Effect of the cross-interaction on the solidification behaviors of Ni/Sn-Ag-Cu/Cu solder joint

The solidification behavior and microstructure of Ni/Sn-3.0Ag-0.5Cu/Cu joint were investigated by using DSC. It was found that the degree of undercooling for Sn-3.0Ag-xCu(x≥0.5wt.%) solders increased with increasing the concentration of Cu and the addition of Ni increased the degree of undercooling of Sn-3.0Ag-0.5Cu significantly. The addition of Ni changed the volume fraction of primary solidification phase of Sn-3.0Ag-0.5Cu solder alloy. Substrate influenced the solidification behavior of joint significantly, and the effect of Ni on the solidification behavior of solder joint depends on the material of substrate. The addition of Ni influenced the microstructure of Sn-3.0Ag-0.5Cu alloy and joints significantly. The size of β-Sn phase and the area of eutectic zone around the boundary of β-Sn in Sn-3.0Ag-0.5Cu solder alloy increase with a minor alloying element of Ni. The addition of Ni in Sn-3.0Ag-0.5Cu /Ni joint not only changed the morphology but also crystal structure of IMC at interface.