In nature, except for gold and platinum, almost all metals are oxidized if they exposed to air, and an oxide layer is formed on the surface, hindering the occurrence of PCB soldering. Therefore, in the process of soldering the PCB circuit board, a material capable of purifying the soldering surface metal and the solder surface to help soldering, that is, flux.
In the wave soldering technics, liquid flux is used, and the flux and solder are used separately. In the reflow technics of printed circuit boards, flux is an important composition of solder paste.
Chemical composition of flux in the traditional PCBA technics, the flux is usually based on rosin. The rosin has weak acidity 、hot melt flow and good insulation, moisture resistance, non-corrosiveness, non-toxicity and long-term stability, which is excellent soldering material.
Rosin has great differences in chemical composition and properties along with variety, origin and production techinics. Therefore, the suitable selection of rosin is the key to ensure the quality of flux. In addition, general-purpose fluxes include active agents, film-forming materials, additives, and solvents.