bluuebunny/crossref_metadata_2025 huggingface dataset:
Vertical Arrays of Copper Nanotube Grown on Silicon Substrate by CMOS Compatible Electrochemical Process for IC Packaging Applications
Authors: Choi Daniel , Fucsko Viola , Yang E. H. , Park Jung-Rae , Khalid Fahad , Kim Young-Kun
Published: October 2015

We present an electrodeposition-based fabrication process which can be complementary metal oxide semiconductor (CMOS) compatible for creating vertical arrays of copper (Cu) nanotubes for integrated circuit (IC) packaging applications. Since such nanotube structures offer high surface-to-volume ratios, low resistivity, and high thermal conductivity, they are especially suited for IC packaging applications requiring efficient heat transfer as well as electrical interconnect applications. In this work, Cu nanotube arrays were electrodeposited into alumina nanopore templates with pore diameters of approximately 50 nm and 100 nm. Simulation and measurements of the vertical arrays of Cu nanotubes showed greatly enhanced thermal conductivity in the direction of nanotube alignment compared with Cu nanowires and bulk Cu. The thermal conductivity of the vertical arrays of Cu nanotubes at 100°C is about 0.35W/m · K compared to the 0.24 W/m · K from Cu bulk materials, which shows an enhancement of about 146% as a result of the more efficient thermal conduction in Cu nanotubes.
Technology and Application of 3D Shaped LTCC Modules for Pressure Sensors and Microsystems
Authors: Slosarčík Stanislav , Vehec Igor , Gmiterko Alexander , Cabúk Pavol , Jurčišin Michal
Published: October 2015

This paper deals with shaping technology of LTCC (low temperature cofired ceramics) and as well on analysis of the possibilities of sensors in 3D shaped modules. Analysis of marginal possibilities of LTCC ceramic shaping was realized on a sample with various bending angles and various layer numbers, where thick-film conductive paths were present. The applicability of the obtained results was demonstrated by the development of a 3D shaped module with a thick-film pressure sensor.
Effects of Die Attachment Induced Stress on the Reliability of a Packaged MEMS Device
Authors: O'Neal Chad B. , Malshe Ajay P. , Schmidt William F. , Gordon Matthew H. , Brown William D.
Published: October 2015

A microelectromechanical systems (MEMS) actuator was selected to study the effects of packaging induced stress on device reliability. In this work, MEMS devices were obtained and packaged using cyanate ester, 96.5/3.5 Sn/Ag, and 92.5/5/2.5 Pb/Sn/Ag die attachment materials. The die attachment materials were then cured or reflowed appropriately and cooled to room temperature which induced stress through the coefficient of thermal expansion mismatches between the silicon die and alumina package. In this work, a MEMS microengine developed at Sandia National Laboratories, which is a device that has been well studied, was selected as a test vehicle to understand the effects of various die attachment solders and related processes parameters on the ultimate functionality of the packaged MEMS microengine. Particularly, the operational lifetime of these devices was measured by testing these devices to failure. These lifetimes were then compared with baseline values to determine the effect of stress on these devices. The maximum stress values observed in these studies ranged from 11–23 MPa based on the die attachment material used for cyanate ester to Pb/Sn/Ag solder, respectively. About 50% of the total population tested failed between 105 and 106 cycles, while 25% failed above 106 cycles and the remaining 25% failed below 105 cycles. The reliability results agreed well with previous results. The effect of stress did not seem to adversely affect the device lifetimes for this class of MEMS device, suggesting that these ranges of solders can be safely used to package MEMS devices.
Electromagnetically Actuated Membrane-Based Micropumps with Integrated Magnetic Yoke
Authors: Lederer Thomas , Heinisch Martin , Hilber Wolfgang , Jakoby Bernhard
Published: October 2015

Micropumps are an essential part of laboratory-on-a-chip applications, which are used for cell manipulations, DNA sequencing, and clinical diagnostics, just to name a few. Electromagnetic actuators are used for fluid transportation, because of relatively high forces and high displacements. Most published electromagnetic actuators for micro pumps are designed without a magnetic flux guiding yoke. In our paper, we present electromagnetic micro pumps with two alternative actuation principles, that is, Lorentz forces and reluctance forces, both with an integrated magnetic yoke. The high magnetic permeability and the higher magnetic flux enhance the mechanical force at the same electric energy input or primarily enable the functionality of the reluctance pump. The electromagnetic forces are used to drive a fluid flow via membrane deflection and passive valves without moving parts. The geometry of these passive valves is optimized to via finite element simulations (Comsol Multiphysics). Design parameters and theoretical considerations are discussed in this paper, and fabricated prototypes are presented.
Design and Process of 3D MEMS System-in-Package (SiP)
Authors: Lau John H.
Published: October 2015

The design and assembly process of 10 different 3D MEMS packages will be presented and discussed in this study. These 3D MEMS packages integrate the MEMS devices from the MEMS wafer (with either wirebonding pads, or solder-bumped TSV, through silicon via, substrate, or solder-bumped flip chip without TSV), the ASIC chips from the ASIC wafer (either with or without TSV), and the cavity package cap from the cap wafer (either with or without TSV). The assembly process consists of release (etching), singulation, wire bonding, flip chip, TSV, cavity etching, chip-to-wafer (C2W) bonding, and wafer-to-wafer (W2W) bonding. It can be shown that these packages lead to a small packaging footprint, high electrical performance, and potentially low cost.
Interfacial Reactions Between Electrodeposited Sn-Cu, Sn-Ag-Cu Solders and Cu, Ni Substrates
Authors: Han Chunfen , Liu Qi , Ivey Douglas G.
Published: October 2015

Interfacial reactions between two near eutectic Pb-free solders, Sn-1.1Cu and Sn-3.6Ag-1.8Cu, and two common base materials, Cu and Ni, were studied by characterizing the formation and growth of intermetallic compounds (IMCs) during reflowing and aging using SEM, XRD, and TEM. A continuous bilayer of thin, uniform Cu3Sn and thick, nonuniform Cu6Sn5 was formed at the interfaces of both Sn-1.1Cu/Cu and Sn-3.6Ag-1.8Cu/Cu, with the Cu3Sn layer adjacent to the Cu substrate. This is attributed to the diffusion of Cu from the Cu substrate to the solder to first form Cu6Sn5, then Cu3Sn. The inclusion of Ag in the Sn-3.6Ag-1.8Cu solder film inhibited the diffusion of Cu and, therefore, the growth of Cu3Sn. For both Sn-1.1Cu/Ni and Sn-3.6Ag-1.8Cu/Ni, an intermetallic film of (Ni,Cu)3Sn4 was formed at the interface, and the film had three distinct morphologies: a continuous planar layer at the Ni interface, followed by long, thin needles and large, polygonal crystals. The layers and the crystals were thinner at the Sn-3.6Ag-1.8Cu/Ni interface, indicating that the addition of Ag slowed down the growth of the (Ni, Cu)3Sn4 films. At the Sn-3.6Ag-1.8Cu/Ni interface, Ag3Sn particles were also observed and they coarsened with aging time. No separate Ag particles were observed.
Low Frequency Noise and TCR Mechanisms in Polymer Thick Film Resistors
Authors: Poornaiah B. , Rao G. Srinivasa , Kumar A.V. Prathap , Rao Y. Srinivasa
Published: October 2015

The paper aims to propose a more realistic low frequency noise and TCR mechanisms in polymer thick film resistors. The variation of low frequency noise (also called current noise) and TCR of polymer thick film resistor, namely, PVC-graphite thick film resistor, with parameters such as high volume fraction and grain size has been studied. A model is proposed to explain the observed variations, which assumes that the texture of the polymer thick film resistor consists of densely packed conducting particles with a cavity at the center of the structure. Further, the effect of the cavity diameter of polymer thick film resistor on current noise and TCR is explained using the same model. The current noise of these resistors is controlled mainly by the average relative resistance fluctuations between the conducting particles and the number of contacts each particle has with its neighbors. The TCR of these resistors is controlled mainly by the expansion properties of the insulating medium. The variation of TCR with high voltage is also due to the change in number of contacts and the contact area between the conducting particles.
Cooling Management of Highly Powered Chips Packed in an Insulated Cavity Filled with a Phase Change Material
Authors: Faraji Mustapha
Published: October 2015

This work describes and analyses a novel computer's thermal management system based on a phase change material (PCM) heat storage reservoir. The proposed heat sink consists of a PCM filled enclosure heated by substrate-mounted protruding heat sources (micro processors). PCMs, characterized by high energy storage density and small transition temperature interval, are able to store a high amount of generated heat; which provides a passive cooling of microprocessors. The advantage of this cooling strategy is that the phase change materials are able to absorb a high amount of generated heat without energizing the fan. The proposed strategy is suitable and efficient for situations where the cooling by air convection is not practical (thermal control of recent multiprocessors computers, for example). The problem is modelled as, two dimensional, time dependent and convection–dominated phenomena. A finite volume numerical approach is developed and used to simulate the physical details of the problem. This approach is based on the enthalpy method which is traditionally used to track the motion of the liquid/solid front and obtain the temperature and velocity profiles in the liquid phase. The study gives an instruction on the presentation of PCM heat sink used for cooling management of recent computers. Numerical investigations have been conducted in order to examine the impact of several parameters on the thermal behaviour and efficiency of the proposed PCM-based heat sink. Correlation for the secured operating time (time required by the heat sink before reaching the critical temperature, Tcr) is developed.
Analysis, Design, and Optimization of Thermal In-Plane Microactuator—Chevron Type
Authors: Puneeth K.B. , Seetharamu K.N.
Published: October 2015

A predictive model of thermal actuator behavior has been developed and validated that can be used as a design tool to customize the performance of an actuator to a specific application.

Modeling thermal actuator behavior requires the use of two sequentially or directly coupled models, the first to predict the temperature increase of the actuator due to the applied voltage and the second to model the mechanical response of the structure due to the increase in temperature. These models have been developed using ANSYS for both thermal response and structural response. Consolidation of FEA (finite element analysis) results has been carried out using an ANN (artificial neural network) in MATLAB. It is seen that an ANN can be successfully employed to interpolate and predict FEA results, thus avoiding necessity of running FEA code for every new case. Furtheroptimization of geometry for maximum actuation length has been carried out using a GA (genetic algorithm) in MATLAB. The results of the GA were verified against the ANN and FEA results.
Using Permanent and Temporary Polyimide Adhesives in 3D-TSV Processing to Avoid Thin Wafer Handling
Authors: Zussman M. P. , Milasincic C. , Rardin A. , Kirk S. , Itabashi T.
Published: October 2015

3D chip integration processes use thinned silicon wafers in conjunction with through silicon vias. Polyimide adhesives are evaluated for use as temporary and permanent adhesives to enable handling of thinned wafers and subsequent bonding into 3D stacks. These adhesives are found to have a combination of thermal and mechanical properties and processing capabilities required for 3D chip integration applications.
The Effects of Temperature Profile of Accelerated Temperature Cycling Tests on the Reliability of ACA Joints in RFID Tags
Authors: Saarinen Kirsi , Frisk Laura
Published: October 2015

Anisotropic conductive adhesives (ACAs) are used in radio frequency identification tags (RFID tags) because of their advantages compared with conventional solders. However, some reliability problems may occur in the joints when the tags are exposed to high or fluctuating temperatures. Temperature cycling tests and constant temperature tests can be used to study the effects of temperature on reliability. With these tests, the failure modes and mechanisms can be found faster. Nevertheless, if an excessively rigorous test is chosen, the failure mechanisms and modes may not be the primary causes of failure in the operating environment of the tags. In this study, the reliability of a tag with ACA joints was studied with two different temperature cycling tests and two different constant temperature tests. Four different test series with varying bonding parameters were tested. The reliability of the tags was verified in each test by monitoring the daisy chain resistance of the ACA joints. The results from the test with the wider temperature range were achieved fastest. However, the behavior of the test series varied when compared with each other during different temperature cycling tests and differences in failure modes between the two temperature cycling tests were observed. Consequently, the test with the wider temperature range revealed failure mechanisms different from those seen during the less rigorous test. Due to this, the test with the wider temperature range may not have shown the primary failure modes and it is possible that these results do not correctly reflect the differences between the test series under use conditions.
An Efficient Implementation of Polymer Viscoelastic Behavior Through a Pseudo Viscoelastic Model
Authors: Raghavan Sathyanarayanan , Okereke Raphael. I. , Sitaraman Suresh K.
Published: October 2015

Modeling of viscoelastic relaxation of polymer materials is important to understand the thermo-mechanical behavior of organic microelectronic systems. However, incorporation of viscoelastic behavior into numerical models makes the models compute-intensive. This paper presents a different technique to incorporate the polymer viscoelastic behavior into the numerical models such that the computation time is not adversely affected without compromising the accuracy of the results obtained. In the proposed “pseudo viscoelastic” modeling technique, the modulus of the viscoelastic material is computed as a function of time and temperature loading history outside of the finite-element simulation, and is then input into the simulation as a thermo-elastic material incorporating the viscoelastic relaxation of the material. This paper compares the warpage results obtained through the proposed technique against a complete viscoelastic simulation model and experimental data, and it is seen that the maximum warpage predicted using the proposed technique agree within 10% compared with the results obtained from a “full” viscoelastic model. Also, it is shown through some of our simulations that the proposed technique could result in a computational time saving of more than 50% and hard disk space saving of 65%.
Novel Technology Options for Multilayer-Based Ceramic Microsystems
Authors: Partsch Uwe , Goldberg Adrian , Ihle Martin , Hagen Gunter , Arndt D.
Published: October 2015

Ceramic multilayer technologies such as LTCC (low temperature cofired ceramics) or HTCC (high temperature cofired ceramics) are applied for the fabrication of highly integrated ceramic microelectronic packages. Furthermore, ceramic multilayer technologies offer the possibility of additionally integrating 3D structures for multilayer-based microsystems.

This paper presents a new machine for tape/multilayer structuring that combines micro punching tools and micro UV-laser ablation/cutting. The application for the production of different multilayer-based components is described (e.g., LTCC-based PEM fuel cell system, LTCC-based pressure sensors).

Aerosol jet printing is a new technology, for example, for rapid prototyping for LTCC multilayer and 3D deposition of functional layers on LTCC. Advantages and limitations of the technology are discussed.
New GaN Power-Electronics Packaging Solutions: A Thermal Analysis Using Raman Thermography
Authors: Faqir M. , Manoi A. , Mrotzek T. , Knippscheer S. , Massiot M. , Buchta M. , Blanck H. , Rochette S. , Vendier O. , Kuball M.
Published: October 2015

Raman thermography measurements were performed on AlGaN/GaN multifinger high electron mobility transistors (HEMTs) to determine their channel temperature at various power levels. The devices were mounted on both silver diamond composite and CuW baseplates, in order to benchmark the thermal performance of novel diamond composite baseplates compared with traditional materials. We illustrate that AlGaN/GaN HEMT devices mounted on silver diamond composite baseplates show peak temperatures that are 50% lower than the peak temperatures exhibited by devices mounted on traditional CuW baseplates. This is a dramatic improvement in terms of heat extraction as a basis to enable longer device lifetimes and better performance. In addition, time-resolved Raman thermography measurements were carried out to obtain the thermal dynamics of devices on the silver-diamond baseplate and on heat diffusion during pulsed device operation. This time-dependent information is of great importance for reliability and failure analyses, as pulsed operation of a HEMT is a typical device operation condition. Finite-element thermal simulations were performed for comparison with experimental results, and good agreement with the experimental data was obtained.
Compensation Scheme of a 50 Ω Bond Wire Interconnect Using Time Domain Reflectometry
Authors: Webb K. , Song H.
Published: October 2015

A compensation scheme that reduces the impact of the excess reactance of bond wires is introduced. From the 3D finite element code and the time domain reflectometry (TDR), physical models were evaluated and the excess reactance of the signal path was determined to optimize the compensation structure. The presented method can be employed to reduce the negative impact caused by the excess reactances in bond wires for high signal integrity integrated circuit (IC) packaging applications.
System-on-Chip Integrated MEMS Packages for RF LNA Testing and Self-Calibration
Authors: Kim Bruce C. , Kannan Sukeshwar , Evana Sai Shravan , Noh Seok-Ho
Published: October 2015

In this paper, we present MEMS-enhanced integrated package design which provides the capability to self-test and self-calibrate integrated circuit chips. We have developed a novel test technique where the test stimulus is generated by modulating the RF carrier signal with another signal mixed with additive white Gaussian noise. This novel test stimulus is provided as the input to the RF circuit and the peak-to-average ratio (PAR) is measured at the output. Simulations were carried out for fault-free and fault-induced circuit conditions, and their corresponding PARs were stored in the look-up table (LUT). Test simulations were performed and the results were compared with the look-up table to verify whether the device is fault-free. In faulty circuit conditions, calibration was performed using a tuning circuit made of MEMS switches. The entire validation of the design using the test technique and self-calibration of the RF circuit was automated using the calibration algorithm. This testing and self-calibration technique is exhaustive and efficient for present-day communication systems.
Assessment and Characterization of Stress Induced by Via-First TSV Technology
Authors: Parès G. , De Crecy F. , Moreau S. , Maurice C. , Borbely A. , Mazuir J. , Chapelon L.L. , Sillon N.
Published: October 2015

Through silicon via (TSV) is a key enabling technology for 3D stacking. One of the main concerns regarding the TSV introduction inside the IC fabrication is the resulting stress buildup in the silicon substrate that may induce warpage or expansion at the wafer level, strain and crystalline defects in the neighboring silicon of the TSV, and finally can impact the performance and reliability of the CMOS devices as well. Polysilicon, tungsten, and copper are the three main conductors that are currently considered for TSV fabrication. In the first part of this paper, the different factors that contribute to the stress in these three TSV types, including the geometry, the materials, and the process, will be reviewed.

After bonding on a temporary carrier and thinning of the substrate to expose the via, the stress built up during the fabrication of the TSV can be also revealed by the expansion of the silicon membrane.

We present thermomechanical FEM simulations and compare them with the experimental findings. We also present some characterizations of silicon defects by chemical revelation around the TSV structures. For characterization of the stress in TSV structures, different techniques as EBSD, microRaman, and XRD are presented. Finally, we conclude that with the optimization of some key processing steps, the stress induced in via-first technology may be acceptable for IC integration.
Quantitative Assessment of the Effects of Strain on Future III-V Digital Applications
Authors: Gomes Umesh P. , Ranjan Kumud , Chowdhury Subhra , Das Palash , Rathi Servin , Biswas Dhrubes
Published: October 2015

In this paper the strain effects on the performance and reliability of future digital III-V device are discussed. Strain is incorporated in the device during fabrication, packaging, and operation. A high amount of strain can introduce defects and cracks in the epilayer. The band structure of the active device region is also altered due to strain. These strain induced changes determine performance, reliability, and lifetime of the device. Therefore, it is necessary to consider strain effects while designing a device for a particular application. Here, compressive-strain-induced changes are used as design parameters and their impact on the logic performance of the device is studied. It is interpreted that the design significantly decreases the gate leakage current and improves the subthreshold slope.
Cold Embossing of Ceramic Green Tapes
Authors: Härtel Anja , Richter Hans-Jürgen , Moritz Tassilo
Published: October 2015

Hot embossing of ceramic green tape allows high throughput manufacturing. Tensile tests were carried out to investigate the embossing ability of alumina green tape at room temperature. The deformation behavior was analyzed based on powder content and the use or absence of plasticizer within the ceramic green tape. Furthermore, cold embossing tests with uniaxial compression tools were carried out. A channel structure was used as a test vehicle to allow investigations into stability against elastic recovery. In the first series of tests, various green tape compositions were investigated. Inferences were made, based on the elastic and plastic material behavior. The characterisation of structured tapes in the green state was carried out by using SEM and by scanning the surface area by confocal white light microscopy.
Design and Robustness of Quilt Packaging Superconnect
Authors: Khan M. Ashraf , Kulick Jason M. , Kopp David , Fay Patrick , Kriman Alfred M. , Bernstein Gary H.
Published: October 2015

Quilt packaging (QP) is a novel high-speed super-connect (i.e., direct interchip interconnect), developed to improve electrical performance—signal delay, power loss, and so on. Ultrahigh bandwidth has already been demonstrated for QP, but its unique structure requires thermal reliability issues to be studied. To this end, simulation models were developed to study the robustness of QP. QP structures were fabricated, and thermal cycling tests were performed focusing on the reliability for various shapes of nodules, the basic physical interconnect unit of QP. Simulations were performed to determine stress over a range of temperatures and estimate low cycle fatigue lifetimes. Simulations considered two types of solder and several adhesives. Thermal cycling experiments indicate that QP provides a robust structure, in agreement with the simulation results.
40 μm Ag/Au Flip-Chip Joints by Solid-State Bonding at 200°C
Authors: Lin Wen P. , Sha Chu-Hsuan , Lee Chin C.
Published: October 2015

In this research, 40 μm silver/gold (Ag/Au) composite flip-chip interconnect joints between silicon (Si) chips and copper (Cu) substrates were demonstrated. The bonding was achieved by a solid-state process at a low temperature of 200°C for 5 min with the pressure applied at 250–400 psi (1.7–2.7 MPa), corresponding to 0.22–0.35 g of force per joint. To begin with, an array of 50 × 50 30 μm Ag/10 μm Au columns with 40 μm in diameter and 100 μm in pitch was fabricated by photolitho-graphic and electroplating processes on silicon (Si) chips which were first coated with chromium (Cr) and Au films. The columns on the chip were then bonded to a Cu substrate by solid-state bonding. Cross-sectional scanning electron microscopy (SEM) images show that the exposed Ag/Au columns were well bonded to the Cu substrate. No joint breakage was observed despite the large coefficient of thermal expansion (CTE) mismatch between Si and Cu. A pull test was conducted. The breaking force and fracture strength are 6.5–7.3 kg and 2,940–3,310 psi (20.2–22.8 MPa), respectively. The breaking force is 2.5× of the criterion specified in MIL-STD-883E. Fracture modes were examined. Three modes were classified by fracture interfaces as Si-glue, Si/Cr/Au/Ag, and Au-Cu bonding interface. Of all joints evaluated, 27% of them break on the Au-Cu substrate bonding interface. Accordingly, the bonding interface is least likely to break among interfaces of the joint structure.
Mechanical Stress Analyses of Packaged Pressure Sensors for Very High Temperatures
Authors: Zeiser Roderich , Ayub Suleman , Hempel Jochen , Berndt Michael , Wilde Juergen
Published: October 2015

Methods for investigations of stresses specialized for devices operating up to 500°C are presented in this study. Resistive pressure sensors and test chips with microstrain (μ-strain) gauges are processed in thin film technology. The sensor structure was a Wheatstone bridge on a silicon membrane with platinum resistors. The μ-strain gauges were characterized with tensile tests in combination with optical strain measurements. A gauge factor of 3.6 was measured at room temperature. After characterization as bare dice, the chips were mounted with a borosilicate glass solder on two ceramic substrates, AlN and Si3N4. We generated a FE model of the sensor assemblies including temperature-dependent material properties. The distribution of mechanical strains and stresses in the sensor was analyzed. The chip warpage dependent on temperature up to 500°C was obtained from FE simulations and compared with high-precision 3D deformation measurements. Deformation results from digital image correlation (DIC) verified the utilized FE model. The correlation of experimental results for the chip warpage exhibited good agreement with the numerical results obtained from FEM. The chip deflection from the center to the edges in the out-of-plane direction on AlN was 4.5 μm; on Si3N4 a concave warpage of 3 μm at 25°C was found. Temperature-induced deformations of the sensor chip in the range of micrometers were recorded up to 500°C. The output signal of the pressure sensors is strongly affected by superimposed strains based on the sensor assembly. The bridge voltage increased by 40% after the glass solder process on AlN and by 34% for devices on Si3N4. The analysis of the μ-strain gauges showed compressive strains in the sensor membrane of −1.39% on average for assemblies on AlN and of −0.168% for glass soldered chips on Si3N4. The FEM simulations revealed an average in-plane stress in the sensor membrane of −45 MPa for chips on AlN and −20 MPa for Si3N4 substrates. The compressive strains in the membrane obtained by FEM were verified by the μ-strain gauge measurements. A higher strain and stress gradient in the membrane of devices on AlN was found with FEM, which is consistent with the higher signal offset of assembled pressure sensors that was measured in this study.
Redistribution Layers (RDLs) for 2.5D/3D IC Integration
Authors: Lau J. , Tzeng P. , Lee C. , Zhan C. , Li M. , Cline J. , Saito K. , Hsin Y. , Chang P. , Chang Y. , Chen J. , Chen S. , Wu C. , Chang H. , Chien C. , Lin C. , Ku T. , Lo R. , Kao M.
Published: October 2015

Redistribution layer (RDL) is an integral part of 3D IC integration, especially for 2.5D IC integration with a passive interposer. The RDL allows for circuitry fan-outs of and allows for lateral communication between the chips attached to the interposer. There are at least two ways to fabricate the RDL, namely (1) polymers to make the passivation and Cu-plating to make the metal layer, and (2) semiconductor back-end-of-line Cu damascene. In this study, the materials and processes of these methods are presented. Emphasis is placed on the Cu damascene method.
Thermal Cycling Reliability of Alternative Low-Silver Tin-Based Solders
Authors: George Elviz , Osterman Michael , Pecht Michael , Coyle Richard , Parker Richard , Benedetto Elizabeth
Published: October 2015

Sn-3.0Ag-0.5Cu (SAC305) alloy is the most widely used solder in electronic assemblies. However, issues associated with cost and drop/shock durability have resulted in a search for alternative lead-free solder alloys. One approach to improve the drop/shock reliability has been to reduce the silver content in Sn-Ag-Cu alloys. Another approach is doping Sn-Ag-Cu solder with additional elements. In 2008, the International Electronics Manufacturing Initiative (iNEMI) started the “Characterization of Pb-Free Alloy Alternatives” project to provide a comprehensive study of 15 tin-based solder interconnect compositions benchmarked against the eutectic tin-lead solder. For this study, temperature cycle durability was the primary focus and solders were selected to study the effect of varying silver content, microalloy additions, and aging. This paper reports the findings from one of the test conditions conducted under the iNEMI project. The cycles to failure for a temperature cycling test condition from −15°C to 125°C, with dwell times of 60 min at both extremes, are presented. The test assembly consisted of 16 of the 192 I/O BGAs and 16 of the 84 I/O BGAs soldered onto an LG451HR laminate. Test results revealed that the reduction of silver resulted in a reduction in cycles to failure. In all cases, the 15 tin-based solders were more durable than the eutectic SnPb solder. Aging at 125°C for 10 d did not affect the cycles to failure in SAC105 solder; however, the cycles to failure decreased with aging in SAC305 solder. In addition, aging resulted in a wider distribution of cycles to failure in 192 I/O BGAs. Failure analysis was carried out on all solder materials to identify the failure site and failure mode.
Characterization of the Hot-Cutting Defect Generated from Shape Machining of Alumina Green Tape in the Ceramic-Package Manufacturing Process
Authors: Zeng Chao , Wang Chunqing , Tian Yanhong , Hang Chunjin , Liu Wei , An Rong
Published: October 2015

This paper characterizes the rarely mentioned but very damaging defects formed during the hot-cutting process of alumina green tape. Surface and edge morphologies of the hot-cutting surface and a natural surface were examined by optical microscope and scanning electron microscope before and after the sintering process. Obviously different from the natural surface, the hot-cutting surface had a transverse crack-like defect scattered over the surface and a tearing, notch-like defect on the lower edge. A 31 × 22 full factorial experiment was conducted to evaluate the flexural strength controlled by the hot-cutting defect and inherent defects in ceramics. Variance analysis revealed a significant interaction between surface and wearing. The wearing factor had a statistically significant impact on the fracture strength of the top surface but not that of the side and bottom surfaces.
Direct-Bond-Copper Switch Module for Management of Temperature and Noise in 220-W/in3 Power Assembly
Authors: Kim Woochan , Shin Jongwon , Ngo Khai D. T.
Published: October 2015

Achieving high-power density is a challenge in the presence of stringent specifications on temperature rise and switching noise. Integration of the direct-bond-copper module with PCB mother board was found to be the right approach to achieve 220-W/in3 power density, 2-kW output power, and 48.9°C junction-temperature rise. The reduced layout inductance (2.89 nH) at the source and the negative coupling between source and drain layout inductances suppressed turn-off noise. The prototyped dc-dc boost converter switched between 400 kHz to 1 MHz without self-turn-on problems.
Reliability Assessment of Flip-Chip Assembly of Al Bumps
Authors: Tanisawa Hidekazu , Hiyama Kohei , Anzai Takeshi , Takahashi Hiroki , Murakami Yoshinori , Sato Shinji , Watanabe Kinuyo , Kato Fumiki , Sato Hiroshi
Published: October 2015

This article reports on a flip-chip bonding technology using an Al bump at high temperatures, such as for SiC semiconductors. In recent years, double-sided mounting structures have been proposed for purposes of miniaturization and low inductance. The surface-mounting method requires durability against high temperatures. We propose a new technique for the flip-chip bonding of an Al bump made from bonding wire. The recrystallization temperature of Al is under 250°C. As a result, there is an expectation of mitigating mechanical stress between the chip and the bonded substrate. We conducted a high-temperature aging test at 250°C for 3,000 h and a thermal shock test between −40°C and 250°C for 3,000 cycles. Results indicate that the shear strength of the Al bump meets the requirements specified in the IEC60749-19 guideline up to 2,000 cycles at room temperature.
Effect of Process Parameters on Free Air Ball Integrity in Copper and Palladium-Coated Copper Bonding Wires
Authors: Araki Noritoshi , Ichiyama Yasutomo , Oishi Ryo , Haibara Teruo , Yamada Takashi
Published: October 2015

The free air ball (FAB) formation processes of fine diameter Cu wires were observed, and the effects of process parameters were studied on the basis of high-speed camera observation. It was revealed that the FAB formation process is characterized by preheating before melting, melting that accompanies ball rising, and solidification periods. The relationships between the electronic flame-off (EFO) condition and the FAB formation were summarized for both bare Cu and palladium-coated Cu (PCC) wires. Further study was performed on the changes in FAB shape with different EFO conditions, wire types, and FAB sizes. Off-centered FABs were observed in the bare Cu wire whereas they were rarely observed in the PCC wire. The off-center tended to be affected by shielding gas condition, EFO torch gap, and FAB size. The mechanisms of the off-centered FAB formation were proposed through the high-speed camera observations. The optimization of process parameters to achieve defect-free, consistent FAB is discussed based on these findings, which is useful for the next generation high-density packaging.
‘Ecclesia reformata semper reformanda’ Church renewal from a Reformed perspective
Authors: Koffeman Leo J.
Published: October 2015

With a view to the theme of church renewal, this article explores the role of a well-known and popular phrase in the Reformed tradition within Protestantism, that is, ecclesia reformata semper reformanda [‘the reformed church should always be reformed’]. Is this a helpful slogan when considering the possibilities and the limitations of church renewal? Firstly, the historical background of this phrase is described: it is rooted in the Dutch Reformed tradition, and only in the 20th century it was widely recognised in Reformed circles. Against this background the hermeneutical problem, linked with the principle of sola Scriptura, is presented, and put into an ecumenical ecclesiological perspective: the church is grounded in the gospel. Finally, the article focuses on church polity as an important field of renewal, taking into account Karl Barth’s interpretation of this phrase. From this perspective, a balanced and ecumenical approach of church renewal is possible.
"FISHed" out the diagnosis
Authors: Bajaj S , Thombare TS , Tullu MS , Agrawal M
Published: October 2015

Our patient presented with congenital heart disease (CHD: Tetralogy of Fallot), hypocalcemia, hypoparathyroidism, and facial dysmorphisms. Suspecting DiGeorge syndrome (DGS), a fluorescence in situ hybridization (FISH) analysis for 22q11.2 deletion was made. The child had a hemizygous deletion in the 22q11.2 region, diagnostic of DGS. Unfortunately, the patient succumbed to the heart disease. DGS is the most common microdeletion syndrome, and probably underrecognized due to the varied manifestations. This case stresses the importance of a detailed physical examination and a high index of suspicion for diagnosing this genetic condition. Timely diagnosis can help manage and monitor these patients better and also offer prenatal diagnosis in the next pregnancy.
Неравенство Никольского и функциональные классы на компактных группах Ли
Authors: Nursultanov Erlan Dautbekovich , Ruzhansky Mikhael Vladimirovich , Tikhonov Sergei Yur'evich
Published: October 2015

В данной работе мы изучаем функциональные классы Бесова, Трибеля-Лизоркина, Винера и Берлинга на компактных группах Ли. При изучении свойств этих пространств важную роль играет неравенство Никольского.
Достаточное условие несингулярности дискретного конечнозонного при одной энергии двумерного оператора Шрeдингера на квад-графе
Authors: Vasilevskii Boris Olegovich
Published: October 2015

Используя конечнозонный подход, строится двумерный дискретный оператор Шредингера на квад-графе - планарном графе, у которого грань является четырехугольником. Предлагается определение несингулярности этого оператора: оператор несингулярен, когда все его коэффициенты положительны. Далее приводятся условия на спектральную кривую и квад-граф, достаточные для несингулярности построенного по ним оператора.
Замечания о квантовых марковских состояниях
Authors: Bezhaeva Zinaida Ivanovna , Oseledets Valery Iustinovich
Published: October 2015

Определение квантового марковского состояния было дано Аккарди в 1975 г. В классическом случае это определение дает скрытые марковские меры, которые, вообще говоря, марковскими не являются.
Марковскую меру можно задать с помощью неотрицательной трансфер матрицы. Мы выделяем с помощью неотрицательно определенных трансфер матриц класс квантовых марковских состояний (в смысле Аккарди) на $C^*$-индуктивном пределе матричных алгебр $M_{d^n}$. Определенные Аккарди и Фидалео сцепленные квантовые марковские состояния входят в наш класс. Для случая, когда неотрицательно определенная матрица имеет ранг $1$, мы вычисляем спектр и собственные вектора матриц плотности, задающих квантовое марковское состояние. Последовательность энтропий фон Неймана этих матриц плотности ограничена.
Детерминантные меры, связанные с большими полиномами $q$-Якоби
Authors: Gorin Vadim , Olshanski Grigorii Iosifovich
Published: October 2015

Мы определяем новый комбинаторный объект - расширенный граф Гельфанда-Цетлина с копереходными вероятностями, зависящими от параметра $q$. Граница этого графа допускает явное описание. Мы вводим семейство вероятностных мер на границе и описываем их корреляционные функции. Эти меры являются $q$-аналогом спектральных мер, ранее исследованных в контексте задачи гармонического анализа на бесконечномерной унитарной группе.
Nueva propuesta reconstructiva para una relectura crítica de la documentación arqueológica de Siracusa en época griega
Authors: Caruso Fabio , Gabellone Francesco , Ferrari Ivan , Giuri Francesco
Published: October 2015

[IT] Lo studio ricostruttivo di un monumento antico risente fortemente di lacune informative, errata trascrizione delle fonti, errata traduzione o peggio ancora, di interpretazioni soggettive che possono compromettere drasticamente il risultato finale, portando a ricostruzioni anche notevolmente diverse tra di loro. Questo lavoro vuole presentare i risultati di uno studio ricostruttivo condotto filologicamente su alcuni monumenti di Siracusa in età greca, cercando di evidenziare il contributo specifico dell'archeologia virtuale nei processi interpretativi, al fine di proporre una presentazione efficace rivolta ad un target specifico di turisti. Seguendo questo approccio sono stati ricostruiti il Tempio di Apollo, il complesso monumentale di piazza Duomo ed il Teatro greco, cercando di fornire output di visualizzazione che fossero adeguati ad una consultazione da smartphone e coerenti alle finalità generali del progetto "PON Energia Smart City". Questo progetto prevede un approccio "smant" alla visita di Siracusa, privilegiando principalmente logiche di fruizione efficiente on-site grazie all'adozione di tecnologie basate sulla Realtà Aumentata, la visione dei monumenti da punti inusuali e la visita virtuale multimodale dei punti di interesse. Emerge da questo studio la nuova fisionomia di quei monumenti che, per motivi diversi, sono stati rappresentati negli anni in forme e modi del tutto differnti, tali da rendere a volte irriconoscibili le diverse ricostruzioni dello stesso oggetto. Grazie alle tecnologie di restituzione 3D basate sull'immagine è stato possibile integrare le parti mancanti di alcuni elementi architettonici e scultorei che, ricollocati virtualmente nella posizione originaria, permettono una lettura dinamica che combina l'aspetto reale con quello virtuale.
Interactive effects of and light on growth rates and RUBISCO content of small and large centric diatoms
Authors: Li G. , Campbell D. A.
Published: October 2015

Abstract. Among marine phytoplankton groups, diatoms span the widest range of cell size, with resulting effects upon their nitrogen uptake, photosynthesis and growth responses to light. We grew two strains of marine centric diatoms, the small Thalassiosira pseudonana and the larger T. punctigera in high and low nitrogen media, across a range of growth light levels. Nitrogen and total proteins per cell decreased with increasing growth light in both species when grown under low nitrogen media. Surprisingly, low nitrogen increased the cellular allocation to RUBISCO and the rate of electron transport away from Photosystem II for the smaller diatom under low growth light, and for the larger diatom across the range of growth lights. Low nitrogen decreased the growth rate of the smaller diatom, particularly under higher light, but stimulated the growth rate of the larger diatom. Our results show that the high nitrogen in common growth media favours the growth rate of a small diatom but inhibits growth of a larger species.
Seasonal sea ice predictions for the Arctic based on assimilation of remotely sensed observations
Authors: Kauker F. , Kaminski T. , Ricker R. , Toudal-Pedersen L. , Dybkjaer G. , Melsheimer C. , Eastwood S. , Sumata H. , Karcher M. , Gerdes R.
Published: October 2015

Abstract. The recent thinning and shrinking of the Arctic sea ice cover has increased the interest in seasonal sea ice forecasts. Typical tools for such forecasts are numerical models of the coupled ocean sea ice system such as the North Atlantic/Arctic Ocean Sea Ice Model (NAOSIM). The model uses as input the initial state of the system and the atmospheric boundary condition over the forecasting period. This study investigates the potential of remotely sensed ice thickness observations in constraining the initial model state. For this purpose it employs a variational assimilation system around NAOSIM and the Alfred Wegener Institute's CryoSat-2 ice thickness product in conjunction with the University of Bremen's snow depth product and the OSI SAF ice concentration and sea surface temperature products. We investigate the skill of predictions of the summer ice conditions starting in March for three different years. Straightforward assimilation of the above combination of data streams results in slight improvements over some regions (especially in the Beaufort Sea) but degrades the over-all fit to independent observations. A considerable enhancement of forecast skill is demonstrated for a bias correction scheme for the CryoSat-2 ice thickness product that uses a spatially varying scaling factor.
Long-Term Survival in a Patient with Head and Neck Paraganglioma Treated with Tailored Modalities for 20 Years: A Case Report
Authors: Belgioia Liliana , Pupillo Francesco , Bacigalupo Almalina , Corvò Renzo
Published: October 2015

Aims and background

Primary paragangliomas of nasal cavity and paranasal sinus are rare conditions that could show aggressive behavior with local recurrence and metastasis development. The diagnosis of malignancy is challenging because there are no available histopathologic criteria. In these cases, the prognosis is usually poor.

Methods

We report a case of a woman with malignant paranasal sinus paragangliomas.

Results

The patient was treated with several surgical approaches, radiotherapy, and medical therapy for different recurrences.

Conclusions

Despite the malignant behavior of the disease, this patient is still alive many years after first diagnosis.
Chemotherapy and Pelvic Radiotherapy-Induced Bladder Injury
Authors: Çetinel Bülent
Published: October 2015

An understanding of the basics of the anatomy of the bladder mucosa is essential to better understand the pathophysiology of chemo-and radiotherapy-induced cystitis. Following an overview of bladder anatomy and the definitions and causes of bladder injury, the mechanisms of cyclophosphamide (CP)-induced bladder injury are discussed as a specific example.
Índices de anillos de crecimiento en dos coníferas del Centro de México
Authors: Gómez-Guerrero Armando , Martínez-Molina Gabriel , Martínez-Trinidad Tomás , Velázquez-Martínez Alejandro , Sardiñas Gómez Oreste , Rivera Carlos , Toruño Pedro José
Published: October 2015

Se determinaron índices de anillo de crecimiento (IAC) en Abies religiosa (Kunth Schltdl. et Cham) (oyamel) y Pinus hartwegii (Lindl.) (pino) en un transecto sobre el Eje Neo-volcánico Transversal, en México. La toma de muestras de anillos se realizó en seis montañas que presenan condiciones climáticas, geología, edafología suelo y vegetación similares. Las montañas son: Nevado de Colima, Pico de Tancítaro, Nevado de Toluca, Cerro Tláloc, La Malinche y Pico de Orizaba. Se colectaron virutas de incremento de al menos 20 árboles longevos de cada especie en cada sitio; sin embargo, para fines de este estudio se seleccionaron los árboles más representativos quedando entre 6 y 17 árboles de cada especie en cada montaña (144 árboles en total). Los resultados mostraron tendencias diferentes entre especies y montañas. Sin embargo, estimando valores promedio de IAC para el transecto, se observa que en el año 1935 hubo una reducción de crecimiento para ambas especies. El Oyamel mostró mayor variación en los IAC. De las dos especies, sólo en Oyamel se observó relación significativa entre los índices de anillo y la precipitación.