Degradation of Polyimide Film by Corona Aging under Bipolar Pulse Voltage

Abstract

Corona aging of 100CR polyimide (PI) film under bipolar pulse voltage was studied by using atomic force microscopy (AFM) and Confocal Raman microspectroscopy. AFM results show that the 100CR film near the breakdown hole is much rougher than the outside region. In the region away from the breakdown hole, no Raman shift is detected, but the intensity of all Raman peaks shows clearly decrease with the measuring region approaching more closely to the aging center. It is suggested that the damage of the PI film initiates from the surface in the presence of voids due to the partial discharge, and then gradually extends to interior, and these partial discharge cause progressive deterioration, and ultimately lead to the electrical breakdown of PI film with continuous aging.