JP2008091374A - Manufacturing method of etching foil for electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an etching foil for an electrolytic capacitor capable of increasing electrostatic capacity by making generation and growth of an etching pit more suitable. <P>SOLUTION: In the manufacturing method of the etching foil for the electrolytic capacitor for chemically and/or electrochemically etching an aluminum foil in an etchant containing at least chlorine ions, ethylene diamine tetraacetate or its salt is added to the etchant. Further the etchant contains at least one kind of phosphoric ions, nitrate ions, sulfate ions and oxalate ions. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing an electrolytic capacitor etching foil.

  The aluminum foil for electrolytic capacitors is generally roughened in surface area by chemically or / and electrochemically etching the aluminum foil in an etching solution containing chlorine ions for both anode and cathode. The enlargement is aimed at (for example, refer nonpatent literature 1).

  The etching solution may further contain phosphate ions, nitrate ions, sulfate ions, oxalic acid and the like.

Isaya Nagata, “Electrolytic Cathode Aluminum Electrolytic Capacitor”, Nihon Denki Kogyo Kogyo Co., Ltd., February 24, 1997, 2nd edition, 1st edition, pages 221-257

  In recent years, the demand for miniaturization of electrolytic capacitors has been increasing, and accordingly, the electrode foil used in electrolytic capacitors is required to have higher capacitance than before, and the surface area of aluminum foil can be expanded more efficiently. Is desired.

  However, in the conventional etching method, the inside of the formed etching pit is in a state where the aluminum ion concentration in the vicinity of the surface is high due to the dissolved aluminum, which is an obstacle to the efficient generation and growth of the etching pit.

  In view of the above problems, an object of the present invention is to provide a method for manufacturing an etching foil for an electrolytic capacitor capable of increasing the capacitance by optimizing the generation and growth of etching pits. It is in.

  In order to solve the above problems, in the method for manufacturing an electrolytic capacitor etching foil according to the present invention, an electrolytic capacitor for chemically or / and electrochemically etching an aluminum foil in an etching solution containing at least chlorine ions. In the manufacturing method of etching foil, ethylenediaminetetraacetic acid or its salt is mix | blended with the said etching liquid.

  In this invention, it is preferable that the density | concentration of the ethylenediaminetetraacetic acid or its salt in the said etching liquid is 0.09-0.5 wt% with respect to the whole etching liquid.

  In the present invention, the etching solution further comprises at least one of phosphate ions, nitrate ions, sulfate ions, and oxalate ions. .

In the present invention, by adding ethylenediaminetetraacetic acid (EDTA) or a salt thereof to the etching solution, the generation and growth of etching pits can be further optimized, and the capacitance per unit area can be increased. it can.
The reason is that, in the etching solution, aluminum is dissolved by the anode cycle, but EDTA or a salt thereof forms a chelate with the aluminum dissolved in the cathode cycle, so that the dissolved aluminum ions are electrically removed from the aluminum surface. It is considered that the etching pits are efficiently generated and grown on the entire surface of the aluminum foil in order to separate and reduce the aluminum ion concentration near the surface.

  The present invention can also be applied to the case where at least one of phosphate ions, nitrate ions, sulfate ions, and oxalate ions is added to the etching solution. Such ions have a film-forming ability with respect to aluminum, and when such ions are mixed in an etching solution, both dissolution of aluminum and film formation occur, and the generation and growth of etching pits are further optimized. Can do.

  When EDTA or a salt thereof is added to such an etching solution, the effect becomes greater. The reason for this is that when EDTA or a salt thereof is added to the etching solution, both dissolution of aluminum and film formation occur efficiently, so that the generation and growth of etching pits can be further optimized.

  Hereinafter, based on the Example of this invention, this invention is demonstrated in detail.

  In Examples and Comparative Examples described below, Examples 1 to 8 were used using an etching solution containing 10.0 wt% hydrochloric acid, 2.0 wt% phosphoric acid, 2.0 wt% nitric acid, and 1.0 wt% sulfuric acid as a base. Then, EDTA · 2Na having a concentration (wt%) shown in Table 1 was added to the etching solution.

  Here, the aluminum foil is an anode foil for low voltage having a purity of 99.9%.

Etching conditions were such that the electrolyte temperature was 30 ° C., the voltage waveform was a sine wave, the frequency was 60 Hz, and the current density was 0.4 A / cm ² .

  Under any conditions, after the aluminum foil was etched, chemical cleaning was performed by a known method using an alkali and an acid.

  The obtained etching foil was anodized in an aqueous solution of ammonium adipate under the condition that the applied voltage was 20V. The results of measuring the capacitance value are shown in Table 1 and FIG. FIG. 1 is a graph showing the relationship between the amount of EDTA · 2Na added to the etching solution and the capacity ratio relative to the comparative example.

[Examples 1-7]
Etching solution containing 0.02 wt%, 0.04 wt%, 0.07 wt%, 0.09 wt%, 0.13 wt%, 0.22 wt%, 0.43 wt%, respectively, added to the above etching solution It was used.

(Comparative example)
An etching solution to which EDTA · 2Na was not added was used in the etching solution.

[Test results]
As apparent from Table 1 and FIG. 1, the addition and growth of etching pits were efficiently performed by adding EDTA · 2Na, and the formation capacity could be improved. Here, with regard to the amount of EDTA · 2Na added, the effect of improving the capacitance is small when 0.02 to 0.07 wt% is added, but the capacitance can be sufficiently improved when 0.09 to 0.43 wt% is added. I understand that Since dissolution reaches a limit when it exceeds 0.5 wt%, the amount of EDTA · 2Na added is preferably in the range of 0.09 to 0.5 wt%.

  In the above embodiment, EDTA · 2Na is used. However, the present invention is not limited to this, and the same effect can be obtained by using EDTA or other salts.

  In the above embodiment, the etching solution is composed of 10.0 wt% hydrochloric acid, 2.0 wt% phosphoric acid, 2.0 wt% nitric acid, and 1.0 wt% sulfuric acid. However, the present invention is not limited to this. .

  Furthermore, in the above-described embodiment, the anode foil for low voltage is targeted. However, even when the anode foil for cathode or medium / high voltage is used, the capacitance is increased by adding EDTA or a salt thereof. be able to.

It is a graph which shows the relationship between the addition amount of EDTA * 2Na in an etching liquid, and the electrostatic capacitance ratio of the Example with respect to a comparative example.

Claims (3)

In a method for producing an etching foil for an electrolytic capacitor, in which an aluminum foil is chemically or / and electrochemically etched in an etching solution containing at least chlorine ions,
The manufacturing method of the etching foil for electrolytic capacitors characterized by mix | blending ethylenediaminetetraacetic acid or its salt with the said etching liquid.   The manufacturing method of the etching foil for electrolytic capacitors of Claim 1 whose density | concentration of ethylenediaminetetraacetic acid or its salt in the said etching liquid is 0.09-0.5 wt% with respect to the whole etching liquid.   3. The electrolytic capacitor etching foil according to claim 1, wherein the etching solution further contains at least one of phosphate ions, nitrate ions, sulfate ions, and oxalate ions. 4. Production method.

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