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

Hi Group,
After some inconsistent results on retouches and second-side masking,
I did some test using some common pens and other materials.

The photos of the steps in the tests, along with my conclusions, are
in the Photo section, album Ted-KX4OM. The best results for
retouching, which should not be surprising to the group, were with
Staedtler Lumocolor permanent pens, specifically colors blue and red.
On each of the pen tests, I wrote some text normally, drew a line
underneath, and went back and heavily "dotted" in a second layer of
ink for the first half of the line. A liquid Stylist Black pen look
superb on unetched copper, but, alas, it turned out to be water based
and immediately washed off.

The other test was for masking large areas, such as the second side of
a board, either as-yet unetched, or previously etched. Of the tapes
and liquids, only Future Floor finish did not give good results. One
problem, yet unsolved, which was not part of the test, is performance
of tape when it has to overlap for coverage. I've been getting some
seepage under the overlaps at the edge of the boards using 3M 33+
electrical tape. The liquids (and the pen ink) were allowed to dry
overnight.

It occurs to me that if using one of the more flowable liquids, such
as Spar Varnish, the liquid should be applied to the second side and
allowed to dry prior to drilling alignment holes. Otherwise, the
liquid will likely flow through the holes. This would almost
guarantee that the varnish, etc., would stick to whatever surface
(paper towel) while ironing. It shouldn't cause a problem with the
more easliy removed liquids, however.

Another problem, which may be the next test I do, is retouching toner
traces with the more successful pens. With my Brother HL-2040 laser
toner, I've had problems with Lumocolor red when thickening a
weakly-transferred line. It appears that there is a reaction or
something that causes further erosion of the trace while etching.

All my tests and my production etching are done with room temperature
ferric chloride, typically for 20 minutes under a 60 watt lamp,
rocking the pyrex dish constantly as the etching occurrs.

Regards,
Ted