Working with Backdrilling in Allegro PCB Designer: Best Practices
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Effects of setting a manufacturing stub length
• The Layer Pairs tab will report a Yellow Cell under the depth column where the
total thickness of the "To Layer" + "Dielectric" is less than the entered stub
value.
• When this violation exists, the fabricator might have a difficult time backdrilling
because just stopping at the To Layer (layer before the Must Not Cut Layer) will
need to back off from the To Layer to meet their manufacturing limitations.
• You can leave it up to the fabricator to adjust the drill depth or have the layer
pairs adjusted during the Layer Pair Initialization analysis.
o The environmental variable, BACKDRILL_LAYER_PAIR_ADJUSTMENT,
will automatically shift the layer pair for a given backdrill candidate to meet
the fabricator minimum manufacturing stub length.
Layer Pairs tab feedback – Depth column yellow cells
