Showing papers in "IEEE Transactions on Components, Packaging and Manufacturing Technology in 2016"

Wearable AMC Backed Near-Endfire Antenna for On-Body Communications on Latex Substrate

Abstract: A near-endfire, artificial magnetic conductor (AMC) backed wearable antenna is proposed in this paper for wireless body area networks operating in the 2.4-GHz industrial, scientfic and medical (ISM) radio band. The latex substrate permittivity has accurately been characterized for realizing a flexible planar Yagi-Uda antenna printed on it using a large-area screen-printing process. The bidirectional-endfire radiation of Yagi-Uda antenna is changed to an off-axis near-endfire radiation using an AMC reflector also printed on latex. The antenna is separated from the upper AMC surface using flexible Styrofoam of thickness $0.044\lambda _{o}$ at 2.4 GHz for the best compromise between keeping the antenna structure low profile and achieving an off-axis beam-tilt radiation of $\sim 74^{\circ }$ toward the endfire direction. The 0° reflection phase single-layered AMC and double-layered AMC (D-AMC) surfaces are proposed to reduce the body-absorbed radiation and, consequently, minimize the peak specific absorption rate (SAR) level for 2.4-GHz frequency band. Antenna performance in terms of return loss, radiation efficiency, extent of frequency detuning, gain, and SAR level is studied for free space as well as the CST MWS tissue-equivalent voxel model for all the proposed antenna designs. Antenna deformation bending study when placed on the human body is also performed in this paper. The antenna design is first optimized and fabricated on printed circuit board to verify the concept and then designed over the latex for actual human on-body all-flexible configuration. The Yagi-Uda antenna backed with D-AMC reflector demonstrates the measured return loss bandwidth of 45 MHz (2.425–2.47 GHz) and the gain of 0.12 dBi in the endfire direction with an improved on-body (chest) radiation efficiency of 78.97% and a reduced peak SAR level of 0.714 W/kg (average over 10-g tissue) for the compact overall flexible latex antenna volume of $0.4\lambda _{o} \times 0.4\lambda _{o} \times 0.076\lambda _{o}$ at 2.4 GHz. To the best of our knowledge, this is the first latex-based endfire antenna for on-body 2.4-GHz wireless communications backed with an AMC periodic metamaterial surface.

Metallic 3-D Printed Rectangular Waveguides for Millimeter-Wave Applications

Abstract: This paper explores the potential of metallic 3-D printing technology for millimeter-wave (mmWave) applications. It uses the selective laser melting (SLM) technology to melt the Cu-15Sn powder layer by layer to build up rectangular waveguides at $E$ - (60–90 GHz), $D$ - (110–170 GHz), and $H$ -band (220–325 GHz). Different from nonmetallic 3-D printed waveguides, SLM Cu-15Sn waveguides are printed once in a whole piece. Postelectroplating and assembling are not necessary. Besides, the SLM waveguide also outperforms the nonmetallic 3-D printed waveguide in mechanical robustness. Compared with nonmetallic 3-D printed and commercial metallic waveguides, SLM waveguides demonstrate comparable performance at $E$ -band with averaged dissipative attenuation 7.51 dB/m and 7.76 dB/m for 50- and 100-mm waveguides, respectively. The attenuation of SLM waveguides is acceptable up to $D$ -band. We prove the potential of the SLM technology for mmWave applications in both prototyping and mass production.

Heterogeneous Integration for Performance and Scaling

Abstract: Moore’s law has so far relied on the aggressive scaling of CMOS silicon minimum features of over $1000\times $ for over four decades, and recently, on the adoption of innovative features, such as Cu interconnects, low- $k$ dielectrics for interconnects, strained channels, and high- $k$ materials for gate dielectrics, resulting in a better power performance, cost per function, and density every generation. This has spawned a vibrant system-on-chip (SoC) approach, where progressively more function has been integrated on a single die. The integration of multiple dies on packages and boards has, however, scaled only modestly by a factor of three to five times. In this paper, we show that with the apparent slowing down of semiconductor scaling and the advent of the Internet of Things, there is a focus on heterogeneous integration and system-level scaling. Packaging is undergoing a transformation that focuses on overall system performance and cost rather than on individual components. We propose ways in which this transformation can evolve to provide a significant value at the system level while providing a significantly lower barrier to entry compared with a chip-based SoC approach that is currently used. This transformation is already under way with 3-D stacking of dies and will evolve to make heterogeneous integration the backbone of sustaining Moore’s law in the years ahead.

Package Inductors for Intel Fully Integrated Voltage Regulators

Abstract: Intel fourth-generation and fifth-generation Core microprocessors are powered by high-frequency integrated switching voltage regulators. The inductors required to implement these regulators are constructed using the routing layers of conventional organic flip chip packaging. This paper provides an overview of the construction of these inductors including representative results from production packages. Measured inductors reported in this paper span from 1 to 6.7 nH under 2.4 mm2 and achieve $Q$ of up to 24 at 140 MHz (the switching frequency).

Triple-Mode Bandpass Filters on CSRR-Loaded Substrate Integrated Waveguide Cavities

Abstract: In this paper, a novel approach is proposed to design and explore a class of triple-mode bandpass filters on substrate integrated waveguide (SIW) structure. Two degenerate modes of an SIW rectangular cavity and one resonant mode of a complementary split-ring resonator (CSRR) are employed to implement these filters. As the primary advantage, the CSRR mode is utilized instead of the fundamental mode of the SIW cavity to provide us with an attractive capacity in easily controlling the frequency band of the designed SIW filters through the dimensions of this CSRR. Moreover, the positions of transmission zeros can be properly adjusted by the metallic vias. Finally, three examples of SIW multimode bandpass filters are designed, fabricated, and tested to verify the effectiveness of the proposed approach. The measured results are found in good agreement with the simulated ones, showing that these filters have achieved high out-of-band rejection and sharp skirt selectivity.

A New IC Solder Joint Inspection Method for an Automatic Optical Inspection System Based on an Improved Visual Background Extraction Algorithm

Abstract: In the field of automatic optical inspection (AOI), defect recognition for an integrated circuit (IC) solder joint is a long-standing task. Inspired by a visual background extraction (ViBe) algorithm, an object detection method in computer vision, we propose a new inspection method for IC solder joints with an improved ViBe algorithm. To the best of our knowledge, we are the first to consider the defect inspection problem as an object detection problem. We build a solder joint model using the ViBe model updating scheme. Then, we compare the solder joint image with the well-trained model to detect potential defects. Finally, we introduce a frequency map method and define a metric named defect degree to evaluate the qualities of the solder joints. Experimental results show that our method is universal, accurate, and easily debugged compared with the other existing methods.

Design and Modeling of Membrane-Based Evaporative Cooling Devices for Thermal Management of High Heat Fluxes

Abstract: We present a high-heat-flux cooling device for advanced thermal management of electronics. The device incorporates nanoporous membranes supported on microchannels to enable thin-film evaporation. The underlying concept takes advantage of the capillary pressure generated by small pores in the membrane, and minimizes the viscous loss by reducing the membrane thickness. The heat transfer and fluid flow in the device were modeled to determine the effect of different geometric parameters. With the optimization of various parameters, the device can achieve a heat transfer coefficient in excess of 0.05 kW/cm2-K, while dissipating a heat flux of 1 kW/cm2. When applied to power electronics, such as GaN high-electron-mobility transistors, this membrane-based evaporative cooling device can lower the near-junction temperature by more than 40 K compared with contemporary single-phase microchannel coolers.

Theoretical Design of Broadband Multisection Wilkinson Power Dividers With Arbitrary Power Split Ratio

Abstract: This paper describes a new approach for the theoretical design of unequal multisection Wilkinson power dividers, using single-layer microstrip lines. Similar to most multisection structures, the presented unequal divider can provide a broadband performance. To provide the design guideline, closed-form formulas are derived for the divider with odd or even number of sections. In each case, various simulations have been conducted to investigate the performance of dividers over the frequency band. For experimental verifications, two 1:2 power dividers with a center frequency of 1 GHz are fabricated, having three and four sections. The simulated and measured results are presented, and good agreements between them are observed.

Fabrication of Fully Inkjet-Printed Vias and SIW Structures on Thick Polymer Substrates

Abstract: In this paper, a novel fully inkjet-printed via fabrication technology and various inkjet-printed substrate-integrated waveguide (SIW) structures on thick polymer substrates are presented. The electrical properties of polymethyl methacrylate (PMMA) are thoroughly studied up to 8 GHz utilizing the T-resonator method, and inkjet-printable silver nanoparticle ink on PMMA is characterized. A long via fabrication process up to 1 mm utilizing inkjet-printing technology is demonstrated, and its characteristics are presented for the first time. The inkjet-printed vias on 0.8-mm-thick substrate have a resistance of $\sim 0.2~\Omega $ . An equivalent circuit model of the inkjet-printed stepped vias is also discussed. An inkjet-printed microstrip-to-SIW interconnect and an SIW cavity resonator utilizing the proposed inkjet-printed via fabrication process are also presented. The design of the components and the fabrication steps are discussed, and the measured performances over the microwave frequency range of the prototypes are presented.

Impact of Ground via Placement in Grounded Coplanar Waveguide Interconnects

Abstract: Methods for higher order parallel plate mode suppression in grounded coplanar waveguides (GCPW) using unique ground via structures are presented in this paper. Suppression of these higher order modes can increase GCPW bandwidth. The ground via fence parameters that affect the bandwidth of the GCPWs are also discussed. Two new structures using staggered ground via fences and with defected side ground planes, for improving GCPW performances while meeting fabrication and routing requirements, are discussed. These two methods improve the interconnect bandwidth by 62.2% and 27.8%, respectively. The measured and simulated results of a test GCPW structure are in close agreement.

Integration Design of Filtering Antenna With Load-Insensitive Multilayer Balun Filter

Abstract: Integration design of a filtering antenna fed by a load-insensitive multimode balun bandpass filter is proposed in this paper. The balun filter is designed and realized using multilayer structure for miniaturization. To be directly integrated into the antenna, both amplitude and phase performances of the balun filter are investigated with different complex load impedances. With insensitive responses against the load, this balun filter is utilized to design a filtering antenna as the feeding of a quasi-Yagi antenna, which is considered as a frequency-dependent differential complex load. The radiation characteristics are improved by applying a metallic shield as the package for the proposed design. To verify the design concept, an experimental filtering antenna is designed, fabricated, and measured with almost the same passband as that of the balun filter benefiting from the load-insensitive property of the latter. The simulated and measured results are presented, showing good agreement.

Synthesis Method for Substrate-Integrated Waveguide Bandpass Filter With Even-Order Chebyshev Response

Abstract: A synthesis method for an even-order Chebyshev bandpass filter of a substrate-integrated waveguide (SIW) is proposed in this paper. The transformation of a Chebyshev polynomial is studied and applied to achieve an equal source and load termination for an even-order filtering response. This transformed Chebyshev polynomial is used to design a millimeter-wave (mmW) SIW bandpass filter through electric coupling of SIW resonators or cavities. The cascaded resonators are formed by properly etching the slots on the top metal plane of a single SIW cavity, and these slots create electric coupling as desired in a filter design. The proposed synthesis procedure of coupled-resonator bandpass filter with an even-order Chebyshev response is given and discussed here in detail. The theoretical and extracted external quality factor ( $Q_{E}$ ) and coupling coefficient ( $K$ ) are utilized to determine the filter circuit dimensions. Two fourth-order bandpass filters are designed at 140 GHz under a Chebyshev response using magnetic coupling and electric coupling as design examples. These two filters are used to prove the correctness of the proposed synthesis method as well as the advantages of electric coupling in mmW. In order to prove the validity, the previously proposed fourth-order filter using electric coupling is fabricated. The filter is fabricated in a single substrate layer using a low-temperature cofired ceramic technology and measured in a frequency band around 140 GHz. The measured results are in good agreement with simulated results.

A Novel Intermittent Fault Detection Algorithm and Health Monitoring for Electronic Interconnections

Abstract: There are various occurrences and root causes that result in no-fault-found (NFF) events but an intermittent fault (IF) is the most frustrating. This paper describes the challenging and most important area of an IF detection and health monitoring that focuses toward NFF situation in electronics interconnections. The experimental work focuses on mechanically-induced intermittent conditions in connectors. This paper illustrates a test regime, which can be used to repeatedly reproduce intermittence in electronic connectors, while subjected to vibration. A novel algorithm is used to detect an IF in interconnection. It sends a sine wave and decodes the received signal for intermittent information from the channel. This algorithm has been simulated to capture an IF signature using PSpice (electronic circuit simulation software). A simulated circuit is implemented for practical verification. However, measurements are presented using an oscilloscope. The results of this experiment provide an insight into the limitations of existing test equipment and requirements for future IF detection techniques. Aside from scheduled maintenance, this paper considers the possibility for in-service intermittent detection to be built into future systems, i.e., can IFs be captured without external test gear?

Forecasting Obsolescence Risk and Product Life Cycle With Machine Learning

Abstract: Rapid changes in technology have led to an increasingly fast pace of product introductions. For long-life systems (e.g., planes, ships, and nuclear power plants), rapid changes help sustain useful life, but at the same time, present significant challenges associated with obsolescence management. Over the years, many approaches for forecasting obsolescence risk and product life cycle have been developed. However, gathering inputs required for forecasting is often subjective and laborious, causing inconsistencies in predictions. To address these issues, the objective of this research is to develop a machine learning-based methodology capable of forecasting obsolescence risk and product life cycle accurately while minimizing maintenance and upkeep of the forecasting system. Specifically, this new methodology enables prediction of both the obsolescence risk level and the date when a part becomes obsolete. A case study of the cell phone market is presented to demonstrate the effectiveness and efficiency of the new approach. Results have shown that machine learning algorithms (i.e., random forest, artificial neural networks, and support vector machines) can classify parts as active or obsolete with over 98% accuracy and predict obsolescence dates within a few months.

Varactor-Tuned Compact Dual-Mode Tunable Filter With Constant Passband Characteristics

Abstract: This paper presents a second-order Chebyshev constant fractional bandwidth (CFBW) tunable bandpass filter with compact size and frequency invariant-passband characteristics using tunable external quality factors. The filter is designed using a stub loaded dual-mode resonator and two sets of varactors for tuning the center frequency and the return loss level. The design is featured with the net-type filter of a short grounded-stub so that the CFBW property can be assured. In addition to the conventional design, a pair of varactors is included at the ends of feeding transmission lines to keep the external quality factors constant while tuning. Within the tunable range of the varactors, the proposed filter is tunable from 1.7 to 2.1 GHz with a 5% CFBW. The measurement results show a 20-dB return loss and insertion loss below 2.9 dB over the entire tuning range.

Triple-Mode Dielectric-Loaded Cylindrical Cavity Diplexer Using Novel Packaging Technique for LTE Base-Station Applications

Abstract: This paper proposes a triple-mode dielectric-loaded cylindrical cavity diplexer by using a novel packaging technique for long term evolution (LTE) base station applications. Four metal cavities, loaded by a triple-mode dielectric resonator (DR), are designed to resonate at two different frequencies for the diplexer operation. In this context, three resonant modes of a single cavity are classified as a TM mode and a pair of hybrid degenerate modes (HE modes). The two degenerate modes in the same cavity are properly excited by employing an off-centered DR instead of a traditional corner-cut structure as a perturbation element. Finally, such a diplexer is designed and fabricated, and good agreement between measurement and simulation is achieved.

Metallic Nanowires and Their Application

Abstract: Metallic nanowire films, especially silver nano-wires (AgNWs) and copper nanowires (CuNWs), with a random mesh structure have attracted considerable attention as high-performance flexible transparent films to replace the traditional, expensive, and brittle indium tin oxide films. These films have been widely used in displays, touchscreens, and solar cells to achieve next-generation electronics that can be bent, stretched, compressed, twisted, and deformed into complex, nonplanar shapes but maintain good conductive performance, reliability, and integration. Recent researches have indicated that the application of metallic nanowires has been accelerated due to these promising properties. This paper reviews the wet-chemical synthesis of AgNWs and CuNWs, fabrication and posttreatment of nanowire films, as well as their applications as conductive materials in some devices. It provides a latest overview of metallic nanowires and exhibits the developing prospects of high-performance conducting materials for future flexible and wearable optoelectronic devices.

Performance Evaluation of Circuit Breaker Electrical Contact Based on Dynamic Resistance Signature and Using Health Index

Abstract: High-voltage circuit breakers (CBs) are extremely important components for the function of power supply system. The need to predict proper function of CB has increased over the years. Dynamic resistance measurement (DRM) is an effective method to evaluate the condition of CB’s contact. This paper aims to predict the correlation between the various levels of contact degradation and characteristics of dynamic resistance waveform. Five diagnosis parameters are extracted from DRM curve. Using scoring and weighting techniques, heath index is applied to clearly identify the condition of CB as healthy, need caution, and risky. The proposed method is implemented with ten healthy and ten faulty electrical contacts as examples for illustrating the effectiveness of the method in assessing the CB condition.

Chip to Facility Ramifications of Containment Solution on IT Airflow and Uptime

Abstract: We developed a generalized testing methodology in which IT fans’ internal and external impedance effects are collapsed into a single curve (i.e., flow curve). Such curves can give accurate flow rate predictions of the IT equipment based on RPM logging. Flow curves cover the three possible airflow regions for IT in a contained environment. The experimental procedure is introduced to rank IT equipment based on its air systems, and the flow regions are correlated with the CPU performance. The strength of the IT air system is characterized by the free delivery and the critical pressure points. In addition, the experimentally obtained active flow curves can be used as a numerical boundary condition in various containment designs. Accordingly, for the first time in the literature, the aerodynamic interaction of IT with different air systems in the containment (i.e., BladeCenters, servers, and switches) can numerically be investigated. It is found that stacking IT in a contained environment with no physical consideration can lead to radical reliability problems. The region of reverse flow is discovered to be very possible upon events in the data center. In such a case, the weak IT (e.g., 1U switch) behaves as an open leakage into the sealed containment. On the other hand, at the critical pressure point, minimum forced convection occurs in the weak IT, leading to CPU overheating.

60-GHz Air Substrate Leaky-Wave Antenna Based on MEMS Micromachining Technology

Abstract: In this paper, a 60-GHz air substrate leaky-wave antenna based on microelectromechanical system (MEMS) bulk micromachining is proposed Using penetration dry etching and gold plating processes, the air-filled leaky-wave slots, waveguide, and coupling slot, which are located in the top, middle, and bottom silicon-based layers, respectively, are generated The three layers are stacked and clamped together using two location pins and five metal screws The most distinctive feature of the proposed antenna is that the electromagnetic wave cannot see any substrates, except for the air medium, leading to good antenna performance Good agreement between simulation and measurement demonstrates that the MEMS micromachining process fulfills the millimeter-wave (mm-wave) accuracy To the best of the authors’ knowledge, this is the first time that an air substrate mm-wave antenna is fabricated using the MEMS bulk micromachining technology The fabricated prototype with a bandwidth of 173% and a peak gain of 114 dBi is attractive for mm-wave wireless communication applications Validity of the feasibility provides the possibility to realize the system-in-package solutions

A Study on the Failure Mechanism and Enhanced Reliability of Sn58Bi Solder Anisotropic Conductive Film Joints in a Pressure Cooker Test Due to Polymer Viscoelastic Properties and Hydroswelling

Abstract: A study of the failure mechanism and the enhanced reliability performance of SnBi58 solder ACF joints were investigated by considering the total influence of polymer viscoelastic and hygroscopic properties on the cross-sectional morphologies and the electrical properties of Sn58Bi solder joints in a pressure cooker test (PCT) for 120 h. The Sn58Bi solder failure mechanism is demonstrated that, when polymer resin absorbed moisture, the $T_{g}$ values of polymer resins decreased, and the coefficient of thermal expansion (CTE) values of polymer resins increased, due to a hydroswelling effect. Considering the total influence of polymer viscoelastic and hygroscopic properties on the cross-sectional morphologies and the reliability of Sn58Bi solder joints in a PCT for 120 h, four typical polymer resins were evaluated. As a result, cationic epoxy (128 ppm/°C) with the smallest CTE mismatch (112 ppm/°C) with SnBi58 solder joints (16 ppm/°C) in a PCT aging test (121 °C, 100% humidity, and 2 atm) showed a stable electrical property in terms of joint contact resistance and remained a complete cross-sectional Sn58Bi solder joint morphology after PCT reliability for 120 h.

Design, Modeling, Fabrication and Characterization of 2–5- $\mu \text{m}$ Redistribution Layer Traces by Advanced Semiadditive Processes on Low-Cost Panel-Based Glass Interposers

Abstract: This paper presents the latest advances in extending semiadditive process (SAP) methods to 2–5 $\mu \text{m}$ lines and spaces, achieved using dry film photoresists on thin glass substrates, toward meeting the routing requirements for 20- $\mu \text{m}$ bump pitch interposers. High-density chip-to-chip interconnections on 2.5-D interposers are a key enabler to meet the high logic to memory bandwidth needs of next-generation electronic systems. Such 2.5-D interposers require ultrafine redistribution layer (RDL) traces with line widths and spacing below $5~\mu \text{m}$ . This paper reports on the extension of panel scale and lower cost SAPs to achieve less than $5~\mu \text{m}$ lines and spaces, based on the ultrasmooth surface and improved dimensional stability of thin glass panels. A modified low-cost SAP method with newly developed differential seed layer etching was employed to fabricate the fine line and space patterns and coplanar waveguide (CPW) transmission on thin glass panels. Fine lines down to 2- $\mu \text{m}$ lines and spaces and CPW lines with signal lengths up to 5 mm and ground-to-signal gaps down to $5.5~\mu \text{m}$ at 15- $\mu \text{m}$ signal widths were successfully fabricated on ultra-thin glass panels. For comparison, the same processes were also applied to a silicon wafer. The signal insertion losses of CPW lines on the glass were 0.024 dB/mm better at 15 GHz than those on the silicon, as confirmed by simulations as well as VNA measurements. The measured insertion loss of 5-mm long CPW lines on glass interposer was 0.7 dB at 10 GHz and matched well to the simulated values.

A Novel Technique for Evaluating the Effective Permittivity of Inhomogeneous Interconnects Based on the Monotonicity Property

Abstract: This paper presents a novel homogenization technique to retrieve the effective permittivity of an interconnect embedded in inhomogeneous dielectrics, with an arbitrary number of conductors. The technique is based on the monotonicity property of suitable matrices associated with the transmission line model. The effective permittivity values are obtained by checking an index related to the eigenvalues of such matrices. The technique requires only the knowledge, at a single frequency point, of any of the terminal matrices describing the original line (e.g., impedance, admittance, or scattering matrices), either obtained by measurements or by simulations. Depending on the applications, the technique can identify one or two values for the effective permittivity. In the first case, the original inhomogeneous line can be replaced by an equivalent line, embedded in a homogeneous dielectric. In the second case, two equivalent homogeneous lines are identified, which cannot replace the inhomogeneous line, but can be used to obtain the lower and upper bounds to its performance (in terms of significant physical signatures, such as stored energy, propagation velocities, delay times, and characteristic impedance). The mathematical theorems supporting the technique are rigorously proven. The technique is shown to be consistent with the existing results in the literature and is experimentally validated. Several case studies are carried out, including cables, microstrips, and multilayered interconnects.

General Dual-Band Impedance Transformer With a Selectable Transmission Zero

Abstract: This paper presents general design formulas for a dual-band impedance transformer with an inherent and selectable transmission zero. The inherent transmission zero can block unwanted signal or interference and improve the overall circuit performance by suppressing spurious response and enhancing selectivity. The considered load has unequal complex impedances at two uncorrelated frequencies. The proposed transformer consists of three sections of transmission lines and two shunt stubs. The parameters of each transmission line and stub are obtained using the derived analytical formulas without any time-consuming try-and-error procedure or numerical solution. The proposed design formulas reduce the need to use a transmission line with extremely high or low impedance. Two impedance transformers are designed and fabricated. Good agreement between numerical and measured results validates the proposed design formulas.

Microwave and Millimeter-Wave LTCC Filters Using Discriminating Coupling for Mode Suppression

Abstract: In this paper, a new discriminating coupling mechanism, which is realized by choosing suitable coupling region between the feeding lines and resonators, is proposed to suppress the unwanted resonance modes without affecting the desirable operating modes. Utilizing such a coupling mechanism, two low-temperature cofired ceramic (LTCC) bandpass filters (BPFs) are designed operating at microwave and millimeter-wave bands. One BPF realizes a wide stopband, since the third and fifth harmonics are suppressed by the discriminating coupling. The other one is an oversized 60-GHz BPF with the fundamental mode suppressed by the discriminating coupling. Due to the multilayer characteristics of the LTCC techniques, the circuit layout can be controlled flexibly to realize desirable discriminating coupling. The two filters are theoretically analyzed and implemented. Good agreement between the simulation and the measurement validates the proposed method.

A $D$ -Band Packaged Antenna on Organic Substrate With High Fault Tolerance for Mass Production

Abstract: A grid array antenna working around 145 GHz is proposed in this paper. The antenna is built on liquid crystal polymer (LCP) and designed for the $D$ -band antenna-in-package application. The intrinsic softness of the LCP material is a limiting factor of the antenna’s aperture size. A 0.5-mm-thick copper core is used to compensate. By doing this, the rigidness of the antenna is effectively improved, compared with an antenna without the copper core. Wet etching is used to realize the patterns on the top and bottom conductor. Compared with a low-temperature cofired ceramic counterpart, we obtain a considerable cost reduction with acceptable performance. The proposed antenna has an impedance bandwidth of 136–157 GHz, a maximum gain of 14.5 dBi at 146 GHz, and vertical beams in the broadside direction between 141 and 149 GHz. The fabrication procedures of the antennas are introduced, and a parametric study is carried out, which shows the antenna’s robustness against fabrication tolerances, such as the not-well-controlled etching rate and the substrate surface roughness. This makes the antenna a promising solution for mass production.

Electrothermal Cosimulation of 3-D Carbon-Based Heterogeneous Interconnects

Abstract: Electrothermal characteristics of some novel 3-D carbon-based heterogeneous interconnects, consisting of vertical carbon nanotube bundle via and horizontal multilayer graphene, are investigated by utilizing in-house developed algorithm based on a finite-element method. With present fabrication capability, these heterogeneous interconnects can have larger electrical resistance but smaller thermal resistance in comparison with their Cu counterpart. Both the local on-chip interconnects for ballistic regime and global through-silicon via channel for diffusive regime are evaluated numerically, and their 3-D transient temperature distribution and hot spots are characterized and compared. During the electrothermal cosimulation, the anisotropic property of electrical and thermal conductivities of carbon nanomaterials is treated in an appropriate way. It is believed that this paper will be useful for the design as well as the realization of new generation carbon-based interconnects with high reliability and better thermal performance.

Humidity Build-Up in a Typical Electronic Enclosure Exposed to Cycling Conditions and Effect on Corrosion Reliability

Abstract: The design of electronic device enclosures plays a major role in determining the humidity build-up inside the device as a response to the varying external humidity. Therefore, the corrosion reliability of electronic devices has direct connection to the enclosure design. This paper describes the internal humidity build-up in a typical enclosure prescribed for electronic applications as a function of external humidity conditions and enclosure-related parameters. Investigated parameters include external temperature and humidity conditions, the temperature and time of the internal heating cycle, thermal mass, and port/opening size. The effect of the internal humidity build-up on corrosion reliability has been evaluated by measuring the leakage current (LC) on interdigitated test comb patterns, which are precontaminated with sodium chloride and placed inside the enclosure. The results showed that the exposure to cycling temperature causes significant change of internal water vapor concentration. The maximum value of humidity reached was a function of the opening size and the presence of thermal mass inside the enclosure. A pumping effect was observed due to cycling temperature, and the increase in the level of absolute humidity at each cycle led to condensation, which caused a sudden increase in LC.

Bending Properties of Anisotropic Conductive Films Assembled Chip-in-Flex Packages for Wearable Electronics Applications

Abstract: In this paper, a chip-in-flex (CIF) assembly that has an excellent bending performance, including a minimum bending radius without a chip fracture and the capacity to withstand dynamic bending, is developed. Chip-on-flex (COF) and CIF assemblies are fabricated using anisotropic conductive films (ACFs) as interconnection materials. The COF package is composed of 40- $\mu \text{m}$ -thin silicon chips, ACF, and flexible substrates. The CIF package is fabricated by attaching a cover adhesive film and a polyimide film on the COF package to encapsulate the silicon chip. Through static bending tests, the optimal thickness of the cover adhesive film is established. The optimized CIF assembly allows a minimum bending radius of 4 mm without a chip fracture, while the chip in the COF assembly fractures at a bending radius of 10 mm. A finite-element analysis of the static bending test is performed to understand the internal stress state of the assemblies. A bending reliability test of the CIF package is also conducted at a bending radius of 7.5 mm for 160k cycles, by measuring the daisy-chain resistance during the test. The effect of the elastic modulus of the ACF resin on the fatigue endurance is investigated through the bending fatigue test. The higher modulus of the ACF resin resulted in excellent fatigue reliability with stable ACF joints showing neither delamination nor resin crazing after 160k cycles of bending.

Through-Silicon Vias: Drivers, Performance, and Innovations

Abstract: To address the abating performance improvements from device scaling, innovative 2.5-D and 3-D integrated circuits with vertical interconnects called through-silicon vias (TSVs) have been widely explored. This paper reviews TSVs with focus on the following: 1) key drivers for TSV-based integration; 2) TSV fabrication techniques; 3) TSV electrical and thermomechanical performance fundamentals and characterization techniques; and 4) novel technologies to attain enhanced performance beyond the state-of-the-art TSVs.