The purpose of using solder paste for PCB assembly
The purpose of applying solder paste in PCB assembly is to evenly apply an appropriate amount of solder paste on the pads of the printed circuit board to ensure that the chip assembly and the pad corresponding to the printed circuit board achieve a good electrical connection and have sufficient machinery strength. Solder paste application is a key process in the SMT reflow process. There are three ways to apply solder paste in PCB assembly: drip coating, screen printing and metal stencil printing. In recent years, non-contact solder paste spraying technology has been introduced. Among them, metal stencil printing is currently the most widely used method.
Solder paste printing is a key process to ensure PCB assembly quality. According to statistics, on the premise of ensuring the design specifications of printed circuit boards, the quality of components and printed circuit boards, about 60% to 709% of quality problems are caused by PCB assembly and printing processes. The amount of solder paste used in PCB assembly should be uniform. The solder paste graphics should be clear, and adjacent graphics should not stick together as much as possible. The solder paste pattern and the pad pattern should be the same, try not to be misaligned.
Under normal circumstances, the amount of solder paste per unit area on the pad should be about 0.8 mg/mm3, and it should be about 0.5 mgmm2 for the distance between the pieces. The solder paste brushed on the SMT chip processing substrate can allow a certain deviation from the desired weight value. As for the area of solder paste covering each pad, it should be above 75%. When using no-clean technology, the solder paste is required to be completely on the pad, and the lead-free solder paste completely covers the pad.
After the solder paste is printed, there should be no serious collapse, the edge image is neat, and the misalignment does not exceed 02 mm, to accommodate the spacer pads, the misalignment does not exceed 00 mm. The surface of the substrate assembled by PCB must not be contaminated with solder paste. When no-clean technology is used, the solder paste can be completely positioned on the pad by reducing the size of the template opening.
The above explained is the purpose of using solder paste for PCB assembly. I hope it will be helpful to you after reading. If you want to learn more about PCB assembly, please feel free to consult customer service online or call our service hotline (website Upper right corner) for consultation, we will wholeheartedly provide you with quality service!