1. Activator:
solder flux can effectively remove oxides on the surface layer of PCB copper film pads and soldering parts of parts, and at the same time have the function of reducing the surface tension of tin and lead;
2. Thixotropic agent: solder flux plays the role of adjusting the viscosity of solder paste and printing performance, and can prevent tailing and adhesion during printing;
3. Resin: solder flux can increase the adhesion of solder paste, and it can protect and prevent the PCB board from being re-oxidized after soldering; it also plays an important role in fixing parts;
4. Solvent: It is the solvent in the solder flux, which plays a role in regulating the uniformity of the solder paste during the stirring process, and has a certain impact on the life of the solder paste.
5. Selection of solder flux
1. Match the melting point
In order to cooperate with the use of solder, the melting point of the selected solder flux should be 10-30°C lower than that of the solder. If the melting point of the solder flux is too lower than the melting point of the solder, it is easy to melt prematurely and cause premature failure of the active components of the solder flux.
2. According to the surface oxide film characteristics
For an alkaline oxide film, an acidic solder flux should be selected; for an acidic oxide film, an alkaline solder flux should be selected.
3. According to the brazing process
Choose different forms of solder flux according to the specific process, such as liquid solder flux for wave soldering, paste solder flux for high frequency or intermediate frequency induction brazing, powder solder flux or paste flux for flame brazing, etc. .
4. According to the characteristics of the substrate
Due to the different oxide films on the surface of different substrate materials, there are also great differences in the types of solder fluxes to be selected, especially for some difficult-to-solder metals, such as magnesium-containing aluminum alloys, stainless steel, and hard alloys. In order to ensure the welding performance of magnesium-containing aluminum alloys, solder fluxes with strong activity are usually selected.
