JP2534574B2 - Method for manufacturing solid electrolytic capacitor - Google Patents

Description

The present invention relates to a method for manufacturing a solid electrolytic capacitor.

(Prior Art) A conventional solid electrolytic capacitor has a structure in which fine powder of tantalum or the like is molded and fired to form a porous sintered body, and the tantalum wire or the like is pre-filled in the porous sintered body or welded to the end face. The element is used.

Then, anodize this element to form an oxide film, then provide a manganese dioxide layer, carbon layer, and silver paste layer, weld the anode terminal to the tantalum wire, and fix the cathode terminal to the silver paste layer with a conductive paste. However, the whole is covered with resin.

(Problems to be Solved by the Invention) This solid electrolytic capacitor is used as an electronic component in an electronic circuit, and particularly, one having a small impedance in a high frequency region is required.

An object of the present invention is to provide a method for manufacturing a solid electrolytic capacitor, which is capable of improving the above-mentioned drawbacks and improving impedance characteristics in a high frequency region.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the invention of claim 1 manufactures a solid electrolytic capacitor in which an oxide film is formed on a sintered body of a fine powder of valve action metal to serve as an anode. In the method, a solution containing a metal salt, a metal oxide or a metal hydroxide of a Group Ib or Group VIII element is attached to the surface of the oxide film, and then chemically reduced to form a cathode layer. A method for manufacturing a solid electrolytic capacitor is provided.

According to a second aspect of the present invention, in the method for producing a solid electrolytic capacitor in which an oxide film is formed on a sintered body of a fine powder of valve action metal as an anode, titanium, zirconium, indium, tin is formed on the surface of the oxide film. The present invention provides a method for producing a solid electrolytic capacitor, which comprises forming a positive electrode layer by depositing a metal salt solution of zinc or ruthenium and then heating in a gas containing nitrogen or oxygen.

(Function) The impedance of the solid electrolytic capacitor is the resistance of the oxide film (virtual equivalent series resistance), the distribution circuit resistance such as the manganese dioxide layer, the carbon layer, the silver paste layer, the specific resistances of the terminals, the interlayers, and the like. It is a combined value with the contact resistance with the terminal.

Therefore, if the manganese dioxide layer is omitted and a cathode layer made of a carbon layer or the like is directly provided on the surface of the oxide film, the distributed circuit resistance, the space between the oxide film and the manganese dioxide layer, and the space between the manganese dioxide layer and the carbon layer are formed. Each contact resistance of is eliminated, and the impedance can be reduced accordingly.

(Example) Hereinafter, the present invention will be described based on examples.

First, one end of a tantalum wire is embedded in fine powder of tantalum, press-molded, and fired in a vacuum to form a sintered body.

Next, this sintered body is anodized or vapor-phase oxidized to form a tantalum oxide film.

After forming the tantalum oxide film, the cathode layer is directly formed on the surface of this film. One method of forming the cathode layer is to immerse the sintered body in a solution containing a metal salt, a metal oxide, or a metal hydroxide of a Group 1-b element such as copper or silver or a group VIII element such as iron. The solution is impregnated and dried, and then a chemical reducing agent such as ammonia, hydrazine, hydrazine hydrate, hydrazine sulfate, succinic acid, tartaric acid, formalin, hypophosphorous acid, sodium formate, sodium borohydride, hydroxylamine, formic acid. Etc. to reduce. Other methods are titanium and zirconium,
A sintered body is immersed in a metal salt solution of indium, tin, zinc, and ruthenium and heated in nitrogen or a gas containing oxygen to form a film made of a conductive metal nitride or a conductive metal oxide. .

After forming the cathode layer, the anode lead wire is welded to the lead frame, the cathode layer is connected to the lead frame by the conductive paste, and the outer casing is formed by resin molding.

Next, the impedance of 100 KHz was measured along with the conventional example for the example manufactured as described above with the sintered body being 1.05 × 1.0 × 0.8 mm square. The manufacturing conditions of each example and the conventional example are as follows. The number of samples shall be 500 each.

Example 1) Tantalum oxide film: A sintered body is dipped in a 0.1% nitric acid solution, and a voltage of 23 V is applied to perform chemical conversion.

Cathode layer: The sintered body is dipped in a 1N silver nitrate solution and dried by air. After drying, soak in 0.1N ammonia water and semi-dry. After semi-drying, soak in 80% hydrazine hydrate solution and wash with water. After washing with water, baking is performed at a temperature of 260 ° C. to form a silver cathode layer. Connect to the lead frame with silver paste.

Example 2) Same as Example 1 except that the cathode layer is formed under the following conditions.

The sintered body is successively immersed in an aqueous solution of 0.5N palladium chloride, 2N aqueous ammonia and a 80% hydrazine hydrate solution to deposit metal particles and wash with water. After washing with water, temperature 260
Firing is performed in a non-oxidizing atmosphere at 0 ° C. to form a cathode layer made of palladium.

Example 3) Under the same conditions as in Example 2, except that chloroplatinic acid was used instead of palladium chloride to form a cathode layer made of platinum.

Example 4) The same conditions are used as in Example 2 except that copper chloride is used instead of palladium chloride to form a cathode layer made of copper.

Example 5) The same conditions are used as in Example 2 except that nickel nitrate is used instead of palladium chloride to form a cathode layer made of nickel.

Example 6) Same as Example 1 except that the cathode layer is formed under the following conditions.

The sintered body is dipped in a 0.5 N gold chloride solution and dried by air. After drying, soak in 0.1N caustic soda solution and semi-dry. After being semi-dried, it is immersed in a saturated aqueous solution of hydroquinone and washed with water. After washing with water, baking is performed at a temperature of 290 ° C. to form a cathode layer made of gold. This cathode layer is fixed to the lead frame with Pb-Sn solder.

Example 7) Same as Example 1 except that the cathode layer is formed under the following conditions.

The sintered body is dipped in a mixed solution of 50% by volume of 1N silver nitrate solution and 50% by volume of 0.5N palladium nitrate solution, and after being pulled up, is dipped in 1N ammonia water. After pulling up
Immerse in 80% hydrazine hydrate solution to precipitate metal particles and wash with water. After washing with water, baking is performed in an argon atmosphere at a temperature of 260 ° C. to form a cathode layer made of a composite of silver and palladium.

Example 8) Tantalum Oxide Film: The sintered body was heated in a humid air flow at a temperature of 450 ° C. for 24 hours.
Form by heating.

Cathode layer: 15 parts by weight of a solution obtained by dissolving 1 part by weight of indium nitrate in 1 part by weight of acetylacetone, 1 part by weight of a solution obtained by adding 10 parts by weight of nitric acid and 5 parts by weight of metallic tin to 1 part by weight of acetylacetone and stirring. Mix parts. Then, the sintered body is immersed in this mixed solution and heated in the atmosphere at a temperature of 500 ° C. to form a cathode layer made of a solid solution of indium oxide and tin oxide. The cathode layer is fixed to the lead frame with silver paste.

Example 9) Same as Example 8 except that the cathode layer is formed under the following conditions.

The sintered body is dipped in a 5N ruthenium chloride solution and dried by air. After drying, it is heated at a temperature of 900 ° C. in the atmosphere to form a ruthenium oxide cathode layer.

Example 10) Same as Example 8 except that the cathode layer is formed under the following conditions.

The sintered body is immersed in a 3N solution of titanium tetrachloride dissolved in cold water and dehydrated at a temperature of 110 ° C. After dehydration, it was heated to a temperature of 800 ° C. in the atmosphere to form a cathode layer made of gold-colored titanium nitride.

Example 11) Same as Example 8 except that the cathode layer is formed under the following conditions.

The sintered body is dipped in a 50% aqueous solution of silver nitrate and dried.
After drying, it is heated in air at a temperature of 400 ° C. to form a cathode layer made of silver. This cathode layer is fixed to the lead frame with copper paste.

Conventional Example 1) A sintered body on which a tantalum oxide film is formed under the same conditions as in Example 1 is immersed in a manganese nitrate solution, dried, and fired, and the treatment is repeated several times to form a manganese dioxide layer on the surface of the tantalum oxide film. To form.

After forming the manganese dioxide layer, it is immersed in a colloidal carbon solution and dried to form a carbon layer.

After forming the carbon layer, it is dipped in a low-viscosity silver paste and dried to form a silver layer.

Then, the silver layer is fixed to the lead frame with silver paste.

Conventional Example 2) Same as Conventional Example 1 except that the cathode layer is formed under the following conditions.

The sintered body after the formation of the manganese dioxide layer is immersed in a 1N aqueous silver nitrate solution and dried by air. After drying, it is soaked in a 0.1 N aqueous caustic soda solution and semi-dried. After semi-drying, it is immersed in a hydrazine hydrate solution at 80 ° C and washed with water. After washing with water, baking is performed at a temperature of 260 ° C. to form a silver cathode layer.

The impedance measurement results are shown in the figure. As is clear from the figure, Examples 1 to 11 are about 0.3 to 1.2Ω, and Conventional Example 1 and Conventional Example 2 are about 0.7 to 7Ω, and the former is lower than the latter as a whole.

(Effects of the Invention) As described above, according to the manufacturing method of the invention of claim 1, a metal salt of a Group Ib or Group VIII element is formed on the surface of the oxide film.
After depositing a solution containing metal oxide or metal hydroxide, chemical reduction is performed to directly form the cathode layer, so that a solid electrolytic capacitor capable of reducing impedance can be obtained.

Also, according to the production method of the invention of claim 2, after depositing a metal salt solution of titanium, zirconium, indium, tin, zinc or ruthenium on the surface of the oxide film,
Since the cathode layer is directly formed by heating in nitrogen or a gas containing oxygen, a solid electrolytic capacitor capable of reducing impedance can be obtained.

[Brief description of drawings]

 The figure shows a graph of impedance values.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ken Sato Fumishima Prefecture, Miharu Town, Oita Kumagai Odaira 16 Hiritsu Capacitor Co., Ltd. Co., Ltd. (72) Inventor, Kazuhiko Ishiuchi, Ohira, Kumabe, Miharu, Miharu-cho, Tamura-gun, Fukushima 16 Inspector, Hitachi Capacitor Co., Ltd. Shinichi Yamazaki (56)

Claims (2)

(57) [Claims] 1. A method for producing a solid electrolytic capacitor in which an oxide film is formed on a sintered body of a fine powder of a valve metal and used as an anode, wherein a metal salt of a group Ib or a group VIII is formed on the surface of the oxide film. A method for producing a solid electrolytic capacitor, which comprises forming a cathode layer by chemically reducing after depositing a solution containing a metal oxide or a metal hydroxide. 2. A method for producing a solid electrolytic capacitor in which an oxide film is formed on a sintered body of fine powder of a metal having valve action to form an anode, and titanium, zirconium, indium, tin, zinc or A method for producing a solid electrolytic capacitor, comprising depositing a metal salt solution of ruthenium and then heating in nitrogen or a gas containing oxygen to form a cathode layer.