What are the recommended aperture sizes for making a solderpaste stencil for SM3ZS067U310AMR1200 ?
I’m getting solder bridges with my current stencil. (I’m using a proper pick-n-place machine and reflow oven.) My stencil apertures are the same size as the recommended pad size: 1.55mm x 0.3mm. I have tried two different stencil thicknesses: 5mil and 6mil. They both have solder bridges after reflow.
Greetings,
Assembly is something of a scientific art unto itself, and a bit outside the scope of our expertise at DK.
While aperture size is obviously a major factor in the successful assembly of fine-pitch devices, there are a number of other variables that can come into play; choice of solder paste, presence of solder mask between pads, reflow profiles, equipment and process factors, what a person ate for lunch last Tuesday, etc.
While component manufacturers may in some circumstances offer guidance in such matters, it’s not a thing that can be expected, and something akin to a recipe one might find on the side of a container of corn meal; a suggestion that some have found useful but by no means the only path to success.
Speaking from a position of gross ignorance in matters of production assembly yet substantial experience in handmade prototype-y work, I’d offer the observation that surface tension is one’s frenemy; keep a dry space between pads and it’ll suck parts into alignment and compensate for a great many wrongs, but let the flux amoebas touch and it becomes a path for rogue solder balls to reach out and touch someone.
Have you put any of your assemblies pre-reflow under a microscope to check for the presence of precursor bridging phenomena?
