Basic Modes of PCB Layout

This Gold Phoenix PCB Knowledge Center article covers three basic PCB layout modes: right-angled layout, differential layout, and S-shaped layout, including their rules, advantages, and tradeoffs in high-speed design.

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PCB layout is one of the basic skills of the PCB designers. It will affect the performance of the whole system, and most of the high-speed designing theory should eventually be verified through PCB layout. In a word, PCB layout is critical for high-speed PCB designing. Generally, PCB layout is divided into right-angled layout, differential layout and S-shaped layout.

As usual, right-angled PCB layout should be avoided in the PCB designing. Right-angled layout is not so bad for the PCB routing. In the sub-GHz applications, capacitors, reflection and EMI cannot be found out by TDR test. The high-speed PCB design engineers should pay more attention to the placement, power ground design, vias and so on. Although the problem of right-angled layout is not so serious, it does not mean that right-angled layout should be applied freely. Every engineer should be detail-oriented.

The differential signal is used widely in high-speed circuit designing and most of the critical signals in the circuit are designed by differential layout. Compared to single-ended signal traces, there are a lot of advantages with differential PCB layout, such as strong anti-interference, effective suppression to EMI, and accurate timing positioning. The popular low voltage differential signaling is one of the examples of the differential signal technology with small amplitude. The most important rule of the differential layout in the PCB design is to match the line length. The others can be adjusted according to the design requirements and practical application.

S-shaped layout is a common mode of PCB layout. It’s mainly used to adjust the delay to meet the design requirements of system timing. As S-shaped layout will destroy the signal quality and change the propagation delay, it should be avoided as much as possible. However, in order to ensure enough retention time for the signal or reduce the timing offset between the signals of the same group, S-shaped layout has to be chosen.

In the future, Gold Phoenix will keep on improving the technology of PCB layout in order to meet market demands, facilitate global collaboration, accelerate time-to-market, increase profit margins, and optimize PCB reliability. For any related product needs, please contact Gold Phoenix.