Lateral performance evaluation of laser micromachining by high precision optical metrology and image analysis

Today several techniques are available for micro-manufacturing. Yet, it is difficult to assess the precision and lateral X,Y accuracy of these techniques. The available accuracy information is usually based on specifications given by machine suppliers. This information is based on in-house laboratory tests performed by dedicated machine operators and within an adapted environment. In practice, the accuracy is likely to vary due to environmental conditions, materials and operator skills. In order to check the specifications in realistic environments the EUMINAfab infrastructure consortium initiated a set of independent high precision onsite verification tests on different laser micromachining installations. In addition to providing performance verification, it gave the participating partners real capability information of their equipment and possibilities to improve machining performance to a higher level. In this study a comprehensive verification test was designed and carried out by using a high precision metrology method for 2D measurements based on subpixel resolution image analysis. This methodology improved our knowledge of the capabilities of three laser micromachining installations, and showed that specifications at single micron levels are hard to obtain.     

飞秒激光正交线扫描诱导表面微纳结构

通过控制激光偏振与扫描方向,利用飞秒脉冲激光正交线扫描的微加工方式,在硅和不锈钢表面诱导出了规则分布的复合表面微纳结构并分析了激光能量密度对微纳表面结构形成的影响。实验显示:当激光的能量密度接近材料烧蚀阈值时,在硅表面诱导出了周期条纹嵌套纳米孔的双层复合二维结构,在不锈钢表面则诱导出了依赖于激光偏振方向的纳米点阵列分布,分析认为纳米点阵列是由周期条纹结构边缘发生断裂而生成的。另外,当激光的能量密度大于材料烧蚀阈值时,在硅和不锈钢表面会烧蚀出规则分布的微米级孔洞结构。实验结果表明:第一次扫描诱导出的表面微纳结构增加了对入射激光的吸收,促进入射激光与表面等离子体波的耦合,加强了后扫描的烧蚀效果,使得后扫描诱导出的微纳结构占主导。文中提出的正交线扫描的加工方式为微纳表面结构的制备提供了新的思路。     

Research on Microelectromagnetic Relays

A new microelectromagnetic relay is presented and fabricated based on micromachining technology, aiming at the miniaturization and high manufacturing efficiency of electromagnetic relays. This microrelay is composed of a lower magnetic circuit, a planar exciting coil, and an upper magnetic armature. A complete magnetic circuit is composed, and the “ON” and “OFF” states are controlled by the current of the exciting coil. The dimension of this microrelay is 5 mm × 5 mm × 0.4–mm. The fabrication process mainly includes lithography, sputtering, electroplating, etching, sacrifice-layer technology, etc. Electromagnetic force is calculated theoretically. The calculation results are used for the optimization design of the armature and the number of turns of the exciting coil. A microelectromagnetic relay is fabricated and the initial test results are given. The resistance of the exciting coil is about 300 Ω. The switch-on state resistance is about 1.7 Ω at an exciting current of about 50–mA. Translated from Journal of Beijing University of Technology, 2004, 30(2) (in Chinese)     

硅基MEMS技术

结合MEMS技术的发展历史,概括了当今硅基MEMS加工技术的发展方向。指出表面牺牲层技术和体硅加工技术是硅基MEMS加工技术的两条发展主线;表面牺牲层技术向多层、集成化方向发展;体硅工艺主要表现为键合与深刻蚀技术的组合,追求大质量块和低应力以及三维加工。SOI技术是新一代的体硅工艺方向;标准化加工是MEMS研究的重要手段。     

高频窄脉冲微细电解加工实验研究

加工间隙是电解加工的核心工艺参数,利用在45钢薄片上打微细孔,通过实验分析来探索高频、窄脉冲微细电解加工中频率、电压和电解液浓度对加工间隙及电极截面和加工稳定性的影响规律。     

LPFG和FBG级联结构双参数光纤传感器研究

提出了一种长周期光纤光栅(LPFG)级联布拉格光纤光栅(FBG)的温度/应变双参数光纤传感器。利用飞秒激光直写制作LPFG并级连FBG,且FBG波谷位置为1 551.9 nm,LPFG波谷位置为1 559.1 nm,最高对比度为-12.7 d B。在30~70℃温度变化范围内对传感器温度特性进行测试,并在25℃超净环境下对0~500με应变变化范围内对传感器应变特性进行测试。实验结果表明,升温过程FBG中心波长发生红移,灵敏度15.00 pm/℃,线性度0.981 3;LPFG中心波长发生蓝移,灵敏度-11.75 pm/℃,线性度0.945 3。降温过程FBG中心波长发生蓝移,灵敏度18.25 pm/℃,线性度0.953 8;LPFG中心波长发生红移,灵敏度-15.42 pm/℃,线性度0.980 2。加载过程FBG中心波长发生红移,灵敏度0.93 pm/με,线性度0.991 5;LPFG中心波长发生蓝移,灵敏度-1.51 pm/με,线性度0.986 3。卸载过程FBG中心波长发生蓝移,灵敏度0.92 pm/με,线性度0.990 9;LPFG中心波长发生红移,灵敏度-1.51 pm/με,线性度0.972 8。结果表明,该光纤传感器灵敏度高,线性度好,可以同时动态实现应变和温度的测量。     

A Study on Electrochemical Micromachining for Fabrication of Microgrooves in an Air-Lubricated Hydrodynamic Bearing

A specially built electrochemical micromachining/pulsed electrochemical micromachining (EMM/PECM) cell, a electrode tool filled with non-conducting material, a electrolyte flow control system and a small and stable gap control unit, are developed to achieve accurate dimensions for spindle recesses. Two electrolytes, aqueous sodium nitrate and aqueous sodium chloride are applied in this study. The former electrolyte has better machinability than the latter because of its ability to change appropriately to the transpassive state without forming pits on the surface of the workpiece. It is easier to control the machining depth precisely by micrometer with pulse current than direct current. This paper also presents an identification method for the machining depth by the in-process analysis of the machining current and interelectrode gap size. The interelectrode gap characteristics, including pulse current, effective volumetric electrochemical equivalent and electrolyte conductivity variations, are analysed, based on the model and experiments. ID="A1"Correspondance and offprint requests to: E.-S. Lee, Department of Mechanical Engineering, Inha University, 253, Yonghyun-Dong, Nam-Gu, Incheon, 402–751, Korea. E-mail: leees@inha.ac.kr     

微机电系统的微细加工技术

详细阐述了硅微加工工艺以及近几年内国际上开发的一些新的加工技术,如3D电化学微加工、EFAB工艺等,并提出了目前这些方法中存在的缺陷。     

基于窄带水平集的三维平面工艺模拟系统

表面工艺是MEMS制造的一种重要方法,实现其加工过程的计算机仿真可以为相关MEMS工艺研究和器件开发提供技术支持,减少相关MEMS产品的开发成本,缩短其开发周期.基于窄带水平集算法完成了表面加工工艺的三维表面工艺模拟系统.窄带水平集算法稳定,计算速度快处理拓扑变形非常灵活,本文将其应用于该软件仿真系统中,并进行了一列的仿真实验,将仿真结果与实际的流片电镜图对比,验证了仿真系统的精确性.     

Evanescent wave long-period fiber grating within D-shaped optical fibers for high sensitivity refractive index detection

By now long-period fiber gratings (LPFGs) represent a well-assessed in-fiber technology. Their peculiar spectral properties and the intrinsic surrounding refractive index (SRI) sensitivity, together with the well known advantages of optical fibers, make these structures one of the most powerful tools, especially in the sensing field. Unfortunately, their main limitation relies on the need of opportunely coating the glass substrate when significant sensitivity enhancement and/or specific functionalization are required. In this work, the possibility to realize a self-functionalized and high sensitivity LPFG is demonstrated. The principle of operation is based on the exploitation of the evanescent wave interaction of the propagating light with a periodically patterned overlay. A D-shaped optical fiber is used as fiber substrate, that is made SRI sensitive by means of wet chemical etching based on hydrofluoric acid. Due to its peculiar geometry the process results easier in comparison with that to perform with standard single-mode fibers. In addition the chemical step can be stopped once the desired sensitivity is achieved. Successively a high refractive index (HRI) overlay is deposited on the flat surface of the fiber. Finally the HRI layer is periodically patterned by means of laser micromachining technique. The spectral characteristics of the fabricated device, together with the flexibility of the adopted fabrication method could allow the realization of innovative LPFGs to be adopted as technological platform for a multitude of chemical sensing applications, depending on the nature of the material deposited onto the flat surface of the etched D-fiber.