1. Pull the point, generally after printing the solder paste on the solder pad will be a hill shape.
Cause: it may be caused by the gap of scraper or the viscosity of solder paste is too large.
Avoidance or solution: adjust the gap of scraper properly or select the solder paste with appropriate viscosity in SMT patch processing.
2. The solder paste is too thin.
Causes are: 1. The template is too thin; 2. The scraper pressure is too large; 3. Poor flow of solder paste.
Avoid or solve: choose the appropriate thickness of the template; Choose solder paste with appropriate particle size and viscosity; Decrease the scraper pressure.
3. After printing, the thickness of solder paste on the solder pad is different.
Causes: 1. welding paste mixing is not uniform, so that the particle size is not common; 2. The template is not parallel to the printed board.
Avoid or Solution: Mix solder paste thoroughly before printing; Adjust the position of the template relative to the printed board.
4. The thickness is not the same, the edge and appearance of the burr.
Causes: may be the low viscosity of solder paste, template hole wall rough.
Avoid or solve: choose the solder paste with slightly higher viscosity; Check the etching quality of the template hole before printing.
5. The fall. After printing, the solder paste falls towards both ends of the solder pad.
Causes: 1. scraper pressure is too large; 2. the printed board positioning is not firm; 3. Too low viscosity or metal content of solder paste.
Avoid or solve: adjust stress; The printed board is fixed from scratch; Choose the solder paste with appropriate viscosity.
6. The printing is incomplete, which means that there are some places on the solder pad that are not printed with solder paste.
Causes are: 1. hole plugging or some solder paste stuck to the bottom of the template; 2. The viscosity of solder paste is too small; 3. there are large scale metal powder particles in the solder paste;
7. Scraper wear.
Avoid or Solution: Clean the holes and the bottom of the template; Select the solder paste with proper viscosity, and make the solder paste printing effectively cover the whole printing area;
Select the solder paste corresponding to the size of the metal powder particle and the size of the hole; Check and replace the scraper.
