The PCB signal layers must follow typical good practice guidelines including:
- Layer changes must be minimized for single-ended signals.
- Individual differential pairs can be routed on different layers, but the signals of a given pair must not change layers.
- Stubs are to be avoided.
- Only voltage or low-frequency signals can be routed on the outer layers, except as noted previously in this document.
- Double data rate signals must be routed first.
- Pin swapping on components is not allowed.
The PCB must have a solder mask on the top and bottom layers. The mask must not cover the vias.
- Except for fine pitch devices (pitch ≤ 0.032 inches), the copper pads and the solder mask cutout are to be of the same size.
- Solder mask between pads of fine pitch devices must be removed.
- In the BGA package, the copper pads and the solder mask cutout must be of the same size.