JPH03155110A - Manufacture of solid electrolytic capacitor - Google Patents

Abstract

PURPOSE:To improve high frequency characteristics and to reduce leakage current by introducing alcohol solution of oxidizing agent to the surface of deviative of a porous formed body, by bringing it into contact with water solution of pyrrole or pyrrole deviate and by forming a solid electrolyte through oxidation polymerization. CONSTITUTION:Oxidizing agent alcohol solution is introduced to the surface of deviative of a porous formed body; thereafter, it is brought into contact with water solution of pyrrole or pyrrole deviative and oxidation and polymerization are carried out; and then, a solid electrolytic layer which consists of highly conductive polypyrrole or dielectric thereof is formed on a surface of a dielectric inside a fine hole. Since oxidization agent is alcohol solution, it penetrates well inside the fine hole to cover a surface thereof. Since it is brought into contact with water solution of pyrrole or dielectric of pyrrole in the state, pyrrole or dielectric of pyrrole also penetrate well inside the fine hole and come into contact with oxidizing agent. Thereby, a solid electrolytic layer consisting of polymer of uniform and highly conductive polypyrrole or pyrrole deviative is formed on the surface of deviative inside the fine hole in a short time.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is utilized for manufacturing a solid electrolytic capacitor using a conductive polymer compound as a solid electrolyte. The present invention relates to a method for manufacturing a solid electrolytic capacitor with excellent high frequency characteristics, using a polymer compound as a solid electrolyte.

〔overview〕

The present invention provides a method for manufacturing a solid electrolytic capacitor in which a surface oxide film of a film-forming metal porous molded body is used as a dielectric and a conductive polymer compound is used as a solid electrolyte, in which an alcohol solution of an oxidizing agent is applied to the porous molded body. The solid electrolyte is introduced onto the surface of a dielectric material and then brought into contact with an aqueous solution of pyrrole or a pyrrole derivative for oxidative polymerization, thereby making it possible to manufacture a solid electrolyte capacitor having good high frequency characteristics and low leakage current. This is what I did.

[Conventional technology]

Conventionally, solid electrolytic capacitors use a porous molded body of a film-forming metal such as tantalum or aluminum as the first electrode (anode), and the surface oxide film is used as a dielectric material such as manganese dioxide or 7,7,8,8-tetracyano. It has a structure in which a solid electrolyte such as a quinodimethane complex salt is part of the second electrode (cathode). In this case, the solid electrolyte is required to have the ability to electrically connect the entire surface of the dielectric inside the porous molded body and the electrode leads, but because conventional solid electrolytes have low conductivity, the ESR of the capacitor ( (equivalent series resistance) is large,
High frequency characteristics were insufficient.

On the other hand, the development of new materials has progressed in the field of polymers, resulting in conjugated polymers such as polyacetylene, polyparaphenylene, polypyrrole, and conductive polymers doped with electron-donating or electron-withdrawing compounds. is being developed. The conductivity of conductive polymers depends on the type and synthesis method, but it is several tens to several hundred S/cm for those synthesized by cationic oxidation polymerization, and several hundred S/crn for those synthesized by electrolytic oxidation polymerization. This is significantly higher than manganese dioxide, which is a conventional solid electrolyte, and it is considered that it can be advantageously used as a solid electrolyte for electrolytic capacitors.

Among the methods for synthesizing conductive polymers, the electrolytic oxidation polymerization method is a method in which aromatic compounds are electrochemically anodized to deposit a polymer on the electrode surface. Significant difficulties are involved in carrying out such electrode reactions at surfaces.

Moreover, it is nearly impossible to completely fill the pores of the porous molded body used in the electrolytic capacitor using this method.

On the other hand, the formation of a conductive polymer by oxidative cationic polymerization occurs through contact between an aromatic compound and an oxidizing agent, and the conductive polymer can be easily formed even on the surface of a dielectric material. but,
Since aromatic compounds begin to polymerize immediately upon contact with an oxidizing agent, conventionally, a first layer containing either an oxidizing agent or an aromatic compound is first formed on a substrate, and after drying, the other aromatic compound is added. A group compound or an oxidizing agent was brought into contact with this.

In this method, the formation of a conductive polymer starts on the surface of the first layer, and as it grows, the diffusion of the second aromatic compound or oxidizing agent is suppressed, so that the conductive polymer is formed throughout the first layer. Reactions must continue for a long time to form molecules. In particular, in order to fill the intricate pores of porous molded bodies used in electrolytic capacitors, it was necessary to reduce the thickness of the first layer and repeat the polymerization operation.

[Problem to be solved by the invention]

As explained above, in the electrolytic oxidative polymerization method, it is difficult to fill the pores of the porous molded body that constitutes the solid electrolytic capacitor with conductive polymer, and even in the oxidative cationic polymerization method, complicated operations are required. there were.

Therefore, although conductive polymers are expected to be advantageously used as solid electrolytes in electrolytic capacitors, their performance has not yet been fully utilized, that is, they have good characteristics up to the high frequency range and are highly reliable. The problem is that no method has been developed to easily manufacture solid electrolytic capacitors.

An object of the present invention is to provide a method for manufacturing a solid electrolytic capacitor having good high frequency characteristics and excellent reliability by solving the above-mentioned problems.

[Means to solve the problem]

The present inventors conducted various studies to solve the above problems. As a result, they discovered a method for forming a solid electrolytic capacitor in which the pores of a porous molded body of film-forming metal are filled with a conductive polymer compound that has excellent performance as a solid electrolyte by a simple means, and the present invention was achieved. .

That is, the present invention provides a method for manufacturing a solid electrolytic capacitor in which a surface oxide film of a film-formed porous metal molded body is used as a dielectric and an oxidized polymer of pyrrole or a pyrrole derivative is used as a solid electrolyte. In the present invention, the solid electrolyte is formed by introducing the solid electrolyte onto the dielectric surface of the porous molded body, and then bringing it into contact with an aqueous solution of pyrrole or a pyrrole derivative for oxidative polymerization. These are aluminum, niobium, titanium, zirconium, magnesium, zinc, bismuth, silicon, hafnium, etc., and are used in the form of rolled metal foils, fine powder sintered products, plates, and etched products of rolled foils. be able to.

The oxidizing agent used in the present invention includes conventionally known oxidizing cationizing agents such as ferric halides, cupric halides, and benzoquinones used in the synthesis of conductive polymers, but the In terms of the morphology of the polymer, the cation has a high oxidation number Fe'', (: u 2 + Cr'', M n
1+, and transition metal ions such as Sn'+, anions such as alkylbenzenesulfonate ions, naphthalenesulfonate ions, alkylnaphthalenesulfonate ions,
Organic sulfonate ions such as alkyl sulfonate ions, α-olefin sulfonate ions, sulfosuccinate ions, and N-acylsulfonate ions, or alkyl sulfate ions, polyethylene oxide alkyl ether sulfate ions, and polyethylene oxide alkylphenol ether sulfate ions. Metal salts that are organic sulfate ions are preferred.

Specific examples of particularly preferred oxidizing agents include p-toluenesulfonic acid, dodecylbenzenesulfonic acid, butylnaphthalenesulfonic acid, 012-C18
alkyl sulfonic acids, and ferric or cupric salts such as dodecyl sulfuric acid.

Further, the solvent for dissolving these oxidizing agents is an alcoholic solvent such as methanol, ethanol, pentanol, octyl alcohol, and ethylene glycol. In the present invention, these solvents are used alone or in combination of two or more, and further in combination with other solvents as necessary.

In the production method of the present invention, the oxidizing agent alcohol solution is introduced into the pores of the porous molded product of the film-forming metal having an oxide film formed thereon, and an aqueous solution of pyrrole or a pyrrole derivative such as N-alkylvirole is added to the oxidizing agent alcohol solution. By contacting
Oxidative polymerization of pyrrole or a pyrrole derivative occurs to form a solid electrolyte layer made of polypyrrole or its derivative.

The method of introducing the oxidizing agent solution into the pores of the porous molded body of the film-forming metal may be selected as appropriate depending on the shape of the porous molded body to be used. There are methods such as dipping a porous molded body.

Further, the contact between the oxidizing agent solution and pyrrole or its derivatives is carried out by immersing the porous molded body into which the oxidizing agent solution has been introduced, without drying it as it is, or after suitably drying it, in an aqueous solution of pyrrole or its derivatives. Here, if it is completely dried, it tends to be difficult to form a uniform and dense polypyrrole layer, which is not preferable.

The most preferred method is to immediately immerse it in an aqueous pyrrole (derivative) solution without going through a drying process.

By the above operation, the oxidizing agent in the pores of the porous molded product of film-forming metal is brought into contact with the pyrrole or its derivative, whereby oxidative polymerization of pyrrole or its derivative occurs in the pores, and at the same time, the oxidizing agent solution and the pyrrole or its derivative occur. Since the monomer aqueous solution can be mixed in the pores of the porous molded body, compared to the conventional method of introducing only one side first, drying it, and then contacting the other side, it is possible to create a more uniform mixture of conductive polypyrrole or its derivatives. A solid electrolyte layer can be obtained in a short time.

Furthermore, if a water-insoluble organic sulfonic acid compound or a transition metal salt of an organic sulfuric acid compound as described above is used as the oxidizing agent, unreacted oxidizing agent will flow out from the porous molded body into the aqueous solution of pyrrole or its derivative. There isn't.

In the production method of the present invention, the concentration of the oxidizing agent solution and the concentration of the aqueous solution of pyrrole or its derivative to be introduced into the pores of the porous molded product of the film-forming metal are not particularly limited, and are below the saturation concentration for each solvent. Select as appropriate within the range. Furthermore, the temperature at which the oxidizing agent solution is introduced into the pores of the porous molded body and the temperature at which the oxidizing agent solution is brought into contact with the aqueous solution of pyrrole or its derivatives are not particularly limited, and are appropriately selected within a range below the boiling point of the solvent used. do.

In the present invention, the product thus obtained is washed and dried as required, and an extraction electrode is provided in a conventional manner and assembled into a capacitor. Moreover, it is also possible to repeat each step of forming the solid electrolyte layer.

Compared to conventional capacitors using manganese dioxide as a solid electrolyte, the solid electrolytic capacitor manufactured by the manufacturing method of the present invention has no thermal stress during electrolyte formation, so damage to the dielectric is suppressed and leakage current is small.

Furthermore, since the conductivity of the conductive polymer that is the solid electrolyte is 10 to 100 times higher than that of manganese dioxide, the ESR is also small and the high frequency characteristics are improved compared to conventional ones.

In addition, compared to solid electrolytes made of polypyrrole, etc. obtained through conventional chemical oxidative polymerization, it is possible to easily form a solid electrolyte layer that is more uniform and has a higher filling rate. A solid electrolytic capacitor with low current can be obtained.

[Effect]

The present invention provides high conductivity on the dielectric surface inside the pores by introducing an oxidizing agent alcohol solution onto the dielectric surface of a porous molded body, and then bringing it into contact with an aqueous solution of pyrrole or a pyrrole derivative for oxidative polymerization. A solid electrolyte layer made of polypyrrole or a derivative thereof is formed. In this case, since the oxidizing agent is in the form of an alcohol solution, it easily penetrates into the pores and covers their surfaces. In this state, the aqueous solution of pyrrole or pyrrole derivative is brought into contact with the pyrrole or pyrrole derivative, so that the pyrrole or pyrrole derivative also penetrates into the pores and comes into contact with the oxidizing agent. A uniform and highly conductive solid electrolyte layer made of polypyrrole or pyrrole derivative polymer is formed on the body surface. This makes it possible to easily manufacture a solid electrolytic capacitor with excellent high frequency characteristics and low leakage current.

〔Example〕

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited only to these Examples.

Example 1 Disc-shaped fine tantalum powder sintered pellets (porosity 50%) with a diameter of 5 mm and a thickness of 0.8 mm were dissolved in a nitric acid aqueous solution at a temperature of 100%.
Anodized with V, washed and dried Beref) wo 25
wt.% iron(I) dodecylbenzenesulfonate in methanol. After 2 minutes, this pellet was taken out and immediately immersed in a 0°1M pyrrole aqueous solution and held for 1 hour, whereupon polymerization of pyrrole occurred in the pores and a tank pellet sample filled with polypyrrole was obtained.

After washing this sample with methanol, it was dried under reduced pressure at 80° C. for 1 hour, and leads were drawn out from the surface using silver paste to complete a capacitor.

Table 1 shows the capacitance, tan δ (tangent of loss angle), and ESR (equivalent series resistance) at the resonant frequency of the obtained capacitor. This capacitor had a small capacitance change rate with respect to frequency, tan δ, and ESR at the resonant frequency, and had good high frequency characteristics.

Example 2 Using the anodized fine tantalum powder sintered pellets of Example 1, filling with polypyrrole, washing and drying according to the method of Example 1 was repeated four times, and the leads were pulled out to complete a capacitor. The capacitance of the capacitor obtained,
Table 1 shows the ESR at tan δ and resonance frequency.

This capacitor has a rate of change of capacitance with respect to frequency, t
Both anδ and ESR at the resonant frequency were small, and the high frequency characteristics were good.

Example 3 The anodized fine tantalum sintered pellets of Example 1, 25 Wt, % iron dodecylbenzenesulfonate (II[
) in an ethanol solution. After 2 minutes, this pellet was taken out and immediately immersed in a 0.1 M pyrrole aqueous solution and held for 1 hour, whereupon polymerization of pyrrole occurred in the voids and a tank pellet sample filled with polypyrrole was obtained. This sample was washed and dried by the method of Example 1, and the leads were pulled out to complete the capacitor. Table 1 shows the capacitance, tan δ, and ESR at the resonant frequency of the obtained capacitor. This capacitor had a small capacitance change rate with respect to frequency, tan δ, and ESR at the resonant frequency, and had good high frequency characteristics.

Example 4 The anodized fine tantalum sintered pellets of Example 1 were immersed in a methanol solution of 25 wt 0% iron(III) alkyl sulfonate (mixture of alkyl chain lengths C1□, CI3, and CI4). After 2 minutes, this pellet was taken out and immediately immersed in a 0.1M pyrrole aqueous solution and kept for 1 hour, whereupon polymerization of pyrrole occurred in the voids.
Tanker pellet samples filled with polypyrrole were obtained. This sample was washed and dried by the method of Example 1, and the leads were pulled out to complete the capacitor. The capacitance of the obtained capacitor, tan δ and E at the resonant frequency
SR is shown in Table 1. This capacitor had a small change rate of electrostatic capacitance with respect to frequency, tan δ, and ESR at the resonant frequency, and had good high frequency characteristics.

Example 5 The anodized fine tantalum sintered pellets of Example 1 were immersed in a methanol solution of 25 wt.% copper dodecyl sulfate (If). After 2 minutes, this pellet was taken out and immediately immersed in a 0.1 M pyrrole aqueous solution and held for 1 hour, whereupon polymerization of pyrrole occurred in the voids and a tank pellet sample filled with polypyrrole was obtained. This sample was washed and dried by the method of Example 1, and the leads were pulled out to complete the capacitor. The capacitance, tan δ, and ESR at the resonant frequency of the obtained capacitor are
Shown in the table. This capacitor had a small capacitance change rate with respect to frequency, tan δ, and ESR at the resonant frequency, and had good high frequency characteristics.

Example 6 Instead of the tantalum pellets in Example 1, the surface area was expanded by 12 times by etching, and the film thickness was 50 μI, 11%, 1 side, 1
cm square aluminum foil was anodized, washed and dried in the same manner as in Example 1, and then
wt.% iron(I) dodecylbenzenesulfonate in methanol. After 2 minutes, this aluminum foil was taken out and immediately immersed in a 0.1M pyrrole aqueous solution.
When kept for a while, an aluminum foil whose surface was coated with black polypyrrole was obtained.

This sample was washed and dried by the method of Example 1, and the leads were pulled out to complete the capacitor. Capacitance, tan δ and ESR at resonant frequency of the obtained capacitor
are shown in Table 1. This capacitor has a rate of change of capacitance with frequency, tan δ, and ESR at the resonant frequency.
Both were small and had good high frequency characteristics.

Example 7 Instead of the tankle pellets of Example 1, cylindrical fine aluminum powder sintered pellets (porosity 50%) with a diameter of 5 mm and a height of 3 m+++ were used, and anodized in the same manner as in Example 1. Washed, dried, and weighed 25wt.

% iron(III) dodecylbenzenesulfonate in methanol. After 2 minutes, remove the pellet and
When it was immediately immersed in a 0.1M pyrrole aqueous solution and kept for 1 hour, a fine aluminum powder sintered body pellet whose surface was coated with black polypyrrole was obtained.

This sample was washed and dried by the method of Example 1, and the leads were pulled out to complete the capacitor. Capacitance, tan δ and ESR at resonant frequency of the obtained capacitor
are shown in Table 1. This capacitor has a rate of change of capacitance with frequency, tan δ, and ESR at the resonant frequency.
Both were small and had good high frequency characteristics.

Comparative Example The anodized fine tantalum sintered pellets of Example 1 were immersed in a methanol solution of 25 wt 1% iron dodecylbenzenesulfonate (1). After 2 minutes, the pellet was taken out, dried at 60° C. for 3 hours, and then exposed to saturated steam of pyrrole at 25° C. for 1 hour, to obtain a tankle pellet sample with polypyrrole formed on the surface. This sample was washed and dried by the method of Example 1, and the leads were pulled out to complete the capacitor.

As shown in Table 1, the capacitance, tan δ, and ESR at the consonant frequency of the obtained capacitor show reasonable characteristic values for a solid electrolytic capacitor, but at high frequencies (
The decrease in the amount of electrostatic v and the increase in tan δ at 100 kl + phantom were significantly large, and were inferior to each of the examples described above.

Table 1 [Effects of the Invention] As explained above, according to the present invention, a solid electrolytic capacitor with excellent high frequency characteristics and low leakage current can be
It can be produced by a simple method and has great effects.

Claims (3)

[Claims] 1. A method for manufacturing a solid electrolytic capacitor in which a surface oxide film of a porous molded body of a film-forming metal is used as a dielectric and an oxidized polymer of pyrrole or a pyrrole derivative is used as a solid electrolyte, wherein an alcohol solution of an oxidizing agent is added to the porous molded body. A method for manufacturing a solid electrolytic capacitor, comprising forming the solid electrolyte by introducing the solid electrolyte onto the surface of a dielectric material and then bringing it into contact with an aqueous solution of pyrrole or a pyrrole derivative for oxidative polymerization. 2. 2. The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein the oxidizing agent is an organic sulfonic acid compound or a transition metal salt of an organic sulfuric acid compound. 3. The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein the alcohol is methanol or ethanol.