JPH09180968A - Aluminum foil for electrolytic capacitor electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To distribute etching pits uniformly at a high density by permitting the aluminum purity to be at a specific value or more at a specified core part and permitting the foil to have a specified quantity of Sb and Pb on a surface layer part with specified depth from the surface of at least one face of the foil. SOLUTION: An aluminum ingot is removed by 0.1μm from the surface, is cold-rolled and is annealed so as to provide the core part of the aluminum foil. Then, Sb-Pb alloy is deposited on the copper foil, heat diffusion is performed, and the aluminum foil which has a Sb-Pb concentrating layer on the surface layer part is manufactured. The aluminum purity of the surface layer part 0.1μm from the surface is 99.8% or more, containing 10-10000ppm Sb, and 10-1000ppm Pb, and the content of the crystal grain boundary with an orientation difference of 10 deg. or less at the core part is permitted to be 80% or more of the whole part.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an aluminum foil for an electrode of an electrolytic capacitor.

[0002]

2. Description of the Related Art An Al foil generally used as an electrode material for an aluminum electrolytic capacitor usually has a large effective area to increase the capacitance per unit area.
An electrochemical or chemical etching process is performed.

[0003] However, a sufficient capacitance cannot be obtained simply by etching the foil. For this reason, generally, in the final annealing step after foil rolling, a high temperature heat treatment of about 450 ° C. or higher is performed in order to improve the etching characteristics of the foil by forming a texture having many cubic orientations. Regarding the chemical composition of the foil, it has been practiced to add a trace element to the entire foil or the surface layer portion (JP-A-6-316737, etc.).

[0004]

However, the aluminum foil which has been subjected to the above-mentioned high temperature heat treatment or the aluminum foil to which trace elements have been added sufficiently satisfies the recent demand for high capacitance of electrolytic capacitors. Did not get

The present invention has been made in view of the above technical background, and an object of the present invention is to provide an aluminum foil for an electrolytic capacitor electrode capable of increasing electrostatic capacitance.

[0006]

In order to achieve the above object, the inventors of the present invention have made earnest studies and, as a result, found that Sb--
By providing a Pb surface concentrated layer, adding a trace element, or further defining the orientation difference of the crystal grain boundaries, the etching pits can be uniformly and densely distributed, and a high capacitance foil can be obtained. I found it.

The present invention has been made on the basis of such findings, and in the core portion excluding the thickness of 0.1 μm from the surface, the aluminum purity is 99.8% or more, and at least one surface of the foil is From the surface layer portion having a thickness of 0.1 μm, Sb: 100 to 10,000 ppm and P
b; The basic gist is to contain 10 to 1000 ppm.

The aluminum purity of the aluminum foil according to the present invention is required to be 99.8% or more because it is 99.8.
If the purity is less than%, the growth of etching pits during etching is hindered by the presence of many impurities, and even the formation of the Sb-Pb concentrated layer within the scope of the present invention cannot form uniform deep tunnel-shaped etching pits. Therefore, an aluminum foil having a high capacitance cannot be obtained. The aluminum purity is preferably 99.9% or more.

Sb and Pb on the surface of aluminum foil
Is an element necessary for uniformly distributing pits with high density by etching. That is, generally, in the initial stage of etching, uneven unevenness of the surface existing on the foil surface, oil, deposits such as roll coating, or those that have been altered cause uneven local dissolution pits, resulting in uneven etching pit density. The property (sparse / dense) occurs, and in the remarkable case, the surface melts like a crater. This non-uniformity remains even after the end of the etching, causing a decrease in capacitance. Therefore, in order to prevent such defects,
Attempts have been made to control the non-uniformity factor of the etching pits existing on these surfaces, but as a result of earnest research on this point, the inventor has found that the aluminum foil having the Sb-Pb surface concentrated layer has localized etching pits. It was found that it has the effect of eliminating the property and forming it at a high density. That is, when the Sb-Pb surface concentrated layer is present, the wettability with Al is improved as compared with the case where Sb alone or Pb is present alone, and it becomes easier to uniformly disperse in the Al matrix, and the alloy layer is etched. Since it becomes the core of the pits, etching pits that are uniformly and densely dispersed are generated. In order to obtain such an effect, the Sb content is 100 pp in the surface layer portion having a thickness of 0.1 μm from the surface.
It is necessary to have m or more, but if it exceeds 10000 ppm, the concentration is too high and remarkable surface dissolution occurs, so that a high capacitance foil cannot be obtained. Therefore, the Sb content in the surface layer portion having a thickness of 0.1 μm from the surface is 100 to 10000 pp.
m. Particularly preferably 200 to 5000
It is good to use ppm. For the same reason, Pb
The content needs to be 10 to 1000 ppm, and particularly preferably 20 to 500 ppm. Such Sb-Pb
The thickened layer may be present on at least one side of the foil. Of course, it may exist on both sides.

The production of the aluminum foil containing a high concentration of Sb and Pb in the surface layer as described above is not particularly specified, but the following method can be exemplified. That is, an Sb-Pb alloy is vapor-deposited on the surface of an aluminum foil produced through chamfering, hot rolling, cold rolling (including intermediate annealing), and final annealing on an aluminum ingot having the composition of the core. Alternatively, an Sb-Pb alloy layer is formed on the foil surface by immersing an aluminum foil in a molten Sb-Pb alloy, and then diffusion treatment is performed by heating at 400 to 600 ° C for 1 hour or more. At that time, the composition ratio of the Sb-Pb alloy used for vapor deposition or immersion is Sb / Pb ≧ 6 by weight ratio.
It is preferably 5/35. This is because when it is completely liquefied beyond the solid-liquid phase line in the Sb-Pb alloy phase diagram, the grain boundary diffusivity is enhanced and the concentration distribution of Sb and Pb becomes nonuniform. Further, the thickness of the surface layer portion and the Sb content and Pb content in the layer are the same as the above Sb-Pb.
It can be adjusted by the composition and thickness of the alloy layer, the diffusion treatment conditions, and the like.

Further, the capacitance can be further increased by adding the following trace elements to the core of the foil.

When Cu and Zn form a solid solution in the Al matrix, they increase the solubility of the foil, promote the growth of etching pits, and increase the capacitance. In such an effect, Cu and Zn are equivalent, and at least one kind may be contained. If the Cu content is less than 5 ppm, the above effect is poor, and if it exceeds 80 ppm, the local solubility is increased, which hinders the uniform distribution of etch pits. Therefore, the Cu content is preferably in the range of 5 to 80 ppm, particularly preferably 8 to 50 ppm. Also, the Zn content is preferably 5 to 50 ppm, and particularly preferably 8 to 20 ppm for the same reason as Cu.

Ga is an element which is easily segregated at the crystal grain boundaries or sub-grain boundaries and causes an uneven distribution of etch pits by itself. Has the effect of increasing the uniform dispersibility of If the Ga content is less than 5 ppm, the above effect is poor, and if it exceeds 50 ppm, the local solubility is enhanced, which hinders the uniform distribution of etch pits. Therefore, the Ga content is preferably 5 to 50 ppm, particularly preferably 8 to 20 p.
pm.

Fe and Si easily form a compound with Al in the matrix, and the etch pit distribution can be made uniform by controlling the dispersed state of these elements. In such an effect, Fe and Si are equivalent, and at least one kind may be contained. However, if the content is large, it causes overdissolution at the time of etching and the electrostatic capacity is lowered. Therefore, the Fe content is preferably 5 to 60 ppm, particularly preferably 10 to 20 ppm. Further, the Si content is preferably 5 to 80 ppm, particularly preferably 15 to 30 ppm.

The above-mentioned additional elements contribute to an increase in electrostatic capacity when contained in the core of the aluminum foil, but do not limit the content in the surface layer.

Further, the capacitance can be increased by defining the orientation difference of the crystal grain boundaries in the core portion. That is, when the misorientation of the crystal grain boundaries of the matrix becomes large, the diffusion of the additional element preferentially proceeds at the crystal grain boundaries, so that the grain boundary etching property is strengthened and the nonuniformity of the etch pit is increased. Therefore, it is preferable that the crystal grain boundaries having an orientation difference of 10 ° or less occupy 80% or more of the whole, and particularly preferably that the orientation difference is 5 ° or less and the occupation ratio is 90% or more.

[0017]

Next, specific examples of the aluminum foil for an electrolytic capacitor electrode of the present invention will be described.

First, in order to form the core of the aluminum foil, aluminum ingots of various compositions a to k shown in Table 1 are chamfered, and then hot-rolled and cold-rolled (including intermediate annealing).
Then, final annealing was performed. Then, on the foil surface,
After depositing Sb-Pb alloys with different compositions, at 550 ° C
× Heat diffusion treatment for 3 hours, and finally the thickness is 100
An aluminum foil having a Sb-Pb concentrated layer on the surface layer was produced with a thickness of μm. No. 14 in Table 2 is Sb and P
No. 15 b was not vapor-deposited, but in No. 15, Pb was vapor-deposited and then heat diffusion treatment was performed under the same conditions.

For each of the aluminum foils produced as described above, the Sb content and the Pb content in the surface layer portion having a thickness of 0.1 μm from the surface were measured, and the crystal grains having an orientation difference of 10 ° or less in the core portion were measured. I investigated the occupation rate of the world. Table 2 shows these results.

Next, each aluminum foil was etched under the following conditions, and the capacitance of the obtained aluminum foil was measured at 250 V in 5% boric acid solution. The results are shown in Table 2 as a relative comparison when the capacitance of Sample No. 15 is 100%.

[Etching Conditions] Pretreatment: None Primary etching liquid composition: 5% HCl + 10% H ₂ SO ₄ , liquid temperature: 70 ° C. Current density: DC 20 A / dm ² , time: 100 seconds Secondary etching liquid composition: 5 % HCl, liquid temperature: 80 ° C., current density: direct current 5 A / dm ² , time: 8 minutes

[Table 1]

[0022]

[Table 2]

From the results shown in Tables 1 and 2, the products of the present invention having the Sb-Pb surface concentrated layer within the scope of the present invention on the surface were:
It was confirmed that the capacitance can be increased as compared with the comparative product that deviates from the scope of the present invention. In addition, Cu, Zn, G is added to the core.
It was also confirmed that the capacitance can be further increased by adding a, Fe, and Si in a predetermined range or by increasing the occupancy rate of crystal grain boundaries having a small misorientation.

[0024]

EFFECTS OF THE INVENTION The aluminum foil for electrolytic capacitor electrodes according to the present invention basically has an aluminum purity of 99.8% or more in the core portion excluding the thickness of 0.1 μm from the surface and at least one side of the foil. 0.1 from the surface of
In the surface layer portion of μm, Sb; 100 to 10,000 pp
m and Pb: 10 to 1000 ppm are contained, so that the density of the etch pits can be increased and the pits can be uniformly dispersed, and an extremely large surface area ratio can be obtained by the etching treatment. Therefore, it is possible to provide an aluminum foil for an electrolytic capacitor electrode having a large capacitance and excellent electrical characteristics.

As the composition of the core of the foil having the above Sb-Pb concentrated layer, the aluminum purity is set to 99.8% or more, and Cu: 5 to 80 ppm, Zn: 5 to 5 ppm.
By containing at least one of 50 ppm, the solubility of the foil during etching is increased, and an aluminum foil for an electrolytic capacitor electrode having a larger capacitance can be obtained. In addition, the Ga content in the core is 5 to
By setting the content to 50 ppm, the uniform dispersibility of etch pits is further enhanced, and an aluminum foil for electrolytic capacitor electrodes having a larger capacitance can be obtained. Further, by setting the Fe content in the core portion to 5 to 60 ppm and / or the Si content to 5 to 80 ppm, the distribution of etch pits becomes more uniform, and aluminum for electrolytic capacitor electrodes having a larger capacitance is obtained. Can be made with foil.

Further, in the core portion of the foil having the above Sb-Pb concentrated layer, the occupancy rate of the crystal grain boundaries having an orientation difference of 10 ° or less is set to 80% or more, so that the grain boundaries are preferentially occupied. Etching is suppressed, the distribution of etch pits becomes more uniform, and an aluminum foil for electrolytic capacitor electrodes having a larger capacitance can be obtained.

Front page continuation (72) Inventor Kotoku Sugimoto 6-224 Kaiyamacho, Sakai City Showa Aluminum Co., Ltd.

Claims (9)

[Claims] 1. A core portion excluding a thickness of 0.1 μm from the surface has an aluminum purity of 99.8% or more, and a surface layer portion having a thickness of 0.1 μm from at least one surface of the foil, Sb; 100. ~ 10,000 ppm and P
b; Aluminum foil for electrolytic capacitor electrodes, which contains 10 to 1000 ppm. 2. The core portion excluding a thickness of 0.1 μm from the surface contains at least one of Cu: 5 to 80 ppm and Zn: 5 to 50 ppm and has an aluminum purity of 99.8% or more. , And Sb in the surface layer portion having a thickness of 0.1 μm from at least one surface of the foil;
100-10,000 ppm and Pb; 10-1000
Aluminum foil for electrolytic capacitor electrodes, which contains ppm. 3. The core portion, excluding the thickness of 0.1 μm from the surface, contains Ga; 5 to 50 ppm, has an aluminum purity of 99.8% or more, and has a thickness of 0 from at least one surface of the foil. At the surface layer of 1 μm,
Sb; 100-10,000 ppm and Pb; 10-1
Aluminum foil for electrolytic capacitor electrodes, which contains 000 ppm. 4. The core portion excluding a thickness of 0.1 μm from the surface contains at least one of Fe: 5 to 60 ppm and Si: 5 to 80 ppm, and has an aluminum purity of 99.8% or more. , And Sb in the surface layer portion having a thickness of 0.1 μm from at least one surface of the foil;
100-10,000 ppm and Pb; 10-1000
Aluminum foil for electrolytic capacitor electrodes, which contains ppm. 5. The core portion, excluding the thickness of 0.1 μm from the surface, contains at least one of Cu: 5 to 80 ppm and Zn: 5 to 50 ppm, Ga: 5 to 50 ppm, and has an aluminum purity. Is 99.8% or more, and the thickness is 0.1 μ from at least one surface of the foil.
In the surface layer portion of m, Sb; 100 to 10,000 ppm
And Pb; 10 to 1000 ppm are contained, The aluminum foil for electrolytic capacitor electrodes characterized by the above-mentioned. 6. In a core portion excluding a thickness of 0.1 μm from the surface, at least one of Cu: 5 to 80 ppm and Zn: 5 to 50 ppm, Fe: 5 to 60 ppm, S:
i: containing at least one of 5 to 80 ppm, having an aluminum purity of 99.8% or more, and having a thickness of 0.1 μm from at least one surface of the foil.
The aluminum foil for electrolytic capacitor electrodes, characterized in that Sb; 100 to 10,000 ppm and Pb; 7. In the core portion excluding the thickness of 0.1 μm from the surface, Ga: 5 to 50 ppm and Fe: 5 to 60 pp
m, Si: at least one of 5 to 80 ppm, the aluminum purity is 99.8% or more, and the thickness of the foil is 0.1 from at least one surface.
In the surface layer portion of μm, Sb; 100 to 10,000 pp
m and Pb; 10 to 1000 ppm are contained, The aluminum foil for electrolytic capacitor electrodes characterized by the above-mentioned. 8. In a core portion excluding a thickness of 0.1 μm from the surface, at least one of Cu: 5 to 80 ppm and Zn: 5 to 50 ppm, Ga: 5 to 50 ppm, and F:
e: 5-60 ppm, Si: 5-80 ppm, and at least one of aluminum has a purity of 99.8% or more, and a surface layer portion having a thickness of 0.1 μm from at least one surface of the foil. In, Sb; 100
-10,000 ppm and Pb; 10-1000 ppm
An aluminum foil for an electrolytic capacitor electrode, which comprises: 9. The crystal grain boundaries having an orientation difference of 10 ° or less occupy 80% or more of the whole in the core portion.
An aluminum foil for an electrolytic capacitor electrode according to any one of 1.