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RE: [Homebrew_PCBs] Re: Toner Dusting pcb process

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  • Tony Smith
    Yeah, powder is as cheap as anything, you don t even bother working out the coat of what you used (unless it s the glow in dark $$$ stuff. Clear is the
    Message 1 of 19 , Nov 1, 2008
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      Yeah, powder is as cheap as anything, you don't even bother working out the
      coat of what you used (unless it's the 'glow in dark' $$$ stuff. Clear is
      the cheapest. The differences in composition is mainly related to UV
      stability (colour fading), which isn't an issue here.

      The furniture industry (think offices) is shifting from laminates to powder
      coated MDF. The idea is that MDF can be milled to any shape possible, and
      then powder coated, giving a result equal to laminates. With laminates,
      you're somewhat limited in shapes. Eg, the edge on your desk is square, not
      rounded, and you can't put laminate on a rounded edge like that. Drilled
      holes would be coated, not bare wood (well MDF) as is now. Like laminates,
      powder coat can have textures. No wood grain though! Expect to see some
      interesting stuff in a few years (but boring colours - but hey, it's an
      office) as production ramps up.

      I was ordering some high-temp tape (Kapton, used in marking for powder coat,
      see <
      http://stores.ebay.com.au/High-Temp-Tape-store_powder-coating-tapes_W0QQfsub
      Z19781913> or
      <http://stores.ebay.com.au/High-Temp-Tape-store_high-temp-Polyimide-tapes-KP
      T_W0QQfsubZ19781912>) when I had a flash back to the 'good old days' with
      photo-resists, mark the tracks with tape, spray with powder, cure, remove
      tape, etch. Bonus conformal coating in a weird colour.

      Now I'm wondering if crankorgan's 'scratch & etch' idea would work here.
      Coat the blank PCB (even both sizes), partially cure (fully cured powder
      coat is bloody hard to get off), scratch off the isolation traces, fully
      cure the powder, and etch. Downside is the pads are still covered in powder
      coat (a very hot iron would burn the powder off), but you could make your
      PCBs a hot pink (Barbi) colour.

      Rather than 'scratch', the powder could be blown off the traces with a very
      fine air stream. I've actually done this (not on PCBs), but the PCB needs
      to be very carefully handled. I don't like your chances for very fine work.

      Some less lazy than me should go try it.

      Tony


      > Tony,
      > Good link to the eBay sources of ES paint powder. A pound of paint will do
      > acres of pcbs :)
      >
      > That is the standard process for ES painting. In this case we are
      "cheating"
      > a bit by using the wet inkjet ink as a temporary adhesive.
      >
      > Overall, it works very well. I found it a lot easier than regular toner
      > transfer. No fighting with multiple runs through a laminator and removing
      > the paper afterward..
      >
      > Myc
      >
      > On Thu, Oct 30, 2008 at 6:34 AM, Tony Smith <ajsmith@...> wrote:
      >
      > > > I knew from Voltan's work that he was able to print a solder mask.
      (I
      > > was
      > > > never able to correctly cure the ink) and decided to try the Toner
      > > Dusting
      > > > process instead.
      > > >
      > > > I was looking at replacing the black toner with other fusible fine
      > > powder,
      > > > hopefully a white or yellow one, to use as component legends. I had
      seen
      > > > some electrostatic painting on a TV show and thought it might work,
      > > though
      > > > most of the time the metal items were baked at a very high temp. I did
      a
      > > > search and found that the ES paint was also used on MDF, so a lower
      temp
      > > > fuse was possible. There are a few different types of ES powder.
      > > >
      > > > I found some ES powder paint at SEARS for only $6 and am trying it. I
      am
      > > > told it also is available at some auto parts stores. The SEARS version
      > > has
      > > > slightly larger particle sizes.
      > > >
      > > > I've just started playing with it. It seems to give a very thick
      coating.
      > > > Try to avoid the gold fleck version, The goldish particles are very
      small
      > > > and are hard to remove.
      > > >
      > > > Toner dusting is a very simple process and easy to try. Like toner
      > > > transfer you have to fine tune it to your set up.
      > > >
      > > > Myc
      > >
      > > You're describing powder coating, searching for that will turn up more
      > > stuff. As you say, it's not that hard.
      > >
      > > Plenty of powder on eBay, in any colour you want, typically under $10
      per
      > > pound, and a pound goes a long way.
      > >
      > > The standard way to apply is blow the powder past high voltage (say
      > > 15-100kV), this applies a charge to the powder which causes it to stick
      to
      > > the metal. To do wood such as MDF it needs to be coated with something
      to
      > > make it conductive first. You may have trouble finding that and the low
      > > temperature cure powder.
      > >
      > > The other way is to heat the part up (~150C / 300F) and either dip it in
      > > the
      > > powder or sprinkle the powder onto it. Either way the powder will melt
      and
      > > stick to it. I'm not sure if it'll stick to the PCB material (copper
      traces
      > > are ok), someone will need to try it. With a mask you could do it cold,
      put
      > > the mask over the PCB, sprinkle the powder, then put it (very
      carefully!)
      > > into an oven to cure.
      > >
      > > Powders are typically cured at 200C (~400F) for about 10 minutes,
      although
      > > you can trade temp for time, eg 350F for 15 minutes etc. The oven can
      just
      > > be one of those little toaster ovens. This is to cure it properly, it'll
      > > still stick if not properly cured, it just won't be as resistant to
      > > chipping
      > > etc.
      > >
      > > It also needs to be absolutely clean otherwise the powder may not stick.
      In
      > > this case it's not a huge drama, and the normal PCB cleaning procedures
      > > (wipe with acetone, rinse with distilled water etc) are ok.
      > >
      > > Powder coating is good fun, it beats painting hands down.
      > >
      > > Tony
      > >
      > >
      > >
      >
      >
      > [Non-text portions of this message have been removed]
      >
      >
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