U.S. patent application number 13/705532 was filed with the patent office on 2013-04-18 for heat sink and method of forming a heatsink using a wedge-lock system.
This patent application is currently assigned to GE FANUC INTELLIGENT PLATFORMS, INC.. The applicant listed for this patent is Ge Fanuc Intelligent Platforms, Inc.. Invention is credited to David L. McDonald, David S. Slaton.
Application Number | 20130092363 13/705532 |
Document ID | / |
Family ID | 40328487 |
Filed Date | 2013-04-18 |
United States Patent
Application |
20130092363 |
Kind Code |
A1 |
Slaton; David S. ; et
al. |
April 18, 2013 |
HEAT SINK AND METHOD OF FORMING A HEATSINK USING A WEDGE-LOCK
SYSTEM
Abstract
The present disclosure is related to a heatsink and a method for
forming a heatsink. In one embodiment, a method for forming the
heatsink includes forming at least one thermo pyrolytic graphite
element. The at least one TPG element includes a first side having
a wedge-shaped surface and a second side having a flat surface. The
method further includes layering a metal material over the at least
one TPG element, the metal configured to be complementary to the
first side of the at least one TPG element, and applying pressure
to fasten the metal material to the at least one TPG element.
Inventors: |
Slaton; David S.;
(Huntsville, AL) ; McDonald; David L.; (Lacey's
Spring, AL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ge Fanuc Intelligent Platforms, Inc.; |
Charlottesville |
VA |
US |
|
|
Assignee: |
GE FANUC INTELLIGENT PLATFORMS,
INC.
Charlottesville
VA
|
Family ID: |
40328487 |
Appl. No.: |
13/705532 |
Filed: |
December 5, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11966201 |
Dec 28, 2007 |
8347502 |
|
|
13705532 |
|
|
|
|
Current U.S.
Class: |
165/185 ;
29/890.03 |
Current CPC
Class: |
F28F 21/085 20130101;
H01L 2924/0002 20130101; F28F 21/02 20130101; H01L 23/4006
20130101; H01L 2023/4068 20130101; H01L 23/373 20130101; H01L
2023/4075 20130101; F28F 21/084 20130101; H01L 21/4882 20130101;
Y10T 29/4935 20150115; F28F 3/02 20130101; H01L 2924/0002 20130101;
H01L 23/367 20130101; H01L 2924/00 20130101; H01L 2924/3011
20130101 |
Class at
Publication: |
165/185 ;
29/890.03 |
International
Class: |
F28F 21/02 20060101
F28F021/02 |
Claims
1. A method for forming a heatsink, the method comprising: forming
at least one thermo pyrolytic graphite (TPG) element, the at least
one TPG element comprising a first side having a wedge-shaped
surface and a second side having a flat surface; layering a metal
material over the at least one TPG element, the metal material
configured to be complementary to the first side of the at least
one TPG element; and applying pressure to fasten the metal material
to the at least one TPG element.
2. A method in accordance with claim 1, wherein the at least one
TPG element is formed as a strip.
3. A method in accordance with claim 1, wherein a plurality of TPG
elements are formed.
4. A method in accordance with claim 1, wherein the at least one
TPG element is attached to a strip retention plate, wherein the
strip retention plate is attached to the second side of the TPG
element.
5. A method in accordance with claim 1, wherein the at least one
TPG element is further attached to the metal material using
thermally conductive adhesive.
6. A method in accordance with claim 1, wherein the metal material
being selected from the group consisting of aluminum, copper, and
combinations thereof is layered over the at least one TPG
element.
7. A method in accordance with claim 6, wherein the metal material
comprising a metal fin assembly is layered over the at least one
TPG element.
8. A method in accordance with claim 6, wherein the metal material
comprising a conduction-cooled heatframe is layered over the at
least one TPG element.
9. A method in accordance with claim 1, further comprising layering
a thermal spacer over the second side of the at least one TPG
element, wherein the at least one TPG element is positioned between
the thermal spacer and the metal material.
10. A method in accordance with claim 9, wherein the thermal spacer
being comprised of a material selected from the group consisting of
aluminum, copper, and combinations thereof, is layered over the
second side of the at least one TPG element.
11. A method in accordance with claim 1, further comprising
applying a metal-based coating material to the first side of the at
least one TPG element prior to layering the metal material.
12. A method in accordance with claim 1, further comprising
applying a thermal interface material between the metal material
and the at least one TPG element.
13. A heatsink comprising: at least one thermo pyrolytic graphite
(TPG) element, the at least one TPG element comprising a first side
having a wedge-shaped surface and an opposing second side having a
flat surface; and a metal material coupled to the first side of the
at least one TPG element.
14. A heatsink in accordance with claim 13, further comprising a
strip retention plate coupled to the second side of the at least
one TPG element.
15. A heatsink in accordance with claim 13, wherein a thermal
interface material is disposed between the metal material and the
at least one TPG element.
16. A heatsink comprising: at least one thermo pyrolytic graphite
(TPG) element, the at least one TPG element comprising a first side
having at least one hole through the at least one TPG element,
wherein the at least one TPG element is configured to be
complementary to at least one expandable bushing; and a metal
material coupled to an inner surface of the at least one hole in
the at least one TPG element.
17. A heatsink in accordance with claim 16, further comprising a
thermal interface material disposed between the metal material, the
at least one TPG element, and the at least one expandable bushing.
Description
[0001] This application is a divisional of U.S. Ser. No. 11/966,201
filed on Dec. 28, 2007, the entire disclosure of which is
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] This disclosure relates generally to methods of fastening
thermo pyrolytic graphite (TPG) to metal materials to serve as
heatsinks for various uses and, more particularly, to releasably
fastening TPG elements to a metal material using a wedge-lock
system to form a heatsink.
[0003] Modern embedded computer systems contain very high thermal
power electrical components in a volumetrically constrained
environment. The volumes typically do not change as the power
dissipation of the components increase, presenting significant
challenges in the management of component temperatures. In the
past, a variety of direct cooling techniques such as active or
passive heatsinks composed of high thermally conductive materials
such as aluminum and/or copper have been used to manage rising
temperatures. These materials, however, are only sufficient if a
relatively large amount of surface area is presented to the
airstream, necessitating a physically larger heatsink structure
that occupies a large amount of the total available volume. As the
physical size of the heatsink increases, the ability of the
material to rapidly carry heat to the extremities of the heatsink,
thereby exposing the heat to the airstream, is diminished.
[0004] Thermo Pyrolytic Graphite (TPG) materials have been found to
have the ability to provide better heat conduction in a single
(X-Y) plane as compared to conventional metal materials.
Furthermore, TPG has been found to have an improved overall
conductivity as compared to copper. Recently, a method has been
developed to embed TPG into an aluminum structure using a diffusion
bonding process. The diffusion bonding process, while resulting in
a very good thermal contact between the TPG material and the
aluminum structure, has limitations in that specialized equipment
is needed to create the TPG-embedded structures in a time-consuming
process, resulting in an expensive product.
[0005] As such, there is a need for a method to create a
cost-effective product having TPG fastened to a metal material,
such as an aluminum structure, to form a metal heat-conducting
structure (i.e., heatsink) to provide effective thermal
conductivity in the X-Y plane. Additionally, it would be
advantageous if the method were easily reproducible and could be
performed in many various facilities using many various types of
equipment.
BRIEF DESCRIPTION OF THE INVENTION
[0006] In one aspect, a method for forming a heatsink is provided.
The method includes forming at least one TPG element, wherein the
at least one TPG element has a first side having a wedge-shaped
surface and a second side having a flat surface; layering a metal
material over the at least one TPG element, wherein the metal
material is configured to be complementary to the first side of the
at least one TPG element; and applying pressure to fasten the metal
material to the at least one TPG element.
[0007] In another aspect, a method for forming a heatsink is
provided. The method includes forming at least one hole through at
least one TPG element, wherein the at least one TPG element is
configured to be complementary to at least one expandable bushing;
forming at least one hole through a metal material, the at least
one hole being configured larger than the at least one expandable
bushing; and inserting the at least one expandable bushing into the
at least one hole in the metal material using a fastener.
[0008] In yet another aspect, a heatsink is provided. The heatsink
includes at least one TPG element comprising a first side having a
wedge-shaped surface and a second side having a flat surface.
Additionally, the heatsink includes a metal material coupled to the
first side of the at least one TPG element.
[0009] In yet another aspect, a heatsink is provided. The heatsink
includes at least one TPG element, the at least one TPG element
having a first side having at least one hole through the at least
one TPG element; and a metal material coupled to an inner surface
of the at least one hole in the at least one TPG element. The at
least one TPG element is configured to be complementary to at least
one expandable bushing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 depicts a TPG element and a metal material to be
fastened according to an exemplary method of the present
disclosure.
[0011] FIG. 2 depicts an end of the TPG element of FIG. 1.
[0012] FIG. 3 depicts an exploded view of an exemplary heatsink
formed using an exemplary method according to the present
disclosure.
[0013] FIG. 4 depicts a perspective view of a metal fin assembly
positioned over a TPG element according the method of FIG. 3.
[0014] FIG. 5 depicts an X-plane, a Y-plane, and a Z-plane of
thermal conductivity in a heatsink.
[0015] FIG. 6 depicts an exploded view of an exemplary heatsink
formed using an exemplary method according to the present
disclosure.
DETAILED DESCRIPTION OF THE INVENTION
[0016] The present disclosure is related to fastening thermo
pyrolytic graphite (TPG) to a metal material for forming heatsinks.
As used herein, "TPG" refers to any graphite-based material in
which the graphite is aligned in one direction for optimal heat
transfer. The materials are typically referred to as "aligned
graphite", "TPG", and "Highly Oriented Pyrolytic Graphite (HOPG)".
The TPG elements provide improved thermal conductivity in the X-Y
plane of the heatsink. More specifically, it has been found that by
using the methods of fastening TPG elements to a metal material as
provided in the present disclosure, temperatures created by the use
of electrical systems, such as computer systems, can be lowered by
about 10.degree. C. or more as compared to conventional thermal
solutions. This improved temperature release allows for almost a
doubling of the electrical systems' power capacity in the same
volume environment. Furthermore, the increase in power may result
in systems being supported that could not have otherwise been so,
or may allow existing systems to be used in environments having
higher ambient temperatures.
[0017] As noted above, the heatsink is formed by fastening TPG to a
metal material. TPG elements can be obtained using any suitable
method and/or equipment known in the art for fabricating TPG
elements and guided by the teachings herein provided. The TPG
elements can further be obtained commercially from suppliers, such
as Momentive Performance Material located in Wilton, Conn.
[0018] More specifically, the method generally includes forming at
least one wedge-shaped TPG element. A metal material is layered
over the wedge-shaped TPG element, and configured to be
complementary to a wedge-shaped surface side of the TPG element.
Pressure is applied to fasten the metal material to the
wedge-shaped TPG element.
[0019] As shown in FIG. 1, a TPG element 100 is configured to be a
wedge-shaped element. More specifically, the wedge-shaped TPG
element 100 includes a strip having a first side 10 having a
wedge-shaped surface and a second side 12 having a flat surface. As
shown in FIG. 1, the first side 10 of the TPG element 100 is
tapered on opposing first surface 30 and second surface 32 at
approximately a 45 degree angle with respect to an intermediate
surface 34. While shown in FIG. 1, as being opposing surfaces, it
should be recognized by one skilled in the art that first surface
30 and second surface 32 can be is direct contact with one another
without departing from the scope of the present disclosure.
[0020] In a particular embodiment, as shown in FIG. 2, the
wedge-shaped TPG element 100 has a thickness at or near first
surface 30 different than a thickness at or near second surface 32.
Without being limiting, as shown in FIG. 2, first surface 30 has a
thickness of approximately 0.060 inches, while second surface 32
has a thickness of approximately 0.050 inches. While shown in FIG.
2 as having different thicknesses, it should be understood by one
skilled in the art that the thickness at or near first surface 30
can be equal to the thickness at or never second surface 32 without
departing from the scope of the disclosure. It should be noted that
the thickness of wedge-shaped TPG element 100 may vary from one
surface 30 to the opposing surface 32 (or does not vary), but a
width of first surface 30 and a width of second surface 32 may
still be equal. Furthermore, it should be understood that first
surface 30 may be thinner second surface 32. It should also be
recognized that more than one surface (i.e., first surface 30) can
be wedge-shaped without departing from the scope of the present
disclosure.
[0021] While one or more dimensions of TPG element 100 may vary,
TPG element 100 in one embodiment has a thickness of approximately
from about 0.05 inches to about 0.06 inches.
[0022] At least one TPG element 100 is formed for use in the method
of the present disclosure. Dimensions of TPG element 100, a number
of TPG elements 100 and/or spacing between adjacent TPG elements
100 will depend on the desired end product. Typically, however, it
is suitable to use more than one TPG element 100 to form the
heatsink (indicated in FIG. 3 at 500).
[0023] As noted above, the method further includes layering a metal
material 300 to one or more TPG elements 100. Metal material 300 is
typically made from a material having a high thermal conductivity.
For example, metal material 300 includes aluminum and/or copper. In
one embodiment, metal material 300 is aluminum. Both aluminum and
copper have been shown to provide high conductivity when used in
heatsinks. More specifically, aluminum provides good thermal
conductivity in the "Z" plane (shown in FIG. 5) when used in
heatsinks. However, as noted above, aluminum and copper alone fail
to provide sufficient heat transfer in the X-Y plane and, as such,
the present disclosure has combined TPG with aluminum and/or
copper.
[0024] In one embodiment, metal material 300 is configured to be
complementary to first side 10 of TPG element 100. More
specifically, as shown in FIG. 1, metal material 300 is layered or
positioned over first side 10 of TPG element 100. This
configuration allows for a locking fastening system as described
more fully below.
[0025] In one embodiment, as shown in FIG. 3, metal material 300
includes a metal fin assembly 302. Metal fin assembly 302 provides
greater surface area for thermally conduction, thereby facilitating
a more efficient and effective heat release from a heat source
element (not shown), such as an integrated semiconductor circuit,
like a CPU, or the like. In a particular embodiment, metal fin
assembly 302 is approximately 6 inches.times.5 inches and is
approximately 0.3 inches in thickness. Fin assembly 302, in one
embodiment, includes a plurality of fins 304, each approximately
0.24 inches in height and approximately 0.024 inches thick. A
spacing between adjacent fins 304 of fin assembly 302 is
approximately 0.096 inches. It should be understood by one skilled
in the art that fins 304 of metal fin assembly 302 can be sized and
spaced other than as described above without departing from the
scope of the present disclosure.
[0026] In an alternative embodiment, metal material 300 is a
conduction-cooled heatframe (not shown) intended to transfer heat
to one or more edges of the heatframe which it interfaces with a
cold wall, instead of with the air. Conduction-cooled heatframes
are known in the art and can be commercially supplied, such as from
the commercial supplier Simon Industries located in Morrisville,
N.C.
[0027] In addition to TPG element 100 and metal material 300, in
some embodiments (such as shown in FIGS. 3 and 4), thermal spacer
400 is layered over the TPG element 100 (or a strip retention plate
200, when used) in such a configuration so that TPG element 100 is
positioned between thermal spacer 400 and metal material 300.
Thermal spacer 400 is used to couple a heat source element (not
shown) to heatsink 500. Furthermore, thermal spacer 400 is capable
of spreading the heat to the edges of metal material 300.
[0028] Typically, thermal spacer 400 is configured to be
complementary to a heat source element, as described below. Thermal
spacer 400 can be made from the same material or a different
material than metal material 300 described above. Suitable
materials for providing thermal spacers 400 include, for example,
metal materials including aluminum and/or copper. In one
embodiment, thermal spacer 400 is copper.
[0029] As noted above, thermal spacer 400 is typically configured
to be complementary to a heat source element. Generally, the heat
source element is an electrical heat source element, such as an
integrated semiconductor circuit, or a CPU. As noted above, during
use of the heat source element, such as a CPU, a large amount of
heat is generated that must be released to the outside environment
to prevent overheating and/or malfunctioning of the heat source
element. For example, an integrated circuit may dissipate
approximately 30 Watts or greater of thermal power, with die
temperatures reaching an excess of about 100.degree. C. This heat
must be released to prevent overheating of the integrated
circuit.
[0030] As shown in FIGS. 3 and 4, in one embodiment, once layered,
TPG element(s) 100 and metal material 300 are coupled to strip
retention plate 200. More specifically, the flat surface of second
side 12, shown in FIG. 1, of TPG element 100 is coupled to a planar
strip retention plate 200. By way of example, in one embodiment as
shown in FIG. 3, TPG element 100 is attached to strip retention
plate 200 using a mechanical coupling means, such as one or more
screws 120. While shown in FIG. 3 as a screw, it should be
understood by one skilled in the art that TPG element 100 may be
coupled to strip retention plate 200 using any suitable mechanical
coupling means known in the art.
[0031] Generally, strip retention plate 200 is provided to apply a
force to TPG elements 100 against metal material 300, thereby
minimizing the thermal interface between TPG elements 100 and metal
material 300, and further, adding structural support and strength
to heatsink 500.
[0032] Typically, strip retention plate 200 is made from aluminum
and/or copper. In one embodiment, strip retention plate 200 is made
from aluminum.
[0033] In one embodiment, the method of the present disclosure
includes applying a metal-based coating material to first side 10
of TPG element 100. More specifically, when used, the metal-based
coating material is typically applied to first side 10 of TPG
element 100 facing towards metal material 300. A layer of metal,
such as aluminum, copper, iron, silver, gold, nickel, zinc, tin, or
a combination thereof, is applied to first side 10 of TPG element
100. In a particular embodiment, the metal-based coating material
is a copper coating material with a nickel overcoat. In an
alternative embodiment, a coating of indium is used as the
metal-based coating material.
[0034] The metal-based coating material suitably provides
mechanical strength. The metal-based coating material is typically
at least about 0.001 inches thick. More suitably, the metal-based
coating material has a thickness of from about 0.006 inches to
about 0.025 inches.
[0035] The metal-based coating material can be applied to first
side 10 of TPG element 100 in any suitable pattern known in the
art. For example, in one embodiment, the metal-based coating
material is applied in a cross-hatched pattern. In an alternative
embodiment, the metal-based coating material is applied in a
striped pattern.
[0036] In addition to the metal-based coating material, in one
embodiment, the method includes applying a thermal interface
material 20 to first side 10 of TPG element 100. More specifically,
as shown in FIG. 1, the thermal interface material, generally
indicated at 20, suitably is disposed between metal material 300
and TPG element 100. Thermal interface material 20 may be desired
to reduce the thermal resistance between two components in heatsink
500, for example, between first side 10 of TPG element 100 and
metal material 300. One exemplary suitable thermal interface
material 20 is Bergquist TIC4000, commercially available from
Bergquist located in Chanhassen, Minn.
[0037] The method of the present disclosure includes fastening TPG
element 100 (and retention plate 200, when used) to metal material
300 (and, to thermal spacer 400, when used) to form heatsink 500.
Suitably, TPG element 100 and metal material 300 are fastened to
form heatsink 500 configured to facilitate conduction of heat from
the heat source element to thermal spacer 400 (when used), and then
through TPG element 100 and metal material 300 to the surrounding
environment.
[0038] Suitably, the fastening step includes applying pressure to
wedge-lock metal material 300 and TPG element 100 together.
Pressure can be applied using any suitable means known in the art.
The amount of pressure will typically depend upon the metal
material used and the dimensions and/or number of TPG elements 100
to be locked together.
[0039] As noted above, TPG element 100 is releasably fastened to
metal material 300 using the methods of the present disclosure.
That is, the wedge-lock system used in the present disclosure for
fastening allows the heatsink 500 to be disassembled and
reassembled in a convenient and easy manner.
[0040] In one alternative embodiment, a thermally conductive
adhesive (not shown) is further used to fasten TPG element 100 to
metal material 300. Typically, the adhesive is applied to at least
one of TPG element 100 and metal material 300, and thermal spacer
400 (when used). More specifically, the adhesive may generally be
applied in a semi-solid state, such as in a paste, or gel-like form
using any method known in the art.
[0041] In one embodiment, the thermally conductive adhesive is
Arctic Silver Epoxy, commercially available from Arctic Silver,
Inc., located in Visalia, Calif. Amounts of adhesive used will
typically depend upon the specific heatsink configuration. In one
embodiment, approximately 1.5 mL of adhesive is applied using a
syringe and a spatula to spread the adhesive into a thin layer over
TPG element 100, metal material 300, and thermal spacer 400.
[0042] In another embodiment, as shown in FIG. 6, at least one TPG
element 700 is configured to contain at least one hole 750 of a
size complementary to an expandable bushing 900. As used herein,
expandable bushing 900 can be any suitable expandable bushing known
in the art. Furthermore, the specific method for expanding
expandable bushing 900 may be any method known in the art for
expanding expandable bushings 900. The size and/or dimensions of
expandable bushing 900 will typically depend on the size of at
least one hole 750 and the specific heatsink configuration and/or
dimensions.
[0043] Additionally, metal material 600 contains at least one hole
610 sized sufficiently larger than hole 750 in TPG element 700 such
that expandable bushing 900, when expanded, presses against the
inner surfaces of TPG element 700 instead of metal material 600.
The shape of expandable bushing 900 is such that its outer surfaces
expand when a fastener 740 is inserted therein. In one embodiment,
as shown in FIG. 6, a tapered screw 740 is inserted through
expandable bushing 900. Furthermore, tapered screw 740 is inserted
through expandable bushing 900, through retention plate 800 that
has a hole 820 large enough to accept tapered screw 740, and into a
nut 742. When tapered screw 740 is tightened, the outer surfaces
(also referred to herein as walls) of expandable bushing 900
expand, pressing against the inner surfaces of TPG element 700,
thereby reducing the thermal interface.
[0044] In one embodiment, the outer surfaces of expandable bushing
900 are coated with a thermal interface material (not shown). The
thermal interface material fills imperfections in the outer
surfaces of expandable bushing 900 to create a thermal interface
with a lower thermal impedance. In one embodiment, a thermal
interface material is TIC-4000, commercially available from
Bergquist located in Chanhassen, Minn., and is applied in a striped
pattern to expandable bushing 900.
[0045] While the invention has been described in terms of various
specific embodiments, those skilled in the art will recognize that
the invention can be practiced with modification within the spirit
and scope of the claims.
* * * * *