Abstract:
A conductive path is provided to discharge electrostatic charges from a slider in a magnetic disk drive directly to the housing of the disk drive. In one embodiment conductive fibers electrically connect the slider with the housing. In another embodiment a cantilevered conductive finger electrically connects the slider with the housing. By providing a discharge path the accumulation of potentially damaging electrostatic charges is prevented.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates in general to disk drives used for information storage in a computer, and more specifically to a device allowing electrostatic discharge of the slider within the disk drive. 
     2. Description of the Background Art 
     Disk drives using magnetic recording of digital information are used to store most of the information in contemporary computer systems. A disk drive typically has a housing with at least one rotatable magnetic disk having a plurality of concentric tracks of magnetically stored data. There is at least one recording head typically with a separate write element and read element for writing and reading data on the tracks. The recording head is constructed on a slider and the slider is attached to a suspension. The suspension is connected to an actuator which positions the recording head over a specific track of interest. The actuator first rotates to seek the track of interest and after positioning the recording head over that track maintains the recording head in close registration to that track. 
     The slider carrying the recording head has a disk facing surface upon which an air bearing is constructed. The purpose of the air bearing is to allow the slider to float on a cushion of air over the rotating disk and to be positioned close to the disk surface. Alternatively the disk facing surface of the slider may be designed to be in contact with the disk. 
     There is an advantage in designing the suspension to lift the slider away from the disk surface when the disk rotation is stopped. The disk surface may be very smooth thus enabling higher recording densities without the risk of encountering stiction between the slider and the disk. Accordingly some conventional disk drives have a plastic load/unload fixture having a base portion and a ramp portion attached to the disk drive housing. In addition, in these disk drives there is a tab on the suspension designed to engage the ramp portion of the load/unload fixture. In the prior art the entire load/unload fixture is formed from an insulating material. 
     To achieve very high recording density, the recording head must be very small. Unfortunately very small recording heads are subject to damage from electrostatic discharge. This is particularly true of the read element in the recording head. The smaller the read element, the greater the damage from a given amount of electrical discharge. Static electrical charge may accumulate on the slider from either van deGraff charging resulting from close proximity to the moving disk or tribological charging. In the past, partially conductive epoxy has been used to attach the slider to the metallic suspension. The resistance of the epoxy connection can vary substantially thus in some disk drives there is a residual amount of charge on the slider which can then discharge through the read element to the disk causing damage to the read element. Furthermore, the suspension usually does present an ideal conductive path to the housing because the electrical connection is through a bearing assembly which has only intermittent conduction. Thus, the discharge path between the slider and the disk drive housing is uncertain and indirect. The problem of electrical discharge causing damage to the read sensor is exacerbated with ever decreasing sizes of the read sensor. 
     From the foregoing it is apparent that an apparatus offering improved and safe static discharge of sliders is needed. 
     SUMMARY OF THE INVENTION 
     In a preferred embodiment, the invention provides for a conduction path directly from the slider to the housing of the disk drive. 
     In one embodiment, one or more conductive fibers are configured to provide an electrical discharge path between the slider and the disk drive housing. The conductive fibers can conveniently be permanently connected electrically to a conducting portion of the load/unload ramp which is connected to the housing and can be configured to touch the slider when it is unloaded from the disk surface. In an alternate embodiment a low force conductive cantilevered finger is permanently connected electrically to the housing and is used to touch the slider. 
     An embodiment of an electrical discharge device according to the present invention substantially reduces the risk of read element damage. Other aspects and advantages of the present invention will become apparent from the following detailed description which when taken in conjunction with the accompanying drawings illustrate by example the principles of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates a disk drive having a load/unload fixture; 
     FIG. 2 a  illustrates a detailed perspective view of a slider and a portion of a suspension; 
     FIG. 2 b  illustrates an end view of a slider; 
     FIG. 2 c  illustrates a side view of a slider; 
     FIG. 3 a  illustrates a top view of a load/unload fixture; 
     FIG. 3 b  illustrates a side view of a load/unload fixture; 
     FIG. 3 c  illustrates a top view of a load/unload fixture and an unloaded slider; 
     FIG. 4 a  illustrates a top view of a load/unload fixture according to a first embodiment of the invention; 
     FIG. 4 b  illustrates a side view of a load/unload fixture according to a first embodiment of the invention; 
     FIG. 4 c  illustrates a side view of a load/unload fixture along and unloaded sliders according to a first embodiment of the invention; 
     FIG. 5 a  illustrates a top view of a load/unload fixture according to a second embodiment of the invention; 
     FIG. 5 b  illustrates a side view of a load/unload fixture according to a second embodiment of the invention; and, 
     FIG. 5 c  illustrates a side view of a load/unload fixture along with unloaded sliders according to a second embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An embodiment of the present invention provides a direct conductive path between the slider in a disk drive and the housing of the disk drive. This conductive path prevents dangerous electrostatic charges from accumulating on the slider and causing damage by discharging through the recording head. 
     In the Figures to follow, features are labeled with a three digit reference number. The first digit refers to the specific Figure. The latter two digits refer to the specific features. Features common to more than one Figure have the same latter two digits in the reference number. 
     Referring to FIG. 1, a magnetic disk drive  100  has at least one rotatable magnetic disk  102  supported by a spindle  104  and rotated by a motor (not shown). There is at least one slider  106  with an attached recording head  108  positioned over the disk  102  surface while reading and writing. The slider  106  is attached to a suspension  110  with partially conductive epoxy (not shown) and the suspension  110  is attached to an actuator  112 . The actuator  112  is pivotally attached  114  to the housing  116  of the disk drive  100  and is driven by a voice coil motor  118 . As the disk  102  is rotating, the slider  106  along with the suspension  110  is positioned by the actuator  112  radially or along an arcuate path  120  over the disk  102  surface to access the data track of interest. 
     Typically during operation of the disk drive  100 , the motion of the rotating disk  102  relative to the slider  106  generates an air bearing between the slider  106  and the disk  102  surface which exerts an upward force on the slider  106 . This force is balanced by a spring force from the suspension  110  urging the slider  106  toward the surface of the disk  102 . Alternatively, the slider  106  may be in either partial or continuous contact with the disk  102  surface during operation. 
     FIG. 1 also shows a load/unload tab  122  on the distal end of the suspension  110 . This load/unload tab  122  operates in conjunction with a load/unload fixture  124  to lift the slider  106  away from the disk  102  surface when the disk drive  100  is turned off or goes into a power saving mode. When an unload operation is initiated, the actuator  112  rotates far enough in a clockwise direction  126  such that the load/unload tab  122  engages with the load/unload fixture  124 . The load/unload tab  122  then slides up the load/unload fixture  124  gently lifting the slider  106  off of the disk  102  surface. FIG. 1 also shows the electrical connection  128  as wires or a flex cable between the recording head  108  and the preamplifier  130 . 
     FIG. 2 a  shows a more detailed perspective view of the slider  206  and a portion of the suspension  210 . The recording head  208  is shown on the trailing surface of the slider  206 . The load/unload tab  222  on the suspension  210  is illustrated. FIG. 2 b  shows an end view of the slider  206 . In FIG. 2 b  the location of the partially conductive epoxy  232  between the slider and the suspension is illustrated. FIG. 2 c  shows a side view of the slider  206 , the suspension  210 , the load/unload tab  222 , and the partially conductive epoxy  232 . FIG. 2 c  also shows that the recording head  208  is separated from the slider  206  by a thin layer of insulating material  234  such as alumina. One discharge path for electrostatic charge on the slider  206  is across the thin layer of insulating material  234  and through the recording head  208 . In addition to damaging the recording head  208 , electrostatic discharge can also go through the electrical connection  128  and damage the preamplifier  130 . 
     FIG. 3 a  shows a top view of the main features of a load/unload fixture  324 . The term “load/unload fixture” refers to the entire structure shown in FIG. 3 a . The load/unload fixture has a ramp portion  340  and a base portion  336 . There is also typically a hole  338  through which the load/unload ramp may be attached to the disk drive housing  116  by means such as a screw or registration pin. FIG. 3 b  shows a side view of the load/unload fixture  324 . Generally, there is a recording head for each surface of a disk. Accordingly, the side view of the load/unload fixture shown in FIG. 3 b  illustrates a dual load/unload fixture wherein the top ramp  340  is used for the recording head on the top surface of the disk (not shown) and the bottom ramp  341  is used for the recording head on the bottom surface of the disk (not shown). The top ramp  340  and bottom ramp  341  share a common base portion  336 . FIG. 3 c  shows a top view of a suspension  310  with an unloaded slider  306  on the load/unload fixture  324 . The load/unload tab  322  of the suspension  310  is shown in FIG. 3 c  as engaged with the ramp  340  of the load/unload fixture  324 . 
     FIG. 4 a  illustrates one embodiment of the present invention. The base portion  436  is formed from a suitable conductor such as aluminum or aluminum alloy. The base portion  436  is attached directly to the disk drive housing  116  and therefore presents a very low resistance electrical path to the disk drive housing  116 . The ramp  440  is conveniently formed from a suitable plastic material such as teflon, nylon or other suitable material which permits sliding of the tab on the surface of the ramp without wear damage or creation of particulate debris. The ramp  440  is joined with the conductive base portion  436  by an appropriate means such as swaging, gluing, or the like. One or more conductive fibers  442  is attached to or imbedded in the base portion  436  of the load/unload fixture  424 . The fibers  442  stick up from the surface of the base so that they contact the slider as the tab is moved onto the ramp  440 . The conductive fibers  442  may conveniently be connected to or imbedded into the base portion  436  by means such as press fitting or clamping. Each conductive fiber  442  may conveniently be formed from any resilient conductive material such as carbon impregnated nylon or a thin metal wire such as copper. The number of fibers in the bundle is preferably chosen to limit the overall force on the slider to approximately 100 dynes or lower to prevent any alteration of the alignment of the slider relative to the suspension. The number of fibers can be as low as one as long as the fiber provides a direct electrical discharge path between the slider and the base portion of the load/unload fixture and hence to the disk drive housing. 
     A view of the cross section of the load/unload fixture having a bundle of one or more conductive fibers is illustrated in FIG. 4 b . FIG. 4 c  shows a cross sectional view of the load/unload fixture  424  having a bundle of one or more conductive fibers  442  in contact with a slider  406 . The load/unload tab  422  of the suspension is shown on the ramp portion  440  of the load/unload fixture  424 . 
     An alternative embodiment of the invention is illustrated in FIGS. 5 a ,  5   b , and  5   c . FIG. 5 a  illustrates a top view of a load/unload fixture  524  which has a conductive base portion  536  and a ramp portion  540 . In addition, there is a cantilevered conductive finger  544  which is attached to the base portion  536  by convenient means such as spot welding, swaging, screwing, and riveting. The conductive finger may be conveniently formed from a metal such as copper, or copper alloy. The force of contact on the slider is preferably about  100  dynes or lower. The conductive finger may also be formed from a conductive polymer. FIG. 5 b  illustrates a side view of the load/unload fixture  524 . The cantilevered conductive finger  544  is attached at one end  546  to the base portion  536  of the load/unload fixture  524 . The other end  548  of the conductive finger  544  extends upward from the base portion  536  and is able to touch the slider  506  when present thus providing a direct conductive path for electrical discharge between the slider  506  and the disk drive housing  116 . FIG. 5 c  illustrates a side view of the load/unload fixture  524  with the cantilevered conductive finger  544  when a slider  506  is present. 
     From the foregoing it will be appreciated that the embodiments of the electrostatic discharge devices provided by the invention prevent potentially damaging accumulations of electrostatic charge on the slider. The devices provided by the invention are effective, inexpensive, and easy to implement. A discharge path embodying the invention is much more effective in discharging the slider body compared with using only partially conductive epoxy between the slider and the suspension. Although specific embodiments of the invention have been described and illustrated here, the invention is not to be limited to the specific forms or configurations so described and illustrated. The invention is limited only by the claims.