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

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

3.4.1. HSSI Pin-Field Breakout for VPBGA

An optimized high-speed serial I/O (HSSI) pin-field breakout routing is crucial to reduce the impact of impedance discontinuity. As demonstrated in VPBGA PCB Layout Guideline section, the high-speed transceivers ball pitch of 0.77/0.75 mm is optimized for high-speed signals, dog-bone fan-out structure is recommended, and both single ended or differential traces can be implemented depending on the routing strategy and fabrication requirement.

Typical 8 mils drill through hole via dimensions including drill hole size, max stub, and so forth are shown in the following table. Note that some of the following simulation results are based on 8 mils drill hole size vias with 16 mils pad size for thin board and better SI. Simulation results of 18 mils pad size in BGA area are also presented for comparison. As long as simulation results are good, you can also use larger pad size (such as 18 mils) for high speed signals vias.

Table 3.  Typical 8 mils Drill Through Hole via DimensionsThe design recommendations for through hole via with design parameters are shown in this table.

Structure

Dimension

Unit

Drill hole size

8

mil

Finished hole size

6

mil

Pad size

18

mil

Anti-pad size

24

mil

Backdrill anti-pad size

26

mil

Max stub length after backdrilling

10

mil