JP2657262B2 - Aluminum alloy foil for anode of electrolytic capacitor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to an aluminum alloy foil for an anode of an electrolytic capacitor, and more particularly, to a method of controlling the content of silicon, iron and copper in high-purity aluminum to a certain level. By satisfying the conditions, it is an object of the present invention to provide an aluminum alloy foil for an anode of an electrolytic capacitor, which can achieve a large capacitance despite a small dissolution loss during etching.

[Conventional technology]

Conventionally, the aluminum alloy foil for an electrolytic capacitor anode can adjust the content of a specific element in the aluminum alloy foil for the anode of an electrolytic capacitor, and achieve a large capacitance even though the dissolution loss during etching is small. Attempts have been made to not provide foil.

For example, Japanese Patent Publication No. 45-25978 discloses that, in an aluminum alloy foil for an anode of an electrolytic capacitor composed of high-purity aluminum of 99.99% or more, when the copper content is adjusted to a range of 40 to 100 ppm, the dissolution loss during etching is reduced. It is reported that effects such as reduction in size and achievement of a large capacitance can be obtained.

In addition, the effect of various elements on the aluminum alloy foil for the anode of electrolytic capacitors is described in
No., JP-B-44-29577, JP-A-50-104710, JP-A-5-104710
Various reports have been made in publications such as 3-107657 and JP-A-54-98959.

[Problems to be Solved by the Invention] and [Action] However, the above-mentioned report mainly reports the influence of trace elements alone in the aluminum alloy foil, and the influence by the interaction between different elements. Was not actively studied.

For this reason, even if the specific trace element is set within the allowable range prescribed in each invention, defective products that do not achieve the intended purpose may occur depending on the variation of the trace element within the patent range. There were many things.

In view of the above circumstances, the present inventor has reached a result of research to provide an aluminum alloy foil for an anode of an electrolytic capacitor capable of achieving a small amount of dissolution during etching and achieving a large capacitance with higher reproducibility. is there.

[Means for solving the problem]

That is, the present invention is based on high-purity aluminum of 99.99% or more, and the contents of silicon, iron and copper are respectively reduced to 6 to
An aluminum alloy foil for an anode of an electrolytic capacitor, wherein the aluminum alloy foil is adjusted to 30 ppm, 5 to 18 ppm, 30 to 60 ppm, and the value of silicon content / iron content is adjusted to 1.1 or more.

According to JIS H 2111, refined aluminum ingots are
For special ingots manufactured in a three-layer electrolytic furnace and made of high-purity aluminum of 99.995% or more, the content of silicon, iron and copper should be 20 ppm or less, and made of high-purity aluminum of 99.990% or more. For seed metal, silicon, iron,
Classification is carried out so that the content of copper in the three components is 50 ppm or less.

Therefore, it seems that some aluminum alloy foils for anodes of electrolytic capacitors using the above-mentioned JIS aluminum ingot satisfy the above-mentioned conditions of the present invention in terms of form.

However, the above merely defines the upper limit of the content of silicon, iron and copper for the type of aluminum ingot. By the way, in September 1965, "Journal of Metals
944P to 947P "report one example of the content of various trace elements contained in high-purity aluminum manufactured in a three-layer electrolytic furnace. According to this, Si 6 ppm, Fe 8 ppm, Cu 5 pp
m, Na 6 ppm, Mg 1 ppm, Ca 2 ppm, and other elements 25.9 ppm.

High-purity aluminum ingots from this three-layer electrolytic furnace are
Even if attention is paid only to the copper content, it is unsuitable as it is as an aluminum alloy foil for an anode of an electrolytic capacitor.

Therefore, the above-mentioned prior art also considers various elements that are inevitably mixed into the high-purity aluminum ingot, and in order to make these more suitable as aluminum alloy foil for the anode of electrolytic capacitors, specific trace elements are used. Is set as a condition, and this is the same in the present invention.

However, the present invention is characterized in that the content of each element of silicon, iron and copper is strictly set, and the value of silicon content / iron content is set to a certain value or more. .

That is, according to many experiments of the present inventors, silicon,
It is necessary to set the content of each element of iron and copper strictly in order to achieve the intended purpose, but this setting alone is not sufficient, and the value of silicon content / iron content is set to 1.1. As described above, it is necessary to set the value to preferably 1.3 or more.

In the present invention, the fact that the value of silicon content / iron content is important is, for example, a change in capacitance when the content of iron and copper is kept constant and only the content of silicon is changed, That is, the results are as shown in the results of Examples and Comparative Examples below (the results of Examples 1, 2 and 5, the results of Examples 7 and 8, the results of Example 9 and Comparative Example 3, and the comparative examples). 1, see 5).

From the above results alone, it is difficult to determine an appropriate range of the silicon content and the iron content by absolute values. However, when the iron content is 4 ppm, even when the value of silicon content / iron content satisfies the above, sufficient etch pits cannot be obtained, so that the capacitance is considerably deteriorated. (Refer to the results of Comparative Example 8 with respect to the results of Example 5).

Therefore, the iron content should be at least 5 ppm or more.

Conversely, when the iron content exceeds 18 ppm, even when the value of silicon content / iron content is appropriate, the amount dissolved at the time of etching increases, and the capacitance slightly decreases (Examples). 12).

Based on the above results and the results of the examples described later, the iron content is appropriately 5 to 18 ppm.

On the other hand, the lower limit of the silicon content is considered to be about 6 ppm in consideration of the lower limit of the iron content, the value of silicon content / iron content, and the results of other examples described later. Also,
The upper limit of the content of silicon is Comparative Example 1, Comparative Example 12, and Comparative Example
Judging from the result of 18, it is considered to be about 30 ppm.

When copper is used as the aluminum alloy foil for the anode of an electrolytic capacitor based on high purity aluminum ingot of 99.99% or more, the effect of improving the foil strength and etching property has been recognized for a long time. In the present invention, a similar effect was observed in this respect, but the content thereof is suitably in the range of 30 to 60 ppm, including unavoidable copper.

〔Example〕

Based on high-purity aluminum of 99.99% or more, adjust the content of silicon, iron, and copper, including the amount contained in advance, as shown in the attached table, and roll the foil.
It was immersed in a mixed solution of 10 wt% hydrochloric acid and 1 wt% oxalic acid at 90 ° C., and a DC current was applied at a current density of 20 A / dm ² for 6 minutes to perform etching.

Thereafter, the etching foil was washed with water, subjected to a chemical conversion treatment with a 5 wt% aqueous solution of ammonium adipate at 85 ° C. while applying a voltage of 20 V, and the capacitance was measured. The results were as described in the same table.

The base of high-purity aluminum of this example and the comparative example is trace elements Cd, Mg, Ca, Zr other than silicon, iron and copper.
In each case, and in some cases, Zn, Ga, and Na each containing several ppm, and the total amount of the trace elements other than copper, silicon, and iron was 11 to 30 ppm.

[Effects of the Invention] According to the above description, it is possible to minimize the dissolution loss during etching, as in the inventions of JP-B-45-25978 and JP-B-62-37105. However, in the present invention, it is possible to provide an aluminum alloy foil for an anode of an electrolytic capacitor which achieves a larger capacitance with good reproducibility.

 ────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kenji Yamamoto 61-8 Sasaya, Yamadera-cho, Kusatsu-shi, Shiga Japan-made Foil Co., Ltd. Shiga Plant (56) References JP-A-58-1046 (JP, A) Sho-57-110646 (JP, A) JP-B-45-25978 (JP, B1)

Claims (1)

(57) [Claims] (1) Based on high-purity aluminum of 99.99% or more, the contents of silicon, iron and copper are respectively 6 to 30 ppm,
An aluminum alloy foil for an anode of an electrolytic capacitor, wherein the aluminum alloy foil is adjusted to 5 to 18 ppm, 30 to 60 ppm, and the value of silicon content / iron content is adjusted to 1.1 or more.