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TDA4VM: SOM (PROC078E7) Layout Backdrilling

Steven Balick80
Prodigy 40 points

Regarding backdrilling on PROC078E7_BRD.brd – please verify the following backdrill quantities:

  • Backdrill from TOP to L10 – Qty 64
  • Backdrill from BOT to L11 – Qty 128
  • Backdrill from BOT to L4 – Qty 18

These quantities show up on the TI fab drawing/drill chart, though when running the backdrill tool in Allegro the BOT-L11 and BOT-L4 plunges are being combined into one (BOT-L11, qty 146).  Has the BOT-L4 backdrill been eliminated or is there more setup that needs to be done to separate it?  Please advise.

Thanks.

  • 0
    TI__Guru 52065 points

    The BOT to L4 backdrills are still in the design.  These are used to remove the via stubs near the memory device connections for 'T-branched' address/control signals routed on layer 3.  Includes CA[5:0], CLKP/N, CKE0/1.

    When I run the Allegro backdrill report, and get no findings.  Thus - I'm not sure how/if the backrills are setup are setup correctly as 'backdrills' in the Allegro file.  Its possible the PCB file was setup 'manually' to support back-drilling (larger drill/voids on specific vias).