Performance of sinking EDM electrodes made by selective laser sintering technique

Electrical discharge machining (EDM) is a nonconventional machining process widely applied for the manufacture of intricate shapes in hard materials which are not easily machined by conventional machining processes. The production of geometrically complex EDM electrodes is difficult, time consuming, and it can account for about 50 % of the total process costs. Selective laser sintering (SLS) can be an alternative technique to produce EDM electrodes in a faster way. This work conducted an experimental study on the performance of EDM electrodes made by SLS using pure copper, bronze–nickel alloy, copper/bronze–nickel alloy, and steel alloy powders. Important EDM performance measures such as material removal rate and volumetric relative wear were investigated and discussed for finishing, semifinish, and roughing regimes. This work contributes with an insight into the production of EDM electrodes via selective laser sintering, as an alternative technique to conventional machining processes, as well as to evaluate the performance of the electrodes, and also provide directions for future research on this field.     

Continuous separation of multiple size microparticles using alternating current dielectrophoresis in microfluidic device with acupuncture needle electrodes

The need to continuously separate multiple microparticles is required for the recent development of lab-on-chip technology. Dielectrophoresis(DEP)-based separation device is extensively used in kinds of microfluidic applications. However, such conventional DEP-based device is relatively complicated and difficult for fabrication. A concise microfluidic device is presented for effective continuous separation of multiple size particle mixtures. A pair of acupuncture needle electrodes are creatively employed and embedded in a PDMS(poly-dimethylsiloxane) hurdle for generating non-uniform electric field thereby achieving a continuous DEP separation. The separation mechanism is that the incoming particle samples with different sizes experience different negative DEP(n DEP) forces and then they can be transported into different downstream outlets. The DEP characterizations of particles are calculated, and their trajectories are numerically predicted by considering the combined action of the incoming laminar flow and the n DEP force field for guiding the separation experiments. The device performance is verified by successfully separating a three-sized particle mixture, including polystyrene microspheres with diameters of 3 μm, 10 μm and 25 μm. The separation purity is below 70% when the flow rate ratio is less than 3.5 or more than 5.1, while the separation purity can be up to more than 90% when the flow rate ratio is between 3.5 and 5.1 and meanwhile ensure the voltage output falls in between 120 V and 150 V. Such simple DEP-based separation device has extensive applications in future microfluidic systems.     

Chemical patterns of octadecyltrimethoxysilane monolayers for the selective deposition of nanoparticles on silicon substrate

The use of nano-objects to make the active part of reproducible nanodevices requires their controlled assembling on specific areas of substrates. In this work, we propose to use van der Waals interactions to assemble selectively gold particles covered by alkyl-thiol ligands on hydrophobic OctadecylTriMethoxySilane (OTMS) patterns defined on SiO(2)/Si substrates by a process combining nano-imprint lithography (NIL) or high resolution electron beam lithography (HREBL) and atmospheric chemical vapor deposition (CVD) of silane. A study by atomic force microscopy (AFM) reveals that homogeneous patterns of OTMS self-assembled monolayers, extending on several square millimeters, have been made. These OTMS patterns, with a lateral dimension ranging from 2mum down to 50nm, can be located at a precise place of a nanodevice, for example, between nanoelectrodes. Preliminary results of selective nanoparticle deposition on these chemical patterns are presented.     

Development and application of new composite materials as EDM electrodes manufactured via selective laser sintering

The cost of a part manufactured by electrical dischargeEDM machining (EDM) is mainly determined by electrode cost. The production of electrodes by conventional machining processes is complex, time consuming, and can account for over 50 % of the total EDM process costs. The emerging additive manufacturing (AM) technologies provide the possibility of direct fabrication of EDM electrodes. Selective laser sintering (SLS) is an alternative AM technique because it has the possibility to directly produce functional components, reducing the tool-room lead time and total EDM costs. The main difficulty of manufacturing an EDM electrode using SLS is the selection of an appropriate material, once both processes require different material properties. The current work focused on the investigation of appropriate materials that fulfill EDM and SLS process demands. Three new metal-matrix materials composed of Mo–CuNi, TiB₂–CuNi, and ZrB₂–CuNi were developed and characterized. Electrodes under adequate SLS conditions were manufactured through a systematic methodology. EDM experiments using different discharge energies were carried out, and the performance evaluated in terms of material removal rate and volumetric relative wear. The results showed that the powder systems composed of Mo–CuNi, TiB₂–CuNi, and ZrB₂–CuNi revealed to be successfully processed by SLS, and the EDM experiments demonstrated that the new composite electrodes are promising materials. The work also suggests important topics for future research work on this field.     

Holographic study of thermal strains of microelectronic components

Results of a study of elements of solid-state electronics by holographic interferometry are presented. Examples of measurement of thermal strains of real products and control of engineering processes in the production of static induction transistors (SITs) and ultra-high frequency hybrid integrated circuits are given.     

Basic parameters of front-end microelectronic units of detector electronics

Results of the analysis of literature sources on development of microelectronic signal acquisition and processing units for ionizing radiation detectors in large-scale physical experiments are given. The basic parameters of these units, such as the channel number, power consumption per channel, conversion coefficient and noise level are summarized in the generalizing table. Conclusions on the performed analysis are made and trends in the design and implementation of the considered units manufactured as applications specific integrated circuits are noted.     

Atom chips on direct bonded copper substrates

We present the use of direct bonded copper (DBC) for the straightforward fabrication of high power atom chips. Atom chips using DBC have several benefits: excellent copper/substrate adhesion, high purity, thick (>100?μm) copper layers, high substrate thermal conductivity, high aspect ratio wires, the potential for rapid (<8 h) fabrication, and three-dimensional atom chip structures. Two mask options for DBC atom chip fabrication are presented, as well as two methods for etching wire patterns into the copper layer. A test chip, able to support 100 A of current for 2 s without failing, is used to determine the thermal impedance of the DBC. An assembly using two DBC atom chips is used to magnetically trap laser cooled (87)Rb atoms. The wire aspect ratio that optimizes the magnetic field gradient as a function of power dissipation is determined to be 0.84:1 (height:width).     

Quantitative electron spectroscopic imaging studies of microelectronic metallization layers

The combination of focused ion beam (FIB) sample preparation and quantitative electron spectroscopic imaging is an ideal tool for the investigation of layered structures used in microelectronic metallization schemes. In the present work, Si₃N₄/Cu/Si₃N₄/SiO₂/Si and Al/TiN/Ti/SiO₂/Si metallization layers produced by physical vapour deposition are investigated. We apply series of energy filtered images in the low loss region for a mapping of the sample thickness which makes it possible to refine the parameters of the FIB process. We also show how series of energy filtered images in the core loss region can be used to obtain elemental distribution images and chemical bonding information on these samples on a nanometre scale. For materials with a small grain size and/or a strong variation in Bragg orientation, the intensity distribution of the elemental map is strongly influenced by the superimposed Bragg contrast. This detrimental effect can be reduced greatly by using hollow cone illumination, as is demonstrated for polycrystalline Cu. One striking feature observed in Cu layers prepared with FIB is strong, regularly arranged contrast variations caused by subsurface defects in the Cu grains. We suppose that these defects are a consequence of a strong interaction of Ga atoms from the FIB with Cu.     

Precise and reproducible deposition of thin and ultrathin carbon films by flash evaporation of carbon yarn in high vacuum

A simple, small device and its use for reproducible flash evaporation of carbon yarn in high vacuum are characterized. Using this flash evaporator, carbon films of any thickness up to 20 nm can be deposited without spark generation under minimized photon radiation, and with an accuracy better than ±0·2 nm. The films have less background structure (imaged in phase contrast) than conventionally rod evaporated films and are therefore suitable for many kinds of thin and ultrathin carbon film applications in electron microscopy, e.g. as backing for formvar films or sections, as isolating carbon layers for autoradiography, as ultrathin films (floated from mica) for support of macromolecules to be metal shadowed and as support and cover for negative staining of various specimens by the sandwich technique.     

An instrument for simultaneous visual and thermal testing of microelectronic devices

The problem of simultaneous visual and thermal testing of microobjects is considered. For this purpose, a mirror–lens optical system is proposed and constructed. The system has no movable elements and provides identical scales of images in spectral ranges of 0.4–0.8 and 8–14 μm. The technique for calculating its dimensions and an experimental setup on the basis of this scheme are described. The results of its testing using an example of investigating microelectronic devices are presented.     

精冲工艺与模具设计

分析了精密垫片的冲压工艺性,介绍了精密垫片的精冲工艺和精冲压力的计算及在普通冲床上实现精密冲裁的精冲复合模的设计。     

PCBN刀具硬态旋风铣削切屑宏观形貌研究

针对硬态旋风铣削产生锯齿状切屑的不同认识,通过对滚动轴承钢(平均硬度为63.5HRC)旋风铣削的工艺实验研究,提出了锯齿状切屑的微观形貌和宏观形貌的本质区别,分析了硬态旋风铣削的4种典型的切屑形貌特征和产生的工艺条件,为通过切屑建立硬态旋风铣削加工过程在线监控提供了一种新的方法。     

采用光生伏特效应的LED芯片在线检测方法研究

基于pn结的光生伏特效应,本文研究了一种非接触式LED芯片在线检测方法.通过测量pn结光生伏特效应在引线支架中产生的光生电流,检测LED封装过程中芯片质量及芯片与支架之间的电气连接状态.通过分析pn结光生伏特效应的等效电路,详细论述了半导体材料的各种参数及等效电路中各电参数与支架上流过的光生电流的关系.实验对各种不同颜色的LED样品进行了测量.研究表明,该方法可以实现LED芯片的在线检测,有较大的应用价值.     

辅助溶剂对PMMA微流控芯片模内键合的影响

为了提高聚合物微流控芯片的键合效率,以聚甲基丙烯酸甲酯(PMMA)微流控芯片为对象,以微型注塑机为平台,研究了聚合物模内键合方法.利用注塑机提供的合模力作为键合力,利用模温机提供键合温度,选择异丙醇作为辅助溶剂,借助溶剂溶解特性来降低模内键合中的键合温度和压力.在30～70℃,用测量显微镜和台阶仪测试分析了不同键合温度条件下,辅助溶剂对芯片的表面形貌和微通道结构的影响;利用辅助溶剂进行模内键合实验,用电子万能实验机测试了芯片的键合强度,对模内键合工艺参数进行了优化.结果表明:异丙醇对键合质量的影响与键合温度、键合时间有关,在较高温度下会使芯片产生皲裂、微沟槽变形和堵塞;在键合温度为35℃,键合时间为5 min时,芯片的表面质量和微沟槽形貌较完整,键合强度不小于2.64 MPa.     

弹簧管刚度精密测量技术的研究

文中针对电液伺服阀中弹簧管的刚度测量问题进行论述,提出一种新的弹簧管刚度自动测量方法,安装在弹簧管的头部内腔中的角杠杆将弹簧管的角变形转化为角杠杆上某点的线位移,设计基于螺管型电感传感器的位移测量系统.理论分析和实验结果表明:该方法能够将单臂施力法刚度测量中弹簧管头部和测杆之间的接触变形分离出来,避免其对测量精度的影响,能够有效提高测量效率和测量精度.     

大型精密测量设备的微振研究

微振对精密测量设备的测量精度有很大的影响。文中针对一种大型精密测量设备进行微振研究。依据惯性测量原理,对运行中的设备进行微振测试。根据微振测试结果得出设备的谐振点、启停的振荡时长、微振的位移振幅以及不同微振源对精度的影响程度等,并给出解决谐振问题的具体措施。微振研究结果对同类产品的设计具有指导意义。     

InSb精密角位移传感器的研究

本文介绍了以磁阻效应为工作原理的ＩｎＳｂ精密角位移传感器的设计和制作。这种传感器的主要特点是高分辨率、非接触、体积小、重量轻和使用寿命长。性能测试结果表明,在±１２°范围内,其分辨率达０．０１°     

半导体制冷型黑体的高精度温控器

国内高精度黑体的研究中,主要应用的是半导体制冷材料(TEC),文章根据其特点,设计了一种高精度的温控器。它以单片机为核心,采用分段式PID控制算法,外围配以采集处理芯片,经实验证明,该控制器具有很强的实用性和可靠性。     

基于DC-MIKE Actuator精密扫描平台

本文详细介绍了基于DC-MIKE Actuator用于生物芯片检测仪的精密扫描平台的机械结构,驱动、控制方法.设计并实现了以LM629、LMD18245为核心器件的精密平台PID控制器.最后讨论了PID参数整定方法与实验结果,并给出了各项参数的参考值.实验表明整个系统精度完全满足扫描要求,运行可靠.     

A study on the thermomechanical behavior of semiconductor chips on thin silicon substrate

This study is concerned with the deformation or warping behavior of thin layered semiconductor structure comprising a silicon substrate, a pattern layer and a polyimide coating layer with its thickness varying from 100um to 50 um. In contrast with the conventional thick semiconductor structure, today’s semiconductor structure is increasingly thin and therefore the warping is extremely conspicuous, being among the major concerns in the structural design of a chip. In the view of thermomechanical analysis of an extremely thin layer structure considered in the present paper, a few parameters on the deformation should be taken into consideration such as the pattern layer and intrinsic stress. To account for the effect of the pattern layer, we make a well educated guess for the mechanical properties, employing the test results and the CBA (Composite Beam Analysis) theory. In addition, we take into consideration the effect of the intrinsic stress due to moisture absorption on deformation. We show that the chip warpage is accurately predicted when all these are properly considered. Furthermore, we have found that the local instability or wrinkling, associated with the nonuniformity or the inhomogeneity in material properties and bonding quality between any two neighboring layers, appears as one important mode of energy relaxation in addition to the overall warpage when the chip thickness becomes very small.