Patent Publication Number: US-9406651-B2

Title: Chip stack with oleic acid-aligned nanotubes in thermal interface material

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of co-pending U.S. Utility Patent Application entitled, “METHOD FOR CARBON NANOTUBE ALIGNMENT USING MAGNETIC NANOPARTICLES” having Ser. No. 13/936,369, filed Jul. 8, 2013, by Boday et al., which is entirely incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally relates to thermal interface materials, and more particularly, to matrices for rapid alignment of nanotubes containing a magnetic material for stacked chip cooling applications. 
     BACKGROUND 
     Thermal interfaces in microelectronics packages are commonly credited with a majority of the resistance for heat to escape from the chip to an attached cooling device (e.g. heat sinks, spreaders and the like). Thus, in order to minimize the thermal resistance between the heat source and cooling device, a thermally conductive paste, thermal grease, or adhesive is commonly used. Thermal interfaces are typically formed by pressing the heat sink or chip cap onto the backside of the processor chip with a particle-filled viscous medium between, which is forced to flow into cavities or non-uniformities between the surfaces. 
     Thermal interface materials are typically composed of an organic matrix highly loaded with a thermally conductive filler. Thermal conductivity is driven primarily by the nature of the filler, which is randomly and homogeneously distributed throughout the organic matrix. Commonly used fillers exhibit isotropic thermal conductivity and thermal interface materials utilizing these fillers must be highly loaded to achieve the desired thermal conductivity. Unfortunately, these loading levels degrade the properties of the base matrix material (such as flow, cohesion, interfacial adhesion, etc.). 
     It has been determined that stacking layers of electronic circuitry (i.e. 3 dimensional chip stacks) and vertically interconnecting the layers provides a significant increase in circuit density per unit area. However, one significant problem of the three dimensional chip stack is heat dissipation from the inner chips. For a four layer, 3 dimensional chip stack, the surface area presented to the heat sink by the chip stack has only ¼ of the surface area presented by the two-dimensional approach. For a 4-layer chip stack, there are three layer-layer thermal interfaces in addition to the final layer to grease/heat sink interface. The heat from the bottom layers must be conducted up thru the higher layers to get to the grease/heat sink interface. 
     One approach utilizes nanotubes, such as for example carbon nanotubes (CNTs), to promote heat dissipation from the inner chips. However, the CNTs are randomly oriented in the thermal interface material (TIM). CNTs and other thermally conductive carbon structures exhibit anisotropic thermal conductivity such that the thermal conductivity is orders of magnitude greater along one axis. Random distribution of the CNTs does not maximize the thermal conductivity of the TIM. 
     BRIEF SUMMARY 
     The exemplary embodiments of the present invention provide a method for enhancing internal layer-layer thermal interface performance and a device made from the method. In particular, disclosed is a method and system for aligning carbon nanotubes containing a magnetic material in a thermal interface material used in three dimensional chip stacks. 
     An exemplary embodiment includes a method for aligning a plurality of nanotubes containing a magnetic material in a thermal interface material to enhance the thermal interface material performance. The method includes attaching magnetic material to the plurality of nanotubes, dispersing the plurality of nanotubes containing a magnetic material into the thermal interface material, and heating the thermal interface material until the thermosetting polymer un-crosslinks. The method further includes applying a magnetic field of sufficient intensity to align the nanotubes containing a magnetic material in the thermal interface material and cooling the thermal interface material until the thermosetting polymer re-crosslinks. 
     Another exemplary embodiment includes a chip stack of semiconductor chips with enhanced cooling apparatus. Briefly described in terms of architecture, one embodiment of the apparatus, among others, is implemented as follows. The chip stack of semiconductor chips with enhanced cooling apparatus includes a first chip with circuitry on a first side and a second chip electrically and mechanically coupled to the first chip by a grid of connectors. The chip stack further includes a thermal interface material pad between the first chip and the second chip to conduct heat. The thermal interface material pad further comprises a plurality of nanotubes containing a magnetic material, aligned parallel to mating surfaces of the first chip and the second chip, wherein a hydrophobic tail of oleic acid is wrapped around each one of the plurality of nanotubes and a hydrophilic acid head of the oleic acid is attached to the magnetic material. 
     Another exemplary embodiment includes a system for aligning a plurality of nanotubes containing a magnetic material in a thermal interface material to enhance the thermal interface material performance. Briefly described in terms of architecture, one embodiment of the system, among others, is implemented as follows. The system includes a means for attaching magnetic material to the plurality of nanotubes, a means for dispersing the plurality of nanotubes containing a magnetic material into the thermal interface material, and a means for heating the thermal interface material until the thermosetting polymer un-crosslinks. The system further includes a means for applying a magnetic field of sufficient intensity to align the nanotubes containing a magnetic material in the thermal interface material, and a means for cooling the thermal interface material until the thermosetting polymer re-crosslinks. 
     Another exemplary embodiment includes an apparatus comprising a first object, a second object and a thermal interface material. The thermal interface material includes having a thickness between a first surface of the thermal interface material and a second surface of the thermal interface material. The thermal interface material further includes a plurality of nanotubes containing a magnetic material, aligned parallel to the first surface and the second surface, wherein a hydrophobic tail of oleic acid is wrapped around each one of the plurality of nanotubes and a hydrophilic acid head of the oleic acid is attached to the magnetic material. 
     These and other aspects, features and advantages of the invention will be understood with reference to the drawing figures and detailed description herein, and will be realized by means of the various elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following brief description of the drawing and detailed description of the invention are exemplary and explanatory of preferred embodiments of the invention, and are not restrictive of the invention, as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a cross section block diagram illustrating an example of the C4 or flip chip connection channels in a silicon device stack utilizing the thermal interface material with nanotubes containing a magnetic material aligned along the conductive axis in the desired direction of the present invention. 
         FIG. 2A  is a block diagram illustrating an example of the nanotubes in a solution with oleic acid, wherein the oleic acid has a polar, hydrophilic, acid head group, and a hydrophobic tail. 
         FIG. 2B  is a block diagram illustrating an example of nanotubes in a solution with oleic acid where the oleic acid has a hydrophobic tail that wraps around the nanotube leaving the oleic acid functionality extending from the nanotube surface. 
         FIG. 2C  is a graph illustrating an example of the magnetic nanoparticles in an oleic acid solution. 
         FIG. 2D  is a block diagram illustrating an example of the magnetic nanoparticles after each of the magnetic nanoparticles has attached to an oleic acid functionality. 
         FIG. 2E  is a block diagram illustrating an example after the magnetic nanoparticles having oleic acid are dispersed into tetrahydrofuran (THF) and the nanotubes having oleic acid are dispersed into the THF. 
         FIG. 2F  is a block diagram illustrating an example of a nanotube in the THF where the oleic acid has a hydrophobic tail that wraps around the nanotube leaving the oleic acid functionality extending from the nanotube surface to attach to the magnetic nanoparticles. 
         FIG. 2G  is a block diagram illustrating an example of using a magnet to remove the nanotube having attached magnetic nanoparticles from the THF solution. 
         FIG. 3A  is a block diagram illustrating an example of the carbon nanotubes containing a magnetic material, randomly dispersed in a thermal interface material. 
         FIG. 3B  is a block diagram illustrating an example of the heated thermal interface material with nanotubes containing a magnetic material aligned by a magnetic field to orient the conductive axis in the desired direction in the thermal interface material. 
         FIG. 3C  is a block diagram illustrating an example of the slicing the thermal interface material into the desired footprint. 
         FIGS. 4A and 4B  are block diagrams illustrating an example of the thermal interface material with graphite nanofibers aligned by a magnetic field and heat to orient the conductive axis in perpendicular directions to the thermal interface material, and having a plurality of punch holes formed at various locations thereon. 
         FIG. 4C  is a block diagram illustrating an example of a top view of the thermal interface material with graphite nanofibers aligned by a magnetic field to orient the conductive axis in perpendicular directions to the thermal interface material, and having a plurality of punch holes formed at various locations thereon. 
         FIG. 4D  is a block diagram illustrating an example of the vectors in which the graphite nanofibers are aligned. 
         FIG. 5  is a block diagram illustrating an example of the thermal interface material with nanofibers containing a magnetic material arranged such that two opposite sides of the thermal interface material with nanofibers are aligned to conduct heat in the east/west direction and another two opposite sides conduct heat in the north/south direction, as wherein the core of the thermal interface material conducts heat perpendicular to the east/west direction and north/south directions. 
         FIG. 6  is a block diagram illustrating another example of the thermal interface material with nanofibers containing a magnetic material arranged such that two opposite sides of the thermal interface material with nanofibers containing a magnetic material are aligned to conduct heat in the east/west direction and another two opposite sides conduct heat in the north/south direction, wherein the core of the thermal interface material conducts heat perpendicular to the east/west direction and north/south directions. 
         FIG. 7  is a flow chart illustrating an example of a method of forming a silicon device utilizing the thermal interface material with nanotubes containing magnetic nanoparticles that are heated and aligned to orient the conductive axis in the desired direction of the present invention. 
         FIG. 8  is a flow chart illustrating an example of a method of forming a silicon device utilizing the thermal interface material with nanotubes containing magnetic nanoparticles that are aligned by using a solvent to orient the conductive axis in the desired direction of the present invention. 
     
    
    
     The detailed description explains the preferred embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. 
     DETAILED DESCRIPTION 
     The present invention may be understood more readily by reference to the following detailed description of the invention taken in connection with the accompanying drawing figures, which form a part of this disclosure. It is to be understood that this invention is not limited to the specific devices, methods, conditions or parameters described and/or shown herein, and that the terminology used herein is for the purpose of describing particular embodiments by way of example only and is not intended to be limiting of the claimed invention. 
     One or more exemplary embodiments of the invention are described below in detail. The disclosed embodiments are intended to be illustrative only since numerous modifications and variations therein will be apparent to those of ordinary skill in the art. 
     One or more exemplary embodiments of the invention disclose a thermal interface material formulation, wherein carbon nanotubes are dispersed in oleic acid in which the hydrophobic tail of the oleic acid will wrap around the carbon nanotube, leaving the oleic acid functionality extending from the carbon nanotube surface. Then the oleic acid modified carbon nanotubes are added dropwise to the magnetic nanoparticles in THF. The acid functionality will displace surface water and non-covalently bonded surfactants to bind the nanoparticles to the carbon nanotubes. The carbon nanotubes containing magnetic nanoparticles are then removed from solution using a magnet, dispersed in a silicone matrix, and a magnetic field is applied to align the carbon nanotubes. 
     One or more exemplary embodiments of the invention is directed to providing a thermal interface material that is placed between chips in a chip stack. The thermal interface material having carbon nanotubes, containing a magnetic material, is aligned to efficiently transfer heat to at least two sides (e.g., east and west, or north and south) of a chip stack. 
     In one embodiment, all nanotubes containing a magnetic material are aligned “east/west” and draw the heat to heat sinks (i.e. heat dissipating objects) on the east and west sides of the chip stack. In another embodiment, the pads are alternated among chips so that alternating layers draw heat to heat sinks on the east/west sides of the chip stack and to the north/south side of the chip stack. In still another embodiment, pieces of the pads are arranged such that two opposite sides of the arrangement conduct heat east/west and another two opposite sides conduct heat north/south. In this embodiment, the nanotubes containing a magnetic material are arranged so that both ends are perpendicular to the closest edge of the pad. 
     A thermal interface material is used to fill the gaps between thermal transfer surfaces, such as between microprocessors and heat sinks, in order to increase thermal transfer efficiency. These gaps are normally filled with air, which is a very poor conductor. A thermal interface material may take on many forms. The most common is the white-colored paste or thermal grease, typically silicone oil filled with aluminum oxide, zinc oxide, or boron nitride. Some brands of thermal interface materials use micronized or pulverized silver. Another type of thermal interface materials are the phase-change materials. The phase change materials are solid at room temperature, but liquefy and behave like grease at operating temperatures. 
     A phase change material is a substance with a high heat of fusion which, melting and solidifying at a certain temperature, is capable of storing and releasing large amounts of energy. Heat is absorbed or released when the material changes from solid to liquid and vice versa; thus, phase change materials are classified as latent heat storage units. 
     Phase change materials latent heat storage can be achieved through solid-solid, solid-liquid, solid-gas and liquid-gas phase change. However, the only phase change used for thermal interface materials is the solid-liquid change. Liquid-gas phase changes are not practical for use as thermal storage due to the large volumes or high pressures required to store the materials when in their gas phase. Liquid-gas transitions do have a higher heat of transformation than solid-liquid transitions. Solid-solid phase changes are typically very slow and have a rather low heat of transformation. 
     Initially, the solid-liquid phase change materials behave like sensible heat storage materials; their temperature rises as they absorb heat. Unlike conventional sensible heat storage, however, when phase change materials reach the temperature at which they change phase (i.e. melting temperature) they absorb large amounts of heat at an almost constant temperature. The phase change material continues to absorb heat without a significant rise in temperature until all the material is transformed to the liquid phase. When the ambient temperature around a liquid material falls, the phase change material solidifies, releasing its stored latent heat. A large number of phase change materials are available in any required temperature range from −5 up to 190° C. Within the human comfort range of 20° to 30° C., some phase change materials are very effective. They can store 5 to 14 times more heat per unit volume than conventional storage materials such as water, masonry, or rock. 
     It is well known that the incorporation of certain types of carbon nanotubes into thermal interface material can impart thermal conductivity to such materials. Carbon nanotubes, can be dispersed in thermal interface material by various well-known techniques. These techniques include, but are not limited to, melting, kneading and dispersive mixers to form an admixture that can be subsequently shaped to form a thermally conductive article. 
     Carbon nanotubes (CNTs) are allotropes of carbon with a cylindrical nanostructure. Nanotubes have been constructed with a length-to-diameter ratio of up to 132,000,000:1, significantly larger than any other material. They exhibit extraordinary strength and unique electrical properties, and are efficient thermal conductors. Nanotubes are members of the fullerene structural family, which also includes the spherical buckyballs. The ends of a nanotube may be capped with a hemisphere of the buckyball structure. Their name is derived from their size, since the diameter of a nanotube is on the order of a few nanometers (approximately 1/50,000th of the width of a human hair), while they can be up to 18 centimeters in length. 
     Carbon nanotubes have received considerable attention in the electronics field due to their remarkable thermal conductivity. Moreover, the thermal conductivity of carbon nanotubes are anisotropic. Anisotropy is the property of being directionally dependent, as opposed to isotropy, which implies homogeneity in all directions. Therefore, the present invention takes advantage of the anisotropic nature of the carbon nanofibers and nanotubes by effectively aligning them along the conductive axis, thereby generating a thermal interface material with exceptional thermal conductivity at comparatively low loading levels. Diamond, graphite, and graphite fibers have been known as excellent heat conductors with a high thermal conductivity up to 3000 W/m-K. 
     Currently in known thermal interface materials, the polymeric matrix when the alignment would occur is very viscous. This makes alignment difficult. In one embodiment of the present invention is a TIM formulation that allows for carbon nanotube-like structures to be aligned once dispersed into a silicon matrix. This allows for a more facile method of alignment. Once alignment is accomplished, the silicon matrix is cured (i.e. temperature is applied) and the TIM converts to a solid gel. 
     Referring now to the drawings, in which like numerals illustrate like elements throughout the several views.  FIG. 1  is a cross section block diagram illustrating an example of a controlled collapse chip connection  17  (i.e. C4) or flip chip electrically conductive channels  16  and thermal conductive channels  15  utilized in a chip stack  10 . 
     The chip stack  10  comprises a multitude of chips  13  (A-D) that further include one or more electrically conductive channels  16  and/or thermal conductive channels  15 , which extend through a chip  13  from the top surface to the bottom surface. In one embodiment, the “conductive channel” is really a combination of two or more thru-silicon-vias (TSVs) connected sequentially by one or more controlled collapse chip connections  17  (C4s). 
     Preferably, the electrically conductive channels  16  are formed of tungsten or copper; however, other conductive materials may be used and are contemplated. The electrically conductive channels  16  selectively conduct electrical signals to and from portions of the circuitry  14  thereon or simply couple to solder bumps  17  to interconnect differing chips  13  in the chip stack  10  (e.g., chips  13 A and  13 B), or both. The solder bumps  17  are located within an area  41  of a thermal interface material (TIM) pad  40 . In one embodiment, the area  41  is punched out of the TIM pad  40 . In another embodiment, the area  41  is formed during the creation of the TIM pad  40 . 
     The TIM pad  40  comprises carbon nanotubes (CNTs), carbon nanofibers (CNF), graphitic nanofibers (GNFs) or the like, that are dispersed in a phase change material (PCM) or a silicone matrix. After dispersing the CNTs, CNFs or GNFs in the PCM, they are then aligned in the xy plane (i.e. positioned parallel to the surface of the chip  13 ). This is so that heat may be brought to the edges of the chip stack  10 . Once the heat is brought to the edges of the chip stack  10 , multiple heat sinks or other type devices may be utilized to more efficiently dissipate that heat of the chip stack  10 . 
     In one embodiment, CNTs, CNFs or GNFs are aligned in the thermal interface material  30  in one direction by an applied magnetic field. Aligning the CNTs, CNFs or GNFs along the conductive axis in the xy plane of the 3D chip stack  10  creates a TIM pad  40  with exceptional thermal conductivity at comparatively low loading levels. The system and method for aligning graphitic nanofibers to enhance thermal interface material performance are described in commonly assigned and co-pending U.S. Patent Application entitled “A METHOD AND SYSTEM FOR ALLIGNMENT OF CARBON NANOFIBERS FOR ENHANCED THERMAL INTERFACE MATERIAL PERFORMANCE”, Ser. No. 12/842,200 filed on, Jul. 23, 2010, and U.S. Patent Application entitled “A System and Method to Process Horizontally Aligned Graphite Nanofibers in a Thermal Interface Material Used in 3D Chip Stacks”, Ser. No. 13/188,572 filed on, Jul. 22, 2011, both herein incorporated by reference. 
     Preferably, the thermal conductive channels  15  are formed and filled with conductive materials, metal or alternatively are formed of thermal grease. The thermal grease is typically silicone oil filled with aluminum oxide, zinc oxide, or boron nitride; however, other conductive materials may be used and are contemplated. Some brands of thermal conductive channels  15  use micronized or pulverized silver. Another type of thermal conductive channels  15  are the phase-change materials. The phase change materials are solid at room temperature, but liquefy and behave like grease at operating temperatures. The thermal conductive channels  15  conduct heat to and from portions of the circuitry  14  thereon. The thermal conductive channels  15  couple to solder bumps  17  to interconnect differing chips  13  in the chip stack  10  (e.g., chips  13 A and  13 B), couple to heat sink  11  through thermal grease  12  or TIM pad  40  of the present invention, that conducts the heat to the side of the chip stack  10 . 
     The electrically conductive channels  16  couple to solder bumps  17  on a bond pad (not shown) on the bottom surface of chip  13  (A-C). The solder bumps  17  are electrically isolated from the chip  13  and one another according to conventional practice. In addition, the electrically conductive channels  16  are preferably electrically insulated from the chip  13  by insulating regions (not shown) which are disposed between the electrically conductive channels  16  and the chip  13 . The insulating regions preferably are silicon dioxide (SiO 2 ); however, other insulating materials may be employed and are contemplated as falling within the scope of the present invention. The insulating regions prevent the signals being transmitted in the electrically conductive channels  16  from disturbing the bias voltage of the chip  13  (which is typically either at ground potential or a Vdd). Of course, in some cases, one of the terminals of the circuitry  14  on the top surface may be held at a substrate potential, in which case, the appropriate electrically conductive channel  16  may be non-insulated and thus be in electrical contact with the chip  13  being held at a similar potential, as may be desired. 
     As shown, each chip  13  uses electrically conductive channels  16  in a controlled, collapse chip connection (C4) structure (also often called solder bump or flip-chip bonding). The chip stack  10  includes a base chip  13 A. Solder bumps  17  are then placed on a bond pad (not shown) for the electrically conductive channels  16  of a second (or top) chip  13 A, which is oriented face-down (i.e., flip-chip), aligned and brought into contact with the electrically conductive channels  16 . Electrical interconnections between the electrically conductive channels  16  are formed by heating the solder bumps  17  to a reflow temperature, at which point the solder flows. After the solder flows, subsequent cooling results in a fixed, electrically conductive joint to be formed between the electrically conductive channels  16 . 
     The base chip  13 A on one side is attached to a heat sink  11  with thermal grease  12 . In an alternative embodiment, a thermal interface material incorporating vertically aligned carbon (graphite) nanofibers can be utilized in place of thermal grease  12  as a very effective thermal interface material between a top of base chip  13 A and a heat sink  11 . Such an arrangement is disclosed in U.S. Patent Application (entitled “A METHOD AND SYSTEM FOR ALLIGNMENT OF CARBON NANOFIBERS FOR ENHANCED THERMAL INTERFACE MATERIAL PERFORMANCE”, Ser. No. 12/842,200. Other chips  13 B- 13 D can have C4 connection structures implemented on both the top surface and bottom surface thereof, as illustrated in  FIG. 1 . In such instances, a second chip  13 B may similarly be oriented facedown with respect to the base chip  13 A and coupled thereto-using solder bumps  17 . 
     The C4 structure of  FIG. 1  overcomes one disadvantage of the connection methodologies. Initially, because the ball-bonding attachment technique is avoided, significantly less stress is placed on the solder bump  17  during connection, which allows circuitry  14  (A-C) to be formed under the solder bump  17 . The circuitry  14  (A-C) is formed according to any one of many conventional semiconductor processing techniques. However, the C4 structure of  FIG. 1  has one major disadvantage of not being able to dissipate the heat generated by circuitry  14  (A-D). The TIM pad  40  of the present invention comprises carbon nanotubes (CNTs), carbon nanofibers (CNFs) or graphitic nanofibers (GNFs) that are dispersed in a phase change material (PCM) or a silicone matrix. The CNTs, CNFs or GNFs are aligned in the position parallel to the surface of the chip  13 . This is so that heat may be brought to the edges of the chip stack  10 . Once the heat is brought to the edges of the chip stack  10 , multiple heat sinks or other type devices may be utilized to more efficiently dissipate that heat of the chip stack  10 . In one embodiment, all carbon nanotubes are aligned “east/west” and draw the heat to heat sinks on the east and west sides of the chip stack. 
       FIG. 2A  is a block diagram illustrating an example of the carbon nanotubes  31  in container  18 , in a solution  27  containing oleic acid  23 . The oleic acid  23  has a polar, hydrophilic, acid head group  22 , and a hydrophobic tail  24 . Oleic acid  23  acts as a surfactant and causes the hydrophobic tail  24  to wrap around the carbon nanotube  31 . Oleic acid  23 , being a long chain (18 carbon atoms) fatty acid, behaves as a surfactant. That is, the long carbon tail is a hydrophobic tail  24 , whereas the acid head group  22  is carboxylic and therefore hydrophilic. Using the ‘like dissolves like’ rule, when the carbon nanotubes  31  are dispersed in the solution  27  with oleic acid  23 , the hydrophobic tail  24  of oleic acid  23  will wrap around the carbon nanotubes  31  driven by thermodynamics. An example of this wrapping of the hydrophobic tail  24  of oleic acid  23  is illustrated in  FIG. 2B .  FIG. 2B  is a block diagram illustrating an example of carbon nanotubes  31  in container  18 , in the solution  27  with oleic acid  23 , where the oleic acid  23  has a hydrophobic tail  24  that wraps around the carbon nanotube  31  leaving the oleic acid  23  functionality extending from the surface of the carbon nanotube  31 . 
       FIG. 2C  is a graph illustrating an example of magnetic nanoparticles  25  in a solution  28  containing oleic acid  23  in container  19 . Exemplary magnetic nanoparticles  25  include, but are not limited to: Magnetite (Fe 3 O 4 ), Ferrite (BaFe 12 O 19 ), Metallic nanoparticles with a shell, e.g., CoO layer on the surface of a Co nanoparticle, Maghemite (Fe 2 O 3 , γ-Fe 2 O 3 ), and the like. As such, the magnetic nanoparticles  25  will invariably contain surface water. Upon addition of oleic acid  23 , the hydrophilic acid head  22  of oleic acid  23  will displace the surface water molecules from the magnetic nanoparticles  25 .  FIG. 2D  is a block diagram illustrating an example of the magnetic nanoparticles  25  after each of the magnetic nanoparticles  25  has attached to the hydrophilic acid head  22  of oleic acid  23 . 
       FIG. 2E  is a block diagram illustrating an example of the magnetic nanoparticles  25  with the long carbon chain of attached oleic acid  23  extending off of them, illustrated in  FIG. 2C-D , dispersed into a solution  29  of tetrahydrofuran (THF) in container  21 . Then the carbon nanotubes  31  having oleic acid  23  are dispersed into the solution  29  of THF. 
       FIG. 2F  is a block diagram illustrating an example of a carbon nanotube  31  in the THF solution  29  in container  21 . The oleic acid  23  has a hydrophobic tail  24  that wraps around the carbon nanotube  31  leaving the oleic acid  23  functionality extending from the carbon nanotube  31  surface to attach to the magnetic nanoparticles  25 . The long hydropbic chains  24  intertwine, the result being magnetic nanoparticles  25  attached to carbon nanotubes  31 . 
       FIG. 2G  is a block diagram illustrating an example of using a magnet  26  to remove the carbon nanotubes  31  having attached magnetic nanoparticles  25  from the THF solution  29  in container  21 . The carbon nanotubes  31  having attached magnetic nanoparticles  25  are then dried by evaporating off the THF The carbon nanotubes  31  having attached magnetic nanoparticles  25  are then placed into a thermal interface material  30 . 
       FIG. 3A  is a block diagram illustrating an example of the carbon nanotubes  31  containing a magnetic material, randomly dispersed in the thermal interface material  30 . The carbon nanotubes  31  are disbursed into the melted thermal interface material  30  using well-established methods. In one embodiment, a high-speed dispersive mixer can be utilized. The carbon nanotubes  31  typically are dispersed essentially homogeneously throughout the bulk of the thermal interface material  30 . As shown there is thermal interface material  30  in a crucible  39 . The crucible  39  is heated to a temperature so that the thermal interface material  30  melts. 
     In the preferred embodiment, heat from well-established heating apparatuses  34  is applied to un-crosslink the least one polymer in the thermal interface material  30 . In this embodiment, the thermal interface material  30  is melted at a temperature  10 C- 20 C above the thermal interface material  30  melting temperature. In an alternative embodiment, a solvent or reactive chemical is applied to the thermal interface material  30  to un-crosslink the least one polymer in the thermal interface material. In still another alternative embodiment, a disulfide crosslinked epoxy can be used. The disulfide bond can be reduced using phosphines and then oxidized to reform the disulfide bond. Each example embodiment renders the gel like thermal interface material  30  into a lower viscosity material allowing for a more facile method of alignment. 
       FIG. 3B  is a block diagram illustrating an example of the thermal interface material  30  with carbon nanotubes  31  aligned by a magnetic field  38  to orient the conductive axis in the desired direction in the thermal interface material  30 . In one embodiment, crucible  39  is surrounded on two sides by electromagnet  33 . The magnetic fields  38  are generated in the electromagnet  33  by coils  36  around the electromagnet  33 . The coils are connected to switch  37 , which enables power to be applied. In the preferred embodiment, a magnetic field  38  is applied in a direction parallel to sides of a pad that would be in contact with semiconductor chips or other like electronic devices. The field is strong enough to align the carbon nanotubes  31  containing magnetic nanoparticles  25 . The carbon nanotubes  31  can be aligned in the xy plane. In one embodiment, the long axis of the carbon nanotubes  31  are aligned in an orientation parallel to the mating surfaces as illustrated in  FIGS. 4A and 4B . In another embodiment, the carbon nanotubes  31  are aligned in an orientation perpendicular to the mating surfaces as illustrated in  FIG. 4C . In still another embodiment, the carbon nanotubes  31  are aligned in an orientation parallel to the mating surfaces, such that two opposite sides of the thermal interface material  30  have carbon nanotubes  31  aligned in one direction parallel with the sides of the thermal interface material  30  and other carbon nanotubes  31  on opposite sides aligned in a second direction perpendicular to the first direction and still parallel with the mating surfaces as illustrated in  FIGS. 5 and 6 . 
     The crucible  39  is cooled to approximately room temperature. Once the crucible  39  with the aligned carbon nanotubes  31  in the phase change material has cooled to approximately room temperature, the thermal interface material  30  is removed from the crucible  39 . In one embodiment, room temperature is normally within the range of 60 to 80° F., or 15° C. to 27° C. The thermal interface material  30  can be, but is not limited to, paraffins (C n H 2n+2 ); fatty acids (CH 3 (CH 2 ) 2n COOH); metal salt hydrates (M n H 2 O); and eutectics (which tend to be solutions of salts in water). In still another embodiment, the thermal interface material  30  can be silicone-based gels or pastes that are eventually cured into pads. 
     According to the present disclosure, the thermal conductivity at desired locations is increased by TIM pads  40  and block  45  with aligned carbon nanotubes  31  between the multiple chips  13 A-D. By utilizing the TIM pad  40  with aligned carbon nanotubes  31  between multiple chips  13 A-D, more heat transfer to the edge of the chip stack  10  can be achieved. The advantage of this solution is that it further reduces chip temperatures through no modification to the chip surface and does not require changes to the manufacturing line or the addition of more components to the system such as liquid coolants and microchannel heat exchangers. 
       FIG. 3C  is a block diagram illustrating an example of the slicing of the thermal interface material  30  into the desired footprint or TIM pad  40  and block  45 . TIM pads  40  of appropriately sized geometry (length X and width Y) are cut from the slab of thermal interface material  30  using conventional techniques of dicing apparatus  35  known to those skilled in the art. The geometry of TIM pads  40  and TIM blocks  45 , are dictated by the footprint of the integrated circuitry  14  on chips  13 (A-D) to which the TIM pads  40  and  45 , will be mated. TIM blocks  45  of appropriately sized geometry (length X and width Y) are cut from the slab of thermal interface material  30  using conventional techniques of dicing apparatus  35  known to those skilled in the art. The block  45  is rotated so that the carbon nanotubes  31  are vertically aligned. In one embodiment, the footprint of the vertical shaft to which the TIM pads  50  or  60 , is constructed around the geometry of block  45  as shown in  FIGS. 5 and 6  as blocks  55  and  65  respectively. 
       FIGS. 4A and 4B  are block diagrams illustrating an example of a top view of the TIM pad  40  with carbon nanotubes  31  aligned by a magnetic field  38  to orient the conductive axis in perpendicular directions to the TIM pad  40 , and having a plurality of areas  41  formed at various locations thereon. Areas  41  provide space for the solder bumps  17  that are formed on electrically conductive channels  16 , on the chip  13 . The solder bumps  17  rest on electrically conductive channels  16  to connect one chip to another chip through TIM pad  40  to electrically conductive signals from, for example, chip  13 A to another chip  13 B. In another embodiment, the solder bumps  17  can conduct heat from, for example, chip  13 A to another chip  13 B thru thermal conductive channels  15  and eventually to heat sink  11 . In another embodiment, the solder bumps  17  can conduct heat laterally from the solder bumps  17  through TIM pad  40 (A-B) and between two chips  13 (A-D) to the edges of the chip stack  10 . In still another embodiment, the direction of the carbon nanotubes  31  in TIM pads  40  are alternated among chips so that alternating layers draw heat to heat sinks on the east/west sides of the chip stack and to the north/south side of the chip stack. 
     As shown, the plurality of solder bumps  17  and areas  41  are circular, however, this is for illustration only and the solder bumps  17  and areas  41  may be of any shape including, but not limited to, triangular, rectangular, square, circular, elliptical, irregular or any four or more sided shape. The size and shape of areas  41  are generally determined by the size and shape of solder bump  17 . This is in order to provide a space in the TIM pad  40  for the solder bumps  17 . 
     Also as shown, the solder bumps  17  and areas  41  in one embodiment are laid out in regular patterns, however, this is for illustration only and the solder bumps  17  and areas  41  have the flexibility to be laid out in any desired pattern. This additional level of flexibility allows the circuitry on chips  13 (A-D) to be laid out without regard to the solder bumps  17  and areas  41  locations. This further allows the solder bump  17  locations above the circuitry on chips  13 (A-D) to be located in an optimized fashion, to directly couple with circuitry on another chip  13 . In another embodiment, the solder bumps  17  and areas  41  may be formed in a pattern where the electrically conductive channels  16  provide power at the periphery of the chip  13  to aid in cooling the chip  13 . Therefore, the solder bumps  17  and areas  41  may be located anywhere on the chip  13 A-D as illustrated in  FIG. 1 , without the need to form such interconnections on peripheral edges of the die. The solder bumps  17  are located within an area  41  ( FIG. 4 (A-C)) of a thermal interface material (TIM) pad  40 . In one embodiment, the area  41  is punched out of the TIM pad  40 . In another embodiment, the area  41  is formed during the creation of the TIM pad  40 . A TIM pad  40  is used to remove any gaps between thermal transfer surfaces, such as between chips  13  (A-D), microprocessors and heat sinks, in order to increase thermal transfer efficiency. Any gaps are normally filled with air, which is a very poor conductor. 
       FIG. 4C  is a block diagram illustrating a top view example of the TIM block  45  with carbon nanotubes  31  oriented with the conductive axis in parallel with the electrically conductive channels  16  and/or thermal conductive channels  15  on the TIM block  45 . There are a plurality of areas  41  formed at various locations thereon. These areas  41  are for the solder bumps  17  to connect chips  13 (A-D) together. In an alternative embodiment, a second TIM block  45  is in thermal contact with the center of TIM blocks  45  between chips  13 (A-D) to effectively draw heat to a chip above and below to ultimately connect to heat sink  11  on a top of the chip stack  10 . In another alternative embodiment, the additional TIM blocks  45  are in thermal contact with edges of TIM pads  40  hanging out between chips  13 (A-D) to effectively draw heat to a heat sink  11  on the sides of the chip stack  10 . 
       FIG. 4D  is a block diagram illustrating an example of the vectors in which the carbon nanotubes  31  are aligned. In this illustration, the carbon nanotubes  31  are either horizontally (i.e. XWY plane) or vertically (i.e. XWZ plane) aligned through the chip stack using carbon nanotubes  31 , as shown in  FIGS. 4A-4C . The vertical carbon nanotubes  31  (i.e XWZ plane) are in a plane perpendicular to the horizontal carbon nanotubes  31  (i.e. XWY plane). In order to differentiate the carbon nanotubes  31  oriented in the horizontal plane (i.e. XWY plane) from the carbon nanotubes  31  oriented in the vertical plane (i.e. XWZ plane), from now on those carbon nanotubes oriented in the vertical plane (i.e. XWZ plane) will be referred to as carbon nanotubes  32 . This means that the carbon nanotubes  31  are always aligned in the horizontal plane (i.e. XWY plane) perpendicular to the closest side edge (i.e. not top or bottom) of TIM pad  50 . Whereas, carbon nanotubes  32  on block  45  are aligned in the vertical plane (i.e. XWZ plane) and always perpendicular to all carbon nanotubes  31 . 
       FIG. 5  is a block diagram illustrating a top down view example of the TIM pad  50  with carbon nanotubes  31  arranged such that two opposite sides of the TIM pad  50  with carbon nanotubes  31  conduct heat in one direction parallel with the sides of the TIM pad  50  in contact with chip  13  and another two on opposite sides conduct heat in a second direction perpendicular to the first direction and still parallel with the sides of the TIM pad  50  in contact with chip  13 . The illustrated example also shows the TIM pad  50  with a vertical TIM block  55  (i.e. thermal channel) that includes carbon nanotubes  32  that are perpendicular to all carbon nanotubes  31  in the TIM pad  50 . In this embodiment, the bi-directional TIM pad  50  displayed in the top down view illustrated in  FIGS. 4A and 4B  can be easily sectioned and connected together to conduct heat to all four sides of the chip stack using carbon nanotubes  31 , and vertically through the vertical heat transmission block  45  using carbon nanotubes  32 , as shown. The vertical TIM block  55  is formed (i.e. cut) from block  45  illustrated in  FIG. 4C . This means that the carbon nanotubes  31  are always aligned in the horizontal plane (i.e. XWY and VZU plane) perpendicular to the closest edge of TIM pad  50 . Whereas the carbon nanotubes  32  on vertical TIM block  55  are aligned in the vertical plane (i.e. YWZ plane) and always perpendicular to all carbon nanotubes  31 . In this embodiment, the pattern areas for the chip solder bumps  17  on TIM pad  50  are generally applied after assembling the TIM pad  50 . This is to ensure that the area for the chip solder bumps  17  on chips  13 (A-D) are properly aligned. The solder bumps  17  are located within an area  51  of a thermal interface material (TIM) pad  50 . In one embodiment, the area  51  is punched out of the TIM pad  50 . In another embodiment, the area  51  is formed during the creation of the TIM pad  50 . 
       FIG. 6  is a block diagram illustrating another example of the TIM pad  60  with carbon nanotubes  31  arranged such that two opposite sides of the TIM pad  60  with carbon nanotubes  31  conduct heat in one direction parallel with the sides of the TIM pad  60  in contact with chip  13  and another two on opposite sides conduct heat in a second direction perpendicular to the first direction and still parallel with the sides of the TIM pad  60  in contact with chip  13 . The illustrated example also shows the TIM pad  60  with a vertical TIM block  65  (i.e. channel) that includes carbon nanotubes  32  that are perpendicular to all carbon nanotubes  31  in the TIM pad  60 . In this embodiment, the bi-directional TIM pad  60  displayed in the top down view illustrated in  FIGS. 4A and 4B  can be easily sectioned and connected together to conduct heat to all four sides of the chip stack using carbon nanotubes  31  and vertically through the vertical heat transmission block  45  illustrated in  FIG. 4C  using carbon nanotubes  32 , as shown. This means that the carbon nanotubes  31  are always aligned in the XY plane perpendicular to the closest edge of TIM pad  60 . Whereas the carbon nanotubes  32  in vertical TIM block  65  are aligned in the ZWX or WZU plane and always perpendicular to all carbon nanotubes  31 . In this alternative embodiment, the bi-directional TIM pad  60  displayed in a top down view illustrated in  FIGS. 4A and 4B  can be easily sectioned and connected together to conduct heat to all four sides of the chip stack as shown, so that the carbon nanotubes  31  conduct heat to the closest edge of the TIM pad  60 . In this alternative embodiment, the TIM pad  60  is in a rectangular shape where the area of region A=B=C=D no matter what the W/L ratio of the rectangle. In this alternative embodiment, a chip stack  10  of memory chips is covered. The pattern areas for the chip solder bumps  17  on TIM pad  60  are generally applied after assembling the TIM pad  60 . This is to ensure that the area for the chip solder bumps  17  on chips  13  are properly aligned. 
       FIG. 7  is a flow chart illustrating an example of a method of forming a chip stack  10  utilizing the TIM pad  40  with carbon nanotubes  31  containing magnetic nanoparticles  25 , aligned by a magnetic field  38  and heated to orient the conductive axis in the desired direction of the present invention. There are a couple approaches to forming the individual chips  13 (A-D), and subsequent assembly, so the following is just one example of a method of constructing silicon devices in a multilayer chip stack  10  utilizing the thermal interface material pad  40  with aligned carbon nanotubes  31 . 
     At step  101 , the carbon nanotubes  31  are disbursed into a container  18  containing a solution  27  of oleic acid  23  using well-established methods. In one embodiment, a high-speed dispersive mixer can be utilized. The amount of carbon nanotubes  31  in the solution  27  of oleic acid  23  will typically be in the range of 4 to 10 weight percent based on the amount of solution  27  of oleic acid  23 . The carbon nanotubes  31  typically are dispersed essentially homogeneously throughout the solution  27  of oleic acid  23  The oleic acid  23  has a polar, hydrophilic, acid head group  22 , and a hydrophobic tail  24 . Oleic acid  23  acts as a surfactant and causes the hydrophobic tail  24  to wrap around the carbon nanotube  31 . Oleic acid  23 , being a long chain (18 carbon atoms) fatty acid, behaves as a surfactant. That is, the long carbon tail is a hydrophobic tail  24 , whereas the carboxylic acid head group  22  is hydrophilic. Using the ‘like dissolves like’ rule, when the carbon nanotubes  31  are dispersed in the solution  27  with oleic acid  23 , the hydrophobic tail  24  of oleic acid  23  will wrap around the carbon nanotubes  31  driven by thermodynamics. In an alternative embodiment, carbon nanofibers may be substituted for the carbon nanotubes  31 . 
     At step  102 , magnetic nanoparticles  25  are disbursed into a container  19  of solution  28  of oleic acid  23 . Exemplary magnetic nanoparticles  25  include, but are not limited to: Magnetite (Fe 3 O 4 ), Ferrite (BaFe 12 O 19 ), Metallic nanoparticles with a shell, e.g., CoO layer on the surface of a Co nanoparticle, Maghemite (Fe 2 O 3 , γ-Fe 2 O 3 ), and the like. Upon the addition of oleic acid  23 , the hydrophilic acid head  22  of oleic acid  23  will displace the surface water molecules from the magnetic nanoparticles  25 . 
     At step  103 , the magnetic nanoparticles  25  with a long carbon chain of attached oleic acid  23  extending off of them, are dispersed into a solution  29  of tetrahydrofuran (THF) in container  21 . At step  104 , the oleic acid  23  with a hydrophobic tail  24  that wraps around the carbon nanotube  31  leaving the oleic acid  23  functionality extending from the carbon nanotube  31  surface are dispersed into a solution  29  of THF in container  21 . The long hydropbic chains intertwine, the result being magnetic nanoparticles  25  attached to carbon nanotubes  31 . 
     At step  105 , a magnet  26  is used to remove the carbon nanotubes  31  having attached magnetic nanoparticles  25  from the THF solution  29  in container  21 . 
     At step  106 , at least one thermosetting polymer is added to create the thermal interface material  30  foundation. In one embodiment, the thermal interface material  30  is prepared according to the following procedure. To a 25 mL round bottom flask, aminopropylmethyl-Dimethylsiloxane copolymer (5 g, 0.002 moles APTES) (This polymer is commercially available from Gelest Inc.) is added along with anhydrous tetrahydrofuran (THF), a solvent (15 mL) and a stir bar. To this solution, furfuryl isocyante (0.262 g, 0.002 moles) is added drop wise. The reaction is stirred for 24 hrs at 50 C. THF is removed via distillation to yield the desired furfuryl polydimethylsiloxane (PDMS). 
     In an alternative embodiment, polymer 2 was prepared according to the following procedure. To a 100 mL round bottom flask, a furan protected maleic anhydride (0.5 g, 0.002 moles) is dissolved in 30 mL of benzene followed by the addition of a magnetic stir bar. To this solution, aminopropylmethyl-dimethylsiloxane copolymer (5 g, 0.002 moles APTES) (This polymer is commercially available from Gelest Inc.) is added drop wise along with benzene (20 mL). This reaction is magnetic mixed for 2 hrs at 80 C. Then ZnCl 2  (0.27 g, 0.002 moles) is added and magnetically stirred for 30 min. Then a solution of hexamethyldisilazane (HMDS) (0.48 g, 0.003 moles) and benzene (2.0 mL) is added drop wise and the reaction was brought to reflux and mixed for 1 h. The solution is filtered and washed with 0.5 N HCl to work up. The organic layer is dried with magnesium sulfate and the volatiles removed by distillation. 
     
       
         
         
             
             
         
       
     
     To prepare the TIM formulation, polymer 1 and polymer 2 are to be used at equal weight percents. While mixing polymer 1 and 2 together, the carbon nanotube-like structures can be added and mixed. Once mixed in, it can be applied and allowed to cure from room temperature to 70 C. When ready to align, the temperature is brought to approximately 110 C, at which point the polymer will under go a retro Diels Alder reaction and un-crosslink the polymer, thus reducing the viscosity significantly and allowing for facile alignment via an external field. This will allow for optimal alignment of the carbon nanotube-like  31  structures. Below is an example to demonstrate the retro-Diels Alder reaction. 
     
       
         
         
             
             
         
       
     
     Below is another example of a TIM formulation, which would allow for rapid viscosity changes to facilitate alignment of the carbon nanotube-like  31  structures. 
     
       
         
         
             
             
         
       
     
     Another suitable matrix based on reversible isocyanate reaction with phenol functionality is as follows where the R group can be a wide number of functional groups which will change the reversibility temperature as long as one R group is bound to a polymer to create a TIM formulation: 
     
       
         
         
             
             
         
       
     
     At step  107 , the carbon nanotubes  31  having attached magnetic nanoparticles  25  are disbursed into the melt using well-established methods. In one embodiment, a high-speed dispersive mixer can be utilized. The amount of carbon nanotubes  31  in the thermal interface material  30  of the present invention will typically be in the range of 4 to 10 weight percent based on the amount of thermal interface material  30 , preferably ˜5 weight percent. The carbon nanotubes  31  typically are dispersed essentially homogeneously throughout the bulk of the thermal interface material  30 . In an alternative embodiment, carbon nanofibers may be substituted for the carbon nanotubes  31 . 
     At step  108 , the thermal interface material  30  with the carbon nanotubes  31  is cooled to approximately 23° C.-75° C. in order to cure. At step  109 , the thermal interface material  30  with the carbon nanotubes  31  is heated to a temperature to un-crosslink the polymers in the thermal interface material  30 . In the preferred environment, the temperature of the thermal interface material is heated to and maintained at approximately 110° C.-125° C. 
     At step  110 , a magnetic field  38  ( FIG. 3B ) of sufficient intensity is applied to the thermal interface material  30  containing the carbon nanotubes  31 , in order to align the carbon nanotubes  31 . In one embodiment, the long axis of the carbon nanotubes  31  are aligned along the conductive axis of the graphite fibers. In another embodiment, the carbon nanotubes  31  are aligned in an orientation perpendicular to the mating surfaces. In still another embodiment, the magnetic field is normally within the range of 500-100,000 Gauss or 0.05-10 Tesla. 
     At step  111 , the thermal interface material  30  containing the carbon nanotubes  31  is cooled to approximately 23° C.-75° C. in order to re-cure the polymers in the thermal interface material  30 . At step  112 , the TIM pads  40  are cut to the desired footprint. TIM pads  40  of appropriately sized geometry (length X, width Y and thickness Z) are cut from the slab of thermal interface material  30  using conventional techniques known to those skilled in the art. The geometry of TIM pad  40  is dictated by the footprint of the integrated circuit to which the TIM pads  40  will be mated. 
     At step  113 , solder bumps  17  are then formed on the on the bottom surface of the chip  13 . These solder bumps  17  are generally in alignment with the electrically conductive channels  16  on chip  13  in order to conduct electrical signals. In an alternative embodiment, thermal conductive channels  15  may conduct heat instead of electronic signals and use a solder bump  17  with thermal conductive ability. In one embodiment, a homogenous process could be used to create solders bump  17  for both electrically conductive channels  16  and any thermal conductive channels  15 . 
     At step  114 , areas  41  are placed within the pads  42  corresponding with solder bumps  17  on chips  13 . This will allow these solder bumps on chip  13  to extend through TIM pads  40  in order to mechanically and electrically connect another chip  13 . At step  115 , the chips  13  in the chip stack  10  are assembled with the TIM pads  40  in between two adjacent chips  13 . 
     At step  116 , the chip stack  10  is heated to a reflow temperature, at which point the solder in the solder bumps  17  flows. Subsequent cooling results in a fixed, electrically conductive joint to be formed between the electrically conductive channels  16 . An example of this is to have the bottom surface of a first chip  13 A coupled to a top surface of a second chip  13 B with a TIM pad  40 A ( FIG. 1 ) in between. 
     At step  117 , it is determined if the circuitry on chips  13  in chip stack  10  are to be tested. If it is determined in step  117  that testing the circuitry in the chip stack  10  is not to be performed, then the method  100  skips to step  119 . However, if it is determined at step  114  that the circuitry on chips  13  in chip stack  10  are to be tested, then the circuitry is tested for electrical performance, at step  118 . 
     At step  119 , the method  100  attaches a heat sink  11  to one or more surfaces of one or more chips  13 . 
       FIG. 8  is a flow chart illustrating an example of a method of constructing silicon devices in a multilayer chip stack  10  utilizing the thermal interface material  30  with carbon nanotubes  31  containing magnetic nanoparticles  25 , heated and aligned by using a solvent to orient the conductive axis of the carbon nanotubes  31  in the desired direction of the present invention. 
     At step  121 , the carbon nanotubes  31  are disbursed into a container  18  containing a solution  27  of oleic acid  23  using well-established methods. In one embodiment, a high-speed dispersive mixer can be utilized. The amount of carbon nanotubes  31  in the solution  27  of oleic acid  23  will typically be in the range of 4 to 10 weight percent based on the amount of solution  27  of oleic acid  23 . The carbon nanotubes  31  typically are dispersed essentially homogeneously throughout the solution  27  of oleic acid  23  The oleic acid  23  has a polar, hydrophilic, acid head group  22 , and a hydrophobic tail  24 . Oleic acid  23  acts as a surfactant and causes the hydrophobic tail  24  to wrap around the carbon nanotube  31 . Oleic acid  23 , being a long chain (18 carbon atoms) fatty acid, behaves as a surfactant. That is, the long carbon tail is a hydrophobic tail  24 , whereas the carboxylic acid head group  22  is hydrophilic. Using the ‘like dissolves like’ rule, when the carbon nanotubes  31  are dispersed in the solution  27  with oleic acid  23 , the hydrophobic tail  24  of oleic acid  23  will wrap around the carbon nanotubes  31  driven by thermodynamics. In an alternative embodiment, carbon nanofibers may be substituted for the carbon nanotubes  31 . 
     At step  122 , magnetic nanoparticles  25  are disbursed into a container  19  of solution  28  of oleic acid  23 . Exemplary magnetic nanoparticles  25  include, but are not limited to: Magnetite (Fe 3 O 4 ), Ferrite (BaFe 12 O 19 ), Metallic nanoparticles with a shell, e.g., CoO layer on the surface of a Co nanoparticle, Maghemite (Fe 2 O 3 , γ-Fe 2 O 3 ), and the like. Upon the addition of oleic acid  23 , the hydrophilic acid head  22  of oleic acid  23  will displace the surface water molecules from the magnetic nanoparticles  25 . 
     At step  123 , the magnetic nanoparticles  25  with a long carbon chain of attached oleic acid  23  extending off of them, are dispersed into a solution  29  of tetrahydrofuran (THF) in container  21 . At step  124 , the oleic acid  23  with a hydrophobic tail  24  that wraps around the carbon nanotube  31  leading the oleic acid  23  functionality extending from the carbon nanotube  31  surface are dispersed into a solution  29  of THF in container  21 . The long hydropbic chains intertwine, the result being magnetic nanoparticles  25  attached to carbon nanotubes  31 . 
     At step  125 , a magnet  26  is used to remove the carbon nanotubes  31  having attached magnetic nanoparticles  25  from the THF solution  29  in container  21 . 
     At step  126 , at least one thermosetting polymer is added to create the thermal interface material  30  foundation. In one embodiment, the thermal interface material  30  is prepared according to the following procedure. To a 25 mL round bottom flask, aminopropylmethyl-Dimethylsiloxane copolymer (5 g, 0.002 moles APTES) (This polymer is commercially available from Gelest Inc.) is added along with anhydrous THF (15 mL) and a stir bar. To this solution, furfuryl isocyante (0.262 g, 0.002 moles) is added drop wise. The reaction is stirred for 24 hrs at 50 C. THF is removed via distillation to yield the desired furfuryl PDMS. 
     At step  127 , the carbon nanotubes  31  are disbursed into the melt using well-established methods. In one embodiment, a high-speed dispersive mixer can be utilized. The amount of carbon nanotubes  31  in the thermal interface material  30  of the present invention will typically be in the range of 4 to 10 weight percent based on the amount of thermal interface material  30 , preferably ˜5 weight percent. The carbon nanotubes  31  typically are dispersed essentially homogeneously throughout the bulk of the thermal interface material  30 . In an alternative embodiment, carbon nanotubes may be substituted for the carbon nanotubes  31 . 
     At step  128 , the thermal interface material  30  with the carbon nanotubes  31  is cooled to approximately 23° C.-75° C. in order to cure. At step  129 , a solvent is added to the thermal interface material  30  with the carbon nanotubes  31  to assist in un-crosslinking the polymers in the thermal interface material  30 . In the preferred environment, the solvent is THF or other suitable solvent known to those skilled in the art. 
     At step  130 , a magnetic field  38  ( FIG. 2B ) of sufficient intensity is applied to the thermal interface material  30  containing the carbon nanotubes  31 , in order to align the carbon nanotubes  31 . In one embodiment, the long axis of the carbon nanotubes  31  are aligned along the conductive axis of the graphite fibers. In another embodiment, the carbon nanotubes  31  are aligned in an orientation perpendicular to the mating surfaces. In still another embodiment, the magnetic field is normally within the range of 500-100,000 Gauss or 0.05-10 Tesla. At step  131 , the solvent within the thermal interface material  30  containing the carbon nanotubes  31  is evaporated off. In an alternative embodiment, a vacuum stripping method can be used, where the material is simply subjected to a vacuum. At step  128 , the thermal interface material  30  with the carbon nanotubes  31  is cooled to approximately 23° C.-75° C. in order to re-cure the polymers in the thermal interface material. 
     At step  132 , the TIM pads  40  are cut to the desired footprint. TIM pads  40  of appropriately sized geometry (length X, width Y and thickness Z) are cut from the slab of thermal interface material  30  using conventional techniques known to those skilled in the art. The geometry of TIM pad  40  is dictated by the footprint of the integrated circuit to which the TIM pads  40  will be mated. 
     At step  133 , solder bumps  17  are then formed on the bottom surface of the chip  13 . These solder bumps  17  are generally in alignment with the electrically conductive channels  16  on chip  13  in order to conduct electrical signals. In an alternative embodiment, thermal conductive channels  15  may conduct heat instead of electronic signals and use a solder bump  17  with thermal conductive ability. In one embodiment, a homogenous process could be used to create solder bumps  17  for both electrically conductive channels  16  and any thermal conductive channels  15 . 
     At step  134 , areas  41  are placed within the pads corresponding with solder bumps  17  on chips  13 . This will allow these solder bumps on chip  13  to extend through TIM pads  40  in order to mechanically and electrically connect another chip  13 . At step  135 , the chips  13  in the chip stack  10  are assembled with the TIM pads  40  in between two adjacent chips  13 . 
     At step  136 , the chip stack  10  is heated to a reflow temperature, at which point the solder in the solder bumps  17  flows. Subsequent cooling results in a fixed, electrically conductive joint to be formed between the electrically conductive channels  16 . An example of this is to have the bottom surface of a first chip  13 A coupled to a top surface of a second chip  13 B with a TIM pad  40 A ( FIG. 1 ) in between. 
     At step  137 , it is determined if the circuitry on chips  13  in chip stack  10  are to be tested. If it is determined in step  136  that testing the circuitry in the chip stack  10  is not to be performed, then the method  120  skips to step  139 . However, if it is determined at step  136  that the circuitry on chips  13  in chip stack  10  are to be tested, then the circuitry is tested for electrical performance, at step  138 . 
     At step  139 , the method  120  attaches a heat sink  11  to one or more surfaces of one or more chips  13 . 
     The terminology used herein is for describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     The flowchart and block diagrams in the Figures illustrate the functionality, and operation of possible implementations of systems and methods according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or task to be performed, which comprises one or more executable steps for implementing the specified function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the Figures. For example, two blocks shown in succession may in fact be performed substantially concurrently or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. 
     It should be emphasized that the above-described embodiments of the present invention, particularly any “preferred” embodiments, are merely possible examples of implementations set forth for a clear understanding of the principles of the invention. Many variations and modifications may be made to the above-described embodiment(s) of the invention without departing substantially from the spirit and principles of the invention. All such modifications and variations are intended to be included herein within the scope of this disclosure and the present invention and protected by the following claims.