U.S. patent application number 12/717898 was filed with the patent office on 2011-02-10 for heat dissipation structure and heat dissipation system adopting the same.
This patent application is currently assigned to TSINGHUA UNIVERSITY. Invention is credited to SHOU-SHAN FAN, QING-WEI LI, CHANG-HONG LIU.
Application Number | 20110030938 12/717898 |
Document ID | / |
Family ID | 43533924 |
Filed Date | 2011-02-10 |
United States Patent
Application |
20110030938 |
Kind Code |
A1 |
LIU; CHANG-HONG ; et
al. |
February 10, 2011 |
HEAT DISSIPATION STRUCTURE AND HEAT DISSIPATION SYSTEM ADOPTING THE
SAME
Abstract
A heat dissipation structure includes a thermal interface
material and a transition layer. The thermal interface material
includes a matrix and a plurality of carbon nanotubes dispersed in
the matrix. The thermal interface material has a first surface and
a second surface opposite to the first surface. The transition
layer is positioned on one of the first surface or the second
surface of the thermal interface material. A thickness of the
transition layer is in a range from about 1 nanometer to about 100
nanometers. The transition layer is in contact with the carbon
nanotubes of the thermal interface material. An interface thermal
resistance between the transition layer and the heat source is less
than that between the plurality of carbon nanotubes and the heat
source. The present application also relates to a heat dissipation
system adopting the heat dissipation structure.
Inventors: |
LIU; CHANG-HONG; (Beijing,
CN) ; LI; QING-WEI; (Beijing, CN) ; FAN;
SHOU-SHAN; (Beijing, CN) |
Correspondence
Address: |
Altis Law Group, Inc.;ATTN: Steven Reiss
288 SOUTH MAYO AVENUE
CITY OF INDUSTRY
CA
91789
US
|
Assignee: |
TSINGHUA UNIVERSITY
Beijing
CN
HON HAI PRECISION INDUSTRY CO., LTD.
Tu-Cheng
TW
|
Family ID: |
43533924 |
Appl. No.: |
12/717898 |
Filed: |
March 4, 2010 |
Current U.S.
Class: |
165/185 |
Current CPC
Class: |
H01L 2924/0002 20130101;
H01L 23/3733 20130101; F28F 21/02 20130101; H05K 7/2039 20130101;
H01L 2924/00 20130101; F28F 2013/006 20130101; H01L 2924/0002
20130101; H01L 23/373 20130101; H01L 23/3737 20130101; F28F 21/08
20130101; F28F 21/06 20130101 |
Class at
Publication: |
165/185 |
International
Class: |
F28F 21/02 20060101
F28F021/02; H01L 23/373 20060101 H01L023/373 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 5, 2009 |
CN |
200910109568.6 |
Claims
1. A heat dissipation structure for dissipating heat from a heat
source, comprising: a thermal interface material comprising a
matrix and a plurality of carbon nanotubes dispersed in the matrix,
the thermal interface material having a first surface and a second
surface opposite to the first surface; and a transition layer
positioned on one of the first surface or the second surface of the
thermal interface material, wherein a thickness of the transition
layer is in a range from about 1 nanometer to about 100 nanometers;
the transition layer contacts with the carbon nanotubes of the
thermal interface material; an interface thermal resistance between
the transition layer and the heat source is less than that between
the plurality of carbon nanotubes and the heat source.
2. The heat dissipation structure of claim 1, wherein the plurality
of carbon nanotubes is substantially parallel to each other and
substantially perpendicular to the first surface and the second
surface of the thermal interface material.
3. The heat dissipation structure of claim 2, wherein ends of at
least some of the plurality of carbon nanotubes protrude out of one
of the first surface and the second surface, and are embedded in
the transition layer.
4. The heat dissipation structure of claim 3, wherein the
transition layer is positioned at each of the first surface and the
second surface.
5. The heat dissipation structure of claim 4, wherein two ends of
the plurality of carbon nanotubes extend out of the first and
second surfaces of the thermal interface material and are buried in
the transition layers.
6. The heat dissipation structure of claim 1, wherein a mass
percent of the plurality of carbon nanotubes in the thermal
interface material is in a range from about 0.1% to 5%.
7. The heat dissipation structure of claim 1, wherein a material of
the transition layer is selected from the group consisting of
silicone, polyethylene glycol, polyethylene, polyester, epoxy
resin, hypoxia glue, glue series of acrylic, and rubber.
8. The heat dissipation structure of claim 1, further comprising a
plurality of thermal conductive particles dispersed in the
matrix.
9. The heat dissipation structure of claim 8, wherein the thermal
conductive particles are at least one of metal particles, alloy
particles, oxide particles, and non-metal particles.
10. The heat dissipation structure of claim 1, wherein a thickness
of the transition layer is about 50 nanometers.
11. A heat dissipation system, comprising: a heat sink; a heat
source; and a heat dissipation structure positioned between the
heat sink and the heat source, the heat dissipation structure
comprising a thermal interface material and a transition layer, the
thermal interface material comprising a matrix and a plurality of
carbon nanotubes dispersed in the matrix, the thermal interface
material having a first surface and a second surface opposite to
the first surface, and the transition layer being positioned on one
of the first surface or the second surface of the thermal interface
material, wherein a thickness of the transition layer is in a range
from about 1 nanometer to about 100 nanometers; the transition
layer contacts with the carbon nanotubes of the thermal interface
material; an interface thermal resistance between the transition
layer and the heat source or the heat sink is less than that
between the plurality of carbon nanotubes and the heat source or
the heat sink.
12. The heat dissipation system of claim 11, wherein the plurality
of carbon nanotubes is substantially parallel to each other and
substantially perpendicular to the first surface and the second
surface of the thermal interface material.
13. The heat dissipation system of claim 11, wherein one end of at
least some carbon nanotubes of the plurality of carbon nanotubes
extends out of one surface of the thermal interface material and is
buried in the transition layer.
14. The heat dissipation system of claim 11, wherein the transition
layer comprises a first transition layer and a second transition
layer opposite to the first transition layer the first transition
layer is positioned between the heat sink and the thermal interface
material, and the second transition layer is positioned between the
heat source and the thermal interface material.
15. The heat dissipation system of claim 14, wherein two ends of
the plurality of carbon nanotubes extend out of the first and
second surfaces of the thermal interface material and are buried in
the first and second transition layers.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims all benefits accruing under 35
U.S.C. .sctn.119 from China Patent Application No. 200910109568.6,
filed on Aug. 5, 2009 in the China Intellectual Property
Office.
BACKGROUND
[0002] 1. Technical Field
[0003] The present disclosure relates to heat dissipation
structures and heat dissipation systems and, particularly, to a
heat dissipation structure and a heat dissipation system adopting
the same.
[0004] 2. Description of Related Art
[0005] Electronic components such as semiconductor chips are
becoming progressively smaller, while heat dissipation requirements
are increasing. A thermal interface material is commonly utilized
between the electronic component and a heat sink to efficiently
dissipate heat generated by the electronic component.
[0006] A conventional thermal interface material is made by
diffusing high heat conduction coefficiency particles in a base
material. The particles can be made of graphite, boron nitride,
silicon oxide, alumina, silver, or other metals. However, a heat
conduction coefficiency of these thermal interface materials is now
considered too low for many contemporary applications, because it
cannot adequately meet the heat dissipation requirements of modern
electronic components.
[0007] One thermal interface material, which conducts heat by using
carbon nanotubes, has been developed. A matrix material is filled
in interspaces between carbon nanotubes of a carbon nanotube array
to take full advantage of the axial thermal conductive property of
the carbon nanotubes. Ends of the carbon nanotubes extend out of
the surface of the matrix. Example of the thermal interface
material is taught by U.S. Pat. No. 7,253,442 to Huang et al.
Referring to FIG. 6, the thermal interface material 40 includes a
macromolecular material 32, and a plurality of carbon nanotubes 22
dispersed therein. The thermal interface material 40 has a first
surface 42 and a second surface 44 opposite to the first surface
42. Ends of the carbon nanotubes 22 are exposed out of the first
surface 42 and the second surface 44. The carbon nanotubes 22 are
dispersed uniformly throughout the macromolecular material 32, and
extend from the first surface 42 to the second surface 44. However,
in use, when the carbon nanotubes 22 contact the heat sink or a
heat source, the interface thermal resistance between the thermal
interface material 40 and the heat sink or heat source is large
because of the carbon nanotubes directly contacting the heat sink
or heat source, thereby affecting the heat dissipation efficiency
of the thermal interface material.
[0008] What is needed, therefore, is a heat dissipation structure
with a low interface thermal resistance and a heat dissipation
system adopting the same.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Many aspects of the embodiments can be better understood
with references to the following drawings. The components in the
drawings are not necessarily drawn to scale, the emphasis instead
being placed upon clearly illustrating the principles of the
embodiments. Moreover, in the drawings, like reference numerals
designate corresponding parts throughout several views.
[0010] FIG. 1 is a schematic structural view of a first embodiment
of a heat dissipation structure.
[0011] FIG. 2 is a schematic structural view of a second embodiment
of a heat dissipation structure.
[0012] FIG. 3 is a schematic structural view of a third embodiment
of a heat dissipation structure.
[0013] FIG. 4 is a schematic structural view of one embodiment of a
heat dissipation system.
[0014] FIG. 5 is a graph of an interface thermal resistance between
the heat dissipation structure and the heat sink as a function of a
thickness of a transition layer.
[0015] FIG. 6 is a schematic structural view of a conventional
thermal interface material.
DETAILED DESCRIPTION
[0016] The disclosure is illustrated by way of example and not by
way of limitation in the figures of the accompanying drawings, in
which like references indicate similar elements. It should be noted
that references to "an" or "one" embodiment in this disclosure are
not necessarily to the same embodiment, and such references mean at
least one.
[0017] Referring to FIG. 1, a first embodiment of a heat
dissipation structure 10 includes a thermal interface material 110
and a transition layer 120. The thermal interface material 110 has
a first surface 116 and a second surface 117 opposite to the first
surface 116. The transition layer 120 is positioned on the first
surface 116 of the thermal interface material 110.
[0018] The thermal interface material 110 includes a matrix 114 and
a plurality of carbon nanotubes 112 dispersed in the matrix 114. A
material of the matrix 114 includes a phase change material, such
as resin material, thermal plastic, rubber, silicone, and a mixture
thereof. The resin includes epoxy resin, acrylic resin or silicone
resin. In one embodiment, the material of the matrix 114 is silicon
elastomer kit.
[0019] The plurality of carbon nanotubes 112 can be substantially
parallel to each other, and substantially perpendicular to the
first surface 116 of the thermal interface material 110. One end of
each of the plurality of carbon nanotubes 112 extends out of the
first surface 116 of the thermal interface material 110. In one
embodiment, the plurality of carbon nanotubes 112 forms a carbon
nanotube array distributed in the matrix 114. A height of the
carbon nanotubes 112 can be set as desired. Each of the carbon
nanotubes 112 includes a first end 122 and a second end 124
opposite to the first end 122. A mass percent of the carbon
nanotubes 112 in the thermal interface material 110 can be in a
range from about 0.1% to about 5%. In one embodiment, the mass
percent of the plurality of carbon nanotubes 112 in the thermal
interface material 110 is about 2%. The carbon nanotubes 112 can be
single-walled carbon nanotubes, multi-walled carbon nanotubes, or
any combination thereof.
[0020] In one embodiment, the first surface 116 of the thermal
interface material 110 is substantially parallel to the second
surface 117. The carbon nanotubes are multi-walled carbon
nanotubes, and the multi-walled carbon nanotubes form a
multi-walled carbon nanotube array. The carbon nanotubes 112 are
substantially parallel to each other and substantially
perpendicular to the first surface 116 and the second surface
117.
[0021] The carbon nanotubes 112 extend from the second surface 117
to the first surface 116. The first ends 122 of the carbon
nanotubes 112 are at the first end of the carbon nanotube array.
The second ends 124 of the carbon nanotubes 112 are at the second
end of the carbon nanotube array. The first end of the carbon
nanotube array extends substantially out of the first surface
116.
[0022] The first ends 122 of the plurality of carbon nanotubes 112
are buried in the transition layer 120. A material of the
transition layer 120 can be silicone, polyethylene glycol,
polyethylene, polyester, epoxy resin, hypoxia glue, glue series of
acrylic, or rubber. The polyester includes polymethylmethacrylate
(PMMA). In another embodiment, the material for the transition
layer 120 is silicone.
[0023] The interface thermal resistance between the transition
layer 120 and the heat sink or the heat source is less than that
between the carbon nanotubes and the heat sink or the heat source.
A thickness of the transition layer 120 cannot be too great. An
interface thermal resistance between the heat dissipation structure
10 and the heat sink or the heat source depends on the thermal
resistance of the transition layer 120 and the interface thermal
resistance between the transition layer 120 and the heat sink or
the heat source. If the thickness of the transition layer 120 is
too great, the thermal resistance of the transition layer 120 would
be too high, resulting in a high interface thermal resistance
between the heat dissipation structure 10 and the heat sink or the
heat source. If the thickness of the transition layer 120 is too
small, the interface thermal resistance between the transition
layer 120 and the heat sink or the heat source would also be high,
resulting in a high interface thermal resistance between the heat
dissipation structure 10 and the heat sink or the heat source.
Thus, the thickness of the transition layer 120 can be in a range
from about 1 nanometer to about 100 nanometers. In one embodiment,
a thickness of the transition layer 120 is about 50 nanometers.
[0024] The heat dissipation structure 10 can further include a
plurality of thermal conductive particles 118. The plurality of
thermal conductive particles 118 can be dispersed in the matrix
114. The plurality of thermal conductive particles 118 has a high
heat conduction coefficient, and can improve the heat conduction
coefficiency of the heat dissipation structure 10. The thermal
conductive particles 118 are at least one of metal particles, alloy
particles, oxide particles, and non-metal particles. The metal
particles can be tin, copper, indium, lead, antimony, gold, silver,
bismuth, aluminum, or other metals. The alloys can be tin, copper,
indium, lead, antimony, gold, silver, bismuth, aluminum, or any
combination thereof. The oxide particles can be made of metal
oxides or silicon oxides. The non-metal particles can be made of
graphite or silicon. In one embodiment, the thermal conductive
particles 118 are graphite particles. It is understood that the
thermal conductive particles 118 are optional.
[0025] The heat dissipation structure 10 is applied to an
electronic device, the plurality of carbon nanotubes 112 can
contact with the electronic device by the transition layer 120. The
transition layer 120 can effectively reduce the interface
resistance between the heat dissipation structure 10 and the
electronic device, and ensure the thermal conductive properties of
the carbon nanotubes along the axis direction (e.g., the length of
the carbon nanotube) is being fully utilized. Thus, a high
interface resistance because of the carbon nanotubes directly
contacting the electronic device can be avoided. The heat
dissipation efficiency of the heat dissipation structure 10 is
increased. Furthermore, the plurality of thermal conductive
particles 118 can also increase the heat conduction coefficiency of
the matrix 114, thereby increasing the heat conduction coefficiency
of the heat dissipation structure 10.
[0026] It is understood that the carbon nanotubes 112 in the heat
dissipation structure 10 can be replaced by carbon fibers or a
combination of carbon nanotubes and carbon fibers.
[0027] The heat dissipation structure 10 can be prepared by the
following steps. Firstly, a carbon nanotube array is supplied. The
carbon nanotube array includes a plurality of carbon nanotubes 112.
A liquid matrix material and a plurality of thermal conductive
particles 118 are filled in interspaces of the carbon nanotubes 112
in the carbon nanotube array. Thereby, the thermal interface
material 110 having the matrix 114, and the plurality of carbon
nanotubes 112 and the plurality of thermal conductive particles 118
dispersed in the matrix 114, is formed. The thermal interface
material 110 has the first surface 116 and the second surface 117
opposite to the first surface 116. The plurality of carbon
nanotubes 112 have first ends 122 exposed out of a first surface
116 of the thermal interface material 110. The transition layer 120
is formed on the first surface 116 of the thermal interface
material 110. The first ends 122 of the plurality of carbon
nanotubes 112 are buried in the transition layer 120.
[0028] The carbon nanotube array can be formed on a substrate, with
the second ends 124 of the carbon nanotubes 112 contacting with the
substrate.
[0029] The thermal interface material 110 can be formed by the
following steps. The plurality of thermal conductive particles 118
is dispersed in a liquid matrix material to form a mixture. The
carbon nanotube array on the substrate is immersed in the mixture.
The mixture fills in the interspaces of the carbon nanotubes 112 in
the carbon nanotube array. The carbon nanotube array with the
substrate is then taken out. The liquid matrix material is cured to
form the matrix 114. The second surface 117 of the thermal
interface material 110 is adjacent to the substrate. The first
surface of the thermal interface material 110 is etched so that the
first ends 122 of the plurality of carbon nanotubes 112 are exposed
out of the first surface 116. Then, the substrate is removed. The
carbon nanotube array is cut along a direction of the axis thereof,
with a slicing machine, thereby forming the thermal interface
material 110. The second ends 124 of the plurality of carbon
nanotubes 112 are coplanar with the second surface 117.
[0030] It is understood that the matrix 114 can be free of the
plurality of thermal conductive particles 118.
[0031] The step of forming the transition layer 120 on the first
surface 116 can be executed by coating a solution of the transition
layer 120 on the first surface 116 by spin-coating, printing,
brushing, or other coating methods. A thickness of the transition
layer 120 can be in a range from about 1 nanometer to about 100
nanometers.
[0032] The step of forming the transition layer 120 on the first
surface 116 can be executed by coating a precursor solution of the
transition layer 120 on the first surface 116 and then curing the
precursor solution of the transition layer 120 to form the
transition layer 120. For example, a silicone rubber solution can
be coated to the first surface 116, and then the silicone rubber
solution is cured to form the first transition layer 120.
[0033] Referring to FIG. 2, a second embodiment of a heat
dissipation structure 20 includes a thermal interface material 210
and a first transition layer 220 and a second transition layer 230.
The thermal interface material 210 includes a first surface 216 and
a second surface 217 opposite to the first surface 216. The first
transition layer 220 is positioned on the first surface 216 of the
thermal interface material 210. The second transition layer 230 is
positioned on the second surface 217 of the thermal interface
material 210.
[0034] The thermal interface material 210 includes a matrix 214, a
plurality of carbon nanotubes 212 and a plurality of thermal
conductive particles 218. The plurality of carbon nanotubes 212 and
the plurality of thermal conductive particles 218 are dispersed in
the matrix 214. The plurality of carbon nanotubes 212 is
substantially perpendicular to the first surface 216 of the thermal
interface material 210. The plurality of carbon nanotubes 212
includes first ends 222 and second ends 224 opposite to the first
ends 222.
[0035] The second embodiment of the heat dissipation structure 20
is similar to the first embodiment of the heat dissipation
structure 10, except that the first ends 222 of the plurality of
carbon nanotubes 212 extends out of the first surface 216 of the
thermal interface material 210, and the second ends 224 of the
plurality of carbon nanotubes 212 extends out of the second surface
217 of the thermal interface material 210. The first transition
layer 220 covers the first surface 216 of the thermal interface
material 210. The first ends 222 of the plurality of carbon
nanotubes 212 are buried in the first transition layer 220. The
second transition layer 230 covers the second surface 217 of the
thermal interface material 210. The second ends 224 of the
plurality of carbon nanotubes 212 are buried in the second
transition layer 230. A thickness of the first transition layer 220
and the second transition layer 230 is in a range from about 1
nanometer to about 100 nanometers. In one embodiment, the thickness
of the first transition layer 220 and the second transition layer
230 is about 50 nanometers. A material of the first transition
layer 220 and the second transition layer 230 is the same as the
transition layer 120 in the heat dissipation structure 10.
[0036] The heat dissipation structure 20 can be prepared by the
following steps. A carbon nanotube array is provided. The carbon
nanotube array includes a plurality of carbon nanotubes 212. A
liquid matrix material and a plurality of thermal conductive
particles 218 are filled in interspaces of the carbon nanotubes 212
in the carbon nanotube array. Thereby, the thermal interface
material 210 having the matrix 214, the plurality of carbon
nanotubes 212 and the plurality of thermal conductive particles 218
dispersed therein, is formed. The plurality of carbon nanotubes 212
has first ends 222 exposed out of a first surface 216 and second
ends 224 exposed out of the second surface 217. The first
transition layer 220 is formed on the first surface 216, and the
second transition layer 230 is formed on the second surface 217.
The first ends of the plurality of carbon nanotubes 212 are buried
in the transition layer 220. The second ends of the plurality of
carbon nanotubes 212 are buried in the second transition layer
230.
[0037] The method for preparing the second embodiment of the heat
dissipation structure 20 is similar to the method for preparing the
first embodiment of the heat dissipation structure 10, except that
the step for forming the thermal interface material 210 further
comprises having the second ends 224 of the plurality of carbon
nanotubes 212 exposed out of the second surface 217. After removing
the substrate on which the carbon nanotube array is grown, the
second surface 217 of the thermal interface material 210 is etched
to expose the second ends 224 of the plurality of carbon nanotubes
212 out of the second surface 217 of the thermal interface material
210. A step for forming the second transition layer 230 on the
second surface 217 is further provided.
[0038] Both ends of the plurality of carbon nanotubes 212, when the
heat dissipation structure 20 is applied to an electronic device,
contact with the electronic device or heat sink by the first
transition layer 220 or the second transition layer 230. This can
reduce the interface resistance between them effectively, thereby
increasing the heat dissipation efficiency of the heat dissipation
structure 20.
[0039] Referring to FIG. 3, a third embodiment of a heat
dissipation structure 30 includes a thermal interface material 310
and a first transition layer 320 and a second transition layer 330.
The thermal interface material 310 includes a first surface 316 and
a second surface 317 opposite to the first surface 316. The first
transition layer 320 is positioned on the first surface 316 of the
thermal interface material 310. The second transition layer 330 is
positioned on the second surface 317 of the thermal interface
material 310.
[0040] The thermal interface material 310 includes a matrix 314, a
plurality of carbon nanotubes 312 and a plurality of thermal
conductive particles 318. The plurality of carbon nanotubes 312 and
the plurality of thermal conductive particles 318 are dispersed in
the matrix 314. The plurality of carbon nanotubes 312 is
substantially perpendicular to the first surface 316 of the thermal
interface material 310. The plurality of carbon nanotubes 312
includes first ends 322 and second ends 324 opposite to the first
ends 322.
[0041] The third embodiment of the heat dissipation structure 30 is
similar to the second heat dissipation structure 20, except that
the first ends 322 of the plurality of carbon nanotubes 312 are
coplanar with the first surface 316 of the thermal interface
material 310, and the second ends 324 of the plurality of carbon
nanotubes 312 are coplanar with the second surface 317 of the
thermal interface material 310.
[0042] The heat dissipation structure 30 can be prepared by the
following steps. A carbon nanotube array is provided. The carbon
nanotube array includes a plurality of carbon nanotubes 312. A
liquid matrix material and a plurality of thermal conductive
particles 318 are filled in interspaces of the carbon nanotubes 312
in the carbon nanotube array. Thereby, the thermal interface
material 310 having the matrix 314, the plurality of carbon
nanotubes 312 and the plurality of thermal conductive particles 318
dispersed therein, is formed. The plurality of carbon nanotubes 312
has the first ends 322 coplanar with the first surface 316 and the
second ends 324 coplanar with the second surface 317. The first
transition layer 320 is formed on the first surface 316. The first
ends 322 of the plurality of carbon nanotubes 312 are buried in the
first transition layer 320. Thus, the second transition layer 330
is formed on the second surface 317. The second ends 324 of the
plurality of carbon nanotubes 312 are buried in the second
transition layer 330.
[0043] The method for preparing the third embodiment of the heat
dissipation structure 30 is similar to the method for preparing the
second embodiment of the heat dissipation structure 20, except that
a cutting process is used to make the plurality of carbon nanotubes
312 having first ends 322 coplanar with the first surface 316 and
second ends 324 coplanar with the second surface 317.
[0044] Referring to FIG. 4, one embodiment of a heat dissipation
system 400 adopting the first embodiment of the heat dissipation
structure 10 includes a heat sink 420, the heat dissipation
structure 10 and a heat source 430 mounted in sequence.
[0045] The transition layer 120 of the heat dissipation structure
10 can contact directly with the heat sink 420. The thermal
interface material 110 can contact directly with the heat source
430. The heat sink 420 can be a metal heat sink. In one embodiment,
the heat sink 420 is copper heat sink. The heat source 430 can be
chips, power transistors, CPU and other electronic devices. In one
embodiment, the heat source 430 is a chip.
[0046] Referring to FIG. 5, a graph of an interface thermal
resistance between the heat dissipation structure 10 and the heat
sink 420 as a function of a thickness of the transition layer 120
is shown. The interface thermal resistance between the heat
dissipation structure 10 and the heat sink 420 is about
1.52.times.10.sup.-4 m.sup.2K/W when the heat dissipation structure
10 is without the transition layer 120. The interface thermal
resistance between the heat dissipation structure 10 and the heat
sink 420 is reduced to about 1.37.times.10.sup.-4 m.sup.2K/W when
the thickness of the heat dissipation structure 10 is about 1
nanometer, because the interface thermal resistance between the
transition layer 120 and the heat sink 420 is lower than that
between the carbon nanotubes and the heat sink 420, and the thermal
resistance of the transition layer 120 is less than the interface
thermal resistance between the transition layer 120 and the heat
sink 420. The interface thermal resistance between the transition
layer 120 and the heat sink 420 is reduced gradually with the
increase of the thickness of the transition layer 120. The
interface thermal resistance between the heat dissipation structure
10 and the heat sink 420 is lowest and reaches about
1.06.times.10.sup.-4 m.sup.2K/W when the thickness of the
transition layer 120 is increased to about 50 nanometers.
[0047] The thermal resistance of the transition layer 120 dominates
the interface thermal resistance between the heat dissipation
structure 10 and the heat sink 420 when the thickness of the
transition layer 120 is greater than about 50 nanometers. The
larger the thickness of the transition layer 120, the larger the
thermal resistance of the transition layer 120, and thus the larger
the interface thermal resistance between the heat dissipation
structure 10 and the heat sink 420. The interface thermal
resistance between the heat dissipation structure 10 and the heat
sink 420 reaches about 1.37.times.10.sup.-4 m.sup.2K/W when the
thickness of the transition layer 120 is increased to about 100
nanometers. The interface thermal resistance between the heat
dissipation structure 10 and the heat sink 420 is increased sharply
to about 1.52.times.10.sup.-4 m.sup.2K/W when the thickness of the
transition layer 120 is larger than about 100 nanometers. In one
embodiment, the thickness of the transition layer 120 is in a range
from about 1 nanometer to about 100 nanometers, the interface
thermal resistance between the heat dissipation structure 10 and
the heat sink 420 is low, and the heat dissipation system 400
adopting the heat dissipation structure 10 has a good heat
dissipation effect.
[0048] It is understood that the second embodiment of the heat
dissipation structure 20 or the third embodiment of the heat
dissipation structure 30 can also be applied to the heat
dissipation system 400 in a similar way.
[0049] The heat dissipation structure 10, 20, 30 and the heat
dissipation system 400 adopting the same have merits. Firstly,
since the interface thermal resistance between the transition layer
120, 220, 230, 320, 330 and the heat source is less than that
between the plurality of carbon nanotubes 112, 212, 312 and the
heat source, the interface thermal resistance between the
transition layer 120, 220, 230, 320, 330 and the heat sink or heat
source is reduced, thereby avoiding the high interface thermal
resistance caused by the two ends of the carbon nanotubes 112, 212,
312 directly contacting with the heat sink or heat source. Thus,
the heat dissipation efficiency of the heat dissipation structure
10, 20, 30 and the heat dissipation system 400 is increased.
Secondly, the plurality of thermal conductive particles 118, 218,
318 can also increase the heat conduction coefficiency of the
matrix 114, 214, 314, thereby increasing the heat conduction
coefficiency of the heat dissipation structure 10, 20, 30 and the
heat dissipation system 400 adopting the same. Lastly, the method
for producing the heat dissipation structure 10, 20, 30 is
simple.
[0050] It is to be understood that the above-described embodiment
is intended to illustrate rather than limit the disclosure.
Variations may be made to the embodiment without departing from the
spirit of the disclosure as claimed. The above-described
embodiments are intended to illustrate the scope of the disclosure
and not restricted to the scope of the disclosure.
[0051] It is also to be understood that the above description and
the claims drawn to a method may include some indication in
reference to certain steps. However, the indication used is only to
be viewed for identification purposes and not as a suggestion as to
an order for the steps.
* * * * *