JP3423557B2 - Aluminum foil for electrode of electrolytic capacitor - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an aluminum foil for an electrolytic capacitor electrode (including an aluminum alloy foil; the same applies hereinafter).

[0002]

2. Description of the Related Art With the miniaturization of electronic parts, it is required to improve the electrostatic capacity of aluminum foil for electrodes of electrolytic capacitors incorporated in electronic parts. Therefore, after etching the aluminum foil for electrolytic capacitor electrodes, Many attempts have been made to increase the surface area of the.

The etching of the aluminum foil for electrolytic capacitor electrodes is usually carried out by electrochemically or chemically treating it in a solution containing chlorine ions. Especially continuous <10
A tunnel-like etch pit in the 0> direction is desirable.

Several proposals have been made so far to control the morphology of the surface of an aluminum foil to make the distribution of etch pits formed by etching uniform and high density. For example, cylindrical projections of a specific shape are formed on the surface of an aluminum foil substrate at specific intervals (see Japanese Patent Laid-Open No. 6-14
5922), or by controlling the unevenness of the transfer marks of the roll mark formed on the surface of the aluminum foil (Japanese Patent Laid-Open No. 6-314637), it has been proposed to increase the surface expansion rate.

However, in the above method, the etch pits are likely to be concentrated on the same straight line or the same curve of the concave portion or the convex portion of the aluminum foil surface, and the pits are united with each other to mechanically drop the surface. There is a problem that the concave portions and the convex portions do not act effectively as the generation points of the etch pits.

[0006]

DISCLOSURE OF THE INVENTION In order to solve the above problems of the conventional aluminum foil for electrolytic capacitor electrodes, the present invention is formed by the shape and distribution state of the ridges and recesses on the surface of the aluminum foil and the etching treatment. It was made as a result of various experiments and studies on the relationship between the shape and distribution of the etch pits,
Its purpose is to allow for increased surface area after etching,
An object of the present invention is to provide an aluminum foil for electrolytic capacitor electrodes, which can increase the electrostatic capacity.

[0007]

The aluminum foil for an electrolytic capacitor electrode according to claim 1 of the present invention for achieving the above object has a height (H) on the surface of 0.05 to 10 μm.
The pyramidal protrusions are arranged in a zigzag pattern, and the interval (λ) between the protrusions is 0.1 to 20 μm.

The aluminum foil for electrolytic capacitor electrodes according to claims 2 and 3 is characterized in that, in claim 1, recesses having a depth (D) of 0.05 to 10 μm are formed between the ridges. Item 2 is characterized in that the shape of the recess is an inverted pyramid.

In the present invention, as shown in FIGS. 1 and 2, the height (H) on the surface of the aluminum foil 1 is from 0.05 to 0.05.
The ridges 2 of 10 μm are spaced apart by 0.1 to 20 μm (λ)
And, they are alternately arranged in a staggered pattern. When the aluminum foil for electrolytic capacitor electrodes is subjected to etching treatment, nuclei of pits are formed at the initial stage of etching, but in the aluminum foil of the present invention, the nucleation site becomes a raised portion.

If the height (H) of the raised portion 2 is less than 0.05 μm, pits are also formed in the peripheral portion of the raised portion. If it exceeds 10 μm, the ridges may fall off during etching or a plurality of pits may be formed in the ridges, which may cause surface dissolution.

When the interval (λ) between the raised portions 2 is less than 0.1 μm, coalescence of pits is likely to occur in the chemical conversion treatment after etching, and the capacitance is lowered. When the distance (λ) exceeds 20 μm, pits do not coalesce even when high-voltage formation is performed, but the number of pits generated is too small to increase the capacitance. By alternately arranging the raised portions 2 in a zigzag manner as shown in FIG. 1, the pit density is maximized, which is effective in increasing the capacitance.

As for the shape of the raised portion, it is preferable to form a pyramidal shaped raised portion 3 as shown in FIGS. Since the protrusions of the pyramidal ridges are sharp, the frequency of occurrence of a plurality of pits per one ridge is low, and high capacitance can be obtained.

As shown in FIG. 5, the recess 4 surrounded by the three vertices of the raised portion shown in FIGS. 1 and 3 is for suppressing dissolution in the horizontal <100> direction during etching. It has the effect of growing pits only in the <100> direction, which is the vertical direction. As shown in FIGS. 6 and 7, the shape of the recess is preferably an inverted pyramid-shaped recess 5, which can surely suppress dissolution in the horizontal <100> direction. Figure 1
And the recess shown in FIG. 3 is formed between the raised portions 3, and the bottom surface of the recess is the same as the surface of the aluminum foil. In this case, the depth (D) of the recess is zero. .

In the embodiment shown in FIGS. 6 and 7, the bottom of the recess 5 is located below the surface of the aluminum foil. In this case, the distance from the horizontal surface to the bottom of the recess is the depth (D) of the recess. In order to suppress dissolution in the <100> direction in the horizontal direction, the depth (D) of the recess is 0.05 to 10 μm.
m is preferred. If the thickness is less than 0.05 μm, dissolution in the horizontal direction progresses during etching, and improvement in capacitance cannot be achieved. When the depth (D) of the concave portion exceeds 10 μm, many pits are generated not only in the raised portion but also in the concave portion, so that the pits are united with each other to cause surface dissolution and an increase in capacitance cannot be obtained.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, 99.90% or more of a material is suitable as an aluminum foil base material.
The method of transferring the polishing streaks of the rolling roll when the aluminum foil is rolled is the simplest and most efficient method for forming the raised portion, and is also advantageous in terms of cost. A method of electrolytically etching an aluminum foil or a method of dry etching can also be applied.

In the case of transferring by a rolling roll, it may be carried out in any step before or after finish rolling of the aluminum foil, or before or after finish annealing. When forming the raised portions on the surface of the aluminum foil by the transfer of the rolling roll, the arrangement of the raised portions may be tilted any number of times with respect to the rolling direction. The height of the formed ridge is important for forming pits by etching, and the width of the ridge is not particularly limited.

[0017]

EXAMPLES Examples of the present invention will be described below. Example 1 A ridge having the form shown in Table 1 was formed on the surface of an aluminum foil (thickness: 100 μm) having an aluminum purity of 99.98 wt% by transferring a rolling roll. These aluminum foils were mixed with a mixed acid solution of hydrochloric acid 1 mol / l and sulfuric acid 3 mol / l at a temperature of 85 ° C. and a current density of 25 A / dm.
^An etching treatment was performed for 8 minutes under the condition of ² , and thereafter, chemical conversion was performed at 330 V, and the capacitance was measured.

Table 1 shows the measurement results of the capacitance. In addition,
Capacitance is the same as standard rolled aluminum foil (average roughness R
a: 0.4 μm), the electrostatic capacity of the test material subjected to the above-mentioned etching treatment and chemical conversion treatment was set to 100% for relative comparison. Further, the height (H) of the raised portion and the depth (D) of the recessed portion were observed using an atomic force microscope. Test material No.
Pyramidal protrusions were formed on 8, 10, 12 and 18, and inverted pyramidal recesses were formed on test materials Nos. 10, 13 and 20. As can be seen from Table 1, all the test materials according to the present invention show excellent capacitance exceeding 100%.

[0019]

[Table 1]

Comparative Example 1 Similar to Example 1, the aluminum purity was 99.98 wt.
% Of the aluminum foil (thickness: 100 μm), a ridge was formed by transfer of a rolling roll, followed by electrolytic etching and chemical conversion under the same conditions as in Example 1 to measure the capacitance. Table 2 shows the dimensions and capacitance of the raised portions. As shown in Table 2, the test materials in which the height (H) of the ridges and / or the interval (λ) between the ridges are outside the conditions of the present invention,
In any case, the improvement in capacitance cannot be achieved. In Table 2, those that do not satisfy the conditions of the present invention are underlined.

[0021]

[Table 2]

[0022]

As described above, according to the present invention, by forming the ridges of specific dimensions in the specific distribution form on the surface of the aluminum foil base material, it is possible to surely obtain a high capacitance. An aluminum foil for a capacitor electrode is provided.

[Brief description of drawings]

FIG. 1 is a partial plan view showing a distribution form of raised portions on a surface of an aluminum foil according to the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a partial plan view showing a preferable distribution pattern of raised portions on the surface of the aluminum foil in the present invention.

FIG. 4 is a sectional view taken along line BB of FIG.

FIG. 5 is a partial cross-sectional view showing a dissolution state of a raised portion on the surface of an aluminum foil during etching.

FIG. 6 is a partial sectional view showing a more preferable distribution form of raised portions and concave portions on the surface of the aluminum foil in the present invention.

FIG. 7 is a sectional view taken along line CC of FIG.

[Explanation of symbols]

1 aluminum foil 2 ridge 3 Pyramidal protrusion 4 recess 5 Inverse pyramidal recess

Continuation of the front page (56) Reference JP-A-6-314638 (JP, A) JP-A-6-145922 (JP, A) JP-A-6-310384 (JP, A) Jitsuko Sho-35-28652 (JP , Y1) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01G 9/055 H01G 9/04 304

Claims (3)

(57) [Claims] 1. The surface has a height (H) of 0.05 to 10 μm.
The pyramidal protrusions are arranged in a zigzag manner, and the interval (λ) between the protrusions is 0.1 to 20 μm. 2. The depth (D) between the raised portions is 0.05 to 10.
A recess having a size of μm is formed.
Aluminum foil for the electrolytic capacitor electrode described. 3. The aluminum foil for electrolytic capacitor electrodes according to claim 2, wherein the shape of the recess is an inverted pyramid.