How to choose the right film
They are available in several different types of plastic film, each with its own set of unique characteristics:POLYESTERThe low cost of polyester (Mylar) film combined with its high volumetric efficiency makes it a very popular choice for many general purpose, generally DC, operations. Polyester capacitors are also available in versions rated to operate at up to 125°C, making them suitable for some semi-critical, high temperature applications. However, polyester film exhibits poor temperature stability and frequency response when compared to other plastic films; this makes them generally unsuitable for precision circuits or high frequency applications.POLYCARBONATEWhen temperature stability is critical, polycarbonate film was the dielectric of choice for many years. Polycarbonate is very stable and rated to operate between -55°C and +125°C, offering the availability of tight tolerance capacitors over a wide temperature range, making them very suitable for precision applications such as timing circuits and high performance military applications. However, the primary manufacturer of polycarbonate film has ceased manufacture, stockpiles are depleted and ongoing availability compromised.