JPH0642445B2 - Method for manufacturing solid electrolytic capacitor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a solid electrolytic capacitor having good performance using lead dioxide as a conductor layer.

2. Description of the Related Art As described in, for example, Japanese Patent Publication No. 58-21414, a solid electrolytic capacitor using lead dioxide as a conductor layer is known. However, in the conventional solid electrolytic capacitor described above, the method of forming lead dioxide on the dielectric film is a method of thermally decomposing the reaction mother liquor containing lead ions, and thus the dielectric film is thermally cracked. There is also a problem that it is chemically damaged by the generated gas.

In order to prevent such drawbacks, for example, US Pat.
As described in 6,247, a method is known in which lead tetraacetate is steamed to form a lead dioxide layer on the dielectric film. However, in this method, the dielectric loss tangent of the obtained solid electrolytic capacitor is not satisfactory, probably because steam does not reach the pores of the dielectric oxide film.

Problems to be Solved by the Invention An object of the present invention is to provide a method for producing a solid electrolytic capacitor having a small dielectric loss tangent, in which a lead dioxide layer is formed on a dielectric film without utilizing a thermal decomposition reaction. is there.

Means for Solving the Problems As a result of various studies to solve the above-mentioned drawbacks of the prior art, the present inventors have found that lead dioxide is chemically formed into a dielectric film from a reaction mother liquor containing lead tetraacetate and a compound containing water of crystallization. It has been found that the above object can be achieved very effectively by forming by a precipitation method, and the present invention has been completed.

That is, according to the present invention, in producing a solid electrolytic capacitor having lead dioxide as a conductor layer, the lead dioxide is chemically deposited on a dielectric film from a reaction mother liquor containing lead tetraacetate and a compound containing water of crystallization. There is provided a method for manufacturing a solid electrolytic capacitor, which is characterized in that the solid electrolytic capacitor is formed.

The solid electrolytic capacitor of the present invention has a structure in which a part of lead dioxide has entered into the pores of the oxide film of the valve metal foil or sintered body of aluminum, tantalum, niobium, or the like. The method of forming an oxide film on the valve metal foil or sintered body is
Methods known in the art can be used.

As typical examples of the water of crystallization containing compound used in the present invention, for example, oxalic acid dihydrate, diacetylenecarboxylic acid dihydrate, potassium tartarate tetrahydrate, sodium tartarate tetrahydrate, tartaric acid 4 Hydrate, tartaric acid monohydrate, cysteic acid monohydrate, phenol hemihydrate, ammonium hydrogen salicylate monohydrate, paraaminobenzenesulfonamide monohydrate, mercaptopurine monohydrate, thymine Monohydrate, 1,5-naphthyridine dihydrate, aniline sulfonic acid monohydrate, calcium benzoate monohydrate, sodium benzoate dihydrate, benzoic acid trihydrate, copper naphthalene sulfonate Hexahydrate, barium cinnamate dihydrate, lead acetate trihydrate, sodium sulfate decahydrate, zinc sulfate heptahydrate, sodium chloride dihydrate, tin chloride dihydrate, carbonic acid sodium Hydrate, copper sulfate pentahydrate, nickel sulfate hexahydrate, cobalt chloride hexahydrate, cobalt sulfate heptahydrate, chromium sulfate heptahydrate, chromium chloride tetrahydrate, cesium manganese sulfate 12 Hydrate, copper nitrate trihydrate, iron chloride hexahydrate, iron nitrate nonahydrate, potassium chromium sulfate 12 hydrate, manganese phosphate monohydrate, manganese sulfate 5
Hydrate, ammonium cobalt sulfate hexahydrate, chromium ammonium selenate dodecahydrate, nickel ammonium sulfate hexahydrate, nickel iodate dihydrate, K ₃ [Cr (C ₂ O ₄ ).
₃ ] ・ Trihydrate, K ₄ [Mn (CN) ₆ ] ・ Trihydrate, K ₄ [Mn (NC
S) ₆ ] • trihydrate, [Ni bipyridyl) ₃ ] Cl ₂ hexahydrate,
[Pt (NH ₃ ) ₄ ] Cl ₂ monohydrate, (NH ₄ ) ₂ VO (NCS) ₄ pentahydrate, K ₄ Mo (CN) ₈ dihydrate, Na ₂ Fe (CN ) ₅ (NO) · 2 _{hydrate, Na 2 S 3 O 6 ·} 3 hydrate, NaHPHO ₃ · 5/2 hydrate, MgMoO ₄
・ 7/5 hydrate, Nd (SeO ₄ ) ₃ hexahydrate, clathrate compound hydrate clathrated by clathrate compound such as cyclodextrin, and the like. You may use 2 or more types of these crystal water containing compounds. The concentration of the crystal water-containing compound in the reaction mother liquor is
It is determined in consideration of the amount of water of crystallization (free water of crystallization) at the reaction temperature and the concentration of lead tetraacetate. In the present invention, the molar ratio of water of crystallization in the compound containing water of crystallization to lead tetraacetate is 9 to 0. Used within the range of .5. The molar ratio is 9-0.5
Outside the range, a solid electrolytic capacitor having a small dielectric loss tangent cannot be obtained. The concentration of lead tetraacetate in the reaction mother liquor is preferably in the range of 0.05 mol / from the concentration which gives the saturated solubility. If the concentration of lead tetraacetate is less than 0.05 mol / mol, one-time chemical deposition cannot provide a solid electrolytic capacitor with good performance.

The reaction mother liquor consists of lead tetraacetate, a water of crystallization compound, and a suitable solvent capable of dissolving both of these components. In addition, a soluble polymer which is soluble in the reaction mother liquor may be added to the reaction mother liquor in order to further improve the adhesion and stability between the dielectric film layer and the lead dioxide layer. Examples of the soluble polymer include polyvinylpyrrolidone and polymethylmethacrylate. The amount of the soluble polymer compounded is determined by conducting a preliminary test so that the electric conductivity of the lead dioxide layer formed by chemical precipitation does not ^fall below 10 ^-2 S · cm ⁻¹ .

As a method of chemically depositing the lead dioxide conductor layer on the dielectric film, for example, a method may be mentioned in which a solution containing lead tetraacetate and a compound containing a water of crystallization is mixed and then applied to the dielectric film. After application, it is left to stand and the resulting lead dioxide layer is washed and dried.

Effects of the Invention The solid electrolytic capacitor manufactured by the method of the present invention has the following advantages as compared with the conventionally known solid electrolytic capacitors.

Since a lead dioxide conductor layer can be formed on the dielectric film without heating to high temperatures, there is no risk of damaging the dielectric film of the anode and there is no need to perform anodic oxidation (reformation) for repair. . Therefore, the rated voltage can be increased to several times that of the conventional one, and a capacitor having the same capacity and the same rated voltage can be downsized in comparison with the conventional one.

Small leakage current.

A high breakdown voltage capacitor can be manufactured.

Good high frequency characteristics.

The dielectric loss tangent is small.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. The characteristic values of the solid electrolytic capacitors of each example are shown in Table 1.

Example 1 An aluminum foil having a thickness of 100 μm (purity 99.99%) was used as an anode, and the surface of the foil was electrochemically etched by alternately using direct current and alternating current to have an average pore diameter of 2 μm and a specific surface area of 12 m ^2. / g of porous aluminum foil. Then
This etched aluminum foil was immersed in a solution of ammonium borate to electrochemically form a thin layer of a dielectric on the aluminum foil in the solution.

A reaction mother liquor was obtained by adding an acetic acid solution in which 0.5 mol of copper tetrabenzoate dihydrate was added to a saturated acetic acid solution of lead tetraacetate. This reaction mother liquor was applied to the above-mentioned dielectric thin layer. After leaving under reduced pressure at 80 ° C. for 1 hour, the lead dioxide layer formed on the dielectric thin layer was thoroughly washed with water to remove the acetic acid solvent. Then, it dried at 120 degreeC for 3 hours.

Then, a carbon paste was applied and dried, and then a silver paste was applied and dried again. An aluminum foil was used as the cathode, and the resin was sealed to produce a solid electrolytic capacitor.

Example 2 After applying a solution of lead tetraacetate in chloroform (0.6 mol /) to a thin dielectric layer similar to that in Example 1, a solution of tin chloride dihydrate in ethyl acetate (0.3 mol /, tetra A solution of lead acetate in 3 times the molar amount of a chloroform solution) was applied and left under reduced pressure at 50 ° C. for 2 hours. Then, the produced lead dioxide layer was thoroughly washed with ethyl acetate to remove unreacted materials, and then a solid electrolytic capacitor was produced in the same manner as in Example 1.

Example 3 Instead of the ethyl acetate solution of tin chloride dihydrate in Example 2, a glycerin solution of copper sulfate pentahydrate (0.4 mol /,
3 times the molar ratio of lead tetraacetate in chloroform)
A solid electrolytic capacitor was produced in the same manner as in Example 2 except that the produced lead dioxide layer was left under reduced pressure at 0 ° C. for 2 hours and washed with methyl alcohol.

Example 4 Instead of the glycerin solution of copper sulfate pentahydrate in Example 3, an ethyl alcohol solution of lead acetate trihydrate (0.4 mol / mol)
, Lead tetraacetate chloroform solution 7 times mol), and polymethylmethacrylate 0.05 mol /
A solid electrolytic capacitor was produced in the same manner as in Example 3 except that the addition reaction temperature was 50 ° C.

Comparative Example 1 Solid electrolyte was formed in the same manner as in Example 1 except that a lead dioxide layer was formed on an aluminum foil having a dielectric thin layer similar to that of Example 1 by a conventionally known thermal decomposition method of a lead nitrate solution. A capacitor was produced.

Comparative Example 2 Solid electrolysis was performed in the same manner as in Example 1 except that the lead dioxide layer was formed on the aluminum foil having the same thin dielectric layer as in Example 1 according to the method described in the above-mentioned US Pat. No. 3,066,247. A capacitor was produced.

Claims (2)

[Claims] 1. In producing a solid electrolytic capacitor having lead dioxide as a conductor layer, the lead dioxide is formed on a dielectric film from a reaction mother liquor containing lead tetraacetate and a compound containing water of crystallization by a chemical deposition method. And a method for manufacturing a solid electrolytic capacitor. 2. The method for producing a solid electrolytic capacitor according to claim 1, wherein the molar ratio of water of crystallization in the compound of water of crystallization to lead tetraacetate in the reaction mother liquor is 9 to 0.5.