bluuebunny/crossref_metadata_2025 huggingface dataset:
About Face: The Rebirth of the Portrait Gallery in the Twenty‐first Century
Authors: Pachter Marc
Published: January 2010

Abstract  Given the Victorian origins of the idea of a national portrait gallery, how relevant are such institutions today? The rebirth of the National Portrait Gallery in Washington, D.C. has involved a reinvestigation of notions of greatness, national identity, and the ongoing vitality of portraiture as an artistic form. Who should be deemed crucial to the telling of our national history? The evolution of thinking in our own day about the nature of national identity has undergone a dramatic shift. We have made decisions that might curl a Victorian's toes.
The Right Stuff in the Right Place: The Institution of Contemporary Art
Authors: Wedde Ian
Published: January 2010

Abstract  A long walk in the “world” of contemporary art gives multiple views of interlocking ecologies that, in their particularities, contradict the stereotypes suggested by language, invert “north” and “south,” question what is “traditional” in artistic practices, reflect on the intermix of society and art, glimpse the colonial mind in postmodern dress, and illuminate a restless subculture of professional migrants. What does our ramble reveal about the institution of contemporary art? “Diversity” hardly seems an adequate word.
The Case for Holistic Intentionality
Authors: Korn Randi
Published: January 2010

Abstract  Museums that strive for excellence by continually clarifying their purpose and realigning all practices and resources to achieve that purpose are operating holistically within a cycle of intentionality. Working within a cycle of intentionality means that a museum, among many other activities, carefully writes intentions that reflect and describe the essence of the museum and its unique value and potential impact. Intentions represent staff members' deepest passions and meld together their hopes and expectations with community needs. A museum that works within a cycle of intentionality has created an inclusive, process‐oriented infrastructure so it can write a purposeful mission and measurable intentions, and can demonstrate the value of the museum in people's lives and in its community through repeated assessment, while offering continuous learning opportunities for all staff.
Welcome to Art City: Place‐based Education through a Local Museum
Authors: Gray Sharon R. , Black Sharon
Published: January 2010

Abstract  The town of Springville, Utah, has a multi‐faceted relationship with its Museum of Art. The museum reflects and preserves the ethnic and cultural identity of the area, including its history, its landscapes, and its philosophy/religion. Through place‐based education—including observation and activities—k‐12 children and youth are given opportunities to experience their local culture on multiple levels. As museum artifacts are carefully chosen and lessons are purposefully structured, students receive cognitive, creative, and social benefits as well. Museum educators collaborate with local school personnel, along with educators from nearby Brigham Young University, to produce cross‐disciplinary lesson plans and teaching materials. Benefits Springville educators are finding in place‐based education are included in this article, along with specific ideas for lessons and activities.
Behind the Findings: Yes, the Science Explorations Program Worked, but Why?
Authors: Lackey Jill Florence , Borkin Susan Sullivan , Torti Vanessa , Welnetz Timothy , Moberg D. Paul
Published: January 2010

Abstract  The Science Explorations program was developed by the Milwaukee Public Museum (MPM) out of a desire to use the unique resources of MPM to advance informal science education and to address a community need of local and national concern: improving science education and accessibility for underserved audiences. In 2002, with support from the National Science Foundation (NSF) and private donors, MPM launched this after‐school program for a target group of urban, mostly minority, middle school girls, a group at risk for underachievement in science and technology. The museum staff built a combined program with five middle schools and also sought to reach out to family members of the participating girls in order to increase support for the young women's science endeavors. A three‐year evaluation of the Science Explorations program demonstrated positive findings from primarily quantitative data. An aim of this article is to present findings from the qualitative data to shed light on the reasons this program met nearly all of its targets. Findings from case studies and qualitative interviews suggest that the museum staff's efforts to demystify science—a process that provided ongoing access to real scientific endeavors and invited personal contact with scientists—influenced the program's success. Findings also suggest that strong school liaisons may help increase family support for young women's scientific pursuits, which can in turn play a role in their success in this program.
Books
Authors: Lindauer Margaret A.
Published: January 2010

Reshaping Museum Space: Architecture, Design, Exhibitions: Edited by Suzanne MacLeod

Museum Texts: Communication Frameworks: By Louise J. Ravelli
Recollections of Expo 70: Visitors' Experiences and the Retention of Vivid Long‐Term Memories
Authors: Anderson David , Shimizu Hiroyuki
Published: January 2010

Abstract  This study reports on outcomes of an investigation of visitors' longterm memories of the 1970 Japan World Exposition, Osaka. The paper reports in two parts the emergent outcomes of a study that provides understanding of the nature of visitors' long‐term memories of their experiences in an informal leisure‐time context. First, the paper discusses the common and most dominant recollections that emerged from 48 visitors' memories of this event 34 years ago. An overall explication of visitors' memories of their experiences of the event reveals an interesting mix of reactions: wonderment about the world and the amazing technological advances of the era, blended with personal discomfort and frustrations associated with the memories. These mixed feelings are presented against the backdrop of Japanese national identity re‐emergent on the world stage. Second, an analysis and discussion of qualitative data provides case examples of how three psychological and behavioral factors (affect, agenda fulfillment, and rehearsal) shape the vividness of episodic and/or autobiographical memories of the episodes as they are recalled 34 years later. This paper vividly illustrates the power of qualitative data to illuminate understanding of visitors' long‐term memories and presents some significant issues for museum staff to consider as they plan for visitor experiences that will have lasting impact.
Participatory Communication with Social Media
Authors: Russo Angelina , Watkins Jerry , Kelly Lynda , Chan Sebastian
Published: January 2010

Abstract  Major museums worldwide are starting to use social media such as blogs, podcasts and content shares to engage users via participatory communication. This marks a shift in how museums publicly communicate their role as custodians of cultural content and so presents debate around an institution's attitude towards cultural authority. It also signifies a new possible direction for museum learning. This article reports on a range of initiatives that demonstrate how participatory communication via social media can be integrated into museum practices. It argues that the social media space presents an ideal opportunity for museums to build online communities of interest around authentic cultural information, and concludes with some recent findings on and recommendations for social media implementation.
Promoting Sustainability: Audience and Curatorial Perspectives on The Human Factor
Authors: Sutter Glenn C.
Published: January 2010

Abstract  Humanity faces a growing list of socio‐economic and environmental problems, which impel us all to foster more sustainable forms of development. This paper examines how museums might encourage the kind of awareness that can lead to sustainability, by assessing responses to The Human Factor, a permanent exhibition at the Royal Saskatchewan Museum, which raises questions about values, beliefs, and actions associated with the industrialized worldview. Responses to the exhibition were assessed through quantitative exit surveys and a novel technique involving heart rate monitors. Additional qualitative insights were gained from responses of participants in a high school Youth Forum on Sustainability that used the exhibition to catalyze discussion. Together, these studies suggest that provocative exhibitions can foster understanding and awareness among teenagers and adults through a combination of cognitive and emotional responses, and that a focus on sustainability can be challenging both for visitors and for museums as cultural institutions.
Books
Authors: Di Giovine Michael A.
Published: January 2010

Book reviewed in this article:

Heritage Interpretation: Edited by Alison Hems and Marion Blockley

Uses of Heritage: By Laurajane Smith
Greetings from the Factory Floor: Industrial Tourism and the Picture Postcard
Authors: Marsh Allison C.
Published: January 2010

Abstract Since the late nineteenth century, it's been popular to visit factories as a leisure time activity, a practice that continues up to the present day. This article provides a general overview of factory tours, as shown through the material culture and history of postcards. It explores the benefits and limitations of this unusual primary source and suggests how ephemera can be used more generally in capturing the intentions of and reactions to museum exhibits.
At Hospitality's Threshold: From Social Inclusion to Exilic Education
Authors: Doron Edith
Published: January 2010

Abstract Describing actual museum‐wide events developed for the culturally charged arena of the Brooklyn Children's Museum, this article explores the philosophical and pedagogical double binds that have brought multiculturalism to a political impasse. Museums have strived to be valued resources in an increasingly diverse society. In aspiring to broaden their audience base, their work has shifted from developing educational policies that are “object‐centered” to those that are “community‐centered” — a change of strategy affecting everything from programs to exhibit design. Children's museums — distinct (if not marginalized) from the serious work of the traditional art or ethnographic or natural history museum — know and indeed say in their very name — “children'smuseum” — that they are for the sake ofsomeoneand not aboutsomething. They have always already been attuned to the visitor at the threshold.
“A Large Object with a Small Museum”: A Narrative Analysis of Tlotlo's Experience of an Astronomy Science Center
Authors: Lelliott Anthony , Pendlebury Shirley
Published: January 2010

Abstract  This paper presents a narrative analysis of an elementary school student's view of his visit to an astronomy science center in South Africa. We illustrate the power of narrative in illuminating the importance of the student's perspective in understanding the conditions for learning in a museum setting. Using principles of narrative presentation, the paper describes Tlotlo's thinking throughout his participation in a school visit to the visitors' center at a radio telescope. The paper discusses six features of the visit: student misconceptions; inadequate preparation and followup; memories and imaginings; enjoyment; discussing the visit afterwards; and socioeconomic constraints on visits. These features are examined within the context of a developing country: both confirming previous research on school visits and providing new insights into how such visits can be interpreted. The significance of narrative analysis for science center educators is discussed and suggested as appropriate for current research in museums.
The Anticipated Utility of Zoos for Developing Moral Concern in Children
Authors: Fraser John
Published: January 2010

Abstract  This study asked why parents value zoo experiences for themselves and their children. It proposes a new theory regarding the psychological value of such experiences for the development of identity. The study used a constructivist grounded theory approach to explore parenting perspectives on the value of zoo visits undertaken by eight families from three adjacent inner‐city neighborhoods in a major American city. The results suggest that parents use zoo visits as tools for promoting family values. These parents felt that experiences with live animals were necessary to encourage holistic empathy, to extend children's sense of justice to include natural systems, and to model the importance of family relationships. The author concludes that parents find zoos useful as a tool for helping their children to develop skills with altruism, to transfer environmental values, to elevate children's self‐esteem, and to inculcate social norms that they believe will aid in their children's social success in the future.
Thermal and Structural Analysis of a Suspended Physics Package for a Chip-Scale Atomic Clock
Authors: Laws A. D. , Lee Y. C.
Published: January 2010

Power dissipation for chip scale atomic clocks (CSAC) is one of the major design considerations. 12 mW of the 30 mW power budget is for temperature control of the vertical-cavity surface-emitting laser (VCSEL) and the alkali-metal vapor cell, each must be maintained at 70±0.1°C even over large ambient temperature variations of 0°C to 50°C. The physics package of a CSAC device is composed of the cell, VCSEL and optical components. This package is heated to 70±0.1°C, but must be very well insulated to dissipate less than 12 mW. To create such a high level of insulation the physics package is enclosed in a gold coated vacuum package and is suspended on a specially designed Cirlex structure. The thermal performance of the suspended physics package has been evaluated by measuring the total thermal resistance from a mockup package with and without an enclosure. Without and enclosure the resistance was found to be 1.07°C/mW. With the enclosure the resistance increases to 1.71°C/mW. These two cases were modeled using FEA, which was found to match well. A FEA model of the real design of the enclosed, suspended physics package was then modeled an was found to have a thermal resistance of 6.28°C/mW, which meets the project requirements. The structural performance of the physics package was measured by shock testing the physics package mockup and recording the response with a high speed video camera. The shock testes were modeled using dynamic FEA and were found to match the measured displacements well. A FEA model of the real design of the physics package was created and it was found that the package will survive an 1800 g shock of any duration in any direction without exceeding the Cirlex yield stress, 49 MPa. In addition the package will survive a 10,000 g shock of any duration in any direction without exceeding the Cirlex tensile stress, 229 MPa.
Natural Convection From Finned Heat Sinks
Authors: Yeh L. T. , Yeh Joseph , Chung B. T. F.
Published: January 2010

A CFD (computational fluid dynamics) analysis is performed on the finned heat sinks. For convenience, a commercial CFD code, Flotherm, is utilized in the analysis. Though the code can handle the radiation heat transfer, the present analysis is limited to the natural convection with the base of the heat sink at a constant temperature. The continuous fin configuration is first considered due to the importance of its applications. Several experimental data are available for the vertically straight-fin heat sink and a useful correlation is also developed. For given overall fin dimensions of 15″ × 10.341″ × 2.2″, the correlations are first employed to determine the optimal fin spacing. This optimal fin spacing of 0.439 in is then used to develop the baseline CFD model. The dimensions of the baseline CFD model are as follows: Fin width (in): 10.341. Heat sink length (in): 15. Fin spacing (in): 0.439. Fin height (in): 2.0. Fin thickness (in): 0.1. Fin base plate thickness (in): 0.2. Fin numbers: 20. The baseline model with various fin spacing is analyzed and the results (heat loss from the finned heat sink) compare well with those obtained through the correlations. The analysis is extended to the staggered and in-line fin configurations because of their practical applications. Three different fin lengths, including 1″, 3″ and 5″ fin length for the staggered fin array are examined. The results indicate that the effectiveness of heat transfer is increased as the fin length increasing. The continuous fin configuration is the most efficient, and is followed by the staggered fins and then by the in-line fins.
Force Air Cooled Electronic Equipment Under Loss of Cooling Condition With Blocked Air Duct
Authors: Wang Frank Fan
Published: January 2010

There are many electronic equipments are cooled by forced cooling airs. Some equipment’s forced cooling air is supplied by air ducts, where air blower is located at a distance. In many cases, when the remote blower is out of order, the buoyancy of heated air cannot generate enough pressure to overcome the long air ducts and the blower. There is no air flow at all through the normal cooling air duct. That is called loss of cooling thermal condition. Loss of cooling condition is usually the worst case thermal challenge. In aerospace applications, most forced convection cooled electronic equipments need to meet the loss of cooling operation requirement. During loss of cooling, the electronic equipment needs to obtain cooler ambient surrounding air from a different inlet other than the supply air inlet. However, the passive cooling air inlet cannot interfere with the normal cooling situation. In normal cooling situation, forced cooling air is provided to lower the electronics temperature to a level of meeting the mean time between failure (MTBF) requirements. This paper will discuss a few trade studies of how different design approaches meet this loss of cooling air challenges; present a detailed CFD calculation of one of the design options. Many other considerations are also to be presented other than just thermal design concerns.
SnAgCu (SAC) Durability Under Vibration Loading at Different Isothermal Temperature Conditions
Authors: Plaza G. , Zhou Y. , Osterman M. , Dasgupta A.
Published: January 2010

The high cycle fatigue (HCF) durability of SAC solders has not been investigated to the same extent as SnPb solder [1] [2] [3], especially as a function of temperature. This is a first essential step towards understanding the interaction between thermal cycling damage and vibration damage [4] [5]. In this study, vibration durability is investigated under step-stress broad-band random vibration excitation at different temperatures. The test vehicle consists of various common surface mount components soldered onto a test PWB. The solder system, plating system and thermal pre-conditioning are systematically varied. Twenty printed wiring assemblies are tested at a time in a specially designed fixture on an electrodynamic shaker. The test setup is first characterized before conducting the durability experiment, by collecting strain histories at different sites on the PWB, mounted at different locations on the fixture, under different loading conditions. These strain results are useful to be able to compare the performance of the assemblies at different strain conditions and as inputs for subsequent finite element analysis (FEA) to estimate acceleration factors for various field environments [6]. In order to check the temperature dependence of the vibration durability, the broad-band vibration durability tests have been repeated at room temperature, high temperature and low temperature. Test results are reported in this paper, and important trends are identified for SAC and SnPb solder systems. Destructive failure analysis (cross-sectioning, polishing and microscopy) is used to confirm that the failure is by solder fatigue.
Assembly Cost Reduction With Wafer Level Die Attach Film
Authors: Dunlap Stewart
Published: January 2010

Die attach adhesive is used to connect silicon die together in a chip package. Traditionally, liquid or film adhesive was applied on the surface of the die that was to be attached, and the die was placed on the adhesive. Today the number of dies stacked are increasing, and the thickness of the dies are decreasing. Adhesive lamination quality, adhesive to die edge accuracy, and reduced assembly process steps are all necessary moving forward. An innovative method of applying film on the wafer before the dies are separated, accomplishes these goals. A poster will be used to compare unit versus wafer level die attach film. The poster will clearly show the reduction of the process steps, reduction of the equipment, and the improvement in quality resulting from wafer level die attach film.
Data Center Workload Placement for Energy Efficiency
Authors: Bash Cullen , Forman George
Published: January 2010

Data center costs for computer power and cooling have been steadily increasing over the past decade. Much work has been done in recent years on understanding how to improve the delivery of cooling resources to IT equipment in data centers, but little attention has been paid to the optimization of heat production by considering the placement of application workload. Because certain physical locations inside the data center are more efficient to cool than others, this suggests that allocating heavy computational workloads onto those servers that are in more efficient places might bring substantial savings. This paper explores this issue by introducing a workload placement metric that considers the cooling efficiency of the environment. Additionally, results from a set of experiments that utilize this metric in a thermally isolated portion of a real data center are described. The results show that the potential savings is substantial and that further work in this area is needed to exploit the savings opportunity.
Thermo-Mechanical and Hygro-Mechanical Stress Analyses of an Organic Multilayer Sheet
Authors: Ikeda Toru , Mizutani Tomonori , Miyazaki Noriyuki
Published: January 2010

A polarizing plate, which is an important part of a liquid crystal display panel, is made by sandwiching an organic polarizer between protecting films. An organic polarizer is both a hygroscopic and orthotropic material. The hygroscopic swelling and drying shrinkage of the organic polarizer can cause the polarizing plate to crack and the liquid crystal display panel to warp. The diffusion coefficient and Henry’s law coefficient were measured using a thermo-gravimetric analyzer (TGA) under controlled humidity, while the coefficient of moisture expansion (CME) was measured using a thermo-mechanical analyzer (TMA), also under controlled humidity. The thermo-mechanical and hygro-mechanical deformation of a polarizing plate was analyzed using the finite element method (FEM). This analysis was performed as follows. The distribution of the moisture concentration was analyzed according to Fick’s law. The equation of Fick’s law is similar to that of the transient heat conduction, and the FEM for the transient heat conduction was utilized for the transient diffusion analysis. The hygro-mechanical analysis was then carried out in a way similar to the thermal stress analysis. Thermal stress was analyzed separately using the FEM. Finally, the obtained hygro-mechanical strain and stress were added to the thermal strain and stress, respectively. The measured CME of a polarizing plate corresponds to the analyzed CME using the CMEs of a polarizer and protecting films. The warpage of a liquid crystal display panel sometimes causes light leakage along the frame of the display panel due to contact of the display panel with the bezel of the frame. The warpage was analyzed according to the thermo-mechanical strain and the hygro-mechanical strain. The contact between the display panel and the bezel, which causes the light leakage, was estimated.
Analysis of Thermal Displacements Due to CTE Mismatches Using FEA Simulation and Experimental Validation With a Differential Variable Reluctance Transducer
Authors: Asghari Tony A. , Janas Joseph
Published: January 2010

Deformation induced by thermal loading in a severe automotive environment, between an electronic ceramic substrate — bonded to an aluminum heatsink — and an adjacent nylon material, was investigated by numerical and experimental methods. The goal of this paper is to quantify the relative displacement of certain points of interest, where an aluminum wire bond exists. This displacement is caused by 1) coefficient of thermal expansion (CTE) mismatches of various parts of the assembly when temperature distribution is uniform, and 2) when temperature gradients exist in either steady-state or transient conditions due to thermal cycling (between +150°C and −40°C) as well as power cycling. ANSYS Workbench™ finite element analysis (FEA) software was used to model the system level deformation under various conditions. A unique, quick, and repeatable method of experimentally measuring displacement using a Differential Variable Reluctance Transducer (DVRT®) was utilized. The DVRT® and its signal conditioner provide an analog DC voltage output, which is proportional to linear displacement (resolution as fine as 1.5 micrometer). Error inherent to the DVRT® was adjusted by further testing using a modified sample of Invar. The numerical and experimental results showed good overall correlation.
CMOS Compatible Wafer-Scale Encapsulation MEMS Resonators
Authors: Kim Bongsang , Hopcroft Matthew A. , Melamud Renata , Jha Chandra M. , Agarwal Manu , Chandorkar Saurabh A. , Kenny Thomas W.
Published: January 2010

A unique MEMS encapsulation process on the use of epipolysilicon as a packaging and sealing layer is demonstrated. This process provides a very clean and stable environment for MEMS, is compatible with CMOS integration, and can be carried out in a conventional CMOS facility with standard tools. Silicon resonators fabricated inside the ‘epi-seal’ encapsulation showed quality factors over 10,000 and commercial level long-term stability (ppm level drift for over 1 year of operation). In addition, several modifications and improvements, such as Si-SiO2 composite resonators for reduced temperature coefficient of frequency and thermal isolated anchors for direct temperature control were successfully added to this process for improvements in resonator stability over temperature.
Low-Cycle Fatigue Reliability Evaluation for Lead-Free Solders in Vehicle Electronics Devices
Authors: Yu Qiang , Shibutani Tadahiro , Tanaka Akifumi , Koyama Takahiro , Shiratori Masaki
Published: January 2010

The changeover from eutectic Sn-Pb solder to lead-free solder (Sn-Ag-Cu) has been driven by environmental concerns in the last few years. In this study, in order to obtain the low-cycle fatigue characteristic of Sn-Ag-Cu lead-free solder joints, an isothermal mechanical fatigue test with a large strain range, which can clarify the crack generation process and shorten the examination time, was carried out. FEM analysis was also performed in order to evaluate the relationship between the inelastic strain range and the low-cycle fatigue life. As a result, compared with fatigue life longer than 1000 cycles, the scatter of the fatigue cycles from 100 to several hundred cycles becomes larger. So, it seems that it is necessary to carefully evaluate the low-cycle fatigue life in the reliability evaluation. Moreover, in large chip components, not only crack initiation, but also crack propagation, affects the failure life. Thus, the crack path was simulated and the failure cycle of the large chip was evaluated based on Miner’s rule, and reliability of including the fatigue crack propagation can be evaluated by the analytical approach.
Effect of Packaging Stress in a Laser Chip on Its Radiation Spectrum
Authors: Kitamura Atsushi , Kawauchi Taira , Suzuki Ken , Miura Hideo , Sasaki Minoru
Published: January 2010

A wavelength division multiplexing system is a basic infrastructure for the next coming optical fiber network. Since the band gap of a laser chip that determines the wavelength of a radiated laser beam is varied by strain in a laser chip, packaging-induced stress may change a radiation spectrum of a mounted laser chip. The final residual strain in an active layer of a laser chip varies significantly depending on the thin film deposition process for interconnections and mirrors, and thus, changes the radiation spectrum of the laser chip. Thus, the change of residual stress caused by packaging was analyzed by a finite element method. The estimated change reached about several hundreds MPa depending on materials of a substrate, adhesion material, and deflection of the package. In order to confirm the effect of such an additional strain on a radiation spectrum of a laser beam, mechanical stress (strain) was applied directly to a laser chip and the change of the spectrum of the laser chip under the applied strain was measured. A four-point bending test was used for applying mechanical stress to a laser chip. It was confirmed that the radiation spectrum of a laser chip, such as wavelength and width of the spectrum, changes almost linearly with the amplitude of the applied uni-axial strain. The wavelength of the laser chip decreased and a width of the spectrum of the laser chip at the threshold current increased with the increase of the magnitude of the applied strain. The change rate of the wavelength was about 0.4-nm/micro-strain. Therefore, it is very important to control the final residual stress or strain in an active layer of a laser chip to assure the precise optical characteristics of the laser chip.
Optoelectronic Methodology for Development of MEMS
Authors: Pryputniewicz Ryszard J. , Marinis Ryan T. , Klempner Adam R. , Hefti Peter
Published: January 2010

Development of microelectromechanical systems (MEMS) constitutes one of the most challenging tasks in today’s micromechanics. In addition to design, analysis, and fabrication capabilities, this task also requires advanced test methodologies for determination of functional characteristics of MEMS to enable refinement and optimization of their designs. Until recently, this characterization was hindered by lack of a readily available methodology. However, building on recent advances in photonics, electronics, and computer technology, we have developed an optoelectronic methodology particularly suitable for development of MEMS. In this paper, we describe the optoelectronic methodology and illustrate its use with representative examples. By quantitatively characterizing performance of MEMS, under different vibration, thermal, and other operating conditions, we can make specific suggestions for their improvements. Then, using the optoelectronic method, we can verify the effects of these improvements. In this way, we can develop better understanding of functional characteristics of MEMS, which will ensure that they are operated at optimum performance, are reliable, and are durable.
A Highly Accelerated Thermal Cycling (HATC) Test for Solder Reliability Assessment in BGA Packages
Authors: Long X. , Dutta I. , Guduru R. , Prasanna R. , Pacheco M.
Published: January 2010

A thermo-mechanical loading system, which can superimpose a temperature and location dependent strain on solder joints, is proposed in order to conduct highly accelerated thermal-mechanical cycling (HATC) tests to assess thermal fatigue reliability of Ball Grid Array (BGA) solder joints in microelectronics packages. The application of this temperature and position dependent strain produces generally similar loading modes (shear and tension) encountered by BGA solder joints during service, but substantially enhances the inelastic strain accumulated during thermal cycling over the same temperature range as conventional ATC (accelerated thermal cycling) tests, thereby leading to a substantial acceleration of low-cycle fatigue damage. Finite element analysis was conducted to aid the design of experimental apparatus and to predict the fatigue life of solder joints in HATC testing. Detailed analysis of the loading locations required to produce failure at the appropriate joint (next to the die-edge ball) under the appropriate tension/shear stress partition are presented. The simulations showed that the proposed HATC test constitutes a valid methodology for further accelerating conventional ATC tests. An experimental apparatus, capable of applying the requisite loads to a BGA package was constructed, and experiments were conducted under both HATC and ATC conditions. It is shown that HATC proffers much reduced cycling times compared to ATC.
Measurements of Microjet Cooling and Phase Change Characteristics Using Microcantilever Heaters
Authors: Lee Jungchul , Hunter Hanif , Goericke Fabian , Naik Nisarga , Allen Mark , Glezer Ari , King William P.
Published: January 2010

This paper reports novel microcantilever metrology tools to investigate free microjets emanating from a micromachined nozzle having 10 μm diameter. Microcantilever sensors are well-suited to interrogate these flows due to their high spatial and temporal resolution. In this work, microcantilevers with integrated piezoresistors have been used to detect the breakup distance of free microjets, and microcantilevers with integrated resistive heaters have been applied to study microjet cooling and phase change characteristics. Measured microjet thrusts were in the range of 10 – 60 μN and heat fluxes were measured in the range of 25 – 350 °C. The convective heat fluxes by microjet impingement boiling were estimated at 2.9 – 7.6 kW/cm2. The techniques reported herein are promising to characterize microscale flows.
Engineering New Package Ideal Materials Using Polymer Resins and Nanoparticles
Authors: Sarihan Vijay , Xu Steven , Keser Beth
Published: January 2010

The trend in new electronic packages is to deliver smaller, thinner space-sensitive packages that meet or exceed customer package reliability expectations. This poses new material challenges in terms manufacturability and reliability. Size, space and manufacturability constrain typical packaging material choices available to meet the desired package performance. This often results in non optimal package performance and some times results in severe reliability challenges. Instead of compromising reliability expectations, the proposed approach engineers new materials to meet or exceed the desired packaging performance while meeting manufacturability criteria. In this paper, nano-particles are used as filler particles for polymer resins to modify the composite material properties. However, instead of a trial and error approach, a predictive simulation based approach is used to achieve the desired results. Advanced nonlinear finite element methodology first determines the desired material properties necessary to meet package reliability requirements. Then, achievable material property variations for a system of polymer resins and nano-particles are predicted. The optimal match is determined between achievable properties and those that will maximize package reliability. A new material was formulated using the predicted polymer resin nano-particle combination. Formulation addressed additional manufacturability issues of uniform dispersion, particle surface chemistry and a manufacturing necessity of photo definition capability. Mechanical properties were characterized to validate the property prediction capability. This validated simulation based approach is very effective in determining the ideal formulation resulting in the desired achievable properties and package reliability.
Design and Verification of Cray XT- 4 Supercomputer Cooling System
Authors: Yatskov Alexander
Published: January 2010

Cray supercomputers are purpose-built to meet the special needs of capability class HPC applications. Recent advances in Cray scalar supercomputer systems resulted in the introduction of the higher density compute cabinet that consumes significant amounts of electrical power and produces an extraordinary amount of heat. Due to the new design requirements, which have tremendous consequences with regard to thermal management, new cooling concepts were required. The XT4 can have up to 30,000 dual-core Opterons, and the SeaStar2 interconnection chip plugs right into the Hyper Transport links on the Opteron processors to make a very fast mesh of processors and memory for applications. Such a machine consumes about 5.2 megawatts of power to deliver around 1.15 petaflops. That is twice the size of Red Storm, but more than a factor of 10 more performance. The extra power density required additional modification to the cooling system. This article describes the design, simulations and verification of the XT-3 and XT-4 systems. Over the past few years thermal design for cooling microprocessors has become increasingly challenging, as silicon technology continues to scale in accordance with Moore’s law. The industry has traditionally relied on gradual improvements in air cooled, solid metal heat sinks to keep pace with change in microprocessor design to provide cost effective solution for removing from microprocessors. In Cray’s XT-4 system, chip power density is expected to almost double that of it’s Red Storm/XT-3 predecessors, while maintaining the same cabinet size.
Failure Mode and Thermal Performance Analysis of Stacked Panel Level Package (PLP)
Authors: Wei Hsiu-Ping , Yew Ming-Chih , Huang Chao-Jen , Chiang Kuo-Ning
Published: January 2010

In this paper, a new packaging technology, chip-on-metal (COM) panel level package (PLP), with stacking and fan-out capabilities is proposed. Moreover, the concept of the COM PLP and the process of its fabrication are described. During the manufacturing process, the trench around the chip is filled with the filler polymer material. Therefore, the solder bumps could be located on both the filler polymer and the chip surfaces by the redistribution lines, and the pitch of the chip side is fanned-out. In our previous research, it was shown that the physical behavior of the COM PLP is different from that of the conventional wafer level package (WLP). To assess the thermal performance and thermo-mechanical characteristic of the proposed PLP, the finite element analysis (FEA) in board level is carried out. The junction temperature and thermal resistance of the COM PLP and the stacked PLP are discussed to study the thermal performance. At the same time, the mean cycle to failure of the solder joints is predicted, and the result shows that the reliability of solder joints can be highly improved by the proposed packaging technology. However, the new failure mode may occur at the metallic traces so the reliability assessment of the signal trace is also investigated. In addition, the parametric analysis of the COM PLP is studied to enhance the thermal performance and reliability characteristic. Thus, the PLP technology will have high potential for various applications in the near future.
Thermal Management Design of a Nanoscale Biocalorimeter
Authors: Kowalski Gregory J. , Talakoub Amir , Larson Dale
Published: January 2010

A nanoscale calorimeter design based on temperature induced changes in a surface plasmon based photonics effect has the potential to decrease the mass of experimental compounds consumed and to increase the throughput of experiments investigating drug development. This calorimeter is based on a demonstrated surface plasmon biosensor in which index of refraction changes as small as 10−5 % caused by biochemical reactions on the sensor surface are detected. To achieve this sensitivity require that the device’s temperature be held constant to within ± 0.001 K. In the biosensor the temperature was held constant to measure the concentration changes. For the calorimeter the concentration is held constant and temperature changes are monitored. In the calorimeter design the nanohole array sensor will be used as a sensitive thermometer that will be used to determine the enthalpy of binding, equilibrium binding constant and entropy changes of biochemical reactions. The numerical analysis described in this work demonstrates that nanoscale calorimetry is possible. The simulations demonstrate that two designs can produce temperature rises of 5.5 and 40 C, respectively well above the (10−3) C resolution of the sensors. These results were obtained using less than three orders of magnitude less reactants than is currently being used in calorimetry studies which is a significant advance of this technology.
Analysis and Performance Comparison of Competing Desktop Cooling Technologies
Authors: Kumari Niru , Krishnan Shankar , Garimella Suresh V.
Published: January 2010

The present work compares the performance of various competing thermal management technologies for the desktop sector. An air-cooled heat sink used for the Intel Pentium 4 Processor is used as the baseline for comparison. Heat sinks based on metal foams, microchannels (with single-phase liquid) and jet impingement (with air and single-phase liquid) are compared based on total heat sink system thermal resistance and heat dissipation capacity. The analysis is carried out under the constraints of a fixed heat sink volume available in a typical desktop, and a fixed ambient air temperature. The comparison of thermal resistances is made under the constraint of the same pumping power as in the baseline heat sink. The maximum heat dissipation possible using a particular heat sink technology is estimated and this can be used to select technologies to meet future thermal challenges as outlined in the International Technology Roadmap for Semiconductors (ITRS). The results show that microchannel and liquid jet impingement cooling provide the greatest heat removal rates under the given constraints. The maximum power dissipation for these cases is almost double that of the baseline air-cooled heat sink. Under the chosen constant value of the junction to heat sink resistance, only modest improvements in heat removal rate are obtained with the microchannel and jet impingement technologies even if the pumping power constraint is relaxed, and a specific pump curve is used instead. The junction to heat sink resistance is significantly higher than the heat sink to ambient resistance, and is the key determinant in the comparisons.
Effect of Ag and Cu Concentrations on Creep of Sn-Based Solders
Authors: Chen T. , Dutta I. , Jadhav S.
Published: January 2010

The creep behavior of Sn1Ag0.5Cu, Sn2.5Ag1Cu and Sn4Ag0.5Cu ball grid array (BGA) solder balls and 99.99% pure polycrystalline Sn bulk was studied using impression creep. The microstructures of the as-reflowed solders was characterized. It was found that SnAgCu solders consist of primary dendrites/grains of β-Sn, and a eutectic microconstituent comprising fine Ag3Sn and Cu6Sn5 particles in β. With increasing concentrations of Ag and Cu in the alloy, the proportion of the eutectic microconstituent in relation to the primary β phase increases. In pure Sn and Sn-1Ag-0.5Cu, the β grains form the continuous matrix, whereas in Sn2.5Ag1Cu and Sn4Ag0.5Cu, the eutectic microconstituent forms a continuous network around the β grains, which form isolated islands within the eutectic. The steady state creep behavior of the alloys was dominated by the response of the continuous microstructural constituent (β-Sn or solid solution β for pure Sn and Sn1Ag0.5Cu, and the eutectic microconstituent for Sn2.5Ag0.5Cu and Sn4Ag0.5Cu). In general, the steady-state creep rate decreased with increased alloy content, and in particular, the volume fraction of Ag3Sn and Cu6Sn5 precipitates. The rate-limiting creep mechanism in all the materials investigated here was core diffusion controlled dislocation climb. However, subtle changes in the stress exponent n and activation energy Q were observed. Pure Sn shows n = 5, Q = 42kJ/mole, Sn1Ag0.5Cu shows n = 5, Q = 61kJ/mole, whereas both Sn2.5Ag1Cu and Sn4Ag0.5Cu show n = 6 and Q = 61kJ/mole. Rationalizations for the observed changes of n and Q are provided, based on the influence of the microstructure and the solute concentrations.
Nodal Topology in Compact Thermal Models
Authors: Greisen D. H. , Manno V. P.
Published: January 2010

Compact Thermal Models (CTMs) utilize a few connected thermal nodes to represent the thermal characteristics of electronic packages. These models are preferable to highly discretized models in preliminary design and system level analysis because of their computational efficiency. Surface heat flux non-uniformities often make it necessary to subdivide the package surfaces into multiple CTM nodes. This division is often quantified as the surface area ratio. This work assesses CTM performance sensitivity to area ratio changes and variation in heat transfer coefficient boundary conditions. CTMs for benchmark TQFP and BGA packages are developed using an admittance matrix approach. While optimum area ratios are identified, a direct correlation between these optimal values and the heat flux distributions computed from fully-discretized models was not obtained. CTM performance was found to be sensitive to changes in the heat transfer coefficient used to generate the CTM parameter values. A critical generating heat transfer coefficient was determined such that the resulting CTM, when optimized for a single boundary condition, was relatively accurate over the whole set of boundary conditions considered. This single boundary condition also provided an upper bound for error. This finding could be significant in future CTM development procedures.
Multidisciplinary Heat Generating Logic Block Placement Optimization Using Genetic Algorithm
Authors: Suwa Tohru , Hadim Hamid
Published: January 2010

A multidisciplinary optimization methodology for placement of heat generating logic blocks on integrated circuit chips is presented. The methodology includes thermal and wiring length criteria, which are optimized simultaneously using the genetic algorithm. An effective thermal performance prediction methodology based on a superposition method is used to calculate the temperature distribution on a silicon chip due to multiple heat generating logic blocks. Using the superposition method, the predicted temperature distribution in the silicon chip is obtained in a much shorter time than with a detailed finite element model and with comparable accuracy. The main advantage of the present multi-disciplinary design and optimization methodology is its ability to handle multiple design objectives simultaneously for optimized placement of heat generating logic blocks. To demonstrate its capabilities, the present methodology is applied to benchmark cases involving placement optimization of multiple heat generating logic blocks on a silicon chip. The results indicate that the maximum temperature on a silicon chip can be reduced by up to 7.5 °C, compared with the case in which only the wiring length is minimized.
Reliability of Indium Solder for Cold Temperature Packaging
Authors: Wu Rui , McCluskey F. Patrick
Published: January 2010

A failure model has been developed for indium die attach fatigue in extreme cold temperature environment applications, such as distributed control systems for planetary exploration. The model contains both a stress component, which is based on the packaging structure, and a damage component, which is based solely on the material properties. The stress model is developed for a wire bonded, hermetic ceramic module containing a SiGe hetero-junction bipolar transistor intended for use in a lunar base. The model was calibrated using results from −196°C to 125°C thermal shock testing.
Electrical, Optical and Thermofluidic Chip I/O Interconnections
Authors: Bakir Muhannad S. , Dang Bing , Meindl James D.
Published: January 2010

This paper describes microscale fluidic chip I/O interconnects to enable the delivery of a coolant from substrate-level fluidic channels to a CMOS chip with an integrated silicon microchannel heat sink. It is shown that the fluidic I/Os are flip-chip compatible and can be assembled simultaneously with C4 bumps. The cooling of >300 W/cm2 is demonstrated using the microfluidic chip I/Os. Their compatibility with optical I/Os and the mechanical compliance characterization of the optical I/Os are also described. Experimental research is reported in the fabrication, assembly, and testing of a chip with electrical and fluidic I/O interconnects.