Low Molecular Weight Z-Tetraol Boundary Lubricant Films in Hard Disk Drives

R J Waltman,H Deng

doi:10.1155/2012/964089

Abstract

Lower molecular weight Z-Tetraol films exhibit increased mechanical spacing in the slider-disk interface due to a lower z-profile. An increased resistance to lubricant disturbance on the disk surface (e.g., lube moguls) with decreasing film thickness is attributed to an increasing contribution from the polar component of the disjoining pressure. Evaporative loss at temperatures typically encountered in a hard-disk drive also increases with decreasing molecular weight but is strongly dependent on the initial bonded fraction.

Highlights

In order to keep pace with the higher areal storage density requirements of hard-disk drives (HDDs), the spacing between the read-write element of the slider and the surface of the rigid magnetic disk has been reduced to 1-2 nm
Low zprofile PFPEs can be attained by reducing the film thickness, the main chain molecular weight, and its flexibility [1,2,3]
The mechanical clearance of the PFPE lubricants was quantified by measuring the acoustic emission (AE) generated at the head-disk interface as a function of sliderdisk clearance

Summary

Introduction

In order to keep pace with the higher areal storage density requirements of hard-disk drives (HDDs), the spacing between the read-write element of the slider and the surface of the rigid magnetic disk has been reduced to 1-2 nm. Perfluoropolyether (PFPE) boundary lubricant films having reduced dynamic expansion perpendicular to the disk surface (“low z-profile”) have allowed lower flying. Low zprofile PFPEs can be attained by reducing the film thickness, the main chain molecular weight, and its flexibility [1,2,3]. Based on these studies, a useful mnemonic relating sliderdisk mechanical clearance, Δclearance, to these PFPE main chain properties is given in (1) as follows: Δclearance ∝. We compare the boundary lubrication properties of lower MW Z-Tetraols for their potential use in HDDs. the effect on mechanical clearance, surface energy, lubricant dewetting, and lubricant evaporation at drive temperatures is quantified

Experimental

Results

Discussion