press-n-peel revisited

[Paul Perry]

Thanks to everyone who responded on p'n'p, and Batz who sent a sheet.
There are a number of sites mentioning p'n'p, with not much agreement.
So here's my take so far:

Theory:
The theory of 'toner transfer' pcb making is this:
you laser print or photocopy a mirrored image of your traces and pads
onto a sheet of *something* and then place this on the raw board, and
iron it. This remelts the toner (which is a plastic and graphite
powder) which then sticks to the copper, forming a resist.
Then etch, and dissolve the toner resist with acetone.

Practice:
Majority opinion is that Teknics Press-n-Peel Blue is the best. 
I agree.

What can go wrong?
Fuckups copying, especially remembering for a double sised board what 
should be mirrored.
Some copiers are 'blacker' than others (ultrafast modern ones have 
not enough toner).
The iron has to be 'just the right heat' and 'just the right pressure'
and 'just the right time' and your mileage will vary,but once you have
got it right, it will stay right.

The board must be **REALLY** clean to accept the toner. One person said
clean the board, then etch the blank board for a few minutes before 
drying it and ironing on the p'n'p. I think this helps. You want the 
board matt, not shiny. Fingerprints and grease are fatal.

Is it possible to get traces between DIP pads? Yes, but you wish you 
didn't have to.

Weird Shit:
Some people say you can do it with clay coated paper (which is about 
3 cents a sheet, rather than the $1.50 for p'n'p). That is the paper you
 use for high quality printing, it is shiny on one side and very white due
to clay or some pigment being rolled into the paper with pressure.
Soak the paper and board for 20 mins.

One person says you can make a copy on normal paper, then take a swab 
with solvent, run it over the paper, and the toner will dissolve and 
move onto the copper. Yeah right. <sarcasm> But, I did find that if you were 
going to transfer a coarse pattern to copper, for the method where you punch
dimples  for the holes and then draw the traces with a pen, this works OK.

And, those expensive 'resist' pens are FUCKED, they dry out in nanoseconds.
Everyone says use a sharpie, whatever that is.
I'm using a Staedtler Lumocolor 313 permanent. Anything not water soluble 
should work.

If you want to do much of this stuff, one of those little plastic etch 
tanks is well worth it (about $50). I used a minimum size fish bubble
motor to drive it. Etches vastly faster & better than rocking in a tray.

That's it from me. Anyone wants to put this on a site, that's OK by me.
And, always keen to hear how others get on in this field.

BTW, for a double sided board, for a klutz like me, its easier to 
do two single sided and put them back2back. It's possible to get
'thin' pcb material. And, maybe, if you tried to iron on both sides, the
other side would melt.

And, persulphate doesn't etch stainless steel sinks, or anyway not nearly
as badly as ferric chloride does. (yeah I'm in deep doodoo, guys.)

paul perry Melbourne Australia