JP2638038B2 - Manufacturing method of electrode foil for aluminum electrolytic capacitor - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for producing an electrode foil for an aluminum electrolytic capacitor.

2. Description of the Related Art Conventionally, electrode foils for aluminum electrolytic capacitors have been obtained by electrochemically or chemically etching an aluminum foil serving as an electrode body to increase the surface area in order to reduce the size and cost of the capacitor. You are using

Problems to be Solved by the Invention Various methods have been studied to increase the surface area of this aluminum electrode foil, but it is very difficult to increase the surface area while maintaining the mechanical strength of the aluminum electrode foil. Was. That is, in the conventional etching technology,
In general, when an attempt is made to increase the density of etching holes to increase the surface area, the surface of the aluminum electrode foil also dissolves at the same time, so that not only does the surface area not increase as much as expected, but also the mechanical strength of the aluminum electrode foil is impaired. There was a problem that was.

The present invention solves the above problems, and provides a method for manufacturing an electrode foil for an aluminum electrolytic capacitor that can increase the density of etching holes and increase the surface area while maintaining the mechanical strength of the aluminum electrode foil. Things.

Means for Solving the Problems In order to solve such conventional problems, the present invention provides
A first-stage etching step in which DC etching is performed in an aqueous solution containing 0.1 to 10% of at least one of potassium chloride, sodium chloride, and ammonium chloride, and formation of a porous film including sulfuric acid, oxalic acid, and phosphoric acid in 2 to 15% of hydrochloric acid A second-stage etching step in which DC etching is performed in an aqueous solution to which at least one kind of acid is added in an amount of 5 to 35%.

According to the structure of the present invention, since the aqueous solution containing at least one of potassium chloride, sodium chloride, and neutral salt of ammonium chloride is used in the first stage etching, chemical etching of the aluminum foil surface is prevented. First, an etching hole is generated from an active portion, that is, a defective portion of the surface oxide film. In the subsequent second-stage etching, an aqueous solution obtained by adding at least one of a porous film-forming acid composed of sulfuric acid, oxalic acid and phosphoric acid to hydrochloric acid is used.
First, a porous film is formed on the surface having relatively few defective portions where the step etching holes are not generated, and the holes are eroded by chlorine ions to generate more etching holes. Therefore, while maintaining the mechanical strength with little surface dissolution,
Etching holes can be generated with high density and uniform distribution.

Examples Hereinafter, examples of the present invention will be described.

Specific etching conditions are described for each of the first-stage etching process and the second-stage etching process.

First-stage etching process In order to generate etching holes with high density and uniformity,
DC etching using an aqueous solution containing at least one of potassium chloride, sodium chloride and ammonium chloride is required.

In any of the above-mentioned aqueous solutions of neutral salts, if the concentration is less than 0.1%, the etching effect is small, and if it exceeds 10%, the entire surface is dissolved. Therefore, it is preferably in the range of 0.1% to 10%, particularly preferably 1% to 5%. Within such a preferable range, a high-density and uniform etching hole can be generated with almost no surface melting. The temperature of the etching solution also has an important effect. If the temperature is lower than 50 ° C., the etching effect is small. Therefore, the temperature is preferably in the range of 50 to 100 ° C, particularly 70 to 90 ° C.

When the current density is less than 5 A / dm ² , the etching effect is small, and when the current density exceeds 70 A / dm ² , the entire surface is dissolved. Thus within the scope of 5~70A / dm ^2, in particular 8~30A / dm ² is preferred.

Second-stage etching process Further etching holes are generated while suppressing surface dissolution,
In order to increase the amount, direct current etching using an aqueous solution in which at least one of a porous film-forming acid composed of sulfuric acid, oxalic acid, and phosphoric acid is added to hydrochloric acid is required. Hydrochloric acid concentration is 2
%, The etching effect is small, and if it exceeds 15%, the entire surface is dissolved. Therefore, within the range of 2 to 15%, particularly 3 to 8% is preferable. Regarding the amount of acid that can form the porous film, if the amount of sulfuric acid, oxalic acid, or phosphoric acid is less than 5%, the formation of the porous film is insufficient. Rather, the dissolution reaction becomes stronger and the entire surface is dissolved. Therefore, within the range of 5 to 35%, particularly 15 to 25% is preferable. Within such a preferred range, a porous film having high density and uniform pores is formed on the surface of the aluminum foil, and the pores are eroded by chlorine ions to form etching holes. Since the surface is covered with the film, dissolution of the surface is suppressed, and as a result, a new uniform etching hole can be generated without destroying the etching hole formed by the first-stage etching.

The liquid temperature is 50-100 ℃ for the same reason as the first stage etching
Is good, and 70 to 90 ° C. is particularly preferable.

In addition, the current density was 5 times as in the first stage etching.
~70A / dm ² ranges good, especially 10~40A / dm ² is preferred.

Hereinafter, specific examples of the present invention will be described together with comparative examples.

However, the aluminum foil of the sample has a purity of 99.99% and a thickness of 1
What was annealed at 00 μm was used.

(Comparative Example 1) The first-stage etching was performed by applying a direct current having a current density of 30 A / dm ² for 120 seconds with an aqueous solution at a liquid temperature of 80 ° C in which 5% of hydrochloric acid and 25% of sulfuric acid were added, followed by the second-stage etching Oxalic acid in hydrochloric acid 7%
A direct current having a current density of 10 A / dm ² was applied for 380 seconds using an aqueous solution at a liquid temperature of 90 ° C. to which 0.1% was added.

(Comparative Example 2) The first-stage etching was performed by applying a direct current having a current density of 15 A / dm ² for 240 seconds using an aqueous solution of 4% sodium chloride and a liquid temperature of 80 ° C, and then the second-stage etching was performed to 7% hydrochloric acid. The test was performed by applying a direct current having a current density of 10 A / dm ² for 380 seconds with an aqueous solution at a liquid temperature of 90 ° C. to which 0.1% of oxalic acid was added.

(Example) First stage etching was performed by applying a direct current having a current density of 15 A / dm ² for 240 seconds with an aqueous solution of sodium chloride 4% and a liquid temperature of 80 ° C., and then the second stage etching was performed using 5% hydrochloric acid and sulfuric acid. This was performed by applying a direct current having a current density of 30 A / dm ² for 120 seconds using an aqueous solution at a liquid temperature of 80 ° C. to which 25% was added.

Table 3 shows the results of measuring the capacitance and bending strength of the etched foils of the above three examples after forming them at 370 V with a boric acid aqueous solution (1.0 R, 200 g load, bending 90 °, one round trip). -1.

Effects of the Invention As described above, according to the present invention, an electrode foil for an aluminum electrolytic capacitor having a large capacitance and excellent mechanical strength can be obtained.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Ryoichi Shimatani 1006 Kazuma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. In-company (56) References JP-A-57-66615 (JP, A) JP-A-60-63916 (JP, A) JP-A-60-219721 (JP, A) JP-A-1-212428 (JP, A) )

Claims (3)

(57) [Claims] An etching treatment is performed in two stages, a first stage and a second stage. An aqueous solution containing 0.1 to 10% of at least one of potassium chloride, sodium chloride and ammonium chloride as the first stage etching. DC etching in a second step, and DC etching in an aqueous solution obtained by adding at least one of a porous film forming acid consisting of sulfuric acid, oxalic acid, and phosphoric acid to 2 to 15% of hydrochloric acid and 5 to 35% as a second stage etching. Characteristic method for manufacturing electrode foil for aluminum electrolytic capacitors. 2. The method according to claim 1, wherein the temperature of the etching solution is 50 to 100 ° C. 3. The method according to claim 1, wherein the current density is 5 to 70 A / dm ² .