Discontinuity impacts and design considerations of high speed differential signals in FC-PBGA packages with high wiring density

Various discontinuities along the package signal path cause reflections and serious performance impact on high speed signals. This paper discusses performance impacts of BGA and PTH via structures as major discontinuities in FCPBGA packages on high speed SerDes (HSS) signals operating in differential mode using S-parameters and TDR waveforms from simulations and measurements of HSS signals on an FC-PBGA package of 4 to 6Gbps application. It also discusses design suggestions to ensure sufficient performance in both isolation between neighboring HSS signals in concern of high coupling noise and reflection minimization at individual differential pairs for optimal performance in packages with high wiring density.