Issue link: https://resources.pcb.cadence.com/i/1180264
Working with Backdrilling Backdrilling October 2019 9 Product Version 17.4-2019 © 1999-2020 All Rights Reserved. Figure 1-1 Backdrill Flow in Allegro PCB Designer Exclusions, Overrides, and Restrictions Verify Padstack Backdrill Data Initial Layer Pair Creation Apply the BACKDRILL_EXCLUDE property to symbols, pins or vias to exclude these elements from backdrill processing Minimize electrical stub length Minimize layer pairs Apply the BACKDRILL_MIN_PIN_PTH property to a symbol or pins to ensure that the backdrill depth does not violate min plating depth rules Apply the BACKDRILL_PRESSFIT_CONNECTOR property to a symbol which prevents the backdrilling of the critical pin contact area for press fit compliant pins (manufacturer requirement) Assign the BACKDRILL_MAX_PTH_STUB property to nets targeted for backdrilling Apply the BACKDRILL_OVERRIDE property to symbols, pins or vias for explicit from each backdrill side to a specific layer in stack- up (used on test coupons Manual layer pair initialization based on deepest backdrill layer from each backdrill side Enter manufacturing stub length in the Drill Parameters tab of Backdrill and Analysis form. Fabrication vendor remaining stub without comprising the Must Not Cut Layer (Optional) Layer Pair Creation Based on Analysis (Layer Pair Initialization – Analysis) Analysis, Reporting, and Backdrill Verify that padstacks in the design contain backdrill data which is used at backdrill locations. Select the Details button under Padstack Parameters tab for a report of padstack missing backdrill data Provide report to librarian so backdrill data in library Under Padstack Parameters tab, verify undersize and padstacks can be updated and padstacks can be Once satisfied with setup and analysis results, run Backdrill command to commit backdrill to design. Resolve any possible DRC caused by increased clearance at backdrill locations. Supporting Documentation Run Analyze to generate Backdrill plunge counts – manual layer pair initialization only Evaluate layer pairs and number backdrill plunges per Review log file for violations, exclusions, overrides, NC Drill & Legends – Enable Include Backdrill option. Backdrill Cross Section Chart – Enable Backdrill span option. Each backdrill pass represented as unique legend or file. Actual backdrill size and no oversizing. Each backdrill pass represented showing backdrill depth and tapered end Must Not Cut Layer surface. layer pair. Adjust layer pairs, routing, max stub length as required to yield the best backdrill solution. and general backdrill statistics oversize values. These values used during backdrill to update padstacks Net Identification refreshed in the design (recommended)