JPH0770438B2 - Method for manufacturing solid electrolytic capacitor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a solid electrolytic capacitor, and particularly to a method for manufacturing a solid electrolytic capacitor having an excellent impregnation rate of a semiconductor layer on an anode substrate and excellent performance. Regarding

[Prior Art] Generally, in an element of a solid electrolytic capacitor, an oxide film layer is formed on an anode substrate made of a valve metal, and a semiconductor layer such as manganese dioxide is formed on the outer surface of the oxide film layer as a counter electrode. A conductor layer such as paste is formed to reduce the contact resistance. However, the method of forming a semiconductor layer applied to such a solid electrolytic capacitor is, for example, a method of thermally decomposing an aqueous solution containing manganese ions, so that the oxide film is thermally cracked, Had a problem of being chemically damaged by the generated gas.

To prevent such a problem, for example, Japanese Patent Publication No. 49-
As described in Japanese Patent No. 29374, on the oxide film,
A method of forming lead dioxide as a semiconductor layer by chemical deposition is known. However, this method requires silver ions as a catalyst for chemically precipitating lead dioxide, so that there is a problem that silver or a compound of silver is attached to the surface of the oxide film and the insulation resistance decreases. .

From this point of view, the inventors of the present invention did not utilize a thermal decomposition reaction, and did not use a catalyst such as silver ion which adversely affects the performance of the capacitor, and a semiconductor layer made of lead dioxide and lead sulfate on the oxide film. We proposed a solid electrolytic capacitor formed by chemical deposition (Japanese Patent Application No. 61-93451).

[Problems to be Solved by the Invention] On the other hand, the solid electrolytic capacitor previously proposed by the present inventors with the recent demand for a smaller volume of electronic parts,
By increasing the impregnation rate of the semiconductor layer on the anode substrate,
It was necessary to measure high capacity in a small volume.

[Means for Solving Problems] As a result of various studies to solve the above-mentioned problems, the inventors of the present invention have focused on the formation temperature of the semiconductor layer and formed the semiconductor layer in a low temperature range, The present inventors have completed the present invention by finding that a solid electrolytic capacitor having a very effective purpose and good performance can be obtained.

That is, according to the present invention, on the surface of the anode substrate made of a metal having a valve action, a dielectric oxide film layer, lead dioxide produced by a chemical deposition method using an oxidizing agent, or lead dioxide and lead sulfate as main components. In the method for manufacturing a solid electrolytic capacitor in which a semiconductor layer and a conductor layer are sequentially formed, a method for manufacturing a solid electrolytic capacitor in which the temperature for forming the semiconductor layer is in the range of 28 ° C to 44 ° C is provided.

[Specific Configuration and Action of the Invention] Hereinafter, a method for manufacturing the solid electrolytic capacitor of the present invention will be described.

Examples of the valve metal substrate used as the anode of the solid electrolytic capacitor of the present invention include aluminum, tantalum,
Any metal having a valve action such as niobium, titanium and alloys having these as substrates can be used.

The oxide film layer on the surface of the anode substrate may be an oxide layer of the anode substrate itself provided on the surface layer of the anode substrate, or may be a layer of another dielectric oxide provided on the surface of the anode substrate. It may be present, but it is particularly preferable that the layer is made of an oxide of the anode valve metal itself. In any case, as a method for providing the oxide layer, a conventionally known method such as an anodization method using an electrolytic solution can be used.

The solid electrolytic capacitor manufactured by the method of the present invention has a structure in which a part of the semiconductor layer has entered the pores having the oxide film of the valve metal foil, wire or sintered body described above.

In the present invention, to form a semiconductor layer, lead dioxide,
Alternatively, it is formed by a chemical precipitation method using lead dioxide as a main component and lead sulfate, and the formation temperature of this semiconductor layer is set in the range of 28 ° C to 44 ° C.

That is, in the case of forming a semiconductor layer containing lead dioxide as a main component, a reaction mother liquor is prepared by mixing a solution containing a lead-containing compound and a solution containing an oxidizing agent, and then the reaction mother liquor is coated with the above-mentioned oxide film. The temperature of the reaction mother liquor is adjusted by immersing the provided anode substrate.
Chemically precipitate in the range of 28 ° C to 44 ° C. When the reaction temperature is lower than this range, the reaction is difficult, and when it is higher, the solid electrolytic capacitor has a large loss coefficient.

Examples of the lead-containing compound include oxine, acetylacetone, pyromeconic acid, salicylic acid, alizarin, polyvinyl acetate, porphyrin compounds, crown compounds,
Lead-containing compounds in which lead atoms are coordinate-bonded or ionic-bonded to chelate-forming compounds such as cryptate compounds, lead citrate, lead acetate, basic lead acetate, lead chloride, lead bromide, lead perchlorate, Examples thereof include lead chlorate, lead sulfamate, lead silicon hexafluoride, lead bromate, lead borofluoride, lead acetate hydrate, and lead nitrate. These lead-containing compounds are
It is appropriately selected depending on the solvent used for the reaction mother liquor. Water or an organic solvent is used as the solvent. Two or more lead-containing compounds may be mixed and used.

The concentration of the lead-containing compound in the reaction mother liquor is within the range of 0.05 mol / concentration from the concentration providing the saturated solubility, preferably within the range of 0.1 mol / concentration from the concentration providing the saturated solubility, more preferably the saturated solubility is imparted. The concentration ranges from 0.5 mol / mol. If the concentration of the lead-containing compound in the reaction mother liquor is less than 0.05 mol / mol, a solid electrolytic capacitor having good performance cannot be obtained. Further, when the concentration of the lead-containing compound in the reaction mother liquor exceeds the saturation solubility, the merit of increasing the addition amount is not recognized.

Examples of the oxidizing agent include quinone, chloranil, pyridine-N-oxide, dimethylsulfoxide, chromic acid, potassium permanganate, selenium oxide, mercury acetate, vanadium oxide, sodium chlorate, ferric chloride,
Examples thereof include hydrogen peroxide, coconut powder, and benzoyl peroxide. These oxidizing agents may be appropriately selected depending on the solvent used in the reaction mother liquor. Further, two or more kinds of oxidizing agents may be mixed and used.

The amount of the oxidizing agent used is 0.1 to 5 of the molar amount of the lead-containing compound used.
It is preferably within a double molar range.

When the proportion of the oxidizing agent used is more than 5 times the mole amount of the lead compound used, there is no cost advantage, and when it is less than 0.1 times the mole amount, a solid electrolytic capacitor having good performance cannot be obtained.

Further, when the semiconductor layer is composed of a layer containing lead dioxide which originally functions as a semiconductor and lead sulfate which is an insulating material as a main component, the leakage current value of the capacitor can be reduced by blending lead sulfate. On the other hand, the compounding of lead sulfate lowers the electric conductivity of the semiconductor layer and thus increases the loss coefficient value, but a high level of performance can be maintained and expressed even when compared with the conventional solid electrolytic capacitor. Therefore, the semiconductor layer is
If it is composed of a mixture of lead dioxide and lead sulfate,
Good capacitor performance can be maintained and expressed in a wide range of composition of 90 parts by weight or less of lead sulfate with respect to 10 parts by weight or more and less than 100 parts by weight, but lead sulfate is preferably used for 20 to 50 parts by weight of lead dioxide. 80 to 50 parts by weight, more preferably 25 to 35 parts by weight of lead dioxide, and 75 to 65 parts by weight of lead sulfate provide a good balance between the leakage current value and the loss coefficient value. If the amount of lead dioxide is less than 10 parts by weight, the conductivity deteriorates, the loss factor increases, and the capacity does not appear sufficiently.

The semiconductor layer composed mainly of lead dioxide and lead sulfate should be formed by chemical deposition with an aqueous solution containing lead ions and persulfate ions as the reaction mother liquor and with the temperature of the reaction mother liquor in the range of 28 ° C to 44 ° C. You can Moreover, you may add the suitable oxidizing agent which does not contain a persulfate ion.

The concentration of lead ion in the mother liquor is calculated from
0.05 mol / preferably from the concentration that gives saturated solubility
It is within the range of 0.1 mol / percent, and more preferably 0.5 mol / percent from the concentration providing the saturated solubility. If the concentration of lead ions is higher than the saturation solubility, there is no merit by increasing the amount. If the concentration of lead ions is lower than 0.05 mol / mol, the lead ions in the mother liquor are too thin, and the number of times of coating must be increased.

On the other hand, the concentration of persulfate ions in the mother liquor is in the range of 5 to 0.05 in terms of molar ratio with respect to lead ions. If the concentration of persulfate ion is more than 5 with respect to the lead ion, unreacted persulfate ion remains, resulting in higher cost, and the concentration of persulfate ion is less than 0.05 with respect to the lead ion. If so, unreacted lead ions remain and the conductivity deteriorates, which is not preferable.

Examples of compounds that give lead ion species include lead citrate, lead perchlorate, lead nitrate, lead acetate, basic lead acetate, lead chlorate, lead sulfamate, lead hexafluoride, lead bromate, and chloride. Examples thereof include lead and lead bromide. Two or more kinds of compounds that give these lead ion species may be mixed and used.

On the other hand, examples of the compound that gives a persulfate ion species include potassium persulfate, sodium persulfate, and ammonium persulfate. Two or more kinds of these compounds giving the persulfate ion species may be mixed and used.

Examples of the oxidizing agent include hydrogen peroxide, calcium hypochlorite, calcium chlorite, calcium chlorate, calcium perchlorate, and the like.

A conductor layer is formed on the semiconductor layer produced in the present invention by forming a metal layer, a carbon layer, or by forming a metal layer on the carbon layer. The method of forming the carbon layer on the semiconductor layer is not particularly limited, and a conventionally known method, for example, a method of applying a carbon paste is adopted. As a method of providing the metal layer, for example, silver, nickel, copper, silver-coated copper, a method of applying a paste containing a metal oxide, or silver,
Examples thereof include a method of plating or vapor depositing nickel, copper or the like.

Thus, the solid electrolytic capacitor manufactured by the method of the present invention can be made into a general-purpose capacitor product for various applications by, for example, resin molding, a resin case, a metal outer case, resin dipping, and a laminate film outer package. .

[Examples] Hereinafter, the present invention will be described with reference to Examples and Comparative Examples.

Example 1 An aluminum foil having a length of 2.5 cm and a width of 0.7 cm was used as an anode, and the surface of the foil was electrochemically etched by an alternating current.
Crim the anode terminal to the etched aluminum foil,
The anode terminal was connected. Next, electrochemical treatment is carried out in an aqueous solution of phosphoric acid and diammonium phosphate to form an oxide film of alumina.
μF / cm ² ) was obtained. Next, after winding the formed foil in a spiral shape,
The portion of the chemical conversion foil other than the anode terminal is immersed in a mixed solution of lead acetate trihydrate (2.4 mol / mol) and ammonium persulfate (4 mol / mol) in water, that is, the reaction mother liquor, and the reaction mother liquor is depressurized at about 50 ° C for 5 minutes. The etched aluminum chemical conversion foil was sufficiently permeated into the pores. Next, the reaction mother liquor was reacted for 60 minutes at 25 ° C. in the atmosphere using a water bath, but it did not react, so I tried to react at 27 ° C., but it did not react either.
Then, the mixture is reacted at 28 ° C for 60 minutes, after which the semiconductor layer made of lead dioxide and lead sulfate formed on the dielectric oxide film layer is thoroughly washed with water to remove unreacted materials, and then dried, and then silver. A conductor layer was formed with the paste, and the cathode terminal was taken on the conductor layer with a silver paste, which was then housed in an aluminum can and sealed with a resin to produce a solid electrolytic capacitor. Hereinafter, the temperature of the reaction mother liquor was set in the range of 30 ° C. to 70 ° C. and a similar solid electrolytic capacitor was produced. It was confirmed by X-ray analysis and infrared spectroscopic analysis that each of the generated semiconductor layers was composed of lead dioxide and lead sulfate, and contained about 25% by weight of lead dioxide.

Example 2 A portion of a chemical conversion foil similar to that of Example 1 other than the anode terminal was immersed in a mixed solution of an aqueous solution of 1 mol / mol of lead acetate and 0.5 mol of hydrogen peroxide with respect to lead acetate, that is, a reaction mother liquor, Under reduced pressure, the reaction mother liquor was permeated into the pores of the chemical conversion foil at about 50 ° C for 50 minutes. Next, the reaction mother liquor is used in the air using a water bath.
After reacting for 60 minutes at ℃, it did not react, so I tried to react at 27 ℃, but it did not react. Then at 28 ° C
After reacting for 60 minutes, the semiconductor layer made of lead dioxide formed on the dielectric oxide film layer was thoroughly washed with water, and then a conductor layer was formed in the same manner as in Example 1 to prepare a solid electrolytic capacitor. did. Below, the temperature of the reaction mother liquor is 30 ℃ to 70 ℃
The same solid electrolytic capacitor was produced by setting the range to.

The characteristic values of the solid electrolytic capacitor produced in Example 1 are shown in Table 1, and the characteristic values of Example 2 are shown in Table 2.
Each is an average value of 5 samples.

[Effects of the Invention] As described above, according to the present invention, when a lead dioxide or a semiconductor layer containing lead dioxide and lead sulfate as a main component is formed by a chemical deposition method using an oxidizing agent, an aqueous solution of a lead-containing compound and oxidation are used. By setting the temperature of the reaction mother liquor, which is an aqueous solution of the agent, in the range of 28 ° C to 44 ° C, it is possible to manufacture a solid electrolytic capacitor having a small loss coefficient and a large capacitance.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazumi Naito 2-24-25 Tamagawa, Ota-ku, Tokyo Inside Showa Denko K.K. (56) Reference JP-A-62-114210 (JP, A)

Claims (1)

[Claims] 1. A dielectric oxide film layer, a lead dioxide formed by a chemical deposition method using an oxidizing agent, or a semiconductor layer containing lead dioxide and lead sulfate as main components on a surface of an anode substrate made of a metal having a valve action. And a method for manufacturing a solid electrolytic capacitor in which conductor layers are sequentially formed, wherein the temperature for forming the semiconductor layer is in the range of 28 ° C to 44 ° C.