JPS5992517A - Method of producing aluminum electrode foil for electrolyticcondenser - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing aluminum electrode foil for electrolytic capacitors.

Structures of conventional examples and their problems In general, aluminum electrode foils for electrolytic capacitors are manufactured by subjecting rolled hard aluminum foils or annealed soft aluminum foils to chemical or chloride-containing aqueous solutions containing chlorine ions, such as sodium chloride or hydrochloric acid. Vanes are manufactured by electrochemically etching the aluminum foil to enlarge its surface area, and then applying a chemical conversion treatment to form a dielectric oxide film on the surface.

Since the capacitance of an aluminum electrode foil for an electrolytic capacitor is approximately proportional to the surface area of the aluminum foil, the larger the surface area expansion rate, the more desirable.

The surface area expansion rate of the aluminum foil due to this etching increases in proportion to the amount of etching, but beyond a certain limit, the increase slows down and eventually shows a tendency to decrease. Also,
The mechanical strength of the aluminum foil decreases with the amount of etching, so if the aluminum foil is excessively etched, there is a risk that it will break during electrolytic capacitor manufacturing processes such as etching and chemical 2 assembly. For these reasons, the optimum amount of etching is determined so that the aluminum foil has enough mechanical strength to prevent breakage during the manufacturing process of electrolytic capacitors and has as large a surface area expansion ratio as possible.

On the other hand, it is desired that aluminum electrolytic capacitors be made smaller and have a larger capacity.Currently, aluminum electrodes with sufficient mechanical strength and a certain amount of etching have a larger surface area expansion ratio. Foil is highly sought after and much research is being conducted.

OBJECTS OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a method for manufacturing aluminum foil for electrolytic capacitors having a higher surface area ratio than the conventional method.

Structure of the Invention The method for producing aluminum foil for electrolytic capacitors of the present invention is to apply oxygen ions to aluminum foil at 6×1 level before etching.
011~5 X 10'''/crl After ion implantation, heat treatment is performed in a temperature range of 200'C or less, and then,
Etching is carried out chemically or electrochemically in an aqueous solution containing chlorine ions. That is, after performing the above etching, a dielectric conversion film is further formed by chemical conversion treatment, so that it has sufficient mechanical strength.
It is possible to manufacture an aluminum electrode foil for an electrolytic capacitor that has a larger capacitance per unit area than conventional ones.

As mentioned above, when aluminum foil for electrolytic capacitor anodes contains chlorine ions, it is chemically or electrochemically etched in a solution to increase its surface area and is chemically converted before use. The rate depends on many factors such as the rolling process of the aluminum foil, annealing, the amount of impurities in the aluminum foil, the composition of the etching solution, and the electrolytic conditions.

Etching of aluminum in an aqueous solution containing chlorine ions begins with etch pit nuclei where chlorine ions are adsorbed on the surface, and as etching progresses, corrosion of the aluminum foil occurs internally in the form of pitting corrosion, and the surface area gradually expands. . These chlorine ions preferentially adsorb to weak points in the surface oxide film due to impurities or dislocations caused by rolling, etc., forming etch pit nuclei, and further etching progresses along the dislocations, expanding the surface area. Therefore, a larger surface area expansion has more of this dislocation;
It is necessary that it is uniformly dispersed.

Ion implantation of oxygen atoms into aluminum foil
(-Di) has the effect of straining the crystal lattice, increasing and uniformizing dislocations, and forming an aluminum oxide film uniformly on the surface.In general, aluminum foil for electrolytic capacitors is made of aluminum with a small number of Mixed with seed impurities, melted, cast and rolled.

Manufactured through processes such as annealing. The contained impurities mainly precipitate near the surface, but segregation is likely to occur and uniform dispersion is difficult to obtain. For this reason, dislocations are also non-uniformly distributed. This can be seen from the presence of overcrowded and depopulated areas in the etch pit due to etching.

The ion implantation of the present invention allows more dislocations in the aluminum foil to be dispersed uniformly, and the implanted oxygen ions form an oxide film layer uniformly on the aluminum surface, making etch pits more uniform. generate,
Expansion of surface area can be measured. The lower limit of the ion implantation amount is the minimum amount at which the effect of enlarging the surface area by etching is recognized, and the upper limit is the maximum amount limited by the adverse effect on the effect of enlarging the surface area due to the concentration of etch pits. In other words, the present invention has an ion implantation amount of 5×10” to 6×101
The effect of increasing the surface area is shown within the range of 3 ions/Ca, and when the ion implantation amount is less than the lower limit, no effect on etching is observed, and when it exceeds the upper limit, the surface area expansion rate decreases.

After ion implantation, heat treatment is performed at a temperature of 200° C. or less, but if the heat treatment temperature exceeds 200° C., the surface area expansion rate decreases, which is not preferable.

The subsequent etching is carried out in an aqueous solution containing chlorine ions, as in the past, and is usually etched by a predetermined amount in an aqueous solution such as di-salt hydrochloric acid at a current density of 0.1 to 1 A/ct/I at a temperature of 60 to 90°C. be done. Further, the chemical conversion treatment is also performed in the same manner as in the conventional method. Note that, depending on the type of foil and the condition of the foil, mechanical processing such as rolling or stretching may be performed between the above heat treatment and the subsequent etching.

The aluminum electrode foil for electrolytic capacitors obtained by the present invention has mechanical strength and tan δ comparable to those of conventional ones, a large capacitance per unit area, and a small leakage current. Enables smaller size and larger capacity aluminum 7 page nium electrolytic capacitors.

Description of examples The present invention will be explained below based on examples.

Oxygen ions were implanted at 1010 to 1016/Ca ions onto both sides of a high purity aluminum foil sample with a purity of 99.99% and a thickness of 100μ. Next, this sample was heat-treated for 60 minutes at a temperature range of room temperature to 550°C, and then etched in a 20% by weight saline solution at a temperature of 90°C, a current density of o, and a5A/crtl for 4 minutes to form an etched area of 1 cm x 1.
crn), and further at a temperature of 80°C in an aqueous solution containing 1 part by weight of boric acid.
, the chemical formation was carried out under the conditions of a formation voltage of 23V. The capacitance, tanδ, and leakage current of the obtained chemically formed foil were measured.

The following table shows the amount of etching during etching, the capacitance tan δ after chemical formation, and the leakage current. In addition, the measurement is 6wt%
Sn foil was used as a cathode in an ammonium borate aqueous solution of 30
It was carried out at 120 Hz with an AC bridge at a temperature of .degree.

Furthermore, since the amount of etching has a close correlation with the surface area expansion ratio 2 mechanical strength, it is shown as reference data for comparison at a constant amount of etching.

(blank space below) 9 vanes゛] ] Kotsusunto] ] Description] As is clear from the table above on page 10, by implanting oxygen ions into aluminum foil, the effective surface area expansion rate during etching is improved, and the unit An aluminum electrode foil for an electrolytic capacitor having a large capacitance per area, a small leakage current, and the same mechanical strength as conventional aluminum foils can be obtained.

Effects of the Invention As described above, the method of manufacturing aluminum electrode foil for electrolytic capacitors according to the present invention involves implanting oxygen ions into the aluminum foil before etching, and then chemically or electrochemically implanting the aluminum foil in an aqueous solution containing chlorine ions. The aluminum electrode foil for electrolytic capacitors obtained by this method has the same mechanical strength as conventional foils, and has a higher capacitance per unit area than conventional foils. Moreover, since leakage current can be reduced, aluminum electrolytic capacitors can be made smaller and have larger capacities, which is extremely effective in practice.

Claims (1)

[Claims] Oxygen ions on aluminum foil from 6 x 1011 to 6 x 10
An aluminum electrode foil for an electrolytic capacitor, which is characterized in that after implanting 13 ions/cl ions, it is heat treated in a temperature range of 200'C or less, and then chemically or electrochemically etched in an aqueous solution containing chloride ions. Production method.