Power Device Interface Characterization With Low-Cost Thermal System Identification

This article develops a technique, requiring no dedicated temperature sensing calibration step, to rapidly characterize transient heat transfer in packaged, power semiconductor components. It is presented as an alternative to traditional step response characterization methods by exploiting the phase delay metric native to frequency response function (FRF) analysis in the field of system identification. This article presents the principles of power device physics and transient waveform analysis to identify the design space in which FRF data extracted from experiments are robust. Electronic circuitry is introduced, providing the needed, periodic heat actuation, and a measurement strategy leveraging direct processing of a temperature-sensitive electrical parameter (TSEP). The developed method is applied to make a key measurement confirming the high-frequency-only thermal FRF sensitivity to component die-attach condition. The measurement is shown to align with an output from a partial differential thermal model embedding a single, corrective scaling factor. Overall, this article highlights the emergent opportunity to measure a packaged power device’s transient thermal impedance with standard lab equipment and the ongoing opportunity to realize converter degradation self-sensing.