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

Abstract

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 °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/μm. This corresponds to a dissipated volume power density between 2 and 5 mW/μm3. Such values report the limit of the electro-thermal equilibrium in PI film.

New Approach for Fabricating of Deep Submicron Free-Standing Polyimide Thin Film

“…Using this method, we found that the ablation threshold for the 1000 nm PI film with KrF laser was about 28 mJ/cm 2 [Fig. 4b], which was agreement with the results reported in the literature [17,18]. To obtain the dependency of average ablation rate on the laser flux, the Glass/PI film was irradiated with fluxes 45 mJ/cm 2 and 75 mJ/cm 2 each for 30 pulses.…”

Examining the Mechanism of Current Conduction at Varying Temperatures in Polyimide Nanocomposite Films

“…Table 2 provides an overview of the experimental slope values, calculated β S /kT values, measured and computed dielectric constants, as well as the derived γ values for reference. γ = (Slope×kT) 2 4πε 0 ε r q 3 (9) When evaluating the dominance of Schottky emission in conduction, it is expected that a plot of log (J) against E 1/2 will exhibit a proportional relationship, forming a linear curve in accordance with Equation (5). Initially, we calculate the β S coefficients based on the slopes of the log (J) vs. E 1/2 plots.…”

“…Polyimide (PI) film, known for its exceptional dielectric properties, remarkable thermal and chemical stability, and high breakdown strength, finds wide-ranging applications in critical industries [1,2]. These applications include superconducting cable insulation, wind power generator winding insulation, variable-frequency motor winding insulation, and aerospace technologies [3][4][5]. Furthermore, these thin films serve versatile roles as coating films for electronic devices, buffer coatings, intermetallic layers, protective surface coatings in spacecraft, and enameling for electric motor insulation.…”