LAUSR

This article develops the techniques for actively tracking response shifts, induced by thermal–mechanical degradation over components lifetimes’, in spatiotemporal thermal response dynamics. The methodology considers both boundary (e.g., cooling) and internal (e.g., voiding) sources of degradation, and it is considered in the context of power semiconductor devices and packages, including power modules. This article quantifies the transient thermal response sensitivity to degradation using electrothermal impedances viewed with key frequency response function (FRF) metrics over wide dynamic ranges. A developed sensitivity analysis is applied using models and experimental evaluation to relate temperature sensing spatial location, harmonic content of semiconductor device losses, and source of degradation in terms of normalized FRFs that are rapidly interpreted. Complementary loss model parameter sensitivity analysis reveals the advantages in tracking variation in thermal FRF phase delay, rather than amplitude. Finally, to complement pure-FRF approaches for sensing degradation, which use nonparametric data, a method for directly estimating degradation-sensitive physical parameters, in real time, is developed. Experiments demonstrate the automatic estimation of a thermal resistance parameter.