Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, "Phil" <phil1960us@y...> wrote:
> It seems there are two bondings going on here:  toner to paper and 
> toner to board.  The goal is to increase the ratio of bonding to the 
> board vs bonding to the paper so the paper will release.  Of course 
> there needs to be a minimum level of bonding to the board.  coated 
> paper works because the toner only bonds to the board-side layer and 
> soaking causes the layers to seperate.
> 
> The starch method of decreasing paper bonding is very promising but 
> I've not been able to get smooth enough paper to feed cleanly.  My 
> best effort got creases and spacial distortion of the transfer 
> pattern.  I'm skeptical of this working well for 8 mil traces and 
> tqfp packages.  I've got some 90 lb paper that might maintain its 
> integrity during starch treatment and will give it a try.  There may 
> be other products that don't wet the paper but decrease the paper-
> toner bonding. a very thin coating of a light oil (wd40 springs to 
> mind) might do it.

Yes, as has been covered here in depth, paper contraction due to the
heat of a laser printer/copier causes problems. I'd imagine a sheet of
paper wetted and not sufficiently dried is going to be worse.

I think your analysis of bonding is correct.

As for WD-40, speaking as an electronics tech: Don't do it! WD-40 and
electronics do -not- mix. WD-40 is -not- an oil. It's volatile, which
means heat is going to cause it to evaporate anyway. It's main use is
as a water displacer. My father destroyed the hinges on a truck of
mine, because unknown to me he was spraying all the hinges on my truck
with WD-40 every time I visited. I couldn't figure out why my doors
kept squeeking and sticking, I'd grease them, and in a short time
they'd stick again. He'd hosed out all the grease with WD-40 and
within a short time all the WD-40 had evaporated, leaving nothing but
metal to metal contact with some dust thrown in.

I suspect coatings are the answer. I tried inkjet transparencies, on
the theory that the coating on the plastic is water soluble and so
would easily let go of the toner when soaked. I was right, the
transparency got slimy when wet and let go easily. The problem was I
could not get water all the way under the plastic and the toner stuck
better to dry inkjet transparency than it did to copper.

And as has been pointed out here, the plastic caused the traces to all
mash out.

Steve