The effect of Pb contamination on the microstructure and mechanical properties of SnAg/Cu and SnSb/Cu solder joints in SMT

The effects of Pb contamination on the microstructure and shear strength of lead‐free solder joints with non‐lead containing finishes on both the PCB and terminals of 1,206 chip capacitors at different temperatures were investigated. Two kinds of lead‐free solders (Sn96.5Ag3.5 and Sn95Sb5) were selected, and different amounts of eutectic Sn‐Pb were added to these lead‐free solders according to the potential Pb contamination in a 1,206 chip capacitor solder joint. It was found that there was no difference in shear strength of solder joint at room temperature for those with or without Pb contamination, but the shear strength at 1258C for the solder joint without Pb contamination was about 15 percent higher than for those with Pb contamination.