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Orcad: carbon pad

Discussion in 'CAD' started by engcif, Feb 22, 2007.

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  1. engcif

    engcif Guest


    We are working on a telephone circuit layout. We have drawn a carbon
    pad for silicone keypads in layout and attached the drawing to a pin
    so that the whole drawing became a pin that can be used as a
    footprint. But we are not so happy with our carbon pad footprint. Is
    there a better/common way of doing this or any tricks?

    Thanks everyone.

  2. qrk

    qrk Guest

    If your switch pad is moderately complicated, create the pad outlines
    in a 2D drawing program like AutoCad or the drawing package that comes
    with layout. You can import the the graphics into Layout via a DXF
    import. You need to look at the maxdxf.ini file in the Layout
    installation directory for instructions for layer names. When you
    import the DXF into a Layout footprint, you will have obstacles. Edit
    the obstacles to place them on the proper layer, give them the proper
    obstacle type, and attach it to a pin. You will have a beautiful
    footprint which will draw oohs and aahs.
  3. Marra

    Marra Guest

    Not convinced this will work as the final pad has to be able to be
    described by the Gerber command set.
    Just tweak the pad until it is right in orcad.
  4. Joel Kolstad

    Joel Kolstad Guest

    That's just a question of the right conversion programs. Starting with
    something like DXF, you can have something like CorelDraw output HPGL (it'll
    convert all the fancy curves, fills, etc. into the simple "strokes" that HPGL
    supports), and from there something like GerbView can convert HPGL to Gerber.
    Most PCB packages can import Gerber.

    Of course, many PCB packages can import DXF as well, although which commands
    they support is often limited. Pulsonix, for instance, doesn't support the
    DXF "SPLINE" command, so I use the approach described above.
    You know the use of ALL CAPS on drawings/PCBs have been slowly dying ever
    since the point where Xeroxing drawings (one of the main reasons ALL CAPS were
    used historically) became uncommon? :)

    The way you label nets is similar to how the LabView guys like to do it...

  5. qrk

    qrk Guest

    I am assuming that he is using Orcad Layout, but he didn't use an
    uppercase "L" when he used the word "layout".

    Obstacles are drawn with lines, thus, they can be represented by
    Gerber commands. You need to compensate your DXF drawing for the line
    width used in the obstacle definition.

    The technique I describe works quite well. In Orcad Layout, you can
    import a DXF file to create a PCB max file or a footprint library
    file. You can't use polylines, however. After you import the DXF file,
    you edit the footprint by tweaking the obstacles that were imported
    from the DXF file. The tweaking might be to change the obstacle type
    from free track to copper area and adjust the width. You add a small
    padstack for your pin so your pad doesn't protrude outside of your DXF
    defined area. You associate the obstacle with the pin so it will pass

    The last four boards I have done all required using this technique. My
    BGA packages with a predefined fanout are done using a similar
    technique, however, I have a program that spits out an ASCII MIN file
    which is converted into a footprint. It's all the same concept.
  6. SrB

    SrB Guest

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  7. Marra

    Marra Guest

    That sounds interesting.
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