JP2007035902A - Method of manufacturing anode foil for aluminum electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a formation method capable of restraining an increase of leakage current even in case of trying to obtain a high electrostatic capacity, by reducing the film thickness of an anodic oxidation film of an anode foil for an aluminum electrolytic capacitor. <P>SOLUTION: The method of manufacturing the anode foil for the aluminum electrolytic capacitor which forms an anodic oxidation film on an etched aluminum foil has a process for depositing silicon or silicon dioxide in the etching foil, a process for immersion in high temperature pure water, and a process for performing anodic oxidation. The thickness of the deposition layer of silicon or silicon dioxide is 5 to 200 nm, and the immersion duration in high temperature pure water is 5 to 30 minutes. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing an anode foil for an aluminum electrolytic capacitor (hereinafter referred to as anode foil), and more particularly to a chemical conversion method that is effective in improving capacitance.

Conventionally, an anode foil is formed by immersing an etched aluminum foil (hereinafter referred to as an etching foil) in high-temperature pure water to form a pseudo boehmite film, and then anodizing (chemical conversion) in a barrier film forming solution such as ammonium borate. ).
In addition, as a general anodizing treatment, after reaching a predetermined formation voltage, voids in the oxide film that cause leakage current by so-called depolarization treatment such as heat treatment or acid immersion treatment, A desired anodic oxide film is formed by exposing cracks and the like and further repeating the repair formation (see, for example, Non-Patent Document 1).
Isada Nagata, “Electrolytic Cathode Aluminum Electrolytic Capacitor (Aluminum Dry Electrolytic Capacitor Supplement Revised Version)”, Nihon Denki Kogyo Kogyo Co., Ltd., February 24, 1997, 2nd edition, 1st edition, pages 310-314

With the recent progress in miniaturization and weight reduction of electric and electronic devices such as mobile phones and notebook personal computers, miniaturization and high capacitance of aluminum electrolytic capacitors are required.
Accordingly, there is a strong demand for higher capacitance in the anode foil.

However, in order to obtain an anode foil having a high capacitance, it is necessary to increase the crystallinity of the anodized film and reduce the film thickness of the anodized film per withstand voltage.
However, as crystallization progresses, voids and cracks in the anodized film increase, and there is a problem that leakage current increases due to voids and cracks that could not be repaired by the repair conversion.
For this reason, the conventional method has a limit in increasing the capacitance without increasing the leakage current.

  Due to the above-mentioned problems, even when the thickness of the anodic oxide film per withstand voltage is reduced when forming the anodic oxide film, voids and cracks in the oxide film do not increase and the increase in leakage current is suppressed. There was a need for a means to do that.

The present invention solves the above problems, and in the method for producing an aluminum foil for an aluminum electrolytic capacitor, an anodized film is formed on an etched aluminum foil.
A method for producing an anode foil for an aluminum electrolytic capacitor, comprising the steps of depositing silicon or silicon dioxide on an etching foil, a step of immersing in high-temperature pure water, and an anodizing step.

  The method for producing an anode foil for an aluminum electrolytic capacitor is characterized in that the deposited layer of silicon or silicon dioxide has a thickness of 5 to 200 nm and an immersion time of 5 to 30 minutes in high-temperature pure water. .

As a pretreatment to form an anodic oxide film on the etching foil, after silicon or silicon dioxide is deposited on the etching foil, it is immersed in high-temperature pure water to form a pseudo boehmite film, and up to a predetermined voltage in the chemical conversion liquid By anodizing (chemical conversion), a crystalline oxide film modified from a pseudo boehmite film containing silicon can be formed.
Therefore, the above-mentioned crystalline oxide film containing silicon can produce an anode foil with a reduced oxide film thickness per withstand voltage without increasing leakage current, and increase the capacitance of the electrolytic capacitor. , Leakage current can be reduced.

Hereinafter, the present invention will be specifically described based on examples.
The anode aluminum foil for electrolytic capacitors etched to an area ratio of 30 times was used as a test material, and a chemical conversion treatment was performed by the following method.

[Examples 1 to 9]
Silicon was deposited on the etching foil to a thickness of 3 to 300 nm.
Next, a hydration treatment was performed by immersing in pure water at 90 ± 2 ° C. for 10 minutes to form a pseudo boehmite film.
Thereafter, 500 V was applied in an aqueous solution of ammonium borate at 85 ± 2 ° C. adjusted to a specific resistance of 1,000 Ω · cm and pH 4.5, and the same voltage was maintained for 60 minutes.
Furthermore, voids, cracks, etc. in the oxide film were exposed by so-called depolarization treatment (depolarization treatment) of heat treatment and acid soaking treatment, and restoration conversion was performed twice with the boric acid aqueous solution.

(Conventional example)
Using the same etching foil as in the above example, the formation of pseudo boehmite film, anodization (chemical conversion), depolarization treatment, and repair chemical conversion were performed under the same conditions as in the example except that the above vapor deposition treatment was not performed. went.

  Table 1 shows the results of measuring the capacitance and leakage current at 400 V for the anode foils according to Examples 1 to 9 and the conventional example.

As is clear from Table 1, in Example 1 according to the present invention, the leakage current is equivalent to that of the conventional example by performing the process of forming the pseudo boehmite film after forming the deposited layer of silicon. The capacitance can be increased.
In addition, as for the film thickness in said vapor deposition process, the range of 5-200 nm is desirable. When the film thickness is 3 nm, the effect of improving the electrostatic capacity is not sufficient (Example 1), and when the film thickness is 300 nm, the electrostatic capacity is not improved and the cost and the man-hour are disadvantageous (Example 9).

[Examples 10 to 15]
Next, Table 2 shows the results of measuring the electrostatic capacity and the leakage current at 400 V with the hydration time when forming the pseudo boehmite film being 3 to 30 minutes under the conditions of Example 6 above.

  As is apparent from Table 2, the leakage current is equivalent to that of the conventional example by forming a pseudo-boehmite film by hydration after forming a deposited layer of silicon for 5 minutes or longer. The capacitance can be increased. When the hydration time is 3 minutes, the capacitance decreases (Example 10), and when it exceeds 30 minutes, it is not preferable from the viewpoint of man-hours. Therefore, the hydration time is preferably 5 to 30 minutes.

In the above embodiment, silicon was vapor-deposited on the etched aluminum foil, but the same effect can be obtained even if silicon dioxide is vapor-deposited.

Claims (2)

In the method for producing an anode foil for an aluminum electrolytic capacitor in which an anodized film is formed on an etched aluminum foil,
A method for producing an anode foil for an aluminum electrolytic capacitor, comprising a step of depositing silicon or silicon dioxide on an etching foil, a step of immersing in high-temperature pure water, and an anodizing step.   A method for producing an anode foil for an aluminum electrolytic capacitor, wherein the deposited layer of silicon or silicon dioxide according to claim 1 has a thickness of 5 to 200 nm and an immersion time of 5 to 30 minutes in high-temperature pure water.