Algorithms for simultaneous escape routing and layer assignment of dense PCBs

As die sizes are shrinking, and circuit complexities are increasing, the printed circuit board routing problem becomes more and more challenging. Traditional routing algorithms cannot handle these challenges effectively, and many high-end designs in the industry require manual routing efforts. This paper proposes a problem decomposition that distinguishes routing under dense components from routing in the intermediate area. In particular, it proposes an effective methodology to find the escape routing solution for multiple components simultaneously such that the number of crossings in the intermediate area is minimized. For this, the problem is modeled as a longest path with forbidden pairs problem, and two algorithms are proposed for it. The first is an exact polynomial-time algorithm that is guaranteed to find the maximal planar routing solution on one layer. The second is a randomized algorithm that has good scalability characteristics for large circuits. Then, these algorithms are used to assign the maximal subset of planar nets to each layer, and then the remaining nets are distributed at the end. This paper demonstrates the effectiveness of these algorithms through experiments on industrial circuits.