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Backdrill definition

istvanfortinet

In Cadence Allegro the backdrilling table defines for each backdrill type what the end layer will be, and not the depth or distance from layer. Then Allegro calculates the drill-depth from the stackup for the final report.
The manufacturer/fabs typically provide manufacturing capability as stub length after backdrill will be 8mil +/-4mil.

How do you use it?
a) for layer-3 signals you define end-layer to be layer-5. Hopefully layer-5 is around 8mil from layer-3.
b) for layer-3 signals you define end-layer to be layer-3, and separately specify stub length. The allegro drill depth will reach layer-3, so it has to be avoided to cut layer-3, by overriding the drill depth. how do you specify?

  • steve
    All the backdrill info can be found in <your_install_dir>\doc\algrobackdrill\algrobackdrill.pdf
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