Capacitor self-healing process

What is self healing metallized capacitor?

Self- healing is the ability of a metallized capacitor to clear a fault area where a momentary short occurs due to dielectric breakdown under voltage. The conditions that lead to a fault vary. In the production of the dielectric film, contamination can occur or a process control problem can result in compromised dielectric strength.

Can a self-healing process destroy a capacitor?

Unfortunately, this mechanism can be dificult to control, and in the worst case, a run-away process can result, causing the destruction of the entire capacitor in short order. To avoid this, KYOCERA AVX developed a controlled self-healing process in 1974 based on the segmentation of overall capacitance into elementary cells protected by fuse gates.

How can metallized film capacitors improve self-healing efficiency?

A significant increase in the efficiency of modern metallized filmcapacitors has been achieved by the application of special segmented nanometer-thick electrodes. The proper design of the electrode segmentation guarantees the best efficiency of the capacitor's self-healing (SH) ability.

What is self-healing in polymer capacitors?

Self-healing in polymer capacitors involves (i) thermal rupture of the filaments, (ii) formation of voids in the cathode layers, and (iii) charge trapping in the polymer cathode that decreases anomalous currents caused by drying and discharging during breakdown. This work was sponsored by the NASA Electronic Parts and Packaging (NEPP) program.

What happens if a metallized film capacitor is self-cleared?

During self-clearing of metallized film capacitors, there is a gradual decrease of capacitance as a result of an increasing number of self-clearing events, which eventually leads to catastrophic breakdown of the capacitor; for example, see Figure 4 B.

How does deposition thickness affect the self-healing characteristics of a capacitor?

The deposition thickness of the metallized electrode directly influences the self-healing characteristics of the capacitor. Clearing energies of 0.050-0.150 joules are typically considered the proper range for clean clearings.