基于磁流变效应柔性夹持超薄钛酸锶电子陶瓷基片精密磨粒加工研究

Strontium titanate electronic ceramic is the key material of electronic components such as high-performance chip capacitors and microwave circuit boards due to the unique high dielectric constant. With the development of its applications, the 2 inch strontium titanate ceramic substrate need to get smooth and flat surface, whose thickness reaches up to 0.1mm and roughness smaller than 0.01μm. However, it is difficult to be processed because the characteristic of ultrathin, soft, brittle and warp. Base on the earlier research, we propose a new technological method，which use the magneteroheogical effect(MR effect) flexible fixturing technology to solve the fragmentation problem during fixturing and machining, remove the uneven and warp surface quickly by use the MR effect flexible fixturing and the cluster MR effect high efficiently lapping technology, then get the high quality smooth and flat surface by use vacuum adsorption and cluster MR effect low scathe plane polishing technology. The project carry out systematic research on the abrasive machining of rough substrate in the aspects of flexible fixturing, position automatic adjustment mechanism, material stress & deformation control, subsurface damage, material ductile-brittle removal pattern transform, surface formation mechanism, machining efficiency, surface integrity and so on. According to the research, MR effect flexible fixturing theory and the material removal mechanism of strontium titanate ceramic substrate base on the cluster MR effect lapping and polishing will be revealed thoroughly. It is expected to achieve no broken and high efficiently machining of ultrathin and soft-brittle electronic ceramic substrate, which is benefit to the development of electronic ceramic material and its components.

钛酸锶电子陶瓷由于独有的高介电常数成为高性能电子元器件和微波电路基板的核心材料，随着应用需求的发展，需要钛酸锶陶瓷基片尺寸达到2英寸厚度小到0.1mm并具有光滑平坦表面（Ra≤0.01μm），但是钛酸锶陶瓷本身决定了其毛坯具有"薄、软、脆、翘"的特征，难以有效加工。基于前期研究，提出采用磁流变效应的柔性夹持解决装夹和加工过程中的基片破碎问题，应用集群磁流变高效研磨快速去除基片毛坯面的凹凸不平和翘曲，利用真空吸附和集群磁流变低损伤平面抛光获取高质量光滑平坦表面的工艺方法。对磨粒加工过程中的毛坯柔性夹持、位置自动调整机制、材料应力与变形控制、亚表面损伤、材料脆塑性去除模式转换、表面形成机理、加工效率和表面完整性等进行系统研究，形成磁流变效应柔性夹持理论，揭示钛酸锶电子陶瓷基片在集群磁流变研抛作用下的材料去除机理，实现大尺寸超薄软脆电子陶瓷基片的零破碎高效加工，促进电子陶瓷材料及元器件的发展。

针对钛酸锶电瓷毛坯具有“薄、软、脆、翘”的特征、难以有效加工等问题。项目对钛酸锶电瓷基片进行了纳米压痕试验，表明400mN载荷时钛酸锶的硬度和模量分别为8.4Gpa和246.3Gpa。提出了一种“防破碎研磨”方法，采用厚度略大于基片翘度的聚氨酯行星齿轮对翘曲基片进行有效固定，基片与行星齿轮“共磨”实现钛酸锶双面凸起优先去除而平坦化，行星齿轮对研磨压力的分担而避免陶瓷基片破碎。采用该方法对钛酸锶基片进行了深入的工艺研究，获得了表面粗糙度为Ｒa0.268μm、去除率为4.6 μm/min、厚度为0.19 mm，以及TTV小于0.01 mm的钛酸锶电瓷基片。接着对钛酸锶电瓷基片进行了超光滑抛光加工试验，获得整体表面粗糙度为Ra0.01µm局部表面粗糙度Ra4nm的超光滑基片。对集群磁流变效应平面抛光技术磁场特性进行了静磁场有限元优化，基于Preston方程和加工材料属性, 建立了集群磁流变抛光的材料去除数学模型，并验证了其合理性。对集群磁流变平面抛光力进行了测试，构建了集群磁流变效应“微磨头”对磨料的“容没”效应模型，并进行了实验验证。通过对光电晶体基片加工出弧形抛光带，验证了集群磁流变效应抛光膜的集群特性并优化了抛光工艺参数，获得纳米级粗糙度表面。在集群磁流变的基础上提出了一种磁流变抛光垫实时修整的动态磁场磁流变抛光平面抛光方法和一种集群动态磁场控制抛光垫刚度的双面抛光方法，研制了动态磁场试验装置，对钛酸锶电瓷基片进行了系统试验研究，采用优化的磁流变液和抛光工艺，能够获得表面粗糙度和材料去除率分别为Ra8nm和0.154μm/min的光滑基片。对各种工艺下获得的钛酸锶电瓷基片材料去除机理及表面完整性进行了研究分析。项目获授权发明专利5项，新申请发明专利7项（2项PCT专利），发表论文17 篇（SCI/EI论文13篇），对促进超精密加工技术的发展具有一定的理论价值和实际意义。