JPH09246112A - Manufacture of electrode foil for aluminum electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of an electrode foil for an aluminum electrolytic capacitor which enables easy formation of a protective film having excellent characteristics on the surface of an aluminum foil by temporarily interrupting etching during an etching process. SOLUTION: In an etching process for chemically or electrochemically etching an aluminum foil 31 in a solution mainly containing hydrochloric acid so as to enlarge the surface area of the aluminum foil 31, etching is temporarily interrupted during this etching process, and immersion processing for immersing the aluminum foil 31 into acid containing phosphorus or a solution containing phosphate is performed once or a plurality of times.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an electrode foil for an aluminum electrolytic capacitor, and more particularly to an etching technique.

[0002]

2. Description of the Related Art Generally, in a method of manufacturing an electrode foil for an aluminum electrolytic capacitor of this kind, when etching is continuously performed, fine irregularities on the surface of the aluminum foil which are initially generated are gradually dissolved and lost. It is difficult to obtain a large surface expansion effect. Therefore, it is indispensable to provide some means for protecting the fine irregularities on the surface of the aluminum foil generated at the initial stage of etching in order to increase the capacity of the electrode foil for an aluminum electrolytic capacitor.

As one of the protection measures, Japanese Patent Publication No.
In JP-A-21541 and JP-A-55-127013, a thermal oxide film or a chemical conversion film is formed on the surface of an aluminum foil by a physical method or an electrochemical method such as an anodic oxidation method during the interruption of etching. It is disclosed that fine irregularities on the surface of an aluminum foil are prevented from being directly exposed to an etching solution and being dissolved.

[0004]

However, among the above methods for forming a protective film for an etching solution, the method for forming a chemical conversion film on the surface of an aluminum foil by an electrochemical method such as an anodic oxidation method is a method for forming a film. For this reason, there is a problem that the equipment becomes complicated and expensive due to the need for a power supply, or the chlorine ion concentration remaining on the surface of the aluminum foil must be kept fairly low in order to perform anodization. There is a problem that a special treatment is required before anodizing. Further, in a method other than the anodizing method, for example, in a method of forming a thermal oxide film on the surface of the aluminum foil by heating and drying the aluminum foil or boiling, the thermal oxide film formed is too weak to serve as a protective film. Not play a role,
There is a problem that it is difficult to form a protective film having sufficient performance such as unevenness in etching due to partial variation in strength of the thermal oxide film. When a substance other than aluminum, such as an oil film, is used as the protective film material, the etching liquid may be contaminated by the substance, or the substance may remain on the aluminum foil and adversely affect it. Had.

The present invention solves the above-mentioned conventional problems, and an aluminum electrolytic capacitor capable of easily forming a protective film having excellent characteristics on the surface of an aluminum foil by interrupting the etching during the etching process. It is an object of the present invention to provide a method for manufacturing an electrode foil for use.

[0006]

In order to achieve the above object, a method of manufacturing an electrode foil for an aluminum electrolytic capacitor according to the present invention comprises etching an aluminum foil chemically or electrochemically in a solution mainly containing hydrochloric acid. In the etching step of increasing the surface area of the aluminum foil, the etching is temporarily interrupted in the middle of this etching step and the aluminum foil is immersed in a solution containing an acid or a phosphate containing phosphorus once or plural times. According to this manufacturing method, the etching can be temporarily interrupted during the etching process to easily form the protective film having excellent characteristics on the surface of the aluminum foil.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention is an etching step for increasing the surface area of an aluminum foil by chemically or electrochemically etching the aluminum foil in a solution mainly containing hydrochloric acid. In the middle of this etching process, the etching is temporarily interrupted and the aluminum foil is immersed in a solution containing phosphorus-containing acid or phosphate to be dipped once or plural times. For example, after interrupting etching,
By simply immersing the aluminum foil in a solution containing phosphorus-containing acid or phosphate, a phosphoric acid film having a desired strength can be formed as a protective film on the surface of the aluminum foil, and the protective film can be used for subsequent etching. It is possible to suppress the dissolution of fine irregularities on the surface of the aluminum foil and efficiently expand the surface area, and thereby to increase the capacitance per unit area.

According to the second aspect of the present invention, the etching is temporarily interrupted in the middle of the etching step, and the aluminum foil is dipped in a solution containing an acid or a phosphate containing phosphorus a plurality of times. In the latter half of the etching process, the immersion treatment time in the immersion treatment is longer than the previous immersion treatment time.According to this manufacturing method, there are many fine irregularities on the surface of the aluminum foil and the surface drop-off occurs. A stronger protective film will be formed in the latter half of the etching process in which the occurrence of the above occurs more frequently, which can suppress the dissolution of fine irregularities on the surface of the aluminum foil due to the subsequent etching. Therefore, the capacitance per unit area can be increased.

According to the third aspect of the present invention, the etching is temporarily interrupted during the etching step, and the aluminum foil is dipped in a solution containing an acid or a phosphate containing phosphorus a plurality of times. In the dipping treatment, the concentration of the phosphorus-containing acid or phosphate in the dipping treatment solution is set to be higher in the latter half of the etching step than in the previous concentration. A stronger protective film will be formed in the latter half of the etching process in which the number of minute irregularities on the surface increases and the frequency of surface dropouts increases, which allows subsequent etching to produce minute irregularities on the aluminum foil surface. It is possible to increase the capacitance per unit area because it can suppress the dissolution of That.

In the invention according to claim 4, the etching is temporarily interrupted in the middle of the etching step, and the aluminum foil is immersed in a solution containing an acid or a phosphate containing phosphorus a plurality of times. In the latter half of the etching process, the temperature of the dipping treatment solution in the dipping treatment is set to be higher than the temperature of the dipping treatment solution before that. According to this manufacturing method, fine irregularities are formed on the surface of the aluminum foil. The surface of the aluminum foil will become more likely to come off, and a stronger protective film will be formed in the latter half of the etching process. Since it can be suppressed to a low value, the capacitance per unit area can be increased.

Specific embodiments of the present invention will be described below with reference to the accompanying drawings. (Embodiment 1) FIG. 1 shows a process chart of a method for manufacturing an electrode foil for an aluminum electrolytic capacitor according to Embodiment 1 of the present invention. In FIG. 1, 1 is a pretreatment tank and 2 is pretreatment. A first water washing tank provided after the tank 1, 3 is a first etching tank provided after the first water washing tank 2, and 4 is a second water washing tank provided after the first etching tank 3. Reference numeral 5 denotes an immersion treatment tank provided after the second water washing tank 4, and the immersion treatment tank 5 contains a solution containing 0.02 to 30 wt% of an acid or phosphate containing phosphorus as a solution for immersion treatment. And the liquid temperature is set to 65 ° C., and the immersion treatment time is set to 180 seconds. 6 is a third water washing tank provided after the immersion treatment tank 5, 7 is a second etching tank provided after the third water washing tank 6, and 8 is a second
A fourth washing bath provided after the etching bath 7 of
Is a post-treatment tank provided after the fourth water washing tank 8, 10 is a dryer, and 11 is an aluminum foil.

Electrodes 12 and 13 are installed in the first etching bath 3 and the second etching bath 7, respectively, and a solution obtained by adding 2 wt% of aluminum chloride to 5 wt% of hydrochloric acid is put therein. And the liquid temperature is 40
Set to ° C.

In the above structure, the aluminum foil 11 is made of a soft foil having a purity of 99.9%. When etching the aluminum foil 11, as shown in FIG. The aluminum foil 11 is pretreated, then washed with water in the first water washing tank 2 and then chemically or electrochemically etched in the first etching tank 3 to etch the aluminum foil 11
Increase the surface area of. After this etching is over
After performing water washing in the second water washing tank 4, the etching is temporarily interrupted, and the aluminum foil 11 is placed in the dipping treatment tank 5 in which a solution containing 0.02 to 30 wt% of an acid or phosphate containing phosphorus is placed. Immersion in the solution for immersion treatment, then water washing in the third water washing tank 6, and then etching again in the second etching tank 7 and then water washing in the fourth water washing tank 8. The aluminum foil 11 thus etched is post-treated in the post-treatment tank 9, and finally dried in the dryer 10.

(Embodiment 2) FIG. 2 shows a process chart of a method for manufacturing an electrode foil for an aluminum electrolytic capacitor according to Embodiment 2 of the present invention. In FIG. 2, 21 is a pretreatment tank, 22 Is a first etching tank, 23 is a first immersion processing tank, 24 is a second etching tank, 25 is a second immersion processing tank, 26 is a third etching tank, 27 is a third immersion processing tank, 28 is a fourth etching tank, 29 is a post-treatment tank,
30 is a dryer and 31 is an aluminum foil.

The first etching tank 22 and the second etching tank
Electrodes 32, 33, 34, and 35 are installed in the etching tank 24, the third etching tank 26, and the fourth etching tank 28, respectively, and 2 wt.
A solution containing t% aluminum chloride is included. Although not shown in FIG. 2, the pretreatment bath 21
And the first etching bath 22, the first etching bath 22 and the first immersion bath 23, the first immersion bath 23 and the second etching bath 24, the second Between the etching bath 24 and the second immersion bath 25, between the second immersion bath 25 and the third etching bath 26, between the third etching bath 26 and the third immersion bath 27 Between the third immersion treatment bath 27 and the fourth etching bath 28, between the fourth etching bath 28 and the post-treatment bath 29, and the post-treatment bath 29.
A washing tank is provided between the dryer and the dryer 30.

In FIG. 2, the aluminum foil 31 is used.
Uses a soft foil having a purity of 99.9%. When etching the aluminum foil 31, first, as shown in FIG. 2, the aluminum foil 31 is pretreated in the pretreatment tank 21, and then, After washing with water in a washing tank (not shown), the aluminum foil 31 is chemically or electrochemically etched in the first etching tank 22 to increase the surface area of the aluminum foil 31. After this etching is finished, the aluminum foil 31 is washed with water in a water washing tank (not shown), and then the aluminum foil 31 is filled with a solution containing 0.02 to 30 wt% of an acid or phosphate containing phosphorus. The first etching treatment tank 23 is dipped in the solution to perform the first immersion treatment, and then the second etching tank 24 is washed with water in a water washing tank (not shown).
Etch again, and after this, wash tank 8
A second dipping treatment bath 25 in which a solution containing 0.2 to 30 wt% of an acid or a phosphate containing phosphorus is contained in the aluminum foil 31 by temporarily stopping the etching after washing with water (not shown). It is dipped in the solution in the inside to carry out a second dipping treatment, then, after being washed in a water washing tank (not shown), etched again in the third etching tank 26, and thereafter, a water washing tank (not shown). Water), and then, the etching is temporarily stopped to make the aluminum foil 31 0.2 to 30 wt% of an acid or phosphate containing phosphorus.
The third etching treatment tank 27 containing a solution containing 100% of water is subjected to a third immersion treatment, and then a fourth washing tank 28 is washed with water in a water washing tank (not shown). After that, the aluminum foil 31 which has been etched is post-treated in a post-treatment bath 29, and then washed in a water-wash bath (not shown). Finally, the dryer 30 is used for drying.

As shown in FIGS. 1 and 2, when the aluminum foils 11 and 31 are etched, there are few irregularities formed on the surfaces of the aluminum foils 11 and 31 at the beginning of the etching process, so that they are very strong. However, in the latter half of the etching process, the irregularities on the surface of the aluminum foils 11 and 31 also become finer and increase, and as the fine irregularities increase, the surface drops off. As the frequency increases, the increase in capacitance becomes slower. In order to minimize this surface dropout, in FIG. 2, a phosphoric acid film as a protective film may be formed frequently on the surface of the aluminum foil 31 at short intervals, but simply by shortening the interval, it is possible to manufacture. It is not realistic because the efficiency becomes low. Therefore, the interval for forming the phosphoric acid film, which is the protective film, is lengthened at the beginning of the etching process in which there are few irregularities formed on the surface of the aluminum foil 31 and a strong protection is not required, and fine irregularities increase. In the latter half of the etching process, shortening is a method that makes sense from the viewpoint of increasing the capacitance and manufacturing efficiency. In this case, shortening the interval for forming the phosphoric acid film as the protective film means that after performing the dipping treatment for forming the phosphoric acid film as the protective film,
This means that the next dipping treatment is performed before the amount of irregularities formed on the surface of the aluminum foil increases, and this is done by dipping the aluminum foil while the new amount of aluminum dissolved by etching is small. This means forming a phosphoric acid film.

In FIG. 2 described above, the sizes of the first etching tank 22, the second etching tank 24, the third etching tank 26, and the fourth etching tank 28 are different from each other. In the latter half of the above, by making it equal to or smaller than that of the previous etching tank, the time until the immersion treatment is gradually shortened, and the amount of aluminum dissolved by etching is gradually reduced.

Further, in FIG. 2, the first immersion treatment tank 2
3, the size of the second immersion treatment bath 25 and the size of the third immersion treatment bath 27 are made different, and by making the size larger than the previous immersion treatment bath in the latter half of the etching process. In the latter half of the etching process, the immersion treatment time is set to be longer than the previous immersion treatment time to enhance the effect of the immersion treatment. As described above, the immersion treatment time is set to be longer than the previous immersion treatment time in the latter half of the etching step, so that the surface of the aluminum foil 31 has a large number of fine irregularities, and the frequency of occurrence of surface dropout increases. A stronger protective film will be formed in the latter half of the etching step, which can suppress the dissolution of fine irregularities on the surface of the aluminum foil 31 due to the subsequent etching, and thus can reduce the unit area. The electrostatic capacity per unit can be increased.

Table 1 shows phosphorus contained in the dipping treatment solution to be placed in the dipping treatment bath 5 in the method for manufacturing the electrode foil for an aluminum electrolytic capacitor according to the first embodiment of the present invention shown in FIG. Acid or phosphate content of 0.0
2wt%, 0.05wt%, 5.0wt & 10wt
%, 20 wt%, and 30 wt%, respectively, and the electrostatic capacitance index is shown.

The capacitance was measured by forming an etching foil with a forming voltage of 22V.

[0022]

[Table 1]

As is apparent from Table 1, when the aluminum foil is immersed in a solution containing an acid or a phosphate containing phosphorus and the etching is temporarily interrupted during the etching process, the aluminum foil is not Therefore, the capacitance is increasing. This increase in capacitance depends on the content of the phosphorus-containing acid or phosphate in the dipping solution. Generally, the higher the content, the greater the effect, but considering the cost. The range of the content that increases the capacitance particularly effectively is between 0.05 and 20 wt%.

In the second embodiment of the present invention described above, the immersion treatment time in the immersion treatment performed a plurality of times is
In the latter half of the etching process, the example in which the immersion treatment effect was enhanced by configuring the immersion treatment time to be longer than that before was described, but other than this, for example, the immersion treatment solution in a plurality of immersion treatments. In the latter half of the etching process, the concentration of the phosphorus-containing acid or phosphate in the latter is set to be higher than that before it, or the temperature of the dipping treatment solution in multiple dipping treatments is set in the latter half of the etching process. Even when the temperature is higher than the temperature of the immersion treatment solution before that, the same effects as those of the second embodiment are obtained.

[0025]

As described above, according to the method for producing an electrode foil for an aluminum electrolytic capacitor of the present invention, the surface area of the aluminum foil is chemically or electrochemically etched in a solution containing hydrochloric acid as a main component. In the etching process for enlarging, the etching is temporarily interrupted in the middle of this etching process, and the aluminum foil is immersed in a solution containing an acid or a phosphate containing phosphorus one or more times. After the etching is interrupted, a phosphoric acid film having a desired strength can be formed as a protective film on the surface of the aluminum foil simply by immersing the aluminum foil in a solution containing a phosphoric acid or a phosphoric acid salt. Efficient surface area is achieved by suppressing the dissolution of fine irregularities on the aluminum foil surface due to the subsequent etching. Can be enlarged, thereby it is capable of increasing the capacitance per unit area.

[Brief description of drawings]

FIG. 1 is a process diagram showing a method for manufacturing an electrode foil for an aluminum electrolytic capacitor according to a first embodiment of the present invention.

FIG. 2 is a process chart showing a method for manufacturing an electrode foil for an aluminum electrolytic capacitor according to a second embodiment of the present invention.

[Explanation of symbols]

 3 1st etching tank 5 Immersion processing tank 7 2nd etching tank 11 Aluminum foil 22 1st etching tank 23 1st immersion processing tank 24 2nd etching tank 25 2nd immersion processing tank 26 3rd etching Tank 27 Third immersion treatment tank 28 Fourth etching tank 31 Aluminum foil

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Koichi Kojima 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. In an etching process of chemically or electrochemically etching an aluminum foil in a solution containing hydrochloric acid as a main component to increase the surface area of the aluminum foil, the etching is temporarily interrupted during the etching process to remove aluminum. A method for producing an electrode foil for an aluminum electrolytic capacitor, wherein the foil is dipped in a solution containing an acid containing phosphorous or a solution containing a phosphate to perform the dipping treatment once or plural times. 2. Immersion treatment in which etching is temporarily interrupted in the middle of the etching step and the aluminum foil is immersed in a solution containing phosphorus-containing acid or phosphate is performed a plurality of times, and the immersion treatment time in these immersion treatments is increased. The method for producing an electrode foil for an aluminum electrolytic capacitor according to claim 1, wherein the latter half of the etching step is configured to be longer than the immersion treatment time before that. 3. An immersion treatment in which the etching is temporarily interrupted in the middle of the etching step and the aluminum foil is immersed in a solution containing an acid or a phosphate containing phosphorus, and a solution for immersion treatment in these immersion treatments is performed. 2. The method for producing an electrode foil for an aluminum electrolytic capacitor according to claim 1, wherein the concentration of the phosphorus-containing acid or phosphate therein is higher in the latter half of the etching step than in the previous concentration. 4. An immersion treatment in which the etching is temporarily interrupted in the middle of the etching step and the aluminum foil is immersed in a solution containing phosphorus-containing acid or phosphate, and the immersion treatment solution is used in these immersion treatments. 2. The method for producing an electrode foil for an aluminum electrolytic capacitor according to claim 1, wherein the temperature is higher than the temperature of the immersion treatment solution before the latter half of the etching step.