Abrading – Abrading process – With tool treating or forming
Reexamination Certificate
2000-03-15
2001-07-03
Morgan, Eileen P. (Department: 3723)
Abrading
Abrading process
With tool treating or forming
C451S443000
Reexamination Certificate
active
06254461
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to utilizing diamond matrix-coated dressing disks to dress the surfaces of polishing pads of a glass disk polishing machine and, more specifically, a process to dress these polishing pads of a glass disk polishing machine.
BACKGROUND OF THE INVENTION
In the manufacture of magnetic disk drive data storage devices, the magnetic disk drives incorporate one or more magnetic data storage disks. Each magnetic data storage disk typically is made of a thin flat glass disk with its planar surfaces closely controlled to be flat and parallel to each other. The surfaces of the data storage disks are coated with a layer of magnetically alterable material which will accept and maintain different magnetic orientations within very small domains. The magnetic data storage disks are incorporated into and rotated at a very high speed by the magnetic disk drive. The magnetic disk drive also incorporates at least one magnetic read/write head positionable adjacent the data recording surface. As the data recording disk rotates, the air flow proximate the data recording surface of the disk causes the read/write head to “fly” or levitate a very small distance above the magnetic data storage disk surface. The read/write head does not make contact with the recording surface during normal operations due to the flow of the air between the disk surface and the read/write head. The closer the read/write head can fly to the surface of the data disk without impacting or contacting the surface at the disk, the more densely the data may be recorded, thereby both increasing the data storage capacity of the magnetic storage disks and shortening the requisite read/write cycles to either retrieve or record the data.
In order to accommodate a very close read/write head flight height, it is necessary to present a very flat and very smooth data disk surface to the read/write head. The basis for a flat and smooth recording surface is a very flat and very smooth substrate surface. A flat and smooth surface of a glass disk substrate is created by polishing flat surfaces on a glass disk with polishing pads, typically hard pads of urethane incorporating therein particles of cerium. Cerium is a soft malleable metal which lends itself to high quality polishing. The cerium provides the abrasive needed both to accomplish the removal of the minute quantities of glass if used with a polishing fluid to produce the required, very smooth surface on the glass disk. A liquid containing a fine suspension of cerium particles is flooded between the surfaces being polished and a polishing pad to further abrade the glass disk surface and to carry away the minute glass particles removed during polishing from the glass disks. During the polishing of the disks, a conventional and well-known process, the urethane/cerium polishing pads become glazed with glass residue of the polishing process and small cerium particles that are eroded from the polishing pad. Any degradation of the surface of the polishing pads reduces the polishing efficiency of the polishing operation.
The cerium loaded urethane polishing pads are available fro Universal Photonics, Hicksville, N.Y. 11801. The preferred polishing pads are designated L66 Cerium Loaded Urethane Pads.
Therefore, dressing the polishing pads of a polishing machine is a normal but very time consuming maintenance requirement in a high quality polishing process to achieve the desired, high quality, polished surfaces. In order to renew the polishing surfaces of the polishing pad and remove the glazing and other debris from the surface of the polishing pad, a small portion of the surface of the polishing pad must be removed, abrading or cutting off and rendering exposed new surfaces of the cerium particles trapped in the urethane pad. The newly exposed surfaces of the cerium particles incorporated in the urethane matrix are abraded to a smooth surface.
Refer now to
FIGS. 1
,
2
and
3
. Apparatus of the prior art as illustrated in
FIG. 1
is a schematic of a portion of a conventional planetary polishing machine
10
, as viewed from the top. Central rotary drive
12
is provided with a gear-shaped outer circumference
15
forming, in effect, a driven sun gear
14
. Central rotary drive
12
is engaged by the outwardly projecting gear teeth
30
on the periphery of driven planetary ring
16
. Planetary ring
16
is positioned intermediate the central rotary drive
12
and fixed interior ring gear
18
, which is either formed into or positioned within the interior of tub
20
. The tub
20
remains stationary; with gear teeth
30
on planetary ring
16
engaged with interior gear
18
, the central rotary drive
12
rotates planetary ring
16
, and thus, planetary ring
16
will be driven around the interior ring gear
18
within tub
20
. Tub
20
supports a polishing pad
22
for polishing glass substrate disks (not shown) from which magnetic data storage disks are made.
The dressing rings
16
are annular rings
16
of a high strength metal such as steel or stainless steel, which support on each of their annular surfaces
26
a plurality of pellets
24
, typically thirty to forty. These pellets
24
, approximately 0.25 inches (6.4 mm) in height, 0.75 inch (19.1 mm) in diameter, are a matrix of material binding diamond particles
36
. The pellets
24
are formed by sintering a hot isostatically pressed body of a mixture of nickel particles and diamond particles
36
. The pellets
24
are bonded onto the metal ring
16
. The metal rings
16
are provided with gear teeth
30
cut into the outer periphery
32
to mesh with the gear-shaped outer circumference
15
of central rotary drive
12
. Dressing rings of the type described above may be secured from Mitsui Mining and Smelting Co., Osaka, Japan.
The planetary rings
16
are employed in sets; a plurality, preferably five, are used at one time in the polishing machine
10
. Prior to the use of the dressing rings
16
in a dressing operation as well as at repeated intervals during the life of the dressing rings
16
, the faces
34
of the pellets
24
are ground not only to be flat but also to be a uniform height above the ring surface
17
. The surfaces
34
of the pellets
24
on opposite sides of rings
16
also must be ground completely parallel to each other to prevent one leading edge
28
of a pellet
24
from gouging the polishing pad
22
.
The dressing of the polishing pads
22
is accomplished by lowering a similar polishing pad (not shown) onto the dressing rings
16
and particularly onto faces
34
of pellets
24
and rotating the central rotary drive
12
. Because the pellets
24
move over the polishing pad
22
, the sharp corners or leading edge
28
of the pellets
24
and the exposed edges of diamonds
36
cut and remove thin layers of urethane and cerium from the polishing pad
22
, the smooth flat faces of the diamond particles smooth the surface of polishing pad
22
. A fluid is flowed over the polishing pad
22
and dressing rings
16
to flush away dressed particles removed from the polishing pads
22
. The fluid typically is water provided in a large enough flow to accomplish the desired flushing function.
To avoid damaging polishing pads
22
by concentrating excessive force on the interface between the polishing pad
22
and the nickel/diamond matrix pellets
24
, polishing machine
10
is operated at a reduced speed and with only a moderate force exerted on the polishing pads
22
and on each dressing ring
16
by pellets
24
.
The polishing machine
10
is operated in the dressing operation for a period of an hour or more, which is non-productive down time.
OBJECTS OF THE INVENTION
It is an object of the invention to rapidly but accurately remove glazing, abrasive and matrix material from polishing surfaces of polishing pads of a planetary polishing machine.
It is another object of the invention to improve the utility of the polishing machine.
It is still another object of the invention to eliminate the need for maintaining precise flatness on the dressing face of diamond matrix pe
Benning Frederick P.
Fox Dennis L.
Hagan James A
Lindemann Kerry R.
Mabe Donald L.
International Business Machines - Corporation
Letson Laurence R.
Morgan Eileen P.
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