Negative Pressure Slider Research Articles

A circular arc slider with a high flying height supported by parallel flat springs for optical disc devices

We have investigated a circular arc slider with a high flying height that is suitable for optical disc devices to reduce the thickness of the device and to achieve a higher recording density over a wider recording area. Our proposed slider was supported by parallel flat springs to reduce the tilting motions of the slider in the pitching and rolling directions. Two types of slider were examined: (1) a positive pressure slider with a single shallow pocket on the slider surface, and (2) a negative pressure slider with two shallow pockets. The static and dynamic characteristics of our proposed slider were investigated both theoretically and experimentally. It was found that our proposed sliders followed a disc surface with the amplitude of axial runout of 100 μm with a focusing error of 30 μmp-v in the focusing direction and a tilt angle of <6 minp-v in the pitching and rolling directions.

Development of Nanometer Flying-Height Slider for Small Magnetic Disk Drives

The 90nm and 15nm flying-height sliders we designed for small magnetic disk drives are based on a basic design guide we previously proposed that covers (1) a very small slider, (2) a multipad slider or side-step slider, and (3) a negative-pressure slider use in low spacing mode alone. These experimentally prototyped sliders were confirmed to fly stably on the disk at the prescribed 90nm and 15nm heights, and have been commercialized for 3.5-inch and 2.5-inch hard disk drives. These practical results demonstrate the feasibility of the proposed basic design guide.

Basic Design Guide Proposal on Nanometer Flying-Height Slider for Small Magnetic Disk Drives

We propose a basic design guide to design a very low spacing slider for small magnetic disk drives. The design features; (1) A multipad or side-step slider to avoid a sudden decrease in flying height due to the yaw angle of the swing actuator. (2) The slider must be as small as possible to be stable because the very low flying height makes the slider tend to vibrate unstably. (3) High spacing mode must be avoided to stabilize the negative-pressure slider used in constant density recording (CDR) suitable for high-density magnetic media.

Adaptive multilevel method for the air bearing problem in hard disk drives

An adaptive grid-generating algorithm is constructed and integrated with the multigrid method to form a numerical scheme that suits slider air-bearing simulation of hard disk drives. The relative truncation error, a by-product of the multigrid method, is used in grid adaptation criteria. Finer meshes are constructed over nodes of the current finest grid where the relative truncation error exceeds a predetermined tolerance. The union of these finer meshes forms a new level of grid, which may not cover the entire domain of the coarse grid underneath. The final grid system thus constructed is composed of levels of uniform grids with decreasing mesh sizes. This composite grid structure incorporates with numerical resolution as needed and efficiency of computation. A shaped rail, negative pressure slider is used to demonstrate the effectiveness of this numerical scheme. Compared with the traditional multigrid method, the proposed adaptive multilevel method can significantly reduce the computation work for achieving the same level of accuracy.

浮上スライダの耐衝撃特性(情報機器コンピュータメカニクス1 -ヘッド・ディスク・インターフェース,IIP2004 情報・知能・精密機器部門講演会)

The report is about a simulation of a negative pressure slider due to a shock. In the simulation, a shock with downward direction and a shock with upward direction are used. The shock is set as a triangle wave with maximum value 9800m/s^2(1000G) and varied duration. It is clear that squeeze effect of air bearing surface play an important role when a shock is gave to slider. In the case under downward shock, the flying height variation in short duration is smaller than in long duration, and in the case under upward shock, the suction face in short duration is larger than in long duration.The suction force of ABS under a upward shock is larger than the suction force that occurs in normal flying situation.

An experimental study of dimple separations and head-disk impacts of negative pressure slider in unload process

This paper presents an experimental study of the dimple separation and head-disk impact of negative pressure slider in unloading process. Two types of negative pressure sliders and HGAs with different limiters were used in the experiments. The dimple impacts, which reflect the close of separated dimple in unloading process, were observed in most of the tested cases by using AE measurements. The head-disk impact was occasionally observed for HGA with under larger unload speed, by using electrical resistance measurements. By using LDV and AE measurements, the dimple impact frequencies were characterized from the response of unloaded HGA to an impulse excitation. FEM analysis shows that the HGA with separated dimple has two cantilever mode frequencies, which are correlated with the measured dimple impact frequencies. It was also found that the effects of the difference of the two negative pressure sliders on the impacts features are not obvious, whereas the effect of the limiters and the unloading condition are essential to the impacts.

Studies of fly stiction

A study of fly stiction caused after a head slider flew over a disk surface was conducted to understand the mechanisms responsible for high stiction. In this paper, laser-textured disks and three types of nanosliders (50 per cent of the standard size) were used. Friction/stiction was measured and the r. m.s. acoustic emission was recorded in both a short sweep test where the slider swept for periods of 1 h and a long-sweep test where the slider swept for periods of 6 days. The surface of the head slider after tests was analysed using optical microscopy, atomic force microscopy/frictional force microscopy and Raman spectroscopy. Results showed that, in the short sweep test, stiction was sensitive to environmental humidity. Stiction was low at low humidities and increased with increase in the humidity. In the long-sweep test, liquid droplets accumulated during flying were observed on the head slider surface. The vortex around the head slider was found to be responsible for the accumulation of liquid droplets. The droplets then migrated to the rail surface and led to fly stiction during the following start-up. Stiction was sensitive to these liquid droplets in addition to the humidity. Both negative and positive-pressure sliders could cause fly stiction. A lower flying height was found to be more susceptible to fly stiction. A disk with a fully bonded lubricant film lowered the stiction. Increasing the disk speed could increase the stiction of a negative-pressure slider whereas it lowered the stiction of a positive-pressure slider because of the effects of flying heights, lubricant spin-off and intensity of the vortex

A force identification method for slider/disk contact force measurement

Slider/disk contacts existing during operation in almost all current disk drives significantly affect drive reliability and performance. We propose a force identification method to measure the contact force from a single impact. Laser Doppler Vibrometers (LDV) are used to measure the slider's response. A procedure, which combines experiment and FE analysis, is proposed to model the system, and it is claimed to have many advantages over other methods. The proposed method is successfully applied to measure the contact forces of two nano sliders when they make contact with a bump on a disk. A smaller contact force was noted with the negative pressure slider. Also, the contact force is smaller at higher rpm for these two sliders.

Dynamics for Micromachined Mother Ship Negative Pressure Slider Bearings With an Integrated Microsuspension Mechanism in Proximity Magnetic Recording

This paper describes head/disk interface dynamics for micromachined mother ship negative pressure slider bearings with an integrated microsuspension mechanism that we proposed, at steady-state flying in proximity magnetic recording. The authors first indicated the analytical model for air bearing dynamics of mother ship slider mechanisms, and the advantages of the mechanisms were discussed from the dynamics points of view, compared with conventional flying head slider mechanisms. Dynamic design considerations and optimization for micromachined mother ship negative pressure slider bearings with an integrated microsuspension mechanism were also investigated. Finite element simulation for the stiffness analysis of a microsuspension mechanism was carried out and the design optimization for low stiffness gimbals was studied. Furthermore, the effects of slider mass ratio and slider car film stiffness ratio of a secondary slider to a primary slider on mother shipslider dynamics were analyzed numerically. Considering those numerical simulationresults, system optimization for sliders as well as microsuspension gimbals was established to achieve head/disk interface reliability in high density proximity magnetic recording.

Stiffness and Damping Evaluation of Air Bearing Sliders and New Designs With High Damping

We apply the dynamic simulation and modal analysis method to analyze the dynamic properties of slider-air bearings. First, the theoretical background and proposed methods are described. Then, five basic types, one of which is first proposed in this paper, of the air bearing surfaces (ABS) are briefly discussed. The dynamic properties of the sliders are investigated, and compared with each other. It is found that a negative pressure slider has the highest stiffness and lowest damping, the TPC and two newly proposed sliders demonstrate higher damping. Finally, the general ABS design problem is briefly discussed. A new advanced slider is designed, analyzed, and compared with the other sliders. The air bearing of the new slider design has larger stiffness and the highest damping of those studied.

Component level investigations of liquid accumulation on sliders-"fly stiction"

When carbon coated sliders are flown over lubricated thin film disk surfaces over an extended period of time, there is a marked increase in stiction compared to values observed during rest stiction or instant measurements on the same surface. This phenomenon, commonly referred to now as "fly stiction", is the result of excessive liquids that accumulate over the slider air-bearing surface, the trailing edge of the slider as well as in the etch cavity areas of a negative pressure slider. The physical origins of this stiction increase, processes that lead to higher stiction and the influence of test variables are discussed.

Pole tip recession studies of thin-film rigid disk head sliders II. Effects of air bearing surface and pole tip region designs and carbon coating

Pole tip recession (PTR) results in an increase in spacing between recording elements and magnetic media which is undesirable for high-density recording. The effects of air bearing surface (ABS) designs, pole tip region designs and carbon coating on the growth of PTR with increasing start-stop cycles have been investigated. A better ABS design for less PTR should reduce contact time between slider and disk during take-off and landing of the slider. Among the two-rail, tail-dragger and negative pressure sliders, the negative pressure slider has shortest contact time during take-off and landing, followed by the two-rail slider and tail-dragger slider. The growth mechanisms of PTR for two-rail slider with or without U-shaped slot consists of knocking-off protruded poles, generation of wear particles and three-body abrasive wear. The PTR reaches a saturated value after a certain start-stop cycles. However, for the tail-dragger slider with square-shaped slot, there is a fourth step of erosion which leads to no saturation of PTR and a relatively rough surface of poles. Mechanisms of PTR for negative pressure slider is similar to the two-rail slider but with a lower saturated PTR value. Carbon coating minimizes or eliminates the PTR growth through reducing static and kinetic friction during take-off and landing, providing a wear-resistant protective layer and eliminating dissimilarities of ABS, thin film structure and poles. Based on this study, we find that negative pressure slider which minimizes contact at head-disk interface and carbon coating which protects thin-film region are desirable alternatives for slider designs. Initial recession is desirable as compared to protrusion.

Flying characteristics of a novel negative pressure slider “Papillon”

This paper proposes a novel design of a 50% shaped rail negative pressure air bearing slider, the Papillon slider. This design attains constant fly height and near-zero roll characteristics across the disk, simultaneously. The head roll due to seek acceleration is suppressed by controlling static roll angle and improving roll stiffness of the air bearing. It is shown that the side rail shape can be configured so as to improve the roll stiffness. Experiments also show that the Papillon slider has good takeoff and contact start/stop performance.

Ductile Regime Cutting of Brittle Materials Using a Flying Tool under Negative Pressure

The importance of ductile regime cutting has been emphasized in the production of large-diameter optics and semiconductor substrates over the last ten years. However the available technology has not yet been implemented in industry. The reason is that cutting technology based on the motion-copying principle is too sensitive for error motions of a machine tool to maintain the actual depth of cut stably below the critical depth. A new cutting technology using a flying tool under negative pressure has been developed. In this technology, a flying tool glides over a workpiece surface while maintaining a small height like a negative-pressure slider of a magnetic disc drive. Using the tool system, ductile regime cutting of optical glass and monocrystalline silicon was examined, and a mirror-surface finish with no cracks was achieved on a face lathe having a 0.1μm order of error motion.

Ductile Regime Cutting of Brittle Materials Using a Flying Tool Under Negative Pressure.

The importance of ductile regime cutting has been emphasized in the production of large-diameter optics and semiconductor substrates over the last ten years. However, the available technology has not yet been implemented in industry. The reason is that cutting technology based on the motion-copying principle is too sensitive for error motions of a machine tool to maintain a stable actual depth of cut below the critical depth. A new cutting technology using a flying tool under negative pressure has been developed. In this technology, a flying tool glides over a workpiece surface while maintaining a small constant height, like a negative-pressure slider of a magnetic disc drive. Using the tool system, ductile regime cutting of optical glass and monocrystalline silicon was examined, and a mirror-surface finish with no cracks was achieved on a face lathe having a 0.1 μm order of error motion.

Vibro-loading of magnetic head assemblies for hard disk drives

Experimental results of a new load unload method, called vibro-loading, are reported. This self-loading method uses a negative-pressure slider without any additional mechanisms to carry the slider to the loading point. Vertical natural frequency vibrations of the suspension are excited by a voice coil motor. Experimental results show that low-level seek acceleration enables stable loading with a working distance of 100 mm.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A negative pressure microhead slider for ultralow spacing with uniform flying height

A negative-pressure head slider for ultralow flying has been developed which features a newly shaped air bearing surface that gains sufficient suction force because the distance between the two side rails gradually widens from the leading to the trailing edge of the slider. The slider has a fast takeoff, and the flying height is insensitive to disk velocity. It also avoids the dust accumulation problem seen in the conventional negative-pressure slider. The slider's absence of taper suppresses generation to floating force, resulting in a microslider with relatively wide siderails. The flare angle of the siderails also contributes to making the flying height insensitive to the yaw angle, resulting in a uniform flying height over the entire disk surface. The recess needed to generate suction is a shallow 2 mu m, so the flexible rail shape is easily manufactured using photolithography. >

Reliability in Head-Disk-Interface with Negative Pressure Slider

The head-disk interface of a negative-pressure slider is evaluated. The damage occurring on seeking and tracking is caused by dust invading the space between the slider and the disk and wearing down the disk surface. Such damage is suppressed by controlling the cleanliness and wear resistance of the disk surface. The slider does not make contact with the disk even at a flying height of 0.1 ?m, because damage does not occur under conditions of high cleanliness. The environment cleanliness and disk surface wear resistance (environment stress) were varied in accelerated lifetime tests; the results indicated that the interface has a long lifetime of over 300,000 hours. In start/stop operation using loading/unloading, the slider sustained no damage in over 30,000 cycles.

Submicron Spacing of a Self-Loading Flying Head Slider Mechanism. 3rd Report, Criteria for Reliable Dynamic Self-Loading.

The authors have previously announced the development of a new design concept for flying head slider mechanisms to be used for information storage. These mechanisms operate under completely noncontact start stop mode conditions with magnetic disk media based on negative pressure slider self-loading. The reliability of this system's dynamic self-loading depends on the self-loading velocity, which is defined as the velocity when the slider approaches toward the disk surface under control of suction force provided at the slider air bearing surface hydrodynamically. Therefore, the critical governing factors in its self-loading dynamics were studied in detail in order to achieve high head/disk interface reliability. The disk surface velocity and the initial slider pitch orientation are confirmed to be the most critical parameters for reliable self-loading. The optimum self-loading criteria for the proposed self-loading flying head slider mechanisms have been successfully derived.

負圧スライダーの浮上信頼性

Head-disk-interface of negative pressure slider is evaluated. The damage at seeking and tracking is from the dust invading the spacing between the slider and the disk, wearing down the disk surface. Occurrence is suppressed by controlling of cleanliness and wear rate of disk surface. The slider does not contact the disk even at 0.1μm flying height, because damage does not occur at high cleanliness. Cleanliness and wear rate of disk surface are selected as stress for acceleration life test. The results indicate that the interface has a high life span of over 300,000 hours. In start-stop method using loading/unloading, the slider has no damage for over 30,000 cycles.