无线多媒体传感器网络部署控制算法

已有的无线多媒体传感器网络（WMSNs）研究针对传感器放置在目标区域内的情况进行,且没有考虑节点通过云台的转动获得的整个可能感知区域对覆盖率的影响。本文首先针对节点放置点高于目标区域的应用进行研究,综合考虑节点感知区域和可能感知区域,建立了延时和无延时感知模型,并针对不同的感知模型提出了传感器网络部署控制算法（IVPDCA）,算法中改进了虚拟势场算法,定义了节点质量的概念来表示节点间覆盖重叠的大小,建立受力模型,使得节点在合力作用下进行重新部署,同时关闭冗余节点,既延长了网络寿命,又提高了区域覆盖率。仿真结果验证了算法的有效性。     

直拉式单晶炉整体结构静力分析

TDR-120型直拉式单晶炉的底部多块垫铁的受力为超静定问题,从材料力学的角度,无法准确获得每块垫铁上的受力。采用ANSYS软件进行静力分析,建立机架部分有限元模型,以该单晶炉在不同工作情况下的受力为研究对象,对比分析了两种不同的方案下3种典型工况机架的变形情况和应力分布,利用软件后处理从微观应力云图提取来确定宏观力,进而获得炉体底座下各垫铁承受的力。通过计算出的各垫铁的支承力对比分析了两种方案下机架结构的稳定性要求,验证单晶炉机架结构静态性能,为单晶炉结构方案的改进提供依据。     

利用有限元法分析设计扬声器振膜

把一个连续结构看成是由有限个单元通过节点组合起来的整体,只要取出其中某个单元来分析,利用能量守恒原理导出节点受力与位移的关系,再由节点位移求出单元体内各处的应变与应力,然后由这些单元重建原来的系统,就能获得整个振膜的振动和声辐射特性。这是本文的基本思想。随着计算机技术的发展,把有限元法用于扬声器振膜的分析和设计已进入实用化阶段。本文介绍了程序设计的基本思想、数学模型、程序框图及计算值与实测值的比较。     

髋关节表面置换后股骨侧应力分布的有限元分析

目的通过有限元分析探讨髋关节表面置换后股骨侧的生物力学意义.方法采用有限元构建分析软件ANSYS workbench v10．0,通过对髋关节表面置换后股骨侧的结构进行拆分,分别将3部分构建后生成体积建立髋关节表面置换后股骨侧三维有限元模型,利用MSC patran2007计算软件,采用四面体10节点自由划分网格,共38147节点,187547单元,其中假体模型57446单元、水泥壳模型28265单元、股骨部分101836单元,分析髋关节表面置换后股骨侧的应力分布情况：结果所构建的三维有限元模型,逼真反映髋关节表面置换后股骨侧的真实几何形态及其生物力学。结论有限元模型的构建,可以为髋关节表面置换术的生物力学行为以及假体优化设计提供精确模型.     

扫描方式对激光直接成形过程中热力耦合场与残余应力分布的影响

利用有限元中的"单元生死"技术,通过ANSYS参数化设计语言(APDL)编程研究了长边扫描、短边扫描以及交错扫描方式对成形过程的热力耦合场以及残余应力分布的影响,并详细分析了各种扫描方式下,所选节点温度和热应力随时间的变化规律及残余应力沿各方向的分布规律。在与模拟过程相同条件下,实际成形实验所得结果与模拟结果吻合较好。     

预应力装配式叶片连接单元状态监测

提出了一种基于压电陶瓷激励与传感技术的预应力装配式风电叶片连接单元的状态监测方法。通过逐级施加螺栓预拉力对连接单元进行安装,再对连接段施加轴心拉力直至试件破坏,将压电陶瓷片粘贴在连接单元两侧分别作为驱动端和接收端,对受力全过程进行监测。比较不同激励信号下各阶段测量信号基于小波包分析的健康指标的变化,发现在连接界面脱开时信号出现明显衰减。该文的方法可实现装配式风力发电机叶片连接段状态的有效监测。     

散射体面电流矩量法分析结果的彩色云图生成方法

以矩量法(MOM)求解出的多天线--散射体系统中散射体的面电流为基础,研究了面电流彩色云图的生成方法,它包括面单元(三角形、四边形)离散、面单元内电流的插值计算、电流数值与颜色的映射、云图的生成与动态显示.为达到对云图精度的控制以及能产生质量好的离散元,提出了质心--中点法;针对四边形单元内电流的插值,推导出一组双线性插值计算式;考虑到面电流数值小的特点,通过对电流值取对教建立了电流数值与颜色的映射;基于通用图形平台和AVI技术,实现了云图的动态显示.实践表明,文中给出的方法能反映出面电流的分布以及随时间变化的情况,具有满意的可视化效果.     

一种改进的窄带算法在彩色序列图像人脸跟踪中的应用

该文提出了一种基于几何主动轮廓模型的人脸跟踪方法.通过直方图反向投影,使人脸区域表现为一个一致性区域与背景相区别.研究了一种改进的窄带算法实现曲线演化:以等间隔分布的节点表示运动曲线,只在这些节点上计算Level set函数的变化值,窄带区内其余点的Level set值的更新通过插值和查表的方法实现;根据节点的局部图像信息决定节点的运动方向和时间步长值.实验表明该算法能在满足一定精度的前提下,快速地对运动人脸进行跟踪.     

基于TinyOS的CC2430 RSSI定位的设计与实现

为解决现Z-Stack定位程序代码量大,结构复杂等问题,提出一种基于TinyOS的CC2430定位方案。在分析TinyOS组件架构基础上,设计实现盲节点、锚节点与汇聚节点间的无线通信以及汇聚节点与PC机的串口通信。在此基础上实现PC对各锚节点RSSI(Received Signal Strength Indicator)寄存器值的正确读取,确定实验室环境下对数-常态无线传播模型的具体参数,并采用质心算法来提高定位精度。实验显示,在由四个锚节点组成的4.8×3.6 m2矩形定位区域中,通过RSSI质心定位算法求得的盲节点坐标为(2.483 1,1.018 5),实际坐标为(2.40,1.20),误差为0.199 6 m,表明较好地实现对盲节点的定位。     

激光喷丸强化IN718合金孔周表面残余主应力分布特性

采用Abaqus软件建立有限元模型,分析了激光功率密度对孔周表面残余主应力分布的影响。进行了不同功率密度下的激光喷丸(LP)试验,通过X射线应力分析仪测量了孔周区域特征点三个方向的残余应力值,并计算了各点对应的主应力。结果表明,LP之后孔周的残余应力呈现各向异性;最小残余主应力可有效表征喷丸强化效果,随着激光功率密度的提高,最小残余主应力值减小。另外,LP后小孔附近出现典型的残余压应力环,最小残余主应力明显小于其他喷丸区域的;当功率密度超过一定阈值时,此环呈现远离孔壁的趋势。     

金丝楔形键合强度的影响规律分析

金丝楔形键合是一种通过超声振动和键合力协同作用来实现芯片与电路引出互连的技术。现今,此引线键合技术是微电子封装领域最重要、应用最广泛的技术之一。引线键合互连的质量是影响红外探测器组件可靠性和可信性的重要因素。基于红外探测器组件,对金丝楔形键合强度的多维影响因素进行探究。从键合焊盘质量和金丝楔焊焊点形貌对键合强度的影响入手,开展了超声功率、键合压力及键合时间对金丝楔形键合强度的影响研究。根据金丝楔焊原理及工艺过程,选取红外探测器组件进行强度影响规律试验及分析,指导实际金丝楔焊工艺,并对最佳工艺参数下的金丝键合拉力均匀性进行探究,验证了金丝楔形键合强度工艺一致性。     

Prediction of sawing force for single-crystal silicon carbide with fixed abrasive diamond wire saw

Fixed abrasive diamond wire saw has been used to cut hard-and-brittle materials into wafers, such as silicon carbide. The force of a single abrasive determines the cutting depth, and affects material removal mode and crack propagation length. Therefore, the sawing force is a key factor that affects the surface/subsurface quality of wafers. In this paper, a numerical sawing force predicting method considering wire saw parameters was proposed with the combination of both ductile removal and brittle fracture removal for each single abrasive. A new calculation method of single abrasive cutting force considering frictional force component and new material removal way considering the effect of lateral crack were adopted. Then the influences of process parameters and wire parameters on sawing force were analyzed. Finally, mathematical sawing force formulas described by both process parameters and wire saw parameters were obtained using the new sawing force prediction method. The validity of this prediction method and sawing force formulas was verified through experiments in the literature under the same process parameters and wire saw parameters.     

Iterative optimization of tail breaking force of 1 mil wire thermosonic ball bonding processes and the influence of plasma cleaning

An online tail breaking force measurement method is developed with a proximity sensor between wire clamp and horn. The wire under the tensile load measures about 1.5 cm extending from the bond location to the wire clamp. To increase the sensitivity, the bondhead speed is reduced to 2 mm/s during breaking the tail bond. It takes roughly 10 ms to break the tail bond. The force resolution of the method is estimated to be better than 5.2 mN. An automatic wire bonder used to continuously bond up to 80-wire loops while recording the on-line proximity signals. All wires are directed perpendicular to the ultrasound direction. The tail breaking force for each bond is evaluated from the signal and shown automatically on the bonder within 2 min after bonding.Results are obtained for a typical Au wire and a typical Cu wire bonding process. Both wires are 25 mm in diameter and bonded on Ag plated diepads of standard leadframes at 220 °C. An average Cu tail breaking force of higher than 50 mN is obtained if the leadframe is plasma cleaned before the bonding with 100% Ar for 5 min. This result is comparable to that obtained with Au wire. The standard deviation of the Cu tail breaking force is about twice that obtained with Au wire. The tail breaking force depends on the bonding parameters, metallization variation, and cleanliness of the bond pad. The cleanliness of the bonding pad is more important with Cu wire than with Au wire.     

特柔软型钢丝铠装复合电缆设计探讨

本文主要探讨特柔软型钢丝铠装复合电缆的设计,根据特殊用户实际应用情况,设计出大拉力、超柔软钢丝铠装电缆,设计过程中不仅考虑电缆所应有的电性能,同时还要考虑电缆高强度抗张情况和应用中处于反复收放状态,而且所设计的电缆还要满足恶劣环境.     

银键合丝力学性能对键合质量的影响

通过调节微合金元素的含量获得3种具有不同力学性能的银键合丝.利用拉伸试验、键合试验、焊线挑断力、焊球推力测试等手段,研究了银键合丝力学性能对键合质量的影响.结果表明,在延伸率相同的条件下,随着微合金元素含量的降低,3种键合丝的断裂负荷降低,初始模量先减小后增大,键合后焊线挑断力和焊球推力均降低,电极金挤出率先减小后增大.银键合丝初始模量较低时在超声和压力的作用下易于变形,焊线内残余应力较低且第二焊点与引线框架结合较好,因此挑断测试时第二焊点与框架材料界面处不易发生脱离,有利于获得更高的键合成功率.     

Effect of BOE etching time on wire bonding quality

The dependence of wire bond-pull strength on the morphology of the underlying polycrystalline silicon (poly-Si) beneath the bondpad metal is studied using atomic force microscopy (AFM). Statistical analysis shows that the roughness of the poly-Si is correlated with the wire bond-pull strength. The correlation is believed to be due to the effectiveness of thermal dissipation through poly-Si during the wire bonding process. Statistical analysis also shows that the roughness of the poly-Si is correlated to the buffered oxide etch (BOE) etching time before the bondpad metal deposition. In this work, it is concluded that the BOE etching time has a significant effect on the wire bonding quality. The roughness parameter that links the BOE etching time to the wire bond-pull strength is found to be the localization factor     

C73004-1/ZF型硅铝丝微细线拉丝机的设计分析与应用

从硅铝丝微细线拉丝机的设计及使用角度,较详细地论述了该设备的设计思路和原理,并进行了拉丝过程和拉丝受力分析。     

A study on the tensile fracture mechanism of 15 μm copper wire after EFO process

In this study, 15 μm copper wires were bonded on substrates with thermosonic process, and the tensile fracture characteristics of FAB, as well as bonded samples, were investigated. For electronic packaging applications, all 15 μm wires were fully annealed, and the microstructures consisted of equiaxed grains. After EFO (electric flame-off) process, the microstructure of wire can be divided into three parts: (1) free air ball (FAB) with columnar grains, (2) heat-affected zone (HAZ) with equal-diameter grains, (3) annealing zone with equiaxed grains. According to tensile test results, EFO process simultaneously reduced UTS and elongation of the wire. For both FAB and bonded samples, the tensile fracture zones were either in the region of equal-diameter grains or in coarse grains located within 100 μm from the ball. And it was observed that the breakage sites appeared near the twins and the columnar grains when tensile fracture happened. Meanwhile, the relationship between hardness and microstructure of wires after EFO process were analyzed with nano-indentation. The nano-hardness value of 15 μm wire was 1.2-1.45 GPa.     

Structural reliability assessment of multi-stack package (MSP) under high temperature storage (HTS) testing condition

Wire ball open failure at the interface of the gold wire and bonding pad of a multi-stack package (MSP) under high temperature storage (HTS) condition of 150 °C is studied. Failure analysis using FIB-SEM was conducted by in-plane moiré interferometry and FEA to clarify the failure mechanism. The ball open failure due to Kirkendall void that results from metal diffusion at high temperature was accelerated by the tensile stress imposed at the gold wire. The tensile stress developed at the gold wire when packages showing different warpage behaviours were stacked. Mechanical interaction between top and bottom packages caused unstable warpage, readily twisted and saddled. The wire came in contact with the photo-sensitive solder resist (PSR) dam because of the unstable warpage and this contact resulted in tensile stress at the gold wires. Solder flux residues reacted with the encapsulant, and as a result, the encapsulant of the top package adhered to the chip of the bottom package, and this adherence created additional tensile stress at the gold wires. To reduce the tensile stress at the wires, the PSR dam was removed, loop shape was altered from 45° to 90°, water soluble flux was applied, and cleaning process was added. HTS reliability was significantly improved and guaranteed after reducing the tensile stress at the wires.     

Advanced process characterization for 125 kHz wire bonder ultrasonic transducers

A high frequency ultrasonic transducer for wire bonding is conceived, designed, prototyped, tested and industrially produced. The influence of each feature of the ultrasonic transducer design, such as constituent material, amplifier geometry, mounting flange, capillary fixing, on the wire bonding process results is clearly identified and carefully analyzed through thorough process tests. The assembly and aging characteristics of the transducers are measured and the scattering of the vibration properties in the mass production is statistically quantified by laser interferometer measurements and compared with that of conventional horns. The transducer is mounted on the wire bonder with a flange whose special geometry is calculated by means of FEM simulations and patented. This flange allows the mechanical stiffness of the coupling transducer-wire bonder to be dramatically increased and the parasitic mechanical dynamical vibrations at the horn tip to be significantly reduced. Process tests show that the reduction in mechanical vibrations obtained in this way allows a wire bonder scarcely capable normally to attain the 80 /spl mu/m fine pitch process, to perform easily the 60 /spl mu/m fine pitch process. A beneficial impact of the mechanical coupling horn-wire bonder on the process performance is ascertained. The use of titanium as horn material, characterized by a low thermal expansion coefficient, is proven by process tests to be effective in improving the placement accuracy of the wire bonder. The high vibration frequency of the transducer (125 kHz) is proven by process tests to be effective in improving the ball roundness and the fine pitch wire bonding capabilities of the wire bonder and in decreasing the minimum wire bonding temperature and the applied bond force. The new approach to characterize the process performance of new ultrasonic transducer designs is of general importance for wire bonding technology.