• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.833-836
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• 2007

Load/Unload technology has more benefits than the conventional CSS technology. However, it remains unsolved technical problem on the unloading process. While the slider climbs up the ramp at the outer edge of the disk, the possibility of the slider-disk contact by lift-off force and rebound of the slider increases. This paper focuses on no slider-disk contact. To prevent the slider-disk contact, we apply the disk bump on disk outer edge proceeding unload. Firstly, in the simulation, the bump dimension is determined by changing bump design parameters. Secondly, dynamic stability of slider have to be checked on disk bump before unload analysis, and unload analysis is performed by applying stable bump shapes to unload simulation. Thirdly, we select optimal bump shape to improve unload performance by unload analysis. Finally, in the experiment, the disk bump is mechanically manufactured by pressing disk surface using diamond tip. That is variously processed by changing pressing pressure. After confirming bump shape by nano-scanner, proper bump shape is applied to real experimental unload process. Through this investigation, we propose the optimal bump design to prevent the slider-disk contact, and then we can realize improved unloading performance.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.140-143
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• 2006

Load/Unload(L/UL) technology includes the benefits, that is, increased areal density, reduced power consumption and improved shock resistance. The main issues of L/UL are no slider-disk contact and no media damage. To make sure L/UL stability, we consider many design parameters in L/UL systems. This paper is focused on disk design parameters through designing a disk bump in outer guard band(OGB). In the case of bump design on the disk, we create a bump by changing bump design parameters as like size and amplitude. From dynamic analysis, we choose optimal bump model with the highest flying height and the longest rising time. When a slider passes over a bump in dynamic system, the slider rise above bump according to bump shape. On the basis of this rising effect on the bump, we apply bump design to classical L/UL system having slider-disk contact possibility. This study is based on the simulation, we finally realize improved slider unloading performance by applying slider dynamic result on unload simulation.

• Transactions of the Society of Information Storage Systems
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• v.3 no.4
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• pp.183-190
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• 2007

In most hard disk drives that apply the ramp load/unload technology, the head is unloaded at the outer edge of the disk while the disk is rotating. During the unloading process, slider-disk contacts may occur by lift-off force and rebound of the slider. The main issue of this paper is to prevent the slider-disk contact by rebound, and we apply a disk bump to the unloading process. To do so, first, the ranges of bump dimension are determined. Second, the stability of each bump is checked by dynamic simulation. Finally, unload simulations are performed for stable bump designs. As a result of these steps, the effect of the bump design and the position for the unloading performance were investigated. As a consequence, we propose the optimal bump design to improve the unloading performance. Furthermore, we can identify to remove rebound contact by applying a bump on disk during the unloading process.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1276-1279
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• 2007

The main objectives of the Load/Unload are no slider-disk contact and no media damage. But, it remains unsolved technical problems on the unloading process. While the slider climbs up the ramp at the outer edge of the disk, the possibility of the slider-disk contact by lift-off force and rebound of the slider increases. Keeping in mind of these points, to prevent the slider-disk contact, we apply the disk bump on disk outer edge proceeding unload. First, referring to the simulation results, we select the optimal bump shapes to improve unload performance by unload analysis. Second, the disk bump is mechanically manufactured by pressing disk surface using tungsten tips. The bumps are variously processed by changing pressing pressure of tungsten tips. After confirming bump shape by nano-scanner, the optimal bump shape is applied to experimental unload process. Through this experiment, it is conformed that the unload performance was improved by using the optimal disk bump to prevent the slider-disk contact.

• Journal of Mechanical Science and Technology
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• v.14 no.7
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• pp.744-751
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• 2000

To achieve lower flying height for high areal recording density, the laser zone texturing of the disk needs to be designed to reduce glide height. One problem of the laser bump design is that the regular laser bump pattern often produces glide resonance phenomenon, which leads to failure of the glide height test. However, it was found in this study that glide resonance is an intrinsic problem of the glide head used and resonance phenomenon depends on the type of the head slider, that is, the natural frequency of the slider body. Therefore, higher glide height or glide failure caused by glide resonance does not lead to head/media interface problem in the real drive operating conditions in which the data head is used. Pseudo-random bump pattern greatly reduces the glide resonance. Smaller bump pitch will also help to reduce the glide resonance. However, as bump spacing becomes smaller, glide height will be increased due to increased air pressure developed around the bumps. Lowering bump height is the most effect way to reduce glide avalanche.

• Tribology and Lubricants
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• v.19 no.2
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• pp.102-108
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• 2003

The height of laser bumps has been considered as the limit of the minimum flying height in the contact start-stop (CSS) of hard disk drives. In this paper, tribological interactions at flying height under laser bumps are investigated in a spin stand for development of ultra-low flying head-disk interface. With the reduction of the spinning speed in a spin stand, the flying height is decreased under the height of laser bumps and, then, head-disk interactions are investigated using AE and stiction/friction signals. During seek tests and 20000 cycle-sweep tests, AE and stiction/friction signals are not significantly changed and there are no catastrophic failures of head-disk interface. Bearing analysis and AFM analysis show that there are signs of wear and plastic deformation on the disks. It is suggested that flying height could be as low as and, sometimes, lower than laser bump height.

• KSTLE International Journal
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• v.3 no.2
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• pp.114-118
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• 2002

In this work, head-disk interactions are studied when flying height becomes lower than laser bump height on the landing zone of a disk. With the reduction of the spinning speed in a spin stand, the flying height is decreased under the height of laser bumps. Conventional and padded pico sliders sweep between landing Bone and data zone and, then, the dynamic behavior of the pico sliders and head-disk impacts are investigated using AE and stiction/friction signals. After 200n cycle-sweep tests, bearing analysis and AFM analysis indicate that there are some signs of wear and plastic deformation in the landing zone of a disk, although AE and stiction/friction signals are not significantly changed during the sweep tests. The experimental results of this paper suggest that in CSS tests at component level, more rigorous examination methods of wear and plastic deformation might be necessary as flying height becomes getting lower.

• Tribology and Lubricants
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• v.17 no.1
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• pp.64-71
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• 2001

This paper presents dynamic responses of disk flutter and bump in HDD slider. The slider is modeled for three degree-of-freedom systems, which are capable of lifting, pitching, and rolling motions. In numerical analysis, loads from air pressure, preload and static moments from the slider, and stiffness and damping coefficients of the suspension are considered for investigating the dynamic characteristics analysis. The numerical results are presented as functions of typical parameters such as a disk velocity, stiffness and damping coefficients of the suspension, and skew angle.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.10a
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• pp.106-114
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• 1998

Tribological investigation of ultra thin film magnetic storage disks which have two different kinds of start/stop zone of laser textured bump disk and mechanically textured disk for before CSS test and after CSS test. To measure surface roughness, height reduction before/after CSS test and obtain accurate topographies, AFM(Atomic Force Microscope) which is most powerful recently has been used. The result of statistical analysis showed that both laser textured bump height and mechanically textured zone height have been reduced about 4~7nm after 15000 cycle CSS test. Using commercial Nano-Indenter, ramping load scratch test has been performed to investigate friction characteristic for laser textured zone and mechanically textured zone before/after CSS test.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1577-1582
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• 2000

In this study, the experimental modal analysis is performed to investigate the dynamic characteristics of slider-air bearings in hard disk drives. Bump response of the slider is acquired by measuring the relative velocity for two points using the laser interferometer, in which the disk is scratched lightly by a sharp knife to make a bump. From the measurements, the modal parameters of the head slider, modal frequencies and damping ratios of roll and pitch, are estimated by data processing and parameter estimation.