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Positive Resist always being out of date on the shelf & the price that 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


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