Readback Signal Decrease Due to Dynamic Load Head-Disk Contacts

Abstract

The effect of head-disk impacts due to repeated dynamic load is investigated experimentally. Loading conditions more severe than those typically found in ramp-load disk drives are applied to ensure that contacts occur, and disk-synchronized head loading motions are applied so that the head-disk contact points are all distributed within a small area on the disk. The resulting readback signal decrease was observed to correlate with the head-disk impact velocity and hence the slider’s vertical approaching velocity. With a larger vertical velocity, readback signal decrease appeared earlier and the amount of decrease was larger. The results indicate that dynamic load-unload should be quite reliable under typical loading conditions, and the reliability of dynamic load-unload can be achieved by controlling the vertical approaching velocity of the slider. This is comparatively easier than controlling the narrow manufacturing tolerances of the slider’s pitch and roll of the head-suspension assembly. The technological trend toward using smaller-sized head-suspension assemblies and higher-coercivity magnetic disks may further enhance the dynamic load head-disk interface durability.

Catastrophic damage of magnetic recording disk caused by slider-disk impact during loading/unloading

“…Recently, studies of dynamics of a slider during loading/unloading using a strain gauge sensor, an acoustic emission (AE) transducer, and a laser Doppler vibrometer (LDV) have been reported [3], [4]. Furthermore, studies of magnetic erasures and degrease of read back signals due to impact of head-disk contacts have been reported [5]- [7]. Recently, the data-erase problem due to the penetration of environmental particles in HDI has been one of the severe problems for actual magnetic disk drives with the loading/unloading operation.…”