Effect of various physical factors on thin lubricant film migration on the flying head slider at the head-disk interface of hard disk drives

Abstract

The mechanism of lubricant migration on a flying slider’s air bearing surface in magnetic hard disk drives is examined in this paper. As the head-disk spacing diminishes, the lubricant contamination from the disk and its migration behavior on the flying head slider becomes an increasing concern. The spatiotemporal behavior of the thin lubricant film on a slider surface is complicated, and it is affected by many physical factors. We investigate the contributions and functionalities of the potentially related physical factors and parameters on the lubricant film dynamics by numerical simulation. The analysis results show that the air bearing shear stress is the primary driving force in the lubricant migration, while the air bearing pressure makes only a minor contribution. The relative strength and direction of the Couette and Poiseuille flow components of the air bearing shear stress govern the lubricant migration direction and the points of lubricant stagnation. The lubricant surface free energy plays an important role while the contribution of diffusion is relatively small through the Laplace pressure but relatively large through the lubricant disjoining pressure which is determined by the surface energy gradient. We also find that the lubricant viscosity affects the lubricant dynamics as a time scaling factor. These results reveal the underlying physical framework of the complex phenomena and provide useful insight for developing the head disk interface of magnetic disk drives.