PURPOSE: To produce a metallic sheet for lead frame excellent in strength and electric conductivity at a low cost by casting a Cu alloy plate containing specific amounts of Fe, Cr, and other elements under specific cooling conditions, successively applying pickling treatment, primary cold rolling, annealing, ageing treatment, and secondary cold rolling to the above sheet to work this sheet to the final sheet thickness, and then applying Cu plating to the surface.

CONSTITUTION: A molten Cu alloy having a composition which consists of, by weight, 20-95% Cu and the balance Fe and Cr and in which the proportion of Cr to Fe is regulated to 6-12% or further ≤0.5% of one or two elements among Al, Ti, Ni, Nb, Zn, P, La, Ce, Y, Mn, V, Ca, Be, Mg, and W are incorporated or ≤1% each of Zn and Si and ≤4% each of Ni and Sn are incorporated is cooled rapidly by a twin-roll method, etc., at ≥100°C/sec cooling rate and formed into a metal plate. The surface is pickled to undergo the removal of oxide film, and an Fe phase is selectively etched. Successively, the above metal plate is subjected to primary cold rolling at >50% reduction of area, to annealing and ageing treatments, and to secondary cold rolling at 5-50% reduction of area and then Cu plating is applied to the resulting rolled sheet.