Additional microstructural analysis on the samples examined in the paper ‘Are high resolution resistometric methods really useful for the early detection of electromigration damage?’

In a previous paper (A. Scorzoni, S. Franceschini, R. Balboni, M. Impronta, I. De Munari, and F. Fantini, Are high resolution resistometric methods really useful for the early detection of electromigration damage? Microelectr. Reliab. 1997;37(10/11):1479–1482), we reported largely different electromigration lifetimes and different high resolution early resistance changes measured on two nominally identical lots of 4 μm wide lines tested at moderately accelerated stress conditions. A microstructural analysis on unstressed samples was performed in order to detect the reason which induced these differences. The analysis confirmed a major defectivity of the lot with shorter lifetime: we detected the presence of TiAl₃ precipitates at the interface between the Al–Cu and the Ti-based metal barrier. This was not easily detectable by means of simple visual inspection. These additional findings confirm that a quick electrical detection of the metallization quality could be feasible by means of high resolution resistance measurements without the need of time-consuming direct examination of production lots.     

H_2-077数控机床镶钢导轨表面激光热处理应用研究

研究以４５＃钢代替原Ｈ_２－０７７数控机床镶钢导轨用ＧＣｒ１５钢,以激光表面淬火工艺取代原全件淬火工艺,达到减小导轨变形及降低生产成本的目的。试验结果表明,用优化了的激光工艺参数加工的镶钢导轨表面,其金相组织硬度得到了一定程度的提高,同时,大大减小了导轨的变形。     

The effects of underfill on the reliability of flip chip solder joints

Thermal fatigue damage of flip chip solder joints is a serious reliability concern, although it usually remains tolerable with the flip chip connections (of smaller chips) to ceramic boards as practiced by IBM for over a quarter century. However, the recent trend in microelectronics packaging towards bonding large chips or ceramic modules to organic boards means a larger differential thermal expansion mismatch between the board and the chip or ceramic module. To reduce the thermal stresses and strains at solder joints, a polymer underfill is customarily added to fill the cavity between the chip or module and the organic board. This procedure has typically at least resulted in an increase of the thermal fatigue life by a factor of 10, as compared to the non-underfilled case. In this contribution, we first discuss the effects of the underfill to reduce solder joint stresses and strains, as well as underfill effects on fatigue crack propagation based on a finite element analysis. Secondly, we probe the question of the importance of the effects of underfill defects, particularly that of its delamination from the chip side, on the effectiveness of the underfill to increase thermal fatigue life. Finally, we review recent experimental evidence from thermal cycling of actual flip chip modules which appears to support the predictions of our model.     

5个中华按蚊种群对溴氰菊酯的抗性及抗性选择反应

经浙江省 5个中华按蚊自然种群和敏感品系对溴氰菊酯抗性测定 ,发现其致死中浓度 ( LC50)都比各自的敏感品系高 ,特别是来自温州的中华按蚊 ,其抗性比率 ( RR50)达 11倍之多 . 将各自然种群的蚊虫进行抗性筛选 12代 ,发现其抗性水平与敏感品系相比 ,高达 130～ 190倍; 与其自然种群相比达 10～40倍 . 来自温州种群的抗性品系的选择性反应 ( R值 )小于 0. 1,而其它抗性品系大于 0. 1,这表明从抗性概率较高的自然种群中筛选的抗性品系 ,其抗性增加速率低于那些从抗性概率较低的自然种群中所筛选的抗性品系 ,即 5个自然种群的抗性潜能应该是相似的 . 最后对相应的蚊虫防治策略进行了讨论 .     

Properties of a large La1.92Sr0.08CuO4+δ single crystal grown by the travelling-solvent floating-zone method

A centimeter size single crystal of La_2−xSr_xCuO_4+δ (volume=1.32 cm³) with x_Sr=0.08 has been grown by the travelling-solvent floating-zone (TSFZ) method using a double ellipsoidal-type optical furnace as the heat source. The crystallised phase was checked solvent free by X-ray powder diffraction experiments, the crystal dimensions and quality being investigated by X-ray and neutron Laüe techniques. Several rocking curves of the Bragg peaks were performed by neutron diffraction giving a full width at half maximum (FWHM) of 0.200° for (006) reflection and clearly showing the presence of twin domains as expected for such an orthorhombic structure. The superconducting critical temperature of the as-grown crystal under 2 oxygen bar was determined by SQUID measurements with T_c=18–20 K. Thermal treatments at different oxygen pressures were carried out showing no significant improvement of the transition sharpness and the T_c value. Normal state susceptibility was also measured from 6 to 800 K for two different field orientations and can be interpreted as an antiferromagnetic insulating state behaviour. The resistivity measurements display an insulating behaviour perpendicular to the CuO₂ planes and a metallic behaviour in the planes, with a high anisotropy ratio R_c/R_b350 at room temperature and a zero resistivity achieved at 27 K in both directions. The specific heat measurements have revealed no anomalies in the temperature range 15–300 K.     

含贵金属的BaZrO3 储存NOx 催化剂结构及性能研究

A series of perovskite-type BaZrO3 catalysts are prepared by the sol-gel method. Their NOx storage capacity（NSC）and the resistance of SO2 poison are measured. XRD,XPS and FT-IR techniques are also used to characterize their structures and the influence of the structures on performance. The results indicate that,after calcinations at 750 and 900 ℃,the Ba and Zr species mainly exist in the form of perovskite BaZrO3 phase,and the BaCO3 and ZrO2 phases also exist. The presence of bulk nitrate is shown by XRD and FT-IR after BaZrO3 absorbing NOx . The Rh/BaZrO3 is prepared by doping 0.5%Rh on the BaZrO3 with the impregnation method. It is found that the Rh mainly deposits on the surface of catalyst. However,the noble metals 0.5% Rh or Pt well disperse on the surface of the sample after the BaZrO3 is mixed with γ-Al2O3 in equal weight proportion. The structure of perovskite BaZrO3 may be partly broken after doping Rh or Pt,because of the reduction by hydrogen in the process of preparing samples,and then some ZrO2 is enriched on the surface. The BaZrO3 catalysts possess high NSC and high resistance ability of SO2 poison. The NSC of Rh/BaZrO3 decreases compared to that of BaZrO3 . However,the NSC of the samples Pt/BaZrO3/γ-Al2O3 and Rh/BaZrO3/γ-Al2O3 increases by 78% and 15% respectively. It is noticed that the NSC enhances for all the samples containing noble metal Pt or Rh duing the 0.01%SO2 mixed with the NO and O2 . It implies that the NO oxidation is improved by SO2 .     

Study on resistance coefficient in compound channels

This paper presents a further study of the Manning and Darcy-Weisbach resistance coefficients, as they play a significant role in assessing the cross-sectional mean velocity, conveyance capacity and determining the lateral distribution of depth mean velocity and local boundary shear stress in compound channels. The relationships between the local, zonal and overall resistance coefficients, and a wide range of geometries and different roughness between the main channel and the flood plain are established by analyzing a vast amount of experimental data from a British Science and Engineering Research Council Flood Channel Facility (SERC-FCF). And the experimental results also show that the overall Darcy-Weisbach resistance coefficient for a compound channel is the function of Reynolds number, but the function relationship is different from that for a single channel. By comparing and analyzing the conventional methods with the experimental data to predict composite roughness in compound channels, it is found that these methods are not suitable for compound channels. Moreover, the reason why the conventional methods can not assess correctly the conveyance capacity of compound channels is also analyzed in this paper.The project supported by the National Natural Science Foundation of China (50279024), the National Key Basic Research and Development Program of China (973 Program) (2003CB415202) and the Specialized Research Fund for the Doctoral Program of Higher Education (20030610039)The English text was polished by Ron Marshall     

光纤固定软钎焊焊点的三维形态模拟

本文在建立光纤固定软钎焊焊点模型及能量边界条件的基础上,利用有限元方法对焊点三维形态进行数值模拟并分析材料及结构等参数对焊点形态的影响规律.基于能量最小原理并利用形态模拟数据,得出钎料量及焊盘尺寸对光纤与焊盘间隙高度的影响规律,以及光纤横向偏移量对回复力的影响规律.研究结果表明:针对一定的焊盘相对尺寸,当钎料量大于临界值,最小间隙高度随着钎料量的增加而成线性增加;光纤横向偏移量小于一定值时,回复力随着偏移量的增加成线性增加.研究结果对于通过调整结构及工艺参数来控制光纤对准偏移具有指导意义.     

ITO材料在减反射膜设计中的应用

改变ITO材料通常作为透明导电膜单独使用的状况,将其作为减反射膜系中的一层,能够在很大程度上增加ITO透明导电膜在可见光部分的透过率.通过使用将ITO材料置于膜系的内层和最外层两类不同的设计思想,可以使ITO透明导电膜达到相当优良的应用效果.使用低压反应离子镀方法制备了设计的两类减反射膜系,实验证明,膜层在可见光部分的透过率显著提高,剩余反射率明显下降,并得到了平均透过率为95.83%,最高透过率达到97.26%,方块电阻为13.2～24.6Ω/□的试验结果.     

含非理想空间棱柱铰的多体系统接触分析

传统的接触分析方法通过物体间的相对运动确定接触位置. 将这种方法用于多体系统中铰内的接触分析时, 无论铰内间隙是否十分微小都必须解除铰的运动学约束, 从而导致求解效率和求解精度方面的诸多弊端. 基于铰约束反力与铰内接触力之间的力系等效关系, 以及铰内可能接触点运动之间内在的运动学关系, 以矩形截面的棱柱铰为例, 提出了一种对空间棱柱铰进行摩擦接触分析的方法, 可在不解除铰的运动学约束的前提下得到铰内接触模式和接触力. 数值算例验证了方法的可行性.