"RST Engineering" wrote in
:


Hello Jim

I use a similar setup to make boards all the time and it works
reasonably well. No 8mil tracks tho.

15 mils is easy. 10 mils with some care. Below that, no promises.


The paper is made by Pulsar and is Digi-Key P/N 182-1003-ND. If
you want to try it get the "GreenTRF" film to go with it, P/N
182-1021-ND. The GreenTRF film is just applied over the toner after
it is transfered from the paper and leaves the image on the board
completely sealed with a glossy green finish. I believe the paper
was
about $1 per 8.5x11 sheet and I don't remember how much the
"GreenTRF" cost me, but it wasn't much for an 8in by 15ft piece.

I use the glossy photo basic paper from Staples, or Costco, or Sam's
Club, or whatever branded private label -- it works better than the
"premium" variety photo paper for whatever reason. It all seems to
work the same. The trick is to use copper-brite scouring powder made
specifically for copper and brass along with one of those green dish
scouring pads to clean and microscratch the bejabbers out of the
board
before applying the resist. It also helps to preheat the board for
about 5 minutes at 150F in a toaster oven after cleaning but before
ironing on the resist.


I've been using ammonium persulfate for etchant and just picked up
some peroxide and acid so I can try making my own etchant.

I've used ferric chloride, ammonium persulfate, and muriatic acid -
hydrogen peroxide and I MUCH prefer the muriatic-peroxide
combination.
What I have NOT perfected in the etch process yet is a method of
agitation for the etchant. Right now I'm using an aquarium with an
air pump and a "bubbling stone", but would love to find another
method. Perhaps I'll work on a magnet with shrink sleeving and RTV
to
seal the ends and another magnet on a motor underneath the aquarium
bottom. That seems like a lot of hassle for a simple agitation, but
I
haven't found a better way.



I have a drill stand for my Dremel Moto-tool that was made by
Dremel
that I use for drilling the boards. I use a #10 Opti-Visor and have
no trouble drilling the boards even with my pathetic eyesight. The
etched drill guide holes in the center of the pads really helps
hitting the holes dead center. With just a little care drills will
last until they get dull. As a matter of fact the only time I break
one is when I get careless trying to go too fast.

The school I teach for has a half dozen good PCB drills, so I'm not
yet forced into that corner. I've also got a BIG pcb shop down the
hill a bit, and they throw away carbide drills by the sackful. I've
gotten them to throw a few sacks my way.


Jim



For etchant I find that CuCl2 and HCl work very nice -- and it is
especially advantagous to agitate by bubbling air thru the solution
since not only does it agitate but the oxygen in the air helps
regenerate the CuCl2 in situ. You can continue to bubble air thru it
after the etching is done to completely regenerate the etchant.

The reactions:
Etching: CuCl2 + Cu - 2CuCl
Regenerating: 4(CuCl) + O2 + 4HCl - 4(CuCl2) + 2(H2O)

Dr. G.