How does SMT chip processing prevent solder paste defects?


Some details of the SMT placement process can eliminate bad conditions, such as incorrectly printing solder paste and removing solder paste from the circuit board. Our goal is to deposit solder paste at the desired location. The misalignment of stained tools, dry solder paste, stencil and circuit board can cause unwanted solder paste to be generated on the bottom of the stencil even during assembly. Common solder paste problems: Can you use a small squeegee to remove misprinted solder paste from the board? Will this cause solder paste and small solder balls to enter pores and small gaps? Using a small scraper to remove solder paste from the wrong printed circuit board can cause problems. Printing plates with printing errors can usually be immersed in a compatible solvent, such as water containing additives, and small particles of tin can be removed from the plate with a soft brush. I like to soak and wash repeatedly instead of violently dry brushing or shovel. After printing the solder paste, the longer the operator waits to clear the printing error, the more difficult it is to remove the solder paste. When a problem is found, the improperly printed board should be immediately placed in the soaking solvent, because the solder paste is easily removed before drying. Wipe it with a cloth and avoid it, in order to prevent solder paste and other contaminants on the surface of the circuit board. After soaking, scrubbing with a gentle spray usually helps remove unnecessary cans. At the same time, SMT chip processing plants also recommend hot air drying. If a horizontal stencil cleaner is used, the clean side should be down to allow the solder paste to come off the board. SMT chip processing prevents solder paste defects: During the printing process, the printing cycle wipes between templates in a specific pattern. Make sure that the stencil is on the pad, not the solder mask, to ensure a clean solder paste printing process. Online, real-time slurry inspection and pre-welding reflow welding are all process steps to reduce pre-welding process defects. For fine stencils, if damage occurs between thin pins due to the bending of the stencil section, the solder paste between the pins may deposit, resulting in printing defects and/or short circuits. Low viscosity can also cause solder paste printing defects. For example, high operating temperature or high speed blades can reduce the viscosity of solder paste during use, leading to printing defects and excess solder paste deposition caused by bridges.