JP3242464B2 - Method for manufacturing solid electrolytic capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a solid electrolytic capacitor, and more particularly to a method for impregnating a solid electrolyte.

[0002]

2. Description of the Related Art A conventional solid electrolytic capacitor in which a solid electrolyte is interposed between an anode electrode made of a valve metal having an anodic oxide film on its surface and a cathode electrode opposed to the electrode is used. Has used manganese dioxide.
However, in this method, when manganese dioxide is formed on the electrode, the general anodic body electrode is immersed in a manganese nitrate solution and then thermally decomposed, so that the anodized film is damaged, and in addition, the manganese dioxide is used. There is a disadvantage that the repairability is poor.

As a method for compensating for these drawbacks, a solid electrolytic capacitor using an organic semiconductor such as a TCNQ complex as a solid electrolyte has appeared. As a typical example of this impregnation method, as described in JP-A-57-173928, an organic semiconductor containing a TCNQ complex is liquefied by heating and melting, and the element is put into the device until decomposition, followed by rapid cooling and solidification. It is to let. However, this solid electrolytic capacitor has low conductivity of the TCNQ complex, poor bonding with electrodes, high cost, and the like.
In terms of characteristics as a capacitor, it has a drawback that the capacitance is small, the dielectric loss is large, and the heat resistance is poor due to the thermal weakness of the TCNQ complex.

[0004] Based on this background, the conductivity is good,
A solid electrolytic capacitor using a conductive polymer as a solid electrolyte, which has a good bondability with a dielectric film and can also be adapted to solder heat resistance, has appeared. An example of this attempt is disclosed in, for example, Japanese Patent Application Laid-Open No. 62-118510, in which a polymer compound having a π-electron conjugate system such as polypyrrol, polythiophene, poly (isothianaphthene) is coated with a dielectric oxide film. Electrolytic polymerization is carried out directly thereon, and if necessary, an electron-donating compound such as a protonic acid or an alkali metal ion is doped as a doping agent to improve conductivity characteristics. However, in this method, when a polymer compound is polymerized and formed on the electrode, only a special portion such as a defective portion of the dielectric oxide film reacts, the impregnation property is extremely poor, the defective film portion increases, and the repair formation is increased. , The leakage current characteristics were extremely poor.

For the purpose of solving such a problem, a method disclosed in Japanese Patent Application Laid-Open No. 63-173313 has been disclosed. According to this, first, a conductive polymer layer is formed on a dielectric oxide film by chemical polymerization using an oxidizing agent, and the main conductive polymer is electrolytically polymerized via the polymer to form a solid electrolyte layer. It is formed. However, according to this method, since the conductive polymer layer generated by chemical polymerization is used as a power supply part in the subsequent electrolytic polymerization, productivity is significantly inferior, and considerable production technology is required. There's a problem. Also, the yield is not good. Furthermore, when the polymer is oxidized in the dielectric oxide film due to the chemical polymerization reaction, the film itself also undergoes an oxidation-reduction reaction when the polymer is chemically bonded, and the withstand voltage of the oxide film is greatly reduced, resulting in leakage current characteristics. Is unstable.

[0006]

The problem to be solved by the present invention is to form a conductive polymer as a solid electrolyte, to provide a power supply method for electrolytic polymerization with a good yield, and to provide a dielectric oxide film and a conductive material. The purpose of the present invention is to prevent a film from being deteriorated by a redox reaction during chemical bonding with a conductive polymer.

[0007]

The inventor of the present invention has conducted various studies to solve the above problems, and as a result, has found means for solving the above problems. The basic idea of the present invention is that when power supply during electrolytic polymerization is performed through a dielectric oxide film, the deterioration between the polymer and the film is reduced by chemical bonding based on electrochemical redox. Therefore, it is necessary to change from current dependence to electric field dependence during electropolymerization.To do so, an oxide with a strong redox ability is attached to the oxide film surface to prevent film deterioration and to make the film oxidized by the polymer. When reduced by the reaction, it is necessary that the film is immediately oxidized and repaired, and that the metal oxide itself has good conductivity.

When a metal oxide was selected by satisfying the above conditions, it was found that permanganate was good. Manganese changes very rapidly depending on the surrounding environment, such as pentavalent, pentavalent, tetravalent, and divalent, and promotes the oxidation reaction.
However, manganese dioxide has some conductivity but is inferior to conductive polymers. Therefore, it is necessary to further improve the conductivity, and upon examination, it has been found that a mixture with lead dioxide has an extremely good conductivity. When the lead acetate solution was reacted with permanganate to form lead dioxide, manganese dioxide was formed simultaneously with the formation of lead dioxide, and a desired mixed oxide could be formed.

That is, in a method for manufacturing a solid electrolytic capacitor using a conductive polymer compound as a solid electrolyte, lead acetate and peroxide are used as pretreatment for forming a conductive polymer on a capacitor anode electrode by chemical polymerization or electrolytic polymerization. manga
The electrode is immersed in a mixed aqueous solution of
A mixture of lead dioxide and manganese dioxide by redox reaction
A method for producing a solid electrolytic capacitor, wherein the method is performed on the electrode .

[0010]

When permanganate is added to lead acetate, lead dioxide is produced by the oxidizing action of permanganate, and at the same time, permanganate is also reduced to produce manganese dioxide. Since both lead dioxide and manganese dioxide have poor solubility in an aqueous solution, they are quickly deposited on a dielectric oxide film simultaneously with their formation. Both manganese dioxide and lead dioxide can be used as a solid electrolyte of an electrolytic capacitor, and when a mixture of both is used, the conductivity becomes better than that of a single electrolyte. The damage of the dielectric oxide film during this reaction is a precipitation reaction due to the redox reaction between lead acetate and permanganic acid, so the oxidation-reduction reaction with the dielectric oxide film does not occur during the deposition, and the film deteriorates. Is extremely small. This is a great effect of the present invention. If this is the same as before, for example, the reaction between lead acetate and persulfuric acid, only the precipitation of lead dioxide reduces a part of the dielectric oxide film at the time of deposition, causing film deterioration and causing a large increase in leakage current, resulting in unstable characteristics. Had become a major factor.

Further, when a mixture of manganese dioxide and lead dioxide is formed in advance and then a conductive polymer such as polypyrrol is formed by electrolytic polymerization, a method of supplying power to the oxide mixture is unnecessary. In addition, even if a method of directly supplying power to the capacitor anode electrode is used, the dielectric oxide film is not damaged. This is because permanganic acid, which could not be converted to manganese dioxide, remains in the mixture of manganese dioxide and lead dioxide, and even if the dielectric oxide film deteriorates during electrolytic polymerization, the film remains under the electric field of the anode. This causes the film to be immediately oxidized and repaired.

[0012]

EXAMPLES Specific examples of the present invention will be described below. (Example 1) High-purity aluminum foil having a thickness of 90 μm (9
(9.99%) by electrolytic etching with alternating current
An electrode foil having twice the surface magnification was prepared, and subjected to a chemical conversion treatment with a neutral phosphoric acid solution at 30 V to form a dielectric film. Then 100 g / l potassium permanganate aqueous solution and 300 g
g / l of an aqueous lead acetate solution was prepared, and both were mixed and immediately immersed in the electrode foil. The reaction was carried out at room temperature for 30 minutes to precipitate a mixture of lead dioxide and manganese dioxide on the electrode. Next, 0.1 mol of pyrrole and 0.05 mol
Was subjected to electrolytic polymerization at a current of 1 mA / cm ² for about 40 minutes in an acetonitrile solution containing tri-n-butylammonium p-toluenesulfonic acid. The power was supplied directly to the electrode foil at that time. After the electrolytic polymerization was completed, a colloidal carbon was applied and formed, and a cathode lead was taken out with a silver paste, and then packaged with an epoxy resin to produce a solid electrolytic capacitor.

Example 2 A mixture of lead dioxide and manganese dioxide was produced in the same manner as in Example 1 using the electrode foil treated in the same manner as in Example 1. Next, an aqueous solution containing 10% sodium peroxodisulfate and 5% benzenesulfonic acid was applied. Thereafter, it was exposed to an atmosphere composed of nitrogen and pyrrole vapor to carry out oxidative polymerization of polypyrrole. After the polymerization was completed, a colloidal carbon was applied and formed, and a cathode lead was taken out with silver paste.
Thereafter, the package was covered with an epoxy resin to produce a solid electrolytic capacitor.

Example 3 Using an electrode foil treated in the same manner as in Example 1, an aqueous solution of 80 g / l of potassium permanganate and an aqueous solution of 200 g / l of lead acetate were prepared and mixed. The electrode foil was immediately immersed. 6 at room temperature
The reaction was carried out for 0 minutes to precipitate a mixture of lead dioxide and manganese dioxide on the electrode. Next, 1 m of acetonitrile solution containing 0.1 mol of pyrrole and 0.05 mol of tri-n-butylammonium salt of p-toluenesulfonic acid was used.
Electropolymerization was performed at a current of A / cm ² for about 40 minutes. The power was supplied directly to the electrode foil at that time. After the electrolytic polymerization was completed, a colloidal carbon was applied and formed, and a cathode lead was taken out with a silver paste, and then packaged with an epoxy resin to produce a solid electrolytic capacitor.

COMPARATIVE EXAMPLE An electrode foil treated in the same manner as in Example 1 was used.
l and 0.05 mol / l of an aqueous solution of p-toluenesulfonic acid under reduced pressure for 5 minutes, then dried and then immersed in an acetonitrile solution containing 2 mol / l of pyrrole to form a polypyrrol thin film by chemical oxidation polymerization. Generated. Next, electrolytic polymerization was carried out at a current of 1 mA / cm ² for about 40 minutes in an acetonitrile solution containing 0.1 mol of pyrrole and 0.05 mol of tri-n-butylammonium salt of p-toluenesulfonic acid. At that time, power was supplied through the above-mentioned chemically oxidized and polymerized polypyrrole thin film. After the electrolytic polymerization was completed, a colloidal carbon was applied and formed, and a cathode lead was taken out with a silver paste, and then packaged with an epoxy resin to produce a solid electrolytic capacitor. Table 1 shows the above results.

[0016]

[Table 1]

[0017]

As shown in Table 1, the solid electrolytic capacitor manufactured according to the present invention has a significantly improved leakage current characteristic, and also has an improved bonding state with the electrodes and a good impregnation property, so that the capacitance is improved. Increases and the loss is also apparently reduced. In addition, the workability is greatly improved as compared with the conventional polymer impregnation method, so that the yield is improved, and there are industrial and practical values of great value.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01G 9/02

Claims (1)

(57) [Claims] 1. A method for manufacturing a solid electrolytic capacitor using a conductive polymer compound as a solid electrolyte, wherein lead acetate and peroxide are used as pretreatment for forming a conductive polymer on a capacitor anode electrode by chemical polymerization or electrolytic polymerization. Manganic acid
The electrode is immersed in a mixed aqueous solution of salt and subjected to chemical redox.
The mixture of lead dioxide and manganese dioxide by reduction reaction
A method for producing a solid electrolytic capacitor, wherein the method is formed on an electrode .