bluuebunny/crossref_metadata_2025 huggingface dataset:
Using Identity‐Related Visit Motivations as a Tool for Understanding Adult Zoo and Aquarium Visitors' Meaning‐Making
Authors: Falk John H. , Heimlich Joseph , Bronnenkant Kerry
Published: January 2010

Abstract Considerable time and effort have been invested in understanding the motivations of museum visitors. Many investigators have sought to describe why people visit museums, resulting in a range of descriptive categorizations. Recently, investigators have begun to document the connections between visitors' entering motivations and their exiting learning. Doering and Pekarik have proposed starting with the idea that visitors are likely to enter a museum with an “entry narrative” (1996; see also Pekarik, Doering and Karns 1999). Doering and Pekarik argue that these entry narratives are likely to be self‐reinforcing, directing both learning and behavior, since visitors' perceptions of satisfaction will be directly related to experiences that resonate with their entering narrative. Falk took these ideas one step further and proposed that—although people have diverse reasons for choosing to visit museums—these diverse reasons tended to cluster around a relatively small number of motivational categories (2006). These categories appeared to be related to visitors' desires to use the museum for fulfilling identity‐related needs. Each of us assumes many identities over the course of our life. Some of our identities are enduring and long‐lasting; others are more ephemeral and situation‐specific; all help us navigate through the complexities of life.
Competing Agendas: Young Children's Museum Field Trips
Authors: Anderson David , Piscitelli Barbara , Everett Michele
Published: January 2010

Abstract  Visitors to museum settings have agendas that encompass a wide variety of missions. Agendas are known to directly influence visitor behavior and learning. Numerous agendas are at play during a visit to a museum. We suggest that in a museum‐based learning experience, children's agendas are often overlooked, and are at times in competition with the accompanying adult's agendas. This paper describes and qualitatively analyzes three episodes of competing agendas that occurred on young children's field trips to museums in Brisbane, Australia. The aim is to elucidate the kinds of tensions over agendas that can arise in the experience of young museum‐goers. Additionally, we hope to alert museum practitioners to the importance of considering children's agendas, with the aim of improving their museum experience. Suggestions are also made for ways in which educators can address children's agendas during museum visits in order to maximize learning outcomes.
Pathways for Communicating about Objects on Guided Tours
Authors: Camhi Jeff
Published: January 2010

Abstract  Guided tours offer special opportunities for lively and varied presentations that match the methods of interpretation to the characteristics of the participating visitors. Most tour guides rely on rather limited, unidirectional (guide‐to‐visitor) communication. Instead, this paper outlines six different pathways of communication that are possible among guide, visitors, and object. Each pathway offers several specific types of communicative acts. In addition, 35 guided tours in several different kinds of venue were examined to identify the pathways and types of acts that were used. The professional literature describes other types of acts, and more have been developed at the writer's home museum. All in all, the 58 different types of communicative acts described here present a wide range of opportunities for guides to communicate with visitors.
The Relative Credibility of Zoo‐Affiliated Spokespeople for Delivering Conservation Messages
Authors: Fraser John , Taylor Anthony , Johnson Erin , Sickler Jessica
Published: January 2010

Abstract  Zoos aspire to be leaders in environmental conservation through their work in environmental education. This study examined whether a spokesperson's job title impacts credibility when conservation messages are delivered to the public. Visitors to a zoo were presented with seven environmental messages. They then selected—from a list of zoo‐related job titles—the one they deemed most credible and the one considered least credible. Statistical analysis established that three “credible” job titles were selected significantly more often, while three were generally selected as “least credible.” The authors demonstrate that some job titles have greater credibility than others among visitors, and recommend that more attention be given to this variable if attitude and behavior change are desired outcomes. They caution that while source credibility may vary based on job title, the influence it has on persuasiveness is yet to be determined.
Books
Authors: McClellan Andrew
Published: January 2010

Curiosity and Enlightenment: Collectors and Collections from the Sixteenth to the Nineteenth Century, Arthur MacGregor
Identifying Behaviors to Target During Zoo Visits
Authors: Smith Liam
Published: January 2010

Abstract  Although many zoos and zoo associations state the capability and importance of influencing the behavior of zoo visitors, the little research conducted to date gives limited support for these statements. Addressing this deficit involves more research, but zoos also need to design communication strategies with the specific purpose of influencing visitor behavior. However, it's important, before designing a communication campaign, that zoos identify which behaviors to target. As a first step toward doing this, five nominal group technique (NGT) sessions were conducted with general staff from three zoos in Australia, as well as an executive body overseeing three zoos and members of a volunteer group for an urban zoo. Following NGT protocol, desired on‐site and off‐site visitor behaviors were identified and their importance prioritized. The most prioritized behaviors are presented here. The discussion in this paper focuses on the efficacy of the NGT sessions, the need for further capacity‐building in Australian zoos, and proposals for some areas of future research.
Slavery, Memory, and Museum Display in Baltimore: The Great Blacks in Wax and the Reginald F. Lewis
Authors: Wood Marcus
Published: January 2010

Abstract  This paper meditates upon a conundrum: Can there be a right way to represent the traumatic experience of Atlantic slavery within the context of a museum setting? The analysis deals with the question by focusing on the radically contrasting museological, aesthetic, and ethical codes of the Great Blacks in Wax Museum, and the Reginald Lewis Museum, both situated in Baltimore, Maryland. Three key sites are isolated for discussion: the names of the museums, their approaches to the topic of the Middle Passage, and lynching. While both museums have made important cultural contributions to the public memorialization of highly charged subjects, the Great Blacks in Wax emerges as the more radical institution, closely in touch with the dynamic and creative museum aesthetic of the wider Black Atlantic Diaspora, and of Brazil in particular.
Museums, Meaning Making, and Memories: The Need for Museum Programs for People with Dementia and Their Caregivers
Authors: Rhoads Libby
Published: January 2010

Abstract  At times considered an unreachable audience, people with dementia have found a wealth of positive and meaningful experiences in museum settings. Making a case for the creation of museum programs for people with dementia and their caregivers, this article describes the experience of dementia both for those diagnosed with the disease and for those providing care; highlights several existing museum programs for people with dementia; and offers suggestions for future programming options.
Computational Study of Hybrid Cooling Solution for Thermal Management of Data Centers
Authors: Mulay Veerendra , Karajgikar Saket , Agonafer Dereje , Schmidt Roger , Iyengar Madshusudan , Nigen Jay
Published: January 2010

The power trend for server systems continues to grow thereby making thermal management of data centers a very challenging task. Although various configurations exist, the raised floor plenum with Computer Room Air Conditioners (CRACs) providing cold air is a popular operating strategy. In prior work, numerous data center layouts employing raised floor plenum and the impact of design parameters such as plenum depth, ceiling height, cold isle location, tile openings and others on thermal performance of data center were presented. The air cooling of data center however, may not address the situation where more energy is expended in cooling infrastructure than the thermal load of data center. Revised power trend projections by ASHRAE TC 9.9 predict heat loads as high as 5000W per square feet of compute servers’ equipment footprint by year 2010. These trend charts also indicate that heat load per product footprint has doubled for storage servers during 2000–2004. For the same period, heat load per product footprint for compute servers has tripled. Amongst the systems that are currently available and being shipped, many racks exceed 20kW. Such high heat loads have raised concerns over air cooling limits of data centers similar to that of microprocessors. A hybrid cooling strategy that incorporates liquid cooling along with air cooling can be very efficient in such situations. The impact of such an operating strategy on thermal management of data center is discussed in this paper. A representative data center is modeled using commercially available CFD code. The change in rack temperature gradients, recirculation cells and CRAC demand due to use of hybrid cooling is presented in a detailed parametric study. It is shown that the hybrid cooling strategy improves the cooling of data center which may enable full population of rack and better management of system infrastructure.
Development of an Automated Solder Inspection System With Neural Network Using Oblique Computed Tomography
Authors: Teramoto Atsushi , Murakoshi Takayuki , Tsuzaka Masatoshi , Fujita Hiroshi
Published: January 2010

The high density LSI packages such as BGA is being utilized in the car electronics and communications infrastructure products. These products require a high-speed and reliable inspection technique for their solder joints. In this paper, an automated X-ray inspection system for BGA mounted substrate based on oblique computed tomography are proposed. Automated inspection consisted of OCT capturing, position adjustment, bump extraction, character extraction and judgment. Five characteristic features related to the bump shape are introduced. And by combining the characteristic features using artificial neural network, the condition of solder bump was judged. In the experiments, these techniques were evaluated using actual BGA mounted substrate. As a result, the correct rate of judgment reached 99.7%, which shows the clear evidence that proposed techniques may be useful in the practice.
Design Optimization of a Wafer Level Package for Surface Acoustic Wave Filters
Authors: Hong Jupyo , Gao Shan , Ha Job , Yang Sijoong , Kang Ingoo , Kim Taehoon , Choi Seogmoon , Yi Sung
Published: January 2010

In this paper, wafer level packaging of a surface acoustic wave (SAW) filter is considered. Numerical studies based on a three-dimensional finite element method (FEM) have been conducted in order to evaluate the reliability of a wafer level SAW package. The effects of package geometric parameters, such as the diameter of via hole and wafer thickness, on the reliability of the wafer level SAW package have been studied. The results show that the diameter of via hole for interconnection plays a key role in the reliability of the SAW package because the CTE mismatch between the filling materials of via holes (copper) and surrounding cap wafer martial (LiTiO3) is the highest among the material pairs in the package. Such CTE mismatch leads to the maximum stresses and warpages. The optimal thermo-mechanical properties of packaging materials have been proposed to achieve the minimum thermal stress during reflow process. Moreover, numerical results have also been compared with the experimental ones to validate the FEM model.
Effect of Underfilling Materials and Processes on the Reliability of System in Package
Authors: Kim Tae Hyun , Yi Sung , Roh Jae Ky , Jung Chang Mu , Guo Yan Shuang , Do Jae Chun , Kim Jin Gu , Guo Shan , Hong Jupyo
Published: January 2010

During the manufacturing process of the system-in-package, it has become susceptible to defects and internal residual stresses when dies, components, electric functionality and geometric complexity have increased. The mismatch of thermal expansion coefficient (CTE) among packaging materials and devices may lead to various failure modes during manufacturing processes, such as die broken, solder crack, substrate interface delamination. In this paper, the effect of underfill on the reliability of a system-in-package has been studied. A Bluetooth package is considered. The dimension of the package is 4.84 (L) × 6.15 (W) × 1.32 (H) mm. It contains an IC chip and several passive components such as crystals and filters. The substrate is NSMD type. Three underfill materials are considered. Materials were selected based on the numerical simulation. The causes of void formation during the underfill process have been investigated. In addition, the adhesion test of die passive material and PCB solder register was performed.
On-Line Hardness Characterization of Novel 2-mil Copper Bonding Wires
Authors: Hang C. J. , Lum I. , Lee J. , Mayer M. , Zhou Y. , Wang C. Q. , Hong S. J. , Lee S. M.
Published: January 2010

In order to eliminate the chip cratering for copper wire applications in IC packaging, it is worthwhile to develop new Cu wire chemistries to obtain a soft copper wire with a soft free-air ball (FAB). The conventional hardness characterization of a new bonding wire is a labour intensive, time-consuming work. Therefore an on-line hardness characterization method is presented that enables the hardness comparison of a larger number of different wires within a shorter time. The influences of capillary change, bonding substrate metallization and temperature on this method is quantified. It is found these influences need to be held constant during a hardness comparison study. With this method, the wire and FAB hardness comparison of nine novel 2-mil copper bonding wires, Cu 1 to Cu 9, and one 2-mil Au wire are performed. The wire hardness (wireside) and FAB hardness are characterized. It is found that the Cu 4 and Cu 5 have the softest wireside hardness and FAB hardness.
Analysis of Constant-Heat-Flux Heat Transfer in Metal Foam
Authors: Dukhan Nihad , Chen Kuan-Chin
Published: January 2010

The use of open-cell metal foam in contemporary heat exchange technologies is increasing rapidly. The high surface area density of metal foam places them among the best options for heat exchanger core materials. Certain simplifying assumptions for the combined conduction/convection heat transfer analysis in metal foam have not been exploited. Solving the complete, and coupled, fluid flow and heat transfer governing equations numerically is time consuming. A simplified two-dimensional analytical model for the heat transfer in open-cell metal foam block subjected to constant heat flux, and cooled by a low-conductivity fluid, is presented. The model assumes local thermal equilibrium between the solid and fluid phases in the foam, and neglects the conduction in the fluid. The local thermal equilibrium assumption is supported by previous studies performed by other workers. The velocity profile in the foam is taken as non-Darcean slug flow. An approximate solution for the temperature profile in the foam is obtained analytically. The temperature profile decays in what looks like an exponential fashion as the distance from the heat base increases, and increases in the flow direction. The model along with the simplifying assumptions were verified by direct experiment using air and an aluminum foam block heated from above by constant heat flux, for a range of Reynolds numbers. Very good agreement was found between the analytical and the experimental results.
Thermal Degradation and Mass Transport of Underfill Material
Authors: Lee Wen-Hao , Liang D. S. , Wang W. P. , Hsiao C. S.
Published: January 2010

In order to enhance the reliability of flip chip packages, the initiation and propagation of various interfacial failures and robust interfacial bonds between the underfill and the other components are highly desired. The water molecules inside the plastic material were chemically bonded with polymers by hydrogen bonds in the microholes formed by the polymer molecule chains. The bonding of water molecules and polymers reduced the adhesion strength at the interface between epoxy material and die. In this study, the interfacial bond strengths of commercial underfills with silicon nitride passivation are measured using bottom shear test. The thermal degradation of epoxy-based underfill material has been studied by thermogravimetric analysis (TGA). The results show that adhesion strength is correlated with TGA weight loss curve. Besides, epoxy is sensitive to moisture at high temperature storage. Moisture diffusion characterization at high temperatures in polymeric packaging materials is important since moisture absorption of polymeric packaging materials plays a determining role in “popcorn cracking” of IC packages during the solder reflow process especially for lead-free solder reflow profile. The moisture absorption was measured by using mass transport and diffusion theory.
Benchmark Testing of LGA Sockets for Server Applications
Authors: Beaman Brian
Published: January 2010

Recent trends for industry standard microprocessors show a transition from using micro PGA (pin grid array) sockets to using LGA (land grid array) sockets to meet the increased performance challenges for new server applications. These new industry standard LGA sockets use a hybrid construction with a solder ball connection to the printed circuit card and a compression connection to the contact pads on the bottom surface of the microprocessor package. Custom LGA sockets have been used for many years in high end server applications and provide improved electrical performance compared to these new hybrid LGA sockets. New LGA socket technologies continue to be developed to meet the variety of server application requirements. Benchmark testing has been performed on a variety of custom LGA sockets along with the hybrid LGA sockets used for industry standard applications. The benchmark testing includes evaluations of contact reliability performance, high speed electrical performance, and high current performance. The test hardware was designed to simulate the product application including the processor package construction, the printed circuit card cross section, along with the heat sink and retention hardware configuration. The results from the benchmark testing identify the limitations for various types of LGA sockets and provide critical insights for selecting the optimum solution for a given application.
Subcooled Pool Boiling Studies on Nano-Textured Surfaces
Authors: Sathyamurthi Vijaykumar , Banerjee Debjyoti
Published: January 2010

Heat transfer in subcooled pool boiling on nano-textured surfaces is reported in this study. Silicon wafers coated with Multiwalled Carbon Nanotubes (MWCNT) forests 9 microns (Type-A), and 25 microns (Type-B) in height and 8–15 nm in diameter with a randomized pitch of 16–30 nm, form the test surfaces. The test fluid is a fluoroinert (PF-5060, Manufacturer: 3M Co.) with a boiling point of 56°C. The test rig is of the constant heat flux type. Heat transfer enhancement of approximately 1.3 to 32% is observed in the nucleate boiling regime for Type-A at subcooling levels of 20°C. Type-B CNT shows an enhancement of about 13–30% in the nucleate boiling regime for 20°C subcooling. Digital images acquired during the tests show increased nucleation occurring on surfaces coated with MWCNT. Potential factors that could explain the observed heat transfer enhancement are: the enhanced surface area (nano-fin effect), disruption of the “microlayer” region in nucleate boiling, an increase in the size of cold-spots and the high thermal conductivity of MWCNT.
Effect of Process Parameters on TED-Based Q-Factor of MEMS
Authors: Pryputniewicz Ryszard J. , Pryputniewicz Dariusz R. , Pryputniewicz Emily J.
Published: January 2010

Continued advances in microelectromechanical systems (MEMS) technology have led to development of numerous applications including, but not limited to: automotive, communication, information technology, deep-space, medical, safety, national security, etc. These developments are being made possible because of creative designs and novel packaging based on use of some of the most sophisticated analytical and experimental tools available today. These tools are also employed to overcome limitations due to inherent behavior of materials fabricated into miniature shapes subjected to extremely harsh operating conditions while satisfying very challenging specifications/requirements of their applications. Thermoelastic internal friction is present in all structural materials and has been found experimentally in miniature silicon resonators (e.g., microgyroscopes, accelerometers, as well as biological, chemical, and other sensors/actuators) that rely on vibrations of either sensing elements or application-specific elastic suspensions that resonate. Regardless of their applications, sensors are always designed to provide the most sensitive responses to the signals they are developed to detect and/or monitor. One way to describe this sensitivity is to use the Quality (Q) factor. Most recent experimental evidence indicates that as the physical sizes of sensors decrease (especially because of continued advances in fabrication, e.g., by surface micromachining) the corresponding Q-factors become more and more dependent on thermoelastic damping (TED). This form of damping depends on material properties such as coefficient of thermal expansion, thermal conductivity, specific heat, density, and modulus of elasticity. It is also related to such design/operating parameters as resonator dimensions and temperature. This paper reviews a theoretical analysis of the effects that thermoelastic internal friction has on the Q-factor of microscale resonators and shows that the internal friction relating to TED is a fundamental damping mechanism in determination of quality of high-Q resonators over a range of operating conditions. Furthermore, the analysis also shows that the Q of resonators can be critical to the development of modern sensors. Microscale resonators are often used as basic sensing elements in the modern micromachined sensors. These sensors are frequency-modulated devices and exhibit a change in output frequency that is related to measurements and/or control of a physical variable. Accuracy and precision of these measurements/controls are inherently dependent on the frequency stability of the sensor/device output. This, in turn, greatly depends on damping in the resonating element itself.
Reliability Modeling of Lead Free Solder Joints in Wafer-Level Chip Scale Packages
Authors: Zhao Jie-Hua , Gupta Vikas , Lohia Alok , Edwards Darvin
Published: January 2010

Board level thermomechanical fatigue lifetimes of five different wafer-level chip scale packages (WCSP’s) with lead-free solder joints were studied by both experiment and finite element method modeling. The effect of three different constitutive laws of the lead-free solder, namely Anand viscoplasticity, power law break-down creep and time hardening creep are also investigated for each of the five packages. The fatigue correlation parameters based on the increment of volume-averaged inelastic strain energy density are deduced for each of the corresponding three constitutive laws. It is demonstrated that the relative error of the predicted lifetime for WCSP with lead-free solder joints can be within 10% compared to experiment. It is found that the fatigue correlation parameters depend strongly on the specific constitutive law. Another important finding is that the fatigue correlation parameters depend on the specific package family. It is also demonstrated that when fatigue correlation parameters calibrated for other package families are applied to WCSPs, the error in predicted lifetimes is consistently large.
Evaluation on Use of Thermoelectric Devices for Electronics Cooling
Authors: De Bock H. Peter J. , Icoz Tunc
Published: January 2010

As Thermoelectric devices are getting cheaper and more powerful in cooling, these devices are getting more popular for electronics cooling applications. However, due to the additional heat production inside the thermoelectric device, the application of a TE-cooler might not always be appropriate. In some applications, use of thermoelectric devices or coolers might cause higher temperature rises on heat generating electronics than conventional cooling solutions. To authors’ best knowledge, there exists no literature that studies whether thermoelectric cooling is better than traditional convective cooling without Thermoelectrics. This study aims to evaluate the performance and effectiveness of thermoelectric cooling for electronics. Two figures of merit are proposed, to compare performances of conventional and thermoelectric cooling techniques. An attempt is made to derive this figure of merit analytically with assumptions reflecting common electronics applications. Selective case studies will be presented based on constant heat flux and constant temperature difference.
Analysis of Alternative Data Center Cooling Approaches
Authors: Hannemann Robert , Chu Herman
Published: January 2010

The average equipment rack in most of today’s high-performance data centers is limited to 1–3 kW with a typical overall heat load density of less than 100 W/ft2. Near-future racks, however, will dissipate up to 15 kW; in 2–4 years, computer and communications rack heat loads are projected to balloon to 30 kW with heat load densities exceeding 500W/ft2. Handling these heat loads is becoming increasingly difficult and expensive using traditional rack and data center cooling approaches. Based on an analysis of a realistic data center expansion plan, the current paper compares capital and operating costs associated with three alternative cooling approaches: (1) a business-as-usual approach, (2) employment of cooling augmentation systems based on chilled water and refrigerant-based heat exchangers, and (3) deployment of water- and refrigerant-based device-level cooling for some of the heat load. A major conclusion of the work is that challenging current industry norms can result in significant energy savings while allowing the benefits associated with increased functional density.
Failure Analysis of Contact Probe Pins for SnPb and Sn Applications
Authors: Jang Changsoo , Park Seungbae , Infantolino Bill , Lehman Lawrence , Morgan Ryan , Sengupta Dipak
Published: January 2010

A failure mechanism of pogo-type probe pin is investigated. A probing tester with actuation capable in three-axes is used to simulate the actual inspection process experimentally. Force required to break in surface oxides and develop electrical contact is measured. Contact resistance history reveals that pins mating to Sn surfaces fail earlier than SnPb surfaces. Through periodic inspection of pin using microprobe/EDS as a function of probing count, the general root cause of pin failure is turned out to be pin tip wear out associated with Sn oxide growth on its surface. The cause of earlier failure of the pin probing matte Sn surface is identified as severe wear out by a rough and abrasive characteristic of matte Sn.
Evaluation Method of Interaction Relation Between Design Factors and Simple Assessment Approach for BGA Package Reliability
Authors: Kondo Satoshi , Yu Qiang , Shibutani Tadahiro , Shiratori Masaki
Published: January 2010

The recent development of electric and electronic devices has been remarkable. The miniaturization of electronic devices and high integration are progressing by advances in mounting technology. As a result, the reliability of fatigue life has been prioritized as an important concern, since the thermal expansion difference between a package and printed circuit board causes thermal fatigue. It is demanded a long-life product which has short development time. However, it is difficult because of the interaction between each design factor. The authors have investigated the influence of design factors on the reliability of soldered joints in BGA model by using response surface method and cluster analysis. By using these methods, the interaction of all design factors was clarified. Based upon these analytical results, design engineers can rate each factor’s effect on reliability and assess the reliability of their basic design plan at the concept design stage.
Design of an Absorption Based Miniature Heat Pump System for Cooling of High Power Microprocessors
Authors: Kim Yoon Jo , Joshi Yogendra K. , Fedorov Andrei G.
Published: January 2010

An absorption based miniature heat pump system, which can be driven by the low quality waste heat, is designed for chip cooling applications. Miniaturization is achieved, as the chemically-driven absorption/desorption process permits pressurization of the working fluid in liquid phase, requiring much smaller displacement volume than in vapor compression systems. The goal of this work is to design a system that keeps the chip junction temperature near room temperature, while removing 100 W of heat load. Water/LiBr pair is used as a working fluid. A dual micro-channel array evaporator is used to reduce both the mass flux through each micro-channel and the channel length, thus minimizing the pressure drop. Microchannel arrays for the desorber and condenser are placed in intimate communication with each other using a hydrophobic membrane, which provides a common chemically-selective interface between the desorber and condenser to separate the water vapor from LiBr solution. The separated water vapor is immediately cooled and converted into a liquid phase at the condenser side. For direct air cooling of the condenser and absorber, offset strip fin arrays are used. The performance of the components and the entire system is numerically evaluated and discussed.
A Modified Particle Swarm Optimization Scheme and Its Application in Electronic Heat Sink Design
Authors: Alrasheed M. R. , de Silva C. W. , Gadala M. S.
Published: January 2010

Particle Swarm optimization (PSO) is a robust stochastic evolutionary computation technique which is based on the movement and intelligence of swarms. In this paper the PSO algorithm is modified to improve its performance in a class of design applications in heat transfer. The developed approach includes a new term called a chaotic acceleration factor (Ca) into the algorithm, which enhances its convergence rate and its accuracy. The modified PSO is empirically tested with well-known benchmark functions. Next it is applied in plate-fin design with the objective of dissipating the maximum heat generation from an electronic component by minimizing the entropy generation rate to obtain the highest heat transfer efficiency.
Closed-Loop Flow Boiling Module With a Plated Heat Sink
Authors: Sakamoto Hitoshi , Mikubo Kazuyuki
Published: January 2010

A compact flow boiling module was developed for cooling a 100-W class package of about one-inch square in size. The cold plate, where heat is transferred from the package was made with a porous plating inside to augment boiling heat transfer. Heat transfer increased by a maximum of 50 percent when an organic refrigerant HFE-7100 was used, while the conditions for heat rejection to the ambient were kept unchanged. The heat rejection was achieved with an 80-mm fan with a matching corrugated fin radiator, whose effectiveness limits the overall size of the cooling module. The microscopic structure in the cold plate negatively influenced boiling of water, holding large patches of vapor bubbles on the surface. When the convective effect was increased by decreasing the cross sectional area of the channel by 10 times, heat transfer was further augmented approximately by 2 folds, making the use of the organic refrigerant an attractive option as the working fluid.
Cooling Design for the Next Generation Optical Disc Drive
Authors: Fujimoto Takayuki , Isoshima Nobuyuki , Toyoda Hiroyuki , Yamauchi Yoshiaki , Matsushima Hitoshi , Nishida Ikuo
Published: January 2010

Recently, the data transfer rate and the memory capacity of optical disc drives have been increasing dramatically. To obtain the high data transfer rate and greater memory capacity, the disc rotation speed and the laser power also need to be increased and these cause an increase in the temperature of the laser diode. Therefore, to develop the next generation optical disc drives, an enhanced cooling system is indispensable for the optical pick-up unit that contains the laser diode. As the temperature of the pick-up unit is influenced by the inside air flow induced by the disc rotation, it is quite necessary to grasp the velocity and temperature distribution inside the drive, and also the influence of the disc rotation speed on the temperature of the pick-up unit. Hence we applied PIV measurements and CFD simulations to visualize the flow field and the internal temperature. Then, during the actual disc recording process we measured the temperature of the pick-up unit and the internal air of the drive. As a result, we made clear the dependence of the disc rotation speed on the pick-up unit temperature. In addition, as an example for next generation optical disc drives, we evaluated the cooling system applying a small axial fan inside the drive and confirmed the validity of this fan system.
A Semi-Empirically Thermal Optimization for Heat Sink/TEC Assemblies With Various External Thermal Resistances
Authors: Wu M. C. , Wu T. Y. , Horng J. T. , Chang S. F. , Chen P. L. , Hung Y. H.
Published: January 2010

An effective semi-empirical method that combines thermal network models and empirical correlations for exploring the thermal performance of heat sinks and HS/TEC assemblies under different external thermal resistances is successfully established. A series of parametric studies, including the effects of external thermal resistance, input current of TEC and pumping heat capacity, on thermal performance improvements of HS/TEC assemblies have been performed. The Response Surface Methodology (RSM) is applied to establish explicit models of the thermal performance of HS/TEC assemblies under various external thermal resistances in terms of the design variables through statistical fitting method. Furthermore, the numerical optimization results for HS/TEC assemblies under different constraints are obtained. With constrained optimal designs of HS/TEC assemblies, the HS/TEC assemblies can provide excellent thermal performance improvements on (1) the reduction of thermal resistance, (2) the enhancement of module heat loads and (3) the improvement of external thermal resistance.
Thermal Optimal Design for Heat Sinks or Heat Sink/TEC Assemblies in a Ducted Flow
Authors: Wu T. Y. , Wu M. C. , Horng J. T. , Chang S. F. , Chen P. L. , Hung Y. H.
Published: January 2010

A series of experimental studies on the heat transfer characteristics from heat sinks or Heat Sink/TEC assemblies in a ducted flow have been performed. Their effects on heat transfer characteristics in ducted flow have been systematically explored. From the results, new performance correlations of the temperature difference (ΔT) and terminal voltage (V) of the TEC modules are proposed. Besides, two new correlations of steady-state average Nusselt number and external thermal resistance in terms of relevant influencing parameters for confined ppf heat sinks in a ducted flow are also proposed, respectively. The statistical sensitivity analysis of ANOVA F-test is employed to estimate the contributions of relevant parameters. Furthermore, a series of RSM models for evaluating heat transfer characteristics including average Nusselt number, average external thermal resistance and Tc−Ta are established. A Sequential Quadratic Programming with multi-starting-point method is successfully employed to automatically and efficiently seek a globally optimal thermal performance. An optimal design of HS/TEC assemblies under both COP ≥ 2 and pumping power limitation larger than 30 W can be achieved with a reduction of 75% on thermal resistance.
Fixed Vane Stator Development for Axial Fan Performance Improvement in Electronics Cooling
Authors: Stanley Gavin D.
Published: January 2010

An analysis and development method for augmenting flow and pressure performance of electronic cooling axial fans using a fixed vane stator is established using classical hand calculations, 2-dimensional (2D) Computational Fluid Dynamics (CFD) analysis, data from a design of experiments, and 3-dimensional (3D) CFD modeling. Where the size of electronic enclosures may disallow an increase in diameter of axial fans but allow for an increase in depth; a fixed vane stator is implemented to recapture lost dynamic pressure associated with swirl and radial flow vectors from the axial fan blades thus augmenting the pressure/flow curve of the unit. Stator blade effectiveness is evaluated and optimized first using data associated with National Advisory Committee for Aeronautics (NACA) airfoil shapes and then using 2-dimensional (2D) CFD analyses on both the impeller and stator blades. CFD modeling approaches and solving methods are discussed. A Design of Experiments (DOE) is utilized to verify and optimize the performance of the stator vanes and identifies the effectiveness of the stator vane angle, curvature of the stator leading edge, and number of stator vanes. At a constant back pressure the best performing DOE geometry delivered a 22% improvement in flow at constant electrical power input and a 41% improvement in flow at constant acoustic noise. This result was confirmed using a 3D CFD modeling. This analysis and development method provides a good baseline for evaluating and choosing proper stator vane geometries for flow improvement in axial fans.
Modeling and Optimization of Multilayer Minichannel Heat Sinks in Single-Phase Flow
Authors: Lei Ning , Ortega Alfonso , Vaidyanathan Ranji
Published: January 2010

Liquid-cooled small channel heat sinks are a promising heat dissipation method for high power electronic devices. Traditional mini and microchannel heat sinks consist of a single layer of high aspect ratio rectangular channels. An alternative approach investigated in this paper is to stack multiple layers of low aspect ratio (circular or square cross-section) channels together to create multiple layer minichannel heat sinks. These multilayer heat sinks can achieve high heat flux due to the high heat transfer coefficients from small channels coupled with the large surface areas from the multilayer structure. In this research, multilayer copper and silicon carbide (SiC) minichannel heat sinks were experimentally and computationally characterized in single-phase flow over various flow rates. The experimental data indicated that in many cases, multilayer heat sinks have significant advantages over single-layer equivalents with reductions in thermal resistance and pressure drop. In order to investigate the optimal design of such structures, a detailed 3-D resistance network model was developed and used to predict the heat sink surface temperature and fluid pressure drop. The model uses an uncoupled approach and was validated by compared with conjugate CFD simulations and the experimental data. An extensive parametric study was performed on copper and SiC heat sinks with respect to channel geometry, number of layers, and thermal conductivity. The simulations indicated that for a fixed overall heat sink flow rate, an optimum number of channel layers exists for copper and SiC because of the competing trends of increasing surface area and decreasing per channel flow rate as the number of layers increases. In addition, the heat sink “effectiveness” decreases with increasing number of layers as the thermal resistance from the top surface, where heat is applied, to the lower layers of the heat sink becomes excessive. In the simulation the optimized number of layers is highly dependent on material, channel width, channel aspect ratio, and wall thickness. If the pumping power is an important issue for the optimization, the heat sink with medium channel width is a wise choice, which achieves small thermal resistance with reasonable pressure drop.
Experiments and Modeling of Two-Phase Heat Transfer in Single-Layer and Multilayer Minichannel Heat Sinks
Authors: Lei Ning , Ortega Alfonso , Vaidyanathan Ranji
Published: January 2010

Boiling in small channels has been studied by many investigators due to its promising applications in high power electrical devices. Most of research has been conducted on single channel or single-layer channel heat sinks. An alternative approach investigated in this paper is to stack multiple layers of square channels together to create multiple layer heat sinks. The thermal and hydraulic characteristics of single-layer and multilayer copper heat sinks were compared in this study. It was found the multilayer copper heat sinks had smaller average surface temperature than their single-layer counterpart at low heat flux. However multilayer copper heat sinks may lose stability at high heat flux, which results in surface overheating presumably due to dryout in the hottest channels. The boiling heat transfer coefficient correlations for conventional size channels have been thoroughly studied and docmumented by many researchers. The boiling correlations for small channels are sparse and mostly based on data from unique experiments, which are limited to certain working fluids and channel dimensions. This paper presents a systematic approach to validate and choose the best boiling correlations for modeling minichannel heat sinks. Combining a 3-D numerical model and a three zone flow model, several heat transfer coefficient correlations for conventional size channels and for small channels were compared. The traditional macro channels boiling correlations were found to overestimate the saturated boiling heat transfer coefficient in two-phase flow and consequently show large error in temperature predictions. The temperature predictions based on boiling correlations for small channels were more consistent with experimental measurements. The correlation of Yu et al. provided the closest agreement to the experimental data.
Fabrication and Characterization of SiOx/Parylene and SiNx/Parylene Thin Film Encapsulation Layers
Authors: Kim Namsu , Yoo Seunghyup , Potscavage William , Domercq Benoit , Kippelen Bernard , Graham Samuel
Published: January 2010

Successful commercialization of flexible organic electronic devices is largely dependent on proper encapsulation that protects them from permeation of oxygen and water vapor. At present, low permeation encapsulation materials generally consist of multilayer films of organic/inorganic materials which can be deposited by plasma enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD), and vapor phase deposition. For this study, we report the effective water vapor transmission rates (WVTR) for multilayer thin films consisting of low temperature PECVD deposited SiNx and SiOx combined with a parylene organic layer. The effective WVTR was measured as a function of the number of bilayer pairs using Ca corrosion tests. The effective WVTR at 20 °C and 50% relative humidity [RH] for three bilayer pairs of SiOx/parylene ranged between 4.4–8.0 × 10−4 g/m2/day while SiNx/parylene had a transmission rate 1.3×10−4 g/m2/day. In general, additional layers were found to decrease the permeation rates to as low as 3.9×10−5 g/m2/day, while the SiNx/parylene coatings performed the best overall.
A New Resistor-Capacitor (RC) Transient Thermal Network Approach for Power Amplifier Module in Handheld Telecommunication
Authors: Yu Youmin , Chiriac Victor Adrian , Lee Tien-Yu Tom
Published: January 2010

When a Power Amplifier (PA) device is operated at a given duty cycle (power on and off periodically), the device temperature responds accordingly with the peak and valley values occurring per cycle. Detailed transient thermal analysis is required to predict the device’s thermal characteristics at specific timeframes or at steady-state. Many thermal evaluations are conducted using the steady state condition at 100% duty cycle (power on continuously), requiring less computational time than the transient analysis, but providing conservative prediction without details of the transient response. Another shortcoming of the numerical prediction is the large amount of computational time and the inability to estimate temperatures for long cycle times. A new thermal Resistor-Capacitor (RC) network approach to predicting transient thermal responses in semiconductor packages is presented in this study. The proposed compact thermal model for a given package is a thermal RC network extracted by curve fitting the temperature response predicted by simulation to a step power input. Non-grounded Foster network is adopted for the proposed RC network, as its special structure makes it simple to change the RC topology during RC network extraction. The procedure to obtain RC values in each RC topology is iterated to get optimal RC values. The RC topology and values yielding minimum RMS error between the thermal RC network and simulation are accepted as the extracted compact thermal model for the given package. The extracted model is then applied to predict the transient temperature of a given power pulse. The thermal RC networks in both model extraction and subsequent prediction are expressed in Laplace domain first, and then inverted to the time domain. This ensures two advantages: (1) curve fitting during model extraction is simplified and accelerated; (2) the extracted model can predict the temperature responses to essentially all power pulses in practice. The proposed approach is validated on a PA module. The results show that the approach works accurately in the case of single heat source in the module. The approach combined with method of superposition can accurately predict temperature responses in the cases of multiple heat sources as well. To address further challenges of self and interactive heating in multiple heat sources, a direct fit method is also proposed. Validation results show that it is an effective alternative to predict transient temperatures of packages in specific situations.
Reliability Evaluation of Lead Free Solder Joints Subjected to Multi-Loads
Authors: Tosaka Akihiko , Yu Qiang , Shibutani Tadahiro , Kondo Satoshi , Shiratori Masaki
Published: January 2010

The miniaturization and the high integration of electronic device parts were progressed by the advance in technology, and it leads the problems of warpage of high-integrated component during mounting processes. This kind mismatch would be released slowly after the components are assembled. Therefore, it is concerned that the deformation of the solder joints caused by the warpage should give some impact on the thermal fatigue reliability of solder joints, because the solder joints are subjected not only to the cyclic thermal mismatch but also to the considerable one direction bending load. This state is called as multi-loads in this study. The thermal cyclic fatigue reliability of solder joints had been studied by using analytical and heat cyclic testing approaches, and it is shown that the fatigue life can be assessed by Manson-Coffin’s law. However, the reliability evaluation techniques for multi-loads problem have not been established. In this study, the relation between the fatigue reliability and the multi-loads conditions was studied and the BGA (Ball Grid Array) package was chosen as the target. The author proposed a new cyclic bending test method to achieve the different conditions of the multi-loads, and based upon the experimented and analytical results it was found that impact of the multi loads some cases neglected for could not be.