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Issue with Via-Via Constraints

WG20250730781

Hi all, 

I have an issue with the via-via constraints of my design.

1. Normally, the via-via distance is defined in the constraints manager. However, the thru via to thru via spacing is defined by the air gap between the two vias. The issue is that this air gap accounts for the pad size to pad size distance of the via, and not the hole-to-hole distance itself. Often in manufacturing, hole-to-hole distance is more important in fabrication. How do I account for actual hole-to hole distance itself?

2. Under the constraints manager, there is a column that specifies 'hole to hole'. When I double click it, it pops up another window and further classifies into so many other line items:



However, under the general constraints manager window, there is already 'Thru via to Thru via'. How are these two different?

I appreciate some professional help.

Thank you.

Parents
  • +1

    Hi

    In Allegro there is the option to do Hole to Hole checking of various objects such as vias etc. Typically this analysis mode is not enabled in the constraint manager and would need to be enabled. To check that in the constraint manager go to Analyze > Analysis Mode. Under spacing you can check that "Hole To" is enabled for the various objects such as vias etc.

    The hole to hole spacing checks the distance between the edge of the hole barrel between holes in the board. If you do a search in the help file for Hole to Hole it explains what it does with a graphic as a visual cue.

    The main difference between this mode and  say standard via to via to via checking is that with standard via to via checking the drc is basically checking the space between the via pads and ignores the drill.

    This hole checking mode maybe tied to a certain license option in Allegro, not too sure. On the Orcad pro ver 17.2 x I have not had success in getting this rule to work. Perhaps someone can chime in on that and clarify.

    You could probably test it fairly easily on your vias by entering a value that exceeds any via to via spacing so as to see it is actually checking hole to hole spacing or not.

    Best Regards.

  • 0 in reply to excellon1

    Hello,

    My understand is if an entity (ie copper pad) is bigger that the hole, then copper pad drc take precedence over hole clearance. Hole to hole clearance works if copper pas is not present or smaler that hole. Effectivly, be aware of setup in analysis mode.

    This works in 17.2, either with orcad or allegro performance licence.

    Guess will work with 17.4 and higher

Reply
  • 0 in reply to excellon1

    Hello,

    My understand is if an entity (ie copper pad) is bigger that the hole, then copper pad drc take precedence over hole clearance. Hole to hole clearance works if copper pas is not present or smaler that hole. Effectivly, be aware of setup in analysis mode.

    This works in 17.2, either with orcad or allegro performance licence.

    Guess will work with 17.4 and higher

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