The coated-foil capacitor

The use of thin layers of organic material as capacitor dielectric is of considerable interest in connection with miniaturization techniques. A technique has been established for the manufacture of capacitors, employing aluminium foil coated with lacquer on both sides; edge insulation is achieved by etching away the exposed metal at one edge, and the second electrode is of evaporated metal. Using a 3¿m coating of polyisocyanate lacquer, miniature capacitors, having a performance at 50 V and 50° C equal to that of paper capacitors, can be manufactured with an improvement in space factor of at least six. The etching technique is shown to have no adverse effect on life characteristic and enables small capacitors to be made with good high-frequency characteristics.