JP4163022B2 - Manufacturing method of etching foil for electrolytic capacitor - Google Patents

Description

【００１７】
表１から分かるように、実施例では第１工程で、硝酸アルミニウムまたは硝酸マグネシウムの水溶液濃度が０．５〜１０ｗｔ％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、１０ｗｔ％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。２００℃を下回ると、水和皮膜の均一性が維持できず、水和皮膜が溶解し、静電容量が低下するので不適当である。また、５００℃を超えると、耐電圧が低いγ型の結晶を含む酸化皮膜が成長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、硝酸アルミニウム、硝酸マグネシ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、化成工程における水和皮膜の溶解を防止することができるため、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]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing an electrolytic capacitor etching foil, and more particularly to a post-etching treatment method capable of increasing the capacitance of an electrolytic capacitor electrode foil after chemical conversion treatment.
[0002]
[Prior art]
In recent years, with the miniaturization of electrolytic capacitors, there has been a need to increase the capacitance per unit area of electrolytic capacitor electrode foils. However, when manufacturing aluminum electrode foils for electrolytic capacitors of 160 WV or more, etching was performed. Thereafter, it is known that when a chemical conversion treatment is performed on an etching foil that has been hydrated with hot water, the capacitance increases (for example, see Non-Patent Document 1).
[0003]
[Non-Patent Document 1]
Isaya Nagata "Electrolytic Cathode Aluminum Electrolytic Capacitor", 2nd edition, 1st edition, Nippon Electric Storage Co., Ltd., p. 266-272, p. 294-304
[0004]
[Problems to be solved by the invention]
However, the hydration treatment with hot water was effective in terms of increasing the capacitance and reducing the amount of chemical power for aluminum electrolytic capacitors exceeding the working voltage of 160 WV, but for lower working voltages. It was not available enough.
The reason for this is that the reaction between hot water and aluminum is extremely intense, making it difficult to control the formation of a thin film, and the porous portion formed on the surface fills up the small holes existing in the low-pressure etching surface and By reducing the capacity.
Due to the above problems, there is a method for manufacturing an electrolytic capacitor electrode foil that can control the reaction between hot water and aluminum and increase the capacitance with respect to an aluminum electrolytic capacitor having a working voltage of 160 WV or less. It was requested.
[0005]
[Means for Solving the Problems]
The present invention solves the above-described problem, and includes an electrochemical etching step, a dechlorination treatment step, a post-treatment step, and a heat treatment step, wherein the post-treatment step comprises a first step of hydration treatment, a metal It is a manufacturing method of the etching foil for electrolytic capacitors characterized by including the 2nd process immersed in salt solution.
[0006]
The method for producing an etching foil for an electrolytic capacitor is characterized in that the metal salt used in the second step is aluminum nitrate or magnesium nitrate.
[0007]
Furthermore, it is a manufacturing method of the etching foil for electrolytic capacitors characterized by the density | concentration of the metal salt aqueous solution used at the said 2nd process being 0.5-10 wt%.
[0008]
And the temperature of the said heat processing process is 200-500 degreeC, It is a manufacturing method of the electrode foil for electrolytic capacitors characterized by the above-mentioned.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
After the etched aluminum foil is hydrated, it is immersed in a metal salt aqueous solution of aluminum nitrate and magnesium nitrate to make the hydrated film uniform. Next, by performing heat treatment, the hydrated film is fixed in a uniform state, and it is possible to prevent dissolution of the hydrated film during formation after heat treatment. Small holes existing on the etched surface of the foil are not filled, and a decrease in capacitance can be suppressed.
[0010]
【Example】
First, the aluminum foil is subjected to electrochemical etching in an acidic solution. Next, dechlorination is performed. This dechlorination treatment is performed for the purpose of removing chlorine ions on the etching surface, and an aqueous solution of sulfuric acid or nitric acid is used.
[0011]
First step: After the dechlorination treatment, a hydration treatment is performed. Hydration was performed by immersing in warm pure water at 60 ° C. for 1 minute.
[0012]
Second step: After the above hydration treatment, the substrate is immersed in an aqueous solution of aluminum nitrate at 35 ° C. or lower, or a 0.5-10 wt% aqueous solution of magnesium nitrate. When this concentration is less than 0.5 wt%, the effect of immersion does not appear. On the other hand, when the content exceeds 10 wt%, the surface of the etching foil is dissolved, so that pit destruction occurs and the electrostatic capacity decreases. And when temperature exceeds 35 degreeC, since the etching foil surface melt | dissolves, a pit destruction will occur and an electrostatic capacitance will fall, and it is unsuitable.
[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. and 1 to 5 minutes. Below 200 ° C., the uniformity of the hydrated film cannot be maintained, the hydrated film dissolves, and the capacitance decreases, which is inappropriate. On the other hand, if it exceeds 500 ° C., an oxide film containing a γ-type crystal having a low withstand voltage grows, which is not preferable.
[0014]
In the chemical conversion performed after the heat treatment, a constant current conversion was performed by applying a chemical voltage of 20 V in an aqueous solution of 8 wt% ammonium adipate at 85 ° C., and then the capacitance value was measured.
[0015]
Table 1 shows specific examples.
The immersion conditions in the second step were such that the metal salt was aluminum nitrate or magnesium nitrate, the concentration of the aqueous metal salt solution was in the range of 0.5 to 10 wt%, and the capacitance values were measured and compared. In addition, the capacitance values were measured for samples that were out of the above range, 0.3 wt%, 15 wt%, and those that were not subjected to the second step as a conventional example. The results are shown in Table 1.
[0016]
[Table 1]

[0017]
As can be seen from Table 1, in the first embodiment, the capacitance can be increased in the first step as compared with the comparative example and the conventional example when the aqueous solution concentration of aluminum nitrate or magnesium nitrate is in the range of 0.5 to 10 wt%. If it is less than 0.5 wt%, the effect of immersion in aqueous solution does not appear. On the other hand, when the content exceeds 10 wt%, the surface of the etching foil is dissolved, so that pit destruction occurs and the electrostatic capacity decreases.
And the range of 200-500 degreeC is suitable for heat processing temperature. Below 200 ° C., the uniformity of the hydrated film cannot be maintained, the hydrated film dissolves, and the capacitance decreases, which is inappropriate. On the other hand, if it exceeds 500 ° C., an oxide film containing a γ-type crystal having a low withstand voltage grows, which is not preferable.
[0018]
In addition, it is preferable that a hydration process is immersed in the pure water of 40-70 degreeC, ion-exchange water, and pH 8-11 aqueous solution for 30 second-8 minutes. Examples of the aqueous solution having a pH of 8 to 11 include a sodium hydroxide aqueous solution and a sodium aluminate aqueous solution.
Electrochemical etching is not particularly limited, and a known method can be used, and pre-etching treatment may be appropriately performed.
[0019]
【The invention's effect】
As described above, the method for producing an electrolytic capacitor etching foil according to the present invention hydrates the etched aluminum foil, and then immerses it in an aqueous solution of aluminum nitrate and magnesium nitrate to make the hydrated film uniform, Next, by performing heat treatment, the hydrated film is fixed in a uniform state, and dissolution of the hydrated film in the chemical conversion step can be prevented. Therefore, the low-pressure aluminum electrode foil of 160 WV or less A small hole existing on the etched surface is not filled, and a decrease in capacitance can be suppressed.
.

Claims (4)

It has an electrochemical etching step, a dechlorination treatment step, a post-treatment step, and a heat treatment step, and the post-treatment step comprises a first step for hydration treatment and a second step for immersion in a metal salt aqueous solution. The manufacturing method of the etching foil for electrolytic capacitors characterized by these. 2. The method for producing an electrolytic capacitor etching foil according to claim 1, wherein the metal salt used in the second step is aluminum nitrate or magnesium nitrate. The method for producing an etching foil for an electrolytic capacitor according to claim 1, wherein the concentration of the aqueous metal salt solution used in the second step is 0.5 to 10 wt%. The temperature of the said heat treatment process is 200-500 degreeC, The manufacturing method of the electrode foil for electrolytic capacitors of Claim 1 characterized by the above-mentioned.