JPS63110623A - Manufacture of solid electrolytic capacitor - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for manufacturing a solid electrolytic capacitor, and more particularly to a method for manufacturing a solid electrolytic capacitor with an improved manganese oxide layer.

(Prior art) Valve metals (T a , N b , AI!,
T i, Z r.

In solid electrolytic capacitors, a porous sintered body made of Hf, etc.) is anodized to form a chemical conversion film, and a solid electrolyte layer is formed on the surface of the chemical conversion film, a thermal decomposition reaction of an aqueous solution of manganese nitrate is generally used. A solid electrolyte layer made of manganese oxide, preferably manganese dioxide, is formed. That is, after impregnating and adhering a manganese nitrate aqueous solution to a porous sintered body on which a chemical conversion film (dielectric layer) has been formed, the manganese dioxide layer is sintered by heating to 100 to 350"C to cause a thermal decomposition reaction. Form uniformly on the chemical conversion coating from the porous surface to the inside of the aggregate.Next, a carbon layer,
A solid electrolytic capacitor is produced by forming a silver layer, attaching a cathode lead part with solder, and applying a resin exterior.

In such a production method, carrying out the thermal decomposition reaction of manganese nitrate at 150 to 200°C means that β-MnO□ (
It is said to be suitable for the formation of pyroluthite). β-M
nO2 is the most stable of manganese dioxide, has the lowest electrical resistance (specific resistance 10-' to 10Ω (approximately)), and has the best ability to repair chemical conversion films, providing optimal performance as an inorganic solid electrolyte. It is something that you have.

(Problem to be solved by the invention) However, when manganese nitrate is thermally decomposed, β-MnO□ is not necessarily formed, but manganese dioxide with low crystallinity or high resistivity and chemical conversion coating. Lower oxides such as Mn2O3, which are inferior in repair ability, are often produced as by-products.

In particular, manganese dioxide and low-order oxides with low crystallinity are likely to be produced as side effects near the outside of the sintered body and in small products, resulting in a problem that the loss (tan δ) of the solid electrolytic capacitor becomes large.

The present invention solves the above-mentioned problems and effectively suppresses by-products of low-crystalline manganese dioxide and lower oxides, resulting in loss (t).
An object of the present invention is to provide a solid electrolytic capacitor with improved an δ).

(Means for Solving the Problems) In order to solve the above problems, the present invention generates a chemical conversion film on the surface of a porous sintered body made of a valve metal, and forms a manganese oxide layer on the chemical conversion film. A method for producing a solid electrolytic capacitor in which a chemical conversion film is formed includes impregnating and adhering a manganese nitrate aqueous solution containing a chlorate or a perchlorate to the porous sintered body in which the chemical conversion film is formed, and then firing the porous sintered body. The present invention provides a method for manufacturing a solid electrolytic capacitor with characteristics.

The porous sintered body used in the method of the present invention is preferably a porous sintered body made of a valve metal such as tantalum, niobium, aluminum, titanium, zirconium, or hafnium.

A chemical conversion film (dielectric layer) is formed on the surface of this sintered body by a method such as anodic oxidation using nitric acid, phosphoric acid, etc., and a layer made of manganese oxide is formed as a semiconductor layer on this chemical conversion film. To form the manganese oxide layer, the steps of impregnating and adhering the sintered body with a manganese nitrate aqueous solution containing chlorate or perchlorate and firing are repeated several to several times.

Although the concentration of the manganese nitrate aqueous solution used in the present invention is not particularly limited, a concentration of 10 to 80% by weight is usually used.

In the present invention, the cationic components of the chlorate and perchlorate contained in the manganese nitrate aqueous solution are
Alkali metals such as lithium, potassium, and sodium;
Salts of alkaline earth metals such as magnesium or ammonium are preferably used.

The content of these salts in the manganese nitrate aqueous solution is 0.0
Setting the amount to 1 to 10% by weight, preferably 0.1 to 5% by weight effectively suppresses by-products of manganese dioxide and lower oxides with poor crystallinity, and produces dense dioxide with excellent crystallinity. Desirable for obtaining a manganese layer.

Firing is performed under normal firing conditions, for example, in an air atmosphere or a steam atmosphere at a temperature of about 100 to 350°C for 5 to 30 minutes.

In addition, suitable additives such as nitric acid can also be used together as necessary.

(Function) In the present invention, although the mechanism of action of the chlorate or perchlorate contained in the manganese nitrate aqueous solution is not clear,
The reason why a manganese dioxide layer with excellent crystallinity is formed is considered to be as follows.

The thermal decomposition reactions that occur during calcination of manganese nitrate are as follows: (1) dehydration, (2) formation of manganese oxynitrate, (
3) formation of manganese dioxide, and (4) formation of lower oxides.

Mn (Not)z ・nl(z O−M n (N
03) Z + n H2O (11M n (N O
2) t −M n ON O3+ N Oz
(21MnONOz −MnOt+NOt
(31M n O2=Mnt Ox +1/2
0z (41 Among these, the reaction from manganese nitrate to manganese dioxide requires a strong oxidizing power such as a nitric acid group. Generally, gases such as water vapor and nitrogen peroxide are released as a result of thermal decomposition of manganese nitrate. Therefore, in order to form a pinhole-free manganese dioxide layer with a predetermined thickness, it is necessary to repeat the impregnation and firing process several to several times.

150~ to generate β-MnO2 with excellent crystallinity
Although it is preferable to carry out thermal decomposition of manganese nitrate at 200°C, in practice, calcination is carried out at a relatively high temperature, for example, 200 to 350°C, because it is necessary to shorten the reaction time.

When thermal decomposition is carried out rapidly at high temperatures, it is thought that a considerable portion of the nitric acid groups in manganese nitrate are eliminated and released outside the reaction system, and the crystallinity of the manganese dioxide produced often deteriorates. , the amount of by-products of lower oxides increases.

In the method of the present invention, Mn20. It is considered that the production of β-M n O2 is effectively promoted by suppressing the production of lower oxides such as .

The lower the concentration of chlorate or perchlorate, the greater the oxidizing ability (However, if it exceeds a certain limit, the amount of chlorine ions and hydrogen chloride gas generated will increase, degrading the chemical conversion coating. or cation components may be incorporated into the crystal structure of manganese dioxide.

(Example) Hereinafter, the present invention will be specifically described based on Examples and Comparative Examples.

Example 1 Pellets made of tantalum of 40CFV/P were made,
18 at room temperature in a 0.01% phosphoric acid solution
0 ■ Chemical conversion was performed. In addition, after reaching a predetermined voltage, aging and chemical conversion was performed for 2 hours. After the chemical formation was completed, it was washed in pure water at 90°C.

Next, after immersing for 30 seconds in a 14x4% manganese nitrate aqueous solution containing 2% by weight of ammonium perchlorate,
Bake at 50°C for 5 minutes. After repeating this process twice, 28% by weight containing 2% ammonium perchlorate
The sample was immersed in a manganese nitrate solution for 30 seconds and fired under the same conditions as above. Repeat this process two more times. Then,
60% by weight containing 2% ammonium perchlorate
The process of immersing the sample in a manganese nitrate solution for 30 seconds and firing under the same conditions as above was repeated five times. During this period, each time the firing was completed, the voltage was set at 60V in a 0.001% by weight phosphoric acid solution at room temperature.
The defective part of the chemical conversion film is repaired by applying it again.

Next, cathode formation is performed. That is, after immersing it in a 4% by weight graphite solution and drying it at 150°C for 10 minutes,
Silver paint is applied as a current collector and cured at 150°C for 30 minutes to form a capacitor element. Electrode leads were attached to this element, it was covered with Epoquine resin, and after aging, the characteristics as a capacitor were evaluated and the structure of the manganese oxide was analyzed, and the results are shown in Table 1.

Examples 2 to 4 1% by weight of perchlorate was contained in an aqueous solution of manganese nitrate, and the cation components of the perchlorate were potassium, sodium,
and magnesium, respectively, the second and third
As a fourth example, a capacitor was manufactured in the same manner as in Example 1, and the characteristics were evaluated. The results are shown in Table 1.

Example 5 2% by weight of ammonium chlorate in manganese nitrate aqueous solution
A capacitor was produced in the same manner as in Example 1, except that it was added, and the characteristics were evaluated. The results are shown in Table 1.

Examples 6 to 8 Examples 6, 7, and 8 are cases in which 1% by weight of chlorate is contained and the cationic components of the chlorate are potassium, sodium, and magnesium, and the other conditions are as follows. A capacitor was produced in the same manner as in the first example,
Characteristics were evaluated and the results are shown in Table 1.

Example 9 A capacitor was produced in the same manner as in Example 1, except that 2% by weight of ammonium perchlorate was added to an aqueous manganese nitrate solution containing 5% by weight of nitric acid based on Mn' ions, and the characteristics were determined. The evaluation was carried out and the results are shown in Table 1.

Example 10 Example 1 except that 200CFV/P pellets were used.
A prototype capacitor was manufactured in the same manner as above, and the characteristics were evaluated. The results are shown in Table 1.

Example 11 Using a pellet of 80CFV/P, the formation voltage was 80V,
A capacitor was produced in the same manner as in Example 1 except that the reconstitution voltage was 35 V, and the characteristics were evaluated. The results are shown in Table 1.

(Wood page, blank space below) Comparative Example 1 A capacitor was produced in the same manner as in Example 1 except that the manganese nitrate aqueous solution did not contain any other components, and the characteristics were evaluated and the results are shown in Table 2.

Comparative Example 2 A capacitor was produced in the same manner as in Example 10 except that the manganese nitrate aqueous solution did not contain any other components, and the characteristics were evaluated and the results are shown in Table 2.

Comparative Example 3 A capacitor was produced in the same manner as in Example 11 except that the manganese nitrate aqueous solution did not contain any other components, and the characteristics were evaluated. The results are shown in Table 2.

Table 2 (Effects of the Invention) As explained above, according to the present invention, the production of solid manganese dioxide and lower oxides with low crystallinity is effectively suppressed, and the loss (tan δ) is improved. You can get an electrolytic capacitor.

Claims (2)

[Claims] (1) A method for manufacturing a solid electrolytic capacitor in which a chemical conversion film is formed on the surface of a porous sintered body made of a valve metal, and a manganese oxide layer is formed on the chemical conversion film, in which the chemical conversion film is formed. A method for manufacturing a solid electrolytic capacitor, which comprises impregnating and adhering a manganese nitrate aqueous solution containing chlorate or perchlorate to a porous sintered body and firing the resultant. (2) The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein the concentration of the chlorate or perchlorate in the manganese nitrate aqueous solution is 0.01 to 10% by weight.