Homebrew PCBs

> <snip>
> the problem is we do not know if we can apply a good layer of resist
> directly on copper.
> <snip>
> ST

Well, actually, I'm not doing this to print resist.  The first
experiment I'm going to do is print straight ink onto a mixture of
powdered flux and powdered solder.  Powder, not paste.  Given that the
powder won't stick to the blank board on it's own, I have to make the
head move, or the acceleration of the board will leave the powders
behind.  I think it will also help for repeatability.
The first test is to see if the ink, by wetting the flux/solder
powders, will bind them enough to hold them still while I clean off
the remainder.  In effect, I lay down the powder and turn it to paste
where I want to keep the trace.  If this works, then I can print
circuit boards without chemicals.  I will try and find something other
than fiberglass for the substrate, as I want something that the
reflowed solder/flux won't just bead up on.  I was thinking of trying
thick cardstock, or non-corrogated cardboard.  My concern is to get
something that is rough enough for the solder to hold onto when it
solidifies, but that does not burn too fast.
If it does not work, then I buy some water based/silver based
conductive ink from Precisa, which is $52 for 0.1 Kg (smallest order).
 I don't know how many ml, but I suspect it is in the single digits
range.  The silver flakes are 3-5 microns, so I don't think it's an
issue feeding through the inkjet.  The tech guy for Precisa said the
issue with inkjet printing of their inks is settling.  I'm planning on
sacraficing a black Epson 400 cartridge to determine construction.  I
want to set it up so I can shake it.  I think that by default it's
filled with foam, but need to find out for sure.  That ink gets
everywhere, and stains in a heartbeat ;)
Richard