I was experimenting with my CO2 laser product last night and I did the
following:
1) convert Gerber to DXF
2) cut DXF at 30% laser power on mylar film on top of copperclad
->results in nice mylar cutout of the traces
3) remove excess mylar leaving the traces
4) raster scan at 5% laser power to weld traces to copper without evaporating it
Results were a nicely stuck on piece of plastic trace on the pcb ready
for etching with no surface prep or drying time!
This is the way to do it for large pcbs. Takes a minute or two by
laser and I can stick any size in their up to 12"x12".
I'll post pics whenever I have the time.
Also these guys sell a nice laser solution for both traces AND Solder
mask:
http://www.youtube.com/watch?v=mW1zVyaY_ZUIt comes in tape form (costs a lot more than mylar though) and you
just laser over it and it leaves just the traces. Apparently it is
rock hard and heat resistant so would form a nice mask. With
experimentation you could laser the traces, etch it, mask it and then
drill it all with the laser.