Homebrew PCBs

At 2:19 pm ((PDT)) Mon Aug 6, 2007, in Digest 2254 Gordon Couger wrote:

>Why not just a brush and a few coats of  India Ink

Except that India Ink is lampblack (carbon)
suspended in gum arabic solution.

In solution the gum arabic acts as a colloidal
suspension medium and in the dried ink as a
binder to retain the carbon particles.

Gum arabic is a reversible colloid, so the ink
will wash off again in water (or etchant).

Like albumen and gelatine, it has been used
successfully in photographic processes for
lithography and print-making, so it is possible to
turn it into an etch resist by chemically tanning it
or heat-curing it.

However, with Indian Ink that still leaves the film
punctured by millions of porous carbon granules
which make it more liable to failure - a mechanism
which may also explain in the direct inkjet printing
pcb process the poorer performance of black
pigment ink compared with colour inks.


Regards, LenW
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