Comparison of advantages and disadvantages of metal film capacitors

The metal film capacitor directly evaporates a metal film on the paper as an electrode, also called a metallized paper capacitor. The electrode is evaporated to a much thinner metal film than the aluminum foil. This capacitor is characterized by self-healing. If the voltage is too high, causing a certain point in the internal dielectric of the capacitor to be broken, the short-circuit current will evaporate the metal film at the damage of the medium, thereby avoiding a short circuit between the two pole pieces and allowing the capacitor to continue to operate. Of course, the range of breakdown 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 moisture resistance is good.

From the principle analysis, the metal film capacitor does not have a short-circuit failure mode, and the metal foil capacitor will have many short-circuit failure phenomena. Metal film capacitors have the above-mentioned great advantages, but they also have disadvantages compared with metal foil capacitors:

1. The capacity stability is not as good as that of the foil capacitor. This is because the metallized capacitor can cause capacity loss after long-term working conditions, and the capacity can be reduced. Therefore, if it is used in an oscillation circuit that requires high capacity stability, Metal foil capacitors should be used better.

2. The ability to withstand large currents is poor, because the metallized film layer is much thinner than the metal foil, and the ability to carry large current is weak. In order to change the shortcoming of metallized film capacitors, there are currently improved high current metal film capacitor products in the manufacturing process. Because the resistance of the metal film capacitor is more excellent, and it is satisfactory in terms of solderability and self-resetting property, the size space is greatly saved.