Effects of Ultra-Thin Liquid Lubricant Films on Dynamics of Nano-Spacing Flying Head Sliders

This paper describes the effects of ultra-thin liquid lubricant film on air bearing dynamics and flyability of nano-spacing flying head sliders in hard disk drives. The dynamics of slider is monitored using Acoustic Emission (AE) and Laser Doppler Vibrometer (LDV). The disks with lubricant on one half of disk surface thicker than the other half as well as with uniform thickness lubricant are used to investigate the interactions between slider and lubricant film experimentally. As a result, it is found that the flying height at which the contact between slider and lubricant film occurs depends on the lubricant film thickness and it increases as the lubricant film thickness increases. Its flying height is also in good agreement with the estimated results based on the theory of capillary waves. Further, we can find out that its flying height also depends on the mobile lubricant film thickness and it increases as the mobile lubricant thickness increases under the condition that the lubricant film thicknesses are the same. Regard to an air bearing instability due to the interactions between slider and lubricant film, it also depends on the mobile lubricant film thickness as well as the total lubricant film thickness and intensifies as the mobile lubricant thickness decreases. Furthermore, the effects of non-uniform lubricant film distribution on head-disk interface dynamics are studied. It is found that the periodic lubricant re-distribution caused by slider-lubricant interactions can be observed.