About the characteristics of film capacitors

The film capacitor has many excellent characteristics, so it is a kind of capacitor with excellent performance.Its main characteristics are as follows: non-polarity, high insulation resistance, excellent frequency characteristics (wide frequency response), and low dielectric loss.Based on the above advantages, film capacitors are widely used in analog circuits.Especially in the signal cross-connection part, capacitors with good frequency characteristics and extremely low dielectric loss must be used to ensure that the signal will not be too distorted when it is transmitted.Among all plastic film capacitors, polypropylene (PP) capacitors and polystyrene (PS) capacitors have the most remarkable characteristics, Of course, the prices of these two types of capacitors are relatively high.However, in recent years, in order to improve the sound quality of audio equipment,the parts and materials used have become more and more advanced，the price is not the most important factor, so in recent years the frequency and quantity of PP capacitors and PS capacitors used in audio equipment is also more and more higher.Readers can often see a certain brand of equipment, known by the brand name of a certain number of capacitors quality PP or PS quality capacitors to as an endorsement on the sound quality, the truth in this.

The usual method of making film capacitors is to use metal foils such as aluminum as electrodes and plastic films to be overlapped and wound together. However, there is another manufacturing method for film capacitors, called Metallized Film. The method is to deposit a thin layer of metal on a plastic film by vacuum evaporation to serve as an electrode. In this way, the thickness of the electrode foil can be omitted, and the volume of the capacitor per unit capacity can be reduced. Therefore, the film capacitor can be easily made into a small and large-capacity capacitor. For example, the common MKP capacitor is the name of the metallized polypropylene film capacitor, and the MKT is the name of the metallized polyester film capacitor.

Films used in metallized film capacitors include polyethylene, polypropylene, polycarbonate, etc.In addition to winding type, there are also laminated type.The metallized film type of capacitor has a so-called self-healing action, which assumes that when the tiny part of the electrode is short-circuited due to the weak electrical boundary, the electrode metal around the short-circuited part will be caused. Due to the electrostatic energy or short-circuit current carried by the capacitor at that time, a larger area of melting and evaporation will be caused to restore the insulation, and the capacitor will resume the function of the capacitor.