Develop this 5 Rules set before starting any PCB design

The first thing you should do after importing the net list to your PCB design tool, is to define the rules.

The rules definitions actually start at the schematic design phase. Here you should define the net classes and group the similar nets together, eg. power nets, 50 ohm single ended signals, differential signals of various impedances, etc. The net classes later can be used to define rules specifically for these net groups.

When it comes to rules, regardless how its defined in your design suit, here are the 5 things your rules must address.

#1 Routing

First is the width of the trace, here the classes come in handy especially for the power nets and differential nets. Next rule you can define is if you need some classes on certain layers, this comes in handy for multilayer boards.

#2 Vias

A via drill size of 0.15 mm is possible, but is it reasonable? Don’t go to the edge of what your PCB fab can do, be reasonable. If you are doing via for high speed signals, you need to remove the non-functional pad shapes and add rule about stubs.

#3 Timing

Here you need to define how big of a skew is allowed in a differential pair and also in some cases skew within groups of differential pair.

#4 Crosstalk

Here you need to define a minimum clearance between the traces to avoid signal coupling. Depending on your EDA tool, you could go very granular and define clearance between various elements on your PCB.

#5 Reference planes

Reference planes are where the return current flows, you need to define rules so that the DRC triggers an error when a trace has no reference layer below it.

Defining rules is a good practice regardless of the complexity of your board.