JP2001284190A - Solid electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid electrolytic capacitor that can prevent mechanical stresses that are applied to a lead wire from being transmitted to the inside of a capacitor element, and at the same time, can improve the electrical characteristics. SOLUTION: A winding-type capacitor element 1 is accommodated into a closed-end outer packaging case 2 made of aluminum or the like, and the inside and entire-periphery surface are covered with an epoxy resin layer 3. The opening part of the outer packaging case 2 is sealed with a sealing body 4 that is composed by combining a hard member 4a with an elastic member 4b. The sealing body 4 is composed by covering the bottom and side surfaces of the hard member 4a, such as a bakelite plate with the elastic member 4b, such as butyl rubber. In the sealing body 4, a through-hole 6 for inserting a lead wire 5 is formed. Then, arrangement is made so that the cylinder part 5a of the lead wire 5 is positioned in the through-hole 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid electrolytic capacitor, and more particularly, to a solid electrolytic capacitor in which a sealing member housed at an opening end of an outer case is improved.

[0002]

2. Description of the Related Art In an electrolytic capacitor using a metal having a valve action such as tantalum or aluminum, a valve action metal as an anode-side counter electrode is formed into a shape of a sintered body or an etching foil to expand a dielectric material. By using such a structure, it is possible to obtain a large capacity with a small size. In particular, a solid electrolytic capacitor using a solid electrolyte as an electrolyte has characteristics that it is small, large-capacity, low equivalent series resistance, easy to chip, and suitable for surface mounting. It is indispensable for miniaturization, high performance, and low cost of electronic devices.

In this type of solid electrolytic capacitor, for small size and large capacity applications, generally, an anode foil and a cathode foil made of valve metal such as aluminum are wound with a separator interposed therebetween to form a capacitor element. The capacitor element is impregnated with a driving electrolyte, and the capacitor element is housed in a metal case such as aluminum or a synthetic resin case, and has a sealed structure. Note that as the anode material, aluminum, tantalum, niobium, titanium, or the like is used, and as the cathode material, the same kind of metal as the anode material is used.

As a solid electrolyte used for a solid electrolytic capacitor, manganese dioxide, 7, 7, 8, 8-
A tetracyanoquinodimethane (TCNQ) complex is known, but recently, polyethylenedioxythiophene (hereinafter, referred to as PEDT), which has a slow reaction rate and excellent adhesion to an oxide film layer of an anode electrode, has been developed. There is a technique (Japanese Patent Laid-Open No. 2-15611) that has been focused on.

[0005] Such a solid electrolytic capacitor generally has a solid electrolyte layer formed on a wound capacitor element.
It is housed in a metal outer case together with a sealing body made of an elastic member, and is formed by caulking the open end of the outer case.

[0006]

However, the conventional solid electrolytic capacitors described above have the following problems. That is, when the lead wire of the solid electrolytic capacitor is formed or mounted on a printed circuit board, mechanical stress is applied to the lead wire. Then, the mechanical stress applied to the lead wire is transmitted to the inside of the capacitor element, and the mechanical stress may damage the oxide film layer of the electrode foil of the capacitor element. In particular, a solid electrolytic capacitor has a poor ability to repair an oxide film, and such damage to the oxide film causes an increase in leakage current.

[0007] In particular, in the case of a solid electrolytic capacitor using PEDT as a solid electrolyte, there is a problem that when moisture enters from the outside, the characteristics are deteriorated.
It is considered that the moisture infiltration route is considered to be that the moisture in the atmosphere penetrates into the interior through the sealing body made of the elastic member, and therefore, conventionally, a sealing body with low moisture permeability is required. .

The present invention has been proposed to solve the above-mentioned problems of the prior art, and an object of the present invention is to prevent a mechanical stress applied to a lead wire from being transmitted to the inside of a capacitor element. It is an object of the present invention to provide a solid electrolytic capacitor which can be improved in electric characteristics.

[0009]

Means for Solving the Problems To solve the above problems, the present inventors have been able to prevent the mechanical stress applied to the lead wire from being transmitted to the inside of the capacitor element, and have a low moisture permeation performance. As a result of intensive studies on
The present invention has been completed. That is, the present inventors use a sealing member formed by combining a hard member and an elastic member as the sealing member, so that the mechanical stress applied to the lead wire at the time of forming the lead wire or mounting it on a printed circuit board is reduced. It has been found that transmission to the inside of the capacitor element can be prevented. In addition, since a hard member such as a bake plate has a low moisture permeability, it has been found that the use of this hard member as a sealing member can prevent intrusion of moisture from the outside.

That is, according to the first aspect of the present invention, the anode foil and the cathode foil are wound with a separator interposed therebetween, and the solid electrolyte layer is provided on the capacitor element having a terminal for leading out from one of the winding end faces. While forming, in a solid electrolytic capacitor in which this capacitor element is housed in a bottomed cylindrical outer case, and the opening of the outer case is sealed by a sealing body having a through hole through which the external lead-out terminal is inserted, The present invention is characterized in that a sealing member formed by combining a hard member and an elastic member is used as the sealing member.

According to a second aspect of the present invention, in the solid electrolytic capacitor according to the first aspect, the sealing member covers at least a side of the top, bottom, and side surfaces of the hard member with the elastic member. It is characterized by comprising. According to a third aspect of the present invention, in the solid electrolytic capacitor according to the second aspect, an inner surface of a through hole of the sealing body is configured to be covered with the elastic member.

According to a fourth aspect of the present invention, in the solid electrolytic capacitor according to any one of the first to third aspects, the hard member is a bake plate. According to a fifth aspect of the present invention, in the solid electrolytic capacitor according to any one of the first to fourth aspects, the elastic member is butyl rubber.

According to the first to fifth aspects of the present invention, the pressure applied to the sealing body when the opening end of the outer case is swaged is absorbed by the elastic member of the sealing body. Thus, the open end of the outer case can be sealed. In addition, since the lead wire of the capacitor element is firmly supported by the hard member of the sealing body, mechanical stress on the lead wire when forming the lead wire or mounting it on a printed circuit board is reduced by the internal stress of the capacitor element. Can be prevented. Further, since a hard member such as a bake plate has a low moisture permeability, the invasion of moisture from the outside can be prevented.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a solid electrolytic capacitor according to the present invention will be specifically described below with reference to FIGS.

[1. Configuration] [1-1. Solid Electrolytic Capacitor] FIG. 1 shows a solid electrolytic capacitor according to the present invention. A wound type capacitor element 1 is housed in a bottomed cylindrical outer case 2 made of aluminum or the like. In addition, the entire outer peripheral surface is covered with an epoxy resin layer 3, and the opening of the outer case 2 is sealed by a sealing body 4 formed by combining a hard member 4a and an elastic member 4b. Note that reference numeral 5 in the figure denotes a lead wire derived from the capacitor element 1.

As shown in FIG. 2, the sealing member 4 is formed by covering the bottom and side surfaces of a hard member 4a such as a bake plate with an elastic member 4b such as butyl rubber. A through hole 6 through which the reference numeral 5 is inserted is formed.
The round bar portion 5a of the lead wire 5 is inserted into the through hole 6.
Is configured to be located.

The solid electrolytic capacitor having such a configuration is manufactured by the following procedure. First, a capacitor element 1 is formed by winding a bipolar electrode foil made of a valve action metal such as aluminum and having an oxide film layer formed on the surface thereof through a separator made of vinylon fiber or the like to form a capacitor element 1. A solid electrolyte layer made of polyethylene dioxythiophene (PEDT) or the like is formed between the electrode foils.

Next, the capacitor element 1 is housed in the outer case 2 and the space between the outer case 2 and the capacitor element 1 is filled with an epoxy resin or the like. Subsequently, the sealing member 4 formed by combining the hard member 4a and the elastic member 4b is attached to the opening of the outer case 2, and the outer case 2 is sealed by caulking the opening end of the outer case 2. Thereafter, by heating and curing at a temperature corresponding to the type of the epoxy resin, the epoxy resin layer 3 covering the inside and the entire outer peripheral surface of the capacitor element 1 is formed.

[1-2. Sealing Body] In addition to the structure shown in FIG. 2, the sealing body 4 has a structure in which only the side surface of a hard member 4a is covered with an elastic member 4b as shown in FIG.
As shown in (B), a material in which the entire surface of the hard member 4a is covered with the elastic member 4b can be used. Further, as shown in FIGS. 4 (A) to 4 (C), the through-hole 6 of the sealing body 4 is formed.
May be used by coating the inner surface with an elastic member 4b. In addition, as shown in FIG. 5, by adjusting the relative positional relationship between the structure of the sealing body and the crimping position of the outer case so that the pressure due to the lateral crimping is transmitted to the round bar portion 5a of the lead wire. Since the round bar portion 5a and the through hole 6 of the sealing body 4 can be further brought into close contact with each other, the effect of preventing moisture from entering from outside can be further enhanced.

[1-3. Material of Sealing Body] As the hard member 4a constituting the sealing body 4, besides a bake plate, polyamide resin, urea resin, epoxy resin, melamine resin, PP
Examples include S, polyimide, Teflon (registered trademark), and an Al plate. Further, as the elastic member 4b, EPDM, fluorine rubber, or the like can be used in addition to butyl rubber.

[2. Operation / Effect] The operation of the present embodiment having the above configuration is as follows. That is, in the present embodiment, the sealing member 4 formed by combining the hard member 4 a and the elastic member 4 b is attached to the opening of the outer case 2, and the opening end of the outer case 2 is swaged.
Is sealed, the pressure applied to the sealing body when caulking is absorbed by the elastic member 4b.

The round bar portion 5a of the lead wire 5 of the capacitor element is inserted into a through hole 6 formed in the hard member 4a of the sealing member 4, and is firmly supported by the hard member 4a. The mechanical stress applied to the lead wire when the lead wire is formed or mounted on a printed circuit board is not transmitted to the inside of the capacitor element 1.

Further, the sealing body 4 attached to the opening of the outer case 2 is constituted by combining a hard member 4a and an elastic member 4b, and a hard member such as a bake plate has a low moisture permeability. Intrusion of moisture from the outside can be prevented. In particular, polyethylene dioxythiophene (P
Since the solid electrolyte layer made of an organic conductive polymer material such as EDT) is easily affected by moisture, the epoxy resin layer 3
By preventing the intrusion of moisture by the double sealing structure including the outer case 2 and the sealing body 4, the life characteristics of the capacitor can be greatly improved.

Although a bottomed cylindrical outer case made of aluminum or the like is used in the embodiment, a bottomed cylindrical outer case made of resin may be used. In this case, the opening of the outer case may be sealed by press-fitting a sealing body slightly larger than the inner diameter of the outer case. In this case, a step such as caulking is not required. Further, the sealing body may be housed in the opening of the outer case after the capacitor element is housed in the outer case, or may be housed in the outer case together with the capacitor element after being mounted on the end face of the capacitor element.

In the above embodiment, the case where a solid electrolyte layer made of polyethylene dioxythiophene (PEDT) or the like is described, but a solid electrolyte layer made of other various materials such as manganese dioxide or polypyrrole is described. Is similarly applicable to the case of generating

[0026]

EXAMPLES Next, examples of the solid electrolytic capacitor according to the present invention will be specifically described in comparison with comparative examples. First, the same capacitor element and the same outer case were formed, and these were used to produce solid electrolytic capacitors having the same rating according to the present invention and the prior art, respectively. That is, as an example according to the present invention, as described in the above-described embodiment, as a sealing body, a sealing body formed by combining a hard member and an elastic member, specifically, a bottom surface and side surfaces of a resin bake plate A solid electrolytic capacitor using a sealing body coated with butyl rubber was prepared, and as a comparative example according to the prior art, a solid electrolytic capacitor using a sealing body consisting only of an elastic member made of butyl rubber was manufactured as the sealing body.

[Test 1] With respect to the solid electrolytic capacitors of the embodiment and the comparative example manufactured as described above, the operation of bending the lead wire by hand and returning to the original state was repeated 10 times, and the electrical characteristics before and after that were examined. And the results shown in Table 1 were obtained.

[Table 1]

As is evident from Table 1, in the comparative example, the LC (leakage current) after bending was greatly increased by about 38 times as compared with that before bending. On the other hand, in the example, LC after bending increased only about three times as compared with that before bending. When the LC after bending was compared between the example and the comparative example, the LC of the comparative example was about 15 times that of the example. As is clear from the results, in the embodiment using the sealing member formed by combining the hard member and the elastic member, the oxide film layer of the electrode foil of the capacitor element is damaged by the mechanical stress applied to the lead wire. It has been found that can be largely prevented.

[Test 2] Subsequently, the solid electrolytic capacitors of Examples and Comparative Examples produced as described above were heated at 85 ° C.
The device was left for 1000 hours in a state where a rated voltage (6.3 V) was applied to an environment with a humidity of 85%, and the electrical characteristics before and after that were examined. The results shown in Table 2 were obtained.

[Table 2]

As apparent from Table 2, in the comparative example, the capacitance after standing was reduced to about 85% of that before standing.
On the other hand, in the example, the capacitance after the standing was the same as that before the standing. As evident from this result,
In the embodiment using the sealing member in which the hard member and the elastic member are combined, even when left for a long time in a high-temperature and high-humidity state, there is no significant change in the electrical characteristics,
It was shown that moisture in the atmosphere did not enter the inside of the solid electrolytic capacitor. On the other hand, in the comparative example, it is considered that since the capacitance after being left significantly decreased, moisture in the air entered the inside of the solid electrolytic capacitor, and as a result, the electrical characteristics decreased.

From both results, it is clarified that the entry path of the moisture in the atmosphere is a sealing member made of an elastic member. As in the present invention, a hard member and an elastic member are combined as a sealing member. The effectiveness of using such a sealing body was shown.

[0032]

As described above, according to the present invention,
It is possible to provide a solid electrolytic capacitor capable of preventing mechanical stress applied to a lead wire from being transmitted to the inside of a capacitor element and improving electrical characteristics.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a solid electrolytic capacitor according to the present invention.

FIG. 2 is a cross-sectional view showing an example of a sealing body attached to an open end of the solid electrolytic capacitor according to the present invention and configured by combining a hard member and an elastic member.

FIGS. 3A and 3B are cross-sectional views showing another example of a sealing body formed by combining a hard member and an elastic member.

4A, 4B, and 4C are cross-sectional views each showing an example in which an inner surface of a through hole of the sealing body shown in FIGS. 2 and 3 is covered with an elastic member.

FIG. 5 is a sectional view showing an example of a solid electrolytic capacitor using the sealing body shown in FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Capacitor element 2 ... Outer case 3 ... Epoxy resin layer 4 ... Sealing body 4a ... Hard member 4b ... Elastic member 5 ... Lead wire 5a ... Round bar part 6 ... Through-hole

Claims (5)

[Claims] An anode foil and a cathode foil are wound with a separator interposed therebetween, and a solid electrolyte layer is formed on a capacitor element having an external lead-out terminal drawn out from one of the winding end faces. In a solid electrolytic capacitor housed in a bottom cylindrical outer case, and the opening of the outer case is sealed by a sealing body having a through hole through which the terminal for external drawing is inserted, a hard member and an elastic member are used as the sealing body. A solid electrolytic capacitor using a sealing body formed by combining members. 2. The solid electrolytic capacitor according to claim 1, wherein the sealing member is formed by covering at least a side surface among the top surface, the bottom surface, and the side surface of the hard member with the elastic member. . 3. The solid electrolytic capacitor according to claim 2, wherein an inner surface of the through hole of the sealing body is configured to be covered with the elastic member. 4. The solid electrolytic capacitor according to claim 1, wherein the hard member is a bake plate. 5. The solid electrolytic capacitor according to claim 1, wherein the elastic member is butyl rubber.