Aluminum nitride-filled thermally conductive silicon composition

Abstract

The composition comprises (a) a curable silicone composition, wherein (i) vinyldimethylsiloxy-terminated polydimethylpolysiloxane having a viscosity of 30 to 400 mPa*s; (ii) a SiH-functional crosslinking agent; and (iii) a hydrosilylation catalyst, wherein the molar ratio of the crosslinking agent SiH-functional group to the vinyl-functional group is 0.5:1 to 1:1; (b) an alkyl trialkoxysilane and / or mono-trialkoxysiloxy-terminated dimethylpolysiloxane treatment agent; and (c) a filler mix, wherein (i) spherical and irregularly shaped AlN particles, each having an average size of 30 micrometers or more, comprising 40 weight% or more of spherical and irregularly shaped AlN particles, wherein the spherical AlN filler is 40 to 60 weight% of the weight of the AlN filler; (ii) 25 to 35 weight percent of spherical Al2O3 particles having an average size of 1 to 5 micrometers; (iii) 10 to 15 weight percent of additional thermally conductive filler having an average size of 0.1 to 0.5 micrometers; and (iv) optionally, a filler mix comprising a BN filler having an average size greater than 20 micrometers, wherein the filler mix is ​​90 to 97 weight percent, and weight percent is relative to the weight of the composition unless otherwise noted.

Description

Technology Field

[0001] The present invention relates to a thermally conductive silicon composition containing an aluminum nitride filler. Background Technology

[0002] The industry's demand for smaller and more powerful electronic devices has increased the demand for thermally conductive materials useful for dissipating heat generated by these devices. For example, the telecommunications industry is undergoing a generational shift to 5G networks, which requires smaller, highly integrated electrical devices, accompanied by a doubling of required power (from 600 watts to 1,200 watts). If the heat generated by high power in smaller devices is not efficiently dissipated, it can damage the device. Thermally conductive interface materials are frequently used in electronics to thermally connect heat-generating and heat-dissipating components. To efficiently transfer heat between combined components, the thermally conductive composition preferably has a thermal conductivity of at least 8.0 watts per meter (W / m*K) when measured according to ASTM method D5470. At the same time, as electronic devices become miniaturized, it has become more critical to accurately and precisely apply the thermally conductive composition to the appropriate components during rapid production processes. In this regard, it is desirable for the thermally conductive material to have a large extrusion rate (ER) of more than 40 grams per minute (g / min) when measured at a pressure of 0.62 megapascals (90 pounds per square inch) in a standard 30 cubic centimeter EFD syringe package using the procedure described below in this application.

[0003] It is difficult to achieve both thermal conductivity and extrusion speed simultaneously in thermally conductive materials. Increasing the amount of thermally conductive filler can increase thermal conductivity, but it also increases viscosity, which hinders extrusion speed. Since boron nitride is a filler with high thermal conductivity, it might be thought that the thermal conductivity of the composition could be increased at a sufficiently low concentration to avoid excessively high viscosity. However, because boron nitride has a plate-like shape, even at a concentration of 40 volume% or more, the viscosity of the thermally conductive composition becomes too high, making it impossible to achieve an ER of more than 40 g / min.

[0004] There is a need to specify a thermally conductive composition capable of simultaneously achieving an ER of more than 40 g / min and a thermal conductivity of at least 8.0 W / m*K.

[0005] The present invention provides a thermally conductive material that simultaneously achieves an extrusion speed of more than 40 g / min and a thermal conductivity of at least 8.0 W / m*K. Additionally, the thermally conductive material is reactive and can be cured into a cured thermally conductive material.

[0006] The present invention is the result of a discovery that, in part, a specific blend of spherical and irregularly shaped aluminum nitride fillers having a particle size of 30 micrometers or more can be blended with a specific amount of spherical aluminum oxide filler having a particle size of 1 to 5 micrometers, and an additional amount of filler having an average particle size of 0.1 to 0.5 micrometers will provide a thermally conductive material that simultaneously achieves an ER of 40 g / min and a thermal conductivity of at least 8.0 W / m*K even in the absence of boron nitride.

[0007] In a first aspect, the present invention

[0008] (a) a curable silicone composition comprising: (i) a vinyldimethylsiloxy-terminated polydimethylpolysiloxane having a viscosity in the range of 30 to 400 millipascals*seconds; (ii) a silicon hydride functional crosslinker; and (iii) a hydrosilylation catalyst, wherein the molar ratio of silicon hydride functional groups to vinyl functional groups in the crosslinker is in the range of 0.5:1 to 1:1; (b) a filler treatment agent comprising one or both of alkyl trialkoxysilane and mono-trialkoxysiloxy-terminated dimethylpolysiloxane; (c) a thermally conductive filler mix comprising: (i) an aluminum nitride filler comprising a blend of spherical and irregularly shaped aluminum nitride particles in an amount of 40 weight% or more, wherein both the spherical and irregularly shaped particles have an average particle size of 30 micrometers or more, and the spherical aluminum nitride filler having a particle size of 30 micrometers or more is present at a concentration of 40 to 60 weight% of the total weight of the aluminum nitride filler having a particle size of 30 micrometers or more; (ii) spherical aluminum oxide particles in an amount of 25 weight% to 35 weight% having an average particle size of 1 to 5 micrometers; and (iii) an additional thermally conductive filler in an amount of 10 weight% to 15 weight% having an average particle size of 0.1 to 0.5 micrometers; and (iv) optionally, a thermally conductive composition comprising a thermally conductive filler mix including a boron nitride filler having an average particle size of more than 20 micrometers, wherein the weight percent of each thermally conductive filler is relative to the weight of the composition unless otherwise noted, and the total amount of the thermally conductive filler mix is ​​90 to 97 weight percent of the weight of the composition.

[0009] In a second embodiment, the present invention is an article comprising the thermally conductive composition of the first embodiment on another material.

[0010] The thermally conductive composition of the present invention is useful, for example, as a thermally conductive interface material between components of an electronic device. Specific details for implementing the invention

[0011] Where a date is not indicated along with a test method number, the test method refers to the most recent test method from the priority date of this document. References to test methods include both references to the testing association and the test method number. The following test method abbreviations and identifiers apply herein: ASTM refers to ASTM International methods; EN refers to European Norm; DIN refers to the Deutsches Institut für Normung; ISO refers to the International Organization for Standards; and UL refers to Underwriters Laboratory.

[0012] Products identified by trademark names refer to compositions available under these trademark names on the priority date of this document.

[0013] "Multiple" means two or more. "And / or" means "and, or alternatively." All ranges include endpoints unless otherwise specified. Unless otherwise noted, all weight % (wt%) values ​​are for the weight of the composition, and all volume % (vol%) values ​​are for the volume of the composition.

[0014] Unless otherwise noted, the “viscosity” of individual polysiloxanes is determined by ASTM D 445 using a glass capillary Cannon-Fenske type viscometer at 25°C (°F).

[0015] standard 1 H, 13 C and 29The chemical structure of the polysiloxane is determined by Si nuclear magnetic resonance (NMR) analysis. The average particle size of the filler particles is determined as the median particle size (D50) using a laser diffraction particle size analyzer (CILAS920 particle size analyzer or Beckman Coulter LS 13 320 SW) according to the operation software.

[0016] The thermally conductive composition comprises a curable silicone composition comprising vinyldimethylsiloxy-terminated polydimethylpolysiloxane (PDMS), a silicon-hydride (SiH) functional crosslinker, and a hydrosilylation catalyst. The relative concentrations of vinyldimethylsiloxy-terminated PDMS and the SiH functional crosslinker may be in the range of a molar ratio of SiH functional groups to vinyl functional groups from the crosslinker from 0.5:1 to 1:1, and may be 0.5:1 or higher, 0.6:1 or higher, 0.7:1 or higher, 0.8:1 or higher, or even 0.9:1 or higher, and simultaneously 1:1 or lower, 0.9:1 or lower, 0.8:1 or lower, 0.7:1 or lower, or even 0.6:1 or lower.

[0017] Vinyldimethylsiloxy-terminated PDMS has a viscosity of 30 millipascals*seconds (mPa*s) or more, preferably 45 mPa*s or more, 60 mPa*s or more, and may have a viscosity of 90 mPa*s or more, 100 mPa*s or more, 120 mPa*s or more, 140 mPa*s or more, 160 mPa*s or more, and even 180 mPa*s or more, and simultaneously has a viscosity of 400 mPa*s or less, 300 mPa*s or less, 200 mPa*s or less, 180 mPa*s or less, even 160 mPa*s or less, 140 mPa*s or less, 120 mPa*s or less, 100 mPa*s or less, 80 mPa*s or less, or even 60 mPa*s or less. If the viscosity is too high, the viscosity of the thermally conductive composition becomes too high, making it impossible to achieve the desired extrusion speed. If the viscosity is too low, the thermally conductive composition becomes too low, leading to poor mechanical properties and a risk of chalking.

[0018] Vinyldimethylsiloxy-terminated PDMS preferably has the following chemical structure (I):

[0019] Vi(CH3)2SiO-[(CH3)2SiO] n -Si(CH3)2Vi (I)

[0020] In the above formula, "Vi" refers to a vinyl group (-CH=CH2), and n refers to the average number of dimethylsiloxane units, which is the degree of polymerization (DP) for vinyldimethylsiloxy-terminated PDMS. n is selected to achieve a desired viscosity for vinyldimethylsiloxy-terminated PDMS. Typically, n is a value of 25 or more, and may be 30 or more, 35 or more, 40 or more, 45 or more, 50 or more, 60 or more, 70 or more, 80 or more, or even 90 or more, and at the same time, typically 200 or less, 190 or less, 180 or less, 170 or less, 160 or less, 150 or less, 140 or less, 130 or less, 120 or less, 100 or less, 90 or less, 80 or less, 70 or less, 60 or less, or even 50 or less.

[0021] Preferably, vinyldimethylsiloxy-terminated PDMS contains 1.2 to 1.4 weight percent of vinyl functional groups.

[0022] Suitable divinyl PDMS materials can be prepared by ring-opening polymerization of cyclosiloxanes using vinyl end blockers for termination, as taught in U.S. Patent No. 5883215A. Suitable commercially available divinyl PDMSs include polysiloxanes available from Gelest under the name DMS-V21.

[0023] The SiH functional crosslinker is a polysiloxane containing SiH functional groups. Preferably, the SiH functional crosslinker contains two or more, even three or more, SiH functional groups per molecule. Preferably, the SiH functional crosslinker has a concentration of SiH that is 0.1 wt% or more, 0.2 wt% or more, 0.3 wt% or more, 0.4 wt% or more, 0.5 wt% or more, 0.6 wt% or more, 0.7 wt% or more, 0.8 wt% or more, or even 0.9 wt% or more, based on the weight of the SiH functional crosslinker. At the same time, the SiH has a concentration of 1.0 wt% or less, 0.9 wt% or less, 0.8 wt% or less, 0.7 wt% or less, 0.6 wt% or less, 0.5 wt% or less, even 0.4 wt% or less, or 0.3 wt% or less.

[0024] The SiH functional crosslinker may preferably comprise one or more polysiloxanes having a chemical structure selected from (II) and (III):

[0025] H(CH3)2SiO-[(CH3)2)SiO)] x -Si(CH3)2H (II)

[0026] (CH3)3SiO-[(CH3)HSiO] y [(CH3)2)SiO] z -Si(CH3)3(III)

[0027] In the above formula,

[0028] The subscript x has a value in the range of 10 to 100, and may be 10 or more, 15 or more, 20 or more, 30 or more, 40 or more, 50 or more, 60 or more, 70 or more, or even 80 or more, and at the same time, generally 100 or less, 90 or less, 80 or less, 70 or less, 60 or less, 50 or less, 40 or less, 30 or less, or even 20 or less;

[0029] The subscript y has a value in the range of 3 to 30, and may be 3 or greater, 4 or greater, 5 or greater, 10 or greater, 15 or greater, 20 or greater, or even 25 or greater, and at the same time generally 30 or less, 25 or less, 20 or less, 15 or less, 10 or less, 9 or less, 8 or less, 7 or less, 6 or less, 5 or less, or even 4 or less;

[0030] The subscript z has a value in the range of 3 to 100, and can be 3 or more, 5 or more, 10 or more, 15 or more, 20 or more, 30 or more, 40 or more, 50 or more, 60 or more, 70 or more, and even 80 or more, and at the same time generally 100 or less, 90 or less, 80 or less, 70 or less, 60 or less, 50 or less, 40 or less, 30 or less, 20 or less, 10 or less, and can be 5 or less, and even 4 or less.

[0031] Suitable commercially available SiH functional crosslinkers include those available from Gelest under the names HMS-071, MHS-301, and DMS-H11.

[0032] The hydrosilylation catalyst may be any suitable hydrosilylation catalyst. Preferably, the hydrosilylation catalyst comprises a platinum-based catalyst, such as a Speier catalyst (H2PtCl6) and / or a Karstedt catalyst (an organoplatinum compound derived from a divinyl-containing disiloxane, also identified as a platinum-divinyltetramethyldisiloxane complex or a 1,3-diethenyl-1,1,3,3-tetramethyldisiloxane platinum complex). The hydrosilylation catalyst may or may not be encapsulated (typically in a phenyl resin). The concentration of the hydrosilylation catalyst is typically 0.01 wt% or more, 0.02 wt% or more, 0.03 wt% or more, 0.04 wt% or more, and even 0.05 wt% or more with respect to the weight of the thermally conductive composition, and at the same time exists at a concentration of 0.10 wt% or less, 0.09 wt% or less, 0.08 wt% or less, 0.07 wt% or less, or even 0.06 wt% or less.

[0033] The thermally conductive composition also comprises one or more filler treatment agents. The filler treatment agents comprise one or both of alkyl trialkoxysilane and mono-trialkoxysiloxy-terminated dimethylpolysiloxane.

[0034] The alkyltrialkoxysilane is preferably a 6 to 20 carbon (C6-C20) alkyl trimethoxysilane, preferably a C8-C12 alkyl trimethoxysilane, and may be an n-decyltrimethoxysilane. Suitable alkyltrialkoxysilanes include DOWSIL™ Z-6210 silane from Dow, Inc. (DOWSIL is a trademark of The Dow Chemical Company) or an n-decyltrimethoxysilane available from Gelest under the name SID2670.0.

[0035] An example of a suitable mono-trialkoxysiloxy-terminated dimethylpolysiloxane has the chemical structure (IV):

[0036] (CH3)3SiO-[(CH3)2SiO] a -Si(OR')3(IV)

[0037] In the above formula, the subscript a has a value of 20 or greater, and may be 30 or greater, 40 or greater, 50 or greater, 60 or greater, 70 or greater, 80 or greater, or even 90 or greater, and at the same time is typically 150 or less, 140 or less, 130 or less, 120 or less, 110 or less, 100 or less, 90 or less, 80 or less, 70 or less, 60 or less, 50 or less, 40 or less, or even 30 or less. A value of a is preferably 20 or greater (degree of polymerization 20 or greater), because the mono-trialkoxysiloxy-terminated dimethylpolysiloxane has greater stability than when a is less than 20. However, it is desirable to keep the value of a below 150 because short chain lengths lower viscosity more efficiently than long chain lengths. R' is preferably an alkyl group containing 1 to 12 carbon atoms (C1-C12), and most preferably methyl.

[0038] Suitable mono-trialkoxysiloxy-terminated dimethylpolysiloxane can be synthesized in accordance with the teachings of U.S. Patent Application Publication US2006 / 0100336.

[0039] Preferably, the alkyltrialkoxysilane is typically present at a concentration of 1.8 wt% or more, 2.0 wt% or more, 2.5 wt% or more, 3.0 wt% or more, and even 3.5 wt% or more, and at the same time is typically present at a concentration of 4.0 wt% or less, 3.5 wt% or less, or even 3.0 wt% or less, where wt% is relative to the weight of the thermally conductive composition.

[0040] At the same time, or alternatively, mono-trialkoxysiloxy-terminated dimethylpolysiloxane is present at a concentration of preferably 0.05 wt% or more, 0.1 wt% or more, 0.2 wt% or more, 0.3 wt% or more, or even 0.4 wt% or more with respect to the weight of the thermally conductive composition, and at the same time, typically at a concentration of 0.5 wt% or less, 0.4 wt% or less, 0.3 wt% or less, or 0.2 wt% or less.

[0041] The thermally conductive composition further comprises a thermally conductive filler mix. The thermally conductive filler mix includes all thermally conductive fillers in the thermally conductive composition. Thermally conductive fillers refer to fine particles that facilitate heat conduction through the thermally conductive composition.

[0042] The filler mix comprises a blend of spherical and irregularly shaped aluminum nitride particles. "Spherical" shaped particles refer to particles having an aspect ratio of 1.0 + / - 0.2. The aspect ratio of the particles is determined by taking the average ratio of the longest dimension (major axis) and the shortest dimension (minor axis) of at least 10 particles using scanning electron microscope (SEM) imaging. "Irregular" shaped particles have an aspect ratio other than 1.0 + / - 0.2 and have at least three faces evident by SEM imaging, which distinguishes them from "plate-shaped" particles having an aspect ratio other than 1.0 + / - 2 and two faces.

[0043] Both spherical and irregular aluminum nitride fillers have an average particle size of 30 micrometers or more, and at the same time, typically have an average particle size of 200 micrometers or less, 175 micrometers or less, 150 micrometers or less, 125 micrometers or less, 100 micrometers or less, or even an average particle size of 90 micrometers or less, or 80 micrometers or less.

[0044] The concentration of aluminum nitride filler in this blend is preferably 40 wt% or more, 41 wt% or more, 42 wt%, 43 wt% or more, 44 wt% or more, 45 wt% or more, 50 wt% or more, 55 wt% or more, and 60 wt% or more, based on the weight of the thermally conductive composition as the sum of any and all aluminum nitride fillers in the thermally conductive composition, and at the same time generally 63 wt% or less, 60 wt% or less, 55 wt% or less, 50 wt% or less, 45 wt% or less, 44 wt% or less, and even 43 wt% or less.

[0045] Spherical aluminum nitride particles are present at a concentration of 40 wt% or more, 45 wt% or more, 50 wt% or more, or even 55 wt% or more, and simultaneously present at a concentration of 60 wt% or less, and may be present at a concentration of 55 wt% or less, 50 wt% or less, or even 45 wt%, where wt% is relative to the total weight of aluminum nitride having a particle size of 30 micrometers or more. In particular, the thermally conductive composition may have aluminum nitride filler particles in addition to a specific blend of spherical and irregularly shaped aluminum nitride particles described above, or the thermally conductive composition may not have aluminum nitride filler particles in addition to a specific blend of spherical and irregularly shaped aluminum nitride particles described above.

[0046] The thermally conductive filler mix further comprises spherical aluminum oxide particles. The spherical aluminum oxide particles may have an average particle size of 1 micrometer or more, 2 micrometers or more, 3 micrometers or more, or even 4 micrometers or more, and simultaneously have an average particle size of 5 micrometers or less, 4 micrometers or less, even 3 micrometers or less, or 2 micrometers or less. The concentration of spherical aluminum oxide particles may be 25 weight% or more and 30 weight% or more based on the weight of the thermally conductive composition, and simultaneously 35 weight% or less and 30 weight% or less.

[0047] The thermally conductive filler mix comprises one or more additional thermally conductive fillers having an average particle size of 0.1 micrometer or more, 0.2 micrometer or more, 0.3 micrometer or more, or even 0.4 micrometer or more, and simultaneously having an average particle size of 0.5 micrometer or less, and may have an average particle size of 0.4 micrometer or less, 0.3 micrometer or less, or even 0.2 micrometer or less. The total amount of additional thermally conductive fillers may be present at a concentration of 10 wt% or more, 11 wt% or more, 12 wt% or more, 13 wt% or more, or even 14 wt% or more, and simultaneously may be 15 wt% or less, 14 wt% or less, 13 wt% or less, 12 wt% or less, or even 11 wt% or less, where wt% is relative to the weight of the thermally conductive composition. An additional thermally conductive filler is selected from any filler known in the art, including metal nitrides and metal oxides (e.g., aluminum oxide, magnesium oxide, and zinc oxide). Preferably, the additional thermally conductive filler is zinc oxide.

[0048] Optionally, the thermally conductive filler mix may contain a boron nitride filler having an average particle size greater than 20 micrometers. At the same time, typically, the boron nitride filler will have an average particle size of 200 micrometers or less, 175 micrometers or less, 150 micrometers or less, 125 micrometers or less, and even 100 micrometers or less, 75 micrometers or less, or 50 micrometers or less.

[0049] The thermally conductive filler may include thermally conductive fillers other than those mentioned, or may not include thermally conductive fillers other than those mentioned. The thermally conductive filler mix preferably consists of the aluminum nitride filler described above, aluminum oxide particles, additional thermally conductive fillers, and optional boron nitride fillers. The thermally conductive filler mix (and the thermally conductive composition as a whole) may not contain magnesium oxide fillers, boron nitride fillers, or both magnesium oxide fillers and boron nitride fillers.

[0050] The concentration of the thermally conductive filler mix in the thermal composition may be 90 wt% or more, 91 wt% or more, 92 wt% or more, 93 wt% or more, 94 wt% or more, 95 wt% or less, and even 96 wt% or more, based on the weight of the thermally conductive composition, and at the same time may be 97 wt% or less, even 96 wt% or less, and even 95 wt% or less.

[0051] The thermally conductive composition may further comprise or may not comprise any combination of any one or more of the following additional components: an inhibitor (e.g., methyl(tris(1,1-dimethyl-2-propynyloxy))silane), a thermal stabilizer and / or pigment (e.g., copper phthalocyanine powder), a thixotropic agent, fumed silica (preferably surface-treated), and a spacer additive (e.g., glass beads).

[0052] The thermally conductive composition achieves an extrusion rate of over 40 g / min when measured at a pressure of 0.62 megapascals (90 pounds per square inch) in a standard 30 cubic centimeter EFD syringe package (details are provided under the extrusion rate characteristics analysis below). These characteristics allow the thermally conductive composition to be easily dispensed for application onto other materials.

[0053] At the same time, the thermally conductive composition achieves the objective of having a thermal conductivity of at least 8.0 W / m*K when measured according to ASTM D-5470 using a LonGwin Model LW 9389 TIM thermal resistance and conductivity measuring instrument. Having such high thermal conductivity and being easily distributable makes the thermally conductive composition particularly useful as a thermal interface material (TIM). TIMs are used to thermally bond two articles or components of a device. For example, TIMs are particularly useful in electronic products for thermally bonding a heating device with a heat sink, cooling plate, metal cover, or other heat dissipation component. In such applications, the thermally conductive composition exists between at least two components, typically a heating device and at least one of the following—a heat sink, cooling plate, metal cover, or other heat dissipation component—and is in thermal contact with them.

[0054] Examples

[0055] Table 1 lists materials for use in the thermally conductive composition of the samples described below in this application. Note: "Vi" refers to a vinyl group. "Me" refers to a methyl group. SYL-OFF and DOWSIL are trademarks of The Dow Chemical Company.

[0056] [Table 1]

[0057]

[0058]

[0059] Sample manufacturing

[0060] The formulations for the samples are in Tables 2 and 3, and the amount of each component is reported in grams (g). Note: "Weight % spherical AlN" refers to the weight % of spherical AlN of 30 micrometers or larger relative to all AlN particles of 30 micrometers or larger.

[0061] A sample is prepared using Flack Components’ SpeedMixer™ DAC 400 FVZ to mix the components together. Vi polymer, crosslinker, treatment agent, and C2 and C3 TC fillers are added to the SpeedMixer cup. Mix at 1,000 revolutions per minute (RPM) for 20 seconds, then mix at 1,500 RPM for 20 seconds. Add half of the C1 TC filler and mix at 1,000 RPM for 20 seconds, then mix at 1,500 RPM for 20 seconds. Add the remaining C1 TC filler and mix in the same manner. To ensure mixing, scrape the composition from the cup, then add inhibitor E-1 and pigment F-1 and mix in a similar manner to obtain a thermally conductive composition sample.

[0062] Sample Feature Analysis

[0063] Each sample is characterized for extrusion speed and thermal conductivity using the following test methods:

[0064] Extrusion Speed ​​Characteristic AnalysisDetermine the extrusion rate ("ER") for the sample using Nordson EFD dispensing equipment. Load the sample material into a 30 cubic centimeter syringe (Nordson Company EFD syringe) with a 2.54 mm opening. Dispense the sample through the opening by applying a pressure of 0.62 MPa to the syringe. After 1 minute, the mass of the sample, expressed in grams (g), corresponds to an extrusion rate of grams per minute (g / min). The object of the present invention is to achieve an extrusion rate of greater than 40 g / min, preferably greater than 50 g / min, and more preferably greater than 60 g / min. In particular, some samples are reported to have an ER of 0 because they are powder pastes that cannot be extruded (and TC is not measured).

[0065] Analysis of thermal conductivity characteristics The thermal conductivity ("TC: thermal conductivity") for each sample is measured according to ASTM D-5470 using the LonGwin Model LW 9389 TIM thermal resistance and conductivity measuring device of Longwin Science and Technology Corporation of Taiwan. The object of the present invention is to achieve a thermal conductivity of at least 8.0 watts (W / m*K) per meter*Kelvin.

[0066] [Table 2]

[0067]

[0068] [Table 3]

[0069]

[0070] Data Analysis / Discussion

[0071] All formulations in Table 2 achieve two objectives: an ER greater than 40 g / min and a TC greater than 8.0 W / m*K. In contrast, the formulations in Table 3 do not achieve at least one of these objectives.

[0072] Samples 1 to 7 show thermally conductive compositions having spherical aluminum nitride particles of 30 micrometers or more and a total aluminum nitride particle weight of 30 micrometers or more ranging from 40% by weight to 60% by weight, and show formulations in this range having aluminum nitride particles of various sizes.

[0073] Samples 1 through 5 also contain boron nitride particles, whereas samples 6 and 7 do not. These samples demonstrate that target TC and ER are achievable in formulations with or without boron nitride. These samples also show that the inclusion of boron nitride generally produces a more desirable higher TC formulation.

[0074] Samples A to C exemplify formulations having only irregularly shaped aluminum nitride particles of 30 micrometers or larger, and indicate that when only irregularly shaped aluminum nitride exists with a size of 30 micrometers or larger, the ER is less than 40 g / min.

[0075] Samples D, E, G to I, and M exemplify formulations having only spherical aluminum nitride particles of 30 micrometers or larger, and indicate that the TC values ​​of these formulations are less than 8.0 W / m*K. Formulations G to I explore the effect of adding boron nitride, magnesium oxide, or aluminum oxide to increase the TC, but still fail to obtain a TC value of 8.0 W / m*K or higher.

[0076] Sample F exemplifies a formulation having a blend of spherical and irregularly shaped aluminum nitride particles, but with the weight percentage of spherical particles slightly exceeding 60 weight% to 67 weight%. The formulation is a powder paste that cannot be extruded.

[0077] Sample J exemplifies a formulation having a blend of spherical and irregularly shaped aluminum nitride particles having a weight percentage of 40 to 60 weight% of spherical particles, but using irregularly shaped aluminum oxide instead of spherical aluminum oxide with a particle size range of 1 to 5 micrometers. The resulting formulation is a powder paste that cannot be extruded.

[0078] Samples K and L exemplify formulations using a blend of spherical and irregular aluminum nitride particles having a particle size of 30 micrometers or more, but with the weight of spherical particles being more than or less than 40 to 60 weight percent. The resulting TC value is less than 8.0 W / m*K.

Claims

Claim 1 As a thermally conductive composition, a. as a curable silicone composition: i. vinyldimethylsiloxy-terminated polydimethylsiloxane having a viscosity in the range of 30 to 400 millipascals*seconds; ii. silicon hydride functionalized crosslinker; and iii. a hydrosilylation catalyst, wherein the molar ratio of silicon hydride functional groups to vinyl functional groups in the crosslinker is in the range of 0.5:1 to 1:1; b. a filler treatment agent comprising one or both of alkyl trialkoxysilane and mono-trialkoxysiloxy-terminated dimethylpolysiloxane; c. as a thermally conductive filler mix, i. ii. an aluminum nitride filler comprising a blend of spherical and irregularly shaped aluminum nitride particles in an amount of 40 weight% or more, wherein both the spherical and irregularly shaped particles have an average particle size of 30 micrometers or more, and the spherical aluminum nitride filler having a particle size of 30 micrometers or more is present at a concentration of 40 to 60 weight% of the total weight of the aluminum nitride filler having a particle size of 30 micrometers or more; iii. 25 weight% to 35 weight% of spherical aluminum oxide particles having an average particle size of 1 to 5 micrometers; and iii. A thermally conductive composition comprising a thermally conductive filler mix comprising 10% to 15% by weight of an additional thermally conductive filler having an average particle size of 0.1 to 0.5 micrometers, wherein the weight percentage of each thermally conductive filler is relative to the weight of the composition unless otherwise noted, and the total amount of said thermally conductive filler mix is ​​90% to 97% by weight of said composition, and is free of boron nitride fillers. Claim 2 A thermally conductive composition according to claim 1, wherein the vinyldimethylsiloxy-terminated polydimethylpolysiloxane has a viscosity in the range of 60 to 80 millipascals*seconds and comprises 1.2 to 1.4 weight% of vinyl functional groups. Claim 3 In claim 1, the silicon hydride functional crosslinking agent comprises one or more polysiloxanes having a chemical structure selected from (II) and (III): H(CH3)2SiO-[(CH3)2)SiO)] x -Si(CH3)2H (II)(CH3)3SiO-[(CH3)HSiO] y [(CH3)2)SiO] z -Si(CH3)3(III) In the above formula, the subscript x has a value in the range of 10 to 100, the subscript y has a value in the range of 3 to 30, and the subscript z has a value in the range of 3 to 100, a thermally conductive composition. Claim 4 In paragraph 3, the silicon hydride functional crosslinking agent is a thermally conductive composition having chemical structure (II). Claim 5 In claim 1, the alkyl trialkoxysilane is selected from C6 to C12 alkyl trimethoxysilanes, and the mono-trialkoxysiloxy-terminated dimethylpolysiloxane is selected from mono-trimethoxy-terminated dimethylpolysiloxanes having an average chemical structure (IV): (CH3)3SiO[(CH3)2SiO] a A thermally conductive composition, wherein Si(OCH3)3(IV) in the above formula, the subscript a is a value in the range of 30 to 110. Claim 6 A thermally conductive composition without magnesium oxide filler according to claim 1. Claim 7 A thermally conductive composition according to claim 1, wherein the additional thermally conductive filler is zinc oxide. Claim 8 An article comprising a thermally conductive composition according to any one of claims 1 to 7, wherein the thermally conductive composition is present between a heat-generating component of an electronic device and one or more of the following—a heat sink, a cooling plate, and a metal cover for said electronic device—and is in thermal contact with them. Claim 9 delete Claim 10 delete

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