bluuebunny/crossref_metadata_2025 huggingface dataset:
Auditeurs des états financiers, attention !
Authors: Morin Danielle
Published: October 2015

Les scandales survenus au début des années 2000 ont montré que la manipulation des états financiers s’est souvent soldée par la constatation hâtive de produits ou par la constatation de produits fictifs. S’y ajoutaient les opérations entre parties liées, les évaluations à la juste valeur, les écritures de journal non standard, les états financiers intermédiaires et la comptabilisation des courus. Certaines de ces pratiques avaient vraisemblablement échappé aux auditeurs des firmes aussi réputées qu’Andersen (notamment pour Enron et Worldcom), KPMG (pour Xerox) et Deloitte et Grant Thornton Italia (pour Parmalat). Quelles leçons les auditeurs des états financiers peuvent-ils en tirer aujourd’hui ?
Travailler en mode collaboratif : pour aller plus loin
Authors: Jacob Réal , Poitras Jean
Published: October 2015

Avant les années 1980, les organisations devaient gérer le changement pour se distinguer. Entre 1980 et 2001, elles ont dû ajouter une nouvelle corde à leur arc : apprendre. Mais voilà qu’aujourd’hui, le monde change tellement vite et devient si complexe, si incertain et si volatil qu’elles doivent maîtriser une toute nouvelle compétence pour survivre : travailler en mode collaboratif. Ainsi, l’innovation, l’efficacité et la productivité passent aussi par la collaboration.
Les neuf piliers du pouvoir et de l’influence
Authors: Lainey Pierre
Published: October 2015

Une bonne idée qu’on n’arrive pas à faire passer... Un dossier stratégique qui stagne... Un changement qui prend du temps à s’opérer... Voilà autant de situations frustrantes et déconcertantes auxquelles les organisations risquent tôt ou tard de se heurter. Pourquoi une idée longuement mûrie et testée ne trouve-t-elle pas écho ? Pourquoi un dossier jugé stratégique n’avance-t-il pas ? Pourquoi le changement, dont on a pourtant démontré le bien-fondé, est-il au point mort ?
L’exploitation intelligente des données : une stratégie payante
Authors: Bellavance François
Published: October 2015

Savez-vous combien pourrait vous rapporter l’exploitation intelligente de vos données ? Ça se calcule. Et quand les calculs sont bons, cette opération peut être très payante. L’ère numérique et l’avènement des mégadonnées peuvent permettre aux entreprises de créer de la valeur et de propulser leur performance vers de nouveaux sommets. Les spécialistes en analyse de données volumineuses l’ont bien compris et savent comment exploiter ces données de manière intelligente. Voici quelques exemples qui illustrent de quelle façon l’analyse des données peut apprendre aux entreprises à innover et à accroître considérablement leur productivité.
Visual Tracking of Box Jellyfish
Authors: Oskarsson Magnus , Kjellberg Tobias , Palmér Tobias , Nilsson Dan-Eric , Åström Kalle
Published: October 2015

In this chapter a system for tracking the motion of box jellyfish Tripedalia cystophora in a special test setup is investigated. The goal is to measure the motor response of the animal given certain visual stimuli. The approach is based on tracking the special sensory structures - the rhopalia - of the box jellyfish from high-speed video sequences. The focus has been on a real-time system with simple building blocks in the system. However, using a combination of simple intensity based detection and model based tracking promising tracking results with up to 95% accuracy are achieved.
Automatic Estimation of Soil Biochar Quantity via Hyperspectral Imaging
Authors: Tong Lei , Zhou Jun , Bai Shahla Hosseini , Xu Chengyuan , Qian Yuntao , Gao Yongsheng , Xu Zhihong
Published: October 2015

Biochar soil amendment is globally recognized as an emerging approach to mitigate CO2 emissions and increase crop yield. Because the durability and changes of biochar may affect its long term functions, it is important to quantify biochar in soil after application. In this chapter, an automatic soil biochar estimation method is proposed by analysis of hyperspectral images captured by cameras that cover both visible and infrared light wavelengths. The soil image is considered as a mixture of soil and biochar signals, and then hyperspectral unmixing methods are applied to estimate the biochar proportion at each pixel. The final percentage of biochar can be calculated by taking the mean of the proportion of hyperspectral pixels. Three different models of unmixing are described in this chapter. Their experimental results are evaluated by polynomial regression and root mean square errors against the ground truth data collected in the environmental labs. The results show that hyperspectral unmixing is a promising method to measure the percentage of biochar in the soil.
An Approach to Design-Based Implementation Research to Inform Development of EdSphere®
Authors: Swartz Carl W. , Hanlon Sean T. , Childress E. Lee , Stenner A. Jackson
Published: October 2015

Fulfilling the promise of educational technology as one mechanism to promote college and career readiness compels educators, researchers, and technologists to pursue innovative lines of collaborative investigations. These lines of mutual inquiry benefit from adopting and adapting principles rooted in design-based implementation research (DBIR) approaches. The purposes of this chapter are to: (a) provide the research foundation on which a personalized learning platform was developed, (b) present the evolution of EdSphere, a personalized learning platform that resulted from a deep and long-term collaboration among classroom teachers, school and district administrators, educational researchers, and technologists, and (c) describe a need for development of innovative technologies that promote college and career readiness among our earliest readers.
Evidence-Centered Concept Map in Computer-Based Assessment of Critical Thinking
Authors: Rosen Yigal , Mosharraf Maryam
Published: October 2015

A concept map is a graphical tool for representing knowledge structure in the form of a graph whose nodes represent concepts, while arcs between nodes correspond to interrelations between them. Using a concept map engages students in a variety of critical and complex thinking, such as evaluating, analyzing, and decision making. Although the potential use of concept maps to assess students' knowledge has been recognized, concept maps are traditionally used as instructional tools. The chapter introduces a technology-enabled three-phase Evidence-Centered Concept Map (ECCM) designed to make students' thinking visible in critical thinking assessment tasks that require students to analyze claims and supporting evidence on a topic and to draw conclusions. Directions for future research are discussed in terms of their implications to technology tools in large-scale assessment programs that target higher-order thinking skills.
Assessment of Task Persistence
Authors: DiCerbo Kristen E.
Published: October 2015

Task persistence is defined as the continuation of activity in the face of difficulty, obstacles, and/or failure. It has been linked to educational achievement, educational attainment, and occupation outcomes. A number of different psychological approaches attempt to explain individual and situational differences in persistence and there is mounting evidence that interventions can be implemented to increase persistence. New technological capabilities offer the opportunity to seamlessly gather evidence about persistence from individuals' interactions in digital environments. Two examples of assessment of persistence in digital games are presented. Both demonstrate the ability to gather information without interruption of activity and the use of in-game actions as evidence. They also both require consideration of the student/player model, task model, and evidence models. A design pattern outlining each of these elements is presented for use by those considering assessment of persistence in digital environments.
Mentoring Girls in Science
Authors: Farland-Smith Donna
Published: October 2015

Content area specialists (scientists) are often recruited as mentors of students to address issues in science education. These scientists are frequently recruited to help with the teaching of science, however, quite often do not have the pedagogy skills needed to be role models for young children. Guidance in the selection appropriate mentors would help maximize the potential influence on students understanding of who does science, where science is done and what scientists do. This study illustrates six case studies of scientists as they worked with middle school girls and identifies five characteristics educators should look for in selecting science mentors successful in broadening students' perceptions of scientists. The data was collected during ‘Side-by-Side' interaction with scientists/mentors during a summer camp experience and has implications for classroom practice as the use of mentors can be structured to support the infusion of Science as a Human Endeavor. As the students' experiences with mentor scientists helped to shape their perception of those who pursue careers in science and what it is that scientists do, careful consideration and preparation of mentors were critical to the success of the program, and so this paper also provides suggestions to help highly trained and highly educated scientists in these mentorship roles.
Meat Production and Consumption
Authors: Brügger Paula , Marinova Dora , Raphaely Talia
Published: October 2015

This chapter presents the results of studies that unveil how meat and other animal derived products are causing severe environmental impacts, social problems and ethical concerns regarding both human and non-human animals. Although there are many ways to tackle the issue a critical non-anthropocentric education that encompasses ethics as a dimension of sustainability, is proposed. Traditional non environmental education often legitimizes values that are averse to an ethic that could be described as correct regarding the relationship between humans and the other animal species and even many educational currents that call themselves “environmental” are guided by a shallow conservationist point of view. Although welfarist practices may in some contexts be of help, the authors propose the animal abolitionist perspective as the unique genuine foundation for education to build this new paradigm.
Ion-Exchange Removal of Fe(III) and Mg(II) in the Analysis of Rare Earth Elements in Rocks by Inductively Coupled Plasma Mass Spectrometry
Authors: Skvortsova Lidiya N. , Podprugin Aleksey S. , Otmakhov Vladimir I.
Published: October 2015

Tiron has been proposed for the removal of Fe (III) and Mg (II) ions from the test solution by ion exchange in the REE trace analysis in rocks by ICP-MS. The conditions for Fe (III) isolation on a column with anion-exchange resin АВ-17-8,Cl– and for Mg (II) on a column with cation-exchange resin Purolite С100 have been found. The concentration of Fe (III) is reduced up to 10 times, and Mg (II) – more than 100 times. Correction factors have been used in order to eliminate the systematic error in the determination of REE due to their partial sorption on the anion-exchange resin in the form of complexes with Tiron. The correctness and accuracy of the developed sample preparation method and of the correction factors have been confirmed in the analysis of standard samples base on natural geochemical objects.
The Electric Field and Ultrasonic Treatment Casing of Titanium Dioxide
Authors: Smirnova Valentina V. , Ilyin Alexander P. , Brichkov Anton S. , Zabolotskaya Anastasiya V.
Published: October 2015

This article deals with the study of direct current (DC), ultrasonic, and of electrolyte of the influence on the change of titanium dioxide sorption properties. The TiO2 prepared by the TiCl4 hydrolysis method. Attention is drawn to charging exchange processes the surface of titanium dioxide particles after they pass through a layer of counter ions in an aqueous medium under the influence of a DC. The stages of the end product’s formation using methods of the X-ray diffraction, the differential thermal and the infrared spectrometric and the gas adsorption analysis were proposed. Dependence of redistribution sorption active centers at the surface of TiO2 was proved.
Thermal Investigation of GaAs Microwave Power Transistors
Authors: Hanreich G. , Mayer M. , Mündlein M. , Nicolics J.
Published: October 2015

The lower thermal conductivity of gallium arsenide (GaAs) compared to silicon (Si) requires a careful thermal design for optimizing device performance and reliability. In this paper a recently developed thermal simulation tool (TRESCOM II) is applied for investigating the thermal behavior of a heterojunction GaAs power field effect transistor (FET). Main features of the simulation tool are an easy model creation procedure and an efficient numerical solver. Moreover, the tool allows to consider temperature dependent material properties and temperature dependent boundary conditions. The investigation of the thermal behavior of the power transistor has two goals. First goal is to establish the temperature distribution within the active layer of the FET to allow predictions of thermal-electrical interactions. A deeper insight into thermal-electrical interaction will lead to better equivalent circuit models used in electrical circuit design. Due to the fact that reliability of the component is mainly determined by thermal load and induced thermomechanical stress, second goal of this work is to investigate the influence of chip thickness and die bonding variations on the thermal behavior. Thermal response on different power levels is investigated and the influence of chip thickness tolerances and die bonding on the thermal performance of the device is discussed.
Influence Of Solder Joint Shape On The Thermo-Mechanical Reliability Of CSP's
Authors: van Veen Co , Vandevelde Bart , Beyne Eric
Published: October 2015

Not only the stand-off height but also the shape of a solder joint has a strong influence on the joint reliability under temperature cycling. The shape determines the size of the local stress and strain concentrations. It is therefore very important to know well the joint shape after reflow. In a previous paper closed analytical expressions were derived for liquid bump shapes, as a function of pad size and bump height [1]. The bump deformation as a function of the chip weight could be derived from the force constant.

In the present paper closed analytical expressions are derived for the force constant for liquid bumps having unequal spherical pad sizes. It turns out that the force constant for compression can be optimized as a function of the ratio of those pad sizes. The shape of the bump and especially the contact angle is of interest for modeling activities where geometrical effects do play a role. Furthermore from the variation in bumps heights on a chip an estimate can be made of the tilt of the chip after assembly. The solder profile estimation by the analytical expressions is validated by experimental results. Also a comparison with the solder profile estimation by the simulation software Surface Evolver is done. Both comparisons showed that the analytical estimation of the standoff height is very good as long as the gravitation energy contributed by the chip weight is less than 10% of the total energy.

Finally, an example is shown where the analytical model and Surface Evolver are the geometrical input for a finite element model. The example considers a CSP assembled at both sides of the printed circuit board.
Heat Spreading Enhancement in High Power Amplifier Heat Sinks – Comparison of Measurements with Numerical Predictions
Authors: Maguire Luke , Behnia Masud , Morrison Graham
Published: October 2015

A comprehensive study has been undertaken to better understand the thermal conditions within high power, radio frequency (r.f.) signal amplifiers. The majority of the heat generated is dissipated from four high power transistors, mounted directly to a large extruded aluminum heat sink measuring 300mm long × 220mm wide × 72mm high. The transistors each dissipate up to 130W across a footprint of only 1.96cm2 and as such, act as high flux, point heat sources across the heat sink base. At maximum power levels the transistor junction temperatures have been shown to approach the manufacturers rated limit of 200°C [1] when ambient temperatures reach 60°C. The prohibitively high cost of replacing the electronic circuits and cooling air delivery system across the entire transmitter network means that design changes to the heat sink that will reduce device temperatures and can be implemented on a retrofit basis are extremely attractive. Numerical and experimental methods have been used to assess the incorporation of high thermal conductivity materials into the heat sink design to improve cooling performance. Numerical simulation of a copper heat spreader embedded into the base of the existing aluminum heat sink predicted a reduction of transistor junction temperatures of up to 11°C. However, in experiments, a maximum temperature drop of only 5°C was achieved due to the introduction of an additional thermal resistance at the copper/aluminum interface.
Measurements of Thermal Conductivity of Thin Films by Means of Comparative Method
Authors: Achmatowicz Selim , Wyżkiewicz Iwona , Zwierkowska Elżbieta , Łobodziński Wojciech
Published: October 2015

The comparative method has been employed to approximate thermal conductivity of thin layers (10 to 100 μm thick). The method is based on measurement of temperature distribution on the surface of horizontally positioned plate heated in the central spot to a constant temperature in a steady state. The paper contains description of the method, a few examples of conducted measurement and evaluation of the accuracy of the method.
Simulation of Balanced Mold Filling in Transfer Molding for Newtonian Fluids
Authors: Liang Chu Wee , Kulkarni Venkatesh M. , Aswataha Narayana P.A.A. , Seetharamu K.N.
Published: October 2015

This paper presents the study of flow encapsulation processes as carried out in electronic packaging industry. A two dimensional Hele-Shaw model has been adopted to study the flow of Newtonian fluids into cavities at various distances from transfer ram in the transfer molding process. Velocity field obtained from Hele-Shaw is used in pseudo-concentration algorithm for front tracking with an artificial diffusion term added to allow partial slip at the fluid-wall interface and to damp numerical oscillation to a minimum level. Finite Element Method is employed to reduce the governing partial differential equations to algebraic form. Parametric studies have shown that by altering the dimensions and parameters of the mold tool, which will introduce different hydraulic resistances at the runner, gate and cavity, will lead to balanced filling in transfer molding. All the model dimensions or parameters remain constant except the one which is altered accordingly to allow different hydraulic resistances that will effectively enhance the filling and achieve balanced filling.
Spiral Inductors with Multi-Strip Coils Processed on Sapphire and Bulk Silicon Substrates
Authors: Karjalainen Päivi H. , Rapelo Juha , Ristolainen Eero O.
Published: October 2015

Improvements in inductor properties are demonstrated using inductors fabricated by the SOS and CMOS processes. Inductor coils are constructed in the form of several separate strips and the effect of the coil layout on the inductance and quality factor is examined with respect to traditional (“un-slit”) inductors. Optimized multi-strip layout increases the inductance and the quality factor of an inductor. The coil layout has very little influence on the self-resonance frequency of the inductor. Multi-strip layout of the inductor coil increases the coil's series resistance, which in conjunction with the proximity effect causes the critical frequency to increase. The number of slits, the spacing between coils, and the width of the slits are the determining factors for improving the inductor characteristics when using a multi-strip arrangement. The layout produces an improvement especially in the case of SOS inductors. A ladder-type lumped element model for multi-strip inductors is presented. (The words “strip/slit” are equivalent to “track/space” or “line/space”)
Research on Power Electronic Integrated Module for SMPs
Authors: Qiaoliang Chen , Xiangjun Zeng , Xu Yang , Zhaoan Wang
Published: October 2015

A novel structure for a power module used in switching mode power supplies (SMPs) is presented in this paper. The power module employs the three-dimensional terrace structure resulting in lowered parasitic parameters and a higher power density. Based on this structure, the characteristics of the power module, such as parasitic parameters and thermal management performance are evaluated through simulation analysis and experimental research. The measured results for a 1kw prototype demonstrate that the power module based on an aluminum substrate has higher power density, smaller volume and better thermal performance when compared to a module using a conventional structure.
Study of Laser Microdrilling for Applications in Microelectronics and Packaging
Authors: Han Wei , Pryputniewicz Ryszard J.
Published: October 2015

Advances in microelectronics and packaging require new fabrication techniques such as, e.g., laser microdrilling. In laser microdrilling processes, profile of the heat affected zone (HAZ) and the geometry of the holes strongly depend on settings of the laser parameters such as peak power, pulse length, pulse repetition rate, focal condition, etc. In addition, the processing results are strongly influenced by geometry, dimensions, and material properties of the workpiece. Therefore, it is very critical to model and control the profiles of laser drilled microholes in order to obtain desirable results. This paper presents a study of laser process for drilling of micrometer size holes in thin metal flat stock using a pulsed Nd:YAG laser. Analytical and computational modeling of the temperature distribution is performed and can be used to determine profiles of the HAZs. The effects of different laser parameters on the hole geometry are characterized using optical microscope and scanning electron microscope to investigate the geometry of the holes and surface topography in their vicinity, and it was observed that, the laser power density had the most significant influence on the dimensions of the holes, the number of laser pulses drastically affected the cross sectional profiles of the holes, and the laser pulse length should be carefully chosen for each individual thin metal stock to avoid laser-supported absorption (LSA) by the absorbing plasma which results in the lack of through holes by laser microdrilling. The experimental observations provided practical, useful information in laser microdrilling characteristics and can serve as a guideline on the laser parameters required to drill holes in thin metal stock of a required dimension and cross sectional profile.
Screen-Printed Fe2O3/ZnO thick films for gas sensing applications
Authors: Arshak K. , Gaidan I. , Cavanagh L.
Published: October 2015

This paper investigates iron-oxide and zinc-oxide thick-films for gas sensing applications. The films were printed onto glass substrates with silver electrodes. The effects of propanol, methanol and ethanol vapor on the devices at room temperature (in the concentration range 500–2000ppm) were investigated. The percentage relative resistance change, ΔR = ((Rgas − Rair)/Rair) ×100, was seen to increase linearly with increasing gas vapor concentration. The sensitivity of the films to the gas vapor was determined from the slope of the graphs. It was observed that various film compositions showed a higher sensitivity to propanol than to methanol and ethanol. Moreover, the sensitivity to propanol increased from 0.077 to 0.166 to 0.173%/ppm for the three samples with molecular weight composition ratios of: 90%/10%, 80/20% and 70%/30% of Fe2O3 to ZnO respectively. The response times of sensors 1, 2 and 3 (to 1000ppm step changes in propanol concentration) were 48.6 seconds, 86.4 seconds and 76.5 seconds, while the recovery times were 117 seconds, 186 seconds and 153 seconds respectively.
Modeling Thermal Behavior of System-in-Package with Dynamic Compact Model
Authors: Kaija Kimmo , Heino Pekka , Ristolainen Eero O.
Published: October 2015

Integrating more functionality into smaller size increases the heat dissipation density and emphasizes the need for thermal simulations and accurate thermal models. With a compact thermal model (CTM) the dynamic and steady state thermal behavior of a package with several heat dissipating dice can be modeled. The optimization of the model's parameters requires a properly defined cost function. In this paper a two-phase optimization routine was used to find simultaneously good capacitance and resistance values. The accuracy of the model was improved when effective surface areas defined the convections of a CTM. Parameter optimization in time domain, for variable thermal load and nonlinear system, was tested and found accurate, but time consuming.
Advanced Assembly Techniques For Silicon Sensors
Authors: Szczepański Zbigniew , Kalenik Jerzy
Published: October 2015

Some assembly approaches which were carried out with silicon gas sensor and silicon humidity sensor are presented and described in this paper. Some of these sensors were based on silicon 3-D structures with so called “backside contacts” which need special assembly solutions. Flip chip solder and adhesive bonding were used for silicon humidity sensor. Experimental specifications concerning applied assembly solutions and obtained results are presented and described.
Engineering Model for Interfacial Stresses of a Heated Bimaterial Structure with Bond Material Used in Electronic Packages
Authors: Sujan D. , Murthy M. V. V. , Seetharamu K. N. , Hassan A. Y.
Published: October 2015

A model is proposed for the shearing and peeling stresses occurring at the interface of two thin bonded objects as a function of the effect of bond materials at the interface. The existing uniform temperature model proposed by Suhir is upgraded to account for different temperatures of the layers by incorporating a temperature ratio parameter and eventually a correction factor to Suhir's model. Then the model is further upgraded to account for the linear temperature gradients in the layers by incorporating two temperature drop ratios and eventually a second correction factor. This upgraded model can be considered as a generalized one for predicting temperature conditions which may occur in the bonded materials. A simpler method of solution is used to develop this model which does not involve solving integro-differential equations as found in the Suhir's method. The results are presented for the case of die and die attach as commonly found in electronic packaging and are compared to the case where a bond is absent. The results are also compared with those obtained by Finite Element Method (FEM) analysis.
Interfacial Stresses in a Tri-Material Assembly Subjected to Differential Temperatures in the Layers in Electronic Packaging
Authors: Sujan D. , Murthy M. V. V. , Seetharamu K. N. , Hassan A. Y.
Published: October 2015

Schmidt's trimaterial model for shearing stress for uniform temperature is upgraded to account for differential temperatures in the layers. Subsequently a model for peeling stress is proposed from the consideration of moment equilibrium combined with the above mentioned upgraded shear stress model. The results are presented in terms of two parameters m1 and m2, relating the two temperature ratios at die-die attach interface and at die attach-substrate interface respectively. The results are also presented in terms of another two parameters n1 and n2, representing coefficient of thermal expansion ratios between die and die attach materials and die attach and substrate materials respectively. The obtained results can be useful resources in future analysis of trimaterial assemblies for proper design and material selection.
Study of Interfacial Delamination by Considering the Effect of Temperature and Moisture during Solder Reflow for QFN Package
Authors: Wong Fu-Mauh , Seetharamu K.N
Published: October 2015

Experiment has been conducted to measure the solubility Csat of mold compound and to obtain the moisture weight loss curves at various temperature. Moisture desorption modeling has been conducted to calculate the moisture diffusivity for desorption D(T) by matching with the experimental results. Finite Element Analysis (FEA) has also been conducted to calculate the transient development of strain energy release rate (ERR) at the interfacial crack tip due to thermal stress only (Gt), hygrostress only (Gh), and the combined effect (Gtotal) during solder reflow. ERR is computed based on the Virtual Crack Closure Technique (VCCT). It is found that Gh is significantly smaller than Gt, however the effect of hygrostress significantly increases the total strain energy release rate when combined with the thermal effect. The maximum Gtotal occurs at the peak of the solder reflow profile. The effects of crack size and geometrical parameters have been studied. The result imply that the interfacial crack is unstable and has a high tendency of growing to a significant extent. ERR is strongly influenced by the thickness of the package while length between the edge of die and pad has a moderate affect on the ERR.
Electrical approach to Nondestructive Analysis on WB-PBGA with TDR Technology
Authors: Chen Ming-Kun , Tai Cheng-Chi , Huang Yu-Jung
Published: October 2015

Time Domain Reflectometry (TDR) is a powerful measurement technique that uses the reflection of a pulse sent down a transmission line to characterize the impedance of that line. The voltage of a reflection will vary depending on the distance to the fault and on the amount of energy reflected. In this paper we develop a simple and effective electrical nondestructive analysis (NA) system for the evaluation of the interconnection of wire-bonded plastic ball grid array (WB-PBGA) package. An open-end fixture (OEF) was employed to connect fast rising edge signals to the package which was monitored for its time delay and reflection voltage parameters. This technology represents a valuable new method for the NA of WB-PBGA packages, and it has enabled the rapid and efficient detection and location of faults. Comparative TDR measurements accurately predicted the location of opens and short circuits in the copper traces of the substrate, bond wire, and solders balls. The TDR analysis was verified by using X-ray analysis. The paper establishes the use of a TDR system incorporating an open-end fixture for locating opens and shorts in WB-PBGA packages.
Ball Bonding Process Robustification with regard to Space Applications
Authors: Libon S.P. , Paelinck P. , Goffin B.
Published: October 2015

Space applications require being able to pass 100% pull test, before and after thermal aging, and to conform to visual inspection. Gold thermosonic wirebonding (ball bonding) on Aluminum metallized silicon dies, is usually felt to be a sensitive process, due to the need for effectively controlling intermetallic. As the criteria are very stringent, the process setup of small batches can be a cumbersome and costly operation. In this paper, we propose an original sequence of methods to ensure correlation of success in all these aspects, while using only a pull tester and keeping the batch setup time and cost down. It relies on design of experiments (DoE) and analysis of variance (ANOVA), to estimate the effects of significant factors and determine an optimum. An original statistic is used to better answer the objective. The visual aspects of the bonds are also studied. The purpose is to offer a process map showing safe bonding conditions, where changes made to improve visual aspects will not impact the pull test values. Finally, we have quantified the visual quality, and have related it to the pull test.
Chip-On-ACB (Anodized Circuit Board) Package for High Power Light-Emitting Diode
Authors: Shin Kyuho , Shin Suho , Kweon Soon Cheol , Kwon Kihwan , Choi Seogmoon , Lee Youngki
Published: October 2015

A new light-emitting diode (LED) package module based on anodized circuit board (ACB) is developed in this study. ACB represents the selectively anodized aluminum board, in which the aluminum oxide layer, formed by anodizing process, serves as a dielectric layer and the electric signal lines are formed on it. LED chips can be directly attached to the metal pads on the aluminum core of ACB, which acts as p-electrode and at the same time easily spreads out the heat generated from the chips. The use of ACB in LED packaging has the benefit that ACB provides an excellent heat dissipation path from junction to board. This characteristic cannot be obtained from metal-core printed circuit board (MC-PCB), because it inevitably has a dielectric layer for electrical insulation of signal lines from metal base, which acts as a blocking layer in the heat path. By using the thermal transient method, the thermal resistance of the LED package (from junction to board) is measured to be about 4 °C/W. Also, we have performed the simulation of heat conduction, of which the results agree well with the experimental results. This chip-on-ACB LED package module has a potential application as a back light unit for display panel.
A Systematic Approach to Thinning Silicon Wafers to the sub-40μm Thickness Range
Authors: Arunasalam Parthiban , Gordon Matthew H. , Schaper Leonard W.
Published: October 2015

The present trend in electronics packaging is the stacking of die at the wafer or chip level. However to ensure stacked chip packages maintain overall low height and weight package profile, silicon wafers have to undergo extensive wafer thinning processes. In this work, a systematic approach to thinning silicon wafers down to sub-40μm in thickness is presented. This paper will cover a detailed three stage wafer thinning method, which includes the mechanical back-lapping method for the bulk removal process and a combination of mechanical polishing and spin-spray wet chemical etch method for the fine removal wafer thinning process. The results will show that by just utilizing the mechanical back-lapping and mechanical polishing process the wafers can be easily thinned from 380μm to less than 50μm with ±2.5μm Total Thickness Variation (TTV). These back-lapped wafers are then further thinned by the spin-spray etching method to achieve final wafer thickness of less than 40μm. The paper will also show that by utilizing a modified carrier wafer, the handling of these sub-40μm ultra-thin wafers do not require custom made tools and can be easily integrated into existing wafer handling tools.
Analysis of A Larger Die, Copper Pillar Bump Flip Chip Package with No-Flow Underfill
Authors: Zhang Xiaowu , Pinjala D. , Wong E. H. , Chew Grace , Ma Zhaohui , Tan Teck Tiong , Chew Jimmy
Published: October 2015

In the flip chip assembly process, no-flow underfill (NFU) has the advantage over traditional capillary-flow underfill because of the elimination of processing steps and the reduction of packaging cost. However, currently one of the major technical obstacles in applying no-flow underfill technology is the fillet cracking of no-flow underfill during the reflow after the moisture preconditioning. In this paper, comprehensive thermo-mechanical and hygroswelling models are established to study a larger die flip chip package with no flow underfill during reflow after moisture preconditioning. The adhesion strengths between no-flow underfill and die have been characterized. Based on the modelling results and the adhesion strength data, the reason why the crack on the no-flow underfill starts and propagates, leading to fillet cracking, is also explained. A series of parametric studies are also performed to eliminate or reduce the fillet crack. The results show that a lower coefficient of thermal expansion (CTE), a lower Young's modulus (E) and a higher cure temperature of no-flow underfill are desirable for the robustness of the package. The results also show that thinner die thickness is desirable for the robustness of the package. These findings form design guidelines for the design of larger die, copper pillar bump flip chip package with no-flow underfill.
Fabrication of Conductors and Inductors by Nano-Particle Deposition through Direct Write Technology
Authors: Colvin Jacob , Carter Michael , Sears James
Published: October 2015

Direct Write Technologies are being utilized in antennas, engineered structures, sensors, and tissue engineering. One form of the Direct Write Technologies is Maskless Mesoscale Material Deposition (M3D) for Optomec, Inc. M3D is a process that uses aerosol formation, transport and deposition. Inks for the M3D utilize nano-particles in suspension for deposition. Several different conductive inks were deposited with M3D and characterized for electrical resistivity and microstructure. Soft magnetic material was formulated as an ink suspension, deposited and characterized.

This paper will report on the results obtained after sintering conductive nano-particle inks and soft magnetic material. Sintering was performed with a 2W frequency doubled Nd:YAG CW laser, a conventional muffle furnace and a novel photonic curing method. Depositions of various conductive inks were examined for physical dimensions (width and thickness) and microstructure. A study of the sintering characteristics if these ink was also included. This paper will also report on the results obtained from depositing a soft magnetic material. Permeability results were calculated from magnetic structures created with the deposition. These results are compared to conventional methods of soft magnetic material formation and construction. Physical properties of the deposited inks are also measured and reported.
An LTCC Based Filter and Front End Module using Heterogeneous Dielectrics
Authors: Kim Jun Chul , Kim Dongsu , Cho Hyun Min , Park Jong Chul , Kang Nam Kee
Published: October 2015

This paper presents a multi-layered bandpass filter (BPF) and a power amplifier module (PAM) integrated with a SAW duplexer based on heterogeneous ceramic substrates. The heterogeneous substrates are composed of two different ceramic layers with εr = 7.4 and 17.5 in order to take advantage of their own properties. In the PAM substrate, a DC blocking capacitor and a shunt capacitor for an output matching network of a power amplifier are embedded with a material of εr = 17.5 to reduce occupied areas of the capacitors. On the other hand, a quarter-wave-length stripline and RF chokes are realized with a material of εr = 7.4 to reduce signal delay time. In the multi-layered BPF, a coupled stripline and a high shunt capacitor are embedded with materials of εr = 7.4 and 17.5, respectively, resulting in improved spurious characteristics.
Three-dimensional fluidic microsystem fabricated in Low Temperature Cofired Ceramic Technology
Authors: Golonka Leszek J. , Zawada Tomasz , Roguszczak Henryk , Malecha Karol , Chudy Michal , Stadnik Dorota , Dybko Artur
Published: October 2015

A three-dimensional (3D) Low Temperature Cofired Ceramics (LTCC) fluidic microsystem integrated with an optical detection unit is presented in this article. The structure is applied to quantitative analysis of chemical compounds using colorimetric methods. The fabricated microfluidic system consists of a serpentine mixer, fluidic channels, heater, embedded temperature sensor and integrated optical fibers for detection of light transmission and/or fluorescence. A new inexpensive material for the embedded temperature sensor is described. The fluidic system is designed using computer CFD (Computational Fluid Dynamics) simulations. Fluid flow in the mixer is observed through a transparent polymer material bonded to the LTCC structure. The importance of positioning of optical fibers and their influence on the absorbance and fluorescence measurements is presented.
MEMS Technologies and Devices for Single-Chip RF Front-Ends
Authors: Nguyen Clark T.-C.
Published: October 2015

Micromechanical (or “μmechanical”) components for communication applications fabricated via IC-compatible MEMS technologies and capable of low-loss filtering, mixing, switching, and frequency generation, are described with the intent to not only miniaturize and lower the parts counts of wireless front-ends via higher levels of integration, but also to eventually raise robustness (against interferers) and lower power consumption when used in alternative architectures that take advantage of the abundant frequency control enabled by RF MEMS devices. Among the devices described are vibrating micromechanical resonators with Q's exceeding 10,000 at GHz frequencies; mechanical circuits comprised of such vibrating resonators; tunable MEMS-based capacitors and inductors with much higher Q than achievable by conventional IC counterparts; and RF MEMS switches with insertion losses and linearity superior to those attainable by present-day semiconductor switches.
Micromachined LCP Connectors for Packaging MEMS Devices in Biological Environments
Authors: Dean Robert , Weller Jenny , Bozack Mike , Farrell Brian , Jauniskis Linas , Ting Joseph , Edell David , Hetke Jamille
Published: October 2015

Micro- and nano-MEMS technology is being increasingly exploited in biological applications, such as large electrode-count neural prosthesis probe arrays. However, a bottleneck in fully utilizing this technology has been the interconnect between the implanted MEMS device and the external system connected to the implanted device. Since the implanted MEMS device is capable of having a large number of elements, the interconnect must have a sufficient number of electrical connections to communicate with each and every element. Complicating this is the fact that the interconnect requirements may include electrical signals, microfluidics transport and optical signals, all packaged in a miniature biocompatible interconnect cable. Micromachined liquid crystal polymer (LCP) is a promising technology for this application, due to LCP's biocompatibility, chemical inertness, electromechanical properties and its ability to be micromachined. This paper presents the results from the development of MEMS packaging technology suitable for use in biological environments, and is demonstrated in the realization of a prototype micromachined LCP biomedical interconnect device. In particular, the development of the interconnect device demonstrates the realization of biocompatible connectors with high-density ultra-fine pitch electrical traces.
Transient Thermal Characterization of a Stacked Multichip Package
Authors: Kaija Kimmo , Heino Pekka
Published: October 2015

This paper is a case study of the thermal behavior of a stacked multichip package (SMCP). The aim is to measure temperature responses when heat is dissipated on different dice and to characterize the behavior with a compact thermal model (CTM) that accurately models steady-state and transient responses with a simple thermal RC -network. The measured package consists of three stacked layers, where each layer has one thinned flip chip attached die on an aramid interposer. The package's thermal responses were measured with thermal test dice that contain heaters and temperature sensors. The package was modeled with a finite element method (FEM) and the simulated temperature responses showed reasonable agreement with measured data. The FE model was further used to provide reference thermal data under different boundary conditions for CTM synthesis. The obtained CTM models accurately the steady-state and transient behavior and can be used as simplified model of the measured SMCP for further thermal analysis.
Nanoceramic Processing for High-Power Multi-channel Electron Multiplier in Low Temperature Cofire Ceramic (LTCC)
Authors: Zheng Feng , Jones W. Kinzy , Wu Wenzhong , Seelaboyina Raghunandan
Published: October 2015

Nanoceramic processing technologies are brought together with standard LTCC materials to demonstrate a dynode structured electron multiplier with integrated cooling. Process developments include the integration of numerous components, including an embedded passive, high-density interconnect, and high-performance thermal management system. Enhanced processing capabilities utilize nanoparticles to control sintering kinetics. Cofirable thick Ag tapes have been demonstrated that allow multilayer structures to include a thick (up to 0.5mm) solid Ag layer. The development of 3-D cavities using fugitive inserts have produced meso- and micro-scale channels, with X-Y-Z channels of 50 μm diameter demonstrated. Nano-sized MgO, processed using electrophoretic deposition, has been developed for a secondary electron emitter (SEE) with a gain factor of 2.0. To minimize thermal run-away and, subsequently, thermal failure, a positive temperature coefficient (PTC) resistor system compatible with LTCC processing is being developed to reduce supplied power to the individual multiplier structures to control localized heating. In this study the synthesis of nanostructure MgO is shaped by electrophoretic deposition that consists of the deposition of particles at dynodes submerged in a solution of magnesium methoxide. Charged particles of MgO are suspended in the solution and forced to move toward the dynode (which bears the opposite charge) by applying an electric field, thus forming a thin coating of collected MgO particles on the dynode. Different annealing conditions are used to optimize the microstructure and secondary electron emission (SEE) of the deposited materials.
Flight Qualification and Circuit Development of Sensor Front-End Electronics for PACS/Hershel at Liquid Helium Temperature
Authors: Merken Patrick , Souverijns Tim , Putzeys Jan , Creten Ybe , Van Hoof Chris
Published: October 2015

In the framework of the development of the European Space Agency's Herschel Space Observatory (HSO), IMEC designed the cold-readout electronics (CRE) for the PACS instrument. Key specifications for this circuit were high linearity, low power consumption, high uniformity, and very low noise at an operating temperature of 4.2K (liquid helium temperature, LHT). To ensure high production yields and uniformity, relatively easy availability of the technology, and portability of the design, the circuit was implemented in a standard CMOS technology. The circuits are functional at room temperature, which allows screening prior to integration and qualification and has an important impact on the production yield and time. The circuit was mounted on an Al2O3 substrate for optimum electrical performance. On the same substrate, bias signal generation, short-circuit protection circuitry, and decoupling capacitors for the power lines were integrated. This led to a relatively complex substrate containing over 30 passives and one die, integrated by means of conducting and nonconducting glue and nearly 80 wire bonds. Because the detector arrays will be cooled down to 4.2K prior to launch, reliability and launch-survivability of the mounted substrate at this temperature and in this harsh environment had to be demonstrated. For this purpose, the quality and associated reliability of every assembly step is verified during substrate mounting. This included verification of the compatibility of the bond material, optimization of the bond yield, and temperature cycling (between room temperature and LHT) of the devices. Other tests on qualification models would focus on circuit functionality under proton and gamma irradiation, cryogenic vibration tests to demonstrate launch survivability, and exhaustive temperature cycling to qualify the assembly procedure. We present in this paper the complete integration and qualification of the developed circuits, including assembly and verification during production of the flight models and qualification of the assembly method on the qualification models.