Sorting-based I/O connection assignment and non-Manhattan RDL routing for flip-chip designs

In modern VLSI designs, a flip-chip package is widely used to meet the higher integration density and the larger I/O counts of circuits. Recently the I/O buffers are mapped onto bump balls without changing the module placement using re-distribution layer (RDL) in flip-chip designs. In this research, a sorting-based I/O connection assignment and non-Manhattan RDL routing method is proposed for area I/O flip-chip designs. The approach initially assigns the I/O buffers to bump balls by sorting the Manhattan distance between them. Three kinds of pair-exchange procedures are then carried out to improve the initial assignment. Then to shorten the wire length, non-Manhattan RDL routing is adopted to connect the I/O buffers and bump balls. Finally some un-routed connections are ripped up and rerouted. The experimental results show that the proposed method is able to obtain the routes with shorter wire length in reasonable CPU times.