Amélioration et caractérisation de l'autocicatrisation dans les condensateurs à films de polypropylène métallisés

In this study, we describe a way to improve self-healing in metallized polypropylene (PP) films capacitors. A PECVD (Plasma Enhanced Chemical Vapor Depositon) thin nitride organosilicon (or SiNOCH) coating is deposited on the surface of the PP film just before the metallization with zinc. The low pressure and high density plasma is inductively coupled and the gas mixture is made with HMDSO (hexamethyldisiloxane) and N2. FTIR (Fourier Transform Infra-Red) and XPS (X-ray photoelectron spectrometry) measurements are leading to the characterization of the composition and the structure of the thin coatings, while OES (Optical Emission Spectroscopy) provides information on the composition of the gaseous phase. Then, we have measured the current and voltage variations during self-healing and the size of the demetallized surface. Evidence has been made that a thin SiNOCH coating is useful since it allows to divide by a factor three the electrical energy needed for self-healing. In order to understand self-healing mechanisms, we analyzed the self-healed metallized polypropylene film surface by chemical imaging and spatially resolved XPS. The self-healing process leads to a cleared PP surface around the breakdown point. Moreover, a fraction of the coatings SiNOCH and Zn is deposited at the frontier between the cleared surface and the metallized surface.