JPH02184013A - Manufacture of solid electrolytic capacitor - Google Patents

Abstract

PURPOSE:To reduce leakage currents(LC) by aging operation by forming a dielectric oxide film layer and a semiconductor layer, which has lead dioxide or lead dioxide and lead sulfate for its main ingredients, at the surface of an anode substrate of valve acting metal, and then soaking them in an organic solvent, being soluble in water, and water, and laminating a conductive layer and a resin layer on the semiconductor layer. CONSTITUTION:An etching aluminum foil is electrochemically treated in aqueous solution of phosphoric acid and phosphoric acid ammonium so as to form an oxide film of alumina, thus an etching aluminum chemical conversion foil for low pressure is obtained. Next, it is soaked in reactive mother liquid where lead acetate trihydrate and persulfuric acid ammonium are mixed so as to react it. A semiconductor layer, which is generated on a dielectric oxide film layer and consists of lead dioxide and persulfuric acid, is washed and dried. And the generated semiconductor layer consists of lead dioxide and lead sulfate, and this semiconductor layer is soaked in ethanol, and then it is taken out and further it is soaked in purified water. And after applying paste, consisting of silver powder, lead dioxide, and acrylic resin, on this semiconductor layer, a cathode is taken out using this paste and is dipped in liquid-form epoxy resin.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a solid electrolytic capacitor with low leakage current while maintaining good dielectric loss characteristics.

(Prior art) A solid electrolytic capacitor in which a semiconductor layer and a conductor layer are laminated on the surface of an anode substrate made of a valve metal is made of manganese dioxide, lead dioxide, lead dioxide, and lead sulfate as semiconductor layers. It is known to use organic semiconductors such as mixtures with , TCNQ salts, and conductive polymers. Among these, those using lead dioxide or a mixture of lead dioxide and lead sulfate as the semiconductor layer are particularly excellent in terms of temperature characteristics and high frequency characteristics.

(Problem to be solved by the invention) However, in the solid electrolytic capacitor described above, the dielectric oxide film layer is more or less damaged when forming the semiconductor layer, so it is necessary to repair the dielectric oxide film layer by an aging operation. . In addition, when manufacturing solid electrolytic capacitors using lead dioxide or a mixture of lead dioxide and lead sulfate as a semiconductor layer, the leakage current (hereinafter abbreviated as LC) is reduced by an aging operation, or the knee-jink time is reduced in industrial production. There was a desire for a method for producing solid electrolytic capacitors that were as short as possible and had low leakage current.

(Means for Solving the Problems) The present invention has been made to solve the above-mentioned problems, and its gist is to provide a dielectric oxide film layer on the surface of an anode substrate made of a metal having a valve action. After forming a semiconductor layer mainly composed of lead dioxide or lead dioxide and lead sulfate on the body oxide film layer, the semiconductor layer is sequentially immersed in a water-soluble organic solvent and water, and then a conductive layer is formed on the semiconductor layer. A solid electrolytic capacitor is manufactured by laminating a resin layer on top of the solid electrolytic capacitor.

The method of the present invention will be explained in more detail below.

As the valve metal substrate used as the anode of the solid electrolytic capacitor according to the manufacturing method of the present invention, any metal having a valve action can be used, such as aluminum, tantalum, niobium, titanium, and alloys using these as substrates.

The dielectric oxide film layer provided on the surface of the anode substrate.

It may be an oxide layer of the anode substrate itself provided on the surface portion of the anode substrate, or it may be another dielectric oxide layer provided on the surface of the anode substrate, but in particular, the anode valve It is desirable that the layer be made of an oxide of the metal itself.

In either case, the oxide layer can be provided by a conventionally known method such as an anodization method using an electrolytic solution.

Further, the semiconductor layer used in the present invention can be produced using lead dioxide, or lead dioxide and lead sulfate as main components, by a conventionally known chemical deposition method or electrochemical deposition method.

When forming a semiconductor layer containing lead dioxide as a main component, for example, a chemical precipitation method involves preparing a reaction mother liquor by mixing a solution containing a lead-containing compound and a solution containing an oxidizing agent. The anode substrate provided with the above-mentioned dielectric oxide film layer is immersed in the solution, and a semiconductor layer of lead dioxide is deposited on the oxide film layer. Furthermore, a semiconductor layer containing lead dioxide and lead sulfate as main components can be chemically precipitated using, for example, an aqueous solution containing lead ions and persulfate ions as a reaction mother liquor (Japanese Patent Application Laid-open No. 51621/1983). .

On the other hand, examples of electrochemical deposition methods include a method in which lead dioxide is deposited by electrolytic oxidation in an electrolytic solution containing a high concentration of lead ions (Japanese Patent Application Laid-Open No. 185307-1982).
Publication No.).

Next, the anode substrate on which the semiconductor layer has been formed by the method described above is first immersed in a water-soluble organic solvent. Examples of organic solvents include monohydric alcohols, phenols, and ethers such as methanol, ethanol, n-propyl alcohol, isopropyl alcohol, dioxane, and tetrahydrofuran; acids and esters include formic acid, acetic acid, butyric acid, methyl lactate,
Polyhydric alcohols and their ethers, such as ethyl lactate, triethyl phosphate, γ-butyrolactate, trifluoroacetic acid, etc.
Esters include ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether, ethylene glycol monoacetate, ethylene glycol monomethyl ether acetate, ethylene glycol dimethyl ether, diethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monomethyl ether, and diethylene glycol monomethyl ether. Recall dimethyl ether, triethylene glycol, propylene glycol, hexylene glycol, glycerin, etc. Aldehydes, acetals, and ketones include acetone, methylal, ethyl methyl ketone, and acetylacetone; , ethylenecyamine, picoline, monoethanolamine, jetanolamine, morpholine, dimethylformamide, hexamethylphosphortriamide, etc. Examples of the sulfur compound include sulfite anhydride, sulfolane, dimethylsulfoxide, and the like. Among these organic solvents, methanol, ethanol, acetone, etc. are mainly used.

The immersion conditions for the organic solvent are as follows: immersion at a temperature of room temperature to room temperature + lO<0>C for 30 minutes to 30 minutes.

Next, the anode substrate is removed from the organic solvent and immersed in water. Purified water or ion-exchanged water may be used, and the immersion conditions may be the same as those for organic solvents.

Next, the anode substrate is removed from the water, left to dry, and then a conductor layer made of a conventionally known conductive paste such as silver paste is formed on the semiconductor layer. A resin layer such as a resin mold, a resin case, resin dipping, or a laminate film exterior is laminated on the capacitor, and then aging is performed to make a general-purpose capacitor product for various uses.

[Effect]

A dielectric oxide film layer and a semiconductor layer mainly composed of lead dioxide or lead dioxide and lead sulfate are formed on the surface of the anode substrate made of valve metal, and then sequentially soaked in a water-soluble organic solvent and water. By performing the dipping operation, moisture permeates well into the dielectric oxide film layer. Since the dielectric oxide film layer damaged when the semiconductor layer was formed is well permeated with moisture, it is thought that an aging operation brings about an excellent repair effect.

(Example) Hereinafter, the uninvention will be explained by showing Examples and Comparative Examples.

Example 1 An aluminum foil with a length of 2 cra and a width of 0.5 CI was used as an anode, and the surface of the foil was electrochemically etched using alternating current, and then the anode terminal was caulked to the etched aluminum foil to connect the anode terminal. Next, an oxide film of alumina is formed by electrochemical treatment in an aqueous solution of phosphoric acid and ammonium phosphate to form an etched aluminum foil for low pressure use. ! l (approximately lOp, F/cm') was obtained. Then, it was immersed in a reaction mother liquor containing a mixture of a 2.4 mol/l aqueous solution of lead acetate trihydrate and a 4 mol/l aqueous solution of ammonium persulfate, and allowed to react at 80°C for 30 minutes. 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 produced semiconductor layer was composed of lead dioxide and lead sulfate, and it was confirmed by mass spectrometry, X-ray analysis, and infrared spectroscopy that it contained about 25% lead dioxide.

The formed semiconductor layer was immersed in ethanol for 5 minutes, taken out, and further immersed in purified water for 5 minutes.

Thereafter, after leaving the semiconductor layer for 20 minutes at room temperature, a paste consisting of 30 parts of silver powder, 60 parts of lead dioxide, and 10 parts of acrylic resin was applied onto the semiconductor layer, and after drying, the cathode was removed using this paste, and liquid epoxy resin was applied. (11 Ciba Geigy XNR-1218) at 150'c after dip.
After drying for a while and sealing with resin, a solid electrolytic capacitor was produced.

Example 2 A solid electrolytic capacitor was produced in the same manner as in Example 1 except that ethanol was replaced with acetone.

Example 3 A solid electrolytic capacitor was produced in the same manner as in Example 1 except that purified water in Example 1 was replaced with ion-exchanged water.

Example 4 The same chemically modified foil as in Example 1 was used as an anode, and the cathode was subjected to ordinary processing.
1.2 Using unetched aluminum foil
Electrolytic oxidation was carried out in a mol/l lead acetate aqueous solution. The applied voltage at this time was 15V.

The chemically formed foil on which the lead dioxide layer had been deposited was left in water for 30 minutes, and then dried under reduced pressure at 120°C. continuation.

After immersion in ethanol and water in the same manner as in Example 1, a conductor layer and a resin layer were formed to produce a solid electrolytic capacitor.

Comparative Example 1 A solid electrolytic capacitor was produced in the same manner as in Example 1, except that after forming the semiconductor layer in Example 1, immersion in ethanol and purified water was not performed.

Comparative Example 2 A solid electrolytic capacitor was produced in the same manner as in Example 4, except that after forming the semiconductor layer in Example 4, immersion in ethanol and purified water was not performed.

As described above, the solid electrolytic capacitors produced in Examples 1 to 4 and Comparative Examples 1 to 2, 20 each, 120 in total, were left in a constant temperature bath at 125°C, and a voltage of 30 V was applied to each to age for 30 minutes. . At this time, the number of pieces whose LC is 0.5 pots A or less is considered the "yield".

Table 1 shows the performance of the solid electrolytic capacitor.

After forming the first surface layer and the semiconductor layer containing lead dioxide or lead dioxide and lead sulfate as main components, the film is sequentially immersed in a water-soluble organic solvent and water. After that, a conductor layer and a resin layer are laminated on the semiconductor layer, and a knee-jink operation is used to manufacture a solid electrolytic capacitor with a high LC yield while maintaining good 81A current loss characteristics. can.

Claims (1)

[Claims] (1) After forming a dielectric oxide film layer on the surface of an anode substrate made of a metal having valve action, and forming a semiconductor layer mainly composed of lead dioxide or lead dioxide and lead sulfate on this dielectric oxide film layer, Sequentially immersed in a water-soluble organic solvent and water,
Thereafter, a conductor layer is formed on the semiconductor layer, and a resin layer is formed on the conductor layer.