MANUFACTURING METHOD OF COPPER ALLOY SHEET
Manufacturing method of a copper alloy sheet including melting and casting a raw material of a copper alloy having a composition containing 1.0 mass % to 3.5 mass % Ni, 0.5 mass % to 2.0 mass % Co, and 0.3 mass % to 1.5 mass % Si with a balance being composed of Cu and an unavoidable impurity. The method includes the steps of first cold rolling, intermediate annealing, second cold rolling, a solution heat treatment and aging. The solution heat treatment includes: heating at 800° C. to 1020° C.; first quenching to 500° C. to 800° C.; maintaining the 500° C. to 800° C. temperature for 10 seconds to 600 seconds; and second quenching to 300° C. or lower.