| 摘要 |
This invention provides a copper alloy having excellent stress relaxation resistance, comprising Ni: 0.1 to 3.0% (% by mass; the same shall apply hereinafter), Sn: 0.01 to 3.0%, and P: 0.01 to 0.3% with the balance consisting of copper and unavoidable impurities, characterized in that the content of Ni in an extraction residue after extraction separation on a filter having an opening size of 0.1 μm by an extraction residue method is not more than 40% in terms of the proportion to the content of Ni in the copper alloy. In the extraction residue method, 10 g of the copper alloy is immersed in 300 ml of a methanol solution having an ammonium acetate concentration of 10% by mass. This copper alloy is used as an anode. On the other hand, platinum is used as a cathode. Galvanostatic electrolysis is carried out at a current density of 10 mA/cm. A solution containing this copper alloy dissolved therein is subjected to suction filtration by a polycarbonate membrane filter having an opening size of 0.1 μm, and the insolubles as the residue are separated and extracted on the filter. The content of Ni in the extraction residue is determined by dissolving the insolubles as the residue on the filter in a solution composed of a mixture of aqua regia and water at a ratio of 1 : 1, and then analyzing the solution by ICP emission spectrometry.
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