The main measures to reduce surface tension and viscosity in pcba welding are as follows.

①Increase the temperature. Elevating the temperature can increase the molecular distance within the molten solder and reduce the attraction of the molecules within the liquid solder to the surface molecules. Therefore, increasing the temperature can reduce the viscosity and surface tension.

②Adjust the metal alloy ratio. The surface tension of Sn is very large, and the addition of Pb can reduce the surface tension. When the content of lead is increased in Sn-Pb solder, when the content of Pb reaches 37%, the surface tension is obviously reduced.

③ increase the active agent. This can effectively reduce the surface tension of the solder, and can also remove the surface oxide layer of the solder.

④ Improve the welding environment. Nitrogen-protected pcba soldering or vacuum soldering can reduce high temperature oxidation and improve wettability.