Ordered Escape Routing with Consideration of Differential Pair and Blockage

Abstract

Ordered escape routing is a critical issue in high-speed PCB routing. Differential pair and thermal-blockage-avoided are useful in PCB design to obtain high noise immunity and low electromagnetic interference. In this article, a Min-cost Multi-commodity Flow (MMCF) approach is proposed to solve the ordered escape routing. First, the characteristic of grid pin array and staggered pin array is analyzed and then a basic network model is used to convert ordered escape routing to MMCF model. To satisfy the constraints of ordered escape routing, three novel transformations, such as non-crossing transformation, ordering transformation, and capacity transformation, are used to convert the basic network model to the final correct MMCF model. After that, the differential pair in ordered escape routing is discussed. Finally, a method to deal with the blockage issue is proposed. Experimental results show that our method achieves 100% routability for all the test cases. The method can get both a feasible solution and an optimal solution for ordered escape routing. Compared to published approaches, our method improves in both wire length and CPU time remarkably. At the same time, the proposed method can effectively avoid the blockage and deal with the differential pair.