Physicochemical and microstructural approaches for modeling the degradations of power electronic component interconnection

Electro-thermal and thermo-mechanical aging of topside metallic components of semiconductor power devices are the main reasons behind shortening their lifetimes. This study has been conducted to focus on the aging processes at such metallic contacts, composed of metallization layers connected to bonding wires. The approach followed in this study is not like the previous traditional ones, by which the fatigue problem is studied here in a physicochemical way, through interpreting the microstructural changes occurring, and relating them to the degradation processes. The effects of the evolutions in the microstructure and materials properties on aging processes were reviewed from the literature and after applying experimental analysis. Therefore, a correlation was thought about between the device failure's driving force, the crack propagation, and the main physicochemical-microstructural properties affecting the aging processes. Consequently, relationships linking these physicochemical-microstructural aspects to the parameters of the damage-based cohesive zone model were found.As a result, this model combines both finite element Multiphysics modeling and physicochemical-microstructural concepts. When the combination was built, a two-dimensional geometrical model of an IGBT module was constructed using the ANSYS APDL software. Hexagons were integrated at the metallic interconnection positions to represent metallic grains. Cohesive zone models were afterward implemented at the edges of the hexagons in order to interpret the crack evolution microstructurally. This results in hexagons associated with different properties in accordance with the characteristics of the local microstructure. Two separate simulations were subsequently applied. The first one is electrothermal to obtain the thermal distribution among the different components of IGBT upon cycling. Thereafter, a mechanical simulation was applied using the thermal data of the electrothermal simulation to see the distribution of constraints at the metallic contact zone and simulate the crack evolution taking place at the hexagonal edges. The results of these simulations were then compared to some experimental data to see the compatibility of this physicochemical-microstructural model.