There is no clean solder flux in the whole welding process. The flux removes the oxide layer on the surface of the welding material through the action of its own active substances, reduces the surface tension between the tin liquid and the material to be welded, and enhances the flow and penetration of the tin liquid. It has good performance and helps to complete the soldering, so its name is "flux". Solder alloys bond well with the material to be soldered and form a solder joint. In this process, the main role is the activator and other substances in the flux, which can quickly remove the pads and component pins. And sometimes it also protects the solder material from oxidizing before soldering is complete.