Abrading – Abrading process – Side face of disk
Reexamination Certificate
1999-10-19
2001-09-04
Rose, Robert A. (Department: 3723)
Abrading
Abrading process
Side face of disk
C451S168000, C451S173000
Reexamination Certificate
active
06283838
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an apparatus and method for burnishing the surfaces of a disk, and more specifically burnishing the surfaces of a disk with burnishing tape and pads.
BACKGROUND
Magnetic memory disks, such as the type typically used in a computer hard drive, have a smooth surface over which the read/write head flies during operation. The trend has been to reduce the fly height of the read/write head over the surface of the disk to increase the data recording density on the disk. While it is desirable for a read/write head to fly as close as possible to the surface of the disk, it is important that the read/write head does not contact the disk or defects on the surface of the disk. A defect on the surface of the disk that physically contacts the read/write head may damage the read/write head, the disk, or both. Consequently, care must be taken during the disk processing and testing to assure that there are no defects on the surface of the disk that are greater than the fly height of the read/write head, which today is approximately 1 &mgr;″ (microinch) or less.
Typical magnetic disks include an aluminum, glass, or silicon substrate that is plated with a NiP (nickel phosphate) layer and then textured, e.g., for the contact start stop zone. An underlayer of Cr (chromium) or NiP is sputtered on the plated NiP layer, a thin film of magnetic recording material, typically a Co (cobalt) alloy, is sputtered on the underlayer, followed by the deposition of a protective coating and a lubrication layer. The disk is then burnished to remove any asperities prior to testing the disk to assure the disk meets the required surface specifications. Presently, some magnetic disks are specified to have a roughness less than or equal to about 30 angstroms (3 nanometers).
In conventional methods of burnishing the surfaces of a disk, an abrasive burnishing tape is used. Prior art devices for burnishing a disk with an abrasive tape include the use of air knives and rollers and in some instances the combination of the two. A disadvantage with the use of air knives and rollers is that it is difficult to control the force used to press the burnishing tape against the disk and to ensure that an equal amount of force is applied to both sides of the disk. Without precise control of the force applied to both sides of the disk, one side of the disk may be burnished more than the other. Further, if one side of the disk has a much greater force applied to it than the other, the disk may be damaged. In addition, with air knives it is difficult to control the precise area of the burnishing tape that is pressed against the disk. It is also difficult to burnish with an adequate amount of force without scratching the surface of the disk. Further, rollers are difficult to keep flat against the surface of the disk.
SUMMARY
A burnishing head in accordance with an embodiment of the present invention includes burnishing pads that press a burnishing tape against the surfaces of a disk. The pads are mounted on pad holders that move to press the burnishing tape against the surfaces of the disk with the pads. The burnishing apparatus also includes tape guides that hold the burnishing tape away from the pads when the pads are not pressed against the surfaces of the disk. With the burnishing tape separated from the pads, the burnishing tape may be indexed without damaging or dislodging the pads from the pad holders. As the pad holders move the pads away from the disk, the tape guides apply tension to the burnishing tape used to keep the burnishing tape from contacting the pads. As the pad holders move the pads into contact with the disk, the tape guides release tension on the burnishing tape to prevent uncontrolled deformation of the pads. Consequently, the entire footprint of each pad is used to press the burnishing tape into contact with the surfaces of the disk.
The burnishing apparatus operates by mounting a disk on a disk handling apparatus, such as a motor driven spindle. The disk is then moved between the pads of the burnishing apparatus. As the pads are moved to press the burnishing tape against the surfaces of the disk, the tape guides release tension on the burnishing tape. Because there is little or no tension on the burnishing tape during the burnishing process, the entire footprint of the pads press the burnishing tape against the surfaces of the disk.
Once the disk is burnished, the pad holders are separated, e.g., by way of a pneumatic actuator or a stepper motor. As the pads are moved away from the surface of the disk, tension is applied to the burnishing tape. The burnishing tape is held away from the pads as the burnishing tape is indexed. Additionally, the disk is removed from between the burnishing pads, and the disk is replaced with the next disk to be burnished. The next disk is then moved between the pads, which then are moved to press an unused portion of the burnishing tape into contact with the surfaces of the next dish.
In accordance with another embodiment of the present invention, the pads are mounted on pad holders that are coupled together with a tension spring. The tension spring biases the pad holders together such that the pads automatically press against the surfaces of the disk with an equal amount of force. The pad holders are slidably mounted on a rail which permits the pad holders to slide away from and toward each other. The pad holders have the freedom to slide in unison so that when the pads are pressed against the surfaces of the disk, the pads automatically align with the center of the disk. A separating mechanism, such as a pneumatic actuator, is used to overcome the bias of the spring and to move the pads away from the disk, for example, when the disk is being replaced and the burnishing tape is indexed.
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Blake Elree
Chen Shaun H.
Hipsley Scott M.
Walsh Daniel K.
Halbert Michael J.
Komag Incorporated
Rose Robert A.
Skjerven Morrill & MacPherson LLP
Steuber David E.
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