Thin thermal interface materials and methods for making the same

Abstract

The present disclosure relates to thin thermal interface materials including a nanoparticle and a Cs to C40 alkyl chain. The thermal interface materials may fill defined cavities to increase contact surface areas and increase thermal conductivity. Methods for preparing thermal interface materials are also described herein.

Description

[0001] THIN THERMAL INTERFACE MATERIALS AND METHODS FOR MAKING THE SAME

[0002] Inventors: Kaoru Ueno, Josiah Arevalo Piceno, and Jeffery Hammaker

[0003] FIELD

[0004] The present disclosure generally relates to thermal interface materials and more particularly, but not exclusively, to thermal interface materials exhibiting phase change properties.

[0005] BACKGROUND

[0006] Thermally conductive and phase changing materials, compounds or compositions, which may be in a powder form for example, may be used in the semiconductor industry (amongst others) as a gap filler and / or as a bonding material. Some traditional phase-change heat conductive materials may rely on polymer technologies, and may be mixed with phase transformation fillers such as an organic polymer material, heat conductive filler, and paraffin. At high temperature these materials become liquid which may result in pollution of periphery electronic devices and components.

[0007] In the field of electronic components, such as CPUs and GPUs for example, one or more thermally conductive materials may be frequently utilized, including for example in the attachment of heat sinks to provide heat dissipation to optimize function of the component(s). Thermally conductive materials used in this manner may include thermal interphase materials which may be used to transfer excess heat from the electronic component to a heat spreader and then subsequently to a heat sink. The electronic components may include one or more metals, such as aluminium alloys, but the adhesion of aluminium to other metals present in the electronic components with one or more of the aforementioned thermal interphase materials may provide less than idea thermal conductivity which results in decreased heat transfer (e.g. due to increased thermal resistance) and cooling efficiency of the electronic components.

[0008] Based on the foregoing, there is a need for additional contributions in this area of technology, including for example the provision of a thermal interface material exhibiting desired adhesive, thermal conductivity, thermal resistance, followability, and / or electrically insulative properties.

[0009] SUMMARY

[0010] The present disclosure generally relates to thermal interface materials or thermally conductive composite adhesives, and to methods for their preparation

[0011] In one embodiment, a thermal interface material may be according to the following general Formula (1 ):

[0012] NP — C5-C40 alkyl

[0013] (Formula I).

[0014] In Formula I, NP may be an inorganic nanoparticle which may have a thermal conductivity above 5 W / mK. In some forms, the thermal interface material may have or exhibit a first phase at a first temperature and a second phase at a second temperature. In one aspect, the difference between the first temperature and the second temperature may be less than about 10 °C. In some forms, the thermal interface material may further include a linker between the NP and the C3 to C40 alkyl group, although forms in which the NP and the C5-C40 alkyl chain are mixed together and not linked by a linker are also possible. By way of non-limiting example, when present the linker may include a carbamate ester such that the NP may be linked or connected to the Cs to C40 alkyl group by the carbamate ester. In some forms, the inorganic nanoparticle may include one or more of silica (SiCte), alumina (AI2O3), AIN (aluminum nitride), cBN (cubic boron nitride), MgOH (magnesium hydroxide), and MgO (Magnesium oxide). In some forms, the inorganic nanoparticle may have an average particle diameter of about 1 nanometer (1 X 10'9meters) to about 10 microns (10 X 10-6meters). In one aspect, the inorganic nanoparticle may have an average particle diameter of less than about 30 nm to about 40 nm. In some forms, the thermal interface material may further include a primary amine. In some forms, a thermal interface material as described herein may be disposed within a polymer matrix.

[0015] In some forms, a thermal interface material according to Formula I may include one of the following:

[0016] AIN + 1 ,3-dioctadecyl urea (DODU) (TIM-6).

[0017] In these examples, the thermal interface material may exhibit or have a first phase at a first temperature and a second phase at a second temperature. In some forms where the NP is a nitride nanoparticle it may be at least partially covered with one or more hydroxy groups and hydroxylated element(s), and / or functionalized with a hydroxy group.

[0018] In some forms, the thermal interface material described herein may include one or more of at least one urea compound and at least one amide compound. In some forms, the urea compound may include one or more of N-alkyl urea and N,N’-dialkyl urea. In some forms, the amide compound may include an alkylene diamide. In some forms, the compound further may include a porous material comprising SiC>2, AI2O3, MgO, AIN, c-BN, or a combination thereof

[0019] In one embodiment, a thermally conductive element may include a porous material defining a number of cavities and a thermal interface material as described herein may be disposed within the cavities defined by the porous material. In some forms, the porous material may include copper.

[0020] In another embodiment, a computer construct with a thermal interface material may include a substrate and at least one computer element. The substrate and the at least one computer element may define surface cavities therein, and the thermal interface material may be disposed within the surface cavities to fill the surface cavities and provide a greater contact surface with the substrate, at least one computer element, and / or thermal interface material and the material disposed thereupon. In some forms, the computer construct may further include a thermal pad having a first thermal pad surface facing the substrate and the at least one computer element defining surface cavities therein with at least about 75% of the thermal pad surface in contact with the greater contact surface. In some forms, the presence of air voids within a polymer matrix may be reduced by the presence of a thermal interface material described herein.

[0021] In one embodiment, a computer construct may include a substrate having a substrate surface and one or more computer elements disposed upon the substrate surface with the substrate and one or more computer elements defining a number of cavities. The construct may further include a package lid, and first and second layers of a thermal interface material. The first layer of thermal interface material may be disposed between the substrate and the one or more computer elements and the package lid to provide increased contact area between the first layer of thermal interface material and the substrate and the one or more computer elements, and the second layer of thermal interface material may be disposed between the package lid and the first layer of thermal interface material to provide an increased contact layer between the first layer of thermal interface material and the package lid.

[0022] BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG. 1 is a schematic illustration of a porous sheet including a thermal interface material described herein.

[0024] FIG. 2 is a schematic illustration of a computer construct.

[0025] FIGS. 3 and 4 illustrate results of the thermal conductivity of an overall mixture of a modified thermal interface material and an unmodified nanoparticle. FIG. 5 illustrates thermal conductivity of composites of grafted powder and pristine powder.

[0026] FIG. 6 illustrates thermal conductivity of pristine powder and organic compound powder.

[0027] FIGS. 7 and 8 illustrate various thermal properties of an AIN / 1 ,3-dioctadecyl urea (DODll) composite.

[0028] FIG. 9 is a XRD spectra of modified and unmodified nanoparticle embodiments described herein.

[0029] FIG. 10 is a DSR spectra illustrating the melting temperature of various thermal interface materials.

[0030] DETAILED DESCRIPTION

[0031] The present disclosure generally relates to a thermal interface material, related thermally conductive composites, and methods for making the same. The materials disclosed herein may exhibit a melting-like behaviour that allows them to effectivity fill gaps or cavities, allowing for a more even surface and / or increased contact area which may provide improved thermal conductivity.

[0032] In one embodiment, a thermal interface material (TIM) may be according to the following Formula (I):

[0033] NP - (C5-C40 alkyl)

[0034] (Formula I)

[0035] In Formula (I), NP may be representative of an inorganic particle such as an inorganic nanoparticle. In some forms, the inorganic particle may have a thermal conductivity above 5 W / mK. Further, the NP may be linked and / or grafted to the Cs- C40 alkyl chain in Formula (I), although forms in which the NP and the C5-C40 alkyl chain are mixed together without any linking or grafting are also possible. In some forms where the NP is linked to the C5-C40 alkyl chain, the linkage may be provided by a carbamate ester and / or a polyurethane linkage / linker. In some forms, the TIM may have a first phase at a first temperature and a second phase at a second temperature. By way of non-limiting example, the first phase may be a solid and the second phase may be a liquid. In some forms, the TIM may include one or more of silica (SiCh), alumina (AI2O3), aluminum nitride (AIN), cubic boron nitride (CBNs), magnesium hydroxide (MgOH), and magnesium oxide (MgO). In forms where the TIM includes a nitride such as aluminum nitride and / or boron nitride, the nitride may be a nanoparticle covered in part with at least one hydroxy group on the surface thereof, hydroxylated elements such as aluminum nitride covered with aluminum trihydroxide, and / or hydroxyl groups on the surface thereof such as aluminum nitride covered with aluminum trihydroxide (AI(0H)3. In some forms, the TIM may include a primary amine.

[0036] In one embodiment, a composition includes a polymer matrix and a TIM as described herein where the TIM may be disposed within the matrix.

[0037] More particular but non-limiting examples of TIMs disclosed herein include the following:

[0038] AIN + DODU. It is believed that various properties (such as thermal conductivity, cooling effectiveness, thermal resistance, etc.) of a TIM as described herein may at least partially be provided by the inclusion of nanoparticles within a specified size range and the interaction between adjacent long alkyl chains of adjacent grafted or functionalized particles to reduce air void presence therein.

[0039] In some forms, a TIM may include one or more of at least one urea compound and at least one amide compound. In some forms, the urea compound may include o o

[0040] N-alkyl urea , N, N’-dialkyl urea ), or a combination thereof. In some forms, the amide compound may include an alkylene diamide ( o o ). In some forms, a TIM described herein may include a material with structure according to the following each n is 5-

[0041] 25. One particular but non-limiting example according to the above is 1 ,3-dioctadecyl urea. In some aspects of this form, the TIM may include the NP mixed with this structure without any linker or linkage therebetween. In one particular aspect, the NP in these forms may be AIN. In other aspects, it is contemplated that a TIM described herein may be mixed with a compound according to this structure. For example, in one form it is contemplated that TIM-4 may be mixed with a compound according to this structure such as 1 ,3-dioctadecyl urea.

[0042] In some forms, a TIM described herein may further include a porous material including a composite such as S iO2, AI2O3, MgO, AIN, c-BN, or a combination thereof. In some forms, the porous material may include a copper mesh, or a copper mesh including copper particles In some forms, the porous material may be filled with the composite such as SiC , AI2O3, MgO, AIN, c-BN, or a combination thereof.

[0043] In one embodiment, a thermally conductive element may include a porous material including cavities defined therein and a thermal interface material described herein may be disposed within the cavities of the porous material. In some embodiments, the porous material may include copper. In another embodiment, a computer construct with a thermal interface material described herein may include a substrate and at least one computer element, and the substrate and at least one computer element may define surface cavities therein. A thermal interface material described herein may be disposed within the surface cavities to fill the surface cavities and provide a greater contact surface with the substrate, at least one computer element, and / or a TIM and the material disposed thereupon. In some forms the computer construct may further include a thermal pad having a first thermal pad surface, and the thermal pad may be disposed atop the substrate and the at least one computer element defining the surface defining cavities therein. In this form, at least about 50%, about 75%, about 80%, or about 90% of the thermal pad surface is in contact with the greater contact surface. In some forms, a TIM described herein may reduce the presence of air voids within the polymer matrix / TIM which may increase thermal conductivity and decrease thermal resistance. In some forms, incorporation of the TIM layer reduces the presence of air voids within the TIM materials, polymer, and / or materials containing such between various layers.

[0044] As indicated above, NP in Formula I may represent an inorganic particle such as an inorganic nanoparticle or microparticle. In some forms, the inorganic particle may have an average particle size of 1 nanometer (1 X 10'9meters) to 10 microns (10 X 10-6meters). In one or more forms, the inorganic particle may have an average particle size of less than about 30 nm to about 40 nm or between about 1 -3 microns. In some forms, NP may be a nanoparticle which includes a metal oxide and / or metal nitride. In some forms, the nanoparticle or the TIM including the same may include silica (SiC ), alumina (AI2O3), aluminum nitride (AIN), cubic boron nitride (CBN), magnesium hydroxide (MgOH), magnesium oxide (MgO) particles and / or mixtures or combinations of such particles thereof.

[0045] In some forms, the NP and the alkyl chain may be connected to each other by a urethane bond or a carbamate ester. In some forms, the TIM may include a linker or linkage which may be a urethane bond In some forms, the linker or linkage may include an isocyanate coupling. In some forms, the linker or linkage may include a carbamate ester linkage. In some embodiments, the linker may include the following: In some forms, the linkage may include a primary amine.

[0046] In some forms, the TIM may include an alkyl chain and the alkyl chain may be a factor in providing materials that enable the dual phase functionality (the first temperature displaying a first phase and the second temperature displaying a second phase) of the TIM. In some forms, several considerations, e g., the length of the alkyl group, the presence and / or location of a carbon-carbon double bond, the resultant cis or trans configuration, presence of crosslinking, presence or absence of bulky side groups, flexibility of the polymer chain, film thickness, and / or carbon chain branching may be modified to alter or tailor a desired glass transition temperature. In some forms, the length of the alkyl chain may be between C3, Cs, C7, C9, C11 to C20, C23, C25, C28, C30, C32, C35, C38, C40, and C40 or any permutation of the values described, e.g., C17, Cia, C19. In some embodiments, the alkyl chain may include no carbon-carbon double bonds (“saturated”), or may include at least one, two, three, and / or four carbon-carbon double bonds. In some forms, the alkyl chain may include a trans and / or cisconfiguration.

[0047] As indicated above, in some forms the NP may be linked and / or grafted to the C5-C40 alkyl chain in Formula (I). In these and other forms, the nanoparticle may have a melting temperature, Tm (melting point) at which an amorphous polymer changes from a hard / rigid / glassy state, below the Tm, to a soft / leathery / fluid / mobile state, e.g., above the Tm, or vice versa. The T of a material may be related to the strength, capabilities, and characteristics of the selected material, including but not limited to, the length of the alkyl chain segment, and / or the number and / or positioning of the cis / trans / carbon double bonds within the alkyl chain. In some forms, the nanoparticle may have a Tmbetween about 5 °C and about 80 °C, e.g., between about 45 °C and about 70 °C. For example, at a first temperature, e.g., below at least one of the Tm, e.g., for the alpha, beta, and / or gamma form, the TIM may be an amorphous, glassy, hardened and / or solid form. In some forms, for example at a second temperature, e.g., above the Tm, the TIM may be a in a softer, liquid or fluid form. This may provide for the application of the material in a fluid state into the defined cavities and upon dropping the temperature below the Tm, hardening or solidifying within the defined cavities and evening out the surface area and / or increasing the contact between elements provided above an irregularly shaped motherboard / sub-elements. In some forms, the temperature difference between the first and second temperatures may be less than about 10°C, or about 5°C. In some forms, the temperature difference may be about 1.0 °C, about 2.5 °C, about 4 °C, about 5 °C, about 7.5 °C to about 9 °C, about 10 °C, about 12.5 °C, about 15 °C, and / or about 25 °C or any permutation of the aforementioned values or range of the aforementioned temperature differences, e.g., about 5 °C to about 15 °C.

[0048] In some forms, the NP may have an average particle diameter of less than 100 nm. In some forms, the NP may have an average particle size of 100 nanometers (100 X 10'9meters) to 0.010 microns (0.01010 X 10'6meters). In some forms, the average particle diameter may be less than about 30 nm to about 40nm. In forms where the NP includes BN for example, the average particle diameter may be about 1 -3 microns, and where the NP includes BN and / or AIN 1 , the average particle diameter may be about a micron.

[0049] In some forms where the NP is an inorganic particle, it may include S iOz, AI2O3, MgO, MgOH, and / or CuO. In some forms, the inorganic particle may include aluminum nitride cubic boron nitride (cBN). In some forms, the inorganic particle may for example, without any addition or modification, have a minimum thermal conductivity of for example about 0.25 W / mK, about 0.35 W / mK, or about 0.40 W / mK to about 1 .0 W / mK, about 1.1 W / mK, about 1 .2 W / mK, about 1 .4 W / mK, about 1 .5 W / mK, or about 2.0 or any permutation of the aforementioned values. The following table provides non- limiting examples of inorganic particles and related properties thereof:

[0050] In some forms, the overall thermal conductivity of the grafted or ungrafted nanoparticle and / or mixtures of the grafted and ungrafted nanoparticles can be greater than about 1.0 W / mK, about 2 0 W / mK, about 2 5 W / mK, about 3 0 W / mK, about 4 0 W / mK, about 5 W / mK, about 7.5 W / mK, or about 10 W / mK, just to provide a few nonlimiting examples. Referring now to FIG. 1 , there is illustrated a modified porous sheet 2 which includes a porous material 4 defining a plurality of cavities 6A and 6B therein. The sheet 2 also includes a TIM 8 as described herein, and in the illustrated form the TIM is disposed within the cavity 6B, although forms in which the TIM 8 is disposed within additional or alternative cavities are also possible. In some forms the porous material 4 may include a screen like interwoven material defining the cavities, e.g., between the weaving wires and / or within the individual structure portions therein. In some forms, the porous material 4 may include an electrically conducting metal such as copper. In some forms, the electrically conducting metal may be in the form of a screen or a sheet. In these forms for example, the length and / or width measurements of the conducting metal may be greater than the depth or thickness dimension thereof. By filling one or more of the cavities of the sheet 2, air voids are reduced or eliminated and, in turn, thermal conductivity of the sheet 2 may be increased while thermal resistance of the sheet 2 may be reduced. As such, the sheet 2 including a TIM as described herein filling one or more cavities thereof may be used in situations where smooth and efficient transfer or transport of heat may be desired. In addition, the sheet 2 may provide reinforcement to the TIM in instances where it may reach a temperature at or near which it becomes flowable or softened.

[0051] Referring now to FIG. 2, there is schematically illustrated a computer construct 10 which includes a substrate 12. The substrate 12 may be, for example, a motherboard, backboard, etc., which includes a resin, plastic, fiberglass or other non- conductive material. The construct 10 may include one or more sub-elements such as sub-elements 14A, 14B, 14C and 14D which may represent a computer processing unit, a hard-drive, memory and / or power source, just to provide a few examples. The sub-elements 14A, 14B, 14C and 14D are disposed on the substrate 12 in an arrangement where cavities and / or spaces are positioned therebetween; e.g., between the sub-elements 14A, 14B, 14C and 14D, and / or between the sub-elements 14A, 14B, 14C and 14D and the substrate 12. In the illustrated form, a thermal interface material 16 is disposed within the cavities and / or spaces and defines a top surface 18 of the thermal interface material 16. Moreover, as a phase change material exhibiting different phases at different temperatures, the thermal interface material 16 may fill any voids, cavities or uneven portions of the substrate 12 so as to increase the surface area of contact between the substrate 12 and the thermal interface material 16 and provide enhanced thermal conductively and lower thermal resistance therebetween. Similarly, by filing other voids or cavities between the sub-elements 14A, 14B, 14C, 14D and the substrate 12, the thermal interface material 16 reduces or eliminates associated air voids which in turn enhances overall thermal conductivity and reduces thermal resistance of the construct 10.

[0052] In the illustrated form, a second TIM layer 20 is disposed on top of the thermal interface material 16 or interposed between the thermal interface material 16 and any other layer (such as another TIM layer), and / or a package lid 22 which in the illustrated form is positioned on the second thermal interface material 20. In some embodiments, the top surface 18 of the thermal interface material 16 may be substantially even such that it increases the surface contact area between the top surface 18 and any other material disposed thereupon, including the second thermal interface material 20. In some forms, the surface contact area may be at least about 25%, about 33%, about 40%, about 50%, about 60%, about 75%, about 80% and / or about 90% of the surface area of the top surface 18 and the contacting surface of the material disposed above the contacting surface 18 such as the second TIM layer 20 or the package lid 22. Similarly, when the second TIM layer 20 is present, as a phase change material which exhibits different phases at different temperatures, it may fill any voids, cavities or uneven portions of the package lid 22 so as to increase the surface area of contact between the package lid 22 and the thermal interface material 20 and provide enhanced thermal conductivity and lower thermal resistance therebetween.

[0053] In one embodiment, a method for thermally protecting an uneven surface and / or increasing the contact surface area between layers may include providing a substrate with at least one computer element disposed thereupon. The substrate and / or the at least one computer element disposed thereupon may define cavities, recesses or generally uneven areas within a first surface. The method also includes heating an amount of a thermal interface material (TIM) (e.g., a dual phase material) above a first temperature, and dispersing the heated thermal interphase material within the cavities sufficient to at least partially fill the cavities. In some forms, the cavities may be sufficiently filled so as to provide a substantially even surface layer, and / or increase the contact surface area of the substrate and the at least one computer element and thermal interface material. In some forms, the thermal dual phase material includes a Cs to C40 alkyl surface functionalized nanoparticle. In some forms the functionalized nanoparticle may include a metal oxide particle.

[0054] Other embodiments described herein relate to a thermally conductive layer comprising a thermal interphase material and a method for making the same. The thermal interphase material may include a first layer including one or more metal oxide particles, and the first layer may be disposed above an uneven surface. A second layer may include metal oxide particles, and the second layer may be disposed below a heat sink and above a package lid (HIS). In some forms, the thermal conductivity of a bond present in the thermal interphase material may exceed 50 WmM K -1 . Other embodiments and methods for preparing thermally conductive composites are described herein.

[0055] EXAMPLES

[0056] The following examples are intended to be illustrative in nature, and they are not meant to limit the scope or underlying principles of the subject application.

[0057] Preparation of grafted inorganic particles by isocyanate coupling

[0058] Grafting

[0059] Grafting of SiO? particles (reference or trace experiment)

[0060] As received SiO2 particles (2.0 g, 10-20 nm, 6807NM, SkySpring Nanomaterials, Inc., Houston, TX, USA) were immersed in 30 mL of triethylamine (>99.5%, 471283, Sigma Aldrich, St. Louis , MO, USA) with 1.0 wt.% dibutyltin dilaurate (DBTDL) (95%, 291234, Sigma Aldrich) in a two-neck round bottom flask. The flask was purged with argon, and then placed in a sonication bath (XUB5, Grant Instruments Lts, Royston, United Kingdom) at 60°C for 30 minutes. The flask was transferred to a hot plate (AREX-6 Digital Pro) with a heating mantle. An addition funnel with 10 0 g octodecyl isocyanate (ODI) (technical grade, 01807, Sigma Aldrich) was secured to the flask, and the ODI was added dropwise to the solution while stirring at 400-600 rpm with a magnetic stir bar. Once the ODI was completely added to the solution, the flask was again purged with argon gas, sealed, and heated to 85°C. The reaction was allowed to proceed for 20 hours.

[0061] Grafting of Mg O nanoparticles Hydration of MgO

[0062] To provide sufficient surface functionalization for isocyanate coupling, as received 2.0 g of MgO nanoparticles (10-30 nm, 481 ONH, SkySpring Nanomaterials, Inc ) were immersed in 150 ml_ Milli-Q water in a sealed round bottom flask for 72 hours at room temperature. The particles were then collected, dried and ground before functionalization.

[0063] Grafting of MgO / Mg (OH) particles

[0064] 2.0 g of partially hydrated MgO were immersed in 30 mL of triethylamine (>99.5%, 471283, Sigma Aldrich) with 1.0 wt.% dibutyltin dilaurate (DBTDL) (95%, 291234, Sigma Aldrich) in a two-neck round bottom flask. The flask was purged with argon, and then placed in a sonication bath (XUB5, Grant Instruments) at 60°C for 30 minutes. The flask was transferred to a hot plate (AREX-6 Digital Pro) with a heating mantle. An addition funnel with 10.0 g of octodecyl isocyanate (ODI) (technical grade, 01807, Sigma Aldrich) was secured to the flask, and the ODI was added dropwise to the solution while stirring at 400-600 rpm with a magnetic stir bar. Once the ODI was completely added to the solution, the flask was again purged with argon gas, sealed, and heated to 85 °C. The reaction was allowed to proceed for 20 hours. Labeled as ODI-nano-MgO.

[0065] Grafting of MgO micro particles

[0066] MgO (using micron sized particles [MgO (US1130M, MgO, 1000nm, US Research Nanomaterials, Inc.] nanoparticles were prepared as described above, except that no hydration step immersion in 150 ml Milli-Q water was used before the grafting. Same as above, but no hydration before grafting

[0067] Grafting of Y-AI2O3 particles

[0068] As received Y-AI2O3 particles (2.0 g, 8-12 nm, SkySpring Nanomaterials, Inc.) were immersed in 30 mL of triethylamine (>99.5%, 471283, Sigma Aldrich) with 1.0 wt.% dibutyltin dilaurate (DBTDL) (95%, 291234, Sigma Aldrich) in a two-neck round bottom flask. The flask was purged with argon, and then placed in a sonication bath (XUB5, Grant Instruments) at 60 °C for 30 minutes. The flask was transferred to a hot plate (AREX-6 Digital Pro) with a heating mantle. An addition funnel with 10.0 g of octodecyl isocyanate (ODI) (technical grade, 01807, Sigma Aldrich) was secured to the flask, and the ODI was added dropwise to the solution while stirring at 400-600 rpm with a magnetic stir bar. Once the ODI was completely added to the solution, the flask was again purged with argon gas, sealed, and heated to 90 °C. The reaction was allowed to proceed for 20 hours.

[0069] Grafting of AIN particles

[0070] Hydration of AIN

[0071] Before grafting of AIN, the surface of AIN was hydrated as follows. 30 g of AIN (Type H, Tokuyama Corp., Japan) was immersed in 1 L MilliQ water (room temperature) with stirring for different duration (0 - 100 min.) The hydrated AIN powder was vacuum filtrated on filter paper (Whatmann 1 ) and washed with isopropanol. Then, the AIN powder was dried in an 80 °C convection oven for overnight and further dried in an 80 °C vacuum oven for 2 hours. The hydrated AIN are labeled as AIN-OH100 (100 min. hydration), AIN-OH60 (60 min. hydration), etc.

[0072] Grafting of AIN

[0073] AIN and cBN grafted nanoparticles were prepared as described above for the grafting of y-AI2O3 and MgO.

[0074] Grafting of cBN (cubic-boron nitride) particles

[0075] Hydroxylation of cBN

[0076] 6 g of cBN (1 - 3 pm, MSE supplies) was immersed in 5 mol dm'3NaOH aqueous solution for 24 hours under stirring. The powder was washed with MilliQ water through centrifugation until pH became neutral. Then, the powder was further washed with acetone twice through centrifugation for removing water. The powder was dried in an 80 °C convection oven for overnight and further dried in an 80 °C vacuum oven for 2 hours. The hydroxylated cBN is labeled as cBN-OH.

[0077] Post process of grafted particles

[0078] After the allotted reaction time, the reaction solution was transferred to a 600 mL beaker and allowed to cool to room temperature. The cooled product was then washed with alternating rinses of toluene (500 mL, >99.5%, TX0735, Sigma Aldrich), acetone (500 mL, >99.5%, AX0120, Sigma Aldrich) and methanol (500 mL, >99.8%, MX0485, Sigma Aldrich) with vacuum filtration. After the product was dry, the material was collected, ground and run through a 125-micron sieve (Cole Parmer No. 120) with acoustic mixing for 45 seconds with 40% intensity at 60 Hz (Resodyn LabRAM). The sieved powder was placed in a vacuum oven (AVO-200V CR) at 70°C and -0.1 mPa for 5 hours to ensure complete removal of residual solvents.

[0079] Syntheses of 1 -alkyl urea, 1,3-dialkyl urea and alkylene diamide

[0080] Syntheses of 1 -alkyl urea

[0081] Example 1 : 1 -hexyl urea and 1 -octyl urea

[0082] 6.00 g of urea (Aldrich) and an equivalent molar amount of alkyl amine (13.2 mL of N- hexyl amine or 16.5 mL of N-octyl amine) were added into a 100 mL 2-neck round bottom flask attached with a condenser. The 2-neck flask was heated on a heat block on a hotplate to 120 °C under gentle stirring. After urea was fully dissolved in the alkyl amine, the mixture was kept stirring for 12 hours. After cooling down to room temperature (~ 20 °C), the obtained solid was dispersed into water. Solid content was filtered, washed with water several times, and dried in 100 °C vacuum oven for 2 hours. The dried powder was dissolved in hot (~ 70 °C) isopropanol, and recrystallized at room temperature.

[0083] Syntheses of 1,3-dialkyl urea

[0084] Example 2:

[0085] Example 2 (1,3-dihexylurea): 4-nitrobenzoyl chloride (25.00 mmol, 5040 mg) and hexan-1 -amine (125.0 mmol, 16.5 mL) were stirred in dry DCE (50 mL) under argon and heated to 60 °C for 30 minutes, then cooled to room temperature. The mixture was loaded directly onto a 220g column and purified by flash chromatography on silica gel (0% EtOAc / DCM (2 CV) 20% (10 CV)). Fractions containing product were evaporated to dryness in vacuo to give a white solid, 3060 mg (54% yield). MS (APCI): calculated for Chemical Formula: C13H28N2O (M+H) 229; found: 229. 1 H NMR (400 MHz, CDCI3) 54.66 - 4.36 (m, 2H), 3.14 (td, J = 7.2, 5.7 Hz, 4H), 1.57 - 1.41 (m, 4H), 1 .38 - 1.19 (m, 12H), 0.94 - 0.81 (m, 6H).

[0086] Example 3:

[0087] Example 3 (1,3-didodecylurea): CDI (25.00 mmol, 4053 mg) and dodecan-1 -amine (75.00 mmol, 13902 mg) were stirred in dry DCE under argon as above overnight. The DCE was evaporated and the residue triturated with methanol, filtering off the resulting solid. The solid was dried by suction to give a white solid, 9918 mg (100% yield). MS (APCI): calculated for Chemical Formula: C17H36N2O (M+H) 397; found: 397. 1 H NMR (400 MHz, CDCI3) 5 4.17 (d, J = 5.8 Hz, 2H), 3.15 (q, J = 6.6 Hz, 4H), 1.48 (q, J = 7.1 Hz, 4H), 1 .27 (d, J = 11 .6 Hz, 36H), 0.88 (t, J = 6.7 Hz, 6H).

[0088] Example 4:

[0089] Example 4 (1 ,3-dioctylurea) CDI (30.00 mmol, 4863 mg) octan-1 -amine (75.00 mmol, 12.4 mL), and triethylamine (75.00 mmol, 10.5 mL) were stirred in dry DCE (50 mL) at 60 °C under argon for 60 minutes. The reaction mixture was evaporated to dryness in vacuo, diluted with DCM / hexanes, and ~40g of flash silica gel was added. The reaction mixture was evaporated to dryness in vacuo, and packed into a loader. The mixture was purified by flash chromatography on silica gel (220g, 0% acetone / DCM (2 CV) 30% (20 CV)). Fractions containing product were evaporated to dryness in vacuo to give a white solid, 5174 mg (61 % yield). MS (APCI): calculated for Chemical Formula: C17H36N2O (M+H) 285; found: 285. 1 H NMR (400 MHz, CDCI3) 5 4 25 (t, J - 5.7 Hz, 2H), 3.15 (td, J = 7 1 , 5.6 Hz, 4H), 1.49 (p, J - 7.0 Hz, 4H), 1.36 - 1.18 (m, 20H), 0.94 - 0.83 (m, 6H). Example 5:

[0090] Example 5 (1,3-didecylurea): CDI (30.00 mmol, 4863 mg), decan-1-amine (75.00 mmol, 15.0 mL), and triethylamine (75.00 mmol, 10.5 mL) were stirred in dry DCE (50 ml) at 60 °C under argon for 30 minutes, then the DCE was evaporated in vacuo. The residue was evaporated onto ~40g of flash silica gel in vacuo, packed into a loader, and purified by flash chromatography on silica gel (220g, 0% acetone / DCM (2 10% (10 CV)). Fractions containing product were evaporated to dryness in vacuo to give a white solid, 4282 mg (42% yield). MS (APCI): calculated for Chemical Formula: C21H44N2O (M+H) 341 ; found: 341. 1 H NMR (400 MHz, CDCI3) 5 4.25 (t, J = 5.6 Hz, 2H), 3 15 (td, J - 7 2, 5 7 Hz, 4H), 1 .49 (p, J = 7.1 Hz, 4H), 1 27 (d, J = 11 .0 Hz, 28H), 0.88 (t, J = 6.8 Hz, 6H).

[0091] Example 6:

[0092] Example 6 (1 ,3-ditetradecylurea): CDI (30.00 mmol, 4863 mg), tetradecan-1 -amine (75.00 mmol, 16006 mg), and triethylamine (75.00 mmol, 10.5 mL) were stirred in dry DCE (50 mL) at 60 °C under argon for 90 minutes, then cooled to room temperature. The reaction mixture was diluted with ~5% v / v hexanes and the resulting white solid filtered off and then washed with 95:5 DCM:hex. The precipitate was dried by suction to give a white solid, 11291 mg (85% yield). MS (APCI): calculated for Chemical Formula: C29H60N2O (M+H) 453; found: 453. 1 H NMR (400 MHz, CDCI3) 5 4 14 (d, J = 6.0 Hz, 2H), 3.15 (td, J = 7.1 , 5.6 Hz, 4H), 1.48 (q, J = 7.0 Hz, 4H), 1.38 - 1.18 (m, 44H), 0.88 (t, J = 6.7 Hz, 6H).

[0093] Example 7: Example 7 (1 -hexadecylurea): Phenyl carbamate (33.90 mmol), hexadecan-1 -amine (30.00 mmol, 7244 mg), and triethylamine (66.00 mmol, 9.2 ml_) were stirred in dry THF (50 mL) at 60 °C under argon for four hours, then room temperature overnight. The DCE was removed in vacuo and the product recrystallized from hot EtOAc, and cooled to room temperature. The product was filtered off, and washed with EtOAc. The product was dried by suction to give a white solid, 7497 mg (88% yield). MS (APCI): calculated for Chemical Formula: C17H36N2O (M+H) 285; found: 285. 1 H NMR (400 MHz, DMSO) 5 5.85 (s, 1 H), 5.32 (s, 2H), 2.92 (d, J = 6.8 Hz, 2H), 1.31 (s, 2H), 1 .24 (s, 28H), 0.84 (d, J = 7.9 Hz, 3H).

[0094] Example 8:

[0095] Example 8 (1,3-dihexadecylurea): CDI (30.00 mmol, 4863 mg), hexadecan-1 -amine (75.00 mmol, 18110 mg), and triethylamine (75.00 mmol, 10.5 mL) were stirred in dry THF (50 mL) at 75 °C under argon for 120 minutes. The reaction was cooled to room temperature, the THF evaporated to dryness in vacuo, the residue was taken up in -400 mL of EtOAc and heated to boiling, then diluted with 50 mL of hexanes, cooled to room temperature, the precipitate was filtered off, washed with a small amount of EtOAc, then hexanes, and dried by suction to give a white solid, 11576 mg (76% yield). MS (APCI): calculated for Chemical Formula: C33H68N2O (M+H) 509; found: 509. 1 H NMR (400 MHz, CDCI3) 5 4.13 (s, 2H), 3.15 (q, J = 6.7 Hz, 4H), 1.50 (d, J = 7.2 Hz, 4H), 1.25 (s, 52H), 0.88 (t, J = 6.7 Hz, 6H).

[0096] Example 9:

[0097] Example 9 (1 -decylurea): Phenyl carbamate (55.00 mmol, 7541 mg), decan-1 -amine (50.00 mmol, 10.0 mL), and triethylamine (110.0 mmol, 15.3 mL) were stirred in dry THF (50 mL) at 60 °C under argon for 180 minutes, then cooled to room temperature. The THF was removed in vacuo and the residue taken up in -200 mL of hot EtOAc, cooled to room temperature, filtered off, washed with a small amount of EtOAc, and dried by suction to give a white solid, 8860 mg (87% yield). MS (APCI): calculated for Chemical Formula: C11 H24N2O (M+H) 201 ; found: 201. 1 H NMR (400 MHz, CDCI3) 6 4.45 (s, 1 H), 4.30 (s, 2H), 3.15 (td, J = 7.2, 5.7 Hz, 2H), 1.50 (p, J = 7.1 Hz, 2H), 1.27 (d, J = 8.7 Hz, 14H), 0.88 (t, J = 6.8 Hz, 3H).

[0098] Example 10:

[0099] Example 10 (1 -pentylurea): Phenyl carbamate (88.00 mmol, 12065 mg), pentan-1 - amine (80.00 mmol, 9.2 mL), and triethylamine (176.0 mmol, 24.5 mL) were stirred in dry THF (50 mL) at 60 °C for 120 minutes, then cooled to room temperature The THF was removed in vacuo and the residue taken up in hot EtOAc (-100 mL). The mixture was cooled to room temperature, then scratched to induce crystallization. The mixture was diluted with hexanes (-80 mL) and allowed to stand overnight. Crystals were filtered off, washed withl : 1 EtOAc: hexanes, and dried by suction to give a white solid, 7064 mg (67% yield). MS (APCI): calculated for Chemical Formula: C6H14N2O (M+H) 131 ; found: 131. 1 H NMR (400 MHz, CDCI3) 5 4.69 (s, 1 H), 4.46 (s, 2H), 3.15 (td, J = 7.2, 5.7 Hz, 2H), 1 .51 (p, J = 7.3 Hz, 2H), 1.41 - 1 .21 (m, 4H), 0.98 - 0.80 (m, 3H).

[0100] Example 11 :

[0101] Example 11 (1 -dodecylurea): Phenyl carbamate (49.50 mmol, 6786 mg), dodecan- 1 -amine (45.00 mmol, 8341 mg), and triethylamine (99.00 mmol, 13.8 mL) were heated in dry THF (50 mL) at 60 °C for 60 minutes, then cooled to room temperature. The THF was removed in vacuo and the residue recrystallized from hot EtOAc. The mixture was cooled to room temperature and the product filtered off, washed with EtOAc and dried by suction to give a white solid, 9319 mg (91 % yield). MS (APCI): calculated for Chemical Formula: C13H28N2O (M+H) 229; found: 229. 1 H NMR (400 MHz, CDCI3) 3 4.39 (s, 1 H), 4.26 (s, 2H), 3.15 (td, J = 7.2, 5.7 Hz, 2H), 1.51 (h, J = 6.7 Hz, 2H), 1.26 (s, 22H), 0.88 (t, J = 6.7 Hz, 3H).

[0102] Example 12: o H2N^^

[0103] JJ N^N N^NDCE (dry)

[0104] 600C

[0105] Example 12 (1,3-dipropylurea): CDI (70.00 mmol, 1 1347 mg), propan-1 -amine (175.0 mmol, 14.4 mL), and triethylamine (175.0 mmol, 24.4 mL) were stirred in dry DCE (50 mL) at 60 °C overnight under argon. The reaction mixture was cooled to room temperature, quenched with 6N HCI to pH ~1 , and filtered through a polypropylene frit to retain water, eluting with DCM. The organic filtrate was evaporated to dryness, dissolved in DCM, evaporated onto ~40g of flash silica gel in vacuo, packed into a loader, and purified by flash chromatography on silica gel (120g, 10% acetone / DCM

[0106] Example 13 (glutaramide): glutaroyl dichloride (100.0 mmol, 12.8 mL) was dissolved in dry DCE (190 mL) and cooled to 0 °C under argon. Without stirring, concentrated ammonium hydroxide (600.0 mmol, 40.0 mL) was added, floating it on top of the DCE layer After a few minutes, slow stirring was started, and then stepwise faster stirring over ~20 minutes. The organics were evaporated and the residue taken up in ~10% MeOH / water. The residue was purified by Cis flash chromatography (MeOH / water) in many small injections (275g Cis material). Fractions containing pure product were evaporated to dryness in vacuo to give a white solid, 3758 mg (29% yield). Contaminated with a lot of the amido-acid (major by-product). MS (APCI): calculated for Chemical Formula: C5H10N2O2 (M+H) 131 ; found: 131. 1 H NMR (400 MHz, DMSO) 6 7.23 (s, 2H), 6.70 (s, 2H), 2.03 (t, J = 7.5 Hz, 4H), 1.74 - 1.56 (m, 2H).

[0107] Example 14:

[0108] Example 14 (decanediamide): decanedioyl dichloride (50 00 mmol, 10.7 mL) was dissolved in 100 mL of dry DCE at 0 °C and treated with concentrated ammonium hydroxide (250.0 mmol, 35.7 mL) similar to the previous procedure. The layers were separated by filtration through a polypropylene frit to retain water, eluting DCM. The DCM was evaporated to dryness in vacuo. The residue was partially dissolved in hot MeOH, cooled in an ice-water bath, then filtered cold, washed with a small volume of MeOH, and dried by suction to give a white solid, 8650 mg (86% yield). MS (APCI): calculated for Chemical Formula: C10H20N2O2 (M+H) 201 ; found: 201. 1 H NMR (400 MHz, DMF) 5 7.34 (s, 2H), 6.68 (s, 2H), 2.15 (t, J = 7.5 Hz, 4H), 1.55 (q, J = 7.2 Hz, 4H), 1.28 (d, J = 3.1 Hz, 8H).

[0109] Example 15:

[0110] Example 15 (octanediamide): Octanedioyl dichloride (25.00 mmol, 4.5 mL) was dissolved in dry hexanes (100 mL) and cooled to -20 °C (MeOH / water-ice), then stirring was stopped. Concentrated ammonium hydroxide (125.0 mmol, 8.3 mL) was slowly added such that it formed a layer under the organic layer. Stirring was increased in small increments from zero to max RPM over ~15 minutes. The residue was evaporated to dryness, taken up in methanol, recrystallized / triturated with hot MeOH, cooled to room temperature, and the product filtered off, washing with a small volume of methanol. Contains some ammonium chloride. Washed with water, then dried by suction to give a white solid, 2879 mg (67% yield). MS (APCI): calculated for Chemical Formula: C8H16N2O2 (M+H) 173; found: 173. 1 H NMR (400 MHz, DMSO) 6 7.20 (s, 2H), 6.66 (s, 2H), 2.01 (t, J = 7.4 Hz, 4H), 1.46 (dq, J = 9.6, 6.8 Hz, 4H), 1.23 (p, J = 3.6 Hz, 4H).

[0111] Example 16:

[0112] Example 16 (nonanediamide): Nonanedioyl dichloride (25.00 mmol, 4.9 mL) and concentrated ammonium hydroxide (125 0 mmol, 8.3 mL) were reacted in the same way as the previous reaction, then worked up the same way to give a white solid, 4040 mg (87% yield). MS (APCI): calculated for Chemical Formula: C9H18N2OO2 (M+H) 187; found: 187. 1 H NMR (400 MHz, DMSO) 5 7.20 (s, 2H), 6 65 (s, 2H), 2.01 (t, J = 7.4 Hz, 4H), 1.46 (p, J = 7.2 Hz, 4H), 1.31 - 1 12 (m, 6H).

[0113] Example 17:

[0114] Example 17 (dodecanediamide): Dodecanedioyl dichloride (25.00 mmol, 6.2 mL) and concentrated ammonium hydroxide (125.0 mmol, 8 3 mL) were stirred in dry hexanes (100 mL) at -20 °C in the same manner as before. The workup was the same and gave a white solid, 4040 mg (77% yield). MS (APCI): calculated for Chemical Formula: C12H24N2O2 (M+H) 229; found: 229. 1 H NMR (400 MHz, DMSO) 5 7.20 (s, 2H), 6.65 (s, 2H), 2.01 (t, J = 7.4 Hz, 4H), 1 .46 (t, J = 7.2 Hz, 4H), 1 .23 (s, 12H).

[0115] Preparation of composites

[0116] Composites of grafted powder and pristine inorganic powder Composites were prepared by mixing the grafted powder and pristine (not grafted) powder. The grafted powder and pristine (not grafted) powder at a desired ratio (0 - 60 wt% of the pristine powder) were dispersed in ethanol at concentration of ~ 0.1 g / mL. The dispersion was sonicated for 30 minutes at room temperature.

[0117] Composites of organic compound powder and pristine inorganic powder

[0118] A mixture of inorganic powder such as AIN (Type H, Tokuyama, Japan), h-BN (3 - 5 pm, 1367HM, SkySpring, USA), and c-BN (1 - 3 pm, P06904, MSE Supplies, USA) and an organic compound were ground with mortar and pestle in acetone. The obtained powder mixture was dried in vacuum oven at 80 °C for 1 - 2 hours.

[0119] Preparation of porous Cu / meltable powder composites

[0120] A small amount of the dispersion of the grafted powder or the composites was dropped onto a release liner PET (2” x 2”) sheet (G10JRM, The Tape Casting Warehouse, Inc., Morrisville, PA, USA) placed on a 70 °C hot plate. After full evaporation of EtOH, a further amount of dispersion was dropped. Then, an Si wafer was placed on a 160 °C hot plate for melting the powder, and the Si wafer was placed again on the 70 °C hot plate for solidifying. Porous Cu (EQ-bccf-80um, MTI corp., Richmond, CA, USA) cut into 1 ” x 1” was sandwiched between the grafted powder coated PET. Then, the PET / grafted powder / porous Cu / grafted powder / PET was placed and pressed manually on a 160 °C hot plate for melting the powder and filling the pores with the melt powder.

[0121] In some cases, dry powder was melted directly on polyimide sheet on a hot plate (~ 160 °C or higher than melting point), and the copper mesh was placed on the melt powder. Separately prepared melt powder / polyimide was placed on the copper mesh to make a polyimide / melt powder / copper mesh / melt powder / polyimide structure. The structure was pressed to impregnate the melt powder into the copper mesh and squeeze out the excess melt powder.

[0122] Determination of thermal conductivity

[0123] The thermal conductivity of the grafted particles and composites (k [Wm'1K'1]) was determined by the following equation: k = a x Cpx p where a [mm2s'1], CP[JK'1g'1] and p [germ3] are thermal diffusivity, specific heat capacity and bulk density, respectively.

[0124] Thermal diffusivity

[0125] Thermal diffusivity of organic compound powder

[0126] Thermal diffusivity of the powder compounds was determined with TWA (Temperature Wave Analyzer, ai-Phase, Japan). Powder compound was pelletized with a 13 mm KBr Die Set (International Crystal Laboratories). The powder compound was weighed as the final pellet thickness to be 200 - 3000 pm, and the powder compound was pelletized at 100 kN under vacuum. More specifically, 0.3 - 0.4 g of powder compound was put into the KBr Die Set, and the Die Set was evacuated for 4 minutes followed by pressing at 100 kN with continued evacuation. Then, thermal diffusivity of the pellets was determined with TWA.

[0127] Thermal diffusivity of composites

[0128] The composite powder mixture was pelletized in same manner as the powder compound mentioned above. Then thermal diffusivity of the pellet was determined with TWA

[0129] In some cases, thermal diffusivity was determined after the composite powder was melted on a Si wafer above melting point and solidified at room temperature. The Si wafer / solidified powder / glass samples were prepared as follows. The powder was dispersed in ethanol (Aldrich) at the concentration of ~ 0.1 g / mL, and the dispersion was sonicated for 30 minutes at room temperature. A small amount of dispersion was dropped on the non-polished side of a Si wafer (2313, University Wafer, 1 ” diameter, ~ 280 pm thickness, one-side polish) placed on a 70 °C hot plate. After full evaporation of EtOH, a further amount of dispersion was dropped. Then, the Si wafer was placed on a 160 °C hot plate for melting the powder, and the Si wafer was placed again on the 70 °C hot plate for solidifying. The above process was repeated several times until the amount (thickness) of the solidified powder became enough for making glass / powder / Si structure with powder layer thickness of ~ 200 °C. The Si wafer was put in a vacuum oven (160 °C) for removing trapped air. Glass beads (150 - 212 pm) / silicone paste was put on Si wafer for a spacer, and then a glass plate (~ 100 pm) was placed. Heat capacity

[0130] Heat capacity (Cp[JK'1g-1]) was measured by DSC (TA Instruments Discovery DSC2500) using samples prepared with the above described press process.

[0131] Density of organic compound powder The density of organic compound powder was determined with a gas pycnometer (Ultrapyc 5000 Micro, Anton Paar).

[0132] The density of the composites was calculated using mass fractions from thermogravimetric analysis (TA Instruments Discovery TGA550) using the following equation: where X is the mass fraction and p is the specific density determined with the pycnometer of the specified components.

[0133] Results

[0134] Thermal conductivity of grafted particles The results from the described analyses on the grafted particles are summarized in the table below.

[0135] The results of the thermal conductivity of an overall mixture of the modified TIM and unmodified nanoparticle are shown in FIGs. 3 and 4.

[0136] Thermal conductivity of organic compounds Thermal conductivity of 1 -alkyl urea, 1 ,3-dialkyl urea and amide is summarized in the Table below.

[0137]

[0138] Thermal conductivity of composites of grafted powder and pristine powder are shown in Fig. 5 and thermal conductivity of composites of pristine powder and organic compound powder are shown in Fig. 6. Further, Figs. 7 and 8 illustrate various thermal properties of an AIN / 1 ,3-dioctadecyl urea (DODU) composite.

[0139] Powder XRD characterization: Powder samples of an ungrafted AIN sample as received from the vendor, and an AIN grafted with alkyl chains as described above were also analyzed using powder x-ray diffraction using Cu K-alpha radiation (Bruker, D8 Advance [Madison, Wl, USA]) with 1o / min. The result of the X-ray diffraction is shown in FIG. 7, as additional diffraction pattern peaks appear after surface modification of aluminum nitride (AIN), which may reveal that the TIM layer may have a crystalline structure (most likely, alkyl chain may be aligned to radial direction). It is believed that the fillers are now connected through the high thermal conductivity interface material described herein, resulting in high thermal conductivity of the solidified meltable powder.

[0140] Powder DSR characterization:

[0141] Thermograph data was generated using differential scanning calorimetry (DSC). The sample size used was between 3-5 mg per test. For each test, the temperature was first equilibrated at -20 °C. It was heated at a rate of 10 °C / min to a maximum temperature of 130 °C. Then it was cooled at the same rate to -10 °C. From -10 °C, it was heated at 10 °C / min to 130 °C. This was repeated for a third cycle.

[0142] The data displayed in the plot of FIG. 8 represents the data generated in the 3rd cycle.

[0143] Use of the term “may” or “may be” should be construed as shorthand for “is” or “is not” or, alternatively, “does” or “does not” or “will” or “will not,” etc. For example, the statement “a thermally conductive composite adhesive may further comprise a backing layer” should be interpreted as, for example, “In some embodiments, a thermally conductive composite adhesive further comprises a backing layer,” or “In some embodiments, a thermally conductive composite adhesive does not further comprise a backing layer.”

[0144] Unless otherwise indicated, all numbers expressing quantities of ingredients, properties, such as, molecular weight, reaction conditions, and so forth used in the specification and embodiments are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the specification and attached embodiments are approximations that may vary depending upon the desired properties sought to be obtained At the very least, and not as an attempt to limit the application of the doctrine of equivalents. To the scope of the embodiments, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0145] For the processes and / or methods disclosed, the functions performed in the processes and methods may be implemented in differing order, as may be indicated by context. Furthermore, the outlined steps and operations are only provided as examples and some of the steps and operations may be optional, combined into fewer steps and operations, or expanded into additional steps and operations.

[0146] This disclosure may sometimes illustrate different components contained within, or connected with, different other components. Such depicted architectures are merely examples, and many other architectures may be implemented which achieve the same or similar functionality.

[0147] The terms used in this disclosure and in the appended embodiments, (e.g., bodies of the appended embodiments) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including, but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes, but not limited to,” etc.). In addition, if a specific number of elements is introduced, this may be interpreted to mean at least the recited number, as may be indicated by context (e.g., the bare recitation of “two recitations,” without other modifiers, means at least two recitations of two or more recitations). As used in this disclosure, any disjunctive word and / or phrase presenting two or more alternative terms should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phase “A or B”: will be understood to include the possibilities of “A” or “B” or “A and B.”

[0148] The terms “a,” “an,” “the” and similar referents used in the context of describing the present disclosure (especially in the context of the following embodiments) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The use of any and all examples, or representative language (e.g., “such as”) provided herein is intended merely to better illuminate the present disclosure and does not pose a limitation on the scope of any embodiments. No language in the specification should be construed as indicating any non-em bodied element essential to the practice of the present disclosure.

[0149] Groupings of alternative elements or embodiments disclosed herein are not to be construed as limitations. Each group member may be referred to and embodied individually or in any combination with other members of the group or other elements found herein. It is anticipated that one or more members of a group may be included in, or deleted from, a group for reasons of convenience and / or patentability. When any such inclusion or deletion occurs, the specification is deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended embodiments.

[0150] Certain embodiments are described herein, including the best mode known to the inventors for carrying out the present disclosure. Of course, variations on these described embodiments, will become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventor expects skilled artisans to employ such variations as appropriate, and the inventors intend for the present disclosure to be practiced otherwise than specifically described herein. Accordingly, the embodiments include all modifications and equivalents of the subject matter recited in the embodiments as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is contemplated unless otherwise indicated herein or otherwise clearly contradicted by context. In closing, it is to be understood that the embodiments disclosed herein are illustrative of the principles of the embodiments. Other modifications that may be employed are within the scope of the embodiments. Thus, by way of example, but not of limitation, alternative embodiments may be utilized in accordance with the teachings herein. Accordingly, the embodiments are not limited to the embodiments precisely as shown and described.

Claims

CLAIMSWhat is claimed is:1 . A thermal interface material according to Formula (1 ):NP — C5-C40 alkyl(Formula (1 )) wherein NP represents an inorganic nanoparticle having a thermal conductivity above about 5 W / mK, and wherein the thermal interface material exhibits a first phase at a first temperature and a second phase at a second temperature.

2. The thermal interface material of claim 1 , wherein an ester links the NP and C3 to C40 alkyl group.

3. The thermal interface material of claim 2, wherein the ester comprises a carbamate.

4. The thermal interface material of claim 1 , wherein the inorganic nanoparticle comprises at least one of silica, alumina, AIN, cBN, MgOH, and MgO.

5. The thermal interface material of claim 4, wherein the inorganic nanoparticle has an average particle diameter of less than about 30 nm to about 40 nm.

6. The thermal interface material of claim 1 , further comprising a primary amine.

7. The thermal interface material of claim 1 , wherein the difference between the first temperature and the second temperature is less than about 10 °C.

8. The thermal interface material of claim 1 , comprising one of the following:AIN + DODU.

9. The thermal interface material of claim 1 , further comprising one or more of at least one urea compound and at least one amide compound.

10. The thermal interface material of claim 9, wherein the urea compound comprises at least one of N-alkyl urea and N, N’-dialkyl urea, and the amide compound comprises an alkylene diamide.11 . The thermal interface material of claim 10, further comprising a porous material selected from at least one of SiO2, AI2O3, MgO, AIN, and c-BN.

12. The thermal interface material of claim 1 , comprising a mixture of the NP and C3 to C40 alkyl group.

13. A polymer matrix comprising a thermal interface material according to any one of claims 1-12 disposed therein.

14. A thermally conductive material, comprising: a porous material including one or more cavities; and a thermal interface material of any one of claims 1 -11.

15. The thermally conductive material of claim 14, wherein the porous material comprises copper.

16. A computer construct with a dual phase material, comprising: a substrate having at least a first surface including surface cavities defined therein; and a thermal interface material according to any one of claims 1 -12 disposed within and filling the surface cavities.

17. The computer construct of claim 16, further comprising a thermal pad, the thermal pad having a first thermal pad surface facing the first surface of the substrate, wherein at least 75% of the thermal pad surface is in contact with first surface of the substrate.

18. A computer construct, comprising: a substrate;at least one computer element positioned on the substrate; a package lid; and first and second layers of thermal interface material; wherein the first layer of the thermal interface material is disposed between the substrate and the at least one computer element and the package lid to provide increased contact area between the first layer of the thermal interface material and the substrate and the at least one computer element; and wherein the second layer of the thermal interface material is disposed between the package lid and the first layer of thermal interface material to provide an increased contact layer between the first layer of thermal interface material and the package lid.

19. The computer construct of claim 18, wherein the substrate and the at least one computer element include a number of cavities.

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