Lead-free solder used in lead-free environmentally friendly solder paste has become a reality today. These flux formulations enhance the soldering process and are formulated to provide excellent wetting performance and the increased chemical and thermal stability required for lead-free assembly. Traditional fluxes used with tin-lead alloys are not necessarily adequate to prevent the slow wetting of lead-free alloys and the higher temperatures typically associated with lead-free solders. Solder paste is fluxed. One is to isolate the air to prevent oxidation, and to increase capillary action, increase wettability, and prevent virtual soldering. Solder paste: white crystalline powder. Content 99.0%, acid value 0.5mgKOH/g, mp112℃, easily soluble in ethanol and isopropanol.

Flux formulations designed for lead-free soldering require new activator kits and thermally stable gel and wetting formulations to avoid solder defects. Since many lead-free alloys have slow wetting rates and high surface tension, selecting the correct flux for lead-free soldering can prevent the build-up of solder defects and can go a long way in maintaining production output. Preheating after flux application can gradually increase the temperature of the PCB and activate the flux. This process can also reduce the thermal shock generated when the assembly enters the crest. It can also be used to evaporate any moisture that might be absorbed or to dilute the flux carrier solvent, which if not removed would boil over the crest and cause solder sputtering, or produce vapor that would remain inside the solder and form a hollow Solder joints or blisters.