray elements of the connecting circuit on the failure of parallel connected IGBT during turn-off at very high collector current with very low gate resistance. The failure mechanism can be associated to the unequal distribution of the current among the devices whose effects are particularly enhanced by the combination of gate resistance and stray inductance in the emitter circuit. The experimental characterization has been executed by means of a non-destructive tester set-up, in order to reduce the number of required devices.