Film capacitors use metalized film as the dielectric, and one characteristic of these capacitors is that they will cause an open failure if an overcurrent passes through them. This characteristic of film capacitors is referred to as the self-healing function. A fuse pattern is also sometimes used in products requiring high reliability, for situations where the self-healing function does not work.
Another benefit of film capacitors is that they will not undergo wear-out failure if used under appropriate voltage and temperature conditions. They therefore last longer than aluminum electrolytic capacitors and other capacitors that undergo wear-out failure. However, using them in high-voltage or high-temperature environments could result in reduced capacity due to undergoing open failure. Conditions will therefore need to be carefully considered.
If there is an electrical weak point in film, or if insulation breakdown occurs due to applying excessive voltage, the surrounding deposited film will be instantly oxidized and the insulation will be recovered. This self-recovery function helps improve the reliability of film capacitors.