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

Stephen Lane wrote:
I'm new to the Forum, I have been making PCBs via the UV exposure
method for years, I also make a Theatrical effect called a Gobo from
etched Brass using the same techniques as PCB manufacture, having
become increasingly disappointed with the easy to find Electrolube
Positive Resist always being out of date on the shelf & the price that
was steadily escalating I looked for some new ideas & I found them on
this forum so using the info accumulated on the site I come up with the
following instantly successful way of creating an etchable object (I use
the same process for Brass or copper it dosen't matter which except the
PCB material has to be fed thru a modified printer (details for this are
avail on this forum & its a project for me in the next few weeks to mod
my printer to accept boards horizontally))
So to summerise
Hardware is plain clone computer with P4 3Ghz & 2Gig RAM & an
Epson C87 with original Durabrite Inks in it & a GMC Heat Gun (Hot Air
Paint Stripper), Software is Protel 99SE & Paint Shop Pro when needed,
touch ups are performed with Staedtler 318 markers or Texta Parcelmate
Markers & I etch in Ferric Chloride.

1. Prepare the Artwork as clearly as possible with what ever package
allows you to print a Raster picture of the finished layer you are
going to etch be careful of the mirror image issues as you are
usually looking down on the component side of the board & you need
to print the mirror image of the bottom layer for instance. One
thing that might help here & I use this for the later steps is
export the layout as a picture(.bmp, .jpg or .tif for instance) if
you can this helps later but do a check print for dimensional
accuracy.
2. When the you are happy with the Artwork bring it into the Paint
Program & change the track color to 100% Yellow 40% Magenta (this
creates a deep brown color (& yellow & magenta polymerise best &
remain the most resistant in the following steps. The Brown color
could be achieved via the printer driver to I think but I haven't
tried it yet).
3. Prepare your board material THIS IS CRITICAL to the success of any
of the procedures for Homebrew PCBs & cannot be stressed enough.
The board must be free of all oxides & contaminants particularly
oily greasy ones & should ideally be roughened to provide a key
for the resist(ink or otherwise) to sit on & slightly penetrate
the surface of the board. I use AJAX powder cleanser & a green
potscrubber (which has never been in contact with a greasy pan in
its life (In fact I buy a cheap pack of 6 & cut one into quarters
& throw away after a couple of boards if nesc. You scrub the
surface of the copper in at least 3 directions edge to edge with
some of the powder cleanser & wash off, when its clean water won't
bead on the surface it flows evenly (turn it over or try an
uncleaned bit & compare you will see what I mean) dry the board as
quick & as gently as possible (I use a convection microwave on
convection only set to 130 degrees C for 10mins) when no water on
surface is observed remove from the oven & let cool off. As soon
as cool wipe surface off with Acetone (note the last of the Black
Deposit that comes off the Copper onto the tissue). This stuff has
to happen inside a 15 to 30 min window of time because the copper
will start to oxydise immediately & this will stuff up the
etching later (In fact if you arn't going to etch as soon as
you've printed don't start until you can finish the whole
process), clean the 2nd side if nesc. before drying & cleaning
with Acetone
4. With your freshly modified printer that allows you to feed the
board thru horizontally do a test print to work out where the to
stick the piece of Board then align your board to your carrier
using this test print. Stick or mount your board using a heat
proof tape to the carrier. Then print the picture/tracks on the
copper side of the board
5. Dry the Ink on the board by subjecting it to heat hot enough to
polymerise the resin in the ink My Heat Gun says that its a 300C
to 350C the critical thing is to watch the surface of the ink at
an Angle so you can see it go dull & solid try & keep away from
the tape because you may want to reprint the design & registration
is critical. Instead of reprinting if any defects in the big bits
bother you, you can dot them out with a black texta (I use
Parcelmates but Stedtler 318 Perm Marker works very well) the
tracks tend to not have issues but the big open earth plains can
cause the pooling that people talk about & feeding the board thru
twice when wet makes a ral mess of your nice clean printer & drags
the good bits of the 1st layer off the right places (Very messy &
you have to clean the board all over again). Repeat for the 2nd
side of the board if nesc or coat the 2nd side of the board with a
varnish or thick black texta..
6. Etch the board, I have found the side to side rocking has the best
effect. I also activate the Ferric Chloride by microwaving for 5
to 10 sec (any longer will melt plastic or cause the Ferric
Chloride to be too active & strip the resist as well as the
copper) before I start (for a 100mm by 100mm size board this is
sufficient for the whole etch run). Once the thin tracks have been
etched use the black texta to protect them from undercutting &
keep etching until finished (remove wash in fresh water & spot dry
with soft tissue before touching up with texta and continuing)
7. You should have a usable board at this point which still needs
drilling & a conformal coating or tinning to stop corrosion.

Long Post sorry
However thanks for all the people that documented what they have
achieved in the Forum. I used the above method which is a consolidation
of all the documentation & my own tried & true cleaning techniques to
achieve instant success the 1st time I tried to etch an object.
So I hope this helps

Regards
Stephen Lane


[Non-text portions of this message have been removed]