Effect of substrate metallization on interfacial reactions and reliability of SnZnBi solder joints
The scope of this paper covers a comprehensive study of the lead-free SnZnBi solder system, on Cu, electrolytic Ni/Au and electroless Ni(P)/Au surface finishes. This includes a study of the shear properties, intermetallic compounds at the substrateball interface and dissolution of the under bump metallization. The Sn8Zn3Bi (wt.%) solder/Cu system exhibited a low shear load with thick IMCs formation at the interface. The dissolution of the Cu layer in the SnZn3Bi solder is higher than that of the other two Ni metallizations. It was found that the formation of a thick NiZn intermetallic compound (IMC) layer at the solder interface of the electrolytic Ni bond pad reduced the mechanical strength of the joints during high temperature long time liquid state annealing. The solder ball shear-load for the Ni(P) system during extended reflow increased with an increase of reflow time. No spalling was noticed at the interface of the SnZn3Bi solder/Ni(P) system. Sn8Zn3Bi solder with electroless Ni(P) metallization appeared as a good combination in soldering technology.
intermetallic compounds dissolution under bump metallization snznbi lead free solder