JP4565475B2 - Electrolytic capacitor electrode manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing an electrode for an electrolytic capacitor using an aluminum foil that is easily dissolved uniformly during etching.
[0002]
[Prior art]
Aluminum foil is used in various applications, and is particularly suitable for use in etching treatment. Specifically, it is suitably used for electrolytic capacitor electrodes and circuit formation of printed wiring boards. When applied to electrolytic capacitor electrodes, by applying direct current or alternating current etching to the aluminum foil, a large number of etching pits are formed on the surface of the aluminum foil, the surface area of the aluminum foil is enlarged, and an electrode having a high capacitance Get the foil. In addition, when applied to the circuit formation of a printed wiring board, an aluminum foil 2 is bonded onto the substrate 1, masking 3 having a predetermined shape is applied to the surface of the aluminum foil 2, and then an etching process is performed to form a non-masking portion. The aluminum foil 2 exposed in 4 is dissolved and removed to obtain a printed wiring board having a circuit matching the shape of the masking 3.
[0003]
As described above, it is of course important to be able to etch uniformly in applications where etching is performed. For example, in an electrode for an electrolytic capacitor, the electrostatic capacity is insufficient at a non-uniformly etched portion. In the case of a printed wiring board, the aluminum foil is not sufficiently dissolved and removed at a portion to be dissolved and removed, and there is a possibility that the circuit is short-circuited.
[0004]
For this reason, various aluminum foils that can be etched uniformly have been developed. For example, the elemental composition of the aluminum foil is devised, or the rolling method or the annealing method in the manufacturing process of the aluminum foil is devised. By such a device, an aluminum foil that can be etched uniformly is generally obtained. However, there has been a case where an aluminum foil having a portion (an unetched portion) that is hardly etched is obtained completely or accidentally. For example, even if an aluminum foil is obtained by the same method, there is a case where an unetched portion is not found in one lot but an unetched portion is found in another lot.
[0005]
[Problems to be solved by the invention]
Therefore, the present inventors have studied why such an unetched portion occurs. However, it has been found that such an unetched portion occurs in the state shown in FIG. 1 and has the following characteristics. (I) The size of each unetched portion 5, that is, the size of each unetched portion 5 varies, but most of them have a diameter in the range of 50 μm to 1 mm. (Ii) Most unetched portions 5 have unetched portions 5 of almost the same size on the corresponding back surface. (Iii) The unetched portions 5 are generated at regular intervals. (Iv) The unetched part can be visually confirmed and is glossy (since it is not etched, it has the original gloss). However, as described above, the characteristic points are known to some extent, but the cause has not been clarified at all.
[0006]
However, when the present inventors analyzed the elemental composition of the unetched part, it was found that a large amount of elements other than aluminum (for example, copper or iron) were present.
Accordingly, it has been found that the unetched portion is generated due to the inclusion of copper or iron in the aluminum foil. However, elements such as copper and iron exist in the production environment of aluminum foil, and it is practically difficult to completely prevent the contamination. For example, in the rolling process of aluminum foil, a steel roll or the like is used, and iron powder due to wear of this roll adheres to the surface of the aluminum foil, and in the cleaning process, copper and iron are present in the liquid. It adheres to the aluminum foil surface. Furthermore, copper and iron adhering to the operator may adhere to the surface of the aluminum foil.
[0007]
As a result of further investigations, the present inventors have found that an unetched portion is limited to a case where copper powder or iron powder having a certain size or more adheres to the surface of the aluminum foil. The present invention has been made based on such knowledge.
[0008]
[Means for Solving the Problems]
That is, the present invention, homogenization, hot rolling, cold rolling, intermediate annealing, final cold rolling, upon the production of aluminum foil subjected to final annealing at washing and a temperature 500 ° C. or higher, the final cold rolling The rolling oil sometimes applied is filtered with a filter capable of removing foreign matters of 5 μm or more, and the cleaning liquid applied at the time of cleaning is filtered with a filter capable of removing foreign matters of 5 μm or more. The present invention relates to a method for producing an electrode for an electrolytic capacitor in which an aluminum foil having a homogeneous etching property in which copper powder or iron powder having a diameter of 5 μm or more is not present on the surface is etched .
[0009]
The aluminum foil used in the present invention is generally a high-purity aluminum foil having an aluminum purity of 99.9% by weight or more. If the aluminum purity is less than 99.9% by weight, the amount of impurities becomes excessive, and when obtaining an electrode foil for an electrolytic capacitor, over-dissolution tends to occur during etching, and the surface area of the aluminum foil cannot be increased. It is not preferable.
[0010]
Moreover, the aluminum foil used with the manufacturing method of the electrode for electrolytic capacitors which concerns on this invention is finally annealed at the temperature of 500 degreeC or more at the final stage of the manufacture . When the final annealing is performed at a temperature of less than 500 ° C., even if copper powder or iron powder adheres to the surface of the aluminum foil, the copper powder or iron powder element hardly diffuses into the aluminum foil, and the copper powder or iron powder. Is only on the surface of the aluminum foil and is detached from the surface of the aluminum foil at the time of etching, so that an unetched portion does not occur. That is, when the final annealing is performed at a temperature of 500 ° C. or more, the copper powder or iron powder elements adhering to the surface of the aluminum foil are diffused and alloyed in the aluminum foil and remain as they are during the etching. Is formed. The final annealing temperature is generally 500 to 580 ° C.
[0011]
The method according to the present invention, the aluminum foil surface to be employed, its size has the greatest feature in that there is no more copper powder or iron powder diameter 5 [mu] m. Even if copper powder or iron powder having a diameter of less than 5 μm adheres, it is easily dissolved under etching conditions for obtaining an electrode foil for electrolytic capacitors, and an unetched portion does not occur. Moreover, even if an etching failure portion that does not correspond to the unetched portion of (i) to (iv) above occurs, the gloss cannot be confirmed on the appearance and the range is narrow, so that it is acceptable. It is. In the present invention, the meaning that there is no copper powder or iron powder having a diameter of 5 μm or more means that none of the aluminum powder is present in the aluminum foil coil (having a winding length of several m to several thousand m).
[0012]
In addition, in this invention, the diameter of copper powder or iron powder measures the circumference of the copper powder or iron powder of arbitrary forms, and remove | divides it by the circumference ratio ((pi)).
[0013]
In the present invention, the reason for limiting to copper powder or iron powder is that copper or iron is an element that causes an unetched portion. Even if elements other than copper and iron adhere to the surface of the aluminum foil, it is difficult to produce an unetched portion.
[0014]
The method for manufacturing an electrode for an electrolytic capacitor according to the present invention is to prevent copper powder or iron powder having a predetermined size or more from adhering to the surface of the aluminum foil before the final annealing of the aluminum foil. Even if copper powder or iron powder adheres after the final annealing, they do not adhere firmly to the surface of the aluminum foil, so they are easily detached during etching. However, if copper powder or iron powder of a predetermined size or more adheres before the final annealing, it adheres firmly to the surface of the aluminum foil by the final annealing and will not be detached even during etching.
[0015]
In order to prevent copper powder or iron powder having a predetermined size or more from adhering to the surface of the aluminum foil before the final annealing, it is preferable to employ a specific means mainly in the following steps . That is, a specific means is adopted in the slit process, the cleaning process, and the rolling process before the final annealing process. Specific means include filtration of rolling oil used in the rolling process, filtration of cleaning liquid used in the cleaning process, cleaning of slit blades used in the slit process, cleaning of rolls used in each process, and the like. Among these, since rolling oil is applied directly to the surface of the aluminum foil, the filtration is essential . Specifically, it is essential to filter the rolling oil using a filter that can remove foreign matters of 5 μm or more. In particular , the rolling oil is passed through a filter equipped with a filter capable of removing foreign matters of 25 μm or more, and after removing large foreign matters, the rolling oil is further passed through a filter equipped with a filter capable of removing foreign matters of 5 μm or more, Thereafter, this rolling oil is preferably applied to the surface of the aluminum foil.
[0016]
Further, since the cleaning liquid is also directly applied to the surface of the aluminum foil by means such as immersion or spraying, this filtration is also essential . This filtration may be performed in the same manner as in the case of rolling oil. Further, in the cleaning process, it is preferable to devise the composition of the cleaning liquid or to use brushing of the aluminum foil surface so that copper powder or iron powder of 5 μm or more is removed as much as possible. Cleaning of slit blades and rolls has been performed conventionally, but it is preferable to make the cleaning standard more strict or to provide an accessory device that is always automatically cleaned.
[0017]
The aluminum foil obtained as described above is used as an electrode for an electrolytic capacitor having an increased capacitance by increasing the surface area of the surface of the aluminum foil by etching.
[0018]
【Example】
EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited to an Example. The present invention is a special means based on the knowledge that, when a copper powder or iron powder of 5 μm or more adheres to the surface of the aluminum foil before the final annealing performed at 500 ° C. or more, an unetched portion appears in appearance. Should be construed as having characteristics in that such copper powder or iron powder is prevented from adhering .
[0019]
Example 1
An aluminum ingot having an aluminum purity of 99.99% was prepared. The ingot was subjected to homogenization treatment, hot rolling, cold rolling and intermediate annealing to obtain an aluminum plate having a thickness of 0.5 mm. Thereafter, final cold rolling was performed to obtain an aluminum foil having a thickness of 0.1 mm. In the final cold rolling step, the rolling oil applied to the aluminum plate was filtered with a filter capable of removing foreign matters of 5 μm or more. And after spraying the washing | cleaning liquid of 3% sodium hydroxide aqueous solution on the aluminum foil surface, it wash | cleaned, brushing the surface. At this time, the cleaning liquid used was filtered through a filter capable of removing foreign matters of 5 μm or more. Thereafter, the aluminum foil was wound to form a coil, and final annealing was performed in an argon gas atmosphere at a temperature of 550 ° C. and a holding time of 7 hours. As described above, an aluminum foil having homogeneous etching properties was obtained.
[0020]
Example 2
An aluminum foil having homogeneous etching properties was obtained in the same manner as in Example 1 except that methacrylene was used in place of the 3% aqueous sodium hydroxide solution as the cleaning liquid.
[0021]
Comparative Example 1
An aluminum foil was obtained in the same manner as in Example 1 except that the washing process was not performed.
[0022]
Comparative Example 2
An aluminum foil was obtained in the same manner as in Example 2 except that brushing was not used.
[0023]
Each aluminum foil obtained in Examples 1 and 2 and Comparative Examples 1 and 2 was etched under the following conditions. First, each aluminum foil was pretreated by being immersed in a 0.1% NaOH aqueous solution at 40 ° C. for 30 seconds. Thereafter, the aluminum foil is immersed in an aqueous solution of 4.4 molar HCl + 0.76 molar H ₂ SO ₄ +0.28 molar AlCl ₃ .6H ₂ O (+0.1 millimolar Cu ²⁺ ) at 85 ° C. An initial pit formation process was performed for 1 minute. Next, the substrate was immersed in a 1 molar HCl + 3 molar H ₂ SO ₄ aqueous solution at 75 ° C. for 10 seconds, and then subjected to electrolytic etching for 1 minute at a current density of 0.2 A / cm ² to complete the etching process. The molar concentration in the aqueous solution means mol / l.
[0024]
As a result, in the aluminum foil having homogeneous etching properties obtained in Examples 1 and 2, no unetched portion was generated. On the other hand, in the aluminum foils obtained in Comparative Examples 1 and 2, unetched portions were generated at a rate of 1 piece per 2 m in the longitudinal direction of the aluminum foil.
[0025]
[Operation and effect of the invention]
The aluminum foil having homogeneous etching properties used in the present invention does not have copper powder or iron powder having a diameter of 5 μm or more on the surface thereof, and therefore, when etched, no unetched portion is generated. Therefore, the homogeneity etching property for electrolytic capacitors was obtained aluminum foil is etched electrode with, because there is no non-etched portion having a gloss, homogeneous that it is etched in appearance can be easily confirmed, It has a particularly remarkable effect that it can be used with confidence.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view showing an example in which an unetched portion is generated in an aluminum foil.
FIG. 2 is a schematic side view showing a state where masking is performed when a printed wiring board is formed using an aluminum foil.
[Explanation of symbols]
1 Substrate 2 Aluminum foil 3 Masking 4 Non-masking part 5 Unetched part

Claims (1)

Homogenization, hot rolling, cold rolling, intermediate annealing, final cold rolling, upon the cleaning and the temperature 500 ° C. or more is subjected to final annealing to produce an aluminum foil, rolling oil applied during the final cold rolling The surface is characterized by being filtered with a filter capable of removing foreign matters of 5 μm or more, and the cleaning liquid applied at the time of washing is filtered with a filter capable of removing foreign matters of 5 μm or more. The manufacturing method of the electrode for electrolytic capacitors which etches the aluminum foil which has the homogeneous etching property in which copper powder or iron powder with a diameter of 5 micrometers or more does not exist.

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