JP2001210558A - Solid electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid electrolytic capacitor having superior ESR characteristic at high frequencies. SOLUTION: A solid electrolytic capacitor, which consists of a heat treated capacitor element made of anode foil and cathode foil wound via a separator and of an impregnated solid electrolyte, is characterized in that the separator consists mainly of sisal fiber and the weight after heat treatment is 0.30-0.70 times that prior to the heat treatment.

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 separator.

[0002]

2. Description of the Related Art In recent years, the speed and power saving of electronic equipment have been promoted, and a solid electrolytic capacitor which is a component of the electronic equipment has a high frequency equivalent series resistance (hereinafter referred to as ESR).
Low is required.

Conventionally, a solid electrolytic capacitor has an anode foil in which an oxide film layer serving as a dielectric is formed on a valve metal surface such as tantalum or aluminum having fine holes or etching pits, and a valve action having etching pits. A capacitor element in which a natural oxide film or surface-treated cathode foil is wound on a metal surface via a separator mainly made of manila paper,
It was impregnated with the TCNQ complex.

However, in an electrolytic capacitor using a TCNQ complex as a solid electrolyte, since the ESR at a high frequency does not become sufficiently low, a solid electrolytic capacitor using a functional polymer such as pyrrole, aniline or thiophene as an electrolyte has recently been developed. Was done.

[0005]

When electrolytic paper mainly composed of manila paper is used for the separator of the capacitor element and functional polymer is used for the solid electrolyte, the manila fiber in the electrolytic paper is synthesized with the functional polymer. Therefore, there is a problem that impregnation cannot be performed sufficiently or that it takes a long time for impregnation.
Heat treatment of the capacitor element to carbonize the paper in order to suppress the influence of such manila paper improves impregnation, but on the other hand, there is a problem that the shape of the capacitor element tends to collapse, and it is possible to sufficiently carbonize. Did not.

[0006]

As a result of various studies to solve the above-mentioned problems, it has been found that when heat treatment is carried out particularly on a separator mainly composed of sisal fibers after forming the capacitor element, the separator at a high frequency can be formed without breaking the shape of the capacitor element. It has been found that ESR is possible. That is, in a solid electrolytic capacitor obtained by impregnating a solid electrolyte into a capacitor element in which an anode foil and a cathode foil are wound via a separator,
A solid electrolytic capacitor characterized in that the separator is mainly made of sisal fiber and the weight of the separator after heat treatment is 0.30 to 0.70 times the weight before heat treatment.

[0007] Further, the solid electrolyte comprises at least one of pyrrole, aniline, thiophene or a derivative thereof.
A solid electrolytic capacitor characterized by being subjected to seed polymerization.

A sisal fiber content of the separator is 50 to 100%.

As the pyrrole derivative, a hydroxyl group, acetyl group,
A pyrrole derivative having at least one of a carboxyl group, an alkyl group and an alkoxy group as a substituent can be given.

The aniline derivative includes an aniline derivative having an aniline skeleton and having at least one of an alkyl group, a phenyl group, an alkoxy group, an ester group and a thioether group as a substituent.

Further, as the thiophene derivative, a thiophene derivative having at least one of a hydroxyl group, an acetyl group, a carboxyl group, an alkyl group and an alkoxy group as a substituent at the 3-, 3- and 4-positions or the S-position of the thiophene skeleton. Or 3,4-alkylenedioxythiophene.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A capacitor element is formed by winding an anode foil and a cathode foil through a separator mainly composed of sisal fiber, and after heat treatment of the capacitor element, a functional polymer is used as a solid electrolyte. Impregnation to produce a solid electrolytic capacitor. By using the separator, the ESR characteristics at a high frequency can be improved without breaking the shape of the capacitor element.

[0013]

EXAMPLE After slitting an aluminum anode foil and an aluminum cathode foil manufactured by a known method to desired dimensions, a lead rod was attached to each electrode foil, and a separator (thickness 4
0 μm) to form a capacitor element. Since no oxide film was formed on the end face of the anode foil of the capacitor element, a chemical conversion treatment was performed at 60 ° C. in a 1.0 wt% aqueous solution of ammonium adipate. Next, the weight retention rate of the separator after heat treatment (weight after heat treatment / weight before heat treatment) was about 0.5.
Heat treatment was performed at 300 ° C. to carbonize the separator, and a chemical conversion treatment was performed again in the above aqueous solution. After immersion in a polymerization solution (monomer: oxidant = 1: 1.5 (molar ratio)) in which 3,4-ethylenedioxythiophene and iron (III) p-toluenesulfonate are dissolved in i-propanol, 10
The solid electrolyte layer of polyethylene dioxythiophene (PEDT) was formed by chemical polymerization by holding at 0 ° C. for 60 minutes. Then, the capacitor element having the solid electrolyte layer formed therein is put in a case, and the opening is sealed with a sealing member. Then, a surface mounting seat plate is attached to the sealing member side, and a surface mounting type having a rated voltage of 4 V and a rated capacitance of 100 μF. Each 100 solid electrolytic capacitors were produced.

[0014]

[Table 1]

Table 1 shows the electrical characteristics (capacitance, ESR) of the solid electrolytic capacitors for surface mounting of Examples 1 to 4, the comparative example, and the conventional example, and the number of assembly failures due to collapse of the capacitor element shape.

As is clear from Table 1, Examples 1 to 4 are superior in electrical characteristics and less in defective assembly as compared with those using a conventional separator.

FIG. 1 is a characteristic diagram showing the relationship between the sisal fiber content in the separator and the ESR. FIG. 1 shows that the content of the sisal fiber in the separator is preferably 50 to 100%.

FIG. 2 is a characteristic diagram showing the relationship between the weight retention rate of the separator after heat treatment, the ESR and the defective assembly rate. FIG. 2 shows that the weight retention of the separator after the heat treatment was 0.1%.
It turns out that 30-0.70 is preferable. When the weight retention is 0.20, carbonization proceeds excessively, and there is a problem that defective assembly increases. When the weight retention is 0.80, carbonization is not sufficiently advanced, and the improvement of ESR is insufficient.

In the embodiment, PEDT is used as the solid electrolyte. However, even if polypyrrole, polyaniline, polythiophene or their derivatives are used, the same excellent characteristics can be obtained in both electric characteristics and assembly failure.

The method of forming the polymer is not particularly limited, and a single or a plurality of solid electrolytes may be formed by chemical polymerization. The solid electrolyte layer by chemical polymerization is used as a precoat layer, and power is supplied to the precoat layer. A solid electrolyte layer may be formed by electrolytic polymerization.

Further, in order to facilitate the operation of putting the capacitor element having the solid electrolyte formed in the case, a resin or the like may be applied or impregnated to the capacitor element after forming the solid electrolyte.

The fiber mixed with the sisal fiber is
Known fibers such as Manila hemp fiber, kraft fiber, and esparto fiber can be used.

[0023]

As described above, the solid electrolytic capacitor using the separator mainly composed of the sisal fiber according to the present invention and having a weight retention of 0.30 to 0.70 of the separator by carbonization has a shape of the capacitor element. Thus, the ESR characteristics at high frequencies can be improved without breaking down, and the industrial and practical value is great.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram of the content of sisal fiber and ESR contained in a separator.

FIG. 2 is a characteristic diagram of a weight retention ratio, an ESR, and a defective assembly ratio of a separator after heat treatment.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor, Kiichi Bessho, Nichicon Co., Ltd.

Claims (3)

[Claims] 1. A solid electrolytic capacitor obtained by heat-treating a capacitor element in which an anode foil and a cathode foil are wound via a separator and impregnating a solid electrolyte, wherein the separator mainly comprises sisal fibers, A solid electrolytic capacitor, wherein the weight of the separator is 0.30 to 0.70 times the weight before heat treatment. 2. The solid electrolytic capacitor according to claim 1, wherein said solid electrolyte is obtained by polymerizing at least one kind of pyrrole, aniline, thiophene or a derivative thereof. 3. A solid electrolytic capacitor according to claim 1, wherein the sisal fiber content of the separator is 50 to 100%.