Relationship Between Prestress Breakdown and Space Charge in Micrometer-Thin Metalized Polymer Films

Micrometer-thin polymer films often endure harsh operating environments such as high electric fields and high temperatures, when utilized as insulating or capacitive media. These conditions may cause significant space charge accumulation, potentially leading to premature breakdown of the film. However, due to the limitations in space charge measurement techniques, there are few reports on the relationship between space charge accumulation and prestress breakdown in micrometer thin films. In this work, the relationship between the space charge and the prestress failure in double-sided metalized biaxially oriented polypropylene (BOPP) film with a thickness of $3.8~\mu $ m is investigated. Both dc prestress treatment and breakdown testing of the thin films are conducted using a ball plate electrode. The Weibull breakdown distribution illustrates the impact of prestress voltage and duration on the breakdown strength of the thin films. The residual electric field of the films, induced by space charge accumulation during prestress treatment, is measured using the thermal pulse method (TPM). The data indicate that the breakdown strength of the samples subjected to prestress treatment decreases, with the degree of decrease in breakdown strength basically consistent with the highest residual electric field of prestress treatment in numerical values. This experimentally demonstrates that the accumulation of space charges is the direct cause of the decrease in breakdown field strength in micrometer-thin films.