Patent ID: 7090732

Claim:
A sheet of a copper alloy having a high-mechanical strength, the copper alloy consisting of 3.5 to 4.5% by mass of Ni, 0.7 to 1.0% by mass of Si, 0.01 to 0.20% by mass of Mg, 0.05 to 1.5% by mass of Sn, 0.2 to 1.5% by mass of Zn, and less than 0.005% by mass (including 0% by mass) of S, optionally 0.01 to 0.5% by mass at a total content of at least one selected from the group consisting of B, Fe, Zr, P, Mn, Ti, V, Pb, Bi and Al, and optionally 0.005 to 2.0% by mass at a total amount of at least one selected from the group consisting of Ag, Co and Cr, with the balance being made of Cu and inevitable impurities, wherein the alloy has a tensile strength of 800 N/mm 2 or more, and wherein the alloy has a stress relaxation ratio of 10% or less when the alloy is maintained at a temperature of 150° C. for a period of 1000 hours.