Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, "Dean Batute" <phix_it@y...> wrote:
...
> The scratch and etch idea has been tossed around, experimented, and
> succcesfully tried by others. All have relied on dragging a sharp
> point across a "Blued" or coated circuit board.
> The biggest problem was finding a suitable "Resist" that scratched
> CLEANLY yet still gave protection from the etchant.

Not really. The metal coatings meant for metalworking have worked just
fine. Dykem was suggested here, and I bought another brand at a local
welder's supply and tested it and it worked a treat.

...
> Pager vibrating motors are VERY small...VERY light... and require
> VERY little power to drive them. How about removing the offset
> weight, sharpening the shaft to a point, and using the power that
> drives the up/down solonoid of the plotter (thru a resistor since
> little power is needed) to drive the motor. It'll fit EASILY into the
> pen holder (in fact it's probably TOO small and will need an adapter)
> and will give a clean "Scratch" thru even the THICKEST of Etch resist
> coating. The biggest obstacle will be sharpening the tip.

I had no problems with a small HP pen plotter (forgot the model, 74xx
letter size) scratching through. Bought a metal scratching pen with
replaceable tips, glued one of the carbide tips into an emptied
plotter pen. Then filled it with lead shot and superglued it in place.

Without the weight, it skips. With it and making sure you let the
metal marking fluid dry thoroughly, it works fine. If you don't let it
dry fully, it tears and skips.

Steve Greenfield