JP2791392B2 - Aluminum foil for anode of electrolytic capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to an aluminum foil suitable for obtaining a high capacity electrolytic capacitor anode foil.

[Prior art]

Conventionally, an aluminum foil having a purity of 99.9% or more has been used to obtain a high capacity electrolytic capacitor anode foil. And a higher capacity electrolytic capacitor anode foil is required,
Aluminum foil with a purity of 99.99% or more is used.
However, the demand for higher capacity has become more stringent,
It is desired to produce an electrolytic capacitor anode foil using 99.999% or more of 4 aluminum foil. In order to produce an aluminum foil having a purity of 99.999% or more, a high-purity aluminum metal is naturally required. Aluminum ingots are produced by refining ores containing aluminum. However, in order to obtain high-purity ones, the refining process becomes complicated and the aluminum ingots become expensive. In particular, aluminum ingot having a purity of 99.999% or more is very expensive. Therefore, the purity obtained from this metal is 99.9
More than 99% of aluminum foil becomes very expensive,
As a result, it is not economically feasible to use it as an anode foil.

[Problems to be solved by the invention]

Accordingly, the present invention provides an aluminum foil having a purity of about 99.99% by including a specific element in the aluminum foil in a specific amount, so that the aluminum foil having a purity of about 99.999% or higher is used. An electrolytic capacitor anode foil having a capacity is obtained.

Means and Action for Solving the Problems

That is, the present invention, Fe4 ~ 13ppm, Si4 ~ 15ppm, Cu15 ~ 65
ppm, total of unavoidable elements 35 ppm or less, balance Al, Cu
And the amount of Fe satisfies the relationship of (80-5 × Fe) ≦ Cu ≦ (85-5 × Fe), where the unit is ppm. The aluminum foil for an anode of an electrolytic capacitor according to the present invention contains Fe, Si, and Cu as essential component elements other than Al. Fe is contained in an amount of 4 to 13 ppm. Note that 1 ppm is 0.0001% in%. If Fe is less than 4 ppm, the Al purity must be about 99.999%, which is not preferable because the aluminum base metal becomes expensive. On the other hand, when Fe exceeds 13 ppm, overdissolution occurs during etching of the aluminum foil, and a high-capacity anode foil cannot be obtained, which is not preferable. Si is contained at 4 to 15 ppm. If the content of Si is less than 4 ppm, the purity of Al must be about 99.999%, which is not preferable because the aluminum base metal becomes expensive. In addition, Si
If it exceeds 15 ppm, overdissolution occurs during etching of the aluminum foil, and a high-capacity anode foil cannot be obtained. Cu is contained in an amount of 15 to 65 ppm. If the Cu content is less than 15 ppm, the foil surface becomes difficult to dissolve during the etching of the aluminum foil, and a high-capacity anode foil cannot be obtained. On the other hand, if Cu exceeds 65 ppm, overdissolution occurs during etching of the aluminum foil, and a high-capacity anode foil cannot be obtained. The total amount of unavoidable elements must not exceed 35 ppm. Examples of inevitable elements include Mg, Mn, Ti, Zn, and Ga. If the total amount of the unavoidable elements exceeds 35 ppm, overdissolution occurs during the etching of the aluminum foil, and the tensile strength of the aluminum foil decreases, which is not preferable. In the present invention, it is necessary that the amounts of Fe and Cu have the following relationship. That is, (80−5 × Fe) ≦
Cu ≦ (85−5 × Fe) [where the unit is ppm]. If Cu <(80−5 × Fe), the foil surface becomes difficult to dissolve during etching of the aluminum foil, and a high-capacity anode foil is not obtained, which is not preferable. Cu> (85-5 × Fe)
In such a case, excessive melting occurs during etching of the aluminum foil, and a high-capacity anode foil cannot be obtained, which is not preferable. The aluminum foil for an anode of an electrolytic capacitor according to the present invention can be manufactured by a conventionally known method. That is, it can be produced by preparing an ingot having the above component composition and subjecting it to soaking treatment, hot rolling, cold rolling, intermediate annealing and final annealing as required.

EXAMPLES Ingots having the component compositions shown in Table 1 were prepared by water-cooled casting. The dimensions of this ingot are 60mm thickness x 300mm width x 800
mm in length. After the surface of this ingot was ground, it was soaked at 560 ° C. for 4 hours and further at 480 ° C. for 8 hours. Thereafter, hot rolling was performed at an outlet temperature of 250 ° C., and then cold rolling was repeated at about 50% per pass reduction to obtain an aluminum foil having a thickness of 90 μm. Then, this aluminum foil was degreased with a petroleum-based solvent, and finally annealed in an inert atmosphere to obtain an aluminum foil for an anode of an electrolytic capacitor. The aluminum foil for an anode of an electrolytic capacitor was etched as follows. That is, sulfuric acid: hydrochloric acid: distilled water =
This aluminum foil is immersed in an etching solution having a composition of 800: 40: 3160 (volume ratio) and a temperature of 70 to 85 ° C., and a direct current of 4.0 A / 5
Etching was performed by applying a current of 0 × 2 cm ² for 5 minutes. Then, the dissolution loss at this time was measured. Dissolution weight loss was evaluated relative to that of Example 3, that is, 1 as a relative evaluation. The results are as shown in Table 2. In addition, the thing whose dissolution loss is in the range of 0.95 to 1.05 passes. If the dissolution loss is less than 0.95, there is a portion where the aluminum foil surface remains in its original state, fine irregularities are not sufficiently formed on the foil surface, the surface area cannot be expanded, and a high capacity anode foil Can not be obtained. Also, when the dissolution loss exceeds 1.05, relatively large recesses are formed on the foil surface due to super-dissolution, fine irregularities are not sufficiently formed, the surface area cannot be increased, and a high capacity anode foil cannot be obtained. . As is evident from the above results, it is understood that the use of the aluminum foil for an anode of an electrolytic capacitor according to the example can provide a high-capacity anode foil without a decrease in strength.
In contrast, when the aluminum foil according to the comparative example is used,
It turns out that a high capacity anode foil cannot be obtained.

【The invention's effect】

As described above, the aluminum foil for an anode of an electrolytic capacitor according to the present invention is composed of a specific component composition. Therefore, even if the Al purity is about 99.99%, the etching property is good. A high capacity anode foil can be obtained. Therefore, relatively inexpensive Al can be used without using expensive aluminum foil with an Al purity of 99.999% or more.
By using an aluminum foil having a purity of about 99.99%, it is possible to obtain an anode foil having the same high capacity as the former. Therefore, the present invention has an effect that an inexpensive high-capacity anode foil can be provided.

────────────────────────────────────────────────── ─── Continuation of front page (56) References Patent 2657262 (JP, B2) Japanese Patent Publication No. 45-25978 (JP, B1) (58) Fields investigated (Int. Cl. ⁶ , DB name) C22C 21/00 H01G 9/042

Claims (1)

(57) [Claims] (1) Fe4 to 13 ppm, Si4 to 15 ppm, Cu15 to 65 ppm,
Total of 35 ppm or less of unavoidable elements, balance of Al, Cu and Fe
The amount of (80-5 × Fe) ≦ Cu ≦ (85-5 × Fe) [however,
The unit is ppm], an aluminum foil for an anode of an electrolytic capacitor.