A Lifetime Evaluation Method of IGBT Modules Considering Dynamic Cumulative Update of Solder Layer’s Inelastic Energy Dissipation Density

Existing lifetime evaluation methods for IGBT modules can hardly account for either the increase in thermal load or the stress accumulation caused by solder-layer fatigue, which often leads to an overestimation of module lifetime. To address this issue, this paper proposes a lifetime evaluation method that considers the dynamic cumulative updating of the inelastic energy dissipation density of the solder layer. Firstly, based on the Clech algorithm, the variation of inelastic energy dissipation density under adjustments to mechanical parameters and increases in thermal load is analyzed, and the positive feedback of solder-layer fatigue on the accumulation of inelastic energy dissipation density is derived analytically. On this basis, the thermal resistance is adopted as a characterization parameter of the aging state of the IGBT module. A scaling factor describing the influence of the aging state on the thermal–mechanical parameters is defined to iterate the inelastic energy dissipation density, and a dynamic accumulation update strategy for inelastic energy dissipation density under solder-layer fatigue is thereby proposed. Then, the update strategy is introduced into the lifetime evaluation process to compensate for the influence of thermal resistance degradation on the thermal–mechanical parameters, thus improving the accuracy of IGBT module lifetime evaluation. Finally, the correctness and effectiveness of the proposed method are verified by comparison with commonly used lifetime evaluation methods.