Study on Cauer Thermal Network Model Considering Bidirectional Heat Transfer

Wide-band gap semiconductor devices based on GaN materials, such as high electron mobility transistors (HEMT), are gradually replacing traditional Si devices in industrial applications owing to their excellent electrothermal properties. Nonetheless, reliability concerns and accurate junction temperature estimation remain critical in the deployment of these devices. This paper proposes an enhanced Cauer thermal network model accounting for bidirectional heat transfer. The improved model takes into account the path from the junction via the top case to the ambient. Additionally, it utilizes the top case temperature rise to identify thermal parameters and establishes the relationship between the top case temperature time constant and the Cauer model’s thermal parameters. This method eliminates the need for measuring power losses or invasively modifying the original devices, nor does it require detailed structural and material parameters of the packaged device. The feasibility and reliability of the obtained thermal network parameters are verified through simulation and validated through experimentation.