Dielectric breakdown of polyimide films: Area, thickness and temperature dependence

Changes in the dielectric breakdown field of polyimide (PI) films have been studied from 25 to 400°C under dc ramps. Both the area (from 0.0707 to 19.635 mm²) and thickness (from 1.4 to 6.7 ¿m) dependences of the dielectric breakdown field have been carried out using the Weibull distribution function. The 63%-breakdown field value (i.e. the ¿-scale parameter) of PI shows a decrease with increasing area, thickness and temperature but always remains above 2 MV/cm. The ß-scale parameter of the distribution shows a typical decrease with increasing area, however, it exhibits an increase with increasing thickness. This ´curious´ behavior is discussed on the basis of the percolation theory. No temperature-dependence is clearly observed. Moreover, physical interpretations are carried out using the pre-breakdown current analysis.