Paper mediated capacitors are capacitors composed of paper with a very thin dielectric thickness as the medium, aluminum foil as the electrode, wound into a cylindrical shape, and then immersed in a casing or epoxy resin potting. It has advantages such as low cost, but large loss. It is mainly used for bypassing, coupling and filtering in circuits with lower frequency.

Paper mediated capacitors are a type of capacitors with paper as the medium. In fact, the capacitor medium is not simply capacitor paper, but a composite medium in which the capacitor paper is impregnated with impregnating material. This composite medium and polar plates are used to form a capacitor. After the capacitor paper and the polar plate are wound into a core, they are impregnated (the impregnating material is polar or non-polar, solid, liquid and semi-liquid), and then sealed. Sealed forms include aluminum shell filled with resin, iron shell, high pressure and even ceramic shell. Paper capacitors have a larger tgδ, so the application range is only in DC and low-frequency circuits. Moreover, it is easy to age. After aging, the dielectric strength of the capacitor gradually decreases with time. The capacitor has poor thermal stability, so the capacitance stability is not high, the operating temperature is low, and it is easy to absorb moisture. Therefore, good sealing conditions are required to ensure the quality of the capacitor.