Altitude insensitive air bearing using pitch compensation for data storage application

An air bearing slider for supporting a magnetic read/write head on a moving disk includes at least one front force carrying pad located in front of a suspension pivot point of an air bearing slider, at least one rear force-carrying pad located behind the suspension pivot point of the air bearing slider, and a trailing-edge pad having a magnetic read/write head embedded in a rear portion of the trailing-edge pad. Each front force-carrying pad carries a front air bearing force that is generated by a relative motion between a surface of the disk and the slider when the surface of the disk has a predetermined disk velocity with respect to the slider. Each rear force-carrying pad carries a rear air bearing force that is generated by the relative motion between the surface of the disk and the slider. The trailing edge pad carries substantially no air bearing force. According to the invention, as an atmospheric pressure associated with the air bearing slider decreases, a flying height associated with each front force-carrying pad and each rear force-carrying pad decreases so that a pitch angle of the air bearing slider decreases and a flying height associated with the trailing-edge pad at the magnetic read/write head changes by less than 5 nm at a predetermined disk velocity.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to the field of data storage devices. More 
particularly, the present invention relates to an air bearing slider for 
use with a read/write head of a disk drive. 
2. Description of the Related Art 
FIG. 1 shows a high RPM disk drive 10 having a two-stage, or piggy-back, 
servo system for positioning a magnetic read/write head (or a recording 
slider) over a selected track on a magnetic disk 11. The two-stage servo 
system includes a voice-coil motor (VCM) 13 for coarse positioning a 
read/write head suspension 12 and a microactuator, or micropositioner, for 
fine positioning the read/write head over the selected track. FIG. 2 shows 
an enlarged exploded view of the read/write head end of suspension 11. An 
electrostatic rotary microactuator 14 is attached to a gimbal structure 15 
on suspension 12, and a slider 16 is attached to the microactuator. A 
read/write head 17 is fabricated as part of slider 16. 
Air bearing slider designs for a data storage applications, such as the 
disk drive 10, provide a flying interface between a magnetic head and a 
magnetic medium recording disk. The interface is cushioned by a thin layer 
of air that prevents excessive, undesirable head/disk contacts that can 
cause damage to the head or the disk. The air bearing force that acts to 
maintain the head/disk spacing, however, is influenced by the atmospheric 
pressure. As the atmospheric pressure decreases, such as when a disk drive 
is used at an altitude above sea level, the flying height of the air 
bearing slider usually decreases and unwanted head/disk contacts may 
occur. In the situation when the flying height of the air bearing slider 
increases as the atmospheric pressure decreases, the magnetic read head 
may lose signal amplitude, therefore rendering the disk drive 
non-functional. 
It has always been a primary design objective to minimize the altitude 
flying height change of a magnetic element on an air bearing slider as a 
function of atmospheric pressure. Conventional positive-pressure air 
bearing designs have a large altitude sensitivity. Conventional 
negative-pressure air bearing designs have improved the altitude 
sensitivity of sliders, but have not totally eliminating the effect. 
What is needed is an air bearing slider that is virtually altitude 
insensitive, and is applicable to both positive- and negative-pressure air 
bearing types. 
SUMMARY OF THE INVENTION 
The present invention provides an air bearing slider that is virtually 
altitude insensitive, and is applicable for both positive- and 
negative-pressure air bearing types. The advantages of the present 
invention are provided by an air bearing slider that includes at least one 
front force-carrying pad located in front of a suspension pivot point of 
an air bearing slider, at least one rear force-carrying pad located behind 
the suspension pivot point of the air bearing slider, and a trailing-edge 
pad having a magnetic read/write head embedded in a rear portion of the 
trailing-edge pad. Each front force-carrying pad carries a front air 
bearing force, while each rear force-carrying pad carries a rear air 
bearing force. The trailing edge pad carries substantially no air bearing 
force. According to the invention, as an atmospheric pressure associated 
with the air bearing slider decreases, a flying height associated with 
each front force-carrying pad and each rear force-carrying pad decreases 
so that a pitch angle of the air bearing slider decreases and a flying 
height associated with the trailing-edge pad at the magnetic read/write 
head changes by less than 5 nm at a predetermined disk velocity. 
One embodiment of the present invention is a negative-pressure air bearing 
slider having two front force-carrying pads and two rear force-carrying 
pads. Another embodiment of the present invention is a negative-pressure 
air bearing slider having two front force-carrying pads and one rear 
force-carrying pad. Still another embodiment of the present invention is a 
positive-pressure air bearing slider having two front force-carrying pads 
and two rear force-carrying pads. Yet another embodiment of the present 
invention is a positive-pressure air bearing slider having two front 
force-carrying pads and one rear force-carrying pad.

DETAILED DESCRIPTION 
The present invention provides an altitude insensitive air bearing slider 
(AIABS) that is applicable for both positive- and negative-pressure air 
bearing types. FIG. 3 shows a side view of an air bearing slider 30 having 
pitch compensation according to the present invention. Air bearing slider 
30 includes a slider body 31 that is attached to a suspension in a 
well-known manner. Point S on slider body 31 is the pivot point of the 
suspension. Slider 30 also includes at least one front force-carrying pad 
32 located in front of suspension pivot point S, and at least one rear 
force-carrying pad 33 located behind suspension pivot point S. A 
trailing-edge pad 34 is attached to slider 30 at a rear edge of slider 30. 
Trailing-edge pad 34 has a magnetic read/write head 35 that is embedded in 
a rear portion of trailing-edge pad 34. 
Each front force-carrying pad 32 carries a front air bearing force. 
Similarly, each rear force-carrying pad 33 carries a rear air bearing 
force. According to the invention, trailing edge pad 34 carries 
substantially no air bearing force. As an atmospheric pressure associated 
with air bearing slider 30 decreases, a flying height associated with each 
front force-carrying pad 32 and each rear force-carrying pad 33 decreases 
so that a pitch angle .alpha. of the air bearing slider decreases and a 
flying height h associated with trailing-edge pad 34 changes by less than 
5 nm at a predetermined disk velocity U. For example, slider 30 has a 
pitch angle .alpha..sub.1 at sea level for a predetermined disk velocity 
U. As the atmospheric pressure decreases, either through a weather-related 
change in an ambient atmospheric pressure or by an increase in altitude, 
the pitch angle of slider 30 decreases to pitch angle .alpha..sub.2. 
Flying height h of trailing-edge pad 34 remains substantially the same, 
whether the pitch angle of slider 30 is .alpha..sub.1 or .alpha..sub.2. 
FIG. 4A shows an exemplary omnipad configuration 40 for a negative-pressure 
air bearing according to the present invention. FIGS. 4B and 4C 
respectively show minimum fly height and element fly height versus radius 
of rotation for different atmospheric pressures for the negative-pressure 
omnipad air bearing slider configuration of FIG. 4A. Omnipad configuration 
40 can be made to be a negative-pressure type air bearing slider using a 
shallow etch process in a well-known manner to form step areas 41 and 43, 
with a step area 42 being formed by a deep etch process in a well-known 
manner. Alternatively, omnipad configuration 40 can be made to be a 
positive-pressure type air bearing slider using a deep etch process in a 
well-known manner to form step areas 41 and 42, with step area 43 being 
formed by a shallow etch process in a well-known manner. In FIGS. 4B and 
4C (and FIGS. 5B, 5C, 6B, 6C, 7B, 7C, 8B and 8C), a square-shaped data 
point is at sea level, a diamond-shaped data point is at 5000 feet above 
sea level, and a triangular-shaped data point is at 10,000 feet above sea 
level. At any radius of rotation, the flying height h associated with 
trailing-edge pad 34 changes by less than 5 nm as the atmospheric pressure 
decreases. 
FIG. 5A shows a first exemplary four-pad configuration 50 for a 
negative-pressure air bearing slider according to the present invention. 
FIGS. 5B and 5C respectively show minimum fly height and element fly 
height versus radius of rotation for different atmospheric pressures for 
the first negative-pressure four-pad air bearing slider configuration 50 
of FIG. 5A. In FIG. 5A, two front force-carrying pads 32 are separated by 
a gap 51, which is part of an etch region 53, while the rear 
force-carrying pad 33 is a single rear force-carrying pad. The first 
four-pad configuration 50, as with the configuration shown in FIG. 6A, can 
be made to be a negative-pressure type air bearing slider using a shallow 
etch process in a well-known manner to form step area 52 and a deep etch 
process in a well-known manner to form step area 53. 
FIG. 6A shows a second exemplary four-pad configuration 60 for a 
negative-pressure air bearing slider according to the present invention. 
FIGS. 6B and 6C respectively show minimum fly height and element fly 
height versus radius of rotation for different atmospheric pressures for 
the second negative-pressure four-pad air bearing slider configuration 60 
of FIG. 6A. In FIG. 6A, two front force-carrying pads 32 are separated by 
a gap 61, which is part of a shallow etch region 52, while the rear 
force-carrying pad 33 is a single rear force-carrying pad. 
FIG. 7A shows a first exemplary four-pad configuration for a 
positive-pressure air bearing slider 70 according to the present 
invention. FIGS. 7B and 7C respectively show minimum fly height and 
element fly height versus radius of rotation for different atmospheric 
pressures for the first positive-pressure four-pad air bearing slider 
configuration 70 of FIG. 7A. In FIG. 7A, two front force-carrying pads 32 
are separated by a gap 71, which is part of a deep etch region 72, while 
the rear force-carrying pad 33 is a single rear force-carrying pad 
surrounded by a shallow etch region 73. 
FIG. 8A shows a second exemplary four-pad configuration 80 for a 
positive-pressure air bearing slider according to the present invention. 
FIGS. 8B and 8C respectively show minimum fly height and element fly 
height versus radius of rotation for different atmospheric pressures for 
the second positive-pressure four-pad air bearing slider configuration of 
FIG. 8A. In FIG. 8A, two front force-carrying pads 32 are separated by a 
gap 81, which is part of a deep etch region 82, while the rear 
force-carrying pad 33 is a single rear force-carrying pad surrounded by a 
shallow etch region 83. Configuration 80 differs from configuration 70 by 
rear force-carrying pad 33 of configuration 80 being larger and farther 
forward than rear force carrying pad 33 of configuration 70. 
While the present invention has been described in connection with the 
illustrated embodiments, it will be appreciated and understood that 
modifications may be made without departing from the true spirit and scope 
of the invention.