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June 2018 – Benefits of using Film/Foil Capacitors

Published on: 29/06/2018

GD Rectifiers share the benefits of using film/foil capacitors

Benefits of using Film/Foil Capacitors. London underground train going through a tunnel having left the platform.

Film/foil capacitors consist of two aluminium foils acting as the electrodes. The foil electrodes are separated by a polymer film dielectric. These materials are non-inductively wound to form the capacitor element. The wire leads are soldered directly to the aluminium foil electrode which extends out on both sides of the capacitor element.

A sufficient thickness of dielectric film is essential to withstand the applied electric field, this is because the foil electrodes are typically about 5 micrometres thick and the dielectric is usually thicker than metallised film capacitors.

The electrodes in metallised film capacitors usually have an extremely thin layer of metal which is vacuum-deposited directly onto the dielectric film. The wire lead is connected to the electrodes by a metal spray which is applied to each end of the capacitor element, the lead wire is soldered to this metal end spray.

Metallised film capacitors are manufactured using a much thinner dielectric film than those typically used in the same rated film/foil design. This is because the self-healing characteristics of the metallised film, it removes a fault or short circuit in the dielectric film by vaporizing the metal electrode surrounding the defect and isolating area.


Benefits of using Film/Foil Capacitors

Film/foil capacitor designs usually offer higher insulation resistance, better capacitance stability, high current carrying capabilities for pulse applications and a lower dissipation factor.  The metal foil electrodes act as a heat conductor, transferring the the heat out from the interior of the unit enabling excellent heat dissipation. The superb heat dissipation allows for a higher voltage application, in comparison to the metallised capacitor at the same frequency. The extended foil design also allows for operation at higher peak currents and faster duty cycles.

Capacitors using polymer film technology provide a wide range benefits, including:

  • High reliability
  • High pulse currents
  • Non-standard values and/or tight tolerance
  • Low dielectric absorption
  • Extremely small capacitance changes with applied voltage
  • Capacitance stability over frequency
  • Small variation in capacitance with temperature change


GD Rectifiers offers a wide range of API Capacitors, including: AC Capacitors, DC Capacitors, Energy Storage Capacitors, Snubber Capacitors, Track Circuit Capacitors, Low Temperature Capacitors, Ultra Low Temperature Capacitors and Custom Designed Capacitors.

For further information on their wide range of capacitors, please call: 01444 243 452 or email:


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