| 摘要 |
In a Sn-coated copper alloy strip including a surface coating layer comprising a Ni layer, a Cu-Sn intermetallic compound layer, and a Sn layer formed in this order over the surface of a base material comprising a copper alloy strip, a contact reliability (low contact resistance) after a long time at high temperature is improved. An average thickness of the Ni layer is 0.1 to 3.0 µm, an average thickness of the Cu-Sn intermetallic compound layer is 0.2 to 3.0 µm, an average thickness of the Sn layer is 0.01 to 5.0 µm, and the Cu-Sn intermetallic compound layer comprises only an ·-phase (Cu 6 Sn 5 ) or the ·-phase and an µ-phase (Cu 3 Sn). When the Cu-Sn intermetallic compound layer comprises the µ-phase and the ·-phase, the µ-phase is present between the Ni layer and the ·-phase, and the µ-phase thickness ratio (the ratio of an average thickness of the µ-phase to an average thickness of the Cu-Sn intermetallic compound layer) is 30% or less. Further, resistance to heat separation is improved by defining the µ-phase length ratio (ratio of a length of the µ-phase to a length of the Ni layer in the cross section of the surface coating layer) as 50% or less. |
