Two types of PCB routing strategies

Different types of single boards have different wiring strategies. This article mainly introduces two types of PCB wiring strategies.

Type one PCB layout strategy

1) The main features of Type 1 are as follows: strict length rules, strict crosstalk rules, topology rules, differential rules, power ground rules, etc.

2) Processing of key networks: bus


Define Class;

It is required to meet certain topological structure, stub and its length (time domain) constraints;

Two types of PCB routing strategies

Diagram of balanced daisy chain and intermediate drive daisy chain

Set virtual pins to control the topology;

Two types of PCB routing strategies

Virtual T point diagram

Limit STUB. Set the maximum stub length, the delay/length should be given a range; it is forbidden to go out from the long side of the pad; it is allowed to have a junction on the terminal.

3) Processing of critical network: clock line

Define Class, set sufficient line spacing or the spacing between Class and Class;

Set the clock line in a specific layer and area.

4) Processing of key network: differential line

Generally need to specify the wiring layer;

Use parallel mode, avoid tandem mode;

Define the length matching of the two differential lines and the length matching of the differential pairs;

The usual way to set the spacing between differential line pairs is to define the differential pair as a class, and then define the spacing between Class to class.

5) Crosstalk control

There must be sufficient clearance between the network groups; for example, there must be spacing constraints between the data lines, address lines and control lines, set these networks to the corresponding class, and then between the data line and the address line, the data line and the control line Set crosstalk control rules between lines, between address lines and control lines.

6) Shield

Shielding methods: parallel (parallel), coaxial (coaxial), cascade (tandem);

After the rules are set, you can use manual or automatic wiring.

Two types of PCB routing strategies

Type 2 PCB layout strategy

1) Type 2 PCB design has both physical realization challenges and electrical rules realization challenges.

2) “Guide” is required during the wiring process, such as: Fanout, layer division, automatic wiring process control, forbidden area definition, wiring sequence, etc., need to be properly interfered.

3) Test and analyze the feasibility of wiring;

4) Consider the realization of physical rules first, and then the realization of electrical rules;

5) For conflicts or errors, it is required to comprehensively analyze the causes and adjust the wiring strategy in a targeted manner.

For PCB engineers, PCB wiring strategy is essential knowledge, and everyone should be proficient in it.