Creep behavior of a lead-free solder alloy and construction of a validated Deformation Mechanism Map

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With ongoing concerns regarding environmental pollutants, lead is being targeted in the electronic industry and there has been a strong push in recent years to go lead-free. In 2002 the European Union enacted legislations that restrict or eliminate the use of lead in most electrical and electronic equipment later followed by Japan and the United States. The introduction of lead-free solders means that new standards will need to be updated and thus new data on properties and performance will be required. The partner company in this proposal, Cistel, is working on obtaining better information on properties and performance of lead-free solder material used in printed circuit boards (PCB) for applications in avionics. The main issues with PCB is their failure which is related to thermal fatigue where thermal shock and thermal cycling can take place either during PCB manufacture or in service. Creep of solder joints, which is a time-dependent deformation under a constant load, and its effect of fatigue was recognized to be fundamental to understand thermal fatigue of soldered joints and thus to predict PCB lifetime. With new lead-free material coming in the electronic arena, more data is required to understand the creep mechanisms at play in these alloys. The predominant lead free solder is known as "SAC" from the ternary alloy of Sn-Ag-Cu. In this study the creep behavior of one formulation of Sn-Ag-Cu lead free solder alloy is investigated.