Analysis of the Loading Process of a Slider With Reflowed Lubricant in a Hard Disk Drive

As the recording density of hard disk drives has increased exponentially recently, the load/unload process can be affected severely by the nanolevel changes in the air-bearing surface (ABS) induced by the reflow behavior of perfluoropolyether molecules. In this paper, clean-up time and reflow time were first measured by using thermal flying controller measurements to check whether reflowed lubricant can affect loading performance. The measured clean-up time and reflow time were 120 s and 40 min, respectively. Because the clean-up time is so much longer than the loading process, almost all the reflowed lubricant remained on the bottom of the ABS during the loading process. Next, the lubricant behavior at rest was modeled and simulated theoretically by using a diffusion process. At rest, the time-dependent profiles of the reflowed lubricant were investigated. In addition, the ABS was modified with reflowed profiles at various time intervals and loading process was carried out with the modified ABS for various parameters such as reflow time and loading velocity. As a result, the slider-disk contact distinctly occurred during the loading process in the case with reflowed lubricant profiles. The simulation results were verified with the experimental results. Consequently, the effects of reflowed lubricant should be considered when designing the loading process of a slider to improve head-disk interface reliability.