In SMT chip processing, solder paste printing is a complex process, which is prone to bring some shortcomings and affect the quality of finished products. Therefore, in order to avoid some faults in printing,
I. sharpening. Generally, the solder paste on the pad will be in the shape of a hill after printing. Cause: it may be caused by the gap of scraper or too large viscosity of solder paste.
Avoidance or solution: SMT patch processing, appropriately reduce the gap of scraper or select solder paste with appropriate viscosity.
2.The solder paste is too thin.The causes are as follows: The formwork is too thin; Scraper pressure is too high; And poor fluidity of solder paste.
Avoidance or solution: select formwork with appropriate thickness; Select solder paste with appropriate particle size and viscosity; Lower the scraper pressure.
3、 After printing, the thickness of solder paste on the pad is different. Causes: Uneven mixing of solder paste makes the particle size different. The template is not parallel to the printed board;
Avoidance or solution: fully mix the solder paste before printing; Adjust the relative orientation between the template and the printed board.
4、 The thickness is different, and there are burrs on the edge and appearance.Cause: it may be that the viscosity of solder paste is low and the hole wall of template opening is rough.
Avoidance or solution: select solder paste with slightly higher viscosity; Check the etching quality of the template opening before printing.
5、 Fall. After printing, the solder paste falls to both ends of the pad.Causes: The scraper pressure is too high; The printed board is not positioned firmly; Solder paste viscosity or metal content is too low.
Avoidance or solution: adjust the pressure; Fix the printed board from the head; Select the solder paste with appropriate viscosity.
6、 Printing is not even.The causes are as follows: The opening is blocked or some solder paste is stuck at the bottom of the formwork; The viscosity of solder paste is too small; There are large-scale metal powder particles in the solder paste; The scraper is worn.
Avoidance or solution: clean the opening and the bottom of the formwork; Select the solder paste with appropriate viscosity and make the solder paste printing effectively cover the whole printing area; Select the solder paste with the particle size of metal powder corresponding to the opening size; Check and replace the scraper.
Post time: Mar-28-2022