Failure Mechanism Investigations of Bond Wires Lifting-Off and Die-Attach Solder Aging Considering the Thermal Coupling Effects

Failure mechanisms investigation (FMI) is crucial for reliability evaluation of power modules, and thus, attracts high popularity in power converters. However, complex failure modes caused by thermal coupling effects (TCEs) make it difficult to clarify the failure mechanism. To address this, an FMI for bond wires lifting-off and die-attach solder aging is conducted in this article, in which the TCEs are carefully considered, and consequently an accurate mechanism analysis is provided. In the present FMI, with the assistance of the power cycling tests, the TCEs on the failure modes and junction temperature distribution are provided. Then, based on the finite elements model, a thorough mechanism explanation of failure modes with TCEs is developed. The results reveal that the TCEs enable to change the chip surface and die-attach solder layer temperature distribution uniformity, and then affect the failure modes of power modules. More specifically, the effects of TCEs on the stress distribution of multiple bond nodes and the strain energy density distribution of the die-attach solder, jointly result in the change of failure mode.