Many friends who are engaged in the electronic soldering industry often confuse the concepts of flux, rosin and solder paste
. In fact, rosin and solder paste belong to flux. Its purpose is to increase the reliability of welding between the solder and the object to be welded during the welding process. The main function of the flux is the wetting effect. , Remove oxidation, assist heat conduction, reduce metal surface tension, make solder joints beautiful, etc.
There are many types of fluxes on the market, which can generally be divided into the following three series:
(1) Inorganic series fluxes, usually the inorganic series fluxes have strong chemical action and very good fluxing performance, but they are highly corrosive and belong to acidic fluxes. Because it dissolves in water, it is also called water-soluble flux, which includes two types of inorganic acids and inorganic salts.
(2) Organic series flux (OA). The fluxing effect of organic series flux is between inorganic series flux and resin series flux. It is also acidic and water-soluble flux.
(3) Resin-based fluxes are resin-based fluxes that are used in the largest proportion in the soldering of electronic products. Because it can only dissolve in organic solvents, it is also called organic solvent flux, and its main component is rosin. The main components of rosin are abietic acid and pimaric acid. Generally, the neutral liquid rosin has a certain activity and shows weak acidity. It reacts with oxides on the metal surface to form compounds such as copper abietic acid, which are suspended on the surface of solder and used. No corrosion at all times, strong insulation, generally speaking, rosin is a commonly used better flux.
Its melting point is 127°C and its activity can last up to 315°C. The optimal temperature for soldering is 240-250°C, so it is within the active temperature range of rosin, and its soldering residue does not have corrosion problems. These characteristics make rosin a non-corrosive flux and are widely used in electronic equipment. Welding. Solid flux is suitable for soldering iron soldering, while liquid and pasty fluxes are suitable for wave soldering respectively. In actual use, it is found that when rosin is a monomer, its chemical activity is weak, and it is often not sufficient to promote the wetting of solder. Therefore, it is necessary to add a small amount of activator to improve its activity.