DIY Soldermask for PCB

[Fusion916]

Does anybody have any experience with this? Care to share techniques?

[JMFahey]

1) If you need a classic soldermask, the "normal" and still within the DIYer's possibilities technique is through Silk Screening.
Most PCB software can generate it, you need to print it on transparency film (or Vellum) and burn the screen.
Then process it (wash, fix, dry, etc.) and finally print your soldermask.
Neither too hard or expensive, but you can easily spend a couple hours to a full afternoon on this.
Acceptable for small runs (say, 10 or 20 boards), maybe too much for "just one" because you'll spend exactly the same time and money printing from 1 to 100.
Well, almost.
Actual printing is 20 seconds per PCB, the rest of the 2 or more hours lies in burning, processing, washing the screen, a messy and boring job.

2) you *may* use a photographic process, by spraying or rolling photoemulsion (similar to Silkscreen emulsion) over the already etched and washed PCB and them selectively burning it through a transparency with black dots covering the copper pads you want to leave exposed, the rest will be covered by hardened emulsion.
Again, too much work (in my opinion) for "just one" but it still is possible, from a technical standpoint.

3) if you just want to protect the copper side , what I do is cover copper with a thick layer of rosin_in_alcohol solution and let it dry.
Sometimes I dye it blue, so the PCB really *looks* like a PRO made PCB. Cool.
The thick rosin layer is good protection against oxidation, yet melts when soldering, adding to the flux in solder.
All soldered pads are bright and rounded. Cool.

Here's one batch of PSU+100W Pwr PCBs, already sprayed, drying overnight:



In this case, the rosin flux was left undyed, but a few drops of Permanent Marker refill ink work very well.

PS: *maybe* you can print your solder mask on Photo Paper or PnP Blue and thermal transfer it to the PCB copper side, even if you get some cracks, pinholes or even missing some small areas, because in this case it's not that critical ... but your solder mask will be ugly dull black.
Correct that to very ugly ;(