Save time, save money and save your sanity. Solder stencils are invaluable if you’re making a printed circuit board with tiny SMD (surface mount parts). The low tech way to deal with SMD PCB’s is a syringe, and dabbing each spot with a tiny blob of solder paste by hand.
The better way is to use a solder stencil, which only allows solder to flow where you want it to. The concept is very similar to creating a silkscreen for a t-shirt actually. It’s amazing how skills bleed across disciplines.
Solder stencils are usually expensive, although there are services that do them cheaper. I recently found one that will print them for $5, but I haven’t used them yet so I can’t recommend them. Nevermind the price though, what I’m talking about here is being in a bind. You need a solder stencil, and for whatever reason (lack of planning, quick turn around) you don’t have one, and ordering one could take weeks.
Another method would be to use kapton film and a laser engraver. My laser is currently on loan to a friend though, so it was time to experiment!
The process is actually pretty simple:
-If you’re using Eagle to design your pcb’s, create a cam job, select the tCream layer (that’s the top paste layer) and choose to save it as an eps.
-Click ‘process job’. This will create the eps vector file.
-Open in adobe illustrator (or another vector program) if your cad software can’t import an eps. I used 3ds max so I needed to convert it to an AI file first.
-After import, convert the outline to an editable polygon and extrude it to desired thickness. 0.3mm seems to be perfect.
-Print at the highest resolution possible, ( e.g. 0.1mm layer height).
You should end up with something paper thin. In fact, it’ll feel a lot like paper. It may be a little rough around some of the holes depending on your printer, but it’ll do the job. You can clean it up or fill any areas it misses with a syringe. I’d much rather fix 10 pads with a syringe than 300.