Post-route alleviation of dense meander segments in high-performance printed circuit boards

Abstract

Length-matching is an important technique to balance delays of bus signals in high-performance PCB routing. Existing routers, however, may generate dense meander segments with small distance. Signals propagating across these meander segments exhibit a speedup effect due to crosstalks between the segments of the same wire, thus leading to mismatch of arrival times even with the same physical wire length. In this paper, we propose a post-processing method to enlarge the width and the distance of meander segments and distribute them more evenly on the board so that the crosstalks can be reduced. In the proposed framework, we model the sharing combinations of available routing areas after removing dense meander segments from the initial routing, as well as the generation of relaxed meander segments and their groups in subareas. Thereafter, this model is transformed into an ILP problem and solved efficiently. Experimental results show that the proposed method can extend the width and the distance of meander segments about two times even under very tight area constraints, so that the crosstalks and thus the speedup effect can be alleviated effectively in high-performance PCB designs.