bluuebunny/crossref_metadata_2025 huggingface dataset:
Spectral-Directional Emittance of High Temperature Oxidized Aluminum
Authors: Teodorescu George , Jones Peter D. , Overfelt Ruel A. , Guo Baojian
Published: April 2009

Spectral-directional emittance measurements for high purity aluminum, oxidized in air for an extended period of time (150h) at high temperature are presented. The data presented here cover the spectral range between 3 and 14 μm, directional range from surface normal to 72° polar angle and temperatures from 400 to 600°C with a step increment of 100°C. The measurements were performed using a radiometric, direct emission method. The experimental setup used was comprised of a Fourier transform infrared spectrometer and a blackbody cavity. The Al sample has a nominal surface roughness of 0.635 μm. Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) were used as surface techniques to characterize the aluminum oxide film that formed on the metallic surface.
Use of Printed Circuit Board as Electrode in EHD-Enhanced Condensation Experiments for a Shell/Tube Bundle Heat Exchanger
Authors: Wu J. , Ohadi M. M. , Dessiatoun S. , Qi J.
Published: April 2009

Electro-hydrodynamic (EHD) enhancement of external condensation of refrigerant R-134a for a twenty-four tube bundle heat exchanger was studied experimentally. The tubes used in the bundle were state of the art enhanced tubes provided by a heat transfer tube manufacturer. Printed circuit board was used as the electrode and it was inserted between the tube columns to reduce the bundle effect. Different heat flux levels were tested, ranging from 10 to 20 kW/m2. The saturation temperature was 30°C and the applied electric field voltage ranged from 0 to 20 kV. The obtained test results indicated that PCB electrode worked effectively as the electrode in the tube bundle test and up to 31% enhancement was achieved. Comparison with single tube test showed that bundle was reduced to a satisfactory level.
Heat Transfer and Pressure Drop Experimental Correlations for Air-Water Bubbly Flow
Authors: Cui Wenzhi , Li Longjian , Chen Qinghua , Liao Quan , Jen Tien-Chien
Published: April 2009

In this work a uniquely designed air-water bubbly flow heat transfer experiment is accomplished to investigate the characteristics of pressure drop of airflow and heat transfer between water and tubes for its potential application in evaporative cooling. The attempts to reduce the pressure drop at the condition of maintaining higher heat transfer coefficient have been done by decreasing the bubble layer thickness though the water pump circulation. Pressure drops of air passing through the sieve plate and the bubbling layer are measured for different heights of bubble layer, hole area ratio of the sieve plate and the air velocity through the holes. Experimental data show that the increase of bubble layer height and air velocity both make the pressure drop larger while the effect of the hole area ratio of the sieve plate is relatively sophisticated. A correlation including the effects of all the tested parameters is proposed, which has a mean absolute deviation of 14.5% to that of the experimental data. Heat transfer coefficients of the water and the outside tube wall are measured and the effect of heating flux is also considered. The results show that even at a considerably lower height of bubbling layer the heat transfer coefficient can exceed 5 kW/m2-K. A heat transfer coefficient correlation with a mean absolute deviation of 9.7% is developed based on the experimental data.
Computational Insights Into Air-Side Flow and Heat Transfer in Compact Heat Exchangers
Authors: Tafti D. K.
Published: April 2009

The paper describes two- and three-dimensional computer simulations which are used to study fundamental flow and thermal phenomena in multilouvered fins used for air-side heat transfer enhancement in compact heat exchangers. Results pertaining to flow transition, thermal wake interference, and fintube junction effects are presented. It is shown that a Reynolds number based on flow path rather than louver pitch is more appropriate in defining the onset of transition, and characteristic frequencies in the louver bank scale better with a global length scale such as fin pitch than with louver pitch or thickness. With the aid of computer experiments, the effect of thermal wakes is quantified on the heat capacity of the fin as well as the heat transfer coefficient, and it is established that experiments which neglect accounting for thermal wakes can introduce large errors in the measurement of heat transfer coefficients. Further, it is shown that the geometry of the louver in the vicinity of the tube surface has a large effect on tube heat transfer and can have a substantial impact on the overall heat capacity.
Measurement of Local Convective Heat Transfer Coefficients With Temperature Oscillation IR Thermography and Radiant Heating
Authors: Freund S. , Kabelac S.
Published: April 2009

A method using temperature oscillations to measure local convection coefficients from the outside of a heat-transferring wall has been developed. This method is contact-free, employing radiant heating with a laser and an IR camera for surface temperature measurements. The numerical model extends previous research to three dimensions and allows for rapid evaluation of the convection coefficients distribution of sizable heat exchanger areas. The technique relies first on experimental data of the phase-lag of the surface temperature response to periodic heating, and second on a numerical model of the heat-transferring wall that computes the local convection coefficients from the processed data. The temperature data processing includes an algorithm for temperature drift compensation and Single Frequency Discrete Fourier Transformations. The inverse heat conduction problem of deriving a surface map of convection coefficients from the phase-lag data is solved with a new numerical approach based on a complex 3-D finite-difference method. To validate the experimental approach, measurements of the temperature response of a semi-infinite specimen were analyzed. The results obtained were within 1.6% agreement with the analytical solution. The numerical model was verified by comparison with data generated by the FEM program ANSYS. The results of preliminary experiments investigating the local Nusselt number of water entering a tube are in agreement with established correlations. Future applications of this method will involve an aerodynamic vortex generator in a wind tunnel and plate heat exchangers. Another possible application of the experimental method is non-destructive testing of materials known as Lock-In Thermography.
Heat Transfer and Bubble Movement of Double- and Single-Side Heating Subcooled Flow Boiling in Narrow Channels
Authors: Pan Liang-Ming , He Chuan , Xin Ming-Dao , Jen Tien-Chien , Chen Qinghua
Published: April 2009

Compared with conventional channels, narrow and micro channels have significant heat transfer enhancement characteristic. With smooth internal surface, such channels can efficiently avoid encrustation at the washing of the high-speed liquid. Moreover, heat transfer elements can be easily assembled. These types of channels have been adopted extensively in many engineering applications, e.g. microelectronic cooling, advanced nuclear reactor, cryogenic, aviation and space technology and thermal engineering. Geometrical size of flow passage-away affects heat exchange of flow boiling, with the result that the bubble in narrow channel acts very different from those in non-narrow channel. This paper experimentally compared the bubble behavior with different heating methods of narrow rectangular channels, and the bubble behavior of subcooled flow boiling of R-12 in the narrow channels both with double side and single heating. Experimental settings are: the heating length of test-section is 400 mm, the cross-section is 35 mm in width and 2mm in gap size, mass flux is 700∼1500 kg.m−2.s−1, the heat flux is 25∼70kW.m−2 and the pressure is 1.3∼2.0 MPa. Comparisons were made on Onset of Nucleate Boiling (ONB) point and bubble characters with various flow patterns. Results revealed that the characteristics of double and single side heating shown good agreement with proper modifications.
Development and Application of Mechanical and Reliability Models for Connectors and Sockets
Authors: Iannuzzelli Raymond J. , Seyyedi Javad A. , Callahan Daniel L.
Published: April 2009

Designing a modern server today requires considerable attention to interconnect details. Connectors & sockets represent a class of interconnect that find abundant use in most computers. Due to their continual evolution toward smaller footprints, tighter pitch, shorter paths, and better electrical performance, connectors and sockets are at the technological forefront in computer packaging. The challenges in designing, understanding, and applying connectors & sockets can be addressed through the application of advanced modeling techniques. This paper will address the development and application of mechanical models for a Rambus In-line Memory Module (RIMM®) connector and a Land Grid Array (LGA) interposer socket. Common issues of material properties, appropriate boundary conditions, and loads will be addressed. The models are applied to show the importance in understanding: connector design, friction, load-unload hystereses, and non-linear contacting.
The Performance of Small Heat Sinks for LSI Packages in Combined Natural and Forced Convection Air Flows
Authors: Ishizuka Masaru , Nakagawa Shinji , Honma Toru
Published: April 2009

Cooling performances of small finned heat sinks were investigated in combined natural and forced air convection environment, and the way to use the data in designing a heat sink on a LSI package is explored. An experimental study was performed providing natural and forced air convection over the heat sink. Several heat sinks having different base areas, fin spacing and heights were tested. The test heat sink was heated up by an electrical heater to produce a specific heat flux on its base. The increase in fin temperature was measured by small thermocouples. In natural convection experiments, the effect of the supplied wattage on the temperature rise of the heat sink was examined. In forced convection experiments, a wind tunnel was used. The hear sink was set near the downstream end of the wind tunnel and a specific heat flux was applied to it. A correlation between the air velocity and the temperature rise of the heat sinks was developed. Furthermore, the results are reduced to non-dimensional expressions to facilitate the design of small heat sinks.
Dynamic and Thermal Elastic Problems for STM Flatpack Hardware
Authors: Cutting Fred
Published: April 2009

A common problem with SMT flatpack components relates to the package resonant frequencies being within the dynamic range of the random vibration Power Spectral Density (PSD). The body of the package provides both the mass and the rotational inertia while the leads, as a group, provide the linear and torsional springs to create several mass-spring resonances with the associated natural frequencies. Please note that the quad SMTs have higher resonances because the leads at the “ends” provide sufficient stiffness to drive the rotational and linear modes above our PSD limiting frequency usually at 2 kHz. As packages become large and heavier with smaller leads due to finer pitch, it is possible the quad flatpacks could present a similar problem in the future. However heat dissipation design from these larger packages may change structural considerations for the better.
Heat Transport Characteristics of the Capillary Pumped Loop for Cooling the Tower-Type Computer
Authors: Tsujimori Atsushi , Kato Masashi , Morita Hajime , Uchida Maiko
Published: April 2009

In this study the capillary pumped loop was manufactured as a cooling device for the tower-type personal computer and the heat transport characteristics of this cooling device was investigated. The experimental equipment consisted of the evaporator, the condenser, the liquid tube, the vapor tube and the reservoir. The length and the diameter of the evaporator were 150mm and 27mm respectively and had capillary wick in it with equivalent diameter of 5μm. In the experiment, the heat flux to the evaporator and the cooling water temperature were changed. And the effects of enclosed quantity of the working fluid (R134a) in the reservoir and the evaporator height above the condenser on heat transport rate were also investigated. Experimental results shown that this capillary pumped loop was able to transport heat rate of 15 to 95W (heat flux of 995 to 6051 W/m2) with highest temperature of 343K and that the temperature difference in the loop was 16.7 to 43.9 K in the case of 2500mm in its heat transport length and cooling temperature of 293K. And it was derived that the working fluid enclosed rate affected the maximum heat transport rate. The computer code was also developed to evaluate the effect of the refrigerant enclosed rate and the wick thickness on the heat transport rate considering the pressure drop to the circumference direction in the wick.
Characterization of Electrical Failure Modes in Chip-on-Board Assemblies for Extreme Temperature Environments
Authors: Schatzel Donald V. , Shapiro Andrew A.
Published: April 2009

Future space missions to Mars and the outer planets will have to operate on the planet surface in temperatures that range from −200°C to 40°C. These missions will require sensors, instruments and motors to operate for extended periods that exceed the duration of any planetary surface mission to date. Currently the Mars Science Laboratory rovers planned for 2009 will be required to survive a mission life of about 500 Martian sols. The Martian solar day is called a sol and is equal to 24 hours and 39 minutes of an Earth day. This extended mission requirement is beyond the reliability threshold of present electronic materials and interfaces such as those used on the Mars Exploration Rovers. The combination of correct materials, electrical interconnection and packaging design are critical to ensuring long life when the range between minimum and maximum temperatures approach or exceed 200°C. The Jet Propulsion Laboratory as part of the Mars Technology program is performing a series of designed experiments to determine the best electronic packaging materials that would survive 500 Martian sols in the temperature range of −120°C to 85°C. This technology development is part of the preparation effort to design and build survivable electronics for the Mars Science Laboratory rovers and related future outer planet missions. This technology development program is called Temperature Cycle Resistant Electronics (TCRE) and is a 3 year design for electrical interface reliability activity. The experiment team assembled 27 different types of test vehicles which are the result of a full factorial designed experiment. There were 10 samples of each type assembled for statistical confidence to yield a total of 270 test vehicles. The basic test vehicle design consists of silicon die mounted to a substrate with gold wire bond electrical interconnects. Continuous electrical paths were designed into the substrate and the dice. The basic experiment consists of assembling three different types of substrates, three different types of die attach materials and three different types of over coat material. The test vehicles were subjected to 1500 thermal cycles (three times required mission life) from −120°C to 85°C over nine months. Open electrical circuits were observed over time due to material interactions over this temperature range that created electrical failures. This paper summarizes the failure results and identifies the material sets that survived this phase of the experiment for 1500 extreme temperature cycles.
Assessments of Single-Phase Liquid Cooling Enhancement Techniques for Microelectronic Systems
Authors: Zhang H. Y. , Pinjala D. , Iyer M. K. , Nagarajan R. , Joshi Y. K. , Wong T. N. , Toh K. C.
Published: April 2009

In this paper, quantitative assessments of single-phase liquid cooled heat sinks based on three types of enhancement microstructures are presented for microelectronics applications. The first type is a metallic microchannel heat sink (MMCHS) made of aluminum with the channel dimensions of 15 mm (L) × 0.2 mm (W) × 2 mm (H). The second type are two silicon microchannel heat sinks (SMCHS) made through the deep reactive ion etching (DRIE) technique, with identical channel height of 0.45mm and average channel widths of 66.6 μm and 46.6μm, respectively. Metallic foam heat sinks (MFHSs) are the third type, which were formed by brazing porous foam materials of high pore density and enlarged surface area onto a copper base plate. All the three types of heat sinks were fabricated and experimentally characterized incorporating electronic packages. Characterization results indicate that the MMCHS and MFHSs can achieve equivalent thermal performance above 100 W/cm2 and the silicon MCHS above 200 W/cm2 at the expense of larger pressure drop. A comparison of the pressure drops, thermal enhancement and manufacturability of the three types of heat sinks is also presented.
Solder Joint Reliability Improvement Using the Cold Ball Pull Metrology
Authors: Raiser George F. , Amir Dudi
Published: April 2009

The various methods for improvement of package solder joint reliability (SJR) have centered on the broad categories of (i) reductions in the thermomechanical and mechanical stresses and strains applied to the joints, and (ii) strengthening of the solder interconnect interfaces and materials themselves. In practice, the success of the former depends first and foremost on the latter — an adequate and consistent interconnect ‘strength’ during the package development and production cycles. With the advancement of various pad-plating technologies (most notably ENIG – Electroless Nickel Immersion Gold), sphere chemistries, fluxes and processing conditions, each with their own stability issues, the interconnect strengths can easily undergo seemingly random drifts over time. The Dage™ Cold Ball Pull (CBP) technique, however, has emerged as an attractive alternative to the traditional ball-shear metrology as an interconnect strength monitor. The open issues preventing its adoption are related to identifying the best test conditions (e.g. aging time, pull speed, jaw pressure, etc...), all of which are addressed here. After identifying the best test conditions, we present a number of experimental results that highlight the powerful capability of this tool for optimizing and monitoring solder-joint strength. A full metrology characterization to demonstrate accuracy, repeatability and reproducibility has been performed. Moreover, interesting results have been obtained with respect to solder-aging, multiple-reflow, and time-above-liquidus effects on interconnect strength. Examples of direct correlation between CBP measurements and solder-joint shock performance are demonstrated. CBP is also shown to correlate well to other strength metrologies, such as three-point bend. Finally, CBP is used here to show how to strengthen interconnects by the proper selection of pad plating chemistries, sphere compositions, fluxes, reflow conditions, etc… Maintaining those strengths through development and production can be handled effectively using CBP as a monitor. Looking forward, CBP data presented here shows that certain material and processing choices can maximize lead-free solder interconnect strength and lead-free solder joint reliability.
Shadow Moire´ Evaluation of Motherboard Warpage Under Preload CPU Thermal Solutions
Authors: Geng Phil , Martinson Robert R. , Williams Richard L. , Mello Michael , Cho Steve
Published: April 2009

This work investigated the motherboard coplanarity and preload correlation using the shadow moire´ interferometry. Motherboards under three different preloads in the CPU area were examined at room temperature and elevated temperature. Both the global board warpage and the local board warpage around the CPU area were measured for preload and temperature correlations. The measured board coplanarity was correlated to the board preload successfully. The results clearly identified a failure mode from the outlier, which has totally different warpage shape and corresponds to the uneven preload case. Also, the creep effect under preload during heating stage was observed and quantified.
Forced Air Cooling With Synthetic Jet Ejectors
Authors: Mahalingam Raghav , Glezer Ari
Published: April 2009

This paper discusses the concept of synthetic jet ejectors for forced air cooling and some practical implementations of the same. Synthetic or “zero-mass-flux” jets, unlike conventional jets, require no mass addition to the system, and thus provide means of efficiently directing airflow across a heated surface. Because these jets are zero net mass flux in nature and are comprised entirely of the ambient fluid, they can be conveniently integrated with the surfaces that require cooling without the need for complex plumbing. A synthetic jet ejector mechanism for obtaining high heat transfer rates at low flow rates is discussed. Synthetic jet ejectors consist of a primary “zero-mass-flux” unsteady jet driving a secondary airflow through a channel. Several practical implementations of synthetic jets are introduced from low form factor, low power spot cooling applications to high heat dissipation applications and flow bypass control where synthetic jets are used to enhance fan performance.
Cooling of Notebook PCs by Flexible Oscillating Heat Pipes
Authors: Miyazaki Yoshiro
Published: April 2009

An oscillating heat pipe consists of a micro channel which turns many times between the heating section and the cooling section. Herein, a developmental study on flexible oscillating heat pipes for cooling notebook personal computers is presented. The heat pipe functions to transport heat from the CPU to the rear surface of the folding display, which serves as a radiating surface. The heat pipe tubes at the hinge are flexible so that the heat pipe may fold. In order to evaluate the thermal performance of the cooling system, flexible oscillating heat pipes were fabricated and tested. The heat pipes consist of copper capillary tubes and Teflon flexible tubes. Excellent thermal performance was obtained in the test: the thermal resistance was 0.3 K/W and the maximum heat transport capability was 100 W.
Plastic Strain Based Criterion for Reliability Assessment of CSP Packages Subjected to Dynamic Shock Loads
Authors: Zhu Liping , Williams Rick
Published: April 2009

Drop impact induced crack in ball grid array (BGA) solder joint is one of the most dominant failure modes found in BGA package under mechanical load. The failure in BGA due to its excess stress resulting from over bended deformation in a PCB board during shock event is not only a function of solder material but a board and package structure as well. Due to extremely difficult and infeasible in directly measuring responses in BGA solder joint during drop shock event, computer modeling approach has been increasingly played an important role in evaluating product reliability performance during product development. Modeling technique with a comprehensive failure criterion and metric including high strain rate effect is necessary to be developed to quantitatively evaluate and benchmark BGA package reliability performance for different board designs. In this paper, dynamic responses in CSP/BGA in different boards and product phone have been characterized by using nonlinear dynamic finite element software, LS-Dyna. Different failure criteria, such as plastic strain and stress based are investigated and compared. It is shown that a good correlation between validation test and numerical result can be achieved by using proposed plastic strain based criterion only and thus it can be used in cross comparisons between different board designs.
Acoustic Microscopy for Micro Electrical Interconnections
Authors: Tohmyoh Hironori , Akaogi Tsuyoshi , Saka Masumi
Published: April 2009

This paper describes on acoustic microscopy for evaluation of micro electrical interconnection. We visualize the joint interface between silicon chip and the printed circuit board by means of acoustic microscopy, and show the limitation in the evaluation of the electrical interconnection by acoustical manner. Also we design the optimum dry-coupling ultrasonic transmission system, and visualize the joint interface under a dry condition.
Simulation of Warpage Considering Both Thermal and Cure Induced Shrinkage During Molding in IC Packaging
Authors: Teng Shiang-Yu , Hwang Sheng-Jye
Published: April 2009

Warpage is an important issue for IC packages after molding. Due to laminated structure of IC packages, significant warpage occurs owing to differences in shrinkage among constituent materials. Thermal shrinkage is usually considered as the main cause for IC warpage. However, cure induced warpage is also important during the molding process. Analysis without considering cure induced shrinkage can not predict the amount of warpage well. In this paper, TSOP LOC54L package product, which is manufactured by ChipMos Corporation, is used as the simulation model. The P-V-T-C (Pressure, Volume, Temperature, and Conversion) relation and CTE (Coefficients of Thermal Expansion) of an encapsulation material are used to predict the amount of warpage and experimentally verifying the results in this study. By comparing the simulations with the experiments, the preliminary results of the study indicate this approach is capable of estimating warpage in IC packages without prohibitive computational effort.
Effect of Solder Composition and Substrate Surface Finish on Board Level Drop Test Reliability
Authors: Jiang Don-Son , Hung Joe , Wang Yu-Po , Hsiao C. S.
Published: April 2009

For handheld or portable telecommunication devices such as mobile phone, PDA, etc., board level joint reliability during drop impact is a great concern to simulate mishandling during usage. In general, solder composition and substrate surface finish would principally determine the solder joint reliability. Board level drop test reliability of two solder compositions (SnPb and lead free SnAgCu) and surface finishes (Ni/Au and OSP) were examined in this study. The result indicated SnAgCu lead free solder showed poorer reliability life than Sn-Pb solder during drop impact. The crack path in SnPb solder joint almost went through bulk solder near substrate side. However, another IMC/Ni interfacial failure mode near substrate side was found in SnAgCu solder to cause lower reliability. This difference could attribute to higher strength of SnAgCu solder and deformation with higher strain rate in drop test. Comparison between two surface finishes indicated Ni/Au is better than OSP in both SnPb and SnAgCu lead free solder joints. In SnAgCu lead free solder joint with OSP, there are thicker Cu6Sn5 IMC and many large Ag3Sn IMC plates in interface to degrade the interfacial bonding, so drop impact would easily cause the all cracks through IMC/Cu interface and then reduce the reliability.
Polyimide Multi-Layer Substrate for High-Density Semiconductor Package
Authors: Takenaka Shoichi , Ito Shoji , Kishihara Ryoichi , Okamoto Masahiro , Nakao Osamu
Published: April 2009

We have developed a polyimide multi-layer substrate for semiconductor package. Interstitial via holes filled with conductive paste make the electrical connection in any layers in the multi-layer substrate to realize high-density wiring. The substrate shows reliable resistance to moisture and heat. Use of polyimide film make the substrate considerable thin compared to the conventional method using glass-epoxy. The present multi-layer substrate can be applied to a promising interposer for high-density semiconductor such as multi-chip module and stacked chip.
Efficient Cooling of Multiple Components in a Shielded Circuit Pack
Authors: Kolodner Paul , Bolle Cristian , Hodes Marc
Published: April 2009

We describe technology in which multiple components inside a circuit pack shielded from electromagnetic interference (EMI) are efficiently cooled by individual heat sinks that protrude into an external airflow through openings in the lid of the shield. Compliant, electrically conductive gaskets are used to form a perimeter seal between the bases of the heat sinks and the lid of the enclosure. The gaskets accommodate variations in the heights of the components and allow solid-to-solid contact in the thermal-grease-filled interface between the components and their heat sinks without compromising EMI shielding. This technology provides efficient cooling because the heat sinks can be tailored to the thermal loads of the individual components. Moreover, a set of small heat sinks presents a lower impedance to the cooling airflow than the conventional configuration of fins covering the entire lid of an EMI shield. We have examined the implementation of this solution using ICEPAK® thermal modeling software and by experiment. It leads to acceptable thermal performance and lower impedance to air flow relative to the conventional approach. It also has important potential advantages in cost, weight, and ease of rework.
Sizing of Pellets in Thermoelectric Modules (TEMs)
Authors: Hodes Marc
Published: April 2009

Sizing the height and cross sectional area of the pellets within thermoelectric modules (TEMs) used to cool, heat and generate power is necessary to optimize their efficiency and/or performance. Here the heat flux that a TEM can accommodate, its coefficient of performance, and its operating current and voltage in refrigeration mode are provided as a function of pellet geometry. This enables designers to, for example, size pellets to refrigerate a load such that the total power consumption of a TEM and a power supply (that converts available voltage to that required by the TEM) is minimized. In generation mode, power output, conversion efficiency and operating voltage and current are provided as a function of pellet geometry and the electrical resistance of a load connected to a TEM. Finally, the effects of electrical contact resistance at the pellet interconnects on the aforementioned parameters are addressed.
Die Stress Analysis in Stacked Die Chip Scale Packages (SCSP)
Authors: Chaparala Satish C. , Andros Frank E. , Infantolino Bill , Sammakia Bahgat G. , Guttikonda Satish C. , Zhao Julia , Sengupta Dipak
Published: April 2009

As board real estate becomes more precious and market demand for increased functional density in modules rises, engineers are looking at 3-dimensional packaging to provide the solutions. Stacked die technology, which involves stacking the die one above another, is fast becoming the preferred packaging option for memory applications in handheld consumer products where board space is a premium. The current study focuses on the stacked die wire bonded CSP (SCSP). The CSP offers reduced package size while the vertical stacking provides a smaller form for multi-chip integration compared to a horizontal layout. In some test chip designs, it has been observed that passivation cracks occur on the functional surface of the top die as a result of thermal cycling. Stress analysis using the finite element method has been carried out to understand the effect of package parameters on die stress under cycling conditions. The distribution of the stress components that may cause this passivation cracking are discussed. The stress magnitudes observed in the SCSP are compared with those of a single die package where no passivation cracks have been observed to obtain a quantitative perspective of the stress. Results reported for parametric studies include the effect of variation of die thickness, spacer size and thickness, and thickness of overmold compound above the die. Finally, design considerations for two-die, over-molded, wire-bond, stacked die packages are presented based on the above study.
Thermal Resistance and Pressure Drop of Silicon Based Micro Pin Fin Heat Exchanger Under Cross Flow
Authors: Prasher Ravi S. , Dirner John , Chang Je-Young , Myers Alan , Chau David , He Dongming , Prstic Suzana
Published: April 2009

We have performed a parametric study of the thermal and hydraulic performance of silicon-based micro pin fin heat exchangers with water as the fluid. Circular and square micro pin fins have been fabricated. The pin dimensions ranged from 50 μm to 150 μm. The test chip is unique because it has 20 micro temperature sensors of the size 75 μm × 75 μm to accurately capture the thermal resistance of the micro pin fin heat exchanger. Data shows that there is no difference in the hydraulic and the thermal resistance of circular and square pins. Conventional correlations for friction factor and Nusselt number match well with the data.
A Conjugate Numerical-RC Network Prediction of the Transient Thermal Response of a Power Amplifier Module in Handheld Telecommunication
Authors: Lee Tien-Yu Tom , Chiriac Victor A. , Stout Roger
Published: April 2009

A study compares two different approaches (numerical vs. RC Network) used to predict the transient thermal response of a Radio Frequency (RF) Power Amplifier (PA) module at a given duty cycle (power on and off periodically) in handheld telecommunication. In the numerical approach, commercial software is used to predict device’s transient thermal response at any arbitrary time of interest for a given set of material properties. To predict the peak and valley temperatures of the device when it reaches steady state, a new methodology is presented, combining the steady state temperature at an averaged power and the temperature difference between single-pulse (at averaged power) and a periodical curve at peak or valley. For multiple heat sources, a linear superposition theory applies. Temperature at any given junction and at any specific time, is a linear superposition of its response to the power applied at all junctions (including itself) summed up over all preceding time history. In the analytical Resistor-Capacitor (RC) network approach, the R’s (thermal resistances) and τ’s (time constants) in a single-pulse are predicted using linear regression curve fitting techniques. For a single-pulse RC model, superposition methodology is applied to solve the transient response in any waveform (single or multiple waves in a cycle). A formulated spreadsheet performs the calculation, with inputs such as pulse width, waiting time (before the pulse is initiated), pulse magnitude and period. The peak and valley temperatures at steady state for a single square wave per cycle are predicted through closed form solutions. For multiple square waves per cycle, individual wave responses must be added together throughout the entire range of the steady state cycle to determine the locations (time) of the peaks and valleys. In order to compare these two approaches, two case studies were conducted on a PA module for a cell phone application: at 12.5% duty cycle and at three-square wave per cycle. Results show good agreement between the numerical and RC model approaches, either at any arbitrary time or at “peak and valley” in steady state. Although the RC network method requires an intermediate creation of the RC model from single pulse numerical solutions (or from experimental measurement), the total time and effort to achieve similar results as compared to the direct numerical method may be considerably reduced. Further, once created, the RC model permits essentially unlimited flexibility and extremely rapid computation for arbitrary power cycling, whereas the direct numerical approach requires “starting over” with every different power cycling description of interest.
CAM Systems Based on Traveling Salesman Problem From Time Perspective for High Density Through-Hole Drilling
Authors: Hirogaki Toshiki , Aoyama Eiichi , Ogawa Keiji , Hashimoto Naohide , Matsumura Mitsutaka
Published: April 2009

This paper focuses on shortening drill-movement time in an X-Y plane. Traveling Salesman Problem (TSP) has been applied to determine a moving route of Printed Wiring Board (PWB) hole arrangements. Thus, some papers dealt with shortening the calculating time and increasing the accuracy of the TSP method to obtain the shortest route in geometrical problems. However, considering both the characteristics of PWB hole arrangements and the feed-control characteristics of machine tools, the shortest route for geometrical problems by TSP is not always in agreement with that of the moving time problem. Therefore, we propose a CAM system for PWB drilling considering the feed-control characteristics of machine tools using a new TSP method to obtain the shortest moving time.
Evaluation System for Ionic Migration On/In the Superconnect Leveled Printed Circuit Board by Means of AC Impedance Method
Authors: Yoshihara Sachio
Published: April 2009

Micro-fabricated Printed Circuit Boards (PCB) using environmental friendly materials and processes will be desirable candidates for future electronic packaging technologies. To investigate the ionic migration for thus developed PCB, quite new measurement method has been developed by the authors, which enables real time monitoring of the growth process of ionic migration using AC impedance method. Electric reliability of the newly developed copper printed circuit boards by Japan NEDO project (L/S = 4/6, 8/12, 12/16 μm) using polyimide, etc as the insulating layer have been evaluated under 85°C, 85%RH. The generation of the migration was also tested by conventional time dependence of current under bias of 5.0 V or 100 V. The progress of the migration could be investigated by AC Impedance method (Cole-Cole plots). The degradation of the diameter of the impedance loop suggested the intimation of migrations.
System Level Considerations in the Incorporation of a Component Thermal Model for an Automotive Application
Authors: Chiriac Victor , Lee Tom , Krishna Arvind , Krishnan Venkata , Lawrence Rodney
Published: April 2009

A detailed evaluation of modeling techniques used to incorporate a complex component level steady-state thermal model of a 32-pin SSOP package in a system level simulation is described. The device is an Application Specific IC designed for the present system, intended for use in a demanding automotive environment. The paper discusses the development of a compact model, used to enable the incorporation into a system level model with reasonable computational detail. The methodology involves a preliminary system level thermal analysis to estimate the ambient conditions in the vicinity of the device, followed by a detailed model of the device analyzed for various boundary conditions. A simplified compact model of the device is developed and validated against the detailed model. The compact model is shown to be accurate in the prediction of peak temperature in the package and boundary condition independent within realistic extremes of the operating environment. The fact that a compact model may not match the more detailed model at all points in the package is scrutinized in the context of correlation of the model to experimental results. The study highlights the significance of board-level conductivity enhancement and thermal vias under the package in reduction of package temperature.
Non-Destructive Inspection Method for Detecting Open Failures in Flip Chip Structures
Authors: Sato Yuhki , Miura Hideo
Published: April 2009

A new nondestructive evaluation method of adhesion condition between a Si chip and small metallic bumps in a flip chip bonding structure is proposed. The local deformation of a surface of a Si chip mounted on a substrate increases drastically between two bumps with decrease of the thickness of the chip thinner than 200 μm. The magnitude of the local deformation exceeds 100 nm easily. Once the lack or delamination of the metallic bumps occurs at the interface, the local deformation at a surface of a Si chip around the bump changes remarkably. The change of the magnitude of the local deformation reaches about 50 nm to 600 nm depending on the thickness of the chip. Such a small change of deformation can be measured using a scanning blue laser microscope. Therefore, the adhesion condition of the area-arrayed bumps can be examined by measuring the local deformation of a surface of an LSI chip mounted on a substrate.
Experimental and Numerical Evaluation of Residual Stress in IC Chips
Authors: Koganemaru Masaaki , Ikeda Toru , Miyazaki Noriyuki
Published: April 2009

The high residual stress in an electronic package sometimes causes not only mechanical failure but also the instability of electronic functions. Therefore the residual stress in resin-molded electronic packages should be evaluated. In this paper, the residual stress in a resin-molded electronic package was evaluated by the combination of experimental method using a test chip including piezoresistive gauges and the finite element method (FEM). The linear thermal elastic analysis of the resin-molded electronic package was carried out using the three dimensional FEM model. Stress-free temperature for the analysis was experimentally determined using the piezoresistive test chip. It was demonstrated that the residual stress at room temperature obtained by the FEM analysis well corresponds with the stress measured using the test chip. It was found from the results that compressive residual stress of over 100MPa was distributed on the top surface of a semiconductor chip in a plastic package. This study presents a simple evaluation technology of the residual stress in resin-molded semiconductor chips using the combination of experimental and numerical methods.
Cu-Direct Via-Hole Drilling of Aramid Fiber Reinforced Build-Up Layer by CO2 Laser Beam
Authors: Aoyama Eiichi , Hirogaki Toshiki , Ogawa Keiji , Doi Nobuyuki , Minagi Ryu
Published: April 2009

This report describes the features of Cu-direct laser drilled hole quality on multi-layer Printed Wiring Boards (PWBs). Cu-direct laser drilling drills the outer copper foil and build-up layer at the same time, which makes it difficult to form a blind via hole (BVH) with high quality because the copper foil has high reflection coefficient for a CO2 laser with wavelength 10.6 μm. Therefore, this study focused on improving drilled hole qualities such as diameter and overhang. First, the influence of laser irradiation conditions on forming BVH and the drilled hole diameter were investigated in detail. Second, a new method employing thermography was proposed in order to evaluate the absorption of copper foil after surface treatment. Third, the effect of mixing fillers into the build-up layer in order to reduce the amount of overhang was shown to be effective both experimentally and theoretically. As a result, it is clear that decreasing the difference in the laser absorption rate of the outer copper foil is an effective means to control the hole diameter and reducing the heat characteristic difference between the outer copper foil and the build-up layer can effectively decrease overhang.
Convective Heat Transfer From Confined Heated Surfaces With Slot Jet Impingement
Authors: Liu L. K. , Fang C. J. , Wu M. C. , Peng C. H. , Hung Y. H.
Published: April 2009

A series of experimental investigations with a stringent measurement method on the transient-/steady-state heat transfer behavior for confined smooth surfaces with slot jet impingement have been successfully conducted. From the results, a generalized correlation is proposed to represent the distributions of normalized transient convective heat flux. The highest heat transfer during the transient period occurs at the surface center of confined heated smooth or extended surface. The transient local Nusselt number decreases along the distance from the surface center toward the surface edge. The transient-/steady-state local and average Nusselt numbers are almost independent of Grs, and they are more significantly affected by ReD as compared with H/W. They will increase with increasing ReD. Maximum local and average Nusselt numbers can be found between H/W = 3 and H/W = 5. The effects of Grs and H/W on the dimensionless local Nusselt number distribution are insignificant; and the distribution can be expressed as a generalized bell-shaped profile, which is only dependent of ReD. Finally, a new composite correlation of steady-state average Nusselt number for mixed convection from confined smooth due to slot jet impingement and buoyancy are presented.
3D-SOP Millimeter-Wave Functions for High Data Rate Wireless Systems Using LTCC and LCP Technologies
Authors: Lee J.-H. , Sarkar S. , Pinel S. , Papapolymerou J. , Laskar J. , Tentzeris M. M.
Published: April 2009

In this paper, the development of three-dimensional (3-D) millimeter-wave functions in multilayer low temperature cofired ceramic (LTCC) and liquid crystal polymer (LCP) technologies is presented for millimeter-wave compact and easy-to-design passive solutions for high data rate wireless systems. Both ceramic and organic technologies are candidates for the 3-D integration of system-on-package (SOP) miniaturized RF/microwave/millimeter-wave systems. LTCC has been widely used as a packaging material because of its process maturity/stability and its relatively high dielectric constant that enables a significant reduction in the module/function dimensions. As an alternative, LCP is an organic material that offers a unique combination of electrical, chemical, and mechanical properties, enabling high-frequency designs due to its ability to act as both the substrate and the package for flexible and conformal multilayer functions. A LTCC patch resonator filter that uses vertical coupling overlap and transverse cuts as design parameters has been designed to achieve a high level of miniaturization and a great compromise between compactness and power handling. Excellent agreement between the simulation and the measurement has been verified for two operating frequency bands (58–60GHz/38–40GHz) of RF communications and sensors for applications such as wireless broadband internet or inter-satellite communications. A band pass filter has been fabricated on LCP substrate, offering a very simple, low loss flexible and low lost filtering solution for wideband millimeter waves applications such as 60 GHz WLAN short-range gigabit wireless systems. The design exploits the ripple near the cut off frequency of Tchebysheff low pass filter to create a band pass response and it exhibits the insertion loss as low as 1.5 dB at the center frequency of 60GHz and 3-dB bandwidth of 16.7% (∼10 GHz).
High Dense Plate Fin Heat Sinks Characterization and Validation
Authors: Xu Guoping , Akella Chakravarthy , Follmer Lee
Published: April 2009

Plate fin heat sinks are commonly used in electronics cooling including high end processors. A number of empirical and analytical methods are available to predict their performance but most of the models are valid for fin pitch larger than 3 mm heat sinks in laminar flow. The present work is to investigate high dense plate fin heat sink in both laminar and turbulent regimes. Thermal and hydraulic performance of several dense plate-fin heat sinks were characterized for high end processors in a fully-ducted wind tunnel. All the three heat sinks tested have the same dimensions of 89 mm (L) × 56 mm (W) × 50 mm (H), and fin number varied between 23 and 33. Heat sink base for all heat sinks was made of solid copper, while different fin materials of Aluminum and Copper are used. Several analytical methods for laminar flow from literature were reviewed in this study. A new heat transfer analytical method was proposed for both laminar and turbulent flows. The characterization data from these three parallel plate heat sinks were compared with the analytical methods. Finally, empirical heat transfer correlations were developed for both laminar and turbulent flows.