The role of Surface Mount Technology (SMT) in the process of solder paste printing in SMT assembly is important. In this case, the scraper blade plays an important part when using automatic printing machines for solder paste printing. Here are a few techniques to adjust and prepare scraper blades for SMT placement that may be useful for everyone.
Firstly, it is important to set the angle of the scraper blade between 45° and 60° in order to roll good paste and consequently obtain better printing results.
Secondly, an appropriate speed should be maintained within the range of 20 to 40 mm/s such that optimal printings are achieved by the scraper blade.
Another critical factor is adjusting pressure which ranges from 5 -12N/(25mm) so as to ensure total removal of solder paste from stencil surface by means of a squeegee.
Moreover, designers commonly pay attention towards selecting a size for a squeegee that would exceed PWB length by about fifty millimeters while ensuring contact with metal template6s.
When installing PCBs and stencils together, usually there is zero clearance. However, sometimes the PCB plane might have to be slightly higher than stencil plane due to different reasons specific to each machine involved in manual adjustments.
At last, this is a short break when the stencil deviates from the solder paste pattern to guarantee achievement of an improved printing pattern.
To put it briefly, SMT assembly can be described as a process that involves connecting electric components on PCBs and has many different steps. Accordingly, changing and fixing angles, speeds, pressures and the breadth of the squeegee blades in solder paste screen-printing are essential. I hope these techniques will help everyone.