Nichicon Application Guidelines for Aluminium Electrolytic Capacitors

Application Guidelines for Aluminum Electrolytic Capacitors is Nichicon Corporation's technical note CAT.8101H, a 28-page guide to how aluminium electrolytic capacitors are built, how they fail and how they should be used, stored and disposed of. Its safety guidelines follow the JEITA (formerly EIAJ) guideline RCR-2367D of March 2019.^[1]

1 General description: principles, capacitance, the aluminium oxide dielectric, the electrolyte, manufacturing, characteristics (leakage current, temperature characteristics)
2-1 Application guidelines, including maintenance inspection, emergencies, storage and disposal
2-2 Failure modes
2-3 Operating voltage and safety; 2-4 charging and discharging; 2-5 balance resistors in series connections
2-6 Storage performance; 2-7 restriking voltage; 2-8 use at high altitude
2-9 Life and reliability, with life estimation
2-10 Effects of halogens, cleaning agents, fixing and coating materials
2-11 CR timing circuits; 2-12 setting up capacitors, in-rush current, surface-mount types

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What it says that matters for repair

Venting

Larger capacitors have a pressure relief vent. If it operates, switch off the power. What comes out is vaporised hydrogen gas and electrolyte, not smoke from combustion, and it is over 100 °C, so keep hands and face away. Nichicon's first aid is to flush eyes with water, rinse the mouth and throat with water if the gas is breathed in, and wash electrolyte off skin with soap and water. Do not spill alkaline or acidic solutions on or near a capacitor.^[1]

Failure modes

Nichicon lists four failure modes in the field. Short circuits are very rare. Open circuits come from mechanical stress on the lead-to-tab joint, from halogen-containing cleaning or fixing agents getting into the capacitor and corroding the leads, foil and tabs, and from electrolyte drying out through a failed seal (high temperature, heat conducted through the board, excess ripple, long use). Capacitance drop and high loss (high ESR) come from reverse voltage, excess ripple or AC, and extreme charge-discharge duty. The fourth is operation of the pressure relief vent.^[1]

Storage and reforming

Store capacitors at 5-35 °C and 75 % relative humidity or less. During long storage without voltage the leakage current rises; applying voltage restores it (voltage treatment). Nichicon's treatment for a single capacitor is to charge it to its rated voltage through about 1 kΩ and hold it there for about 30 minutes. For a capacitor already in equipment with an adjustable supply, run the equipment at about half voltage for ten minutes and then raise the voltage gradually while watching it; with a fixed supply, run it for about 30 minutes. Capacitors stored for less than two years at 5-35 °C can be used without treatment.^[1]

Removal, cleaning and disposal

Discharge a capacitor before removing it from a board or disposing of it. Halogen-based cleaning agents, adhesives and coatings are not recommended; Nichicon recommends alcohol-based cleaning agents and gives the conditions for each type in section 2-10-2.^[1]

References

↑ ^1.0 ^1.1 ^1.2 ^1.3 ^1.4 ^1.5 Nichicon Corporation, Application Guidelines for Aluminum Electrolytic Capacitors, Technical Notes CAT.8101H, PDF; page numbers are PDF pages. Section 1 (general description, pp. 1-10), 2-1 (application guidelines, pp. 10-12), 2-1-5 (emergency, p. 11), 2-1-6 and 2-1-7 (storage and disposal, p. 12), 2-2 (failure modes, pp. 12-13), 2-6 (storage performance, p. 18), 2-9 (life, pp. 20-23), 2-10 (halogens and cleaning, p. 25).

[nc-1] 1.0 ^1.1 ^1.2 ^1.3 ^1.4 ^1.5 Nichicon Corporation, Application Guidelines for Aluminum Electrolytic Capacitors, Technical Notes CAT.8101H, PDF; page numbers are PDF pages. Section 1 (general description, pp. 1-10), 2-1 (application guidelines, pp. 10-12), 2-1-5 (emergency, p. 11), 2-1-6 and 2-1-7 (storage and disposal, p. 12), 2-2 (failure modes, pp. 12-13), 2-6 (storage performance, p. 18), 2-9 (life, pp. 20-23), 2-10 (halogens and cleaning, p. 25).

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