U.S. patent application number 11/583353 was filed with the patent office on 2008-04-24 for low-melting point superabrasive tools and associated methods.
Invention is credited to Chien-Min Sung.
Application Number | 20080096479 11/583353 |
Document ID | / |
Family ID | 39318508 |
Filed Date | 2008-04-24 |
United States Patent
Application |
20080096479 |
Kind Code |
A1 |
Sung; Chien-Min |
April 24, 2008 |
Low-melting point superabrasive tools and associated methods
Abstract
Superabrasive tools and their methods of manufacture are
disclosed. In one aspect, a method for making a low-melting point
superabrasive tool having a plurality of superabrasive particles is
provided. Such a method may include coating each of the plurality
of superabrasive particles with a reactive element that chemically
bonds to each of the plurality of superabrasive particles and
bonding together the plurality of superabrasive particles with a
molten braze that wets the reactive element at a temperature of
less than about 700.degree. C. In some aspects, the method may
further include arranging the plurality of superabrasive particles
on a leveling surface and bonding the plurality of superabrasive
particles together with the molten braze such that, upon formation
of the superabrasive tool, the plurality of superabrasive particles
have been leveled by the leveling surface to an RA value of less
than about 40 .mu.m.
Inventors: |
Sung; Chien-Min; (Taipei
County, TW) |
Correspondence
Address: |
THORPE NORTH & WESTERN, LLP.
P.O. Box 1219
SANDY
UT
84091-1219
US
|
Family ID: |
39318508 |
Appl. No.: |
11/583353 |
Filed: |
October 18, 2006 |
Current U.S.
Class: |
451/539 |
Current CPC
Class: |
B24B 53/017 20130101;
B24B 53/12 20130101; B24D 18/00 20130101 |
Class at
Publication: |
451/539 |
International
Class: |
B24D 11/00 20060101
B24D011/00 |
Claims
1. A method for making a low-melting point superabrasive tool
having a plurality of superabrasive particles, comprising: coating
each of the plurality of superabrasive particles with an
intermediate layer that bonds to each of the plurality of
superabrasive particles; arranging the plurality of superabrasive
particles on a leveling surface; and bonding together the plurality
of superabrasive particles with a molten braze that has a melting
temperature of less than about 700.degree. C.
2. The method of claim 1, wherein upon formation of the
superabrasive tool, the plurality of superabrasive particles have
been leveled by the leveling surface to an RA value of less than
about 40 .mu.m.
3. The method of claim 2, wherein the leveling surface is removed
from the superabrasive tool.
4. The method of claim 2, wherein arranging the plurality of
superabrasive particles further comprises: disposing a spacer layer
on the leveling surface; and disposing the plurality of
superabrasive particles at least partially within the spacer layer
such that a portion of each of the plurality of superabrasive
particles contact the leveling surface.
5. The method of claim 1, wherein the plurality of superabrasive
particles are mechanically bonded together with the molten
braze.
6. The method of claim 1, wherein the plurality of superabrasive
particles are chemically bonded together with the molten braze.
7. The method of claim 1, wherein the plurality of superabrasive
particles are bonded together with a molten braze that has a
temperature of less than about 500.degree. C.
8. The method of claim 1, wherein the plurality of superabrasive
particles includes diamond.
9. The method of claim 8, wherein the intermediate layer includes a
carbide former.
10. The method of claim 9, wherein the carbide former includes a
member selected from the group consisting of aluminum (Al), boron
(B), chromium (Cr), lithium (Li), magnesium (Mg), molybdenum (Mo),
manganese (Mn), nirobium (Nb), silicon (Si), tantalum (Ta),
titanium (Ti), vanadium (V), tungsten (W), zirconium (Zr), and
combinations thereof.
11. The method of claim 9, wherein the carbide former includes
Ti.
12. The method of claim 9, wherein the carbide former includes
Si.
13. The method of claim 1, wherein the plurality of superabrasive
particles includes cubic boron nitride.
14. The method of claim 13, wherein the intermediate layer includes
a nitride former.
15. The method of claim 14, wherein the nitride former includes a
member selected from the group consisting of aluminum (Al), boron
(B), chromium (Cr), lithium (Li), magnesium (Mg), molybdenum (Mo),
manganese (Mn), nirobium (Nb), silicon (Si), tantalum (Ta),
titanium (Ti), vanadium (V), tungsten (W), zirconium (Zr), and
combinations thereof.
16. The method of claim 1, wherein the braze includes a member
selected from the group consisting of Al, Ag, Sb, Zn, Pb, Cd, Cu,
Tl, Bi, Sn, In, Ga, and combinations thereof.
17. The method of claim 1, wherein the braze is an alloy including
a member selected from the group consisting of Al-Si, Babbit,
Cu-Mg, Al-Cu, Al-Mg, Cu-Zn, Al-Ge, Cu-Sn, Al-Sn, Sn-Zn, Sn-Tl,
Sn-Pb, Sn-Cu-Ag, and combinations thereof.
18. The method of claim 17, wherein the braze alloy includes
Al-Si.
19. The method of claim 17, wherein the braze alloy includes
Sn-Cu-Ag.
20. The method of claim 1, further comprising applying a wetting
layer to the intermediate layer to improve the wetting between the
intermediate layer and the braze.
21. The method of claim 20, wherein the wetting layer includes a
member selected from the group consisting of Si, Cu, Ni, Cr, and
combinations thereof.
22. The method of claim 20, wherein the intermediate layer is Ti,
the wetting layer is Si, and the braze is Al-Si.
23. The method of claim 1, wherein the intermediate layer is Si and
the braze is Al-Si.
24. The method of claim 1, wherein the braze is substantially free
of Cu.
25. The method of claim 2, wherein the tips of the superabrasive
particles are leveled to an RA value of less than about 30
.mu.m.
26. The method of claim 2, wherein the tips of the superabrasive
particles are leveled to an RA value of less than about 20
.mu.m.
27. The method of claim 2, wherein the tips of the superabrasive
particles are leveled to an RA value of less than about 10
.mu.m.
28. The method of claim 2, wherein the superabrasive particles are
leveled to a predetermined height that is along a designated
profile.
29. A low-melting point superabrasive tool, comprising: a plurality
of superabrasive particles coated with an intermediate layer and
bonded together with a braze having a melting temperature of less
than about 500.degree. C. said plurality of coated superabrasive
particles having tips leveled to an RA value of less than about 40
.mu.m.
30. (canceled)
31. The superabrasive tool of claim 29, wherein the tips of the
superabrasive particles have an RA value of less than about 30
.mu.m.
32. The superabrasive tool of claim 29, wherein the tips of the
superabrasive particles have an RA value of less than about 20
.mu.m.
33. The superabrasive tool of claim 29, wherein the tips of the
superabrasive particles have an RA value of less than about 10
.mu.m.
34. The superabrasive tool of claim 29, wherein the plurality of
superabrasive particles are of substantially the same size.
35. The superabrasive tool of claim 29, wherein the plurality of
superabrasive particle are from about 30 microns to about 500
microns in size.
36. The superabrasive tool of claim 29, wherein the plurality of
superabrasive particles are from about 100 microns to about 200
microns in size.
37. The superabrasive tool of claim 29, wherein the plurality of
superabrasive particles are less than about 100 microns in
size.
38. The superabrasive tool of claim 29, wherein the superabrasive
tool is a polishing or grinding pad.
39. The superabrasive tool of claim 29, wherein the superabrasive
tool is a CMP pad dresser.
40. The superabrasive tool of claim 29, wherein the superabrasive
tool is for shaping dental materials.
41. The superabrasive tool of claim 29, wherein the superabrasive
particles protrude to a predetermined height that is along a
designated profile.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to tools having
superabrasive particles embedded in a support matrix having a
low-melting point and associated methods. Accordingly, the present
invention involves the chemical and material science fields.
BACKGROUND OF THE INVENTION
[0002] Many industries utilize a chemical mechanical polishing
(CMP) process for polishing certain work pieces. Particularly, the
computer manufacturing industry relies heavily on CMP processes for
polishing wafers of ceramics, silicon, glass, quartz, and metals.
Such polishing processes generally entail applying the wafer
against a rotating pad made from a durable organic substance such
as polyurethane. A chemical slurry is utilized that contains a
chemical capable of breaking down the wafer substance and an amount
of abrasive particles which act to physically erode the wafer
surface. The slurry is continually added to the rotating CMP pad,
and the dual chemical and mechanical forces exerted on the wafer
cause it to be polished in a desired manner.
[0003] Of particular importance to the quality of polishing
achieved is the distribution of the abrasive particles throughout
the pad. The top of the pad holds the particles by means of fibers
or small pores, which provide a friction force sufficient to
prevent the particles from being thrown off of the pad due to the
centrifugal force exerted by the pad's spinning motion. Therefore,
it is important to keep the top of the pad as flexible as possible,
to keep the fibers as erect as possible, and to assure that there
is an abundance of open pores available to receive newly applied
abrasive particles.
[0004] One problem that arises with regard to maintaining the pad
surface, however, is an accumulation of polishing debris coming
from the work piece, the abrasive slurry, and the pad dresser. This
accumulation causes a "glazing" or hardening of the top of the pad,
mats the fibers down, and thus makes the pad surface less able to
hold the abrasive particles of the slurry. These effects
significantly decrease the pad's overall polishing performance.
Further, with many pads, the pores used to hold the slurry, become
clogged, and the overall asperity of the pad's polishing surface
becomes depressed and matted. A CMP pad dresser can be used to
revive the pad surface by "combing" or "cutting" it. This process
is known as "dressing" or "conditioning" the CMP pad. Many types of
devices and processes have been used for this purpose. One such
device is a disk with a plurality of superhard crystalline
particles such as diamond particles attached to a metal-matrix
surface.
[0005] Ultra-large-scale integration (ULSI) is a technology that
places at least 1 million circuit elements on a single
semiconductor chip. In addition to the tremendous density issues
that already exist, with the current movement toward size
reduction, ULSI has become even more delicate, both in size and
materials than ever before. Therefore, the CMP industry has been
required to respond by providing polishing materials and techniques
that accommodate these advances. For example, lower CMP polishing
pressures, smaller size abrasive particles in the slurry, and
polishing pads of a size and nature that do not over polish the
wafer must be used. Furthermore, pad dressers that cut asperities
in the pad which can accommodate the smaller abrasive particles,
and that do not overdress the pad must be used.
[0006] There are a number of problems in attempting to provide such
a pad dresser. First, the superabrasive particles must be
significantly smaller than those typically used in currently know
dressing operations. Generally speaking, the superabrasive
particles are so small that a traditional metal matrix is often
unsuitable for holding and retaining them. Further, the smaller
size of the superabrasive particles necessitates the precise
leveling of particle tip height in order to uniformly dress the
pad. Traditional CMP pad dressers can have particle tip height
variations of more than 50 .mu.m without compromising dressing
performance. However, such a variation would render a dresser
useless if it were required to dress a CMP pad and achieve a
uniform asperity depth of 20 .mu.m or less, for example.
[0007] In addition to issues with properly holding very small
superabrasive particles, traditional metal braze alloys have the
tendency to warp and buckle during a heating process, causing
additional issues in obtaining a CMP pad dresser having
superabrasive particle tips leveled to within a narrow tolerance
range.
[0008] As a result, a CMP pad dresser that is suitable for dressing
a CMP pad that meets the demands placed upon the CMP industry by
the continual reductions in semiconductor size is still being
sought.
SUMMARY OF THE INVENTION
[0009] Accordingly, the present invention provides superabrasive
tools and methods that are, without limitation, suitable to groom
the CMP pads used for the delicate polishing applications as
recited above. In one aspect, a method for making a low-melting
point superabrasive tool having a plurality of superabrasive
particles is provided. Such a method may include coating each of
the plurality of superabrasive particles with an intermediate layer
that chemically bonds to each of the plurality of superabrasive
particles and bonding together the plurality of superabrasive
particles with a molten braze that wets the intermediate layer at a
temperature of less than about 700.degree. C. In some aspects, the
method may further include arranging the plurality of superabrasive
particles on a leveling surface and bonding the plurality of
superabrasive particles together with the molten braze such that,
upon formation of the superabrasive tool, the plurality of
superabrasive particles have been leveled by the leveling surface
to an RA value of less than about 40 .mu.m.
[0010] Various methods of arranging the plurality of superabrasive
particles are also contemplated. For example, in one aspect
arranging the plurality of superabrasive particles may include
disposing a spacer layer on the leveling surface and disposing the
plurality of superabrasive particles at least partially within the
spacer layer such that a portion of each of the plurality of
superabrasive particles contact the leveling surface.
[0011] Numerous braze materials having low-melting temperatures are
contemplated, all of which are considered to be within the scope of
the present invention. Non-limiting examples may include Al, Ag,
Sb, Zn, Pb, Cd, Cu, Tl, Bi, Sn, In, Ga, and combinations thereof.
The braze materials may also include alloys having low-melting
temperatures. Examples may include, without limitation, Al--Si,
Babbit, Cu--Mg, Al--Cu, Al--Mg, Cu--Zn, Al--Ge, Cu--Sn, Al--Sn,
Sn--Zn, Sn--Tl, Sn--Pb, Sn--Cu--Ag, and combinations thereof.
[0012] In one aspect of the present invention, a wetting layer may
be applied to the intermediate layer to improve the wetting between
the reactive element and the braze. Various wetting layer materials
are contemplated, non-limiting examples of which may include Si,
Cu, Ni, Cr, and combinations thereof.
[0013] The present invention also provides superabrasive tools
comprised of low-melting braze materials. In one aspect, for
example, a low-melting point superabrasive tool is provided. The
superabrasive tool may include a plurality of superabrasive
particles coated with an intermediate layer and bonded together
with a braze having a melting point less than about 700.degree. C.,
the plurality of coated superabrasive particles having tips leveled
to an RA value of less than about 40 .mu.m. In another aspect, the
tips of the superabrasive particles may have an RA value of less
than about 30 .mu.m. In yet another aspect, the tips of the
superabrasive particles may have an RA value of less than about 20
.mu.m. In a further aspect, the tips of the superabrasive particles
may have an RA value of less than about 10 .mu.m.
[0014] There has thus been outlined, rather broadly, various
features of the invention so that the detailed description thereof
that follows may be better understood, and so that the present
contribution to the art may be better appreciated. Other features
of the present invention will become clearer from the following
detailed description of the invention, taken with the accompanying
claims, or may be learned by the practice of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a cross-sectional view of a superabrasive particle
disposed in a metal matrix in accordance with one embodiment of the
present invention.
[0016] FIG. 2 is a cross-sectional view of a superabrasive particle
disposed in a metal matrix in accordance with another embodiment of
the present invention.
[0017] FIG. 3 is a cross-sectional view of a superabrasive particle
disposed in a metal matrix in accordance with yet another
embodiment of the present invention.
[0018] FIG. 4 is a cross-sectional view of a superabrasive tool in
accordance with one embodiment of the present invention.
[0019] FIG. 5 is a cross-sectional view of a superabrasive tool in
accordance with another embodiment of the present invention.
[0020] FIG. 6 is a cross-sectional view of a superabrasive tool in
accordance with yet another embodiment of the present
invention.
[0021] FIG. 7 is a cross-sectional view showing a step in the
manufacture of a superabrasive tool in accordance with one
embodiment of the present invention.
[0022] FIG. 8 is a cross-sectional view showing a step in the
manufacture of a superabrasive tool in accordance with another
embodiment of the present invention.
[0023] FIG. 9 is a cross-sectional view showing a step in the
manufacture of a superabrasive tool in accordance with yet another
embodiment of the present invention.
[0024] FIG. 10 is a cross-sectional view showing a step in the
manufacture of a superabrasive tool in accordance with a further
embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0025] Definitions
[0026] In describing and claiming the present invention, the
following terminology will be used in accordance with the
definitions set forth below.
[0027] The singular forms "a," "an," and, "the" include plural
referents unless the context clearly dictates otherwise. Thus, for
example, reference to "a particle" includes reference to one or
more of such particles, and reference to "the reactive material"
includes reference to one or more of such materials.
[0028] As used herein, "superhard" and "superabrasive" may be used
interchangeably, and refer to a crystalline, or polycrystalline
material, or mixture of such materials having a Vicker's hardness
of about 4000 Kg/mm.sup.2 or greater. Such materials may include
without limitation, diamond, and cubic boron nitride (cBN), as well
as other materials known to those skilled in the art. While
superabrasive materials are very inert and thus difficult to form
chemical bonds with, it is known that certain reactive elements,
such as chromium and titanium are capable of chemically reacting
with superabrasive materials at certain temperatures.
[0029] As used herein, "metallic" refers to a metal, or an alloy of
two or more metals. A wide variety of metallic materials is known
to those skilled in the art, such as aluminum, copper, chromium,
iron, steel, stainless steel, titanium, tungsten, zinc, zirconium,
molybdenum, etc., including alloys and compounds thereof.
[0030] As used herein, "particle" when used in connection with a
superabrasive material, refer to a particulate form of such
material. Such particles may take a variety of shapes, including
round, oblong, square, euhedral, etc., as well as a number of
specific mesh sizes. As is known in the art, "mesh" refers to the
number of holes per unit area as in the case of U.S. meshes.
[0031] As used herein "wetting" refers to the process of flowing a
molten metal across at least a portion of the surface of a
superabrasive particle. Wetting is often due, at least in part, to
the surface tension of the molten metal, and may lead to the
forming of chemical bonds between the superabrasive particle and
the molten metal at the interface thereof, when a reactive element
is present.
[0032] As used herein, "chemical bond" and "chemical bonding" may
be used interchangeably, and refer to a molecular bond that exert
an attractive force between atoms that is sufficiently strong to
create a binary solid compound at an interface between the atoms.
Chemical bonds involved in the present invention are typically
carbides in the case of diamond superabrasive particles, or
nitrides or borides in the case of cubic boron nitride.
[0033] As used herein, "coat," "coating," and "coated," with
respect to a superabrasive grit or particle, refers to an area
along at least a portion of an outer surface of the particle that
has been intimately contacted with a reactive metal, or reactive
metal alloy, and that contains chemical bonds between the particle
and the alloy, or that will contain such chemical bonds upon the
liquification and solidification of the reactive metal, or reactive
metal alloy. In some aspects, the coating may be a layer which
substantially encases or encloses the entire superabrasive
particle. It is to be understood that such layers are limited in
some instances to a certain minimum thickness. Further, it is to be
understood that such a coating may be applied to particles on an
individual basis, or as a group of particles, and that such a
coating may be effected as a separate step made prior to
incorporation of the superabrasive particles into a tool, for
example, in order to form a tool precursor which can be combined
with a support matrix to form certain tools. Moreover, it is
possible that a number of coated particles be consolidated
together, either with or without additional abrasive particles and
used as a tool in and of themselves, without the need for
incorporation into a support matrix.
[0034] As used herein, "mechanical bond" and "mechanical bonding"
may be used interchangeably, and refer to a bond interface between
two objects or layers formed primarily by frictional forces. In
some cases the frictional forces between the bonded objects may be
increased by expanding the contacting surface areas between the
objects, and by imposing other specific geometrical and physical
configurations, such as substantially surrounding one object with
another.
[0035] As used herein, "mechanical force" and "mechanical forces"
refer to any physical force that impinges on an object that causes
mechanical stress within or surrounding the object. Example of
mechanical forces would be frictional forces or drag forces. As
such, the terms "frictional force" and "drag force" may be used
interchangeably, and refer to mechanical forces impinging on an
object as described.
[0036] As used herein, "mechanical stress" refers to a force per
unit area that resists impinging mechanical forces that tend to
compact, separate, or slide an object.
[0037] As used herein, the term "profile" refers to a contour above
a solidified braze layer surface to which the superabrasive
particles are intended to protrude.
[0038] As used herein, "leading edge" means the edge of a CMP pad
dresser that is a frontal edge based on the direction that the CMP
pad is moving, or the direction that the pad is moving, or both.
Notably, in some aspects, the leading edge may be considered to
encompass not only the area specifically at the edge of a dresser,
but may also include portions of the dresser which extend slightly
inward from the actual edge. In one aspect, the leading edge may be
located along an outer edge of the CMP pad dresser. In another
aspect, the CMP pad dresser may be configured with a pattern of
abrasive particles that provides at least one effective leading
edge on a central or inner portion of the CMP pad dresser working
surface. In other words, a central or inner portion of the dresser
may be configured to provide a functional effect similar to that of
a leading edge on the outer edge of the dresser.
[0039] As used herein, "centrally located particle," "particle in a
central location" and the like mean any particle of a tool that is
located in an area of the tool that originates at a center point of
the tool and extends outwardly towards the tool's edge for up to
about 90% of the radius of the tool. In some aspects, the area may
extend outwardly from about 20% to about 90% of the radius. In
other aspects, the area may extend out to about 50% of the radius.
In yet another aspect, the area may extend out to about 33% of the
radius of a tool.
[0040] As used herein, "peripherally located," "particles in a
peripheral location" and the like, mean any particle of a tool that
is located in an area that originates at the leading edge or outer
rim of a tool and extends inwardly towards the center for up to
about 90% of the radius of the tool. In some aspects, the area may
extend inwardly from about 20% to 90% of the radius. In other
aspects, the area may extend in to about 50% of the radius. In yet
another aspect, the area may extend in to about 33% of the radius
of a dresser (i.e. 66% away from the center).
[0041] As used herein, "working end" refers to an end of a particle
which is oriented towards the work piece being abraded by a tool.
Most often the working end of a particle will be distal from a
substrate to which the particle is attached.
[0042] As used herein, "ceramic" refers to a hard, often
crystalline, substantially heat and corrosion resistant material
which may be made by firing a non-metallic material, sometimes with
a metallic material. A number of oxide, nitride, and carbide
materials considered to be ceramic are well known in the art,
including without limitation, aluminum oxides, silicon oxides,
boron nitrides, silicon nitrides, and silicon carbides, tungsten
carbides, etc.
[0043] As used herein, "grid" means a pattern of lines forming
multiple squares.
[0044] As used herein, "attitude" means the position or arrangement
of a superabrasive particle in relation to a defined surface, such
as a substrate to which it is attached, or a work piece to which it
is to be applied during a work operation. For example, a
superabrasive particle can have an attitude that provides a
specific portion of the particle in orientation toward the work
piece.
[0045] As used herein, the term "substantially" refers to the
complete or nearly complete extent or degree of an action,
characteristic, property, state, structure, item, or result. For
example, an object that is "substantially" enclosed would mean that
the object is either completely enclosed or nearly completely
enclosed. The exact allowable degree of deviation from absolute
completeness may in some cases depend on the specific context.
However, generally speaking the nearness of completion will be so
as to have the same overall result as if absolute and total
completion were obtained. The use of "substantially" is equally
applicable when used in a negative connotation to refer to the
complete or near complete lack of an action, characteristic,
property, state, structure, item, or result. For example, a
composition that is "substantially free of" particles would either
completely lack particles, or so nearly completely lack particles
that the effect would be the same as if it completely lacked
particles. In other words, a composition that is "substantially
free of" an ingredient or element may still actually contain such
item as long as there is no measurable effect thereof.
[0046] As used herein, a plurality of items, structural elements,
compositional elements, and/or materials may be presented in a
common list for convenience. However, these lists should be
construed as though each member of the list is individually
identified as a separate and unique member. Thus, no individual
member of such list should be construed as a de facto equivalent of
any other member of the same list solely based on their
presentation in a common group without indications to the
contrary.
[0047] Concentrations, amounts, and other numerical data may be
expressed or presented herein in a range format. It is to be
understood that such a range format is used merely for convenience
and brevity and thus should be interpreted flexibly to include not
only the numerical values explicitly recited as the limits of the
range, but also to include all the individual numerical values or
sub-ranges encompassed within that range as if each numerical value
and sub-range is explicitly recited. As an illustration, a
numerical range of "about 1 to about 5" should be interpreted to
include not only the explicitly recited values of about 1 to about
5, but also include individual values and sub-ranges within the
indicated range. Thus, included in this numerical range are
individual values such as 2, 3, and 4 and sub-ranges such as from
1-3, from 2-4, and from 3-5, etc.
[0048] This same principle applies to ranges reciting only one
numerical value. Furthermore, such an interpretation should apply
regardless of the breadth of the range or the characteristics being
described.
[0049] The Invention
[0050] The present invention provides low-melting point
superabrasive tools including methods for their use and
manufacture. Though much of the following discussion relates to CMP
pad dressers, it should be understood that the methods and tools
according to aspects of the presently claimed invention are equally
applicable to any tool that utilizes abrasive or superabrasive
materials, all of which are considered to be within the scope of
the present invention. As has been discussed, superabrasive tools
that are constructed with traditional molten braze materials are
necessarily made at high temperatures that often warp the tool.
Such warpage causes movements in the relative positions of the
superabrasive particles as the tool cools. It is thus very
difficult to obtain precise leveling of the tips of superabrasive
particles in such tools for applications requiring very precise
polishing. It has now been found that the variance between the tip
heights of a plurality of superabrasive particles in a tool can be
greatly reduced by utilizing a braze having a low-melting point to
bond the superabrasive particles. Such low-melting point braze
materials do not generate significant warpage due to the lower
temperatures utilized to construct the tool. In addition, the
inventor has also discovered that precisely leveling the tips of
the plurality of superabrasive particles in the tool reduces the
mechanical stress impinging on any individual superabrasive
particle, thus counteracting the relatively lower retention
strength of many low-melting point brazes as compared to
traditional braze alloys. By reducing such impinging stress,
superabrasive particles can be more readily retained in the
solidified braze, particularly when used for delicate tasks.
[0051] Accordingly, in one aspect of the present invention a method
for making a low-melting point superabrasive tool having a
plurality of superabrasive particles is provided. Such a method may
include coating each of the plurality of superabrasive particles
with an intermediate layer that chemically bonds to each of the
plurality of superabrasive particles, and bonding together the
plurality of superabrasive particles with a molten braze having a
melting temperature of less than about 700.degree. C. In another
aspect, the plurality of superabrasive particles may be bonded
together with a molten braze having a melting temperature of less
than about 500.degree. C.
[0052] As is shown in FIG. 1, an intermediate layer 12 is coated
onto a superabrasive particle 14 that is then disposed in a
low-melting point braze 16. The intermediate layer 12 may be
utilized for a variety of non-limiting purposes. In one aspect, for
example, such a coating may improve the retention of the
superabrasive particle 14 in the solidified braze 16. In one aspect
the intermediate layer 12 may be chemically bonded to the
superabrasive particle 12. For example, if the superabrasive
particle is diamond and the intermediate layer is titanium (Ti),
carbide bonds can be formed between the diamond and the Ti. The
formation of carbide bonds can therefore occur at higher
temperatures because the intermediate layer is applied to the
superabrasive particles prior to incorporation into a superabrasive
tool, thus minimizing warping during the manufacture of the tool.
As has been suggested, the intermediate layer may also be
mechanically bonded to the surface of the superabrasive particle to
improve retention in the solidified braze material. Retention may
be improved, for example, in those situations wherein the
low-melting point braze adheres more strongly to the intermediate
layer than to the surface of the superabrasive particle.
[0053] Following incorporation into a superabrasive tool, in one
aspect the exposed portions 18 of the intermediate layer 12
protruding from the low-melting point braze 16 may be removed, as
is shown in FIG. 2. Removal of the intermediate layer 12 from the
superabrasive particle 14 may be accomplished by any method known
to one of ordinary skill in the art, including, without limitation,
mechanically abrading, sand blasting, chemical etching, etc. In
another aspect, the intermediate layer may be left intact following
incorporation of the superabrasive particle into a superabrasive
tool.
[0054] As has been suggested herein, a plurality of superabrasive
particles coated according to aspects of the present invention may
be incorporated into superabrasive tools having a variety of
configurations. For example, in one aspect, a support substrate 22
may be incorporated into a superabrasive tool as is shown in FIG.
4. Thus the plurality of superabrasive particles 14 coated with an
intermediate layer 12 may be metallurgically bonded to the support
substrate 22. In another aspect, a plurality of superabrasive
particles 14 coated with an intermediate layer 12 may be
metallurgically bonded together to form a superabrasive tool
lacking a support substrate as shown in FIG. 5. Additionally,
superabrasive particles 14 may be disposed along one surface of a
superabrasive tool as shown in FIG. 5, or along multiple surfaces
as shown in FIG. 6.
[0055] The superabrasive particles used in embodiments of the
present invention may be selected from a variety of specific types
of diamond and non-diamond materials. The selection of a particular
superabrasive material may be somewhat dependent on the selection
of the intermediate layer and low-melting braze materials to be
used in the tool and vice versa. A given intermediate layer
material may wet or bond better to a particular superabrasive
material than to another, and such bonding affinity may influence
the selection of materials. In one aspect, the superabrasive
particle may be diamond, including natural diamond, synthetic
diamond, and polycrystalline diamond (PCD). In yet another aspect,
the superabrasive particle may be cubic boron nitride (cBN), either
single crystals or polycrystalline. In yet another aspect, the
superabrasive particle may be a member selected from the group
consisting of SiC, Al.sub.2O.sub.3, ZrO.sub.2, and WC.
[0056] Superabrasive particles according to various aspects of the
present invention may take a number of different shapes and sizes
as required to accommodate a specific purpose for the tool into
which it is anticipated that they will be incorporated.
Superabrasive particle shape may affect retention as well as
cutting characteristics of the superabrasive tool. As such, the
selection of superabrasive particle shape for a given tool may
depend to some extent on intended use, particularly for those
applications requiring specific cutting characteristic or where
retention may become problematic. Superabrasive particles may be of
any shape known to one of ordinary skill in the art, including,
without limitation, triangular, cubic, rectangular, trapezoidal,
hexagonal, etc. In one aspect, substantially all of the
superabrasive particles of a particular tool may be of a
substantially uniform shape. In another aspect, the superabrasive
particles incorporated into a superabrasive tool may have a more
random shape distribution, with little or no intended uniformity of
shape of the superabrasive particles across the surface of the
tool. In yet another aspect, various shapes of superabrasive
particle may be used in the same tool. For example, different
shapes may be distributed in different regions of a superabrasive
tool. In a spinning disk, for example, it may be beneficial to
locate square or blocky particles near the center of the disk where
the rotational velocity is lower, and more slender particles with
defined cutting edges near the periphery where the rotational
velocity is greater. In this way, the shape of the superabrasive
particles may be selected to equalize the mechanical stress
impinging on each particle as a function of physical location on
the tool. Additionally, superabrasive particles having specific
shapes can be located at particular locations on the tool in order
to produce particular cutting patterns.
[0057] Similar to superabrasive particle shape, the size of
particles incorporated into a tool may vary depending on intended
use. In some cutting or polishing operations a high level of
uniformity in the tool pattern may not be required or desired. For
example, in one aspect the superabrasive particles may have no
intended size distribution across the surface of the tool. In
another aspect, substantially all of the superabrasive particles
incorporated into the superabrasive tool may be of substantially
the same size. In another aspect, various sizes of superabrasive
particles may be located at specific locations across the surface
of the superabrasive tool. Such partitioning of superabrasive
particles according to size may equalize the mechanical stress
impinging on each of the superabrasive particles across the surface
of the tool, and thus may be used to increase overall retention of
the particles. In a spinning disk, for example, larger
superabrasive particles may be located more centrally and smaller
superabrasive particles may be located more peripherally in order
to counteract location-dependent variations in mechanical stress
associated with rotational velocity. Such partitioning may also be
utilized to produce a particular cutting pattern in a work piece.
Although a variety of sizes are contemplated, in one aspect the
plurality of superabrasive particle may be from about 5 microns to
about 500 microns in size. In another aspect, the plurality of
superabrasive particles may be from about 30 microns to about 200
microns. In yet another aspect the plurality of superabrasive
particles may be from about 100 microns to about 200 microns in
size. In a further aspect, the plurality of superabrasive particles
may be from about 5 microns to about 50 microns.
[0058] The intermediate layers according to various aspects of the
present invention may include any material known that may improve
the bonding between the superabrasive particles and the low-melting
braze material. In one aspect, the intermediate layer may include a
reactive element capable of forming chemical bonds with the
superabrasive particle, regardless of whether or not chemical bonds
are actually formed during the manufacture of the superabrasive
tool. Various reactive elements are known that are capable of
forming chemical bonds with various superabrasive materials.
Particular reactive elements may bond more favorably with
particular superabrasives. For example, in one aspect the
intermediate layer may include a reactive element that is a carbide
former. Carbide formers are capable of forming chemical bonds with
carbon-containing superabrasive materials such as diamond. Examples
of carbide formers may include, without limitation, aluminum (Al),
boron (B), chromium (Cr), lithium (Li), magnesium (Mg), molybdenum
(Mo), manganese (Mn), nirobium (Nb), silicon (Si), tantalum (Ta),
titanium (Ti), vanadium (V), tungsten (W), zirconium (Zr), and
combinations thereof. In one specific aspect the carbide former may
include Ti, and thus be capable of forming TiC bonds with a
superabrasive material such as diamond. In another specific aspect,
the carbide former may include Si, and thus be capable of forming
SiC bonds with the superabrasive material. In one specific aspect,
for example, the intermediate layer may be Si and the braze
material may be Al--Si. Intermediate layers including carbide
formers may typically be formed by conventional methods, such as
the solid state and vapor deposition techniques discussed
herein.
[0059] Intermediate layers may also include reactive elements that
are nitride formers, and thus are capable of forming chemical bonds
with nitride-containing superabrasive materials such as cBN.
Examples of nitride formers may include, without limitation, Al, B,
Cr, Li, Mg, Mo, Mn, Nb, Si, Ta, Ti, V, W, Zr and combinations
thereof. In one specific aspect the nitride former may include Al,
and thus be capable of forming AlN bonds with a superabrasive
material such as cubic boron nitride. In another specific aspect,
the nitride former may include Si, and thus be capable of forming
SiN bonds with the superabrasive material. As with carbide formers,
intermediate layers including nitride formers may typically be
formed by conventional methods, such as the solid state and vapor
deposition techniques discussed herein.
[0060] Many low-melting point alloys may not wet and thus not bond
well to many intermediate layer elements. As is shown in FIG. 3, in
these situations it may be beneficial to an additional layer, such
as a wetting layer 20, to the intermediate layer 12 in order to
facilitate increased interaction with the low-melting braze 16. The
selection of wetting layer materials may thus depend on the
compositions of the intermediate and the superabrasive materials.
Suitable wetting layer materials may include, without limitation,
Si, Cu, Ni, Cr, and combinations thereof. For example, intermediate
layers containing Ti may not be wet effectively by various
low-melting braze materials. In one aspect, wetting can be
improved, however, by coating the intermediate layer with a wetting
layer including Si, particularly when utilizing Si-containing braze
materials such as Al--Si. The thickness of the wetting layer may
vary widely depending on the particular manufacturing techniques
used, and the intended use of the resulting superabrasive
particles. In one aspect, however, the wetting layer may be about 1
micron thick. In another aspect, the wetting layer may be from
about 0.1 micron to about 5 microns thick. In another aspect, the
wetting layer may be less than about 1 micron thick.
[0061] The intermediate layer-coated superabrasive particles may be
formed into a tool or bonded to a support matrix with a low-melting
point braze. As has been described, the use of a low-melting point
braze allows a superabrasive tool to be formed at lower
temperatures, and thus the leveling of the tips of the incorporated
superabrasive particles may be maintained in the finished tool. In
one aspect low-melting is intended to describe any braze material
that is capable of melting and forming a tool at temperatures below
about 700.degree. C. In another aspect, low-melting is intended to
describe any braze material that capable of melting and forming a
tool at temperatures below about 500.degree. C.
[0062] With respect to specific materials, any low-melting point
braze material known that is capable of retaining coated
superabrasive particles may be used to construct the superabrasive
tools according to aspects of the present invention. In one aspect,
the low-melting point braze material may be substantially a single
metal having a low-melting point. Non-limiting examples of such
materials may include Al, Ag, Sb, Zn, Pb, Cd, Cu, Tl, Bi, Sn, In,
Ga, and combinations thereof. A few single metal braze materials
are shown in Table I, along with their approximate melting
temperatures.
TABLE-US-00001 TABLE I Braze Material Melting Point (C..degree.) Al
660.5.degree. Sb 630.8.degree. Zn 420.0.degree. Pb 327.5.degree. Cd
325.1.degree. Tl 304.0.degree. Bi 271.4.degree. Sn 232.0.degree. In
156.6.degree. Ga 29.8.degree.
[0063] In another aspect of the present invention, low-melting
point braze materials may include braze alloys. Alloying at least
two metals or a metal with a non-metal generally decreases the
melting point of the alloy, thus greatly expanding the number of
available materials that can be utilized to construct a
superabrasive tool. The components and exact ratios of the braze
alloy may be selected to provide an alloy that has a melting point
within a desired range for a particular superabrasive tool being
constructed. In practice, at least two braze materials may be
selected and combined in proper amounts to reduce the melting
temperature of both materials and yield a braze alloy having a
melting temperature of less than about 700.degree. C. In yet
another aspect, the melting temperature may be below about
500.degree. C. Such alloys may be binary, ternary, or other
multi-component alloys. Non-limiting examples of such braze alloys
may include Al--Si, Babbit, Cu--Mg, Al--Cu, Al--Mg, Cu--Zn, Al--Ge,
Cu--Sn, Al--Sn, Sn--Zn, Sn--Tl, Sn--Pb, Sn--Cu--Ag, and
combinations thereof. A few examples of such alloys are shown in
Table II. The wt % is provided in Table II for the first named
element in the metal alloy, unless otherwise indicated.
TABLE-US-00002 TABLE II Metal Alloy Wt % Melting Point (C..degree.)
Al--Si 12.6 577.degree. Babbitt Alloy -- 480.degree. Cu--Mg 60
457.degree. Al--Cu 32 548.2.degree. Al--Mg 85 10 437 450.degree.
Cu--Zn 99.3 425.degree. Al--Ge 51.6 420.0.degree. Sn--Pb 5
312.degree. Cu--Sn 99.3 227.degree. Al--Sn 99.4 220.degree.
Sn--Cu--Ag 0.8 (Cu) 208.degree. 0.7 (Ag) Sn--Zn 91.2 198.5.degree.
Sn--Tl 43 168.degree.
[0064] As will be recognized by those of ordinary skill in the art,
numerous combinations of specific braze materials may be alloyed in
different ratios or amounts to achieve an alloy that bonds to the
reactive element coating of the superabrasive particle, and that
has a suitable melting point.
[0065] As has been discussed, the use of braze materials having a
lower melting temperature reduces problems associated with warping,
but tends to increase the likelihood of superabrasive particles
pulling out of the tool during use. Retention of superabrasive
particles in the braze matrix may be improved by arranging the
superabrasive particles in the solidified braze such that
mechanical stress impinging on any individual superabrasive
particle is minimized. By minimizing such stresses, superabrasive
particles can be more readily retained in the solidified braze,
particularly for use in delicate tasks.
[0066] Though various methods of minimizing mechanical stress are
possible, in one aspect the arrangement of the plurality of
superabrasive particles may be configured to uniformly distribute
frictional forces across substantially all superabrasive particles.
Such a uniform distribution of frictional force prevents any
individual superabrasive particle from being overstressed and
pulling out of the solidified braze layer.
[0067] Various configurations or arrangements are contemplated for
minimizing the mechanical stress impinging on the superabrasive
particles held in a tool. One potentially useful parameter may
include the height that the superabrasive particles protrude above
the solidified braze layer. A superabrasive particle that protrudes
to a significantly greater height as compared to other
superabrasive particles will experience a greater proportion of the
impinging mechanical forces, and is thus more prone to pull out of
the solidified braze layer. Thus an even height distribution of
superabrasive particles may function to more effectively preserve
the integrity of the superabrasive tool as compared to tools
lacking such an even height distribution. Accordingly, the
superabrasive particle tips may be leveled to spread the mechanical
forces impinging on the tool across substantially all of the
particles. In one aspect, for example, the plurality of
superabrasive particles may be arranged on a leveling surface and
bonded together with the molten braze such that, upon formation of
the superabrasive tool, the plurality of superabrasive particles
have been leveled by the leveling surface to an RA value of less
than about 40 .mu.m. In another aspect, the tips of the
superabrasive particles may be leveled to an RA value of less than
about 30 .mu.m. In yet another aspect, the tips of the
superabrasive particles may be leveled to an RA value of less than
about 20 .mu.m. In a further aspect, the tips of the superabrasive
particles may be leveled to an RA value of less than about 10
.mu.m.
[0068] It should also be noted that mechanical forces impinging on
leveled superabrasive particle tips may also be somewhat dependent
on superabrasive particle spacing. In other words, the greater the
distance separating superabrasive particles, the more the impinging
forces will affect each superabrasive particle. As such, patterns
with increased spacing between the superabrasive particles may
benefit from even smaller variations from a predetermined
height.
[0069] It may also be beneficial for the superabrasive particles to
protrude from the solidified braze layer to a predetermined height
or series of heights that is/are along a designated profile.
Numerous configurations for designated profiles are possible,
depending on the particular use of the superabrasive tool. In one
aspect, the designated profile may be a plane. In planar profiles,
the highest protruding points of the superabrasive particles are
intended to be substantially level. It is important to point out
that, though it is preferred that these points align with the
designated profile, there may be some height deviation between
superabrasive particles that occur due to limitations inherent in
the manufacturing process.
[0070] In addition to planar profiles, in another aspect of the
present invention the designated profile has a slope. Tools having
sloping surfaces may function to more evenly spread the frictional
forces impinging thereon across the superabrasive particles,
particularly for rotating tools such as disk sanders and CMP pad
dressers. For example, the greater downward force applied by higher
central portions of the tool may offset the higher rotational
velocity at the periphery, thus reducing the mechanical stress
experienced by superabrasive particles in peripheral locations. As
such, the slope may be continuous from a central point of the tool
to a peripheral point, or the slope may be discontinuous, and thus
be present on only a portion of the tool. Similarly, a given tool
may have a single slope or multiple slopes. In certain aspects, the
tool may slope in a direction from a central point to a peripheral
point, or it may slope from a peripheral point to a central point.
Various slopes are contemplated that may provide a benefit to
solidified braze layer tools. It is not intended that the claims of
the present invention be limited as to specific slopes, as a
variety of slopes in numerous different tools are possible. In one
aspect, however, a CMP pad dresser may benefit from an average
slope of 1/1000 from the center to the periphery.
[0071] As a variation on tools having a slope, in certain aspects
the designated profile may have a curved shape. One specific
example of a curved shape is a dome shape tool. Such curved
profiles function in a similar manner to the sloped surfaces. Tools
may include such curved profiles in order to more effectively
distribute the frictional forces between all of the superabrasive
particles, thus reducing failures of individual particles and
prolonging the life of the tool. Superabrasive particles may be
aligned along various designated profiles by any means known to one
of ordinary skill in the art. In one aspect, however, the
superabrasive particles may be arranged along a leveling surface
that has a shape corresponding to a particular designated
profile.
[0072] As has been mentioned herein, while it is intended that the
tips of the superabrasive particles align along the designated
profile, some level of deviation may occur. These deviations may be
a result of the design or manufacturing process of the tool. Given
the wide variety of sizes of superabrasive particles that may
potentially be utilized in a given tool, such deviations may be
highly dependent on a particular application. Also, when referring
to the designated profile, it should be noted that the term "tip"
is intended to include the highest protruding point of a
superabrasive particle, whether that point be an apex, an edge, or
a face. As such, in one aspect a majority of the plurality of
superabrasive particles are arranged such that their tips vary from
the designated profile by from about 1 micron to about 150 microns.
In another aspect, the plurality of superabrasive particles are
arranged such that their tips vary from the designated profile by
from about 5 microns to about 100 microns. In yet another aspect,
the plurality of superabrasive particles are arranged such that
their tips vary from the designated profile by from about 10
microns to about 75 microns. In a further aspect, the plurality of
superabrasive particles are arranged such that their tips vary from
the designated profile by from about 10 microns to about 50
microns. In another aspect, the plurality of superabrasive
particles are arranged such that their tips vary from the
designated profile by from about 50 microns to about 150 microns.
In yet another aspect, the plurality of superabrasive particles are
arranged such that their tips vary from the designated profile by
from about 20 microns to about 100 microns. In a further aspect,
the plurality of superabrasive particles are arranged such that
their tips vary from the designated profile by from about 20
microns to about 50 microns. In another aspect, the plurality of
superabrasive particles are arranged such that their tips vary from
the designated profile by from about 20 microns to about 40
microns. Additionally, in one aspect, the plurality of
superabrasive particles are arranged such that their tips vary from
the designated profile by less than about 20 microns. In another
aspect the plurality of superabrasive particles are arranged such
that their tips vary from the designated profile by less than about
10 microns. In yet another aspect, the plurality of superabrasive
particles is arranged such that their tips vary from the designated
profile by less than about 5 microns. In yet another aspect, the
plurality of superabrasive particles is arranged such that their
tips vary from the designated profile by less than about 1 microns.
In a further aspect, a majority of the plurality of superabrasive
particles are arranged such that their tips vary from the
designated profile to less than about 10% of the average size of
the superabrasive particles.
[0073] Variations in superabrasive particle size between different
locations on the tool may also help to more evenly distribute the
frictional forces impinging thereon. Larger superabrasive particles
will most likely experience greater frictional force than would
smaller particles. Additionally, in the case circumferentially
rotating tools such as CMP pad dressers, superabrasive particles
located near the periphery will most likely experience greater
frictional force than particles located more centrally due to the
greater rotational velocity at the periphery. In such a case,
frictional forces may be distributed across the CMP pad by locating
larger superabrasive particles more centrally to offset this
increase. As a result, the frictional forces are more evenly spread
across all superabrasive particles, thus reducing particle failure.
As such, in one aspect superabrasive particles in a central
location of the tool are larger in size than superabrasive
particles in a peripheral location on the tool. In another aspect,
superabrasive particles in a central location of the tool may be
smaller than superabrasive particles in a peripheral location on
the tool. This configuration may provide benefit to
circumferentially rotating tools, where the mechanical stresses on
superabrasive particles are greater at the periphery. The larger
superabrasive particles extend deeper into the solidified braze
layer, and are thus more firmly supported therein. Also, for CMP
pad dressers, larger particles at the periphery may provide more
slurry clearance than smaller particles. Additionally, although a
variety of sizes are contemplated, in one aspect the plurality of
superabrasive particle may be from about 30 microns to about 500
microns in size. In another aspect the plurality of superabrasive
particles are from about 100 microns to about 200 microns in size.
It is also contemplated that the plurality of superabrasive
particles may be of substantially the same size.
[0074] Variations in the attitude of superabrasive particles in the
solidified braze layer may also function to more effectively
distribute frictional forces across the tool. Orienting
superabrasive particles in particular locations of the tool such
that similar apexes, edges, and/or faces are exposed may allow a
more even distribution of frictional forces, particularly if the
densities of superabrasive particles in those locations are
concomitantly arranged. As such, in one aspect securing the
plurality of superabrasive particles in the solidified braze layer
may include arranging the plurality of superabrasive particles
according to a predetermined attitude. In various aspects, the
predetermined attitude may be a uniform attitude across
substantially all of the plurality of superabrasive particles. In
other words, similar apexes, edges, or faces for substantially all
of the superabrasive particles in the tool may be facing the same
direction. In one aspect, the plurality of superabrasive particles
may be substantially configured with an apex portion oriented
towards a work piece. As such, impinging frictional forces may be
reduced by orienting the plurality of superabrasive particles such
that their tips or apexes are substantially oriented towards the
work piece. This may be partially due to the smaller surface area
of the apex region of the superabrasive particles coming in contact
with the work piece during abrading as compared to the larger
surface areas of the edge or face regions. Also, the attitude of
the plurality of superabrasive particles can also vary depending on
the location of particles on the tool. For example, in one aspect
superabrasive particles in a central location on the tool may be
configured with an apex or an edge portion oriented towards a work
piece, and superabrasive particles in a peripheral location on the
tool may be configured with a face oriented towards the work piece.
In another aspect, superabrasive particles in a central location on
the tool may be configured with an apex portion oriented towards a
work piece, superabrasive particles in a peripheral location on the
tool may be configured with a face oriented towards the work piece,
and superabrasive particles in a middle location on the tool may be
configured with an edge oriented towards the work piece.
[0075] It may be preferable to utilize superabrasive particles
smaller than about 40 microns when orienting face portions towards
the work piece. In this case, the face is not big enough to
overstress those superabrasive particles. Faces also have the
advantage of having four edges that can be used to cut the work
piece.
[0076] The distribution of frictional forces may also be varied
through the arrangement or distribution of the superabrasive
particles in the solidified braze layer. For example, in one aspect
the plurality of superabrasive particles may be arranged as a grid.
Though the even or uniform spacing of the superabrasive particle
can exhibit wide variation across abrading tools, in one specific
aspect the plurality of superabrasive particles may be evenly
spaced at a distance of from about 2 times to about 4 times the
average size of the superabrasive particles. In another specific
aspect the plurality of superabrasive particles may be evenly
spaced at a distance of from about 3 times to about 5 times the
average size of the superabrasive particles. In yet another
specific aspect the plurality of superabrasive particles may be
evenly spaced at a distance of from about 3 times to about 4 times
the average size of the superabrasive particles. In a further
aspect, the plurality of superabrasive particles may be evenly
spaced at a distance of from about 4 times to about 5 times the
average size of the superabrasive particles. In yet another aspect,
the plurality of superabrasive particles may be evenly space at a
distance of from about 100 microns to about 800 microns. As has
been discussed herein, however, if all superabrasive particles are
evenly spaced, those particles near the periphery will experience
greater mechanical stress due to the higher rotational velocity of
the tool at that location. The larger the tool, the greater the
disparity in the impinging mechanical forces between the center of
the tool and the periphery. Because of this, it may be beneficial
to vary the spacing of the superabrasive particle depending on
location to more effectively distribute frictional forces across
the tool. In one aspect, for example, superabrasive particles in a
peripheral location on the tool may be spaced farther apart than
superabrasive particles in a central location on the tool. In this
way, the increased frictional forces due to the greater density of
superabrasive particles in the central location may offset the
increased frictional forces at the periphery due to the greater
rotational velocity of the tool.
[0077] Various methods for making a superabrasive tool according to
embodiments of the present invention are contemplated. In those
aspects where strong chemical bonding is desired at the surface of
the superabrasive particle, the intermediate layer can be applied
to the superabrasive particles and chemical bonds can be formed
therebetween prior to leveling the superabrasive particle tips. In
other words, heat used to create chemical bonding is applied prior
to incorporating the superabrasive particles into the tool so that
warping can be minimized.
[0078] Various methods of disposing superabrasive particles on a
substrate are contemplated, all of which would be considered to be
within the scope of the present invention. For example,
superabrasive particles may be disposed according to an arranged
pattern by applying spots of glue to a substrate, by creating
indentations in the substrate to receive the particles, by adhesive
transfer, vacuum transfer, or by any other means known to one
skilled in the art. Additional methods may be found in U.S. Pat.
Nos. 6,039,641 and 5,380,390, which are incorporated herein by
reference.
[0079] Orienting superabrasive particles according to a particular
attitude can be accomplished by various methods, all of which would
be considered to be within the scope of the present invention. For
example, in various aspects the plurality of superabrasive
particles may have an apex oriented away from the plane of the
braze matrix. In one specific aspect, superabrasive particles may
be picked up and positioned with a surface containing numerous
flared holes providing suction. An apex portion of a superabrasive
particle is sucked into the flared section of each of the holes in
the surface. Because the flared portion and the holes are smaller
than the superabrasive particles, the particles will be held in a
pattern along the surface. Also, due to the shape of the flared
sections, the apex portions of the superabrasive particles will be
oriented towards the surface. This pattern of superabrasive
particles can then be disposed along a substrate having an adhesive
or directly into an temporary spacer material. Accordingly, the
tips of the superabrasive particles will have the same orientation
or attitude.
[0080] In another aspect, it may be desired to orient apexes and
edges away from the plane of the braze matrix. This can be
accomplished by applying a micro sieve such as nylon or other
similar template-like material to a substrate that is coated with
an adhesive. The holes in the micro sieve may be, without
limitation, approximately 1/2 the size of the superabrasive
particles. A template oriented on the micro sieve can position the
superabrasive particles in a pattern. Apexes and edges but not the
faces of the superabrasive particles can pass through the micro
sieve and into the adhesive. Those faces that do adhere to the
adhesive through the micro sieve will not affect the cutting of the
tool, as they will be recessed in height as compared to
superabrasive particles having tips and edges oriented towards the
adhesive, and thus will not contact the work piece during abrading
or dressing.
[0081] Following manufacture of such a tool in a braze matrix, a
portion of the braze can be removed along with the sieve to expose
the superabrasive particles. Care should be taken, however, to
carefully control the amount of braze matrix removed when exposing
the superabrasive particles. Removing too much will overexposed the
superabrasive particles, and thus cause increased pullout. Removing
too little will not expose the superabrasive particles sufficiently
to allow efficient penetration for cutting, debris removal, and
slurry flow in the case of CMP pad dressers.
[0082] Various reverse casting methods may be utilized to
manufacture the superabrasive tools, and particularly the CMP pad
dressers according to aspects of the present invention. As shown in
FIG. 7, a spacer layer 32 may be applied to a working surface 34 of
a temporary substrate 36. Intermediate layer-coated superabrasive
particles 30 may be disposed at least partially into the spacer
layer 32, such that they protrude at least partially from the
spacer layer 32 opposite the working surface 34 of the temporary
substrate 36. Any method of disposing superabrasive particles into
a spacer layer such that the superabrasive particles protrude to a
predetermined height may be utilized in the present invention. A
fixative may be optionally applied to the working surface 34 to
facilitate the attachment of the spacer layer 32 to the temporary
substrate 36. A fixative may also be optionally applied to the
spacer layer 32 to hold the superabrasive particles 30 essentially
immobile along the spacer layer 32. The fixative used on either
surface of the spacer layer may be any adhesive known to one
skilled in the art, such as, without limitation, a polyvinyl
alcohol (PVA), a polyvinyl butyral (PVB), a polyethylene glycol
(PEG), a pariffin, a phenolic resin, a wax emulsion, an acrylic
resin, or combinations thereof. In one aspect, the fixative is a
sprayed acrylic glue.
[0083] A press may be utilized to apply force to the superabrasive
particles in order to dispose the superabrasive particles into the
spacer layer. The press may be constructed of any material know to
one skilled in the art able to apply force to the superabrasive
particles. Examples include, without limitation, metals, wood,
plastic, rubber, polymers, glass, composites, ceramics, and
combinations thereof. Depending on the application, softer
materials may provide a benefit over harder materials. For example,
if unequal sizes of superabrasive particles are used, a hard press
may only push the largest superabrasive particles through the
spacer layer to the working surface. In one aspect of the present
invention, the press is constructed of a porous rubber. A press
constructed from a softer material such as a hard rubber, may
conform slightly to the shape of the superabrasive particles, and
thus more effectively push smaller as well as larger superabrasive
particles through the spacer layer to the working surface.
[0084] The spacer layer may be made from any soft, deformable
material with a relatively uniform thickness. Examples of useful
materials include, but are not limited to, rubbers, plastics,
waxes, graphites, clays, tapes, grafoils, metals, powders, and
combinations thereof. In one aspect, the spacer layer may be a
rolled sheet comprising a metal or other powder and a binder. For
example, the metal may be a stainless steel powder and a
polyethylene glycol binder. Various binders can be utilized, which
are well known to those skilled in the art, such as, but not
limited to, a polyvinyl alcohol (PVA), a polyvinyl butyral (PVB), a
polyethylene glycol (PEG), a pariffin, a phenolic resin, a wax
emulsions, an acrylic resin, and combinations thereof.
[0085] Referring now to FIG. 8, a low-melting point braze may be
applied to the spacer layer 32 opposite the working surface 34 of
the temporary substrate 36. A mold may be utilized to contain the
low-melting point braze during manufacture. Upon solidifying the
braze material, a low-melting point braze matrix 38 is formed,
bonding at least a portion of each superabrasive particle 30. In
some aspects, a permanent substrate may be coupled to the
low-melting point braze matrix 38 to facilitate its use as a
superabrasive tool.
[0086] As shown in FIG. 9, the spacer layer and the temporary
spacer layer have been removed from the low-melting point braze
matrix 38 to expose the superabrasive particles 30. This may be
accomplished by peeling, grinding, sandblasting, scraping, rubbing,
abrasion, etc. The distance of the protrusion of the superabrasive
particles 30 from the low-melting point braze matrix 38 will be
approximately equal to the thickness of the now removed spacer
layer. The braze material may be etched, sandblasted or abraded to
further expose the superabrasive particles. Additionally, a portion
of the intermediate layer may be removed as described herein in
order to expose a portion 40 of the surface area of the
superabrasive particles 30, as is shown in FIG. 10.
[0087] One distinction between the various methods of disposing
superabrasive particles into the spacer layer may be seen upon
removal of the spacer layer. In those aspects where the
superabrasive particles are pressed into the spacer layer, the
spacer layer material in close proximity to a superabrasive
particle will be deflected slightly towards the working surface of
the temporary substrate. In other words, the spacer layer material
surrounding an individual superabrasive particle may be slightly
concave on the side opposite of the working surface due to the
superabrasive particle being pushed into the spacer layer. This
concave depression will be filled with braze material during the
manufacture of the tool, and thus the braze material may wick up
the sides of the superabrasive particle. For those aspects where
the spacer layer is pressed onto the superabrasive particles, the
opposite is true. In these cases, the spacer layer material in
close proximity to a superabrasive particle will be deflected
slightly away from the working surface of the temporary substrate.
In other words, the spacer layer material surrounding an individual
superabrasive particle may be slightly convex on the side opposite
of the working surface due to the spacer layer being forced around
the superabrasive particle. This convex protrusion may cause a
slight concave depression in the braze matrix surrounding each
superabrasive particle. This slight concave depression may decrease
retention, resulting in premature superabrasive grit pullout from
the braze matrix.
[0088] The temporary substrate may be made of any material capable
of supporting the braze material and withstanding the temperatures
experienced during manufacture. Example materials include glasses,
metals, woods, ceramics, polymers, rubbers, plastics, etc.
Additionally, the working surface of the temporary substrate may be
of any shape beneficial to the construction of a superabrasive
tool. Accordingly, the working surface may be level, sloped, flat,
curved, or any other shape that would be useful in the manufacture
of a CMP pad dresser or other superabrasive tool. Additionally, the
working surface may be roughened to improve the orientation of the
superabrasive particles as has been described herein. When a
superabrasive particle is pressed onto a very smooth temporary
substrate, it may be more likely that a flat surface of the
superabrasive particle will align parallel to the temporary
substrate. In this situation, when the spacer layer is removed the
flat surface of the superabrasive particle will protrude from the
braze matrix. Roughening the surface of the temporary substrate
will create pits and valleys that may help to align the
superabrasive grit such that the tips of individual superabrasive
particle will protrude from the braze matrix.
[0089] Due to the soft nature of many low-melting point braze
materials, it may also be beneficial to utilize a reinforcing
material to improve the retention of the superabrasive particles.
For example, in one aspect the superabrasive particles may be
disposed or packed in a reinforcing material such as silica and
then infiltrated with the molten braze material. It should be noted
that any reinforcing material that improves the retention of the
superabrasive particles in a braze material should be considered to
be within the present scope.
[0090] Of course, it is to be understood that the above-described
arrangements are only illustrative of the application of the
principles of the present invention. Numerous modifications and
alternative arrangements may be devised by those skilled in the art
without departing from the spirit and scope of the present
invention and the appended claims are intended to cover such
modifications and arrangements. Thus, while the present invention
has been described above with particularity and detail in
connection with what is presently deemed to be the most practical
and preferred embodiments of the invention, it will be apparent to
those of ordinary skill in the art that numerous modifications,
including, but not limited to, variations in size, materials,
shape, form, function and manner of operation, assembly and use may
be made without departing from the principles and concepts set
forth herein.
* * * * *