A Cu-Ni-Si-based copper alloy plate that contains Ni and Si. At a plate thickness–direction center part, the Cu-Ni-Si-based copper alloy plate includes 0.4–5.0 mass% of Ni and 0.05–1.5 mass% of Si, the remainder being Cu and unavoidable impurities. The Ni concentration at the plate surface of the Cu-Ni-Si-based copper alloy plate is no more than 70% of a center Ni concentration that is the Ni concentration at the thickness center part. The Cu-Ni-Si-based copper alloy plate has a surface layer part that goes from the plate surface to a depth at which the Ni concentration is 90% of the center Ni concentration. At the surface layer part, the Ni concentration increases from the plate surface toward the thickness center part at a concentration gradient of 5.0–100 mass%/μm. This Cu-Ni-Si-based copper alloy plate has better electrical connection reliability in high-temperature environments, and even when a plating film of Sn or the like has been provided thereon, this Cu-Ni-Si-based copper alloy plate has better electrical connection reliability in high-temperature environments, better solder wettability, and better plating film adhesion.
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