While I was assembling all the components required for my new project, I also found a cool new Android app: ElectroDroid . I've really only poked around so far, but it looks exceptionally groovy. The resistor calculator, op amp calculator, and 7400 pinout reference look amazingly useful. Looks much more convenient than flipping through my old electrical engineering textbook, and finally gives some justification for buying an expensive tablet PC.
ANYWAY, on with the projects!
I decided to etch a board this weekend. I finally broke down and bought some blue transfer paper online, and was sufficiently bored to put it to use. The Scrambler Clone project comes with its own PC board design, so that seemed like a logical place to start.
(Apologies if this is all old hat to you; I'm used to sticking wires into protoboards or soldering on breadboards, so the whole process was strange and terrifying.)
I followed TonePad's two-part tutorial on printing and etching with Ferric Chloride. Both were excellent, and leave very little in the way of clarification. I won't do a step-by-step process here, since I think TonePad handles the whole thing well. I will, however, give some notes and impressions about the whole thing.
Firstly, the whole process was incredibly error-free. Almost disconcertingly so. I'm fairly accident-prone so I expected to turn myself orange, or to sustain at least a few minor burns. Aside from a 1/32" drill bit failing catastrophically (more on that later), though, everything went according to plan.
Having said that, nothing will prepare you how ferric chloride smells. It's completely hideous. It's easily in the top five worst things I've ever smelled, surpassing even the week my downstairs neighbors left raw meat uncovered and unattended on the kitchen counter. It's groady to the max in the original, Biblical sense. The tutorial recommends you do the actual etching in a well-ventilated area, and I wholeheartedly agree. I did mine in the bathroom, directly under the window, with the fan running full bore and it was still overpowering. Beware! Also, it stains everything it touches a lovely shade of orange.
The reaction requires heat to work quickly. The tutorial recommends heating the solution with a 150W bulb, but none of my CFL bulbs put out that kind of heat. Instead, I submerged the etching container in a pan of very hot water (the hottest I could get from the tap.) I was able to etch the entire board in just under fifteen minutes, so I'm guessing that's a decent substitute.
Strangely enough, the TonePad tutorial gives only one-sentence descriptions for what are actually the most menial, time-consuming, and nerve-wracking portions of the entire project: scrubbing the etch-resist material off the board, and drilling the whole thing out.
Removing the etch-resist material took quite a lot of elbow grease, and a significant amount of nail polish remover. I press-ganged an old toothbrush into service, but it still took a good ten minutes of constant scrubbing to remove everything. It's possible I was using the wrong solvent; it's also possible that my toothbrush hasn't been doing nearly as good a job as I've been lead to believe.
Drilling out the PC board was the last step, and also the most time-consuming. I stopped counting around the fifty hole mark. The first twenty or so were done with a cordless drill; the bit was thin enough that it visibly bowed and wobbled every time I started it, and I spent most of the time in mortal fear that I'd accidentally drill through a trace or dig a groove across the board. Eventually, I twisted the whole assembly the wrong way and shattered the bit. After that, I remembered an old Dremel drill press buried in the utility closet. After getting everything together and scrounging another 1/32" drill bit, I was able to finish the rest of the board without incident.
And that's it! I'm now the proud owner of one printed circuit board, ready to be utterly spoiled by my horrible soldering technique. I'll try to update once I've got a few components tacked on.
(I took a few pictures of the whole process, but haven't found a place to upload them yet. Maybe that's for the best.)