Electricity: electrical systems and devices – Electrolytic systems or devices – Solid electrolytic capacitor
Reexamination Certificate
2001-11-09
2004-11-16
Nguyen, Ha Tran (Department: 2812)
Electricity: electrical systems and devices
Electrolytic systems or devices
Solid electrolytic capacitor
C361S538000, C361S540000
Reexamination Certificate
active
06819546
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a packaged solid electrolytic capacitor of the type which comprises a capacitor element made of a valve metal such as tantalum, niobium or aluminum, and a synthetic resin package enclosing the capacitor element. The present invention also relates to a method of making such a capacitor.
2. Description of the Related Art
A conventional method for collectively producing a plurality of packaged solid electrolytic capacitors may utilize a metal lead frame as shown in
FIG. 154
of the accompanying drawings. Specifically, the illustrated lead frame A is elongated in one direction and includes a number of pairs of right and left lead portions B and C. The respective pairs of the lead portions B and C are arranged at regular intervals longitudinally of the lead frame A. As shown, a capacitor element D is mounted on each pair of the right and left lead portions B, C.
Each capacitor element D is provided with an anode D
1
and a cathode D
2
which are connected to the right lead portion B and the left lead portion C, respectively. After being thus mounted, the capacitor element D as a whole is enclosed by a protection package E made of a thermosetting resin. Then, the packaged capacitor element D is cut off the lead frame A, with the paired lead portions B and C remaining to protrude from the package E. Finally, as shown in
FIG. 155
, the protruding lead portions B and C are downwardly bent and further toward the bottom surface of the package E.
According to the conventional method, the respective packages E are made separately from each other by e.g. transfer molding of a synthetic resin. In this manner, disadvantageously, each package E tends to be rather bulky to compensate for inaccurate mounting of the capacitor element D. Specifically, as indicated by broken lines in
FIGS. 155 and 156
, the capacitor element D to be mounted on the lead portions B and C may positionally deviate vertically (
FIG. 155
) and/or horizontally (FIG.
156
). To deal with such positional deviation, it is necessary to cause the vertical dimensions H
1
′ and H
2
′ of the package E (
FIG. 155
) and the horizontal dimension W
1
′ (
FIG. 156
) to be unduly large. Accordingly, the overall height H′ and width W′ of the conventional capacitor need to be increased. This means that the volumetric efficiency or ratio of the capacitor element to the entirety of the capacitor is degraded. Disadvantageously, the conventional capacitor is unduly large for the capacitance of the capacitor element.
Further, the conventional capacitor is provided with two protruding leads B, C bent toward the bottom surface of the package E to be surface-mounted onto e.g. a printed circuit board. With such leads B and C provided, the overall weight and length L of the conventional capacitor are unnecessarily increased, and the production cost becomes unduly large.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a solid electrolytic capacitor designed to overcome the above problems.
Another object of the present invention is to provide a method of making such capacitors collectively.
According to a first aspect of the present invention, there is provided a solid electrolytic capacitor comprising: a capacitor element having an anode and a cathode; a base sheet member having an obverse surface for mounting the capacitor element and a reverse surface opposite to the obverse surface; a protection package formed on the obverse surface of the sheet member to enclose the capacitor element, the package having a first side surface adjacent to the anode of the capacitor element and a second side surface opposite to the first side surface; a conductive outer anode layer electrically connected to the anode of the capacitor element; and a conductive outer cathode layer electrically connected to the cathode of the capacitor element. The outer anode layer is formed on at least either one of the package and the sheet member. Likewise, the outer cathode layer is formed on at least either one of the package and the sheet member.
With the above arrangement, the overall height of the capacitor is rendered smaller than that of the conventional capacitor, since the capacitor element is supported by the base sheet member. Further, since the capacitor element is mounted on the sheet member, the positional deviation of the capacitor element is advantageously reduced.
According to a preferred embodiment, the solid electrolytic capacitor may further comprise an upper sheet member for shielding the capacitor element. In this case, the capacitor element may be arranged between the base sheet member and the upper sheet member.
Preferably, the package may be formed with an at least partially slanted portion so that the polarities of the anode layer and the cathode layer are readily discerned.
Preferably, the outer anode layer may be formed on at least either one of the first side surface of the package and the reverse surface of the base sheet member. Likewise, the outer cathode layer may be formed on at least either one of the second side surface of the package and the reverse surface of the base sheet member.
According to a preferred embodiment, the anode may be exposed at the first side surface of the package to come into contact with the outer anode layer.
According to another preferred embodiment, the solid electrolytic capacitor may further comprise a metal piece attached to the anode of the capacitor element. The metal piece may be exposed at the first side surface of the package to come into contact with the outer anode layer.
According to another preferred embodiment, the solid electrolytic capacitor may comprise both a metal piece attached to the anode of the capacitor element and an anode connection layer formed on the obverse surface of the base sheet member. The anode connection layer may be connected to the metal piece and exposed at the first side surface of the package to come into contact with the outer anode layer.
According to another preferred embodiment, the base sheet member may be formed with a through-hole for connecting the anode connection layer to the outer anode layer.
According to another preferred embodiment, the solid electrolytic capacitor may further comprise a cathode connection layer formed on the obverse surface of the base sheet member and connected to the cathode of the capacitor element. The cathode connection layer may be exposed at the second side surface of the package to come into contact with the outer cathode layer.
Preferably, the solid electrolytic capacitor may comprise a cathode bump arranged on the cathode of the capacitor element. The cathode bump may be exposed at the second side surface of the package to come into contact with the outer cathode layer.
According to a preferred embodiment, the solid electrolytic capacitor may comprise a cathode connection layer formed on the obverse surface of the base sheet member and connected to the cathode of the capacitor element. The base sheet member may be formed with a through-hole for connecting the cathode connection layer to the outer cathode layer.
According to a second aspect of the present invention, there is provided a method of making a solid electrolytic capacitor comprising the steps of: preparing a sheet member having an obverse surface and a reverse surface, the obverse surface being provided with at least one cathode connection layer; placing a capacitor element having an anode and a cathode onto the obverse surface of the sheet member so that the cathode of the capacitor element comes into contact with the cathode connection layer; forming a resin plate on the obverse surface of the sheet member to enclose the capacitor element; cutting the resin plate to generate a first cut surface and a second cut surface, the anode of the capacitor element being exposed at the first cut surface, the cathode connection layer being exposed at the second cut surface; forming an anode terminal layer on the first cut surface;
Merchant & Gould P.C.
Nguyen Ha Tran
Rohm & Co., Ltd.
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