To build the boards, you’ll, of course, need all the parts available. You’ll also need a list of parts, bunched and sorted by package height. You want to be able to place the smaller components first, otherwise you risk bumping things.Next crack out the stencil. The stencil is used to apply a very thin layer of solder paste to the PCB.
First you need to carefully remove it from the backing plate. I ordered an un-framed stencil. If you order a frame around it, it’ll cost more, but is sturdier.
You need to treat these stencils very carefully. If you have any bend in them, they will be effectively useless.
So several rules when using stencils:
- Treat them like they are made of tissue paper.
- Always keep them clean before and after use – you can use isopropynol for this.
- When not in use, keep them secure in the backing.
- Did I mention to always keep them clean?
Once you have your stencil cleaned up, you’ll need to stick down some holders that hold the PCB in place.Remember you’re dealing with fractions of a mm here. So, it needs to be secure. Also make sure that the PCB is stuck down, otherwise it might lift up when you remove the stencil.
Next arrange a bunch of spare PCBs around the place. This avoids the stencil warping when you press down on it.Then spend some time lining up the stencil with the pads. The easiest way is to pick the largest hole first and roughly line things up. Then pick a smaller package, ideally an MCU, to fine tune it.Next tape down the corners securely. You don’t want that thing moving one fraction of a mm.