JP2826590B2 - Manufacturing method of aluminum alloy foil for anode of electrolytic capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to a method for producing an aluminum alloy foil for an anode of an electrolytic capacitor having good etching characteristics and high tensile strength.

[Prior art]

Conventionally, high purity aluminum foil having a purity of about 99.98 to 99.99% has been used as an aluminum foil for an anode of an electrolytic capacitor. This aluminum foil is required to have excellent etching characteristics in order to obtain a high capacitance, and to have a large tensile strength in order to wind it to a predetermined size when forming it into an anode foil. Etching characteristics and tensile strength greatly affect the A1 purity of the aluminum foil. That is, when the A1 purity is increased, the etching state is good (many fine concave portions are formed).
And the capacitance increases, while the etching rate decreases. Conversely, if the A1 purity is lowered, the etching state is poor (no fine recesses are formed, each recess is large)
And the rate of increase of the capacitance is small. In addition, when the A1 purity of the aluminum foil is increased, recrystallization occurs, coarse grains are likely to be generated, and the tensile strength decreases. Conversely, when the A1 purity is reduced, fine grains are formed, and the tensile strength is improved. Note that it was explained here
The relationship between A1 purity and tensile strength is such that A1 purity is about 99.99%. For these reasons, it has conventionally been difficult to provide an aluminum alloy foil for an anode for an electrolytic capacitor having both good etching characteristics and high tensile strength.

[Problems to be solved by the invention]

Therefore, the present inventor conducted various studies to obtain an aluminum alloy foil for an anode for electrolytic capacitors having both good etching characteristics and high tensile strength, and as a result, specified an aluminum ingot containing a certain amount of a specific element. It has been found that by performing the treatment according to the above method, an aluminum alloy foil for an anode of an electrolytic capacitor having both of the above two properties can be stably obtained, and the present invention has been accomplished.

Means and Action for Solving the Problems

That is, the present invention relates to Fe 0.0013 to 0.0030%, Si 0.0013 to
0.0030%, Cu 0.0025-0.0050%, unavoidable impurities 0.0030
% Or less, the ingot of the remaining Al is homogenized at a temperature of 550 to 600 ° C., then hot-rolled and cold-rolled to obtain a foil having a predetermined thickness, and then the surface of the foil is washed. The present invention relates to a method for producing an aluminum alloy foil for an anode of an electrolytic capacitor, which comprises annealing at a temperature of 380 ° C. In the present invention, first, an aluminum base metal purified by a three-layer electrolytic method, a segregation method, or the like is prepared. The ratio of the component elements of the aluminum ingot is measured, and if necessary, predetermined amounts of Fe, Si, and Cu are added to form an ingot having a specific component composition. The composition range of the constituent elements of this ingot is as follows.
In addition, in this invention, all% represent weight%. Fe is 0.0013 to 0.0030%. Fe is contained in bauxite. Purification of aluminum by a three-layer electrolysis method or the like significantly reduces the Fe content. However, in the present invention, it is necessary to contain 0.0013 to 0.0030%.
If the Fe content is less than 0.0013%, the Al purity increases and a material having high tensile strength cannot be obtained, which is not preferable. Fe is 0.00
If it exceeds 30%, the etching state is poor and the capacitance does not increase. Si is 0.0013 to 0.0030%. Si is also included in bauxite. When aluminum is purified by a three-layer electrolysis method or the like, the Si content is significantly reduced, but in the present invention, it is necessary to contain 0.0013 to 0.0030%.
If the content of Si is less than 0.0013%, the purity of Al increases and a material having high tensile strength cannot be obtained, which is not preferable. Si is 0.00
If it exceeds 30%, the etching state is poor and the capacitance does not increase. Cu is 0.0025 to 0.0050%. Cu is contained only in trace amounts in bauxite compared to Fe and Si. Therefore,
In the present invention, it is generally necessary to add Cu actively. If the Cu content is less than 0.0025%, the Al purity increases and a material having high tensile strength cannot be obtained, which is not preferable. Cu
Exceeds 0.0050%, the etching state is poor, and the capacitance does not increase. Inevitable impurities are 0.0030% or less. As unavoidable impurities, there are cases where Mn, Mg, Zn, Ga, Ti, Ni, and the like are mixed. If these unavoidable impurities exceed 0.0030%, Al
It is not preferable because the purity is lowered and the etching state becomes poor, and the capacitance does not increase. The ingot is heated at a temperature of 550-600 ° C., particularly preferably 560-5
Homogenize at 80 ° C. The time may be a generally employed time, and specifically, is about 3 to 25 hours. When the temperature is lower than 550 ° C., the obtained alloy foil is excessively dissolved in the etching solution, and the etching state tends to be poor. When the temperature exceeds 600 ° C., the etching rate of the obtained alloy foil tends to decrease. After the homogenization treatment, hot rolling and cold rolling are performed. These rollings are performed by a conventionally known method. The surface of the foil obtained by hot rolling and cold rolling is washed. The washing may be performed with hot water or with an aqueous sodium hydroxide solution. If not washed, an oxide film remains on the surface of the foil or a carbon residue of the rolling oil remains, which tends to cause uneven etching. After cleaning the surface of the foil, annealing is performed at a temperature of 270-380 ° C. Annealing at a temperature lower than 270 ° C. tends to cause over-dissolution in the etchant, or may cause a decrease in elongation. If the annealing temperature exceeds 380 ° C., the etching rate tends to be slow, or an oxide film may be formed on the surface, causing uneven etching. By subjecting the thus obtained aluminum alloy foil for an anode of an electrolytic capacitor to an etching treatment, an anode foil having a high capacitance and a high tensile strength can be obtained.

【Example】

High-purity aluminum metal refined by three-layer electrolysis
The ingot of the composition shown in Table 1 (thickness 40
cm). The ingot was homogenized under the conditions shown in Table 2 and then hot-rolled to obtain an aluminum plate having a thickness of 5 mm. Thereafter, cold rolling was repeated to obtain an aluminum foil having a thickness of 90 μm. This aluminum foil was passed through an aqueous solution of sodium hydroxide for about 30 seconds to perform a cleaning treatment. In some cases, the cleaning process is not performed in the comparative example. After the cleaning treatment, annealing was performed in a non-oxidizing atmosphere under the conditions shown in Table 2. After etching the thus obtained aluminum alloy foil for an anode of an electrolytic capacitor, the dissolution amount, the capacitance and the tensile strength were measured to evaluate the performance. The results are shown in Table 2. The etching was performed at an etching solution of 56 ° C. (H ₂ O: HCl:
The aluminum alloy foil is immersed in C ₂ H ₂ O (2H ₂ O): AlCl ₃ (6H ₂ O) = 20: 2.4: 1: 1), and a pulse power source of 30 Hz ± 0.4 A / cm ² is applied.
Run for minutes. Dissolution amount (G) was carried out by immersing the etched 100 mm square aluminum alloy foil in a 15.5% HCl aqueous solution at 80 ° C. for 2.5 minutes, and measuring the weight loss. Capacitance (μF / cm ² ) is 8.3% HN
It was measured at 0 vf using a capacitance meter in an O ₃ aqueous solution. The tensile strength (kg / cm) is a value obtained by measuring a breaking load when a tensile test is performed on an aluminum alloy foil having a width of 1 cm after etching. As is clear from these results, the capacitance of each of the examples is higher than that of the comparative example. Comparative Example 1, in which the proportions of both Fe and Si are small, is inferior to those of Examples in terms of tensile strength and dissolution amount. Comparative Examples 2, 3 and 6, in which the proportion of any of Fe and Si is small, are inferior to those of the Examples also in terms of tensile strength.

【The invention's effect】

As described above, the aluminum alloy foil for electrolytic capacitor anode obtained by the method according to the present invention is Fe, Si and C
Since the amount of u is set within a certain range, an effect of obtaining an anode foil excellent in capacitance and tensile strength can be obtained when etching is performed. Further, according to the production method of the present invention, there is an effect that an aluminum alloy foil for an anode of an electrolytic capacitor having excellent characteristics as described above can be reliably obtained.

────────────────────────────────────────────────── (5) References JP-A-59-918 (JP, A) JP-A-53-125920 (JP, A) JP-B-45-25978 (JP, B1) (58) Field (Int.Cl. ⁶ , DB name) H01G 9/04

Claims (1)

(57) [Claims] (1) 0.0013 to 0.0030% Fe, 0.0013 to 0.0030% Si
%, Cu 0.0025-0.0050%, unavoidable impurities 0.0030% or less, the ingot of the remainder A1 is homogenized at a temperature of 550-600 ° C,
Then, after hot rolling and cold rolling into a foil of a predetermined thickness, the surface of the foil is washed, and further subjected to annealing at a temperature of 270 to 380 ° C. Production method.