Cadence PCB Best Practices

Working with Backdrilling Backdrilling October 2019 19 Product Version 17.4-2019 © 1999-2020 All Rights Reserved. Backdrill Exclusions It may be necessary to exclude certain objects from backdrilling even though stub violations are present. The BACKDRILL_EXCLUDE property can be applied to symbols, pins or vias at both the library and design level using Edit – Properties. Common examples might include solder tail connectors or a dense pin escape pattern in BGA areas. The PCB designer should consult with a manufacturing engineer before assuming all pin/via objects are suitable for backdrilling. Tip Develop a plan to incorporate the following properties at the library level: BACKDRILL_MIN_PIN_PTH, BACKDRILL_EXCLUDE, and BACKDRILL_PRESSFIT_CONNECTOR. Value values measured from the side the component is placed and defined the pin contact range (database units); this value must be obtained from manufacturer Objects Symbols Backdrill analysis flag n/a Property BACKDRILL_EXCLUDE Purpose Excludes objects from backdrilling even though stub may be present Usage Optional Value EXCLUDE_TOP EXCLUDE_BOTTOM EXCLUDE_BOTH Objects Symbols, pins, vias Backdrill analysis flag X

• 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