What are flux systems designed for lead-free soldering processes?
Flux systems designed for lead-free soldering differ from traditional fluxes for Sn63Pb37 in several ways. For solder pastes, the flux must have a greater ability to reduce the surface tension of lead-free alloys, which tend to have slightly higher values. This reduction in surface tension will promote adequate wetting and spread. Also the flux system must remain active at higher temperatures and not char or discolor at these temperatures. The flux system must also possess excellent hot slump behavior as to not case bridging during the preheat time. In wave soldering, the flux must be thermally stable at higher temperatures and longer contact times, plus have the ability to adequately reduce of surface tension to promote good hole-fill. The flux must remain easily removable if it is a water wash type. In hand-soldering the flux must be able to reduce wetting rapidly and give good wetting as to not extend the contact times with the parts to be soldered. The flux must remain unaffected b
