As we all know, the soldering of lead-free tin wire
is more difficult than the soldering of lead-tin wire. When transitioning to a lead-free process, we need to have an in-depth understanding of some of the characteristics of lead-free tin wires in order to achieve good work. Therefore, before working, it is necessary to remove the dirt, metal oxides, other impurities or gas layers attached to the metal surface.
The following four points illustrate the important role of flux in welding:
First, the flux has the effect of reducing the surface tension and increasing the diffusivity: because the dissolved solder has a large surface tension, in order to allow the solder to better extend and penetrate between the metal surfaces to be joined, it is required that the solder should reduce the surface tension;
Second, the flux has a cleaning effect: because the metal surface has been oxidized at room temperature, it is actually easier to be oxidized at higher temperatures. The outer metal layer is usually covered by an oxide film. If this layer of oxide film is not removed, the dissolved solder cannot penetrate into the surface of the object to be soldered, and the soldering operation cannot be completed. Therefore, the important role of the flux is to use the chemical action generated during welding to remove the attached oxides, so that the clean metals can be more easily combined.
Third, the flux has the effect of preventing oxidation: the flux has quickly covered the surface of the solder and the solder joint surface before the solder flows out, so that the solder can easily flow in, and then a thin flux layer is formed on the solder surface.
Fourth, the flux has a corrosive effect: if it is not used properly, it will cause corrosion to the object to be welded. Therefore, when welding, we must pay attention to the use environment, production process, and the quality of lead-free tin wires to avoid unnecessary losses.