The quality of solder paste is very important in SMT chip processing and production. Qualified solder paste should meet the following specific requirements:

① It shall have a long storage life. It can be stored for 3~6 months at 0~10 ℃, without chemical change or separation of solder powder and flux, and keep its viscosity

The degree and adhesion remain unchanged.

② It shall have good wetting performance. The active flux and wetting agent components in the flux should be selected correctly to meet the wetting performance requirements.

③ It has a long working life. After the solder paste is printed or coated on the PCB, as well as in the subsequent reflow preheating process, it can be placed at room temperature for 12 to 24 hours, and its performance basically remains unchanged, maintaining its original shape and size, without drying and blocking.

④ There shall be no solder spatter, tin bead and other defects during welding. This mainly depends on the water absorption of solder paste, the type of solvent in solder paste, boiling point and dosage, and the type and content of impurities in solder powder.

⑤ It has good welding strength. After welding, it shall be ensured that components will not fall off due to vibration and other factors.

⑥ The residue after welding has good stability, no corrosion, high insulation resistance and easy cleaning.