SMD-Stencils are precision tools which have to comply with high requirements, as they take a key role in the SMT (surface mount technology) process. We offer following SMD-Stencils:
Solder paste stencils are used to apply solder depots on printed circuit boards with a screen printing technique. SMD components (SMD = surface mounted device) are placed within these depots subsequently and soldered with a following reflow- or vapor phase process.
Stencils for adhesives are primarily used for mixed assembly, as substitution for a dispenser, and are necessary before component mounting and wave soldering.
Our lasered SMD-Stencils (made of stainless steel) allow a precise placement and strenght-of-shape of the solder- / adhesive- depots on the PCB and therefore accomodate the small track-widths and spacings as well as the hightech multipin components. Our SMD-Stencils are perfectly suited for finepitch and BGA assembly.
Terms in this Design-Aid:
top side = squeegee side, top view
bot side = opposite side of squeegee, bottom view
aperture = hole in the stencil, stencil pad
Processing of the stencil pads
Generally we recommend a reduction of the stencil pads (apertures) by 10%. This could be the done by the customer (with export of the paste data) or is done by us on request.
Modification of the pad form
Generally, you should (along with your assembly) make a decision in respect of angular or rounded pads.
Text on the stencil
At Multi-CB 100 characters of text are inclusive (more text is feasible for a small fee). The text can be produced half lasered and lasered.
Half lasered text
Stencils are generally lasered from the bottom-side. The production-related conical cross-section is then wider on the side opposite to the squeegee and allows a better peeling after the aplication of solder paste / adhesive (glue). Half lasered text is thus on the bottom side of the stencil.
As the half lasered text, also the lasered text is cut from the bottom side. You can decide whether the text is readable from the bottom or top side. To ensure best stability, lasered text is executed in a special font which prevents breaking out of the letters.
Placement of PCB data
If we get no information regarding data placement from the customer, the PCB data is placed based on the available data centrally on the stencil. Thus based on the board outline, or the pads (copper). If a different placement is wished, please let us know when ordering (text, sketch).
When ordering your stencil along with your PCB, you ideally have the stencil data already integrated in the digital production data and placed a note in your order to notify us
Examples of default layers for stencil data.
On request, we can add the required perforation to your stencil for all established, licence-free quick clamping frames / holders.
In this case, please send us the data sheet of the quick clamp together with your order or contact us.
In the IPC-design directive for SMD stencils (IPC-7525A) is mentioned, as other applicable policy for the cleaning of stencils and misprinted printed circuit boards, IPC-7526 (Stencil and Misprinted Cleaning Handbook).
In the production of our SMD laser stencils, we place great value on 100% quality. That's why we measure all the pads for dimensional accuracy and the real presence of the pads after production of your SMD stencil.
The application of registration / fiducial marks ensures the correct positioning of the stencil to the PCB, by the vision system of the assembly company.