Spatiotemporal Analysis of Interfacial Charges in High Voltage Power Module Packaging Under Square-Wave Stress

Power modules are widely used in electric vehicles, renewable energy systems, and power grids, where stable insulation is critical for safe and efficient operation. Interfacial charge accumulation in the packaging insulation of power modules significantly affects long-term reliability, especially under high-voltage operation. This study proposes a non-invasive method for measuring interfacial charges and investigates the influence of square-wave excitation parameters, including frequency, rise time, and duty cycle. Experimental results show that higher frequencies promote greater charge accumulation, while longer rise times reduce it. It indicates that rapid voltage transitions are more effective in triggering transient interfacial processes, such as charge injection and dipole polarization. Additionally, a relatively higher duty cycle may introduce negative charge injection near the grounded electrode, which can suppress the apparent net charge. These findings reveal the critical role of waveform characteristics in shaping interfacial charge accumulation and offer valuable insights for insulation design in high-voltage power modules.