JP2009246103A - Manufacturing method of cathode foil for aluminum electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of cathode foil capable of improving water resistance of cathode foil for an aluminum electrolytic capacitor. <P>SOLUTION: This manufacturing method of cathode foil for an aluminum electrolytic capacitor is characterized in that a first immersion process of immersing etched cathode foil in a solution that has been subjected to pH adjustment by phosphoric acid and ammonia water is executed, thereafter a first heat treatment is carried out, then a second immersion process of immersing the cathode foil after the first heat treatment in the solution that has been subjected to the pH adjustment by phosphoric acid and ammonia water is executed, and thereafter a second heat treatment is carried out. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a production method for improving the water resistance of a cathode foil for an aluminum electrolytic capacitor.

In recent years, while the electrolytic capacitor is required to have a low impedance, the electrolytic solution used in the low impedance product has a structure containing a large amount of water.
In an electrolyte containing a large amount of water, the aluminum cathode foil not only deteriorates due to a hydration reaction, but also due to the dissolution reaction of aluminum by the activation of the complexing reaction of various organic acids added as solutes. Deterioration is promoted. Therefore, the cathode foil for electrolytic capacitors used for low impedance products is required to have excellent water resistance and stability against complexing reaction.

  Conventional cathode foils for electrolytic capacitors are generally prepared by etching aluminum foil to roughen the surface by etching to increase the surface area, and then chemically cleaning with an aqueous solution containing phosphoric acid, nitric acid, sulfuric acid, etc. The etching film containing is dissolved. Furthermore, after the immersion treatment in the phosphoric acid aqueous solution is performed, the water resistance is improved by performing a drying treatment at 350 ° C. or more to adhere phosphoric acid to the etching foil.

  Conventionally, it is well known that when the cathode foil is subjected to immersion treatment or chemical conversion treatment with an aqueous phosphoric acid solution, the water resistance of the electrode foil is improved. (For example, see Non-Patent Document 1 and Patent Document 1)

Isaya Nagata, “Electrolytic Cathode Aluminum Electrolytic Capacitor”, Nihon Denki Kogyo Kogyo Co., Ltd., February 24, 1997, 2nd edition, 1st edition, P339-341 Japanese Patent Laid-Open No. 11-162791

  However, the electrolytic solution used in the current low impedance products is an electrolytic solution containing more water than the conventional electrolytic solution, and the conventional immersion treatment with phosphoric acid cannot obtain a sufficient effect. .

  In addition, the method of increasing water resistance by chemical conversion treatment with a phosphoric acid aqueous solution or the method of immersing by increasing the phosphoric acid concentration of the phosphoric acid aqueous solution improves the water resistance, but the electrostatic capacity is greatly reduced. A means for improving the water resistance without reducing the electric capacity has been demanded.

  In order to solve the above problems, the present invention provides a method for producing a cathode foil for an aluminum electrolytic capacitor, after performing a first immersion treatment in which an etched cathode foil is immersed in a solution adjusted in pH with phosphoric acid and ammonia water. The first heat treatment is performed, and then the second heat treatment is performed after the second heat treatment is performed in which the cathode foil after the first heat treatment is immersed in a solution adjusted in pH with phosphoric acid and ammonia water.

  In this invention, it is preferable that the temperature of the solution of the said 2nd immersion process is 10-60 degreeC, and phosphoric acid concentration is 0.30-0.75 wt%.

  In the present invention, it is preferable that the pH of the solution for the first immersion treatment is 3.2 to 7.5, and the pH of the solution for the second immersion treatment is 5.5 to 7.8.

  In this invention, it is preferable that the temperature of said 1st and 2nd heat processing is 100-200 degreeC.

In the present invention, after the first immersion treatment is performed in which the etched cathode foil is immersed in a solution adjusted in pH with phosphoric acid and aqueous ammonia, a first heat treatment is performed, and then the cathode foil after the heat treatment is phosphoric acid. After performing the second dipping treatment in which the solution is adjusted in pH with ammonia water, the second heat treatment is performed, thereby improving the water resistance while suppressing a decrease in the capacitance.
The reason is not necessarily clear, but the film is dehydrated by dipping in a solution of phosphoric acid and ammonia water and then heat-treated to form a base film. It is considered that a highly water-resistant film is formed.

  Hereinafter, the present invention will be specifically described based on examples.

[Examples 1-1 to 1-4] Comparison of the first heat treatment temperature [Examples 1-3, 1-5 to 1-7] Comparison of the second heat treatment temperature A roughening process was performed to produce an etching foil. After the etching treatment, it was immersed in a phosphoric acid solution at 45 ° C. and 0.5 wt% to remove residual chlorine ions.
Next, the etching foil is immersed for 1 minute in an aqueous solution having a temperature of 60 ° C. adjusted to pH = 7.0 ± 0.2 with aqueous ammonia of 0.60 wt%, and a first immersion treatment is performed. Thereafter, the first heat treatment was performed for 3 minutes in accordance with the conditions shown in Table 1.
Next, the etching foil was immersed for 1 minute in an aqueous solution having a temperature of 60 ° C. adjusted to pH = 7.0 ± 0.2 with aqueous ammonia of 0.60 wt% phosphoric acid, and a second immersion treatment was performed. Thereafter, the second heat treatment was performed for 3 minutes according to the conditions in Table 1. Finally, a known drying process (for example, 450 ° C. for 20 seconds) was performed to prepare a cathode foil sample.
For these cathode foil samples (size: 2 × 5 = 10 cm ² ), capacitance and hydration time were measured. In addition, about the hydration time, it was set as the time until the said cathode foil sample was immersed in hot water and gas began to generate | occur | produce. The results are shown in Table 1. In addition, it was set to 120 or more about the sample in which gas did not generate | occur | produce after 120-minute immersion.

(Conventional example 1-1, 1-2)
Further, in the conventional examples 1-1 and 1-2, a cathode foil sample was prepared under the same conditions as in the above examples except that the second immersion treatment, the drying and the second heat treatment were not performed, and the same measurement was performed. It was. The results are shown in Table 1.

[Comparison of first heat treatment temperature] Examples 1-1 to 1-4
As is clear from Table 1, in the conventional examples 1-1 and 1-2 in which only the first immersion treatment and the first heat treatment were performed and the second immersion treatment and the second heat treatment were not performed, the capacitance was 250 μF / cm ^2. Although it becomes above, since a hydration time will be less than 80 minutes, it is unpreferable.
In Examples 1-1 to 1-4, the capacitance is 250 μF / cm ² or more and the hydration time is 80 min or more, which is superior to those of Conventional Examples 1-1 and 1-2. I understand. In particular, in Examples 1-2 and 1-3 in which the first heat treatment temperature is 100 to 200 ° C., the capacitance is 260 μF / cm ² or more and the hydration time is 90 minutes or more, which is further excellent. I understand.

[Comparison of Second Heat Treatment Temperature] Examples 1-3 and 1-5 to 1-7
From Examples 1-3 and 1-5 to 1-7, when the temperature of the second heat treatment is 100 to 200 ° C., the capacitance is 260 μF / cm ² or more and the hydration time is 90 min or more. preferable.

[Examples 2-1 to 2-5, 1-3] Comparison of second immersion treatment solution-phosphoric acid concentration [Examples 2-6 to 2-11, 1-3] Comparison of second immersion treatment temperature Examples 2-12 to 2-18] Comparison of first immersion treatment solution-pH [Examples 2-19 to 2-23] Comparison of second immersion treatment solution-pH

Etching (roughening) treatment was performed by the same method as in Examples 1-1 to 1-7 to prepare an etching foil, and residual chlorine ions were removed.
Next, the etching foil is immersed for 1 minute in an aqueous solution having a temperature of 60 ° C. adjusted to pH = 7.0 ± 0.2 with aqueous ammonia of 0.60 wt%, and a first immersion treatment is performed. After that, the first heat treatment was performed for 3 minutes according to the conditions in Table 1.
Next, after adjusting the pH of the aqueous phosphoric acid solution with ammonia water under the conditions shown in Table 2 and immersing the etching foil in an aqueous solution set for temperature for 1 minute to perform a second immersion treatment, 2 Heat treatment was performed for 3 minutes. Finally, a known drying process (for example, 450 ° C. for 20 seconds) was performed to prepare a cathode foil sample.
For these cathode foil samples (size: 2 × 5 = 10 cm ² ), capacitance and hydration time were measured. In addition, about the hydration time, it was set as the time until the said cathode foil sample was immersed in hot water and gas began to generate | occur | produce. The results are shown in Table 2. In addition, it was set to 120 or more about the sample which immersion gas did not generate | occur | produce after 120 minutes.

As is clear from Table 2, the examples according to the present invention have a capacitance of 250 μF / cm ² or more and a hydration time of 80 min or more, which is superior to the conventional examples 1-1 and 1-2. I understand that.

[Comparison of second immersion treatment solution-phosphoric acid concentration] Examples 2-1 to 2-5, 1-3
From Examples 1-3 and 2-2 to 2-4, when the phosphoric acid concentration is 0.30 to 0.75 wt%, the capacitance is 260 μF / cm ² or more and the hydration time is 100 min or more. preferable.

[Comparison of second immersion treatment temperature] Examples 2-6 to 2-11, 1-3
Further, from Examples 2-6 to 2-10 and 1-3, when the second immersion treatment temperature is 10 to 60 ° C., the capacitance is 260 μF / cm ² or more and the hydration time is 100 min or more. preferable.

[Comparison of first immersion treatment solution-pH] Examples 2-12 to 2-18
Furthermore, from Examples 2-13 to 2-17, when the pH of the first immersion treatment solution is 3.2 to 7.5, the capacitance is 250 μF / cm ² or more and the hydration time is 100 min or more. It is more preferable.

[Comparison of second immersion treatment solution-pH] Examples 2-19 to 2-23
And from Examples 2-20 to 2-22, when the pH of the second immersion treatment solution is 5.5 to 7.8, the capacitance is 250 μF / cm ² or more and the hydration time is 100 min or more. It is more preferable.

Claims (4)

  In the method for producing a cathode foil for an aluminum electrolytic capacitor, a first heat treatment is performed by immersing an etched cathode foil in a solution adjusted to pH with phosphoric acid and aqueous ammonia, and then a first heat treatment is performed. A method for producing a cathode foil for an aluminum electrolytic capacitor, wherein a second heat treatment is performed after a second immersion treatment in which the heat-treated cathode foil is immersed in a solution adjusted in pH with phosphoric acid and aqueous ammonia.   The temperature of the solution of said 2nd immersion process is 10-60 degreeC, and phosphoric acid concentration is 0.30-0.75 wt%, The manufacture of the cathode foil for aluminum electrolytic capacitors of Claim 1 characterized by the above-mentioned. Method.   The pH of the solution for the first immersion treatment is 3.2 to 7.5, and the pH of the solution for the second immersion treatment is 5.5 to 7.8. A method for producing a cathode foil for an aluminum electrolytic capacitor as described in 1 above.   The temperature of the said 1st and 2nd heat processing is 100-200 degreeC, The manufacturing method of the cathode foil for aluminum electrolytic capacitors of any one of Claims 1-3 characterized by the above-mentioned.