Recent research development in flip-chip routing

The flip-chip package is introduced for modern IC designs with higher integration density, larger I/O counts, faster speed, better signal integrity, etc. To ease design changes, an extra metal layer is introduced to redistribute nets between wire-bonding (I/O) pads in a die and bump pads in a package carrier. Flipchip routing is performed by redistributing and interconnecting nets between the I/O and bump pads. As the design complexity grows, routing has played a pivotal role in flip-chip design. In this paper, we first introduce popular flip-chip structures, their routing-region modeling, and induced routing problems, survey key published techniques for flip-chip routing with respect to specific structures and pad assignment methods, and provide some future research directions for the modern flip-chip routing problem.