bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of Cooling Structures for Blu-Ray Disc Compatible Optical Disc Drives Using Computational Fluid Dynamics Based on Cartesian Grid Method
Authors: Isoshima Nobuyuki , Fujimoto Takayuki , Abe Yukinobu , Watanabe Masatoshi , Yamauchi Yoshiaki , Nishida Ikuo
Published: January 2010

High-performance, simple cooling structures for optical disc drives compatible with the Blu-ray disc (BD) were developed using unsteady numerical flow simulation based on the Cartesian grid method. In the new structure, an additional hole in the tray outside of the disc induced a secondary upward flow, which is caused by a pressure difference and rotating-disc flow. The secondary flow decreases the ambient air-temperature of the laser diode below the hole, and furthermore it increases the velocity around the laser diode and enhances the heat transfer rate. The experimental results indicate that the cooling effect of the laser diode increases, and the disc vibration is not influenced by the additional hole in the tray. The cooling structures are applied to the so-called super-multi BD drive, which achieved 4X high-speed recording for the first time in the industry.
Challenges and Advances of Heat Pipes in Cooling Notebook Systems
Authors: Machiroutu Sridhar V. , Pokharna Himanshu , Kuroda Masahiro
Published: January 2010

Notebooks represent an increasing percentage of PC client market with growth surpassing that of desktop computers. Heat pipe has been an integral part of notebook computer system cooling and will remain so for the foreseeable future. Heat pipe allows for efficient transport of heat from the CPU and other high power components to a location where there is more room for accommodating motherboard cutout for a fan and a heat exchanger. The thermal resistance along this path must be minimized to enable maximum cooling. This paper first briefly describes the contributing resistance in a heat pipe and ways to measure them for a notebook thermal solution. Since there are several parameters that can affect the performance of the heat pipes, we use an experimental procedure utilizing DOE (Design of Experiments) to first understand the sensitivities of these design, manufacturing and usage parameters on performance and then to arrive at an optimum level of these parameters to minimize various resistances in a heat pipe. We show that for various different wick technologies, it is possible to optimize the heat pipes to achieve an evaporator performance of the level of 0.1 C-cm2/W. Furthermore, we show some simple design rules to minimize the condenser resistance and also results of a design study to optimize the design of heat pipe block at the CPU end to minimize the evaporator resistance. We want to encourage the heat pipe vendor community to use these methods to optimize their products for performance as well as process enhancements to produce higher performing parts, at lower cost.
Various Levels of Drop Analysis for BGA in Mobile Phones
Authors: Katahira Takayoshi , Fujita Masato , Shibata Tsuyoki , Shiratori Masaki , Yu Qiang
Published: January 2010

To final product quality of mobile phones, key reliability requirements are drop, bend and thermal cycling. Especially in terms of IC-device, drop reliability is the most significant of the three, and also difficult to optimize since it is a dynamic phenomenon in high speed and drop reliability is influenced by 1) system-level factors, 2) board-level and 3) micro-level. In this paper, system-level is defined as phone-level drop, specifically simplified mono-block phone including multiple devices on PWB. System-level enables to evaluate various factors, drop height, drop directions, materials to drop on, phone weight and phone mechanics. Board-level indicates IC-package, PWB and solder joints connecting in between. The board-assembled PWB is fixed onto fixture at 2∼6 points. Drop direction is flat drop only. This paper defines micro level as more detailed model than board level. PWB is modeled as composite structure consisting of dielectric materials with orthotropic properties, copper layers and micro via. IC-package is modeled as well. System level drop shows significant differences in drop directions and also the interactions between drop direction and component location. Micro level simulation results are well-correlative with experimental in failure mode. This paper will discuss overview of 3 levels of drop modeling and will focus on micro level and system level analysis in conjunction with board level.
Investigation of Drill Hole Quality of Multi-Layer PWBs for High Current Capacity
Authors: Aoyama Eiichi , Hirogaki Toshiki , Ogawa Keiji , Mori Kenichi , Itagaki Yuusuke
Published: January 2010

Recently, as a result of changes in the automotive industry, a large number of electronic systems have been installed in cars. The thickness of the copper foil used for printed wiring boards (PWBs) has tended to increase in response to the large current capacity required for such electronic equipment. Therefore, the nail head generated in the inner layer copper foil was examined with respect to the influence of the thickness of the copper foil on the through-hole quality. In the present study, the size of the nail head generated in the copper foil after drilling a through hole was used as the objective variable. The explaining variables included drill wear, frequency, feed rate, chip load, drill temperature, copper foil thickness, copper foil cutting distance, and number of drill holes. We investigated the relationships between these explaining variables and the objective variable and found that the copper foil cutting distance was a very important parameter in generating nail heads. In addition, we found that the chip load is important for controlling nail head generation.
A Study of Acoustic Emission Produced by Strength Test on Bio-Ceramics: Dependency of AE Duration Time and Mean Frequency on the Material Property
Authors: Nakayama Mitsuyuki
Published: January 2010

Comparing the mechanical characteristics of bio-ceramics with a elaborate bone, there are two important conditions required for biomaterial. First, the strength must be three times larger than that of a elaborate bone. Second, Young’s modulus must be two or three times larger than that. However, still the biomaterial hasn’t developed which satisfies these conditions. The purpose of this research is to improve the strength of bio-ceramics. It was discussed how the duration time and mean frequency of acoustic emission (AE) parameters depend on time. These parameters are calculated with AE wave on breaking test of a bio-ceramics. The following main results were obtained. First, AE generating pattern is changed by the property of the materials. Second, in tetragonal zirconia polycrystals (TZP), the phase transformation has affected AE parameters. Consequently, it was shown that AE parameters had the material dependability.
Micro Texture-Induced Variation of Mechanical Properties of Electroplated Copper Thin Films
Authors: Otani Muneyuki , Sakutani Kazuhiko , Tamakawa Kinji , Suzuki Ken , Miura Hideo
Published: January 2010

The mechanical properties of copper thin films formed by cold-rolling and electroplating were measured using a tensile test and nano-indentation. Both the Young’s modulus and the tensile strength of the films were found to vary drastically depending on the microstructure of the films. The Young’s modulus of the cold-rolled film was almost same as that of the bulk material. However, the Young’s modulus of the electroplated thin film was about a fourth of that of the bulk material. The microstructure of the electroplated film was polycrystalline and a columnar structure with a diameter of a few hundred-micron. The strength of the grain boundaries of the columnar grains seemed to be rather week. Such a columnar structure with porous grain boundaries caused the cooperative grain boundary sliding. As a result, the effective elasticity of the film became rather low and the superplastic deformation of the film appearred under an uni-axial tensile load. In addition, there was a sharp distribution of Young’s modulus along the thickness direction of the film. Though the modulus near the surface of the film was close to that of the bulk material, it decreased drastically to about a half at the depth of 1 μm. There was also a planar distribution of Young’s modulus near the surface of the film.
Reliability Analysis of Solderless Press-Fit Interconnections
Authors: Tohmyoh Hironori , Yamanobe Kiichiro , Saka Masumi , Utsunomiya Jiro , Nakamura Takeshi , Nakano Yoshikatsu
Published: January 2010

This paper treats typical mechanical problems met in a solderless press-fit assembly. First, the elastic-plastic properties of a pin and the friction coefficient of the pin in thin plated through hole (TH) are determined by the experiments and the three-dimensional finite element (FE) analysis. The elastic-plastic properties of the press-fit pin are determined by the small scale three-point bending. The friction coefficient of the pin in the TH is successfully determined from the load-displacement relationship of the pin during press-fit assembly. The validity of the determined parameters is to be clarified by conducting the press-fit assemblies into the holes with different diameters. By comparing the damaged area of the printed circuit boards after assembly and the stress distributions obtained numerically, the failure stress of the board is determined. Finally, both the retention force of the pin and the damage of the printed circuit board after assembly become possible to be predicted by the numerical analysis.
Study of Heat Transfer in Microscale Systems
Authors: Pryputniewicz Ryszard J. , Pryputniewicz Dariusz R.
Published: January 2010

Progress in micromachining technology enabled fabrication of micron-sized mechanical devices, which have had a major impact on many disciplines. These devices have not only led to development of miniature transducers for sensing and actuation, but also a chip-based chemical laboratory (μChemLab) and other microelectromechanical systems (MEMS). Applications of these microscale systems frequently demand heat removal and temperature control. This paper presents preliminary results of a study of heat transfer in microscale systems. Computational modeling is based on Thermal Analysis System (TAS), which facilitates multiscale modeling/simulation, and measurements are made using infrared (IR) microscopy. Representative applications describe multiscale modeling and measurement results obtained for a microhotplate of a μChemLab and a high-power GaAs FET amplifier. Comparison of the preliminary experimental/measurement and computational/modeling results shows good correlation.
Heat Transfer Characteristics for a Confined Rotating MCM Disk With Round Jet Array Impingement
Authors: Lee C. Y. , Fang C. J. , Peng C. H. , Lin T. W. , Hung Y. H.
Published: January 2010

An effective method of design of experiments combined with Central Composite Design for exploring the heat transfer characteristics for a confined rotating Multi-Chip Module (MCM) disk with round jet array impingement has been successfully developed. The relevant parameters influencing heat transfer performance include the steady-state Grashof number (Grs), ratio of jet separation distance to nozzle diameter (H/d), jet Reynolds number (Rej) and rotational Reynolds number (Rer). Their effects on heat transfer characteristics have been systematically explored. An axisymmetrical temperature distribution is ensured for various Grs, Rej, Rer and H/d ratios. As compared with the mutual effects of jet array impingement and disk rotation cause a more non-uniform distribution of chip temperatures. For heat transfer behavior, a new correlation of stagnation Nusselt number for jet array impingement at r/R = 0 in terms of Rej and H/d is presented. As compared with the experimental steady-state data of single round jet impingement, the average heat transfer enhancement at stagnation point r/R = 0 of jet array impingement is 607%. For the rotating MCM disk cases, the highest chip heat transfer occurs at the MCM disk rim, and decreases sharply along the distance from the surface edge toward the surface center.
Impact of Thermodiffusion on Temperature Fields in Stationary Nanofluids
Authors: Gharagozloo Patricia E. , Goodson Ken E. , Eaton John K.
Published: January 2010

The research community has reported a large variety of at times contradictory thermal conductivity enhancements for nanofluids. Some of the differences may result from thermodiffusion, which is the coupled transport of heat and nanoparticles in a temperature gradient. Thermodiffusion can influence the apparent conductivity observed in a given experimental setup. This work explores the potential impact of thermodiffusion on the inconsistencies of the previous results and on the observed temperature dependence of the thermal conductivity enhancement. The thermal conductivity variation with temperature is captured using infrared microscopy. The thermal conductivity distribution varies significantly over the temperature range 27 – 73°C. This work also explores the potential impact of aggregation, gravitational separation, and thermodiffusion on the time-evolution of the thermal conductivity. For 1 percent by volume aluminum oxide in deionized water, this work finds a thermal conductivity enhancement of between 1 and 15 percent depending on temperature and time, which corresponds to an enhancement factor of between 1 and 15. For 0.2 percent by volume carbon nanotubes in silicone oil, this work finds a thermal conductivity enhancement of 8 percent with no dependence on temperature, which corresponds to an enhancement factor of 40.
Numerical Model for Thermal Transport in 3-D Nanotube Composites
Authors: Kumar Satish , Murthy Jayathi Y.
Published: January 2010

The effective thermal conductivity of three dimensional (3-D) nanocomposites composed of carbon nanotube (CNT) dispersions is computed using Fourier conduction theory. The random ensemble of nanotubes is generated numerically and each nanotube is discretized using a finite volume scheme. The background substrate mesh is also discretized using a finite volume scheme. We incorporate all parameters crucial for thermal transport studies, i.e. tube aspect ratio, tube density, composite sample size, substrate-CNT conductivity ratio and the interfacial resistance due to tube-tube and tube-substrate contact. Two-dimensional (thin film) nanocomposites are also simulated for comparison. Numerical predictions of effective thermal conductivity are in excellent agreement with the effective medium approximation (EMA) for both 2-D and 3-D nanocomposites at low tube densities, but depart significantly from EMA predictions when tube-tube interaction becomes significant. It is found that the effect of tube-tube contact on effective thermal conductivity is more significant for 2-D composites than 3-D composites. Hence percolation effects may play a more significant role in thermal transport in 2-D nano-composites.
Shape Prediction of Molten Micro-Solder Joints Using Particle Method and Application to Evaluation of Fracture Life
Authors: Tanie Hisashi
Published: January 2010

The reliability of a micro-solder joint in a semiconductor structure greatly depends on the solder shape. Therefore, many methods to predict the shape of the molten solder have been proposed [1–3]. However, some problems arise when conventional methods are applied to predict the solder shape of miniaturized and lead-free joints. The first problem is the difficulty in expressing the large deformation and topology change of the solder. In a miniaturized joint, the shape of molten solder changes significantly during the reflow process, and even topology changes (e.g., merging with other solder in a neighboring joint or splitting into several pieces) can occur. These phenomena need to be expressed if we are to predict the solder shape of the miniaturized joint. The second problem is the difficulty in expressing the effect of solder wettability. The solder shape is known to depend on the solder wettability, and the wettability of lead-free solders is different from conventional solders. To predict the lead-free solder shape, we need to express the effect of the wettability. Therefore, I developed a new shape prediction method that solves these problems using the moving-particle semi-implicit (MPS) method [4, 5]. MPS is suitable for calculating incompressible flow and can be used to easily express large deformation and topology changes. However, the original MPS method cannot sufficiently express the effect of solder wettability. Therefore, I enhanced the surface tension formulation of MPS, making it possible to express this effect. I applied this method to predict the solder shapes of various packages (e.g., a thin small outline package (TSOP) and a flip-chip package) and found that the method is effective in predicting the solder shapes of miniaturized joints. Moreover, I was able to evaluate the fracture life of a solder joint with the predicted solder shape by coupling the shape prediction method with our crack propagation analysis method, which was demonstrated at a previous InterPACK [6]. In this crack propagation analysis method, crack initiation points and propagation paths are automatically calculated, and the fracture life is evaluated quantitatively by finite element analysis. I applied these combined methods to evaluate the fracture life of solder joints that had different solder shapes due to different wettability conditions. As a result, I was able to find the differences in crack initiation points and to evaluate crack propagation paths and fracture lives in different wettability conditions.
Development of an Industry-Oriented Graduate Course on Microelectronic Packaging in China
Authors: Cheng Xiu-Lan , Fu Yu-Zhuo , Yang Cheng , Chen Yan
Published: January 2010

With the rapid growth of IC industry in China, microelectronic packaging industry is playing more and more important role in this country. And the lack of talents on microelectronic packaging becomes the bottleneck to limit the development of microelectronic packaging industry in China. So with the great support from Intel, an industry-orientated graduate course on microelectronic packaging was developed in Shanghai Jiao Tong University and opened to all graduates or senior undergraduates in this university. This course is designed to serve as an introduction and a review on microelectronic packaging. Some topics about design considerations, materials, process flow and typical techniques of microelectronic packaging including advanced packaging technologies are addressed. Fundamentals and methodologies of reliability and failure analysis are also covered in this course. At last, a brief introduction on PCB assembly is concerns. A laboratory experiment and factory visiting on packaging process are included in this course to improve the students’ practice ability and deepen their comprehension on modern packaging manufacturing. Most of lectures in this course are taught by experienced engineers from industry to increase its characterization on industrialization. This course will be helpful to students intending to specialize in microelectronic packaging. At last further plans on this course and related curriculum about microelectronic packaging are introduced briefly.
Frequency Analysis on Pulsating Heat Pipe
Authors: Qu Wei , Li Yuhua , Ma Tongze
Published: January 2010

The pulsating heat pipe should have one eigen frequency based on the temperature visualization of pulsating heat pipe. The preliminary model of pulsating heat pipe is established by the force balance between the driving force, the inertial force and the frictional force. The results show that different structural parameter of pulsating heat pipe influences the eigen frequency differently. If a pulsating heat pipe has less turning number, or has micro or mini capillary, or has higher filling ratio, then the eigen frequency will change quickly. The frequency stands for the springiness of the system. The results can explain why some pulsating heat pipes with less turning number are hard to operate.
Metrics and an Infrastructure Model to Evaluate Data Center Efficiency
Authors: Belady Christian L. , Malone Christopher G.
Published: January 2010

This work describes two data center efficiency metrics: Power Usage Effectiveness (PUE) and Compute Power Efficiency (CPE). PUE characterizes the fraction of the total data center power used for IT work. CPE characterizes the overall data center efficiency, considering IT equipment utilization as well as how power is used in the data center. The PUE results from three data center studies are presented here. The data suggests that a carefully designed and managed data center has a PUE of 2.0. More studies are required to determine the range of values for the typical data center. A data center infrastructure and energy cost model is presented to compare hardware costs to infrastructure and energy costs. The impact of PUE on these costs is examined to illustrate the impact of data center efficiency on the total cost of operating a data center.
Study of Horizontal-Base Pin-Fin Heat Sinks in Natural Convection
Authors: Sahray D. , Magril R. , Dubovsky V. , Ziskind G. , Letan R.
Published: January 2010

The present paper deals with horizontal-base pin fin heat sinks in free convection. The sinks have the same base dimensions and variable fin pitch. They are made of aluminum, and there is no contact resistance between the base and the fins. The fins have a constant square cross-section. The effect of fin pitch on the performance of the sink is studied experimentally and numerically. In the experiments, the heat sinks are heated using foil electrical heaters. The heat input is set, and temperatures of the base and fins are measured. In the corresponding numerical study, the sinks are modeled using the Fluent 6 software. The results show that heat transfer enhancement due to the fins is not monotonic. The differences between sparsely and densely populated sinks are analyzed. Also analyzed are the effects of the sink edges on the total heat transfer. A relative contribution of outer and inner fin rows in the sink is assessed, together with the effect of fin location in the array on the heat transfer rate from an individual fin. Dimensional analysis of the results is attempted, and a correlation presenting the Nusselt number vs. the Rayleigh number is suggested, where the inter-fin spacing serves as the characteristic length.
High Power LED Integrated With Silicon-Based Thermoelectric Cooler Package
Authors: Dai Ming-Ji , Yu Chih-Kuang , Liu Chun Kai , Kuo Sheng-Liang
Published: January 2010

A new thermal management application of silicon-based thermoelectric (TE) cooler integrated with high power light emitting diode (LED) is investigated in present study. The silicon-based TE cooler herein is fabricated by MEMS fabrication technology and flip-chip assembly process that is used for high power LED cooling. An electrical-thermal conversion method is used to estimate the junction temperature of LED. Moreover, the Integrating Sphere is also used to measure the light efficiency of LED. The thermal images photographed by infrared camera demonstrated the cooling function of the silicon-based TE devices. The results also show that high power LED integrated with silicon-based thermoelectric cooler package can effectively reduce the thermal resistance to zero. In addition, the light efficiency of the LED (1W) will increase under low TE cooler input power (0.55W), which is about 1.3 times of that without TE cooler packaging.
Dominant Structural Factors of Local Residual Stress in Three-Dimensionally Stacked LSI Chips Mounted Using Flip Chip Technology
Authors: Ueta Nobuki , Miura Hideo
Published: January 2010

Since mechanical stress and strain change both electronic functions and reliability of LSI chips, it has become strongly important to control the residual stress and strain in them to assure their reliable performance. In this study, the authors discuss the stress distribution in chips stacked using area-arrayed metallic bumps. The average residual stress in the stacked two chips changes drastically depending on the distance from a bending neutral axis of the stacked structure, and the local residual stress also varies depending on the relative position of bumps between an upper and a bottom interconnection layer. However, the residual stress of the top chip with a free surface is not affected by the bump alignment in lower interconnection layers. It is very important, therefore, to optimize the thickness of a chip and other structural factors as mentioned above to control not only the average residual stress but also the amplitude of the periodic stress. Finally, the estimated stress distribution in the stacked two chips was proved in detail by the experiment using stress-sensing chips with 2μm long strain gauges consisted of single-crystalline Si.
Adhesive Tiecoat/Polyimide Interactions in High Temperature Flex Packaging
Authors: Schoeller Harry , Knobloch Aaron , Xia Hua , Shaddock David , Kapusta Chris , Durocher Kevin , Cho Jungyun
Published: January 2010

The high temperature reliability of flex-based Cu/tiecoat/polyimide structures was evaluated through finite element simulation and experimental approach. This study is part of an effort to characterize and optimize polyimide flex as a substrate material for electronics packages rated to greater than 204°C. The peel strength of several common adhesion metals (Ti, Cr, Ni, Cu) on Kapton E was quantified at room temperature and after high temperature storage in inert and highly oxidizing environments. These results were used in tandem with thermal-mechanical simulations to characterize the behavior of several tiecoat materials. Experimental results showed diminished peel strengths of both the Ti and Cr after a 100-hour 250°C heat treatment in air. However when annealed in an inert N2 environment at 250°C for 100 hours, Cr, Ni, and Ti retained their as-sputtered peel strength. Ni and Cu exhibited lower mechanical stresses in the simulation; however, their relatively low reactivity limits their adhesion strength at the interface in oxidizing environments. To further understand the origin of the thermal-mechanical stress, the effect of mismatched CTE was compared to mismatched elastic modulus. Both properties were found to contribute to stress generation; however elastic modulus mismatches had a much greater influence on the overall magnitude of the stress. Through experimentation and FEA analysis this study aims to develop a flexed-based high temperature packaging solution and to shed light onto high temperature tiecoat/polyimide interactions.
Nonmetallic Conduction Property of a DNA Templated Gold Nanowire
Authors: Kodama Takashi , Jain Ankur , Goodson Kenneth E.
Published: January 2010

Nanowires based on DNA are exciting materials with several possible applications in nanoelectronics because of the self-assemble capability for the designed nanostructure. In this study, we have carried out electrical and thermal conduction measurements on a metallized single DNA molecule. The measured values of the electrical and thermal conductivity were about 1.42 × 101 S/cm and 149.8 W/mK at room temperature, respectively. The measured value of the Lorentz number was about 3.6 × 10−4, which is incompatible with that predicted by the Wiedemann-Franz law. The temperature dependent electrical conductivity shows that electron transport in metallized DNA occurs by the hopping process similar to that in nonmetallized DNA. Atomic force microscopy reveals nanoscale discontinuities in the gold layer around the DNA. While the gold layer assists the DNA in electron conduction, the overall conduction of the metallized DNA is dominated by the DNA rather than the coating. These results suggest that the DNA is potentially a better thermal conductor than the metal coating and that its effective conductivity may be large. This interesting physical property may make the DNA useful for bioapplications involving significant heat transfer.
Thermal Contact Resistance of a Silicon Nanowire on a Substrate
Authors: Singh Dhruv , Fisher Timothy S. , Murthy Jayathi Y.
Published: January 2010

Increased interest in determining the thermal contact resistance encountered in various nanoscale devices derives from its role as a critical bottleneck to thermal transport at submicron scales. In the present work, the contact resistance of one such configuration — a silicon nanowire on a Si substrate — has been studied. A model based on the phonon Boltzmann transport equation (BTE) in the solid and Fourier conduction in the surrounding gas is used, in conjunction with a previously published finite volume method. This approach enables the accurate computation and examination of the relative magnitudes of constriction resistance, air thermal resistances, and the bulk resistance of the wire on transverse heat transport. The results confirm that the effective resistance is dominated by constriction resistance even for low and moderate wire acoustic thicknesses and that the constriction resistance is well represented by ballistic-limit models. In the mesoscale regime when the constriction is partially diffusive, a simple addition of diffusive and ballistic resistances is shown to work reasonably well, in agreement with previously published estimates. For higher wire acoustic thicknesses, the effects of bulk scattering in the wire cannot be ignored and a simple additive formula is inadequate. The fluid surrounding the wire can act as a complementary parallel pathway for thermal transport; however, in the high gas-phase Knudsen regime, the constriction resistance remains the controlling factor for overall thermal conductance.
Hermetic Encapsulation Technique Developed for the IBM Z-Server Multi-Chip Module
Authors: Coico Patrick A. , Arvelo Amilcar , Messina Gaetano P. , Pompeo Frank L. , Scheider Donald W.
Published: January 2010

The large MCM developed to package the main processor unit used in the IBM z9 Server makes use of a novel sealing design that imparts many desirable characteristics to the module assembly process, performance and reliability. These packages consist of a large ceramic chip carrier encapsulated using a copper cooling cap and a metal sealing ring. The sealing technique not only provides the hermetic environment needed to protect the non-underfilled devices contained within the module, but also allows for easy rework of the assembly. The seal used can withstand the thermally induced stresses and strains driven by the thermal expansion coefficient mismatch between the carrier and the cap. Depending on the system requirements or application, it can do this and reliably maintain the level of hermeticity needed to protect the encapsulated devices over a thousand or more thermal cycles. In addition to this, the seal and module design must compensate for mechanical tolerances of the carrier and devices that affect the assembled condition of the module. In the z-Server module design these considerations, as well as thermal performance factors, are all taken into account. This paper will cover the various aspects of the module design, focusing on the novel application of the hermetic seal employed. The seal will be described and its design parameters will be discussed. Seal, component and module level qualification testing that is performed to insure that the assembly meets the package reliability requirements will be presented.
High Temperature Lead-Free Attach Reliability
Authors: McCluskey Patrick , Quintero Pedro O.
Published: January 2010

The increasing demand for electronics capable of operating at temperatures above the traditional 125°C limit is driving major research efforts. Wide band gap semiconductors have been demonstrated to operate at temperatures up to 500°C, but packaging is still a major hurdle to product development. Recent regulations, such as RoHS and WEEE, increase the complexity of the packaging task as they prohibit the use of toxic materials in electronic products; lead being a major concern due to its widespread use in solder attach. In this investigation, a series of Pb-free die attach technologies have been identified as possible alternatives to Pb-based materials for high temperature applications. This paper describes the fabrication sequence used to create attachments with these materials and their resultant microstructure. The long term reliability is also determined by accelerated thermal cycling and physics-of-failure modeling.
Forced-Convection Boiling Characteristics Based on Mass and Energy Conservation
Authors: Horiuchi Keisuke , Ohashi Shigeo
Published: January 2010

This paper presents an experimental study and theoretical interpretation of two-phase flow in a closed loop. The objective of this work is to find the optimum flow rate with respect to the thermal design power (amount of heat to be rejected). We assume that forced-convection boiling characteristics are explained based on mass and energy conservation, and claim that our proposed coefficient (C ≡ QL / Q : a ratio of amount of evaporated liquid to the flow rate) indicates the optimum flow rate for wide variation of evaporator-shapes and working fluids. In order to verify our model, we have measured the thermal resistance of evaporator with respect to heater input power for various flow rates. Hydrofluoro ether (HFE) and Fluorinert™ refrigerants were used as the working fluid in the experiment. Here flow rate of 40∼120ml/min and thermal design power of 50∼200W were controlled by the pump and by the heater, respectively. We observed that the coefficient resulted in the optimum flow rate is almost the same regardless of working fluids and evaporator shapes. The data which indicates the optimum flow rate were quite well reproduced by our proposed theory when the value of this coefficient is C ≈ 0.7∼0.95. For the demonstration, we designed the assembled-type two-phase cooling module with the optimum flow rate based on our model, and we observed that the evaporator had a relatively small thermal resistance of 0.1K/W.
Stress Isolation Structures in MEMS Gyroscope Packages
Authors: Yun C. H. , Zhang X. , Kumar V. , Edwards M. G.
Published: January 2010

This paper describes the impact of lead frame design to minimize mechanical and thermal stresses to a MEMS (micro-electromechanical systems) gyroscope in a plastic premold cavity package. Design ideas for incorporating stress-isolation structures by etching the die paddle in a lead frame were evaluated with finite element modeling (FEM) and experimental verifications. The results showed that the null drift due to external mechanical stress was significantly improved by more than one order of magnitude, and the temperature variation of the device output was also improved by 30%, both by mounting the device on the lead frame etched with stress-isolation structures.
Thermomechanics of High-Pressure MEMS Sensors
Authors: Pryputniewicz Ryszard J.
Published: January 2010

Increasing demand for high performance, stable, and affordable sensors for applications in process control industry has led to development of a miniature pressure sensor. This development, made possible by recent advances in microelectromechanical systems (MEMS) fabrication, utilizes polysilicon-sensing technology. The unique polysilicon piezoresistive sensor (PPS) measures differential pressure (DP) based on deformations of a multilayer/multimaterial diaphragm, which is about 2 μm thick. Deformations of a diaphragm, subjected to changes in pressure, are sensed by the piezoresistive bridge elements. Determination of the loading pressures from strains of the piezoresistors is based on computations relying on a number of material specific and process dependent coefficients that, because of their nature, can vary, which may lead to uncertainties in displayed results, especially when temperature changes also. To establish an independent means for measurements of the thermomechanical (TM) deformations of the PPS diaphragms and to validate the coefficients used, a hybrid methodology, based on measurements using optoelectronic laser interferometric microscope (OELIM) and finite element method (FEM) computations coupled with uncertainty analysis provided by unique closed form formulations, was developed. This methodology allows highly accurate and precise measurements of TM deformations of diaphragms, as well as their computational modeling/simulations, and is a basis for “design by analysis” approach to efficient and effective developments of new MEMS sensors. In this paper the hybrid approach is described and its use is illustrated by representative examples addressing high-pressure MEMS sensors.
Thermal Management in RF MEMS Ohmic Switches
Authors: Pryputniewicz Ryszard J.
Published: January 2010

Today, an ideal microelectromechanical systems (MEMS) switch is no longer a designer’s dream, yet electrothermomechanical (ETM) effects still limit the design possibilities and may adversely affect reliability of microswitches, especially the Ohmic-type cantilever contact switches. The ETM effects are a result of Joule heat generated at the switch contact areas (i.e., electrical interfaces). This heat is due to an electrical signal passing through a microswitch, internal resistance of contact materials, and characteristics of the electrical contact interface. It significantly raises temperature of a microswitch, thus adversely affecting mechanical and electrical properties of the contacts, leading to their wear or even welding, which is a major reliability issue. Fundamental research is being performed to minimize Joule heat effects in the electrical interface area, thus improving the microswitch performance and reliability. Thermal analysis conducted computationally on an Ohmic-type RF MEMS switch indicate heat affected zones (HAZ) and the influence that various parameters have on those zones. Such analysis facilitates mitigation of thermal management issues that may otherwise be detrimental to functional operation of a microswitch.
Quantitative Characterization of Microsystem Dynamics
Authors: Pryputniewicz Ryszard J. , Pryputniewicz Emily J.
Published: January 2010

Development of microelectromechanical system (MEMS) sensors for various applications requires the use of analytical and computational modeling/simulation coupled with rigorous physical measurements. This requirement has led to advancement of an approach that combines computer aided design (CAD) and multiphysics modeling/simulation tools with the state-of-the-art (SOTA) measurement methodology to facilitate reduction of high prototyping costs, long product development cycles, and time-to-market pressures while devising MEMS for a variety of applications. In this approach, a unique, fully integrated software environment for multiscale, multiphysics, high fidelity modeling of MEMS is combined with the optoelectronic laser interferometric microscope methodology for quantitative measurements. The optoelectronic methodology allows remote, noninvasive full-field-of view (FFV) measurements of deformations/motions (under operating conditions) with high spatial resolution, nanometer accuracy, and in near real-time. In this paper, both, the modeling environment (including an analytical process used to quantitatively show the influence that various parameters defining a sensor have on its dynamics — using this process dynamic characteristics of a sensor can be optimized by constraining its nominal dimensions and finding the optimum set of uncertainties in these dimensions that best satisfy design requirements/specifications) and the optoelectronic methodology are described and their applications are illustrated with representative examples demonstrating viability of the approach, combining modeling and measurements, for quantitative characterization of microsystem dynamics. These representative examples demonstrate capability of the approach described herein to quantitatively determine effects of dynamic loads on performance of selected MEMS.
Data Center Housing the World’s 3rd Fastest Supercomputer: Above Floor Thermal Measurements Compared to CFD Analysis
Authors: Schmidt Roger , Iyengar Madhusudan , Caricari Joe
Published: January 2010

With the ever increasing heat dissipated by IT equipment housed in data centers it is becoming more important to project the changes that can occur in the data center as the newer higher powered hardware is installed. The computational fluid dynamics (CFD) software that is available has improved over the years and some CFD software specific to data center thermal analysis has been developed. This has improved the timeliness of providing some quick analysis of the effects of new hardware into the data center. But it is critically important that this software provide a good report to the user of the effects of adding this new hardware. And it is the purpose of this paper to examine a large cluster installation and compare the CFD analysis with environmental measurements obtained from the same site. This paper shows measurements and CFD analysis of high powered racks as high as 27 kW clustered such that heat fluxes in some regions of the data center exceeded 700 Watts/ft2 (7535 W/m2). This paper describes the thermal profile of a high performance computing cluster located in an IBM data center and a comparison of that cluster modeled with CFD software. The high performance Advanced Simulation and Computing (ASC) cluster, developed and manufactured by IBM, is code named ASC Purple. It is the World’s 3rd fastest supercomputer [1], operating at a peak performance of 77.8 TFlop/s. ASC Purple, which employs IBM pSeries p575, Model 9118, contains more than 12,000 processors, 50 terabytes of memory, and 2 petabytes of globally accessible disk space. The cluster was first tested in the IBM development lab in Poughkeepsie, NY and then shipped to Lawrence Livermore National Labs in Livermore, California where it was installed to support our national security mission. Detailed measurements were taken in both data centers of electronic equipment power usage, perforated floor tile airflow, cable cutout airflow, computer room air conditioning (CRAC) airflow, and electronic equipment inlet air temperatures and were report in Schmidt [2], but only the IBM Poughkeepsie results will be reported here along with a comparison to CFD modeling results. In some areas of the Poughkeepsie data center there were regions that did exceed the equipment inlet air temperature specifications by a significant amount. These areas will be highlighted and reasons given on why these areas failed to meet the criteria. The modeling results by region showed trends that compared somewhat favorably but some rack thermal profiles deviated quite significantly from measurements.
Comparison Between Numerical and Experimental Temperature Distributions in a Small Data Center Test Cell
Authors: Iyengar Madhusudan , Schmidt Roger R. , Hamann Hendrik , VanGilder Jim
Published: January 2010

Information Technology equipment is continuing to increase in power, leading to significant challenges from the room air conditioning perspective. Numerical models are the dominant techniques for designing new data centers and optimizing existing ones. It is thus critical to understand the inherent error in the model prediction of flow and temperature distributions in the data center, with emphasis on the vicinity of the server rack. This study uses a simulated server rack in a small room where detailed temperature (3D), flow, and power measurements were carried out for a single scenario under steady state conditions. A numerical model was constructed to represent the data center cell for this case. Model results were then compared with three dimensional experimentally obtained temperature maps and the discrepancy between the two was quantified as an error in temperature. The difference between test data and model results was found to be the highest in the exhaust air path from the rear of the simulated server rack to the inlet of the air conditioning unit. The dominant sources of error are likely to be in the use of the standard k-ε turbulence model, and the simplistic rack representation in which rack exhaust airflow is assumed uniform. Both modeling limitations tend to pronounce hot and cold spots and inhibit the mixing of hot and cold air streams within the data center. This is the first study on comparison between three dimensional temperature distributions obtained via modeling and from actual data collection.
Stress-Induced Effects in Electronic Characteristics of n-Type MOSFETs in Resin-Molded Packages
Authors: Koganemaru Masaaki , Ikeda Toru , Miyazaki Noriyuki , Tomokage Hajime
Published: January 2010

The shift of the DC characteristics of nMOSFETs during a resin-molding process was investigated experimentally. A silicon chip including the nMOSFETs was encapsulated in a quad flat package, and the drain current and transconductance shifts were measured. The drain current decreased during the resin-molding process, while no significant shift in threshold voltage was observed. The experimental results were estimated adequately from the residual stress predicted by numerical and experimental analysis, and from the stress sensitivity of the nMOSFETs measured by the four-point bending method. Also, we verified the validity of an electron mobility model that includes the effect of stress, used for drift-diffusion device simulation, by comparison with experimental results, and several improvements to the electron mobility model were found out.
Thermal Management on Hot Spot Elimination / Junction Temperature Reduction for High Power Density System in Package Structure
Authors: Chou Chan-Yen , Wu Chung-Jung , Wei Hsiu-Ping , Yew Ming-Chih , Chiu Chien-Chia , Chiang Kuo-Ning
Published: January 2010

In this paper, a thermal enhanced design for a high power density system in package (SiP) is proposed to resolve the challenge faced by the packaging research community in eliminating the hot spot and reducing the junction temperature in a high operation temperature. The SiP structure includes seven sub-chips which are attached to the chip carrier. The dissipated heat is conducted to the metal slug by thermal vias, while some heat is conducted to the pads by metal traces. Finally, the whole module is connected to the test board by solder paste material. In the thermal enhanced design, a highly conductive material such as solder paste is applied to make an attachment between the chip carrier and the highest power density chip (the power amplifier chip). Besides, some thermal vias are constructed to conduct the dissipated heat from the chip carrier to the metal slug. The new structure greatly improves the thermal performance of the SiP structure. Moreover, the hot spot on the chip carrier is also eliminated in this thermal enhanced SiP structure.