Effects of calcium and palladium on mechanical properties and stored energy of hard-drawn gold bonding wire

The effects of dopants on the mechanical properties of 4N gold ball-bonding wires has not been widely investigated for some years despite the importance of wire-bonding and the move towards ultra-fine pitch applications. This paper presents results on the effects of two well-known and widely used dopants in gold ball-bonding wire, Ca and Pd, the objective being to move towards a better understanding of the solid-state mechanisms by which these dopants affect wire properties. Ternary micro-alloys of high purity 4N gold with Ca and Pd were drawn into 25-mum-diameter wires without annealing in order to examine the effects of the dopants on the mechanical properties and stored mechanical energy in the wires. The stored energy of the wires increased with Ca content but Pd had a negligible effect. The break load and percentage elongation of the wires increased with Ca but Pd had no significant effect. Various mechanisms, including grain boundary segregation and dislocation loop generation are postulated to account for the change in wire properties due to Ca. (C) 2004 Elsevier B.V. All rights reserved.