Optimum Design And Experimental Investigation Of Slider Air Bearing For High-density Hard Disks

Optimum design of head slider is one of the key problems in the development of magnetic storage technology, which is also one of the most important approaches for improving the performance of high density magnetic storage systems. In the thesis, some issues related to the optimum design of sliders are explored theoretically and experimentally.First of all, analysis of the air lubrication in head-disk interfaces is studied with numerical simulation methods. The modified Reynold equation is solved with the finite difference method, the accuracy of the numerical solutions is verified by comparing with analytical and DSMC solutions. The multi-grid method is adopted to improve the calculation efficiency, and the effects of the intermolecular force on the head-disk interface are also taken into account.Secondly, based on the developed numerical analysis method, the methodology for optimal design of the topology of air bearing surface of sliders is investigated. A new coding method for the genetic algorithm, which takes the slider step depth information into account, has been proposed, which enlarges the solution space. Different predefined structures based on the design experiences are adopted to improve the optimum design efficiency. It is demonstrated that the calculation time required for an optimal design can be saved greatly by combination of the topology optimum design with dimension optimum design methods.Then, a substitution slider for flying height test is fabricated with micromachining processes on silicon wafer. The key issues, including mask design, silicon etching and dicing etc., are explored and their effects on the quality of slider are discussed. A suitable fabrication process for fabricating the silicon slider is found. Surface topography measurement results show that the fabricated silicon slider can meet the requirements for flying height test.In addition, the characteristics of acoustic emission (AE) signals under various flying states are detected and analyzed. By comparing the time and frequency domain characteristics of the AE signals, it has been shown that the vibration of the slider suspension is closely related to the occurence of head-disk collision.Finally, the flying heights of two silicon sliders are measured with a home-made symmetrical common-path heterodyne interferometer. The experimental and prediction results coincide well with each other, which implies that the theoretical models and numerical analysis in this work are correct, and the fabricated silicon slider can be used as a substitution for real slider in flying height test.