JP3063640B2 - Solid electrolytic capacitor and method of manufacturing the same - Google Patents

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 using polyaniline or a derivative thereof as a solid electrolyte and having excellent high-frequency characteristics and high reliability, and a method for producing the same.

[0002]

2. Description of the Related Art Polyaniline and its derivatives are conductive polymers that exhibit high conductivity by using a protonic acid as a dopant, and have higher stability in the air than other conductive polymers such as polypyrrole. It is known to exhibit sex.

It is known that various inorganic acids (hydrochloric acid, sulfuric acid, etc.) or organic acids (carboxylic acid, sulfonic acid, organic phosphoric acid, etc.) can be used as the above-mentioned protonic acid. In addition, by using a sulfonic acid compound as a protonic acid, it is possible to obtain polyaniline and its derivative having particularly high conductivity and high heat resistance (Japanese Patent Application Laid-Open No. H06-1994).
No. 234852).

Although polyaniline having conductivity is generally insoluble in a solvent, a soluble polyaniline can be obtained by a special production method (Masao Abe (Masao Abe)).
Abe) et al., Journal of the Chemical Society, Chemical Communication (Journ)
al of the Chemical Society
y Chemical Communication
s), 1989, pp. 1736-1738).

[0005] Since polyaniline and its derivatives show excellent electrical properties, they may be widely used industrially and there are reports of many applications. As one of them, application to a solid electrolytic capacitor is known. By using highly conductive and highly reliable polyaniline or its derivative for the solid electrolyte of the solid electrolytic capacitor, a solid electrolytic capacitor that is small, has a large capacity, can maintain good capacitor characteristics up to a high frequency range, and has excellent heat resistance. It is known that this can be achieved.

Japanese Patent Application Laid-Open No. 62-029124 discloses a capacitor using polyaniline as a solid electrolyte with an arylsulfonic acid or the like as a dopant. As dopants in this case, arylsulfonic acid (toluenesulfonic acid, benzenesulfonic acid), tetracyanoethylene, 7,7,8,8-tetracyanoquinodimethane,
Alternatively, quinones are effective.

JP-A-64-24410 and JP-B-5-5
JP-83167 discloses a method for manufacturing a polyaniline solid capacitor, in which a sulfonic acid compound such as naphthalenedisulfonic acid or ethanedisulfonic acid is used as a polyaniline dopant.

Japanese Patent Application Laid-Open No. 5-041338 discloses that a polyaniline soluble in an organic solvent is used, a polyaniline solution is applied on a dielectric oxide film, the solvent is removed, and then doping is performed. An electrolytic capacitor using polyaniline as a solid electrolyte and a method for manufacturing the same are disclosed. In order to improve moisture resistance, polysulfonic acids having two or more sulfonic acid groups in the molecule (arylene disulfonic acid: naphthalenedisulfonic acid, benzenedisulfonic acid, etc., alkylenedisulfonic acid: ethanedisulfonic acid,
Propanedisulfonic acid, etc.) are disclosed as effective dopants.

Further, the present inventors have filed an application for a solid electrolytic capacitor using polyaniline synthesized by chemical polymerization using a sulfonic acid compound (such as a mono- or disulfonic acid compound) as a dopant and a method for producing the same ( JP-A-6-234852, Japanese Patent Application No. 6-1923
No. 53).

[0010]

The characteristics (conductivity, heat resistance, moisture resistance, etc.) of doped polyaniline and its derivative, and the characteristics of a solid electrolytic capacitor using doped polyaniline or its derivative as a solid electrolyte are as follows. It is known that it greatly depends on the chemical structure of sulfonic acid as a dopant of the derivative. In particular, when used for a solid electrolytic capacitor, long-term reliability under high-temperature conditions or high-temperature and high-humidity conditions, and heat resistance to soldering (230 to 260 ° C.) during mounting on a printed circuit board are serious problems.

By using a doped polyaniline material having higher reliability (high moisture resistance and high heat resistance) or higher conductivity for the solid electrolyte of the solid electrolytic capacitor, a solid electrolytic capacitor having higher reliability can be realized. .

As a solid electrolytic capacitor, there has been disclosed a capacitor using polyaniline as a solid electrolyte with an arylsulfonic acid as a dopant (Japanese Patent Application Laid-Open No. 62-029124). is not. In particular, moisture resistance and solder heat resistance required for mounting the capacitor on a printed circuit board (230 to 26
Thermal stability at 0 ° C.) is inadequate and needs to be improved.

JP-A-5-041338 discloses that (1) a capacitor using a special polyaniline soluble in an organic solvent as a solid electrolyte, and (2) a capacitor using polysulfonic acid as a dopant of the solid electrolyte polyaniline. It has been disclosed that the moisture resistance of the material can be remarkably improved. However, this manufacturing method can be applied to a widened aluminum foil which is usually used for an anode, but a high-viscosity tantalum sintered body has a penetration of a high-viscosity polymer solution into its fine pores. Is difficult to cover, and the appearance rate of the capacitance of the tantalum capacitor is low. Further, while the moisture resistance is improved, the conductivity and the high temperature heat resistance (260 ° C. or higher) are not practical. .

Accordingly, an object of the present invention is to provide a solid electrolytic capacitor using polyaniline or a derivative thereof as a solid electrolyte, and a polyaniline or a derivative thereof using a novel tetrasulfonic acid derivative having a structure in which two benzenedisulfonic acid derivatives are connected as a dopant. It is an object of the present invention to provide a solid electrolytic capacitor having low impedance in a high frequency region and further improved reliability, particularly under high-temperature and high-humidity conditions, by using as a solid electrolyte.

[0015]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object. As a result, a novel tetrasulfonic acid compound, that is, a tetrasulfonic acid derivative having a structure in which two benzenedisulfonic acid derivatives are linked to each other has been found to be useful, and has led to the present invention.
By using highly conductive polyaniline or a derivative thereof using these as a dopant for a solid electrolyte, a solid electrolytic capacitor having high performance (heat resistance and moisture resistance) was successfully obtained.

According to a first aspect of the present invention, there is provided a solid electrolytic capacitor in which a dielectric thin film is formed on an anode metal and a solid electrolyte is further formed on the dielectric thin film, wherein the solid electrolyte is formed by connecting two benzenedisulfonic acid derivatives. The present invention relates to a solid electrolytic capacitor comprising polyaniline or a derivative thereof using a tetrasulfonic acid derivative having a structure as a dopant.

The second invention relates to the solid electrolytic capacitor according to the first invention, wherein the tetrasulfonic acid derivative is a sulfonic acid derivative represented by the following structural formula (I).

[0018]

Embedded image (X is S, SO ₂ , O, Se, Te, NH, CO, C
H ₂ , C ₂ H ₄ , or a single bond. In a third aspect, the tetrasulfonic acid derivative is diphenyl ether-2,2 ′, 4,4′-tetrasulfonic acid,
Alternatively, the present invention relates to a solid electrolytic capacitor according to the first invention, which is biphenyl-2,2 ′, 4,4′-tetrasulfonic acid.

According to a fourth aspect of the present invention, in the first and second aspects, the anode metal is tantalum, and the solid electrolyte is polyaniline.
Alternatively, the present invention relates to a solid electrolytic capacitor according to a third aspect.

According to a fifth aspect of the present invention, there is provided the method for manufacturing a solid electrolytic capacitor according to the first aspect, wherein the polyaniline or the derivative thereof is formed by using an oxidizing agent on the surface of the anode metal on which the dielectric thin film is formed. And a method for producing a solid electrolytic capacitor, which is carried out by a method of oxidative polymerization.

According to a sixth aspect, aniline or an aniline derivative is introduced on the surface of the metal anode on which the dielectric thin film is formed,
Thereafter, an oxidizing agent is introduced, and oxidative polymerization is performed to form polyaniline or a derivative thereof.

The seventh invention relates to the method for producing a solid electrolytic capacitor according to the fifth or sixth invention, wherein the tetrasulfonic acid derivative is a sulfonic acid derivative represented by the structural formula (I).

An eighth invention is directed to the fifth invention, wherein the tetrasulfonic acid derivative is diphenyl ether-2,2 ', 4,4'-tetrasulfonic acid or biphenyl-2,2', 4,4'-tetrasulfonic acid. Alternatively, the present invention relates to a method for manufacturing a solid electrolytic capacitor according to a sixth aspect.

The ninth invention relates to the method for producing a solid electrolytic capacitor according to any one of the fifth to eighth inventions, wherein the anode metal is tantalum and the solid electrolyte is polyaniline.

A tenth invention relates to the method for producing a solid electrolytic capacitor according to any one of the fifth to ninth inventions, wherein the oxidizing agent is a peroxodisulfate.

The polyaniline or the derivative thereof using the novel tetrasulfonic acid derivative as a dopant according to the present invention is characterized by a sulfonic acid compound having a structure in which two benzenedisulfonic acid derivatives having a rigid skeleton in the molecule are linked. Is used as a dopant, high conductivity and high heat resistance can be expected. Further, since a sulfonic acid compound having a plurality of sulfonic acid groups in the same molecule is used as a dopant, good moisture resistance can be expected.

[0027]

Embodiments of the present invention will be described below in detail.

The tetrasulfonic acid derivative used in the present invention is a sulfonic acid compound having a structure in which two benzenedisulfonic acid derivatives are linked, and is obtained by substituting the benzene nucleus of the benzenedisulfonic acid derivative with various substituents. Including.

In the present invention, the polyaniline derivatives include those having various substituents on the benzene nucleus of polyaniline. Examples of the substituent include an alkyl group, a phenyl group, an alkoxy group, an ester group, and a thioether group. The polyaniline derivative includes a copolymer comprising one to four substituents or one to four substituents of these substituents. Further, the polyaniline derivatives include those substituted at the N-position with the above substituent. However, since polyaniline provides higher conductivity, polyaniline is preferable to these derivatives.

In the present invention, when polyaniline or a derivative thereof doped with a tetrasulfonic acid derivative dopant is formed as an electrolyte of a solid electrolytic capacitor, for example, the method disclosed by the present inventors in JP-A-6-234852 is used. It is more preferable to synthesize. That is, for example, it is obtained by oxidative polymerization of aniline using an oxidizing agent in an aqueous solution containing 10 to 50% by weight of a tetrasulfonic acid derivative.

The oxidizing agent used for the aniline polymerization is not particularly limited, and a conventionally known oxidizing agent can be used. For example, ammonium peroxodisulfate, potassium dichromate, sodium dichromate, ammonium dichromate, hydrogen peroxide, potassium permanganate, sodium permanganate, ammonium permanganate, ferric chloride, ferric sulfonate , Cupric chloride sulfonate,
Lead oxide, potassium perchlorate, sodium perchlorate, ammonium perchlorate, potassium periodate, sodium periodate, ammonium periodate and the like can be used.

The oxidizing agent preferably satisfies the condition that in the process of oxidizing aniline or a derivative thereof, the pKa value of a by-product generated from the oxidizing agent after accepting electrons is equal to or higher than the pKa value of protonic acid. Specifically, potassium dichromate, sodium dichromate, ammonium dichromate, aqueous hydrogen peroxide, potassium permanganate, sodium permanganate, ammonium permanganate, ferric sulfonate, cupric sulfonate, oxide Lead and the like are preferred.

As the oxidizing agent, ammonium peroxodisulfate is preferable. By using ammonium peroxodisulfate as an oxidizing agent according to the method described in Japanese Patent Application No. 7-289461, highly heat-resistant polyaniline or a derivative thereof can be obtained.

In forming polyaniline and its derivatives to be used as a capacitor electrolyte, the solvent for polymerizing aniline or its derivatives is not particularly limited, but those having high polarity are preferable. For example, water, acetone, ethanol, methanol, tetrahydrofuran, toluene, acetonitrile, nitrobenzene, chloroform, dichloroethane,
Various halogenated ethers, various halogenated esters, cresol, etc., or a mixture thereof are used.

The solid electrolytic capacitor of the present invention has a structure in which a film-forming metal is used as an anode, a dielectric thin film such as an oxide film is formed thereon, and a solid electrolyte is formed thereon.

The film-forming metal used for the anode in the solid electrolytic capacitor of the present invention includes tantalum, aluminum,
Niobium, titanium, zirconium, magnesium, silicon and the like can be used in the form of a rolled foil and a fine powder sintered product. Among them, it is preferable to use tantalum, which can easily obtain excellent leakage current characteristics.

In the production of the solid electrolytic capacitor of the present invention, the above film-forming metal is anodically oxidized in an electrolyte solution to form an oxide film serving as a dielectric. However, the electrolyte and the solvent used are not particularly limited, and are conventionally known. Anything can be used.
In addition, a constant voltage method or a constant current method can be applied as a method of anodic oxidation, and the method of increasing the voltage / current, the holding time after the voltage becomes constant, the temperature, etc. are not limited and can be set as necessary. can do.

In the solid electrolytic capacitor of the present invention, the anode metal provided with the dielectric thin film is heat-treated at a predetermined temperature and a predetermined atmosphere in order to improve characteristics such as a capacitance appearance ratio and an equivalent series resistance of the capacitor. The anode metal may be subjected to various surface treatments.

The method of polymerizing aniline or a derivative thereof during the production of the solid electrolytic capacitor of the present invention is not particularly limited.
It is desirable that polyaniline or a derivative thereof be formed on the surface of the anode metal on which the dielectric thin film is formed by an oxidative polymerization method using an oxidizing agent. According to this method, even when formed on a porous formed body such as a sintered body of tantalum or the like, a film can be easily formed in the fine pores, and excellent capacitor characteristics (capacity appearance rate, etc.) ) Can be obtained.

As such a method, an oxidizing agent or a mixture of an oxidizing agent and a tetrasulfonic acid derivative, as it is or dissolved in an appropriate solvent, is introduced into a porous forming body of a film forming metal having an oxide film formed thereon. After that, a method of contacting with a gas or a solution of aniline or a mixture of aniline and a tetrasulfonic acid derivative, or introducing aniline or a mixture of aniline and a tetrasulfonic acid derivative into a porous formed body of a film-forming metal first After that, a method of contacting with an oxidizing agent or a mixture of an oxidizing agent and a tetrasulfonic acid derivative may, for example, be mentioned.

In the above method, after the polymerization is completed, the capacitor element can be washed with water or a solvent in which the oxidizing agent is easily soluble to remove the oxidizing agent that does not contribute to the conductivity. Further, each step of the above-mentioned polymerization operation, washing and the like can be repeated.

After the formation of the electrolyte polyaniline, drying is carried out if necessary, then a silver layer and a graphite layer are formed, and a lead electrode is provided by a usual method and assembled into a capacitor. In the present invention, the silver layer and the graphite layer are not particularly limited, and conventionally known layers can be used.

In the present invention, polyaniline or a derivative thereof using a tetrasulfonic acid derivative as a dopant is excellent in heat resistance and moisture resistance, and it has been confirmed that a capacitor using the same as a solid electrolyte has good moisture resistance and heat resistance. .

[0044]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Examples 1 to 10 show examples of a capacitor using polyaniline using a tetrasulfonic acid derivative as a dopant or its derivative as a solid electrolyte, and a method for manufacturing the same. In addition, the solid electrolytic capacitors using the polyaniline manufactured by the conventional technology are compared with Comparative Examples 1 to 5.
3 is shown.

The conductivity of polyaniline or its derivative was measured as follows. 4.5 using IR tablet press
A polyaniline pellet was prepared by applying a pressure of × 10 ⁴ ton / m ² , and then cut into 10 mm × 1 mm strips and subjected to conductivity measurement. The conductivity of polyaniline was measured by a four-terminal method. Apply a constant current from the stabilized power supply to the current terminal,
The voltage between the voltage terminals was measured to determine the conductivity. The measurement was performed at room temperature under reduced pressure.

Thermogravimetric analysis of polyaniline was performed using TG-DTA2000 manufactured by Mac Science Corporation. In the air or nitrogen atmosphere, the heating rate is 1
The measurement was performed at 0 ° C./min in a temperature range of 25 to 700 ° C.

The heat resistance is measured in nitrogen or air.
After leaving a strip of polyaniline in an oven set to a predetermined temperature for a predetermined time, the strip was taken out and evaluated by measuring its conductivity.

The solder heat resistance was evaluated by wrapping a strip of polyaniline in aluminum foil, immersing it in a solder bath at 240 ° C. or 260 ° C., taking it out after a predetermined time, and measuring the conductivity.

In the water resistance test, about 0.5 g of polyaniline was dispersed in 1 L of pure water at room temperature (25 ° C.), and after a predetermined time, about 0.05 g of polyaniline was taken out and used for conductivity measurement. did.

The frequency characteristics of the capacitor were measured using an impedance analyzer 4194A manufactured by Yokogawa-Hewlett-Packard Co., Ltd.

The heat resistance and solder heat resistance of the capacitor were evaluated in the same manner as in the case of the polyaniline material. In the case of solder heat resistance, the capacitor was directly immersed in the solder bath for a predetermined time.

(Example 1) <Polyaniline using diphenylethertetrasulfonic acid as a dopant and a tantalum solid electrolytic capacitor using the same as a solid electrolyte> Diphenylethertetrasulfonic acid is obtained by connecting two benzenedisulfonic acids with an ether group. The molecular structure is shown by the following formula.

[0054]

Embedded image

Synthesis of Polyaniline 11.1 ml of an aqueous solution of a tetrasulfonic acid derivative (N = 3.90 in terms of sulfonic acid group) was dropped into 120 ml of an aqueous solution, and 2.0 g of an aniline monomer was added and dissolved with stirring. 3. The ammonium peroxodisulfate is maintained at 2-5 ° C. in an ice bath with vigorous stirring.
30 mmol of an aqueous solution in which 6 g had previously been dissolved was added dropwise. The reaction took place after about 30 minutes, and the reaction solution gradually turned deep blue-green. Thereafter, the reaction was further performed with stirring for 3 hours. The obtained product was filtered and washed, then dispersed in 1 L of pure water, stirred for 30 minutes, and then filtered. This operation was repeated twice. The polyaniline thus washed with pure water was further dispersed in 500 ml of methanol, stirred for 30 minutes, and then filtered and dried. The obtained polyaniline is 2.
7 g. The conductivity initial value was 2.7 S / cm.

Preparation of Capacitor A cylindrical tantalum fine powder sintered pellet having a diameter of 1.5 mm, a height of 2 mm, and a powder CV value per gram (the product of the capacity and the formation voltage) of 30,000 CV / g was added to 0.05 wt% nitric acid. After being anodized at 60 V in an aqueous solution, it was washed and dried.

The tantalum pellets were first immersed at room temperature in a water / ethanol (1: 1) solution of aniline and 5 wt% aniline containing equal amounts of diphenyl ether tetrasulfonic acid for 30 seconds. After 5 minutes, an oxidizing agent containing ammonium peroxodisulfate and diphenyl ether tetrasulfonic acid (the molar ratio of ammonium peroxodisulfate / diphenylethertetrasulfonic acid is 1: 1 and the content of ammonium peroxodisulfate is 10% by weight) maintained at 0 ° C. It was immersed in the aqueous solution for 30 seconds. The tantalum pellets were taken out and kept in the air for further 10 minutes to carry out polymerization. Thereafter, the resultant was washed with water and ethanol and dried under reduced pressure, whereby black polyaniline was formed on the surface of the dielectric.

A series of operations of filling the aniline, contacting with the oxidizing agent solution, polymerization, washing and drying were repeated five times. After that, a graphite paste and a silver paste were sequentially applied, the cathode lead was pulled out, and sealed with an epoxy resin to complete the capacitor.

Comparative Example 1 <Polyaniline Using Toluenesulfonic Acid As A Dopant And Tantalum Solid Electrolytic Capacitor Using It As A Solid Electrolyte> Except for using toluenesulfonic acid instead of diphenylethertetrasulfonic acid in Example 1, Polyaniline was synthesized in exactly the same manner as in Example 1. The yield of the resulting polyaniline was 2.6 g. The conductivity initial value (σ) was 0.2 S / cm. Further, a tantalum solid electrolytic capacitor using polyaniline as a solid electrolyte was produced in exactly the same manner as in Example 1.

(Comparative Example 2) <Polyaniline using benzenedisulfonic acid as a dopant and tantalum solid electrolytic capacitor using the same as a solid electrolyte> A benzenedisulfonic acid was used in place of diphenylethertetrasulfonic acid in Example 1. Polyaniline was synthesized in exactly the same manner as in Example 1. The yield of the resulting polyaniline was 2.7 g. The initial conductivity value was 2.1 S / cm. Further, a tantalum solid electrolytic capacitor using polyaniline as a solid electrolyte was produced in exactly the same manner as in Example 1.

(Comparative Example 3) <Polyaniline using polystyrenesulfonic acid as a dopant and tantalum solid electrolytic capacitor using the same as a solid electrolyte> A polyaniline was used in place of diphenylethertetrasulfonic acid in Example 1 except that polystyrenesulfonic acid was used. Polyaniline was synthesized in exactly the same manner as in Example 1. The yield of the obtained polyaniline was 2.8 g. The initial conductivity value was 0.2 S / cm. Further, when a tantalum solid electrolytic capacitor using polyaniline as a solid electrolyte was produced in exactly the same manner as in Example 1, the capacitance appearance rate was 5%.
Since it was 0% or less and sufficient performance as a capacitor was not recognized, the evaluation of various characteristics of the polyaniline electrolyte and the evaluation of the reliability of the capacitor were not further performed.

FIG. 1 shows the results obtained by dispersing polyaniline powder using toluenesulfonic acid, benzenedisulfonic acid and diphenylethertetrasulfonic acid as dopants in a large excess of water and measuring the conductivity after a predetermined time (water resistance). Sex evaluation). From FIG. 1, it can be seen that the conductivity of polyaniline using diphenylethertetrasulfonic acid as a dopant is significantly suppressed by dedoping in water, and the water resistance is higher than that of conventional polyaniline using toluenesulfonic acid or benzenedisulfonic acid as a dopant. It turns out that it is excellent.

Elemental analysis was performed on a part of the evaluation samples, and the results are summarized in Tables 1 to 3. FIG. 2
2 shows the relationship between the molar ratio of S / N reflecting the dopant concentration of polyaniline and the time for dispersing polyaniline in water. From FIG. 2, it can be seen that the decrease in conductivity of polyaniline dispersed in water is due to the elimination of dopants,
Further, it can be seen that the elimination of the dopant is significantly suppressed when diphenyl ether tetrasulfonic acid is used.

[0064]

[Table 1]

[0065]

[Table 2]

[0066]

[Table 3]

FIG. 3 shows one example of polyaniline (Example 1) using diphenyl ether tetrasulfonic acid as a dopant.
The change with time in conductivity at 25 ° C. is shown (heat resistance evaluation). The conductivity of polyaniline once increased initially in a nitrogen atmosphere, and then decreased with time, but to a lesser extent. Although reduced in the air, it exhibited superior heat resistance as compared with polythiophene, polypyrrole, and conventional polyaniline.

FIG. 4 shows the results of thermogravimetric analysis of polyaniline (Example 1) using diphenyl ether tetrasulfonic acid as a dopant. The pyrolysis initiation temperature was 300 ° C. or higher in both nitrogen and air, indicating good heat resistance.

Table 4 summarizes the results of the soldering heat test of polyaniline using diphenylethertetrasulfonic acid as a dopant (Example 1) in comparison with the results of conventional polyaniline (Comparative Examples 2 and 3). It can be seen that this polyaniline has excellent high temperature heat resistance.

[0070]

[Table 4]

(Example 2) <Tantalum solid electrolytic capacitor using polyaniline as a solid electrolyte using diphenyl ether tetrasulfonic acid as a dopant> Tantalum pellets were prepared in the same manner as in Example 1.

On the other hand, water / ethanol (30: 7 by volume)
0) Diphenyl ether tetrasulfonic acid, aniline, and ammonium peroxodisulfate were sequentially charged into the mixed solvent of 1) while stirring so that the aniline concentration became 5 wt% at a molar ratio of 1: 1: 1 to prepare a mixed reaction solution. The temperature was reduced to -40C. Next, the tantalum pellet on which the dielectric layer was formed was immersed in the above mixed solution for 30 seconds, filled with the reaction solution, taken out, and kept at room temperature for 30 minutes to perform polymerization. Thereafter, the resultant was washed with water and ethanol and dried under reduced pressure, whereby black polyaniline was formed on the surface of the dielectric.

After filling, polymerization, washing and drying of the above reaction solution were repeated three times, a graphite paste and a silver paste were sequentially applied, a cathode lead was pulled out, and a capacitor was completed by sealing with an epoxy resin.

(Example 3) <Aluminum solid electrolytic capacitor using polyaniline as a solid electrolyte with diphenyl ether tetrasulfonic acid as a dopant> A 150 μm thick aluminum foil (1 cm × 0.5 mm) whose surface area was enlarged almost 20 times by etching.
cm square) was anodized at 70 V in a 5% aqueous solution of ammonium borate, washed and dried. A capacitor was produced in exactly the same manner except that the aluminum foil was used in place of the tantalum fine powder sintered compact pellets of Example 1.

(Example 4) <Polyaniline using biphenyltetrasulfonic acid as a dopant and tantalum solid electrolytic capacitor using the same as a solid electrolyte> Biphenyltetrasulfonic acid is one in which two benzenedisulfonic acids are directly connected. The molecular structure is shown below.

[0076]

Embedded image

A polyaniline was synthesized and a tantalum solid electrolytic capacitor was produced in the same manner as in Example 1, except that biphenyltetrasulfonic acid was used in place of diphenylethertetrasulfonic acid in Example 1. The yield of polyaniline was 2.6 g. The initial value of the conductivity was 2.7 S / cm.

As a result of evaluating the water resistance, heat resistance and solder heat resistance of polyaniline using biphenyltetrasulfonic acid as a dopant, it was found that the polyaniline exhibited properties equivalent to those of polyaniline using diphenylethertetrasulfonic acid as a dopant.

(Example 5) <Polyaniline using diphenylthioethertetrasulfonic acid as a dopant and a tantalum solid electrolytic capacitor using the same as a solid electrolyte> Diphenylthioethertetrasulfonic acid is obtained by linking two benzenedisulfonic acids with a thioether group. The molecular structure is shown by the following formula.

[0080]

Embedded image

A polyaniline was synthesized and a tantalum solid electrolytic capacitor was manufactured in the same manner as in Example 1 except that diphenylthioethertetrasulfonic acid was used instead of diphenylethertetrasulfonic acid. The yield of polyaniline was 2.6 g. The initial value of the conductivity was 1.8 S / cm.

The water resistance, heat resistance and solder heat resistance of polyaniline using diphenylthioethertetrasulfonic acid as a dopant were evaluated. As a result, it was found that the polyaniline exhibited characteristics equivalent to those of polyaniline using diphenylethertetrasulfonic acid as a dopant.

(Example 6) <Polyaniline using diphenylsulfonetetrasulfonic acid as a dopant and a tantalum solid electrolytic capacitor using the same as a solid electrolyte> Diphenylsulfonetetrasulfonic acid is obtained by linking two benzenedisulfonic acids with a sulfonyl group. The molecular structure is shown by the following formula.

[0084]

Embedded image

A polyaniline was synthesized and a tantalum solid electrolytic capacitor was manufactured in the same manner as in Example 1 except that diphenylsulfonetetrasulfonic acid was used instead of diphenylethertetrasulfonic acid. The yield of polyaniline was 2.5 g. The initial value of the conductivity was 1.5 S / cm.

The water resistance, heat resistance and solder heat resistance of polyaniline using diphenylsulfonetetrasulfonic acid as a dopant were evaluated. As a result, it was found that the polyaniline exhibited properties equivalent to those of polyaniline using diphenylethertetrasulfonic acid as a dopant.

(Example 7) <Polyaniline using benzophenonetetrasulfonic acid as a dopant and a tantalum solid electrolytic capacitor using the same as a solid electrolyte>
Two benzenedisulfonic acids are linked by a carbonyl group, and the molecular structure is shown by the following formula.

[0088]

Embedded image

A polyaniline was synthesized and a tantalum solid electrolytic capacitor was produced in the same manner as in Example 1 except that benzophenonetetrasulfonic acid was used instead of diphenylethertetrasulfonic acid in Example 1. The yield of polyaniline was 2.7 g. The initial value of the conductivity was 2.0 S / cm.

The water resistance, heat resistance and solder heat resistance of polyaniline using benzophenonetetrasulfonic acid as a dopant were evaluated. As a result, it was found that the polyaniline exhibited characteristics equivalent to those of polyaniline using diphenylethertetrasulfonic acid as a dopant.

(Example 8) <Polyaniline using diphenylmethanetetrasulfonic acid as a dopant and tantalum solid electrolytic capacitor using the same as a solid electrolyte> Diphenylmethanetetrasulfonic acid is obtained by connecting two benzenedisulfonic acids with a methylene group. The molecular structure is shown below.

[0092]

Embedded image

A polyaniline was synthesized and a tantalum solid electrolytic capacitor was manufactured in the same manner as in Example 1, except that diphenylmethanetetrasulfonic acid was used instead of diphenylethertetrasulfonic acid.
The yield of polyaniline was 2.6 g. The initial value of the conductivity was 1.1 S / cm.

As a result of evaluating the water resistance, heat resistance and solder heat resistance of polyaniline using diphenylmethanetetrasulfonic acid as a dopant, it was found that the polyaniline exhibited characteristics equivalent to those of polyaniline using diphenylethertetrasulfonic acid as a dopant.

(Example 9) <Poly (orthoethoxyaniline) using diphenylethertetrasulfonic acid as a dopant and a tantalum solid electrolytic capacitor using it as a solid electrolyte> Orthoethoxyaniline was used in place of aniline in Example 1. Except for the above, a polyaniline derivative was synthesized and a tantalum solid electrolytic capacitor was manufactured in the same manner as in Example 1.
The yield of poly (orthoethoxyaniline) was 2.8 g. The initial value of the conductivity was 0.3 S / cm.

The water resistance, heat resistance and solder heat resistance of this polyaniline were evaluated. As a result, it was found that the polyaniline exhibited properties equivalent to those of the polyaniline of Example 1 using diphenylethertetrasulfonic acid as a dopant.

(Example 10) <Polyaniline using diphenylethertetrasulfonic acid as a dopant and tantalum solid electrolytic capacitor using the same as a solid electrolyte> Synthesis of polyaniline An aqueous solution of a tetrasulfonic acid compound (in terms of sulfonic acid group) was added to a 120 ml aqueous solution. (N = 3.90) 22.2 ml was added dropwise, and 2.0 g of an aniline monomer was added and dissolved with stirring. While the solution was kept at 2 to 5 ° C. in an ice bath and vigorously stirred, 30 mmol of an aqueous solution in which 1.9 g of ammonium dichromate was previously dissolved was added dropwise. The reaction was performed with stirring for 3 hours. The obtained product was filtered and washed, then dispersed in 1 L of pure water, stirred for 30 minutes, and then filtered. This operation was repeated twice. The polyaniline thus washed with pure water was further dispersed in 500 ml of methanol, stirred for 30 minutes, and then filtered and dried. The obtained polyaniline was 2.8 g. The initial value of the conductivity was 2.5 S / cm.

The water resistance, heat resistance and solder heat resistance of this polyaniline were evaluated. As a result, it was found that the polyaniline exhibited characteristics equivalent to those of the polyaniline prepared in Example 1 using ammonium peroxodisulfate as an oxidizing agent.

Preparation of Capacitor A tantalum pellet similar to that in Example 1 was first immersed in a water / ethanol (1: 1) solution of aniline and 5 wt% aniline containing equal amounts of diphenyl ether tetrasulfonic acid for 30 seconds at room temperature. After 5 minutes, an oxidizing agent containing ammonium dichromate and diphenyl ether tetrasulfonic acid (the molar ratio of ammonium dichromate / diphenyl ether tetrasulfonic acid is 1: 2 and the content of ammonium dichromate is 10 wt%) kept at 0 ° C. 3 in aqueous solution
Dipped for 0 seconds. The tantalum pellets were taken out and kept in the air for further 10 minutes to carry out polymerization. Then water,
After washing with ethanol and drying under reduced pressure, black polyaniline was formed on the dielectric surface.

A series of operations of charging the aniline, contacting with the oxidizing agent solution, polymerization, washing and drying was repeated 5 times. After that, a graphite paste and a silver paste were sequentially applied, the cathode lead was pulled out, and sealed with an epoxy resin to complete the capacitor.

FIGS. 5 and 6 show the frequency characteristics of the capacitance and impedance of the solid electrolytic capacitor obtained in Example 1 in comparison with a conventional capacitor using manganese dioxide as an electrolyte. It can be seen that the impedance in the high frequency range of the solid electrolytic capacitor of the present invention is remarkably improved as compared with a conventional capacitor using manganese dioxide as an electrolyte, and the frequency characteristics are excellent.

Table 5 shows that Examples 1 to 10 and Reference Examples 1 and 2 were obtained immediately after the capacitor was manufactured and at 260 ° C.
Capacity appearance rate after 100 seconds treatment (after soldering) (100 × C /
C. (%), C. : Volume in electrolyte solution), and 1
The equivalent series resistance (R) at 00 kHz is shown. Table 6
Under the conditions of 125 ° C. and 80 ° C./95% RH, 500
5 shows a change in the frequency characteristic of the capacitor after time.
From these results, the capacitor obtained by the example of the present invention has a small equivalent series resistance and good high frequency characteristics, and has almost no deterioration in characteristics even at a solder test at 260 ° C. for 10 seconds. In particular, it was confirmed that the composition had excellent reliability under high temperature and high humidity conditions.

[0103]

[Table 5]

[0104]

[Table 6]

FIG. 7 is a diagram schematically showing a cross-sectional structure of a solid electrolytic capacitor manufactured according to an embodiment of the present invention. The surface of the metal foil 1 serving as an anode is etched or a metal is sintered to form a large number of micropores to increase the surface area. The metal oxide dielectric thin film 2 is formed along the pore wall surface of this surface. The polyaniline layer 3 of the solid electrolyte of the present invention is formed on the surface of the dielectric thin film 2 so as to penetrate deep into the pores. A metal electrode 5 serving as a cathode is attached to the opposite side of the solid electrolyte layer 3. A graphite layer 4 may be used between the electrode 5 and the polyaniline layer 3 in order to maintain good contact. Electrode leads 6 and 7 are attached.

FIG. 8 shows an overall configuration of an example of a method for manufacturing a solid electrolytic capacitor according to the present invention. When the metal 1 serving as the anode is an aluminum foil, the aluminum foil is etched to form many pores on the surface. When the metal 1 serving as the anode is a tantalum powder, the tantalum powder is pressed into a sintered body. Then
The metal foil or the sintered body is subjected to chemical conversion to form an oxide film serving as a dielectric. Thereafter, polyaniline serving as a solid electrolyte is formed, and the dopant concentration of the electrolyte is set to a predetermined value. Subsequently, a carbon paste and a silver paste are applied and baked, lead wires are connected, and finally sealing is performed to obtain a product.

[0107]

As is apparent from the above description, according to the present invention, it is possible to provide a solid electrolytic capacitor having excellent high-frequency characteristics and high reliability under high temperature and high humidity conditions.

[Brief description of the drawings]

FIG. 1 is a graph showing the water resistance (change in conductivity over time) of a solid electrolyte used in the present invention and a conventional solid electrolytic capacitor.

FIG. 2 is a graph showing the water resistance (change in dopant concentration over time) of a solid electrolyte used in the present invention and a conventional solid electrolytic capacitor.

FIG. 3 is a graph showing the heat resistance (change in conductivity over time) of a solid electrolyte used in the solid electrolytic capacitor of the present invention.

FIG. 4 is a graph showing a thermogravimetric analysis result of a solid electrolyte used for the solid electrolytic capacitor of the present invention.

FIG. 5 is a graph showing frequency characteristics of capacitance and tan delta of the solid electrolytic capacitor of the present invention and a conventional solid electrolytic capacitor.

FIG. 6 is a graph showing frequency characteristics of resistance and impedance of the solid electrolytic capacitor of the present invention and a conventional solid electrolytic capacitor.

FIG. 7 is a schematic cross-sectional view showing a structure of a solid electrolytic capacitor manufactured according to an example of the present invention.

FIG. 8 is a process chart showing an example of a method for manufacturing a solid electrolytic capacitor of the present invention.

[Description of Signs] 1 Metal foil or sintered body 2 Dielectric thin film 3 Electrolyte polyaniline layer 4 Graphite layer 5 Silver layer 6, 7 Electrode lead

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Etsuo Hasegawa 5-7-1 Shiba, Minato-ku, Tokyo Within NEC Corporation (56) References JP-A-4-48710 (JP, A) (58) Survey Field (Int.Cl. ⁷ , DB name) H01G 9/028

Claims (10)

(57) [Claims] 1. A solid electrolytic capacitor comprising a dielectric thin film formed on an anode metal and a solid electrolyte formed thereon, wherein the solid electrolyte has a structure in which two benzenedisulfonic acid derivatives are connected. A solid electrolytic capacitor comprising polyaniline or a derivative thereof using a sulfonic acid derivative as a dopant. 2. The solid electrolytic capacitor according to claim 1, wherein said tetrasulfonic acid derivative is a sulfonic acid derivative represented by the following structural formula (I). Embedded image (X is S, SO ₂ , O, Se, Te, NH, CO, C
H ₂ , C ₂ H ₄ , or a single bond. ) 3. The method according to claim 1, wherein the tetrasulfonic acid derivative is diphenyl ether-2,2 ′, 4,4′-tetrasulfonic acid,
2. The solid electrolytic capacitor according to claim 1, wherein the solid electrolytic capacitor is biphenyl-2,2 ', 4,4'-tetrasulfonic acid. 4. The solid electrolytic capacitor according to claim 1, wherein said anode metal is tantalum, and said solid electrolyte is polyaniline. 5. The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein said polyaniline or a derivative thereof is formed by oxidative polymerization using an oxidizing agent on an anode metal surface on which a dielectric thin film is formed. A method for producing a solid electrolytic capacitor, which is performed by a method. 6. An aniline or aniline derivative is introduced on the surface of the metal anode on which the dielectric thin film is formed, and then an oxidizing agent is introduced and oxidative polymerization is performed to form polyaniline or a derivative thereof. Claim 5
The manufacturing method of the solid electrolytic capacitor described in the above. 7. The tetrasulfonic acid derivative represented by the structural formula (I)
The method for producing a solid electrolytic capacitor according to claim 5, which is a sulfonic acid derivative represented by the following formula: 8. The tetrasulfonic acid derivative is diphenyl ether-2,2 ′, 4,4′-tetrasulfonic acid or biphenyl-2,2 ′, 4,4′-tetrasulfonic acid. Method for manufacturing solid electrolytic capacitor. 9. The method for manufacturing a solid electrolytic capacitor according to claim 5, wherein the anode metal is tantalum, and the solid electrolyte is polyaniline. 10. The method for producing a solid electrolytic capacitor according to claim 5, wherein the oxidizing agent is a peroxodisulfate.