JP2004193339A - Manufacturing method of electrode foil for electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing an electrode foil of an electrolytic capacitor of a large capacitance. <P>SOLUTION: The manufacturing method of an electrode foil of an electrolytic capacitor has an etching process for performing coarse surface finishing to an aluminum or an aluminum alloy foil in etchant including chlorine ion, electrically and/or chemically, a heat treatment process, and a chemical cleaning process for eliminating chlorine ion adhering to the foil. Making the heat treatment temperature 150-500<SP>o</SP>C and making the annealing time 30 seconds to 5 minutes, thereby restraining wasteful resolution of etching pit and formation of a coating film in the chemical cleaning process, so that an etching film for a large capacitance can be provided. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００１２】
表１よりケミカル洗浄工程前に熱処理を施した本発明による実施例１〜１０は、熱処理を施さない従来例より静電容量が高いことが分かる。ここで、熱処理条件が１００℃・６分の実施例１および５５０℃・１５秒の実施例１０は、その他の実施例より熱処理による効果が少ないことから、熱処理温度は１５０〜５００℃、熱処理時間は３０秒〜５分の範囲が好ましい。
【００１３】
箔表面の不純物の付着について調べるために、実施例３，４，７および従来例で得られたエッチング箔を純水で１０分間煮沸し、イオンクロマトグラフを用いて定量分析を行った結果とリン酸−クロム酸溶液によるエッチング箔の皮膜量の測定結果を表２に示す。
【００１４】
【表２】

【００１５】
表２より、熱処理した実施例は、従来例と同様に塩素イオンが除去されていることがわかる。さらに、ケミカル洗浄液の成分であるリン酸イオンは、従来例より少なく、本発明は、エッチング箔に付着した不純物を低減できることが分かる。また、エッチング箔の皮膜量も実施例は従来例より低減されている。
【００１６】
本発明は実施例に限定されるものではなく、公知のエッチング方法やケミカル洗浄工程後、容量アップや皮膜安定化のための後処理工程を設けてもよい。
【００１７】
【発明の効果】
上述の如く、エッチング工程とケミカル洗浄工程との間に熱処理工程を設けることにより、ケミカル洗浄工程での静電容量低下を抑制することで電極箔の高容量化が可能となり、さらに、その後の化成工程や製品信頼性に悪影響を及ぼすことが懸念されるケミカル洗浄液成分の付着やケミカル洗浄による皮膜生成を抑制することができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing an electrode foil for an electrolytic capacitor, and particularly to a cleaning method.
[0002]
[Prior art]
Electrode foils for electrolytic capacitors are generally subjected to etching in a solution containing chlorine in order to increase the effective area and increase the capacitance per unit area. By this etching process, an etching film with chloride etc. attached to the foil surface is formed, but chloride present in this film has a bad effect in the chemical conversion process and capacitor products. After washing the surface of the electrode foil with water, it was immersed in a solution containing sulfuric acid or the like to dissolve and remove the etching film together with the chloride (for example, see Non-Patent Document 1). This chloride removal step using a chemical such as an acid is generally called a chemical cleaning step.
[0003]
[Non-patent document 1]
Isaya Nagata, "Electrolyte Cathode Aluminum Electrolytic Capacitors", Nippon Denki Co., Ltd., February 24, 1997, p. 247-249
[0004]
[Problems to be solved by the invention]
In the chemical cleaning step, the etching film is dissolved to remove the chloride. However, there was a problem that was reduced. In addition, there is also a problem that aluminum ions due to dissolution of the etching pits form a new film containing a chemical used for chemical cleaning, which adversely affects subsequent processes and product reliability.
[0005]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention is to modify an etching film before a chemical cleaning step.
That is, an etching step of electrically and / or chemically roughening an aluminum or aluminum alloy foil in an etching solution containing chlorine ions, a heat treatment step, and a chemical cleaning step of removing chloride ions attached to the foil. This is a method for producing an electrode foil for an electrolytic capacitor, which is sequentially processed.
[0006]
And the temperature of the said heat treatment process is 150-500 degreeC, It is the manufacturing method of the electrode foil for electrolytic capacitors characterized by the above-mentioned.
[0007]
Furthermore, there is provided a method for producing an electrode foil for an electrolytic capacitor, wherein the time of the heat treatment step is 30 seconds to 5 minutes.
[0008]
Further, the cleaning liquid in the chemical cleaning step preferably contains at least one of sulfuric acid, phosphoric acid and nitric acid.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention is used in a method for manufacturing an electrode foil of an electrolytic capacitor. The etching film roughened by electrolytic and / or chemical etching is subjected to a heat treatment step before a chemical cleaning step to form an etching film. By performing the modification, it is possible to suppress a decrease in the capacity of the etching foil in the chemical cleaning step. Although the theory of suppression of capacity reduction by heat treatment is not always clear, a strong thermal oxide film is formed by heat treatment at the interface between the etching film formed by etching and the aluminum substrate, that is, inside the etching film, and is protected by the thermal oxide film It is considered that the etched pits did not dissolve in the chemical cleaning step, only the unnecessary etching film was dissolved, and the unnecessary film was hardly generated.
[0010]
【Example】
Hereinafter, the present invention will be specifically described. A hard material of aluminum foil having a purity of 99.86% and a thickness of 50 μm was used at 40 ° C. in an electrolytic solution containing 5.0 wt% of hydrochloric acid, 1.0 wt% of phosphoric acid, and 2.0 wt% of aluminum chloride. AC electrolytic etching was performed. The alternating current was a sine wave, 20 Hz, and the current density was 280 mA / cm ² . After the AC etching, the substrate was washed with pure water and heat-treated under the conditions shown in Table 1. Thereafter, a chemical cleaning treatment was performed with a 3.0 wt% aqueous phosphoric acid solution at 45 ° C. for 2 minutes, followed by washing with pure water, followed by drying to obtain an electrode foil for an electrolytic capacitor. The capacitance was measured after application and formation, and the results in Table 1 were obtained.
[0011]
[Table 1]

[0012]
From Table 1, it can be seen that Examples 1 to 10 according to the present invention in which heat treatment was performed before the chemical cleaning step had higher capacitance than the conventional example in which no heat treatment was performed. Here, in the heat treatment conditions of Example 1 at 100 ° C. for 6 minutes and Example 10 at 550 ° C. for 15 seconds, the heat treatment effect is less than that of the other examples. Is preferably in the range of 30 seconds to 5 minutes.
[0013]
In order to investigate the adhesion of impurities on the foil surface, the etching foils obtained in Examples 3, 4, and 7 and the conventional example were boiled in pure water for 10 minutes, and the results of quantitative analysis using ion chromatography and phosphorus were performed. Table 2 shows the measurement results of the film amount of the etching foil with the acid-chromic acid solution.
[0014]
[Table 2]

[0015]
From Table 2, it can be seen that in the heat-treated example, chlorine ions were removed as in the conventional example. Furthermore, the amount of phosphate ions, which is a component of the chemical cleaning liquid, is smaller than that of the conventional example, and it can be seen that the present invention can reduce impurities attached to the etching foil. In addition, the coating amount of the etching foil is also reduced in the embodiment compared to the conventional example.
[0016]
The present invention is not limited to the embodiments, and a post-treatment step for increasing the capacity or stabilizing the film may be provided after a known etching method or a chemical cleaning step.
[0017]
【The invention's effect】
As described above, by providing a heat treatment step between the etching step and the chemical cleaning step, it is possible to increase the capacity of the electrode foil by suppressing a decrease in capacitance in the chemical cleaning step. It is possible to suppress the adhesion of a chemical cleaning liquid component, which is likely to adversely affect the process and product reliability, and the formation of a film due to the chemical cleaning.

Claims (3)

An etching step of electrically and / or chemically roughening an aluminum or aluminum alloy foil in an etching solution containing chlorine ions, a heat treatment step, and a chemical cleaning step of removing chloride ions attached to the foil. A method for producing an electrode foil for an electrolytic capacitor. The method for producing an electrode foil for an electrolytic capacitor, wherein the temperature of the heat treatment step according to claim 1 is 150 to 500 ° C. 3. The method for producing an electrode foil for an electrolytic capacitor according to claim 1, wherein the time of the heat treatment step is 30 seconds to 5 minutes.