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  1. #1
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    Plane filled with copper/ground plane on one single PCB layer

    Hi All,

    I am not sure what would be better. In the case that we have a one single layer PCB what would be more advantageous for EMC?. Would we prefer to create a ground plane that would contribute to less inductive impedance at high frequencies but on the other hand it could create current loops, or would we prefer to have two power rails, one for VCC and another one for GND to put close those rails to benefit from cancelation but on the other hand in this case the inductive impedance would be higher.

    If we decide not to have a ground plane ( so to have two power rails), filling the board with copper ( unconnected to any potential) would give us a benefit?.

    Thanks in advance,
    Winsu.

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    Re: Plane filled with copper/ground plane on one single PCB layer

    Hi

    Use two layers.
    One layer completely GND. Not other signals, no splits.

    This is the safe way for not very experienced PCB layout designers.

    Klaus
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    Re: Plane filled with copper/ground plane on one single PCB layer

    Hi Klauss,

    The reason I asked is because it is a typical constrain when designing LED boards that are sitting on a heat sink. I always have that doubt when I have to decide what to do.

    Regards,
    Winsu



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    Re: Plane filled with copper/ground plane on one single PCB layer

    There can't be a ground plane on a single layer PCB, just copper pours in the unused space.

    It's however not quite clear which EMC problems you expect respectively which EMC related circuit properties you want to achieve. I agree that it's useful to implement specific cirtuit branches with low inductance. But you want to analyze which circuit branches are particularly critical in this regard and which not.

    In addition, ground loops are rarely a problem in power electronic circuits. Copper pours are generally advantageous unless you want reduce circuit capacitance.



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    Re: Plane filled with copper/ground plane on one single PCB layer

    Thanks, could you be more specific why ground plane can not be used on a single layer PCB?. Also what benefits bring putting copper pours in the unused space?.

    Regards,
    Winsu.



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    Re: Plane filled with copper/ground plane on one single PCB layer

    Hi,

    The reason I asked is because it is a typical constrain when designing LED boards that are sitting on a heat sink.
    What is a "LED board"? Only L.EDs? Tell the complete story ... otherwise we need to guess and you possiply get wrong informations.

    could you be more specific why ground plane can not be used on a single layer PCB?.
    What he meant is:
    From an EMI/EMC (high frequency) view a "copper pour" is no "GND plane".
    A GND plane is a low impedance (high frequency), solid reference for zero voltage.
    A copper pour is cut in pieces, it has high impedance from one piece to the other.

    High frequency EMI/EMC considerations take the length of a current loop and the enclosed area of the current loop into account.

    Klaus
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    Re: Plane filled with copper/ground plane on one single PCB layer

    Hi,

    What I meant with LED board is a board where you have a input stage ( DC or AC) with a full rectification and a cap bank for filtering. Then you have a few LED strings( depending of the size of the board), those LED string are driven by a DC/DC converter which its maximum current is 1A. The system is designed to work typically with 24 V DC or 24V AC.

    I understand that a ground plane provides a low impedance reference point for current to sink and I think ( I just think actually that it is achieved because of the large conducting area). About the copper pours I can imagine that it is done for manufacturing purposes mainly but I don't know if it provides any electrical benefit to the system.

    I know that every case need to be studied in isolation but could we say for an general specific reason that for single layer boards we shouldn't include a ground plane?, instead we should put just power rails and then any empty space remaining fill it with copper pours?.

    Thanks,
    Winsu.

    Thanks,
    Winsu



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    Re: Plane filled with copper/ground plane on one single PCB layer

    Why do you assume that copper pours are not connected to ground and don't perform an electrical function? A ground area, broken by components and traces isn't considered a "plane" in usual PCB terminology. The particular problem with single layer design is that you would need ground jumpers to implement a low inductance ground that can halfway act like a plane.



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    Re: Plane filled with copper/ground plane on one single PCB layer

    Hi,

    From what I read ... you still think the copper(pour)!as DC resistance.

    But your question is about EMC, which means high frequency ... and impedance.

    HF impedance does not depend on wire width. It rather depends on frequency, substrate thickness and dielectric constant of the substrate (non conductive!)
    It does not much depend on copper thickness, nor copper width...

    Klaus
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    Re: Plane filled with copper/ground plane on one single PCB layer

    ok,l see... I have always considered ground plane or planes in general an area of the same potential and that area could be also broken by components.

    Then why is better to put copper pours rather than just tracks?. In the way I see it by putting copper pours some components would have lower impedance path to ground than others, I guess this should be something to be considered...



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    Re: Plane filled with copper/ground plane on one single PCB layer

    Hi,

    Then why is better to put copper pours rather than just tracks?.
    I simply don't agree with this.
    There will be a slight improvement.. but it's so minimal, that I don't call it "better".

    In my eyes copper pour is misunderstood to be a GND plane...usually by not that experienced PCB layouters.
    It may be an improvement when there additionally is a true GND layer.
    And it is an improvement for the PCB production process, because it minimizes the copper to be etched away.

    Klaus
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    Re: Plane filled with copper/ground plane on one single PCB layer

    I also agree that copper pours can lead to unbalances in grpund which can cause misfunction of components, but I agree it is a DC problem.

    I had in the back of my mind that by increasing the area of the ground plane ( or at least using copper pours), we could reduce the inductance and it ultimately would decrease the impedance at high frequency ( EMC).

    - - - Updated - - -

    Then if it is just an improvement for manufacturing purposes, why not to use always just tracks?. With tracks we could benefit from cancelation if VDD is sitting next to Vss...



  13. #13
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    Re: Plane filled with copper/ground plane on one single PCB layer

    Hi,

    Then if it is just an improvement for manufacturing purposes, why not to use always just tracks?. With tracks we could benefit from cancelation if VDD is sitting next to Vss...
    No, not just as manufacturing improvement...

    Properly used they will be a benefit in DC or low frequency applications.
    And properly used by an experienced PCB designer it will be a benefit in HF, too.
    ..but only if the designer has the knowledge...

    And it may be an improvement in heat spreading ....

    Klaus
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    Re: Plane filled with copper/ground plane on one single PCB layer

    Hi,

    I Can see how it could transmit the heat from the LEDs to the heat sink, I guess in that context you want to have as much copper around for hitting spreading.

    Why would be a benefit for DC and low frequency applications?. Would it be to reduce DC resistance when DC or low frequency?, would there be any other benefit?. This conversation is being very rewarding for me, thanks.



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  15. #15
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    Re: Plane filled with copper/ground plane on one single PCB layer

    Hi,

    Why would be a benefit for DC and low frequency applications?.
    For low frequency application the DC resistance counts.
    The resistance will drop with copper thickness and copper width.

    Klaus
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