Thermally conductive composition

Abstract

Disclosed is a composition comprising a polymer and at least one thermal conductivity improver. The composition has a dispensing amount of more than 12 g / min at 90 psi when determined using a Nordson's EFD automatic dispenser and a 30-cc syringe having a 2-mm opening, and also has a thermal conductivity of more than 12 W / mK when determined by the hot disk method or the ASTM D5470 method.

Description

Thermally conductive composition

[0001] The present invention relates to compositions comprising a polymer and at least one thermal conductivity enhancer, resulting in high thermal conductivity and high throughput.

[0002] As electronic devices develop toward miniaturization and high-density integration, the heat generated by electronic devices gradually increases, and thermal failures become a major problem that impairs the performance, reliability, and lifespan of electronic devices. Therefore, efficient thermal management is crucial to solving this problem. To improve heat removal from electronic devices, thermal interface materials (TIMs) are widely used between two solid contact surfaces, i.e., a heat source and a heat sink. These materials come in various forms, such as greases, gap fillers, pre-cured gels, curable materials (one-component or two-component), phase-change materials, elastomeric pads, adhesives, thermal tapes, metal alloys, and solders. The gap between the two solid surfaces (chip and heat sink) is non-uniform or otherwise filled with air, which has low thermal conductivity. The thermal interface material fills this gap to provide a thermal conduction path. If desired, multiple thermal interface materials may be used between different solid surfaces to provide a continuous conduction path for heat removal.

[0003] The emergence of 5G communication technology in the telecommunications sector and the Internet of Things (IoT) in the consumer and industrial sectors will further increase the performance demands on TIMs. 5G and IoT devices (using 5G) will operate at higher frequencies, higher device densities, higher bandwidths, lower latency, small feature sizes, and lower power, along with the demands for much higher reliability and availability. These factors have made the heat removal requirements for electronic devices much more stringent, and a general trend in industry has been to move from low thermal conductivities of 3-5 W / mK to TIMs with an average of 6-10 W / mK, and to develop even higher thermal conductivities exceeding 10 W / mK. The development of next-generation integrated circuits (ICs), three-dimensional (3D) integration, and ultra-high-speed, high-power-density communication devices is placing extremely stringent demands on thermal management.

[0004] Conventional TIMs filled with thermally conductive particles require a high volume fraction (v > 50%) of fillers such as alumina or ZnO to achieve composite thermal conductivity (TC) in the range of 1–5 W / mK. Many products also utilize metallic fillers such as aluminum when electrical conductivity requirements are relaxed. However, additional fillers such as BN fillers, AlN fillers, diamond fillers, SiC fillers, and combinations thereof have been disclosed in numerous patent applications to achieve high TC (> 10 W / mK). The advantage of these fillers is that they are electrically insulating and have much higher thermal conductivity (high TC fillers). In addition to thermal conductivity, TIM formulations must exhibit a variety of other important properties for use in applications. These may include low thermal resistance, low volatility, low pump-out, low bleed-out, low cracking, thermal stability, hardness, high output rate for application at a given viscosity, shear rate, pump pressure, etc. Property stability during low-high temperature cycling / impact should also be demonstrated by testing up to 1000-2000 hours. These properties are achieved by careful design of the TIM formulation, combining the appropriate polymer-resin-dispersant combination with high filler loading in the composition, as disclosed below.

[0005] Japanese Patent No. 7007161 describes a composition containing a diamond filler, in which the diamond filler has a granular shape (non-spherical, more preferably polyhedral, more preferably hexahedral, octahedral, etc., and particularly preferably hexahedral), has 10 to 18 faces, and has a sphericity of more than 0.2. The size of the diamond is 0.01 to 100 μm. The difference between the true specific gravity of the diamond and the true specific gravity of the thermal conductivity improver is 0.2 to 4 g / cm. ３The ratio of the volume average particle size of the thermal conductivity enhancer to the volume average particle size of the diamond is 0.01 to 0.5. The overall thermal conductivity shown is low, <10 W / mK. Japanese Patent No. 7084143 describes a heat dissipation composition, a heat dissipation member, and a filler aggregate for a heat dissipation member. The composition contains diamond (greater than 15 volume % diamond) along with multiple fillers exhibiting a thermal conductivity greater than 10 W. It also mentions a total void volume (<3%), a contact angle (<70°) of the polymer matrix to the thermally conductive filler containing diamond particles, and the diamond particles have a surface oxygen content (>5%). Japanese Patent No. 2938428 describes a heat-reducing grease containing liquid silicone in combination with diamond and a thermally conductive inorganic filler such as AlN, having a consistency ranging from 280 to 350 and a thermal conductivity ranging from 2.5 to 4 W / mK. Chinese Patent No. 112226199 describes an insulating composition of ultra-high thermal conductivity curable paste, which contains thermally conductive fillers such as diamond and functional fillers such as ferric oxide, and has a thermal conductivity of 11.8 W / mK and a throughput of 33 g per minute.

[0006] However, there is room for improvement in the jettability and thermal conductivity of such compositions.

[0007] The present invention provides thermal conductivity greater than 12 W / mK while maintaining good jettability and meeting all of the desired properties of low pump-out, low bleed-out, low cracking, low hardness increase, and reliability during low-temperature cycling / shock (-40°C to 150°C) for up to 500-1000 hours. The present invention incorporates diamond as the primary filler in a thermally conductive composition.

[0008] The following presents a summary of the disclosure to provide a basic understanding of some aspects of the invention. This summary is not intended to identify key or critical elements, nor is it intended to define any limitations on the embodiments or claims. Moreover, this summary may provide a simplified overview of some aspects that may be described in more detail in other parts of the disclosure.

[0009] In one embodiment, there is provided a composition comprising a polymer and at least one thermal conductivity enhancer, the composition having a delivery rate of greater than 12 g / min at 90 psi using a Nordson EFD automated dispenser using a 30 cc syringe with a 2 mm opening, and a thermal conductivity of greater than 12 W / mK as determined by the hot disk method described in ISO 22007-2 or the test method according to ASTM D5470.

[0010] In one embodiment, the polymer is a silicone polymer.

[0011] In one embodiment, the silicone polymer is: (i) an alkenyl-functionalized diorganopolysiloxane M of formula (Ia): １ ａ M ２ ｂ D １ ｃ D ２ ｄ T １ ｅ T ２ ｆ Q ｇ (Ia) [wherein, 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 , R５ , R ６ , R ８ , R ９ , R １０ , R １２ are each independently selected from monovalent aliphatic, aromatic and fluorohydrocarbon groups or alkoxy groups having 1 to 60 carbon atoms; R １ , R ７ , R １１ are each independently selected from monovalent aliphatic, aromatic, or fluorohydrocarbon radicals having from 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 0 or positive integers, subject to the limitations that 1≦a+b+c+d+e+f+g≦6000 and a+c+e≧1; and (ii) a hydrogen-functionalized organopolysiloxane M of formula (Ib): １ ａ′ M ２ ｂ′ D １ ｃ′ D ２ ｄ′ T １ ｅ′ T ２ ｆ′ Q ｇ′ (1b) [wherein, 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 is a monovalent aliphatic, aromatic or fluorohydrocarbon radical having 1 to 60 carbon atoms; R １３ , R １９ , R ２３ is hydrogen; and the subscripts a', b', c', d', e', f' and g' are 0 or positive integers, subject to the limitations that 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 the crosslinked product of (i) and (ii).

[0012] In one embodiment, the composition comprises a first thermal conductivity enhancer and a second thermal conductivity enhancer.

[0013] In another embodiment, the first thermal conductivity enhancer is diamond, preferably single crystal diamond.

[0014] In yet another embodiment, the second thermal conductivity enhancer is selected from the group consisting of aluminum oxide, zinc oxide, boron nitride, SiC, and aluminum nitride.

[0015] In another embodiment, the viscosity of the composition is greater than 100 Pa s, measured using a Brookfield type rotational viscometer at 23° C. with a No. 7 rotor at 4 rpm after 3 minutes.

[0016] In yet another embodiment, the polymer is present in an amount ranging from 1 to 6% by weight of the composition.

[0017] In another embodiment, the gradient of the change in thermal resistance value with respect to the change in thickness of the composition is 100 Kmm ２ / W or less.

[0018] In another embodiment, the composition has a Shore E hardness of 0-90.

[0019] In another embodiment, the composition has a bond line thickness (BLT) of 150 μm or greater.

[0020] In another embodiment, the composition is 1×10 １０ It has a volume resistivity of Ω·cm or greater.

[0021] In another embodiment, the composition has a dielectric strength of 5 kV / mm or greater.

[0022] FIG. 1 shows the test data for the vertical stability behavior of Example 6.

[0023] 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 that structural and functional changes may be made. Furthermore, features of various embodiments may be combined or substituted. Thus, the following description is presented by way of example only and is not intended to limit in any way the various alternatives and modifications that may be made to the exemplary embodiments. In this disclosure, numerous specific details are provided to provide a thorough understanding of the subject disclosure. It should be understood that aspects of the present disclosure may be implemented using other embodiments that do not necessarily include all of the aspects set forth herein.

[0024] As used herein, the words "example" and "exemplary" mean an instance or illustration. The words "example" or "exemplary" do not indicate a primary or preferred aspect or embodiment. The word "or" is intended to be inclusive rather than exclusive, unless the context suggests otherwise. As an example, the phrase "A uses B or C" includes any inclusive permutation (e.g., A uses B, A uses C, or A uses both B and C). As a separate matter, the articles "a" and "an" are generally intended to mean "one or more," unless the context suggests otherwise.

[0025] As used herein, the term "thermal conductivity enhancer" refers to 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 or mixtures thereof, such as boron nitride, aluminum nitride, aluminum oxide, zinc oxide, aluminum metal, silicon carbide, carbon-based fillers such as graphite and diamond, and metal fillers such as aluminum and silver.

[0026] As used herein, the terms "precured gel" or "crosslinked silicone gel" refer to a fluid-extended polymer system that may contain a continuous polymer phase or network, which may be chemically or physically crosslinked, for example, by ionic or covalent bonds, and an oil, such as a silicone or other oil, a plasticizer, unreacted monomer, or other fluid extender that fills the interstices of the network by swelling or otherwise. The crosslink density and extender proportion of such a network can be controlled to adjust the modulus, i.e., softness, and other properties of the gel. The term "precured gel" should also be understood to encompass materials that may be broadly classified as pseudogels or gel-like substances, which have a "loose" crosslinked network formed by relatively long crosslinked chains, but which otherwise have viscoelastic properties similar to gels, for example, by not having a fluid extender.

[0027] 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 allenyl, and may contain heteroatoms.

[0028] The term "alkyl" means any monovalent saturated linear, branched, or cyclic hydrocarbon group; the term "alkenyl" means any monovalent linear, branched, or cyclic hydrocarbon group containing one or more carbon-carbon double bonds, where the point of attachment of the group may be at the carbon-carbon double bond or elsewhere therein; and the term "alkynyl" means any monovalent linear, branched, or cyclic hydrocarbon group containing one or more carbon-carbon triple bonds and optionally one or more carbon-carbon double bonds, where the point of attachment of the group may be at the carbon-carbon triple bond, the carbon-carbon double bond, or elsewhere therein. Examples of alkyl include methyl, ethyl, propyl, and isobutyl. Examples of alkenyl include vinyl, propenyl, allyl, methallyl, ethylidenylnorbornane, ethylidenenorbornyl, ethylidenylnorbornene, and ethylidenenorbornenyl. Examples of alkynyl include acetylenyl, propargyl, and methylacetylenyl.

[0029] The terms "cyclic alkyl," "cyclic alkenyl," and "cyclic alkynyl" include bicyclic, tricyclic, and higher polycyclic structures, as well as those cyclic structures which are further substituted with alkyl, alkenyl, and / or alkynyl groups. Representative examples include norbornyl, norbornenyl, ethylnorbornyl, ethylnorbornenyl, cyclohexyl, ethylcyclohexyl, ethylcyclohexenyl, cyclohexylcyclohexyl, and cyclododecatrienyl.

[0030] 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 an equal number of identical and / or different aryl (as defined herein) groups; and the term "allenyl" means any aryl group (as defined herein) in which one or more hydrogen atoms are replaced by an equal number of identical and / or different alkyl groups (as defined herein). Examples of aryl include phenyl and naphthalenyl. Examples of aralkyl include benzyl and phenethyl. Examples of allenyl include tolyl and xylyl.

[0031] The present disclosure provides one-component thermally conductive grease compositions, reworkable thermally conductive pre-cured gel compositions, and two-component thermally conductive compositions containing crosslinked silicone gel, alkenyl-functionalized diorganopolysiloxane fluid, hydrogen-functionalized organopolysiloxane, alkoxy-functionalized surface wetting agent (dispersant) or hydrolyzable organopolysiloxane, thermally conductive filler, additives, and pigments. Ultra-high thermal conductivity was achieved by using dispersants and organo-functionalized silicone fluids in conjunction with diamond and other thermally conductive fillers. Although these thermally conductive compositions may consist of diamond and hard fillers such as AlN fillers, they have demonstrated very stable long-term discharge rates and remarkable thermal stability at very high temperatures (150°C) for over 1,000 hours, based not only on the optimization of fillers and filler ratios, but also on the optimization of the composition using the organo-functionalized silicone fluid in combination with the dispersant.

[0032] The one-component thermally conductive pre-cured gel composition achieved a discharge rate of more than 12 g per minute and a thermal conductivity of more than 14 W / mK, and the hardness (Shore E) was within 10 at 150°C even after aging for 1000 hours, demonstrating stable dischargeability.

[0033] The two-component, post-cured (addition curable) thermally conductive composition achieved thermal conductivities of over 15 W / mK with output rates of over 13 g / min, exhibited less hardness increase at temperatures as high as 150°C, and showed stable output rates after aging.

[0034] The one-component thermally conductive grease composition may also include additives. The additives used in the present disclosure may be selected from one or a combination of two or more of the following: pigments, lubricants, viscosity modifiers, heat stabilizers, light stabilizers, antioxidants, flame retardants, inhibitors, adhesion promoters.

[0035] Thermal conductivities of over 12 W / mK have been achieved with one-component thermally conductive grease compositions, along with output rates of over 19 g / min.

[0036] Filler combinations are optimized to arrive at the best possible combination that provides a high TC and highly jettable composition. Therefore, while any two, three, or more fillers can be combined to obtain a composition, it should be noted that such an approach is rarely successful and results in powdery or low TC compositions. Only after experimental design and optimization can an optimal filler combination be obtained that improves filler packing, thus providing high thermal conductivity while maintaining paste-like rheology, viscosity, and flow properties. Filler combinations can be described as consisting of three or more fillers—(C-I) being the smallest fillers with a D50 of up to 1 micron, which may consist of alumina, ZnO, SiC, diamond, BN, and / or aluminum nitride fillers, or combinations thereof—which, despite their large surface area, improve the overall TC by providing multiple filler-polymer-dispersant contacts, along with filler-filler and filler-substrate contacts. They can also provide the desired lubricity and thixotropy effects to the composition. The next fillers (C-II) are intermediate size fillers ranging from 5 to 30 micrometers, which provide improved contact between larger fillers and gap filling. These fillers consist of alumina, diamond, BN, or aluminum nitride powder, or combinations thereof. The third filler (C-III) is the largest filler type (>30 micrometers), which provides the largest crystalline domain size to provide high thermal conductivity pathways, i.e., improved thermal conductivity. The largest fillers utilize materials with inherently high TC, such as BN, cubic BN, SiC, diamond, and AlN, which improve the overall conductivity of the composition. Careful experimental studies have revealed excellent thermal conductivity (>12 W / mK), throughput (>12 g / min), electrical insulation (volume resistivity >1×10 １０In order to achieve a thermally conductive composition that is flexible and moldable, has a high resistance to moisture (Ω-cm), and is easily manufacturable at low cost, specific fillers and combinations of fillers are demonstrated herein to be used as thermally conductive fillers, and the present invention has been completed.

[0037] Herein, filler optimization was performed using diamond and other thermally conductive fillers to achieve ultra-high thermal conductivity combined with good and stable discharge and good thermal stability.

[0038] The present disclosure may specify many different ranges for one or more components in the composition, and it will be understood that the numerical values ​​in each range can be combined to form new unspecified ranges.

[0039] In one aspect, there is provided a composition comprising a polymer and at least one thermal conductivity enhancer, the composition having a dispense rate of greater than 12 g / min as determined at 90 psi using a Nordson EFD automated dispenser using a 30 cc syringe with a 2 mm opening, and a thermal conductivity of greater than 12 W / mK as determined by the hot disk method described in ISO 22007-2 or the test method according to ASTM D5470.

[0040] In one embodiment, the polymer is a silicone polymer.

[0041] In one embodiment, the silicone polymer is: (i) an alkenyl-functionalized diorganopolysiloxane M of formula (Ia): １ ａ M ２ ｂ D １ ｃ D ２ ｄ T １ ｅ T ２ ｆ Q ｇ (Ia) [wherein, M １ =R １ R ２ R ３ SiO １／２ M ２ =R４ 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 are each independently selected from monovalent aliphatic, aromatic and fluorohydrocarbon groups or alkoxy groups having 1 to 60 carbon atoms; R １ , R ７ , R １１ are each independently selected from monovalent aliphatic, aromatic, or fluorohydrocarbon radicals having from 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 0 or positive integers, subject to the limitations that 1≦a+b+c+d+e+f+g≦6000 and a+c+e≧1; and (ii) a hydrogen-functionalized organopolysiloxane M of formula (Ib): １ ａ′ M ２ ｂ′ D １ ｃ′ D ２ ｄ′ T １ ｅ′ T ２ ｆ′ Q ｇ′ (1b) [wherein, M １ =R １３ R １４ R １５ SiO １／２M 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 is a monovalent aliphatic, aromatic or fluorohydrocarbon radical having 1 to 60 carbon atoms; R １３ , R １９ , R ２３is hydrogen; and the subscripts a', b', c', d', e', f', and g' are 0 or positive integers, subject to the restrictions that 1≦a'+b'+c'+d'+e'+f'+g'≦6000 and a'+c'+e'≧1, with the proviso that when a'+c'+e'=1, a+c+e>1, and when a+c+e=1, a'+c'+e'>1; or a crosslinked product of (i) and (ii). Component (i) is an organopolysiloxane represented by formula (Ia) and has at least two alkenyl groups bonded to silicon atoms per molecule. The viscosity of component (i) at 25°C may be in the range of 0.01 to 10 Pa·s, and preferably 0.06 to 1 Pa·s. If the viscosity at 25°C is less than 0.01 Pa·s, the storage stability of the composition deteriorates, while if it exceeds 10 Pa·s, flowability cannot be ensured. The viscosities described above and elsewhere in this application are measured using a Brookfield rotational viscometer. Such organopolysiloxanes are not particularly limited as long as they satisfy the above-mentioned viscosity and alkenyl group content, and known organopolysiloxanes can be used. Examples of the molecular structure of the organopolysiloxane include linear, branched, partially branched linear, and dendrimer. The molecular structure is preferably linear or partially branched linear. Component (i) may 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. Component (i) may also be used in combination with a monoalkenyl-terminated organopolysiloxane having one alkenyl group bonded to a silicon atom per molecule. The viscosity of this organopolysiloxane at 25°C may be in the range of 0.001 to 1 Pa·s, preferably 0.006 to 0.1 Pa·s. By using this polyorganosiloxane in combination with component (i), i.e., an organopolysiloxane having at least two silicon-bonded alkenyl groups per molecule, improved fluidity is obtained, and the cured product is more likely to achieve the low hardness required for a thermal interface material. Component (ii) is an organohydrogenpolysiloxane represented by formula (1b), which has hydrogen atoms directly bonded to silicon atoms.That is, it is an organohydrogenpolysiloxane having at least two hydrogen atoms (hydrosilyl groups) directly bonded to silicon atoms per molecule, and functions as a crosslinker for component (i). The hydrosilyl groups in component (ii) and the alkenyl groups in component (i) undergo addition via a hydrosilylation reaction promoted by a platinum group metal curing catalyst, as described below, to form a three-dimensional network structure with a crosslinked structure. If the number of hydrosilyl groups in component (ii) is less than two, curing is not achieved. The amount of component (ii) added is such that the ratio of hydrosilyl groups in component (ii) is 0.1 to 5.0 moles per mole of alkenyl groups in component (i), i.e., such that the number of moles of hydrogen atoms directly bonded to silicon atoms is 0.1 to 5.0 times the number of moles of alkenyl groups in component (i), preferably 0.2 to 2.0 moles, and more preferably 0.3 to 1.0 mole. If the amount of hydrosilyl groups in component (ii) is less than 0.1 moles per mole of alkenyl groups in component (i), curing may not be achieved or the strength of the cured product may be insufficient to handle as a molded article, whereas if the amount exceeds 5.0 moles, the cured product will lose flexibility and become brittle.

[0042] In one embodiment, the composition comprises a first thermal conductivity enhancer and a second thermal conductivity enhancer.

[0043] In another embodiment, the first thermal conductivity enhancer is diamond.

[0044] In yet another embodiment, the second thermal conductivity enhancer is selected from the group consisting of aluminum oxide, zinc oxide, boron nitride, SiC, and aluminum nitride.

[0045] In another embodiment, the viscosity of the composition is greater than 100 Pa s. Viscosity was measured using a Brookfield viscometer according to ASTM-D2196, No. 7 rotor, 4 rpm after 3 minutes.

[0046] In yet another embodiment, the polymer is present in an amount ranging from 1 to 6% by weight of the composition.

[0047] In another embodiment, the gradient of the change in thermal resistance value with respect to the change in thickness is 100 Kmm ２ / W or less.

[0048] In another embodiment, the composition has a Shore E hardness of 0-90.

[0049] In another embodiment, the composition has a bond line thickness (BLT) of 150 μm or more when the composition is sandwiched between two 10×10×0.5 mm Si chips and a pressure of 1 MPa is applied for 30 seconds.

[0050] In another embodiment, the composition has a thermal conductivity of 1×10 at 500 V and 1 mm thickness as measured according to ASTM D257. １０ It has a volume resistivity of Ω·cm or greater.

[0051] In another embodiment, the composition has a dielectric strength of 5 kV / mm or greater as measured in accordance with ASTM D149.

[0052] It will be appreciated that the thermal conductivity enhancer may include a mixture of compounds of a single type, but with compounds of different average particle sizes. In one embodiment, the thermal conductivity enhancer includes aluminum nitride, boron nitride, SiC, and aluminum oxide.

[0053] The particle size of the thermal conductivity enhancer can be selected as desired for a particular purpose or intended use. As used herein, "particle size" refers to the volume average particle size, unless the context indicates otherwise. In embodiments, the thermal conductivity enhancer has an average particle size of about 0.01 to about 500 μm, about 0.1 to about 250 μm, about 1 to about 100 μm, about 5 to about 75 μm, or even about 10 to about 50 μm. It will be understood that the composition can include a combination of thermal conductivity enhancers of different average particle sizes. Such combinations can be selected as desired for a particular purpose or intended use. In one embodiment, the composition includes a first thermal conductivity enhancer having an average particle size of about 0.01 μm to less than about 1 μm, a second thermal conductivity enhancer having an average particle size of about 1 μm to about 30 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 have the same or different filler chemical makeup. The particle size can be determined by any suitable method. The average particle size is often provided or reported by the material supplier. The average particle size can be determined by measuring particle size distribution using a laser diffraction / scattering method in accordance with JIS R1629. In this study, the volume-based median diameter (D50) obtained by measurement was used as the average particle size. The filler(s) can be present in an amount of about 80 wt % to about 99 wt %, about 82 wt % to about 96 wt %, or about 85 wt % to about 95 wt %, based on the total weight of the composition.

[0054] Crosslinked silicone gels may also be referred to herein as precured gels or polymer gels. Crosslinked silicone gels are made by reacting an alkenyl-functionalized diorganopolysiloxane with a hydrogen-functionalized organopolysiloxane. This reaction can be carried out under hydrosilylation reaction conditions using an appropriate catalyst. Common hydrosilylation catalysts are platinum-based catalysts (e.g., but not limited to, Karstedt's catalyst). In one embodiment, precured gels can be made by reacting a linear vinyl-end-capped polysiloxane with a pendant poly(hydrosiloxane) or poly(methylhydrosiloxane) copolymer (crosslinker) or a crosslinked MT or MQ resin containing Si—H reactive groups through a Pt-catalyzed hydrosilylation reaction. Similar gel networks can also be achieved through a Pt-catalyzed hydrosilylation route by reacting pendant vinyl silicone polymers with end-capped poly(hydrosiloxane) or poly(methylhydrosiloxane) copolymers or crosslinked MT or MQ resins containing Si—H reactive groups. The effective Si—H / Si-alkenyl molar ratio [r] reacted to form Si—C bonds must satisfy r≦0.3. The final "gel rheology" must satisfy the following conditions: a) 0.2≦G′≦1000 (Pa) b) 0.1≦G″ / G′≦10 Here, the term G′ represents the “storage shear modulus” of the final pre-cured gel composition used in the thermal interface material composition, measured at T=25°C under an oscillation frequency of 1 Hz or 6.28 rad / s using a stress or strain controlled rheometer, and the term G″ represents the “loss shear modulus” of the final pre-cured gel composition used in the thermal interface material composition, measured at T=25°C under an oscillation frequency of 1 Hz or 6.28 rad / s using a stress or strain controlled rheometer. G″ and G′ are measured together in their respective viscoelastic regions.

[0055] The following examples are intended to illustrate aspects and embodiments of the present technology. All parts and percentages are by weight and all temperatures are in degrees Celsius unless expressly stated otherwise. All patents, other publications and U.S. patent applications referenced in this application are hereby incorporated by reference in their entirety.

[0056] Example

[0057] Steady shear viscosity and thixotropy were determined using a TA Instruments rheometer (DHR-3) using parallel plate geometry (measurement geometry gap 300 μm).

[0058] The cured (two-part) formulations were hardness tested using an ASTM D2240 type durometer (Shore E).

[0059] The bulk thermal conductivity of the thermally conductive compositions was measured at 22°C using a hot disk apparatus, and the thermal resistance and thermal conductivity were measured according to ASTM D5470.

[0060] The sample was filled into a 30 cc syringe having an opening of 2 mm, called Optimum by EFD, and dispensed at 90 psi using an EFD automatic dispenser manufactured by Nordson Corporation, and the amount dispensed per minute was measured.

[0061] The composition was sandwiched between two Si chips of 10 x 10 x 0.5 mm, and a compression of 1 MPa was applied to the Si chips for 30 seconds to determine the BLT (bond line thickness).

[0062] The volume resistivity was measured in accordance with ASTM D257, and the dielectric strength was measured in accordance with ASTM D149.

[0063] Vertical sliding tests (vertical stability performance) were performed by placing 2 grams of the composition in a circle between an aluminum / alumina Q panel and a glass plate measuring 5 cm x 5 cm, using spacers of 0.5 mm, 1 mm, and 2 mm. The plates were clamped together with paper clips, placed in a vertical position, and subjected to temperature cycling or shock (-40 to 150°C).

[0064] The crystallite size was measured by XRD using an X-ray diffractometer with a copper target (Kα radiation) of 1.54 Å wavelength, an acceleration voltage of 40 kV, a tube current of 30 mA, a scan rate of 4° per minute, and a step width of 0.02°.

[0065] The surface oxygen content was measured using an Al Kα radiation source at a vacuum level of 2×10 －９ Torr, hemispherical analyzer, dwell time 0.7 seconds, energy step 1 eV and HR scan 0.1 eV were measured by XPS using an X-ray photoelectron spectrometer.

[0066] Compositions were prepared according to the examples shown in Tables 1, 2 and 3.

[0067] The divinyl-terminated organopolysiloxane (A-1a) has a viscosity of 0.1 Pa·s and is represented by the following formula: wherein each X is vinyl and n is 42. The divinyl-terminated organopolysiloxane (A-1b) has a viscosity of 0.03 Pa·s and is represented by the following formula: wherein each X is vinyl and n is 20.

[0068] The monovinyl-terminated organopolysiloxane (A-2a) had a viscosity of 0.02 Pa·s and was represented by the following formula: wherein X is vinyl and m is 30. The monovinyl-terminated organopolysiloxane (A-2b) has a viscosity of 0.01 Pa·s and is represented by the following formula: In the formula, X is vinyl and m is 20.

[0069] The crosslinker organohydrogenpolysiloxane (B-1) has a viscosity range of 0.01 to 0.1 Pa·s with an Si—H content of 0.05 to 0.5 wt %, and a compound of the following formula having a viscosity of 0.02 Pa·s was used in the examples:

[0070] Synthesis of a crosslinked silicone gel (X-1) with a viscosity of 11.6 Pa·s: Vinyl-terminated PDMS (500 g, MW ∼17280 g / mol, vinyl milliequivalent ∼0.115) along with a Pt catalyst (2 wt% Karstedt catalyst, 10 ppm Pt) and an inhibitor (Surfynol® 61, 200 ppm) were added to a double planetary mixer at room temperature and mixed at 20 rpm for 30 minutes at room temperature. Silicone hydride (55.4 g, MW ∼40802, hydride milliequivalent ∼0.1586) was added to the reaction mixture at 50°C, and mixing was continued at 20 rpm for an additional hour. While continuing mixing at the same speed at 50°C, a vacuum was applied for 60 minutes to remove the inhibitor and form a gel network. The reaction temperature was then increased to 90°C and continued until all the hydride was consumed and a gel was formed.

[0071] Precured gel compositions were prepared using a Thinky mixer. First, specific amounts of dispersant, vinyl-terminated PDMS fluid, and gel were weighed into a plastic container and mixed at 2000 rpm for 30 seconds. Diamonds and other thermally conductive fillers of various particle sizes were added to this mixture in stages, and all materials were mixed using the Thinky mixer at 2000 rpm for 30 seconds each time. After each 30-second mixing, the composition was hand-mixed for 2 minutes using a broad-blade spatula. Finally, one or two passes of mixing at 2000 rpm for 30 seconds were performed to obtain a uniform paste.

[0072] A two-component curable composition was also prepared in the same manner as the pre-cured gel composition: Components A and B were prepared separately, mixed in equal amounts, and cured at 70°C for 1 hour.

[0073] Irregular polycrystalline diamond was purchased from either HongXiang Company or Hexanovation Company.

[0074] Aluminum nitride was purchased from Toyo Aluminum Co., Ltd.

[0075] Nano zinc oxide was obtained from Zochem.

[0076] Irregular polycrystalline diamond (C-1) with a volume average particle size of 5.2 micrometers, a crystallite size of 428 Å, and a surface oxygen content of 8.1%

[0077] Irregular polycrystalline diamond (C-2) with a volume average particle size of 89 micrometers, a crystallite size of 1070 Å, and a surface oxygen content of 6.9%

[0078] Single crystal diamond (C-3) with a volume average particle size of 165 micrometers, a crystallite size of 1206 Å, and a surface oxygen content of 13.5%.

[0079] Single crystal diamond (C-4) with a volume average particle size of 107 micrometers, a crystallite size of 905 Å, and a surface oxygen content of 16.7%.

[0080] Single crystal diamond (C-4a) with a volume average particle size of 125 micrometers

[0081] Alumina nitride with volume average particle diameters of 1.2, 5, and 20 micrometers (C-5a, C-5b, and C-5c, respectively)

[0082] Nano zinc oxide (C-6) with a volume average particle size of 0.16 micrometers

[0083] (D-1) is a hydrolyzable organopolysiloxane (II-i) represented by the compound of the following formula:

[0084] (D-2) is a hydrolyzable polyorganosiloxane represented by the compound of formula (II-ii).

[0085] E-1 is decyltrimethoxysilane used as an additive in the composition.

[0086] Thermally conductive grease-type compositions using diamond in conjunction with other fillers

[0087] Table 1 shows four different optimizations that were performed for a thermally conductive grease composition that achieves high thermal conductivity and good discharge rate.

[0088] When irregularly shaped diamonds were used in the compositions (Comparative Examples 1 and 2), low delivery rates were observed and the compositions were not stable.

[0089] Single crystal diamond was used in conjunction with other thermally conductive fillers to improve the thermal conductivity, dischargeability, and stability of the thermally conductive compositions (Table 1). As can be seen from Table 1, Examples 1-4 have thermal conductivities of over 12 W / mK with discharge rates of over 19 g per minute.

[0090] Ultra-high thermal conductivity two-component addition-curing thermally conductive composition

[0091] TIA2101GF is a commercially available two-part silicone composition manufactured by Momentive Performance Materials.

[0092] Two-component, addition-curable thermally conductive compositions with different filler loadings were prepared, achieving ultrahigh thermal conductivity (>20 W / mK) with very good and stable discharge rates (>20 g / min) and good thermal stability (Table 2). Components A and B were mixed in a 1:1 ratio and cured at 70°C for 1 hour. The H / Vi ratios of the cured samples ranged from 0.4 to 0.9. F-1 is a 1.5 wt% solution of bis-{(1,1-dimethyl-2-propynyl)oxy}dimethyl-silane in a crosslinker organohydrogenpolysiloxane (viscosity 0.02 Pa·s). G-1 is a platinum-based catalyst: an 18 wt% solution of a vinyl dimer complex with 2% platinum in a monovinyl-terminated organopolysiloxane (viscosity 0.02 Pa·s). The amount of platinum may be 7 ppm in the composition.

[0093] As can be seen from Table 2, Examples 5 to 9 exhibited a thermal conductivity of more than 12 W / mK along with a discharge rate of more than 13 g per minute, and also exhibited a smaller increase in hardness at a high temperature of 150°C, and exhibited a stable discharge rate after aging.

[0094] As shown in FIG. 1, the vertical stability performance under thermal shock (from bottom to top, gaps of 0.5 mm, 1 mm, and 2 mm) of Example 6 after 500 hours under thermal shock (−40° C. to 150° C.) showed very good vertical stability.

[0095] Ultra-high thermal conductive crosslinked silicone gel composition

[0096]

[0097] As can be seen from Table 3, Examples 10 to 14 exhibited a discharge rate of more than 12 g per minute and a thermal conductivity of more than 14 W / mK, and the hardness (Shore E) was within 10 at 150°C even after aging for 1000 hours, indicating a stable discharge rate.

[0098] What has been described above includes examples of the present specification. While it is, of course, not possible for purposes of describing the present specification to describe every conceivable combination of elements or methodologies, one skilled in the art will recognize that many further combinations and permutations of the present specification are possible. Accordingly, the present specification is intended to embrace all such alternatives, modifications, and variations that fall within the spirit and scope of the appended claims. Furthermore, to the extent that the term "comprising" is used in either the detailed description or the claims, such term is intended to be as inclusive as "comprising," as the term "comprises" is interpreted when used as a transitional phrase in the claims.

[0099] The above description identifies various non-limiting embodiments of the thermally conductive gel composition. Modifications will occur to those skilled in the art and those able to make and use the invention. The disclosed embodiments are merely exemplary and are not intended to limit the scope of the invention or the subject matter defined in the claims.

Claims

1. A composition comprising a polymer and at least one thermal conductivity enhancer, the composition having a delivery rate of greater than 12 grams per minute at 90 psi using a Nordson EFD automated dispenser using a 30 cc syringe with a 2 mm opening, and a thermal conductivity of greater than 12 W / mK as determined by the Hot Disk Method or ASTM D5470 method.

2. The composition of claim 1, wherein said polymer is a silicone polymer.

3. The silicone polymer is: (i) an alkenyl-functionalized diorganopolysiloxane M of formula (Ia) １ ａ M ２ ｂ D １ ｃ D ２ ｄ T １ ｅ T ２ ｆ Q ｇ (Ia) [wherein, 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 are each independently selected from monovalent aliphatic, aromatic and fluorohydrocarbon groups or alkoxy groups having 1 to 60 carbon atoms; R １ , R ７ , R １１ are each independently selected from monovalent aliphatic, aromatic or fluorohydrocarbon radicals 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 0 or positive integers, subject to the limitations that 1≦a+b+c+d+e+f+g≦6000 and a+c+e≧1; and (ii) a hydrogen-functionalized organopolysiloxane M of formula (Ib): １ ａ′ M ２ ｂ′ D １ ｃ′ D ２ ｄ′ T １ ｅ′ T ２ ｆ′ Q ｇ′ (1b) [wherein, 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 is a monovalent aliphatic, aromatic or fluorohydrocarbon radical having 1 to 60 carbon atoms; R １３ , R １９ , R ２３ is hydrogen; and the subscripts a', b', c', d', e', f' and g' are 0 or positive integers, subject to the limitations that 1≦a'+b'+c'+d'+e'+f'+g'≦6000 and a'+c'+e'≧1, with the proviso that when a'+c'+e'=1, a+c+e>1, and when a+c+e=1, a'+c'+e'>1; or the crosslinked product of (i) and (ii).

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

5. The composition of claim 4, wherein said first thermal conductivity enhancer is diamond.

6. The composition of claim 4, wherein said second thermal conductivity enhancer is selected from the group consisting of aluminum oxide, zinc oxide, boron nitride, SiC and aluminum nitride.

7. The composition according to any one of claims 1 to 6, having a viscosity of more than 100 Pa·s.

8. The composition of any one of claims 1 to 6, wherein the polymer is present in an amount ranging from 1 to 6% by weight of the composition.

9. 100Kmm ２ The composition according to any one of claims 1 to 6, having a gradient of change in thermal resistance with respect to change in thickness of 1 / W or less.

10. The composition according to any one of claims 1 to 6, having a Shore E hardness of 0 to 90.

11. The composition of any one of claims 1 to 6, having a bond line thickness (BLT) of 150 μm or greater.

12. 1×10 １０ The composition of any one of claims 1 to 6, having a volume resistivity of Ω-cm or greater.

13. The composition according to any one of claims 1 to 6, having a dielectric strength of 5 kV / mm or more.

14. The composition according to any one of claims 1 to 13, which is a one-component crosslinked silicone gel composition, a two-component composition or a grease composition.

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