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 degrees C under dc ramps. Both the area (from 0.0707 to 19.635 mm(2)) and thickness (from 1.4 to 6.7 mu m) dependences of the dielectric breakdown field have been carried out using the Weibull distribution function. The 63%-breakdown field value (i.e. the alpha-scale parameter) of PI shows a decrease with increasing area, thickness and temperature but always remains above 2 MV/ cm. The beta-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.