Patent Application
20050231852
The present invention relates to magnetic hard disk drives. More specifically, the present invention relates to the shape and size of the slider of a head gimbal assembly.
Hard disk drives are common information storage devices essentially consisting of a series of rotatable disks that are accessed by magnetic reading and writing elements. These data transferring elements, commonly known as transducers, are typically carried by and embedded in a slider body that is held in a close relative position over discrete data tracks formed on a disk to permit a read or write operation to be carried out. In order to properly position the transducer with respect to the disk surface, an air bearing surface (ABS) formed on the slider body experiences a fluid air flow that provides sufficient lift force to “fly” the slider and transducer above the disk data tracks. The high speed rotation of a magnetic disk generates a stream of air flow or wind along its surface in a direction substantially parallel to the tangential velocity of the disk. The air flow cooperates with the ABS of the slider body which enables the slider to fly above the spinning disk. In effect, the suspended slider is physically separated from the disk surface through this self-actuating air bearing.
Some of the major objectives in ABS designs are to fly the slider and its accompanying transducer as close as possible to the surface of the rotating disk, and to uniformly maintain that constant close distance regardless of variable flying conditions. The height or separation gap between the air bearing slider and the spinning magnetic disk is commonly defined as the flying height. In general, the mounted transducer or read/write element flies only approximately a few nanometers above the surface of the rotating disk. The flying height of the slider is viewed as one of the most critical parameters affecting the magnetic disk reading and recording capabilities of a mounted read/write element. A relatively small flying height allows the transducer to achieve greater resolution between different data bit locations on the disk surface, thus improving data density and storage capacity. With the increasing popularity of lightweight and compact notebook type computers that utilize relatively small yet powerful disk drives, the need for a progressively lower flying height has continually grown.
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Reducing the size of the slider allows for lower flying heights at lower production costs. The smaller slider size may create a smaller air-bearing surface area, lowering the flying height. The smaller slider size also means that more sliders can be produced on a wafer. One version of a slider has a size of 1 mm to 3.0 mm in length, 1 mm to 2.5 mm in width, and less than 0.65 mm in thickness.
a-b provides an illustration of one embodiment of a FEMTO slider and a PICO slider, as known in the prior art.
a-b compare in table format the air-bearing stiffness matrix as a percentage of a PICO slider stiffness for a slider of the present invention with the air-bearing stiffness matrix as a percentage of a PICO slider stiffness for a FEMTO slider.
An improved slider design is disclosed. While the width of the slider may be less than 1.0 mm, the length of the slider is greater than 0.85 mm. The slider may have a thickness of 0.23 mm. The air-bearing surface (ABS) of the slider may have a two-tiered U-shaped rail on the leading edge. A two-tiered main compression pad, straddled by two outlying compression pads, may extend from the trailing edge of the ABS.
In one embodiment, different features may be added to the ABS 430 to improve the ability of the ABS 430 to “fly” above the surface of the hard disk. A U-shaped rail 440 may extend from the leading edge of the slider on the ABS 430. The U-shaped rail 440 may be two-tiered, having a first surface 442 and a second surface 444 at a different level from the first surface 442. A main compression pad 450 may extend from the trailing edge of the slider on the ABS 430. The main compression pad 450 may be two-tiered, having a first surface 452 and a second surface 454 at a different level from the first surface 452. Two outlying compression pads 460 may straddle the main compression pad 450. The outlying compression pads 460 may be on the same level as the second surface 454 of the main compression pad 450. While the above ABS design is described as an example, any ABS design may be used.
The air-bearing formed between the slider and the rotating disk may be thought of as similar to a very stiff spring. The stiffness of the air-bearing may be a function of the ABS design, ABS area, atmospheric conditions, flying height, and other factors. Counteracting the external forces created by manufacturing tolerances is an important goal in ABS design. As the read/write element is located along the centerline of the slider body at the trailing edge, the external pitch torque has the greatest effect on the allowable flying height tolerance. The two main sources of the pitch torque is the slider alignment and suspension pitch-static-attitude (PSA) tolerance. FEMTO slider flying height is especially vulnerable to the changes in pitch torque because of its shorter length. The slider length of this embodiment provides more leverage to counteract the external pitch torque resulting in lower flying height variation.
Although several embodiments are specifically illustrated and described herein, it will be appreciated that modifications and variations of the present invention are covered by the above teachings and within the purview of the appended claims without departing from the spirit and intended scope of the invention.
