Fundamental properties of Pb-Free solder alloys

Abstract

The search for a global Pb-free replacement for Sn-Pb eutectic alloy has been an evolving process as the threat of a regional lead ban became a reality in July 2006. Over the twelve years from 1994 through 2006, the manufacturing, performance, and reliability criteria for Pb-free solder joints have become increasingly complex as relationships between the solder alloy, the circuit board materials and construction, and the component designs and materials have been revealed through widespread experimentation by companies, industrial consortia, and university researchers. The focus of this chapter is to examine the primary criteria used to develop the current generation of Pb-free solder alloys, the tradeoffs made between various properties once these primary criteria were satisfied, and the open questions regarding materials and processes that are as yet unanswered. © 2007 Springer-Verlag US.