U.S. patent application number 10/314721 was filed with the patent office on 2004-06-10 for inside-out heat sink.
Invention is credited to Dugas, Roger.
Application Number | 20040108101 10/314721 |
Document ID | / |
Family ID | 32468546 |
Filed Date | 2004-06-10 |
United States Patent
Application |
20040108101 |
Kind Code |
A1 |
Dugas, Roger |
June 10, 2004 |
Inside-out heat sink
Abstract
A heat sink has a fenestrated outer surface and internal
structure supporting the outer surface to facilitate heat transfer
from, and provide structural rigidity to, the heat sink.
Inventors: |
Dugas, Roger; (Chester,
NH) |
Correspondence
Address: |
MORGAN & FINNEGAN, L.L.P.
345 Park Avenue
New York
NY
10154-0053
US
|
Family ID: |
32468546 |
Appl. No.: |
10/314721 |
Filed: |
December 9, 2002 |
Current U.S.
Class: |
165/80.4 ;
165/185; 165/80.5; 257/E23.099; 257/E23.102 |
Current CPC
Class: |
H01L 2924/0002 20130101;
H01L 23/367 20130101; H01L 23/467 20130101; H01L 2924/0002
20130101; H01L 2924/00 20130101 |
Class at
Publication: |
165/080.4 ;
165/080.5; 165/185 |
International
Class: |
F28F 007/00 |
Claims
What is claimed is:
1. An inside-out heat sink comprising: a body having at least three
faces, the at least three faces defining an outer surface of the
body and a volume within the outer surface, the body comprising a
heat conductive material, at least one of the faces being
configured to be coupled to an integrated circuit containing
optical chips and electronic circuitry which, when operating, acts
as a heat source, the at least one of the faces being further
configured to receive heat from the heat source by conductive heat
transfer, a set of walls enclosed within the body and defining
multiple inter-linked passages, each of the passages extending from
at least one of the faces into the volume, at least some of the
passages being oriented differently with respect to others of the
passages, and wherein at least a few of the passages extend from
one of the faces to another of the faces, the passages being
arranged relative to each other so as to permit entry of a cooling
medium into several of the passages from multiple directions
external to the body, allow the cooling medium to flow through the
passages to facilitate convective heat transfer between the walls
and the fluid, and allow the cooling medium to exit to external to
the body, and the set of walls further defining multiple continuous
sections linearly extending from each of the at least three faces
to each of the other of the at least three faces.
2. The heat sink of claim 1 wherein at least some of the walls are
located so as to be equal in extent to a linear cross section of
the body taken through each of the at least some walls in the plane
of the wall, and wherein the at least some of the walls form a
lattice within the body that provides structural rigidity to the
body while allowing for convective heat transfer between the core
and the fluid when the fluid is passing through a set of the
passages.
3. A heat sink comprising: a heat conductive core comprising a
specified material and having a series of interconnecting internal
passages that provide a multi-directional pathway for a fluid from
an exterior surface of the core into the core, through the core,
and external to the core; the heat conductive core forming a
structural lattice within the heat sink to provide rigidity to the
heat sink; a portion of the heat conductive core being sized for
coupling to an integrated circuit heat source to conduct heat
generated by the integrated circuit heat source into the core for
dissipation through convective heat transfer to the fluid when it
is passing through the interconnecting internal passages; and the
heat sink apparatus occupying an overall volume such that it has
both a lower mass and greater heat transfer ability than either a
pin-type heat sink or a fin-type heat sink made of the specified
material that occupies the overall volume under identical
environmental conditions of generated heat, fluid type and fluid
flow.
4. A cooling device comprising: an outer surface, wherein the outer
surface is fenestrated to allow for passage into the device, from
multiple directions, of a cooling fluid from external to the device
through some of the fenestrations and to allow for passage out of
the device of the cooling fluid from internal to the device; a core
within the device, and bounded by the outer surface, to provide
structural support and flexural rigidity to the outer surface, the
core comprising a predetermined heat conductive material and having
a conductive heat transfer surface configured to sink heat
generated by a circuit module, having aligned optical components
therein, into the core when the circuit module is coupled to the
conductive heat transfer surface and is operational; a set of
passages within the core and interconnecting at least some of the
fenestrations to other of the fenestrations, the passages having
walls defining convective heat transfer surfaces of sufficient
dimensions to allow for transfer of heat from the core to the
cooling fluid by convection when the cooling fluid passes through
at least some of the passages of the set of passages; the cooling
device occupying an overall volume such that the cooling device is
more rigid, has a lower mass, and a greater heat transfer ability
than either a non-fenestrated pin-type heat sink or a
non-fenestrated fin-type heat sink made of the predetermined
material and occupying the overall volume under identical
environmental conditions.
5. The device according to claim 4 wherein the predetermined
material comprises a metal.
6. The device according to claim 5 wherein the metal comprises at
least one of aluminum, copper, iron, steel, brass, nickel, silver,
or gold.
7. The device according to claim 5 wherein the predetermined
material comprises an alloy.
8. The device according to claim 5 wherein the outer surface
defines a parallelepiped.
9. The device of claim 8 wherein the parallelepiped is a right
paralellepiped.
10. The device according to claim 9 wherein the outer surface
defines a cuboid.
11. The device according to claim 5 wherein the outer surface
defines a cylinder.
12. The device according to claim 5 wherein the outer surface
defines a pyramidal frustum.
13. The device according to claim 5 wherein the outer surface
defines an N-hedron.
14. The device according to claim 5 wherein the outer surface
defines a prism.
15. The device according to claim 5 wherein the outer surface
defines a cruciate shape.
16. The device according to claim 5 wherein the outer surface
comprises at least four sides and wherein there are at least three
fenestrations on each of the at least four sides.
17. The device according to claim 5 wherein passages in the set of
passages are parallel to each other.
18. The device according to claim 5 wherein particular passages in
the set of passages. are at an angle to each other.
19. The device according to claim 18 wherein the angle is a right
angle.
20. The device according to claim 18 wherein a first of the
passages, a second of the passages and a third of the passages are
all at right angles to each other.
21. The device according to claim 5 wherein the surface defines a
longitudinal axis and a designated set of passages have an equal
spacing with respect to the longitudinal axis.
22. The device according to claim 18 wherein the designated set of
passages radially extend between the longitudinal axis and a
designated set of fenestrations.
Description
FIELD OF THE INVENTION
[0001] This invention relates to heat sinks, and more particularly,
to heat sinks used to cool integrated circuits.
BACKGROUND OF THE INVENTION
[0002] Heat sinks are used to regulate the amount of latent heat in
a device and transfer excess heat from the device to some cooling
medium.
[0003] FIG. 1 shows one example of a conventional heat sink 100,
referred to herein as a "pin-type" heat sink in both isometric and
orthographic projection. The heat sink 100 of FIG. 1 has a body 102
that is illustratively "L" shaped. The forward face 104 of the heat
sink 100 is designed to be placed in contact with an integrated
circuit (not shown) and to draw heat from the integrated circuit by
conductive heat transfer. A set of pins 106 extend outward from the
body and are spaced apart from each other and arranged to allow for
the cooling medium to pass among the pins 106 to thereby remove
heat from the pins by convective heat transfer.
[0004] FIG. 2 is another example of a conventional heat sink 200,
referred to herein as a "fin-type" heat sink. The heat sink of FIG.
2 is identical to the heat sink of FIG. 1 except, instead of pins,
the heat sink of FIG. 2 has a series of fins 202 extending
outwardly from the body 204 in planes perpendicular to the
longitudinal axis of the heat sink 200.
[0005] While both of the above heat sinks 100, 200 are useful for
cooling integrated circuits, when used with integrated circuits
containing active optical devices such as lasers and/or detectors
and passive optical components such as fibers, lenses or modulators
(among other components) they have several problems due to various
factors largely unique to such devices. First, alignment among the
optical components is often critical. A misalignment of even a
micron can cause one or more components to be useless.
[0006] Second, the operational characteristics of active optical
devices can be very heat sensitive. Temperature changes can cause
the wavelength of a given laser to change because excess latent
heat increases the effective cavity size of a laser.
[0007] Third, heat sinks act as a moment arm and transmit applied
forces to the integrated circuit to which they are attached. This
is not a problem for devices that generally remain fixed however,
where such heat sinks are part of a module that will be repeatedly
connected and disconnected from another item (generically referred
to herein as "coupled" or "coupling"), such as a connector plug,
and alignment between the module and the connector plug are
critical the flexing forces transmitted by the heat sink during
coupling can introduce misalignments in excess of one micron.
[0008] Fourth, the structural rigidity of the heat sinks 100, 200
of FIG. 1 and FIG. 2 are different in each of the X, Y and Z
directions. In fact, the rigidity of both those heat sinks 100, 200
is lowest with respect to bending forces applied rotationally in
the Y-Z plane because of the narrow thickness of parts of the body
100, 200 in that plane. This difference in directional structural
rigidity means that thermal fluctuations can cause the heat sinks
themselves create and transmit or apply flexing forces to the
integrated circuit to which they are attached, thereby causing
misalignment.
[0009] Finally, the efficiency of the heat sink is a function of
the number of pins or fins, the size of the pins or fins, the heat
sink body material, the pin or fin material and the pin or fin
placement relative to the direction of movement of the cooling
medium. However, the maximum volume the heat sink can occupy limits
the extent to which each can be varied and hence the maximum
efficiency.
[0010] Thus, there is a need for a heat sink that can be used with
integrated circuits having components susceptible to misalignment,
that reduces the likelihood of heat sink related misalignment while
occupying the same overall volume as a conventional pin-type or
fin-type heat sink, the "overall volume" as used herein having the
definition of the volume that would be occupied by the smallest
solid rectangular or cylindrical block that can contain the heat
sink.
SUMMARY OF THE INVENTION
[0011] I have devised an "inside-out" heat sink that addresses the
problems of conventional heat sinks, making it possible to provide
a heat sink that occupies the same overall volume as a conventional
pin-type or fin-type heat sink but: a) is structurally more rigid
than the conventional pin-type or fin-type heat sink made of the
identical material and occupying the same overall volume, and b) is
a more efficient heat sink than the conventional pin-type or
fin-type heat sink made of the identical material and occupying the
same overall volume under identical, typical operational conditions
in terms of cooling medium, direction of flow, and temperature of
cooling medium.
[0012] The advantages and features described herein are a few of
the many advantages and features available from representative
embodiments contained herein and are presented only to assist in
understanding the invention. It should be understood that they are
not to be considered limitations on the invention as defined by the
claims, or limitations on equivalents to the claims. For instance,
some of these advantages are mutually contradictory, in that they
cannot be simultaneously present in a single embodiment. Similarly,
some advantages are applicable to one aspect of the invention, and
inapplicable to others. Thus, this summary of features and
advantages should not be considered dispositive in determining
equivalence. Additional features and advantages of the invention
will become apparent in the following description, from the
drawings, and from the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is an example of a conventional pin-type heat
sink;
[0014] FIG. 2 is an example of a conventional fin-type heat
sink;
[0015] FIG. 3 is one illustrative example of an inside-out heat
sink implementation according to the present invention;
[0016] FIG. 4 is another illustrative example of an inside-out heat
sink implementation according to the present invention;
[0017] FIG. 5 is another illustrative example of an inside-out heat
sink implementation according to the present invention;
[0018] FIG. 6 is another illustrative example of an inside-out heat
sink implementation according to the present invention;
[0019] FIG. 7 is another illustrative example of an inside-out heat
sink implementation according to the present invention;
[0020] FIG. 8 is another illustrative example of an inside-out heat
sink implementation according to the present invention;
[0021] FIG. 9 is another illustrative example of an inside-out heat
sink implementation according to the present invention;
[0022] FIGS. 10-17 are representative illustrative examples of some
of the myriad of outer surfaces that can be used for creating
inside-out heat sinks according to the present invention;
[0023] FIG. 18 is an example of an example application for a
representative inside-out heat sink according to the present
invention; and
[0024] FIG. 19 is an example module incorporating a representative
inside-out heat sink according to the present invention.
DETAILED DESCRIPTION
[0025] FIG. 3 is an example of one implementation of a heat sink
300 incorporating the present invention.
[0026] As shown in FIG. 3, the body 302 of the heat sink 300 is
shaped like a pair of discrete abutting rectangular boxes 304, 306
geometrically referred to as right rectangular parallelepipeds,
with the surface 308 of the body 302 defining an internal volume
for the body. The smaller of the two "boxes" 304 is a solid
"conduction" portion and the larger of the two "boxes" 306 is a
fenestrated "convection" portion.
[0027] The conduction portion 304 includes a face 310 that is
suitably sized and dimensioned to be coupled to an integrated
circuit (not shown), that contains precision aligned elements and
generates heat when it is operating, in order to sink generated
heat into the conductive portion 304 through conductive heat
transfer. As shown, the conductive portion 304 has a rectangular
conduction face 310 to serve that purpose. The conductive portion
304 also abuts the convective portion 306 at a common face 312 of
suitable size to ensure that a desired level of heat transfer from
the conductive portion 304 to the convective portion 306 will
occur.
[0028] Both the conductive portion 304 and the convective portion
306 are made of heat conductive material, for example a metal such
as aluminum, copper, brass, iron, zinc, etc. or an alloy.
[0029] Depending upon the particular implementation, the conductive
portion 304 and the convective portion 306 can be made of a common
material (preferably having a high conductivity) or of different
materials. In addition, depending upon the particular
implementation, the conductive portion 304 and the convective
portion 306 can be physically formed simultaneously, concurrently
or sequentially.
[0030] Where different materials are used for the two portions, it
is desirable that both have a high conductivity. It is also highly
desirable, but not mandatory, that the material used for the
convective portion 306 have a lower conductivity than the
conductive portion 304 if the two are made of different materials.
In addition, where different materials are used, care should be
taken in material selection to ensure that detrimental galvanic
coupling or corrosion between the two materials does not occur.
[0031] As shown in FIG. 3, the convective portion 306 has six
faces, the "common" or intermediate face 312, a top face 314, a
rear face 316, a right side face 318, a left side face 320 and a
bottom face 322.
[0032] As shown in FIG. 3, fenestrations 324 cover part of the
outer surface 308 of the convection portion 306 of the body 302. In
particular, in FIG. 3 there are fenestrations 324 on the top 314,
rear 316, right 318 and left 320 faces. A set of passages 326
within the body 302 interconnect some of the fenestrations 324 to
others. For example, as shown in FIG. 3, straight-through passages
connect the fenestrations on the right face 318 with the
fenestrations on the left face 320. In contrast, straight passages
extend into the body 320 from the fenestrations on the top face
314, and from the back face 316 but they all "dead end" within the
body 302 (i.e. they do not go all the way through the body 302 ).
The passages are deliberately placed at particular locations and
interval spacings so as to create a series of interconnections
among the passages 326. As a result, any given fenestration on the
surface 308 will be connected to at least one other fenestration,
with most being connected to two or more other fenestrations via
the interconnections.
[0033] As shown in FIG. 3, the passages extending inward from each
of the fenestrations on a given face are all parallel to each
other. In addition all of the passages illustratively shown in FIG.
3 interconnect at right angles. In addition, the passages extending
inward from the rear face 316 all run parallel to the longitudinal
axis of the body 302 of the heat sink 300.
[0034] Despite the interconnections, in this and the examples
below, passage placement is organized to ensure that structure
exists between the walls 328 that define particular passages so as
to create multiple continuous sections that linearly span the body
302. The structure between the passage walls 328 thereby forms a
structural core or lattice within the outer surface 308 of the body
302 which provides support for the outer surface 308 and structural
rigidity to the body 302, as a whole, approaching that of the body
302 if it were solid--at least with respect to the typical forces
encountered or applied when the heat sink is part of a module or
connector and the module is in operation, or those normally
encountered, when the module or connector is part of an assembly
that can be repeatably coupled, during coupling.
[0035] As shown in FIG. 3, the fenestrations and passages are all
circular in cross section. Depending upon the particular
implementation however, as shown below in connection with other
example, other cross-sectional shapes can be used, for example,
ovals, triangles, squares, rectangles, etc. the particular shape
being more a function of manufacturability and application than of
the invention.
[0036] It should be understood however that the particular shape
used for the fenestrations or passages and their placement will
affect the rigidity of the body as well as its ability to
efficiently function such that certain combinations will be
unsuitable for particular applications and others may be reasonably
considered unmanufacturable or unusable.
[0037] FIG. 4 is another illustrative example of the orthographic
projection for an inside-out heat sink 400 implementation according
to the present invention. The heat sink 400 of FIG. 4 is identical
to the heat sink 300 of FIG. 3 except that the fenestrations 402 on
the outer surface 404 and the passages interconnecting the
fenestrations are square in cross section.
[0038] FIG. 5 is another illustrative example of an inside-out heat
sink implementation according to the present invention. The heat
sink 500 of FIG. 5 is similar to the heat sink of FIG. 4 in that
the outer surface 502 of the body 504 is of identical shape and
size to the heat sink of FIG. 4 and the fenestrations are all
square. However, there are only two fenestrations 506 on each of
the right face 508 and left face 510. In addition, the passages 516
interconnecting the fenestrations on the right face 508 to the
fenestrations on the left face 510 are angled with respect to those
faces so that the fenestration closest to the conduction portion
512 is connected to the fenestration on the opposite face closest
to the rear face 514. As a result, the two passages 516 intersect
at about the middle of the body 504. There are also fenestrations
on the rear face 514, however they are smaller in size than those
on the right face 508 or left face 510 so that four fit within the
same area on the surface 502 of the body. Like the passages
extending inward from the fenestrations on the rear face 316 of
FIG. 3, the passages extending inward from the fenestrations on the
rear face of FIG. 5 run parallel to each other along the
longitudinal axis of the heat sink 500. However, unlike FIG. 4, the
passages extending from the rear face 514 of FIG: 5 extend to
different depths within the body 504 and the spacing between some
of the passages and their adjacent passages differs so that the
upper row 518 of passages is closer to the lower row 520 than the
outermost columns 522, 524 are to the innermost columns 526, 528.
In addition, the two innermost columns 526, 528 are spaced from
each other by almost twice the distance as between the outermost
columns 522, 524.and the innermost columns 526, 528. In addition,
the fenestrations on the upper face 530 are irregularly spaced
relative to each other because they are arranged for maximum
intersection with the other passages within the body. Finally, as
with the fenestrations of the heat sink of FIG. 3, in FIG. S
passages extend through the body 504 to connect the right face
fenestrations to the left face fenestrations, whereas none of the
rest of the passages extend fully through the body 504 to the
opposite face. As a result, a part of the body 504 remains solid
beyond the intermediate face 532. This effectively extends the
conduction portion 534 farther into the body 504.
[0039] FIG. 6 is another illustrative example of an inside-out heat
sink implementation according to the present invention. The heat
sink 600 of FIG. 6 is similar to the heat sinks of FIG. 3 and FIG.
5. Like the heat sink 300 of FIG. 3, the fenestrations and passages
are all circular, and the passages extending inward from a given
face are all parallel to each other.
[0040] In addition, like the heat sink 500 of FIG. 5, passages
extending inward from the rear face 624 go to different depths
within the body 602 so that a larger portion of the body 602 is
solid and serves as the conduction portion 604.
[0041] However, unlike the heat sinks 300, 500 of FIG. 3 and FIG.
5, with the heat sink 600 of FIG. 6, only the rear-most eight
fenestrations 606 on the right face 608 have associated passages
that extend through the body to corresponding fenestations on the
left face 610. In addition, the bottom face 612 has two rows 614,
616 of fenestrations directly below the outermost rows 618, 620 of
fenestrations on the top face 622 so that parallel passages
extending perpendicular to the top and bottom faces connect the
outermost rows 618, 620 of fenestrations on the top face 622 to the
coinciding fenestrations on the bottom face 612. Finally, unlike
the heat sinks of FIG. 3, FIG. 4 and FIG. 5, the heat sink of FIG.
6 is not symmetrical with respect to a plane passing through the
longitudinal axis parallel to the right face 608 or left face
610.
[0042] FIG. 7 is another illustrative example of an inside-out heat
sink 700 implementation according to the present invention. Unlike
the example heat sinks of FIG. 3 through FIG. 6 however, the outer
surface 702 of the body 704 of the heat sink of FIG. 7 is
cylindrical in shape whereas the outer surfaces of the heat sinks
of FIG. 3 through FIG. 6 were made up of right parallelepipeds. In
addition, there is no clear demarcation between the conduction
portion 706 and the convection portion 708, although there is a
clearly delineated conduction face 710 of suitable size for
coupling to the integrated circuit of interest.
[0043] In the heat sink of FIG. 7, a series of columns, defined by
planes perpendicular to the longitudinal axis, of eight circular
fenestrations are located around the outer surface 702 of the body
704 with the fenestrations within and among the columns being
equally spaced from each other. In addition, the fenestrations in
each column are longitudinally aligned with each other.
[0044] Passages 712 extend radially inward from the fenestrations
on the outer surface 702 at alternating depths so that the
fenestrations on the X-axis interconnect as do the fenestrations on
the Y-axis. However, the fenestrations between the X-axis and the
Y-axis only extend partway inward.
[0045] As with the prior examples, the rear face 714 is also
fenestrated. In the example of FIG. 7, the fenestrations on the
rear face 714 are arranged to form a pair of concentric circles and
are aligned with the inwardly extending passages from the
fenestrations on the outer "cylinder portion" of the outer surface
702. A set of parallel passages extend inward from the
fenestrations on the rear face 714 parallel to the longitudinal
axis 716 of the heat sink 700 in order to intersect with the
passages extending radially into the body 704. The passages from
the fenestrations on the rear face 714 also extend to different
depths with the passages from the outermost circle fenestrations
extending all the way to the column closest to the conduction face
710 whereas the passages from the inner circle only extend to about
the middle of the body 704. As with the prior examples, the
placement of the passages creates a core or lattice within the body
704 made up of multiple continuous linear sections in different
directions spanning the body 704 for structural rigidity.
[0046] FIG. 8 is another illustrative example of an inside-out heat
sink 800 implementation according to the present invention. The
heat sink 800 of FIG. 8 is similar to the heat sink 700 of FIG. 7
in that it is cylindrical in shape and is fenestrated on the outer
surface. However, unlike the heat sink 700 of FIG. 7, the
fenestrations on the heat sink 800 of FIG. 8 are arranged in
quadrants 802, 804, 806, 808 of three fenestrations per quadrant
802, 804, 806, 808 in a given column on the outer surface 810. The
outer surface fenestrations of FIG. 8 are, however, longitudinally
aligned as with the outer surface fenestrations of FIG. 3.
[0047] Passages extend inward from the fenestrations of a given
quadrant 802, 804 parallel to each other so that they connect those
fenestrations with the fenestrations on the opposite quadrant 806,
808. As a result therefore, as shown in FIG. 8, all the passages
connecting the fenestrations on the outer surface 810 are either
parallel to the Y-axis or parallel to the X-axis leaving the
material that forms the walls that provide for heat transfer and
form the linear sections of the internal core or lattice.
[0048] Similar to FIG. 7, the rear face 812 of the heat sink 800 of
FIG. 8 is also fenestrated however, the fenestrations are aligned
along the X-axis and the Y axis instead of being placed radially
about the longitudinal axis. The passages extending into the body
defined by the outer surface 810 from the rear face 812 are all
parallel to each other and extend to the same depth so as to
intersect the passages of the column closest to the conduction face
814. As a result, any given fenestration in a particular quadrant
is connected to a fenestration in every other quadrant and to a
fenestration on the rear face 812.
[0049] FIG. 9 is another illustrative example of an inside-out heat
sink 900 implementation according to the present invention. In the
example of FIG. 9, the convection portion 902 of the body 904 is of
cruciform cross section having an outer surface 906 defined by
twelve faces 908 each a right rectangular polygon in shape. Each
face 908 is fenestrated as described above with passages
interconnecting various fenestrations and intersecting each other
at right angles. The passages within each of the "arms" of this
heat sink 900 interconnect fenestrations on opposite parallel faces
to each other. In addition, the front faces 910 of the "arms" are
also fenestrated and passages extending into the body 904 from the
rear face 912 of the body at the "arms" interconnect the
fenestartions on the arms of the rear face 912 to the fenestrations
on the opposite parallel fenestrations on the front faces 910 of
the arms. As shown, the rear face 912 also has a central
fenestration 914 concentric with the central longitudinal axis of
the heat sink 900. However, the passage extending inward from the
central fenestration 914 on the rear face 912 that only extends far
enough into the body 904 to intersect the passages closest to the
conduction portion 916.
[0050] Having illustrated a number of examples of inside out heat
sinks implementing the invention, it should be appreciated that
numerous other configurations are possible. For example, in
addition to varying the material(s) used, the size and/or shape of
the fenestrations, the cross sectional shape of the passages and/or
their orientation (whether relative to some plane or axis or each
other), different outer surface shapes can also be used.
[0051] FIGS. 10 through 17 are representative illustrative examples
of the myriad of outer surface shapes that can be used for creating
inside-out heat sinks according to the present invention. In each
of FIGS. 10 through 17 the fenestrations and passages are not shown
so that the outer surface shapes can be more clearly understood
without clutter. Advantageously, use of the invention provides the
ability to vary the shape of the outer surface so that the amount
of cooling medium that can enter the body from multiple directions
can be maximized for the application.
[0052] FIG. 10 is an example of an outer surface 1000 shaped like a
representative frustum of a pyramid. In this example, cross
sections of the pyramid parallel to its base are squares of
differing sizes. Of course, for particular applications, a heat
sink using this shape could use any one of the faces as the
conduction portion. In addition, all the faces need not be equally
fenestrated and, as illustrated above, some may not be fenestrated
at all.
[0053] FIG. 11 is an example of an outer surface 1100 shaped like
another representative frustum of a pyramid. In this example, cross
sections of the pyramid parallel to its base are pentagons of
differing sizes. As with FIG. 10, for particular applications, a
heat sink using this shape could use any one of the faces as the
conduction portion. In addition, as with all the heat sinks
incorporating the invention, all the faces need not be equally
fenestrated and, as illustrated above, some may not be fenestrated
at all.
[0054] FIG. 12 is an example of another outer surface 1200. In the
example of FIG. 12, the conduction portion 1202 is disc shaped and
the convention portion 1204 has a triangular cross section of
uniform size along the longitudinal axis.
[0055] FIG. 13 is another example of a polyhedral outer surface
1300 shape made up of two parallel facing equally sized octagons
1302, 1304 connected by eight rectangular faces 1306 (some of which
are obscured from view).
[0056] FIG. 14 is another example of a polyhedral outer surface
1400 shape made up of parallel facing hexagons 1402, 1404. In the
example of FIG. 14 however, the conduction portion 1406 is of
uniform cross section whereas the convection portion 1408 is of
increasing cross sectional area as the distance from the conduction
portion 1406 increases in a longitudinal direction.
[0057] FIG. 15 is another example of a polyhedral outer surface
1500 shape made up of two parallel facing equally sized seven sided
polygons. As shown, there is a clear delineation 1502 between the
conduction portion 1504 and the convection portion 1506. This is
intended to illustrate and remind the reader that, although of
uniform cross section, the heat sinks described herein can be, and
in this example it is, made up of different materials.
[0058] The above examples have illustrated outer surfaces where the
two ends are of a common shape. It should be understood however
that, for some implementations of the invention, this need not
necessarily be the case. For example, FIG. 16 shows an example
polyhedral outer surface 1600 where one end 1602 is square in shape
and the end 1604 facing the square and 1602 is octagonal in shape,
and the two are connected by faces that are alternatingly
rectangular and triangular in shape. Similarly, in the outer
surface 1700 example of FIG. 17, one end 1702 is rectangular in
shape and the other end 1704 is oval. The two are connected by four
planar triangles (only three of which are shown) each sharing a
common side with the square end 1702, and a set of four curved
triangular surfaces 1708 (only two of which are visible).
[0059] Thus, it should now be understood that by combining
different shapes a myriad of different outer surfaces can be
obtained. As a result, we collectively refer to outer surfaces that
are not square or rectangularly "box" shaped, or uniformly
cylindrical (i.e. they are cone shaped or made up of polygons where
at least one face is of a shape other than a rectangle or square)
as being an "N-hedron" or "N-hedron" in shape for simplicity.
[0060] Having described a number of different inside-out heat sink
structures, the function and operation of such heat sinks will now
be described, for simplicity with reference to example structures
shown in simplified manner in FIG. 18 and FIG. 19.
[0061] With reference to FIG. 18, the example inside-out heat sink
1800 is coupled to an integrated circuit 1802, for example, a
circuit chip containing active optical devices 1804 as lasers
and/or detectors hybridized to an electronic chip 1806. The
electronic chip 1806 contains, for example, the drive, and possibly
also control, circuitry for those optical devices 1804. This
hybridized unit is, in turn, connected to a circuit board 1808 (and
possibly other components) shown for purposes of simplicity as a
"ghost" box.
[0062] Depending upon the particular application, the coupling of
the heat sink 1800 to the integrated circuit 1802 will either be a
direct physical connection, with the two being in actual physical
contact, or it will be indirect, with the two having some
conductive medium or media, such as a thermal cream(s) and/or
thermal expansion interface matching materials, in between.
[0063] FIG. 19 is a more detailed side view of an example
inside-out heat sink 1900 such as shown in FIG. 3 used in
conjunction with an example module 1902. The module 1902 contains a
hybridized unit 1904 (made up of at least a group of active optical
devices 1906 and an electronic chip 1908 that drives and controls
the active optical devices). The active optical devices 1906 are
precisely placed so as to be aligned with devices and/or fiber
bearing element(s) to which the module 1902 can be coupled. The
hybridized unit 1904 is, in turn, connected to a circuit board 1910
via, for example, a ball grid array 1912, leads or pins. The module
1902 may also have other connection points 1914 through which the
module 1902 can be connected to other devices or elements not
relevant to the invention.
[0064] The module 1902 is placed so that the heat sink 1900 is
exposed to a flow of a cooling medium external to the heat sink
1902. In the example of FIG. 19, the cooling medium is air,
although with straightforward modification to protect the optical
and/or electronic components, it should be understood that other
cooling media, including various gasses or liquids could be
used.
[0065] The fenestrations allow the cooling medium to flow, in a
number of directions, from external 1916 to the heat sink body into
the heat sink body 1918. The cooling medium then flows through the
internal passages until exiting the body 1918. During device
operation, heat is conducted away from the unit 1904 (through
conductive heat transfer) by the conduction portion and internal
body material lattice (i.e. core of the heat sink). As the cooling
medium passes through the body interior, heat will be transferred
to the fluid (by convective heat transfer) via the walls of the
passages. The fluid then exits the body via other fenestrations.
Depending upon the orientation of the heat sink and the
direction(s) of fluid flow, the specific amount of cooling will
vary however, in most cases, the cooling will be significantly
better than a pin-type or pin-type heat sink of the same overall
volume and material under internal conditions.
[0066] Notably, for a given overall volume, inside-out heat sinks
constructed according to the invention can have significantly
better cooling ability under identical environmental conditions
than non-fenestrated pin-type or non-fenestrated fin-type heat
sinks of identical material and overall volume. One example of the
significance of the invention is illustrated with reference to
Table 1. Table 1 compares the cooling ability of a non-fenestrated
pin-type heat sink similar to that of FIG. 1 with an inside-out
heat sink similar to that of FIG. 3 having the same overall volume
and made of the same material under the same environmental
conditions.
1 TABLE 1 DELTA TEMPERATURE (chip temp. to ambient in degrees
Celsius) Air Flow Direction Side Top Rear Side/Rear Velocity 200
200 200 200 LFM Pin-type Heat Sink 25.1 10.3 29.1 25.1 (1.4 Watt)
Inside-Out Heat Sink 14.6 7.3 16.5 18.1 (1.4 Watt) % Improvement
41.8 29.1 43.3 27.9
[0067] As shown in Table 1, use of an inside-out heat sink improves
the cooling ability by at least 27% and by as much as 43+%
depending upon the particular direction of fluid flow, in this case
air, at a fluid flow rate of 200 linear feet per minute (LFM). In
addition, the inside-out heat sink was at least as rigid in each of
the x, y and z directions, and in the y direction more rigid, than
the pin-type heat sink to which it was compared.
[0068] I knew that, when the integrated circuit to which it was
connected was operating, the pin-type heat sink of Table 1 was
quite hot to the touch. Remarkably, the inside-out heat sink was
actually cool to the touch under the same operating conditions. The
degree of difference was significant and well beyond what I
expected under the circumstances.
[0069] Table 2 shows a comparison, obtained through simulation, of
the cooling ability of other pin-type heat sinks as compared with
fenestrated heat sinks configured according to the present
invention used in conjunction with larger integrated circuits
generating the power shown below. In Table 2, the type#1 heat sink
is a larger version of the heat sink of FIG. 3. The pin-type heat
sink to which it is compared is similar to the heat sink of FIG. 1
but has the same overall volume as the type#1 heat sink for
comparison. The type#2 heat sink is the heat sink of FIG. 6. The
pin-type heat sink to which it is compared is similar to the heat
sink of FIG. 1 but has the same overall volume as the type#2 heat
sink for comparison.
2TABLE 2 DELTA TEMPERATURE (chip Type temp. to ambient in degrees
Celsius) Air Flow Direction Side Velocity LFM 200 Pin-type Heat
Sink (2.2 27.6 Watt) #1 Inside-Out Heat Sink (2.2 17.3 Watt) %
Improvement 37.3 Pin-type Heat Sink (6.4 50.3 Watt) #2 Inside-Out
Heat Sink (6.4 33.4 Watt) % Improvement 33.6
[0070] Notably, both the type#1 and type#2 heat sinks show more
than a 30% improvement in cooling when the air flow is purely from
the side. Based upon Table 1 and Table 2, I expect that analogous
results in Table 2 would be achieved for the other directions from
Table 1.
[0071] Having now described the invention by way of a number of
example implementations and an example operation, it should be
appreciated that many different variants can be created. For
example, as noted above, the heat sink can be made of any heat
conductive material. In addition, the fenestrations can be
virtually any geometric shape. Similarly, the passages can be of
virtually any manufacturable cross sectional shape. In addition,
the passages and/or the fenestrations can be flared where they
join, for example to provide a smoother flow path for the fluid
used as the cooling medium. The cross sectional shape of a given
passage and the fenestration(s) to which it connects can be of
different shapes with a shape transition area in-between. Multiple
fenestration shapes can be used on a single heat sink. Multiple
passage shapes can be used within a single heat sink. The heat sink
body can be formed by any method usable for forming the intended
material into the desired shape including, for example, one or more
of the following alone or in combination: molding, casting,
sintering, laminating, electro-depositing, forging, rolling,
milling, turning, to name a few. Similarly, the fenestrations can
be formed as part of the process, or thereafter through, for
example drilling, milling, other machining processes, etc. Finally,
bodies of one type can be formed from bodies of other types. For
example, a heat sink such as shown in FIG. 3 can be made into a
heat sink similar to the one of FIG. 8 by, for example, taking the
heat sink of FIG. 3 and turning it in a lathe, or rounding it over
using a milling or grinding process, assuming of course proper
fenestration and passage placement.
[0072] Thus, while we have shown and described various examples
employing the invention, it should be understood that the above
description is only representative of illustrative embodiments. For
the convenience of the reader, the above description has focused on
a representative sample of all possible embodiments, a sample that
teaches the principles of the invention. The description has not
attempted to exhaustively enumerate all possible variations given
the myriad of different possibilities that can be achieved merely
from using different permutations or combinations of those features
described, let alone variations involving equivalents to those
features. That alternate embodiments may not have been presented
for a specific portion of the invention, or that further
undescribed alternate embodiments or other combinations of
described portions may be available, is not to be considered a
disclaimer of those alternate embodiments. It should be understood
that many of those undescribed embodiments are within the literal
scope of the following claims, and others are equivalent.
* * * * *