Patent Abstract:
A system and method for an improved magnetic head arm assembly (HAA) is disclosed. The HAA includes three principal components, a head gimbal assembly (HGA), a flexible printed circuit (FPC) assembly, and an actuator coil assembly. The design allows for HAA rigidity, yet each of the components is designable and manufacturable independent of one another, in addition to other advantages over current methods.

Full Description:
BACKGROUND INFORMATION  
         [0001]    The present invention relates to magnetic hard disk drives. More specifically, the present invention relates to a system for an improved magnetic head arm assembly (HAA).  
           [0002]    Among the better known data storage devices are magnetic disk drives of the type in which a magnetic head slider assembly floats on an air bearing at the surface of a rotating magnetic disk. Such disk drives are often called ‘Winchester’-type drives. In these, one or more rigid magnetic disks are located within a sealed chamber together with one or more magnetic head slider assemblies. The magnetic disk drive may include one or more rigid magnetic disks, and the slider assemblies may be positioned at one or both sides of the magnetic disks.  
           [0003]    Typically, each magnetic head slider assembly in magnetic disk drives of the type referred to is coupled to the outer end of an arm or load beam. FIG. 1 provides a top view of a typical magnetic head arm (HAA) base plate. The slider assembly  102  is mounted in a manner which permits gimbaled movement at the free outer end of the arm  106  such that an air bearing between the slider assembly  102  and the surface of the magnetic disk can be established and maintained. The elongated arm is coupled to an appropriate mechanism, such as a voice-coil motor (VCM)  104 , for moving the arm  106  across the surface of the disk so that a magnetic head contained within the slider assembly  102  can address specific concentric data tracks on the disk for writing information on to or reading information from the data tracks.  
           [0004]    An example of an HAA  108  having a gimbaled mount for a magnetic head slider assembly  102  is provided by U.S. Pat. No. 3,931,641 of Watrous. The HAA  108  described in the Watrous patent includes a relatively rigid load beam (arm)  106  having a rigid bearing member at a free outer end thereof for receiving a protuberance on a spring element. The spring element is spot welded to the load beam and has an end thereof defining a flexure. The flexure includes a pair of stiff crosslegs mounted on an opposite pair of flexible outer fingers and a central finger. The central finger mounts a magnetic head slider assembly, and gimbaled movement is provided by the load protuberance on the spring element that is held in contact with the bearing member at the end of the rigid load beam. Such arrangements provide desired gimballing action by allowing pitch and roll of the slider assembly around mutually orthogonal axes while resisting radial, circumferential, and yaw motions. Other patents, such as U.S. Pat. No. 3,931,641, No. 4,620,251, No. 4,796,122, and No. 5,313,353, describe other HAA designs.  
           [0005]    [0005]FIG. 1 is representative of these designs, which are typical in the art. The slider  102  is potted to the HAA suspension and the head gimbal assembly (HGA)  110 . The HGA  110  connects to the arm  106  through a ball stacking process (See FIG. 2). A flexible printed circuit (FPC) is bonded to the arm  106  by solder. Further, a rotational bearing  114  is screwed to an arm bearing hole, and the voice coil motor (VCM)  104  is glued to the arm  106  by epoxy.  
           [0006]    [0006]FIG. 2 illustrates a typical process of ball stacking for the purpose of securing the HGA  210  to the arm  206  and the problem of stress and warpage due to said process. As seen in FIG. 2 a,  to secure the HGA  210  to the arm  206 , the HGA  210  is located such that a raised portion  212  of the ball stacking assembly (of the HGA  210 ) is inserted into an opening  214  in the arm  206 . A swag ball  216  is inserted into a ball-stacking hole  218  (See  118 , FIG. 1). Then the swag ball  216  is forced  220  downward into the ball-stacking hole  218 . Because the middle diameter of the ball-stacking hole  218  is less than that of the swag ball  216 , the walls of the raised portion  212  are expanded as the swag ball  216  enters. This expansion causes forced contact between the outer walls of the raised portion  212  and the inner walls of the opening  214 , securing the HGA  210  to the arm  206 .  
           [0007]    Although ball stacking works well to secure the HGA  210  to the arm  206 , the deformations to the HGA  210  and arm  206  adversely affect the gram load of the HGA. FIG. 2 b  illustrates the deformation and residual stress experienced by the HGA  210  and the arm  206 .  
           [0008]    Many problems exist with the described designs typical in the art. In addition to the problem of the gram load change occurring after ball stacking, a problem is suspension/arm/coil motion independence. Motion tolerance between the components is often too great because of play involved in the securing means between the components.  
           [0009]    Because of the strict dimensional parameters needed for implementation of ball-stacking, improper (too large) tolerance may lead to one or more negative consequences. For example, HGA  210  and arm  206  may be seriously deformed leaving a great amount of residual stress. As a result, the load-gram pitch/roll performance of HGA  210  after ball-stacking may become fairly poor. As another negative consequence, with even a small amount of deformation and residual stress, the assembly is more likely to come apart under usage, reducing reliability.  
           [0010]    Further, if the HGA  210  is secured to arm  206  by ball stacking, it is possible that a large amount of torque would be necessary for component separation. A large amount of torque could damage the components. By contrast, if the torque requirement is too low, the device may come apart when not desired, such as during operation.  
           [0011]    Because of the motion independence and HGA/arm deformation due to ball stacking, correct head alignment is difficult. Further, the typical method of design and manufacture for such HAA&#39;s is complicated and expensive, and the re-work process is difficult as well.  
           [0012]    It is therefore desirable to have a system and method for an improved magnetic head arm assembly (HAA) that avoids the above-mentioned problems, in addition to other advantages.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 provides a top view of a typical magnetic head arm assembly.  
         [0014]    [0014]FIG. 2 illustrates a typical process of ball stacking for the purpose of securing the HGA to the arm and the problem of stress and warpage due to said process.  
         [0015]    [0015]FIGS. 3 a - d  provide a illustrations of the components of a three-piece magnetic head and their assembly according to principles of the present invention.  
         [0016]    [0016]FIGS. 4 a - e  provides an illustration of the components of a universal (unimount) HGA assembly and their assembly according to principles of the present invention.  
         [0017]    [0017]FIG. 5 provides an illustration of the components of an FPC assembly according to principles of the present invention.  
         [0018]    [0018]FIG. 6 provides an illustration of the components of an actuator coil assembly according to principles of the present invention.  
         [0019]    [0019]FIG. 7 illustrates methods for securing the FPC assembly to the actuator coil assembly.  
         [0020]    [0020]FIG. 8 illustrates methods for securing the unimount HGA assembly to the actuator coil assembly. 
     
    
     DETAILED DESCRIPTION  
       [0021]    [0021]FIGS. 3 a - d  provide a illustrations of the components of a three-piece magnetic head and their assembly according to principles of the present invention. In an embodiment, the first of three pieces is a unimount head gimbal assembly (HGA)  302 ; the second piece is a flexible printed circuit (FPC) assembly  304 ; and the third piece is an actuator coil assembly  306 .  
         [0022]    In an embodiment, the FPC assembly  304  is secured to the actuator coil assembly  306 . For this securement, a part of the FPC (the FPC mating portion)  314  is attached to the actuator body  310  at an actuator mating portion (second actuator mating portion)  318  by rivet deformation. Adhesive bonding and solder bonding are each alternative embodiments. Also for this securement, in an embodiment, a coil  312  is attached to an FPC trace by solder bonding. Stitch bonding is also an alternative embodiment. (See FIG. 7). In an embodiment, the interface surfaces of the mating portions  314 , 318  are flat and smooth to aid bonding with materials such as adhesive, solder, etc. Further, having flat, smooth mating surfaces of non-complex contours simplifies the process of designing and manufacturing each of the components of the three-piece magnetic head assembly independently of each other. As long as the mating portions match up, the components can be coupled together.  
         [0023]    In an embodiment, the unimount HGA assembly  302  is secured at an HGA mating portion  320  to a first mating portion  322  of the actuator coil assembly  306 . In one embodiment, this is done by adhesive bonding. Rivet deformation and screw mounting bonding are each alternative embodiments. (See FIG. 8). As above, in an embodiment, the interface surfaces of the mating portions  320 , 322  are flat and smooth to aid bonding with materials such as adhesive, solder, etc. Further, having flat, smooth mating surfaces of non-complex contours simplifies the process of designing and manufacturing each of the components of the three-piece magnetic head assembly independently of each other. As stated, as long as the mating portions match up, the components can be coupled. Accordingly, mating portions  314 ,  318 ,  320 , and  322  can be referred to as “universal” in that they are designed to interface with a variety of differently designed and manufactured components.  
         [0024]    In an embodiment, the unimount HGA assembly  302  is secured to the FPC assembly  304 . For this securement, in an embodiment, a flex-suspension assembly (FSA)  316  is attached to an FPC bonding pad  318  by tape automated bonding (TAB). Anisotropic conductive film (ACF) bonding is envisioned for an alternative embodiment.  
         [0025]    [0025]FIGS. 4 a - e  provides an illustration of the components of a universal (unimount) HGA assembly and their assembly according to principles of the present invention. In an embodiment, the first component is a unimount baseplate  402 . Second, in an embodiment, is a multi-piece loadbeam  404 . Third, in an embodiment, is an FSA trace  416 . And fourth, in an embodiment, is a slider  406 .  
         [0026]    In an embodiment, the multi-piece loadbeam  404  is secured to the unimount baseplate  402  by laser welding. Also, in an embodiment, the FSA trace  416  is secured to the HGA assembly (unimount baseplate  402  and the multi-piece loadbeam  404 ) by ultra-violet (UV) epoxy bonding. Utilizing these methods of securement prevents the residual stress and deformation problems of ball stacking (swaging). The slider  406  is attached to the assembly, thereafter.  
         [0027]    [0027]FIG. 5 provides an illustration of the components of an FPC assembly according to principles of the present invention. In an embodiment, a metal bracket  502  is attached to one end of the FPC  508  by lamination. In an embodiment, a plastic bracket  504  is attached to the opposite end of the FPC  508  by pin  510  insertion.  
         [0028]    [0028]FIG. 6 provides an illustration of the components of an actuator coil assembly according to principles of the present invention. In an embodiment, the coil  612  is attached to the actuator body  610  by epoxy  614 .  
         [0029]    [0029]FIG. 7 illustrates methods for securing the FPC assembly  304  to the actuator coil assembly  706 . As stated, in an embodiment, the FPC  708  is attached to the actuator body  710  by rivet  730  deformation. As stated, in an embodiment, the coil  712  is attached to the FPC  708  by solder  732  bonding.  
         [0030]    [0030]FIG. 8 illustrates methods for securing the unimount HGA assembly  802  to the actuator coil assembly  806 . In one embodiment, this is done by ultra-violet (UV) epoxy  830 . In another embodiment, this is done by rivet  832  deformation. In another embodiment, this is done by screw  834  mounting.  
         [0031]    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.

Technology Classification (CPC): 6