U.S. patent application number 10/729488 was filed with the patent office on 2004-10-14 for backing plate and its manufacturing process.
This patent application is currently assigned to Komatsu, Ltd.. Invention is credited to Furukoshi, Takayuki, Kuriyama, Kazuya.
Application Number | 20040200888 10/729488 |
Document ID | / |
Family ID | 17038181 |
Filed Date | 2004-10-14 |
United States Patent
Application |
20040200888 |
Kind Code |
A1 |
Kuriyama, Kazuya ; et
al. |
October 14, 2004 |
Backing plate and its manufacturing process
Abstract
A backing plate of Ti for supporting a Ti sputtering target is
formed of at least two components welded together. The backing
plate is welded by interposing a Cu or Zr foil or powder between
faces to be welded, and then heating the assembly to a reaction
temperature high enough to melt one of the Ti and Cu or Zr to
produce a liquid phase. The heating temperature is retained for a
time long enough to permit diffusion of the Cu or Zr into the Ti to
produce a liquid phase diffusion weld. By permitting diffusion to
occur, a separate metallic compound is not produced at the welding
face. In effect welding is accomplished without producing a welding
face, whereby no interface exists in the finished weld. The
resulting weld has a strength substantially equal to the strength
of the Ti material, and very good welding qualities.
Inventors: |
Kuriyama, Kazuya; (Osaka,
JP) ; Furukoshi, Takayuki; (Osaka, JP) |
Correspondence
Address: |
DARBY & DARBY P.C.
P. O. BOX 5257
NEW YORK
NY
10150-5257
US
|
Assignee: |
Komatsu, Ltd.
Tokyo
JP
107-0052
|
Family ID: |
17038181 |
Appl. No.: |
10/729488 |
Filed: |
December 5, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10729488 |
Dec 5, 2003 |
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10170081 |
Jun 11, 2002 |
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6732909 |
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10170081 |
Jun 11, 2002 |
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09136674 |
Aug 19, 1998 |
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Current U.S.
Class: |
228/194 ;
228/245; 228/246; 228/248.1 |
Current CPC
Class: |
B23K 35/302 20130101;
C23C 14/3407 20130101; B23K 35/32 20130101; B23K 35/005
20130101 |
Class at
Publication: |
228/194 ;
228/245; 228/246; 228/248.1 |
International
Class: |
B23K 031/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 19, 1997 |
JP |
9-238982 |
Claims
1. A process for joining at least two components of Ti material
comprising: interposing a Cu material on a welding face between
said two components; heating said two components and said Cu
material to a welding temperature at which said Cu material is
liquified; maintaining said welding temperature for a sufficient
time to permit a substantial diffusion of said Cu material into
said two components; and said substantial diffusion being
sufficient to substantially remove liquid Cu material from said
welding face by said diffusion of said Cu into said Ti
material.
2. A process according to claim 1, wherein said welding temperature
is one of an eutectic reaction temperature or more of Ti--Cu alloy
and a reaction temperature or more of an intermetallic compound
formed by said Ti and Cu materials.
3. A process according to claim 1, wherein said at least two
components form a backing plate for a sputtering process.
4. A process according to claim 1, further comprising performing
the step of heating in an atmosphere of one of a vacuum, an inert
gas, and a reducing gas.
5. A process according to claim 1, wherein said Cu material is at
least one of a Cu foil and a Cu powder.
6. A process according to claim 1, wherein the step of heating
includes heating to a temperature of from about 887.degree. C. to
about 1670.degree. C.
7. A process according to claim 1, wherein the step of maintaining
includes maintaining said welding temperature for at least 600
seconds.
8. A process for joining at least two components of Ti material
comprising: interposing a Zr material on a welding face between
said two components; heating said two components and said Zr
material to a welding temperature at which said Zr material is
liquified; maintaining said welding temperature for a sufficient
time to permit a substantial diffusion of said Zr material into
said two components; and said substantial diffusion being
sufficient to substantially remove liquid Zr material from said
welding face by said diffusion of said Zr into said Ti
material.
9. A process according to claim 8, wherein said welding temperature
is one of an eutectic reaction temperature or more of Ti--Zr alloy
and a reaction temperature of an intermetallic compound formed by
said Ti and Zr materials.
10. A process according to claim 8, wherein said at least two
components form a backing plate for a sputtering process.
11. A process according to claim 8, further comprising performing
the step of heating in an atmosphere of one of a vacuum, an inert
gas, and a reducing gas.
12. A process according to claim 8, wherein said Zr material is at
least one of a Zr foil and a Zr powder.
13. A backing plate produced by the process of claim 1.
14. A backing plate produced by the process of claim 8.
15. A process according to claim 5, wherein said Cu foil comprising
a thickness of about 18 .mu.m to about 60 .mu.m.
16. A process according to claim 5, wherein said Cu foil comprising
a thickness of about 18 .mu.m to about 30 .mu.m.
17. A process according to claim 5, wherein said Cu powder
comprising a particle size diameter of about 25 .mu.m to about 30
.mu.m.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a backing plate and its
manufacturing process for producing a sputtering target to be used
in a sputtering process. The invention relates to a welding process
of a Ti material which welds with high reliability and strength a
titanium (hereafter referred to as Ti) material to be used suitably
for the backing plate or the like.
BACKGROUND OF THE INVENTION
[0002] Sputtering is a well-known process for forming a thin film
on an integrated circuit or the like. A sputtering target is used
in processes of physical sputtering (PVD) and reactive sputtering.
The sputtering target is composed of a target member upon which
ions are impacted, and a backing plate at its rear for supporting
the target member. Cooling channels between the target member and
the backing plate generally carry liquid coolant to keep the
operating temperature of the target within an operating range.
Concretely, it is known that a specified metallic material target
member is soldered to the backing plate made of a Ti material. For
example, it is disclosed in Japanese Patent Application Laid Open
No. 6-293963 that Ti material is used in the backing plate.
[0003] FIG. 12 is an exploded sectional view showing a conventional
backing plate. The backing plate is composed of a substrate 21 for
supporting a target member on one surface, and a cover member 22 to
be affixed on the other surface of the substrate 21. The cover
member 22 has groove notches 23 machined in advance on the side of
the joining face to be soldered to the other surface of the
substrate 21. A space defined by the grooves 23 and the facing
surface of the substrate 21 forms channels for cooling water after
welding of the cover member 22 to the substrate 21. The described
configuration is called water-cooled jacket construction. A backing
plate of the water-cooled jacket construction is disclosed in, for
example, Japanese Patent Application Laid-Open No. 7-197248. The
groove for forming the water channel machined in advance is
disclosed in, for example Japanese Patent Application Laid-Open No.
5-132774.
[0004] Referring now also to FIG. 13, the joint between the cover
member and the substrate 21 may be silver soldered using silver
solder 24 (Japanese Patent Application Laid-Open No. 5 132774,
Japanese Patent Application Laid-Open No. 3-140464).
[0005] Other methods of affixing the cover member 22 to the
substrate include bolting, high-energy beam welding (Japanese
Patent Application laid-Open No. 7-197248) using, for example, EBW
(electron beam welding), and LBW (laser beam welding), or other
conventional welding or joining processes.
[0006] In order to manufacture the backing plate with silver
solder, the sealing area must be substantially larger, because the
strength of silver solder is lower than that of base metal. The
increased welding area requires that the backing plate must be
larger in size.
[0007] If the cover member 22 is bolted to the substrate, an
increased thickness is required to accommodate a screw portion in
the backing plate to obtain a sufficient strength. This increases
the backing plate thickness.
[0008] When the backing plate is manufactured with high energy beam
welding, the specified welding strength is possible because the
strength of the welded joint is almost the same as that of the base
metal. But, since welding is not conducted between the facing
surfaces, the possible shapes available for fabrication of the
backing plate and the water channel are limited.
[0009] Machining costs for forming the groove portion 23 for the
water channel in the cover member 22 increase the cost of the
product.
[0010] Accordingly, an object of this invention is to provide a
backing plate and its manufacturing process which can weld a
plurality of components of Ti material with high reliability and
strength.
[0011] It is a further object of the invention to provide a backing
plate that is thinner and increases the degree of freedom of shape
in the construction.
[0012] Another object of this invention is to provide a Ti material
welding process which can be used preferably for manufacturing the
backing plate and can weld the Ti material with high reliability
and strength.
[0013] In a manufacturing process of a backing plate composed of a
plurality of components, made of the Ti material, welded together,
a manufacturing process of a backing plate comprises the steps of
interposing a copper (hereinafter referred to as Cu) material on
the welding face of the components, heating the material to a
welding temperature selected to an eutectic temperature or more of
Ti--Cu alloy, or preferably a decomposition temperature or more of
an intermetallic compound to be formed by both of the materials so
as to produce a liquid phase of the Cu material. The welding
temperature is maintained long enough to permit the Cu material to
diffuse sufficiently in the Ti material.
[0014] Briefly stated, the present invention provides a backing
plate of Ti for supporting a Ti sputtering target. The backing
plate is formed of at least two components by interposing a Cu or
Zr foil or powder between faces to be welded, and then heating the
assembly to a reaction temperature high enough to melt one of the
Ti and Cu or Zr to produce a liquid phase. The heating is retained
for a time long enough to permit diffusion of the Cu or Zr into the
Ti to produce a liquid phase diffusion weld. By permitting
diffusion to occur, a separate metallic compound is not produced at
the welding face. In effect welding is accomplished without
producing a welding face, whereby no interface exists in the
finished weld. The resulting weld has a strength substantially
equal to the strength of the Ti material, and very good welding
qualities.
[0015] According to an embodiment of the invention, there is
provided a process for joining at least two components of Ti
material comprising: interposing a Cu material on a welding face
between the two components, heating the two components and the Cu
material to a welding temperature at which the Cu material is
liquified, maintaining the welding temperature for a sufficient
time to permit a substantial diffusion of the Cu material into the
two components, and the substantial diffusion being sufficient to
substantially remove liquid Cu material from the welding face by
the diffusion of the Cu into the Ti material.
[0016] According to a feature of the invention, there is provided a
process for joining at least two components of Ti material
comprising: interposing a Zr material on a welding face between the
two components, heating the two components and the Zr material to a
welding temperature at which the Zr material is liquified,
maintaining the welding temperature for a sufficient time to permit
a substantial diffusion of the Zr material into the two components,
and the substantial diffusion being sufficient to substantially
remove liquid Zr material from the welding face by the diffusion of
the Zr into the Ti material.
[0017] According to a further feature of the invention, there is
provided a process for welding first and second components of Ti
materials at a welding face comprising: interposing a layer of a
second metallic material between the first and second Ti materials
at the welding face, the second metallic material being of a type
capable of diffusion into Ti materials at a reaction temperature,
heating the first and second components and the second metallic
material to the reaction temperature, and maintaining the reaction
temperature for a sufficient time to permit a diffusion of the
second material into the Ti material until substantially none of
the second material remains between the first and second
components.
[0018] According to a still further feature of the invention, there
is provided a backing plate comprising: at least first and second
components, the first and second components being of a Ti material,
a first welding face on the first component, a second welding face
on the second component, the first and second welding faces being
welded to each other to form a weld between the first and second
welding faces, and the weld including a second metallic material
diffused though the first and second welding faces, and leaving
substantially none of the second material between the first and
second welding faces.
[0019] The above, and other objects, features and advantages of the
present invention will become apparent from the following
description read in conjunction with the accompanying drawings, in
which like reference numerals designate the same elements.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a side sectional view showing the construction of
a test piece to be used in the diffusion welding test.
[0021] FIG. 2 is a schematic view of a model three-chamber type
vacuum furnace using the diffusion welding test.
[0022] FIG. 3 is a microphotograph showing the metallic structure
near the welded face when the test piece is heated to 1020.degree.
C. and is retained.
[0023] FIG. 4 is a microphotograph showing the metallic structure
near the welded face when the test piece is heated to 950.degree.
C. and is retained for one hour.
[0024] FIG. 5 is a transverse exploded sectional view showing a
backing plate in one embodiment of this invention.
[0025] FIG. 6 is a central axial cross section of the backing plate
of FIG. 5.
[0026] FIG. 7 is a transverse exploded sectional view showing
another embodiment of the invention.
[0027] FIG. 8 is a central axial cross section of the embodiment of
FIG. 7.
[0028] FIG. 9 is a transverse exploded sectional view showing still
another embodiment of the invention.
[0029] FIG. 10 is a central axial cross section of the embodiment
of the invention in FIG. 9.
[0030] FIG. 11 is a transverse sectional view showing a further
embodiment of the invention.
[0031] FIG. 12 is a sectional view showing the conventional
example.
[0032] FIG. 13 is a sectional view showing the conventional
embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0033] In the above backing plate manufacturing process, the
backing plate is heated with the Cu material interposed on the
welding face. The Cu material is melted to produce a liquid phase
to manufacture the backing plate using so-called liquid phase
diffusion welding with the Cu material being diffused in the Ti
material. The welding temperature is at least a decomposition
temperature of an intermetallic compound Ti.sub.2Cu formed between
the liquified Cu and solid Ti materials. Alternatively an eutectic
reaction temperature or more of Ti--Cu alloy may be used. The
welding temperature is retained until the Cu material is
sufficiently diffused in the Ti material. Thus, the intermetallic
compound which is more fragile than the Ti material does not remain
in a face condition on the welded face. The Cu material diffuses
and almost disappears, whereby the interface virtually does not
exist. Since the welded portion is not remelted when heating is
conducted again, the strength of the welding material is almost
equal to that of the Ti material. Thus, the welding strength is
improved as compared with silver soldering, and the area of welded
surface is improved as compared with the high energy beam welding.
This also permits making the welding portion of the backing plate
thinner as compared with that possible when the joining is by
bolting.
[0034] Although the foregoing description supposes that diffusion
is continued until virtually no liquid copper remains at the
interface, in fact, applications may make it desirable to permit at
least some copper to remain at the interface. The claims must be
interpreted in this light.
[0035] The Ti material to be used above includes pure Ti for
industry use, and Ti alloy for industry use. Concretely there can
be Ti-5A1-2.5Sn (residue is inevitable impurity and Ti by weight %,
hereinafter the same) Ti-6A1-4Zr-1V, Ti-8A1-1Mo-1V, Ti-8A1-12Zr,
Ti-3A1-2.5V, Ti-8Mn, Ti-4A1-4Mn, Ti-6A1-4V, Ti-7A1-4Mo,
Ti-3A1-11Cr-13V and so on. The Cu material includes pure Cu for
industry, and Cu alloy for industry.
[0036] The whole component is preferably heated to produce the
weld. Heating in this manner reduces residual stress remaining near
the welding face, and the Ti material is softened and flowed on the
lowermost face, whereby the backing plate remains substantially
undistorted.
[0037] Although the manufacturing process can be conducted in the
ambient atmosphere, the cleanliness of the backing plate is
improved by conducting the welding process in a vacuum, inert gas
or reducing gas atmosphere. Also, if welding is performed in the
ambient atmosphere, when the backing plate is used in a sputtering
operation in superhigh vacuum, outgassing from the backing plate is
increased. If the welding is done in a vacuum or an inert
atmosphere, outgassing from the backing plate is reduced during
sputtering and results in better sputtering. Concretely, it is
preferable to conduct in welding in a vacuum of 10.sup.-3 Torr or
less.
[0038] Although the Cu material to be used in the manufacturing
process can be in any form, it is preferable to use the Cu material
of foil or powder, whereby the handling and the interposing
operation to the welding face are simplified. For example, when the
Cu foil is used, the foil thickness should be within the range of
10 .mu.m through 100 .mu.m. It is confirmed that there is no
difference in the welding strength within the range of 18 .mu.m
through 60 .mu.m. Generally the Cu foil of 18 .mu.m through 30
.mu.m is easily available. When powdered Cu is used, instead of Cu
foil, Cu powder particle sizes between about 25 .mu.m through 30
.mu.m diameter should preferably be used. The powder layer
thickness should preferably be approximately 100 .mu.m. Although it
can be possible to use a thinner layer, this may increase the time
required to do the interposing operation. It is relatively easy to
increase the thickness. A maximum thickness of up to 1 mm is
permissible. When a particular component has a plurality of welding
faces in one plane, the operation can be easier to do by applying
the Cu material over the whole of one plane face. The Cu material
that is outside the welding area does no harm, and any Cu that is
not diffused into the Ti material can be ignored. The amount of the
Cu material used can be minimized, if necessary, by interposing the
Cu material only between the faces that will be welded.
[0039] When foil is used, the welding faces of the Ti material and
the surfaces of the foil should be de-greased and washed with an
organic solvent like alcohol or acetone. Or the surface roughness
should be approximately ".gradient." working (35 s through 100 s)
or should be a little coarse. High surface precision is not
required, because close adherence between the Ti material welding
face and the foil surface is not important. The foil becomes molten
and enters the liquid phase, and thereafter diffuses into the Ti
material.
[0040] Although the welding faces can be welded using pressure
applied in a direction near the welding areas, it is preferable to
not require the application of pressure from the point of view of
the simplification of the welding apparatus. But where there is
camber in faces of the Ti material, it should be desirably pressed
so that the planarity becomes approximately 1.0 mm or less.
[0041] The welding temperature, which is a decomposition
temperature of intermetallic compound or more, or an eutectic
reaction temperature, should be either at or below a melting point
of the Ti material. This limits the maximum welding temperature to
about 1670.degree. C. For pure Cu material, the welding temperature
should preferably be above about 887.degree. C. For Cu material
containing commonly found impurities, the welding temperature
should preferably be above about 887.degree. C. The welding
temperature should more preferably remain within the range of
approximately 990.degree. C. through 1670.degree. C.
[0042] Although it is possible to conduct a better welding
operation when the diffusing time is sufficient to obtain welding
at the eutectic reaction temperature (approximately 887.degree.
C.), the welding temperature of approximately 990.degree. C. or
more should be adopted in practical use. A first reason for the
higher temperature is because it is desired to modify the pure Ti
to .beta. phase to achieve welding in a reasonable time. But in
practical use, welding at the eutectic temperature does not achieve
a sufficiently high diffusion rate. Although the modifying point
from the .alpha. phase of the pure Ti to the .beta. phase is
approximately 885.degree. C., the modifying point is assumed to be
approximately 930.degree. C. through 940.degree. C. in the Ti for
industry where some impurities are allowed to be contained. A
second reason is because the decomposition temperature or more of
the intermetallic compound should preferably be higher to prevent
the intermetallic compound from remaining at the welding face.
[0043] The decomposition temperature of the TiCu, which is the
intermetallic compound, is approximately 975.degree. C. and the
decomposition temperature of Ti.sub.2Cu is approximately
990.degree. C. Accordingly, the welding temperature should be
preferable to be at least 990.degree. C. The top limit is selected
as approximately 1670.degree. C., because the melting point of the
Ti is approximately 1668.degree. C. Thus, in the above temperature
range, the diffusing operation can be caused in the Ti material by
causing a liquid phase of Cu in a condition where an intermetallic
compound is not produced. The resulting welding strength is almost
the same as that of the Ti material by using liquid phase diffusion
welding. This increased strength results from the fact that the
interface hardly exists in the welding portion. Improved welding
efficiency of 90% or more can be realized. Absolutely constant
temperature during welding is not required. Some fluctuation is
permissible within the temperature range.
[0044] The welding time required is that which is sufficient for
the Cu material to diffuse into the Ti material and for the liquid
phase to disappear. The welding time should be preferably 600
seconds or more, although the welding time is selected in
accordance with the thickness of the interposed Cu material. The
welding time of 600 seconds is based on the use of a 10 .mu.m Cu
foil. If thicker foil or powder thickness is used, the welding time
is adjusted accordingly.
[0045] In a manufacturing process of a backing plate composed of a
plurality of components, made of Ti material, welded to each other,
the backing plate manufacturing process according to the invention
also includes the steps of interposing zirconia (hereinafter
referred to as Zr) material on the welding face of the components,
heating the material to a welding temperature selected at a
decomposition temperature or more of an intermetallic compound that
is formed by the two materials so as to cause a liquid phase of the
Zr material. The welding temperature is maintained for a time long
enough so that the Zr material is diffused sufficiently into the Ti
material.
[0046] In the manufacturing process of the invention, the welding
operation is conducted with Zr material on the welding face,
whereby the same welding effect is accomplished as when using the
Cu material.
[0047] Since the backing plate manufactured by the manufacturing
process of the invention is welded using a plurality of components
by liquid phase diffusion welding, the welding strength and welding
area between the components are improved more than before. Even in
a backing plate where a plurality of components composed of the Ti
material are face-welded, for example, by interposing a Ti material
on the welding face, the welding strength and the welding area
between the components are improved more than before.
[0048] A weld, as described above is obtained if the area of the
welding portion is reduced by improvements in the welding strength
and the welding area. In the backing plate of water-cooled
construction using the three-layer construction of the invention,
the substrate of the block member for producing the cooling water
channels and the welding area to the cover member can be made
smaller. The thickness of the water channel portion can be reduced
while obtaining the same capacity of water cooling as before by
correspondingly reducing the thickness. Thus, the whole backing
plate and the welding portion can both be made thinner. Thus, high
permeability of the magnetic field from the magnet positioned
behind the backing plate can be achieved, whereby better sputtering
can be realized.
[0049] The engraving work by machining on the cover member is not
required as before, because of the three-layer construction. Thus,
the manufacturing cost is reduced, the water channel is easier to
form, and the degree of freedom of the water channel design is
increased. That is, even a water channel having a complex shape, as
aforementioned, can be realized easily by building the block member
by combining members of comparatively simple shapes. The cooling
water flow becomes turbulent because of the complex water channel
formed. The difference in the temperature distribution of the
cooling water within the water channel is reduced, thus improving
the cooling performance. Further, the component yield is improved
by dividing the structure into more components. The invention also
includes the backing plate (the cover member and the block member
integrally formed) of a conventional two layer construction, but
using the welding technique of the invention.
[0050] By integrally forming the cover member and the block member
by pressing the one piece of plate-shaped body, the structure can
be easily made even if the shape is relatively complex, and the
cost is reduced by increasing the design freedom of the water
channel shape. The integrally formed cover member and the block
member can be made thinner, the weight reducted and the high
permeability of the magnetic field can be improved.
[0051] A welding process of the Ti material according to the
invention comprises the steps of interposing Cu material on the
welding face of the Ti material, heating the material to a welding
temperature selected to be an eutectic temperature or more of
Ti--Cu alloy, or a decomposition temperature or more of an
intermetallic compound of the two metals so as to produce a liquid
phase of the Cu material, and maintaining the welding temperature
while the Cu material diffuses sufficiently into the Ti
material.
[0052] In the welding process of the Ti material of the invention,
the Ti material is heated with Cu material interposed on the
welding area. The Cu material becomes molten to cause a liquid
phase to weld the Ti material by liquid phase diffusion welding for
welding by diffusing the Cu material into the Ti material. The
welding temperature is an eutectic temperature or more of Ti--Cu
alloy, or preferably a decomposition temperature or more of an
intermetallic compound formed with the Ti material and the Cu
material, and the welding temperature is retained while the Cu
material diffuses sufficiently into the Ti material. Thus, the
intermetallic compound which is more fragile than the Ti material
does not remain on the welding portion. That is, the Cu material
diffuses into the Ti material and almost disappears, whereby the
interface does not exist. The welding portion does not become
molten upon reheating. The strength of the welding portion is
almost equal to that of the Ti material. Thus, the welding strength
is improved as compared with silver soldering, and the welding area
is increased as compared with the high energy beam welding. Also,
the backing plate thinner as compared with the bolting.
[0053] By heating the whole Ti material to be welded, residual
stress is prevented from remaining near the welding area, and the
Ti material is softened and flowed on the lowermost face, whereby
the Ti material after welding remains substantially
undistorted.
[0054] Although the welding process can be conducted in the ambient
atmosphere, the cleanliness of the Ti material after the welding is
improved by conducting the welding in a vacuum, in inert gas or in
a reducing gas atmosphere. When a backing plate for use in a
sputtering process is manufactured by welding in a vacuum or inert
atmosphere, the amount of outgassing from the backing plate in the
superhigh vacuum of the sputtering process is reduced, whereby
better sputtering can be realized.
[0055] For the Cu material to be used in the welding process,
although it is in any embodiment, the Cu material of foil or powder
can be preferably used, whereby the handling and the interposing
operation to the welding face are simplified. The welding
temperature is at least a decomposition temperature of the
intermetallic compound, and preferably higher, but should remain at
or below the melting point of the Ti material. The welding
temperature should preferably stay within the range of
approximately 887.degree. C. through 1670.degree. C., but more
preferably in the range of approximately 990 to 1670.degree. C.,
and the welding time should preferably be 600 seconds or more.
[0056] Referring to FIG. 1, three plates P1, P2 and P3 of Ti (pure
Ti for industry) 300 mm.times.300 mm.times.6 mm were prepared. A
diffusion welding test was conducted using a test piece 31 of a Cu
foil (pure Cu for industry) of 18 .mu.m thickness interposed
between the Ti plates P1 and P2. A Cu foil of 35 .mu.m thickness
was interposed between the Ti plates P2 and P3. The Ti plates P1
through P3, were washed with isopropyl alcohol, were not pressed
with a jib or the like, but were merely superposed and held down
with their own weight. The test piece 31 was placed on a ceramic
plate 32 resting on a carbon tray 33.
[0057] Referring to FIG. 2, heat treatment of the assembly of FIG.
1 was conducted using a transverse three chamber type vacuum
furnace. The test piece 31 was carried by a conveyor 34 through, in
order, a heating chamber 35, a treating chamber 36 and a cooling
chamber 37. In the heat treating conditions, the test piece 31 was
heated for about 70 minutes at a heating rate of 15.degree.
C./minute to a temperature 1020.degree. C. The test piece 31 was
retained in the heating chamber 35 for one hour. The test piece 31
was furnace-cooled as low as 500.degree. C. and then was cooled
below 500.degree. C. using N.sub.2. The test piece 31 was moved at
500.degree. C. because of the three-chamber type vacuum furnace.
After heating in the heating chamber 35, the test piece 31 was
moved to the treating chamber 36 when the temperature reached
500.degree. C. in the heating chamber 35. For cooling, the test
piece 31 was moved to the cooling chamber 37 when the temperature
in the treating chamber 36 reached 500.degree. C. The vacuum was
maintained at approximately 10.sup.-2 to 10.sup.-3 Torr in the
heating chamber 35 and the cooling chamber 37, and approximately
10.sup.-3 to 10.sup.-4 Torr in the treating chamber 36.
[0058] FIG. 3 is a microphotograph showing the metal structure near
the welding face produced by the diffusion welding test with the
structure heated up to the welding temperature of 1020.degree. C.
Table 1 shows the results of the qualitative analysis (EDAX) of the
metal structure of each region.
1TABLE 1 Region Ti (wt %) Cu (wt %) 1-1 75.19 24.81 1-2 88.06 11.94
1-3 75.69 24.31 1-4 95.52 4.48 1-5 99.30 0.70
[0059] When the ratio of the weight % between Ti and Cu. was
approximately 60:40, it was considered that the metallic compound
Ti.sub.2Cu existed. As shown in Table 1,
Ti:Cu.apprxeq.approximately 75:25 even in the regions 1-1, and 1-3
where the ratio of Cu was relatively high. It was confirmed that Cu
was sufficiently diffused to Ti, and large Ti.sub.2Cu, which would
reduce the strength, was absent. Ti.sub.2Cu could exist regions
where the analysis was not conducted. In this case, it was not
proved that the intermetallic compound existed in, for example,
laminations on the whole welding face, and was dotted, thereby
hardly influencing the welding condition.
[0060] It was confirmed that the test piece after treating had a
welding strength of 250 N/mm.sup.2 shear strength, and 350
N/mm.sup.2 tensile strength at room temperature. The welding
strength was almost the same as that of Ti material which was the
base metal. When silver soldering was used, the welding strength
was 159 N/mm.sup.2 shear strength, and 230 N/mm.sup.2 tensile
strength. With the present invention, the welding strength was
improved. It was confirmed that the welding efficiency of the Ti
plates P1 and P2 was approximately 90%, and the welding efficiency
of the Ti plates P2 and the P3 was 99% or more. The planarity was
approximately 1.5 mm before welding, but after welding, the
planarity was confirmed to be improved by approximately 0.5 mm.
Comparative Example
[0061] A diffusion welding test was conducted using the
aforementioned test piece 31 under the same conditions as the
diffusion welding test, except for the heating up to the welding
temperature 950.degree. C. (below the decomposition temperature of
975.degree. C. FIG. 4 is a microphotograph showing the metallic
structure near the welding face when the diffusion welding test for
heating to 950.degree. C. was conducted. Table 2 shows the result
of the qualitative analysis of the metallic structure in each
region.
2TABLE 2 Region Ti (wt %) Cu (wt %) 2-1 63.52 36.48 2-2 76.89
23.11
[0062] Although the region 2-2 is a diffusion layer, the region 2-1
was considered to be Ti.sub.2Cu layer. It was confirmed that the
Ti.sub.2Cu lamination existed in the layer across the whole welding
face, and the welding portion was too fragile. With the welding
temperature 900.degree. C., it was confirmed that it was required
to retain the test piece 31 under heat treatment for 166 hours to
obtain a welding condition as good as in the embodiment. Also, it
was confirmed that there were mixed results with a welding
temperature 950.degree. C. In some cases the results were better
welding condition, and in other cases the welding condition could
not be obtained.
[0063] Referring now to FIGS. 5 and 6, a manufacturing process of
the backing plate using the above welding process will be
described. The backing plate was a three-stage jacket in
construction. Roughly, the substrate 1, the cover member 2 and the
block member 3 are welded. The substrate 1 has a target member on
one surface 1a. A cooling water channel is formed between the cover
member 2 and the block member 3. The cover member is welded on the
rear surface 1b of the substrate 1. The block member 3 is comprised
of an outer frame member 4 and three compartment members 5.
[0064] The members 5 were welded with the aforementioned welding
process with the Cu foil 6 respectively interposed between the rear
surface 1b of the substrate 1 and the block member 3. In addition
Cu foil 6 is interposed between an inner surface 2a of the cover
member 2 and the block member 3. Thus, better welding operation
with improved welding strength and welding area was obtained.
[0065] By improving the welding strength and the welding area in
this way, a strength at least equal to a conventional structure can
be obtained even if the area of the welding face reduced. Thus, the
welding area to the substrate 1 of the block member 3 and the cover
member 2 can be smaller, and the thickness of the water channel
portion can be made thinner while retaining the cooling water
amount equal to that of the conventional device by reducing the
corresponding thickness. The thickness of the welding portion does
not need to increase, as when attachment by bolting is used, and
the welding portion can also be made thinner. Thus, the whole
backing plate can be made thinner. Thus, the high permeability of
the magnetic force from the magnet positioned in the back portion
of the backing plate can be achieved, whereby better sputtering can
be realized.
[0066] Referring now to FIGS. 7 and 8, when a plurality of welding
faces exist on one plane as on the rear surface 1b of the substrate
1 and inner surface 2a of the cover member 2 as shown in FIG. 5,
the Cu foil 7 may be made large enough to cover the entire surfaces
1b and 2a. This is possible because the Cu which does not
contribute directly towards the welding is diffused into the Ti and
does not remain as a Cu layer on the surface. Thus, the portions of
Cu lying between mating parts enter the welding process, and the
portions not contributing to the welding process effectively
disappear by diffusion. The operation is simplified as compared
with a case where the individual provision is conducted as in FIG.
5.
[0067] The provision of the Cu foils 7 and 8 on the whole plane
including the welding face is conducted so that the design freedom
of the water channel increases and more complex form can be made.
For example, as shown in FIG. 8, a plurality of cylindrical
projections 11, 11 . . . can be positioned respectively in four
water channels from the cooling water entrance 9 to the cooling
water exit 10. The presence of the cylindrical projections 11, 11 .
. . in the flow path produces turbulent flow which increases the
effective surface area and thereby increases the cooling
efficiency.
[0068] As shown in FIG. 9, even when the conventional grooved
backing plate composed of the substrate 21 and the cover member 22
is used, the welding operation can be conducted as described above
using Cu or Zr foil or powder 7 to effect the weld.
[0069] The components of the backing plate can be manufactured by
further division thereof with the use of such a liquid phase
diffusion welding operation as described in this invention. For
example, as shown in FIG. 10, the outer frame member 4 can be
manufactured as four separate rod-shaped members 12, 13, 14 and 15
having a rectangular or square cross section, with four welding
faces 17a through 17d. The welding faces 17a through 17d are welded
as shown, according to the above description, thus improving the
yield of the components.
[0070] As another embodiment, as shown in FIG. 11, the cover-block
member 16, formed integrally by press-working the cover member 16.
The cover member 16 is welded to the surface of the substrate 1
using Cu or Zr foil or powder. By using such an integrally formed
member 16, complex shaped water channels can be realized with low
price and ease, and can be made thinner.
[0071] Having described preferred embodiments of the invention with
reference to the accompanying drawings, it is to be understood that
the invention is not limited to those precise embodiments, and that
various changes and modifications may be effected therein by one
skilled in the art without departing from the scope or spirit of
the invention as defined in the appended claims.
* * * * *