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

Interesting! Thanks for posting.

How about dipping the film in a liquid that will make the toner sticky and
the toner dries slowly. Then sprinkle lots of powder over it and hopefully
the [powder will stick in the still sticky toner. After drying, shake off
the extra powder.

Bertho







From: Emil Johnsen Sent: Thursday, August 30, 2012 10:11



Hi.
I have been printing artwork for making PCB's using negative photo resist.
The first problem I ran into was the lack of opacity of the toner. It looks
nice and dark until I hold it up to a light, then it's easy to see how
translucent it really is.

I tried using the whiteboard marker method mentioned on this list before,
but had problems getting it to work consistently. Usually I can't removed
the marker from the clear part of the foil without also removing some of the
toner.

I have tried dipping the foil in acetone or xylene. The toner looks much
better, but is only marginally more opaque.

Heating the foil gives basically the same result as the solvents, but
somewhat more opaque.

I tried spraying the foil with clear paint. Doesn't help at all, but it
looks very nice. Might be useful for other purposes like panels.

The method I found to work best us to bond an opaque powder to the toner.

I used a very fine cerium oxide powder, normally used for polishing
telescope mirrors. I will try aluminium oxide when I remember where I put
it. I also tried powdered graphite, but it did not work nearly as well as
the cerium oxide.

I put a clothes iron upside down and the put the foil on top of it, with the
non-printed side touching the iron. I then brush CeO2 powder on it until no
more powder will stick. After it has cooled for a few seconds I wash it with
water and detergent. The result looks gray but is very opaque. It took some
experimenting to find the correct temperature setting so that the toner
would bond to the powder while not shrinking, but there seems to be a wide
range that works.

I also tried mixing the CeO2 with xylene and dip the foil in it before
leaving it to dry. After it was dry I washed off the excess powder. This
works, but the result was less consistent and not as opaque as the melting
method.
Emil



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