This auxiliary materials for reliable soldering. They should
1) dissolve and remove oxides and impurities from the surface of the solder metals
2) defend during the soldering process the metal surface and the molten solder from oxidation
3) reduce the surface tension of the molten solder,
4) to improve the spreadability of the solder and wetting them connected surfaces.
The effect of the metal exposed to solder, fluxes are divided into several groups.
1. Active, or acid fluxes. They are prepared on the basis of active substances: hydrochloric acid. chloride and fluoride compounds metals etc. These fluxes, rapidly dissolve the oxide film on the metal surface, which ensures good adhesion, and therefore, high mechanical strength of the junction. The remainder of the flux after soldering causes intense corrosion of the weld and the base metal. Therefore, these fluxes are applied only in the case when possible by a thorough rinsing and complete removal of flux residues.
During Assembly soldering electroradiation application of active fluxes is unacceptable.
2. Acid-free fluxes. The so-called rosin and fluxes, prepared on its basis with the addition of inactive substances (alcohol, glycerin).
3. Activated fluxes. The so-called fluxes, prepared on the basis of rosin with the addition of activators — small amounts of hydrochloric acid or phosphate of aniline, salicylic acid, hydrochloric acid diethylamide, etc. the High activity of some activated flux allows soldering without prior removal of oxides after degreasing.
4. Corrosion fluxes. It fluxes based on phosphoric acid with the addition of various organic compounds and solvents, as well as fluxes based on organic acids. The residues of these fluxes do not cause corrosion.