U.S. patent application number 09/876573 was filed with the patent office on 2002-12-12 for heat sink and thermal interface having shielding to attenuate electromagnetic interference.
Invention is credited to Flynn, Gary E., Freuler, Raymond G..
Application Number | 20020186537 09/876573 |
Document ID | / |
Family ID | 25368047 |
Filed Date | 2002-12-12 |
United States Patent
Application |
20020186537 |
Kind Code |
A1 |
Freuler, Raymond G. ; et
al. |
December 12, 2002 |
HEAT SINK AND THERMAL INTERFACE HAVING SHIELDING TO ATTENUATE
ELECTROMAGNETIC INTERFERENCE
Abstract
Heat sink and electrically non-conducting thermal interface
having shielding to attenuate electromagnetic interference. The
interface comprises a generally planar substrate having first and
second outwardly facing surfaces. The substrate is formed from a
material, preferably a polymer, that is both thermally conductive
and has a high dielectric strength. Formed upon the outwardly
facing surfaces are layers of a thermally conductive compound for
facilitating heat transfer. The invention further comprises an
improved heat sink comprising a baseplate coupled with a folded-fin
assembly, the latter being compressively bonded thereto via a
pressure clip and pressure spreader assembly. The base plate is
attachable to a heat-dissipating component, and may optionally
include a ground contact connection for use with components that
are not already grounded.
Inventors: |
Freuler, Raymond G.; (Laguna
Hills, CA) ; Flynn, Gary E.; (Coto de Caza,
CA) |
Correspondence
Address: |
MATTHEW A. NEWBOLES
STETINA BRUNDA GARRED & BRUCKER
Suite 250
75 Enterprise
Aliso Viejo
CA
92656
US
|
Family ID: |
25368047 |
Appl. No.: |
09/876573 |
Filed: |
June 7, 2001 |
Current U.S.
Class: |
361/713 ;
257/E23.107; 257/E23.114 |
Current CPC
Class: |
H01L 2924/0002 20130101;
Y10T 428/28 20150115; H01L 23/552 20130101; H01L 2924/0002
20130101; H05K 9/0024 20130101; Y10T 428/24917 20150115; H01L
23/3737 20130101; H01L 2924/00 20130101 |
Class at
Publication: |
361/713 |
International
Class: |
H05K 007/20 |
Claims
In the claims:
1. A thermal interface for facilitating heat transfer from an
electronic component to a heat sink and suppressing electromagnetic
interference emitted from said heat sink comprising: a) a generally
planar substrate, said substrate having first and second surfaces;
and b) at least one layer of conformable, heat conducting material
formed upon the first and second surfaces of said substrate, said
heat conducting material being formulated to enhance the heat
transfer from said electronic component to said heat sink.
2. The thermal interface of claim 1 wherein said second substrate
comprises a polymer.
3. The thermal interface of claim 1 wherein said second substrate
is fabricated from a non-electrically conductive material.
4. The thermal interface of claim 3 wherein said second substrate
comprises KAPTON-type MT.
5. The thermal interface of claim 3 wherein said second substrate
comprises ULTEM.
6. The thermal interface of claim 1 wherein said layer of
conformable, heat conducting material is formulated to have
selective phase-change properties such that said material exists in
a solid phase at normal room temperature, but melts when subjected
to temperatures of approximately 51.degree. C. or higher.
7. A heat sink for dissipating heat transferred thereto by an
electric component comprising: a) a baseplate mountable to said
electronic component, said baseplate having a platform surface; and
b) a folded-fin assembly mountable upon said platform surface of
said baseplate when said baseplate is mounted to said electronic
component.
8. The heat sink of claim 7 further comprising: a) a layer of
thermally conductive material formed upon said platform surface of
said baseplate intermediate said folded-fin assembly, said heat
conducting material being formulated to facilitate the transfer of
heat from said baseplate to said folded-fin assembly.
9. The heat sink of claim 7 further comprising: a) a compression
apparatus attachable to said baseplate for imparting a downwardly
compressive force against said folded-fin assembly such that said
folded-fin assembly is caused to be compressively bonded to said
baseplate.
10. The heat sink of claim 7 wherein said heat sink further
comprises a thermal interface disposed upon said platform surface,
said interface system being comprised of a heat conductive
substrate having a high dielectric capability.
11. The heat sink of claim 9 wherein said compression apparatus
comprises: a) an elongate pressure clip attachable to said
baseplate, said pressure clip being configured to extend over said
folded-fin assembly when said folded-fin assembly is mounted upon
said platform surface and impart a downwardly compressive force
thereto to cause said folded-fin assembly to become compressively
bonded with said baseplate; and b) an electrically isolated
pressure spreader positionable intermediate said pressure clip and
said folded-fin assembly, for evenly distributing the downwardly
compressive force imparted by said pressure clip upon said
folded-fin assembly.
12. The heat sink of claim 11 wherein said pressure clip comprises
an elongate member having opposed ends and a downwardly extending
leg and foot formed upon each respective opposed end, said pressure
clip further including an elongate mid-portion extending over said
folded-fin assembly for imparting a downwardly compressive force
thereto, said baseplate further having formed thereon a pair of
opposed slots for receiving and interconnecting with a respective
one of said feet of said pressure clip.
13. The heat sink of claim 14 wherein said compression apparatus
comprises: a) a plurality of said elongate pressure clips
attachable to said baseplate; and b) a plurality of pressure
spreaders, each respective pressure spreader being positionable
intermediate a dedicated one of said plurality of pressure clips
and said folded-fin assembly.
14. The thermal interface of claim 2 wherein said polymer comprises
a polyimide.
15. The heat sink of claim 10 wherein said heat conductive
substrate comprises a polyimide.
16. The heat sink of claim 7 wherein said base plate is formed from
an electrically conducted material, said base plate having formed
thereon a ground contact connection.
17. The heat sink of claim 16 wherein said heat sink further
comprises: a) a layer of thermally-conductive, electrically
insulated material interposed between said base plate and said
electronic component when said electronic component is mounted
thereto.
18. The heat sink of claim 17 wherein said layer of
thermally-conductive, electrically insulated material comprises a
thermal interface, said thermal interface comprising a generally
planar, non-electrically conductive substrate having first and
second surfaces and at least one layer of conformable heat
conducting material formed upon said first and second surfaces,
said heat conducting material being formulated to enhance the heat
transfer from said electronic component to said heat sink.
Description
BACKGROUND OF THE INVENTION
[0001] Interface systems for use in transferring heat produced from
a heat-dissipating electronic component to a heat dissipator or
heat sink are well-known in the art. In this regard, such
electronic components, the most common being computer chip
microprocessors, generate sufficient heat to adversely affect their
operation unless adequate heat dissipation is provided. To achieve
this end, such interface systems are specifically designed to aid
in the transfer of heat by forming a heat-conductive pathway from
the component to its mounting surface, across the interface, and to
the heat sink.
[0002] In addition to facilitating the transfer of heat, certain
applications further require electrical insulation. Accordingly,
such interface systems are frequently further provided with
materials that are not only effective in conducting heat, but
additionally offer high electrical insulating capability. Among the
materials frequently utilized to provide such electrical insulation
are polyimide substrates, and in particular KAPTON (a registered
trademark of DuPont) type MT.
[0003] Exemplary of such contemporary thermal interfaces are
THERMSTRATE and ISOSTRATE (both trademarks of Power Devices, Inc.
of Laguna Hills, Calif. The THERMSTRATE interface comprises
thermally conductive, die-cut pads which are placed intermediate
the electronic component and the heat sink so as to enhance heat
conduction therebetween. The THERMSTRATE heat pads comprise a
durable-type 1100 or 1145 aluminum alloy substrate having a
thickness of approximately 0.002 inch (although other aluminum
and/or copper foil thickness may be utilized) that is coated on
both sides thereof with a proprietary thermal compound, the latter
comprising a paraffin base containing additives which enhance
thermal conductivity, as well as control its responsiveness to heat
and pressure. Such compound advantageously undergoes a selective
phase-change insofar the compound is dry at room temperature, yet
liquifies below the operating temperature of the great majority of
electronic components, which is typically around 51E .degree. C. or
higher, so as to assure desired heat conduction. When the
electronic component is no longer in use (i.e., is no longer
dissipating heat), such thermal conductive compound resolidifies
once the same cools to below 51E .degree. C.
[0004] The ISOSTRATE thermal interface is likewise a die-cut
mounting pad that utilizes a heat conducting polyimide substrate,
namely, KAPTON (a registered trademark of DuPont) type MT, that
further incorporates the use of a proprietary paraffin based
thermal compound utilizing additives to enhance thermal
conductivity and to control its response to heat and pressure.
Advantageously, by utilizing a polyimide substrate, such interface
is further provided with high dielectric capability.
[0005] Additionally exemplary of prior-art thermal interfaces
include those disclosed in U.S. Pat. No. 5,912,805, issued on Jun.
15, 1999 to Freuler et al. and entitled THERMAL INTERFACE WITH
ADHESIVE. Such patent discloses a thermal interface positionable
between an electronic component and heat sink comprised of first
and second generally planar substrates that are compressively
bonded to one another and have a thermally-conductive material
formed on the outwardly-facing opposed sides thereof. Such
interface has the advantage of being adhesively bonded into
position between an electronic component and heat sink such that
the adhesive formed upon the thermal interface extends beyond the
juncture where the interfaces interpose between the heat sink and
the electronic component.
[0006] The process for forming thermal interfaces according to
contemporary methodology is described in more detail in U.S. Pat.
No. 4,299,715, issued on Nov. 10, 1981 to Whitfield et al. and
entitled METHODS AND MATERIALS FOR CONDUCTING HEAT FROM ELECTRONIC
COMPONENTS AND THE LIKE; U.S. Pat. No. 4,466,483, issued on Aug.
21, 1984 to Whitfield et al. and entitled METHODS AND MEANS FOR
CONDUCTING HEAT FROM ELECTRONIC COMPONENTS AND THE LIKE; and United
States Pat. No. 4,473,113, issued on Sep. 25, 1984 to Whitfield et
al. and entitled METHODS AND MATERIALS FOR CONDUCTING HEAT FROM
ELECTRONIC COMPONENTS AND THE LIKE, the contents of all three of
which are expressly incorporated herein by reference.
[0007] In addition to the construction of thermal interfaces, there
have further been advancements in the art with respect to the
thermal compositions utilized for facilitating the transfer of heat
across an interface. Exemplary of such compounds include those
disclosed in U.S. Pat. No. 6,054,198, issued on Apr. 25, 2000 to
Bunyan et al. and entitled CONFORMAL THERMAL INTERFACE MATERIAL FOR
ELECTRONIC COMPONENTS, and U.S. Pat. No. 5,930,893, issued on Aug.
3, 1999 to Eaton and entitled THERMALLY CONDUCTIVE MATERIAL AND
METHOD OF USING THE SAME, the teachings of which are expressly
incorporated by reference.
[0008] In addition to being able to facilitate the transfer of heat
and provide electrical insulation, many interface systems
additionally employ a grounded substrate formed from a conductive
material, such as copper, to suppress radiated emissions, namely
electromagnetic interference (EMI), generated in high frequency
transistor applications. In this regard, such grounded substrate is
utilized to minimize capacitance to the heat sink to which it is
attached, as well as to provide shielding effectiveness and
attenuation of radiated EMI. With respect to the latter, it has
been shown that electrically grounded copper substrates can provide
shielding effectiveness to 60 dB at 1000 KHz, which is an
attenuation percentage of 99.9%.
[0009] One such commercially-available thermal interface
incorporating a grounded conductive substrate is EMI-STRATE (a
registered trademark of Power Devices, Inc. of Laguna Hills, Calif.
Such interface comprises a grounded copper substrate sandwiched
between two polyimide film substrates, the latter being comprised
of KAPTON-type MT. The exterior sides of such interface are further
coated with a proprietary thermal compound to thus facilitate the
transfer of heat away from the electronic component to a heat
sink.
[0010] Notwithstanding the effectiveness of thermal interfaces
currently in use, a substantial need exists in the art for an
interface that provides greater EMI attenuation, shielding
effectiveness, and thermal conductivity. In this regard, newer
electronic componentry continues to have ever increasing power
dissipation and EMI emission. While such electronic componentry
typically is constructed and/or packaged to be electrically
isolated, the aforementioned increases in power dissipation and EMI
emission currently present drawbacks that must be addressed if such
componentry is to perform optimally. Additionally, as such advances
are made in such componentry, it is certain that the aforementioned
concerns regarding radiated emission and power dissipation will
continue to create a demand for an interface system that can
adequately address the same.
[0011] Prior art interface systems, however, are ill-suited to meet
such needs insofar as such interface systems, because of their
multiple-layer construction, substantially reduces the flow of heat
thereacross. In this regard, it has been found that the use of
thermal interface systems having six layer construction does not
provide desirable heat transfer from a given electronic component
to a heat sink. Moreover, not only does each individual layer
impede heat flow, but, as those skilled in the art will appreciate,
each interface of adjacent layers additionally inhibits heat flow.
In this respect, each layer contributes three distinct impediments
to heat flow, namely, each layer introduces the material of which
the layer itself is comprised, as well as the two interfaces at
either surface of the layer. Thus, it will be appreciated that it
is highly desirable to minimize the number of layers, and
consequently the number of interfaces, comprising such interface
system. In addition to the foregoing, it should be noted from a
practical standpoint that manufacturing such interface systems
having multiple layers is expensive.
[0012] In addition to the need for improved interface systems is
the need for improved heat sinks to be used therewith that are
capable of more effectively and efficiently dissipating the heat
transfer thereto. In this regard, most heat sinks in use, which are
typically fabricated from extruded aluminum, are formed to have a
base with a plurality of fins extending therefrom. The fins are
equidistantly spaced from one another and are formed to have
sufficient surface area to dissipate the heat into the surrounding
air. In this respect, a fan is frequently used to assure adequate
circulation of air over the fins, so as to maintain desirable heat
dissipation therefrom.
[0013] Unfortunately, however, the number of fins and the spacing
therebetween is limited by the aluminum extrusion process. As is
well-known, fins spaced closer together than 0.2 inches tends to
block natural convection air flow and cannot be optimized for use
in forced convection. Additionally, conventional extrusion
technology limits the amount of surface area, namely, the height of
the fins of the heat sink, which further constrains heat removal.
In this respect, it is well-known that the amount of surface area
is proportional to the amount of heat that can be removed. Hence, a
decrease in surface area thus translates into limited heat
removal.
[0014] To partially address the aforementioned inadequacies with
extruded aluminum heat sinks has been the introduction of
folded-fin heat sinks. Such assemblies comprise a relatively thin
base section and a set of fins folded into corrugated sections
mounted thereon. The base section is typically formed to be either
very thin to reduce mass or, alternatively, thicker to act as a
heat spreader. The folded fins coupled to the base act as a
heat-transfer area, allowing a stream of forced air to remove heat
from the base. Currently, such folded-fin heat sinks offer the
maximum potential in surface area and reduced weight. In this
respect, thermal resistance as low as 0.40E .degree. C. C/W can be
reached with folded-fin assemblies in forced-air cooling at 500
ft/min of air velocity. Moreover, in utilizing a corrugated piece
of aluminum or copper, there is thus eliminated the restrictions
otherwise faced in the extrusion process.
[0015] Notwithstanding the desirability of such folded-fin heat
sinks, the same still suffer from the drawback of failing to
achieve optimal heat transfer and dissipation insofar as current
folded-fin heat sinks fail to achieve optimal heat transfer from
the base to the folded-fin assembly coupled thereto. As such, the
maximum amount of heat that could otherwise be dissipated by the
assembly is not attained.
[0016] Accordingly, there is a need in the art for a thermal
interface that provides greater thermal conductivity and greater
electrical insulation than prior art interfaces. There is
additionally a need in the art for such a thermal interface that is
of low cost, easy to manufacture, and may be readily utilized with
existing componentry requiring the integration of a thermal
interface system. Moreover, there is a need in the art for an
improved heat sink that is more effective and efficient at
dissipating heat transferred thereto from an electronic component.
There is further a need for such an improved heat sink that is
particularly more effective in transferring heat from a given heat
source to the fins or other apparatus by which the same is
dissipated.
BRIEF SUMMARY OF THE INVENTION
[0017] The present invention specifically addresses and alleviates
the aforementioned deficiencies in the art. Specifically, the
present invention is directed to an interface system for use with
electronic componentry that has superior electrical insulation and
thermal conductivity properties than prior art systems. In the
preferred embodiment, the interface system of the present invention
comprises the combination of a generally planar substrate,
preferably being comprised of a non-conductive material having a
high dielectric strength. The planar substrate defines two
outwardly facing flatwise surfaces that are configured to mate with
the interface surfaces formed on the electronic component and the
interface surface formed on the heat dissipator or heat sink, on
the other surface Each respective outwardly facing surface has
formed thereon a layer of a thermally conductive compound having a
high degree of thermal conductivity to thus further facilitate the
transfer of heat. In a preferred embodiment, such compound is
preferably formed to have selective phase-change properties whereby
the composition exists in a solid phase at normal room temperature,
but melts, and therefore assumes a liquid phase, when subjected to
the elevated temperatures at which the electronic component usually
operates.
[0018] The present invention further includes an improved heat sink
that is more efficient and effective in dissipating heat
transferred thereto via an electronic component. Specifically, such
improved heat sink comprises the combination of a base plate
attachable to a heat-dissipating component and a folded-fin
assembly compressively attached thereto. In a preferred embodiment,
the heat sink is provided with one or more pressure clips (or other
fastener arrangement) detachably fastenable to the baseplate that
apply a compressive force, via a pressure spreader engagable
therewith, against the folded-fin assembly that causes the assembly
to remain compressively bonded with the baseplate from which the
heat to be dissipated is received. To further facilitate the
transfer of heat from the baseplate to the folded-fin assembly,
there is preferably provided upon the baseplate a layer of a
thermally-conductive compound having selective phase-change
properties (i.e., liquefies during the operational temperature of
the electronic component coupled to the heat sink), to eliminate
any air gaps or voids between the baseplate and folded-fin assembly
that would otherwise impede the transfer of heat. Alternatively, to
the extent a greater degree of electrical isolation is desired, a
thermal interface having a high dielectric capability may be
interposed between the baseplate and folded-fin assembly.
[0019] The present invention thus provides a thermal interface
system that provides both electrical insulation and sufficient
thermal conductivity to effectively facilitate the removal of heat
therefrom more so than prior art interface systems.
[0020] The present invention further provides a thermal interface
having electrical isolation capability that utilizes a minimal
number of layers in the construction thereof.
[0021] Another object of the present invention is to provide a
thermal interface that is relatively simple and inexpensive to
manufacture compared to prior art interface systems, and may be
readily and easily utilized in a wide variety of commercial
applications.
[0022] Another object of the present invention is to provide an
improved heat sink that is more effective and efficient at
dissipating heat transferred thereto from an electronic component,
and especially more so than conventional heat sinks formed from
extruded aluminum.
[0023] Another object of the present invention is to provide an
improved heat sink that is capable of more effectively transferring
heat received thereby to the heat-dissipating component thereof
than prior art heat sinks.
[0024] A still further object of the present invention is to
provide an improved heat sink that is of simple construction, may
be readily and easily fabricated from existing materials well-known
to those skilled in the art, is relatively inexpensive, and may be
readily and easily utilized in numerous commercial
applications.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] These as well as other features of the present invention
will become more apparent upon reference to the drawings
wherein:
[0026] FIG. 1 is an exploded perspective view of an extruded heat
sink positioned for attachment to an electronic component showing a
preformed thermal interface pad of the present invention being
disposed therebetween;
[0027] FIG. 2 is a cross-sectional view taken along line 2?2 of
FIG. 1;
[0028] FIG. 3 is a perspective view of the respective layers
comprising the thermal interface of the present invention;
[0029] FIG. 4 is a perspective view of the respective layers
comprising a prior art thermal interface;
[0030] FIG. 5 is a perspective view of an improved heat sink
constructed in accordance to a preferred embodiment of the present
invention; and
[0031] FIG. 6 is an exploded perspective view of the heat sink
depicted in FIG. 5.
DETAILED DESCRIPTION OF THE INVENTION
[0032] The detailed description set forth below in connection with
the appended drawings is intended merely as a description of the
presently preferred embodiment of the invention, and is not
intended to represent the only form in which the present invention
may be constructed or utilized. The description sets forth the
functions and sequence of steps for construction and implementation
of the invention in connection with the illustrated embodiments. It
is to be understood, however, that the same or equivalent functions
and sequences may be accomplished by different embodiments that are
also intended to be encompassed within the spirit and scope of the
invention.
[0033] Referring now to the drawings, and initially to FIG. 1,
there is shown a thermal interface 10 constructed in accordance
with one embodiment of the present invention. The thermal interface
10 is specifically designed and configured to facilitate the
transfer of heat away from an electronic component 12 to a heat
sink 14. In addition to facilitating the transfer of heat, the
thermal interface 10 of the present invention is further provided
with electrical insulating capability to thus substantially
electrically isolate the electronic component 12 during the
operation thereof.
[0034] As illustrated, the thermal interface 10 is specifically
designed and adapted to be interposed between the electronic
component 12 and heat sink 14. As is well-known, such heat sink 14
is provided with structures such as fins or other protuberances 14a
having sufficient surface area to dissipate the heat into the
surrounding air. Although not shown, to facilitate such heat
dissipation, a fan is frequently utilized to provide adequate air
circulation over the fins or protuberances 14a.
[0035] Preferably, the thermal interface 10 is die-cut or
pre-formed to have a shape or footprint compatible with the
particular electronic component and/or heat sink to thus enable the
thermal interface 10 to maximize surface area contact at the
juncture between the electronic component 12 and heat sink 14.
Alternatively, the thermal interface 10 of the present invention
may also be manually cut from a sheet of interface material,
similar to other interface pads currently in use, so as to provide
a custom fit between a given electronic component and heat
sink.
[0036] Referring now to FIG. 2, there is shown a cross-sectional
view of the thermal interface 10 of the present invention. As
illustrated, the thermal interface 10 is comprised of three layers
16-20. The first layer 16 comprises a thermally conductive compound
formulated to facilitate and enhance the ability of the interface
10 to transfer heat away from the electronic component to the heat
sink. Similar to other prior art compositions, such layer 16 is
preferably formulated to have certain desired phase-change
properties. Specifically, at room temperature, i.e., when the
electronic device is not operating, the layer of thermal compound
16 remains substantially solid.
[0037] The thermally conductive composition may take any of those
disclosed in Applicant's co-pending patent application entitled
PHASE CHANGE THERMAL INTERFACE COMPOSITION HAVING INDUCED BONDING
PROPERTY, filed on Apr. 12, 2001, Ser. No. not yet assigned, and
Applicant's co-pending patent application entitled GRAPHITIC
ALLOTROPE INTERFACE COMPOSITION AND METHOD OF FABRICATING THE SAME,
filed on May 18, 2000, and assigned application Ser. No.
09/573,508, the teachings of which are expressly incorporated
herein by reference. Such thermal compounds have the desirable
phase-change properties of assuming a solid phase at normal room
temperature, but liquify at elevated temperatures of approximately
51.degree. C. or higher, which is typically just below the
operating temperatures at which most electronic components are
intended to operate. It should be understood, however, that a wide
variety of alternative thermally conductive materials and compounds
are available and readily known to those skilled in the art which
could be deployed for use in the practice of the present
invention.
[0038] The second layer 18 is a generally planar substrate layer
provided with an outwardly facing side and an inwardly facing side,
the latter being bonded to the thermal component layer 16.
Preferably, the substrate 18 is formed from a material that is both
thermally conductive and has high dielectric strength. In a
preferred embodiment, a substrate is fabricated from a polymer and
preferably a polyimide. Not by way of limitation, one such highly
preferred polyimide substrate includes KAPTON-type MT. However,
other similar materials well-known to those skilled in the art may
also be utilized, including ULTEM, a registered trademark of
General Electric Corporation.
[0039] Advantageously, by using a substrate formed of a material
having a high dielectric strength, there is thus provided a high
degree of electrical insulation. Along these lines, while the
interface of the present invention is specifically designed and
adapted to be utilized with electronic componentry that already is
electrically isolated, such added electrical insulation, as
provided by the substrate 18, additionally ensures such electrical
isolation, which as those skilled in the art will recognize is
frequently required in such applications.
[0040] To further facilitate and enhance the thermal performance of
the thermal interface 10 of the present invention, there is
preferably provided a second layer 20 of a thermally conductive
compound formed upon the outwardly facing surface of substrate 18.
As with first layer 16, second layer 20 is preferably formulated to
have certain desired phase-change properties, namely, assumes a
solid phase when the electronic component is not operating, but
liquifies when subjected to the operating temperature of the
electronic component, so as to ensure that any voids or gaps formed
by surface irregularities present upon the surface of the heat sink
become filled, thereby maintaining a generally continuous
mechanical contact to thus facilitate the transfer of heat to the
heat sink coupled therewith.
[0041] As will be recognized by those skilled in the art, the
interface 10 of the present invention, because of its novel
construction, will only be fabricated from three layers of
material, namely, the first layer of thermal compound 16,
intermediate substrate 18 and second layer of thermal compound 20,
perspectively illustrated in FIG. 3. Such construction, due to the
minimal amount of layers utilized, is specifically configured for
optimal heat transmission therethrough, and thus is ideally suited
for application as a thermal interface for facilitating heat
transfer from an electronic component to a heat sink. As those
skilled in the art will appreciate, by eliminating additional
layers of material, which are typically present in prior art
interfaces, there is thus facilitated the performance of heat
transfer from the electronic component to a heat sink. More
specifically, it is well-known that the rate of heat transfer
through such interface is reduced by each layer added thereto.
[0042] In contrast, as depicted in FIG. 4, there is shown a prior
art interface 26 having a seven-layer construction. The layers
comprising the prior art interface 26 comprise, from bottom to top,
a first or external thermal compound layer 28, a first
non-conductive substrate 30, a first or internal adhesive layer 32,
a layer of conductive material 34, a second internal adhesive layer
36, a second non-conductive substrate 38, and a second external
thermal compound layer 40. As discussed above, such multi-layer
construction substantially reduces the rate of heat transfer
therethrough, with the addition of each additional layer providing
that much more of an impediment in achieving the desired thermal
conductivity. Additionally, by using fewer layers, the thermal
interface 10 of the present invention is provided with a reduced
thickness than such prior art interfaces, which, as a result, even
further enhances the flow of heat therethrough.
[0043] Referring now to FIGS. 5 and 6, and initially to FIG. 5,
there is shown an improved heat sink 50 constructed in accordance
to a preferred embodiment of the present invention. As shown, the
heat sink 50 comprises the combination of a baseplate 52 and a
folded-fin assembly 60, the latter being compressively mounted upon
an electrically insulated platform surface 52a formed on the
baseplate 52 (shown in FIG. 6), via a pair of pressure clips 68a,
68b and electrically insulated pressure spreaders 64a, 64b. In
order to provide the desired electrical insulation, the platform
surface 52a may have formed thereon a sheet of electrically
insulated material, such as KAPTON-type MT. Similarly, the pressure
clips 68a, 68b will preferably be formed from electrically
non-conductive materials such as fiberglass, or other like
materials.
[0044] The baseplate 52 is provided with a plurality of apertures
54 to enable the same to be fastened, via bolts and the like, to a
given heat-dissipating component (not shown). The baseplate 52
further has formed thereon opposed pairs of slots 56a, a' and 56b,
b' that are designed and configured to receive respective ones of
pairs of feet 70a, a' and 70b, b' formed upon pressure clips 68a,
68b, more clearly seen in FIG. 6. As will be appreciated by those
skilled in the art, slots 56a, a' and 56b, b' provide points of
leverage by which pressure clips 68 can impart a downwardly
compressive force, via pressure spreader 64a, 64b, upon the
folded-fin assembly 60, and more particularly the upper folds 60b
thereof. The baseplate 52 is preferably formed from a material
having excellent thermally conductive properties, such as aluminum
and other like metals.
[0045] The folded-fin assembly 60 preferably comprises a unitary
piece of corrugated metal, such as aluminum or other like materials
well-known to those skilled in the art, that have ideal
heat-dissipating properties. As illustrated, the folded-fin
assembly 60 is formed to have a generally serpentine configuration
such that the same is provided with a plurality of downwardly
facing bends 60a that are oriented to mate with the electrically
insulated upper platform surface 52a of baseplate 52, more clearly
seen in FIG. 6, and a plurality of upwardly oriented folds 60b, the
latter being forced compressively downward via pressure clips 68a,
68b, and pressure spreader 64a, 64b.
[0046] As will be recognized by those skilled in the art, by using
a folded-fin assembly 60, the heat sink 50 is thus provided with a
heat-dissipating component that is not limited by prior art
extrusion processes. As is well-known, prior heat sinks formed from
extruded aluminum possess substantial limitations insofar as most
extrusion processes limit the height of such fins formed thereon to
dissipate heat, as well as the spacing therebetween. Such
limitations do not apply to the folded-fin assembly 60, in
contrast, by virtue of having fins folded into such corrugated
sections 60a, 60b.
[0047] To maximize and facilitate physical contact, and thus
enhance thermal conductivity between the folded-fin assembly 60 and
baseplate 52, there are provided pressure clips 68a, 68b and
pressure spreaders 64a, 64b that cooperate to impart a downwardly
compressive force upon the outwardly extending bends 60b of the
folded-fin assembly 60 thus forcing the folded-fin assembly to
remain firmly seated and compressed against the baseplate 52. In
the preferred embodiment shown, each pressure clip 68a, 68b is
provided with downwardly extending legs 72a, a' and 72b, b' having
outwardly extending feet 70a, a' and 70b, b' formed at the
distalmost ends thereof. The legs 72 are connected to one another
via an elongate segment defined by downwardly-biased sections 74
and mid-portion 76. As will be readily appreciated by those skilled
in the art, when the feet 70 of each respective pressure clip 68a,
68b are received within those dedicated slots 56 formed upon
baseplate 52, such downwardly biased sections 74 and mid-portion 76
are caused to impart the aforementioned downwardly compressive
force.
[0048] Pressure spreaders 64a, 64b, which are preferably
electrically insulated, are provided to impart a more even
distribution of force about the upwardly extending bend 60b of
folded-fin assembly 60. As shown, the pressure spreaders 64a, 64b
preferably comprise elongate beams that are designed and configured
to align with downwardly-biased sections 74 and mid-portion 76 of
each respective pressure clip and become sandwiched between the
clip 68 and the top fold 60b of folded-fin assembly 60.
Advantageously, by compressively bonding the folded-fin assembly 60
against baseplate 52, thermal conductivity and, ultimately, heat
dissipation is maximized and allows for greater heat transfer than
prior art heat sinks.
[0049] To further facilitate the transfer of heat, there is
optionally provided upon the upper platform surface 52a of
baseplate 52 a layer of thermally conductive compound formulated to
have the aforementioned desired phase-change properties to thus
ensure maximum mechanical contact between the folded-fin assembly
60 and baseplate 52. Alternatively, to the extent desired, an
interface pad or other like system may be positioned upon the
platform surface 52a to provide further desired properties (e.g.,
electrical insulation) in addition to facilitating the transfer of
heat.
[0050] In yet another optional embodiment of the present invention,
base plate 52 maybe provided with a ground contact connection 78,
shown in phantom in FIGS. 5 and 6, to thus enable an electronic
utilized therewith to become electrically grounded. Along these
lines, while most electronic componentry typically in use is
constructed and/or packaged to be electrically isolated, to the
extent such componentry is not grounded, ground contact connection
58 will thus facilitate that end. It will be readily recognized by
those skilled in the art, however, that in such applications, base
plate 52 will be for the heat sink 50 will further include an
electrically insulated pad or layer, such as 80 depicted in phantom
in FIGS. 5 and 6, to ensure electrical isolation of the base plate
52. In this respect, it is contemplated that such optional pad or
layer 80 may take the form of an interface pad or other like system
that, in addition to providing electrical insulation, can further
facilitate the transfer of heat.
[0051] Although the invention has been described herein with
specific reference to a presently preferred embodiment thereof, it
will be appreciated by those skilled in the art that various
additions, modifications, deletions and alterations may be made to
such preferred embodiment without departing from the spirit and
scope of the invention. For example, with respect to the improved
heat sink of the present invention, any of a variety of mechanisms
may be utilized to impart the compressive force against the
folded-fin assembly whereby the latter is caused to be
compressively bonded to the baseplate coupled therewith.
Additionally, upper platform surface 52a need not necessarily be
formed to be electrically insulated, but may simply comprise an
outwardly facing surface of the baseplate 52. Accordingly, it is
intended that all reasonably foreseeable additions, modifications,
deletions and alterations be included within the scope of the
invention as defined in the following claims.
* * * * *