Abstract:
A system and method for improving piezoelectric micro-actuator operation by preventing undesired micro-actuator motion hindrance and by preventing micro-actuator misalignment during manufacture.

Description:
BACKGROUND INFORMATION  
         [0001]    The present invention relates to magnetic hard disk drives. More specifically, the present invention relates to a system and method for improving piezoelectric micro-actuator operation by preventing undesired micro-actuator motion hindrance and by preventing micro-actuator misalignment.  
           [0002]    In the art today, different methods are utilized to improve recording density of hard disk drives. FIG. 1 provides illustrations of a typical drive arm configured to read from and write to a magnetic hard disk. Typically, voice-coil motors (VCM)  102  are used for controlling a hard drive&#39;s arm  104  motion across a magnetic hard disk  106 . Because of the inherent tolerance (dynamic play) that exists in the placement of a recording head  108  by a VCM  102  alone, micro-actuators  110  are now being utilized to ‘fine-tune’ head  108  placement, as is described in U.S. Pat. No. 6,198,606. A VCM  102  is utilized for course adjustment and the micro-actuator  110  then corrects the placement on a much smaller scale to compensate for the VCM&#39;s  102  (with the arm  104 ) tolerance. This enables a smaller recordable track width, increasing the ‘tracks per inch’ (TPI) value of the hard drive (increased drive density).  
           [0003]    [0003]FIG. 2 provides illustrations of a drive arm as used in the art. To provide electrical connections to the head  202 , a flex-cable suspension assembly (FSA)  204 , having electrical traces  206 , is provided and attached to the arm  212 . The FSA  204  provides electrical connectivity between bond pads  208  near the VCM (not shown) and bonding pads  210  at the head  202 .  
           [0004]    Attaching the head  202  directly to the FSA  204  as shown presents problems in head alignment as well as problems with micro-actuator operation, as explained below. Further, the present means of attaching the FSA  204  to the arm  212  causes problems relating to assuring suspension stiffness and correct head attitude as well as other problems. It is therefore desirable to have a system and method to prevent the above-mentioned problems in addition to having other benefits. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]    [0005]FIG. 1 provides illustrations of a typical drive arm configured to read from and write to a magnetic hard disk.  
         [0006]    [0006]FIG. 2 provides illustrations of a drive arm as used in the art.  
         [0007]    [0007]FIG. 3 provides illustrations of a drive arm with FSA under principles of the present invention.  
         [0008]    [0008]FIG. 4 further illustrates the assembly of the FSA, shim, and drive arm under principles of the present invention.  
         [0009]    [0009]FIG. 5 provides a close-up image of the arm with the FSA and shim and without the head and piezoelectric transducers attached under principles of the present invention.  
         [0010]    [0010]FIG. 6 provides a close-up image of the arm with the FSA and shim and with the head and piezoelectric transducers attached under principles of the present invention.  
     
    
     DETAILED DESCRIPTION  
       [0011]    [0011]FIG. 3 provides illustrations of a drive arm with FSA under principles of the present invention. In one embodiment, the FSA has an (‘O’-shaped) opening that allows the FSA to fit over the micro-actuator  304  without interference. In an embodiment, the micro-actuator  304  is composed of an actuator frame  306  that cradles the head  308  and piezoelectric members  310  on either side to perform fine adjustments of the head  308  location. To provide shock resistance, a suspension tongue  312 , which is attached to the actuator frame  306  by an adhesive such as epoxy or resin, is utilized. In another embodiment, the suspension tongue  312  is attached to the actuator frame  306  by a welded bond, such as by laser welding. The suspension tongue  312  is restrained at one end by a ‘hammer’ or ‘T’-shaped element (second hook element)  314  and supported at the other end by a dimple  316 .  
         [0012]    To provide correct suspension function and for proper head alignment in an embodiment, there needs to be a 25 to 50 micro-meter (um) gap  317  between the actuator frame  306  and the suspension tongue  312  over the dimple  316 . Utilizing an FSA  204  similar in design to the one illustrated in FIG. 2 for an actuator similar to the one illustrated in FIG. 3, proper head alignment is difficult. Because the head  202  is attached to the FSA  204  and the FSA  204  is attached to the arm  212 , force must be applied to the suspension components through the head  308  and FSA  302  as the head  308  is coupled to the FSA  302  and the FSA  302  is coupled to the actuator frame  306 . During the process of bonding with adhesives such as epoxy or resin, force must be applied to enable a proper bond. Because the suspension enables the actuator frame  306  to move, force applied to the head  308  is transferred to the suspension components, potentially over-bending and damaging the suspension tongue  312 , throwing the head  308  out of alignment (angle of attitude). Further, suspension damage, etc. may occur upon removal of the head  308  or FSA  302  (for replacement of a defective component, etc.) by over-exerting the suspension tongue. Also, with an FSA  204  such as is shown in FIG. 2, the stiffness of the FSA  204  greatly affects the process of ramp loading/unloading. FSA  204  stiffness, which is too great, would require increased loading force for the system.  
         [0013]    In one embodiment of the present invention, a shim  318  of a material such as stainless steel is utilized with an FSA  302  having an opening for a micro-actuator  304 . As shown in FIG. 3, the shim  318  is coupled to the FSA  302  with a bonding agent such as epoxy or resin. The FSA  302  is coupled to a suspension structure  322  at the end of a drive arm (not shown) with a bonding agent such as epoxy or resin on portions of the FSA  302  closer to the VCM (not shown) than the micro-actuator  304 . Because the shim  318 , which is rigid, is coupled to the FSA  302  before the FSA  302  is attached to the suspension structure  322 , along with the fact that the FSA  302  is bonded directly to the actuator frame  306  only at the front (away from the VCM), no undue pressure needs to be applied directly to the suspension tongue  312 , preventing potential damage/misalignment.  
         [0014]    In one embodiment, the micro-actuator frame is coupled to the suspension tongue  312  before the FSA  302  (with shim  318 ) is coupled to the suspension structure  322 . In an alternative embodiment, the FSA  302  (with shim  318 ) is coupled to the suspension structure  322  before the micro-actuator frame is coupled to the suspension tongue  312 .  
         [0015]    In one embodiment, the head  308  and piezoelectric transducers  305  are coupled to the micro-actuator frame  306  before the micro-actuator frame  306  is coupled to the suspension tongue  312 . In an alternative embodiment, the micro-actuator frame  306  is coupled to the suspension tongue  312  before the head  308  and piezoelectric transducers  305  are coupled to the micro-actuator frame  306 .  
         [0016]    As explained above, the shim  318  is bonded to the FSA  302  and then the FSA is coupled to the suspension structure  322 . In an embodiment, this is done by fitting the shim  318  (attached to the FSA  302 ) under motion-limiting, angled tabs (first hook), bonding the FSA to the suspension structure  322  at the back (toward the VCM), and bonding the shim  318  to the front edge  307  of the actuator frame  306 . This makes it possible to avoid applying direct pressure to the suspension tongue  312 .  
         [0017]    [0017]FIG. 4 further illustrates the assembly of the FSA, shim, and suspension structure under principles of the present invention. In one embodiment, the shim  402  is bonded to the FSA  404  (to the underside of the FSA  404 , as depicted). The FSA  404  and shim  402  are positioned to hook the (motion-limiting) angled tabs  406  over the ends of the shim  402 . In an embodiment, the shim  402  which is bonded to the FSA  404  is bonded to the front portion  410  of the actuator frame  408  (to the top side of the actuator frame  408 , as depicted), and the FSA  404  is bonded to the suspension structure (end piece of the drive arm)  412 . Alignment holes  414  are used for correct positioning of the shim  402  and FSA  404  over the suspension structure  412 .  
         [0018]    [0018]FIG. 5 provides a close-up image of the suspension structure  502  with FSA  504  and shim  506  and without the head and piezoelectric transducers attached under principles of the present invention, and FIG. 6 provides a close-up image of the suspension structure  602  with FSA  604  and shim  606  and with the head  608  and piezoelectric transducers  610  attached under principles of the present invention.  
         [0019]    Although several embodiments are specifically illustrated and described herein, it will be appreciated that modifications and variations of the present invention are covered by the above teachings and within the purview of the appended claims without departing from the spirit and intended scope of the invention.