Thermal conductive composition

Abstract

A composition comprising a polymer and at least one thermal conductivity enhancing agent is disclosed, the composition has a hardness of less than 50 as determined using ASTMD2240 Type durometer (Shore E) and a thermal conductivity of more than 12W / mK as determined by the hot disk method or the ASTM D5470 method.

Description

THERMAL CONDUCTIVE COMPOSITION FIELD OF INVENTION

[0001] The present invention relates to a composition comprising a polymerand at least one thermal conductivity enhancing agent, resulting in ultra-high thermal conductivity and very good thermal stability. BACKGROUND

[0002] With the development of electronic devices toward miniaturizationand high density and integration, the heat generation of electronic devices is gradually increasing, and thermal failure becomes the primary problem hindering the performance, reliability, and life of electronic devices. Hence, efficient thermal management becomes the key to solving this challenge. Thermal interface materials (TIMs) are widely employed between the two solid contact surfaces of heat sources and heat sinks to increase heat removal for electronic devices. These materials come in variety of formats such as greases, gap-fillers, pre-cured gels, curable materials (1 or 2 parts), phase change materials, elastomeric pads, adhesives, thermal tapes, metal alloys and solders etc. The gap between two solid surfaces (chip and heat sink) is uneven, and otherwise filled with air which has poor thermal conductivity. This gap is filled with a thermal interface material to provide the heat conduction pathway. Depending on the requirement, multiple thermal interface materials may be used between different solid surfaces to provide continuous conductive pathways for heat removal.

[0003] The advent of 5G communications technology, in telecom space andinternet of things (IoT) in consumer and industrial spaces will further elevate the performance requirement for TIMs.5G and IoT devices (using 5G) work at higher frequencies, higher device densities, higher bandwidths, lower latency, small feature sizes and low power along with much higher reliability and availability requirements. These factors have made the heat removal requirement from electronic devices much more stringent and there is general trend in industry to move towards higher performance, i.e., higher thermal conductivity TIMs, for 1 35749272.1example going from low thermal conductivity of 3-5 W / mK to average of 6-10 W / mK and prompted for development of even higher thermal conductivities > 10 W / mK. The development of the next generations of integrated circuits (ICs), three- dimensional (3D) integration, and ultrafast high-power density communication devices makes the thermal management requirements extremely severe.

[0004] Conventional TIMs filled with thermally conductive particlesrequire high-volume fractions v of filler (v > 50%) like Alumina, ZnO to achieve thermal conductivity (TC) of the composite in the range of 1−5 W / mK. Many products also utilize metallic fillers like Aluminum when electrical conductivity conditions are relaxed. However, to achieve high TC (>10 W / mK) additional fillers such as BN, AlN, Diamond, SiC fillers and their combinations are disclosed in many patent applications. The advantage of these fillers is that they are electrically insulating and possess much higher thermal conductivities (High TC Fillers). Apart from thermal conductivity, TIM formulations must demonstrate a range of other critical properties to be utilized in applications. These may include low thermal resistance, low volatiles, pump-out, bleed out, cracking, thermal stability, low hardness buildup, high dispensing flow-rate for application at defined viscosities, shear-rate, pump pressure etc. Stability of properties during in low-high temperature cycling / shock also needs to be shown by conducting testing up to 500- 1000 hrs. These properties are achieved by careful design of TIM formulation combining high filler compositional loadings with suitable polymer-resin- dispersing agent combinations as disclosed below.

[0005] CN116814081A described a composition comprising a fillercombination of diamond, alumina and cubic boron nitride filler wherein cubic boron nitride is a mixture with the grain diameter of 5um and the grain diameter of 30um and the diamond with the grain diameter of 100um, alongwith nano alumina powder with the particle size of 30nm. The composition results in ultra-high heat conduction low dielectric interface material with the heat conductivity coefficient larger than 7 and the dielectric constant smaller than 5.

[0006] CN112457673A describes high-thermal-conductivity insulatingsilica gel gasket comprising of at least one of nano aluminum nitride, cubic boron 2 35749272.1nitride and nano silicon carbide and dodecyltrimethoxysilane modified spherical aluminum oxide. Through filler modification treatment and compounding design, the silica gel has excellent properties of high thermal conductivity, high insulation, chemical stability and the like, the thermal conductivity coefficient can reach 8 W / mK or above.

[0007] CN116751458A describes a high-heat-conductivity single-component gel comprising modified filler, vinyl silicone oil, cross-linking agent, inhibitor and catalyst, wherein the modified filler comprises filler and modifier, and the filler comprises cubic boron nitride and one or more of spherical aluminum oxide, single crystal aluminum oxide, zinc oxide, magnesium hydroxide, aluminum nitride and hexagonal boron nitride. The composition results in heat conductivity of >15 W / mK, and dispensability >12 g / min.

[0008] These proposed solutions, however, do not address the need for athermal conductive composition that possesses a combination of desired attributes by using a combination of thermally conductive fillers. SUMMARY

[0009] The present invention offers thermal conductivity > 12W / mK withvery low hardness buildup at very high temperature 150oC. The present invention incorporates Cubic boron nitride as the key filler into thermal formulations.

[0010] The following presents a summary of this disclosure to provide abasic understanding of some aspects of the invention. This summary is intended to neither identify key or critical elements nor define any limitations of embodiments or claims. Furthermore, this summary may provide a simplified overview of some aspects that may be described in greater detail in other portions of this disclosure.

[0011] In one aspect, provided is a composition comprising a polymer andat least one thermal conductivity enhancing agent, wherein the composition has a thermal conductivity of more than 12 W / mK as determined by the hot disk method according to ISO 22007-2 and the test method according to ASTM D5470 and a hardness of less than 50 as determined using ASTMD2240 Type durometer (Shore E). 3 35749272.1

[0012] In one embodiment, the polymer is a silicone polymer.

[0013] In one embodiment, the silicone polymer comprises(i) an alkenyl-functionalized diorganopolysiloxane of formula (Ia) M1aM2bD1cD2dT1eT2fQg (Ia) wherein: M1= R1R2R3SiO1 / 2 M2= R4R5R6SiO1 / 2D1= R7R8SiO2 / 2 D2= R9R10SiO2 / 2 T1= R11SiO3 / 2 T2= R12SiO3 / 2 Q = SiO4 / 2 where R2, R3, R4, R5, R6, R8, R9, R10, R12are each independently selected from an aliphatic, aromatic, or fluoro monovalent hydrocarbon groups having from 1 to 60 carbon atoms or alkoxy groups; R1, R7, R11are each independently selected from an aliphatic, aromatic, or fluoro monovalent hydrocarbon having from 1 to 60 carbon atoms and containing at least one terminal olefin bond; and the subscripts a, b, c, d, e, f, and g are zero or a positive integer subject to the following limitations: 1≤a+b+c+d+e+f+g ≤6000, and a+c+e≥1; and (ii) a hydrogen-functionalized organopolysiloxane of formula (Ib) M1a'M2b'D1c'D2d'T1e'T2f’'Qg'(1b)M2= R16R17R18SiO1 / 2 4 35749272.1D1= R19R20SiO2 / 2 D2= R21R22SiO2 / 2T1= R23SiO3 / 2 T2= R24SiO3 / 2Q = SiO4 / 2 where R14, R15, R16, R17, R18, R20, R21, R22, R24are aliphatic, aromatic or fluoro monovalent hydrocarbon groups having from 1 to 60 carbon atoms; R13, R19, R23are hydrogen; the subscript a’, b’, c’, d’, e’, f’, and g’ are zero or a positive integer subject to the following limitations: 1≤a’+b’+c’+d’+e’+f’+g’ ≤6000, and a’+c’+e’ ≥ 1; with the proviso that when a’+c’+e’ =1 then a+c+e >1 and when a+c+e =1 then a’+c’+e’ >1; or a crosslinked product of (i) and (ii)

[0014] In one embodiment, the composition comprises a first thermalconductivity enhancing agent, a second thermal conductivity enhancing agent and a third thermal conductivity enhancing agent.

[0015] In another embodiment, the first thermal conductivity enhancingagent is selected from boron nitride, cubic boron nitride, silicon carbide, diamond and aluminum nitride.

[0016] In still another embodiment, second thermal conductivity enhancingagent is selected from the group consisting of aluminum oxide, , boron nitride, cubic boron nitride and aluminum nitride.

[0017] In still another embodiment, the third thermal conductivityenhancing agent is selected from the group consisting of aluminum oxide, zinc oxide, SiC, and aluminum nitride.

[0018] In another embodiment the viscosity of the composition is more than100 Pa.s at 1 s-1. Steady shear viscosity and thixotropy were determined using Rheometer (RS-600) instrument with parallel plate geometry (measuring geometry gap was 500 µm). 5 35749272.1

[0019] In yet another embodiment, the polymer is present in an amountranging from 1 to 8 wt% of the composition.

[0020] In another embodiment, the gradient of change in a thermalresistance value with respect to change in a thickness of the composition is 100 K mm2 / W or less.

[0021] In another embodiment, the composition has a dispensability of 4g / min or more.

[0022] In another embodiment, the composition has a shore E hardness of0 to 90.

[0023] In another embodiment, the composition has a bond line thicknessof less than 350 µm.

[0024] In another embodiment, the composition is one-part cross-linkedsilicone gel formulation, two-part curable formulation, or a grease formulation. BRIEF DESCRIPTION OF DRAWING FIGURES

[0025] Figure 1 is a graph showing the hardness buildup data (Shore E) of1-Part Pre-cured silicone Gel CBN based thermal compositions at 150oC aging (Ex- 3-7). DETAILED DESCRIPTION

[0026] Reference will now be made to exemplary embodiments, examplesof which are illustrated in the accompanying drawings. It is to be understood that other embodiments may be utilized, and structural and functional changes may be made. Moreover, features of the various embodiments may be combined or altered. As such, the following description is presented by way of illustration only and should not limit in any way the various alternatives and modifications that may be made to the illustrated embodiments. In this disclosure, numerous specific details provide a thorough understanding of the subject disclosure. It should be understood that aspects of this disclosure may be practiced with other embodiments not necessarily including all aspects described herein, etc. As used herein, the words “example” and “exemplary” means an instance, or illustration. The words 6 35749272.1“example” or “exemplary” do not indicate a key or preferred aspect or embodiment. The word “or” is intended to be inclusive rather than exclusive, unless context suggests otherwise. As an example, the phrase “A employs B or C,” includes any inclusive permutation (e.g., A employs B; A employs C; or A employs both B and C). As another matter, the articles “a” and “an” are generally intended to mean “one or more” unless context suggest otherwise. As used herein, the term “thermal conductivity enhancing agent” means a solid compound or a mixture of compounds that enhances the thermal conductivity of a composition. Examples of thermal conductivity enhancing agent include, but are not limited to, solid inorganic compounds such as boron nitride, aluminum nitride, aluminum oxide, zinc oxide, aluminum metal, silicon carbide, carbon based fillers like graphite and diamond, metal fillers like aluminum, silver or a mixture thereof.

[0027] As used herein, the term “pre-cured gel” or “cross-linked siliconegel” means a fluid-extended polymer system which may include a continuous polymeric phase or network, which may be chemically, e.g., ionically or covalently, or physically cross-linked, and an oil, such as a silicone or other oil, a plasticizer, unreacted monomer, or other fluid extender which swells or otherwise fills the interstices of the network. The cross-linking density of such network and the proportion of the extender can be controlled to tailor the modulus, i.e., softness, and other properties of the gel. The term “pre-cured gel” also should be understood to encompass materials which alternatively may be classified broadly as pseudogels or gel-like as having viscoelastic properties similar to gels, such has by having a “loose” cross-linking network formed by relatively long cross-link chains, but as, for example, lacking a fluid-extender.

[0028] The expression “monovalent hydrocarbon” means any hydrocarbongroup from which one or more hydrogen atoms has been removed and is inclusive of alkyl, alkenyl, alkynyl, cyclic alkyl, cyclic alkenyl, cyclic alkynyl, aryl, aralkyl and arenyl and may contain heteroatoms.

[0029] The term “alkyl” means any monovalent, saturated straight,branched or cyclic hydrocarbon group; the term “alkenyl” means any monovalent straight, branched, or cyclic hydrocarbon group containing one or more carbon- 7 35749272.1carbon double bonds where the site of attachment of the group can be either at a carbon-carbon double bond or elsewhere therein; and, the term “alkynyl” means any monovalent straight, branched, or cyclic hydrocarbon group containing one or more carbon-carbon triple bonds and, optionally, one or more carbon-carbon double bonds, where the site of attachment of the group can be either at a carbon-carbon triple bond, a carbon-carbon double bond or elsewhere therein. Examples of alkyls include methyl, ethyl, propyl and isobutyl. Examples of alkenyls include vinyl, propenyl, allyl, methallyl, ethylidenyl norbornane, ethylidene norbornyl, ethylidenyl norbornene and ethylidene norbornenyl. Examples of alkynyls include acetylenyl, propargyl and methylacetylenyl.

[0030] The expressions “cyclic alkyl”, “cyclic alkenyl”, and “cyclicalkynyl” include bicyclic, tricyclic and higher cyclic structures as well as the aforementioned cyclic structures further substituted with alkyl, alkenyl, and / or alkynyl groups. Representative examples include norbornyl, norbornenyl, ethylnorbornyl, ethylnorbornenyl, cyclohexyl, ethylcyclohexyl, ethylcyclohexenyl, cyclohexylcyclohexyl and cyclododecatrienyl.

[0031] The term “aryl” means any monovalent aromatic hydrocarbongroup; the term “aralkyl” means any alkyl group (as defined herein) in which one or more hydrogen atoms have been substituted by the same number of like and / or different aryl (as defined herein) groups; and, the term “arenyl” means any aryl group (as defined herein) in which one or more hydrogen atoms have been substituted by the same number of like and / or different alkyl groups (as defined herein). Examples of aryls include phenyl and naphthalenyl. Examples of aralkyls include benzyl and phenethyl. Examples of arenyls include tolyl and xylyl.

[0032] The present disclosure provides one-part grease composition,reworkable pre-cured thermal gel composition and two-part post curable compositions consisting of cross-linked silicone gel, alkenyl-functionalized diorganopolysiloxane fluids, hydrogen-functionalized organopolysiloxane, alkoxy functionalized surface wetting agent (dispersing agent) or hydrolyzable organopolysiloxane, thermal conductive fillers, additives and pigments. By using dispersing agent and organofunctional silicone fluids, with cubic boron nitride and 8 35749272.1other thermal conductive fillers, ultra-high thermal conductivity was achieved. Even though these thermal compositions consisted of hard fillers like cubic boron nitride and AlN fillers, they showed remarkable thermal stability at very high temperature (150oC) for more than 1000h owing to not only the optimization of fillers and filler ratios but also optimization of composition of organofunctional silicone fluids along with dispersing agent.

[0033] In one-part pre-cured thermal gels compositions, thermalconductivity >12 W / mK with low hardness buildup.

[0034] In the two-part post curable (addition curable) thermalcompositions, thermal conductivity >16 W / mK with dispensability >9 g / min was achieved

[0035] The combination of fillers is optimized to arrive at bestcombinations which can provide us with high TC as well as dispensable formulations. It may be noted that, as such any two or three or more fillers can be combined to arrive at a formulation, but such an approach seldom works and results in powdery or low TC Formulations. Only after doing DOE and optimization can we arrive at optimal filler combinations that enhance the filler packing, thus providing for high thermal conductivity while maintaining paste like rheology, viscosity and flow properties. The filler combination can be described as made up of 3 or more fillers – (C-1) is the largest filler type (50-200 μm), which provides the biggest crystal domain sizes to provide for high heat conductive path and thus enhanced thermal conductivity. For largest filler, intrinsically high TC materials like BN, cubic BN, SiC, Diamond and AlN, which enhances the overall conductivity of the formulation are utilized. The next fillers, (C-2) are the middle size fillers ~0.5-120 μm, which provide enhanced contacts and gap-filling between the large-fillers, these fillers are made up of Alumina, cubic BN or Aluminum Nitride powders or their combination. The smallest fillers (C-3) of D50 ~ 0.01-15 μm, which can be made up of ZnO, Alumina, SiC, and / or Aluminum nitride fillers or combination – these fillers even though they have large surface areas, they enhance the overall TC by building multitude of filler-polymer-dispersing agent contacts, along with filler-filler and filler-substrate contacts. They may also provide 9 35749272.1the desired lubrication and thixotropic effect for the formulation. As a result of careful experimental studies, we are demonstrating here, specific fillers and filler combinations, to be used as the heat conductive filler to achieve a heat conductive formulation that is excellent in thermal conductivity (>12W / mK), electrical insulation flexibility and moldability, and can be easily manufactured at low cost, and the present invention has been completed.

[0036] Herein, to achieve ultra-high thermal conductivity along with goodthermal stability, filler optimization was done using Cubic BN and other thermal conductive fillers.

[0037] The disclosure may identify a number of different ranges for acomponent or components in the composition. It will be appreciated that the numerical values of the respective ranges can be combined to form new and non- specified ranges.

[0038] In one aspect, provided is a composition comprising a polymer andat least one thermal conductivity enhancing agent, wherein the composition has a hardness of less than 25 as determined using ASTMD2240 Type durometer (Shore E). and thermal conductivity of more than 12W / mK as determined by the hot disk method or ASTM D5470 method.

[0039] In one embodiment, the polymer is a silicone polymer.

[0040] In one embodiment, the silicone polymer comprises(i) an alkenyl-functionalized diorganopolysiloxane of formula (Ia) M1aM2bD1cD2dT1eT2fQg(Ia) wherein: M1= R1R2R3SiO1 / 2 M2= R4R5R6SiO1 / 2D1= R7R8SiO2 / 2 D2= R9R10SiO2 / 2T1= R11SiO3 / 2 T2= R12SiO3 / 2Q = SiO4 / 2 10 35749272.1where R2, R3, R4, R5, R6, R8, R9, R10, R12are each independently selected from an aliphatic, aromatic, or fluoro monovalent hydrocarbon groups having from 1 to 60 carbon atoms or alkoxy groups; R1, R7, R11are each independently selected from an aliphatic, aromatic, or fluoro monovalent hydrocarbon having from 1 to 60 carbon atoms and containing at least one terminal olefin bond; and the subscripts a, b, c, d, e, f, and g are zero or a positive integer subject to the following limitations: 1≤a+b+c+d+e+f+g ≤6000, and a+c+e≥1; and (ii) a hydrogen-functionalized organopolysiloxane of formula (Ib)M1= R13R14R15SiO1 / 2M2= R16R17R18SiO1 / 2 D1= R19R20SiO2 / 2D2= R21R22SiO2 / 2 T1= R23SiO3 / 2T2= R24SiO3 / 2 Q = SiO4 / 2where R14, R15, R16, R17, R18, R20, R21, R22, R24are aliphatic, aromatic or fluoro monovalent hydrocarbon groups having from 1 to 60 carbon atoms; R13, R19, R23are hydrogen; the subscript a', b', c', d', e', f', and g' are zero or a positive integer subject to the following limitations: 1≤a'+b'+c'+d'+e'+f'+g' ≤6000, and a'+c'+e' ≥ 1; 11 35749272.1with the proviso that when a'+c'+e' =1 then a+c+e >1 and when a+c+e =1 then a'+c'+e' >1; or a crosslinked product of (i) and (ii).

[0041] The component (i) is an organopolysiloxane represented byformula (Ia) and having, in one molecule, at least two alkenyl groups bonded to silicon atoms. The viscosity of the component (i) at 25 °C may be in the range of 0.01 to 10 Pa·s, preferably 0.06 to 1 Pa·s. If the viscosity at 25 °C is below 0.01 Pa·s, the storage stability of the composition deteriorates, and if it exceeds 10 Pa·s, flowability cannot be maintained. The viscosity values mentioned above and elsewhere in the application are measured using a Brookfield rotary viscometer. The organopolysiloxane is not particularly limited as far as it meets the aforementioned viscosity and alkenyl group content and known organopolysiloxanes may be used. The molecular structure of the organopolysiloxane may be straight-chain, branched-chain, partially branched straight-chain, dendritic, or the like. Preferably, the structure is straight-chain or partially branched straight-chain. The component (i) may be a single polymer with such structure, a copolymer with such structure, or a mixture of two or more organopolysiloxanes having different viscosities. Further, the component (i) may be used in combination with a mono alkenyl-terminated organopolysiloxane having one alkenyl group bonded to a silicon atom per molecule. The viscosity of this organopolysiloxane at 25 °C may range from 0.001 to 1 Pa·s, preferably 0.006 to 0.1 Pa·s. Combining this organopolysiloxane with the component (i), an organopolysiloxane having at least two alkenyl groups bonded to silicon atoms per molecule, improves fluidity and facilitates, in the case of cured products, achieving the necessary low hardness for thermal interface materials.

[0042] The component (ii) is an organohydrogen polysiloxanerepresented by formula (Ib) and having hydrogen atoms directly bonded to silicon atoms. Specifically, it is an organohydrogen polysiloxane having at least two hydrogen atoms directly bonded to silicon atoms (hydrosilyl groups) in one molecule, and functions as a crosslinking agent for the component (i). The hydrosilyl groups of the component (ii) and the alkenyl groups of the component 12 35749272.1(i) are added together by way of a hydrosilylation reaction promoted by a platinum- based metal catalyst, later described, resulting in a three-dimensional network structure including crosslinked structures. If the number of hydrosilyl groups is less than two in the component (ii), curing is not obtained. The amount of addition of the component (ii) is such that the hydrosilyl groups of the component (ii) are 0.1 to 5.0 moles relative to one mole of alkenyl groups of the component (i), i.e., the molar quantity of hydrogen atoms directly bonded to silicon atoms is 0.1 to 5.0 times the molar quantity of alkenyl groups of the component (i), preferably 0.2 to 2.0 moles, and more preferably 0.3 to 1.0 moles. If the quantity of hydrosilyl groups of the component (ii) is less than 0.1 mole relative to one mole of alkenyl groups of the component (i), curing may not be obtained or the strength of the cured product may be insufficient, making it difficult to handle as a molded object. If it exceeds 5.0 moles, the flexibility of the cured product is lost, and the cured product becomes brittle.

[0043] In one embodiment, the composition comprises a first thermalconductivity enhancing agent, a second thermal conductivity enhancing agent and a third thermal conductivity enhancing agent.

[0044] In another embodiment, the first thermal conductivity enhancingagent is selected from boron nitride, cubic boron nitride, silicon carbide, diamond and aluminum nitride.

[0045] In still another embodiment, second thermal conductivity enhancingagent is selected from the group consisting of aluminum oxide, , boron nitride, cubic boron nitride and aluminum nitride.

[0046] In still another embodiment, the third thermal conductivityenhancing agent is selected from the group consisting of aluminum oxide, zinc oxide, SiC, and aluminum nitride.

[0047] In another embodiment the viscosity of the composition is more than100 Pa.s at 1 s-1. Steady shear viscosity and thixotropy were determined using Rheometer (RS-600) instrument with parallel plate geometry (measuring geometry gap was 500 µm). 13 35749272.1

[0048] In yet another embodiment, the polymer is present in an amountranging from 1 to 8 wt% of the composition.

[0049] In another embodiment, the gradient of change in a thermalresistance value with respect to change in a thickness of the composition is 100 K mm2 / W or less.

[0050] In another embodiment, the composition has a dispensability of 4g / min or more.

[0051] In another embodiment, the composition has a shore E hardness of0 to 90.

[0052] In another embodiment, the composition has a bond line thicknessof less than 350 µm. Compression was applied at 1MPa for 30seconds on 10 x 10 x 0.5mm Si chip.

[0053] In another embodiment, the composition is one-part cross-linkedsilicone gel formulation, two-part curable formulation, or a grease formulation.

[0054] It will be appreciated that the thermal conductivity enhancing agentmay comprise a mixture of a single type of compound where the mixture includes compounds of different average particle size. In one embodiment, the thermal conductivity enhancing agent comprises cubic boron nitride, ZnO, aluminum nitride, boron nitride, SiC, and aluminum oxide.

[0055] The particle size of the thermal conductivity enhancing agent maybe chosen as desired for a particular purpose or intended application. As used herein, “particle size” refers to a volume average particle size unless the context indicates otherwise. In embodiments, the thermal conductivity enhancing agent has an average particle size of from about 0.01 µm to about 500 µm; from about 0.1 to about 250 µm; from about 1 to about 100 µm; from about 5 to about 75 µm; even from about 10 to about 50 µm. It will be appreciated that the composition may comprise a combination of thermal conductivity enhancing agents of different average particle sizes. Such combinations may be chosen as desired for a particular purpose or intended application. In one embodiment, the composition comprises a first thermal conductivity enhancing agent having an average particle size from about 0.01 to less than 15 µm; a second thermal conductivity enhancing agent 14 35749272.1having an average particle size of about 0.5 µm to about 120 µm; and a third thermal conductivity enhancing agent having an average particle size of about 50 µm to about 200 µm. The first, second, and third thermal conductivity enhancing agents may be the same or different from one another in terms of the chemical makeup of the filler. Particle size can be determined by any suitable method. Average particle size is often provided or reported from the supplier of the material. The average particle size can be determined by measuring the particle size distribution by laser diffraction and scattering according to JIS R1629. In this study, the median diameter (D50) on a volume basis obtained from the measurement was used as the average particle diameter. The filler(s) may be present in an amount of from about 80 wt.% to about 99 wt.%, from about 82 wt.% to about 96 wt.%, or from about 85 wt.% to about 95 wt.% based on the total weight of the composition.

[0056] The cross-linked silicone gel may also be referred to herein as a pre-cured gel or a polymer gel. The cross-linked silicone gel is made by reacting the alkenyl-functionalized diorganopolysiloxane with hydrogen-functionalized organopolysiloxane. The reaction may be conducted via hydrosilylation reaction conditions using an appropriate catalyst. A conventional hydrosilylation catalyst are platinum-based catalysts (such as, but not limited to, Karstedt’s catalyst). In one embodiment, the pre-cured gel can be made by reacting a linear vinyl capped polysiloxanes with pendent poly(hydrosiloxane) or poly(methylhydrosiloxane) copolymers (cross-linker) or a crosslinked MT or MQ resin containing Si-H reactive groups through Pt catalyzed hydrosilylation reaction. A similar gel network can also be achieved by reacting a pendant vinyl silicone polymer with an end capped poly(hydrosiloxane) or poly(methylhydrosiloxane) copolymers or a crosslinked MT or MQ resin containing Si-H reactive groups via Pt catalyzed hydrosilylation route. The effective Si-H / Si-alkenyl mole ratio [r] which will be made to react to form a Si-C linkage must satisfy r ≤ 0.3. The final “Gel Rheology” must satisfy the condition a) 0.2 ≤ G′ ≤ 1000 (Pa); b) 0.1 ≤ G′′ / G′ ≤ 10; 15 35749272.1where the term G′ represents the “storage shear modulus” of the final pre-cured gel composition to be used in the thermal interface material formulation measured at T= 25oC under an oscillation frequency of 1 Hz or 6.28 rad / s by a stress or strain controlled rheometer, and the term G′′ represents the “loss shear modulus” of the final pre-cured gel composition to be used in thermal interface material formulation measured at T= 25oC under an oscillation frequency of 1 Hz or 6.28 rad / s by a stress or strain-controlled rheometer. G′′ and G′ are collectively measured in the respective viscoelastic region.

[0057] The following examples are intended to illustrate aspects andembodiments of the present technology. All parts and percentages are by weight and all temperatures are in Celsius unless explicitly stated otherwise. All patents, other publications, and U.S. patent applications referred to in the instant application are incorporated herein by reference in their entireties.

[0058] Examples

[0059] Steady shear viscosity and thixotropy were determined usingRheometer (RS-600) instrument with parallel plate geometry (measuring geometry gap was 500 µm). Hardness test of cured (2-Part) formulations were measured using ASTMD2240 Type durometer (Shore E).

[0060] Bulk thermal conductivity of the thermal compositions wasmeasured using hot disk instrument at 22 °C and also ASTM D5470 was used to measure the thermal resistance and thermal conductivity.

[0061] Dispensability measurements were made by filling EFD's Optimum30cc syringe having 2mm opening with sample and dispensing at 90 psi, using an automatic dispenser Nordson EFD, and measuring the dispensed volume per minute.

[0062] BLT was determined by applying the compression at 1MPa for30seconds on 10 x 10 x 0.5mm Si chip.

[0063] Crystallite size was measured by XRD using X-ray diffractometersystem with copper target (Kα line) of wavelength 1.54 Å, accelerating voltage of 40 kV, tube current of 30 mA, scan speed of 4° / min with step width of 0.02°. 16 35749272.1

[0064] Surface oxygen content was measured by XPS using X-rayPhotoelectron spectroscope with Al K alpha source, vacuum level of 2 X 10-9 Torr, hemispherical analyzer, dwell time of 0.7 sec, energy step of 1eV and HR scan 0.1eV.

[0065] Compositions were prepared according to the examples listed inTables 1 and 2.

[0066] Divinyl terminated organopolysiloxane (A-1a) has a viscosity of 0.1Pa·s and represented by the following formula:to 400.

[0067] Divinyl terminated organopolysiloxane (A-1b) has a viscosity of0.03 Pa·s and represented by the following formula:wherein each X is vinyl and n is 10 to 20

[0068] Monovinyl terminated organopolysiloxane (A-2a) has a viscosity of0.02 Pa·s and represented by the following formula:organopolysiloxane (A-2b) has a viscosity of0.01 Pa·s and represented by the following formula: 17 35749272.1wherein X is vinyl and m is 10 to 20.

[0070] Crosslinker organohydrogenpolysiloxane (B-1) has the viscosityranges from 0.01 to 0.1 Pa·s with Si-H content from 0.05 to 0.5 wt%, and a compound of the following formula having a viscosity of 0.02 Pa·s is used in Examples:.

[0071] Wherein o is 20 to 100 and p is 2 to 20

[0072] Synthesis of cross-linked silicone gel (X-1) of viscosity 11.6 Pas:Vinyl stopped PDMS (500 g, MW ~ 17280 g / mol, Vinyl meq ~0.115) along with Pt catalyst (2 wt. % Karstedt’s catalyst, 10 ppm Pt) and inhibitor (Surfynol® 61, 200 ppm) were charged to a double planetary mixer at room temperature and allowed to mix at room temperature for 30 minutes at 20 rpm. To the reaction mixture at 50oC, silicone hydride (55.4 g, MW ~ 40802, Hydride meq ~0.1586) was added and continued the mixing for an additional 1 hour at 20 rpm. While the mixing continues at the same speed at 50oC, the vacuum is applied for 60 minutes to remove the inhibitor to form the gel network. The reaction temperature then increases to 90oC and is continued till all the hydride gets consumed and a gel is being formed.

[0073] The Pre-cured Gel formulations were made in Thinky mixer. First,the specific amount of dispersing agent, Vinyl PDMS fluids and gel were weighed in plastic container and mixed for 30 sec at 2000 rpm. To this mixture, diamond and other thermal conductive fillers with the variable particle size were added step wise and all the materials were mixed using Thinky mixer at 2000 rpm for 30 sec at each step. In each step, after mixing of 30 sec, the formulation was hand mixed 18 35749272.1with broad blade spatula for 2 min. At the end, 1-2 times mixed for 30 sec at 2000 rpm to get the uniform paste.

[0074] 2-part curable formulations were also made similar to pre-cured gelformulations. A part and B part were made separately and mixed equal amount and cured at 70oC for 1 h.

[0075] Cubic boron nitride was purchased from Funik (China).

[0076] Aluminum nitride was purchased from Toyo aluminum.

[0077] Nano Zinc oxide was procured from Zochem

[0078] Cubic BN with a volume-averaged particle size of 50-200 μm ((C-1a:90 μm), (C-1b:152 μm), (C-1c:95 μm), (C-1d:113 μm), (C-1e:114 μm)) with surface oxygen content of more than 5%.

[0079] Aluminum nitride with a volume-averaged particle size of 1.2 , 5, 20and 70 μm size (C-2a, C-2b, C-2c and C-2d respectively).

[0080] Nano Zinc oxide with a volume-averaged particle size of 0.16 μmsize (C-3).

[0081] (D-1) is a hydrolyzable organopolysiloxane (II-i) represented by acompound of the formula:

[0082] (D-2) is a hydrolysable polyorganosiloxane represented by acompound of the formula (II-ii): 19 35749272.1(Formula II-ii)

[0083] E-1 is selected from Didodecyl3,3′-thiodipropionate or 2,4,6-Tris(3',5'-di-tert-butyl-4'-hydroxybenzyl)mesitylene used as an additive in the formulations.

[0084] F-1 is an inhibitor, Bis(1,1-dimethyl-2-propynyloxy) dimethylsilane

[0085] G-1 is a platinum-based catalyst: 18 wt% solution of 2% platinumamount vinyl dimer complex in monovinyl terminated organopolysiloxane (viscosity 0.02 Pa·s). The platinum amount may be 7 ppm in compositions. Ultra-high Thermal Conductive two-part addition curable thermal Compositions:

[0086] TIA2101GF is a commercial two-part silicone formulation producedby Momentive performance Materials.

[0087] Two-part addition curable thermal compositions were made withdifferent filler percentage loading and achieved ultra-high thermal conductivity (>16 W / mK) with good dispensability (>13 g / min). By mixing 1:1 ratio of part-A and part-B, it was cured at 70oC for 1 h. The cured samples H / Vi ratios are in the range of 0.4-1.0. F-1 is 1.5 wt% solution of BIS-{(1,1-DIMETIL-2- PROPINIL)OXI DIMETIL-SILAN in cross-linker organohydrogenpolysiloxane (viscosity 0.02 Pa·s). 20 35749272.1Table 1 WihtTIA2101GF Ex-1 Ex-2 t 421 35749272.12 malconductivity >16 W / mK with dispensability >9 g / min

[0089] Ultra-high Thermal Conductive cross-linked silicone gel thermalcompositions: Table 2 Components (wt%) Ex.3 Ex.4 Ex.5 Ex.6 Ex.722 35749272.1

[0090] As can be seen from table 2, examples 3,4,5 and 7 show thermalconductivity >12W / mK with low hardness buildup (shore E was within the 25 even after 1000 h of aging at 150oC.

[0091] Figure 1 shows hardness buildup data (Shore E) of 1-Part Pre-curedsilicone Gel CBN based thermal compositions at 150oC aging (Examples 3 to 7).

[0092] What has been described above includes examples of the presentspecification. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the present specification, but one of ordinary skill in the art may recognize that many further combinations and permutations of the present specification are possible. Accordingly, the present specification is intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the appended claims. Furthermore, to the extent that the term “includes” is used in either the detailed description or the claims, such term is intended to be inclusive in a manner similar to the term “comprising” as “comprising” is interpreted when employed as a transitional word in a claim.

[0093] The foregoing description identifies various, non-limitingembodiments of thermal gel composition. Modifications may occur to those skilled in the art and to those who may make and use the invention. The disclosed embodiments are merely for illustrative purposes and not intended to limit the scope of the invention or the subject matter set forth in the claims. 23 35749272.1

[0094] Further embodiments of the present invention are provided in thefollowing.

[0095] Embodiment 1: A composition comprising a polymer and at leastone thermal conductivity enhancing agent, wherein the composition has a hardness of less than 50 as determined using ASTMD2240 Type durometer (Shore E), and thermal conductivity of more than 12W / mK as determined by the hot disk method or ASTM D5470 method.

[0096] Embodiment 2: The composition according to Embodiment 1wherein the polymer is a silicone polymer.

[0097] Embodiment 3: The composition according to Embodiment 2wherein the silicone polymer comprises (i) an alkenyl-functionalized diorganopolysiloxane of formula (Ia) M1aM2bD1cD2dT1eT2fQg (Ia) wherein: M1= R1R2R3SiO1 / 2 M2= R4R5R6SiO1 / 2D1= R7R8SiO2 / 2 D2= R9R10SiO2 / 2T1= R11SiO3 / 2 T2= R12SiO3 / 2Q = SiO4 / 2 where R2, R3, R4, R5, R6, R8, R9, R10, R12are each independently selected from an aliphatic, aromatic, and fluoro monovalent hydrocarbon groups having from 1 to 60 carbon atoms or alkoxy groups; R1, R7, R11are each independently selected from an aliphatic, aromatic, or fluoro monovalent hydrocarbon having from 1 to 60 carbon atoms and containing at least one terminal olefin bond; and 24 35749272.1the subscripts a, b, c, d, e, f, and g are zero or a positive integer subject to the following limitations: 1≤a+b+c+d+e+f+g ≤6000, and a+c+e≥1; and (ii) a hydrogen-functionalized organopolysiloxane of formula (Ib) M1a'M2b'D1c'D2d'T1e'T2f’'Qg' (1b)M1= R13R14R15SiO1 / 2 M2= R16R17R18SiO1 / 2 D1= R19R20SiO2 / 2 D2= R21R22SiO2 / 2 T1= R23SiO3 / 2 T2= R24SiO3 / 2 Q = SiO4 / 2where R14, R15, R16, R17, R18, R20, R21, R22, R24are aliphatic, aromatic or fluoro monovalent hydrocarbon groups having from 1 to 60 carbon atoms; R13, R19, R23are hydrogen; the subscript a', b', c', d', e', f', and g' are zero or a positive integer subject to the following limitations: 1≤a'+b'+c'+d'+e'+f'+g' ≤6000, and a'+c'+e' ≥ 1; with the proviso that when a'+c'+e' =1 then a+c+e >1 and when a+c+e =1 then a'+c'+e' >1; or a crosslinked product of (i) and (ii).

[0098] Embodiment 4: The composition according to embodiment 1 to 3,wherein the composition comprises a first thermal conductivity enhancing agent, a second thermal conductivity enhancing agent and a third thermal conductivity enhancing agent. 25 35749272.1

[0099] Embodiment 5: The composition according to embodiment 4,wherein the first thermal conductivity enhancing agent is selected from boron nitride, cubic boron nitride, silicon carbide, diamond and aluminum nitride.

[0100] Embodiment 6: The composition according to embodiment 4,wherein the second thermal conductivity enhancing agent is selected from the group consisting of aluminum oxide, , boron nitride, cubic boron nitride and aluminum nitride.

[0101] Embodiment 7: The composition according to embodiment 4,wherein the third thermal conductivity enhancing agent is selected from the group consisting of aluminum oxide, zinc oxide, SiC, and aluminum nitride.

[0102] Embodiment 8: The composition according to any one of theEmbodiments 1 to 7 wherein the composition has a viscosity of more than 100 Pa·s.

[0103] Embodiment 9: The composition according to any one of theEmbodiments 1 to 7 wherein the polymer is present in an amount in the range of 1 to 8 wt% of the composition.

[0104] Embodiment 10: The composition according to any one of theEmbodiments 1 to 7 wherein the composition has a gradient in change in thermal resistance with respect to change in a thickness of 100 K mm2 / W or less.

[0105] Embodiment 11: The composition according to any one of theEmbodiments 1 to 7 wherein the composition has a shore E hardness of 0 to 90.

[0106] Embodiment 12: The composition according to any one of theEmbodiments 1 to 7wherein the composition has a has a dispensability of 4 g / min or more.

[0107] Embodiment 13: The composition according to any one of theEmbodiments 1 to 7 wherein the composition has a bond line thickness of less than 350 µm.

[0108] Embodiment 14: The composition according to any of Embodiments1-13, wherein the composition is one-part cross-linked silicone gel formulation, two-part curable formulation or a grease formulation. 26 35749272.1

Claims

WE CLAIM:

1. A composition comprising a polymer and at least one thermal conductivityenhancing agent, wherein the composition has a hardness of less than 50 as determined using ASTMD2240 Type durometer (Shore E), and a thermal conductivity of more than 12W / mK as determined by hot disk method or ASTM D5470 method.

2. The composition as claimed in claim 1, wherein the polymer is a siliconepolymer.

3. The composition as claimed in claim 2, wherein the silicone polymercomprises (i) an alkenyl-functionalized diorganopolysiloxane of formula (Ia) M1aM2bD1cD2dT1eT2fQg (Ia) wherein: M1= R1R2R3SiO1 / 2M2= R4R5R6SiO1 / 2 D1= R7R8SiO2 / 2D2= R9R10SiO2 / 2 T1= R11SiO3 / 2T2= R12SiO3 / 2 Q = SiO4 / 2where R2, R3, R4, R5, R6, R8, R9, R10, R12are each independently selected from an aliphatic, aromatic, and fluoro monovalent hydrocarbon groups having from 1 to 60 carbon atoms or alkoxy groups; R1, R7, R11are each independently selected from an aliphatic, aromatic, or fluoro monovalent hydrocarbon having from 1 to 60 carbon atoms and containing at least one terminal olefin bond; and the subscripts a, b, c, d, e, f, and g are zero or a positive integer subject to the following limitations: 1≤a+b+c+d+e+f+g ≤6000, and a+c+e≥1; and 27 35749272.1(ii) a hydrogen-functionalized organopolysiloxane of formula (Ib) M1a'M2b'D1c'D2d'T1e'T2f’'Qg'(1b) wherein: M1= R13R14R15SiO1 / 2M2= R16R17R18SiO1 / 2 D1= R19R20SiO2 / 2D2= R21R22SiO2 / 2 T1= R23SiO3 / 2T2= R24SiO3 / 2 Q = SiO4 / 2 where R14, R15, R16, R17, R18, R20, R21, R22, R24are aliphatic, aromatic or fluoro monovalent hydrocarbon groups having from 1 to 60 carbon atoms; R13, R19, R23are hydrogen; the subscript a', b', c', d', e', f', and g' are zero or a positive integer subject to the following limitations: 1≤a'+b'+c'+d'+e'+f'+g' ≤6000, and a'+c'+e' ≥ 1; with the proviso that when a'+c'+e' =1 then a+c+e >1 and when a+c+e =1 then a'+c'+e' >1; or a crosslinked product of (i) and (ii).

4. The composition as claimed in any one of claims 1 to 3, wherein thecomposition comprises a first thermal conductivity enhancing agent, a second thermal conductivity enhancing agent and a third thermal conductivity enhancing agent.

5. The composition as claimed in claim 4, wherein the first thermalconductivity enhancing agent is selected from boron nitride, cubic boron nitride, silicon carbide, diamond and aluminum nitride.

6. The composition as claimed in claim 4, wherein the second thermalconductivity enhancing agent is selected from the group consisting of aluminum oxide, , boron nitride, cubic boron nitride and aluminum nitride. 28 35749272.

17. The composition as claimed in claim 4, wherein the third thermalconductivity enhancing agent is selected from the group consisting of aluminum oxide, zinc oxide, SiC, and aluminum nitride.

8. The composition as claimed in any one of claims 1 to 7, wherein thecomposition has a viscosity of more than 100 Pa·s.

9. The composition as claimed in any one of claims 1 to 7, wherein the polymeris present in an amount in the range of 1 to 8 wt% of the composition.

10. The composition as claimed in any one of claims 1 to 7, wherein thecomposition has a gradient in change in thermal resistance with respect to change in a thickness of 100 K mm2 / W or less.

11. The composition as claimed in any one of claims 1 to 7, wherein thecomposition has a shore E hardness of 0 to 90.

12. The composition according to any one of the claims 1 to 7 wherein thecomposition has a has a dispensability of 4 g / min or more.

13. The composition as claimed in any one of claims 1 to 7, wherein thecomposition has a bond line thickness of less than 350 µm.

14. The composition as claimed in any one of claims 1 to 13, wherein thecomposition is one-part cross-linked silicone gel formulation, two-part curable formulation, or a grease formulation. 29 35749272.1

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