Heat flux-dependent partial discharge behavior in a two-phase fluorinated liquid: Role of the microstructured heating surface

Abstract

Fluorinated liquids are essential dielectric coolants used in immersion cooling and near-junction thermal management of high-voltage, high-power-density semiconductors. The impact of thermally induced bubbles on the partial discharge behavior of fluorinated liquids has been widely noted; however, the differences in their partial discharge characteristics with varying heat flux on smooth and microstructured surfaces remain unclear. Here, partial discharge experiments on a two-phase fluorinated liquid are conducted, and the relationship between boiling behavior and partial discharge characteristics is revealed. On the smooth surface, intensified boiling leads to a concurrent rise in discharge frequency and charge magnitude, accompanied by a continuous reduction in the partial discharge inception voltage. In contrast, the microstructured surface regulates the bubble dynamics, mitigating the deterioration of insulating performance as the heat flux increases. Moreover, the concentrated electric field at the sharp edges of the microstructures triggers partial discharges that fragment newly formed bubbles, thereby inhibiting the occurrence of severe discharges. This study lays the foundation for the synergistic improvement of thermal and electrical performance of immersion cooling or near-junction cooling based on fluorinated liquids for future high-voltage, high-power-density chips.