Metal working – Burnishing
Reexamination Certificate
2001-08-30
2003-03-04
Vidovich, Gregory M. (Department: 3726)
Metal working
Burnishing
C451S063000, C451S290000
Reexamination Certificate
active
06526639
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to burnishing devices for hard disks, and more particularly to a method for burnishing hard disks using a partially flying burnish head having a plurality of burnishing pads.
2. Description of the Prior Art
A hard disk is cleaned and burnished following the deposition of thin film layers to remove debris and asperities from the surface. Such debris and asperities must be removed, or at least reduced in height, such that a slider will fly smoothly over the disk surface. As slider flying heights become lower for improved higher density disks, the disks must be burnished to a greater extent than was heretofore necessary to lower the projection height of such asperities and more efficiently remove disk surface debris.
Several different burnishing pad designs are currently utilized. Some heads have a burnishing ridge providing a burnishing edge that extends across the entire front surface of the head. Other current head designs have burnishing members on the left side and right side of the burnishing head, but have a lengthwise channel between the left and right burnishing members. In such heads, a significant portion of the burnishing head does not burnish the disk, resulting in significant inefficiency in the burnishing process.
A further prior art burnishing head is described in U.S. Pat. No. 4,845,816. It has a waffle type pattern of burnishing pads; that is, a plurality of diamond shaped burnishing pads that are disposed on the burnishing head surface. The diamond shaped pads are oriented such that the point of each diamond shaped pad is directed towards the media to be burnished. In distinction to this pad configuration, burnishing pads of the present invention each have a straight burnishing edge that is directed towards the media to be burnished. In a prior art variation of this waffle patterned head the leading burnishing pads may be triangularly shaped, as are the leading pads of the present invention.
In the prior art method for burnishing hard disks, the burnishing head is placed upon the surface of a rotating disk and moved radially across the surface of the disk as the disk rotates. There is full contact between the surface of the burnishing head and the surface of the rotating disk. In this disk burnishing method both high asperities and low asperities are contacted by the burnishing pads of the burnishing head and are removed. A large quantity of surface debris is thereby generated in the burnishing process. Significantly, it is not necessary to remove many of the low asperities, in that the flying height of a magnetic head slider of a disk drive is higher than the low asperities. Therefore, the prior art full contact burnishing head method of disk burnishing removes more asperities than are necessary, and thereby creates more surface debris which must be removed than is necessary.
A need therefore exists for improvements in the methods for burnishing hard disks in which high asperities are removed and in which low asperities are not removed, such that the creation of surface debris in the burnishing process is minimized while the failure rate of hard disks following burnishing is decreased. The present invention provides a method for burnishing hard disks that accomplishes these results.
SUMMARY OF THE INVENTION
The disk burnishing method of the present invention utilizes a burnishing head as described above in a disk contact flying configuration. That is, the disk burnishing process is conducted such that the leading edge of the burnishing head is disposed above the surface of the disk, while the trailing edge of the burnishing head makes contact with the surface of the disk; this partially flying burnishing head configuration is termed “contact flying” herein. The contact flying configuration of the burnishing head is obtained by controlling the rotating disk RPM in conjunction with the burnishing head design characteristics, such that the forward edge of the burnishing head is lifted off the disk surface while the trailing edge makes contact with the disk surface.
A preferred embodiment of a burnishing head for hard disk processing according to the method of the present invention includes a solid body having generally rectangular surfaces, including an upper surface, a burnishing pad surface, a front surface, a rear surface and two side surfaces. A plurality of burnishing pads are disposed upon the burnishing pad surface. The pads are shaped such that each pad has a burnishing edge that is generally parallel to said front surface and therefore orthogonal to the direction of media travel. The burnishing pads are preferably configured such that two frontward leading pads are disposed proximate the front surface in a spaced apart relationship and one leading middle pad is disposed rearwardly of the two frontward leading pads and generally between the two frontward leading pads. Two rear pads are disposed generally rearwardly of the leading middle pad in a spaced apart relationship, and one rearward pad is disposed rearwardly of the two rear pads and generally between the two rear pads. In the preferred embodiment the pads are generally triangular in shape and the outer surface of the leading and rearward pads is tapered.
When disk burnishing is performed utilizing the contact flying burnishing head, the burnishing edges of the several burnishing pads are disposed at different heights relative to the disk surface, such that the leading burnishing pad edges are higher than the trailing burnishing pad edges. In this contact flying configuration, high asperities are trimmed by the burnishing pads while low asperities are not. Thus, a disk is properly burnished for subsequent hard disk drive performance with a minimum of surface debris being created by the burnishing process.
It is an advantage of the present invention that a more efficient disk burnishing method is provided.
It is another advantage of the disk burnishing method of the present invention that the amount of surface debris generated during the disk burnishing process is minimized.
It is a further advantage of the disk burnishing method of the present invention that high asperities on a hard disk are removed, while low asperities are not removed.
It is yet another advantage of the disk burnishing method of the present invention that the disk qualification glide height can be reduced.
It is yet a further advantage of the disk burnishing method of the present invention that the hard disk failure rate following burnishing is reduced.
It is still another advantage of the disk burnishing method of the present invention that the disk production yield is increased.
It is still a further advantage of the disk burnishing method of the present invention that the burnishing head wear is reduced, such that the head lifetime is increased.
It is yet another advantage of the disk burnishing method of the present invention that damage to disks during the burnishing process is reduced.
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Duan Shanlin
Lee Wei-Ming
Lo Yu
Guillot Robert O.
Intellectual Property Law Offices
Omgba Essama
Vidovich Gregory M.
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