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.