Abstract:
An apparatus and method for assembling baseplates, which are joined to head suspensions, to actuator arms of an E-block for use in disk drives employ an assembly fixture for orienting and holding the head suspensions with reference to a pivot bearing formed in the E-block. An adhesive is interposed in a gap formed between each baseplate and corresponding actuator arm to maintain the suspensions in alignment relative to the pivot bearing. The assembly fixture includes clamps for maintaining the suspensions in a proper orientation. Each suspension has a locating surface that is planar with the gap for alignment of the suspensions.

Description:
FIELD OF THE INVENTION 
     The present invention relates to hard disk drives and in particular to means of attaching a magnetic head suspension assembly to an E-block. 
     BACKGROUND OF THE INVENTION 
     Hard disk drives typically include multiple disks that have a magnetic memory storage surface for storing data. A magnetic head including a read/write transducer passes over the disk surface for reading and writing data. The transducer must be precisely positioned on particular disk tracks in a consistent way to quickly and reliably read and write the data. In the disk drive industry, there is a trend to fit more and more disk tracks per unit of disk surface to maximize the disk storage capacity. Accordingly, precise positioning of the transducer with respect to the disk surface is critical. 
     Prior art hard disk drives have an E-block that pivots on a pivot bearing. The E-block has multiple actuator arms. Suspensions attach to the actuator arms to suspend the magnetic heads above the disk surface. The suspensions are typically spring loaded, having a particular gram load, to enable the heads to maintain a desired flying height just above the spinning disk surface. Changes in this gram load affect the flying height of the head. 
     Changes in the gram load are influenced by many factors. These factors include misalignment and deformation of critical components. For example, the suspension and actuator arm may misalign during assembly. The pivot bearing of the E-block may misalign within the E-block. Bearing and actuator arm defects may cause misalignment. Pivot bearing inner race runout, bore inaccuracies in the E-block, or bearing installation errors are examples of common causes for bearing and E-block misalignment that can result in gram load variations. The actuator arm tips may end up varying from a desired height and orientation, causing attached suspensions to have varying gram loads. 
     Often, gram load changes are associated with the process of attaching the suspension to an actuator arm. Swaging is the most common method of attaching the suspension to the actuator arm and involves pressing swage balls through the hub of a suspension baseplate. The swage balls expand the hub against the actuator arm to hold the suspension and actuator arms together. Pressing swage balls though the hub may distort the baseplate, changing the suspension gram load. 
     There are known ways of adhesively bonding a suspension to an actuator arm to overcome the undesirable effects of swaging. For example, a doughnut-shaped adhesive washer has been interposed between the actuator arm and the suspension hub. When the suspension hub inserts into the actuator arm opening, heat is applied to melt the washer and thereby create a bond. 
     There are drawbacks to known adhesive attachment methods. Heating the doughnut-shaped washer melts the washer. As the washer melts, it deforms. This deformation can allow the suspension to misalign relative to the actuator arm, changing the suspension gram load. Another drawback of the adhesive washer is that the hub locates relative to the actuator arm tip to create a bond. When the actuator arm tips misalign, the suspension will also misalign. There is no provision for correcting for actuator arm tip variations that cause gram load variations. What is desired is a way of correcting fabrication misalignment and distortion errors to maintain a consistent gram load. 
     SUMMARY OF THE INVENTION 
     An actuator for pivoting a magnetic transducer of a hard disk drive includes an E-block having a pivot bearing, actuator arms formed as part of the E-block, and suspensions bonded to the actuator arms. Each actuator arm has an arm tip with a bonding surface. The suspensions have an integrated baseplate that adhesively attaches to the bonding surface of the actuator arm tip. 
     The E-block pivot bearing is used as an alignment reference when bonding the suspensions to the actuator arms. The baseplate and the actuator arm bonding surface define a gap therebetween. Adhesive bridges the gap between the suspension and the actuator arm and bonds the suspension to the actuator arm tip. Because the suspensions use the pivot bearing as a reference and the adhesive flows to bridge the gap, the adhesive cures into a shape that automatically compensates for component alignment errors including actuator arm tip variations, pivot bearing inner race run-out, E-block bore inaccuracies, and bearing installation error. Additionally, adhesive bonding avoids gram load changes associated with swaging. Improved gram load precision can be achieved with adhesive bonding. 
     The bonding surface of the actuator arm tip has numerous possible configurations. One configuration includes a recessed bonding surface that is planar. The bonding surface defines a channel extending between the top and the bottom of the actuator arm for adhesive to flow into, according to a variation of the invention. The channel holds adhesive to enable the suspension/actuator arm bond to resist shear forces. According to another aspect of the invention, the bonding surface has a raised portion. The raised portion may include posts, rails or texture to prevent shear. 
     A method of assembling a suspension to an actuator arm of a an E-block, in accordance with the present invention, eliminates distortion error caused by swaging, and compensates for other errors caused by pressing the pivot bearing into the E-block arm. 
     The method includes the step of first inserting a pivot bearing into the E-block, and then referencing the pivot bearing to align the suspension in a desired position. The suspension and the actuator arm define a gap in the desired position relative to the bearing. The next step is bonding the suspension to the actuator arm with an adhesive to fill the gap and to maintain the suspension in the desired position. Filling the gap with adhesive forms an adhesive bridge between the actuator arm and the suspension. This bridge enables orientation of the suspension to compensate for variations in the actuator arm tips, bearing bore or race run-out, and bearing installation error, for example. 
     In keeping with this invention, a pivot bearing defines an axis and a z-datum. In the novel method, the step of referencing includes referencing the axis and the z-datum to align the suspension with respect to the pivot bearing. According to another aspect of the invention, the step of referencing includes attaching an assembly fixture to the pivot bearing and holding the suspension with the assembly fixture. The step of attaching includes mechanically clamping the suspension, or applying a vacuum to the suspension to hold the suspension in the desired position with respect to the pivot bearing. 
     The step of bonding preferably includes the steps of maintaining the suspension in the desired position with respect to the bearing, interposing the adhesive between the actuator arm and the suspension, and curing the adhesive with ultraviolet light. Accordingly, the present invention eliminates gram load changes associated with the swaging process. Additionally, since the suspension does not require location with respect to the E-block, or actuator arm tip as in the prior art, variations in gram load and static attitude caused by arm tip height and angle variations during fabrication are eliminated. Furthermore, locating the suspension with respect to the actuator bearing eliminates bearing related variations such as inner race run-out, bore inaccuracies and bearing installation misalignment. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described in greater detail with reference to the drawings in which: 
     FIG. 1 is a perspective view of an E-block assembly. 
     FIG. 2 is a cross-sectional side view of an assembly fixture holding an E-block assembly. 
     FIG. 3 is a view of the E-block assembly and assembly fixture as seen along the section line  3 — 3  of FIG.  2 . 
     FIG. 4 is a perspective view of an actuator arm tip in accordance with the present invention. 
     FIG. 5 is a perspective view of another actuator arm tip in accordance with the present invention. 
     FIG. 6 is a perspective view of an alternative actuator arm tip in accordance with the present invention. 
     FIG. 7 is a perspective view of another alternative actuator arm tip in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In FIG. 1, an E-block  10  includes a pivot bearing  12 , actuator arms  14 , and suspensions  16 . Each suspension  16  has an integral baseplate  15  at one end and a slider  18  at the other end. The slider  18  includes a magnetic transducer for reading and writing data to a hard disk drive. 
     The baseplate  15  of each suspension  16  and actuator arm  14  form an adhesive-fillable gap  32 . The gap  32  fills with adhesive  28  to bond the baseplate  15  of the suspension  16  to the actuator arm  14 . The adhesive  28  is selectively curable. Preferably, the adhesive  28  is ultraviolet light (UV) curable. 
     The baseplate  15  is a rigid planar component capable of attachment via a weld to the suspension. Once welded to the suspension  16 , the baseplate  15  improves the rigidity of the suspension  16  to enable the suspension  16  to attach to an actuator arm  14 . The baseplate  15  has an end portion that overhangs one end of the suspension  16 . The other end portion of the baseplate  15  is bonded by the adhesive  28  to the actuator arm  14 . The suspension has a locating surface  59  used in prior testing and measurement of gram load and attitude of the suspension, as well as locating the suspension to the E-block during the assembly process. 
     FIG. 2 shows the E-block  10 . An assembly fixture  30  attaches to the pivot bearing  12  and holds each suspension  16  in a desired position. The assembly fixture  30  distances and orients each suspension  16  with respect to the pivot bearing  12 . Accordingly, the assembly fixture  30  locates the suspension  16  with respect to the pivot bearing  12 . 
     Each suspension  16  has a bonding surface  58 . Each actuator arm  14  has a bonding surface  60 . The bonding surface  60  of each actuator arm  14  and the bonding surface  58  of each suspension  16  form the gap  32 . Adhesive  28 , which may be an epoxy, fills the gap  32  to bond each suspension  16  to the actuator arm  14 . Filling the gap  32  with adhesive enables the adhesive to cure into a shape that automatically corrects for component misalignment, including actuator arm  14  tip variations. 
     While the assembly fixture  30  holds the suspensions  16  and the pivot bearing  12  with a mechanical linkage, various other devices for holding the suspensions  16  during assembly can utilize the pivot bearing  12  as a reference. For example, a device that does not directly attach to the pivot bearing  12  can be used. An assembly fixture with an optical sensor, for example, can distance and orient the suspensions  16  with respect to the pivot bearing  12 . A datum common to both the pivot bearing  12  and to the suspensions  16  may be used as an alignment reference instead of the pivot bearing  12  according to a variation of the invention. 
     The assembly fixture  30  includes mechanical clamps  34  and vacuum actuated clamps  36  for holding the suspensions  16  in a desired position and orientation with respect to the pivot bearing  12 . Each suspension  16  includes a locating surface  59 . The clamps  34  and  36  selectively hold each suspension  16  at the locating surface  59  during suspension/actuator arm  14  assembly. 
     The bonding method includes inserting the pivot bearing  12  into the E-block  10 . The next step aligns the suspension  16  with respect to the pivot bearing  12 , thus forming a gap  32  between the suspension  16  and an actuator arm  14 . The next step includes interposing the adhesive  28  between the actuator arm  14  and the suspension  16  to fill the gap  32 . After the adhesive  28  fills the gap  32 , UV light cures the adhesive  28 , bridging the gap  32 . The adhesive  28  maintains the suspension  16  in the desired alignment with respect to the pivot bearing  12 . 
     If the pivot bearing  12  and actuator arm  14  misalign for any reason bridging the gap  32  with adhesive  28  compensates for misalignment of the E-block and each actuator arm  14 . Although mechanical and vacuum clamps  36  are used in combination, there are various clamp types, which may be substituted in accordance with the present invention. Additionally, vacuum clamps  36  may be used exclusively. In an alternative embodiment, mechanical clamps  34  may be used exclusively. 
     The pivot bearing  12  defines a z-datum  40  and an axis  42 . The pivot bearing  12  is cylindrical in shape, having two ends, an inner race and an outer race. According to one aspect of the invention, the z-datum  40  is a line defined at one end of the pivot bearing  12 , intersecting the axis  42  at a right angle. It can be appreciated that while the z-datum intersects the axis  42  at one end of the pivot bearing  12 , the z-datum can also be arbitrarily fixed along another line, or at a point, to enable the suspensions  16  to align with respect to the pivot bearing  12 . 
     The assembly fixture  30  holds each suspension  16  at a predetermined z-distance from the z-datum  40  and at a desired x-y position. Supports  50  hold the sliders  18  apart by separating the suspensions  16 . The assembly fixture  30  holds the suspensions  16  in the desired position while the actuator arms  14  and suspensions  16  bond. 
     The axis  42  establishes a y-datum to distance the suspensions  16  from the bearing. The use of the assembly fixture  30  with a direct mechanical linkage between the pivot bearing  12  and the suspensions  16  fixes a desired distance between the pivot bearing and the suspensions. The assembly fixture  30  holds each suspension  16  at a predetermined distance from the axis  42  to establish the y position of the slider  18  during assembly of the suspensions  16  and the actuator arms  14 . 
     The present invention can also apply to correcting undesired pitch and roll of the actuator arm  14 . Since the suspension  16  does not mechanically lock on the actuator arm  14 , as in the prior art, the suspension  16  is held by the assembly fixture  30  in the desired static orientation i.e. pitch and roll position when adhesively bonded to the actuator arm  14 . 
     FIG. 3 shows a sectional view of the E-block  10  of FIG.  2 . The pivot bearing  12  normally enables the E-block  10  to pivot along the arc  52 . The suspension  16  includes the locating surface  59  and piezoelectric element  57  for fine positioning of the air bearing slider  18  during operation. The assembly fixture  30  includes discrete supports  46 ,  48  and  50 . The support  46  prevents rotation of the E-block. The support  48  prevents extension of the suspension  16  from the E-block  10 . The supports  50  hold the air bearings  18  apart (FIG.  2 ). The fixture  30  firmly holds the locating surface  59  to prevent any movement of the suspension  16 . 
     The pivot bearing  12  defines a datum point  53 . The support  46  contacts the actuator arm  14  to align the actuator arm  14  with respect to the pivot bearing  12 , and particularly with respect to the datum point  53 , and to prevent rotation of the E-block in the direction of the arc  52 . The support  48  locates and holds the suspension  16  at point  49 . The fixture  30  also locates the suspension at the points  47 . Points  47  locate the suspension  16  in the transverse direction. The locate point  56  has a perimeter defining a recess for engaging the assembly fixture  30 , as an alternative to support  48  for longitudinal location of the suspension  16 . 
     The fixture  30  may have any of a variety of mechanical alignment features, which can take various shapes and sizes. Various non-mechanical alternatives exist. It can be appreciated that optical verification of alignment can be used. Additionally, various suspensions eliminating various features, or containing features such as micro-actuator, chip-on-suspension, shock limiters and the like may be used. 
     FIG. 4 shows a tip  20  of an actuator arm  14 . The tip  20  includes a top  64 , a bottom  66 , two lateral sides  70 , and a bonding surface  60  on the top  64 . The bonding surface  60  defines four channels  68  extending between the top  64  and the bottom  66 . The channels  68  have a dove-tail shaped cross-section and extend fully across each lateral side  70  from the top  64  and the bottom  66 . The channels  68  are configured to fill with flowing adhesive. Flowing adhesive in the channels  68  prevents lateral movement of the adhesive (towards the lateral sides) and thereby prevents the suspension  16  from shearing away from the actuator arm  14  during use. 
     Although lateral channels  68  are shown, the channels  68  can be formed within the bonding surface  60  and may have various cross-sectional shapes including a circular cross-sectional shape. The channels  68  extend partially through the tip  20  of the actuator arm  14  according to a variation of the invention. 
     FIG. 5 shows another tip  20  of an actuator arm  14 . The end includes a bonding surface  60  with raised portions, namely four posts  72  defined on each lateral side and extending perpendicular from the top  64  and the bottom  66 . The bonding surface  60  has a generally rectangular periphery. The posts  72  define corners of the generally rectangular periphery of the bonding surface  60  to provide shear resistance and the raised portions prevent the suspension  16  from shearing away from the actuator arm  14 . 
     The posts  72  have a generally rectangular cross-sectional shape and squared ends. The posts  72  may take any of a number of shapes and, for example, may have tapered ends, or rounded ends. Further, the number and location of the posts  72  may be modified in accordance with the present invention. 
     FIG. 6 shows an alternative tip  20  of the actuator arm  14 . The bonding surface  60  includes raised portions, namely rails  76  extending from each bonding surface  60  on each lateral side  70 , and texture  80 . The rails  76  and texture provide shear resistance and prevent the adhesive bonded to the bonding surface  60  from shearing. According to one aspect of the invention, the texture  80  includes parallel ridges. 
     FIG. 7 shows another alternative tip  20  of the actuator arm  14 . The bonding surface  60  is planar and recessed from the actuator arm  14 . Alternatively, the bonding surface may not be recessed. 
     Various modifications, additions and variations of the apparatus and method can be made within the scope of the invention. For example, the texture  80  can assume any of a number of texture patterns to hold adhesive. Additionally the baseplate  15  of the suspension  16  can have a textured or raised bonding surface for holding adhesive. The various raised portions of the actuator arm  14  bonding surface  60  can assume any of a number of configurations.