Improving signal integrity by optimal design of power/ground plane stack-up structure

Abstract

This paper focuses on the signal integrity due to non-ideal return path on multi-layer packages, such as normal BGA or flip-chip BGA. The main effect of non-ideal return path of a signal is that several resonant modes will be derived at specific frequencies, and these resonant modes will degrade the signal integrity depending on the location of non-ideal return path. The resonant characteristic is inherent in electronic packages that use solid power and ground planes because a pair of power/ground planes behaves like a resonant cavity with induced displacement currents from signal transitions or switching noise. In order to solve the problem mentioned above, stack-up of power/ground planes must be arranged carefully. Besides, adding proper amount of power/ground vias on proper locations can help to eliminate power/ground plane effect on signal trace. This paper discuss how the non-ideal return path affects signal integrity of signals in both strip-line and microstrip line, and try to find out a optimal stack-up design of a multi-layer package.