Effect of Trap Characteristics on Insulation Performance of Polyimide Film at Different Temperatures

With excellent dielectric properties and high & low temperature resistance, the polyimide film is widely applied in spacecraft surfaces. In order to study the effects of different temperatures on trap characteristics and insulation properties of polyimide film, firstly, we charged the surface of polyimide by the corona discharge method, and then the isothermal surface potential decay method and double index mathematical model was used to calculate the trap distribution parameter. The trap distribution at different temperatures (25 ℃, 50 ℃, 70 ℃ and 90 ℃)were researched and analyzed. Secondly, we measured the volume conductivity and dielectric spectrum characteristics of polyimide films at different temperatures, and analyzed the effect of trap distribution characteristics on the dielectric properties and volume conductivity of polyimide film. The results show that the shallow trap energy level of polyimide do not change significantly with the increase of temperature, but the deep trap energy level decreases slightly and the deep trap density decreases significantly; the trapping effect on carriers weakens with the increase of temperature, and carrier mobility and carrier concentration increases, leading to an increase in conductivity; the decrease of deep trap density leads to the surge of carriers and the polarization of space charge, which leads to the increase of dielectric constant in low frequency region. Based on the bipolar charge transport model, the effect mechanism of temperature on the insulating property is analyzed from the perspectives of electrode injection and internal charge transport, which provided a theoretical basis for further improving the insulating property of polyimide film in extreme application environment. © 2022 Science Press. All rights reserved.