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Autorouters in PCB Design: Pros & Cons

Introduction to Autorouters in PCB Design

In electronics, as PCB design complexity continues to rise, optimizing PCB design processes has become increasingly essential. Advanced tools often achieve this optimization in PCB design processes. In this context, designers often consider autorouters, specialized software for PCB layout. Autorouters, specialized PCB design software for PCB layout, have advantages and disadvantages for designers.

This article explores the advantages and disadvantages of autorouters. It also provides insights into PCB design best practices, particularly on manual PCB routing. Whether you’re an experienced PCB designer or new to the field, this guide offers valuable insights. It balances automated and manual methods in PCB layouts, an important part of PCB design best practices.

Autorouters in PCB Design: Advantages and Drawbacks

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

In electronic circuit design, autorouters are tools that aim to automate the routing of a printed circuit board (PCB). While they claim to increase efficiency and reduce errors, the industry debates their effectiveness. This guide objectively examines the advantages and disadvantages of using autorouters in PCB design. It focuses on prominent industry PCB design tools: Altium and Allegro.

Understanding Autorouters: Their Role in PCB Design

Autorouters, which are specialized software tools, play a pivotal role in electronic circuit design. They achieve this primarily by implementing various routing strategies. 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. Factors such as distance, direction, layer, and signal integrity influence this function. Autorouters employ diverse methods, ranging from maze routing to advanced component optimization. They aim to find the most cost-efficient path for every trace and via.

Benefits of Autorouters in PCB Design

Benefits of autorouters in PCB design
  • Efficiency Enhancement: Autorouters significantly expedite the design process, shortening design times and potentially saving numerous hours, especially for PCBs with multiple connections. One of the primary advantages of autorouters is automating the often laborious task of trace and via routing. This automation allows designers to save time and redirect their efforts toward more strategic aspects 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 trace 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 in PCB Design

limitations of autorouters
  • Complexity Concerns: While advanced, extremely intricate designs can sometimes overwhelm traditional autorouters. The emergence of auto interactive routers, a more advanced type of autorouter, addresses some of these complexities. However, they may not always find the best solution for high-complexity layouts, still requiring 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: Advanced algorithms form the basis of operation for autorouters. However, they lack the intuition and experience that 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.

Exploring the Algorithms Behind Autorouters

Autorouters in circuit board design rely on sophisticated algorithms to automate the routing process. Understanding these algorithms reveals how they tackle complex design tasks, their efficiency in various scenarios, and their inherent limitations. This section delves into the core algorithms that power autorouters.

Key Algorithms Used in Autorouters

A visual representation of the maze routing algorithm for autorouting in PCB design, with numbered cells leading to a goal.
  • Maze Routing Algorithm
    • Function: Navigates through the PCB layout like solving a maze, finding paths for traces.
    • Efficiency: Effective for simpler designs; can struggle with highly dense or complex boards.
    • Limitations: May not find the shortest or most optimal path in intricate designs.
  • Lee’s Algorithm
    • Function: Explores multiple routes simultaneously, expanding like a wave.
    • Efficiency: Better at handling moderately complex designs compared to maze routing.
    • Limitations: Can be computationally intensive, potentially slowing down the routing process.
  • A* Search Algorithm
    • Note on the Name: The algorithm is named “A*” (pronounced “A-star”). This is not a typographical error; the asterisk (*) is part of the official name.
    • Function: Combines features of both maze routing and Lee’s algorithm. It prioritizes routes with the lowest cost using a heuristic approach.
    • Efficiency: Highly effective for complex and high-density designs where precision in pathfinding is crucial.
    • Limitations: Requires more processing power, which may not be necessary for simpler PCB layouts.

Contextual Application in PCB Design

  • Each algorithm has its niche, varying effectiveness based on the design’s complexity and specific requirements.
  • Autorouters in PCB design often combine these algorithms, choosing the most suitable one based on the design task.

Efficiency in Different Scenarios

  • Simple Layouts: Maze routing can quickly generate paths, making it ideal for less complicated designs.
  • Moderate Complexity: Lee’s algorithm offers a balance, handling more complex paths without excessive computational demands.
  • High Complexity: A* search is best suited for dense, intricate designs where optimal pathfinding is crucial.

Understanding Limitations

  • Computational Load: More advanced algorithms like A* can tax the system, requiring powerful hardware for smooth operation.
  • Optimization Challenges: While effective, these algorithms might not always discern the most efficient path. This is particularly true regarding specific factors like signal integrity or thermal management.
  • Human Oversight: Autorouters, regardless of the algorithm, benefit from manual oversight, especially in critical areas of the design.

By exploring these algorithms, we gain insight into how autorouters function and make decisions in PCB design. This exploration highlights the importance of choosing the right tool for the right task.

Addressing User Concerns with Autorouters in PCB Design

  • Loss of Design Control: With advancements in PCB autorouting technology, users can set stringent design rules. This ensures that autorouted designs remain closely aligned with original specifications, addressing a key concern in PCB autorouting.
  • 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. Verifying the necessity of these additions is crucial for maintaining 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 PCB editor 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 advancements in autorouting technology, specific scenarios prefer the expertise of an experienced designer. In these cases, the designer’s expertise is preferred and crucial. Let’s discuss some of these instances in detail:

RF (Radio Frequency) Designs:

RF routing and disadvantages of autorouters
  • 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 specific impedance requirements. They can also minimize parasitic effects through this manual adjustment.
  • EMI: Designers can use manual routing to place CPUs or memory unit ground planes and shielding to reduce EMI. This ensures 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 like 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. These unconventional shapes can present specific design challenges. An experienced designer can create routing patterns that serve functional purposes while catering to design aesthetics.
  • Branding: Products with visible PCBs, like clear gadgets or educational kits, aim for a unique look with special designs. This customization makes them stand out and reinforces their brand identity. It involves manual routing expertise to enhance aesthetics.
  • Optimal Space Utilization: Human touch ensures efficient use of every inch of the board while maintaining an aesthetic appeal.

High-Speed Designs:

high speed design autorouter challenges
  • 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 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 PCB design automation and human expertise ensures that PCB designs are efficient and functional.

Leveraging the strengths of autorouters, a key component of PCB design automation, is crucial. At the same time, acknowledging their limitations is important. This approach can yield a harmonious blend of advanced automation and human intuition. Such a balance promises optimized PCB designs.

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