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Solid versus polygon

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  • Solid versus polygon

    Hi Guys

    Some people recommend to use polygon instead of solid plane,
    - can we compare them, what is pros and cons?
    - does it affect impedance or simulation results?
    - what about tool side? do we need to consider it in stack up setting?
    - what about manufacturer side? do we need to set some parameter for mask generation or MFG will know the setting from design files?


  • #2
    Polygon can absolutely be used as a plane, but the two entities behave very differently in Altium. When you use a plane it is made to be used exactly for that. That's why the plane is smarter in this occasion - for example it updates itself automatically and doesn't need to be re-poured if changes are made. Also split planes are easy to make - you just draw the borders between them.

    Planes have some drawbacks as well, though. If you use split planes and you delete a border between two split planes, it automatically merges them into one and randomly keeps one of the nets assigned to the common split plane. That can mess up your net assignments. A bigger drawback of using planes is that you can't have a micro via ending on a plane layer, since the layer can't contain the via pad (if a remember correctly). Also having tracks and other similar primitives on plane layers is not very convenient, since they are negative layers. Also to me personally is not as visually clear when I use split planes, compared to when I use polygons.

    Polygons give you a little bit more flexibility, although they are a bit more annoying to work with sometimes. You can configure all sorts of options using their properties, you can shelve them temporarily not to be on the way, you can configure the drawing order and others.

    I like using planes for very simple designs with a few layers, because of their simplicity. However, for more involved designs I always use polygons because of their advantages (and necessity sometimes - uvias).

    About the impedance - it doesn't matter what you use, you can achieve the same results. I have never done simulations in Altium, so I can't help you about that.

    What do you mean by tool side?

    I didn't get the part with "mask generation" either?


    • #3
      Thank Mairomaster,
      regarding two ambiguous:

      "What do you mean by tool side?"
      In order to use polygon and setting up stack, should I declare all layer as signal or need to do other?

      "I didn't get the part with "mask generation" either? "
      Suppose that everything is set and finished the design, generating mask for manufacturing, is it just generate Gerber or I need to inform manufacturer about set up?



      • #4
        Yes, just declare all layers as signal layers if you don't use Altium planes.

        I export the solder mask as gerber, together with all other gerber files. Just make sure you have proper solder mask expansion set for your pads and you comply with the manufacturers specifications about that.


        • #5
          I would like to add, that some simulation software may only count PLANES as reference planes and they will not consider polygons as a reference plane.