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Strange powerplane layering issue

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  • Brad Levy

    I think the answer is not to define the plane as a power plane, but as a regular signal plane. (The help has a caution about placing traces on a plane defined as a power plane, probably for this reason.) That doesn't mean it can't serve as a power plane - just that it won't try to mix the positive and negative plots. You can still do a copper pour of the area you want to serve as a power plane, with the pour assigned to the proper net. You should be able to check the result with your gerber viewer.

    It is in the wee hours of the night here, so post back if my answer needs clarification. Maybe someone else with relevant experience can advise, too.

     

    -Brad

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  • Boss .

    I queried the plot options available while testing V8.1.2 and received the following description.

    This is an explanation of the four types available:-

    Negative only plot gaps : only plots the oversized design items to produce a negative plot of places that will be ‘not copper’ on the final board. 

    Positive only plot items : plots the plane as though it were a normal positive electrical layer, and can be combined with a photo-reversed ‘negative plot only gaps’ output to produce a full positive plot.

    Positive plane and items : produces a full plot of everything that should end up as copper on the finished board. This should be the equivalent of combining a photo-reversed ‘negative only plot gaps’ with a ‘positive only plot items’ output.

     Negative plot isolation : plots only the gaps between items, and is a full negative plot (that needs to be reversed/inverted to get the positive plot image) and is the equivalent of combining ‘negative only plot gaps’ with a photo-reversed ‘positive only plot items’ output. It is the exact negative of ‘positive plane and items’.

    It should also be noted that the first two are both required in combination to produce a full definition for a layer, but the last two are self-contained. 

    From this I believe the default choice to use is "Positive Plane and Items".  Unfortunately my discussions were after the release and it was not included in Help, but I am informed a FAQ including the above is scheduled.

    Check out this option in the Gerber viewer.

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  • colin leamy

    @brad When I attempt your suggestion and then try to add any net to the layer it says that it should "not be set as a power plane as it already contains poured copper". This happens regardless of what type of plane the net is associated with and regardless of the bias of the layer itself.

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  • colin leamy

    @Boss it looks like it worked

    Can I assume that all of the red is copper in this scenario? In all the other layers, the black is considered copper. I just want to be sure.

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  • Brad Levy

    @colin, regarding my advice, if you make it an ordinary (signal) plane instead of a power plane, then you assign the net to the copper pour, not to the plane. That should have avoided the error message you got. (If you were assigning it to the pour and not the plane, let me know - just so I increase my understanding.)

    But it sounds like Boss has provided an approach that is working.
    And if the result with your current setting is inverted with respect to copper vs bare, you can choose Negative Plot Isolation instead of Positive Plane and Items (or vice-versa) to get the opposite sense of copper:bare.

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