For electronic engineers who are new to PCB design, PCB routing is not only a core link that determines circuit performance, but also a skill that requires mastering basic rules and practical operations. This guide will systematically sort out the whole process of PCB routing from scratch, focusing on routing rule setting and step-by-step practical operation skills, helping beginners quickly get started and avoid common routing mistakes.

1. Introduction

PCB routing is the process of connecting each component pin on the PCB board through copper traces according to the circuit schematic. Reasonable routing can ensure the stable transmission of signals, reduce electromagnetic interference, and improve the overall reliability of the circuit. For beginners, the key to getting started with PCB routing is to first clarify the basic routing rules, and then practice step by step combined with actual cases.

2. Preparations: Key PCB Routing Rule Setting

Before starting routing, setting reasonable routing rules is the premise of ensuring routing quality. Most PCB design software (such as Altium Designer, KiCad) provides a complete rule setting system, which mainly includes the following core contents:

2.1 Trace Width and Spacing Rules

Trace width: It is determined according to the current carrying capacity of the line. Generally, the larger the current, the wider the trace. For low-current signal lines, the trace width can be set to 0.2–0.3mm; for power lines with large current, it is necessary to increase the trace width to 0.5mm or more, and even add copper pouring to enhance the current carrying capacity.

Trace spacing: It is related to the voltage between adjacent lines. The higher the voltage, the larger the spacing. For general signal lines, the spacing can be set to be equal to the trace width (that is, 1:1); for high-voltage lines, the spacing needs to be increased to prevent breakdown and discharge between lines.

2.2 Via Rules

Vias are used to connect traces between different layers of a multi-layer board, and their setting rules include:

Via size: Including outer diameter and inner diameter. The size should be selected according to the PCB board thickness and processing capacity. For general consumer electronics PCBs, the outer diameter of the via can be set to 0.6mm and the inner diameter to 0.3mm.

Via spacing: Avoid too dense vias, otherwise it will affect the mechanical strength of the PCB and increase the processing difficulty. The spacing between vias is generally not less than twice the outer diameter of the via.

2.3 Component Placement Related Routing Rules

Component orientation: Try to keep the same type of components in the same orientation, which is conducive to unified routing and improves the aesthetics and maintainability of the board.

Routing area restriction: Set the prohibited routing area (such as the area where the PCB is fixed by screws, the area where connectors are installed) to prevent traces from being routed into these areas and causing installation conflicts.

3. Step-by-Step Practical Routing Operations

After completing the rule setting, we can start the actual routing operation. Taking a simple single-layer analog circuit as an example, the operation steps are as follows:

3.1 Prioritize Power and Ground Routing

Power and ground lines are the "blood vessels" of the circuit, and their priority routing can ensure the stability of power supply.

First, connect the power pin of each component to the main power line, and use a wider trace for the main power line according to the current size.

Connect the ground pin of each component to the ground wire, and try to make the ground wire form a "mesh" structure as much as possible (for multi-layer boards, a separate ground layer can be set), which helps to reduce ground noise.

3.2 Route Core Signal Lines

Core signal lines refer to signal lines that have a great impact on circuit performance, such as clock lines, analog signal transmission lines, etc. When routing these lines, pay attention to:

Keep the trace short and straight, and avoid unnecessary bends and detours to reduce signal delay and attenuation.

Avoid parallel routing of core signal lines and other signal lines for a long distance, so as to prevent signal crosstalk.

3.3 Route General Signal Lines

General signal lines (such as ordinary I/O port connection lines) have relatively low requirements on routing. They can be routed according to the remaining space of the PCB, but they still need to comply with the trace width and spacing rules set in advance. When the routing space is tight, you can use vias to switch layers for routing (note that the number of vias should be minimized to reduce signal loss).

3.4 Check and Optimize Routing

After completing all routing, it is necessary to check the entire PCB board comprehensively:

Use the DRC (Design Rule Check) function of the software to check whether there are violations of routing rules (such as trace width that does not meet the requirements, too small spacing between lines).

Check whether there is any open circuit or short circuit in the routing, and optimize the unreasonable trace layout (such as adjusting the position of vias to avoid dense distribution).

4. Common Mistakes for Beginners to Avoid

Ignoring the current carrying capacity of traces and using too narrow traces for power lines, which may lead to overheating and burning of traces during use.

Routing core signal lines in parallel for a long distance, resulting in serious signal crosstalk and affecting circuit performance.

Setting the via size too small blindly, which exceeds the processing capacity of the PCB factory and leads to an increase in the production reject rate.

5. Conclusion

For PCB routing beginners, mastering the basic rule setting method and step-by-step practical operation process is the key to getting started. Only by combining theoretical rules with practical operations, and summing up experience in continuous practice, can we design PCB boards with stable performance and reasonable layout.