Abstract:
A disc storage system includes a rotating disc and a transducer. The transducer is carried on a slider which is supported by an armature. The armature is used to move the slider radially across the disc surface whereby information may be read from or written to the disc surface of the transducer. The slider includes an air bearing surface which faces the disc surface. As the disc rotates, the air bearing surface causes the slider to “fly” over the disc surface. Pads are provided on the air bearing surface to improve operational characteristics of the system and texturing is provided to a landing zone region on the disc surface.

Description:
The present invention claims priority to Provisional Application Serial No. 60/151,105, filed Aug. 27, 1999; and application Ser. No. 09/029,276, filed Dec. 9, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to disc storage systems for storing information. More specifically, the present invention relates to sliders used in such systems. 
     Disc drives are used for storing information, typically as magnetically encoded data, and more recently as optically encoded data, on a disc surface. A transducing head is carried on a air-bearing slider that rides on a bearing of air above the disc surface as the disc rotates at high speed. In another technique, the slider contacts the disc surface with no air bearing interface such as is shown in U.S. Pat. Nos. 5,453,315 and 5,490,027. The head is then positioned radially over the disc to read back or write at a desired location. Benefits associated with an air bearing design are lost in such “contact” sliders. 
     In an air bearing design, the air bearing provides an interface between the slider and the disc which prevents damage to the disc over the life of the system, provides damping if the disc drive system undergoes shock due to external vibrations. The air bearing is also used to provide a desired spacing between the transducing element and the disc surface. A bias force is applied to the slider by a flexure armature in a direction toward the disc surface. This bias force is counteracted by lifting forces from the air bearing until an equilibrium is reached. The slider will contact the disc surface if the rotating speed of the disc is insufficient to cause the slider to “fly.” This contact typically occurs during start up or shut down of the disc. If the slider contacts a region of the disc which carries data, the data may be lost and the disc permanently damaged. 
     In many disc drive systems, a lubricant is applied to the disc surface to reduce damage to the head and the disc surface during starting and stopping. Air or gas also acts as a lubricant. However, a phenomenon known as “stiction,” which is caused by static friction and viscous shear forces, causes the slider to stick to the disc surface after periods of non use. The lubricant exacerbates the stiction problem. The stiction can damage the head or the disc when the slider is freed from the disc surface. Additionally, the spindle motor used to rotate the disc must provide sufficient torque to overcome the stiction. 
     One technique used to overcome the problem associated with stiction is to provide texturing to at least a portion of the disc surface. As the fly height of disc drive system has been continually reduced to produce smaller and smaller transducer spacing, mechanical interference is increased. This is especially true in discs which use a textured landing zone such as that provided by laser texture bumps. Such laser texturing is provided to reduce the high levels of stiction that are generated by the smooth surfaces of the head and disc when they contact. However, using present laser texturing technology, the required height of the bumps in the landing zone textured region require to mitigate the stiction is greater than the nominal flying height of the head. This causes excessive wear and interference in the landing zone region. However, if the texturing in the landing zone is reduced, the stiction quickly increases to unacceptable levels. 
     SUMMARY OF THE INVENTION 
     A disc storage system includes a rotating disc and a transducer. The transducer is carried on a slider which is supported by an armature. The armature is used to move the slider radially across the disc surface whereby information may be read from or written to the disc surface of the transducer. The disc surface includes a landing zone region which is textured, for example, through laser texturing techniques. The slider includes an air bearing surface which faces the disc surface. As the disc rotates, the air bearing surface causes the slider to “fly” over the disc surface. Pads are provided on the air bearing surface and cooperate with bumps or other texturing in the landing zone region to reduce stiction without damaging the slider. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a simplified diagram of a storage disc system in accordance with the present invention. 
     FIG. 2 is a side view showing a slider interacting with a landing zone of the disc of FIG. 1 in accordance with the present invention. 
     FIG. 3 is a bottom plan view of one embodiment of a slider including pads. 
     FIG. 4 is a bottom plan view of another embodiment of the slider including pads. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 is a top view of a disc drive  10  including a slider in accordance with the present invention. Disc drive  10  includes a magnetic disc  12  mounted for rotational movement about and axis defined by spindle  14  within housing  16 . Disc drive  10  also includes an actuator  18  mounted to a base plate  20  of housing  16  and pivotally moveable relative to disc  14  about axis  22 . A cover  24  covers a portion of actuator  18 . Drive controller  26  is coupled to actuator  18 . In the preferred embodiment, drive controller  26  is either mountable within disc drive  10 , or is located outside of disc drive  10  with suitable connection to actuator  18 . Actuator  18 , includes an actuator arm assembly  28 , a rigid support member  30 , and a head gimbal assembly  32 . Head gimbal assembly  32  includes a load beam or flexure arm  34  coupled to rigid member  30 , and a slider  36  coupled by a gimbal (not shown) to load beam  34 . Slider  36  operates in accordance with the embodiments set forth herein and supports a transducer for reading information from and encoding information on disc  12 . 
     During operation, drive controller  26  receives position information indicating a portion of disc  12  to be accessed. Drive controller  26  receives the position information from an operator, from a host computer, or from another suitable controller. Based on the position information, drive controller  26  provides a position signal to actuator  18 . The position signal causes actuator  18  to pivot about axis  22 . This, in turn, causes actuator  18  to pivot about axis  22 . This, in turn, causes slider  36  (and consequently the transducer mounted on slider  36 ) to move radially over the surface of disc  12  in a generally arcuaic path indicated by arrow  38 . Drive controller  26  and actuator  18  operate in a known closed loop, negative feedback manner so that the transducer carried by slider  36  is positioned over the desired portion of disc  12 . Once the transducer is appropriately positioned, drive controller  26  then executes a desired read or write operation. 
     Recording density can be increased by reducing the fly height of slider  36 . Close proximity of slider  36  with disc  12  allows greater accuracy in reading and writing information onto disc  12 . 
     Stiction and fly/stiction are two major phenomena that impair the use of ultra-low flying recording heads to increase recording areal density. The solution to these problems has been to generate, in a controlled fashion, some asperities, or texture, on the media surface to reduce the area of contact at the head-media interface. The presence of these asperities on the media surface, although they can be confined to within a small dedicated zone  40  (i.e., a “landing zone”), enhances the chance of head-media contact during operation and thereby sets the limit to the true attainment of ultra-low flying. Using current laser texturing technology, the height of the bumps in the landing zone required to mitigate stiction is surpassing the nominal flying height of the head. This causes interference between the slider surface and the textured landing zone. This interference can result in increased head and media wear which will eventually lead to interface failure. If the size of the bumps in the textured region is reduced, the stiction quickly increases to unacceptable levels, ranging from 10 grams to as high as 50 grams or more, depending upon the amount of height reduction. 
     The present invention utilizes pads on the slider surface in conjunction with texturing of the landing zone region. With the present invention, the spacing required to mitigate stiction is shared between the slider and the disc. Examples of slider and pad configurations are described in U.S. patent application Ser. No. 09/029,276, filed Dec. 9, 1998 and entitled “SLIDER FOR DISC STORAGE SYSTEM” which is assigned to the present assignee and is incorporated herein by reference in its entirety. 
     FIG. 2 is a side cross-sectional view of a portion of disc  12 , approximate landing zone  40  showing a relationship between slider  36  which carries head  42  and landing zone  40 . Landing zone  40  is textured using any appropriate texturing technique such as laser texturing to thereby form bumps, protrusions, reliefs or other asperities  44 . Asperities  44  can have any desired shape, configuration, size or density and can be formed as protrusions from disc  12  or as reliefs into disc  12 . Slider  36  includes a plurality of pads  46 . Asperities  44  and pads  46  function in conjunction to reduce stiction between slider  36  and landing zone  40 . This configuration allows the slider  36  to fly at a lower level because some of the spacing used to reduce stiction is shared with asperities  44 . The lower fly height improves recording performance and allows for increased storage density. Pads  46  can be, for example, made of diamond-like carbon (DLC) which has excellent tribological properties. However, other materials can also be used such as silicon carbon (SiC). 
     The pads  46  also permit a higher level of interference between the slider  36  and the disc  12  because they are made of diamond-like carbon which has excellent wear properties. This wear occurs on pads  46  instead of on the slider  36  or on disc  12 . If the height and placement of pads  46  is chosen appropriately, the wear will reach a steady state and stiction will remain at very low levels over the entire life of the interface. The addition of diamond-like carbon pads to the slider  36  allows a reduction in the height of asperities  44  while still providing good stiction and wear performance. Because a higher level of interference is tolerable when pads  46  are made from diamond-like carbon, it is desirable to provide reduced laser texturing in landing zone  40  rather than no laser texturing, because of the added margin against stiction and the significantly reduced susceptibility to disc curvature variation. 
     FIG. 3 is a bottom plan view of a slider  36  in accordance with one embodiment of the present invention. Slider  36  includes rails  50  and center island  52  each carrying pads  36  thereon. In the embodiment of FIG. 3 pads  46  near the trailing edge  54  of slider  36  have a reduced height in comparison to the other pads. Pads  46  can be formed of diamond-like carbon. The configuration shown in FIG. 3 provides good protection against contact between the air bearing surface  56  of slider  36  and asperities  44  of landing zone  40  shown in FIG.  2 . The reduced heights of the pads  46  near the trailing edge  54  provides more complete coverage of the entire air bearing surface  56  with pad heights which will not interfere with performance of the head. The optimum height for pads  46  over the majority of the air bearing surface  56  may be too high to allow the pads  46  to be placed on the center island  52  and the trailing portions of rails  50  because they could contact the surface of disc  12  and cause increased spacing between the transducing head and the disc surface. It is very important to account for the distribution of the air bearing performance across multiple sliders when placing pads  46  to ensure that the entire population of sliders  36  will not experience increased transducer spacing due to pad contact. For the design of FIG. 3, the head to disc separation can be analyzed over the entire air bearing surface for optimum placement of pads  46 . 
     FIG. 4 is a perspective view of sliders  36  in accordance with another embodiment. In the embodiment of FIG. 4, fewer pads  46  are provided, however they provide a larger area than the pads shown in FIG.  3 . Of course, there are many variations of pad shapes, sizes, locations and distributions that can be used in accordance with the present invention. Further, all of the pads can have the same height across the entire air bearing surface. 
     The present invention provides a technique which provides pads on the slider and asperities in the landing zone of the disc to provide the benefits of both configurations. The addition of the diamond-like carbon pads on the air bearing surface of the head allows a reduction in the height of the texturing in the landing zone while still maintaining good stiction performance. Further, the height of the pads on the slider can be reduced to thereby lower fly height, improve performance and increase recording density. The pads can be designed to wear until a steady state is reached. Further, wear will not occur on the slider or on the disc. The present invention allows an increased level of interference between the head and the disc because the contact occurs on diamond-like carbon pads. In one preferred embodiment, the laser texturing on the disc surface is designed to have a glide avalanche equal or below the fly height. The height of the pads located on the head are designed to normally clear the disc in the data zone (untextured region). With the above mentioned goals and knowing the performance of the air bearing, a laser bump height is selected, and the pad height and location are derived. For example, 
     fly height=0.5 μ:inches 
     media texturing=0.5 μ:inches 
     pad height=300 Å and the location of bumps are 10-12 mils from trailing edge. In one embodiment, the laser texturing on the disc surface is 60-90 Å in height, 4-6 μm in diameter, with spacing from 11×11 to 16×16 μm and the pads on the slider surface are about 20 μm in diameter, 250-300 Å in height, with the trailing row positioned based on flying clearance, spaced 60 to 80 μm center to center, with 40 to 60 total pads (FIG.  3 ). The trailing rows of pads on the slider may be at a lower height than the leading pads (100 to 200 Å) based on flying clearance. Other variations of pad diameter and count may also be employed (FIG.  4 ). In another embodiment, laser texturing height is 40-100 Å and diameter is 3-8 μm with spacing from 11×11 to 25×25 μm. A texturing on the disc has a density of 8500 1/mm 2  to 1600 1/mm 2 . This can be formed by laser texturing the surface. 
     Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. In general, the pads may be placed along any protruding portion of the air bearing surface such as the side rails, a center rail, a center island, etc. In general, the present invention includes any size, shape, height, placing, configuration, density, etc. of the pads or texturing set forth herein. The texturing or the pads can be made in accordance with process as desired. The invention may be used with any type of transducing element including inductive, magnetoresistive, optical elements or others.