Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

I joined this group recently to see if I could find any
reccomendations for the Green TRF film from pulsar.gs, but I've been
experimenting with methods that don't require expensive mail-order
products and thought I'd share some of my results first:

I don't do PCBs, I do the photo etching method for brass for hobby
parts, stencils, etc. But the basic idea is the same.

I started by using Press-n-Peel, which has always been difficult for
me to transfer with an iron. I'd always wind up drawing a significant
part of the patterns back onto the brass afterwards (The best pens
I've found for touchup are Faber-Castell's Multimark 1523 fine line
pen for details, and Sharpie CD markers for big areas, the CD markers
seem to leave a thicker ink than the regular ones) A hint for those of
you using irons: part of the transfer problem is tiny air pockets
trapped underneath whatever you're using (paper, transparency, etc). I
found that by cutting air holes in as many spots where there was no
toner made it transfer much better than before, though there were
still issues. I've tried it with multiple laser printers and copiers
and have found that Press'n'Peel still 'pits' even with a perfect
transfer.

I recently bought the GBC Creative laminator from Staples for $40 this
week and have found it works excellently with Press'n'Peel from an HP,
Canon, and Xerox copier (I don't have model numbers, I used the
display copiers at several office supply stores, and a Xerox at
Kinkos). I only had two sheets of Press'n'Peel though, and started
experimenting with transparencies in the laminator. I tried Apollo
brand, both inkjet and laser, and the inkjet one didn't work at all,
the laser ones worked all right but would still leave gaps. Also I
found that the Brother MFC line of laser printers have extremely high
fusion temperatures - it simply would not transfer to the metal at
all!

I noticed color copiers tend to have a 'better' black than standard
copiers, so I went back to Staples and used the transparencies in
their DocuColor 12 (every Staples in this area seems to have this
particular model) both with transparencies and with HP's Photo Paper
for Laser Printers (Glossy) (barcode 8 29160 63872 0 product Q6608A -
states, oddly, that it is not compatible with the HP Color Laserjet
1500/1500L/2500N/2500L/2500TN) since I had read about the inkjet paper
suggested here, but have had bad results trying that in standalone
photocopiers (Press'n'Peel will also melt in many of them). The
transparencies worked a little better than others, but I figured I
would try the paper anyway. It adhered extremely well, enough that
trying to take the paper off without soaking it simply made the first
layer of paper rip off. After soaking it for a few minutes, and
scrubbing it (I used a Dobie 'no scratch' sponge, I think it's
Scotchbrite brand) the transfer is 100% perfect, no toner came off
during scrubbing. It doesn't have the 'dotted' look that most
toner-only transfers I've done have (even the transparencies from the
same printer). I think this paper would be a very good substitute for
those that can't find the other reccomended type.

A few hints on the chemicals: I've asked about the chemistry here and
have gotten wildly different theories, equations, etc, so I'm just
going to focus on what works. I used to use Radio Shack ferric
chloride until spent, then drop it off at the hazmat. Back when there
was much less information on the internet, I tried regenerating it
with HCl, which worked a little, but not too well. A little more
research, and I was able to find 40 Volume pure H2O2 at Sally Beauty
Supply, which worked to make it as good as it was before (add SLOWLY,
while stirring, it will foam up like baking soda and vinegar). After
diluting a gallon to two gallons, I ordered about 2 gallons worth of
dried ferric chloride and added it to the same mixture. I also
switched to the larger bottles of H2O2 from Sally (32 oz per 2 gallons
of etchant). These, however, also have Phosphoric Acid, and Trisodium
Phosphate in them. I don't know if these had much, if any affect on
it, but it seemed to me that the etchant worked even faster once
regenerated. I haven't added any HCl in quite awhile, but I have heard
that I should eventually in order to keep the acidity of the solution
high enough for it to keep working.

I etch in a 12 qt sweater box (says #5 plastic) from Wal-Mart. If you
leave your supplies outside, check the plastic for brittleness and buy
new ones if it looks like it will crack. Etching seems to work the
best, with less uneven-ness or undercutting when the item is
face-down. I use an acrylic sheet, with plastic legs like a small
table to hold it about an inch and a half off of the bottom. The feet
are glued with Goop, the underside has plastic runners attatched with
superglue so I can just slide the brass sheets in and out without
having to worry about taping or suspending them with holes. The top
has a long handle (make sure it's not taller than the lid of the box
so you can cover it in case it starts raining) so I can pick it up and
tilt it to check the progress. Make sure when you put the item in you
swirl the holder around so no air bubbles get trapped against the
etching side - I also made the feet on one end of the holder shorter
so it's 'tilted' while in the etchant. I eventually glued rocks to the
top of it as well, since it would float occasionally. Since the brass
I etch is .005 or .010", which is probably thicker than a circuit
board, I don't bother heating or agitating the etchant. It works in
about an hour or two, depending on strength and temperature. I rinse
the board with a squirt bottle of water into a bucket (takes so little
that it evaporates more than I use it, so so far I haven't had to take
anything to hazmat pickup), then neutralize it in water with baking
soda in it.

A few questions: Has anyone done the paper transfer and successfully
used the Green TRF film over it if you get all the paper residue off
of the toner? I'd prefer to avoid pitting altogether, though since I
use the back of the brass (I spray it with oil based Rust-Oleum
"Painter's Touch" then remove it with acetone - pour a little on, let
the paint bubble a little, let it dry a bit then it will lift off in a
whole sheet, but the paint must be dry for a few days or it'll still
be tacky against the brass) it's not a huge problem, but every so
often a pit will go all the way through to the other side if I miss
touching it up. Is there an issue with the copper buildup in the
etchant over time? At this point I've saved enough regenerating it
that it won't be too big a deal if I have to dispose of it and start
over, but if I can keep it going indefinitely, that would be a huge
bonus. Also, since I mass produce certain patterns, would there be any
'aging' issues if I go back and make 100 copies of it on this copier
so just in case they replace it, I'll have plenty of extras for
awhile? Will it eventually harden or become non-transferrable?

Thanks for all the suggestions this group has made - it helped me come
up with some ideas to make better transfers. Now that I've found a
paper/toner combination that works well, I won't spend all my time
touching up intricate details.