What is PCB routing?

PCB routing, also known as printed circuit board, is the process of creating pathways for electrical signals on a printed circuit board (PCB). It involves the physical layout of the electrical connections between the various components on a PCB, such as resistors, capacitors, transistors, and integrated circuits.

In PCB routing, the electrical signals are routed along conductive pathways, known as traces, which are etched onto the surface of the PCB. The routing process determines the placement and routing of these traces, taking into consideration factors such as signal integrity, electrical noise, crosstalk, and electromagnetic interference (EMI).

PCB routing is typically performed using computer-aided design (CAD) software, which allows designers to visualize and optimize the electrical connections on the PCB. The routing process is a critical step in the design of a PCB and can significantly impact the performance and reliability of the final product.

It is correct that routing a circuit board can be a challenging process, especially when dealing with miniaturized boards and high-speed signals. In these cases, the limitations of the physical space on the PCB, as well as the need to maintain signal integrity and minimize electrical noise, require careful consideration and planning.

Miniaturized boards often have limited space for routing traces, making it difficult to achieve a functional and reliable design. High-speed signals require specialized routing techniques, such as controlled impedance and differential pair to ensure the signals are transmitted accurately and without loss.

To address these challenges, PCB designers must have a deep understanding of the electrical characteristics of the components and signals they are routing, as well as the impact of trace geometry and routing topology on signal integrity and EMI. They must also be familiar with advanced routing techniques and be able to use advanced CAD tools to visualize and optimize their designs.

Here are some important PCB routing practices that help ensure reliable and high-performance circuit boards:

Don’t rely on your Autorouter

It’s important to note that while autorouting tools can be a helpful tool for generating initial routes, they should not be relied upon as the sole method for routing a PCB. Autorouters often produce suboptimal results and can introduce routing errors that need to be corrected manually.

Manual routing provides greater control and allows the designer to address specific routing requirements and constraints, ensuring that the final routing is optimized for performance and reliability. By combining the use of an autorouter with manual routing, designers can take advantage of the time-saving benefits of the autorouter while maintaining the precision and control necessary for a high-quality design. 

Route high-speed signals over a solid ground plane

Routing high-speed signals over a solid ground plane is an important best practice in PCB design. By routing over a solid round plane, designers can ensure that the trace connection remains solid, minimize the risk of impedance, and simplify the process of connecting trace components to the board.

Having a solid ground plane helps to reduce the impact of electromagnetic interference (EMI) and improve the signal integrity of high-speed signals. It also helps to reduce the amount of return current noise, which can degrade signal quality. By routing high-speed signals, designers can help to ensure that the board performs reliably and meets the required signal integrity specifications.

Ensure vias are placed in a grid

Vias should be arranged in a regular pattern for optimal performance. By placing vias in a regular grid pattern, designers can ensure that the vias are evenly distributed and that there is minimal variation in the impedance of the signal trace. This helps to minimize the risk of signal reflections and ensure that the signal is transmitted accurately.

Having vias placed in a grid pattern also makes it easier to route signals to different layers of the PCB, as vias can be used to transition signals between layers. Additionally, a grid pattern can help to simplify the process of adding or removing vias, as vias can be added or removed in a consistent and predictable manner.

Use a 135-degree trace band

It is recommended to avoid using a 90-degree trace band when routing PCBs. This angle results in a trace width that is narrower than the recommended standard. While this may not seem like a significant issue, it can lead to several problems with the final layout of the PCB. The narrow outside edge of a 90-degree trace bend is also a potential heat trap that can cause shorts. Instead, it is recommended to use a 135-degree trace bend, which ensures that the board has a proper layout and avoids short issues.

Increase the spacing between traces to avoid crosstalk 

When routing a PCB, it is important to maintain the appropriate distance between traces to prevent crosstalk. Crosstalk is caused by the interaction between two or more traces, where one signal could overpower another. This interaction can result in circuit shorts, which can compromise the functionality of the board. To avoid this, be mindful of the spacing between traces to ensure that signals are transmitted without interference.

Ensure adequate trace width to prevent overheating

Choosing the right trace width is essential in order to prevent overheating and broken connections on your printed circuit board. If the trace width is too narrow, it can cause excessive heat buildup, leading to a failure in the electrical connection between the traces. By properly identifying the trace width before routing your PCB, you can reduce the risk of overheating and broken connections, ensuring a successful and functional circuit board.

Original source: https://www.articleted.com/article/597964/185519/Top-10-Best-PCB-Routing-Practices