Study on wettability and corrosivity of a new no-clean flux for lead-free solder paste in electronic packaging technology

Solder paste plays a critical role in SMT (surface mount technology) and reflow soldering. And flux is an important material in composition of solder paste. Due to the drive towards lead-free electronic packaging and no-clean soldering technology, a new no-clean flux contained composite activators was formulated specifically for lead-free paste. Spread test was carried out to evaluate the activity of the newly developed flux with Sn3.0Ag0.5Cu lead-free solder. Influence of flux residues on corrosivity of cu substrate was also investigated. The results showed that the new no-clean flux contained composite activators exhibited better soldering performance. Corrosivity of flux residues related to activators in fluxes. The new no-clean flux contained composite activators had less residues and minor corrosivity than flux which contained simple activators of organic acids. Therefore, composite activators are promising no-clean flux ingredients for lead-free solder paste.