537 research outputs found

    Novel fine pitch interconnection methods using metallised polymer spheres

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    There is an ongoing demand for electronics devices with more functionality while reducing size and cost, for example smart phones and tablet personal computers. This requirement has led to significantly higher integrated circuit input/output densities and therefore the need for off-chip interconnection pitch reduction. Flip-chip processes utilising anisotropic conductive adhesives anisotropic conductive films (ACAs/ACFs) have been successfully applied in liquid crystal display (LCD) interconnection for more than two decades. However the conflict between the need for a high particle density, to ensure sufficient the conductivity, without increasing the probability of short circuits has remained an issue since the initial utilization of ACAs/ACFs for interconnection. But this issue has become even more severe with the challenge of ultra-fine pitch interconnection. This thesis advances a potential solution to this challenge where the conductive particles typically used in ACAs are selectively deposited onto the connections ensuring conductivity without bridging. The research presented in this thesis work has been undertaken to advance the fundamental understanding of the mechanical characteristics of micro-sized metal coated polymer particles (MCPs) and their application in fine or ultra-fine pitch interconnections. This included use of a new technique based on an in-situ nanomechanical system within SEM which was utilised to study MCP fracture and failure when undergoing deformation. Different loading conditions were applied to both uncoated polymer particles and MCPs, and the in-situ system enables their observation throughout compression. The results showed that both the polymer particles and MCP display viscoelastic characteristics with clear strain-rate hardening behaviour, and that the rate of compression therefore influences the initiation of cracks and their propagation direction. Selective particle deposition using electrophoretic deposition (EPD) and magnetic deposition (MD) of Ni/Au-MCPs have been evaluated and a fine or ultra-fine pitch deposition has been demonstrated, followed by a subsequent assembly process. The MCPs were successfully positively charged using metal cations and this charging mechanism was analysed. A new theory has been proposed to explain the assembly mechanism of EPD of Ni/Au coated particles using this metal cation based charging method. The magnetic deposition experiments showed that sufficient magnetostatic interaction force between the magnetized particles and pads enables a highly selective dense deposition of particles. Successful bonding to form conductive interconnections with pre-deposited particles have been demonstrated using a thermocompression flip-chip bonder, which illustrates the applicable capability of EPD of MCPs for fine or ultra-fine pitch interconnection

    Part clamping and fixture geometric adaptability for reconfigurable assembly systems.

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    Masters of Science in Mechanical Engineering. University of KwaZulu-Natal. Durban, 2017.The Fourth Industrial Revolution is leading towards cyber-physical systems which justified research efforts in pursuing efficient production systems incorporating flexible grippers. Due to the complexity of assembly processes, reconfigurable assembly systems have received considerable attention in recent years. The demand for the intricate task and complicated operations, demands the need for efficient robotic manipulators that are required to manoeuvre and grasp objects effectively. Investigations were performed to understand the requirements of efficient gripping systems and existing gripping methods. A biologically inspired robotic gripper was investigated to establish conformity properties for the performance of a robotic gripper system. The Fin Ray Effect® was selected as a possible approach to improve effective gripping and reduce slippage of component handling with regards to pick and place procedures of assembly processes. As a result, the study established the optimization of self-adjusting end-effectors. The gripper system design was simulated and empirically tested. The impact of gripping surface compliance and geometric conformity was investigated. The gripper system design focused on the response of load applied to the conformity mechanism called the Fin Ray Effect®. The appendages were simulated to determine the deflection properties and stress distribution through a finite element analysis. The simulation proved that the configuration of rib structures of the appendages affected the conformity to an applied force representing an object in contact. The system was tested in real time operation and required a control system to produce an active performance of the system. A mass loading test was performed on the gripper system. The repeatability and mass handling range was determined. A dynamic operation was tested on the gripper to determine force versus time properties throughout the grasping movement for a pick and place procedure. The fluctuating forces generated through experimentation was related to the Lagrangian model describing forces experienced by a moving object. The research promoted scientific contribution to the investigation, analysis, and design of intelligent gripping systems that can potentially be implemented in the operational processes of on-demand production lines for reconfigurable assembly systems

    Publications of the Jet Propulsion Laboratory July 1965 through July 1966

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    Bibliography on Jet Propulsion Laboratory technical reports and memorandums, space programs summary, astronautics information, and literature searche

    Probing multivalent particle–surface interactions using a quartz crystal resonator

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    The rise in market-approved cellular therapies demands for advancements in process analytical technology (PAT) capable of fulfilling the requirements of this new industry. Unlike conventional biopharmaceuticals, cell-based therapies (CBT) are complex “live” products, with a high degree of inherent biological variability. This exacerbates the need for in-process monitoring and control of critical product attributes, in order to guarantee safety, efficacious and continuous supply of this CBT. There are therefore mutual industrial and regulatory motivations for high throughput, non-invasive and non-destructive sensors, amenable to integration in an enclosed automated cell culture system. While a plethora of analytical methods is available for direct characterization of cellular parameters, only a few satisfy the requirements for online quality monitoring of industrial-scale bioprocesses. [Continues.

    Design, Construction and Validation of a New Generation of Bioreactors for Tissue Engineering Applications.

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    132 p.The thesis reports on the design, fabrication and validation of a new generation of bioreactors for cell culture stimulation, in order to improve cell proliferation in advanced tissue engineering strategies. Bioreactors are developed to take advantage of responsive materials allowing to mimic cell microenvironments, resembling some of the most common physical stimuli within the human body. Some stimuli can be produced by polymer-based scaffolds such as magnetoelectric, which can work as mechanical and electrical actuators.Two types of bioreactors were developed: one for bone tissue engineering through magnetoelectric stimulation (through mechanical vibration and piezoelectricity) and another for muscle tissue engineering through mechanical stretching and controlled current impulses.This project encompasses several fields of engineering such as device engineering, design, mechanics and electronics, having also into account proper material selection and the final biomedical application

    Volume 3 – Conference

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    We are pleased to present the conference proceedings for the 12th edition of the International Fluid Power Conference (IFK). The IFK is one of the world’s most significant scientific conferences on fluid power control technology and systems. It offers a common platform for the presentation and discussion of trends and innovations to manufacturers, users and scientists. The Chair of Fluid-Mechatronic Systems at the TU Dresden is organizing and hosting the IFK for the sixth time. Supporting hosts are the Fluid Power Association of the German Engineering Federation (VDMA), Dresdner Verein zur Förderung der Fluidtechnik e. V. (DVF) and GWT-TUD GmbH. The organization and the conference location alternates every two years between the Chair of Fluid-Mechatronic Systems in Dresden and the Institute for Fluid Power Drives and Systems in Aachen. The symposium on the first day is dedicated to presentations focused on methodology and fundamental research. The two following conference days offer a wide variety of application and technology orientated papers about the latest state of the art in fluid power. It is this combination that makes the IFK a unique and excellent forum for the exchange of academic research and industrial application experience. A simultaneously ongoing exhibition offers the possibility to get product information and to have individual talks with manufacturers. The theme of the 12th IFK is “Fluid Power – Future Technology”, covering topics that enable the development of 5G-ready, cost-efficient and demand-driven structures, as well as individual decentralized drives. Another topic is the real-time data exchange that allows the application of numerous predictive maintenance strategies, which will significantly increase the availability of fluid power systems and their elements and ensure their improved lifetime performance. We create an atmosphere for casual exchange by offering a vast frame and cultural program. This includes a get-together, a conference banquet, laboratory festivities and some physical activities such as jogging in Dresden’s old town.:Group 8: Pneumatics Group 9 | 11: Mobile applications Group 10: Special domains Group 12: Novel system architectures Group 13 | 15: Actuators & sensors Group 14: Safety & reliabilit

    Cadmium sulphide transducers : thick vacuum-deposited films for ultrasonic shear-mode low-frequencey operation

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    The primary aim of this research project was to deposist thick-film (low-frequency) s-mode CdS piezoelectric transducers directly onto copper or aluminium rods which formed part of the welding-electrode of a spot-welding machine. These transducers were to replace the discrete transducers used in a set-up for the "on-machine" evaluation of spot-welds. A secondary aim was to deposit very thin CdS films on glass slides for use as microwave resonators. The dependence of film adhesion on film thickness, and crystallographic orientation changes with thickness imposed an upper limit on the thickness of transducers with adequate properties for applications. The final goal, established through experience on the project, was to determine how thick piezoelectric films could be deposited to make useful transducers. Highly stoichiometric (deviations from stoichiometry of the order of 1 part in 10^13 ) and highly resistive (> 10^10 Ω.m.), and highly oriented films up to 100 μm thick have been successfully deposited on Ae rod substrates. Two deposition techniques were used : CdS/S electron beam bombardment evaporation and Cd/S isothermal cells. Provided that the temperature of the vapour molecules was less than 400 degrees C and that the pumping speed could be increased at will , then, the faster the deposition rate, the sharper the oblique c-axis preferred orientation, and the better the piezoelectric performance of the films. The pumping speed limited the deposition rate to 10 μm.h^- 1. Appreciable thermal stresses in the films gave rise to large forces which induced the thick-films to flake off or disintegrate. The dependence of film adhesion on film thickness is explained in terms of the inequality between the forces which bind the film to the substrate (independent of thickness) and the forces which induce the film to flake off (proportional to thickness). Thick CdS films were made to adhere to the substrate by making the substrate surface rouqher so that the films "keyed-in". No appreciable temperature gradients existed in the CdS films during growth, either across their thicknesses or along their surfaces. No changes in temperature gradients occurred in the films due to changes in film orientation, and vice versa. Up to a certain critical thickness, the c-axes of most CdS film crystallites aligned themselves with the direction of the vapour beam. When the thickness of the film exceeded the critical thickness, the growth of oblique crystallites was stifled and the film's c-axis tilted towards the substrate-normal and eventually became parallel to it. This was confirmed by etching-back a thick CdS film which was deposited at oblique vapour incidence. A model is presented for the "stifling process” which gives the relation between the critical thickness, the grain size and the deposition angle of the film. For a given deposition environment, the stifling process imposed an upper limit on the thickness of an s-mode transducer. The use of copper substrates, and of copper parts inside the deposition chamber, was abandoned because of the corrosive action of sulphur on copper. Cu/CdS junctions were nearly ohmic, and the anomalous behaviour of these junctions is explained in terms of the reaction between Cu and S to form Cu2S. CdS s-mode transducers with untuned two-way insertion loss of 35 dB in a 50 ohm system have been successfully deposited on glass slides for operation at frequencies down to 20 MHz. The stress in CdS films on glass slides was much less than that on Ae rods. It is possible that the higher stress in films on Ae rods weakened their piezoelectric performance

    Roadmap on emerging concepts in the physical biology of bacterial biofilms: from surface sensing to community formation

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    Bacterial biofilms are communities of bacteria that exist as aggregates that can adhere to surfaces or be free-standing. This complex, social mode of cellular organization is fundamental to the physiology of microbes and often exhibits surprising behavior. Bacterial biofilms are more than the sum of their parts: single-cell behavior has a complex relation to collective community behavior, in a manner perhaps cognate to the complex relation between atomic physics and condensed matter physics. Biofilm microbiology is a relatively young field by biology standards, but it has already attracted intense attention from physicists. Sometimes, this attention takes the form of seeing biofilms as inspiration for new physics. In this roadmap, we highlight the work of those who have taken the opposite strategy: we highlight the work of physicists and physical scientists who use physics to engage fundamental concepts in bacterial biofilm microbiology, including adhesion, sensing, motility, signaling, memory, energy flow, community formation and cooperativity. These contributions are juxtaposed with microbiologists who have made recent important discoveries on bacterial biofilms using state-of-the-art physical methods. The contributions to this roadmap exemplify how well physics and biology can be combined to achieve a new synthesis, rather than just a division of labor
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