| CPC C25D 5/505 (2013.01) [B32B 15/01 (2013.01); B32B 15/20 (2013.01); C22C 9/06 (2013.01); C25D 3/30 (2013.01)] | 11 Claims |

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1. A Cu—Ni—Si based copper alloy plate comprising
0.4% by mass or more and 5.0% by mass or less of Ni, 0.05% by mass or more and 1.2% by mass or less of Si, and the balance Cu with inevitable impurities in a thickness center portion in a plate thickness direction; wherein
a surface Ni concentration at a plate surface is 70% or less of a center Ni concentration at the thickness center portion,
in a surface layer portion with a depth from the plate surface to where a Ni concentration becomes 90% of the center Ni concentration, the Ni concentration increases at 5% by mass/μm or more and 100% by mass/μm or less of a concentration gradient from the plate surface toward the thickness center portion.
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