A study of cathode agitation in ultrasonic-aided microelectroforming

In this study, a composite processing technique that combines ultrasonic vibration and electroforming process was utilised to investigate the machining performance of copper electroforming. Supersonic agitation mechanisms were mounted on a cathode and electrolyte separately to evaluate the processing performance of electroforming. Results revealed that a copper deposit speed can be raised by cathode agitation of ultrasonic-aided electroforming. Processed copper surface of cathode agitation is better than no agitation. An array multi-mould microstructure is fabricated by cathode agitation of ultrasonic-aided copper electroforming .     

Two-dimensional simulations of ion concentration distribution in microstructural electroforming

A theoretical model is constructed to predict the metal ion concentration distribution during the electroforming of high-aspect-ratio microstructures. Two-dimensional numerical simulations are then performed using COMSOL Multiphysics^TM software to investigate the effect of the processing conditions and the microstructure geometry on the electroforming results. The electroforming outcome is significantly dependent upon the current density and the microstructure aspect ratio, respectively. The simulation results for the electroforming of microstructural posts with an aspect ratio of 10:1 are found to be in good agreement with the analytical solutions.     

活动屏蔽膜板高深宽比微细电铸技术研究

针对金属微结构器件制造难的问题,提出了活动屏蔽膜板高深宽比微细电铸技术,通过屏蔽膜板动态地限制电沉积的区域,可以用低深宽比的膜板图形加工出高深宽比的金属微结构,并且免除了去胶等难题。在对活动屏蔽膜板微细电铸电场及传质进行分析的基础上,开展试验研究,获得了特征尺寸为500μm,深宽比分别为3和5的微静电梳状驱动器梳齿及微圆柱电极阵列。
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金属微结构阵列的电铸成型技术研究

详细讨论了微结构的电铸特点,在分析微细电铸的电场与流场特性的基础上,深入研究了铸层厚度的不均匀现象及搅拌方式、电流密度对微细电铸质量的影响。得出：由于高深宽比胶膜存在,单一搅拌对电铸区域的影响只集中在微区的入口部分。扩散过程成为金属沉积的限制性因素;随着胶膜深宽比的增大,电场等势线弯曲的程度加大,导致电铸微区内金属离子传输能力不均匀。实验表明：微细电铸过程中,搅拌速度提高并不能改善金属沉积的传质条件,辅助超声的复合搅拌在相同条件下能提高金属沉积速度、减少铸层缺陷;最佳电流密度不宜超过0.9～1.0A/dm2。实现了高分辨率,侧壁陡直的金属微结构的电铸成型。     

高深宽比微细结构电铸时传质过程数值分析

针对高深宽比微细结构电铸时存在严重传质受限的问题,以微深槽特征为分析对象建立液相传质两种数学模型——维扩散模型和二维对流—扩散模型,并分别用Matlab专用工具箱和Fluent 6.2流体仿真软件进行数值求解,依次分析以扩散、强制对流－扩散、复合对流(强制对流和自然对流)－扩散等为主导传质模式作用下微细电铸时,流场和离子浓度场的空间变化规律及其对液相传质效果的影响,并进行试验验证。结果表明：微细结构电铸时,单一扩散作用仅能用于深宽比小于2且电流密度小于2 A/dm2的液相传质场合;槽外强制对流只能对深宽比小于2的微槽内电解液产生一定搅拌作用;强化槽内自然对流作用并与槽外强制对流协同配合时,槽(深宽比为5)内可形成独特的单个或多个占据整个槽空间的涡流循环胞,涡流流速约为强制对流流速的1/20～1/2,明显改善传质效果,试验结果与此相印证。     

电铸和半导体薄膜电沉积的发展和应用

主要总结了电沉积制造中电铸和半导体薄膜的原理及其应用。首先分析了电铸的电流密度、波形、溶液运动形式等主要影响因素的作用机理和目前研究状况。接着分析了电铸不均匀的原因,验证了用机械搅拌的方法可提高沉积层的均匀性。然后介绍了电铸和半导体薄膜技术在近年来的最新应用成果,包括半导体薄膜材料、LCD彩色滤光片。最后预测了该行业的发展趋势。     

屏蔽膜板随动式微细电铸技术基础研究

提出了屏蔽膜板随动式微细电铸技术，屏蔽阳极膜板随电沉积层的增加而微量移动，从而可以用厚度有限的屏蔽层制造出原理上高度不受限制的三维金属微结构。针对该工艺的特点研制了试验装置，利用紫外光刻制作的屏蔽阳极膜板开展了两种随动方式的研究，分别得到了侧壁陡直的微齿轮和具有倾斜轮廓的微十字结构。     

在金属基底上制作高深宽比金属微光栅的方法

根据光学领域对高深宽比金属微器件的需求,利用UV-LIGA工艺在金属基底上制作了具有高深宽比的金属微光栅。采用分层曝光、一次显影的方法制作了微电铸用SU-8胶厚胶胶模,解决了高深宽比厚胶胶模制作困难的问题。由于电铸时间长易导致铸层缺陷,故采取分次电铸等措施得到了电铸光栅结构;同时通过线宽补偿的方法解决了溶胀引起的线宽变小问题。在去胶工序中,采用"超声-浸泡-超声"循环往复的方法。最终,制作了周期为130μm、凸台长宽高为900μm×65μm×243μm的金属微光栅,其深宽比达到5,尺寸相对误差小于1%,表面粗糙度小于6.17nm。本文提出的工艺方法克服了现有方法制作金属微光栅时高度有限、基底易碎等局限性,为在金属基底上制作高深宽比金属微光栅提供了一种可行的工艺参考方案。     

Flow-restricted Etching Method on Isotropic Substrates and Its Mechanism

With the development of analytical instrumentation to minimization,integration and automation,the microfluidic chips,which are more integrated,complex and diversified,have been applied widely on the manufacturing of analytical instrumentation.However,the present photolithography-based microfabrication technology,which is only able to pattern microchannels with simple inside structures,can not follow the rapid development of requirements.For solving the problem,a fabrication method based on the restricting effect of laminar flow is proposed for the micro etching on isotropic substrates.Experiments were conducted inside glass-based microchannels,in which certain etchant was used to form complicated microstructures.The flow parameters' effects on the aspect ratio,side wall profile and etching rate were revealed by the experiments.The experimental results reveal that the topography of micro structures patterned with the restricted flow etching method is mainly determined by the flowrates of separator and etchant.The computational fluid dynamics(CFD) model on the interface between multiple streams was established for the etching process,and analysis on the causes of various micro topographies was conducted based on the CFD simulation results.The experimental data consisted with the simulation results very well.The investigation depicted in this paper indicate that the flow restricted etching method provides sufficient references for the research and understanding on the mass transport at the liquid-liquid surface in the microchannel and can be used to pattern complex micro structures with high aspect ratios,meantime,it greatly enriches the microfabrication technology for microfluidic chips.     

UV-LIGA技术制作微型螺旋形加速度开关

微型加速度开关是用于空间飞行体中感受加速度并完成致动的重要惯性器件。本文采用UV-LIGA技术,结合SU-8厚胶工艺、微电铸工艺以及牺牲层技术,制作了微型螺旋形加速度开关。研究了牺牲层工艺、SU-8光刻技术以及螺旋形弹簧形变控制等微细加工的工艺细节;分析了多种牺牲层材料的特性,优选了与工艺相适应的Zn牺牲层体系,解决了微结构易脱落的工艺问题。通过优化微电铸工艺来减小金属膜层的内应力,优化牺牲层释放工艺来避免腐蚀过程对弹簧膜结构的冲击。实验结果表明,通过工艺优化可得到平整的微型螺旋形弹簧—质量块结构,螺旋弹簧厚度为20μm,质量块厚度达200μm,本文的工作可为大批量、低成本地研制微型加速度开关提供工艺基础。     

无掩膜流动刻蚀技术研究

为了实现玻璃材料高深宽比微结构的加工,提出了一种基于微尺度下流体分层流动现象的微流道内无掩膜流动刻蚀方法。通过对玻璃基体材料进行大量的工艺实验,明确了流动参数对于刻蚀成型微结构深宽比、侧壁形状、刻蚀速率的影响。证明了可以通过改变刻蚀剂与隔离剂的流动参数实现对成型微结构形貌的控制。实验结果表明约束流动刻蚀工艺可以在玻璃基体材料上加工出形态复杂、大深宽比的微结构,微结构的形貌取决于微流道中流体的流速。本实验的结果对于微尺度下分层流动的特性研究有一定的参考价值,并可为解决各向同性材料的微结构加工难题提供有效的解决方案。     

Abrasive-assisted Nickel Electroforming Process with Moving Cathode

In traditional electroforming process for revolving parts with complex profiles, the drawbacks on surface of deposits, such as pinholes and nodules, will lead to varying physical and mechanical properties on different parts of electroformed components. To solve the problem, compositely moving cathode is employed in abrasive-assisted electroforming of revolving parts with complicated profiles. The cathode translates and rotates simultaneously to achieve uniform friction effect on deposits without drawbacks. The influences of current density and translation speed on the microstructure and properties of the electroformed nickel layers are investigated. It is found that abrasive-assisted electroforming with compound cathode motion can effectively remove the pinholes and nodules, positively affect the crystal nucleation, and refine the grains of layer. The increase of current density will lead to coarse microstructure and lower micro hardness, from 325 HV down to 189 HV. While, faster translational linear speed produces better surface quality and higher micro hardness, from 236 HV up to 283 HV. The weld-ability of the electroformed layers are also studied through the metallurgical analysis of welded joints between nickel layer and 304 stainless steel. The electrodeposited nickel layer shows fine performance in welding. The novel compound motion of cathode promotes the mechanical properties and refines the microstructure of deposited layer.     

研究UV-LIGA微电铸电极过程的交流阻抗法

在给定的电铸液组分和工艺路线下,运用交流阻抗法研究了微电铸镍结构的电极过程动力学特性。建立了微电铸体系的等效电路,根据实验获得的交流阻抗图和电阻电抗频率响应,分析了搅拌、整平剂对微电铸体系交流阻抗的影响,计算了电极过程的交换电流密度。结果表明,加入十二烷基硫酸钠整平剂数量存在一个使交流阻抗最小的最佳值,大小为3 g/L,在有搅拌、加入最佳量的整平剂时,体系电极过程的交换电流密度为0.171 A/dm²。在微电铸过程中有搅拌、加入适量整平剂使电铸液交流阻抗下降,阴极电流效率提高,可以改善微电铸镍结构的表面性能、致密度和高度均匀性。     

Local pool boiling coefficients on horizontal tubes

Local pool boiling on the outside and inside surfaces of a 51 mm diameter tube in horizontal direction has been studied experimentally in saturated water at atmospheric pressure Much variation in local heat transfer coefficients was observed along the tube periphery On the outside surface the maximum and the minimum are observed at θ=45° and 180°, respectively However, on the inside surface only the minimum was observed at θ=0° Major mechanisms on the outside surface are liquid agitation and bubble coalescence while those on the inside surface are micro layer evaporation and liquid agitation As the heat flux increases liquid agitation gets effective both on outside and inside surfaces The local coefficients measured at θ=90° can be recommended as the representative values of both outside and inside surfaces     

Measurement of mass flow rate and evaluation of heat transfer coefficient for high-pressure pneumatic components during charge and discharge processes

Both the mass flow rate and heat transfer characteristics are significant factors to the flow behavior of the high-pressure air; however, they are not easy to be obtained by analytical model during discharge and charge processes. In this paper, the mass flow rate characteristics of high-pressure pneumatic components (HPPC) are measured by a compounding approach; two components under test with the same geometry and dimension are needed to be connected in series. Both the effective cross-section area and critical pressure ratio of HPPC are determined accurately, and only the pressure variation and the steady-state temperature of air in the chamber are utilized. The compared results between experimental and simulation data show that the accuracy of the measured effective cross-section area and critical pressure ratio of the HPPC is high when the sonic and adiabatic releasing time is less than 2 s. And then, a new combined method of calculating the heat transfer coefficient during discharging and charging processes for the high-pressure air is proposed. The computational fluid dynamics (CFD) method is used to illustrate the intensity of heat exchange between the high-pressure air inside the chamber and outer atmosphere. The dynamic flow behavior is analyzed based on the tested flow rate characteristics of HPPC, mixed heat transfer theory and numerical results. The results show that the heat-transfer coefficient during charge process is much greater than discharge process, and the forced convection heat exchange happened owing to the strong “air agitation” during the charge process. The experimental results also validate that the proposed method of calculating the transient heat transfer coefficient is more reasonable to describe the heat transfer behavior. The findings may also have general implication in the development of the design and analysis of the high-pressure pneumatic system.     

极板放置方式对电铸层中微米/纳米SiC复合量影响的研究

在分析固体颗粒自身重力对复合电铸过程影响的基础上，就极板放置方式对复合电铸层中微米颗粒和纳米颗粒复合量的影响进行了研究，用SEM测定了两种复合电铸层的表面形貌并进行了表面能谱分析，探讨了间歇搅拌对复合共沉积过程的影响。研究表明。极板放置方式和间歇搅拌对提高微米颗粒在复合电铸层中的复合量有一定程度的影响，而对提高纳米颗粒在复合电铸层中的复合量影响甚微。     

电子设备芯片沸腾换热应用试验研究

针对电子设备单芯片热耗超过500 W、热流密度超过50 W/cm²、单个机柜超过50 kW 的散热需求,采用沸腾换热结合微槽道的方法为大热耗、高热流芯片散热提供了新的解决方案。通过试验验证了微槽道与常规通道蒸发器的流动和换热差异。结果表明,微槽道相比常规流道,其散热温差降低了44%,细长结构的微槽道蒸发器能获得更优越的换热性能,流动沸腾换热系数可达2 ~ 3 W/(cm²·K)。     

Vibration assisted electrochemical micromachining of high aspect ratio micro features

The most used processes for generation of high aspect ratio microchannels are Nd: YAG laser technology on silica substrate and ultra violate lithography (UV-LIGA) process on metals. There are a few micromachining technologies such as micro mechanical milling, micro electro discharge machining (EDM) and electrochemical micromachining (EMM) for production of high-aspect-ratio micro features on highly stressed and anticorrosive metal like stainless steel. This paper discusses the micro fabrication of high aspect ratio micro features at the intended location on high strength stainless steel sheet of very small thickness to high thickness with highest average aspect ratio 14.33 achieved during microchannel generation by EMM with the help of coated microtool. Mathematical model relating aspect ratio with various parameters and machining conditions is derived to explore the ways to increase the aspect ratio of micro features. Experimental investigations were carried out to know the effect of vibration of microtool, frequency of pulsed voltage, microtool tip shape, thickness of work piece and non-conducting layer coated microtool on high aspect ratio micro features. Vibration of microtool with very small amplitude improved the stability of micromachining due to improved flow of electrolyte.     

基于UV-LIGA技术制造微结构器件试验研究

试验研究了UV-LIGA各工艺环节（包括前后烘、曝光、显影、去胶、电铸等）对金属基片上制造金属微结构器件质量的影响，并组合优化了操作条件和工艺参数。试验结果表明：采用优化后的UV—LIGA工艺条件，制造出的金属微结构器件（如微齿轮、微流道）轮廓清晰，表面质量好，无明显缺陷，与基底结合良好。     

铜纳米流体的制备及微流动特性研究

采用混合法配制了铜纳米粒子质量分数分别为1%和2%的铜-水纳米流体,通过添加相同质量分数的十二烷基苯磺酸钠分散剂并施加超声振动,使纳米流体的粒子稳定悬浮时间达30~40h。实验研究了所配制的纳米流体在压力驱动下流经直径分别为25μm和50μm的不同长度微圆管道的流动特性,并与蒸馏水流动特性及理论估算值进行了对比,发现纳米流体流量-压力特性基本呈线性关系,与理论估算值存在一定偏差,这主要是由尺度效应等所致。