Homebrew PCBs

Mike,
Long ago Model Railroaders used the silver paint to make a conductive 
path between one wheel to a resistor, then from the other side of the 
resistor to the other wheel. The purpose was to provide a resistive 
load between the two rails to allow signal and other circuits to 
activate when boxcars were left on the main line (otherwise, as the 
wheels are normally insulated from each other, the signals would NOT 
show the presence of a car) and thereby stop approaching model 
trains. I used some silver paint long ago (yes very $$$ back then) 
and I may have some left over way, way down in the bottom of the junk 
box somewhere. My experience was that while it did conduct, it didn't 
last very long - maybe the application was the problem.  I would hope 
that better paint/bonding agents would be used in today's paint, but 
unsure. 

Personally, with soldering a scrap piece of wire, or using one of the 
other discussed via methods being so easy (and repairable) I will not 
be spending the money on the paint.  Remember, when paint dries it 
tends to become brittle and possibly even crack with heat. I guess if 
it really worked that good/reliably, the "big boys" would be using 
something like that on the professional boards. Just a thought.

Keep us posted if you decide to try it.
Mike R.

<snip>
> When the subject of conductive silver paint arises, it usually gets 
> sidetracked into the use of activators, copper plating etc, but 
> nobody so far seems to have tried using silver paint to create the 
> actual body of the vias. According to the manufacturers, a typical 
> paint has a resistance of 200 microOhms per cm, and it can be 
> thinned. 2 or 3 applications should be enough. Whilst it is 
> expensive, I would imagine 3 grammes of the stuff would go a heck 
of 
> a long way.