Failure Mechanism of Die-Attach Solder Joints in IGBT Modules Under Pulse High-Current Power Cycling

Abstract

Applications under extreme conditions, such as solid circuit breakers and electromagnetic launching systems, are great challenges to semiconductor power devices. The die-attach solder joint is as one of the most vulnerable structures and critical to the reliability of insulated-gate bipolar transistor (IGBT) modules. In this paper, IGBT modules were cross sectioned and tested under pulse high-current power cycling. The failure mechanism of the die-attach solder in IGBTs at pulse high-current modes was investigated. Evolution of microdefects in the die-attach solder during power cycling was characterized and factors for the failure of die-attach solder joints was discussed. The results revealed that voids, cracks, and detachment of interface were the major microdefects in the die-attach solder layer. A detachment of the Si/Sn-Ag-Cu (SAC) interface is verified as the major failure mode under pulse high-current power cycling. Interface cracks between the Si-chip and die-attach solder layer were found to initiate first at the solder layer edges and then extended to the center of the solder layer with the increase of power cycles. The detachment of Si/SAC interface was more similar to the brittle fracture. The junction temperature swing and heating rate were the key factors for detachment of the Si/SAC interface.