8 research outputs found

    ISOTHERMAL MECHANICAL AND THERMO-MECHANICAL DURABILITY CHARACTERIZATION OF SELECTED PB-FREE SOLDERS

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    Due to the hazards of Pb in the environment and its effect on humans and marketing competition from Japanese electronics manufacturers, the conversion to Pb-free solders in the electronics industry appears imminent. As major mechanical, thermal, and electrical interconnects between the component and the PWB, solder joints are crucial for the reliability of the most electronic packages. There is an urgent need for constitutive properties, mechanical durability and thermo-mechanical durability of Pb-free solders. A partitioned constitutive model consisting of elastic, plastic, primary creep and secondary creep models is obtained for the Sn3.9Ag0.6Cu solder and the baseline Sn37Pb solder from comprehensive monotonic and creep tests conducted on Thermo-Mechanical-Microscale (TMM) setup. The comparison between two solders shows that Sn3.9Ag0.6Cu has much better creep resistance than Sn37Pb at the low and medium stresses. The isothermal mechanical durability of three NEMI recommended Pb-free solders, Sn3.9Ag0.6Cu, Sn3.5Ag, Sn0.7Cu, is tested on the TMM setup under low creep and high creep test conditions. The damage propagation rate is also analyzed from the test data. The generic Energy-Partitioning (E-P) durability model is obtained for three Pb-free solders by using the incremental analytic model developed for TMM tests. The scatter of the test results from the prediction by these E-P durability model constants is small. The thermo-mechanical durability of the Pb-free Sn3.8Ag0.7Cu solder is investigated by a systematic approach combining comprehensive thermal cycling tests and finite element modeling. The effects of mixed solder systems, device types, and underfill are addressed in the tests. Thermal cycling results show that Sn3.8Ag0.7Cu marginally outperforms SnPb for four different components under the studied test condition. The extensive detailed three-dimensional viscoplastic FE stress and damage analysis is conducted for five different thermal cycling tests of both Sn3.8Ag0.7Cu and Sn37Pb solders. Power law thermo-mechanical durability models of both Sn3.8Ag0.7Cu and Sn3Pb are obtained from thermal cycling test data and stress and damage analysis. The energy-partitioning durability models of two solders are also obtained. It is found that the slopes of the plastic and creep curves in the E-P damage model of Pb-free solders for thermal cycling are steeper than those for mechanical cycling and those of Sn37Pb solders

    Locally Adaptive Stereo Vision Based 3D Visual Reconstruction

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    abstract: Using stereo vision for 3D reconstruction and depth estimation has become a popular and promising research area as it has a simple setup with passive cameras and relatively efficient processing procedure. The work in this dissertation focuses on locally adaptive stereo vision methods and applications to different imaging setups and image scenes. Solder ball height and substrate coplanarity inspection is essential to the detection of potential connectivity issues in semi-conductor units. Current ball height and substrate coplanarity inspection tools are expensive and slow, which makes them difficult to use in a real-time manufacturing setting. In this dissertation, an automatic, stereo vision based, in-line ball height and coplanarity inspection method is presented. The proposed method includes an imaging setup together with a computer vision algorithm for reliable, in-line ball height measurement. The imaging setup and calibration, ball height estimation and substrate coplanarity calculation are presented with novel stereo vision methods. The results of the proposed method are evaluated in a measurement capability analysis (MCA) procedure and compared with the ground-truth obtained by an existing laser scanning tool and an existing confocal inspection tool. The proposed system outperforms existing inspection tools in terms of accuracy and stability. In a rectified stereo vision system, stereo matching methods can be categorized into global methods and local methods. Local stereo methods are more suitable for real-time processing purposes with competitive accuracy as compared with global methods. This work proposes a stereo matching method based on sparse locally adaptive cost aggregation. In order to reduce outlier disparity values that correspond to mis-matches, a novel sparse disparity subset selection method is proposed by assigning a significance status to candidate disparity values, and selecting the significant disparity values adaptively. An adaptive guided filtering method using the disparity subset for refined cost aggregation and disparity calculation is demonstrated. The proposed stereo matching algorithm is tested on the Middlebury and the KITTI stereo evaluation benchmark images. A performance analysis of the proposed method in terms of the I0 norm of the disparity subset is presented to demonstrate the achieved efficiency and accuracy.Dissertation/ThesisDoctoral Dissertation Electrical Engineering 201

    Development of high-speed fibre-optical laser scanning system for defect recogntion

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    High-speed fibre-optic laser scanning systems are being used in automated industrial manufacturing environments to determine surface defects. Recent methods of surface defect detection involve the use of fibre-optic light emitting and detection assemblies. This thesis deals with the design and development o f a new high-speed photoelectronic system. In this work, two sources of emitting diode were examined, LED (light emitting diode) and laser diode. A line of five emitting diodes and five receiving photodiodes were used as light sources and detectors respectively. These arrays of emitting diodes and photodectectors were positioned opposite each other. Data capture was controlled and analysed by PC using Labview software. The system was used to measure the dimensions of the surface defects, such as holes (1 mm), blind holes (2 mm) and notches in different materials. The achieved results show that even though this system was used mainly for 2-D scanning, it may also be operated as a limited 3-D vision inspection system. This system furthermore showed that all the metal materials examined were able to reflect a signal of the infrared wavelength. A newly developed technique o f using an angled array o f fibres allows an adjustable resolution to be obtained with the system, with a maximum system resolution of approximately 1 0 0 |im (the diameter o f the collecting fibre core). This system was successfully used to measure various materials surface profile, surface roughness, thickness, and reflectivity. Aluminum, stainless steel, brass, copper, tufnol, and polycarbonate materials were all capable of being examined with the system. The advantages of this new system may be seen as faster detection, lower cost, less bulky, greater resolution and flexibility

    Listening to twining chords and wedded words in Joyce's Ulysses: an interdisciplinary approach

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    This research study aims to shed light on how Joyce made use of music in Ulysses to create a literary work that exceeded the borders of literature until then, producing an extradimensional and transdisciplinary work of art that did not fit in the classification ranks that existed in the early stage of the twentieth century. This interdisciplinary study is organised according to its main concern, which is the analysis of the influence of music in both the structure and the characterisation of Ulysses. The first section deals with the musical structure found in Joyce's masterpiece as a whole – and in each of the chapters – with a particular emphasis on the 'Sirens' episode. The next section studies the characters in Ulysses as performers, and it can subsequently be divided into two parts: the analysis of the characterisation in the work – with Joyce's own concept and use of the leitmotif –, and the study of the counterpoint between characters in Ulysses. Finally, an annex is included in which the reader will observe how Joyce referred to his work – as a whole or in parts – in terms that can be expected to describe a musical composition instead of literature. The conclusion of the annex is the result of the analysis of Joyce's letters in Ellmann's compound, and it contextualises the starting point of the study

    Stretchable and washable electronics for embedding in textiles

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    Recent Advances in Thin Film Electronic Devices

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    This reprint is a collection of the papers from the Special Issue “Recent Advances in Thin Film Electronic Devices” in Micromachines. In this reprrint, 1 editorial and 11 original papers about recent advances in the research and development of thin film electronic devices are included. Specifically, three research fields are covered: device fundamentals (5 papers), fabrication processes (5 papers), and testing methods (1 paper). The experimental data, simulation results, and theoretical analysis presented in this reprint should benefit those researchers in flat panel displays, flat panel sensors, energy devices, memories, and so on
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