JPH09180965A - Manufacture of electrode foil for aluminum electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformly generate pits on aluminum material foil by impregnating the aluminum foil with aqueous solution which generates film on the aluminum foil surface prior to the pre-etching or in the middle of the pre-etching. SOLUTION: An aluminum material foil is impregnated with phosphoric aqueous solution with concentration of 0.2-10% for approximately one minute prior to pre-etching. Then, the aluminum material foil is impregnated with acid aqueous solution, direct current is applied and pre-etching is performed or in the middle of pre-etching, namely during the pre-etching, the aluminum material foil is impregnated with phosphoric aqueous solution with concentration of 0.2-10% approximately for one minute. Then, the pre-etching is performed again. Then, the aluminum material foil is impregnated with hydrochloric aqueous solution, direct current is applied and the latter etching, namely, the final etching, is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an electrode foil for an aluminum electrolytic capacitor, and more particularly to a technique for etching an anode aluminum foil for medium and high voltage.

[0002]

2. Description of the Related Art In recent years, with the miniaturization and high reliability of sets, the need for aluminum electrolytic capacitors from users (miniaturization and cost reduction) has been rapidly increasing. Also referred to as electrode foil), it is necessary to increase the capacitance per unit area more than ever before.

A conventional method for manufacturing an electrode foil will be described below. In order to reduce the size of the aluminum electrolytic capacitor, an electrode foil is used that has an effective surface area enlarged by electrochemically or chemically etching the aluminum foil. Various etching methods have been studied to expand this surface area.In general, aluminum foil is continuously inserted into several different etching tanks, and current is applied in each etching tank or the surface area of aluminum foil is changed by chemical dissolution. Is gradually expanded, and a final wash is performed. In particular, how to efficiently and evenly generate pits from the surface of the aluminum raw foil, which is uneven due to trace impurities, natural oxide film, rolling scratches, etc., is an important point to increase the capacitance per unit area. Becomes Conventionally, iron, silicon, copper,
Alternatively, these intermetallic compounds are uniformly dispersed on the surface to increase the starting point of etching, and then pits are generated by electroetching in an acidic aqueous solution containing chlorine ions.

[0004]

However, the above-mentioned conventional technique is affected by a slight amount of impurities contained in the aluminum original foil, a natural oxide film, rolling scratches, etc. in the pit generation process, and in addition, actually, In the electrode foil manufacturing process, the current was interrupted during the etching pit generation process, and as a result, it was difficult to uniformly generate pits from the surface of the aluminum original foil.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a method of manufacturing an electrode foil for an aluminum electrolytic capacitor, which can manufacture an electrode foil having a high capacitance per unit area. To do.

[0006]

In order to achieve the above object, the method for producing an electrode foil for an aluminum electrolytic capacitor according to the present invention is an aluminum foil produced by performing an etching treatment in at least two stages, a first stage and a second stage. In the method for manufacturing the electrode foil for electrolytic capacitors, the aluminum foil is immersed in an aqueous solution that forms a film on the surface of the aluminum foil before the etching in the previous step or in the middle of the etching in the previous step. According to the method, an electrode foil having a high capacitance per unit area can be manufactured.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention is a method for producing an electrode foil for an aluminum electrolytic capacitor, which is produced by performing an etching treatment in at least two stages of a former stage and a latter stage. The aluminum foil is immersed in an aqueous solution that forms a film on the surface of the aluminum foil before etching or in the middle of the previous etching. When the aluminum foil is immersed in the aqueous solution to be generated, impurities present unevenly on the aluminum foil surface,
When the natural oxide film is dissolved and removed, a new uniform film can be formed, and when the aluminum foil is immersed in an aqueous solution that forms a film on the surface of the aluminum foil during the previous etching step, The film on the aluminum foil surface, which had been non-uniform due to etching until the current was interrupted, was to be uniformly generated again by immersion in an aqueous solution.
Since the starting points of the pits are uniformly distributed, pits are uniformly and densely formed on the surface of the aluminum foil, and an electrode foil having a high capacitance per unit area can be obtained.

According to the second aspect of the invention, as the aqueous solution for forming a film on the surface of the aluminum foil, one kind of acid selected from phosphorus-containing acid and oxalic acid, a mixed acid thereof, or a salt thereof is used. It was done like this.

According to the third aspect of the present invention, the concentration of the aqueous solution for forming a film on the surface of the aluminum foil is set within the range of 0.2 to 10%. The formed film is not uniform. On the other hand, when it exceeds 10%, a large amount of acid promotes surface dissolution, so that a uniform film is not formed.

Hereinafter, embodiments of the present invention will be described. (Embodiment 1) A raw aluminum foil having a purity of 99.98% and a thickness of 100 μm is heated to a liquid temperature of 50 before the etching of the former stage.
Immerse in a phosphoric acid aqueous solution having a concentration of 1% at a temperature of 1 minute. After that, the substrate is immersed in an acidic aqueous solution (hydrochloric acid concentration 10%, sulfuric acid concentration 10%) having a liquid temperature of 85 ° C., and a direct current having a current density of 20 A / dm ² is applied for 200 seconds to perform the former etching. After this,
After immersing in a hydrochloric acid aqueous solution having a liquid temperature of 80 ° C. and a concentration of 5%, and applying a direct current having a current density of 15 A / dm ² for 600 seconds, the latter stage,
That is, the final stage etching is performed.

(Embodiment 2) The same aluminum original foil as in Embodiment 1 is used for the same etching. In Embodiment 2, however, 100 seconds have elapsed in the middle stage of the pre-stage etching, that is, the pre-stage etching. By the way, Embodiment 1
Immerse in the same phosphoric acid aqueous solution for 1 minute. Then, the etching of the former stage is performed again for 100 seconds.

(Embodiment 3) Although the same aluminum original foil as in Embodiment 1 is used, in this Embodiment 3, the etching of the former stage is performed with two kinds of etching solutions. First, the first-stage etching is performed by immersing in an acidic aqueous solution (hydrochloric acid concentration 10%, sulfuric acid concentration 10%) at a liquid temperature of 85 ° C.
A direct current of 0 A / dm ² is applied for 100 seconds, and thereafter, it is immersed in a phosphoric acid aqueous solution having a liquid temperature of 50 ° C. and a concentration of 1% for 1 minute, and then the second-stage etching of the previous stage is performed. This second etching in the previous stage was performed by immersing in an aqueous solution of a neutral salt (sodium chloride concentration 5%) at a liquid temperature of 85 ° C. to obtain a current density of 20.
A direct current of A / dm ² is applied for 100 seconds. Finally, the same post-stage etching as in Embodiment 1 is performed.

(Comparative Example) The first embodiment of the present invention described above.
The same etching is performed with the same aluminum raw foil as ~ 3,
Immersion of the phosphoric acid aqueous solution is not performed before the first-stage etching or in the middle of the first-stage etching.

The etching foils in the above-mentioned comparative example and the first to third embodiments of the present invention were formed with a concentration of 10% and a liquid temperature of 50 ° C.
After washing for 1 minute in a nitric acid aqueous solution, the concentration is 8% and the temperature is 9
A 500 V chemical conversion was performed in a 0 ° C. boric acid aqueous solution, and the capacitance and bending strength (1.0 mmR, 5
(Table 1) shows the results of measurement of one reciprocation under a condition of 0 g load and a bending angle of 90 degrees.

[0015]

[Table 1]

This Table 1 shows the characteristics of the electrode foil of the comparative example and the characteristics of the electrode foils of the first to third embodiments immersed in an aqueous solution (phosphoric acid) which forms a film on the surface of the aluminum foil. As is clear from this (Table 1), when immersed in an aqueous solution, pits on the surface of the aluminum raw foil are generated uniformly and with high density, so that the capacitance per unit area can be increased. It is a thing.

In the first to third embodiments of the present invention described above,
The concentration of phosphoric acid, which is an aqueous solution, is 1%, but the concentration of the acid or its salt used for immersion is preferably in the range of about 0.2 to 10%. That is, if the concentration is less than 0.2%, the film formed by dipping will not be uniform, while
When it is more than 0%, a large amount of acid promotes surface dissolution and a uniform film is not formed, and as a result, the effect of increasing the capacitance cannot be obtained.

As described above, by dipping the aluminum foil in an aqueous solution for forming a film on the surface of the aluminum foil before the etching of the former stage or in the middle of the etching of the former stage, the conventional method (comparative example) is obtained. Compared with this, the maximum capacitance was increased by about 15%.

In the above-described embodiment of the present invention, the case where the substrate is immersed only once in the aqueous solution before the etching in the former stage or in the middle of the etching is shown. It may be immersed for etching, and even when the etching solution changes at the etching stage, the same effect as that of the above-described embodiment can be obtained by immersing before etching.

[0020]

As described above, according to the method for manufacturing an electrode foil for an aluminum electrolytic capacitor of the present invention, an aqueous solution for forming a film on the surface of the aluminum foil before the etching of the first stage or in the middle of the etching of the first stage. The aluminum foil is soaked in it.Before the etching of the previous stage,
When the aluminum foil is immersed in an aqueous solution that forms a film on the surface of the aluminum foil, impurities and non-uniform oxides that exist unevenly on the surface of the aluminum foil can be dissolved and removed to form a new uniform film. If the aluminum foil is immersed in an aqueous solution that forms a film on the surface of the aluminum foil during the previous etching process, the film on the surface of the aluminum foil that was not uniform due to etching until the current was interrupted. Since the pits will be uniformly generated again by immersion in the aqueous solution, the pit generation starting points will be evenly distributed, so pits will be generated uniformly and at high density from the surface of the aluminum foil. The surface area is enlarged and the electrostatic capacity can be increased. Further, this increase in capacitance can contribute to downsizing of the aluminum electrolytic capacitor and cost reduction.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Koichi Kojima 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] 1. A method of manufacturing an electrode foil for an aluminum electrolytic capacitor, which is manufactured by performing an etching treatment in at least two stages, a first stage and a second stage, in a stage before the first stage etching or in the middle stage of the first stage etching.
A method for producing an electrode foil for an aluminum electrolytic capacitor, which comprises immersing the aluminum foil in an aqueous solution for forming a film on the surface of the aluminum foil. 2. The aluminum electrolytic capacitor according to claim 1, wherein the aqueous solution for forming a film on the surface of the aluminum foil is one kind of acid selected from phosphorus-containing acids and oxalic acid, mixed acids thereof, or salts thereof. Of manufacturing electrode foil for automobile. 3. The method for producing an electrode foil for an aluminum electrolytic capacitor according to claim 1, wherein the concentration of the aqueous solution for forming a film on the surface of the aluminum foil is in the range of 0.2 to 10%.