U.S. patent application number 14/498678 was filed with the patent office on 2015-04-02 for performance enhanced heat spreader.
The applicant listed for this patent is Specialty Minerals (Michigan) Inc.. Invention is credited to Richard James Lemak, Robert John Moskaitis.
Application Number | 20150090434 14/498678 |
Document ID | / |
Family ID | 51662389 |
Filed Date | 2015-04-02 |
United States Patent
Application |
20150090434 |
Kind Code |
A1 |
Lemak; Richard James ; et
al. |
April 2, 2015 |
Performance Enhanced Heat Spreader
Abstract
Embodiments of the present invention include methods of
disposing a metallic coating layer comprising a metal in an
amorphous and/or fine grain microstructure over at least a portion
of a surface of a pyrolytic graphite substrate, the metal
comprising Nickel, Iron, a Nickel-Iron Alloy, or any combination
thereof, and the grains of the metal being of 1 nm to 10000 nm in
size. Embodiments of the invention also encompass the coated
pyrolytic graphite articles. The coated substrate exhibits a
thermal conductivity not less than the uncoated substrate.
Inventors: |
Lemak; Richard James;
(Allentown, PA) ; Moskaitis; Robert John; (Easton,
PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Specialty Minerals (Michigan) Inc. |
Bingham Farms |
MI |
US |
|
|
Family ID: |
51662389 |
Appl. No.: |
14/498678 |
Filed: |
September 26, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61884818 |
Sep 30, 2013 |
|
|
|
Current U.S.
Class: |
165/185 ;
427/404 |
Current CPC
Class: |
H01L 2924/0002 20130101;
C25D 3/562 20130101; C25D 7/00 20130101; C23C 16/26 20130101; H01L
23/373 20130101; F28F 21/02 20130101; H01L 23/3733 20130101; H01L
2924/0002 20130101; C25D 15/00 20130101; C25D 5/54 20130101; F28F
21/089 20130101; H01L 23/3736 20130101; H01L 2924/00 20130101 |
Class at
Publication: |
165/185 ;
427/404 |
International
Class: |
F28F 21/02 20060101
F28F021/02; F28F 21/08 20060101 F28F021/08 |
Claims
1. A method: disposing a metallic coating layer comprising a metal
over at least a portion of a surface of a pyrolytic graphite
substrate, the metal comprising Nickel, Iron, a Nickel-Iron Alloy,
or any combination thereof, and the grains of the metal being of 1
nm to 10000 nm in size, the metal being amorphous, or both.
2. The method of claim 1, wherein the pyrolytic graphite is highly
oriented pyrolytic graphite, chemical vapor deposition deposited
pyrolytic graphite, or a combination thereof.
3. The method of claim 1, wherein the coating is a Nanovate.TM.
N2040 coating.
4. The method of claim 1, wherein the metal grain size is from 2 nm
to 5000 nm.
5. The method of claim 1, wherein the coating comprises an alloying
addition.
6. The method of claim 5, wherein the alloying addition is selected
from the group consisting of B, C, H, O, P, S, and combinations
thereof.
7. The method of claim 1, wherein the coating comprises solid
particulate of metals; metal oxides; carbides of B, Cr, Bi, Si, W,
or a combination thereof; carbon; glass; polymer materials;
MoS.sub.2, or any combination thereof.
8. The method of claim 7, wherein the coating comprises up to 95%
by volume solid particulates.
9. The method of claim 1, wherein the metallic layer coating
thickness is 10 .mu.m to 50 mm.
10. The method of claim 1, wherein one or more intermediate coating
layers are applied before the application of the metallic coating
layer.
11. The method of claim 10, wherein the intermediate coating layer
comprises a metal, a polymer, or both a metal and a polymer.
12. The method of claim 10, wherein the intermediate coating layer
thickness is less than the metallic coating layer thickness.
13. The method of claim 1, wherein the metallic coating layer
covers all of the exterior surface of the substrate.
14. The method of claim 1, wherein the metallic coating layer
covers only a portion of the exterior surface of the substrate.
15. The method of claim 1, wherein the substrate coated with the
metallic coating layer exhibits a thermal conductivity not less
than the uncoated substrate.
16. The method of claim 1, wherein the substrate coated with the
metallic coating layer exhibits a thermal conductivity of about
105% of the thermal conductivity of the uncoated substrate, or of
not less than 105% of uncoated substrate and also not more than
250% of the uncoated substrate.
17. The method of claim 1, wherein the substrate coated with the
metallic coating layer exhibits a thermal conductivity of about
110% of the thermal conductivity of the uncoated substrate, or of
not less than 110% of uncoated substrate and also not more than
250% of the uncoated substrate.
18. The method of claim 1, wherein the substrate coated with the
metallic coating layer exhibits a thermal conductivity of about
115% of the thermal conductivity of the uncoated substrate, or of
not less than 115% of uncoated substrate and also not more than
250% of the uncoated substrate.
19. The method of claim 1, wherein the metallic coating layer has a
room temperature coefficient of linear thermal expansion in all
directions of less than 25.times.10.sup.-6 K.sup.-1.
20. An article comprising: a substrate of pyrolytic graphite; a
metallic coating layer comprising a metal deposited over at least a
portion of a surface of the pyrolytic graphite substrate, the metal
comprising Nickel, Iron, a Nickel-Iron Alloy, or any combination
thereof, and the grains of the metal being of 1 nm to 10000 nm in
size, the metal being amorphous, or both.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application claims the benefit of U.S.
Provisional patent application No. 61/884,818, filed on Sep. 30,
2013, which is incorporated herein by reference in its entirety,
and expressly including any drawings.
BACKGROUND
[0002] The present invention relates to methods of applying a
coating to a substrate of pyrolytic graphite and the coated
pyrolytic graphite which exhibits an improved thermal conductivity.
The coated pyrolytic graphite can be used as a heat spreader for
conducting heat from a device. Electronic components are becoming
smaller while heat dissipation requirements are becoming greater.
In order to dissipate heat generated by these electronic
components, heat spreaders are utilized between the electronic
component and a heat sink. Heat spreaders can be made of a solid
thermally conductive metal. The solid conductive metal has a
limited ability to spread heat and has limited thermal conductivity
characteristics.
INCORPORATION BY REFERENCE
[0003] All publications, patents, and patent applications mentioned
in this specification are herein incorporated by reference to the
same extent as if each individual publication, patent, or patent
application was specifically and individually indicated to be
incorporated by reference, and as if each said individual
publication, patent, or patent application was fully set forth,
including any figures, herein.
SUMMARY
[0004] Non-limiting embodiments of the invention are described in
the following labeled paragraphs:
[0005] Embodiments of the present invention encompass methods of
disposing a metallic coating layer comprising a metal over at least
a portion of a surface of a pyrolytic graphite substrate, the metal
comprising Nickel, Iron, a Nickel-Iron Alloy, or any combination
thereof, and the grains of the metal being of 1 nanometers (nm) to
10000 nm in size, the metal being amorphous, or both.
[0006] Embodiments of the present invention encompass articles
comprising a metallic coating layer comprising a metal disposed
over at least a portion of a surface of a pyrolytic graphite
substrate, the metal comprising Nickel, Iron, a Nickel-Iron Alloy,
or any combination thereof, and the grains of the metal being of 1
nm to 10000 nm in size, the metal being amorphous, or both.
[0007] In embodiments of the present invention, such as, but not
limited to, the method described in paragraph [0001] or the article
described in paragraph [0002], the pyrolytic graphite substrate is
highly oriented pyrolytic graphite, chemical vapor deposition
deposited pyrolytic graphite, or a combination thereof.
[0008] In embodiments of the present invention, such as, but not
limited to, the method described in paragraph [0001] or the article
described in paragraph [0002], the pyrolytic graphite substrate is
PYROID.RTM. HT, PYROID.RTM. SN, PYROID.RTM. CN, or a combination
thereof.
[0009] In embodiments of the present invention, such as, but not
limited to, any one of the methods or articles described in
paragraphs [0001]-[0004], a Nanovate.TM. N2040 coating disposed
over the substrate comprises the metallic coating layer.
[0010] In embodiments of the present invention, such as, but not
limited to, any one of the methods or articles described in
paragraphs [0001]-[0005], the metallic coating layer comprises a
fine grained metal of metal grain size from 2 nm to 5000 nm.
[0011] In embodiments of the present invention, such as, but not
limited to, any one of the methods or articles described in
paragraphs [0001]-[0006], the metallic coating comprises a fine
grained metal of metal grain size from 5 nm to 1000 nm.
[0012] In embodiments of the present invention, such as, but not
limited to, any one of the methods or articles described in
paragraphs [0001]-[0007], the metallic coating comprises a fine
grained metal of metal grain size from 10 nm to 500 nm.
[0013] In embodiments of the present invention, such as, but not
limited to, any one of the methods or articles described in
paragraphs [0001]-[0005], the metallic coating comprises a fine
grained metal of a metal grain size in a range having a minimum
size selected from 2 nm, 5 nm, and 10 nm, and having a maximum size
selected from 100 nm, 500 nm, 1000 nm, 5000 nm, and 10,000 nm.
[0014] In embodiments of the present invention, such as, but not
limited to, any one of the methods or articles described in
paragraphs [0001]-[0009], the coating comprises an alloying
addition.
[0015] In embodiments of the present invention, such as, but not
limited to, any one of the methods or articles described in
paragraph [0010], the alloying addition is selected from the group
consisting of B, C, H, O, P, S, and combinations thereof.
[0016] In embodiments of the present invention, such as, but not
limited to, the methods or articles described in paragraph [0010],
the alloying addition is selected from the group consisting of Ag,
Au, B, Cr, Mo, P, Pb, Pd, Rh, Ru, Sn, Zn, and combinations
thereof.
[0017] In embodiments of the present invention, such as, but not
limited to, any one of the methods or articles described in
paragraphs [0001]-[0012], the coating comprises solid particulates
where the solid particulates are metals; metal oxides; carbides of
B, Cr, Bi, Si, W, or a combination thereof; carbon; glass; polymer
materials; MoS.sub.2, or any combination thereof.
[0018] In embodiments of the present invention, such as, but not
limited to, any one of the methods or articles described in
paragraph [0013], the polymer materials are selected from the group
consisting of polytetrafluoroethylene, polyvinyl chloride,
polyethylene, polypropylene, acrylonitrile-butadiene-styrene, epoxy
resins, and combinations thereof.
[0019] In embodiments of the present invention, such as, but not
limited to, any one of the methods or articles described in
paragraphs [0001]-[0014], the coating comprises up to 95% by volume
solid particulates.
[0020] In embodiments of the present invention, such as, but not
limited to, any one of the methods or articles described in
paragraphs [0001]-[0014], the coating comprises 1% to 95% by volume
solid particulates.
[0021] In embodiments of the present invention, such as, but not
limited to, any one of the methods or articles described in
paragraphs [0001]-[0016], the metallic coating layer thickness is
10 .mu.m to 50 mm.
[0022] In embodiments of the present invention, such as, but not
limited to, any one of the methods or articles described in
paragraph [0017], the metallic coating layer thickness is 25 .mu.m
to 25 mm.
[0023] In embodiments of the present invention, such as, but not
limited to, any one of the methods or articles described in
paragraph [0018], the metallic coating layer thickness is 30 .mu.m
to 5 mm.
[0024] In embodiments of the present invention, such as, but not
limited to, any one of the methods or articles described in
paragraphs [0001]-[0019], one or more intermediate coating layers
are applied to the substrate before the metallic coating layer is
applied.
[0025] In embodiments of the present invention, such as, but not
limited to, any one of the methods or articles described in
paragraphs [0001]-[0020], at least one of the intermediate coating
layer(s) comprises a metal, a polymer, or both a metal and a
polymer.
[0026] In embodiments of the present invention, such as, but not
limited to, any one of the methods or articles described in
paragraphs [0001]-[0021], the intermediate coating layer thickness
is less than the metallic coating layer thickness by at least
20%.
[0027] In embodiments of the present invention, such as, but not
limited to, any one of the methods or articles described in
paragraphs [0001]-[0022], the metallic coating layer, and the
intermediate coating layer(s), if present, covers all of the
exterior surface of the substrate.
[0028] In embodiments of the present invention, such as, but not
limited to, any one of the methods or articles described in
paragraphs [0001]-[0022], the metallic coating layer, and the
intermediate coating layer(s), if present, covers only a portion of
the exterior surface of the substrate.
[0029] In embodiments of the present invention, such as, but not
limited to, any one of the methods or articles described in
paragraphs [0001]-[0024], the thermal conductivity of the coated
pyrolytic graphite is not less than the uncoated pyrolytic graphite
substrate.
[0030] In embodiments of the present invention, such as, but not
limited to, any one of the methods or articles described in
paragraphs [0001]-[0025], the substrate coated with the metallic
coating layer exhibits a thermal conductivity of about 105% of the
thermal conductivity of the uncoated substrate, or of not less than
105% of uncoated substrate and also not more than 250% of the
uncoated substrate.
[0031] In embodiments of the present invention, such as, but not
limited to, any one of the methods or articles described in
paragraphs [0001]-[0026], the substrate coated with the metallic
coating layer exhibits a thermal conductivity of about 110% of the
thermal conductivity of the uncoated substrate, or of not less than
110% of uncoated substrate and also not more than 250% of the
uncoated substrate.
[0032] In embodiments of the present invention, such as, but not
limited to, any one of the methods or articles described in
paragraphs [0001]-[0027], the substrate coated with the metallic
coating layer exhibits a thermal conductivity of about 115% of the
thermal conductivity of the uncoated substrate, or of not less than
115% of uncoated substrate and also not more than 250% of the
uncoated substrate.
[0033] In embodiments of the present invention, such as, but not
limited to, any one of the methods or articles described in
paragraphs [0001]-[0028], the substrate coated with the metallic
coating layer exhibits a flexural strength greater than that of the
uncoated substrate.
[0034] In embodiments of the present invention, such as, but not
limited to, any one of the methods or articles described in
paragraphs [0001]-[0029], the substrate coated with the metallic
coating layer exhibits a flexural strength of about 110% of the
flexural strength of the uncoated substrate, or of not less than
110% of the uncoated substrate and also not more than 2000% of the
uncoated substrate.
[0035] In embodiments of the present invention, such as, but not
limited to, any one of the methods or articles described in
paragraphs [0001]-[0030], the metallic coating layer has a room
temperature coefficient of linear thermal expansion in all
directions of less than 25.times.10.sup.-6 K.sup.-1.
[0036] In embodiments of the present invention, such as, but not
limited to, any one of the methods or articles described in
paragraphs [0001]-[0030], the metallic coating layer has a room
temperature coefficient of linear thermal expansion in all
directions in the range between 5.0.times.10.sup.-6 K.sup.-1 and
25.times.10.sup.-6 K.sup.-1.
[0037] In embodiments of the present invention, such as, but not
limited to, any one of the methods or articles described in
paragraphs [0001]-[0032], the substrate is a heat spreader.
[0038] In embodiments of the present invention, such as, but not
limited to, any one of the methods or articles described in
paragraph [0033], the heat spreader is any one of those described
in U.S. Pat. Nos. 8,085,531, 7,859,848, 7,808,787, and
8,059,408.
BRIEF DESCRIPTION OF THE DRAWINGS
[0039] FIG. 1 shows an example of the structure of a graphite
sheet.
[0040] FIG. 2 shows a manufacturing method of highly oriented
pyrolytic graphite.
DETAILED DESCRIPTION
[0041] Use of the singular herein, including the claims, includes
the plural and vice versa unless expressly stated to be otherwise.
That is, "a," "an" and "the" refer to one or more of whatever the
word modifies. For example, "an article" may refer to one articles,
two articles, etc. By the same token, words such as, without
limitation, "articles" would refer to one article as well as to a
plurality of articles unless it is expressly stated or obvious from
the context that such is not intended.
[0042] As used herein, words of approximation such as, without
limitation, "about," "substantially," "essentially," and
"approximately" mean that the word or phrase modified by the term
need not be exactly that which is written but may vary from that
written description to some extent. The extent to which the
description may vary from the literal meaning of what is written,
that is the absolute or perfect form, will depend on how great a
change can be instituted and have one of ordinary skill in the art
recognize the modified version as still having the properties,
characteristics and capabilities of the modified word or phrase. In
general, but with the preceding discussion in mind, a numerical
value herein that is modified by a word of approximation may vary
from the stated value by .+-.15%, unless expressly stated
otherwise.
[0043] As used herein, any ranges presented are inclusive of the
end-points. For example, "a temperature between 10.degree. C. and
30.degree. C." or "a temperature from 10.degree. C. to 30.degree.
C." includes 10.degree. C. and 30.degree. C., as well as any
temperature in between.
[0044] As used herein, a material that is described as a layer or a
film (e.g., a coating) "disposed over" an indicated substrate
refers to, e.g., a coating of the material deposited directly or
indirectly over at least a portion of the surface of the substrate.
A "layer" or a "coating" of a given material is a region of that
material whose thickness is small compared to both its length and
width (e.g., the length and width dimensions may both be at least
5, 10, 20, 50, 100 or more times the thickness dimension in some
embodiments). Direct depositing means that the coating is applied
directly to the surface of the substrate. Indirect depositing means
that the coating is applied to an intervening layer that has been
deposited directly or indirectly over the substrate. A coating is
supported by a surface of the substrate, whether the coating is
deposited directly, or indirectly, onto the surface of the
substrate. As used herein a layer need not be planar, for example,
taking on the contours of an underlying substrate. Layers can be
discontinuous. A layer may be of non-uniform thickness. The terms
"coating", "layer", and "coating layer" will be used
interchangeably and refer to a layer, film, or coating as described
in this paragraph.
[0045] As used herein, the term "coating thickness" or "layer
thickness" refers to the depth in a deposit direction.
[0046] The invention will now be described in detail by reference
to the following specification and non-limiting examples. Without
further elaboration, it is believed that one skilled in the art
can, using the preceding description, utilize the present invention
to its fullest extent. The following embodiments are, therefore, to
be construed as merely illustrative, and not limitative of the
remainder of the disclosure in any way whatsoever.
[0047] Embodiments of this invention encompass methods which
include applying one or more metallic coating layer(s) including a
metal, or including a metal matrix composite, or including both, to
a substrate comprising pyrolytic graphite. The microstructure of
the metal of the metallic coating layer may be amorphous,
fine-grained metal, or a combination thereof. As used herein, a
"fine-grained metal" is metal having an average grain size between
1 and 5,000 nm. As used herein, the term "metal matrix composite"
(MMC) is defined as particulate matter embedded in a fine-grained
and/or amorphous metal matrix (metal having an average grain size
between 1 and 5,000 nm). The metallic coating layers have a room
temperature coefficient of linear thermal expansion (CLTE) in all
directions of less than 25.times.10.sup.-6 K.sup.-1, for example,
in the range between 5.0.times.10.sup.-6 K.sup.-1 and
25.times.10.sup.-6 K.sup.-1. Embodiments of the invention also
encompass the coated pyrolytic graphite articles, and specifically,
heat spreaders.
[0048] The coatings comprising the fine grained metals, amorphous
metals, or both, and methods of applying them are described in U.S.
Patent Application Publication No. 2010/0028714, published Feb. 4,
2010, and U.S. Pat. No. 8,394,507, issued on Mar. 12, 2013. Such
coatings are available as Nanovate.TM. coatings from Integran
Technologies, Inc., Toronto, Canada. In a preferred embodiment, the
coating is a Nanovate.TM. N2040 coating, a high strength, low
coefficient of thermal expansion nanostructured Nickel-Iron
coating, from Integran Technologies, Inc., Toronto, Canada.
[0049] The application of the Nanovate.TM. N2040 coating, a high
strength, low coefficient of thermal expansion nanostructured
Nickel-Iron coating, from Integran Technologies, Inc., Toronto,
Canada to a substrate of pyrolytic graphite, specifically,
PYROID.RTM. HT pyrolytic graphite, led to an increase of
approximately 10% in the thermal conductivity of the sample. In all
previous work, coating the pyrolytic graphite led to a decrease in
thermal conductivity due to the increased thermal resistance of the
coating. In addition, the Nanovate.TM. N2040 coating increased the
mechanical properties, such as but without limitation, the flexural
strength of the sample.
[0050] MMCs can be produced e.g. in the case of using an
electroplating process by suspending particles in a suitable
plating bath and incorporating particulate matter into the
electrodeposit by inclusion or e.g. in the case of cold spraying by
adding non-deformable particulates to the powder feed. Other
methods of producing the metallic coating layers include DC or
pulse electrodeposition, electroless deposition, physical vapor
deposition (PVD), chemical vapor deposition (CVD), and gas
condensation or the like. Some exemplary methods include those
described in the following: U.S. Patent Application Publication No.
2005/0205425 A1, published on Sep. 22, 2005; U.S. Pat. No.
7,387,578, issued on Jun. 17, 2008; and DE 10,288,323.
[0051] Solid particulate materials that may be used in forming the
MCCs include metals (Ag, Al, Cu, In, Mg, Si, Sn, Pt, Ti, V, W, Zn);
metal oxides (Ag.sub.2O, Al.sub.2O.sub.3, SiO.sub.2, SnO.sub.2,
TiO.sub.2, ZnO); carbides of B, Cr, Bi, Si, W; carbon (carbon
nanotubes, diamond, graphite, graphite fibers); glass; polymer
materials (polytetrafluoroethylene, polyvinyl chloride,
polyethylene, polypropylene, acrylonitrile-butadiene-styrene, and
epoxy resins); and self-lubricating materials such as, but without
limitation, MoS.sub.2. The solid particulates may be up to 95% by
volume of the coating, preferably, 1% to 95% by volume, more
preferably 5% to 75% by volume, and even more preferably from 10%
to 50% by volume.
[0052] Alloying additions may be used in the metallic coating
layers and are described in U.S. Patent Application Publication No.
2010/0028714, and U.S. Pat. No. 8,394,507, issued on Mar. 12,
2013.
[0053] There may be one or more intermediate coating layers between
the substrate surface and the metallic coating layer(s). The
intermediate coating layer(s) may include, but are not limited to,
a metal, a polymer, or both a metal and a polymer. Materials used
in intermediate layers are described in U.S. Pat. No. 8,394,507,
and U.S. Patent Application Publication No. 2010/0028714.
[0054] The surface of the substrate may be pre-treated by suitably
roughening or texturing at least one of the surfaces to be mated to
form specific surface morphologies, termed "anchoring structures"
or "anchoring sites" as described in U.S. Pat. No. 8,394,507.
[0055] With respect to the substrates used, U.S. Pat. No. 8,394,507
discusses polymeric or polymer composites as substrates, but carbon
substrates are not disclosed. U.S. Patent Application Publication
No. 2010/0028714 discloses substrates of "carbon based materials
selected from the group of graphite, graphite fibers and carbon
nanotubes."
[0056] Graphite is made up of layer planes of hexagonal arrays or
networks of carbon atoms. These layer planes of hexagonal arranged
carbon atoms are substantially flat and are oriented so as to be
substantially parallel and equidistant to one another. The
substantially flat parallel layers of carbon atoms are referred to
as basal planes and are linked or bonded together in groups
arranged in crystallites. Conventional or electrolytic graphite has
a random order to the crystallites. Highly ordered graphite has a
high degree of preferred crystallite orientation. As seen in FIG.
1, the graphite sheet 2 has hexagonal covalent bonds in a stacked
crystal structure, and the graphite layers of each graphite sheet 2
are connected by van der Waals forces. The graphite sheet 2 has a
thermal conductivity in the X-Y plane of the graphite sheet 2 of a
value greater than in the thickness direction, i.e. the Z
direction. Another way of characterizing graphite is as having two
principal axes, the "c" axis or direction which is generally
identified as the axis or direction perpendicular to the carbon
layers and the "a" axes or directions parallel to the carbon layers
and transverse to the c axes. This alternative nomenclature is also
shown in FIG. 1. The "c" axis is equivalent to the Z direction, and
the two "a" axes are equivalent to the X-Y plane. As used herein
with reference to the axes of a graphite sheet, the term "XY" will
be used interchangeably with "a" and "a-a," and the term "Z" will
be used interchangeably with "c."
[0057] Graphite materials that exhibit a high degree of orientation
include natural graphite and synthetic or pyrolytic graphite.
Natural graphite is commercially available in the form of flakes
(platelets) or as a powder. Pyrolytic graphite is produced by the
pyrolysis of a carbonaceous gas on a suitable substrate at elevated
temperature. Briefly, the pyrolytic deposition process may be
carried out in a heated furnace and at a suitable pressure, wherein
a hydrocarbon gas such as methane, natural gas, acetylene etc. is
introduced into the heated furnace and is thermally decomposed at
the surface of a substrate of suitable composition such as graphite
having any desirable shape. The substrate may be removed or
separated from the pyrolytic graphite. The pyrolytic graphite may
then be further subjected to thermal annealing at high temperatures
to form a highly oriented pyrolytic graphite commonly referred to
as HOPG.
[0058] For use in heat spreaders, it is preferable to use highly
oriented pyrolytic graphite having thermal conductivities more than
1,500 W/m degree K and a suitable example for use in particular is
brand name PYROID.RTM. HT made by MINTEQ International Inc. in New
York, N.Y. Generally, thermal conductivity is caused by the free
electrons and the lattice vibration. The high thermal conductivity
(1000-2000 W/m degree K) of diamond is caused by lattice vibration,
while the thermal conductivity of the extremely anisotropic HT
graphite is equal to or less than diamond due to both free electron
and the lattice vibration.
[0059] However, PYROID.RTM. HT pyrolytic graphite has many useful
characteristics, such as the following: density 2.22 g/cc, tensile
strength 28900 kPa (XY direction), elastic modulus 50 GPa (XY
direction), flexural modulus 33200 MPa (XY direction), coefficient
of thermal expansion 0.6.times.10.sup.-6/degrees Celsius (XY
direction), 25.times.10.sup.-6/degrees Celsius (Z direction),
thermal conductivity 1,700 Watts/m degree K (XY direction), 7
Watts/in degree K (Z direction), 5.0.times.10.sup.-4 electric
specific resistance .OMEGA.cm (XY direction), 0.6 .OMEGA.cm (Z
direction), oxidation threshold 650 degrees Celsius (XY direction),
and permeability 10.sup.-6 mmHg.
[0060] The thermal conductivity of PYROID.RTM. HT pyrolytic
graphite in the XY direction compared with other materials thermal
conductivity is extremely high, for example about 6 times the
values of aluminum nitride (A1N) and beryllia (BeO), and about 4
times the value of the overall thermal diffusion of the material
copper (Cu) in particular.
[0061] PYROID.RTM. HT pyrolytic graphite is produced by the CVD
method as shown in FIG. 2. In chamber 20 under vacuum by a vacuum
pump 21, hydrocarbon gas supplied from cylinder 22 as raw material
gas is decomposed by the gas being heated to more than 2,000
degrees Celsius by heater 23, and while minute carbon nucleus C
which deposit and crystallize on substrate 24, stack and deposit in
stratified formation, and PYROID.RTM. HT pyrolytic graphite is
produced. PYROID.RTM. HT pyrolytic graphite is available in
thicknesses of from 0.25 mm to 20 mm, and can be produce as a board
of a variety of sizes as large as 300 mm square shaped structure by
controlling stacking and deposit time.
[0062] MINTEQ International Inc. in New York, N.Y. also makes
PYROID.RTM. SN (substrate nucleated) and PYROID.RTM. CN
(continuously nucleated) grades of pyrolytic graphite also produced
by the CVD process. These have lower thermal conductivity than the
PYROID.RTM. HT pyrolytic graphite.
[0063] Embodiments of the invention also encompass the coated
pyrolytic graphite articles. A specific use of the coated pyrolytic
graphite is in a heat spreader. In preferred embodiments,
PYROID.RTM. HT pyrolytic graphite is used although other grades of
PYROID.RTM. graphite, or other grades of pyrolytic graphite may be
used. In these embodiments, the heat spreader is coated on all
exterior surfaces, or substantially all exterior surfaces, with one
or more metallic coating layers, and optionally including one or
more intermediate layers. The coating encases or encapsulates or
essentially encases or encapsulates the heater spreader. Examples
of heat spreaders that may be coated include any of those described
in U.S. Pat. Nos. 8,085,531, 7,859,848, 7,808,787, and 8,059,408.
In preferred embodiments, the coating includes a Nickel-Iron alloy
as a fine grained metal, amorphous metal, or combination thereof,
optionally including a solid particulate, preferably a solid
particulate that is a polymer material. In preferred embodiments,
the fine-grained metal, if present, is of a grain size of 2 nm to
5000 nm. In preferred embodiments, the metallic layer coating
thickness is 10 to 500 .mu.m.
[0064] In a preferred embodiment, the substrate is PYROID.RTM. HT
pyrolytic graphite, which is used as a heat spreader, coated on all
surfaces or essentially all surfaces, with a 25 to 50 .mu.m
Nanovate.TM. N2040 coating, a high strength, low coefficient of
thermal expansion nanostructured Nickel-Iron coating, from Integran
Technologies, Inc., Toronto, Canada, and method of coating
PYROID.RTM. HT pyrolytic graphite on all surfaces or essentially
all surfaces with a 25 to 50 .mu.m Nanovate.TM. N2040 coating.
EXAMPLES
[0065] The examples presented in this section are provided by way
of illustration of the current invention only and are not intended
nor are they to be construed as limiting the scope of this
invention in any manner whatsoever.
Example 1
[0066] Ten samples of PYROID.RTM. HT pyrolytic graphite were tested
for thermal conductivity using ASTM E1461 Flash Method for Thermal
Conductivity determination. In Table 1, for the first five samples,
the thermal conductivity was measured in the XY orientation, and
for the second five samples, the thermal conductivity was measured
in the Z direction. As shown in Table 1, the thermal conductivity,
A in W/m-K, ranges from 1567 to 1737 in the XY direction.
TABLE-US-00001 TABLE 1 ASTM E1461 Flash Method Thermal Conductivity
Results thickness bulk specific .DELTA.x @ density temperature heat
diffusivity conductivity 25.degree. C. .rho. @ 25.degree. C. T
c.sub.p .alpha. .lamda. Sample (mm) (g/cm.sup.3) (.degree. C.)
(J/g-K) (mm.sup.2/s) (W/m-K) Pyroid-HT FAOBond 3.022 2.26 25 0.761
1010 1737 Lot# 11028-FAO Pyroid-HT 2.970 2.24 25 0.772 967 1672
Lot# 12172 Plate 2C Pyroid-HT CN 3.003 2.23 25 0.767 916 1567 Lot#
12172 Plate 9C Pyroid-HT 2.940 2.22 25 0.770 930 1590 Lot# 12172
Plate 10C Pyroid-HT 3.011 2.25 25 0.777 975 1705 Lot# 12172 Plate
17C Pyroid-HT 3.208 2.30 25 0.846 24.6 47.9 Lot# 10062-8805- Copper
Plate 5A Pyroid-HT 3.180 2.31 25 0.882 23.4 47.7 Lot#
12172-CN-8805- Copper Plate 9C Pyroid-HT 3.146 2.31 25 0.807 22.1
41.2 Lot# 12172-8805- Copper Plate 10C Pyroid-HT 3.101 2.32 25
0.838 27.2 52.9 Lot# 12172-CN-VHB- Copper Plate 9C Pyroid-HT 3.027
2.30 25 0.813 25.6 47.9 Lot# 12172-VHB- Copper Plate 10C
Example 2
[0067] Five samples of PYROID.RTM. HT pyrolytic graphite were
tested for thermal conductivity using ASTM E1461 Flash Method for
Thermal Conductivity determination. Samples #1-#3 labeled UA1051,
UA1052, and UA1053 were coated with a Nanovate.TM. Nickel-Iron
alloy coating of coating thicknesses of 25 .mu.m, 50 .mu.m, and 50
.mu.m, respectively. Samples #4 and #5 were uncoated. The thermal
conductivity of samples #1 and #2 was determined in the XY
direction. For samples #3-#5, the thermal conductivity was
determined in the Z direction. As shown in Table 2, the .lamda. in
W/m-K for each of the two coated samples measured in the XY
direction, samples #1 and #2, was higher than any of the 5 uncoated
samples measured in Example 1. In addition, the thermal
conductivity in the Z direction was higher for coated sample #3 as
compared to uncoated samples #4 and #5.
TABLE-US-00002 TABLE 2 ASTM E1461 Flash Method Thermal Conductivity
Results Thickness bulk specific .DELTA.x @ density temperature heat
diffusivity conductivity 25.degree. C. .rho. @ 25.degree. C. T
c.sub.p .alpha. .lamda. Sample (mm) (g/cm.sup.3) (.degree. C.)
(J/g-K) (mm.sup.2/s) (W/m-K) UA1051 2.859 2.42 25 0.743 1082 1946
(#1) UA1052 2.895 2.47 25 0.720 982 1746 (#2) UA1053 2.905 2.42 25
0.742 5.47 9.82 (#3) 11028 2.976 2.24 25 0.771 4.40 7.60 (#4) 12172
2.995 2.24 25 0.833 4.32 8.06 (#5)
Example 3
[0068] The flexure extension in the XY direction of 10 uncoated
PYROID.RTM. HT pyrolytic graphite samples of 0.0625 inches in
thickness and 0.5625 inches in width and 0.90 inches in length at a
temperature of 73.degree. F. and a relative humidity of 50% was
determined using the ASTM D790 testing procedure. The results of 10
samples are shown in Table 3:
TABLE-US-00003 TABLE 3 Flexure stress at Load at Flex Yield Flex
Yield Maximum Maximum Point Point Calculations Yield Strain
Calculations (psi) (%) (lb.sub.f) 1 4891.09228 5.13 -9.55 2
5061.94668 5.09 -9.89 3 5132.65699 5.14 -10.02 4 4907.34853 0.41
-9.58 5 5340.14713 0.43 -10.43 6 5490.64692 0.42 -10.72 7
5059.92494 1.32 -9.88 8 5007.05097 1.24 -9.78 9 4720.94366 1.21
-9.22 10 5369.86506 1.26 -10.49 Mean 5098.16242 2.16 -9.96 Standard
240.43257 2.07130 0.46959 Deviation
Example 4
[0069] The flexure extension in the Z direction of 4 uncoated
PYROID.RTM. HT pyrolytic graphite samples of 0.0625 inches in
thickness and 0.5625 inches in width and 0.90 inches in length at a
temperature of 73.degree. F. and a relative humidity of 50% was
determined using the ASTM D790 testing procedure. The results of 4
samples are shown in Table 4:
TABLE-US-00004 TABLE 4 Flexure stress at Load at Flex Yield Flex
Yield Maximum Maximum Point Point Calculations Yield Strain
Calculations (psi) (%) (lb.sub.f) 1 7318.15204 0.79 -14.29 2
7535.14671 0.71 -14.72 3 10004.47820 -0.04 -19.54 4 9512.44969 0.40
-18.58 Mean 8592.55666 0.47 -16.78 Standard 1364.05628 0.37846
2.66417 Deviation
Example 5
[0070] The flexure extension in the Z direction of 4 coated
PYROID.RTM. HT pyrolytic graphite samples of 0.0625 inches in
thickness and 0.5625 inches in width and 0.90 inches in length at a
temperature of 73.degree. F. and a relative humidity of 50% was
determined using the ASTM D790 testing procedure. Sample #1 was
coated with a Nanovate.TM. Nickel-Cobalt alloy coating of 25 micron
in thickness. Sample #2 was coated with a Nanovate.TM. Nickel-Iron
alloy coating of 25 micron in thickness. Sample #3 was coated with
a Nanovate.TM. Nickel-Cobalt alloy coating of 50 micron in
thickness. Sample #4 was coated with a Nanovate.TM. Nickel-Iron
alloy coating of 50 micron in thickness. The Nanovate.TM. coatings
were provided by and applied by Integran Technologies, Inc. The
results for the 4 samples are shown in Table 5:
TABLE-US-00005 TABLE 5 Flexure stress at Load at Flex Yield Flex
Yield Maximum Maximum Point Point Calculations Yield Strain
Calculations (psi) (%) (lb.sub.f) 1 14700.55896 0.59 -28.71 2
20956.63154 3.00 -40.93 3 37968.68219 1.57 -74.16 4 59287.40545
4.68 -115.80 Mean 33228.31954 2.46 -64.90 Standard 19961.79046
1.78007 38.98787 Deviation
As seen in Table 5, the flexture stress was higher for each four of
the samples in Table 5 as compared to the samples shown in Table 4.
The yield strain was higher for all samples in Table 5 except
sample #1.
[0071] Accordingly, it is understood that the above description of
the present invention is susceptible to considerable modifications,
changes and adaptations by those skilled in the art, and that such
modifications, changes and adaptations are intended to be
considered within the scope of the present invention, which is set
forth by the appended claims.
* * * * *