Space charge behavior in multilayered polyimide films under DC high stress near breakdown strength

We investigated the relationship between the space charge accumulation characteristics and the breakdown in various combination of multilayered polyimide samples under dc stress using the pulsed electro acoustic (PEA) method. In recent years, there are many examples which a multilayered polyimide film is used as the flexible Printed-Circuit Board (PCB) inside an advanced electronic devices or motor windings. Therefore, it is necessary to investigate the insulation performance of the multilayered polyimide. In previous work, it has been revealed that a space charge accumulated in polyimide film under a high stress and it is closely related to the electrical breakdown. Therefore, it is also necessary to investigate the space charge accumulation characteristics of the multilayered type sample. In this paper, we measured the space charge accumulation in various combinations of the multilayered samples under dc high electric field at 80°C by using the PEA method. From the space charge measurement, we found that the multilayered sample has more superior insulating properties than the single layer sample. Furthermore, we found that it is hard to have the breakdown by arranging a thin layer putting next to the anode electrode.