  Increasing data rates, spectrum efficiency and energy efficiency have been
driving major advances in the design and hardware integration of RF
communication networks. In order to meet the data rate and efficiency metrics,
5G networks have emerged as a follow-on to 4G, and projected to have 100X
higher wireless date rates and 100X lower latency than those with current 4G
networks. Major challenges arise in the packaging of radio-frequency front-end
modules because of the stringent low signal-loss requirements in the
millimeter-wave frequency bands, and precision-impedance designs with smaller
footprints and thickness. Heterogeneous integration in 3D ultra-thin packages
with higher component densities and performance than with the existing 2D
packages is needed to realize such 5G systems. This paper reviews the key
building blocks of 5G systems and the underlying advances in packaging
technologies to realize them.
