Thermodynamic analysis of influence of Pb contamination on Pb-free solder joints reliability

摘要

Because the infrastructure for electronic component manufacturing is not ready for Pb-free processing, Pb contamination of Pb-free solder joints cannot be avoided in the near future. In this work thermodynamically calculated phase diagrams are used to analyze the formation of microstructure in the Pb-contaminated Sn-Ag, Sn-Ag-Cu, and Sn-Bi solder joints. Non-equilibrium effect of solidification on the formation of microstructure is considered. Due to high cooling rate, the Pb-contaminated solder joint is prone to the formation of non-equilibrium eutectic structure. The influence of this structure on solder joint reliability is discussed.