The effect of reflow time on reactive wetting, evolution of interfacial IMCs and shear strength of eutectic Sn–Cu solder alloy

In the present work, the effect of reflow time on wetting behaviour, microstructure and shear strength of the eutectic Sn–0.7Cu lead-free solder on Cu substrate were studied. The reflow time was varied from 10 to 10,000 s. The contact angle decreased with the increase in reflow time. The growth of intermetallic compounds (IMCs) increased with the reflow time. The thickness of the Cu6Sn5 IMC layer formed during a reflow time of 10 s was about 3.76 μm and its thickness increased to 3.89, 6.2, 6.68, 7.6 and 19.83 μm during 100, 300, 500, 1,000 and 10,000 s reflow time respectively. The joint shear test was performed to assess the integrity of Sn–0.7Cu solder solidified on copper substrate surfaces. The shear strength decreased with increase in reflow time after an optimum value.