Solder paste printing is a complicated process in the SMT patch proofing process, and it is easy to show some defects and affect the quality of the final product. Therefore, in order to prevent some shortcomings often appearing in printing, SMT processing solder paste printing rare defects prevention or treatment methods:
1. Draw the tip, usually the solder paste on the pad will be hill-shaped after printing. The reason: it can be formed by the squeegee gap or the viscosity of the solder paste is too large. Prevention or treatment method: SMT patch proofing processing properly adjust the gap of the scraper or select the solder paste with suitable viscosity.
2. The solder paste is too thin. The reasons are: 1. The template is too thin; 2. The pressure of the squeegee is too large; 3. The mobility of the solder paste is poor. Prevention or treatment method: choose a template with a suitable thickness; choose a solder paste with a suitable particle size and viscosity; reduce the squeegee pressure.
3. After printing, the thickness of solder paste on the pad is different.
1. The solder paste is not evenly mixed, making the particle size not common.
2. The template and the printed board are not parallel; prevention or treatment methods: mix the solder paste before printing; adjust the position of the template and the printed board.
Fourth, the thickness is not opposite, and there are burrs on the edge and surface. Reasons: It may be that the viscosity of the solder paste is low, and the wall of the template hole is rough. Prevention or treatment method: select a solder paste with a slightly higher viscosity; check the etching quality of the template opening before printing.
Five, fall. After printing, the solder paste sinks into the middle of the pad. Reason:
1. The scraper pressure is too large;
2. The printed board is not firmly fixed;
3. The viscosity or metal content of the solder paste is too low. Prevention or treatment method: adjust the pressure; fix the printed board from the beginning; select the solder paste suitable for the viscosity.
6. Incomplete printing means that there is no solder paste printed in the middle of the pad. The reasons are:
1. Open hole infarction or some solder paste sticking to the bottom of the template;
2. The viscosity of the solder paste is too small;
3. There are large-scale metal powder particles in the solder paste;
4. The scraper is worn. Prevention or treatment method: clean the opening and the bottom of the template; select a solder paste with suitable viscosity, and make the SMT patch proofing solder paste printing can effectively cover the entire printing area; select the solder paste corresponding to the metal powder particle size and the opening size; Introspect to change the scraper.
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