Patent Publication Number: US-2002008939-A1

Title: Pad design concepts for slider air-bearings

Description:
RELATED APPLICATION  
     [0001] This application claims the benefit of U.S. Provisional Application Serial No. 60/196,746, filed Apr. 12, 2000 under 35 U.S.C. 119(e). 
    
    
     
       FIELD OF THE INVENTION  
       [0002] The present invention relates to the field of mass storage devices. More particularly, this invention relates to sliders used in such devices.  
       BACKGROUND OF THE INVENTION  
       [0003] One key component of any computer system is a device to store data. Computer systems have many different places where data can be stored. One common place for storing massive amounts of data in a computer system is on a disc drive. The most basic parts of a disc drive are an information storage disc that is rotated, an actuator that moves a transducer to various locations over the disc, and electrical circuitry that is used to write and read data to and from the disc. The disc drive also includes circuitry for encoding data so that it can be successfully retrieved and written to the disc surface. A microprocessor controls most of the operations of the disc drive as well as passing the data back to the requesting computer and taking data from a requesting computer for storing to the disc.  
       [0004] The transducer is typically placed on a small ceramic block, also referred to as a slider, that is aerodynamically designed so that it flies over the disc. The slider is passed over the disc in a transducing relationship with the disc. Most sliders have an air-bearing surface (ABS) which includes rails and a cavity between the rails. When the disc rotates (generally, at rotational speeds of 5,200 RPM or higher), air is dragged between the rails and the disc surface causing pressure, which forces the head away from the disc. At the same time, the air rushing past the cavity or depression in the air-bearing surface produces a negative pressure area. The negative pressure or suction counteracts the pressure produced at the rails. The slider is also attached to a load spring, which produces a force on the slider directed toward the disc surface. The various forces on the slider equilibrate, so that the slider flies over the surface of the disc at a particular desired fly height. The fly height is the distance between the disc surface and the transducing head, which is typically the thickness of the air lubrication film. This film eliminates the friction and resulting wear that would occur if the transducing head and disc were in mechanical contact during disc rotation. When a disc drive is turned off, most disc drives are designed to have one of two things occur. In some disc drives, the actuator removes the slider or flying portion of the disc drive from the disc, and in other disc drives, the actuator moves the slider to a parking area on the disc. The second type of disc drive is known as a comtact start/stop mainframe (“CSS”) drive. In a CSS drive, it is important that the slider lift off from the disc surface quickly. In addition, it is also important that measures be taken to eliminate or reduce a phenomenon known as stiction. However, stiction is caused by static friction and viscous shear forces, and causes the slider to stick to the disc surface after periods of non-use. The lubricant on the disc exasperates 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. Therefore, it is desired to limit the sticking friction (“stiction”) between the slider and the disc surface during the start and stop of disc rotation.  
       [0005] One technique used to overcome the problem associated with stiction, is to provide texturing to at least a portion (landing zone) of the disc surface, which reduces the contact area between the slider and the disc surface when the slider is at rest within the landing zone. However, this reduces the effective recording area of the disc. Additionally, as the flying heights are reduced to achieve higher recording densities, it becomes difficult to implement a textured landing zone since the height of the roughness peaks that is required to limit the stiction forces in the textured landing zone may be higher than the flying height of the slider. This difficulty has led to the use of head-disc interfaces in which the air-bearing surface of the slider includes texture or one or more discrete pads on the air-bearing surfaces. These pads provide small surface areas for contacting the disc surface without significantly affecting the bearing characteristics.  
       [0006] Improvements can be made to the discrete pads and more specifically to the placement of the discrete pads on the air-bearing surfaces of a slider. It should be noted that a slider or small ceramic block carrying a transducer, while flying, is tilted or pitched. In other words, just like an airplane wing or a water ski, the front or leading edge of the slider is tilted upward at a farther distance than the trailing edge or back edge of a wing or ski or slider. As a result, pads that are placed near to the trailing edge of the slider, generally have more effect on the flying characteristics of the slider. As a result, placement of the various features near the trailing edge of the slider is much more critical than placing the features near the leading edge of a slider. In order to assure that all the various manufactured sliders have approximately the same flying characteristics, it is critical to have very precise placement of the features near and at the trailing edge of the slider.  
       [0007] Therefore, what is needed is a process that allows for very precise placement of features with respect to the air bearing geometry. What is also needed is an improved pad design for the bearing surface of the slider that minimizes stiction with the disc surface during take-off from the disc surface, and at the same time meets the increasing demand to produce smaller and smaller head-disc spacing to improve read/write performances of disc drives.  
       SUMMARY OF THE INVENTION  
       [0008] A slider includes a cavity dam, a subambient pressure cavity, and first and second elongated rails. The subambient pressure cavity trails the cavity dam and has a cavity floor. The first and second rails are disposed about the subambient pressure cavity. Each of the rails has a rail width measured from an inner rail edge to an outer rail edge, a leading bearing surface, a trailing bearing surface, and a recessed area extending between the leading and trailing bearing surfaces. The recessed area is recessed from the bearing surfaces and raised from the cavity floor, across the rail width. First and second convergent channels are recessed within the trailing bearing surfaces of the first and second rails, respectively. Each channel has a leading channel end open to fluid flow from the respective recessed area, non-divergent channel side walls, and a trailing channel end closed to the fluid flow and forward of a localized region of the respective trailing bearing surface. Each of the channels has a side wall on either side of the leading channel ends. The slider also includes a raised bar traversing each of the trailing bearing surfaces of the first and second rails such that the raised bar is near the leading channel end. The raised bar provides a separation between the bearing surfaces and a disc surface when the head slider is at rest on the disc surface. The raised bar is positioned on the trailing bearing surfaces such that it has a reduced impact on the overall flying characteristics of the head slider. In addition, the raised bar can be precisely positioned on the trailing bearing surface with respect to the trailing edge so that consistent flying characteristics are achieved in various manufactured sliders. Further, the bar separates the slider from the disc and significantly reduces stiction forces between the slider and the disc surface. In some embodiments, the raised bar is made of diamond-like carbon material (“DLC”).  
       [0009] Another aspect of the present invention relates to a disc slider, which includes a leading slider edge, a trailing slider edge, a cavity dam, and a subambient pressure cavity. The subambient pressure cavity trails the cavity dam and has a cavity floor. The first and second rails are disposed about the subambient pressure cavity. Each of the rails has a rail width measured from an inner rail edge to an outer rail edge, a leading bearing surface, a trailing bearing surface, and a recessed area extending between the leading and trailing bearing surfaces. The recessed area is recessed from the bearing surfaces and raised from the cavity floor, across the rail width. First and second convergent channels are recessed within the trailing bearing surfaces of the first and second rails, respectively. Each channel has a leading channel end open to fluid flow from the respective recessed area, non-divergent channel side walls and a trailing channel end closed to the fluid flow and forward of a localized region of the respective trailing bearing surface. The disc slider further has at least one raised pad positioned on each of the leading bearing surfaces of the first and second rails. The pads on the leading bearing surface are made of DLC. The slider also includes at least one raised pad positioned on each of the recessed areas of the first and second rails. The raised pads positioned on the recessed areas extend beyond the air-bearing surface of the slider to provide a separation between the bearing surfaces and a disc surface when the slider is at rest on the disc surface. The raised pads associated with the recess include a cap of DLC or wear-enhancing material. The raised pad positioned on the recessed areas sit on a longer column than the pads on the leading bearing surfaces, which reduces surface tension between the slider and a lubricant disposed on a disc surface. Because of the increased effective height of the pad (longer column on which the raised pad is placed), the radius of curvature formed by the meniscus between the column and the disc surface is larger which accounts for the reduced surface tension. Reduced surface tension equates with reduced stiction. Furthermore, since the pad location is determined very precisely by the air-bearing mask, the pads produce consistent flying characteristics since positional variations in the raised pad with respect to the recessed areas are minimized.  
       [0010] The head slider further includes first and second convergent channels, which are recessed within the trailing bearing surfaces of the first and second rails, respectively. Each of the first and second channels has a leading channel end open to fluid flow from the respective recessed area, non-divergent channel side walls, and a trailing channel end closed to the fluid flow and forward of a localized region of the respective trailing bearing surface. Each of the first and second channels further has a side wall on either side of the leading channel ends.  
       [0011] The slider further includes a raised center rail positioned along the trailing slider edge and between the first and second elongated raised side rails. The raised center rail has a leading step surface. The leading step surface is substantially parallel to and recessed from a center rail bearing surface. The center rail bearing surface is at a height similar to the height of the leading and trailing bearing surfaces. In fact, the center rail bearing surface, the leading bearing surfaces and the trailing bearing surfaces form what is commonly known as the air-bearing surface of the slider. The recess between the leading bearing surface and the trailing bearing surface on each side rail, as well as the step surface in front of the raised center rail bearing surface, are all on a similar level known as the step level. Finally, the cavity is at its own level with respect to the air-bearing surface of the slider. In some embodiments, pads may be placed or positioned on the cavity which extend to a position beyond the air-bearing surface of the slider. These pads are known as pedestals and there can be one or more of these pedestals positioned in the cavity. These pads can also be very precisely positioned since their position is determined by the air-bearing mask. The pads within the cavity are on relatively long columns and, therefore, are referred to as pedestals. The pedestals are capped with a wear-resistant material such as DLC.  
       [0012] Yet another aspect of the present invention relates to a disc drive assembly, which includes a housing, a disc, an actuator and a slider. The disc is rotatable about a central axis within the housing and has a recording surface with a data area and a landing area, which are non-textured. The actuator is mounted within the housing. The slider is supported over the recording surface by the actuator and includes a cavity dam, a subambient pressure cavity and first and second elongated rails. The subambient pressure cavity trails the cavity dam and has a cavity floor. The first and second rails are disposed about the subambient pressure cavity. Each of the rails has a rail width measured from an inner rail edge to an outer rail edge, a leading bearing surface, a trailing bearing surface, and a recessed area extending between the leading and trailing bearing surfaces. The recessed area is recessed from the bearing surfaces and raised from the cavity floor, across the rail width. The slider further includes a raised center rail with a leading step surface. The leading step surface is parallel to and recessed from a center rail bearing surface. The center rail step surface is at a height similar to the height of the recess on each rail. The center rail step includes one or more pads. The pads are capped with DLC or another long-wearing material. The placement of these center rail step pads can be carefully and precisely controlled with the air-bearing mask to produce consistent flying characteristics.  
       [0013] Advantageously, the improved slider designs described above reduce variations in the flying characteristics of the slider due to placement variations in placement of the raised bars and raised pads near the trailing edge of the slider. This improves read/write performance of the disc drives while lessening stiction problems. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0014]FIG. 1 is an exploded view of a disc drive with a multiple disc stack.  
     [0015]FIG. 2 is a perspective view of one embodiment of a slider shown in FIG. 1, according to the teachings of the present invention.  
     [0016]FIG. 3 is a perspective view of another embodiment of a slider shown in FIG. 2, according to the teachings of the present invention.  
     [0017]FIG. 4 illustrates radius of curvature of the meniscus formed on pads.  
     [0018]FIG. 5 is a perspective view of another embodiment of a slider shown in FIG. 3, according to the teachings of the present invention.  
     [0019]FIG. 6 is a perspective view of another embodiment of a slider shown in FIG. 5, according to the teachings of the present invention.  
     [0020]FIG. 7 is a schematic view of a computer system.  
     [0021]FIG. 8 is a perspective view of another embodiment of a slider according to the teachings of the present invention.  
     [0022]FIG. 9 is a perspective view of yet another embodiment of a slider according to the teachings of the present invention.  
     [0023]FIG. 10 is a perspective view of another embodiment of a slider according to the teachings of the present invention.  
     [0024]FIG. 11 is a perspective view of another embodiment of a slider according to the teachings of the present invention.  
     [0025]FIG. 12 is a perspective view of another embodiment of a slider according to the teachings of the present invention.  
     [0026]FIG. 13 is a perspective view of yet another embodiment of a slider according to the teachings of this invention.  
     [0027]FIG. 14 is a perspective view of another embodiment of a slider according to the teachings of this invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0028] In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings, which form a part hereof, and in which are shown by way of illustration specific embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention.  
     [0029] The invention described in this application is useful with all mechanical configurations of disc drives having either rotary or linear actuation. In addition, the invention is also useful in all types of disc drives including hard disc drives, zip drives, floppy disc drives and any other type of drives where unloading the transducer from a surface and parking the transducer may be desirable.  
     [0030] The terms “slider,” “disc head slider,” and “head slider” are used interchangeably throughout this document.  
     [0031]FIG. 1 is an exploded view of one type of disc drive  100  having a rotary actuator. The disc drive  100  includes a housing or a base  112 , and a cover  114 . The base  112  and cover  114  form a disc enclosure. An inertia ring  500  is attached to the cover  114 . Rotatably attached to the base  112  on an actuator shaft  118  is an actuator assembly  120 . The actuator assembly  120  includes a comb-like structure  122  having a plurality of arms  123 . Attached to the separate arms  123  on the comb  122 , are load beams or load springs  124 . Load beams or load springs are also referred to as suspensions. Attached at the end of each load spring  124  is a slider  126 , which carries a magnetic transducer  150 . The slider  126  with the transducer  150  form the head. It should be noted that many sliders have one transducer  150  and as is shown in the figures. It should also be noted that this invention is equally applicable to sliders having more than one transducer, such as an MR or magneto resistive head in which one transducer  150  is generally used for reading and another is generally used for writing. On the end of the actuator arm assembly  120 , opposite the load springs  124  and the sliders  126 , is a voice coil  128 .  
     [0032] Attached within the base  112  is a first magnet  130  and a second magnet  131 . As shown in FIG. 1, the second magnet  131  is associated with the cover  114 . The first and second magnets  130 ,  131  and the voice coil  128  are the key components of a voice coil motor, which applies a force to the actuator assembly  120  to rotate it about the actuator shaft  118 . Also mounted to the base  112  is a spindle motor. The spindle motor includes a rotating portion called the spindle hub  133 . In this particular disc drive, the spindle motor is within the hub. In FIG. 1, a number of discs  134  are attached to the spindle hub  133 . Each of the discs  134  has a recording surface  135 . Only one disc  134  is numbered for the sake of clarity. In other disc drives a single disc or a different number of discs may be attached to the hub. The invention described herein is equally applicable to disc drives which have a plurality of discs as well as disc drives that have a single disc. The invention described herein is also equally applicable to disc drives with spindle motors, which are within the hub  133  or under the hub.  
     [0033] As discussed in more detail below, slider  126  forms a hydrodynamic bearing, when flying or moving over the disc surface  135 . The air-bearing surfaces generate discrete areas of localized pressure while the slider flies over the disc surface  135 . When non-operational or when the slider is parked over a landing area, various features of the slider  126  prevent meniscus formation of disc lubricant and reduce contact area between the slider and the disc. These features allow discs  134  to be fabricated with a smooth or less-textured slider landing zone  111 , without causing unreasonably high stiction forces between the slider and the disc surface.  
     [0034] Referring now to FIG. 2, there is shown a perspective view  200  of one embodiment the slider  126  of FIG. 1. FIG. 2 shows the air-bearing surface  203  of the slider  200 . It should be noted that the vertical dimension of all the figures that show the air bearing surface is exaggerated for the sake of illustrating the concepts of the invention. In other words, the vertical dimension of the air bearing surface is exaggerated in FIGS.  2 - 6  and  8 - 13 . Returning to FIG. 2, the air-bearing surface  203  is the surface confronting the discs  134  when the slider  200  is flying or passing over the surface  135  of the disc  134  during normal operation. The slider  200  has a leading edge  201 , a trailing edge  202 , side edges  204  and  206 , and a lateral center line  208 . Elongated, raised side rails  210  and  212  are positioned along side edges  204  and  206 , respectively. Rails  210  and  212  extend generally from leading edge  201  toward trailing edge  202  and terminate prior to trailing edge  202 . Each rail  210  and  212  has an inside rail edge  214 , an outside rail edge  216 , a leading air-bearing surface  218 , a trailing air-bearing surface  220  and a recessed waist portion  222 . Recessed waist portion  222  extends from leading air-bearing surface  218  to trailing air-bearing surface  220 . In some embodiments, the waist portion is generally parallel to and recessed from each leading air-bearing surface  218  and each trailing air-bearing surface  220  by a step having a depth of about 0.1 to 0.5 micrometers. Of course, other depths can also be used in other embodiments. The recessed portions are generally considered to be at a step level along with several other elements of the slider  200 . The recessed waist portions reduce the contact area of the slider  126  when at rest on the surface  135  of the disc  134  or during inadvertent contact with the disc. The recessed waist portions also develop substantially ambient pressure during flight.  
     [0035] A cavity dam  230  extends between rails  210  and  212 , along leading edge  201 . Cavity dam  230  has a leading edge  232  and a trailing edge  234 . Cavity dam  230  and side rails  210  and  212  define a subambient pressure cavity  236 , which trails cavity dam  230  relative to a direction of air flow from the leading edge  201  toward trailing edge  202 . A subambient pressure cavity  236  is recessed from leading and trailing air-bearing surfaces  218  and  220  as well as those surfaces at the step level. The cavity floor is at the cavity level. Generally the surface of the waist portion  222  of each side rail  210 ,  212  is recessed from bearing surfaces  218  and  220 . Waist portions  222  remain raised from the floor of the cavity  236  such that the waist portions  222  continue to define the shape of the cavity  236  and contain subambient pressure within the cavity  236 . In other words, the surface of the waist portion  222  of each side rail  210 ,  212  is at the step level between the floor of cavity  236  and the surface defined by bearing surfaces  218 ,  220 . The surface of the cavity dam  230  is also at the step level.  
     [0036] In some embodiments, the cavity dam  230  is generally parallel to and recessed from bearing surfaces  218  and  220  by a step depth of 0.1 to 0.5 micrometers, for example. Other depths can also be used. In addition, cavity dam  230  can be formed with a tapered leading edge in alternative embodiments, if desired.  
     [0037] A raised center pad or rail  240  is positioned along the trailing slider edge  202  and can be centered along the lateral center line  208 . In some embodiments, the center pad  240  can be skewed or offset with respect to the line  208 . The center pad  240  has a leading surface  241  at the step level, and an air-bearing surface  242 . The leading surface is at the step level as are the recesses in the side rails and the cavity dam  230 . Leading step surface  241  is generally parallel to and recessed from the bearing surface  242  by a step depth of 0.1 to 0.5 micrometers, for example, for providing pressurization of the bearing surface  242  from air flow venting from the cavity  236 . The center pad  140  supports a read/write transducer  244  near the trailing slider edge  202  of the slider  200 . In some embodiments, transducer  244  can be positioned at other locations on slider  126 . However when placed at or near the trailing slider edge  202 , transducer  244  is located at the closest point on slider  126  to the surface  135  of disc  134  when the slider is flying or passed over the disc  134 . When the leading edge  201  flies slightly higher than the trailing edge  202  of the slider  200 , the slider is said to fly at a positive pitch angle. When the slider  200  flies with a positive pitch angle, the trailing slider edge  202  is closer to the surface  135  of the disc  134  than the leading slider edge  201  and the transducer  244  is closely spaced with respect to the disc  134 .  
     [0038] Rails  210  and  212  terminate prior to the trailing slider edge  202  to allow the slider  110  to roll slightly about the lateral center line  208  and minimize the risk of contact between the trailing rail edges  224  and the disc surface  134 . Therefore, the trailing edge of center pad  240  remains the closest location on the slider  126  to the disc surface  135  during flight at various roll angles, thereby improving read and write performance. However, truncating the side rails  210  and  212  reduces the amount of positive pressure developed along the rails near the trailing slider edge  202 , which in turn, reduces pitch and roll stiffness.  
     [0039] In order to limit the reduction in pitch and roll stiffness, in some embodiments the slider  126  further includes convergent channel features  260 ,  262 , and  264 , which are recessed within trailing air-bearing surfaces  220  of the side rails  210  and  212  and within the air-bearing surface  242  of the center rail  240 . These channels are also referred to as trenches. Channels  260 ,  262 , and  264  each have a leading channel end  266 , non-divergent side walls  268 , a trailing channel end  270 , and a channel floor (a “step surface” which actually is at the step level)  272 . In the embodiments shown, the channel floors  272  of channels  260  and  262  are coplanar and contiguous with recessed waist portions  222  of rails  210  and  212 , while channel floor  272  of channel  264  is coplanar and contiguous with leading step surface  241  of the center rail  240 . In other embodiments, the channel floors  272  and waist portions  222  may be at different levels.  
     [0040] In channels  260  and  262 , the leading channel end  266  is open to fluid flow from recessed areas  222  of the side rails  210  and  212 , respectively. However, the trailing channel end  270  is closed to the fluid flow. A portion of the fluid flow from the recessed areas  222  is directed into the channels  260  and  262  and is forced to exit the channels over the trailing channel ends  270 . This creates localized positive pressure areas on the trailing bearing surfaces  220  at and near the trailing channel ends  270 . In some embodiments, the trailing bearing surfaces  220  have a length measured from the trailing channel ends  270  to the trailing rail edges  224  that is equal to or greater than the width of the channels  260  and  262 , as measured between side walls  268 . This provides sufficient bearing surface on which the localized positive pressure can act. The localized positive pressure developed on the trailing air-bearing surfaces  220  increases the roll stiffness of the slider  126 . The localized positive pressure also prevents or lessens the chance of inadvertent contact between the slider and the disc  134 . The localized pressure also increases the pitch stiffness. The center pad  240  includes a similar feature.  
     [0041] With respect to the channel  264  on the center rail  240 , the leading end  266  of this channel is open to fluid flow from the cavity  236 , and the trailing channel end  270  is closed to the fluid flow. A portion of the fluid flow from cavity  236  is directed into the channel  264  and is forced to exit the channel over the trailing channel end  270 . Again, this creates a localized positive pressure area on the air-bearing surface  242 , rearward of the trailing channel end  270 . In some embodiments, the center rail air-bearing surface  242  has a length between trailing channel end  270  and the trailing slider edge  202  that is at least the width of the channel  264 , as measured between the side walls  268 . The localized positive pressure developed on center rail air-bearing surface  242  increases the pitch stiffness of the slider  126 .  
     [0042] During operation, the side walls  268  to either side of leading channel ends  266  present themselves as a substantial pressure rise to the local fluid flow. Since the opening to each channel, at the leading channel ends  266 , does not have the same pressure rise, it is seen as a preferential path for the fluid flow to travel. Once the fluid flow enters the channels  260 ,  262 , and  264 , the flow is essentially bounded by the channel side walls  268  and trailing channel end  270  and is forced to rise over trailing channel end  270 . This creates localized pressure areas at discrete regions near trailing slider edge  202 . Channels  260 ,  262 , and  264  can be symmetrical about the lateral center line  208 , as shown in FIG. 1, or can be asymmetrical to provide preferential pressurization at certain slider skew angles.  
     [0043] The size and intensity of the localized positive pressure areas depend on the channel length-to-width ratio, the absolute sizes of the channels and the depth and shape of the channel floors. In some embodiments, the ratio of the channel lengths to the channel widths range from 0.5 to 5.0 micrometers but may vary outside that range depending on the design purpose of the channel feature. In some embodiments, the length-to-width ratio ranges from 2.0 to 2.5.  
     [0044] Each of the leading air-bearing surfaces  218  includes at least one raised pad  292  protruding from the first and second rails  210  and  212 . The raised pads  292  prevent or lessen stiction in contact start stop (“CSS”) disc drives. Generally, the raised pad  292  has a surface area that has little or no effect on the overall flying characteristics of the head slider  200 . The at least one raised pad  292  provides a separation between the leading air-bearing surfaces  218  and the disc surface  135  to significantly reduce stiction forces between the disc surface  135  and the slider  126 . In some embodiments, the raised pads  292  extend from the air-bearing surfaces  218  in the range of about 5-70 nanometers and preferably in the range of 10-30 nanometers. The raised pads  292  associated with the leading air-bearing surfaces  218  are made of DLC material or another high-wear material.  
     [0045] It should be noted that the raised pads  292  associated with the leading air-bearing surface  218  are positioned toward the leading edge of the slider  200 . Since the slider  200  flies in a pitched relationship where the leading edge is higher than the trailing edge, the raised pads  292  associated with the leading air-bearing surface  218  have little effect on the flying characteristics of the slider  200 . Features which are closer to the trailing edge of the slider  200  or of any slider for that matter, generally affect the flying characteristics of the slider more than those near the leading edge of the slider.  
     [0046] Slider  126  further includes two raised bars  290 . Each of the trailing bearing surfaces  220  includes a raised bar  290  that extends slightly from the surface of the trailing air-bearing surface. The raised bar  290  is disposed near the side walls  280 . In some embodiments, the raised bars  290  extend from the trailing bearing surfaces  220  approximately in the range of about 5 to 70 nanometers. The raised bars  290  serve the same purposes as the raised pads  292  in a CSS drive, namely to provide a separation between the trailing edge air-bearing surfaces  220  and the disc surface  135  when the slider  126  is at rest on the disc surface  135 . Since the raised bars  290  are more closely located near the trailing edge of the slider  200 , they have more impact on the overall flying characteristics of the slider. The positional variations of the bar  290  are carefully controlled to minimize changes to the flying characteristics. The raised bar  290  is much less susceptible to variation in flying characteristics because of the width of the bar  290 . The bar  290  is less dependent on pad mask placement when compared to individual pads. Generally, the flying characteristics of the slider depend on the position of pads and the bars on the slider  200 . Therefore, it becomes critical to design the slider including the pads and the bars to be less sensitive to such positional variations on the slider  200 . The raised bar  290  is formed of DLC or another wear-enhancing material.  
     [0047] The separation produced by bars  290  between the trailing edge air-bearing pads and the surface of the disc  134  significantly reduces the stiction forces between the slider  126  and the disc surface  134 . The bar  290  is less sensitive to the positional variations than individual raised statures. Each raised bar  290  can extend generally from the outer rail edges  216  to the inner side walls  268 . Each raised bar  290  can be parallel to the side walls  280 . Each raised bar  290  can be of the same length as the side walls  280 . In some embodiments, the raised bar  290  has a width in the range of about 5 to 100 micrometers. The width of each raised bar  290  generally runs from the leading edge  201  toward the trailing edge  202 . The raised bar  290  can have cross sections in the shape of a square, or a rectangle. The cross section of the at least one raised bar  290  can be from the outer rail edge  216  toward the inner rail edge  214 . The raised bar  290  is similar to the raised pads  292  in its functionality in reducing the stiction between the slider  126  and the disc surface  135 . If several raised pads were used to replace the bar  290 , the flying characteristics of a slider would be more sensitive to variation in the placement of raised pads on a trailing air-bearing surface. The advantage of one raised bar  290  is that there is no variation in position across the bar, unlike the placement of one or more raised pads (not shown in FIG. 2) on the trailing bearing surfaces  220 . Raised pads would be sensitive in the width direction. Using the raised bar  290  instead of raised pads reduces the sensitivity to overall flying characteristics and significantly improves the design performance of the slider. The location of the raised bar  290  is less likely to significantly change the flying characteristics of the slider  200 . During manufacture, the raised bars are made from diamond-like carbon material or other high-wear material on the surface associated with the air bearing. Bar  290  is less likely to significantly change the flying characteristics of the slider. A further advantage of the bar  290  is that it can be placed onto the air-bearing surface with lots of variation in respect to the width of where the bar is positioned. In other words, the position of the bar with respect to the trailing edge of the slider  200  needs to be very precisely positioned. However, the actual width dimension across or transverse to the side rails need not be carefully positioned. During manufacture, a diamond-like carbon bar that is overly wide will be placed onto the slider using a first mask for features which will be on air-bearing surfaces of the slider. Several other masks will be used to define the cavity and its shape and depth as well as the recesses and all the features placed on or at the step level of the slider  200 . These other two masks are used to control etching processes such as reactive ion etching or ion milling or acid etching, each of which are used to remove material from unmasked portions of the ceramic slider. The placement of these masks for the etching is very, very precise so that if the width of the raised bar  290  is overly wide, subsequent masks used to etch away material and form the final slider geometry can be very precisely placed so that any over-wide portion is merely removed by a subsequent etching process. The final result is a very carefully placed raised bar  290  which has very consistent effects on the flying characteristics of the slider and also which has very low variation in terms of the effects on the flyability.  
     [0048] Referring now to FIG. 3, there is shown a perspective view  300  of another embodiment of a slider  300 . The slider  300  shown in FIG. 3 is very similar to the slider  200  shown in FIG. 2, except that the trailing air-bearing surface  320  of slider  300  does not include a raised bar. Instead, the slider  300  includes at least one raised pad  310  extending from each of the recessed areas  322  of the first and second rails  210  and  212 . As shown in FIG. 3 each side rail  210 ,  212  includes a pair of raised pads  310 . The raised pads  310  are positioned on the side rail  210 ,  212  between the trailing air-bearing surface  320  and the leading air-bearing surface  318 . The raised pads  310  provide a separation between the trailing bearing surfaces  220  and a disc surface  135  when the slider  300  is at rest on the disc surface  135 . The raised pads  310  extend from the recessed areas  222  such that the extension reduces surface tension between a lubricant disposed on a disc surface  135  and the disc  134 . The raised pads  310  are on longer columns than the raised pads  292 . Therefore, when a meniscus is formed between the pads  310  having a very long column or sitting on a longer column than the raised pads  292 , the raise of curvature of the lubricant formed by the meniscus is a larger radius than a shorter pad. This reduces the stiction forces between the slider  300  and the disc surface  134  and is further explained below with respect to FIG. 4. The raised pads  310  extend to substantially the same heights as the raised pads  292  on the leading edge bearing surface  318 . Each of the pads  310  is capped with diamond-like carbon (“DLC”) and shown by reference numeral  3101 . The DLC provides for a high wear surface in a CSS disc drive. As mentioned previously, the pads  292  are made of DLC.  
     [0049] The raised pads  310  associated with the recessed areas  222  of the first and second rails  210  and  212 , are positioned on longer columns of material than the pads  292 . The longer the column on which a pad  292 ,  310  sits, determines the effective height. In other words, the effective height of the raised pads  310  is higher than the raised pads  292  even though the free end of the pad  292 ,  310  is at the same height with respect to the recessed area  222 . The inclusion of raised pads  310  considerably reduces dwell stiction between the disc surface  135  and the slider bearing surfaces  218  and  222  because the longer column associated with the raised pads  310  increase the radius of curvature of the meniscus formed by the lubricant on the disc surface  135  and the column of the raised pads  310 . Increasing the radius of the curvature of the meniscus further reduces surface tension. Also, the raised pads  310  with an effective height higher than the raised pads  292  prevent formation of a second radius between the attachment point of the raised pads  310  and the level of the slider  300 . Therefore, slider  300  has a reduced stiction force when compared to the slider shown in FIG. 2. In the embodiment shown in FIG. 3 there are two raised pads on each of the recessed areas  222 . The raised pads  310  are disposed on the recessed areas  222  such that the raised pads  310  are closer to the side walls  280 . The raised pads  310  are also symmetrical about the leading channel ends  266 . Other configurations of raised pads are contemplated. The advantage of this configuration is that the raised pads  310  and the rails  210 ,  212  can both be formed at the same time. A step level mask is placed on the ceramic block to form the recessed areas  222 , the cavity dam  230  and the step surface or leading surface  241  associated with the center pad. The step level mask is very carefully controlled which minimizes variations in the location of the raised pads  310  with respect to the rails  210  and  212 . In fact, the rails  210  and  212  and the raised pads  310 , the recessed areas  222 , the cavity dam  230  and the leading surface  241  are all formed using the step level mask and this prevents variation in location of the raised pads  312  with respect to other elements of the slider since all these elements are formed by the same mask. Initially, the slider is provided with deposits of DLC in the general vicinity of the raised pads  310 . The DLC is laid down initially on the air-bearing surface of the slider. Basically, a relatively large patch of DLC is placed onto the slider. The large patch of DLC encompasses all the various tolerances with which the step level mask can be placed onto the ceramic block. In other words, a large enough patch of DLC is laid down so that despite where the step level mask is positioned, given the tolerance it has, a raised pad  310  may be formed having a cap of DLC. This considerably simplifies the manufacturing process because the physical location of the DLC portion of the raised pads  310  on the recessed areas  222  can have a wider tolerance with respect to the rails  210  and  212 . This also eliminates any fly height sigma addition due to placement of raised pads  310  on the recessed areas  222 .  
     [0050]FIG. 4 shows a disc  134  having a disc surface  135  and slider  126  resting on the disc surface  135 . The slider  126  includes a leading edge bearing surface  218  having a pad  292  and a recessed surface  222  with a raised pad  310 . The column length of the raised pad  310  is larger than the column length of the raised pad  292 . The surface  35  of the disc  134  is covered with a thin layer of lubricant  420 .  
     [0051]FIG. 4 shows the difference in the formation of meniscus by the lubricant  420  disposed on the disc surface  135  between the pad  292  and the pad  310  and the disc surface  135 . It can be seen from FIG. 4 that the shorter pad  292  produces a decreased radius of curvature  410  in the meniscus due to a surface tension between the shorter raised pad  292  and the lubricant  420 . On the raised pad  292 , a meniscus  410  is formed between a surface of the disc  135 , and at the leading air-bearing surface  218 . The decreased radius of curvature  410  increases the surface tension between the pad  292  and the lubricant  420 . Increased surface tension results in higher stiction force between the pad  292  and the disc surface  135 . Also, shown in FIG. 4 is that a meniscus forms between the leading air-bearing surface  218  and the column  405 .  
     [0052] A taller pad  310  (such as the one used in FIG. 3) produces an increased radius of curvature. Taller pad  310  also prevents the formation of another radius and meniscus between the surface  222  and the raised pad  310  (generally due to not having enough lubricant  420  on the disc surface  134 ). The stiction force for the taller pad is reduced by half when compared with stiction force developed between the shorter pad  405  and the lubricant  420 . FIG. 4 shows the advantage of having a higher effective height. Essentially, by increasing the radius of curvature of the meniscus formed, the surface tension and stiction is minimized.  
     [0053] Referring now to FIG. 5, there is shown a perspective view of another embodiment of a slider  500 . The slider  500  shown in FIG. 5 is very similar to the slider  300  shown in FIG. 3. The similar elements will not be discussed. The focus of the discussion will be on the differences. The slider  500  includes two raised pedestals or pads  510  extending from the floor of the subambient pressure cavity  236 . In some embodiments, the slider  500  can have one or less than the two raised pedestals or pads  510  extending from the subambient pressure cavity  236 . The two raised pads  510  are disposed proximate the raised center rail  240 . The two raised pads  510  can be disposed symmetrically about the lateral center line  208 . The pedestals  510  of slider  500  have many of the same advantages described above with reduced surface tension. In addition, the pedestals or raised pads  510  prevent stiction between the air-bearing surfaces and the disc surface  135 . Reduced stiction improves the performance of the disc drive  100 . The pedestals or raised pads  510  further include a layer of diamond-like carbon material  515  over the raised pads  510 . Of course, the elongated column raised pads  510  could be arranged in various geometric configurations. The raised pads  510  could also be combined with the other raised pads  292 ,  310 . The raised pads  510  or pedestals are also formed from the mask associated with the step surface and, therefore, can be precisely placed with respect to the trailing edge feature and other air-bearing features formed by the masking and etching processes used to form the geometry of the air-bearing surface. Like the pads  310 , the pads  510  have a cap of diamond-like material. The diamond-like material forming the cap is initially placed on the air-bearing surface of the slider before etching or masking takes place. The DLC forming the top of the pedestal or raised pad  510  is placed across a wide area so that no matter what the tolerance of the step mask is, the top of the pedestal or top of the raised pad will always have diamond-like carbon or another wear-enhancing material at the top of the pedestal or top of the raised column. Once the steps have been formed, namely recesses  222 , cavity dam  230 , the air-bearing surface  242  of the center rail  240 , and the channel floors  272  of the channels  264 , these surfaces are then masked while etching is continued so that the ambient cavity can be formed on the slider. The step layer mask includes the pads  310  and  510 . Certain portions of the slider, namely the step surfaces, are masked off and then the etching to remove the material will continue. In addition, the cavity level mask includes the features for the pedestals or raised pads  510  and these continue to stay in place throughout the etching process so that the end result will be a column or pedestal attached to the floor of the subambient cavity.  
     [0054] Referring now to FIG. 6, there is shown a perspective view of another embodiment of the slider  600 . The slider  600  shown in FIG. 6 is very similar to the slider  500  shown in FIG. 5, except that in addition to what is shown in FIG. 5, the slider  600  includes two raised pads  610  on the leading step surface  241  of the center rail  240 . In other embodiments, one raised pad  610  may be used. In other embodiments, a plurality of raised pads  610  may be useful. The configuration of the raised pads  610  may be changed to include other configurations than the configuration shown in which the two raised pads disposed closer to the side walls  280  of the channel  264  on the center rail  240 . As shown, the two raised pads  610  are disposed symmetrically to the lateral center line  208 . Raised pads  610  can be equal to or less than the height of the other pads disposed on the slider  600 . Raised pads  610  are included to prevent center rail  240  from contacting the bearing surfaces  218  and  220  when parked or non-operational. The raised pads  610  prevent the center rail  240  of the slider  600  from contacting the disc  134 . The raised pads  610  include a layer of diamond-like carbon material  615  over the raised pads  610 .  
     [0055] The raised pads  610  are also formed using the step level mask so that the position of raised pads  610  with respect to the trailing edge and other step level mask features varies minimally. In addition, the DLC that ultimately forms the top cap of the raised pads  610  is placed using the step level mask so a less than accurate placement of DLC need be made. The DLC is placed so that it will be within tolerances of the step level mask.  
     [0056]FIG. 8 shows yet another embodiment of a slider  800  that includes a set of raised bars which traverse a trench  862  on the trailing edge bearing surface  820 . The trailing edge surfaces  820  appear to be pads upon each side rail  810  and  812  of the slider. A second set of raised bars  892  traverses each side rail in the area or on the leading edge bearing surface  818 . The slider  800  includes a median line  808  about which the air-bearing surface  803  of the slider is symmetrical. Each of the raised bars  890 ,  892  are on lines which traverse the median line  808  of the slider  800 . It should be noted that, as shown, the raised bars are on lines which are substantially perpendicular to the median line  808 . The lines formed by the raised bars merely have to traverse the median line and could be at angles other than a perpendicular angle. In addition, the bars which traverse the median line could have different spacings. In other words, on the leading air-bearing surface  818  there could be a set of two closely spaced bars on each of the leading edge surfaces  818 . Of course, any geometric configuration can be used. The raised bars may be placed anywhere along one of the side rails  810 ,  812 . For example, in some configurations of a slider there is no recess  822  along the length of the rail  810 ,  812 , and a bar could be placed across that portion of the rail. The raised bars  890 ,  892  are made of DLC or another durable material. Of course, the features of the slider  800  are formed by depositing various materials onto a ceramic substrate and then mask and etch until the various features are formed. The bars are made of DLC placed atop the ceramic block, such as AlTiC, which is used to form the main body of the slider.  
     [0057] The DLC is precisely placed with respect to the trailing edge but does not have to be precisely placed with respect to the side rails. As a result, the bars can be quickly placed with a mask that is somewhat less than accurate with respect to the transverse rail direction. The DLC only has to be of a dimension so that after placing the step level mask and etching away certain portions of the slider, the DLC is still positioned to form a raised bar across the side rail. Typically, the DLC is placed onto the surface of the substrate using a mask. After depositing the DLC, the mask is removed and another step level mask is put in place and exposed to remove portions of the mask so that etching of the step level and cavity level can be accomplished. Of course, the deeper etchings require longer exposure times to ion mills so after the step level is formed, the step levels are masked and ion milling is continued to form the cavity. Most of the caps of DLC are laid down in an area which can accommodate the tolerances of the step mask. The cap is formed by precisely etching the substrate of the ceramic substrate which forms the slider end product.  
     [0058] Raised bars, such as  290 ,  890  and  892 , are all formed generally of wear material such as diamond-like carbon. These bars are also manufacturable or easy to manufacture since they can be laid down with a less than accurate machine. The accuracy occurs when the step level mask is used and material is etched away. The slider is formed from a block of ceramic material which is etched away to form the various features on the air-bearing surface. In terms of making a bar  290 ,  890  or  892 , the block or the slider surface which will eventually turn into the air-bearing surface can be either covered entirely with diamond-like carbon material or it can be masked and diamond-like carbon material can be placed in the general vicinity of the raised bar  890 ,  892 ,  290 . The reason that the horizontal bar is more manufacturable is that because diamond-like carbon does not have to be placed precisely on what will turn into the air-bearing surface as an initial step.  
     [0059] As mentioned previously, successive masks are put in place and removed to produce various features on the air-bearing surface of the slider. A first mask is for features on the air-bearing surfaces. The second mask or shelf level mask is for all other features. After the shelf level features are formed, some may be masked to provide a protective layer while the cavity is formed. These masks, for example, can protect certain areas, such as the top of the bar, from ever being exposed to etching or removal of material of the block to produce the air-bearing surface.  
     [0060] The same holds true for raised pads  310 ,  510 ,  610 ,  810 ,  910 ,  1010  and  1110 . The pads must be very precisely placed during the time when material is going to be removed from the surface of a ceramic block to form an air-bearing surface. However, the diamond-like carbon layer that typically covers the pads can be placed with loose tolerances so that another data may be selected for placement of the pads or pedestals.  
     [0061]FIG. 9 shows another embodiment of a slider  900 . In this particular case, the slider  900  is very similar to the slider  300  shown in FIG. 3. The differences between the slider  300  and the slider  900  will be highlighted rather than setting forth an entire new description. The basic difference between the slider  900  and the slider  300  is the elimination of the raised pads  293  on the leading edge surface  318 . The leading edge surface can be left avoid of raised features or can include a raised bar or can be roughened by other means so as to reduce stiction if the slider  900  is to be used in a contact start stop disc drive.  
     [0062]FIG. 10 shows yet another embodiment of slider  1000 . The slider  1000  differs from the slider  500  shown in FIG. 5 in that two additional pedestals or elongated raised pads  1012  are positioned in the sub-ambient cavity and yet closer to the cavity and the leading edge of the slider. Of course, it should be noted that the pedestals or elongated raised pads  1010  and  1012  are all capped with DLC. Furthermore, it should be noted that although four pedestals or elongated pads  1010 ,  1012  are shown in FIG. 10, that there could be more or less pads formed that will prevent or reduce stiction between the slider  1000  and the disc surface  135 .  
     [0063]FIG. 11 shows another embodiment of a slider  1100 . The slider  1100  is very close to the slider  600  shown in FIG. 6. The center rail  1140  includes a trench  1142 . The surface of the center pad includes a pair of raised pads  1110 . The raised pads  1110  are forward of the trench in that they are toward the leading edge  1120  of the slider  1100 . It should be noted that the slider  1100 , as shown, includes two of these pads  1110 , but that the slider may include a different number of pads including a single pad  1110  or a plurality of pads beyond the two shown.  
     [0064]FIG. 12 shows another embodiment of a slider  1200 . The slider  1200  is very close or differs only slightly from the slider  1000  shown in FIG. 10. In FIG. 12, the slider  1200  includes a set of raised pads  1210  and  1212  which are on the step surface toward the leading edge of the slider or which are positioned on the cavity dam of the slider. The raised pads  1210 ,  1212  are capped with a durable or a long-wearing material such as DLC. In this particular slider, step level features  1210  and  1212  are combined with the four elongated pedestals  1010  and  1012 . Each of the raised features shown and described  1010  and  1012 , 1210  and  1212 , are capped with DLC  1015 . Of course, other geometric patterns could be formed and more or less of the pedestals or raised pads could be used in this invention and are considered within the scope of this invention shown in FIG. 12.  
     [0065]FIG. 13 shows an embodiment of a slider  1300  which is symmetrical and includes two side rails  1310 ,  1312  with trenches  1320 ,  1322  and a center rail  1330  with a trench  1332 . This particular slider  1300  also includes a relatively thin cavity dam portion. The relatively thin dimension of the cavity dam may make it nearly impossible to place raised features on the cavity dam and, therefore, raised bars  1392  are placed across or transverse the cavity dam. In other words, the raised bars  1392  are dimensioned so that their long dimension roughly parallels the slide rail  1310 ,  1312  of the slider  1300 . Of course, bars  1392  positioned across the cavity dam could also be combined with other raised features on the cavity dam.  
     [0066]FIG. 14 is a perspective view of another embodiment of a slider  1400  according to the teachings of this invention. The slider  1400  is very similar to the slider  300  of FIG. 3. Slider  1400  differs from slider  300  in that the trailing air bearing surface  320  in that the trench in the trailing air bearing surface  320  has been removed in the slider  1400 . The remaining elements are essentially the same as indicated by the identical reference numbers. It should be noted that the various pads described in each of the embodiments previously described are equally effective in the absence of trenches. In other words, the pads are equally effective in air bearing designs with out trenches as air bearing designs with trenches.  
     [0067]FIG. 7 is a schematic view of a computer system. Advantageously, the invention is well suited for use in a computer system  700  and more specifically for use in a peripheral such as a disc drive. The computer system  700  may also be called an electronic system or an information handling system and includes a central processing unit, a memory and a system bus. The information handling system includes a central processing unit  704 , a random access memory  732 , and a system bus  730  for communicatively coupling the central processing unit  704  and the random access memory  732 . The information handling system  702  may also include an input/output bus  710  and several peripheral devices, such as  712 ,  714 ,  716 ,  718 ,  720 , and  722  may be attached to the input output bus  710 . Peripheral devices may include hard disc drives, magneto-optical drives, floppy disc drives, monitors, keyboards and other such peripherals. Any type of disc drive may include any of the sliders described herein.  
     Conclusion  
     [0068] In conclusion, a slider  200  includes a cavity dam  230 , a subambient pressure cavity  236 , and first and second elongated rails  210  and  212 . The subambient pressure cavity  236  trails the cavity dam  230  and has a cavity floor. The first and second rails  210  and  212  are disposed about the subambient pressure cavity  236 . Each of the rails  210  and  212  has a rail width measured from an inner rail edge  214  to an outer rail edge  216 , a leading bearing surface  218 , a trailing bearing surface  220 , and a recessed area  222  extending between the leading and trailing bearing surfaces  218  and  220 . The recessed area  222  is recessed from the bearing surfaces  218  and  220  and raised from the cavity floor, across the rail width. First and second convergent channels  260 ,  262  are recessed within the trailing bearing surfaces of the first and second rails  210  and  212 , respectively. Each channel  260  and  262  has a leading channel end  266  open to fluid flow from the respective recessed area, non-divergent channel side walls  268 , and a trailing channel end  270  closed to the fluid flow and forward of a localized region of the respective trailing bearing surface  220 . Each of the channels  260  and  262  has a side wall  280  on either side of the leading channel ends  266 . The slider  200  also includes a raised bar  290  protruding from each of the trailing bearing surfaces  220  of the first and second rails  210  and  212  such that the raise bar  290  is near the leading channel end  266 . The raised bar  290  provides a separation between bearing surfaces  218  and  220  and a disc surface  135  when the head slider  200  is at rest on the disc surface  135 . The at least one raised bar  290  protrudes from the trailing bearing surfaces  220  such that it has a reduced impact on the overall flying characteristics of the head slider  200  due to positional variations in the width direction of the raised bar  290  with respect to the trailing bearing surfaces  220 . Further, the separation significantly reduces stiction forces between the head slider  200  and the disc surface  134 .  
     [0069] Another aspect of the present invention relates to a disc slider  200 , which includes a leading slider edge  201 , a trailing slider edge  202 , a cavity dam  230 , and a subambient pressure cavity  236 . The subambient pressure cavity  236  trails the cavity dam  230  and has a cavity floor. The first and second rails  210  and  212  are disposed about the subambient pressure cavity  236 . Each of the rails  210  and  212  has a rail width measured from an inner rail edge  214  to an outer rail edge  216 , a leading bearing surface  218 , a trailing bearing surface  220 , and a recessed area  222  extending between leading and trailing bearing surfaces  218  and  220 . The recessed area  222  is recessed from the bearing surfaces  218  and  220  and raised from the cavity floor, across the rail width. First and second convergent channels  260  and  262  are recessed within the trailing bearing surfaces  220  of the first and second rails  210  and  212 , respectively. Each channel  260  and  262  has a leading channel end  266  open to fluid flow from the respective recessed area, non-divergent channel side walls  268  and a trailing channel end  270  closed to the fluid flow and forward of a localized region of the respective trailing bearing surface  220 . The slider  200  further has at least one raised pad  292  protruding from each of the leading bearing surfaces  218  of the first and second rails  210  and  212 . In some embodiments, the slider  300  also includes at least one raised pad  310  protruding from each of the recessed areas  222  of the first and second rails  210  and  212 . The at least one raised pad  310  protruding from the recessed areas  222  provides a separation between the bearing surfaces  218  and  220  and a disc surface when the head slider  300  is at rest on the disc surface. The at least one raised pad  310  protrudes from the recessed areas  222  such that the protrusion reduces surface tension between a lubricant disposed on a disc surface  134 . Also, the at least one raised pad  310  significantly reduces stiction forces between the head slider  300  and the disc surface  134 . Further, the at least one raised pad  310  protrudes from the recessed areas  222  such that it has a reduced impact on the overall flying characteristics of the head slider  300  due to positional variations in the location of the raised pad  310  with respect to the recessed areas  222 .  
     [0070] The head slider  200  further includes first and second convergent channels  260  and  262 , which are recessed within the trailing bearing surfaces  220  of the first and second rails  210  and  212 , respectively. Each of the first and second channels  260  and  262  has a leading channel  266  open to fluid flow from the respective recessed areas  222 , non-divergent channel side walls  268 , and a trailing channel end  270  closed to the fluid flow and forward of a localized region of the respective trailing bearing surface  220 . Each of the first and second channels  260  and  262  further has a side wall  280  on either side of the leading channel ends  266 .  
     [0071] The head slider  200  further includes a raised center rail  240  positioned along trailing slider edge  202  and between the first and second elongated raised side rails  210  and  212 . The raised center rail  240  has a leading step surface  241 . The leading step surface is substantially parallel to and recessed from a center rail bearing surface  242 . The center rail bearing surface  242  is at a height similar to the height of the leading and trailing bearing surfaces  218  and  220 .  
     [0072] Yet another aspect of the present invention relates to a disc drive assembly  100 , which includes a housing  112 , a disc  135 , an actuator  120  and a slider  126 . The disc  135  is rotatable about a central axis within the housing  112  and has a recording surface with a data area  134  and a landing area  111 , which are non-textured. The actuator  120  is mounted within the housing  112 . The slider  126  is supported over the recording surface  134  by the actuator  126  and includes a cavity dam  230 , a subambient pressure cavity  236  and first and second elongated rails  210  and  212 . The subambient pressure cavity  236  trails the cavity dam  230  and has a cavity floor. The first and second rails  210  and  212  are disposed about the subambient pressure cavity  236 . Each of the rails  210  and  212  has a rail width measured from an inner rail edge  214  to an outer rail edge  216 , a leading bearing surface  218 , a trailing bearing surface  220 , and a recessed area  222  extending between the leading and trailing bearing surfaces  218  and  220 . The recessed area  222  is recessed from the bearing surfaces  218  and  220  and raised from the cavity floor, across the rail width. The slider  126  further includes at least one raised pad  310  protruding from each of the recessed areas  222  of the first and second rails  210  and  212 . The at least one raised pad  310  provides a separation between the bearing surfaces  218  and  220  and a disc surface  134  when head slider  126  is at rest on disc surface  134 . The at least one raised pad  310  protrudes from the recessed areas  222  such that the protrusion reduces surface tension between a lubricant disposed on a disc surface  134 . Also, the at least one raised pad  310  significantly reduces stiction forces between the head slider  300  and the disc surface  134 . Further, the at least one raised pad  310  protrudes from the recessed areas  222  such that it has a reduced impact on the overall flying characteristics of the head slider  300  due to positional variations in the location of the raised pad  310  with respect to the recessed areas  222 . The slider  126  further includes at least one raised pad  510  in the subambient pressure cavity  236 .  
     [0073] First and second convergent channels  260  and  262  are recessed within the trailing bearing surfaces  220  of the first and second rails  210  and  212 , respectively. Each channel  260  and  262  has a leading channel end  266  open to fluid flow from the respective recessed area  222 , non-divergent channel side walls  280  and a trailing channel end  270  closed to the fluid flow and forward of a localized region of the respective trailing bearing surface  220 . A raised center rail  240  is positioned along trailing slider edge  202  and between the first and second elongated raised side rails  210  and  212 . The raised center rail  240  has a leading step surface  241 . The leading step surface  241  is substantially parallel to and recessed from a center rail bearing surface  242 . The center rail bearing surface  242  is at a height similar to the height of the leading and trailing bearing surfaces  218  and  220 . It is to be understood that the above description is intended to be illustrative, and not restrictive. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.