Abstract:
A method and apparatus for providing a three step air bearing with improved fly height performance is disclosed. The slider includes a funnel structure for directing air flow to a predetermined location toward a trailing edge of the slider and a collection structure for gathering air flow at the predetermined location. The slider is formed using three etch depths. A crossrail and side rails may be provided. The elements of the slider form five negative pressure areas to provide improved air bearing stiffness and minimize fly height sigma performance. The collection structure includes angled sides and the side rails further include trailing ABS side angles, wherein the trailing ABS side angles and the angled sides of the collection structure directing air flow around the collection structure to prevent contamination buildup.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     This disclosure relates in general to air bearing pads for magnetic storage devices, and more particularly to a method and apparatus for providing a three step air bearing with improved fly height performance  
         [0003]     2. Description of Related Art  
         [0004]     Fixed magnetic storage systems are now commonplace as a main non-volatile storage in modern personal computers, workstations, and portable computers. Storage systems are now capable of storing gigabyte quantities of digital data, even when implemented in portable computers.  
         [0005]     Magnetic recording systems that utilize magnetic disk and tape drives constitute the main form of data storage and retrieval in present-day computer and data processing systems. Many important advances have been made that provide higher data density and thus increased storage capacities for storage systems. These advances include faster access speeds and faster access times resulting in a greater bandwidth of data communicated to and from the storage systems. Advances have also been made by greatly reducing the size and weight of the storage systems, resulting in the availability of ultra-light portable computers having state-of-the art capabilities and performance.  
         [0006]     A disk drive is one example of a magnetic storage system. A disk drive storage system, for example, uses a rotatable disk with concentric data tracks containing information, a head for reading and/or writing data onto the various tracks, and an actuator connected to a sensor for moving the sensor to a desired track and maintaining the sensor over the track centerline during read and write operations. The sensor is suspended in close proximity to a recording medium. For example, the sensor may be suspended over a magnetic disk having a plurality of concentric tracks. Another type of magnetic storage system includes a magnetic tape system. However, storage systems are not limited merely to the above-mentioned magnetic storage systems.  
         [0007]     Disk drive storage systems utilize thin film head designs that are mostly variations of a merged design or a piggyback design. The merged design, as well as the piggyback design, places a write element atop a read sensor. In these dual-element designs, an inductive coil element used for writing and a magnetoresistive (MR) element used for reading are spaced apart from one another in a direction perpendicular to the trailing end of the merged head.  
         [0008]     In the recording process, information is written and stored as magnetization patterns on the magnetic recording medium. Scanning a write head over the medium and energizing the write head with appropriate current waveforms accomplish this recording process. In a read-back process, scanning a magnetoresistive (MR) sensor over the medium retrieves the stored information. This MR read head sensor intercepts magnetic flux from the magnetization patterns on the recording medium and converts the magnetic flux into electrical signals, which are then detected and decoded.  
         [0009]     There are typically a plurality of disks stacked on a hub that is rotated by a disk drive spindle motor. A housing supports the drive motor and head actuator and surrounds the head and disk to provide a substantially sealed environment for the head-disk interface. The head carrier is typically an air-bearing slider that rides on a bearing of air above the disk surface when the disk is rotating at its operational speed. The slider is maintained in very close proximity to the disk surface by a relatively fragile suspension that connects the slider to the actuator. The spacing between the slider and the disk surface is called the flying height and its precise value is critical to the proper function of the reading and writing process.  
         [0010]     The inductive write head and MR read head may be patterned, for example, on the trailing end of the slider, which is the portion of the slider that flies closest to the disk surface. An important factor affecting areal density is the distance between the transducer and the recording surface, referred to as the fly height. It is desirable to fly the transducer very close to the medium to enhance transition detection. Some fly height stability is achieved with proper suspension loading and by shaping the air bearing slider surface (ABS) for desirable aerodynamic characteristics. To achieve such results, the slider may be biased toward the disk surface by a small spring force from the suspension, or “self-loaded” to the disk surface by means of a “negative-pressure” air-bearing surface on the slider.  
         [0011]     Another important factor affecting fly height is the slider&#39;s resistance to changing conditions. An air bearing slider is subjected to a variety of changing external conditions during normal operation. Changing conditions affecting fly height include, for example, change in the relative air speed and direction, and variations in temperature. If the transducer fly height does not stay constant during changing conditions, data transfer between the transducer and the recording medium may be adversely affected. Fly height is further affected by physical characteristics of the slider such as the shape of the ABS. Careful rail shaping, for example, will provide some resistance to changes in air flow.  
         [0012]     As can be envisioned, it is desired to minimize variation in head clearance or flying height. However, it is becoming increasingly more difficult to achieve this lower fly height due to inherent limitations of slider and media process consistency. Improved slider designs are therefore desired that can account for these inherent process limitations while providing very low and stable flying heights. No solution provides improvement to altitude, protrusion and speed performance as much as a three-step air bearing surface design. Yet, a three step air bearing in itself is not sufficient to provide the required fly height sigma and roll stiffness.  
         [0013]     It can be seen that there is a need for a method and apparatus for providing a three step air bearing with improved fly height performance.  
       SUMMARY OF THE INVENTION  
       [0014]     To overcome the limitations described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses a method and apparatus for providing a three step air bearing with improved fly height performance.  
         [0015]     The present invention solves the above-described problems by providing an air bearing design that funnels and collections air flow to improve dynamic performance. Three etch steps are used in forming the air bearing design.  
         [0016]     A slider in accordance with the principles of an embodiment of the present invention includes a funnel structure disposed toward a leading edge of the slider for directing air flow to a predetermined location toward a trailing edge of the slider and a collection structure disposed proximate the trailing edge of the slider for gathering air flow at the predetermined location.  
         [0017]     In another embodiment of the present invention, another slider design is provided. This slider includes a funnel structure disposed toward a leading edge of the slider for directing air flow to a predetermined location toward a trailing edge of the slider.  
         [0018]     In another embodiment of the present invention, another slider design is provided. This slider includes a collection structure disposed proximate the trailing edge of the slider for gathering air flow at the predetermined location.  
         [0019]     In another embodiment of the present invention, a magnetic storage system is provided. The magnetic storage system includes at least one magnetic storage medium, a motor for moving the at least one magnetic storage medium, a slider having a magnetic head mounted thereon for reading and writing data on the at least one magnetic storage medium and an actuator, coupled to the slider, for positioning the slider relative to the at least one magnetic storage medium, wherein the slider further comprises a funnel structure disposed toward a leading edge of the slider for directing air flow to a predetermined location toward a trailing edge of the slider and a collection structure disposed proximate the trailing edge of the slider for gathering air flow at the predetermined location.  
         [0020]     In another embodiment of the present invention, another magnetic storage system is provided. This magnetic storage system includes at least one magnetic storage medium, a motor for moving the at least one magnetic storage medium, a slider having a magnetic head mounted thereon for reading and writing data on the at least one magnetic storage medium and an actuator, coupled to the slider, for positioning the slider relative to the at least one magnetic storage medium, wherein the slider further comprises a funnel structure disposed toward a leading edge of the slider for directing air flow to a predetermined location toward a trailing edge of the slider.  
         [0021]     In another embodiment of the present invention, another magnetic storage system is provided. This magnetic storage system includes at least one magnetic storage medium, a motor for moving the at least one magnetic storage medium, a slider having a magnetic head mounted thereon for reading and writing data on the at least one magnetic storage medium and an actuator, coupled to the slider, for positioning the slider relative to the at least one magnetic storage medium, wherein the slider further comprises a collection structure disposed proximate the trailing edge of the slider for gathering air flow at the predetermined location.  
         [0022]     In another embodiment of the present invention, a method for providing an air bearing pad with improved roll angle sigma is provided. The method includes forming a slider surface, forming a funnel structure, using a three etch process, for directing air flow to a predetermined location at a trailing edge of the slider and forming an angled collector structure, using the three etch process, at the trailing edge for collecting air flow.  
         [0023]     These and various other advantages and features of novelty which characterize the invention are pointed out with particularity in the claims annexed hereto and form a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to accompanying descriptive matter, in which there are illustrated and described specific examples of an apparatus in accordance with the invention.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]     Referring now to the drawings in which like reference numbers represent corresponding parts throughout:  
         [0025]      FIG. 1  illustrates a hard disk drive (HDD) including disks according to the present invention;  
         [0026]      FIG. 2  is a perspective view of an actuator assembly;  
         [0027]      FIG. 3  illustrates a greatly enlarged view of a head gimbal assembly;  
         [0028]      FIG. 4  illustrates a slider design having a three step air bearing with improved fly height performance according to an embodiment of the present invention;  
         [0029]      FIG. 5  illustrates the trailing structure for an air bearing with improved fly height performance according to an embodiment of the present invention;  
         [0030]      FIG. 6  shows the negative pressure pockets for slider design according to an embodiment of the present invention;  
         [0031]      FIG. 7  illustrates the length scales for the trailing edge structure according to an embodiment of the present invention;  
         [0032]      FIG. 8  illustrates the contamination robustness of the three step air bearing design according to an embodiment of the present invention; and  
         [0033]      FIG. 9  is a flow chart of a method for providing a three step air bearing with improved fly height performance according to an embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0034]     In the following description of the embodiments, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration the specific embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized because structural changes may be made without departing from the scope of the present invention.  
         [0035]     The present invention provides a method and apparatus for providing a three step air bearing with improved fly height performance. The present invention uses a funnel structure and a collection structure for improving dynamic performance. Three etch steps are used in forming the air bearing design.  
         [0036]      FIG. 1  illustrates a hard disk drive (HDD)  100  including disks  118 A,  118 B according to the present invention. The HDD  100  includes a disk  118  and a hard disk controller (hereinafter referred to as HDC)  130 . The disk part has a motor  114  for rotating a shaft  112  at a high speed. A cylindrical support  116  is attached to the shaft  112  so that the axes are in coincidence. One or more information recording disks  118 A and  118 B are mounted to support  116 . Magnetic heads  120 A,  120 B,  120 C and  120 D are respectively provided to face the disk surface, and these magnetic heads are supported from an actuator  124  by access arms  122 A,  122 B,  122 C, and  122 D, respectively. The individual magnetic heads  120 A to  120 D receive the drive force transmitted from an actuator drive device  128  by a shaft  126  and rotates about the shaft  126  as the axis of rotation, and fly over the disk  118  to a predetermined position.  
         [0037]      FIG. 2  is a perspective view of an actuator assembly  200 . Actuator assembly  200  includes base portion  222 , a plurality of actuator arms  226 , a plurality of load beams  228 , and a plurality of head gimbal assemblies  216 . Base portion  222  includes a bore that is, in the preferred embodiment, coupled for pivotal movement about axis  221 . Actuator arms  226  extend from base portion  222  and are each coupled to the first end of either one or two load beams  228 . Load beams  228  each have a second end, which is coupled to a head gimbal assembly  216 . According to the present invention, multiple, independently controlled actuator assemblies  200  are provided in a disk drive.  
         [0038]      FIG. 3  illustrates a greatly enlarged view of a head gimbal assembly  300 . Head gimbal assembly  300  includes gimbal  330 , which has a pair of struts  332  and  334 , and a gimbal bond tongue  336 . Head gimbal assembly  300  also includes slider  338 , which has an upper surface  340 , and a lower, air bearing surface  342 . Transducers  344  are also preferably located on a trailing edge of slider  338 . The particular attachment between slider  338  and gimbal  330  is accomplished in any desired manner. For example, a compliant sheer layer may be coupled between the upper surface  340  of slider  338  and a lower surface of gimbal bond tongue  336 , with an adhesive. A compliant sheer layer permits relative lateral motion between slider  338  and gimbal bond tongue  336 . Also, gimbal bond tongue  336  preferably terminates at a trailing edge of slider  338  with a mounting tab  346  which provides a surface at which slider  338  is attached to gimbal bond tongue  336 .  
         [0039]     A conventional slider design starts off with a flat polished surface, from which a patterned ABS is created by a removal process such as etching or ion milling. The ABS is always the top most polished surface and pressurizes with positive pressure to lift the ABS up producing an air cushion above the disk. Air bearing surfaces are formed by single or dual etch processing which result in either 2 or 3 surface levels, respectively.  
         [0040]      FIG. 4  illustrates a slider design  400  having a three step air bearing with improved fly height performance according to an embodiment of the present invention. In  FIG. 4 , the slider  400  includes a crossrail  410  and two side rails  440 ,  442 . In  FIG. 4 , a funnel structure  470  formed by front air bearing structures  450 ,  452  is provided proximate the leading edge  402 . A dual funnel collection feature  420  is provided at the trailing edge  430  to collect air flow. As can be seen in  FIG. 4 , three etch depths  480 ,  482 ,  484  with appropriate step width are used to cut altitude loss. The first and second etch steps are preferrably 0.15 μm±0.5 μm. The third step depth is deeper than the first two step depths and preferably is 2.00 μm±0.5 μm. The first etch step improves speed sensitivity and works with the second etch step to provide improved altitude performance. The third step depth  484  helps improve fly height speed sensitivity.  
         [0041]      FIG. 5  illustrates the trailing structure  500  for an air bearing with improved fly height performance according to an embodiment of the present invention. As shown in  FIG. 5 , the trailing structure  500  consists of two funnels  522 ,  524 . The trailing structure  500  also comprises three edge depths  580 ,  582 ,  584 . The two funnels  522 ,  524  are provided to collect as much air flow at the trailing end as possible and direct the air flow to the very trailing part of the ABS surface. In this manner, the trailing part of the ABS surface can be decreased dramatically while providing significant improvement in protrusion compensation function and minimum fly height sigma. The trailing structure  500  also helps to decrease ABS area, which decreases contact force. The trailing structure  500  also makes the air bearing much less sensitive to the skew angle change from ID to OD or during seek motion.  
         [0042]      FIG. 6  shows the negative pressure pockets for slider design  600  according to an embodiment of the present invention. In  FIG. 6 , the slider  600  includes a crossrail  610  and two side rails  640 ,  642 . In  FIG. 6 , a funnel structure  670  formed by front air bearing structures  650 ,  652  is provided proximate the leading edge  602 . A dual funnel collection feature  620  is provided at the trailing edge  630  to collect air flow. In  FIG. 6 , five pressure pockets  690 - 64  are provided. A first negative pressure area  690  is proximate the center-leading edge  602 . A second  691  and third  692  negative pressure area are provided near the middle on each side of the slider  600 . Two additional negative pressure areas  693 ,  694  are provided near the trailing edge on each side of the trailing structure  620 . The five negative pressure areas  690 - 64  provide good air bearing stiffness, especially for roll motion. The five negative pressure zones  690 - 694  also help minimize fly height sigma performance as well as dynamic motions.  
         [0043]      FIG. 7  illustrates the length scales  700  for the trailing edge structure according to an embodiment of the present invention. In  FIG. 7  three length scales are shown, t 1 , t 2 , and t 3 . The length scale range of t 1 , t 2  and t 3  are carefully designed along with three depths to provide significant improvement in altitude loss and speed insensitive performance.  
         [0044]      FIG. 8  illustrates the contamination robustness of the three step air bearing design  800  according to an embodiment of the present invention. In  FIG. 8 , the slider  800  includes a crossrail  810  and two side rails  840 ,  842 . In  FIG. 8 , a funnel structure  870  formed by front air bearing structures  850 ,  852  is provided proximate the leading edge  802 . A dual funnel collection feature  820  is provided at the trailing edge  830  to collect air flow. As can be seen in  FIG. 8 , the trailing ABS side angles  896 ,  897  provide contamination robustness. The angles  896 ,  897  of the trailing features allow air from side, as illustrated by arrows  898 ,  897 , to blow any accumulation of contaminants out of the head/disk interface thereby providing contamination robustness.  
         [0045]      FIG. 9  is a flow chart  900  of a method for providing a three step air bearing with improved fly height performance according to an embodiment of the present invention. A slider surface is formed  910 . A funnel is formed for direct air flow to the trailing edge of the slider using a three etch process  920 . An angled collector structure is formed at the trailing edge for collecting air flow using the three etch process  930 .  
         [0046]     The foregoing description of the exemplary embodiment of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be limited not with this detailed description, but rather by the claims appended hereto.