A New Approach to Multi-Layer PCB Routing with Short Vias

The routing problem for Printed-Circuit Boards (PCB´s) is crucial in the fabrication of today´s digital systems. Traditionaly, this problem has been divided into two main sub-problems: layer assignment and routing. Considering these two problems apart from each other may cause uneven wire distribution both among the wiring layers and within each layer. Uneven wire distribution among the wiring layers could increase the number of wiring surfaces required for the routing. Uneven wire distribution within a layer could result in an unfeasible routing. We propose a new approach to deal with the routing of PCB´s in technologies which allow short vias. The proposed metodology considers the layer assignment and routing problems in a unified fashion. Based on some global information, our algorithm first estimates the initial number of layers required for the routing. It then determines an ordering in which nets should be considered during the layer assignment process. The results of our experiments show that our algorithm is of practical use.