Finite element thermal modelling of power MOSFET packages

Abstract

This paper proposes a methodology for complete thermal description of power MOSFETs (LFPak56 and LFPak56D) to be used in electronic assembly level simulations. By describing all relevant heat paths through the packages, various types of cooling solutions can be assessed from early development phases. The described modelling approach comprises of measurement and calibration of the three paths through the package: via the slug, pins, and mold, by tuning each material property, to fit the thermal transient response (Zth). The automated calibration of all three heat paths of the MOSFETs described in the paper, greatly simplifies, and streamlines the buildup of the models lowering both development times and costs. The novelty of the paper is the introduction of concurrent calibration of all three paths with the help of optimization software and the measurement and model setups for an improved workflow. Using the described methods, standardized models can be built for quick assessments of different hardware configurations and thermal designs of electronic control units. The high accuracy of these models makes them appropriate for describing complex high-power transient loads and fast switching times.