Electricity: electrical systems and devices – Electrolytic systems or devices – Double layer electrolytic capacitor
Reexamination Certificate
2003-05-13
2004-08-03
Dinkins, Anthony (Department: 2831)
Electricity: electrical systems and devices
Electrolytic systems or devices
Double layer electrolytic capacitor
C361S508000, C361S516000
Reexamination Certificate
active
06771486
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a storage cell for surface mounting for use in various types of electronic devices and, more particularly, to a horizontal-type storage cell for surface mounting which is suitable for high-density mounting on a printed wiring board.
BACKGROUND OF THE INVENTION
There are an electric double layer capacitor, a button battery and the like as storage cells for surface mounting. In an electric double layer capacitor, for example, as is apparent from an outline of its configuration shown in
FIG. 7
, a pair of electric double layer electrodes
41
a
,
41
b
are disposed to oppose to each other through an insulating separator
44
and housed in a twofold metal container. In this pair of electric double layer electrodes, polarizable electrodes
43
a
,
43
b
each of an activated carbon layer are formed on disk-like sheets (or foil)
42
a
,
42
b
each of valve metal. The disk-like sheet (or foil)
42
a
of valve metal is bonded to the inner surface of a top cover
46
of the metal container and the disk-like sheet (or foil)
42
b
of valve metal is bonded to the inner surface of a case
45
of the metal container.
The case
45
and the top cover
46
are bonded together in a hermetically sealed manner, with a ring packing
47
interposed in a marginal area of the two, and a nonaqueous electrolyte (not shown) is charged into the interior of the metal container so as to fill up the electric double layer electrodes
41
a
,
41
b
and the separator
44
.
A coin-shaped electric double layer capacitor
50
configured as described above is mounted on a printed wiring board,
53
,
58
as shown in
FIGS. 8A and 8B
.
FIG. 8A
shows the coin-shaped electric double layer capacitor
50
vertically mounted on a substrate
53
. External lead terminals
51
,
52
are connected to the outer surface portions of the case
45
and top cover
46
, respectively, of the electric double layer capacitor
50
, and the external lead terminals
51
,
52
are inserted into holes of the printed wiring board
53
and these portions are soldered. Also,
FIG. 8B
shows the coin-shaped electric double layer capacitor
50
horizontally mounted on the substrate
58
. External lead terminals
56
,
57
are connected to the outer surface portions of the case
45
and top cover
46
, respectively, of the electric double layer capacitor
50
, and the external lead terminals
56
,
57
are inserted into holes of the printed wiring board
58
and these portions are soldered.
In addition to such a mounting method as described above, there is a method by which external lead terminals
62
,
63
are connected to the outer surfaces of the case
45
and top cover
46
of the electric double layer capacitor
50
, and the respective leading end portions of the external lead terminals
62
,
63
kept parallel to the land surfaces
64
a
,
64
b
of a printed wiring board
64
are soldered by the reflow process.
On the other hand, also in a button battery, electrodes each having a separator interposed between a positive pole and a negative pole are housed in a twofold metal container and the external structure of this button battery is similar to that of the above-described electric double layer capacitor
50
.
However, when a storage cell, such as an electric double layer capacitor and a button battery of the above-described configuration, is amounted on a printed wiring board for high-density mounting, the mounting height is large in a vertical type and the mounting area is large in a horizontal type, thus posing problems.
In a printed wiring board for high-density mounting, parts are mounted on both the front and back surfaces thereof. Therefore, after parts have been mounted on the front surface, these parts are caused to undergo displacement when the back surface of the printed wiring board is mounted with parts, with the result that problems such as poor contact or falling off of the parts may sometimes arise.
For this reason, large parts such as a coin-shaped storage cell are subjected to the reflow process after they are fixed onto a printed wiring board by use of an adhesive, posing a problem that the process becomes complicated.
Furthermore, in a case where a plurality of storage cells for surface mounting are connected in series, conventionally, a plurality of storage cells for surface mounting are inserted in a stacked manner into a case having a shape of cylinder, polygonal cylinder or the like, and the storage cells are brought into contact with each other under pressure by use of an electrically conductive elastic member such as a spring plate. Therefore, problems such as poor conductivity arose when an upsized substrate was used for mounting parts thereon, or when an urging force of an electrically conductive elastic member such as a spring plate is insufficient.
In order to solve such problems, it was conceivable to caulk a case having a plurality of storage cells for surface mounting inserted in a stacked state. However, if pressure for caulking increases, excessive stresses are applied to the storage cells and an electrolyte may leak. Thus, in view of reliability, it was difficult to introduce this method.
The present invention was made to solve such conventional problems and has as its object to provide a storage cell for surface mounting which can reduce the mounting area and increase the reliability of soldering even when high-density mounting is performed on a printed wiring board.
DISCLOSURE OF THE INVENTION
According to a first aspect of the invention, there is provided a storage cell for surface mounting, which includes: a polar storage cell having a component composed of a pair of electrodes and an insulative separator interposed between the pair of electrodes, the component being housed between a case disposed on an anode side of the component and a top cover disposed on a cathode side of the component and being sealed with an insulator; an anode terminal which is connected to an outer surface of the case; and a cathode terminal which is connected to an outer surface of the top cover. In this storage cell for surface mounting, the anode terminal is provided with an external connection which is connected to a printed wiring board, the cathode terminal is provided with an external connection which is connected to the printed wiring board and a fixing portion for mounting (or a mounting-fixing portion) which is connected to the top cover, and a plated layer is formed on the external connections of the anode terminal and cathode terminal and on the mounting-fixing portion of the cathode terminal. Because in mounting the storage cell for surface mounting on a printed wiring board, the mounting-fixing portion of the cathode terminal is also connected to a dummy land portion provided in the printed wiring board at the same time with each external connection, it is possible to reduce defects such as displacement and a short circuit caused by displacement even when the reflow process is performed after the mounting of the storage cell for surface mounting, and it is also possible to increase the reliability of soldering because each external connection has a plated layer.
In this first aspect of the invention, it is preferred that the plated layers formed in the external connections of the anode terminal and cathode terminal and the mounting-fixing portion of the cathode terminal be provided on the side where the storage cell for mounting is connected to the printed wiring board or on both sides.
Further, in the first aspect of the invention, the mounting area for mounting the storage cell for surface mounting on the printed wiring board can be reduced by arranging the anode terminal and the cathode terminal so that the external connection formed by bending one end of the anode terminal and the external connection of the cathode terminal are position in parallel in the same direction.
Further, in the first aspect of the invention, by positioning the mounting-fixing portion in the center of the top cover, the storage cell for surface mounting can be positively
Ashizaki Masashige
Imai Hideki
Morikawa Koichi
Shinjou Masayuki
Dinkins Anthony
Parkhurst & Wendel L.L.P.
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