1. Scraper pressure, scraper speed and demoulding speed. Single process parameters have a great impact on the printing quality of solder paste. Soldering on different types of pads

Paste printing quality has the same response to the change of process parameters, and the printing quality of pad spacing and small size pad is more It is easy to fail to meet the acceptance criteria.

2. The scraper pressure has no obvious effect on the printing quality of solder paste on the premise that it is higher than the internal pressure of solder paste, but too high pressure will The alignment accuracy of laser steel mesh and PCB is affected, and the wear of steel mesh and scraper is accelerated. At the same time, the printed solder paste first increases and then decreases with the increase of scraper pressure, and the height of solder paste decreases with the increase of scraper pressure.

3. The speed of the scraper has a great impact on the printing quality. The printing quality decreases with the increase of the speed. The main table is lack of printing, contamination, etc.At the same time, the volume of printed solder paste decreases first and then increases with the increase of scraper speed, and the height of solder paste has no obvious relationship with the scraper speed.

4. The printing quality decreases with the increase of the demoulding speed, which is mainly shown by the sharp drawing on the QFP and other slender pads, blocking the SMT steel mesh opening and causing missing prints. At the same time, the volume of printed solder paste increases first and then decreases with the increase of the demoulding speed, and the height of solder paste increases first and then decreases with the increase of the demoulding speed.

5. Based on the solder paste printing process and the clay characteristics of the solder paste, it is determined through analysis that the above effects of various process parameters on the printing quality are caused by welding The edge performance of the solder paste and the pressure on the content of the solder paste are combined.

6. The process window of solder paste printing was determined through experiments, and the influence of process parameters on welding was verified through a complete surface mounting test The research of paste printing performance has verified the accuracy of the process window, which can provide reference for actual production.