Space Charge Formation and Electric Breakdown with EVA Film at Room Temperature Region

In order to understand dc breakdown characteristics of a polar polymer at the room temperature, a space charge study on ethylene-vinyl acetate copolymer (EVA) film was carried out using the pulsed electroacoustic method. Both fast negative carrier and slow positive carrier were injected. The positive carrier became dominant several tens of seconds after the voltage application, and increased the anode field. The breakdown did not take place when the electrode field reached the maximum value, but took place after it had fallen down due to the injection of the counter charge. It is concluded that the generation of injected and/or dissociated carriers increase the conduction current, and would bring the final breakdown. The temperature distribution of film surface until the electric breakdown was also measured by thermograph. Partial heating was observed before the electric breakdown. This suggested thermal electric breakdown in EVA film at room temperature region.