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Removing solder mask from gold fingers - is it possible?

Discussion in 'Electronic Components' started by JW, Mar 26, 2007.

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  1. JW

    JW Guest


    We have a problem with one of our circuit board vendors who applied solder
    mask to the gold fingers on a lot of 100 boards. Naturally, the 100 boards
    were built up and the problem wasn't discovered until test. Does anyone
    know of a way to remove it without losing the gold on the fingers?
    Solvent or ??

  2. Try oven cleaner, have had some success with that before.

  3. clifto

    clifto Guest

    There might be some acid which will eat the tincoat without eating the
    gold. If so it's probably nasty stuff.
  4. ian field

    ian field Guest

    If you mean that green varnish type solder resist, you could try Nitromors
    paint stripper otherwise a possibly more difficult to track down solution is
    Oxley Developments Resin Dissolver. A company I worked for years ago used
    this stuff to dissolve thermosetting bonding mats used to stick ultrasonic
    transducers to the bottom of cleaning tanks - you don't want to soak PCBs in
    it though, it'll dissolve them as well!

    Hold on though - cant the PCB firm tell you what'll shift it?!

  5. What does the board house use to clean its equipment with?

    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
  6. Roy

    Roy Guest

    If it is the dark green probimer you have a major problem. It is
    usually applied and lightly dried in an oven at low temperature. After
    exposure to UV it is developed to remove the unwanted resist and then
    baked at a high temperature. After the high temperature bake its
    bloody difficult to remove. ( I dont know of any solvent that works
    without board damage at this point, although I am not saying there is
    not one) The only way that I know of would be scraping or bead
    blasting which obviously is going to result in some loss of plating.
  7. Guest

    Agreed. The only thing I've seen able to remove solder mask is the
    electrolyte from leaking caps, and that destroys the copper. And it
    does it from the inside as it is under it, doesn't matter what you
    plate it with.

    Grind it off, or maybe since it is liable to be quite flat, mill it
    off with a milling machine.

  8. I tried acetone and strong caustic soda solution, the stuff doesn't budge.

    Assuming chemical is useless, and physical is likely to wreck the bits you
    want, try optical.

    An IR pulsed laser should be a good match for absorption by dark green, and
    the gold will reflect it, as will the copper, and the partial trasparency
    of the substrate should dissipate safely what isn't absorbed by the resist

    In order of rising price (and general butchness) try hair removal lasers,
    tattoo removal lasers, and stone cleaning lasers. Take care not to angle
    the thing such that it can reflect off gold or copper right back up the
    waveguide, as that will likely damage or even instantly destroy the laser
    cavity, especially if it's a direct-from-diode sort of pulsed laser.
  9. rebel

    rebel Guest

    Mechanical means are going to have an impact on the plating, so (unless the
    pulsed-laser trick works) I suspect you're stuck with chemical attack.

    Dumb question #1: Seeing your board-fab botched their bit, have you tried
    actually asking them WTF the stuff is, and then talking to an industrial
  10. Thixotropic organic paint remover?
  11. Didn't have any.
  12. Al

    Al Guest

    Tetramethylguanidine might do the trick. I've used it in decapsulating
    plastic encapsulated electronic devices. It really stinks and you need a
    hood to use it.

  13. JeffM

    JeffM Guest

    What is it you are agreeing with?

    This is NOT Google Groups.
    Most people don't see what YOU see
    when YOU read Usenet at Google Groups.*-*-*-*-*-*-*-*-*-*-*-*-*

    There is a standard way of postiing to Usenet:*.*+*-for-your-readers

    By now
    you should have recognized that paradigm
    and emulated what you see the majority of other Usenet users doing.*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
    The part in yellow is called CONTEXT.
    The rest of the post explains why it is important.
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