Aluminum Foil Capacitors

	product name:	Aluminum Foil Capacitors
	Place of Origin:	Peoples Republic of China
	Post Date:	February 10, 2011
	Edit Date:	March 30, 2011

Detailed Product Description:

Aluminum Foil Capacitors

Aluminum foil is employed in paper capacitors because it is the cheapest electrical conductor for the application. It is also used in electrolytic capacitors because it is the cheapest conductor, but more importantly because its oxide coating is the best practical dielectric for the application. Such capacitor foils are made of high purity aluminum (99.99 percent or better in some cases), and other purities also, depending upon the electrical conductivity and/or thickness and quality of oxide required for the specific application. 

Paper Capacitors

The utility of aluminum foil in this application lies chiefly in its good electrical conductivity and low cost. Two strips or "plates" of foil gauges of 0.00035 in. and under are employed, with the thinner gauges being in demand for solid-state type and special-use capacitors, where compactness is a basic requirement. The dielectric plate is a waxed or otherwise impregnated paper and is wound between the foil conductor plates.

Electrolytic Capacitors

This application of aluminum foil employs not only its good electrical conductivity but also its oxide coating, specially formed (anodized) to make a superior dielectric layer between the two conductors. The dielectric constant of aluminum oxide is higher than that of waxed paper and many other dielectric materials, therefore it can store more electrons per unit of area. The oxide dielectric plate, which determines the size of a given capacitor, does not have to be as large as a paper dielectric "plate" for an equal capacity. Further, the oxide film, even a "thick" one, is thinner than the thinnest tissue paper. This thin film of aluminum oxide reduces the bulk of the capacitor; but more important, its thinness also increases the capacitance per unit of area. 

Another advantage of aluminum foil for electrolytic capacitors is that the foil is readily etched. This is important because etching greatly increases the true surface area which, when anodized, results in a far larger dielectric plate capacity. 

Types of Applications

Aluminum foil capacitors are used in practically every type of electrical equipment, including radios, televisions, telephones, computers, microwave ovens, electrical welders, magnetos, electronic testing equipment, copy machines, air conditioners, automobiles, fluorescent lights, mercury vapor street lamps, power transmission equipment, electric motors, control units, and others.