U.S. patent application number 13/058356 was filed with the patent office on 2011-12-22 for thermally conductive gel packs.
This patent application is currently assigned to PARKER HANNIFIN CORPORATION. Invention is credited to Philip Blazdell, Michael H. Bunyan, Eoin O'Riordan, Harish Rutti, Gary Wood.
Application Number | 20110308781 13/058356 |
Document ID | / |
Family ID | 41403006 |
Filed Date | 2011-12-22 |
United States Patent
Application |
20110308781 |
Kind Code |
A1 |
O'Riordan; Eoin ; et
al. |
December 22, 2011 |
THERMALLY CONDUCTIVE GEL PACKS
Abstract
A conformable, thermally-conductive gel pack is provided having
a thermal gel encapsulated by a compliant packaging material formed
from a dielectric polymer. The gel pack is adapted for emplacement
between opposed heat transfer surfaces in an electronic device. One
heat transfer surface can be part of a heat-generating component of
the device, while the other heat transfer surface can be part of a
heat sink or a circuit board.
Inventors: |
O'Riordan; Eoin;
(Buckinghamshire, GB) ; Blazdell; Philip;
(Bicester, GB) ; Wood; Gary; (Windham, NH)
; Bunyan; Michael H.; (Chelmsford, MA) ; Rutti;
Harish; (Slough Berks, GB) |
Assignee: |
PARKER HANNIFIN CORPORATION
Cleveland
OH
|
Family ID: |
41403006 |
Appl. No.: |
13/058356 |
Filed: |
September 24, 2009 |
PCT Filed: |
September 24, 2009 |
PCT NO: |
PCT/US09/58188 |
371 Date: |
June 1, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61100297 |
Sep 26, 2008 |
|
|
|
Current U.S.
Class: |
165/185 |
Current CPC
Class: |
H05K 7/20454 20130101;
H01L 2924/0002 20130101; H01L 2924/09701 20130101; H01L 2924/0002
20130101; H01L 23/3737 20130101; H01L 2924/00 20130101; H01L
2924/3011 20130101 |
Class at
Publication: |
165/185 |
International
Class: |
F28F 7/00 20060101
F28F007/00 |
Claims
1. A conformable thermally-conductive gel pack adapted to be
positioned intermediate a first heat transfer surface and an
opposing second heat transfer surface to provide a thermal pathway
there between, the gel pack comprising a thermally conductive
polymeric gel encapsulated in a compliant package comprising a
layer of a polymeric material.
2. The gel pack of claim 1 wherein one of the first or second heat
transfer surfaces is located on a heat-generating source.
3. The gel pack of claim 2 wherein: the heat-generating source is
an electronic component; and the other one of the first or second
heat transfer surface is located on a thermal dissipation
member.
4. The gel pack of claim 3 wherein the thermal dissipation member
is a heat sink or a circuit board.
5. The gel pack of claim 1 wherein the gel comprises a silicone
polymer.
6. The gel pack of claim 1 wherein the gel is filled with a
thermally-conductive particulate filler.
7. The gel pack of claim 6 wherein the particulate filler is
selected from the group consisting of boron nitride, titanium
diboride, aluminum nitride, silicon carbide, graphite, metals,
metal oxides, and mixtures thereof.
8. The gel pack of claim 6 wherein the filled gel comprises between
about 20-80% by weight of the filler.
9. The gel pack of claim 6 wherein the filler has a thermal
conductivity of at least about 20 W/m-K.
10. The gel pack of claim 6 the filled gel has a thermal
conductivity of at least about 0.5 W/m-K.
11. The gel pack of claim 1 wherein the interface has a thermal
impedance of less than about 1.degree. C.-in.sup.2/W (6.degree.
C.-cm.sup.2/W).
12. The gel pack of claim 1 wherein the polymeric material forming
the layer of the package is a dielectric.
13. The gel pack of claim 1 herein the polymeric material forming
the layer of the package is selected from the group consisting of
polyimides, polyamides, and copolymers and blends thereof.
14. A thermal management assembly comprising: a first heat transfer
surface; a second heat transfer surface opposing said first heat
transfer surface; and a conformable thermally-conductive gel pack
disposed intermediate said first and said second heat transfer
surfaces to provide a thermally-conductive pathway there between,
the gel pack comprising a thermally-conductive polymeric gel
encapsulated in a compliant package comprising at least one layer
of a polymeric material.
15. The assembly of claim 14 wherein one of the first or second
heat transfer surfaces is located on a heat-generating source.
16. The assembly of claim 15 wherein: the heat-generating source is
an electronic component; and the other one of the first or second
heat transfer surface is located on a thermal dissipation
member.
17. The assembly of claim 16 wherein the thermal dissipation member
is a heat sink or a circuit board.
18. The assembly of claim 14 wherein the gel comprises a silicone
polymer.
19. The assembly of claim 14 wherein the gel is filled with a
thermally-conductive particulate filler.
20. The assembly of claim 19 wherein the particulate filler is
selected from the group consisting of boron nitride, titanium
diboride, aluminum nitride, silicon carbide, graphite, metals,
metal oxides, and mixtures thereof
21. The assembly of claim 19 wherein the filled gel comprises
between about 20% to about 80% by weight of the filler.
22. The assembly of claim 19 wherein the filler has a thermal
conductivity of at least about 20 W/m-K.
23. The assembly of claim 19 the filled gel has a thermal
conductivity of at least about 0.5 W/m-K.
24. The assembly of claim 14 wherein the interface has a thermal
impedance of less than about 1.degree. C.-in.sup.2/W (6.degree.
C.-cm.sup.2/W).
25. The assembly of claim 14 wherein the polymeric material forming
the layer of the package is a dielectric.
26. The assembly of claim 14 herein the polymeric material forming
the layer of the package is selected from the group consisting of
polyimides, polyamides and copolymers and blends thereof
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/100,297, filed on Sep. 26, 2008, the disclosure
of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a new thermal product or
form factor which combines the thermal and mechanical performance
of a fully dispensable material with the ease of use of traditional
gap filler pads. In particular, the invention relates to a thermal
gel material encapsulated in a compliant polymeric dielectric
package that can be conveniently utilized in an electronic
application requiring thermal management.
[0003] Circuit designs for modem electronic devices such as
televisions, radios, computers, medical instruments, business
machines, communications equipment, and the like have become
increasingly complex. For example, integrated circuits have been
manufactured for these and other devices which contain the
equivalent of hundreds of thousands of transistors. Although the
complexity of the designs has increased, the size of the devices
has continued to shrink with improvements in the ability to
manufacture smaller electronic components and to pack more of these
components in an ever smaller area.
[0004] In recent years, electronic devices have become smaller and
more densely packed. Designers and manufacturers are now facing the
challenge of dissipating the heat generated in these devices using
various thermal management systems. Thermal management has evolved
to address the increased temperatures created within such
electronic devices as a result of the increased processing speed
and power of these devices. The new generation of electronic
components squeeze more power into a smaller space; and hence the
relative importance of thermal management within the overall
product design continues to increase.
[0005] An integral part of a thermal design process is the
selection of the optimal Thermal Interface Material ("TIM") for a
specific product application. New designs have been devised for
thermal management to help dissipate the heat from electronic
devices for further enhancing their performance. Other thermal
management techniques utilize concepts such as a "cold plate", or
other heat sinks which can be easily mounted in the vicinity of the
electronic components for heat dissipation. The heat sink may be a
dedicated, thermally-conductive metal plate, or simply the chassis
or circuit board of the device.
[0006] To improve the heat transfer efficiency through the
interface, a pad or other layer of a thermally-conductive,
electrically-insulating material often is interposed between the
heat sink and electronic component to fill in any surface
irregularities and eliminate air pockets. Initially employed for
this purpose were materials such as silicone grease or wax filled
with a thermally-conductive filler such as aluminum oxide. Such
materials usually are semi-liquid or solid at normal room
temperature, but may liquefy or soften at elevated temperatures to
flow and better conform to the irregularities of the interface
surfaces.
[0007] The greases and waxes of the aforementioned types generally
are not self-supporting or otherwise form-stable at room
temperature, and are considered to be messy to apply to the
interface surface of the heat sink or electronic component.
Consequently, these materials are typically provided in the form of
a film, which often is preferred for ease of handling, a substrate,
a web, or other carrier which introduces another interface layer in
or between the surfaces in which additional air pockets may be
formed. Moreover, the use of such materials typically involves hand
application or lay-up by the electronics assembler which increases
manufacturing costs.
[0008] Alternatively, another approach is to substitute a cured,
sheet-like material in place of the silicone grease or wax. Such
materials may contain one or more thermally-conductive particulate
fillers dispersed within a polymeric binder, and may be provided in
the form of cured sheets, tapes, pads, or films. Typical binder
materials include silicones, urethanes, thermoplastic rubbers, and
other elastomers, with typical fillers including aluminum oxide,
magnesium oxide, zinc oxide, boron nitride, and aluminum
nitride.
[0009] Exemplary of the aforesaid interface materials are alumina
or boron nitride-filled silicone or urethane elastomers.
Additionally, U.S. Pat. No. 4,869,954 discloses a cured,
form-stable, sheet-like, thermally-conductive material for
transferring thermal energy. The material is formed of a urethane
binder, a curing agent, and one or more thermally conductive
fillers. The fillers, which may include particles of aluminum
oxide, aluminum nitride, boron nitride, magnesium oxide, or zinc
oxide.
[0010] Sheets, pads, and tapes of the above-described types have
garnered general acceptance for use as interface materials in the
conductive cooling of electronic component assemblies such as
semiconductor chips, as described in more detail in U.S. Pat. No.
5,359,768. In certain applications, however, fastening elements
such as springs, clamps, and the like are required to apply enough
force to conform these materials to the interface surfaces in order
to attain enough surface for efficient thermal transfer. This
represents a distinct disadvantage for deploying these materials in
practical applications.
[0011] Phase-change materials have recently been introduced which
are self-supporting and form-stable at room temperature for ease of
handling, but which liquefy or otherwise soften at temperatures
within the operating temperature range of the electronic component
to form a viscous, thixotropic phase which better conforms to the
interface surfaces. These phase-change materials, which may be
supplied as free-standing films, or as heated screens printed onto
a substrate surface, advantageously function much like greases and
waxes in conformably flowing within the operating temperature of
the component under relatively low clamping pressures. Such
materials are further described in U.S. Pat. No. 6,054,198.
[0012] For typical commercial applications, the thermal interface
material may be supplied in the form of a tape or sheet which
includes an inner and outer release liner and an interlayer of a
thermal compound. Unless the thermal compound is inherently tacky,
one side of the compound layer may be coated with a thin layer of a
pressure-sensitive adhesive (PSA) for application of the compound
to the heat transfer surface of a heat sink. In order to facilitate
automated dispensing and application, the outer release liner and
compound interlayer of the tape or sheet may be die cut to form a
series of individual, pre-sized pads. Each pad thus may be removed
from the inner release liner and bonded to the heat sink using the
adhesive layer in a conventional "peel and stick" application which
may be performed by the heat sink manufacturer.
[0013] U.S. Pat. No. 6,054,198 discloses a thermally-conductive
interface for cooling a heat-generating electronic component having
an associated thermal dissipation member such as a heat sink. The
interface is formed as a self-supporting layer of a
thermally-conductive material which is form-stable at normal room
temperature in a first phase, and substantially conformable in a
second phase to the interface surfaces of the electronic component
and thermal dissipation member. The material has a transition
temperature from the first phase to the second phase which is
within the operating temperature range of the electronic
component.
[0014] U.S. Pat. No. 7,208,192 discloses the application of a
thermally and/or electrically conductive compound to fill a gap
between a first and second surface. A supply of fluent, form-stable
compound is provided as an admixture of a cured polymer gel
component and a particulate filler component. The compound is
dispensed from a nozzle under an applied pressure onto one of the
surfaces which is contacted with the opposing surface to fill the
gap there between.
[0015] The respective disclosures of each of the patents and patent
applications listed above are incorporated by reference herein in
their entireties.
[0016] In view of the variety of materials and applications
currently used in thermal management, as exemplified by the
foregoing, it is to be expected that continued improvements in
thermal management materials and applications would be
well-received by electronics manufacturers.
[0017] Accordingly, it is an objective of the present invention to
provide improved thermal managements materials which provide a high
degree of heat transfer efficiency and heat dissipation, are fully
conformal to the particular application, and are easy to use and
manufacture.
SUMMARY OF THE INVENTION
[0018] The invention is a thermal gel material encapsulated in a
dielectric polymer, such as a polyimide, polyamide or other such
material, formed into a package, a bag or similar enclosure that
confers the benefits of a fully cured, dispensable gap filler
material without the need for using or investing in expensive
dispensing equipment. This allows the customer to use
ultra-compliant materials for sensitive applications, while
maintaining the ease of pick-and-place technology and a convenient
product form factor.
[0019] In one embodiment, the invention is a conformable,
thermally-conductive interface adapted to be positioned between two
heat transfer surfaces to provide a thermal pathway there between,
the interface comprising a thermally conductive polymeric gel
encapsulated in a compliant package comprising a polymeric
material. In one aspect, the thermally conductive polymeric gel
comprises a silicone polymer containing a thermally conductive
particulate filler, such as particles of boron nitride, and the
polymeric packaging material is a dielectric polymer such as a
polyimide or a polyamide. In another aspect, the package comprises
two layers of heat sealable polymeric material encapsulating the
thermally conductive gel, with one layer optionally comprising a
thermal tape layer.
[0020] In another embodiment, a conformable, thermally-conductive
interface material is prepared by dispensing a thermally conductive
polymeric gel onto a first layer of a dielectric polymer or a
thermal tape. A second layer of dielectric polymer is place over
the first layer, and heat sealed (or sealed with an adhesive) to
the first layer to encapsulate the thermally conductive gel. The
resulting gel packs can be manufactured as discrete items or using
automated processing machinery, if desired, to dispense the gel
pack in a roll on an assembly line. The amount of polymeric gel in
the gel pack can be varied depending on customer requirements and
can address a range of thickness requirements. The packaging
material can additionally be slit or cut to allow for material
displacement under load.
[0021] The gel pack can be used in an electronic device where it
can be disposed between a first heat transfer surface and a second
heat transfer surface. The first heat transfer surface can be part
of a component designed to absorb heat, such as a heat sink or a
circuit board. The second heat transfer surface can be part of a
heat generating source, such as an electronic component. In use,
the gel pack is place between the first and second surfaces and is
displaced under low deflection forces allowing the material to
conform to the joint surfaces, thereby providing excellent thermal
conductivity using only a low closure pressure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a cross-sectional view of one embodiment of the
invention showing a gel pack comprising a thermally conductive gel
sandwiched between two layers of plastic sheet material heat sealed
at the edge portions thereof to encapsulate the gel.
[0023] FIG. 2 is a cross-sectional view of another embodiment of
the invention showing a gel pack comprising a thermally conductive
gel sandwiched between a layer of plastic sheet material and a
thermal tape heat sealed at the edge portions thereof to
encapsulate the gel.
[0024] Those skilled in the art will appreciate that elements in
the figures are illustrated for simplicity and clarity and have not
necessarily been drawn to scale. For example, the dimensions of
some of the elements in the figures may be exaggerated relative to
other elements to help to improve understanding of embodiments of
the present invention. Certain terminology may be employed in the
description to follow for convenience rather than for any limiting
purpose.
DETAILED DESCRIPTION OF THE INVENTION
[0025] The invention provides a thermally conductive gel pack
adapted to be positioned between two heat transfer surfaces of
components used in electronic devices. The gel pack of the
invention has improved heat transfer and handling characteristics
for enhanced thermal management as compared to other products
currently in use.
[0026] As used herein, the term "thermal management" refers to the
capability of keeping temperature-sensitive elements in an
electronic device within a prescribed operating temperature in
order to avoid system failure or serious system performance
degradation.
[0027] The term "EMI shielding" includes, and is interchangeable
with, electromagnetic compatibility (EMC), electrical conduction
and/or grounding, corona shielding, radio frequency interference
(RFI) shielding, and anti-static, i.e., electro-static discharge
(ESD) protection.
[0028] A "conformable" product is one which displays sufficient
flexibility to conform to the contours of the interface with
minimal or low force deflection characteristics.
[0029] As described herein, the thermally and/or
electrically-conductive gel packs of the invention are principally
described in connection with the usage of such gel packs within a
thermal management assembly as a thermal interface material
interposed between adjacent heat transfer surfaces. The heat
transfer surfaces may be part of heat generating components, such
as electronic components, or heat dissipation components, such as
heat sinks or electronic circuit boards. However, one skilled in
the art will readily appreciate that the present gel packs can have
other uses which are fully intended to be within the scope of the
present invention.
[0030] In accordance with the present invention, therefore, a gel
pack is provided comprising a flexible, conformable plastic
package, such as a bag or other container, having an interior
compartment for containing a thermal conductive substance, such as
a thermally conductive polymeric gel. Preferably, the plastic is a
conformable dielectric polymer, such as a polyamide or a
polyimide.
[0031] The package can be conveniently formed from two layers of
plastic material by, for instance, dispensing the gel onto a first
plastic layer, and placing a second plastic layer over the first
layer to thereby encapsulate the gel within both layers of plastic.
The plastic layers can then be heat sealed or glued at the outer
edges where the layers overlap to form the gel pack. The resulting
gel pack is fully conformable so as to be capable of filling gaps
between adjoining surfaces of the circuitry components, circuit
boards, and housings of electronic devices and electrical
equipment, or between other adjoining surfaces such as may be found
in building structures and the like.
[0032] Gels useful as the polymer gel component of the invention
include gels based on silicones, i.e., polysiloxanes, such as
polyorganosiloxane, as well as gels based on other polymers, which
may be thermoplastic or thermosetting, such as polyurethanes,
polyureas, fluoropolymers, chlorosulfonates, polybutadienes,
butyls, neoprenes, nitrites, polyisoprenes, and buna-N, copolymers
such as ethylene-propylene (EPR), styrene-isoprene-styrene (SIS),
styrene-butadiene-styrene (SBS), ethylene-propylene-diene monomer
(EPDM), nitrile-butadiene (NBR), styrene-ethylene-butadiene (SEB),
and styrene-butadiene (SBR), and blends thereof such as ethylene or
propylene-EPDM, EPR, or NBR. Suitable thermal gels include the
THERM-A-GAP.TM. gel products, which are highly conformable,
pre-cured, single-component compounds requiring only a relatively
small compression force.
[0033] As used herein, the terms "polymer gel" or "polymeric gel"
generally have their conventional meaning of a fluid-extended
polymer system which may include a continuous polymeric phase or
network, which may be chemically, e.g., ionically or covalently, or
physically cross-linked, and an oil, such as a silicone or other
oil, a plasticizer, unreacted monomer, or other fluid extender
which swells or otherwise fills the interstices of the network. The
cross-linking density of such network and the proportion of the
extender can be controlled to tailor the modulus, i.e., softness,
and other properties of the gel. The term "polymer gel" or
"polymeric gel" should also be understood to encompass materials
which alternatively may be classified broadly as pseudogels or
gel-like having viscoelastic properties similar to gels, such as by
having a "loose" cross-linking network formed by relatively long
cross-link chains, but as, for example, lacking a
fluid-extender.
[0034] In accordance with one aspect of the present invention, the
polymer gel component is rendered thermally-conductive by loading
the gel with a filler component which may comprise one or more
thermally-conductive particulate fillers. In this regard, the
polymer gel component generally forms a binder into which the
thermally-conductive filler is dispersed. The filler is included in
proportion sufficient to provide the thermal conductivity desired
for the intended application, and generally will be loaded in an
amount of between about 20% and about 80% by total weight of the
compound. The size and shape of the filler is not critical for the
purposes of the present invention. In this regard, the filler may
be of any general shape, referred to broadly as "particulate,"
including solid or hollow spherical or microspherical flake,
platelet, irregular, or fibrous, such as chopped or milled fibers
or whiskers, but preferably will be a powder to assure uniform
dispersal and homogeneous mechanical and thermal properties. The
particle size or distribution of the filler typically will range
from between about 0.01 mil to about 10 mil (0.25 .mu.m-250 .mu.m),
which may be a diameter, imputed diameter, length, or other
dimension of the particle, but may further vary depending upon the
thickness of the gap to be filled. If desired, the filler may be
electrically-nonconductive such that compound may be both
dielectric or electrically-insulating and thermally-conductive.
Alternatively, the filler may be electrically-conductive in
applications where electrical isolation is not required.
[0035] Suitable thermally-conductive fillers generally include
oxide, nitride, carbide, diboride, graphite, and metal particles,
and mixtures thereof, and more particularly boron nitride, titanium
diboride, aluminum nitride, silicon carbide, graphite, metals such
as silver, aluminum, and copper, metal oxides such as aluminum
oxide, magnesium oxide, zinc oxide, beryllium oxide, and antimony
oxide, and mixtures thereof. Such fillers characteristically
exhibit a thermal conductivity of at least about 20 W/m-K. For
reasons of economy, an aluminum oxide, i.e., alumina, may be used,
while for reasons of improved thermal conductivity a boron nitride
would be preferred. Loaded with the thermally-conductive filler,
the compound typically may exhibit a thermal conductivity, per ASTM
D5470, of at least about 0.5 W/m-K, which may vary depending upon
the thickness of the compound layer.
[0036] In accordance with another aspect of the present invention,
the polymer gel component can be rendered electrically-conductive
by loading with an electrically-conductive filler, which may be
provided in addition to, i.e., a blend, or instead of a
thermally-conductive filler. Also, depending upon the filler
selected, such filler may function as both a thermally and an
electrically-conductive filler. The use of electrically conductive
materials provides the gel with EMI shielding characteristics.
[0037] Suitable electrically-conductive fillers include: noble and
non-noble metals such as nickel, copper, tin, aluminum, and nickel;
noble metal-plated noble or non-noble metals such as silver-plated
copper, nickel, aluminum, tin, or gold; non-noble metal-plated
noble and non-noble metals such as nickel-plated copper or silver;
and noble or non-noble metal plated non-metals such as silver or
nickel-plated graphite, glass, ceramics, plastics, elastomers, or
mica; and mixtures thereof. The filler again may be broadly
classified as "particulate" in form, although the particular shape
of such form is not considered critical to the present invention,
and may include any shape that is conventionally involved in the
manufacture or formulation of conductive materials of the type
herein involved including hollow or solid microspheres, elastomeric
balloons, flakes, platelets, fibers, rods, irregularly-shaped
particles, or a mixture thereof. Similarly, the particle size of
the filler is not considered critical, and may be or a narrow or
broad distribution or range, but in general will be from about
0.250 .mu.m to about 250 .mu.m.
[0038] The thermal gel is packaged in a plastic film by
encapsulating the gel in a dielectric polymer. Exemplary dielectric
polymers include various thermoplastic polymers, such as polyimides
(e.g. Kapton.RTM.), polyamides, and copolymers and blends thereof.
These thermoplastic polymers can be formed into films and heat
sealed at the edge portions, thereby enclosing the thermal gel in a
sealed bag or pouch. In practice, the thermal gel is deposited on a
first layer of polymer film, and a second layer of polymer film is
placed over and heat sealed to the first film layer. In one
embodiment, both the first and second layers are dielectric polymer
film layers, preferably formed from the same polymer. In another
embodiment, one of the layers, typically the bottom layer, is a
thermal tape. Suitable thermal tapes include the THERMATTACH.RTM.
thermally conductive attachment tapes, which are based on a
polyimide carrier and have excellent dielectric strength.
[0039] Multiple gel packs can be advantageously and efficiently
manufactured in an automated assembly process on an assembly line,
thereby allowing the packs to be produced in rolls and individually
cut prior to use.
[0040] The gel packs are adapted to be used with electronic
equipment by emplacement intermediate a first heat transfer surface
and a second heat transfer surface to provide a thermal pathway
there between. One heat transfer surface can be a component
designed to absorb heat, such as a heat sink or an electronic
circuit board. The other (opposed) heat transfer surface can be a
heat generating source, such as a heat generating electronic
component. The opposed heat transfer surfaces preferably have a
thermal impedance of less than about 1.degree. C.-in.sup.2/W
(6.degree. C.-cm.sup.2/W).
[0041] Typical electronic equipment within the scope of the present
invention include, by way of example, automotive electronic
components and systems, telecom base stations, and consumer
electronics, such as computer monitors and plasma TVs.
[0042] Referring now to the figures, FIGS. 1 and 2 show two
embodiments of the thermal gel packs according to the present
invention. In FIG. 1, thermal gel 1 is shown encapsulated by an
upper layer 2 and a lower layer 3 of a dielectric polymer film. The
edges of the upper and lower layers of film are heat sealed to
enclose the gel. FIG. 2 is similar to FIG. 1 and shows thermal gel
4 encapsulated by an upper film layer of dielectric polymer 5 and a
lower layer of a thermal tape 6. The thermal gel packs of the
invention can be prepared individually, or can be part of a number
of such packs prepared in an automated manufacturing process.
[0043] It is anticipated that certain changes may be made in the
present invention without departing from the concepts herein
involved, and it is intended that all matter contained in the
foregoing description shall be interpreted as illustrative and not
in a limiting sense. All references including any priority
documents cited herein are expressly incorporated by reference
herein in their entirety.
* * * * *