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Metallized thin film capacitors are made by depositing a layer of metal film on the surface of polyester film instead of metal foil as electrodes. Because the thickness of the metallized film layer is much smaller than that of the metal foil, the volume after winding is much smaller than that of metal foil capacitors.

The biggest advantage of metallized film capacitors is their self-healing characteristics. The so-called self-healing characteristic is that if a thin film medium has defects at a certain point and a breakdown short circuit occurs under overvoltage, the metallized layer at the breakdown point can instantly melt and evaporate under the action of an arc, forming a small non-metallic zone, allowing the two electrodes of the capacitor to re insulate and continue to work, thus greatly improving the reliability of capacitor operation.

Disadvantages and improvements:

From a theoretical analysis, there should be no short circuit failure mode in metallized thin film capacitors, while metal foil capacitors will experience many short circuit failure phenomena (such as the 27 pbxxxx-jxx series). Although metalized thin film capacitors have the aforementioned huge advantages, they also have two disadvantages compared to metal foil capacitors: firstly, their capacity stability is not as good as that of foil capacitors. This is because metalized capacitors are prone to capacity loss and self healing under long-term working conditions, which can lead to capacity reduction. Therefore, if used in oscillation circuits that require high capacity stability, metal foil capacitors should be chosen for better performance.

Another major drawback is the poor ability to withstand high currents, which is due to the fact that the metallized film layer is much thinner than the metal foil, and its ability to withstand high currents is weaker. To improve the drawback of metallized thin film capacitors, there are already improved high current metallized thin film capacitor products in the manufacturing process, and the main ways to improve them are as follows:

(1) Using double-sided metallized thin films as electrodes;

(2) Increase the thickness of the metallized coating;

(3) Improvement of end face metal welding process to reduce contact resistance.