U.S. patent application number 12/573107 was filed with the patent office on 2011-04-07 for cold plate with pins.
This patent application is currently assigned to Wolverine Tube, Inc.. Invention is credited to Sy-Jenq LOONG, Donald Lynn Smith.
Application Number | 20110079376 12/573107 |
Document ID | / |
Family ID | 43822294 |
Filed Date | 2011-04-07 |
United States Patent
Application |
20110079376 |
Kind Code |
A1 |
LOONG; Sy-Jenq ; et
al. |
April 7, 2011 |
COLD PLATE WITH PINS
Abstract
A cold plate includes an enclosure with an inlet, an outlet, a
base and a lid. The inlet and outlet are in fluid communication, so
fluid can flow from the inlet though the enclosure to the outlet.
The base is formed from a base plate, and the base plate includes
an island facing into the enclosure. A plurality of pins extends
from the island toward the lid. The pins can have a spiral shape,
where the cross sectional profile of the pins change along the
length of the pin.
Inventors: |
LOONG; Sy-Jenq; (Madison,
AL) ; Smith; Donald Lynn; (Danville, AL) |
Assignee: |
Wolverine Tube, Inc.
Huntsville
AL
|
Family ID: |
43822294 |
Appl. No.: |
12/573107 |
Filed: |
October 3, 2009 |
Current U.S.
Class: |
165/185 ;
29/890.03 |
Current CPC
Class: |
H01L 23/473 20130101;
B23P 15/26 20130101; B21J 5/068 20200801; H01L 23/3677 20130101;
B01D 8/00 20130101; Y10T 29/49359 20150115; F28F 3/022 20130101;
F28F 3/048 20130101; H01L 2924/0002 20130101; H05K 7/20254
20130101; Y10T 29/4935 20150115; H01L 21/4878 20130101; H01L
2924/0002 20130101; H01L 2924/00 20130101 |
Class at
Publication: |
165/185 ;
29/890.03 |
International
Class: |
F28F 7/00 20060101
F28F007/00; B21D 53/02 20060101 B21D053/02 |
Claims
1. A cold plate comprising: an enclosure having an inlet, an
outlet, a base and a lid; a base plate forming the enclosure base,
where the base plate includes an island; and a plurality of pins
extending from the island toward the enclosure lid, the pins
including a bottom where the pin connects to the base plate, a top
opposite the bottom, a length extending from the bottom to the top,
an axis central to the pin, a side surface, and a generally
quadrilateral cross sectional profile having an orientation, where
the orientation of the cross sectional profile spirals along the
length of the pin, the axis bends along the length of the pin, the
side surface includes at least two textures where one texture
includes a plurality of dimples, and the pin and the base plate are
monolithic.
2. The cold plate of claim 1 where the pin further includes a cross
sectional area, and where for at least a portion of the pin the
cross sectional area increases with increased distance from the pin
bottom.
3. A cold plate comprising: an enclosure having a base, a lid, an
inlet and an outlet; a base plate forming the enclosure base, where
the base plate includes an island; and a plurality of pins within
the enclosure extending from the base plate toward the enclosure
lid, where each pin has a length and a cross sectional profile with
an orientation, and where the cross sectional profile orientation
changes along the pin length.
4. The cold plate of claim 3 where the pin has an axis, a bottom
and a top, and the pin axis bends between the bottom and the
top.
5. The cold plate of claim 3 where the pin has a cross sectional
area and a bottom where the pin connects to the base plate, and for
at least some portion of the pin the cross sectional area increases
with an increased distance from the pin bottom.
6. The cold plate of claim 3 where the pin has side surfaces with
at least two different textures on the side surfaces, and where at
least one texture includes a plurality of dimples.
7. The cold plate of claim 6 where the pin has at least three
different textures on the side surface.
8. The cold plate of claim 3 where the pin has a width essentially
perpendicular to the length, and the pin has an aspect ratio of
twenty to one, where the aspect ratio is the ratio of the pin
length to the pin width.
9. The cold plate of claim 3 including a flow line essentially
straight between the inlet and outlet, and where the pins are
aligned essentially parallel to the flow line.
10. The cold plate of claim 3 including a flow line essentially
straight between the inlet and outlet, and where the pins are
staggered relative to the flow line.
11. The cold plate of claim 3 where the pin is monolithic with the
base plate.
12. A cold plate comprising: an enclosure having a base, a lid, an
inlet, and an outlet; a base plate forming the enclosure base,
where the base plate includes an island; and a plurality of pins
extending from the island toward the enclosure lid, where each pin
includes at least two textures, and where at least one texture
includes a plurality of dimples.
13. The cold plate of claim 12 where the pin has a bottom and a
cross sectional area, and where for at least a portion of the pin
the cross sectional area increases with increasing distance from
the bottom.
14. The cold plate of claim 12 where the pin has a bottom, a top,
and an axis, and where the axis bends between the bottom and the
top.
15. The cold plate of claim 12 where the pin is monolithic with the
base plate.
16. A cold plate comprising: an enclosure having an inlet, an
outlet, a base and a lid; a base plate forming the enclosure base,
where the base plate includes an island; and a plurality of pins
extending from the island toward the enclosure lid, where each pin
includes a length and an axis, and where the axis bends along the
pin length.
17. The cold plate of claim 16 where the pin includes a bottom and
a cross sectional area, and where the cross sectional area
increases with increased distance from the bottom for at least a
portion of the pin.
18. A cold plate comprising: an enclosure having an inlet, an
outlet, a base and a lid; a base plate forming the enclosure base,
where the base plate includes an island; and a plurality of pins
extending from the island toward the enclosure lid, where each pin
has a cross sectional area, a bottom where the pin connects to the
island, and a top opposite the bottom, and where for at least a
portion of the pin the cross sectional area increases with an
increased distance from the pin bottom.
19. A method of producing a cold plate comprising: slicing a base
plate to form a plurality of fins; cross-slicing the base plate
after the fins are formed to form a plurality of pins; attaching a
cover to the base plate such that the plurality of pins are
contained within an enclosure between the cover and the base plate;
and forming an inlet and an outlet to the enclosure.
20. The method of claim 19 where the base plate is sliced such that
the pins spiral between a pin bottom and a pin top.
21. The method of claim 19 where the base plate is sliced such that
a pin axis bends along a length of the pin.
22. The method of claim 19 where the base plate is sliced without
removing material so the fins elevate from the base plate.
23. The method of claim 19 where the base plate is sliced without
removing material so the pins elevate from the fins.
24. The method of claim 19 where the base plate is sliced with a
tool to produce at least two textures on a side surface of the
pins.
25. The method of claim 24 where at least one texture of the side
surface includes a plurality of dimples.
26. The method of claim 19 where the base plate is sliced such that
a lower portion of the pin tapers to a smaller cross sectional area
further towards a pin bottom.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to the production and use of a cold
plate, which is used to transfer heat.
[0003] 2. Description of the Related Art
[0004] Certain electronic devices generate heat as they operate,
and this heat has to be removed or dissipated for the device to
continue operating properly. Several techniques have been used to
cool electronic equipment. Examples include fans, which are used to
blow air over electronic equipment. This air serves to convectively
cool the electronic equipment with normal ambient air. Other
techniques that have been used include liquid cold plates. Liquid
cold plates are plates with channels through which liquid flows.
The electronic equipment is mounted in contact with a liquid cold
plate and the heat generated by the electronic equipment is
transferred to the coolant inside the plate. This can provide
better cooling than the convective cooling provided by a fan with
considerably less flow volume. It can also provide better
temperature consistency with less acoustic noise.
[0005] Cold plates can be directly affixed to a heat-producing
piece of electronic equipment, such as an electronic chip or an
insulated gated bipolar transistor (IGBT). Typically, the cold
plate includes an inlet and an outlet for liquid coolant flow. The
liquid coolant absorbs the heat produced by the electronic
equipment, and transfers the absorbed heat to the coolant which
then flows out of the cold plate. Many cold plates provide cooling
with a relatively low flow of liquid coolant. They can provide a
degree of temperature consistency, minimal acoustic noise and the
cooling power of liquid coolants.
[0006] Several factors impact the performance and desirability of
cold plates, and different factors are important for different
uses. Some important factors include cost of production and ease of
producing relatively large quantities. Cooling efficiency should be
high, and cold plates should be securely sealed so as to prevent
any leak of liquid coolant onto the electronic equipment being
cooled.
[0007] In some applications, the coolant may not be particularly
clean, which can result in plugging of the cold plate. For example,
a cold plate used in an automobile may utilize the anti-freeze
liquid for cooling, and the anti-freeze can contain small
particulates. In other applications, there may be a phase transfer
within a cold plate to help facilitate cooling. It is also possible
for a cold plate to be used for heating a component buy replacing
the coolant with a heating fluid. One primary difference between a
coolant and a heating fluid in one phase heat transfer is the
temperature of a coolant is lower than the item being cooled, and
the temperature of a heating fluid is higher than the item being
cooled.
BRIEF SUMMARY OF THE INVENTION
[0008] The current invention comprises a cold plate and a method of
producing the cold plate. The cold plate has an enclosure with an
inlet, an outlet, a base, and a lid. The base is formed from a base
plate, and the base plate includes an island. A plurality of pins
extends from the island into the enclosure, so a fluid can flow
about the pins. The pins can have a spiral shape, where the cross
sectional profile of the pins change along the pin length,
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0009] FIG. 1 shows a cooling system using a cold plate.
[0010] FIG. 2 is an exploded view of one embodiment of a cold
plate.
[0011] FIG. 3 is a cross sectional side view of one embodiment of a
cold plate.
[0012] FIG. 4 is a perspective view of a base plate.
[0013] FIG. 5 is a perspective view of a base plate with a
different pin pattern.
[0014] FIG. 6 is a partial cross sectional side view of two pins as
part of a base plate.
[0015] FIG. 7 a side view of one pin.
[0016] FIG. 8 is a perspective view of one pin sectioned into four
pieces.
[0017] FIG. 9 is a perspective view of a tool forming fins in a
base plate.
[0018] FIG. 10 is a side cross sectional view of a tool forming
fins in a base plate.
[0019] FIG. 11 is a side cross sectional view of a tool forming
fins at a different angle in a base plate.
[0020] FIG. 12 is a perspective view of a tool forming a pin from a
fin.
DETAILED DESCRIPTION
[0021] Some electronic components are limited by the heat they
produce. Cooling can help to increase the utilization of some of
these components. Different cooling techniques are more appropriate
for different equipment or different circumstances. One cooling
method uses fans to blow air over an electronic component for
convection cooling. This technique is simple and safe, but does not
provide the cooling potential of some other techniques. The
utilization of a liquid coolant can provide more efficient cooling,
but many electronic components can malfunction when splashed with a
liquid, so some can be cautious when using liquid cooling.
Nevertheless, liquid cooling can increase the overall efficiency of
some electronic components, as well as providing certain other
benefits. Secondary benefits can include decreased acoustical noise
and superior temperature consistency in the electronic
component.
Heat Transfer Fundamentals
[0022] This description will focus on single phase heat transfer.
It is recognized that cold plates and other heat transfer devices
can be used for two phase cooling, and the invention is not limited
to single phase cooling, but this description focuses on single
phase heat transfer for simplicity and clarity.
[0023] Air or other gases could be used as the cooling medium in a
cold plate, but liquids are preferred. Liquid cooling is different
than gas cooling for several reasons. For example, liquids are
denser than gases so more thermal mass is available to absorb heat
from the electronic equipment. Also, liquids generally have higher
thermal conductivities so heat will transfer into and through the
liquid more rapidly than heat will transfer into and through a gas.
Furthermore, liquids tend to have a higher specific heat than gases
so a set quantity of liquid will absorb and transfer more heat than
a comparable amount of gas. Because of this, when electronic
equipment is utilized which produces large amounts of heat, many
manufacturers may choose liquid cooling devices.
[0024] Reducing resistance to heat flow improves the efficiency of
a heat transfer device. Two significant forms of resistance to heat
flow include resistance through one material and resistance across
an interface between two separate components or parts. Resistance
to heat flow through a single material is minimized if the material
is a heat conductor, instead of a heat insulator. Metals are
usually relatively good conductors, and they can be formed and
shaped in many ways. Copper is a metal which readily conducts heat,
and it is relatively malleable, so copper is often used in cold
plates. However, other materials can also be used, such as
aluminum, titanium, steel, gold, or even non-metallic materials
like graphite or ceramics.
[0025] Another source of resistance to heat flow is at the
interface between two components or parts. Typically, when heat
flows from a first component to another component which contacts
the first, there is resistance to heat flow between the two
components. Forming a heat transfer device from one solid substrate
can help improve heat transfer. If one were to produce one heat
transfer component separately and then affix that component to
another, there would be a resistance to heat flow at the joint
between the two components. This is true even if the separate
components were made from the same material, such as copper.
Forming a heat transfer device from fewer components can improve
heat transfer. When one piece is formed from another so there is no
joint between the two, the pieces are said to be monolithic in this
description.
[0026] Heat flow can also be improved by increasing the surface
area where two different materials contact each other. When a
liquid flows over a solid, heat is transferred between the two
materials where the liquid contacts the solid. Increasing the
surface area where the liquid contacts the solid is another way to
decrease resistance to heat transfer, and increase the efficiency
of a heat transfer device.
[0027] In some cases, liquids will flow across a solid in what is
referred to as laminar flow. In laminar flow, the layer of liquid
directly contacting the solid surface remains essentially
stationary at the solid surface. The layer of liquid directly above
that layer moves very gradually across the first layer. The next
layer up moves a little more swiftly, etc., such that the highest
flow rate will be at a point relatively far from the solid surface.
The lowest flow rate, which is essentially zero, will be at the
solid surface. Each different layer of liquid which is sliding over
the adjacent layers provides its own resistance to heat flow.
Therefore, if the liquid can be mixed during flow, the liquid
directly contacting the solid surface can absorb heat from the
solid surface and then be mixed with the entire body of cooling
liquid to spread the absorbed heat into the liquid more
rapidly.
[0028] Turbulent flow causes liquids to mix as they flow across a
solid surface, as opposed to laminar flow. This tends to keep the
liquid in contact with the solid surface cooler, which facilitates
a faster transfer of heat from the solid surface to the liquid.
Some things which tend to increase turbulent flow include faster
flow rates, uneven surfaces, projections into a flowing liquid, and
various obstructions that force a liquid to change path and flow
another way. To maximize turbulence, one can include sharp bends,
twisting edges, curved pillars, and any of a wide variety of flow
obstructions that cause rapid change in the direction of flow of a
liquid. Many structures which increase turbulence can also increase
pressure drop across a cold plate. Increased pressure drop can
lower the flow rate, so a balance must be observed to ensure
efficient heat transfer. Obstructions which tend to increase the
amount of fluid flow close to the solid surface also tends to
increase heat transfer, because this reduces the thickness of any
stagnant liquid layer at the solid liquid interface, and it also
reduces the distance heated liquid has to travel to intermix with
the main body of cooling liquid.
Cold Plate Cooling System
[0029] A cold plate 10 can be connected to an electronic component
12 or some other device to help cool the electronic component 12 or
other device, as seen in FIG. 1. The cold plate 10 could also be
used to heat a device in the same manner as cooling a device, but
this description is directed towards cooling for simplicity and
clarity. A cooling liquid, also referred to as coolant, is used to
absorb heat from a heat source, such as an electronic component 12.
After the coolant has absorbed the heat, it can be circulated to a
different location where the coolant itself is cooled before being
re-used for cooling. In one embodiment, a fan 14 blows cool air
over a convective cooling device 16, similar to an automobile
radiator, through which the coolant is circulated. A heat exchanger
using facility water or other cooling systems could be used in
place of the convective cooling device 16. It is also possible to
simply move the heated fluid through a cooler area, such as by
pumping the coolant through tubes exposed to air which is cooler
than the coolant.
[0030] A pump 18 or other flow-inducing device can circulate the
coolant through the cold plate 10. The cold plate 10 is affixed to
an electronic component 12, such as with adhesive, sonic welding,
brazing, soldering, diffusion bonding, or any other appropriate
technique. Certain adhesives readily conduct heat, and can help
minimize resistance to heat flow. Direct connection of the cold
plate 10 to the electronic component 12 can minimize resistance to
heat transfer. Use of a thermo-electric cooler between the cold
plate 10 and the electronic component 12 can improve performance,
but thermo-electric coolers are beyond this discussion. In one
embodiment, the heat generated by the electronic component 12 is
transferred to the coolant in the plate 10, and the coolant is then
pumped to the convective cooling device 16 which is cooled with air
from a fan 14. It is possible to connect a plurality of cold plates
10 or other heat exchanger devices in a single loop, so several
electronic components 12 or other heat producing devices can be
cooled with a single pump 18 and convective cooling device 16. For
example, an automobile could use the water pump 18 to deliver
antifreeze (a coolant) through the engine block to cool the engine,
and also to deliver antifreeze to a water block 10 for cooling an
electronic component 12.
[0031] Evaporative cooling can also be used, where a liquid is
evaporated by the heat from the electronic component 12 or other
heat source. Typically, the liquid is evaporated into a gas in an
evaporator, and then the gas is re-condensed into a liquid in a
condenser. It is also possible for the liquid to be evaporated and
discharged from the system. A cold plate 10 can be used as an
evaporator and/or a condenser. Many materials can be used as the
coolant, including water, a water and glycol mixture, chloro fluoro
carbons (CFCs), hydro chloro fluoro carbons (HCFCs), ammonia, brine
solutions, oils, and many other materials.
Cold Plate
[0032] The cold plate 10 includes several structural components, as
seen in FIGS. 2, 3, and 4, with continuing reference to FIG. 1.
Coolant in the cold plate 10 flows through an enclosure 20, and the
enclosure 20 has a base 22 and a lid 24. The enclosure 20 will also
typically include side walls 26. The base 22 is at the bottom of
the enclosure 10, and the lid 24 is at the top. The side walls 26
may be incorporated as part of a single structure used to make the
lid 24, or the side walls 26 can be a separate structure, or the
side walls may be a part of the base 20. It is also possible for
the base 22 and lid 24 to gradually slope together, so there is no
sharp demarcation between the side walls 26 and the base 22 and/or
lid 24. The enclosure 20 can be almost any shape, so if the
enclosure is round or cylindrical, the side walls 26 could be one
continuous wall.
[0033] Coolant or other fluids enter and exit the enclosure 20
through an inlet 28 and an outlet 30. The inlet 28 and/or outlet 30
may penetrate the lid 24, a side wall 26, or the base 22, as long
as the inlet 28 and outlet 30 allow for fluid to enter and exit the
enclosure 20. The inlet 28 and outlet 30 are in fluid communication
through the enclosure 20, so fluid enters the enclosure 20 through
the inlet 28, travels through the enclosure 20, and then exits the
enclosure 20 through the outlet 30. This direction of flow could
also be reversed. It is also possible for there to be more than one
inlet 28, and/or more than one outlet 28. A nozzle 31 or similar
device can be connected to the cold plate 10 at the inlet 28 and/or
outlet 30 to facilitate fluid flow.
[0034] The positioning of the inlet 28 and outlet 28 influence the
flow pattern through the enclosure 20. A flow line 32 is defined as
a line straight between the inlet 28 and the outlet 30, as seen in
FIG. 5, with continuing reference to FIGS. 1-4. In some
embodiments, the flow pattern will tend to follow the flow line 32,
but some structures within the enclosure 20 can alter the flow
pattern. The angle at which the inlet 28 and/or outlet 30 penetrate
into the enclosure 20 can also influence the flow pattern, because
the inlet 28 can serve as a jet to direct flow, and the outlet can
serve as a drain to direct flow. The location of the inlet 28
and/or outlet 30 can also influence the flow pattern, and this can
be utilized with the angle at which the inlet 28 and/or outlet 30
penetrate the enclosure 20 to establish a more desirable flow
pattern. In some embodiments, a flow pattern which covers most of
the base 22 is desired to maximize the area being cooled by flowing
fluid.
[0035] The base 22 of the enclosure 20 is formed from a base plate
34. The base plate 34 includes an island 36, which is on the side
of the base plate 34 facing into the enclosure 20. In some
embodiments, a base plate back side 78, or the side of the base
plate 34 opposite the island 36, is attached to the electronic
component 12 or other heat producing device. It is also possible to
attach a different part of the cold plate 10 to a heat producing
device, if desired.
[0036] The base plate 34 can include an attachment area 38 around
the island 36 for attaching side walls 26 and/or a lid 24. The
connection of the base plate 34 to the lid 24 or side walls 26
should be water tight, to prevent the leakage of liquids (if the
cooling fluid is a liquid). A smooth surface for the attachment
area 38 can facilitate a water tight connection, but other surfaces
may be useful as well. The attachment area 38 could include a
groove with a matching lip on the lid 24 or side wall 26, or a
roughed surface for use with an adhesive, or any of a wide variety
of other options. In some embodiments, the lid 24 and/or side walls
26 slide completely around the base plate 34, so the attachment
area 38 can be on a sideways facing surface of the base plate 34
which is perpendicular to the surface of the island 36. In other
embodiments, the attachment area 38 can be raised up so a flat lid
24 can complete the enclosure 20. A wide variety of design options
can be used for the attachment area 38.
[0037] A plurality of pins 40 extend from the island 36 upward
toward the lid 24. The pins 40 can extend all the way to the lid
24, so the pins actually touch the lid 24, or the pins 40 can
extend to a point short of the lid 24, so there is a gap between
the pins 40 and the lid 24. The pins 40 in the cold plate 10 are
arranged in some pattern. The pattern can be random, or the pattern
can be ordered. In one embodiment, the pins 40 are aligned along
lines parallel with the flow line 32, as shown in FIG. 5. This
pattern is referred to as the aligned pattern. Having the pins 40
aligned with the flow line 32 tends to result in the coolant
flowing between different rows of pins 40. This flow can help to
reduce pressure drop in the cold plate 10. The spiral of the pins
40 in the aligned pattern can provide a cold plate 10 with some
similarities to a cold plate 10 with a wavy fin design. In an
alternate embodiment, the pins 10 are aligned in rows which cross
the flow line 32, as shown in FIG. 4. This pattern is referred to
as the staggered pattern. The rows of pins 10 can be set at almost
any angle to the flow line 32, such as a forty five degree angle, a
thirty degree angle, or essentially any other angle. In the
staggered pattern, the fluid is forced to flow around the staggered
pins, so the fluid can not flow in a straight line parallel with
the flow line 32. This tends to cause a zig zag flow pattern, which
tends to increase turbulence and also increase pressure drop across
the cold plate 10.
Pin Shape
[0038] The pins 40 have a shape, and the shape can affect the heat
transfer efficiency of the cold plate 10, as seen in FIGS. 6, 7,
and 8, with continuing reference to FIGS. 1-5. The pins 40 have a
pin bottom 42, which is where the pin 40 attaches to the island 36
of the base plate 34, and the pins 40 have a top 44 at the opposite
end of the pin 40 from the pin bottom 42. So, the top 44 is
generally the portion of the pin 40 closest to the lid 24. A pin
length 46 is measured from the pin bottom 42 to the pin top 44, and
a pin axis 48 runs down the center portion of the pin 40. The axis
48 runs through the center of the pin 40, so the axis 48 would be
at the center point of any cross section of the pin 40. The pin 40
also includes a side surface 50, which is the outer surface of the
pin 40 on the side, running from the bottom 42 to the top 44.
[0039] Each pin 40 has a cross sectional profile 52, where a cross
section is perpendicular to the axis 48. The cross sectional
profile 52 is the shape of the cross section. This cross sectional
profile 52 can be many different shapes, but in some embodiments it
is generally a quadrilateral. Each cross sectional profile 52 also
has a cross sectional orientation 54, which refers to the way the
cross section is facing. A quadrilateral, or any other shape, does
not have a clear, set front end, but any side or point along the
perimeter of the cross section can be selected as a point of
reference for the cross sectional orientation 54. The cross
sectional profile 52 can change along the pin length 46, so the
size or general shape is not necessarily fixed and constant for the
entire length 46 of the pin 40. The cross section also has a cross
sectional area 56, which is the area of the cross section. The
cross sectional area 56 can also vary along the length 46 of the
pin 40, so the pin 40 can get fatter or skinnier at different
points along the pin length 46.
[0040] The pins 40 of the current invention have some specific
structural aspects. In one embodiment, the pins 40 have a spiral
shape. The cross sectional orientation 54 changes along the pin
length 46, and the point of reference used for the cross sectional
orientation 54 tends to consistently move in the same direction
from the pin bottom 42 to the top 44. The cross sectional
orientation 54 may not change along the entire pin length 46, but
it does change along at least a portion of the pin length 46. This
gives a spiral appearance to at least a portion of the pin 40. In
other embodiments, the point of reference may move in one direction
for one portion of the pin 40, move another direction for a
different portion of the pin 40, and may possible not move for yet
a different portion of the pin 40. A polyhedral shape, such as a
quadrilateral, results in edges along the pin side surface 50. The
varying cross sectional orientation 54 along the pin length 46
results in the edges changing position along the pin length 46.
This variation in the edges can increase turbulence in fluids
flowing around the pin 40, and may therefore improve the efficiency
of the cold plate 10. The incline angle of the pin 40 can also be
manipulated by presetting an angle of a cutting tool used in the
formation of the pin 40, as discussed in greater detail below.
[0041] The pin 40 may also have a bend in some embodiments. The pin
40 is said to be bent when the axis 48 bends along the pin length
46. Because of possible changes in the cross sectional profile 52
of the pin along the pin length 46, it is possible for one side of
a pin 40 to appear relatively straight, and the other side to
appear bent, but the axis 48 of the pin 40 still bends along the
pin length 46. In some embodiments, the bent shape of the pin 40
appears similar to a banana, however the appearance of the pin 40
varies in different embodiments. In some embodiments, there is a
"fish hook" 59 present near the pin top 44, where the fish hook 59
is a more sharply bent portion of the pin 40; however in other
embodiments the fish hook shape is not present. The fish hook 59
looks somewhat like the stem of a banana. The bent shape of the pin
40 presents an obstacle with a varying shape for fluid to flow
around, which may increase turbulence in the cold plate 10. The
bent shape can direct fluid flow up and/or down to further vary the
fluid flow pattern, and thereby possibly increase turbulence. Fluid
flow directed downward toward the base plate 34 comes nearer to
what may be the hottest part of the cold plate 10. This increased
flow nearer to the pin bottom 42 may increase heat transfer. There
can be a larger temperature differential between the solid material
of the cold plate 10 near the pin bottom 42 and mixed coolant
flowing nearby, and an increased temperature differential can
increase the overall cold plate efficiency.
[0042] In other embodiments, the pin 40 can have at least two
different textures 58 on the side surface 50. At least one of these
textures 58 includes dimples 60, and can appear somewhat like an
orange peel. The dimples 60 are indentations extending into the pin
40 from the surface for at least some distance. The different
textures 58 can be on different faces of the quadrilateral or
polyhedral shape of the pin 40. In some embodiments, the side
surface 50 will include at least three different textures, and
there can be two different textures 58 along one face of the
polyhedral shape of the pin 40. The different surface textures 58
provide additional structure which can cause turbulence and help
increase heat transfer. The dimples 60 provide varying surface
structure which does tend to increase turbulence in fluid flowing
past the pin 10, and a change in texture may also cause
turbulence.
[0043] The pin 40 may also have a varying thickness along the pin
length 46 in some embodiments. There may be a taper to the pin 40
at the pin bottom 42, so the thickness of the pin 40 is decreasing
closer to the pin bottom 42. Stated more technically, the cross
sectional area 56 can increase with an increasing distance from the
pin bottom 42 for a least a portion of the pin 40. This is
consistent with the banana shape of the pin 40, because a banana
tends to taper near the end of the banana opposite the stem. This
can result in a pin 40 which is thicker near the middle or top 44
than at the pin bottom 42. Providing more room for fluid to flow
near the pin bottom 42 than higher up on the pin 40 urges fluid to
flow closer to pin bottom 42 and the base plate 34. The base plate
34 can be connected to the heat producing item to be cooled, so
increased fluid flow near the base plate 34 can increase heat
transfer efficiency. In other embodiments, the pin 40 does not
become thicker further from the bottom 42, so any taper is present
is a thinning of the pin 40 progressing from the bottom 42 to the
top 44.
[0044] In some embodiments, the pin 40 can be monolithic with the
base plate 34, which means there is no joint between the pin 40 and
base plate 34. This can be accomplished by forming the pin 40
directly from the base plate 34, instead of forming the pin 40
separately and then securing the pin 40 to the base plate 34 in
some manner. Having the pin 40 monolithic with the base plate 34
can increase heat transfer by reducing the resistance to heat flow
from the base plate 34 up the pin 40. As heat flows up the pin 40,
fluid flows past the pin 40, absorbs the heat from the pin 40, and
increases the overall heat transfer efficiency of the cold plate
10. The pins 40 provide additional surface area for heat transfer
from the base plate 34, and a low resistance to heat flow between
the base plate 34 and the pins 40 increases overall heat transfer
efficiency.
[0045] The pins 40 can include an aspect ratio of twenty to one in
some embodiments, where the pin length 46 is twenty times the
distance across the pin 40, or pin width 62. Heat transfer is
increased by increasing the aspect ratio, because a longer pin 40
with the same width 62 tends to have more surface area, and
increasing surface area tends to increase heat transfer
efficiency.
[0046] The various aspects of the pin shape described above can be
present in the pins 40 in isolation, or any combination. This
includes the quadrilateral cross section, the spiral shape, the
bent shape, the plurality of textures, the taper shape, the
monolithic connection to the base plate, the incline angle, and the
aspect ratio. Each pin 40 may include only one of these structures,
or any combination of the structures, depending on manufacturing
techniques and heat transfer properties desired, amongst other
factors.
Production Method of the Base Plate
[0047] The current invention also includes a method of producing
the cold plate 10, as seen in FIGS. 9-12, with continuing reference
to FIGS. 1-8. The cold plate 10 is constructed by preparing a base
plate 34, and attaching a lid 24 to the base plate 34. There can be
other structures included as well, such as separate side walls 26.
The lid 24 is attached to the base plate 34 such that there is an
enclosure 20 positioned between the lid 24 and base plate 34.
Standard production techniques can be used to produce the lid 24
and side walls 26. This includes stamping, cutting, casting, metal
injection molding, machining and other techniques. The lid 24 and
base plate 34 can also be joined by many standard techniques, such
as brazing, welding, soldering, gluing, and other connection
methods.
[0048] The production of the base plate 34 requires additional
steps. The pins 40 are produced by first slicing fins 70 into the
base plate 34, and then performing a second set of slices across
the fins 70. The second set of slices essentially cross cut the
fins, and this cross cutting produces the pins 40. One process used
to slice the base plate 34 is called micro deformation technology
(MDT), and it is described in U.S. Pat. No. 5,775,187, issued Jul.
7, 1998, which is hereby incorporated in full into this
description. In this process, a base plate 34 is sliced with a tool
72 without removing material from the base plate 34. The MDT
process is different than a saw or router, which removes material
as cuts are made, and is more similar to the cutting of meat with a
knife.
[0049] The slicing of the base plate 34 is done with the tool 72.
As the tool 72 contacts the material of the base plate 34, a fin 70
is cut from the main block of material. This forms a channel 74
between adjacent fins 70, and can be done without removing material
from the base plate 34. Preferably, there are no shavings produced
in the formation of the fins 70. The tool 72 cuts fins 70 in to the
base plate 34, and the space produced as the tool 72 passes through
the base plate 34 material deforms and forces material in the fins
70 upwards. This cutting and deformation of the base plate 34
material causes the fins 70 to rise to a fin height 76 which is
higher than the original base plate 34. The MDT cutting tool
design, the depth of cutting, the width of the fins 70 and the
channel 74 are factors which affect the fin height 76. This process
is repeated until a bed of fins 70 has been produced.
[0050] The pins 40 are made by slicing across the fins 70. The
second set of slices can also uses the MDT method, and raises the
pins 40 to a length 46 greater than the fin height 76. As the
slices are made, no material is removed from the base plate 34, so
the moved material is instead directed into the remaining pin 40 or
fin 70. This causes the remaining pin 40 or fin 70 raise to a
height higher than the material from which the pin 40 or fin 70 was
cut. The second set of slices can be made at an angle other than
ninety degrees to the fins 70, but it has been found that the pin
length 46 tends to vary when angles other than about ninety degrees
are used. A cold plate 10 can be made with varying pin lengths 46
if desired, or the pin lengths 46 can be kept more consistent by
making the second set of slices at about ninety degrees to the fins
70. In an alternate embodiment, the fins 70 are made without using
the MDT process, and the pins 40 are then formed from the fins 70
using the MDT process. In another alternate embodiment, the fins 70
are made using the MDT process, and the pins 40 are then formed
from the fins 70 using a conventional cutting process. This can
generate a non-spiral structure of pins 40.
[0051] The technique of cross slicing the base plate 34 to produce
the pins 40 contributes to the final shape of the pins 40. The
first slice makes a fin 70 with two flat sides, and the second
slice tends to make a pin 40 with two more flat sides, for a total
of four relatively flat sides. The four relatively flat sides
produce the quadrilateral cross sectional profile 52 for the pin
40. The quadrilateral cross sectional profile 52 provides edges
between different side surfaces 50 which tend to increase
turbulence in fluid flowing over those edges. Additionally, the
slicing of the pins 40 from the base plate 34 results in the pins
40 being monolithic with the base plate 34, which improves heat
transfer as discussed above. Additionally, the incline angle of the
pin 40 and/or the fin 70 can be manipulated by the angle of the
tool 72 as the slices are made. A modification of the incline angle
of the fin 70 can change the incline angle of the pin 40.
[0052] The cutting action of the tool 72 on the material of the
base plate 34 provides different textures to the material as it is
cut. The surface which is cut and pushed up to form a fin 70 or pin
40 takes the texture of the cutting surface of the tool 72, which
can be very smooth. The base plate surface on the opposite side of
the tool simply has material cut away from it, and this tends to
produce an orange peel texture 58, or a texture including a
plurality of dimples 60. This results in the two surfaces facing
each other across a channel 74 having different textures 58. The
original surface texture 58 of the base plate 34 before any slices
are made also remains on a portion of the pin 40. The original base
plate surface is cut and lifted up in the fin 70, and then it is
cut and lifted again in the second set of slices to form the pin
40. This surface texture 58 remains on a portion of the pin 40,
which can provide a third texture 58 on the pin. The different
textures 58 on the pin side surfaces 50 can increase turbulence by
providing changes in the fluid flow pattern. The dimples 60 in
particular tend to cause swirls, mixing, and turbulence more so
than a smooth surface.
[0053] Slicing the pins 40 from fins 70 provides the bent shape of
the pins 40, and can also provide the spiral shape of the pins 70.
The fins 40 are free standing, so the cutting action of the tool 72
tends to bend the pin 40 over as it is cut. The fin 70 is more
stable near the pin bottom 42, because this portion is attached to
the base plate 34. The higher portions of the fin 70 do not have
the support of the lower portions, and these higher portions tend
to be bent over as the pin 40 is cut and formed. The tool 72 is
only cutting on one side of the pin 40 as it is formed, so the
bending force is only applied to one side of the pin 40. Because
the bending force is only applied to one side of the pin 40, part
of the bending force can serve to twist the pin 40, resulting in a
spiral effect. The bent and spiral shaped pin 40 may increase
turbulent flow and urge flow closer to the base plate 34, which can
increase heat transfer efficiency as discussed above. One method
which can help keep the flow path of the cold plate 10 more fully
open is to slice the fins 70 in essentially a perpendicular
direction to the final flow line 32, and then make the secondary
slice to form the pins 40 essentially parallel to the flow line
32.
[0054] The taper and banana shape of the pin 40 can also result
from the slicing of the MDT method. As a cut is made, the newly
formed fin 70 or pin 40 is pushed upward to accommodate the
material moved by the cutting action. The material near the pin
bottom 42 is pushed up into the body of the pin 40, and can result
in a thicker central portion of the pin 40. This thicker central
portion provides the tapered shape of the pin bottom 42, and can
also provide an opposite tapered shape near the pin top 44. The
tool 72 can also catch the top portion of the fin 70 as it passes,
and more readily mold this thinner material such that the fish hook
59 is formed. The fish hook 59 can be eliminated by trimming off
the tip of the fin 70 prior to the second cutting process, if
desired, or the fish hook 59 can be left in place. This fin
trimming process also helps to control the final pin length 46.
[0055] The dual cross slicing to first form the fins 70, and then
to form the pins 40, pushed material into the pin 40. This
technique has been used to produce aspect ratios of twenty to one,
as described above. The slices with the tool 72 can be done using
known techniques with a wide variety of machines, including but not
limited to a milling machine, a shaper, or even a lathe. The
slicing of a base plate 34 can provide an efficient, relatively low
cost method of producing pins 40 for a cold plate 10.
Production Method of the Cold Plate
[0056] After an island 36 of pins 40 are formed, the base plate 34
can be prepared for assembly into a cold plate 10. The lid 24 is
attached to the base plate 34, perhaps through a side wall 26
piece, to form the enclosure 20. An inlet 28 and an outlet 30
penetrate into the enclosure 20 to provide access for a coolant or
other fluid. The inlet 28 and outlet 30 can be made before the base
plate 34 and lid 24 are assembled, or after. Nozzles 31 can be
attached to the inlet 28 and/or outlet 30 to facilitate fluid flow,
and the shape of the inlet 28 and outlet 30 can vary. For example,
the inlet 28 and outlet 30 can be a round hole, a square hole, a
manifold covering the entire side of the cold plate 10, or any of a
wide variety of other shapes. The inlet 28 and outlet 30 can be
drilled, stamped, cut, or produced in a number of known
techniques.
[0057] To prepare the base plate 34 to receive the lid 24 or side
wail 26, an attachment area 38 is made. The attachment area 38 can
be made in several different ways. In one embodiment, the entire
upper surface of the base plate 34 is formed into pins 40, and the
side surface of the base plate 34 is used as an attachment area 38.
In an alternate embodiment, the attachment area 38 is formed on the
outer edges of the upper surface of the base plate 34, with the
island 36 of pins 40 positioned inside of the attachment area 38.
In one embodiment, the attachment area 38 can be formed by
machining after the entire upper surface of the base plate 34 is
formed into pins 40. In an alternate embodiment, the attachment
area 38 is machined to a lower level than the island 36 prior to
forming the pins 40, and the slices of the tool 72 are set to pass
over the attachment area 38. In this way, the island 36 of pins 40
is formed inside the attachment area 38 without disrupting the
surface of the attachment area 38. A wide variety of other options
using known techniques can also be used to produce the attachment
area 38. The attachment area 38 can take many forms, depending on
the type of attachment to be made, as discussed above.
[0058] The alignment of the pins 40 in the cold plate 10 can vary,
including an aligned pattern or a staggered pattern. For a
rectangular cold plate 10, the aligned pattern can be made by
slicing the fins 70 and pins 40 in slices perpendicular to the edge
of a rectangular base plate 34. The cold plate 10 is then
constructed and with the inlet 28 and outlet 30 centered along one
edge of the base plate 34. The staggered pin pattern can be made
with the same base plate 34 as used for the aligned pattern, where
the corners of the base plate 34 are removed to produce new edges.
These new edges are no longer in line with the pins 40 sliced into
the base plate, and the cold plate 10 can be constructed as before.
In an alternative embodiment, the staggered pin pattern can be made
by slicing the fins 70 and pins 40 at an angle to the edge of the
base plate 34. The cross slices for the fins 70 and pins 40 can
still be at ninety degrees, but the resulting pin pattern is not in
rows parallel and perpendicular to the edges of the base plate 34.
Other methods and techniques can also be used to produce different
patterns of pins 40.
[0059] The back side 78 of the base plate 34, which is opposite the
pins 40, may need to be very flat to make a good thermal connection
with the electronic component 12 or other item to be cooled. It may
be desirable to take steps to flatten the base plate back side 78
before the cold plate 10 is used. This back side 78 can be
flattened in several ways, and it can be flattened before or after
the pins 40 are formed. In some embodiments, the back side 78 is
flattened after the pins 40 are formed to correct any warp or
bending which may have occurred as the pins 40 were formed. Known
techniques can be used to produce a flat back side 78 of the base
plate 34. In embodiments where the back side 78 of the base plate
34 is flattened after the pins 40 are formed, measures can be taken
to prevent damage to the pins 40. This can include a jig to suspend
the pins 40 while machining the back side 78 of the base plate 34,
and/or a vacuum system may be employed to hold the base plate 34
for subsequent flattening.
Dimensions, Use, and Example
[0060] The cold plate 10 can be used for many different purposes.
Different designs are better suited to different purposes. For
example, if the cold plate 10 is used in motor vehicle with engine
coolant fluid, the cold plate 10 should be designed to withstand
some particulates in the coolant. If the cold plate 10 is used in a
computer with a very clean, filtered coolant, particulate concerns
are not as important. The dimensions discussed below can be used
with a coolant having particulates up to one millimeter in
diameter.
[0061] In one embodiment of the cold plate 10, the enclosure 20 is
sized so the pins 40 essentially contact the lid 24. The pins 40
are approximately five millimeters high and approximately one
millimeter wide. The gap between neighboring pins 40 is
approximately one millimeter, and the total cold plate size is
approximately fifteen centimeters by fifteen centimeters.
[0062] The performance of three different cold plates 10 was
modeled with a computer simulation. In the model, the first cold
plate 10 include fins 70, the second cold plate 10 included pins 40
with an aligned pattern, and the third cold plate 10 included pins
40 with a staggered pattern. The pins 40 in the model include
spirals and bends as described in this description.
[0063] In each of the three computer models, the coolant was
ethylene glycol with a density of 1,027 kilograms per cubic meter
(kg/m.sup.3), a dynamic viscosity of 0.00169 Pascal seconds (Pa*s),
a specific heat of 3,300 joules/kilogram degree Kelvin (J/(kg*K)),
and a thermal conductivity of 0.388 watts per meter degree Kelvin
(W/(m*K)). The flow rate of the coolant through the cold plates 10
was five liters per minute (I/min), and the temperature of the
coolant at the inlet 28 was twenty degrees centigrade (C). The heat
source was three components generating one hundred sixty six watts
(w) each, where each component has an area of fifteen by twelve
millimeters (mm), for a total of approximately five hundred watts
(w). The coolant flowed sequentially past each heat source.
[0064] The specific structure of the cold plates 10 was used in the
computer model, and each cold plate 10 had the same length and
width. The first cold plate 10 with fins 70 had ten fins per inch,
with a fin thickness of one millimeter, a fin height of four point
seven millimeters, and a gap between neighboring fins 70 of one
millimeter. The second cold plate 10 with pins 40 in an aligned
pattern had ten pins per inch, a pin thickness of one millimeter, a
pin height of four point seven millimeters, and a gap between
neighboring pins 40 of one millimeter. The third cold plate 10 with
pins 40 in a staggered patter had ten pins per inch, a pin
thickness of one millimeter, a pin height of four point seven
millimeters, and a gap between neighboring pins 40 of one
millimeter.
[0065] The model calculated the steady state temperature of each
heat source. The coolant flowed past the three heat sources
sequentially, so each heat source increased the temperature of the
coolant as the coolant passed. Therefore, the first heat source,
which was closest to the inlet 28, was cooled by the coldest
coolant, and reached the coldest steady state temperature. The
third heat source was cooled by coolant that had been warmed by the
first two heat sources, so the third heat source reached the
hottest steady state temperature. The second heat source was
between the first and third heat sources, so the second heat source
reached a steady state temperature between that of the first and
third heat source. The steady state temperatures are listed in the
table below in degrees centigrade. The computer model also
calculated the pressure drop across each cold plate 10, and that
value is listed below in pounds per square inch.
TABLE-US-00001 First Heat Second Heat Third Heat Pressure Cold
Plate Number Source Source Source Drop First (fins) 40.9 43.2 43.5
1.53 Second (aligned pins) 35.3 37.8 38.9 1.85 Third (staggered
pins) 31.4 33.8 34.8 2.21
[0066] This model shows the use of pins 40 can increase heat
transfer efficiency over the use of fins 70. Developing a better
pin 40 may increase the heat transfer efficiency even more.
[0067] While the invention has been described with respect to a
limited number of embodiments, those skilled in the art, having the
benefit of this disclosure, will appreciate that other embodiments
can be devised which do not depart from the scope of the invention
as disclosed here.
* * * * *