Detection of joule heating in polyimide films at high electric field and high temperature by infrared thermography

This paper reports an original way for dielectric characterizations under high electric field and high temperature based on the coupling between electric current measurements and real-time fast infrared (IR) thermography. Particularly, the Joule heating phenomena were quantified by 2D-temperature cartography in a polyimide (PI) film exposed to an initial temperature of 300 °C through IR observations of the electrode. In a first part, we describe the measurement setup and parameters used during the study. Then, the calibration methodology is presented from emissivity estimation to the verification of the sample temperature. Finally, 2D-temperature cartography is presented highlighting the surface (equivalent to bulk due to the low thickness of PI film) temperature increase when increasing the applied electric field. A Joule heating of 16 °C above the sample temperature is quantified in the investigated field range showing for the first time a clear experimental proof of the thermal origin of the breakdown mechanism in polymer materials under high field/high temperature.