Junction Temperature Estimation Method Based on Transverse Temperature Distribution Function in Soldered IGBT Modules

The thermal resistance of soldered Insulated-Gate Bipolar Transistor (IGBT) modules is commonly calculated using a fixed interlayer heat transfer angle, which can lead to junction temperature errors due to inaccurate thermal resistance extraction—especially under varying operating conditions. To address this issue, this paper investigates the internal heat transfer characteristics of soldered IGBT modules and introduces a Transverse Temperature Distribution (TTD) function, defined as a two-dimensional Gaussian function fitted from each material layer temperature data. The TTD function captures the lateral temperature distribution within each material layer and can be updated in real time. By computing the parameters of the TTD function, both transverse and longitudinal heat fluxes at specific coordinate points are derived, allowing the dynamic estimation of local heat flux angles and correction of thermal resistances. Finally, a Cauer thermal network model with real-time thermal resistance adjustment is employed to accurately predict the junction temperature.