With Sn plating Cu-Ni-Si copper alloy sheet and a manufacturing method thereof

摘要

PROBLEM TO BE SOLVED: To provide a Cu-Ni-Si based copper alloy sheet having excellent spring critical value and stress relaxation resistance and having satisfactory thermal peeling resistance after Sn plating.;SOLUTION: The copper alloy sheet has a composition comprising, by mass, 1.0 to 4.0% Ni and 0.2 to 0.9% Si, and the balance Cu with inevitable impurities, and in which, in the crystal structure of the surface, the ratio of all the special grain boundary lengths Lσ of special grain boundaries to all the grain boundary lengths L of the crystal grain boundaries measured by an EBSD method by a scanning type electron microscope with a back scattering electron diffraction image system, (Lσ/L) is 60 to 70%, the number of Ni-Si precipitation grains having a grain size above 100 nm is 0.2 to 0.7 pieces/μm², and the concentration of Si solid-soluted in the crystal grains is 0.03 to 0.6 mass%.;COPYRIGHT: (C)2014,JPO&INPIT