Aluminum electrolytic capacitor is a polar capacitor. Its positive plate is anodized by aluminium foil immersed in the electrolyte. A layer of aluminium oxide film is formed on the surface of the aluminium foil. Its thickness is generally 0.02 - 0.03 um. This oxide film is the insulating medium between positive and negative plates. The negative electrodes of capacitors are composed of electrolytes, which are generally composed of boric acid, ammonia, ethylene glycol, etc. In order to facilitate the manufacture of capacitors, the electrolyte solution is usually impregnated on special paper, and then bonded with a paper impregnated with the electrolyte solution, which can easily lead out the negative electrode on the original aluminum foil.
