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

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.

Thermal Fly-Height Controlled Glide for Disk Defect Detection and In-Situ Defect Size Estimation for Disk Drives

2013 ◽  
Author(s):  
Aravind N. Murthy ◽  
Karl A. Flechsig ◽  
Wes Hillman ◽  
Keith Conard ◽  
Remmelt Pit
Keyword(s):  
Hard Disk Drives ◽  
Sem Analysis ◽  
Disk Drives ◽  
Size Estimation ◽  
Optical Surface ◽  
Force Microscopy ◽  
Height Control ◽  
Atomic Force ◽  
Fly Height

Current hard disk drives (HDD’s) use thermal fly-height control (TFC) during read/write operations. In this study, we use TFC technology during the disk glide process to determine sub-5nm height defects. We also utilize TFC to measure the height of the defect during glide operation. Addtionally, we magnetically mark the disk locations where defects are detected for further post-processing of the defects using optical surface analysis (OSA), atomic force microscopy (AFM), and scanning electron microscopy (SEM). The defect height estimation during the glide was confirmed to be accurate by AFM and SEM analysis. Finally, we will present the TFC glide sensitivity showing capability of detecting smaller defects than conventional non-TFC glide technologies.

Temperature Study of Embedded Contact Sensor for HDDS by Using Scanning Thermal Microscopy

2014 ◽  
Author(s):  
Masaru Furukawa ◽  
Junguo Xu ◽  
Jianhua Li ◽  
Kiyoshi Hashimoto ◽  
Makoto Satou
Keyword(s):  
Hard Disk Drives ◽  
Disk Drives ◽  
Scanning Thermal Microscopy ◽  
Height Control ◽  
Head Slider ◽  
Self Bias ◽  
Key Factor ◽  
Contact Sensor ◽  
Sensor Temperature ◽  
Fly Height

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.

An Insight Into the Nonlinear Touchdown Dynamics of TFC Active Slider

2013 ◽  
Author(s):  
Gang (Sheng) Chen ◽  
Jianfeng Xu ◽  
J.-Y. Chang
Keyword(s):  
Nonlinear Dynamics ◽  
Hard Disk Drives ◽  
Disk Surface ◽  
Flying Height ◽  
Disk Drives ◽  
Height Control ◽  
Intermittent Contact ◽  
Fly Height ◽  
Insight Into ◽  
Small Spacing

Storage of 10 Tb/in 2 in hard disk drives within the next decade requires a significant change to reduce the physical spacing as little as 0.25 nm at the read-write transducer location. A lot of tribology issues exist to such a low flying height, the touch down and take off instability and hysteresis, the flying height avalanche, the influences of surface topography and morphology, the lubricant modulation and pick-up, robust air bearing surface and suspension design, just to name a few. Understandings of the complex tribo-dynamics issues in the near contact and contact states are very important to further reduce the flying height. At such a small spacing intermittent contact between the slider and disk surface becomes inevitable and the current MEMS-based thermal fly-height control (TFC) technology needs further improvement to satisfy the future needs. How to control the slider to reduce touchdown instability and eventually eliminate bouncing has been a pressing and challenging research topic. Most of existing work on touchdown dynamics applied conventional nonlinear dynamics theory and spectrum as well as harmonics analysis, which could suffer from the assumptions of small nonlinearity and stationary. This study presents a concurrence plot and Lyapunov exponent analysis which could offer an insight to the problem in the context of contemporary nonlinear dynamics theory.

Novel Dielectric Stack Actuators for Dynamic Applications

2012 ◽  
Author(s):  
Sven Herold ◽  
William Kaal ◽  
Tobias Melz
Keyword(s):  
Simulation Model ◽  
Surface Resistance ◽  
Design Concept ◽  
Metal Electrodes ◽  
High Quality ◽  
Complex Material ◽  
Simulation Results ◽  
Actuator Design ◽  
Load Conditions

In order to realize dielectric elastomer stack actuators suitable for dynamic applications a new actuator design with rigid, perforated electrodes is developed. The low surface resistance of the metal electrodes predestines this concept for dynamic applications where higher currents are present. Detailed numerical analyses are performed to show the potential of this approach, to study the complex material deformation and to optimize the aperture geometry. A multilayer stack actuator is then manufactured and characterized experimentally under various load conditions to gain suitable parameters for a parametrized model. It is subsequently used to attenuate vibrations of a truss structure. By careful adjusting the parameters it functions both as passive absober and as actuator. A comparison of experimental and simulation results proves the high quality of the simulation model. The work shows the great potential of the new design concept for future applications especially in the field of smart structures.

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

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.

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.

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

2009 ◽  
Vol 45 (11) ◽  
pp. 5026-5029 ◽  
Author(s):  
Lionel Ng ◽  
Mingsheng Zhang ◽  
Bo Liu ◽  
Yansheng Ma
Keyword(s):  
Height Control ◽  
Disk Contact ◽  
Fly Height

Contact and temperature rise of thermal flying height control sliders in hard disk drives

2012 ◽  
Vol 18 (9-10) ◽  
pp. 1693-1701 ◽  
Author(s):  
Liane Matthes ◽  
Uwe Boettcher ◽  
Bernhard Knigge ◽  
Raymond de Callafon ◽  
Frank E. Talke
Keyword(s):  
Temperature Rise ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Flying Height ◽  
Disk Drives ◽  
Height Control ◽  
Thermal Flying Height Control

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.

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