Impact of Solder Degradation on VCE of IGBT Module: Experiments and Modeling

Solder degradation is one of the main packaging failure modes in insulated gate bipolar transistor (IGBT) modules, which is usually evaluated through the change of thermal resistance. However, due to the strong electrothermal coupling in the IGBT module, solder degradation also affects electrical characteristics, such as ON-state voltage VCE. The impact mechanism of solder degradation on VCE is analyzed in this paper first. For the study of the solder degradation independently, a press-packing setup is designed for the accelerated aging test, which can remove the influence of bond wires degradation and significantly improve the experimental efficiency. Then, the IGBT equivalent resistance is defined, which conforms to Ohm's law in the calculation and can respond to the real-time dynamic current. So, it could be conveniently used in the finite element method (FEM)-based simulation. Meanwhile, a realistic 3-D degradation model of the solder layer is constructed by an image processing method. Furthermore, an electrothermal coupling model based on the finite element is constructed to study the impact of solder degradation on the electrical and thermal characteristics of IGBT. Finally, the proposed degradation mechanism is verified by simulation and experimental results.