The Effect of PFPE Film Thickness and Molecular Polarity on the Pick-Up of Disk Lubricant by a Low-Flying Slider

Abstract

Lubricant pick-up by a low-flying slider is investigated for hydroxyl-terminated perfluoropolyethers as a function of the number of hydroxyl (OH) groups and of film thickness on the surface of finished rigid disks. The total number of hydroxyl (OH) groups per main chain is 2, 4, and 8 for Zdol, Z-Tetraol, and ZTMD, respectively. The amount of disk lubricant that is picked up by the low-flying slider decreases with decreasing PFPE film thickness and increasing number of OH functional groups. The results are discussed in terms of the disjoining pressure characterizing the lubricant film on the disk surface.

Laser-Induced Thermo-Desorption of Perfluoropolyether Lubricant from the Surface of a Heat-Assisted Magnetic Recording Disk: Lubricant Evaporation and Diffusion

“…This result is at least an order of magnitude smaller than a previous measurement of an ''effective'' diffusion coefficient obtained using the distance traveled by a lubricant film on a CN x overcoat during a fixed time increment and meant to show the relative differences in specific lubricant molecular polarity [16]. We attribute the difference between these results to the approximate nature of the ''effective'' diffusion coefficient [16] and the probable increased ''bonding'' of the Ztetraol on our N 2 -plasmatreated COC surface. The diffusion coefficient of typical hard disk drive lubricants is usually thickness dependent, especially in the range of one monolayer [33].…”

“…Furthermore, due to head-disk-interface (HDI) concerns, its thickness on the media surface must not be appreciably altered from the asdeposited film (thicker or thinner) during the course of repetitive HAMR writing. For example, if it becomes thicker on the media surface, it will be an impediment to flyability and if thinner, it will poorly coat the COC [16,17].…”

Z-Tetraol Reflow in Heat-Assisted Magnetic Recording

“…Depending upon the read-write duty cycle, the mobility of the boundary lubricant film, and the local supply of the lubricant film, reflow from the surrounding area into the thickness-depleted area may, or may not, occur at a fast enough rate to maintain tribological robustness under HAMR conditions. Many recent tribological studies indicate that lubricant coverage is the significant determinant for contamination robustness and head-disk interface reliability [12][13][14][15]. Tribological robustness must still be satisfied in the HAMR interface.…”

Single-Chain Conformational Analysis on the Dynamic Main Chain Expansion of a Tethered Perfluoropolyether Boundary Lubricant Film

“…These can occur by the combined effects of the air shear stress, the air bearing pressure, and the van der Waals attractive forces operating between the slider and the disk surface [1][2][3][4][5]. Locally thicker films are more easily transferred to the slider, leading to reliability failure in HDD [6,7]. This is further compounded by the fly-height sensing technology used in today's HDDs.…”