阅读说明：本技术 导热组合物以及使用所述组合物的方法和装置 (Thermally conductive compositions and methods and devices using the same ) 是由 胡小链 张纪光 郑艳 陈红宇 陈晨 D·巴格瓦格 D·汉森 于 2018-11-07 设计创作，主要内容包括：本发明提供一种高导热组合物,所述组合物包含：(A)有机聚硅氧烷组合物；(B)填料处理剂；(C)热稳定剂；和(D)导热填料混合物,其包含：(D-1)平均尺寸至多为3μm的小颗粒导热填料,(D-2)平均尺寸为50至150μm的球形氮化铝,(D-3)平均尺寸为20至200μm的氮化硼。(The present invention provides a highly thermally conductive composition comprising: (A) an organopolysiloxane composition; (B) a filler treating agent; (C) a heat stabilizer; and (D) a thermally conductive filler mixture comprising: (D-1) a small particle heat conductive filler having an average size of at most 3 μm, (D-2) spherical aluminum nitride having an average size of 50 to 150 μm, and (D-3) boron nitride having an average size of 20 to 200 μm.)

1. A composition, comprising:

(A) an organopolysiloxane composition;

(B) a filler treating agent;

(C) a heat stabilizer; and

(D) a thermally conductive filler comprising:

(D-1) a small particle heat conductive filler having an average size of at most 3 μm;

(D-2) spherical aluminum nitride having an average size of 50 to 150 μm;

(D-3) boron nitride having an average size of 20 to 200 μm.

2. The composition of claim 1, wherein component (a) comprises:

an organopolysiloxane of the general formula (I)

R¹ ₃Si-(R¹R²SiO)_a(R¹ ₂SiO)_b-R³-SiR¹ ₃ (I)

Wherein each R¹Independently is C1-C6 alkyl, each R²Is aryl, each R³Selected from oxygen atoms or divalent hydrocarbon groups, subscript a is 0 or has an average value of at least 1, and subscript b has an average value of at least 1.

3. The composition of claim 1, where component (a) is curable.

4. The composition of claim 3, where component (A) is a combination of organopolysiloxanes comprising:

(A'1) an alkenyl-containing organopolysiloxane having the following general formula:

R¹ _(3-p)R⁴ _pSiO(R¹ ₂SiO)_c(R¹R²SiO)_d(R¹R⁴SiO)_eSiR¹ _(3-q)R⁴ _q， (II)

R¹ ₃SiO(R¹ ₂SiO)_f(R¹R²SiO)_g(R¹R⁴SiO)_hSiR¹ ₃(III) or

The combination of the components is that,

wherein each R1 is independently alkyl, R2 is independently aryl, R4 is independently alkenyl, subscript d and subscript e may be 0 or a positive number, and subscripts p and q are independently 0, 1 or 2, provided that p, q and e cannot all be 0 at the same time; and

(A' -2) an organohydrogenpolysiloxane comprising a compound of the formula:

R₃SiO(R₂SiO)_i(RHSiO)_jSiR₃ (IV)，

R₂HSiO(R₂SiO)_k(RHSiO)_lSiR₂H (V)，

or a combination thereof,

wherein each R is independently a monovalent organic group, subscript i has an average value in the range of from 0 to 2000, subscript j has an average value in the range of from 2 to 2000, subscript k has an average value in the range of from 0 to 2000, and subscript l has an average value in the range of from 0 to 2000, wherein the molar ratio of alkenyl groups in component (a '1) to silicon-bonded hydrogen atoms in component (a'2) is in the range of from 10:1 to 1: 10.

5. The composition of claim 3 or 4, wherein component (A) is cured.

6. The composition according to any one of claims 1 to 5, wherein component (B) comprises a silicone and/or a silane.

7. The composition of claim 6, wherein component (B) is selected from the group consisting of: alkyl trialkoxysilanes and trialkoxysiloxy terminated dimethylpolysiloxanes.

8. The composition of claim 7, wherein the trialkoxysiloxy-terminated dimethylpolysiloxane is further alkenyl-terminated.

9. The composition according to claim 8, wherein component (B) is selected from the group consisting of n-decyltrimethoxysilane and dimethylvinylsiloxy-and trimethoxysiloxy-terminated dimethylpolysiloxanes.

10. The composition of any one of claims 1 to 9, where component (C) is a phthalocyanine with or without a metal associated therewith.

11. The composition according to any one of claims 1 to 10, further comprising an additional ingredient selected from the group consisting of: (G) a spacing agent, (H) an antioxidant stabilizer, (I) a pigment, (J) a vehicle, or (K) a wetting agent, and combinations thereof.

12. The composition according to any one of claims 3 to 10, wherein component (a) is a curable composition further comprising (E) a curing catalyst and/or (F) a curing inhibitor.

13. A method comprising inserting the composition of any one of claims 1-12 along a thermal path between a heat source and a heat sink.

14. The method of claim 13, wherein the heat source comprises an (opto) electronic component.

15. A device, comprising:

a) a source of heat in the form of a heat source,

b) the composition of any one of claims 1 to 12, and

c) a heat sink;

wherein the composition is located between the heat source and the heat sink along a thermal path extending from a surface of the heat source to a surface of the heat sink.

Technical Field

The invention discloses a high-thermal-conductivity silicone composition, a preparation method and a use method thereof, and a device containing the same. The silicone composition can be used as part of thermal interface materials and heat dissipation materials in electronic devices.

Background

With the transition of the telecommunications industry to 5G networks, highly integrated electronic devices with smaller sizes will bring about double the power consumption (power units from 600W to 1200W), and if no one is present, higher heat generation will impair performance. Therefore, a more efficient thermal management system is urgently needed.

Various thermally conductive materials are known. WO2016190189A describes a composition containing spherical thermally conductive fillers that contain aluminum (Al) or Boron Nitride (BN), but not both. US6255257B1 describes a composition containing two different size distributions (up to 20 μm) of aluminum nitride (AlN) power as thermally conductive filler, optionally with the addition of zinc oxide (ZnO), alumina, BN and/or silicon carbide (SiC) powder fillers. KR10-1864505B1 describes a composition containing ZnO, alumina (Al)₂O₃) And AlN of at most 5 μm as a thermally conductive filler. WO2018074247A1 describes a composition containing AlN in two different size distributions, i.e.up to 5 μm and more than 50 μm. WO2017203924a1 describes a composition containing AlN and crushed alumina as thermally conductive filler. EP896031B1 describes a composition containing fillersThe filler is selected from powders of AlO, alumina, AlN, BN and SiC in various size distributions. JP3142800B2 describes a composition containing a filler comprising AlN and ZnO powder. However, the prior art has not heretofore achieved the levels of thermal conductivity now required in the industry.

Disclosure of Invention

The present invention provides a silicone composition having a thermal conductivity greater than 8W/mK, wherein the thermally conductive composition comprises a combination of an organopolysiloxane and at least three thermally conductive fillers. The present invention is also a method comprising inserting a thermally conductive composition of the present invention along a thermal path between a heat source and a heat sink. Such heat sources may include (opto) electronic components, central processing units, current converters, batteries, such as lithium ion batteries, and any other parts and units that generate heat when powered primarily by or involving electricity. Another aspect of the invention is a device comprising: a) a heat source, b) a thermally conductive composition of the present invention, and c) a heat sink, wherein the composition is located between the heat source and the heat sink along a thermal path extending from a surface of the heat source to a surface of the heat sink. Such heat sources may include electronic components. The devices include telecommunication and computing equipment such as servers, personal computers, tablet computers and hand-held devices, electronic modules, in particular power electronic modules, electronic control units in automobiles and batteries for electric automobiles.

Detailed Description

All amounts, ratios and percentages are by weight unless otherwise indicated. The following terms are used herein, which are intended to have the meanings as described below.

The articles "a", "an" and "the" each mean one or more. "combine" means to put two or more items together by any method. "cSt" means centiStokes. "DP" means the degree of polymerization, i.e., the number of monomers found in a polymer molecule. For linear polysiloxanes, the terminal siloxy units (R) are determined by 29Si-NMR³Number of SiO-) and chain-forming divalent siloxy units (-R)²The ratio of the number of SiO-) determines the DP. In the resin, DP is accurately calculated from the structure of the starting material. For other polysiloxanes, DP is calculated from the molecular size of the polymer as determined by gel permeation chromatography (with polystyrene as standard and known side chains); the siloxy units to which the methyl groups are attached are about 100 g/mol. "possible" means selected. "mPas" means mPas. By "surface treated" is meant that all or a portion of the reactive groups on the particles have been rendered non-reactive by any suitable chemical or non-reactive means. The abbreviation "W" means Watt, "W/mK" means Watt/meter Kelvin, and "μm" means micrometers.

As used herein, "alkyl" means an aliphatic saturated group, which unless otherwise specified consists of carbon and hydrogen, non-limiting examples of which are methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, decyl, undecyl, dodecyl, octadecyl, and eicosyl and isomers thereof when more than 3 carbon atoms are present. "cycloalkyl" means an alkyl group in which some or all of the carbon atoms participate in the formation of a cyclic structure with no aliphatic unsaturation in the ring, such as cyclopentyl and cyclohexyl.

As used herein, "alkenyl" means a group having aliphatic unsaturation and consisting of carbon and hydrogen, non-limiting examples of which are vinyl, allyl, butenyl, pentenyl, hexenyl, heptenyl, decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl, pentadecenyl, hexadecenyl, heptadecenyl, octadecenyl, nonadecenyl, eicosenyl, and isomers thereof when more than 3 carbon atoms are present. As used herein, "aryl" means a group derived from monocyclic and polycyclic aromatic hydrocarbons by the removal of a hydrogen atom from a ring carbon atom, non-limiting examples of which are phenyl, tolyl, xylyl, naphthyl, benzyl, and phenylethyl. The term "ppm" means parts per million by weight.

Unless otherwise stated, viscosity is measured at 25 ℃ using a viscosity glass capillary (CTM 0004A) according to ASTM D-445, IP 71, wherein the kinematic viscosity of the liquid is determined by measuring the time required for a fixed volume sample to pass through a glass capillary calibrated using gravity flow.

Thermally conductive composition.

The thermally conductive composition of the present invention comprises: (A) an organopolysiloxane composition; (B) a filler treating agent; (C) a heat stabilizer; and (D) a thermally conductive filler that is a mixture of at least three different types of fillers: (D-1) a small particle heat conductive filler having an average size of at most 3 μm; (D-2) spherical aluminum nitride having an average size of 50 to 150 μm; and (D-3) boron nitride having an average size of 20 to 200 μm, and may further comprise other thermally conductive particles.

(A) The component (a) of the thermally conductive composition may be a non-curable or curable organopolysiloxane composition. Examples of the non-curable component (A) include organopolysiloxanes having the general formula (I)

R¹ ₃SiO-(R¹R²SiO)_a(R¹ ₂SiO)_b-R³-SiR¹ ₃ (I)

Wherein each R¹Independently a monovalent organic group free of aliphatic unsaturation, i.e., a straight or branched chain alkyl group, preferably consisting of 1, 2, 3, or up to 6 carbon atoms. R¹May be a methyl group. Each R²Is an aryl group. R²May be phenyl. Each R³Selected from oxygen atoms or divalent hydrocarbon groups. R³Being an oxygen atom or being a divalent hydrocarbon group depends on the process used for preparing the organopolysiloxane of formula (I). The divalent hydrocarbon group may consist of 1 or more, 2 or more, 3 or more, 4 or more, 5 or more, and at the same time generally consists of up to 6, up to 10, or up to 12 carbon atoms. Preferably, R³Is an oxygen atom. Subscript "a" can be 0, or have an average value of at least 1, and subscript "b" has an average value of at least 1. Subscript "a" and subscript "b" may have average values such that the sum (a + b) is sufficient to provide an organopolysiloxane of formula (I) having a viscosity of 10 or more, 20 or more, 40 or more and simultaneously in the range of 100 or less, 200 or less, 300 or less or up to 400mpa.s, but in the range of from 20 to 400mpa.sIs desirable for good processability. An exemplary viscosity is 100 mpa.s. The sum (a + b) is a positive number in the range of 20 or more, 50 or more, 80 or more and at the same time up to 100, 120, 150 or 200. The sum (a + b) may preferably be in the range of 20 to 150. The molar ratio of a/b may be in the range of 0, 0.2, or alternatively 0.38 up to 4.2.

The organopolysiloxane of formula (I) may be a trimethylsiloxy end-capped poly (dimethylsiloxane/methylphenylsiloxane) copolymer, which may be DOWSIL^TM510Fluid or 550Fluid is available from Dow Silicones Corporation of Midland, Michigan, USA, Midland.

When subscript "a" is zero, the organopolysiloxane of formula (I) can be a trimethylsiloxy-terminated polydimethylsiloxane commercially available from a variety of sources.

The organopolysiloxanes of formula (I) can be prepared by well-known methods well described in the literature, such as hydrolysis and condensation of the corresponding organohalosilanes or equilibration of cyclic diorganopolysiloxanes. For example, the organopolysiloxane can be prepared by ring-opening polymerization of a cyclic diorganopolysiloxane using a lithium catalyst to produce an organopolysiloxane having silicon-bonded hydroxyl groups. Thereafter, the organopolysiloxane having silicon-bonded hydroxyl groups can be reacted with an alkoxysilane to prepare component (a). Alternatively, organopolysiloxanes suitable for use as component (a) can be prepared by methods such as disclosed in U.S. Pat. No. 4,962,174.

The organopolysiloxanes of component (A) can also be branched, having a small number of monoalkylsiloxane units (R) at the branching points¹SiO_3/2) As long as the viscosity of component (a) is from 10 to 400mpa.s, or more specifically, 10 or higher, 20 or higher, 40 or higher, and at the same time 100 or lower, 200 or lower, 300 or lower, or up to 400 mpa.s.

Component (a) may be a single base polymer or a combination comprising two or more base polymers that differ in at least one of the following characteristics: structure, viscosity, average molecular weight, siloxane units, and order.

Another example of component (a) is a curable mixture comprising component (a'1), an organopolysiloxane having at least two silicon-bonded alkenyl groups; and component (a '2), one or more silanes or organopolysiloxanes having on average at least two silicon-bonded hydrogen atoms in one molecule, which participate in the hydrosilylation reaction with the alkenyl groups of component (a'1), and are thus capable of crosslinking and curing component (a).

The polymer constituting the component (A'1) may have a linear molecular structure or a branched linear or dendritic molecular structure to some extent. It may be in the form of a single polymer, a copolymer or a mixture of two or more polymers. The average size of the polymers of component (a'1) may have a DP of greater than 10, greater than 20, greater than 30, greater than 40, greater than 50, greater than 75 or greater than 100 and at the same time less than 200, less than or 150 or less than 120. Preferably, component (A'1) has a DP of 50. The viscosity may be in the range of 10 to 400mpa.s, and more specifically in the range of 10 or higher, 20 or higher, 40 or higher and at the same time 80 or less, 100 or less, 200 or less, 300 or less or up to 400 mpa.s. Preferably, the viscosity may be in the range of 20 to 400 mpa.s. The silicon-bonded alkenyl groups of component (A'1) are preferably vinyl, allyl or hexenyl groups. More than one alkenyl group can be seen in one molecule. Such alkenyl groups in component (a'1) may be located at terminal, pendant, or both terminal and pendant positions.

The remaining silicon-bonded organic groups in component (a'1) may be alkyl groups having 1, 2, 3,4, 5, or 6 carbon atoms; a cycloalkyl group; and an aryl group; and 3,3,3, -trifluoropropyl or similar haloalkyl groups. Preferably, the organic group is methyl or phenyl. The remaining silicon-bonded organic groups are preferably methyl groups.

The terminal groups may be alkyl or aryl groups as described in the preceding paragraph, alkoxy groups such as methoxy, ethoxy or propoxy groups or hydroxyl groups.

Certain exemplary molecules of component (a'1) can be described by the following formulas (II) and/or (III):

R¹ _(3-p)R⁴ _pSiO(R¹ ₂SiO)_c(R¹R²SiO)_d(R¹R⁴SiO)_eSiR¹ _(3-q)R⁴ _q， (II)

R¹ ₃SiO(R¹ ₂SiO)_f(R¹R²SiO)_g(R¹R⁴SiO)_hSiR¹ ₃(III) or a combination thereof.

In the formulae (II) and (III), each R¹As described above, i.e., independently, a monovalent organic group free of aliphatic unsaturation, such as a straight or branched chain alkyl group. R¹May be a methyl group. Each R²As described above, i.e. aryl. R²May be phenyl. Each R⁴Independently an alkenyl group. Subscripts p and q are independently 0, 1, or 2, provided that p, q, and e cannot all be 0 at the same time. Subscript c has an average value of at least 0.1, typically at least 2, more typically at least 20, and also typically at most 100, or at most 150. Subscript d and subscript e may be 0. Alternatively, subscript e may have an average value in the range of greater than 0 to 150. The sum (c + d + e) is at least 0.1, at least 2, or usually at least 20 and at the same time at most 100, 150 or 200. Subscript f has an average value of at least 0.1, at least 2, or typically at least 20, and also typically at most 100, or at most 150 or less. Subscript g may be 0. Subscript h is a positive number. The sum (f + g + h) is at least 0.1, at least 2, usually at least 20 and at the same time at most 100, 150 or 200.

Exemplary molecules that can be used as component (a'1) are linear organopolysiloxanes in which both molecular terminals are capped with certain groups as described below:

a dimethylvinylsiloxy terminated dimethylpolysiloxane; a methylphenylvinylsiloxy terminated dimethylpolysiloxane; a dimethylvinylsiloxy terminated methylphenylsiloxane-dimethylsiloxane copolymer; trimethylsiloxy end-capped methylvinylsiloxane-dimethylsiloxane copolymer; a dimethylvinylsiloxy terminated methylvinylsiloxane-dimethylsiloxane copolymer; dimethyl vinyl silanyloxy terminated methyl (3,3, 3-trifluoropropan)Radical) polysiloxanes; a dimethylvinylsiloxy terminated methyl (3,3, 3-trifluoropropyl) siloxane-dimethylsiloxane copolymer; a silanol terminated methylvinylsiloxane-dimethylsiloxane copolymer; silanol terminated copolymers of methylvinylsiloxane, methylphenylsiloxane and dimethylsiloxane; or an organosiloxane copolymer consisting of siloxane units represented by the formula: (CH)₃)₃SiO_2/2、(CH₃)₂(CH₂＝CH)SiO_2/2、CH₃SiO_3/2And (CH)₃)₂SiO_2/2. The organopolysiloxanes of component (A'1) may also have small amounts of monoalkylsiloxane units (R)¹SiO_3/2) As long as the viscosity of component (a) is less than 10,000 mpa.s.

Component (a '2) comprises a silane or organohydrogenpolysiloxane having an average of at least 2 silicon-bonded hydrogen atoms ("SiH") in one molecule, which is capable of participating in a hydrosilation reaction with the aliphatically unsaturated organic groups of component (a'1), and thus rendering component (a) crosslinkable and curable. Component (a'2) may have a linear, branched, partially branched linear, cyclic, dendritic or resinous molecular structure. The silicon-bonded hydrogen atoms in component (a'2) may be located at terminal, pendant, or both terminal and pendant positions. Component (a'2) may be a combination of two or more organohydrogenpolysiloxanes differing in at least one of the following characteristics: structure, average molecular weight, viscosity, siloxane units, and order.

The amount of component (a '2) relative to component (a'1) should be sufficient to provide a molar ratio of SiH groups in component (a '2) to aliphatically unsaturated organic groups in component (a'1) in the range of 10:1 to 0.1:1 (commonly referred to as SiH: Vi ratio). In certain embodiments, the SiH to Vi ratio is in the range of 2:1 to 0.1:1, and preferably 1.5:1 to 0.2:1, and more preferably 0.5:1 to 0.6: 1.

The silicon-bonded group other than the silicon-bonded hydrogen atom of the component (a'2) may be an alkyl group; a cycloalkyl group; an aryl group; benzyl, phenethyl or similar aralkyl groups; or 3,3, 3-trifluoropropyl, 3-chloropropyl or similar haloalkyl groups. Preferred are alkyl and aryl groups, specifically methyl and phenyl.

Component (A'2) may comprise compounds of the formulae (IV) and/or (V)

R₃SiO(R₂SiO)_i(RHSiO)_jSiR₃， (IV)

R₂HSiO(R₂SiO)_k(RHSiO)_lSiR₂H， (V)

Or a combination thereof.

In formulas (IV) and (V) above, subscript i may be 0, or an average having a positive number of at most 150, subscript j has an average in the range of 2 to 30, subscript k may be 0, or an average having a positive number of at most 150, and subscript l may be 0, or an average having a positive number of at most 150. Preferably, the sum (i + j) and the sum (k + l) are each independently 2 or more, 3 or more, 12 or more, 20 or more, 27 or more, 35 or more, 50 or more, 75 or more, 100 or more, and at the same time are usually at most 100, at most 120, or at most 150. Each R is independently a monovalent organic group having saturated or unsaturated aliphatic bonds, including alkyl groups; a cycloalkyl group; an alkenyl group; alkynyl groups such as ethynyl, propynyl, and butynyl; and an aryl group.

Exemplary molecules that can be used as component (a'2) are linear alkyl hydrogen polysiloxanes, wherein both molecular ends are terminated with certain groups as described below:

trimethylsiloxy end-capped methylhydrogenpolysiloxanes; trimethylsiloxy end-capped methylhydrosiloxane-dimethylsiloxane copolymer; a dimethylhydrosiloxy terminated dimethylpolysiloxane; dimethyl hydrosilicon alkoxy end-capped methyl hydrogen polysiloxane; a dimethylhydrosilalkoxy terminated methylhydrogensiloxane-dimethylsiloxane copolymer; a cyclic methyl hydrogen polysiloxane; an organosiloxane composed of siloxane units represented by the formula: (CH)₃)₃SiO_1/2、(CH₃)₂HSiO_1/2And SiO_4/2. Dimethylhydrogensiloxy terminated polydimethylsiloxanes having a relatively low Degree of Polymerization (DP), for example in the range of from 3 to 50, are generally referred to as chain extenders, and part of component (a'2) may be a chain extender.

Component (a'2) may be or include a silane. Examples of silanes are tetrakis (dimethylhydrosilalkoxy) silane and methyl-tris (dimethylhydrosilalkoxy) silane.

Methods for preparing linear, branched and cyclic organohydrogenpolysiloxanes suitable for use as component (A'2), such as hydrolysis and condensation of organohalosilanes, are well known in the art. Processes for preparing organohydrogenpolysiloxane resins suitable for use as component (a'2) are also well known, as described in us patent 5,310,843; 4,370,358; and 4,707,531.

The total amount of component (a) depends on various factors, including the organopolysiloxane selected for component (a) and the thermally conductive filler selected for component (B). However, the total amount of component (a) (i.e., all of the combined organopolysiloxanes) can be in the range of 2 vol% to 35 vol%, alternatively 10 vol% to 15 vol%, and alternatively 10 vol% to 35 vol% of the total volume of all components in the thermally conductive composition.

The curable component (a) may remain uncured, be cured during preparation of the thermally conductive silicone composition, be cured after placement of the thermally conductive silicone composition in the proximal end of a heat-resistant article through which heat is conducted from the article, or be cured by a hydrosilation reaction prior to addition to the thermally conductive silicone composition. Component (a) may be partially or fully cured to give a cured composition having a viscosity/hardness of shore 00(5 to 85) and may have a soft putty texture, the hardness of which cannot be measured.

(B) Component (B) of the thermally conductive composition comprises a reactive silane and/or a reactive silicone for filler surface treatment. Treatments and methods of treatment are known in the art, see, for example, U.S. patent 6,169,142 (column 4, line 42 to column 5, line 2).

The amount of component (B) may vary depending on various factors, including the type and amount of filler selected for component (D), and whether the filler is treated with component (B) in situ or prior to combination with other components of the thermally conductive composition. Regardless, the thermally conductive composition may include component (B) in an amount ranging from 0.1% to 2% and any value in between.

Component (B) may comprise an alkoxysilane having the formula:

R⁵ _rSi(OR⁶)_(4-r)， (VI)

wherein subscript r is 1, 2, or 3; preferably r is 3.

Each R⁵Independently a monovalent organic group, such as a monovalent hydrocarbon group of 1 or more, preferably 6 or more and at the same time 50 or less, preferably 18 or less carbon atoms. R⁵May be saturated or unsaturated, branched or unbranched and unsubstituted. R⁵Examples of (A) are alkyl and aryl, and in particular methyl, ethyl, hexyl, octyl, decyl, dodecyl, octadecyl, phenyl or phenethyl, and also R as described below⁶Any of the above. Preferably, R⁵Is decyl.

Alternatively, R⁶May be an alkyl group of 1 to 4 carbon atoms and alternatively 1 to 2 carbon atoms. The alkoxysilanes used for component (B) are exemplified by hexyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, tetradecyltrimethoxysilane, phenyltrimethoxysilane, phenethyltrimethoxysilane, octadecyltrimethoxysilane, octadecyltriethoxysilane, and combinations thereof. Component (B) may be n-decyltrimethoxysilane.

Component (B) may also be an alkoxy-functional oligosiloxane. Alkoxy-functional oligosiloxanes and their preparation are known in the art, see for example EP1403326B1 and US 6844393. Suitable alkoxy-functional oligosiloxanes include those of the formula:

[R⁷ _sR⁸ _(3-s)SiO(R⁷ _tR⁸ _(2-t)SiO)_m(R⁸ ₂SiO)_n(R⁸ _u(OR⁹)_(2-u)SiO)_o]_vSiR⁸ _[4-(v+x)](OR⁹)_x (VII)。

in this formula, each R⁷Can be independently selected from alkenyl groups having 2 or more and simultaneously 6 or less, 8 or less, 10 or less, 12 or less carbon atoms, including alkenyl groups attached to a cyclic alkyl or aryl group (e.g., vinylcyclohexyl, vinylphenyl, vinylbenzyl, vinylethoxyphenyl); r⁷Preferably vinyl, allyl or hexenyl. Each R⁸May be independently selected from straight or branched chain alkyl, cycloalkyl, aryl and aralkyl groups having at least 1 carbon atom and up to 20 carbon atoms (i.e., aryl-substituted alkyl groups such as benzyl or phenethyl); r⁸May be halogenated. Preferably, R⁸Is methyl or ethyl. Each R⁹May be the same or different from each other and may be an alkyl, alkoxyalkyl, alkenyl or acyl group, each preferably having 1, 2, 3,4, 6 or up to 10 carbon atoms and may be straight, branched or cyclic. Preferred alkyl groups are methyl, ethyl or propyl; preferred alkoxyalkyl groups are methoxyethyl, ethoxyethyl or methoxypropyl; preferred alkenyl groups are vinyl, allyl or isopropenyl; the acyl group may be acetyl. All subscripts are integers and are each selected from the following ranges or selections; subscript s is 0 to 3; subscript t is 1 or 2; subscript u is 0, 1, or 2; and subscript v is 1, 2, or 3; subscript x is 0 to 3; provided that v and x are selected such that the sum (v + x) is from 1 to 4. Subscripts m, n, and o are each independently an integer of from 0 to 100, with the proviso that when s is 0, m is 1 or more, when x is 0, u is 0 or 1 and at the same time o is 1 or more, and the sum (m + n + o) is 1 or more and not more than 200. Preferably, m, n, and o are each independently 1 or greater, 5 or greater, or 10 or greater, and at the same time 10 or less, 25 or less, 50 or less, or 75 or less, up to 100. Preferred oligosiloxanes may be trialkoxysiloxy-terminated dimethylpolysiloxanes, such as (MeO)₃Si(OSiMe₂)₁₁₀OSiMe₃And may also contain an alkenyl group at the terminus, e.g. (MeO)₃Si(OSiMe₂)₂₅OSiMe₂Vi, wherein "Me" represents CH₃- (methyl), and "Vi" stands for-CH ═ CH₂(vinyl group). Component (B) may be a dimethylvinylsiloxy and a methyltrimethoxysiloxy end-blocked bisMethyl siloxane.

The metal filler may also be treated with, for example, octadecyl mercaptan and other alkyl mercaptans and fatty acids such as oleic acid, stearic acid, titanates, titanate coupling agents, zirconate coupling agents, and combinations thereof.

(C) A thermally conductive composition contains (C) a thermal stabilizer. Indanthrene blue (indacene blue), terphenyl, phthalocyanines, or metal phthalocyanines are examples of heat stabilizers that impart degradation resistance to a specified type of silicone elastomer in the presence of heat and ionizing radiation. Polynuclear benzene-like compounds such as copper phthalocyanine and dye-like (ingoid dye) are also known to improve the thermal stability of silicone elastomers cured using organic peroxides. Specifically, phthalocyanines with or without conjugated metal atoms are used in thermally conductive compositions.

Suitable phthalocyanine compounds are represented by formula (VIII) and the metal chelated state is represented by formula (IX).

Each X independently represents a hydrogen or halogen atom. Suitable halogen atoms are chlorine, bromine and iodine. In formula (IX), M is a metal atom selected from the group consisting of copper, nickel, cobalt, iron, chromium, zinc, platinum and vanadium. When M is copper, all X's are hydrogen. Preferably, the phthalocyanine compound is 29H, 31H-phthalocyanine and the preferred metal chelating phthalocyanine compound is 29H, 31H-phthalocyaninate (2-) -N29, N30, N31, N32 copper. Phthalocyanine compounds are commercially available, such as Stan-tone from Evenlepigraven, Ohio (Polyone Corporation, Avon Lake, Ohio, USA), USA^TM40SP03 or 50SP 01.

Component (C) is added to the thermally conductive organopolysiloxane composition in an amount such that the phthalocyanine compound is desirably present in a weight unit of% or more, 0.05% or more, even 0.07% or more, while desirably present in 5.0% or less, 0.2% or less, or even 0.1% or less of the entire composition.

(D) The thermally conductive composition of the present invention is characterized by three different groups of filler particles that act synergistically to provide high thermal conductivity. Each of these three groups is defined by the size distribution and material type contained by the filler particles. The shape of the particles may be spherical, nearly spherical, hemispherical or irregular as long as the aspect ratio is not more than 3 as determined by electron micrographs. In some particles, the aspect ratio is in the range of 2:1 to 30: 1.

The average particle size is determined by a laser diffraction particle size analyzer (e.g., CILAS920 particle size analyzer or Beckman Coulter LS 13320 SW) according to the operating software. The average particle size can be estimated based on measuring surface area according to 8-11ASTM D4315 or by using sieves of various mesh sizes and calculating the average from the cumulative weight of each size fraction (size fraction). These alternative methods provide average particle size estimates similar to those determined by laser diffraction methods.

Group (D-1) contains small-particle thermally conductive fillers having an average size of at most 3 μm. The average size may be as small as 0.1 μm. The particles in the group (D-1) may contain zinc oxide, aluminum oxide or aluminum nitride.

Group (D-2) comprises particles having an average size of 50 to 150 μm. The average size in μm may be 50 or more, 70 or more, 100 or more, or even 120 or more, while it may be 150 or less, 100 or less, 70 or less, and even 50 or less. A preferred material is aluminum nitride. The filler may be a metal filler having a surface layer of aluminum nitride.

Group (D-3) comprises particles having an average size of 20 to 200. mu.m. The average in μm may be 20 or more, 50 or more, 70 or more, 100 or more, 120 or more or 150 or more, and at the same time may be 150 or less, 100 or less, 70 or less, 50 or less or even 20 or less. A preferred material is boron nitride. Boron nitride was found to be an agglomerate and may be spherical or have an irregular shape.

Each of the (D-1), (D-2), and (D-3) groups may contain more than one homogeneous filler group. For example, each group may comprise particles having two or more size distribution peaks. (D-1) may comprise particles having different compositions, such as containing both zinc oxide and aluminum oxide.

The preferred weight ratio of spherical aluminum nitride in the thermally conductive composition is in the range of 40-60 wt%, and the preferred weight ratio of boron nitride in the silicone composition is in the range of 1-10 wt%, relative to the total weight of the thermally conductive composition. Small particle fillers may be added such that the total amount of filler in the thermally conductive composition is 50 wt% up to 97 wt%. The shape of the thermally conductive filler particles is not particularly limited, however, when the thermally conductive filler in the composition is highly loaded, the round particles can prevent the viscosity from increasing to an undesirable level.

The thermally conductive composition may further comprise other thermally conductive particles. Such additional fillers may be selected from the group consisting of: aluminum trihydrate, barium titanate, beryllium oxide, carbon fibers, diamond, graphite, magnesium hydroxide, magnesium oxide, metal particles, onyx (onyx), silicon carbide, tungsten carbide, zinc oxide, and combinations thereof. The additional filler may also be metal particles. Suitable metal fillers are exemplified by particles of a metal selected from aluminum, copper, gold, nickel, silver, and combinations thereof, and alternatively aluminum. Suitable metal fillers are further exemplified by particles of the metals listed above having on their surface a layer selected from the group consisting of aluminum oxide, copper oxide, nickel oxide, silver oxide, and combinations thereof.

The additional filler may comprise bismuth (Bi), gallium (Ga), indium (In), tin (Sn), or alloys thereof, and is therefore meltable. The alloy may include gold (Au), silver (Ag), cadmium (Cd), copper (Cu), lead (Pb), tin (Sn), or a combination thereof. Examples of alloys include Ga, In-Bi-Sn alloys, Sn-In-Zn alloys, Sn-In-Ag alloys, Sn-Ag-Bi alloys, Sn-Bi-Cu-Ag alloys, Sn-Ag-Cu-Sb alloys, Sn-Ag-Cu alloys, Sn-Ag-Cu-Zn alloys, and combinations thereof. The fusible filler has a melting point in the range of 50 ℃ to 250 ℃, alternatively 150 ℃ to 225 ℃. The fusible filler may be a eutectic alloy, a non-eutectic alloy or a pure metal.

These fillers are commercially available. For example, the different particle sizes of alumina can be Alunabeads^TMFrom Showa Denko K.K., Japan and from Sumitomo Chemical Co., Ltd. (Japan) as AA-04, AA-2 and AA 18. Zinc oxide is available, for example, from American Zinc recycle (American Zinc Rec) of Pittsburgh, PaCyling Corp, Pittsburgh, PA, U.S.A) (trade mark) Or Zochem LLC from Dickson, Tenn, USA (Zochem LLC, Dickson, TN, U.S.A.). Metal fillers are available from Indium corporation of ewika, new york, usa (Indium corp., Utica, NY, u.s.a.); aronium Specialty Alloys Company (aronium Specialty Alloys Company, Providence, RI, u.s.a.) of providences, rhode island, usa; and AIM Metals and alloys, montreal, canada (AIM Metals)&Alloys LP, Montreal, Canada). Aluminum fillers are commercially available, for example, from Toyal America, Inc. of Neppervier, Ill.U.S.A. and Valimet, Stockton, Calif., U.S.A. of the United states. Silver fillers are available from the mettalol Technologies group of Switzerland (Metalor Technologies SA, Switzerland).

Additional ingredients

When the component (a) is a curable composition, the thermally conductive composition may further comprise (E) a curing catalyst and/or (F) a curing inhibitor. The thermally conductive composition may further comprise one or more additional ingredients selected from the group consisting of: (G) a spacer, (H) a stabilizer, (I) a pigment, (J) a vehicle, (K) a wetting agent, and (L) a flame retardant.

(E) Component (E) is a catalyst which promotes the hydrosilylation reaction. Suitable hydrosilation catalysts are well known in the art and are commercially available. Component (E) may comprise a platinum group metal selected from: platinum, rhodium, ruthenium, palladium, osmium or iridium metal or organometallic compounds, complexes or ligands thereof, or combinations thereof.

Component (E) is exemplified by fine platinum metal powder, platinum black, platinum dichloride, platinum tetrachloride; chloroplatinic acid, alcohol-modified chloroplatinic acid, chloroplatinic acid hexahydrate; and complexes of the compounds, such as platinum complexes of olefins, platinum complexes of carbonyls, platinum complexes of alkenylsiloxanes (e.g. 1, 3-divinyltetramethyldisiloxane), platinum complexes of low molecular weight organopolysiloxanes, for example 1, 3-divinyl-1, 1,3, 3-tetramethyldisiloxane, complexes of chloroplatinic acid with beta-diketones, complexes of chloroplatinic acid with olefins, and complexes of chloroplatinic acid with 1, 3-divinyltetramethyldisiloxane. These complexes may be microencapsulated in a resin matrix or core-shell type structure, or may be mixed and embedded in a thermoplastic organic resin powder composed of methylmethacrylate, carbonate, polystyrene, silicone or similar resins.

Component (E) is used in an amount such that the platinum group metal is generally present in an amount of 0.01ppm or more, 0.1ppm or more, 1ppm or more, 2ppm or more or even 5ppm or more, and at the same time generally 1,000ppm or less, 500ppm or less, 200ppm or less or even 150ppm or less, in terms of weight units, relative to the total weight of components (A) and (B).

(F) Component (F) is a hydrosilylation inhibitor to prevent premature curing of the curable composition and to adjust the curing speed, thereby improving the handling of the composition under industrial conditions. Such inhibitors are, for example, acetylenic alcohols (e.g., acetylenic alcohols), enynic compounds, benzotriazoles, amines (e.g., tetramethylethylenediamine), dialkyl fumarates, dienyl fumarates, dialkoxyalkyl fumarates, maleates (e.g., diallyl maleate), and combinations thereof. Specific examples of such inhibitor compounds are: acetylenic compounds, such as 2-methyl-3-butin-2-ol, 3-methyl-1-butin-3-ol, 3, 5-dimethyl-1-hexin-3-ol, 2-phenyl-3-butin-2-ol, 3-phenyl-1-butin-3-ol, 1-ethynyl-1-cyclohexanol, 1-dimethyl-2-propynyl) oxy) trimethylsilane, methyl (tris (1, 1-dimethyl-2-propynyl oxy)) silane; enyne compounds, such as 3-methyl-3-penten-1-yne, 3, 5-dimethyl-3-hexen-1-yne; triazoles, such as benzotriazole; a hydrazine-based compound; a phosphine-based compound; a thiol-based compound; cycloalkenylsiloxanes, for example methylvinylcyclosiloxanes, such as 1,3,5, 7-tetramethyl-1, 3,5, 7-tetravinylcyclotetrasiloxane, 1,3,5, 7-tetramethyl-1, 3,5, 7-tetrahexenylcyclotetrasiloxane. The amount of such inhibitors in the hydrosilylation-curable, thermally conductive silicone composition may be in the range of 0.0001 to 5 wt% of component (a). Suitable hydrosilylation cure inhibitors are disclosed in, for example, U.S. Pat. nos. 3,445,420; 3,989,667; 4,584,361, respectively; and 5,036,117.

(G) Component (G) is a spacer, a non-conductive particle. The spacer may comprise organic particles, inorganic particles, or a combination thereof. The particle size of the spacer can be in the range of at least 50 μm, at least 100 μm or at least 150 μm and at the same time at most 125 μm or at most 250 μm. The spacer may comprise monodisperse beads, such as glass or polymer (e.g. polystyrene) beads. The amount of spacer depends on various factors including the distribution of the particles, the pressure to be applied during placement, and the temperature during placement. Component (G) may be added to control the thickness of the adhesive layer of the cured product of the curable composition. The thermally conductive silicone composition may contain at least 0.05 wt%, alternatively at least 0.1 wt% and at the same time at most 1 wt%, alternatively at most 2 wt%, at most 5 wt% or at most 15 wt% of a spacing agent.

(H) Component (H) the antioxidant stabilizer may be added to the thermally conductive silicone composition in an amount ranging from 0.001% to 1%. Suitable stabilizers may be antioxidants, which are known in the art and are commercially available. Suitable antioxidants include phenolic antioxidants and combinations of phenolic antioxidants with stabilizers. Phenolic antioxidants comprise both fully hindered phenols and partially hindered phenols. Stabilizers include organophosphorus derivatives, such as trivalent organophosphorus compounds, phosphites, phosphonates, and combinations thereof; thiosynergists, such as organosulfur compounds, including sulfides, dialkyldithiocarbamates, dithiodipropionates, and combinations thereof; and hindered amines such as tetramethyl piperidine derivatives.

Commercially available stabilizers include vitamin E and1010 comprising pentaerythritol tetrakis (3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate) available from BASF Corporation, Charlotte, North Carolina, USA.

(I) Suitable component (I), examples of pigments include readily commercially available carbon blacks. The amount of pigment depends on various factors including the selected pigment and the hue of the desired color, however, when present, the amount of pigment can range from 0.0001% to 1% by combined weight of all ingredients in the thermally conductive silicone composition.

(J) Additional component (J) is a vehicle, such as a solvent or diluent. Component (J) may be added during the preparation of the thermally conductive silicone composition, for example, to aid in mixing and delivery. All or a part of component (J) may be additionally removed after the preparation of the heat conductive silicone composition. Component (J) may be an organic solvent. Alternatively, component (J) may be a polydialkylsiloxane fluid (e.g., polydimethylsiloxane) having a viscosity in the range of from 0.5cSt to 10cSt, alternatively from 1cSt to 5 cSt. Suitable polydimethylsiloxane fluids for use as vehicles are known in the art and may be sold under the trade name DOWSIL^TM200Fluids and OS Fluids are commercially available from the Dow silicone company of Midland, Mich. The amount of vehicle depends on various factors, including the type and amount of organopolysiloxane of component (a) and the filler of component (D), however, the amount of vehicle can be in the range of 0.0001 wt% to 3 wt%, alternatively 0.0001 wt% to 1 wt%, by combined weight of all ingredients in the thermally conductive silicone composition.

(K) The additional component (K) is a wetting agent or a surfactant. Suitable wetting agents include anionic, cationic and nonionic surfactants known in the art for use as wetting agents. Suitable surfactants include silicone polyethers, ethylene oxide polymers, propylene oxide polymers, copolymers of ethylene oxide and propylene oxide, other nonionic surfactants, and combinations thereof. The composition may comprise up to 0.05% by weight of the composition of a surfactant. The anionic wetting agent is exemplified by TERGITOL^TMNo.7, cationic wetting agent is exemplified by TRITON^TMX-100 and the nonionic wetting agent is exemplified by TERGITOL^TMNR 27, all of which are commercially available from Dow chemical company, Midland, Mich.

Method for preparing heat conductive composition

The thermally conductive compositions described above may be prepared by mixing all of the ingredients at ambient or elevated temperature using any suitable mixing device, such as a centrifugal mixer (available from Hauschild) or a Baker-Perkins mixer.

Use for thermally conductive compositions

The thermally conductive composition described above may be used as a Thermal Interface Material (TIM). A thermally conductive silicone composition may be inserted along a thermal path between a heat source and a heat sink. The thermally conductive silicone composition may be inserted by application to a heat source (e.g., (opto) electronic components) and a heat sink in any order or simultaneously. The thermally conductive silicone composition can be inserted by any suitable means, such as wet dispensing, screen printing, stencil printing, or solvent casting the thermally conductive silicone composition.

The device according to the invention comprises: a) a heat source, b) the thermally conductive silicone composition described above, and c) a heat sink, wherein the thermally conductive silicone composition is located between the heat source and the heat sink along a thermal path extending from a surface of the heat source to a surface of the heat sink.

In the methods and devices described herein, the heat source may comprise (opto) electronic components, such as LEDs, semiconductors, transistors, ICs or discrete devices. The heat sink may include fins, thermally conductive plates, thermally conductive covers, fans, a circulating coolant system, or a combination thereof.

The thermally conductive silicone composition may be used in direct contact with a heat source (TIM 1). For example, the thermally conductive silicone composition may be applied to the (opto) electronic component and the heat spreader plate in any order or simultaneously. Alternatively, a thermally conductive silicone composition may be used in direct contact with the first and second heat spreaders (TIM 2). The heat conductive silicone composition may be applied to the first heat dissipation plate (e.g., metal cover) and thereafter applied to the second heat dissipation plate (e.g., heat sink), or the heat conductive silicone composition may be applied to the second heat dissipation plate and thereafter applied to the first heat dissipation plate.

Examples of the invention

These examples are intended to illustrate the invention to those skilled in the art and should not be construed as limiting the scope of the invention as set forth in the claims. Samples of thermally conductive silicone compositions were prepared using the following ingredients. The components used are listed in table 1 below. Component (A) is exemplified by (a-1). Component (A '1) is exemplified by (a' 1-1). Component (A '2) is exemplified by (a '2-1) and (a ' 2-2). Component (B) is exemplified by (B-1), (B-2) and (B-3). Component (C) is exemplified by (C-1). Component (D-1) is exemplified by (D1-1) and (D1-2). Component (D-2) is exemplified by (D2-1) and (D2-2). Component (D-3) is exemplified by (D3-1) and (D3-2). Component (E) is exemplified by (E-1). Component (F) is exemplified by (F-1).

TABLE 1

The particle size of (d1-1) was determined by a Beckmann Coulter counter and also by electron microscopy. Surface area (m) according to the vendor provided using the 8-11ASTM D4315 method²G) determining the particle size of (d 1-2). The particle size of (d2-1) was determined using a CILAS920 particle size Analyzer. The granularity of (d2-2) was determined using a Beckmann Coulter counter. The pattern was 80 μm, with a numerical average of 70 μm. The particle sizes of (d3-1) and (d3-2) were determined using sieves having a +80 to-270 US mesh. 100 μm and 120 μm are the mode and mean values of (d3-1) and (d3-2), respectively.

Preparation of silicone compositions-amounts of components are listed in table 2. The components used to prepare the silicone composition of the invention were mixed in a SpeedMixer from flaktake corporation (Flack Tek Inc.)^TMDAC 400.1 FVZ. A heat stabilizer (c-1) (copper phthalocyanine: CuPc), a silicone matrix component (including silicone oil (a-1) or vinyl polymer (a '-1) for a non-reactive matrix), a crosslinking agent (a'2) and an inhibitor (f) for a curable silicone composition, and a suitable surface treatment agent (b-1, b-2 or b-3) are weighed into a cup of a speedMixer. The smaller size filler (0.2 μm) (d1-2) and the middle size filler (2 μm) (d1-1) were then weighed and added to the cup. This mixture was mixed by a SpeedMixer (1500rpm for 20 seconds followed by 2000rpm for 20 seconds). After mixing, half the larger filler size is weighed (>10 μm) (d2-1, d2-2), added and then mixed by a SpeedMixer under the same mixing conditions. If obtained, areThe mixture paste was not homogeneous, the paste was scraped into a cup and mixed again under the same mixing conditions. Subsequently, the other half of the larger sized filler boron nitride (d3-1, d3-2) was added and mixed at 1500rpm for 20 seconds, scraped off and mixed again to form a sample. For the reactive composition, the platinum catalyst (e-1) was added and further mixed. The samples were left at room temperature overnight and then tested for compositions not designed for curing. For the curable composition, the sample was formed into a block of 29mm × 29mm × 8mm and heated at 150 ℃ for 15 minutes. At least two of each sample formulation were cured.

characterisation-Thermal Conductivity (TC) was measured by the Hotdisk transient technology sensor C5501 with a heating time and power of 3-5s/500 mW. Two cups were filled with each fluid material, and a planar sensor was placed in the cup. For cured materials, the planar sensor is placed in two curing blocks. A fine tuning analysis with temperature drift compensation and time correction selected between points 50-150 is used.

Extrusion Rate (ER) was measured by norson (Nordson) EFD dispensing equipment. The sample material was packaged into a 30cc syringe and dispensed at a pressure of 0.62 MPa. The weight of the sample dispensed at 1 minute (min) was used as the extrusion rate.

Table 2 lists formulations of thermally conductive silicone compositions of examples of the invention (Inv) and comparative examples (Comp) in volume ratios. The volumes of component (a) and component (B) (together representing the fluid organopolysiloxane) and component (C) the thermal stabilizer are fixed in all formulations with non-reactive silicone fluids. The filler of component (D) is added in an amount such that the volume percent and the weight percent are generally comparable to each other, except for comparative example 5, which cannot be loaded that much because of its viscosity. All examples contained 2 μm spherical Al₂O₃(D1-1) and 0.2 μm zinc oxide (D1-2) as (D-1) fillers. In the examples of the invention, 80 μm spherical aluminum nitride (D2-2) was present as filler (D-2) and 100 μm high-density agglomerate boron nitride (D3-1) or 120 μm spherical agglomerate boron nitride (D3-2) was present as filler (D-3). In the comparative example, 70 μm spherical alumina (D2-1) was present instead of aluminum nitride, or only one of (D-2) or (D-3). Comparative example-1 contains alumina in addition to a small amount of filler, butAluminum nitride and boron nitride are not included. Comparative example-4 contained aluminum nitride, but no boron nitride. In comparative example-2 and comparative example-3, a combination of alumina and boron nitride was used, but no aluminum nitride was used. Comparative example-4 used aluminum nitride alone; in comparative example-5, boron nitride only was used. In inventive example 3, there was a platinum catalyst (e-1) and an inhibitor (f-1) for a controlled curing reaction.

Table 2:

in volume ratios, except that the amount of catalytic platinum is in ppm

Table 3 shows the thermal properties of the samples, shown as TC and ER data.

TABLE 3

The inventive examples show at least 10% higher thermal conductivity than the comparative examples. Spherical aluminum nitride alone (80 μm; comparative example-4) provided a thermal conductivity that was about 20% higher than that of spherical aluminum oxide (70 μm; comparative example-1). Although boron nitride materials are known to provide higher thermal conductivity, boron nitride fillers are difficult to mix in large amounts (e.g., greater than 5 wt%) into the substrate (comparative example-5), thus resulting in compositions with lower thermal conductivity and lower extrusion rates.

By using aluminum nitride and boron nitride having a certain size together, a significantly higher thermal conductivity can be obtained (inventive example-1, inventive example-2). Replacing aluminum nitride with aluminum oxide (comparative example-1, comparative example-4) reduced the thermal conductivity, which could not be compensated by adding boron nitride (comparative example-2, up to 30%; comparative example-3). AlN/BN combination shows the same effect as s-Al₂O₃the/BN system has a significantly higher thermal conductivity (up to a 30% increase) compared to the other. The thermal conductivity of the s-AlN/BN system can be up to 9.4W/mK while maintaining the same as that of s-Al₂O₃Similar extrusion rates for the BN systemsAnd (4) rate. The combination of fillers in the silicone composition provides unique thermal conductivity capabilities in excess of 8W/mK.

INDUSTRIAL APPLICABILITY

The thermally conductive compositions described above are useful as thermal interface materials in various electronic devices to transfer heat from a heat generating or resistant portion of the device to a heat sink or portion of the heat sink. The thermally conductive composition provides a level of thermal conductivity not previously available for such use, thereby improving the efficiency and effectiveness of heat transfer.