Solder paste placement is probably the most critical stage of the PCB assembly process, and most surface-mount assembly problems can be traced back to poor paste placement. If you want to avoid time-consuming manual rework on your assembled boards, it’s essential that you have a clean, precisely positioned layer of solder paste. A few extra minutes ensuring that your paste layer is correct can easily save hours of rework with a hot air gun and a soldering iron later.
You’re bound to figure that out for yourself as soon as you start trying to automate any of your assembly, but as part of a series of tutorials on the different steps involved in small-scale manufacturing, I’ve tried to describe the basic process I use applying solder paste every day. Obviously there are a number of solutions for this (for a wide variety of budgets), but I’ve tried to describe what works for me making a few dozen panels a day, representing an investment of under $200 (stencils not included).
If you’re just getting started with surface-mount devices and solder paste, here are some suggestions for where to get stencils, paste, etc. but of course you should check your favorite electronics supply shop as well:
Laser Cut Stencils
- Plastic (Kaption, Mylar, etc.) – North America: Ohararp or Pololu
- Metal – Europe: laser-stencil.com
- Metal – North America: Stencils Unlimited
Isopropanol (IPA) Wipes:
- North America: HMC Electronics
- Europe: Reflow-Kit
- Alternative: Isopropanol can be bought off ebay and you can use a lint-free cloth
- North America: Digikey, etc.
- Europe: Reflow-Kit is one relatively easy to order from source
You might also want to have a look at these other helpful tutorials from Adafruit:
Have a tip? Post’em up in the comments!