Highly versatile and applicable in a multitude of systems, capacitors are critical components in electronic circuits. Specifically, film capacitors, often called polyester or mylar capacitors, are non-polarized capacitors that use thin films as dielectrics.
HISTORICAL DEVELOPMENT
In 1876, a British man, D. G. Fitzgerald, invented the paper capacitor with oil and wax, which became the first generation of film capacitors. Originally produced as a laboratory curiosity, the first paper capacitors were made from double layers, bulky in size and not reliable. In the following years, these capacitors evolved from using powdered metal to foil strips. Eventually, these methods were combined to create capacitors that used both oil, wax, and metal, creating self-healing capabilities along with increased material reliability. With the development of science & technology, the models, process materials, and functions of the film capacitor became more diverse, becoming a widely used component in the modern world.
CHARACTERISTICS
High insulation resistance
Good frequency
Low dissipation factor
High capacitance stability
TYPES
Dielectrics: Polypropylene (PP), Polyester (PET), Polyphenylene sulfide (PPS), Polytetrafluoroethylene (PTFE), etc.
PP film—commonly used in industrial capacitors and power capacitors— absorbs less moisture than other films and features very low temperature and frequency dependencies.
PET film capacitor features small physical size and low cost. It is mainly used for general purpose applications.
PPS film capacitor can only be produced as a metallized film capacitor. It has a very small temperature dependence, low frequency dependence, and low output noise. Compared to a PP film capacitor, it usually has a higher cost.
PTFE film is famously known by the trademark Teflon of DuPont. Polytetrafluoroethylene film capacitor features high temperature resistance, up to 260°C, but is thicker than a PP film capacitor. Furthermore, because of the precision required for even film thickness, Polytetrafluoroethylene film production is difficult and highly limited.
APPLICATIONS
Its high insulation resistance, excellent frequency characteristics, and small dielectric loss make film capacitors highly compatible with audios, speakers, automobiles and other products.
DIFFERENCES BETWEEN FILM CAPACITORS AND CERAMIC CAPACITORS
Over the past decade, film capacitors have gradually replaced other capacitors, such as electrolytic capacitors or ceramic capacitors in the automobile industry and other fields. The first difference between these capacitors is the dielectric types used. As their names indicate, film capacitor uses plastic film, and ceramic capacitor uses ceramic materials.
Furthermore, capacitor performances are impacted by the manufactured design and dielectrics. Although they have high capacity and long service life, ceramic capacitors can only be applied for circuits with low capacitance requirements. On the other hand, film capacitors provide a wide selection of capacitance values, and their low distortion factor makes them more suitable for analog signal processing circuits. Durable and long-lasting, film capacitors are ultimately the best choice for high voltage and high frequency applications.
