2015 Volume 56 Issue 6 Pages 798-802
The kinetics of the solid-state reactive diffusion in the (Sn–Cu)/Ni system was experimentally observed to examine effects of addition of Cu into Sn on the growth behavior of compounds at the interconnection between the Sn-base solder and the multilayer Au/Ni/Cu conductor during energization heating. In this experiment, sandwich (Sn–Cu)/Ni/(Sn–Cu) diffusion couples with Cu concentrations of y = 0.01–0.03 were isothermally annealed at solid-state temperatures of T = 453–473 K for various periods up to 1972 h, where y is the mol fraction of Cu. After annealing, an intermetallic layer consisting of (Cu,Ni)6Sn5 and Ni3Sn4 was recognized between the Sn–Cu and Ni specimens in the diffusion couple. The total thickness of the intermetallic layer is proportional to a power function of the annealing time, and the exponent of the power function takes values of 0.37–0.44 at T = 453 K and those of 0.63–0.69 at T = 473 K. Thus, the growth of the intermetallic layer is controlled by boundary and volume diffusion at T = 453 K. On the other hand, at T = 473 K, interface reaction and interdiffusion contribute to the rate-controlling process of the intermetallic growth. The addition of Cu into Sn accelerates the intermetallic growth within the experimental annealing times.