1. Field of the Invention
The present invention relates to an electric double layer capacitor and more particularly to a chip type electric double layer capacitor.
2. Description of the Prior Art
As a means for obtaining a capacitor having a large capacitance while making use of an electric double layer capacitor, there has been known, as disclosed in U.S. Pat. No. 3,536,963, a capacitor having a large capacitance in which an electric double layer is formed by carbon powder coming into contact with an electrolyte as shown in FIG. 1.
FIG. 1 is a sectional view of a unitary electric double layer capacitor element 11 which comprises a pair of electronic conducting and ionic insulating separators 8, carbon paste electrodes 7 each comprising a mixture of activated carbon powder and an electrolyte and arranged between these two conductive separators 8, an ionic conducting and electronic insulating porous separator 9 which is positioned to prevent the electric conduction between the carbon paste electrodes 7 and non-conductive gaskets 10 for holding the carbon paste electrodes 7 and for isolating the electrodes from the outside.
In addition, FIG. 2 is a sectional view of a conventional electric double layer capacitor which comprises a stacked element 12 comprising a plurality of unitary elements 11 stacked together each of which has the same construction as that of the element 11 shown in FIG. 1, a conductive metal case 15 accomodating the stacked element 12 therein and an assembled electrode 14.
The assembled electrode 14 comprises an insulating case 13c for preventing short circuits between the inner wall of the conductive metal case 15 and the stacked element 12 and for covering the upper surface of the stacked element 12 and first and second electrode plates 13a and 13b. Each electrode plate has a lead terminal and is disposed on the upper or lower face of the upper portion of the insulating case 13c. In this electric double layer capacitor, a pressure ranging from 1 to 100 kg/cm.sup.2 is applied to the stacked element 12, the pressure acting from its upper and lower sides. The capacitor assembly is sealed by inwardly caulking the open edge of the conductive metal case 15 while holding the pressure applied thereto in order to reduce the contact resistance in the carbon paste electrodes 7.
However, the aforementioned conventional electric double layer capacitors are limited in the directions in which lead terminals, may be drawn out which is peculiar to those comprising elements accomodated in metal cases. For this reason, these capacitors are inevitably in the self-supporting forms. Thus the surface-mounting thereof on, for instance, a printed circuit board is very difficult.
USPTO Backgrounds
USPTO Backgrounds