A routing framework for technology migration with bump encroachment

Abstract

Technology migration plays a critical role in the time-to-market competition. Most existing works focus on layout compaction or hardware description language re-synthesis, and pay little attention to the I/O interface in flip chips. The complication of bumping process as well as electrical and reliability considerations prevent the bumps from scaling with transistor sizes. On the other hand, the number of signal bumps cannot be reduced and sometimes even increases due to the demands for wider bandwidth and various peripheral devices. As a result, the allocated die area for I/O can no longer afford the number of bumps a chip requires. This issue, known as bump encroachment, puts a stringent requirement on the redistribution layer (RDL) routing. In this paper, we first formulate the problem of RDL routing with bump encroachment, and then propose a network flow based algorithm to efficiently address it. Experimental results on a few benchmarks with parameters extracted from industrial designs show that compared with a maze routing-based approach, our algorithm can achieve up to 72% wire length reduction.