Large-area dielectric breakdown performance of polymer films - Part I: Measurement method evaluation and statistical considerations on area-dependence

A multi-breakdown measurement method for large-area dielectric breakdown characterization of polymer films is presented and evaluated. Based on the self-healing breakdown capability of metalized film, large amount of breakdown data can be obtained from a relatively large total film area, thus enabling the execution of detailed breakdown performance analysis. The studied films include non-metalized laboratoryscale, pilot-scale and commercial capacitor-grade bi-axially oriented polypropylene films in the thickness range of 14-25 μm. With the active measurement area of 81 cm² per sample, breakdown distributions covering total film areas of 486-972 cm² are presented. Various aspects encompassing the sample film preparation, measurement procedure, breakdown progression, discharge event characterization, breakdown field determination, data validation and statistical analysis are discussed. Comparative small-area breakdown measurements were performed in order to study the relationship between the large-area multi-breakdown measurement method and a conventional small-area (1 cm²) manual breakdown measurement method. Implications of the areadependence and the applicability of the Weibull area-scaling are also discussed.