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Home SMT Stencil FAQsSMT Stencil FAQs
1. What is the difference between a solder mask Gerber file and a solder paste Gerber file
Answer: The solder mask Gerber file has all of the mask openings including surface mount, component holes, and vias. The solder paste file has openings for just the surface mount pads and usually they are smaller e.g. a 50 by 50 mask opening will translate into a 48 x 48 paste opening.
2. What is squeegee view
Answer: The squeegee view refers to the side of the board that paste is to be applied to. If you are looking at the image, and that is the side you want to apply paste to, that is the squeegee view.
3. Which layer file do I need to send you to make a solder paste stencil
Answer: We prefer the Solder Paste Gerber file to cut the stencil. If you do not have this file you can send us the Copper or Solder Mask Gerber file which we can convert to a Solder Paste Gerber file. The pads in the Solder Mask Gerber files are usually larger than the ones on the Solder Paste Gerber files. If you provide the Solder Mask Gerber file you need to provide the reduction information. If you are ordering a bottom side stencil you need to include the silkscreen Gerber file for the bottom side too.
4. I am interested in knowing more about your stencils to use for screen printing, such as mesh tension, estimated impression life, durability of mesh to stencil bonding.
Answer: Tension is about 30 Newtons per square centimeter. Thread count is 60-125. Print life varies drastically from customer to customer, depending on squeegee pressure, under board support, and handling. Average usage is100,000- 200,000 cycles.
5. What guidelines do I need to follow to specify the correct thickness of a stencil when using 0402 components, or is this something you recommend during fabrication
Answer: Stencil thickness is determined by the desired paste height. Typically the paste height is 1 mil less than the stencil thickness. For example .006 thick stencil would deposit .005 paste height. So choose the thickness by the paste height you desire.
6. What else can I use to clean stencils besides stencil wipes
Answer: We recommend using IPA to clean stencils. It should be electronic grade IPA at 99%.
7. Whats fiducial marks
Answer: Fiducial marks can be used to align the stencil to the board. Depending on the printer vision location, the fiducials can be half etched on either the squeegee side or the board side, also can be etched through. The fiducial marks are normally 1.0mm in diameter. If fiducials are required, ensure they are contained in the Gerber files and indicate the side they are required on.