JPS63283116A - Manufacture of solid electrolytic capacitor - Google Patents

Abstract

PURPOSE:To enable even the capacity of a solid electrolytic capacitor element using synthetic foil in the same dimension to be increased by forming a semiconductor layer under vibration with ultrasonic. CONSTITUTION:The surface of a foil is electrochemically etched by AC assuming an aluminium foil in length of 2 cm and width of 0.5 cm as an anode and then an anode terminal is caulked to the etching aluminium foil for connection. The etching aluminium foil is immersed in a mother liquer of reaction comprising water solution of 2.4 mole/l of lead acetic acid tri-hydrate mixed with another water solution of 4 mole/l of persulfuric acid ammonium and then the reacting solution is vibrated by application of ultrasonic waves whose output is 60 W and frequency is 45 kHz at 90 deg.C for one minute. A lead dioxide produced on a dielectric oxide film layer and a semiconductor layer are washed to clean up not yet reacted element and then the aluminum foil is subjected to suction drying at 120 deg.C. Finally, a cathode is taken out using a paste for resin sealing process.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a solid electrolytic capacitor with a good impregnation rate of a semiconductor layer into an anode substrate and excellent performance.

[Prior art] In general, a solid electrolytic capacitor element is made by forming an oxide film layer on an anode substrate made of a valve metal, forming a semiconductor layer such as manganese dioxide as a counter electrode on the outer surface of this oxide film layer, and then forming a semiconductor layer made of manganese dioxide or the like as a counter electrode. A conductive layer such as paste is formed to reduce contact resistance.

[Problems to be Solved by the Invention] However, it is quite difficult to impregnate the anode substrate with a semiconductor layer. , usually around 5 to 10 times. Moreover, as the number of times of impregnation increases, the deterioration of the oxide film layer becomes significant, so a step of repairing the oxide film layer is required. Since the manufacturing cost of a solid electrolytic capacitor that involves such a multi-step process is obviously high, a manufacturing method that requires fewer impregnations of the semiconductor layer has been desired.

[Means for Solving the Problems] The present invention has been made to achieve the above object, and the gist thereof is to provide a dielectric oxide film, a semiconductor, and In the method for manufacturing a solid electrolytic capacitor, the semiconductor layer is formed under ultrasonic vibration. Further, the semiconductor layer is preferably a layer containing lead dioxide or lead dioxide and lead sulfate as main components.

[Specific Structure and Effects of the Invention] The method for manufacturing a solid electrolytic capacitor of the present invention will be described below.

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

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 another dielectric oxide layer provided on the surface of the anode substrate. However, it is particularly desirable that the layer be made of an oxide of the anode valve metal itself. In either case, a conventionally known method can be used to provide the oxide layer.

Although there are no particular limitations on the composition and manufacturing method of the semiconductor layer used in the present invention, in order to improve the performance of the capacitor, lead dioxide or lead dioxide and lead sulfate may be used as main components, and conventionally known chemical precipitation methods may be used. , or preferably by an electrochemical deposition method.

Examples of the chemical precipitation method include a method of chemically precipitating from a solution containing a lead-containing compound and an oxidizing agent.

Examples of lead-containing compounds include those in which a lead atom has a coordinate bond or an ionic bond with a chelate-forming compound such as oxine, acetylacetone, pyromeconic acid, salicylic acid, alizarin, polyvinyl acetate, porphyrin compounds, crown compounds, and cryptate compounds. lead-containing compounds,
Lead citrate, lead acetate, basic lead acetate, lead chloride, lead bromide,
Examples include lead perchlorate, lead chlorate, lead sulfamate, lead silicon hexafluoride, lead bromate, lead borofluoride, lead acetate hydrate, and lead nitrate. These lead-containing compounds are appropriately selected depending on the solvent used for the reaction mother liquor.

Further, two or more of these lead-containing compounds may be used in combination.

The concentration of the lead-containing compound in the reaction mother liquor is within the range of 0.05 mol/g from the concentration that provides saturated solubility, preferably within the range of 0.1 mol/g from the concentration that provides saturated solubility, and more preferably is 0.0 from the concentration that gives saturation solubility.
It is in the range of 5 mol/g.

If the concentration of the lead-containing compound in the reaction mother liquor is less than 0.055 mol/mol, a solid electrolytic capacitor with good performance cannot be obtained. Further, if the concentration of the lead-containing compound in the reaction mother liquor exceeds the saturation solubility, no merit can be observed by adding an increased amount.

Examples of the oxidizing agent include quinone, chloranil, pyridine-N-oxide, dimethyl sulfoxide, chromic acid, potassium permanganate, selenium oxide, mercury acetate,
Examples include vanadium oxide, sodium chlorate, ferric chloride, hydrogen peroxide, benzoyl peroxide, calcium hypochlorite, calcium chlorite, calcium chlorate, and calcium perchlorate. These oxidizing agents may be appropriately selected depending on the solvent used. In addition, two or more oxidizing agents may be used in combination C).

The ratio of the oxidizing agent used is 5 to 5 molar amount of the lead-containing compound used.
It is preferably within the range of 0.1 times the mole. If the ratio of the oxidizing agent used is more than 5' times the molar amount of the lead compound used, there is no cost advantage, and if it is less than 0 or 1 times the molar amount of the lead compound used, a solid electrolytic capacitor with good performance cannot be obtained. do not have.

As a method for forming a semiconductor layer containing lead dioxide as a main component, for example, 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 above-mentioned oxide film is added to the reaction mother liquor. A method of chemically depositing the anode by immersing the anode substrate therein can be mentioned.

On the other hand, examples of electrochemical deposition methods include a method previously proposed by the present inventors in which lead dioxide is deposited by electrolytic oxidation in an electrolytic solution containing a high concentration of lead ions (
(Japanese Patent Application No. 61-26952).

Furthermore, if the semiconductor layer is composed of a layer whose main components are lead dioxide, which originally plays the role of a semiconductor, and lead sulfate, which is an insulating material, the leakage current value of the capacitor can be reduced by adding lead sulfate. On the other hand, although the inclusion of lead sulfate lowers the electrical conductivity of the semiconductor layer and increases the loss factor value, it is possible to maintain and exhibit a high level of performance compared to conventional solid electrolytic capacitors. Therefore, when the semiconductor layer is composed of a mixture of lead dioxide and lead sulfate, 10 parts by weight or more of lead dioxide and less than 100 parts by weight and 9 parts by weight of lead sulfate.
Good capacitor performance can be maintained over a wide range of compositions of 0 parts by weight or less, but preferably 80 to 50 parts by weight of lead sulfate to 20 to 50 parts by weight of lead dioxide;
More preferably, a good balance between the leakage current value and the loss coefficient value can be achieved in the range of 75 to 65 parts by weight of lead sulfate to 25 to 35 parts by weight of lead dioxide. If the amount of lead dioxide is less than 10 parts, the conductivity will be poor, the loss factor will be large, and sufficient capacity will not be obtained.

For example, a semiconductor layer whose main components are lead dioxide and lead sulfate is
It can be formed by chemical precipitation using an aqueous solution containing lead ions and persulfate ions as a reaction mother liquor. Additionally, a suitable oxidizing agent that does not contain persulfate ions may be added.

The lead ion concentration in the mother liquor is 0.05 mol/g from the concentration that gives saturated solubility, preferably 0.1 mol/Ω from the concentration that gives saturated solubility, more preferably 0.5 mol/g from the concentration that gives saturated solubility. is within the range of If the concentration of lead ions is higher than the saturation solubility, there is no benefit from adding an increased amount. In addition, the concentration of lead ions is 0.05 mol/
If it is lower than g, lead ions in the mother liquor are too dilute, so there is a problem that the number of reactions must be increased.

On the other hand, the concentration of persulfate ions in the mother liquor is within the range of 5 to 0.05 in molar ratio to lead ions. If the concentration of persulfate ions is more than 5 in molar ratio to lead ions, unreacted persulfate ions remain, resulting in high costs, and the concentration of persulfate ions is 0.05 in molar ratio to lead ions. If the amount is less, unreacted lead ions remain and conductivity deteriorates, which is not preferable.

Examples of compounds that provide lead ion species include lead citrate, lead perchlorate, lead nitrate, lead acetate, basic lead acetate, lead chlorate, lead sulfamate, lead silicon hexafluoride, lead bromate, and lead chloride. , lead bromide, etc. Two or more of these compounds providing lead ion species may be used in combination. On the other hand, as compounds that provide persulfate ion species, for example,
Examples include potassium persulfate, sodium persulfate, ammonium persulfate, and the like. Two or more of these compounds that provide persulfate ion species may be used in combination.

On the other hand, examples of the oxidizing agent include hydrogen peroxide, calcium hypochlorite, calcium chlorite, calcium chlorate, and calcium perchlorate.

When producing the semiconductor layer described above by chemical precipitation method,
An anode substrate having an oxide film is immersed in a reaction mother liquor that is a mixture of a solution containing a lead-containing compound and a solution containing an oxidizing agent, and a semiconductor layer is formed on the oxide film layer while the reaction mother liquor is vibrated with ultrasonic waves. need to be formed. Furthermore, when manufacturing by electrochemical deposition, a semiconductor layer is similarly formed while vibrating an electrolytic solution containing a high concentration of lead ions using ultrasonic waves.

The output and frequency of the ultrasonic waves vary depending on the type of valve metal base used, the thickness of the oxide film layer, the type of semiconductor layer, etc., and are generally determined by preliminary experiments. Further, while forming the semiconductor layer, ultrasonic vibrations may be applied intermittently. The temperature to form the semiconductor layer is higher than the temperature at which the semiconductor layer can be formed, and the time required is longer than the time required to form the semiconductor layer, but in order to prevent excessive deterioration of the oxide film due to ultrasonic vibration, It is preferable to carry out the process at high temperature for a short time.

In the present invention, the conductor layer provided in the semiconductor layer is disclosed in Japanese Patent Application No. A6EO-193184, Japanese Patent Application No. 1981-192499, Japanese Patent Application No. 61-2660, for example.
Examples include the conductor layer proposed in No. 92 and the like. In this,
Particularly good is the one proposed in Japanese Patent Application No. 61-266092, in which the conductive layer is made of a conductive paste containing metal powder and metal oxide powder as main components.

The solid electrolytic capacitor element according to the present invention described above can be made into a general-purpose capacitor product for various uses by, for example, being molded with a resin, a resin case, a metal outer case, an outer case with a resin dipping laminated film, or the like.

As mentioned above, solid electrolytic capacitors containing lead dioxide or lead dioxide and lead sulfate as the main components as semiconductor layers have been mentioned, but the present invention also covers solid electrolytic capacitors having semiconductor layers other than these (for example, manganese dioxide, etc.). It is obvious that this method can also be applied to the manufacture of capacitors.

[Example] Hereinafter, the present invention will be explained by showing Examples and Comparative Examples.

Example 1 An aluminum foil having a length of 2 cm and a width of 0.5 cm was used as an anode, and after the surface of the foil was electrochemically etched using alternating current, an anode terminal was caulked to the etched aluminum foil to connect the anode terminal. Next, an alumina oxide film was formed by electrochemical treatment in an aqueous solution of boric acid and ammonium borate to obtain etched aluminum chemical foil for low pressure (approximately 1.0 μF/cJ). Next, an aqueous solution of 2.4 mol/g of lead acetate trihydrate and ammonium persulfate 4
It is immersed in a reaction mother liquor mixed with an aqueous solution of mol/ρ, and the output is 6.
While applying ultrasonic vibrations of 0W1 frequency of 45 kHz to this reaction mother liquor, the reaction was carried out at 90° C. for 1 minute. The semiconductor layer made of lead dioxide and lead sulfate formed on the dielectric oxide film layer was washed with water to remove unreacted substances, and then dried under reduced pressure at 120°C.

The generated semiconductor layer is composed of lead dioxide and lead sulfate, and mass spectrometry,
Confirmed by infrared spectroscopy.

Next, a paste consisting of 30 parts of silver powder, 60 parts of lead dioxide, and 10 parts of acrylic resin was applied onto this semiconductor layer, and after drying, the cathode was taken out using this paste and sealed with resin to produce a solid electrolytic capacitor. .

Example 2 In Example 1, the ultrasonic vibration output was 35W and the frequency was 41K.
A solid electrolytic capacitor was produced in the same manner as in Example 1 except that llz was used instead.

Example 3 Electrolytic oxidation was carried out in a 1.2 mol/g lead acetate aqueous solution using the same chemically formed foil as in Example 1 as an anode and an aluminum foil that had not been subjected to ordinary etching as a cathode. The applied voltage at this time was 15 V, and ultrasonic vibrations with an output of 35 W and a frequency of 41 kHz were applied to the electrolytic solution during electrolytic oxidation. After leaving the chemical foil with the lead dioxide layer deposited in water for 30 minutes,
It was dried under reduced pressure at 20°C.

Subsequently, a conductor layer was formed in the same manner as in Example 1, and then a solid electrolytic capacitor was produced.

Comparative Example 1 A solid electrolytic capacitor was produced in the same manner as in Example 1 except that ultrasonic vibration was not applied to the reaction mother liquor.

Comparative Example 2 A solid electrolytic capacitor was produced in the same manner as in Example 3 except that ultrasonic vibration was not applied to the electrolyte.

Table 1 shows the average performance values of the five solid electrolytic capacitors produced in Examples 1 to 3 and Comparative Examples 1 and 2.

Table 1 [Effects of the Invention] According to the method for manufacturing a solid electrolytic capacitor of the present invention, since the semiconductor layer is formed while applying ultrasonic vibration, the semiconductor layer is well impregnated into the dielectric oxide film, and the impregnation rate is low. increase Therefore, the capacity of a solid electrolytic capacitor element using chemically formed foil of the same size can be greatly increased, and a solid electrolytic capacitor with a large capacity can be manufactured even with a small solid electrolytic capacitor element.

Claims (1)

[Claims] 1. A method for manufacturing a solid electrolytic capacitor in which a dielectric oxide film, a semiconductor layer, and a conductive layer are sequentially formed on the surface of an anode substrate made of a metal having a valve action, wherein the semiconductor layer is A method for manufacturing a solid electrolytic capacitor, the method comprising forming the solid electrolytic capacitor under ultrasonic vibration. 2. The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein the semiconductor layer is a layer containing lead dioxide as a main component. 3. The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein the semiconductor layer is a layer containing lead dioxide and lead sulfate as main components.