JPH0665208B2 - Aluminum electrolytic capacitor - Google Patents

Description

TECHNICAL FIELD The present invention relates to an aluminum electrolytic capacitor used in various electronic devices.

Conventional example configuration and its problems Conventional aluminum electrolytic capacitors of this type are usually formed by electrolytically etching in an electrolytic solution containing chlorine ions, winding an aluminum foil with an expanded effective surface area, and insulating paper to form a driving electrolytic solution. The impregnated capacitor element was enclosed in a case.

The effect of increasing the surface area of the electrode foil by electrolytic etching is a number of factors, such as etching current waveform, current density, type of etching solution, concentration, temperature, and type and concentration of additives, as well as pretreatment, intermediate treatment, and posttreatment. It is affected by the type of aluminum foil.

Studies on the current waveform have been conducted for some time, and as methods of using a rectangular wave current, British Patent No. 1,169,234, JP-A-57-132322 and the like are known. These methods are methods in which a rectangular wave current is passed in an aqueous solution containing chloride as chlorine ions to carry out electrolytic etching.

However, in these methods, since neutral salt solution is used, aluminum ions eluted during electrolytic etching produce aluminum hydroxide precipitates, which adhere to production equipment and pipes, etc. Therefore, there is a drawback in that the equipment must be regularly stopped, and the operating rate of the equipment is reduced.

The object of the present invention is to eliminate the above-mentioned conventional drawbacks, by producing a high-magnification electrode foil in a liquid composition that does not cause precipitation of aluminum hydroxide, by improving the operating rate of production equipment, The purpose is to reduce the cost of the aluminum electrolytic capacitor.

In order to achieve the above object, the aluminum electrolytic capacitor of the present invention, in an aqueous solution containing hydrochloric acid and aluminum chloride as chlorine ions, between the aluminum foil and the counter electrode, the potential of the aluminum foil to the counter electrode is positive or negative. The rectangular wave current has a positive current density of 0.5 to 2 A / c flowing from the aluminum foil to the counter electrode while the aluminum foil is electrolytically etched by applying a rectangular wave current.
m ² and the flowing time is 1 to 15 ms, while the negative electrode current density flowing from the counter electrode to the aluminum foil is 0.1 to 0.5 A / c.
An aluminum foil configured by using a square wave current having a flowing time of 1 to 5 ms at m ² was used as an anode foil.

According to the above configuration, when the aluminum foil is electrolytically etched, since it is performed in an aqueous solution containing hydrochloric acid and aluminum chloride as chlorine ions, no aluminum hydroxide precipitate is generated, and the aluminum foil is energized. The square wave current has a positive current density of 0.5 to ^{2 A} / cm ² , a flowing time of 1 to 15 ms, and a negative current density of 0.
Since it is set to 1 to 0.5 A / cm ² and the flowing time is set to 1 to 5 ms, there is no excessive oxide film on the surface of the aluminum foil, and the melting can be performed uniformly, which results in a high surface expansion ratio. In addition to being able to obtain the same, the precipitation of aluminum hydroxide is prevented from adhering to the production equipment, pipes, etc., so that the operating rate of the production equipment can be improved and the cost of the aluminum electrolytic capacitor can be greatly reduced.

Description of Embodiments Embodiments of the present invention will be described below with reference to the drawings.

Example 1 FIG. 1 shows the examination result of the surface enlargement magnification when the positive current time was changed, and FIG. 2 shows the examination result of the surface enlargement magnification when the negative current time was changed. is there.

The experimental conditions are as follows.

Experimental conditions positive current time in the first view: 1~21ms (2ms step) the positive current density: 1.0A / cm ² negative current time: 1.0 ms negative current density: 0.2 A / cm ² Etching time: 1 minute etching temperature: 90 ° C Liquid composition: HCl 5%, AlCl ₃ 5% Experimental conditions in Fig. 2 Positive current time: 15ms Positive current density: 1.0A / cm ² Negative current time: 1 to 15ms (2ms step) Negative current density: 0.2A / cm ² Etching time: 1 minute Etching temperature: 90 ° C. Liquid composition: HCl 5%, AlCl ₃ 5% As can be seen from FIGS. 1 and 2, positive current flow time is 1 to 15 ms, negative current flow time is 1 High surface expansion ratio is obtained in the range of ~ 5ms.

The reason why the width of the optimum value of the negative current time is shorter than the width of the optimum value of the positive current time is considered to be that the oxide film is excessively attached to the surface when the negative current time is 5 ms or more, so that the dissolution becomes nonuniform.

Example 2 FIG. 3 (a) shows the examination result of the surface expansion ratio when the positive current density was changed, and FIG. 3 (b) shows the examination of the surface expansion ratio when the negative current density was changed. The results are shown.

The experimental conditions are as follows.

Figure 3 (a) experimental conditions positive current time: 15 ms positive current density: 0.3~2.3A / cm ² Current Time: 1.0 ms negative current density: 0.2 A / cm ² Etching time: 1 minute etching temperature: 90 ° C. solution Composition: HCl 5%, AlCl ₃ 5% Experimental conditions in Fig. 3 (b) Positive current time: 15ms Positive current density: 1.0A / cm ² Negative current time: 1.0ms Negative current density: 0.1 to 1.3A / cm ² Etching Time: 1 minute Etching temperature: 90 ° C Liquid composition: HCl 5%, AlCl ₃ 5% As shown in Figs. 3 (a) and 3 (b), the positive current density is
In the range of 0.5 to ^{2 A} / cm ² and the negative current density of 0.1 to 0.5 A / cm ² , high surface expansion ratio is obtained.

Example 3 The table below shows a comparison between the etching surface enlargement ratio under the conditions of the present invention and the conventional conditions.

Method 1 is a conventional method. Method 3 is an example of the present invention. Method 2 is a case where the HCl concentration becomes zero in the present invention. This method also does not cause precipitation, but since the conductivity of the liquid is low, more power consumption is required to obtain the same loss on dissolution.

As described above, the aluminum electrolytic capacitor of the present invention is
When electrolytically etching aluminum foil, since it is performed in an aqueous solution containing hydrochloric acid and aluminum chloride as chlorine ions, aluminum hydroxide precipitates do not occur, and the square wave current applied to the aluminum foil is a positive current. The density is 0.5 to ^{2 A} / cm ² and the flowing time is 1
And ～15Ms, further negative current density was 0.1~0.5A / cm ^2,
Moreover, since the flowing time is set to 1 to 5 ms, the surface of the aluminum foil will not be overly coated with an oxide film, and the dissolution can be carried out uniformly, whereby a high surface expansion ratio can be obtained and aluminum hydroxide can be obtained. Since the deposit of No. 1 does not adhere to the production equipment, piping, etc., the operating rate of the production equipment can be improved and the cost of the aluminum electrolytic capacitor can be greatly reduced.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing the relationship between the positive current time and the surface expansion ratio,
FIG. 2 is a characteristic diagram showing the relationship between the negative current time and the surface expansion ratio,
3 (a) and 3 (b) are characteristic diagrams showing the relationship between the positive current density and the negative current density and the surface expansion ratio.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Kenichi Toyama 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Nobuyoshi Kanzaki 1006, Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. 72) Inventor Koichi Kojima, Kadoma City, Osaka Prefecture 1006 Kadoma, Matsushita Electric Industrial Co., Ltd. (56) References JP-A-58-223311 (JP, A) JP-A-59-70800 (JP, A)

Claims (1)

[Claims] 1. A rectangular wave current is repeatedly applied between an aluminum foil and a counter electrode in an aqueous solution containing hydrochloric acid and aluminum chloride as chlorine ions so that the potential of the aluminum foil with respect to the counter electrode becomes positive or negative. And electrolytically etching the aluminum foil, the square wave current has a positive current density of 0.5 to 2 A / c flowing from the aluminum foil to the counter electrode.
m ² and the flowing time is 1 to 15 ms, while the negative current density flowing from the counter electrode to the aluminum foil is 0.1 to 0.5 A / cm ²
Then, an aluminum electrolytic capacitor using an aluminum foil, which is formed by using a rectangular wave current having a flowing time of 1 to 5 ms, as an anode foil.