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

Stephen wrote:
I use 0.005" thick Brass Shim from a Non Ferrous Metal supplier who
had a end of roll at a good price 300mm wide by about 5 meters long I
think. To etch patterns thru it I
1 Clean it completly within an hour of using it closer the better
otherwise the self oxidation of the surface reprotects it from the
Ferric Chloride or stops the Ink from the Ink Jet printer sticking to
the Brass (also serves the same as a microetch mentioned in other threads)
2 Feed it thru my Epson C87 taped to a piece of paper as a carrier using
the standard Durabrite Inks but use a mix of Magenta & Yellow to produce
a really crappy brown colour this is the most resistant I have found to
Ferric Chloride
3 Carefully remove it from the paper carrier & using a paint stripping
grade hot air gun (super hairdryer should work as well but I've not
tried one) wave the hot air stream over the damp ink surface & I've
found as it drys/cures it releases a small amount of steam/solvent smoke.
4 Leave for a min to cool down. Coat the back with PCB Lacquer
(Conformal Coating whatever) dry in an oven at 70 C for 15 mins or so.
5 Check for blemishes & patch with a Staedtler Perm Lumocolor (318-9)
if nesc.
6 Warm up some Ferric Chloride to 37 to 40 degrees or so place the item
ink up in the FeCl in a Glass or Plastic dish & with slow careful
rocking motion for 10 to 15min tops. I always pull it out at 7 mins,
10min, 12min etc to check for early punch thrus & to prevent
undercutting over etching wash off & touch up the done bits with the
Lumocolor or Parcelmate Texta, if it takes longer than 20mins something
is wrong (either etchant is old, the brass has self oxidised & isn't
etching)
7 The ink & Lacquer both move with Acetone (use in a well ventilated area)

the finest lines I've etched & measured using this method is 6 thou
(0.006") wide & experience tells me I could get it at least a thou
thinner but I've not had the need yet

This method is a method I have previously outlined in another post back
in November & it was developed by adapting info found in the Archives of
this list plus experience with things like the Conformal coating & the
texta/Lumocolor from other projects.

I hope this helps as having to plan the painting the back of a piece of
brass days ahead then having to clean the front again seems like hard
work. The above method from start to finish takes about hour & a half if
all the bits are lined up & ovens are warm, critical things are really
clean dry dust free brass shim before you start, fresh warm FeCl &
patience because this is the shortest way of I've worked out of doing it
reliably & this is a list of my "shortcuts".

Have fun

Regards
Stephen Lane