Recursive Pattern Autorouter: A New Approach to Circuit Board Routing

The challenge of routing printed circuit boards (PCBs) has long been a bottleneck in electronics design. Traditional autorouters often struggle with complex layouts, leaving designers to manually complete difficult sections. A new approach called "recursive pattern autorouter" promises to change this by using pattern recognition and recursive decomposition to tackle routing problems more intelligently.

How Traditional Autorouters Work

Most existing autorouters use grid-based or shape-based routing algorithms. They typically work by:

• Placing components on a grid
• Attempting to connect pins using shortest-path algorithms
• Avoiding obstacles and respecting design rules
• Backtracking when dead ends are reached

This approach works well for simple designs but becomes exponentially slower as complexity increases. The number of possible paths grows rapidly, and the router often gets stuck in local minima, requiring extensive manual intervention.

The Recursive Pattern Approach

The new recursive pattern autorouter takes a fundamentally different approach. Instead of treating the entire board as one massive routing problem, it breaks the problem down into smaller, manageable patterns that can be solved recursively.

Pattern Recognition

The algorithm first scans the board to identify common routing patterns - T-junctions, crossings, parallel runs, and other typical configurations. These patterns are stored in a library and can be matched against the current routing problem.

Recursive Decomposition

When faced with a complex routing task, the algorithm recursively breaks it down:

1. Identify the largest recognizable pattern in the current problem
2. Solve that pattern using the appropriate template
3. Recursively solve any remaining sub-problems
4. Combine the solutions

This is similar to how divide-and-conquer algorithms work in computer science, but applied to the spatial problem of circuit routing.

Advantages of the Recursive Approach

The recursive pattern method offers several key advantages:

• Speed: By solving smaller problems rather than one massive one, computation time is dramatically reduced
• Quality: Pattern-based solutions tend to be more elegant and adhere better to design rules
• Scalability: The approach handles boards of any size by breaking them into manageable chunks
• Learning: The pattern library can be expanded over time to handle more complex scenarios

Real-World Performance

Early testing of the recursive pattern autorouter shows promising results. In benchmark tests against traditional autorouters:

• Routing completion time was reduced by 60-80% on average
• The number of vias (connection points between layers) was reduced by 25%
• Design rule violations were cut in half
• Manual cleanup time was reduced by 70%

These improvements translate directly to faster design cycles and lower manufacturing costs.

Limitations and Challenges

Despite its advantages, the recursive pattern approach isn't perfect. Some challenges remain:

• Pattern library dependency: The quality of routing depends heavily on the completeness of the pattern library
• Memory usage: Storing and matching patterns requires significant memory
• Complex topologies: Some highly irregular board layouts may not decompose well into recognizable patterns
• Learning curve: Designers need to understand how the algorithm works to use it effectively

The Future of PCB Routing

The recursive pattern autorouter represents a significant step forward in PCB design automation. As the pattern libraries grow and the algorithms improve, we can expect even better performance.

Future developments might include:

• Machine learning to automatically generate and optimize patterns
• Integration with other design tools for seamless workflow
• Cloud-based pattern libraries that improve with community contributions
• Real-time routing visualization for interactive design

The days of spending hours manually routing complex PCBs may soon be behind us, thanks to this innovative approach to an age-old problem.

For those interested in trying the recursive pattern autorouter, it's available as a plugin for popular PCB design tools like KiCad and Altium Designer. The source code and pattern libraries are open-source, allowing the community to contribute and improve the system.