Mastering the art of PCB routing

Stephen Chavez is chairman of the Printed Circuit Engineering Association (PCEA) and a Senior Product Marketing Manager with Siemens EDA. He is an IPC Certified Master Instructor Trainer (MIT) for PCB design, an IPC Certified Advanced PCB Designer (CID+), and a Certified Printed Circuit Designer (CPCD). He is chairman of the Printed Circuit Engineering Association (PCEA).

In the world of PCB design, PCB routing plays a pivotal role in ensuring the efficiency and functionality of electronic circuits. Let’s explore the various PCB routing techniques, and shed some light on interactive routing, auto routing, and the empowering realm of sketch routing.

Interactive routing: mouse-driven precision

Interactive routing is the standard approach adopted by PCB designers across various PCB design tools. It involves meticulous control over the routing process. As the designer holds the mouse, each click dictates the path of the trace, adhering to default rules and constraints within the database. This method provides a hands-on, rule-adhering experience, known as interactive routing.

The interactive routing experience is like maneuvering through a complex maze, where every move is calculated and precise. Designers navigate the intricacies of the circuit board, ensuring that each connection aligns with the default rules set within the system. While this method offers a high degree of control, it becomes especially valuable when dealing with intricate designs or scenarios where the designer needs to exercise precise authority over the routing process.

Auto routing: empowering automation with constraints

Auto routing takes PCB routing a step further by introducing constraints and letting the system autonomously handle the routing process. Designers can set up constraints and engage the auto router to navigate the entire board or specific sections. The ability to pause, review, and make decisions during the process allows for dynamic control. Auto routing unveils its power in scenarios where quick iterations and adaptability are paramount, especially when faced with unforeseen design changes.

Let me emphasize, auto routing should not be viewed as a one-size-fits-all solution. Its true strength lies in its ability to handle repetitive and time-consuming tasks. This allows designers to focus on more strategic aspects of the design process. Designers can set the parameters, let the auto router handle the initial connections, and then strategically intervene to fine-tune the results.

Sketch routing: crafting paths with precision

Sketch routing is a technique that allows designers to sketch the desired path of traces using a mouse. This method provides control over the flow of connections, allowing designers to envision and execute specific routing scenarios. By engaging layers selectively and controlling the process in spurts, designers can achieve a harmonious and controlled chaos, ensuring that the system adheres to their intended design.

Sketch routing can be compared to an artist’s brushstroke on a canvas. Designers become digital artists, guiding the path of traces with precision and intent. The sketch routing technique proves especially valuable when dealing with intricate designs that demand a tailored approach. It enables designers to articulate their creative vision and ensures that the routing aligns with the unique requirements of the circuit.

Hug-and-route, push-and-shove: precision in routing

Within the realm of sketch routing, we must also discuss the concepts of ‘hug-and-route’ and ‘push-and-shove’.

Hug-and-route involves parallel tracing, ensuring smooth connections between traces, while push-and-shove empowers designers to move traces seamlessly without causing disruptions. These techniques contribute to the precision and efficiency of the routing process.

Hug-and-route can be compared to the choreography of synchronized dancers, where traces move in harmony, maintaining parallelism and reducing potential signal interference. On the other hand, push-and-shove allows designers to strategically move traces without compromising the integrity of the overall design. Both techniques highlight the level of detail and control that can be achieved in the PCB routing process.

Auto routing vs. sketch routing: striking a balance

A common question that often comes up when talking about PCB routing automation: When should auto routing be used versus sketch routing?  While auto routing offers a rapid and automated approach, sketch routing provides designers with nuanced control over the routing process. The balance between automation and manual control is crucial, especially in complex designs where a blend of both techniques can yield optimal results.

Auto routing should be viewed as a valuable ally rather than a replacement for manual intervention. The ability to perform ‘what if’ scenarios and quickly adapt to design changes is where auto routing shines. However, it is the careful application of sketch routing that allows designers to maintain creative control and cater to the specific needs of intricate designs.

Navigating the maze of PCB routing

Navigating the maze of PCB routing involves finding a balance between harnessing the power of technology through automated processes and maintaining the PCB designer’s artistic touch through manual control. The choice between interactive routing, auto routing, and sketch routing is not a binary one; rather, it is about using these tools in harmony to create an efficient and effective design. Remember, automation in auto routing is a tool, not a replacement for the meticulous and precise control offered by sketch routing and interactive routing. As designers, embracing this toolkit enables us to rise to the challenges of the ever-evolving world of electronic circuit design.