US20120118552A1

US20120118552A1 - Systems and methods for thermal management of electronic components

Info

Publication number: US20120118552A1
Application number: US13/294,698
Authority: US
Inventors: Brian White; Craig Lombard; David S. Lashmore
Original assignee: Nanocomp Technologies Inc
Current assignee: Nanocomp Technologies Inc
Priority date: 2010-11-12
Filing date: 2011-11-11
Publication date: 2012-05-17
Also published as: EP2637868A4; WO2012065107A1; JP2014505319A; EP2637868A1

Abstract

The device for extracting heat from carbon nanotubes wires or cables used under high power applications is provided. The device can include a thermally conductive member for placement against a heat source and for directing heat away from the heat source to a heat dissipating medium. The device can further include an electrically conductive member positioned on the thermally conductive member and made from a layer of carbon nanotubes, to reduce electrical resistance along the electrically conductive member. A geometric pattern can be imparted to the electrically conductive member to enhance dissipation of heat away from the thermally conductive member and the heat source.

Description

RELATED APPLICATION(S)

The present application claims benefit of and priority to U.S. Provisional Application Ser. No. 61/413,087, filed Nov. 12, 2010, which application is hereby incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to devices and methods for thermal management of electronic components, and more particularly to a device for dissipating heat from based wires or cables used under high power applications.

BACKGROUND ART

Heat transfer for thermal management between two materials at different temperatures often may be accomplished by conduction, radiation and/or convection. In the area of electronics, in a narrow region at, for instance, an interface between a die lid (e.g., commonly a copper-tungsten material) of the integrated circuit and the heat sink, the temperature present in the integrated circuit (IC) can typically be between about 40° C. to 200° C. For such a situation, thermal management may typically be accomplished through conduction. However, the use of flat plates at the interface to facilitate the heat transfer from the integrated circuit to the heat sink has proved not to be optimal. In particular, the use of a flat plate may provide only between 20 to 50 atomic points of contact between the integrated circuit and/or the heat sink. As a result, the heat that flows out of the hot integrated circuit can only pass through these few contact spots.
To enhance the transfer of heat to the heat sink, current technology usually involves placing a thermally conducting grease between the die lid of an integrated circuit and the heat sink device. The heat sink device, in general, may be of any type, including a passive heat sink, a Peltier cooler, a refrigerated copper block, a heat pipe, an active fan type, or a copper block in which embedded heat pipes can carry heat to a water-cooled bus outside of the system.
Presently, thermal greases that are commercially available typically contain silver powder or silver flake, and may be used by applying to machined, and occasionally, lapped heat sinks and integrated circuit lids. However, the thermal conductivity of these commercially available greases may, at best, be about 9 watts/m-deg K. For example, (i) Arctic Silver III has a thermal conductivity of about 9.0 W/m-deg K, (ii) AOS Thermal Compounds has a thermal conductivity of about 7.21 W/m-deg K, (iii) Shin-Etsu G751 has a thermal conductivity of about 4.5 W/m-deg K, (iv) AOS Thermal Compounds HTC-60 has a thermal conductivity of about 2.51 W/m-deg K, (v) Thermagon T-grease has a thermal conductivity of about 1.3 W/m-deg K, and (vi) Radio Shack Thermal Grease has a thermal conductivity of about 0.735 W/m-deg K. In one example, a 20 degree difference between the heat source and the heat sink can indicate a thermal resistance at the junction and can suggest that the potential to carry heat to the sink may be hindered by the poor interface provided by the grease.
It has been known that metal fiber structures and material can provide a low loss connection at greatly reduced forces, thereby providing high-efficiency, low force electrical contact. The capability of fiber brushes to efficiently transfer electrical current across interfaces, which can be in relative motion or at rest, is analogous to their capability to similarly transfer heat. In particular, since they operate at low loads and have a very low resistance, fibers structures can dissipate relatively much more heat than a smooth surface. Moreover, the fiber brushes can provide a substantial number of contact points between the heat source and heat sink to permit efficient heat transfer. As a result, metal fiber brushes have been used in a thermal interface as heat conduits for cooling or heating purposes such as disclosed in U.S. Pat. No. 6,245,440.

SUMMARY OF THE INVENTION

The present invention, in one aspect, is directed to a device for dissipating heat or thermal energy from a heat source, such as wires or cables (i.e. conductor or coaxial cable) used in connection with high power applications. The device, in one embodiment, includes a thermally conductive member for placement against a heat source and for directing heat away from the heat source, and an electrically conductive member positioned about the thermally conductive member and made from a layer of carbon nanotubes to reduce electrical resistance along the electrically conductive member. The device further includes a geometric pattern imparted to the electrically conductive member to enhance dissipation of heat away from the thermally conductive member.
In some embodiments, the thermally conductive member has a circumference sufficient for placement about a heat source and, while the electrically conductive member can be placed circumferentially about of the thermally conductive member.
In some embodiments, the device can be used as a an electrical conductor, while in other embodiments, the device may be incorporated as part of a cable or cable assembly. In some embodiments, the device can be incorporated within a coaxial cable to dissipate heat from a center conductor of a coaxial cable.
In some embodiments, the thermally conductive member may be made from a material having a relatively high thermal conductivity characteristic. For example, thermally conductive member may be made from a material having a heat spreading characteristic. In some embodiments, the thermally conductive member may be made from one of graphite fiber, film or foil, or a combination thereof. In some embodiments, the thermally conductive member may be made from a plurality of individually conductive fibers, made, for example from carbon nanotubes. The thermally conductive fibers may be wound into yarns or woven into a sheet, mat or textile material for use in connection with the present invention. The thermally conductive member may also comprise a porous mesh to enhance dissipation of heat from the heat source. In some embodiments, the thermally conductive member includes a polymeric material dispersed therethroughout. The polymeric material can include one of polyamide, epoxy or a combination thereof.
In some embodiments, the electrically conductive member is made from a plurality of carbon nanotube wires. In some embodiments, the electrically conductive member is made from one of individual and conductive yarns, fibers, wires, sheets, mat or textile material. The electrically conductive member may be braided or woven about the thermally conductive member. In some embodiments, the electrically conductive member is a sheet made from carbon nanotubes. The electrically conductive member may be laminated onto the thermally conductive member.
The electrically conductive member may also be formed as a lattice circumferentially about the thermally conductive member. The electrically conductive member may alternatively include a plurality of electrically conductive layers circumferentially situated about the thermally conductive member. In some instances, the plurality of electrically conductive layers may be spirally wound upon itself. In some embodiments, the plurality of electrically conductive layers form a spiral with at least one thermally conductive layer between each pair of adjacent electrically conductive layers.
In some embodiments, the device further comprises an adhesive to maintain the electrically conductive member on the thermally conductive member. In some embodiments, the device further comprises fins to help facilitate the transfer of thermal energy away from the heat source.
The present invention, in one aspect, is directed to a method of dissipating heat from a heat source, such as a conductor. In some embodiments, a thermally conductive layer may be situated against a heat source, to dissipate heat while an electrically conductive layer may be positioned about the thermally conductive layer. A pattern may be imparted to the electrically conductive layer to enhance dissipation of heat away from the heat source.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a heat-conducting medium in accordance with an embodiment of the present invention.

FIGS. 2A-2B illustrate a cross-sectional view of a heat-conducting medium in accordance with one embodiment of the present invention.

FIGS. 3A-3B illustrate other embodiments of a heat-conducting medium having thermal dissipation fins in accordance with an embodiment of the present invention.

FIGS. 4A-4B illustrate another embodiment of a heat-conducting medium in accordance with an embodiment of the present invention.

FIG. 5 illustrates the frequency and resistivity of carbon nanotube wires compared to the frequency and resistivity of Aluminum and Copper wires.

FIGS. 6A-6B illustrate the temperature as function of the applied power in non-insulated and insulated carbon nanotubes wires.

FIG. 7 illustrates the temperature as function of the applied power in carbon nanotube conductor with or without a thermally conductive member.

DESCRIPTION OF SPECIFIC EMBODIMENTS

The present invention provides, in one embodiment, a device for thermal management of electronic components. The device, in an embodiment, may be designed to dissipate heat or thermal energy from a heat source, such as wires or cables used in connection with high power applications. In some embodiments, the device may be designed to reduce impedance within the based wires or cables. The wires or cables, in certain instances, can be a coaxial cable and/or a twisted pair of cable.
The device, in an embodiment, may include a thermally conductive member for placement against a heat source and for directing heat away from the heat source, and an electrically conductive nanostructural member made from, for example, a plurality of carbon nanotubes in contact with the thermally conductive member.
With reference to FIG. 1, there is illustrated a device 10 for thermal management in accordance with an embodiment of the present invention. The device 10, in an embodiment, includes a thermally conductive member 11 and an electrically conductive member 15 situated about the thermally conductive member 11.
The thermally conductive member 11, in an embodiment, may be designed for placement about a heat source, such as a center conductor in a coaxial cable, and for directing heat away from a heat source. In other words, the thermally conductive member 11 may act to facilitate the transfer of heat by a variety of measures, for instance, conduction, connection, etc., from the heat source. To that end, heat generated from the heat source may be carried by the thermally conductive member 11 toward its surface. In some embodiments, the thermally conductive member 11 may, at its surface, be designed to couple to a heat sink, including any material that passively conducts heat along the thermally conductive member 11 away from the heat source.
To direct heat away from the heat source (e.g. center conductor in a coaxial cable), the thermally conductive member 11 may be formed from any material that is substantially thermally conductive. The thermally conductive member 11 may also be formed from any material having a thermal conductivity greater than about 100 W/m*K. In a certain instance, the thermally conductive member 11 may be formed from any material having a relatively high in-plane thermal conductivity, while having a relatively low through-plane thermal conductivity. Yet in other instance, the thermally conductive member 11 may be formed from any material having a relatively high through-plane thermal conductivity, while having a relatively low high-plane thermal conductivity. In one embodiment, the thermally conductive member 11 may be formed from high thermal conductivity graphite fiber, film or foil. The thermally conductive member 11 can also be formed, in one embodiment, from yarns 14 that have been wound from individuals fibers, bundled together, or from sheets, mats or other relevant textile materials. If desired, the thermally conductive member 11 may be formed from yarns or sheets 14 made from carbon nanotubes, such as those disclosed in U.S. Pat. No. 7,611,579, incorporated herein by reference.
To enhance and facilitate the conduction of heat away from the heat source, the thermally conductive member 11, in an embodiment, can be a mesh, can be provided with a porous configuration, be tubular in nature, or be a combination thereof. In this way, air or other fluid may be permitted to flow through channels formed by the mesh, pores, or tubes in the thermally conductive member 11 to assist in heat dissipation and further enhance heat conduction away from the heat source.
Still looking at FIG. 1, device 10 may further include an electrically conductive member 15 positioned on the thermally conductive member 11. The presence of the electrically conductive member 15 can act to reduce thermal resistance within the device 10 by pulling heat from the thermally conductive member 11. In addition, the electrically conductive member 15 can act to conduct electricity along its length. In this way, the electrically conductive member 15, in an embodiment, can also act to control impedance within the device 10.
In an embodiment, the electrically conductive member 15 may be a plurality of self-supported wire-like materials 16 braided or weaved about the thermally conductive member 11 so as to provide a lattice or matrix about the thermally conductive member 11. The pattern or design utilized in braiding or weaving the electrically conductive member 15, in an embodiment, can be any geometric pattern, as the present invention is not intended to be limited in this manner. In addition, it should be appreciated that the number of passes about the thermally conductive member 11 may be affected by the diameter of the thermally conductive member 11 or the gauge of the wire-like material 16.
In accordance with an embodiment of the present invention, the electrically conductive member 15 may be formed from any material that is substantially electrically conductive. In this way, the material used in the electrically conductive member 15 can act to reduce electrical resistance along the length of the electrically conductive member 15. In one embodiment, the electrically conductive member 15 may be made from a material that can also reduce thermal resistance within the device 10. For example, the electrically conductive member 15 may be formed from carbon nanotubes similar to those generated and disclosed in U.S. Pat. No. 7,611,579, incorporated herein by reference. The electrically conductive member 15 can also be formed, in one embodiment, from carbon nanotubes that have been wound from individuals yarn, fibers, bundled together, wires or from sheets, mats or other relevant textile materials.
In one embodiment, the carbon nanotubes used in connection with the electrically conductive member 15 of the present invention may be wound into wires 16 of any gauge. In one instance, the carbon nanotube wires 16 may have a gauge ranging from about 20 AWG to about 45 AWG. The carbon nanotube wires 16 may also be insulated or may be bare. It should be appreciated that the lattice or matrix design of the electrically conductive member 15 can further help device 10 to facilitate in conducting heat away from the heat source, by allowing more air or fluid to flow through the channels formed by the mesh of the electrically conductive member 15. Should it be desired, the electrically conductive member 15, in one embodiment, may be infiltrated with polymeric material dispersed there throughout to enhance its structural integrity and/or to enhance its electrical and/or thermal capabilities. Examples of polymeric materials include, for instance, polyamide, epoxy, other polymers or a combination thereof.
With reference now to FIG. 3A, in accordance with some embodiments, should it be desired, device 10 may be provided with fins 30 to further facilitate the transfer of thermal energy from the heat source. In particular, fins 30 may be designed to allow more heat energy to be directed to the fins 30 from the thermally conductive member 11 so that heat or thermal energy can be radiated and convected away from the device 10, including by a flow of air across the device 10.
As shown in FIG. 3A, fins 30 may be a plurality of members situated along the length of the device 10. The fins 30 may be spaced apart so as to maximize the removal of heat from the thermally conductive member 11. The fins 30, in an embodiment, may be positioned substantially transverse to the thermally conductive member 11. It should be noted that the number of fins 30 used may vary according to the application involved. Moreover, although a plurality of fins 30 is illustrated, in an embodiment, one fin 30 may be used. It should be noted that the fins 30 may be made from any material, including materials made from carbon nanotubes used in connection with the present invention, so long as the material can facilitate in the removal of heat from the thermally conductive member 11. It should further be appreciated that the fins 30 may have any geometrical shape as the present invention is not limited in this manner.
To make the embodiments shown in FIGS. 1 and 3A, the thermally conductive member 11 may need to first be constructed in accordance with known methods in the art. Once the thermally conductive member 11 is constructed, an electrically conductive member 15 may be placed about the thermally conductive member 11. The electrically conductive member 15 may be in the form of a mesh, as shown in FIG. 1. The mesh can be weaved about the conductive member 11 or can be a tube that can be slipped onto the conductive member 15. If desired, fins 30 may be added along the length of the device to maximize removal of heat.
In use, the device shown in FIGS. 1 and 3A may act to absorb heat from a heat source. In particular, heat from the source may be directed through the thermally conductive member 11 and away from the source. As heat is being transported away from the source, the electrically conductive member 15 may reduce thermal resistance within the device 10. After passing through the thermally conductive member 11, the heat may move outwards. Fins 30 may aid in moving heat away from the heat source.
FIGS. 2A-2B shows another device 20 for thermal management in accordance with further embodiment of the present invention. Device 20 is substantially similar to device 10 in that device 20 includes a thermally conductive member 21, and an electrically conductive member 25.
Thermally conductive member 21, in an embodiment, can be the same thermally conductive member as that illustrated in FIG. 1. In particular, the thermally conductive member 21 may be designed for directing heat from a heat source. The thermally conductive member 21 may act to facilitate the radial transfer of heat from the heat source so that the heat from the heat source may subsequently be carried to, for instance, a heat sink. In an embodiment, the thermally conductive member 21 may be designed to couple to a heat sink, including any material that passively conducts heat along the thermally conductive member 21 away from the heat source.
The thermally conductive member 21 may be formed from any material that is substantially thermally conductive. The thermally conductive member 21 may also be formed from any material having a thermal conductivity greater than about 100 W/m*K. In a certain instance, the thermally conductive member 21 may be formed from any material having relatively high in-plane thermal conductivity in the plane while having relatively low thermal conductivity through the plane. Yet in other instance, the thermally conductive member 21 may be formed from any material having a relatively high through-plane thermal conductivity, while having a relatively low high-plane thermal conductivity. The thermally conductive member 21 can also be formed, in one embodiment, from yarns that have been wound from individuals fibers, bundled together, or from sheets, mats or other relevant textile materials. In one embodiment, the thermally conductive member 21 may be formed from high thermal conductivity graphite fiber, film or foil. If desired, the thermally conductive member 21 may be formed from yarns or sheets made from carbon nanotubes.
The electrically conductive member 25, on the other hand, may be formed, in one embodiment, from a sheet of carbon nanotubes. The sheet of carbon nanotubes that forms the electrically conductive member 25, in an embodiment, may be wrapped around the thermally conductive member 21 to provide one or more layers. In an embodiment, a plurality of layers 26 of the electrically conductive member 25 may be provided, similar to that shown in FIG. 2A. The layers 26 may be formed, in one embodiment, by one sheet that is wrapped multiple times about the thermally conductive member 21 to form multiple layers 26. Alternatively, the layers 26 may be formed by multiple sheets being stacked on one another and wrapped around one time to form multiple layers 26.
In certain instances, it may be desirable to condense or reduce the layers 26 of the electrically conductive member 25 onto the thermally conductive member 21 so as to eliminate or reduce the interfaces between the layers 26. The condensation of the layers 26, in an embodiment, can act to reduce thermal resistance within device 20 by reducing the path length that heat must travel, as well as the electrical resistance within device 20. A variety of solutions including for example, one or more chemicals or one or more solvents, may be used to condense the layers 26 onto the thermally conductive member 21. Any solution or solvent known in the art may be used to condense the layers 26.
With reference now to FIG. 3B, in accordance with some embodiments, should it be desired, device 20 may also be provided with fins 30 to further facilitate the transfer of thermal energy from the heat source. In particular, fins 30 may be designed to direct thermal energy from the heat source to the surface of the device 20, thereby allowing the thermal energy to be radiated and convected away by a flow of air across device 20.
As shown in FIG. 3B, fins 30 may be a plurality of members situated along the length of the device 20. The fins 30 may be spaced apart so as to maximize the removal of heat from the thermally conductive member 21. The fins 30, in an embodiment, may be positioned substantially transverse to the thermally conductive member 21. It should be noted that the number of fins 30 used may vary according to the application involved. Moreover, although a plurality of fins 30 is illustrated, in an embodiment, one fin 30 may be used. It should be noted that the fins 30 may be made from any material, including materials made from carbon nanotubes used in connection with the present invention, so long as the material can facilitate in the removal of heat from the thermally conductive member 21. It should further be appreciated that the fins 30 may have any geometrical shape, as the present invention is not limited in this manner.
To make the embodiments shown in FIGS. 2A-2B and 3B, the thermally conductive member 21 may need to first be constructed in accordance with known methods in the art. Once the thermally conductive member 21 is constructed, an electrically conductive member 25 may be placed about the thermally conductive member 21. The electrically conductive member 25 may be in the form of a sheet, as shown in FIG. 2A-2B. In certain embodiments, the electrically conductive member 25 may be formed from a plurality of layers 26. In some instances, it may be desirable to condense the layers 26 using a solvent to eliminate or reduce layer interfaces between the layers 26. Condensation of the layers 26 may act to reduce the electrical and thermal resistance within device 20. If desired, fins 30 may be added along the length of the device to maximize removal of heat from the thermally conductive member 21.
In use, the device shown in FIGS. 2A-2B and 3B may act to absorb heat from a heat source. Specifically, heat from the source may be directed through the thermally conductive member 21 and away from the source. As heat is being dissipated away from the source, the thermal resistance within the device 20 may be reduced. After passing through the thermally conductive member 21, the heat may dissipate outwards to the electrically conductive member 25. Fins 30 may aid in moving heat away from the heat source.
Looking now at FIGS. 4A-4B, a device 40 is shown for thermal management in accordance with further embodiment of the present invention. Device 40, similar to device 10, may include a thermally conductive member 41, and an electrically conductive member 45. As shown in FIG. 4A, the thermally conductive member 41 may include a substantially planar surface. Similar to the embodiment discussed above, the thermally conductive member 41 may be formed from a plurality of individual and conductive fibers that may be arranged to form a substantially planar surface. Alternatively, a sheet or strip of a conductive material may be used.
Device 40, in an embodiment, may be designed for directing heat away from a heat source. As such, the thermally conductive member 41 may act to facilitate the removal of heat from the heat source so that the heat from the heat source may subsequently be carried to, for instance, a heat sink, including any material that passively conducts heat away from the thermally conductive member 41.
To direct heat away from the heat source, the thermally conductive member 41 may be formed from any material that is substantially thermally conductive. The thermally conductive member 41 may also be formed from any material having a thermal conductivity greater than about 100 W/m*K. In a certain instance, the thermally conductive member 41 may be formed from any material having a relatively high in-plane thermal conductivity while having a relatively low through plane thermal conductivity. Yet in other instance, the thermally conductive member 41 may be formed from any material having a relatively high through-plane thermal conductivity, while having a relatively low high-plane thermal conductivity. The thermally conductive member 41 can also be formed, in one embodiment, from yarns that have been wound from individuals fibers, bundled together, or from sheets, mats or other relevant textile materials. In one embodiment, the thermally conductive member 41 may be formed from high thermal conductivity graphite fiber, film or foil. If desired, the thermally conductive member 41 may be formed from yarns or sheets made from carbon nanotubes capable of removing the heat generated, so as to keeping the conductor at a desired temperature. To enhance and facilitate in conducting heat away from the heat source, the thermally conductive member 41, in an embodiment, may be a mesh or may be provided with a porous configuration. In this way, air or other fluid may be permitted to flow through channels formed by the mesh or pores in the conductive member 41 to assist in heat dissipation and further enhance heat removal away from the heat source.
As noted, the device 40 may also include an electrically conductive member 45. In an embodiment, the electrically conductive member 45 may be formed from any substantially electrically conductive material, for example, a sheet of carbon nanotubes, such as that used in connection with the embodiments illustrated above. The thermally conductive member or media 41, as shown in FIGS. 4A-B may be positioned on the electrically conductive member 45. The electrically conductive member 45 can be formed, in one embodiment, from carbon nanotube yarns that have been wound from individuals fibers, bundled together, or from carbon nanotube woven or non-woven sheets. In an embodiment, to secure it to the electrically conductive member 45, the thermally conductive member 41 may be laminated onto the substantially planar surface of the electrically conductive member 45. It should be appreciated that materials such as Resol-pyrolyzed to glassy carbon, polyamide, epoxy, other polymers or a combination thereof may be used. In some embodiments, the electrically conductive member 45 and the thermally conductive member 41 can be rolled to form a sandwich or wrap structure, as shown in FIG. 4B.
To make the embodiments shown in FIG. 4A-4B, the thermally conductive member 41 may initially be constructed or manufactured in accordance with known methods in the art. Once the thermally conductive member 41 has been constructed, an electrically conductive member 45 may be placed on top of the thermally conductive member 41 and secured thereto. The electrically conductive member 45, in an embodiment, may be laminated onto the surface of the thermally conductive member 41. In some embodiments, the electrically conductive member 45 and the thermally conductive member 41 can be rolled to form a sandwich or wrap structure, as illustrated, so as to provide a device 40 having a plurality of layers of electrically conductive member and a plurality of layers of the thermally conductive member. It should be appreciated that this design allows the electrical conductive member to conduct electricity while allowing the thermally conductive member to remove heat from each layer
In use, the device 40 shown in FIGS. 4A-4B may act to direct heat away from a heat source. Specifically, heat from the source may be directed through the thermally conductive member 41 and away from the source to the electrically conductive member 45. As heat is being dissipated away from the source, thermal resistance within the device 40 may be reduced. In an example, when the conductor (e.g. cable) has a temperature coefficient of resistivity greater than one, the design illustrated in FIGS. 4A-4B can act to reduce heat in the conductor. In addition, with this design, the electrical conductivity through the device 40 may increase. After passing through the thermally conductive member 41, the heat may dissipate outwards away from the device 40.
It should be noted that in each of the embodiments shown in FIGS. 1-4, an adhesive may be used to maintain the electrically conductive member 45 on the thermally conductive member 41. In one embodiment of the invention, adhesives such as Resol, glassy carbon, polyamide, epoxy, other polymers or a combination thereof may be used. Alternatively or in addition to, the adhesives may be a coating deposited or electroplated between the electrically and thermally conductive members. Deposition or electroplating of the electrically conductive member onto the thermally conductive member can be carried out using methods well known in the art. Examples of electroplated adhesives include gold, silver, nickel, aluminum, copper, bismuth, tin, zinc, cadmium, tin-nickel alloy, copper alloy, tin-zinc alloy, bismuth-copper alloy, copper-nickel alloy, cadmium-nickel alloy, other conductive metals and their alloys, or a combination thereof. In an embodiment, one or more adhesives may be located anywhere on the thermally conductive member.
The adhesive, in an embodiment, may be deposited or electroplated onto the electrically conductive member substantially uniformly, so as to permit substantial uniform contact of the nanotubes in the electrically conductive member across a contact surface area on the thermally conductive member. As such, the adhesive can act to substantially maximize the number of conductive nanostructures within the electrically conductive member that can be actively involved in conductivity to enhance efficiency of electrical and thermal transport.
Applications
The device for thermal management of the present invention can be used in variety of applications, including, for instance, as electrical conductors. Due to the unique design of the device of the present invention, the electrically conductive component can act as a electrical conductor, while the thermally conductive component can act to dissipate heat. The carbon nanotube conductors of the present invention have been observed to outperform copper and aluminum at high frequencies, due to their extremely high theoretical and experimental conductivity and ability to increase in conductivity into the THz region. Furthermore, carbon nanotube conductors of the present invention may not experience the same fatigue issues that other metals do, and may be more chemically resistant and lighter with a density of less than 1.5 g/cc.
In addition, these conductors, as provided by the various embodiments of the present invention, can be assembled into cables, cable assemblies, or coaxial cables. The utilization of the conductors of the present invention, for instance, as carbon nanotube data cables and/or carbon nanotube power cables have shown that for both carbon nanotube cores and shielding, weight savings can approach about 50% for data cables and about 25% for power cables. Even if copper cores are maintained, both weight and the volume reductions can be achieved, utilizing the conductor designs of the present invention.

EXAMPLE 1

FIG. 5 shows a graph comparing the frequency and resistivity of carbon nanotube wires with the frequency and resistivity of Aluminum and Copper wires. Specifically, this experiment was conducted using a 6-ply non-insulated carbon nanotube wire and 35 AWG gauge Aluminum and Copper wires at 20° C. and 100° C. The electrical measurements performed were conducted with less than about 1 Watt.
As shown in FIG. 5, bulk materials composed of carbon nanotubes exhibit improvements in conductivity at higher frequencies. For example, at about 1.E+05 Hz, bulk materials composed of carbon nanotubes exhibit a drop in resistivity from about 1.E-04 Ω-cm to about 1.E-05 Ω-cm. In some cases, carbon nanotube wires may be doped for better electrical behavior.

EXAMPLE 2

An experimental setup for testing the temperature versus power of the thermal management devices included using two sets of carbon nanotube wires. The first set included two six-inch samples of non-insulated large diameter carbon nanotube wires. The diameters of the carbon nanotube wires includes plies of 25 (˜29 AWG), 50 (˜26 AWG), 100 (˜23 AWG), and 150 (˜21 AWG). These carbon nanotube wires were formed and plated with nickel followed by copper on both ends. The second set included the same diameter carbon nanotube wires that were insulated with a zero inner diameter shrink tubing rated to 300° C. Each set was hung in air, and a DC power supply was used to run current through and a voltage across the sample. The Power applied ranged from about 0 Watts to about 10 Watts. The power supply was set to be current limiting and readings were taken every half volt once the temperature stabilized. The temperature measured ranged from about 0° C. to about 200° C. The temperature was measured with Wahl Heat Spy HSI3000 Thermal Imager. Both insulated and non-insulated wires were tested to at least 150° C.
The results are shown FIGS. 6A and 6B. As shown in FIGS. 6A and 6B, the non-insulated and the insulated carbon nanotube wires can handle approximately 2 watts before reaching 100° C. This result may be due to the low thermal conductivity of the non-insulated carbon nanotube wires and their fairly high resistance relative to copper.

EXAMPLE 3

An experimental setup for testing the temperature versus power of the thermal management devices included using a sheet of carbon nanotube electrical conductor (i.e., electrically conductive member) and laminating with a thin layer of a high thermally conductive graphite (i.e., thermally conductive member). The resulting laminated structure was then rolled tightly to form a cylinder approximately six inches long. The sample was hung in air, and a DC power supply was used to run a current through and a voltage across the sample. The Power applied ranged from about 0 Watts to about 10 Watts. The power supply was set to be current limiting and readings were taken every half volt once the temperature stabilized. The temperature measured ranged from about 0° C. to about 200° C. The temperature was measured with Wahl Heat Spy HSI3000 Thermal Imager. The response is shown in FIG. 7 and is compared to the pure carbon nanotube (CNT) conductor without any thermal dissipation assistance.

EXAMPLE 4

An experimental setup for testing the temperature versus power of the thermal management devices included using a sheet of carbon nanotube (CNT) electrical conductor (i.e., electrically conductive member) and wrapping it around a high thermal conductivity carbon fiber (i.e., thermally conductive member). The CNT conductor was condensed with acetone to remove voids and increase contact the interface between the layers. The sample was hung in air, and a DC power supply was used to run current a through and a across the sample. The Power applied ranged from about 0 Watts to about 10 Watts. The power supply was set to be current limiting and readings were taken every half volt once the temperature stabilized. The temperature measured ranged from about 0° C. to about 200° C. The temperature was measured with Wahl Heat Spy HSI3000 Thermal Imager. The response is shown in FIG. 7 and is compared to the pure CNT conductor without any thermal dissipation assistance and the high thermal conductivity carbon fiber without a CNT electrical conductor.
While the invention has been described in connection with the specific embodiments thereof, it will be understood that it is capable of further modification. Furthermore, this application is intended to cover any variations, uses, or adaptations of the invention, including such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains.

Claims

1. A device, comprising:

a thermally conductive member for directing heat away from a heat source;

an electrically conductive member positioned about the thermally conductive member and made from a layer of carbon nanotubes to reduce electrical resistance along the electrically conductive member; and

a geometric pattern imparted to the electrically conductive member to enhance dissipation of heat away from the thermally conductive member.

2. The device as set forth in claim 1, wherein the thermally conductive member is made from a material having a relatively high thermal conductivity characteristic.

3. The device as set forth in claim 1, wherein the thermally conductive member is made from a material having a heat spreading characteristic.

4. The device as set forth in claim 1, wherein the thermally conductive member is made from one of graphite fiber, film or foil, or a combination thereof.

5. The device a set forth in claim 1, wherein the thermally conductive member comprises a porous mesh to enhance dissipation of heat from the heat source.

6. The device as set forth in claim 1, wherein the electrically conductive member is circumferentially situated about the thermally conductive member.

7. The device as set forth in claim 1, wherein the electrically conductive member is made from one of individual and conductive yarns, fibers, wires, sheets, mat or textile material.

8. The device as set forth in claim 1, wherein the electrically conductive member is braided or woven about the thermally conductive member.

9. The device as set forth in claim 1, wherein the electrically conductive member forms a sheet and is laminated onto the thermally conductive member.

10. The device as set forth in claim 1, wherein the geometric pattern imparted to the electrically conductive member is a lattice circumferentially situated about the thermally conductive member.

11. The device as set forth in claim 1, wherein the geometric pattern imparted to the electrically conductive member includes a plurality of electrically conductive layers circumferentially situated about the thermally conductive member.

12. The device as set forth in claim 1, wherein the geometric pattern imparted to the electrically conductive member includes a plurality of layers spirally wound upon itself

13. The device as set forth in claim 1, further including fins to help facilitate the transfer of heat away from the heat source.

14. The device as set forth in claim 1, further comprising an adhesive material between the thermally conductive member and the electrically conductive member.

15. The device as set forth in claim 1 for use as an electrical conductor.

16. The device as set forth in claim 1, wherein the conductor is incorporated as part of a cable or cable assembly.

17. The device as set forth in claim 1, wherein the conductor is incorporated as part of a coaxial cable.

18. A method of dissipating heat, the method comprising:

(a) situating a thermally conductive layer against a heat source to dissipate heat from the heat source;

(b) positioning an electrically conductive layer about the thermally conductive layer; and

(c) imparting a pattern to the electrically conductive layer to enhance dissipation of heat away from the heat source.

19. The method of claim 18, wherein in the step of placing, the heat source is a conductor.