硅微球轴承设计与制造基础研究

发布时间：2018-04-11 20:16

  本文选题：微球轴承 + MEMS　； 参考：《北京理工大学》2015年博士论文

【摘要】：微球轴承比平面接触式微轴承摩擦系数低,而比非接触式微轴承支承稳定,易与微发动机、微马达和微泵等微机电系统(Micro-Electro-Mechanical System,MEMS)组合集成,因而被当作未来旋转MEMS器件的首选支承。然而,由于微球轴承的结构设计和制造工艺存在问题,极易发生由于微球与硅滚道之间直接接触而导致的轴承摩擦磨损,影响轴承的可靠性和寿命,因而无法提供鲁棒的支承。针对以上问题,本文主要研究内容如下:1.提出了微球轴承的设计方案。考虑到微球轴承滚道可能发生磨损的位置,以及键合工艺中装夹对准硅片困难的问题,提出了微球轴承滚道结构和轴承腔通气孔的设计方案,减少了因微球与键合界面接触而产生的摩擦和磨损,降低了键合过程中由于微球质量很小、易受振动而从滚道溢出的可能性。2.对滚道涂覆硬薄膜的微球轴承接触性能进行了理论研究,考察了不同薄膜弹性模量和厚度,以及不同微球材料和直径对微球—滚道接触特性的影响。结果表明:高弹性模量的厚薄膜可以降低微球轴承滚道表面的最大径向拉应力和薄膜/基底界面剪应力,但却提高了最大接触压力;轴承内的最大轴向von Mises等效应力和薄膜/基底界面应力梯度可通过减小薄膜的弹性模量或增加薄膜厚度来降低;与氮化硅(Si3N4)和氧化锆(ZrO2)微球相比,440C不锈钢微球可以改善滚道涂覆硬薄膜的微球轴承的接触性能;对于同一微球材料的轴承来说,直径较大的微球与滚道之间的接触性能更好。在摩擦系数较大的情况下,薄膜表面的径向应力在接触区域前缘为拉应力,沿摩擦力作用方向,逐渐变为压应力;随着摩擦系数的增加,微球和滚道所受最大von Mises等效应力值逐渐增加,其轴向位置向滚道表面移动,且表面所受径向拉应力和压应力的最大值增加。3.针对微球轴承多特征尺寸结构的加工困难问题,提出了采用环形刻蚀(Halo Etch)和嵌套刻蚀(Nest Etch)方法的工艺流程,提高了刻蚀速率的一致性和图形精度,从而有利于降低转子的不平衡量,保证微球轴承的高速运转稳定性;针对轴承腔加工问题,提出了中间层键合(Intermediate-Layer Bonds)技术和遮罩(Shadow Mask)技术相结合的工艺流程,避免了过高直接键合温度给微球带来的热变形,同时避免了中间层材料沉积在滚道中而引起的轴承腔堵塞和微球粘着滚道。4.针对本文设计和制造的微球轴承,提出了其封装方案;研制了微滚动摩擦测试平台,实现了轴承转速、角位移、法向载荷,以及供气压力和流量的实时测量,获得了法向载荷与摩擦转矩的定量关系;采用三维轮廓仪、扫描电子显微镜和能量色散谱仪分析了微球轴承滚道的磨损情况。分析结果表明:微球轴承的磨损主要是由于微球与SiC薄膜之间的接触面在瞬时高温下受很高的接触应力作用而产生的粘着磨损。
[Abstract]:In view of the above problems, the main contents of this paper are as follows: 1.The design scheme of micro ball bearing is put forward.Considering the possible wear position of the micro ball bearing raceway and the difficulty of clamping the silicon wafer in the bonding process, the design scheme of the raceway structure and the bearing cavity ventilation hole of the micro ball bearing is put forward,The friction and wear caused by the contact between the microspheres and the bonding interface are reduced, and the possibility of spilling from the raceway due to the low mass and easy vibration of the microspheres during the bonding process is reduced.The contact properties of micro ball bearings coated with hard film on raceway were studied theoretically. The effects of different film elastic modulus and thickness as well as different materials and diameters of microspheres on the contact characteristics of microspheres and raceways were investigated.The results show that the thick film with high elastic modulus can reduce the maximum radial tensile stress on the raceway surface and the shear stress at the film / substrate interface, but increase the maximum contact pressure.The maximum axial von Mises equivalent stress in the bearing and the stress gradient at the film / substrate interface can be reduced by decreasing the elastic modulus of the film or increasing the thickness of the film.Compared with silicon nitride Si _ 3N _ 4) and zirconia zirconia ZrO _ 2), 440C stainless steel microspheres can improve the contact properties of the roller bearing coated with hard film, and for the bearing with the same microsphere material, the contact performance between the larger diameter microspheres and the roller is better.When the friction coefficient is large, the radial stress on the surface of the film is tensile stress at the front edge of the contact area, and gradually becomes compressive stress along the direction of friction force, and with the increase of friction coefficient,The maximum effect force such as von Mises on microspheres and raceways increases gradually, its axial position moves to the surface of the raceway, and the maximum value of radial tensile stress and compressive stress on the surface increases by .3.In view of the difficulty in machining the multi-feature size structure of microsphere bearings, the technological process of ring etching Halo Etch) and nested etching nest Etchhas been put forward, which improves the consistency of etching rate and the graphic accuracy.Therefore, it is advantageous to reduce the unbalance of the rotor and ensure the stability of the high speed operation of the microball bearing. In view of the machining problem of the bearing cavity, the process flow of the interlayer bonding intermediate-Layer Bondstechnology and the shadow Mask technology is put forward.The thermal deformation of microspheres caused by excessive direct bonding temperature is avoided, and the clogging of bearing cavity and adhesion of microspheres to raceways caused by deposition of interlayer materials in the raceway are avoided.For the micro ball bearing designed and manufactured in this paper, the encapsulation scheme is put forward, and the micro rolling friction test platform is developed, which realizes the real time measurement of the bearing speed, angular displacement, normal load, air supply pressure and flow rate.The quantitative relationship between normal load and friction torque is obtained, and the wear of micro ball bearing raceway is analyzed by using 3D profilometer, scanning electron microscope and energy dispersive spectrometer.The results show that the wear of microball bearings is mainly due to the adhesive wear of the contact surface between the microsphere and the SiC film under the high contact stress at the instantaneous high temperature.
【学位授予单位】：北京理工大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TH133.3
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本文编号：1737509