U.S. patent application number 12/499947 was filed with the patent office on 2010-01-14 for heat dissipation device and method for manufacturing the same.
This patent application is currently assigned to TSINGHUA UNIVERSITY. Invention is credited to SHOU-SHAN FAN, KAI-LI JIANG, CHANG-HONG LIU, LIANG LIU.
Application Number | 20100006278 12/499947 |
Document ID | / |
Family ID | 41504077 |
Filed Date | 2010-01-14 |
United States Patent
Application |
20100006278 |
Kind Code |
A1 |
FAN; SHOU-SHAN ; et
al. |
January 14, 2010 |
HEAT DISSIPATION DEVICE AND METHOD FOR MANUFACTURING THE SAME
Abstract
A heat dissipation device for a heat generating element includes
a fastening layer and a plurality of carbon nanotubes. The
fastening layer is formed on the heat generating element. The
carbon nanotubes are arranged in an array structure. The carbon
nanotubes are arranged in a predetermined pattern. Ends of the
carbon nanotubes are connected to the fastening layer.
Inventors: |
FAN; SHOU-SHAN; (Beijing,
CN) ; JIANG; KAI-LI; (Beijing, CN) ; LIU;
CHANG-HONG; (Beijing, CN) ; LIU; LIANG;
(Beijing, CN) |
Correspondence
Address: |
PCE INDUSTRY, INC.;ATT. 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: |
41504077 |
Appl. No.: |
12/499947 |
Filed: |
July 9, 2009 |
Current U.S.
Class: |
165/185 ;
29/890.03; 428/323 |
Current CPC
Class: |
H01L 23/3677 20130101;
Y10T 428/25 20150115; Y10T 29/4935 20150115; H01L 2924/0002
20130101; H01L 23/373 20130101; F28F 2013/006 20130101; H01L
2924/0002 20130101; F28F 3/022 20130101; H01L 2924/00 20130101 |
Class at
Publication: |
165/185 ;
29/890.03; 428/323 |
International
Class: |
F28F 7/00 20060101
F28F007/00; B21D 53/02 20060101 B21D053/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 11, 2008 |
CN |
200810068460.2 |
Claims
1. A heat dissipation device for a heat generating element,
comprising: a fastening layer formed on the heat generating
element; and a plurality of carbon nanotubes arranged in an array
structure, the plurality of carbon nanotubes arranged in a
predetermined pattern and having ends of the carbon nanotubes
connected to the fastening layer.
2. The heat dissipation device as claimed in claim 1, wherein the
fastening layer is made of thermal conductive material including a
metal with a melting point lower than that of the heat generating
element.
3. The heat dissipation device as claimed in claim 1, wherein the
fastening layer comprises a metal selected from the group
consisting of tin, indium, lead, antimony, silver, bismuth, and
alloy thereof.
4. The heat dissipation device as claimed in claim 1, wherein the
fastening layer comprises a composite selected from the group
consisting of polymer composite and the ceramic composite.
5. The heat dissipation device as claimed in claim 1, wherein a
thickness of the fastening layer ranges from about 0.1 mm to 1
mm.
6. The heat dissipation device as claimed in claim 1, wherein the
carbon nanotubes are substantially parallel to each other and
extend from the fastening layer.
7. The heat dissipation device as claimed in claim 1, wherein
portions of the carbon nanotubes exposed from the fastening layer
have substantially unequal lengths.
8. The heat dissipation device as claimed in claim 1, wherein the
ends of carbon nanotubes are embedded in the fastening layer.
9. The heat dissipation device as claimed in claim 8, wherein the
ends of the carbon nanotubes are contacting the surface of the heat
generating element.
10. The heat dissipation device as claimed in claim 1, wherein the
carbon nanotubes are arranged to be substantially perpendicular to
a surface of the heat generating element.
11. The heat dissipation device as claimed in claim 10, wherein the
surface of the heat generating element is a non-planar surface.
12. The heat dissipation device as claimed in claim 1, wherein the
carbon nanotubes have lengths ranging from about 0.5 mm to about
5.0 mm.
13. The heat dissipation device as claimed in claim 1, wherein any
two adjacent carbon nanotubes are spaced by a distance in a range
of about 0.1 nm to 5.0 nm.
14. The heat dissipation device as claimed in claim 1, wherein a
plurality of channels are defined by the carbon nanotubes within
the predetermined pattern; the plurality of channels allow air
convection.
15. The heat dissipation device as claimed in claim 1, wherein the
predetermined pattern is selected from the group consisting of
crisscross pattern, circular pattern, annular pattern and wavy
pattern.
16. A method for manufacturing a heat dissipation device, the
method comprising: providing a fastening layer in a molten state on
a surface of a heat generating element; forming a carbon nanotube
array on a substrate, the carbon nanotube array comprising a
plurality of carbon nanotubes; bringing the carbon nanotubes to the
fastening layer in the molten state and inserting ends of the
carbon nanotubes, which are far away from the substrate, into the
fastening layer in the molten state; cooling the fastening layer to
change from the molten state to a solid state; removing the
substrate on which the carbon nanotube array was formed; and making
the carbon nanotubes connected to the fastening layer into a
predetermined pattern.
17. The method as claimed in claim 16, wherein the fastening layer,
while in the molten state, is coated or printed on the surface of
the heat generating element.
18. The method as claimed in claim 16, wherein the fastening layer
is cooled at room temperature.
19. The method as claimed in claim 16, wherein the substrate is
removed by mechanical polishing or chemical etching.
20. The method as claimed in claim 16, wherein the carbon nanotubes
are made into the predetermined pattern by a laser beam.
Description
BACKGROUND
[0001] 1. Technical Field
[0002] The disclosure relates to heat dissipation devices and
methods for manufacturing the same, particularly, to a heat
dissipation device based on carbon nanotubes and a method for
manufacturing the same.
[0003] 2. Description of Related Art
[0004] Currently, it is possible to combine multiple electronic
elements into an efficient module to perform complex tasks.
However, electronic devices with high efficiency, such as central
processing units (CPUs), will generate a great amount of heat
during operation. If the heat is not dissipated efficiently, the
electronic devices may become unstable or damaged. Generally, a
heat sink is attached to an outer surface of a CPU to dissipate
heat from the CPU. Meanwhile, miniaturization is a continuing trend
in the production of electronic devices. Consequently, there is a
demand for developing a heat sink that meets miniaturization
requirements.
[0005] A typical heat sink includes a substrate and a plurality of
parallel fins extending up from the substrate. The heat sink abuts
a heat source, such as a CPU. The heat sink transfers heat from the
heat source to the surroundings, thus lowering the temperature of
the heat source. Particularly, the heat sink is attached to the
heat source via a thermal interface material. The thermal interface
material is disposed between the heat sink and the heat source to
provide a large contact surface area, and ensuring good heat
transfer from the heat source to the heat sink. The thermal
interface material is commonly a composite made of a polymer base
and a plurality of electrically conductive particles dispersed in
the polymer base. The electrically conductive particles are made of
a material such as graphite, boron nitride, silicon dioxide,
aluminum oxide, or silver.
[0006] As the efficiency of electronic devices improves, the demand
for better heat dissipation increases. However, the thermal
conductivity of material currently used cannot meet the increasing
demand.
[0007] Furthermore, the thermal interface material between the heat
sink and the heat source, causes additional difficulty in
production of thin-type electronic devices.
[0008] What is needed, therefore, is a heat dissipation device
having high heat dissipation efficiency and suitable to be employed
in thin-type electronic devices.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Many aspects of the present heat dissipation device and
method for manufacturing the same can be better understood with
reference to the following drawings. The components in the drawings
are not necessarily to scale, the emphasis instead being placed
upon clearly illustrating the principles of the present heat
dissipation device.
[0010] FIG. 1 is a cross-sectional view of a first embodiment of a
heat dissipation device on a heat generating element.
[0011] FIG. 2 is a vertical view of the heat dissipation device of
FIG. 1.
[0012] FIG. 3 is a cross-sectional view of a second embodiment of a
heat dissipation device on a heat generating element.
[0013] FIG. 4 is a cross-sectional view of a third embodiment of a
heat dissipation device on a heat generating element.
[0014] FIG. 5 is a flow chart of an exemplary embodiment of a
method for manufacturing the heat dissipation device.
[0015] FIG. 6 is a schematic view of the method for manufacturing a
heat dissipation device on a heat generating element.
[0016] Corresponding reference characters indicate corresponding
parts throughout the several views. The exemplifications set out
herein illustrate at least one embodiment of the present heat
dissipation device and method for manufacturing the heat
dissipation device, in one form, and such exemplifications are not
to be construed as limiting the scope of the disclosure in any
manner.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0017] Referring to FIG. 1 and FIG. 2, a first embodiment of a heat
dissipation device 20 for a heat generating element 30, includes a
fastening layer 201 and a plurality of carbon nanotubes 203. The
fastening layer 201 is formed on the heat generating element 30.
Ends of the carbon nanotubes 203 are connected to the fastening
layer 201. The fastening layer 201 is configured to fix the carbon
nanotubes 203 in a predetermined arrangement. In the present
embodiment, the heat dissipation device 20 dissipates heat from the
heat generating element 30 For example, the heat generating element
30 can be a central processing unit (CPU), but can be deployed for
use with a variety of heat generating elements, whether they be
micro-scale devices or large-scale devices..
[0018] The fastening layer 201 is made of thermal conductive
material. The thermal conductive material can be a composite with
electrically conductive properties, such as a polymer composite or
a ceramic composite. For example, the thermal conductive material
can be a composite of plastic and carbon nanotubes. Alternatively,
the thermal conductive material can include a metal with a low
melting point, such as tin (Sn), indium (In), lead (Pb), antimony
(Sb), silver (Ag), bismuth (Bi), or alloys thereof. The alloy can
be an alloy of tin and lead, an alloy of indium and tin, or an
alloy of tin and silver.
[0019] In the present embodiment, the fastening layer 201 should be
designed to have suitable thicknesses allowing the heat dissipation
device 20 to achieve a required performance. If the fastening layer
201 is too thick, the heat dissipation will have low heat
dissipation efficiency. On the contrary, if the fastening layer 201
is too thin, the carbon nanotubes 203 cannot be firmly fastened on
the heat generating element 30. In the present embodiment, a
thickness of the fastening layer 201 ranges from 0.1 mm to 1
mm.
[0020] The carbon nanotubes 203 are arranged in an array structure
(as shown in FIG. 2). The array is formed by arranging the carbon
nanotubes 203 substantially parallel to each other. Any two
adjacent carbon nanotubes are spaced by a distance in a range of
about 0.1 nanometers (nm) to about 5.0 nm. The carbon nanotubes 203
extend from the fastening layer 201, with embedded ends 203a of the
carbon nanotubes 203 embedded in the fastening layer 201 and
exposed portions 203b of the carbon nanotubes 203 exposed from the
fastening layer 201, as shown in FIG. 1. The parallel carbon
nanotubes 203 may be substantially perpendicular to a surface of
the fastening layer 201. The fastening layer 201 holds the carbon
nanotubes 203 upright. The exposed portions 203b of the carbon
nanotubes 203 absorb and dissipate heat from the heat generating
element 30 to the surrounding environment, thereby cooling the heat
generating element 30.
[0021] Referring to FIG. 1 to FIG. 3, the carbon nanotubes 203
exposed from the fastening layer 201 may be made into a
predetermined pattern. That is, the array of carbon nanotubes 203
may be patterned into a specific configuration. Particularly, some
portions of the carbon nanotubes 203 exposed from the fastening
layer 201 may be removed to form a crisscross pattern (as shown in
FIG. 1 and FIG. 3), a circular pattern, or an annular pattern.
Moreover, the exposed portions 203b of the carbon nanotubes 203
remaining on the fastening layer 201 can be further treated to have
substantially equal lengths (as shown in FIG. 1) or unequal lengths
(as shown in FIG. 3). In the present embodiment, a space P is
defined by the carbon nanotubes 203 with the predetermined pattern,
e.g. the channels defined by the crisscross pattern. The space P is
provided to allow convection, causing heat to be transferred to the
surrounding environment rapidly. Alternatively, referring to FIG.
4, the array of carbon nanotubes 203 on the fastening layer 201 can
be made to present a wavy pattern.
[0022] In the present embodiment, each of the carbon nanotubes 203
has a length in a range from about 0.5 mm to about 5.0 mm. For
example, lengths of the carbon nanotubes 203 are about 1 mm. It is
understood that the carbon nanotubes 203 are longer than the
thickness of the fastening layer 201. Thus, the carbon nanotubes
203 aid in conducting heat to the surrounding environment because
of the exposed portions 203b. In the present embodiment, the carbon
nanotubes 203 can be selected from the group of consisting of
single-walled carbon nanotubes (SWCNTs), double-walled carbon
nanotubes, multi-walled carbon nanotubes (MWCNTs), and combinations
thereof. In such case, a diameter of each of the SWCNT is in a
range from about 0.5 nm to about 100 nm. A diameter of each the
double-walled carbon nanotube is in a range from about 1.0 nm to
about 100.0 nm. A diameter of each the MWCNT is in a range from
about 1.5 nm to about 100.0 nm. Moreover, any two adjacent carbon
nanotubes are spaced apart from each other by a distance in a range
from about 0.1 nm to about 5.0 nm.
[0023] The heat dissipation device 20 of the present embodiment can
be deployed for use in a variety of heat generating elements with
almost any shape, because the carbon nanotubes 203 are flexible.
That is, regardless of the configuration of a heat generating
element, the heat dissipation device 20 of the present embodiment
is suitable to be attached to a non-planar surface.
[0024] Referring to FIG. 5 and FIG. 6, an embodiment of a method
for manufacturing a heat dissipation device 20 is shown. Step S1
includes providing a fastening layer 201 in a molten state on a
surface of a heat generating element 30. In step S2, a carbon
nanotube array having a plurality of carbon nanotubes 203 is formed
on a substrate 204. In step S3, ends of the carbon nanotubes 203
are inserted into the fastening layer 201 while it is in the molten
state. In step S4, the fastening layer 201 is cooled. In step S5,
the substrate 204 is removed. In step S6, the carbon nanotubes
array is made into a predetermined pattern.
[0025] The method is described in more detail as follows.
[0026] In step S1, the fastening layer 201 in the molten state is
applied on the surface of the heat generating element 30. In the
present embodiment, the fastening layer 201 is disposed on the heat
generating element 30 by a coating process or a printing process.
Since the fastening layer 201 is applied while in a molten state,
the fastening layer 201 can conform to the surface of the heat
generating element 30. Furthermore, in order to avoid the heat
generating element 30 from being damaged while the molten fastening
layer 201 is applied, the fastening layer 201 is chosen to have a
melting point lower than that of the heat generating element 30.
The fastening layer 201 is made of thermal conductive material
including a metal with a low melting point, such as Sn, In, Pb, Sb,
Ag, Bi or alloys thereof. The alloy can be an alloy of tin and
lead, an alloy of indium and tin or an alloy of tin and silver. In
the present embodiment, the fastening layer 201 is made of
silver.
[0027] In step S2, the carbon nanotube array is formed on the
substrate 204 by, for example, chemical vapor deposition (CVD),
arc-discharge deposition, or laser vaporization deposition. In the
present embodiment, the carbon nanotube array is formed by chemical
vapor deposition. Particularly, the carbon nanotube array is
obtained by the following steps: firstly, the substrate 204, which
is substantially flat and smooth, is provided. In the present
embodiment, the substrate 204 can be made of glass, silicon,
silicon dioxide, metal, or metal oxide. Preferably, the substrate
204 is made of silicon dioxide. Then, a catalyst layer is uniformly
formed on the substrate 204. The catalyst layer can be made of a
material selected from the group consisting of iron (Fe), cobalt
(Co), nickel (Ni) and alloys thereof. Secondly, the substrate 204
with the catalyst layer is annealed in air at about 700.degree. C.
to about 900.degree. C. for about 30 minutes to about 90 minutes.
The treated substrate 204 is put into a furnace. The furnace is
then heated to about 500.degree. C. to about 740.degree. C. with a
protecting gas flowing therein. Next, a carbon source gas is
introduced into the furnace for about 5 minutes to about 30 minutes
to grow a plurality of parallel carbon nanotubes 203 on the
substrate 204. Thus, the carbon nanotube array is obtained and the
carbon nanotubes 203 are substantially perpendicular to the
substrate 204.
[0028] In the present embodiment, the carbon source gas can be
acetylene, ethylene or methane. The protecting gas can be inert gas
or nitrogen. Particularly, acetylene is chosen as the carbon source
gas while argon gas is chosen as the protecting gas.
[0029] In step S3, the substrate 204 on which the carbon nanotube
array is formed is flipped over to allow the carbon nanotubes 203
to approach the fastening layer 201 in a molten state. Then, ends
of the carbon nanotubes 203, which are far away from the substrate
204, are slowly inserted into the fastening layer 201. In this
step, it is noted that the fastening layer 201 should be maintained
in the molten state to facilitate insertion of the carbon nanotubes
203. The ends of the carbon nanotubes 203 can be inserted to
various depths in the fastening layer 201 according to practical
needs. In the present embodiment, the carbon nanotubes 203 are
inserted deeply until the carbon nanotubes 203 are contacting the
heat generating element 30.
[0030] In step S4, the fastening layer 201 in which the ends of the
carbon nanotubes 203 are inserted is cooled at room temperature to
allow the fastening layer 201 to change from the molten state to a
solid state. Thus, the ends of the carbon nanotubes 203 are fixed
and standing upright in the fastening layer 201.
[0031] In step S5, the substrate 204 on which the carbon nanotube
array is formed is removed by, for example, mechanical polishing or
chemical etching. In the present embodiment, the substrate 204 is
removed by chemical etching. In use, an etchant having a capacity
of dissolving the substrate 204 is provided. In the present
embodiment, hydrochloric acid is chosen as the etchant for removing
the substrate 204 made of silicon dioxide. The substrate 204
carrying the carbon nanotubes is immersed into the etchant for
about 30 minutes to 1 hour. Then, the substrate 204 and the
catalyst layer formed on the substrate 204 will be removed
completely. The opposite ends of the carbon nanotubes 203, which
are far away from the fastening layer 201, are exposed to the
surrounding environment (as shown in FIG. 6).
[0032] In step S6, the carbon nanotubes array fastened by the
fastening layer 201 and disposed on the heat generating element 30
is made into a predetermined pattern, thereby obtaining the final
heat dissipation device 20. In the present embodiment, the carbon
nanotubes array is patterned by a laser beam, using for example, a
carbon dioxide laser. In addition, the track of the laser beam
emitted from the carbon dioxide laser can be controlled by the
computer. Particularly, the predetermined pattern can be designed
in advance and inputted into the computer program. That is, the
emitted laser beam can be controlled by the computer program to
trace the predetermined pattern, thereby forming the predetermined
pattern on the carbon nanotubes array. In the present embodiment, a
laser beam with a power density in a range from about 70000
watts/mm.sup.2 to about 80000 watts/mm.sup.2 is employed. The laser
is driven to move with a velocity in a range of about 1000 to about
1200 mm/second.
[0033] In conclusion, the heat dissipation device of the present
embodiment is formed directly on a heat generating element. In
principle, the heat energy from the heat generating element travels
to the fastening layer and then to the carbon nanotube array, where
it is dissipated, thereby lowering the temperature of the heat
generating element. The heat dissipation efficiency is improved by
virtue of having good thermal transfer capacity along the axial
directions of the carbon nanotubes because the carbon nanotubes are
substantially perpendicular to the surface of the heat generating
element. Furthermore, due to a large ratio of length to diameter of
the carbon nanotube, the heat dissipation efficiency on the heat
dissipation device is increased by way of an increase of heat
dissipation surface.
[0034] Finally, it is to be understood that the above-described
embodiments are intended to illustrate rather than limit the
disclosure. Variations may be made to the embodiments without
departing from the spirit of the disclosure as claimed. The
above-described embodiments illustrate the scope of the disclosure
but do not restrict the scope of the disclosure.
[0035] It is also to be understood that 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.
* * * * *