Lead free solder paste flux evaluation and implementation in personal communication devices

This paper outlines the printing and wetting experimentation and the findings of a lead free solder paste comparison, and identifies one flux vehicle capable of performing across a wide temperature range of reflow profiles. The study included a lead free alloy using three different flux vehicles. The test boards used were a copper surface finish with organic surface protection (OSP) and Ni-Au. The goal was to understand the printing performance over time and the effect of time above liquidus and peak temperatures on the wetting characteristics for each solder paste in an air and nitrogen reflow atmosphere. The volumetric data from the printing experiment revealed little difference between the pastes and determined that the wetting characteristics would carry the most weight for the decision of a lead free solder paste. The wetting results clearly showed that only one of the solders used performed well in all the reflow profiles tested, while the others exhibited wetting problems in air as the volume of printed solder decreased. The identification of one flux vehicle allowed for the manufacturing process to be optimized, and shared with other sites globally.