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PADS PCB won't length minimize GND rats

Discussion in 'Electronic Design' started by Andrew Holme, Jan 18, 2013.

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  1. Andrew Holme

    Andrew Holme Guest

    I want to use an old board as a starting point for a new one; but the old
    one has a problem: length minimize doesn't work on the GND net. Other nets
    are OK; but I'm getting lots of GND rats needlessly crisscrossing the board
    after I ECO in the changes. The only way to get rid of them is to actually
    route GND pins. Anyone seen this? I have other designs that are not
    affected but I don't know what it is about this particular board.

    TIA
     
  2. Guest

    Isn't it becoming more or less the standard way of diong it?
    afaict the "plane" stuff is some historic leftover from using
    tape where a plane was basically a inverted image of all the pads so
    you didn't have to tape as much

    all the layers being equal with tracks and pours seems much more
    straight
    forward

    -Lasse
     
  3. Andrew Holme

    Andrew Holme Guest

    "John Larkin" wrote in message
    Thanks. Topology was already showing as "minimized" in the GUI. And, yes,
    I am using a copper pour in a routing layer for my ground plane.

    After spending hours wrestling with this I may have found a fix.

    I got around to playing with "Import" and "Export" and looking at the
    differences between good and bad pcb files.
    Just exporting connections and nothing else, good boards have:

    *SIGNAL* GND 0 -2

    in fact all signals, not just ground, have SIGFLAG=0 and COLOR=-2. Bad
    boards have:

    *SIGNAL* GND 2147483649 -2

    and all other nets are 0 -2.

    Exporting connections from a good file and importing into a bad file fixes
    it with warnings about duplicate connections.

    Editing the ASC file down to a one-liner just defining:

    *SIGNAL* GND 0 -2

    and importing that fixes it with no warnings.
     
  4. Nico Coesel

    Nico Coesel Guest

    That sounds like a specific setting for the GND net in that design. I
    don't know about Pads but the software I'm using allows me to use
    several settings for reconnecting nets. Some result in exactly what
    you are describing. So look at the properties of the GND net and
    compare with other nets.
     
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