U.S. patent application number 10/459847 was filed with the patent office on 2004-02-26 for heat dissipation tower for circuit devices.
Invention is credited to Connors, Matthew J., Garner, Scott, Hartenstine, John R., McKee, David, Todd, John J..
Application Number | 20040035558 10/459847 |
Document ID | / |
Family ID | 31891278 |
Filed Date | 2004-02-26 |
United States Patent
Application |
20040035558 |
Kind Code |
A1 |
Todd, John J. ; et
al. |
February 26, 2004 |
Heat dissipation tower for circuit devices
Abstract
A heat transfer device such as a heat sink has one or more heat
pipe tubes mounted in a base plate. The heat pipe tubes have a
working fluid in a vessel with a wicking material between an
evaporator and condenser. The heat pipe traverses a through opening
in the base plate and extends along a receptacle in the base plate
facing the heat source, this portion preferably defining the heat
pipe evaporator. The heat pipe has legs extending perpendicularly
from the base plate, and preferably hold spaced heat transfer fins,
the legs forming the condenser part of a stacked tower of fins on
the base plate. Preferably two or more heat pipes are provided in
the form of U-shaped or L-shaped tubes that are flattened along the
underside of the base plate to bear against the heat source.
Inventors: |
Todd, John J.; (Chester
Springs, PA) ; Connors, Matthew J.; (Lancaster,
PA) ; McKee, David; (Lancaster, PA) ;
Hartenstine, John R.; (Mountville, PA) ; Garner,
Scott; (Lititz, PA) |
Correspondence
Address: |
SAMUEL W. APICELLI
DUANE MORRIS LLP
305 NORTH FRONT STREET
P.O. BOX 1003
HARRISBURG
PA
17108-1003
US
|
Family ID: |
31891278 |
Appl. No.: |
10/459847 |
Filed: |
June 12, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60388779 |
Jun 14, 2002 |
|
|
|
Current U.S.
Class: |
165/104.26 ;
165/104.21; 165/67; 165/80.5; 257/E23.088; 257/E23.102 |
Current CPC
Class: |
H01L 2924/0002 20130101;
H01L 2924/0002 20130101; H01L 23/367 20130101; F28F 1/24 20130101;
F28D 15/0275 20130101; H01L 23/427 20130101; F28F 1/32 20130101;
H01L 2924/00 20130101 |
Class at
Publication: |
165/104.26 ;
165/104.21; 165/80.5; 165/67 |
International
Class: |
F28D 015/00; F28F
009/00; F28F 007/00 |
Claims
What is claimed is:
1. A heat transfer device for dissipating heat from a heat source,
the device comprising: a heat pipe including a vessel to be placed
in thermally conductive relation to the heat source, the heat pipe
comprising thermally conductive material at least at an evaporator
part and at a condenser part that are in fluid communication with
one another and contain a heat transfer fluid for movement in a
cycle between the evaporator and the condenser; a base plate for at
least partly supporting the heat pipe, the base plate having a side
to be directed toward a heat source, and at least one through
opening leading into a receptacle on the side of the base plate
directed toward the heat source; wherein the at least a part of the
heat pipe extends into the through opening to the receptacle and is
positioned for contact with the heat source.
2. The heat transfer device of claim 1, further comprising a heat
sink disposed opposite from the side of the base plate directed
toward the heat source.
3. The heat transfer device of claim 2, wherein the evaporator is
disposed in the receptacle and the condenser is in thermal transfer
relation with the heat sink.
4. The heat transfer device of claim 1, further comprising a
wicking material in the vessel, capable of supporting a capillary
flow of the heat transfer fluid at least for part of the cycle
between the condenser to the evaporator.
5. The heat transfer device of claim 1, wherein the receptacle
forms a channel on the side of the base plate directed toward the
heat source and the vessel comprises an elongated tubular structure
disposed in the channel.
6. The heat transfer device of claim 5, wherein the base plate has
a thickness greater)than an outside of the elongated tubular
structure, and wherein the receptacle is dimensioned to complement
an outside, shape of the elongated tubular structure, such that the
elongated tubular structure rests substantially in surface contact
with the base plate at the receptacle.
7. The heat transfer device of claim 6, wherein the elongated
tubular structure is flattened along a surface coextensive with a
surface of the base plate on the side directed toward the heat
source.
8. The heat transfer device of claim 7, wherein the base plate has
at least one further through opening leading into the receptacle on
the side of the base plate directed toward the heat source, and
wherein the elongated tubular structure forms a U-shape or L-shape
with legs traversing the through openings and a bottom disposed in
the receptacle.
9. The heat transfer device of claim 8, wherein the legs comprise
parallel sections extending from the base plate and a transverse
bend adjacent to the bottom.
10. The heat transfer device of claim 9, wherein the receptacle
forms a U-shape or L-shape in a plane perpendicular to the leg
sections and the vessel is press fit into the U-shape or L-shape of
the receptacle.
11. The heat transfer device of claim 10, further comprising at
least one heat sink mounted on the leg sections.
12. The heat transfer device of claim 11, comprising a plurality of
heat transfer fins carried on said legs sections and spaced along
the leg sections from the base plate.
13. The heat transfer device of claim 8, comprising at least one
further said heat pipe comprising an elongated tubular structure
forming a further U-shape or L-shape affixed in a further
receptacle and having further leg sections.
14. The heat transfer device of claim 13, further comprising a
plurality of heat transfer fins spaced from the base plate, wherein
the leg sections and further leg sections form spaced parallel
columns supporting the heat transfer fins.
15. The heat transfer device of claim 14, wherein the elongated
tubular structures are compressed in surface contact with the base
plate along a surface of the receptacles and are flattened
coextensive with a surface of the base plate on a side facing the
heat source.
16. The heat transfer device of claim 15, wherein the elongated
tubular structures comprise tubing having a round cross section
with a flattened side.
17. The heat transfer device of claim 15, wherein the elongated
tubular structures have at least two flattened surfaces.
18. The heat transfer device of claim 15, wherein the vessels are
affixed to the base plate by at least one of a press fit, a potting
compound, an adhesive and a solder.
19. The heat transfer device of claim 18, wherein the heat transfer
fins are affixed to the leg sections by at least one of a press
fit, a potting compound, an adhesive and a solder.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the priority from co-pending
Provisional Patent Application Serial No. 60/388,779, filed Jun.
14, 2002, and entitled MULTIPLE HEAT PIPE TOWER--THERMAL
ENHANCEMENT FEATURE.
FIELD OF THE INVENTION
[0002] The invention relates to heat exchangers, and in particular
to a heat dissipation tower arrangement for transferring heat
energy away from a thermal source, such as an integrated circuit
package, into the ambient air. At least one, and preferably a
plurality of transfer heat pipe conduits are fit into complementary
channels extending through a base plate and along a surface in
thermal contact with the source. The heat pipe conduits transfer
heat energy along their length and serve as supporting columns for
stacked heat transfer fins. The heat transfer pipes can be arranged
in double ended U-shapes or single ended L-shapes with transverse
bends to optimize support and heat transfer surface contact.
BACKGROUND OF THE INVENTION
[0003] Certain semiconductor devices in electrical and electronic
circuits, such as large scale integrated circuits, voltage
regulators, current switching devices, high current drivers and
other similar devices, generate heat that is deleterious to their
operation and must be dissipated. An individual semiconductor
junction may be subject to thermal runaway current conduction
leading to further heating and damage. In large scale digital
integrated circuits, operation at or above the maximum rated
temperature can result in spurious switching operations and
functional failure.
[0004] The power dissipation or rate of generation of heat per unit
of time, is a matter of resistive or Joule heating resulting from
conduction of current through semiconductors that have a
corresponding resistance, the relationship being W=I.sup.2R. In a
highly integrated semiconductor device such as a computer
processor, a single semiconductor switching transistor may conduct
little concurrent on its own, but is densely mounted with many
other transistors. A single integrated device may generate heat
energy of a hundred Watts or more, and require supplemental cooling
arrangements in addition to convective cooling by heat driven
circulation of ambient air.
[0005] Some heat energy may be dissipated by conduction from the
integrated circuit package into the adjacent air, circulating by
convection. There is also some thermal conduction through circuit
lands and the like. These minimal means for thermal conduction
often are not adequate, and maintaining operational temperatures
within design ranges can be a problem. Thermally conductive heat
sink devices, normally of cast or sheet metal and potentially
having a substantial surface area exposed to the air, are mounted
so as to bear physically against the heat generating circuit
element.
[0006] In highly integrated computer processor circuits and similar
devices, a clamping mounting may be provided to press a finned heat
exchanger block down against the circuit package when mounted,
e.g., in a snap-in mounting on a motherboard. The heat exchanger
has a base pressed against the integrated circuit and may include a
mounting for a small electrically powered fan to force air over the
heat exchanger. This spreads out the heat energy within the housing
of the associated device. Another fan may be provided to circulate
air between the housing and the ambient room air.
[0007] Integrated circuit devices are available according to more
or less demanding temperature specifications, but devices that have
a relatively wider temperature range also are more expensive.
Standard commercial computer processor components, for example, may
be rated up to 70.degree. C. The most durable military application
devices may be rated up 125.degree. C. Within these constraints, it
is often necessary to provide supplemental cooling.
[0008] In order to assist in the movement of thermal energy from an
integrated circuit or other localized heat source, toward a remote
area or toward a structure that carries the heat away, it is
necessary to rely on one or more of thermal conduction, convection
and radiation. Conduction of heat energy requires contact between
thermally conductive masses and proceeds at a rate that depends in
part on the difference in temperature between the masses.
Convection requires movement of a heat transfer fluid (gas or
liquid) and involves differences in fluid density due to
differences in fluid temperature.
[0009] Heat transfer arrangements can involve passing a current of
cooler air or other heat transfer fluid over a hotter surface to be
cooled. In a heat pipe or thermal siphon arrangement, a captive
heat transfer fluid is provided in closed volume and is arranged to
circulate. The fluid is heated by a source of heat energy that is
in heat transfer relationship with one part of the closed volume. A
heat sink is arranged in heat transfer relationship with another
part of the closed volume. The heat transfer fluid advantageously
undergoes cyclic phase changes, each such phase change storing or
releasing a quantity of heat energy due to the latent thermal
energy involved in the phase change itself.
[0010] In this way, a liquid phase change heat transfer fluid can
be evaporated (vaporized) at the heat source and condensed again at
the heat sink. Different techniques can be used to return the
condensed liquid from the condenser to the evaporator, which need
not be powered by outside energy sources. A return path is
possible, for example, over a gravity flow path. Apart from
gravity, a return path for the condensed liquid can be provided by
lining the vessel confining the heat transfer fluid with a wicking
material that supports capillary flow, such as a sintered
particulate or powder lining wire mesh screen, felt or grooves. In
either gravity or capillary flow return, the heat source and the
heat sink can be thermally coupled to remote parts of a vessel of
simple shape such as a cylinder or other such shape. There is no
requirement for complex shapes and flow paths.
[0011] Assuming that the heat transfer fluid is confined in an
integral metal vessel, some thermal conduction from the heat source
to the sink can occur. It is desirable on grounds of efficiency to
separate the evaporator and condenser sections by a distance or to
interpose a thermal barrier, so that the dominant thermal transfer
phenomena are heat transfer from the source to the fluid at the
evaporator and from the fluid to the sink at the condenser, rather
than conduction along the vessel walls from the source to the sink.
Nevertheless, phase change heat exchange circuits as described can
operate with a very modest temperature difference between the
source and the sink and can efficiently move heat energy to assist
in heat dissipation.
[0012] There are a number of design considerations for thermal
transfer arrangements, sometimes known as heat pipes. In addition
to the ability to handle the necessary flow of thermal energy to
keep the heat source within desired temperature limits, the
evaporator and the condenser should have a good heat transfer
coupling with the heat source and sink, respectively. The thermal
transfer characteristics of the heat pipe structures, the various
dimensions and quantities, is etc. need to operate over the range
of expected temperatures. Preferably the device is compact and does
not interfere unduly with necessary access to structures associated
with the heat source and sink.
[0013] A number of heat pipe arrangements according to the
foregoing general description are available from Thermacore
International, Inc., Lancaster, Pa., and are disclosed in US
patents assigned to their licensor, Thermal Corp., Georgetown,
Del.
[0014] It would be advantageous if thermal efficiency, mechanical
complexity and production ease could be maximized in a finned heat
pipe arrangement. The production of a heat pipe, of course, is more
involved than mounting a tube to a heat source and a heat sink at
different points. Assuming that the relative dimension issues have
been decided, and in addition to the mechanical affixations that
will be needed during assembly, the heat pipe envelope needs to be
charged with the working fluid. The vessel typically is evacuated
and back-filled with a small quantity of working fluid, for example
enough liquid coolant to ensure saturation of the wick. The vessel
is sealed, which must be done while the vessel is accessible.
[0015] The liquid and vapor phases of the heat transfer medium in a
heat pipe reach an equilibrium in the absence of temperature
differences and remain substantially stagnant. When heat energy is
then added at the evaporator, vaporization of the heat transfer
medium leads to increased local vapor pressure in that area. The
added vapor expands and a portion arrives at the condenser. The
condenser is at a slightly lower temperature. The vapor is cooled
by contact with the condenser and condenses, releasing the latent
heat energy of vaporization. The condensed liquid phase heat
transfer medium flows back to the evaporator due to capillary
forces developed in the wick structure, and the cycle can repeat.
Where there is a positive temperature difference between the
evaporator (e.g., warmed by an electrical circuit element) and the
condenser (e.g., cooled by convection, forced air, contact with a
thermal sink, etc.) the cycle can continue indefinitely, moving
heat energy. The technique is operative at low thermal gradients.
The operation is passive in that it can be driven wholly by the
heat energy that it transfers.
[0016] U.S. Pat. Nos. 6,381,135--Prasher; 6,389,696--Heil; and
6,382,309--Kroliczek teach additional heat dissipation apparatus
intended for cooling integrated circuit devices and the like, as
described. These references are hereby incorporated for their
teachings of heat pipe or thermal siphon devices.
[0017] A stacked-fin heat sink device for a large scale integrated
circuit or processor chip package is disclosed in U.S. Pat. No.
6,061,235--Cromwell et al. In that device, a mounting fixture is
attached to the motherboard or other circuit card to surround the
processor, and the fixture receives a spring biased mounting that
presses a thermally conductive plate into full-surface mechanical
and thermal contact with the processor package. A heat pipe is
contained in a cylindrical vessel disposed centrally on and
longitudinally extending perpendicular to the thermally conductive
plate. A plurality of heat transfer fins are disposed parallel to
one another and perpendicular to the extension of the cylindrical
vessel. In this patent, which is hereby incorporated in this
disclosure, the thermally conductive plate at the bottom end of the
heat pipe vessel can function as the evaporator, having a slightly
higher temperature than the finned sidewalls of the vessel remote
from the bottom, which maintain a lower temperature and can
function as the condenser. In the standing configuration shown,
gravity can power the return path. In other orientations, a wicking
material can be provided so that capillary action drives the return
path.
[0018] The Cromwell arrangement represents a straightforward
application of a heat pipe to the known sort of finned heat
exchanger blocks that often are clamped to processor and VLSI
chips. However there is room for improvement.
[0019] The thermal plate arranged to contact the heat source (the
IC package) is an integral and continuous over the area of contact.
This would appear to provide good thermal coupling, but as a
result, the mounting of the heat pipe must be accomplished by
affixing the bottom of the cylindrical vessel to the flat opposite
face of the thermal plate. There are exacting production steps
involved to produce a cut cylinder bottom that matches the thermal
plate and to solder or otherwise securely affix the cylinder to the
plate in a manner that also seals the vessel to confine the heat
transfer fluid.
[0020] The spaced air-contact fins in Cromwell also present a
potential assembly demand. Whereas the fins are rectangular and the
heat pipe is a cylinder, there are issues respecting vertical,
horizontal and rotational alignment of the plates to the one
another, and attachment to the cylinder in good thermally
conductive contact. These problems appear to have been addressed by
affixing the fins to opposed side plates, thus requiring additional
parts and assembly while affecting the extent of available air
circulation. Air circulation characteristics and heat transfer
characteristics are also affected by the relative size of the heat
pipe and the fins.
[0021] A mounting plate arrangement has certain potentially useful
aspects in connection with a heat transfer device. A plate is
useful to present a large surface area for contact with a heat
source having a planar surface, such as a processor or VLSI
circuit. The rate of heat transfer by conduction is partly a
function of the area and intimacy of contact. The plate can have a
reasonably substantial thickness, which provides a thermal storage
capacity and leads to rapid heat transfer throughout the material
of the plate. Apart from these benefits, the drawbacks include the
complications associated with mounting the plate to the heat
source, the need to mount the thermal siphon vessel to the plate or
to form a vessel using the plate, and complication of attaching
heat dissipation structures such as fins for convective or forced
air contact.
[0022] In U.S. Pat. No. 5,826,645--Meyer, a thermal siphon vessel
comprises a tubular vessel wherein one end of the tubular vessel
forms the evaporator and is affixed in a channel in a thick plate.
A manufacturing challenge is to obtain intimate contact between the
plate and the tubular vessel for good thermal energy transfer. In
that patent, the problem is addressed by forming thin tabs at the
surface of the channel and bending the tabs against the vessel to
press the vessel against the bottom of the channel. This
arrangement provides for good contact between the tube and the
bottom of the channel, at the expense of contact elsewhere. It
would be advantageous to improve on such a structure both as to
thermal energy transfer efficiency and ease of manufacture.
[0023] It would be advantageous, to adapt the idea of thermal
siphon devices to dissipating unwanted concentrations of thermal
energy, in a way that optimally maximizes the efficiency of thermal
transfer, but minimizes the complexity and expense of such
devices.
SUMMARY OF THE INVENTION
[0024] It is an object of the invention concurrently to improve the
thermal energy transfer efficiency of a heat dissipation device and
the ease of manufacture of the device.
[0025] It is an object to employ at least one and preferably a
plurality of heat pipe vessels as structural support elements that
function to mount an air-exchange heat transfer fins on a
source-contact heat transfer base.
[0026] It is another object to minimize the number and complexity
of parts needed to construct a heat dissipation device.
[0027] It is still another object to modify structural aspects of a
heat pipe for a heat dissipation device, and a base for mounting
the device, to enable contact between the heat pipe and a heat
source directly from the source to the heat pipe as well as through
the base as a thermally conductive element.
[0028] These and other objects are met in a heat transfer device
such as a heat sink having one or more heat pipe tubes mounted in a
base plate. The heat pipe tubes have a working fluid in a vessel
with a wicking material between an evaporator and condenser. The
heat pipe traverses a through opening in the base plate and extends
along a receptacle in the base plate facing the heat source, this
portion preferably defining the heat pipe evaporator. The heat pipe
has legs extending perpendicularly from the base plate, that
preferably hold spaced heat transfer fins, the legs forming the
condenser part of a stacked tower of fins on the base plate.
Preferably two or more heat pipes are provided in the form of
U-shaped or L-shaped tubes that are flattened along the underside
of the base plate to bear against the heat source.
[0029] According to an inventive aspect, the leg(s) of one or more
U-shaped or L-shaped tubular heat pipes form the structural columns
that carry a column of stacked fins. According to another aspect,
these legs are rigidly held in position due to a transverse bend
formed in between the legs and the portions of the heat pipes that
extend through the openings in the base plate and along the
receptacle on the side of the base plate facing the heat
source.
[0030] The device as thus configured is easily and inexpensively
manufactured. The heat pipes can be charged and sealed before
assembly or afterwards, because the ends of the U-shapes or
L-shapes remain accessible. Although not excluded, no supplemental
fasteners are needed to arrange and support the assembled parts.
The base plate can be clamped with spring clips or the like to a
computer processor or VLSI chip to form an effective convection
heat dissipation device that actively moves heat into the ambient
air and can be scaled larger or smaller or coupled to fan for
additional cooling capacity as needed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] These and other features and advantages of the present
invention will be more fully disclosed in, or rendered obvious by,
the following detailed description of the preferred embodiments of
the invention, which are to be considered together with the
accompanying drawings wherein like numbers refer to like parts and
further wherein:
[0032] FIG. 1 is a perspective view of a heat dissipation tower for
circuit devices according to an embodiment of the invention having
two dual heat pipes;
[0033] FIG. 2 is a perspective view of the invention as shown in
FIG. 1, turned over to show details of the underside;
[0034] FIG. 3 is a perspective view illustrating a different
embodiment of the invention and showing the manner of assembly;
[0035] FIG. 4 is a perspective illustration of one form of dual
heat pipe for use with the invention;
[0036] FIG. 4A is a partially broken-away, partially
cross-sectional view of the dual heat pipe shown in FIG. 4, as
taken along lines 4A-4A;
[0037] FIG. 4B is a broken-away cross-sectional view of the dual
heat pipe shown in FIG. 4, as taken along lines 4B-4B;
[0038] FIG. 5 is an elevation view along lines 5-5 in FIG. 4,
showing the contour of the heat pipe including a flattened bottom
portion;
[0039] FIG. 6 is a perspective view showing an alternative heat
pipe structure with a transverse bend;
[0040] FIG. 6A is a partially broken-away, partially
cross-sectional view of the dual heat pipe shown in FIG. 6, as
taken along lines 6A-6A;
[0041] FIG. 7 is an elevation view along lines 7-7 in FIG. 6;
[0042] FIG. 8 is an elevation view, partly in section, showing
mounting of the heat dissipation tower on a heat source such as an
integrated circuit;
[0043] FIG. 9 is an exploded perspective view in which the
invention is applied to a single post heat pipe; and
[0044] FIG. 10 is an elevation view of the embodiment of FIG. 9 as
assembled.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0045] This description of preferred embodiments is intended to be
read in connection with the accompanying drawings, together forming
the description of the invention and illustrating certain
nonlimiting examples. The drawing figures are not necessarily to
scale and certain features are represented in schematic form in the
interest of clarity and conciseness.
[0046] Spatial and relative terms denoting an overall orientation,
such as "horizontal," "vertical," "up," "down," "top" and "bottom"
as well as their derivatives (e.g., "horizontally," "downwardly,"
"upwardly," etc.) are intended to refer to the orientation as then
described or as shown in the drawing figure under discussion. These
terms are used for convenience of description and are not intended
to require a particular orientation unless that is clear in the
context.
[0047] Likewise, internally relative terms such as "inwardly"
versus "outwardly," "longitudinal" versus "lateral" and the like
are to be interpreted relative to one another or relative to an
axis of elongation, rotation, assembly or the like, as appropriate
to the description.
[0048] Terms stating relationships of attachment, coupling and the
like, such as "connected" and "interconnected," refer to a
relationship wherein the structures can be attached, coupled,
connected (etc.) directly or indirectly through intervening
structures. Such attachments, couplings and the like can be movable
or rigid attachments, unless the description indicates otherwise.
Where elements are "operatively" connected, attached, or coupled,
that connection, attachment or coupling is intended to denote a
connection or the like that allows the pertinent structures to
operate as stated, by virtue of such relationship.
[0049] Insofar as the description and claims recite
means-plus-function clauses or elements are defined by their
function, those elements are intended to encompass the structures
described, suggested, or obvious in view of the written description
and/or drawings for performing the recited function.
[0050] Referring to FIGS. 1 through 10, a heat transfer device 20
according to the invention includes a heat pipe 22 forming a vessel
24 to be placed in thermally conductive relation to a heat source
25 (shown in FIG. 8). The heat pipe 22 has thermally conductive
material at least at an evaporator part 27 and at a condenser part
29 that are in fluid communication with one another, namely by
being connected to one another as different locations in the same
vessel 24. A heat transfer fluid 31 (shown in FIGS. 4a, 6a) is
contained in the vessel 24, and moves between the evaporator part
27 and the condenser part 29 for transferring heat energy.
[0051] Preferably the cyclic movement of the heat transfer fluid 31
is driven substantially by the heat energy of the heat source 25,
using a phase change cycle. The heat energy of the source 25 warms
and vaporizes the heat transfer fluid 31 at the evaporator 27, thus
storing latent heat energy. The vaporized heat transfer fluid
diffuses through the vessel 24. Latent heat energy is given up when
vaporized heat transfer fluid 31 is condensed due to cooling at the
condenser 29. The condensed heat transfer fluid 31 is returned to
the evaporator 27 and the cycle repeats. Return of the condensed
heat transfer fluid preferably involves capillary flow through a
wicking material 32 provided on the inside walls of the vessel 24
as shown in FIGS. 4a, 6a.
[0052] A base plate 33 at least partly supports the heat pipe 22
and preferably forms a substantial part of the thermally conductive
path from the heat source 25 to the heat transfer fluid 31 in
vessel 24. The base plate 33 has a side 35 that can be directed
toward the heat source 25, preferably being held against the heat
source. At least one through-opening or passage 36 through the base
plate 33 leads from a recess or opening 42 forming a receptacle for
the evaporator part 27 of the heat pipe 22. The recess or
receptacle 42 positions the evaporator 27 so as to absorb heat
energy from the heat source 25.
[0053] The heat pipe vessel 24 forms a passage coupling through the
base plate 33, namely from the evaporator part 27 at the receptacle
42 on the heat source side of the base plate 33, through the base
plate 33 to a heat sink 43 that, in the example shown, is defined
by a number of spaced fins 44 in thermal contact with the
evaporator part 29 on the opposite side of the base plate 33 from
the heat source 25. Part of the heat pipe 22 in the area of the
evaporator 27 preferably is in direct contact with the heat source
25. It is also possible for at least part of the heat pipe
functioning as the evaporator part 27 to be in contact or to have
an intervening structure (not shown) that couples heat energy to
the evaporator on a side of the base plate 33 opposite from the
heat transfer fins 44 or other heat sink 43. In any event, the heat
transfer fluid 31 at the evaporator 27 is heated, preferably but
not necessarily by a close contact thermal relationship, with the
heat source 25.
[0054] The heat transfer device 20 a heat sink 43 thermally coupled
to the heat pipe 22 apart from the evaporator 27 and base plate 33,
where the heat pipe is cooled by convection or by another thermal
path at which heat energy is dissipated. The heat sink 43 in the
embodiment shown comprises a stack of thermally conductive fins 44
in contact with ambient air that may be forced air or may be
circulated by convection due to heating from fins 44. The fins 44
are in thermal contact with the heat pipe 22 and dissipate heat
energy from the condenser part 29 of the heat pipe 22, at a
location that is relatively spaced from the evaporator 27 on the
side of the base plate 33 that is directed toward the heat source.
Other relative locations are possible, but the condenser 29 at
least is sufficiently distinct and/or distant from the evaporator
27 that the condenser 29 maintains a lower temperature than the
evaporator 27.
[0055] The fins 44 can be subjected simply to convection air or
currents due to localized heating. Alternatively, the fins 44 can
be in a forced air path. Other heat dissipation structures are also
possible, such as a heat exchange relationship with a liquid medium
as opposed to air. It is also possible to employ more than one form
of heat dissipation at the same time, in parallel or serial heat
energy transfer paths.
[0056] In the embodiment shown in the drawings, the receptacle 42
under the base plate 33 forms a channel or other recess that apart
from the through opening to the condenser extends only part way
through the thickness of the base plate 33, on the side or base
plate 33 directed toward the heat source 25. In the embodiment of
FIGS. 1 and 2, for example, the vessel 24 defines the evaporator 27
and the condenser 29 at different longitudinal positions along an
elongated tubular structure. The evaporator part can be at an end
or at an intermediate point disposed in the receptacle channel 42
of the base plate. The condenser part 29 forms a hollow supporting
column 52 protruding at the opposite side of the base plate 33 and
structurally supporting the fins 44.
[0057] The base plate 33 could have a thickness that is less than
or equal to that of the evaporator 27. Preferably, however, the
base plate 33 is thicker than an outside diameter or thickness of
the elongated tubular vessel or similar structure including the
evaporator 27. The receptacle 42 on the base plate 33 is
dimensioned to complement an outside shape of this elongated
tubular vessel structure, which preferably can be press fit or
otherwise intimately and securely fitted so as to support thermal
energy transfer. For optimal heat transfer contact, the heat pipe
22 and its tubular structure rest substantially in surface contact
with the base plate 33 at the receptacle 42, or are potted in the
receptacle by a material (not shown) having good heat transfer
characteristics, such as a metal solder or thermally conductive
adhesive or resin.
[0058] It is convenient and inexpensive to use a heat pipe
structure based on a cylindrical tube (i.e., a tube with a round
cross section), which can be formed or bent somewhat more easily
than other cross sections, such as rectangular tubes. However,
forming a rectangular channel to complement a rectangular tube is
likely to be an easier manufacturing job than forming a channel
with a rounded-bottom U-shaped or L-shaped contour for a round
tube. According to one aspect of the invention, a U-shaped or
L-shaped or preferably half-round contour in the base plate 33 can
be used for the receptacle 42 carrying a heat pipe tube with a
round cross section of complementary size, providing substantially
full surface contact between the heat pipe and the base plate over
part the sides of the receptacle 42. The tube can be press fit into
the receptacle. However the side 54 of the round heat pipe tube
facing toward the heat source 25 is flattened along a surface that
is substantially flush with the outside of the base plate 33. This
structure, shown in FIGS. 4a and 6a, provides a substantially
continuous surface oriented toward the heat source 25, preferably
contacting the heat source 25.
[0059] At least part of the flattened surface 54 corresponds with
is the evaporator part 27 of the heat pipe 22. The walls of the
heat pipe 22 can be relatively thin compared to the thickness of
the base plate, and as a result, heat energy can be coupled
efficiently into the evaporator 27 to vaporize the heat transfer
fluid 31.
[0060] In the respective drawings, several alternative arrangements
are shown for a heat dissipation device as described. Referring to
FIG. 1, one embodiment includes a base plate 33 comprising a
thermally conductive material and several tubular heat pipe columns
52 carried on the base plate 33 and in turn supporting parallel
spaced air-contact heat transfer fins 44. FIG. 2 shows, however,
that the several heat pipe columns 52 (four being shown) can be
paired columns associated with two dual heat pipe vessels. That is,
each of the two vessels 24 has an evaporator portion 27 along a
central part of the vessel 22 disposed parallel to and in the
recess 42 of the base plate 33 and exposed along a bottom side of
the base plate 33. Each of these vessels 22 has two opposite ends
that are diverted from the plane of the base plate 33 and the
exposed bottom side. These opposite ends are turned upwardly, the
opposite ends forming the columns 52 standing on the base plate 33
and providing structural support for the air-transfer fins 44.
[0061] FIGS. 1 and 2 show an embodiment with U-shaped dual heat
pipe vessels 62 in which the lowermost horizontal portion 64 of the
heat pipe vessel is disposed on the side of the base plate 33 that
is to face the heat source 25 when mounted as shown in FIG. 8. This
evaporator or central part 64 is disposed in a groove on the
underside of the baseplate 33 such that the evaporator is inset in
the groove and resides substantially flush with the surface of the
base plate 33 on its underside. The columns are formed by the legs
66 of the U-shape or L-shape at the ends of the vessel 22, which
are turned upwardly from the plane of the base is plate 33,
extending through the openings in the base plate 33 to support the
fins 44. This provides a good structural connection of the heat
pipe 22 to the base plate 33, for supporting the base plate, heat
pipe and air transfer fins in fixed relative positions.
[0062] There are a number of specific shapes possible wherein one
or more heat pipes 22 extends from an evaporator 27 exposed on the
underside of a base plate 33, through the base plate to support a
heat exchanger 43 such as a stack of air contact heat transfer fins
or plates 44. The four heat pipe columns in FIG. 1, which are the
dual condensers on the opposite ends of heat pipe vessels with
central evaporators, are generally U-shaped. The bottom 64 of each
U-shape (the evaporator) is generally parallel to the base plate 33
and exposed on the underside of the base plate. The sides or legs
66 of the U-shapes are perpendicular to the base plate.
[0063] The receptacle or slot 42 in the underside of the base plate
33 is straight for the embodiments in FIGS. 3-5. The receptacle or
slot in FIG. 2, however, also is U-shaped in a plane parallel to
that of the base plate, by virtue of a transverse bend 72 in the
bottom 64, namely a bend a plane that is perpendicular to the plane
of the U-shape that includes the legs 66. This transversely curved
slot receives a heat pipe vessel wherein a part of the vessel,
specifically the evaporator 27 in the embodiment shown, forms a
U-shape in a plane perpendicular to the plane of the leg sections.
The vessel nonetheless can be press fit into the U-shape of the
receptacle 42. Additionally, a solder or thermally conductive resin
or potting formulation can fill any spaces between the material of
the base plate 42 and that of the evaporator vessel 27. The bottom
side 54 of the evaporator 27, which preferably is flattened and
disposed flush with the base plate surface, can be treated to
enhance thermal conductivity by contact with the housing of the
circuit package. For example, the evaporator surface can be fly-cut
so as to be flat and smooth, for example to a local dimensional
flatness tolerance of 0.001", and thus complement a flat and
incompressible circuit package surface. Alternatively, if the
circuit passage is compressible, the evaporator surface can be
roughened or patterned to increase the surface area of contact.
[0064] The transverse bends shown in FIG. 2, wherein the legs 66
and bottom 64 on the one hand and the U-bottoms 64 on the other
hand, form separate perpendicular U-shapes. This shape with a
transverse bend in the bottom, where the heat pipe vessels 24 are
inserted into and engaged by the base plate 33, also shown apart
from the base plate in FIG. 6, avoids play or freedom of movement
that could enable the heat pipe vessel to become displaced. By
comparison, the shape of FIG. 4, for example, wherein the U-bottom
is in the same plane as the perpendicular legs 66, could be subject
to a tendency to rotate relative to the axial center of the
receptacle or slot holding the evaporator of the heat pipe, at
least within the range of any clearance. The embodiment of FIG. 2,
having a heat pipe vessel with a transverse bend that in this case
forms a U-shape in a plane parallel to the base plate, provides an
inherently rigid assembly when the heat pipe vessel and the base
plate are assembled, and is preferred. This structure in turn forms
a rigid and durable support for the air contact heat transfer fins
that are stacked on the condenser columns protruding on the
opposite side of the base plate.
[0065] FIG. 3 illustrates an arrangement in which a plurality of
heat pipe vessels 24 are provided, each of the heat pipe vessels in
this embodiment has an evaporator 27 and a condenser 29 in a right
angle arrangement. The base plate 33 has slots or receptacles 42
along an underside to be oriented toward a heat source (not show in
FIG. 3). These slots can be precisely complementary to the
evaporator ends of the heat pipes that are to reside along the
underside of the base plate when oriented as shown. Alternatively
and as also shown, the slots can extend across the full width
between the opposite edges of the base plate. Preferably, any
portion of the slots that is not occupied by the evaporators is
filled with a potting compound 77 or the like, to improve thermal
transfer.
[0066] The evaporator parts of the heat pipes 22 are set into the
slots 42 and the condenser parts 29 of the heat pipes extend
through the base plate 33 to engage and support the heat
dissipation fins 44. As in the embodiment of FIGS. 1 and 2, the
L-shaped arrangement of FIG. 3 comprises heat pipes wherein the
condenser ends are turned up and passed through openings that are
at least partly perpendicular to the plane of the base plate. In
this way, the heat pipes not only provide for a thermal transfer
route to pass heat energy from a heat source at the evaporator area
to the air contact heat dissipation fins, but moreover, the heat
pipes also form the columns that support the assembly as a unit. As
shown in FIG. 4 in perspective and FIG. 5 in end elevation, the
L-shaped arrangement of FIG. 3 can be replaced with a dual
arrangement in which two standing condenser columns 52 are coupled
in a U-shaped arrangement with a bottom evaporator portion 27
connecting between them.
[0067] In each of these embodiments, the evaporator parts of the
heat pipes are arranged to transfer heat efficiently by contact
with a heat source disposed under the base plate 33, such as an
integrated circuit package or the like against which the base plate
is clamped (not shown in FIG. 3). For best efficiency, the contact
is as intimate as possible between the heat source and the heat
transfer fluid inside the heat pipe vessel in the area of the
evaporator. Thus the wall of the heat pipe in the area of the
evaporator should be thin and constructed of a thermally conductive
metal or the like. Furthermore, according to an inventive aspect,
the heat pipe vessel is flattened at the evaporator as shown in
FIG. 4a, as compared to the preferred shape of the columns 52,
shown in FIG. 4b and preferably round. That is, the elongated
tubular structure of the heat pipe is flattened along a surface 54
coextensive with a surface of the base plate 33 on the side
directed toward the heat source. This increases the surface area
and provides more direct transfer of heat energy into the heat
transfer fluid, than does a round evaporator tube cross
section.
[0068] A round cross section is possible for the evaporator, but
the evaporator is carried in a receptacle slot having a downwardly
opening U-shaped contour, so a round evaporator contour is
characterized by a very limited area of surface contact between the
evaporator and the heat source (assuming that the heat source is
typically flat). Such an embodiment could provide a gap in the area
of contact, where the heat source and either the evaporator or the
base plate are spaced, particularly at the lateral edges of the
slots 42. The embodiments shown in FIG. 4, 4a, 4b and 5 have round
column condensers and flattened bottoms 54 on the evaporators 27 to
avoid such a gap. This provides a wide area of contact between the
evaporators 27 and the heat source 25, and also substantially fills
the available area between the lateral sides of the slots. In this
way, there is intimate contact and good heat transfer efficiency
between the source and the heat transfer fluid in the evaporator.
Alternatively, a solder or potting compound can close the gap.
[0069] As an alternative, the heat pipe vessel 22 can be formed of
square tubing (not shown) at least in the area of contact with the
heat source and with portions of the base plate. Square tubing has
a flat bottom side that can contact the heat source. A squared
channel as the receptacle for the evaporator part 27 of the heat
pipe is relatively easy to manufacture by machining or otherwise
providing a squared-side channel. The engagement of a squared
tubing form (or a tubing form that has at least two flattened faces
bearing respectively on the heat source and on at least one
complementary flat surface of the receptacle in the base plate) is
also an inherently rigid structural connection, i.e., one that
unlike a tubular connection is inherently held from rotating.
[0070] FIGS. 6, 6a and 7 illustrate that the flat bottom evaporator
configuration also is applicable to other specific configurations,
most notably including the embodiments of FIGS. 1 and 2, wherein
the heat pipes comprise dual condenser tubes with U-shapes having
at least one transverse bend. The embodiments shown are
structurally simple examples in which a U-shaped planar
configuration is provided with two bends of about 40 degrees, in
the same is direction, forming a symmetrical shape. Other specific
bends are possible, such as bends in opposite directions forming an
S-shape or zigzag, bends that are less discrete and form curves or
arcs, closed shapes such as polygons, etc.
[0071] In its general form, the heat pipe vessel extends through
the base plate so as to place the evaporator on the exposed
underside of the base plate and the condenser column extending from
the opposite side. The heat pipe vessel 22 also can be formed in
part from the structure of the base plate 33, for example having an
evaporator defined by a slot on the bottom of base plate 33 with a
cover closing the vessel 9 (not shown). In that case, tubes for
columns 52 can be inserted into sockets at openings communicating
with the evaporator through the base plate 33 from the opposite
side.
[0072] However in the preferred arrangement, the heat pipe vessel
22 is a discrete tube that is affixed to the base plate. In
addition to the opening at which the vessel extends through the
base plate 33 to couple the evaporator 27 to one condenser column
52, the preferred base plate has at least one further through
opening leading to a second condenser column 52. The evaporator is
exposed on the side of the base plate directed toward the heat
source. The elongated tubular structure of the vessel forms a
U-shape with legs traversing two spaced through openings connecting
through the base plate to the condensers. The preferred orientation
of the legs is perpendicular to the plane of the base plate. The
legs comprise parallel sections extending from the base plate, with
a bend to join perpendicularly with the evaporator at the bottom of
the U-shape, and preferably at least one transverse bend at the
bottom or the U-shape.
[0073] FIG. 8 illustrates the relationship between the heat source
25, which in this example comprises an integrated circuit 82 in a
packaged housing 84, and the heat transfer device 20 of the
invention. The integrated circuit comprises an active semiconductor
device in a housing that can be plastic or ceramic and is thermally
conductive. The housing is typically mounted by snap fit into a
receptacle 86 capable of making the necessary electrical
connections with leads that couple signal and power lines to the
circuit 82. The base plate 33 of the heat transfer device is
clamped directly in contact with the housing 84 of the
semiconductor device, for example via spring clips 88. In this way
the evaporator 27 on the underside of the base plate 33 takes up
thermal energy by direct contact with the housing 84 of the
semiconductor device and also by indirect thermal transfer from the
housing to the base plate and then to the evaporator. The thermal
transfer from the base plate to the evaporator can be enhanced by
appropriate choice of potting compound or solder to affix the
evaporator in the receptacle on the underside of the base
plate.
[0074] The heat transfer fins attached to the columnar condenser
parts of the heat pipe vessels provide a heat sink apparatus in
that the heat released by the heat transfer fluid in the heat pipe
vessels is coupled by thermal conduction to the fins 44. The fins
can be press fit, soldered, or epoxied to the columnar condenser
parts 52. The fins 44 can be wholly flat sheets with openings that
slide onto the condenser columns 52. Alternatively, the fins 44 can
be stamped to include flanges or collars of metal surrounding the
openings for the columnar condensers (not shown). Insofar as such
flanges extend for a short distance perpendicular to the plane of
the fins, the flanges improve the rigidity of structural connection
and also increase the intimacy of thermally conductive contact
between the condenser parts and the fins. The flanges can also
assist in obtaining equal close spacing of the fins along the
spaced parallel columns of the condensers.
[0075] The respective dimensions of the heat pipe, base plate and
fins are subject to variations as necessary for the circumstances.
In a typical exemplary application, the heat source is a packaged
highly integrated processor circuit chip that may produce heat at a
rate of 100 Watts, but in a typical ambient air temperature up to
40.degree. C. may need to be maintained at or below 70.degree. C.
for dependable operation. Such a chip may be 9 to 11 mm thick and
up to 30 mm on a side.
[0076] The heat dissipation device of the invention can have a base
plate with the same area or footprint as the circuit package, so as
to be attachable to bear against the circuit package as shown in
FIG. 8. The heat pipe columns are arranged so that the evaporator
parts that are exposed on the underside of the base plate occupy a
central area of the chip package, namely the area that aligns with
the semiconductor element that actually produces the heat. The
dimensions and capacity of the heat pipes is then chosen to provide
the necessary rate of heat dissipation.
[0077] An advantage of the invention is that in addition to
functioning as structural columns, the use of several heat pipes of
relatively smaller diameter produces greater surface area per unit
volume than a single larger diameter structure (or perhaps a
smaller number, such as two columns instead of four. As a is
result, there is a comparable heat transfer efficiency achieved in
a smaller heat pipe volume.
[0078] Another advantage of the invention is that the exposure of
the evaporator part of the heat pipe on the lower face of the base
plate provides a more direct thermal conduction path than a
comparable arrangement in which an evaporator is coupled to the top
surface of a base plate, or even an arrangement in which the
baseplate forms a relatively thick bottom wall of an evaporator.
This advantage of direct thermal contact can be achieved in an
arrangement having fewer than four heat pipe structural columns,
for example two or three, or even a single column 92 as shown in
FIGS. 9 and 10. In this embodiment, the single column 92 is
provided by a heat pipe tube that has a relatively wider evaporator
section 94 on the bottom of a coaxial cylindrical column 96 forming
the condenser. Of course a non-round cross sectional shape is also
possible. The evaporator resides in a receptacle or recess 98 that
is complementary with the evaporator part, namely round in this
example. The condenser column, as in the previous embodiments, is
connected to the evaporator part by a part of the heat pipe
extending through an opening in the base plate. The evaporator part
is thereby positioned for direct contact with the heat source (not
shown in FIGS. 9, 10). The condenser part forms a structural
support column for the air heat exchange fins.
[0079] The embodiment of FIGS. 9 and 10, which has a single column
heat pipe, generally results in a more substantial obstruction to
air flow than a plurality of smaller width heat columns as in the
previous embodiments. This larger obstruction is not preferred in a
forced air situation, such as an installation in which is a fan
(not shown) directs a flow of air over the fins, in a direction
perpendicular to the longitudinal extension of the condenser. For
such installations, a larger number of smaller columns are
preferred for providing good structural support for the fins on the
base plate, with optimal surface area of contact between the
condensers and the fins at points that are generally distributed
over the fins as opposed to concentrated. The attachment of the
evaporator(s) in the recess in the base plate, and the attachment
of the condenser(s) in the fins, can be made by a press fit, a
potting compound, an adhesive, a solder or other specific
connections that are capable of conveying heat energy across the
attachment.
[0080] The internal arrangements of the heat pipe in the overall
heat dissipation or heat sink device can otherwise incorporate a
number of the aspects of known heat pipes. The heat pipe vessel(s)
form an envelope containing a working fluid, and are either
oriented for gravity return of condensed fluid to the evaporator,
or have a wicking material along the inside walls so as to return
the condensed fluid by capillary action. The wick can be structured
as sintered particles, fibers or the like, and in a preferred
arrangement includes micro-encapsulated phase change particles that
are adhered to the inside surfaces of the walls of the vessel. The
vessel is vacuum tight and may be formed from a sealed tube of
thermally conductive material, e.g., aluminum, copper, titanium
alloy, tungsten, etc. Although shown as substantially tubular with
flattened surfaces for contact with the heat source, the heat pipe
vessels can take other shapes.
[0081] The working thermal transfer fluid can be selected from a
variety of well known two phase fluids depending upon expected
operational conditions such as the operating temperature range over
which the heat transfer device will operate. Appropriate fluids may
include, for example, one or more of water, Freon, ammonia,
acetone, methanol, ethanol and the like. The prime requirements for
a suitable working fluid are compatibility with the materials
forming wick and the envelope wall, good thermal stability, ease of
wetting of the wick and wall materials as well as viscosity and
surface tension attributes suitable for capillary flow.
[0082] The working fluid can be charged into the heat pipe vessels
before or after the assembly with the base plate and heat transfer
fins, because the arrangement is characterized by access to the
heat pipe vessel after assembly, at least at an end located at the
uppermost fin. In that case, the vessel is first shaped and
attached, but is unsealed at a limited point such as a charging
tube as shown in FIG. 9. The working fluid is added, usually after
partially evacuating the air in the vessel, and the charging tube
is then plugged by adhesive, soldering and/or crimping
operations.
[0083] The pressure and working fluid charge are arranged to obtain
an operating vapor pressure in the vessel over the working
temperature range, within vapor pressure limits that permit
evaporation and condensation to occur at different points in the
vessel (i.e., at the evaporator and condenser parts) when
maintained at design temperature differences. For optimal results,
at all points within the temperature range, the working fluid has
advantageous characteristics including high latent heat storage
capacity, high thermal conductivity, low liquid and vapor
viscosities, high surface tension and an acceptable freezing or
pour point. Preferably, the quantity of working fluid in the vessel
is at least enough to saturate any wick material provided, or to
support a gravity flow in a circulating manner in the absence of a
wick.
[0084] In a preferred arrangement, the heat pipe vessel comprises
one or more metals such as silver, gold, copper, aluminum, titanium
or their alloys. Polymeric materials are also useful, including
materials known in the electronics industry for heat transfer
applications, such as thermoplastics (crystalline or
non-crystalline, cross-linked or non-cross-linked), thermosetting
resins, elastomers or blends or composites thereof. Some
illustrative examples of useful thermoplastic polymers include,
without limitation, polyolefins, such as polyethylene or
polypropylene, copolymers (including terpolymers, etc.) of olefins
such as ethylene and propylene, with each other and with other
monomers such as vinyl esters, acids or esters of unsaturated
organic acids or mixtures thereof, halogenated vinyl or vinylidene
polymers such as polyvinyl chloride, polyvinylidene chloride,
polyvinyl fluoride, polyvinylidene fluoride and copolymers of these
monomers with each other or with other unsaturated monomers,
polyesters, such as poly(hexamethylene adipate or sebacate),
poly(ethylene terephthalate) and poly(tetramethylene
terephthalate), polyamides such as Nylon-6, Nylon-6,6, Nylon-6,10,
Versamids, polystyrene, polyacrylonitrile, thermoplastic silicone
resins, thermoplastic polyethers, thermoplastic modified cellulose,
polysulphones and the like.
[0085] Examples of some useful elastomeric resins for potting and
adhesive aspects include, without limitation, elastomeric gums and
thermoplastic elastomers, natural or synthetic. The term
"elastomeric gum", refers to polymers which are noncrystalline and
which exhibit after cross-linking rubbery or elastomeric
characteristics. The term "thermoplastic elastomer" refers to
materials which exhibit, in various temperature ranges, at least
some elastomer properties. Such materials generally contain
thermoplastic and elastomeric moieties. For purposes of this
invention, the elastomer resin can be cross-linked or non
cross-linked when used in the inventive compositions.
[0086] Illustrative examples of some suitable elastomeric gums for
use in this invention include, without limitation, polyisoprene
(both natural and synthetic), ethylene-propylene random copolymers,
poly(isobutylene), styrene-butadiene random copolymer rubbers,
styrene-acrylonitrile-butadie- ne terpolymer rubbers with and
without added copolymerized amounts of unsaturated carboxylic
acids, polyacrylate rubbers, polyurethane gums, random copolymers
of vinylidene fluoride and, for example, hexafluoropropylene,
polychloroprene, chlorinated polyethylene, chlorosulphonated
polyethylene, polyethers, plasticized poly(vinyl chloride),
substantially non-crystalline random co- or ter-polymers of
ethylene with vinyl esters or acids and esters of unsaturated
acids, silicone gums and base polymers, for example, poly(dimethyl
siloxane), poly(methylphenyl siloxane) and poly(dimethyl vinyl
siloxanes).
[0087] Some illustrative examples of thermoplastic elastomers
suitable for use in the invention include, without limitation,
graft and block copolymers, such as random copolymers of ethylene
and propylene grafted with polyethylene or polypropylene
side-chains, and block copolymers of -olefins such as polyethylene
or polypropylene with ethylene/propylene or
ethylene/propylene/diene rubbers, polystyrene with polybutadiene,
polystyrene with polyisoprene, polystyrene with ethylene-propylene
rubber, poly(vinylcyclohexane) with ethylene-propylene rubber,
poly(-methylstyrene) with polysiloxanes, polycarbonates with
polysiloxanes, poly(tetramethylene terephthalate) with
poly(tetramethylene oxide) and thermoplastic polyurethane
rubbers.
[0088] Examples of some thermosetting resins useful herein include,
without limitation, epoxy resins, such as resins made from
epichlorohydrin and bisphenol A or epichlorohydrin and aliphatic
polyols, such as glycerol, and which can be conventionally cured
using amine or amide curing agents. Other examples include phenolic
resins obtained by condensing a phenol with an aldehyde, e.g.,
phenol-formaldehyde resin. Other additives can also be present in
the composition, including for example fillers, pigments,
antioxidants, fire retardants, cross-linking agents, adjuvants and
the like.
[0089] It is to be understood that the invention is not limited
only to the particular constructions herein disclosed and shown in
the drawings, but also encompasses modifications or equivalents
within the scope of the appended claims.
* * * * *