Advanced Power Cycling Test Integrated With Voltage, Current, Temperature, and Humidity Stress

In this article, an advanced power cycling test (PCT) with high voltage, large current, high temperature, and high humidity stress is proposed to get closer to the actual working conditions of power electronics in the accelerated aging test. The proposed test, integrated with high-voltage high-humidity high-temperature reverse bias test and standard dc PCT, achieves precise measurement at the microsecond, millivolt, and microampere accuracy. A 6-kV/750-A prototype is built to verify the feasibility and effectiveness, and the noise mitigation method for measurement under high voltage is analyzed. The proposed test was carried out on the full-bridge power modules for electric vehicles, and the lifetime exhibits lower than the standard PCT. The root cause is the increment of thermal resistance at an early stage due to moisture invasion, which results in a failure mode change. Finally, the electrochemical corrosion signs induced by sulfur/carbon under voltage, temperature, and humidity stress are also revealed by optical inspection and scanning electron microscope.