JPH0379859B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD This invention relates to a method of manufacturing an aluminum electrode material for an electrolytic capacitor. BACKGROUND ART Aluminum foil used as an aluminum electrode material for electrolytic capacitors is required to have as large a surface area as possible and a large capacitance per unit volume. For this reason, the effective surface area of the aluminum foil is generally expanded by electrochemical or chemical etching treatment, and etching holes are also added to increase the area expansion ratio as much as possible. In order to make the foil thicker, deeper, and thicker, various studies are being conducted, including improving materials, improving etching methods, and researching the manufacturing process of foil. Problems to be Solved by the Invention However, in practice, in the conventionally known etching techniques, the locations where etching holes are generated are generally uneven, and when attempting to increase the number of etching holes, the etching holes communicate with each other, resulting in coarse holes. If this occurs, the surface of the aluminum foil will melt at the same time, which will not only impair the mechanical strength of the foil, but also cause defects such as the etching holes not being deep, so the results are not as expected. There was a problem in that it was difficult to obtain the effect of increasing the area expansion ratio. In particular, regarding the non-uniformity of the location where etching holes occur, uneven etching pits are generated during etching due to the segregation of impurity atoms contained in the aluminum foil, the presence of intermetallic compounds, crystal grain agglomerates, etc. This was difficult to avoid. The present invention solves these problems and makes it possible to uniformly form a large number of deep etched holes while maintaining the necessary mechanical strength in aluminum foil, and has an excellent surface area ratio, that is, capacitance. The purpose of this work was to obtain an aluminum electrode material for electrolytic capacitors that could be used as an aluminum electrode material for electrolytic capacitors. Means for Solving the Problems For this purpose, the present invention applies a coating material mixed with metal or non-metal fine particles to the surface of an aluminum foil, and then removes the fine particles, thereby applying an electrolytic etching solution to the foil surface. It is characterized by integrally depositing a resistant film with a large number of micropores that are resistant to etching nuclei and that form etching nuclei, thereby eliminating intermetallic compounds in the material, Regardless of the presence of crystal grain agglomerates, etc., it is possible to predetermine the location where etching holes will occur and erode only the portion of the aluminum foil that corresponds to the micropores during the etching process, thereby making it possible to uniformly form a large number of deep etching holes. The electrode material was successfully manufactured. The fine particles mixed into the coating material may be either metal fine particles or non-metal fine particles,
Alternatively, it may be a mixture of these. Examples of the metal elements constituting the metal fine particles include Fe,
Co, Ag, Au, V, Mn, Cd, In, Sn, Sb, Pb,
Bi etc. can be given. On the other hand, non-metallic fine particles include C fine particles, but are not limited to elemental fine particles, and can also be fine particles of organic water-soluble polymeric materials such as acrylic, polyester, and epoxy resins. good. These fine particles are dissolved and removed by subsequent processing to form fine pores for forming etching nuclei. Therefore, the arrangement, size, quantity, etc. of the fine particles are different from those of the fine pores, that is, the etching holes. The quantity directly affects the final capacitance, mechanical strength, etc. of the aluminum foil. From this point of view, it is desirable that the blending ratio of fine particles to the coating material be in the range of about 5 to 80% by volume, with a particularly preferable range of 30 to 50%, and the size of the fine particles is 0.01 μm in diameter.
Can be selected in the range of ~ several μm, especially 1 μm
It is preferable to set it as approximately. In order to uniformly generate etching holes, it is necessary to uniformly disperse such fine particles in the coating material. An example of the coating material is a commercially available resist agent for semiconductor photomasks. Next, to explain the manufacturing process, firstly, the coating material containing the above-mentioned large number of fine particles is
Apply a thin layer to the surface of 99.90-99.99% aluminum foil. The coating thickness of the coating material needs to be such that all the particles are not completely buried in the coating material, and should be determined depending on the size of the particles. This is because the fine particles are brought into direct contact with the solution etc. during the fine particle removal treatment in the next step. As a coating method that satisfies such requirements, a roll coating method, a spin coating method, or the like can be adopted. Next, after drying, the fine particles are removed. This removal treatment is most commonly carried out by bringing the coated surface of the coating material into contact with a dissolving solution to dissolve and remove it. As the dissolving liquid, it is sufficient as long as it can dissolve and remove the fine particles, and acids, alkalis, water, etc. can be used as appropriate in combination with the fine particles.
The degree of dissolution and removal does not necessarily mean that the fine particles are completely eliminated, but may be partially dissolved as long as they can serve as starting points for etching during the etching process. After the fine particles are dissolved and removed, the formation of a film having a large number of micropores for forming etching nuclei on the surface of the aluminum foil is completed. As is clear from the above explanation, such a film is intended to prevent corrosion of the aluminum foil surface during etching, except for the areas corresponding to the micropores, and therefore, it must be resistant in nature, i.e. , provided that it is insoluble and corrosion resistant. The electrode material according to the present invention manufactured in this way includes:
Thereafter, an electrochemical or chemical etching treatment is performed in an acid or alkaline bath. The etching solution used in the etching process is not particularly limited, and a known 2 to 15% hydrochloric acid aqueous solution, or an aqueous solution in which an acid such as chromic acid, sulfuric acid, or oxalic acid is further added to the solution, etc. can be arbitrarily selected. Can be used. All other etching processing conditions, ie, liquid temperature, current density, etching time, etc., may also be employed as conventionally known etching processing conditions. By this etching treatment, while suppressing surface dissolution of the portion of the aluminum foil to which the resistant coating is attached, it is possible to intensively erode only the portions corresponding to the micropores, thereby making it possible to form deep and thick etching holes. After the etching process, the aluminum foil is
Subsequently, the resistant film adhering to the foil surface is removed by immersing it in an alkaline solution such as a few percent Na or OH solution. Effects of the Invention As explained above, according to the present invention, a coating material mixed with metal or non-metal fine particles is applied to the surface of the aluminum foil, and then the fine particles are removed, thereby forming a large number of fine pores on the surface of the aluminum foil. As a result of being able to manufacture an aluminum electrode material on which a uniformly resistant film is integrally deposited, during the subsequent etching treatment applied to the electrode material, surface dissolution of the resistant film-attached portion of the aluminum foil is performed on the film layer. Therefore, while suppressing the etching, it is possible to intensively erode only the portions corresponding to the micropores as etching nuclei. Therefore, as a result,
It is possible to uniformly form a large number of deep and thick etching holes in aluminum foil regardless of the presence of intermetallic compounds, crystal grain agglomerates, etc., and to achieve a significantly high area ratio without compromising mechanical strength. This makes it possible to provide an ideal aluminum electrode material with extremely high capacitance and excellent electrical properties. Examples Next, examples of the present invention will be shown in comparison with comparative examples. Cu microparticles and NaCl microparticles with an average particle size of 1 μm were mixed at a volume ratio of 40% into a commercially available photoresist agent whose main component was dichromic acid/hydrophilic polymer liquid, and after thorough stirring, a thickness of 100 μm was obtained. purity
A thin layer was applied to the surface of each 99.99% annealed aluminum foil by roll coating. After that, for aluminum foil coated with resist containing Cu fine particles (sample No. 1), 5% HCl was applied.
On the other hand, by immersing it in an aqueous solution for about 30 seconds.
The aluminum foil coated with a resist containing NaCl fine particles (sample No. 2) was washed with pure water to dissolve and remove the Cu and NaOH fine particles, and the aluminum foil had many fine pores on its surface. An electrode material according to the present invention on which a film was formed was obtained. After washing and drying, each electrode material was subjected to pre-electrolytic etching using an etching solution: 5wt% hydrochloric acid aqueous solution, temperature: 80°C, DC current density: 20A/dm ² , etching time: 2 minutes, followed by the same etching process. After performing post-electrolytic etching under the conditions of liquid composition, same temperature, DC current density: 5A/dm ² and etching time of 10 minutes, the film was removed by immersion in a 5wt% sodium hydroxide aqueous solution at 25℃ for 2 seconds. I processed it. The etched foil obtained above was placed in a boric acid bath.
After converting to 380V, the capacitance of the foil was measured. On the other hand, this result was compared with that of an aluminum foil (comparative example) in which the same aluminum material as above was used and only etching was performed under the same etching conditions. The results were as shown in the table below.

[Table] As shown in the results in the above table, according to the present invention, only the portions corresponding to the many micropores uniformly provided in the resistant coating of the aluminum foil can be deeply eroded as etching nuclei. , it can be seen that it can be made to have a larger capacitance and excellent electrical characteristics than the comparative example.

Claims (1)

[Claims] 1. A coating material containing metal or non-metal fine particles is applied to the surface of the aluminum foil, and then the fine particles are removed, thereby making the foil surface resistant to electrolytic etching solution. A method for manufacturing an aluminum electrode material for an electrolytic capacitor, which comprises integrally depositing a resistant film having a large number of micropores to form etching nuclei. 2. The method for manufacturing an aluminum electrode material for an electrolytic capacitor according to claim 1, wherein the step of removing the fine particles is carried out by bringing the coated surface of the coating material into contact with a dissolving solution to dissolve and remove the particles.