Comparison of isothermal mechanical fatigue properties of lead free solder joints and bulk solders

Low cycle isothermal mechanical fatigue testing of both bulk solders and solder joints of eutectic Sn-37wt%Pb and Sn-3.5wt%Ag and Sn-4.0wt%Ag-0.5wt%Cu were carried out in a systematic manner at room temperature over a wide range of strain ranges (1%-10%). The eutectic Sn-37wt%Pb was used as a reference. Both for bulk solders and solder joints, the low cycle fatigue behavior of the solder alloys tested was found to be strongly dependent on strain rate. Regarding solder joints, both lead free solders also depicted somewhat better fatigue properties, compared to Sn-37Pb. The experimental results from both experimental methods (bulk solder specimens and solder joints) were compared. Concluding from an environmental point of view, and from the present bulk and solder joint isothermal mechanical fatigue experiments, both Sn-3.5wt%Ag and Sn-4.0wt%Ag0.5wt%Cu lead-free solders are advisable replacements to Sn-37wt%Pb.