Mica capacitors are manufactured out of silvered mica plates staked alternatively between layers of metallic foils (brass, tin, alloy, lead or copper) and then clamped together to produce voids between the foils and the dielectric, as well as, to reduce the capacitance variation and size to improve stability. On each of the stake an annealed copper lead wire contact or terminal is soldered.
The assembly is dip coated with phenol formaldehyde or other selected natural or synthetic resins and then vacuum impregnated with high melting petroleum wax to eliminate the deterioration effect of the moisture and finally encapsulated. The type of encasing materials employed are important s their dielectric leakage and temperature limitations often restrict the performance of mica capacitors.