scholarly journals Parametric Investigations at the Head-Disk Interface of Thermal Fly-Height Control Sliders in Contact

2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Sripathi V. Canchi ◽  
David B. Bogy ◽  
Run-Han Wang ◽  
Aravind N. Murthy
Keyword(s):  
Hard Disk Drives ◽  
Air Bearing ◽  
Head Disk Interface ◽  
Bearing Surface ◽  
Surface Design ◽  
Disk Interface ◽  
Height Control ◽  
Experimental Findings ◽  
And Control ◽  
Fly Height

Accurate touchdown power detection is a prerequisite for read-write head-to-disk spacing calibration and control in current hard disk drives, which use the thermal fly-height control slider technology. The slider air bearing surface and head gimbal assembly design have a significant influence on the touchdown behavior, and this paper reports experimental findings to help understand the touchdown process. The dominant modes/frequencies of excitation at touchdown can be significantly different leading to very different touchdown signatures. The pressure under the slider at touchdown and hence the thermal fly-height control efficiency as well as the propensity for lubricant pickup show correlation with touchdown behavior which may be used as metrics for designing sliders with good touchdown behavior. Experiments are devised to measure friction at the head-disk interface of a thermal fly-height control slider actuated into contact. Parametric investigations on the effect of disk roughness, disk lubricant parameters, and air bearing surface design on the friction at the head-disk interface and slider burnishing/wear are conducted and reported.

Boundary Effect on Particle Motion in the Head Disk Interface

2007 ◽  
Author(s):  
Nan Liu ◽  
David B. Bogy
Keyword(s):  
Drag Force ◽  
Particle Motion ◽  
Boundary Effect ◽  
Hard Disk Drives ◽  
Areal Density ◽  
Air Bearing ◽  
Disk Drives ◽  
Head Disk Interface ◽  
Bearing Surface ◽  
Disk Interface

Simulation of particle motion in the Head Disk Interface (HDI) helps to understand the contamination process on a slider, which is critical for achieving higher areal density of hard disk drives. In this study, the boundary effect—the presence of the slider and disk—on particle motion in the HDI is investigated. A correction factor to account for this effect is incorporated into the drag force formula for particles in a flow. A contamination criterion is provided to determine when a particle will contaminate a slider. The contamination profile on a specific Air Bearing Surface is obtained, which compares well with experiments.

Thermal Fly-Height Control Slider Instability and Dynamics at Touchdown: Explanations Using Nonlinear Systems Theory

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
Sripathi Vangipuram Canchi ◽  
David B. Bogy
Keyword(s):  
Nonlinear Systems ◽  
Systems Theory ◽  
Resonance Condition ◽  
Hard Disk Drives ◽  
Jump Condition ◽  
Surface Design ◽  
Disk Interface ◽  
Height Control ◽  
Low Head ◽  
Fly Height

Thermal fly-height control sliders are widely used in current hard disk drives to control and maintain subnanometer level clearance between the read-write head and the disk. The peculiar dynamics observed during touchdown/contact tests for certain slider designs is investigated through experiments and analytical modeling. Nonlinear systems theory is used to highlight slider instabilities arising from an unfavorable coupling of system vibration modes through an internal resonance condition, as well as the favorable suppression of instabilities through a jump condition. Excitation frequencies that may lead to large amplitude slider vibrations and the dominant frequencies at which slider response occurs are also predicted from theory. Using parameters representative of the slider used in experiments, the theoretically predicted frequencies are shown to be in excellent agreement with experimental results. This analytical study highlights some important air bearing surface design considerations that can help prevent slider instability as well as help mitigate unwanted slider vibrations, thereby ensuring the reliability of the head-disk interface at extremely low head-disk clearances.

A Method to Reduce Head-Disk Interface (HDI) Degradation Risk During Thermal Asperity (TA) Mapping in a Hard Disk Drive

2020 ◽  
Author(s):  
Abhishek Srivastava ◽  
Rahul Rai ◽  
Karthik Venkatesh ◽  
Bernhard Knigge
Keyword(s):  
Hard Disk Drive ◽  
Bias Voltage ◽  
Disk Drive ◽  
Test Time ◽  
Head Disk Interface ◽  
Disk Interface ◽  
Height Control ◽  
Contact Sensor ◽  
Fly Height ◽  
Sample Set

Abstract One of the issues in thermal asperity (TA) detection using an embedded contact sensor (ECS) is the degradation caused to the read/write elements of the head while interacting with the TA. We propose a method to reduce such head-disk interaction (HDI) during TA detection and classification by flying higher at low thermal fly-height control (TFC) power, which minimizes the interaction of the TA with the head. The key idea is to scan the head at higher fly height, but with higher ECS bias voltage. Initial experiments have shown that the TA count follows a negative cubic relationship with the backoff at various bias levels, and that it follows a square relationship with bias at various backoff levels. Using a sample set, the calibration curves i.e. the golden relationship between these parameters can be established. Using these, one can start the TA detection at the highest backoff and high ECS bias, and start to estimate the nominal TA count. By mapping out these TAs and ensuring the head does not fly over them again to prevent HDI, the fly height can then be lowered, and the rest of the TA cluster can be scanned. Following this method iteratively, the entire TA cluster can be mapped out with minimal interaction with the head. Although this method entails an increase in the test time to detect and map all TAs, compared to detecting them with TFC being on, this can help improve the reliability of the drive by protecting the sensitive read/write elements especially for energy assisted recording from HDI.

Pumping Effect of Slider Air Bearing Surface for Non-Langmuir Adsorption

2010 ◽  
Author(s):  
Bo Zhang ◽  
Akira Nakajima
Keyword(s):  
Disk Surface ◽  
Air Bearing ◽  
Head Disk Interface ◽  
Bearing Surface ◽  
Adsorption Model ◽  
Adsorbed Film ◽  
Disk Interface ◽  
Langmuir Adsorption ◽  
Langmuir Adsorption Model ◽  
Slider Air Bearing

Numerical analysis of the adsorbed film thickness at the air bearing surface is conducted using the non-Langmuir adsorption model. It is found that the adsorbed film at the air bearing surface becomes significant when the viscosity of adsorbed film is higher than about 1 Pa s. The adsorbed contaminant will accumulate at the rear end of the slider, and it is possible that the accumulated liquid-like contaminant may form a liquid tail which will directly contact with the disk surface, resulting in a crush of the head/disk interface.

Contact Take-Off Characteristics of Proximity Recording Air Bearing Sliders in Magnetic Hard Disk Drives

1999 ◽  
Vol 121 (4) ◽  
pp. 948-954 ◽  
Author(s):  
Yong Hu
Keyword(s):  
Hard Disk Drives ◽  
Air Bearing ◽  
Disk Drives ◽  
Head Disk Interface ◽  
Taper Angle ◽  
Wear Factor ◽  
Disk Interface ◽  
Partial Contact ◽  
Magnetic Hard Disk ◽  
Wear Law

A partial contact air bearing model and Archard’s wear law are used to investigate the air bearing and wear characteristics of proximity recording sliders during a take-off process. The air bearing pitch torque, pitch and contact force are used to characterize the contact take-off process. In addition, the wear factor derived from the Archard’s wear law is employed to measure the take-off performance. The results indicate the existence of two distinct take-off stages: a period of rapidly increasing pitch preceding a relatively steady take-off event. The proper range of taper angle and step height, which produce a rapid initial pitch increase and steady subsequent take-off as well as less wear in the head/disk interface, are determined through simulation. While the simulation results demonstrate the negligible effect of crown height on the rate of the initial pitch increase, larger crown values are shown to yield higher pitch and smaller wear in the head/disk interface during the take-off process. In summary, the partial contact air bearing simulation and the wear factor calculation of the take-off process, developed in this study, offers a fast and accurate analytical tool to optimize ABS design for the fast take-off performance.

Air-bearing surface chemical modification for low-friction head–disk interface

2006 ◽  
Vol 13 (8-10) ◽  
pp. 811-816 ◽  
Author(s):  
Yuki Shimizu ◽  
Junguo Xu ◽  
Shozo Saegusa ◽  
Noritsugu Umehara
Keyword(s):  
Chemical Modification ◽  
Air Bearing ◽  
Surface Chemical ◽  
Head Disk Interface ◽  
Bearing Surface ◽  
Low Friction ◽  
Disk Interface ◽  
Surface Chemical Modification

A Heat Transfer Study in the Head Disk Interface and an Insight to Heat Assisted Magnetic Recording Design

2017 ◽  
Author(s):  
Haoyu Wu ◽  
David Bogy
Keyword(s):  
Heat Transfer ◽  
Magnetic Recording ◽  
Convective Heat Transfer Coefficient ◽  
Head Disk Interface ◽  
Heat Assisted Magnetic Recording ◽  
Disk Interface ◽  
Height Control ◽  
Contact Sensor ◽  
Series Of Experiments ◽  
Fly Height

Understanding the heat transfer in the head disk interface (HDI) in the heat assisted magnetic recording (HAMR) is important. In this paper, we report on a series of experiments to study the heat transfer in the HDI using the perpendicular magnetic recording (PMR) heads and media. The temperature increase of the embedded contact sensor (ECS) and the thermal fly-height control (TFC) heater was compared in the fly setup and non-fly setup. A series of simulations were performed to explain the results. We show that the design of the air bearing surface can significantly affect the pressure distribution in the read/write transducer area, and thereby affect the convective heat transfer coefficient.

Effect of Slider Burnish on Disk Damage During Dynamic Load/Unload

1998 ◽  
Vol 120 (2) ◽  
pp. 332-338 ◽  
Author(s):  
M. Suk ◽  
D. Gillis
Keyword(s):  
Contact Stress ◽  
Disk Surface ◽  
Hertzian Contact ◽  
Radius Of Curvature ◽  
Air Bearing ◽  
Head Disk Interface ◽  
Bearing Surface ◽  
Disk Interface ◽  
Current Design ◽  
Hertzian Contact Stress

Two of the most difficult issues to resolve in current design of head/disk interface in magnetic recording devices are stiction and durability problems. One method of overcoming these problems is by implementing a technology known as load/unload, where the system is designed so that the slider never touches the disk surface. One potential problem with this type of system is slider/disk contact induced disk defects. The objective of this paper is to show that the likelihood of disk scratches caused by head/disk contacts during the load/unload process can be significantly decreased by rounding the edges of the air-bearing surface. Using the resistance method, we observe that head/disk contacts burnish the corners of the slider and thereby decrease exponentially with load/unload cycles. A well burnished slider rarely causes any disk damage thus resulting in an interface with significantly higher reliability. A simple Hertzian contact stress analysis indicates that the contact stress at the head/disk interface can be greatly decreased by increasing the radius of curvature of the air-bearing surface edges.

A Method for Characterizing the Head-Disk Interface Dynamics Near the Touchdown Conditions Using the Magnetic Fly-Height

2020 ◽  
Author(s):  
Rahul Rai ◽  
Abhishek Srivastava ◽  
Bernhard Knigge ◽  
Aravind N. Murthy
Keyword(s):  
Hard Disk Drives ◽  
Areal Density ◽  
Disk Surface ◽  
Disk Drives ◽  
Head Disk Interface ◽  
Soft Contact ◽  
Disk Interface ◽  
Magnetic Spacing ◽  
Bearing Stiffness ◽  
Fly Height

Abstract Recent growth in the cloud storage industry has created a massive demand for higher capacity hard disk drives (HDD). A sub-nanometer head media spacing (HMS) remains the most critical pre-requisite to achieve the areal density needed to deliver the next generation of HDD products. Designing a robust head-disk interface (HDI) with small physical clearance requires the understanding of slider dynamics, especially when the head flies in proximity to the disk surface. In this paper, we describe a method using the magnetic read-back signal to characterize the head fly-height modulations as it undergoes a transition from a free-flying state to soft contact with the disk surface. A technique based on the magnetic fly-height sensitivity is introduced for the identification of the transition plane that corresponds to the onset of the touchdown process. Additionally, the proposed magnetic spacing based meteorology is used to study the effect of the air bearing stiffness on the magnitude of the slider vibrations induced by intermittent head-disk interactions. The information about the minimum spacing while maintaining the stable flying conditions can help in reducing the head-disk interaction risk that can enable a low clearance interface.

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