The Rise of Heterogeneous Integration as an Industry Standard
Every market, from defense to commercial wireless applications, has two overarching goals: to reduce the size of components and subsystem packaging while integrating as many functions as possible. This is a tall order, as the two requirements inherently conflict, creating entirely new packaging methods while enhancing existing ones is necessary.
As a result, these applications demand unprecedented levels of integration, minimal signal loss, and superior thermal management, all while keeping costs competitive. Traditional packaging approaches, which often rely on wire bonding and conventional printed circuit board materials, simply cannot meet these demanding specifications without significant performance degradation.
Emerging solutions such as wafer-level packaging, advanced organic substrates, and novel interconnect technologies are reshaping the RF packaging domain. These innovations enable the integration of multiple RF functions into smaller form factors while improving electrical performance and thermal characteristics. For instance, recent developments in silicon interposers and through-silicon via (TSV) technology have made it possible to create highly integrated RF modules with minimal parasitic effects, a crucial requirement for millimeter-wave applications.
The rise of heterogeneous integration has opened new possibilities for combining different semiconductor technologies within a single package. This allows designers to optimize performance by selecting the best process technology for each function, and is particularly valuable in complex RF systems, where different components may require different semiconductor processes to achieve optimal performance.
High-frequency operation has driven the development of materials with low dielectric loss, such as advanced ceramics and organic substrates, which minimize signal degradation, and the 3D packaging techniques allow denser integration of components, reducing parasitic effects.
Adopting chip-scale packaging (CSP) and flip-chip technology has minimized interconnect lengths, improving signal integrity and thermal management. Innovations like embedded heat spreaders and advanced thermal interface materials have also addressed thermal challenges. Additive manufacturing and precision machining techniques further enable the fabrication of intricate structures for enhanced electromagnetic shielding and compact designs.
The packaging of RF and microwave devices has evolved significantly from traditional hermetic packages to advanced solutions that optimize performance and cost. Early ceramic and metal packages have given way to plastic over-molded packages incorporating enhanced thermal management and electrical shielding. Modern packages frequently integrate multiple dies, passive components, and antenna structures in system-in-package configurations. Surface-mount technology has primarily replaced through-hole mounting, enabling higher frequency operation and improved manufacturing efficiency. Recent developments include wafer-level packaging techniques that minimize parasitic effects and package size while maintaining environmental protection.
Advanced thermal solutions now incorporate diamond heat spreaders and micro-channel cooling. EMI shielding has progressed from simple metal cases to sophisticated conformal coatings and embedded shield structures. Package designers now routinely employ 3D electromagnetic simulation to optimize signal integrity and minimize crosstalk. Test and characterization capabilities have also improved, with automated systems measuring package performance at millimeter-wave frequencies. These advances support emerging 5G communications, automotive radar, and satellite communications applications, where size, cost, and performance requirements are demanding.
Chip-Scale Packages Driving Compact RF and Microwave Design
Chip-scale packages have become increasingly popular for several reasons. The primary advantage lies in miniaturization, as CSPs are extremely small, often only slightly larger than the die they contain. This makes them ideal for RF and microwave applications where size and weight are critical considerations, such as in mobile devices, satellite communications, and radar systems. CSPs also offer significant improvements in electrical and thermal characteristics compared to larger packages.
They also typically have better heat dissipation capabilities, which is crucial for high-power RF and microwave devices. From a manufacturing perspective, CSPs can be more cost-effective than traditional packaging technologies, especially for high-volume applications. Their smaller size and more straightforward construction often result in lower manufacturing costs.
CSPs serve various essential functions across the RF and microwave industry. RF front-end modules (FEMs) in smartphones and other wireless devices frequently utilize CSPs, with these modules typically containing multiple components such as power amplifiers, filters, and switches, all integrated into a single package. CSPs provide efficient packaging solutions for MMICs and RFICs in which the chips perform various functions, including amplification, filtering, and frequency conversion.
In antenna applications, some designs integrate directly into a CSP, creating an Antenna-in-Package (AiP) solution. This is particularly beneficial for millimeter-wave applications where traditional antenna designs are bulky and inefficient. The sensor market also benefits from CSP technology, with various RF and microwave sensors, such as those used in radar systems, proximity detectors, and environmental monitoring, utilizing these compact packages.
Featured RFMW Suppliers Innovating Advanced Packaging Processes
ED2 Corporation
Among the most innovative developments in the field is ED2 Corporation’s Advanced Glass Packaging Technology (AGPT™). Founded in 2018, this Tucson, Arizona-based company has made AGPT™ its core competency, developing a process that leverages the unique properties of fused silica. Fused silica, or fused quartz, is a specialized silicon dioxide glass (SiO2) and combines high purity, low thermal expansion, and exceptional thermal shock resistance. Its extremely low refractive index and ability to transmit UV light also make it well suited for optical lenses and prisms.
AGPT™ offers several key advantages. It produces hermetically sealed packages that maintain extremely low dielectric loss, even at millimeter-wave frequencies. Fused silica’s high thermal conductivity enables efficient heat dissipation from packaged electronics. The process allows ED2 to achieve high dimensional precision in creating intricate packages with tight tolerances, which is crucial for sensitive RF circuits where minor variations can significantly impact performance.
The technology creates a hermetic seal around components, protecting against moisture and contaminants. Fused silica’s low dielectric constant helps minimize unintentional electromagnetic radiation and interference, which is particularly valuable in densely packed wireless environments such as those required by 5G networks. The material’s chemical resistance also makes AGPT™ packages suitable for harsh environmental conditions where other materials might deteriorate.
The ED2-0023 phased array in a glass module (Figure 1) demonstrates these capabilities in practice. This design integrates the phased array antenna with various electronic components—amplifiers, filters, and phase shifters—into a single multi-core glass substrate. The substrate serves multiple functions, providing mechanical support and electrical isolation while acting as a waveguide. The module incorporates the Renesas F5288 beamforming half-duplex transceiver to achieve 2 x 2 radiating elements, delivering a 100 ns mode-switching time, 20 ns gain and phase settling time, and 1.4 deg. of phase error. These components, along with an integrated bandgap generator, internal temperature sensor, and power detector, are contained within a compact 10 x 10 x 0.5 mm glass package.
Nuvotronics
Cubic Nuvotronics has pioneered a unique approach to RF and microwave packaging centered around their patented PolyStrata® technology (Figure 2). This technology enables the fabrication of high-performance, micro-coaxial interconnects and packaging solutions using a novel 3D printing process.
At the core of the technology is a specialized 3D printing process that creates intricate, three-dimensional micro-coaxial structures within the package. These structures serve multiple functions, acting as transmission lines, waveguides, and other passive components, which enables highly integrated and miniaturized designs.
A distinctive feature of these micro-coaxial structures is their air-dielectric construction. Using air as the dielectric material achieves extremely low loss and excellent high-frequency performance—a crucial advantage for millimeter-wave applications where traditional dielectric materials often introduce significant signal attenuation.
PolyStrata® technology also excels in component integration, allowing various passive components such as filters, couplers, and baluns to be incorporated directly within the package. This integration capability reduces overall size and enhances system performance by minimizing interconnect distances and optimizing signal paths. The packages are designed with surface-mount compatibility, facilitating straightforward integration with printed circuit boards (PCBs) and streamlining manufacturing processes.
Environmental protection is addressed through Nuvotronics’ sealing solution for PolyStrata® packages. This approach uses a small ceramic chip to seal the air-coaxial transmission lines, enabling a cavity package substrate to be lidded and sealed, protecting RF and microwave components from environmental degradation. Thermal management is another key consideration, with PolyStrata® packages typically utilizing copper as the base material. This choice provides excellent thermal conductivity for efficient heat dissipation, essential for high-power applications and densely integrated circuits where heat buildup can compromise performance and reliability.
By combining these approaches, Nuvotronics’ PolyStrata® technology represents a compelling RF and microwave packaging solution, particularly for applications demanding high performance, miniaturization, and integration. The technology enables the creation of highly compact and efficient modules that push the boundaries of traditional packaging technologies.
Smiths Interconnect
Smiths Interconnect employs techniques to enhance packaging performance, starting with selecting advanced materials. Their approach incorporates low-loss polymers, ceramics, and composites to create packages that minimize signal loss and maintain high performance at high frequencies. These carefully chosen materials deliver excellent thermal and mechanical properties, ensuring reliability in demanding environments.
The company’s hyperboloid contact technology is one of its signature innovations, providing a high-reliability, high-density interconnect solution. This technology proves particularly effective for high-frequency applications, as it minimizes signal distortion and ensures consistent performance. Smiths Interconnect developed specialized spring probe contacts in the testing domain that provide reliable connections for testing and burn-in applications. These designs minimize stress on the device under test while ensuring accurate measurements.
Their integrated packaging solutions demonstrate advanced miniaturization techniques by combining multiple components—filters, amplifiers, and antennas—into single packages. This approach not only reduces size and weight but also improves performance through the minimization of interconnect distances. The company is committed to customization, working closely with customers to develop tailored solutions that meet specific needs and requirements, including options for various materials, connector types, and package configurations.
Amkor Technology
Amkor Technology has developed an extensive portfolio of innovative approaches to RF and microwave semiconductor packaging solutions. The company uses advanced materials incorporating low-loss polymers, ceramics, and composites to create packages.
At Amkor’s System-in-Package (SiP) technology integrates multiple components, such as filters, amplifiers, and antennas, into a single package. This miniaturization strategy reduces size and weight and enhances performance by minimizing interconnect distances and optimizing signal paths. Amkor’s pioneering work complements this approach in Antenna-in-Package (AiP) solutions (Figure 3), where antennas are integrated directly into the package. This innovation proves particularly valuable for millimeter-wave applications, where traditional antenna designs can be bulky and inefficient, allowing for smaller, more streamlined devices with improved performance.
The company’s High-Density Fan-Out (HDFO) packaging technology represents another significant advancement, enabling high-density interconnects and fine-pitch routing crucial for complex RF and microwave devices. This technology facilitates greater component integration while maintaining superior signal integrity. Amkor further pushes the boundaries of miniaturization through its embedded die technology, which incorporates active and passive components within the substrate. This approach reduces package size and improves electrical and thermal performance, making it particularly beneficial for RF modules where minimizing interconnect lengths is essential for optimal performance.
Qorvo
Qorvo’s packaging technology begins with sophisticated materials selection. The company incorporates low-loss polymers, ceramics, and composites to create packages that minimize signal loss while maintaining high performance. The company’s System-in-Package (SiP) technology ingrates multiple components, such as filters, amplifiers, and switches, into a single package. This miniaturization strategy reduces size and weight and enhances performance by minimizing interconnect distances and optimizing signal paths. Complementing this capability, Qorvo employs advanced heterogeneous integration techniques to combine semiconductor technologies within a single package, including GaAs, GaN, and CMOS. This approach allows designers to choose between the unique strengths of each technology while optimizing performance for specific applications.
Qorvo’s wafer-level packaging (WLP) technology represents another significant advancement. It creates highly integrated and compact packages that offer advantages in size, performance, and cost-effectiveness, which is particularly beneficial for high-volume applications. The company further enhances interconnect performance through its copper pillar bumping technology, which creates high-density connections between the die and package substrate. This innovation improves electrical and thermal performance, proving especially valuable for high-power applications.
Thermal management is another crucial element of Qorvo’s packaging strategy. The company incorporates advanced techniques such as heat sinks and thermal vias to ensure efficient heat dissipation. These thermal management solutions help maintain optimal operating temperatures for its RF and microwave devices, contributing to its packaging solutions’ overall reliability and performance.
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