U.S. patent application number 13/413836 was filed with the patent office on 2013-09-12 for system, method and apparatus for polishing workpieces.
This patent application is currently assigned to Hitachi Global Storage Technologies Netherlands B.V.. The applicant listed for this patent is Xing-Cai Guo, Thomas E. Karis, Bruno Marchon. Invention is credited to Xing-Cai Guo, Thomas E. Karis, Bruno Marchon.
Application Number | 20130237131 13/413836 |
Document ID | / |
Family ID | 49114530 |
Filed Date | 2013-09-12 |
United States Patent
Application |
20130237131 |
Kind Code |
A1 |
Guo; Xing-Cai ; et
al. |
September 12, 2013 |
System, Method and Apparatus for Polishing Workpieces
Abstract
A method of polishing workpieces includes final tape polishing
(FTP) a media disk by rotating the media disk; applying a liquid
that is substantially pure to the media disk adjacent to an FTP
tape; applying the FTP tape to the media disk at a pad load to
polish the media disk, such that the liquid acts as a transient
lubricant between the media disk and the FTP tape; and completing
FTP. The FTP process is completely independent of the final disk
lubricant, such that the final disk lubricant may be applied before
or after FTP.
Inventors: |
Guo; Xing-Cai; (Tracy,
CA) ; Karis; Thomas E.; (Aromas, CA) ;
Marchon; Bruno; (Palo Alto, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Guo; Xing-Cai
Karis; Thomas E.
Marchon; Bruno |
Tracy
Aromas
Palo Alto |
CA
CA
CA |
US
US
US |
|
|
Assignee: |
Hitachi Global Storage Technologies
Netherlands B.V.
Amsterdam
NL
|
Family ID: |
49114530 |
Appl. No.: |
13/413836 |
Filed: |
March 7, 2012 |
Current U.S.
Class: |
451/59 |
Current CPC
Class: |
B24B 21/10 20130101 |
Class at
Publication: |
451/59 |
International
Class: |
B24B 1/00 20060101
B24B001/00 |
Claims
1. A method of polishing a workpiece, comprising: (a) rotating the
workpiece; (b) applying a liquid that is substantially pure to the
workpiece adjacent to a polishing tape; (c) applying the polishing
tape to the workpiece at a pad load to polish the workpiece, such
that the liquid acts as a lubricant between the workpiece and the
polishing tape; and then (d) completing polishing of the
workpiece.
2. A method according to claim 1, wherein the workpiece is a media
disk, and further comprising sputtering the media disk with layers
of material prior to step (a).
3. A method according to claim 1, wherein the workpiece is
lubricated with a lubricant prior to step (a).
4. A method according to claim 3, wherein the lubricant has a
thickness of about 10 .ANG. or less.
5. A method according to claim 3, wherein the lubricant is bonded
to the workpiece, such that the lubricant is substantially
unremoved by the liquid.
6. A method according to claim 5, wherein the lubricant is soluble
in the liquid.
7. A method according to claim 3, wherein the lubricant is not
bonded to the workpiece, and the lubricant is non-soluble in the
liquid.
8. A method according to claim 1, wherein the workpiece is
lubricated after step (d).
9. A method according to claim 1, wherein the liquid is applied to
the workpiece without an abrasive, such that no abrasive is used in
the method other than the polishing tape.
10. A method according to claim 1, wherein the liquid is a neat,
undiluted volatile solvent that is applied via a pump-operated
needle syringe.
11. A method according to claim 1, wherein the liquid comprises a
fluorinated hydrocarbon and is inert relative to the workpiece,
such that the liquid does not texture the workpiece.
12. A method according to claim 1, further comprising adjusting the
pad load on the workpiece.
13. A method according to claim 1, further comprising adjusting an
injection speed of the liquid onto the workpiece.
14. A method according to claim 1, further comprising adjusting a
linear velocity and a transverse velocity of the polishing tape
relative to the workpiece.
15. A method according to claim 1, further comprising spin-coating
the liquid onto the workpiece before step (c), and spinning off the
liquid prior to step (d).
16. A method according to claim 1, wherein the liquid substantially
completely evaporates from the workpiece prior to step (d).
17. A method according to claim 1, wherein the liquid substantially
completely evaporates from the workpiece in less than about 10
seconds.
18. A method according to claim 1, wherein the liquid substantially
completely evaporates from the workpiece in less than about 1
second.
19. A method according to claim 1, further comprising circulating
the liquid through a particle filtration system prior to step
(b).
20. A method of polishing workpieces, comprising: (a) rotating a
workpiece having no lubricant; (b) applying a liquid to the
workpiece adjacent to a polishing tape; (c) applying the polishing
tape to the workpiece at a pad load to polish the workpiece, such
that the liquid acts as a transient lubricant between the workpiece
and the polishing tape; and then (d) lubricating the workpiece.
21. A method according to claim 20, wherein the workpiece is a
media disk and is sputtered with layers of material prior to step
(a), the liquid is applied to the workpiece without an abrasive,
and no abrasive is used in the method other than the polishing
tape.
22. A method according to claim 20, wherein the liquid is a neat,
undiluted volatile solvent that is applied via a pump-operated
needle syringe.
23. A method according to claim 20, wherein the liquid comprises a
fluorinated hydrocarbon and is inert relative to the workpiece,
such that the liquid does not texture the workpiece; and further
comprising at least one of: adjusting the pad load on the
workpiece; adjusting an injection speed of the liquid onto the
workpiece; and adjusting a linear velocity and a transverse
velocity of the polishing tape relative to the workpiece.
24. A method according to claim 20, further comprising circulating
the liquid through a particle filtration system prior to step (b),
spin-coating the liquid onto the workpiece before step (c), and
spinning off the liquid prior to step (d).
25. A method according to claim 20, wherein the liquid
substantially completely evaporates from the workpiece in less than
about 1 second and prior to step (d).
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Disclosure
[0002] The present invention relates in general to polishing
workpieces and, in particular, to an improved system, method and
apparatus for final tape polishing magnetic media disks for disk
drives.
[0003] 2. Description of the Related Art
[0004] Disks in hard disk drives are provided with a layer of
lubricant to better protect disks and the heads used to read data
from and write data to the disks. There continues to be interest in
reducing the thickness of the lubricant layer in order to increase
hard disk drive capacity. However, goals for lubricant thickness
have been reduced to such a value (e.g., approximately 10 .ANG. or
less) that it has become increasingly difficult to maintain a high
yield while manufacturing media through the final tape polish (FTP)
process.
[0005] FTP has set an upper limit on lubricant thickness that has
become somewhat of a road block in the implementation of new types
of lubricants. It would be advantageous to develop a new FTP
process that is completely independent of disk lubricant. Ideally,
such an FTP process would be useful and not affect media yield
regardless of whether FTP was performed before or after the
lubricant was applied to the disk, the type of lubricant used, and
the thickness of the lubricant (if present). Thus, there continues
to be interest in developing improved FTP processes.
SUMMARY
[0006] Embodiments of a system, method and apparatus for polishing
workpieces are disclosed. For example, a method of polishing a
workpiece may comprising rotating the workpiece; applying a liquid
that is substantially pure to the workpiece adjacent to a polishing
tape; applying the polishing tape to the workpiece at a pad load to
polish the workpiece, such that the liquid acts as a lubricant
between the workpiece and the polishing tape; and then completing
polishing of the workpiece.
[0007] Some embodiments of a method of polishing a workpiece may
comprise rotating the workpiece having no lubricant; applying a
liquid to the workpiece adjacent to a polishing tape; applying the
polishing tape to the workpiece at a pad load to polish the
workpiece, such that the liquid acts as a transient lubricant
between the workpiece and the polishing tape; and then lubricating
the workpiece.
[0008] Other embodiments of a method of final tape polishing (FTP)
a media disk may comprise rotating the media disk; applying a
liquid that is substantially pure to the media disk adjacent to an
FTP tape; applying the FTP tape to the media disk at a pad load to
polish the media disk, such that the liquid acts as a transient
lubricant between the media disk and the FTP tape; and completing
FTP.
[0009] In still other embodiments, a method of final tape polishing
(FTP) a media disk comprises mounting a media disk having no
lubricant to a spindle; rotating the media disk on the spindle;
applying a liquid to the media disk adjacent to an FTP tape;
applying the FTP tape to the media disk at a pad load to polish the
media disk, such that the liquid acts as a transient lubricant
between the media disk and the FTP tape; completing FTP and
removing the media disk from the spindle; and then lubricating the
media disk.
[0010] The foregoing and other objects and advantages of these
embodiments will be apparent to those of ordinary skill in the art
in view of the following detailed description, taken in conjunction
with the appended claims and the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] So that the manner in which the features and advantages of
the embodiments are attained and can be understood in more detail,
a more particular description may be had by reference to the
embodiments thereof that are illustrated in the appended drawings.
However, the drawings illustrate only some embodiments and
therefore are not to be considered limiting in scope as there may
be other equally effective embodiments.
[0012] FIG. 1 is a schematic diagram of an embodiment of an FTP
system and apparatus;
[0013] FIG. 2 is a plot of the performance of various embodiments
disclosed herein with regard to friction and injection speed;
[0014] FIG. 3 discloses plots of the roughness performance of
various embodiments disclosed herein with regard to unpolished
media; and
[0015] FIG. 4 is schematic plan view of an embodiment of a disk
drive.
[0016] The use of the same reference symbols in different drawings
indicates similar or identical items.
DETAILED DESCRIPTION
[0017] Embodiments of a system, method and apparatus for polishing
workpieces are disclosed. For example, and as shown in FIG. 1, a
system and apparatus 11 may be used for final tape polishing (FTP)
a media disk 13. The media disk 13 may be lubricated before or
after FTP. The method may comprise mounting the media disk 13 to a
spindle 15, and rotating the media disk 13 on the spindle 15. The
disk may be sputtered with layers prior to this initial step.
[0018] In some embodiments, a liquid 17 is applied to the media
disk 13 adjacent an FTP tape 19. The liquid 17 may be substantially
pure, such as a neat, undiluted volatile solvent that is applied
via a pump-operated needle syringe 21. For example, the liquid 17
may comprise a fluorinated hydrocarbon and is inert relative to the
media disk, such that the liquid does not texture the media disk.
The liquid may be circulated through a particle filtration system
prior to application to the disk. The liquid 17 is applied to the
media disk 13 without an abrasive. Moreover, the method may
comprise using no abrasive other than the FTP tape 19.
[0019] The method may further comprise applying the FTP tape 19 to
the media disk 13 at a pad load (e.g., via pad 23) to polish the
media disk 13, such that the liquid 17 acts as a lubricant between
the media disk 13 and FTP tape 19. The method also may comprise
completing FTP and removing the media disk 13 from the spindle 15.
As shown in FIG. 1, both sides of the media disk 13 may be
simultaneously polished in this manner.
[0020] In some embodiments, the disk 13 is lubricated with a
lubricant prior to FTP. The lubricant may have a thickness on the
media disk of about 10 .ANG. or less. The lubricant may be bonded
to the media disk, such that the lubricant is substantially
unremoved by the liquid 17. Alternatively, the lubricant may be
soluble in the liquid. In still other alternatives, the lubricant
is not bonded to the media disk, and the lubricant is non-soluble
in the liquid.
[0021] In still other embodiments, the method may further comprise
adjusting a pad load (i.e., in an axial direction) on the media
disk; adjusting an injection speed of the liquid onto the media
disk; and/or adjusting a linear velocity (i.e., in a
circumferential direction) and a transverse velocity (i.e., in a
radial direction) of the FTP tape relative to the media disk.
[0022] The method also may comprise spin-coating the liquid 17 onto
the media disk 13 before applying the FTP tape 19, and spinning off
the liquid prior to unloading the media disk. The liquid may
substantially completely evaporates from the media disk prior to
disk removal. The liquid may substantially completely evaporate
from the media disk in less than about 10 seconds, or in less than
about 1 second.
[0023] Prototypes were tested on a desktop FTP tool using the
solvent Vertrel XF as the liquid in a pump-operated needle syringe.
FTP friction was tested at both the disk inner and outer diameters
versus relative injection speed at two pad loads (i.e., 100 g and
150 g). As shown in FIG. 2, the FTP friction was reduced with
solvent injection in a controllable manner through both injection
speed and pad load.
[0024] As shown in FIG. 3, the effectiveness of such FTP processes
may be depicted with roughness parameters. The roughness was
measured by atomic force microscopy (AFM) on non-lubricated smooth
media as well as non-lubricated rough media. Measurements were
taken at both the inner diameter (ID) and the middle diameter (MD)
between the ID and the outer diameter (OD). Some disk IDs were not
final tape polished but also were measured for comparison.
Generally, a reduction in maximum peak height (Rp) is provided with
media treated by the embodiments disclosed herein. FIG. 3 also
discloses media measurements of average roughness (Rq or RMS) and
maximum valley depth (Rv). Performance varies based on the initial
roughness of the media (i.e., prior to FTP), as well as the
abrasiveness of the FTP tape.
[0025] The embodiments disclosed herein may be used to inject a
volatile liquid onto a disk near the FTP pad. The injected liquid
may be spin-coated on the disk region right before the FTP tape
engages the disk. The liquid may subsequently spin off the disk and
evaporate. Injection speed, pad load, linear and transverse
velocity, etc., may be adjusted for optimal results. The liquid may
comprise fluorinated hydrocarbons, such as Vertrel XF or HFE 7100,
which are commonly used as solvents for lubricants. In addition,
the liquid may be circulated through a particle filtration system
such as those used on lubricant dipping baths.
[0026] In some embodiments, a method of final tape polishing (FTP)
a media disk comprises (a) rotating the media disk; (b) applying a
liquid that is substantially pure to the media disk adjacent to an
FTP tape; (c) applying the FTP tape to the media disk at a pad load
to polish the media disk, such that the liquid acts as a transient
lubricant between the media disk and the FTP tape; and (d)
completing FTP. The media disk may be lubricated after step
(d).
[0027] The media disk may be sputtered with layers prior to step
(a), or the media disk may be lubricated with a lubricant prior to
step (a). The lubricant may have a thickness on the media disk of
about 10 .ANG. or less. The lubricant may be bonded to the media
disk, such that the lubricant is substantially unremoved by the
liquid. The lubricant may be soluble in the liquid. The lubricant
may not be bonded to the media disk, and the lubricant may be
non-soluble in the liquid.
[0028] The liquid may be applied to the media disk without an
abrasive, such that no abrasive is used in the method other than
the FTP tape. The liquid may comprise a neat, undiluted volatile
solvent that is applied via a pump-operated needle syringe. The
liquid may comprise a fluorinated hydrocarbon and is inert relative
to the media disk, such that the liquid does not texture the media
disk.
[0029] The method may further comprise at least one of adjusting
the pad load on the media disk; adjusting an injection speed of the
liquid onto the media disk; and adjusting a linear velocity and a
transverse velocity of the FTP tape relative to the media disk. The
method also may further comprise spin-coating the liquid onto the
media disk before step (c), and spinning off the liquid prior to
step (d). The liquid may be substantially completely evaporated
from the media disk prior to step (d) in, for example, less than
about 10 seconds, or less than about 1 second. The method also may
comprise circulating the liquid through a particle filtration
system prior to step (b).
[0030] In still other embodiments, a method of final tape polishing
(FTP) a media disk comprises mounting a media disk having no
lubricant to a spindle; rotating the media disk on the spindle;
applying a liquid to the media disk adjacent to an FTP tape;
applying the FTP tape to the media disk at a pad load to polish the
media disk, such that the liquid acts as a transient lubricant
between the media disk and the FTP tape; completing FTP and
removing the media disk from the spindle; and then lubricating the
media disk.
[0031] These systems, methods and apparatus have several advantages
over conventional solutions. Such an FTP process is completely
independent of lubricant presence, type and thickness. It can be
done before or after lubricant application (e.g., dipping), and is
readily incorporated into existing FTP equipment with minimal
modification. These embodiments do not require additional
processes, tools, delay time, floor space or operations. This
solution saves time and cost in FTP process optimization when
lubricant type or thickness is altered.
[0032] FIG. 4 depicts a hard disk drive assembly 100 comprising a
housing or enclosure 101 with one or more media disks 111 rotatably
mounted thereto. The disk 111 comprises magnetic recording media
rotated at high speeds by a spindle motor (not shown) during
operation. Disk 111 may be configured, manufactured and fabricated
as described elsewhere herein.
[0033] Magnetic data tracks 113, which may be concentric, are
formed on either or both of the disk surfaces to receive and store
information. The tracks are formed by the creation of bit-patterned
islands with one magnetic property which are surrounded by material
with a different magnetic property.
[0034] A write head is used to direct the magnetic state of the
magnetic bits to one of two directions to write data. The resting
state of the magnetization of the bit can be pointed perpendicular
to the plane of the disk. A read head is used to detect which
direction the magnetization is pointed in. Typically the read and
write heads are integrated on a single slider and the slider is
attached to a suspension which is rotated to different radii on the
disk to read and write information from various tracks. The read
head is also uses to control servo positioning of the head.
[0035] Embodiments of a read/write slider 110 having read/write
heads may be moved across the disk surface by an actuator assembly
106, allowing the slider 110 to read and/or write magnetic data to
a particular track 113. The actuator assembly 106 may pivot on a
pivot 114 or by a linear actuator. The actuator assembly 106 may
form part of a closed loop feedback system, known as servo control,
which dynamically positions the read/write slider 110 to compensate
for thermal expansion of the magnetic recording media 111 as well
as vibrations and other disturbances or irregularities. Also
involved in the servo control system is a complex computational
algorithm executed by a microprocessor, digital signal processor,
or analog signal processor 116 that receives data address
information from a computer, converts it to a location on the disk
111, and moves the read/write slider 110 accordingly.
[0036] In some embodiments of hard disk drive systems, read/write
sliders 110 periodically reference servo patterns recorded on the
disk to ensure accurate slider positioning. Servo patterns may be
used to ensure a read/write slider 110 follows a particular track
113 accurately, and to control and monitor transition of the slider
110 from one track to another. Upon referencing a servo pattern,
the read/write slider 110 obtains head position information that
enables the control circuitry 116 to subsequently realign the
slider 110 to correct any detected error.
[0037] Servo patterns or servo sectors may be contained in
engineered servo sections 112 that are embedded within a plurality
of data tracks 113 to allow frequent sampling of the servo patterns
for improved disk drive performance, in some embodiments. In a
typical magnetic recording media 111, embedded servo sections 112
may extend substantially radially from the center of the magnetic
recording media 111, like spokes from the center of a wheel. The
servo features may be similarly sized to the data features or may
be larger. The size of the features is determined by the mask
pattern. Unlike spokes however, servo sections 112 form a subtle,
arc-shaped path calibrated to substantially match the range of
motion of the read/write slider 110. Both sides of the disk can be
patterned.
[0038] Alternate embodiments are suitable for still other
applications and other types of workpieces. For example, other than
FTP, some embodiments may be adapted for the final polish of raw
disk substrates (e.g., glass, AlMg, etc.) that are typically free
of any kind of lubricant. The disk substrates are typically
inspected for cleanliness and roughness prior to a wash process,
which itself precedes layers of material (e.g., magnetic layers)
being added to them, such as by sputtering. Other embodiments
include the polishing of sliders for hard disk drives. The sliders
are typically integrally formed as a wafer that is lapped and
polished and then cut to fabricate the individual sliders. The
wafer of sliders may be characterized as having an air bearing
surface (ABS) side that may be polished as a workpiece as described
herein.
[0039] Additional embodiments may include polishing any type of
highly technical workpiece, such as lenses, minors, single
crystals, windows for transmitting infrared or ultraviolet light,
etc. For example, a method of polishing a workpiece may comprising
rotating the workpiece; applying a liquid that is substantially
pure to the workpiece adjacent to a polishing tape; applying the
polishing tape to the workpiece at a pad load to polish the
workpiece, such that the liquid acts as a lubricant between the
workpiece and the polishing tape; and then completing polishing of
the workpiece. Other embodiments of a method of polishing a
workpiece may comprise rotating the workpiece having no lubricant;
applying a liquid to the workpiece adjacent to a polishing tape;
applying the polishing tape to the workpiece at a pad load to
polish the workpiece, such that the liquid acts as a transient
lubricant between the workpiece and the polishing tape; and then
lubricating the workpiece.
[0040] This written description uses examples to disclose the
embodiments, including the best mode, and also to enable those of
ordinary skill in the art to make and use the invention. The
patentable scope is defined by the claims, and may include other
examples that occur to those skilled in the art. Such other
examples are intended to be within the scope of the claims if they
have structural elements that do not differ from the literal
language of the claims, or if they include equivalent structural
elements with insubstantial differences from the literal languages
of the claims.
[0041] Note that not all of the activities described above in the
general description or the examples are required, that a portion of
a specific activity may not be required, and that one or more
further activities may be performed in addition to those described.
Still further, the order in which activities are listed are not
necessarily the order in which they are performed.
[0042] In the foregoing specification, the concepts have been
described with reference to specific embodiments. However, one of
ordinary skill in the art appreciates that various modifications
and changes can be made without departing from the scope of the
invention as set forth in the claims below. Accordingly, the
specification and figures are to be regarded in an illustrative
rather than a restrictive sense, and all such modifications are
intended to be included within the scope of invention.
[0043] As used herein, the terms "comprises," "comprising,"
"includes," "including," "has," "having" or any other variation
thereof, are intended to cover a non-exclusive inclusion. For
example, a process, method, article, or apparatus that comprises a
list of features is not necessarily limited only to those features
but may include other features not expressly listed or inherent to
such process, method, article, or apparatus. Further, unless
expressly stated to the contrary, "or" refers to an inclusive-or
and not to an exclusive-or. For example, a condition A or B is
satisfied by any one of the following: A is true (or present) and B
is false (or not present), A is false (or not present) and B is
true (or present), and both A and B are true (or present).
[0044] Also, the use of "a" or "an" are employed to describe
elements and components described herein. This is done merely for
convenience and to give a general sense of the scope of the
invention. This description should be read to include one or at
least one and the singular also includes the plural unless it is
obvious that it is meant otherwise.
[0045] Benefits, other advantages, and solutions to problems have
been described above with regard to specific embodiments. However,
the benefits, advantages, solutions to problems, and any feature(s)
that may cause any benefit, advantage, or solution to occur or
become more pronounced are not to be construed as a critical,
required, or essential feature of any or all the claims.
[0046] After reading the specification, skilled artisans will
appreciate that certain features are, for clarity, described herein
in the context of separate embodiments, may also be provided in
combination in a single embodiment. Conversely, various features
that are, for brevity, described in the context of a single
embodiment, may also be provided separately or in any
subcombination. Further, references to values stated in ranges
include each and every value within that range.
* * * * *