Experimental and Simulation Study of Thermal Protrusion-Induced Head-Disk Contact Instabilities in Hard Disk Drives

Abstract

Stability of the thermal fly height control slider has profound effects on the read-write performance and reliability of the head-disk interface. As magnetic storage technologies evolve aggressively toward higher areal density in hard disk drives, the fly height around the transducer area on the slider has achieved a read-write physical spacing of \({\sim }2\) nm, and is expected to be even lower to meet the magnetic storage road map in the near future. At such a low spacing, instabilities can occur in terms of slider vibration and prominent lubricant transfer from the disk to the slider, resulting in significant interface change that raises reliability concerns. In this paper, we experimentally investigate the thermal protrusion induced slider instability at contact proximities, and perform numerical simulations to explain the measured dynamics at head-disk contacts. The results suggest that as the slider's thermal protrusion area approaches the disk surface, instabilities mainly come from down-track force excitations. These excitations lead to more significant vibrations in the down-track direction and on the slider's leading edge rather than its trailing edge. The behavior of slider vibration at disk proximity is also dependent on the head-gimbal-assembly design.