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Pros & Cons of Autorouters in PCB Design Explained


In the intricate world of electronics, the design and complexity of printed circuit boards (PCBs) continue to escalate. Central to simplifying this detailed design journey is the autorouter—a software tool that effortlessly maps out the pathways on a PCB. While autorouters have undeniably enhanced efficiency, they also come with their own set of challenges and considerations. In this article, we explore the multifaceted world of autorouters, highlighting their distinct advantages and potential limitations. Whether you’re an experienced PCB designer or new to the field, this guide offers a comprehensive look into the balance between automation and manual design in PCB layouts.

Autorouters in PCB Design: Advantages and Drawbacks

Close-up view of a PCB highlighting its intricate design pathways

In the dynamic field of electronic circuit design, autorouters play an indispensable role. These advanced software tools automatically map out the intricate pathways of traces and vias on a printed circuit board (PCB). They promise increased efficiency and reduced errors. However, like all tools, they present challenges. In this guide, we’ll dissect the benefits and limitations of using autorouters in PCB design, spotlighting industry titans: Altium and Allegro.

Understanding Autorouters: Their Role in PCB Design

Autorouters are pivotal in electronic circuit design. These software algorithms navigate the complex pathways of components and pads on a PCB. Operating within a grid framework, each cell has a unique cost function influenced by factors like distance, direction, layer, and signal integrity. With diverse methods from maze routing to advanced component optimization, autorouters aim for the most cost-efficient path for every trace and via.

Benefits of Autorouters in PCB Design

Highlighted pathways on a PCB showing the role of autorouters.
  • Efficiency Boost: Autorouters dramatically accelerate the design process. These tools can save countless hours, especially for PCBs brimming with multiple connections. By automating the often tedious task of trace and via routing, designers can channel their energies toward more strategic elements of the design process.
  • Error Reduction: Even the most seasoned professionals can make mistakes. Autorouters, governed by stringent algorithms, substantially reduce the risk of human error. By following specific and consistent routing patterns, they improve PCB performance. They are particularly adept at preventing common design pitfalls, such as crosstalk and interference.
  • Cost Savings: In the long run, autorouters can significantly save costs. Reduced errors mean fewer iterations and prototypes, translating to cost efficiency.
  • Consistent Design Patterns: Autorouters often produce more consistent design patterns than manual routing. This uniformity can be crucial for larger-scale manufacturing.

Limitations of Autorouters

Comparison between optimal and flawed PCB designs from autorouters
  • Complexity Concerns: While autorouters are advanced, they might sometimes be overwhelmed by extremely intricate designs. They may not always find the best solution for high-complexity layouts, necessitating manual adjustments.
  • Trade-offs: Blind reliance on autorouters can sometimes yield less-than-ideal results. They might suggest routes or vias that a seasoned designer wouldn’t choose. Balancing manual oversight with automation ensures the design retains a human touch and intuition.
  • Over-automation: There’s a risk of sidelining human expertise. Specific scenarios, like RF designs or critical power paths, require a designer’s touch. Over-dependence on automation can also diminish a designer’s troubleshooting acumen.
  • Limited Intuition: While autorouters operate based on advanced algorithms, they lack the intuition and experience a human designer might bring to complex designs. They don’t “understand” the broader context of a design, which can lead to sub-optimal decisions.
  • Potential for Increased Costs: Autorouters might sometimes introduce unnecessary layers or components, inadvertently increasing production costs and even impacting signal integrity.

Addressing User Concerns with Autorouters

  • Loss of Design Control: With advancements in autorouter technology, users can set stringent design rules. This ensures that autorouted designs remain closely aligned with original specifications.
  • Quality of Automated Routes: Continuous improvements in autorouting algorithms have enhanced their efficiency. However, post-routing analysis remains essential. Manual oversight ensures designs are free from potential interference, particularly for high-speed signals.
  • Layer Count Considerations: Some designs might witness a surge in layer counts when using autorouters. It’s crucial to verify if these additions are necessary to maintain the design’s efficiency and cost-effectiveness.
  • Striking the Right Balance: A harmonious blend of automation and manual design intuition ensures optimal results. While autorouters offer unmatched efficiency, a designer’s unique perspective can address challenges that software might overlook.
  • Predictability in Design: Occasionally, autorouters might make unconventional routing choices. Regular monitoring can help designers spot and rectify these anomalies.

Manual Routing Preference

Despite the advancements in autorouting technology, there are particular scenarios where the touch of an experienced designer is not just preferred but crucial. Let’s discuss some of these instances in detail:

RF (Radio Frequency) Designs:

Detailed view of an RF circuit design on a PCB.
  • Complexity: RF circuits are notoriously intricate. They operate at high frequencies where minute design changes can lead to significant functional alterations.
  • Tuning: An experienced designer can manually fine-tune trace lengths, widths, and spacings to meet the specific impedance requirements and to minimize parasitic effects.
  • Electromagnetic Interference (EMI): Manual routing allows for strategically placing CPUs or memory unit ground planes and shielding to counteract EMI, ensuring the design’s robustness against external and internal interference.

Critical Power Paths:

  • Power Distribution: Efficient power distribution demands precise and calculated trace widths and paths. This ensures components receive the requisite power without voltage drops.
  • Thermal Management: Manually routing power paths can assist in heat dissipation. A designer might strategically place traces to optimize cooling and avoid thermal hotspots.
  • Reliability: Critical circuit components, such as CPUs or memory units, rely on stable power. Manual routing ensures that these components receive power consistently without interruptions.

Unique Aesthetic Demands:

  • Custom Shapes: Some PCBs, especially in consumer electronics like wearables or custom lighting solutions, may need to conform to unique shapes. An experienced designer can craft paths that not only serve functional purposes but also cater to design aesthetics.
  • Branding: For products where the PCB might be visible, like transparent gadgets or educational kits, brands might want a specific layout, logo, or design pattern incorporated. This demands the finesse of manual routing.
  • Optimal Space Utilization: A human touch ensures that every inch of the board is utilized efficiently while maintaining an aesthetic appeal.

High-Speed Designs:

A designer's hand manually sketching routes on a PCB
  • Signal Integrity: At high speeds, signal reflection, crosstalk, and timing become critical. An experienced designer can manually route these paths, ensuring optimal signal integrity.
  • Timing Constraints: Meeting specific timing requirements demands the precision of manual routing. It ensures that signals reach their destinations synchronously, preventing data corruption or loss.


While autorouters offer unmatched efficiency and consistent design patterns, they’re not a one-size-fits-all solution. Striking a balance between automated routing and human expertise ensures that PCB designs are both efficient and functional. Leveraging the strengths of autorouters while acknowledging their limitations can yield a harmonious blend of automation and intuition, promising optimized PCB designs.

Pros & Cons of Autorouters in PCB Design Explained
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Pros & Cons of Autorouters in PCB Design Explained
Explore the benefits and limitations of autorouters in PCB design, offering insights into their optimal use and potential impact on design outcomes.
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