A BOARD-LEVEL HEAT TRANSFER APPARATUS FOR COMMUNICATION
PLATFORMS
TECHNICAL FIELD
The present invention is directed, in general, to a
cooling apparatus and methods for operating and
manufacturing the same .
BACKGROUND
This section introduces aspects that may be helpful
to facilitating a better understanding of the inventions.
Accordingly, the statements of this section are to be readin
this light and are not to be understood as admissions
about what is in the prior art or what is not in the prior
art .
Presently, cooling is known to make a substantial
contribution to the operating cost of electronic and/or
optical systems that are located in telecom central
offices. In addition, such central offices are typically
crowded so that the availability of space for devices and
cooling equipment is limited.
SUMMARY
One embodiment includes an apparatus, comprising a
rack and a cooler. The apparatus also comprises a
plurality of electronic circuit boards located in
corresponding slots of the rack, each of the electronic
circuit boards being held against a portion of the cooler
by a corresponding force, some of the electronic circuit
boards having a localized heat source thereon The
apparatus also comprises a plurality of heat spreaders,
each heat spreader configured to form a heat conducting
path over and adjacent to one of the electronic circuit
boards from one or more of the localized heat sources
thereon to the portion of the cooler. The apparatus also
comprises a plurality of compliant thermal interface pads,
each of the pads being compressed between end of one of
the heat spreaders and the portion of the cooler to form a
heat conduction path therebetween.
In some embodiments of the apparatus, one or more of
the compliant thermal interface pads has a thermal
conductivity of at least 1 W/m-K. In some embodiments, at
least one of the compliant thermal interface pads is an
elastic thermal interface pad. In some embodiments, a
thickness of the elastic thermal interface pad is
compressible by at least about 10 percent when subjected
to the force on the corresponding one of the boards and
the thickness returns substantially back to its precompression
value when the force on the corresponding one
of the boards is not applied to the elastic thermal
interface pad. In some embodiments, one or more of the
compliant thermal interface pads are configured to be
fixed to one or both of the heat spreader or the common
cooler. In some embodiments, one or more of the compliant
thermal interface pads have an electrically insulating
outer surface. In some embodiments, one or more of the
compliant thermal interface pads have a substantially
planar surface that is configured to interface with a
planer surface of the heat spreader and with a planar
surface of the common cooler. In some embodiments, each
force is created by a spring-loaded or leaver-actuated
latch applied to a faceplate of the corresponding one of
the electronic circuit boards. In some embodiments, the
electronic circuit boards fit into single slot of less
than about 25 mm in width. In some embodiments, some of
the circuit boards swappable out of the rack without
interrupting electrical power provided to the other ones
of the plurality of circuit boards. In some embodiments,
heat spreader is mechanically attached to one of the
localized heat sources. In some embodiments, a portion of
the heat spreader facing the portion of the cooler is a
planar surface that is parallel to a planar surface of the
portion of the cooler. In some embodiments, the cooler is
configured as an evaporator having a two-phase cooling
loop. In some embodiments, the portion of the cooler is
positioned in a space between the circuit boards and an
electronic backplane of the rack. In some embodiments, the
cooler is configured to circulate a refrigerant that is a
gas at an ambient temperature and pressure. Some
embodiments further include an air-flow device located in
the rack and configured to remove heat from the circuit
boards .
Another embodiment is a method assembling an
apparatus . The method comprises installing a plurality of
electronic circuit boards in slots of a rack such that
each of the installed electronic circuit boards is held
against a portion of a cooler for the rack by a
corresponding force. Some of the installed electronic
circuit boards have localized heat sources thereon and
having heat spreaders configured to form heat conducting
paths from the localized heat sources to the cooler. The
installing includes causes a compliant thermal interface
pad to be compressed between an end of each of the heat
spreaders and the cooler such that the compressed thermal
interface pad completes a heat conducting path between the
end and the cooler.
Some embodiments of the method further include
attaching an air-flow device in the rack, the air-flow
device configured to direct a flow of air over the circuit
boards and the heat spreader.
Another embodiment is a method swapping out an
electronic circuit. The method comprises detaching an
installed electronic circuit board from slots of a rack,
thereby breaking a connection between a compliant thermal
interface pad, and a heat spreader or a cooler inside the
rack .
Some embodiments of the method further include
replacing the detached electronic circuit board with a
different electronic circuit board by applying a force to
the different circuit board, such that the compliant
thermal interface pad is in-between the heat spreader of
the different circuit board and the cooler.
BRIEF DESCRIPTION OF THE DRAWINGS
Various embodiments are best understood from the
following detailed description, when read with the
accompanying FIGURES . Some features in the figures may be
described as, for example, "top," "bottom," "vertical" or
"lateral" for convenience in referring to those features.
Such descriptions do not limit the orientation of such
features with respect to the natural horizon or gravity.
Various features may not be drawn to scale and may be
arbitrarily increased or reduced in size for clarity of
discussion. Reference is now made to the following
descriptions taken in conjunction with the accompanying
drawings, in which:
FIG. 1 presents a plan view of an example apparatus
of the present disclosure;
FIG. 2 presents a detailed plan view of portion of
the example apparatus shown in FIG. 1 corresponding to
view 2 in FIG. 1 ;
FIG. 3 shows a detailed side view of a portion of the
example apparatus along view line 3—3 shown in FIG. 2 ;
FIG. 4 presents a flow diagram illustrating an
example method for assembling an apparatus of the
disclosure such as the any of the embodiments of the
example apparatuses discussed in the context of FIGs . 1-3;
and
FIG. 5 presents a flow diagram illustrating an
example method for swapping out an electronic circuit of
the disclosure such as the any of the an electronic
circuit embodiments of the example apparatuses discussed
in the context of FIGs. 1-3.
DETAILED DESCRIPTION
The description and drawings merely illustrate the
principles of the invention. It will thus be appreciated
that those skilled in the art will be able to devise
various arrangements that, although not explicitly
described or shown herein, embody the principles of the
invention and are included within its scope. Furthermore,
all examples recited herein are principally intended
expressly to be only for pedagogical purposes to aid the
reader in understanding the principles of the invention
and the concepts contributed by the inventor (s) to
furthering the art, and are to be construed as being
without limitation to such specifically recited examples
and conditions. Moreover, all statements herein reciting
principles, aspects, and embodiments of the invention, as
well as specific examples thereof, are intended to
encompass equivalents thereof. Additionally, the term,
"or, " as used herein, refers to a non-exclusive or, unless
otherwise indicated. Also, the various embodiments
described herein are not necessarily mutually exclusive,
as some embodiments can be combined with one or more other
embodiments to form new embodiments .
In shelf configurations, the cooling of higher
powered board-level electronic and optical components is
becoming increasingly difficult with forced air convection
cooling techniques. In addition, constraints on allowable
acoustic noise levels often limit practical volumetric air
flow rates in convection cooling. Various embodiments
implement hybrid cooling of a circuit board in which
forced air convective cooling is supplemented via heat
spreader (s) and heat conducting path(s) to one or more
higher power components on the board. Various embodiments
also enable "hot" swapping and/or replacement of said
circuit board from a rack, e.g., to allow flexibility in
the deployed functionalities on said rack.
FIG. 1 schematically illustrates an example apparatus
100 of the present disclosure. FIG. 2 presents a detailed
plan view of a portion view 2 of the example apparatus 100
of FIG. 1 . FIG. 3 shows a detailed side view of a portion
of the example apparatus 100 along view line 3—3 of FIG.
Some embodiments of the example apparatus 100
comprises an equipment rack 105 having at least one
electronic backplane 110 therein. The rack 105 comprises
a plurality of electronic circuit boards 115. Each of the
electronic circuit boards 115 are held against the
electronic backplane 110 in the rack 105 by an insertion
force 120. For example, the insertion force ensures an
electrical connection and a direct thermal connection
between an individual one of the circuit boards 115 and
the electronic backplane 110) . Some of the electronic
circuit boards 115 have a localized heat source 125
thereon. The apparatus 100 also comprises a common cooler
130 located next to the electronic backplane 110 and a
plurality of heat spreaders 135 that connect to
corresponding localized heat sources 125 on the circuit
boards 115.
In some cases the rack 105 can include one or more
shelves 140, each shelf 140 may be configured to hold one
of the electronic backplanes 110. Some embodiments of the
circuit boards 115 may include other heat spreaders 145
thereon (e.g., heat sinks) which are not physically
coupled to the common cooler 130. These other heat
spreaders 145 can be configured to cool other components
on the circuit board 115 that generate smaller amounts of
heat than the localized heat sources 125.
As further illustrated in FIGs . 2 and 3 , each heat
spreader 135 is configured to form a heat conducting path
210 over and adjacent to one of the electronic circuit
boards 115. The heat conducting path goes from a region
220 adjacent to one or more of the localized heat sources
125 to the common cooler 130.
Herein, a heat conducting path is a conduction path
that does not include an air air-convection segment whose
length is a substantial part of the total physical length
of the conduction path. For example, the heat conduction
path may not have any air convection segment.
Alternately, the heat conduction path may have an airconvection
segment whose length is less than 20% of the
total length of the conduction path or is less than 10% of
the total length of the conduction path.
As illustrated in FIG. 1 , the apparatus 100 further
comprises one or more compliant thermal interface pads
150. Each compliant thermal interface pad 150 is located
in-between one of the heat spreaders 135 and the common
cooler 130. Each compliant thermal interface pad 150 is
also compressed by a portion of the insertion force 120 to
ensure direct physical contact between the thermal
interface pad 150 and adjacent portions of both the heat
spreader 135 and the common cooler 130.
The characteristics of the compliant thermal
interface pad 150 may be selected to increase the
conductive heat transfer from the heat spreader 135 to the
common cooler 130. For instance, the compliant thermal
interface pad's shape, size, including its thickness 225,
compressibility, and thermal conductivity properties may
be selected to increase such conductive heat transfer. The
optimization of selections for said characteristics may
depend upon the size of the heat spreader 135, the gap
distance 230 between the heat spreader 135 and common
cooler 130, the amount of heat produced by the heat source
125, the extent of cooling from the common cooler 130,
and/or the extent of cooling from convective air flow in
the rack 105.
In some embodiments for conventional circuit boards
mounted on shelves in telecom central offices, one or more
of the compliant thermal interface pads 150 have a thermal
conductivity of at least about 1 /m-K and in some cases,
at least about 2 W/m-K, and in still other cases at least
about 5 W/m-K. Such high thermal conductivities
facilitate conductive heat transfer through the heat
conducting path 210 from the heat source 125 through the
pad 150 to the common cooler 130 . Non-limiting examples
of suitable material for the compliant thermal interface
pads 150 includes thermal gap filler such as Tflex™ (MH&W
International, Mahwah, NJ) or GAP PAD® (The Bergquist
Company, Chanhassen, MN) . Based upon the present
disclosure, one skilled in the art would understand the
other type of materials from which the compliant thermal
interface pad 150 could be formed.
In some embodiments, one or more of the compliant
thermal interface pads 150 have a degree of
compressibility that is able to complete the heat
conductive pad 210 for a range of different gap distances
230. For instance, in some embodiments, a thickness 225 of
at least one of the compliant thermal interface pads 150
is compressible by at least about 10 percent when
subjected to the insertion force 120. Variable gap
distances 230 between the heat spreader 135 and the common
cooler 130 can occur such that different ones of the
compliant thermal interface pads 150 have different
thicknesses when installed. For instance, there can be
variations in the size or placement of the end(s) of the
heat spreaders 135 on the circuit board 115, variations in
the size of the circuit board 115, variations in the
seating of the circuit board 115 in the electronic
backplane 110, or variations in the location of the common
cooler 130 relative to the circuit board 115.
In some embodiments, one or more of the compliant
thermal interface pads 150 is reversibly compressible. For
instance, in some cases the compliant thermal interface
pad 150 can be an elastic thermal interface pad. For
instance, in some embodiments, the pad's thickness 225 can
return substantially back to its pre-compression value
{e.g., a same thickness 225 ± 1 percent) when the
insertion force 120 is not applied to the pad 150. It may
also be desirable for such a reversibly compressible pad
150 to be creep resistant such that it will continue to
provide the thermal path 210 while tolerating a repeated
number of circuit board 115 insertion/removal cycles
(e.g., at least about 10 cycles, and in some cases at
least about 100 cycles, in some embodiments) without
permanent set or stress relaxation. Such material
properties help to preserve the on-going functionality of
the apparatus 100 by allowing a "hot" swapping or
replacement of any one circuit board 115 from the shelf
140 while other circuit boards 115 of the same shelf 140
remain operational. Such hot swapping or replacing may be
performed at various times during the design life of the
apparatus 100 or its subcomponents (e.g., during the
design lives of the circuit boards 115 on the shelves 140
in the rack 105) .
In some embodiments, one or more of the compliant
thermal interface pads 150 forms a reversible or removable
physical connection between both the heat spreader 135
and the common cooler 130. This can provide the advantage
of the ability to easily replace the pad 150 if necessary,
e.g., because the pad's 150 useful life has been reached
or because a different sized pad 150 is needed to better
establish the heat conducive path 210.
However, in some cases, the compliant thermal
interface pads 150 can be configured to be physically
fixed to the heat spreader 135 or to the common cooler
130, or to both the heat spreader 135 and the common
cooler 130. For instance, one or both of the surfaces
240, 245 of the pad 150 can include an adhesive that
permanently bonds or fixes the pad 150 to either the heat
spreader 135 or the common cooler 130. In some cases, it
can be advantageous to physically fix the pad 150 to the
common cooler 130 such that, when a circuit board 115 is
swapped, the same pad 150, remains attached to the common
cooler 130 for use to re-establish the heat conducting
path 210 when a new circuit board 115 is swapped in
without further manipulation or adjustment of the pad 150.
In still other embodiments, the compliant thermal
interface pads 150 can be physically fixed to the heat
spreader 135 or to the common cooler 130 using mechanical
structure (s) . For instance, clamp (s), screw (s), frame (s),
ledge (s) or similar structures can be used to hold the pad
150 in-place adjacent to the common cooler 130 and/or the
adjacent end of one of the heat spreaders 135 when the
circuit board 115 is removed from the electronic back
plane 110. In still other embodiments, however, the
compliant thermal interface pad 150 {e.g., which in some
cases can bean elastic thermal interface pad) is
configured to be physically held in place in-between one
of the heat spreaders 135 and the common cooler 130 by the
insertion force 120 alone.
In some embodiments, one or more of the compliant
thermal interface pads 150 can have an electrically
insulating outer surface. Such an electrically insulated
outer surface can help avoid electrical short-circuits
when hot-swapping the circuit board 115 with another
circuit board 115.
As illustrated in FIGs . 2 and 3 , in some embodiments,
to facilitate efficient heat transfer, one or more of the
elastic thermal interface pads 150 can have a
substantially planar surface 240 that is configured to
interface with a planar surface 250 of one of the heat
spreaders 135 and with a planar surface 255 the common
cooler 130. In some embodiments, to facilitate efficient
heat transfer through the pad 150, a portion of the heat
spreader 135 facing the common cooler 130 is shaped to
have a planar rectilinear surface 245 or other planar
surface that can be substantially parallel to a planar
surface 255 of the common cooler 130 when the circuit
board 115 is inserted into the electronic backplane 110.
For example, as viewed from a top plan view FIG. 2 , the
heat spreader 135 can form a T-shaped end having a surface
245 that opposes and is substantially parallel to the
planar surface 255 of the common cooler 130. Based on the
present disclosure one of ordinary skill would appreciate
the end of the heat spreader 135 opposing the common
cooler could have other shapes such as L- or U-shapes to
provide a surface 245 to facilitate efficient heat
transfer to the common cooler 130.
A s further illustrated in F Gs . 2 and 3 , in some
embodiments, the heat spreader 135 can be mechanically
attached to one of the localized heat sources 125. For
instance, mounting structures 260 such as screws, or
spring-loaded screws, or clamps can be used to facilitate
mechanical attachment. In some cases, to facilitate heat
transfer, there can be a thin layer of thermal interface
material 262 between the heat spreader 135 and the
localized heat sources 125. In some cases, the attachment
to the circuit board 115 can be completed during the
circuit board's manufacturing process, prior to the
circuit board's placement in the rack 105. In some
embodiments, the heat spreader 135 can be permanent
attached to the circuit board 115, but in other cases the
mechanical attachment can be reversible. For instance it
may be desirable to disassemble the heat spreader 135 from
the circuit board 115 in the field using hand tools.
As illustrated in FIG. 2 , some embodiments of the
heat spreader 135 have thicknesses 264 of less than 2.5
mm. As further illustrated in FIG. 2 , some embodiments of
the heat spreader 135 can have non-planar geometries,
e.g., to facilitate bridging other heat spreaders 145
situated over convection cooled, lower powered or
unpowered, devices 266 mounted on the circuit board 115,
while not unsuitably reducing the thermal conductivity
along the heat transfer path 210.
In some embodiments, the heat spreader 135 can
include a nano-heat spreader or a vapor chamber. Some
embodiments of the heat spreader 135 can include one or
more heat pipes. Some embodiments of the heat spreader
135 can have a thermal conductivity of at least about
2W/m-K, and in some cases at least about 5W/m-K. In some
cases, a heat spreader 135 having a heat pipe
configuration can facilitate forming high aspect ratio
form factors (e.g., length 268 :thickness 264 or width
305 :thickness 2 4 ratios of greater than 10:1 and in some
cases greater than 100:1).
In some embodiments of the apparatus 100, the
insertion force 120 is created by a spring-loaded or
leaver-actuated latch applied to a faceplate 270 of each
of the electronic circuit boards 115. The insertion force
12 0 provides the necessary pressure to form the thermally
conductive path 210, through the pad 150, between the heat
spreader 135 and the common cooler 130.
As illustrated in FIG. 3 , in some embodiments of the
apparatus 100, the electronic circuit boards 115 have a
single slot 310 of less than about 25 mm in width 315 that
is configured to fit into a receptacle 320 of the
electronic backplane 110. In some such embodiments, the
localized heat source 125 (or sources in some cases) can
be high-powered optical or electrical component (or
components) , and consequently generate, large amounts of
heat compared to amounts of heat generated by other
discrete components on the same circuit board 115. For
example, in some cases, the localized heat sources 125 can
use at least about 10 Watts of power, and in some cases at
least about 50 Watts of power, and in still other cases at
least about 100 Watts of power. Examples of such highpowered
localized heat sources 125 may include an optical
differential phase-shift keying demodulator or a laser
source .
In contrast to solely forced air convection cooling
techniques, the cooling structures disclosed herein can
adequately remove heat for localize high-dissipation
optical or electrical components, i.e., local heat sources
125. In addition, the optical or electrical component
local heat sources 125 may have large lateral areas on a
circuit board 115 that has a single slot 310 width of
less than or equal to the 25 mm of conventional slots for
individual circuit boards in telecom central offices.
Because of maximum allowable acoustic noise levels, it
might be necessary to substantially increase (e.g., double
in some cases) the space for individual circuit board
115 in the shelf 140 to provide adequate cooling in the
absence of hybrid techniques described herein. Thus, the
embodiments based on hybrid cooling can enable the use of
narrow slots for individual circuit boards 115 than in
systems whose cooling is based only on convective air
cooling .
The cooling structures disclosed herein are also in
contrast to directly mounting cooling loop evaporators to
high-powered optical or electrical component local heat
sources 125. Again consider the example of optical or
electrical component local heat sources 125 on a circuit
board 115 having a single slot 310 with a conventional
width of less than or equal to 25 mm. To achieve cooling
using directly mounted cooling loop evaporators, it may be
necessary to provide an additional slot volume (e.g., a
larger slot width 315) and/or additional slots, to
accommodate the directly mounted evaporators . Such a
solution is often not desirable because the self's useful
through-put capacity (typically measured as bits of data
switched or processed per volume of equipment) is often
roughly inversely related to the slot width, i.e., is
roughly directly related to the number or slots thereon.
For instance, the through-put capacity may be reduced by
half by a doubling of the slot width 315 of the shelf 140
from 25 mm to 50 mm. Additionally, in some cases,
directly mounting such cooling loop evaporators to the
local heat sources 125 can result in the loss of the
ability to easily "hot" swap or replace circuit boards
115, without typically a long duration physical deinstallation
procedures.
In contrast, in certain embodiments, each of the
circuit boards 115 is configured to be reversibly or
removably held in the corresponding slot against to the
electronic backplane 110, and in some cases, any one of
the circuit boards 115 can be removed from the electronic
backplane 110 without interrupting electrical power
provided to the other ones of the plurality of circuit
boards 115. Additionally, in some embodiments of the
apparatus 100, the one or more circuit boards 115 can each
have multiple slots 310, or, have a single slot 310 with a
width 315 of about 25 mm or more, if desired.
Returning to FIG. 1 , in some embodiments of the
apparatus 100, the common cooler 130 can be configured to
circulate a refrigerant. For instance, in some cases the
common cooler 130 can be configured as an evaporator
(e.g., a microchannel evaporator in some cases) having a
two-phase cooling loop. In other embodiments, however,
the common cooler 130 can be configured a solid structure
having a high thermal conductivity (e.g., a metal bar) .
As illustrated in FIG. 3 in some embodiments of the
apparatus 100, portions of the common cooler 130 are
positioned in a space 330 between the circuit boards 115
and the electronic backplane 110. Such a positioning of
said portions of the common cooler 130 can facilitate
efficient thermal coupling of each of the heat spreaders
135 to the common cooler 130 as well as reducing the
amount of space occupied within the rack 105 by the common
cooler 130.
In some cases, the common cooler 130 can be part of a
cooling system 170 that further includes supply and return
lines 172, 174, a pumping mechanism 176 for circulating
the liquid and/or vapor phases of a refrigerant 178
through the closed loop, and a condenser sub-unit 180. In
some cases, the supply and return lines 172, 174 can be
flexible lines and use a "quick-disconnect" end fitting
that allows the on-site installation of the common cooler
130 as well as the modular serial or parallel connection
of multiple common coolers 130 to a single condenser subunit
180. For instance, in some cases, each common cooler
130 can be located on a corresponding shelf 140 of the
rack 105 and/or can be associated with a different
electronic back plane 110. In some cases, the condenser
sub-unit 180 can be located remotely from the rack 105. In
some cases, the condenser sub-unit 180 can be configured
to interface with the building chilled water supply.
However, in other cases, the condenser sub-unit 180 can be
configured to interface with other heat dissipating
mechanisms, such as a separate air-conditioning AC cooling
loop, heat sinks or the ambient room air.
In some embodiments the common cooler 130 is
configured to circulate a refrigerant 178 that is a gas at
an ambient temperature and pressure (e.g., about 20°C and
about 1 atmosphere pressure) . For such embodiments, in
the event of a refrigerant 178 leak, no liquid phase
refrigerant would be present in the equipment space,
thereby reducing the possibility of damage to circuit
boards 115 and their component parts component or board
module damage. Similarly, some embodiments use examples of
the refrigerant 178 that are organic dielectrics, to
reduce the possibility of damage to circuit boards 115 and
their component parts, e.g., in the event of leakage from
the common cooler 130. Non-limiting examples of suitable
refrigerants include 1 , 1 , 1 ,2-tetraf luoroethane, also known
as R134a or HFC-134a, or similar haloalkane refrigerants,
or other refrigerants familiar to those of ordinary skill
in the art.
Based on the present disclosure one of ordinary skill
in the art would understand how heat could be transferred
from the localized heat source 125, to the common cooler
130 where the refrigerant is vaporized, to facilitate
higher heat transfer rates by exploiting the latent heat
of vaporization of the refrigerant 178. The vapor phase of
the refrigerant 178 is moved by the pumping mechanism 17 6
to the condenser 180 where heat transfer occurs, thereby
condensing the refrigerant 178 back to a liquid. The
condensed liquid refrigerant 178 is returned to the common
cooler 130 where the cycle continues, thus completing a
closed cooling loop.
Some embodiments of the present disclosure provide a
hybrid cooling solution that uses both conductive cooling
at the level of individual electronic circuit boards 115,
as described herein, and convective air flow cooling. For
instance, as further illustrated in FIG. 3 , some
embodiments of the apparatus 100 further include an air
flow device 340 located in the rack 105 and configured to
remove heat from the circuit boards 115. In some
embodiments, the air-flow device 340 includes one or more
fan trays 342, 344 located inside of the rack 105. The
air flow heat exchange device 340 can be configured to
deliver an air flow in an average direction 350 that is
parallel to the major surface of the electronic circuit
boards 115. For instance, in some cases, the air flow
direction 350 can be the from bottom to top of the rack
105 and provided by an array of air movers (e.g., axial
fans) housed in the one or more fan trays 342, 344 that
are positioned either above and/or below a shelf 140. In
some cases, because of the cooling efficiencies gained
from conductive cooling, there can be a reduced input
power for air-flow device 340 , e.g., due to reduced fan
speeds. For example, in some cases the airflow in cubic
feet per minute for the air-flow device 340 can be reduce
by 20-50 percent with proportional reductions in power
consumption, as compared to cooling without conductive
cooling as described herein.
Another embodiment is a method of assembling an
apparatus. FIG. 4 presents a f ow diagram illustrating an
example method 400 for assembling an apparatus of the
disclosure. Any of the embodiments of the apparatus 100,
and its component parts such as described in the context
of FIGs . 1-3, can be assembled in accordance with the
method 400.
With continuing reference to FIGs. 1-3 throughout,
the method 400 comprises a step 410 of installing a
plurality of electronic circuit boards 115 in slots 310 of
a rack 105 such that each of the installed electronic
circuit boards 115 is held against a portion of a cooler
130 for the rack 105 by a corresponding force 120, some of
the installed electronic circuit boards 115 having
localized heat sources 125 thereon and having heat
spreaders 135 configured to form heat conducting paths
210 from the localized heat sources 125 to the cooler 130.
Some embodiments of the method 400 further include a
step 415 of providing the rack 105 having at least one
electronic backplane 110 therein, and, a step 420 of
positioning a cooler 130 (e.g., a common cooler) next to
the electronic backplane 110. In some cases, each heat
spreader 135 s configured to form a heat conducting path
210 over and adjacent to one of the electronic circuit
boards 115 from a region adjacent to one or more of the
localized heat sources 125 thereon to the cooler 130.
Some embodiments of the method 400 further include a
step 430 of attaching an air-flow device 340 in the rack
105, the air-flow device 340 configured to direct a flow
of air 350 over the circuit boards 115 and the heat
spreaders 135 or other heat spreaders 257. For instance,
attaching an air-flow device 340 in step 440 can include
attached one or more fan trays 342, 344 configured to
force air over the circuit board 115. For instance fan
trays 342, 344 can be located above and below the row of
circuit boards 115 and configured to push or pull air over
the surfaces of the circuit boards 115 at the same time
that the heat is being transferred from one or more of the
circuit boards 115 to the common cooler 130. A s notedabove,
the additional cooling provided by transfer
conductive heat transfer through the heat spreaders 135 to
the common cooler 130, in turn, may permit the air-flow
device 340 to be operated at lower speeds resulting in
less acoustic noise and/or power consumption associated
with cooling the structures in the rack 105.
Another embodiment is a method of swapping out an
electronic circuit. FIG. 5 presents a flow diagram
illustrating an example method 500 for swapping out an
electronic circuit. The method 500 can be applied to any
of the embodiments of the apparatus 100, and its component
parts such as described in the context of FIGs . 1-3.
With continuing reference to FIGs. 1-3 throughout,
the method 500 comprises a step 510 of detaching an
installed electronic circuit board 115 from slots 310 of a
rack 105, thereby breaking a connection between a
compliant thermal interface pad 150, and a heat spreader
135 or a cooler 130 (e.g., a common cooler) inside the
rack 105.
Some embodiments of the method 500 further include a
step 520 of replacing the detached electronic circuit
board 115 with a different electronic circuit board 115 by
applying a force to the different circuit board 115, such
that the compliant thermal interface pad 150 is in-between
the heat spreader 135 of the different circuit board 115
and the cooler 130.
Although various embodiments of the present invention
has been described in detail, those skilled in the art
should understand that they can make various changes,
substitutions and alterations herein without departing
from the scope of the claimed inventions .
WHAT IS CLAIMED IS:
1 . An apparatus, comprising:
a rack;
a cooler;
a plurality of electronic circuit boards located in
corresponding slots of the rack, each of the electronic
circuit boards being held against a portion of the cooler
by a corresponding force, some of the electronic circuit
boards having a localized heat source thereon;
a plurality of heat spreaders, each heat spreader
configured to form a heat conducting path over and
adjacent to one of the electronic circuit boards from one
or more of the localized heat sources thereon to the
portion of the cooler; and
a plurality of compliant thermal interface pads,
each of the pads being compressed between end of one of
the heat spreaders and the portion of the cooler to form
a heat conduction path therebetween.
2 . The apparatus of claim 1 , wherein one or more
of the compliant thermal interface pads has a thermal
conductivity of at least 1 W/m-K.
3 . The apparatus of claim 1 , wherein at least one
of the compliant thermal interface pads is an elastic
thermal interface pad.
4 . The apparatus of claim 3 , wherein a thickness
of the elastic thermal interface pad is compressible by
at least about 10 percent when subjected to the force on
the corresponding one of the boards and the thickness
returns substantially back to its pre-compression value
when the force on the corresponding one of the boards is
not applied to the elastic thermal interface pad.
5 . The apparatus of claim 1 , wherein one or more
of the compliant thermal interface pads are configured to
be fixed to one or both of the heat spreader or the
common cooler .
6 . The apparatus of claim 1 , wherein one or more
of the compliant thermal interface pads have an
electrically insulating outer surface.
7 . The apparatus of claim 1 , wherein one or more
of the compliant thermal interface pads have a
substantially planar surface that is configured to
interface with a planer surface of the heat spreader and
with a planar surface of the common cooler.
8 . The apparatus of claim 1 , wherein some of the
circuit boards swappable out of the rack without
interrupting electrical power provided to the other ones
of the plurality of circuit boards.
9 . A method of assembling an apparatus,
comprising :
installing a plurality of electronic circuit boards
in slots of a rack such that each of the installed
electronic circuit boards is held against a portion of a
cooler for the rack by a corresponding force, some of the
installed electronic circuit boards having localized heat
sources thereon and having heat spreaders configured to
form heat conducting paths from the localized heat
sources to the cooler; and
wherein the installing includes causing a compliant
thermal interface pad to be compressed between an end of
each of the heat spreaders and the cooler such that the
compressed thermal interface pad completes a heat
conducting path between the end and the cooler.
10. A method of method swapping out an electronic
circuit, comprising:
detaching an installed electronic circuit board from
slots of a rack, thereby breaking a connection between a
compliant thermal interface pad, and a heat spreader or a
cooler inside the rack .