Mixed-Crossing-Avoided Escape Routing of Mixed-Pattern Signals on Staggered-Pin-Array PCBs

Escape routing has become a critical issue in high-speed PCB routing. Most of the previous work paid attention to either differential-pair escape routing or single-signal escape routing, but few considered them together. In this paper, a significant three-stage algorithm is proposed to solve the problem of escape routing of both differential pairs and single signals (mixed-pattern signals). First, differential pairs are preconditioned to reduce the complication of the problem. Then, a unified ILP model is used to formulate the problem and a novel Boolean coding-driven algorithm is proposed to avoid mixed crossings. Finally, a slice-based method is presented to prune the variables and speed up the algorithm. Experimental results show that the proposed method is very effective. For single-pattern escape routing, it can solve all the test cases in short time and reduce wire length and chip area by 16.1% and 15.5%, respectively. For mixed-pattern escape routing, it can increase the routability by 17.5% and reduce the wire length by 14.1% compared to a two-stage method. At the same time, the proposed method can effectively avoid mixed crossings with only a little increase on wire length. Furthermore, with slice-based speedup strategy, the method can reduce the solving time by 76.7%.