接地线的搭接

人们通常把电气设备接地点的对地电压与入地电流之比叫做接地电阻。接地电阻是由导体的自身电阻、导体与导体的接触电阻和流散电阻组成。导体自身电阻都很小 ,接触电阻与导体的搭接方式、搭接点的腐蚀程度有关 ,流散电阻与土壤的电阻率、温度及接地体的几何形状、敷设方式等因素有关。《中国有线电视》2 0 0 2年第 9期马亮同志的《广播电视系统设备的接地》一文和其他相关文章对接地的作用、要求以及接地系统的施工方法都作了比较详细的论述 ,在此不再叙述。现对人们容易忽视而对接地电阻产生重要影响的接地线搭接问题进行分析。接地装置敷…     

飞机复合材料搭接结构导电性研究

分析了复合材料的组成、导电特性,以及与复合材料导电性相关的因素.介绍了航空设备中部分复合材料结构件的装配工艺方法,描述了这种方法可能对其电性能和EMC性能的影响,并结合试验结果给出了工艺指导意见.     

搭接系统的射频特性研究及其有效性分析

文章郑重考察了影响搭接条电气性能的几个参数R、L和C，及其与结构尺寸的关系；并给出了典型搭接系统的等效电路图，分析其产生谐振的条件。衡量一个搭接系统是否有效的评定标准是搭接效能，一个正的搭接效能值表示搭接条是有效的。通过实例测试，发现搭接效能的评定与搭接阻抗的评定是一致的，因此，可以用搭接的阻抗特性来衡量搭接系统的有效性。     

基于SPN的军用飞机备件供应保障建模

采用随机Petri网(SPN)对军用飞机备件供应保障进行建模;并对建立的模型进行合理性分析,从分析结果可以看出:建立的模型是正确的,能够较好地对军用飞机备件供应保障进行描述。在此建立的模型可扩展性强,能用于该型飞机以及其他机型飞机的备件供应保障研究及更高层次军事系统仿真的组成部分。     

一种高精度高可靠性的火工品阻值测量方法

火工品有很多属于电流触发型器件,阻值一般小于10Ω,其阻值大小都有一个标准值,在标准值的误差范围以外,表明火工品出现故障不可使用。在火工品安装和使用前须对其阻值进行测量,测量电流不可超过安全电流,否则会引起误触发。文章设计的阻值测量方法可以将测量电流控制在安全电流范围以内,通过恒流源电路、放大电路和电流监控电路的设计,可以高精度、高可靠性地测量出火工品的阻值。     

一种新颖的MEMS表面工艺牺牲层厚度的电测量方法

牺牲层厚度是MEMS表面工艺中的一个重要参数,对它的测量和控制有着重要的意义。目前大多采用光机械的方法来测量,但是测试方法复杂、测试时间长。本文介绍了一种新颖的MEMS表面工艺牺牲层厚度测试技术,实现了牺牲层厚度的电测量。测试方法简单快捷,并且很便于测试系统集成。     

军用飞机修理中的无损检测技术探讨

本文着重介绍军用飞机维护修理中的无损检测技术及其特点,以军用飞机复合材料构件损伤检修为例,针对以往相关无损检测技术应用中固有的局限性,比如抗干扰能力差、检测速度慢等问题,提出一种基于信息过滤的无线电定位方法,即雷达技术.     

基站地网系统设计及地阻测量方法

电信行业通常将5欧姆作为接地和铁塔的电阻值标准,并且从成本上和物理上尽可能追求最低的接地电阻。本文通过对地网系统的原理分析,介绍了几种地网系统的设计和地阻测量方法,加强地网设计的经济性,提高地网及整个接地系统对通信基站的保护的长期有效性。     

An in situ technique to measure gold resistance oscillations during the first stages of growth

An experimental technique developed for measuring the oscillating behavior of the electrical resistance during the first stages of growth of thin gold films deposited on silicon (1 0 0) substrate is described. The in situ technique uses the small electrical resistivity of the Si substrate to apply a fixed voltage through it and measure the electrical current generated during film growth. Thermal evaporation of gold at very low deposition rates produces changes on the electrical current which can be acquired meanwhile the first atoms impinges on the substrate. High precision and repeatability were achieved with the proposed method as demonstrated with the measured oscillating behavior of the resistance. The implemented technique and the obtained results could be useful to compare the proposed theoretical models to explain this behavior.     

基于变焦显微测量技术的键合金丝参数测量

欧美国家在半导体行业一直以来对我国实行技术封锁政策,我国许多关键技术和设备只能依靠进口,其中就包括键合金丝参数测量设备。键合金丝参数测量设备主要用于自动检测键合金丝的拱高和跨度等参数。由于键合金丝的回波损耗、驻波等微波传输特性与键合金丝的拱高、跨度等参数呈对应关系,因此可以通过测量相关参数的方法来检测键合金丝的微波传输特性是否合格。通过这一方法可以解决人工测量导致的速率低下的问题,提高键合质量检测效率,降低检测成本。本文基于变焦显微测量技术实现了键合金丝参数的测量。该方法通过自主设计的图像采集平台,获取到键合金丝的一组图像,然后进行聚焦区域提取,从而实现键合金丝的三维重建及参数测量。该方法对键合金丝拱高的测量精度<0.01 mm,相对误差<1.5%,对键合金丝跨度的测量精度<0.005 mm,相对误差<0.7%,可以满足自动检测键合金丝参数的设计需求。     

Effects of generation/recombination processes and leakage current through interfacial “punctures” on electrical characterization of unipolar directly bonded semiconductor structures

Numerical simulations have been performed to analyze the influence of generation/recombination processes and leakage current through “interfacial” punctures on the results of electrical characterization of unipolar directly bonded semiconductor junctions by the methods previously proposed by the present author [Mater. Sci. Semicond. Process. 4 (2001) 177]. Physical quantities that characterize the electrical state of the bonded junction and phenomena brought about by the generation/recombination processes in the junction (static and high-frequency conduction due to minority carriers, influence of generation/recombination processes on the interfacial charge, etc.) are discussed.     

Research progress of III-V laser bonding to Si

The vigorous development of silicon photonics makes a silicon-based light source essential for optoelectronics'' integration. Bonding of III-V/Si hybrid laser has developed rapidly in the last ten years. In the tireless efforts of researchers, we are privileged to see these bonding methods, such as direct bonding, medium adhesive bonding and low temperature eutectic bonding. They have been developed and applied to the research and fabrication of III-V/Si hybrid lasers. Some research groups have made remarkable progress. Tanabe Katsuaki of Tokyo University successfully implemented a silicon-based InAs/GaAs quantum dot laser with direct bonding method in 2012. They have bonded the InAs/GaAs quantum dot laser to the silicon substrate and the silicon ridge waveguide, respectively. The threshold current of the device is as low as 200 A/cm². Stevan Stanković and Sui Shaoshuai successfully produced a variety of hybrid III-V/Si laser with the method of BCB bonding, respectively. BCB has high light transmittance and it can provide high bonding strength. Researchers of Tokyo University and Peking University have realized III-V/Si hybrid lasers with metal bonding method. We describe the progress in the fabrication of III-V/Si hybrid lasers with bonding methods by various research groups in recent years. The advantages and disadvantages of these methods are presented. We also introduce the progress of the growth of III-V epitaxial layer on silicon substrate, which is also a promising method to realize silicon-based light source. I hope that readers can have a general understanding of this field from this article and we can attract more researchers to focus on the study in this field.     

A three-scale approach to the numerical simulation of metallic bonding for MEMS packaging

In this work we present a numerical, multi-scale approach to estimate the strength of a wafer-to-wafer metallic thermo-compression bonding. Following a top-down approach, the mechanical problem is handled at three different length scales. Taking into account control variables such as temperature, overall applied force over the wafer and contact surface roughness, it is shown that the proposed approach is able to provide an estimate of the sealing properties, especially in terms of bonding strength.     

More uniform Pd distribution in free-air balls of Pd-coated Cu bonding wire using movable flame-off electrode

The currently high price of gold wire has led to the development of bonding wire made from palladium-coated-copper as a lower cost alternative. Increasing the uniformity of the Pd distribution in free-air balls, formed by melting the wire end with an electric spark, is of interest as it can influence the uniformity of process and reliability. To study this Pd distribution, free-air balls are made using four distinct electrical flame-off (spark) processes with short and long spark times from wire bonders with fixed and movable electrodes. Elemental analysis of the free-air ball surfaces reveal a higher Pd concentration on the movable electrode free-air balls than on the fixed electrode free-air balls. Elemental analysis of cross-sections show that the Pd distribution in free-air balls made with a fixed electrode has Pd trails flowing from the neck into the Cu ball center. Furthermore, micro- and nano-voids are observed to follow the Pd trails. In contrast, free-air balls made with a movable electrode exhibit less severe voiding and retain a uniform, thin Pd layer along the surface up to the tip of the free-air ball (shorter spark time). This can help to increase process consistency and reliability.     

THEORY AND APPLICATION OF FIELD PERTURBATION TO ELECTRICAL IMPEDANCE TECHNIQUE FOR MEDICINE

A new approach called field perturbation theory is presented to analyze the electricalimpedance technique for medicine.The formula of constant voltage and constant current fieldperturbation,modified G-L formula and the formula of electrical field perturbation evoked bysound field are derived.The application results of the theory in electroglottography are alsointroduced.     

A thermomechanical study of the electrical resistance of Cu lead interconnections

The choice of liquid crystal display (LCD) driver packaging technology significantly influences the display performance of flat panel displays. Tape automated bonding (TAB) is generally the method of choice for connecting the LCD and the LCD driver circuit in flat panel displays. To achieve a finer pitch, an easier assembly, and a greater connection reliability, the design of the inner Cu lead must not only consider thermomechanical failure aspects, but must also maintain an acceptable joint resistance. This paper proposes an analytical model to predict the unit change in resistance of the copper foils used for TAB inner lead interconnections under various thermal environments and stressstrain states. The analytical model is based on a constitutive equation of the copper foil and the working principle of strain gages. Copper foil specimens are tensile tested at temperatures of 25°C, 50°C, 75°C, and 100°C at strain rates of 0.2/min. and 0.5/min., respectively, to confirm the validity of the developed analytical model. The numerical results and the experimental data are found to be in good agreement. Hence, the analytical method provides the means of predicting the thermal effect on the electrical and mechanical properties of the copper foils. Finally, by implementing finite-element method (FEM) solutions in the developed analytical model, this study constructs electrical resistance design charts to predict the variation in the electrical resistance of the copper foils under different thermal-mechanical conditions.     

Thermosonic bonding of gold wire onto silver bonding layer on the bond pads of chips with copper interconnects

A copper pad oxidizes easily at elevated temperatures during thermosonic wire bonding for chips with copper interconnects. The bondability and bonding strength of a gold wire onto a bare copper pad are seriously degraded by the formation of a copper oxide film. A new bonding approach is proposed to overcome this intrinsic drawback of the copper pad. A silver layer is deposited as a bonding layer on the surface of copper pads. Both the ball-shear force and the wire-pull force of a gold wire bonded onto copper pads with silver bonding layers far exceed the minimum values stated in the JEDEC standard and MIL specifications. The silver bonding layer improves bonding between the gold ball and copper pads. The reliability of gold ball bonds on a bond pad is verified in a high-temperature storage (HTS) test. The bonding strength increases with the storage time and far exceeds that required by the relevant industrial codes. The superior bondability and high strength after the HTS test were interpreted with reference to the results of electron probe x-ray microanalyzer (EPMA) analysis. This use of a silver bonding layer may make the fabrication of copper chips simpler than by other protective schemes.     

飞机机体红外辐射特性研究

建立了飞机机体红外辐射强度的计算模型。在综合考虑气动对流作用、环境辐射、内热源加热、蒙皮热传导等因素的基础上建立了热网络方程,由此导出壁面热流密度函数,并将其作为浮动的热边界条件,通过机体外流场的数值计算得到了机体表面的温度分布,并计算得出不同视线方向上、不同波段的机体总体红外辐射强度,在计算视线上的机体总辐射时考虑了面元之间的遮挡,最后讨论了太阳辐射、飞行速度、飞行高度对飞机机体红外辐射的影响。