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Interfacial reactions of the Ni/AuSn/Ni and Cu/AuSn/Ni joints are experimentally studied at 330℃for various reflow times.The microstructures and mechanical properties of the as-solidified solder joints are examined.The as-solidified solder matrix of Ni/AuSn/Ni presents a typical eutecticξ-(Au,Ni)_5Sn+δ-(Au,Ni)Sn lamellar microstructure after reflow at 330℃for 30 s.After reflow for 60 s,a thin and flat(Ni,Au)_3Sn_2 intermetallic compound(IMC) layer is formed,and some needle-like(Ni,Au)_3Sn_2 phases grow from the IMC layer into the solder matrix.On the other hand,a cellular-typeξ(Cu) layer is found at the upper AuSn/Cu interface in the Cu/AuSn/Ni joint after reflow for 30 s,and a(Ni,Au,Cu)_3Sn_2 IMC layer is also formed at the lower AuSn/Ni interface. For both joints the IMC layer grows significantly with the increase of reflow time,but the growth rate of(Ni,Au,Cu)_3Sn_2 IMC in the Cu/AuSn/Ni joint is smaller than that of the(Ni,Au)_3Sn_2 layer in the Ni/AuSn/Ni joint.The comparisons of the shear strength and fracture surface between the Ni/AuSn/Ni and Cu/AuSn/Ni joints suggest that the coupling effect of the Cu/AuSn/Ni sandwich joint is helpful to prevent the excessive growth of(Ni,Au)_3Sn_2,which in turn enhances the mechanical reliability of the solder joint.
Interfacial reactions of the Ni / AuSn / Ni and Cu / AuSn / Ni joints are experimentally studied at 330 ° C for various reflow times. The microstructures and mechanical properties of the as-solidified solder joints are. / AuSn / Ni presents a typical eutectic ξ- (Au, Ni) _5Sn + δ- (Au, Ni) Sn lamellar microstructure after reflow at 330 ° C for 30 s. After reflow for 60 s, a thin and flat (Ni, Au) _3Sn_2 intermetallic compound (IMC) layer is formed, and some needle-like (Ni, Au) _3Sn_2 phases grow from the IMC layer into the solder matrix. On the other hand, a cellular-type ξ AuSn / Cu interface in the Cu / AuSn / Ni joint after reflow for 30 s, and a (Ni, Au, Cu) _3Sn_2 IMC layer is also formed at the lower AuSn / Ni interface. the increase of reflow time, but the growth rate of (Ni, Au, Cu) _3Sn_2 IMC in the Cu / AuSn / Ni joint is smaller than that of the (Ni, Au) _3Sn_2 layer in the Ni / AuSn / Ni joint. The comparis ons of the shear strength and fracture surface between the Ni / AuSn / Ni and Cu / AuSn / Ni joints suggest that the coupling effect of the Cu / AuSn / Ni sandwich joint is helpful to prevent the excessive growth of (Ni, Au) , which in turn enhances the mechanical reliability of the solder joint.