How to Clean and Scrap SMT Stencils

After the Production Line Has Stopped Running:

1. Disassemble the stencils. Remove any remaining welding paste from the front of the
stencil using a scraper and throw away the dried paste.

2. Spray a cleaning agent evenly onto the stencils and wipe them with the wiping paper
until the welding paste is gone and there are no impurities visible on either the upper or lower side of
the stencil.

3. Wipe the stencils on both the upper and the lower side with two pieces of wiping
papers, using a cleaning agent. Continue until there is no visible welding paste residue.

4. The stencil holes should be blown out thoroughly using an air gun, in order to blow
them from top to left and from bottom to right. Pay special attention to BGA, QFP and the smaller
spacing IC area.

5. Repeat the cleaning process until the stencil holes are clean.

Shenzhen Guangming District, SMT Processing Factory: Scrapping Stencils

1. After confirmation by the engineering staff, stencils that are damaged and cannot
guarantee normal silkscreen characters will be scrapped. The stencils that have been scrapped should be
marked outside the outer frame, and then placed in the scrapped-stencils area.

2. If the tension of the steel plate 55*65 is less than 30N/cm or that of the stencils
42*52 is less than 25N/cm and the maximum tension difference is greater than 10N/cm then it should be
scrapped.

3. This steel plate must be scrapped if the total number of productions and prints
exceeds 50,000.

4. The engineering staff confirms that it was a result of the PCB upgrade and discards
it.

5. The stencils must be reopened due to the quality improvement. The stencils that were
used before the improvement are discarded.