JP2008121089A - Method for manufacturing aluminum foil for electrolytic capacitor electrode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aluminum foil for electrolytic capacitor electrodes which has excellent etching characteristics and reliability and to which electroless etching can be applied. <P>SOLUTION: A rolled aluminum alloy material, which has a composition composed of, by mass, 0.01 to 0.30% Si, 0.01 to 0.30% Fe, 0.0051 to 0.05% Ni and the balance Al with inevitable impurities and further containing, if necessary, 0.0030 to 0.10%, in total, of at least one or more elements among Zn, Sn, In and Ga and also has a sheet thickness resulting from a draft of 75 to <98% at cold rolling after hot rolling, is subjected to process annealing at 300 to 500°C and formed into the aluminum foil for electrolytic capacitor electrodes. By this method, high-density uniform pits can be formed at etching even in the case of electroless etching and the electrolytic capacitor electrodes combining high electrostatic capacity with high reliability can be manufactured at a low cost. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing an aluminum foil for an electrolytic capacitor electrode that is etched when used as an electrode for an electrolytic capacitor, and is particularly suitable for a method for producing an aluminum foil for a cathode.

As the aluminum foil used for the cathode of the electrolytic capacitor, pure Al type and alloy type (mainly Al-Cu type and Al-Mn type) are used. Among these, the pure Al system has few impurities and high reliability, but has low solubility, so that electrolytic etching is employed and has a problem of high cost. On the other hand, the alloy system has many impurities and is considered to have low reliability. For example, although Al-Cu system (for example, refer patent document 1) improves etching property by inclusion of Cu, when it is incorporated in a capacitor, Cu eluted in the electrolytic solution is precipitated, and safety such as a short circuit is caused. (Reliability) issues occur. Moreover, although Al-Mn type | system | group (for example, patent document 2) improves etching property by containing Mn, the problem (environmental problem) on the waste-liquid process of the etching liquid containing Mn eluted at the time of etching generate | occur | produces. However, since these alloy systems have high solubility, electroless etching is possible, and a low-cost manufacturing method can be employed.
Accordingly, a pure Al system is selected from the viewpoint of emphasizing reliability, and an alloy system is selected from the viewpoint of emphasizing cost.
JP 2002-80927 A JP 2004-076059 A

Recently, with the improvement of the overall quality level of products in which capacitors are used, reliability has become more important for capacitors, and aluminum foil used for electrodes is also highly reliable. Al type tends to become mainstream. However, as described above, the conventional pure Al-based aluminum foil has a problem of high cost because it requires electrolytic etching. For this reason, there is an increasing demand for development of pure Al-based aluminum foil that can be electrolessly etched at a lower cost.
On the other hand, the present inventors have proposed an aluminum foil that enables electroless etching by adding Ni or the like to a pure Al base. However, in the aluminum foil, the etching tends to concentrate on the unevenness of the rolling line, and as a result, the unetched region remains in a streak shape, causing problems such as poor uniformity and poor appearance.

  The present invention has been made against the background of the above circumstances, and provides a method for manufacturing an aluminum foil that is capable of highly uniform etching even in electroless etching, and thus is low in cost and high in reliability. Objective.

  That is, the manufacturing method of the aluminum foil for electrolytic capacitor electrodes according to the first aspect of the present invention is mass%, Si: 0.01 to 0.30%, Fe: 0.01 to 0.30%, Ni : Aluminum containing 0.0051 to 0.05%, with the balance being Al and inevitable impurities, and having a plate thickness of 75% or more and less than 98% in the cold rolling after hot rolling The alloy rolled material is subjected to intermediate annealing at 300 ° C. to 500 ° C.

  The manufacturing method of the aluminum foil for electrolytic capacitor electrodes of 2nd invention is the mass%, Si: 0.01-0.30%, Fe: 0.01-0.30%, Ni: 0.0051-0. 05%, containing at least one of Zn, Sn, In, and Ga in a total amount of 0.0030 to 0.10%, with the balance being composed of Al and inevitable impurities, after hot rolling An aluminum alloy rolled material having a sheet thickness of 75% or more and less than 98% in cold rolling is subjected to intermediate annealing at 300 ° C. to 500 ° C.

According to the present invention, intermediate annealing is performed on a cold-rolled material in a state of being rolled at an appropriate reduction rate, and further cold rolling is performed to concentrate the elements contributing to etching on the surface, thereby forming a surface layer. Etching property can be improved. Even when the aluminum foil is subjected to electroless etching, the etching pits can be uniformly formed without any unetched gloss.
The reasons for limiting the components of aluminum foil and the production conditions defined in the present invention will be described below.

Si: 0.01-0.30%
Si forms precipitates that serve as starting points for etching. However, if it is less than 0.01%, the absolute amount of Si is small, and its action is not sufficiently exhibited. On the other hand, if it exceeds 0.30%, precipitation proceeds and overdissolution occurs, the etching form becomes non-uniform, and the capacitance decreases. For this reason, Si content is defined to the said range. For the same reason, it is desirable that the lower limit of the Si content is 0.02% and the upper limit is 0.15%.

Fe: 0.01 to 0.30%
Fe has the effect of forming precipitates as starting points for etching and increasing the strength. However, if it is less than 0.01%, the absolute amount of Fe is small, and its action is not sufficiently exhibited. In addition, the cost increases due to high purity. On the other hand, if it exceeds 0.30%, precipitation proceeds and overdissolution occurs, the etching form becomes uneven, and the capacitance decreases. For this reason, Fe content is defined to the said range. For the same reason, it is desirable that the lower limit of the Fe content is 0.02% and the upper limit is 0.15%.

Ni: 0.0051 to 0.05%
Ni forms an Al- (Ni, Fe) -based precipitate. These are noble in potential, cause a local cell reaction with the bulk, and improve the etching property. However, if it is less than 0.0051%, a sufficient number of Al— (Ni, Fe) -based precipitates cannot be obtained and the dispersion is insufficient, resulting in a non-uniform etching pattern. On the other hand, if it exceeds 0.05%, large precipitates are easily formed, and coarse pits are generated by etching, which is not preferable. For this reason, Ni content is defined to the said range. For the same reason, it is desirable that the lower limit of the Ni content is 0.0075% and the upper limit is 0.03%.

At least one or more of Zn, Sn, Ga, and In: 0.0030 to 0.10% in total
Like Ni, these elements are concentrated in the surface layer by intermediate annealing, and the potential of the bulk surface layer is reduced, so that they are contained as desired. This increases the potential difference between the Al- (Ni, Fe) -based precipitates that are noble in the surface layer and the bulk that is base, particularly increases the solubility in the surface layer, improves the end etch gloss of the surface, and is uniform. Etching is performed. When the content is less than 0.0030%, the above effect is insufficient, and when it exceeds 0.10%, the amount of impurities is excessively increased and excessive dissolution occurs. Therefore, the total content of the above elements is set within the above range. For the same reason, it is desirable that the lower limit is 0.0050% and the upper limit is 0.05%.

Intermediate annealing: 300-500 ° C
Ni is concentrated in the surface layer by heat treatment at 300 ° C. or higher. Therefore, Ni is concentrated on the surface layer by intermediate annealing at an appropriate temperature, and appropriate precipitation occurs, thereby improving the etching property. If the temperature of this intermediate annealing is less than 300 ° C., the temperature is insufficient and Ni concentration does not occur. On the other hand, when the temperature exceeds 500 ° C., Ni is excessively concentrated on the surface layer, and Ni is excessively precipitated to cause over-dissolution. Therefore, the heating temperature in the intermediate annealing is performed at 300 to 500 ° C. In addition, intermediate annealing can be normally performed in a batch furnace, and the holding time can be 1 to 9 hours, for example. Concentration to the surface layer of Ni can be reliably performed by holding for 1 hour or more. On the other hand, if the holding time exceeds 9 hours, excessive precipitation occurs with concentration of Ni and causes overdissolution, so the above holding time is desirable.

Reduction ratio: less than 75 to 98% Cold rolling until intermediate annealing provides a driving force for concentrating Ni on the surface. However, when the rolling reduction is less than 75%, the rolling reduction is low and the driving force becomes insufficient, and the Ni surface layer is not sufficiently concentrated. On the other hand, when the rolling reduction is 98% or more, the rolling reduction after the intermediate annealing decreases, and sufficient strength cannot be ensured. Therefore, the reduction ratio after hot rolling before the intermediate annealing is set in the above range.

  As described above, according to the method for producing an aluminum foil for electrolytic capacitor electrodes of the present invention, Si: 0.01 to 0.30%, Fe: 0.01 to 0.30%, Ni: A composition containing 0.0051 to 0.05%, further containing 0.0030 to 0.10% of Zn, Sn, In, or Ga as desired, and the balance of Al and inevitable impurities. The aluminum alloy rolled material having a thickness of 75% or more and less than 98% in the cold rolling after hot rolling is subjected to an intermediate annealing of 300 ° C. to 500 ° C. Etching is made uniform by the concentrated elements, and good etching without unetched portions is possible even in electroless etching. As a result, an aluminum foil for electrolytic capacitor electrodes with low cost and high reliability can be obtained.

Below, one Embodiment of this invention is described based on FIG.
The aluminum alloy adjusted to the alloy composition of the present invention is melted by a conventional method such as semi-continuous casting (step 1). In the present invention, the melting method is not particularly specified. The obtained alloy ingot is desirably subjected to a homogenization treatment (step 2) at 550 ° C. or higher for 1 hour or longer. The homogenization treatment can be performed using an appropriate heating furnace or the like, and the heating method and heating means are not particularly limited. The aluminum alloy after the homogenization treatment can be hot-rolled by a conventional method. Before hot rolling (step 4), the aluminum alloy can be soaked (step 3), for example, heated to 530 ° C. or higher. The conditions in the hot rolling are not particularly limited as the present invention. After hot rolling, cold rolling including foil rolling is performed.

In the case of cold rolling, intermediate annealing is essential. Before this intermediate annealing, cold rolling (step 5) is performed at a rolling reduction of 75% or more and less than 98%. The intermediate annealing (step 6) can be performed with a holding time of 1 to 9 hours on the condition of a heating temperature of 300 to 500 ° C. The intermediate annealing can be performed using a known annealing furnace, and the configuration of the apparatus for performing the intermediate annealing is not particularly limited as the present invention. After the intermediate annealing, cold rolling (step 7) is performed to a final thickness foil. Although the rolling reduction after intermediate annealing is not particularly limited as the present invention, it can be, for example, a rolling reduction of 70 to 99%.
An aluminum foil having a thickness of, for example, several tens to 100 μm can be obtained by the cold rolling, but the thickness of the aluminum foil as a final product is not particularly limited in the present invention.

The aluminum foil obtained through the above steps is then subjected to an etching treatment (step 8) without being subjected to heat treatment. If heat treatment is performed after the end of cold rolling, recovery or recrystallization occurs and causes a decrease in strength. Therefore, it is desirable not to perform heat treatment after cold rolling.
The etching step can be performed by electrolytic etching or electroless etching using an electrolytic solution mainly composed of hydrochloric acid or an electrolytic solution not containing hydrochloric acid (1000 ppm or less). In terms of cost, electroless etching is advantageous.
In the etching process, the pits are uniformly formed with high density, and a high roughening rate can be obtained without generating an unetched portion. This foil is subjected to a chemical conversion treatment to obtain a required withstand voltage, and then a capacitor having a high capacitance is obtained by incorporating it as an electrode in an electrolytic capacitor by a conventional method. In the present invention, the chemical conversion treatment method is not particularly limited.

  The present invention is preferably used as a cathode of an electrolytic capacitor. However, the present invention is not limited to this, and for example, it can also be used as an anode of an electrolytic capacitor having a low formation voltage.

Next, examples of the present invention will be described.
In the composition shown in Table 1 (the balance Al and other impurities), an aluminum alloy ingot was melted by a conventional method, and the aluminum alloy ingot was homogenized at 560 ° C. for 6 hours. The ingot is soaked at 530 ° C. for 4 hours, finished to a thickness of 7 mm by hot rolling, then cold-rolled at the reduction shown in Table 1, and then subjected to intermediate annealing under the conditions shown in Table 1. Went. Thereafter, cold rolling was performed to a final plate thickness of 50 μm to obtain a test material.

The above test materials
First stage: 6M-HCl + 0.5M-H ₃ PO ₄ , 50 ° C. × 60 sec
Second stage: 2M-HCl + 1.5M-H ₃ PO ₄ , 40 ° C. × 180 sec
After performing the etching process under the conditions of 3V in the ammonium adipate solution at 85 ° C., the capacitance was measured. The electrostatic capacity is the test material No. The relative evaluation was performed with a capacitance of 1 as 100. These results are shown in Table 1.
As is clear from Table 1, the test material of the present invention has high capacitance and high strength. On the other hand, the comparative example is inferior to the material of the present invention in terms of both capacitance and strength because any one of the composition, the rolling reduction before intermediate annealing, and the temperature conditions of intermediate annealing are out of the scope of the invention.

It is a flowchart which shows the process order in one Embodiment of this invention.

Claims (2)

  A composition containing, by mass%, Si: 0.01 to 0.30%, Fe: 0.01 to 0.30%, Ni: 0.0051 to 0.05%, and the balance consisting of Al and inevitable impurities An electrolytic capacitor characterized by subjecting a rolled aluminum alloy material having a sheet thickness of 75% or more and less than 98% to a rolling reduction in cold rolling after hot rolling to 300 ° C to 500 ° C intermediate annealing. Manufacturing method of aluminum foil for electrodes.   In terms of mass%, Si: 0.01 to 0.30%, Fe: 0.01 to 0.30%, Ni: 0.0051 to 0.05%, and at least one of Zn, Sn, In, and Ga A thickness of 0.0030 to 0.10% in total including seeds, the balance having a composition consisting of Al and inevitable impurities, and a reduction ratio in cold rolling after hot rolling of 75% or more and less than 98% A method for producing an aluminum foil for electrolytic capacitor electrodes, comprising subjecting an aluminum alloy rolled material having an intermediate annealing temperature of 300 ° C. to 500 ° C.

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