AVS 46th International Symposium
    Vacuum Metallurgy Division Tuesday Sessions
       Session VM+MI+AS-TuA

Invited Paper VM+MI+AS-TuA5
Air Bearing Collision Dynamics

Tuesday, October 26, 1999, 3:20 pm, Room 620

Session: Magnetic Recording: Head/Disk Interface and Overcoats
Presenter: S.E. Stupp, Quantum Corporation
Authors: S.E. Stupp, Quantum Corporation
R.J. Blanco, Quantum Corporation
T. Riener, Quantum Corporation
B.D. Strom, Quantum Corporation
Correspondent: Click to Email
A few years ago, a disk drive program encountered an unusual problem: drives built with one vendor's heads (vendor A) suffered from an excessive number of thermal asperity events (TAs); drives built with head's from another vendor (vendor B) did not have as many TAs, but they did have a number of crashes. Spinstand experiments confirmed that there was a significant difference in the response of the two vendor's air bearings to collision with the 100 nm high asperities found in these drives. For example, the fly height of vendor A's heads was essentially unchanged on contact with an asperity, while vendor B's heads exhibited a fly height change (these differences may explain the drive results). The underlying problem in the drive program was ultimately traced to particulate contamination and was corrected. However, the experiments raise an interesting question: Why is there a difference in the dynamic response of the two vendor's heads? In this work we present a systematic study of this problem, which we christen Air Bearing Collision Dynamics (ABCD). The asperity collision responses of several different air bearing designs (including full rail and island type) were studied by measuring the TA signal, the change in flying height, acoustic emission (AE), and laser Doppler vibrometry, in controlled experiments on a spinstand. Since a large enough asperity can cause any head to crash, the asperity size was modest (approximately equal to the fly height). In agreement with our earlier experiments, differences in the response of the different air bearings were found. In addition, the AE signals indicate that certain island type air bearing designs can undergo multiple head-disk contacts after the asperity has passed. These results are potentially concerning, because many head vendors are moving towards this type of air bearing design. Finally, in an attempt to understand the origin of the differences in the dynamic response of different air bearing designs, we report the results of numerical modeling of the asperity and air bearing designs.