The interfacial reaction between Sn–Ag alloys and Co substrate

Interfacial reactions between Sn or Sn–3.5 wt.%Ag and Co substrate at 573 K for different durations were studied. Only one intermetallic compound (IMC), CoSn3, was detected as a product of interfacial reaction, although there are several other IMCs in the Co–Sn binary system. This observation has been discussed from both the driving force for nucleation of the IMCs and diffusion of Co across the interface. Change of the thickness of CoSn3 layer with annealing time obeys a parabolic rule with time exponent of about 0.5, implying a diffusion-controlled mechanism. In addition, addition of Ag into Sn decreases the growth rate of the CoSn3 layer.