A Comparison of Lead-Free vs. Eutectic Solders

T he use of lead in the electronics industry today accounts for approximately 7% of total lead consumption.' The single largest use of lead is in the manufacture of storage batteries, which accounts for 60% of the total lead produced.2 The use of lead is closely regulated in plumbing, paint and gasoline industries. Currently, the electronics industry has been exempted from the existing requirements regarding lead, but it is increasingly apparent that lead in electronics may well be disallowed in the not too distant future. As a result, efforts have been underway during the last two years to investigate lead-free alternatives for the interconnection of electronic assemblies. Studies have been conducted to evaluate suitable repIacements for 63/37 Sn/Pb s ~ l d e r . ~ These studies have examined many facets of the issue of lead-free replacements, including the adverse health effects of lead, lead in the environment and physical and mechanical properties of the lead-free replacements. However, there has been little data published regarding the wetting and solderability test performance of lead-free terminations. In this study, three lead-free solder alternatives were chosen for comparison with the standard 63/37 Sn/Pb solder. Wetting balance, steam aging solderability testing and board-level soldering performance were chosen as the discriminating variables for the comparison.