JPH07109815B2 - Method for manufacturing electrode foil for aluminum electrolytic capacitor - Google Patents

Description

The present invention relates to a method for manufacturing an aluminum electrolytic capacitor electrode foil.

[Conventional technology]

Generally, this kind of electrode foil is manufactured as follows. First, prepare the etched aluminum foil,
Immerse this aluminum foil in an aqueous solution of phosphoric acid or boric acid,
Anodizing treatment (chemical conversion treatment) is performed by applying a constant voltage to form an oxide film having a desired thickness. Then, depolarization treatment by immersing in acid or alkaline aqueous solution and several hundred
A heat treatment step of leaving it in a high temperature atmosphere of ° C for several minutes is performed. These chemical conversion treatment, depolarization treatment and heat treatment are usually repeated several times.

[Problems to be Solved by the Invention]

However, with this method, there is a limit to increase the electrostatic capacity, and it is not possible to meet the recent demand for smaller size and higher capacity.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for manufacturing an electrode foil for an aluminum electrolytic capacitor, which is capable of obtaining a higher capacitance.

[Means for Solving the Problems]

In order to achieve the above-mentioned object, in the present invention, the etched aluminum foil is first immersed in high temperature pure water for a predetermined time, and then, as the main conversion step, at least an aliphatic saturated dicarboxylic acid or a salt thereof is contained. The aluminum foil is immersed in a boric acid aqueous solution, and anodization is performed by applying a voltage for a predetermined time.In the re-forming step, the aluminum foil is immersed in a boric acid aqueous solution containing boric acid or a salt thereof, and the voltage is kept for a predetermined time. It is applied so that reanodization is performed. In this chemical conversion step, the aluminum foil is first immersed in a boric acid aqueous solution, and voltage is applied for a predetermined time to perform a first anodic oxidation, and then the aluminum foil contains an aliphatic saturated dicarboxylic acid or a salt thereof. It is also possible to perform multi-stage anodic oxidation by immersing in a boric acid aqueous solution and applying a voltage for a predetermined time to perform the second anodic oxidation. Further, it is also effective to replace the first anodic oxidation process with the second anodic oxidation process.

The aliphatic saturated dicarboxylic acid is represented by the chemical formula XOOC- (CH ₂ ) _n -COOX (where X is H ⁺ or NH ₄ ⁺ , n = 1 to 12, preferably n = 1 to 8), and its representative Examples include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid and the like.

In the present invention, a precursor thereof may be appropriately used instead of the aliphatic saturated dicarboxylic acid or its salt. Examples of the precursor in this case include acid amide, ester, and acid anhydride.

The pH of the aqueous boric acid solution during this chemical conversion is 3 to 9, preferably 4.5 to
Set to 7. The concentration of the saturated aliphatic dicarboxylic acid in this aqueous boric acid solution is 0.002 to 1.0%, and the liquid temperature is 70 to 100 ° C.
Is preferred. Further, it is preferable that the concentration of boric acid or its salt at the time of re-chemical conversion is 0.5 to 10 wt% and the liquid temperature is 70 to 100 ° C.

According to this, the capacitance is increased by about 6 to 11% or more as compared with the conventional method. In addition, for depolarization treatment after this chemical conversion, ammonia water with a pH of 7-9 and a liquid temperature of 50-90 ° C (concentration 0.001-0.2 wt%),
Alternatively, an aqueous solution of phosphoric acid having a pH of 4 to 8 (concentration of 0.1 to 8 wt%) is used, and the immersion time is set to about 1 to 5 minutes. The heat treatment is preferably at 400 to 500 ° C. for about 1 to 3 minutes.

Example 1 (A) An aluminum etching foil having a purity of 99.99% and a thickness of 100 μm was prepared. In this case, the etching magnification is 20 times that of a non-etched flat foil.

(B) This aluminum etching foil was boiled for 15 minutes in pure water having a liquid temperature of 98 ° C. or higher.

(C) Next, the aluminum etching foil was immersed in a boric acid aqueous solution containing 20 g of boric acid and 0.1 g of ammonium succinate per 1 pure water and a liquid temperature of 85 ° C., and a current having a current density of 10 mA / cm ² was applied to form the chemical composition. The voltage was increased to 600 V and the same voltage was applied for 40 minutes to perform this chemical conversion.

(D) The aluminum etching foil after chemical conversion has a liquid temperature of 70 ° C,
Depolarization treatment was carried out by immersing in ammonia water adjusted to pH 7 to 9 for 3 minutes.

(E) Heat treatment was performed for 2 minutes in a heating atmosphere of 500 ° C.

(F) 20 g boric acid and 0.5 g ammonium borate per 1 pure water
The solution was dissolved in an aqueous solution of 85 ℃, and the current density was
A current of 10 mA / cm ² was flown to raise the formation voltage to 600 V, and the same voltage was applied for 13 minutes for re-formation.

(G) As in (E) above, 2 in a 500 ° C heating atmosphere
Heat treated for minutes.

(H) Again, it is immersed in an aqueous solution in which 20 g of boric acid and 0.5 g of ammonium borate are dissolved per 1 pure water, a liquid temperature of 85 ° C., a current having a current density of 10 mA / cm ² is passed, and the formation voltage is increased to 600 V,
The same voltage was applied for 13 minutes for re-formation.

(I) After washing with water and drying, the capacitance of the formed foil was measured and found to be 0.458 μF / cm ² .

(J) This formed foil (15 mm x 270 mm) was used as an anode, while an aluminum foil (15 mm x 300 mm) with a purity of 99.2% and a thickness of 20 µm and an etching magnification of 50 times was used as a cathode, and was wound with a separator interposed between the capacitor element. It was created. Then, when this capacitor element was impregnated with an electrolytic solution and enclosed in a case to prepare an electrolytic capacitor rated at 400 V and 16 μF, its capacitance was 18.2 μF.

In addition, between the steps (H) and (I), a dipping treatment was performed for 4 minutes in an aqueous solution of 85 wt% phosphoric acid 25 ml /, which was adjusted to pH 6.5 with ammonia water and had a liquid temperature of 30 ° C. You may intervene the process to perform. The electrolytic capacitor to which this step is added can prevent deterioration due to leakage current of the product in a high temperature storage test at 105 ° C. for 1000 hours.

Example 2 (A) An aluminum etching foil having a purity of 99.99% and a thickness of 100 μm was prepared. In this case, the etching magnification is 20 times that of the unetched flat foil.

(B) This aluminum etching foil was boiled for 15 minutes in pure water having a liquid temperature of 98 ° C. or higher.

(C) 20 g of boric acid and 0.1 g of ammonium adipate were added per 1 part of pure water, and the aluminum etching foil was immersed in a solution temperature of 85 ° C., and a current density of 10 mA / cm ² was applied, and the formation voltage up to 600 V This formation was performed by raising the voltage and applying the same voltage for 40 minutes.

(D) The aluminum etching foil after chemical conversion has a liquid temperature of 70 ° C,
Depolarization treatment was carried out by immersing in ammonia water adjusted to pH 7 to 9 for 3 minutes.

(E) Heat treatment was performed for 2 minutes in a heating atmosphere of 500 ° C.

(F) 20 g boric acid and 0.5 g ammonium borate per 1 pure water
The solution was dissolved in an aqueous solution of 85 ℃, and the current density was
A current of 10 mA / cm ² was flown to raise the formation voltage to 600 V, and the same voltage was applied for 13 minutes for re-formation.

(G) Heat treatment was performed for 2 minutes in a heating atmosphere of 500 ° C.

(H) Again, it is immersed in an aqueous solution in which 20 g of boric acid and 0.5 g of ammonium borate are dissolved per 1 pure water, a liquid temperature of 85 ° C., a current having a current density of 10 mA / cm ² is passed, and the formation voltage is increased to 600 V,
The same voltage was applied for 13 minutes for re-formation.

(I) After washing with water and drying, the capacitance of the formed foil was measured and found to be 0.448 μF / cm ² .

(J) When this formed foil (15 mm × 270 mm) was used as an anode, an electrolytic capacitor having a rating of 400 V and 16 μF was prepared in the same manner as in Example 1. Its electrostatic capacity was 17.8 μF.

Example 3 (A) An aluminum etching foil having a purity of 99.99% and a thickness of 100 μm was prepared. In this case, the etching magnification is 20 times that of the unetched flat foil.

(B) This aluminum etching foil was boiled for 15 minutes in pure water having a liquid temperature of 98 ° C. or higher.

(C) Aluminum etching foil is immersed in a boric acid aqueous solution containing 20 g of boric acid and 0.1 g of ammonium sebacate per pure water, at a liquid temperature of 85 ° C., and a current density of 10 mA / cm ² is applied until the formation voltage is 600 V. This formation was performed by raising the voltage and applying the same voltage for 40 minutes.

(D) The aluminum etching foil after chemical conversion has a liquid temperature of 70 ° C,
Depolarization treatment was carried out by immersing in ammonia water adjusted to pH 7 to 9 for 3 minutes.

(E) Heat treatment was performed for 2 minutes in a heating atmosphere of 500 ° C.

(F) 20 g boric acid and 0.5 g ammonium borate per 1 pure water
The solution was dissolved in an aqueous solution of 85 ℃, and the current density was
A current of 10 mA / cm ² was flown to raise the formation voltage to 600 V, and the same voltage was applied for 13 minutes for re-formation.

(G) Heat treatment was performed for 2 minutes in a heating atmosphere of 500 ° C.

(H) Again, it is immersed in an aqueous solution in which 20 g of boric acid and 0.5 g of ammonium borate are dissolved per 1 pure water, a liquid temperature of 85 ° C., a current having a current density of 10 mA / cm ² is passed, and the formation voltage is increased to 600 V,
The same voltage was applied for 13 minutes for re-formation.

(I) After washing with water and drying, the capacitance of the formed foil was measured and found to be 0.460 μF / cm ² .

(J) Using this formed foil (15 mm × 270 mm) as an anode, an electrolytic capacitor having a rating of 400 V and 16 μF was prepared in the same manner as in Example 1, and its electrostatic capacity was 18.3 μF.

Comparative Example 1 (a) An aluminum etching foil having a purity of 99.99% and a thickness of 100 μm was prepared. In this case, the etching magnification is 20 times that of the unetched flat foil.

(B) The aluminum etching foil was boiled for 15 minutes in pure water having a liquid temperature of 98 ° C or higher.

(C) A boric acid aqueous solution containing 20 g of boric acid per 1 pure water,
The aluminum etching foil was immersed in a liquid temperature of 85 ° C., a current having a current density of 10 mA / cm ² was applied to raise the formation voltage to 600 V, and the same voltage was applied for 40 minutes to perform the main formation.

(D) Liquid temperature of the aluminum etching foil after chemical conversion is 70 ° C,
Depolarization treatment was carried out by immersing in ammonia water adjusted to pH 7 to 9 for 3 minutes.

(E) Heat treatment was performed for 2 minutes in a heating atmosphere at 500 ° C.

(F) Aqueous solution under the same conditions as in (c) above, that is, pure water 1
Boric acid aqueous solution containing 20 g per boric acid, soaked again in liquid temperature 85 ℃, current density 10mA / cm ²
The voltage was raised to 600 V, and the same voltage was applied for 13 minutes for re-formation.

(G) Heat treatment was performed in a heating atmosphere of 500 ° C. for 2 minutes.

(H) Again, it is immersed in a boric acid aqueous solution containing 20 g of boric acid / pure water at a liquid temperature of 85 ° C., a current density of 10 mA / cm ² is applied, the formation voltage is increased to 600 V, and the same voltage is applied for 13 minutes. And re-formed.

(I) After washing with water and drying, the capacitance of the formed foil was measured and found to be 0.296 μF / cm ² .

(J) When this formed foil (15 mm × 270 mm) was used as an anode to prepare an electrolytic capacitor rated at 400 V and 16 μF as in Example 1, the electrostatic capacity was 11.7 μF.

Comparative Example 2 (a) An aluminum etching foil having a purity of 99.99% and a thickness of 100 μm was prepared. In this case, the etching magnification is 20 times that of the unetched flat foil.

(B) The aluminum etching foil was boiled for 15 minutes in pure water having a liquid temperature of 98 ° C or higher.

(C) 20 g boric acid and 0.5 g ammonium borate per 1 pure water
The aluminum etching foil was immersed in an aqueous solution of boric acid added with a solution of 85 ° C., a current density of 10 mA / cm ² was applied, the formation voltage was increased to 600 V, and the formation voltage was applied for 40 minutes to perform the main formation. .

(D) Liquid temperature of the aluminum etching foil after chemical conversion is 70 ° C,
Depolarization treatment was carried out by immersing in ammonia water adjusted to pH 7 to 9 for 3 minutes.

(E) Heat treatment was performed for 2 minutes in a heating atmosphere at 500 ° C.

(F) 20 g boric acid and 0.5 g ammonium borate per 1 pure water
Was re-immersed in an aqueous solution of boric acid to which was added a solution temperature of 85 ° C., a current having a current density of 10 mA / cm ² was applied to increase the formation voltage to 600 V, and the same voltage was applied for 13 minutes for re-formation.

(G) Heat treatment was performed in a heating atmosphere of 500 ° C. for 2 minutes.

(H) Again, it was immersed in a boric acid aqueous solution containing 20 g of boric acid and 0.5 g of ammonium borate per 1 pure water, at a liquid temperature of 85 ° C., a current density of 10 mA / cm ² was applied, and the formation voltage was increased to 600 V. The voltage was applied for 13 minutes for re-formation.

(I) It was washed with water and dried, and the capacitance of the formed foil was measured and found to be 0.423 μF / cm ² .

(J) When an electrolytic capacitor having the same rating as in Comparative Example 1 was prepared, its capacitance was 16.8 μF.

For reference, the following table shows the foil capacitance of the chemical conversion foil obtained in each of the above Examples and Comparative Examples and the capacitance of the electrolytic capacitor prototyped using the chemical conversion foil.

As is clear from this table, according to the present invention, both the capacitance of the foil and the capacitance of the product are increased by about 8 to 9% as compared with the comparative example by the conventional method.

〔The invention's effect〕

As described above, according to the present invention, the etched aluminum foil is boiled with pure water, and then the aluminum foil is immersed in a boric acid solution containing at least an aliphatic saturated dicarboxylic acid or a salt thereof as the present chemical conversion step, Anodization is performed by applying a voltage for a predetermined period of time, and in the subsequent re-chemical conversion step, an electrode foil having a high capacitance is manufactured by immersing it in an aqueous solution containing boric acid or its salt and applying a voltage for a predetermined period of time. It

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yu Endo 2-2-1 Tsujido Shinmachi, Fujisawa-shi, Kanagawa Elner Co., Ltd. (72) Inventor Noboru Haga 2-2-1 Tsujido Shinmachi, Fujisawa-shi, Kanagawa Elner Incorporated (72) Inventor Mikio Sasaki 2-1-2 Marunouchi, Chiyoda-ku, Tokyo Asahi Glass Co., Ltd.

Claims (3)

[Claims] 1. A pure water boiling step of immersing the etched aluminum foil in high temperature pure water for a predetermined time, and then immersing the aluminum foil in a boric acid aqueous solution containing at least an aliphatic saturated dicarboxylic acid or a salt thereof. Then, a main chemical conversion step of applying voltage for a predetermined time to perform anodization,
A method for producing an electrode foil for an aluminum electrolytic capacitor, which comprises a re-chemical conversion step of immersing the aluminum foil in a boric acid aqueous solution containing boric acid or a salt thereof and applying a voltage for a predetermined time to perform re-anodization. 2. The aliphatic saturated dicarboxylic acid comprises a compound represented by the chemical formula XOOC- (CH ₂ ) _n -COOX (where X is H ⁺ or NH ₄ ⁺ , n = 1 to 12). 1. The method for producing an electrode foil for an aluminum electrolytic capacitor as described in 1. 3. The method for producing an electrode foil for an aluminum electrolytic capacitor according to claim 1, wherein the chemical conversion step further includes anodic oxidation in a boric acid aqueous solution containing boric acid or a salt thereof.