Influence of Si on the kinetics of the reactive diffusion between Au and Sn was experimentally examined at solid-state temperatures. Binary Sn–Si alloys with Si concentrations of 1 and 3wt% were used to prepare (Sn–Si)/Au/(Sn–Si) diffusion couples by a diffusion bonding technique. The diffusion couples were isothermally annealed at 433, 453 or 473K for various times up to 200h in an oil bath with silicone oil. After annealing, AuSn4, AuSn2 and AuSn layers were observed at the (Sn–Si)/Au interface in the diffusion couple. The total thickness of the Au–Sn compound layers was expressed as a power function of the annealing time. The exponent of the power function takes values between 0.37 and 0.41. The exponent smaller than 0.5 indicated that grain boundary diffusion as well as volume diffusion contributed to the rate-controlling process of the reactive diffusion and grain growth occurred at certain rates in the compound layers. The higher the Si concentration of the Sn–Si alloy is, the slower the overall growth of the compound layers occurred. This indicated that the addition of Si into the Sn-based solder alloy decelerated growth of the Au–Sn compounds at the interconnection between Au/Ni/Cu multilayer conductor and Sn-based solder alloys during energization heating.

Influence of Si on Reactive Diffusion between Au and Sn at Solid-State Temperatures. A.Furuto, M.Kajihara: Materials Science and Engineering A, 2007, 445-446, 604-10