JPH0377651B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD This invention relates to a method for manufacturing a cathode material for an electrolytic capacitor. In this specification, the term aluminum includes not only pure aluminum but also aluminum alloys. Prior Art Conventionally, cathode materials for electrolytic capacitors have been manufactured by etching aluminum foil to increase its surface area. Problems to be Solved by the Invention However, with conventional cathode materials, there has been a problem in that the performance as a cathode material, mainly in capacitance, varies depending on the material of the aluminum foil, heat treatment conditions, etching conditions, etc. Furthermore, since etching is a wet process, there is a problem in waste liquid treatment, which requires treatment equipment, which increases costs and makes the work troublesome. Therefore, the present applicant has developed a method for manufacturing aluminum foil for electrolytic capacitors, in which the surface of the aluminum foil is first roughened by etching, and then aluminum of higher purity than the aluminum foil is vapor-deposited on the rough surface in vacuum. proposed. however,
This method also includes an etching process, so
The above-mentioned problems with performing the etching process still exist. Furthermore, if aluminum is deposited in vacuum after the surface has been roughened by etching, the rough surface of the aluminum foil will be smoothed and the effect of increasing the surface area will be reduced. This invention solves the above-mentioned problems at once, and provides a method for manufacturing a cathode material for electrolytic capacitors that has less variation in performance such as capacitance, is low in cost, and has a porous surface with a significantly increased surface area. The purpose is to provide Means for Solving the Problems The method for producing a cathode material for an electrolytic capacitor of the present invention involves depositing a conductive metal having a higher dielectric constant than the aluminum foil on the surface of the aluminum foil. The distance to the evaporation source containing a reactive metal is 10 to 100 cm, and the evaporation rate is 10 to 5000 Å/in an inert gas atmosphere.
It is characterized by being deposited at sec. In the above, conductive metals with higher permittivity than aluminum foil include Au, Ag, Ti, Cr, Zn,
Al, Si, Ge, Co, Sn, Ta, Fe, Cu, Pb, Ni,
Bi, Mn, etc. or their alloys are used, but
Among them, Au, Ag, Ti, and Cr are representative. Methods for forming a deposited film include an ion plating method and a vacuum deposition method. Formation of the vapor deposited film should be performed in an inert gas atmosphere such as argon or helium. When a deposited film is formed in an inert gas atmosphere, metal vapor can be scattered and the size of deposited crystals can be reduced. Therefore, the obtained vapor-deposited film becomes porous, and fine recesses are uniformly and densely formed on its surface, expanding the surface area of the cathode material and increasing the capacitance. When a conductive metal with a higher dielectric constant than the aluminum foil is evaporated onto the aluminum foil, the distance between the aluminum foil and the evaporation source containing the above-mentioned highly conductive metal should be 10 to 100 cm. , The reason is as follows. That is,
If the above distance is less than 10cm, the aluminum foil will be too close to the evaporation source, and there is a risk that the aluminum foil will melt due to the heat generated during evaporation of the metal, and the aluminum foil will become hot, causing the surface of the aluminum foil to This is because the metal substance constituted by the evaporated particles that have arrived will melt and spread, preventing the evaporated film from becoming porous, and if the thickness exceeds 100 cm, the film formation efficiency will deteriorate. Further, the deposition rate should be 10 to 5000 Å/sec, and the reason is as follows. That is,
If it is less than 10Å/sec, productivity will be poor, and if it is less than 5000Å/sec,
To exceed sec, it is necessary to heat the conductive metal to a considerably high temperature, so there is a risk that the aluminum foil will melt due to the heating when the metal is evaporated, and the aluminum foil will become hot enough to reach the surface of the aluminum foil. This is because the metal substance formed by the evaporated particles will not melt and spread and the evaporated film will not become porous. Examples Next, examples of the present invention will be shown together with comparative examples. Example: A 0.1 mm thick surface with a cleaned surface was placed on the top of a vacuum chamber maintained at an argon gas pressure of 9×10 ^-4 Torr.
An aluminum foil made of A1100-H was placed. On the other hand, an evaporation source containing an evaporation substance made of tin was placed in the lower part of the vacuum chamber and below the aluminum foil. The distance between the aluminum foil and the evaporation source was 25 cm. Then, by ion plating, a 1.0 μm thick vapor deposition film of tin was formed on the surface of the aluminum foil at a vapor deposition rate of 1000 Å/sec. In this way, a cathode material was obtained in which a vapor-deposited tin film was formed on the surface of an aluminum foil. Fine depressions were uniformly and densely formed on the surface of this deposited film. Comparative example: Aluminum foil with a purity of 99.8wt% and a thickness of 0.1mm,
A cathode material was obtained by etching in a 2 wt % hydrochloric acid solution at a liquid temperature of 60° C. at a current density of DC 20 A/50 cm ² for 300 seconds. The capacitances of the two types of cathode materials obtained as described above were each measured in a 10 wt % ammonium borate solution at a liquid temperature of 30°C. The results are summarized in the table below.

[Table] As is clear from the above results, the electrolytic capacitor cathode material produced by the method of the present invention has a larger capacitance than conventional cathode materials. Effects of the Invention According to the method for producing a cathode material for an electrolytic capacitor of the present invention, when depositing a conductive metal having a higher dielectric constant than the aluminum foil on the surface of the aluminum foil, the aluminum foil and the conductive metal are provided. The distance to the evaporation source is 10 to 100 cm.
Deposition rate 10-5000 in inert gas atmosphere
Because the vapor deposition is performed at a rate of Å/sec, the resulting vapor-deposited film made of conductive metal becomes porous, with fine depressions uniformly and densely formed on its surface, which improves the quality of the produced cathode material. surface area increases significantly. Further, according to the method of the present invention, a conductive metal vapor deposition film having a large dielectric constant can be formed on the surface of the aluminum foil, regardless of the material of the aluminum foil. Therefore, together with the surface area increasing effect, the capacitance of the produced cathode material increases significantly. Moreover,
The produced cathode materials are free from variations in performance, primarily capacitance. Furthermore, by appropriately selecting the material of the aluminum foil, the mechanical strength of the resulting cathode material can be increased. Further, since there is no need to perform etching treatment as in the conventional method, there is no problem of waste liquid treatment, resulting in lower costs and easier work.

Claims (1)

[Claims] 1. When depositing a conductive metal with a higher dielectric constant than the aluminum foil on the surface of the aluminum foil, the distance between the aluminum foil and the evaporation source containing the conductive metal is set at 10 to 100 cm, and an inert gas atmosphere is set. In the middle, the deposition rate is 10~5000Å/
A method for producing a cathode material for an electrolytic capacitor, characterized by vapor deposition using sec.