Issue link: https://resources.pcb.cadence.com/i/1180264
Working with Backdrilling Backdrilling October 2019 10 Product Version 17.4-2019 © 1999-2020 All Rights Reserved. Terminology The following terms are associated with backdrilling. Net Identification The first step in the backdrill application is the identification of nets targeted for potential backdrilling. The word potential is used, as ultimately backdrilling only affects pins and vias on nets that violate the maximum stub rule. Although a net is identified, it may be omitted from backdrilling if a required layer pair does not exist and the stub lengths are within margin. The net level property BACKDRILL_MAX_PTH_STUB can be applied at the schematic level, Cadence or third party, Allegro canvas using edit property command (Edit – Properties) or within Allegro Constraint Manager. The value of this property is the maximum allowable PTH stub and is restricted to length in database units. Applying the BACKDRILL_MAX_PTH_STUB Property in Constraint Manager The BACKDRILL_MAX_PTH_STUB property can be easily assigned to nets in Constraint Manager as follows: 1. Open the General Properties worksheet located in the Net Workbook. 2. Scroll across the worksheet to the Backdrill column. 3. Select relevant cells where backdrill property is to be applied. 4. Right-click and choose Change. Backdrill Secondary drilling process that removes the unused section of plated through holes Counter-bore Alternative term for backdrilling Gbps Giga Bits per Second PTH Plated through-hole Press fit Connector whose pins are forced (spring loaded) in PCB, not soldered Stub Unused section of a plated through hole resulting in signal quality issues (reflections, impedance discontinuity)