Condition monitoring and evaluation of Ron degradation during power cycling in switching mode of SiC-Mosfets power modules

Abstract:
The possibility of performing power cycling tests on MOSFET-SiC power modules is investigated here since such tests can be affected by the threshold voltage (Vth) drift problem. The life test has been carried out in switching (PWM) mode in order to minimize the impact of the threshold voltage instability on the test results. Both the power cycling test bench and the test protocol are discussed. Preliminary tests were carried out in order to estimate the drifts of Vth which will be obtained under the test conditions and to verify how the temperature is distributed in the parallelized chips constituting the switch of the MOSFET-SiC power module used. As results, it was found that the drift of Vth remains relatively low, making such aging tests practicable. It was shown that the thermal stress (DeltaTj) was under control and was not impacted by the low Vth drift. In addition, the drift in the electrical parameter used as an indicator of aging has been found to be solely due to irreversible degradations at the bond-wires contact interconnections.