A High-Repetition Short Circuit Study for Thermal-Electric Stress Analysis of SiC MOSFET and IGBT Power Modules

Abstract

Short-circuit robustness is a crucial requirement for automotive traction inverter power modules. Due to the high nominal currents, parallel dies are typically employed. However, validating the thermal-electric stress homogeneity of multiple parallel dies under short-circuit conditions poses a significant challenge for characterization. This paper explores the use of thermal IR camera inspection under high-repetition short-circuit type 1 stress tests. Although the IR camera lacks the bandwidth to capture the peak temperatures during the short-circuit transient pulse, it provides a comprehensive view of the device temperatures in thermal steady state at high repetition rates above 30 Hz, which exceeds the IR camera's bandwidth. This allows for an analysis of the individual chip's short-circuit energy dissipation and homogeneity within the topological switch. To demonstrate the method, a Si/SiC Fusion switch, consisting of a parallel IGBT die and parallel SiC dies, is used, and various short-circuit durations are investigated. The IR camera analysis offers valuable insights into the individual die's short-circuit energy dissipation. The key finding for the Si/SiC Fusion switch is that extremely short pulse durations during short-circuit stresses primarily the SiC MOSFET dies, while prolonged pulse durations shift the stress increasingly to the IGBT die. The proposed method provides a novel, simplified analysis tool for power module design and characterization, applicable to a wide range of different power module applications.