Pb-free plating: a process and solder joint reliability study

Abstract

The lead-free (Pb-free/100% tin) lead finish quality from two plating suppliers was compared to that of standard 90wt%Sn-1 0wt%Pb plating. A characterization study of the properties of the electroplated tin (Sn) showed that the finish exhibited large stable grains, high purity, comparable ionic contamination levels, and solderability. The assembled modules that employed Pb-free paste for the Sn finish showed better temperature cycling (T/C) performance, as those with Sn-Pb paste showed distinguished crack propagation. Sn whisker observation and characterization were performed on the components at time-zero, after module reflow and with the progression of T/C. The Sn whisker growth rates are explained in relation to tensile and compressive stresses on the plated layer