Part 1: Photo resist, Masking, Exposing, Developing....
Nice eh? the smallest lines on this one are 8mil
Anyhow here we go:
PCB blanks: Ours are from PCB Depot and they are the best I have found- the copper does not lift off the FR4 material even on small pads and heavy abuse. It comes clean and stays un-oxidized for months. The 0.8mm double sided 1oz material we use is easy to score and break.
PCB Depot has a great range of single- and double-sided FR4 material
in various copper and FR4 thicknesses, and in various
sheet sizes, with free shipping in the USA.
The photo resist we use is the negative type and we get it from supplier in china, you can get it from Goldpart on eBay and it comes in different colors. From my experiance all the different colors are the same stuff you can use them as etch resist solder mask or silk screen.
Let me warn you this stuff is nasty, you can never clean it up and it's hard to apply evenly without a sprayer.
We use a paint sprayer/air brush, diluted 75/25 ethanol/resist. Ethanol without water (alcohol at the pharmacy).
Spray both sides of the board evenly:
Now we dry the resist in a reflow oven for 30min at 105degC
Then comes masking- we print on acetate in a laser printer (HP LaserJet 1102), with an original toner cartridge that we use only for mask printing. Distortions are minimal - about a 2 mil error across an A4 sheet. Lines are perfectly black. 2mil dots can be printed and etched.
And exposing: standard 9W UV 370nm fluorescent- just make sure the spectrum kind of matches that of the photo resist.10minutes and it comes out perfect. Will try to do it with UV LED’s next.
Developing can be done with ethanol in 30 seconds, actually it's not developing it's washing away the unexposed resist. Comes out perfect. Don't bother with theire developer it does not work as good...
Stay tuned for how to reverse plate/etch perfect details in 3 minutes flat!