Green electronics – it’s not the soldermask
On last week’s Amp Hour, Chris and Dave were discussing laser etching PCBs. I’m not sure they realized it, but this is actually a fairly hot area in PCB processing research right now, along with printed electronics. Currently, PCBs are processed by copper-cladding a substrate material, like FR-4. There are a couple ways to get the circuit layout onto the board. The first possibility is that the circuit layout is printed onto the board using screen printing. The copper you want to keep is covered in an impermeable ink. A second method uses a photomask. The areas you want to keep are exposed to light, which will harden the mask. The unexposed areas are still soft and removed chemically. The final step in both processes involves removal of unwanted copper using a chemical such as ferric chloride or ammonium persulfate. (Note: A third method can involve the use of a…