Routing

Useful rules

1- General planes

Ground planes and Power planes are very useful

Since ground and power are needed by almost every component, it is useful to have them available everywhere on the board

If we work with 4-layers boards, we can afford to dedicate an entire layer to each plane.

We can split the power plane in multiple parts, one for each needed voltage.

2- Return path

Each signal should be close to its return path to ground

This is needed to minimize noise coupling

Having a ground plane simplifies this.

3- Differential signals

Should be routed as a pair

This is because common-mode noise will be rejected, so you want them to be exposed to the same noise.

4- Trace width

Power traces are wider than signal traces

It's important to know the impedance of the traces used for:

• high currents
• High speed signals
• Analog signals

Trace width is correlated to trace impedance!

5- Avoid using 90 degree trace angles

Use 45-degree angles insead

The reasons are multiple (and very debatable).
Key reason (for us): DIY manufacturing 90 degree trace angles is difficult

If Pollock was a PCB designer

Other things

• Overlaid traces for higher current
• Via fences for better EMI immunity
• High-speed signals requirements awareness
• Every other constraint