JP2004349725A - Chip-like solid electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inexpensively provide a chip-like solid electrolytic capacitor having a good leakage current value without manufacturing any expensive mold. <P>SOLUTION: This chip-like solid electrolytic capacitor comprises an aluminum electrolytic capacitor element, in which an anode 7 is provided at its end, and a semiconductor layer 3 and a conductor layer 4 are sequentially formed on the dielectric oxide coating film layer 2 of planar aluminum foil having the layer 2 on its surface; a first lead connected to the anode section 7; and a second lead connected to the conductor layer 4. This capacitor is sealed with an external resin except parts of the first and second leads. In addition, part of the anode section 7 is extended to the first lead and, at the same time, the anode 7 and first lead are electrically connected to each other through metallic wires. In connecting the capacitor element and the projecting section of a lead frame to each other, the bending of a main anode body is relieved by providing a step on the projecting section of the lead frame for avoiding the bending of the main anode body although they have different heights. Since the connection between the anode 7 of the solid electrolytic capacitor element and lead frame is made through the metallic wires and no stress is applied to the main anode body, the solid electrolytic capacitor having the good leakage current value can be manufactured efficiently. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a chip-shaped solid electrolytic capacitor that is inexpensive and has a good leakage current value.

  As shown in FIGS. 3 and 4, a conventional chip-shaped solid electrolytic capacitor has a flat anode substrate 1 made of a valve metal such as aluminum, tantalum, or niobium having a dielectric oxide film layer 2 on its surface. A solid electrolytic capacitor element 5 (hereinafter, referred to as a capacitor element) is formed by sequentially laminating the semiconductor layer 3 and the conductor layer 4 except for a part to be a part, and then the capacitor element 5 is connected to a lead frame 6. The two convex portions 6a and 6b of the lead frame 6 are opposed to each other with an interval, and the anode portion 7 of the capacitor element 5 and the conductor layer forming portion 8 are placed on the respective convex portions 6a and 6b. .

  The former is welded 9 or the like, and the latter is electrically and mechanically connected to the protrusions 6a and 6b of the lead frame 6 with a conductive material 10 such as a silver paste, and then sealed with an exterior resin 11 to form a chip. A solid electrolytic capacitor 12 is configured. The sealed solid electrolytic capacitor is a product that satisfies electrical performance such as a predetermined capacity, tan δ, and leakage current.

  The conductor layer forming portion of the above-described capacitor element is thicker than the anode portion because the semiconductor layer and the conductor layer are laminated on the surface of the anode base such as aluminum foil. For this reason, when the anode portion and the protrusion of the lead frame are connected to each other, in an extreme case, the anode base bends to deteriorate the leakage current.

  In order to prevent such a drawback, it is conceivable to provide a step on the convex portion of the lead frame in advance by the difference in thickness between the anode portion and the conductor layer forming portion to reduce the curvature of the anode base at the time of connection described above. However, every time the shape of the anode substrate is changed, an expensive mold must be manufactured to produce a lead frame, which poses problems in production and cost. Therefore, there has been a demand for a chip-shaped solid electrolytic capacitor which is inexpensive and has a good leakage current value.

The present invention has been made to solve the problems described above,
[1] An aluminum electrolytic capacitor element in which a semiconductor layer and a conductor layer are sequentially provided on the dielectric film layer of a flat aluminum foil having an anode portion at an end and a dielectric oxide film layer on the surface,
A chip-shaped chip provided with a first lead connected to the anode part and a second lead connected to the conductor layer, and sealed with an external resin except a part of the first and second leads; A solid electrolytic capacitor,
Developing a chip-shaped solid electrolytic capacitor in which a part of the anode part extends to the first lead, and the anode part, the anode part, and the first lead are electrically connected via a metal wire. This has solved the above problem.

  The chip-shaped solid electrolytic capacitor of the present invention is a solid electrolytic capacitor in which the anode portion of the solid electrolytic capacitor element and the lead frame are connected via a metal wire, and the anode base is not subjected to stress so that the leakage current value is good. It can be manufactured efficiently.

Hereinafter, the solid electrolytic capacitor of the present invention will be described in detail.
As the anode substrate having a valve action used as the anode of the solid electrolytic capacitor in the present invention, any metal having a valve action such as aluminum, tantalum, and alloys using these as a substrate can be used. The shape of the anode substrate may be a flat aluminum foil or plate.

  The dielectric oxide film layer provided on the surface of the anode substrate may be an oxide layer of the valve action metal itself provided on the surface portion of the valve action metal, or may be provided on the surface of the valve action metal foil. It may be a layer of another dielectric oxide, but is preferably a layer made of an oxide of the valve metal itself.

  In the present invention, the anode portion is provided in one section of the end portion of the flat anode substrate having the dielectric oxide film layer formed on the surface, and the semiconductor is formed on the remaining dielectric oxide film layer other than the anode portion. Although the layer is formed, the type of the semiconductor layer is not particularly limited, and a conventionally known semiconductor layer can be used.

  Among these, in particular, a semiconductor layer made of lead dioxide or lead dioxide and lead sulfate (Japanese Patent Application Laid-Open Nos. 62-256423 and 63-51621) filed by the applicant of the present application is a high-frequency solid electrolytic capacitor manufactured. It is preferable because of good performance. Further, a method of forming a complex of tetrathiotetracene and chloranil as a semiconductor layer (Japanese Patent Application Laid-Open No. 62-29123), a method in which thallium oxide is chemically formed from a reaction mother liquor containing thallium ions and persulfate ions. The method of precipitation (Japanese Patent Application Laid-Open No. 62-38715) is also one example.

  A conductive layer is formed by laminating a conventionally known conductive paste such as a carbon paste and / or a silver paste on such a semiconductor layer to form a conductive layer forming portion. Further, in the present invention, if the resin layer portion is formed in advance in a spiral shape with an insulating resin at the interface between the anode portion and the conductor layer forming portion, the formation area of the semiconductor layer when the semiconductor layer is formed Is constant and the capacity is small.

  Next, a method of connecting the capacitor element formed up to the conductor layer in this way to a pair of opposing lead frames will be described. FIGS. 1 and 2 are cross-sectional views showing a state where the solid electrolytic capacitor element 5 is joined with a conductive material 10 and a metal wire 13.

  In FIG. 1, a solid oxide capacitor element 5 in which a dielectric oxide film layer 2 is formed on the surface of an anode substrate 1, a semiconductor layer 3 is further formed thereon, and a conductor layer 4 is further formed thereon is connected to a lead frame 6. After being placed on the other convex portion 6b, a part of the conductor layer forming portion 8 is joined with the conductive material 10, and one convex portion 6a of the lead frame 6 and the anode portion 7 are joined with the metal wire 13. Have been. In FIG. 2, a part of the anode 7 of the solid electrolytic capacitor element 5 extends to one protrusion 6 a of the lead frame 6, and the anode 7 and one protrusion 6 a are joined by a metal wire 13.

  Examples of the conductive material 10 include a known conductive paste such as a silver paste and a fusible metal such as a cream solder. Known materials such as iron, nickel, copper, aluminum, and alloys thereof may be used as the material of the metal wire 13, and the metal wire may be plated with solder or the like. The thickness of the metal wire is several microns to several millimeters, and is selected depending on the ease of connection with the lead frame, the shape of the solid electrolytic capacitor element, and the like. The length of the metal wire is usually several millimeters, but is determined by the outer shape and the size of the solid electrolytic capacitor described later. Generally, it is preferable that the metal wire has a play to connect between the lead frame and the anode portion in order to reduce a stress at the time of packaging described later. The metal wire is connected to the lead frame and the anode section by welding, conductive paste, solder, or the like.

  1 and 2, the number of the metal wires 13 is shown as one each, but a plurality of metal wires 13 may be connected to strengthen the connection. Further, as a connection order of the metal wires, a lead frame in which the metal wire 13 is connected to one of the protrusions 6a of the lead frame 6 in advance is used to connect the anode portion 7 when the solid electrolytic capacitor element 5 is mounted. Is also good. Alternatively, the metal wire 13 may be connected to the anode portion 7 in advance, and may be connected to the one convex portion 6a when the solid electrolytic capacitor element 5 is mounted on the lead frame 6. In the latter case, the metal wire 13 may be connected to the anode 7 before or after the formation of the semiconductor layer 3 or after the formation of the conductor layer 4.

  The solid electrolytic capacitor element connected to the lead frame in this manner is sealed with a transfer molding machine or the like using an exterior resin 11 such as an epoxy resin while leaving a part of the lead frame, and then the lead frame is sealed. The protruding portion is cut near the capacitor element to form a chip-shaped solid electrolytic capacitor.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

(Example 1)
A 4 × 3 mm small piece of a 45 μF / cm ² aluminum etching foil (hereinafter referred to as a chemical conversion foil) having a dielectric oxide film layer formed on the surface thereof by a chemical conversion treatment in an aqueous solution of phosphoric acid and ammonium phosphate was prepared. A portion of 1 × 3 mm from the end of this chemical conversion foil is used as an anode portion, and the remaining 3 × 3 mm portion is a mixed solution of a 2.4 mol / l aqueous solution of lead acetate trihydrate and a 4.0 mol / l aqueous solution of ammonium persulfate. And left at 60 ° C. for 20 minutes to form a semiconductor layer composed of lead dioxide and lead sulfate.

  After such an operation was performed three times, a carbon paste and a silver paste were sequentially laminated on the semiconductor layer to form a conductor layer, and a capacitor element was manufactured. On the other hand, using a separately prepared lead frame (material 42 alloy, thickness 0.1 mm, size of convex portion: width 3 mm, gap at the tip of the convex portion 1 mm), the above-described capacitor element was placed on the other convex portion, and silver paste was applied. At the same time, an aluminum wire having a diameter of 0.25φ and a length of 4 mm was passed between the center of the tip of the anode part and the center of the tip of one of the projections, and both ends were connected by welding. Thereafter, transfer molding was performed using an epoxy resin to produce a chip-shaped solid electrolytic capacitor having an outer dimension of 7 × 4 × 3 mm.

(Example 2)
The same capacitor element as in Example 1 was used, and the conductor layer forming portion 3 of the capacitor element was formed on the other convex portion of the lead frame in the same manner as in Example 1 except that the tip gap of the protrusion of the lead frame was 0.5 mm. × 3 mm, connected with silver paste, and placed so that the 0.5 mm portion of the anode part of the capacitor element is placed on one convex part of the lead frame. A nickel wire (thickness: 0.3φ, length: 4 mm) was passed from the end of the lead frame to a central position in the width direction of the protrusion at a distance of 1.2 mm from the end of one of the protrusions of the lead frame, and was connected by welding. . Thereafter, transfer molding was performed using an epoxy resin to produce a chip-shaped solid electrolytic capacitor having an outer dimension of 7 × 4 × 3 mm.

(Examples 3 and 4)
Except that the semiconductor layer was immersed in a 2.0 mol / l aqueous solution of lead acetate trihydrate in Examples 1 and 2 to form lead dioxide electrochemically formed with a separately prepared platinum cathode. In the same manner as in Examples 1 and 2, a chip-shaped solid electrolytic capacitor was produced.

(Comparative Example 1)
The connection between the anode part and the lead frame on the anode part side was carried out in the same manner as in Example 2 except that the anode part and the convex part of the lead frame were directly welded without using a metal wire. A capacitor was manufactured. The gap between the lower surface of the anode part and the protrusion of the lead frame was 1 mm.

  Table 1 shows the performance of the solid electrolytic capacitor immediately after being manufactured as described above. Each example or comparative example is an average value of all the numerical values n = 100 points.

  In the solid electrolytic capacitor of the present invention, the connection between the anode portion of the solid electrolytic capacitor element and the protrusion of the lead frame is performed by a metal wire, so even if there is a gap between the anode portion and the protrusion of the lead frame, the connection is established. Occasionally, no stress is applied to the anode substrate and the anode substrate does not bend, so that a chip-shaped solid electrolytic capacitor having good productivity and good leakage current value can be manufactured.

FIG. 4 is a cross-sectional view showing a state where the solid electrolytic capacitor element is mounted on a lead frame. It is sectional drawing of the other example which shows the state which mounted the solid electrolytic capacitor element on the lead frame. FIG. 10 is a plan view showing a state in which a conventional chip-shaped solid electrolytic capacitor is mounted on a lead frame. It is sectional drawing which shows the state which mounted the conventional chip-shaped solid electrolytic capacitor on the lead frame.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Anode base 2 Dielectric oxide film layer 3 Semiconductor layer 4 Conductive layer 5 Solid electrolytic capacitor element 6a One convex part of lead frame 6b The other convex part of lead frame 7 Anode part 8 Conductive layer forming part 9 Welding 10 Conduction Material 11 Exterior resin 12 Chip-shaped solid electrolytic capacitor 13 Metal wire

Claims (1)

An aluminum electrolytic capacitor element in which an anode portion is provided at an end, a semiconductor layer and a conductor layer are sequentially provided on the dielectric film layer of a flat aluminum foil having a dielectric oxide film layer on the surface,
A chip-shaped chip provided with a first lead connected to the anode part and a second lead connected to the conductor layer, and sealed with an external resin except a part of the first and second leads; A solid electrolytic capacitor,
A chip-shaped solid electrolytic capacitor in which a part of the anode section extends to the first lead, and the anode section, the anode section, and the first lead are electrically connected via a metal wire.

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