Abstract:
An air bearing surface (ABS) for a head assembly for a data storage device is described. The ABS includes a member, comprising a first extended region and a second extended region, wherein these two regions define a channel. This channel is open to the leading edge (LE) of the ABS, and is configured so as to allow air to flow along the channel toward the trailing edge (TE) of the ABS. As a result, the pressure of the air flowing along the channel does not experience significant fluctuations in pressure until approaching the trailing edge.

Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates generally to head assemblies used in data storage devices, and more particularly to the air bearing surface on the slider affixed to the transducer suspension system. 
     2. Related Art 
     Hard disk drives are used in almost all computer system operations. In fact, most computing systems are not operational without some type of hard disk drive to store the most basic computing information such as the boot operation, the operating system, the applications, and the like. In general, the hard disk drive is a device which may or may not be removable, but without which the computing system will generally not operate. 
     The basic hard disk drive model includes a storage disk or hard disk that spins at a designed rotational speed. An actuator arm is utilized to reach out over the disk. The arm carries a head assembly that has a magnetic read/write transducer or head for reading/writing information to or from a location on the disk. The transducer is attached to a slider, such as an air-bearing slider, which is supported adjacent to the data surface of the disk by a cushion of air generated by the rotating disk. The transducer can also be attached to a contact-recording type slider. In either case, the slider is connected to the actuator arm by means of a suspension. The complete head assembly, e.g., the suspension and head, is called a head gimbal assembly (HGA). 
     In operation, the hard disk is rotated at a set speed via a spindle motor assembly having a central drive hub. Additionally, there are tracks evenly spaced at known intervals across the disk. When a request for a read of a specific portion or track is received, the hard disk aligns the head, via the arm, over the specific track location and the head reads the information from the disk. In the same manner, when a request for a write of a specific portion or track is received, the hard disk aligns the head, via the arm, over the specific track location and the head writes the information to the disk. 
     Over the years, the disk and the head have undergone great reductions in their size. Much of the refinement has been driven by consumer demand for smaller and more portable hard drives such as those used in personal digital assistants (PDAs), MP3 players, and the like. For example, the original hard disk drive had a disk diameter of 24 inches. Modern hard disk drives are much smaller and include disk diameters of less than 2.5 inches (micro drives are significantly smaller than that). Advances in magnetic recording are also primary reasons for the reduction in size. 
     This continual reduction in size has placed steadily increasing demands on the technology used in the HGA, particularly in terms of power consumption, shock performance, and disk real estate utilization. One recent advance in technology has been the development of the Femto slider, which is roughly one-third of the size and mass of the older Pico slider, which it replaces; over the past 23 years, slider size has been reduced by a factor of five, and mass by a factor of nearly 100. 
     These smaller sliders have substantially smaller surface areas, which increases the difficulties associated with achieving and maintaining a suitable fly height. Additionally, several of the applications for Femto sliders call for smaller disks, to better fit in portable electronic devices, and lower rotational speeds, to better conserve power. Coupled with concerns for temperature and ambient pressure insensitivity, so that drives using Femto sliders can be used in uncontrolled environmental conditions and at differing altitudes, it has proven very difficult to find an appropriate design for the air bearing surface of a slider that sufficiently meets the needs imposed by current demand. 
     SUMMARY 
     An air bearing surface (ABS) for a head assembly for a data storage device is described. The ABS includes a member, comprising a first extended region and a second extended region, wherein these two regions define a channel. This channel is open to the leading edge (LE) of the ABS, and is configured so as to allow air to flow along the channel toward the trailing edge (TE) of the ABS. As a result, the pressure of the air flowing along the channel does not experience significant fluctuations in pressure until approaching the trailing edge. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a hard disk drive and a controller unit in block form, in accordance with one embodiment of the present invention. 
         FIG. 2  is a top view of a hard disk drive system, in accordance with one embodiment of the present invention. 
         FIG. 3  is a top view of an air bearing surface of a slider, in accordance with one embodiment of the present invention. 
         FIG. 4  is a depiction of a Center Line Pressure of a Traditional ABS Design. 
         FIG. 5  is a depiction of a Center Line Pressure of ABS  300 . 
         FIG. 6  is a depiction of Traditional ABS vs. ABS  300  at Higher Altitudes. 
     
    
    
     DETAILED DESCRIPTION 
     A head assembly and a data recording device configured to use a head assembly are disclosed. Reference will now be made in detail to several embodiments of the invention. While the invention will be described in conjunction with the alternative embodiment(s), it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternative, modifications, and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims. 
     Furthermore, in the following detailed description of the present invention, numerous specific details are set forth in order to provide a through understanding of the present invention. However, it will be recognized by one of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well known methods, procedures, components, and circuits have not been described in detail as not to unnecessarily obscure aspects of the present invention. 
     With reference now to  FIGS. 1 and 2 , a side and top view of a hard disk drive  110  is shown. Drive  110  has a disk pack having at least one media or magnetic disk  112 , mounted to a spindle  114 . A spindle motor  116  rotates the spindle  114  and the disk or disks  112 . The spindle motor  114  and an actuator shaft  130  are attached to the chassis  120 . A hub assembly  132  rotates about the actuator shaft  130  and supports a plurality of actuator arms  134 , referred to as a “comb.” A rotary voice coil motor  140  is attached to the chassis  120  and to a rear portion of the actuator arms  134 . 
     A plurality of suspension assemblies  150  are attached to the actuator arms  134 . A plurality of transducer heads or sliders  152  are attached respectively to the suspension assemblies  150 . The sliders  152  are located proximate to the disks  112  for reading and writing. The rotary voice coil motor  140  rotates actuator arms  134  about the actuator shaft  130  in order to move the suspension assemblies  150  to the desired radial position on disks  112 . The shaft  130 , hub  132 , arms  134 , and motor  140  may be referred to collectively as a rotary actuator assembly. 
     A controller unit  160  provides overall control to system  110 . Controller unit  160  typically includes (not shown) a central processing unit (CPU), a memory unit and other digital circuitry, although it should be apparent that one skilled in the computer arts could also enable these aspects as hardware logic. Controller  160  is connected to an actuator control/drive unit  166  that in turn is connected to the rotary voice coil motor  140 . This configuration allows controller  160  to control rotation of the disks  112 . A host system  180 , typically a computer system, is connected to the controller system  160 . The host system  180  may send digital data to the controller  160  to be stored on disks  112 , or it may request that digital data at a specified location be read from the disks  112  and sent to the system  180 . The basic operation of DASD units is well known in the art and is described in more detail in The Magnetic Recording Handbook, C. Dennis Mee and Eric D. Daniel, McGraw-Hill Book Company, 1990. 
     With reference now to  FIG. 3 , an air bearing surface (ABS) of a slider is shown, in accordance with one embodiment of the present invention. ABS  300 , in this embodiment, is created via a known two-etch process, using a combination of ion mill etching and reactive ion etching. The surface of the ABS is etched down to a first depth, leaving behind only selected features, and the surface is hereinafter described as surface level  310 . This first etching is 0.12 micrometers deep. The first depth is then further etched, leaving behind only selected features, and the first depth is hereinafter described as middle level  320 . This second etching is 0.52 micrometers deep. The second depth, as a result, is 0.64 micrometers below surface level  310 . This second depth is hereinafter described as bottom level  330 . The number of etchings and the depth of each was selected for convenience, to conform to a process for 15 creating an already-existing slider. Other embodiments of the present invention use different numbers of etchings, and different depths for the etchings. 
     ABS  300 , in this embodiment, has a leading edge (LE)  301 , and a trailing edge (TE)  302 . When incorporated into a hard drive or other data storage device, a transducer or other read element is mounted at TE  302 , at point  305 . ABS  300  also includes, in this embodiment, channel  350 , which is bounded by two channel walls  355 , which are part of surface level  310 , and is created in the first etching pass. Other embodiments use multiple channels. Other embodiments use multiple etching passes to create a channel  350 . ABS  300  also includes several negative pressure pockets  360 , partially bounded by regions of surface level  310 . Other embodiments include differing numbers of negative pressure pockets  360 . Other embodiments partially bound negative pressure pocket  360  with regions of middle level  320 . 
     For this invention, one important consideration was improving the air pressure at point  305 . This is accomplished in this embodiment by the inclusion of a shallow channel  350 , running from the leading edge back to near point  305 . In operation, air passes over LE  301 , and into channel  350 . At this point, the pressure of the air is still near-ambient. In the depicted embodiment, the air is at a slightly higher pressure than ambient, as channel  350  narrows as it approaches point  305 . In other embodiments, air pressure along channel  350  remains constant, or decreases slightly. An important feature of this invention is that the air pressure at point  305  be maximized; various configurations of channel  350 , combined with different shapes for the rest of ABS  300 , lead to different results. 
     In this embodiment, air from LE  301  also passes over surface level  310 , and then into negative pressure pockets  360 . The air is first compressed by passing over surface level  310 , as less space is available between surface level  310  and the surface of the disk of the hard drive. The air then expands in negative pressure pockets  360 , creating suction and attracting ABS  300  to the surface of the disk of the hard drive. This suction counteracts the repulsion caused by air at higher-than-ambient pressures, over other portions of ABS  300 . 
     ABS  300 , in one embodiment, is used with a center pivot point. In another embodiment, ABS  300  is used with a front pivot point. Other embodiments position the pivot point in other locations. 
     Traditional ABS designs lacked channel  350 . Some traditional designs included a single large negative pressure pocket, spanning most of the ABS, and then used a multilevel step up to try to increase air pressure at the read/write element. Embodiments of ABS  300  compare very favorably to such traditional designs in most respects, and much better in others. 
       FIG. 4  depicts air pressure relative to position along the center line of a traditional ABS design. The horizontal axis depicts the length of an exemplary femto slider, in micrometers; femto sliders are typically 850 micrometers long. The vertical axis depicts air pressure at a given point along the center line of the ABS, in terms of the ratio of air pressure at that point to ambient pressure. Air enters the traditional ABS at the leading edge, at ambient pressure (i.e. 1.0). As it passes over the leading edge, and reaches a portion of the ABS at a higher level, the air is compressed, and pressure increases. Air passes the higher level, and flows into a negative pressure pocket; the air pressure drops significantly below ambient levels (here, to approximately one third of the ambient pressure). The air then flows towards the trailing edge and the read/write element, and pressure increases again, until it reaches the highest peak at the read/write element. 
       FIG. 5  below, depicts air pressure along the center line of one embodiment of the present invention, such as ABS  300 . Again, the horizontal axis depicts the length of ABS  300 , in micrometers, and the vertical axis depicts air pressure at a given point along the center line of the ABS, in terms of the ratio of air pressure at that point to ambient pressure. 
     Air enters ABS  300  at LE  301  at ambient pressure (1.00), and flows into channel  350 . As the air flows along channel  350 , it is compressed slightly as channel  350  narrows, then depressurizes slightly where channel  350  widens. The air pressure does not drop significantly below ambient pressure at any point along channel  350 . When channel  350  ends, and the air flows up over surface level  310  towards point  305  and TE  302 , the air pressure increases tremendously, and far more significantly than in the traditional design. 
     One benefit of the present invention is that, under conditions with lower ambient pressures (e.g. higher altitude), embodiments such as ABS  300  have a higher fly height.  FIG. 6  shows the fly heights of a traditional ABS design and ABS  300 , relative to their position on the radius of a hard drive disk, both at sea level and at 10,000 feet. ABS  300  has nearly identical performance at both altitudes, while the traditional design varies substantially depending on altitude. 
     Embodiments of the present invention described above thus relate to a personal portable storage device as well as a hard disk apparatus configured for use as a personal portable storage device. While the present invention has been described in particular exemplary embodiments, the present invention should not be construed as limited by such embodiments, but rather construed according to the following claims and their equivalents.