Critical clearance and lubricant instability at the head-disk interface of a disk drive

2008 ◽  
Vol 92 (3) ◽  
pp. 033104 ◽  
Author(s):  
Rohit P. Ambekar ◽  
David B. Bogy ◽  
Qing Dai ◽  
Bruno Marchon
Keyword(s):  
Disk Drive ◽  
Head Disk Interface ◽  
Disk Interface

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.

Dynamic Analysis of Sliding Contacts at Head-Disk Interface

2002 ◽  
Author(s):  
T.-J. Chuang ◽  
S. M. Hsu
Keyword(s):  
Data Storage ◽  
High Speed ◽  
Time History ◽  
Disk Drive ◽  
Element Model ◽  
Disk Surface ◽  
Magnetic Data ◽  
Head Disk Interface ◽  
Sliding Contacts ◽  
Disk Interface

As magnetic data storage technology moves towards higher areal data density with higher rotational speeds and lower flying heights, the propensity of severe sliding contacts at the head-disk interface is bound to increase. The tribological performance of the head-disk interface will have significant impact on the durability and service life of the hard disk drive (HDD). A 3D finite element model is constructed to simulate the high speed impact event of a slider on the disk surface. For a given design of the disk with known layer thicknesses and properties, as well as that of the slider with its surface texture, the model predicts contact zone, depth force and duration as well as time-history of energy transfer and its partition, substrate stress and plastic zone for a given impact velocity. The effects of the material properties and layer thicknesses on the performance of the HDD are investigated.

Head-Disk Interface Issues for Near Contact Recording

2001 ◽  
Author(s):  
R. H. Wang ◽  
V. Raman ◽  
U. V. Nayak
Keyword(s):  
Ambient Pressure ◽  
Disk Drive ◽  
Flying Height ◽  
Head Disk Interface ◽  
Disk Interface ◽  
Magnetic Spacing ◽  
Wear And Corrosion ◽  
Disk Lubricant ◽  
Contact Recording

Abstract As the magnetic recording density increases towards hundreds of Gb/in2, both the magnetic spacing and head-disk clearance decrease to < 10 nm. By one estimate, the magnetic spacing for 1 Tb/in2 is about 6 nm and the read width is ∼ 30 nm. There are at least two different approaches to achieving this. The first one is an extension of the traditional flying interface and the second is contact recording. In the former case one needs to be concerned about maintaining adequate clearance both at sea level and at higher elevation whereas in the latter case the wear and corrosion of the heads and disks may pose major challenges. In the flying regime, an accelerated test to assess the relative integrity of the head-disk interface is described here. This is accomplished by monitoring the acoustic emission, capacitance or friction between the head and the disk as the ambient pressure is reduced. The pressure at which an abrupt change in the above signals takes place is called take-off pressure (TOP). This is also known as altitude avalanche measurement. With this method it is possible to compare different disk and head designs at the full velocity of the slider. We present results correlating the TOP with disk roughness and the influence of disk lubricant. An example of how head-disk interference takes place in a disk drive will be given for an experimental 10 nm flying slider. The effects of radial flying height profile, take-off height of the disk, and the disk curvature on mechanical spacing are presented. The results of changes occurring on the air bearing surface and the disks after long term flyability test are discussed.

Wear Analysis of Head-Disk Interface During Contact

2005 ◽  
Vol 127 (1) ◽  
pp. 171-179 ◽  
Author(s):  
Wei Peng ◽  
James Kiely ◽  
Yiao-Tee Hsia
Keyword(s):  
Hard Disk Drive ◽  
Wear Mechanism ◽  
Adhesive Wear ◽  
Contact Stiffness ◽  
Hard Disk ◽  
Disk Drive ◽  
Head Disk Interface ◽  
Wear Coefficient ◽  
Disk Interface ◽  
Fly Height

To achieve a higher storage density in a hard disk drive, the fly height of the air bearing slider, as part of the magnetic spacing, has to be minimized. At an ultralow fly height, the intermittent–continuous contact at the head–disk interface (HDI) is unavoidable and directly affects the mechanical and magnetic performance of the hard disk drive, and is of great interest. The HDI wear has a nonlinear and time-varying nature due to the change of contact force and roughness. To predict the HDI wear evolution, an iterative model of Coupled Head And Disk (CHAD) wear, is developed based on the contact mechanics. In this model, a composite transient wear coefficient is adopted and multiple phases of the wear evolution are established. A comprehensive contact stiffness is derived to characterize the contact at the HDI. The abrasive and adhesive wear is calculated based on the extended Archard’s wear law. The plastic and elastic contact areas are calculated with a three-dimensional (3D) sliding contact model. Based on the CHAD wear model, for the first time, the coupling between head and disk wear evolutions is thoroughly investigated. Accelerated wear tests have also been performed to verify the disk wear effect on the slider wear. A wear coefficient drop with time is observed during the tests and it is attributed to a wear mechanism shift from abrasive to adhesive wear. A shift in the type of contact from plastic to elastic accounts for the wear mechanism change.

Effect of Non-Operational Shock on Interaction Between Suspension Lift-Tab and Load/Unload Ramp

2005 ◽  
Author(s):  
Aravind N. Murthy ◽  
Eric M. Jayson ◽  
Frank E. Talke
Keyword(s):  
Hard Disk Drive ◽  
Failure Modes ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Areal Density ◽  
Disk Drive ◽  
Disk Drives ◽  
Head Disk Interface ◽  
Disk Interface ◽  
Operational Shock

Most hard disk drives manufactured in the last few years have Load/Unload (L/UL) technology. As opposed to the Contact Start/Stop (CSS) technology, L/UL technology has the advantage of improved areal density because of more disk space availability and better shock performance. The latter characteristic has significant benefits during the non-operational state of the hard disk drive since head/disk interactions are eliminated and the head is parked on a ramp adjacent to the disk. However, even if head/disk interactions are absent, other failure modes may occur such as lift-tab damage and dimple separation leading to flexure damage. A number of investigations have been made to study the response of the head disk interface with respect to shock when the head is parked on the disk ([1], [2]). In this paper, we address the effect of non-operational shock for L/UL disk drives.

Protecting the head/disk interface from the chemical environment with disk drive filtration

2003 ◽  
Vol 39 (2) ◽  
pp. 769-774 ◽  
Author(s):  
D.E. Fowler ◽  
R. Duque ◽  
T. Anoikin ◽  
Jian Zhou
Keyword(s):  
Disk Drive ◽  
Chemical Environment ◽  
Head Disk Interface ◽  
Disk Interface
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