Multiscale Heat-Generation and Heat-Transfer Mechanisms and Coupling Effects in IGBT Modules

Insulated-gate bipolar transistor (IGBT) modules exhibit thermal behavior governed by interacting mechanisms spanning carrier transport, chip-scale diffusion, multilayer heat spreading, coolant convection, and thermomechanical response. This study presents an energy-consistent computational framework whose novelty lies not in the individual solvers, but in the explicit cross-scale energy interfaces, multirate synchronization, and observation operators that distinguish local-maximum, area-averaged, current-weighted, and sensor-related junction temperatures. Published first-principles and transport data for bulk silicon are used as reference-calibrated priors; the calculations implemented here comprise terminal-loss evaluation, prescribed energy-normalized spatial sources, analytical and two-dimensional diffusion reconstructions, three-dimensional finite-element thermal analysis, and a reduced-order Cauer network. For an 80 μm silicon chip at 400 K, the Fourier diffusion time is 0.12 ms, whereas the convention δ_T = 2√(αt) reaches the chip thickness at 0.030 ms; these values represent different diffusion criteria. In an illustrative boundary-sensitivity case, increasing h from 650 to 2000 W m⁻² K⁻¹ lowers the modeled maximum temperature from 132.1 to 99.6 °C without eliminating the central hotspot. The chip-side and cold-side cross-model differences are 1.28–2.98% and 9.54–12.56%, respectively, when terminal boundaries differ, while temperature-dependent loss raises the lumped Cauer peak by approximately 11 K. Mesh, time-step, and energy checks verify the numerical implementation, and cross-model comparisons assess consistency.