Effect of Cu addition on interfacial reactions between Sn-9Zn lead-free solder and Ni substrate

This study investigates interfacial reactions of (Sn–9Zn) + xCu/Ni systems. Ni₅Zn₂₁, Cu₅Zn₈, (Ni,Zn,Cu)₃Sn₄, (Cu,Ni,Zn)₆Sn₅, and Cu₆Sn₅ phases were formed on the Sn–9Zn/Ni interface at 240–270 °C, when 0–10 wt% Cu was added to the Sn–9Zn solder. Experimental results indicate that changing the concentration of Cu in the Sn–9Zn solder dramatically changes the formation of intermetallic compounds (IMCs) in the (Sn–9Zn) + xCu/Ni system. Different diffusion and segregation rates of elements are the main reasons for a change in the IMC evolution.