Multiple ground ties

FormerMember
FormerMember

Hi,

I'm relatively new to Allegro 16.6, but know enough to get in trouble. I have a board that I'm working on now and trying to tie multiple grounds to the same copper areas.  I have a switching power supply that gets a ground  tied through vias to the center pad under the part.  This pour attached to that pad is set as a dynamic shape and the vias flood to the pour without thermal relief.  I need this done as well to the main ground pour on a different layer without the vias isolating and there being any clearance around them.  I want them to short. I managed to get it achieved by creating a static copper area on the main ground layer and covered all of the vias so they would be solid to that ground as well. Basically adding a "slab" of copper over the vias in the center of that pad.  Is there a way to do this without causing a shorting error?  Maybe a special property added to the pad? W I managed to get the shorts to be waived, but had to jump through hoops and sequences to make that happen. Just wondering if there are any tricks to get separate grounds tied without errors. Thanks for any help!

  • You can add a net_short property to a pin, via or static shape that has a value of netname1:netname2 and so on. Which will remove the DRC. There's an app note orcad.co.uk/.../Netshort_Definition.pdf with more detail if you want to drive this from the schematic.
  • FormerMember
    FormerMember in reply to steve
    Hi Steve, thanks for answering my question. So I assume you can't add this property to a dynamic shape. I have a dynamic copper pour on an inner 1 layer for the whole board and three different dynamic pours for 3 individual grounds on an inner 4 layer. This is a 6 layer board. My guess for solving it completely would be to make the individual pours on the inner 4 layer as static and then manual void the vias on that layer to clear the copper, then attach a net short property to it. But would that still flag errors because of a solid dynamic pour on the inner 1? I have waived errors in those areas now, do you know if there is any significant danger to just posting (post processing) the board with the waived errors?
  • Look at the app note, there is an example where this property has been added to a pin. In regard to waived DRC's yes but the issue with this is that you accidently waive a DRC that needs fixing so just make sure the are waiving them for the correct reason.
  • FormerMember
    FormerMember in reply to steve
    Thanks Steve. Unfortunately it didn't work completely, but it did take a few of the errors away. I can live with the others.
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