Addressing industry knowledge gaps regarding new Pb-free solder alloy alternatives

Abstract

Recently, the industry has seen an increase in the number of Pb-free solder alloy choices beyond the common neareutectic Sn-Ag-Cu (SAC) alloys. The increasing number of Pb-free alloys provides opportunities to address important issues, such as the poor drop/shock performance, alloy cost, copper dissolution, and poor mechanical behavior in bend/flex. Most recently, investigations into new solder paste alloys for mass reflow have begun. At the same time, the increase in choice of alloys presents challenges in managing the supply chain and introduces a variety of risks. Poor solder joint formation when BGAs with low Ag alloy balls are soldered at the low end of the conventional Pb-free process window is one example. The full impact of these new alloys on overall printed circuit assembly (PC A) reliability has yet to be determined. This paper provides the results of an iNEMI study of the present state of industry knowledge on Sn-Ag-Cu alloy "alternatives," including an assessment of existing knowledge and critical gaps. Based on this assessment, focus areas have been identified for closing key gaps. Plans and progress in addressing the gaps are described, including efforts to update industry standards to account for the new alloys and to better manage supply chain complexity and risk.