bluuebunny/crossref_metadata_2025 huggingface dataset:
Unattended Sensors in Marine Environments
Authors: Nor Rizal Mohd , Nesterenko Mikhail
Published: October 2015

This chapter discusses the use of unattended sensors and its use in marine environment. The authors present challenges of designing a marine sensor in harsh environments and a case study in implementing a marine sensor to study hypoxia. Hypoxia is a world-wide anthropogenic phenomenon related to pollution. The authors describe the construction of an inexpensive sensor buoy system, Oxybuoy, designed for long-term unattended oxygen sensor measurements. The technology is available to construct such sensor buoys. The authors showed a prototype based on commercial off-the shelf components: an embedded PC, an optical dissolved oxygen sensor, a temperature sensor, a Wi-Fi transmitter and a satellite transmitter. Its total cost is around $5,000 to construct, program and test a proof of concept of such sensor. The authors describe the buoy's architectural design and three experiments that the authors carried out to demonstrate its viability.
Using the Collegiate Learning Assessment to Address the College-to-Career Space
Authors: Zahner Doris , Kornhauser Zachary , Benjamin Roger W. , Wolf Raffaela , Steedle Jeffrey T.
Published: October 2015

Issues in higher education, such as the rising cost of education, career readiness, and increases in the achievement gap have led to a movement toward accountability in higher education. This chapter addresses the issues related to career readiness by highlighting an assessment tool, the Collegiate Learning Assessment (CLA), through two case studies. The first examines the college-to-career space by comparing different alternatives for predicting college success as measured by college GPA. The second addresses an identified market failure of highly qualified college graduates being overlooked for employment due to a matching problem. The chapter concludes with a proposal for a solution to this problem, namely a matching system.
A Tough Nut to Crack
Authors: Liu Lei , Hao Jiangang , von Davier Alina A. , Kyllonen Patrick , Zapata-Rivera Juan-Diego
Published: October 2015

The purpose of our project is to explore the measurement of cognitive skills in the domain of science through collaborative problem solving tasks, measure the collaborative skills, and gauge the potential feasibility of using game-like environments with avatar representation for the purposes of assessing the relevant skills. We are comparing students' performance in two conditions. In one condition, students work individually with two virtual agents in a game-like task. In the second condition, dyads of students work collaboratively with two virtual agents in the similar game-like task through a chat box. Our research is motivated by the distributed nature of cognition, extant research on computer-supported collaborative learning (CSCL) which has shown great value of collaborative activities for learning, and the framework for the Programme for International Student Assessment (PISA) framework. This chapter focuses on the development and implementation of a conceptual model to measure individuals' cognitive and social skills through collaborative activities.
Using Technology to Assess Real-World Professional Skills
Authors: Brunner Belinda , Becker Kirk A. , Tagoe Noel
Published: October 2015

Innovative item formats are attractive to the sponsors of professional certification or qualification examinations because they provide greater fidelity to the real world than traditional item formats. Using the design of the Chartered Institute of Management Accountant's professional qualification examinations as a case study, this chapter presents an in-depth exploration of the issues surrounding the use of innovative items to assess higher-order thinking skills required for professional competency, beginning with a discussion of approaches taken by various academic disciplines to define and characterize higher order thinking. The use of innovative, authentic assessments is examined in the context of validity arguments. A framework for principled thinking about the construct map of the assessment is introduced, and a systematic process for designing innovative items to address the desired constructs is provided.
Analyzing Process Data from Problem-Solving Items with N-Grams
Authors: He Qiwei , von Davier Matthias
Published: October 2015

This chapter draws on process data recorded in a computer-based large-scale program, the Programme for International Assessment of Adult Competencies (PIAAC), to address how sequences of actions recorded in problem-solving tasks are related to task performance. The purpose of this study is twofold: first, to extract and detect robust sequential action patterns that are associated with success or failure on a problem-solving item, and second, to compare the extracted sequence patterns among selected countries. Motivated by the methodologies of natural language processing and text mining, we utilized feature selection models in analyzing the process data at a variety of aggregate levels and evaluated the different methodologies in terms of predictive power of the evidence extracted from process data. It was found that action sequence patterns significantly differed by performance groups and were consistent across countries. This study also demonstrated that the process data were useful in detecting missing data and potential mistakes in item development.
Livestock and Climate Change
Authors: Mayes Xavier
Published: October 2015

A global shift away from diets dominated by meat, dairy and eggs to mainly plant-based diets is as necessary in mitigating anthropogenic climate change as the shift away from fossil fuels. Yet a large awareness gap exists about animal agriculture's contribution to greenhouse gas emissions. Recent studies in Australia and the United States show this issue is represented in less than 1 percent of all newspaper articles about climate change. This chapter examines the opportunities and barriers in addressing the livestock sector's impact on climate change. Policy recommendations in the literature are compared with the responses of governments, industry and the NGO sector. Australia's unique socioeconomic and cultural ties to livestock production and the consumption of animal products represent a significant barrier to demand-side mitigation. An analysis of newspaper articles mentioning animal agriculture's link to climate change in The Sydney Morning Herald between 2006 and 2014 provides insights into the facilitation and shaping of public awareness on the issue to date. The findings can inform strategies to increase future media coverage and encourage a more engaged discourse on demand-side mitigation.
Exploring Flexitarianism
Authors: Dagevos Hans
Published: October 2015

Broad scholarly consensus exists nowadays that high meat consumption is particularly critical from an ecological perspective. Traditionally, technological progress and efficiency innovations in food supply processes are identified as key to solving food sustainability problems. However, it is increasingly recognised that technological innovation and efficiency gains alone are not enough to reduce the environmental impacts of growing meat production and consumption. Therefore, this chapter's point of view is consumption-oriented. Are consumers part of the solution by making transitions towards more sustainable consumption patterns in general and less meat-centric diets specifically? This chapter explores flexitarianism as a present-day food style that consists of different forms or levels, ranging from minor adjustments to regular meat consumption patterns to fundamental departure from habitual meat eating practices.
Prediction of User Interests for Providing Relevant Information Using Relevance Feedback and Re-ranking
Authors: Ramesh L. Sai , Ganapathy S. , Bhuvaneshwari R. , Kulothungan K. , Pandiyaraju V. , Kannan A.
Published: October 2015

Predicting user interest based on their browsing pattern is useful in relevant information retrieval. In such a scenario, queries must be unambiguous and precise. For a broad-topic and ambiguous query, different users may with different interests may search for information from the internet. The inference and analysis of user search goals using rules will be helpful to enhance the relevancy and user experience. A major deficiency of generic search system is that they have static model which is to be applied for all the users and hence are not adaptable to individual users. User interest is important when performing clustering so that it is possible to enhance the personalization. In this paper, a new approach is proposed to infer user interests based on their queries and fast profile logs and to provide relevant information to users based on personalization. For this purpose, a framework is designed to analyze different user profiles and interests while query processing including relevance analysis. Implicit Feedback sessions are also constructed from user profiles based on mouse and button clicks made in their current and past queries. In addition, browsing behaviors of users are analyzed using rules and also using the feedback sessions. Temporary documents are generated in this work for representing the feedback sessions effectively. Finally, personalization is made based on browsing behavior and relevant information is provided to the users. From the experiments conducted in this work, it is observed that the proposed model provide most accurate and relevant contents to the users when compared with other related work.
A Pagerank-Inspired Heuristic Scheme for Influence Maximization in Social Networks
Authors: Zhang Bo , Wang Yufeng , Jin Qun , Ma Jianhua
Published: October 2015

This article focused on seeking a new heuristic algorithm for the influence maximization problem in complex social networks, in which a small subset of individuals are intentionally selected as seeds to trigger a large cascade of further adoptions of a new behavior under certain influence cascade models. In literature, degree and other centrality-based heuristics are commonly used to estimate the influential power of individuals in social networks. The major issues with degree-based heuristics are twofold. First, those results are only derived for the uniform IC model, in which propagation probabilities on all social links are set as same, which is rarely the case in reality; Second, intuitively, an individual's influence power depends not only on the number of direct friends, but also relates to kinds of those friends, that is, the neighbors' influence should also be taken into account when measuring one's influential power. Based on the general weighted cascade model (WC), this article proposes Pagerank-inspired heuristic scheme, PRDiscount, which explicitly discounts the influence power of those individuals who have social relationships with chosen seeds, to alleviate the “overlapping effect” occurred in behavior diffusion. Then, the authors use both the artificially constructed social network graphs (with the features of power-law degree distribution and small-world characteristics) and the real-data traces of social networks to verify the performance of their proposal. Simulations illustrate that PRDiscount can advantage over the existing degree-based discount algorithm, DegreeDiscount, and achieve the comparable performance as greedy algorithm.
Analysis of the Oxygen-Containing Organic Substances of Natural Water Using Solid Phase Extraction of Distillates
Authors: Khasanov Victor , Slizhov Yuri , Makarycheva Alexandra , Chumakov Anton
Published: October 2015

Analysis of organic acids in natural water samples using by the distillation followed by the SPE procedure at Strata-X and GC-MS of trimethylsilane derivatives. Influence of distillation and elution, as well as a cartridge housing material, on the compounds recovery was discussed. Data on organic acids in some natural samples are provided.
Spectral Analysis of Hair to Determine the Elemental Status of Human
Authors: Otmakhov Vladimir I. , Kataeva Nadegda G. , Kuskova Irina S. , Petrova Elena V. , Shilova Inessa V.
Published: October 2015

The article presents the data on development of methods for spectral analysis of human biological substrates in order to determine and restore its elemental balance. The developed method of mass concentration measurement of elements in human biological substrates (hair) by the method of arc atomic emission spectrometry using multichannel analyzer of emission spectra has been submitted for inclusion in the Federal register of RF techniques. By this technique we examined the concentration of macro- and microelements in the hair of 63 patients with ischemic stroke accompanied by depressive disorders (group 1) and post-stroke cognitive impairment (group 2) received in the order of emergency medical care in hospitals. There has been determined the increase of the upper limits of physiological norm of Co, Cd and Al in comparison with the reference values for both groups. In the second group of patients significantly higher content of Cr, Fe, Cd, Pb, Cu, Mn is observed. It is shown the necessity of introduction of new treatment protocols for stroke patients, including macro - and micronutrients to start pharmacological correction treatment as soon as possible.
Luminescent Materials on the Basis of Yttrium Oxide and Yttrium Aluminum Garnet Used for Photodynamic Therapy
Authors: Bakhmetyev Vadim V. , Lebedev Lev A. , Vlasenko Anna B. , Bogdanov Sergey P. , Sovestnov Alexander E. , Minakova Tamara S. , Minakova Ludmila Yu. , Sychov Maxim М.
Published: October 2015

Finely-dispersed phosphors of Y2O3:Eu and Y3Al5O12:Eu have been synthesized with the help of Pechini method and the method of self-propagating high-temperature synthesis (SHS). During the synthesis of phosphors on the basis of Y2O3 carried out with Pechini method the size of crystallites increases with the enlargement of concentration of yttrium, but it decreases when the method of SHS is applied. The structure of phosphors on the basis of Y3Al5O12 (YAG) is strongly amorphized. This fact agrees with the data of XRD and with the prevalence of the band with λmax = 613 nm in the spectra of this phosphor. The enlargement of yttrium concentration in it promotes the amorphisation of yttrium aluminum garnet and the decrease of a crystal phase content. The sample of Y3Al5O12:Eu synthesized with Pechini method has the maximum intensity, while in conditions of excitement with “high-level” X-ray radiation which corresponds to the radiation of industrial medical X-ray apparatus, the phosphor of Y2O3:Eu synthesized with the help of SHS showed the largest intensity. Colloid solutions prepared with the use of the samples synthesized by SHS method revealed a higher steadiness and a lower disposition to the sedimentation process. The samples of Y2O3:Eu phosphor possessing the smallest size of particles and the highest intensity of X-ray luminescence are the most suitable for the creation of pharmacological drugs used for photodynamic therapy.
Structure and Friction Behavior of UHMWPE/Inorganic Nanoparticles
Authors: Okhlopkova Aytalina A. , Borisova Raisa V. , Okhlopkova Tatyana A. , Nikiforov Leonid A.
Published: October 2015

We investigated tribological properties and worn surfaces morphology of polymer nanocomposite (PNCs) based on ultrahigh-molecular-weight polyethylene and aluminum and silicon oxide and nitride nanoparticle (NP) fillers by several methods to establish wear mechanisms. Joint mechanical activation in a planetary mill was used for the PNC preparation. PNCs with Al2O3 showed the best wear resistance. Scanning electron microscopy suggests that worn surfaces of PNCs with different fillers had different wear mechanisms. IR-spectroscopy and EDS analysis showed that oxidation processes occurred during friction and wear. Oxides of aluminum and silicon might be catalysts of oxidation processes. Due to tribochemical processes, cross-linked structures were formed on the PNCs surfaces. Probably, these cross-linked structures provide increase of wear resistance.
Prediction of Microelectronics Thermal Behavior in Electronic Equipment: Status, Challenges and Future Requirements
Authors: Rodgers Peter
Published: October 2015

Developing virtual perfonnance- and reliability predictive techniques has become essential for the development of (micro)electronic systems. This paper provides an overview of current predictive methodologies, challenges and requirements for the modeling of microelectronics thennal behavior. Critical modeling issues are discussed, from optimizing Integrated Circuit (IC) packaging thennal perfonnance to predicting operational temperature in application environments. A systematic assessment of numerical predictive accuracy for board-mounted electronic component heat transfer is presented. From this evaluation, perspective is given on the current capabilities of Computational Fluids Dynamics (CFD) as a design tool to predict component operational temperature in electronic systems. Potential development areas are discussed for improved analysis.
Board Via Effect On Thermal Performance Of A Leadless Package
Authors: Pape Heinz , Schiller Kay , Kutscherauer Rudolf
Published: October 2015

The thermal resistance “junction-to-ambient” θJA of a leadless plastic package P-VQFN-24 on a 4-layer (2s2p) PCB according to standard JESD51-7 was calculated using the FE code ANSYS® and measured using samples with thermal test dies. Measurements were done for chip sizes of 1.6mm2 and 3.2mm2, calculations for several die sizes to cover the possible range of this package from 0.5–4.2mm2. Package mounting on two different PCB types was investigated: one has an insulating solder resist layer in the area below the exposed die pad of the package, the other has Cu-lands for die pad soldering and 4 thermal vias for heat conduction to a buried Cu-ground layer. With this mounting condition, θJA can be reduced from 88 to 46 K/W and from 80 to 43 K/W for the small and the larger die, respectively. However with the die pad soldered to the PCB also 3 of 14 samples showed a θJA of about 60K/W in measurements. If these samples where omitted, measurement and simulation agreed within 6% or better. To clarify the cause of the bad thermal performance of some samples, an analysis using Acoustic Scanning Microscopy (SAM), X-ray photography and finally cross-sectioning was done. Die attach and solder quality was found to be good. The reason for bad thermal performance was the thermal via quality. The metal wall thickness in a via hole always steadily decreased with depth, in some vias of bad samples even to zero before contacting the buried ground plane. In that case a thermal via has no effect any more. Besides presenting thermal data of the VQFN-24 package, the work also shows the strong influence of PCB mounting details on the thermal performance of packages with exposed die pad.
Epoxies for OptoElectronic Packaging; Applications and Material Properties
Authors: Hodgin Michael J.
Published: October 2015

Epoxies are used in the packaging and assembly of three opto-electronic devices, including Fiber Optics, LEDs, and LCDss. In fiber optics, you need epoxy for the cable and for the opto-packaging. The fiber optic components are usually packaged in hybrid technology, which mean several micro-electronic grade joining materials will be used. For LEDs, the silver epoxy is needed for both electrical and thermal properties. Optically clear epoxy is used for the potting, molding, or encapsulation of the LED. In LCDs, there are many different applications of epoxy of which 2 are presented. These include silver filled for interconnecting the ITO conductive layers to the circuitry on the substrate, while the second is the optical epoxy for making the glass sandwhich. This paper will discuss the epoxies which are used, the key design attributes which make them ideal, and the processing of them for assembly and manufacture. Analytical techniques for characterization and optimization of the epoxy properties will be discussed. Material properties such as Tg, outgassing, thermal conductivity, thermal resistance, hermeticity, strength, and fluorescence will be the focal point of the discussion.
Planarization and Dielectric Properties of Thin Photosensitive and Nonphotosensitive BCB
Authors: Dusch Brian , Kohl Paul A.
Published: October 2015

Thin films (0.2 μm to 1.8 μm) of photosensitive and nonphotosensitive BCB were fabricated and the degree of planarization (DOP) and dielectric properties were investigated. It was found that a high DOP for wide spaces (>20 μm spaces with 1 μm of BCB) was possible with nonphotosensitive BCB but not photosensitive BCB because of the cross-linking reaction during the photo-process. Thin films (as thin as 0.2 μm) exhibited dielectric properties similar to thick films. The dielectric properties of the photosensitive BCB were slightly higher than nonphotosensitive BCB. Low loss properties were observed at all thickness.
Immersion Cooling of Vertically Mounted Plastic Packages Using Various Flourinert Liquids
Authors: Bharatham Logendran , Quadir G. A. , Hassan A. Y. , Seetharamu K.N.
Published: October 2015

Liquid immersion cooling offers an alternative means to counter the high amount of heat dissipated by electronic packages. This study focuses on conjugate heat transfer analysis of a double PLCC packages mounted on a vertical PCB cooled by different Flourinert liquids such as FC 77, FC 3283, FC 43 and FC 70 with the aid of a CFD software. The effects of package power, flow velocity and the use of different types of dielectric liquids on the performance of the above PLCC packages are investigated. A comparison with air-cooled cases clearly indicates that a very much lower surface temperature exists on the operating packages in the case of dielectric liquids. For the convenience of application in the electronic industry, the results are presented in the form of correlations for junction temperature for each package.
Analysis of Capacitive and Inductive Coupling inside Hybrid Integrated Power Electronic Module
Authors: Zeng Xiang-jun , Yang Xu , Xi'an Zhao-an Wang
Published: October 2015

Electromagnetic compatibility has to be given enough attention in the design of hybrid Integrated Power Electronic Module (IPEM) due to the sharply decreased distances between power devices and the control/driving circuits as compared to such distances for conventional power electronic equipment built with discrete devices. The high dν/dt, di/dt and high frequency parasitic ringing emanating from the switching circuit can cause serious EMI within the control/driving circuit due to cross-coupling. This paper analyzes the capacitive and inductive cross-coupling problems inside an IPEM. Finite Element Method (FEM) is used to extract the mutual capacitances between the metal bars in the model. Then the influence of dν/dt can be estimated. The high frequency circulating current in the bridge circuits is also investigated since it causes magnetic interference due to mutual inductance coupling. The mutual inductance is calculated with the simplified Partial Element Equivalent Circuit (PEEC) approach and image method. The experiment validates the effectiveness of this evaluation. In the end, the electromagnetic shielding is discussed.
A Tenfold Reduction in Interface Thermal Resistance for Heat Sink Mounting
Authors: Van Heerden D. , Rude T.R. , Newson J. , He J. , Besnoin E. , Knio O.M. , Weihs T.P.
Published: October 2015

Reactive NanoTechnologies (RNT) has developed a new platform joining technology that can form a metallic bond between a chip package and a heat sink and thereby offer a thermal interface resistance that is up to ten times lower than current thermal interface materials (TIM). The joining process is based on the use of reactive multilayer foils as local heat sources. The foils are a new class of nano-engineered materials, in which self-propagating exothermic reactions can be initiated at room temperature with a hot filament or laser. By inserting a multilayer foil between two solder layers and a chip package and heat sink, energy generated by a chemical reaction in the foil heats the solder to melting and consequently bonds the components. The joining process can be completed in air, argon or vacuum in approximately one second. The resulting metallic joints exhibit thermal resistances up to an order of magnitude lower, than current commercial TIMs. We also demonstrate, using numerical modeling, that the thermal exposure of microelectronic packages during joining is very limited. Finally we show numerically that reactive joining can be used to solder Si dies directly to heat sinks without thermally damaging the chip.
Mechanical Reinforcement for Sphere Attach Applications
Authors: Brown Maureen , Jung Richard , Liu Jin , Stipp John , Fattahian Amir , Shashipadme Sandy
Published: October 2015

A novel sphere attach material for BGA and CSP packages was developed that streamlines attach process and enhances the mechanical properties of the interconnect. This enabling technology is based on a multi-functional No Clean Polymer Flux (NPF) that is a drop-in replacement for water washable assembly processes or no clean tacky soldering fluxes (TSF) and offers the added benefit of providing a polymer collar at the base of the soldered joint. The residues from the NPFs are unaffected by subsequent assembly processes due to their cross-linked polymeric properties. A multi-phased design of experiments approach was used to develop, validate, and optimize the material and process parameters to increase ball shear by more than 35% when compared to commercially available No Clean TSFs as a result of the structurally supportive polymer collar. Enhanced interfacial integrity by complete wetting of the sphere to oxidized copper was confirmed. NPF technology provides a novel, economical and easily implemented solution to sphere attach applications.
New Trim Configurations for Laser Trimmed Thick-Film Resistors – Experimental Verification
Authors: Kaminski Slawomir , Mis Edward , Szymendera Maciej , Dziedzic Andrzej
Published: October 2015

Laser trimming is the most effective and popular trimming method of thick-film and LTCC resistors at present. It is also still a subject of continuing theoretical and experimental analysis and optimization. Very recently a new approach to this process was suggested. It consists in replacing two-contact bar resistors by three-contact distributed structures trimmed by narrow cuts just around additional contact of different shape [1,2]. This paper presents experimental verification of such an approach. The relative trim characteristic and sensitivity are analyzed as a function of additional contact shape and cut length. Next long-term stability, pulse durability and low frequency noise are compared for two- and three-contact resistors versus trim pathway length. These investigations are completed by simulation of electrical potential distribution in two- and three-contact resistors with various length of trimming kerf.
Investigation of Steady State and Transient Thermal Management in Portable Telecommunication Product – Part 1
Authors: Yee Cheang Soon , Seetharamu K.N. , Quadir G.A. , Zainal Z.A.
Published: October 2015

Steady state and transient thermal management in a portable telecommunication product was investigated. The steady state analysis portion will be discussed in details in Part 1. The investigation was conducted using finite element analysis (FEA) simulation on a cellular phone model. The three-dimensional simulation is based on a solid conduction cellular phone model cooled by natural convection and radiation. The FEA simulation method was verified with experimental results. In this paper, simulation study was carried out to examine various thermal solution options to improve on the heat transfer from the package to the surrounding. As conduction is the predominant heat transfer within the cellular phone, the thermal resistance can be reduced by creating a solid conduction path between the heat dissipating packages with the housing wall and improving the housing wall conduction material.
A New Method of Determining the Thermal Resistance of Microelectronic Packages
Authors: Teoh King-Long , Seetharamu K.N. , Hassan Ahmad Yusoff
Published: October 2015

A critical literature review on the determination of thermal resistance in a package is presented. Finite element simulation of three types of packages, namely, Leadless Chip Carrier (LCC), Bump Chip Carrier (BCC) and Plastic Ball Grid Array (PBGA) as representative of the packages used in the electronic industry, is carried out both at package level and board level separately. Based on the results obtained from 204 simulations, a new methodology of determining the junction temperature even in cases where the specification of the board is not known a priori is developed. The prediction of the junction temperature from the new methodology agrees well with the results of the package and the board simulated simultaneously. The junction temperature obtained by simulation agrees well with experimental data or literature value. A methodology is presented to transform the results for a JEDEC standard board to a non-JEDEC standard board. The coefficient of performance of a non-JEDEC standard board has been introduced and evaluated. The effect of junction temperature in a given package on the reliability has been investigated. Some cases where components failed due to temperature effect are presented.
Low Temperature Rapid Curing of Polymer Dielectrics on Metallized Organic Laminates by Variable Frequency Microwave Processing
Authors: Sung Taehyun , Bidstrup Allen Sue A. , Kohl Paul A.
Published: October 2015

The curing of polymer dielectrics on organic laminates by variable frequency microwave (VFM) processing was studied. Polymer dielectrics, such as polyimides, normally require long cure times at elevated temperatures resulting in processing incompatibility with epoxy-based laminates due to the low thermal stability of the organic laminates. In this study, VFM processing was investigated as an alternative, low temperature technique for curing polyimide and benzycyclobutene (BCB) on metallized bismaleimide triazine/epoxy (BT) board. The VFM heating characteristics of the metallized (BT) boards were studied. The VFM heating rates of the BT boards strongly depended on the configuration, size, and shape of the copper patterns on the boards. The VFM curing of polyimide and BCB on the metallized BT boards was also performed. The curing condition was optimized to minimize board degradation. At the same board degradation level, the chemical, thermo-mechanical and electrical properties of the VFM cured film were compared with a film thermally cured using a conventional convection furnace. A higher degree of curing and lower dielectric constant was achieved for benzocyclobutene (BCB) films on BT boards processed using VFM curing than was obtained using conventional curing. VFM cured polyimide (PI 2611) showed a similar degree of curing and Young's modulus to conventionally cured PI 2611. However, the VFM cured PI 2611 showed a higher residual content solvent and a higher dielectric constant than conventionally cured PI 2611.
Thermal Design Optimization of Optoelectronic Package
Authors: Karim N. Aizar A. , Narayana P.A. Aswatha , Seetharamu K.N.
Published: October 2015

To drive light-emitting diodes (LEDs) at high power, the construction of the LED has to be thermally efficient to ensure good optical and reliability performance. A shorter design cycle can be achieved through a fast and accurate modeling prior to prototyping. In this paper, a surface mount (SMT) LED was modeled using a commercial computational fluid dynamics code. The simulation was done based on Joint Electron Device Engineering Council's (JEDEC's) thermal resistance measurement set-up and the model was validated using actual samples. Thermal resistance between junction to pin and between junction to ambient of LED packages were measured using a thermal resistance tester in compliance with the Electronic Industries Association/JEDEC Standard (EIA/JESD) measurement method. A series of sensitivity analyses were done based on the validated simulation and considering key design features. Effect of die-attach material at different bond line thicknesses (BLT) and adding heat spreaders having different sizes were analyzed. Applying a combination of key sensitivity analyses results, the junction to pin thermal resistance of the redesigned LED was reduced by 42%.
Reliability of anisotropic conductive joints for bumpless flip-chip on flex packages under thermal stresses
Authors: Ali Lafir , Chan Y. C. , Alam M.O.
Published: October 2015

The reliability of ACF (Anisotropic conductive film) interconnection is a serious concern especially under thermal loading condition. This paper focuses on the online contact resistance behavior of the ACF joint for bumpless flip-chip on flex packages during different thermal cycling conditions. In this work, flip chips of 11×3 mm2 having bare aluminum pad were used. Real time contact resistance (i.e. live measurement contact resistance variation with temperature) was measured by four points probe method when the packages were inside thermal shock chamber.

Tests for three different thermal cycling profiles (125°C to −55°C, 140°C to −40°C and 150°C to −65°C) were carried out. The samples bonded at temperature 180°C and pressure of 2.42Mpa was used. The initial contact resistance of the bumpless samples was 0.4Ω. Contact resistance increased with the number of thermal cycles, however the effect was severe when the temperature variation was above the glass transition temperature (Tg) of the ACF matrix (131°C). Differences in co-efficient of thermal expansion (CTE) between the chip and the substrate generated thermal stresses during temperature fluctuation, which caused the pad of the substrate to slide over the Al pad of the chip. Thus variation of the contact resistance was also observed along the interconnection position in the package, i.e. corner joint showed higher value of increase in contact resistance than the middle position. Even though flex substrate was used in this study; the sliding effect was severe at the corner Al pads of the chip, where cumulative forces generated due to the thermal stress. Results show that for thermal cycling profile 140°C to −40°C, online contact resistance increased to 1.2 Ω in corner joint, whereas for the middle joints the contact resistance just increased to 0.5 Ω. Glass transition temperature (Tg) of the ACF material plays an important role on the high temperature contact resistance. For every thermal cycling profile, there is an incubation period that would have significant impact in the application of ACF. After the incubation period the contact resistance increases rapidly and the joints are no longer reliable.
Development of Biocompatible MEMS Wireless Capacitive Pressure Sensor
Authors: Janardhanan Shankaran , Delalic Joan. Z. , Catchmark Jeffrey , Saini Dharanipal
Published: October 2015

The objective of this research was to develop a wireless pressure sensor useful for monitoring bladder pressure. The wireless sensor consists of an active capacitive element and an inductor coil. The changes in pressure are related to the changes in the resonant frequency of the internal sensor. The existing pressure sensors have inductors formed on both sides of the substrate. The changes in internal capacitance of these sensors are related to the changes in pressure by impedance matching of the internal LC circuit. The deviation in bladder pressure is an important variable in evaluating the diseased state of the bladder. The inductor designed for this application is a spirally wound inductor fabricated adjacent to the capacitor. The external sensing uses equivalent changes in internal LC. The resonant frequency of the internal sensor is defined by the deformation of the plate, causing the plate to touch the dielectric on the fixed capacitive plate, which is reflected as changes in capacitance(C). The deformation of the plate has been modeled using Finite Element Analysis. The finite element analysis optimizes the dimensions of the design. Remote sensing is achieved through inductive coupling and the changes in pressure are determined. The device is tested for pressures ranging from 0–150 mmHg, bladder pressure. The RF Telemetry system has been modeled using Sonnet. The frequency range is between 100–670 MHz which is in compliance to that specified by Federal Communications Commission (FCC) regulations.
Acceleration Factor to relate Thermal Cycles to Power Cycles for Ceramic Ball Grid Area Array Packages
Authors: Perkins Andy , Tunga Krishna , Sitaraman Suresh
Published: October 2015

There is a need for a new Acceleration Factor (AF) that can relate Accelerated Thermal Cycle (ATC) fatigue life to Power Cycle (PC) fatigue life quickly and accurately in order to avoid over designing electronic packages for benign environments. An AF, such as the Norris-Landzberg AF, is only applicable when using it to predict fatigue life within the same environment, i.e. ATC to ATC or PC to PC. This work proposes an AF that takes into account the differences between ATC tests and PC tests for ceramic ball grid array (CBGA) packages by considering relevant design and environmental parameters.

The new AF is based on relevant design parameters such as substrate size, substrate thermal conductivity, substrate thickness, coefficient of thermal (CTE) mismatch between the substrate and printed wiring board (PWB), PWB thickness, and environmental parameters such as temperature range (ΔT), frequency of cycles (f), and peak/junction temperature (Tj). Finite Element Models (FEM), experimental data, laser moiré interferometry, Design of Simulation (DOS), ANOVA, and regression analysis are used to develop the new AF. The new AF can be used to more accurately assess PC fatigue life from ATC tests so that expensive over-designing of electronic packages can be avoided for desktop/server/laptop applications.
Fatigue Assessment of Solder Bumps on Board Assemblies Affected by PWB Warpage
Authors: Tan Wei , Ume I. Charles
Published: October 2015

Out-of-plane displacement (warpage) has been a major reliability concern for board-level electronic packaging. Printed wiring board (PWB) and component warpage results from CTE mismatch among the materials that make up the PWB assembly (PWBA). Warpage occurring during surface-mount assembly processes and normal operations may lead to severe solder bump failures. In this research, the effect of PWB warpage on the low cycle fatigue of the solder bumps in plastic ball grid array (PBGA) packages was studied. Finite element modeling (FEM) was used for the strain-based life prediction of solder bumps on board assemblies. In this paper, 3-D models of PWBAs with varying board warpage were used to estimate the solder bump fatigue life for different types of PBGAs mounted on PWBs. In order to improve the accuracy of FE results, the projection moiré method was used to measure the initial warpage of PWBs, and this warpage was used as a geometric input to the FEM. The PWBAs with known PWB warpage were modeled to determine the influence of various levels of initial PWB warpage on the low cycle fatigue failure of solder bumps. The effect of different types of PBGAs with varying locations on solder bump fatigue was studied. Both Sn-Pb and lead-free solder materials were used in this study. The FE models were validated with experimental results obtained using the projection moiré technique. The FE results showed that the initial PWB warpage has significant a effect on the fatigue reliability of solder bumps in PBGA packages.
Development and Manufacture of a Linear 16-Pixel FIR Array—The PACS Module
Authors: Richter Hilmar H. , Harr Michael , Dinges Peter , Krüger Heribert , Todisco Alexandra , Zimmermann Bernd
Published: October 2015

The high- and low-stressed photodetector array camera and spectrometer (PACS) modules (linear 16-pixel arrays) are the basic constituents of the 16 × 25 pixel far-infrared (57–220 μm) PACS cameras aboard the Herschel satellite. The essentials for the stress application and the pixel stacking technique originate from detectors aboard the Infrared Space Observatory (ISO, 1995–1998) and for the field imaging far infrared line spectrometer (FIFI-LS) aboard the Stratospheric Observatory for Infrared Astronomy (SOFIA). To meet the mass budget of the cameras and provide the required high tensile strength, the only usable material for the module body turned out to be an aluminum alloy (AL 7075 T651). Especially challenging was the tight thermal budget for the PACS modules. Compared to FIFI-LS, in the case of the PACS module the heat dissipation from the front end electronics (FEE) and harness substrates at about 4 K to the module body containing the pixel stack at about 2 K had to be reduced drastically. A genuine suspension concept and packaging for the respective substrates was developed and successfully applied, allowing reliable electrical wiring from the harness over the FEE on to the pixels. The FEE with the cryogenic readout electronics (CRE) is contributed by the Interuniversity Microelectronics Centre (IMEC).
Design and Implementation of Baluns at 60 GHz on LTCC
Authors: Rentsch Sven , Müller Jens
Published: October 2015

Passive structures for working frequencies at 60 GHz open up new dimensions for wireless broadband applications. The bandwidth available allows even faster data transfer. Thanks to the technology development and RF characterization of low-sintering glass-ceramics, 3D structures and low-cost production will be achievable. A detailed description of the design and the manufacturing of planar galvanically coupled and planar field coupled passive baluns, such as Marchand baluns, is given in this paper. Baluns are mostly built up with partly lumped elements, which are realized as embedded passives. This is currently not possible at the 60-GHz–range in thick-film technology. Electromagnetic 3D FEM simulations are therefore carried out in order to optimize and analyze baluns at 60 GHz. Several types of baluns were produced in low-temperature co-fired ceramic (LTCC). Due to the required pattern resolution (line width, 60 μm; minimum gap, 40 μm) a fine-line screen printing process as well as micro via punching (70 μm) are necessary. Printing tolerances and process-related dimensional stability are evaluated. In addition, material properties, such as permittivity, are investigated up to 67 GHz. With the help of asymmetrical test equipment, cascaded baluns in series are characterized. A symmetrical MMIC amplifier was mounted via flip-chip in order to demonstrate its performance in real applications. Gold-stud-bumping is used for this purpose. The stud bumps, which are 60 μm in diameter, were placed in a pitch of 100 μm.
Development of Reliability Allocation and Assessment Algorithms for Designing Multilevel Microelectronic Systems
Authors: Kim Injoong , Pucha Raghuram V. , Peak Russell S. , Sitaraman Suresh K.
Published: October 2015

Design-for-reliability of complex systems involves top-down reliability allocation approaches, reliability prediction of both random and wear-out failures, and bottom-up reliability assessment approaches to provide more insight into the system-level reliability.

Designing complex microelectronic systems, while considering reliability in the early design stages, is a challenge because these systems have multilevel structure and logical groups, and numerous components are associated with failure modes and mechanisms. To address these difficulties and to design reliable systems in a systematic way, reliability allocation and reliability assessment algorithms and associated reliability predictions methodologies are presented in this paper in the context of a System-Design-for-Reliability (SDfR) framework. Reliability allocation algorithms are presented for both parallel and series systems that calculate the target reliability of subsystems from the given target reliability of their parent systems. The reliability allocation algorithm is demonstrated for random failures in a video broadcasting system that consists of a four-level packaging structure. The reliability assessment algorithm is demonstrated for wear-out failures in a USB board system that consists of multiple logical groups and various failure modes and mechanisms. The reliability assessment algorithms also demonstrate the use of physics-based reliability prediction of each logical group before assessing the system reliability. The demonstrated results show that the algorithms are useful for determining system configurations and design parameters. Such design changes will reduce the burden of downstream reliability activities.
Packaging MEMS Die on E-Glass Substrates
Authors: Black M. , Boyett H. , Sanders N. , Weller J. , Dean R. , Johnson R.W. , Kranz M.
Published: October 2015

Packaging MEMS devices is challenging, especially when the MEMS device is a sensor that requires direct exposure to and simultaneous protection from the operating environment. Because E-glass PCB laminate (FR4) is often used as a substrate for electronic components, a technique for directly integrating MEMS devices onto these substrates at the die level would be useful. This has been accomplished by attaching a bare die HMX2000 MEMS humidity sensor to an FR-4 carrier by forming a Au–Sn eutectic bond between the Au stud bumped die and tin–silver coated landings on the carrier. Prototype devices were then integrated with other electronics and environmentally evaluated. Test results indicated that this packaging technique was reliable.
Reflection by Embedded Copper Plane and Volumetric Heating in Laser Microvia Drilling
Authors: Zhang Chong , Salama Islam A. , Li Yonggang , Quick Nathaniel R. , Kar Aravinda
Published: October 2015

A finite difference thermal model is developed to analyze volumetric heating during laser drilling. The substrates of interest are multilayered polymeric sheets containing an embedded copper plane, which are generally used for high-density microelectronics packaging, and the laser of interest is a CO2 laser of wavelength 9.3 μm. Both the incident laser beam propagating toward the embedded copper plane and the beam reflected upward by the copper plane contribute to the volumetric heating of the substrate, which is the main mechanism for material removal. When the polymer layer above the copper sheet thins down as drilling progresses, the exit of the laser beam from the polymer layer after reflection by the copper sheet and the heat conduction within copper increase the energy loss significantly, making the process energetically inefficient. Consequently, the material-removal capability of the process diminishes, and a very thin polymer layer is left as residue on top of the copper sheet. The thickness of the residue depends mainly on the laser pulse width as predicted by the model. A nanosecond pulsed laser is found to effectively reduce the residue thickness to about 0.1 μm. The reflected laser energy, however, is found to contribute to the drilling process when the thickness of the polymer is higher than the absorption depth.
Multi-Layer Ceramic Packaging for High Frequency Mixed-Signal VLSI ASICS
Authors: Dove Lewis
Published: October 2015

Mixed-signal Application Specific Integrated Circuits (ASICs) have traditionally been used in test and measurement applications for a variety of functions such as data converters, pin electronics circuitry, drivers, and receivers. Over the past several years, the complexity, power density, and bandwidth of these chips has increased dramatically. This has necessitated dramatic changes in the way these chips have been packaged. As the chips have become true VLSI (Very Large Scale Integration) ICs, the number of I/Os have become too large to interconnect with wire bonds. Thus, it has become necessary to utilize flip chip interconnects. Also, the bandwidth of the high-speed signal paths and clocks has increased into the multi Gbit or GHz ranges. This requires the use of packages with good high-frequency performance which are designed using microwave circuit techniques to optimize signal integrity and to minimize signal crosstalk and noise.