System-on-package Research Articles

Additively manufactured flexible on-package phased array antennas for 5G/mmWave wearable and conformal digital twin and massive MIMO applications

This paper thoroughly investigates material characterization, reliability evaluation, fabrication, and assembly processes of additively manufactured flexible packaging and reconfigurable on-package antenna arrays for next-generation 5G/mmWave wearable and conformal applications. The objective is to bridge the technology gap in current Flexible Hybrid Electronics (FHE) designs at mmWave frequencies and address the challenges of establishing future design standards for additively manufactured flexible packages and System-on-Package (SoP) integrated modules. Multiple 3D printed flexible materials have been characterized for their electrical and mechanical properties over the 5G/mmW frequency band (26–40 GHz), and the inkjet printed interconnects on 3D printed Polypropylene (PP) substrates demonstrated excellent electrical and mechanical performance during a 10,000-time cyclic bending test over typical wearable flexible radii down to 1 inch. A proof-of-concept flexible on-package phased array with an integrated microfluidic cooling channel on 3D printed substrates was fabricated and measured, demonstrating pm 37^{circ } beam steering capability with efficient cooling. The proposed reconfigurable design and low-temperature fabrication approach using additive manufacturing can be widely applied to next-generation highly-complex on-demand FHE, flexible multi-chip-module integration, and on-package phased-array modules for 5G/mmWave wearable and conformal smart skin, digital twin and massive MIMO applications.

BCB-Based Thin-Film Ka-Band Quarter-Mode SIW Packaged Filters With Ultrawide Stopband and Independently Controlled TZs

In this article, quarter-mode substrate-integrated waveguide (QMSIW) filters featuring ultrawide stopband and flexibly allocated transmission zeros (TZs) are proposed. Eight higher modes with resonant frequencies up to 4.7 times of the fundamental mode are highly suppressed. It is realized by the combination of three approaches without extra circuit areas. First, a slot is cut in the first and last QMSIW resonators to make their resonant frequencies of higher modes different from those of other resonators. Second, avoid exciting the specific higher modes by setting the feed point in the area where the electric field strength of the higher modes is weak. Third, mismatch the higher modes when matching the passband. It is realized by using a stripline impedance transformer with its main body not exceeding the area of QMSIW resonators. Furthermore, except for the TZs derived by the classical cross-coupling matrix, two more independently controlled TZs are generated. The packaged filter is fabricated by using a benzocyclobutene (BCB)-based microelectromechanical systems (MEMS) process, which is suitable for millimeter-wave 3-D system-on-package (SOP) applications. The fabricated thin-film filter is measured with an insertion loss of 2.96 dB at 29.4 GHz and a fractional bandwidth (BW) of 17%. Higher mode suppressions up to 138.3 GHz are achieved.

Signal and Power Integrity Challenges for High Density System-on-Package

As the increasing desire for more compact, portable devices outpaces Moore’s law, innovation in packaging and system design has played a significant role in the continued miniaturization of electronic systems.Integrating more active and passive components into the package itself, as the case for system-on-package (SoP), has shown very promising results in overall size reduction and increased performance of electronic systems.With this ability to shrink electrical systems comes the many challenges of sustaining, let alone improving, reliability and performance. The fundamental signal, power, and thermal integrity issues are discussed in detail, along with published techniques from around the industry to mitigate these issues in SoP applications.

Additive Manufacturing of a W-Band System-on-Package

In this article, we demonstrate the design, fabrication, and characterization of a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$W$ </tex-math></inline-formula> -band system-on-package (SoP). This package is fully additively manufactured using a chip-first process and aerosol jet printing. With this method, we implement a transceiver consisting of two bare die amplifiers for transmitted and received signals, a bare die switch, printed bypass capacitors, surface-mount resistors for biasing networks, and a printed patch antenna, operating between 77.1 and 79.0 GHz. The second patch antenna of the same design, fabricated simultaneously, is used to characterize the antenna performance alone and the packaged components. Package substrates (dielectrics), conductors, and interconnects are printed around bare die attached to a carrier. Thin-film bypass capacitor dielectrics were printed using multimaterial aerosol jet printing (MMAJP), where aerosols of barium titanate and polyimide inks are mixed in place to form a high <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\epsilon _{r}$ </tex-math></inline-formula> polymer matrix nanocomposite film. <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$W$ </tex-math></inline-formula> -band interconnect performance is achieved using conformal-shaped ramp interconnects, allowing for frequency agnostic performance of the interconnect with no impedance discontinuity, within the physical limits of the printer. The antenna alone achieves a maximum gain of 6.7 dBi at 78.3 GHz, and the SoP achieves a gain of 16.4 dBi for the package. We estimate the package loss to be 2.8 dB or 0.6 dB/mm, including interconnects.

A Fully Integrated Arbitrary Power Divider on Printed Circuit Board by a Novel SMD-Resistor-Free Isolation Network

An arbitrary power divider (PD), which can be fully integrated on a multilayered printed circuit board (PCB), is presented without using the surface-mounted device (SMD) resistors. In the proposed SMD-resistor-free isolation network, a new multiple microstrip gap-coupled resonators (MM-GCRs) is designed in an FR4 substrate based on an optimization algorithm to achieve an equivalent grounded resistor in the desired frequency band. Consequently, the acquired output matching and isolation bandwidths are designable and much wider than that of other existing SMD-resistor-free PDs with both output matching and isolation characteristics. To verify it, the design of PCB-based SMD-resistor-free PDs with the power division ratio being 1–3 is given. For all fabricated PDs, the measured input return loss and extra insertion loss are, respectively, better than 20 dB and less than 0.52 dB, respectively, at the operating frequency. In addition, the measured output return loss and isolation loss are better than 15 dB from 2.4 to 2.5 GHz. Moreover, the measured output matching and isolation bandwidths are, respectively, 8 and 3.5 times wider than that of other existing SMD-resistor-free PD with both output matching and isolation characteristics. Since the proposed PD is synthesized based on distributed elements without using any SMD resistor, the proposed PD thus possesses the advantages of being suitable for system-on-package (SoP), cost-efficient, suitable for millimeter-wave (mm-Wave) application, and capable to be fully integrated on a multilayered PCB.

A Compact Millimeter-Wave Frequency Conversion SOP (System on Package) Module Based on LTCC Technology

A novel compact millimeter-wave system on package (SOP) module is proposed in this paper. To achieve high integration, the 14 layers substrate of module is fabricated with low temperature co-fired ceramic (LTCC) technology, which is advanced in incorporating the passive components in multi-layers, thus realizing the signal vertical propagation for the SOP. The designed SOP covering 30~40 GHz is the core module for the millimeter-wave radar system. When the transmitting state of the system is initiated, the introduced SOP will up mix input intermediate frequency (IF) signal with local signal (LO) to millimeter-wave band. And the received millimeter-wave signal will be down-converted to the IF signal during the receiving state. The SOP integrates two frequency conversion channels and 34 monolithic microwave integrated circuit (MMIC) chips, with final size of 35 mm × 48 mm. In the whole working band, transmitting signal has a power range of 10~13 dBm with out-of-band spurious suppression below 50 dBc, while the channel under receiving has a gain of 11~15 dB with automatic gain control (AGC) of 0~50 dB and 1dB-step. The receiving and transmitting isolation between the two channels are both greater than 40 dB, and the T/R isolation in one channel is better than 40 dB.

Gain Enhancement of Millimeter-Wave On-Chip Antenna Through an Additively Manufactured Functional Package

The antenna-on-chip (AoC) presents an excellent solution for applications requiring higher integration levels and lower cost; however, its radiation performance is poor due to the inherent lossy Si substrate in conventional complementary metal–oxide–semiconductor (CMOS) processes. It is well known that every chip requires a package to protect it from the environment; however, this package does not provide any functionality, despite adding to the cost and required space. In this article, we propose a functional package that has been designed to enhance the gain of the AoC. A 71 GHz coplanar waveguide (CPW)-fed on-chip monopole antenna, driven by a voltage-controlled oscillator (VCO) and frequency doubler, was realized in the standard 0.18 $\mu \text{m}$ CMOS technology. As a first step to enhance its gain, the AoC was designed on top of an artificial magnetic conductor (AMC) surface. Further gain enhancement was achieved by transforming the chip package into a combination of a superstrate layer and a Fresnel lens, qualifying this as a system-on-package (SoP). The package has been realized through additive manufacturing to maintain the low-cost aspect. Overall, the measured gain of the packaged AoC is 6.8 dBi, which has been enhanced by ~20 dBs compared to the unpackaged antenna without an AMC layer.

Organically Packaged Components and Modules: Recent Advancements for Microwave and mm-Wave Applications

The wireless industry is moving at a faster pace than ever before. The number of mobile phone applications is growing rapidly; high-definition video, automotive radars, and high-resolution imaging markets are creating a demand for high-speed communication that goes well beyond what today's wireless systems can handle. Component integration, size miniaturization, cost reduction, reliability, and performance enhancement have become the primary focus of current wireless systems. To achieve these objectives, advanced packaging techniques have been developed that replace traditional bulky package configurations. These concepts include system-on-chip (SoC), system-in-package (SIP), and systemon-package (SoP) technologies, as illustrated in Figure 1.

Three-Dimensional Thermal Modeling and Management of System on Package with Gold and Nano Based Material

Abstract A detailed computational fluid dynamic based thermal model and simulation of exposed pad SOIC package on PCB is developed with Nano and gold-based material to characterize the thermal behavior or cooling capability of the package. Achieving lower thermal resistance of electronic packaging is one of the important points of interest in electronic application. In this paper, exposed small outline IC package on PCB is compared with different composition of Au-Sn die attach materials and Nano-foil preform material to understand the thermal behavior of the package which will provide cooling through low thermal resistance between junction-to-case. Thermal reliability of electronic packaging depends on the package design and selection of materials. Package material design plays an important role in thermal management of the product. Nano-based package material can be a good choice to improve the thermal performance of system on package. Developed a 3 D model of exposed small outline IC (E-SOIC) package on a printed circuit board (PCB). Au-Sn solder paste is used as die attach material and Nano-Foil preform is used to develop the system on package (SOP) model of exposed pad SOIC package on PWB. Different types of composition of Au-Sn solder paste, such as 78Au22Sn and 80Au20Sn are considered for die attach purpose. The reason for choosing the AuSn solder paste is good reliability and performance. Au-Sn has higher thermal conductivity than other solder materials, such as Pb-free solder paste, 96.5Sn3.5Ag and leaded solder paste, 37Pb63Sn. Two types of thermal model developed to compare the package material and design of the different die attach materials and Nano-Foil preforms. In this paper simulation and data analysis will show how the optimum thermal management depends on the material selection and design of the system on package (SOP). Surface mount type SOIC package with exposed pad design is selected to enhance the thermal purpose. Gold-tin and Nano-Foil preform will be used as alternative of lead-free package materials.

Fully printed 3D cube-shaped multiband fractal rectenna for ambient RF energy harvesting

The Internet of Things (IoT) is an emerging paradigm that requires billions of wirelessly connected devices in a complex radio-frequency (RF) environment. With such a huge number of devices in this scenario, recharging or replacing batteries becomes impractical. Therefore, powering IoT devices by harvesting energy from ambient sources, such as that available in the RF spectrum, is an attractive solution. The antenna for the RF energy harvester must work on multiple bands to capture as much power as possible. This paper presents a fully printed 3D cube triple band Cantor fractal rectenna based on the system-on-package (SoP) concept; the antenna is realized on the package that houses a rectifier circuit and a multiband matching network. The combination of additive manufacturing and SoP ensures a lower cost and the efficient use of available space. The rectenna harvests RF power from GSM900, GSM1800, and 3 G 2.1 GHz frequency bands. Field tests of the RF energy harvester conducted in a real ambient environment confirm that up to 200 mV output voltage can be harvested. Also, 550 mV is harvested when the rectenna is near a smartphone during a live phone call. The promising results and lower cost make this design a suitable candidate to power IoT devices.

Inkjet-Printed Multilayer Bandpass Filter Using Liquid Crystal Polymer System-on-Package Technology

This paper presents the fabrication of an inkjet-printed multilayer bandpass filter using the liquid crystal polymer (LCP) system-on-package (SOP) technology. The LCP-SOP technology adopted by lamination bonding process reduces the occupied area of a device and is suitable for radio frequency (RF) package applications. The surface morphologies and RF performance of the inkjet-printed silver film on an LCP substrate after the lamination bonding process, which entails applying high temperatures and pressures, were observed and analyzed. Acceptable performance of the inkjet-printed silver film of an optimal lamination bonding condition was 0.69 MPa at 270 °C. Using the inkjet-printing and LCP-SOP technologies, a miniature bandpass filter was created with a minimal $S_{21}$ value and a maximal $S_{11}$ value of −1.5 and −17.4 dB at 10.6–14.5-GHz passband, respectively. A strain effect of silver line and bandpass filter was also analyzed. The results demonstrated the effectiveness of the proposed design methodology and the fabrication technique.

Surfing the Millimeter-Wave: Multilayer Photoimageable Technology for High Performance SoP Components in Systems at Millimeter-Wave and Beyond

Ever-growing demand and emerging applications in the millimeter-wave (mmW) range for both commercial and military purposes require high-performance yet compact circuits and systems at a reasonable cost [1], [2]. Multilayer multichip module (MCM) or system-on-package (SoP) technologies are widely regarded as an excellent means to meet these advanced requirements [3]-[5]. A variety of multilayer MCM technologies-including low-temperature cofired ceramic (LTCC), liquid crystal polymer (LCP), organic, and thin film on glass-have been developed [7]-[14]. However, when conventional thick film is used, it is very difficult in applications requiring high mmW bands to realize either 1) lumped/passive components having a high self-resonance frequency (SRF), quality factor (Q), and also compactness or 2) substrate integrated waveguide (SIW) components with continuous sidewalls [10], [13].

A 37.5-mW 8-dBm-EIRP 15.5&lt;formula formulatype="inline"&gt;&lt;tex Notation="TeX"&gt;$^{\circ}$&lt;/tex&gt;&lt;/formula&gt;-HPBW 338-GHz Terahertz Transmitter Using SoP Heterogeneous System Integration

A low-cost terahertz transmitter is proposed by using system-on-package (SoP) heterogeneous system integration. A signal source in 40-nm CMOS is integrated with an antenna array on a Benzocyclobutene carrier through a broadband low-loss terahertz interconnect. The signal source adopting triple-push oscillator topology is able to produce a differential output without any additional balun circuit. Hence, the power consumption and the chip area can be reduced. The antenna array containing 50 patch antennas is differentially excited to give simulated directivity, efficiency, and antenna gain as high as 22.6 dB, 88%, and 22 dBi, respectively, at 335 GHz. The terahertz interconnect employs a resonator coupling technique to provide low-loss and broadband performance while occupying a small area. Measured results show that the proposed terahertz transmitter can work at 338.4 GHz with equivalent isotropically radiated power (EIRP) of 8.0 dBm while consuming only 37.5 mW from a 1-V supply. The measured half-power beam-width can be as narrow as 15.5 $^{\circ}$ . The EIRP can be further raised to 9.5 dBm as the supply $V_{ DD}$ is increased to 1.3 V. The CMOS chip only occupies an area as small as 0.028 ${\hbox {mm}}^{2}$ . All of the design efforts enable the proposed terahertz transmitter to feature in small form factor, low power dissipation, low cost, and high performance. To the best of the authors' knowledge, this is the most compact, lowest power, lowest cost, and high-performance SoP-based terahertz transmitter reported thus far.

Three‐dimensional RF SoP technologies: LTCC versus LCP

ABSTRACTThe system on package (SoP) is an emerging platform, introduced to provide enhanced functionality, and immense miniaturization through vertically integrated passive components in a multilayer process. This way the package is not a mere holder or cover but is a functional part of the system. The leading multilayer packaging technologies for SoP designs: low temperature co‐fired ceramic (LTCC) and liquid crystal polymer (LCP) are compared in this work for the first time. Passive components and filters have been implemented in both technologies to show the advantages of the three‐dimensional nature of these technologies. The comparison results show that parallel plate capacitors implemented in the ultra‐thin LCP provides the highest capacitance density. For spiral inductors, conversely, LTCC inductors have the highest inductances while LCP inductors offer the highest self‐resonant frequencies and the highest quality factors (Q). In a circuit level, simulated and measured results of a bandpass filter at 1.5 GHz show that both LCP and LTCC can provide similar performances with an incredible size reduction for the case of ultra‐thin LCP. Also, the thin LCP filter exhibits a large degree of mechanical flexibility which makes this technology suitable for future flexible modules. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:434–441, 2015

밀리미터파 SoP 응용을 위해 광대역 수직천이를 집적한 초소형 LTCC 팻치안테나

In this work, a compact patch antenna based on a low temperature cofired ceramic (LTCC) has been presented for V-band system-on-package (SoP) applications. In order to integrate it with transceiver block, a waveguide (W/G) to embedded microstrip line (eMSL) vertical transition was designed using slot-fed double stacked patch antennas for easy assembly and wide bandwidth. The <TEX>$2{\times}2$</TEX> patch antenna integrating the transition was designed and fabricated in the 5-layer LTCC dielectrics. The whole size of the fabricated antenna including the <TEX>$2{\times}2$</TEX> patches, transition and W/G was <TEX>$20{\times}24{\times}5.39mm^3$</TEX>. The fabricated antenna has achieved a 10 dB impedance bandwidth of 2.45 GHz from 61 to 63.45 GHz.

Miniaturized, Lumped-Element Filters for Customized System-on-Package L-Band Receivers

The system-on-package (SoP) approach to design wireless front ends has proven to optimize the tradeoff between performance and size. In this paper, two new and highly compact bandpass filters are presented that show the greatest degree of miniaturization of any bandpass filters presented to date when their volume is measured in guided wavelengths. A novel packaging technique where most of the filter components are folded beneath the resonator inductors allows for this level of miniaturization. The filters are designed as lumped-element equivalent circuits and fabricated in standard low-permittivity low-temperature cofired ceramic technology that makes them suitable for embedding within a mass-producible SoP solution. In addition, electric and magnetic couplings are used to create finite transmission zeros that enhance the selectivity of these filters. The second-order filter demonstrates an insertion loss of 2.2 dB and a 3-dB bandwidth of 11% at a center frequency of 1.524 GHz. Meanwhile, the fourth-order implementation shows an insertion loss of 4.92 dB and a 3-dB bandwidth of 6.6% at a center frequency of 1.521 GHz. In both cases, the agreement between simulations and measurements is excellent. Careful analysis of individual capacitors and inductors comprising the filters is provided to explain the link between process parameters and actual measured performances.

60-GHz amplitude shift-keying transceiver LTCC system-on-package module

A highly integrated amplitude shift-keying (ASK) transceiver (TRx) system-on-package (SoP) module is presented for 60-GHz wireless communications applications.The ASK TRx SoP module has been implemented with a six-layer low-temperature co-fired ceramic (LTCC) substrate embedding eight GaAs RF integrated circuit chips, one low-pass filter, a high-isolation via fence, and DC bias components. The fabricated ASK TRx SoP is as small as 17.8 × 17.9 × 0.6 mm3. In the transmitter (Tx) part, an output power of 12.8 dBm is obtained at 62.24 GHz. The receiver (Rx) part reveals a conversion gain of 38 dB, intermediate frequency flatness of below −2 dBm, and good eye pattern of the 1.25 Gb/s data. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:48–51, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27264

System-on-Package MHMIC Milimeter-Wave Frequency Synthesizer for 60 GHz WPANs

We present a low-cost millimeter-wave frequency synthesizer with ultralow phase noise, implemented using system-on-package (SoP) techniques for high-data-rate wireless personal area network (WPAN) systems operating in the unlicensed 60 GHz ISM band (57–64 GHz). The phase noise specification of the proposed frequency synthesizer is derived for a worst case scenario of an 802.11.3c system, which uses a 64-QAM 512-carrier-OFDM modulation, and a data rate of 5.775 Gbps. Our design approach adopts commercial-of-the-shelf (COTS) components integrated in a low-cost alumina-based miniature hybrid microwave integrated circuit (MHMIC) package. The proposed design approach reduces not only the system cost and time-to-market, but also enhances the system performance in comparison with system-on-chip (SoC) designs. The synthesizer has measured phase noise of -111.5 dBc/Hz at 1 MHz offset and integrated phase noise of 2.8° (simulated: 2.5°) measured at 57.6 GHz with output power of +1 dBm.

An electromagnetic energy harvesting system for low frequency applications with a passive interface ASIC in standard CMOS

This paper presents a compact energy harvesting system, which consists of an electromagnetic (EM) generator converting ambient low frequency vibrations to DC voltage by using a highly efficient full-wave rectifier in a System-on-Package (SoP). Frequency Up-Conversion technique has been utilized by the in-house EM transducer to harvest energy from very low frequency vibrations (<5Hz). The interface ASIC is a passive rectifier based on the boot-strap rectification (BSR) technique to decrease the effective threshold voltage of the utilized diodes, attaining a high AC/DC conversion efficiency in a standard 0.35μm CMOS process. The energy harvesting system has been tested within a frequency range of 2–10Hz. The autonomous system with a volume of 21cm3, delivers 128μW DC power to an 80μA load at an external vibration frequency of 2Hz and 72mg peak acceleration while a 1.6V DC voltage is generated. The maximum overall power density is measured as 6.1μW/cm3. Furthermore, the reliable operation of a commercially available temperature sensor, as a realistic load, has also been demonstrated by using the energy harvester as a DC supply.

System-on-Package Platform with Thick Benzocyclobutene Layer for Millimeter-Wave Antenna Application

Integrated antennas operating at millimeter-wave (mm-wave) frequency have been implemented on a benzocyclobutene (BCB)-based system-on-package (SOP) substrate. A novel BCB-based SOP substrate with a Si bump and a Si cavity was proposed to increase the BCB thickness, thus enhancing the gain of the microstrip patch array antenna and reducing the transfer loss of the transmission line. The mechanical issues of adhesion and stress of BCB are studied. The adhesion between gold and BCB was improved significantly by the insertion of a layer of Si oxide (SiO2) by plasma-enhanced chemical vapor deposition (PECVD). SiO2 can also reduce the wafer bow by stress compensation. Wafer bow of whole structure was decreased from 79.3 to 55.2 µm by the insertion of a 1-µm-thick SiO2 layer. A series-fed 1 ×8 linear array antenna is impedance matched well at 77 GHz. The process flow including BCB chemical mechanical polishing (CMP) was described. The proposed SOP substrate can be a candidate for overcoming the constraint of BCB thickness.