Homebrew PCBs

I'm surprised to hear that printing directly on copper works without
any kind of coating.  I've tried that in many different laser printers
and it's never even come close to working without the gel.  I guess
the straight path you've set up combined with the flat board allows
the toner to sit undisturbed and therefore not smear.  With the copper
foil going through the various bends of the printer, the (dried) gel
allows the toner to stick to the copper.

Dave


--- In Homebrew_PCBs@yahoogroups.com, mlerman@... wrote:
>
> I've spent the last month or so looking at all the discussions re
direct laser printing on boards. There are all sorts of warnings, nay
sayers, etc who say it can't work. Then I saw the post and site of
laserpcb, where Dave says (he has a patent)that he can print on copper
foil using his special "gel" then glue it to FR4 to make a PCB. So, if
it is possible to put toner on copper foil, it should be possible to
put it on boards directly.
> 
> I took a Samsung ML-2510 and modified the paper path to be straight
and flat, and moved the feed sensor (also inverted it) then I simply
ran a board through. No problem. A few sparks, but the image seems
very good, no distortion, very crisp. I tried Dave's Gel (sorry Dave),
but the image seems identical with and without the gel. 
> 
> I haven't finished experimenting, which is why I wanted the test
pattern. I seem to easily be able to print 1 mil traces, but I'm not
sure yet of the spacing I can use, though I would guess 5-8 mil. 
> 
> The board comes out of the printer with the toner as powder
electrostatically stuck to the board, so it has to be fused. I am
reluctant to use the fuser on the printer for several reasons. One is
that it is a pain to move it to a flat path - I would have to move a
gear, among other things. Secondly, the speed might easily be too fast
to fuse the toner. Also, if the toner is smudged or not perfect, it is
very easy to wipe and reprint the board if it isn't fused. 
> 
> An advantage of fusing it is that it (hopefully) will be stuck in
place, even if it isn't fused completely. Obviously there is a lot of
work to do here.
> 
> I think I have demonstrated that direct laser printing of pcb's is
possible. If anyone wants further information, I will be happy to share.
> 
> Mark
>