PCB Design Guidelines: Agilex™ 3 FPGAs and SoCs

ID 853726
Date 8/20/2025
Public
Document Table of Contents

5.4.3. PCIe* Add-In Card Edge Finger

Ensure that you do not place any inner-layer conductors, including ground or power planes, beneath the edge fingers for 15 mil when supporting a PCIe* 3.0 add-in card.

You can add inner plane layers beneath any of the edge fingers, provided that:

  • The inner plane layers extend no more than 2 mm into the edge finger region from the main routing area of the board and
  • The inner plane layers are at a minimum depth of 15 mil (0.38 mm) beneath the edge finger copper pads on the surface of the PCB.
Figure 23. Add-In Card Edge Finger Regions with Allowed Inner Layer Plane

Ensure that the distance between the top edge ground fingers and the bottom edge of the ground via pads does not exceed 15 mil for add-in card ground fingers. Connect the adjacent ground edge fingers at the lowered via location to improve the ground resonance.

Figure 24. Add-In Card Edge Fingers Indicating Adjacent Ground Vias