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