The Role of Dielectric Heating and Effects of Ambient Humidity in the Electrical Breakdown of Polymer Dielectrics

Polymer-based dielectric materials have potential applications in microelectronics, power electronics, photovoltaics, flexible electronics, MEMS, and sensing industries. The possibility of premature electrical breakdown due to high electric fields, particularly at high frequencies and in high ambient temperature and humidity conditions, has restricted its widespread adoption. In this paper, we generalize the thermochemical model of dielectric breakdown and establish dielectric heating as the primary ac degradation mechanism in polymers and develop an analytical dielectric breakdown model that satisfactorily explains measured trends in constant and ramp stress tests under both ac and dc electric fields applied to 5-μm-thick PBO capacitors. We also study and quantify the effects of exposure to ambient relative humidity on the electrical breakdown lifetime of polymer dielectrics. Our study provides a fundamental physical understanding of the frequency, ambient humidity, and thickness dependencies of lifetime and breakdown strength for polymer dielectrics; the proposed breakdown model suggests far more optimistic dielectric lifetimes when accelerated test results are scaled to normal operating conditions.