RF Packaging Research Articles

Board Level Reliability Testing of RF Packages

Board level reliability testing is becoming a requirement amongst users for acceptance of components and packages. Standard component level JEDEC tests are not sufficient to qualify a supplier, this must be accompanied with Board level reliability data to ensure assembly and field reliability. The paper presents a summary of board level reliability test performed on RF packages, the assembly process controls and monitoring, mechanical and environmental reliability tests, understanding of failure modes and lessons learned.

IMAPS 2022 Conference Qorvo SHIP-RF

Presentation will describe the Department of Defense (DoD) State of the Art (SOTA) Heterogeneous Integrated Packaging (SHIP) RF program which is developing and validating a sustainable and scalable model for access to SOTA microelectronics RF packaging of customized DoD microelectronic devices produced using a standard commercial production flow. RF package platforms developed are progressing from least complex to more complex throughout the course of the program. The SHIP-RF roadmap and status will be presented and will include Qorvo’s SOTA capabilities that are being incrementally developed and deployed via the SHIP-RF Design Center (DC) and the Assembly and Test Center (ATC).

Glass Devices for Next-Generation Packaging and RF Signal Conditioning

The push for higher communications frequencies, greater system integration, and smaller space imparts many unique challenges on RF and packaging engineers in the development of next generation cellular products for 5G, WiFi 6, Military, and other applications. Traditional materials, such as LTCC, organic laminates, and silicon face major limitations to dramatically improve system size, weight, and performance (SWAP). Photosensitive Glass-Ceramics (PSG) have gained a lot of attention as a next generation RF and RF packaging substrate for their ability to simultaneously solve these two important challenges. In this paper the authors will present on our work using PSG for RF and RF packaging solutions. We will share (1) the advantages of using PSG for advanced RF packages, and (2) our work demonstrating glass as an RF substrate integrating discrete components and embedded die for passive RF filters, and (3) our work towards building vertically stacked glass packages for advanced RF systems-in-package (SiP). The described work presents a manufacturing platform for the production of vertically stacked glass substrates with integrated high Quality Factor passive devices, such as inductors and capacitors, and heterogeneously integrated surface mount devices for advanced RF systems-in-package. The presented material demonstrates a production and assembly process for the manufacturing of advanced systems. In this paper, we present design, production, assembly considerations that impact size, weight, and performance (SWAP) metrics for a variety of product definitions and multiple simulation vs. product testing to demonstrate a reliable design to product flow.

RF Packaging and Design for Development of High Performance 5G mmWave Modules

5G sub-6GHz networks have already been deployed in many regions around the world. However, the deployment of 5G mmWave networks is yet to meet expectations. This is partly because of the challenges associated with hardware development of 5G mmWave systems. One example of such a challenge is to overcome the severe degradation of signal-to-noise (SNR) ratio due to intra- and inter-system signal losses at mmWave frequencies. This deteriorates the signal quality, limits transmission distances and may lead to unreliable mobile communication. In this work, we present RF packaging platforms and technologies as well as an approach for scalability of 5G RF frontend integrated circuits (ICs) and antennas which overcome intra- and inter-system losses. This leads to the development of high-performance and scalable 5G MIMO (multiple input multiple output) modules for reliable mobile communication at mmWave frequencies. The platforms provide very short and low-loss signal paths with few geometrical discontinuities between the frontend ICs and antennas. This leads to significant reduction in signal reflections and attenuation, thus improving the matching efficiency of the antennas and the equivalent isotropic radiated power (EIRP) of the entire system. The platforms also enable antennas to be integrated on layers directly above the ICs, and thereby ensures scalability of the ICs and antennas in both lateral dimensions for 5G mmWave massive MIMO. To demonstrate the functionality of our proposed packaging platforms, technologies and antennas, we performed in-depth RF designs, measurements and characterization of packaging materials, technologies and platforms as well as antennas for 5G mmWave applications.

Next Generation High Powered RF and Optical Packages

RF signals are radio waves that are very crucial for telecommunications. Quality communications require reliable materials which are appropriately processed to house high-powered semiconductors such as GaN and GaAs. It is equally crucial to accommodate passive electronic components along with these semiconductors into the housings for the Next Generation RF package or GenPack™. Evolving semiconductor technologies demand fail-safe packages to protect the devices in all applications and environmental conditions. Future aircraft, EV cars, spacecraft, augmented and/ or virtual reality headsets, medical devices and many more technologies require operating at a higher power and frequency with a proper thermal and power management platform. The higher speeds of telecommunications hinge on the performance of semiconductors and their packages. Therefore, the GenPack™ and packaging process are becoming crucial pieces of the supply chain. Rugged GenPack™ RF packages differ in several ways compared to the traditional air cavity packages. For instance, FR-4 or Flame-Retardant glass-reinforced epoxy laminate material can be replaced with Aluminum Nitride or Alumina Oxide, Silicon Nitride or even Sapphire. The switch offers mechanical bonding directly onto the thermal spreader. Traditional circuits created on printed circuit boards have limited ability to dissipate heat due to the low thermal conductivity of FR4. Circuits created on ceramic can dissipate higher amounts of heat. As in the organic FR4 boards, multiple vias can be formed in the ceramic substrates to create metal pads top the ceramic that are grounded to the flange beneath the ceramic. A metal flange can be positioned beneath the ceramic to provide a heat spreader and electrical ground that can be bolted onto a heatsink. Flanges can be made from a diamond metal matrix composite instead of lower thermal conductivity materials to provide much more efficient thermal transfer. Furthermore, narrow leads offer optimized impedance at RF and microwave frequencies. A range of ceramic and flange materials can be selected to optimize GenPack™ RF Packages with cost, quality, and performance in considerations for the respective applications.

Embedded Microfluidic Cooling in Aluminum Nitride HTCC Substrate for High-Power Radio Frequency Chip Array

Abstract Radio frequency (RF) electronics are developing toward high power, high integration, and high-power density, resulting in a continuous increase in heat flux. The traditional high-power RF package, which is usually composed of aluminum nitride (AlN) substrate, aluminum silicon housing shell, and aluminum alloy cold plate, exhibits poor heat dissipation ability and high thickness due to excessive interfaces and a long thermal conduction path. In this paper, aimed at improving heat dissipation ability and reducing the thickness of RF electronics, the microchannel was transferred from the cold plate to the AlN high-temperature co-fired ceramic (HTCC) substrate which plays the role of electrical connection, structural support, and liquid cooling cold plate. The embedded AlN microchannel cooler was firstly designed. Then, a prototype of the AlN substrate with 64 simulated chip arrays and microchannels was fabricated and the thermal performance was evaluated using an experimental setup. Finally, the thermal performances of the proposed and traditional cooler were compared using a CFD simulation. The results indicated that the proposed embedded cooling structure could enhance the heat-flux dissipation ability by 61% and reduce the packaging thickness by 40% compared with the traditional cooling structure.

An Ultracompact, Low-Cost, and High-Performance RF Package Technique for Wi-Fi FEM Applications

With the advent of next-generation Wi-Fi technology, the demand for shrinking Wi-Fi front end module (FEM) product size is voracious. In this letter, a novel package technique called hot-via chip-scale package (HVCSP) is proposed. HVCSP has benefits such as ultrasmall package size, low cost, bump-free, substrate-free, and outstanding RF performance. In this letter, a 5-GHz Wi-Fi FEM using GaAs-based Bi-HEMT technology and HVCSP is also demonstrated. Due to the wire and lead frame-free structure, the package size can be further reduced by over 40% compared to the traditional QFN package. By employing a hot-via transformer structure, the measurement loss from chip to package is below -0.5 dB from 0 to 67 GHz. With these advantages, HVCSP is suitable for Wi-Fi FEM applications perfectly.

Evaluation of die to organic laminate to PCB interconnects up to 50GHz

Abstract Ceramic substrates have traditionally been used in RF and microwave packaging applications because of the electrical properties at high frequencies. However, there is significant interest in using organic laminates due to its tighter wiring ground rules for high density packaging and lower cost of fabrication. The high frequency performance of interconnection from die to PCB using an organic packaging substrate has not yet been studied in detail. In this work, the interconnect performance of die to organic laminate to PCB up to 50 GHz was modeled and characterized using a test vehicle assembly. The test vehicle was specifically designed with test pads to characterize the interconnect performance at multiple levels of interconnection. A comparison study using a ceramic package substrate was also carried out. The modeling and hardware testing results from this study showed −3dB bandwidth of more than 50GHz for printed circuit board (PCB) to organic laminate and a bandwidth of 40GHz for the die to organic laminate to PCB interconnection. The results from this study showed that the organic laminate demonstrated a high frequency performance comparable to that of the ceramic substrate, which makes it suitable as a packaging substrate material for high frequency applications.

A Compact Ku-Band Active Electronically Steerable Antenna with Low-Cost 3D T/R Module

This paper presents a novel compact Ku-band active electronically steerable antenna array design with a low-cost and integrated T/R 3D module employed for airborne synthetic aperture radar (SAR) systems. The entire system adopts 3D multilayer technology with vertical interconnection to construct the hermetically packaging RF modules. By assembling different multifunctional modules into a whole multilayer board, the 3D T/R technique greatly improves the system integration and reduces implementation cost and size. Besides, a wideband circular polarized antenna array was designed in LTCC and connected to the proposed T/R modules to form a complete AESA. The whole proposed antenna system has been fabricated and experimentally investigated. Measurement results showed very good phased array performances in terms of gain, axial ratio, and radiating patterns. The low-cost, lightweight, and low-power features exhibited by the proposed design validate its applicability for weight and power constrained platforms with great electronic steering ability.

Quasi-Static Surface-PEEC Modeling of Electromagnetic Problem With Finite Dielectrics

This paper presents a quasi-static surface-based partial element equivalent circuit (PEEC) model for electromagnetic problems consisting of coupled conductors and heterogeneous dielectrics of finite size. The PEEC model is based on the surface equivalent principle. Unlike the traditional surface-based PEEC models, in which the integral equations are set up by enforcing the field continuity in the true field region, the homogeneous integral equations in this model are obtained by enforcing the tangential null field condition in the null field regions. Simplified integral equations are obtained under the quasi-static assumption, in which the circuit elements carrying electric currents and magnetic charges on the dielectric surfaces are vanished. Consequently, the size of the subcircuit describing dielectrics is reduced significantly compared to the full-wave surface-PEEC (S-PEEC) model. Since the quasi-static S-PEEC model only contains frequency-independent circuit elements, it can be conveniently used for time-domain simulation. Three numerical examples are presented to validate the new PEEC model for typical embedded RF passive components, packaging and interconnection problems in both the frequency domain and the time domain. Excellent agreement is observed between the results of the proposed PEEC model, S-PEEC model, and those of commercial software within the quasi-static frequency range.

Photosensitive Glass-Ceramics for Heterogeneous Integration

The push for heterogeneous integration requires very unique material properties with respect to processing, material constants, and integration capabilities with other materials (such as copper, II...

Compact and Reliable T/R Module Prototype for Advanced Space Active Electronically Steerable Antenna in 3-D LTCC Technology

The aim of this paper is to present a novel and compact transmit/receive module (TRM) for enhancing antenna performances to be employed in space applications. The key advancement is the use of a 3-D technology which, to the best of our knowledge, would be for the first time introduced in the space industry for hermetically packaging RF modules. The 3-D module development is based on the highly demanding specifications of space active electronically steerable antennas (AESAs); the TRM consists of two “submodules” electrically connected by an ad hoc interposer. The complete electrical design process, together with a comprehensive discussion on electromagnetic, mechanical, and thermal aspects, is presented, and the achieved module performances such as gain and return losses are detailed. Moreover, several manufactured samples are measured to validate the simulated design, and the excellent results in terms of gain, noise figure, and output power fulfilling the target specs are presented and discussed. The presented data, characterized by a limited variability among the 10 measured samples, make the proposed design and the manufacturing process a good candidate in terms of potential reliability for building the next generation of high-performance space AESA.

Miniaturized and high-performance RF packages with ultra-thin glass substrates

Advanced RF packages are demonstrate with active (low-noise amplifier, RF switch) and passive integration in ultra-thin 3D glass packages with miniaturization and enhanced performance. The novelty of this RF packages is three-fold: 1) Ultra-thin 100 μm glass, 2) Double-side thinfilm RF circuits interconnected with Through-Package Vias (TPVs), and 3) Direct assembly of the glass-core package to the board with Land Grid Array (LGA) connections. An innovative double-via process, starting from prefabricated vias in bare glass, polymer filling and via drilling, is utilized for a robust and high-yield substrate fabrication process. Scalable and low-cost panel laminate processes are utilized to form the RF circuits on the build-up layers. The performance benefits are demonstrated through interconnect loss, impedance match, electrical gain and noise figure measurements. Compared to existing RF substrates, the glass substrates show 2.5X miniaturization in substrate thickness with extensibility to thinner substrates.

Special issue on Design, Test, Integration and Packaging of MEMS and MOEMS (DTIP 2015), held in Montpellier, France, April 27–30, 2015

The 2015 edition of the Symposium on Design, Test, Integration and Packaging of MEMS and MOEMS (DTIP) was held in Montpellier, France, 27–30 April 2015. Established in 1999 by our colleague Dr Bernard Courtois, DTIP is definitively the premier MEMS scientific event in Europe. DTIP’2015 was the 17th edition and has been extremely appreciated by an hundred of attendees for the quality of both scientific and social programs. Oral and poster presentations were carefully selected by the Program Committee to insure a high scientific level and awesome plenary speakers have been invited. This Symposium brought together participants interested in manufacturing of microstructures and participants interested in design tools to facilitate the design of these microstructures. This special issue is composed of 20 extended versions of the best papers presented at the Symposium. Extended papers have been refereed, along the usual refereeing process in force at Microsystem Technologies. Selected papers cover a broad range of topics including compact thermal modelling, thermal testing, electrostatic and thermal actuation, simulation, accelerometers, electronic front-end for sensors, magnetic nanoparticles and materials, RF MEMS, Quantum dots, piezoelectric films, Micro-transducers, magnetometers, microfluidic devices, resonant sensors, micro-fabrication, wafer bonding, Packaging, flexible interconnects and MEMS reliability. We hope that you will enjoy these contributions as much as we did and if you want to join the DTIP community do not hesitate to attend our next event or to visit our website.

Design, fabrication, characterization of micromachined capacitive shunt switches with low actuation voltages and low temperature packaging

This paper reports the design, fabrication, electrical characterization and packaging of micromachined shunt capacitive switch with low actuation voltage. These switches are fabricated on a low resistive silicon substrate using only a four mask surface micromachining process. The co-planar waveguide is patterned using chrome/gold layer. Positive photoresist S1813 is used as the sacrificial layer. The top beam membrane is made of gold. The membranes are released through a wet release process through Piranha solution. Supercritical point drying tools were used for the top beam release after wet etching to provide anti-stiction. The switches are 300 µm long with 10 μm holes on the top membrane to lower both residual stress and pull-in voltages. These switches exhibit low actuation voltages in the range of 5.5–6.4 V. The RF characterization shows that these switches have low insertion loss and high isolation in the frequency range of interest. The packaging was carried out using commercially available surface mount style RF packages. However, the whole packaging process is performed under low temperature in order to free the MEMS structures of thermally induced stress which otherwise would affect the performance of the switch. The adhesion of the die to the bottom package is excellent and is tested by die shear test. The packaged switch has passed the non-destructive pull test.

Wedge Bonding Wire and Ribbon to Support RF and Optoelectronic Packaging

Abstract The proliferation of mobile devices, video on-demand mobile and home, and Internet of Things (IoT), continues to drive an exponential growth in data bandwidth. Meeting the data demand requires continuous improvements in bandwidth and capacity for RF base station modules and optoelectronic modules. RF and Optoelectronic modules have many similar wire bond packaging requirements, especially as optoelectronic data rates continue to increase from 10G through 400G. This paper will provide a survey of RF and Optoelectronic Packages and their common wire and ribbon bond requirements. The paper will also survey the packaging challenges and solutions available to process engineers. Challenges include bonding on a variety of materials, signal pins, RF loop spans and shapes for wire and ribbon, program strategies to maintain constant loop span, referencing challenges, and simplified machine user interactions. The paper will also discuss collaborations between manufacturer and equipment supplier with helpful tips leveraging each other's strengths to transition from concept to production.

3D TSV-based Inductor Design for a Secure Internet of Things

Abstract This paper describes the design and modeling of through-silicon via (TSV)-based high-density 3D inductors for Internet of Things (IoT) applications and presents some possible challenges for TSV-based inductors in IoT applications. For cybersecurity infrastructure, we designed IoT with hardware security in mind. We provide a secure design for Internet of Things based on secure 3D inductors and then show case studies of high-density RF packages with TSV-based inductors that require hardware security, such as military applications. We use ferromagnetic materials to achieve high inductance with good quality factor.

The path to 5G: mmWave aspects

The wide spectrum and propagation characteristics over the air give mmWave communication unique advantages as well as design challenges for 5G applications. To increase the system speed, capacity, and coverage, there is a need for innovation in the RF system architecture, circuit, antenna, and package in terms of implementation opportunities and constraints. The discuss mmWave spectrum characteristics, circuits, RF system architecture, and their implementation issues are discussed. Moreover, the transmitter key components, i.e., the receiver, antenna, and packaging are reviewed.

Heterogeneous Packaging of Organic Electro-Optic Modulators With RF Substrates

As organic-based electro-optic (EO) modulators continually improve toward meeting the high performance required by new and developing photonic technologies, the challenge of compact and low loss packaging needs to be addressed.Because organic-based EO modulators and RF circuitry are traditionally built on different substrates homogeneous integration would require developing new designs and fabrication processes. In addition, the organic-based EO modulators most often implement microstrip transmission lines for optimal poling and modulation field overlap meaning the ground plane is encapsulated and unavailable for direct contact. In this letter, a heterogeneous RF packaging scheme featuring a wire bond transition between a ceramic feed coplanar waveguide and a thin-film polymer microstrip is presented. The transition introduces less than 1 dB of RF loss at 50 GHz and was demonstrated on an organic-based EO phase modulator which generated optical sidebands out to 40 GHz.

Planar architecture for microstrip interfaced packaging of coplanar-waveguide-based radio frequency microelectromechanical system switches

This paper describes the architecture of microstrip (MS) interfaced packaging of a coplanar-waveguide (CPW)-based radio frequency microelectromechanical systems (RF MEMS) switch in a hermetic metal-ceramic RF package. The switch is integrated along with CPW to MS (CPW-MS) transitions within the package itself. This makes the MS interfaced packaged switch module readily mountable on MS based RF boards and subsystems. The CPW-MS transition for the package was designed as a separate off-chip entity on an alumina substrate and utilizes via hole. The integrated three-dimensional model of the package consisting of the RF MEMS switch and the transitions was simulated using high frequency structure simulator. The realized module shows an insertion loss of 0.2 and 1.1 dB at 100 MHz and 7 GHz, respectively. The measured isolation is better than 60 dB at 100 MHz and 30 dB at 7 GHz. The return loss is better than 15 dB up to 7 GHz. The estimated packaging and transitioning loss is 0.5 dB at 5 GHz. This packaging architecture is a planar solution for the MS interfaced packaging of CPW based RF MEMS switches for designers who do not have access to high-end technologies, such as zero-level packaging, through silicon via or low temperature co-fired ceramics.