Abstract:
One embodiment of the present invention is a disk drive head stack assembly with a grounding path between a head and a disk drive ground, the disk drive head stack assembly including: (a) a suspension which carries the head and includes a first portion of the grounding path; and (b) an arm which carries the suspension and which includes a second portion of the grounding path, which second portion is electrically connected to the disk drive ground.

Description:
TECHNICAL FIELD OF THE INVENTION  
       [0001]     One or more embodiments of the present invention relate to disk drives, and more particularly, to disk drive head stack assemblies with improved grounding paths.  
       BACKGROUND OF THE INVENTION  
       [0002]     Grounding paths for disk drive head stack assemblies are important for helping: (a) to provide good signal-to-noise ratios (SNRs) in read/write operations; and (b) to minimize crosstalk caused by electrical magnetic interference (EMI).  
         [0003]     Providing grounding paths for disk drive head stack assemblies of small form factor disk drives used in mobile devices markets presents a challenge due to a desire to fit more read/write heads in a limited space. As is well known, thickness is a design constraint in small form factor drives, i.e., the smaller the disk drive thickness, the better the market acceptance. This is so because the market values a thinner and lighter disk drive that can provide a more compact end product, which compact end product will be better for use in mobile computing and storage applications. In light of this, since storage capacity is directly proportional to the number of heads and disks, a present trend is to utilize multiple heads and disks while making the heads (also referred to as sliders) and disks thinner (as is well known, the thickness of the disk drive is affected by the height of the disk drive head stack assembly). Specifically, head or slider designs have progressed through design generations, illustratively, from a mini-slider to a micro-slider, from a micro-slider to a nano-slider, from a nano-slider to a pico-slider, and from a pico-slider to a femto-slider; wherein each new generation has resulted in about a 30% reduction in thickness from the previous generation.  
         [0004]     A Giant Magnetoresistive (GMR) head that is typically used in prior art disk drives has four (4) read/write elements (R+, R-, W+ and W-). As such, in a disc drive head stack assembly of a prior art disk drive that uses such GMR heads, each suspension, i.e., flex-on-suspension (FOS) or trace suspension assembly, has: (a) one conductive trace for each of the four (4) read/write elements; and (b) one conductive trace (a grounding trace) that provides a grounding path between the head and a common ground in a flex print circuit assembly (FPCA) of the disk drive. As is well known, and in accordance with prior art designs, the width of each grounding trace becomes a constituent of the height of the head stack assembly, and the whole disk drive receives a contribution to its height from grounding traces that is proportional to the number of its heads. For example, the height of a four-headed disk drive that utilizes GMR heads (such as the GMR head described above) includes the widths of four (4) grounding traces and the width of a grounding trace for each GMR head.  
         [0005]     Another problem in providing grounding traces in accordance with the prior art is the cost and time involved in manufacturing disk drives utilizing such grounding traces. In accordance with typical manufacturing methods, each grounding trace is connected to the FPCA by applying a dot of conductive epoxy or by providing a soldering joint. Both methods are time consuming and costly due to: (a) adding additional manufacturing operations; and (b) a need to perform such manufacturing operations inside a class  100  clean room because of outgassing and cleanliness concerns. In addition, such time and cost requirements increase as the number of grounding traces increases.  
         [0006]     In light of the above, there is a need in the art for a disk drive head assembly that solves one or more of the above-identified problems.  
       SUMMARY OF THE INVENTION  
       [0007]     One or more embodiments of the present invention solve one or more of the above-identified problems. In particular, one embodiment of the present invention is a disk drive head stack assembly with a grounding path between a head and a disk drive ground, the disk drive head stack assembly comprising: (a) a suspension which carries the head and comprises a first portion of the grounding path; and (b) an arm which carries the suspension and comprises a second portion of the grounding path, which second portion is electrically connected to the disk drive ground. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0008]      FIG. 1  shows a disk drive head stack assembly (HSA) that is fabricated in accordance with one or more embodiments of the present invention wherein conducting traces of the HSA are connected to a flex printed circuit assembly (FPCA) of the disk drive;  
         [0009]      FIG. 2  shows a suspension with a 90-degree bend that is one component of the HSA shown in  FIG. 1 ;  
         [0010]      FIG. 3  shows an FPCA wherein part of its height is determined by a number of conducting traces emanating from the HSA shown in  FIG. 1 ;  
         [0011]      FIG. 4  shows a grounding pin of the HSA shown in  FIG. 1 ; and  
         [0012]      FIG. 5  shows the grounding pin shown in  FIG. 4  being connected to a spacer of the HSA shown in  FIG. 1 . 
     
    
     DETAILED DESCRIPTION  
       [0013]      FIG. 1  shows disk drive head stack assembly (HSA)  100  that is fabricated in accordance with one or more embodiments of the present invention wherein conducting traces of HSA  100  are connected to flex printed circuit assembly (FPCA)  16  of the disk drive (not shown). As shown in  FIG. 1 , HSA  100  comprises heads  11 , also referred to herein as sliders  11  (as shown in  FIG. 1 , HSA  100  includes four heads or sliders). As further shown in  FIG. 1 , heads  11  are electrically connected to and carried on suspensions  12 . In accordance with one or more embodiments of the present invention, the electrical connections may be provided, for example and without limitation, by use of a conductive trace. As further shown in  FIG. 1 , suspensions  12  are electrically connected to and carried on arms  13 . In accordance with one or more embodiments of the present invention, the electrical connections may be provided: (a) by fabricating each component (suspension and arm) from a conductive material such as, for example and without limitation, steel; (b) by use of conductive elements such as, for example and without limitation, conductive traces, in each component (suspension and arm); or (c) by use of a combination of a conductive component (suspension or arm) and a conductive element in the other.  
         [0014]     As further shown in  FIG. 1 , arms  13  are separated from each other by spacers  14 , and arms  13  are electrically connected to adjacent ones of spacers  14  through contact of conductive elements therein. In accordance with one or more embodiments of the present invention, the electrical connection may be provided: (a) by fabricating each component (arm and spacer) from a conductive material such as, for example and without limitation, steel; (b) by use of conductive elements such as, for example and without limitation, conductive traces, in each component (arm and spacer); or (c) by use of a combination of a conductive component (arm or spacer) and a conductive element in the other. In accordance with one or more embodiments of the present invention, and as shown in  FIG. 3 , spacers  14  are electrically connected to each other through contact at conductive inner ring  33 .  
         [0015]     Lastly, as shown in  FIG. 1 , grounding pin  15  is electrically connected between one of spacers  14  to short tail  16   a  of FPCA  16  by, for example and without limitation, solder joint  17 . In accordance with one or more embodiments of the present invention, the electrical connection may be provided: (a) by fabricating each component (spacer and grounding pin) from a conductive material such as, for example and without limitation, steel; (b) by use of conductive elements such as, for example and without limitation, conductive traces, in each component (spacer and grounding pin); or (c) by use of a combination of a conductive component (spacer or grounding pin) and a conductive element in the other. In accordance with one or more embodiments of the present invention, short tail  16   a  serves as a ground for the disk drive (not shown). Thus, in accordance with one or more embodiments of the present invention, and as was described above, grounding paths are provided from heads  11  to short tail  16   a  which serves as a ground of the disk drive.  
         [0016]     As shown in  FIG. 1 , conductive traces emanating from heads  11  are carried on suspensions  12  (a suspension is also referred to as a flex-on-suspension (FOS) or a trace suspension assembly), and are connected to FPCA  16  at suspension-FPCA connections  18 .  FIG. 2  shows an embodiment of suspension  12  (FOS  12 ). As shown in  FIG. 2 , conductive traces  21  of FOS  12  are laid out in a side-by-side configuration. However, in order to align properly with the orientation of suspension-FPCA connections  18  of FPCA  16 , suspension  12  has a 90-degree bend  22  so that conductive traces  21  may have a proper orientation with respect to suspension-FPCA connections  18  shown in  FIG. 1 . As one can readily appreciate, given a fixed width of a conductive trace, the number of conductive traces  21  determines width  24  of suspension  12  prior to 90-degree bend  22  and height  23  of suspension  12  after 90-degree bend  22 . Thus, given 90-degree bend  22 , width  24  (and hence height  23 ) of suspension  12  determines the minimum height of FPCA  16 , and hence determines the minimum thickness of the disk drive. Advantageously in accordance with one or more embodiments of the present invention, as was described above, the width of suspension  12  is reduced. For example, in a typical prior art giant magnetoresistive (GMR) head having four read/write elements (R+, R-, W+ and W-), the number of conductive traces  21  on each suspension of suspensions  12  is five. By providing grounding paths in accordance with one or more embodiments of the present invention, the number of conductive traces  21  may become four, and the per-head minimum height may be reduced by the width of a grounding trace.  
         [0017]      FIG. 3  shows FPCA  16  wherein part of its height  31  is determined by a number of conducting traces emanating from HSA  100  shown in  FIG. 1 . In addition, the minimum of height  31  is determined by the number of conducting traces emanating from HSA  100  because the number of conducting traces determines the number of contact points  32  on FPCA  16 , and each of contact points  32  has a predetermined height. Thus, for four-headed HSA  100  shown in  FIG. 1 , based on grounding in accordance with one or more embodiments of the present invention, the number of contact points  32  shown in  FIG. 3  is sixteen whereas, in a prior-art four-head disk drive, the number of contact points  32  would have been twenty. In addition, providing grounding traces in accordance with one or more embodiments of the present invention can advantageously save cost and time in disk drive manufacturing.  
         [0018]      FIG. 4  shows grounding pin  15  of HSA  100  that is fabricated from conductive material in accordance with one or more embodiments of the present invention.  
         [0019]      FIG. 5  shows grounding pin  15  of  FIG. 4  being connected to spacer  14 . In accordance with one or more embodiments of the present invention, grounding pin  15  is connected by laser tacking using dot  51  of conductive epoxy wherein laser tacking is well known to those of ordinary skill in the art. Advantageously, the use of laser tacking in accordance with one or more embodiments of the present invention provides low electrical resistance. In addition, and in accordance with one or more further embodiments of the present invention, an end of grounding pin  15  is covered with conductive epoxy, and the epoxy is conventionally cured. Advantageously, after being fully cured, the conductive epoxy provides better conduction and good adhesion. In further addition, and in accordance with one or more further embodiments of the present invention, a substantial part of grounding pin  15  may be covered by overmold, i.e., covered by a nonconductive material, so that only its contacting ends are exposed.  
         [0020]     Advantageously, a disk drive fabricated in accordance with one or more embodiments of the present invention and utilizing a particular head design may have: (a) a reduced height for a predetermined number of heads; or (b) an increased storage capacity for a predetermined height due to an ability to utilize more heads. In addition, the cost and time for manufacturing the disk drive may be reduced.  
         [0021]     The embodiments of the present invention described above are exemplary. Many changes and modifications may be made to the disclosure recited above, while remaining within the scope of the invention. The scope of the invention should, therefore, be determined not with reference to the above description, but instead should be determined with reference. to the appended claims along with their full scope of equivalents.