Laser-assisted deposition of Cu bumps for microelectronic packaging

Cu bump was transferred using a focused laser pulse for microelectronic packaging.An Nd:YAG laser pulse (maximum energy of 500 mJ;wavelength of 1064 nm;fluences of 0.4-2.1 kJ/cm2) was irradiated on a sacrificial absorption layer with copper coating.The focused laser beam induced plasma between the semi-transparent donor slide and the sacrificial layer,causing a shock wave.The shock wave pressure pushed the Cu layer and transferred material to deposit a bump on substrate.A beam-shaper was used to produce uniform pressure at the interface to reduce fragmentation of the transferred material on the substrate.The calculated shock wave pressure with respect to laser fluence was 1-3 GPa.A Cu bump of diameter of 200 μm was successfully deposited at laser fluence of 0.6 kJ/cm 2.The pressure control at the sacrificial layer using a laser pulse was critical to produce a bump with less fragmentation.The technique can be applied to forming Cu bump for an interconnecting process in electronics.     

Internal modification in transparent hybrid germanium-silica plates using plasma formation induced by a femtosecond laser

The fabrication of an internal diffraction grating with photoinduced refractive index modification in planar hybrid germanium-silica plates was demonstrated using low-density plasma formation excited by a high-intensity femtosecond (150 fs) Ti:sapphire laser (λp=790 nm).The refractive index modifications with diameters ranging from 400 nm to 3 μm were photoinduced after plasma formation occurred upon irradiation with peak intensities of more than 2×1013 W/cm2.The graded refractive index profile was fabricated to be a symmetric around from the center of the point at which low-density plasma occurred.     

Influence of substrate bias on microstructure and morphology of ZrN thin films deposited by arc ion plating

Zirconium nitride thin films were fabricated using arc ion plating under negative substrate biases to investigate the influence of substrate bias on the ZrN films. The phase, composition, and surface morphology of the ZrN ?lms, with respect to substrate bias, were studied by XRD, EPMA, and FE-SEM, respectively. The results show that cubic ZrN and hexagonal Zr phases form in the ZrN films. The competition between surface energy and strain energy makes the preferred orientation change from (111) to (200) and then back to highly (111) preferred orientation as a function of substrate bias. With the increase of bias voltage, the crystallite size of ZrN films reduces from 30 to 15 nm. Meanwhile, the film microstructure evolves from an apparent columnar structure to a highly dense equiaxed structure, indicating that the ion bombardment enhanced by substrate bias can suppress the columnar growth in the ZrN films. Deposition rate and mole ratio of Zr to N increase with the increase of bias voltage and reach the maximum at –50 V, and then show a decline trend when bias voltage further increases.     

HYSYS的二次开发及其在多组分气体膜分离过程模拟中的应用

通过把自行开发的膜分离数学模拟软件嵌入HYSYS,形成了膜分离计算模块(M-100),成功实现对商业化工计算软件进行二次开发.与其它类似软件的对比显示,该模块用于多组分气体膜分离过程模拟时具有较高的可靠性.在此基础上运用该软件对含CO2多组分气体膜分离过程进行了模拟计算.计算结果显示:采用单级膜分离过程,渗透气循环工艺的分离效率高于尾气循环工艺,但能耗较高;采用多级膜分离过程,串联工艺分离产物中CO2的浓度较高,而并联工艺渗透气流量较高,通过串/并联组合可获得较理想的分离效果.     

Limit load analyses of helical coiled steam generator tubes with a volumetric flaw

Maintaining structural integrity of piping has always been an important effort in the nuclear power industry. To resolve piping issues such as unanticipated failures caused by diverse planar and volumetric flaws, several guidelines were developed and used especially for assessment of steam generator tubes. However, because the major components of new reactors have dissimilar geometric features and loading conditions compared with those of conventional operating reactors, most of existing assessment methods are not expected to be applicable; therefore, new alternative assessment guidelines are required. In this paper, a systematic structural integrity assessment of helical coiled steam generator tubes for a small and medium modular reactor, which is currently being designed, is introduced. Three‐dimensional detailed finite element (FE) limit analyses have been carried out to simulate the behaviours of the tube containing a volumetric flaw such as elliptical wear‐type, rectangular wear‐type and tapered wear‐type defects subjected to external pressure. Failure pressures were calculated from the FE analyses by changing defect depth, defect length and defect angle affecting the load‐carrying capacity of the tube. Thereby, engineering equations were developed as a function of these key parameters to predict structural failures and system reliability to enable more reasonable design and manufacturing decisions.     

协同过滤系统的矩阵稀疏性问题的研究

应用奇异值算法得到一个无缺失的矩阵,引进了一种增强的、基于参数的Pearson相关系统算法来提高相关性算法的准确性。提出一个基于奇异值分解和增强Pearson系数的“HybridSVD”算法,用MovieLens数据集来评价该算法,并和其他经典的传统算法做了比较。实验结果证明,“HybridSVD”算法比其他传统算法能更好地处理协同过滤中的稀疏性问题。     

Experimental and thermodynamic investigations on MnO-SiO_2-Al_2O_3-MnS system

MnO-SiO₂-Al₂O₃-MnS oxysulfide system has been investigated by experimental phase diagram and activity measurement coupled with thermodynamic modeling.Phase equilibria of the MnO-MnS,MnO-SiO₂-MnS, MnO-Al₂O₃-MnS and MnO-SiO₂-Al₂O₃-MnS systems under low oxygen partial pressure have been experimentally investigated for the temperature range of 1 185 to 1 500℃using equilibration and quenching techniques. Equilibrium phases were analyzed by scanning electron microscope,electron probe X-ray microanalysis（EPMA）, and differential thermal analysis（DTA ）.Phase diagrams were successfully constructed for the systems investigated.Two ternary compounds in the MnO-SiO₂-MnS system were found.Activities of MnO and MnS in MnO-SiO₂-Al₂O₃-MnS liquid oxysulfide solution from very low sulfur concentration to high sulfur concentration at solid MnS saturation were investigated employing gas/liquid/Pt - Mn alloy under controlled atmosphere at 1 500℃.As X（SiO₂）/（X（MnO） + X（SiO₂）） increases in liquid oxysulfide solution,activity coefficient of MnO decreases while that of MnS increases.As X(AlO_1.5) increases,the activity coefficient of MnS increases while no remarkable change was observed for the activity coefficient of MnO.Quantitative analysis of the thermodynamic properties of the oxysulfide solution as well as phase diagram of the system was also earned out by employing the Modified Quasichemical Model in the quadruplet approximation.In view of inclusion utilization for free - cutting steel,it might have an advantage to decrease the Al₂O₃ content and increase the MnO/SiO₂ ratio.     

Advancement in materials for energy-saving lighting devices

This review provides a comprehensive account of energy efficient lighting devices, their working principles and the advancement of these materials as an underpinning to the development of technology. Particular attention has been given to solid state lighting devices and their applications since they have attracted the most interest and are the most promising. Solid state lighting devices including white light emitting diodes (LEDs), organic LEDs (OLEDs), quantum-dot LEDs (QLEDs) and carbon-dot LEDs (CLEDs) are promising energy efficient lighting sources for displays and general lighting. However there is no universal solution that will give better performance and efficiency for all types of applications. LEDs are replacing traditional lamps for both general lighting and display applications, whereas OLEDs are finding their own special applications in various areas. QLEDs and CLEDs have advantages such as high quantum yields, narrow emission spectra, tunable emission spectra and good stability over OLEDs, so applications for these devices are being extended to new types of lighting sources. There is a great deal of research on these materials and their processing technologies and the commercial viability of these technologies appears strong.     

EFFECT OF MESH DISTORTION ON THE ACCURACY OF TRANSVERSE SHEAR STRESSES AND THEIR SENSITIVITY COEFFICIENTS IN MULTILAYERED COMPOSITES

SUMMARY

A study is made of the effect of mesh distortion on the accuracy of transverse shear stresses and their first-order and second-order sensitivity coefficients in multilayered composite panels subjected to mechanical and thermal loads. The panels are discretized by using a two-field degenerate solid element, with the fundamental unknowns consisting of both displacement and strain components, and the displacement components having a linear variation throughout the thickness of the laminate. A two-step computational procedure is used for evaluating the transverse shear stresses. In the first step, the in-plane stresses in the different layers are calculated at the numerical quadrature points for each element. In the second step, the transverse shear stresses are evaluated by using piecewise integration, in the thickness direction, of the three-dimensional equilibrium equations. The same procedure is used for evaluating the sensitivity coefficients of transverse shear stresses. Numerical results are presented showing no noticeable degradation in the accuracy of the in-plane stresses and their sensitivity coefficients with mesh distortion. However, such degradation is observed for the transverse shear stresses and their sensitivity coefficients. The standard of comparison is taken to be the exact solution of the three-dimensional thermoelasticity equations of the panel.     

船用5052-O铝合金在海水中的力学和电化学性能(英文)

采用电化学实验和SEM表面形貌观察,对船用5052-O铝合金在海水中的腐蚀保护电位进行优化,以克服诸如点蚀、腐蚀、应力腐蚀开裂和氢脆等行为的发生。在外加电流阴极保护的条件下,最优的保护电位范围为-1.3V～-0.7V。在此电位下,试样的腐蚀电流密度较低,经恒电位实验后,试样表面形貌保持得较好。