Thermal Profiling to Overcome Flux Residue Formation in a No-clean Solder Paste for Lead-free Surface Mount Technology

This paper presents the behavior of SnAgCu (SAC) solder paste when analyzed using thermal profiling when exposed to (1) conventional reflow and (2) newly adjusted profiles. Thermal gravimetric analyzer (TGA) was used extensively to study the thermal properties of the flux and to simulate the heating processes the material undergoes during ball-attach reflow process. Experiments have proved that slower ramp rate will allow gradual evaporation of volatiles prior the non-volatile reaction of flux material at soak zone. This understanding of the reaction that takes place prior to soak zone will enable ball-attach engineers to reduce the residue contamination on the ball surface by preventing the amount of solid components to be dragged atop the ball surface during rapid outgassing of solvents at a faster pre-heat ramp rate.