Characterization of Thermally Actuated Pole Tip Protrusion for Head-Media Spacing Adjustment in Hard Disk Drives

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Sung-Chang Lee ◽  
Brian D. Strom
Keyword(s):  
Hard Disk Drives ◽  
Hard Disk ◽  
Disk Drive ◽  
Intermolecular Forces ◽  
Field Application ◽  
Model Calculations ◽  
Disk Interface ◽  
Thermal Actuation ◽  
Thermally Actuated ◽  
Adhesive Forces

The effect of thermomechanically actuated pole tip protrusion on adhesive forces is characterized through model and experiment. The roughness of a thermomechanically actuated region is characterized by atomic force microscopy. Using the extracted roughness parameters and estimated apparent area associated with thermal actuation, the intermolecular forces at the head-disk interface (HDI) are calculated using the ISBL (improved sub-boundary lubrication) code. Both roughness and nominal area of contact are found to be significant factors determining adhesive forces. The adhesive forces for various HDI designs—including thermal actuation—are also characterized experimentally in situ using commercial hard disk drive samples. The experimental results are found to be consistent with the model calculations and imply certain advantages for thermally actuated HDI designs. However, the experiments also raise concerns regarding the field application of the technology.

Optimization of Air Bearing Contours for Shock Performance of a Hard Disk Drive

2003 ◽  
Author(s):  
Eric M. Jayson ◽  
Frank E. Talke
Keyword(s):  
Hard Disk Drive ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Disk Drive ◽  
Element Model ◽  
Time Dependent ◽  
Air Bearing ◽  
Disk Interface ◽  
Shock Response ◽  
Shock Event

Hard disk drives must be designed to withstand shock during operation. Large movements of the slider during shock impulse can cause reading and writing errors, track misregistration, or in extreme cases, damage to the magnetic material and loss of data. The design of the air bearing contour determines the steady state flying conditions of the slider as well as dynamic flying conditions, including shock response. In this paper a finite element model of the hard disk drive mechanical components was developed to determine the time dependent forces and moments applied to the slider during a shock event. The time dependent forces and moments are applied as external loads in a solution of the dynamic Reynolds equation to determine the slider response to a shock event. The genetic algorithm was then used to optimize the air bearing contour for optimum shock response while keeping the steady flying conditions constant. The results show substantial differences in the spacing modulation of the head/disk interface after a shock as a function of the design of the air bearing contour.

On the Touchdown-Takeoff Hysteresis Observed at the Head-Disk Interface in Hard Disk Drives

2005 ◽  
Author(s):  
Rohit P. Ambekar ◽  
David B. Bogy
Keyword(s):  
Experimental Approach ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Intermolecular Forces ◽  
Disk Drives ◽  
Head Disk Interface ◽  
Contributing Factors ◽  
Factors Affecting ◽  
Disk Interface

The touchdown-takeoff velocity hysteresis observed in hard disk drives during CSS or L/UL tests is analyzed using an experimental approach. Tests similar to L/UL were conducted for different slider-disk combinations at different humidities. Factors affecting the touchdown and takeoff velocity were identified on the basis of their domain of operation. It is concluded that the intermolecular forces and meniscus forces are contributing factors to hysteresis, which is also influenced by disk topography and slider dynamics.

Effect of Spinning Disk–Parking Ramp Collison on the Operational Shock Performance of a Mobile Hard Disk Drive

2010 ◽  
Author(s):  
Rahul Rai ◽  
David B. Bogy
Keyword(s):  
Hard Disk Drives ◽  
Excitation Frequency ◽  
Hard Disk ◽  
Disk Drive ◽  
Disk Model ◽  
Disk Interface ◽  
Spinning Disk ◽  
Reliable Performance ◽  
Shock Resistance ◽  
Operational Shock

With the introduction of netbook computers two years ago, the demand for hard disk drives (HDD) for mobile applications has greatly increased. High shock resistance is an important requirement for the reliable performance of HDDs in such applications. In this paper we conduct a numerical investigation to understand the failure mechanism of the head disk interface (HDI) during an operational shock. Simulation results suggest that the excitation frequency spectrum has a strong influence on HDI failure. We also investigate the effect of the parking or load unload (LUL) ramp on shock resistance using a new spinning disk model. The results suggest that asymmetric excitations induced by ramp-disk collision causes failure of the HDI at lower shock magnitudes. This study can be helpful in improving the design of HDD components and air bearing sliders (ABS) for better shock performance.

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.

Optimization of Air Bearing Contours for Shock Performance of a Hard Disk Drive

2005 ◽  
Vol 127 (4) ◽  
pp. 878-883 ◽  
Author(s):  
Eric M. Jayson ◽  
Frank E. Talke
Keyword(s):  
Hard Disk Drive ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Disk Drive ◽  
Element Model ◽  
Time Dependent ◽  
Air Bearing ◽  
Disk Interface ◽  
Shock Response ◽  
Shock Event

Hard disk drives must be designed to withstand shock during operation. Large movements of the slider during a shock impulse can cause reading and writing errors, track misregistration, or in extreme cases, damage to the magnetic material and loss of data. The design of the air bearing contour determines the steady-state flying conditions of the slider as well as dynamic flying conditions, including shock response. In this paper a finite element model of the hard disk drive mechanical components was developed to determine the time dependent forces and moments applied to the slider during a shock event. The time-dependent forces and moments are applied as external loads in a solution of the dynamic Reynolds equation to determine the slider response to a shock event. The genetic algorithm was then used to optimize the air bearing contour for optimum shock response while keeping the steady flying conditions constant. The results show substantial differences in the spacing modulation of the head-disk interface after a shock as a function of the design of the air bearing contour.

scholarly journals Flying Instability due to Organic Compounds in Hard Disk Drive

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
Koji Sonoda
Keyword(s):  
High Temperature ◽  
Hard Disk Drive ◽  
Organic Compounds ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Disk Drive ◽  
Disk Drives ◽  
Head Disk Interface ◽  
Disk Interface

The influence of organic compounds (OCs) on the head-disk interface (HDI) was investigated in hard disk drives. The drives were tested at high temperature to investigate the influence of gaseous OC and to confirm if the gaseous OC forms droplets on head or disk. In the experiment, errors occurred by readback signal jump and we observed the droplets on the disk after full stroke seek operation of the drive. Our results indicate that the gaseous OC condensed on the slider and caused flying instability resulting in drive failure due to slider contact with a droplet of liquid OC. Furthermore, this study shows that kinetic viscosity of OC is an important factor to cause drive failure using alkane reagents.

A Method to Detect Head Media Spacing Change in a Hard Disk Drive Using an Embedded Contact Sensor

2019 ◽  
Author(s):  
Rahul Rai ◽  
Puneet Bhargava ◽  
Bernhard Knigge ◽  
Aravind N. Murthy
Keyword(s):  
Hard Disk Drives ◽  
Hard Disk ◽  
Disk Drive ◽  
Disk Surface ◽  
Physical Change ◽  
Disk Drives ◽  
Head Disk Interface ◽  
Disk Interface ◽  
Frequency Components ◽  
Contact Sensor

Abstract Growth in the demand for higher capacity hard disk drives (HDD) has pushed the requirement for head-media spacing (HMS) to sub-nanometer levels. The drop in operational clearance makes a head-disk interface (HDI) more susceptible to potential head-wear and contamination related issues. Such degradation processes are often accompanied by a noticeable shift in the head-disk clearance. Hence monitoring an interface for a spacing change can be helpful in early detection of its imminent failure. In this paper, we present a method to detect the change in head-disk spacing using an embedded contact sensor (ECS). This technique involves the analysis of ECS dynamic response for an interface that is subjected to heater induced spacing modulations. As the head moves closer to the disk surface, the magnitude of the ECS frequency components can be used to determine the ‘characteristic spacing’ which can be used as a metric to detect any physical change for a given interface.

Operational Shock Failure Mechanisms in Hard Disk Drives

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Liping Li ◽  
David B. Bogy
Keyword(s):  
Work Performance ◽  
Structural Model ◽  
Failure Mechanisms ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Disk Drive ◽  
Air Bearing ◽  
Disk Interface ◽  
Bearing Force ◽  
Positive Shock

The work performance of a hard disk drive (HDD) in mobile devices depends very much on its ability to withstand external disturbances. In this study, a detailed multibody structural model integrated with a complete air bearing model is developed to investigate the disk drive's response during external shocks. The head disk interface (HDI) failure mechanisms when the HDD is subjected to different shock cases are discussed. For a negative shock case in which the disk initially moves towards the head, with long pulse width, the air bearing becomes very stiff before the slider crashes on the disk, and the HDI fails only when the external load overcomes the air bearing force. For other shock cases, the slider contacts the disk due to a negative net bearing force caused by the slider-disk separation. Finally, a stiffer suspension design is proposed to improve the drive shock performance, especially during a positive shock, as under these conditions, the slider contacts the disk primarily due to the stiffness difference of the different drive components.

scholarly journals Low Molecular Weight Z-Tetraol Boundary Lubricant Films in Hard Disk Drives

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
R. J. Waltman ◽  
H. Deng
Keyword(s):  
Molecular Weight ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Disk Drive ◽  
Disk Surface ◽  
Polar Component ◽  
Disk Drives ◽  
Disk Interface ◽  
Boundary Lubricant ◽  
Evaporative Loss

Lower molecular weight Z-Tetraol films exhibit increased mechanical spacing in the slider-disk interface due to a lower z-profile. An increased resistance to lubricant disturbance on the disk surface (e.g., lube moguls) with decreasing film thickness is attributed to an increasing contribution from the polar component of the disjoining pressure. Evaporative loss at temperatures typically encountered in a hard-disk drive also increases with decreasing molecular weight but is strongly dependent on the initial bonded fraction.

Frictional Heating Effect on Thermal Protrusion in Head Disk Interface

2013 ◽  
Author(s):  
Jianhua Li ◽  
Junguo Xu ◽  
Masaru Furukawa
Keyword(s):  
Frictional Heating ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Areal Density ◽  
Disk Drive ◽  
Critical Issue ◽  
Disk Interface ◽  
Thermal Protrusion ◽  
The Status ◽  
Touchdown Point

For increasing areal density in hard disk drives (HDDs), the physical clearance between the read/write element and the surface of the disk has been continuously decreasing to 1 nm or below [1]. At such a low clearance, the contact between the head and the disk is inevitable to occur, so head wear is becoming a critical issue in the development of HDD. The contact between the head and the disk induces a frictional heating, which may generate an additional thermal protrusion in the contact area of the head, and causes more wear. On the other hand, the target clearance in a HDD is generally determined by pulling back a setting TFC power from the touchdown point, accurately identifying the touchdown point is very significant for the clearance control in hard disk drive. A thermal protrusion is caused by friction-heating in the status of touchdown. Therefore, it is very necessary to quantitatively understand on friction induced thermal protrusion and clearance loss.

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