Classifications

• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B21/00—Head arrangements not specific to the method of recording or reproducing
  • G11B21/16—Supporting the heads; Supporting the sockets for plug-in heads
  • G11B21/20—Supporting the heads; Supporting the sockets for plug-in heads while the head is in operative position but stationary or permitting minor movements to follow irregularities in surface of record carrier
  • G11B21/21—Supporting the heads; Supporting the sockets for plug-in heads while the head is in operative position but stationary or permitting minor movements to follow irregularities in surface of record carrier with provision for maintaining desired spacing of head from record carrier, e.g. fluid-dynamic spacing, slider
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
  • G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
  • G11B5/4806—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed specially adapted for disk drive assemblies, e.g. assembly prior to operation, hard or flexible disk drives
  • G11B5/4826—Mounting, aligning or attachment of the transducer head relative to the arm assembly, e.g. slider holding members, gimbals, adhesive

Definitions

• the present invention relates to a data storage device, and more particularly, to a disk drive operating at low flying heights including a novel mounting of the head slider to the flexure.
• disk drives for use in work stations, personal computers, and portable computers are required to provide a large amount of data storage within a minimum physical space.
• disk drives operate by positioning a read/write transducing head over respective tracks on a magnetic recording disk. Positioning of the head over the tracks is accomplished by an actuator coupled to control electronics, which control the positioning of the actuator and the read/write functions of the heads.
• FIGs. 1A and IB show a conventional actuator assembly 10 for supporting a read/write head 12 with respect to a disk 14.
• head 12 is supported on a flexure 16, which is in turn mounted on a load beam 18.
• the load beam 18 is attached to an actuator arm 20, which is attached to a voice coil motor (not shown) for pivoting the actuator assembly to position the head 12 over the desired data track on the disk 14.
• the load beam 18 is provided to exert a force or load to bias the head 12 toward the surface of disk 14.
• the force of the load beam 18 opposes and counteracts the force of the cushion of air under the slider so that the head reaches an equilibrium state at the desired flying height.
• flexure 16 includes a tongue 22 provided at an angle with respect to the main body of flexure 16. The angle is provided to compensate for the angle that the load beam 18 forms with respect to the disk surface.
• the head 12 is generally parallel to the surface of the disk 14.
• the head is mounted on the surface of tongue 22 by an epoxy, such as for example ABLESTIK manufactured by Ablebound Corp. In conventional head assemblies, the epoxy is spread over substantially all or all of the tongue 22 in order to securely mount the head thereon.
• the read/write head 12 is generally comprised of a transducer (not shown) for transferring the data to and from the disk, and a slider 24 for supporting the transducer at the desired flying height.
• Slider 24 generally includes rails 26a and 26b on the underside of the slider (shown inverted on Fig. 2) , which rails are supported on the pressurized cushion of air during operation of the disk drive to provide the head flying height.
• the slider is formed with a slight bow across both its length and its width, as shown in Figs. 3A and 3B, respectively.
• the bow has been exaggerated in the Figures for clarity.
• the distance d_ in Fig. 3A is commonly referred as the “crown”, and represents the amount the slider has bowed across the length of the slider.
• the distance d 2 in Fig. 3B is commonly referred as the “camber”, and represents the distance the slider has bowed across the width of the slider.
• a positive crown or camber is a crown or camber wherein the middle of the slider is closer to the disk surface than the edges of the slider.
• the slider shown in Figs. 3A and 3B has a positive crown and positive camber. It has been found that a positive crown enhances the formation of the air bearing under the slider, and thus allows the head to take-off from the disk in a shorter period of time upon start-up of the disk drive. As such, there is less time that the head is dragging in contact with the rotating disk prior to take-off. Similarly, when the head is provided at higher skew angles, a positive camber in the slider facilitates a better air bearing for the air contacting the slider from the side of the slider.
• the crown and camber on a slider are formed two ways. First, the slider is provided with a positive crown and camber during the slider fabrication process. Second, the positive crown and camber are enhanced during the curing process used to secure the slider to the tongue of the flexure. In the curing process after the epoxy has been applied between the slider and the tongue, the slider and flexure are heated to evaporate the liquid in the epoxy to thereby solidify the epoxy.
• the flexure is formed from steel or aluminum, and when it is heated, it expands.
• the slider is conventionally formed of a ceramic material which expands only slightly upon heating. After the epoxy solidifies and the bond is secure, the slider and flexure are cooled.
• a positive crown may be advantageously formed anywhere from 0.3 ⁇ " to 3 ⁇ " and a positive camber may be advantageously formed anywhere from 0.05 ⁇ " to 0.25 ⁇ ".
• flying heights have been reduced to the point where changes in the flying height as result of a loss of the positive crown and/or camber have become a significant consideration in the head/disk tribology.
• low flying heights for example 1 to 4 ⁇
• a variation in the flying height, as by a change in the temperature for example, could cause repeated intermittent contact of the head with the disk, and drive failure in an unreasonably short period of time.
• the disk drive includes an adhesive-bonded slider and head suspension design which will not lose its positive crown or camber with a change in temperature.
• the adhesive is applied at discrete points.
• a change in the crown and/or camber results in a change in the flying height of the head over the disk. Therefore, by substantially preventing a change in the crown or camber with a change in temperature, the head flying height remains relatively constant over a wide range of temperatures.
• FIGURE 1A is a side view of a conventional actuator assembly
• FIGURE IB is a top view of a conventional actuator assembly
• FIGURE 2 is an exploded perspective view of a flexure and a slider
• FIGURE 3A is a side view of a slider showing the crown
• FIGURE 3B is a front view of a slider showing the camber
• FIGURE 4 is a top view a disk drive according to the present invention.
• FIGURE 5 is an exploded perspective view of a flexure, slider and epoxy points according to the present invention.
• FIGURE 6 is an enlarged top view of a tongue and an epoxy application pattern according to the present invention
• FIGURE 7 is a graph of the change in the slider crown with a change in temperature.
• Figs. 4 through 7 generally relate to a disk drive with a novel method for securely bonding a read/write head to a flexure. It is understood that the present invention may be utilized with disk drives of various sizes and designs, and used with various data storage technologies.
• Fig. 4 there is shown a disk drive 50 including a storage disk 52 and a read/write head 54.
• Read/write head 54 includes a transducer 55 mounted to a slider 56.
• the slider 56 is in turn supported on an actuator assembly 58.
• Transducer 55 may be a conventional inductive transducing element, or in an alternative embodiment, may be a magneto- resistive (MR) transducing element.
• the actuator assembly 58 is pivotally mounted so as to pivot around pin 60 in response to a force exerted on the actuator assembly by voice coil motor 62.
• voice coil motor 62 As is known in the art, during operation of the drive 50, disk 52 is rotated by a spin motor (not shown) and actuator assembly 58 pivots read/write head 54 across the surface of the disk so that data is transferred between the read/write head 54 and the disk 52 in a plurality of concentric data tracks.
• Slider 56 includes a pair of rails (not shown on Fig.
• the head may have a flying height between 1-4 ⁇ ", and optimally about 2.5 ⁇ ".
• the actuator assembly 58 includes a conventional flexure 59 having a tongue 66 (Fig. 5) , which flexure may preferably be formed of steel or aluminum.
• the flexure is provided to support the slider 56 in parallel relation to the disk surface.
• Slider 56 may preferably be formed of conventional ceramic materials, such as calcium titanate or a titanium carbide/aluminum oxide composition.
• the coefficient of thermal expansion of the flexure, whether steel or aluminum, is greater than that of the ceramic slider.
• a head slider is conventionally bonded to the tongue of the flexure by applying an epoxy over substantially the entire surface between the slider and the tongue. With such a bonding method, the slider tends to lose the positive crown and camber at higher temperatures as result of the thermal expansion of the flexure tongue being greater than the thermal expansion of the slider.
• the epoxy is applied in discrete points 64 over the contact area between the slider 56 and the flexure tongue 66.
• Fig. 5 which is an enlarged top view of the tongue 66 and the discrete epoxy points 64 shown in Fig. 5, there are preferably four such epoxy points.
• the discrete epoxy points 64 are preferably evenly spaced around the contact area between the slider 56 and the tongue 66 so as to create a relatively uniform bond area between the slider and tongue.
• a conventional epoxy for use in the present invention is ABLESTIK 868-7 manufactured by Ablebound Corp. Other epoxies or adhesives may be used in alternative embodiments.
• the slider may preferably be formed with a slightly greater crown and camber during the slider fabrication process as compared to conventional head and flexure assemblies.
• the slider 56 may be secured to the tongue 66 in an ultra violet ("UV") bonding process, as opposed to a conventional curing process.
• UV ultra violet
• holes are provided through the tongue 66, one hole for each epoxy point 64.
• the epoxy is then provided in the holes, the slider is mounted on the tongue, and a UV light is applied to the back side of the tongue.
• the UV light causes the epoxy in the holes to solidify, thereby bonding the slider to the tongue. UV light is unable to penetrate the slider.
• the epoxy must be provided in the holes in the tongue. Accordingly, this process is not feasible with conventional epoxy applications, where the epoxy is applied over all or substantially all of the interface between the tongue and slider.
• the shear stress created in the discrete epoxy points is much higher than the shear stress created in conventional epoxy applications. However, it has been determined through testing that the discrete epoxy points according to the present invention are able to withstand a shear stress of at least 900 grams. This stress is higher than any stress which may be created in the epoxy points as result of the thermal expansion mismatch between the flexure 59 and the slider 56. It is understood that the epoxy application according to the present invention may be used with any head suspension design at the contact area where the head slider is mounted to the head suspension.
• a change in the crown over temperature has a slightly greater effect on the flying height than does a change in the camber.
• the crown ⁇ _ in Fig. 3A can change at least 0.5 ⁇ " over a 30°C change in temperature in drives using conventionally bonded head/flexure assemblies.
• it was determined through testing that the change in the crown over a similar 30°C change in temperature was only about 0.1 ⁇ ". It has further been determined by testing that, at least over a limited range of crown dimensions, there is a substantially linear relationship between a change in crown with temperature and a change in the flying height.
• a disk drive according to the present invention may operate at a substantially constant flying height, independent of temperature, and repeated intermittent contact which may otherwise occur at higher temperatures is avoided.

Landscapes

• Supporting Of Heads In Record-Carrier Devices (AREA)
• Adjustment Of The Magnetic Head Position Track Following On Tapes (AREA)

Applications Claiming Priority (3)

Publications (1)

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• 1994
  • 1994-11-07 EP EP95902439A patent/EP0728355A1/de active Pending
  • 1994-11-07 JP JP7513887A patent/JPH09508999A/ja active Pending
  • 1994-11-07 WO PCT/US1994/012674 patent/WO1995013612A1/en not_active Ceased

Non-Patent Citations (1)

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