JPH02309616A - Manufacture of solid electrolytic capacitor - Google Patents

Abstract

PURPOSE:To assure good characteristics as a capacitor and an excellent contact property to a positive electrode by impregnating the positive electrode with an organic silver solution comprising a specific polymer to form a fixed electrolyte film. CONSTITUTION:A solid electrolyte film is formed by employing a polymer being a monomer represented by a formula I and impregnating a positive electrode with a solution of said polymer utilizing the solubility of the polymer I, X is a sulfur atom or an NH group, R<1> and R<2> are substituents or atoms, each of which combines to three or four positions of a ring, each independently indicating a hydrogen atom, and an alkyl group and an alkoxy group of a four or more carbon number or a group indicated by a general formula-R<3>-O(R<4>- O)nR<5> (herein R<3> is a lower alkylene group or a single bond, R<4> a lower alkylene group, R<3> a lower alkyl group, and n a 1 to 5 integer), but R<1> and R<2> not indicating a hydrogen atom simultaneously. Hereby, there can easily be yielded a solid electrolytic capacitor with a high impregnation rate, with satisfactory contact property to the electrode, and with excellent electrical characteristics.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention provides an anode having a dielectric oxide film on its surface.
The present invention relates to a method of manufacturing a solid electrolytic capacitor having a polymer thin film layer.

(Prior art) Conventionally, in a solid electrolytic capacitor whose anode body is a metal having a dielectric oxide film on its surface, manganese dioxide (MnO□) or tetracyanoquinodimethane (
A method using a complex salt (TCNQ) is well known. These solid electrolytes are formed by repeatedly dipping the coating components and heating and solidifying them, but the process is complicated and it is difficult to control the film thickness of the solid electrolyte.Since the process is complicated and the productivity is low, it is difficult to manufacture small capacitors. It is unsuitable for manufacturing, and conversely, since high-temperature heating is required to manufacture large-capacity capacitors, the influence of thermal distortion becomes large. Since these solid electrolytes are immersed and solidified by heating at a considerably high temperature, it is difficult to create a pattern with an insulating material on the surface of the anode body and form an electrolyte layer locally. is a granular material,
It is also not possible to carry out processes such as forming a solid electrolyte or other materials and cutting them into chips, and therefore these technologies are currently only capable of realizing capacitors of medium capacity.

In recent years, to compensate for these drawbacks, solid electrolytic capacitors having a thin film layer of a polymer such as polythiophene or polypyrrole as a solid electrolyte have been developed.

If this technology is used, most of the above problems will be solved, and there will be a greater degree of freedom in process selection, making it possible to manufacture a wide range of products from chip-type small capacitance capacitors to large capacitance capacitors using appropriate processes.

(Problems to be Solved by the Invention) The polymer solid electrolyte layer is prepared by dissolving thiophene, virol, etc. in an electrolyte solution such as acetonitrile.
It is formed by electrolytic polymerization on an anode having a dielectric oxide film on its surface, but thiophene polymers and pyrrole polymers tend to form poorly on the dielectric oxide film and have poor adhesion. Although the reason for this is not clear, it is thought that the dissolution reaction of the electrode is larger than the polymerization reaction. When doping is performed after electrolytic oxidative polymerization, it is thought that the strength of the film further decreases.

An object of the present invention is to provide a method for easily manufacturing a solid electrolytic capacitor formed with a polymer solid electrolyte membrane that eliminates the above-mentioned drawbacks and has excellent adhesion to the anode and provides good characteristics as a capacitor. be.

(Means for Solving the Problem) The present invention has been made to solve the problem, and is directed to the production of a solid electrolytic capacitor having a polymer thin film layer on an anode having a dielectric oxide film on the surface. ,
General formula (H [wherein, X represents a sulfur atom or NH group, R1 and R2
is a substituent or atom bonded to the 3rd or 4th position, and each independently represents a hydrogen atom, an alkyl group having 4 or more carbon atoms, an alkoxy group, or the general formula -R'-0(R'-0)n
A group represented by R' (where R3 represents a lower alkylene group or a single bond, R4 represents a lower alkylene group, R5 represents a lower alkyl group, and n represents an integer from 1 to 5), but R
1 and R2 do not exhibit hydrogen atoms at the same time, and by utilizing the solubility of this polymer in organic solvents, a solution of the polymer is placed on the anode. A solid electrolyte membrane is formed by impregnation, and a solid electrolytic capacitor with a high impregnation rate, excellent adhesion to electrodes, and excellent electrical characteristics can be easily manufactured.

In the present invention, the polymer used as a raw material can be produced by an electrolytic polymerization method or a chemical polymerization method of a monomer represented by general formula (1).

The electrolytic polymerization method uses an electrolytic solution in which the above monomers are dissolved, a current density of 0, 01 to 100 mA/cm2, and an electrolytic voltage of 1 to 30 mA/cm2.
Anodic oxidation polymerization may be carried out at 0V.For chemical polymerization, for example, the above monomers may be dissolved in a solvent in the presence of a polymerization catalyst and polymerized.

In addition, after changing the monomer to a dihalogeno monomer, for example, a 2゜5 dihalogeno monomer, it is heated in tetrahydrofuran together with magnesium, and subjected to dehalogenation polycondensation under a NiCl□ (2,2'-bipyridine) catalyst. It is also possible to manufacture by

Among the monomers represented by general formula (1) used in these methods, preferred are those having R1 at one of the 3- and 4-positions of thiophene or pyrrole and R2 at the other.

When at least one of R1 and R2 is an alkyl group, it is preferably an alkyl group having 4 to 20 carbon atoms.When both R+ and R2 are an alkyl group, these groups are preferably an alkyl group having 4 to 6 carbon atoms. An alkyl group is particularly preferred, and when one is a hydrogen atom and the other is an alkyl group, the alkyl group is particularly preferably an alkyl group having 6 to 15 carbon atoms.

When at least one of R1 and R2 is an alkoxy group, it is preferably an alkoxy group having 1 to 5 carbon atoms.

At least one of R1 and R2 is -R'-0 (R'-0
) nR', R3 is a single bond or a methylene group,
Preferably, R4 is a methylene group, ethylene group, or propylene group, n is an integer of 1 to 3, and R5 is a methyl group or an ethyl group.

Specific examples of these monomers include 3-hexylthiophene, 3-dodecylthiophene, 3-hedylpyrrole, 3-nonylpyrrole, 3,4-dibutylthiophene,
3-Butyl-4-pentyl-thiophene, 3.4-dibutylpyrrole, 3.4-dipentylvirol, 3-hexylthiophene, 3.4-dibutylthiophene, 3.4
- Dipentylvirol, 3-methoxypyrrole, 3-ethoxythiophene, 3-propoxythiophene, 3-methoxyethoxymethylthiophene, 3-methoxyethoxyethoxymethylvirol, and the like.

Organic solvents for dissolving the polymer include hydrocarbons such as tetrahydronaphthalene, cyclic ethers such as tetrahydrofuran, halogenated hydrocarbons such as dichloromethane, dichloroethane, and chloroform, dialkyl sulfoxides such as dimethyl sulfoxide, dialkyl formamides such as dimethylformamide, and acetone. Any organic solvent that can dissolve the polymer to some extent can be used, such as dialkyl ketones such as methyl ethyl ketone, ethanol, and alcohols such as propatool.
Also, two or more of these solvents may be used in combination.

In the present invention, in order to form a polymer solid electrolyte membrane on a dielectric oxide film, the dielectric surface is impregnated with a solution of the polymer. This impregnation treatment is carried out by normal pressure impregnation method,
It is possible to carry out any of the vacuum impregnation methods. In the present invention, the thickness of the solid electrolyte membrane depends on the concentration and amount of the polymer impregnated onto the dielectric material, so the concentration of the polymer used The thickness of the solid electrolyte membrane can be adjusted by selecting the amount of impregnation as necessary.

After impregnation, the solvent is evaporated. Heat treatment may be performed to volatilize the solvent.

In the present invention, the dopant is not used unless the polymer is manufactured using a compound that can be a dopant in the process of manufacturing the polymer from the monomer and the resulting polymer is given appropriate electrical conductivity. It is necessary to dope it to give it electrical conductivity. In addition, when a polymer is produced using a compound that can be a dopant together with a monomer, this dopant may be undoped and then a new dopant may be doped. Doping may be done by chemical doping or electrochemical doping. Any method of doping can be employed.

For example, dopants for chemical doping include various electron-accepting compounds and electron-donating compounds, namely (1)
Halogens such as iodine, bromine and bromine iodide, (n) metal halides such as arsenic pentafluoride, antimony pentafluoride, silicon tetrafluoride, phosphorus pentachloride, aluminum chloride, aluminum bromide, (III) sulfuric acid, Nitric acid, fluorosulfuric acid,
Protonic acids such as chlorosulfuric acid, (1'/) sulfur dioxide,
Oxidizing agents such as nitrogen dioxide, difluorosulfonyl peroxide, (V)AgC-IQ<, (V[)tetracyanoethylene, tetracyanoquinodimethane 1.2.
3-dibrome-5゜6-dicyatsubarabenzoquinone, 2
．． 3-dibromo-5,6-dicyazparabenzoquinone,
(■) Alkali metals such as Li, Na, etc. can be mentioned.

On the other hand, as dopants to be electrochemically doped, (1) P F @-+ SbF I-, AsF s
-, 5bc1. - Halide anions of group Va elements such as BF4-; Anionic dopants such as anions, and (II) Li', Na'',
Examples include, but are not necessarily limited to, alkali metal ions such as K'', cationic dopants such as quaternary ammonium ions, p-toluenesulfone M quaternary ammonium salts, naphthalene-2-sulfonic acid quaternary ammonium salts, etc. These dopants may be used alone or in combination of two or more.

The dielectric oxide film on the anode used in the method of the present invention includes:
In addition to the coating made of Al2O3, Ta, Os, Nb2o,
, T i O2, ZrO2, etc., for example, A I
The 203 coating can be formed by oxidizing the surface of the aluminum layer. As the oxidation method, various known methods may be used, such as anodic oxidation at a voltage of 70V. The electrical oxidation conditions can be adjusted depending on the thickness of the oxide film or the material of the aluminum layer used, such as the operating voltage and oxidation time. can.

It is preferable that the layer of aluminum, etc., which becomes the anode substrate in the present invention, be made by etching an aluminum foil or the like to make it porous.The conditions for this etching treatment may also be selected as appropriate depending on the degree to which the aluminum layer is made porous. It can be done with

(Examples) The present invention will be specifically explained below using Examples, but the present invention is not limited to these Examples.

Example 1: 3-hexylthiophene and tetraethylammonium hexafluorophosphate (TEAPFs) were dissolved in propylene carbonate, and the concentration of 3-hexylthiophene was 0.2 mol/1 and the TEAPFs concentration was 0. An electrolyte solution of .05 mol/l was prepared. Then, using a platinum electrode in this electrolyte, a current density of 10 mA/am'' was applied.
After time electrolytic polymerization, the zero-order polymer was dedoped by reversing the potential and was dissolved in tetrahydronaphthalene to prepare a solution having a polymer concentration of 1% by weight. After etching aluminum foil using this solution, an impregnation treatment was performed on the dielectric oxide film formed by anodic oxidation to form a solid electrolyte membrane. Thereafter, chemical doping was performed using sulfur trioxide under reduced pressure, washing and drying, and the cathode was taken out using carbon paste and silver paste, placed in a case, and sealed with resin to form a solid electrolytic capacitor.

Example 2 0.05 mol of 3.4-dibutylthiophene and 0.1 mol of ferric chloride were dissolved in ether and chemically polymerized to form poly(
3,4-dibutyl-2,5-chenylene) was synthesized.

This polymer was dissolved in tetrahydrofuran in an amount of 1.9% by weight at room temperature. A chemically formed aluminum foil treated in the same manner as in Example 1 was impregnated with this polymer solution to form a solid electrolyte membrane. The electrical conductivity of this membrane is I x 10-'
S, Cs-', electrochemical doping was performed at +1.7 V vs SCE in a 0.1 mol/1 solution of tetraethylammonium hexafluorophosphate in acetonitrile. Thereafter, it was washed and dried, and the cathode was taken out using carbon paste and silver paste, and the cathode was placed in a case and sealed with resin to create an electrolytic capacitor.

Example 3: 3-methoxyer versus benzonitrile? -4 Jetoxymethylthiophene (monomer) and tetrabutylammonium hexafluorophosphate (TBAPF) were dissolved, monomer concentration 0.28 mol/1, tetraethylammonium p-toluenesulfo 712 (TEA
An electrolytic solution having a concentration of 0.03 mol/1 (P F s ) was prepared. In this electrolyte, using a platinum electrode, 1! Flow density 2 m
Electrolytic polymerization was carried out for 2 hours at A/cm". Since the electrical conductivity of the obtained polymer was 101050S-e', the polymer was diluted with tetrahydrofuran: dichloromethane, 1-dichloro-2-monochloroethane, while it was in the doped state. It was dissolved in a mixed solution of = 1:4:1 at a concentration of 2 weights and impregnated onto chemically formed aluminum foil treated in the same manner as in Example 1 to form a solid electrolyte membrane.The electrical conductivity of this membrane was 0
．． 38.Cl111 was then washed and dried, and the cathode was taken out using carbon paste and silver paste, placed in a case, and sealed with resin to produce an electrolytic capacitor.

Example 4 In dimethylformamide, 3-MeI-xyvirol Qtffi and tetrabutylammonium hexafluorophosphate as a dopant imparting agent were dissolved, and A1
．． body concentration 0.2 mol/I, dopant imparting agent concentration 0.
An electrolytic solution of 0.01 mol/1 was prepared.

In this electrolyte, using a platinum electrode, the current density was 1.5 mA/
Poly(3-methoxy-2,
5-pyrrorylene) was synthesized. This polymer was dissolved in dimethyl sulfoxide to form a 1.1% by weight solution, and a chemically formed aluminum foil treated in the same manner as in Example 1 was impregnated with this solution to form a solid electrolyte membrane. The electrical conductivity of this film was 0.018-am-'.

Next, it was washed and dried, and the cathode was taken out using carbon paste and silver paste, and the cathode was placed in a case and sealed with resin to create an electrolytic capacitor.

Example 5: 3-dodecylthiophene monomer and tetraethylammonium hexafluorophosphate as a dopant imparting agent were dissolved in nitrobenzene, and the monomer concentration was 0.2.
An electrolytic solution having a dopant-imparting agent concentration of 0.05 mol/I and a dopant-imparting agent concentration of 0.05 mol/1 was used. Electrolytic polymerization was carried out in this electrolytic solution at a current density of 101 aA/cI112 using a 3 cm x 3 cm platinum plate electrode. The produced polymer was filtered, washed and dried, and then dissolved in tetrahydronaphthalene to give a polymer concentration of 2.
A solution of % by weight was prepared and treated in the same manner as in Example PA4 to produce an electrolytic capacitor.

The electrical characteristics of the products manufactured in the above examples are shown in Tables 1 and 2.

In the table, the specific example is a conventional solid electrolytic capacitor using manganese dioxide as the electrolyte, impregnated with manganese nitrate, and 250°
It was fired at C for 20 minutes.

Table 1 shows the initial values, and Table 2 shows the values at 10V and 110°C.
The results are shown after 2000 hours.

Table 1 Table 2 Tables 1 and 2 show that the solid electrolytic capacitor of the present invention has a higher capacity per unit area than that of the comparative example.
It can be seen that the loss value, equivalent series resistance value, and leakage current are low, and the material has excellent thermal stability and durability.

(Effects of the Invention) As explained in detail above, according to the method of the present invention, mass production is possible because the polymer is separately produced by electrolysis, and dielectric oxidation is possible by dissolving the polymer in an organic solvent. Since the film is impregnated to form a solid electrolyte, the impregnation rate is high.
A solid electrolyte membrane with good adhesion can be formed, and as a result, an electrolytic capacitor with excellent electrical properties, thermal stability, and durability can be easily manufactured.

Claims (3)

[Claims] (1) In the production of solid electrolytic capacitors that have a polymer thin film layer on an anode with a dielectric oxide skin on the surface, the following general formula (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) [In the formula , X represents a sulfur atom or NH group, R^1 and R
^2 is a substituent or atom bonded to the 3rd or 4th position, and each independently represents a hydrogen atom, an alkyl group having 4 or more carbon atoms, an alkoxy group, or the general formula -R^3-O(R^4
-O) A group represented by nR^5 (where R^3 is a lower alkylene group or a single bond, R^4 is a lower alkylene group,
R^5 represents a lower alkyl group, n represents an integer from 1 to 5), but R^1 and R^2 do not represent a hydrogen atom at the same time] A method for manufacturing a solid electrolytic capacitor, comprising impregnating the anode with an organic solvent solution of the polymer to form a solid electrolyte membrane. (2) In general formula (I), R^1 is a hydrogen atom at the 4th position, R^2 is an alkyl group having 6 to 15 carbon atoms at the 3rd position,
An alkoxy group having 1 to 5 carbon atoms, or -CH_2O(C_
2. The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein a polymer of monomers having 2H_4O)_2CH_3 groups is used. (3) In general formula (I), R^1 has 4 carbon atoms at the 3rd position
2. The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein a polymer of a monomer is used, wherein R^2 is an alkyl group having 4 to 6 carbon atoms at the 4-position.