Validated Model Calibration for Simulation Aided Thermal Design

The search for better, more accurate thermal models is an ongoing challenge in many industries, including automotive. In most automotive electronic control units (ECU) the heat-generating electronic components are soldered to a circuit board and the quality of the associated component models play a major role in getting the right answers from the ECU thermal model. Our goal is to improve the temperature predictions of finite element (FE) analysis by improving the accuracy of the component models. We describe the implementation details and obtained results of a method that calibrates individual thermal component models to experimental datasets. In particular, we used multiple experimental test setups in which different heat paths were active in the studied component, and the resulting measurement results were taken as reference for the FE model optimization process. The focus of the proposed paper is the FE component model optimization process, but also touches on experimental aspects, like spread and noise in the data. Results presented are for a MOSFET in LFPAK88 (SOT1235 [7]) package, which employs soldered clip connections instead of the more traditional wire bonding, and as consequence presents at least three significant heat paths within the package: through the heat-slug (Drain), through the pins (Source), and through the thin plastic mold. Our optimized FE model describes all these heat paths with a high degree of accuracy, leading to excellent results in the model validation experiments performed on a PCB-mounted test vehicle.