Issue link: https://resources.pcb.cadence.com/i/1180264
Working with Backdrilling Backdrilling October 2019 39 Product Version 17.4-2019 © 1999-2020 All Rights Reserved. Effects of Setting a Manufacturing Stub Length: ■ The Layer Pairs Tab reports 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 may have a difficult time backdrilling because just stopping at the To Layer (layer before the Must Not Cut Layer) needs to backed 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 Layer Pair Initialization analysis. ❑ The environmental variable BACKDRILL_LAYER_PAIR_ADJUSTMENT automatically shifts the layer pair for a given backdrill candidate to meet the fabricator minimum manufacturing stub length. Layer Pairs tab feedback – Depth column yellow cells: The layer pair rows for TOP to LAYER_4_P and BOTTOM to LAYER_7_P is not being reported as an issue because the minimum stub length after backdrill can be achieved, for example: ❑ To Layer (1.20 mils) + Dielectric (16.00 mils) = 17.20 mils ❑ Total Thickness is 17.20 mils, which is greater than 10.00 mils stub length.