U.S. patent application number 11/761167 was filed with the patent office on 2007-10-04 for integrated circuit coolant microchannel with compliant cover.
Invention is credited to Patrick D. Boyd, Je-Young Chang, Chia-pin Chiu, Gregory M. Chrysler, Alan M. Myers, Ravi Prasher, Ioan Sauciuc.
Application Number | 20070230116 11/761167 |
Document ID | / |
Family ID | 36943020 |
Filed Date | 2007-10-04 |
United States Patent
Application |
20070230116 |
Kind Code |
A1 |
Myers; Alan M. ; et
al. |
October 4, 2007 |
INTEGRATED CIRCUIT COOLANT MICROCHANNEL WITH COMPLIANT COVER
Abstract
An apparatus includes a microchannel structure having
microchannels formed therein. The microchannels are to transport a
coolant and to be proximate to an integrated circuit to transfer
heat from the integrated circuit to the coolant. The apparatus also
includes a cover positioned on the microchannel structure to define
a respective upper wall of each of the microchannels. The cover
presents a compliant surface to the microchannels.
Inventors: |
Myers; Alan M.; (Menlo Park,
CA) ; Chang; Je-Young; (Phoenix, AZ) ;
Prasher; Ravi; (Phoenix, AZ) ; Sauciuc; Ioan;
(Phoenix, AZ) ; Chrysler; Gregory M.; (Chandler,
AZ) ; Boyd; Patrick D.; (Aloha, OR) ; Chiu;
Chia-pin; (Tempe, AZ) |
Correspondence
Address: |
BUCKLEY, MASCHOFF & TALWALKAR LLC
50 LOCUST AVENUE
NEW CANAAN
CT
06840
US
|
Family ID: |
36943020 |
Appl. No.: |
11/761167 |
Filed: |
June 11, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11069540 |
Mar 1, 2005 |
7243705 |
|
|
11761167 |
Jun 11, 2007 |
|
|
|
Current U.S.
Class: |
361/689 ;
257/E23.098 |
Current CPC
Class: |
H01L 23/473 20130101;
H01L 2924/00 20130101; H01L 2924/0002 20130101; H01L 2924/0002
20130101; F28F 3/12 20130101 |
Class at
Publication: |
361/689 |
International
Class: |
H05K 7/20 20060101
H05K007/20 |
Claims
1. An apparatus comprising: a microchannel structure having
microchannels formed therein, said microchannels to transport a
coolant and to be proximate to an integrated circuit to transfer
heat from the integrated circuit to the coolant; and a cover
positioned on the microchannel structure to define a respective
upper wall of each of said microchannels, said cover presenting a
compliant surface to said microchannels.
2.-5. (canceled)
6. The apparatus of claim 1, wherein said cover includes a flexible
pad secured to said cover.
7. The apparatus of claim 6, wherein said flexible pad is formed of
rubber.
8.-22. (canceled)
23. An apparatus comprising: an integrated circuit (IC); and a
microchannel assembly thermally coupled to the IC and having
microchannels formed therein, each microchannel defined by a
respective plurality of walls, at least one of said walls which
defines said each microchannel being formed of a compliant
material.
24. (canceled)
25. The apparatus of claim 23, wherein a respective upper wall of
each of the microchannels is formed by a rubber pad.
26. A system comprising: a microprocessor integrated circuit die; a
microchannel structure thermally coupled to the microprocessor
integrated circuit die, the microchannel structure having
microchannels formed therein, said microchannels to transport a
coolant; a cover positioned on the microchannel structure to define
a respective upper wall of each of said microchannels, said cover
presenting a compliant surface to said microchannels; and a chipset
in communication with the microprocessor integrated circuit
die.
27. (canceled)
28. The system of claim 26, wherein said cover includes a rubber
pad secured to a lower surface of said cover.
29.-30. (canceled)
31. The apparatus of claim 6, wherein the cover includes a recess
in which the flexible pad is located.
32. The apparatus of claim 6, wherein the pad is formed of
polydimethylsiloxane elastomer.
33. The apparatus of claim 25, wherein the rubber pad is located in
a recess in a cover.
34. The system of claim 28, wherein the cover includes a recess in
which the rubber pad is located.
Description
BACKGROUND
[0001] As microprocessors advance in complexity and operating rate,
the heat generated in microprocessors during operation increases
and the demands on cooling systems for microprocessors also
escalate. Also, it may be important that a microprocessor and
cooling system be able to withstand cold temperatures (e.g., minus
forty degrees Celsius). For example, a Personal Computer (PC) may
be exposed to low temperatures while being shipped from a
manufacturer to a distributor or retailer, or a laptop computer may
be exposed to freezing temperatures when stored in a user's car
overnight. Exposure to low temperatures may be a significant issue
with respect to a cooling system that utilizes a liquid
coolant.
[0002] Another issue that may be presented in a cooling system that
utilizes a liquid coolant is localized increase in pressure if the
coolant were to boil at the locus of a hotspot on the
microprocessor die. Such an increase in pressure may interfere with
uniform coolant flow and may thus compromise the cooling
system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0003] FIG. 1 is a schematic diagram of a system.
[0004] FIG. 2 is a schematic side cross-sectional view of a
microchannel assembly according to some embodiments, the view taken
at line II-II in FIG. 1.
[0005] FIG. 3 is a view similar to FIG. 2 of a microchannel
assembly according to some other embodiments.
[0006] FIG. 4 is a view similar to FIGS. 2 and 3 of a microchannel
assembly according to still other embodiments.
[0007] FIG. 5 is a view similar to FIG. 4 and showing the
microchannel assembly of FIG. 4 in a condition to accommodate
freezing of a coolant (not shown) therein.
[0008] FIG. 6 is a view similar to FIGS. 2-4 of a microchannel
assembly according to other embodiments, when in a condition to
accommodate freezing of a coolant (not shown) therein.
[0009] FIG. 7 is a view similar to FIG. 6, showing the microchannel
assembly of FIG. 6 in a normal operating condition.
[0010] FIG. 8 is a front elevation view of the microchannel
assembly of FIGS. 6 and 7 in a normal operating condition.
[0011] FIG. 8A is a view similar to FIGS. 2-4, 6 and 7 of a
microchannel assembly according to additional embodiments, when in
a condition to accommodate freezing of a coolant (not shown)
therein.
[0012] FIG. 9 is a view similar to FIGS. 2-4 and 6 of a
microchannel assembly according to still other embodiments, in a
condition in which coolant is expelled from the microchannel
assembly.
[0013] FIG. 10 is a view similar to FIG. 9, showing the
microchannel assembly of FIG. 9 in a condition in which coolant
(not shown) is present in the microchannel assembly.
[0014] FIG. 11 is a schematic side view of an integrated circuit
die having mounted thereon a microchannel assembly in accordance
with one of FIGS. 2-10.
[0015] FIG. 12 is a block diagram showing a die with additional
components of a cooling system according to some embodiments.
[0016] FIG. 13 is a block diagram of a computer system according to
some embodiments that includes an example of an integrated circuit
die associated with a cooling system as in one or more of FIGS.
2-12.
DETAILED DESCRIPTION
[0017] FIG. 1 is a block diagram of a system 100 including an
Integrated Circuit (IC) 110. The IC 110 may be associated with, for
example, an INTEL.RTM. PENTIUM IV processor. To help remove heat
generated by transistors (not separately shown) located on the
front-side (not shown) of the IC 110, a liquid coolant maybe
received in an inlet reservoir or chamber 130 through an inlet
opening 120. For example, a pump may move the coolant through the
inlet opening 120.
[0018] Microchannels may be formed directly in the rear surface of
the IC 110 or may be formed in a separate piece of silicon or in a
piece of copper that is eutectically (e.g.) bonded to the back of
the IC 110. The IC 110 may be thinned to reduce thermal resistance
between the transistors and the microchannels.
[0019] The inlet chamber 130 may comprise, for example, a manifold
which opens into a number of channels 140 that lead to an outlet
chamber 150 (e.g., another manifold). The coolant may flow through
these channels 140 and then exit the outlet chamber 150 through an
outlet opening 160. The channels 140 may be located proximate to
the IC 110 to facilitate the removal of heat from the system 100.
That is, heat may be transferred from the IC 110 to the coolant,
which may then leave the system 100. The heated coolant may then
cool at a remote location before returning to the system 100.
[0020] In a typical manner of implementing a microchannel cooling
system, a hard, inflexible cover is bonded to the top of the
microchannel assembly. The top cover may be made of glass, silicon,
or metal. Bonding methods such as anodic, eutectic or direct
bonding are typically used.
[0021] To efficiently facilitate a transfer of heat, a coolant with
a relatively high thermal conductivity and high heat capacity may
be used. Moreover, it may be beneficial if the coolant is
relatively inexpensive and easy to pump. Note that water has a
relatively high thermal conductivity, a relatively high beat
capacity, is relatively inexpensive, and can be readily pumped. It
may also be important that the system 100 be able to withstand cold
temperatures (e.g., minus forty degrees Celsius). Note, however,
that water expands in size when it freezes, and, as a result, the
channels 140 may become damaged if water were to freeze therein.
For example, the channels 140 may crack if water were to turn to
ice therein.
[0022] FIG. 2 is a schematic side cross-sectional view of a
microchannel assembly 200 according to some embodiments. The
microchannel assembly 200 includes a microchannel structure 202
having microchannels 204 formed therein. The microchannels 204 are
channels or passages each having a width of about 20 to 500
micrometers, although other widths may be used. The microchannels
204 transport (e.g., allow to flow therein) a coolant (not shown).
The microchannel structure 202 may be any body, such as a metal or
silicon cold plate in which microchannels are formed, and which is
to be mounted on the back-side of a microchip (e.g., on an IC such
as a microprocessor die) so that the microchannels are proximate to
the IC to transfer heat from the IC to the coolant. The
microchannel structure may alternatively be the microchip die
itself having microchannels formed in a rear surface thereof.
[0023] In some embodiments, the microchannels 204 may have a height
of about 300 microns and a width of about 100 microns, but other
dimensions of the microchannels 204 are possible. In a practical
embodiment, the number of microchannels may be much more than the
relatively few microchannels depicted in the drawing. The
microchannels may, but need not, all be straight and parallel to
each other. In general, FIGS. 1 and 2 and the other drawings herein
are not to scale.
[0024] The microchannel assembly 200 may also include a compliant
membrane 206 which spans the microchannels 204. The membrane 206
may serve as a cover positioned on the microchannel structure 202
to define a respective upper wall 208 of each of the microchannels
204. Since the membrane 206 is compliant, it presents a compliant
surface to the microchannels 204. As used herein and in the
appended claims, "compliant" has its common meaning of bending or
yielding in response to pressure.
[0025] The microchannel assembly 200 may also include a cap member
208 positioned on the microchannel structure 202 with the membrane
206 sandwiched between the cap member 208 and the microchannel
structure 202. It will be noted that the microchannel structure 202
includes opposed walls 210 which define side walls 212 of the
microchannels 204. The walls 210 may, but need not, all be of
uniform width. The cap member 208 may also include opposed walls
214 to define relief channels 216 in the cap member 208. The walls
214 of the cap member 208 may each be aligned with, and may have
the same width as, a respective one of the walls 210 of the
microchannel structure 202. The membrane 206 is sandwiched between
the lower surfaces 218 of the walls 214 and the upper surfaces 220
of the walls 210. Each relief channel 216 is located above a
respective one of the microchannels 204, with the membrane 206
forming a bottom wall 222 of each relief channel 216. (As a matter
of convention, the downward or vertical direction will be taken to
be the direction from the microchannel assembly to the IC die.)
[0026] The membrane 206 may be adhered to the upper surfaces 220 of
the walls 214 of the microchannel structure 202. In some
embodiments, the membrane 206 may be formed of a material such as
polydimethylsiloxane (PDMS) elastomer. According to one manner of
forming the membrane, the microchannel structure 202 is filled with
a 1% solution of agarose in water that has been heated above its
melting point of about 85.degree. C. Drain holes (not shown) in the
bottom of the microchannel structure 202 may have been sealed with
Capton tape or the like before introduction of the agarose
solution. The microchannel structure is then allowed to cool so
that the agarose gel solidifies. Thereafter, a layer of PDMS may be
spin-coated on the surface formed by the solid agarose and the
upper surfaces of the walls 214, and the resulting PDMS layer is
then cured. The PDMS may be diluted up to about 40% with hexane so
that the viscosity of the PDMS, and hence the thickness of the
resulting membrane, can be controlled. The curing may vary as a
function of the hexane concentration but may be in the range of 2-5
hours at 80.degree. C. The thickness of the membrane may be chosen
to provide mechanical strength as well as flexibility
(compliance).
[0027] After the membrane is cured, the drain holes are unsealed
and the microchannel structure is immersed in a bath of water at,
e.g., 90.degree. C. for about 5 minutes to melt the agarose gel and
to allow the agarose to drain from the microchannel structure.
[0028] In accordance with another manner of making the microchannel
assembly, a pre-fabricated PDMS membrane may be adhered to the
upper surfaces of the walls 214 after cleaning the microchannel
structure with methanol or the like. Whether the membrane is
pre-fabricated or is cured in situ, the cap member 208 is mounted
as shown in FIG. 2 with the PDMS membrane adhered to the
microchannel structure. The cap member 208 may be formed of silicon
or metal, for example. One way the cap member 208 may be bonded to
the membrane 206, in the case where the cap member is made of
silicon, may be by pressing the cap member and the microchannel
structure together with the membrane in between with exposure to an
oxygen plasma. Holes may be punched in the membrane to provide an
inlet and an outlet for the coolant.
[0029] During normal operation, coolant such as water (not shown)
is present in the microchannels 204 and flows therethrough to
remove heat from the IC 110 (FIG. 1). In the event that the system
100 encounters freezing temperature while being stored or
transported, the water in the microchannels 204 may freeze and
expand, causing the membrane 206 to bulge upward into the relief
channels 216. The bulging of the membrane 206 may allow the
freezing and expansion of the water to occur without resulting in
cracking, damage or breakage of the microchannel structure 202
itself. Thus the provision of the membrane and associated relief
channels may allow the system 100 to endure freezing temperatures
without suffering damage.
[0030] Also, the compliant membrane may be helpful in accommodating
phase conversion of the coolant from liquid to vapor, as may occur
over hotspots on the IC. This occurrence is referred to as
two-phase flow. In a conventional, rigid microchannel, boiling of
the coolant over a hotspot may result in an increase in pressure
which may result in a decrease of coolant flow in the channel
relative to other channels. Such a decrease in flow may compromise
the cooling ability of the cooling system. However, if in
accordance with embodiments described herein a compliant membrane
forms the upper wall of the microchannel, the membrane may flex to
relieve the pressure increase and to maintain the flow of coolant
through all channels.
[0031] FIG. 3 is a view similar to FIG. 2 of a microchannel
assembly 300 according to some other embodiments.
[0032] The microchannel assembly 300 may include the same
microchannel structure 202 that was described above in connection
with FIG. 2. In addition, the microchannel assembly 300 includes a
cover 302 positioned on the microchannel structure 202 to define
the upper walls of the microchannels 204. The cover 302 is formed
of a rigid cover member 304 (e.g., of metal or silicon) which has
formed therein a downward-facing recess 306. The cover 302 also
includes a pad 308 in the recess 306 and secured to the lower
surface 310 of the rigid cover member 304. The pad 308 may be
formed of rubber or another flexible material. The pad 308 may be
formed of PDMS, for example. The securing of the pad 308 to the
surface 310 may be by adhesive or by other means, including simply
pressure applied to the pad from below by the microchannel
structure 202. The pad 308 is compliant and thus presents a
compliant surface to the microchannels 204. A space (not shown) may
be provided above the pad 308 as part of the recess 306 to allow
the pad 308 to flex into the recess if the coolant freezes. The
cover 302 may be clamped to the microchannel structure 202 by a
mechanical device (e.g., a clamp). A layer of titanium followed by
a layer of gold may be deposited on the surfaces of the
microchannel structure which contact the pad to prevent the pad
from adhering to the microchannel structure. Again, if the system
100 encounters freezing temperatures so that the coolant in the
microchannels freezes and expands, the expansion of the coolant may
be accommodated by compression and yielding of the pad 308 so that
the possibility of damage to the microchannel structure and/or to
the cover may be reduced.
[0033] During normal operation, the pad may be tightly pressed
between the microchannel structure and the cover so as to seal the
tops of the microchannels.
[0034] FIG. 4 is a view similar to FIGS. 2 and 3 of a microchannel
assembly 400 according to still other embodiments.
[0035] The microchannel assembly 400 may include the same
microchannel structure 202 that was described above in connection
with FIG. 2. In addition, the microchannel assembly 400 includes a
cover 402 which is formed of a flexible material such as plastic
(e.g., Teflon) or bi-metal (e.g., copper-aluminum or
aluminum-titanium). The cover 402 defines upper walls of the
microchannels 204. The cover 402 is sealingly secured to the
microchannel structure 202 at perimeter walls of the microchannel
structure such as side walls 404, 406 and fore and aft walls which
are not shown. Because the cover 402 is flexible, it presents a
compliant surface to the microchannels. In the event of exposure of
the system to freezing temperatures, the cover may flex upwardly,
as illustrated in FIG. 5, to accommodate freezing and expansion of
the coolant. Such flexing of the cover may also occur to
accommodate local increases in pressure due to phase changes over
hotspots during normal operation.
[0036] A microchannel assembly 600 according to still other
embodiments is schematically illustrated in FIGS. 6-8. The
microchannel assembly 600 may include a microchannel structure 602
and a cover 604. The microchannel structure 602 may be similar to
the above-described microchannel structure 202 of other
embodiments. FIG. 6 is a side cross-sectional view showing the
microchannel assembly 600 in a condition in which freezing and
expansion of coolant (not shown) has caused the cover 604 to be
lifted upwardly from the microchannel structure 602. FIG. 7 is a
view similar to FIG. 6, but showing the microchannel assembly 600
in a normal operating condition with the cover 604 positioned on
the microchannel structure 602 to define upper walls of the
microchannels. FIG. 8 is a front elevation view of the microchannel
assembly 600 in the normal operating condition.
[0037] The cover 604 may be a rigid member of silicon or metal, for
example. Referring to FIG. 8, the microchannel assembly 600 may
further include a bias mechanism 606 that may be constituted, for
example, of two springs 608 each mounted at a respective side of
the microchannel assembly 600 and attached to the microchannel
structure 602 and to the cover 604 and tensioned to downwardly bias
the cover 604 toward the microchannel structure 602. The tensioning
of the springs 608 may be such as to allow the cover 602 to be
compliant to a force applied (e.g., by expansion of the coolant
upon freezing) upwardly to the cover 604 from the microchannels.
Thus, by virtue of the manner in which it is mounted, the cover may
present a compliant surface to the microchannels.
[0038] Although only two springs are shown in the drawing, in some
embodiments the bias mechanism may include a different number of
springs, such as four springs (e.g., one mounted at each side of
the microchannel assembly or one mounted at each corner of the
microchannel assembly) or one spring (e.g., mounted interiorly of
the cover at a central location thereof).
[0039] The microchannel assembly 600 may also include a bellows
610, made of foil or the like, which joins a lower periphery 612
(FIG. 6) of the cover 604 to an upper periphery 614 of the
microchannel structure 602 to seal the gap that may be formed when
the cover is lifted and thus to prevent the coolant from escaping
between the cover and the microchannel structure.
[0040] The manner of mounting the cover in this embodiment may
allow for accommodation of freezing of the coolant and thus may
prevent such freezing from causing damage to the cover and/or to
the microchannel structure.
[0041] FIG. 8A is a view similar to FIGS. 2-4 and 6 showing a
microchannel assembly 800 in a condition to accommodate freezing
and expansion of coolant (not shown).
[0042] The microchannel assembly 800 includes a microchannel
structure 802 and a multi-part cover 804 positioned on (e.g.,
bonded to) the microchannel structure 802. The microchannel
structure 802 has microchannels 806 formed therein. Interior
opposed walls 808 of the microchannel structure 806 define side
walls of the microchannels 806. The exterior walls 810 of the
microchannel structure 802 are stepped and each include a step
surface 812 which is co-planar with the upper surfaces 814 of the
interior walls 808. The exterior walls 810 also include upward
extensions 816 which extend upwardly beyond the plane defined by
step surfaces 812 of the walls 810 and upper surfaces 814 of the
walls 810.
[0043] The multi-part cover 804 includes an upper member 818 which
may be generally planar and which spans the upward extensions 816
of the walls 810. The cover 804 further includes a lower member 820
mounted to a lower surface 822 of the upper member 818 by a leaf
spring 824. The lower member 820 of the cover 804 may be generally
planar and spans the step surfaces 812 of the walls 810. The cover
804 also includes an O-ring 826 mounted around a horizontal
perimeter of the lower member 820 to sealingly close a gap 828
between the lower member 820 and the upward extensions 816 of the
walls 810.
[0044] The leaf spring 824 functions as a bias mechanism to
downwardly bias the lower member 820 toward the upper surfaces 814
of the walls 808 and the step surfaces 812 of the walls 810 so
that, during normal operation (a condition not illustrated in FIG.
8A), the lower member 820 closes the tops of the microchannels 806
and defines the upper walls of the microchannels 806. Because of
the manner of mounting the lower member 820, the lower surface 830
of the lower member 820 is presented as a compliant surface to the
microchannels 806 so that in the event of freezing of the coolant
(not shown), expansion of the coolant may force the lower member
820 upward against the force of the leaf spring 824 to a condition,
such as that illustrated in FIG. 8A. Thus the spring-mounted member
820 may accommodate freezing and expansion of the coolant to allow
such expansion to occur with reduced risk of damage to the
microchannel assembly.
[0045] FIG. 9 is a view similar to FIGS. 2-4 and 6 of a
microchannel assembly 900 according to still other embodiments, in
a condition in which coolant is expelled from the microchannel
assembly. FIG. 10 is a view similar to FIG. 9, showing the
microchannel assembly 900 in a condition in which coolant (not
shown) is present in the microchannel assembly.
[0046] The microchannel assembly 900 may include the same
microchannel structure 202 as in previous embodiments and may also
include a cover 902 which may be a rigid member, like cover 604
(FIG. 6) but fixedly and liquid-tightly secured to close the
microchannels and to define the upper walls of the microchannels.
In addition, the microchannel assembly 900 includes a filler
material 904, such as n-isopropylacrylamide (NIPAM) which is
present in the microchannels. The NIPAM is a polymer which exhibits
shrinking to a great extent upon exposure to heat. For example,
upon a suitable increase in temperature NIPAM shrinks to about
one-tenth of its previous size. At a relatively low temperature,
below 40.degree. C., the NIPAM occupies enough space to completely
obstruct the microchannels in the microchannel assembly 900. As the
temperature rises above 40.degree. C., the NIPAM shrinks to
substantially one-tenth of its previous size and so is in a
condition such that the microchannels are substantially
unobstructed. The NIPAM is a solid in both conditions.
[0047] Before beginning operation, the NIPAM is in its low-density,
high space occupancy state and the microchannels are completely
filled and obstructed by the NIPAM (FIG. 9). As operation of the
system begins, the IC (not shown in FIGS. 9 and 10) generates heat
and warms the NIPAM to a temperature at which the NIPAM drastically
shrinks (FIG. 10) and allows the coolant to be circulated through
the microchannels. The shrinking of the NIPAM occurs at around
40.degree. C., which is well below the temperature (e.g.,
100.degree. C.) at which cooling of the IC begins to be needed, so
that the presence of the NIPAM does not interfere with cooling
operation of the system which includes the microchannel
assembly.
[0048] When operation of the system ceases and the IC and the
microchannel assembly cool off, the NIPAM expands to its full size,
forcing substantially all of the coolant out of the microchannels.
Consequently, in the event that the system is thereafter exposed to
freezing temperatures, there will be substantially no coolant in
the microchannels to damage the microchannels by freezing and
expansion.
[0049] In some embodiments, the NIPAM may be adhered to a lower
surface of the cover 902 at the locus of the microchannels (i.e.,
the NIPAM may be adhered to the upper walls of the microchannels).
In other embodiments, the NIPAM may be adhered to one or more other
walls of the microchannels, in addition to or instead of being
adhered to the cover. However, it may be the case, if the NIPAM is
adhered to more than one surface, that shrinking of the NIPAM upon
heating thereof may pull the NIPAM away from one or more of the
surfaces and/or may adversely affect the structural integrity of
the NIPAM. In some embodiments, the NIPAM may be adhered to the
lower surface of the cover and/or to one or more other walls of the
microchannels by means of an interface of elastic fibers. It may be
advantageous to adhere the NIPAM only to the lower surface of the
cover, since if the NIPAM is present on the side or bottom walls of
the microchannel structure, the NIPAM may reduce heat transfer from
the microchannel structure to the coolant.
[0050] In some embodiments, inlets and or outlets (both not shown)
in the cover may be positioned to coincide with hotspots on the IC
die, since the NIPAM will remain in its "hot" shrunken condition
longest at these locations, allowing the coolant to flow out of the
inlets/outlets.
[0051] FIG. 11 is a schematic side view of an integrated circuit
die 110 with a microchannel assembly 1100 mounted thereon. The
microchannel assembly 1100 may be any one of the types of
microchannel assembly described hereinabove. The microchannel
assembly 1100 may be bonded to the back-side 1101 of the integrated
circuit die 110 by, e.g., a layer of thermal interface material
(TIM) 1102 to thermally couple the microchannel assembly 1100 to
the integrated circuit die 110. In other embodiments, the
microchannel assembly may be thermally coupled in another manner to
the integrated circuit die. The transistors (not separately shown)
of the IC die 110 are formed at the front side 1104 of the IC die
110.
[0052] In other embodiments, the microchannels may be formed
directly in the rear-side of the IC die, so that the microchannel
structure and the IC die are one integrated piece. In these
embodiments, no TIM would be required, and a cover like one of the
covers described above may be provided to accommodate freezing
and/or boiling of the coolant.
[0053] FIG. 12 is a block diagram showing an IC die 1210 and
additional components of a cooling system 1200. For purposes of
illustration the microchannel assembly 1240 (which may be any one
of the microchannel assemblies described above) is shown as a
single block. The cooling system 1200 includes a coolant
circulation system 1290 to supply the coolant to the microchannel
assembly 1240. The coolant circulation system 1290 may be in fluid
communication with the microchannel assembly 1240 via one or more
coolant supply channels or lines 1292 and one or more coolant
return channels 1294. Although not separately shown, a pump and a
heat exchanger located remotely from the die 1210 maybe included in
the coolant circulation system 1290.
[0054] Coolant supplied by the coolant circulation system 1290 may
flow through the microchannels of the microchannel assembly 1240 at
or above the rear surface of the IC die 1210 to aid in cooling the
IC die 1210. In some embodiments, the coolant is operated with two
phases--liquid and vapor. That is, in some embodiments at least
part of the coolant in the microchannels is in a gaseous state. In
other embodiments, the coolant is single phase--that is, all
liquid. In either case, the microchannel assembly accommodates
freezing of the coolant while reducing the possibility of damaging
the microchannel assembly as a result of the freezing, or expels
the coolant from the microchannels to prevent damage from
freezing.
[0055] The IC die 1210 may be associated with a microprocessor in
some embodiments. FIG. 13 is a block diagram of a system 1300 in
which such a die 1310 may be incorporated. In particular, the die
1310 includes many sub-blocks, such as an Arithmetic Logic Unit
(ALU) 1304 and an on-die cache 1306. The microprocessor on die 1310
may also communicate to other levels of cache, such as off-die
cache 1308. Higher memory hierarchy levels, such as system memory
1311, may be accessed via a host bus 1312 and a chipset 1314. In
addition, other off-die functional units, such as a graphics
accelerator 1316 and a Network Interface Controller (NIC) 1318, to
name just a few, may communicate with the microprocessor on die
1310 via appropriate busses or ports.
[0056] The IC die 1310 may be cooled in accordance with any of the
embodiments described herein. For example, a pump 1390 may
circulate a coolant (e.g., including water) through a cold plate
1340 proximate to the IC die 1310 and having at least one
microchannel to transport the coolant. Moreover, an arrangement to
reduce or prevent damage due to freezing may be provided in
accordance with any of the embodiments described above.
[0057] The system architecture shown in FIG. 13 is exemplary; other
system architectures may be employed.
[0058] The several embodiments described herein are solely for the
purpose of illustration. The various features described herein need
not all be used together, and any one or more of those features may
be incorporated in a single embodiment. Therefore, persons skilled
in the art will recognize from this description that other
embodiments may be practiced with various modifications and
alterations.
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