Layer assignment for multi-layer PCB and VLSI routing

The layer assignment problem for VLSI routing is the problem of determining which layers can be used for routing the wire segments in the interconnections of nets so that the number of vias is minimized. In this paper, we first transform the problem of layer assignment for multi-layer routing to the graph contractability problem and then a heuristic algorithm is proposed on the basis of the graph contractability model. The algorithm was evaluated using Deustch’s five-layer difficult example. The result showed that the number of vias is reduced 38.5 percent.