The metalized film capacitors is to deposit a metal film on the surface of the polyester film instead of metal foil as the electrode. Because the thickness of the metallized film layer is much smaller than the thickness of the metal foil, the volume after winding is also larger than that of the metal foil capacitor The volume is much smaller. The biggest advantage of metalized film capacitors is the “self-healing” characteristic. The so-called self-healing property is that if the thin film medium has defects at a certain point and a breakdown short circuit occurs under the action of overvoltage, the metallization layer of the breakdown point can melt and evaporate instantly under the action of the arc to form a small metal-free zone , The two pole pieces of the capacitor are re-insulated from each other and can still continue to work, thus greatly improving the reliability of the capacitor work. From the principle analysis, there should be no short-circuit failure mode for metalized film capacitors, and metal foil capacitors will have many short-circuit failure phenomena. Although metalized film capacitors have the above-mentioned huge advantages, compared with metal foil capacitors, they also have the following two disadvantages:
First, the capacity stability is not as good as foil capacitors. This is because metalized capacitors are prone to capacity loss and self-healing in long-term working conditions, which can lead to capacity reduction. Therefore, if used in an oscillation circuit that requires high capacity stability Metal foil capacitors should be used better.
Another major disadvantage is the poor ability to withstand large currents. This is because the metallized film is much thinner than the metal foil, and its ability to carry large currents is weak. In order to improve the shortcomings of metallized film capacitors, there have been improved high-current metallized film capacitor products in the manufacturing process. The main ways to improve are:
1. Use double-sided metallized film as electrode;
2. Increase the thickness of the metallized coating;
3. The metal welding process on the end face is improved to reduce the contact resistance.
