Abstract:
An actuation assembly for use in a disc drive having a recording disc rotatable about an axis and a slider supporting a transducing head for transducing data with a disc. The actuation assembly supports the slider to position the transducing head adjacent a selected radial track of the disc. The actuation assembly includes a movable actuator arm and a load beam supported by the actuator arm. A gimbal for supporting the slider and having a slider opposing face is connected to a distal end of the load beam. The gimbal has at least one standoff extending from the slider opposing face toward the disc with the standoff providing a direct contact between the gimbal and the slider.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S)  
       [0001]    This application claims priority from Provisional Application No. 60/245,048, filed Nov. 1, 2000, for “SUSPENSION DESIGN AND METHOD FOR ATTACHING MAGNETIC RECORDING HEAD” by Michael L. Rancour, Richard L. Segar and Sandeepan Bhattacharya. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates to attaching a slider to a suspension assembly. More particularly it relates to a gimbal for supporting a slider that provides a direct contact between the gimbal and the slider.  
           [0003]    Air bearing sliders have been extensively used in disc drives to appropriately position a transducing head above a rotating disc. The transducing head is typically carried by the slider. Conventionally, head positioning is accomplished by operating an actuator arm with a large-scale actuation motor, such as a voice coil motor (VCM), to radially position the slider on a gimbal at the end of the actuator arm. Typically, disc drive systems include a suspension assembly attached to the actuator arm for supporting and positioning the slider. The suspension assembly includes a load beam attached to the actuator arm and has a gimbal disposed on the other end of the load beam. The air bearing slider carrying the transducing head is mounted to the gimbal. This type of suspension is used with both magnetic and nonmagnetic discs. The VCM rotates the actuator arm and the suspension assembly to position the transducing head over a desired radial track of the disc.  
           [0004]    In order for the VCM to correctly position the slider and transducing head over the desired track of the disc, the disc drive communicates with the slider electrically through conductive traces disposed along the suspension assembly. The traces extend along the gimbal and end at gimbal bond pads formed adjacent to the slider. The slider has bond pads disposed on a forward face such that a connection can be made between the traces and the slider.  
           [0005]    Difficulties arose in prior art systems for attaching the slider to the gimbal, specifically with vertical alignment of the slider on the gimbal. In particular the slider bond pads should be precisely positioned proximate to the gimbal bond pads so that a connection can be made between the two. One prior art system uses laminated circuit material to provide vertical alignment of the flex circuit to the slider bond pads. Other systems use notches in the slider to allow alignment of the slider with the gimbal bond pads. Some systems use conductive adhesives to reduce the electrical resistance between the slider and the gimbal, but these adhesives did not reduce the area of contact between the gimbal and the slider. The use of conductive adhesives increases the cost and manufacturing time of assembling a slider to a gimbal, whereas the use of laminated circuit material and notches increases the cost of the final assembly and the manufacturing time for the components.  
           [0006]    In prior art systems that do not use conductive adhesives, the thick adhesive bond line between the slider and the gimbal increases the electrical resistance between the transducing head and the suspension. The thick adhesive bond line and poor vertical alignment reduces conductivity between the gimbal and slider. Poor conductivity allows a charge to build on the slider, which results in poor electrical performance by increasing the noise in data read by the transducing head. When the layers between the gimbal and slider are large, poor static attitude adjustment results, and in particular poor static attitude control exists over the pitch and roll position of the slider.  
           [0007]    A gimbal design is needed in the art for allowing a slider to be attached to a gimbal in a manner that reduces the area of contact between the gimbal and the slider, increases conductivity, improves static attitude control and is more efficient for manufacturing.  
         BRIEF SUMMARY OF THE INVENTION  
         [0008]    The present invention relates to a disc drive having a recording disc rotatable about an axis, a slider supporting a transducing head for transducing data with the disc, and an actuation assembly supporting the slider to position the transducing head adjacent a selected radial track of the disc. The actuation assembly includes a movable actuator arm, a load supported by the actuator arm, and a gimbal. The gimbal is connected to a distal end of the load beam. The gimbal supports the slider and has a slider opposing face. At least one standoff extends from the slider opposing face toward the disc. The standoff provides a direct contact between the gimbal and the slider. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    [0009]FIG. 1 shows a top perspective view of a disc drive actuation system for positioning a slider over tracks of a disc.  
         [0010]    [0010]FIG. 2 shows an exploded perspective view of a distal portion of the disc drive actuation system of FIG. 1.  
         [0011]    [0011]FIG. 3 is a bottom view of an embodiment of a gimbal of the present invention.  
         [0012]    [0012]FIG. 4 is a bottom view of a second embodiment of a gimbal of the present invention.  
         [0013]    [0013]FIG. 5 is a bottom view of a third embodiment of a gimbal of the present invention.  
         [0014]    [0014]FIG. 6 is a bottom perspective view of the distal end portion of the disc drive actuation system showing the gimbal of FIG. 5.  
         [0015]    [0015]FIG. 7 is a bottom perspective view of the distal end portion of the disc drive actuation system with the slider attached.  
         [0016]    [0016]FIG. 8 is an upside-down cross-sectional view of the distal end portion of the disc drive actuation system.  
         [0017]    [0017]FIG. 9 is an upside-down cross-sectional view of the distal end portion of a prior art disc drive actuation system. 
     
    
     DETAILED DESCRIPTION  
       [0018]    [0018]FIG. 1 is a perspective view of a disc drive  10  including an actuation system for positioning a slider  12  over a track  14  of a disc  16 . Disc drive  10  includes a voice coil motor (VCM)  18  arranged to rotate an actuator arm  20  on a spindle around an axis  22 . A load beam  24  is connected to actuator arm  20  at a head mounting block  26 . A gimbal  28  is connected to an end of load beam  24  and slider  12  is attached to gimbal  28 . Slider  12  carries a transducing head (not shown in FIG. 1) for reading and/or writing data on concentric tracks  14  of disc  16 . Disc  16  rotates around an axis  30 , so that windage is encountered by slider  12  to keep it aloft a small distance above the surface of disc  16 .  
         [0019]    [0019]FIG. 2 is an exploded perspective view of a distal portion of disc drive  10  (shown in FIG. 1). Shown in FIG. 2, from top to bottom are load beam  24 , gimbal  28  and slider  12  carrying a transducing head  32 . Gimbal  28  is attached to load beam  24  and slider  12  attaches to a bottom surface of gimbal  28 . Gimbal  28  provides a spring connection between slider  12  and load beam  24 . Slider  12  includes a disc opposing face (not shown) and a gimbal opposing face  34  which is attached to a slider opposing face (not shown) on the bottom surface of gimbal  28 . Slider  12  has a leading edge  36  and a trailing edge  38 . Gimbal  28  is configured such that it allows slider  12  to move in pitch and roll directions to compensate for fluctuations in the spinning surface of disc  16 . Transducing head  32  is located proximate to trailing edge  38  of slider  12 . In operation, load beam  24  and gimbal  28  carrying slider  12  move together as coarse positioning is performed by VCM  18  (FIG. 1) to rotate actuator arm  20  (FIG. 1).  
         [0020]    [0020]FIG. 3 is a bottom view of a first embodiment of gimbal  28  according to the present invention. Gimbal  28  has a slider opposing face  40  on its bottom surface. Slider opposing face  40  engages gimbal opposing face  34  of slider  12  (FIG. 2). Gimbal  28  has a front edge  42 , a rear edge  44 , a first side edge  46  and a second side edge  48 . Front edge  42  of gimbal  28  is attached to load beam  24  (FIG. 2). An opening  50  extends through gimbal  28 . Opening  50  is bounded by the four edges  42 ,  44 ,  46  and  48 . Gimbal  28  has a tongue  52  lying in the same horizontal plane as gimbal  28 . Tongue  52  extends from rear edge  44  into opening  50 . Tongue  52  has a first side edge  54  and a second side edge  56 . Tongue  52  is preferably substantially rectangular, although those skilled in the art will recognize tongue  52  may be other shapes, such as circular or triangular.  
         [0021]    Standoffs  58  are formed on tongue  52  and extend from slider opposing face  40 . Slider  12  (FIG. 2) is attached to standoffs  58  with adhesive in an exemplary embodiment. In the embodiment of gimbal  28  shown in FIG. 3, standoffs  58  are configured as four bumps  60 . Each bump  60  is substantially circular, although the bumps could also take other forms, such as triangular or rectangular. Although the embodiment shown in FIG. 3 shows four bumps on tongue  52 , those skilled in the art will recognize that there may be fewer or more bumps. Bumps  60  are located on tongue  52  with at least two bumps ( 60   a  and  60   b ) proximate and substantially parallel to first side edge  54  of gimbal  28 . The other two bumps ( 60   c  and  60   d ) are proximate and substantially parallel to second side edge  56 .  
         [0022]    [0022]FIG. 4 is a bottom view of a second embodiment of gimbal  28  according to the present invention. The structure of gimbal  28  is the same as the structure disclosed with respect to FIG. 3 (the first embodiment). Standoffs  58  of the second embodiment of gimbal  28  are configured as two rails  62 . Preferably there is a first rail  62   a  and a second rail  62   b  formed on tongue  52 . First rail  62   a  is substantially parallel and proximate to first side edge  54  of tongue  52 . Second rail  62   b  is substantially parallel to and proximate to second side edge  56  of tongue  52 . Those skilled in the art will recognize there may be fewer or more rails and that the rails may have alternate configurations on tongue  52 , for example rails  62  may lie perpendicular to side edges  54  and  56 .  
         [0023]    [0023]FIG. 5 is a bottom view of a third embodiment of gimbal  28  according to the present invention. The structure of the third embodiment of gimbal  28  is substantially similar to the structure of the first embodiment of gimbal  28  shown in FIG. 3. However, standoffs  58  of the third embodiment are configured as wings  64 . Wings  64  extend out of the horizontal plane of gimbal  28  toward disc  16  (FIG. 1). A first wing  64   a  is located proximate and substantially parallel to first side edge  54 . A second wing  64   b  is located proximate and substantially parallel to second side edge  56 . Wings  64  extend along a substantial portion of tongue  52  and have a distal end  66  adjacent to opening  50  and a proximal end  68  adjacent to rear edge  44 .  
         [0024]    [0024]FIG. 6 is a bottom perspective view of the distal end portion of a disc drive actuation system employing the present invention. The third embodiment of gimbal  28  is shown with wings  64 . Wings  64  are portions of tongue  52  extending out of the horizontal plane of gimbal  28  toward disc  16  (FIG. 1). A first form line  70  and a second form line  72  are formed into tongue  52  thereby allowing portions of tongue  52  to be folded to form wings  64   a  and  64   b.  First form line  70  is located near proximal end  68  of tongue  52  and is substantially perpendicular to first side edge  54 . Second form line  72  is located near proximal end  68  of tongue  52  and is substantially perpendicular to second side edge  56 . Each wing  64   a  and  64   b  has two parts, a shoulder portion  74  and an arm portion  76 . Shoulder portion  74  extends away from tongue  52  toward disc  16  (FIG. 1). Arm portion  76  lies substantially parallel to the horizontal plane of gimbal  28  between gimbal  28  and disc  16  (FIG. 1).  
         [0025]    [0025]FIG. 7 shows a bottom perspective view of the distal end portion of the disc drive actuation assembly with slider  12  attached to gimbal  28 . A flex circuit material  78  is disposed on slider opposing face  40  of gimbal  28 . In the preferred embodiment of gimbal  28 , flex circuit material  78  is not disposed on tongue  52  and therefore no flex circuit material lies between slider  12  and standoffs  58  of gimbal  28 . During operation, when slider  12  flies above the disc, gimbal  28  typically permits three primary degrees of movement for slider  12 , which are vertical motion, pitch and roll rotation.  
         [0026]    Slider  12  has a disc opposing face  80  and a gimbal opposing face  34  (FIG. 2). Gimbal opposing face  34  of slider  12  is attached to gimbal  28  on the standoffs  58  located on tongue  52 . Slider  12  has a forward face  82  located proximate and substantially parallel to front edge  42  of gimbal  28 . Slider bond pads  86  are located on forward face  82  of slider  12 . Flex circuit material  78  is disposed upon gimbal  28  prior to attaching slider  12 , and forms an edge  84  proximate to forward face  82  of slider  12 . No flex circuit material  78  is located between slider  12  and gimbal  28  such that there is a direct contact between the slider and the gimbal. An adhesive (not shown) is used to bond slider  12  to tongue  52  of gimbal  28 .  
         [0027]    A trace layer  88  is formed upon flex circuit material  78  disposed on gimbal  28 . Trace  88  completes a circuit connection between the electronic components of the disc drive (not shown) and slider  12 . Trace  88  travels along the underside of actuator arm  20 , load beam  24  and gimbal  28 . Trace  88  is typically made of copper with gold plated on top of the copper layer. Each trace  88  ends at a gimbal bond pad  90 . In an exemplary embodiment there is at least one gimbal bond pad  90  located on gimbal  28  for each slider bond pad  86 . Gimbal bond pads  90  are located along edge  84  of gimbal  28 . Typically, a gold bond ball  92  is disposed on each gimbal bond pad  90 . Bond ball  92  is bonded to gimbal bond pad  90  and its respective slider bond pad  86 . An electrical connection is made between slider  12  and trace  88  through the slider bond pads  86  and gimbal bond pads  90 . Bond balls  92  act as an electrical conduit and complete the electrical connection between slider  12  and trace  88 . Standoffs  58  provide a surface for placing slider  12  on gimbal  28  such that slider bond pads  86  and gimbal bond pads  90  are vertically aligned.  
         [0028]    [0028]FIG. 8 is an upside-down cross-sectional view of the distal end portion of the disc drive actuation system of FIG. 1. Slider  12  is attached to gimbal  28  such that disc opposing face  80  faces disc  16  (FIG. 1). Standoffs  58  extend from slider opposing face  40  of gimbal  28 . Slider  12  is bonded to standoffs  58  with an adhesive  94 . Flex circuit material  78  extends to forward face  82  of slider  12  but not between slider  12  and gimbal  28 . Gimbal bond pad  90  lies on flex circuit material  78  along edge  84  of flex circuit material  78 . Slider bond pad  86  is affixed to forward face  82  of slider  12 . Gold bond ball  92  is bonded to slider bond pad  86  and gimbal bond pad  90  to provide an electrical connection between slider  12  and the electrical components of the disc drive connected to flex circuit material  78 . Standoffs  58  raise slider  12  above gimbal surface  28  such that slider  12  does not interfere with or contact flex circuit material  78  or gimbal bond pad  90 . In order for the electrical connection to slider  12  to work, slider  12  must be placed in a precise position on gimbal  28  such that gimbal bond pads  90  line up with their respective slider bond pad  86 . Standoffs  58  allow slider  12  to be properly placed on gimbal  28  such that bond pads  86  and  90  line up with each other.  
         [0029]    [0029]FIG. 9 is an upside-down cross-sectional view of the distal end portion of a prior art disc drive actuation system and is shown to illustrate an improvement of the present invention from the prior art systems. The prior art system includes the gimbal  28  having a slider opposing face  40 . In the prior art system, flex circuit material  78  is layered upon the entire slider opposing face  40  of gimbal  28 , including the area between gimbal  28  and slider  12 . Trace  88  terminates at gimbal bond pad  90  located along front edge  42  of gimbal  28 . Slider bond pad  86  is located on forward face  82  of slider  12 . Gold bond ball  92  is bonded to slider bond pad  86  and gimbal bond pad  90  to provide an electrical connection between trace  88  and slider  12 . Adhesive  94  is used to connect slider  12  to flex circuit material  78  on gimbal  28 . Flex circuit material  78  and adhesive  94  do not have a combined height that raises slider  12  completely above gimbal bond pad  90 . Therefore, to precisely position slider  12  upon gimbal  28  (including flex circuit material  78 ) such that each slider bond pad  86  lines up with its respective gimbal bond pad  90 , a notch  96  is formed in slider  12 . Notch  96  is formed on gimbal opposing face  34  of slider  12  adjacent to forward face  82  of slider  12 . Notch  96  serves as a positioning reference to place slider  12  upon gimbal  28  such that slider bond pad  86  and gimbal bond pad  90  are aligned. The present invention (FIG. 8) does not require notch  96  in order to position slider  12  onto gimbal  28 . The slider is positioned onto gimbal  28  with respect to standoffs  58 .  
         [0030]    In FIG. 9, slider  12  is located on top of flex circuit material  78  disposed on gimbal  28 . Static attitude is the relationship between the plane of the disc opposing face of the slider to a reference point on load beam  24  (FIG. 2), typically where head mounting block  26  (FIG. 2) contacts load beam  24 . Static attitude impacts fly height, take off velocity and the reliability of the head disc interface. The increased layers between slider  12  and gimbal  28  in the prior art system and the non-planar surface of flex circuit material  78  results in poor static attitude. The worse static attitude is, or the non-planarity of the surface slider  12  is attached to, the less control there is over the pitch and roll position of slider  12 . Introducing more layers between gimbals  28  and slider  12  results in more variation in the static attitude, thereby there is less control over slider  12 . Furthermore, if the slider cannot be attached to the gimbal with the required static attitude, a post assembly adjustment must be done to change the static attitude at an additional cost and with detrimental effects to other suspension characteristics.  
         [0031]    Prior art disc actuation systems result in poor vertical alignment between slider bond pads  86  and gimbal bond pads  90 . In addition, correcting the poor alignment requires post assembly adjustment that increases costs and takes additional time. The thick adhesive bond line and the poor vertical alignment reduces the conductivity between gimbal  28  and slider  12 . Poor conductivity permits slider  12  to charge up and is associated with poor electrical performance by increasing the noise in the slider signal.  
         [0032]    In the present invention, the standoffs reduce the area of contact between the gimbal and the slider, improves static control, increases conductivity, and is more efficient and less costly for manufacturing. The present invention removes the flex circuit material from the gimbal and adds formed features, or standoffs, to the gimbal. The standoffs provide a surface for placing the slider on the gimbal such that the slider bond pads and gimbal bond pads have improved vertical alignment. This differs from prior art systems by allowing vertical alignment of the slider to suspension bond pads to be achieved without the need for slider notches or flex circuit standoffs on the gimbal. The standoffs also provide a direct contact between the gimbal and the slider. Head suspension resistance is reduced by the intimate contact between the gimbal and the slider without a thick adhesive bond line in those areas. Improved vertical alignment and direct contact improved the conductivity between the gimbal and the slider, thereby resulting in better electrical performance of the slider and preventing the slider from charging up during operation.  
         [0033]    The use of standoffs on the gimbal for attaching the slider reduces the layers between the gimbal and the slider. Reducing the layers between the gimbal and the slider improves the planarity of the surface the slider is attached to and thereby improves static attitude. Improved static attitude means more control over the pitch and roll position of the slider. Finally, by improving the static attitude of the slider and the vertical alignment between the gimbal and the slider eliminates the need for post assembly adjustment to the slider. Thus, manufacturing time and cost is reduced.  
         [0034]    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.