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A Review of 5G Front-End Systems Package Integration

Atom O. Watanabe, Muhammad Ali, Sk Yeahia Been Sayeed, Rao R. Tummala, P. Markondeya Raj

arXiv:2009.07208v1eess.SP

TL;DR

5G packaging must support higher data rates, spectrum efficiency, and energy efficiency despite stringent mm-wave loss, impedance, footprint, and thickness requirements. This review surveys 5G system building blocks and packaging advances, including heterogeneous integration, antenna-in-package structures, and demonstrated mm-wave modules.

  • Problem

    Mm-wave 5G front-end packaging must satisfy low-loss and precision-impedance requirements while reducing package footprint and thickness.

  • Method

    The paper reviews 5G system building blocks, packaging challenges, heterogeneous integration technologies, materials, passive components, antenna-in-package structures, and recent demonstrations.

  • Results

    The review documents heterogeneous package-integration demonstrations including 28-GHz modules above 50 dBm EIRP, 52-dBm EIRP at 29 GHz, and 14.7-dBi antenna-array gain at 60 GHz.

  • Takeaways & Limitations

    Compact heterogeneous integration brings antennas, transceivers, passives, and interconnects closer together to address mm-wave loss and support 5G front-end systems.

Abstract

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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.

I. PATH TO 5G

5G expands cellular networking beyond earlier voice- and internet-focused systems toward broadband, ultra-reliable low-latency, and massive machine communications. These use cases require higher capacity, fast response, reliability, and connectivity for many devices.

  • 5G vs 4G Communications: Unlike LTE, 5G is presented as an entirely new network supporting users across consumers, businesses, services, utilities, and cities.Speed, capacity, connected-device count, latency, and reliability drive its broad requirements.
  • 5G Applications (eMBB, URLLC, mMTC): 5G introduces three major use cases: enhanced mobile broadband, ultra-reliable low-latency communication, and massive machine-type communication.They target different combinations of data rate, response time, reliability, device density, and power consumption.
  • 5G Applications (eMBB, URLLC, mMTC): eMBB increases capacity and end-user data rates through additional spectrum, mm-wave bands, antenna arrays, massive MIMO, and beamforming.The resulting applications include Ultra-HD and 360° streaming, augmented reality, and virtual reality.
  • 5G Applications (eMBB, URLLC, mMTC): URLLC provides <1-ms latency, 99.9999% connection availability, and high-speed mobility for mission-critical applications.Examples include vehicle-to-everything communication, healthcare, utilities, security, cloud, and real-time monitoring.
  • 5G Applications (eMBB, URLLC, mMTC): mMTC supports billions of low-cost, densely connected devices with low data rates, low power consumption, long range, and long maintenance intervals.Its primary focus is machine-to-machine communication with minimal human interaction, including sensor networks.

C. 5G Frequency Bands

5G frequency planning spans standardized FR1 and FR2 ranges and supports both rapid deployment through NSA and independent operation through SA. The added bands and deployment choices increase hardware and miniaturization complexity.

  • 5G Frequency Bands: FR1 covers 450 MHz–6000 MHz in 3GPP Release 15 V15.4.0 and 410 MHz–7125 MHz in Release 15 V15.5.0, while FR2 covers 24250 MHz–52600 MHz.FR1 includes low- and mid-frequency bands; FR2 is solely for mm-wave bands.
  • 5G Frequency Bands: 5G spectrum is classified into low-, mid-, and high-bands, with mid-band defined as sub-7 GHz and high-band as mm-wave above 24 GHz.The cited mid-band range is 1 GHz–7.125 GHz.
  • Deployment Approaches: Non-standalone 5G combines the LTE radio access network and core with added 5G support for a fast-to-launch deployment approach.NSA initially supports 5G low- and mid-bands, including sub-7 GHz.
  • Deployment Approaches: Standalone 5G provides independent end-to-end deployment with a next-generation core, improved efficiency, lower costs, and support for URLLC and mMTC.It also requires new infrastructure, creating time-consuming and cost-demanding deployment challenges.
  • Hardware Implications: Additional low- and mid-bands and new FR2 hardware increase hardware-design complexity and miniaturization challenges.The paper links these changes to advances across system hardware, from integrated circuits to devices and cellular equipment.

II. 5G SYSTEM DRIVERS

5G system drivers arise from different equipment constraints, higher-frequency propagation losses, and the need to form focused beams. These pressures shape beamforming, transceiver, power-amplifier, and antenna-in-package choices.

  • System Classes: User equipment prioritizes miniaturization and reduced power, whereas infrastructure equipment prioritizes gain, range, massive MIMO, and broadband operation.5G systems are classified as user equipment, customer premise equipment, and base-station or infrastructure equipment.
  • Beamforming and MIMO: Higher-frequency signals experience greater free-space attenuation, motivating narrow beams produced by beamforming and higher-order antenna arrays.These arrays are driven by multiple active components and support communication with target nodes.
  • Beamforming and MIMO: Analog beamforming uses one RF chain with passive beam control, while digital beamforming offers full beam control and multiple simultaneous beams at higher hardware and power cost.Hybrid beamforming combines advantages of analog and digital approaches.
  • Beamforming and MIMO: Frequency- and code-multiplexing techniques can reduce digitizer power requirements by 10 to 32X.The approach is described in the context of innovative digital beamforming architectures.
  • Antenna-in-Package: Antenna-in-package integration reduces RFIC-to-antenna interconnect length, mitigating feed-line loss and improving antenna efficiency.The trend is especially prominent for 28-GHz and 39-GHz consumer-electronics systems.
  • Power Amplifiers and Transceivers: CMOS and SiGe PAs are optimized for 25 dBm and 30% power efficiency, GaAs reaches 30–35 dBm, and GaN provides capabilities beyond 45 dBm.A 64-element array may require up to 5 W per PA, while linear operation and 8-dB backoff make efficiency challenging.

III. PACKAGING CHALLENGES IN MM-WAVE 5G

5G mm-wave packaging must integrate RF, analog, digital, antenna, passive, and power-management functions in compact modules while preserving signal, power, and electromagnetic integrity. The resulting designs require tight routing, controlled thickness, and multiphysics analysis.

  • Integration Requirements: 5G packaging integrates RF, analog, digital, passive, antenna, filter, diplexer, amplifier, switch, and power-management functions in a single heterogeneous module.Integration is driven by antenna–transceiver proximity, new FR1 and FR2 bands, and add-on RFFE modules.
  • Module Architecture: Mm-wave modules combine antenna arrays, transceiver ICs, power-management ICs, logic-memory stacks, and surface-mounted passives.Reported packaging-substrate thickness ranges from 0.15 mm to 1.2 mm.
  • Form Factor: Entire module thickness ranges from 0.5 mm to 2 mm because antenna requirements, components, interconnects, and mold height determine total package dimensions.Antenna-integrated modules need greater thickness because increased ground-plane separation can provide higher antenna bandwidth.
  • Signal and Power Integrity: Multiple components in limited space complicate signal routing and power delivery while requiring signal integrity, power integrity, and electromagnetic-interference control.The dielectric thickness for routing and power distribution can be 15 µm or less.
  • Multiphysics Design: Stable operation under signal, power, and thermomechanical loads requires accurate multiphysics modeling across electrical, materials, chemical, and mechanical domains.The package structure affects both signal and power distribution and the electrical performance of individual components.

D. Co-Simulation of package, circuit and device

5G mm-wave packaging requires co-design across phased antennas, transceiver or beamforming ICs, passives, electromagnetic compatibility, and thermal behavior. Materials and manufacturing must also preserve impedance control while enabling increasingly fine-pitch integration.

  • Co-design phased antenna arrays with transceiver or beamforming ICs and passive components to meet power-distribution and signal-integrity requirements.The design should also consider electromagnetic compatibility and thermal behavior.
  • Low-loss dielectrics reduce dissipation in in-package interconnects, feedlines, and antennas, increasing antenna efficiency.Low loss is characterized by a low dissipation factor, or loss tangent (tan δ).
  • 5/5 µm to 2/2 µm line/space by 2025 and 1/1 µm by 2030 are targeted while maintaining impedance control and minimizing manufacturing tolerances.Heterogeneous integration for massive MIMO increases the need for finer-pitch I/O among chips, packages, and antenna arrays.
  • 5G mm-wave packaging requires integrated heat-spreading structures because greater component density and reduced distances increase thermal-management demands.5G mm-wave systems are expected to consume more power than earlier wireless generations.

IV. 5G PACKAGING TECHNOLOGY BUILDING BLOCKS

5G mm-wave packages integrate baseband and antenna-transceiver functions under stringent impedance, loss, form-factor, material, and routing constraints. Packaging advances combine interconnection, substrate, dielectric, and embedding technologies to support dense heterogeneous integration.

  • System-level packaging: System-level mm-wave packages are partitioned into baseband modules and antenna-integrated transceiver modules.Interconnections must provide impedance control, low insertion loss, acceptable return loss, and compact form factor.
  • Interconnection technologies: Wire-bonding, flip-chip, and IC-embedding or fan-out are the principal interconnection approaches for RF/mm-wave miniaturization.Flip-chip and fan-out offer fine pitch and low electrical parasitics that are increasingly important in RF/mm-wave packages.
  • Interconnection technologies: Wire-bonding causes significant signal loss and impedance discontinuity, whereas flip-chip improves performance through shorter bump-based interconnections and supports smaller form factors.Fan-out eliminates wire bonding and reduces high-frequency loss, parasitics, and footprint for high-pin-count dies.
  • Substrate materials: Multi-layer organic substrates remain mainstream because they are cost-effective and compatible with existing PCB-like supply chains and high-volume consumer-electronics manufacturing.LCP and PTFE attract attention for their low tan δ at mm-wave frequencies but require higher-temperature and higher-pressure lamination processes.
  • Substrate materials: Glass substrates provide Dk 3.7–8, Df 0.0003–0.006, dimensional stability below 2 µm for 20 mm substrates, large-panel scalability, and fine-pitch through vias.These properties address mechanical and process limitations associated with organic laminates.
  • Routing and dielectrics: RDL and microvias enable high-density interconnects below 10 µm, while dry-film and liquid-based low-loss dielectrics support dense integration and fine features.Filled dry films improve modulus and CTE but can narrow the process window, reduce adhesion, and challenge harsh-environment reliability.

C. Integration of Passive Components

Passive components support impedance matching, filtering, tuning, biasing, and signal-combination functions in 5G systems. Their integration increasingly depends on low-loss build-up dielectrics and photosensitive materials for high-density routing.

  • Passive components provide matching, filtering, tuning, biasing, coupling, balancing, combining, dividing, phase-shifting, circulation, and isolation functions.They are also paired with RF ICs as duplexers for nominal system operation.
  • Low-loss build-up dry films are used for high-density signal routing in high-frequency applications.The supplied passage identifies the technology category, while the table caption names its application context.
  • Low-loss photosensitive or photo-imageable dielectrics are used for high-density signal routing in high-frequency applications.The supplied table caption identifies the material class and routing context.
  • 90% of component count, 80% of size, and 70% of cost are typically attributed to passive components.

Discrete Lumped Circuits for sub-6 GHz 5G bands:

5G passive-component research spans LTCC, organic laminates, fan-out wafer-level packaging, and laminated glass, with emphasis on smaller footprints, lower loss, and integration into mm-wave packages. Demonstrated filters and dividers show how substrate and fan-out technologies support these goals.

  • LTCC and organic substrates: LTCC enabled complex 3D multilayer passive structures but faces fabrication complexity, cost, mm-wave loss, surface roughness, routing-density, and scalability challenges.A reported LTCC 30 GHz filter used five metal layers, 4.67% FBW, and 2.95 dB insertion loss.
  • LTCC and organic substrates: 35 GHz SIW filters on Rogers RT/Duroid 6002 achieved 3.7% FBW and 1.25 dB insertion loss using a low-cost PCB process.Transmission zeros were placed on either side of the passband for high rejection between neighboring channels.
  • Fan-out and distributed components: 0.35 dB/mm CPW loss and 0.34 dB/mm microstrip loss were achieved in integrated power-divider work for 5G antenna arrays.These advances combine performance improvements, physical miniaturization, and functional integration with wafer fan-out packaging.
  • Laminated glass: Glass-based passive components used six metal layers and SAP processing, achieving less than 2% dimensional variance and insertion loss of 0.1 dB/mm or 0.05 dB/mm depending on dielectric thickness.Package-integrated filters smaller than 0.5λ0×0.5λ0 were developed for 28 and 39 GHz bands, with cross-sectional height below 200 µm.
  • Laminated glass: Package-integrated ultra-thin 5G filters combine ultra-short 3D interconnects with off-chip discrete-filter insertion loss and on-chip-like interconnect losses.The filters can be embedded components or integrated passive devices and configured as diplexers.

D. Antenna Systems in Package (AiP)

Mm-wave antenna arrays can be implemented on PCBs, in packages, or directly on chips, with AiP offering a practical balance between integration and performance. Patch and dipole antennas provide different radiation, polarization, bandwidth, and integration trade-offs.

  • Patch antennas: Patch antennas support elevation-direction radiation and dual polarization, but their miniaturization and bandwidth require trade-offs in material choice, thickness, gain, and alignment.High-Dk materials reduce size but degrade bandwidth and gain, while stacked patches require accurate layer-to-layer alignment.
  • Dipole antennas: Dipole antennas cover the azimuth direction with single polarization and generally provide wider bandwidth than patch antennas.Yagi-Uda topologies increase gain by adding directors, and dipole-based structures use differential transmission-line feeds.
  • Antenna implementation options: AiP is the most viable option for 5G mm-wave applications, whereas PCB antennas are lower cost and antenna-on-chip offers the lowest feed-line loss and parasitics.PCB implementations face coarse design rules and tolerance challenges; antenna-on-chip additionally faces efficiency, scalability, yield, cost, reliability, and flexibility concerns.
  • Antenna implementation options: Three mm-wave antenna implementation approaches are antennas on PCB, antennas in package, and antennas on chip or wafer.These alternatives are compared as distinct locations for integrating the antenna array with the RF front end.
  • Packaging structures: Packaging structures for antenna integration include flip-chip-based configurations and IC-embedded configurations.These structures organize the principal integration approaches used for antenna-in-package systems.

V. CURRENT DEVELOPMENT IN HETEROGENEOUS PACKAGE INTEGRATION FOR 5G

5G heterogeneous antenna-package integration has progressed through flip-chip AiP and chip-embedded structures using organic, glass, LTCC, molding-compound, and fan-out technologies. Demonstrations show high-frequency operation, beam scanning, high EIRP or gain, and reduced package dimensions.

  • Integration categories: Recent mm-wave AiP packages are classified as chip-last or flip-chip structures and chip-embedded structures according to their interconnection techniques.The review discusses system architectures together with packaging structures and materials.
  • Flip-chip AiP demonstrations: IBM’s 28-GHz organic-laminate AiP integrated 64 embedded antennas, four backside flip-chip transceiver ICs, thermal management, and a 70×70×2.7 mm3 module.The module achieved more than 50 dBm EIRP in transmit mode and ±40° scanning range.
  • Flip-chip AiP demonstrations: Intel and Qualcomm demonstrated compact organic AiP modules integrating RFICs, antenna arrays, shielding, and multiple bands or polarizations for 5G devices and base stations.Intel reported a 30×15×1.5 mm3 package with 1500 connections per transceiver IC, while Qualcomm’s second-generation module supported 28- and 39-GHz operation.
  • Material platforms: LTCC AiP preserved 14 dBi gain with 8 elements and 16.5 dBi gain with 16 elements across a 10-GHz bandwidth around 60 GHz.Glass-based AiP is also investigated for electrical properties, dimensional stability, and panel scalability toward 500×500 mm2.
  • Chip-embedded AiP: Chip-embedded structures reduce form factor and thickness through shorter interconnects, while fan-out wafer- and panel-level packaging support integrated antenna arrays.Reported examples include a 10×10×0.5 mm3 package with 14.7 dBi gain at 60 GHz and a TSMC InFO system with 6 dBi gain.

VI. 5G AND BEYOND – 6G

6G is expected to extend communications into higher-frequency and wider-bandwidth regimes, especially the THz range. This shift requires heterogeneous integration of precision antennas, low-loss interconnects and waveguides, and active devices because traditional RF packaging approaches become unsuitable.

  • 6G requirements: 6G is expected to operate primarily in the THz gap and deliver 100 Gbps–1 Tbps data rates, compared with 10–20 Gbps for 5G.Research on sub-THz applications and use cases is already underway.
  • 6G requirements: 6G key performance indicators are compared with those of 5G.The comparison is summarized in the cited figure.
  • 6G package concepts: A conceptual heterogeneously integrated quasi-optical THz package is presented for 6G communications.The figure represents a package-level architecture for integrating future THz communication components.
  • 6G applications: 6G use cases include high-resolution AR/VR, XR, wireless AI, smart sensors, and IoT-driven applications requiring ubiquitous, ultra-low-latency, high-fidelity networks.The passage frames these requirements as drivers for identifying technologies and evolving use cases.
  • Packaging challenges: Many traditional RF-package approaches are not applicable to sub-THz and THz radios because increasing frequency introduces multiple packaging challenges.The proposed direction is incremental advancement of precision antenna arrays, low-loss interconnects and waveguides, and active devices.

VII. SUMMARY

The review classifies and synthesizes packaging technologies addressing mm-wave losses, power, integration, and system complexity in 5G. It identifies increasingly compact, heterogeneous, and inorganic package architectures as important directions toward higher-frequency systems.

  • Summary: Advances in III-V devices, IC-package co-design, beamforming architectures, and test methodologies have addressed key mm-wave limitations and made 5G systems a reality.The review systematically classifies the underlying technologies across relevant product segments and operating requirements.
  • Summary: 5G antenna arrays are integrated into smaller 3D packages, with AiP phased arrays widely adopted in user-equipment and base-station products.The packaging focus includes transmission losses below 0.1 dB/mm and 1–5% process variations for stringent signal specifications.
  • Summary: Organic packages face dimensional-instability and line-width-control limits, motivating inorganic substrates such as glass for density and impedance continuity.Additional organic-package layers can increase via-transition losses and package thickness.
  • 6G outlook: THz and 6G systems require compact, high-output power sources and highly responsive low-noise detectors to address high path loss at THz frequencies.These requirements accompany projected increases in network speed and new virtual-reality and high-resolution video applications.
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