U.S. patent application number 12/629822 was filed with the patent office on 2010-06-03 for partable thermal heat pipe.
Invention is credited to Donald Carson Lewis.
Application Number | 20100132925 12/629822 |
Document ID | / |
Family ID | 42221734 |
Filed Date | 2010-06-03 |
United States Patent
Application |
20100132925 |
Kind Code |
A1 |
Lewis; Donald Carson |
June 3, 2010 |
Partable Thermal Heat Pipe
Abstract
A heat pipe for conducting heat away from an electronic device
attached to a removable electronic module includes two
self-aligning sections. A source section is attached to the
removable electronic module and a target section passes through and
is retained by a fixed member. One end of the source section is in
thermal contact with a heat source and the other end includes a
self aligning female thermal interface. One end of the target
section includes a self aligning male thermal interface and the
other end includes a heat sink. The female end of the source
section and the male end of the target section are moved into
contact with each other to form a thermal connection that permits
heat from the heat source to be transferred to the heat sink.
Inventors: |
Lewis; Donald Carson;
(Richmond, CA) |
Correspondence
Address: |
ROBERT SCHULER
45 GROTON ROAD
SHIRLEY
MA
01464
US
|
Family ID: |
42221734 |
Appl. No.: |
12/629822 |
Filed: |
December 2, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61200717 |
Dec 3, 2008 |
|
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Current U.S.
Class: |
165/104.26 |
Current CPC
Class: |
F28D 15/0275 20130101;
H01L 2924/0002 20130101; F28F 2013/008 20130101; H01L 23/427
20130101; H01L 2924/0002 20130101; H01L 2924/3011 20130101; F28F
2013/006 20130101; H01L 2924/00 20130101; F28D 15/0233
20130101 |
Class at
Publication: |
165/104.26 |
International
Class: |
F28D 15/02 20060101
F28D015/02 |
Claims
1. A self-aligning partable heat pipe comprising: a source section
attached to a removable electronic module, the distal end of the
source section in thermal contact with a heat source and the
proximal end of the source section forming a female interface
element; a target section passes through and is retained by both of
an aperture in a fixed member and an aperture in a carrier member
and is able to translate towards and away from an insertion
direction of the removable electronic module, and the target
section includes a thermal target and a proximal end of the target
section forms a male interface element; and the female interface
element of the source section and the male interface element of the
target section together comprise a partable, self-aligning
thermally conductive interface through which heat from the heat
source is transferred to the thermal target.
2. The thermally conductive interface of claim 1, wherein the
female interface element is comprised of a hollow wedge shaped
receptacle and the male interface element is comprised of a solid
wedge that fits inside the hollow wedge shaped receptacle of the
female interface element.
3. The female interface element of claim 2, wherein the hollow
wedge shaped receptacle is comprised of an inner cavity surface and
the sides are wedge shaped.
4. The male interface element of claim 2, wherein the wedge is a
two-sided wedge and the width of the wedge is smaller than the
opening in the female interface element.
5. The wedge shaped form of claim 4, wherein the sides of the wedge
are wedge-shaped.
6. The female interface element of claim 2, wherein the wedge is
conical.
7. The male interface element of claim 2, wherein the wedge is
conical.
8. The partable heat pipe of claim 1, wherein the removable
electronic module is a printer circuit board.
9. The partable heat pipe of claim 1, wherein the heat source is an
electronic device.
10. The partable heat pipe of claim 1, wherein the fixed member is
any one of a bulkhead, other chassis member, electrical backplane,
circuit board and second module.
11. The partable heat pipe of claim 1, wherein the carrier member
is fastened to the fixed member.
12. The partable heat pipe of claim 1, wherein the thermal target
is a thermal radiator.
13. The partable heat pipe of claim 1, wherein the target section
is spring loaded.
14. The hollow wedge shaped receptacle of claim 3, wherein the
inner cavity surface is coated with thermal grease.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to U.S. Patent Application
No. 61/200,717 filed Dec. 3, 2008, which application is
incorporated herein by references in its entirety.
BACKGROUND
[0002] 1. Field of the Invention
[0003] The present disclosure relates generally to thermal
management, and more particularly to devices and methods for
transferring heat from a removable module within a chassis.
[0004] 2. Description of Related Art
[0005] High-performance semiconductor devices sometimes produce
more waste heat than can be carried away from the device package by
thermal radiation, conduction, and/or convection across the device
package. Cooling problems may arise due to the power density of the
device relative to its cooled surface area, difficulty in providing
sufficient coolant flow across the device, and/or due to difficulty
in providing a sufficiently large temperature differential between
the device package and the coolant flowing across the device.
Coolant temperature problems may arise due to the ambient
temperature in which a system operates, and/or due to heating of
the coolant flow prior to the coolant reaching the device package.
Problematic device packages can be fitted with heat sinks and/or
secondary cooling fans to assist in removing waste heat.
[0006] In some systems, spacing and packaging constraints and or
local airflow/air temperature conditions prevent the successful
application of a heat sink and/or secondary cooling fan directly to
a semiconductor package. In such cases, a thermally conductive
"heat pipe" can be fitted to the device package and used to draw
heat away from the device package to a remote location. One end of
the heat pipe maintains thermal contact with the device package to
be cooled; the opposite end of the heat pipe is kept at a lower
temperature, e.g., by immersing the second end in a relatively cool
fluid stream. The temperature differential between the ends of the
heat pipe draws heat away from the device to be cooled.
[0007] One difficulty with heat pipes arises when a device to be
cooled by the heat pipe is built into a removable module, and the
cooling fluid stream used by the heat pipe is located outside the
module. In such cases, it may be difficult or even undesirable to
design the heat pipe in a way that allows extraction of the heat
pipe from the fluid stream and/or system when the module is removed
from the system.
[0008] FIG. 1 illustrates a prior art cooling apparatus 100 that
employs a "partable" thermal heat pipe that is useful, e.g., when
the hot end of a heat pipe is located in a removable part of the
system and the cool end of the heat pipe is fixed in the system. A
bulkhead 110 contains an aperture 112 through which a heat pipe
extends. The heat pipe is constructed in two sections 120 and 130.
Heat pipe section 120 has one end thermally coupled to a device to
be cooled 124, and its other end terminated in a thermal contact
plate 122. Heat pipe section 130 has one end terminated in a
thermal contact plate 132, and its other end fashioned as a thermal
radiator 134, e.g., located in a fluid stream 140. When the system
is assembled, thermal contact plates 122 and 132 have their facing
sides coated in thermal grease and held in contact with each other,
allowing heat transfer between the device 124 and the thermal
radiator 134. When the module containing device 124 is to be
removed from system 100, heat pipe section 120 is removed through
aperture 112, while heat pipe section 130 remains fixed in
place.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The present invention can be best understood by reading the
specification with reference to the following Figures, in
which:
[0010] FIG. 1 illustrates a prior art partable heat pipe in side
view;
[0011] FIGS. 2, 3, and 4 contain side views of a partable heat pipe
according to an embodiment at three stages of coupling;
[0012] FIGS. 5 and 6 contain perspective views of two partable heat
pipe embodiments;
[0013] FIGS. 7 and 8 contain, respectively, side and perspective
views of another partable heat pipe embodiment; and
[0014] FIGS. 9A and 9B show the FIG. 8 embodiment used in a circuit
board that accepts removable electro-optic modules.
DETAILED DESCRIPTION
[0015] It has now been discovered that prior art partable heat
pipes contain several disadvantageous design features. First, the
mating faces on the heat pipe section contact plates must be flat
and perfectly parallel in order to maintain effective thermal
contact between the two heat pipe sections. Slight misalignments
between the two contact plates may sharply curtail the contact area
and consequently the heat transfer capability of the heat pipe.
Second, the "fully inserted" position of a module containing heat
pipe section 120 is determined by the full contact position of the
contact plates. In a system that mates electrical connectors
through the same insertion sequence that causes contact between the
heat pipe contact plates, the full mating of the electrical
connectors can be critical to system operation. Thus electrical
connectors and heat pipe sections must be critically aligned on
both the module and the fixed portion of the system, or else at
least one of the electrical and thermal connections will suffer.
Third, the contact faces may require a large surface area to lower
the thermal impedance of an imperfect (or even perfect) contact
position, defeating miniaturization gains elsewhere in the system.
Finally, the thermal grease present on the face of the contact
plate 122 is subject to contact by a user when a module containing
heat pipe 120 is removed from system 100. Not only may the user
inadvertently spread thermal grease in places other than that
desired, causing annoyance to the user, but the user may
inadvertently or purposely remove the grease that is critical to
the thermal interface function.
[0016] The present disclosure includes low-profile, self-aligning
partable heat pipe embodiments that generally can be used to
overcome the deficiencies noted above. FIG. 2 contains a
cross-section of a first exemplary embodiment 200, prior to joining
the two partable heat pipe sections. A fixed member 210, such as a
bulkhead, other chassis member, electrical backplane, circuit
board, second module, etc., serves as a reference point for the
embodiment. A target heat pipe 230 is assembled in a carrier 220,
and the carrier 220 is fastened to fixed member 210, e.g., using
fasteners 212, 214. A source heat pipe 250 is fixed to a removable
module 240. The source heat pipe 250 removes heat from a source
device 242, e.g., through a contact section 258 in thermal contact
with source device 242 (thermal grease between source device 242
and contact section 258 may be used to improve heat transfer). The
target heat pipe 230 transfers the heat to a thermal target, e.g.,
a thermal radiator 234 located in a cooling fluid stream 202.
[0017] Heat transfer between the source heat pipe and the target
heat pipe occurs at a partable conical or wedge shaped interface.
Source heat pipe 250 includes a female interface element 252 in the
form of a hollow cone or wedge with a conical or wedge-shaped inner
cavity surface 260. Target heat pipe 230 includes a male interface
element 232 in the form of a solid cone or wedge having the same
release angle as the inner cavity surface 260. When the source and
target heat pipes are brought together (see FIG. 3), the male
interface element 232 fits against the inner cavity surface 260 of
the female interface element 252 and forms a thermal connection.
Thermal grease on the two surfaces (male and female interface
surfaces) assists in forming an effective thermal joint.
[0018] Several advantages accrue from the use of a cone or wedge
interface between the two heat pipes. Depending on the release
angle selected (angles between 0.5 degrees and 45 degrees are
preferred), the wedge interface can have a substantially lower
profile than the flat face interface of the prior art. When
combined with the articulation and spring-loading features
described below, the wedge interface is also substantially
self-aligning due to the complementary forces exerted by the cone
or wedge faces. Thermal expansion of the receptacle, if greater
than that of the wedge 232 due to higher temperature, merely causes
a repositioning of the wedge in the receptacle, but does not
decrease the contact area between the wedge and the receptacle or
cause the wedge to stick in the receptacle. Thermal grease can be
applied to both inner cavity surface 260 and wedge 232. The thermal
grease inside receptacle 252 is inaccessible to the user when
module 240 is removed from the system (at least for small cavity
openings).
[0019] Carrier 220 is positioned with respect to an aperture 216,
through which target heat pipe 230 passes, in fixed member 210.
Carrier positioning nominally aligns target heat pipe 230 with the
insertion direction 280 of module 240. A grommet or gasket 222
further positions heat pipe 230 within aperture 216, while
providing some environmental sealing between the two sides of fixed
member 210, if so desired. Grommet 222 allows target heat pipe 230
to translate along the insertion direction 280, and may also flex
to allow minor translation of heat pipe 230 perpendicular to the
insertion direction and/or to allow small angular variations in the
alignment of target heat pipe 230. Carrier 220 also holds target
heat pipe with a relatively loose tolerance that allows the
translation and angular variations in the positioning of target
heat pipe 230 with respect to fixed member 210.
[0020] Heat pipe 230 is spring-loaded to control the holding force
between the target heat pipe 230 and source heat pipe 250 over a
range of module 240 positions. In FIG. 2, a compression spring 224,
placed over a center section of target heat pipe 230, rests between
carrier 220 and a collar 236 (which may or may not be flexible) on
target heat pipe 230. Spring 224 compresses once wedge 232 is fully
inserted in receptacle 252 and further force is applied in the
insertion direction 280, such that the contact force remains
relatively constant (see FIG. 4, where spring 224 is compressed).
Spring-loading keeps an appropriate pressure between the heat pipe
sections, lowering alignment tolerances and providing headroom for
expansion of the two heat pipe sections with temperature.
[0021] FIGS. 2-4 show an insertion sequence that mates the source
and target heat pipes, and simultaneously mates a module electrical
connector 270 with a fixed electrical connector 272. FIG. 2 shows
module 240 separated from the remainder of system 200. In FIG. 3,
module 240 has been moved in insertion direction 280 until the
target heat pipe wedge is fully contacting inner wedge surface 260.
Electrical connectors 270 and 272 have begun to mate, but are not
yet fully connected and the spring 224 is not yet compressed. In
FIG. 4, electrical connectors 270 and 272 are fully mated, and
spring 224 has been compressed.
[0022] The inner cavity surface 260 and wedge 232 are designed with
a desired number of contact surfaces. FIGS. 5 and 6 show two
possible wedge designs in perspective view. FIG. 5 illustrates a
source heat pipe 520 with an integrated female receptacle (see the
illustrated cavity with inner surface 522), and a target heat pipe
530 with a wedge 532 on one end and a thermal radiator 534 on the
opposite end. Wedge 532 is conical, as is the contact surface 522
on the inside of source heat pipe 520.
[0023] FIG. 6 illustrates a source heat pipe 620 with an integrated
female receptacle (see the illustrated cavity with inner surface
622), and a target heat pipe 630 with a wedge 632 on one end and a
thermal radiator 634 on the opposite end. Wedge 632 forms a
traditional two-sided wedge, as does the contact surface 622 on the
inside of source heat pipe 530. The width of wedge 632 is
preferably somewhat smaller than the width of the opening in source
heat pipe 620, forming a natural lateral alignment tolerance.
Alternately, and particularly useful with larger release angles on
the top and bottom surfaces, the sides of the wedge and opening can
also be wedge-shaped and designed to contact when the source heat
pipe and target heat pipe are in full contact.
[0024] FIGS. 7 and 8 illustrate respectively in side and
perspective views, an alternate partable heat pipe embodiment 700.
The source heat pipe is a flattened metal member 710 with an
opening 712 in one end. The target heat pipe 720 includes a
flattened wedge 722 on one end, integral cooling fins along the
bulk of the heat pipe, and a spring/support cantilever section 724
on the end opposite the wedge 722. The free end of cantilever 724
can be fixed to a desired support. Opening 712 includes an enlarged
recess, with the wedge contact surface set back into the opening to
further contain the thermal grease.
[0025] One use for embodiment 700 is to provide cooling for a
compact form-factor electro-optic module that provides network
connectivity to a computer, router, switch, etc. Such modules
typically contain semiconductor lasers and drivers, receivers, and
interface electronics in a small module package. The module can
generate a substantial amount of waste heat, but the heat may be
difficult to remove due to interference from the cage that holds
the module and/or close proximity to similar modules that impede
airflow.
[0026] FIGS. 9A and 9B illustrate the use of a partable heat pipe
such as embodiment 700 to cool a compact form-factor electro-optic
module. FIG. 9A depicts an embodiment 900 consisting of pluggable
optic module 910 and an interface card 930. Different versions of
pluggable optic module 910 can support, in the same form factor,
different optical (or copper) physical interface standards or
wavelengths externally, and a common electrical interface to
interface card 930 internally. The top surface of module 910 is at
least partially formed from a source heat pipe 920. The internal
heat-generating components of module 910 preferably thermally
couple to the lower surface of heat pipe 920. The rear end of heat
pipe 920 contains an opening (not visible) of the type shown as
opening 712 in FIGS. 7 and 8.
[0027] Interface card 930 includes a substrate that is or includes
a printed circuit board. A module cage 932, fixed to the printed
circuit board, includes electrical connectors for providing
signal/power connectivity between module 910 and supporting
electronics on card 930. The module cage 932 also provides
mechanical features to engage and hold module 910 when the module
is inserted in the cage.
[0028] A target heat pipe 940 includes a heat transfer wedge 942,
coated in thermal grease, integral cooling fins, and a
spring/support 944. Spring support 944 fixes to card 930 at a
position behind cage 932, such that the heat transfer wedge is
cantilevered over the cage 932 in nominal alignment with the
inserted position of source heat pipe 920.
[0029] FIG. 9B shows an assembled view of embodiment 900. Heat from
the internal heat-generating components of module 910 is
transferred to source heat pipe 920, through the wedge interface
between source heat pipe 920 and target heat pipe 940, and then to
a cooling air stream through the cooling fins of the target heat
pipe 940. Spring/support 944 maintains positive thermal contact for
the wedge interface. If so desired, spring/support 944 can also
transfer a latch release force to module 910 through the source
heat pipe 920. When a module release trigger is activated,
spring/support 944 pushes the module to an unlatched position to
facilitate removal.
[0030] Those skilled in the art will appreciate that the
embodiments and/or various features of the embodiments can be
combined in other ways than those described. For instance, although
spring/support 944 is shown connected directly to a horizontal
circuit board, the support can alternately connect to a vertical
member or to an integral portion of the module cage. Various other
locations for a spring means are possible and comprehended as
within the scope of the disclosure. Other variations on the number
of wedge contact surfaces are possible. The release angles of each
surface need not be the same. The wedge need not come to a point.
The source heat pipe may also comprise cooling and/or heat capture
fins.
[0031] Although the specification may refer to "an", "one",
"another", or "some" embodiment(s) in several locations, this does
not necessarily mean that each such reference is to the same
embodiment(s), or that the feature only applies to a single
embodiment.
* * * * *