How do you clean and scrap SMT stencils?

After the production line stops running:

1. The stencils should be disassembled. Carefully remove any residual welding paste on the front using a welding paste scraper, and discard the dried welding paste.

2. Use a special cleaning agent to spray evenly on the surface of the stencils, and use the wiping paper to wipe the stencils repeatedly until there is no visible welding paste and impurities on the upper and lower sides of the stencils.

3. Use two pieces of wiping paper with a cleaning agent to wipe the upper and lower sides of the stencils separately until no obvious welding paste residue is seen.

4. Use an air gun to thoroughly blow the stencil holes in the order from top to bottom and from left to right, paying special attention to the BGA, QFP, and smaller spacing IC areas.

5. Repeat the above cleaning steps until there is no visible welding paste residue in the stencil holes.

Scrapping of stencils in Shenzhen Guangming District SMT processing plant

1. Stencils showing obvious damage and unable to guarantee normal silk screen characters will be scrapped after confirmation by engineering staff. The scrapped stencils should be marked on the outside of the outer frame and placed in the scrapped stencils area;

2. When the tension of the 55*65 steel plate is less than 30N/cm, 42*52 stencils are less than 25N/cm, or the maximum difference of the tension test is greater than 10N/cm, it should be scrapped immediately.

3. If the cumulative number of production and printing reaches more than 50,000 times, this steel plate should be scrapped.

4. Due to the PCB version upgrade, it is confirmed by the engineering staff and discarded.

5. Due to quality improvement, the stencils need to be reopened, and the stencils before improvement is discarded.