JPH0748461B2 - Aluminum electrode foil for electrolytic capacitor and manufacturing method thereof - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum electrode foil for an electrolytic capacitor, in which the winding strength of a core portion of an element winding of a capacitor is improved, and a manufacturing method thereof.

2. Description of the Related Art Generally, an aluminum electrode foil for an electrolytic capacitor is generally subjected to electrolytic etching and chemical etching individually or in combination for the purpose of expanding its effective surface area. It is usually processed at the source.

However, in order to increase the effective surface area of the aluminum electrode foil, the amount of corrosion due to etching must be increased, but when the amount of corrosion is increased, the physical strength of the foil is reduced, and therefore the effective surface area is increased. However, in order to maintain the strength of the foil, conventionally, there has been proposed a method of forming a non-etched line-shaped or strip-shaped non-corroded portion on the surface of the foil.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, providing a strip-shaped or strip-shaped non-corrosive portion has a defect that it impedes the expansion of the length effective area, and when expanding the effective surface area, the physical strength of the foil is Since it lowers, it becomes fragile and easily broken when it is used after forming it.Therefore, at the stage of winding it around the winding core of the capacitor element, it is necessary to increase the diameter of the winding core to increase the radius of curvature for winding. However, when the diameter of the winding core portion is increased, there is a disadvantage that a space is wasted in the central portion of the capacitor element, and the volumetric efficiency of the capacitor with respect to the electrostatic capacity is lowered. Therefore, the conventional etching method is effective. It was extremely difficult to solve the contradictory effects of increasing the area and maintaining the physical strength at the same time.

Then, this invention aims at solving the above-mentioned conventional difficult problems.

Means for Solving the Problem Conventional aluminum electrode foils are etched under the same conditions on both sides of the foil. Therefore, even if there is an error, the amount of corrosion and the shape of corrosion on both sides are the same. There is no difference in the physical strength even if it is wound around the winding core of the capacitor element with the surface of the inside being the inside.

However, since either one of the electrode foils is always on the inside and is wound around the winding core of the capacitor element, as long as the winding strength when one surface is on the inside is strong, It does not matter if the winding strength is weak when the opposite side is the inside, and if the winding strength is improved only when one side is the inside, corrosion of the electrode foil Noting that the shape should be different on both sides, the inventor has conducted several experiments in which the shape of corrosion of the electrode foil is different on both sides. That is, the degree of corrosion from the surface of the aluminum foil to the inside depends largely on the etching temperature, the current density, the amount of electricity, etc., so these can be changed independently or appropriately combined,
Also, as a result of repeated experiments such as designing separately so that the shape of corrosion going from the aluminum foil surface to the inside is different on both sides, and performing etching treatment under different conditions on each side,
With electrode foils that have the same corrosion depth on both sides and different corrosion weights on both sides, the strength is the same when both sides are wound with one side with less corrosion weight inside being wound. However, it was found that it becomes stronger than the electrode foil when the obtained electrostatic capacitances are equal.

In the case of foils with the same corrosion depth and corrosion weight on the front and back and different corrosion shapes on the front and back, the strength is the same on both sides when a certain surface is wound inside due to the combination of the shapes. It was found that it is stronger than the electrode foil in the case of performing the etching treatment and making the obtained capacitances equal.

FIG. 1 shows the relationship between the capacitance with respect to the weight ratio of corrosion weight loss and the winding strength for an electrode foil for medium and high pressure in which the etch pit has a tunnel shape. μF / cm ² ), on the other vertical axis, the minimum diameter (mm) of the metal rod that can be wound without breaking the electrode foil to express the strength of the electrode foil is shown, and on the horizontal axis, The ratio of corrosion weight loss on the front and back sides is shown. As is clear from Fig. 1, when the weight ratio of corrosion weight loss on both sides is less than 1: 1.01, the strength when wound with the side with less corrosion weight loss inside However, when the weight ratio exceeds 1: 1.40, there is a marked decrease in capacitance compared to the electrode foil with both sides equally etched. The turning strength is improved when the weight ratio of corrosion weight loss on both sides of the etching foil is 1: It was found to be in the range 1.01 to 1: 1.40.

Also, in the case where the corrosion depth on both sides is the same, the weight loss on both sides is also the same, and the corrosion shapes on one side and the other side are different, the combination of the front and back shapes It turned out that the strong side was changing.

In the above, the same depth of corrosion on both sides, and as an electrode foil etching method in which the corrosion weight loss of one surface is different from the corrosion weight loss of the other surface, the electrode foil in a general chloride solution in the previous stage. In the case where the etching is carried out at 1, and then the subsequent etching is carried out by electrolysis, the difference in the corrosion weight loss on both sides is provided by electrolyzing with different amount of electricity on each side. In this case, the current density and the electrolysis time may be set independently on both sides to electrolyze both sides separately, or the same electrolysis time may be taken on both sides and only the current density may be changed to perform electrolysis. When etching by the method, the ratio of the amount of electricity on both sides is 1: 1.01 or less, no clear improvement in the winding strength is observed, and when the ratio is greater than 1: 5.0,
If one side is excessively corroded and the capacitance decreases,
Alternatively, one side of the surface is not corroded enough, so that the electrostatic capacity does not increase.Therefore, the winding strength is improved by the electrostatic capacity ratio when the ratio of the electric quantities of the two surfaces in the latter etching is 1:
The range is from 1.01 to 1: 5.0.

When the electrode foil is etched in a general chloride solution and then the latter is chemically etched,
Treat one side separately and make a difference in treatment time to make the weight loss on both sides different. In this case, when the ratio of the chemical etching treatment time is 1: 1.01 or less, no clear improvement is observed in the winding, and when the ratio is greater than 1: 5.0, the corrosion weight loss on one side is too large and the electrostatic capacitance becomes large. Or
Alternatively, the corrosion loss on one side is too small, and the capacitance does not increase.Therefore, the reason why the winding strength is improved in comparison with the capacitance is that the processing time ratio of the subsequent chemical etching is 1: 1.01. To 1: 5.0. Further, in addition to the method of making a difference in the processing time of the front and back, the method of making a difference in the temperature of the processing liquid of the front and the back and the method of changing the composition of the processing liquid of the front and the back can also make the corrosion weight loss of the front and the back different.

Also, in the two-stage etching of the former stage where the pits are generated in the aluminum foil and the latter stage where the pits generated in the former stage are enlarged to a necessary and sufficient thickness, the corrosion electric power of one surface and the other surface is It is also possible to make the corrosion shapes on both sides different by differentiating the amount of corrosion and by differentiating the amount of corrosion electricity on each surface in the latter stage as well so that the total amount of corrosion electricity in the former stage and the latter stage are equal. It is possible.

Even in this case, when the ratio of the amount of corrosive electricity in the former stage is 1: 1.01 to 1: 5.0, the ratio of the amount of corrosive electricity in the latter stage is 1.01:
It is preferable to make the total amount of corrosion electricity on both sides equal as 1 to 5.0: 1, and when smaller than the above range,
No improvement in the winding strength is observed, and when it is larger than the above range, excessively large pits are formed at a low density and the capacitance is lowered.

Example [Example 1] In the case of an electrode foil for medium- and high-pressure tunnels having etching pits, a soft material made of aluminum foil having a purity of 99.99% and a thickness of 104 µm was used, and the preceding etching was performed in a general chloride solution. After that, the aluminum foil was subjected to direct current etching under the etching conditions shown in Table 1 below, respectively, and then the aluminum foil was washed with water and dried to carry out the usual 375V chemical conversion. After chemical formation, width 10 mm and length 20 parallel to the rolling direction of the foil
A mm test piece was taken out, this was put on a metal rod having a smooth surface, both ends of the test piece were aligned and pulled while gradually increasing the load at a rate of 1.5 kg per second. Initially, use a metal rod with a diameter of 6.0 mm, and if the load at break of the test piece at that time is 1 kg or more, replace the metal rod with one with a diameter of 0.5 mm smaller, and in this way gradually change the diameter of the metal rod. The measurement was repeated by thinning in 0.5 mm increments, and the diameter of the thinnest metal rod was used as an index of the winding strength of the aluminum electrode foil. The results are shown in Table 1. In Table 1, the side with the most corrosion is A
The surface and the smaller surface are shown as the B surface.

Further, FIG. 2 shows a sectional view of the electrode foil which has been subjected to the etching treatment according to the above-mentioned Example 1.

According to Table 1, when the A-side of the one with much corrosion is placed outside,
It withstands metal rods up to 3.0 mm in diameter, and is able to improve the foil strength by three ranks as compared with the conventional example in which both sides are etched under the same etching conditions.

[Example 2] When the etching pit was an electrode foil for medium- and high-pressure tunnels, a soft material of aluminum foil having a purity of 99.99% and a thickness of 104 µm was used, and the previous etching was performed in a general chloride solution. Under the etching conditions shown in Table 2 below, the A-side and the B-side of the aluminum foil were individually subjected to chemical etching, followed by washing with water and drying, followed by chemical conversion at 375 V, which was normally performed, and the same as Example 1. Was measured.

According to Table 2, when the A side of the one with much corrosion is placed outside,
Withstanding metal rods up to 3.0 mm in diameter, the foil strength was improved by 3 ranks as compared with the conventional example in which both surfaces were etched under the same etching conditions.

[Example 3] In the case of an intermediate- and high-pressure electrode foil having a tunnel-shaped etching pit, a soft material of aluminum foil having a purity of 99.99% and a thickness of 104 µm was used and shown in Table 3 below in a general chloride solution. Under the etching conditions, that is, the amounts of corrosive electricity to the surface A and B in the previous stage and the amounts of electrical charge to the surface A and B in the subsequent stage are made different from each other, and the front and rear stages are different from each other. In order to make the total amount of corrosive electricity to the A surface and the total amount of corrosive electricity to the B surface in (3) are equal, the A surface and the B surface of the aluminum foil are separately subjected to direct current etching, washed with water and dried,
The usual chemical conversion of 375V was performed, and the same measurement as in Example 1 was performed.

According to Table 3, when the B side, which is more corroded in the previous stage, is set inside, it withstands metal rods with a diameter of up to 3.0 mm, and compared with the conventional example in which both sides were etched under the same etching conditions. The foil strength of the 3rd rank was improved. The third is a cross-sectional view of the electrode foil etched according to Example 3,
Corrosion depth and weight loss are the same on both sides, but only the shape is different.

[Example 4] In the case of an electrode foil for low voltage, a soft material of aluminum foil having a purity of 99.9% and a thickness of 90 µm was used, and an alternating current was applied in a general chloride solution under the etching conditions shown in Table 4 below. After etching, it was washed with water, dried, and subjected to the usual chemical conversion of 20V. After the chemical conversion, the foil strength test was conducted in the same manner as in Example 1, and the results are shown in Table 4.

According to Table 4, when the A side of the one with much corrosion is placed outside,
It withstands metal rods up to 0.5 mm in diameter, compared to the conventional one that has been etched on both sides under the same etching conditions.
The foil strength of 1 rank was improved.

EFFECTS OF THE INVENTION According to the aluminum electrode foil for electrolytic capacitors of the present invention, the electrode foil is wound to form a capacitor element as compared with the conventional electrode foil in which both surfaces of the electrode foil are etched under the same etching conditions. When the winding strength of the winding core portion is significantly improved, it is possible to reduce a foil cutting accident in the element winding, and thus it is possible to improve the yield of the electrode foil and the workability of the element winding. It has the advantage of cost reduction, and since the diameter of the winding core of the capacitor element can be reduced,
The volume efficiency of the capacitor with respect to the electrostatic capacity is increased, and it is effective in miniaturizing the capacitor.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between an index of a winding strength and a capacitance with respect to a weight ratio of corrosion weight loss, FIG. 2 is a sectional view of an etching foil showing a difference in corrosion weight loss between front and back, and FIG.
It is sectional drawing of the etching foil which shows the difference of the corrosion shape on the front and back.

Claims (6)

[Claims] 1. Aluminum for electrolytic capacitors, characterized in that in an aluminum etching foil, the corrosion depths on both sides are made equal, and the shape of corrosion on one surface and the shape of corrosion on the other surface are made different. Electrode foil. 2. The aluminum electrode foil for an electrolytic capacitor according to claim 1, wherein the weight loss of corrosion on one surface is different from the weight loss of corrosion on the other surface, and the weight ratio is 1: 1.01 to 1: 1.40. . 3. The aluminum electrode foil for an electrolytic capacitor according to claim 1, wherein both sides have the same corrosion weight loss. 4. A method of manufacturing an aluminum electrode foil for an electrolytic capacitor, wherein an aluminum foil is etched in two stages, a front stage and a rear stage, and a corrosive electricity amount on one surface and a corrosive electricity amount on the other surface in the latter electrolytic etching. The ratio of 1: 1.
A method for manufacturing an aluminum electrode foil for an electrolytic capacitor, characterized in that it is 01 to 1: 5.0. 5. A method for producing an aluminum electrode foil for an electrolytic capacitor, comprising the steps of etching an aluminum foil in two stages, a front stage and a rear stage, wherein the ratio of the corrosion time on one surface to the corrosion time on the other surface in the chemical etching in the latter step is calculated. A method for manufacturing an aluminum electrode foil for an electrolytic capacitor, characterized in that the ratio is 1: 1.01 to 1: 5.0. 6. A method for producing an aluminum electrode foil for an electrolytic capacitor, comprising the steps of etching an aluminum foil in two stages, a front stage and a rear stage. The ratio is 1: 1.01 to 1: 5.0, and the total amount of corrosive electricity on both sides is made equal by providing a difference between the amount of corrosive electricity on one surface and the amount of corrosive electricity on the other surface in the subsequent electrolytic etching. A method for producing an aluminum electrode foil for an electrolytic capacitor, which comprises: