Some details in the SMT placement process can eliminate undesirable 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 dye 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.
SMT patch
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 squeegee to remove solder paste from the wrong printed circuit board can cause problems. The printing plate 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 easy to remove before it dries.
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 to remove unnecessary cans. At the same time, SMT chip processing plants also recommend hot air drying. If using a horizontal stencil cleaner, the clean side should be down to allow the solder paste to fall off the board.
SMT chip processing prevents solder paste defects:
During the printing process, the printing cycle wipes between the templates in a specific pattern. Make sure that the stencil is on the pad, not the solder mask, to ensure that the solder paste printing process is clean. Online, real-time slurry inspection and reflow before welding are all process steps to reduce process defects before welding.
For fine stencils, if damage occurs between the thin pins due to the bending of the stencil section, the solder paste between the pins may deposit, causing 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.