JPH11293428A - Production of high capacitance aluminum foil for electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing Al foil for an electrolytic capacitor in which the occupancy ratio of the (100) crystal face in the surface of Al foil for an electrolytic capacitor is regulated to >=95% and capable of the increase of capacitor. SOLUTION: Foil obtd. by subjecting a high purity aluminum ingot having >=99.9% aluminum purity to homogenizing heat treatment, hot rolling and cold rolling respectively is subjected to process annealing at 200 to 300 deg.C at a temp. rising rate of 10 to 50 deg.C/hr and is thereafter subjected to final cold rolling in a rolling ratio of 5 to 40% and final annealing at 450 to 600 deg.C to regulate the occupancy ratio of the (100) crystal face in the surface of the foil to >=95%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high capacitance aluminum foil for an electrolytic capacitor, and more particularly to a method for producing an aluminum foil for an electrolytic capacitor suitable for high pressure.

[0002]

2. Description of the Related Art Aluminum (hereinafter referred to as Al) can increase its surface area by electrochemical etching.
In addition, a voltage-resistant oxide film is formed on the surface by anodic oxidation, and can be used as a dielectric. When used as an electrode foil of an electrolytic capacitor, a relatively large capacitance can be obtained. Therefore, Al electrolytic capacitors are small and large-capacity compared to other capacitors and can be manufactured at low cost, and are widely used as indispensable electronic components for electronic circuits such as electronic devices.

[0003] The basic structure of an Al electrolytic capacitor is that a separator paper is sandwiched between two aluminum foils, an anode Al foil and a cathode Al foil, on each of which lead wires are arranged, and the aluminum foil is wound in a cylindrical shape. And impregnated in the package. Usually, this Al foil or Al alloy foil material includes Al
High purity Al having a purity of 99.96% or more or 99.9% or more for the anode and 99% or more or 99.8% or more for the cathode is used.

[0004] The capacitance (C) of the Al electrolytic capacitor having such a structure mainly depends on the surface area of the Al foil (especially the anode Al foil) and the dielectric oxide film (the etching pit) provided on the surface (etching pit) of the anode Al foil. Determined by the thickness of the barrier oxide film, specifically, the following equation: C = 8.855 × 10 ⁻⁸ εS / d
(μF) [where, ε: dielectric constant (8 to 9), S: surface area of dielectric (cm ² ), d: thickness of dielectric (cm ² )].

Therefore, in order to increase the capacitance of the Al electrolytic capacitor, it is important to increase the surface area of the Al foil and increase the surface area of the dielectric. The expansion of the surface area of this Al foil is based on the material Al foil coil (0.02-0.11m thick).
m, about 500 mm in width) in a chloride ion-containing electrolyte such as hydrochloric acid, and apply AC or DC current,
This is performed by continuous or stepwise electrolytic etching. Then, by this electrolytic etching, fine concave or rough pit layers (hereinafter referred to as etching pits) are continuously formed on the surface of the Al foil, and as a result, the effective area of the surface of the Al foil is increased, Secure high capacitance as electrode foil.

In the case of an Al electrode foil for an anode, a barrier oxide film as a dielectric layer is required on the surface of the Al foil.
The formation of the barrier oxide film is also continuously performed by a chemical conversion (anodizing) treatment step following the AC or DC electrolytic etching step.

As described above, in the electrolytic etching step, the surface area of the Al foil is increased (the surface of the Al foil is roughened), the effective area is increased, and a high capacitance per unit area is secured. To enable the miniaturization and high capacity of capacitors,
It is a very important process.

[0008] Of these, especially in the case of Al foil for high pressure, the formation voltage in the formation (anodization) treatment step after electrolytic etching is 20%.
It is performed at a high pressure of 0 to 700 V, and the thickness of the generated oxide film is 0.
Thick, about 2 to 0.7 μm. For this reason, if the electrolytic etching pit is shallow, the pit will be filled with this oxide film. Therefore, the electrolytic etching pit needs a pit depth that cannot be filled with the oxide film.
Including this point, and also from the above-mentioned increase in the capacitance, the required etching pit depth tends to be further increased. More specifically, a tunnel-shaped etching pit required for a high-pressure Al foil is required. The depth has reached about 30 to 40 μm. On the other hand, the thickness of the aluminum foil for an electrolytic capacitor has been reduced to 110 μm or less, and in some cases, to a thickness of 90 μm or less in accordance with the miniaturization and high capacity of the electrolytic capacitor.
Thus, in the case of recent high-pressure Al foil, the thickness is 110 μm.
It is necessary to provide tunnel-like etching pits with a total depth of about 60 to 80 μm on both sides of the foil for thin foils of less than m.

Conventionally, tunnel etching by direct current electrolytic etching has been employed for forming tunnel-shaped etching pits of this high-pressure Al foil. In this tunnel etching, electrolytic etching is performed step by step to form a large number of fine and deep tunnel-shaped etching pits in the foil surface in the thickness direction of the foil, and the etching is further performed in the foil thickness direction starting from the initial etching pit. This is a method of forming pits continuously. According to the tunnel etching by the DC electrolytic etching, the deep etching pit is not formed in a very fine etching pit, such as a spongy etching pit obtained by the AC electrolytic etching of the Al foil for low pressure, but in the thickness direction of the foil. Can be.

This tunnel-shaped etching pit is made of Al
It is related to the crystal orientation of the foil surface, especially growing perpendicular to the (100) crystal plane. For this reason, many (1)
Various methods have been proposed for forming a crystal plane, that is, increasing the occupancy (cube abundance ratio) of the (100) crystal plane on the surface of the Al foil.

For example, JP-A-59-918 discloses Fe,
After casting, hot rolling, and cold rolling high-purity Al with the amount of impurities such as Si regulated to 30 ppm or less and the amount of other impurities also regulated to 10 ppm or less, recrystallization does not occur and sub-recrystallized grains (Subgrain) formation temperature 150 ~ 250 ℃ 1
Intermediate annealing for more than an hour, then final cold rolling at a rolling reduction of 40% or less, and then final annealing at 500 ° C or more for 30 minutes or more, the sub-grains serve as nuclei for (100) crystal plane generation. Is disclosed.

[0012] Japanese Patent Application Laid-Open No. Sho 60-110853 discloses that an Al plate is subjected to (1) (a) 200 to 400 ° C. between a hot rolling step and a final annealing step.
(B) a step of cold rolling at a rolling reduction of 75% or more; (2) (a) a primary annealing treatment at 200 to 400 ° C + (b) 75%
Cold rolling at the above reduction rate + (c) Secondary annealing treatment at 200 to 400 ° C + (d) Cold rolling at a reduction rate of 5 to 35% is provided, and recrystallization aggregation after final annealing It is disclosed that the number of cubic-oriented crystals = (100) crystal planes in the structure is increased.

Japanese Patent Application Laid-Open No. 01-201447 discloses that, when finally performing recrystallization annealing, a temperature range of at least 100 to 300 ° C. at the time of temperature rise of recrystallization annealing is increased at a rate of 1.5 ° C./min or less. It is disclosed that upon heating, a small number of (100) recrystallized grains generated at a low temperature can grow large as energy from the surrounding unrecovered processed structure.

Japanese Patent Application Laid-Open No. 05-287465 discloses that in the final annealing process, since the amount of segregation of trace elements in the vicinity of the foil surface is peaked, the temperature is higher than the temperature after recrystallization is completed. It is disclosed that the annealing temperature is controlled so as not to be.

[0015]

In the above-mentioned prior art, it is common to obtain a cube existence ratio of 90% or more. However, in recent years, high capacitance has been increasingly required for Al foil for electrolytic capacitors for high pressure. Therefore, according to the findings of the present inventors, in order to form a tunnel-like etching pit of Al foil adapted to this high capacitance during DC electrolytic etching, the cube existence ratio must be 95%. % Or more, preferably
Must be at least 98%.

However, in the above prior art, even in each of the embodiments, only a cube existence ratio of at most about 94% was obtained, and the cube existence ratio was 95% or more with good reproducibility, preferably, 95% or more. Cannot exceed 98%.

In view of these points, the present invention provides an electrolytic capacitor having a (100) crystal plane occupation ratio (cube abundance ratio) of 95% or more on the surface of an aluminum foil for an electrolytic capacitor, thereby enabling high capacitance. An object of the present invention is to provide a method for producing an aluminum foil for use.

[0018]

In order to achieve this object, the gist of the method for producing a high-capacity aluminum foil for an electrolytic capacitor of the present invention is that a high-purity aluminum ingot having an aluminum purity of 99.9% or more is homogenized. Heat treatment, hot rolling, and cold rolling are each subjected to intermediate annealing at a heating rate of 10 to 50 ° C / hr and at a temperature of 200 to 300 ° C, and then at a rolling rate of 5 to 40%. Final cold rolling and 450-600 ° C
The final annealing is performed for 30 minutes or more at the above temperature, and the occupation ratio of the (100) crystal plane on the foil surface is set to 95% or more.

The present inventors have found that in the manufacturing process of the aluminum foil for an electrolytic capacitor, particularly the conditions of the intermediate annealing in the cold rolling, and the temperature increase rate of the intermediate annealing which is not disclosed in the above prior art, especially It was found that the occupancy of the (100) crystal plane on the foil surface was significantly related.

Further, the temperature rise rate of the intermediate annealing is 10 to 50 ° C./hr.
, Preferably at a specific range of 20 to 40 ° C./hr, and by setting the rolling rate of final cold rolling and the temperature and time of final annealing to specific ranges, the (100) crystal plane of the foil surface It has been found that the occupancy of the can be 95% or more.

More specifically, by setting the temperature rise rate of the intermediate annealing within the above range, three or more recrystallized grains are present in the thickness direction of the foil after the intermediate annealing and are present inside the foil ( It is possible to make the 100) crystal plane 0.1 to 5.0 times the X-ray diffraction intensity of the (200) crystal plane of the random aluminum in the X-ray diffraction intensity of the (200) crystal plane inside the foil. And the (100) crystal plane that exists inside this foil,
It grows from the inside of the foil during the final annealing, penetrates the foil surface, and guarantees high occupancy of the (100) crystal plane on the foil surface. In the present invention, the amount of the (100) crystal plane present inside the foil after the intermediate annealing correlates well with the amount of the (100) crystal plane.
It is expressed in terms of the amount of (200) crystal planes that can be quantitatively measured by X-ray diffraction intensity.

Then, the foil having such a pre-structure is
By processing the product foil at a specific range of final cold rolling reduction and processing the product foil at the final annealing temperature and time,
The occupancy of the (100) crystal plane on the surface of the product foil before electrolytic etching can be 95% or more. Therefore, the DC electrolytic etching of the foil provides a deep and dense tunnel-like etching pit, and a high capacitance when used as an electrolytic capacitor.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION (Purity of Al Foil) First, the purity of Al foil in the present invention will be described below. The Al foil used in the present invention needs to be high purity Al of 99.9% or more, preferably 99.98% or more. If the purity of the Al foil is less than 99.9%, the amount of impurities is too large, and it is difficult to make the occupation ratio of the (100) crystal plane of the foil surface 95% or more, and high capacitance cannot be achieved. .

In the present invention, Fe, Cu, Si, Z in Al foil
n, Mn, Ga, P, V, Ti, B, Cr, Ni, Ta, Zr, C, B
Elements such as e, In, and rare earth elements are basically impurities. When these impurity elements are large, these elements concentrated on the foil surface are inevitably contained in the dielectric oxide film formed by the chemical conversion treatment after the electrolytic etching, and deteriorate the dielectric oxide film. When the dielectric oxide film is deteriorated, especially in the case of a high-voltage electrolytic capacitor that requires a high withstand voltage of 250 V, a leakage current may occur during use. For example, as many as 100 to several hundred electrolytic capacitors are used per personal computer. If even one of the electrolytic capacitors becomes defective due to the leakage current, the entire personal computer becomes unusable. Therefore, the content of these impurity elements should be as low as possible. However, there are also technical restrictions on the reduction of these impurity elements and problems of reduction costs, so that the content of 30 ppm or less is permitted in each case.

Next, the critical significance of the requirements of each manufacturing process of the present invention will be described. (Homogenization heat treatment) First, the homogenization heat treatment conditions of the Al alloy ingot may be a normal method, and while achieving homogenization, taking into account the effect on the Al alloy characteristics and preventing remelting,
The treatment is preferably performed at a temperature of 500 to 600 ° C.

(Hot Rolling) The hot rolling after the homogenizing heat treatment may be performed under the conditions of a normal Al sheet hot rolling method. However, the occupancy of the (100) crystal plane on the foil
% Or more, the rolling ratio from rough rolling to finish rolling is preferably 95 to 99.5%, and the finishing temperature is
The temperature is preferably between 240 and 300 ° C. These conditions are necessary for uniformly accumulating the strain introduced into the Al plate during the hot rolling in the Al plate and for stably generating the subsequent texture. If the rolling reduction is less than 95%, the distortion introduced into the Al plate becomes uneven, while if the rolling reduction exceeds 99.5%, the distortion introduced into the Al plate becomes excessive. If the finishing temperature is lower than 240 ° C., the distortion introduced into the Al plate becomes excessive, while if the finishing temperature exceeds 300 ° C., the distortion introduced into the Al plate becomes too small.

(Cold Rolling) After the hot rolling, ordinary cold rolling is performed. The cold rolling before the intermediate annealing is for making the Al plate manufactured by hot rolling to the thickness of the Al foil, and the rolling ratio of the cold rolling before the intermediate annealing may be a desired value depending on the thickness of the foil, It is determined by the thickness of a foil that can be made into a product foil of about 100 mm in the final cold rolling described later. Considering these, the preferred range of the rolling rate of cold rolling is approximately 95 to 99.5%
It is.

(Intermediate Annealing) Then, after performing cold rolling on the foil, at a temperature rising rate of 10 to 50 ° C./hr and 200 to 30 ° C.
Intermediate annealing is performed at a temperature of 0 ° C. The conditions of the intermediate annealing, particularly the condition of the heating rate, are such that three or more, preferably five or more recrystallized grains are present in the thickness direction of the foil and the inside of the foil is present.
(200) It is important for the crystal plane to exist in a predetermined amount.

If the temperature rise rate of the intermediate annealing is less than 10 ° C./hr, preferably less than 20 ° C./hr, recrystallization proceeds during the temperature rise process, and three or more recrystallized grains exist in the thickness direction of the foil. You can't do that. Further, since the foil surface is recrystallized and crystal grains other than the (100) plane cannot be rotated and remain as they are even after further processing, a high cube abundance ratio cannot be obtained. That is, (1
00) The X-ray diffraction intensity of the (200) crystal plane inside the foil cannot be 0.1 to 5.0 times the X-ray diffraction intensity of the random aluminum (200) crystal plane. . As a result, by the subsequent final cold rolling and final annealing, the occupation ratio of the (100) crystal plane on the surface of the Al foil cannot be increased to 95% or more, and crystal grains other than the (100) crystal plane increase. For this reason, the lower limit of the rate of temperature rise during intermediate annealing is 10 ° C / hr.
Or more, preferably 20 ° C./hr or more.

On the other hand, if the heating rate of the intermediate annealing exceeds 50 ° C./hr, abnormal growth of crystal grains occurs during the heating process due to high-purity Al, and the crystal grains become coarse. For this reason, three or more recrystallized grains cannot be present in the thickness direction of the foil. Further, since the foil surface is recrystallized and crystal grains other than the (100) plane cannot be rotated and remain as they are even after further processing, a high cube abundance ratio cannot be obtained. Further, increasing the rate of temperature rise of the foil coil further has difficult aspects in terms of equipment or economy. Therefore, the upper limit of the rate of temperature rise during the intermediate annealing is set to 50 ° C./hr or less, preferably 40 ° C./hr or less.

In the present invention, the crystal plane to be present on the foil surface after intermediate annealing is defined not by the (100) crystal plane but by the X-ray diffraction intensity of the (200) crystal plane is that the (100) crystal plane This is because its own X-ray diffraction intensity cannot be measured due to the extinction law. The X-ray diffraction intensity of the (100) crystal plane itself is calculated as (2
00) The method of defining the ratio with the X-ray diffraction intensity of the crystal plane is as follows:
Light Metal (1981), Vol. 31, No. 5, pp. 334-340, `` 9
Influence of hot rolling temperature on rolling and restructuring of 9.99% Al
This is a method usually used to identify a specific crystal orientation inside Al. That is, (111), (200), (220), (3)
11), (222), (400), (331), (420), and (422) powder samples each having the same ratio of nine crystal planes were used as random Al = standard samples. (200)
The ratio between the X-ray diffraction intensity of the crystal plane and the X-ray diffraction intensity of the (200) crystal plane of the Al foil to be measured is determined. Therefore, the random Al referred to in the present invention refers to the standard sample widely used in the present technical field in order to obtain crystal planes of various orientations inside an Al plate or an Al foil by X-ray diffraction. Also, X
X-ray irradiation angle (2θ)
= 30 ° to 140 °.

The occupancy of the (100) crystal plane on the product foil surface can be measured directly by macro-observation of the foil surface structure, as in the examples described later. However, it is difficult to measure the (100) crystal plane inside the foil after intermediate annealing, which is an intermediate material during manufacturing, by macroscopic observation. Therefore, in the present invention,
The (100) crystal plane present on the foil surface correlates well with the amount of the (100) crystal plane and can be measured by X-ray diffraction intensity (2
00) Numerical values are obtained by measuring by replacing with the X-ray diffraction intensity of the crystal plane. The (100) crystal plane and the (200) crystal plane are strictly different crystal planes. However, both have the same normal (direction), and compared to the other plane (other crystal plane),
(100) Close to crystal plane. In this regard, more strictly, it is possible to measure the (100) crystal plane inside the foil by the etching pit method, but this method requires many times longer than the method based on the macro observation, and is realistic. is not. Therefore, a method of measuring by replacing with the X-ray diffraction intensity of the (200) crystal plane is widely used.

In the present invention, as described above, after the final annealing,
As a guide to ensure that the occupancy of the (100) crystal plane of the Al foil surface is 95% or more, the X-ray diffraction intensity of the (200) crystal plane is random, and the X-ray diffraction of the (200) crystal plane of Al is random. Diffraction intensity of 0.
It is necessary to make it 1 to 5.0 times, preferably 0.5 to 5.0 times.

However, the rate of temperature rise in the intermediate annealing in the conventional Al foil manufacturing process is slow, and is inevitably at a level of less than 10 ° C./hr. This is because a large amount of air is drawn into the gap between the foils when the aluminum of the foil is thin and is wound around the coil, and thereby the heat transfer rate (heating rate) of the foil coil becomes very slow. As a result, as will be described later, at the conventional heating rate of the intermediate annealing, three or more recrystallized grains are present in the thickness direction of the foil after the intermediate annealing as in the present invention, and (2)
00) The crystal plane could not be present at 0.1 to 5.0 times the X-ray diffraction intensity of the random (200) crystal plane of Al.

(Final Cold Rolling) The final cold rolling reduction is specified to be 5 to 40%. When the rolling reduction is less than 5%, three or more recrystallized grains exist in the thickness direction of the foil after intermediate annealing, and there are many (100) crystal faces expressed by the diffraction intensity of the (200) crystal face inside the foil. Even after the final annealing
(100) There is no driving force to recrystallize the crystal grains, and (100)
The surface portion of the foil where crystal grains other than the crystal plane grow grows.
On the other hand, if the rolling ratio exceeds 40%, the driving force for grain growth becomes too large, and again after the final annealing, the grains grow as grains other than the (100) crystal plane. Therefore, in any case, the occupation ratio of the (100) crystal plane of the Al foil surface after the final annealing of 95% or more cannot be reliably ensured.

(Final Annealing) The final annealing needs to be performed in a temperature range of 450 to 600 ° C. for 30 minutes or more. The final annealing conditions are for making the Al foil after the final cold rolling into a sufficiently recrystallized structure and for occupying the (100) crystal plane on the Al foil surface to be 95% or more. If the final annealing temperature is less than 450 ° C and the final annealing time is less than 30 minutes, sufficient recrystallized grains of the (100) crystal plane cannot be obtained, and the number of other crystal planes other than the (100) crystal plane increases, (100) The occupation ratio of the crystal plane cannot be set to 95% or more. For this reason, the area enlargement ratio after DC etching is reduced, and a high capacitance cannot be obtained.

On the other hand, if the temperature of the final annealing exceeds 600 ° C., when the Al foil is annealed in the state of a coil, the thin Al foils are blocked by diffusion bonding, and thus cannot be commercialized. The preferred final annealing temperature range for more effectively exhibiting these final annealing effects is as follows.
500-580 ° C.

Further, even if the time of the final annealing is long, the occupancy of the (100) crystal plane on the surface of the Al foil does not decrease.
It is not economical because productivity decreases. For this reason, the upper limit of the time of the final annealing is preferably set to about 10 hours.

In addition, Al, which is not particularly described in the present invention,
Face milling of ingot, winding of Al plate after hot rolling, or Al
Pretreatment steps such as degreasing or cleaning of foil and Al foil,
Ancillary steps such as straightening of the Al foil, slitting of the Al foil to a predetermined width and slitting of the Al foil, etc., are all performed according to a conventional method and are appropriately and selectively performed. In addition, the Al foil of the present invention is used in an electrolytic capacitor after the appropriate pretreatment as described above and the surface of the foil is enlarged by direct current electrolytic etching.

[0040]

Next, embodiments of the present invention will be described. A high-purity Al ingot with an Al purity of 99.9% or more was produced by DC casting, and 54
0 ° C x 6 hours homogenizing heat treatment, 9 at 250 ° C finishing temperature
Hot rolling was performed at a rolling rate of 8.7% and cold rolling was performed at a rolling rate of 97.4% to obtain Al foil. After that, intermediate annealing of the Al foil was performed at the heating rate and processing temperature shown in Table 1, respectively, and the number of recrystallized grains in the thickness direction of the foil and the inside of the foil were each shown in Table 1.
(200) The crystal plane X-ray diffraction intensity was used. Further, this foil was subjected to final cold rolling and final annealing at the rolling rates shown in Table 1 to obtain a coiled product foil having a thickness of 100 mm and a width of 500 mm. Table 1 shows the occupancy of the (100) crystal plane on the foil surface.

The sampling site for the analysis of the foil after the intermediate annealing and the foil after the final annealing was each at the center of the coil. The number of recrystallized grains in the thickness direction of the foil after intermediate annealing was determined by polishing the cross section in the direction parallel to the rolling direction of the foil sample after intermediate annealing, electrolytic etching, and observing the microstructure with a 200-fold optical microscope. I asked. Furthermore, (200) inside the foil
For the crystal plane, the diffraction intensity of the (200) plane was measured by an X-ray diffraction method, and the (200) plane of the random Al surface as a standard sample was measured.
The ratio to the X-ray diffraction intensity of the crystal plane ((200) plane X-ray diffraction intensity of sample / (200) plane X-ray diffraction intensity of random Al) was determined. In addition, the occupancy of the (100) crystal plane on the foil surface was determined by macro-etching the foil sample after the final annealing using a mixed acid of hydrochloric acid, nitric acid, and hydrofluoric acid. Observed using, binary valued, (10
0) While identifying the crystal plane,
The occupancy was determined in comparison with the standard samples in which the occupancy of the (100) crystal plane was 88% and 95%.

Then, the coil-shaped product foil is further
5wt% hydrochloric acid + 20wt% sulfuric acid aqueous solution, liquid temperature 85 ℃, current density
Perform the first DC electrolytic etching under the conditions of 0.2 A / cm ² × electrolysis time 50 seconds, provide an initial etching pit, and then
A second DC electrolytic etching was performed with a t% hydrochloric acid + 0.4 wt% oxalic acid aqueous solution under the conditions of a liquid temperature of 85 ° C., a current density of 0.07 A / cm ^{2, and an} electrolysis time of 650 seconds to provide desired etching pits. The aluminum foil coil after these electrolytic etchings was subjected to a chemical conversion treatment with an aqueous solution of ammonium adipate (60 ° C) and a chemical conversion voltage of 375V.
(Anodizing treatment) to provide a dielectric (barrier type oxide film). Capacitance (μF / cm ² ) of the end of the foil coil in the width direction and the center in the width direction using an equivalent series circuit (measurement solution; aqueous solution of ammonium adipate, 30 ° C., measurement frequency; 120 Hz, measurement voltage 50 mv) Was respectively measured. Table 1 also shows these results.

Further, the bending strength of the foil after electrolytic etching was also measured, and these results are also shown in Table 1. The bending strength of the foil is evaluated using an MIT type testing machine. Specifically, bending the foil of the test material at a 45 ° angle, then returning it to its original state, and bending it in the opposite direction at a 45 ° angle once is repeated until the foil is cut. It is evaluated by measuring the number of times it has been performed. The bending conditions of the MIT type testing machine were such that the bending radius of the bending surface of the test material was 1 mm, a tensile load of 250 g was applied, and the repetition rate was 175 times per minute.

For comparison, a foil having a low Al purity (Comparative Example No. 5), a foil deviating from the range of the intermediate annealing, the rolling reduction rate of the final cold rolling and the range of the final annealing of the present invention (Comparative Example) Examples Nos. 6 to 13) were also manufactured in the same manner as the manufacturing conditions of the above-mentioned invention examples except for these conditions, and the respective characteristics were measured or evaluated in the same manner as in the above-mentioned invention examples. Table 1 also shows these results.

As can be seen from Table 1, Al of Invention Examples Nos. 1 to 4
Since the foil satisfies the requirements of the present invention or is manufactured within the range of the present invention, the cube abundance ratio after the final annealing is
It is 95% or more, and the capacitance and bending strength of the foil after electrolytic etching are remarkably high. Among the invention examples Nos. 1 to 4, the foil of the invention example No. 4 manufactured in a preferable condition range,
The cube existence ratio after the final annealing is 98% or more, and the capacitance and the bending strength of the foil after the electrolytic etching are higher than those of the other invention examples. Therefore, these results support the critical significance of the requirements of the present invention and the significance of the preferred requirements.

On the other hand, Comparative Example No.
5.Comparative Example No. 6 in which the rate of temperature rise in the intermediate annealing is too low, and Comparative Example No. 7 in which the rate of temperature rise in the intermediate annealing is too high, all have three or more recrystallized grains in the thickness direction of the foil. Can not do. In addition, the X-ray diffraction intensity of the (200) crystal plane is too low in Comparative Example No. 8, the final cold rolling reduction is too low in Comparative Example No. 9, the final cold rolling reduction is too high in Comparative Example No. 10, Comparative Example No. 11 with too low annealing temperature, Comparative Example No. 1 with too high final annealing temperature
2. In Comparative Example No. 13 in which the final annealing time was too short, the occupation ratio of the (100) crystal plane on the foil surface after final annealing was 95% or less. Therefore, in each of these comparative examples, the capacitance and the bending strength of the foil after electrolytic etching are significantly inferior to those of the invention. Therefore, these results also support the critical significance of the requirements of the present invention.

[0047]

[Table 1]

[0048]

According to the present invention, Al for electrolytic capacitors is provided.
The occupancy of the (100) crystal plane on the foil surface (cube abundance ratio)
When it is set to 95% or more, it is possible to provide a method for producing an Al foil for an electrolytic capacitor which can increase the capacitance. Therefore, it has a great industrial value in that the function of the Al foil for an electrolytic capacitor can be improved and its use can be expanded.

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁶ Identification symbol FI C22F 1/00 661 C22F 1/00 685Z 685 686B 686 691B 691 691C 694A 694 H01G 9/04 346

Claims (8)

[Claims] 1. A high-purity aluminum ingot having an aluminum purity of 99.9% or more is subjected to a homogenizing heat treatment, a hot rolling and a cold rolling to a foil at a heating rate of 10 to 50 ° C./hr for 200 Intermediate annealing at a temperature of ~ 300 ° C, then 5 ~ 40
% Cold rolling at a rolling rate of 450%
A method for producing a high-capacitance aluminum foil for electrolytic capacitors, wherein a final annealing is performed for 30 minutes or more, and an occupancy of a (100) crystal plane on a foil surface is 95% or more. 2. The intermediate annealing causes three or more recrystallized grains to be present in the thickness direction of the foil and reduces the X-ray diffraction intensity of the (200) crystal plane inside the foil by random (200)
The method for producing a high-capacitance aluminum foil for an electrolytic capacitor according to claim 1, wherein the X-ray diffraction intensity is 0.1 to 5.0 times the X-ray diffraction intensity of the crystal plane. 3. The method according to claim 2, wherein five or more recrystallized grains are present in the thickness direction of the foil. 4. The aluminum of which (200) crystal plane has a random X-ray diffraction intensity of 0.
The method for producing a high-capacitance aluminum foil for an electrolytic capacitor according to claim 2 or 3, wherein the ratio is 5 to 5.0 times. 5. The method for producing a high-capacitance aluminum foil for an electrolytic capacitor according to claim 1, wherein a rolling reduction in the final cold rolling is 5 to 20%. 6. The method for producing a high-capacitance aluminum foil for an electrolytic capacitor according to claim 1, wherein the final annealing temperature is 500 to 580 ° C. 7. The method for producing a high-capacitance aluminum foil for an electrolytic capacitor according to claim 1, wherein the high-purity aluminum has an aluminum purity of 99.98% or more. 8. The method for producing a high-capacitance aluminum foil for an electrolytic capacitor according to claim 1, wherein the electrolytic capacitor is for high pressure.