Solder paste is an indispensable solder material in SMT process, it is a paste mixture formed by mixing solder powder, flux and other surfactants and thixotropic agents. It is mainly used for the welding of electronic components such as PCB surface resistance, capacitor and IC in SMT process.
Chemical composition of solder paste
Solder paste, mainly composed of flux and solder powder
(1) The main compositions of the flux and their effects:
A. Activation: The composition mainly functions to remove the oxidized substances on the surface of the PCB pad and the soldering parts of the components, and has the effect of reducing the surface tension of tin and lead.
B. Thixotropic: The composition mainly used to adjust the viscosity of the solder paste and the printing performance, so as to prevent the occurrence of tailing, adhesion and the like in printing.
C. Resins: The composition mainly serves to increase the adhesion of the solder paste, and has the function of protecting and preventing the reoxidation of the PCB after soldering; the composition plays an important role in fixing the components.
D. Solvent: The composition is a solvent for the flux, and plays a uniform role in the stirring process of the solder paste, and has a certain influence on the life of the solder paste.
(2) Solder powder:
Solder powder, also known as tin powder, is mainly composed of tin-lead, tin-bismuth, tin-silver-copper alloy, and the general ratio is SN63/PB37, SN42BI58, SN96.5CU0.5AG3.0 and SN99CU0.7AG0.3
