| 摘要 |
PURPOSE:To remarkably reduce the leakage current of the anode foil of an Al electrolytic capacitor by heat treating an Al foil of low purity at a specific temp., followed by dipping in an aq. soln. of phosphoric acid and an aq. soln. of nitric acid in succession, washing and chemical treatment. CONSTITUTION:An Al foil of such a purity that obtd. by rolling primary electrolytic Al is heat treated at 400-600 deg.C for 10-60 min to precipitate impurity Fe on the Al grain boundaries. The foil is then cooled to room temp., dipped in a 2-20% aq. soln. of phosphoric acid at room temp.-70 deg.C for 5-10 min, further dipped in a 2-20% aq. soln. of nitric acid at room temp.-70 deg.C for 2-10 min to remove Fe, Fe-Al cpd. and insol. Al phosphate as impurities, washed with water, and chemically treated to form an oxide film on the foil surface. Thus, a chemical film having a leakage current about equal to that of an Al foil of 99.99% purity can be obtd. from a foil of primary electrolytic Al of about 99% purity. |
