| 摘要 |
PROBLEM TO BE SOLVED: To provide a copper alloy excellent in punching workability and suitable for a lead frame or the like. SOLUTION: In a copper alloy containing, by weight, 0.2 to 0.35% Cr, 0.1 to 0.5% Sn and 0.1 to 0.5% Zn, and the balance Cu with inevitable impurities, a precipitated phase A composed of Cr or a Cr compound having the maximum particle size of 0.1 to 10μm is present by the number density of 1×103 to 3×105 pieces/mm2 in a Cu parent phase, and also, a precipitated phase B of Cr or a Cr compound having the maximum particle size of 0.001 to 0.030μm is present by the number density of 10 times the number density of the precipitated phase A or more. The copper alloy is excellent in punching workability and strength characteristics since the coarse precipitated phase A improves the punching workability, and the fine precipitated phase B improves the strength characteristics. Thus, in the case of being applied, e.g. for a lead frame of multipins and narrow pitches to be finely subjected to punching, its productivity improves.
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