A wire comprising a core comprising or consisting of (a) nickel in an amount in the range of from 0.005 to 5 wt.-%, (b) optionally, silver in an amount in the range of from 0.005 to 1 wt.-%, (c) copper in an amount in the range of from 94 wt.-% to 99.98 wt.-%, and (d) 0 to 100 wt.-ppm of further components, wherein all amounts in wt.-% and wt.-ppm are based on the total weight of the core, wherein the core has an average size of crystal grains in the range of from 1.5 to 30(mu)m, the average size determined according to the line intercept method, wherein the wire has an average diameter in the range of from 8 to 80 (mu)m.