| 摘要 |
PROBLEM TO BE SOLVED: To provide a Cu-Mg-P based copper alloy Sn plated sheet having a low friction coefficient and suitable for using as a fitting type connection terminal.SOLUTION: The Cu-Mg-P based copper alloy Sn plated sheet includes: a copper alloy sheet, as base material 2, having a composition containing 0.2 to 1.2 mass% of Mg and 0.001 to 0.2 mass% of P and the balance Cu with inevitable impurities; and a plating coating film layer 5 after a reflow treatment constituted of a Sn phase 6 having a thickness of 0.3 to 0.8 μm, a Sn-Cu alloy phase 7 having a thickness of 0.3 to 0.8 μm, a Cu phase 8 having a thickness of 0 to 0.3 μm in this order from a surface to the base material 2. A ratio of Mg concentration of the Sn phase 6 (A) to Mg concentration of the base material 2 (B), (A/B) is 0.005 to 0.05. A ratio of Mg concentration (C) at a boundary layer 4 between the plating film layer 5 and the base material 2 and having a thickness of 0.2 to 0.6 μm to Mg concentration of the base material 2 (B), (C/B) is 0.1 to 0.3. |
