Inserting a blind and a buried via???

Hi,

Please see attached file. May be it will be helpfull to you.

Define the blind/buried via either though the padstack editor or within the Allegro design using Setup >Vias > Define B/B Via or Setup > Vias >Auto Define B/B Via. Using the setup bb vias GUI you can copy the pad definition of an existing via, set the start and end layers. Using the Auto define GUI you select the input pad name, with an optional prefix, set the start and end layers, set the rule set(s) and generate the via.

Add the via(s) to the physical constraint set(s) if you didn't use the Auto define methodology.

When in add connect set the start (Active) and end (Alternate) ayers and select which via you want to use

 I have a 6 layer board in Allegro PCB Design XL 16.3 that I am trying to individually place blind vias from the bottom layer to an internal ground plane. I understand how to set up a blind or buried via under Setup-B/BVia definitions-Define B/B via however I do not know how to actually place the via on the layout. I have tried going to Route-Connect, then selecting a pad and opening the right click menu to place a via there, but I only get a generic through hole via that crosses every layer. Any suggestions?

Once you have added the BB Via you need to add it to the Physcial Constraint Rule. Go into Constraint Manager - Physcial Tab, then Physcial Constraints All Layers. In the PCS rules on the RHS there is a Vias area, click here and you can then add the vias from the library or database (your bbvias will appear in this list). Double Click to add to the design. Make sure the order of the via list is set for how you want to use them (top of the list is the default one).

 Thanks, those steps were something I was unaware of. I see that there are tabs for creating via structures and via arrays, but is there any way to place individual vias? Even after completing the consetraints, when I try to place a via on an existing surface only pad through route-connect-mouserightclick-addvia, I still get the generic via that touches every layer. I'll continue searching the documentation on how to do this, but any help has been and will be greatly appreciated.

Edit: I was able to place a via running from the bottom to ground plane simply by selecting the ground layer when placing the via. I believe that the via order in the constraints is critical to which via is selected as well.

Thanks again Steve.