Polymer Film Capacitors

Plastic film capacitors

Often, a distinction is made in this type of capacitor between film capacitors and metal foil capacitors. The following description gives a brief information about their technical features.

Film Capacitors

Film capacitors usually consist of two aluminum foil electrodes with plastic films as a dielectric. In order to ensure the necessary safety and reliability of a capacitor, it is necessary to use a sufficient layer thickness. Typical advantages that have relatively large film capacitors over smaller metallized capacitors are

• their higher insulation resistance,
• their better capacity stability and
• their good ampacity.
• High voltage and good impulse handling capability are additional features of these capacitors.
• Contact connections are made by welding.

Metallized film capacitors

In contrast to film capacitors which use aluminum foils as electrodes, the electrodes of metal film capacitors consist of a thin metal layer (about 0.03 micron thick) which is vacuum deposited on the dielectric film. The connection of metallized capacitors takes place by means of a metal spraying process and by welding the leads to the sprayed ends. The main advantages of metallized capacitors are

• relatively small dimensions, a result of vacuum deposited electrodes, and
• self-healing property. Due to the self-healing property, relatively thin films for metallized capacitors can be used as film / foil capacitors.