Numerical Simulation of Thermal Fly-Height Control Slider Touchdown Test for Achieving Ideal Subnanometer Clearance Head Slider Touchdown Behaviors

An embedded contact sensor (ECS), which is a thermal sensor built into a head slider, has been used for contact detection between the head slider and the disk in hard disk drives. Our previous research showed that ECS could successfully detect pits on the disk and spacing modulation between the head and disk. In this work, the sensor temperature effect caused by self heating and by the thermal fly height control (TFC) heater was studied in a non-flying condition for better understanding ECS. The results showed that the temperature dependency of the TFC heater was 10 times that of ECS self-bias heating. TFC heating is dominant and the key factor in ECS sensitivity to pit detection and spacing monitoring.

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Performance Optimization of Thermal Nano-Actuator for Fly Height Control in Disk Drives

ASME/STLE 2009 International Joint Tribology Conference ◽

10.1115/ijtc2009-15137 ◽

2009 ◽

Author(s):

Haisan Tan ◽

Bo Liu ◽

Mingsheng Zhang ◽

Shengkai Yu

Keyword(s):

Performance Optimization ◽

Power Input ◽

Vertical Position ◽

Disk Drives ◽

Height Control ◽

Line Spacing ◽

Simulation Results ◽

Heater Design ◽

Fly Height ◽

Actuator Design

Slider with thermal fly height control (TFC) uses a thermal heater to produce localized thermal protrusion and adjust the vertical position of the read/write head. This paper reports authors’ efforts in exploring large protrusion stroke with minimal heater power input whilst preserving heater robustness in the TFC slider, with an optimized thermal nano-actuator design. Effects of both heater line width and line spacing on TFC slider performances are investigated. A novel ‘Stream-River’ heater design approach is proposed. Simulation results conclude that the “Stream-River” approach is of both high power-protrusion efficiency and high heater robustness.

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Ranking of Thermal Asperity (TA) Interaction During Seeking Under Various Fly-Height Conditions

ASME 2020 29th Conference on Information Storage and Processing Systems ◽

10.1115/isps2020-1962 ◽

2020 ◽

Author(s):

Abhishek Srivastava ◽

Bernd Lamberts ◽

Ning Li ◽

Bernhard Knigge

Keyword(s):

Theoretical Analysis ◽

State Interaction ◽

Idle State ◽

Height Control ◽

Interaction Mechanisms ◽

Industry Standard ◽

Maximum Benefit ◽

Protection Mechanisms ◽

Fly Height ◽

Experimental Corroboration

Abstract HDD heads have various interaction mechanisms with thermal asperities (TAs), and protection mechanisms need to be put in place to ensure the head-disk interaction (HDI) resulting from them is eliminated or minimized to the highest extent possible. It is straightforward to not allow the head sit-on-track on cylinders that have such TAs on them, and the same principle can be extended to so-called high TAs (HTAs), whose height is more than the fly height of the head, so heads do not inadvertently interact with the TA even when motion is triggered on another head, since the entire head stack moves together. Similar TA interactions also occur when the head seeks across the tracks. Typical short seeks have thermal fly-height control (TFC) turned on while it is turned on during long seeks, which is greater than a few hundred tracks. Heads can also interact with TAs during retract and arrival of the head during such long seeks. Finally, background media scan (BGMS), which is an industry standard, when the drive enters an idle state. Interaction with HTAs can also occur when the drive enters such a state. Typical seek avoidance attempts to eliminate TA interaction during seeking, however it is not straightforward to determine which of the seek mechanism: TFC On during short seeks, retract/arrival during long seeks, HTA interaction during long seeks with TFC off, or idle TA interaction causes the greatest HDI. Through theoretical analysis and experimental corroboration, this paper intends to rank the various modes of TA interaction, so by developing features for eliminating or minimizing them in that order could help bring the maximum benefit for achieving minimum lifetime reduction of the head due to such interaction.

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

ASME 2020 29th Conference on Information Storage and Processing Systems ◽

10.1115/isps2020-1960 ◽

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.

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Development of Active Head Slider for Flying Height Control

The proceedings of the JSME annual meeting ◽

10.1299/jsmemecjo.2002.1.0_263 ◽

2002 ◽

Vol 2002.1 (0) ◽

pp. 263-264

Author(s):

Kenji SUZUKI ◽

Takayuki AKIMATSU ◽

Kenji SASAKI

Keyword(s):

Flying Height ◽

Height Control ◽

Head Slider

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Numerical Simulation of Thermal Flying-Height Control Sliders to Dynamically Minimize Flying Height Variations

IEEE Transactions on Magnetics ◽

10.1109/tmag.2012.2221473 ◽

2013 ◽

Vol 49 (4) ◽

pp. 1337-1342 ◽

Cited By ~ 10

Author(s):

Pablo A. Salas ◽

Frank E. Talke

Keyword(s):

Numerical Simulation ◽

Flying Height ◽

Height Control ◽

Thermal Flying Height Control

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Slider-Disk Contact Characterization Using a Thermal Fly-Height Control Slider

IEEE Transactions on Magnetics ◽

10.1109/tmag.2009.2029596 ◽

2009 ◽

Vol 45 (11) ◽

pp. 5026-5029 ◽

Cited By ~ 4

Author(s):

Lionel Ng ◽

Mingsheng Zhang ◽

Bo Liu ◽

Yansheng Ma

Keyword(s):

Height Control ◽

Disk Contact ◽

Fly Height

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

Advances in Tribology ◽

10.1155/2012/303071 ◽

2012 ◽

Vol 2012 ◽

pp. 1-11 ◽

Cited By ~ 7

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.

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