AC Time-Dependent Dielectric Breakdown in polymer-based galvanic isolators: evidence of an impact of the electromechanical stress

We present a wafer-level experimental investigation on the AC Time-Dependent Dielectric Breakdown (TDDB) in galvanic isolators based on polymeric dielectrics. The collected evidence clearly indicates that the electromechanical stress involved in AC operation is a key degradation mechanism for the devices, and it can even become the dominant factor limiting device lifetime under certain operating conditions. The phenomenon is shown to be triggered by the change of polarity of the stress voltage and its main dependences are carefully explored, paying special attention to frequency and temperature. Results highlight that keeping electromechanical stress under control during the on-field operation of the devices is mandatory for the development of highly reliable polymer-based galvanic isolators.