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Reducing the Viscous Force (Stiction) of Magnetic Head Sliders on Lubricated Magnetic Disks

IP.com Disclosure Number: IPCOM000045266D
Original Publication Date: 1983-Feb-01
Included in the Prior Art Database: 2005-Feb-06
Document File: 3 page(s) / 48K

Publishing Venue

IBM

Related People

Hinkel, H: AUTHOR [+4]

Abstract

The stiction of sliders with magnetic heads on magnetic disks is eliminated by locally heating the lubricant between the slider and magnetic disk for a short time. This heating, before the magnetic disks are started from the inoperative state, temporarily reduces the viscosity of the lubricant and thus the dynamic stiction force which is directly proportional to the viscosity. Heating is effected, for example, by electric resistors arranged on the sliders or by hot air fanning the slider and the disk area in contact with it.

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Reducing the Viscous Force (Stiction) of Magnetic Head Sliders on Lubricated Magnetic Disks

The stiction of sliders with magnetic heads on magnetic disks is eliminated by locally heating the lubricant between the slider and magnetic disk for a short time. This heating, before the magnetic disks are started from the inoperative state, temporarily reduces the viscosity of the lubricant and thus the dynamic stiction force which is directly proportional to the viscosity. Heating is effected, for example, by electric resistors arranged on the sliders or by hot air fanning the slider and the disk area in contact with it.

Magnetic disks of storage systems are lubricated with a thin film of prefluorinated hydrocarbons to ensure optimal tribological properties. If too little lubricant is used, debris collects at the slider, leading to head-disk interference and disk failure, whereas too much lubricant, although preventing such interference, leads to stiction, causing the slider to adhere to the disk when the system is in the switched-off state. Upon start-up, stiction frequently bends the arm carrying the slider, thus leading to system failure.

Research into the stiction phenomenon has shown that it is largely attributable to viscous friction; the static component (adherence) being much smaller than the dynamic component (viscous force). The maximum stiction force F(m) is reached only shortly after start-up and is
F(m) approx. S/EtaA square root of LR1 S is the distance between slider and disk, A is the area of the slider rails, Eta is the viscosity of the lubricant, L is the slider length, 1 is the disk acceleration, and R is the track radius.

With normal operating data, F(m) is 2 to 4 N, thus exceeding by a factor 2 to 4 the maximum tolerable value of about 1 N. Of the equation parameters, only the angular acceleration 1 seems to be suitable for substantially reducing the stiction force F. As F(m) approx. square root of 1, 1 must be reduced by a factor 16 if F(m) is to be cut to a quarter of the original value. This necessitates a torque control of the drive motor and considerably increases the starting period.

It is also possible to vary F(m) over a wide...