bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of Local Residual Stress of a Flip Chip Structure Using a Stress Sensing Chip
Authors: Ueta Nobuki , Miura Hideo
Published: April 2009

Local residual stress at a surface of a silicon chip mounted on a substrate using flip chip technology was measured using a stress sensor chip that was composed of 168 strain gauges of 10-μm in length. Each strain gauge was made of polycrystalline silicon films deposited on a silicon wafer. The periodic stress distribution was measured at a surface of the sensor chip between two bumps. Five gauges were aligned at a interval of 20-μm between the bumps. When the thickness of the chip was less than 200 μm, the amplitude of the stress increased drastically, as was predicted by a finite element analysis. The amplitude of the stress reached about 150 MPa, when the thickness of the chip was thinned to 50 μm. The amplitude of the stress is a strong function of the thickness of a silicon chip and the intervals of the bumps.
Transient Performance of a Finned PCM Heat Sink
Authors: Shatikian V. , Ziskind G. , Letan R.
Published: April 2009

The present study explores numerically the transient performance of a heat sink based on a phase change material (PCM), during the process of melting. Heat is transferred to the sink through its horizontal base, to which vertical fins made of aluminum are attached. The phase change material is stored between the fins. Its properties, including the melting temperature, latent and sensible specific heat, thermal conductivity and density in solid and liquid states, are based on a commercially available paraffin wax. A parametric investigation is performed for melting in a relatively small system, 10mm high, where the fin thickness is 1.2mm, and the distance between the fins varies from 2mm to 8mm. The temperature of the base varies from 12°C to 24°C above the mean melting temperature of the PCM. Transient numerical simulations are performed, yielding temperature evolution in the fins and the PCM. The computational results show how the transient phase-change process, expressed in terms of the volume melt fraction of the PCM, depends on the thermal and geometrical parameters of the system, which relate to the temperature difference between the base and the mean melting temperature, and to the thickness of the PCM layer.   This paper was also originally published as part of the Proceedings of the ASME 2005 Heat Transfer Summer Conference.
Thermal Optimal Design for Partially-Confined Compact Heat Sinks
Authors: Wang M. P. , Chen H. T. , Horng J. T. , Wu T. Y. , Chen P. L. , Hung Y. H.
Published: April 2009

An effective method for predicting the optimal thermal performance of partially-confined compact heat sinks under multi-constraints of pressure drop and heat sink mass has been successfully developed. The design variables of PPF compact heat sinks include: heat sink fin and base material, thickness of heat sink base, heat flux, channel top bypass and inlet flow velocity. A total of 108 experimental cases for confined forced convection are designed by the Central Composite Design (CCD) method. According to the results in ANOVA, a sensitivity analysis for the design factors is performed. From the analysis, the effect of inlet flow velocity, which has the contribution percentage of 86.24%, dominates the thermal performance. The accuracies of the quadratic RSM models for both thermal resistance and pressure drop have been verified by comparing the predicted response values to the actual experimental data. The maximum deviations of thermal resistance and pressure drop are 9.41% and 7.20% respectively. The Response Surface Methodology is applied to establish analytical models of the thermal resistance and pressure drop constraints in terms of the key design factors with a CCD experimental design. By employing the Sequential Quadratic Programming technique, a series of constrained optimal designs can be efficiently performed. The numerical optimization results for four cases under different constraints are obtained, and the comparisons between these predicted optimal designs and those measured by the experimental data are made with a satisfactory agreement.
Forced Convective Heat Transfer for Partially-Confined Compact PPF Heat Sinks With Top-Bypass Effect
Authors: Wu T. Y. , Wang M. P. , Horng J. T. , Chang S. F. , Hung Y. H.
Published: April 2009

A series of experimental investigations with a stringent measurement method on the study of the fluid flow and heat transfer for confined compact heat sinks in forced convection have been successfully conducted. From the results, the thermal capacity of the heat sink and the convective heat dissipation play the major roles for dominating the transient thermal behavior in the beginning of power-on transient period; while, the convective heat dissipation finally becomes the solely dominating term at the end of power-on transient period. The transient/steady-state local and average Nusselt numbers increase with increasing Grs, H/Hc ratio or Re. As compared with the steady-state average Nusselt number for non-compact heat sink (Fin-Al/ Base-Al), the steady-state heat transfer enhancement for compact heat sinks (Fin-Al/Base-Al) is 185.74%. Furthermore, a new correlation of steady-state average Nusselt number in terms of relevant influencing parameters for confined compact PPF heat sinks in forced convection is proposed. As compared with two existing correlations of steady-state average Nusselt numbers for unconfined and confined non-compact PPF heat sinks, the heat transfer enhancements for the present confined compact PPF heat sinks of H/Hc = 0.47 are 423.29% and 219.93%, respectively.
Ceramic Flat Plate Evaporator for Loop Heat Pipe Cooling of Electronics
Authors: Zimbeck Walter , Chaney Jared , Espinoza Patricio , Kroliczek Edward , Bugby David C. , Yun James
Published: April 2009

Two-phase loops are extremely efficient devices for passively transporting heat over long distances with low temperature drop. The heat acquisition component of a two-phase loop, the evaporator, is commonly made from conventional metal materials (aluminum, copper, etc.) and has cylindrical geometry. Neither characteristic is optimally suited for close integration to common electronic or photonic heat sources, which generally have flat interfaces and are constructed from low thermal expansion coefficient (CTE) semiconductor materials. This paper describes the development of a ceramic flat plate evaporator for cooling processor chips in network computers used onboard Navy submarines. The unique requirements of submarines give added motivation for the advantages offered by two-phase loops. The ceramic flat plate evaporator is constructed of low CTE, high thermal conductivity material and thus enables a low thermal resistance interface between the heat source and the working fluid of the loop heat pipe. Alumina and aluminum nitride flat plate evaporators were integrated into a water-based two-phase loop and thermally tested to a heat flux of 30 W/cm2.
Convective Performance of Package Based Single Phase Microchannel Heat Exchanger
Authors: Chang Je-Young , Prasher Ravi , Chau David , Myers Alan , Dirner John , Prstic Suzana , He Dongming
Published: April 2009

Liquid cooling using integrated microscale heat exchangers are a promising future technology to address issues associated with integrated circuit thermal management. This paper reports the first results of microchannel heat exchangers fabricated directly in the back of silicon chips with integrated front side heaters and temperature sensors. These chips were mounted on organic substrates using C4 bumps and underfill and then these packages were mounted onto a motherboard using μPGA (Micro-Pin Grid Array) socket. The chips contained two metallic heaters; a 10 mm × 13 mm heater in order to provide uniform heating and a small 400 μm × 400 μm heater in order to simulate hotspots on actual microprocessors. The chips had multiple metallic temperature sensors distributed over the die area. Three different designs covering different widths and depths of microchannels were fabricated. The smallest width was 61 μm and the smallest depth was 180 μm. Thermal resistances and pressure drops of the three designs were measured. The best thermal resistance (junction to outlet of fluid) of 0.09 °C-cm2/W, was obtained using a 61 μm wide and 272 μm deep microchannel. The chips were also tested under non-uniform heating conditions by powering the hotspot heaters up to a heat flux of 1250 W/cm2.   This paper was also originally published as part of the Proceedings of the ASME 2005 Heat Transfer Summer Conference.
Thermal Performance of Vapor Chambers Under Hot Spot Heating Conditions
Authors: Chang Je-Young , Vadakkan Unnikrishnan , Prasher Ravi , Prstic Suzana
Published: April 2009

Use of heat pipes (or vapor chambers) is considered as one of the promising technology to extend the capability of air cooling. This paper reports the test results of vapor chambers using two different sets of test heaters (copper post heater and silicon die heater). Experiments were conducted to understand the effects of non-uniform heating conditions on the thermal performance of vapor chambers. In contrast to the copper post heater which provides ideal heating condition, silicon chip package was developed to replicate more realistic heat source boundary conditions of microprocessors. The chip contains three metallic heaters: a 10 × 12 mm heater in order to provide uniform heating, a 10 × 3 mm heater in order to simulate a localized heating, and a 400 × 400 μm heater in order to simulate the hot spots on actual microprocessors. In the experiment, the highest heat flux from the hotspot heater was approximately 690 W/cm2. Test results indicated that both conduction heat transfer and phase-change phenomena played key roles in the evaporator. The study found that the evaporator resistance was almost insensitive to non-uniform heating conditions, but was clearly dependent on the amount of power applied over the die area. In addition, a simple one-dimensional thermal model was developed to predict the performance of vapor chambers for non-uniform heating conditions and the results were compared against experiments.
Effect of Line-Shape on Threshold Current Density of Electromigration Damage in Bamboo Lines
Authors: Sasagawa Kazuhiko , Uno Shigeo , Yamaji Nao , Saka Masumi
Published: April 2009

It is known that there is the threshold current density of the electromigration damage in the via-connected line. The evaluation of the threshold current density is one of the great interests from the viewpoint of IC reliability. In this study, a metal line with two-dimensional shape, i.e. an angled metal line is treated. The evaluation method of the threshold current density is applied to the metal line. The method is based on the numerical simulation of the building-up process of the atomic density distribution in the bamboo line by using the governing parameter for electromigration damage. Comparing the evaluated results with that of straight-shaped line, the effect of line-shape on threshold current density of electromigration damage is discussed. Furthermore, the obtained difference in the threshold current density is verified experimentally.
Effect of Voids on Thermal Fatigue Reliability of Lead Free Solder Joint
Authors: Kim Doseop , Yu Qiang , Kobayashi Yusuke , Shibutani Tadahiro
Published: April 2009

There have been serious debates about whether Pb should be removed from solder joints, in view of environmental problems. These debates have now developed to the extent that a remarkable movement to establish regulations for the removal of Pb has emerged, especially in European countries and Japan. Therefore, Many studies have been aggressively undertaken to develop technologies for replacing Sn-Pb solder with lead-free alternative. From the results obtained so far, it has been proven that the fatigue strength in lead-free solder joints is almost equivalent to the fatigue strength of Sn-Pb eutectic solder joints. However, a new problem is that voids are very easily formed in lead-free solder joints during the reflow process, and the effect of the voids on the fatigue strength of solder joints has attracted attention. In this study, the relationship between the voids and fatigue strength of solder joints was examined using mechanical shear fatigue test and FEM (finite element method) analysis. Using the mechanical shear fatigue test, the effect of the position and size of voids on fatigue crack initiation and crack propagation has been investigated. And quantitative evaluation of fatigue life of solder joints with the voids has been enabled by Manson-Coffin’s law and Miner’ rule.
Exergy-Based Optimization Strategies for Multi-Component Data Center Thermal Management: Part II — Application and Validation
Authors: Shah Amip J. , Carey Van P. , Bash Cullen E. , Patel Chandrakant D.
Published: April 2009

Recent work has proposed an exergy-based strategy to achieve optimal system-wide performance via localized control of individual data center thermal management components. This paper presents the results of a case study where the proposed approach is applied to a data center with two rows of computing racks and two Computer Room Air-Conditioning (CRAC) units. The formulated model is used to predict the optimal data center configuration in terms of supply temperatures, flowrates, and rack heat load configurations. Two extreme cases are chosen: one with the maximum experimental heat load in the data center, and one with a minimal experimental heat load. For each case, the optimal settings for each CRAC unit were predicted using the model and using temperature + flow measurements in the data center. The setpoints predicted by the model for optimal CRAC flow and supply temperature were within 25% of the experimentally determined optima.
Study on the Dynamic Behavior of Repetitive Drop Test for Electronic Component and the Reliability
Authors: Yu Qiang , Shibata Tsuyoki , Watanabe Keiji , Tsurusawa Toshihiro , Shiratori Masaki , Katahira Takayoshi
Published: April 2009

The purpose of this research is to investigate the dynamic behavior of repetitive drop test for electronic component and the effect of test conditions on the reliability. Considering reliability of mobile devices such as cellular phones, it is important to establish the drop impact reliability for solder joints. Many test methods have been investigated, but there are several unclear problems, such as dispersion of test result, failure mechanism and so on. In this paper, the authors proposed a repetitive drop test with simple equipments as to standardize the accelerated methods of drop impact reliability. And the authors classified roughly problems for standardization into two groups. One is the problem of repetitive drop test method. It contains collision angle between holder and ground, supporting condition of the specimen, and acceleration rate of repetitive drop test. The other is the mechanical problem of dynamic fracture. It contains interaction between holder and PCB (Printed Circuit Board), dynamic behavior of PCB, and failure modes of solder joints. For the former topics, when repetitive drop test is carried out, it is known that collision angle causes instable results of repetitive drop test. To solve this problem, a hemisphere was remodeled at the center of the holder’s bottom, and how the effect will be on the dynamic behavior of PCB was studied by series of dropping test. In addition, the acceleration test method of repetitive drop test was studied. For the latter topic, it is known that the dynamic behavior of PCB greatly affects failure of solder joints, and it is very important to understand what kind of deformation affects failure. The relation between holder and PCB was studied in view of the energy. In addition, the failure modes observed in repetitive drop test was examined by test results and analysis results.
An Evaluation of Fatigue Damage in Low-Cycle Range for Sn-3.5Ag, Sn-0.7Cu Lead-Free Solders and Sn-Pb Eutectic Solder Using Image Processing to Surface Feature
Authors: Takahashi Takehiko , Hioki Susumu , Shohji Ikuo , Kamiya Osamu
Published: April 2009

The low-cycle fatigue behavior of Sn-3.5mass%Ag, Sn-0.7mass%Cu lead-free solders and Sn-37mass%Pb solder were investigated at strain rate of 0.1%/s with a non-contact extensometer at room temperature (22 ± 3 °C). In addition, the relationship between the surface features in the low-cycle fatigue test and the fatigue life of those solders were investigated by image processing. The fatigue lives of Sn-3.5mass%Ag and Sn-0.7mass%Cu were better than that of Sn-37mass%Pb. The low-cycle fatigue behavior on each solder followed Coffin-Manson equation. The surface deformation in fine wrinkles was observed in the low-cycle fatigue test at each solder. The surface features for each solder were evaluated by image processing from the surface deformation. The surface features in the low-cycle fatigue test did not appear until under 10% of the fatigue life for Sn-3.5mass%Ag, until 10% of the fatigue life for Sn-0.7mass%Cu, and until 20% of the fatigue life for Sn-37mass%Pb.
Experimental Study on the Effects of Human and Electronic-Mechanical Interaction on RF Signal Strength for a Personal Server
Authors: Montero Michael , Pering Trevor , Udaud Umair , Wright Paul , Want Roy
Published: April 2009

This paper describes experimental results for transmission quality based on antenna direction, packaging materials, and interactions with the local environment. Many mobile devices depend heavily on wireless communications for their operation, making antenna efficiency very important for their successful operation. The Personal Server (PS) research platform enables the user to carry with them their palm-size personal computer anywhere they go. By simply approaching another computer, a kiosk, or other computing interface, all of the user’s data is accessible by wireless connection and transferred to the receiving device. The prototype acts like a mobile server that the consumer can take with and depending on the situation can interact with through any available computing device such as laptops, PCs, tablets, etc. Since the PS uses RF transmission to send files and images to the interfacing computers, maintaining reliable and robust signal strength is important for the device. An experimental approach was used to better understand the factors which may degrade or augment signal strength. The approach taken in this investigation quantifies the effects of human and electronic-mechanical factors on the transmission strength of the PS and help guide decisions on design changes that would favor an improved quality of signal. The investigation looked at two specific areas that could potentially influence signal performance: i) human interaction and usage ii) electronic-mechanical design factors. The first part of the investigation looked at how the device performed in the presence of a human body, specifically the way it was positioned with respect to the user as well as the position of the human body with respect to the receiving antenna. In addition, the signal strength was observed when the PS was in the presence of other objects commonly carried along the human body. The remaining part of the experiment concerned itself with the given design of the device, specifically the PCB components and plastic casing. Factors from both the electronic and mechanical domains, such as battery placement, paint presence on housing, and geometry of casing, were varied simultaneously using a Design of Experiment (DOE) approach.
Effect of Microstructural Characteristics of Electroless Nickel Metallisation on Solderability to Pb-Free Solder Alloys
Authors: Liu Changqing , Hutt David A. , Li Dezhi , Conway Paul P.
Published: April 2009

This paper aims to gain an insight into the correlation between the microstructure and surface composition of electroless Ni-P and its behaviour during soldering with Pb free alloys including Sn-3.8Ag-0.7Cu, Sn-3.5Ag and Sn-0.7Cu. Ni-P coatings with different P contents were produced through an industrial process on copper metal substrates. The surface morphology of these coatings was observed by Scanning Electron Microscopy (SEM) and the bulk composition was analyzed by means of Energy Dispersive X-ray analysis (EDX). The mechanical properties of the coatings were evaluated by nano-indentation testing under different maximum loads. However, to understand the behaviour of P in Ni-P coatings and deterioration of the coating surfaces during exposure to air, the surfaces of the coatings were also characterised by X-ray Photoelectron Spectroscopy (XPS) for storage at different temperatures. The dependence of the solderability of Ni-P coatings on the storage time and temperature was investigated by wetting balance testing, using an inactive or active flux with or without an inert N2 atmosphere. Finally, the solderability of Ni-P coatings to Pb free solders is correlated with their composition and microstructure (e.g. surface characteristics).
The Bondabilities of Various Metals Using Ag Metallo-Organic Nanoparticles and These Bonding Mechanisms
Authors: Kobayashi Shinji , Ide Eiichi , Angata Shinji , Hirose Akio , Kobayashi Kojiro F.
Published: April 2009

A novel bonding process using Ag metallo-organic nanoparticles has been proposed. This process is applicable to the alternative to the current high temperature solders, such as Pb-10Sn or Pb-20Sn. In this paper, Al, Ti, Ni, Cu, Ag and Au disc joints were made using the Ag metallo-organic nanoparticles in order to investigate the bondability of the various metals. These joints were evaluated based on the measurement of the shear strength, and the observation of the fracture surfaces and the cross-sectional microstructures. The shear strength of various metal joints increased in the following order: Al, Ti, Ni, Cu, Ag and Au joints. This corresponds to the order of the standard free energy value of the oxide formation for each metal. This result suggests that the carbon atoms generated by the decomposition of the organic shell of the Ag metallo-organic nanoparticles may play a role in deoxidizing the oxide film on the metal surface.
Robust Design of Air-Cooled Server Cabinets for Thermal Efficiency
Authors: Rolander Nathan , Rambo Jeffrey , Joshi Yogendra , Mistree Farrokh
Published: April 2009

Thermal management difficulties in data centers caused by the rapidly increasing power densities of modern computational equipment are compounded by the less frequent upgrading of the facilities themselves, creating a lifecycle mismatch. This paper utilizes the Proper Orthogonal Decompostion (POD) for reduced order modeling of turbulent convection integrated with the compromise Decision Support Problem (DSP) using robust design principles. In the illustrative case study considered thermally efficient cabinet configurations that are insensitive to variations in operating conditions are determined. Results of the application of this approach to an enclosed cabinet example show that the resulting thermally efficient configurations are capable of dissipating up to a 50% greater heat load using the same cooling infrastructure.
Quantum Well Thermoelectric Devices
Authors: Ghamaty S. , Elsner N. B.
Published: April 2009

Fabrication development of high efficiency quantum well (QW) thermoelectric continues with the P-type B4C/B9C and N-type Si/SiGe films. Si/SiC is being developed to replace Si/SiGe for higher temperature operation. Both isothermal and gradient life testing are underway. One couple has achieved 700 hours at TH of 300°C and TC of 50°C with no degradation. Emphasis is now shifting towards couple and module design and fabrication. Preliminary design calculations regarding the development of actual quantum well modules will be presented for both power prediction and cooling applications. These modules can be used in future energy conversion system as well as air conditioning system designs.
Impact of Thermal Sub-Continuum Effects on Electrical Performance of Silicon-on-Insulator Transistors
Authors: Etessam-Yazdani Keivan , Hussin Rozana , Asheghi Mehdi
Published: April 2009

In this manuscript, the impact of scaling on self-heating of silicon-on-insulator (SOI) transistors is investigated. Effect of temperature dependent phonon-boundary scattering in silicon thin films, which results in reduction in thermal conduction in the channel region, is incorporated into a electro-thermal simulation tool. Results of DC electro-thermal simulations are used to study drain current degradation due to self-heating and to obtain the thermal resistance of SOI devices as a function of gate length and silicon layer thickness. The device thermal resistance is increased by nearly a factor of 3 due to the scaling of gate length from 180nm to 10nm. Self-heating in SOI devices with gate length of 10nm can be responsible for up to 30% reduction in the saturation current and neglecting phonon-boundary scattering in the channel region may underestimate the degradation of drain current due to self-heating by nearly a factor of two.
Numerical Model to Analyse IC Chip Encapsulation Process
Authors: Kulkarni Venkatesh M. , Azid Ishak Abdul , Seetharamu K. N. , Aswatha Narayana P. A.
Published: April 2009

In this paper, simulation of the 2D flow of incompressible molten epoxy material in a mold cavity has been carried out. Characteristic Based Split (CBS) was used in its semi-implicit form to analyze the mold filling behavior in underfilling encapsulation process. A two dimensional numerical model was developed and the governing equations were solved by using Characteristic Based Split (CBS) method to get the velocity and pressure fields. The velocity filed was used in pseudo-concentration approach to track the flow front. Pseudo-concentration is based on the Volume of Fluid (VOF) technique and was used to track fluid front for each time step. Simulation has been carried out for a particular geometry of a flip-chip package. The model proposed could provide a means to simulate the underfilling process for flip chip package.
Characterization of Thermal Stress Phenomena Induced Into a Packaged Planar Lightwave Circuit Using Fiber Bragg Grating Sensors
Authors: Grobnic Amelia G. , James Robert , Lu Ping , Mihailov Stephen J.
Published: April 2009

We present a technique for the characterization and analysis of the thermal stress in the optical substrate of packaged photonic devices. This method allows optimization of the package geometry in order to improve the passive compensation of the thermal sensitivity of photonic devices. To the best of our knowledge, we report for the first time the use of strongly chirped, weakly apodized fiber Bragg grating (FBG) sensors to evaluate the stress distribution induced by the package in the planar lightwave circuit (PLC) substrate. We also evaluated the substrate thermal stress using finite element analysis (FEA). We investigated some of the package design parameters that can be used to control and tune the amount of stress that can be applied to the photonic device optical substrate. Our goal is to optimize the design of a package that applies tensile stress to the optical device to compensate unwanted effects due to ambient temperature variation.
Jet Impingement Cooling Using Micro Channels in Low Temperature Cofire Ceramic (LTCC) Substrates
Authors: Jones W. Kinzy , Kappagantula Surya , Zampino Marc
Published: April 2009

With power densities near 200 W/cm2 for devices, new methods for thermal management from the heat generation at the die to heat removal to the ambient must be addressed. Signal interconnect and thermal management are often decoupled, with the I/Os from the substrate to the chip through flip chip solder balls and heat removed through the backside of the chip. However, interconnect substrates could provide both first level interconnect and fluid cooling thermal management. Providing micro channels in the same dimension as the interconnect pitch in the substrate allows for new and novel cooling methods to be integrated at the lowest level of chip assembly. X-Y micro channels less than 2 5 m wide and Z dimension channels 4 5 m wide were fabricated within the LTCC substrate. The integrated micro channels allow for direct jet impingement cooling. Initial thermal testing using single jet impingement demonstrated over a 200X reduction in thermal impedance.
A Characterization Study of Flip Chip Ball Grid Array (FCBGA) Dynamic Response and Performance on Peripheral Component Interconnect (PCI) Board Application
Authors: Wong Shaw Fong , Loh Wei Keat , Lee Yung Hsiang , Yap Eng Hooi , Wong Siang Woen , Hin Tze Yang
Published: April 2009

This paper outlines and discusses the new mechanical characterization metrology applied on PCI board. The dynamic responses of PCI board were monitored and characterized using accelerometers and strain gauges. PCI board bend modes were analyzed to differentiate high risk areas through analysis of board strain responses to solder joint crack performance. Key influences, such as thermal/mechanical enabling preload masses and profiled shock on solder joint crack severity were also conducted to understand the potential SJR performance risk modulators. Commercial simulation software analysis tool was applied to correlate and predict the board’s bend modes; providing key information for product enabling solutions design. With this new characterization and validation concept, a practical stiffener solution for PCI application was designed to improve board SJR performance in its application condition.
Solder Joint Reliability Challenges in Sub 1.00 mm Ball Pitch for Flip Chip Ball Grid Array
Authors: Beh Keh Shin , Loh Wei Keat , Leong Jenn Seong , Tan Wooi Aun
Published: April 2009

FCBGA is an electronic package used to achieve a high Inputs/Outputs (I/Os). To continue to achieve a higher I/O count without increasing package size, ball pitch reduction is inevitable. However, ball pitch reduction using smaller ball size has posed substantial challenges to solder joint reliability (SJR). On top of that, rising power dissipation requirement in FCBGA package has created a need for high performance heat sinks. These heat sinks require significant compression loading to ensure good thermal conductance of thermal interface materials. The impact of these loads on SJR has typically not been considered in thermal cycle stressing. Hence, this paper focuses on different types of heat sinks and their compressive load effect on solder joint thermal fatigue performance. It also covers package size and board thickness effect when heat sink compressive load is taken into account during thermal stressing. Lastly, lead free and eutectic solders at sub 1.00mm ball pitch technology were also evaluated.
Using High Speed Camera for Electronic Board Failure Analysis
Authors: Hezeltine Wade , Liang Frank Z.
Published: April 2009

Historically, the most common failure analyses metrologies have been dye-and-pull, cross-sections, microscopy, optical and SEM. Using these traditional metrologies to find a root cause from a dynamic event can be very time consuming and sometimes inconclusive. The standard methodology is to work backward to reconstruct the “event” that caused or initiated failure. Often times the root cause is not immediately obvious and design improvements require an iterative process to identify the true root cause. This approach is costly in time, materials and resources. A high speed camera (HSC) allows identification of failure from a point of initiation. Using the point of initiation concept with reconstructive modeling allows a design team to discover potential initiating sources and better match a cause to the effect and implement corrective action. This decreases development time, minimizing product design cycle and increases market opportunities.
Transient Mixed-Convection With Applications to Cooling of Biomaterials
Authors: Shrivastava Saurabh , Sammakia Bahgat
Published: April 2009

2-Dimensional transient mixed-convection in a horizontal rectangular enclosed cavity heated from a lower solid block is numerically studied. The enclosure simulates the thermal reservoir for the storage and shipment of biomaterials. The lower solid block containing the thermal biomass that has adiabatic sides and bottom wall, is coupled along the top wall with a hollow cavity of aspect ratio (H/L = 0.5), whose side and top walls are assumed to be surrounded by a phase change material and has been assigned constant temperature of 273K. Initially, the temperature of the biomaterials is raised to 283K; the upper cavity is filled with quiescent air and uniform temperature at time zero. Laminar airflow is assumed with a fan in middle of the cavity. The basic characteristics and flow structures during the transition of natural-convection-dominated flow to forced-convection-dominated flow are determined. The problem is solved for the range of mixed-convection regime and the fluid flow structure and heat transfer is found to be dependent on mixed-convection as determined by the buoyancy parameter Gr/Re2. As anticipated, the forced-convection-dominated flow is found to be more effective in cooling of the thermal biomass than the natural-convection-dominated flow. This study shows that using the assisted forced convection results in an increase in the cooling performance of the biomaterial container in the natural-convection-dominated type mixed-convection flow. Examining the area averaged Surface Nusselt number along the coupled wall with time and the rate of heat transfer from the thermal biomass during the Quasi-steady stage validates the above hypothesis.
Structural Analysis of Microelectronic and Photonic Systems
Authors: Suhir E.
Published: April 2009

We examine some basic attributes of, and challenges in, modeling of the mechanical behavior of materials and structures in microelectronics and photonics (mainly fiber optic). The emphasis is on the role that methods and approaches of Structural Analysis should play (and, in effect, have played) in the design, manufacturing, testing and operation of micro- and opto-electronics assemblies, packages and systems. The objectives, merits and shortcomings of Structural Analysis (analytical modeling) are addressed, as well as the interaction between the analytical (“mathematical”) and numerical (mostly, FEA) modeling. We discuss also the interaction of the theoretical and experimental approaches, which should complement each other, when there is a need to design, build and operate a viable and reliable micro- or opto-electronic system. The review is based primarily on author’s work carried out during his tenure with Ball Laboratories, Physical Sciences and Engineering Research Division, and is a revised, updated and expanded version of an invited lecture presented several years ago at the RPI. It is carried out in connection with the author’s 2004 ASME award (Worcester Warner Reed Medal) “for outstanding contributions to the permanent literature of engineering through a series of papers in Mechanical, Microelectronic, and Optoelectronic Engineering, which established a new discipline known as the Structural Analysis of Microelectronic and Photonic Systems”.
Bond Line Thickness of Thermal Interface Materials With Carbon Nanotubes
Authors: Singaravelu Senthil A. G. , Hu Xuejiao , Goodson Kenneth E.
Published: April 2009

Increasing power dissipation in today’s microprocessors demands thermal interface materials (TIMs) with lower thermal resistances. The TIM thermal resistance depends on the TIM thermal conductivity and the bond line thickness (BLT). Carbon Nanotubes (CNTs) have been proposed to improve the TIM thermal conductivity. However, the rheological properties of TIMs with CNT inclusions are not well understood. In this paper, the transient behavior of the BLT of the TIMs with CNT inclusions has been measured under controlled attachment pressures. The experimental results show that the impact of CNT inclusions on the BLT at low volume fractions (up to 2 vol%) is small; however, higher volume fraction of CNT inclusions (5 vol%) can cause huge increase in TIM thickness. Although thermal conductivities are higher for higher CNT fractions, a minimum TIM resistance exists at some optimum CNT fraction for a given attachment pressure.
Mechanical Shock FE Modeling for ATCA Circuit Board Design
Authors: Liang Frank Z. , Palanuk Larry M. , Hezeltine Wade
Published: April 2009

ATCA is a new form factor for communication equipment applications. Finite element model (FEM) was created to predict the dynamic response of an ATCA design during a table drop shock. The model was built with 2nd order brick elements for minimizing the meshing sensitivity. Modal method was used and followed by dynamic transient analysis with superposition approach and validated by comparing the modal test data for matching the natural frequencies and the modal shapes. The model was further validated by comparing the board displacement with direct displacement measurement using a high speed camera. As a result the localized board strain predictions matched the measured board strain at each networking processor unit. The validated model was used to predict the risk areas for solder joints, which later proved to be accurate during board design verification tests. This paper presents the modeling and model validation processes, as well as the ATCA mechanical design evaluations.
Loading Rate Effect Investigation of Through-Hole-Mounted Solder Joints
Authors: Liang Frank Z. , Palanuk Larry M. , Gabriel Mike
Published: April 2009

This paper presents two simple and unique tests to extract shock-level loading limits for eutectic and lead free solders. A wide range of loading rates, from quasi-static to high speed, was applied to a through-hole-mounted anchor assembly test coupon. The high speed shock tests were conducted on a drop shock table where the impacting velocities were derived through table input adjustments. The quasi-static tests were done using controlled hydraulic linear actuator with a load cell. As would be assumed, the dynamic load to cause solder joint failure was found to increase with higher loading rate. However, at such a high loading rate range, the impact velocity did not change the load to failure. This study leads to an interesting hypothesis that at high loading rates, the solder joint strain rate may not see a significant change as observed at low rates.
The Maisotsenko Cycle for Electronics Cooling
Authors: Maisotsenko Valeriy , Reyzin Ilya
Published: April 2009

The Maisotsenko Cycle (M-Cycle) combines heat exchange and evaporative cooling [1–3] in an effective indirect evaporative cooling process resulting in product flow temperature approaching incoming air dew point (not wet bulb) temperature. Thermodynamically, the M-Cycle is based on air precooling before passing through the heat rejection water evaporating area, so the difference between the enthalpy of the air at its dew point temperature and the same air saturated at a higher temperature is used to provide cooling capacity to reject the heat, for example from the electronics. Today Delphi Corp and Coolerado Inc. are working on producing M-Cycle based heat- and mass exchangers for the Coolerado Coolers™ used in air conditioning. Other market applications, including electronics cooling, are being considered as well. A broad range of the cooling capacity (for example, from 10 W to 50 kW and more) could be obtained from the coolers utilizing M-Cycle. Due to superior thermodynamic process, M-Cycle based air coolers have a very high Energy Efficiency Ratio (EER). As per National Renewable Energy Laboratory (NREL), the average cooling capacity of Coolerado Coolers™ have EER more than 45; relatively to EER equal 13 for the best conventional air coolers. The M-cycle is much more efficient than any other heat rejection/recovery cycle, and the Coolerado Cooler™, as a single air cooling device has better specific characteristics (cooling capacity, air pressure drop, power consumption, etc.) than any existing coolers. Unlike traditional vapor compression, absorption, or thermoelectric refrigeration systems, where increase of air inlet temperature dramatically reduces cooling capacity, the M-Cycle based unit cooling capacity goes up with air inlet temperature rise. M-cycle based device similar to Coolerado Cooler™ can also cool any fluid to the temperature approaching the dew point temperature of incoming air without using compressor and refrigerant. That can revolutionize the electronics cooling market. The Coolerado Cooler was recognized by the prestigious R&D 100 Awards program as one of 2004’s most technologically significant products introduced to the world.
Revolution in Fan Heat Sink Cooling Technology to Extend and Maximize Air Cooling for High Performance Processors in Laptop / Desktop / Server Application
Authors: Mochizuki Masataka , Saito Yuji , Nguyen Thang , Wuttijumnong Vijit , Wu Xiaoping , Nguyen Tien
Published: April 2009

The trend of the processor performance and heat dissipation have been increased significantly every year. In the year 2000, the clock speed of processors used in Personal Computers (PC) was approximately 1GHz and heat dissipation approximately 20 W, but in the year 2004 the processor’s clock speed is higher than 3 GHz and the heat dissipation is approaching 100 W. Heat dissipation has increased but in contrast the size of die on the processor has reduced or remained the same size and thus the heat flux is critically high. The heat flux is about 10–15 W/cm2 in the year 2000 and could reach 100 W/cm2 in 2005. The purpose of this paper is to provide an overview of practical various cooling solutions including the use of heat pipes and vapor chambers for cooling high power processors in a confined space of PCs. This paper discusses how to extend the air cooling capability and maximize its performance. Included in this paper are the design, data, photos and discussion of various fan sink air cooling designs showing how the design changes can push the limit of the air cooling capability.
Piezoelectric Actuators for Low-Form-Factor Electronics Cooling
Authors: Ac¸ıkalın Tolga , Sauciuc Ioan , Garimella Suresh V.
Published: April 2009

The cooling performance of piezoelectric actuators is evaluated for low-form-factor electronics in this work. A piezoelectric actuator is a cantilever made from metal or plastic with a piezoelectric material bonded to it. Under an alternating electrical current, the piezo actuator oscillates back and forth, generating airflow. Compared to conventional fans, these actuators have the advantages of low power consumption, low noise, and smaller dimensions. The parameters investigated in the experiments are actuator orientation, actuator-to-heat source distance, and actuator amplitude. For an actuator power consumption of 31 mW, the heat source temperature was lowered by more than 25°C compared to natural convection conditions (for a 2.45 W heater power dissipation). Performance comparisons against axial fans and natural convection heat sinks show that the piezo actuators perform significantly better in terms of power consumption and cooling volume.   This paper was also originally published as part of the Proceedings of the ASME 2005 Heat Transfer Summer Conference.
Assessing Capabilities and Limitations of Air- and Liquid-Cooling for Low Profile Servers
Authors: Chan Albert , Wei Jie
Published: April 2009

As microprocessor power exceeds 100W, adequate heat removal by convective air-flow through a heatsink increasingly becomes more challenging. This is especially true for low-profile servers with very limited volume for air-flow. It is therefore useful to have an idea of the limitations of air-cooling for such servers. In this paper, three case studies serve to illustrate the capability of typical air-cooled solutions for low-profile servers. These studies show the inherent limitations of air-cooled solutions for volume-constrained computer systems. Liquid-cooling has been used in cooling mainframe processors packaged in MCM format. Its use in low-cost servers is extremely limited. This paper will deal with issues that hinder widespread application of liquid-cooling in commercial servers. The most important issue is cost, followed by lack of commodity components suitable for liquid-cooled systems. One method to reduce cost is to use fabricate the cold plate using heatsink manufacturing techniques. Case studies are presented to show liquid-cooling with these lower cost cold plates can provide performance that exceeds air-cooling solutions. Finally, suggestions are offered for facilitating the introduction of liquid-cooling systems for future low-profile servers.   This paper was also originally published as part of the Proceedings of the ASME 2005 Heat Transfer Summer Conference.
Damage Path Simulation of Solder Joints in QFP
Authors: Mukai Minoru , Hirohata Kenji , Takahashi Hiroyuki , Kawakami Takashi , Takahashi Kuniaki
Published: April 2009

Fatigue life prediction of solder joints is one of the most important areas of research in the development of reliable electronic packages. Recent trends in electronic package development indicate a shift toward smaller solder joints and larger package sizes, and temperature changes under field conditions are also becoming greater. Since reliability design of solder joints has become severer, the estimation of the crack propagation is becoming important like the estimation of the crack initiation. In the present study, a new method of estimating the crack propagation, which is based on finite element analysis without geometrical crack model, was examined, in order to ensure suitability for practical use in electronic package design. On the basis of a damage model assumed for Sn-37Pb solder, the new method called ‘damage path simulation’ was verified for solder joints in QFP (Quad Flat Package). In the case of solder joints of the gull-wing type, fatigue cracks are commonly initiated from the upper surface of the solder fillet, and propagated in the vicinity of the interface with the outer lead. It was clear that the extension of the damage path showed good agreement with the behavior of crack propagation observed in the actual thermal cycle tests. Damage path extension from a pointed end of outer lead is also simulated simultaneously with that from the upper surface of the solder fillet, and both damage paths were finally combined at a gap between outer lead and printed circuit board. The advantage of the present method is especially evident when the fatigue cracks were initiated from two or more regions. From the results of this study, it was concluded that the estimation of the crack propagation in solder joints based on the present method is satisfactory for engineering purposes.
Wafer-Level Packaging Technology With Through-Hole Interconnections in Silicon Substrate
Authors: Yamamoto Satoshi , Saruta Masanobu , Wada Hideyuki , Tomita Michikazu , Suemasu Tatsuo
Published: April 2009

An advanced packaging technology with through-hole interconnections, which enables miniaturization and high-density packaging of electronic devices including MEMS devices and optical devices, has been developed. In this work, through-hole interconnections were applied to an image sensor packaging. Through-holes, 80μm in diameter and 200μm in depth, were formed from backside of the device wafer by Deep Reactive Ion Etching (DRIE). After an insulation layer was formed inside the holes, conductive material such as copper (Cu) or Gold-Tin (Au-Sn) alloy solder was filled into the holes by electroplating method or Molten Metal Suction Method (MMSM). This technology enables wafer-level packaging of the image sensor device. Some electrical characteristics and reliability performances including electric resistance, breakdown voltage, high-temperature storage test, heat cycle test, temperature-humidity test were examined. In this paper, fabrication processes, structural and electrical characteristics and reliability of the package will be reported.