I’m finally taking the plunge and trying out solder paste reflow soldering for my surface mount electronics projects. It turns out, it’s pretty fiddly but not that hard. With practice, I’m sure I could do a pretty good job and make boards quickly.
Using suggestions from some other places, including this other topic of the same name, I put together a SMD solder mask stencil using 0.002" Kapton polyimide film and my Glowforge. Were I to do it again, I’d probably get a different material such as the 4mil mylar referenced in the other post as the Kapton is a bit flimsy and also expensive. It does work well aside from being a bit too thin, though.
The Kapton as it came out of the Glowforge:
After I rinsed off the char with water and dried it:
The power settings I used are:
Engrave (not cut) 1000 speed, power 80, 180 lines/cm, 1 pass.
Also at a suggestion from the other post, I cut a quick alignment sled out of 1/16" inventibles acrylic:
This let me tape down the solder mask with painter’s tape to help keep things aligned. Because the board is 1.6mm thick and the acrylic is 1.5mm thick, I left the paper backing on it to get that extra 0.1mm.
I created the stencil pattern in KiCAD 5 and just exported the solder paste layer as an SVG (without the page borders, but with the board outline that I then just used as an ignored reference in Glowforge). Amazingly, I could just load the SVG straight into the Glowforge without modifying it, as I cut out the perimeter of the design by hand.
