Glide head with side mounted transducer

Details Glide head with side mounted transducer Glide head with side mounted transducer

2000-03-09

2002-01-15

Larkin, Daniel S. (Department: 2856)

Measuring and testing

Surface and cutting edge testing

Roughness

Reexamination Certificate

active

06338269

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to glide heads used to detect defects on the surface of magnetic or magnetic-optical memory disks such as those used in hard disk drives.
BACKGROUND
A computer hard disk drive comprises a memory disk mounted on a spindle which is driven by a motor to rotate the disk at high speed. A read/write head, kept in close proximity to the surface of the rotating disk, reads or writes data on the disk, which may be a magnetic or magneto-optic disk. The read/write head is separated from the surface of the disk by an air bearing created by the high speed rotation of the disk. The read/write head flies on this air bearing, e.g., at a height of approximately 1&mgr;″ (one microinch) above the surface of the disk. The density of the information written on the disk is increased as the read/write head flies closer to the surface of the disk. Thus, it is desirable for the read/write head to fly as close as possible to the surface of the magnetic disk.
Typical memory disks comprise, e.g., an aluminum substrate that is plated with a hard material, such as a nickel phosphorus alloy. The nickel phosphorus is then textured or roughened. An underlayer, a magnetic alloy or magnetic-optical material, and a protective overcoat are then deposited on the nickel phosphorus, e.g., by sputtering. The disk manufacturing process leaves the surface of the disk in a slightly roughened condition. Although magnetic disks are typically textured to have a specified roughness, there has been a trend in the industry to make magnetic disks smoother and smoother. Presently, some magnetic disks are specified to have a roughness less than or equal to about 30 Å (3 nm).
The precision with which the read/write head flies over the magnetic disk requires that care is taken during manufacturing to assure that there are no protrusions or asperities on the disk surface that may interfere with the read/write head. A protrusion on the surface of the disk that contacts the read/write head during use may damage the head or the disk.
Accordingly, tests are performed on finished disks using media certifiers to determine if there are any asperities, voids, or contamination that might interfere with the read/write head. Accurate testing of disks for such defects assures that the disk manufacturer does not unnecessarily reject good quality disks or pass on poor quality disks that may later fail.
Glide heads are used in conjunction with media certifiers to detect the asperities and depressions. Glide heads are similar to read/write heads in that it includes a slider which rests or flys on the air bearing formed by the rotating disk. A transducer is mounted on the glide head. If the glide head collides with a defect on the rotating disk, e.g. an asperity, the mechanical shock from the collision with the defect will cause the transducer to create an electrical signal, which is received by a circuit in the media certifier via wires. This circuit identifies signals caused by collisions between glide head and defects. The larger the defect, the larger the electrical signal created by the transducer and sensed by the circuit within the media certifier.
In general, glide heads, like read/write heads, have continued to decrease in size over time. For example, glide heads, and sliders in general, decreased in size to 70% sliders (the percentage describes the size of the glide head relative to the original slider size, which is known as 100%) to the now industry standard 50% glide heads. An original 100% slider has a length of 0.16 inches, a width of 0.125 inches, and a height of 0.034 inches. The suspension arms to which glide heads are mounted, however, have not had a corresponding reduction in size.
FIGS. 1 and 2
show bottom and front views, respectively, of a conventional 50% glide head
10
. Glide head
10
includes a slider
12
that has two rails
14
and
16
with respective tapered leading ends
15
and
17
. Glide head
10
also includes a wing
18
that serves as an extension to the slider
12
.
FIG. 2
shows a suspension arm
20
mounted to the top surface of slider
12
and a transducer
22
mounted to the top surface of wing
18
. The suspension arm
20
positions glide head
10
over the disk as it rotates while glide head
10
tests the disk for defects. Transducer
22
is conventionally a piezoelectric transducer and is used to convert the mechanical energy that is created by glide head
10
physically contacting an asperity on the surface of the disk to an electric signal. Other types of transducers may also be used.
Glide head
10
is called a 50% glide head because slider
12
is approximately 50% the size of an original 100% glide head. As is well understood in the art, however, with wing
18
serving as an extension to slider
12
, the overall width of glide head
10
, including slider
12
and wing
18
, is approximately the same as an original 100%. A 50% glide head has, e.g., a length L
10
of approximately 0.080 inches, a total width W
TOT10
of approximately 0.10 inches (with slider
12
width W
12
approximately 0.060 inches, and wing width W
18
approximately 0.040 inches), and a height H
10
of approximately 0.024 inches.
FIG. 3
shows a top view of suspension arm
20
mounted to the top surface of glide head
10
. It should be understood that while
FIG. 3
shows a top view of suspension arm
20
, glide head
10
is shown in its entirety, i.e., slider
12
is shown unobscured, for the sake of clarity. As can be seen in
FIG. 3
, the width of slider
12
is approximately the same as the width W
20
of suspension arm
20
, which is approximately 0.070 inches. With larger glide heads, i.e., 100% and 70% glide heads, the slider portion was large enough that the suspension arm
20
did not cover the entire top surface of the slider. Consequently, the transducer could be mounted to the top surface of the glide head slider without interfering with the suspension arm. However, as shown in
FIG. 3
, with a 50% glide head, the slider
12
is approximately the same size as the suspension arm
20
, leaving no room to mount a transducer. Thus, wing
18
is used as an extension to slider
12
and extends the top surface of glide head out from under the suspension arm
20
. Consequently, transducer
22
can be mounted on wing
18
without interfering with suspension arm
20
.
The next reduction in size for glide heads will be 30%, i.e., the glide head slider is 30% of the 100% slider.
FIG. 4
is a perspective view of a conventional 30% slider
30
. Slider
30
includes two rails
32
and
34
with tapered leading ends
33
and
35
, respectively. A conventional slider
30
has dimensions that are approximately 30% of a 100% slider, e.g., a length L
30
of approximately 0.048 inches, a width W
30
of approximately 0.038 inches, and a height H
30
of approximately 0.010 inches.
Because the size of suspension arms have not had a decrease in size corresponding to the decrease in the size of sliders, 30% slider
30
will be much smaller than a suspension arm, leaving no room for a transducer to be mounted to slider
30
. Thus, like the 50% glide head
10
, shown in
FIG. 3
, a transducer cannot be mounted to the top surface of a 30% glide head without the presence of a wing that extends beyond the suspension arm.
FIG. 5
shows a top view of suspension arm
20
mounted to the top surface of a 30% glide head
40
, which includes slider
30
and a wing
36
that extends from slider
30
. As shown in
FIG. 5
, wing
36
extends beyond suspension arm
20
by an amount sufficient for transducer
22
to be mounted to wing
36
without interfering with suspension arm
20
.
FIG. 5
, similar to
FIG. 3
, shows slider
30
in its entirety, i.e., unobscured by the suspension arm
20
, for the sake of clarity. Because wing
36
is required to extend beyond suspension arm
20
and to provide a large enough surface to mount transducer
22
, the wing
36
of glide head
40
is much larger than slider
30
. Consequently, wing
36
will alter the flight characteristics of glide head
40
. For ex

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