Small Package Research Articles

A Postprocessing-Technique-Based Switching Loss Estimation Method for GaN Devices

Gallium nitride (GaN) high electron mobility transistor (HEMT) is a promising candidate for the high-density power converter applications. Due to the low switching loss, the GaN HEMT may lead to a new horizon in the applications, such as fast charger, wireless charging, and 5G power amplifier. However, the fast switching speed of GaN HEMT makes it extremely sensitive to parasitic parameters, especially for the low-voltage GaN devices with small packages. Conventional switching loss estimation methods, which are normally based on the calibration fixture or modification of test circuit, cannot be effectively utilized for GaN HEMT. This article presents an accurate switching loss estimation method using the postprocessing technique. The proposed switching loss technique consists of three parts of signal processing, which are the wavelet denoising process to minimize the influence of background noise, the voltage–current ( $ V-I$ ) alignment process to reduce errors from probe propagation delay, and the linear interpolation process for further improvement of alignment accuracy. In addition, a modified SPICE model is proposed to investigate the influence of parasitic parameters on switching losses by the circuit simulation. Based on the theoretical switching characteristics, the switching loss estimation method is finally validated experimentally on a commercial 40-V/10-A GaN HEMT in a double-pulse test.

Low-Frequency Characteristics of Silicon-Based High-Current Multijunction Thermal Current Converters Fabricated by Wet Chemical Etching

A single-unit thermal converter for precision ac current measurement is desirable because of its relatively small package and low power dissipation. In this article, high-current multijunction thermal converters (HC-MJTCs) on silicon (Si) substrates fabricated by wet chemical etching have been investigated at input rms currents of up to 2 A. The use of wet chemical etching aids the fabrication of a freestanding nitride–oxide membrane, maintaining the Si heat reservoir under the heater of the HC-MJTC intact. Below 10 mPa, the output voltage from the HC-MJTC and the thermal time-constant increase by approximately six times, implying improved efficiency of the thermal current converter. The absolute value of the ac–dc differences of the device was less than $17~\mu \text{A}$ /A over input current levels of up to 2 A at frequencies above 100 Hz. However, input current level-dependent ac–dc differences were observed at frequencies below 400 Hz even under vacuum. This behavior originated primarily from a change in the electrical resistance of the heater in this Si-based device. Therefore, these low-frequency ac–dc differences can be substantially compensated using the measured ac and dc electrical resistances of the heater.

3D Printed Wideband Multilayered Dual-Polarized Stacked Patch Antenna With Integrated MMIC Switch

Capability of 3D printing for developing wideband multilayered antenna systems packaged with active RF circuit components remains relatively unexplored. To address this gap, this manuscript demonstrates wideband patch antenna that is integrated with a polarization selection switch. Antenna bandwidth is enhanced with customized substrate thicknesses and stacked patch layers. Switch is integrated with 3D vertical transitions to achieve wide bandwidth, smaller packaging, and low-loss. To enable future antenna array applications, a detailed investigation is also presented to maximize the performance of the microstrip feed lines by adjusting the substrate thickness and deposition process. The antenna consists of 13 dielectric and conductive layers. Specifically, the manuscript demonstrates the lowest attenuation in the literature for a fully printed microstrip line with 0.25 dB/cm measured loss at 18 GHz. The antenna operates with more than 80% radiation efficiency and 45% bandwidth. The polarization switch is embedded within the antenna structure. The antenna retains a high cross-polarization ratio of ~20 dB due to 3D feed line transitions and symmetric location of the switch with respect to the antenna feeds.

The Sabatier Electrolyzer: Harnessing Proton-Conducting Ceramics to Upgrade Carbon Dioxide into Methane

We present our development of the Sabatier Electrolyzer to synthesize CH4 and O2 from CO2 and H2O feed streams. Our work seeks to integrate steam electrolysis and hydrogen production with carbon dioxide hydrogenation into a single Sabatier Electrolyzer reactor based on proton-conducting ceramic membranes and Sabatier catalysts. When powered by solar- and / or wind-energy, the Sabatier Electrolyzer has the potential to store intermittent renewable electricity in the form of commodity chemicals while simultaneously reducing carbon dioxide emissions, thereby addressing two principle societal concerns in a single device.The Sabatier Electrolyzer concept is illustrated in the figure. H2O and CO2 are fed to steam and fuel electrodes, respectively, of a protonic-ceramic electrolysis cell. An external power source drives H2O splitting at the steam electrode. The product O2 is exhausted from the cell. The product protons are driven across the protonic-ceramic membrane to the fuel electrode, where they react with CO2 to form CH4 and H2O. The combination of processes can match the exothermicity of CO2 hydrogenation with the endothermicity of H2O electrolysis to facilitate thermal balance and high efficiency.Proton-conducting ceramic membranes transport reasonable rates of H+ ions at 400 - 500 ºC with low overpotentials for H2O splitting. This lower operating temperature is reasonably well matched with the CO2-methanation reaction that thermodynamically favors lower-temperatures. The Ni-based catalyst is active for both H2 evolution from the protonic-ceramic material and catalytic methanation of CO/CO2, further promoting the technological combination. Integration of the methanation reactor with the electrolyzer simplifies the system, improves reliability, and provides increased performance within a smaller package than more-prevalent two-stage systems.We have pioneered a larger-area (active area is 5 cm2) Sabatier Electrolyzer cell composed of a BaCe0.4Zr0.4Y0.1Yb0.1O3-δ (BCZYYb4411) electrolyte, a Ni-BCZYYb4411 fuel electrode support, and a BaCo0.4Fe0.4Zr0.1Y0.1O3-δ (BCFZY) steam electrode. The Ni-cermet fuel electrode serves as the CO2-upgrading catalyst. To date, we have demonstrated CO2 conversion and CH4 selectivity at 55% and 63%, respectively, at 450 °C. This result represents the highest reported electrochemical conversion of CO2 and H2O into CH4 in a single device. In this presentation, we will review our efforts in Sabatier Electrolyzer development, targeting the thermodynamically predicted CO2 conversion and CH4 selectivity of 70% and 95%, respectively. Figure 1

Antisway Control of a Multirotor With Cable-Suspended Payload

This brief presents a new trajectory generation and an effective antisway tracking control (ATC) method for a multirotor unmanned aerial vehicle (UAV) with a cable-suspended payload. The UAV transportation system has been developed due to its ability to easily deliver small packages. However, existing methods lack research on transient response accompanied by aggressive rotation of the UAV and inevitable payload swing. Unfortunately, these motions become intensified when the input is dynamically unfeasible, such as step-like changes. Trajectory generation to minimize the swing motion provides a dynamically feasible trajectory between waypoints. The proposed method provides fast settling time with remarkably little payload swing. In addition, the ATC is developed on the basis of linear-quadratic (LQ) control to deal with motion coupling issues. A payload state estimator is also designed that requires no sensor for the payload. Finally, the performance of the proposed method is verified by numerical simulation and experimental results that show the possibility of safe and fast transportation with a minimal swing.

Measurement and Analysis of Vibration Levels in Stacked Small Package Shipments in Delivery Vans as a Function of Free Movement Space

In recent years there has been a very significant increase in parcel delivery shipments all over the world. Moreover, this mode of delivery, in some cases, is facing a very intensive flow of goods, such as in annual festive seasons or, for instance, in situations like COVID-19 when personal purchase of goods is strictly limited in malls. This often means that delivery vehicles operate at almost full capacity, and many same or different kinds of packages are therefore stacked in small delivery vehicles. In this study, we measured and analyzed the vibration levels that occur in smaller stacks of packages in parcel delivery shipments, paying particular attention to those circumstances such as stacking layers and free movement spaces that can affect the vibration in different layers of packages. The goal of this paper was to provide information about the vibration levels that occur in smaller stacks of packages that are not unitized and fixed, as is common in parcel transportation. The recorded vibration events were analyzed in terms of power spectral densities (PSDs) and supplied with statistical data of acceleration events to provide an understanding of the variability of intensity. Based on the results of this study, PSD spectra were developed for various free movement conditions, as well as spectra for each layer in the stacked parcel package shipment. The results showed that the vibration level increases in the stacked load upwards and with an increase of free space of possible movement. The results of this study can be used to simulate the measured vibration conditions in laboratory tests conducted on courier express parcel shipments.

An Integrated Modular Motor Drive With Shared Cooling for Axial Flux Motor Drives

In this article, a circumscribing polygon integrated modular motor drive topology with shared cooling for the power converter and the electrical machine is proposed and benchmarked with the nonintegrated version. The proposed topology is applied on an axial flux permanent magnet synchronous machine. The topology is capable of mechanically mounting the power converter, sufficiently cooling both the power converter and the electrical machine, and combining both of them into the same housing. The mechanical and the thermal design are done to ensure thermal decoupling between the power converter and the motor winding, and to provide a low thermal resistance from the power converter and the electrical machine to the ambient. Due to the limited space available for the power converter module, wide bandgap semiconductor technology is chosen for the implementation of the converter module, thanks to their small package size and low power losses. A highly modular, integrated, and compact drive is achieved compared to the nonintegrated one. A computational fluid dynamics (CFD) model is developed for one module of the proposed integrated drive to evaluate the maximum current that can be injected by one converter module without exceeding the junction temperature limit of the switches and the maximum winding temperature. An experimental setup is built to validate the results of the introduced multiphysics models.

Fabricating a Portable ECG Device Using AD823X Analog Front-End Microchips and Open-Source Development Validation.

Relevant to mobile health, the design of a portable electrocardiograph (ECG) device using AD823X microchips as the analog front-end is presented. Starting with the evaluation board of the chip, open-source hardware and software components were integrated into a breadboard prototype. This required modifying the microchip with the breadboard-friendly Arduino Nano board in addition to a data logger and a Bluetooth breakout board. The digitized ECG signal can be transmitted by serial cable, via Bluetooth to a PC, or to an Android smartphone system for visualization. The data logging shield provides gigabytes of storage, as the signal is recorded to a microSD card adapter. A menu incorporates the device’s several operating modes. Simulation and testing assessed the system stability and performance parameters in terms of not losing any sample data throughout the length of the recording and finding the maximum sampling frequency; and validation determined and resolved problems that arose in open-source development. Ultimately, a custom printed circuit board was produced requiring advanced manufacturing options of 2.5 mils trace widths for the small package components. The fabricated device did not degrade the AD823X noise performance, and an ECG waveform with negligible distortion was obtained. The maximum number of samples/second was 2380 Hz in serial cable transmission, whereas in microSD recording mode, a continuous ECG signal for up to 36 h at 500 Hz was verified. A low-cost, high-quality portable ECG for long-term monitoring prototype that reasonably complies with electrical safety regulations and medical equipment design was realized.

Die Attach Film Bleed out Resolution through Process Optimization on DFN Packages

The development of new technology with thinner and smaller packages has become the movement and focus on semiconductor assembly industry. This paper presents an improvement done in dual-flat no-leads (DFN) package to resolve the quantity of rejection due to die attach film (DAF) bleed out on the die paddle of the leadframe. This reject manifestation was seen after die attach process. Parameter optimization particularly for the bonding with the combination of bond force and bond time parameter was done to eliminate this type of issue after die attach process. With this die attach process optimization and improvement done, DAF bleed out occurrence was eliminated with 100% reduction improvement.

Re-examining Border Clearance in the Age of E-Commerce

Traditional customs clearance processes for goods arriving in ports or at border crossings involve declaration, inspection, revenue collection, and release procedures focused in time and space at the point of arrival. This paradigm for government management of cross-border trade in goods has been incrementally impacted in the 21st century by change drivers ranging from heightened concerns about security and safety risks in international supply chains to the increasingly sophisticated use of prearrival data collection and IT automation in border management processes. Over the past decade, the rapid growth of online retailing, sometimes referred to as e-commerce, has led to an exponential increase in goods, often individually packaged, shipped directly from the seller to consumer. Existing border clearance models for international goods shipments were established in the context of an environment dominated by business-to-business commercial shipments of cargo for further distribution (for example, by retailers) in the country of destination. The rapidly expanding volume of cross-border direct-to-consumer shipments generates large numbers of small package consignments, presenting a challenge for existing goods clearance models in many countries. Contemporary border clearance processes may not be ideally suited to the rapidly expanding volumes of such shipments, and the limited reporting requirements often associated with such consignments may make effective risk management and revenue collection very difficult for governments. Border management modernisation initiatives spearheaded by multilateral organisations have generated some clarity in confirming that e-commerce’s effects do challenge traditional border clearance models, highlighting many of the underlying issues, but they have not generated a clear path forward on policy solutions. As a result, individual countries have been re-examining their national border clearance processes and are starting to take actions to tackle the e-commerce border clearance challenge on their own, highlighting the need for further multilateral work in this area to develop a consensus on policy measures to address the border management concerns identified.

Good things come in small packages…except after spinal injury

Good things come in small packages…except after spinal injury

Mitochondrial DNA Base Editing: Good Editing Things Still Come in Small Packages

The collaborative work of two HHMI groups, one at the University of Washington and the other at the Broad Institute of MIT and Harvard, led to the development of a novel molecular tool to edit single bases in the mtDNA (Mok etal., 2020).

Implementation of 1.7 kV silicon carbide metal oxide semiconductor field effect transistors in auxiliary power supplies for industrial applications

An auxiliary power supply (Aux-PS) has become an essential component of electronic equipment for many industrial applications, such as in motor drives, photovoltaic (PV) inverters, uninterruptible power supply (UPS) systems and modular multilevel converters. The introduction of 1 700 V silicon carbide (SiC) metal oxide semiconductor field effect transistors (MOSFETs) is useful for such applications, providing benefits with respect to a low on-state resistance, smaller package, low switching loss and single-switching implementation. A single end flyback Aux-PS is designed for industrial applications with a wide input voltage range using 1.7 kV SiC MOSFETs. The special design tradeoffs involved in the usage of SiC MOSFETs are discussed in detail, such as those with regard to gate driving voltage selection, isolation transformer design considerations, and clamping circuit design details. A 60 W demonstration hardware is developed and tested under different working conditions. The results verify the higher efficiency and better thermal performance of the proposed hardware relative to those of traditional Si solutions.

CO2 흡수제 함유 김치포장에서 CO2 농도와 제품 숙성도의 상호관련성

CO2 concentration in kimchi package has emerged recently as a potential index of product ripening to be monitored or sensed in intelligent packaging. Considering that addition of CO2 absorber into the flexible kimchi package changes behavior of its CO2 concentration, ripening of kimchi in total acidity, package CO2 concentration in partial pressure (PCO2) and package volume at 10oC were estimated by mathematical model for two size packages included with different CO2 absorbers. In small size package containing 0.5 kg of kimchi, relatively less gas permeable low density polyethylene (LDPE) sachet of the absorber was found to give rise of PCO2 linearly correlated with acidity at acceptable conditions of absorber amount and size. The levels of PCO2 at optimum ripening were different with absorber amount. However, highly gas permeable microporous spunbonded film (Tyvek) sachet did not show the linear relationship except a condition of 1.5 g of CO2 absorbent. In large size package containing 2.0 kg, absorber sachets of LDPE and Tyvek could give the linear relationship between product acidity and package PCO2 but at different levels (PCO2 of package with LDPE sachet: 0.46~0.79 bar, PCO2 of package with Tyvek sachet: 0.00~0.75 bar). The PCO2 at optimal ripening was found to be less variable with LDPE sachets than with Tyvek ones. Use of package CO2 concentration as an indicator of kimchi ripening was shown to be possible on the limited conditions where the linear relationship between them is established or confirmed.

Applying regression techniques in designing optimal trade execution strategy for an asset

The paper aims to construct an optimal trading strategy for procuring a large but fixed volume of a risky asset. The proposed approach splits a large block of trade into smaller packages to minimize the execution cost of the trade. In this study, we suggest an incipient price dynamics for the asset where we express its current market price as a convex combination of the price impervious to our anterior trade in the asset and the execution price carrying the impact of our anterior trade in it. We propose to apply the regression techniques to estimate the unaffected price of the asset. The formulated model is a convex quadratic optimization problem and thus computationally tractable. We evaluate the performance of the proposed model on five stocks namely, Apple, Microsoft, Coca-Cola, Amazon, and Netflix and conclude that the proposed model consistently achieves a lower execution cost than the one obtained from some other models existing in the literature.

Estimation of traffic density from drone-based delivery in very low level urban airspace

Driven by rising consumer demand, interest is growing in the application of autonomous unmanned aerial vehicles (drones) for the last-mile delivery of small express packages and fast-food meals in cities. To be realised, this would require the Very Low Level (VLL) urban airspace to be able to cope with high traffic densities of commercial delivery drones. The potential benefits of such novel drone-based applications are a reduction of traffic congestion in cities, lower greenhouse gas emissions and more efficient transportation operations. To help realise this concept, programs such as U-Space, the unmanned traffic management system for Europe, are developing important services such as deconfliction management and dynamic capacity management. However, for several of these services, design choices will depend on how, and how extensive they will be used. It therefore becomes important to estimate how many delivery drones would operate in a typical city. This paper aims to provide an estimate by establishing a framework to determine the traffic demand for express drone-based package delivery of five European countries. In addition, a detailed case-study is presented for determining traffic density of express package drone delivery for Paris metropolitan area in order to assess the feasibility from a user's perspective. The paper also discusses the potential of fast-food meal delivery drones compared to traditional delivery modes for Paris. Results suggest that hourly traffic densities culminating from express package and fast-food meal delivery drones will exceed today's global commercial aircraft traffic of 10,000 per day by more than six-fold for just one potential metropolitan city.

Crowd logistics: Understanding auction-based pricing and couriers’ strategies in crowdsourcing package delivery

The growth of electronic commerce generates significant demand for the delivery of personal goods. Crowdsourcing applications have the potential to create more flexible alternatives to existing package-delivery services. However, the success of these applications is strongly related to the strategies of the crowd couriers, which are not well-understood in the current literature. In this paper, we analyzed data from a real-world crowdsourcing application that uses an auction-based mobile app to deliver small packages in urban, suburban, and intra-metropolitan areas. Our analysis reveals the spatial strategies of crowdsourced couriers, which are correlated with delivery pricing and the courier's experience. The couriers with strong relationships with specific customers create ongoing trust relations, which makes deliveries over medium distance routes financially reasonable for those couriers. We discuss how our findings can help to maximize package-delivery markets and crowdsourcing markets in general by supporting the couriers' strategies.

Development of Reliable, High Performance WLCSP for BSI CMOS Image Sensor for Automotive Application.

To meet the urgent market demand for small package size and high reliability performance for automotive CMOS image sensor (CIS) application, wafer level chip scale packaging (WLCSP) technology using through silicon vias (TSV) needs to be developed to replace current chip on board (COB) packages. In this paper, a WLCSP with the size of 5.82 mm × 5.22 mm and thickness of 850 μm was developed for the backside illumination (BSI) CIS chip using a 65 nm node with a size of 5.8 mm × 5.2 mm. The packaged product has 1392 × 976 pixels and a resolution of up to 60 frames per second with more than 120 dB dynamic range. The structure of the 3D package was designed and the key fabrication processes on a 12” inch wafer were investigated. More than 98% yield and excellent optical performance of the CIS package was achieved after process optimization. The final packages were qualified by AEC-Q100 Grade 2.

A high-resolution area-change-based capacitive MEMS tilt sensor

Tilt sensors have been widely used in many applications, such as instrumentation leveling, oil drilling and structural health monitoring. With the rapid development of the micro-electromechanical system (MEMS) technology, MEMS accelerometer-based high-performance tilt sensors are capable of replacing conventional tilt sensors in most of application fields. High-sensitivity MEMS resonant accelerometers (MRAs) are fully qualified for tilt sensing. However, MRA chips have to be vacuum packaged and require complex circuits; therefore, they are difficult to be miniaturized and commercialized. In this case, this paper introduces a commercial-oriented capacitive MEMS accelerometer for tilt sensing with both high-resolution and compact size. The proposed MEMS sensor utilizes simplified fabrication processes, the area-change-based capacitive displacement transducer and the capacitance-to-voltage conversion application specific integrated circuit (ASIC) for low-cost, high-sensitivity, low power consumption and miniaturization. The developed MEMS sensor has a package dimension of 14 mm × 14 mm × 3.6 mm with a single +5 V power supply and analog voltage output. Several evaluation experiments have been conducted with the results showing that the developed MEMS tilt sensor has a full measurement range of ±180°, a linear measurement range of ±30° with a nonlinearity of ±2.8%, a sensitivity of 33.6 mV/°, a noise floor of 2 × 10−4°/√Hz, a bandwidth of 100 Hz and an angle resolution of 7 × 10−4° with an integral time of 0.5 s. Compared with other commercial MEMS tilt sensors, the proposed sensor has a better resolution, a lower noise floor, a larger bandwidth, a lower power consumption and a smaller package. The simplified fabrication process and high performance suggest the developed MEMS tilt sensor is promising to be competitive in the market.

Demand Analysis and Distribution of Single-Trip Ticket Cards for Urban Rail Transit

In the current urban rail transit systems, nearly 15% of passengers are noncommuter travelers who use single-trip ticket cards (ticket cards). Accordingly, the effective management of ticket cards is of great importance. This article suggests a time series model for use in predicting ticket card storage based on the characteristics of ticket cards collected by an automatic fare collection (AFC) system. The distribution cycle, station types, and distribution volume of each station are also determined. Then, drawing on small package transportation feasibility theory, an unbalanced distribution model between production and demand (unbalanced distribution model), as well as a hybrid distribution model of loading and unloading (hybrid distribution model), is established. Application of these models to the Beijing Subway system is used to verify the efficiency and feasibility of such a hybrid distribution model. The analysis and results offer insights into usage patterns of urban rail transit ticket cards, providing solid evidence for a relative decision-making process.