Thermal runaway in polyimide at high electric field probed by infrared thermography

An original way for characterizing dielectrics under high electric field and high temperature based on the coupling between electric current measurements and real-time fast infrared (IR) thermography is demonstrated. Particularly, the Joule heating phenomenon at high field is quantified by 2D-temperature cartography in a polyimide (PI) film set at an initial temperature of 300 degrees C through IR observations of the polarized electrode. 2D-temperature cartography highlights the temperature increase with increasing the electric field. The thermal runway occurs prior to the dielectric breakdown from an electric field threshold of 140-150 V/mu m. This corresponds to a dissipated volume power density between 2 and 5 mW/mu m(3). Such values report the limit of the electro-thermal equilibrium in PI film. (C) 2015 AIP Publishing LLC.