Here's a comparison between the factory-fabbed board with wrong FFC connector pitcth (my bad, top), the laser-cutter-exposed chemically etched board (bottom) and the CNC-milled breakout (right). The breakout board is as close as I could get with a V-bit and it might actually work, but its so questionable that I don't want to try it with my only OLED display.
I didn't think to drill out the via-holes in this same step, which was a mistake, so I had to do that by hand on the drill press.
Next, these little copper rivets (0.8mm outer diameter) can be inserted and punched flat on the other side. I'm using a single-sided PCB, so I'll just solder jumpers where a double-sided PCB would have traces on the other side here.
Now I still needed to route out the slot for the FFC cable to pass through. I drilled out the two screw-holes marked by etching on the drill press, and had the CNC mill pilot-drill two holes with the same spacing in a sacrifical piece of wood.
This way I could screw the PCB into place exactly with respect to the CNC's coordinate system and mill out the slot and contour (5x speed also):
Now the PCB can be rinsed with water (in another container, since the Acid remains can't just be flushed) and then the remaining paint can be taken off with a solvent.
Success! The tricky parts at 0.6mm pitch came out perfect, and there is just two little bridges that were easily fixed with a scalpel blade.
Now it goes into ferric chloride (an acid).
If you're doing anything like this, please read up on safety measures and how to dispose of the chemicals safely afterwards. Also check that the container you're going to use is safe to use with the etchant.
It took about 5 minutes to etch this PCB, continuously swirling around the container to expose the copper to fresh acid.
Step 4: The laser doesn't remove *all* of the paint, so I scrubbed it with some fat solvent (window cleaner?). I'm not 100% sure this is necessary, as the acid probably would etch away the grey-ish paint layer too. This is also where I introduced the only problems into the PCB: a moderate amount of pressure is required to get the film off, and in two places I stripped off more paint than I wanted (cut trace middle-left and jagged shape bottom-right).
Trying out a new PCB-making process today, since milling just doesn't cut it for 0.6mm pitch.
Steps 1-3: Clean, Spraypaint and Laser-engrave the board
started like a week ago, chromium + nvidia on Arch Linux. No idea what's happening
like, I don't have Skype installed on Linux, and I recognize that cursor and tooltip right above it.
Also yep, that chrome tab-bar piece on the bottom right has a tab I have open only on windows ("Mieg...")
I am... pretty sure that I see parts of Windows in there? You know, the OS that I just rebooted (which I thought would take the GPU offline and clear its VRAM????)
Some things went wrong though:
the chamfer on the top and the general outline are misaligned somehow. I don't understand why exactly this happens yet, but I guess I will be able to figure it out. The round cutouts for the magnets are also a bit to small.
But I knew there was going to be attempt #2, and I'm actually super stoked with this result!
tinkering between hard- and software, research and development, audio- and visual...
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