JPH11176698A - Solid electrolytic capacitor and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid electrolytic capacitor having improved frequency characteristics, good heat resistance, and an improved life and a manufacturing method therefor. SOLUTION: A solid electrolytic capacitor 12 includes an oxide film 4 attached to a sintered body comprising valve-acting metal powder, and solid electrolytic layers 5 comprising conductive polymer and laminated on the oxide film 4 inside and outside the sintered body, wherein conductivity is imparted to the conductive polymer, by bonding dopants to conjugated polymer. The solid electrolytic layer 5 outside the sintered body contains a higher concentration of dopant than that inside the sintered body.

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 having improved frequency characteristics and heat resistance, and a method for manufacturing the same.

[0002]

2. Description of the Related Art A solid electrolytic capacitor such as a tantalum solid electrolytic capacitor forms an oxide film by forming a sintered body of a valve metal such as aluminum or tantalum, and then forming an oxide film.
An element having a structure in which a solid electrolyte film is laminated on the surface of the oxide film and a carbon layer or a silver layer is formed on the surface of the film is used. The solid electrolyte layer laminated on the surface of the oxide film electrically connects the oxide film inside the sintered body to the external cathode, and also repairs an electrical short circuit caused by a defect in the oxide film. have.

[0003] In general, electronic devices tend to be smaller and more sophisticated. For this reason, a small and highly reliable capacitor is required to be incorporated in an electronic device, and a solid electrolytic capacitor is used to meet the demand. As a solid electrolytic capacitor, a type commonly used in the related art has a structure in which a solid electrolyte layer is formed of manganese dioxide which changes into an insulator due to heat or the like due to short-circuit current.
However, manganese dioxide has relatively low conductivity. For this reason, a solid electrolytic capacitor using manganese dioxide as a solid electrolyte layer has a large impedance particularly in a high frequency region.

Conventionally, in order to improve the characteristics and the like in the high frequency region, instead of manganese dioxide, electron conjugated polymers such as polyacetylene, polyparaphenylene, polypyrrole, polyvinylene, polyphenylenevinylene, polyaniline and the like have an electron donating property and an electron donating property. BACKGROUND ART A solid electrolytic capacitor having a structure in which a solid electrolyte layer is formed using a conductive polymer to which a compound having a suction property (hereinafter referred to as a dopant) is added has been developed.

[0005]

However, a solid electrolytic capacitor having a solid electrolyte layer made of a conductive polymer is
Currently, many are under development and have various advantages as well as advantages. For example, polypyrrole, a kind of conductive polymer, has high conductivity but low heat resistance. For this reason, a solid electrolytic capacitor using polypyrrole as a solid electrolyte can improve the frequency characteristics, but has a disadvantage that it has low heat resistance and is easily deteriorated by heat. In addition, the solid electrolyte layer made of a conductive polymer generally contains a low molecular weight substance and a by-product in addition to the conductive polymer. For this reason, there is a drawback that the effect of reducing the equivalent series resistance (hereinafter, referred to as ESR), which is an excellent property of the conductive polymer, and improving the high frequency characteristics cannot be sufficiently obtained. In addition, there is a disadvantage that the characteristics easily change in a high-temperature atmosphere.

An object of the present invention is to provide a solid electrolytic capacitor capable of improving the above-mentioned drawbacks, improving the frequency characteristics, having excellent heat resistance, and improving the life, and a method of manufacturing the same.

[0007]

According to a first aspect of the present invention, an oxide film is provided on a sintered body made of a valve metal powder, and an electronic film is laminated on the oxide film. In a solid electrolytic capacitor in which a solid electrolyte layer made of a conductive polymer provided with conductivity by bonding a dopant to a conjugated polymer is provided on the inside and the surface of the sintered body, the surface of the solid body is higher than the inner side of the sintered body. An object of the present invention is to provide a solid electrolytic capacitor having a solid electrolyte layer with a higher dopant concentration on the side.

According to the first aspect of the present invention, a solid electrolyte layer made of a conductive polymer is laminated on an oxide film, and the concentration of the dopant contained in a portion of the solid electrolyte layer closer to the surface than the inside of the sintered body. Especially high. For this reason, the electric conductivity of the solid electrolyte layer can be increased. Therefore, the ESR of the solid electrolyte layer can be reduced in a wide frequency range from a low frequency to a high frequency, the frequency characteristics of the solid electrolytic capacitor can be improved, and the heat resistance can be improved.

According to a second aspect of the present invention, after a solid electrolyte layer made of a conductive polymer is laminated on an oxide film, the dopant is bonded to the conductive polymer using a solution containing the dopant having a pH of less than 3. It is intended to provide a method for producing a solid electrolytic capacitor by processing.

According to the present invention, the device after forming the solid electrolyte layer comprising the oxide film and the conductive polymer on the valve metal is immersed in a solution containing a dopant having a pH of less than 3, By spraying the liquid or the like, by-products contained in the conductive polymer are eluted into the solution, and instead, the dopant in the solution enters the conductive polymer and binds to the polymer. . Thereby, the conductivity of the solid electrolyte layer increases, and the ESR decreases. Also,
When using a sintered body formed from a valve metal powder, the dopant in the solution is unlikely to enter the inside of the sintered body.
For this reason, the solid electrolyte layer has a higher dopant concentration especially on the surface side than on the inside of the sintered body. If the pH of the solution becomes 3 or more, the amount of the dopant in the conductive polymer eluted into the solution increases, and the ESR of the solid electrolyte layer increases.

Further, in the invention according to claim 3, the dopant is bonded to the conductive polymer having the oxide film laminated thereon by performing electrolytic oxidation treatment using a solution containing the dopant and having a pH of less than 3.

In the present invention, since the dopant is bonded to the conductive polymer by the electrolytic oxidation treatment, the bonding process can be performed quickly, and the working time can be reduced.

[0013]

Embodiments of the present invention will be described below. First, tantalum, aluminum, titanium or the like is used as the valve action metal. Then, metal pieces of these valve action metals are used, or a sintered body obtained by sintering powder is used. For example,
In the latter case, as shown in FIG. 1, the powder of the valve action metal is coated with an anode lead wire 1 made of a valve action metal such as tantalum.
Is drawn out, compression molded, and sintered to form a sintered body 2
And

A disk-shaped insulating plate 3 made of Teflon, silicone rubber, silicone resin, or the like is fitted and arranged at the root of the anode lead wire 1. This insulating plate 3
For example, the thickness is less than 0.2 mm, preferably about 0.1 mm. That is, the smaller the thickness of the insulating plate 3, the larger the size of the sintered body without changing the size of the entire capacitor, the larger the capacity, and the smaller the capacity when the capacity is fixed. .

After disposing the insulating plate 3, the sintered body 2 is subjected to a chemical conversion treatment to provide an oxide film 4 having a thickness of about 200 to 6000 angstroms.

On the surface of the oxide film 4, a solid electrolyte layer 5 made of a conductive polymer is laminated. The conductive polymer is
Polyacetylene, polyparaphenylene, polypyrrole,
An electron conjugated polymer such as polyvinylene, polyphenylene, polyaniline, polythiophene, polyimidazole, polythiazole, or polyfuran is added with a dopant made of an electron-donating or electron-withdrawing compound. As the dopant, for example, an acid compound such as a sulfonic acid compound, a carboxylic acid compound, and a phosphoric acid compound, and a salt compound such as an ammonium salt, a sodium salt, and a potassium salt of these acid compounds are used. The dopant concentration in the solid electrolyte layer 5 is higher on the surface side than on the inner side of the sintered body 2. That is, since the sintered body 2 is formed by sintering the fine powder of the valve action metal as shown in FIG.
The surface is uneven. Since the oxide film 4 is thin, it is formed along the uneven surface of the sintered body 2. The solid electrolyte layer 5 laminated on the surface of the oxide film 4 usually enters the recesses of the sintered body 2 and is also laminated thickly on the surface of the sintered body 2. Then, the concentration of the dopant in the solid electrolyte layer 5 is changed to the inner part 5-
The portion 5-2 on the front side stacked on the surface is higher than the portion 1.

On the surface of the solid electrolyte layer 5, a carbon layer 6 made of carbon vest is provided. A silver layer 7 made of silver paste is provided on the surface of the carbon layer 6 to form a capacitor element. A cathode terminal 9 is connected to the silver layer 7 with a silver conductive paste. Also, lead wire for anode 1
Is connected to the anode terminal 10. Then, a part of the capacitor element, the cathode terminal 9 and the anode terminal 10 is covered with an exterior 11 such as an epoxy resin to form a solid electrolytic capacitor 12.

Next, a method for manufacturing the above-mentioned solid electrolytic capacitor will be described. First, a binder in which camphor, an acrylic resin, or the like is dissolved in an organic solvent is added to and mixed with fine powder of a valve metal such as tantalum, aluminum, or niobium. After mixing, the mixture is heated to remove the organic solvent by volatilization. Next, the fine powder of the valve action metal is compression-molded by a press or the like into a square or cylindrical shape with the anode lead wire 1 made of a valve action metal such as tantalum pulled out. After compression molding, in an atmosphere such as vacuum, 180
Sintering is performed by heating at a high temperature of about 0 to 2200 ° C. for about 15 to 60 minutes and sintering. During this sintering, impurities in the powder are also evaporated.

After sintering, a disk-shaped insulating plate 3 made of Teflon, silicone rubber, silicone resin, or the like is arranged at the root of the anode lead wire 1.

The tip of the anode lead wire 1 drawn from the sintered body 2 is welded to a metal plate such as aluminum or stainless steel. On metal plates, to improve work efficiency,
A plurality of sintered bodies 2 are attached. Then, in this state, the sintered body 2 is immersed in a chemical conversion solution such as nitric acid or phosphoric acid to a predetermined level visually or the like, and a DC voltage corresponding to the rated voltage is applied to the sintered body 2 to perform a chemical conversion treatment. By this chemical conversion treatment, about 1
An oxide film is generated at a rate of about 6 angstroms / V, and finally an oxide film 4 having a thickness of about 200 to 6000 angstroms is formed.

After the oxide film 4 is formed, a solid electrolyte layer 5 made of a conductive polymer is formed on the surface. This solid electrolyte layer 5 is formed, for example, as follows. That is, the first
First, the sintered body 2 is impregnated with a solution obtained by dissolving an oxidizing agent or a mixture of an oxidizing agent and a substance to which a dopant made of an acid compound or a salt compound is dissolved in an appropriate solvent. Thereafter, when a solution of an oxidizing agent is used, the monomer is chemically impregnated with a solution of a mixture of a monomer and a substance to which a dopant including an acid compound or a salt compound is imparted, and the dopant is bound. To impart conductivity. When a mixed solution of an oxidizing agent and a substance such as an acid compound is used, a monomer or a mixed solution of a monomer and a substance to which a dopant of an acid compound or a salt compound is added is impregnated with the monomer. Is subjected to a chemical oxidative polymerization reaction, and a dopant is bonded to impart conductivity. These impregnation processes are repeated a predetermined number of times to obtain a predetermined thickness, and thereafter, a drying process is performed. In the second method, first, a solution of a monomer or a mixture of a monomer and an acid compound or a salt compound is impregnated into the sintered body 2. Thereafter, when a solution of the monomer is used, a solution of a mixture of an oxidizing agent and a substance to which a dopant of an acid compound or a salt compound is added is impregnated to cause a chemical oxidative polymerization reaction and to impart conductivity. When a mixed solution of a monomer and an acid compound is used, an oxidizing agent or a mixed solution of an oxidizing agent and an acid compound is impregnated, and the monomer is subjected to a chemical oxidative polymerization reaction to impart conductivity. Then, these impregnation processes are repeated a predetermined number of times to obtain a predetermined thickness, and a drying process is performed. Furthermore, the third method is to impregnate a solution obtained by dissolving a mixture of a monomer, a substance imparting a dopant of an acid compound or a salt compound, and an oxidizing agent in a suitable solvent into the sintered body 2 and subject the monomer to a chemical oxidative polyreaction. And imparts conductivity. Then, this impregnation process is repeated a predetermined number of times to obtain a predetermined thickness, followed by a drying process.

When the solid electrolyte layer 5 made of a conductive polymer is formed by the first to third methods, by-products are generated and contained in each case. For example, when ammonium peroxodisulfate (ammonium persulfate) is used as an oxidizing agent, a by-product composed of ammonium sulfate or ammonium hydrogen sulfate is contained in the solid electrolyte layer 5. Further, in the case of the first method and the second method, the monomer solution, the mixed solution of the monomer and the acid compound, the solution of the oxidizing agent, and the mixed solution of the oxidizing agent and the acid compound are alternately impregnated. The amount of the monomer solution and the like adhering to the sintered body 2 and the amount of the oxidant solution and the like adhering to the sintered body 2 are not constant, resulting in excess and deficiency, and excessive components remain in the solid electrolyte layer 5. . Further, in the course of polymerization of the monomer, a low molecular weight (oligomer) in which several molecules of the monomer are bonded is generated, and is contained in the solid electrolyte layer 5 as a by-product. These by-products are formed such that the portion 5-2 on the surface side of the sintered body 2 of the solid electrolyte layer 5 is closer to the inner portion 5-1 at the time of forming a polymer or in a subsequent drying step. Is higher than. In the third method, a necessary amount of a monomer, an acid compound or a salt compound, and an oxidizing agent can be blended in advance. The number can be reduced as compared with the first method and the third method.

As the oxidizing agent, for example, potassium dichromate, sodium dichromate, ammonium peroxodisulfate, hydrogen peroxide, ferric chloride, potassium permanganate, manganese dioxide, lead dioxide and the like are used. 1-1.
Make the concentration about 0 mol / l.

As the acid compound used as the substance for imparting a dopant, a sulfonic acid compound, a carboxylic acid compound, a phosphoric acid compound and the like are used. In particular, as the sulfonic acid compound, a substance having a dissociation constant substantially equal to or smaller than that of naphthalenesulfonic acid or a derivative thereof, and a dopant anion smaller than that of naphthalenesulfonic acid or a derivative thereof is used. As such sulfonic acid compounds, for example, sulfone isophthalic acid and sulfosuccinic acid, methanesulfonic acid, phenolsulfonic acid, sulfosalicylic acid, benzenesulfonic acid, benzenedisulfonic acid, alkylbenzenesulfonic acid and derivatives thereof,
An acid such as camphorsulfonic acid, sulfoneacetic acid, or diphenolsulfonic acid is used. The concentration of this acid compound is 0.0
It is adjusted to about 5 to 1.0 mol / l. In addition, as the salt compound used as the substance imparting the dopant, an ammonium salt, a sodium salt, or a potassium salt of the above-mentioned acid compound is used. That is, in the case of a sulfonic acid compound, ammonium sulfoisophthalate and ammonium sulfosuccinate, ammonium methanesulfonate, ammonium phenolsulfonate, ammonium sulfosalicylate, ammonium benzenesulfonate, and aluminum salts as aluminum salts.
Salts such as ammonium benzenedisulfonate, ammonium alkylbenzenesulfonate and derivatives thereof, ammonium camphorsulfonate, ammonium sulfonate, and ammonium diphenolsulfonate are used. And as the sodium salt, sodium sulfoisophthalate, sodium sulfosuccinate, sodium methanesulfonate, sodium phenolsulfonate, sodium sulfosalicylate, sodium benzenesulfonate,
Salts such as sodium benzenedisulfonate, sodium alkylbenzenesulfonate and derivatives thereof, sodium camphorsulfonate, sodium sulfone acetate and sodium diphenolsulfonate are used. Further, as the potassium salt, potassium sulfoisophthalate, potassium sulfosuccinate, potassium methanesulfonate, potassium phenolsulfonate, potassium sulfosalicylate,
Salts such as potassium benzenesulfonate, potassium benzenedisulfonate, potassium alkylbenzenesulfonate and derivatives thereof, potassium camphorsulfonate, potassium sulfonate, sulfoaniline, and potassium diphenolsulfonate are used. The concentration of these ammonium salt, sodium salt, and potassium salt compounds is also 0.05%.
To about 1.0 mol / l. Further, hydrochloric acid, sulfuric acid, or the like may be added in order to increase the solubility of the salt compound and increase the concentration in the solution.

Further, as the monomer, for example, acetylene, paraphenylene, pyrrole, vinylene, phenylene, aniline, thiophene, imidazole, thiazole, furan or the like is used, and the concentration is about 0.1 to 1.0 mol / l.

After a solid electrolyte layer 5 made of a conductive polymer is formed on the surface of the oxide film 4, a substance to be provided with a dopant made of an acid compound or a salt compound is dissolved in water, an organic solvent, a mixed solvent thereof or the like. The sintered body 2 is immersed in the solution, sprayed with a liquid, or the like, or after immersion, a voltage is applied using the sintered body 2 as an anode and the solution as a cathode to perform electrolytic oxidation treatment. The pH of the solution used for the immersion treatment or the electrolytic oxidation treatment is less than 3. The pH of this solution is preferably about 2 or less, and particularly preferably about 1. When the pH is in this range, the dopant in the solution can be newly bound without almost eluting the dopant in the conductive polymer.

The solution used for the immersion treatment or the like is formed when the conductive polymer is formed, and can dissolve by-products contained in the solid electrolyte layer 5. Therefore, when immersion treatment or the like is performed, by-products in the solid electrolyte layer 5 dissolve in the solution. Then, the solution is impregnated into the voids of the solid electrolyte layer 5 after the by-products are dissolved, and the dopant enters therein and bonds to the polymer. Thereby, the dopant concentration in the solid electrolyte layer 5 increases. In particular, since there is more by-product in the portion 5-2 on the surface side of the sintered body 2 of the solid electrolyte layer 5, a dopant is bonded in place of the by-product in this portion 5-2 to increase the dopant concentration. Become.

In particular, in the electrolytic oxidation treatment, for example, by-products due to an oxidizing agent are attracted to the solution on the cathode side as cations, and dopants such as acid compounds are attracted to the sintered body as anions, so that the by-products Elution and the attachment of the dopant can proceed simultaneously. That is, when ammonium peroxodisulfate is used as the oxidizing agent and a sulfonic acid compound is used as the acid compound, ammonium ions are drawn to the cathode side and sulfonic acid ions are drawn to the sintered body 2 side. In addition, when the conductive polymer is used in the third method, since there are relatively few monomers, acid compounds or salt compounds, and by-products due to excess or deficiency of the oxidizing agent, immersion treatment or electrolytic oxidation treatment is performed. Even if it is performed, the concentration of the dopant in the solid electrolyte layer 5 substantially depends on the amount of the attached acid compound or salt compound.

The concentration of the oxide or the like is, for example,
0.1-5 mol / l, preferably 0.1 mol / l-2 mol
/ L. That is, the concentration of the acid compound is 0.1 mol.
If it is lower than / l, the polymerized polymer dopant elutes into the solution and is undoped, and the effect of improving the frequency characteristics of the capacitor is reduced. On the other hand, when the concentration of the acid compound or the like is higher than 5 mol / l, excessive oxides and the like tend to adhere to the surface of the sintered body and remain. Therefore, the leakage current of the capacitor tends to increase, and the moisture resistance tends to decrease.

The temperature of the solution used for the immersion treatment or the like is as follows:
In the case of performing only the process of immersing the sintered body 2, 20
The range is preferably from 60 ° C to 60 ° C, and particularly preferably from 40 ° C or lower. That is, if the temperature is lower than 20 ° C., the diffusion rate of the solution becomes low, it becomes difficult to increase the dopant concentration in the solid electrolyte layer 5, and the immersion treatment time becomes long. On the other hand, when the temperature is higher than 60 ° C., the solid electrolyte layer 5 is easily separated from the oxide film 4.

Further, when performing the electrolytic oxidation treatment, for example, the current may be limited to a DC voltage to apply a maximum voltage,
It is performed by sweeping from a low voltage to a maximum voltage and applying the voltage. At this time, it is preferable that the maximum voltage applied to the sintered body is equal to or lower than the formation voltage when forming the oxide film 4 on the sintered body.

Next, a carbon paste is applied to the surface of the solid electrolyte layer 5 to form a carbon layer 6. After the carbon layer 6 is formed, a silver paste is applied to the surface to form a silver layer 7.
To form After the silver layer 7 is formed, a cathode terminal 9 is connected to the silver layer 7 with a conductive adhesive 8 such as a silver conductive paste, and an anode terminal 10 is connected to the anode lead wire 1. Then, the resin exterior 11 is formed by a resin molding method, a resin dipping method, or the like to form the solid electrolytic capacitor 12.

[0033]

Next, embodiments of the present invention will be described. Examples 1 to 5: A solid electrolytic capacitor having a structure as shown in FIG. Nominal 30KCV / for valve action metal
g of tantalum powder is used. First, the tantalum powder is compression-molded by a press. At this time, one end of an anode lead wire made of a tantalum wire having a diameter of 0.25 mm is embedded in the tantalum powder, and the other end is pulled out. After compression molding, it is sintered in a vacuum and the size is 1.0mm × 1.0mm × 1.2mm
A corner sintered body is formed. Next, this sintered body is immersed in a dilute nitric acid solution, and a DC voltage of 30 V is applied to form the oxide to form an oxide film. After the formation, a solid electrolyte layer made of polyaniline is formed on the surface of the oxide film by a chemical oxidation polymerization method. That is, the sintered body after chemical formation is immersed in an aqueous solution of 0.2 mol / l ammonium peroxodisulfate for 5 minutes. After this immersion, it is immersed for 5 seconds in a mixed solution of aniline 0.2 mol / l and paratoluenesulfonic acid 0.1 mol / l in an equal volume of water and ethanol at room temperature. Then, it is left in the air for 30 minutes to perform a polymerization treatment. The process from the step of dipping in the aqueous solution of ammonium peroxodisulfate to the standing treatment is repeated 15 times. After the repetition, a drying treatment is performed at a temperature of 80 ° C. for 30 minutes to form a solid electrolyte layer made of black conductive polyaniline. After forming the solid electrolyte layer, the sintered body is immersed in an aqueous solution of paratoluenesulfonic acid having a pH of about 1 and a temperature and a concentration of paratoluenesulfonic acid as shown in Table 1 for 20 to 30 minutes. After immersion, it is dried at a temperature of 110 ° C. for about 30 minutes. After drying, a carbon paste and a silver paste are sequentially applied and cured to form a graphite layer and a silver layer. After forming the silver layer, the cathode terminal is connected to the silver layer with a silver conductive paste, and the anode terminal is welded to the anode lead wire. Then, the epoxy resin is subjected to transfer molding processing to form an exterior, and subjected to aging processing.

Examples 6 to 10: Except for the following conditions,
Example 1 is the same as Example 1 to Example 5. That is, after the formation, the sintered body is immersed in a 0.2 mol / l aqueous solution of ammonium peroxodisulfate for 5 minutes. After immersion, it is immersed for 5 seconds in a mixed solution of aniline 0.2 mol / l and camphorsulfonic acid 0.1 mol / l in an equal volume of water and ethanol. After this immersion, it is left in the air for 30 minutes to perform a polymerization treatment. Then, the process from the immersion process to the leaving process is repeated 15 times. After repetition, it is dried at a temperature of 80 ° C. for 30 minutes. After drying, the sintered body was immersed in a camphorsulfonic acid aqueous solution having a pH of about 1, a temperature and a concentration of camphorsulfonic acid as shown in Table 1 for about 30 minutes, and the sintered body was used as an anode and the solution was stored. 14 to 24 V with the used cell as the cathode
To perform electrolytic oxidation treatment. And about Example 1-Example 10, the distribution state of the dopant in a solid electrolyte layer, the ESR frequency characteristic, and heat resistance were measured with the conventional example and the comparative example.

That is, the distribution state of the concentration of the dopant in the solid electrolyte is determined by immersing the sintered body after the formation of the solid electrolyte layer in a solution containing the dopant or by performing the electrolytic oxidation treatment on the solid electrolyte layer. Is measured. Then, after the immersion treatment or the electrolytic oxidation treatment, as shown in FIG. 2, the solid electrolyte layer 5 of the portion 5-2 laminated on the surface side of the sintered body 2 is separated from the sintered body 2 after the separation. Both are used as samples. Then, the concentration of the dopant contained in the sample of the separated portion 5-2 is set to that of the solid electrolyte layer 5 on the surface side of the sintered body 2. Further, the concentration of the dopant contained in the portion 5-1 of the solid electrolyte layer 5 in the sintered body 2 after the separation is
This is the solid electrolyte layer 5 inside the sintered body 2. Then, from each sample, the amounts of nitrogen N and sulfur S in the solid electrolyte layer were measured, and the general formula of polyaniline was obtained.

[0036]

Embedded image

The acid bound to the backbone represented by ion R-SO ₃ ^- (R is an organic group) determine the relative amount of the S / N (atomic ratio), expressed as the concentration of the dopant. Also,
The difference between the S / N on the front side and the S / N on the inner side is calculated as the S / N on the inner side.
And the degree of increase in the dopant concentration on the front side relative to the dopant concentration on the inner side. For the analysis of nitrogen N and sulfur S, REKIN ELMER's elemental analyzer (Mode
l 2400II).

The frequency characteristics of the ESR are as follows for the solid electrolytic capacitor after the aging treatment and before the heating treatment.
The ESR was measured at a frequency of KHz and 100 KHz.

Further, regarding the heat resistance, the solid electrolytic capacitor after heat treatment at 180 ° C. for 30 minutes in air after the aging treatment was performed at 1 KHz and 100 KHz.
The ESR at a frequency of Hz was measured.

The conventional example and the comparative example have the following conditions. Conventional Example 1: In the same manner as in Examples 1 to 5, except that the solid electrolyte layer is formed and then dried at a temperature of 110 ° C. without performing the treatment of immersing the sintered body in paratoluenesulfonic acid. I do.

Conventional Example 2: The same conditions as in Examples 6 to 10 except that the solid electrolyte layer is formed and then dried at a temperature of 110 ° C. without electrolytic oxidation treatment in a camphorsulfonic acid solution. .

Comparative Example 1: In Examples 1 to 5,
The same conditions are used except that the sintered body after the formation of the solid electrolyte layer is immersed in a 0.1 wt% aqueous solution of p-toluenesulfonic acid at a temperature of 30 ° C. and a pH of 3 or more for 30 minutes.

Comparative Example 2: In Examples 6 to 10, after forming the solid electrolyte layer, the sintered body was immersed in a 0.1 wt% aqueous solution of camphorsulfonic acid having a pH of 3 or more at room temperature. The same conditions are applied except that the electrolytic oxidation treatment is performed by applying a voltage of 24V.

Table 1 shows the measurement results.

[0045]

[Table 1]

That is, as is clear from Table 1, ESR
Before heating, at 1 KHz and 100 KHz, Examples 1 to 10 were 0.58 to 0.62 and 0.28 to 0.33 Ω, whereas Conventional Examples 1 to 2 Are 0.78 to 0.85 and 0.45 to 0.50, and the former is smaller than the latter by 56% to 73%. In addition, after the heat treatment, the ESR of Examples 1 to 10 was 0.1 kHz at 100 KHz.
29 to 0.34, which is almost the same as before the heat treatment. That is, the heat resistance is improved by Examples 1 to 10.

According to the first to tenth embodiments,
S / S is higher on the surface side than on the inner side of the sintered body of the solid electrolyte layer.
It is evident that the value of N is about 1.08 to 1.21 times larger, the latter having a higher sulfur S content and therefore a higher dopant concentration. Furthermore, as is clear from Table 1, Examples 1 to 10 are also different from Comparative Examples 1 and 2 in that both E before and after the heat treatment are E.
The SR is low and the frequency characteristics are improved. In Examples 1 to 10, the ESR hardly changed before and after the heat treatment, whereas in Comparative Examples 1 and 2
Indicates that the ESR after the heat treatment is about 1.31 compared to that before the heat treatment.
１1.42 times. Therefore, it is clear that the former method, such as immersion treatment using a solution containing a dopant having a pH of less than 3, is more effective in reducing ESR and the like.

[0048]

As described above, according to the first aspect of the present invention,
An oxide film is provided on a sintered body made of powder of valve action metal, laminated on this oxide film, a sintered body made of a conductive polymer provided with conductivity by bonding a dopant to an electron conjugated polymer. A solid electrolyte layer with a higher dopant concentration on the surface side than on the inner side is provided inside and on the surface, so that ESR can be reduced from low frequency to high frequency range, and heat resistance is excellent, A solid electrolytic capacitor that can maintain a low ESR later and thus can improve the life is obtained.

According to the manufacturing method of the second aspect of the present invention, after the conductive polymer is laminated on the oxide film, the dopant is bonded to the conductive polymer using a solution containing the dopant having a pH of less than 3. Therefore, similarly, a solid electrolytic capacitor that can reduce ESR, improve heat resistance, and improve life can be obtained.

Further, according to the manufacturing method of the third aspect of the present invention, in particular, since the dopant is bonded to the conductive polymer by electrolytic oxidation using a solution containing the dopant and having a pH of less than 3, A solid electrolytic capacitor can be obtained in which the work time required for the bonding process can be reduced, the ESR can be reduced, the heat resistance can be improved, and the life can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a partially enlarged sectional view showing a state in which an anode terminal and a cathode terminal are connected to the capacitor element according to the embodiment of the present invention;

[Explanation of symbols]

2 ... sintered body, 4 ... oxide film, 5,5-1, 5-2 ...
Solid electrolyte layer, 12 ... Solid electrolytic capacitor.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshiki Hama 16 Okuma Kuhei, Miharu-cho, Tamura-gun, Fukushima Prefecture Inside the Miharu Plant of Hitachi AIC Co., Ltd.

Claims (3)

[Claims] An oxide film is provided on a sintered body made of a valve metal powder, and the oxide film is laminated on the oxide film, and a conductive polymer provided with conductivity by bonding a dopant to an electron conjugated polymer. A solid electrolytic capacitor provided with a solid electrolyte layer on the inside and the surface of the sintered body, wherein the solid electrolyte layer has a higher dopant concentration on the surface side than on the inner side of the sintered body. Capacitors. 2. An oxide film is formed on the valve action metal.
In the method for manufacturing a solid electrolytic capacitor in which a solid electrolyte layer is laminated on an oxide film, a solid electrolyte layer made of a conductive polymer is laminated on the oxide film, and then a pH containing a dopant is added.
A process of bonding a dopant to the conductive polymer using a solution having a value of less than 3. 3. An oxide film is formed on the valve metal, and
In the method for manufacturing a solid electrolytic capacitor in which a solid electrolyte layer is laminated on an oxide film, a solid electrolyte layer made of a conductive polymer is laminated on the oxide film, and then a pH containing a dopant is added.
A process for bonding a dopant to a conductive polymer by electrolytic oxidation treatment with a solution having a concentration of less than 3.