Along with the generation of SMT, lead-free solder paste also came into being. It combines flux and solder powder, as well as thixotropic agent and surfactant, so as to achieve better soldering effect during the soldering process. Lead-free solder paste is usually used in the soldering process of capacitors, resistors and other components on the surface of PCB. At room temperature, the lead-free solder paste also has a certain viscosity so that the electronic components can be pasted on the desired position. When the welding temperature is determined, a better connection effect can be achieved with the function of solvent and other auxiliary additives. For lead-free solder paste, it usually consists of two parts: solder powder and flux, and the different components exert their own unique properties.

Flux mainly includes activators, resins, thixotropic agents and solvents, etc. The activator in the lead-free solder paste can effectively remove the oxide of soldering parts, and can also effectively reduce the surface tension of lead and tin; the solvent can better stir and adjust the uniformity of the lead-free solder paste. Solder powder is usually composed of tin, bismuth and silver-copper alloys, etc., according to the ratio of different areas to achieve better soldering effect. According to different melting point requirements, solder can also be divided into soft and hard. According to customer needs and use requirements, solder can also be divided into various styles such as sheet, rod, block and wire. Solder powders of different materials and shapes also play their own unique functions in the working process. After understanding the function and composition of lead-free solder paste, it is necessary to better preserve it. Usually the solder paste needs to be controlled at 1-10 degrees Celsius, and it can be used for 6 months if it is not opened, and it should not be placed in a place exposed to sunlight.