The effect of adding Zn into the Sn–Ag–Cu solder on the intermetallic growth rate

Due to toxicity of lead in the commercial solder, lead-free solders were proposed. Among the potential lead-free solders, the Sn–Ag–Cu solders were considered as a potential replacement. To further improve the solder properties, a fourth element was added into the Sn–Ag–Cu solder. The present study investigates the effect of different weight percentage of Zn (up to 0.7 wt%) into the Sn-3.5Ag-1.0Cu solder on intermetallic and growth rate ( k ) after long time thermal aging. The solders were prepared using powder metallurgy method and X-ray diffraction analysis shows that there were Cu 6 Sn 5 , Cu 3 Sn, CuZn and Ag 3 Sn phases present after solder preparation. The solders were reacted with Cu substrate at 250 °C for 1 min and aged at 150 °C until 1,000 h. The morphology of the intermetallic was observed under scanning electron microscope and the elemental distribution was confirmed by energy dispersive X-ray. Intermetallic thickness and growth kinetic result show that the additions of 0.4 % zinc is sufficient in retarding the Cu 6 Sn 5 and Cu 3 Sn intermetallic growth.