Compare the advantages and disadvantages of metal film capacitors

Metallized film capacitors are a layer of metallized film directly evaporated on paper as an electrode. Also called metallized paper dielectric capacitor. The electrode is a metallized film that has been evaporated and has a self-healing effect. If the voltage is too high and the dielectric inside the capacitor is broken down at a certain point, the short circuit current will evaporate the metallized film at the dielectric damage. Avoid short circuit between the two pole pieces, so that the capacitor continues to work. The breakdown range should not be too large, which will affect the capacitance of the capacitor. Metal film paper capacitors are usually encapsulated with epoxy resin, which has good moisture resistance.

In principle, there is no short-circuit failure mode for metallized film capacitors, and many short-circuit failures occur for metal foil capacitors. Although metallized film capacitors have the great advantages mentioned above, they also have disadvantages compared to metal foil capacitors:

1. The capacity stability is not as good as foil capacitors. This is because metallized film capacitors are prone to loss of capacity in long-term operating conditions and can reduce capacity after self-healing. Therefore, if used in oscillator circuits that require high capacity stability It is better to use metal foil capacitors.

2. The ability to withstand large currents is poor, because the metallized film is much thinner than metal foil, and the ability to carry large currents is weak. In order to change this disadvantage of metallized film capacitors, there are currently improved high-current metallized film capacitors in the manufacturing process. Because the resistance of metallized film capacitors is more excellent, and is also satisfactory in terms of solderability and self-recovering properties, this greatly saves space in size.