Effect of Ag and Pb Addition on Microstructural and Mechanical Properties of SAC 105 Solders

Abstract

Melting and crystallization processes of lead-free and lead-contaminated alloys in near-equilibrium state were investigated. In addition, the effect of silver content up to 4 wt.% on the microstructure of Sn-Ag-Cu alloys was studied. The volume fraction of b-Sn decreased by half owing to 4 wt.% Ag content. Furthermore, contamination by lead strongly influences the properties of the solidified microstructure. The Pb grains appear as a result of two processes when the Pb content is equal to 0.5 wt.% or higher: Pb phase solidifies in the quaternary eutectic at 176°C, and Pb grains precipitate from the primary b-Sn solid solution grain during a solid state reaction. The freezing range enlarges to 51°C due to 2 wt.% Pb content owing to quaternary eutectic. Above 1 wt.% Pb content, the mechanical properties also improve due to grains of quaternary eutectic Pb and precipitated Pb grains with a size <1 lm.

Archives of Metallurgy and Materials

“…The aim of the present investigation is to follow the evolution of IML thickness and crack initiation/propagation during thermal shock tests of THT SAC solder joints produced by through hole reflow soldering and multiwave soldering. The microstructural characterization of SAC 305 is presented in our previous publication [22].…”