To improve the heat resistance of a Cu/Ni double layer substrate reflow tinned strip using a Cu-Ni-Si-Zn based alloy as a base metal.
Regarding the tinned strip in which a copper based alloy comprising, by mass, 1.0 to 4.5% Ni, Si of 1/6 to 1/4 to the mass% of Ni and 0.1 to 2.0% Zn, and, if required, comprising 0.05 to 2.0% Sn is used as a base metal, and a plating layer is composed of each layer of an Sn phase, an Sn-Cu alloy phase and an Ni phase. The thickness of the Sn phase is controlled to 0.1 to 1.5 μm; the thickness of the Sn-Cu alloy phase is controlled to 0.1 to 1.5 μm; the thickness of the Ni phase is controlled to 0.1 to 2.0 μm; and the concentration of Si and the concentration of Zn in the surface of the Sn phase are respectively controlled to ≤1.0% and ≤3.0%. If required, the concentration of C in the boundary face between the plating layer and the base metal is controlled to ≤0.1%, and the concentration of O is controlled to ≤1%.
Endo Azusa
Takumi Yoshida
Taku Nakajima
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