Interfacial reactions and reliability with lead (Pb)-free solders

Solder interconnection technology plays a very important role in microelectronics packaging. An ideal connection means good electrical property and mechanical strength. The quality of interfacial layer between the solder and substrate is related tightly with the electrical and mechanical properties of solder interconnection. The interfacial reaction and characteristics of four different kinds of lead-free solder were discussed. The relation between the thickness of interfacial layer and soldering time was measured. Moreover, the mechanical property of interconnection was measured corresponding to different reflow curve (which includes the peak temperature and the remaining time above liquid temperature). The results demonstrate that on the substrate of Ni/Au coated, the shear strength of lead-free solders is very sensitive to the reflow curve.