Measuring and testing – Surface and cutting edge testing – Roughness
Reexamination Certificate
2000-03-24
2002-08-20
Larkin, Daniel S. (Department: 2856)
Measuring and testing
Surface and cutting edge testing
Roughness
Reexamination Certificate
active
06435016
ABSTRACT:
FIELD OF INVENTION
The present invention relates to the production and use of magnetic or magneto-optical memory disks. Broadly speaking, the present invention concerns improved slider constructions, such as burnishing heads or glide heads, which may be employed during the production of such disks. The present invention, however, is also more particularly directed to head gimbal assemblies and tests devices incorporating these improved slider constructions.
BACKGROUND OF THE INVENTION
For years, magnetic disks have been employed in various types of data processing systems. A magnetic disk may be in the form of an auxiliary storage device such as a floppy disk, CD ROM, DVD, or the like, which is used to store and retrieve programs and data, or an arrangement of internal storage devices such as hard disks which are permanently enclosed in a drive compartment.
Generally, the hard disk drive within which rigid, magnetic memory disks are mounted is akin to a conventional record turntable in that there is a mechanism for rotating the disk and for translating a read/write data head across the surface of the disk to allow for access to a selected annular track. The magnetic disks are typically journaled for rotation about a spindle in a spaced relationship to one another. A tracking arm is associated with each disk and the data head is mounted to this tracking arm for accessing the desired information. These data heads are typically referred to as “flying” data heads because they do not contact the surface of the disk during rotation. Rather, a data head hovers above the disk surface on an air bearing that is located between the disk and the head.
One concern during the production of rigid, magnetic memory disks is to ensure that asperities (i.e. protrusions on the surfaces of the disks) and particulate debris are adequately removed. Failure to do s o may cause an anomaly when an asperity is encountered by the data head during high speed revolutions, potentially causing errors in the transfer of information or even damage to the data head during operation. In an effort to reduce the occurrences of asperities, manufacturers commonly burnish the memory surfaces of the disks to remove the asperities. This is typically accomplished through the use of a particular head gimbal assembly known in the art as a burnishing head assembly. In the burnishing process, a burnishing head, sometimes more generally referred to as a slider, is mounted in a similar manner relative to the disk as discussed above. During the burnishing process, the burnishing head operates to polish these surface protrusions.
To further illustrate the burnishing process, reference is made to prior art
FIG. 1
where a pair of burnishing head assemblies
10
and
12
are shown in use to remove asperities on opposite surfaces of a rigid magnetic memory disk
20
that is journaled for rotation about a spindle
26
. While
FIG. 1
only depicts the burnishing apparatus associated with a single rigid memory disk
20
, it should be appreciated that a plurality of rigid memory disks may be rotatably journaled about spindle
26
, with each of these memory disks having an associated pair of burnishing head assemblies. Each of burnishing head assemblies
10
and
12
includes an associated burnishing head, a flexure and a mounting structure that are adapted for use with a system for burnishing one of the moving surfaces of disk
20
. Specifically, upper burnishing head assembly
10
has an associated mounting structure
11
to which is secured a flexure
13
and a slider in the form of a burnishing head
15
. Burnishing head assembly
10
is employed to shave asperities and eliminate particulate debris on an upper surface
22
of disk
20
. Similarly, lower burnishing head assembly
12
is employed to shave asperities and eliminate particulate debris on a lower surface
24
of disk
20
, and lower burnishing head assembly
12
includes an associated mounting structure
14
to which is secured a flexure
16
and a slider in the form of a burnishing head
18
.
In the past, alumina titanium carbide (AlTiC) has been the predominant composition by which burnishing heads are fabricated, and many burnishing heads additionally incorporate a diamond-like carbon (DLC) coating. Burnishing heads in the past have also been composed of aluminum oxide (Al
2
O
3
), as discussed in U.S. Pat. No. 4,330,910, issued May 25, 1982 to Schachl et al.
The next step in further refining magnetic disks once the burnishing operation is completed is through the use of a glide head. The purpose of a glide head is to detect, via proximately or contact, any remaining asperities which may come into contact with the data head during use. Glide heads hover and detect asperities which are located above specified data head flying heights. Glide heads, thus, dynamically test the integrity of surfaces of magnetic disk media.
For manufacturers to develop production quality rigid memory disks, it is necessary to utilize glide heads having more sensitive response characteristics. Unfortunately, many glide head assemblies have inherent problems associated with them because it is difficult to precisely control the electrical response characteristics of these devices. U.S. Pat. No. 5,689,064 to Kennedy, et al., issued Nov. 18, 1997, addresses this problem by providing, in part, a glide head assembly which incorporates a piezoelectric transducer disposed between a flexure and a slider in a cantilevered orientation. This problem is also addressed in U.S. Pat. No. 5,864,054 to Smith, Jr., issued Jan. 26, 1999, which discusses a legged piezoelectric transducer projecting from the side wall of a slider.
In any event, a glide head is also required to fly very close to the surface of a disk, at a flying height of less than 1 &mgr;-inch (250 Å), in order to effectively detect the presence of asperities which project above specified data head flying heights. It is, therefore, not uncommon for glide heads also to come into contact with asperities which have not been completely removed during the burnishing process.
Reference is now made to prior art
FIG. 2
to illustrate the ability of a glide head assembly to detect the presence of asperities on disk
20
once the burnishing process is completed. A more detailed discussion of this phase in the manufacturing process may be found in either U.S. Pat. No. 5,689,064 or U.S. Pat. No. 5,864,054, the respective disclosures of which are incorporated herein by reference. In prior art
FIG. 2
, glide head assembly
30
is shown in use detecting the presence asperities on upper surface
22
of rigid magnetic memory disk
20
. Although not shown, another glide head assembly could be employed in a similar fashion to detect asperities on the lower surface of disk
20
. Glide head assembly
30
communicates detection results, via electrical leads
32
and paddleboard
34
to an appropriate processing system (not shown). Throughout the testing procedure, disk
20
rotates with a varying angular velocity “w” so that upper surface
22
passes beneath glide head assembly
30
with a constant linear velocity. As disk
20
rotates, glide head assembly
30
is moved inwardly in the direction “R” a selected speed so that the entire upper surface area of disk
20
passes therebelow.
The magnetic media industry, in particular, is requiring that magnetic recording disks have increasing recording densities. Commensurate with this is the need for burnishing heads and glide heads to hover at ever decreasing flying heights above a disk's surface to produce flatter, smoother finishes on these rigid, magnetic disks. Currently, it is necessary to achieve a disk flatness between approximately 1.5 &mgr;m and 10 &mgr;m and a surface roughness (Ra) value that is between 3 and 12 Angstroms in order to keep up with industry demands. However, existing AlTiC sliders, whether burnishing heads or glide heads, are becoming a less viable solution during the production of rigid memory disks due to the relatively weak bond strength between the different materials. For exam
Bennett Donald A.
Clayton John
Kwon Oh-Hun
Smith, Jr. Stanley C.
Henson Michael R.
Larkin Daniel S.
Martin Timothy J.
Saint-Gobain Ceramics & Plastics, Inc.
Weygandt Mark H.
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