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Beginner looking for advice

Discussion in 'CAD' started by Cat, May 10, 2007.

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  1. Cat

    Cat Guest

    Hello All,

    Please excuse the beginner questions; this is my first attempt at
    etching a PCB.

    I bought some 2oz dbl sided boards, and will be etching them using
    Sodium Persulphate. I've done the traces using press-n-peal blue. I do
    not yet have an elaborate set up, and I'm looking for any advice your
    willing to share.

    I've read that I should add 1/2lb Sodium Persulphate crystals to 1
    gallon of warm water. The board should be submerged until the copper
    that is not protected is dissolved. Am I missing anything? Any tips or
    tricks that would be helpful? will this solution be strong enough? How
    does one dispose of the remaining etching solution?

    Lastly the board is a breakout of sorts, taking a db25 and directing
    the individual wires to terminal connectors. The board will be exposed
    to short pulses (1-3 seconds) of 24VDC @ up to 5 amps. The traces are
    1/16th of an inch thick and separated by only 1/32th of an inch in
    many places. This board will not be used for transferring signals,
    just on or off for short durations. Does this sound ok?

    Thanks,
    Brian
     
  2. Hawker

    Hawker Guest

    Sounds basically good.
    Been a while since I have etched a board by hand. I send all mine out
    these days. But from what I remember.

    Keep a heat source on the etchant. I think I used to use a 150W flood
    lamp. Most folks try to hang the board up and down, not flat and use a
    bubbler, which can be an aquarium air pump with a bunch of pin holes in
    the hose to keep the etchant moving.

    As for trace and space. In the PCB CAD world we talk in mills or mm so
    we would not say 1/16th" trace and 1/32" space we would say 62.5mills
    trace and 32.25 mill space. This BTW is considered huge today.
    Using
    http://www.geocities.com/capecanaveral/lab/9643/TraceWidth.htm
    For continuous 5A and 10c temp rise you can see you need a 54 mill trace
    but you are intermittent (you didn't give a duty cycle) so less would
    work. If you got room though design for continuous - say 50 mills.

    My guess is 30-50 mill is more than enough. 30 mill space sounds good
    for hand etching. 10mill trace and space is more "normal" for signals in
    a low tech area and you can probably get 15-20 mill space to work with a
    decent home made enchant tank if you need the room.

    Based on all that if I were you I would go with 50 mill trace and 20-30
    mill space.
     
  3. JeffM

    JeffM Guest

    Your use of Usenet
    http://www.google.com/search?q=cach...*-*-*-*-*-*-*-*-*-*-*-*-*+*-*-policed&strip=1
    needs improvement.
    If you feel *compelled* to ask the same question
    in MULTIPLE newsgroups, *this* is the prefered technique:
    http://www.google.com/search?q=cach...arked-as-Read-in-ALL-*-groups+Newsgroups.line

    Your technique
    http://groups.google.com/groups/sea...62EG8rhlH0Pnl47z4AZhN98BFg&scoring=d&filter=0
    is selfish and inefficient.

    The last half of this thread explains WHY
    and fleshes out the (more acceptable) cross-posting paradigm:
    http://groups.google.com/group/sci....ups+*-*-*-*-two-groups-*-*-aren't-*-different

    The last post in that thread hints at why (clueless) Google Groupers
    are so reviled by the majority of Usenet readers (who use a
    "newsreader").
     
  4. Marra

    Marra Guest

    I would have put the board out to a professional company to make.
    Home made boards are crap.
     
  5. Joel Kolstad

    Joel Kolstad Guest

    Homemade boards are crap... SPICE with parasitics added is crap... Windows
    file-locking semantics are crap...

    It seems as though you've boxed yourself into a much more restrictive world
    than need be -- if that works for you, great... but a lot of other people
    aren't nearly as self-limiting...
     
  6. Gunnar Gren

    Gunnar Gren Guest

    Joel Kolstad skrev:
    That's becuse it dosen't know very much.
     
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