U.S. patent application number 14/262798 was filed with the patent office on 2015-10-08 for silicon-based heat-dissipation device for heat-generating devices.
The applicant listed for this patent is Gerald Ho Kim, Jay Eunjae Kim. Invention is credited to Gerald Ho Kim, Jay Eunjae Kim.
Application Number | 20150289416 14/262798 |
Document ID | / |
Family ID | 54211020 |
Filed Date | 2015-10-08 |
United States Patent
Application |
20150289416 |
Kind Code |
A1 |
Kim; Gerald Ho ; et
al. |
October 8, 2015 |
SILICON-BASED HEAT-DISSIPATION DEVICE FOR HEAT-GENERATING
DEVICES
Abstract
Embodiments of a silicon-based heat-dissipation device and an
apparatus including a silicon-based heat-dissipation device are
described. In one aspect, an apparatus includes a silicon-based
heat-dissipation device which includes a base portion and a
protrusion portion. The base portion has a first primary side and a
second primary side opposite the first primary side. The protrusion
portion is on the first primary side of the base portion and
protruding therefrom. The protrusion portion includes multiple
fins. Each of at least two immediately adjacent fins of the fins of
the protrusion portion has a tapered profile in a cross-sectional
view with a first width near a distal end of the respective fin
being less than a second width at a base of the respective fin near
the base portion of the heat-dissipation device.
Inventors: |
Kim; Gerald Ho; (Carlsbad,
CA) ; Kim; Jay Eunjae; (Bellevue, WA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kim; Gerald Ho
Kim; Jay Eunjae |
Carlsbad
Bellevue |
CA
WA |
US
US |
|
|
Family ID: |
54211020 |
Appl. No.: |
14/262798 |
Filed: |
April 27, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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14242879 |
Apr 2, 2014 |
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14262798 |
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Current U.S.
Class: |
361/709 ;
165/185 |
Current CPC
Class: |
H01L 23/3672 20130101;
H01L 2924/0002 20130101; F28F 21/00 20130101; F28F 21/089 20130101;
H01L 2924/0002 20130101; H01L 23/3738 20130101; H01L 2924/00
20130101; F28F 3/048 20130101; F28F 21/084 20130101; F28F 13/18
20130101; H01L 23/367 20130101; H05K 7/20418 20130101; F28F 21/085
20130101 |
International
Class: |
H05K 7/20 20060101
H05K007/20; F28F 21/00 20060101 F28F021/00; F28F 21/08 20060101
F28F021/08 |
Claims
1. An apparatus, comprising: a silicon-based heat-dissipation
device comprising: a base portion having a first primary side and a
second primary side opposite the first primary side; and a
protrusion portion on the first primary side of the base portion
and protruding therefrom, the protrusion portion comprising a
plurality of fins, wherein the second primary side of the base
portion is configured to accommodate one or more heat-generating
devices being embedded therein or physically coupled thereto to
dissipate at least a portion of heat generated by the one or more
heat-generating devices to the silicon-based heat-dissipation
device by conduction, wherein the base portion comprises a slit
that communicatively connects the first primary side and the second
primary side of the base portion, at least one portion of the slit
extending in a direction perpendicular to a direction in which the
plurality of fins extend, and wherein at least one fin of the
plurality of fins is dissected by the at least one portion of the
slit into two separate fins.
2. The apparatus of claim 1, wherein the slit partially separates a
first part of the base portion and a second part of the base
portion such that the first part of the base portion is connected
to the second part of the base portion near a first distal end of
the slit and near a second distal end of the slit which is opposite
the first distal end thereof.
3. The apparatus of claim 2, wherein, when each of more than one
heat-generating devices is embedded in or physically coupled to the
base portion, at least a first heat-generating device of the more
than one heat-generating devices is on a first side of the slit and
at least a second heat-generating device of the more than one
heat-generating devices is on a second side of the slit opposite
the first side of the slit such that the slit severs a direct-line
thermal coupling path via conduction through the base portion
between the first and the second heat-generating devices.
4. The apparatus of claim 1, wherein the slit comprises an L-shaped
slit.
5. (canceled)
6. The apparatus of claim 1, wherein the plurality of fins
comprises a plurality of straight fins.
7. The apparatus of claim 6, wherein a ratio of a height of the
fins, measured from the first primary side of the base portion in a
direction perpendicular to the first primary side, to a thickness
of each of the fins, measured across a respective one of the fins
in a direction parallel to the first primary side of the base
portion, is greater than 5:1.
8. The apparatus of claim 6, wherein a ratio of a height of the
fins, measured from the first primary side of the base portion in a
direction perpendicular to the first primary side, to a thickness
of the base portion, measured across the base portion in a
direction perpendicular to the first primary side of the base
portion, is greater than 5:1.
9. The apparatus of claim 6, wherein a spacing between every two
fins of the fins, measured between respective two fins of the fins
in a direction parallel to the first primary side of the base
portion, is greater than or equal to a thickness of each of the
fins, measured across a respective one of the fins in the direction
parallel to the first primary side of the base portion.
10. The apparatus of claim 1, wherein the plurality of fins
comprises a plurality of tapered fins.
11. The apparatus of claim 10, wherein at least a first fin of the
tapered fins has a tapered angle between a surface of the first fin
and a normal line perpendicular to a horizontal plane defined by
the first primary side of the base portion, and wherein the tapered
angle is less than or equal to 5 degrees and greater than 2
degrees.
12. The apparatus of claim 1, further comprising: a copper layer
coupled to the second primary side of the base portion, a thickness
of the copper layer being in a range of approximately 3 .mu.m to 30
.mu.m.
13. The apparatus of claim 2, further comprising: one or more
integrated circuits embedded in the second primary side of the base
portion or one or more electrically-driven devices physically
coupled to the second primary side of the base portion, wherein at
least a first one of the one or more integrated circuits or the one
or more electrically-driven devices is on a first side of the slit,
wherein at least a second one of the one or more integrated
circuits or the one or more electrically-driven devices is on a
second side of the slit opposite the first side of the slit, and
wherein the slit severs a direct-line thermal coupling path via
conduction through the base portion between the first one of the
one or more integrated circuits or the one or more
electrically-driven devices and the second one of the one or more
integrated circuits or the one or more electrically-driven
devices.
14. The apparatus of claim 1, wherein the silicon-based
heat-dissipation device is made from a blank silicon substrate of
single-crystal silicon, and wherein a ratio between a surface area
of the protrusion portion and a surface area of the blank silicon
substrate is in a range approximately between 5:1 and 40:1.
15. An apparatus, comprising: a silicon-based heat-dissipation
device comprising: a base portion having a first primary side and a
second primary side opposite the first primary side, the second
primary side configured to accommodate one or more heat-generating
devices being embedded therein or physically coupled thereto; and a
protrusion portion on the first primary side of the base portion
and protruding therefrom, the protrusion portion comprising a
plurality of fins, wherein the base portion comprises a slit that
communicatively connects the first primary side and the second
primary side of the base portion, wherein the slit partially
separates a first part of the base portion and a second part of the
base portion such that the first part of the base portion is
connected to the second part of the base portion near a first
distal end of the slit and near a second distal end of the slit
which is opposite the first distal end thereof, wherein each of at
least two immediately adjacent fins of the fins of the protrusion
portion has a tapered profile in a cross-sectional view with a
first width near a distal end of the respective fin being less than
a second width at a base of the respective fin near the base
portion of the heat-dissipation device, and wherein at least a
first fin of the tapered fins has a tapered angle between a surface
of the first fin and a normal line perpendicular to a horizontal
plane defined by the first primary side of the base portion, and
wherein the tapered angle is less than or equal to 5 degrees and
greater than 2 degrees.
16. The apparatus of claim 15, wherein at least one portion of the
slit extends in a direction perpendicular to a direction in which
the plurality of fins extend, and wherein at least one fin of the
plurality of fins is dissected by the at least one portion of the
slit into two separate fins.
17. (canceled)
18. The apparatus of claim 15, further comprising: a copper layer
coupled to the second primary side of the base portion, a thickness
of the copper layer being in a range of approximately 3 .mu.m to 30
.mu.m.
19. The apparatus of claim 15, further comprising: one or more
integrated circuits embedded in the second primary side of the base
portion or one or more electrically-driven devices physically
coupled to the second primary side of the base portion, wherein at
least a first one of the one or more integrated circuits or the one
or more electrically-driven devices is on a first side of the slit,
wherein at least a second one of the one or more integrated
circuits or the one or more electrically-driven devices is on a
second side of the slit opposite the first side of the slit, and
wherein the slit severs a direct-line thermal coupling path via
conduction through the base portion between the first one of the
one or more integrated circuits or the one or more
electrically-driven devices and the second one of the one or more
integrated circuits or the one or more electrically-driven
devices.
20. The apparatus of claim 15, wherein the silicon-based
heat-dissipation device is made from a blank silicon substrate of
single-crystal silicon, and wherein a ratio between a surface area
of the protrusion portion and a surface area of the blank silicon
substrate is in a range approximately between 5:1 and 40:1.
Description
CROSS REFERENCE TO RELATED PATENT APPLICATION
[0001] The present disclosure is continuation-in-part and claims
the priority benefit of U.S. patent application Ser. No.
14/242,879, filed on Apr. 2, 2014 and claiming the priority benefit
of U.S. Patent Application No. 61/807,655, filed on Apr. 2, 2013,
which applications are herein incorporated by reference.
TECHNICAL FIELD
[0002] The present disclosure generally relates to the field of
transfer of thermal energy and, more particularly, removal of
thermal energy from electrically-driven devices.
BACKGROUND
[0003] Unless otherwise indicated herein, the approaches described
in this section are not prior art to the claims in this application
and are not admitted to be prior art by inclusion in this
section.
[0004] There are many applications, ranging from consumer
electronics to telecommunications and the like, in which
electrically-driven devices (e.g., semiconductor-based integrated
circuits) capable of performing various tasks are packed in close
proximity in a small form factor to serve various needs. Such
electrically-driven devices may include, for example, driver
circuits, microprocessors, graphics processors, memory chips,
global positioning system (GPS) chips, communications chips, laser
diodes including edge-emitting lasers and vertical-cavity
surface-emitting lasers (VCSELs), light-emitting diodes (LEDs),
photodiodes, sensors, etc. Many of such electrically-driven devices
inevitably generate thermal energy, or heat, in operation and thus
are heat sources during operation as well as for a period of time
after power off. As the number and complexity of the
functionalities performed by such electrically-driven devices
continue to increase and as the distance between
electrically-driven devices in the small form factor continues to
decrease, heat generated by such electrically-driven devices, as
heat sources, present technical challenges that need to be
addressed.
[0005] For one thing, performance, useful lifespan, or both, of an
electrically-driven device may be significantly impacted if the
heat generated by the device is not adequately dissipated or
otherwise removed from the device. Moreover, in many present-day
applications, given the close proximity between two or more
electrically-driven devices on the same substrate, e.g., printed
circuit board (PCB), a phenomenon of thermal coupling between the
two or more devices in close proximity may occur and result in the
heat generated by one of the devices being transferred to one or
more adjacent devices. When thermal coupling occurs, at least a
portion of the heat generated by a first electrically-driven
devices is transferred to a second electrically-driven device in
close proximity due to temperature gradient, such that the
temperature of the second electrically-driven device rises to a
point higher than it would be when no heat is transferred from the
first electrically-driven device to the second electrically-driven
device. More specifically, when thermal coupling occurs and when no
adequate heat transfer mechanism exists, heat generated by
electrically-driven devices in close proximity may detrimentally
deteriorate the performance and useful lifespan of some or all of
the affected devices. As electrically-driven devices generate heat,
they are referred to as heat-generating devices hereinafter.
[0006] Metal heat sinks or radiators, based on copper or aluminum
for example, have been a dominant heat sink choice for electronics
or photonics applications. As the form factor of electronic
components (e.g., integrated circuits or IC) gets smaller it is
impractical to build a small metal heat sink with a large surface
area heat sink. Other problems associated with metal heat sinks
include, for example, difficulty in precision alignment in mounting
laser diode bars, VCSELs, LEDs or chips in laser diode/VCSEL/LED
cooling applications, issues with overall compactness of the
package, corrosion of the metallic material in water-cooled
applications, difficulty in manufacturing, high-precision
fabrication, electrical isolation, etc. Yet, increasing demand for
higher power density in small form factor motivates the production
of a compact cooling package with fewer or none of the
aforementioned issues. Moreover, conventional packages typically
use wire bonding to provide electrical power to the
electrically-driven device(s) being cooled, but wire bonding may
add cost and complexity in manufacturing and may be prone to
defects in addition to occupying space unnecessarily.
SUMMARY
[0007] Various embodiments disclosed herein pertain to a technique,
design, scheme, device and mechanism for isolation of thermal
ground for multiple heat-generating devices on a substrate.
[0008] According to one aspect of the present disclosure, an
apparatus may include a silicon-based heat-dissipation device. The
silicon-based heat-dissipation device may include a base portion
and a protrusion portion. The base portion may have a first primary
side and a second primary side opposite the first primary side. The
protrusion portion may be on the first primary side of the base
portion and may protrude therefrom. The second primary side of the
base portion may be configured to have one or more heat-generating
devices embedded therein or physically coupled thereto such that at
least a portion of heat generated by the one or more
heat-generating devices is dissipated to the silicon-based
heat-dissipation device by conduction. The silicon-based
heat-dissipation device may have a surface area such that, for
every 1 watt of power loading of the one or more heat-generating
devices, the surface area of the silicon-based heat-dissipation
device is in a range of approximately 400 mm.sup.2/watt to 2000
mm.sup.2/watt.
[0009] In at least one embodiment, the base portion may include a
slit that communicatively connects the first primary side and the
second primary side of the base portion.
[0010] In at least one embodiment, when each of more than one
heat-generating devices is embedded in or physically coupled to the
base portion, at least a first heat-generating device of the more
than one heat-generating devices may be on a first side of the slit
and at least a second heat-generating device of the more than one
heat-generating devices may be on a second side of the slit
opposite the first side of the slit such that the slit severs a
direct-line thermal coupling path via conduction through the base
portion between the first and the second heat-generating
devices.
[0011] In at least one embodiment, the slit may include an L-shaped
slit.
[0012] In at least one embodiment, the protrusion portion of the
silicon-based heat-dissipation device may include a plurality of
fins.
[0013] In at least one embodiment, the plurality of fins may
include a plurality of straight fins.
[0014] In at least one embodiment, a ratio of a height of the fins,
measured from the first primary side of the base portion in a
direction perpendicular to the first primary side, to a thickness
of each of the fins, measured across a respective one of the fins
in a direction parallel to the first primary side of the base
portion, may be greater than 5:1.
[0015] In at least one embodiment, a ratio of a height of the fins,
measured from the first primary side of the base portion in a
direction perpendicular to the first primary side, to a thickness
of the base portion, measured across the base portion in a
direction parallel to the first primary side of the base portion,
may be greater than 5:1.
[0016] In at least one embodiment, a spacing between every two fins
of the fins, measured between respective two fins of the fins in a
direction parallel to the first primary side of the base portion,
may be greater than or equal to a thickness of each of the fins,
measured across a respective one of the fins in the direction
parallel to the first primary side of the base portion.
[0017] In at least one embodiment, the plurality of fins may
include a plurality of tapered fins.
[0018] In at least one embodiment, at least a first fin of the
tapered fins may have a tapered angle between a surface of the
first fin and a normal line perpendicular to a horizontal plane
defined by the first primary side of the base portion. The tapered
angle may be less than or equal to 5 degrees.
[0019] In at least one embodiment, the apparatus may further
include a copper layer coupled to the second primary side of the
base portion with a thickness of the copper layer being in a range
of approximately 3 .mu.m to 30 .mu.m.
[0020] In at least one embodiment, the apparatus may further
include one or more integrated circuits embedded in the second
primary side of the base portion or one or more electrically-driven
devices physically coupled to the second primary side of the base
portion. At least a first one of the one or more integrated
circuits or the one or more electrically-driven devices may be on a
first side of the slit. At least a second one of the one or more
integrated circuits or the one or more electrically-driven devices
may be on a second side of the slit opposite the first side of the
slit. The slit may sever a direct-line thermal coupling path via
conduction through the base portion between the first one of the
one or more integrated circuits or the one or more
electrically-driven devices and the second one of the one or more
integrated circuits or the one or more electrically-driven
devices.
[0021] In at least one embodiment, the silicon-based
heat-dissipation device may be made from a blank silicon substrate
of single-crystal silicon. The protrusion portion may have a
surface area of approximately 5 mm.sup.2 to 40 mm.sup.2 surface
area of the protrusion portion per 1 mm.sup.2 surface area of a
blank silicon substrate from which the silicon-based
heat-dissipation device is made.
[0022] According to another aspect, an apparatus may include a
silicon-based heat-dissipation device. The silicon-based
heat-dissipation device may include a base portion and a protrusion
portion. The second primary side may be configured to have one or
more heat-generating devices embedded therein or physically coupled
thereto. The base portion may have a first primary side and a
second primary side opposite the first primary side. The protrusion
portion may be on the first primary side of the base portion and
protruding therefrom. The protrusion portion may include a
plurality of fins. Each of at least two immediately adjacent fins
of the fins of the protrusion portion may have a tapered profile in
a cross-sectional view with a first width near a distal end of the
respective fin being less than a second width at a base of the
respective fin near the base portion of the heat-dissipation
device. The silicon-based heat-dissipation device may have a
surface area such that, for every 1 watt of power loading of the
one or more heat-generating devices, the surface area of the
silicon-based heat-dissipation device is in a range of
approximately 400 mm.sup.2/watt to 2000 mm.sup.2/watt.
[0023] In at least one embodiment, the second primary side of the
base portion may be configured to have one or more heat-generating
devices embedded therein or physically coupled thereto such that at
least a portion of heat generated by the one or more
heat-generating devices is dissipated to the silicon-based
heat-dissipation device by conduction.
[0024] In at least one embodiment, at least a first fin of the
tapered fins may have a tapered angle between a surface of the
first fin and a normal line perpendicular to a horizontal plane
defined by the first primary side of the base portion. The tapered
angle may be less than or equal to 5 degrees.
[0025] In at least one embodiment, the apparatus may further
include a copper layer coupled to the second primary side of the
base portion with a thickness of the copper layer being in a range
of approximately 3 .mu.m to 30 .mu.m.
[0026] In at least one embodiment, the apparatus may further
include one or more integrated circuits embedded in the second
primary side of the base portion or one or more electrically-driven
devices physically coupled to the second primary side of the base
portion. The base portion may include a slit that communicatively
connects the first primary side and the second primary side of the
base portion. At least a first one of the one or more integrated
circuits or the one or more electrically-driven devices may be on a
first side of the slit. At least a second one of the one or more
integrated circuits or the one or more electrically-driven devices
may be on a second side of the slit opposite the first side of the
slit. The slit may sever a direct-line thermal coupling path via
conduction through the base portion between the first one of the
one or more integrated circuits or the one or more
electrically-driven devices and the second one of the one or more
integrated circuits or the one or more electrically-driven
devices.
[0027] In at least one embodiment, the silicon-based
heat-dissipation device may be made from a blank silicon substrate
of single-crystal silicon. The protrusion portion may have a
surface area of approximately 5 mm.sup.2 to 40 mm.sup.2 surface
area of the fins per 1 mm.sup.2 surface area of a blank silicon
substrate from which the silicon-based heat-dissipation device is
made.
[0028] The foregoing summary is illustrative only and is not
intended to be in any way limiting. In addition to the illustrative
aspects, embodiments, and features described above, further
aspects, embodiments, and features will become apparent by
reference to the drawings and the following detailed
description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] The accompanying drawings are included to provide a further
understanding of the disclosure, and are incorporated in and
constitute a part of the present disclosure. The drawings
illustrate embodiments of the disclosure and, together with the
description, serve to explain the principles of the disclosure. It
is appreciable that the drawings are not necessarily in scale as
some components may be shown to be out of proportion than the size
in actual implementation in order to clearly illustrate the concept
of the present disclosure.
[0030] FIG. 1 is a partial cross-sectional view of a
heat-dissipation device in accordance with an embodiment of the
present disclosure.
[0031] FIG. 2 is a partial cross-sectional view of a
heat-dissipation device in accordance with an embodiment of the
present disclosure.
[0032] FIG. 3 is a partial cross-sectional view of a
heat-dissipation device in accordance with an embodiment of the
present disclosure.
[0033] FIG. 4 is a perspective view of a heat-dissipation device in
accordance with an embodiment of the present disclosure.
[0034] FIG. 5 is a partial cross-sectional view of the
heat-dissipation device of FIG. 4.
[0035] FIG. 6 is a perspective top view of a device in accordance
with an embodiment of the present disclosure.
[0036] FIG. 7 is a perspective bottom view of the device of FIG.
6.
[0037] FIG. 8 is a side view of the device of FIG. 6.
[0038] FIG. 9 is a perspective top view of a device in accordance
with another embodiment of the present disclosure.
[0039] FIG. 10 is a perspective bottom view of the device of FIG.
9.
[0040] FIG. 11 is a chart showing the surface area of a silicon fin
structure of a silicon-based heat-dissipation device versus the
temperature of the silicon-based heat-dissipation device.
[0041] FIG. 12 is a perspective view of a heat-dissipation device
in accordance with another embodiment of the present
disclosure.
[0042] FIG. 13 is a partial cross-sectional view of the
heat-dissipation device of FIG. 12.
[0043] FIG. 14 is a perspective view of a heat-dissipation device
in accordance with yet another embodiment of the present
disclosure.
[0044] FIG. 15 is a partial cross-sectional view of the
heat-dissipation device of FIG. 14.
[0045] FIG. 16 is a perspective view of a blank silicon substrate
used to fabricate a heat-dissipation device in accordance with an
embodiment of the present disclosure.
[0046] FIG. 17 is a top perspective view of a heat-dissipation
device utilizing a silicon substrate etched with fins in accordance
with an embodiment of the present disclosure.
[0047] FIG. 18 is a bottom perspective view of the heat-dissipation
device of FIG. 17.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Overview
[0048] A compact heat sink or radiator built with silicon-based
material provide a compact and highly efficient heat sink for all
electronics applications such as driver circuits, microprocessors,
graphics processors, memory chips, GPS chips, communications chips,
laser diodes including edge-emitting lasers and VCSELs, LEDs,
photodiodes, sensors, etc. One advantage of a silicon-based heat
sink or radiator is that it can have a surface area more than ten
times that of a typical metal-based heat sink or radiator which may
be fabricated by extrusion, stamping or machining process. Besides,
the surface quality of the silicon fins of a silicon-based heat
sink or radiator can reach an optically polished quality surpassing
the surface quality of conventional metal-based heat sinks and
radiators. A silicon-based heat sink or radiator does not corrode
or become tarnished in atmosphere due to elements of the
environment. In contrast, metal-based heat sinks and radiators tend
to foul and/or corrode over time. The aforementioned advantages
enhance the reliability and thermal dissipation efficiency of
silicon-based heat sinks and radiators.
Illustrative Implementations
[0049] Each of FIGS. 1-3 respectively illustrates a partial
cross-sectional view of a silicon-based heat-dissipation device in
accordance with an embodiment of the present disclosure. FIG. 4
illustrates a silicon-based heat-dissipation device 101 in
accordance with an embodiment of the present disclosure. FIG. 5
illustrates dimensions associated with the silicon-based
heat-dissipation device of FIG. 4. The following description refers
to FIGS. 1-5.
[0050] Each of FIGS. 1-3 illustrates a respective embodiment of a
cross-sectional view of a fin structure of multiple straight fins
of a silicon-based heat-dissipation device 101. Due to efficient
thermal performance and compact structure of the silicon-based
heat-dissipation device 101, a surface area at least ten times that
of a typical metal-based heat sink or radiator to interact with air
or air-sol cooling can be achieved.
[0051] As shown in FIG. 1, in one embodiment, a fin structure 51 of
multiple straight fins of silicon-based heat dissipation device 101
includes a protrusion portion 51a and a base portion 51b. The
protrusion portion 51a has a number of fins protruding from a
horizontal plane 51c defined by the base portion 51b. Fins of fin
structure 51 have substantially straight and parallel sidewalls.
That is, in fin structure 51, a surface of a sidewall of a given
one of the fins is substantially parallel to a surface of an
opposing sidewall of an immediately adjacent fin. Further, a
surface of a sidewall of a given one of the fins is substantially
perpendicular to the horizontal plane 51c. Moreover, as shown in
FIG. 1, trenches, i.e., where the protrusion portion 51a come in
contact with the base portion 51b, of fin structure 51 are
relatively flat or horizontal with respect to the horizontal plane
51c.
[0052] As shown in FIG. 2, in one embodiment, a fin structure 52 of
multiple straight fins of silicon-based heat dissipation device 101
includes a protrusion portion 52a and a base portion 52b. The
protrusion portion 52a has a number of fins protruding from a
horizontal plane 52c defined by the base portion 52b. Fins of fin
structure 52 have sloped or tapered sidewalls. That is, in fin
structure 52, a surface of a sidewall of a given one of the fins is
not parallel to a surface of an opposing sidewall of an immediately
adjacent fin. Further, a surface of a sidewall of a given one of
the fins is not perpendicular to the horizontal plane 52c.
Referring to FIG. 2, due to the sidewalls of the fins of protrusion
portion 52a being sloped or tapered, a spacing, or gap, between
every two immediately adjacent fins of protrusion portion 52a
increases in a direction moving from base portion 52b toward the
distal ends of the fins of protrusion portion 52a. In other words,
due to the sloped or tapered sidewalls, a spacing or gap between
every two immediately adjacent fins is wider near the distal ends
of the fins (e.g., at the top as shown in FIG. 2) than it is near
the base of the fins (e.g., near the base portion 52b as shown in
FIG. 2). Put differently, given the sloped or tapered sidewalls,
each of one or more fins of the protrusion portion 52a has a
tapered profile in a cross-sectional view (as shown in FIG. 2) with
a first width near the distal end of the respective fin being less
than a second width at the base of the respective fin near the base
portion 52b. Moreover, as shown in FIG. 2, trenches, i.e., where
the protrusion portion 52a come in contact with the base portion
52b, of fin structure 52 may be relatively flat or horizontal with
respect to the horizontal plane 52c. Alternatively, although not
shown in FIG. 2, the trenches of fin structure 52 may be notched,
e.g., shaped as V-shaped notches as those shown in FIG. 3.
[0053] Compared with the fin structure 51 of FIG. 1, fin structure
52 of FIG. 2 tends to improve the aerodynamics for better heat
transfer via convection by a fluid, e.g., air blown by one or more
fans, flowing between the fins. When temperature in the fins rises
and the fluid between the fins, whether flowing through or
stagnant, will be warmed up. Fin structure 51 of FIG. 1 tends to
have relatively less efficiency in heat transfer from the fins to
the fluid, e.g., air, at least for the corner air at the bottom of
the trenches in terms of pushing the air out of the protrusion
portion 51a. In contrast, fin structure 52 of FIG. 2 tends to have
relatively more efficiency in pushing air out of the bottom of the
trenches to come out of the protrusion portion 52a. The difference
in efficiency is in the order of several percentage points.
[0054] As shown in FIG. 3, in one embodiment, a fin structure 53 of
multiple straight fins of silicon-based heat dissipation device 101
includes a protrusion portion 53a and a base portion 53b. The
protrusion portion 53a has a number of fins protruding from a
horizontal plane 53c defined by the base portion 53b. Fins of fin
structure 53 have substantially straight and parallel sidewalls.
That is, in fin structure 53, a surface of a sidewall of a given
one of the fins is substantially parallel to a surface of an
opposing sidewall of an immediately adjacent fin. Further, a
surface of a sidewall of a given one of the fins is substantially
perpendicular to the horizontal plane 53c. Moreover, as shown in
FIG. 3, trenches, i.e., where the protrusion portion 53a come in
contact with the base portion 53b, of fin structure 53 are not flat
or horizontal with respect to the horizontal plane 53c. Rather,
different from fin structure 51 of FIG. 1, the trenches of fin
structure 53 are notched, e.g., shaped as V-shaped notches as those
shown in FIG. 3.
[0055] Fin structure 53 of FIG. 3 tends to have better heat
dissipation performance than that of fin structure 51 of FIG. 1,
but worse than that of fin structure 52 of FIG. 2 due to
aerodynamics, assuming each of fin structures 51, 52 and 53 has the
same amount of surface area for the sidewalls of the fins.
[0056] The silicon-based heat-dissipation device 101 shown in FIG.
4 can be fabricated from a piece of single-crystal silicon by
etching various structural shapes as shown in FIGS. 1-3. As shown
in FIG. 4, the silicon-based heat-dissipation device 101 has a base
portion 2 and a protrusion portion 1. The base portion 2 has a
first primary side (e.g., the side that faces up in FIG. 4) and a
second primary side (e.g., the side that faces down in FIG. 4)
opposite the first primary side. The protrusion portion 1 of the
silicon-based heat-dissipation device 101 is on the first primary
side of the base portion 2 and protrudes therefrom. In the example
shown in FIG. 4, the protrusion portion 1 includes multiple
straight fins. The multiple straight fins of the protrusion portion
1 may be spaced apart from each other by an equidistant spacing 11.
Additionally or alternatively, the protrusion portion 1 may include
pin fins and/or flared fins.
[0057] As shown in FIG. 5, there are several dimensions associated
with the silicon-based heat-dissipation device 101. T1 denotes a
thickness of the base portion 2 that is measured across the base
portion 2 in a direction parallel to the first primary side of the
base portion 2. T2 denotes a height of the protrusion portion 1, or
the fins of the protrusion portion 1, that is measured from the
first primary side of the base portion 2 in a direction
perpendicular to the first primary side of the base portion 2. T3
denotes a width of the spacing 11 between every two adjacent fins
of the protrusion portion 1. T4 denotes a thickness of each of the
fins of the protrusion portion 1, measured across a respective one
of the fins in a direction parallel to the first primary side of
the base portion 2.
[0058] In one embodiment, the ratio T2:T4 is a large number in
order to increase the surface area of the silicon-based
heat-dissipation device 101 in a small footprint of silicon base.
In order to achieve a high convective cooling in the silicon-based
heat-dissipation device 101, the ratio of T2:T4 is greater than
5:1. Similarly, the ratio T2:T1 is greater than 5:1. Moreover, in
one embodiment, T3 is greater than or equal to T4. These dimensions
and ratios provide an optimum performance of the silicon-based
heat-dissipation device 101. For example, if each of the dimensions
T3 and T4 is 100 microns with T2 being 500 microns and T1 being 100
microns, then the silicon-based heat-dissipation device 101 would
have a large amount of surface area in a compact form factor.
However, air flow through the spacing 11 between every two adjacent
fins of the protrusion portion 1 may be restricted due to small
gap, T3 to ineffectively remove all heat from silicon fin. To
maximize thermal convection by air flow through the spacing 11
between every two adjacent fins of the protrusion portion 1, in
various implementations the dimension T3 and air speed can be
increased to achieve quick removal of heat from the fins of the
silicon-based heat-dissipation device 101.
[0059] FIGS. 6-8 illustrate a device 100 in accordance with an
embodiment of the present disclosure. The following description
refers to FIGS. 6-8.
[0060] FIG. 6 shows the device 100 which is a monolithic structure
of IC chip or Silicon-On-Insulator (SOI) combined with the
silicon-based heat-dissipation device 101. Typically integrated
circuits are developed or laid-down on a primary side of a silicon
wafer, and then the backside of the silicon wafer opposite the
primary side is lapped to make a thin silicon IC chip. In one
embodiment, the silicon-based heat-dissipation device 101 is built
or attached to the backside of the IC or SOI chip to increase the
heat dissipation by increasing the surface area of the existing
backside of the IC or SOI structure. The silicon-based
heat-dissipation device 101 built on the backside of the IC or SOI
chip provides more than ten times (10.times.) of surface area to
dissipate heat from the integrated circuits by convection or forced
air, compared to conventional metal-based heat sinks or
radiators.
[0061] As shown in FIGS. 7 and 8, each of heat-generating devices
21-25 is embedded in or physically coupled, mounted or otherwise
attached to the second primary side of the base portion 2. Each of
heat-generating devices 23 and 25 may be an embedded or doped
integrated circuit while each of heat-generating devices 21, 22 and
24 may be a driver chip, microprocessor, graphics processor, memory
chip, GPS chip, communications chip, laser diode (edge-emitting or
VCSEL), LED, photodiode, sensor or the like. Regardless what the
case may be, each of heat-generating devices 21-25 generates heat
when powered on for which heat needs to be removed to prolong the
operational life and enhance the performance of the heat-generating
devices 21-25. One of ordinary skill in the art would appreciate
that, although multiple heat-generating devices are shown in FIGS.
7 and 8, in various embodiments the number of heat-generating
devices may be more or less depending on the actual
implementation.
[0062] FIGS. 9 and 10 illustrate a device 200 in accordance with
another embodiment of the present disclosure. The following
description refers to FIGS. 9 and 10.
[0063] The device 200 and the device 100 are similar in many ways.
In the interest of brevity, detailed description of differences
between the device 200 and the device 100 is provided herein while
similarity therebetween is not repeated. As shown in FIGS. 9 and
10, the device 200 includes a silicon-based heat-dissipation device
102 that has a base portion 6 and a protrusion portion 5. The base
portion 6 has a first primary side and a second primary side
opposite the first primary side. The protrusion portion 5 is on the
first primary side of the base portion 6 and protrudes therefrom.
The protrusion portion 5 may include multiple fins similar to those
of the protrusion portion 1 of the silicon-based heat-dissipation
device 101, and thus detailed description thereof is not
repeated.
[0064] The silicon-based heat-dissipation device 102 includes a
slit 12 on the base portion 6 that cuts off, or severs, a
direct-line thermal coupling path via conduction through the base
portion 6 between a first heat-generating device on one side of the
slit 12 and a second heat-generating device on the other side of
the slit 12. In one embodiment, the slit 12 is an L-shaped slit as
shown in FIGS. 9 and 10. In other embodiments, instead of a slit,
the base portion 6 includes a trench or groove on its first primary
side or second primary side.
[0065] In the example shown in FIG. 10, each of heat-generating
devices 26-29 is embedded in or physically coupled, mounted or
otherwise attached to the second primary side of the base portion
6. As shown in FIG. 10, the heat-generating device 26 is on one
side of the L-shaped slit 12 while the heat-generating devices
26-28 are on the other side the L-shaped slit 12. The slit 12
provides the function of severing a direct-line thermal coupling
path via conduction through the base portion 6 between the
heat-generating device 26 and each of the heat-generating devices
27-29. This way, the absolute temperature of each of the
heat-generating device 27-29 can be lowered. This arrangement may
be suitable, for example, when the heat-generating device 26 (e.g.,
a microprocessor) generates more heat than each of the
heat-generating devices 27-29 during operation. The silicon-based
heat-dissipation device 102 may be fabricated on the backside of an
IC or SOI chip.
[0066] Metal heat sinks built with aluminum or copper are designed
with its physical geometry of fins and base structure to
efficiently dissipate heat into the surrounding of the heat sink by
forced-air convection or natural convection. The optimum
performance of a metal heat sink can be designed based on the
density of the fins and the base structure. Advantageously, a heat
sink built with silicon material in accordance with the present
disclosure adds a distinctive advantage of a high-density fin
design with very smooth surface finish. The present disclosure
provides preferred design parameters, obtained from a designed
experiment, that optimize the design of silicon-based
heat-dissipation devices to provide an optimum performance of
various embodiments of the silicon-based heat-dissipation devices
in accordance with the present disclosure.
[0067] Various embodiments of the silicon-based heat-dissipation
device of the present disclosure may be fabricated with
high-density fin configuration, meaning many silicon fins are
closely packed so that a large surface area is created to
effectively dissipate heat into the surrounding by natural
convection. On one hand, if the silicon fins are too densely
packed, the air convection between the silicon fins would tend to
fail to dissipate the heat. The present disclosure provides an
optimum silicon fin spacing to efficiently dissipate the heat via
natural convection. On the other hand, a loose silicon fin
configuration improves the effectiveness of natural convection, but
the surface area of the loose silicon fin configuration would tend
to have degraded thermal performance.
[0068] Through numerous experiments, inventors of the present
disclosure discovered that an optimal range of the silicon fin
surface area to heat loading is in a range of approximately 400
mm.sup.2/watt to 2000 mm.sup.2/watt. If the silicon fin surface
area per heat loading is below 400 mm.sup.2/watt then the
silicon-based heat-dissipation device would not provide much
advantage over a conventional copper or aluminum heat sink having a
loose fin configuration. If the silicon fin surface area per heat
loading is above 2000 mm.sup.2/watt with a sufficient separation
between silicon fins, the silicon fins may become too thin for
mechanical stability and reliability of the silicon fins. At the
surface power level of 2000 mm.sup.2/watt a thickness of a silicon
fin below 50 microns (.mu.m) may be structurally too fragile.
[0069] In one experiment, the pitch of the silicon fins (i.e., the
distance from the tip of a silicon fin to the tip of an immediately
adjacent silicon fin, or the distance from one side of a silicon
fin to the same side of an immediately adjacent silicon fin) is
fixed at 600 .mu.m and the thickness of each silicon fin is varied
to be 225 .mu.m, 300 .mu.m or 375 .mu.m. The silicon fins are
etched to be approximately 475 .mu.m deep in 525 .mu.m-thick
mono-crystal silicon with the above-listed various silicon fin
thicknesses. The total surface area of the fin structure is not
changed with the silicon fins having the above-listed silicon fin
thicknesses. The experiment test result shows very slight change in
the thermal performance of these designs and the actual tested
silicon heat sink structure with the temperature loaded with 0.5
watt as shown in the Table 1 below.
TABLE-US-00001 Silicon Heat Pitch Thick- Sink Surface Area Silicon
Heat (P1) ness Dimension Gap per 1 watt of Sink in (X1) in W
.times. L .times. (Y1) heat loading Temperature mm mm H (in mm) in
mm (mm.sup.2/watt) (.degree. C.) 0.6 0.225 10 .times. 10 .times.
0.525 0.375 520 65.6 0.6 0.300 10 .times. 10 .times. 0.525 0.300
520 65.8 0.6 0.375 10 .times. 10 .times. 0.525 0.225 520 64.3
[0070] In another experiment, the thickness of each silicon fin is
fixed at 150 .mu.m and the pitch between every two neighboring
silicon fins is varied to be 300 .mu.m, 600 .mu.m, 900 .mu.m or
1200 .mu.m. In this case the silicon fin density (same as surface
area) is changed dramatically by the pitch. The experiment shows
the temperature of silicon heat sink dramatically drops as the
surface area per power reaches above 400 mm.sup.2/watt and the
temperature drops down slowly after 400 mm.sup.2/watt level, with
the drop in temperature flattens out around 2000 mm.sup.2/watt.
Table 2 below shows the design parameters in this experiment.
TABLE-US-00002 Pitch Thick- Silicon Heat Surface Area Silicon Heat
(P1) ness Sink Dimension Gap per 1 watt of Sink in (X1) in W
.times. L .times. (Y1) heat loading Temperature mm mm H (in mm) in
mm (mm.sup.2/1 watt) (.degree. C.) 0.300 0.05 10 .times. 10 .times.
1.2 0.25 1124 72.0 0.300 0.15 10 .times. 10 .times. 0.525 0.15 860
77.5 0.600 0.15 10 .times. 10 .times. 0.525 0.45 520 77.4 1.200
0.15 10 .times. 10 .times. 0.525 1.05 360 90.3
[0071] FIG. 11 is a chart showing the surface area of a silicon fin
structure of a silicon-based heat-dissipation device versus the
temperature of the silicon-based heat-dissipation device. As shown
in FIG. 11, temperature of the silicon heat sink drops relatively
fast until approximately 400 mm.sup.2/watt and the fitted curve
flattens out around 1200 mm.sup.2/watt and beyond. Thus, the
optimum design of the silicon-based heat-dissipation device may be
estimated to be in the range of approximately 400 mm.sup.2/watt to
2000 mm.sup.2/watt for a given power loading of a heat-generating
device from which the silicon-based heat-dissipation device is to
remove heat. That is, for every 1 watt of power loading of the
heat-generating device from which heat is to be dissipated,
optimally the surface area of the silicon-based heat-dissipation
device is in the range of approximately 400 mm.sup.2/watt to 2000
mm.sup.2/watt.
[0072] FIG. 12 is a perspective view of a silicon-based
heat-dissipation device 801 in accordance with another embodiment
of the present disclosure. FIG. 13 is a partial cross-sectional
view of the silicon-based heat-dissipation device 801.
[0073] As shown in FIGS. 12 and 13, silicon-based heat-dissipation
device 801 utilizes fin structure 51 with dimensions of width W1,
length L1 and height H1, and a volume defined by
W1.times.L1.times.H1. Silicon-based heat-dissipation device 801
includes a silicon protrusion portion 81 and a silicon base portion
82, with protrusion portion 81 on and protruding from a first
primary side of base portion 82. Protrusion portion 81 includes a
number of fins and has a height Z1. Each fin of protrusion portion
81 has a thickness X1. Base portion 82 has a thickness of Z2. The
total thickness of silicon-based heat-dissipation device 801 is H1,
with H1=Z1+Z2. The fins of protrusion portion 81 has a pitch P1 and
a gap Y1 between every two immediately adjacent or neighboring fins
of protrusion portion 81.
[0074] For efficient heat dissipation by natural convection, gap Y1
needs to be sufficiently wide enough for air to flow through.
However, the narrower the gap Y1 the more the surface area of
silicon-based heat-dissipation device 801 would be, but the thermal
performance of silicon-based heat-dissipation device 801 would be
reduced. The optimum performance of silicon-based heat-dissipation
device 801 for natural convection depends on a proper thickness X1
and gap Y1 of the fins of protrusion portion 81 as well as the
thickness Z2 of base portion 82. In one embodiment, the thickness
X1 of each fin of protrusion portion 81 is in the range of 0.030 mm
to 1 mm depending on the size of silicon-based heat-dissipation
device 801. In one embodiment, the aspect ratio (Z1/Y1) is greater
than 1. In one embodiment, the ratio of Z1/Z2 is greater than
1.
[0075] One metric for thermal performance of a silicon heat sink,
such as silicon-based heat-dissipation device 801 for example, is
found to be expressed in terms of a surface area per loaded heat
power. Referring to the chart in FIG. 11, a silicon heat sink
according to the present disclosure performs very effectively for
values greater than 400 mm.sup.2/watt. For instance, for any IC
chip dissipating 1 watt of heat, the surface area of the silicon
heat sink (e.g., silicon-based heat-dissipation device 801) is
preferably greater than 400 mm.sup.2. Accordingly, silicon-based
heat-dissipation device 801 is preferably built to satisfy the
following dimensional requirements. The thickness X1 of each fin of
protrusion portion 81 satisfies the requirement of 0.030
mm<X1<1 mm. The ratio of Z1/Y1 satisfies the requirement of
0.5<Z1/Y1. The ratio of Z1/Z2 satisfies the requirement of
Z1/Z2>0.5. For example, for a 1-watt IC chip silicon-based
heat-dissipation device 801 may be built with the following
dimensions: X1=0.05 mm, Y1=0.250 mm, Z1=0.450 mm, Z2=0.050 mm,
L1=15 mm, W1=15 mm and H1=0.5 mm. With pitch P1 being 0.3 mm, this
design would have almost a quantity of 50 fins in the protrusion
portion 81 configured in the total size of 15 mm.times.15
mm.times.0.5 mm of silicon-based heat-dissipation device 801. The
surface area of the topside of protrusion portion 81 is calculated
to be 900 mm.sup.2 and it meets all requirements of the design of
silicon-based heat-dissipation device 801 that is empirically
optimized. Preferably, regardless of the power loading of the
heat-generating device silicon-based heat-dissipation device 801 is
attached to, dimensional parameters of silicon-based
heat-dissipation device 801 satisfy the requirement of being in the
range of approximately 400 mm.sup.2/watt to 2000 mm.sup.2/watt for
a given power loading of a heat-generating device from which the
silicon heat sink is to remove heat.
[0076] FIG. 14 is a perspective view of a silicon-based
heat-dissipation device 802 in accordance with another embodiment
of the present disclosure. FIG. 15 is a partial cross-sectional
view of the silicon-based heat-dissipation device 802.
[0077] As shown in FIGS. 14 and 15, silicon-based heat-dissipation
device 802 utilizes fin structure 52 with dimensions of width W2,
length L2 and height H2, and a volume defined by
W2.times.L2.times.H2. Silicon-based heat-dissipation device 802
includes a silicon protrusion portion 85 and a silicon base portion
86, with protrusion portion 85 on and protruding from a first
primary side of base portion 86. Protrusion portion 85 includes a
number of fins and has a height Z3. Each fin of protrusion portion
81 is a tapered fin, with a thickness X2 at its base and a smaller
thickness at its distal end or tip. The amount of taper of each fin
is measured by a tapered angle Q between the tapered surface of the
fin and a normal line perpendicular to a horizontal plane defined
by the first primary side of base portion 86 from which protrusion
portion 85 protrudes out, as shown in FIG. 15. With tapered fins,
silicon-based heat-dissipation device 802 has a slightly improved
thermal performance compared to that of silicon-based
heat-dissipation device 801 due to a better convection property
under natural convection and forced-air convection. Preferably, the
tapered angle Q is not too large and. In one embodiment, the
tapered angle Q is less than or equal to 5 degrees. In one
embodiment, the tapered angle Q is greater than or equal to 3
degrees and less than or equal to 5 degrees, or 3
degrees.ltoreq.Q.ltoreq.5 degrees. Base portion 86 has a thickness
of Z4. The total thickness of silicon-based heat-dissipation device
802 is H2, with H2=Z3+Z4. The fins of protrusion portion 85 has a
pitch P2 and a gap Y2 between every two immediately adjacent or
neighboring fins of protrusion portion 85.
[0078] For efficient heat dissipation by natural convection, gap Y2
needs to be sufficiently wide enough for air to flow through.
However, the narrower the gap Y2 the more the surface area of
silicon-based heat-dissipation device 802 would be, but the thermal
performance of silicon-based heat-dissipation device 802 would be
reduced. The optimum performance of silicon-based heat-dissipation
device 801 for natural convection depends on a proper thickness X1
and gap Y2 of the fins of protrusion portion 82 as well as the
thickness Z4 of base portion 86. In one embodiment, the thickness
X2 of each fin of protrusion portion 85 is in the range of 0.030 mm
to 1 mm depending on the size of silicon-based heat-dissipation
device 802. In one embodiment, the aspect ratio (Z3/Y2) is greater
than 1. In one embodiment, the ratio of Z3/Z4 is greater than 1.
Preferably, regardless of the power loading of the heat-generating
device silicon-based heat-dissipation device 802 is attached to,
dimensional parameters of silicon-based heat-dissipation device 801
satisfy the requirement of being in the range of approximately 400
mm.sup.2/watt to 2000 mm.sup.2/watt for a given power loading of a
heat-generating device from which the silicon heat sink is to
remove heat.
[0079] FIG. 16 is a perspective view of a blank silicon substrate
901 used to fabricate a heat-dissipation device in accordance with
an embodiment of the present disclosure. FIG. 17 is a top
perspective view of a silicon-based heat-dissipation device 902
utilizing a silicon substrate etched with fins in accordance with
an embodiment of the present disclosure. FIG. 18 is a bottom
perspective view of silicon-based heat-dissipation device 902.
[0080] As shown in FIG. 16, blank silicon substrate 901 has
dimensions of width W3, length L3 and height H3, and a volume
defined by W3.times.L3.times.H3. Blank silicon substrate 901 may be
made of single-crystal silicon. Blank silicon substrate 901 may be
used to fabricate, e.g., by wet etch or dry etch, the silicon-based
heat-dissipation device 902 of FIGS. 17 and 18. Silicon-based
heat-dissipation device 902 may utilize fin structure 51, 52 or 53,
although for simplicity fin structure 51 is depicted in
silicon-based heat-dissipation device 902 in FIGS. 17 and 18.
Moreover, silicon-based heat-dissipation device 902 may represent
any of silicon-based heat-dissipation devices 101, 102, 801 and 802
described above. That is, some or all of the features described
herein regarding silicon-based heat-dissipation device 902 may be
applicable to any of silicon-based heat-dissipation devices 101,
102, 801 and 802.
[0081] As shown in FIGS. 17 and 18, silicon-based heat-dissipation
device 902 has dimensions of width W4, length L4 and height H4, and
a volume defined by W4.times.L4.times.H4. In the case that
silicon-based heat-dissipation device 902 is formed by etching the
blank silicon substrate 901 of FIG. 16, the dimensions W4, L4 and
H4 may be the same as dimensions W3, L3 and H3. Silicon-based
heat-dissipation device 902 includes a silicon protrusion portion
91 and a silicon base portion 92, with protrusion portion 91 on and
protruding from a first primary side of base portion 92. Protrusion
portion 91 includes a number of fins.
[0082] With reference to FIGS. 16-18, another metric that defines
the dimensional requirements to achieve optimum thermal performance
relates to the amount of surface area of the fins of protrusion
portion 91 to the footprint area of blank silicon substrate 901,
which is used to fabricate silicon-based heat-dissipation device
902. Given q=hA.DELTA.T, the increase in surface area due to the
etching of blank silicon substrate 901 to form the fins of
protrusion portion 91 of silicon-based heat-dissipation device 902
is preferably in a range of approximately 500 mm.sup.2 to 4000
mm.sup.2 surface area of cooling fins per 10 mm.times.10 mm silicon
blank surface area. That is, preferably, the protrusion portion 91
of silicon-based heat-dissipation device 902 has a surface area of
approximately 5 mm.sup.2 to 40 mm.sup.2 surface area of cooling
fins per 1 mm.sup.2 surface area of blank silicon substrate 901.
This is applicable to both natural convection and forced-air
convection. Existing fabrication technologies of metal heat sinks
can achieve up to about 4 to 5 mm.sup.2 surface area of cooling
fins per 1 mm.sup.2 surface area of bulk material. In comparison,
embodiments of the present disclosure can achieve 5 mm.sup.2 to 40
mm.sup.2 surface area of fins per 1 mm.sup.2 surface area of a
blank silicon substrate from which the silicon-based
heat-dissipation device is made.
[0083] In one embodiment, silicon-based heat-dissipation device 902
has the following dimensions: thickness of each fin of protrusion
portion 91=50 .mu.m, pitch=100 .mu.m, thickness of base portion 92
of =100 .mu.m, and height H4=2000 .mu.m. Accordingly, the
calculated total surface area of silicon-based heat-dissipation
device 902 is 4061 mm.sup.2. With the blank silicon substrate 901
having the dimensions of 10 mm.times.10 mm.times.2 mm, the
calculated total surface area of blank silicon substrate 901 is 280
mm.sup.2. This design has a metric of 14.5 mm.sup.2 per 1 mm.sup.2
silicon blank surface area.
[0084] In another embodiment, silicon-based heat-dissipation device
902 has the following dimensions: thickness of each fin of
protrusion portion 91=50 .mu.m, pitch=2000 .mu.m, thickness of base
portion 92 of =1950 .mu.m, and height H4=2000 .mu.m. Accordingly,
the calculated total surface area of silicon-based heat-dissipation
device 902 is 283 mm.sup.2. With the blank silicon substrate 901
having the dimensions of 10 mm.times.10 mm.times.2 mm, the
calculated total surface area of blank silicon substrate 901 is 280
mm.sup.2. This design has a metric of 1.0 mm.sup.2 per 1 mm.sup.2
silicon blank surface area.
[0085] Optionally, with reference to FIGS. 17 and 18, to help
quickly spread heat at base portion 92 of silicon-based
heat-dissipation device 902, a thermally-conductive layer 93 may be
coated or deposited on a second primary side of base portion 92
opposite the first primary side thereof. Thermally-conductive layer
93 may be a metal layer or a non-metal layer. For example,
thermally-conductive layer 93 may be a copper layer or an aluminum
layer. Alternatively, thermally-conductive layer 93 may be a layer
of diamond, graphite, aluminum nitrite, or carbon nanotubes.
Thermally-conductive layer 93 may enhance the thermal performance
of silicon-based heat-dissipation device 902 and effectively reduce
the thickness of silicon base 92. For example, one or more
heat-generating devices, such as heat-generating devices 21-25 for
example, may be embedded in or physically coupled, mounted or
otherwise attached to thermally-conductive layer 93.
[0086] Thermal modeling indicates adding a layer of thick metal
layer, such as thermally-conductive layer 93, may improve the
thermal performance of silicon-based heat-dissipation device 902.
Note that it is not practical in current electrical plating process
to have a large thickness for thermally-conductive layer 93 or to
maintain the flatness of thermally-conductive layer 93. In one
embodiment, the thickness of thermally-conductive layer 93 is in a
range of approximately 3 .mu.m to 30 .mu.m to optimize the thermal
performance of silicon-based heat-dissipation device 902.
[0087] In summary, according to one aspect of the present
disclosure, an apparatus may include a silicon-based
heat-dissipation device. The silicon-based heat-dissipation device
may include a base portion and a protrusion portion. The base
portion may have a first primary side and a second primary side
opposite the first primary side. The protrusion portion may be on
the first primary side of the base portion and may protrude
therefrom. The second primary side of the base portion may be
configured to have one or more heat-generating devices embedded
therein or physically coupled thereto such that at least a portion
of heat generated by the one or more heat-generating devices is
dissipated to the silicon-based heat-dissipation device by
conduction. The silicon-based heat-dissipation device may have a
surface area such that, for every 1 watt of power loading of the
one or more heat-generating devices, the surface area of the
silicon-based heat-dissipation device is in a range of
approximately 400 mm.sup.2/watt to 2000 mm.sup.2/watt.
[0088] In at least one embodiment, the base portion may include a
slit that communicatively connects the first primary side and the
second primary side of the base portion.
[0089] In at least one embodiment, when each of more than one
heat-generating devices is embedded in or physically coupled to the
base portion, at least a first heat-generating device of the more
than one heat-generating devices may be on a first side of the slit
and at least a second heat-generating device of the more than one
heat-generating devices may be on a second side of the slit
opposite the first side of the slit such that the slit severs a
direct-line thermal coupling path via conduction through the base
portion between the first and the second heat-generating
devices.
[0090] In at least one embodiment, the slit may include an L-shaped
slit.
[0091] In at least one embodiment, the protrusion portion of the
silicon-based heat-dissipation device may include a plurality of
fins.
[0092] In at least one embodiment, the plurality of fins may
include a plurality of straight fins.
[0093] In at least one embodiment, a ratio of a height of the fins,
measured from the first primary side of the base portion in a
direction perpendicular to the first primary side, to a thickness
of each of the fins, measured across a respective one of the fins
in a direction parallel to the first primary side of the base
portion, may be greater than 5:1.
[0094] In at least one embodiment, a ratio of a height of the fins,
measured from the first primary side of the base portion in a
direction perpendicular to the first primary side, to a thickness
of the base portion, measured across the base portion in a
direction parallel to the first primary side of the base portion,
may be greater than 5:1.
[0095] In at least one embodiment, a spacing between every two fins
of the fins, measured between respective two fins of the fins in a
direction parallel to the first primary side of the base portion,
may be greater than or equal to a thickness of each of the fins,
measured across a respective one of the fins in the direction
parallel to the first primary side of the base portion.
[0096] In at least one embodiment, the plurality of fins may
include a plurality of tapered fins.
[0097] In at least one embodiment, at least a first fin of the
tapered fins may have a tapered angle between a surface of the
first fin and a normal line perpendicular to a horizontal plane
defined by the first primary side of the base portion. The tapered
angle may be less than or equal to 5 degrees.
[0098] In at least one embodiment, the apparatus may further
include a copper layer coupled to the second primary side of the
base portion with a thickness of the copper layer being in a range
of approximately 3 .mu.m to 30 .mu.m.
[0099] In at least one embodiment, the apparatus may further
include one or more integrated circuits embedded in the second
primary side of the base portion or one or more electrically-driven
devices physically coupled to the second primary side of the base
portion. At least a first one of the one or more integrated
circuits or the one or more electrically-driven devices may be on a
first side of the slit. At least a second one of the one or more
integrated circuits or the one or more electrically-driven devices
may be on a second side of the slit opposite the first side of the
slit. The slit may sever a direct-line thermal coupling path via
conduction through the base portion between the first one of the
one or more integrated circuits or the one or more
electrically-driven devices and the second one of the one or more
integrated circuits or the one or more electrically-driven
devices.
[0100] In at least one embodiment, the silicon-based
heat-dissipation device may be made from a blank silicon substrate
of single-crystal silicon. The protrusion portion may have a
surface area of approximately 5 mm.sup.2 to 40 mm.sup.2 surface
area of the protrusion portion per 1 mm.sup.2 surface area of a
blank silicon substrate from which the silicon-based
heat-dissipation device is made.
[0101] According to another aspect, an apparatus may include a
silicon-based heat-dissipation device. The silicon-based
heat-dissipation device may include a base portion and a protrusion
portion. The second primary side may be configured to have one or
more heat-generating devices embedded therein or physically coupled
thereto. The base portion may have a first primary side and a
second primary side opposite the first primary side. The protrusion
portion may be on the first primary side of the base portion and
protruding therefrom. The protrusion portion may include a
plurality of fins. Each of at least two immediately adjacent fins
of the fins of the protrusion portion may have a tapered profile in
a cross-sectional view with a first width near a distal end of the
respective fin being less than a second width at a base of the
respective fin near the base portion of the heat-dissipation
device. The silicon-based heat-dissipation device may have a
surface area such that, for every 1 watt of power loading of the
one or more heat-generating devices, the surface area of the
silicon-based heat-dissipation device is in a range of
approximately 400 mm.sup.2/watt to 2000 mm.sup.2/watt.
[0102] In at least one embodiment, the second primary side of the
base portion may be configured to have one or more heat-generating
devices embedded therein or physically coupled thereto such that at
least a portion of heat generated by the one or more
heat-generating devices is dissipated to the silicon-based
heat-dissipation device by conduction.
[0103] In at least one embodiment, at least a first fin of the
tapered fins may have a tapered angle between a surface of the
first fin and a normal line perpendicular to a horizontal plane
defined by the first primary side of the base portion. The tapered
angle may be less than or equal to 5 degrees.
[0104] In at least one embodiment, the apparatus may further
include a copper layer coupled to the second primary side of the
base portion with a thickness of the copper layer being in a range
of approximately 3 .mu.m to 30 .mu.m.
[0105] In at least one embodiment, the apparatus may further
include one or more integrated circuits embedded in the second
primary side of the base portion or one or more electrically-driven
devices physically coupled to the second primary side of the base
portion. The base portion may include a slit that communicatively
connects the first primary side and the second primary side of the
base portion. At least a first one of the one or more integrated
circuits or the one or more electrically-driven devices may be on a
first side of the slit. At least a second one of the one or more
integrated circuits or the one or more electrically-driven devices
may be on a second side of the slit opposite the first side of the
slit. The slit may sever a direct-line thermal coupling path via
conduction through the base portion between the first one of the
one or more integrated circuits or the one or more
electrically-driven devices and the second one of the one or more
integrated circuits or the one or more electrically-driven
devices.
[0106] In at least one embodiment, the silicon-based
heat-dissipation device may be made from a blank silicon substrate
of single-crystal silicon. The protrusion portion may have a
surface area of approximately 5 mm.sup.2 to 40 mm.sup.2 surface
area of the fins per 1 mm.sup.2 surface area of a blank silicon
substrate from which the silicon-based heat-dissipation device is
made.
Additional and Alternative Implementation Notes
[0107] The above-described embodiments pertain to a technique,
design, scheme, device and mechanism for isolation of thermal
ground for multiple heat-generating devices on a substrate.
Although the embodiments have been described in language specific
to certain applications, it is to be understood that the appended
claims are not necessarily limited to the specific features or
applications described herein. Rather, the specific features and
applications are disclosed as example forms of implementing such
techniques.
[0108] In the above description of example implementations, for
purposes of explanation, specific numbers, materials
configurations, and other details are set forth in order to better
explain the invention, as claimed. However, it will be apparent to
one skilled in the art that the claimed invention may be practiced
using different details than the example ones described herein. In
other instances, well-known features are omitted or simplified to
clarify the description of the example implementations.
[0109] The described embodiments are intended to be primarily
examples. The described embodiments are not meant to limit the
scope of the appended claims. Rather, the claimed invention might
also be embodied and implemented in other ways, in conjunction with
other present or future technologies.
[0110] Moreover, the word "example" is used herein to mean serving
as an example, instance, or illustration. Any aspect or design
described herein as "example" is not necessarily to be construed as
preferred or advantageous over other aspects or designs. Rather,
use of the word example is intended to present concepts and
techniques in a concrete fashion. The term "techniques," for
instance, may refer to one or more devices, apparatuses, systems,
methods, articles of manufacture, and/or computer-readable
instructions as indicated by the context described herein.
[0111] As used in this application, the term "or" is intended to
mean an inclusive "or" rather than an exclusive "or." That is,
unless specified otherwise or clear from context, "X employs A or
B" is intended to mean any of the natural inclusive permutations.
That is, if X employs A; X employs B; or X employs both A and B,
then "X employs A or B" is satisfied under any of the foregoing
instances. In addition, the articles "a" and "an" as used in this
application and the appended claims should generally be construed
to mean "one or more," unless specified otherwise or clear from
context to be directed to a singular form.
* * * * *