Interfacial Charge Dynamics in Power Module Packaging Insulation Based on Non-Invasive Electric Potential Mapping

The application of power modules under higher voltages and power densities has become increasingly widespread. However, this trend also highlights growing concerns regarding the reliability issues related to their packaging insulation. One of the most critical factors affecting insulation reliability lies in the space charge dynamics, especially at the interface between the encapsulation layer and ceramic substrate. Due to the complex packaging structure and operation conditions, interfacial charge dynamics are challenging to investigate with conventional simulation and measurement methods. This study applies a non-invasive electric potential measurement technique, based on an electrostatic probe, to power module-level packaging insulation. The measurement achieves a negligible error, confirming its applicability for the electric potential measurement of power module-level insulation samples during not only the voltage-off but also the voltage-on situation. The corresponding inversion algorithm is then derived to characterize the interfacial charge dynamics. By applying this algorithm, the spatio-temporal interfacial charge dynamics are successfully reconstructed. The accumulation and dissipation processes are analyzed, confirming the impact of charge injection and accumulation within the packaging insulation under various voltages. This study addresses the research gap concerning interfacial charge dynamics in power module packaging insulation and provides experimental insights to support the research on insulation reliability.