Influence of Ni on the refinement and twinning of primary Cu6Sn5 in Sn-0.7Cu-0.05Ni

J.W. Xian, M.A.A. Mohd Salleh, S.A. Belyakov, T.C. Su, G. Zeng, K. Nogita, H. Yasuda, C.M. Gourlay
2018 Intermetallics (Barking)  
The influence of Ni on the size and twinning of primary Cu6Sn5 crystals in Sn-0.7Cu-0.05Ni and Sn-xCu (x=0.7, 0.9, 1.1) (mass%) solder joints is studied using synchrotron radiography and SEM-based EBSD. It is shown that the Ni addition does not cause significant refinement of primary Cu6Sn5 if the alloy is fully melted. However, for peak temperatures ≤ 250°C relevant to industrial soldering, primary Cu6Sn5 are not completely melted in Sn-0.7Cu-0.05Ni and there are 10-100 times more numerous and
more » ... smaller crystals than in Sn-0.7Cu. X-shaped Cu6Sn5 crystals with an angle of ~70° commonly formed in Sn-0.7Cu-0.05Ni/Cu joints and are shown to be penetration twins. This type of growth twinning was only found in partially melted samples, both in Sn-0.7Cu-0.05Ni/Cu joints and binary Sn-1.1Cu alloy. The frequency of twinned crystals was significantly higher in Ni-containing solders. The results are discussed in terms of the influence of Ni on the Cu6Sn5 liquidus slope and on the lattice parameters of (Cu,Ni)6Sn5.
doi:10.1016/j.intermet.2018.08.002 fatcat:un6fi6a6jzcslkg32nlu6fsffy