JP2008113055A - Solid electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid electrolytic capacitor in which equivalent series resistance (ESR) can be further reduced compared with conventional methods, and which has good workability and also has good precision at the time of soldering. <P>SOLUTION: The solid electrolytic capacitor is provided with an anode foil having an anode leading-out means, a cathode foil having a cathode leading-out means, and a conducting polymer as a solid electrolyte, wherein at least a part of the anode leading-out means and the cathode leading-out means is composed of a copper wire having an iron core with copper content ratio of 70% or more. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a solid electrolytic capacitor, and more particularly to a solid electrolytic capacitor that has been improved to reduce the equivalent series resistance (hereinafter referred to as ESR) of the solid electrolytic capacitor and improve workability.

  An electrolytic capacitor using a metal having a valve action such as tantalum or aluminum is obtained by expanding the dielectric by making the valve action metal as the anode-side counter electrode into the shape of a sintered body or an etching foil. Since it is small and a large capacity can be obtained, it is widely used. In particular, a solid electrolytic capacitor using a solid electrolyte as an electrolyte has features such as small size, large capacity, low equivalent series resistance, easy to chip, and suitable for surface mounting. It is indispensable for miniaturization, high functionality and low cost of electronic equipment.

  In this type of solid electrolytic capacitor, for small and large-capacity applications, the anode foil and the cathode foil made of a valve metal such as aluminum are generally made of lead wires made of iron as a core and plated with copper or tin. An electrode lead means comprising an electrode external connection portion and an electrode foil connection portion made of aluminum is connected, and both electrode foils are wound with a separator interposed therebetween to form a capacitor element, and a driving electrolyte is applied to the capacitor element. It is impregnated and has a sealed structure in which a capacitor element is housed in a case made of metal such as aluminum or a case made of synthetic resin. As the anode material, aluminum, tantalum, niobium, titanium and the like are used, and as the cathode material, the same kind of metal as the anode material is used.

  As solid electrolytes used for solid electrolytic capacitors, manganese dioxide and 7,7,8,8-tetracyanoquinodimethane (TCNQ) complexes are known. There is a technique (for example, refer to Patent Document 1) that focuses on a conductive polymer such as polyethylenedioxythiophene (hereinafter referred to as PEDT) having excellent adhesion to an oxide film layer of an electrode.

  By the way, a solid electrolytic capacitor using a conductive polymer such as PEDT as described above has a low impedance of the solid electrolyte, and hence a low impedance as a capacitor, and can meet the demand for a large ripple current accordingly. However, when such a large ripple current is passed, heat generation of the lead wire increases, and in some cases, the lead wire is disconnected due to heat generation.

Therefore, the present applicant uses a member mainly composed of copper or a copper alloy in the anode lead-out means and the cathode lead-out means in order to provide a solid electrolytic capacitor having lower impedance and no deterioration in characteristics even when the ripple current is increased. Proposed that. (For example, see Patent Document 2)
JP-A-2-15611 JP 2001-44078 A

  However, when a member mainly composed of copper or a copper alloy is used for the anode lead-out means and the cathode lead-out means in accordance with the above-described invention, when the capacitor element is attached to the lead frame and transported during the manufacturing process of the solid electrolytic capacitor When a force is applied to the capacitor element, the anode pulling means and the cathode pulling means are bent to cause positioning in the next step.

  Also, when used for surface mounting, if a force is applied to the anode lead means or the cathode lead means, the lead wire is displaced and the dimensional accuracy is deteriorated. Further, if a force is applied to the lead wire during reflow, the lead wire is displaced. In some cases, connection to the circuit of the board did not work.

  The present invention has been proposed to solve the above-described problems of the prior art, and an object thereof is to provide a solid electrolytic capacitor that can further reduce ESR and has good workability. It is in.

  In order to solve the above-mentioned problems, the present inventors have made it possible to further reduce ESR as compared with the prior art while making the hardness of the members constituting the anode lead-out means and the cathode lead-out means appropriate, and good workability Eagerly studied to obtain a solid electrolytic capacitor. As a result, by using a copper wire having an iron core with a copper content of 70% or more as an anode extraction means or a cathode extraction means, workability is good without increasing ESR, and accuracy during solder mounting is also achieved. It was found that a good solid electrolytic capacitor can be obtained.

(Electrode extraction means)
Usually, the electrode lead means is configured as shown in FIG. That is, the capacitor element 4 is formed by winding the anode foil 1 made of a valve action metal such as aluminum and having the oxide film layer formed on the surface thereof, and the cathode foil 2 through the separator 3. Then, this capacitor element 4 is impregnated with a polymerizable monomer such as 3,4-ethylenedioxythiophene and an oxidizing agent solution, and a conductive polymer such as PEDT produced by a chemical polymerization reaction in the capacitor element 4 is solid electrolyte. It is held by the separator 3 as a layer.

  Also, anode extraction means 20 and cathode extraction means 10 for connecting the respective electrodes to the outside are connected to anode foil 1 and cathode foil 2 by known means such as stitching or ultrasonic welding. The anode lead-out means 20 includes an anode foil connection portion 21 connected to the anode foil and an anode external connection portion (anode-side lead wire) 22 responsible for electrical connection with the outside. Is composed of a cathode foil connecting portion 11 connected to the cathode foil and a cathode external connecting portion (cathode side lead wire) 12 responsible for electrical connection with the outside. Among these, when the cathode external connection portion 22 and the anode external connection portion 12 are copper wires having an iron core with a copper content of 70% or more, the electrode lead-out means is bonded to the electrode foil connection portion made of aluminum. It is preferable because it can be made and the workability is good.

  Moreover, 70% or more of the content rate of the copper in the copper wire which has an iron core used for this invention is preferable, More preferably, it is 90% or more. Below this range, the resistance of the copper wire increases and the ESR increases. Moreover, as a copper wire which has an iron core used for this invention, what joined cyclic | annular copper around the iron core, and what gave the copper plating to the steel wire can be used.

  Here, the diameter of the anode lead-out means or the cathode lead-out means according to the present invention, in which at least part of the copper wire has an iron core with a copper content of 70% or more, is preferably 0.3 to 1.1φ. 0.4 to 0.65φ is more preferable. If it is less than this range, the decrease in ESR is small, and if it exceeds this range, workability deteriorates. Furthermore, in order to improve solderability, a copper wire having an iron core with a copper content of 70% or more may be used as a core material, and plating such as solder plating, tin plating, or lead plating may be performed.

(Conductive polymer)
In the solid electrolytic capacitor according to the present invention, the above-described effect can be obtained if the solid electrolyte is a conductive polymer. In particular, when PEDT is used as the conductive polymer, the ESR characteristic of PEDT is low. The contribution of the resistance of the line is increased, and the effect of the present invention is further increased.

According to the present invention, ESR can be reduced by using a copper wire having an iron core with a copper content of 70% or more for at least a part of the anode extraction means and the cathode extraction means. It is possible to provide a solid electrolytic capacitor having excellent properties.

Subsequently, the present invention will be described in more detail based on Examples and Comparative Examples manufactured as follows.
(Example 1)
A lead wire made of a copper wire having an iron core with a copper content of 82% or more is connected to an anode foil and a cathode foil having an oxide film layer formed on the surface, and both electrode foils are wound through a separator. Thus, a capacitor element having an element shape of 5φ × 2.8 L was formed. And this capacitor | condenser element was immersed in ammonium dihydrogen phosphate aqueous solution for 40 minutes, and restoration | restoration conversion was performed. On the other hand, a 40 wt% butanol solution of EDT and ferric p-toluenesulfonate is poured into a predetermined container so that the weight ratio is 1: 3, and a mixed solution is prepared. For 10 seconds, the capacitor element was impregnated with EDT and an oxidizing agent. Then, this capacitor element was left in a constant temperature bath at 120 ° C. for 1 hour to cause a polymerization reaction of PEDT in the capacitor element to form a solid electrolyte layer. And this capacitor | condenser element was inserted in the bottomed cylindrical exterior case, the sealing rubber was attached to the opening edge part, and it sealed by the crimping process. Thereafter, aging was performed by applying a voltage of 8.2 V at 150 ° C. for 120 minutes to form a solid electrolytic capacitor. This solid electrolytic capacitor has a rated voltage of 6.3 WV and a rated capacity of 120 μF. The electrode lead-out means was tin / lead plated. (Comparative example) An iron wire was used as a lead wire. Other conditions and steps are the same as in Example 1.

[Comparison result]
The initial characteristics of the examples and comparative examples obtained by the above method were examined, and the results shown in Table 1 were obtained.
[Table 1]

  As is clear from Table 1, the ESR of Example 1 using a copper wire having an iron core with a copper content of 82% as the lead wire is reduced to about 86.1% of the comparative example using the iron wire. did. There was no difference in capacitance between Example 1 and Comparative Example.

The exploded perspective view which shows an example of the capacitor | condenser element which this invention makes object

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Anode foil 2 ... Cathode foil 3 ... Separator 4 ... Capacitor element 10 ... Cathode extraction means 11 ... Cathode foil connection part 12 ... Cathode external connection part 20 ... Anode extraction means 21 ... Anode foil connection part 22 ... Anode external connection part

Claims (3)

In a solid electrolytic capacitor comprising an anode foil having an anode lead means, a cathode foil having a cathode lead means, and a conductive polymer as a solid electrolyte,
A solid electrolytic capacitor characterized in that at least a part of the anode lead-out means and the cathode lead-out means is composed of a copper wire having an iron core with a copper content of 70% or more.   The solid electrolytic capacitor according to claim 1, wherein the conductive polymer is a polymer of a thiophene derivative.   The solid electrolytic capacitor according to claim 2, wherein the thiophene derivative is 3,4-ethylenedioxythiophene.

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