Vacuum Impregnation of Chip Capacitors for the Reduction of Water Corrosion

Potting protects electronics components from shock, vibration, and moisture by encapsulating them in substances like epoxies, silicones and urethanes, but vacuum impregnation is superior because it removes air and allows the potting material to fill micropores and channels. The goal of this project is to design a vacuum impregnation system that protects capacitors against corrosion by water. The system consists of a vacuum chamber connected to a sealed rotary vane pump. Capacitors and a range of potting agents are placed under vacuum at -15 inches of mercury, which degasses them, and the capacitors are coated with potting material. Vacuum is released and reapplied several times to ensure that voids in the capacitors are degassed and filled with potting material. Potted components are cured in an oven and kept in a humidity chamber for a week at 100 percent humidity and 90 degrees Celsius. Capacitance is monitored during this period; changes in capacitance are directly correlated to water corrosion in the capacitors.