The objective of this research is to explore Alumina Ribbon Ceramic (ARC), a newly developed substrate material technology at Corning Inc., for the first time, for 5G and mm-wave packaging applications. Important characteristics of this material include high dielectric constant (~10) and very low loss tangent (~0.0001), characterized in 10-60 GHz, and high thermal conductivity (36-38 W/m.K). Given the interesting characteristics of ARC, not much is known about its electrical properties over a broad range of frequencies in the mm-wave and sub-mmwave frequency ranges as well as its potential applications for 5G systems. As a result, suitability and viability of ARC substrates is investigated through characterization of their electrical properties (dielectric constant and loss tangent) and demonstration of low-loss interconnects on them up to sub-THz frequency region (3-170 GHz) whereas their effectiveness for 5G mm-wave frequency bands is shown through demonstration of various passive components on them in 0.1-50 GHz, typically used in RF FEMs. Furthermore, the transmission loss and electrical parasitics (resistance and inductance) of through-alumina vias (TAVs) in ARC substrates are characterized for the first time for 5G packaging applications in 0.1-50 GHz. To this end, different passive components such as microstrip ring resonators (MRRs), transmission lines (microstrip, CPW, and SIW), dual-port GSG structures, CPW-TAV daisy chains, filters (lowpass and bandpass), diplexers, couplers, and integrated passive devices (IPDs) are modeled, designed, and fabricated on ultra-thin ARC substrates (40- and 80-µm-thick) and characterized in 5G and mm-wave frequency ranges. In summary, the promising results obtained in this dissertation corroborate the suitability of ARC substrate as a new emerging ultra-thin material for 5G and mm-wave packaging applications as well as its competency for realizing ultra-miniaturized, high-performance passive components for heterogeneously-integrated RF FEMs in 5G wireless communication systems, as compared to their counterparts on the state-of-the-art 5G substrate technologies.