JPH02288215A - Manufacturing method of solid electrolytic capacitor - Google Patents

Abstract

PURPOSE:To obtain a solid electrolytic capacitor having excellent heat resistance and high-frequency characteristics by introducing an oxidizer composed of the transition metal salt of an organic sulfonic acid compound or an organic sulfuric acid compound onto a dielectric and oxidation-polymerizing an aromatic compound on the dielectric. CONSTITUTION:A porous aluminum foil is chemical-conversion treated at 100V in an ammonium borate aqueous solution and an oxide film is formed, and the foil is washed and dried. The foil is dipped in a 25wt.%-methanol solution of dodecyl benzenesulfonic acid-iron (III) salt, and decompression-dried. A glass vessel 1 in which a pyrrole monomer 3 is admitted in a petri dish 2 is sealed with a silicone rubber plug 5 while the porous aluminum foil 4 is hung into the sealed vessel and brought into contact with the vapor of the pyrrole monomer for three hr at a normal temperature and normal pressure. The foil 4 is washed by methanol, and dried. The surface of the porous aluminum foil 4 is covered with dark black and green polypyrrole by the operation. The packing of polypyrrole into the air gap of the porous aluminum foil 4 obtained from the change of weight before and after a reaction after the operation is repeated five times is represented by 95%.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is utilized for manufacturing solid electrolytic capacitors 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 film-forming metal oxide is used as a dielectric and a conductive polymer compound is used as a solid electrolyte, in which an oxidizing agent consisting of an organic sulfonic acid compound or a transition metal salt of an organic sulfuric acid compound is used as the oxidizing agent. A solid electrolytic capacitor having good high frequency characteristics and heat resistance can be manufactured by depositing a conductor on a dielectric material and then oxidatively polymerizing an aromatic compound on the dielectric material to form the solid electrolyte. This is what I did.

[Conventional technology]

In recent years, with advances in science and technology, electronic devices have become smaller and smaller.
In conjunction with the development of digital equipment, there is a growing demand in the field of capacitors for high-capacity capacitors that have good characteristics up to high frequencies and are highly reliable. In response to these demands, the solid electrolytic capacitors that have been developed to date are
Although it has a large capacity and has excellent reliability because the electrolyte is solid, the conductivity of the solid electrolyte is still insufficient, and good characteristics in the high frequency region have not been obtained.

Normally, 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, manganese dioxide and 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 function of electrically connecting the entire surface of the dielectric inside the porous molded body and the electrode leads, and the function of repairing electrical short circuits caused by defects in the dielectric film. As a result, metals with high electrical conductivity but without a dielectric repair function cannot be used as solid electrolytes, and manganese dioxide and the like, which transfer to insulators due to heat generated by short-circuit current, etc., have been used. However, the solid electrolyte conventionally used has insufficient electrical conductivity, and the technology for completely filling the pores of a porous molded body with a complicated shape has not yet been perfected.

On the other hand, the development of new materials has progressed in the field of polymers, resulting in conjugated polymer films such as polyacetylene, polyparaphenylene, and polypyrrole, or addition of electron-donating or electron-absorbing compounds (dopants) (doping). ) conductive polymers have been developed so far. Among these, it is known that aromatic conductive polymers such as polypyrrole can have good conductivity, heat resistance, and stability over time by appropriately selecting the dopant. A solid electrolytic capacitor using a solid electrolyte has been proposed.

For example, JP-A-60-37114 proposes a solid electrolytic capacitor using a doped five-membered heterocyclic compound polymer as a solid electrolyte.

Known methods for synthesizing polypyrrole include electrolytic oxidation polymerization, cationic oxidation polymerization using an oxidizing agent, and Grignard reaction of dihalide derivatives of pyrrole. The electrical conductivity of polypyrrole varies depending on the method of synthesis, but it is several tens to several hundred S/cm when polymerized by chemical oxidation polymerization, and several hundred 3/Cm when polymerized by electrolytic oxidation polymerization. This is significantly higher than that of manganese dioxide, which is a solid electrolyte. Since the characteristics of an electrolytic capacitor in a high frequency region improve depending on the conductivity of the electrolyte, it is considered that polypyrrole can be advantageously used as a fixed electrolyte for a capacitor.

Aromatic polymer compounds such as polypyrrole obtained by electrolytic polymerization can meet the requirements of solid electrolytes for electrolytic capacitors by appropriately selecting polymerization conditions such as the type and concentration of the solvent and supporting electrolyte used during electrolytic polymerization. It is possible to obtain a product that fully satisfies the heat resistance and electrical conductivity. However, it is quite difficult to perform electrolytic oxidative polymerization on a metal oxide film, which is an insulator. Moreover, the film-forming metal is usually a porous body, and it is difficult to fill the pores with polypyrrole, and even if this is possible, very complicated and complicated operations are required.

On the other hand, forming polypyrrole on a metal oxide film by chemical oxidative polymerization is a very simple method, and polypyrrole with high conductivity can be obtained by appropriately controlling the polymerization temperature, oxidizing agent concentration, etc. However, when conventionally known oxidizing agents such as ferric chloride, ferric nitrate, and cupric chloride are used, the polypyrrole produced has poor heat resistance, and gradually The electrical conductivity decreases, which causes deterioration of solder heat resistance and high-temperature load characteristics when used as a solid electrolyte in electrolytic capacitors. Furthermore, in the case of an oxidizing agent containing a halide, the halide ions may be incorporated into the polypyrrole as a dopant, and the halide ions may corrode the metal oxide film or the metal itself.

[Problem to be solved by the invention]

As explained above, although the electrolytic oxidation polymerization method can yield polypyrrole with excellent properties, it requires complicated operations to fill the inside of the pores of the porous material that constitutes the solid electrolytic capacitor, and chemical oxidation Although the polymerization method is easy to operate, there are concerns about the heat resistance of the polypyrrole produced and its corrosivity to metals. Therefore, although polypyrrole is expected to be extremely useful as a solid electrolyte for electrolytic capacitors, its performance has not yet been fully utilized, that is, it has good characteristics up to the high frequency range.
Moreover, there has been a problem in that an electrolytic capacitor with excellent reliability has not yet been developed.

The purpose of the present invention is to solve the above-mentioned problems.
It is an object of the present invention to provide a method for manufacturing a solid electrolytic capacitor having good high frequency characteristics and excellent reliability.

[Means to solve the problem]

The present inventors conducted various studies to solve the above problems. As a result, we discovered a method for forming a solid electrolyte for 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. It's arrived.

That is, the present invention provides a method for manufacturing a solid electrolytic capacitor in which a film-forming metal oxide is used as a dielectric and a conductive polymer compound is used as a solid electrolyte, in which an oxidizing agent consisting of an organic sulfonic acid compound or a transition metal salt of an organic sulfuric acid compound is used. is introduced onto the dielectric, and then an aromatic compound is oxidatively polymerized on the dielectric to form the solid electrolyte.

The oxidizing agent used in the present invention is a metal salt, and is characterized in that the cation is a transition metal ion with a high oxidation number, and the anion is an organic sulfonate ion or an organic sulfate ion.

As a cation, for example, Fe 2+, Cu2+, Cr
6+Mn'=, Mn'°, Sn'+, and the like. Among these, Fe'+ and Cu 2s- are preferred. - On the other hand, suitable organic sulfonate ions as anions include alkylbenzenesulfonate ions, naphthalenesulfonate ions, alkylnaphthalenesulfonate ions, alkylsulfonate ions, α-olefin sulfonate ions, sulfosuccinate ions, and N-
There are acylsulfonate ions, and organic sulfate ions include alkyl sulfate ions, polyethylene oxide alkyl ether sulfate ions, and polyethylene oxide alkylphenol ether sulfate ions.

In addition to these, for example, polypropylene oxide alkyl ether sulfate ion, polybutylene oxide alkyl ether sulfate ion, polypropylene oxide alkylphenol ether sulfate ion, polyisobutylene oxide alkylphenol ether sulfate ion, naphthalene sulfonic acid formalin condensate, etc. can be used. be.

Preferred examples of these anions include, for example, benzenesulfonate ion, paratoluenesulfonate ion, dodecylbenzenesulfonate ion, naphthalenesulfonate ion, butylnaphthalenesulfonate ion, 012
-C18 alkylsulfonate ion, octadecenylsulfonate ion, di-2-ethylhexylsulfosuccinate ion, N-acetylmethyltaurine ion, and the like.

Examples of the organic sulfate ion include octyl sulfate ion, dodecyl sulfate ion, polyethylene oxide dodecyl ether sulfate ion, and polyoxyethylene octylphenol ether sulfate ion.

By carrying out chemical oxidative polymerization of an aromatic compound using the oxidizing agent of the present invention, some of the anions in the oxidizing agent become dopants, and a conductive polymer compound with excellent heat resistance and high electrical conductivity is produced.

As the aromatic compound, pyrrole, aniline, thiophene, furan, benzene, etc. and derivatives thereof can be used, and cyclopyrrole and its derivatives are particularly suitable for the use of the present invention.

As a method for chemical oxidative polymerization of aromatic compounds using the oxidizing agent of the present invention, for example, an oxidizing agent layer is provided on the dielectric surface by coating, dipping, or spraying, and this is applied in the gas phase or liquid phase. An effective method is to polymerize the aromatic compound on the surface of the dielectric by bringing it into contact with the aromatic compound. Particularly preferred is a reaction in the gas phase, that is, a method in which the aromatic compound is brought into contact with the vapor of the aromatic compound. The method for applying the oxidizing agent to the dielectric layer of the film-forming metal can be selected as appropriate depending on the shape of the porous forming body used and the properties of the oxidizing agent. It may be applied, dipped or sprayed after being dissolved in a solvent such as water.

In order to impart film strength to the resulting polymer, it is also effective to add polymers such as polyvinyl alcohol, polyvinyl acetate, and ethyl cellulose to the oxidizing agent or oxidizing agent solution. Further, each of the above steps may be repeated several times as necessary.

[Effect]

In the oxidizing agent of the present invention, that is, the transition metal salt of an organic sulfonic acid compound or an organic sulfuric acid compound, a part of its anions becomes a dopant during chemical oxidative polymerization, and a conductive polymer compound with excellent heat resistance and high electrical conductivity is formed. Generate and close. Moreover, the oxidizing agent can be sufficiently penetrated into the pores of the dielectric by, for example, dissolving it in a solvent such as methanol or water and immersing the dielectric in the solution.

Since oxidative polymerization is carried out by contacting, for example, with the vapor of an aromatic compound, sufficient contact with the oxidizing agent inside the pores is achieved, and as a result, the entire dielectric material including the inside of the pores is heat-resistant. It becomes possible to easily form a solid electrolyte made of a conductive polymer compound with excellent properties and high conductivity.

〔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 A porous aluminum foil having a width of 10 mm and a length of 15 mm was subjected to chemical conversion treatment at 100 V in an ammonium borate aqueous solution to form an oxide film, and then washed and dried.

This was immersed in a 25 wt % methanol solution of dodecylbenzenesulfonic acid-iron (In[) salt, and then dried under reduced pressure. As shown in the cartoon, a glass container 1 containing pyrrole monomer 3 is placed in a petri dish 2 with a silicone rubber stopper.
The porous aluminum foil 4 was suspended in this airtight container and brought into contact with the vapor of pyrrole monomer for 3 hours at room temperature and pressure. Thereafter, it was washed with methanol and dried.

Through this operation, the surface of the porous aluminum foil 4 was coated with polypyrrole having a deep black edge color. Repeat the above steps 5
After repeating the reaction several times, the filling rate of polypyrrole into the voids of this porous aluminum foil 4 was 95%, as determined from the weight change before and after the reaction.

Leads were drawn out from this polypyrrole using silver paste and covered with epoxy resin to complete the capacitor. The resulting capacitor is 2.74μ at 120Hz
It has a capacitance of F, and the tangent of loss angle (tan δ) is 0.
It was 01 or less. The capacitance change rate of this capacitor is less than 10% up to 200 Hz, and the tan δ is also 15
The frequency characteristics were good, with up to 0K)Iz being 0.1 or less. Furthermore, after being left at 220°C for 10 minutes,
When the capacitance and tan δ of 1207 were measured, it was found to be 2.68 μF and 0°01 or less, indicating that it has excellent heat resistance.

Comparative Example Dodecylbenzenesulfonic acid-iron (I) in Example 1
II) An aluminum electrolytic capacitor was created using ferric chloride instead of salt. The capacitance at 1207 is 2.8
2 μF1 and tan δ were 0.01 or less. The capacitance change rate of this capacitor is 10% up to 240KHz.
Further, the frequency characteristics were good, with tan δ being 0.1 or less up to 180K)lz. However, when this was left at 220°C for 10 minutes, the capacitance at 120°C decreased to 0.66μF, and the tan
It was found that δ was as large as 1.5 and the heat resistance was poor.

Example 2 An aluminum electrolytic capacitor was prepared by immersing it in an aqueous solution of pyrrole monomer at a concentration of 0.1 mol/I for 1 hour instead of contacting it with pyrrole monomer vapor for 3 hours in Example 1. The capacitance at 1207 is 2.
50 μp, tan δ was 0.01 or less. The rate of change of capacitance of this capacitor is 600kHz 1
0% or less, and tan δ is 0.1 up to 400kHz.
It was good as below. This was left at 220°C for 10 minutes, and the capacitance and tan at 120 Hz were measured.
When δ was measured, it was found to be 2.50μ and 0.01 or less, indicating excellent heat resistance.

Example 3 Dodecylbenzenesulfonic acid-iron (I) in Example 1
[I) Alkyl sulfonic acid-iron(I) instead of salt (mixture of alkyl group chain lengths of 13.14 and 15)
An aluminum electrolytic capacitor was created using this method. 120H
The capacitance at z is 2.78 μF, tan δ is 0
．． It was 01 or less. The rate of change in capacitance of this capacitor was 500kl (10% or less up to z, and tan δ was 120k) and had good frequency characteristics, with a rate of change up to 1z of 0.1 or less. Leave this at 220°C for 10 minutes, and
It had good frequency characteristics of 0.1 or less up to 20 kHz. This was left at 220°C for 10 minutes, and
When measuring the capacitance and tan δ at 7,
It was found to have excellent heat resistance, which was 2.65 μF and 0.01 or less.

Example 4 Dodecylbenzenesulfonic acid-iron (I) in Example 1
II) An aluminum electrolytic capacitor was produced using dodecyl sulfate-copper (II) salt instead of salt. The capacitance at 1207 was 2.58μl"5tan δ was less than 0.01.The rate of change in capacitance of this capacitor was 200μl"5tan δ was less than 0.01.
The tan δ was good, being 10% or less up to kHz, and 0.1 or less up to 80 kHz. When this was left at 220°C for 10 minutes and the capacitance and tan δ at 120 Hz were measured, they were 2.60 μF and 0.
It was found that it has excellent heat resistance with a temperature of 0.01 or less.

Example 5 Dodecylbenzenesulfonic acid-t (
III) Naphthalenesulfonic acid-copper(I[) instead of salt
An aluminum electrolytic capacitor was created using salt. 120
Capacitance at Hz is 2.76 μF, tan δ
was less than 0.01. The capacitance change rate of this capacitor was 10% or less up to 300 kHz, and the tan δ was 0.1 or less up to 200 kHz, which was good. When this was left at 220°C for 10 minutes and the capacitance and tan δ at 120 Hz were measured, it was 2.72.
It was found that it has excellent heat resistance with μF and 0.06.

Example 6 A cylindrical fine tantalum powder sintered body pellet (porosity 50%) with a diameter of 211110 mm and a height of 2 mm was dissolved in a nitric acid aqueous solution for 10 min.
It was anodized at 0V, washed and dried. This was immersed in a 3Qwt% methanol solution of polyethylene oxide octylphenyl ether sulfate-iron(III), dried, and pyrrole was polymerized on the tantalum oxide film in the same manner as in Example 1. The filling rate of polypyrrole into the voids of this pellet, determined from the weight change before and after the reaction, was 90%.

Next, leads were drawn out from the polypyrrole on the surface of the pellet using silver paste, and the capacitor was completed by covering it with epoxy resin. The obtained capacitor is 120H
At z, the capacitance is 8.86 μF, and the tangent of the loss angle (ta
nδ) was 0.01 or less. The rate of change in capacitance of this capacitor is less than 10% up to 3007, and tan δ
The high frequency characteristics were also good, being less than 0.1 up to 200 KHz. Furthermore, after being left at 250°C for 10 minutes,
When the capacitance and tan δ at 120 Hz were measured, it was found to be 8.94 μF and 0.01 or less, indicating excellent heat resistance.

〔Effect of the invention〕

As explained above, according to the present invention, a solid electrolytic capacitor having good high frequency characteristics and heat resistance can be easily manufactured by a simple method, and the effects thereof are significant.

[Brief explanation of drawings]

The figure is an explanatory diagram showing one embodiment of the present invention. 1... Glass container, 2... Petri dish, 3... Pyrrole monomer, 4... Porous aluminum foil, 5...
・Silicone rubber stopper.

Claims (4)

[Claims] 1. In a method for producing a solid electrolytic capacitor in which a film-forming metal oxide is used as a dielectric and a conductive polymer compound is used as a solid electrolyte, an oxidizing agent consisting of an organic sulfonic acid compound or a transition metal salt of an organic sulfuric acid compound is placed on the dielectric. A method for manufacturing a solid electrolytic capacitor, characterized in that the solid electrolyte is formed by introducing an aromatic compound into the dielectric material and then oxidatively polymerizing an aromatic compound on the dielectric material. 2. 2. The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein the transition metal salt is a ferric salt or a cupric salt. 3. The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein the aromatic compound is pyrrole or a derivative thereof. 4. 2. The method of manufacturing a solid electrolytic capacitor according to claim 1, wherein the oxidative polymerization of the aromatic compound is performed by bringing the dielectric into which the oxidizing agent has been introduced into contact with the vapor of the aromatic compound.