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You can get PCBs made very cheaply these days (dirtypcbs are an example of how cheap), and for $20-$30 you can have a sheetful of stencils lasered for you so th
by Kliment 10y ago
You can get PCBs made very cheaply these days (dirtypcbs are an example of how cheap), and for $20-$30 you can have a sheetful of stencils lasered for you so this is mostly academic, but:
PCBs: You can make PCBs by toner transfer, phototransfer, or milling, just like you'd make PCBs for through hole designs, except you don't need the precision drilling you'd need for through hole parts. The transfer methods need an etch stage, which you can do at home with fairly safe chemicals these days, see for instance http://quinndunki.com/blondihacks/?p=835 http://quinndunki.com/blondihacks/?p=835 for a very detailed tutorial. With a bit of care you can do double layer this way, but if you need lots of layer interconnections it's better to outsource PCB production. It's WAY easier to make PCBs for surface-mount designs at home because there is a lot less drilling involved.
Stencils: If you have a laser cutter available, cut them from construction paper. They'll only work once, but you can make a bunch. If you have one of those label cutting machines, those work too. If you're etching your PCBs, you can etch stencils from thin copper sheet, using the same method. Another excellent material that is already the correct thickness is the wall of an aluminium beverage can. Toner transfer works well for these and can give excellent detail. Remember most have a plastic coating on both sides, so file the outside with the image until you get naked metal (check with a multimeter), transfer on that and then etch. You can get presensitized sheets of various metals for phototransfer as well. If you only have a handful of pads you can also plop bits of solder paste on with a toothpick.
What about breadboards? The most common surface mount packages have breadboard adapter boards available. If there isn't one for the one you want, etch a board with a bunch of 2.54mm pitch pads along the edge (no holes, you want the board vertical so you have lots of breadboard space available). Stick any decoupling caps and pullup/pulldown resistors straight on the PCB so you don't clutter your breadboard with them, solder a bunch of header pins sideways, and there you go. You can put a label for the kind of part it is right into the copper.
Again, unless you're in a hurry or the board is very simple you probably want to outsource PCB production. If you do that, get a stencil made as well. If you can combine a bunch of stencils into one file, they probably won't charge you any extra for a stencil the size of 5 boards compared to one the size of one, so with a bit of planning you can get stencils EXTREMELY cheaply. And you can do tens to hundreds of boards with a single stencil if you take good care of it.
For alignment between stencil and board, if you're getting both manufactured for you, place two holes on opposite corners of the PCB that are exactly 3mm in size, and two identical holes in your stencil. Then you can use normal M3 bolts and nuts to fix them together, and it's super-easy to fine-tune alignment with the bolts in place but not yet tightened. There are pre-made stencils you can buy which have a selection of component footprints, so if you have say a little breakout board with just one difficult component you can apply paste to that with the stencil and do the others with the toothpick method or with a syringe dispenser (safety note: NEVER put solder paste in glass syringes, only use plastic ones).
My point in all this? If you can make through-hole stuff you can make surface-mount stuff, and probably with less effort.