The Influence and Application of Bond Wires Failure on Electrothermal Characteristics of IGBT Module

The bond wires failure is one of the most common failure modes of the insulated gate bipolar transistor (IGBT) module, which will cause an increase in the overall ON-state voltage drop V-CE, and it is generally believed to not affect the junction-to-case thermal resistance R-thjc. The measured V-CE mainly consists of two parts: the voltage drop of the IGBT chip V-CE_Chip and that of the bond wire V-CE_wire; the influence of bond wires failure on VCE should be discussed and explained in two parts. However, these actual measurement parameters are not considered before. In this article, the impact mechanism of bond wires failure on electrothermal characteristics of the IGBT module is analyzed with the help of realistic simulation models and experiment verification. The results show that the bond wires failure only affects V-CE_wire, and the impact on V-CE_ Chip is small, which can be ignored. Meanwhile, the increase in the virtual junction temperature is not caused by the increase in the power loss of the IGBT chip but by the increase in the current density of bond feet, which is caused by the decrease in the effective contact area. Besides, the measured R-thjc is not the intrinsic thermal resistance but slightly smaller than the intrinsic thermal resistance, and it decreases as the bond wires failure. Furthermore, the proposed mechanism can provide method guidance for the separation strategy of concurrent failure modes of IGBT modules only by monitoring the ON-state voltage drop.