2006 Volume 47 Issue 9 Pages 2277-2284
In order to examine microstructure evolution at the interconnection between the Sn-base solder and Au/Ni/Cu multilayer conductor alloys during energization heating, the kinetics of the reactive diffusion between a binary Sn–5 at% Au alloy and pure Ni was experimentally observed at solid-state temperatures. Sandwich (Sn–Au)/Ni/(Sn–Au) diffusion couples were prepared by a diffusion bonding technique, and then isothermally annealed at temperatures of T=433, 453 and 473 K for various periods up to 1057 h. During annealing, AuNiSn8 and Ni3Sn4 compound layers are formed along the (Sn–Au)/Ni interface in the diffusion couple. The total thickness of the compound layers is expressed as a power function of the annealing time. The exponent of the power function is close to 0.5 at T=453–473 K, and equal to 0.7 at T=433 K. Therefore, volume diffusion is the rate-controlling process for the growth of the compound layers at T=453–473 K, but interface reaction contributes to the rate-controlling process at T=433 K. The growth of the compound layers occurs slower for the reactive diffusion between the Sn–5Au alloy and Ni than for that between Sn and Au, but faster for that between the Sn–5Au alloy and Ni than for that between Sn and Ni.