The stencil thickness of the laser stencil and the SMT stencil shall be determined according to the assembly density of the printed board, the size of the components, and the spacing between the leads (or solder balls). Generally speaking, the pads and their larger spacing components require more solder paste, and the corresponding SMT stencil template should be thicker. Conversely, the smaller pads and narrower spacing components (such as narrow pitch) QFP and CSP) require less solder paste, and the corresponding template should be thinner. According to experience, the amount of solder paste on the general SMT component pads should be around 0.8mg/mm2, and the laser steel mesh should be around 0.5mg/mm2 for narrow-pitch components. Too much can easily lead to excessive eating of tin, such as Solder Bridge, and too few problems are likely to cause insufficient tin and insufficient welding strength.

What are the main factors lacking SMT patch stencil printing solder paste?

    1. After the solder paste is printed, the human element is accidentally knocked out. The SMT patch stencil printing paste is too small!

    2. solder paste missing SMT laser steel mesh or circuit board with contaminants (such as PCB packaging, SMT stencil wipes, foreign matter floating in the ambient air, etc.).

    3. The fixed clamping of the circuit board in the printing machine is loose.

    4. solder paste missing laser steel mesh thickness is uneven.

    5. When the printing machine was working, it did not make up for the increase of solder paste in time.

    6. the quality of solder paste is abnormal, mixed with foreign bodies such as hard blocks.

    7. The solder paste that has not been used up has expired and is used twice.

    8. board quality problems, there are inconspicuous masks on the pads, such as solder resists printed on the pads (green oil.

    9. The equipment parameters such as pressure, viewpoint, speed and demoulding speed of the solder paste scraper are not suitable.

    10. The solder paste scraper is damaged and the patch steel mesh is damaged.