Electrostatic Force Manipulation Methodology: Principles, Mechanisms, and Setup for Head–Disk Interactions Monitoring

To achieve higher hard disk drive areal density, the head-disk clearance had been reduced to <;2 nm recently. Head-disk interaction monitoring with high sensitivity and resolution is desired to monitor the intense interactions at near-contact and to prevent head-disk contact. In this paper, head-disk interaction monitoring based on the electrostatic force manipulation (EFM) principle is discussed. The mechanisms of the two setups to apply alternating electrostatic force (F
_es
) across the head-disk interface were investigated. It was shown that the distribution of the applied F
_es
was different for the two setups. This led to further studies of the effects of the F
_es
distribution on interactions monitoring. The results showed that when an alternating F
_es
was distributed at the pole region, the magnitude of the electrodynamically excited first-harmonic vibration increased significantly as the gap fly height was reduced. It was very sensitive to spacing change and useful for the head-disk interactions monitoring at the near-contact regime. The second harmonic was found sensitive to head-disk contact. When the alternating F
_es
was distributed at the slider body, the magnitudes of the first and second harmonics were larger due to larger effective surface area. However, the fly height of the slider body was mainly affected by the protrusion push-up effect, and hence the first and second harmonics showed a reverse trend as compared with the case where F
_es
was distributed at the pole region. In addition, slider pitch motion was also significantly affected. The effective EFM setup was constructed to demonstrate its effectiveness in head-disk interactions monitoring and contact detection.