【作者】 邵力耕；

【导师】 王立鼎； 杜立群；

【作者基本信息】 大连理工大学 ， 机械电子工程， 2011， 博士

【摘要】 在微机电系统中,微电铸广泛应用于微纳金属结构的制造,成为非硅基微结构和器件加工的重要技术。微电铸作为一个复杂的工艺体系,影响其沉积微结构性能的因素有很多,如电流密度、电铸液温度、电铸液组分、沉积速度和添加剂的使用等。纳米电铸是在微电铸发展的基础上,根据细晶强化理论,通过调整微电铸工艺使金属电沉积层中晶粒尺寸部分或全部小于100nm,制备出晶粒细小、组织致密的电铸层,以改善微结构的物理和机械性能。本文对脉冲微电铸过程的电结晶机理进行了研究。利用多电流阶跃法测量了不同脉冲参数下的过电位—时间关系曲线,验证过电位是脉冲微电铸过程中阴极电沉积主要的动力学因素。运用中间态金属吸附原子概念分析脉冲微电铸电结晶过程中的晶种产生和晶核形成,建立了相应晶核形成的模型,合理地解释了脉冲微电铸中的电结晶过程。基于微电铸体系的等效电路,运用交流阻抗法研究微电铸镍结构的电极过程动力学特性。以微流控芯片微模具上十字铸层为例,建立了数学模型,给出了描述微电铸体系电流密度和流体流场的偏微分方程,运用有限元法对影响微电铸铸层生长的阴极电流密度和流体流场进行三维数值分析。微电铸中电流—流体耦合场的电流密度和流场分布的三维数值分析结果,可用于微电铸结构的设计和工艺的制定,能够缩短微电铸工艺的开发周期。在研究脉冲微电铸的基础上,提出了一种采用周期换向正向连续脉冲电流的纳米电铸方法,分析其减小铸层晶粒尺寸的机理。建立了铸层和电铸液间的双扩散层模型,通过双扩散层模型研究了周期换向脉冲纳米电铸的极限电流密度。在电铸液组分相同的条件下,进行了周期换向脉冲电流和正脉冲电流的微电铸实验研究,分析了铸层的微观结构、晶粒尺寸和高度均匀性的变化规律,研究了铸层的显微硬度和耐磨性等机械性能。与正脉冲微电铸相比,周期换向脉冲纳米电铸的极限电流密度比较大,能够在较大的平均电流密度下达到细化晶粒的效果。在脉冲正向导通时间和关断时间与正脉冲微电铸相当的条件下,当正向电流密度大于10A/dm2时,周期换向脉冲纳米电铸铸层的晶粒尺寸小、显微硬度高、耐磨性好。实验结果表明,这种周期换向脉冲纳米电铸能够提高电铸微结构的物理和机械性能。更多还原

【Abstract】 Micro-electroforming is extensively applied to manufacture micro-nano metal structure in micro mechanical electrical system (MEMS), and become a key fabricating technology of non-silicon microstructures and devices. Micro-electroforming as a complicated process, there are many factors impact on the properties of its deposit microstructures, for example, current density, temperature and components of electroforming solution, deposit rate, and use of additives, et al.. Nano-electroforming is based on the development of micro-electroforming, According to fine grain strengthening theory, micro-electroforming process is adjusted to part or all grain sizes of deposit smaller than 100 nm. Microstructures with small grains and high density can be obtained to improve physical and mechanical properties.In this dissertation, electrocrystallization of pulse micro-electroforming is studied on. The relation between overpotential and time is established by mult-current step method under different pulse current parameters. It is shown that overpotential is the primary kinetics factor that induces electrodeposition on the cathode. The concept of metal adatom in intermediate is used to analyse the crystal seed formation and nucleation. A related model of crystal nuclei formation is set up in order to explain electrocrystallization in pulse micro-electroforming. Based on equivalent circuit of micro-electroforming, the electrode process kinetics of micro-electroforming nickel structure is studied with alternating current impedance method. Taken the crossing electroforming layer on micro-mold of micro-fluid chip as the example, the mathematical model is established. The current density and fluid field are describe with partial derential equation. Then three dimension numerical simulation of micro-electroforming is performed with the finite element method. The distribution of current density and fluid feild are helpful to plan and design micro-electroforming process, and reduce the developing time of micro-electroforming process.Periodic pulse reverse micro-electroforming with zero positive on-tmie is proposed, and the reason that the kind of micro-electroforming decreases grain sizes of electroforming layer is analysed. Under pulse reverse micro-electroforming condition, the duplex diffusion lyer between electroforming layer and bulk solution is build. Then the limiting current density of pulse reverse micro-electroforming is studied on. Pulse reverse micro-electroforming and pulse micro-electroforming are done respectively with the same compositions of electroforming solution. Microstructure, grain sizes and height uniformity of deposit change with pulse current are analysed. The mechanical properties, microhardness and wear resistance of electroforming layer is also studied.The limiting current density of pulse reverse micro-electroforming is larger than that of pulse micro-electroforming. The larger average current density effects on refine nanocrystalline structure. The negative average current density is 10% of the positive average current density in pulse reverse micro-electroforming, positive on-time and pulse off-time is correspond to those of pulse micro-electroforming. While positive average current density is larger than 10A/dm2, the average grain size of pulse reverse deposit is smaller; the microhardness of the pulse reverse deposit is higher; the wear resistance is better. This kind of pulse reverse micro-electroforming may improve the quality of electroforming microstructure.更多还原