Soldering terminology

The volatile constituents of flux escape during soldering while the solid fraction remains as a residue. In conventional fluxes, the volatile component is rosin and the nonvolatile components are the activators and surfactants. As rosin-containing flux used to be the more common, solids content reached as much as 30 %. Lately, however, CFC restrictions made it more important to use flux that is cleaned with water or needs no cleaning, decreasing solids content to less than 5%, leading to a growing demand for fluxing agents poor in rosin.