Abstract:
Problems aligning a slider with a dimple in manufacture of head gimbal assemblies for disk drive suspensions are obviated by defining optically readable indicia that serve as a reference for positioning apparatus rather than the dimple.

Description:
REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of application Ser. No. 09/697,880, filed Oct. 26, 2000, which application in turn is a continuation in part of application Ser. No. 09/310,015, filed May 11, 1999, now U.S. Pat. No. 6,212,760, which application claims the benefit of U.S. Provisional Application Serial No. 60/131,619 filed Apr. 28, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to manufacture of head gimbal assemblies, known as HGAs. More particularly, the invention relates to manufactures and manufacturing steps that simplify and make more accurate and less time-consuming the juxtaposing of the slider with the dimple when mounting the slider to the flexure tongue. The invention substitutes added optically readable indicia for the outlines of the dimple as the locating criteria for the slider, thus ensuring accurate placement of the slider every time. 
     2. Related Art 
     In the manufacture of suspensions comprising a load beam, a flexure attached to the load beam and having a tongue, and a slider, mounted for gimbaling movement around a dimple defined by the flexure tongue or the load beam rigid portion, the positioning of the slider by automatic equipment is essential to efficient manufacture. A misplaced slider, that is a slider that is not properly aligned with reference to the dimple, will not gimbal properly or predictably and is a costly defect that reduces manufacturing yield. Taking additional time to properly place the slider increases costs in a very cost conscious industry. 
     SUMMARY OF THE INVENTION 
     This application refers to sliders as the mounted element. The term slider herein is used to encompass not only the slider itself, a typically ceramic body designed to fly over the rotating disk in a disk drive, but also to include the read-write head carried within the slider body and connected to the device electronics. 
     The need for increased accuracy in positioning of sliders must be met at no greater expenditure of manufacturing time. This can be achieved by the use of automatic positioning apparatus using optical reading to locate the correct position. Presently available optical readers, known per se, cannot, however, read with certainty the location of the dimple because the dimple, being an upset or etch formed boss, lacks clear delineation at its junction with the surrounding wall of the flexure tongue or load beam rigid portion. That is, there is not a sufficiently sharp, or uniformly distributed, target for the optical reader to use as a marker for positioning the slider relative to the dimple. 
     It is an object, therefore, of the present invention to provide markers of such sharpness and uniformity of distribution that positioning equipment can read and position the slider with reference to them, as opposed to the dimple, with increased accuracy, better speed and fewer defects. It is a further object to provide a system of optically readable indicia, typically geometric shapes, arranged in a pattern useful in the invention method. It is a further object to provide a series of such indicia arranged in such proximity and uniformity of pattern relative to the dimple as to be useful as a proxy for the dimple in locating the slider properly on the flexure tongue. It is a further object to provide optical readable indicia laterally adjacent the dimple post to enable optical reading of the indicia although the dimple post is hidden from view, and thus to enable the mounting of the slider with great accuracy. 
     These and other objects of the invention, to become apparent hereinafter, are realized in a head gimbal assembly of a load beam comprising a wall, a flexure attached to the load beam and having a tongue, and a slider attached to a first side of the flexure tongue, the load beam defining a dimple comprising a solid post extending normal to the load beam wall and positioned, sized and shaped to allow gimballing movement of the slider by contact with a second side of the flexure tongue, the dimple post being hidden from view from the flexure tongue first side, and, optically readable indicia formed in the load beam wall laterally of the dimple sufficiently to be visible from the first side of the flexure tongue for precisely locating the slider opposite the dimple post by reference to the optically readable indicia rather than the dimple post. 
     In typical embodiments, the load beam is locally etched to define the dimple, the flexure tongue is locally narrowed opposite the indicia to facilitate location of the indicia immediately adjacent the dimple post while maintaining the indicia visible from the flexure tongue first side, the dimple post is cylindrical and the optically readable indicia comprise left an right hand holes on a common axis with the dimple post, the flexure tongue having a dog-bone shape to expose the optically readable indicia. In its method aspects the invention contemplates the method of mounting sliders onto load beams of flexure tongues in position opposite the dimple in a head gimbal assembly comprising a load beam, a flexure having a tongue and a slider, and wherein the load beam defines a dimple as an upstanding post smaller in width than the flexure tongue, that includes marking the situs of the dimple with optically readable indicia comprising left and right hand load beam holes laterally spaced from the dimple post sufficiently to be visible when the dimple post is not visible, and guiding placement of the slider on the flexure tongue with reference to the optically readable indicia rather than the dimple. 
     In this and like embodiments, also, there is included forming the dimple post by etching on the load beam, and shaping the flexure tongue to expose the optically readable indicia for reading. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The invention will be further described as to an illustrative embodiment in conjunction with the attached drawings in which: 
     FIG. 1 is a plan view of the invention head gimbal assembly in which the dimple is formed on the load beam; 
     FIG. 2 is a plan view of the invention head gimbal assembly in which the dimple is formed on the flexure tongue; 
     FIG. 3 is a plan view of the invention head gimbal assembly in which the flexure dimple has a series of annular rings forming the optical indicia; 
     FIG. 4 is a view taken on line  4 — 4  in FIG. 1; 
     FIG. 5 is a view like FIG. 3, having a different pattern of optical indicia; and 
     FIGS. 6,  7  and  8  are fragmentary views of particular optical indicia shapes, patterns and distributions; 
     FIG. 9 is a view like FIG. 1 of an alternate embodiment; and, 
     FIG. 10 is a view taken on line  10 — 10  in FIG.  9 . 
    
    
     DETAILED DESCRIPTION 
     The invention uses optical reading, or vision, equipment known per se and not forming part of the invention to assist in the placement of the sliders on the flexure tongues. Use of such equipment is enhanced in the invention by providing more easily and more accurately read indicia that the line formed at the boundary of the dimple and the surrounding flexure tongue or load beam wall. 
     With reference to FIG. 1, a head gimbal assembly  10  is shown to include the rigid portion  12  of load beam  14  (the base portion, the spring portion and the actuator for shifting the load beam not being shown). Flexure  16  is attached as by welding to the load beam portion  12 . Flexure  16  comprises a frame  18  and a cantilevered tongue  22 . A slider  24 , shown in phantom, is to be attached to the flexure tongue  22  at a location that places the slider  24  precisely opposite the dimple  26  (formed on the load beam portion  12  in this embodiment). Thus placed the slider  24  will be able to gimbal about the dimple  26  with the flexure tongue  22 . 
     In the FIG. 1 embodiment, the flexure tongue  22  is particularly positioned, sized and shaped to expose the invention optically readable indicia  28  by relieving the tongue along its length at laterally opposed locations  32 ,  34  to provide a dog-bone shape as shown rather than the more usual rectangular shape. Any other shape providing the flexure tongue function and exposure for reading of the indicia  28  will be useful as well. 
     The indicia  28  are shown to be a series of circular shaped holes  36  that are typically etched into the load beam around the dimple  26 . Hereinafter described indicia shapes and patterns can also be used in this embodiment. The holes  36 , like the other indicia of the invention, are sharp-edged, at least more sharp than the edge or boundary line  38  between the dimple  26  and the surrounding wall  42  of the load beam portion  12 , and preferably so sharp that the reading equipment can readily identify the marker provided by the holes  36 . The pattern of holes  36  is one of uniform circumferential distribution based on the corners of an imaginary rectangle centered on the axes of the dimple  26 . 
     In FIGS. 2-8 a series of embodiments are shown having in common the presence of the dimple  52  on the flexure tongue  44 , as opposed to the load beam portion  23 . The shape, size, location and sharpness of edge characteristics of the indicia  28  in the first embodiment find their counterparts in the indicia  56  in these embodiments. 
     Thus, in FIG. 2, a series of circular holes  72  arranged at a spacing of 90° is provided as an effective target for the vision equipment to accurately locate and position the slider  28 . In FIGS. 3 and 4 an axially extended, stepped series  44  of annular or arcuate slots  46  are provided formed on the dimple  48  within the periphery  50  of the dimple. In FIG. 5, an axially extended, stepped series  74  of interrupted annular slots or arcuate slots  54  are provided formed on the dimple  58  partially within the periphery  60  of the dimple, and partially without, as at  62 . 
     In FIGS. 6,  7  and  8 , a 90° distribution of indicia is shown at  64 ,  66 , and  68 , comprising respectively, indicia  76  comprising in longitudinal cross-section semi-circles, indicia  78  comprising in longitudinal cross-section diamonds, and indicia  80  comprising arcuate holes, all uniformly spaced around the respective peripheries  82 ,  84  and  86  of the dimples  88 ,  90  and  92 . 
     In the invention method, slider  24  is mounted onto the load beam portion  12  or flexure tongue  22  in position opposite, e.g. the dimple  28 , in the head gimbal assembly  10 , marking the situs of the dimple with optically readable indicia, e.g.  28 , and guiding placement of the slider with reference to the optically readable indicia rather than the dimple. 
     With reference now to FIGS. 9 and 10, head gimbal assembly  910  includes rigid portion  912  of the load beam  914 . Load beam rigid portion  912  comprises generally planner wall  915 . Flexure  916  is suitably weld or glue attached to the load beam portion  912 . Flexure  916  comprises a frame  918  and a cantilevered tongue  922 . Slider  924  (shown in phantom) is attached to a first side  925  of the flexure tongue  922 , at a location to be precisely opposite the dimple post  926 . Dimple post  926  is formed by etching the load beam portion  912  from a suitable thickness roughly equal to the indicated height of the dimple post to form the load beam wall  915  and leave the post upstanding as shown and suitably circularly or polygonally cylindrical, solid, and with a flat or somewhat curved top surface  927  that engages in gimballing relation the second side  929  of the flexure tongue  922 . As with the previous dimple  26 , the solid post dimple  926  extends normal to the load beam wall  915  and is positioned, sized and shaped as shown to allow gimballing movement of the slider by contact with the opposing, second side  929  of the flexure tongue  922 . 
     As shown, dimple post  926  is hidden from view from a vantage point on the flexure tongue first side  925 . There are, however, in accordance with the invention, optically readable indicia  928  formed in the load beam wall  915  laterally of the dimple post  926  sufficiently to be visible from the first side  925  of the flexure tongue  922  for precisely locating the slider  924  opposite the dimple post by reference to the optically readable indicia rather than the dimple post. 
     In typical embodiments, the flexure tongue  922  is locally narrowed at  932 ,  934  generally opposite the indicia  928  so to provide the tongue with a sort of dog-bone shape as shown, that will facilitate placement of the indicia more immediately adjacent the dimple post  926  while maintaining the indicia visible from the flexure tongue first side  925 . 
     The optically readable indicia  928  comprise left and right hand through or partially through holes  933  on a common axis A—A with the dimple post  926 . 
     In its method aspects the invention of FIGS. 9 and 10 mount a slider  924  onto the flexure tongue  922  in proper position opposite the dimple post  926  wherein the dimple post, etched from the load beam wall  915  is smaller in width than the flexure tongue, even with special shaping of the flexure tongue, by marking the situs of the dimple post with optically readable indicia comprising left and right load beam holes  933  laterally spaced from the dimple post sufficiently to be visible when the dimple post is not visible, and guiding placement of the slider on the flexure tongue with the reference to the optically readable indicia rather then the dimple. 
     The invention thus provides markers of such sharpness and uniformity of distribution that positioning equipment can read and position the slider with reference to them, as opposed to the dimple, with increased accuracy, better speed and fewer defects using a system of optically readable indicia, typically geometric shapes, arranged in a pattern useful in the invention method. The provided series of such indicia arranged in such proximity and uniformity of pattern relative to the dimple are useful as a proxy for the dimple in locating the slider properly on the flexure tongue.