Saar Drimer writes about an interesting PCB technique:
When I ran the Boldport Club, I arranged a few community pub meets. It was a great way to meet people from the larger community and to see and hear what they’d been working on. In one of those meets, I serendipitously told Mike Harrison about what I’d been designing: an object that required interconnecting pieces of PCBs. Mike, with his extensive electronics installation experience, gave me a wonderfully effective tip: add small ridges along the slots on both pieces that are meant to be put together.
Getting the thicknesses of PCBs right is tricky. Firstly, PCBs normally have a 10% thickness tolerance and another tolerance for the slot/cutout routing. Secondly, the actual thickness depends on the design and on what’s at the surface of where it matters ─ copper, plating, finish, soldermask, silkscreen. So the variation in thickness from ‘nominal’ (0.8 mm, 1.55 mm, etc.) can be significant. We can’t keep experimenting until we get it right either; it’s expensive and somewhat pointless because of the tolerances. Adding ridges allows us to hedge our bets with a single go.