In this type of capacitors the dielectric consists of one or more layer of extremely thin craft paper which looks very much like cigarette paper. The metal plates consist of aluminium foil and the whole "sandwich" is rolled into an element. The connection to tin metal plates (foils) is made through metallic strips short circuit if single paper contains metal impurities. Paper may also have pin holes. The effect of these pin holes is to reduce effective dielectric constant, breakdown strength and power factor, impregnation with mineral oil fills these voids and also makes capacitor more stable. After rolling ends are sprayed with copper so that lug type or extended foil type connections can be made-protective coating is applied and value is printed.
SPECIFICATIONS
RANGE OF VALUES 1000pf to 1μf
Tolerance 15%
Voltage ratings 400V, 600V, 1200V, 1800V
Power factor at 1K Hz 0.005 to 0.01
Temperature coefficient + 100 to + 200 ppm/0C
APPLICATIONS: These capacitors have large capacitance to volume ratio up to a voltage of 1 μF. As the losses are high frequency and low value capacitors are available, they are used as RF bypasses capacitors and coupling capacitors.