1. FiXED capacitors
a. Film capacitors
Film capacitors consist of a relatively large family of capacitors with the difference being in their dielectric properties. These include polyester (Mylar), polystyrene, polypropylene, polycarbonate, metalized paper, Teflon etc. Film type capacitors are available in capacitance ranges from 5pF to 100uF depending upon the actual type of capacitor and its voltage rating. Film capacitors come in various shapes and case styles such as:
· Wrap and Fill (oval & round) - The capacitor is wrapped in a tight plastic tape and the ends are filled with epoxy in order to seal them.
· Epoxy Case (rectangular & round) - The capacitor is encased in a molded plastic shell which is filled with epoxy.
· Metal hermetically sealed (rectangular & round) - The capacitor is encased in a metal tube or a can and sealed with epoxy.
Note: All the above case styles are available in both Axial and Radial leads.
b. Paper capacitor:
Paper capacitors are made of paper or oil-impregnated paper and aluminum foil layers rolled into a cylinder and sealed with wax. These capacitors were commonly used but are now replaced by the plastic or polymer type of capacitors. The paper capacitors are bulky, highly hygroscopic and soaks moisture which causes loss to the dielectric degrading its overall performance is the major drawback with this type of capacitors. The other variants include oil-impregnated, paper-polyester and Kraft paper capacitor.