I normally outsource my PCBs to a board shop, but every once in a while I have to make a one-off. I'm not sure where I read about it originally, but I use a pr

I normally outsource my PCBs to a board shop, but every once in a while I have to make a one-off. I'm not sure where I read about it originally, but I use a process that doesn't require any special, well anything: * Print copper mask onto transparency film using a laser printer * Very carefully iron the transparency film, print side down, on a standard copper FR4 board * Even more carefully, peel the transparency film back, and the mask should stick to the copper board (you might have to try a few different brands of transparency film for this to work) * Mix 50/50 hydrogen peroxide and vinegar in a tub, put the PCB in but elevate it off the bottom of the tub * Add salt until the copper starts coming off the unmasked parts of the PCB, and agitate the entire thing somehow (I use a busted cell phone with an app that makes the vibrator run continuously) After a while, maybe an hour, you'll be left with an etched board, then rinse and scrub the mask off. It takes some practice to get the quality level to the point where you can reliably make thinner traces on the board, but it's entirely doable for small quantities. I recommend doing 2x2 or 3x3 boards at a time so a few rejects are ok. It's not the fastest or easiest method, but if you're really screwed and you need a board right away, it's possible to do this process with nothing but a Walmart. In case I need to do SMT parts, I don't bother trying to make SMT traces using this method; I keep some SMT to DIP adapter boards around so I can just solder the DIP through holes onto one of these ghetto PCBs. Although H2O2 and vinegar are both common household chemicals, the resulting bath is mildly corrosive to metals and apparently dental enamel, so treat it with some respect and neutralize it with baking soda before putting it down the drain. Don't throw it in your yard, it seems to sterilize any soil it comes into contact with. I'm not entirely clear on the chemistry of what's going on here, but I'm pretty sure the oxidized copper residue left in the bath is low level toxic waste, so filter that out before getting rid of the bath chemicals. I let it dry out and I dispose of it at the battery disposal center in my building.