Toward Lifetime Prediction Under Variable Load Conditions in Power Electronics: Evaluation of Damage Accumulation Rules for Solder System Attach

Power electronic modules experience variable-amplitude thermal cycling in service, where sequence effects drive degradation of solder system attaches. The widely used Palmgren-Miner rule is simple but sequence blind. This work evaluates four cumulative damage models - Miner, HashinRotem anchored at ultimate (HRSu) and endurance (HRSe) strain as well as Batsoulas - in a coupled experimentsimulation framework for a DCB-SAC-Cu stack under passive temperature cycling. Delamination is quantified nondestructively by scanning acoustic microscopy (SAM) every 200 cycles. A finite element (FE) model reproduces the test, includes residual stresses from cool-down, and emulates progressive degradation via element deactivation according to the measured delamination fraction. For each 200-cycle block, the averaged inelastic strain range is extracted using an automatic volume averaging approach, mapped to cycles-to-failure with a Coffin-Manson relation, and accumulated with the four damage models. Using literature Coffin-Manson parameters for SAC305, all models underestimate the measured degradation. Miner yields the largest lifetime under the monotonically decreasing severity caused by delamination, while HRSe, HRSu, and Batsoulas credit prior damage at each load drop to differing degrees. Identifying Coffin-Manson parameters from the same dataset brings predictions within the experimental scatter and highlights sensitivity to both the accumulation rule and life-model parameters. The study provides a mission-profile-aware workflow that links SAM measurements to FE and blockwise damage models, enabling head-to-head comparison of sequence-sensitive rules and a practical calibration route for solder lifetime prediction.