JP2007324243A - Solid electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid electrolytic capacitor which improves the volume efficiency at a low production cost without manufacturing a new die, even at the change of the thickness of a lead frame used for a general-purposed structure. <P>SOLUTION: An anode lead wire is planted on one end face of a capacitor element composed of an oxide film layer, a solid electrolyte layer, and a cathode leading layer in this order on the surface of an anode made of a valve action metal. The anode lead wire is resistance-welded to an anode lead frame, and thereafter the cathode leading layer is connected to a cathode lead frame with conductive adhesives. The cathode lead frame has at least a thinner part facing the capacitor element than portions not covered with the armor resin. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a chip-type solid electrolytic capacitor, and more particularly to a chip-type solid electrolytic capacitor having an improved cathode lead frame shape.

  Conventionally, chip-type capacitors have been widely used in electronic circuits. Among capacitors, solid electrolytic capacitors are used in portable electronic devices and the like because they are relatively small and have a large capacity.

As a conventional solid electrolytic capacitor, there exists a thing of a structure as shown, for example in FIG. In this solid electrolytic capacitor, a valve action metal powder such as tantalum or niobium is press-molded into a desired shape, and the compression-molded body is sintered to form a sintered body 1.
The sintered body is integrated by burying or welding the anode lead-out wire 2, and the surface of the sintered body is anodized to form an oxide film layer 3 serving as a dielectric, such as manganese dioxide, conductive polymer, etc. The solid electrolyte layer 4, the carbon layer 5 serving as the cathode lead layer, and the cathode silver layer 6 are sequentially laminated to form the capacitor element 7.

Further, in order to use this capacitor element as a mounting component, the anode lead wire 2 is welded to the anode lead frame 8 for leading out the external electrode, and the cathode lead frame 9 and the cathode silver layer 6 are connected by the conductive adhesive 10. .
Thereafter, generally, an epoxy-type exterior resin 11 is transfer-molded to the capacitor element using a molding die (see, for example, Patent Document 1).
JP 2001-126959 A

  However, the solid electrolytic capacitor manufactured by the method of Patent Document 1 has a large volume in the exterior resin of the lead frame for leading the electrode, and as a result, the volume of the capacitor element in the exterior resin is limited. Therefore, there is a problem that the capacitor is low in volume efficiency.

The present invention solves the above problems,
Capacitor element in which oxide film layer, solid electrolyte layer and cathode lead layer are sequentially laminated on the anode body surface made of valve action metal, and the anode lead wire and anode lead frame planted on one end face are connected by resistance welding In the solid electrolytic capacitor in which the cathode lead layer and the cathode lead frame are bonded with a conductive adhesive and then covered with an exterior resin,
The chip-type solid electrolytic capacitor is characterized in that the cathode lead frame has a thickness at least a portion facing the capacitor element thinner than a portion not covered with the exterior resin.

  According to the present invention, since the space of the capacitor element that can be secured in the exterior resin is increased by thinning the cathode lead frame at least in the portion facing the capacitor element, the volume of the capacitor element can be increased.

  Furthermore, by thinning the cathode lead frame at the portion facing the capacitor element, the bending angle can be made closer to 90 ° when bending according to the shape of the capacitor element, and the bending radius can be reduced. Since it can be made smaller, the volume of the capacitor element can be increased to a position closer to the cathode lead frame and closer to the outside of the exterior resin.

Normally, if the thickness of the lead frame is reduced, when performing transfer molding, the exterior resin cannot be sealed due to the gap between the reduced thickness portion and the mold die, so a die that matches the thickness of the lead frame must be used. However, according to the present invention, the thinned portion of the lead frame is only the portion located inside the exterior resin, so that no new mold is produced. It is possible to manufacture with an existing mold, and it is possible to expand the volume of the capacitor element without increasing the cost.
Further, when the portion where the external electrode is formed becomes thin, the strength of the electrode becomes weak. However, according to the present invention, the thickness of the portion where the external electrode of the lead frame is formed does not change. The mechanical strength is not reduced.

[Example 1]
An embodiment of the present invention will be described with reference to FIG.
The anode lead wire 2 was embedded in a tantalum powder that is a valve action metal powder, pressure-formed into a desired shape, and the compression-molded body was sintered to form a sintered body 1. Thereafter, an oxide film layer 3 serving as a dielectric was formed by anodic oxidation on the surface, and a solid electrolyte layer 4, a carbon layer 5, and a cathode lead layer of a cathode silver layer 6 were sequentially laminated to produce a capacitor element 7.

This capacitor element is joined to the anode lead frame 8 for leading out the external electrode having a thickness of 0.10 mm and the anode lead wire 2 by resistance welding, and the thickness t1 of the portion located inside the exterior resin is 0.07 mm. The cathode lead frame 9 having the external lead frame thickness t2 of 0.10 mm and the cathode silver layer 6 were connected by the conductive adhesive 10.
Then, the epoxy-type exterior resin 11 was formed by transfer molding using the existing molding die.

[Example 2]
A method similar to that of Example 1 except that the cathode lead frame 8 for leading out the external electrode in which the thickness t1 of the portion located inside the exterior resin is 0.05 mm and the external lead frame thickness t2 is 0.10 mm is used. A solid electrolytic capacitor was produced.

(Conventional example)
As shown in FIG. 2, a solid electrolytic capacitor was produced in the same manner as in Example 1 except that a conventional lead frame having a total thickness of 0.10 mm was used.

  Next, the volume of the capacitor element in the exterior resin was measured for the examples of the present invention and the conventional example. The measurement results are shown in Table 1. The shortest distance between the cathode lead frame of the example and the conventional example and the capacitor element was made the same.

As is clear from Table 1, in both Examples 1 and 2 according to the present invention, the volume of the capacitor element can be increased and the volume ratio can be improved as compared with the conventional example.
This is because a space for housing the capacitor element in the exterior resin can be secured by thinning the cathode side lead frame in the exterior resin.
In addition, since the lead frame thickness has been reduced, it has become easy to perform bending processing in accordance with the shape of the capacitor element, so that the bending angle can be close to 90 ° and the bending radius can be further reduced. The capacitor element can be expanded to a position near the outside and closer to the cathode frame.

The thickness of the cathode lead frame of the present invention is 0.05 mm or 0.07 mm inside the exterior resin and 0.10 mm outside the exterior resin, but the thickness is not limited to this.
Further, the bent shape of the cathode lead frame is not limited to that used this time.

It is sectional drawing of the solid electrolytic capacitor of the Example of this invention. It is sectional drawing of the solid electrolytic capacitor of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sintered body 2 Anode lead-out line 3 Oxide film layer 4 Solid electrolyte layer 5 Carbon layer 6 Cathode silver layer 7 Capacitor element 8 Anode lead frame 9 Cathode lead frame 10 Conductive adhesive 11 Exterior resin t1 Cathode lead frame inside exterior resin Thickness t2 Cathode lead frame thickness of external electrode part

Claims (1)

An anode lead wire and an anode lead frame planted on one end face of a capacitor element in which an oxide film layer, a solid electrolyte layer, and a cathode lead layer are sequentially formed on the anode body surface made of a valve metal are connected by resistance welding. In a solid electrolytic capacitor in which a cathode lead layer and a cathode lead frame are connected with a conductive adhesive and then covered with an exterior resin.
A chip-type solid electrolytic capacitor characterized in that the cathode lead frame has a thickness that is at least a portion facing the capacitor element thinner than a portion not covered with an exterior resin.

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