【作者】 朱保国；

【导师】 王振龙；

【作者基本信息】 哈尔滨工业大学 ， 机械制造及其自动化， 2007， 博士

【摘要】 微机电系统(MEMS)的发展,带动了微细加工技术的发展。电化学加工是利用金属材料发生氧化还原的电化学过程来去除材料和增加材料的,由于加工过程是以离子单位方式进行的,所以在微细加工中占有重要的位置。随着现代电力电子技术的发展,针对电化学加工对精度和表面质量的要求,逐渐采用脉冲电源替代直流电源,而且脉冲电源的频率也在不断提高。另外,计算机控制技术的发展,使采用简单形状电极加工复杂结构的工件成为可能,使电化学加工技术有了广阔的应用前景。通过对微细电化学加工机理的分析,探讨了脉冲电化学微细加工中的关键技术,进而进行了微细电化学加工实验研究。首先,从原理上分析和研究了电化学加工中阳极溶解和阴极沉积的加工过程。通过对脉冲电化学加工电场模型、流场特性和加工速度的分析,从微观角度解释阳极溶解的过程中单个晶粒能否从工件上被去除取决于其脱除能与电场力作用的大小;而阴极沉积是在放电时所需活化能最低的位置进行。在达到金属分解电压或沉积电压后,溶解或沉积的电极反应速度取决于单个脉冲宽度内通过的电量,同时还受脉冲电源占空比的影响。分析了双电层对电化学加工过程的影响,并且依据电化学加工等效电路实际搭接了模拟电路,验证电化学加工模型的正确性。根据脉冲电化学微细加工工艺的需要,研制了纳秒级的脉冲电源。该电源以CPLD为核心,以MOSFET为主开关管,用脉宽调节和频率调节相结合的方法,使输出电压、电流和电源频率连续可调。根据脉冲电化学加工的电场模型,分析了维持电压产生的原因及影响因素,维持电压不受脉冲频率和占空比影响,而只与电解液性质、加工间隙和加工电压有关,且其大小是这三者共同作用的结果。由于这种非准确的波形增大了平均加工电压,影响工件的表面质量和加工精度。因此,采用双路场效应管研制了新型脉冲电源,使其输出特性更能符合脉冲电化学微细加工的需要。研究了脉冲电化学微细加工工具电极的制作方法。首先研究了电火花方法加工微细电极,然后以碱性水溶液加工钨电极为例,分析了电解加工电极的机理,以及影响微细电极形状和表面质量的主要因素。并分别在酸、碱、盐电解液中进行电解加工微细电极的实验研究,成功加工出长径比大于100,锥度小于0.2的微细电极,可以稳定加工出直径5μm左右的微细电极。另外利用钨材料的特性,可以在碱性溶液中加工出尖端半径为纳米尺度的扫描探针,最小半径达到50nm。最后,比较了电火花方法和电化学方法加工微细电极的一些特性,体现了电化学方法加工微细电极的优越性。系统地研究了脉冲电化学微细加工的关键技术。首先以电解加工微细孔为切入点进行研究;然后提出了电解车削加工微细结构的方法,阐述了电解车削的原理和加工范围,分析了电解车削加工的工艺特点及影响因素,进而给出了电解车削的加工实例;研究了电解铣削加工微细结构的工艺,分别研究了阴极侧面铣削、阴极端面单层电解铣削和阴极端面多层电解铣削加工工艺,通过分析加工厚度、工具电极直径和电源参数等对电解铣削表面质量和形状精度的影响情况,给出了微细三维结构的加工实例;最后分析和研究了电化学沉积技术。更多还原

【Abstract】 Developed with micro electro mechanical system (MEMS), the micro machining technology was developed. The metal was wiped off or added when the reaction of the oxidation and deoxidization were occurred in electrochemical machining (ECM). Because the minimum unit was ion in the process, ECM plays an important role in micro machining. Developed with the modern electric and electron technology, the direct current power supply was substituted by the pulse power supply aimed to satisfy the requirements of machining precision and surface roughness in ECM, and the frequency of the pulses power supply became higher and higher. The simple electrode could be used to fabricate complex structure due to the development of the computer control technology. Those made ECM widely application.After the electrochemical micromachining (EMM) mechanism was analyzed, the key techniques were discussed, and then the experimental investigations of the EMM were carried out. The processes of anodic dissolution and cathodic deposition were analyzed and researched firstly. In the microcosmic view, whether the single crystal particle could be wiped off from the workpiece lay on the action between escape energy and electric force during the processes of anodic dissolution. The cathodic deposition was carried out where the activation energy was least. After reached the dissolved voltage or deposited voltage, the machining rate lied on the energy during the pulse on time, and it also was influenced by the duty ratio of pulses power supply. The effect of double layer was analyzed in ECM process. Based on the ECM equivalent circuit, the stimulant circuit was put up practically. The validity of the ECM model was detected.Based on the requirement of the micro ECM technology, the nanosecond pulses power supply was developed. It used CPLD and MOSFET mainly, and combined the PFM and PWM, and then the output voltage, current, and the frequency of power supply could be adjusted continuously. Based on the model of electric field in ECM, the producing reason and the influencing factor of the maintaining voltage were analyzed. The maintaining voltage is disrelated with the frequency and duty ratio of the power supply, it relate with the electrolyte character, machining gap, and machining voltage, and it is decided by their collective action. The nonstandard discharging waveforms make the average voltage become big so the surface roughness and machining precision would be influenced. Therefore, the double MOSFET was used to improve the pulses power supply, and then the EMM would be satisfied with the discharging waveforms better.The fabrication of microelectrode was the preparative work for EMM. The microelectrode with several microns in diameter was fabricated by electrical discharge machining (EDM) firstly. The mechanism of fabricating microelectrode was analyzed by the tungsten microelectrode fabricated in the alkaline electrolyte. The factors were studied which influenced the shape and the surface roughness of the microelectrode. The microelectrodes were fabricated successfully in the acidic, alkaline, or saline electrolyte respectively. Some of them were with more 100 in length diameter ratio, and less 0.2 in taper. The microelectrode about 5 microns in diameter was fabricated stably. Otherwise, the scan probe with nanometers in top radius could be fabricated in the alkaline electrolyte based on the speciality of the tungsten, and the least radius was 50nm. At last, the properties of the microelectrodes which were fabricated by EDM or ECM were compared, and the advantages of ECM were shown.The key techniques of pulses EMM were researched systemly. The micro hole was fabricated by ECM drilling firstly, and the experimental investigation was carried out at the same time. The ECM turning technology was raised, and the mechanism and the machining scope were introduced. The technology characteristic and influenced factors were analyzed, and then the workpieces were fabricated by the ECM turning. The technology of ECM milling micro structure was introduced in detail. The ECM milling with cathode side, one layer ECM end milling, and multilayer ECM end milling were studied. The machining thickness, the microelectrode diameter, and the power supply parameter analyzed which influenced the shape precision and the surface roughness in the ECM milling. Several micro 3D structures were fabricated successfully. At last, the electrodeposition was researched.更多还原