Different products need to choose different solder pastes. How to choose a solder paste is an important problem to be solved in PCBA production. Now combined with relevant domestic and foreign standards, the inspection items of solder paste are introduced as follows. The selection of solder paste includes alloy composition, viscosity , effective working time, storage period.

First: Alloy composition: In addition to the consideration of solderability, the electrical requirements and mechanical properties of solder particles in solder paste recycling solder paste also need to be considered one by one. Generally, 63Sn37Pb tin and lead are still used more in use. , because of its better alloy properties, 60Sn? The tin-lead ratio of 40Pb is also good, and the price is slightly lower. In addition, silver-containing solder paste can also be seen, and its content varies from factory to factory, about 2%. The main purpose is to suppress the use of silver-palladium as a material for the termination of parts , the phenomenon of peeling occurs in the soldering process, and for heat-sensitive parts, low-temperature gold containing bismuth or indium can also be selected, but in addition to the high price, it is necessary to refer to the gold-containing characteristics of the phase and the requirements of related specifications.

Second: Viscosity: This is the most difficult parameter in the use of solder paste. It affects the selection of solder paste. It also causes troubles in the selection of solder paste. You can choose solder paste with a viscosity of 700-1000kcps. For stencil printing, choose 500-700KCPS. In injection mode, in injection mode, lower 300-500KCPS is better.

Third: Effective working time, the solvent contained in the solder paste is too volatile, it is easy to dry the solder paste and it is difficult to work, and it is easy to lose the adhesion to the parts, which will cause trouble to batch production, so when choosing, it should be It is better to choose the effective working time of more than four hours.

Fourth: Shelf life: Recycling of solder paste Due to the presence of chemical additives in solder paste, it is easy to change and lose its original function due to its strength in time. Therefore, its shelf life and service life need to be paid attention to, first use first, do not use Expired, refrigerated in place of the temperature (about 4 degrees) helps to preserve and use the appropriate length of life.