Study on Vacuum Surface Insulation Properties of Sulfur/Fluorine-Containing Specialty Polyimide Films Targeting Space High-Voltage Solar Array Applications

Polyimide (PI), as a critical insulating material for spacecraft solar arrays, has its surface insulation stability directly impacting the reliability of space power systems. With future spacecraft power systems advancing towards higher voltage and higher power levels, the vacuum flashover issue of polyimide is anticipated to become more severe. To address these challenges, this study fabricated specialty polyimide films incorporating sulfur (SO-PI) and fluorine (CF-PI). Utilizing a custom three-parameter evaluation methodology based on the first breakdown voltage (U_fb), conditioned voltage (U_co), and hold-off voltage (U_ho), the surface insulation performance of these materials under vacuum was systematically characterized. Experimental results demonstrate that the specialty films exhibit significantly reduced surface charge accumulation and a higher withstand voltage threshold compared to commercial polyimide. Notably, the U_fb value of CF-PI showed a 24.74% improvement over that of commercial PI. This research provides valuable insights for the design of insulating materials in high-voltage space power systems.