Functions: 

1. Destroy the metal oxide film to make the solder surface clean, which is conducive to the infiltration of solder and the generation of solder joint alloy.

2. It can cover the surface of solder to prevent the solder or metal from continuing to oxidize.

3. Enhance the activity of solder and welded metal surface, and reduce the surface tension of solder.

4. Solder and flux are fused, which can increase the fluidity of solder and further improve the wetting ability.

5. It can accelerate the heat transfer from welding head to the surface of solder and welded objects.

6. Appropriate flux can also make the solder joints beautiful.

Features:

1. Wetting (lateral flow): It means that the molten solder forms a uniform, smooth, continuous and firmly attached solder layer on the metal surface.

2. Diffusion (longitudinal flow): Along with the wetting phenomenon of molten solder diffusion on the welded surface, there is also the phenomenon of solder diffusion into the solid metal.