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Robustness of IGBT transistors under repetitive short-circuit conditions is an important requirement. Shortcircuit is one of the most severe stress conditions on IGBTs since a large current flows through the device while supporting whole supply voltage. In this paper, experimental results concerning the ageing of 600 V IGBT under repetitive short circuit operations are presented. A critical energy, which is dependant on test conditions, has been already pointed out which separates two failure modes. The first one, with a cumulative degradation effect, requires some 10 4 short circuits to reach failure and the other one leads to the failure at the first short-circuit with a thermal runaway effect. This paper is focused on the first failure mode. In order to understand the ageing mechanism, 600 V IGBT dies have been packaged by Microsemi. The packaging has been made in order to make possible the characterization of some degradations by the measurement of different electrical characteristics. In this paper, we will detail effects of device ageing on on-state voltage, shortcircuit current and Al metallization degradation which leads to resistance increase.

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The relevance of the eddy current sensing technique to monitor the ageing state of electronic power modules has been experimentally studied. To do so, a commercial eddy current sensor was implemented for the evaluation of COOLMOS TM transistor chips soldered on a direct copper bonded ceramic substrate of a power module. The measurement data obtained over a large frequency bandwidth were analysed in the normalised complex impedance plane. The analysis shows that the sensor enables the chip and the substrate to be separately sensed. Furthermore, the ageing state of artificially aged chips can be clearly monitored. These preliminary results allow the design of eddy current micro-sensors dedicated to power module in-service monitoring purposes to be envisaged.