U.S. patent application number 14/806018 was filed with the patent office on 2017-01-26 for layered heat pipe structure for cooling electronic component.
The applicant listed for this patent is CompuLab Ltd.. Invention is credited to Irad STAVI, Gideon (Genady) Yampolsky.
Application Number | 20170023306 14/806018 |
Document ID | / |
Family ID | 57833958 |
Filed Date | 2017-01-26 |
United States Patent
Application |
20170023306 |
Kind Code |
A1 |
STAVI; Irad ; et
al. |
January 26, 2017 |
LAYERED HEAT PIPE STRUCTURE FOR COOLING ELECTRONIC COMPONENT
Abstract
A structure for transferring heat from a heat producing element
to a heat sink includes a first layer including a first flat heat
pipe array of a substantially parallel and adjacent heat pipes for
conveying heat substantially along a first array axis and
configured to be thermally coupled to the heat producing element. A
second layer includes a second flat heat pipe array of
substantially parallel and adjacent heat pipes for conveying heat
substantially along a second array axis. The first flat heat pipe
array and the second flat heat pipe array partially overlap and are
in thermal contact. The first array axis and the second array axis
form a nonzero angle, so that the second flat heat pipe array
extends beyond the first flat heat pipe array. The second flat heat
pipe array is configured to be thermally coupled to the heat
sink.
Inventors: |
STAVI; Irad; (Yoqneam Illit,
IL) ; Yampolsky; Gideon (Genady); (Haifa,
IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CompuLab Ltd. |
Yoqneam Illit |
|
IL |
|
|
Family ID: |
57833958 |
Appl. No.: |
14/806018 |
Filed: |
July 22, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F28D 15/0233 20130101;
F28D 15/0275 20130101; F28D 15/04 20130101; F28D 2015/0216
20130101; H01L 23/427 20130101 |
International
Class: |
F28D 15/02 20060101
F28D015/02; F28D 15/04 20060101 F28D015/04 |
Claims
1. A structure for transferring heat from a heat producing element
to a heat sink, the structure comprising: a first layer comprising
a first flat heat pipe array of a plurality of substantially
parallel and adjacent heat pipes for conveying heat substantially
along a first array axis and configured to be thermally coupled to
the heat producing element; and a second layer comprising a second
flat heat pipe array of a plurality of substantially parallel and
adjacent heat pipes for conveying heat substantially along a second
array axis, wherein the first flat heat pipe array and the second
flat heat pipe array partially overlap and are in thermal contact,
the first array axis and the second array axis forming a nonzero
angle, so that the second flat heat pipe array extends beyond the
first flat heat pipe array, the second flat heat pipe array
configured to be thermally coupled to the heat sink.
2. The structure of claim 1, wherein the second array axis is
substantially perpendicular to the first array axis.
3. The structure of claim 1, wherein thermal coupling between the
first flat heat pipe array and the heat producing element comprises
a heat conducting plate.
4. The structure of claim 1, wherein the first array axis is
configured to be substantially horizontal when the heat producing
element is in operation.
5. The structure of claim 1, configured such that the second array
axis is substantially vertical when the heat producing element is
in operation.
6. The structure of claim 1, wherein the first flat heat pipe array
comprises a central region that is configured to be thermally
coupled to the heat producing element, and wherein the second flat
heat pipe array overlaps an end region of the first flat heat pipe
array.
7. The structure of claim 6, wherein the second layer comprises two
flat heat pipe arrays, each of the two flat heat pipe arrays
overlapping and in thermal contact with a different end regions of
the first flat heat pipe array.
8. The structure of claim 1, wherein an interface at the thermal
contact between the second flat heat pipe array and the first flat
heat pipe array includes a thermal interface material.
9. The structure of claim 9, wherein the thermal interface material
comprises a thermal adhesive.
10. An assembly comprising: a heat producing element; a heat sink;
and a structure for transferring heat from the heat producing
element to the heat sink, the structure comprising: a first layer
comprising a first flat heat pipe array of a plurality of
substantially parallel and adjacent heat pipes for conveying heat
substantially along a first array axis from a first region of said
at least one first flat heat pipe array that is thermally coupled
to the heat producing element, to a second region of the first flat
heat pipe array; and a second layer comprising at least one second
flat heat pipe array of a plurality of substantially parallel and
adjacent heat pipes for conveying heat substantially along a second
array axis that forms a nonzero angle with the first array axis,
the second flat heat array overlapping and in thermal contact with
the second region of the first flat heat pipe array and thermally
coupled to the heat sink.
11. The assembly of claim 10, wherein the second array axis is
substantially perpendicular to the first array axis.
12. The assembly of claim 10, further comprising a heat conducting
plate, one face of which is in thermal contact with the heat
producing element, and another face of which is in thermal contact
with the first region the first flat heat pipe array.
13. The assembly of claim 12, wherein an interface of thermal
contact between the heat conducting plate and the heat producing
element comprises an uncured thermal interface material.
14. The assembly of claim 10, wherein the heat producing element is
held in a socket of a circuit board.
15. The assembly of claim 10, configured such that the first array
axis is substantially horizontal and the second array axis is
substantially vertical when the assembly is operating.
16. The assembly of claim 10, wherein the heat sink is configured
to be passively cooled.
17. The assembly of claim 16, wherein the heat sink comprises a
plurality of channels configured to produce an internal flow of air
when heat is conveyed from the heat producing element to the heat
sink and when the channels are substantially vertical.
18. The assembly of claim 10, wherein a length of said at least one
second flat heat pipe array is substantially equal to a length of
the heat sink.
19. The assembly of claim 10, wherein the first region of the first
flat heat pipe array comprises a central region of the first flat
heat pipe array, the second region of the first flat heat pipe
array comprises an end region of the first flat heat pipe
array.
20. The assembly of claim 19, wherein said at least one second flat
heat pipe array comprises two flat heat pipe arrays, each of the
two flat heat pipe arrays overlapping and in thermal contact with a
different end region of the first flat heat pipe array.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to cooling of electronic
components. More particularly, the present invention relates to a
layered heat pipe structure for cooling an electronic
component.
BACKGROUND OF THE INVENTION
[0002] Computer systems and other electronic systems and components
generate heat during their operation. However, the performance of
those systems and components is adversely affected by overheating.
Therefore, such systems include arrangements for generating
heat.
[0003] Heat removal may be either active or passive. Active cooling
may utilize forced convection, e.g., as provided by a fan, pump, or
blower. Such active cooling is often unsuitable for portable or
compact electronic systems. Passive cooling based on heat
conduction and natural convection and radiation (e.g., fins) is
often insufficient to transfer large heat loads away from
electronic components.
[0004] Heat pipes and vapor chambers may enable efficient and
effective passive heat transfer. Heat pipes and vapor chambers
utilize evaporation and condensation of a working fluid (e.g.,
water, acetone, alcohol, or another suitable fluid that is liquid
at the ambient temperature) that is sealed inside to transfer heat
from a source of heat to a cooler periphery. A heat source in the
form of a heat-producing element to be cooled, such as an
electronic component, may be thermally connected to part of (e.g.,
a part close to the center) of the heat pipe or vapor chamber. The
heat-producing element may heat the working fluid at the region of
the connection and vaporize the fluid. The process of evaporation
of the liquid absorbs heat. The vapor may migrate to a cooler
periphery of the heat pipe or vapor chamber. At the cooler
periphery, the vapor condenses back into liquid form, releasing
heat to the environment. The condensed liquid is then transferred
back to the location of the heat-producing component. For example,
the heat pipe or vapor chamber may enclose a wick or other
structure that conducts the condensed liquid by capillary action to
the heat-producing element. In some cases, the heat pipe or vapor
chamber may rely on gravity, an inertial (e.g., centripetal) force,
or another mechanism to conduct the condensed liquid to the
heat-producing element.
[0005] A heat pipe or vapor chamber may be considered to be a
passive device since no additional power, other than the heat that
is generated by component to be cooled, is typically required to
operate the device.
[0006] Heat pipes are configured to transfer heat along an axis of
the heat pipe primarily in a single dimension. (Heat transfer in
other directions may result from conduction by the casing of the
heat pipe, or external radiative and convective effects that are
unrelated to the primary heat transfer function of the heat pipe by
the internal processes of evaporation, migration, and
condensation.) Vapor chambers are planar devices that are
configured distribute heat in two dimensions. Thus, a vapor chamber
is typically more effective than a heat pipe in passively
dissipating heat.
SUMMARY OF THE INVENTION
[0007] There is thus provided, in accordance with an embodiment of
the present invention, a structure for transferring heat from a
heat producing element to a heat sink, the structure including: a
first layer including a first flat heat pipe array of a plurality
of substantially parallel and adjacent heat pipes for conveying
heat substantially along a first array axis and configured to be
thermally coupled to the heat producing element; and a second layer
including a second flat heat pipe array of a plurality of
substantially parallel and adjacent heat pipes for conveying heat
substantially along a second array axis, wherein the first flat
heat pipe array and the second flat heat pipe array partially
overlap and are in thermal contact, the first array axis and the
second array axis forming a nonzero angle, so that the second flat
heat pipe array extends beyond the first flat heat pipe array, the
second flat heat pipe array configured to be thermally coupled to
the heat sink.
[0008] Furthermore, in accordance with an embodiment of the present
invention, the second array axis is substantially perpendicular to
the first array axis.
[0009] Furthermore, in accordance with an embodiment of the present
invention, thermal coupling between the first flat heat pipe array
and the heat producing element includes a heat conducting
plate.
[0010] Furthermore, in accordance with an embodiment of the present
invention, the first array axis is configured to be substantially
horizontal when the heat producing element is in operation.
[0011] Furthermore, in accordance with an embodiment of the present
invention, the structure is configured such that the second array
axis is substantially vertical when the heat producing element is
in operation.
[0012] Furthermore, in accordance with an embodiment of the present
invention, the first flat heat pipe array includes a central region
that is configured to be thermally coupled to the heat producing
element, and wherein the second flat heat pipe array overlaps an
end region of the first flat heat pipe array.
[0013] Furthermore, in accordance with an embodiment of the present
invention, the second layer includes two flat heat pipe arrays,
each of the two flat heat pipe arrays overlapping and in thermal
contact with a different end regions of the first flat heat pipe
array.
[0014] Furthermore, in accordance with an embodiment of the present
invention, an interface at the thermal contact between the second
flat heat pipe array and the first flat heat pipe array includes a
thermal interface material.
[0015] Furthermore, in accordance with an embodiment of the present
invention, the thermal interface material includes a thermal
adhesive.
[0016] There is further provided, in accordance with an embodiment
of the present invention, an assembly including: a heat producing
element; a heat sink; and a structure for transferring heat from
the heat producing element to the heat sink, the structure
including: a first layer including a first flat heat pipe array of
a plurality of substantially parallel and adjacent heat pipes for
conveying heat substantially along a first array axis from a first
region of the at least one first flat heat pipe array that is
thermally coupled to the heat producing element, to a second region
of the first flat heat pipe array; and a second layer including at
least one second flat heat pipe array of a plurality of
substantially parallel and adjacent heat pipes for conveying heat
substantially along a second array axis that forms a nonzero angle
with the first array axis, the second flat heat array overlapping
and in thermal contact with the second region of the first flat
heat pipe array and thermally coupled to the heat sink.
[0017] Furthermore, in accordance with an embodiment of the present
invention, the second array axis is substantially perpendicular to
the first array axis.
[0018] Furthermore, in accordance with an embodiment of the present
invention, the assembly includes a heat conducting plate, one face
of which is in thermal contact with the heat producing element, and
another face of which is in thermal contact with the first region
the first flat heat pipe array.
[0019] Furthermore, in accordance with an embodiment of the present
invention, an interface of thermal contact between the heat
conducting plate and the heat producing element includes an uncured
thermal interface material.
[0020] Furthermore, in accordance with an embodiment of the present
invention, the heat producing element is held in a socket of a
circuit board.
[0021] Furthermore, in accordance with an embodiment of the present
invention, the assembly is configured such that the first array
axis is substantially horizontal and the second array axis is
substantially vertical when the assembly is operating.
[0022] Furthermore, in accordance with an embodiment of the present
invention, the heat sink is configured to be passively cooled.
[0023] Furthermore, in accordance with an embodiment of the present
invention, the heat sink includes a plurality of channels
configured to produce an internal flow of air when heat is conveyed
from the heat producing element to the heat sink and when the
channels are substantially vertical.
[0024] Furthermore, in accordance with an embodiment of the present
invention, a length of the at least one second flat heat pipe array
is substantially equal to a length of the heat sink.
[0025] Furthermore, in accordance with an embodiment of the present
invention, the first region of the first flat heat pipe array
includes a central region of the first flat heat pipe array, the
second region of the first flat heat pipe array includes an end
region of the first flat heat pipe array.
[0026] Furthermore, in accordance with an embodiment of the present
invention, the at least one second flat heat pipe array includes
two flat heat pipe arrays, each of the two flat heat pipe arrays
overlapping and in thermal contact with a different end region of
the first flat heat pipe array.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] In order for the present invention, to be better understood
and for its practical applications to be appreciated, the following
Figures are provided and referenced hereafter. It should be noted
that the Figures are given as examples only and in no way limit the
scope of the invention. Like components are denoted by like
reference numerals.
[0028] FIG. 1 schematically illustrates components of an assembly
in which an electronic component is passively cooled by a layered
heat pipe structure, in accordance with an embodiment of the
present invention.
[0029] FIG. 2A schematically illustrates the assembly whose
components are shown in FIG. 1.
[0030] FIG. 2B shows a schematic rotated view of the assembly shown
in FIG. 2A.
[0031] FIG. 2C shows a schematic lateral cross section of the
assembly shown in FIG. 2A.
DETAILED DESCRIPTION OF THE INVENTION
[0032] In the following detailed description, numerous specific
details are set forth in order to provide a thorough understanding
of the invention. However, it will be understood by those of
ordinary skill in the art that the invention may be practiced
without these specific details. In other instances, well-known
methods, procedures, components, modules, units and/or circuits
have not been described in detail so as not to obscure the
invention.
[0033] Although embodiments of the invention are not limited in
this regard, discussions utilizing terms such as, for example,
"processing," "computing," "calculating," "determining,"
"establishing", "analyzing", "checking", or the like, may refer to
operation(s) and/or process(es) of a computer, a computing
platform, a computing system, or other electronic computing device,
that manipulates and/or transforms data represented as physical
(e.g., electronic) quantities within the computer's registers
and/or memories into other data similarly represented as physical
quantities within the computer's registers and/or memories or other
information non-transitory storage medium (e.g., a memory) that may
store instructions to perform operations and/or processes. Although
embodiments of the invention are not limited in this regard, the
terms "plurality" and "a plurality" as used herein may include, for
example, "multiple" or "two or more". The terms "plurality" or "a
plurality" may be used throughout the specification to describe two
or more components, devices, elements, units, parameters, or the
like. Unless explicitly stated, the method embodiments described
herein are not constrained to a particular order or sequence.
Additionally, some of the described method embodiments or elements
thereof can occur or be performed simultaneously, at the same point
in time, or concurrently. Unless otherwise indicated, us of the
conjunction "or" as used herein is to be understood as inclusive
(any or all of the stated options).
[0034] In accordance with an embodiment of the present invention, a
layered heat pipe structure is configured to dissipate heat in two
dimensions. Each layer of the structure includes one or more flat
and substantially planar arrays of parallel and adjacent heat
pipes. A face of each heat pipe array in each layer (after the
first) of the layered heat pipe structure partially overlaps, and
is in thermal contact with, the face of at least one heat pipe
array of the previous layer. The layered heat pipe structure may be
utilized to dissipate heat that is generated by a heat producing
element. For example, the heat producing element may include an
electronic component, such as a central processing unit (CPU), a
graphics processing unit (GPU), or another element.
[0035] As used herein, a heat pipe is considered to be flat when
two opposite sides of the heat pipe are substantially flat. The
other sides of the heat pipe (e.g., that connect the opposite
faces) are herein referred to as edges or ends of the heat pipe. A
heat pipe array may be considered to be flat when the heat pipes of
the array are flat heat pipes, when the heat pipes of the array are
arranged substantially in a single plane and the heat pipes are all
similarly oriented. Thus, the flat heat pipe array includes two
substantially flat opposite sides, herein referred to as faces or
surfaces of the heat pipe array. The faces or surfaces are
connected to one another at their perimeters by edges or ends of
the heat pipe array. (The faces of the array may include externally
visible grooves along each edge of separation between adjacent heat
pipes of the array.)
[0036] As used herein, an axis of an array of parallel heat pipes
refers to the direction of primary heat transfer along the length
of each of the heat pipes. Primary heat transfer, as used herein,
refers to heat transfer by the mechanism that is characteristic of
heat pipes, and includes evaporation of an internally sealed
working fluid in one region, internal migration of the vapor to a
region of condensation, and internal migration of the condensed
fluid back to the region of evaporation. Any heat transfer in a
heat pipe array in a direction other than that of the axis may be
assumed to be due to secondary or parasitic heat transfer modes
(e.g., heat conduction along the casing or shell of the heat pipe
array, radiative or convective transfer across grooves in the
array, or other secondary effects). The length of the array refers
to the size of a face of the array in direction that is parallel to
the array axis. The width of the array refers to the size of the
face of the array in the direction that is perpendicular to that of
the axis. The thickness of the array refers to the perpendicular
distance between the faces of the array.
[0037] When the layered heat pipe structure is installed, a region
of one face of a flat heat pipe array of a first layer of the
structure is thermally coupled to the heat producing element.
[0038] As used herein, thermal contact or a thermal connection
between surfaces of two bodies refers to a direct connection or
bond between adjacent bodies that enables conductive heat transfer
from one of the bodies to the other. The thermal contact may
include an intermediary medium in the form of a thermal interface
material (TIM) that fills an interface between the surfaces of the
bodies. A used herein, thermal coupling between two bodies or
surfaces refers may include one or more additional thermally
conductive bodies (such as a copper plate) that intervene between
the surfaces of the thermally coupled bodies.
[0039] Typically, the area of the heat pipe array is larger than
the area of the heat producing element. In such a case, the heat
producing element may be thermally connected to one face of a heat
conducting plate. The opposite face of the heat conducting plate
may be thermally connected to a region of a face of a heat pipe
array of the first layer. For example, the heat conducting plate
may be made of a heat conducting metal or other material, e.g.,
copper or another heat conductive material. The width of the face
of the heat conduction plate may be similar to the width of the
heat pipe array. Thus, the heat that is produced by the heat
producing element may be laterally distributed across the width of
the heat pipe array. Such lateral distribution of the produced heat
may increase the effectiveness of the first layer in longitudinally
conducting the produced heat away from the heat producing element.
For example, the effectiveness may be increased by increasing the
number of heat pipes of the array over which the produced heat is
distributed. The heat conducting plate may be incorporated into,
e.g., may be permanently bonded to and may be provided together
with, the layered heat pipe structure.
[0040] A face of each flat heat pipe array of the second layer of
the layered heat pipe structure is thermally connected to a face of
at least one flat heat pipe array of the first layer. The thermal
connection between the first and second layer is such that the face
of the second layer partially overlaps the face of the first layer.
For example, the second layer may be thermally connected to a
region of a face of the first layer that is opposite the region of
the face of the first layer that is thermally coupled to the heat
producing element. Alternatively or in addition, the second layer
may be thermally connected to a longitudinal end region of a face
of the first layer that extends laterally beyond the region of
thermal contact with the heat producing element (e.g., with a
conducting plate that is thermally connected to the heat producing
element).
[0041] The axes of the heat pipe arrays of each layer (subsequent
to the first layer) are arranged at a nonzero angle (e.g., right
angle or oblique angle) to the axes of the heat pipe arrays of the
previous layer. The nonzero angle is sufficient to enable at least
an end region of some or all of the heat pipes of the subsequent
(e.g., second) layer to extend laterally beyond the width of the
previous (e.g., first) layer. Thus, the subsequent layer may act to
increase the area over which the heat is dissipated. For example,
the nonzero angle may be greater than 45.degree.. The area of the
region of dissipation of the heat may be further increased or
maximized if the axis of the heat pipe arrays of the subsequent
layer is substantially perpendicular to the axes of the heat pipe
arrays of the previous layer (the nonzero angle being approximately
90.degree.).
[0042] Typically, heat pipe arrays of a single layer of the layered
heat pipe structure are arranged substantially parallel to one
another. Thus, each layer may be characterized by a single axis. In
some cases, different heat pipe arrays of a layer may be oriented
nonparallel to one another.
[0043] The layered heat pipe structure may be thermally coupled to
a heat sink. For example, a last (e.g., second) layer of the
layered heat pipe structure may be thermally coupled to the heat
sink. The heat sink may be actively cooled by forced convection or
otherwise, or may be passively cooled. For example, the heat sink
may include an array of fins, vertical chimneys, or other structure
that promotes heat dissipation by radiation or natural (e.g.,
guided natural) convection.
[0044] An interface of thermal contact between surfaces of layers
of heat pipe arrays (or of other components) of the layered heat
pipe structure, or between the layered heat pipe structure and the
heat producing element, the conducting plate, or the heat sink, may
include a thermally conductive thermal interface material to reduce
thermal resistance at the interface. The thermal interface material
is heat conductive, thus facilitating conduction of heat from one
surface at the interface to the other.
[0045] The thermal interface material is configured to adhere to
the surfaces at the thermal connection and to enable contiguous
thermal connection (e.g., without holes or spaces) between the two
surfaces. For example, the thermal interface material may include a
thermal grease, paste, adhesive, epoxy, pad, sheet, or other type
or form of thermal material. Where the thermal bond is intended to
be permanent, e.g., between layers of the layered heat pipe
structure, the thermal bond may include a curable thermal interface
material adhesive that permanently bonds to the two surfaces. In
other places, the thermal connection may be anticipated to be
broken at times. Under some circumstances, thermally connected
surfaces may be expected to be separated from one another at some
point after the thermal connection is made. Typically, surfaces may
be separated from one another to enable access to a component for
servicing. For example, the layered heat pipe structure may be
removed from the heat producing element (e.g., a CPU, GPU, or other
integrated circuit device) in order to enable access to the heat
producing element for servicing. In this case, the thermal
connection is expected to be non-permanent. The thermal connection
may include a thermal interface material in the form of non-curable
thermal grease or a similar material that remains in the form of a
gel and enables future separation of the bonded surfaces.
[0046] By using a layered heat pipe structure for heat dissipation,
the heat that is generated by the heat producing element may be
dissipated two-dimensionally. Heat from the heat producing element
that is dissipated by the heat pipe array of the first layer at the
(longitudinal) end regions of the first layer may be dissipated
laterally by the heat pipe array of the second layer.
[0047] The layered heat pipe structure may thus convey heat
two-dimensionally, similarly to performance of a two-dimensional
vapor chamber. However, production of a typical vapor chamber may
be expensive, requiring custom design and production in accordance
with a required size for a particular use or purpose. For example,
production of such a vapor chamber may require manufacture of a top
and bottom plate to size, enclosure of an area of wick material and
a quantity of working fluid between the top and bottom plates, and
closing the plates onto one another while sealing the edges (e.g.,
by soldering or welding).
[0048] On the other hand, a layered heat pipe structure in
accordance with an embodiment of the present invention may be made
relatively inexpensively. Since the structure of a heat pipe array
has one-dimensional longitudinal symmetry, the heat pipe array may
be manufactured by extrusion. The extruded piece includes a
contiguous outer shell that forms the top and bottom and lateral
sides of the array. The contiguous outer shell is impermeable to
the working fluid of the heat pipe array.
[0049] The interior structure of the extruded piece may include
longitudinal barriers at the edges that separate adjacent heat
pipes of the heat pipe array. For example, the edges may be in the
form of longitudinal crimps (e.g., externally visible as
longitudinal grooves). The edges may prevent or inhibit migration
of the working fluid of the heat pipe in a direction that
excessively deviates from the axis of the heat pipe array.
[0050] The interior structure may include a longitudinal
microstructure of ridges, wall, and channels of such size as to
longitudinally conduct the working fluid within the heat pipe array
by capillary action. (As used herein, a microstructure is to be
understood as referring to a structure that is much smaller than
the overall dimensions of the heat pipe array, and not as implying
a particular length scale of the structure.)
[0051] The extruded piece may be cut to length, and its ends sealed
(e.g., by crimping, or by a combination of crimping, soldering,
welding, application of a sealant material, by another method, or
by a combination of methods). Prior to sealing the ends, an
appropriate quantity of the working fluid may be injected or
otherwise introduced into each heat pipe of the heat pipe
array.
[0052] FIG. 1 schematically illustrates components of an assembly
in which an electronic component is passively cooled by a layered
heat pipe structure, in accordance with an embodiment of the
present invention.
[0053] FIG. 2A schematically illustrates the assembly whose
components are shown in FIG. 1. FIG. 2B shows a schematic rotated
view of the assembly shown in FIG. 2A. FIG. 2C shows a schematic
lateral cross section of the assembly shown in FIG. 2A.
[0054] In passively cooled electronic component assembly 10, heat
producing element 12 is passively cooled by layered heat pipe
structure 20. For example, passively cooled electronic component
assembly 10 may represent part of a portable or miniaturized
computer or similar electronic device. Passively cooled electronic
component assembly 10 may be configured to dissipate heat that is
produced by heat producing element 12 in order to ensure proper
operation of heat producing element 12 or another element of the
electronic device.
[0055] The vertical and horizontal orientation of components of
passively cooled electronic component assembly 10 as shown in FIG.
1 approximately corresponds to the orientation of the components
when the electronic device of which passively cooled electronic
component assembly 10 is part is in operation. Thus, a component
that is depicted with a vertical or horizontal orientation is
typically so oriented when the electronic device is in use.
[0056] Heat producing element 12 may represent a CPU, GPU, or
another electronic component that produces heat that is to be
dissipated by layered heat pipe structure 20. Heat producing
element 12 may be mounted in an element socket 14 on a circuit
board 16. Circuit board 16 may be mounted in a case or housing of a
computer or other device. Typically, circuit board 16 may include
additional electronic components and connectors. For example,
circuit board 16 may represent a motherboard of a computing device
or processor.
[0057] Layered heat pipe structure 20 includes at least two layers
of heat pipe arrays. As shown, layered heat pipe structure 20
includes two layers, first layer 20a and second layer 20b. First
layer 20a includes a single first flat heat pipe array 22, and
second layer 20b includes two second flat heat pipe arrays 26.
First array axis 24 is approximately perpendicular to second array
axes 28.
[0058] A layered heat pipe structure may include more than two
layers. Each layer may include one, two, or more heat pipe arrays.
The axes of all heat pipe arrays in a single layer may be parallel
to one another (as are second array axes 28), or may be somewhat
nonparallel (e.g., with a nonzero angle that may be limited by
space constraints). The axes of the heat pipe arrays in adjacent
layers may be perpendicular to one another, or may be oriented at
an oblique angle relative to one another.
[0059] Heat conducting plate 18 may be reversibly thermally
connected to heat producing element 12. For example, front
projecting face 18a of heat conducting plate 18 may be configured
to thermally connect to heat producing element 12. A size and shape
of front projecting face 18a may approximately match a size and
shape of heat producing element 12 (or of a family of similarly
shaped and size heat producing elements 12). An interface between
front projecting face 18a and heat producing element 12 may be
filled by an appropriate thermal interface material. Typically, the
thermal connection between heat producing element 12 and front
projecting face 18a may be non-permanent in order to enable future
access to heat producing element 12. For example, a thermal
interface material that is used to provide a conductive thermal
connection between heat producing element 12 and front projecting
face 18a may include a non-curable thermal grease, paste, pad, or
similar material.
[0060] Heat conducting plate 18 may be constructed of copper or of
another thermally conductive metal or material. The area of rear
face 18b of heat conducting plate 18 is larger than the area of
front projecting face 18a and of heat producing element 12. Thus,
heat conducting plate 18 may function to spread heat that is
produced by heat producing element 12 over an area that is larger
than that of heat producing element 12.
[0061] Rear face 18b of heat conducting plate 18 is thermally
connected to front face 23a of at central region 22b of first flat
heat pipe array 22 of first layer 20a. The thermal connection
between heat conducting plate 18 and front face 23a of first flat
heat pipe array 22 may be permanent, e.g., with a thermal interface
material that is curable or in the form of a thermal adhesive, or
non-permanent.
[0062] First flat heat pipe array 22 includes an array of parallel
oriented, adjacent flat heat pipes. For example, first flat heat
pipe array 22 may be produced by extrusion. The longitudinal
direction of heat transfer within the heat pipes of first flat heat
pipe array 22 is indicated by first array axis 24. For example,
first array axis 24 may be horizontal. Thus, first flat heat pipe
array 22 may convey heat from heat conducting plate 18 laterally
toward array end regions 22a.
[0063] One or both of array end regions 22a of first flat heat pipe
array 22 extend laterally beyond rear face 18b of heat conducting
plate 18. For example, if front face 23a of central region 22b of
first flat heat pipe array 22 overlaps and is thermally connected
to heat conducting plate 18, the heat may be laterally conveyed
toward array end regions 22a. Thus, heat that is produced by heat
producing element 12 may be transferred by first flat heat pipe
array 22 away from heat producing element 12 toward array end
regions 22a.
[0064] Rear face 23b of first flat heat pipe array 22 is thermally
connected to a front face 27a one or more second flat heat pipe
arrays 26 of second layer 20b. For example, a second flat heat pipe
array 26 may partially overlap and be thermally connected to rear
face 23b at each array end region 22a of first flat heat pipe array
22. As another example, a layer that includes a single second flat
heat pipe array may partially overlap and be thermally connected
across the lateral width of first flat heat pipe array 22.
[0065] Front face 27a of a region of second flat heat pipe array 26
that is thermally connected to first flat heat pipe array 22 is
substantially parallel to the surface of first flat heat pipe array
22.
[0066] The thermal connection between rear face 23b of first flat
heat pipe array 22 and front face 27a of each second flat heat pipe
array 26 may be permanent, e.g., with a thermal interface material
that is curable or in the form of a thermal adhesive, or
non-permanent.
[0067] The longitudinal direction of heat transfer within the heat
pipes of second flat heat pipe array 26 is indicated by second
array axis 28. For example, second array axis 28 may be vertical.
Thus, first flat heat pipe array 22 may convey heat from first flat
heat pipe array 22 vertically along second array axis 28 of second
flat heat pipe array 26.
[0068] In the example shown, first flat heat pipe array 22 is
thermally connected to the lower part of second flat heat pipe
array 26. Thus, most of second flat heat pipe array 26 extends
above first flat heat pipe array 22. In some cases, first flat heat
pipe array 22 may be thermally connected to the central part of
second flat heat pipe array 26 such that second flat heat pipe
array 26 extends symmetrically above and below first flat heat pipe
array 22. In some cases, first flat heat pipe array 22 may be
thermally connected to the upper part of second flat heat pipe
array 26 such that most of second flat heat pipe array 26 extends
below first flat heat pipe array 22.
[0069] Although, in the example shown, first array axis 24 is
horizontal and second array axis 28 is vertical, other arrangements
are possible. For example, first array axis 24 may be vertical
while second array axis 28 is horizontal, or one or both may be
slanted at an oblique angle to the vertical and horizontal.
[0070] Rear face 27b of second flat heat pipe array 26 may be
thermally coupled to heat sink 30. For example, rear face 27b of
second flat heat pipe array 26 may be thermally connected to heat
sink 30. The thermal connection between rear face 27b of second
flat heat pipe array 26 and heat sink 30 may be permanent, e.g.,
with a thermal interface material that is curable or in the form of
a thermal adhesive, or may be non-permanent.
[0071] As another example, the thermal coupling may include one or
more intervening structures that are placed between rear face 27b
of second flat heat pipe array 26 and heat sink 30. For example,
one or more conducting plates or additional layers of flat heat
pipe arrays may be placed between second flat heat pipe array 26
and heat sink 30.
[0072] The length of second flat heat pipe array 26 may be selected
to be substantially equal or matched to the length of heat sink 30.
Thus, heat that is conducted along the length of second flat heat
pipe array 26 may be distributed along the length of heat sink 30.
The distribution of heat along the length of heat sink 30 may
facilitate efficient heat dispersion to the ambient atmosphere. The
width of second flat heat pipe array 26 may be selected so as to
approximately match the width of array end region 22a. For example,
in some cases, a layer of second flat heat pipe arrays 26 may cover
a large fraction (e.g., over 50%, in some cases about 70%, or
another fraction) of the surface area of heat sink 30.
[0073] Heat sink 30 may include one or more structures or features
to facilitate convective or radiative dispersion of heat. As shown,
heat sink 30 is passively cooled.
[0074] Alternatively or in addition, a heat sink may be actively
cooled. For example, a fan or blower may be provided to force air
flow through the heat sink, around the heat sink, or both. A liquid
may be circulated through the heat sink and through an external
heat exchanger to remove heat from the heat sink. Heat may be
removed from the heat sink by a circulating refrigerant that cools
the heat sink by evaporative cooling. The heat sink may include
thermoelectric devices that operate to remove heat from the heat
sink. Other active heat removal mechanisms may be used.
[0075] For example, heat sink 30 may include channels 34. Channels
34 may serve to increase the effective area of interface between
heat sink 30 and the ambient atmosphere. In addition, channels 34
may be shaped to promote internal air flow when oriented vertically
as shown. The internal air flow through channels 34 may be induced
and maintained by a chimney effect. For example, air that is heated
within channel 34 may rise to the top of channel 34. The rising may
draw cool air into the bottom of channel 34, which also rises when
heated, thus sustaining the chimney effect air flow. The induced
air flow may further facilitate convective heat transfer to the
surrounding ambient atmosphere.
[0076] Heat sink 30 may include fin structure 32. Fin structure 32
may increase the effective surface area of heat sink 30, thus
facilitating convective heat transfer to the ambient atmosphere.
Surfaces of fin structure 32 may be configured to facilitate
radiative heat transfer to the surroundings. For example, surfaces
of fin structure 32 may be prepared (e.g., painted or coated) to
have a high emissivity. The combination of high emissivity and
increased surface area may promote radiative heat dissipation.
[0077] In some cases, layered heat pipe structure 20 may be
produced as a single unit of permanently connected layers (e.g.,
first layer 20a including first flat heat pipe array 22, and second
layer 20b including second flat heat pipe arrays 22). The single
unit may be thermally connected at a later time (e.g., during
assembly of passively cooled electronic component assembly 10)
directly to a heat producing element 12 or may be thermally coupled
to heat producing element 12 via heat conducting plate 18.
Similarly, the single unit may be thermally coupled at a later time
(e.g., during assembly of passively cooled electronic component
assembly 10) to heat sink 30. In some cases, layered heat pipe
structure 20 may be produced in a unit that includes a permanently
attached heat conducting plate 18, a permanently attached heat sink
30, or both (e.g., passively cooled electronic component assembly
10 produced as a unit).
[0078] Passively cooled electronic component assembly 10 may be
incorporated into a computer or similar device. Typically,
passively cooled electronic component assembly 10 may be
incorporated into a portable or miniaturized device where active
(e.g., forced air) cooling is precluded or undesirable, or
represents a less attractive option.
[0079] For example, where noiselessness is advantageous, passive
cooling may be preferred over possibly noisy operation of a
motorized fan, blower, or pump for active cooling. In a device that
is designed for portability, passive cooling may enable weight
reduction by reducing electrical power requirements (e.g., enabling
reduction of the size of a power supply or storage battery). Where
miniaturization is advantageous, elimination of fans may enable
reducing the size of a case or housing if the device.
[0080] When passively cooled electronic component assembly 10 is in
operation, heat producing element 12 produces heat as a byproduct
of its operation. For example, heat producing element 12 may
include a CPU, GPU, or other electronic or other heat producing
component of a computing device. Heat producing element 12 is
typically held in an element socket 14 on a circuit board 16.
[0081] Heat that is generated by heat producing element 12 is
conducted to front projecting face 18a of heat conducting plate 18.
For example, a thermal interface material may fill an interface at
a thermal connection between heat producing element 12 and front
projecting face 18a. Typically, the thermal interface material
forms a nonpermanent connection between heat producing element 12
and front projecting face 18a. For example, the thermal interface
material may include an uncured thermal grease or paste. The
nonpermanent connection may enable access to heat producing element
12. For example, accessing heat producing element 12 may enable
removal of heat producing element 12 from element socket 14 on
circuit board 16, e.g., for testing or for replacement with a
different heat producing element 12.
[0082] Heat conduction within heat conducting plate 18 (e.g., made
of copper) may conduct the generated heat to rear face 18b of heat
conducting plate 18. Rear face 18b is overlapped by and thermally
connected to front face 23a at a central region 22b of first flat
heat pipe array 22 of first layer 20a of layered heat pipe
structure 20. For example, a thermal interface material may fill an
interface between heat conducting plate 18 and front face 23a at a
central region 22b of first flat heat pipe array 22. The thermal
interface material may be an uncured material to form a
nonpermanent connection, or the thermal interface material may be a
cured thermal adhesive that permanently attaches heat conducting
plate 18 to first flat heat pipe array 22.
[0083] First flat heat pipe array 22 is configured to transfer heat
laterally in a direction parallel to first array axis 24. In
passively cooled electronic component assembly 10, first flat heat
pipe array 22 conveys heat horizontally from heat conducting plate
18. Thus, generated heat may be transferred from central region 22b
of first flat heat pipe array 22 to array end regions 22a that
laterally extend beyond rear face 18b of heat conducting plate
18.
[0084] Rear face 23b of each array end region 22a of first flat
heat pipe array 22 is overlapped by and thermally connected to
front face 27a of a second flat heat pipe array 26 of second layer
20b of layered heat pipe structure 20. In some cases, the second
layer of layered heat pipe structure 20 may include a single second
flat heat pipe array that is wide enough to overlap both array end
regions 22a of first flat heat pipe array 22. For example, a
thermal interface material may fill an interface between rear face
23b of first flat heat pipe array 22 and front face 27a of each
second flat heat pipe array 26. The thermal interface material may
be a cured thermal adhesive that permanently attaches rear face 23b
of first flat heat pipe array 22 to front face 27a of second flat
heat pipe array 26.
[0085] Thus, first flat heat pipe array 22 may distribute heat
along the width of each second flat heat pipe array 26. Each second
flat heat pipe array 26 conveys heat in a direction that is
parallel to second array axis 28, and, as shown, perpendicularly to
the direction of heat distribution (first array axis 24) in first
flat heat pipe array 22. As shown, in passively cooled electronic
component assembly 10 second array axis 28 is configured to convey
heat vertically above and below first flat heat pipe array 22.
[0086] In some cases (e.g., if constrained by other design
considerations), the direction of conveyance of heat by the second
flat heat pipe array may be at an oblique (non-perpendicular) angle
to the direction of conveyance of heat by the first flat heat pipe
array.
[0087] Rear face 27b of each second flat heat pipe array 26 of
second layer 20b of layered heat pipe structure 20 is thermally
connected to heat sink 30. For example, a thermal interface
material may fill an interface between rear face 27b of second flat
heat pipe array 26 and heat sink 30. The thermal interface material
may be an uncured material to form a nonpermanent connection, or
the thermal interface material may be a cured thermal adhesive that
permanently attaches second flat heat pipe array 26 to heat sink
30.
[0088] Heat sink 30 is configured to passively or actively transfer
heat to the ambient atmosphere or to another cooler body. The area
of second flat heat pipe arrays 26 may be matched to the area of
heat sink 30 such that the area of second flat heat pipe arrays 26
is approximately equal to, or covers most of, the area of heat sink
30. Thus, the second layer of layered heat pipe structure 20 may
distribute heat from heat producing element 12 over all or most of
heat sink 30. The distribution of heat over heat sink 30 may enable
efficient transfer of heat from heat producing element 12 to the
ambient atmosphere.
[0089] In some cases, each second flat heat pipe array 26 may be
separately thermally connected or coupled to a separate heat
sink.
[0090] In passively cooled electronic component assembly 10, heat
sink 30 is a passively cooled structure. Heat sink 30 includes an
array of channels 34 that are vertically oriented. Each channel 34,
when a wall of that channel 34 is heated, is designed to generate a
chimney-effect flow of air through that channel 34. Each second
flat heat pipe array 26 may distribute heat vertically along heat
sink 30. Thus, each second flat heat pipe array 26 may distribute
heat along a wall of each channel 34. In this manner, heat may be
distributed along the length of each channel 34. This distribution
of heat along a channel 34 may enable effective cooling by that
channel 34.
[0091] Heat sink 30 may include a fin structure 32 or other
structure to facilitate radiative or convective heat transfer to
the surroundings. Alternatively or in addition, a heat may include
other structures to facilitate passive heat transfer to the
surroundings.
[0092] Different embodiments are disclosed herein. Features of
certain embodiments may be combined with features of other
embodiments; thus certain embodiments may be combinations of
features of multiple embodiments. The foregoing description of the
embodiments of the invention has been presented for the purposes of
illustration and description. It is not intended to be exhaustive
or to limit the invention to the precise form disclosed. It should
be appreciated by persons skilled in the art that many
modifications, variations, substitutions, changes, and equivalents
are possible in light of the above teaching. It is, therefore, to
be understood that the appended claims are intended to cover all
such modifications and changes as fall within the true spirit of
the invention.
[0093] While certain features of the invention have been
illustrated and described herein, many modifications,
substitutions, changes, and equivalents will now occur to those of
ordinary skill in the art. It is, therefore, to be understood that
the appended claims are intended to cover all such modifications
and changes as fall within the true spirit of the invention.
* * * * *