Q: Can I order customized StencilMate™ stencils based on my particular design requirements?
A: Yes, StencilMate™ stencils can have the dimensions customized for any application. Currently, there are only two thicknesses available, 0.008" (0.20mm) and 0.004" (0.10mm). Once the StencilMate™ thickness has been selected, any outside dimensions or aperture patterns can be applied. We can accept .dxf, .dwg or technical data sheets in any format for designing the right apertures for the part. We can accept .dwg, .dxf or cut out sections of the board GERBER files for the board.
Q: If I order some customized StencilMate™ stencils, will there be any additional tooling charges or NRE charges?
A: No, there are no additional fees associated with ordering custom StencilMate™ stencil designs. Depending on the design, there may be a requirement for a minimum order.
Q: How will a StencilMate™ stencil be affected by placement on a warped area of the board / part?
A: StencilMate™ stencils will not be affected at all by a warped area of the board or part. Since the StencilMate™ stencil is flexible, it will conform to all areas. This will ensure that the paste print will be uniform and consistent every time.
Q: How many times can a StencilMate™ stencil be used to perform leadless device rework?
A: The StencilMate™ stencils are designed for single use only. If a StencilMate™ stencil was used correctly, there are only two reasons to repeat the rework process… either the wrong part was placed or it was mis-oriented.
Q: Are StencilMate™ stencils UL approved?
A: No, StencilMate™ stencils have not been UL approved. Both the polyimide material and the acrylic adhesive have been UL approved. However the two materials in combination have not been UL approved. Contact BEST if your application calls for the use of UL approved components only.
Q: Do I need to mask off the areas surrounding the StencilMate™ stencil while I am applying the solder paste, and if I do, what is the best material and method for that?
A: There are two things to look at when determining if you need to mask off areas surrounding the StencilMate™ stencils. One item is the squeegee (See BEST Marketplace section for different sizes). If the squeegee size matches the StencilMate™ stencil size, it should be fairly easy to apply the solder paste without the need to mask surrounding areas. The other item of concern is manual dexterity of the technician performing the rework process. If the technician has poor manual dexterity, it may be necessary to mask off the surrounding areas. If it does become necessary to mask the surrounding areas, we have found that polyimide tape (See Kapton™ tape in the BEST Marketplace section) works well for this. That way if some solder paste ends up outside the dimensions of the StencilMate™ stencil, it can be lifted up out of the rework area along with the tape after the paste application is complete.
Q: What effect will alcohol and other cleaning solvents have on StencilMate™ stencils?
A: Alcohol and other similar solvents may attack the adhesive of the StencilMate™ stencil and cause it to lose its adhesive characteristics. This is generally not a concern after the device has been replaced and reflowed because it has already served its purpose and adhesion to the laminate surface is no longer required.
Q: After the StencilMate™ is adhered to the board, the solder paste printed and reflowed, what does the cross section look like?
A: See a sample cross section below
Q: Is the solder joint as reliable using this method versus other methods?
A: In a reliability study commissioned by an agency of the Department of Defense, the StencilMate™ was demonstrated to produce as a reliable a solder joint then other more traditional and more time-consuming methods.
Q: What does IPC have to say about this rework procedure?
A: This procedure is now part of the IPC 7711/21 “Handbook of PCB Rework and Repair Procedures” IPC 7711/21 Procedure 126.96.36.199. and 188.8.131.52.
Q: After the StencilMate™ is adhered to the part and reflowed and I pull the stencil off-how do I clean the bottom of the device?
A: Use the proper cleaning solution based on flux chemistry you are using. We recommend a water soluble chemistry followed by simple DI water for cleaning.
StencilMate™ Patent Pending, BEST Inc.