Thermally conductive composition

Abstract

Disclosed are compositions comprising a polymer and at least one thermal conductivity enhancer, the compositions having a hardness (Shore E) of less than 50 as determined using an ASTM D2240 type durometer, and a thermal conductivity of greater than 12 W / mK as determined by the hot disk method or the ASTM D5470 method.

Description

Technical Field

[0001] This invention relates to compositions comprising a polymer and at least one thermal conductivity enhancer, resulting in ultra-high thermal conductivity and very good thermal stability. Background Technology

[0002] As electronic devices become increasingly miniaturized, denser, and more integrated, the heat generated by these devices is gradually increasing, and thermal failure has become a major problem hindering their performance, reliability, and lifespan. Therefore, effective thermal management is crucial to addressing this challenge. Thermal interface materials (TIMs) are widely used between the two solid contact surfaces of a heat source and a heat sink to increase heat removal (dissipation) in electronic devices. These materials come in various forms, such as greases, gap fillers, pre-cured gels, curable materials (one or two parts), phase change materials, elastic pads, adhesives, thermal tapes, metal alloys, and solders. The gap between two solid surfaces (chip and heat sink) is non-uniform and, if left untreated, can be filled with air with poor thermal conductivity. This gap is filled with a thermal interface material to provide a heat conduction path. Depending on the requirements, multiple thermal interface materials can be used between different solid surfaces to provide a continuous conduction path for heat removal.

[0003] The advent of 5G communication technology in the telecommunications space and the Internet of Things (IoT) in the consumer and industrial sectors will further increase the performance requirements for thermal conductivity (TIM). 5G and IoT devices (using 5G) operate at higher frequencies, higher device densities, higher bandwidth, lower latency, smaller feature sizes, and lower power consumption, while also requiring significantly higher reliability and availability. These factors have made the requirements for heat removal from electronic devices more stringent, and there is a general trend in industry towards higher performance (i.e., higher thermal conductivity TIM), for example, from low thermal conductivity of 3-5 W / mK to an average of 6-10 W / mK, and prompting the development of even higher thermal conductivity >10 W / mK. The development of next-generation integrated circuits (ICs), 3D integration, and ultrafast high-power-density communication devices makes thermal management requirements extremely stringent.

[0004] Conventional TIMs filled with thermally conductive particles require fillers with a high volume fraction (v>50%) such as alumina and ZnO to achieve a composite thermal conductivity (TC) in the range of 1-5 W / mK. When conductivity conditions are relaxed, many products also utilize metallic fillers such as aluminum. However, to achieve high TC (>10 W / mK), numerous patent applications disclose additional fillers such as BN, AlN, diamond, SiC, and combinations thereof. These fillers have the advantage of being electrically insulating and possessing much higher thermal conductivity (high TC fillers). In addition to thermal conductivity, TIM formulations must demonstrate a range of other key properties for use in the application. These may include low heat resistance, low volatility, pumpability, exudation, cracking, thermal stability, low buildup, and high dispensing flow rate for applications at defined viscosity, shear rate, and pump pressure. Performance stability during low-to-high temperature cycling / shock also needs to be demonstrated through testing for up to 500-1000 hours. These properties are achieved through the careful design of TIM formulations that combine high filler composition loadings with suitable polymer-resin-dispersant combinations, as disclosed below.

[0005] CN116814081A describes a composition comprising a filler combination of diamond, alumina, and cubic boron nitride filler, wherein the cubic boron nitride is a mixture of particles with a diameter of 5 μm and 30 μm, diamond has a particle diameter of 100 μm, and alumina nanoparticles have a particle size of 30 nm. This composition results in an ultra-high thermal conductivity, low dielectric interface material with a thermal conductivity greater than 7 and a dielectric constant less than 5.

[0006] CN112457673A describes a high thermal conductivity insulating silicone gasket containing at least one of nano-aluminum nitride, cubic boron nitride, and nano-silicon carbide, as well as spherical alumina modified with dodecyltrimethoxysilane. Through filler modification and compounding design, the silicone exhibits excellent properties such as high thermal conductivity, high insulation, and chemical stability, with a thermal conductivity coefficient reaching over 8 W / mK.

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

[0008] However, these proposed solutions do not address the need for thermally conductive compositions that possess the desired properties through the use of a combination of thermally conductive fillers. Summary of the Invention

[0009] This invention provides a thermal conductivity >12 W / mK, accompanied by very low hardness accumulation at very high temperatures of 150°C. This invention incorporates cubic boron nitride as a key filler into the thermal formulation.

[0010] The following summary of the invention is presented to provide a basic understanding of some aspects of the invention. This summary is not intended to identify key or essential elements, nor is it intended to limit the implementation or any restrictions on the claims. Furthermore, the summary provides a simplified overview of some aspects that can be described in more detail in other parts of this disclosure.

[0011] In one aspect, a composition is provided comprising a polymer and at least one thermal conductivity enhancer, wherein the composition has a thermal conductivity greater than 12 W / mK as determined by the hot plate method according to ISO 22007-2 and by the test method according to ASTM D5470, and a hardness less than 50 (Shore E) as determined using an ASTM D2240 hardness tester.

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

[0013] In one embodiment, the silicone polymer comprises

[0014] (i) Alkenyl-functionalized diorganopolysiloxanes of formula (Ia)

[0015] M 1 a M 2 b D 1 c D 2 d T 1 e T 2 f Q g (Ia)

[0016] in: M 1 =R 1 R 2 R 3 SiO 1 / 2 M 2 =R 4 R 5 R 6 SiO1 / 2 D 1 =R 7 R 8 SiO 2 / 2 D 2 =R 9 R 10 SiO 2 / 2 T 1 =R 11 SiO 3 / 2 T 2 =R 12 SiO 3 / 2 Q=SiO 4 / 2 Where R 2 R 3 R 4 R 5 R 6 R 8 R 9 R 10 R 12 Each is independently selected from aliphatic, aromatic, or fluorinated monovalent hydrocarbon groups, or alkoxy groups, having 1 to 60 carbon atoms; R 1 R 7 R 11 Each is independently selected from aliphatic, aromatic, or fluorinated monovalent hydrocarbons having 1 to 60 carbon atoms and containing at least one terminal olefinic bond; and The subscripts a, b, c, d, e, f, and g are zero or positive integers subject to the following restrictions: 1 ≤ a + b + c + d + e + f + g ≤ 6000, and a + c + e ≥ 1; and (ii) Hydrogen-functionalized organopolysiloxanes of formula (Ib)

[0017] in: M 1 =R 13 R 14 R 15 SiO 1 / 2 M 2 =R 16 R 17 R 18 SiO 1 / 2 D 1 =R 19 R 20 SiO2 / 2 D 2 =R 21 R 22 SiO 2 / 2 T 1 =R 23 SiO 3 / 2 T 2 =R 24 SiO 3 / 2 Q=SiO 4 / 2 Where R 14 R 15 R 16 R 17 R 18 R 20 R 21 R 22 R 24 It is an aliphatic, aromatic, or fluorinated monovalent hydrocarbon group having 1 to 60 carbon atoms; R 13 R 19 R 23 It is hydrogen; The subscripts a', b', c', d', e', f', and g' are zero or positive integers subject to the following restrictions: 1 ≤ a'+b'+c'+d'+e'+f'+g' ≤ 6000, and a'+c'+e' ≥ 1; The condition is that when a'+c'+e'=1, then a+c+e>1, and when a+c+e=1, then a'+c'+e'>1; Or the cross-linked products of (i) and (ii).

[0018] In one embodiment, the composition comprises a first thermal conductivity enhancer, a second thermal conductivity enhancer, and a third thermal conductivity enhancer.

[0019] In another embodiment, the first thermal conductivity enhancer is selected from boron nitride, cubic boron nitride, silicon carbide, diamond, and aluminum nitride.

[0020] In another embodiment, the second thermal conductivity enhancer is selected from alumina, boron nitride, cubic boron nitride, and aluminum nitride.

[0021] In another embodiment, the third thermal conductivity enhancer is selected from alumina, zinc oxide, SiC, and aluminum nitride.

[0022] In another embodiment, the viscosity of the composition is [value missing] at 1 s [value missing]. -1Greater than 100 Pa·s. Steady-state shear viscosity and thixotropy were determined using a rheometer (RS-600) with a parallel plate geometry (measuring geometry gap of 500 μm).

[0023] In another embodiment, the polymer is present in an amount ranging from 1% to 8% by weight of the composition.

[0024] In another embodiment, the gradient of the thermal resistance of the composition relative to the thickness variation is 100 K mm. 2 / W or smaller.

[0025] In another embodiment, the composition has a dispensability of 4 g / min or greater.

[0026] In another embodiment, the composition has a Shore E hardness of 0 to 90.

[0027] In another embodiment, the composition has an adhesive layer thickness (bond line thickness) of less than 350 μm.

[0028] In another embodiment, the composition is a one-part crosslinked silicone gel formulation, a two-part curable formulation, or a grease formulation. Attached Figure Description

[0029] Figure 1 The graph shows the cumulative hardness data (Shore E) of the thermal composition of a 1-part pre-cured silicone gel CBN aged at 150°C (Examples 3-7). Detailed Implementation

[0030] Reference will now be made to exemplary embodiments, examples of which are illustrated in the accompanying drawings. It should be understood that other embodiments may be utilized, and structural and functional changes may be made. Furthermore, features of various embodiments may be combined or modified. Therefore, the following description is presented by way of illustration only and should not in any way limit the various alternatives and modifications that may be made to the illustrated embodiments. Numerous specific details in this disclosure provide a thorough understanding of the subject matter disclosure. It should be understood that aspects of this disclosure may be practiced, etc., with other embodiments that do not necessarily include all aspects described herein. As used herein, the terms “example” and “exemplary” mean an instance or illustration. The terms “example” or “exemplary” do not indicate a critical or preferred aspect or implementation. Unless the context otherwise requires, the word “or” is intended to be inclusive rather than exclusive. 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). On the other hand, unless the context otherwise requires, the article “a” generally means “one or more”. As used herein, the term "thermal conductivity enhancer" means a solid compound or mixture of compounds that enhances the thermal conductivity of a composition. Examples of thermal conductivity enhancers include, but are not limited to, solid inorganic compounds such as boron nitride, aluminum nitride, alumina, zinc oxide, aluminum metal, silicon carbide, carbon-based fillers such as graphite and diamond, metallic fillers such as aluminum, silver, or mixtures thereof.

[0031] As used herein, the terms "pre-cured gel" or "crosslinked silicone gel" refer to fluid-extended polymer systems that may include a continuous polymer phase or network (which may be chemically, for example, ionicly or covalently, or physically crosslinked), and oils such as silicone or other oils, plasticizers, unreacted monomers, or other fluid extenders that swell or otherwise fill the gaps in the network. The crosslinking density of such a network and the proportion of extenders can be controlled to adjust the modulus (i.e., softness) and other properties of the gel. The term "pre-cured gel" should also be understood to encompass materials that may alternatively be broadly classified as pseudogels or gels because they exhibit viscoelasticity similar to gels, for example, through a "loose" crosslinked network formed by relatively long crosslinked chains, but lack, for example, a fluid extender.

[0032] The term "monovalent hydrocarbon" refers to any hydrocarbon group from which one or more hydrogen atoms have been removed, and includes alkyl, alkenyl, alkynyl, cyclic alkyl, cyclic alkenyl, cyclic alkynyl, aryl, aralkyl and arenyl, and may contain heteroatoms.

[0033] The term "alkyl" refers to any monovalent, saturated, straight-chain, branched, or cyclic hydrocarbon group; the term "alkenyl" refers to any monovalent, straight-chain, branched, or cyclic hydrocarbon group containing one or more carbon-carbon double bonds, wherein the linkage site of the group may be at a carbon-carbon double bond or at other positions therein; and the term "alkynyl" refers to any monovalent, straight-chain, branched, or cyclic hydrocarbon group containing one or more carbon-carbon triple bonds and optionally one or more carbon-carbon double bonds, wherein the linkage site of the group may be at a carbon-carbon triple bond, a carbon-carbon double bond, or at other positions therein. Examples of alkyl groups include methyl, ethyl, propyl, and isobutyl. Examples of alkenyl groups include vinyl, propenyl, allyl, methylallyl, ethylidenylnorbornane, ethylidene norbornyl, ethylidenylnorbornene, and ethylidene norbornenyl. Examples of alkynyl groups include ethynyl, propynyl, and methylethynyl.

[0034] The terms "cyclic alkyl," "cyclic alkenyl," and "cyclic alkynyl" encompass bicyclic, tricyclic, and higher cyclic structures, as well as those further substituted with alkyl, alkenyl, and / or alkynyl groups. Representative examples include norbornyl, norbornenyl, ethylnorbornyl, ethylnorbornenyl, cyclohexyl, ethylcyclohexyl, ethylcyclohexenyl, cyclohexylcyclohexyl, and cyclododecanetrienyl.

[0035] The term "aryl" means any monovalent aromatic hydrocarbon group; the term "aralkyl" means any alkyl group (as defined herein) in which one or more hydrogen atoms are replaced by the same number of the same and / or different aryl groups (as defined herein); and the term "alkylaryl" means any aryl group (as defined herein) in which one or more hydrogen atoms are replaced by the same number of the same and / or different alkyl groups (as defined herein). Examples of aryl groups include phenyl and naphthyl. Examples of aralkyl groups include benzyl and phenethyl. Examples of alkylaryl groups include tolyl and xylyl.

[0036] This disclosure provides single-component grease compositions, reprocessable pre-cured thermogel compositions, and two-component post-curing compositions comprising crosslinked silicone gels, alkenyl-functionalized diorganopolysiloxane fluids, hydrogen-functionalized organopolysiloxanes, alkoxy-functionalized surface wetting agents (dispersants) or hydrolyzable organopolysiloxanes, thermally conductive fillers, additives, and pigments. Ultra-high thermal conductivity is achieved through the use of dispersants and organofunctionalized silicone fluids with cubic boron nitride and other thermally conductive fillers. Although these thermal compositions consist of hard fillers such as cubic boron nitride and AlN fillers, they exhibit remarkable thermal stability exceeding 1000 hours at very high temperatures (150°C), not only due to optimization of the fillers and filler ratios but also due to optimization of the composition of the organofunctionalized silicone fluids and dispersants.

[0037] In single-component pre-cured thermogel compositions, thermal conductivity > 12 W / mK is accompanied by low hardness accumulation.

[0038] In the two-part post-curing (addition-curing) thermal composition, a thermal conductivity of >16 W / mK was achieved, accompanied by dispensability of >9 g / min.

[0039] The filler combination is optimized to achieve an optimal mix that provides high thermal conductivity (TC) and a dispensable formulation. It can be noted that while any two, three, or more fillers can be combined to obtain a formulation, this approach rarely works and results in powdery or low-TC formulations. Only after performing DOE and optimization can we obtain the optimal filler combination that enhances filler packing, thereby providing high thermal conductivity while maintaining paste-like rheological properties, viscosity, and flowability. The filler combination can be described as consisting of three or more fillers: (C-1) is the largest filler type (50-200 μm), which provides the largest domain size to provide high thermal conductivity pathways and thus enhanced thermal conductivity. For the largest filler, inherently high-TC materials such as BN, cubic BN, SiC, diamond, and AlN are utilized, which enhance the overall conductivity of the formulation. The next filler (C-2) is a medium-sized filler of ~0.5-120 μm, which provides enhanced contact and gap filling between the larger fillers. These fillers are composed of alumina, cubic BN, or aluminum nitride powder, or combinations thereof. The smallest filler (C-3) with a D50 of ~0.01-15 μm can be composed of ZnO, alumina, SiC, and / or aluminum nitride fillers, or combinations thereof. Even with their large surface area, these fillers enhance the overall TC by constructing numerous filler-polymer-dispersant contacts, as well as filler-filler and filler-substrate contacts. They also provide the desired lubrication and thixotropic effects to the formulation. As a result of careful experimental studies, we have demonstrated here that specific fillers and filler combinations, when used as thermally conductive fillers, can achieve thermally conductive formulations with excellent thermal conductivity (>12 W / mK), electrical insulation flexibility, and moldability, and can be easily manufactured at low cost, thus completing this invention.

[0040] In this paper, cubic BN and other thermally conductive fillers are used to optimize the filler to achieve ultra-high thermal conductivity and good thermal stability.

[0041] This disclosure can define many different ranges for one or more components in a composition. It will be understood that the values ​​of the individual ranges can be combined to form new and unspecified ranges.

[0042] In one aspect, a composition is provided comprising a polymer and at least one thermal conductivity enhancer, wherein the composition has a hardness (Shore E) of less than 25 as determined using an ASTM D2240 hardness tester, and a thermal conductivity of greater than 12 W / mK as determined by the hot plate method or the ASTM D5470 method.

[0043] In one embodiment, the polymer is a silicone polymer.

[0044] In one embodiment, the silicone polymer comprises

[0045] (i) Alkenyl-functionalized diorganopolysiloxanes of formula (Ia)

[0046] M 1 a M 2 b D 1 c D 2 d T 1 e T 2 fQ g (Ia)

[0047] in: M 1 =R 1 R 2 R 3 SiO 1 / 2 M 2 =R 4 R 5 R 6 SiO 1 / 2 D 1 =R 7 R 8 SiO 2 / 2 D 2 =R 9 R 10 SiO 2 / 2 T 1 =R 11 SiO 3 / 2 T 2 =R 12 SiO 3 / 2 Q=SiO 4 / 2 Where R 2 R 3 R 4 R 5 R 6 R 8 R 9 R 10 R 12 Each is independently selected from aliphatic, aromatic, or fluorinated monovalent hydrocarbon groups, or alkoxy groups, having 1 to 60 carbon atoms; R 1 R 7 R 11Each is independently selected from aliphatic, aromatic, or fluorinated monovalent hydrocarbons having 1 to 60 carbon atoms and containing at least one terminal olefinic bond; and The subscripts a, b, c, d, e, f, and g are zero or positive integers subject to the following restrictions: 1 ≤ a + b + c + d + e + f + g ≤ 6000, and a + c + e ≥ 1; and (ii) Hydrogen-functionalized organopolysiloxanes of formula (Ib)

[0048] in: M 1 =R 13 R 14 R 15 SiO 1 / 2 M 2 =R 16 R 17 R 18 SiO 1 / 2 D 1 =R 19 R 20 SiO 2 / 2 D 2 =R 21 R 22 SiO 2 / 2 T 1 =R 23 SiO 3 / 2 T 2 =R 24 SiO 3 / 2 Q=SiO 4 / 2 Where R 14 R 15 R 16 R 17 R 18 R 20 R 21 R 22 R 24 It is an aliphatic, aromatic, or fluorinated monovalent hydrocarbon group having 1 to 60 carbon atoms; R 13 R 19 R 23 It is hydrogen; The subscripts a', b', c', d', e', f', and g' are zero or positive integers subject to the following restrictions: 1 ≤ a'+b'+c'+d'+e'+f'+g' ≤ 6000, and a'+c'+e' ≥ 1; The condition is that when a'+c'+e'=1, then a+c+e>1, and when a+c+e=1, then a'+c'+e'>1; or the crosslinked products of (i) and (ii).

[0049] Component (i) is an organopolysiloxane represented by formula (Ia) and having at least two alkenyl groups bonded to silicon atoms in one molecule. The viscosity of component (i) at 25°C is 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, it cannot maintain fluidity. The viscosity values ​​mentioned above and elsewhere in this application are measured using a Brookfield rotational viscometer. There are no particular limitations on the organopolysiloxane, as long as it meets the above viscosity and alkenyl content requirements, and known organopolysiloxanes can be used. The molecular structure of the organopolysiloxane can be linear, branched, partially branched linear, dendritic, etc. Preferably, the structure is linear or partially branched linear. Component (i) can be a single polymer having such a structure, a copolymer having such a structure, or a mixture of two or more organopolysiloxanes with different viscosities. Furthermore, component (i) can be used in combination with a monoalkenyl-terminated organopolysiloxane having one alkenyl group bonded to a silicon atom per molecule. This organopolysiloxane has a viscosity range of 0.001 to 1 Pa·s, preferably 0.006 to 0.1 Pa·s, at 25°C. Combining this organopolysiloxane with component (i) (an organopolysiloxane having at least two alkenyl groups bonded to a silicon atom per molecule) improves flowability and, in the case of the cured product, facilitates achieving the low hardness required for thermal interface materials.

[0050] Component (ii) is an organohydrogen polysiloxane represented by formula (Ib) and having hydrogen atoms directly bonded to silicon atoms. Specifically, it is an organohydrogen polysiloxane having at least two hydrogen atoms (hydrosilyl groups) directly bonded to silicon atoms in one molecule and acts as a crosslinking agent for component (i). The hydrosilyl groups of component (ii) and the alkenyl groups of component (i) are added together by a hydrosilylation reaction (described later) promoted by a platinum-based metal catalyst to produce a three-dimensional network structure including a crosslinked structure. If the number of hydrosilyl groups in component (ii) is less than two, curing cannot be obtained. The amount of component (ii) added is such that the hydrosilyl groups of component (ii) are 0.1 to 5.0 moles of alkenyl groups relative to 1 mole of component (i) (i.e., the molar amount of hydrogen atoms directly bonded to silicon atoms is 0.1 to 5.0 times the molar amount of alkenyl groups of component (i), preferably 0.2 to 2.0 moles, and more preferably 0.3 to 1.0 moles. If the amount of silyl group in component (ii) is less than 0.1 moles of alkenyl group in 1 mole of component (i), curing may not be achieved 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 cured product loses its flexibility and becomes brittle.

[0051] In one embodiment, the composition comprises a first thermal conductivity enhancer, a second thermal conductivity enhancer, and a third thermal conductivity enhancer.

[0052] In another embodiment, the first thermal conductivity enhancer is selected from boron nitride, cubic boron nitride, silicon carbide, diamond, and aluminum nitride.

[0053] In another embodiment, the second thermal conductivity enhancer is selected from alumina, boron nitride, cubic boron nitride, and aluminum nitride.

[0054] In another embodiment, the third thermal conductivity enhancer is selected from alumina, zinc oxide, SiC, and aluminum nitride.

[0055] In another embodiment, the viscosity of the composition is [value missing] at 1 s [value missing]. -1 Greater than 100 Pa·s. Steady-state shear viscosity and thixotropy were determined using a rheometer (RS-600) with a parallel plate geometry (measuring geometry gap of 500 μm).

[0056] In another embodiment, the polymer is present in an amount ranging from 1% to 8% by weight of the composition.

[0057] In another embodiment, the gradient of the thermal resistance of the composition relative to the thickness variation is 100 Kmm. 2 / W or smaller.

[0058] In another embodiment, the composition has a dispensability of 4 g / min or greater.

[0059] In another embodiment, the composition has a Shore E hardness of 0 to 90.

[0060] In another embodiment, the composition has an adhesive layer thickness of less than 350 μm. Compression at 1 MPa is applied for 30 seconds on a 10 × 10 × 0.5 mm Si chip.

[0061] In another embodiment, the composition is a single-part cross-linked silicone gel formulation, a two-part curable formulation, or a grease formulation.

[0062] It will be understood that thermal conductivity enhancers may comprise mixtures of compounds of a single type, wherein the mixture includes compounds of different average particle sizes. In one embodiment, the thermal conductivity enhancer comprises cubic boron nitride, ZnO, aluminum nitride, boron nitride, SiC, and aluminum oxide.

[0063] The particle size of the thermal conductivity enhancer can be selected according to the needs of a specific purpose or intended application. As used herein, unless the context otherwise requires, "particle size" refers to the volume average particle size. In embodiments, the thermal conductivity enhancer has the following average particle sizes: about 0.01 μm to about 500 μm; about 0.1 to about 250 μm; about 1 to about 100 μm; about 5 to about 75 μm; and even about 10 to about 50 μm. It will be understood that the composition may comprise a combination of thermal conductivity enhancers with different average particle sizes. Such a combination can be selected according to the needs of a specific purpose or intended application. In one embodiment, the composition comprises a first thermal conductivity enhancer having an average particle size of about 0.01 to less than 15 μm; a second thermal conductivity enhancer having an average particle size of about 0.5 μm to about 120 μm; and a third thermal conductivity enhancer having an average particle size of about 50 μm to about 200 μm. The first, second, and third thermal conductivity enhancers may be the same as or different from each other in terms of the chemical composition of the filler. Particle size can be determined by any suitable method. Average particle size is often provided or reported by the material supplier. Average particle size can be determined by measuring particle size distribution via laser diffraction and scattering according to JIS R 1629. In this study, the median diameter (D50) obtained by measurement based on a volumetric datum is used as the average particle size. The filler may be present in amounts of about 80% to about 99% by weight, about 82% to about 96% by weight, or about 85% to about 95% by weight, based on the total weight of the composition.

[0064] Crosslinked silicone gels may also be referred to herein as pre-cured gels or polymer gels. Crosslinked silicone gels are prepared by reacting an alkenyl-functionalized diorganopolysiloxane with a hydrogen-functionalized organopolysiloxane. The reaction can be carried out using a suitable catalyst via hydrosilylation reaction conditions. Conventional hydrosilylation catalysts are platinum-based catalysts (e.g., but not limited to Karstedt catalysts). In one embodiment, the pre-cured gel can be prepared by Pt-catalyzed hydrosilylation of a linear vinyl-terminated polysiloxane with a side-terminated poly(hydrosiloxane) or poly(methylhydrosiloxane) copolymer (crosslinking agent) or a crosslinked MT or MQ resin containing Si-H reactive groups. Similar gel networks can also be achieved by reacting a side-terminated vinyl silicone polymer with a terminally terminated poly(hydrosiloxane) or poly(methylhydrosiloxane) copolymer or a crosslinked MT or MQ resin containing Si-H reactive groups via a Pt-catalyzed hydrosilylation pathway. The effective Si-H / Si-olefin molar ratio [r] for forming Si-C bonds must satisfy r ≤ 0.3. The final "gel rheology" must meet the following condition: a) 0.2≤G'≤1000 (Pa); b) 0.1≤G” / G'≤10; The term G' represents the "storage shear modulus" of the final pre-cured gel composition in a thermal interface material formulation, measured by a stress- or strain-controlled rheometer at an oscillation frequency of 1 Hz or 6.28 rad / s at T=25°C, and the term G'' represents the "loss shear modulus" of the final pre-cured gel composition in a thermal interface material formulation, measured by a stress- or strain-controlled rheometer at an oscillation frequency of 1 Hz or 6.28 rad / s at T=25°C. G'' and G' are measured together in their respective viscoelastic regions.

[0065] The following examples are intended to illustrate aspects and implementations of the technology. Unless otherwise expressly stated, all parts and percentages are by weight, and all temperatures are in degrees Celsius. All patents, other publications, and US patent applications mentioned in this application are incorporated herein by reference in their entirety.

[0066] Example

[0067] Steady-state shear viscosity and thixotropy were determined using a rheometer (RS-600) with a parallel plate geometry (measuring geometry gap of 500 μm). Hardness of the cured (2-part) formulation was measured using an ASTM D2240 hardness tester (Shore E).

[0068] The bulk thermal conductivity of the thermal composition was measured using a hot plate instrument at 22°C, and thermal resistance and thermal conductivity were also measured using ASTM D5470.

[0069] Dispensability was measured by filling an Optimum 30cc syringe with a 2 mm opening EFD with the sample and dispensing it at 90 psi using an automatic dispenser (Nordson EFD), and measuring the volume dispensed per minute.

[0070] BLT was determined by applying a compression of 1 MPa for 30 seconds on a 10 × 10 × 0.5 mm Si chip.

[0071] The crystallite size was measured by XRD using an X-ray diffractometer system with the following parameters: a copper target (Kα line) at a wavelength of 1.54 Å, an accelerating voltage of 40 kV, a tube current of 30 mA, a scan rate of 4 ° / min, and a step size of 0.02 °.

[0072] Surface oxygen content was measured by XPS using an X-ray photoelectron spectrometer with the following features: Al Kα source, 2 x 10⁻⁹ Torr vacuum level, hemispherical analyzer, 0.7 sec residence time, 1 eV energy step, and 0.1 eV HR scan.

[0073] The compositions were prepared according to the examples listed in Tables 1 and 2.

[0074] The divinyl-terminated organopolysiloxane (A-1a) has a viscosity of 0.1 Pa·s and is expressed by the following formula:

[0075] Each X represents vinyl, and n ranges from 20 to 400.

[0076] The divinyl-terminated organopolysiloxane (A-1b) has a viscosity of 0.03 Pa·s and is expressed by the following formula:

[0077] Each X represents vinyl, and n is 10 to 20.

[0078] The monovinyl-terminated organopolysiloxane (A-2a) has a viscosity of 0.02 Pa·s and is expressed by the following formula:

[0079] Where X is vinyl and m is 20 to 100.

[0080] The monovinyl-terminated organopolysiloxane (A-2b) has a viscosity of 0.01 Pa·s and is expressed by the following formula:

[0081] Where X is vinyl and m is 10 to 20.

[0082] The crosslinking agent, organohydrogen polysiloxane (B-1), has a viscosity range of 0.01 to 0.1 Pa·s, a Si-H content of 0.05 to 0.5% by weight, and in the examples, a compound of the following formula with a viscosity of 0.02 Pa·s is used: .

[0083] Where o is between 20 and 100, and p is between 2 and 20.

[0084] Synthesis of a crosslinked silicone gel (X-1) with a viscosity of 11.6 Pas: Vinyl-terminated PDMS (500 g, MW ~17280 g / mol, vinyl MEQ ~0.115) was added to a dual planetary mixer at room temperature along with a Pt catalyst (2 wt% Karstedt catalyst, 10 ppm Pt) and an inhibitor (Surfynol® 61, 200 ppm), and allowed to mix at 20 rpm for 30 min at room temperature. Silicone hydride (55.4 g, MW ~40802, hydride MEQ ~0.1586) was added to the reaction mixture at 50 °C, and mixing was continued at 20 rpm for an additional 1 h. While mixing continued at the same rate at 50 °C, a vacuum was applied for 60 min to remove the inhibitor and form a gel network. The reaction temperature was then increased to 90 °C and continued until all hydride was consumed and a gel formed.

[0085] The pre-cured gel formulation was prepared in a Thinky mixer. First, specific amounts of dispersant, vinyl PDMS fluid, and gel were weighed into a plastic container and mixed at 2000 rpm for 30 seconds. Diamond and other thermally conductive fillers with variable particle sizes were gradually added to the mixture, and all materials were mixed at 2000 rpm for 30 seconds at each step using the Thinky mixer. After each 30-second mixing step, the formulation was manually mixed for 2 minutes using a wide-bladed spatula. Finally, the mixture was mixed 1-2 times at 2000 rpm for 30 seconds each time to obtain a homogeneous paste.

[0086] A two-part curable formulation, similar to a pre-cured gel formulation, was also prepared. Part A and Part B were prepared separately, mixed in equal amounts, and cured at 70°C for 1 hour.

[0087] Cubic boron nitride was purchased from Funik (China).

[0088] Aluminum nitride was purchased from Toyo Aluminum.

[0089] Nano zinc oxide was purchased from Zochem.

[0090] Cubic BN has a volume average 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)) and a surface oxygen content greater than 5%.

[0091] Aluminum nitride with volume-average particle sizes of 1.2, 5, 20 and 70 μm (C-2a, C-2b, C-2c and C-2d, respectively).

[0092] Nano zinc oxide with a volume average particle size of 0.16 μm (C-3).

[0093] (D-1) is a hydrolyzable organopolysiloxane (II-i) represented by the following formula:

[0094] (Formula II-i)

[0095] (D-2) represents a hydrolyzable polyorganosiloxane represented by a compound of formula (II-ii):

[0096] (Formula II-ii)

[0097] E-1 is selected from 3,3'-thiodipropionate didodecyl ester or 2,4,6-tris(3',5'-di-tert-butyl-4'-hydroxybenzyl)trimethylbenzene, and is used as an additive in formulations.

[0098] F-1 is an inhibitor, bis(1,1-dimethyl-2-propynoxy)dimethylsilane.

[0099] G-1 is a platinum-based catalyst: an 18% by weight solution of a 2% platinum-containing vinyl dimer complex in a monovinyl-terminated organopolysiloxane (viscosity 0.02 Pa·s). The amount of platinum in the composition may be 7 ppm.

[0100] Ultra-high thermal conductivity two-part addition-curing thermal composition: TIA2101GF is a commercial two-part silicone formulation manufactured by Momentive Performance Materials.

[0101] The two-part addition-curable thermal compositions were prepared with different filler percentages and achieved ultra-high thermal conductivity (>16 W / mK) accompanied by good dispensability (>13 g / min). They were cured at 70°C for 1 hour by mixing part-A and part-B in a 1:1 ratio. The H / Vi ratio of the cured samples ranged from 0.4 to 1.0. F-1 was a 1.5 wt% solution of bis-{(1,1-dimethyl-2-propynyl)oxy}dimethylsilane (BIS-{(1,1-DIMETIL-2-PROPINIL)OXI DIMETIL-SILAN) in a crosslinking agent, organohydrogen polysiloxane (viscosity 0.02 Pa·s).

[0102] Table 1

[0103]

[0104] As can be seen from Table 1, Examples 1 and 2 show a thermal conductivity of >16 W / mK, accompanied by distributability of >9 g / min.

[0105] Ultra-high thermal conductivity cross-linked silicone gel thermal composition: Table 2

[0106] As can be seen from Table 2, Examples 3, 4, 5 and 7 even showed a thermal conductivity of >12 W / mK after aging at 150°C for 1000 hours, accompanied by low hardness accumulation (Shore E within 25).

[0107] Figure 1 The cumulative hardness data (Shore E) of the thermal composition based on the pre-cured silicone gel CBN of part 1 after aging at 150°C are shown (Examples 3 to 7).

[0108] The embodiments of the invention have been described above. It is certainly impossible to describe every conceivable combination of components or methods for the purposes of describing the invention, but those skilled in the art will recognize that many further combinations and arrangements of the invention are possible. Therefore, the invention is intended to cover all such changes, modifications, and variations that fall within the spirit and scope of the appended claims. Furthermore, to the extent used in the specific embodiments or claims, such a term is intended to be inclusive in a manner similar to the term "comprising," as illustrated when "comprising" is used as a transitional word in the claims.

[0109] The foregoing description defines various non-limiting embodiments of the thermogel composition. Modifications will be conceived by those skilled in the art, as well as those capable of making and using the invention. The disclosed embodiments are for illustrative purposes only and are not intended to limit the scope of the invention or the subject matter set forth in the claims.

[0110] Other embodiments of the present invention are provided below.

[0111] Embodiment 1: A composition comprising a polymer and at least one thermal conductivity enhancer, wherein the composition has a hardness (Shore E) of less than 50 as measured using an ASTM D2240 hardness tester, and a thermal conductivity of greater than 12 W / mK as measured by the hot plate method or the ASTM D5470 method.

[0112] Embodiment 2: The composition according to Embodiment 1, wherein the polymer is a silicone polymer.

[0113] Embodiment 3: The composition according to Embodiment 2, wherein the silicone polymer comprises

[0114] (i) Alkenyl-functionalized diorganopolysiloxanes of formula (Ia)

[0115] M 1 a M 2 b D 1 c D 2 d T 1 e T 2 f Q g (Ia)

[0116] in: M 1 =R 1 R 2 R 3 SiO 1 / 2 M 2 =R 4 R 5 R 6 SiO 1 / 2 D 1 =R 7 R 8 SiO 2 / 2 D 2 =R 9 R 10 SiO 2 / 2 T 1 =R 11 SiO 3 / 2 T 2 =R 12 SiO 3 / 2 Q=SiO 4 / 2 Where R 2 R 3 R 4 R 5 R 6 R 8 R 9 R 10 R 12 Each is independently selected from aliphatic, aromatic, and fluorinated monovalent hydrocarbon groups, or alkoxy groups, having 1 to 60 carbon atoms; R 1 R 7 R 11 Each is independently selected from aliphatic, aromatic, or fluorinated monovalent hydrocarbons having 1 to 60 carbon atoms and containing at least one terminal olefinic bond; and The subscripts a, b, c, d, e, f, and g are zero or positive integers subject to the following restrictions: 1 ≤ a + b + c + d + e + f + g ≤ 6000, and a + c + e ≥ 1; and (ii) Hydrogen-functionalized organopolysiloxanes of formula (Ib)

[0117] in: M 1 =R 13 R 14 R 15 SiO 1 / 2 M 2 =R 16 R 17 R 18 SiO 1 / 2 D 1 =R 19 R 20 SiO 2 / 2 D 2 =R 21 R 22 SiO 2 / 2 T 1 =R 23 SiO 3 / 2 T 2 =R24 SiO 3 / 2 Q=SiO 4 / 2 Where R 14 R 15 R 16 R 17 R 18 R 20 R 21 R 22 R 24 It is an aliphatic, aromatic, or fluorinated monovalent hydrocarbon group having 1 to 60 carbon atoms; R 13 R 19 R 23 It is hydrogen; The subscripts a', b', c', d', e', f', and g' are zero or positive integers subject to the following restrictions: 1 ≤ a'+b'+c'+d'+e'+f'+g' ≤ 6000, and a'+c'+e' ≥ 1; The condition is that when a'+c'+e'=1, then a+c+e>1, and when a+c+e=1, then a'+c'+e'>1; Or the cross-linked products of (i) and (ii).

[0118] Embodiment 4: The composition according to Embodiments 1 to 3, wherein the composition comprises a first thermal conductivity enhancer, a second thermal conductivity enhancer and a third thermal conductivity enhancer.

[0119] Embodiment 5: The composition according to Embodiment 4, wherein the first thermal conductivity enhancer is selected from boron nitride, cubic boron nitride, silicon carbide, diamond, and aluminum nitride.

[0120] Embodiment 6: The composition according to Embodiment 4, wherein the second thermal conductivity enhancer is selected from alumina, boron nitride, cubic boron nitride, and aluminum nitride.

[0121] Embodiment 7: The composition according to Embodiment 4, wherein the third thermal conductivity enhancer is selected from alumina, zinc oxide, SiC and aluminum nitride.

[0122] Embodiment 8: The composition according to any one of Embodiments 1 to 7, wherein the composition has a viscosity greater than 100 Pa·s.

[0123] Embodiment 9: The composition according to any one of Embodiments 1 to 7, wherein the polymer is present in an amount ranging from 1% to 8% by weight of the composition.

[0124] Embodiment 10: The composition according to any one of Embodiments 1 to 7, wherein the composition has 100 Kmm 2 / W or a smaller gradient of thermal resistance relative to the thickness variation.

[0125] Embodiment 11: The composition according to any one of Embodiments 1 to 7, wherein the composition has a Shore E hardness of 0 to 90.

[0126] Embodiment 12: The composition according to any one of Embodiments 1 to 7, wherein the composition has a dispensability of 4 g / min or greater.

[0127] Embodiment 13: The composition according to any one of Embodiments 1 to 7, wherein the composition has an adhesive layer thickness of less than 350 μm.

[0128] Embodiment 14: The composition according to any one of Embodiments 1-13, wherein the composition is a single-part crosslinked silicone gel formulation, a two-part curable formulation, or a grease formulation.

Claims

1. A composition comprising a polymer and at least one thermal conductivity enhancer, wherein the composition has a hardness (Shore E) of less than 50 as determined using an ASTM D2240 hardness tester, and a thermal conductivity of greater than 12 W / mK as determined by the hot plate method or the ASTM D5470 method.

2. The composition according to claim 1, wherein the polymer is a silicone polymer.

3. The composition according to claim 2, wherein the silicone polymer comprises (i) Alkenyl-functionalized diorganopolysiloxanes of formula (Ia) M 1 a M 2 b D 1 c D 2 d T 1 e T 2 f Q g (Ia) in: M 1 =R 1 R 2 R 3 SiO 1 / 2 M 2 =R 4 R 5 R 6 SiO 1 / 2 D 1 =R 7 R 8 SiO 2 / 2 D 2 =R 9 R 10 SiO 2 / 2 T 1 =R 11 SiO 3 / 2 T 2 =R 12 SiO 3 / 2 Q=SiO 4 / 2 Where R 2 R 3 R 4 R 5 R 6 R 8 R 9 R 10 R 12 Each is independently selected from aliphatic, aromatic, and fluorinated monovalent hydrocarbon groups, or alkoxy groups, having 1 to 60 carbon atoms; R 1 R 7 R 11 Each is independently selected from aliphatic, aromatic, or fluorinated monovalent hydrocarbons having 1 to 60 carbon atoms and containing at least one terminal olefinic bond; and The subscripts a, b, c, d, e, f, and g are zero or positive integers subject to the following restrictions: 1 ≤ a + b + c + d + e + f + g ≤ 6000, and a + c + e ≥ 1; and (ii) Hydrogen-functionalized organopolysiloxanes of formula (Ib) in: M 1 =R 13 R 14 R 15 SiO 1 / 2 M 2 =R 16 R 17 R 18 SiO 1 / 2 D 1 =R 19 R 20 SiO 2 / 2 D 2 =R 21 R 22 SiO 2 / 2 T 1 =R 23 SiO 3 / 2 T 2 =R 24 SiO 3 / 2 Q=SiO 4 / 2 Where R 14 R 15 R 16 R 17 R 18 R 20 R 21 R 22 R 24 It is an aliphatic, aromatic, or fluorinated monovalent hydrocarbon group having 1 to 60 carbon atoms; R 13 R 19 R 23 It is hydrogen; The subscripts a', b', c', d', e', f', and g' are zero or positive integers subject to the following restrictions: 1 ≤ a'+b'+c'+d'+e'+f'+g' ≤ 6000, and a'+c'+e' ≥ 1; The condition is that when a'+c'+e'=1, then a+c+e>1, and when a+c+e=1, then a'+c'+e'>1; Or the cross-linked products of (i) and (ii).

4. The composition according to any one of claims 1 to 3, wherein the composition comprises a first thermal conductivity enhancer, a second thermal conductivity enhancer, and a third thermal conductivity enhancer.

5. The composition according to claim 4, wherein the first thermal conductivity enhancer is selected from boron nitride, cubic boron nitride, silicon carbide, diamond, and aluminum nitride.

6. The composition according to claim 4, wherein the second thermal conductivity enhancer is selected from alumina, boron nitride, cubic boron nitride, and aluminum nitride.

7. The composition according to claim 4, wherein the third thermal conductivity enhancer is selected from alumina, zinc oxide, SiC and aluminum nitride.

8. The composition according to any one of claims 1 to 7, wherein the composition has a viscosity greater than 100 Pa·s.

9. The composition according to any one of claims 1 to 7, wherein the polymer is present in an amount ranging from 1% to 8% by weight of the composition.

10. The composition according to any one of claims 1 to 7, wherein the composition has a density of 100 K mm. 2 / W or a smaller gradient of thermal resistance relative to the thickness variation.

11. The composition according to any one of claims 1 to 7, wherein the composition has a Shore E hardness of 0 to 90.

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

13. The composition according to any one of claims 1 to 7, wherein the composition has an adhesive layer thickness of less than 350 μm.

14. The composition according to any one of claims 1 to 13, wherein the composition is a single-part crosslinked silicone gel formulation, a two-part curable formulation, or a grease formulation.

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