bluuebunny/crossref_metadata_2025 huggingface dataset:
Performance Testing of Ammonia Scrubbing System
Authors: Yanagi H. , Khong M. , Ng K. C.
Published: April 2009

Accidental massive release of ammonia is extremely dangerous for both the environment and the health of those residing or working close to the release especially in a crowded city. Therefore means of mitigating or in the best case scenario containment of a release shall be a priority. A mobile ammonia scrubber was developed. The scrubbing system installed on a vehicle for easy access to the release site allows the recovery of all liquid and gas up to a 4MT storage tank. In this report, we discuss the ammonia effect on the characteristics of impregnated adsorbent. Its heat generation through the process of adsorption as well as its mass transfer during operation, which simulates an actual accident release.
Experiment of Micro Cantilever Deflection by Thermal Bubble Growth in Liquid
Authors: Lee Heon J. , Chang Young-Soo , Kim Ho-Young , Ahn Jong-Seob , Lee Yoon-Pyo
Published: April 2009

Micro cantilevers are significant structure for MEMS devices, such as bio-chips, sensors and STEM/AFM probes. The beam deflection and its characteristics have been studied for various purposes. In this study, expending bubbles from thermal surface exert force on micro-cantilever beam and causes deflection of the beam. Cantilevers were fabricated by classic MEMS fabrication method; photolithography and dry etching. The micro-beam was fabricated from <100> n-type silicon wafer and its thickness varies from 10 micron to 30micron with various geometry (length, width and tip shapes). The distance from thermal surface and cantilever beam is also significant variables for analysis of bubble-beam interaction. We observed beam deflection with respect to various bubble generation conditions (bubble size, contact area and generating frequency). Simple analysis of bubble-beam interaction were performed and compared with experimental results.
Open-Air Synthesis of Carbon Nanotubes by Laser-Induced Chemical Vapor Deposition
Authors: Kwok Kinghong , Chiu Wilson K. S.
Published: April 2009

Carbon nanotubes have unique mechanical, electronic and thermal properties with applications ranging from reinforced composite materials to micro-scale electronic devices, and are considered one of the next generation advanced engineering materials. In this study, a laser-induced chemical vapor deposition (LCVD) process has been developed that is capable of depositing carbon nanotubes in open-air from a gas mixture consisting of propane and hydrogen. A CO2 laser is used to irradiate the substrate covered with metal nanoparticles, subsequently resulting in the growth of multi-wall carbon nanotubes. The effect of laser power and reactant gas flow configuration on carbon nanotube growth kinetics is experimentally investigated. Results indicate that carbon nanotube synthesis is highly dependent on the laser-induced temperature distribution and the carbon radical concentration. Transmission electron microscopy, scanning electron microscopy and Raman spectroscopy are used to relate the composition, microstructure and growth kinetics to the process conditions of carbon nanotubes deposited in this study.
Investigation of Effect of Burner Diameter on Heat Transfer Characteristics of Methane/Air Flame Impinging on a Flat Surface
Authors: Chander Subhash , Ray Anjan
Published: April 2009

An experimental study has been conducted to investigate the effect of burner diameter on heat transfer characteristics of methane/air flames impinging normally to a flat surface. Three different tubes of internal diameter 8 mm, 9.7 mm and 12 mm were selected as flame holders. Effects of firing rates and equivalence ratios were studied on stagnation point and radial heat flux distribution. Three firing rates (0.25 kW, 0.40 kW and 0.50 kW) and three equivalence ratios (0.8, 1.0 and 1.2) were considered. Stagnation point heat flux was compared for different burner diameters under similar conditions. Radial heat flux distributions over the surface for different burner diameters under different firing rates and equivalence ratios were compared. It was found that the heat flux distribution was intimately related to flame shapes and sizes.
Thermal Stress Reduction and Optimization for Orthotropic Composite Boards
Authors: Khalilollahi Amir , Warley Russell L.
Published: April 2009

Composite printed electronic boards are susceptible of structural failure or irreversible damage under thermally raised stresses. A thermal/structural finite element model is integrated in this study to enable the predictions of the temperature and stress distribution of vertically clamped parallel circuit boards that include series of symmetrically mounted heated electronic modules (chips). The board is modeled as a thin plate containing four heated flush rectangular areas that represent the electronic modules. The finite element model should be to able to accept the convection heat transfer on the board surface, heat generation in the modules, and directional conduction inside the board. A detailed 3-D CFD model is incorporated to predict the conjugate heat transfer coefficients that strongly affect the temperature distribution in the board and modules. Structural analyses are performed by a FE model that uses the heat transfer coefficients mentioned above, and structural elements capable of handling orthotropic material properties. The stress fields are obtained and compared for the models possessing different fiber orientations and fiber volume fractions. Appreciable differences in stress and thermal gradient fields were observed. The values of fiber volume fraction and fiber orientation at which to conduct analyses was guided by experimental design (DOE) ideas leading to a metamodel of the stress intensity and temperature gradient in the board which was used to represent the complied results of this study.
Experimental Study on Free-Convection Condensation Heat Transfer From Moist Air
Authors: Nagai Niro , Takeuchi Masanori , Kura Osamu , Masuda Tomoharu
Published: April 2009

Characteristics of free-convection condensation heat transfer from moist air under atmospheric pressure were experimentally investigated, for further improvement of physical modeling on heat and mass transfer of solar distillation device. The cooled metal surface was 50mm width × 100mm height. The experimental conditions were as follows. Moist air temperature range was 40∼100°C for saturated moist air, and 50∼70°C for non-saturated moist air. Relative humidity range was 50∼90%. Inclination angle of cooled surface was 0° (downward facing) ∼ 180° (upward facing). All experimental results of heat transfer characteristics for vertical surface (angle 90°) were well correlated into a single equation with partial air pressure ratio using classical Nusselt’s liquid-film theory. The experimental results for the effects of inclination angle show that heat transfer coefficients for angle 0°∼105° were almost constant with slight peak value at angle 45°, followed by rapid decreasing of heat transfer coefficient over angle 120°.
Numerical Optimization of the Thermoelectric Cooling Devices
Authors: Abramzon B.
Published: April 2009

The present study proposes the unified numerical approach to the problem of optimum design of the thermoelectric devices for cooling electronic components. The method is illustrated with several examples which are based on the standard mathematical model of a single-stage thermoelectric cooler with constant material properties. The model takes into account the thermal resistances from the hot and cold sides of the TEC. Values of the main physical parameters governing the TEC performance (Zeebeck coefficient, electrical resistance and thermal conductance) are derived from the manufacturer catalog data on the maximum achievable temperature difference, and the corresponding electric current and voltage. The independent variables for the optimization search are the number of the thermoelectric coolers, the electric current and the cold side temperature of the TEC. The additional independent variables in other cases are the number of thermoelectric couples and the height-to area ratio of the thermoelectric pellet. The objective for the optimization search is the maximum of the total cooling rate or maximum of COP. In the present study, the problems of optimum design of thermoelectric cooling devices are solved using the so-called Multistart Adaptive Random Search (MARS) method [16].
CFD Heat Transfer Investigation Into the Convective Coefficient of a Perforated Plate
Authors: Hayes Andrew M. , Khan Jamil A. , Spearing Ian G. , Shaaban Aly
Published: April 2009

A computational fluid dynamics (CFD) model investigating the heat transfer convective coefficient of the upstream face, the upstream face and the tube face, and the upstream face, tube face, and leeward face of a perforated sheet was developed. This model was based on the hexagonally shaped flow pattern that exists around each of the holes in a perforated sheet of a certain pitch to diameter ratio. The CFD model used in the investigation of the convective heat transfer coefficient involved a single hole in a thin hexagonally shaped sheet with appropriate boundary conditions. Through a series of models varying the inlet velocity, hole diameter, and the plate temperature and then solving for the exit temperature the convective coefficient could be obtained. After obtaining the convective coefficient, the Nusselt number was calculated. These values were then plotted against the Reynolds number and an equation for the line was obtained of the form: Nu=C1·ReC2(1)
Effect of Heat Transfer and Fluid Flow in a CVD Reactor on the Densification Rate of Carbon Brakes
Authors: Kamel John K. , Paolucci Samuel
Published: April 2009

The effect of heat transfer and fluid flow on the densification rate of carbon brake substrates inside a chemical vapor deposition reactor is investigated using non-Boussinesq equations. These equations are valid for large temperature variations and low Mach number flows. Surface to surface radiation between the reactor walls and the brake substrates is considered, where all surfaces are treated as gray and diffuse, while the gas is assumed to be non-participating. A Brinkman model has been used for the flow within the brake substrates. Moreover, implementation of a simple kinetic mechanism is included to account for chemical reactions.
Sensitivity Analysis of an Inverse Method for Characterizing Industrial Foams
Authors: Salisbury Shaun M. , Jones Matthew R. , Webb Brent W. , Solovjov Vladimir P.
Published: April 2009

Assessing the effect of a foam layer on critical transport phenomena is of significant interest in many industries, so a method for measuring structural and radiative properties of foam is being developed. A model of the propagation of radiation from an amplitude modulated laser beam through a non-absorbing foam layer has been developed using diffusion theory. Relationships between foam layer properties and measurable characteristics of the reflected radiative flux are obtained from this model. A parameter estimation method capable of inferring the targeted properties is being developed. As part of the development, a sensitivity study has been conducted to determine the optimal distance between the source and the detector. Factors influencing the accuracy of the estimated properties are identified, and a method to balance these competing factors is proposed. Simulated experimental measurements were generated using a Monte Carlo method, and the proposed method has been tested for a specific case. The reduced scattering coefficient and the thickness of a non-absorbing foam layer were determined to within 2% in this specific case.
Effect of Gap Distance on Confined Boiling Heat Transfer Over a Saturated Porous Structure
Authors: Schertzer M. J. , Khammar M. , Ewing D. , Ching C. Y. , Chang J. S.
Published: April 2009

An experimental investigation was performed to study the effect that the introduction of a gap between a heated fin and a porous media would have on the heat removal characteristics of a capillary evaporator. In these experiments, a thin stainless steel resistive foil stretched between two copper electrodes was used to heat a saturated porous plate with an effective pore size of 50 microns. The temperature distribution on a 10 mm wide simulated fin was measured by a high-speed infra-red thermal imaging system. The heat removal performance was investigated for gap distances of 0.00 to 1.00 mm and for heat fluxes of 17 to 180 kW/m2. These results showed that the maximum heat transfer rate that could be achieved before persistent hot spots were observed on the surface increased with gap distance. Local temperature measurements made using thermocouples embedded in the porous media indicate that vapour penetration into the porous wick is intermittent, and that there is no stable single phase blanket of vapour. For a gap distance of 0.00 mm, this penetration is more uniformly distributed across the width of the heated fin than at a gap distance of 0.50 mm. In the latter case, the vapour distribution is much higher near the edge of the heated fin.
A Hybrid Approach for Full Numerical Simulation of Heat Exchangers
Authors: Al-Bakhit Hussien , Fakheri Ahmad
Published: April 2009

Understanding the details of flow and temperature fields is important in improving the performance of the heat exchangers. The full numerical solution of heat exchangers are computationally prohibitive because the flow and temperature fields must be simultaneously determined in at least two fluids and the solid surfaces separating the two fluids, making full simulation of heat exchangers practically nonexistent. As complicated as the flow is, there are certain characteristics of heat exchangers that if taken advantage of, make the numerical simulation of the heat exchangers more practical. In this paper, the idea of a hybrid approach is proposed, in which the nonlinear momentum equations for one or two channels are solved by using commercially available CFD codes. The velocity field is then inputted into a user-developed code for solving the linear energy equation for the entire heat exchanger. This is an efficient approach which has been successfully used to fully simulate a parallel flow heat exchanger.
Direct Numerical Simulation of Liquid Flow in a Horizontal Microchannel
Authors: Ku¨krer Cenk Evren , Tarı I˙lker
Published: April 2009

Numerical Simulations of liquid flow in a micro-channel between two horizontal plates are performed. The channel is infinite in streamwise and spanwise directions and its height is taken as 3.1×10−4 m which falls within the dimension ranges of micro-channels. The Navier-Stokes equations with the addition of Brinkman number (Br) to the energy equation are used as the governing equations and a spectral methods based approach is applied to obtain the required accuracy to handle liquid flow in the micro-channel. It is known for micro-channels that Br combines the effects of conduction and viscous dissipation in liquids and is also a way of comparing the importance of later relative to former. A laminar flow of a liquid in a micro-channel shows different characteristics compared to a similar flow in a macro-channel. To observe the differences, three different cases are run over each of a range of Reynolds numbers: one with no axial conduction assumption that correspond to a case similar to macro-channel flow, another case with axial conduction included in the energy equation to simulate one of the main differences and lastly a case with inclusion of Br number in the governing equations. The results are compared with each other to see the effects of axial conduction and Br inclusion. A qualitative comparison is made with the previous results in literature.
Laser-Assisted Friction Stir Lap Welding of Aluminum
Authors: Able Nicholas , Pfefferkorn Frank
Published: April 2009

The objective of this research is to determine the effects of laser preheating on friction stir lap welding. Laser preheating of the top surface of the material during friction stir lap welding is used to reduce the welding forces and torque, thereby reducing the stiffness requirements on the clamping and FSW tool. Preheating also has the potential to enable higher welding speeds and reduced tool wear particularly when applied to welding of higher melting temperature alloys. A transient three-dimensional finite element heat transfer model of the workpieces was developed to predict the influence of preheating on the temperature distribution and heat flux within the workpieces. The model accounts for conduction in the workpieces, contact resistance between them, laser absorption, frictional heat generation under the FSW tool shoulder, and losses to the surroundings. Predicted temperatures at discrete locations were compared with thermocouple measurements and found to be in good agreement. The model showed that the energy deposited by the laser in the top plate does not penetrate into the bottom plate ahead of the tool due to the contact resistance between the plates. Hence, the thermal contact resistance, inherent to lap welds, controls the effectiveness of preheating. The effect of preheating on FSW of aluminum was investigated by varying the laser power and workpiece material while maintaining constant tool geometry and material. The results of the parametric study are presented and show that while forces and torques are reduced by preheating, not as much as in butt welding because of the contact resistance produced by the nature of the weld. It was also found that the total power consumed in the process, defined as the sum of tool power and absorbed laser power, can decrease with preheating.
The Upper Limit of Thermocouple Use and the Lower Limit for Line Reversal Method Used to Measure Temperature
Authors: Hartnett James P. , Fuller William C. , Rohsenow Warren M.
Published: April 2009

Chromel-alumel thermocouples of 30, 32, 35 wire gauge tested in an oxidizing (air) atmosphere were found to have long life at temperatures less than 1900 F. At temperatures up to 2600 F. their useful life decreased at increasing temperatures and decreasing diameters (1).
A Simulation of the Solid Oxide Fuel Cell Electrochemical Light Off Phenomenon
Authors: Haynes Comas L. , Ford J. Chris
Published: April 2009

During latter-stage, “start-up” heating of a solid oxide fuel cell (SOFC) stack to a desired operating temperature, heat may be generated in an accelerating manner during the establishment of electrochemical reactions. This is because a temperature rise in the stack causes an acceleration of electrochemical transport given the typical Arrhenius nature of the electrolyte conductivity. Considering a potentiostatic condition (i.e., prescribed cell potential), symbiosis thus occurs because greater current prevalently leads to greater by-product heat generation, and vice versa. This interplay of the increasing heat generation and electrochemistry is termed “light off”, and an initial model has been developed to characterize this important thermal cycling phenomenon. The results of the simulation begin elucidating the prospect of using cell potential as well as other electrochemical operating conditions (e.g., reactants utilization) as dynamic controls in managing light off transients and possibly mitigating thermal cycling issues.
Analysis and Mitigation of Sample Heating in Thermoreflectance Microscopy
Authors: Miner Andrew C. , Ghoshal Uttam
Published: April 2009

The illumination of a sample when imaged by thermoreflectance thermal microscopy may cause significant heating of the surface. Nonlinearities in the performance of the system being imaged may lead to large measurement induced errors in the observed temperature field. Analytical expressions are presented to estimate the temperature rise and heat flux in a sample. Spatially filtered thermo-reflectance microscopy is introduced as a technique to significantly reduce the incident heat flux without loss of spatial resolution.   This paper was also originally published as part of the Proceedings of the ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems.
Effects of Working Fluid, Fill Ratio and Orientation on Looped and Unlooped Pulsating Heat Pipes
Authors: Nikkanen Kathryn , Lu Christian G. , Kawaji Masahiro
Published: April 2009

Improved miniaturization and a trend towards increasingly dense and compact architectures have led to unmanageably high heat fluxes in electronic components. In order to keep temperatures at operational levels more advanced cooling solutions are being required that go beyond the solid heat sink and forced convection. Pulsating heat pipes made out of multi port extrusion tubing are a proposed solution. Typically, gas-liquid slug flow occurs in the serpentine channel imbedded in the pulsating heat pipe. Vapour is produced in the heated section and condensed in the cooled section located at opposite ends of the heat pipe. In this work, experiments were conducted on four Multi-Port Extruded (MPE) aluminum tubing heat pipes with different internal structures: rectangular channel looped, rectangular channel unlooped, triangular channel looped, and triangular channel unlooped. The effect of changing the working fluid (ethanol or de-ionized water), fill ratio, and orientation were measured and compared for the different heat pipes. It was found that most of the heat pipes performed better with ethanol than de-ionized water. Only the looped rectangular channel heat pipe performed satisfactorily with de-ionized water, which is attributed both to the larger channel size and the looped architecture. The unlooped heat pipes performed best at the lowest fill ratios (10%) while the looped heat pipes showed their best performances between 30 and 50% with marked decrease at the lower and higher fill ratios. Both looped heat pipes performed poorly in horizontal orientation as compared to vertical, however, the unlooped heat pipes performed quite well in both orientations. This may be more the effect of the fill ratio on horizontal performance as literature suggests that horizontal orientation requires a lower fill ratio to perform satisfactorily.
Impact of Cubic Pin Finned Surface Structure Geometry Upon Spray Cooling Heat Transfer
Authors: Silk Eric A. , Kim Jungho , Kiger Ken
Published: April 2009

Experiments were conducted to study the effects of enhanced surface structures on heat flux using spray cooling. The surface enhancements consisted of cubic pin fins machined on the top surface of copper heater blocks. The structure height, pitch, and width were parametrically varied. Each copper block had a projected cross-sectional area of 2.0 cm2. Measurements were also obtained on a heater block with a flat surface for baseline comparison purposes. A 2×2 nozzle array was used with PF-5060 as the working fluid. Thermal performance data was obtained under nominally degassed (chamber pressure of 41.4 kPa) and gassy conditions (chamber with N2 gas at 101 kPa) with a bulk fluid temperature of 20.5°C. Results for both the degassed and gassy cases show that structure width and separation distance have a dominant effect upon the heat transfer for the size ranges used. Cubic pin fin height had little impact upon heat flux. The highest critical heat flux (CHF) attained for any of the surfaces was 121 W/cm2, giving an enhancement of 51% relative to the flat surface case under nominally degassed conditions. The highest CHF in the gassy case was 149 W/cm2, giving an enhancement of 38% relative to the flat surface case.
Redesigns of HSOP Package for High Power Consumption Based on the Numerical Thermal Simulation Analysis
Authors: Chia John , Chen Jinfa
Published: April 2009

A Heat Slug Outline Package (HSOP) with different design concepts to improve its thermal performance is investigated. The thermal performance of the standard designs of TSSOP usually could not pass the requirements for greater functional integration in wireless frquency and reduction in power consumption, e.g. for a radio frequency (RF) front-end IC’s in silicon its power consumption can be increased about twice when the design frequency increases from 2.0 GHz to 3.5 GHz. The configuration of HSOP28 proposed here is redesigned based on the Thin Shrink Small Outline Package (TSSOP) that is a plastic encapsulated semiconductor device complied with a standard Surface Mount Technology (SMT). In order to accommodate a chip with the same size but double it power consumption, various types of lead frame design for HSOP packages are studies. It is therefore an object of the present study to investigate what will be the maximum thermal improvement of HSOP package compared to the corresponding same size of TSSOP package, which is also related to further reliability issue of this type of IC package, i.e. the thermal fatigue life calculation. Studies presented here are also taken into account the thermal performance of HSOP package associated with different multi-layers PCB designs and the thermal conductivity variations, where the package internal heat conduction as function of board thermal conductivity can be made.
Mechanical Design Aspects During Full-Scale Development Process of Electronic Assemblies for Military Systems
Authors: Ramot Medy
Published: April 2009

Full-scale development of an electronic assembly is a very complex process conducted by a multidisciplinary team. The process involves numerous professional skills, the main being: Electrical, Mechanical, Software, Component and Reliability engineering. Electronic assemblies designed for military applications, require high quality performance, long life cycle (storage and mission profiles) and operation in harsh environmental conditions. This paper presents main aspects of the mechanical design and the issues to be considered during the full-scale development process of electronic units used in military systems.
Understanding and Testing for Drop Impact Failure
Authors: Seah S. K. W. , Wong E. H. , Ranjan R. , Lim C. T. , Mai Y.-W.
Published: April 2009

This paper presents the results of experiments aimed at studying the effects of drop impact on portable electronics and reproducing these effects in controllable tests. Firstly, a series of drop tests were performed on consumer products (mobile phones and PDAs) to understand how the printed circuit board (PCB) within a product behaves in actual drop conditions. These product-level drop tests show that in drop impact, there are three possible types of mechanical response which can stress the 2nd level interconnections of CSP and BGA packages, namely: 1) flexing of the PCB on its supports, dominated by the 1st (fundamental) natural frequency; 2) flexing of the PCB resulting from direct impact or knocking against the PCB, typically dominated by higher natural frequencies; and 3) inertia loading on the solder joints due to high accelerations. Next, a series of board-level experiments were designed to separately study each of the three types of mechanical response. Board flexing due to direct impacts is the most severe response due to the strong strain amplitudes generated. Given the same input shock, the conventional board-level test — where the PCB flexes on its supports — produces much lower strain amplitudes. Inertia loading on the solder joints is practically negligible. Since PCB flexing is the main failure driver, a simple vibration test, which reproduces the strains observed in drop impact, is suggested as an alternative to time-consuming drop impact tests.
System Level Thermal Evaluation and Optimization of an Automotive Module Incorporating Several Power Packages
Authors: Chiriac Victor , Lee Tom , Gauen Kim
Published: April 2009

The conjugate thermal performance of a microelectronics module incorporating several power packages and additional passive components in a custom environment is evaluated and further optimized using numerical simulation and experimental validation. The automotive industry deals on a daily basis with various package and module-level thermal issues when managing the routing of very high current. The study provides a better understanding of the strengths and weaknesses of the IC packaging incorporation into a system module level, for both present and future product development. The reference design is evaluated at a system level, and several improvements are identified to enhance the overall thermal performance. The main concern is the possibility of exceeding the thermal budget for the large system incorporating seven power packages with additional sources of heat dissipation in an enclosure, at an external ambient temperature of 85°C. The overall thermal impact of the metal trace dissipation, header heating and other passive components under various powered conditions is evaluated. An additional revised model includes additional passive components (32 LD SOIC and QFN packages) on the PCB, a modified harness extending ∼ 30.4 cm outside the enclosure, and additional heating in the connectors. Several additional cases are investigated, varying the heat transfer coefficients outside the enclosure, at an ambient temperature of 85°C. The peak temperatures range from 121.4°C to 126.4°C and the corresponding junction-to-ambient thermal resistances (Rja) vary from 11.03°C/W to 12.5°C/W. The optimized numerical model approximates closely the empirical results (121–126°C vs. 127.5°C), within 1–2%.
A Novel Discrete Passives Integration on Organic Substrate
Authors: Sunappan Vasudivan , Lu Chee Wai , Wai Lai Lai , Fan Wei , Lok Boon Keng
Published: April 2009

A novel process has been developed to embed discrete (surface mountable) passive components like capacitors, resistors and inductors using printed circuit board fabrication technology. The process comprises of mounting passive components on top surface of a core PCB (printed circuit board) material using surface mount technology. The passive components mounting were designed in multiple clusters within the PCB. Dielectric sheets are sandwiched between top surface of core PCB and second PCB material for lamination process. A direct interconnection of the passive components to one or more integrated circuits (IC) is further accomplished by mounting the ICs on the bottom surface of the core material in an area directly under the passive components. The close proximity of the embedded passive components such as capacitors to an IC improved electrical performance by providing impedance reduction and resonance suppression at high frequency range. The reliability of solder joints was evaluatedd by temperature cycling test.
Design and Driving Methodology of Out-of-Plane Electrostatic Microactuator With Extended Stable Motion Range
Authors: Fukushige Takashi , Hata Seiichi , Hayashi Takehiko , Shimokohbe Akira
Published: April 2009

We present design and driving methodology of out-of-plane electro-static microactuator to extend stable motion range without any closed loop control system. The microactuator employed in this study is a curved cantilever microactuator, which consists of a curved cantilever moving electrode and a taper-shaped substrate electrode. A curved cantilever brings large deflection in the out-of-plane direction. Electrostatic and mechanical model of the device is derived. The equilibrium position and the stability of the cantilever are considered by calculating the stored electrostatic energy, the stored elastic energy and the lost energy from a power source due to the transfer of charges. The design methodology of the electrode shapes using the model is described and a prototype device is designed. The substrate electrode has tapered shape according to a function of distance from the anchor. The prototype is fabricated and its driving characteristics are examined. Stable motion range is extended to 65% of its full stroke by applying DC voltage and to 77% by square-wave AC voltage having a 2-kHz frequency. The calculated driving characteristics by a modified model that includes the existence of particles on insulator surface coincide with the measured one.
The Sintering Process of Ag Metallo-Organic Nanoparticles and the Influence of the Joining Parameters Upon Cu-to-Cu Joining
Authors: Angata Shinji , Ide Eiichi , Hirose Akio , Kobayashi Kojiro F.
Published: April 2009

We propose a novel bonding process using Ag metallo-organic nanoparticles as a new application of nanotechnologies. The average size of the Ag nanoparticle is approximately 11 nm, and each nanoparticle is covered with an organic shell. Usually, the agglomeration of metallic nanoparticles is unavoidable due to its large surface energy. However, on the account of the organic shell, these Ag nanoparticles exist individually, and once the organic shell has been removed, these Ag nanoparticles turn activated and abruptly agglomerate. We analyzed its thermal characteristics, applied the agglomerating of the nanoparticles to Cu-to-Cu joining, and researched the influence of the bonding condition, such as bonding pressure, temperature or holding time, upon the joint strengths. The joint strengths using the nanoparticles were 30–40 MPa, which is strong enough to be applied as a solder. In addition, it came to the conclusion that the strengths increased in accord with the aforesaid three parameters.
Effects of Interlayer Resin Bonding on Fatigue Crack Initiation/Propagation in Laminate Materials With a Surface Layer of Copper Film
Authors: Matsuba Akira , Torii Tashiyuki , Ma DongHui
Published: April 2009

As model specimens to examine the effects of interlayer resin bonding on fatigue properties in laminate materials with a surface film, pure copper films with a thickness of 100μm and 50μm were bonded with epoxy resin to steel base plates. The fatigue crack propagation from the notch root of the specimen was slower for the epoxy-bonded film than for the base specimen, because the epoxy bonding interlayer restricted crack propagation from the surface film to the inner base plate. On the epoxy-bonded film, however, many fatigue cracks initiated at multiple sites sufficiently away from the notch root, and propagated only on the surface copper film. In addition, the number of these multiple fatigue cracks, caused mostly at the site of the annealing twin boundaries, was larger on the surface copper film with a thickness of 100μm than 50μm.
A Vapor Chamber Using Graphite Foams as Wicks for Cooling High Heat Flux Electronics
Authors: Lu Minhua , Mok Larry , Bezama R. J.
Published: April 2009

A vapor chamber using high thermal conductivity and permeability graphite foam as a wick has been designed, built and tested. With ethanol as the working fluid, the vapor chamber has been demonstrated at a heat flux of 80 W/cm2. The effects of the capillary limit, the boiling limit, and the thermal resistance in restricting the overall performance of a vapor chamber have been analyzed. Because of the high thermal conductivity of the graphite foams, the modeling results show that the performance of a vapor chamber using a graphite foam is about twice that of one using a copper wick structure. Furthermore, if water is used as the working fluid instead of ethanol, the performance of the vapor chamber will be increased further. Graphite foam vapor chambers with water as the working fluid can be made by treating the graphite foam with an oxygen plasma to improve the wetting of the graphite by the water.
Effect of Next Generation Computer Graphic Card Blower Fan Speed on Thermal Performance and Acoustic Noise With Psychoacoustic Metrics
Authors: Ule Helen , Novak Colin , Gaspar Robert , Panigrahy Arunima , Refai-Ahmed Gamal
Published: April 2009

Graphic Processor Units (GPUs) on the latest models of computer graphic cards generate significant amounts of heat. In fact, the required dissipation rate is so large that cooling fans mounted on heat-sinks must be used to maintain satisfactory GPU temperatures. The packaging of these fans is small and similar designs have been used for cooling of electronic packaging for decades. The appropriate application of these fans as well as their optimal design for minimal noise generation and maximum air movement has not kept pace with that of large industrial sized fans. Where space limitations allow and heat transfer requirements dictate, blower type fans are implemented because they are capable of delivering relatively high flow rates in high impedance environments when they are compared to more traditional axial flow fans. The operation of these blower fans, particularly at high speeds, results in the generation of noise which is experienced by the user. Both computer manufacturers and consumers alike have deemed this noise to be excessive and annoying. The fan model predictions and the operational reality of the higher fan speeds needed to deliver increased air flow both lead to the reality of higher noise levels. The purpose of this study was to experimentally investigate the realized thermal and acoustic performance of a blower style fan-sink mounted on an advanced graphics port (AGP) card. The goal of this investigation was to determine what thermal benefits of higher flow rate are realized by the blower fan at the expense of increased noise emissions. The experimental results of thermal measurement results spanning the operating speed of the fan are presented and accompanied by the noise data. These data include both traditional acoustic analysis techniques using sound pressure and power level measurements as well as psychoacoustic metrics. The result of the thermal testing suggests that the rate of improvement in thermal performance decreases as the blower fan speed increases. As expected, an increase in noise level was also observed. Of particular interest were the results of the psychoacoustic analysis which indicate a similar detrimental effect with increased fan speed for some metrics, while other metrics indicate no change across the operating speed range of the blower fan.
An Improved Optimization Approach for Thermoelectric Refrigeration Applied to Portable Electronic Equipment
Authors: Taylor Robert A. , Solbrekken Gary L.
Published: April 2009

The electronics industry has relied heavily on air cooling to dissipate waste heat. Each new generation of technology is smaller and more powerful, pushing the limits of air-cooled heat sinks. A competing constraint is that the thermal solutions need to be smaller and lighter, particularly for portable devices. A viable strategy to extend the limits of air-cooled heat sinks in a mass effective way is thermoelectric (TE) cooling. In general, the limiting COP of currently available TE materials requires that TE modules be operated at near optimum conditions. The conventional approach for optimizing TE modules ignores external irreversibilities, such as the heat sink temperature drop between the TE hot side and the ambient. The current study reviews two schemes for optimizing the operating current and compares their performance. The comparison between the COP maximizing current and the junction temperature minimizing current identifies where the two approaches yield the exact same performance. Performance regimes are then identified where the junction temperature minimizing approach provides an advantage over the COP maximizing approach. A significant extension of the current modeling activity over previous studies is allowing the TE module geometry to be optimized in addition to the operating current. When the TE module geometry is allowed to be optimized, it is found that using TE refrigeration operating at the junction temperature minimizing current will always have a performance benefit relative to a heat sink alone. The way this performance is achieved at higher heat loads is that the TE module elements must be made very thin.
An Evaluation of Auxiliary Part Configuration in the Micro Flow Sensor by Using Micro PIV
Authors: Suzuki Daichi , Nagumo Takashi , Honami Shinji , Kamiunten Shoji
Published: April 2009

The paper describes the configuration effects of the auxiliary parts on the flow behavior around the microfluidic device. Recent development of the devices in MEMS is noticeable. The devices are manufactured in more complicated configuration and arrangement with the auxiliary part for the requirement of higher performance. An evaluation of the flow field around the microfluidic device is strongly required in MEMS design. The aim of the paper is to clarify the effect of the auxiliary part arrangement on the flow field around the micro flow sensor which has both the sensing element and the auxiliary parts such as the pins, pillars and electric bonding wires. The flow around the sensor is measured by using the Micro Particle Image Velocimetry (PIV) system. We investigate four types of the micro flow sensor with different configuration and arrangement of the pin, the bonding wires and the pillars. The result shows that the effect of the supporting pillars is negligible.
Fatigue Test of Al-3%Ti Using Axial Loading Testing Machine for MEMS Materials
Authors: Park Jun-Hyub , Choi Hyeon Chang , Lee Chang Seung , Choa Sung-Hoon , Myung Man Sik , Kim Yun-Jae
Published: April 2009

This paper presents high cycle fatigue properties of an Al-3%Ti thin film, used in a RF (radio-frequency) MEMS switch for a mobile phone. The thickness and width of the thin film of specimen are 1.1 μm and 480 μm, respectively. Tensile tests of five specimens are performed, from which the ultimate strength is found to be 144MPa. High cycle fatigue tests of six specimens are also performed, from which the fatigue strength coefficient and the fatigue strength exponent are found to be 336MPa and −0.1514, respectively.
DDRII Memory Packages Electrical Performance Comparison of COSBGA, TFBGA, and Standard TSOPII
Authors: Hsieh Bryan , Chiang Kevin , Wang Y. P. , Hsiao C. S.
Published: April 2009

The memory storage technology revolution has taken the consumer electronics by a storm in just two years. The volatile memory Dynamic Random Access Memory (DRAM) for PC and notebook computing and gaming are increasing in density and speed. With all these improvement, the memory device packaging technology is also evolving rapidly, from the leadframe packages to BGA packages [2]. Under high frequency operation, the parasitics associated with package will significantly degrade the package performance. The DRAM packages are used primarily in the fabrication of DIMM modules that are inserted to the motherboards in PC and notebook computers. With newer DRAM technology in double date rate (DDR) and its second generation, DDR2, to be deployed just two years, it has higher clock rate and I/O number. Packages therefore are changing form the leadframe TSOP type 2 to faster CSPs such as fine pitch BGA (FBGA) and chip on substrate BGA (COSBGA). This paper is focused the COSBGA package [3,4]. In this paper, the packages electrical model have been established and performs signal integrity (SI) simulation. The COSBGA has smallest parasitics when comparison with other two packages. This paper also compares the performance of the COSBGA, TFBGA and TSOPII from crosstalk noise, time skew, insertion loss and return loss for IC designer reference.
Indentation Induced Tin Whisker Formation on Tin Plated Component Leads
Authors: Liang Jin , Li Xiaodong , Xu Zhi-Hui , Shangguan Dongkai
Published: April 2009

Tin whisker formation has been a serious concern for application of pure Tin as a Pb-free component lead finish. It has been long believed that residual stress is the root cause of whisker formation. A fundamental question is if stress produced by other than the plating processing and post-plating metallurgical reactions can induce whisker formation. In this study, micro indents were made on pure Tin plated component leads to induce stress for studying stress induced whisker formation. Nano-indentation was performed to measure hardness and elastic modulus of the Tin coating layer where whiskers initiate. Scanning electron microscopy (SEM) was used to study indentation deformation mechanisms and to monitor the nucleation and growth of whiskers in-situ. In additions, finite element analysis was carried out to theoretically calculate the stress/strain distribution around the indentations. Experimental and theoretical calculation results show that whiskers form at a certain stress level. This suggests that there might exit a critical stress threshold that governs the whisker formation. It is believed that establishment of a quantitative relationship between stress level and whisker formation/growth could lead to a breakthrough in risk and reliability assessment with pure Tin application in the electronic industry and in safeguard for smooth Pb-free transition.
Modeling Melting Solder in System-in-Package Assembly
Authors: Zhao J. F. , Wang J. F. , Yang C.
Published: April 2009

System-in-package (SiP) technologies typically demand an increasing number of passive components assembled into a single package to achieve system level electrical performance. Traditionally, these passive components and their assembly technologies are designed for printed circuit boards and are now integrated at the package level. However, problems may arise when solder joints are used as interconnects between the passive components and the substrate in SiP system. The solder joint may melt during the surface mounting process. Since the size of the solder joint is comparable to that of the passive components, the melting may significantly alter the stress field in the package. Consequent failure may occur if the interconnect structure is not properly designed. It is a challenge to simulate solder melting with commercial finite element codes. In this paper, the interaction between the melting solder and the surrounding structures is investigated. The stress superposition method is used in the finite element model, in which the melting solder is removed from the package and a void with identical geometry was analyzed in its place. The overall stress field is the superposition of the stress field due to temperature change and the stress field caused by the uniform pressure acting on the void surface. This method greatly simplifies the mechanical modeling.
Heat Transfer Enhancement in the Heat Sinks for Electronic Cooling Applications
Authors: Small Evan , Sadeghipour Sadegh M. , Asheghi Mehdi
Published: April 2009

In a design competition by the mechanical engineering students at Carnegie Mellon University, which was the design of heat sinks for electronic cooling applications, twenty seven heat sinks were designed and tested for thermal performance. A heat sink with three rows of 9, 8, and 9 dimpled rectangular fins (staggered configuration) demonstrated the best performance in the test. This heat sink even had the least total volume (about 25% less than the set value). This paper reports on an effort made to verify and quantify the role of dimples on heat transfer enhancement of the heat sinks. This includes measurements and simulations of the thermal fluid properties of the heat sinks with and without dimples. Results of both the measurements and simulations indicate that dimples do in fact improve heat transfer capability of the heat sinks. Albeit, dimpled fins cause more pressure drop in air along the heat sink. Keeping the total volume of the heat sink and the height of the fins constant and changing the number of the fins and their arrangement show that there exist an optimum number of fins for the best performance of the heat sink. However, this number of fins is different for inline and staggered arrangements. To check the role of the roughness type on the heat transfer behavior of the fins, a heat sink with twenty-seven bumped fins with inline arrangement was also simulated. Results indicated that bumps increase both thermal resistance and pressure drop relative to that of the heat sinks with plain fins.