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PCBs correct first time?

Discussion in 'Electronic Design' started by Leon Heller, Nov 25, 2003.

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  1. maxfoo

    maxfoo Guest

    I caught that spelling error to late...guess my mind was wandering.

    Remove "HeadFromButt", before replying by email.
  2. John Larkin

    John Larkin Guest

    Or lots of bugs. It's hard to test quality into code. Rushed,
    unchecked code is at least 'finished', so there's pressure to ship it.
    If you take your time and code carefully, and read/review before it's
    'done', it's hard for anybody to demand that you ship it too soon.

    When the pressure is highest is often the time to slow down.

  3. John Larkin

    John Larkin Guest

    But even the Pope goes to confession.

  4. the nick of time ;)
  5. Alex Gibson

    Alex Gibson Guest

    Block of antistatic foam or
    polystrene with foil over it works well for testing component layout.
    Paperclicks to hold sm parts in place.
  6. Mike Page

    Mike Page Guest

    Reread my post and I hope you see I am not aiming at 5% errors. What I
    said is "95% or better". It depends on the job, on the customer, on the
    Clearly that doesn't scan for all cases. Some PCBs are trivial. Reread
    the second paragraph of the original post and you may agree it's about
    getting the balance right.
    Are you referring to my post ? I'm documenting what I do, not lecturing.
    It would help if you pointed out what has caused offense. Is it some
    word I used, or my argument, or attitude ? Help me out here, Frank.
  7. "Mike Page" <> schreef in bericht

    On second thoughts, I guess I misread your post. The 'why not fix
    up front' part, triggered me. I was not really offended, if I
    were, well, I would have been less mild ;) I'll try to behave myself
    next time.
  8. Greg Neff

    Greg Neff Guest

    On Sat, 29 Nov 2003 16:56:36 +0100, "Frank Bemelman"

    Our PCBs are used in applications where barnacles are prohibited. Our
    boards are used in ground-mobile (passenger rail) applications subject
    to shock and vibration over extended periods of time. Also, they are
    conformally coated. No wires are allowed. The only time we get to
    cheat is when we can make a change in a CPLD or FPGA. This might
    explain why we have more board spins than John.


    Greg Neff
    VP Engineering
    *Microsym* Computers Inc.
  9. John Larkin

    John Larkin Guest

    I've heard of organizations that prohibit jumpers, but I've never
    understood why. A hunk of wire is at least as reliable as a PCB trace.
    If you conformally coat it, it's stuck down even better!

    Zero initial defects should be a goal that is seriously attempted. But
    there may be the occasional goof or deliberate change, and then it's
    silly to throw away sellable hardware. What's not allowed, at least in
    my shop, is a jillion kluges, or a blunder so bad that an entire rev
    must be scrapped.

    Of course in a life-safety application, changes must be controlled
    pretty hard.

  10. Greg Neff

    Greg Neff Guest

    On Mon, 01 Dec 2003 08:46:52 -0800, John Larkin


    I don't know the precise reason why the jumpers are prohibited, but I
    suspect that it's a repair and overhaul issue. In this situation the
    conformal coating is removed, the board is reworked (debug, repair,
    clean, test), and the board is coated again. During this process the
    wire jumper becomes vulnerable. Our boards are expected to be useable
    for 20 years, so many of the rules are to ease test and rework.


    Greg Neff
    VP Engineering
    *Microsym* Computers Inc.
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