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DRC Errors on some nets, but not others of same width

crosland

Eagle 6.3.0 Standard.Four layer stackup.

 

I have minimum trace width and clearances set to 8mil in the design rules. Some 8mil traces fail DRC width check but others (even connected to the same component) are fine.

 

It seems to be that any trace that connects through a via to my ground plane polygon is flagged with a width error. Nets that stay on one layer are OK. Nets that transition to another layer (but not the ground plane) through a via are OK.

 

The errors also go away if I change the net class to "0 default" instead of "1 power" for the ground plane

 

What is it about connecting to the ground plane polygon that causes a DRC error?

 

Andrew

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    On 12/09/2012 02:03 PM, Andrew Crosland wrote:

    Eagle 6.3.0 Standard.Four layer stackup.

     

    I have minimum trace width and clearances set to 8mil in the design

    rules. Some 8mil traces fail DRC width check but others (even

    connected to the same component) are fine.

     

    It seems to be that any trace that connects through a via to my

    ground plane polygon is flagged with a width error. Nets that stay on

    one layer are OK. Nets that transition to another layer (but not the

    ground plane) through a via are OK.

     

    The errors also go away if I change the net class to "0 default"

    instead of "1 power" for the ground plane

     

    What is it about connecting to the ground plane polygon that causes a

    DRC error?

     

    It's not about the ground plane.  It's about the net class of the ground

    plane.

     

    The minimum width requirements in the Class overrides that of the DRC.

    So while the DRC has a minimum width of 8, the requirement for "1 power"

    is greater.

     

    HTH,

        - Chuck

     

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