PCB High-Speed Signal Design Guidelines: Agilex™ 5 FPGAs and SoCs

ID 821801
Date 11/18/2024
Public
Document Table of Contents

3.3.4. Via Drill Size

  • The aspect ratio (AR) is the ratio of a via length or depth to its drill hole diameter. An AR of 1:15 is a common manufacturing capability provided by most PCB vendors. PCB vendors define the exact AR based on the board thickness specified by their manufacturing capabilities.
  • To meet the target differential via impedance, the optimized via anti-pad size is usually larger than the default via anti-pad which may cause a reference issue for breakout routing in the BGA area. Check via impedance with time domain reflectometry (TDR), and use a teardrop or wider trace segment in the breakout area for a smooth impedance transition to the global area.