Current Dynamics during Bipolar TDDB in Galvanic Isolators based on Polymeric Dielectrics

We present an experimental investigation on the dynamics of the current emerging under bipolar electrical stress in galvanic isolators based on polymeric dielectrics. We report that this current shows a nonmonotonic trend with time and can affect device reliability well before Time-Dependent Dielectric Breakdown (TDDB). A physical picture, based on charge injection from the electrodes due to dielectric degradation and charge trapping close to the electrode/polymer interface, is presented to explain the experimental evidence. The work reports preliminary results for the understanding of the role of current and space charge on the TDDB in galvanic isolators based on polymeric dielectrics.