Film Capacitors

Film capacitors use thin plastic film as the dielectric and are classified as electrostatic, non-polarized capacitors. They are known for their excellent electrical characteristics, including stable performance, low loss, and high reliability. Compared to other capacitor types, film capacitors offer favorable parameter stability across a wide range of applications—from small-signal circuits where ceramics are common, to power electronics where electrolytic capacitors are typically used.

Film capacitors are primarily divided into two categories based on electrode construction:

Foil electrode types, which use metal foil as the electrode

Metallized film types, where a thin metal layer is vapor-deposited onto the film

Further subcategories are defined by physical construction, such as wound or laminated structures, and by whether they are inductive or non-inductive.

Various plastic films serve as dielectrics in film capacitors, each offering unique properties. For example:

PET (polyethylene terephthalate) is widely used and often referred to as Mylar (a DuPont brand name).

Polystyrene (styrol) was once popular but has largely been replaced by polypropylene (PP) due to better performance and manufacturability.

PTFE (polytetrafluoroethylene) film capacitors are highly heat-resistant and used in demanding applications such as aerospace and military systems.

Metallized polyester capacitors are favored for their long-term stability in low-cost applications.

When performance is less critical, lower-cost plastics may be used to reduce production costs.