Ion irradiation-induced degradation of surface insulation performance in Cu–PI alternating structures for solar array drive assemblies

The development of high-voltage and high-power spacecraft subjects the vacuum surface insulation reliability of solar array drive assembly conductive slip rings to severe challenges from high-energy charged particle irradiation in space. Addressing the issue that existing studies often neglect the in situ metal–insulator coupling effect, this work focuses on Cu–polyimide (PI) alternating structures to systematically investigate the degradation mechanisms of insulation performance under Ar+ irradiation with different irradiation times. Multi-scale morphological and chemical composition characterizations indicate that the ion irradiation damage is associated with the concurrent occurrence of matrix etching degradation and metal sputtering deposition. Irradiation induces deoxidation, denitrogenation, and main-chain scission of the PI substrate, leading to a structurally disordered porous surface; simultaneously, copper atoms from lateral sputtering aggregate on the PI surface, oxidizing to form Cu-containing nanoclusters. Isothermal surface potential decay measurements reveal that the destruction of the intrinsic PI structure and the introduction of the metal interface lead to an increase in shallow trap density. Concurrently, the surface resistivity decreases significantly, the secondary electron yield (SEY) rises, and the pulsed flashover threshold drops. Analysis based on the secondary electron emission avalanche model indicates that the synergistic effect of the increased shallow traps, decreased surface resistivity, and elevated SEY leads to a drastic reduction in the vacuum pulsed flashover threshold of this alternating structure. The in situ coupled irradiation degradation mechanism of the planar Cu–PI alternating structure investigated in this work can provide an experimental reference for the anti-irradiation design of high-voltage spacecraft insulation structures.