Abstract:
Disclosed is a dual stage actuation suspension, including: a stainless steel component having a plated contact, the plated contact comprising a first material plated directly on a second material, the first material conductive and non-corrosive, the first material comprising a metal or metal alloy, the second material comprising stainless steel of the stainless steel component, the stainless steel component including a stainless steel layer of a flexure; a motor having an electrical contact; and a conductive adhesive joint between the electrical contact of the motor and the plated contact of the stainless steel component, the conductive adhesive joint extending from the motor, over an edge of the motor and into contact with the plated contact on the stainless steel layer of the flexure.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation of U.S. application Ser. No. 14/563,936 filed on Dec. 8, 2014, entitled “SUSPENSION ASSEMBLY HAVING A MICROACTUATOR GROUNDED TO A FLEXURE” to Wing Chun Shum et al. (WD Docket No. T4194.C1.C1), which is a continuation of U.S. application Ser. No. 14/146,710 filed on Jan. 2, 2014, entitled “SUSPENSION ASSEMBLY HAVING A MICROACTUATOR GROUNDED TO A FLEXURE” to Wing Chun Shum et al. (WD Docket No. T4194.C1), which is a continuation of U.S. application Ser. No. 12/827,813 filed on Jun. 30, 2010, entitled “SUSPENSION ASSEMBLY HAVING A MICROACTUATOR GROUNDED TO A FLEXURE” to Wing Chun Shum et al. (WD Docket No. T4194), both of which are hereby incorporated by reference in their entirety. 
     
    
     BACKGROUND 
       [0002]    Information storage devices are used to retrieve and/or store data in computers and other consumer electronics devices. A magnetic hard disk drive is an example of an information storage device that includes one or more heads that can both read and write, but other information storage devices also include heads—sometimes including heads that cannot write. For convenience, all heads that can read are referred to as “read heads” herein, regardless of other devices and functions the read head may also perform (e.g. writing, flying height control, touch down detection, lapping control, etc). 
         [0003]    In a modern magnetic hard disk drive device, each read head is a sub-component of a head gimbal assembly (HGA). The read head typically includes a slider and a read/write transducer. The read/write transducer typically comprises a magneto-resistive read element (e.g. so-called giant magneto-resistive read element, or a tunneling magneto-resistive read element) and an inductive write structure comprising a flat coil deposited by photolithography and a yoke structure having pole tips that face a disk media. 
         [0004]    The HGA typically also includes a suspension assembly that includes a mounting plate, a load beam, and a laminated flexure to carry the electrical signals to and from the read head. The read head is typically bonded to a tongue feature of the laminated flexure. The HGA, in turn, is a sub-component of a head stack assembly (HSA) that typically includes a plurality of HGAs, a rotary actuator, and a flex cable. The mounting plate of each suspension assembly is attached to an arm of the rotary actuator (e.g. by swaging), and each of the laminated flexures includes a flexure tail that is electrically connected to the HSA&#39;s flex cable (e.g. by solder bonding). 
         [0005]    Modern laminated flexures typically include electrically conductive copper traces that are isolated from a stainless steel support layer by a polyimide dielectric layer. So that the signals from/to the head can reach the flex cable on the actuator body, each HGA flexure includes a flexure tail that extends away from the head along the actuator arm and ultimately attaches to the flex cable adjacent the actuator body. That is, the flexure includes electrically conductive traces that are electrically connected to a plurality of electrically conductive bonding pads on the head, and extend from adjacent the head to terminate at electrical connection points at the flexure tail. 
         [0006]    The position of the HSA relative to the spinning disks in a disk drive, and therefore the position of the read heads relative to data tracks on the disks, is actively controlled by the rotary actuator which is typically driven by a voice coil motor (VCM). Specifically, electrical current passed through a coil of the VCM applies a torque to the rotary actuator, so that the read head can seek and follow desired data tracks on the spinning disk. 
         [0007]    However, the industry trend towards increasing areal data density has necessitated substantial reduction in the spacing between data tracks on the disk. Also, disk drive performance requirements, especially requirements pertaining to the time required to access desired data, have not allowed the rotational speed of the disk to be reduced. In fact, for many disk drive applications, the rotational speed has been significantly increased. A consequence of these trends is that increased bandwidth is required for servo control of the read head position relative to data tracks on the spinning disk. 
         [0008]    One solution that has been proposed in the art to increase disk drive servo bandwidth is dual-stage actuation. Under the dual-stage actuation concept, the rotary actuator that is driven by the VCM is employed as a coarse actuator (for large adjustments in the HSA position relative to the disk), while a so-called “microactuator” having higher bandwidth but lesser stroke is used as a fine actuator (for smaller adjustments in the read head position). Various microactuator designs have been proposed in the art for the purpose of dual-stage actuation in disk drive applications. Some of these designs utilize one or more piezoelectric microactuators that are affixed to a stainless steel component of the suspension assembly (e.g. the mounting plate or an extension thereof, and/or the load beam or an extension thereof, and/or an intermediate stainless steel part connecting the mounting plate to the load beam). 
         [0009]    However, if the microactuator is electrically connected to a stainless steel surface of the suspension assembly (e.g. for grounding), an electrochemical reaction may cause an oxidation layer to form on the stainless steel at the connection location. The oxidation layer may be insulative and interfere with desired electrical conduction, and may be exacerbated by hot and humid conditions. Over time, the desired response of the microactuator to applied signals may become diminished, leading to reduced or impaired performance of the information storage device and/or data loss. 
         [0010]    Therefore, there is a need in the information storage device arts for a suspension assembly design that can improve integration with a microactuator by improving the grounding of the microactuator. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is top view of a disk drive that is capable of including an embodiment of the invention. 
           [0012]      FIG. 2  is a bottom perspective view of the head gimbal assembly (HGA). 
           [0013]      FIG. 3  is a top view of a portion of the HGA, according to one embodiment of the invention. 
           [0014]      FIG. 4  is a bottom view of a portion of the HGA, according to one embodiment of the invention, 
           [0015]      FIG. 5  is a cross-sectional view illustrating the epoxy extending through the mounting plate and through the holes of the flexure to ground to the flexure, according to one embodiment of the invention. 
           [0016]      FIG. 6  is a cross-sectional view illustrating the epoxy extending through the flexure to ground to the flexure, according to one embodiment of the invention. 
           [0017]      FIG. 7  is a cross-sectional view illustrating the epoxy extending through the mounting plate and to the flexure and particularly illustrates an air gap, according to one embodiment of the invention. 
           [0018]      FIG. 8  is a schematic diagram of the flexure metal layer including an air gap, according to one embodiment of the invention. 
           [0019]      FIG. 9  is a schematic diagram of the bottom-side of the load beam including an air gap, according to one embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]      FIG. 1  is top view of a disk drive  100  that is capable of including an embodiment of the present invention. The disk drive  100  includes a disk drive base  102 . The disk drive  100  further includes a spindle  106 , rotably mounted on the disk drive base  102 , for rotating a disk  104  that is mounted on the spindle  106 . The rotation of the disks  104  establishes air flow through optional recirculation filter  108 . In certain embodiments, disk drive  100  may have only a single disk  104 , or alternatively, two or more disks. 
         [0021]    The disk drive  100  further includes a rotary coarse actuator  110  that is rotably mounted on disk drive base  102 . The rotary coarse actuator  110  includes an actuator arm  114  that supports a head gimbal assembly (HGA)  118 . Voice coil motor  112  rotates the actuator  110  through a limited angular range so that the HGA  118  may be desirably positioned relative to one or more tracks of information on the disk  104 . Preferably the disk drive  100  will include one HGA  118  per disk surface, but depopulated disk drives are also contemplated in which fewer HGAs are used. Under non-operating conditions the HGAs may be parked on ramp  120 , for example to avoid contact with the disk  104  when it is not spinning. Electrical signals to/from the HGA  118  are carried to other drive electronics, in part via a flex cable (not shown) and a flex cable bracket  116 . 
         [0022]      FIG. 2  is a bottom perspective view of an HGA  200 . Referring additionally to  FIG. 2 , the HGA  200  includes a load beam  202 , and a read head  210  for reading and writing data from and to a magnetic disk (e.g. disk  104 ). The read head  210  includes a slider substrate having an air bearing surface (the label  210  points to this surface) and an opposing top surface (not visible in the view of  FIG. 2 ). The slider substrate preferably comprises AlTiC, although another ceramic or silicon might also be used. The slider substrate of the read head  210  also includes a trailing face  212  that includes a read/write transducer (too small to be practically shown in the view of  FIG. 2 , but disposed on the trailing face  212 ). In certain embodiments, the read/write transducer is preferably an inductive magnetic write transducer merged with a magneto-resistive read transducer. The purpose of the load beam  202  is to provide limited vertical compliance for the read head  210  to follow vertical undulations of the surface of a disk (e.g. disk  104  of  FIG. 1 ) as it rotates, and to preload the air bearing surface of the read head  210  against the disk surface by a preload force that is commonly referred to as the “gram load.” 
         [0023]    In the embodiment of  FIG. 2 , the HGA  200  also includes a laminated flexure  204  attached to the load beam  202 . The laminated flexure  204  includes a tongue  206  that has a read head bonding surface. The head  210  is attached to the read head bonding surface of the tongue  206  of the laminated flexure  204 . Only a portion of the tongue  206  is visible in the view of  FIG. 2  because the read head  210  partially obscures it. A first purpose of the laminated flexure  204  is to provide compliance for the head  210  to follow pitch and roll angular undulations of the surface of the disk (e.g. disk  104 ) as it rotates, while restricting relative motion between the read head  210  and the load beam  202  in the lateral direction and about a yaw axis. A second purpose of the laminated flexure  204  is to provide a plurality of electrical paths to facilitate signal transmission to/from the read head  210 . For that second purpose, the laminated flexure  204  includes a plurality of electrically conductive traces  218  that are defined in an electrically conductive (e.g. copper) sub-layer of the laminated flexure  204 . Electrically conductive traces  218  are isolated from a support layer (e.g. stainless steel) by a dielectric layer (e.g. polyimide). 
         [0024]    In the embodiment of  FIG. 2 , the load beam  202  includes hinge plates  222  and  224 , and is attached to a mounting plate  220  via the hinge plates  222  and  224  and a microactuator mounting structure  300 . These components may be made of stainless steel, and their attachments to each other may be made by a plurality of spot welds, for example. Alternatively, the load beam  202  may have integral hinge plate regions rather than being assembled with separate hinge plate components, so that the load beam  202  and its hinge plates would be a single component having material continuity. In another alternative, the microactuator mounting structure  300  can also be an integral part of the mounting plate  220 . 
         [0025]    The load beam  202  with its hinge plates  222 ,  224  (if any), the microactuator mounting structure  300 , and the mounting plate  220 , may together be referred to as a “suspension assembly.” Accordingly, the mounting plate  220  may also be referred to as a suspension assembly mounting plate  220 . In certain preferred embodiments, the suspension assembly mounting plate  220  includes a swage boss  226  to facilitate attachment of the suspension assembly to an actuator arm (e.g. actuator arm  114 ). In that case, the suspension assembly mounting plate  220  may also be referred to as a “swage mounting plate.” Note that, after the laminated flexure  204  is attached to the load beam  202 , the laminated flexure  204  may be considered to also pertain to the “suspension assembly.” 
         [0026]      FIG. 3  is a top view of a portion of the HGA, according to one embodiment of the invention. The suspension assembly  300  of the HGA includes a mounting plate  304 . The mounting plate  304  may include a swage tower  305  to facilitate attachment of the mounting plate suspension assembly to an actuator arm (e.g. actuator arm  114 ). The mounting plate  304  may have a through-hole  306  extending from a top-side  307  of the mounting plate  304  to a bottom-side of the mounting plate. As will be described, in one embodiment, a microactuator mounting structure ( 340 ,  342 ) is formed in the mounting plate  304  and a microactuator ( 312 ,  313 ) may be mounted in the microactuator mounting structure  304 . An epoxy  329  may be mounted to a microactuator and may extend through the through-hole  306  to bond to a flexure, in which, the epoxy  329  extends through an opening of the flexure to a ground trace of the flexure such that the microactuator is grounded to the flexure. 
         [0027]    In particular, mounting plate  304  may include a pair of approximately square-shaped microactuator mounting structures  340  and  342  that are formed in the mounting plate  304 . Microactuators  312  and  313  may each be mounted in a microactuator mounting structure  340  and  342 , respectively. As is known in the art, microactuators are typically used to position a read head. Further, epoxy lines  330  and  332  of epoxy  329  may each be bonded to a microactuator and may extend through the through-hole  306  to bond to a flexure, in which, the epoxy  329  extends through an opening of the flexure to a gold-plated ground trace of the flexure such that the microactuator is grounded to the flexure. It should be appreciated to those of skill in the art that a single microactuator may be mounted to the mounting plate, a pair of microactuators may be mounted to the mounting plate, or any suitable number of microactuators may be mounted to the mounting plate. 
         [0028]    With reference also to  FIG. 4 , which is a bottom view of a portion of the HGA, according to one embodiment of the invention, the through-hole  306  extends from the top-side  307  of the mounting plate  304  to the bottom-side  309  of the mounting plate  304 . Further, as can be seen on the bottom-side  309  of the mounting plate  304 , flexure  204  is attached to the bottom-side  309  of the mounting plate  304  and flexure  204  is coupled to the microactuators  312  and  313 . As will be described in more detail hereinafter, the flexure  204  may include a metal layer, an insulator layer, a trace layer which includes a ground trace, and an opening, wherein the opening extends through the metal layer and the insulator layer to a gold-plated ground trace of the flexure. 
         [0029]    Thus, in one embodiment, a pair of epoxy lines  330  and  332  of epoxy  329  may be bonded to the microactuators  312  and  313  and may extend through the through-hole  306  to bond to the flexure  204 . In particular, as will be described in more detail hereinafter, the epoxy  329  may extend through an opening of the flexure to the ground trace of the flexure such that the microactuator  312  and  313  are grounded to the flexure  204 . 
         [0030]    In one embodiment, the microactuators  312  and  313  are piezoelectric (PZT) microactuators. The piezoelectric microactuators  312  and  313  may be gold (Au) plated. Further, in one embodiment, the epoxy  329  may include silver (Ag) and is conductive. However, it should be appreciated that any sort of suitable epoxy or solder that is conductive may be utilized. 
         [0031]    With reference now to  FIG. 5 ,  FIG. 5  illustrates a cross-sectional view  500  of the epoxy extending through the mounting plate through the holes of the flexure to ground to the flexure, according to one embodiment of the invention. In particular, looking at  FIG. 5 , epoxy  502  extends through the through-hole  503  of mounting plate  504  and through load beam  506  to extend through an opening  507  of the flexure, and particularly, extends through the steel layer  508  and the insulator layer  512  of the flexure to bond to the gold-plated  520  copper layer  514  of the flexure, which is the ground trace. In this way, microactuators  312  and  313  through epoxy  502  are grounded to the gold-plated ground trace of the copper layer  514  of the flexure. 
         [0032]    With reference also to  FIG. 6 ,  FIG. 6  illustrates a cross-sectional view  600  of the epoxy  502  extending through the flexure  204  to ground to the flexure  204 , according to one embodiment of the invention. As previously described, in one embodiment, the metal layer  508  of the flexure  204  may be stainless steel and the insulator layer  512  may be a polyimide. Further, as shown in  FIG. 6 , flexure  204  may include a gold-plated  520  copper layer  514  that includes a ground trace. As previously described, copper layer  514  of flexure  204  may include a plurality of conductive traces and a ground trace. Further, the ground trace of the copper layer  514  may be grounded by a via  519  to the steel layer  508 . Also, has been previously described, with reference to the functions of the flexure  204 , the read head is typically electrically connected to one or more of the pluralities of conductive traces of the copper layer  514 . 
         [0033]    Thus, in one embodiment, an Ag epoxy  502  may be used to ground the microactuators by extending from the microactuators through a through-hole of the mounting plate  504  and through an opening  507  of the flexure  204  to extend through the steel layer  508  and the insulator layer  512  of the flexure  204  to ground to the ground trace of the exposed gold-plated  520  copper layer  514  of the flexure. Accordingly, there is a direct grounding of the microactuators to the ground trace of the flexure by simply extending an epoxy through a through-hole of the mounting plate. This is advantageous in that it solves problems associated with microactuators that are currently being bonded to the steel of the mounting plate and does so utilizing the current flexure cable with virtually no additional cost or design/process changes. 
         [0034]    Additional embodiments are hereinafter described to let air out so that epoxy can flow down more easily to more easily contact the gold-plated copper layer.  FIG. 7  is a cross-sectional view  700  illustrating the epoxy  502  extending through the mounting plate  504  and into the flexure and particularly illustrates an air gap, according to another embodiment of the invention. In this embodiment, the epoxy  502  extends through the mounting plate  504 , the load beam  506 , the steel layer  508 , and the insulator layer  512  to the gold-plated  520  copper layer  514 . However, this embodiment includes an air hole or gap  710  formed in the gold-plated  520  copper layer  514  to allow for air flow. In one embodiment, a cover  702  that may be formed from a thin insulator material is present. By having the air hole, air is let out so that the epoxy  502  can flow down more easily to more easily contact the gold-plated  520  copper layer  514 . Without the air hole, air bubbles may form preventing the epoxy from more completely covering and contacting the gold-plated copper layer. 
         [0035]    Turning to  FIG. 8 , a schematic diagram of the flexure metal layer  800  is shown. In particular,  FIG. 8  illustrates that gaps  802  may be formed in the metal layer  508  of the flexure  204  adjacent the metal load beam layer  506  to allow for air flow. With reference to  FIG. 9 , a schematic diagram of the bottom-side of the load beam  900  is illustrated. As can be seen in  FIG. 9 , the metal load beam layer  506  may include a gap  902  to let air flow out. These additional embodiments aid in letting air flow out so that the epoxy can flow down more easily to more easily contact the gold-plated copper layer, as previously described. 
         [0036]    In the foregoing specification, the invention is described with reference to specific exemplary embodiments, but those skilled in the art will recognize that the invention is not limited to those. It is contemplated that various features and aspects of the invention may be used individually or jointly and possibly in a different environment or application. The specification and drawings are, accordingly, to be regarded as illustrative and exemplary rather than restrictive. “Comprising,” “including,” and “having,” are intended to be open-ended terms.