Accelerated life studies of polyimide film under electrical and thermal multistress

Accelerated life studies on a high-temperature polyimide film (Kapton) were conducted under simultaneous electrical and thermal stress at 60 Hz and 400 Hz. The breakdown strength and the aging characteristics were obtained at test temperatures of 23 degrees C, 100 degrees C and 200 degrees C. The two-parameter Weibull distribution was used in the evaluation of the experimental data. The experimental results show that electrical aging, by increasing the applied voltage or the applied frequency, is the mechanism responsible for failure under these conditions, and that thermal aging is not a major degradation factor for the Kapton film in the applied temperature range, particularly at the higher frequency of 400 Hz. Several theoretical models were considered to obtain the best approximation to the experimental data. The analysis shows that present physical models cannot take into account acceleration of aging with the applied frequency.<>