U.S. patent application number 10/652346 was filed with the patent office on 2005-08-11 for apparatus for slider curvature modification by substrate melting produced with a pulsed laser beam.
Invention is credited to Chang, Ping-Wei, Poon, Chie Ching, Tam, Andrew Ching.
Application Number | 20050173389 10/652346 |
Document ID | / |
Family ID | 31978934 |
Filed Date | 2005-08-11 |
United States Patent
Application |
20050173389 |
Kind Code |
A1 |
Tam, Andrew Ching ; et
al. |
August 11, 2005 |
Apparatus for slider curvature modification by substrate melting
produced with a pulsed laser beam
Abstract
A method and apparatus for producing very high crown and camber
curvature in slider materials using a laser processing system which
produces fluence which is variable in a controllable manner, by
applying a laser beam to the flex side of the slider material and
varying the fluence of the laser beam to optimize the curvature in
the slider material. The fluence is variable by finely controlling
the power output of the laser or by changing the spot size of the
laser beam. The beam spot size can be changed by using a focusing
lens to establish a focal plane and then varying the relative
positions of the slider relative and the focal plane. An apparatus
for producing high crown and camber is also disclosed, as well as a
slider produced by the process of applying a laser beam to the flex
side of the slider material and varying the fluence of the laser
beam to optimize the curvature in the slider material.
Inventors: |
Tam, Andrew Ching;
(Saratoga, CA) ; Poon, Chie Ching; (San Jose,
CA) ; Chang, Ping-Wei; (San Jose, CA) |
Correspondence
Address: |
GENERAL ELECTRIC COMPANY (PCPI)
C/O FLETCHER YODER
P. O. BOX 692289
HOUSTON
TX
77269-2289
US
|
Family ID: |
31978934 |
Appl. No.: |
10/652346 |
Filed: |
August 29, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10652346 |
Aug 29, 2003 |
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09594979 |
Jun 15, 2000 |
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6710295 |
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Current U.S.
Class: |
219/121.85 ;
G9B/21.026; G9B/5.23 |
Current CPC
Class: |
B23K 26/02 20130101;
B21D 11/20 20130101; B23K 26/0622 20151001; G11B 21/21 20130101;
B23K 26/073 20130101; G11B 5/6005 20130101 |
Class at
Publication: |
219/121.85 |
International
Class: |
B23K 026/00 |
Claims
What is claimed is:
1. A method for producing very high crown and camber curvature in
slider materials having a flex side and an air-bearing side using a
laser processing system which produces a pulsed laser beam,
comprising the steps of: (A) establishing a focal plane for the
laser beam, the laser beam having a pulse width in the range of
1.times.10.sup.-9 seconds to 1.times.10.sup.-3 seconds, with an
energy per pulse in the range of 1 to 1,000,000 microjoules, and a
repetition rate between 1 Hz and 400 kHz; (B) applying the pulsed
laser beam to the flex side of the slider material; and (C) varying
the relative positions of the slider material and the focal plane
of the laser beam to optimize the curvature.
2. The method of claim 1, wherein the laser processing system
further comprises a focusing device, whereby the focal plane of the
laser beam is established.
3. The method of claim 2, wherein said focusing device is at least
one lens mounted on a moveable stage, whereby the position of the
focal plane relative to the slider material can be varied.
4. The method of claim 1, wherein the laser processing system
further comprises a movable stage to which the slider material is
attached, the position of the slider material relative to the focal
plane can be varied.
5. The method of claim 1, wherein the laser is Q-switched.
6. The method of claim 1, wherein the laser beam is conditioned
with a beam expander with adjustable beam expansion.
7. The method of claim 1, wherein the laser beam is produced
through harmonic generation.
8. The method of claim 1, wherein the laser beam is moved by at
least one directing optic.
9. The method of claim 8, wherein at least one directing optic
includes at least one reflecting mirror.
10. The method of claim 1, wherein the slider material is one or
more rows of sliders.
11. A method for producing very high crown and camber curvature in
slider materials having a flex side, using a laser processing
system which produces a laser beam which produces fluence which is
variable in a controllable manner, comprising the steps of: (A)
applying the laser beam to the flex side of the slider material,
the laser beam having a pulse width in the range of
1.times.10.sup.-9 seconds to 1.times.10.sup.-3 seconds, with an
energy per pulse in the range of 1 to 1,000,000 microjoules, and a
repetition rate between 1 Hz and 400 kHz; and (B) varying the
fluence of the laser to optimize the curvature in the slider
material.
12. The method of claim 11, wherein fluence is controllably varied
by changing the power output of the laser.
13. The method of claim 11, wherein fluence is controllably varied
by changing the spot size of the laser beam.
14. The method of claim 13, wherein the spot size of the laser beam
is varied by changing the relative positions of the slider material
and the focal plane of the laser beam.
15. The method of claim 14, wherein the spot size is controllably
varied by moving the focal plane of the laser beam relative to the
slider material.
16. The method of claim 15, wherein the focal plane of the laser is
moved relative to the slider material by using at least one
focusing lens which is attached to a movable mount.
17. The method of claim 14, wherein the slider material is moved
relative to the focal plane of the laser by using a movable mount
to which the slider material is attached.
18. The method of claim 11, wherein fluence is controllably varied
by adjusting the beam expansion of the laser beam.
19. The method of claim 11, wherein the slider material is one or
more rows of sliders.
20. An apparatus for creating high crown and camber curvature in
slider materials having an air bearing surface and a flex side,
comprising: a laser which produces a pulsed laser beam for
machining the slider material, the laser beam having a pulse width
in the range of 1.times.10.sup.-9 seconds to 1.times.10.sup.-3
seconds, with an energy per pulse in the range of 1 to 1,000,000
microjoules, and a repetition rate between 1 Hz and 400 kHz; at
least one beam directing device, which directs the laser beam onto
the flex side of the slider material; and a fluence varying device
so that optimal fluence is achieved to produce optimal
curvature.
21. The apparatus of claim 20, wherein: the fluence varying device
is at least one focusing lens which directs the laser beam to focus
within a focal plane and a movable fixture which varies the
position of the slider material with respect to the focal
plane.
22. The apparatus of claim 21, wherein: the movable fixture is a
movable stage upon which the slider material is attached, and by
which the slider material is moved relative to the focal plane.
23. The apparatus of claim 21, wherein: the movable fixture is a
movable stage upon which the lens is attached, and by which the
focal plane is moved relative to the slider material.
24. The apparatus of claim 20, wherein the laser is Q-switched.
25. The apparatus of claim 20, wherein the laser beam is produced
through harmonic generation.
26. The apparatus of claim 20, wherein the laser beam is moved by
at least one directing device.
27. The apparatus of claim 26, wherein at least one directing optic
includes at least one reflecting mirror.
28. The apparatus of claim 20, wherein the laser beam is
conditioned with a beam expander that has adjustable beam
expansion.
29. The apparatus of claim 20, wherein the slider material is one
or more rows of sliders.
30. A slider having optimized crown or camber curvature prepared
from substrate material having an air-bearing side and a flex side,
prepared by a process using a laser which produces a pulsed laser
beam, the laser beam having a pulse width in the range of
1.times.10.sup.-9 seconds to 1.times.10.sup.-3 seconds, with an
energy per pulse in the range of 1 to 1,000,000 microjoules, and a
repetition rate between 1 Hz and 400 kHz, the process comprising
the steps of: (A) applying the laser beam to the flex side of the
substrate material; and (B) varying the fluence of the laser beam
to optimize the curvature in the substrate material.
31. A slider prepared by the process of claim 30, wherein fluence
is controllably varied by changing the power output of the
laser.
32. A slider prepared by the process of claim 30, wherein fluence
is controllably varied by changing the spot size of the laser
beam.
33. A slider prepared by the process of claim 32, wherein the spot
size of the laser beam is varied by changing the position of the
substrate material relative to the focal plane of the laser
beam.
34. A slider prepared by the process of claim 32, wherein the spot
size is controllably varied by changing the position of the focal
plane of the laser beam relative to the substrate material.
35. A slider prepared by the process of claim 34, wherein the focal
plane of the laser is moved relative to the substrate material by
using at least one focusing lens which is attached to a movable
mount.
36. A slider prepared by the process of claim 30, wherein the laser
beam is conditioned with a beam expander that has adjustable beam
expansion.
37. A slider prepared by the process of claim 30, wherein the
substrate material is one or more rows of sliders, which are then
separated to produce individual sliders.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Reference is made to U.S. patent application Ser. No.
09/444,793, filed Nov. 22, 1999, entitled PROCESSING OF MULTI-PHASE
CERAMIC SLIDER MATERIALS USING HARMONICALLY GENERATED ULTRAVIOLET
LASER RADIATION in the names of Paul M. Lundquist, et. al.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an improved method for the
manufacture of sliders for disk drives. More particularly, the
invention relates to a method for controllably producing very high
crown and camber in the air bearing surface of a slider by applying
pulsed laser energy in accordance with the method of the present
invention to the back side of the slider in order to induce stress,
and thus curvature in the slider material.
[0004] 2. Description of the Background Art
[0005] Magnetic storage disk drives typically include a magnetic
sensor called a "head" suspended in close proximity to the magnetic
disk, which serves as the recording medium. In Winchester-type disk
drives, a magnetic thin film head is embedded in a ceramic block,
called a slider, which is then attached to a flexible suspension.
During operation, the rotation of the magnetic disk relative to the
slider provides an air-flow along the surface of the slider, which
causes it to lift, so that the slider is supported on a cushion of
air. This surface of the slider is referred to as the Air Bearing
Surface (ABS) and its separation from the disk the Fly Height (FH).
The shape of the slider and of the ABS in particular is crucial to
the performance of the head. Contours in the ABS establish the
desired pressure gradients for positioning the slider above the
disk surface. It is therefore typically necessary to form complex
contours in the shape of the slider by micro-machining, etching, or
other processes to obtain the desired performance.
[0006] As more is learned about the dynamics of flying heads, more
subtle changes are being required in the shape of the ABS. To
implement these refinements, it is becoming more and more desirable
to create contours which are complex in three dimensions. Two
parameters pertaining to the curvature or flatness of the ABS that
are considered important are "crown" and "camber". Crown is the
maximum separation of the cylindrical contour along the flying
direction from an imaginary plane drawn between the two end edges,
i.e., the leading and trailing edges, of the ABS. Camber has a
similar definition and is the separation from an imaginary plane
drawn between the two side edges of the slider. For the modern
"pico" sliders, these curvature parameters are typically on the
order of several nanometers (nm), while the slider width and length
are about 1 mm. The curvatures of the ABS are therefore truly
minute, however, the variance of the crown and camber of modern
sliders remains to be a key factor for the slider performance.
Hence, there is an obvious need to develop and implement a method
to finely adjust crown and camber.
[0007] A variety of techniques are currently being practiced for
controlling the slider curvature beyond the capability of
conventional lapping. All these techniques rely on inducing a
surface stress change (.DELTA.S) on at least one slider surface.
This change of surface stress can be (1) positive (i.e., increase
of compressive stress) or (2) negative (i.e., decrease of
compressive stress). The change in surface stress produces a
curvature change in the slider, as shown in FIGS. 1A and 1B. FIG.
1A shows surface layers having residual compressive stresses in the
shaded areas. In FIG. 1B, the surface residual stress on the top
surface, assumed to be the flex side, (also called the back side)
has been reduced by .DELTA.S, while on the bottom (ABS) side, the
residual compressive stress is unchanged. If only one surface is
stress-modified by .DELTA.S, this surface will become more convex
or concave if .DELTA.S is positive or negative, respectively. This
effect is easy to visualize if the original surface is exactly
flat, as shown in FIG. 1A. In this case, the crown change C (which
is the "bulging" of the slider ABS as viewed from the y-direction)
is simply given by:
C=[3(1-.nu.)/4E](L/a).sup.2(.DELTA.S.times.b)
[0008] where L is the length of the slider, a is its thickness, b
is the depth of the surface stress layer, .nu. is Poisson's ratio,
and E is Young's modulus. The camber change is also given by a
similar equation for the "bulging" of the slider as viewed from the
x-direction.
[0009] Several techniques for producing positive or negative stress
changes on a slider surface are known. Techniques to induce
negative stress changes (i.e., reducing the existing compressive
stress, or inducing tensile stress on the surface) are usually
practiced on the flex side of the slider, in order to produce an
increase in the crown or camber at the ABS side. Stress-reducing
techniques that can be used at the flex side include "kiss-lapping"
or plasma etching, which can remove part or all of the stressed
layer on the surface. However, such processes have characteristics
which detract from their use in a commercial environment.
[0010] A more recent approach to slider shaping is the use of laser
scribing. Using a laser for creating curvature in sliders is found
in U.S. Pat. No. 5,982,583 to Strom. It states in claim 1 the use
of a laser to melt and then cool the back surface (here referred to
as the flex side) of a slider to add tensile stress which causes
tensile stress relief cracks in the back surface, and which causes
the air bearing surface to curve thus modifying crown or camber.
Strom's tensile stress relief cracks are oriented predominately
parallel to the crown curvature axis. The present inventors regard
cracks as undesirable, and should be reduced or minimized in number
and size so as not to worsen the surface integrity. The presence of
such tensile stress cracks as required by the prior art is an
indication that excessive laser power is used to melt excessive
amounts of material, and such excessive laser power may damage the
sensor which is embedded in the ceramic slider material.
[0011] Although some presence of micro-cracks are inevitable when
the surface is made "tensile", preferably any cracks made by laser
processing should be only very microscopic micro-cracks, visible
with a Scanning Electron Microscope. Such micro-cracks tend to
orient randomly. An improved approach therefore is to minimize any
tensile stress cracks.
[0012] Consequently, there is a need for an improved method of
laser processing of sliders which does not require the introduction
of tensile stress relief cracks in slider material.
[0013] It is, therefore, an object of the present invention to
provide an improved method for creating controllable crown and
camber in sliders by using pulsed laser energy in accordance with
the present invention to produce specific, controllable minute
curvatures, without the required introduction of tensile stress
relief cracks. Other objects and advantages will become apparent
from the following disclosure.
SUMMARY OF THE INVENTION
[0014] The present invention relates to a method and apparatus for
producing very high crown and camber curvature in slider materials
using a laser processing system which produces fluence, which is
variable in a controllable manner, by applying a laser beam to the
flex side of the slider material and varying the fluence of the
laser beam to form the curvature in the slider material.
[0015] A more thorough disclosure of the present invention is
presented in the detailed description which follows and the
accompanying figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The objects and, advantages and features of the present
invention will be more clearly understood by reference to the
following detailed disclosure and the accompanying drawings in
which:
[0017] FIGS. 1A & B show a side plan view of a block of slider
material first with unrelieved compressive stress on both surfaces,
and then showing the effect of relief of compressive stress on the
upper surface, and the resulting curvature produced;
[0018] FIG. 2 shows a block diagram side view of a laser system of
the present invention;
[0019] FIG. 3 illustrates a detail view of the focal plane of a
laser beam as produced by the laser system of the present
invention, and further detail views of the beam as found at three
positions relative to the focal plane;
[0020] FIG. 4 shows a graph of the effect of varying positional
relationship between the slider material and the focal plane of the
laser;
[0021] FIG. 5 shows the appearance of the melt with microscopic
cracks with no preferred orientation;
[0022] FIG. 6 illustrates the effect of laser scribing as performed
by the present invention in changing the crown of a row of
sliders;
[0023] FIG. 7 illustrates the effect of laser scribing as performed
by the present invention in changing the camber of a row of
sliders; and
[0024] FIG. 8 shows a chart showing the effect of laser beam
focusing position on changes in both crown and camber.
DETAILED DESCRIPTION OF THE INVENTION
[0025] The present invention relates to a method and apparatus for
creating very high crown and camber in sliders by creating
controlled tensile stress in the flex side of the sliders using
variable pulsed laser fluence to melt the slider material without
over-heating the sensor in it and without tensile stress relief
cracks of controlled or preferred orientation.
[0026] The present inventors have found that the production of very
precisely controllable crown in slider material is possible by
treatment of the flex side of the slider, when a pulsed laser beam
is used in accordance with the present invention. The present
invention discloses a method of producing very precise and large
crown and camber.
[0027] It is first preferred for processing of alumina ceramics,
that a pulsed laser having a pulse width between 10 nanoseconds
(10.times.10.sup.-9 secs.) and 1 microsecond (1.times.10.sup.-6
secs.) and a repetition rate of 200-300 kHz is used. This is
preferred because this range of pulse-widths and repetition rates
allows very quick and localized heating of the material at the
point of application, limiting the spreading of heat to the
surrounding material, which can cause thermal damage to the slider
sensors. It also allows melting of material without loss of
material through ablation. Continuous wave lasers having
application times on the order of milliseconds to seconds are more
likely to have damaging effects on the sensitive sensor components,
and considered unsuitable for this type of operation. It is of
course possible that for other substrate materials, other pulse
durations and repetition rates may be preferred, and the method
disclosed herein contemplates changes in other parameters to
accommodate differences in materials and in batches of
materials.
[0028] A second parameter of the present invention is the laser
fluence. The term "fluence" refers to the surface laser energy
density produced by a laser, preferably a pulsed laser, onto a
surface area. In the present invention, it is measured in units of
energy (or energy/pulse) divided by area. The beam spot size is
generally so small, that the fluence will generally lie in the
region of Joules/cm.sup.2.
[0029] Fluence can be adjusted for maximal performance and control
in two primary ways. First, the spot size can remain constant while
the energy per pulse is varied, or second, the energy can remain
constant while the spot size is varied.
[0030] The energy per pulse of a laser can be varied by several
different methods. The current to the excitation mechanism can be
adjusted, which has an effect on the power output of the laser.
However, it is usually necessary to monitor changes in power output
during such changes, since it cannot be relied upon that a 10%
change in current input will directly produce a corresponding 10%
change in the laser output. The process is complicated by the fact
that changes in current input can also produce changes in
pulse-width, which can have other effects on the process.
[0031] The energy of the laser can also be varied by attenuating
the beam by using filters, or using devices such as a Liquid
Crystal Variable Retarder (LCVR), which changes polarization in an
active manner. When used with a polarizer, the LCVR can be used to
reduce the power output in a somewhat controllable manner, although
very fine control in the range of a few percent is still difficult
to achieve.
[0032] Alternatively, a preferred manner of controlling the fluence
of the laser is by controlling the spot size, an operation which
can be easily and inexpensively controlled by use of a lens which
can be adjusted to move the focal plane relative to the slider
material, or by moving the slider piece relative to the focal
plane. This method of increasing the spot size is preferred because
of its simplicity over the traditional method of using an
adjustable beam collimating device to decrease the diameter of the
laser beam before the focusing lens, which has the effect of
increasing the spot size.
[0033] FIG. 2 shows the basic components of the laser processing
system 10 of the present invention. A pulsed laser 12 which may be
pulsed by a number of mechanisms such as a Q-switch (not shown)
produces a laser beam 14 which is preferably reflected from a
directing optic such as a movable mirror 16 mounted on a tiltable
and/or translatable stage 18. The laser beam may have been
conditioned to provide a collimated beam and/or one that has been
expanded 15, by an optional beam expander 19. The beam 14 or the
expanded beam 15 is then directed by a focusing device such as a
lens 20 mounted on a translatable stage 22 which can move the stage
vertically as the beam 14 or 15 is focused on the substrate 24
surface, which it will be assumed is the flex side 26 of a slider
28. The slider 28 is placed on a moveable stage 30 which can move
in either the horizontal or vertical planes. The movement of
movable fixtures, such as the stage 30, lens mount 22 and/or mirror
mount 18 are preferably controlled by a computer controller 32. It
should be understood that any combination of movable fixtures in
this system is possible, so that any or all of the stage 30, lens
mount 22 and mirror mount 18 may be moveable, or that only the lens
mount 22 or stage 30 may be moveable. The use of a reflecting
mirror is also optional, so that the slider 28 could alternately be
placed vertically as seen in FIG. 3.
[0034] The slider 28 will be assumed to be placed at the focal
plane 34 in FIG. 2, to produce a spot 36. This is the point at
which the beam 14 is most tightly focused and the spot size will be
at a minimum. In terms of fluence, this will present the highest
energy concentration per unit area. FIG. 3 shows the effect of
moving the slider 28 relative to the focal plane 34. In the -X
direction, the slider 28 will be beyond the focal plane 34, the
spot size will increase, and the fluence will decrease. In the +X
direction, the slider 28 will be before the focal plane 34, and
once again, the spot size will be increased and the fluence
decreased from that found at the focal plane 34.
[0035] In general terms, the lens 20 and lens stage 22, as well as
the movable slider stage 30, can be thought of as fluence varying
devices, since the spot size, and thus the fluence can be varied
through their adjustment. Another way of varying the fluence is by
adjusting the power output of the laser, which is typically done by
reducing the current to the excitation mechanism (not shown) of the
laser. Examples would include decreasing the current to diodes or
flashlamps in diode-pumped or flashlamp-pumped lasers, or
controlling the voltage to an excimer laser's excitation
mechanism.
[0036] FIG. 4 illustrates a chart showing the measured change in
crown as a function of slider position with respect to the focal
plane, which is identified as 0.0 position, where the spot size is
minimum, and the fluence at maximum. The laser used was operated at
a 100 kHz repetition rate. Two curves are shown, one representing a
2.0 Watt output shown with circles, and a 1.75 Watt output
indicated by triangles. The distances from the focal plane which
produced the most change in the slider crown are noted with arrows
and marked as "optimal fluence" on the chart. At these points the
performance of the laser system has been optimized so that, for
example, for a pulsed laser operating at 100 kHz and producing 2
Watts of power, or 20 micro-joules per pulse, by locating the
slider at either -1.25 mm or +1.5 mm from the focal plane, the
laser beam will melt the slider material just enough to induce the
maximum tension stress, and thus the maximum curvature in the
slider material, when it refreezes. The safety of the sensor is
also thus assured, because pulses of this duration and energy level
will not heat the surrounding substrate so as to cause damage.
[0037] The typical appearance of the melt after laser irradiation
of the slider material is shown in FIG. 5, which is a scanning
electron microscope image of the melt on a slider surface, viewed
at an angle of 45 degrees from normal. The top part of the figure,
which is the surface orthogonal to the surface which has been
melted, shows a cross-section of the melt zone, which is of
sub-micron thickness. The micro-cracks do not have particular
orientation and are typically sub-micrometers in depth.
[0038] As defined above, crown is the maximum separation of the
cylindrical contour along the flying direction from an imaginary
plane drawn between the two end edges, i.e., the leading and
trailing edges, of the ABS. Camber is the separation from an
imaginary plane drawn between the two side edges of the slider. As
shown in FIG. 6, crown 46 is shown being produced in a row of
sliders 38 having their leading edges 40 and their trailing edges
42 at the top and bottom respectively of the Figure. The flex sides
26 of the sliders 28 are facing the viewer, and in this
orientation, optimized crown is produced by scribing parallel
horizontal lines 46. As shown by the dashed line, the row of
sliders 38 is assumed to have an initial crown 46 which is
negative, i.e. convex as seen by the viewer of the Figure,
typically due to unrelieved compressive stress in the material. The
final crown 48 is seen to be positive, i.e. concave as seen from
the flex side 26.
[0039] In a similar way, FIG. 7 shows a row of sliders 38 having
vertical scribed lines 50. The initial camber 52 and the final
camber 54 are shown as the result of the laser processing.
[0040] FIG. 8 shows a chart of the change in both crown and camber
in nanometers and includes the data shown in FIG. 4, plotted
against the actual laser beam focusing position. The crown and
camber changes are obtained at various laser power levels and for
various spot sizes as they are changed from a minimum of
36.times.10.sup.-6 meter beam diameter at the focal plane, labeled
to be at 8.0 mm on the chart. It can be seen that the maximum
curvature change corresponding to optimal fluence is found when the
slider is positioned at either before or after the position of the
focal plane.
[0041] In addition to the use of a fundamental laser wavelength
from a Nd-doped solid-state laser, it is possible that the laser
beam is produced through a process of harmonic generation to yield
a wavelength which is absorbed well by the substrate material, as
disclosed in pending U.S. patent application Ser. No. 09/444,793,
filed Nov. 22, 1999, entitled PROCESSING OF MULTI-PHASE CERAMIC
SLIDER MATERIALS USING HARMONICALLY GENERATED ULTRAVIOLET LASER
RADIATION.
[0042] Although this invention has been described with respect to
specific embodiments, the details thereof are not to be construed
as limitations, for it will be apparent that various embodiments,
changes and modifications may be resorted to without departing from
the spirit and scope thereof; and it is understood that such
equivalent embodiments are intended to be included within the scope
of this invention.
[0043] While various embodiments have been described above, it
should be understood that they have been presented by way of
example only, and not limitation. Thus, the breadth and scope of a
preferred embodiment should not be limited by any of the above
described exemplary embodiments, but should be defined only in
accordance with the following claims and their equivalents.
* * * * *