Cadence PCB Best Practices

Working with Backdrilling Backdrilling October 2019 48 Product Version 17.4-2019 © 1999-2020 All Rights Reserved. Figure 1-21 Test Point additions after backdrill locations has been identified Figure 1-22 Feedback messages on the Allegro Command window NC Drill and Legend Output The output of backdrill data can be compared to the way buried/blind via data is output. Separate legends and NC Drill files are created for each backdrill pass. While dielectric layers are used in analysis calculations, the NC Drill output is based on conductor layers only.

• Cover
• Contents
• Backdrilling
• Introduction
• Licensing
• Prerequisites
• Backdrill Commands, Properties, Parameters, and Subclasses
• Terminology
• Net Identification
• Applying the BACKDRILL_MAX_PTH_STUB Property in Constraint Manager
• Stub Calculation
• Pin Plating Restrictions
• Applying the Minimum Pin Plating Property
• Pressfit Connectors
• Backdrill Exclusions
• User Overrides
• Fabrication Vendor Backdrill requirements (Reference Only)
• Setup and Analysis User Interface
• Initially Launching the Backdrill Setup and Analysis Dialog Box
• Prior to executing Backdrill
• Padstack Parameters Tab of the Backdrill Setup and Analysis Form
• Flag Codes tab of the Backdrill Setup and Analysis form
• Final Backdrill Steps – Executing Backdrill
• Manufacturing Stub Length Analysis (Drill Parameters Tab)
• Effects of Setting a Manufacturing Stub Length:
• Layer Pairs tab feedback – Depth column yellow cells:
• Backdrill Canvas Display Controls
• Backdrill Data Show Element visibility (Pins/Vias)
• DRC and Shape Voiding
• Board Testability
• NC Drill and Legend Output
• Enabling Backdrill Output
• NC Backdrill Legends
• Legend Customization
• Backdrill Cross Section Chart Display