Method of making shallow etch air bearing surface features...

Details Method of making shallow etch air bearing surface features... Method of making shallow etch air bearing surface features...

1997-07-15

2002-07-23

Hall, Carl E. (Department: 3729)

Metal working

Method of mechanical manufacture

Electrical device making

Reexamination Certificate

active

06421908

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates in general to air bearing sliders for use with recording media and more particularly, to a slider having air bearing surface features which minimize the difference between the minimum mechanical slider/disk spacing and the magnetic head/disk spacing.
2. Description of Related Art
Conventional magnetic disk drives are information storage devices which utilize at least one rotatable magnetic media disk with concentric data tracks, a read/write transducer for reading and writing data on the various tracks, an air bearing slider for holding the transducer adjacent to the track generally in a flying mode above the media, a suspension for resiliently holding the air bearing slider and the transducer over the data tracks, and a positioning actuator connected to the suspension for moving the transducer across the media to the desired data track and maintaining the transducer over the data track during a read or a write operation.
In magnetic recording technology, it is continually desired to improve the areal density at which information can be recorded and reliably read. Because the recording density of a magnetic disk drive is limited by the distance between the transducer and the magnetic media, a goal of air bearing slider design is to “fly” an air bearing slider as closely as possible to a magnetic medium while avoiding physical impact with the medium. Smaller spacings, or “fly heights”, are desired so that the transducer can distinguish between the magnetic fields emanating from closely spaced regions on the disk.
Zone bit recording can provide significant performance and capacity improvements in magnetic disk storage files. In order to facilitate this technology, it is desirable to maintain a constant spacing between the read/write head and the disk across all the zones, from the inner-diameter (ID) to the outer-diameter (OD) of the disk. It is also desirable to fly as low as possible across the data zones to increase amplitude and resolution and further increase areal density and file capacity. However, low fly height causes concerns over mechanical reliability in the file, for both start/stop life and long term flyability.
Constant flying heights across the data zones presents a substantial challenge to slider design because the air velocity created by the rotating disk varies in both magnitude and direction relative to the air bearing slider at all radii in rotary actuator files.
An air-bearing slider also experiences fly height variations due to roll. For an air bearing slider with zero skew relative to disk rotation, roll is a measure of the angle of rotation about the longitudinal axis of the air bearing slider. Variations in roll occur when a resiliently mounted slider experiences a skewed air flow or the actuator experiences an impact with the disk. Insensitivity to roll variations is a crucial requirement of air bearing sliders.
Finally, an air bearing slider experiences varying conditions during the high speed radial movement of the actuator as it accesses data on various portions of the disk. High speed movement across the disk can lead to large values of slider roll, pitch and skew and a resultant variation in fly height. This is yet another reason that an air bearing slider must be insensitive to changes in roll, pitch and skew.
Typical taper-flat type sliders cannot satisfy the constant spacing requirements for zone-bit recording. For most rotary actuator configurations, the taper-flat slider flying height increases rapidly as the head is moved out from the ID. As it approaches the middle of the data band, it reaches a maximum spacing, which may be up to twice as large as the initial ID flying height. From there, the clearance drops as the air bearing slider moves toward the outer rim of the disk.
When any of the above described variations in fly height occur, they may result in contact between the air bearing slider and the rapidly rotating recording medium. Any such contact leads to wear of the air bearing slider and the recording surface and is potentially catastrophic.
Prior art slider designs have attempted to avoid this problem by addressing one or more of above described sensitivities, so as to produce an air bearing slider with uniform flying height under the varying conditions that may be experienced by the air bearing slider. Alternative designs for the air bearing surfaces have been developed to provide the required aerodynamic performance. Further, these designs frequently utilize trade-offs between the slider's pitch and roll to achieve the flat head/disk spacing desired. However, the rail width which provides the air bearing surface must also be capable of accommodating the read/write transducer. Consequently, variations in the slider's flying attitude can result in a much lower mechanical slider/disk spacing with a corresponding increase to the magnetic head/disk spacing.
For example,
FIG. 1
a
illustrates a prior art slider
10
having a leading edge
12
, a trailing edge
14
and two side edges
16
,
18
. As the disk begins to rotate, the slider pitches such that the leading edge
12
is raised with respect to the trailing edge
14
as shown in
FIG. 1
a
. The slider illustrated in
FIG. 1
a
includes two side rails
20
,
22
and a center rail
24
for a given performance standard. The two side rails
20
,
22
and the center rail
24
are disposed on a support structure
26
. A transducer
28
is disposed on the center rail
24
at the trailing edge
14
for performing read/write operations on the disk.
FIG. 1
b
illustrates a close-up view of the center rail
24
at the trailing edge
14
of the slider
10
. The head gap
32
of the transducer
28
is also shown. Under the above described conditions, the slider may experience roll, indicated by longitudinal displacement angle
34
, which may cause the slider to contact the rotating disk due to the much lower mechanical slider/disk spacing.
FIG. 2
illustrates how a nominal roll angle
34
causes the mechanical spacing of the center rail edge
42
to be substantially lower than the magnetic gap flying height.
FIG.
2
. illustrates a rear view of the prior art slider
10
along lines A—A of
FIG. 1
a
. The view in
FIG. 2
is exaggerated for clarity. In
FIG. 2
, the center rail
24
is shown disposed on the support structure
26
. As the slider
10
experiences a nominal roll angle
34
, the mechanical spacing
40
between the edge
42
of the center rail
24
and the disk
44
decreases while the magnetic spacing
46
between the head gap
48
and the disk
44
decreases to a lesser degree, remains the same or becomes greater depending upon whether the axis of the roll is displaced from the slider's central longitudinal axis.
FIG. 2
illustrates the situation where the magnetic spacing
46
between the head gap
48
and the disk
44
becomes greater. The magnitude of the difference between the mechanical spacing
40
and the magnetic gap flying height
48
can be substantial. For example, a slider with a 400 &mgr;m trailing edge rail width and a nominal 50 &mgr;rad flying roll attitude will have a minimum mechanical spacing
40
that is ten nanometers (nm) lower than the desired magnetic spacing
46
fly height causing the slider to be raised for increased wear resistance, i.e., increased life-time.
It can be seen then that there is a need for a slider that has air bearing surface features which minimize the difference between the minimum mechanical slider/disk spacing and the magnetic head/disk spacing.
It can also be seen that there is a need for a slider having shallow etch features that allow optimization of transducer spacing.
It can also be seen that there is a need for a disk drive having a slider which exhibits a narrow trailing edge rail while still providing adequate area for the read/write transducer thereby minimizing the difference between the minimum mechanical slider/disk spacing and the magnetic head/disk spacing.
SUMMARY OF THE INVENTION
To overcome the limitations in the prior art

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