Numerical Simulation of Touchdown Dynamics of Thermal Flying-Height Control Sliders

Abstract

With the advent of thermal flying-height control (TFC) technology the physical spacing in magnetic hard disk drives is now reduced to sub-1 nm. At this spacing the tribological flyability and reliability become critical issues for the performance of the read-write head. In this paper a numerical approach is applied to study the touchdown dynamics of TFC sliders by expanding a 3-degree-of-freedom slider dynamics model to a 250-degree-of-freedom head-gimbal assembly dynamics model and considering several significant tribological effects at this ultra-low clearance (adhesion, tribo-charge, friction, contact, etc.). The simulation results show that the slider's vibration amplitude increases substantially at the beginning of touchdown, and it gets suppressed with further reduction in flying height. Analysis in the frequency domain shows the excitation of the second air-bearing pitch mode when instability occurs. The expansion of the dynamic system to include a realistic model of the suspension is shown to be important in determining the frequency of the excited mode. Adhesion force is shown to play an essential role in exciting the second air-bearing pitch mode and causing instability, while electrostatic force and friction force affect only some details of the slider's dynamics at instability. Friction force is also shown to be related to the excitation of the first air-bearing pitch mode.Index Terms-Head-disk interface, head-gimbal assembly, interfacial forces, thermal flying-height control.

Investigation of electrostatically tunable adhesion and instability of flying head slider

“…This is because the actual air bearing is variable stiffness, but it is a constant in the simulation. It is fine for the adhesion study as the previous studies did in this way [5,15,27]. Back to the topic, with the increase of heater power, the slider is pushed to touch down; it vibrates violently at a certain heater power value, and the vibration amplitude continues to increase as the heater power raises regardless of whether there is an external EF.…”

“…As a kind of attractive force, the electrostatic force F e is even larger than the van der Waals force when the slider is lower than a certain threshold [14]; it has great influence on slider motion, affecting some details of the vibration instability of the slider [15], and cannot be ignored. Wang et al [11] found that the F e influenced instability of the slider experimentally, and they discovered that the slider has a faster release rate when the EF was removed, i.e., the instable vibration vanished at a lower TO height.…”

Numerical Analysis of Surface Force of Diamond-Like Carbon Surface Coated with Monolayer Lubricant Film

“…This rough surface adhesion model and analytical method were extensively used for the surface force of the head-disk interface to clarify the static instability of head sliders encountered in the process of reducing the flying height to less than 10 nm [11][12][13]. After a TFC head slider was introduced, Vakis et al [14] and Zheng and Bogy [15,16] evaluated the surface force based on the Stanley- Etsion-Bogy (SEB) theory [8] and analyzed the dynamics of the TFC head slider at touchdown. However, they could not elucidate the peculiar phenomena stated above.…”

Tribological Degradation of Head–Disk Interface in Hard Disk Drives Under Accelerated Wear Condition

“…A bump around 115 mW -118 mW indicates a vigorous slider vibration, which is then suppressed by further increasing the TFC power. The bump in TD process is generally characterized as the flying instability region, in which the slider is bouncing from disk, or intermittently contacting with disk [25]. The suppressed vibration indicates that the slider is continuously sliding on the disk.…”