JP2004356185A - Method of manufacturing etching foil for electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an electrode foil for an electrolytic capacitor which is capable of improving a low-voltage aluminum electrode foil of 160 WV or below in electrostatic capacity. <P>SOLUTION: The method of manufacturing an etching foil for an electrolytic capacitor comprises an electrochemical etching process, a dechlorination process, an after-treatment process, and a thermal treatment process. The after-treatment process comprises a first process of carrying out a hydrating treatment, and a second process of dipping the etching foil into a 0.5 to 10 wt% aqueous solution of yttrium nitrate or zirconium nitrate. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００１７】
表１から分かるように、実施例では第１工程で、硝酸イットリウムまたは硝酸ジルコニウムの水溶液濃度が０．５〜１０．０ｗｔ％の範囲で比較例、従来例に比べ静電容量を高めることができる。０．５ｗｔ％未満の場合、水溶液浸漬の効果が現れない。また、１０．０ｗｔ％を超えるとエッチング箔表面が溶解するためピット破壊が起こり、静電容量が低下する。
そして、熱処理温度は、２００〜５００℃の範囲が適当である。熱処理を行わない比較例や、２００℃を下回る場合（実施例Ａ−６、Ｂ−６）は、大気中の水分で水和皮膜が成長し、静電容量が低下するので不適当である。また、５００℃を超える場合（実施例Ａ−９、Ｂ−９）は、水和皮膜に欠陥が生じ、静電容量が低下するので好ましくない。
【００１８】
なお、水和処理は、４０〜７０℃の純水、イオン交換水、ｐＨ８〜１１の水溶液に３０秒〜８分間浸漬することが好ましい。ｐＨ８〜１１の水溶液としては、水酸化ナトリウム水溶液、アルミン酸ナトリウム水溶液等を挙げることができる。
また、電気化学エッチングは特に限定されるものではなく、公知の方法を使用することができ、適宜エッチング前処理を行ってもよい。
【００１９】
【発明の効果】
以上のように、本発明による電解コンデンサ用エッチング箔の製造方法は、エッチングされたアルミニウム箔を水和処理した後、硝酸イットリウム、硝酸ジルコニウムの水溶液に浸漬することにより、水和皮膜を均一にし、次に、熱処理することにより、均一になった状態で水和皮膜が固定されることになり、化成工程における陽極酸化皮膜の結晶化が進み、１６０ＷＶ以下の低圧用アルミニウム電極箔のエッチング面に存在する小さな穴を埋めることがなくなり、静電容量の低下を抑えることができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to the production of an electrode foil for an electrolytic capacitor, and more particularly to a post-etching treatment method capable of increasing the capacitance of an electrode foil for an electrolytic capacitor after a chemical conversion treatment.
[0002]
[Prior art]
In recent years, with the miniaturization of electrolytic capacitors, the need for increasing the capacitance per unit area has also arisen for electrode foils for electrolytic capacitors, but when manufacturing aluminum electrode foils for electrolytic capacitors of 160 WV or more, etching was performed. It is known that when a chemical conversion treatment is performed on the etched foil that has been subjected to hydration treatment with hot water, the capacitance increases (for example, see Non-Patent Document 1).
[0003]
[Non-patent document 1]
Nagaya Isaya, "Electrolyte Cathode Aluminum Electrolytic Capacitor", 2nd edition, 1st printing, Nippon Denshi Co., Ltd. 266-272, p. 294-304
[0004]
[Problems to be solved by the invention]
However, the hydration treatment with hot water was effective in increasing the electrostatic capacity and decreasing the amount of chemical power for aluminum electrolytic capacitors exceeding a working voltage of 160 WV. Was not fully available.
The reason is that the reaction between hot water and aluminum is extremely violent, and it is difficult to control the formation of a thin film.Moreover, the porous portion formed on the surface fills small holes in the low-pressure By reducing the capacity.
Because of the above-described problems, a method for manufacturing an electrode foil for an electrolytic capacitor that can control the reaction between hot water and aluminum and increase the capacitance for an aluminum electrolytic capacitor having a working voltage of 160 WV or less is known. Had been requested.
[0005]
[Means for Solving the Problems]
The present invention solves the above-described problems, and includes an electrochemical etching step, a dechlorination treatment step, a post-treatment step, and a heat treatment step, wherein the post-treatment step is a first step of hydration treatment. And a second step of dipping in an aqueous solution of a metal salt.
[0006]
Further, there is provided a method for producing an etching foil for an electrolytic capacitor, wherein the metal salt used in the second step is yttrium nitrate or zirconium nitrate.
[0007]
Further, there is provided a method for producing an etching foil for an electrolytic capacitor, wherein the concentration of the aqueous metal salt solution used in the second step is 0.5 to 10.0 wt%.
[0008]
And the temperature of the said heat treatment process is 200-500 degreeC, It is the manufacturing method of the etching foil for electrolytic capacitors characterized by the above-mentioned.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
After the etched aluminum foil is hydrated, it is immersed in an aqueous solution of a metal salt of yttrium nitrate or zirconium nitrate, so that the hydrated film becomes uniform. Then, by performing the heat treatment, the hydrated film is fixed in a uniform state, the crystallization of the anodic oxide film proceeds during the chemical formation after the heat treatment, and the etched surface of the aluminum electrode foil for low pressure of 160 WV or less is formed. Is not filled in, and a decrease in capacitance can be suppressed.
[0010]
【Example】
First, the aluminum foil is subjected to electrochemical etching in an acidic solution. Next, a dechlorination treatment is performed. This dechlorination treatment is performed for the purpose of removing chlorine ions from the etching surface, and an aqueous solution of sulfuric acid, phosphoric acid or nitric acid is used.
[0011]
First step: After the above dechlorination treatment, hydration treatment is performed. The hydration treatment was performed by immersing in hot pure water at 60 ° C. for 1 minute.
[0012]
Second step: After the above hydration treatment, it is immersed in a 0.5 to 10.0 wt% aqueous solution of yttrium nitrate or zirconium nitrate at 35 ° C. or lower. If this concentration is less than 0.5 wt%, the effect of immersion does not appear. On the other hand, if the content exceeds 10.0% by weight, pit destruction occurs because the etching foil surface is dissolved, and the capacitance is reduced. If the temperature exceeds 35 ° C., the surface of the etching foil dissolves, which causes pit destruction and lowers the capacitance.
[0013]
Heat treatment step: After the above immersion treatment, heat treatment is performed. The temperature of the heat treatment is preferably 200 to 500 ° C. for 1 to 5 minutes. When the temperature is lower than 200 ° C., the uniformity of the hydrated film cannot be maintained, the hydrated film dissolves, and the capacitance is lowered, which is not suitable. On the other hand, when the temperature exceeds 500 ° C., an oxide film containing a γ-type crystal having a low withstand voltage grows, which is not preferable.
[0014]
In the formation performed after the heat treatment, a constant current formation was performed by applying a formation voltage of 20 V in an aqueous solution of 8% by weight of ammonium adipate at 85 ° C., and then the capacitance value was measured.
[0015]
Table 1 shows specific examples.
As the immersion conditions in the second step, the metal salt was yttrium nitrate or zirconium nitrate, the concentration of the metal salt aqueous solution was in the range of 0.5 to 10.0 wt%, and the capacitance values were measured and compared. In addition, the capacitance values of 0.3 wt% and 15.0 wt% as those out of the above range, those without the heat treatment as the comparative example, and those without the second step treatment and the heat treatment as the conventional example are shown below. It was measured. Table 1 shows the results.
[0016]
[Table 1]

[0017]
As can be seen from Table 1, in the first step, in the first step, when the aqueous solution concentration of yttrium nitrate or zirconium nitrate is in the range of 0.5 to 10.0 wt%, the capacitance can be increased as compared with the comparative example and the conventional example. . If it is less than 0.5 wt%, the effect of immersion in the aqueous solution will not be exhibited. On the other hand, if the content exceeds 10.0% by weight, pit destruction occurs because the etching foil surface is dissolved, and the capacitance is reduced.
The heat treatment temperature is suitably in the range of 200 to 500C. Comparative examples in which heat treatment is not performed, and cases where the temperature is lower than 200 ° C. (Examples A-6 and B-6) are not suitable because the hydrated film grows due to moisture in the atmosphere and the capacitance decreases. On the other hand, when the temperature exceeds 500 ° C. (Examples A-9 and B-9), it is not preferable because defects occur in the hydrated film and the capacitance decreases.
[0018]
The hydration treatment is preferably immersed in pure water at 40 to 70 ° C., ion-exchanged water, or an aqueous solution having a pH of 8 to 11 for 30 seconds to 8 minutes. Examples of the aqueous solution having a pH of 8 to 11 include an aqueous sodium hydroxide solution and an aqueous sodium aluminate solution.
In addition, the electrochemical etching is not particularly limited, a known method can be used, and an etching pretreatment may be appropriately performed.
[0019]
【The invention's effect】
As described above, the method for producing an etching foil for an electrolytic capacitor according to the present invention comprises, after hydrating the etched aluminum foil, immersing it in an aqueous solution of yttrium nitrate and zirconium nitrate to make the hydrated film uniform, Next, by heat treatment, the hydrated film is fixed in a uniform state, and the crystallization of the anodic oxide film proceeds in the chemical conversion step, which is present on the etched surface of the aluminum electrode foil for low pressure of 160 WV or less. Therefore, it is possible to prevent a small hole from being filled, thereby suppressing a decrease in capacitance.

Claims (4)

The method includes an electrochemical etching step, a dechlorination treatment step, a post-treatment step, and a heat treatment step. A method for producing an etching foil for an electrolytic capacitor, comprising: 2. The method according to claim 1, wherein the metal salt used in the second step is yttrium nitrate or zirconium nitrate. 2. The method according to claim 1, wherein the concentration of the aqueous metal salt solution used in the second step is 0.5 to 10.0 wt%. The method for producing an etching foil for an electrolytic capacitor according to claim 1, wherein the temperature of the heat treatment step is 200 to 500C.