Feasibility of self-structured current accessed bubble devices in spacecraft recording systems

The self-structured, current aperture approach to magnetic bubble memory is described. Key results include: (1) demonstration that self-structured bubbles (a lattice of strongly interacting bubbles) will slip by one another in a storage loop at spacings of 2.5 bubble diameters, (2) the ability of self-structured bubbles to move past international fabrication defects (missing apertures) in the propagation conductors (defeat tolerance), and (3) moving bubbles at mobility limited speeds. Milled barriers in the epitaxial garnet are discussed for containment of the bubble lattice. Experimental work on input/output tracks, storage loops, gates, generators, and magneto-resistive detectors for a prototype device are discussed. Potential final device architectures are described with modeling of power consumption, data rates, and access times. Appendices compare the self-structured bubble memory from the device and system perspectives with other non-volatile memory technologies

A Digital Manufacturing Process For Three-Dimensional Electronics

Additive manufacturing (AM) offers the ability to produce devices with a degree of three-dimensional complexity and mass customisation previously unachievable with subtractive and formative approaches. These benefits have not transitioned into the production of commercial electronics that still rely on planar, template-driven manufacturing, which prevents them from being tailored to the end user or exploiting conformal circuitry for miniaturisation. Research into the AM fabrication of 3D electronics has been demonstrated; however, because of material restrictions, the durability and electrical conductivity of such devices was often limited. This thesis presents a novel manufacturing approach that hybridises the AM of polyetherimide (PEI) with chemical modification and selective light-based synthesis of silver nanoparticles to produce 3D electronic systems. The resulting nanoparticles act as a seed site for the electroless deposition of copper. The use of high-performance materials for both the conductive and dielectric elements created devices with the performance required for real-world applications. For printing PEI, a low-cost fused filament fabrication (FFF); also known as fused deposition modelling (FDM), printer with a unique inverted design was developed. The orientation of the printer traps hot air within a heated build environment that is open on its underside allowing the print head to deposit the polymer while keeping the sensitive components outside. The maximum achievable temperature was 120 °C and was found to reduce the degree of warping and the ultimate tensile strength of printed parts. The dimensional accuracy was, on average, within 0.05 mm of a benchmark printer and fine control over the layer thickness led to the discovery of flexible substrates that can be directly integrated into rigid parts. Chemical modification of the printed PEI was used to embed ionic silver into the polymer chain, sensitising it to patterning with a 405 nm laser. The rig used for patterning was a re-purposed vat-photopolymerisation printer that uses a galvanometer to guide the beam that is focused to a spot size of 155 µm at the focal plane. The positioning of the laser spot was controlled with an open-sourced version of the printers slicing software. The optimal laser patterning parameters were experimentally validated and a link between area-related energy density and the quality of the copper deposition was found. In tests where samples were exposed to more than 2.55 J/cm^2, degradation of the polymer was experienced which produced blistering and delamination of the copper. Less than 2.34 J/cm^2 also had negative effect and resulted in incomplete coverage of the patterned area. The minimum feature resolution produced by the patterning setup was 301 µm; however, tests with a photomask demonstrated features an order of magnitude smaller. The non-contact approach was also used to produce conformal patterns over sloped and curved surfaces. Characterisation of the copper deposits found an average thickness of 559 nm and a conductivity of 3.81 × 107 S/m. Tape peel and bend fatigue testing showed that the copper was ductile and adhered well to the PEI, with flexible electronic samples demonstrating over 50,000 cycles at a minimum bend radius of 6.59 mm without failure. Additionally, the PEI and copper combination was shown to survive a solder reflow with peak temperatures of 249°C. Using a robotic pick and place system a test board was automatically populated with surface mount components as small as 0201 resistors which were affixed using high-temperature, Type-V Tin-Silver-Copper solder paste. Finally, to prove the process a range of functional demonstrators were built and evaluated. These included a functional timer circuit, inductive wireless power coils compatible with two existing standards, a cylindrical RF antenna capable of operating at several frequencies below 10 GHz, flexible positional sensors, and multi-mode shape memory alloy actuators

The Quantum Socket: Three-Dimensional Wiring for Extensible Quantum Computing

Quantum computing architectures are on the verge of scalability, a key requirement for the implementation of a universal quantum computer. The next stage in this quest is the realization of quantum error correction codes, which will mitigate the impact of faulty quantum information on a quantum computer. Architectures with ten or more quantum bits (qubits) have been realized using trapped ions and superconducting circuits. While these implementations are potentially scalable, true scalability will require systems engineering to combine quantum and classical hardware. One technology demanding imminent efforts is the realization of a suitable wiring method for the control and measurement of a large number of qubits. In this work, we introduce an interconnect solution for solid-state qubits: The quantum socket. The quantum socket fully exploits the third dimension to connect classical electronics to qubits with higher density and better performance than two-dimensional methods based on wire bonding. The quantum socket is based on spring-mounted micro wires the three-dimensional wires that push directly on a micro-fabricated chip, making electrical contact. A small wire cross section (~1 mmm), nearly non-magnetic components, and functionality at low temperatures make the quantum socket ideal to operate solid-state qubits. The wires have a coaxial geometry and operate over a frequency range from DC to 8 GHz, with a contact resistance of ~150 mohm, an impedance mismatch of ~10 ohm, and minimal crosstalk. As a proof of principle, we fabricated and used a quantum socket to measure superconducting resonators at a temperature of ~10 mK.Comment: Main: 31 pages, 19 figs., 8 tables, 8 apps.; suppl.: 4 pages, 5 figs. (HiRes figs. and movies on request). Submitte

Evaluation of phase change materials for reconfigurable interconnects

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 76-80).The possible use of programmable integrated circuit interconnect vias using an indirectly heated phase change material is evaluated. Process development and materials investigations are examined. Devices capable of multiple cycles between on/off states for reconfigurable applications have been successfully demonstrated in a standard CMOS-compatible technology. Building computer chips with these vias would create a new kind of field programmable gate array (FPGA), whereby the design can be reconfigured depending on its application. The phase change reprogrammable-via is nonvolatile, unlike SRAM-based technology. It also has a relatively low on-state resistance and occupies less real estate on the chip. As the "switches" are placed at the metallization level, it provides flexibility for the designer to place them. Programmable-via can operate at a relatively low voltage compared to FLASH-based technology. Similar to the case of antifuses, programmable-via interconnect structures are projected to be radiation hard. However, the most challenging part of implementation is the circuit design. Issues such as integration of materials and design with current tools need to be overcome. A lack of expert personnel in this area also makes the implementation of programmable-via FPGAs complicated. The market for FPGA is promising due to the attraction of the programmable logic market. An intellectual Property (IP) analysis indicates there exist a significant new space for exploration in this area. The best-suited business model is as a new start-up that demonstrates feasibility and develops intellectual property. The potential commercialization of such technology is also discussed. Although this concept is promising result, more research is needed to show the reliability and feasibility of such a technology in complex circuits. It will take some time before this approach can be considered for production.by Chee Ying Khoo.M.Eng

The Development of Novel Interconnection Technologies for 3D Packaging of Wire Bondless Silicon Carbide Power Modules

This dissertation advances the cause for the 3D packaging and integration of silicon carbide power modules. 3D wire bondless approaches adopted for enhancing the performance of silicon power modules were surveyed, and their merits were assessed to serve as a vision for the future of SiC power packaging. Current efforts pursuing 3D wire bondless SiC power modules were investigated, and the concept for a novel SiC power module was discussed. This highly-integrated SiC power module was assessed for feasibility, with a focus on achieving ultralow parasitic inductances in the critical switching loops. This will enable higher switching frequencies, leading to a reduction in the size of the passive devices in the system and resulting in systems with lower weight and volume. The proposed concept yielded an order-of-magnitude reduction in system parasitics, alongside the possibility of a compact system integration. The technological barriers to realizing these concepts were identified, and solutions for novel interconnection schemes were proposed and evaluated. A novel sintered silver preform was developed to facilitate flip-chip interconnections for a bare-die power device while operating in a high ambient temperature. The preform was demonstrated to have 3.75× more bonding strength than a conventional sintered silver bond and passed rigorous thermal shock tests. A chip-scale and flip-chip capable power device was also developed. The novel package combined the ease of assembly of a discrete device with a performance exceeding a wire bonded module. It occupied a 14× smaller footprint than a discrete device, and offered power loop inductances which were less than a third of a conventional wire bonded module. A detailed manufacturing process flow and qualification is included in this dissertation. These novel devices were implemented in various electrical systems—a discrete Schottky barrier diode package, a half-bridge module with external gate drive, and finally a half-bridge with integrated gate driver in-module. The results of these investigations have been reported and their benefits assessed. The wire bondless modules showed \u3c 5% overshoot under all test conditions. No observable detrimental effects due to dv/dt were observed for any of the modules even under aggressive voltage slew rates of 20-25 V/ns

Novel patterning technology for the LTCC based packaging of an optical encoder

Powder blasting technology is proposed in this thesis as a new structuring tool for Low Temperature Co-fired Ceramic (LTCC). The process, consisting of mechanical abrasion through high speed particles, is mostly used on brittle material but was successfully adapted for the patterning of microstructures onto the fragile green tape substrate, through the manufacturing of novel stencil masks. These masks are based on high resolution patterned nickel sheet produced using UV-LIGA process or laser cutting coated with a thin layer of photopolymer which prevents efficiently the metal sheet deformations under particles bombardment. The magnetic properties of the metal allowed magnetic clamping to be used to maintain the mask down onto the substrate. The etching rate of the metal was shown to be low enough at a pressure of 50 psi (344kPa) at a distance nozzle-substrate (N-S) of 20mm and 50mm so that the mask could be re-used several times and ensured good pattern transfer quality from the mask to the substrate. The process was systematically characterised on DuPont 951 P2 (~165μm thick) green tapes. The erosion of the green tape ceramic was then characterised with the micro-patterned electroplated masks. It showed that the powder blasted structures had U shape walls and verticality of the walls closed to 90o can be obtained with increasing the number of passes. The structures have smooth edges and do not have any melting parts. Smoother structures were obtained with distance nozzle-substrate of 50mm favouring lower under etching of about 15-20μm at the expense of a three times increase in process duration. Vias as small as 62μm in entry diameter and 20μm exit diameter were produced along with beams 25μm top width and 54μm bottom width were produced. Following the green tape characterisation, a LTCC package for an optical encoder featuring 16 layers with the glass cavity was manufactured. 45x45mm nickel masks coated with LF55gn flexopolymer were produced featuring stacking pins, fiducials, cavities and circular apertures ranging from 100μm to 400μm diameters for interconnections. Each mask was powder blasted at 50 psi for a flow rate of about 0.1g/s, a distance N-S of 20mm and a speed of 5mm/s. The optical encoder was successfully attached on the package and tested

Diode laser modules based on laser-machined, multi-layer ceramic substrates with integrated water cooling and micro-optics

This thesis presents a study on the use of low temperature co-fired ceramic (LTCC) material as a new platform for the packaging of multiple broad area single emitter diode lasers. This will address the recent trend in the laser industry of combining multiple laser diodes in a common package to reach the beam brightness and power required for pumping fibre lasers and for direct-diode industrial applications, such as welding, cutting, and etching. Packages based on multiple single emitters offer advantages over those derived from monolithic diode bars such as higher brightness, negligible thermal crosstalk between neighbouring emitters and protection against cascading failed emitters. In addition, insulated sub-mounted laser diodes based on telecommunication standards are preferred to diode bars and stacks because of the degree of assembly automation, and improved lifetime. At present, lasers are packaged on Cu or CuW platforms, whose high thermal conductivities allow an efficient passive cooling. However, as the number of emitters per package increases and improvements in the laser technology enable higher output power, the passive cooling will become insufficient. To overcome this problem, a LTCC platform capable of actively removing the heat generated by the lasers through impingement jet cooling was developed. It was provided with an internal water manifold capable to impinge water at 0.15 lmin-1 flow rate on the back surface of each laser with a variation of less than 2 °C in the temperature between the diodes. The thermal impedance of 2.7°C/W obtained allows the LTCC structure to cool the latest commercial broad area single emitter diode lasers which deliver up to 13 W of optical power. Commonly, the emitters are placed in a “staircase” formation to stack the emitters in the fast-axis, maintaining the brightness of the diode lasers. However, due to technical difficulties of machining the LTCC structure with a staircase-shaped face, a novel out-plane beam shaping method was proposed to obtain an elegant and compact free space combination of the laser beam on board using inexpensive optics. A compact arrangement was obtained using aligned folding mirrors, which stacked the beams on top of each other in the fast direction with the minimum dead space

SYSTEM-LEVEL APPROACHES FOR IMPROVING PERFORMANCE OF CANTILEVER-BASED CHEMICAL SENSORS

This work presents the development of different technologies and techniques for enhancing the performance of cantilever-based MEMS chemical sensors. The developed methods address specifically the sensor metrics of sensitivity, selectivity, and stability. Different techniques for improving the quality and uniformity of deposited sorbent polymer films onto MEMS-based micro-cantilever chemical sensors are presented. A novel integrated recess structure for constraining the sorbent polymer layer to a fixed volume with uniform thickness was developed. The recess structure is used in conjunction with localized polymer deposition techniques, such as inkjet printing and spray coating using shadow masking, to deposit controlled, uniform sorbent layers onto specific regions of chemical sensors, enhancing device performance. The integrated recess structure enhances the stability of a cantilever-based sensor by constraining the deposited polymer layers away from high-strain regions of the device, reducing Q-factor degradation. Additionally, the integrated recess structure enhances the sensitivity of the sensor by replacing chemically-inert silicon mass with ‘active’ sorbent polymer mass. Finally, implementation of localized polymer deposition enables the use of sensor arrays, where each sensor in the array is coated with a different sorbent, leading to improved selectivity. In addition, transient signal generation and analysis for mass-sensitive chemical sensing of volatile organic compounds (VOCs) in the gas phase is investigated. It is demonstrated that transient signal analysis can be employed to enhance the selectivity of individual sensors leading to improved analyte discrimination. As an example, elements of a simple alcohol series and elements of a simple aromatic ring series are distinguished with a single sensor (i.e. without an array) based solely on sorption transients. Transient signals are generated by the rapid switching of mechanical valves, and also by thermal methods. Thermally-generated transients utilize a novel sensor design which incorporates integrated heating units onto the cantilever and enables transient signal generation without the need for an external fluidic system. It is expected that the thermal generation of transient signals will allow for future operation in a pulsed mode configuration, leading to reduced drift and enhanced stability without the need for a reference device. Finally, A MEMS-based micro thermal pre-concentration (µTPC) system for improving sensor sensitivity and selectivity is presented. The µTPC enhances sensor sensitivity by amplifying low-level chemical concentrations, and is designed to enable coarse pre-filtering (e.g. for injection into a GC system) by means of arrayed and individually-addressable µTPC devices. The system implements a suspended membrane geometry, enhancing thermal isolation and enabling high temperature elevations even for low levels of heating power. The membranes have a large surface area-to-volume ratio but low thermal mass (and therefore, low thermal time constant), with arrays of 3-D high aspect-ratio features formed via DRIE of silicon. Integrated onto the membrane are sets of diffused resistors designed for performing thermal desorption (via joule heating) and for measuring the temperature elevation of the device due to the temperature-dependent resistivity of doped silicon. The novel system features integrated real-time chemical sensing technology, which allows for reduced sampling time and a reduced total system dead volume of approximately 10 µL. The system is capable of operating in both a traditional flow-through configuration and also a diffusion-based quasi-static configuration, which requires no external fluidic flow system, thereby enabling novel measurement methods and applications. The ability to operate without a forced-flow fluidic system is a distinct advantage and can considerably enhance the portability of a sensing system, facilitating deployment on mobile airborne platforms as well as long-term monitoring stations in remote locations. Initial tests of the system have demonstrated a pre-concentration factor of 50% for toluene.Ph.D