Plastic-film-dielectric capacitors

The suitability of plastics as capacitor dielectrics is dependent on a variety of considerations, both electrical and mechanical, but primarily on their ability to be formed into thin uniform continuous films, whether unsupported or supported by a substrate. How far the expected advantages have been realized from the use of `tailored¿ synthetic materials, instead of naturally occurring dielectric materials, is discussed in the light of the properties of capacitors made from some plastic films of established utility such as polystyrene, polyethylene terephthalate, polytetrafluoroethylene and polycarbonate [poly-bis (2-phenyl) propane carbonate]. Miniaturization can be achieved by the usual techniques of depositing surface films of metal of negligible thickness, and also by coating suitable substrates with films of plastic dielectric too thin to be self-supporting.