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Should I combine those two GND polygons or not? Arguments for and against!

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  • Should I combine those two GND polygons or not? Arguments for and against!

    Hello all,
    I am about to finish my 8 layer design and would like to inquire you if you can give me some recommendations on the following question.

    First of all, my stack up is constructed like:

    1.Sig/GND - The Gnd plane here is manly used for improving the reference point and as copper balancing approach (improving the plating index)
    2.GND
    -----------------
    3.Sig/PWR
    4.GND
    -----------------
    5.PWR
    6.Sig/GND
    -----------------
    7.GND
    8.Sig/GND -The Gnd plane here is manly used for improving the reference point and as copper balancing approach (improving the plating index)


    Layer 1 is where a couple of power supplies are placed on.
    Currently the GND potential is being distributed to the power supplies IN and OUT caps thru their own island GND planes for IN and OUT caps (see pic1) attached.
    All blue polygon around the power supplies is also one and the same GND polygon, poured all across layer1.



    The question here is what the pros and cons would be here if I just combine the GND islands of the PWR supplies
    with the entire, poured, GND plane on layer 1??


    Thanks!
    Last edited by Max; 01-14-2022, 04:34 AM.

  • #2
    Honestly, I do not do that, so I am not sure. Maybe someone else can help?

    Comment


    • Max
      Max commented
      Editing a comment
      Hi Robert,
      You mean you do not combine but leave the polygons separated, right?
      Thanks!

  • #3
    I mean, I do not pour GND on signal layer if there is solid GND in the stackup - especially on the layer under components.

    Comment


    • #4
      I would connect those polygons together, like in this video https://www.youtube.com/watch?v=vALt6Sd9vlY
      Copper balancing is a good reason to pour copper on signal layers, but can have drawbacks according to Eric Bogatin, especially when done incorrectly. https://www.youtube.com/watch?v=DIMIzKRmync

      Comment

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