U.S. patent application number 13/257390 was filed with the patent office on 2012-01-12 for grid heat sink.
Invention is credited to Alexandre M. Bratkovski, Graeme W. Burward-Hoy, Lennie K. Kiyama, Viatcheslav Osipov.
Application Number | 20120006514 13/257390 |
Document ID | / |
Family ID | 42781294 |
Filed Date | 2012-01-12 |
United States Patent
Application |
20120006514 |
Kind Code |
A1 |
Bratkovski; Alexandre M. ;
et al. |
January 12, 2012 |
GRID HEAT SINK
Abstract
A grid heat sink includes primary fins extending from a base and
cross fins which intersect the primary fins and form a number of
channels. A fan moves cooling air through the channels to remove
heat from the primary and cross fins. In one illustrative
embodiment, the grid heat sink includes a base, a plurality of
intersecting fins, and a plurality of channels formed by the
intersecting fins. Each of the channels accept cooling air at an
input side of the grid heat sink and direct the cooling air to exit
an output side of the grid heat sink.
Inventors: |
Bratkovski; Alexandre M.;
(Mountain View, CA) ; Kiyama; Lennie K.; (Los
Altos, CA) ; Osipov; Viatcheslav; (East Palo Alto,
CA) ; Burward-Hoy; Graeme W.; (Palo Alto,
CA) |
Family ID: |
42781294 |
Appl. No.: |
13/257390 |
Filed: |
March 25, 2009 |
PCT Filed: |
March 25, 2009 |
PCT NO: |
PCT/US09/38255 |
371 Date: |
September 19, 2011 |
Current U.S.
Class: |
165/121 ;
165/185 |
Current CPC
Class: |
H01L 23/367 20130101;
H01L 2924/00 20130101; H01L 23/467 20130101; H01L 2924/0002
20130101; F28F 3/02 20130101; H01L 2924/0002 20130101 |
Class at
Publication: |
165/121 ;
165/185 |
International
Class: |
F28F 13/00 20060101
F28F013/00; F28F 7/00 20060101 F28F007/00 |
Claims
1. A grid heat sink comprises: a plurality of primary fins
extending from a base; a plurality of cross fins configured to
intersect said primary fins to form a grid, said grid having a
plurality of channels being configured to extend from a first side
to a second side of said grid heat sink; and a fan, said fan being
configured to move cooling air through said plurality of channels,
said cooling air removing heat from said plurality of primary fins
and said plurality of cross fins.
2. The grid heat sink of claim 1, in which said primary fins
comprise a tapered cross-section.
3. The grid heat sink of claim 1, further comprising a formed sheet
of conductive material configured to be placed between said primary
fins to said plurality of channels.
4. The grid heat sink of claim 1, further comprising a top plate,
said top plate being configured to be attached between said distal
ends of said primary fins.
5. The grid heat sink of claim 1, in which said fan is a blower
fan, said blower fan being configured to pressurize said cooling
air and direct said pressurized cooling air into said channels.
6. The grid heat sink of claim 1, in which said primary fins and
cross fins are constructed from a continuous sheet of thermally
conductive material.
7. The grid heat sink of claim 6, further comprising welded joints,
said welded joints joining a first section of said continuous sheet
of thermally conductive material to a second section of said
continuous sheet of thermally conductive material.
8. The grid heat sink of claim 1, in which said grid heat sink
comprises: an extruded base and primary fins; and a sheet metal
cross fins.
9. The grid heat sink of claim 1, in which said grid heat sink
comprises at least one of: a cast metal, a composite material, and
a metal injection molded material.
10. The grid heat sink of claim 1, in which cooling air entering a
first channel does not mix with cooling air entering a second
channel until said cooling air exits said grid heat sink.
11. The grid heat sink of claim 10, in which said fan is configured
to create cooling air with a positive pressure, said positive
pressure varying substantially over an inlet side of said grid heat
sink.
12. The grid heat sink of claim 1, in which said channels have
varying cross-sectional geometries.
13. A grid heat sink comprises: a base; a plurality of intersecting
fins; a plurality of channels formed by said intersecting fins,
each of said channels being configured to accept cooling air at an
input side of said grid heat sink and direct said cooling air to
exit an output side of said grid heat sink.
14. The grid heat sink of claim 13, further comprising a chip, said
chip being in thermal contact with said base and generating thermal
heat, said thermal heat being conducted through said base to said
plurality of intersecting fins, said cooling air being configured
pass through said plurality of channels and to remove said thermal
heat from said intersecting fins.
15. The grid heat sink of claim 13, in which each of said plurality
of channels is enclosed on four sides by said intersecting fins,
each of said channels being mutually parallel to each other and
being parallel to said base.
Description
BACKGROUND
[0001] As an electronic component operates, the electron flow
within the component generates heat. If this heat is not removed,
the electronic component may overheat, causing malfunction or
damage to the component. The heat generated by the electronic
component can be dissipated in a number of ways, including using a
heat sink which absorbs and dissipates the heat via direct air
convection.
[0002] Improvements in integrated circuit design and fabrication
techniques are allowing IC manufacturers to produce smaller IC
devices and other electronic components which operate at
increasingly faster speeds and which perform an increasingly higher
number of operations. As the operating speed of an electronic
component increases, so too does the heat generated by these
components. Further, computer components are being more densely
packaged. These factors contribute to the desire for a heat sink
which has more thermal and volumetric efficiency in removing heat
from these electronic components.
BRIEF DESCRIPTION OF THE DRAWINGS
[0003] The accompanying drawings illustrate various embodiments of
the principles described herein and are a part of the
specification. The illustrated embodiments are merely examples and
do not limit the scope of the claims.
[0004] FIG. 1 is a perspective view of an illustrative heat sink,
according to one embodiment of principles described herein.
[0005] FIG. 2 is a perspective view of an illustrative heat sink,
according to one embodiment of principles described herein.
[0006] FIGS. 3A and 3B are diagrams of an illustrative cooling
system, according to one embodiment of principles described
herein.
[0007] FIG. 4 is a perspective view of an illustrative grid heat
sink according to one embodiment of principles described
herein.
[0008] FIG. 5A is an illustrative diagram of a temperature profile
within a finned heat sink, according to one embodiment of
principles described herein.
[0009] FIG. 5B is an illustrative diagram of a temperature profile
within a grid heat sink, according to one embodiment of principles
described herein.
[0010] FIG. 6A is an illustrative graph of heat removal as a
function of air flux, according to one embodiment of principles
described herein.
[0011] FIG. 6B is an illustrative graph of a difference between
heat sink surface temperature and air exit temperature as a
function of air flux, according to one embodiment of principles
described herein.
[0012] FIG. 7 is a front view of an illustrative grid heat sink,
according to one embodiment of principles described herein.
[0013] FIG. 8 is a front view of an illustrative grid heat sink,
according to one embodiment of principles described herein.
[0014] FIG. 9 is a front view of an illustrative grid heat sink,
according to one embodiment of principles described herein.
[0015] FIG. 10 is a cross-sectional view of an illustrative grid
heat sink, according to one embodiment of principles described
herein.
[0016] FIG. 11 is a front view of an illustrative grid heat sink,
according to one illustrative embodiment of principles described
herein.
[0017] FIG. 12 is a front view of an illustrative grid heat sink,
according to one embodiment of principles described herein.
[0018] FIGS. 13A-D show illustrative steps in forming a grid heat
sink from a continuous sheet of thermally conductive material,
according to one embodiment of principles described herein.
[0019] FIG. 14 is a cross-sectional view of an illustrative grid
heat sink formed with a continuous sheet of thermally conductive
material, according to one embodiment of principles described
herein.
[0020] FIG. 15 is a cross-sectional view of an illustrative grid
heat sink formed with a continuous sheet of thermally conductive
material, according to one embodiment of principles described
herein.
[0021] FIG. 16 is a diagram of an illustrative cooling system which
incorporates a grid heat sink, according to one embodiment of
principles described herein.
[0022] FIG. 17 is a diagram of an illustrative cooling system which
incorporates a grid heat sink, according to one embodiment of
principles described herein.
[0023] FIG. 18 is a diagram of an illustrative cooling system
incorporated into a blade server, according to one embodiment of
principles described herein.
[0024] FIG. 19 is a diagram of an illustrative computer rack
containing a number of blade servers, according to one embodiment
of principles described herein.
[0025] Throughout the drawings, identical reference numbers
designate similar, but not necessarily identical, elements.
DETAILED DESCRIPTION
[0026] As an electronic component operates, the electron flow
within the component generates heat. If this heat is not removed
the electronic component may overheat, causing malfunction or
damage to the component. The heat generated by the electronic
component can be dissipated in a number of ways, including using a
heat sink which absorbs and dissipates the heat via direct air
convection.
[0027] Improvements in integrated circuit design and fabrication
techniques are allowing IC manufacturers to produce smaller IC
devices and other electronic components which operate at
increasingly faster speeds and which perform an increasingly higher
number of operations. As the operating speed of an electronic
component increases, so too does the heat generated by these
components.
[0028] Additionally, computer components are being more densely
packaged which can demand more thermal and volumetric efficiency in
the heat removal systems. For example, the shrinking sizes and
increased functionality of modern electronic devices can result in
much more restricted volumes for heat removal systems. In some
computing architectures, such as arrays of blade servers, these
volume restricted computing devices may be placed in close
proximity to each other.
[0029] In the following description, for purposes of explanation,
numerous specific details are set forth in order to provide a
thorough understanding of the present systems and methods. It will
be apparent, however, to one skilled in the art that the present
apparatus, systems and methods may be practiced without these
specific details. Reference in the specification to "an
embodiment," "an example" or similar language means that a
particular feature, structure, or characteristic described in
connection with the embodiment or example is included in at least
that one embodiment, but not necessarily in other embodiments. The
various instances of the phrase "in one embodiment" or similar
phrases in various places in the specification are not necessarily
all referring to the same embodiment.
[0030] FIG. 1 is a perspective view of an illustrative heat sink
(100) which is in thermal contact with underlying computer chip
(115). The heat sink (100) includes a base (110) and a number of
vertical fins (105). Air passes through the vertical fins (105) and
removes heat from the heat sink (100). The air may be moved by
natural convention or forced convection. Natural convention
utilizes the buoyancy forces of hot air to lift the heated air away
from the fins and draw cool air into the heat sink to replace it.
In forced convection cooling systems, a fan or other device creates
a pressure difference or moving air flow which is channeled through
the fins. Natural conventions systems typically have much lower
cooling capacities than forced convention cooling systems.
[0031] FIG. 2 is an illustrative diagram of heat sink (100) through
which an air flow (200) passes. According to one illustrative
embodiment, the heat sink (100) includes a base (110) with a
thickness "d". The heat sink (100) has a number of vertical fins
(105) and an overall width "b" and length "L." The air flow (200)
passes through the fins (105) parallel to the plane of the
base.
[0032] FIG. 3A is an illustrative diagram of a forced air cooling
system (300) which includes a fan (305). The heat from the chip
(115 ) is transferred into the base (110) which distributes the
heat into the vertical fins (105). The fan (305) may blow air
stream directly into the vertical fins (105) in a process called
impingement cooling. Alternatively, the fan (305) may create
suction by removing air between the fins and blowing it out the top
of the fan. A suction cooling system has inherent limitations in
the amount of pressure differential which can be generated by the
fan or blower.
[0033] FIG. 3B is an illustrative diagram of impingement cooling by
the fan (305). Cooling air (310) is forced from above the fan (305)
into the heat sink (100). A number of inefficiencies can arise in
this configuration. First, the distribution of the air over the
heat sink surfaces is not uniform. For example, the fan blade
velocities are highest at the perimeter of the fan. Consequently,
higher pressures and air flow are generated at the perimeter of the
fan. In the center of the fan, much lower air flow may occur. The
air flow may recirculate beneath the fan. Consequently, the center
of the heat sink may not be effectively cooled.
[0034] Additionally, heated air may be recirculated. For example,
air from the heat sink may escape upwards, curve around the housing
of the fan (305) and be sucked back into the fan (305). This
recirculation may be avoided by having a taller duct which encloses
the fan. However, a taller duct makes the already tall cooling
assembly even taller. Further, even if the heated air is not
recirculated, air which prematurely exits the heat sink is not
utilized to its full capacity and reduces the overall cooling
efficiency of the heat sink for a given air flow rate.
[0035] The amount of cooling provided by a heat sink depends on a
number of factors. These factors may include: the temperature
difference between the cooling air and the surface of the heat
sink, the volume of air forced through the heat sink, and the
surface area of the heat sink.
[0036] FIG. 4 is a perspective view of one illustrative embodiment
of a grid heat sink (400) which has significantly greater surface
area than similarly sized finned heat sink (300). According to one
illustrative embodiment, the grid heat sink (400) includes base
(420) with a number of vertical fins (410). Horizontal fins (415)
intersect the vertical fins (410) to form a grid with a number of
channels (405). The channels may have a variety of geometries
including, but not limited to, square, rectangle, hexagonal, or
other geometries. In some illustrative embodiments, the channels
may extend through the heat sink and maintain a fairly constant
cross-section. In other illustrative embodiments, cross sections of
the channels (405) may vary from channel to channel or vary along
the length of an individual channel.
[0037] FIG. 5A is a cross-sectional diagram of a finned heat sink
(100) which shows the temperature profile (500) in a space between
the fins. For purposes of illustration, only one segment of the
finned heat sink (100) is shown and the entire view has been
rotated to so that the vertical fins (105) are horizontal. The
temperature profile has three segments, a first segment labeled
T.sub.m which represents the temperature through the conductive
base (110). Surface temperature, T.sub.s, represents the
temperature of the surface of the heat sink at a given point. T(x)
represents the air temperature profile through the open space
between the fins (105).
[0038] A heat flux, Q, moves from the underlying chip into the
base. This raises the temperature of the base (110). As shown in
FIG. 5A, there is slight decline in temperature profile T.sub.m as
the heat flux moves through the relatively high thermal
conductivity base material. The air flow interacts with the surface
of the heat sink (100) at the surface temperature (T.sub.s). The
temperature profile, T(x), through the air flow is illustrated as
declining along the length of the profile. The measurement
locations used to generate the temperature profile T(x) are made
along the centerline of the (505) of the heat sink segment. The
height of the temperature profile is higher or lower than the
centerline (505) to show the relative temperature differences
through the temperature profile. Ideally, the air temperature would
be equal to the surface temperature T.sub.s. This would result in a
higher thermal efficiency of the heat sink in removing heat from
the underlying chip. For laminar air flows, the air layers which
travel near the surface of the heat sink are closer to the surface
temperature T.sub.s, while layers that are farther away from the
surface may be at much lower temperatures. For higher air flux
rates, a turbulent flow may develop. In a turbulent flow, a much
higher amount of mixing occurs in the air, which results in a more
uniform temperature distribution and more efficient heat transfer
away from the heat sink.
[0039] FIG. 5B is a diagram of an illustrative section of a grid
heat sink (400). As described above, a temperature flux Q enters
the base (420) and is conducted up the primary fins (410) and into
the cross fins (415). As an air flux passes through the grid heat
sink (400), a temperature profile forms. The temperatures are
measured along the centerline (510). Through the thickness d of the
base (420) there is slight decline in temperature. The additional
surface area provided by the cross fins (415) creates channels
(405) with a characteristic dimension a and additional surface
area. The temperature profile T(x) shows less severe declines and
generates higher thermal efficiencies in removing heat from the
chip because there is a more uniform heating of the cooling air.
Further, the enclosed channel prevents the premature escape and
recirculation problems of the air flow.
[0040] The grid heat sink allows for a much larger amount of heat
removal for the same size of heat sink and the same air flow rate,
or the same heat removal for a smaller coolant flow. Consequently,
for a given system a grid heat sink may be smaller, thereby
reducing the overall volume of the system. Additionally or
alternatively, the increased thermal performance may allow for
lower operating temperatures of the heat generating component. The
heat removal of various heat sinks as a function of air flux can be
estimated using Eq. 1.
W ( j ) = 0.023 mAb .rho. C v ( j ) L ( j ) ( d + a ) ( .rho. dv (
j ) .mu. ) - 0.2 [ 1 - exp ( - L o L ( j ) ) ] ( .THETA. - T ) Eq .
1 ##EQU00001##
[0041] Where:
[0042] W=heat removed from system in Watts
[0043] j=volume flow rate of air through the system
[0044] v=velocity of air
[0045] p=density of air
[0046] C=specific heat of air
[0047] .mu.=Newtonian viscosity of air
[0048] b=width of heat sink
[0049] L=length of heat sink
[0050] d=thickness of heat sink base
[0051] a=dimension of channel
[0052] .theta.=exit temperature of air
[0053] T=surface temperature of heat sink
[0054] m=2 for the fin cooling system and m.apprxeq.4 for the grid
system
[0055] FIG. 6A is an illustrative graph of the heat removed for a
fin system and a grid system as estimated by Eq. 1. The vertical
axis represents heat removed in units of Watts from the heat sink
by the passage of cooling air. The horizontal axis is air flux
through the heat sink in cubic meters per second. The dashed line
represents the heat removed in a grid system and the dash-dot line
represents the heat removed from a fin system. As can be seen from
the graph, a grid system with comparable size and mass removes
significantly more heat than a fin system. For example, at 0.0075
cubic meters of air per second, the fin system removed
approximately 45 Watts of heat. The grid system removed
approximately 85 Watts of heat.
[0056] A measure of the thermal efficiency of the heat sink is the
difference between the exit temperature of the air (.theta.) and
the surface temperature of the heat sink (T). Ideally, the exit air
temperature (.theta.) would be equal to the surface temperature of
the heat sink (T). When the exit air temperature equals the surface
temperature of the heat sink, the air has absorbed all of the heat
possible. To accomplish this level of thermal efficiency is often
impractical because the size of the heat sink becomes infinitely
larger. However, when comparing two heat sinks of similar size, the
thermal efficiency can provide a measure of the efficiency of the
heat sink designs.
[0057] The difference (.DELTA.T) between the exit air temperature
(.theta.) and the surface temperature of the heat sink (T) can be
estimated using the Eq. 2, shown below.
.DELTA. T .ident. ( .THETA. - T ) = W [ AbL ( j ) mh ( j ) d + a [
1 - exp ( - L o L ( j ) ) ] ( .THETA. - T ) ] - 1 Eq . 2
##EQU00002##
[0058] FIG. 6B shows an illustrative graph of the results of Eq. 2
for a grid system and a fin system of comparable size. The
horizontal axis represents the air flow rate through the heat sinks
in cubic meters per second. The temperature difference in degrees
Celsius is shown along the vertical axis, with lower temperature
differences at the bottom of the axis and higher temperature
differences shown proportionally higher on the axis.
[0059] The temperature difference between the exit air and the heat
sink surface for the grid system is shown as a dotted line. The
temperature difference for the fin system is shown as a dot-dashed
line. As can be seen from the curves on the chart, the temperature
differences become smaller for higher volume flow rates. There are
a number of factors which could produce this result including
increased turbulence in higher velocity flows. In general,
turbulent flows are more efficient in transporting heat away from a
surface than more ordered flows. Consequently as turbulence
increases, the efficiency of the heat sink can increase.
[0060] The grid system has lower temperature differences than the
fin system for all flow rates shown in FIG. 6B. For example, at a
flow rate of 0.0075 cubic meters per second, the temperature
difference for the fin system is approximately 6.5 degrees Celsius
and the temperature difference for the grid system is approximately
3 degrees Celsius. Consequently, for a given flux of air through
the heat sink, the grid system can be more efficient than the fin
system in removing heat.
[0061] The grid heat sink could have a variety of configurations
and geometries. FIG. 7 shows a grid heat sink (700) which is in
thermal contact with an underlying chip (725). The grid heat sink
(700) includes a base (720) which distributes heat to the various
vertical fins (710). These primary vertical fins (710) serve as
conduction paths to the overlying structures. According to one
illustrative embodiment, a number of cross fins (715) intersect the
primary vertical fins (710) and provide additional surface area and
structural support for the heat sink (700). As discussed above, the
intersecting fins create a number of channels (730). Air flow is
directed through the channels to provide the desired cooling of the
heat sink (700) and underlying chip (725). These channels may have
a substantially uniform cross-section through the length of the
heat sink (700). Additionally or alternatively, there may be
various disruptions in the channels, such as surface roughness,
offsets of the channel cross-section, etc. These obstructions may
generate additional focused cooling by direct impingement of the
flow on the obstruction or may serve to create additional turbulent
flow within the channel to improve heat transfer. In some
embodiments, the cross section of the channels may increase toward
the exit to allow for expansion of the air flow. The volume and
temperature of the expanding air flow are physically related such
that an expansion of the volume of the air flow results in a lower
temperature within the air flow. Consequently, altering the
cross-section of the channel may be used to make adjustments to the
temperature of the air.
[0062] FIG. 8 is a diagram of an illustrative heat sink (800) which
has tapered primary fins (810). As discussed above, the primary
fins (810) serve as a conduction path for the majority of the heat
which is dissipated in the rest of the structure. By making the
base of the primary fins (810) thicker at the base where there is a
greater amount of heat flux, the heat sink temperature can be more
uniform.
[0063] According to one embodiment, the cross fins (815) may be
significantly thinner than the primary fins (810). The cross fins
(815) need only conduct a relatively small amount of heat from the
adjoining primary fins through the cross fin area. Consequently,
the cross fins could be relatively thin with little performance
degradation. Increasing the thickness of the fins results in a
reduction of the cross area of the air channels (830). A
quantitative trade off between fin geometry and air flow can be
performed for specific designs, heat loads, and fan
combinations.
[0064] Further, the cross-section of the channels (830) may vary
along through the height of the heat sink (820). For example, if
high volume flow rates are desired near the base (820) of the heat
sink (800), the cross sectional area of the channels at the base
could be increased. Alternatively, if high surface areas are
desired at the base, a plurality of smaller channels could be
formed near the base (820).
[0065] According to one illustrative embodiment, the grid heat sink
may be formed by joining a number of stacked tubes. The tubes may
be made from a thermally conductive material such as metal and
joined using any number of techniques. For example, the tubes may
be joined using welding, soldering, adhesive, or other techniques.
The tubes may have various cross-sectional geometries which may
vary from tube to tube and/or along the length of the individual
tubes.
[0066] FIG. 9 is a diagram of one illustrative embodiment of a grid
heat sink (900). The grid heat sink (900) includes a number of
radial primary fins (910) which extend from a base (920). The base
(920) is in direct thermal contact with a chip (925). The heat flux
into the base (920) is concentrated in the center of the base
directly over the chip (925). The radial primary fins arms (910)
connected to the center of the base (920) to more directly conduct
the heat from the base (920). A number of curved cross fins (915)
intersect the radial primary fins (910) to form a number of
channels (930). The channels (930) can be of any suitable geometry
including triangular, rectangular, wedge shaped, or any other
suitable geometry.
[0067] FIG. 10 is a cross-sectional diagram of an illustrative heat
sink (1000) which includes a number of primary fins (1010) which
extend from a base (1020). The base (1020) is in thermal contact
with an underlying chip (1025). The cross fins (1015) extend from
the primary fins (1010) but do not intersect the adjacent primary
fins. The result is a number of open channels (1030) between the
primary fins. The extension of the cross fins (1015) into the open
channels (1030) create a high surface area within the channels. In
some embodiments, higher pressure fluid flow may be applied to one
portion of a heat sink than other portions of the heat sink. For
example, in the embodiment shown in FIG. 10, a higher pressure
fluid flow may be applied to the lower portion of the open channel
(1030) near the base. This could result in a two dimensional fluid
flow, with a portion of the fluid passing axially down the open
channel and a portion of the fluid passing through the serpentine
upper portion of the channel to exit through the top of the heat
sink (1000).
[0068] According to one illustrative embodiment, the grid heat sink
may also have a number of external fins (1035) which extend beyond
the interior grid structure to provide additional cooling by
external force or free convention.
[0069] FIG. 11 is a diagram of an illustrative heat sink (1100)
which includes a base (1120) which is in thermal contact with an
underlying chip (1125). A number of primary fins (1110) extend
upward from the base (1120). The primary fins (1110) and base
(1120) can be formed using metal extrusion processes. The channels
(1145) can be created by inserting bent sheet metal forms (1115,
1130, 1135) into the spaces between the primary fins (1110). The
shape of the sheet metal form determines the size, number and
geometry of the resulting channels (1145). For example, a first
form (1115) has relatively large channels. The second form (1130)
creates smaller and more numerous channels. Consequently the second
form (1130) creates more surface area within the heat sink (1100).
A third form (1135) creates smaller channels closer to the base
(1120) and larger channels near the lid (1140).
[0070] The sheet metal forms (1115, 1130, 1135) may be thermally
and structurally joined to the primary fins (1110) in a number of
ways, including, but not limited to welding, soldering, adhesives,
or spring forces. For example, the lid (1140) could compress the
sheet metal forms between the primary fins (1110) and produce
appropriate thermal contact between the forms (1115, 1130, 1135)
and the primary fins (1110) and base (1120).
[0071] FIG. 12 is an illustrative diagram of a heat sink (1200)
which incorporates a continuous thermally conductive sheet (1215)
which is bent to form channels (1230). The conductive sheet (1215)
is placed over the primary fins (1210) and contacts the base
(1220). A cover (1205) encloses upper portion of the heat sink
(1200) and forms some of the surfaces of the channels (1230).
[0072] FIGS. 13A-13D are illustrations which show steps in forming
a grid heat sink (1300) from a continuous sheet of conductive
material (1305). According to one illustrative embodiment, two
bends (1315, 1310) are made in the sheet (1305) to create a U
shaped geometry as shown in FIG. 13A. FIG. 13B illustrates
additional bends (1325, 1320) being made in the sheet to form a
first channel (1330). As shown in FIG. 13C, this process is
repeated to form a column which includes two additional channels
(1335, 1340). FIG. 13D illustrates the formation of additional
columns to form a grid which is attached to a base (1345). As
discussed above, a variety of methods may be used to attach the
grid to the base or make internal joints in the grid. The resulting
grid heat sink (1300) is formed from a continuous sheet of
conductive material (1305) and a base (1345). The type, thickness,
and other properties of the conductive material (1305) can be
altered according to the specific design needs.
[0073] FIG. 14 is a diagram of an alternative geometry for forming
a grid heat sink (1400) from a continuous sheet of thermally
conductive material (1401). According to one illustrative
embodiment, the thermally conductive material (1401) is bent and
joined at various contact points (1415) to form channels (1405).
The entire grid structure is joined to a base structure (1415).
[0074] FIG. 15 is a diagram of an alternative geometry for forming
a grid heat sink (1500) from a continuous sheet of thermally
conductive material (1510). According to one illustrative
embodiment, the thermally conductive material (1510) is bent and
joined to form relatively open channels (1505). The entire grid
structure is joined to a base structure (1515).
[0075] FIG. 16 is a diagram of an illustrative cooling system
(1600) for a chip (1615). The air flow (1605) is directed through
two ducted fans (1620), into a manifold (1620), and then through a
grid heat sink (1625). The grid heat sink (1625) is thermally
connected to the chip (1615) and conducts heat away from the chip
(1615). The air flow (1605) removes the heat from the grid heat
sink (1625) by convective heat transfer. In this illustrative
embodiment, the ducted fans (1610) are used to create a high air
pressure in the manifold (1620) which forces the air through the
channels in the grid heat sink (1625). This approach may have a
number of advantages for over suction systems where the fan creates
low pressure to suck air through a heat sink. The suction action of
the fan is limited in the pressure differential which can be
generated. A suction fan system can not produce a pressure any
lower than zero. Consequently, the maximum pressure differential
which can be produced by a suction fan system is equal to the
supply pressure, which is typically atmospheric pressure. In
contrast, fan systems which create high pressure at the inlet to
force air through a heat sink do not have a similar limitation in
the maximum pressure which can be generated. Rather, pressure
systems are limited only by the mechanics of the cooling system,
such as the design of the fans, the available power, the physical
strength of the fans, manifold and grid heat sink, etc.
Consequently, a pressure system could produce several atmospheres
of pressure to drive the air flow through the grid heat sink. This
could be particularly advantageous when very small channels are
used in the grid heat sink.
[0076] FIG. 17 shows an illustrative embodiment of the a cooling
system (1700) which includes a blower fan (1710) which attached to
a manifold (1720) which directs the air flow through a grid heat
sink (1725). The grid heat sink (1725) is used to cool an
underlying chip (1715).
[0077] FIG. 18 is a side view of an illustrative cooling system
(1700) within a blade server (1800) which is represented by a
dotted outline. Blade servers (1800) are very compact computers
which may have one or more central processor units (CPUs) (1805).
The grid heat sink (1725) is thermally connected to the CPU (1805).
An air flow (1810) is generated by the fan (1710). The air flow
(1810) through openings in the left of the blade server (1800) and
enters the fan (1710) where it is compressed and ejected into the
manifold (1720). The manifold (1720) directs the air flow (1810)
through the grid heat sink (1725). The air flow (1810) is then
vented out of the right of the blade server (1800).
[0078] The compact design, low profile and thermal efficiency may
make the grid cooling system particularly suitable for applications
which have geometric constraints. FIG. 19 is front view of an
illustrative rack (1900) of blade servers (1800). The rack (1900)
contains 16 blade servers (1800), each of which may have multiple
processors. The front of each of the blade servers (1800) has a
number of openings through cooling air is drawn. After passing over
the various components within the blade server (1800), the heated
air is vented out the back of the rack. A variety of fan
configurations can be used. According to one illustrative
embodiment, one larger fan or array of fans supply pressurized air
for multiple grid heat sinks.
[0079] In sum, a grid heat sink provides increased thermal and
volumetric efficiency when compared to fin heat sinks. The channels
formed by the primary fins and cross fins provide additional
surface area and prevent the premature exit and recirculation of
cooling air. Consequently, grid heat sinks may be particularly
desirable for more compact systems which have concentrated heat
sources.
[0080] The preceding description has been presented only to
illustrate and describe embodiments and examples of the principles
described. This description is not intended to be exhaustive or to
limit these principles to any precise form disclosed. Many
modifications and variations are possible in light of the above
teaching.
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