Difference Between the PWM and Standard DC Power Cycling Tests Based on the Finite-Element Simulation

Pulsewidth modulation (PWM) power cycling, which has complex control strategies and high testing costs, received a lot of attention in recent years because the test conditions are closer to the application of power modules than standard DC power cycling. Therefore, the root difference of the failure modes and lifetime of insulated gate bipolar transistor power modules between DC and PWM power cycling is the concern in this article, based on the finite-element simulation. For stimulating the PWM power cycling with high accuracy and fast speed, an improved PWM (IPWM) power cycling is proposed and verified by a simple model. Then, an electrothermomechanical coupled model of a single chip is established for comparison. It mainly focuses on the current distribution, temperature distribution, and stress distribution. The current distribution comparison results show no difference, while a higher temperature gradient is shown in PWM power cycling due to the additional switching losses. However, the stress distribution results show chip solder layer is still the main failure mechanism both in DC and IPWM power cycling. Therefore, a conclusion can be obtained that there is no difference in failure mechanism and lifetime between DC and PWM power cycling. And the same bond wire failure and similar lifetime of DC and PWM power cycling tests further verify this conclusion.