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Idle Algorithm to Minimize Slider/Disk Lubricant Interactions

IP.com Disclosure Number: IPCOM000016068D
Original Publication Date: 2002-Jul-10
Included in the Prior Art Database: 2003-Jun-21
Document File: 2 page(s) / 109K

Publishing Venue

IBM

Abstract

Background This invention publication relates to an idle algorithm for a disk drive that minimizes the formation of lubricant droplets on the disk. A major problem for disk drives today, as flying heights are rapidly decreasing, is the fact that the slider interacts strongly with the disk lubricant. One phenomenon that has been demonstrated to be a problem is when lubricant gets picked up by the slider during normal operations, and subsequently dropped on the surface of the disk. Most of the time, the droplet spreads back or gets sheared off by the air shear or the slider. However, there is a finite probability that the head will write when the slider encounters a lubricant droplet sitting on the disk. When this happens, a significant vertical excursion of the slider happens and the signal does not get written properly, leading to a hard error. Most of the lubricant pickup to the slider happens when the slider is sitting on-track. This invention publication relates to an idle algorithm whereby the seek sequencing during idle is such that it minimizes the lubricant pickup to the slider and at the same time smears off any potential lubricant accumulation on the disk. Lubricant Depletion from the Disk

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Idle Algorithm to Minimize Slider/Disk Lubricant Interactions

Background

This invention publication relates to an idle algorithm for a disk drive that minimizes the formation of lubricant droplets on the disk.

A major problem for disk drives today, as flying heights are rapidly decreasing, is the fact that the slider interacts strongly with the disk lubricant. One phenomenon that has been demonstrated to be a problem is when lubricant gets picked up by the slider during normal operations, and subsequently dropped on the surface of the disk. Most of the time, the droplet spreads back or gets sheared off by the air shear or the slider. However, there is a finite probability that the head will write when the slider encounters a lubricant droplet sitting on the disk. When this happens, a significant vertical excursion of the slider happens and the signal does not get written properly, leading to a hard error. Most of the lubricant pickup to the slider happens when the slider is sitting on-track. This invention publication relates to an idle algorithm whereby the seek sequencing during idle is such that it minimizes the lubricant pickup to the slider and at the same time smears off any potential lubricant accumulation on the disk.

Lubricant Depletion from the Disk

When the slider is sitting on-track over a spinning disk, it starts depleting lubricant from the disk, and the amount lost from the disk ends up on the slider. This is demonstrated in Figure 1 where a scanning ellipsometer image of a disk lubricated with 18A of Zdol4000, after a few minutes of on-track flying, shows significant lubricant loss. The lubricant that is lost from the disk accumulates on the slider deposited end, as seen on the photograph shown in Figure 2.

Figure 1: Scanning Ellipsometer image of a disk after 5mn of track-following The gray scale contrast corresponds to lubricant thickness (lighter is thinner lubricant)

Figure 2: Photograph of the slider Deposited End (DE) after track following. The arrow marks the spot where lubricant accumulates.

It turns out that there is a very short induction period during which there is no si...