Abstract:
The present invention provides apparatus for measurement of suspension assembly component position and static attitude and for adjustment thereof. An apparatus in accord with the present invention includes modules for the measurment and adjustment of the gimbal portion of suspensions, FSAs, and HGAs.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    Most personal computers today utilize direct access storage devices (DASD) or rigid disk drives for data storage and retrieval. Present disk drives include a disk rotated at high speeds and a read/write head that, in industry parlance, “flies” a microscopic distance above the disk surface. The disk includes a magnetic coating that is selectively magnetizable. As the head flies over the disk, it “writes” information, that is, data, to the hard disk drive by selectively magnetizing small areas of the disk; in turn, the head “reads” the data written to the disk by sensing the previously written selective magnetizations. The read/write head is affixed to the drive by a suspension assembly and electrically connected to the drive electronics by an electrical interconnect. This structure (suspension, electrical interconnect, and read/write head) is commonly referred to in the industry as a Head Gimbal Assembly, or HGA.  
           [0002]    More specifically, currently manufactured and sold read/write heads include an inductive write head and a magnetoresistive (MR) read head or element or a “giant” magnetoresistive (GMR) element to read data that is stored on the magnetic media of the disk. The write head writes data to the disk by converting an electric signal into a magnetic field and then applying the magnetic field to the disk to magnetize it. The MR read head reads the data on the disk as it flies above it by sensing the changes in the magnetization of the disk as changes in the voltage or current of a current passing through the MR head. This fluctuating voltage in turn is converted into data. The read/write head, along with a slider, is disposed at the distal end of an electrical interconnect/suspension assembly.  
           [0003]    An exploded view of a typical electrical interconnect/suspension assembly is shown in FIG. 1, which illustrates several components including a suspension A and an interconnect B. It will be understood that the actual physical structures of these components may vary in configuration depending upon the particular disk drive manufacturer and that the assembly shown in FIG. 1 is meant to be illustrative of the prior art only. Typically, the suspension A will include a base plate C, a radius (spring region) D, a load beam E, and a flexure F. At least one tooling discontinuity  57  G may be included. An interconnect B may include a base H, which may be a synthetic material such as a polyimide, that supports typically a plurality of electrical traces or leads I of the interconnect. The electrical interconnect B may also include a polymeric cover layer that encapsulates selected areas of the electrical traces or leads I.  
           [0004]    Stated otherwise, suspension A is essentially a stainless steel support structure that is secured to an armature in the disk drive. The read/write head is attached to the tip of the suspension A with adhesive or some other means. The aforementioned electrical interconnect is terminated to bond pads on the read/write head and forms an electrical path between the drive electronics and the read and write elements in the read/write head. The electrical interconnect is typically comprised of individual electrical conductors supported by an insulating layer of polyimide and typically covered by a cover layer.  
           [0005]    As mentioned previously, the slider “flies” only a microscopic distance, or fly height, above the spinning media disk. Control of fly height is critical for the operation of a disk drive. If the fly height is too large, the read/write head will not be able to read or write data, and if it is to small, the slider can hit the media surface, or crash, resulting the permanent loss of stored data. As such, the fly height of the slider is determined in much part by the characteristics of the head suspension assembly to which it is mounted. The head suspension imparts a vertical load, commonly referred to as “gram load”, on the slider, normal to the surface of the disk, in order to oppose the “lift” forces created by the air passing between the slider and the spinning disk. As a result, head suspension assemblies are manufactured with a very precise gram load, typically with a tolerance of ±0.2 grams. Another head suspension assembly characteristic that has a significant effect upon the fly height of a slider, is referred to as “static attitude”. Static attitude is the angular attitude of the gimbal to which the slider is mounted. Typically, head suspension assemblies are manufactured with tolerances for static attitude approaching ±30 arc-minutes.  
           [0006]    Successful reading or writing of data between the head and the spinning media also requires that the head be precisely positioned directly under the suspension load point location, such that the act of passing the commonly known preload from suspension to head does not cause the head slider body to pitch or roll.  
           [0007]    Due to manufacturing difficulties within suspension, flex circuit attach (FSA) and head gimbal assembly (HGA) processes, there is a need to inexpensively perform 100% measure and adjustment for static attitude, as well as 100% measurement for component assembled position.  
           [0008]    Common industry equipment for measuring static attitude requires that individual suspensions, FSAs, or HGAs be loaded into a tooling fixture with said tooling fixture precisely aligning the component to an autocollimator beam while bending the component to its designed working z position. This measurement takes a considerable amount of time and requires significant operator handling and requires that the loading mechanism consistently deform the component without damaging said component. Further complications include small X-Y positional misalignments between the autocollimator beam and the component to be measured, which said misalignments can lead to erroneous measurements. A still further complication with common autocollimator based static attitude measurements lies with the fact that the autocollimator beam is masked very close to the measured component. The mask serves to only allow a certain desired location to be measured on the component. This masking technique can interfere with other mechanisms desired to operate in and around the component, blocks a portion of the light trying to return to the autocollimator, and obstructs the visual view of the component.  
           [0009]    While it is also desired to make X-Y and theta measurements of components assembled which make up suspensions, FSAs, and HGAs; said position measurements take extra time and capital thus adding significant cost to a given process.  
           [0010]    While numerous mechanisms exist to mechanically and thermally adjust suspensions, FSAs, and HGAs for static attitude, several limitations exist. A first limitation exists with those methods which act on the load beam, since adjustment to the load beam will cause an undesired shift in load beam dominant resonant frequencies and gains. To avoid the previously mentioned limitation, many have sought to perform adjustments only on the gimbal portion of suspensions, FSAs, and HGAs, but these methods are limited due to misalignment of the adjust mechanisms relative to the components being adjusted. It is very difficult to have precise control over the said static attitude angles of said suspensions, FSAs, and HGAs, when the component geometries are very small, very thin, and fragile.  
         SUMMARY OF THE INVENTION  
         [0011]    It is an object of the present invention to provide a device which can simultaneously measure component position and static attitude and can precisely adjust said static attitude in the gimbal portion of suspensions, FSAs, and HGAs.  
           [0012]    A further objective of the present invention is to hold the components fixed via an optimum vacuum, or other non-deforming means, such that complicated fixturing and deformation prior to measurement is not needed.  
           [0013]    Another object of the present invention is to assure precise autocollimator spot location on the component by directing the spot with vision, including co-located vision feedback.  
           [0014]    A still further objective of the present invention is to use the same vision system to simultaneously extract position information for quality control of component assembly.  
           [0015]    Another object of the present invention is to use the said co-located vision feedback for precisely positioning static attitude adjust mechanisms relative to the gimbal component to significantly improve control over said adjust processes.  
           [0016]    A further objective is to control vision lighting to allow for proper vision system function, while not interfering with the autocollimator return light and not adversely affecting the said static attitude measurements.  
           [0017]    A still further objective is to locate a mask between the autocollimator light source and the autocollimator optics to adequately size the spot on the desired component location, without causing interference with other mechanisms or clipping return light. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    [0018]FIG. 1 illustrates a typical electrical interconnect/suspension assembly.  
         [0019]    [0019]FIG. 2 illustrates a hard disk drive in a top plan, schematic view.  
         [0020]    [0020]FIG. 3 a  illustrates an actuator arm in a side elevation view.  
         [0021]    [0021]FIG. 3 b  illustrates in greater detail in a top plan view the hatched area called out in FIG. 3 a.    
         [0022]    [0022]FIG. 4 illustrates an interconnect assembly in a top plan view.  
         [0023]    [0023]FIG. 5 illustrates the interconnect assembly of FIG. 4 in an exploded perspective view.  
         [0024]    [0024]FIG. 6 illustrates an apparatus in accord with the present invention in a front elevation view.  
         [0025]    [0025]FIGS. 7A and 7B illustrates measurement and adjustment modules in accord with the present invention.  
         [0026]    [0026]FIG. 8 illustrates a static measurement probe in accord with the present invention.  
         [0027]    FIGS.  9 A- 9 C illustrate in further detail a static measurement probe in accord with the present invention.  
         [0028]    [0028]FIG. 10 illustrates optics utilized to collocate the vision field of view and measurement beam from the static attitude measurement probe  
         [0029]    [0029]FIG. 11 illustrates the adjustment module in greater detail in a side elevation view.  
         [0030]    [0030]FIG. 12 illustrates one example of the relative location of the stationary top clamp and the moving top clamp of the adjustment module.  
         [0031]    [0031]FIG. 13 illustrates the clamps of FIG. 12 in a side elevation, cross-sectional view.  
         [0032]    [0032]FIG. 14 illustrates a method for adjusting static attitude as described herein. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0033]    [0033]FIGS. 2, 3A, and  3 B illustrate a hard disk drive  10  in a top plan, highly schematic view. It will be understood that many of the components found in such a disk drive  10 , such as memory cache and the various controllers are not shown in the figure for purposes of clarity. As illustrated, drive  10  includes at least one, and typically several, disks  12  mounted for rotation on a spindle  14 , the spindle motor and bearing not being shown for purposes of clarity. A disk clamp  16  is used to position and retain the disk  12  on the spindle  14 . The disk drive  10  further includes an “E” block  18 , best seen in FIG. 2. The E block  18  gets its name from its shape as viewed from the side. It will be observed that E block  18  includes a plurality of actuator arms  20 ,  22 , and  24 , which are supported for pivotal motion by an actuator pivot bearing  26 . A voice coil motor assembly  28  is used to control the pivoting motion of the actuator arms  20 - 24 .  
         [0034]    Each actuator arm  20 - 24  includes a head gimbal assembly  30  comprising a suspension  32 , a read/write head/slider  34 , and interconnect  36  that extends from the head/slider to the actuator flex  38 . The dashed circle shows an expanded view of the arm  20 , which includes a substrate  40  (wherein the bracket indicates the lateral extend of the substrate relative to the actuator arm  20  in this particular embodiment) upon which electrical leads or traces  42  are supported. The electrical conductors  42  are typically copper or copper alloy with a gold plating.  
         [0035]    The substrate  40  will substantially underlie the traces  42 . Substrate  40  may comprise a synthetic material such as polyimide, which may be of the type sold under the brand name Kapton by I. E. DuPont.  
         [0036]    [0036]FIGS. 4 and 5 illustrate an example of a head suspension/electrical interconnect assembly  44  for which the present invention is intended. Assembly  44 , like that shown in FIG. 1, may have varying configurations depending upon the manufacturer. Assembly  44  is comprised of four primary components; loadbeam  46 , flexure  45 , electrical interconnect  36 , and baseplate (not shown for the purposes of clarity). The loadbeam  46  can be properly described as having a mounting region  48  (to which a baseplate is mounted), a spring region  47 , a load beam body  56 , and a loadpoint  49 . Similarly, the flexure  45  is comprised of a flexure body  55  and a gimbal region  50 . The flexure body  55  is rigidly affixed to the load beam body  56 , typically with one or more spot welds. As such, the gimbal region  50  of the flexure  45  is not rigidly affixed to the loadbeam  46 . Within the gimbal region  50  of the flexure  45 , there is a support pad, commonly referred to as the tongue  51 . The tongue  51  is in point contact with the loadpoint  49 , and provides for a mounting surface to which the slider is affixed with adhesive or some other means. The tongue  51  is connected to the flexure body  55  by resilient springs, commonly referred to as flexure or gimbal arms  52 . This construction of flexure  45  and load beam  46  provides for the tongue  51  to pivot, or gimbal, about the loadpoint  49  when a small torque is applied. The flexure  45  and load beam  46  assembly is referred to as a “conventional” suspension assembly. After the electrical interconnect  36  has been applied to a conventional suspension assembly, the assembly will more properly be referred to as a head suspension/electrical interconnect assembly  44 .  
         [0037]    The electrical interconnect  36 , as described previously, generally consists of a base substrate  40 , such as polyimide, supporting electrical leads or traces  42 . At one end of the electrical interconnect  36  are slider termination pads  54  which form electrical connections to the read/write head. The electrical interconnect  36  may also have an area of substrate that is sandwiched between the flexure tongue  51  and the read/write head slider. The electrical interconnect  36  is attached to the conventional suspension assembly such that is rigidly affixed to the suspension assembly in areas proximal to the flexure body  55  and load beam body  56 . The electrical interconnect  36  may also be rigidly attached to the flexure tongue  51 .  
         [0038]    It is desirable to attach the electrical interconnect  36  to the conventional head suspension assembly as described previously, without significantly impacting the performance of the conventional head suspension assembly. Specifically, while adhesive is needed to affix the electrical interconnect  36  to both the load beam body  46 /flexure body  55  and flexure tongue  51 , adhesive in the flexure arm  52  region of the conventional assembly can cause significant performance issues. Adhesive in the flexure arm  52  region can cause changes to the static angle of the tongue  51  resting on the loadpoint  49 , as well as increases to the rotational stiffness of the gimbal region  50 . Additionally, due to the wicking nature of the adhesive used to attach the electrical interconnect  36  to the conventional head suspension, an adhesive bond is formed not only at the interface between the adjacent surfaces of the electrical interconnect  36  and the conventional head suspension assembly, but also between the adjacent surfaces of the flexure  45  and the load beam  46 . The adhesive bonds resulting from the attachment of the electrical interconnect  36  to the conventional head suspension assembly can significantly affect the resulting bending stiffness of the head suspension/electrical interconnect  44 , thereby changing it&#39;s dynamic resonant characteristics. As such, it is desired that the adhesive bond characteristics are repeatable from one assembly to the next.  
         [0039]    Referring now to FIGS.  6 - 14 , the present invention will be described in broad detail. FIG. 6 illustrates one embodiment  100  of a device in accord with the current invention. The static attitude measurement and adjustment machine shown here includes a frame  102 , computer  104  indicated generally, and related input/output devices such as a touch screen to operate such devices, and an X and Y motion axis and controller  106 . Apparatus  104  further includes an adjustment module  108  and a static attitude measurement module  110 .  
         [0040]    [0040]FIGS. 7A and 7B provide a more detailed view of the adjustment and static attitude measurement modules  108  and  110 , respectively. The static attitude measure module  110  includes a camera  120  and vision optics  121  that are used to optically locate the suspension assemblies, a static attitude measurement probe or auto-collimator  122  (FIG. 8) to measure the relative angular attitude of surfaces of interest, and an optics assembly  124  (FIG. 10) that collocates the laser beam from the measurement probe and the field of view of the vision optics.  
         [0041]    The adjust module  108  generally contains a Z actuator  126  which positions the top clamps  128  in close proximity to the suspension to be adjusted, a piezo actuator  130  which precisely positions the moving top clamp  132  relative to the stationary top clamp  134 , and an LVDT  136  which provides position feedback for control of the piezo actuator  130 . The bottom clamps  138  are spring loaded and guided by the bottom clamp spring housing  140 , and actuated in the Z direction to engage with the top clamps  128  by the bottom clamp actuator  142 , which as shown here is a pneumatic cylinder. FIG. 7B shows the actuator  142  in extended and retracted positions  144  and  146 , respectively.  
         [0042]    [0042]FIG. 8 details the fundamental design of the static attitude measurement probe  110  in accord with the present invention. As mentioned earlier, typical auto-collimator measurement devices require that the laser beam be masked with an aperture in close proximity to the surface being measured. In this case, a laser  148  produces a laser beam that is masked with an aperture  150  prior to the beam entering the optical path of the autocollimator, thereby eliminating the need for a mask near the surface being measured. Additionally, the mask, or aperture,  150  can be moved small amounts to adjust the laser spot location at the surface of the object being measured. FIG. 8 also illustrates a beam splitter  152  and a charged couple device array  154  used for imaging the suspension gimbal  156 .  
         [0043]    FIGS.  9 A- 9 C provides more illustration of the static attitude measurement module  110 , specifically. As mentioned earlier, the static attitude measurement module includes a static attitude measurement probe  122 , a camera and vision optics  120 , and an optical assembly  160  disposed within an optical housing  162  which combines the field of view of the vision system and the measurement laser beam at the same location. A diffuser  164  and light source provide for necessary diffuse illumination of the suspension or HGA. The opal diffuser  164  has an aperture in line with the optical path of the measurement probe and vision system, so as not to obstruct either. The light source is shuttered so that no light is present while the static attitude measurement probe  122  is capturing a measurement.  
         [0044]    [0044]FIG. 10 provides more detail with respect to the optical assembly utilized to collocate the vision field of view and measurement beam from the static attitude measurement probe. A 45 degree mirror  170  and pellicle beamsplitter  172  are used to bring the vision field of view in-line with the laser beam from the measurement probe. The laser beam from the measurement probe passes directly through the pellicle beam splitter  172 , but the reflected image from the pellicle beamsplitter is used for vision purposes. As mentioned earlier, vision can be used to determine the relative location of the suspension or HGA, allowing for precise positioning of the measurement beam and adjust tooling on the suspension or HGA.  
         [0045]    [0045]FIG. 11 provides additional information about the static attitude adjust module  108 . The adjust module includes a Z-actuator  126  which positions the moving and stationary top clamps  132  and  134  in close proximity to the suspension to be adjusted. The piezo actuator  126  precisely positions the moving top clamp  132  relative to the stationary top clamp  134  utilizing feedback from the LVDT  136 . The bottom clamps  138  then engage with the top clamps  128  when the bottom clamp actuator  142  is extended.  
         [0046]    In some cases it is beneficial to do a two stage adjustment on each gimbal arm, wherein the gimbal arm is first bent a large amount in one direction and then adjusted towards its target position. This is referred to as a “Pre-Bend”, and can both improve the adjustability and stability of the adjust process.  
         [0047]    [0047]FIG. 12 illustrates one example of the relative location of the stationary top clamp  134  and the moving top clamp  132 . Generally, the stationary top clamp  134  is positioned on the baseplate side of the moving top clamp  132 . Also shown in the figure is a gimbal  180  including first and second gimbal arms  182  and  184  and a slider  186 .  
         [0048]    [0048]FIG. 13 is a cross-sectional view of the bottom and top clamps  138  and  128 , respectively, engaged. Note that the punch clearance  190  on the bottom clamp ensures that gimbal arms  182  and  184  are not clamped. This helps ensure that the gold plating on the conductors is not damaged by the adjust tooling.  
         [0049]    [0049]FIG. 14 illustrates a process overview  200  of the adjustment cycle. Thus, a process in accord with the present invention would include measuring the static attitude of a gimbal at  202 . From the measurement, a calculation is made at  204  of the amount of adjustment necessary to each gimbal arm to provide the desired static attitude. The first and second arms are respectively adjusted then by clamping the arms and moving the clamps to provide the desired static attitude as indicated at  206  and  208  respectively. The static attitude of the adjusted suspension would then be measured again at  210 . A comparison of the measurement at  210  would be made with the desired specification at  212 . If the static attitude was not within specification, the process would be repeated. If the measured static attitude was within specification, the algorithm controlling the adjustment would be updated at  214  and a new part would be adjusted at  216 .  
         [0050]    The device detailed above provides for an adjustment range of ±4 degrees for both pitch and roll static attitude, and can achieve capabilities of ±0.15° (±3 standard deviations) in static attitude.  
         [0051]    The device and method described above provides information with regards to one embodiment of the present invention, but one skilled in the art can imagine a number of variants that would still be in accord with the scope of this application.  
         [0052]    The present invention having thus been described, other modifications, alterations, or substitutions may also now suggest themselves to those skilled in the art, all of which are within the spirit and scope of the present invention. It is therefore intended that the present invention be limited only by the scope of the attached claims below.