Configuration for High-speed Transmission between Flip-chip Packages Using Low Loss and Flexible Substrate

Abstract

To meet the demand for higher signal transmission speeds, we investigated an interconnect structure using a flexible printed circuit (FPC), and clarified that this facilitated major improvements in the signal integrity. A differential transmission line with a stripline structure was created within the FPC, and by connecting this with the IC packages (PKG) via solder bumps, a stub-less, skew-free interconnect configuration was realized. We evaluated 14 Gbps to 56 Gbps electrical characteristics with a prototype module, and verified that this facilitated a 30% to 60% extension of transmission length compared to a conventional printed circuit board (PCB).