Evaluation of thermal performance of packaged GaN HEMT cascode power switch by transient thermal testing

In this investigation, thermal transient measurements and analyses are used to study the thermal performance of a cascoded GaN power device. The method is based on the thermal characterization of the on-resistance (Ron) of the device and the synchronized current-voltage characteristics under continuous operation. The changes in Ron with temperature (25 °C-180 °C) are measured, statistically studied, and correlations investigated. The proposed method for estimating transient thermal impedance has the following characteristics: (1) it is robust and reproducible; (2) it yields a heating curve to prevent over-heating for the device under test (DUT); (3) it provides in-situ current-voltage characterization; (4) it includes a transient offset correction for initial transient electrical disturbances (such as current collapse); (5) it optimizes a compact thermal model; (6) it is sensitive to package structure and design variables. This monitoring of thermal impedance variation provides a simple and fast non-destructive method for analyzing power switching devices during thermal testing. Satisfactory experimental results confirm the feasibility of in-situ current-voltage characterization and the real power varies with the thermal impedance.