Intelligent control of an automated adhesive dispensing cell.

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Exploration Challenges: Transferring Ground Repair Techniques to Space Flight Application

Fulfilling NASA's Vision for Space Exploration will demand an extended presence in space at distances from our home planet that exceed our current experience in space logistics and maintenance. The ability to perform repairs in lieu of the customary Orbital Replacement Unit (ORU) process where a faulty part is replaced will be elevated from contingency to routine to sustain operations. The use and cost effectiveness of field repairs for ground based operations in industry and the military have advanced with the development of technology in new materials, new repair techniques and new equipment. The unique environments, accessibility constraints and Extra Vehicular Activity (EVA) issues of space operations will require extensive assessment and evolution of these technologies to provide an equivalent and expected level of assurance to mission success. Challenges include the necessity of changes in design philosophy and policy, extremes in thermal cycling, disruptive forces (such as static charge and wind entrainment) on developed methods for control of materials, dramatically increased volatility of chemicals for cleaning and other compounds due to extremely low pressures, the limits imposed on dexterity and maneuverability by current EVA equipment and practices, and the necessity of unique verification methodology. This paper describes these challenges in and discusses the effects on the established ground techniques for repair. The paper also describes the leading repair methodology candidates and their beneficial attributes for resolving these issues with the evolution of technology

Workshop on disruptive information and communication technologies for innovation and digital transformation

The workshop on Disruptive Information and Communication Technologies for Innovation and Digital transformation, organized under the scope of the DISRUPTIVE project (disruptive.usal.es) and held on December 20, 2019 in Bragança, aims to discuss problems, challenges and benefits of using disruptive digital technologies, namely Internet of Things, Big data, cloud computing, multi-agent systems, machine learning, virtual and augmented reality, and collaborative robotics, to support the on-going digital transformation in society. The main topics included: • Intelligent Manufacturing Systems • Industry 4.0 and digital transformation • Internet of Things • Cyber-security • Collaborative and intelligent robotics • Multi-Agent Systems • Industrial Cyber-Physical Systems • Virtualization and digital twins • Predictive maintenance • Virtual and augmented reality • Big Data and advanced data analytics • Edge and cloud computing • Digital Transformation The workshop program included 16 accepted technical papers, 2 invited talks and 1 technical demonstration of use cases. This volume contains six of the papers presented at the Workshop on Disruptive Information and Communication Technologies for Innovation and Digital Transformation.info:eu-repo/semantics/publishedVersio

Scrap Reduction at EFD

This project, sponsored by Electron Fusion Devices, seeks to provide the groundwork and recommendations for reducing costs resulted from wastes produced within the Injection Molding Department. Extensive background research on both Lean and Six Sigma ideals was first conducted. An analysis of their current scrap tracking tools and processes led to a focus on overall scrap reduction and made a pilot study necessary. We designed a new set of scrap tracking sheets and procedures for data collection and analysis, and recommended future steps for the company\u27s endeavor in reducing scraps

ELECTRICAL AND MECHANICAL CHARACTERIZATION OF MWNT FILLED CONDUCTIVE ADHESIVE FOR ELECTRONICS PACKAGING

Lead-tin solder has been widely used as interconnection material in electronics packaging for a long time. In response to environmental legislation, the lead-tin alloys are being replaced with lead-free alloys and electrically conductive adhesives in consumer electronics. Lead-free solder usually require higher reflow temperatures than the traditional lead-tin alloys, which can cause die crack and board warpage in assembly process, thereby impacting the assembly yields. The high tin content in lead-free solder forms tin whiskers, which has the potential to cause short circuits failure. Conductive adhesives are an alternative to solder reflow processing, however, conductive adhesives require up to 80 wt% metal filler to ensure electrical and thermal conductivity. The high loading content degrades the mechanical properties of the polymer matrix and reduces the reliability and assembly yields when compared to soldered assemblies. Carbon nanotubes (CNTs) have ultra high aspect ratio as well as many novel properties. The high aspect ratio of CNTs makes them easy to form percolation at low loading and together with other novel properties make it possible to provide electrical and thermal conductivity for the polymer matrix while maintaining or even reinforcing the mechanical properties. Replacing the metal particles with CNTs in conductive adhesive compositions has the potential benefits of being lead free, low process temperature, corrosion resistant, electrically/thermally conductive, high mechanical strength and lightweight. In this paper, multiwall nanotubes (MWNTs) with different dimensions are mixed with epoxy. The relationships among MWNTs dimension, volume resistivity and thermal conductivity of the composite are characterized. Different loadings of CNTs, additives and mixing methods were used to achieve satisfying electrical and mechanical properties and pot life. Different assembly technologies such as pressure dispensing, screen and stencil printing are used to simplify the processing method and raise the assembly yields. Contact resistance, volume resistivity, high frequency performance, thermal conductivity and mechanical properties were measured and compared with metal filled conductive adhesive and traditional solder paste

Modeling and off-line control of fluid dispensing for electronics packaging

Fluid dispensing is a method by which fluid materials are delivered to substrates, boards or work-pieces in a controllable manner. This method has been widely used in various packaging processes in the electronics manufacturing industry. In these processes, the flow rate of fluid dispensed and the profile of fluid formed on a board are the two most important performance variables to be controlled consistently. This research presents a comprehensive study on the modeling and control of the time-pressure dispensing processes. First of all, the characterization of the rheological behaviour of fluids for electronics packaging is addressed from both time-independent and time-dependent perspectives. Under the assumption that the pressure in the dispensing syringe has reached a steady-state status, a model representative of the steady-state flow rate of fluid dispensed is developed. To represent the profile of fluid formed on a board, the spreading of fluid on a board is addressed and a solution to this problem is established. To consider the influence of time-dependent fluid behaviour in fluid dispensing, a method of applying model updating technique is developed in this study. Based on this method, an off-line control of the dispensing process is developed to improve the consistency in the flow rate of fluid dispensed, which is broken by the time-dependent fluid behaviour. Taking into account air compressibility and the fluid inertia, a model is developed to represent the dynamics of the flow rate of fluid dispensed, which shows that the dynamics is sensitive to the air volume in the syringe. Based on the model, the inconsistency in the fluid amount dispensed due to the variation of the air volume in the syringe over a dispensing process is investigated, and an off-line control is developed to alleviate the amount inconsistency. Experiments on a typical commercial dispensing system are designed and carried out to verify the effectiveness of the models and the off-line control developed in this study. It is shown that the model results have an excellent agreement with the experimental results. Also, with the introduction of the off-line control, the consistency in both the flow rate and the amount of fluid dispensed can be significantly improved

Materials jetting for advanced optoelectronic interconnect: technologies and application

This report covers the work carried out on Teaching Company Scheme No. 2275 "Materials Jetting for Advanced Interconnect" between February 1998 and February 2000. The project was conducted at the Harlow laboratories of Nortel Networks with the support of the Department of Manufacturing Engineering of Loughborough University. Technical direction and supervision has been provided by Mr Paul Conway, Reader, at Loughborough University, Professor Ken Snowdon and Mr Chris Tanner of Nortel Networks. The aim of the project was to produce and deposit minute and precise volumes of a range of materials, such as metallic alloys, glasses and polymers, onto a variety of substrates commonly used in the electronics and optoelectronics fields. The technology, which is analogous to ink-jet printing, firstly had to be refined to accommodate higher processing temperatures of up to 350°C. The ultimate project deliverable was to produce a specification for jetting equipment suited towards volume manufacturing. [Continues.

Digitally driven microfabrication of 3D multilayer embedded electronic systems

The integration of multiple digitally driven processes is seen as the solution to many of the current limitations arising from standalone Additive Manufacturing (AM) techniques. A technique has been developed to digitally fabricate fully functioning electronics using a unique combination of AM technologies. This has been achieved by interleaving bottom-up Stereolithography (SL) with Direct Writing (DW) of conductor materials alongside mid-process development (optimising the substrate surface quality), dispensing of interconnects, component placement and thermal curing stages. The resulting process enables the low-temperature production of bespoke three-dimensional, fully packaged and assembled multi-layer embedded electronic circuitry. Two different Digital Light Processing (DLP) Stereolithography systems were developed applying different projection orientations to fabricate electronic substrates by selective photopolymerisation. The bottom up projection orientation produced higher quality more planar surfaces and demonstrated both a theoretical and practical feature resolution of 110 μm. A top down projection method was also developed however a uniform exposure of UV light and planar substrate surface of high quality could not be achieved. The most advantageous combination of three post processing techniques to optimise the substrate surface quality for subsequent conductor deposition was determined and defined as a mid-processing procedure. These techniques included ultrasonic agitation in solvent, thermal baking and additional ultraviolet exposure. SEM and surface analysis showed that a sequence including ultrasonic agitation in D-Limonene with additional UV exposure was optimal. DW of a silver conductive epoxy was used to print conductors on the photopolymer surface using a Musashi dispensing system that applies a pneumatic pressure to a loaded syringe mounted on a 3-axis print head and is controlled through CAD generated machine code. The dispensing behaviour of two isotropic conductive adhesives was characterised through three different nozzle sizes for the production of conductor traces as small as 170 μm wide and 40 μm high. Additionally, the high resolution dispensing of a viscous isotropic conductive adhesive (ICA) also led to a novel deposition approach for producing three dimensional, z-axis connections in the form of high freestanding pillars with an aspect ratio of 3.68 (height of 2mm and diameter of 550μm). Three conductive adhesive curing regimes were applied to printed samples to determine the effect of curing temperature and time on the resulting material resistivity. A temperature of 80 °C for 3 hours resulted in the lowest resistivity while displaying no substrate degradation. ii Compatibility with surface mount technology enabled components including resistors, capacitors and chip packages to be placed directly onto the silver adhesive contact pads before low-temperature thermal curing and embedding within additional layers of photopolymer. Packaging of components as small as 0603 surface mount devices (SMDs) was demonstrated via this process. After embedding of the circuitry in a thick layer of photopolymer using the bottom up Stereolithography apparatus, analysis of the adhesive strength at the boundary between the base substrate and embedding layer was conducted showing that loads up to 1500 N could be applied perpendicular to the embedding plane. A high degree of planarization was also found during evaluation of the embedding stage that resulted in an excellent surface finish on which to deposit subsequent layers. This complete procedure could be repeated numerous times to fabricate multilayer electronic devices. This hybrid process was also adapted to conduct flip-chip packaging of bare die with 195 μm wide bond pads. The SL/DW process combination was used to create conductive trenches in the substrate surface that were filled with isotropic conductive adhesive (ICA) to create conductive pathways. Additional experimentation with the dispensing parameters led to consistent 150 μm ICA bumps at a 457 μm pitch. A flip-chip bonding force of 0.08 N resulted in a contact resistance of 2.3 Ω at a standoff height of ~80 μm. Flip-chips with greater standoff heights of 160 μm were also successfully underfilled with liquid photopolymer using the SL embedding technique, while the same process on chips with 80 μm standoff height was unsuccessful. Finally the approaches were combined to fabricate single, double and triple layer circuit demonstrators; pyramid shaped electronic packages with internal multilayer electronics; fully packaged and underfilled flip-chip bare die and; a microfluidic device facilitating UV catalysis. This new paradigm in manufacturing supports rapid iterative product development and mass customisation of electronics for a specific application and, allows the generation of more dimensionally complex products with increased functionality