690 research outputs found
Stress analysis and optimization of a Flip chip on flex electronic packaging method for functional electronic textiles
No full textA method for packaging integrated circuit (IC) silicon die in thin flexible circuits has been investigated that enables circuits to be subsequently integrated within textile yarns. This paper presents an investigation into the required materials and component dimensions in order to maximize the reliability of the packaging method. Two die sizes of 3.5 mm x 8 mm x 0.53 mm and 2 mm x 2mm x 0.1 mm have been simulated and evaluated experimentally under shear load and during bending. The shear and bending experimental results show good agreement with the simulation results and verify the simulated optimal thickness of the adhesive layer. Three under-fill adhesives (EP30AO, EP37-3FLF and Epo-Tek 301 2fl), three highly flexible adhesive (Loctite 4860, Loctite 480 and Loctite 4902) and three substrates (Kapton, Mylar and PEEK) have been evaluated and the optimal thickness of each is found. The Kapton substrate, together with the EP37-3FLF adhesive, were identified as the best materials combination, with the optimum under-fill and substrate thickness identified as 0.05 mm. </span
Electronic packaging for functional electronic textiles
No full textAn electronic textile (e-textile) is a textile with integrated electronic functionality. It can be used in many areas, for example, clothing, medical, furniture and aerospace applications. The combination of electronics with textiles requires the use of flexible circuit technology, with electronic components mounted on polymer substrates with conductive tracks, to ensure the textile retains as much as possible their normal physical characteristics and feel. E-textiles in wearable applications are subject to human motion activities and as such the integrated electronic components can be vulnerable to different kinds of stresses such as bending. These forces can potentially shear, pull off or damage the components despite the electronic packaging methods used to protect them. Similarly, temperature changes in the environment can induce thermal expansion stresses in the electronic packaging or components which may result in failure. Therefore the need to develop a new reliable electronic packaging method for e-textiles to mitigate these stresses becomes increasingly important.This thesis presents research into a new reliable packaging technique capable of protecting components against twisting, bending or shear stresses. The use of this packaging technique has been evaluated with the ultra-thin die mounted onto thin flexible polymer film strip which contains conductive tracks for electrical interconnections and power supply for electronics. This electronic strip can be subsequently formed into yarns or woven into a textile. The review of electronic packaging techniques for forming electronic connects between the die and substrate such as flip chip bonding, anisotropic adhesives bonding and wire bonding are also included in this thesis.Finite element analysis (FEA) of the electronic strip is also presented. FEA simulations are used to evaluate the mechanical performance of different electronic packaging assemblies. An FEA investigation is presented in the materials and component dimensions in order to maximize the reliability of the packaging method. The three-point bending, shear, tensile and thermal expansion modelling have been simulated and, in the case of shear load and bending, results validated against an experimental evaluation. The shear and bending experimental results show good agreement with the simulation results and verify the simulated optimal thickness of the adhesive layer. Three under-fill adhesives (EP30AO, EP37-3FLF and Epo-Tek 301 2fl), five highly flexible adhesives (MK055, Nu355, Loctite 4860, Loctite 480 and Loctite 4902) and three substrates (Kapton, Mylar and PEEK) have been evaluated and the optimal thickness of each is found. The Kapton substrate, together with the EP37-3FLF adhesive, was identified as the best materials combination, with the optimum under-fill and substrate thickness identified as 0.05 mm.A novel method for packaging electronics using a thermally deformed Kapton was introduced. The design process for the jig that was used to deform the Kapton and the minimum temperature (360 °C) and time (60 Sec) needed to deform the Kapton has been investigated. This is also the first demonstrated method for reliably incorporating electronic circuits in a textile and that can withstand up to 45, 150,000 and 1470 cycles of machine washing, 180 degree twist test and 90 degree bending test respectively. The new ultra-thin silicon chip (0.025 mm thickness) fabrication method has also been introduced in this thesis to increase the flexibility of the electronic packaging method for functional electronic textiles
Radio frequency-enabled “green” Large Area Electronics: from robust sensors to biodegradable antennas
No full textStress analysis of flexible packaging for the integration of electronic components within woven textiles
No full textThis paper presents the use of Finite Element Analysis (FEA) to model a new packaging technique capable of minimizing the impact of bending or shear stresses on components integrated within the yarn of an electronic textile. FEA has been used to model four conditions: shear load, tensile load, three point bending load and a change in temperature. Three types of adhesive (Dymax 3031, Delomonopox Mk055 and Delomonopox NU355) combined with three substrate materials, PEEK, Kapton and Mylar have been analyzed. The Kapton substrate with the Dymax 3031 adhesive are identified as the preferred material combination for the packaging assembly. The simulation results indicate that the lower Young's modulus of the adhesive and substrate materials produces smaller stresses in the shear, tensile and bending models. The lower coefficient of thermal expansion (CTE) of these materials also produces lower stresses when thermally cycled
Stress analysis and optimization of a Flip chip on flex electronic packaging method for functional electronic textiles
No full textA method for packaging integrated circuit (IC) silicon die in thin flexible circuits has been investigated that enables circuits to be subsequently integrated within textile yarns. This paper presents an investigation into the required materials and component dimensions in order to maximize the reliability of the packaging method. Two die sizes of 3.5 mm x 8 mm x 0.53 mm and 2 mm x 2mm x 0.1 mm have been simulated and evaluated experimentally under shear load and during bending. The shear and bending experimental results show good agreement with the simulation results and verify the simulated optimal thickness of the adhesive layer. Three under-fill adhesives (EP30AO, EP37-3FLF and Epo-Tek 301 2fl), three highly flexible adhesive (Loctite 4860, Loctite 480 and Loctite 4902) and three substrates (Kapton, Mylar and PEEK) have been evaluated and the optimal thickness of each is found. The Kapton substrate, together with the EP37-3FLF adhesive, were identified as the best materials combination, with the optimum under-fill and substrate thickness identified as 0.05 mm
M♮-convexity, S-convexity, and their applications in operations
No full textMany problems in operations management are embedded with substitute structures which often result in parametric optimization models maximizing submodular objective functions, and it is desirable to derive structural properties including monotone comparative statics of the optimal solutions or preservation of submodularity under the optimization operations. Yet, this task is challenging because the classical and commonly used results in lattice programming, applicable to optimization models with supermodular objective function maximization, does not apply. In this thesis, by employing a key concept in discrete convex analysis, M♮-convexity, we establish conditions under which the optimal solutions are nonincreasing in the parameters and the preservation property holds for parametric maximization models with submodular objectives, together with the development of several new fundamental properties of M♮-convexity.
Furthermore, we propose a new concept of S-convexity (and its variant SSQS- convexity) which includes M♮-convexity as a subclass, and extend those results established for M♮-convexity to continuous S-convexity. In addition, we show that S-convex functions form a subclass of supermodular functions which have a one-to-one correspondence with jointly submodular and convex functions through the conjugate operator under mild conditions. A new preservation property which is not enjoyed by M♮-convexity is presented.
Our theoretical results are applied to several notable operations models: a classical multi-product dynamic stochastic inventory model, an assemble-to-order inventory model, a production control problem with two products or facilities, a portfolio contract model, a discrete choice model, and a random yield inventory model. We illustrate that looking from the lens of M♮-convexity and S-convexity allows to facilitate the analysis of monotone comparative statics, simplify or unify the complicated proofs in the literature, and extend the results to more general settings.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2022-12-01The student, Menglong Li, accepted the attached license on 2020-09-01 at 11:22.The student, Menglong Li, submitted this Dissertation for approval on 2020-09-01 at 13:26.This Dissertation was approved for publication on 2020-09-04 at 08:52.DSpace SAF Submission Ingestion Package generated from Vireo submission #15793 on 2021-03-04 at 16:30:11Made available in DSpace on 2021-03-05T21:45:09Z (GMT). No. of bitstreams: 3
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Wearable functional e-textiles based on flexible filament circuits
No full textThe functionalisation of textiles with electronic capabilities presents diverse applications where the electronics provide health monitoring, diagnostic and treatment platforms to the wearer [1]. However, the integration methods for incorporating such electronics into the textile in the research and commercial domains often compromise the natural characteristics and end-of-use recyclability of the textile [2], and more importantly the susceptibility of the wearer where the integrated electronics remain visible to the environment. This paper introduces a platform technology in the EPSRC funded project - Novel manufacturing methods for functional electronic textiles (FETT) in Figure 1, which combines standard microelectronic circuit fabrication and textile production techniques to hide modular electronics in bespoke pockets within textiles in the form 60 µm thick polyamide filament circuits [3]. The filament circuits are not visible after integration to the wearer or their environment. Unlike other integration methods where the textile is not detachable from the integrated circuits bonded to it mechanically or chemically, these filament circuits are loosely secured within the textile and are easily removable so as to enable end-of-use recycling of the textile and prevent electronic contamination. The key novelty of the project is the patented vacuum forming packaging of its filaments before integration within the textile filed with application number PCT/GB2019/052906. The filaments are conformally encapsulated with a thermoplastic film which enhances durability of the filaments by situating the electronic layer on the neutral axis. Prototypes are shown to be reliable surviving more than 1500 bending cycles around a 90ᵒ bending angle and 50 washing cycles at 60 ᵒC. Example demonstrator applications with this technology include accelerometer and temperature sensing e-textile circuits. Textiles with in-situ processing capability using miniaturised microcontrollers have also been demonstrated with digitally sequenced LED lighting patterns on the fabric. <br/
Finite element analysis (FEA) modelling and experimental verification to optimise flexible electronic packaging for e-textiles
No full textIn this paper a three-dimensional model of a novel electronic package has been developed using Finite element analysis to evaluate the shear load, tensile, bending and thermal stresses. Simulations of a complete flexible flip chip electronic packaging method are performed to minimize stresses on the packaged electronic device to improve robustness and reliability. Three component under-fill adhesives (Loctite 4860, Loctite 480 and Loctite 4902) and three circuit substrate materials (Kapton, Mylar and PEEK) are compared and the optimal thickness of each is found by shear load, tensile load, bending test and thermal expansion simulations. A fixed die size of 3.5 mm × 8 mm × 0.53 mm has been simulated and evaluated experimentally under shear and bending load. The shear and bending experimental results show good agreement with the simulation results and verify the simulated optimal thickness of the adhesive layer. The Kapton substrate together with the Loctite 4902 adhesive were identified as the optimum in the simulation. The simulation of under-fill adhesive and substrate thickness identified an optimum configuration of a 0.045–0.052 mm thick substrate layer and a 0.042–0.045 mm thickness of the Loctite 4902 adhesive. The bending simulation has also been used to determine the neutral axis of the encapsulated electronic package in this paper, thus identifying the optimal material and thickness for the encapsulation layer of the package
Processing of printed dye sensitized solar cells on woven textiles
No full textThis paper presents the novel use of screen printing and spray coating techniques to fabricate dye sensitized solar cells on textiles for wearable energy harvesting applications. Multiple functional layers of electrodes and active materials have been deposited on everyday use polyester cotton woven fabric and high-temperature resistant glass fiber fabric. The poly cotton fabric limits processing temperatures to 150 °C, while the glass fiber textile can withstand up to 1200 °C. The surface roughness of the textiles has been significantly reduced by screen printing a polyurethane interface layer on the polyester cotton fabric and a liquid polyimide on the glass fiber textile. A silver bottom electrode layer and a bespoke titanium dioxide electron transport layer formulated for each temperature range were then screen printed onto the planarized surfaces. The devices use Iodine/Iodide (I3-/I-) as the liquid electrolyte and were sealed with a plastic PET/ITO, which also forms the counter electrodes. The printed cells have demonstrated photovoltaic (PV) power conversion efficiencies of 3.24% on polyester cotton and 4.04% on glass fiber textiles, in ambient conditions. The polyurethane and polyimide interface layers significantly enhance the performance and stability of the fabricated cells providing extended operational lifetimes. This approach is potentially suitable for the low-cost integration of PV devices into clothing and other textile applications.</p
Data for: Multi-models in predicting RNA Solvent Accessibility exhibit the contribution from none-sequential attributes and providing a globally stable modeling strategy
No full textTwo datasets used in our work were concluded in this compressed file. All the RNA structral data are in PDB format, but few of them are boundle PDB format since the number of chains are too large
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