Interfacial Reactions Between Columnar or Layered Ni(P) Layers and Sn-Ag-Cu Solder

Comparative study on the interfacial reactions between lead-free Sn-Ag-Cu solder and Ni(P) bond pads (with columnar or layered microstructure) has been performed. The microstructure of the columnar Ni(P) is vertical, while the microstructure of the layered Ni(P) tends to be parallel to the solder/Ni(P) interface. The consumption rate of the columnar Ni(P, 7 at.%) layer is larger than that of the layered Ni(P, 7 at.%). We believe that the faster Ni(P) consumption rate of the columnar Ni(P, 7 at.%) layer is due to the orientation of the grains. Spalling of the interfacial (Cu,Ni)6Sn5 compound can be seen at the reaction interfaces for the columnar Ni(P, 7 at.%) layer. On the contrary, no spalling can be seen for the case of the reacted layered Ni(P).