PCB Design Guidelines (HSSI, EMIF, MIPI, True Differential, PDN) User Guide: Agilex™ 5 FPGAs and SoCs

ID 821801
Date 8/29/2025
Public
Document Table of Contents

4.5.1. HSSI Pin-Field Breakout for VPBGA

An optimized high-speed serial interface 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 mil through-hole via dimensions including drill hole size, maximum stub length, and so forth are listed in the following table.

Note that some of the following simulation results are based on eight mil drill hole size vias with 16 mil pad size for thin board and better signal integrity (SI). Simulation results of 18 mil pad size in BGA area are also presented for comparison. If the simulation results are good, you can also use larger pad size such as 18 mil for high-speed signals vias.

Table 3.  Typical 8 mil Through-Hole via DimensionsThe table lists design recommendations for through-hole via with design parameters..
Structure Dimension (mil)
Drill hole size

8

Finished hole size

6

Pad size

18

Anti-pad size

24

Backdrill anti-pad size

26

Maximum stub length after backdrilling

10