PURPOSE: To prevent contact or sag of a copper wire in the case of a fine pitch and long loop, and improve reliability, by using a copper allay very thin wire of a specified composition.

CONSTITUTION: A copper alloy very thin wire for semiconductor which wire contains Ir of 0.1-50wt.ppm, impurities less than or equal to 5wt.ppm, and copper as the remainder is used as a bonding wire. Further a thin wire composed of the following is used as a bonding wire; Ir of 0.1-50ppm, inevitable impurities less than or equal to 5ppm, one kind or two or more kinds of elements of total amount 0.1ppm-0.5% which elements are selected out of the element group of Be, Cr, Sn, Zn, Zr, Ag, Mg, Ca, rare earth elements, Ti, Hf, V, Nb, Ta, Ni, Pd, Pt, Au, Cd, B, In, Si, Ge, Pb, P, Sb and Bi, and copper as the remainder. Thereby elasticity is increased, and work-hardening in the case of bonding becomes hard to be generated.