| 摘要 |
PROBLEM TO BE SOLVED: To reduce the noise in operating a hard disk drive, to leave a fingerprint with difficulty, to improve the discoloring resistance, and to reduce the price by covering an Sn or Sn alloy layer in a specified thickness on at least one side of a copper alloy sheet containing Zn, Sn of a specified quantity. SOLUTION: An Sn or Sn alloy layer 2 is covered on are surface or both surface of a copper alloy sheet 1 through a substrate layer 3 of such as Ni, as necessary. The copper alloy sheet 1 preferably contains, by weight, 5-42% Zn, 1-3% Sn, and the balance Cu with inevitable impurities. The Sn or Sn alloy layer 2 is preferably formed by the electric plating method in a thickness of 0.5-3μm, and it is preferable to seal pin holes through reflow treatment, and to prevent emission of the out gas. The copper alloy bar prepared is large in specific gravity and small in generation of the noise in operating a hard disk drive, and excellent in discoloring resistance, press forming property, and soldering property.
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