JPH01309938A - Aluminum alloy foil for cathode of electrolytic capacitor - Google Patents

Abstract

PURPOSE:To manufacture the subject alloy foil having extremely excellent etching characteristics by incorporating specific amt. of misch metal into high purity Al. CONSTITUTION:Misch metal, 0.005-0.1%, by weight, is incorporated into Al having >=99.7% purity (preferably about 99.8-99.9%) to prepare Al alloy foil for a cathode of an electrolytic condenser. Inevitable impurities are naturally incorporated into the Al alloy foil as well: various elements of Fe, Cu, Zn, Mn, Si, etc., about 0.00001-0.29%, may forcedly be added thereto. When the Al alloy foil is subjected to etching treatment, the surface area can extremely be increased while retaining its good mechanical strength to furthermore improve the electrostatic capacity.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to an aluminum alloy foil for electrolytic capacitor electrodes, particularly an aluminum alloy foil for cathodes.

Problems of the Invention Since the capacitance of an electrolytic capacitor is proportional to the surface area of its electrodes, aluminum foil for electrodes used for such purposes generally has a surface area that can be expanded by electrochemical etching treatment. It can be measured. Therefore, the most important conditions to be met are that the etching should be able to obtain as large an area expansion ratio as possible, and that corrosion fIin should be relatively low and good mechanical strength should be maintained. Ru.

Means for Solving the Problems In order to meet the above-mentioned demands, the present invention has found, as a result of various experiments and research, that extremely excellent etching characteristics can be obtained by adding a small amount of misch metal to aluminum electrode foil. This is the completed version.

Therefore, this invention targets an aluminum alloy foil for an electrolytic capacitor, especially a cathode, and has an aluminum purity of 9.
9.7% or more, and 0.005 Mitsushmetal
It is characterized by containing ~0.1%.

In addition, in this specification, all "%" means "% by weight"
This shows that.

In general, it goes without saying that aluminum foil of high purity is preferable for use as the cathode of electrolytic capacitors, but due to the relative relationship between price and H requirements, one with a purity of 99.796 or higher is sufficient. - About 99.8 to 99.9% is used for boat fishing. In the case of the cathode foil, an aluminum foil of relatively lower purity is used than in the case of the anode foil, and therefore a relatively large amount of mitsch metal is required in the present invention.

Therefore, in a cathode foil of such a pure purity,
In order for the addition of Mitsushimetal to exhibit the desired effects, its content should be 0.005% or more. However, excessive addition is rather harmful in that it increases corrosion loss on the surface of the foil, and the content should not exceed 0.1%. In particular, the permissible content of Mitshu metal as an aluminum alloy for cathodes is 0.005~
It is specified in the range of 0.1%.

The reason why the capacitance of the aluminum alloy foil for the cathode can be increased by including a trace amount of Mitshu metal in the above range is considered to be due to the following reason. In other words, Mitshu metal easily combines with impurity elements in aluminum foil and easily precipitates intermetallic compounds, and also has a strong bond with oxygen and easily forms oxides.
This is thought to be due to the fact that these particles are densely dispersed in the foil material, effectively forming dense etching nuclei and further enhancing the etching effect.

Note that it is naturally permissible for the aluminum alloy foil for a cathode according to the present invention to contain other elements as unavoidable impurities. Furthermore, as a conventionally known technique, in order to increase the area expansion ratio of aluminum electrode foil and maintain good mechanical strength, various trace elements are actively added to the aluminum electrode foil. The scope of the invention also includes a case in which, in addition to Mitsushimetal, a forcibly added element is additionally included. Such elements include iron, copper, zinc, manganese, silicon, vanadium, titanium, strontium, lead, tin, bismuth, boron, magnesium, indium, arsenic, silver, cadmium, thorium, siliconium, gallium, silicon, etc. The content is generally 0°00001 to 0.2
It is within the range of 95%. When these elements are contained, in addition to the effects due to the inclusion of Mitsushimetal according to the present invention, the effects due to the inclusion of the above-mentioned elements are expected to occur not only as a sum, but also to have a synergistic effect beyond that. Although it is expected that there may be cases, this invention achieves the effect of containing Mitshu metal in any case.
It is included within that scope.

Effects of the Invention This invention is based on having the above structure, and when the aluminum alloy foil is subjected to etching treatment, it is possible to significantly increase the surface area while maintaining good mechanical strength, and therefore to reduce static electricity. This achieves the effect of further improving capacity.

Example Next, examples of the present invention, as well as comparative examples, will be shown.

Aluminum alloys having various chemical compositions as shown in Table 1 were rolled to a thickness of 0.1 # by a conventional method, and then annealed in an inert gas atmosphere to obtain samples 1 to 4 of the present invention and comparative samples. A was produced. These test samples were all based on aluminum ingots with a purity of 99.8%, and were manufactured with various amounts of Mitshu metal added.

Then, for the above samples 1 to 4 and A, each of them was mixed in a 3% hydrochloric acid + 0.5% oxalic acid aqueous solution at 70°C.
After etching for 1.5 minutes using an alternating current with a current density of 30 A/drrt, the capacitance was measured in the unformed state. The results of this measurement were as shown in the right column of Table 1.

[Margin below]

Table 1 As seen in the results shown in Table 1, the aluminum alloy foils of the present invention (Samples 1 to 4) containing mitshu metal in the range of 0.005 to 0.1% were superior to the foils not containing it. (Sample A), a clear increase in capacitance was observed, and it was confirmed that the foil had excellent performance as a foil for an electrolytic capacitor cathode.

that's all

Claims (1)

[Claims] An aluminum alloy foil for an electrolytic capacitor cathode, which has an aluminum purity of 99.7% or more and contains 0.005 to 0.1% misch metal.