A multidentate lubricant for use in hard disk drives at sub-nanometer thickness

Abstract

We describe a second generation of multidentate lubricant structures for use on a magnetic media in a hard disk drive. Building on earlier work where a perfluoropolyether (PFPE) chain with hydroxyl bonding moieties were placed in the middle of the chain as well as on chain ends, creating a structure with two PFPE sub-units for enhanced tribological performance under very low head-disk spacing, this paper focuses on a PFPE chain composed of three, even shorter PFPE subunits. Experimental data focusing on surface characterization of sub-nanometer thickness films, as well as tribological performance, are presented that confirm the high confinement level achieved with the lubricant structure. Molecular dynamics calculations are also discussed, that are consistent with a molecular film of high stiffness, leading to a denser, more compact structure. This approach could pave the way to achieving the sub-nanometer head-disk clearance level, presumed necessary for storage densities exceeding the terabit per square inch density landmark.

Nanometer-Thick Fluorinated Ionic Liquid Films as Lubricants in Data-Storage Devices

“…5,6 To reduce direct head-media contact and protect the magnetic media from wear, nanometer thick lubricants need to be applied on the surface of the media. 7,8 Another example is the nano-and microelectromechanical systems (NEMS/MEMS). In such systems, it has been reported that adhesion is one of the major sources of breakdown in a digital micromirror device and that wear detrimentally affects the data storage system of NEMS-based atomic force microscopy (AFM).…”

“…The application of nanometer thick lubricants is of vital importance to the efficiency and reliability of these devices. , For instance, the head-media spacing (HMS) between the flying magnetic head and the spinning magnetic media (∼10 m/s) is only ∼10 nm in a hard disk drive (HDD), the state-of-the-art data storage device. , The HMS is even approaching as low as 7 nm to go beyond the areal density milestone of 1 Tbit/in. 2 . , To reduce direct head-media contact and protect the magnetic media from wear, nanometer thick lubricants need to be applied on the surface of the media. , Another example is the nano- and microelectromechanical systems (NEMS/MEMS). In such systems, it has been reported that adhesion is one of the major sources of breakdown in a digital micromirror device and that wear detrimentally affects the data storage system of NEMS-based atomic force microscopy (AFM). , Ultrathin lubricants are coated on the surfaces of the NEMS/MEMS devices for better tribological performance.…”

The Head-Disk Interface Roadmap to an Areal Density of Tbit/in2

“…Table 2 shows that a 0.2 nm reduction of lubricant thickness from 1.0-1.2 to 0.8-1.0 is needed. This does not seem like much, but with today's extremely tight reliability/HMS margins, this change is actually significant, and it is believed that inventions will be needed to reach those goals [50,51]. The lubricant industry is now more diversified than before, and new lubricant structures are now routinely offered by at least three different companies.…”

Ionic Liquid Lubricant for Ultra-Low Head-Media Spacing in Hard Disk Drives

“…Low MW PFPE is not a practical solution because there is a trade-off relationship between small monolayer thickness and evaporation loss. In order to reslove this trade-off issue, multidentate PFPE lubricant is developed which has several hydroxy (OH) groups at the intermediate positon along the PFPE main chain [6][7][8][9][10]. The conventional PFPEs such as Z-Dol and Z-Tetraol, have OH groups only at both terminals of the PFPE main chain.…”