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design with flexible PCB

Discussion in 'Electronic Design' started by Michael, Jun 26, 2007.

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  1. Michael

    Michael Guest

    Hi everybody
    I am looking into using flexible board for the new design.

    We need to connect two PCBs. Approximately 20 lines, 0.5" wide or
    narrower (the narrower, the better); top and bottom shielding planes;
    ~2-3" long. It needs to be connectable at least on one side (we need
    to be able to separate the boards).

    One PCB is four layers, another is 8-12.

    I have not used this technology before, I am doing some on-line
    research at the moment.

    What would be the cost difference (compared with the conventional
    rigid FR4)? Prototyping? Production? Any additional requirements to
    Gerbers? How reliable are ZIF connectors?

    Can you recommend any information? Ideas?
    Thank you!
    Michael
     
  2. Guest

    What is wrong with using shielded ribbon cable and conventional IDC
    connectors? The flexy may be cheaper in volume, and probably thinner,
    but your connector is probably going to wipe out most of these
    potential advantages.

    Things to watch with multilayer fexible circuits are keeping the build-
    up balanced, and not bending them around excessively tightly radiused
    bends. Hewlett-Packard used flexies in their linear-motor based X-Y
    recorder back in the 1970's, and wrote up the development at length in
    the Hewlett-Packard Journal at the time. They paid a lot of attention
    to the risk that the flexible circuits involved would become brittle
    with time and break, and did quite a lot of testing to make sure that
    this didn't happen.

    In principle, the contents of the H-P Journals are accessible on-line,
    but I can't get anything out of their search engine.
     
  3. Michael

    Michael Guest

    Flex cable takes less volume. I also hope to find smaller connector
    (at least on one side).
    Cost is not that much of an issue.
    There are ways to attach robust connector to flex cable (U have seen
    TH electrolytic caps on flex board)....
    I have to talk to our board house...
    Thank you.
    Michael
     
  4. PeteS

    PeteS Guest

    Few manufacturers can actually do flex [or more likely rigiflex]
    properly. Cost may not be that much of an issue, but a typical flex will
    cost at least 6x [and probably more] the equivalent rigid +
    interconnect. Many manufacturers say they can do it, but you'll be
    plagued by poor yield unless you go to a much more expensive outfit (who
    are expensive because they _can_ do it).

    Unless you have a compelling reason for flex, I would advise against it.
    I have used rigiflex boards where I needed to, incidentally, and they
    can work great, but they have their drawbacks.

    Cheers

    PeteS
     
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