MEMS压力传感器自动组装系统

研制了MEMS特种压力传感器的组装系统．首先给出了MEMS特种压力传感器组装工艺过程,并通过分析得出组装精度下降将导致传感器灵敏度和线性性能下降的结论．在此基础上确定了自动组装系统的组成结构,并详细介绍了研制的具有力感知功能的微操作手、三工位键合炉以及显微视觉等关键技术模块．通过分析现有硅膜焊盘图形对称性分布的特点,给出了一种芯片中心求取方法,为高精度自动组装奠定了基础．最后,将各模块集成建立了自动组装系统,给出了各个模块的控制节拍和流程,并通过实验证明该系统可实现5μm的组装精度和25s／个的组装效率,适用于多种MEMS传感器的自动组装作业．     

PZT薄膜在MEMS器件中的研究进展

主要介绍在MEMS器件中PZT薄膜制备的方法、制备过程中需要解决的问题、PZT薄膜与MEMS的集成以及PZT在MEMS中的应用的研究进展,并展望了PZT薄膜的应用前景.     

SPC在引线键合中的应用

SPC是英文Statistical Process Control的简称,其中文意思是统计过程控制。它的出现为引线键合过程中解决不稳定性的问题奠定了基础。引线键合的质量直接影响到传感器使用后的稳定性和可靠性。本文着重介绍利用SPC定量地判断生产过程中工艺是否处于受控状态以及解决产;锅失控状态的方法,较好地稳定了工艺的状态。通过不断地反映情况,分析、校对与改良,提高了产品的质量,降低了产品的不合格率。     

系统级模拟的MEMS器件宏模型

MEMS器件的系统级模拟是实现器件优化的重要环节，常用的MEMS器件系统级模拟方法是基于宏模型，该宏模型要能与电路模拟软件相连接，再用电路模拟软件进行系统级模拟，因此，关键是如何建立能满足此种要求的宏模型，本介绍了常用的等效电路宏模型和硬件描述语言宏模型的建立方法以及这两种宏模型的优缺点。     

引线键合系统键合工具振动特性研究

研究微电子封装超声引线键合系统键合工具的动态特性和摩擦行为,运用有限单元法建立了键合工具的动态接触模型,初步掌握微电子超声键合系统键合机理。通过对键合工具施加不同的加载频率和正压力的计算结果进行对比,定性地给出了键合过程中加载频率和正压力的变化对键合工具动态响应和摩擦应力的影响.研究结果表明:键合工具的加载频率偏离固有频率,键合工具针尖部分的幅值响应将迅速减小,同时摩擦应力的均值也相对减小;正压力增大,响应幅值将会相应减小;正压力增大到一定值时,幅值响应将会波动比较大,如果要得到适合的键合点尺寸的要求,同时保证键合质量,就必须选择合适的加载频率和正压力。     

MEMS版图自动生成与工艺匹配系统研究

根据MEMS工艺设计的特点提出了反馈式专家系统运作方式,并据此给出了MEMS版图自动生成与工艺匹配系统的体系结构.同虚拟MEMS加工工艺相比,该系统可实现工艺流水的逆向推理流程,由此,进一步给出了系统逆向推理所需的专家规则描述方式和推理机实现方法,并实现了一个原型系统,该系统可实现由两种标准MEMS工艺制作器件的版图自动生成与工艺匹配工作,初步验证了系统的可行性.     

全自动引线键合机送丝系统受力模型及实验

丝线传输的阻力控制和张紧力控制是引线键合机送丝系统的关键技术之一,对键合质量有着重要的影响．为了解决当前全自动引线键合机送丝系统中的传输阻力大、传输张力不稳定等问题,根据引线键合工艺过程和系统的技术要求,设计了由气体导轨和真空张紧装置组成的低摩擦送丝系统,来实现金丝的低阻传输．建立了金线在气体导轨和真空张紧装置内的受力模型,得出了二者的控制参数与金线作用力的关系;分别对金丝在气体导轨和真空张紧装置内的受力模型进行了实验验证,实验结果表明达到了所要求的低摩擦力要求．     

基于峰值检测的MEMS器件微弱电容检测电路

针对MEMS器件研制中微弱信号的检测问题,提出了一种适用于电容式MEMS器件的微弱电容检测电路.此电路采用峰值检测技术,原理及结构简单;只检测待测电容的变化量,既可用于差分式检测,也可应用于单一待测电容的情况.首先利用正弦载波信号和微分电路对电容量进行载波调制,再通过减法电路得到幅值与电容变化量成比例的正弦信号,最后采用峰值检测方法解调信号,得到直流量输出.利用微小可调电容进行标定,结果表明检测电路的线性度良好,灵敏度约为3.631V/pF,精度达到0.2%.利用该检测电路检测MEMS陀螺上振动频率为2.85kHz的梳齿驱动器的电容量变化,输出信号频率为（2.85±0.02）kHz,误差低于0.7%,说明该电路能够应用于MEMS器件的微弱电容检测.     

飞秒激光微精细加工技术与MEMS动态测试技术

本文阐述了飞秒激光微精细加工技术的原理特点，在微机械和微光学中的应用，及其在加工研究中取得的一些进展；提出一种基于计算机视觉、显微干涉及激光多普勒的MEMS的动态测试技术，实现MEMS器件平面运动幅度的快速测量、平面和离面运动的测量和离面运动的瞬态测量。     

基于小波元胞自动机算法的引线键合去噪

本文针对引线键合过程中图像边缘要求性高的特点,提出一种基于小波与元胞自动机相结合的去噪算法。该算法对图像小波变换,根据像素点的方向信息和边缘有序性设定演化规则,使可能噪声像素进行元胞自动机演化,得到精确的噪声信息。     

Illumination system for wire bonding inspection

A novel lighting system was devised for 3D defect inspection in the wire bonding process. Gold wires of 20 microm in diameter were bonded to connect the integrated circuit (IC) chip with the substrate. Bonding wire defects can be classified as 2D type and 3D type. The 2D-type defects include missed, shifted, or shorted wires. These defects can be inspected from a 2D top-view image of the wire. The 3D-type bonding wire defects are sagging wires, and are difficult to inspect from a 2D top-view image. A structured lighting system was designed and developed to facilitate all 2D-type and 3D-type defect inspection. The devised lighting system can be programmed to turn the structured LEDs on or off independently. Experiments show that the devised illumination system is effective for wire bonding inspection and will be valuable for further applications.     

Fundamentals of thermo-sonic copper wire bonding in microelectronics packaging

Fine copper wire bonding is capable of making reliable electrical interconnections in microelectronic packages. Copper wires of 0.8–6 mil diameter have been successfully bonded to different bond pad metallized and plated substrate materials such as Al, Cu, Ag, Au and Pd. The three metallurgical related factors; solid-solubility and diffusion of dissimilar contact metals, oxide film breakage and plastic deformation of asperities play a critical role in the bonding. Plastic deformation of an asperity is the most significant factor one has to consider to attain good bonding. Soft aluminum metal (30–40 VHN), with a lower % asperity threshold deformation is easier to wire bond than harder metallic surfaces (Ni, W, Mo, Cr, Co, Ta) of 150–500 VHN. Good adhesion of wire bonding is achieved for the surface roughness (Ra) of 0.01–0.15 μm and 0.02–0.6 μm of bare and plated surfaces respectively. It is rationalized that the application of ultrasonic energy principally breaks the oxide film and deform the asperities, while a compressive force increases the proximity of asperities. Hence wire welds to bond pad surface by molecular attraction and inter diffusion. Storage of copper ball bonds at 175 °C for 100–1,000 h forms copper aluminide at the interface. EDAX and Auger analysis reveal 22 at% Al + 78 at% Cu composition of the aluminides and Cu₃Al₂ empirical formula is calculated, which, does not match with any of the reported copper aluminides. Hardness of the copper ball bonds and stitch bonds are higher than wire exhibiting work hardening of the bonds on processing.     

用于MEMS真空封装中的纳米吸气剂

真空的获得和维持是目前MEMS真空封装技术中存在的主要难题之一.实验利用具有高比表面积和自身储气特性的碳纳米管(CNTs)作为骨架,制备一种能在高真空环境(<10-3 Torr,分子状态)和低温(<400℃)下吸收活性气体的新型吸气剂--纳米吸气剂.与传统吸气剂意大利SAES公司的St175相比,在5000C下激活10min后,室温下,单位质量的纳米吸气剂吸气速率约是St175的1000倍;而带温(320℃)下测试,约是St175(750℃下激活10min后冷却至400℃下测试)的20倍.     

气体微机电传感系统中的片上ESD保护

摘要是本文提出了一种应用于微机电系统嵌入式传感器片上系统新工艺上的静电放电防护器件的电路结构.这个静电放电防护结构采用了以地端为参考电位的,多指条晶闸管类器件,包括以下几个部分1)输入/输出防护,2)电源钳位3)微机电处理过程中的内部传感器电极.本工作也提出了一种在有限的芯片面积下实现静电放电防护等级要求的多指条版图布局.这种静电放电防护设计体系在器件级和片上系统级都得到了测试和验证,有效性和鲁棒性都得到了证实.测试数据表明采用了本防护体系的片上系统在不引入闩锁,漏电流只有10-10A的情况下承受了4.1kV的人体放电模式的静电测试.     

基于电感数字变换传感器的智能小车自动循迹系统

为了解决智能循迹小车常用的路径识别传感器易受电磁、光线等干扰的问题,提出了基于电感数字变换传感器的智能小车自动循迹系统。通过分析电感数字变换传感器的工作原理,得出通过扩展传感器感应线圈来扩展感应范围的方法,并基于该方法设计了一种使用单个LDC1000电感数字变换器的传感模块。该模块利用SN74LV4052A模拟开关实现对传感器线圈的扩展;采用MSP430单片机搭建了包括主控模块、电源模块、驱动模块和传感器模块的循迹硬件测试系统;通过实时采集和处理传感器的数据并对小车位置进行调整,实现了硬件测试系统循迹的功能;最后,在测试系统上进行了传感器对金属的感应实验和循迹测试。实验结果表明：该传感器可实时检测到轨道与线圈的水平和垂直距离的变化,可以为循迹功能的实现提供保证;该智能小车在5 mm宽的锡箔纸轨道上可以得到良好的循迹效果。研究结果表明该系统具有适用性强、检测技术稳定的特点,可以广泛应用于工业现场智能循迹。     

Dynamics of an ultrasonic transducer used for wire bonding

The vibration displacement distributions along a transducer used in ultrasonic wire bonding were measured using a heterodyne interferometer, and many nodes and anti-nodes were found. A mechanical finite element method (FEM) was used to compute the resonant frequencies and vibration mode shapes. The displacement distributions of the dominant 2nd axial mode agreed well with the measured values. Undesirable nonaxial modes, including the higher order flexural and torsional modes, also were excited at frequencies very close to the working frequency (2nd axial mode) of the transducer. Hence, the measured displacements were the resultant of all the allowable modes being excited. However, the excitation of these nonaxial modes were small enough not to affect the formation of consistent and high quality wire bonds. Results of the present study were used to determine a suitable location for installing a piezoelectric sensor to monitor the bond quality.     

基于粘附剂键合的圆片级MEMS塑料封装技术

设计了一套采用聚合物粘附剂(Epo-Tek301)键合的圆片级MEMS塑料(polymethyl methac- rylate)封装方法.塑料封装封盖采用热压成型,激光划片形成4寸圆片.封盖和衬底键合工艺的粘附剂优化厚度为12μm,键合过程中不需要加压加温.测试结果显示该工艺的键合强度(1.3～1.6Mpa)可以满足一般封装需要,而所带入的应力也很小.划片采用分开划片:封盖采用激光划片而硅衬底采用机械划片.该方法封装的微流体芯片已经顺利测试和应用.由于工艺简单,成本低廉,该技术除了用于MEMS封装应用,也可作为划片测试保护.     

Surface activated bonding of LCP/Cu for electronic packaging

A lamination technique for liquid crystal polymer (LCP)/Cu was developed for high speed and high performance printed circuit boards (PCB). This approach was accomplished by using a modified surface activated bonding (SAB) process to achieve enhanced adhesion and a smooth interface. Systematic investigation of peel strength of four categories of samples, namely “as bonded”, “annealed”, “Cu-deposited”, and “Cu-deposited and annealed” showed highest peel strength in the “Cu-deposited and annealed” sample. Significant improvements in adhesion were observed in the samples cleaned with argon-radio frequency (Ar-rf) plasma (“as bonded” samples) followed by Cu deposition on LCP, which were heated after bonding in low vacuum pressure at 240∘C (about 70–75 times higher than that of “as bonded”). XPS analyses on peeled surfaces of the “Cu-deposited and annealed” sample reveal bulk fracture in the LCP. Threefold lower loss in conduction of SAB processed laminate than that of conventional heat laminate was most likely due to smooth interface of the SAB processed laminate (surface roughness was ninefold lower than that of conventional heat laminate). A plausible adhesion mechanism of Cu/LCP might be due to bonding of Cu adhesion sites to plasma induced dangling sites of LCP surface, and thermal reconstruction of Cu deposited layers.