JPH03228305A - Manufacture of aluminum solid electrolytic capacitor - Google Patents

Abstract

PURPOSE:To enable the title electrolytic capacitor having excellent capacitor characteristics such as small leakage current and dielectric loss to be manufactured by a method wherein a part of an anode lead and/or dielectric oxide film is covered with an insulating film so as to form a conductive layer on the surface of the insulating film and then a conductive high molecular film is formed by electrolytic polymerization using a conductor brought into contact with the conductive layer as an anode. CONSTITUTION:In order to manufacture the title aluminum solid electrolytic capacitor by successively forming a dielectric oxide film 3, a conductive metallic oxide 4 and a conductive high molecular film 8 on the surface of an aluminum 2 connected to an anode lead 1, a part of the anode lead 1 and/or the dielectric oxide film 3 is covered with an insulating film 6 to form a conductive layer 5 on the surface of the insulating layer 6; the conductive layer 5 is brought into contact with a conductor 7 to be an anode; the conductive high molecular film 8 is formed by electrolytic polymerization performed between an outer cathode. For example, the electrolytic polymerization is performed using a stainless wire 7 as an anode brought into contact with a part of the conductive layer 5 as well as a stainless beaker containing water solution containing sodium benzenesulfonic acid and pyrrole monomer as a cathode so as to form the polypyrrole film 8 (conductive high molecular film 8).

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing an aluminum solid electrolytic capacitor using a conductive polymer as a solid electrolyte.

(Prior Art) First, the present inventors formed a dielectric oxide film on the surface of a valve metal, and then coated the surface with a thin film of a metal or a conductive metal compound, and a conductive film formed by electrolytic polymerization. We proposed a solid electrolytic capacitor formed by forming a polymer film (
Japanese Patent Publication No. 63-158829). This capacitor has superior electrical characteristics, such as superior temperature characteristics and low impedance at high frequencies, compared to conventional electrolyte type capacitors. However, there were still points that needed to be improved, such as improving the efficiency of the manufacturing method, especially electrolytic polymerization.

(Problems to be Solved by the Invention) The object of the present invention is to form a conductive polymer film formed by electrolytically polymerizing a thin film of a metal oxide having conductivity on the surface of aluminum on which a dielectric oxide film has been formed. In solid electrolytic capacitors formed of
It is an object of the present invention to provide a method for manufacturing an aluminum solid electrolytic capacitor having small capacitor characteristics.

(Means for Solving the Problems) As a result of intensive research, the present inventors came to invent a method for manufacturing an aluminum solid electrolytic capacitor that can achieve the above object.

That is, in a method of manufacturing an aluminum solid electrolytic capacitor, a dielectric oxide film, a conductive metal oxide, and a conductive polymer film are sequentially formed on the surface of aluminum to which an anode lead is connected. Alternatively, a part of the dielectric oxide film is covered with an insulating layer, a conductive layer is formed on the surface of the insulating layer, a conductor is brought into contact with this conductive layer to serve as an anode, and electrolytic polymerization is performed between it and an external cathode. This is a method for manufacturing an aluminum solid electrolytic capacitor characterized by forming a conductive polymer film.

The aluminum of the present invention is used in the form of a flat plate, a wound type, a laminated type, a sintered body, or the like.

Next, specific examples of the present invention will be explained with reference to the drawings. FIG. 1 is a schematic diagram of a sintered aluminum capacitor.

After etching the surface of the aluminum sintered body 2 to which the anode lead 1 is connected, a dielectric oxide film 3 is formed. Next, a conductive metal oxide thin film 4 is formed on the surface of the dielectric oxide film 3.

A portion of the anode lead 1 is covered with an insulating layer 6 on which a conductive layer 5 is formed. Conductive layer 5 formed on insulating layer 6
The conductor 7 is brought into contact with a part of the conductor 7, immersed in an electrolytic solution containing a supporting electrolyte and a conductive polymer monomer, and the conductor 7 is used as an anode to conduct electrolytic polymerization between the external cathode and the conductor 7. A conductive polymer film 8 is formed on the metal oxide thin film 4 by electrolytic polymerization. In this electrolytic polymerization, the insulating layer 6
Otherwise, the dielectric oxide film 3 and the conductive metal oxide thin film 4 will be easily damaged by contact with the conductor 7, and the resulting capacitor will have a large leakage current and dielectric loss tangent (
Become.

As the material for the insulating layer used in the present invention, polymeric materials such as silicone resin, epoxy resin, fluororesin, polyimide resin, and polyphenylene sulfide resin are used alone or in combination with inorganic materials such as silica and alumina. These are formed and coated on a part of the anode lead or dielectric oxide film by methods such as adhesion and coating. Also, insert a heat-shrinkable silicone tube, Teflon tube, etc. into the anode lead and cover it with shrinkage.

To form a conductive layer on the surface of an insulating layer, a metal or a metal compound is vapor-deposited or coated in advance, or a conductive polymer film is formed by a method such as chemical oxidation polymerization. Furthermore, in the step of forming a conductive metal oxide on the dielectric oxide film, a conductive layer made of a metal oxide can be formed on the surface of the insulating layer at the same time.

Examples of the conductive metal oxide formed on the surface of the dielectric oxide film include oxides of titanium, manganese, lead, vanadium, ruthenium, tin, cobalt, nickel, and indium. Formation methods include vapor deposition, immersion drying of a solution dispersed in a solvent, immersion of a salt solution and then thermal decomposition.

From the viewpoint of ease of formation and cost, a method in which a salt solution is immersed and then thermally decomposed is preferred, and a method in which a manganese nitrate aqueous solution is immersed and then thermally decomposed to form a manganese dioxide layer is particularly preferred.

In electrolytic polymerization, the supporting electrolyte is 0.01 mol/1 to 2 mol
l/l and 0.01 mol/l of conductive polymer monomer
It is carried out in an electrolytic solution containing 1 to 5 mol/l.

As the conductive polymer used in the present invention, polypyrrole, polythiophene, polyfuran, polyaniline, and derivatives thereof are used, and polypyrrole is preferable from the viewpoint of stability of the conductive polymer.

The supporting electrolyte used in the electrolytic polymerization of the present invention may be one that is commonly used, and these include, for example, JP-A No. 63-158
829. From the viewpoint of the stability of the characteristics of the completed capacitor at high temperatures, a supporting electrolyte made of an aromatic sulfonate anion such as benzenesulfonate anion or toluenesulfonate anion is preferable.

The element with the solid electrolyte layer formed in this way is immersed in colloidal carbon to form a carbon layer, and then a conductive coating layer is formed using conductive paste on top of it, and a part of it is covered with a lead for drawing out the cathode. Connect the lines. The aluminum solid electrolytic capacitor element configured as described above is packaged by sealing it in a resin mold, a resin case, or a metal case to obtain an aluminum solid electrolytic capacitor.

(Function) As in the method of the present invention, a part of the anode lead and/or the dielectric oxide film is coated with an insulating layer, a conductive layer is formed on the surface of the insulating layer, and a conductor is brought into contact with the conductive layer. Solid electrolyte capacitors manufactured using a method of electrolytically polymerizing the anode and the conductor are less likely to damage the conductor's oxide film or conductive metal oxide thin film during electrolytic polymerization, have extremely low leakage current, and have low dielectric loss. An aluminum solid electrolytic capacitor with a small tangent (tan δ) of is obtained.

(Example) Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 10 aluminum sintered elements with anode leads taken out
A dielectric oxide film was formed on the surface by chemical conversion at 0V.

This element was immersed in a 20% manganese nitrate aqueous solution and then thermally decomposed at 300°C. This operation was repeated five times by changing the concentration of the manganese nitrate aqueous solution to 30, 40.50 and 80% to form manganese dioxide on the surface of the dielectric oxide film.

Next, heat-shrinkable silicone tube (Shin-Etsu Silicon 5T-
3DG) was immersed in a virol solution for 5 seconds, then immersed in a 0.1 M ammonium persulfate aqueous solution for 2 minutes, washed, and dried to form a conductive layer on the surface in advance. This tube is 1mm
It was cut into pieces, inserted into an anode lead, and cured by heating, so that a part of the anode lead was covered with an insulating layer with a conductive layer formed on the surface, as shown in FIG. A stainless steel wire was brought into contact with a part of the chemically polymerized polypyrrole conductive layer on this insulating layer to serve as an anode, and 0.2 m of sodium benzene disulfonate was added.
l/l 1 Pyrrole mono? -0.2 mol/l
The sample was immersed in a stainless steel beaker containing an electrolytic solution consisting of an aqueous solution containing .

As a result, a polypyrrole film was formed on the manganese dioxide layer by electrolytic polymerization.

After removing the stainless steel wire, washing and drying, the device was coated with colloidal carbon and silver paste, an anode lead was attached, and molded with epoxy resin to obtain an aluminum capacitor with a rated voltage of 35 V and a nominal capacity of 1.5 μF. Table 1 shows the capacitance (C), tangent of dielectric loss (tanδ), and leakage current (LC) at 35V of the completed capacitor.

Example 2 Dielectric oxide film formed on the surface, thickness 75 μm, width 3 m
An anode lead was attached to a 20 mm aluminum foil by caulking, and the anode lead was cut into a length of 20 mm to obtain an anode foil.

An insulator made of a 1:1 mixture of epoxy resin (Sumimac 9080 manufactured by Sumitomo Bakelite Co., Ltd.) and fine silica powder (reagent silicon dioxide) was applied to a part of the upper end of the anode foil and dried to form an insulating layer.

After immersing this foil in a 40% manganese nitrate aqueous solution,
Thermal decomposition was carried out at 350°C. When this operation was repeated twice, a manganese dioxide layer was formed on the surface of the dielectric oxide film and the surface of the insulating layer. Next, a stainless steel wire was brought into contact with a part of the surface of the manganese dioxide layer on the insulating layer to serve as an anode, and tetraethylammonium para-toluene sulfone mol/11 pyrrole mono? -0, 2mol/1
immersed in a stainless steel beaker containing an acetonitrile solution containing
Constant current electrolytic polymerization was performed for 0 minutes. As a result, a polypyrrole film was formed on the manganese dioxide layer by electrolytic polymerization.

After removing the stainless steel wire, washing and drying, the device was coated with colloidal carbon and silver paste, an anode lead was attached, and molded with epoxy resin to obtain an aluminum capacitor with a rated voltage of 8.3 V and a nominal capacity of 6.7 μF. The capacitance (C) of the completed capacitor, the tangent of the M electric loss (tanδ) and the leakage current at 6.3v (
LC) are shown in Table 1.

Table 1 Example 3 Dielectric oxide film formed on the surface, thickness 90 μm, width 2 m
An anode lead was attached to a 20 mm aluminum foil by caulking, and the anode lead was cut into a length of 20 mm to obtain an anode foil.

This element was immersed for 70'' in an aqueous solution containing 0.08 mol/l of lead acetate and 0.2 mol/l of ammonium persulfate.
The mixture was reacted at C for 30 minutes and dried. Repeat this operation 4 times,
A conductive thin film layer containing lead dioxide was formed on the surface of the dielectric oxide film. Next, a heat-shrinkable silicone tube (5T-3DG manufactured by Shin-Etsu Silicon) was immersed in a pyrrole solution for 5 seconds and then in a 0.1 M ammonium persulfate aqueous solution for 2 minutes, washed, and dried to form a conductive layer on the surface in advance.

This tube was cut into 1 mm pieces, inserted into the anode lead, and heated and cured, so that a part of the anode lead was covered with an insulating layer with a conductive layer formed on the surface, as shown in FIG.

A stainless steel wire was brought into contact with a part of the chemically polymerized polypyrrole conductive layer on this insulating layer to serve as an anode, and 0.3 r of tetraethylammonium para-toluenesulfonic acid was added.
n o l / I N pyrrole monomer 0.3 mo
Immerse it in a stainless steel beaker containing an acetonitrile solution containing l/1, and use the stainless steel beaker as a cathode for 1 m.
Constant current electrolytic polymerization was carried out at A for 30 minutes. As a result, a polypyrrole film was formed by electrolytic polymerization on the conductive layer containing lead dioxide.

After removing the stainless steel wire, washing and drying, the device was coated with colloidal carbon and silver paste, an anode lead was attached, and molded with epoxy resin to obtain an aluminum capacitor with a rated voltage of 10 V and a nominal capacity of 1.0 μF. Capacitance (C), tangent of dielectric loss (tanδ) and leakage current (LC) at 10V of the completed capacitor
are shown in Table 1.

(Effect of the invention) In an aluminum solid electrolytic capacitor formed by forming a conductive polymer film formed by electrolytic polymerization and a thin film of a metal oxide having conductivity on the surface of aluminum on which a dielectric oxide film is formed, the anode lead and/or a solid electrolyte manufactured by a method in which a part of the dielectric oxide film is covered with an insulating layer, a conductive layer is formed on the surface of the insulating layer, a conductor is brought into contact with this conductive layer, and the conductor is used as an anode and electropolymerized. For capacitors, aluminum solid electrolytic capacitors are available that have less risk of the conductor damaging the oxide film or the thin film of the conductive metal compound during electrolytic polymerization, have extremely low leakage current, and have a small tangent of dielectric loss (tanδ). It will be done.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a sintered aluminum solid electrolytic capacitor with an anode lead drawn out from the center. 1. Fist anode lead 2. Aluminum sintered body 3. Dielectric oxide film 4. Metal oxide with O conductivity 5. Conductive layer 6. Insulating layer 7. Fist conductor 8. By electrolytic polymerization conductive polymer membrane

Claims (1)

[Claims] 1. A method for manufacturing an aluminum solid electrolytic capacitor, in which a dielectric oxide film, a conductive metal oxide, and a conductive polymer film are sequentially formed on the surface of aluminum to which an anode lead is connected. , a part of the anode lead and/or the dielectric oxide film is covered with an insulating layer, a conductive layer is formed on the surface of the insulating layer, a conductor is brought into contact with this conductive layer to form an anode, and a part of the dielectric oxide film is coated with an external cathode. 1. A method for producing an aluminum solid electrolytic capacitor, which comprises performing electrolytic polymerization to form a conductive polymer film. 2. The method for manufacturing an aluminum solid electrolytic capacitor according to claim 1, wherein the conductive metal oxide is manganese dioxide or lead dioxide. 3. The method for manufacturing an aluminum solid electrolytic capacitor according to claim 1, wherein the conductive polymer is polypyrrole.