The Key Stage Division and Spatiotemporal Evolution Mechanism of Interfacial Partial Discharge in “Gel–Solid” Structures for High-Voltage Power Modules

Under high-frequency square wave voltage stress, insulation failure frequently occurs in power module packaging due to the synergistic evolution of interfacial partial discharge (IPD) and bubbles at the triple junction of “electrode–substrate–silicone gel”. This study establishes an experimental platform for packaging insulation interface IPD testing and develops a detection system immune to strong electromagnetic interference. In-situ observation captures the bubble evolution and IPD development, analyzing their interaction leading to insulation failure. Results show strong coupling between bubbles and IPD: the interface evolves through four stages—from intact to isolated bubble, elliptical growth, through-growth, and breakdown—corresponding to the initiation, development, intensification, and failure of IPD. The pattern of IPD distribution ranges from dispersed to triangular, then needle-shaped, and finally multi-peak layered. In the pre-breakdown stage, the number of IPD increases nearly exponentially, with a 65.3% rise in maximum amplitude and a 58.4% increase in number of IPD. A positive feedback cycle of “discharge heating–gel vaporization/pyrolysis–bubble expansion–field distortion–discharge enhancement” accelerates eventual breakdown. This paper provides theoretical and technical support for IPD detection, insulation assessment, junction optimization, and reliability improvement in power modules.

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