Over the past few years, I have received emails with a variety of questions
regarding my PCB fabrication technique, so I thought I could create a page
giving more details. The only techique I ever successfully used for
etching PCBs is the following. I never tried the toner transfer method, nor did
I ever try the peroxyde + muriatic acid etching technique so I cannot comment
about those methods.
Nowdays, I'm either busy or lazy so I usually pay to get the boards
done professionally. I might cost more, but there are many advantages:
- You can get away with thiner artwork. This is always becoming more and more necessary.
- All the vias are through plated, so no more endlessly soldering small pieces of
wire to connect them, and no need to adapt the artwork with great pain to reduce the number
- The end result with the green (or other color) solder resist paint not only looks great, it also prevents a lot of accidental solder bridges.
- The presence of a silk screen, if you pay for it, is also of immense help when assembling
- 4 layer boards are possible.
That said, doing it yourself is fun (though maybe not forever) and much faster than ordering
and waiting for the PCBs. I will now explain the technique that worked well for me. At least what
I can remember of it since it has been maybe 8 years since last time...
- Print the artwork on transparency sheets using a laser printer (or photocopier)
- Perform photo transfer using photosensitive copper clad boards. Finding the
right distance and timing is a function of the type of boards you use and of
your light source. Also, making sure there are no shadows and that the transparency
sheet is maintained as close as possible to the board is a must. I used a thin
glass panel for this. Thin to prevent absorbtion of too much UV, but still heavy
enough to do the job.
- Develop the boards. With developer, then rinse with water.
- Etch using Ferric Chloride. This always took time, but with the right setup
it can be speedup a lot. I once had a vertical tank, with an acquarium heater and
air bubble maker in the bottom. I don't remember the exact time it took to
etch, but I can say it was way faster than manually agitating at room temperature.
A simpler way I once used was manual agitation combined with
bain-marie style indirect heating.
- Remove the photo resists with 99% isopropyl alchool.
- Prevent bare copper oxydation using liquid tin:
(This was fun, any dipped copper parts would quickly become grey)
Step 5 and 6 are optional. Soldering despite the presence of photo resist works
quite well, and the photo resist protects the copper. But I did not like what it
looked like so I usually performed steps 5 and 6.