The components of the electrical capacitor according to the present invention consist only of unit cells, terminal plates and a molded portion, and operations such as caulking, etc. are not required so that production of the capacitor can be easily performed, by arranging and pressing electrode plates having terminals at the top and the bottom of the stacked unit cells of an electric double-layer capacitor in the stacked direction thereof, and applying molding process with resin, as it is.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an electric double-layer capacitor and a 
method for producing the same. 
2. Description of the Prior Art 
As one of means for obtaining a capacitor having a large capacity, there is 
a method utilizing the production of an electric double-layer which is 
obtained by contacting activated carbon particles with an electrolytic 
solution as disclosed in the specification of U.S. Pat. No. 3,536,963. 
FIG. 1 is a cross-section view showing a construction of a basic element of 
such electric double-layer capacitor (hereinafter called a unit cell). In 
an actual electric double-layer capacitor, since the withstand voltage of 
the unit cell is comparatively low as described hereinafter, unit cells 
are stacked so as to match working voltage, as shown in FIG. 2. 
First the unit cell will now be described. The unit cell 1 can be produced 
as described below. A gasket 2, which is made of cylindrical and 
non-conductive rubber, is vertically divided by a porous separator 3, 
activated carbon paste electrodes 4, which are produced by kneading 
activated carbon particles and diluted sulfuric acid, are filled into 
upper and lower spaces inside the gasket cylinder, respectively, and 
further the top and bottom of the cylinder are closed up tightly by 
conductive separators. The porous separator 3 is ion-permeable and 
electron non-conductive, while the conductive separators 5 are electron 
conductive and ion-impermeable. 
In the unit cell obtained in such a way, its withstand voltage is 
determined by the electrolysis voltage of diluted sulfuric acid and is low 
and about 1.2 V. A number of cells required to match the working voltage 
are stacked so as to form the stacked unit cells 6 as shown in FIG. 2. The 
stacked unit cells 6 are contained within a metal case 7 as shown in FIG. 
13 so as to form an actual electric double-layer capacitor. It may be 
understood that the stacked unit cells 6 may be constituted by one unit 
cell according to the working voltage. 
Next, the above mentioned stacked unit cells 6 and the completed electric 
double-layer capacitor will now be described with reference to FIG. 3. 
In the electric double layer capacitor shown in FIG. 3, the stacked unit 
cells 6 have a charge holding function and is contained within the metal 
case 7. 
The stacked unit cells 6 have, for example, a construction in which six 
basic cells 1 are stacked. 
The metal case 7, in which the stacked unit cells 6 are contained, applies 
such pressure as described below to the top surface and the bottom surface 
of the stacked unit cells 6 through caulked portions 8 provided by 
caulking an opening end, a first electrode plate 9, an insulator case 10 
and a second electrode plate 11. 
In the stacked unit cells 6 obtained as described above, there exists 
internal resistance which consists of contact resistance between activated 
carbon particles in the activated carbon paste electrode 4 within the unit 
cells 1, contact resistance between respective unit cells 1 forming the 
stacked structure and the like. 
The value of the internal resistance decreases when the pressure applied 
from the top and the bottom of the stacked unit cells 6 increases. 
Therefore, in order to suppress the internal resistance of the entire 
electric double layer capacitor, it is required to apply the pressure to 
the stacked unit cells 6 from the top and the bottom thereof. For the 
purpose of applying the pressure, the above-mentioned caulked portions 8 
are provided. Such caulked portions are described in, for example, U.S. 
Pat. No. 4,394,713 and Japanese Utility Model Laid-open No. 174,338/87. 
The value of the above-mentioned pressure is determined in consideration of 
the value of the internal resistance, pressure resisting capacity of the 
stacked unit cells 6 and so on, and the value is normally about 10 
kg/cm.sup.2. 
Upon operating the electric double-layer capacitor, voltage is applied 
between the first electrode plate 9 and the second electrode plate 11 from 
outside. In this case, the second electrode plate 11 is electrically 
connected to the top of the stacked unit cells 6. The first electrode 
plate 9 is electrically connected to the bottom of the stacked unit cells 
6 through the caulked portions 8 of the metal case 7, the lateral wall and 
the bottom surface. Therefore, the voltage from outside is applied to the 
top and the bottom of the stacked unit cells 6. Consequently the electric 
double-layer capacitor performs function as a condenser. 
By the insulator case 10, the outside surface of the stacked unit cells 6 
is insulated from the inside wall of the metal case 7 and the first 
electrode plate 9 is insulated from the second electrode plate 11. 
The opening of the electrode plate side of the metal case 7 is closed 
tightly by epoxy resin 13 so as to prevent a foreign matter from mingling 
from the outside or to prevent a chemical fluid from invading upon 
washing. 
In order to prevent the electric double-layer capacitor from short 
circuiting with other electronic parts when the capacitor is packaged on a 
printed circuit board, the metal case 7 is covered with an insulator 
sleeve 12. 
In the above-mentioned conventional electric double-layer capacitor since a 
metal case is used as an armor, the capacitor is complicated in the 
structure and a large number of assembly parts are required so as to cause 
it to function as a capacitor. 
Thus an insulator case is required to insulate the unit cells from the 
metal case and to insulate the electrode plates from each other. 
An insulator sleeve is required to prevent the electric double-layer 
capacitor and other electronic parts from short-circuiting with each 
other. 
In order to prevent a foreign matter from mingling into the interior or to 
prevent a chemical fluid such as washing liquid from invading, it is 
required to close tightly the opening of the metal case with resin and the 
like. 
As mentioned above, in the conventional electric double-layer capacitor, 
since the capacitor is complicated in its structure and requires numerous 
parts to be assembled, while it is accompanied by the complicated process 
of production, it was not possible easily to reduce the production cost. 
Generally in the electronic components, it is desired to have various 
directions for leading out lead wires therefrom because of the large 
freedom at the time of packaging of the components. However, in the 
conventional electric double layer capacitor, when the direction for 
leading out the lead wire is tried to be changed, design changes of each 
of the above-mentioned numerous parts are required, and further 
large-scale changes of the production process such as changes of 
production equipments and jigs and tools are required. The direction for 
leading out the lead wire is practically fixed. 
Therefore, when the electric double-layer capacitor was used in an actual 
electronic device, it was difficult to package the parts onto printed 
circuit boards under the improved package density because of small freedom 
of arrangement of the parts. Since surface packaging was difficult, 
automation of packaging was difficult and reduction of packaging cost was 
prevented. 
SUMMARY OF THE INVENTION 
Therefore, it is an object of the present invention to solve the problems 
described above as to the conventional electric double-layer capacitor and 
to provide an electric double-layer capacitor which has a smaller number 
of components easily produced, and in which lead wire terminals can be led 
out in various directions. 
It has been found according to the present invention that in the electrical 
capacitor according to the present invention, the components of the 
electrical capacitor consist only of unit cells, terminal plates and a 
molded portion, and operations such as caulking, etc. are not required so 
that production of the capacitor can be easily performed, by arranging and 
pressing electrode plates having terminals at the top and the bottom of 
the capacitor unit cells in the stacked direction thereof, and applying 
molding process with resin, as it is. 
Thus, the present invention provides an electric double-layer capacitor 
comprising: (a) a stacked unit cells of an electric double-layer 
capacitor; (b) electrode plates having terminals which are arranged in two 
different polar surfaces of said stacked unit cells of an electric 
double-layer capacitor; and (c) a resin armor which covers said stacked 
unit cells of an electric double-layer capacitor and portions other than a 
predetermined portion of said terminal of each said electrode plate so as 
to apply and hold a predetermined pressure to said stacked unit cells of 
an electric double-layer capacitor in the stacked direction. 
The electric double-layer capacitor can be produced by a method comprising 
the steps of (i) arranging electrode plates having terminals so as to 
contact with two different polar surfaces of stacked unit cells of an 
electric double-layer capacitor, thereby setting said electrode plates 
into a metallic mold; and (ii) injecting resin into said metallic mold to 
form an integral structure in the state in which the predetermined 
pressure is applied and held to said stacked unit cells of an electric 
double-layer capacitor from said metallic mold through said electrode 
plates in the stacked direction. 
The present invention also provides an electric double-layer capacitor 
comprising; (a) stacked unit cells of an electric double-layer capacitor; 
(b) electrode plates having terminals which are arranged in two different 
polar surfaces of said stacked unit cells of an electric double-layer 
capacitor; and (c) a resin armor which covers said stacked unit cells of 
an electric double-layer capacitor and portions other than a predetermined 
portion of the terminals of said electrode plates so as to apply and hold 
a predetermined pressure to said stacked unit cells of an electric 
double-layer capacitor in the stacked direction; wherein each said 
electrode plate is constituted by a rectangular metallic plate each of two 
opposite sides of which has a terminal projecting in a horizontal 
direction of each said electrode plate from each said side and bent in a 
perpendicular direction, and a surface of said plate existing in a 
direction opposite to said bending direction is arranged to contact with 
each said polar surface of said stacked unit cells of an electric 
double-layer capacitor; and each said terminal is exposed from said resin 
armor in the lines of intersection of two surfaces perpendicular to said 
stacked direction and a pair of surfaces parallel to said stacked 
direction. 
In this electric double-layer capacitor, each said electrode plate includes 
preferably a reinforcement rib which is formed by bending said electrode 
plate in the same direction as the bending direction of each said terminal 
at each of the two opposite sides different from the sides having said 
terminals. 
Said electric double-layer capacitor can be formed by the method comprising 
the steps of (i) arranging electrode plates having terminals which project 
in the horizontal direction of the rectangular metallic plate from the two 
opposite sides thereof and are bent in the perpendicular direction at said 
two sides, respectively, for the surface in the direction opposite to said 
bending direction to contact with each polar surface of stacked unit cells 
of an electric double-layer capacitor, thereby setting said electrode 
plates into a metallic mold; and (ii) injecting resin into said metallic 
mold to form an integral structure in the state in which the predetermined 
pressure is applied and held to said stacked unit cells of an electric 
double-layer capacitor from said metallic mold through said electrode 
plates in the stacked direction. 
It is preferred to use the electrode plates which is obtained, for example, 
by applying pressing process (punching and bending) to a steel blank, and 
executing surface treating (process for plating the pressed blank, which 
is plated which copper, with solder). 
It is preferred to use, for resin armor, PBT (GF) 30%) which is 
polybutylene terephthalate containing 30% glass fiber and having tensile 
strength of 1420 kg/cm.sup.2 (ASTM D-638), PPS (GF 40%) which is 
polyphenylene sulfide containing 40% glass fiber and so on.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The preferred embodiments of the present invention will now be described in 
detail with reference to the attached drawings. 
The first embodiment of the present invention will now be described in 
order of assembling with reference to FIG. 4 and FIGS. 6(a) and 6(b). 
The stacked units cells 6 used in the first embodiment has the same 
structure as the stacked unit cells 6 of the conventional electric 
double-layer capacitor shown in FIGS. 2 and 3. The pressure to be applied 
to the stacked unit cells 6 is determined in a range between 20 and 80 
kg/cm.sup.2 in consideration of the value of internal resistance and a 
pressure resisting property of the stacked unit cells 6. 
A lower metallic mold 14 for molding the stacked unit cells 6 is worked 
into a square recessed shape. The bottom of the recess is provided with a 
column-like pressing pin 15a. 
In the first embodiment, an electrode plate 17a with a lead wire 16a, which 
is formed into a crank shape, is put on the pressing pin 15a of the lower 
metallic mold 14 such that the crank portion may face upwardly. 
Then, the lead wire 16a is positioned by fitting it into a groove for 
receiving a load wire terminal which groove is engraved in the lower 
metallic mold 14. 
Next, the stacked unit cells 6 are put on the electrode plate 17a, having 
the lead wire such that the center of the pressing pin 15a of the lower 
metallic mold 14 and the center of the stacked unit cells 6 may coincide 
with each other. 
Further an electrode plate 17b having a lead wire 16b, which is formed into 
a crank shape, is put on the stacked unit cells 6 such that the crank 
position may face downwardly. 
Then, similarly, the load wire 16b is positioned by fitting it into a 
groove for receiving a lead wire terminal which groove is engraved in the 
lower metallic mold 14. 
Next, after an upper metallic mold 18 is caused to descend, the both molds 
are clamped to each other. 
Since the upper metallic mold 18 is provided with a column-like pressing 
pin 15b at the position corresponding to the pressing pin 15a of the lower 
metallic mold 14, when clamping the molds, the pressure of 20-80 
kg/cm.sup.2 is applied to the stacked unit cells 6 from above and down by 
the both pressing pins through a pair of electrode plates 17a and 17b 
having load wires. 
The height of each of the pressing pins 15a and 15b is determined by the 
thickness of the resin required to keep the pressure applied to the 
stacked unit cells 6 even after molding. 
Then, an electric double-layer capacitor armored with molded resin as shown 
in FIG. 5 is obtained by injecting thermoplastic resin 20 through a resin 
inlet port 19 of the molding metallic mold at hydrostatic pressure of 600 
kg/cm.sup.2, and molding the resin so as to be integrated. In FIG. 5 
reference numeral 15c is a hole formed within the resin at the position of 
the pressing pins. 
In the electric double-layer capacitor according to the first embodiment 
obtained in such a way, the components required to assemble the capacitor 
are only three that is, the electrode plates 17a and 17b having the lead 
wires and the armor resin 20. 
In the conventional electric double-layer capacitor, the components 
required for assembling were a first electrode plate with the lead wire, a 
second electrode plate with the lead wire, an insulator case, an armoring 
case, epoxy resin and an insulator sleeve. On the contrary, in the present 
invention the components can be reduced by half. 
Next, the second embodiment of the present invention will now be described 
with reference to FIGS. 7 and 8. 
In the first embodiment shown in FIGS. 4 to 6, the pressing pins 15a and 
15b are arranged for the centers of these pins to coincide with the center 
of the stacked unit cells 6. However, in the second embodiment, 3 pressing 
pins 23a and 23b to every lower and upper metallic molds 21 and 22, 
respectively, are arranged to be positioned at vertexes of an equilateral 
triangle. 
Assembling of the electric double-layer capacitor according to the second 
embodiment is executed in order similar to that described in the first 
embodiment. 
The resin used for the molded armor and the condition for the molding the 
armor is same as the resin used in the first embodiment. 
In the above-mentioned second embodiment, since the arrangement of the 
pouring inlet 24 of resin and the electrode plates 17a and 17b with the 
lead wires and the stacked unit cells 6 is more symmetrical than that of 
the first embodiment, the electrode plates with the lead wires are never 
swept away by the flow of the resin when the resin is injected. 
Therefore, the accuracy of the positions of the stacked unit cells 6 and 
the electrode plates 17a an 17b with the lead wires can be improved. 
Next, the third embodiment of the present invention will now be described 
with reference to FIGS. 9 to 13. 
In the third embodiment, the same stacked unit cells as the stacked unit 
cells 6, which are used in the conventional electric double-layer 
capacitor shown in FIG. 2 are used. However, the method for armoring, the 
shape of the armor and the method for leading out the lead wire terminal 
are quite different from those in the prior art. According to the third 
embodiment, the electric double-layer capacitor is an article of a surface 
mount type armored with resin. The lead wire terminal is exposed only at a 
portion of the armor resin 20 so as to conform to the surface packaging. 
The electric double-layer capacitor of the embodiment is produced as 
described below. First, two electrode plates 30 and stacked unit cells 6 
as shown in FIG. 6 are prepared. 
The electrode plate 30 is a metallic plate 0.2 mm thick having sides 9 mm 
long. And each of two opposite sides is provided with a terminal 30a which 
projects horizontally and is bent vertically in the L-shape. The 
projecting portion of the terminal 30a is 2 mm wide and 4 mm long and the 
height of the bent portion is 2 mm. 
Each of the two sides of the electrode plate 30 is provided with a 
reinforcement rib 30b which is formed by bending the side in the L-shape. 
The reinforcement rib 30b is provided for the purpose of preventing 
content resistance of each of the above-mentioned portions and pressure 
resistance from becoming unstable, because the central portion of the 
electrode plate is bent convexly so that uneven pressure may be applied to 
the stacked unit cells 6, when pressure is applied to the stacked unit 
cells 6 from the metallic mold through the terminal 30a in the molding 
process described later. The bending direction of the reinforcement rib 
30b is the same as that of the terminal 30a. The bent portion is 1 mm high 
and the portion extends from one end of the side to the other end thereof 
(namely, is 9 mm long). 
The stacked unit cells 6 have a structure similar to that of the 
conventional electric double-layer capacitor. In this embodiment, the 
stacked unit cells 6 are formed by stacking 6 unit cells. The unit cell is 
a disk having a thickness of 0.5 mm and a diameter of 8 mm. 
Then the electrode plate 30 and the stacked unit cells 6 are combined to 
each other to be set into the molding metallic mold. 
In this case, as shown in FIG. 9 the electrode plates 30 are arranged at 
the top and bottom surfaces of the stacked unit cells 6 so that the 
terminals 30a and the reinforcement ribs 30b are directly outwardly. 
The combined body is set into the lower mold 31. The lower mold 31 is 
provided with a resin injection port 33. 
And as shown in FIG. 9 and FIGS. 12(a) and 12(b), the upper mold 32 is put 
on the lower mold 31 from above. Since the height (2 mm) of the terminal 
of the electrode plate 30 is higher than that (1 mm) of the reinforcement 
rib, pressure between the upper and lower molds 32 and 31, respectively, 
is applied to the stacked unit cells 6 through the upper and lower 
terminals. 
Thereafter, polyphenylene sulfide (PPS), which is heated to melt, is 
injected through the resin injection port 33 under pressure of 600 
kg/cm.sup.2, and is cooled and hardened to mold the surface mount type 
electric double-layer capacitor of this embodiment. 
Thus, the surface mount type electric double-layer capacitor 40 can be 
obtained which is, as shown in FIG. 10, 20 mm long, 20 mm wide and 5 mm 
thick and in which the terminals are exposed at the lines of intersection 
formed between the top and bottom surfaces and the side surfaces. 
FIGS. 13(a) and 13(b) show the electric double-layer capacitor which is 
packaged onto a printed circuit board as described above. 
FIG. 13(a) is a perspective view of the capacitor which is packaged. It is 
clear that the electric double-layer capacitor 40 can be packaged onto the 
surface by connecting the wirings 35a and 35b provided on the printed 
circuit board 34 to the terminals 30a. 
In this embodiment, since the terminal 30a, which are exposed in the 
surface of the resin armor 20, are vertically symmetrical as shown in FIG. 
13(b), the article can be packaged even if it is turned upside down. Thus 
the freedom of packaging is larger than that in the prior art, and there 
is not provided the hole which is formed by the pressing pin in the first 
and third embodiments. 
Though thermoplastic polyphenylene sulfide is described to be used for the 
resin armor 20 in this embodiment, it has the effect similar to that of 
the embodiment to use thermosetting epoxy resin to form the resin armor by 
transfer molding process. 
As explained above, according to the present invention, the number of 
components required for assembling can be decreased compared to the 
conventional electric double-layer capacitor. 
Therefore, since the production process can be simplified and the working 
time can be reduced, production costs can be reduced. 
Further, though the direction in which the lead wire is led out has 
actually not been capable of being diversified in the conventional 
electric double-layer capacitor, the diversification of the 
above-described direction can be easily carried out in the present 
invention. Therefore, freedom of packaging becomes efficiently large.