International Mechanical Engineering Congress Research Articles

Development and assessment of a methodology for abstraction of topology optimization results to enable the substitution of optimized beams

Improving mechanical topology optimization (TO) results by substituting biomimetic beams is one possibility to achieve designs of mechanical components that are highly sustainable and show good mechanical performance. Because of their geometric complexity, such designs were found to be well-suited for production by laser additive manufacturing. One obstacle of incorporating biomimetics beams in TO designs is the lack of detailed design methodologies. Röver et al. [“Methodology for integrating biomimetic beams in abstracted topology optimization results,” in Proceedings of the ASME 2022 International Mechanical Engineering Congress and Exposition. Volume 4: Biomedical and Biotechnology; Design, Systems, and Complexity Columbus, OH, 30 October–3 November (ASME, New York, 2022)] proposed a corresponding design concept. Building on their concept, we present in this work a detailed methodology for abstraction of TO results to a design consisting of ball nodes and cylindrical beams. Using such an auxiliary design, the internal forces and moments of the beams can be evaluated to allow for the substitution of suitable biomimetic beams to generate biomimetic component designs in a next step. We present a skeletonization algorithm based on the potential field approach. Using the skeletonization and an additional analysis of the dimensions of the beams in the TO result, the algorithm develops an auxiliary design of the original TO result. The final algorithm was applied to three common TO results to obtain one auxiliary component design each. The developed algorithm was found to generate abstractions that were well-suited for use in the methodology proposed in Röver et al. [“Methodology for integrating biomimetic beams in abstracted topology optimization results,” in Proceedings of the ASME 2022 International Mechanical Engineering Congress and Exposition. Volume 4: Biomedical and Biotechnology; Design, Systems, and Complexity Columbus, OH, 30 October–3 November (ASME, New York, 2022)], because internal forces and moments in the abstracted beams could be evaluated with less effort. Therefore, our work contributes to a detailed design methodology for biomimetic mechanical components in the field of design for additive manufacturing.

Erratum: “New Compound Fractional Sliding Mode Control and Super-Twisting Control of a MEMS Gyroscope” [ASME Lett. Dyn. Sys. Control, 2022, 2(4), p. 040904; DOI: 10.1115/1.4055878

Abstract Due to a family emergency, this paper could not be presented at the 2022 ASME International Mechanical Engineering Congress and Exposition (IMECE).

Special Section: 2022 IMECE Papers

Abstract This issue includes a special section that features select papers from the 2022 ASME International Mechanical Engineering Congress and Exhibition (IMECE). In an effort to attract more papers from conferences for the ASME Letters in Dynamic Systems and Control (ALDSC), we reached out to IMECE organizers and requested recommendations for papers to consider for this journal. The idea was to offer those authors the opportunity to publish in a refereed journal while being able to still present their paper at the conference.

Special Section: Mobile Robots and Unmanned Ground Vehicles

Abstract Inspired by the fifth-year anniversary celebration of the homonymous symposium at the International Mechanical Engineering Congress & Exposition (IMECE), this Special Section with 10 papers shares the latest research efforts in design, theory, development, and applications for Mobile Robots (MRs) and Unmanned Ground Vehicles (UGVs).

Shared-Memory Parallelization for Two-Way Coupled Euler–Lagrange Modeling of Cavitating Bubbly Flows

Cavitating and bubbly flows are encountered in many engineering problems involving propellers, pumps, valves, ultrasonic biomedical applications, etc. In this contribution, an openmp parallelized Euler–Lagrange model of two-phase flow problems and cavitation is presented. The two-phase medium is treated as a continuum and solved on an Eulerian grid, while the discrete bubbles are tracked in a Lagrangian fashion with their dynamics computed. The intimate coupling between the two description levels is realized through the local void fraction, which is computed from the instantaneous bubble volumes and locations, and provides the continuum properties. Since, in practice, any such flows will involve large numbers of bubbles, schemes for significant speedup are needed to reduce computation times. We present here a shared-memory parallelization scheme combining domain decomposition for the continuum domain and number decomposition for the bubbles; both selected to realize maximum speedup and good load balance. The Eulerian computational domain is subdivided based on geometry into several subdomains, while for the Lagrangian computations, the bubbles are subdivided based on their indices into several subsets. The number of fluid subdomains and bubble subsets matches with the number of central processing unit (CPU) cores available in a shared-memory system. Computation of the continuum solution and the bubble dynamics proceeds sequentially. During each computation time step, all selected openmp threads are first used to evolve the fluid solution, with each handling one subdomain. Upon completion, the openmp threads selected for the Lagrangian solution are then used to execute the bubble computations. All data exchanges are executed through the shared memory. Extra steps are taken to localize the memory access pattern to minimize nonlocal data fetch latency, since severe performance penalty may occur on a nonuniform memory architecture (NUMA) multiprocessing system where thread access to nonlocal memory is much slower than to local memory. This parallelization scheme is illustrated on a typical nonuniform bubbly flow problem, cloud bubble dynamics near a rigid wall driven by an imposed pressure function (Ma et al., 2013, “Euler–Lagrange Simulations of Bubble Cloud Dynamics Near a Wall,” International Mechanical Engineering Congress and Exposition, San Diego, CA, Nov. 15–21, Paper No. IMECE2013-65191 and Ma et al., 2015, “Euler–Lagrange Simulations of Bubble Cloud Dynamics Near a Wall,” ASME J. Fluids Eng., 137(4), p. 041301).

Special Issue of ASME JSEE on Integrated/Sustainable Building Equipment and Systems Notes From Guest Editors

This special issue of JSEE is part of the efforts by the ASME Task Force on Integrated/Sustainable Building Equipment and Systems (ISBES) to identify and evaluate challenges and opportunities for integrating sustainable equipment and systems in individual buildings and within the built environment. Specifically, the ISBES Task Force is primarily interested in fostering new technologies and strategies to enhance building energy efficiency and reduce building energy use. This new approach is proceeding on three different but very important tracks:This first special issue is intended to motivate exchange of innovative ideas, leading-edge concepts, new technologies and devices, ongoing R&D efforts, prototype and demonstration projects, commercialization technologies and projects, and visions of the future related to various tracks of Integrated Sustainable Equipment and Systems for Buildings.Most of the papers selected and further peer-reviewed for this special issue have been presented as part of technical sessions specifically organized during the 2012 ASME International Mechanical Engineering Congress and Exhibition (IMECE-2012). The papers cover all three IBSES tracks including (i) integrating innovative energy efficiency humidification technology into buildings, evaluating the potential of designing high performance buildings in developing countries, and examining the LEED rating system using design and performance data obtained for several US buildings, (ii) assessing the integration of thermo-active foundations and energy storage systems into buildings, and (iii) city-scale analysis of predicting energy demands during extreme heat events as well the environmental impact of large scale integration of PV systems in a coastal community. The selected articles represent worldwide applications of these technologies and leading-edge approaches.It is hoped that this special issue would provide a stepping stone to initiate long-term collaboration between academia, industry, and planners worldwide to solve the challenges inherent for developing integrated and sustainable equipment and systems for the built environment. We hope for the collaborations to be multi and to include expertise in various areas including but not limited to Solar Energy, Energy Efficiency, Hydrogen Energy Technology, Advanced Energy Technologies, Materials, Fluid Mechanics of Buildings, and Architectural designs.

Canned Heat

This article highlights different research efforts to utilize thermal energy and thermal energy storage technologies. At several technical and panel sessions at the November ASME International Mechanical Engineering Congress and Exposition in Houston, there has been much discussion of cutting-edge work in thermal energy storage, including thermal energy storage materials, applications, and systems. Research into thermal energy storage is not limited to the confines of government and academia. Private companies are investigating whether they can incorporate thermal storage into some of their systems. Another potential advantage for solar thermal power is efficiency. Storing thermal energy as sensible heat is the most straightforward of the three methods, and the one that is the most widely deployed. A wide range of materials from simple concrete to synthetic oils has been tried for storing thermal energy. An energy storage system based on latent heat released as a material changes phase can be cost-effective. Thermal energy storage can become a game-changing technology wherever energy demand does not align exactly with energy supply. However, significant development challenges remain before these potential benefits can be realized.

An Experimental and Computational Study on Moisture Induced Epoxy Swelling in Non-hermetic Optoelectronic Packages

Moisture induced epoxy swelling is a potential failure mechanism in nonhermetic packages. Epoxy materials used in the package absorb moisture and swell in a relatively humid environment. This will result in hygroscopic stresses in the material that can eventually lead to failure. The coefficient of hygroscopic swelling (CHS) is a material property that characterizes moisture induced swelling in the material. It is defined as the ratio of hygroscopic strain to the moisture concentration in the material. Prior research investigated the measurement of CHS experimentally using techniques such as thermo mechanical analysis (TMA) (Ardebili et al., 2003, “Hygroscopic Swelling and Sorption Characteristics of Epoxy Molding Compounds Used in Electronic Packaging,” IEEE Trans. Compon. Packag. Technol., 26(1), pp. 206–214; Mckague et al., 1978, “Swelling and Glass Transition Relations for epoxy Matrix Material in Humid Environments,” J. Appl. Polym. Sci., 22, pp. 1643–1654.), Moiré interferometry (Han et al., 2003, “Measurement of the Hygroscopic Swelling Coefficient in Mold Compounds Using Moire Interferometer Experimental Techniques,” IEEE Trans. Compon. Packag. Technol., 27(4), pp. 40–44), and digital image correlation (DIC) (Park and Zhang, 2007, “Investigation of Hygroscopic swelling of Polymers in Freezing Temperature,” ASME International Mechanical Engineering Congress and Exposition). Some of these studies recommended investigation of improved measurement techniques, while others made some procedural assumptions that may not be applicable for all materials. One of the goals of this study was to investigate an improved technique for CHS measurement and helps to better understand the various factors that affect the measurement. The DIC technique was used to measure the moisture swelling of the epoxy material considered for use in the package. Moisture loss during the measurement results in a change in moisture concentration in the sample. While it may be thought that the moisture loss during the DIC scan can be assumed negligible due to the short test time compared with other methods, this assumption did not hold well for the current epoxy material. The ramp rate chosen for the test affects the moisture loss. It introduces a level of nonuniformity in temperature and moisture distribution in the sample. A suitable value that takes into account both of these effects was determined. The moisture loss measured during the DIC scan was accounted for in the CHS computation. In addition to this, the temperature and concentration dependence of the CHS was determined. Results indicated that the temperature and concentration effects are small for the current test material within the test temperature range. The moisture loss found during the DIC measurement leads to a nonuniform moisture distribution in the sample. This was characterized by using experimental and computational methods and the effect on the measurement was determined.

Special Issue on Computational Fluid Mechanics and Fluid–Structure Interaction Preface

This special issue is a collection of the papers contributed by authors who were invited to speak at the symposium on Computational Methods for Fluid–Structure Interaction, ASME International Mechanical Engineering Congress and Exposition, Vancouver, Canada, November 12–18, 2010. The symposium was organized by Yuri Bazilevs (University of California, San Diego), Kenji Takizawa (Waseda University, Tokyo), and Tayfun Tezduyar (Rice University).The special issue contains papers on advances in computational methods for computational fluid dynamics (CFD) and fluid–structure interaction (FSI). FSI is one of the most important classes of multiphysics problems in modern mechanics. It is currently receiving much attention from the academic community, national laboratories, and the industrial sector.The papers mostly focus on moving-grid methods, such as the arbitrary Lagrangian–Eulerian and space–time formulations. The methods discussed address the challenges of coupling rigid objects and free-surface flow, coupling of acoustic fluids and structures using a monolithic FSI approach, and coupling of discrete element and finite element methods in the context of particulate flows.The special issue contains papers on advances in patient-specific cardiovascular hemodynamics, FSI modeling of parachutes, air turbine aerodynamics, aerodynamics of flapping wings, ship hydrodynamics, liquid sloshing in tanks, and turbulence in the upper ocean. Low-order finite element method is the dominant spatial discretization technique in most of the special issue articles. However, spatial and temporal higher-order NURBS-based discretizations, such as those employed in isogeometric analysis, are also discussed and are found to increase the accuracy and robustness of the computations. One of the articles provides the methodology and background mathematical theory for how to correctly define boundary fluxes in coupled multiphysics simulations.We would like to thank the authors for their efforts in preparing the special issue articles, and for meeting the special issue deadlines. These contributions will undoubtedly help advance the fields of CFD and FSI.

Recent Advances in Micro, Nano, and Cellular Composite Materials

It is with great pleasure that we compiled the Special Issue Recent Advances in Micro, Nano, and Cellular Composite Materials of the Journal of Engineering Materials and Technology (JEMT). In this special issue, a total of 18 articles from leading research groups, covering the broad area of multidisciplinary materials in different length and size scales, are presented. All papers published in this special issue were selected from those presented at the ASME International Mechanical Engineering Congress and Exposition (IMECE) in Vancouver, British Columbia, Canada during November 12–18, 2010.It is our expectation that the papers published in this special issue will be of lasting value for researchers and educators, and contribute to our understanding of micro, nano, and cellular composite materials.The editors would like to gratefully acknowledge the authors for their contributions and the reviewers for their insightful suggestions and criticisms. Finally, the editors acknowledge chief editor Dr. Hussein M. Zbib for his motivation and expert guidance throughout the publication process of this special issue.Sincerely,

Heat Transfer Gallery

The Fifteenth Heat Transfer Photogallery was sponsored by the K-22 Heat Transfer Visualization Committee for the 2010 International Mechanical Engineering Congress and Exhibition (IMECE) held in Vancouver, British Columbia in Canada, on November 12–18, 2010. The peer-reviewed evaluation for all of the presented entries identified the 10 entries for publication in the ASME Journal of Heat Transfer August issue of 2011.The purpose of publishing these entries is to draw attention to the innovative features of optical diagnostic techniques and aesthetic qualities of thermal processes. To focus on visualization images and schematics, the text is kept to a minimum and further details should be found directly from the authors. Our wish is that the journal readers enjoy viewing these collections, acquire knowledge of the state-of-the-art features, and also promote their participation in the 2011-IMECE Photogallery to be held in Denver, Colorado on November 11–17 [http://www.asmeconferences.org/Congress2011].The Call for Photogallery for 2011-IMECE is also announced in this issue of Journal of Heat Transfer.Kenneth D. Kihm Department of Mechanical, Aerospace, and Biomedical Engineering, University of Tennessee, Knoxville, TN 37996-2210Chang K. Choi Mechanical Engineering-Engineering Mechanics, Michigan Technological University, Houghton, MI 49931-1295

Recent Advances on Composites and Heterogeneous Materials

It is a pleasure to present to you a collection of 18 papers highlighting Recent Advances on Composites and Heterogeneous Materials offered at the International Mechanical Engineering Congress and Exposition, Orlando, Florida, November 2009.Collection of the “Recent Advances on Composites and Heterogeneous Materials” themed articles was focused on the broad, multidisciplinary and transformative nature of composites and heterogeneous materials. The material systems presented in this collection of papers are at the forefront of current science and technology and are expected to bring important breakthroughs in various technological fields.Topics in this special issue include multiscale characterization of multiphase composites and polycrystalline solids, studies on reinforced elastomers, constitutive modeling of cellular materials, mechanics of bimaterials and functionally graded materials, characterization of nanocomposites, micromechanics and damage of random fiber composites, virtual testing of composite structures, characterization and modeling of composites embedded with piezoelectrics, and structural health monitoring of heterogeneous materials.It is anticipated that papers found in this special issue will serve as reference articles in their respective topics and will contribute in the knowledge advancement of composite and heterogeneous materials.The editors would like to gratefully acknowledge the authors for their original scientific contributions, the reviewers for the insightful and constructive criticism, and the chief editor, Dr. Hussein Zbib, for his encouraging guidance. Their assistance in publishing this special issue in the Journal of Engineering Materials and Technology has been invaluable.With warmest greetings,

Heat Transfer Gallery

The Fourteenth Heat Transfer Photogallery was sponsored by the K-22 Heat Transfer Visualization Committee for the 2009 International Mechanical Engineering Congress and Exhibition (IMECE) held in Lake Buena Vista, Florida, on November 13–19, 2009. The peer-reviewed evaluation for the seven presented entries identified the four entries for publication in the ASME Journal of Heat Transfer August issue of 2010.The purpose of publishing these entries is to draw attention to the innovative features of optical diagnostic techniques and aesthetic qualities of thermal processes. To focus on visualization images and schematics, the text is kept to a minimum and further details should be found directly from the authors. My wish is that the journal readers enjoy viewing these collections, acquire knowledge of the state-of-the-art features, and also promote their participation in the 2010-IMECE Photogallery to be held in Vancouver, Canada on November 12–18 [http://www.asmeconferences.org/Congress10].The Call for Photogallery for 2010-IMECE is also announced in this issue of Journal of Heat Transfer.Kenneth D. KihmDepartment of Mechanical, Aerospace,and Biomedical Engineering,University of Tennessee,Knoxville, TN 37996-2210

A numerical investigation of energy dissipation with a shallow depth sloshing absorber

A liquid sloshing absorber consists of a container, partially filled with liquid. The absorber is attached to the structure to be controlled, and relies on the structure’s motion to excite the liquid. Consequently, a sloshing wave is produced at the liquid free surface within the absorber, possessing energy dissipative qualities. The behaviour of liquid sloshing absorbers has been well documented, although their use in structural control applications has attracted considerably less attention. Generally it is accepted that sloshing absorbers with shallow liquid levels are more effective energy dissipaters than those with higher levels, although there has not yet been a study to reveal an ‘optimum’ design mechanism. The main limitation of numerically modelling such circumstances is the inherent complexity in the free surface behaviour, predictions of which are limited when using grid-based modelling techniques. Considering such limitations, Smoothed Particle Hydrodynamics (SPH) is used in this study to model a 2-dimensional rectangular liquid sloshing absorber. SPH is a Lagrangian method of solving the equations of fluid flow that is suitable to model liquid sloshing due to its grid-free nature, and inherent ability to deal with complex free surface behaviour. The primary objective of this paper is to numerically demonstrate the effect of tuning a container’s width, to complement previous work on the effect of liquid depth [B. Guzel, M. Prakash, S.E. Semercigil, Ö.F. Turan, Energy dissipation with sloshing for absorber design, in: International Mechanical Engineering Congress and Exposition, 2005, IMECE2005-79838]. This study is an attempt to reveal geometry that enables both effective energy transfer to sloshing liquid and to dissipate this energy quickly.

Heat Transfer Photogallery

The Thirteenth Heat Transfer Photogallery was sponsored by the K-22 Heat Transfer Visualization Committee for the 2008 International Mechanical Engineering Congress and Exhibition (IMECE) held in Boston, Massachusetts, on October 31–November 6, 2008. The peer-reviewed evaluation process for the presented entries identified the seven entries for production in the ASME Journal of Heat Transfer August issue of 2009.The purpose of publishing these entries is to draw attention to the innovative features of optical diagnostic techniques and aesthetic qualities of thermal processes. To focus on visualization images and schematics, the text is kept to a minimum and further details should be found directly from the authors. My wish is that the journal readers enjoy viewing these collections, acquire knowledge of the state-of-the-art features, and also promote their participation in the 2009-IMECE Photogallery [http://www.asmeconferences.org/Congress09].The Call for Photogallery for 2009-IMECE is also announced in this issue of Journal of Heat Transfer.

Lab‐scale intervention

From mobile phones and laptop computers to in vitro fertilization and social networks on the Internet, technological devices, products and services are increasingly shaping the lives of people around the world. The pervasiveness of technology and the underlying science that makes it possible has led to a certain ambivalence: most people trust that ‘science’ will eventually help them to live longer, healthier and happier lives. However, they also feel increasingly uncomfortable about certain new technologies, often those that challenge or improve on ‘nature’. Genetically modified crops, gene therapy, stem cell research, cloning, renewed interest in nuclear power: the list of controversial topics involving science and technology is growing steadily and debates on these topics regularly occupy centre stage in public and political arenas. > …the research process itself constitutes a largely overlooked opportunity for addressing social concerns Policy‐makers have responded by calling for increased attention to be paid to the ethical, legal and social aspects of scientific research and technological developments. In particular, new and emerging areas of research—such as genomics, synthetic biology and nanotechnology—have been accompanied by studies of their broader societal implications as well as public‐engagement efforts, in order to guide research and development in ways that respect societal concerns. Such attempts to shape technological trajectories have traditionally occurred both before scientific research, for example, through research policy, technology assessment or public participation, and afterwards, through regulations or market mechanisms. Although these stages are crucial points at which to intervene, the research process itself constitutes a largely overlooked opportunity for addressing social concerns. Indeed, if one acknowledges the central role that scientific research has in the innovation process, this is an area well worth examining. Shaping technological trajectories will, at some point, include shaping the very research processes that help to characterize them (Fisher et al , 2006). Social and …

Vibration Durability Assessment of Sn3.0Ag0.5Cu and Sn37Pb Solders Under Harmonic Excitation

In this paper, the vibration durability of both SAC305 and Sn37Pb interconnects are investigated with narrow-band harmonic vibration tests conducted at the first natural frequency of the test, printed wiring board, using constant-amplitude excitation. A time-domain approach, reported by Upadhyayula and Dasgupta (1998, “Guidelines for Physics-of-Failure Based Accelerated Stress Test,” Proceedings, Reliability and Maintainability Symposium, pp. 345–357), was adapted in this study for the fatigue analysis. The test board consists of daisy-chained components, to facilitate real-time failure monitoring. The response of the test specimens was characterized, and accelerated fatigue tests were conducted at different loading amplitudes to obtain a mix of low-cycle fatigue (LCF) and high-cycle fatigue data points. The SAC305 interconnects were found to have lower fatigue durability than comparable Sn37Pb interconnects, under the narrow-band harmonic excitation levels used in this study. This trend is consistent with most results from broadband vibration tests by Zhou et al. (2006, “Vibration Durability Comparison of Sn37Pb vs. SnAgCu Solders,” Proceedings of ASME International Mechanical Engineering Congress and Exposition, Chicago, IL, Paper No. 13555), Zhou and Dasgupta (2006, “Vibration Durability Investigation for SnPb and SnAgCu Solders With Accelerated Testing and Modeling,” IEEE-TC7 Conference on Accelerated Stress Testing & Reliability, San Francisco, CA), and Woodrow (2005, “JCAA/JG-PP No-Lead Solder Project: Vibration Test,” Boeing Electronics Materials and Processes Technical Report) and from repetitive mechanical shock tests by Zhang et al. (2005, “Isothermal Mechanical Durability of Three Selected Pb-Free Solders: Sn3.9Ag0.6Cu, Sn3.5Ag and Sn0.7Cu,” ASME J. Electron. Packag., 127, pp. 512–522), but counter to findings from quasistatic, LCF, and mechanical cycling studies by Cuddalorepatta and Dasgupta (2005, “Cyclic Mechanical Durability of Sn3.0Ag0.5Cu Pb-Free Solder Alloy,” Proceedings of the ASME International Mechanical Engineering Congress and Exposition, Orlando, FL, Paper No. 81171). Failure analysis revealed two competing failure modes, one in the solder and another in the copper trace under the component. Thus solder fatigue properties extracted with the help of finite element simulation of the test article should be treated as lower-bound estimates of the actual fatigue curves.

Hermeticity and diffusion investigation in polysilicon film encapsulation for microelectromechanical systems

The hermeticity and diffusion behavior of “epi-seal” encapsulation [R. N. Candler et al., J. Microelectromech. Syst. 15, 1446 (2006); B. Kim et al., Proceedings of the ASME 2007 InterPACK Conference (InterPACK’07), 33234 (2007)], an epitaxially deposited polysilicon film encapsulation for microelectromechanical systems (MEMSs), were investigated. MEMS resonators with pressure sensitive quality factor were fabricated inside episeal cavities. By measuring the quality factor and inferring cavity pressure, leakage through the encapsulation was studied as a continuation of previous hermeticity investigations [B. Kim et al., Proceedings of the 2004 ASME International Mechanical Engineering Congress and Exposition, IMECE, pp. 413–416 (2004)]. During long-term monitoring performed at 100 °C in a normal atmosphere, the encapsulated cavity pressure increased at a rate of 5–10 mTorr/yr, whereas no measurable pressure change could be detected in our previous room temperature measurement performed with identically designed and encapsulated resonators. To identify the cause of this pressure increase, the diffusive gas species and diffusion pathways in the epi-seal encapsulation were investigated experimentally. Various gas species in the atmosphere were tested in a 400 °C accelerated environment. These tests identified hydrogen and helium as highly diffusive gas species and showed argon and nitrogen to be much less diffusive under these conditions. Also, a series of devices with modifications of encapsulation geometry was tested in a hydrogen environment at 400 °C. Silicon dioxide, used for sacrificial and passivation layers, was identified as the primary diffusion pathway through the epi-seal encapsulation. These experimental results and diffusion pathway models were compared with the diffusion activation energy of various gas species in semiconductor materials, enabling design and process optimization for improved hermeticity of wafer-scale thin-film encapsulation for MEMS devices.

Electrical method to measure the dynamic behaviour and the quadrature error of a MEMS gyroscope sensor

The electronics on board of a vibrating MEMS sensor is able to compensate only for small changes in the mechanical characteristics of the device. Thus, it is of great importance to find an easy and fast way to evaluate the mechanical parameters, such as the resonance frequency and the damping coefficient, of a MEMS sensor before putting the device on the market [A. Cigada, E. Leo, M. Vanali, Optical and electrical methods to measure the dynamic behaviour of a MEMS gyroscope sensor, Proceedings of IMECE2005 ASME International Mechanical Engineering Congress and Exposition 2005, Orlando, Florida, USA [14]]. Moreover, for a vibrating MEMS gyroscope also the quadrature error, i.e. [Y.Y. Bao, C.L. Yung, Modelling and compensation of quadrature error for silicon MEMS microgyroscope], has to be kept below a given threshold in order to be able to acurately measure low angular speeds. Verification tests are usually carried out at the end of the production process, i.e. when the package is complete. Thus, only electrical measurements are possible. In the present paper, a reliable approach to determine mechanical parameters as well as the quadrature error of the MEMS device through electrical measurements is proposed and results are compared to more traditional optical measurements.

A Numerical Study of Transport in a Thermal Interface Material Enhanced With Carbon Nanotubes

Power dissipation in electronic devices is projected to increase over the next 10years to the range of 150-250W per chip for high performance applications. One of the primary obstacles to the thermal management of devices operating at such high powers is the thermal resistance between the device and the heat spreader or heat sink that it is attached to. Typically the in situ thermal conductivity of interface materials is in the range of 1-4W∕mK, even though the bulk thermal conductivity of the material may be significantly higher. In an attempt to improve the effective in situ thermal conductivity of interface materials nanoparticles and nanotubes are being considered as a possible addition to such interfaces. This paper presents the results of a numerical study of transport in a thermal interface material that is enhanced with carbon nanotubes. The results from the numerical solution are in excellent agreement with an analytical model (Desai, A., Geer, J., and Sammakia, B., “Models of Steady Heat Conduction in Multiple Cylindrical Domains,” J. Electron. Packaging (to be published)) of the same geometry. Wide ranges of parametric studies were conducted to examine the effects of the thermal conductivity of the different materials, the geometry, and the size of the nanotubes. An estimate of the effective thermal conductivity of the carbon nanotubes was used, obtained from a molecular dynamics analysis (Mahajan, S., Subbarayan, G., Sammakia, B. G., and Jones, W., 2003, Proceedings of the 2003 ASME International Mechanical Engineering Congress and Exposition, Washington, D.C., Nov. 15–21). The numerical analysis was used to estimate the impact of imperfections in the nanotubes upon the overall system performance. Overall the nanotubes are found to significantly improve the thermal performance of the thermal interface material. The results show that varying the diameter of the nanotube and the percentage of area occupied by the nanotubes does not have any significant effect on the total temperature drop.