Electrical tree formation in polymer-filler composites

Insulating fillers are often mixed with polymer dielectrics in order to improve dielectric breakdown strength. However, filler-loaded dielectric films show higher variability, which limits their large-scale utility and application. In this paper, we present a computational framework for predicting the spatial distribution of electrical tree formation in a polymer dielectric in the presence of insulating fillers. The framework is based on the numerical solution of Poisson's equation inside the dielectric film and the application of the Monte Carlo model for finding the electric breakdown path. The simulation results explain several puzzles associated with the breakdown of polymer-filler dielectrics, such as (1) the improved breakdown strength with insulating filler mixing, (2) high degree of variability in breakdown measurements, and (3) effects of filler size, shape and position on the breakdown. In addition, the proposed framework not only provides the physical understanding of the breakdown process but also inspires new design concepts to improve the breakdown strength of the polymer composite.