bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Silver Paste Application on Embedded Channels in Low Temperature Co-fired Ceramics
Authors: Kellis Douglas L. , Moll Amy J. , Plumlee Donald G.
Published: October 2015

A monopropellant micropropulsion device is being developed in low-temperature cofired ceramics (LTCC). The device uses catalytic decomposition of hydrogen peroxide as a propellant: hence catalytic channels are embedded internally in these devices. Consistent construction of these channels depends on a wide range of variables both in the design and fabrication of the channel structures. The primary focus of this paper is the characterization of final channel geometry when silver paste is applied to the upper and lower surfaces of an embedded single layer channel. Application of silver paste to the upper and lower channel surfaces has been shown to alter the final shape of the channels within the test structure. Upper and lower surface deflection into the channel area is discussed and characterization of this phenomena is illustrated as a function of channel width. A design of experiment (DOE) method is used to explore how process parameters affect the channel geometry/integrity. Construction of the test structures includes the use of pressure sensitive adhesives and a sacrificial material to maintain the overall channel geometry/integrity. Lamination and firing profiles are modified in order to enhance this construction methodology. Techniques used to produce and characterize these channels are discussed as well as the methods used to maintain channel geometry/integrity.
Fabrication and Testing of an LTCC Microfluidic Serial Dilution Device
Authors: da Cunha Marcio Rodrigues , Gongora-Rubio Mario Ricardo , Alvim Izabela Dutra , Ré Maria Ines
Published: October 2015

Usually in chemical and biotechnology laboratories, preparing liquid reagents and samples with distinctive concentrations is a basic process applied to all experiments. Most of the time, this process is done by manual pipetting whose accuracy and repeatability depend on the researcher's expertise. In addition, preparing reagents and samples is a time-consuming process, because of the amount of time needed for pipette regulation, suction, and infusion. Buffer solutions are solutions that resist change in hydronium ion and hydroxide ion concentration (and consequent pH) upon addition of small amounts of acid or base, or upon dilution. Their resistance to changes in pH makes buffer solutions useful for chemical and biochemical processes. A buffer of carbonic acid (H2CO3), bicarbonate (HCO3−), and phosphate (H2PO4−) is present in blood plasma to maintain a pH between 7.35 and 7.45. Industrially, buffer solutions are used in fermentation processes and in setting in vivo conditions for biotechnological experiments, as well as in chemical analysis and calibration of pH meters. The present work reports the potential of 3D LTCC (Low Temperature Cofired Ceramics) to obtain microfluidic structures for the continuous production of buffer solutions with different pH levels. Design, device simulation, and fabrication as well as experimental results are presented.
Optimization of a Peristaltic Micropump with Multiple Moving Actuators
Authors: Bhadauria Ravi , Pidaparti Ramana M. , Gad-el-Hak Mohamed
Published: October 2015

A design optimization based on coupled solid–fluid analysis is investigated in this paper to achieve specific flow rate through a peristaltic micropump. A micropump consisting of four pneumatically actuated nozzle/diffuser shaped moving actuators on the sidewalls is considered for numerical study. These actuators are used to create pressure difference in the four pump chambers, which in turn drives the fluid through the pump in one direction. Genetic algorithms along with artificial neural networks are used for optimizing the pump geometry and the actuation frequency. A simple example with moving walls is considered for validation by developing an exact analytical solution of the Navier–Stokes equation and comparing it with numerical simulations. Possible applications of these pumps are in microelectronics cooling and drug delivery. Based on the results obtained from the fluid–structure interaction analysis, three optimized geometries result in flow rates that match the predicted flow rates with 95% accuracy. These geometries need further investigation for fabrication and manufacturing issues.
The Way to High Volume Fabrication of Lab-on-a-Chip Devices—A Technological Approach for Polymer Based Microfluidic Systems with Integrated Active Valves and Pumps
Authors: Rupp Jochen , Schmidt Manuela , Günther Bettina , Stumber Michael , Zinober Sven , Müller-Fiedler Roland , Alabsi Bashir , Rothacher Peter , Müller Claas , Reinecke Holger , Zengerle Roland , Daub Martina
Published: October 2015

We present a technology platform suitable for the mass production of laboratory-on-a-chip devices made of polymers with integrated active and passive components. The presented microfluidic platform with integrated valves and pumps for active flow management is realized with three layers consisting of two polymer parts separated by a thin elastic TPE (thermoplastic elastomer) membrane welded together in one step. The elastic TPE membrane acts as an integrated deflectable membrane layer between the two outer polymer layers, each made of a weldable thermoplastic polymer (polycarbonate). Valving is realized by applying pressure in a displacement chamber above a hydraulic channel causing the membrane to deform and to seal the channel. A pump is fabricated using a displacement chamber with a valve on the inlet and outlet. The presented components, namely valve and pump, show excellent behavior regarding response time, sealing quality, and pump rate needing only a low actuation pressure. The three-layer-stack is joined in a single process step by using laser welding, creating devices with high mechanical stability. This production technology fulfills the requirements of a high volume fabrication at high quality and has the potential to manufacture cost-efficient and reliable laboratory-on-a-chip systems. The used materials show a high chemical resistance against a broad range of commonly used liquids and good optical characteristics for the use in μTAS. This consistent technological approach represents a flexible platform for microfluidics with active components to be used in complex applications.
Batch Fabrication of Shape Memory Actuated Polymer Microvalves by Transfer Bonding Techniques
Authors: Grund T. , Megnin C. , Barth J. , Kohl M.
Published: October 2015

Polymer based microvalves offer outstanding properties for biomedical and life science applications. They can be produced cost efficiently by batch fabrication methods. Further, by adapting the polymer material, custom-tailored properties of the valve are possible. For mechanically active microvalves, actuation with smart materials like shape memory alloys is highly attractive due to their high work output per volume and favorable scaling behavior. For the integration of such smart materials, fabrication process incompatibilities between the actuator material and the polymer target system need to be avoided. This can be achieved by novel transfer bonding technologies being optimized for batch fabrication. These technologies are demonstrated for polymer microvalves actuated by a shape memory alloy but they can also be applied to other functional materials and structures.
Critical Issues of TSV and 3D IC Integration
Authors: Lau John H.
Published: October 2015

Moore's law has been the most powerful driver for the development of the microelectronic industry. This law is grounded in lithography scaling and integration (in 2D) of all functions on a single chip, perhaps through system-on-chip (SoC). On the other hand, the integration of all these functions can be achieved through system-in-package (SiP) or, ultimately, 3D IC integration. However, there are many critical issues for 3D IC integration. In this study, some of the critical issues will be discussed and some potential solutions or research problems will be proposed.
A Multistep Process for Thinning Individual Die to sub-35 μm Thickness
Authors: Thompson Jeffrey , Tepolt Gary , Racz Livia , Rogers C.B. , Manno V.P. , White R.D.
Published: October 2015

The drive toward increased packaging density relies on die stacking. In order to maximize functional density, die are generally thinned on the wafer level. However, high-cost low-volume applications may not have full wafers available. Therefore, a method to thin individual die must be developed. In this article, a detailed and reliable process for thinning die to sub35 μm is outlined. The process consists of four steps: pseudo-wafer lamination, mechanical lapping, chemical mechanical planarization (CMP), and die release. A pseudo-wafer is created by adhering die to a glass substrate. Mechanical lapping is used to remove the bulk silicon and reduce die thickness to approximately 50 μm. CMP is used to attain thicknesses of sub35 μm and remove the subsurface damage layer from the die. This process can reliably produce die thinned to sub35 μm with ± 1.5-μm total thickness variation (TTV). The die are then released from the glass substrate and are handled using a customized vacuum carrier.
Improved Heat Dissipation and Optical Performance of High-Power LED Packaging with Sintered Nanosilver Die-Attach Material
Authors: Panaccione Paul , Wang Tao , Chen Xu , Luo Susan , Lu Guo-Quan
Published: October 2015

Heat removal in packaged high-power light-emitting diode (LED) chips is critical to device performance and reliability. Thermal performance of LEDs is important in that lowered junction temperatures extend the LED's lifetime at a given pho-tometric flux (brightness). Optionally, lower thermal resistance can enable increased brightness operation without exceeding the maximum allowable Tj for a given lifetime. A significant portion of the junction-to-case thermal resistance comes from the joint between chip and substrate, or the die-attach layer. In this study, we evaluated three different types of leading die-attach materials; silver epoxy, lead-free solder, and an emerging nanosilver paste. Each of the three was processed via their respective physical and chemical mechanisms: epoxy curing by cross-linking of polymer molecules; intermetalic soldering by reflow and solidification; and nanosilver sintering by solid-state atomic diffusion. High-power LED chips with a range of chip areas from 3.9 mm2 to 9.0 mm2 were attached by the three types of materials onto metalized aluminum nitride substrates, wire-bonded, and then tested in an electro-optical setup. The junction-to-heatsink thermal resistance of each LED assembly was determined by the wavelength shift methodology. We found that the average thermal resistance in the chips attached by the nanosilver paste was the lowest, and it was highest from the chips attached by the silver epoxy. For the 3.9 mm2 die, the difference was about 0.6°C/W, while the difference between the sintered and soldered was about 0.3°C/W. The lower thermal resistance in the sintered joints is expected to significantly improve the photometric flux from the device. Simple calculations, excluding high current efficiency droop, predict that the brightness improvement could be as high as 50% for the 3.9 mm2 chip. The samples will be functionally tested at high current, in both steady-state and pulsed operation, to determine brightness improvements, including the impact of droop. Nanosilver die-attach on a range of chip sizes up to 12 mm2 are also considered and discussed.
The LTCC Chip for Electrochemical Measurement of DNA Concentration
Authors: Bembnowicz Paweł , Herbut Piotr , Halek Patryk , Teterycz Helena , Golonka Leszek J. , Małodobra Małgorzata , Dobosz Tadeusz
Published: October 2015

The LTCC (low temperature cofired ceramics) technology still finds new applications. In this paper LTCC chamber for measurements of DNA (deoxyribonucleic acid) concentration is described. The ceramic chip with electrodes is shown. The platinum paste is used for three buried electrodes construction. The results of electrochemical DNA concentration measurements inside ceramic structure are shown.
Thin Film on LTCC for Connectivity and Conductivity
Authors: Wolf J.A. , Peterson K.A.
Published: October 2015

The topic of this paper is the development and characterization of multilayer thin films on low temperature cofired ceramic (LTCC) for the purpose of attaining robust connectivity and improved conductivity, aimed at the RF single digit GHz frequency range. The aspect of connectivity primarily covers both standard SnPb eutectic solder as well as Au wire/wedge connections to the same thin film materials. This multipurpose film ages well, as do solder joints—even after rework. In circuit development, this allows the reappropriation of solder pads for wire bond purposes and vice versa, greatly enhancing the flexibility of the substrates. The useful lifetime of such substrates has been extended significantly by this work. The photolithographically-defined circuits further enable smaller features and tolerances and better geometric uniformity. Vias received special attention due mainly to topography encountered at via boundaries and at the top of vias. Preparation and pattern generation for the thin film traces and pads will be discussed with attention to each material and thickness. Ion milling and postprocessing for solder masking as well as unique soldering properties of the film edges are also presented. The results for adhesion and performance with respect to the various functions will be presented, as well as a detailed study of the thin film integrity and robustness.
X-Ray Inspection of LTCC Devices: Theory and Practice
Authors: Zaraska Krzysztof , Gaudyn Janina , Bienńkowski Adam , Dohnalik Marek , Czerwiński Andrzej , Płuska Mariusz , Machnik Monika , Wójcik Katarzyna
Published: October 2015

The appeal of the LTCC (low temperature cofired ceramic) process lies in the possibility of creating multilayer (3D) structures, integrating conductor paths between passive elements, such as inductors, resistors, and resonance cavities. Unfortunately, the very nature of a cofired device makes postfiring optical inspection of buried elements impossible, as the ceramic material is opaque to visible light. This limitation, however, does not exist at x-ray wavelengths. The aim of this paper is to provide a practical overview of the application of high resolution x-ray imaging for nondestructive inspection and fault detection in multilayer LTCC structures. First, we present a simplified mathematical description of x-ray absorption inside an LTCC structure and demonstrate that due to the physical properties of the substrate (glass/Al2O3 ceramic), the conductor material (silver), and the cavity fill (air), a high contrast image of the investigated structure can be obtained. Next, we show the application of a commercial off the shelf industrial x-ray system for imaging various faults in LTCC structures, such as via voids (caused by inadequate filling of a via hole with conductor material), microcracks, paste creep (during lamination, excess via conductor leaks out of the via hole and in between the tape layers, shorting the via to an adjacent circuit), interruptions in conductor paths, and alignment errors. We also demonstrate the application of computed tomography to verify 3D geometry of buried resonance cavities and detect tape delaminations. Finally, we discuss the limitations of the method, related to structure thickness (number of layers), material composition, imaging geometry, and equipment characteristics, such as detector resolution and spatial noise.
Excimer Laser Ablation of High Aspect Ratio Microvias Using a Novel Sensitizer-Enhanced Photopolymer
Authors: Sarwar F. , Chen Z. , Wu J. , Webster D.C. , Marinov V.R.
Published: October 2015

A new drop-in sensitizer has been developed for use with COTS negative tone photoresist to facilitate the laser fabrication of high aspect ratio microstructures in a thick film of photopolymer. Microvias with diameters as small as 50 μm have been successfully laser ablated in a 160 μm thick layer of the sensitized photoresist. Ablation rates of up to 86 nm/pulse have been achieved with an excimer laser.
Planar Double-Sided Anode Supported SOFC—Novel Design
Authors: Dziurdzia Barbara , Magonski Zbigniew
Published: October 2015

The paper presents the innovative design of a ceramic high temperature solid oxide fuel cell (SOFC) in which the anode consists of two parts: the bottom supportive part with microchannels for fuel distribution and the upper operating part which takes part in the electrochemical reaction in the cell. Both parts of the anode are made of cofired yttrium-stabilized zirconia (Ni/YSZ) foils. Microchannels as well as the manifold for combustion products are engraved mechanically in the isostatic pressed stack of Ni/YSZ foils before their firing. The electrolyte and the cathode are set on the upper functional part of the anode by successive screen printing and firing of the electrolyte paste and the cathode paste. The paper reveals details of the fuel cell processing, test fixture and measurement setup for testing the cells, as well as the results of open circuit voltage and short-circuit current measurements.
Transfer Molding Technology for Smart Power Electronics Modules: Materials and Processes
Authors: Becker K.-F. , Joklitschke D. , Braun T. , Koch M. , Thomas T. , Schreier-Alt T. , Bader V. , Bauer J. , Nowak T. , Bochow-Ness O. , Aschenbrenner R. , Schneider-Ramelow M. , Lang K.-D.
Published: October 2015

In recent years, within power electronics packaging, there has been a trend toward compact power electronics modules for automotive and industrial applications, where a smart integrated control unit for motor drives is replacing bulky substrates with discrete control logic and power electronics. Most recent modules combine control and power electronics, yielding maximum miniaturization. Transfer molding is the method of choice for cost-effective encapsulation of such modules due to robustness of the molded modules and moderate cost of packaging. But there are challenges with this type of package.

Typically, these packages are asymmetric, and thus a substrate with single sided assembly is overmolded on the component side and the substrate backside is exposed, providing a heat path for optimized cooling. This asymmetric geometry is prone to yielding warped substrates, preventing optimum thermal contact to the heat sink and also putting thermomechanical stress on the encapsulated components, possibly reducing reliability.

Such packages are truly heterogeneous, combining power ICs, wire bonds, SMDs, control ICs, substrate, and lead frame surfaces. As a result, the encapsulant used needs to adhere sufficiently to all surfaces present.

Additionally, those packages need to operate at elevated temperatures for extended time periods, for example, at 150°C for 2000 h and more, so high thermal stability is of prime importance.

Within this paper, a reference application is described integrating power and control logic inside a lead frame based molded package. Taking into account the challenges mentioned above, a detailed description of material selection for this module will be given, including material analysis, such as rheology, reactivity, and change in εr; and thermomechanical properties, in initial stage as f(t,T) and after media storage. Process development tools for module molding are used to ensure manufacturability and usability. Concluding rules for encapsulant material selection and package setup are provided.
Comparison of Gold and Copper Wire Bonding on Aluminum and Nickel-Palladium-Gold Bond Pads for Automotive Application
Authors: Tran Tu Anh , Mathew Varughese , Downey Harold
Published: October 2015

New automotive specifications derived from higher module integration and more stringent environmental requirements expect plastic packages to operate at higher junction temperatures with prolonged duration. Temperature is a key accelerating factor for failures in electronic package devices because of the thermo-mechanical, metallurgical and chemical properties of the materials used in the package. Failures in conventional plastic package at high temperatures such as 175 °C often originate from aluminum – gold wirebonding system because of the formation of Au-Al intermetallic phases and associated Kirkendall voiding which degrades the interface. Methods to overcome such reliability issues in wire bonded devices are to change either the wire material or the bond pad metallurgy or pad finishing other than aluminum which can reliably withstand operations at higher temperature and longer duration.
Inkjet Printing Technology: A Novel Bottom-up Approach for Multilayer Ceramic Components and High Definition Printed Electronic Devices
Authors: Dossou-Yovo C. , Mougenot M. , Beaudrouet E. , Bessaudou M. , Bernardin N. , Charifi F. , Coquet C. , Borella M. , Noguera R. , Modes C. , Lejeune M. , Laurier P. , Detemmerman D. , Escure P. , Laville H. , Delhotes N. , Verdeymes S.
Published: October 2015

This paper describes the methodology of thick film and multilayer ceramic capacitor (MLCC) component manufacturing by inkjet printing. The printing unit is a CeraDrop 3D multimaterial inkjet printer. Aqueous conductive and dielectric inks were formulated according to the printhead specifications in terms of viscosity, surface tension, particle size, and sedimentation. Jetting behavior was controlled and optimized to reach the best droplet characteristics with regard to the design. The numerical processing simulation tool helps to control the printing job and to identify potential beneficial issues during the processing. Therefore, printing parameters (droplet spreading, layer thickness, filling strategy, layer drying, etc.) were optimized according to material and component design characteristics. In this way, high definition and thin conductive tracks were achieved on an alumina substrate with good electrical properties. Moreover, two printheads were used to successively build 3D multimaterial MLCC components with thin dielectric and conductive layers (i) with good precision of margins compared with traditional processes, and (ii) with very high complex configurations thanks to the flexibility of the inkjet printing process. For both applications, large area components were accessible in a single batch.
The Application of PEEK to the Packaging of Implantable Electronic Devices: Water Permeation Calculation Method and Maximum Achievable Lifetime with Desiccant
Authors: Dahan Nathaniel , Donaldson Nick , Taylor Stephen , Sereno Nuno
Published: October 2015

When packaging electronics to protect from the effects of water vapor, it is essential to be able to predict how moisture will permeate the enclosure. In the context of short term medical implants, for instance, packages made of a permeable material such as a polymer may be acceptable, provided calculations and tests show that low internal relative humidity (RH) is guaranteed for the required device lifetime. A method is presented to evaluate the permeation of water vapor into a package with desiccant, and tests are described to evaluate the validity of the model experimentally. Achievable lifetimes for PEEK packages with silica gel are investigated.
Millimeter-Wave Frequency Performance of Conductor-Backed Coplanar Waveguide on FR408 Packaging Material
Authors: Aroor Supreetha , Henderson Rashaunda
Published: October 2015

This work demonstrates the performance of conductor-backed coplanar waveguide (CBCPW) lines on FR408 for millimeter-wave applications. These lines can be used as interconnects to integrate a CMOS IC with an antenna fabricated on FR408 for a low-cost system-in-package solution. To our knowledge, this is the first time coplanar lines on FR4 have been studied for millimeter-wave applications. Ansoft HFSS simulation results for 50 Ω coplanar lines show a return loss of 20 dB and an insertion loss of 0.5 dB/mm at 100 GHz. Measured results up to 67 GHz show that on average, the CBCPW lines have an attenuation constant of 0.22 dB/mm.
Electrical and Mechanical Performance of Quilt Packaging with Solder Paste by Pin Transfer
Authors: Zheng Quanling , Khan M. Ashraf , Kriman Alfred M. , Bernstein Gary H.
Published: October 2015

Electrical and mechanical performance of quilt packaging (QP), a 2D system-in-package chip-to-chip interconnection, is presented. QP employs contacts at the edges of integrated circuit dice along their vertical surfaces. Based on 3D HFSS simulations, the self-inductance of QP can be less than 100 pH, and the self-capacitance can be less than 34 fF due to the shortness of the interconnection path. QP interconnection using solder paste with pin transfer is presented, and mechanical reliability is evaluated. A new pull test system specifically designed for QP is presented. The pull force that causes failure in a set of edge interconnects totaling 3 mm width of nodules is about 658 g-force for Sn63Pb37 and 953 g-force for SAC305.
The Distribution and Transport of Alpha Activity in Tin
Authors: Clark Brett M.
Published: October 2015

The presence of alpha emitters in packaging materials poses an increased risk to device reliability as device size decreases and flip chip and 3D packaging technology becomes more widespread. Particularly troubling is the observation that alpha emission increases over time in some reported instances. Several experiments were conducted to examine alpha flux behavior in tin materials and determine the cause for the temporal alpha emissivity increase. The experiments determined the distribution of the alpha emitters within the material volume, and a mechanism based on microsegregation is presented to explain the nonuniform distribution. Data describing differential isotope distribution within tin are also presented, providing confirmation of 210Po transport within a solid tin matrix. The effects of micro-segregation and 210Po migration on alpha emissivity over time are discussed. Potential impacts from these mechanisms on alpha emissivity in packaging applications are presented.
Development of High Dielectric Strength Ceramic Film Capacitors for Advanced Power Electronics**
Authors: Ma Beihai , Narayanan Manoj , Liu Shanshan , Tong Sheng , (Balu) Balachandran U.
Published: October 2015

Ceramic film capacitors with high dielectric constant and high breakdown strength are promising for use in advanced power electronics, which would offer higher performance, improved reliability, and enhanced volumetric and gravimetric efficiencies. We have grown lead lanthanum zirconate titanate (PLZT) on nickel foils and platinized silicon (PtSi) sub-strates by chemical solution deposition. A buffer layer of LaNiO3 (LNO) was deposited on the nickel foils prior to the deposition of PLZT. We measured the following electrical properties for PLZT films grown on LNO buffered Ni and PtSi substrates, respectively: remanent polarization, ∼25.4 μC/cm2 and ∼10.1 μC/cm2; coercive electric field, ∼23.8 kV/cm and ∼27.9 kV/cm; dielectric constant at room temperature, ∼1300 and ∼1350; and dielectric loss at room temperature, ∼0.06 and ∼0.05. Weibull analysis determined the mean breakdown strength to be 2.6 MV/cm and 1.5 MV/cm for PLZT films grown on LNO buffered Ni and PtSi substrates, respectively. Residual stress analysis by x-ray diffraction revealed compressive stress of ∼−520 MPa in the ∼2-μm-thick PLZT grown on LNO buffered Ni foil, but a tensile stress of ∼210 MPa in the ∼2-μm-thick PLZT grown on PtSi substrates.
High Temperature Characterization up to 450°C of MOSFETs and Basic Circuits Realized in a Silicon-on-Insulator (SOI) CMOS Technology
Authors: Grella K. , Dreiner S. , Schmidt A. , Heiermann W. , Kappert H. , Vogt H. , Paschen U.
Published: October 2015

Standard bulk CMOS technology targets operating temperatures of not more than 175°C. Silicon-on-insulator technologies are commonly used up to 250°C. In this work, we evaluate the limit for electronic circuit function realized in thin film SOI technologies for even higher temperatures. At Fraunhofer IMS, a versatile 1.0 μm SOI-CMOS process based on 200 mm wafers is available. It features three layers of tungsten metallization with excellent reliability concerning electromigration, as well as voltage-independent capacitors, various resistors, and single-poly-EEPROMs. We present a study of the temperature dependence of MOSFETs and basic circuits produced in this process. The electrical characteristics of an NMOSFET transistor and a PMOSFET transistor are studied up to 450°C. In a second step, we investigate the functionality of a ring oscillator (representing a digital circuit) and a band gap reference as an example of a simple analog component. The frequency and the current consumption of the ring oscillator, as well as the output voltage and the current of the band gap reference, are characterized up to 450°C. We find that the ring oscillator still oscillates at this high temperature with a frequency of about one third of the value at room temperature. The output voltage of the band gap reference is in the specified range (change < 3%) up to 250°C. The deviations above this temperature are analyzed and measures to improve the circuit are discussed. The acquired data provide an important foundation to extend the application of CMOS technology to its real maximum temperature limits.
Tunable BaSrTiO3, BaZrTiO3 Ferroelectric Capacitors Embedded Inside Low Temperature Cofired Ceramics (LTCC)
Authors: Tork Hossam S. , Elshabini Aicha , Barlow Fred
Published: October 2015

This paper describes the design and processing of ferroelectric parallel plate capacitors embedded within a low temperature cofired ceramics (LTCC) structure. A capacitor is fabricated by filling a via hole with ferroelectric paste. Using ferroelectric materials, low-loss barium strontium titanate (BST) and barium zirconate titanate (BZT), as dielectric materials provide a wide range of tunability, in addition to low loss and low production cost. In addition, embedding tunable capacitors (varactors) inside LTCC reduces loss, size, weight, and cost. The paper also gives a comparison between the use of BST and BZT as tunable dielectric materials embedded inside an LTCC with respect to preparation process, applied voltage, shrinking factors, and quality factors.
Surface Characteristics of LTCC Substrates Fabricated by Pressure-Assisted Sintering
Authors: Brandt Bjoern , Rabe Torsten
Published: October 2015

Plane LTCC substrates can be produced in zero-shrinkage technology by pressure-assisted sintering. The application of axial pressure during sintering supports densification, enhances cofiring of different materials, and restrains deformation. However, the sintered surfaces are affected by the release tapes and by the setters used in the pressure-assisted sintering process. In this study, the effect of release tape particle size on the surface properties of sintered substrates was investigated. Moreover, the substitution of release tape by the use of a vitreous carbon setter was tested. Surface roughness and sheet resistances of metallic thin films on the respective samples were determined. It was found that the roughness of the substrates is not directly correlated with the adequacy of the surface for thin-film deposition. Compared with a freely sintered sample with an average roughness (Ra) of 0.31 μm, pressure-assisted sintering created smoother surfaces using fine-grained release tapes (Ra = 0.18 μm) and rougher surfaces using coarse release tapes (Ra = 0.46 mm). Still, sheet resistances were higher on all sinter-pressed samples. The vitreous carbon setter created unusual trenched surface structures, characterized by varying roughness values and intermediate sheet resistances on the LTCCs tested.
Transient Thermal Analysis as a Highly Sensitive Test Method for the Reliability Investigation of High Power LEDs During Temperature Cycle Tests
Authors: Elger Gordon , Kandaswamy Shri Vishnu , Derix Robert , Wilde Jürgen
Published: October 2015

Light emitting diodes (LEDs) are today standard and mature light sources. They have several key advantages such as small size, low energy consumption, and long lifetime. However, high reliability of the LED system is required to achieve long lifetime of the light source. Thermomechanical stress due to temperature cycling causes failure of electronic systems. The electronic component itself or the interconnect device, for example, the printed circuit board (PCB), might fail. In many cases, the weakest link is found to be the solder interconnect between the package and the board. Cracking of the interconnect causes an open circuit and the system fails. In this paper the existing methods are compared in order to investigate LED interconnect failures during temperature cycle tests such as the simple light-on test, electric resistance measurement, and the shear test. This paper describes and introduces transient thermal analysis as a measurement method. This paper presents the first reliability data analysis with transient thermal analysis of ceramic high power LED packages on printed circuit boards, that is, insulated metal substrates, during the air-to-air thermal shock test (−40°C to +125°C) and correlates it with cross sections. This work demonstrates the sensitivity of the thermal analysis to detect solder joint failures of the assembly. This paper compares the results with electric resistance measurements and light-on tests and shows that the resolution is significantly higher compared with the methods applied today. The sensitivity of the method enables the detection of a crack in a solder joint much earlier than the final failure of the joint, that is, the open circuit.
Implementing Inductor Function with Vibrating Capacitor Structures
Authors: Marinis Thomas F. , Soucy Joseph W.
Published: October 2015

One of the most common uses of inductors is in filtering electrical signals to remove oscillations over selected frequency ranges. In this application, they are combined with capacitors to build resonant circuits to either block or dissipate signals at the unwanted frequencies. Similar, but larger current capacity filters are used to eliminate oscillatory ripple voltages from DC power supply outputs. Inductors are also essential components in buck converter type power supplies in which they store energy supplied by an oscillatory source to power a circuit, which generates a constant voltage. Inductors of various constructions have proven highly successful in all of these applications, but their performance is not ideal. For one, they dissipate the energy that is stored in them via a number of mechanisms. The conductivity of the wire comprising their windings is finite, so they suffer Ohmic losses. Their magnetic fields induce eddy currents within their cores and dissipative currents in surrounding circuit elements. Inductors also exhibit parasitic capacitance between their windings, which can give rise to dielectric losses. Because of these loss mechanisms, the quality factor of an inductor, which is its time average ratio of stored to dissipated energy, is typically less than a few hundred. By contrast, mechanical resonators, fabricated from single crystal silicon, attain quality factors that are orders of magnitude higher. Hence, mechanical filters could be made with sharper roll offs and smaller bandwidths than inductor based filters. They would also be more efficient in power supply applications. Inductors are also relatively heavy components, when compared with capacitors, resistors, and integrated circuits, due to their high content of copper and iron. A mechanical oscillator could be made significantly lighter than an inductor that is capable of storing the same amount of energy. We have been investigating mechanical oscillators that use flat beams, suspended at both ends above substrates with electrode patterns that form a capacitive dive to excite oscillations in the beam. We are examining a number of configuration variables, including beam geometry, mass distribution and excitation loading. We use finite element analysis and lumped parameter models to characterize beam deflection and MatLab scripts to predict performance in electrical circuits. We are also preparing to fabricate our first design for testing.
Copper Wirebond Compatibility with Organic and Inorganic Ions Present in Mold Compounds
Authors: Mathew Varughese , Chopin Sheila , Higgins Leo , Zhang Yingrui
Published: October 2015

Copper wirebond (CuWB) packaging is emerging as a replacement to gold wire technology because of the increases in the price of gold. However, copper is more susceptible to corrosion than inert gold so there are several reliability concerns regarding the integrity of the Cu-Al interface. Copper wirebond compatibility with the surrounding encapsulating mold compound is critical, as this material combination can produce a corrosive environment in the presence of moisture and ionic impurities. Mold compounds consist of different chemical components that can yield several ionic organic and inorganic species. The effect of chloride on CuWB reliability has been published in the literature but the impact of other ions typically present in the mold compound matrix is not widely discussed. It is important to understand the role of these ions on the CuWB reliability to design appropriate mold compounds for product encapsulation as some of the ions are corrosive while others are benign or beneficial in nature. This paper examines the impact of organic anions such as formate, acetate, and oxalate, and inorganic anions phosphate and nitrites, on CuWB reliability with regard to the integrity of the vulnerable Cu-Al interface. Corrosion depends on the pH conditions of the mold compound matrix in the presence of moisture. Cu-Al integrity under various ionic concentrations and pH conditions will be presented and the effect of these ions on the corrosive behavior of chloride will be examined. The combined influences of different anions on the Cu-Al integrity will be discussed. Finally, a relatively simple method to examine the integrity of the Cu-Al interface will also be described.
Prolonging the Lifetime of PEEK Packages for Implantable Electronic Devices Using Commercially Available Vacuum Thin Film Coatings
Authors: Dahan Nathaniel , Donaldson Nick , Taylor Stephen , Sereno Nuno
Published: October 2015

For short term applications (less than three years), it may be possible to replace traditional long term packaging materials such as titanium with a biocompatible polymer such as PEEK. This paper investigates the use of commercially available thin films to decrease the water vapor permeation rate through the walls of a PEEK package. It was found that most physical vapor deposition (PVD) and plasma assisted chemical vapor deposition (PaCVD) coatings tested did not provide a significant improvement in lifetime, due to the porosity of the films produced. This is mostly linked to the morphology of the films (i.e., growth in columns which are poorly bonded together, creating a porous structure) and is exacerbated by the high surface roughness of the machined substrates. Applying a lacquer before coating reduces this effect significantly, and we found that the time constant of our coated packages was improved by a factor of 2.3. Based on the findings of our group's previous work and this paper, the maximum achievable lifetime of PEEK packages with a thin film coating and desiccant is presented. As an example, a coated cylindrical PEEK package (using atomic layer deposition, ALD) with a uniform wall thickness of 2 mm, an internal cavity size of 1.5 cm3, filled with 20% of desiccant, has a lifetime of 18.8 mo (27.2 mo with 30% of desiccant). This would be sufficient for a range of applications and provide a cheaper and more versatile packaging alternative to traditional packages.
A Resealable, Gas-Tight Packaging Technique for Silicon Microfluidic Devices
Authors: Smith Lilla Safford , Hoople Gordon D. , Cheng Jim C. , Pisano Albert P.
Published: October 2015

Recent efforts have led to the development of a silicon microfluidic cooling device known as the microcolumnated loop heat pipe (μCLHP). The μCLHP, like a traditional heat pipe, utilizes phase change of a liquid to rapidly draw heat away from a concentrated hot spot. Proper gas-tight packaging of this device is critical for the reliable testing of the recirculating fluid. This work presents a novel approach to filling and sealing the μCLHP. A miniature valve (Beswick M3SV-N) is bonded to the silicon fill ports of the μCLHP. The use of a resealable valve, as opposed to a permanent sealing method, allows the device to be filled, sealed, and then evacuated for testing with different fluids and at multiple pressures. Building on earlier work, the fill ports on the μCLHP were metalized with a Cr (10 nm)/Ni (200 nm)/Au (10 nm) stack. Then a lead-based solder was used to bond the stainless steel adapter to the metalized layers. Leak testing of devices sealed using these miniature valves demonstrated average hourly percent weight losses between 0.17% and 0.82%. While this bonding method has been developed specifically for the μCLHP, it is broadly applicable to most ceramic microfluidic devices, especially those fabricated from silicon and glass. Due to the time-intensive manufacturing process of microfluidic devices made from these hard materials, a novel, robust, resealing method that allows reuse of a single silicon microfluidic device for multiple test conditions is highly desirable.
Comparison of Different Methods for Stress and Deflection Analysis in Embedded Die Packages During the Assembly Process
Authors: Macurova K. , Bermejo R. , Pletz M. , Schöngrundner R. , Antretter T. , Krivec T. , Morianz M. , Brizoux M. , Lecavelier A.
Published: October 2015

Important topics for electronic packages are thermally induced stresses created during package manufacturing and their role in mechanical failure. In the present paper, an analytical and a numerical analysis of the assembly process (component attached with an adhesive to a copper foil) is investigated. This process is prior to the lamination of the printed circuit board. Stresses develop due to a mismatch of coefficients of thermal expansion and particularly to shrinkage associated with adhesive polymerization. The analytical investigation is based on the classical laminate theory and an interfacial model. The three-dimensional, numerical, finite element model is capable of using geometric and material properties not possible to investigate analytically. In particular, the influence of the adhesive meniscus and plastic material models for copper and adhesive are investigated. The models are validated experimentally by an x-ray diffraction method (rocking-curve technique) showing a good agreement of the calculated and measured curvature radius values.
Baruch Spinoza and the naturalisation of the Bible: An epistemological investigation
Authors: Gronum Nicolaas J.
Published: October 2015

This article investigates the naturalisation of the Bible. Three voices are of special importance in the narrative presented in this article; they are Aristotle (384–322 BC), Rene Descartes (1596–1650) and Baruc Spinoza (1632–1677). This article will investigate the scientific method and metaphysics espoused by each of the three scholars, thereby highlighting changes in scientific method and metaphysics that lead to the naturalisation of the Bible. Firstly, Aristotle pioneered a scientific method (his logic) that would dominate for centuries, as well as a highly influential metaphysics. Secondly, Descartes, witnessing the horrors of the Thirty Years War and seeing first-hand the new discoveries that brought about the scientific revolution, reacted against Aristotle’s metaphysics. Ironically he then used Aristotle’s scientific method to provide a foundation for the new science resulting in Descartes’s famous dualism. Thirdly, Spinoza, equally horrified by the amount of religious violence of his time, reacts against Descartes’s dualism, providing scholars with a monist metaphysics that would contribute greatly to the naturalisation of the Bible. This article will be relevant to theologians who wish to engage more fully with contemporary Western culture.
A Potential Role for Mononuclear Phagocytes in Cutaneous Ulcer Development in Human Immunodeficiency Virus–Leishmania braziliensis Coinfection
Authors: Guimarães Luiz H. , Saldanha Maíra , Menezes Taís , Moreno Lis , Torres Alex , Costa Rúbia , Passos Sara , Badaró Roberto , Arruda Sérgio , Carvalho Lucas P.
Published: October 2015

Skin ulcer development in cutaneous leishmaniasis due to Leishmania braziliensis infection is associated with a mononuclear cell infiltrate and high levels of tumor necrosis factor (TNF). Herein, we show that despite the absence of Leishmania-driven TNF, a cutaneous leishmaniasis patient with acquired immunodeficiency syndrome developed a skin ulcer. The presence of mononuclear phagocytes and high levels of TNF, chemokine (C-C motif) ligand 2 (CCL2), and metalloproteinase-9 in tissue are identified as potential contributors to immunopathology observed in L. braziliensis-infected patients.
A Unique Plasmodium falciparum K13 Gene Mutation in Northwest Ethiopia
Authors: Bayih Abebe Genetu , Getnet Gebeyaw , Alemu Abebe , Getie Sisay , Mohon Abu Naser , Pillai Dylan R.
Published: October 2015

Artemisinin combination therapy (ACT) is the first line to treat uncomplicated Plasmodium falciparum malaria worldwide. Artemisinin treatment failures are on the rise in southeast Asia. Delayed parasite clearance after ACT is associated with mutations of the P. falciparum kelch 13 gene. Patients (N = 148) in five districts of northwest Ethiopia were enrolled in a 28-day ACT trial. We identified a unique kelch 13 mutation (R622I) in 3/125 (2.4%) samples. The three isolates with R622I were from Negade-Bahir and Aykel districts close to the Ethiopia–Sudan border. One of three patients with the mutant strain was parasitemic at day 3; however, all patients cleared parasites by day 28. Correlation between kelch 13 mutations and parasite clearance was not possible due to the low frequency of mutations in this study.
Increased aridity in southwestern Africa during the warmest periods of the last interglacial
Authors: Urrego D. H. , Sánchez Goñi M. F. , Daniau A.-L. , Lechevrel S. , Hanquiez V.
Published: October 2015

Abstract. Terrestrial and marine climatic tracers from marine core MD96-2098 were used to reconstruct glacial–interglacial climate variability in southwestern Africa between 194 and 24 thousand years before present. The pollen record documented three pronounced expansions of Nama-karoo and fine-leaved savanna during the last interglacial (Marine Isotopic Stage 5 – MIS 5). These Nama-karoo and fine-leaved savanna expansions were linked to increased aridity during the three warmest substadials of MIS 5. Enhanced aridity potentially resulted from a combination of reduced Benguela Upwelling, expanded subtropical high-pressure cells, and reduced austral-summer precipitation due to a northward shift of the Intertropical Convergence Zone. Decreased austral-winter precipitation was likely linked to a southern displacement of the westerlies. In contrast, during glacial isotopic stages MIS 6, 4 and 3, fynbos expanded at the expense of Nama-karoo and fine-leaved savanna indicating a relative increase in precipitation probably concentrated during the austral winter months. Our record also suggested that warm–cold or cold–warm transitions between isotopic stages and substages were punctuated by short increases in humidity. Increased aridity during MIS 5e, 5c and 5a warm substages coincided with minima in both precessional index and global ice volume. On the other hand, austral-winter precipitation increases were associated with precession maxima at the time of well-developed Northern Hemisphere ice caps.