Switch-Mode Power Cycling Test of Silicon Carbide MOSFETsUsing Repetitive Avalanche for Heat Generation

A power cycling test (PCT) using switching losses generated through repetitive unclamped inductive switching (avalanche mode) is presented for the first time. The test results are compared with those obtained through classical DC PCT and clamped switching PCT. The failure mode is the same for all the tests with the devices failing due to bond wire lift-off. The lifetime obtained through repetitive unclamped inductive switching (UIS) based PCT is slightly lower than those obtained by DC PCT and clamped switching PCT. This can be attributed to the higher chip level temperature swing during each avalanche pulse which reached 40 K in this test, while it was less than 5 K for clamped switching PCT and 0 K for DC PCT. The results can be improved by reducing the energy dissipated in each avalanche event through reducing the size of the storage inductance (or reducing the load current) while increasing the switching frequency to maintain the desired temperature swing. In general, the test results show that this is a promising power cycling approach especially for lower voltage class MOSFETs which are rated for avalanche ruggedness.