Homebrew PCBs

I just tried the Seno Positiv 100 resist applicator on a test piece of PCB
material. It's a bit like those shoe cleaning waxes in a container with an
applicator pad.

I had a bit of trouble with the resist flooding out when I pressed the pad
onto the copper, so it would probably be best to use a fairly large piece
and make several boards at once, if they are small. I applied a fairly thin
coat and dried the resist in a warm oven for a few minutes. I used my normal
13 minutes UV exposure and then developed it in my usual NaOH solution
(although the recommended developer is NaOH-free) and etched it in FeCl3.
The results weren't as good as with the pre-coated board material I usually
use as there was some noticeable undercutting. This can probably be
rectified with a thicker coat of the resist and some dilution of the
developer, or by using sodium metasilicate.

To sum up, the resist is definitely usable with some care, unlike the
aerosol spray resist I've tried (the old formulation was OK). It is
expensive, at just under 8 GBP.

Leon
--
Leon Heller, G1HSM
Email: aqzf13@...
My low-cost Philips LPC210x ARM development system:
http://www.geocities.com/leon_heller/lpc2104.html