Surface Mount (SMT) Our mods, hacks, tips and tricks for SMT manufacture…
If you want to do small scale prototype SMT manufacture, it may be faster to just deposit paste by hand onto the PCB instead of getting a stencil made and shipped. We use this for our prototypes and its very fast once you get the hang of it. Instead of stenciling paste on, a small syringe of paste is squeezed onto each pad, sort of like a cake decorator (but with toxic metal).
After the paste is deposited on the pads, each component is handplaced with tweezers. Then the entire board is reflowed. you can use hot air but a plate or oven works best (we’ll have a tutorial about that some day)
This technique works for both lead and lead-free PCB/parts/paste but of course leaded solder is easier to work with.
We use LF-4300 from Amtech for our in-house lead free paste. Its not necessarily the best, just what we use so if you have a favorite brand go with that! We get a syringe of 50g no-clean paste from solderandmore.com altho you can get paste syringe from anywhere. You’ll also need a plunger and tips. You can get a huge assortment of different tips from McMaster. For every day use we like using the 20ga pink plastic tip from the shop above – best for larger parts like SOIC, passives and some larger pitch TQFP.
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