Filamentary electrical conduction in polyimide films detected by infrared thermography before thermal breakdown

An experimental evidence of filamentary electrical conduction existence in polyimide (PI) films under DC voltage just prior to thermal breakdown is reported. This was achieved by real-time surface temperature mapping of PI-metallized samples initially at 300 degrees C using fast infrared thermography coupled to current-voltage measurements until the breakdown. The transition from a full-electrode conduction to a filamentary conduction is clearly identified through the detection of a localized hot spot within the PI samples in the last 100-150 ms before breakdown. A conduction path, with values inferior to 500 mu m in the few ms before the breakdown, was estimated leading to temperature rising up to 100K above the initial temperature. This work confirms the existence of a filamentary conduction in thermoset polymers prior thermal breakdown. Published by AIP Publishing.