JP3403444B2 - Aluminum foil for electrode of electrolytic capacitor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum foil for an electrolytic capacitor electrode. [0002] In this specification, the term aluminum is used to include its alloy. [0003] An aluminum foil used as an aluminum electrode material for an electrolytic capacitor is required to have a surface area as large as possible and to have a large capacitance per unit volume. Therefore, the effective area of the aluminum foil is generally enlarged by performing an electrochemical or chemical etching process. Further, in order to increase the surface area as much as possible, etching pits are formed. Various studies have been made on increasing the depth, thickness, and thickness of the material, such as improvement of the material composition and metal structure, improvement of the etching method, and research on the manufacturing process of the foil. [0004] However, in practice, in the known etching technique, the site of generation of etching nuclei, which forms the basis of the formation of etching pits, is not uniform. Attempting to increase the number of holes causes a disadvantage that the etching pits communicate with each other to form a coarse hole or that the etching pit does not become deep, so that the effect of increasing the area coverage that is sufficiently expected in the result is obtained. There was a problem that it was difficult. SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and makes it possible to form a large number of deep etching pits uniformly and at a high density. The purpose is to provide aluminum foil. [0006] With the above object, the inventor of the present invention has found that, as a result of repeated experiments and studies, the etching nuclei are often formed on the irregularities on the aluminum foil surface. Starting from such knowledge, the present invention was able to be completed as a result of repeating experiments and studies in order to find the irregularities on the aluminum foil surface where etching pits can be uniformly and densely formed. That is, according to the present invention, referring to the reference numerals in the drawings, the average height (H 1) is 0.1 to 10 μm and the average pitch (P 1) is 1 by transferring the concave streaks of the rolling roll to the surface. A first consisting of a plurality of parallel convex streaks (10) of about 20 μm;
The convex muscle group (1) intersects with each convex muscle (10) of the first convex muscle group (1), and has an average height (H2) of 0.1 to 10 .mu.m.
m, a second convex muscle group (2) composed of a plurality of parallel convex muscles (20) having an average pitch (P2) of 1 to 20 μm, and the first convex muscle group (1) An aluminum foil (A) for an electrolytic capacitor electrode characterized by having an intersection angle (α) with the second convex muscle group (2) of 10 to 170 degrees. The aluminum foil (A) has a purity of 99.
A high purity of 99% or more is preferable, but not limited to this, as long as it is within a range used for an electrolytic capacitor. The first and second convex streaks (1) and (2) formed on the surface of the aluminum foil (A) are necessary for securing the starting point of the etching pit, ie, the etching nucleus, at the time of etching. is there. That is, it is presumed that an etching nucleus is formed along each convex muscle (10) (20) belonging to each convex muscle group. Thus, the pitch P1 of the convex muscles (10) of the first convex muscle group (1) and the convex muscles (20) of the second convex muscle group (2)
If both pitches P2 are too large, exceeding 20 μm, the number of etching pits decreases, and conversely, pitches P1, P2
Is smaller than 1 μm, the number of etching pits becomes excessive, and a communication body between adjacent pits is generated. As a result, it is difficult to obtain a large surface area. Accordingly, the pitches P1 and P2 of the convex stripes (10) and (20) are 1 to 20 on average.
μm, preferably 5 to 10 μm. In addition, if the height of the convex streaks is not uniform, there is a risk that etching pits are intensively generated in the streaks having a high height and a local melting phenomenon occurs. Therefore, the average height of the convex muscle in both the first and second convex muscle groups (1) and (2) is 0.1 to 10
μm, preferably 0.5-3 μm. The pitches P1 and P2 or the heights H1 and H2 of the convex muscles in the first convex muscle group (1) and the second convex muscle group (2) may be the same or different. In order to form a sufficient number of etching nuclei more evenly dispersed, according to the present invention, the convex muscle (10) belonging to the first convex muscle group (1) and the second convex muscle group (2 ) Are formed in an intersecting state with the convex muscle (20). The intersection angle α needs to be set to 10 to 170 degrees. Intersection angle α is 1
If less than 0 degree or more than 170 degree, convex streaks (10)
And (20) are too close to each other to cause a joint of adjacent etching pits. As a result, a sufficient number of etching pits cannot be obtained, and the capacitance is inferior. The preferred intersection angle is between 60 and 120 degrees. Further, the inclination angles of the first and second convex muscle groups (1) and (2) with respect to the rolling direction Y are not particularly limited, and as shown in FIG. 1, the first and second convex muscle groups (1). Any of (2) may be inclined with respect to the rolling direction Y, and the first and second convex streaks (1) and (2)
May be in a state parallel to the rolling direction Y,
Alternatively, it may be in a state perpendicular to the rolling direction, or, as shown in FIG. 3, the first and second convex streaks (1).
Any of (2) may be formed in a lattice state that is parallel to the rolling direction Y and the other is orthogonal to the rolling direction. The convex lines (10) and (20) are formed by transferring concave lines of a rolling roll. That is, a first concave streak group and a second concave streak group corresponding to the first and second convex streak groups (1) and (2) are formed on the peripheral surface of the rolling roll, and these are rolled to an aluminum foil during rolling. It is formed by transferring to the surface of (A). When the first and second convex streaks (1) and (2) are formed to be inclined with respect to the rolling direction Y, they are preferably formed symmetrically with respect to the rolling direction Y. This is because when formed asymmetrically, the concave streaks in the rolling roll are asymmetric with respect to the circumferential direction of the roll, so that the aluminum foil is likely to meander during rolling, and the rolling operation becomes complicated. During the etching process, it is assumed that etching starts along the convex lines (10) and (20) on the surface of the aluminum foil (A), and the convex lines are formed in a predetermined state. Therefore, deep and thick etching pits are formed in a uniformly dispersed state over the entire foil surface, and the area coverage is increased and the capacitance is increased. Examples: Fe: 15 ppm, Si: 25 ppm, C
u: A 99.99% pure aluminum ingot containing 30 ppm is subjected to hot rolling and cold rolling according to a conventional method, and then, at the time of foil rolling, a plurality of parallel concave portions crossing each other are formed on the peripheral surface. Foil rolling is performed using a rolling roll having first and second concave streaks composed of streaks, and the first and second concave streaks of the rolling roll are transferred to form a roll including a number of convex streaks parallel to the surface. An aluminum foil having a thickness of 100 μm, in which one convex muscle group and a second convex muscle group consisting of a number of parallel convex muscles intersecting with the one convex muscle group were produced. By using five types of rolling rolls having different concave streaks having different depths, pitches, and crossing angles, the height, pitch, and crossing angle of the convex streaks of the first and second convex streaks can be reduced. 5 types of aluminum foils having different types were manufactured. Next, each aluminum foil was finally annealed at 520 ° C. for 3 hours in an argon atmosphere. The surface of each aluminum foil obtained as described above was observed with a laser surface roughness meter, and the average height, average pitch, and intersection angle of the convex muscles in the first and second convex muscle groups were examined. Table 1 shows the results. In addition, sample No1 ~
For No. 4, the inclination angles of the first and second convex streaks were symmetrical with respect to the rolling direction, and for Sample No. 5, they were formed in a direction parallel to and perpendicular to the rolling direction as shown in FIG. In each sample, the (100) area ratio was 90% or more, and the surface roughness Ra of the foil was about 0.4 μm. Next, the above four types of aluminum electrode foils were electrolytically etched in a mixed solution of 5% hydrochloric acid and 20% sulfuric acid (85 ° C.) at a current density of 20 A / dm 2 for 2 minutes, and then chemically etched for 10 minutes. Etched. Then, after a chemical conversion treatment at 380 V in a boric acid bath, the distribution of etching pits on each electrode foil was observed and the capacitance was measured. Table 1 shows the results. The capacitance is shown by a relative comparison when Comparative Example 1 is set to 100%. [Table 1] As can be seen from the above results, it was confirmed that the product of the present invention had a better distribution of etching pits and an increased capacitance as compared with the comparative product. According to the aluminum foil for an electrolytic capacitor electrode according to the present invention, the first convex stripe composed of a plurality of parallel convex stripes is formed on the surface of the aluminum foil by transferring the concave stripe of the rolling roll. And a second convex muscle group including a plurality of parallel convex muscles intersecting with each convex muscle of the first convex muscle group, and the first convex muscle group and the second convex muscle group are formed. Since the average height, average pitch, and intersection angle of each convex streak are specified, the etching nuclei formed along each convex streak can be uniformly distributed and formed as the whole foil. Therefore, etching pits resulting from the erosion of the etching nucleus portion are concentrated.
In addition to being able to be formed uniformly and at high density, it is possible to prevent each of the etching pits from communicating with each other and to form each one of them thick and deep. As a result, the area expansion ratio of the electrode foil can be remarkably increased, and the capacitance can be increased.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic enlarged plan view showing an example of first and second convex muscle groups. FIG. 2 is a sectional view taken along line II-II of FIG. FIG. 3 is an enlarged schematic plan view showing another example of the first and second convex muscle groups. [Description of Signs] A: aluminum foil 1: first convex muscle group 2: second convex muscle group 10: convex muscle 20: convex muscle

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI C25F 3/04 H01G 9/04 346 (72) Inventor Masaru Kiryu 6,224 Kaiyamacho, Sakai City, Osaka Prefecture Showa Aluminum Co., Ltd. (56) reference Patent flat 6-88298 (JP, a) JP flat 6-145922 (JP, a) JP flat 6-314637 (JP, a) (58 ) investigated the field (Int.Cl. ⁷ , DB name) H01G 9/055 C22F 1/04 C23F 1/00 C23F 1/36 C25F 3/04

Claims (1)

(57) [Claim 1] A plurality of rolls having an average height (H1) of 0.1 to 10 μm and an average pitch (P1) of 1 to 20 μm by transferring a concave streak of a rolling roll onto the surface. A first convex muscle group (1) composed of parallel convex muscles (10) intersects with each convex muscle (10) of the first convex muscle group (1) and has an average height (H2) of 0. .
A second convex muscle group (2) comprising a plurality of parallel convex muscles (20) having an average pitch (P2) of 1 to 10 µm and an average pitch (P2) of 1 to 20 µm; ) And the second convex muscle group (2) have an intersection angle (α) of 10 to 170 degrees.