Looping behaviour of gold ballbonding wire

Abstract

Gold ballbonding is an enabling technology in electronics packaging that accounts for around 90% of the world demand for packaged IC's. Thinner IC packaging demands lower wire loops and the stacked dies used for example in mobile telecommunications applications require a range of loop heights from very high to very low. In addition, multi-tier wirebonding also demands ultra low loop profile for its application. The lowest achievable loop heights are physically constrained by the wire dimensions and the plastic deformation behaviour of the wire. Ultra low loops result in extensive plastic deformation in the heat affected zone (HAZ). This paper examines the correlation between the wire properties (break load, modulus, hardness, grain size, HAZ length) and looping performance. The springback height of the lifted ball due to tension in the wire from bonding, and how it affects the looping behaviour is also discussed.