Background on Solder Flux Chemistry

Soldering (Ref 4) is defined as the process of joining metallic surfaces with solder without the melting of the basis metal. In order for this joining to take place, the metal surfaces must be clean of contamination and oxidation. This cleaning action is performed by the flux (Ref 2), a chemically active compound which, when heated, removes minor surface oxidation, mini- 

It is important to note that lead-free soldering requires higher processing temperatures. Thus, it is anticipated that flux chemistries are changing to deal with this fact. 

Low Solids Flux. Until the mid-1980s, liquid soldering fluxes were formulated in 25 to 35 wt% solids or non-volatile liquid. Then flux chemistries changed and new formulations. 

---