Suntan Construction of Aluminium Electrolytic Capacitors
Today electrolytic capacitors or as they are more correctly termed, Aluminium Electrolytic Capacitors are used in huge quantities. They are very cost effective and able to provide a larger capacitance per volume than other types of capacitor. This gives them very many uses in circuits where high currents or low frequencies are involved. Aluminium Electrolytic Capacitors are typically used most in applications such as audio amplifiers of all types (hi-fi to mobile phones) and in power supply circuits.
The plates of an electrolytic capacitor are constructed from conducting Aluminium foil. As a result they can be made very thin and they are also flexible so that they can be packaged easily at the end of the production process. The two plates, or foils are slightly different. One is coated with an insulating oxide layer, and a paper spacer soaked in electrolyte is placed between them. The foil insulated by the oxide layer is the anode while the liquid electrolyte and the second foil act as cathode.
In order to package them the two Aluminium foils with the electrolyte soaked paper are rolled together to form a cylinder, and they are placed into an Aluminium can. In this way the electrolytic capacitor is compact while being robust as a result of the protection afforded by the can.
There are two geometries that are used for the connection leads or tags. One is to use axial leads, one coming from each circular face of the cylinder. The other alternative is to use two radial leads or tags, both of which come from the same face of the cylinder.
The lead styles give rise to the descriptions used for the overall capacitors. Descriptions of axial and radial will be seen in the component references.
