U.S. patent application number 10/047101 was filed with the patent office on 2003-07-17 for heat sinks and method of formation.
Invention is credited to Broili, Ben M., Carter, Daniel P., Crocker, Michael T..
Application Number | 20030131970 10/047101 |
Document ID | / |
Family ID | 21947067 |
Filed Date | 2003-07-17 |
United States Patent
Application |
20030131970 |
Kind Code |
A1 |
Carter, Daniel P. ; et
al. |
July 17, 2003 |
Heat sinks and method of formation
Abstract
A heat sink (and method of forming a heat sink) is provided that
includes a core having a central axis and a plurality of cooling
fins arranged about the core. Each fin has a base and a tip. The
fins may be shaped to capture a tangential component of air from
the fan. At least one portion (such as upper portion) of the fins
may be bent. A lower portion of each fin may also be bent.
Inventors: |
Carter, Daniel P.;
(Bainbridge Island, WA) ; Crocker, Michael T.;
(Tacoma, WA) ; Broili, Ben M.; (Tacoma,
WA) |
Correspondence
Address: |
ANTONELLI TERRY STOUT AND KRAUS
SUITE 1800
1300 NORTH SEVENTEENTH STREET
ARLINGTON
VA
22209
|
Family ID: |
21947067 |
Appl. No.: |
10/047101 |
Filed: |
January 17, 2002 |
Current U.S.
Class: |
165/80.3 ;
257/720; 257/722; 257/E23.099; 29/890.03; 361/697; 361/704;
361/710 |
Current CPC
Class: |
B21C 23/10 20130101;
H01L 2924/00 20130101; F28F 13/00 20130101; B23P 2700/10 20130101;
H01L 2924/0002 20130101; H01L 2924/0002 20130101; Y10T 29/4935
20150115; H01L 23/467 20130101; F28F 3/022 20130101; B21C 23/14
20130101 |
Class at
Publication: |
165/80.3 ;
257/722; 257/720; 361/704; 361/710; 361/697; 29/890.03 |
International
Class: |
F28F 007/00; H05K
007/20; H01L 023/34; B21D 053/02 |
Claims
What is claimed is:
1. A heat sink comprising: a core having a central axis; and a
plurality of cooling fins arranged about the core, each fin having
a base and a tip, wherein said fins are shaped to capture a
tangential component of air from the fan and wherein at least one
portion of each of said fins is bent.
2. The heat sink recited in claim 1, wherein the fins are curved
towards the tangential component.
3. The heat sink recited in claim 1, wherein an upper portion of
each of the fins is bent towards the tangential component.
4. The heat sink recited in claim 3, wherein a lower portion of
each of said fins is also bent towards the tangential
component.
5. The heat sink recited in claim 1, wherein another portion of
each of said fins is bent.
6. The heat sink recited in claim 1, wherein each of said fins is
provided in a swept manner about said core.
7. A heat sink for use with an axial flow fan comprising: a core
having a central axis; and a plurality of cooling fins arranged
about the core, each fin having a base and a tip, wherein each of
said fins is provided in a swept manner about said core.
8. The heat sink recited in claim 7, wherein an upper portion of
each of the fins is bent.
9. The heat sink recited in claim 8, wherein a lower portion of
each of said fins is also bent.
10. The heat sink recited in claim 7, further comprising: a first
face having a semi-rectangular periphery that is defined by the fin
tips, and which is to thermally contact a heat-generating
electrical component.
11. The heat sink recited in claim 10, further comprising: a second
face, substantially opposite the first face, and having a periphery
that is defined by the fin tips.
12. The heat sink recited in claim 7, wherein the core comprises a
central cavity to receive a thermal plug formed of a material
having a high thermal conductivity.
13. An electronic assembly comprising: a substrate; an electronic
component mounted on a surface of the substrate; an axial flow fan
to move air towards the substrate, the air having an axial
component and a tangential component; and a heat sink including: a
first face in thermal contact with the electronic component; a
second face facing the fan; a core having a central axis; and a
plurality of cooling fins arranged about the core, wherein at least
one portion of each of said fins is bent.
14. The electric assembly recited in claim 13, wherein an upper
portion of each of the fins is bent.
15. The electric assembly recited in claim 14, wherein a lower
portion of each of said fins is also bent.
16. The electric assembly recited in claim 13, wherein another
portion of each of said fins is bent.
17. The electric assembly recited in claim 13, wherein each of said
fins is provided in a swept manner about said core.
18. The electronic assembly recited in claim 13, wherein the
electronic component comprises an integrated circuit (IC).
19. An electronic system comprising: a circuit board; a processor
integrated circuit (IC) mounted on the circuit board; at least one
chipset mounted on the circuit board and electrically coupled to
the processor IC for operation in conjunction with the processor
IC; at least one axial flow fan to move air towards the circuit
board; and at least one heat sink including a first face in thermal
contact with either the processor IC or the chipset; a second face
facing the at least one fan; a core having a central axis; and a
plurality of cooling fins arranged about the core, each fin having
a base and a tip, wherein at least one portion of each of said fins
is bent.
20. The electric assembly recited in claim 19, wherein an upper
portion of each of the fins is bent.
21. The electric assembly recited in claim 20, wherein a lower
portion of each of said fins is also bent.
22. The electric assembly recited in claim 19, wherein another
portion of each of said fins is bent.
23. The electric assembly recited in claim 19, wherein each of said
fins is provided in a swept manner about said core.
24. A method of forming a heat sink, said method comprising:
obtaining a quantity of thermally conductive metal; forming from
the quantity a plurality of fins extending outwardly from a core,
the core having a central axis, each fin having a base coupled to
the core; and forming a bend in each of said fins.
25. The method recited in claim 24, wherein forming said bend in
each of said fins comprises coupling said heat sink to a die and
rotating said die relative to a fixed position so as to create said
bend in each of said fins.
26. The method recited in claim 24, wherein forming said bend in
each of said fins comprises coupling said heat sink to a first die
and to a second die, and rotating said first die relative to said
second die so as to create said bend in each of said fins.
27. The method recited in claim 24, wherein before forming said
bend, said method comprises: separating a portion of each fin from
the core.
28. The method recited in claim 24, wherein forming said plurality
of fins comprises extruding the quantity of thermally conductive
metal through an extrusion die.
29. The method recited in claim 28, wherein the thermally
conductive metal comprises aluminum.
30. The method recited in claim 28, wherein said plurality of fins
are formed in a swept manner about said core.
31. The method recited in claim 28, wherein each of said plurality
of fins are curved.
32. The method recited in claim 24, further comprising forming
another bend in each of said fins.
33. A method of making an electronic assembly, the method
comprising: mounting an electronic component on a circuit board;
providing an axial flow fan, the fan capable of moving air; and
mounting a heat sink between the electronic component and the fan,
the heat sink comprising a plurality of cooling fins arranged about
a core having a central axis, each fin having a base coupled to the
core, wherein a portion of each of said fins is bent.
34. The method recited in claim 32, wherein the electronic
component is from the group consisting of a processor, a chipset
integrated circuit (IC), a digital switching circuit, a radio
frequency (RF) circuit, a memory circuit, a custom circuit, an
application specific IC (ASIC), and an amplifier.
35. The method recited in claim 32, wherein each fin has a tip,
wherein a first face of the heat sink is in thermal contact with
the electronic component and has a periphery that is defined by the
fin tips, and wherein a second face of the heat sink, substantially
opposite the first face, faces the fan and has a periphery that is
defined by the fin tips.
Description
FIELD
[0001] The present invention is directed to a heat sink for an
electronic assembly.
BACKGROUND
[0002] Electronic components, such as integrated circuits (ICs),
are typically assembled into packages by physically and
electrically coupling them to a substrate, such as a printed
circuit board (PCB), to form an "electronic assembly". The
"electronic assembly" can be part of an "electronic system". An
"electronic system" is broadly defined herein as any product
including an "electronic assembly". Examples of electronic systems
include computers (e.g., desktop, laptop, hand-held, server,
Internet appliance, etc.), wireless communications devices (e.g.,
cellular phones, cordless phones, pagers, etc.), computer-related
peripherals (e.g., printers, scanners, monitors, etc.),
entertainment devices (e.g., televisions, radios, stereos, tape and
compact disc players, video cassette recorders, MP3 (Motion Picture
Experts Group, Audio Layer 3) players, etc.), and the like.
[0003] In the field of electronic systems there is an incessant
competitive pressure among manufacturers to drive the performance
of their equipment up while driving down production costs. This is
particularly true regarding the packaging of ICs on substrates
where each new generation of packaging must provide increased
performance, particularly in terms of an increased number of
components and higher clock frequencies, while generally being
smaller or more compact in size.
[0004] As the internal circuitry of ICs, such as processors,
operates at higher and higher clock frequencies, and as ICs operate
at higher and higher power levels, the amount of heat generated by
such ICs can increase their operating temperature to unacceptable
levels, degrading their performance or even causing catastrophic
failure. Thus it becomes increasingly important to adequately
dissipate heat from IC environments including IC packages.
[0005] For this reason, electronic equipment often contains heat
dissipation equipment to cool high-performance ICs. One known type
of heat dissipation equipment includes an impinging fan mounted
atop a heat sink. The heat sink includes a plurality of radial fins
or rods formed of a heat-conductive material such as copper or
aluminum formed around a core. The bottom surface of the core is in
thermal contact with the IC to conduct heat from the IC to ambient
air. The fan moves air over the fins or rods to enhance the cooling
capacity of the heat dissipation equipment. However, with
high-performance ICs consuming ever-greater amounts of power and
accordingly producing greater amounts of heat, heat dissipation
equipment must have higher heat dissipation capability than that
heretofore obtained.
[0006] In order to offer higher capacity heat transfer, it is
difficult for air-cooled heat sinks to grow in size because
equipment manufacturers are under tremendous competitive pressure
to maintain or diminish the size of their equipment packages, all
the while filling them with more and more components. Thus,
competitive heat dissipation equipment must be relatively compact
in size and must perform at levels sufficient to prevent
high-performance components from exceeding their operational heat
specifications.
[0007] For the reasons stated above, and for other reasons stated
below that will become apparent to those skilled in the art upon
reading and understanding the present specification, there is a
significant need in the art for apparatus and methods for packaging
high-performance electronic components in an electronic assembly
that minimize heat dissipation problems.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The foregoing and a better understanding of the present
invention will become apparent from the following detailed
description of example embodiments and the claims when read in
connection with the accompanying drawings, all forming a part of
the disclosure of this invention. While the foregoing and following
written and illustrated disclosure focuses on disclosing example
embodiments of the invention, it should be clearly understood that
the same is by way of illustration and example only and that the
invention is not limited thereto.
[0009] The following represents brief descriptions of the drawings
in which like reference numerals represent like elements and
wherein:
[0010] FIG. 1 is a perspective view of an electronic assembly
including a heat sink attached to an IC package;
[0011] FIG. 2 is a top view of a radial fin heat sink;
[0012] FIG. 3 is a top view of a portion of FIG. 2 showing an
airflow pattern within fins of a radial fin heat sink;
[0013] FIG. 4 is a side view of a section of a radial fin heat sink
positioned upon an IC package;
[0014] FIG. 5 illustrates a perspective view of a curved fin heat
sink;
[0015] FIG. 6 illustrates a perspective view of a bent fin heat
sink;
[0016] FIG. 7 illustrates a perspective view of a curved-bent fin
heat sink;
[0017] FIG. 8a illustrates a perspective view of a swept-bent fin
heat sink according to an example embodiment of the present
invention;
[0018] FIG. 8b illustrates a top view of a swept fin heat sink;
[0019] FIG. 9 illustrates a perspective view of a curved-bent fin
heat sink according to an example embodiment of the present
invention;
[0020] FIG. 10 illustrates a perspective view of a curved
double-bent fin heat sink according to an example embodiment of the
present invention;
[0021] FIG. 11a illustrates a die used for fin bending according to
an example embodiment of the present invention;
[0022] FIG. 11b illustrates a die assembled to an unbent heat sink
according to an example embodiment of the present invention;
[0023] FIG. 11c illustrates a die used in a second bending
operation according to an example embodiment of the present
invention;
[0024] FIG. 12 illustrates a perspective view of a curved
double-bent fin heat sink according to an example embodiment of the
present invention;
[0025] FIG. 13 illustrates a perspective view of a curved
double-bent fin heat sink according to an example embodiment of the
present invention;
[0026] FIG. 14 illustrates a flow diagram of a method of
fabricating a heat sink according to an example embodiment of the
present invention;
[0027] FIG. 15 illustrates a flow diagram of a method of
fabricating an electronic assembly according to an example
embodiment of the present invention; and
[0028] FIG. 16 is a block diagram of an electronic system
incorporating at least one electronic assembly with at least one
heat sink according to an example embodiment of the present
invention.
DETAILED DESCRIPTION
[0029] In the following detailed description, reference is made to
the accompanying drawings, which form a part hereof, and in which
is shown by way of illustration specific arrangements and preferred
embodiments in which the inventions may be practiced. These
arrangements and embodiments are described in sufficient detail to
enable those skilled in the art to practice the invention, and it
is to be understood that other embodiments may be utilized and that
structural, mechanical, compositional, and procedural changes may
be made without departing from the spirit and scope of the present
inventions. The following detailed description is, therefore, not
to be taken in a limiting sense, and the scope of the present
invention is defined only by the appended claims.
[0030] Embodiments of the present invention may provide a solution
to thermal dissipation problems that are associated with packaging
of integrated circuits that have high circuit density and that
operate at high clock speeds and high power levels by employing a
high capacity heat sink.
[0031] A heat sink may include a thermally conductive core. The
core may have a number of thermally conductive fins projecting from
it. The core may have a central cavity into which a thermally
conductive material is inserted. The heat sink fins can be formed
in various shapes. The heat sink may be used in an electronic
assembly having an impinging fan (e.g. an axial flow fan) directing
air onto an upper face of the heat sink. The lower face of the heat
sink may be in thermal contact with a heat-generating electronic
component such as a high performance IC. The heat sink is
structured to capture air from the fan and to direct the air to
optimize heat transfer from the heat sink.
[0032] FIG. 1 is a perspective view of an electronic assembly 1
including a heat sink 2 attached to an IC package 5 according to
one arrangement. Other arrangements are also possible. The
electronic assembly 1 includes a plurality of electronic components
5-9 mounted upon a printed circuit board (PCB) 3. The heat sink 2
may include a relatively thick, flat base plate 12 and an array of
fins 11 extending to the edge of and substantially perpendicular to
the base plate 12. Although the fins 11 shown in FIG. 1 are folded
fins, other heat sinks may not have folded fins. For example, fins
may be brazed, machined, or extruded. A base plate 12 may be
clamped to the IC package 5 through an attachment device 13. The
base plate 12 may be formed of solid copper, and it may contribute
a significant amount of cost and mass to the electronic assembly
1.
[0033] While the sizes of packaged, high performance ICs are
decreasing, the amount of heat generated by these components per
unit volume is increasing. Increasing the heat dissipation
capabilities of the heat sink 2 may require enlarging the surface
area of the base plate 12 and/or the array of the fins 11. This in
turn may result in consuming more PCB real estate, which is
generally not a viable option in an environment where system
packaging densities are increasing with each successive, higher
performance, product generation.
[0034] The heat sink 2 illustrated in FIG. 1 may be used in
conjunction with an axial flow fan (not shown in FIG. 1) to
increase heat dissipation from the array of fins 11. An axial flow
fan has a spinning impeller that is generally shaped like an
airfoil. One component of the air flow emanating from an axial flow
fan moves parallel to the axis about which the impeller rotates,
and this "axial component" is directed normal to the array of fins
11 of the heat sink 2 (i.e., perpendicular to the PCB 3).
[0035] Another component of the airflow from an axial flow fan is
tangential to the impeller's direction of rotation. This
"tangential component" results in air swirling about the impeller's
axis of rotation. The ratio of air being moved by the axial
component versus the tangential component varies with the
particular fan blade geometry. For example, low angles of attack in
the fan blade generally result in a higher ratio of axial flow,
while high angles of attack generally result in a higher ratio of
tangential flow. In some axial flow fans, the ratio is 1:1.
[0036] When an axial flow fan is mounted facing downward on the
heat sink 2, its axial component of airflow may provide
substantially all of the cooling effect because very little of the
tangential component of airflow is captured by the straight
vertical fins 11.
[0037] FIG. 2 is a top view of a radial fin heat sink 20 according
to one arrangement. Other arrangements are also possible. The heat
sink 20 is referred to as a "radial fin heat sink" because its fins
21 emanate radially from a central core 41. The fins 21 are
substantially straight, and the base of each fin 21 is attached to
the core 41 parallel to a central axis 42 (refer to FIG. 4). The
core 41 may have a central cavity 23, and a thermal plug 40 of
thermally conductive material may reside within the cavity 23 to
enhance thermal dissipation.
[0038] FIG. 3 is a top view of the portion within dashed rectangle
22 of FIG. 2 showing an airflow pattern within fins of the radial
fin heat sink 20 shown in FIG. 2. In FIG. 3, a tangential air flow
component 29 from an axial flow fan (not shown) impinges upon fins
26 and 27.
[0039] Before discussing tangential air flow component 29, it
should be first noted that the fins 26 and 27 are substantially
perpendicular to the core 41, and that fins 26 and 27 diverge
considerably as they emanate from the core 41. A radius 43 at the
base of the fins 26 and 27 is substantially smaller than fin tip
distance 28 at the tips of the fins 26 and 27.
[0040] The tangential airflow component 29 may impinge against the
fins of the radial fin heat sink 20 such as the fins 26 and 27. A
major portion 30 of the tangential air flow component 29 moves
outwardly towards the tips of the fins 26 and 27. A smaller portion
33 of the tangential airflow component 29 moves inwardly towards
the bases of the fins 26 and 27.
[0041] Due to the diverging geometry of the fins 26 and 27, air
flow from the tangential component 29, as well as air flow from the
axial component, moves towards the fin tips to escape the region
between adjacent fins 26 and 27, and thus little air flow reaches
the hottest part of the fins 26 and 27 near the core 41. This
results in inefficient thermal dissipation. Consequently, a more
powerful and noisier fan must be substituted, or the electronic
component will not be sufficiently cooled to avoid performance
degradation or catastrophic failure.
[0042] FIG. 4 is a side view of a section taken between dashed line
segments 24 and 25 of FIG. 2 of the radial fin heat sink 20
positioned upon an IC package 34. The fins 31 and 32 are on
opposite sides of the heat sink 20. The lower surface of the
thermal plug 40 is in thermal contact with the upper surface of a
heat-producing IC package 34. Heat is transferred from the IC
package 34 into the thermal plug 40. From the thermal plug 40, heat
is transferred through sidewall 38 of the cavity 23 to the fin 31
(the heat sink core has been omitted to simplify this
illustration), and through sidewall 39 of the cavity 23 to the fin
32. The hottest part of the fins 31 and 32 is nearest the thermal
plug 40.
[0043] A group 36 of air flow vectors is schematically shown to
represent an axial air flow component produced by an axial flow fan
(not shown) downward between adjacent fins, including the fin 31 of
the radial fin heat sink 20. It will be seen that little if any
airflow moves against the hottest part of the fin 31 nearest the
thermal plug 40.
[0044] Likewise, another group 37 of airflow vectors represents an
axial airflow component produced by the axial flow fan (not shown)
downward between adjacent fins including the fin 32. Again, little
if any airflow moves against the hottest part of the fin 32 nearest
the thermal plug 40.
[0045] In addition, it is not readily apparent from FIGS. 3 and 4,
but only an insubstantial amount of airflow from the tangential
component produced by a typical axial flow fan is captured by the
radial fin heat sink.
[0046] It should be apparent that what is needed is a heat sink
structure that significantly increases the amount of air impinging
upon the hottest part of the heat sink, and that significantly
increases the volume and velocity of air moving through the heat
sink fins, including significantly increasing the amount of the
tangential component of an axial flow fan that is captured by the
heat sink.
[0047] FIG. 5 illustrates a perspective view of a curved fin heat
sink 50 according to one arrangement. Other arrangements are also
possible. The curved fin heat sink 50 includes a plurality of
cooling fins 52 arranged about a core 55. The fins 52 are formed of
a material having high thermal conductivity such as a thermally
conductive metal. The fins 52 may be formed of aluminum; however,
they may also be formed of copper or any other suitable thermally
conductive metal or metal alloy.
[0048] The core 55 may have a central axis 58. The core 55 may have
a central cavity 54 for insertion of a thermal plug (not shown).
Each fin 52 has a base and a tip. The base of each fin 52 is
coupled to the core 55 substantially parallel to the central axis
58. Each fin 52 is curved in the same relative direction. The fins
52 of the curved fin heat sink 50 may be shaped to capture the
tangential component of air from an axial flow fan (not shown in
FIG. 5). The fins 52 may also be shaped to direct a relatively
large volume and relatively high velocity of air flow to
substantially the entire surface of each fin 52, including the
hottest portion of each fin 52 adjacent the core 55.
[0049] The fins 52 may be fabricated through an extrusion process.
By using an extrusion process, heat sinks can be made at a
significant savings in manufacturing costs as compared with a
process, for example, in which fins are machined from a heat sink
core, or brazed or soldered onto a heat sink core. Using high
volume manufacturing techniques, extrusions several feet long may
be quickly formed and then cut into individual curved fin heat
sinks each having a plurality of curved fins and, optionally if
desired, a central cavity to accommodate a thermal plug.
[0050] However, the extrusion process for curved fins may be
subject to several process constraints. One constraint is that for
extruding aluminum, for example, the aspect ratio of a curved fin
52 (i.e., the ratio of the length of a fin 52 to its average width)
cannot exceed about 10:1 to 12:1. Another constraint is that the
radius at the base of the fins cannot be less than about 1.0 to 1.2
millimeters.
[0051] Yet another constraint may be to provide as many fins 52 as
possible with each fin 52 as long as possible in order to provide
as great a total heat dissipation surface as possible. In the
situation where the heat sink is being used to cool an IC, the heat
dissipation from the heat sink must be at least sufficient to
maintain a junction temperature within the IC at or below a
predetermined maximum value.
[0052] In view of the above-mentioned process constraints, the core
55 may be shaped to substantially match the shape or footprint of
the curved fin heat sink 50, which may be a semi-rectangular
shape.
[0053] FIG. 6 illustrates a perspective view of a bent fin heat
sink 100 according to one arrangement. Other arrangements are also
possible. The bent fin heat sink 100 includes a plurality of
cooling fins 102 arranged about a core 105. The fins 102 are formed
of a thermally conductive metal. The fins 102 may be formed of
aluminum; however, the fins 102 may also be formed of copper or any
other suitable thermally conductive metal or metal alloy.
[0054] The core 105 has a central axis 101. The core 105 can
optionally have a central cavity 106 for insertion of a thermal
plug (not shown). Each fin 102 has a base and a tip. The base of
each fin 102 is coupled to the core 105 substantially parallel to
the central axis 101.
[0055] Each fin 102 may include a vertical portion 107 and an
angled portion 108. The angled portion 108 of each fin 102 is bent
in the same relative direction. The fins 102 of the bent fin heat
sink 100 may be shaped to capture the tangential component of air
from an axial flow fan (not shown). The fins 102 may also be shaped
to direct a relatively large and relatively high velocity air flow
to substantially the entire surface of each fin 102 including the
hottest portion of each fin 102 adjacent the core 105.
[0056] After forming (e.g. by extrusion) a plurality of straight
unbent fins emanating radially from core 105, the upper portion of
the heat sink 100 may be counterbored to produce a counterbore 104
in which part of the base of each fin 102 is sheared from the core
105 in the vicinity only of the angled portion 108. This allows the
angled portion 108 of each fin 102 to be bent in a subsequent
operation.
[0057] The angle that the angled portion 108 of each fin makes with
the vertical portion 107 may be approximately 150 degrees.
Different angles may be used, depending upon the airflow
characteristics of the particular axial flow fan being used in
conjunction with the bent fin heat sink.
[0058] Instead of counterboring the upper portion of the heat sink
100, a hole saw or other tool may be utilized to make a groove in
the upper portion of the heat sink 100 of sufficient depth to
enable the angled portion 108 of each fin 102 to be bent. Another
method of forming bent (or angled portions) will be described
below.
[0059] Additionally, certain fins in the "corner" regions of the
bent fin heat sink 100 may have their upper tips 109 slightly
clipped to fit into a desired "semi-rectangular" footprint.
[0060] FIG. 7 illustrates a perspective view of a curved-bent fin
heat sink 200 according to one arrangement. Other arrangements are
also possible. The curved-bent fin heat sink 200 may include a
plurality of cooling fins 202 arranged about a core 205. The fins
202 may be formed of a thermally conductive metal. The fins 202 may
be formed of aluminum; however, the fins 202 may also be formed of
copper or any other suitable thermally conductive metal or metal
alloy.
[0061] The core 205 may have a central axis 201. The core 205 may
optionally have a central cavity 206 for insertion of a thermal
plug (not shown). Each fin 202 may have a base and a tip. The base
of each fin 202 may be coupled to the core 205 substantially
parallel to the central axis 201. Each fin 202 may be curved
between its base and its tip, and the curve of each fin 202 may be
towards the same relative direction. In FIG. 7, each fin 202 is
curved towards a counterclockwise direction, opposite to the
direction of rotation of an axial flow fan to be used in
conjunction with the heat sink 200.
[0062] Each fin 202 may include a vertical portion 207 and an
angled portion 208. The angled portion 208 of each fin 202 may be
bent in the same relative direction. The fins 202 of the
curved-bent fin heat sink 200 may be shaped to capture the
tangential component of air from an axial flow fan (not shown). The
fins 202 may also be shaped to direct a relatively large and
relatively high velocity air flow to substantially the entire
surface of each fin 202, including the hottest portion of each fin
202 adjacent the core 205.
[0063] After forming a plurality of curved unbent fins emanating
substantially radially from the core 205, for example using an
extrusion process, the upper portion of the heat sink 200 may be
counterbored to produce a counterbore 204 in which part of the base
(i.e., the inner portion) of each fin 202 is sheared from the core
205 in the vicinity only of the angled portion 208. This allows the
angled portion 208 of each fin 202 to be bent in a subsequent
operation.
[0064] The angle that the angled portion 208 of each fin makes with
the vertical portion 207 may be approximately 150 degrees.
Different angles may be used depending upon the airflow
characteristics of the particular axial flow fan being used in
conjunction with the bent fin heat sink.
[0065] FIG. 8a illustrates a perspective view of a swept-bent fin
heat sink 300 according to an example embodiment of the present
invention. Other embodiments and configurations are also within the
scope of the present invention. The swept-bent fin heat sink 300
may include a plurality of cooling fins 302 arranged about a core
305. The fins 302 may be formed of a thermally conductive metal.
The fins 302 may be formed of aluminum; however, the fins 302 may
also be formed of copper or any other suitable thermally conductive
metal or metal alloy.
[0066] The core 305 may have a central axis 301. The core 305 may
optionally have a central cavity 306 for insertion of a thermal
plug (not shown). Each fin 302 may have a base and a tip. The base
of each fin 302 may be coupled to the core 305 substantially
parallel to the central axis 301. Each fin 302 may include a swept
portion 307 and a bent portion 308. The swept portion 307 of each
fin 302 may be swept in the same relative direction. That is, each
swept fin may extend from the core 305 at approximately the same
angle. To obtain the swept effect, each angle may be other than
perpendicular to the core 305. In another embodiment, the angles of
each of the fins extending from the core 305 may vary. FIG. 8b
shows a top view of the fins 302 provided about the core 305 in a
swept manner (prior to the bending operation). The bent portion 308
of each fin 302 may be bent in the same relative direction. The
fins 302 may be shaped to capture the tangential component of air
from an axial flow fan (not shown in FIG. 8a). The fins 302 are
also shaped to direct a relatively large and relatively high
velocity airflow to the surface of each fin 302, including the
hottest portion of each fin 302 adjacent the core 305.
[0067] According to one embodiment of a swept-bent fin heat sink
300, after forming (e.g. by extrusion) a plurality of swept fins
emanating from the core 305 (as shown in FIG. 8b), the upper
portion of the heat sink 300 may be counterbored to produce a
counterbore in which part of the base of each fin 302 is sheared
from the core 305 in the vicinity only of the bent portion 308.
This allows the bent portion 308 of each fin 302 to be bent in a
subsequent operation. Rather than counterboring the upper portion
of the heat sink 300, a hole saw or other tool may be utilized to
make a groove in the upper portion of the heat sink 300 of
sufficient depth to enable the bent portion 308 to be bent. For
certain fins in the "corner" regions of the swept bent fin heat
sink 300, the upper tips may be slightly clipped to fit into a
desired "semi-rectangular" footprint.
[0068] Embodiments of the present invention may provide an extruded
heat sink having a swept radial fin geometry, a hollow center and
an angular bend in the fins. Similar to that discussed above, a
cooper core may be press fitted into the hollow center for better
conduction to the outer fins. The swept-bent fin heat sink may
better utilize airflow coming off the fan blades for an impinging
flow heat sink due to the coupling of the fan angle of attack and
the bend angle of the fins. The heat sink may be modified for
higher performance depending on the fan geometry. Further, the fins
may be swept such that air coming off the fan may be driven towards
the core.
[0069] FIG. 9 illustrates a perspective view of a curved-bent fin
heat sink 400 according to an example embodiment of the present
invention. Other embodiments and configurations are also within the
scope of the present invention. The curved-bent fin heat sink 400
may include a plurality of cooling fins 402 arranged about a core
405. The fins 402 may be formed of a thermally conductive metal.
The fins 402 may be formed of aluminum; however, the fins 402 may
also be formed of copper or any other suitable thermally conductive
metal or metal alloy.
[0070] The core 405 may have a central axis 401. The core 405 may
optionally have a central cavity 406 for insertion of a thermal
plug (not shown). Each fin 402 may have a base and a tip. The base
of each fin 402 may be coupled to the core 405 substantially
parallel to the central axis 401. Each fin 402 may include a curved
portion 407 and a bent portion 408. The curved portion 407 of each
fin 402 is curved in the same relative direction. In FIG. 9, each
fin 402 is curved towards a counterclockwise direction, opposite to
the direction of rotation of an axial flow fan to be used in
conjunction with the heat sink. The bent portion 408 of each fin
402 may be bent in the same relative direction. The fins 402 may be
shaped to capture the tangential component of air from an axial
flow fan (not shown in FIG. 9). The fins 402 may also be shaped to
direct a relatively large and relatively high velocity of airflow
to the surface of each fin 402, including the hottest portion of
each fin 402 adjacent the core 405.
[0071] According to one embodiment of the curved-bent fin heat sink
400, after forming (e.g. by extrusion) a plurality of curved fins
emanating from the core 405, the upper portion of the heat sink 400
may be counterbored to produce a counterbore in which part of the
base of each fin 402 is sheared from the core 405 in the vicinity
only of the bent portion 408. This allows the bent portion 408 of
each fin 402 to be bent in a subsequent operation. Rather than
counterboring the upper portion of the heat sink 400, a hole saw or
other tool may be utilized to make a groove in the upper portion of
the heat sink 400 of sufficient depth to enable the bent portion
408 to be bent. For certain fins in the "corner" regions of the
curved-bent fin heat sink 400, the upper tips may be slightly
clipped to fit into a desired "semi-rectangular" footprint. Another
method to form the bend will be described below.
[0072] FIG. 10 illustrates a perspective view of a curved
double-bent fin heat sink 500 according to an example embodiment of
the present invention. Other embodiments and configurations are
also within the scope of the present invention. The curved
double-bent fin heat sink 500 may include a plurality of cooling
fins 502 arranged about a core 505. The fins 502 may be formed of a
thermally conductive metal. The fins 502 may be formed of aluminum;
however, the fins 502 may also be formed of copper or any other
suitable thermally conductive metal or metal alloy.
[0073] The core 505 may have a central axis 501. The core 505 may
optionally have a central cavity 506 for insertion of a thermal
plug (not shown). Each fin 502 may have a base and a tip. The base
of each fin 502 may be coupled to the core 505 substantially
parallel to the central axis 501. Each fin 502 may include a first
bent portion 507 and a second bent portion 508 on opposite ends
(i.e., top and bottom) of a curved portion 510. In FIG. 10, each
fin 502 is curved towards a counterwise direction, opposite to the
direction of rotation of an axial flow fan to be used in
conjunction with the heat sink. The first bent portion 507 of each
fin 502 may be bent in the same relative direction. The second bent
portion 508 of each fin 502 may be bent in the same relative
direction. The fins 502 are shaped to capture the tangential
component of air from an axial flow fan (not shown in FIG. 10). The
fins 502 are also shaped to direct a relatively large and
relatively high velocity airflow to the surface of each fin 502,
including the hottest portion of each fin 502 adjacent the core
505.
[0074] According to one embodiment of a curved double-bent fin heat
sink 500, after forming (e.g. by extrusion) a plurality of curved
fins emanating from the core 505, the upper portion of the heat
sink 500 may be counterbored to produce a counterbore in which part
of the base of each fin 502 is sheared from the core 505 in the
vicinity only of the second bent portion 508. Additionally, the
lower portion of the heat sink 500 may be counterbored to produce a
counterbore in which part of the base of each fin 502 is sheared
from core 505 in the vicinity only of the first bent portion 507.
This allows the first bent portion 507 and the second bent portion
508 of each fin 502 to be bent in a subsequent operation. Rather
than counterboring the upper and/or lower portion of the heat sink
500, a hole saw or other tool may be utilized to make a groove in
the upper and/or lower portion of the heat sink 500 of sufficient
depth to enable the first bent portion 507 and the second bent
portion 508 to be bent. For certain fins in the "corner" regions of
the curved double-bent fin heat sink 500, the upper tips may be
slightly clipped to fit into a desired "semi-rectangular"
footprint.
[0075] In an alternative embodiment for both the curved-bent fin
heat sink (FIG. 9) and the curved double-bent fin heat sink (FIG.
10), one or two secondary bending operations may be used. To
perform a first bend at the top part of the heat sink, two female
dies may be used that mate with the unbent heat sink. FIG. 11a
shows an example of a die 520 that may be used for fin bending.
FIG. 11b shows the die 520 of FIG. 11a assembled into an unbent
heat sink (such as the heat sink 500). One of the female dies may
be twisted while the other die remains fixed. One of the dies
engages the heat sink where the bend line will occur. The other die
may contact the fins over a small area along the tops of the fins
while also maintaining a fixed vertical displacement to the die so
as not to dislodge while the bending operation is taking place.
Once the dies are in position, one of the dies may twist over a
predetermined angle, which includes the bend pattern onto the heat
sink. Twisting may be accomplished by hand using levers that mount
to the holes 530 and 540 on the ends of the die 520, or by using
features to mate the die 520 to a spindle. This bend pattern may
maximize the cooling due to its utilization of the airflow velocity
component of a common axial fan.
[0076] After the first bending operation is complete and the dies
are removed from the heat sink, the second bending operation at the
bottom of the heat sink may be performed. The second bending
operation may include inserting a common expanding mandrel into the
hole in the center of the heat sink core. The expanding mandrel may
attach to the sides of the hole and hold the heat sink in place.
FIG. 11c shows a female die 560 that may be inserted onto the base
of the heat sink while the mandrel is attached to the heat sink.
The die 560 may be similar to the previous dies (such as the die
520) and include a predetermined angle cut onto the die teeth that
enables the bending line to be something other than perpendicular
to the core. After the expanding mandrel is engaged and the die 560
is in place, the second bending operation may be achieved by
twisting the mandrel and/or die 560.
[0077] According to an embodiment of a curved double-bent fin heat
sink, an extruded aluminum heat sink with curved fins may have two
secondary bending operations to allow the heat sink to capture and
utilize the radial component of the incoming airflow that is
created by impinging axial fans. The second bending operation may
direct the outgoing flow to a path parallel to the motherboard and
package, which reduces the backpressure that the heat sink produces
by alleviating directly impinging flow onto the package
motherboard. A copper core may be press fitted into the hollow cell
for better conduction to the outer fins.
[0078] The heat sink may be a copper base-folded aluminum fin heat
sink. An aluminum curved double-bent fin heat sink may provide
better performance at a lower cost and lower mass than a folded fin
heat sink. The first bending operation may involve removing a
portion of the top of the core of the heat sink, enabling the
bending of the upper fins at an angle that may utilize the radial
component of the air coming off the fan blades more efficiently.
The second bending operation may turn the air at the bottom of the
heat sink to directly parallel to the motherboard/package, reducing
the pressure drop and increasing heat transfer further.
[0079] FIG. 12 illustrated a perspective view of a curved
double-bent fin heat sink 600 according to an example embodiment of
the present invention. Other embodiments and configurations are
also within the scope of the present invention. The curved
double-bent fin heat sink 600 may include a plurality of cooling
fins 602 arranged about a core 605. The fins 602 may be formed of a
thermally conductive metal. The fins 602 may be formed of aluminum;
however, the fins 602 may also be formed of copper or any other
suitable thermally conductive metal or metal alloy.
[0080] The core 605 may have a central axis 601. The core 605 may
optionally have a central cavity 606 for insertion of a thermal
plug (not shown). Each fin 602 may have a base and a tip. The base
of each fin 602 may be coupled to the core 605 substantially
parallel to the central axis 601. Each fin 502 may be curved and
further include a first bent portion 607 and a second bent portion
608. In FIG. 12, the first bent portion 607 may be an upper part of
the fin 602 and the second bent portion 608 may be a lower part of
the fin 602. In FIG. 12, each fin 602 is curved towards a
counterwise direction, opposite to the direction of rotation of an
axial flow fan to be used in conjunction with the heat sink. The
first bent portion 607 of each fin 602 may be bent in the same
relative direction. The second bent portion 608 of each fin 602 may
be bent in the same relative direction. The fins 602 are shaped to
capture the tangential component of air from an axial flow fan (not
shown in FIG. 12). The fins 602 are also shaped to direct a
relatively large and relatively high velocity airflow to the
surface of each fin 602, including the hottest portion of each fin
602 adjacent the core 605.
[0081] FIG. 13 shows another example of a curved double-bent fin
heat sink according to an example embodiment of the present
invention. The curved double-bent fin heat sink is identical to the
heat sink shown in FIG. 12 except that the heat sink in FIG. 13
does not include a counterbore within the core 605. In one
embodiment, the angle that the first bent portion 607 of each fin
(in both FIG. 12 and FIG. 13) makes with respect to vertical is
approximately 5.degree. to 15.degree.. The angle that the second
bent portion 608 of each fin (of FIG. 12 and FIG. 13) makes with
respect to vertical is approximately 5.degree. to 30.degree.. Other
angles for the first bent portion 607 and the second bent portion
608 are also within the scope of the present invention. That is,
different angles may be used depending upon the airflow
characteristics of the particular axial flow fan being used in
conjunction with the heat sink.
[0082] The curved double-bent fin heat sinks shown in FIGS. 12 and
13 may be manufactured in a similar manner as described above.
[0083] FIG. 14 is a flow diagram of a method of fabricating a heat
sink according to an example embodiment of the present invention.
Other operations and orders of operations are also within the scope
of the present invention. The method begins at block 700. In block
702, a billet of thermally conductive metal (such as aluminum or
copper) is provided. In block 704, a plurality of fins are formed
from the billet, for example by an extrusion or micro-forging
process. The fins extend outwardly from a core in a swept manner
(for the swept-bent fins described above) or in another manner
(such as curved) as desired. The core has a central axis, and each
fin has a base that is coupled to the core substantially parallel
to the central axis. If desired, a central cavity can be formed in
the core. The central cavity may be formed in any suitable manner,
for example as part of the extrusion operation. In block 706, if
the fins are to be bent, then the flow diagram proceeds to block
708; otherwise, the flow diagram may proceed to block 712.
[0084] In block 708, the portions of the fins to be bent may be
separated from the core, for example by forming a cavity (e.g. by
counterboring) or channel (e.g. by machining or sawing) into the
core a predetermined distance along the central axis, from the top
of the heat sink. A portion of each fin may be bent in
substantially the same relative direction in block 710. In block
712, a thermal plug may be inserted into the central cavity to
provide increased thermal dissipation from the IC through the heat
sink core to the heat sink fins. The flow diagram ends at block
714.
[0085] FIG. 15 illustrates a flow diagram of a method of
fabricating an electronic assembly according to an example
embodiment of the invention. Other operations and orders of
operations are also within the scope of the present invention. The
method begins at block 800. In block 802, an electronic component
is mounted on a circuit board. An axial flow fan may be provided in
block 804. The axial flow fan is capable of moving air having a
component normal to the electronic component and a component
tangential to the electronic component. A heat sink may be mounted
between the electronic component and the axial flow fan in block
806. The heat sink may include a number of cooling fins that are
arranged about a core having a central axis. Each cooling fin has a
base coupled to the core substantially parallel to the central
axis. The cooling fins are shaped to capture both components of
air, i.e. the axial component and the tangential component. A first
face of the heat sink is in thermal contact with the electronic
component and may have a semi-rectangular periphery. A second face
of the heat sink faces the fan and may have a semi-rectangular
periphery. The second face is substantially opposite the first
face. The core is shaped to maximize the number of cooling fins
while maintaining a substantially uniform aspect ration in the
cooling fins. The method ends at 808.
[0086] The operations described above with respect to FIGS. 14 and
15 may also be performed in a different order from those described
herein. Also, although the flow diagrams of FIGS. 14 and 15 are
shown as having a beginning and an end, they can be performed
continuously.
[0087] FIG. 16 is a block diagram of an electronic system 901
incorporating at least one electronic assembly 902 with a heat sink
accordance to an example embodiment of the present invention. Other
embodiments and configurations are also within the scope of the
present invention. An electronic system 901 is one example of an
electronic system in which embodiments of the present invention may
be used. In this example, the electronic system 901 includes a data
processing system having a system bus 904 to couple the various
components of the system. The system bus 904 provides
communications links among the various components of the electronic
system 901 and may be implemented as a single bus, as a combination
of busses, or in any other suitable manner.
[0088] An electronic assembly 902 may be coupled to the system bus
904. The electronic assembly 902 may include any circuit or
combination of circuits. In one embodiment, the electronic assembly
902 includes a processor 906 which can be of any type. As used
herein, "processor" means any type of computational circuit, such
as but not limited to a microprocessor, a microcontroller, a
complex instruction set computing (CISC) microprocessor, a reduced
instruction set computing (RISC) microprocessor, a very long
instruction word (VLIW) microprocessor, a graphics processor, a
digital signal processor (DSP), or any other type of processor or
processing circuit.
[0089] Other types of circuits that can be included in the
electronic assembly 902 are a chip set 907 and a communications
circuit 908. The chip set 907 and the communications circuit 908
may be functionally coupled to the processor 906, and they may be
configured to perform any of a wide number of processing and/or
communications operations. Other possible types of circuits (not
shown) that could be included within the electronic assembly 902
include a digital switching circuit, a radio frequency (RF)
circuit, a memory circuit, a custom circuit, an
application-specific integrated circuit (ASIC), an amplifier, or
the like.
[0090] The electronic system 901 may also include an external
memory 912, which in turn can include one or more memory elements
suitable to the particular application, such as a main memory 914
in the form of random access memory (RAM), one or more hard drives
916, and/or one or more drives that handle removable media 918 such
as floppy diskettes, compact disks (CDs), digital video disks
(DVDs), and the like.
[0091] The electronic system 901 may also include a display device
909, one or more speakers 910, and a keyboard and/or controller
920, which can include a mouse, trackball, game controller,
voice-recognition device, or any other device that permits a system
user to input information into and receive information from the
electronic system 901.
[0092] Any reference in this specification to "one embodiment", "an
embodiment", "example embodiment", etc., means that a particular
feature, structure, or characteristic described in connection with
the embodiment is included in at least one embodiment of the
invention. The appearances of such phrases in various places in the
specification are not necessarily all referring to the same
embodiment. Further, when a particular feature, structure, or
characteristic is described in connection with any embodiment, it
is submitted that it is within the purview of one skilled in the
art to effect such feature, structure, or characteristic in
connection with other ones of the embodiments. Furthermore, for
ease of understanding, certain method procedures may have been
delineated as separate procedures; however, these separately
delineated procedures should not be construed as necessarily order
dependent in their performance. That is, some procedures may be
able to be performed in an alternative ordering, simultaneously,
etc.
[0093] This concludes the description of the example embodiments.
Although the present invention has been described with reference to
a number of illustrative embodiments thereof, it should be
understood that numerous other modifications and embodiments can be
devised by those skilled in the art that will fall within the
spirit and scope of the principles of this invention. More
particularly, reasonable variations and modifications are possible
in the component parts and/or arrangements of the subject
combination arrangement within the scope of the foregoing
disclosure, the drawings and the appended claims without departing
from the spirit of the invention. In addition to variations and
modifications in the component parts and/or arrangements,
alternative uses will also be apparent to those skilled in the
art.
* * * * *