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Comparison Of Advantages And Disadvantages Of Metal Film Capacitance
Dec 30, 2018

Metal film capacitor is a layer of metal film directly evaporated on the paper as an electrode, also known as metallized paper capacitor, the electrode is evaporated on the metal film is much thinner than aluminum foil, the characteristics of this capacitor is self-healing. If the voltage is too high, so that the capacitor internal medium is a point of breakdown, short-circuit current will make the medium damage of the metal film evaporation, so as to avoid short-circuit between the two poles, so that the capacitor continues to work. Of course, the breakdown range should not be too large, otherwise it will affect the capacitance of the capacitor. Metal film paper capacitors are usually encapsulated in epoxy resin, so they have good moisture resistance.

In principle, there is no short-circuit failure mode in metal film capacitors, and there are many short-circuit failures in foil capacitors. Although metal film capacitors have the above great advantages, they also have disadvantages compared with foil capacitors:

1. Capacitance stability is not as good as foil capacitors, which is because the metallized capacitors are prone to capacity loss in long-term working conditions and can lead to capacity reduction after self-healing. Therefore, if the oscillation circuit with high requirements on capacity stability is used, foil capacitors should be better.

2. Poor resistance to large current, which is due to the fact that the metallized film layer is much thinner than the foil, and the weak capacity to carry large current. In order to change the shortcoming of metallized film capacitors, there have been improved products of high-current metal film capacitors in the manufacturing process. Because the resistance of metal film capacitors is better, and in the solderability and self-recovery properties are also satisfactory, which greatly saves the size space.