Hydrostatic pressure suppresses the electrical breakdown of flexible-rigid interfaces under deep-sea

Abstract

High-voltage and high-power electronic components intended for deep-sea applications encounter various challenges, including high hydrostatic pressure, temperature fluctuations, and probable seawater ingress. Consequently, encapsulation of deep-sea electronics that provides both efficient electrical insulation and pressure tolerance is crucial. This study investigates the influence of high hydrostatic pressure up to tens of MPa on the electrical breakdown of the flexible-rigid encapsulation interface, using polydimethylsiloxane and FR-4 glass epoxy as experimental materials. The experimental results show that the interface breakdown strength increases with hydrostatic pressure, in which a rapid increase is observed at 0.1 MPa to 0.75 MPa, followed by a slower rise at 0.75 MPa to 30.0 MPa. To explain this phenomenon, the cavity discharge inception field and the enhanced local electric field at contact spots under hydrostatic pressure were calculated based on interfacial contact theory. At relatively lower pressures, cavity discharge predominates in driving the interface breakdown, and the rapid growth of cavity discharge inception field leads to the sharp increase in breakdown strength with hydrostatic pressure. Whereas at higher pressures, the insulation properties of contact spots become the dominant factor. Post-breakdown analyses, including optical microscopy and micro-CT imaging, reveal that high hydrostatic pressure suppresses damage propagation, such as material carbonization, electrode defects, and gas formation. These results indicate that hydrostatic pressure helps suppress the electrical breakdown of the flexible-rigid interface. This study provides insights into the electrical breakdown behavior of flexible-rigid interfaces under high hydrostatic pressure, offering implications for the encapsulation design and optimization of deep-sea electronic components.