JP2792394B2 - Solid electrolytic capacitor and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid electrolytic capacitor using a conductive polymer compound as a solid electrolyte and a method for producing the same, and more particularly to a solid electrolytic capacitor using a copolymer of pyrrole and substituted pyrrole as a solid electrolyte. And a method for manufacturing the same.

[0002]

2. Description of the Related Art With advances in science and technology, there is a demand for miniaturization and improvement in reliability of electronic devices. With regard to capacitors, demands for large-capacity solid electrolytic capacitors that have good characteristics up to a high frequency range and that are excellent in reliability are increasing, and studies are being made to meet such requirements. Normally, a solid electrolytic capacitor uses a porous molded body of a valve metal such as tantalum or aluminum as a first electrode (anode), and uses an oxide film as a dielectric to form manganese dioxide or 7,7 ', 8,8'-. It has a structure in which a tetracyanoquinodimethane complex salt or the like is part of the second electrode (cathode). In this case, the solid electrolyte of the capacitor must have the function of electrically connecting the entire surface of the dielectric inside the porous compact and the electrode leads, and the function of repairing the electrical short-circuit caused by a defect in the dielectric film. It has been. Recently, new materials have been developed in the field of polymers, and as a result, conductive polymers obtained by doping a conjugated polymer such as polypyrrole or polyaniline with an electron-accepting compound have been obtained. Further, as one of the uses, a solid electrolytic capacitor using these conductive polymers as a solid electrolyte has been proposed. Japanese Patent Publication No. 4-56445 describes a capacitor using polypyrrole or its alkyl-substituted product as a solid electrolyte. The capacitor can be formed without heating at a high temperature, so that the leakage current is small and the withstand voltage is high. It is shown to be characteristic. In addition, the above publication discloses polymers such as N-methylpyrrole and N-ethylpyrrole as alkyl-substituted polypyrroles,
No mention is made of the differences in the properties of these polypyrroles.

[0003]

A conventional solid electrolytic capacitor using manganese dioxide as an electrolyte has insufficient high frequency characteristics due to the large resistance of the electrolyte.
In the case of using 8,8'-tetracyanoquinodimethane complex salt as an electrolyte, there is a problem that there is no solder heat resistance due to a low melting point. In the case of a solid electrolytic capacitor using a conductive polymer as an electrolyte, the conductivity of the solid electrolyte is high and the heat resistance is sufficient, but conversely, if a defect occurs in the dielectric film, overcurrent continues to flow. Therefore, there is a problem that reliability is lacking. In order to solve this problem, it is conceivable to repair the defective portion by repeating re-chemical formation.In this case, the formed conductive polymer is immersed again in the electrolytic solution, and a voltage is applied. Oxidation of the conductive polymer proceeds, and the properties are impaired. For the above-mentioned reasons, it is possible to stably obtain a solid electrolytic capacitor having a low electrolyte resistance, sufficient heat resistance, and excellent reliability without overcurrent even when a defect occurs in the dielectric film. There was a problem that it was difficult.

[0004]

Means for Solving the Problems The present inventors have conducted various studies to solve the above problems. As a result, it has been found that a solid electrolytic capacitor using a specific polypyrrole copolymer as an electrolyte has excellent high-frequency characteristics due to the high conductivity of the electrolyte, and that even when an overcurrent flows, it can be reduced. . That is, the present invention provides a solid electrolytic capacitor using, as an electrolyte, a substituted pyrrole-pyrrole copolymer compound doped with an electron-accepting compound, wherein the substituted pyrrole has a hydroxyl group, an acetyl group, or a carboxyl group. A solid electrolytic capacitor characterized by the following. Further, the manufacturing method is a method for manufacturing a solid electrolytic capacitor using, as an electrolyte, a hydroxyl-substituted pyrrole doped with an electron-accepting compound or a copolymer compound of pyrrole and acetyl-substituted pyrrole, comprising an oxide film of a valve action metal. After forming polypyrrole as a solid electrolyte layer on a molded article having a dielectric as a dielectric, it is characterized by including a step of immersing in an aqueous alkali solution or a solution of an acid anhydride of a dicarbonyl compound and, if necessary, re-doping. Or a method for producing a solid electrolytic capacitor using acetyl-substituted pyrrole or a carboxyl-substituted pyrrole and a copolymer compound of pyrrole doped with an electron-accepting compound as an electrolyte. N-acetylpyrrole or pyrrole-β-carboxylic acid and pillow The characterized in that it comprises a step of oxidizing cationic polymerization as a monomer.

In the present invention, the electron accepting compound is
Lewis acid compounds used as pyrrole dopants
And, for example, Cl^-, Br^-, I^-Halogen ions such as H
SO_Four ^-, R-SO_Four ^-(R is an alkyl group or alkenyl
Group), benzenesulfonic acid anion,
p-Toluenesulfonic acid anion, naphthalene sulfone
Acid anion, butylnaphthalenesulfonic acid anion,
Aromatic sulfone such as decylbenzenesulfonic acid anion
Acid anion, HNO_Three ^-, H_TwoPO_Four ^-, CH_ThreeCOO^-Etc.
No. In the present invention, a copolymer constituting a solid electrolyte
The copolymerization ratio of the compound is not particularly limited.
It is effective if it is a copolymer. These are NMR spec
Molecular structure of macromolecules such as
The structure can be confirmed by a conventionally known method.

In the present invention, examples of the pyrrole substituted with a hydroxyl group include 3-hydroxypyrrole and 3,4-dihydroxypyrrole. Pyrrole substituted with an acetyl group includes 3-acetylpyrrole and 3,4-diacetylpyrrole. , N-acetylpyrrole and the like. Examples of the pyrrole substituted with a carboxyl group include 3-carboxyl pyrrole, 3,4-dicarboxyl pyrrole, and N-carboxyl pyrrole.

According to the present invention, a solid electrolytic capacitor using a copolymer of hydroxyl-substituted pyrrole and pyrrole as an electrolyte is formed by forming polypyrrole as a solid electrolyte layer on a molded body having an oxide film of a valve metal as a dielectric. It is manufactured by immersing in an aqueous alkali solution and re-doping if necessary. The method for forming polypyrrole in the present invention is not particularly limited, and a conventionally known method such as an electrolytic polymerization method using pyrrole as a monomer or an oxidized cation polymerization using a salt of an expensive transition metal cation such as Fe ³⁺ as an oxidizing agent. Done in In the present invention, the type and pH are not particularly limited as long as the alkaline aqueous solution is alkaline, and a general aqueous solution such as aqueous ammonia, sodium hydroxide, or potassium hydroxide is used. Also,
The immersion method, immersion time and temperature are not particularly limited.

The solid electrolytic capacitor of the present invention using an acetyl group-substituted pyrrole / pyrrole copolymer compound as an electrolyte is formed by forming polypyrrole as a solid electrolyte layer on a molded body having an oxide film of a valve action metal as a dielectric. It is immersed in a solution of an acid anhydride of a dicarbonyl compound, and re-doped if necessary. Also in this method, the method for forming polypyrrole is not particularly limited, and conventionally known methods such as an electrolytic polymerization method using pyrrole as a monomer and an oxidized cation polymerization using a salt of an expensive number of transition metal cations such as Fe ³⁺ as an oxidizing agent. Done in a way. Examples of the acid anhydride of the dicarbonyl compound include acetic anhydride, but are not particularly limited. The immersion method, immersion time, and temperature are not particularly limited.

According to the present invention, a solid electrolytic capacitor comprising an electrolyte containing a copolymer compound of N-acetylpyrrole and pyrrole is used for forming a molded product having an oxide film of a valve action metal as a dielectric, and using pyrrole and N-acetylpyrrole as monomers. It is produced by oxidative cationic polymerization. The oxidizing cationizing agent is not particularly limited, and salts of expensive transition metal cations such as Fe ³⁺ and Cu ²⁺ conventionally used for pyrrole polymerization can be used. Such oxidizing cationizing agents include:
Ferric dodecylbenzenesulfonate, ferric butylnaphthalenesulfonate, cupric dodecylbenzenesulfonate, cupric butylnaphthalenesulfonate and the like. The reaction proceeds by mixing the monomer and the oxidizing cationizing agent using an organic solvent such as methanol or water. The reaction forms a copolymer of N-acetylpyrrole and pyrrole on the surface of the dielectric. In the present invention, the copolymer is washed with methanol, pure water, or the like, if necessary. Further, the above polymerization can be carried out repeatedly.

According to the present invention, a solid electrolytic capacitor using a copolymer compound of carboxyl-substituted pyrrole and pyrrole as an electrolyte is provided by forming pyrrole and pyrrole-β-carboxylic acid on a molded product having an oxide film of a valve metal as a dielectric. Is produced by oxidative cationic polymerization using as a monomer. The oxidizing cationizing agent is not particularly limited, and salts of expensive transition metal cations such as Fe ³⁺ and Cu ²⁺ conventionally used for pyrrole polymerization can be used. Examples of such an oxidizing cationizing agent include ferric dodecylbenzenesulfonate, ferric butylnaphthalenesulfonate, cupric dodecylbenzenesulfonate, and cupric butylnaphthalenesulfonate. The reaction proceeds by mixing the monomer and the oxidizing cationizing agent using an organic solvent such as methanol or water. A copolymer of carboxyl-substituted pyrrole and pyrrole is formed on the surface of the dielectric by the reaction. In the present invention, the copolymer is washed with methanol, pure water or the like as necessary. Further, the above polymerization can be carried out repeatedly.

A hydroxyl-substituted pyrrole-pyrrole copolymer compound doped with the electron-accepting compound of the present invention;
Acetyl group-substituted pyrrole and pyrrole copolymer compound,
In addition, a solid electrolytic capacitor using a carboxyl-substituted pyrrole-pyrrole copolymer compound as an electrolyte has a smaller leakage current and a higher withstand voltage than those using a polypyrrole homopolymer as an electrolyte. This is because, in the capacitor of the present invention, when the current is concentrated on a defective portion of the dielectric film and the like and heat is generated, one of the components of the copolymer, hydroxyl-substituted pyrrole, acetyl-substituted pyrrole and carboxyl-substituted pyrrole, undergoes some reaction. It is thought that the electrical conductivity of the portion occurred and the conductivity of the portion was lowered, but the details are unknown. According to the study of the present inventors, a phenomenon in which a current decreases with time when a voltage is applied is observed even in a solid electrolytic capacitor using a homopolymer of polypyrrole and a polyalkylpyrrole as an electrolyte, and insulation of a defective portion due to concentration of current is observed. Is expected to occur, the extent is the hydroxyl-substituted pyrrole and pyrrole copolymer compound of the present invention, acetyl group-substituted pyrrole and pyrrole copolymer compound and carboxyl group-substituted pyrrole and pyrrole copolymer compound It was smaller than a capacitor with electrolyte.

In the present invention, after the conductive polymer described above is formed as an electrolyte layer, electrode leads are attached by a conventionally known method using a silver paste and a carbon paste.
Further, molding is performed as necessary to complete a solid electrolytic capacitor.

[0013]

Next, an embodiment of the present invention will be described. Example 1 A 35 wt% methanol solution of ferric dodecylbenzenesulfonate was placed in a glass container kept at -75 ° C., and 3 times the number of moles of ferric dodecylbenzenesulfonate in the solution with stirring. An amount of moles of pyrrole was added dropwise to prepare a mixed solution of ferric dodecylbenzenesulfonate and pyrrole. Next, length 3mm x 2mm x 2.5mm
0.05w of a rectangular parallelepiped tantalum fine powder sintered compact
Anodized at 100 V in a t% phosphoric acid aqueous solution, washed and dried to obtain a pellet having a capacity of 10 μF in the electrolytic solution. The pellet was immersed in the above-mentioned mixed solution of ferric dodecylbenzenesulfonate / pyrrole at -75 ° C.
After 60 seconds, the pellet was taken out, kept in air at 25 ° C. for 30 minutes to polymerize the pyrrole, washed with methanol and dried to obtain a tantalum pellet sample filled with polypyrrole doped with dodecylbenzenesulfonate anion. This sample was immersed in a 0.1 mol% aqueous ammonia solution and kept at room temperature for 30 minutes. Next, it was washed with methanol and dried at 60 ° C. under reduced pressure. The X-ray photoelectron spectrum was measured before and after the treatment with the aqueous ammonia solution, and the C
When the peak was separated from the 1s spectrum, it was found that 3% of the entire pyrrole ring of the main chain of polypyrrole was changed to pyrrole hydroxide after the treatment with the aqueous ammonia solution.
Further, a lead was drawn out from the sample subjected to the ammonia water treatment using a silver paste to complete a solid electrolytic capacitor. The current value measured 60 seconds after applying 35 V to this capacitor was 20 nA, which was 1/10 or less of the standard value. Also, when the voltage was increased at 1V per minute,
It was destroyed at 88V. This withstand voltage value was more than twice as large as that of a capacitor using manganese dioxide as an electrolyte and made of the same tantalum pellets.

Comparative Example 1 Using the tantalum pellet sample filled with polypyrrole of Example 1, the lead was drawn out using silver paste as it was to complete a solid electrolytic capacitor using polypyrrole as an electrolyte. Applying 35V to this capacitor
When the current value after seconds was measured, it was 60 nA, which was lower than the standard value. However, the current value was larger than the case where the copolymer of the hydroxyl-substituted pyrrole and pyrrole in Example 1 was used as the electrolyte. Also, when the voltage was increased at 1 V per minute, 55
Destroyed with V. This is also lower than that of a capacitor using manganese dioxide as an electrolyte prepared using the same tantalum pellets, but inferior to that of Example 1 in which a copolymer of hydroxyl-substituted pyrrole and pyrrole is used as an electrolyte.

Example 2 The tantalum pellet sample filled with polypyrrole of Example 1 was immersed in a 0.1 mol% aqueous solution of acetic anhydride.
It was kept at room temperature for 30 minutes. Then, wash with methanol,
It dried under reduced pressure at ° C. X before and after treatment with aqueous acetic anhydride
The linear photoelectron spectrum was measured, and the C1s spectrum was separated into peaks. As a result, it was found that 3% of the entire pyrrole ring of the main chain of polypyrrole was changed to acetylpyrrole after the treatment. Further, a lead was drawn out from the processed sample using a silver paste to complete a solid electrolytic capacitor. The current value measured 60 seconds after applying 35 V to this capacitor was 18 nA, which was 1 standard value.
/ 10 or less. When the voltage was increased at 1 V per minute, the device was broken at 86 V. This withstand voltage value was more than twice as large as that of a capacitor using manganese dioxide as an electrolyte and made of the same tantalum pellets.

Example 3 The rectangular parallelepiped tantalum fine powder sintered compact pellet of Example 1 was anodized to form a dielectric layer, and the pellet was immersed in a 25 wt% ferric dodecylbenzenesulfonate methanol solution. Two minutes later, the pellet was taken out, immediately immersed in an aqueous solution of 0.01 M N-acetylpyrrole and 0.1 M pyrrole, and held for 1 hour. Next, the pellet was washed with methanol and dried, an X-ray photoelectron spectrum was measured for a part of the polymer formed on the surface, and the C1s spectrum was subjected to peak separation. As a result, the obtained pellet was doped with dodecylbenzenesulfonic acid anion as a dopant. It was found to be filled with a copolymer of N-acetylpyrrole and pyrrole, and the copolymerization ratio was found to be 10:90. Further, a lead was drawn out from the obtained sample by using a silver paste to complete a solid electrolytic capacitor. The current value measured 60 seconds after applying 35 V to this capacitor was 18 nA, which was 1 standard value.
/ 10 or less. When the voltage was increased at 1 V per minute, the device was broken at 85 V. This withstand voltage value was more than twice as large as that of a capacitor using manganese dioxide as an electrolyte and made of the same tantalum pellets.

Example 4 The rectangular parallelepiped tantalum fine powder sintered compact pellet of Example 1 was anodized to form a dielectric layer, and the pellet was immersed in a 25 wt% ferric dodecylbenzenesulfonate methanol solution. Two minutes later, the pellet was taken out, immediately immersed in an aqueous solution of 0.01 M pyrrole-β-carboxylic acid and 0.1 M pyrrole, and held for 1 hour. Next, the pellet was washed with methanol and dried, and an X-ray photoelectron spectrum of a part of the polymer formed on the surface was measured.
When the peak of the C1s spectrum was separated, the obtained pellet was filled with a copolymer of pyrrole-β-carboxylic acid and pyrrole using dodecylbenzenesulfonic acid anion as a dopant, and the copolymerization ratio was 1
0:90 was found. Furthermore, the lead was drawn out from the sample using silver paste to complete a solid electrolytic capacitor. When a current value was measured 60 seconds after applying 35 V to this capacitor, it was 19 nA, which was 1/10 or less of the standard value. When the voltage was increased at 1 V per minute, the device was broken at 89 V. This withstand voltage value was more than twice as large as that of a capacitor using manganese dioxide as an electrolyte and made of the same tantalum pellets.

Example 5 The rectangular parallelepiped tantalum fine powder sintered compact pellet of Example 1 was anodized to form a dielectric layer, and the pellet was immersed in a 25 wt% ferric dodecylbenzenesulfonate methanol solution. Two minutes later, the pellet is taken out, immediately immersed in a 0.1 M pyrrole aqueous solution and held for one hour to polymerize the pyrrole, washed with methanol and dried, and filled with polypyrrole doped with dodecylbenzenesulfonate anion. A pellet sample was obtained. This sample was treated with ammonia water in the same manner as in Example 1,
The lead was drawn out by the method of Example 1 to complete the capacitor. The current value after 60 seconds after applying 35 V to this capacitor was 20 nA, which was 1/1 of the standard value.
0 or less. When the voltage was increased at 1 V per minute, the device was broken at 88 V. This withstand voltage value was more than twice as large as that of a capacitor using manganese dioxide as an electrolyte and made of the same tantalum pellets.

Embodiment 6 Instead of the tantalum fine powder sintered body of Embodiment 1, the surface area is enlarged by 12 times by etching.
Anodized, washed and dried in the same manner as in Example 1 using a square aluminum foil of m m, immersed in a mixed solution of ferric dodecylbenzenesulfonate and pyrrole of Example 1, and immersed in air. When kept at ℃ for 1 hour, an aluminum foil whose surface was coated with polypyrrole using dodecylbenzenesulfonate anion as a dopant was obtained. This sample was treated with ammonia water in the same manner as in Example 1,
The lead was drawn out by the method of Example 1 to complete the capacitor. The current value after 60 seconds after applying 35 V to this capacitor was 30 nA, which was 1/5 of the standard value.
It was below. Further, when the voltage was increased at 1 V per minute, it was found that this capacitor had a high withstand voltage without dielectric breakdown up to 50 V.

[0020]

As described above, according to the present invention, it is possible to provide a highly reliable solid electrolytic capacitor having excellent high frequency characteristics and capable of reducing overcurrent even when flowing. is there.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-213113 (JP, A) JP 4-56445 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01G 9/028

Claims (3)

(57) [Claims] 1. A solid electrolytic capacitor using a substituted pyrrole-pyrrole copolymer compound doped with an electron-accepting compound as an electrolyte, wherein the substituted pyrrole has a hydroxyl group, an acetyl group or a carboxyl group. A solid electrolytic capacitor characterized by the following. 2. A method for producing a solid electrolytic capacitor comprising, as an electrolyte, a hydroxyl-substituted pyrrole doped with an electron-accepting compound or a copolymer compound of acetyl-substituted pyrrole and pyrrole. After forming polypyrrole as a solid electrolyte layer on the molded body to be a dielectric, the solid is characterized by including a step of immersing the resultant in an aqueous alkali solution or a solution of an acid anhydride of a dicarbonyl compound and, if necessary, re-doping. Manufacturing method of electrolytic capacitor. 3. A method for producing a solid electrolytic capacitor using, as an electrolyte, an acetyl group-substituted pyrrole or a carboxyl group-substituted pyrrole-pyrrole copolymer compound doped with an electron-accepting compound. A method for producing a solid electrolytic capacitor, characterized by comprising a step of subjecting a molded product having a dielectric material to oxidative cationic polymerization using N-acetylpyrrole or pyrrole-β-carboxylic acid and pyrrole as monomers.