Advanced power cycling test strategies on discrete SiC MOSFETs in different operating modes and the impact on lifetime

Power cycling tests (PCTs) are important for evaluating the lifetime of power electronic devices. Discrete SiC MOSFETs with improved packaging and interconnection technology have proven high reliability but also show a certain spread in lifetime. For testing those in an appropriate test duration, a high acceleration factor in the test is required. In this paper, a PCT with hybrid testing of the body diode and channel in the reverse direction of discrete SiC MOSFETs has been performed. Depending on the channel contribution, this allows a reduced load current and still a positive temperature coefficient. With this strategy, similar failures to standard PCTs were observed. The test results are compared with standard PCTs in forward and pure body diode mode. A comparable lifetime to the reference test is achieved for an operating regime with a positive temperature coefficient. • 3rd quadrant testing (hybrid mode – parallel body diode and channel) is applicable in PCT with discrete devices • Hybrid mode PCT with positive temp. coef. shows similar lifetime as standard forward PCT in SiC MOSFETs • PCTs in hybrid mode enables lower load current densities and greater flexibility in setting symmetrical test conditions • Even with similar results for the body diode PCT, the negative temp. coef. might lead to premature failure – taking a load current normalization into account