EP4766780A1

EP4766780A1 - HIGH-TEMPERATURE STABLE THERMALLY CONDUCTIVE MATERIALS

Info

Publication number: EP4766780A1
Application number: EP23949396.8A
Authority: EP
Inventors: Zijia ZHANG; Chen Chen; Dorab Edul Bhagwagar; Yan Zheng; Junmin Zhu
Original assignee: Dow Silicones Corp
Current assignee: Dow Silicones Corp
Priority date: 2023-08-23
Filing date: 2023-08-23
Publication date: 2026-07-01
Also published as: WO2025039204A1; TW202509181A; KR20260049322A; CN121712845A

Abstract

Provided is high temperature stable thermally conductive materials. The thermally conductive composition, which comprises: (A1) a metal-containing phthalocyanine; and (A2) a SiH polyorganosiloxane comprising a structural formula: R3-Si-(OSiR2)m-(OSiRH)n-SiR3, where R is independently selected from hydrocarbon groups, and on average n=1 and m=0 to 10; (B) a SiH crosslinker containing on average 2 or more SiH groups per molecule; (C) a polyorganosiloxane containing 2 or more alkenyl groups per molecule; (D) a filler treating agent; (E) a thermally conductive filler; and (F) a hydrosilylation reaction catalyst. The thermally conductive materials can remain soft after long-life aging at elevated temperature.

Description

HIGH TEMPERATURE STABLE THERMALLY CONDUCTIVE MATERIALS

TECHNOLOGICAL FIELD OF THE PRESENT INVENTION
The present disclosure relates to a high temperature stable thermally conductive material, a cured silicone and a thermal interface material made by using the same, as well as a method of conducting heat or dissipating heat using the thermal interface material.

BACKGROUND ART

Thermally conductive materials are widely applied in telecom, computing, automotive, semiconductors, LEDs, power devices, cryogenics, medical devices and photonics to dissipate high heat from electronic devices. Among all the key parameters of properties for the thermally conductive materials, stable hardness under high temperature aging is always of the top challenge for their applications in thermally conductive materials. Usually, it is often found that due to the side chain reaction and the crosslinking reaction during high temperature oxidation aging, the hardness of the thermally conductive materials, especially soft and low modulus thermally conductive materials, occur significant hardness change at high temperature. The main cause appears to be thermally conductive fillers catalyzed oxidation of the siloxane chain likely proceeding through peroxidation to form additional crosslink sites and the evolution of hydrogen, methane, aldehydes, acetic acid and ketones. The severe hardening could result in poor contact between the heat conducting substrate and the electronic component, and further failure of “stress relaxation” and “secured heat pass way” during application.
Patent Document 1 discloses an addition reaction type polyorganosiloxane composition that is fast-curing at room temperature, and the cured product of the composition has excellent stress relaxation under high temperature and high humidity. However, the cured product does not provide higher temperature and longer aging life reliability.
Patent Document 2 discloses a copper-containing phthalocyaninato-based pigment used as a stabilizing additive to prevent the hardness increase of thermally conductive materials under high temperature (90-150℃) aging for long time. However, the thermally conductive materials do not provide higher temperature stability.
Patent Document 3 discloses a thermally stable grease that can be prepared by using silicone fluid as co-thickening agents to improve the thickening efficiency of substituted polyphenylene thickening agents used to thicken perfluoropolyether fluids to a grease consistency. The thermally stable grease can impart thermal stability at 550°F bearing for 261h, but does not provide lower temperature but longer aging life reliability.
Patent Document 4 discloses a method to improve the thermal stability of a silicone gel comprising heating the iron acetylacetonate to form Fe₂O₃ particles in silicone fluid, which allows the gel to maintain low hardness even after extensive heat aging. However, the method forms Fe₂O₃ particles by heating a mixture of iron acetylacetonate and base polymer at a temperature of 180-200℃ under purging N₂, which is complex and may bring some by-products.
Patent Document 5 discloses a gel having improved thermal stability, which uses a phthalocyanine to allow the gel to maintain low hardness after extensive heat aging. Although it discloses a gel that has no thermal conductive fillers and shows improved thermal stability, integration with thermal conductive fillers is not disclosed.
Therefore, there is an unmet need for low modulus thermally conductive materials which remain soft after long-life aging at elevated temperature.
[Prior art Documents]
Patent Document 1: JP Patent No. 6243567B1
Patent Document 2: US Patent No. 2013248163A1
Patent Document 3: US Patent No. 3981812A
Patent Document 4: US Patent No. 20180127552A1
Patent Document 5: US Patent No. 20150130086A1

SUMMARY OF THE INVENTION

PROBLEM TO BE SOLVED BY THE INVENTION
The problem to be solved by the invention is how to keep remain the low modulus thermally conductive materials soft after long-life aging at elevated temperature.
Further, it is other objective of the present invention to provide a method of increasing high temperature stability of a thermally conductive polyorganosiloxane composition.
MEANS FOR SOLVING THE PROBLEM
As a result of persistent investigation, the present inventors discovered a novel composition that has high or ultra-high temperature stability. As the composition of soft thermally conductive materials usually has free vinyl functionalized polyorganosiloxane after curing at 25-120℃, the present disclosure provides an high temperature stable composition incorporated with a metal (e.g., copper) -containing phthalocyanine and a low molecule pendant SiH group-containing polyorganosiloxane with a single SiH group. The metal-containing phthalocyanine works as a heat stabilizer to resist degradation of silicone elastomers in the presence of heat, and the low molecule one-functional SiH group-containing polyorganosiloxane can capture excess vinyl group-containing organopolysiloxane without increasing cross-linking density and preventing its further crosslink under heat aging.
The present inventors found that a metal-containing phthalocyanine and a low molecule one-terminal SiH group-containing polyorganosiloxane work synergistically to stabilize the hardness under elevated temperature in the range of 175-200℃ for long time aging, while the separate effect of a copper-containing phthalocyanine and a low molecule one-terminal SiH group containing polyorganosiloxane on hardness change is limited.
One aspect of the present invention is a thermally conductive composition, which comprises:
(A1) a metal-containing phthalocyanine; and
(A2) a SiH polyorganosiloxane comprising a structural formula:
R₃-Si- (OSiR₂) _m- (OSiRH) _n-SiR₃, where R is independently selected from hydrocarbon groups, and on average n=1 and m=0 to 10;
(B) a SiH crosslinker containing on average 2 or more SiH groups per molecule;
(C) a polyorganosiloxane containing 2 or more alkenyl groups per molecule;
(D) a filler treating agent;
(E) a thermally conductive filler; and
(F) a hydrosilylation reaction catalyst.
In some embodiments, (A1) metal-containing phthalocyanine has an amount of 0.25-0.40 wt%, based on the total weight of the composition.
In some embodiments, (A2) SiH polyorganosiloxane has a SiH content in range of 0.05%to 0.8%.
In some embodiments, (B) SiH crosslinker containing on average 2 or more SiH groups per molecule has a SiH content in range of 0.01%to 0.2%.
In some embodiments, (C) polyorganosiloxane containing 2 or more alkenyl groups per molecule has an amount such that SiH/Vi ratio is in range of 1.07-1.26, based on the total SiH of components A2 and B in the composition.
In some embodiments, (D) filler treating agent comprises at least one of the following:
(D1) mono-trialkoxysiloxy terminated dimethylpolysiloxane;
(D2) alkyl trialkoxysilane; and
(D3) mono-dimethylvinylsiloxy and mono-trimethoxysiloxy terminated dimethylsiloxane.
In some embodiments, (E) thermally conductive filler comprises at least one of the following:
(E1) spherical Al₂O₃ having an average particle size of 10-100μm;
(E2) irregular Al₂O₃ having an average particle size of 0.1 to 5 μm.
In some embodiments, the thermally conductive composition further comprises at least one of the following:
(G) an inhibitor;
(H) a thixotropic agent-surface treated fumed silica; and
(I) a spacer.
A second aspect of the present invention is a cured silicone prepared by curing the thermally conductive composition.
A third aspect of the present invention is a thermal interface material comprising the cured silicone.
In some embodiments, the material comprises a support coated with the cured silicone.
In some embodiments, the thermal interface material dissipates heat.
A fourth aspect of the present invention is a method of increasing high temperature stability of a thermally conductive polyorganosiloxane composition comprising the step of adding components A1 and A2 to the thermally conductive polyorganosiloxane composition:
(A1) a metal-containing phthalocyanine; and
(A2) a SiH polyorganosiloxane comprising a structural formula:
R₃-Si- (OSiR₂) _m- (OSiRH) _n-SiR₃, where R is independently selected from hydrocarbon groups, and on average n=1 and m=0 to 10.
A fifth aspect of the present invention is a method of conducting heat from a first component to a second component wherein the first component has a higher temperature than the second component and the thermal interface material is in contact with the first component and with the second component.
A sixth aspect of the present invention is a method of dissipating heat from a first component wherein the thermal interface material is in contact with the first component.
EFFECT OF THE INVENTION
The present invention is able to provide a thermally conductive composition, which exhibits at least one of the following:
- a thermal conductivity of more than 1.0 W/mK;
- a flowable composition with slope flowability of higher than 40mm;
- a low cured hardness of less than 10 Shore A; and
- a retain softness with hardness of less than Shore A 25 and Shore A 40 after aging up to 175℃ and 200℃, respectively, for 42 days (1000h) .
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows hardness change of Inventive Examples (IE1 to IE4) and Comparative Examples (CE1 to CE10) under 175℃ aging according to the present disclosure.
Figure 2 shows hardness change of Inventive Examples (IE1 to IE4) and Comparative Examples (CE1 to CE10) under 200℃ aging according to the present invention.
Figure 3 is a photograph showing a mold for evaluating slope flowability according to the present invention.
Figure 4 is a photograph showing a 1mL syringe used for packaging sample material to test slope flowability according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs. As disclosed herein, “and/or” means “and, or as an alternative” or “additionally or alternatively” . All ranges include endpoints unless otherwise indicated.
As used herein, the term “polymer” or “polymeric” refers, in the alternative, to a polymer made from one or more different monomers, such as a copolymer, a terpolymer, a tetrapolymer, a pentapolymer etc., and may be any of a random, block, graft, sequential or gradient polymer.
In the present invention, the singular form of the articles "a, " "an, " and "the" includes plural references unless indicated otherwise. In the present invention, the terms "comprise" , “comprising” , “contain” , "containing" , “include” , “including” and their variants are open claim language, i.e., are permissive of additional elements.
In some embodiments of the present invention, the thermally conductive composition comprises, substantially consisting of, or consisting of: (A1) a metal-containing phthalocyanine; (A2) a SiH polyorganosiloxane comprising a structural formula: R₃-Si- (OSiR₂) _m- (OSiRH) _n-SiR₃, where R is independently selected from hydrocarbon groups, and on average n=1 and m=0 to 10; (B) a SiH crosslinker containing on average 2 or more SiH groups per molecule; (C) a polyorganosiloxane containing 2 or more alkenyl groups per molecule; (D) a filler treating agent; (E) a thermally conductive filler; (F) a hydrosilylation reaction catalyst; (G) optionally, an inhibitor; (H) optionally, a thixotropic agent-surface treated fumed silica; and (I) optionally, a spacer.
Component (A1)
Component (A1) is a pigment that has an effect of preserving the desired physical characteristic of the thermally conductive silicone compositions/materials, namely the appropriate softness and compliant nature. Component (A1) comprises a metal-containing phthalocyanine. Component (A1) is added to the thermally conductive polyorganosiloxane composition in an amount such that in terms of weight units the metal-containing phthalocyanine is within the range of 0.05 to 1.00%of the composition as a whole. Alternatively, the metal-containing phthalocyanine is in amount of 0.10 to 0.80%of the composition. Alternatively, the metal-containing phthalocyanine is in amount of 0.25 to 0.40 %of the composition.
Suitable metal-containing phthalocyanine can be represented by the following formula (I) :
In formula (I) , X each independently represents a hydrogen or halogen atom. Suitable halogen atoms are chlorine, bromine, and iodine. M is a metal atom selected from copper, nickel, cobalt, iron, chromium, zinc, platinum, and vanadium. When M is copper, all X are hydrogens. A preferred metal-containing phthalocyanine is 29H, 31H-phthalocyaninato (2-) -N29, N30, N31, N32 copper.
Component (A2)
Component (A2) is a low molecule pendant SiH group-containing polyorganosiloxane with a single SiH group. Component (A2) has a structural formula: R₃-Si- (OSiR₂) _m- (OSiRH) _n-SiR₃, where R is independently selected from hydrocarbon groups, and on average n=1 and m=0 to 10. In some embodiments, R is independently selected from a C1-C6 alkyl group or a C6-C20 aryl group. In some embodiments, m=1 to 8, 2 to 6, or 4 to 5.
By virtue of component (A2) , the thermally conductive composition can appropriately reduce the density of a three-dimensional structure formed by a crosslinking reaction during the curing of the composition, making it possible to improve the stress relaxation/softness property of a cured product of the thermally conductive composition.
In some embodiments, component (A2) is preferably a polymethylhydrogensiloxane having one end blocked by a dimethylhydrogensiloxane unit and another end blocked by a trimethylsiloxane unit, and having an intermediate unit comprising a dimethylsiloxane unit.
In some embodiments, component (A2) is added to the thermally conductive polyorganosiloxane composition in an amount such that in terms of weight units the metal-containing phthalocyanine is within the range of 0.01 to 5.0%of the composition as a whole. Alternatively, component (A2) is in amount of 0.05 to 3.0%of the composition. Alternatively, component (A2) is in amount of 0.1 to 1.0 %of the composition.
In some embodiments, component (A2) has a SiH content in range of 0.05%to 0.8%, 0.10%to 0.6%, 0.15%to 0.4%or 0.20%to 0.3%.
Component (B)
Component (B) is a SiH crosslinker containing on average 2 or more SiH groups per molecule, which participates in a hydrosilylation reaction with alkenyl groups of component (C) and, as a result, cross-links and cures component (C) . Component (B) may have a linear, branched, partially branched linear, cyclic, dendrite, or resinous molecular structure. The silicon-bonded hydrogen atoms in component (B) may be located at terminal, pendant, or at both terminal and pendant positions.
In some embodiments, component (B) can be:
(B1) a SiH cross linker having a formula: MD_y ^HD_xM; and/or
(B2) a SiH chain extender having a formula: M^HD_x ^HM;
wherein M is a siloxane unit of R₃SiO_1/2-, ^HM is a siloxane unit of HR₂SiO_1/2-, D is a siloxane unit of R₂SiO_2/2-, and ^HD is a siloxane unit of HRSiO_2/2-, R is independently selected from hydrocarbon groups, and y=1 to 20 and x=1 to 5.
In some embodiments of the present inventin, the structure of the crosslinker, component (B) , can be defined by the Si-H content which can be 0.1 to 1.2 weight %, 0.3 to 1.0 weight %or 0.5 to 0.8 weight%H atoms attached to Si-H. The amount of component (B) can be defined as a Si-H/Vi ratio from components (B) and (C) , in a range from 0.2 to 1.4, from 0.4 to 0.95 or from 0.6-0.7.
Silicon-bonded groups of component (B) other than silicon-bonded hydrogen atoms may be represented by monovalent hydrocarbon groups which do not contain unsaturated aliphatic bonds, such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, decyl, undecyl, dodecyl, or similar alkyl groups; cyclopentyl, cyclohexyl, or similar cycloalkyl groups; phenyl, tolyl, xylyl, or similar aryl groups; benzyl, phenethyl, or similar aralkyl groups; or 3, 3, 3-trifluoropropyl, 3-chloropropyl or similar halogenated alkyl group. Preferable are alkyl and aryl groups, in particular, methyl and phenyl groups.
Component (B) may comprise siloxane units including, but not limited to, HR³ ₂SiO_1/2, R³ ₃SiO_1/2, HR³SiO_2/2, R³ ₂SiO_2/2, R³SiO_3/2 and SiO_4/2 units, where each R³ is independently selected from monovalent organic groups free of aliphatic unsaturation.
Component (B) may comprise a compound of the formulae
R³ ₃SiO (R³ ₂SiO) _h (R³HSiO) _iSiR³ ₃,
R³ ₂HSiO (R³ ₂SiO) _j (R³HSiO) _kSiR³ ₂H,
or a combination thereof.
In above formulae, subscript h has an average value ranging from 0 to 2000, subscript i has an average value ranging from 2 to 2000, subscript j has an average value ranging from 0 to 2000, and subscript k has an average value ranging from 0 to 2000. Each R³is independently a monovalent organic group. Suitable monovalent organic groups include alkyl such as methyl, ethyl, propyl, pentyl, octyl, decyl, undecyl, dodecyl, and octadecyl; cycloalkyl such as cyclopentyl and cyclohexyl; alkenyl such as vinyl, allyl, butenyl, and hexenyl; alkynyl such as ethynyl, propynyl, and butynyl; and aryl such as phenyl, tolyl, xylyl, benzyl, and 2-phenylethyl.
Exemplary molecules useful as component (B) are:
a methylhydrogenpolysiloxane capped at both molecular terminals with trimethylsiloxy groups;
a copolymer of a methylhydrogensiloxane and a dimethylsiloxane capped at both molecular terminals with trimethylsiloxy groups;
a dimethylpolysiloxane capped at both molecular terminals with dimethylhydrogensiloxy groups;
a methylhydrogenpolysiloxane capped at both molecular terminals with dimethylhydrogensiloxy groups;
a copolymer of a methylhydrogensiloxane and a dimethylsiloxane capped at both molecular terminals with dimethylhydrogensiloxy groups;
a cyclic methylhydrogenpolysiloxane;
an organosiloxane composed of siloxane units represented by the following formulae: (CH₃) ₃SiO_1/2, (CH₃) ₂HSiO_1/2 and SiO_4/2; tetra (dimethylhydrogensiloxy) silane, or methyl-tri (dimethylhydrogensiloxy) silane.
Component (B) may be a combination of two or more organohydrogenpolysiloxanes that differ in at least one of the following properties: structure, average molecular weight, viscosity, siloxane units, and sequence. Component (B) may include a silane. Dimethylhydrogensiloxy-terminated polydimethylsiloxanes having relatively low degrees of polymerization (e.g., DP ranging from 3 to 50) are commonly referred to as chain extenders, and a portion of component (B) may be a chain extender.
Methods of preparing linear, branched, and cyclic organohydrogenpolysiloxanes suitable for use as component (B) , such as hydrolysis and condensation of organohalosilanes, are well known in the art. Methods of preparing organohydrogenpolysiloxane resins suitable for use as component (B) are also well known as exemplified in U.S. Pat. Nos. 5,310,843; 4,370,358; and 4,707,531.
Component (C)
Component (C) is a polyorganosiloxane containing 2 or more alkenyl groups (e.g., vinyl groups) per molecule. The organoalkylpolysiloxane polymer that constitutes component (C) contains in one molecule on average at least 2 silicon-bonded alkenyl groups. The organoalkylpolysiloxane may have a linear molecular structure or, to some extent, branched linear, or dendrite molecular structure. It may be in the form of a single polymer, copolymer, or a mixture of two or more polymers.
The silicon-bonded alkenyl groups of component (C) are exemplified by vinyl, allyl, butenyl, pentenyl, hexenyl, or hepteny groups, of which preferable are vinyl, allyl, or hexenyl groups. More than one kind of alkenyl groups may be found in one molecule. The aliphatically unsaturated organic groups in component (C) may be located at terminal, pendant, or both terminal and pendant positions.
The remaining silicon-bonded organic groups in component (C) may be monovalent organic groups free of aliphatic unsaturation. These monovalent organic groups may have at least one and as many as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 16, 18, and 20 carbon atoms, and are exemplified by, but not limited to alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, octyl, decyl, undecyl, dodecyl and octadecyl; cycloalkyl groups such as cyclopentyl and cyclohexyl; and aromatic (aryl) groups such as phenyl, tolyl, xylyl, benzyl, and 2-phenylethyl; and 3, 3, 3, -trifluoropropyl, or similar halogenated alkyl groups. In certain embodiments, the organic groups are methyl or phenyl groups.
The terminal groups may be alkyl or aryl groups as described in the preceding paragraph, alkoxy groups exemplified by methoxy, ethoxy, or propoxy groups, or hydroxyl groups.
Certain exemplary molecules of component (C) may be described by the following formulae:
R¹ ₂R²SiO (R¹ ₂SiO) _d (R¹R²SiO) _eSiR¹ ₂R²,
R¹ ₃SiO (R¹ ₂SiO) _f (R¹R²SiO) _gSiR¹ ₃, or
a combination thereof.
In above formulae, each R¹is independently a monovalent organic group free of aliphatic unsaturation and each R²is independently an aliphatically unsaturated organic group. Subscript d has an average value of at least 0.1, typically at least 0.5, more typically at least 0.8, and most typically, at least 2, alternatively subscript d may have a value ranging from 0.1 to 2000. Subscript e may be 0 or a positive number. Alternatively, subscript e may have an average value ranging from 0 to 2000. Subscript f may be 0 or a positive number. Alternatively, subscript f may have an average value ranging from 0 to 2000. Subscript g has an average value of at least 0.1, typically at least 0.5, more typically at least 0.8, and most typically, at least 2. Alternatively subscript g may have an average value ranging from 0.1 to 2000. Suitable monovalent organic groups for R¹ include, but are not limited to, alkyl such as methyl, ethyl, propyl, pentyl, octyl, undecyl, and octadecyl; cycloalkyl such as cyclopentyl and cyclohexyl; and aryl such as phenyl, tolyl, xylyl, benzyl, and 2-phenylethyl. Each R² is independently an aliphatically unsaturated monovalent organic group, exemplified by alkenyl groups such as vinyl, allyl, butenyl, pentenyl, hexenyl, or heptenyl group.
Exemplary molecules useful as component (C) are:
a dimethylpolysiloxane capped at both molecular terminals with dimethylvinylsiloxy groups;
a dimethylpolysiloxane capped at both molecular terminals with methylphenylvinylsiloxy groups;
a copolymer of a methylphenylsiloxane and a dimethylsiloxane capped at both molecular terminals with dimethylvinylsiloxy groups;
a copolymer of a methylvinylsiloxane and a dimethylsiloxane capped at both molecular terminals with trimethylsiloxy groups;
a copolymer of a methylvinylsiloxane and a dimethylsiloxane capped at both molecular terminals with dimethylvinylsiloxy groups;
a methyl (3, 3, 3-trifluoropropyl) polysiloxane capped at both molecular terminals with dimethylvinylsiloxy groups;
a copolymer of a methyl (3, 3, 3-trifluoropropyl) siloxane and a dimethylsiloxane capped at both molecular terminals with dimethylvinylsiloxy groups;
a copolymer of a methylvinylsiloxane and a dimethylsiloxane capped at both molecular terminals with silanol groups;
a copolymer of a methylvinylsiloxane, a methylphenylsiloxane, and a dimethylsiloxane capped at both molecular terminals with silanol groups; or
an organosiloxane copolymer composed of siloxane units represented by the following formulae: (CH₃) ₃SiO_1/2, (CH₃) ₂ (CH₂=CH) SiO_1/2, CH₃SiO_3/2 and (CH₃) ₂ SiO_2/2.
Component (C) can be one single base polymer or a combination comprising two or more base polymers that differ in at least one of the following properties: structure, viscosity, average molecular weight, siloxane units, and sequence.
Methods of preparing polyorganoalkylsiloxane fluids suitable for use as component (C) , such as hydrolysis and condensation of the corresponding organohalosilanes or equilibration of cyclic polydiorganosiloxanes, are well known in the art.
In addition to the polydiorganosiloxane described above, component (C) may further comprise a resin such as an MQ resin consisting essentially of R^xSiO_1/2 units and SiO_4/2 units, a TD resin consisting essentially of R^xSiO_3/2 units and R^xSiO_2/2 units, an MT resin consisting essentially of R^xSiO units and R^xSiO_3/2 units, an MTD resin consisting essentially of R^xSiO_1/2 units, R^xSiO_3/2 units, and R^x ₂SiO_2/2 units, or a combination thereof. R^x designates any monovalent organic group, for example but are not limited to, monovalent hydrocarbon groups and monovalent halogenated hydrocarbon groups. Monovalent hydrocarbon groups include, but are not limited to, alkyl such asrethyl, ethyl, propyl, pentyl, octyl, undecyl, and octadecyl; cycloalkyl such as cyclohexyl; alkenyl such as vinyl, allyl, butenyl, and hexenyl; alkynyl such as ethynyl, propenyl, and butynyl; and aryl such as phenyl, tolyl, xylyl, benzyl, and 2-phenylethyl.
In some embodiments, component (C) is added to the thermally conductive polyorganosiloxane composition in an amount within the range of 5.0 to 10.0%of the composition as a whole. Alternatively, component (C) is in amount of 6.0 to 9.0%of the composition. Alternatively, component (C) is in amount of 7.0 to 8.0 %of the composition.
In some embodiments, (C) polyorganosiloxane containing 2 or more alkenyl groups per molecule has an amount such that SiH/Vi ratio is in range of 1.07-1.26, based on the total SiH of components A2 and B in the composition, depending on the desired properties of the cured product of the composition. In certain embodiments, the SiH/Vi ratio is within the range of from 1.10 to 1.20, and in other embodiments, from 1.15 to 1.18.
In some embodiments, (C) polyorganosiloxane containing 2 or more alkenyl groups per molecule has an amount such that SiH/Vi ratio is greater than 0.15, greater than 0.20, based on the SiH of components A2 in the composition
Component (D)
Component (D) is a filler treating agent, which can treat a thermally conductive filler and/or the spacer, if present. Treating agents and treating methods are known in the art, see for example, U.S. Pat. No. 6,169,142 (col. 4, line 42 to col. 5, line 2) .
The amount of component (D) may vary depending on various factors including the type and amounts of fillers selected for the thermally conductive filler and/or the spacer and whether the filler is treated with component (D) in situ or before being combined with other components of the composition. However, the composition may comprise an amount ranging from 0.1%to 2%of component (D) .
The component (D) may comprise an alkoxysilane having the formula: R⁶ _mSi (OR⁷) _(4-m) , where subscript m is 1, 2, or 3; alternatively m is 3. Each R⁶is independently a monovalent organic group, such as a hydrocarbon group of 1 to 50 carbon atoms, alternatively 6 to 18 carbon atoms. R⁶is exemplified by alkyl groups such as hexyl, octyl, dodecyl, tetradecyl, hexadecyl, and octadecyl; and aromatic groups such as benzyl, phenyl and phenylethyl. R⁶can be saturated or unsaturated, branched or unbranched, and unsubstituted. R⁶can be saturated, unbranched, and unsubstituted.
Each R⁷may be an unsubstituted, saturated hydrocarbon group of 1 to 4 carbon atoms, alternatively 1 to 2 carbon atoms. Alkoxysilanes for component (D) are exemplified by hexyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, tetradecyltrimethoxysilane, phenyltrimethoxysilane, phenylethyltrimethoxysilane, octadecyltrimethoxysilane, octadecyltriethoxysilane, and a combination thereof.
Alkoxy-functional oligosiloxanes can also be used as treatment agents. Alkoxy-functional oligosiloxanes and methods for their preparation are known in the art, see for example, EP 1101167A2. For example, suitable alkoxy-functional oligosiloxanes include those of the formula (R⁸O) _nSi (OSiR⁹ ₂R¹⁰) _(4-n) . In this formula, subscript n is 1, 2, or 3, alternatively n is 3. Each R⁸ can be an alkyl group. Each R⁹ can be independently selected from saturated and unsaturated monovalent hydrocarbon groups of 1 to 10 carbon atoms. Each R¹⁰ can be a saturated or unsaturated monovalent hydrocarbon group having at least 11 carbon atoms.
In some preferred embodiments, component (D) comprises at least one of the following: (D1) mono-trialkoxysiloxy terminated dimethylpolysiloxane; (D2) alkyl trialkoxysilane; and (D3) mono-dimethylvinylsiloxy and mono-trimethoxysiloxy terminated dimethylsiloxane. In some embodiments, Said D1 has a formula of Me₃SiO- (Me₂SiO) _p-Si (OMe) ₃, where p=0-110; D2 has a formula of C_nH_2n+1Si (OMe) ₃, where n=6-20; and D3 has a formula of ViMe₂SiO- (Me₂SiO) _m-Si (OMe) ₃, where m=1-25.
Metal fillers can be treated with alkylthiols such as octadecyl mercaptan and others, and fatty acids such as oleic acid, stearic acid, titanates, titanate coupling agents, zirconate coupling agents, and a combination thereof.
Treatment agents for alumina or passivated aluminum nitride may include alkoxysilyl functional alkylmethyl polysiloxanes (e.g., partial hydrolysis condensate of R¹¹OR¹² _pSi (OR¹³) _(4-o-p) or cohydrolysis condensates or mixtures) , or similar materials where the hydrolyzable group may comprise silazane, acyloxy or oximo. In all of these, a group tethered to Si, such as R¹¹ in the formula above, is a long chain unsaturated monovalent hydrocarbon or monovalent aromatic-functional hydrocarbon. Each R¹² is independently a monovalent hydrocarbon group, and each R¹³ is independently a monovalent hydrocarbon group of 1 to 4 carbon atoms. In the formula above, subscript o is 1, 2, or 3 and subscript p is 0, 1, or 2, with the proviso that the sum o+p is 1, 2, or 3. One skilled in the art could optimize a specific treatment to aid dispersion of the filler without undue experimentation.
Component (E)
Component (E) is a thermally conductive filler. Component (E) may be both thermally conductive and electrically conductive. Alternatively, component (E) may be thermally conductive and electrically insulating. Thermally conductive fillers are known in the art, see for example, U.S. Pat. No. 6,169,142 (col. 4, lines 7-33) . Component (E) may comprise a metallic filler, an inorganic filler, a meltable filler, or a combination thereof.
The amount of component (E) in the composition depends on various factors including the silicone cure mechanism selected for the composition and the thermally conductive filler selected for component (E) . However, the amount of component (E) may range from 30%to 97%, alternatively 50%to 95%by volume of the composition.
Metallic fillers include particles of metals and particles of metals having layers on the surfaces of the particles. These layers may be, for example, metal nitride layers or metal oxide layers on the surfaces of the particles. Suitable metallic fillers are exemplified by particles of metals selected from the group consisting of aluminum, copper, gold, nickel, tin, silver, and combinations thereof, and alternatively aluminum. Suitable metallic fillers are further exemplified by particles of the metals listed above having layers on their surfaces selected from the group consisting of aluminum nitride, aluminum oxide, copper oxide, nickel oxide, silver oxide, and combinations thereof. For example, the metallic filler may comprise aluminum particles having aluminum oxide layers on their surfaces.
Inorganic fillers are exemplified by onyx; aluminum trihydrate, metal oxides such as aluminum oxide, beryllium oxide, magnesium oxide, and zinc oxide; nitrides such as aluminum nitride and boron nitride; carbides such as silicon carbide and tungsten carbide; and combinations thereof. barium titanate, carbon fibers, diamond, graphite, magnesium hydroxide, and a combination thereof.
Meltable fillers may comprise Bi, Ga, In, Sn, or an alloy thereof. The meltable filler may optionally further comprise Ag, Au, Cd, Cu, Pb, Sb, Zn, or a combination thereof. Examples of suitable meltable fillers 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 alloys, Sn-Ag-Cu-Zn alloys, and combinations thereof. The meltable filler may have a melting point ranging from 50℃. to 250℃., alternatively 150℃. to 225℃. The meltable filler may be a eutectic alloy, a non-eutectic alloy, or a pure metal. Meltable fillers are commercially available.
The shape of the thermally conductive filler particles is not specifically restricted, however, rounded or spherical particles may prevent viscosity increase to an undesirable level upon high loading of the thermally conductive filler in the composition. The average particle size of the thermally conductive filler will depend on various factors including the type of thermally conductive filler selected for component (E) and the exact amount added to the curable composition, as well as the bondline thickness of the device in which the cured product of the composition will be used. In some particular instances, the thermally conductive filler may have an average particle size ranging from 0.1 micrometer to 80 micrometers, alternatively 0.1 micrometer to 50 micrometers, and alternatively 0.1 micrometer to 10 micrometers.
Component (E) may be a single thermally conductive filler or a combination of two or more thermally conductive fillers that differ in at least one property such as particle shape, average particle size, particle size distribution, and type of filler. In some embodiments, combinations of metallic and inorganic fillers, such as a combination of aluminum and aluminum oxide fillers; a combination of aluminum and zinc oxide fillers; or a combination of aluminum, aluminum oxide, and zinc oxide fillers may be used. In other embodiments, it may be desirable to combine a first conductive filler having a larger average particle size with a second conductive filler having a smaller average particle size in a proportion meeting the closest packing theory distribution curve. An example would be mixing two aluminum oxide preparations having different average particle sizes. In other embodiments, different thermally conductive filler materials with difference sizes may be used, for example, a combination of an aluminum oxide having a larger average particle size with a zinc oxide having a smaller average particle size. Alternatively, it may be desirable to use combinations of metallic fillers, such as a first aluminum having a larger average particle size and a second aluminum having a smaller average particle size. Use of a first filler having a larger average particle size and a second filler having a smaller average particle size than the first filler may improve packing efficiency, may reduce viscosity, and may enhance heat transfer.
Thermally conductive fillers are commercially available. For example, meltable fillers may be obtained from Indium Corporation of America, Utica, N.Y., U.S.A.; Arconium, Providence, R.I., U.S.A.; and AIM Solder, Cranston, R.I., U.S.A. Aluminum fillers are commercially available, for example, from Toyal America, Inc. of Naperville, Ill., U.S.A. and Valimet Inc., of Stockton, Calif., U.S.A. Silver filler is commercially available from Metalor Technologies U.S.A. Corp. of Attleboro, Mass., U.S.A. Zinc oxides, such as zinc oxides having trademarks and are commercially available from Zinc Corporation of America of Monaca, Pa., U.S.A. Further, CB-A20S and Al-43-Me are aluminum oxide fillers of differing particle sizes commercially available from Showa-Denko, and AA-04, AA-2, and AA 18 are aluminum oxide fillers commercially available from Sumitomo Chemical Company. Boron nitride filler is commercially available from Momentive Corporation, Cleveland, Ohio, U.S.A.
In some preferred embodiments, (E) thermally conductive filler comprises at least one of the following: (E1) spherical Al₂O₃ having an average particle size of 10-100μm; and (E2) irregular Al₂O₃ having an average particle size of 0.1 to 5 μm. In some embodiments, (E) thermally conductive filler comprises: (E1) spherical Al₂O₃ having an average particle size of 10-100μm; (E2) irregular Al₂O₃ having an average particle size of 1 to 5 μm; and (E3) irregular Al₂O₃ having an average particle size of 0.1 to 0.7μm.
Component (F)
Component (F) is a catalyst that accelerates the hydrosilylation reaction. Suitable hydrosilylation catalysts are known in the art and commercially available. Component (F) may comprise a platinum group metal selected from platinum, rhodium, ruthenium, palladium, osmium or iridium metal or organometallic compound thereof, or a combination thereof. Preferred are platinum compounds such as a chloroplatinic acid, a reaction product of a chloroplatinic acid and an alcohol, a platinum-olefin complex, a platinum-vinylsiloxane complex, a platinum-ketone complex and a platinum-phosphine complex; rhodium compounds such as a rhodium-phosphine complex and a rhodium-sulfide complex; and palladium compounds such as a palladium-phosphine complex, more preferred are platinum compounds, and especially preferred is a platinum-vinylsiloxane complex.
Component (F) is used in an amount such that in terms of weight units the content of platinum group metal is in the range of 0.01 to 1,000 ppm, alternatively 0.1 to 500 ppm alternatively 1 to 500 ppm, alternatively 2 to 200, alternatively 5 to 150 ppm, per the total weight of components (B) and (C) .
Component (F) is exemplified by a fine platinum metal powder, platinum black, platinum dichloride, platinum tetrachloride; chloroplatinic acid, alcohol-modified chloroplatinic acid, chloroplatinic acid hexahydrate; and complexes of said compounds, such as platinum complex of olefin, platinum complex of carbonyl, platinum complex of alkenylsiloxane, e.g. 1, 3-divinyltetramethyldisiloxane, platinum complex of low molecular weight organopolysiloxanes, for example 1, 3-diethenyl-1, 1, 3, 3-tetramethyldisiloxane, a complex of chloroplatinic acid with β-diketone, a complex a chloroplatinic acid with olefin, and a complex of a chloroplatinic acid with 1, 3-divinyltetramethyldisiloxane.
Component (F) may also be a rhodium compound, such as those expressed by formulae: RhX₃ [ (R⁴) ₂S] ₃; (R⁵ ₃P) ₂Rh (CO) X, (R⁵ ₃P) ₂Rh (CO) H, Rh₂X₂Y₄, H_fRh_g (En) _hCl_i, or Rh [O (CO) R] _3-j (OH) _j (where X designates a hydrogen atom, chlorine atom, bromine atom, or iodine atom; Y designates a methyl group, ethyl group, or a similar alkyl group, CO, C₈H₁₄ or 0.5 C₈H₁₂; R⁴ designates a methyl, ethyl, propyl, or a similar alkyl group; a cycloheptyl, cyclohexyl, or a similar cycloalkyl group; or a phenyl, xylyl or a similar aryl group; R⁵ designates methyl group, ethyl group, or a similar alkyl group; phenyl, tolyl, xylyl, or a similar aryl group; methoxy, ethoxy, or a similar alkoxy group; “En” designates ethylene, propylene, butene, hexene, or a similar olefin; “f” is 0 or 1; “g” is 1 or 2; “h” is an integer from 1 to 4; “i” is 2, 3, or 4; and “j” is 0 or 1) . More particularly, the rhodium compounds are RhCl (Ph₃P) ₃, RhCl₃ [S (C₄H₉) ₂] ₃, [Rh (O₂CCH₃) ₂] ₂, Rh (OCCH₃) ₃, Rh₂ (C₈H₁₅O₂) ₄, Rh (C₅H₇O₂) ₃, Rh (C₅H₇O₂) (CO) ₂, and Rh (CO) [Ph₃P] (C₅H₇O₂) .
Component (F) may also be iridium group catalysts represented by the following formulae: Ir (OOCCH₃) ₃, Ir (C₅H₇O₂) ₃, [Ir (Z) (En) ₂] ₂, or [Ir (Z) (Dien) ] ₂ (where “Z” designates a chlorine atom, bromine atom, iodine atom, or a methoxy group, ethoxy group, or a similar alkoxy group; “En” designates ethylene, propylene, butene, hexene, or a similar olefin; and “Dien” designates cyclooctadiene) tetrakis (triphenyl) . Component (F) may also be palladium, a mixture of palladium black and triphenylphosphine.
Component (G)
In the present disclosure, the thermally conductive composition can optionally further comprises (G) a hydrosilylation catalyst inhibitor. In the present invention, the hydrosilylation catalyst inhibitor can slow the reaction rate by inhibiting the hydrosilylation catalyst as needed so that mixing can be completed before the mixture starts curing reaction. Therefore, it shall be understood that in case curing cannot be conducted quickly during and right after mixing, it may become necessary to add component (G) , but in case curing can be conducted immediately right after mixing, it may not need to add component (G) . Determining whether it needs to add component (G) into the polysiloxane composite is within the capability of one of ordinary skill in the art.
Examples of the hydrosilylation catalyst inhibitor comprise methylvinylcyclosiloxane, tetravinyltetramethyl- cyclotetrasiloxane (vinyl D4) , ethynylcyclohexanol (ECH) and mixtures thereof. With particular preference, the hydrosilylation catalyst inhibitor may be incorporated into the curable silicone-based composition in an amount of from 0%to 2%by weight, from 0.05 %to 1.5 %by weight or from 0.5 %to 1.2 %by weight, such as 0.1 %by weight, based on the total amount of the curable silicone-based composition, which depends on desired curing speed.
In some embodments of the present invention, the amount of component (G) is 0.05～2 parts by weight, 0.1～1.5 parts by weight, 0.5～1.0 parts by weight or 0.7～0.9 parts by weight, based on 100 parts by weight of component (A) .
Component (H)
In the present disclosure, the thermally conductive composition can optionally further comprises (H) a thixotropic agent-surface treated fumed silica.
In some embodments of the present invention, the amount of component (H) is 0.05～2 parts by weight, 0.1～1.5 parts by weight, 0.5～1.0 parts by weight or 0.7～0.9 parts by weight, based on 100 parts by weight of component (A) .
Component (I)
In the present disclosure, the thermally conductive composition can optionally further comprises (I) a spacer.
Component (I) can comprise organic particles, inorganic particles, or a combination thereof. Spacers can be thermally conductive, electrically conductive, or both. Spacers can have a particle size of at least 25 micrometers up to 125 micrometers. Spacers can comprise monodisperse beads, such as glass or polymer (e.g., polystyrene) beads. Spacers can comprise thermally conductive fillers such as alumina, aluminum nitride, atomized metal powders, boron nitride, copper, and silver. The amount of Component (I) depends on various factors including the particle size distribution, pressure to be applied during placement of the curable thermally conductive composition or cured product prepared therefrom, and temperature during placement. However, the thermally conductive composition may contain an amount of Component (I) ranging from 0.05%to 2%, alternatively 0.1%to 1%. Component (I) may be added to control bondline thickness of the cured product of the curable thermally conductive composition.
Process for producing the thermally conductive composition
Typical process are to use high shear mixer with base heating capabilities. In the present invention the thermally conductive composition can be produced as follows: component A1, component A2, component B, component C, component D, and component F were mixed using a Speed mixer in a container, and then component E was loaded gradually under room temperature (RT) , to form a thermally conductive composition in form of paste.
[Examples]
The following is a more detailed description of the present invention with reference to examples. The present invention, however, is not restricted to these examples. All parts and percentages are by weight unless otherwise specified.
[Slope flowability]
Slope flowability was measured by using the mold with a slope gradient of 5° as shown in Fig. 3. The paste (i.e., sample material) was packed into a 1mL syringe as shown in Fig. 4 and was dispensed through the opening. The distance of the paste flowed in mm corresponds to the slope flowability (mm) .
[Shore A hardness]
Cured samples were measured by using a Shore A durometer (Instron Conveloader EAETS-EQ029) for Shore A hardness of the fresh and aged durometer pucks according to the CMT standard method (CTM 0099B) .
[Thermal conductivity]
The thermal conductivity was measured by Hotdisk transient technology with Kapton No. 5456 sensor 5s/80mW.
The information of the raw materials used in Examples is listed in the following Table 1:
Table 1. Raw materials used in Examples
Inventive Examples 1-4 (IE 1～4) and Comparative Examples 1-10 (CE 1-10)
In Inventive Examples 1-4 of the present disclosure, the thermally conductive composition was produced in small scale of lab-made sample using those raw materials and their amounts described in Table 2. Comparative Examples 1-10 were provided here as control. Component C-1, components D-1, D-2 and D-3 as well as other components listed in Table 2 except components E-1, E-2 and E-3 were mixed using a Speed mixer in a container, and then components E-1, E-2 and E-3 were loaded gradually under room temperature (RT) , to form a paste.
Each paste of IE 1-4 and CE 1-10 was measured for the slope flowability. Afterwards an alumina dish was filled with the paste and left the paste to cure at room temperature for 24h. Cured samples were tested for thermal conductivity and hardness of the fresh durometer pucks. Then the durometer pucks were put in an electric oven with a running temperature of 175℃ and 200℃. After keeping for a certain time, such as 3 days, 7 days, 10 days, 14 days, 21 days, 28 days, 35 days and 42 days, the durometer pucks was taken out and cooled at room temperature, then tested for the hardness in a Shore A durometer.
Table 2: Formulations used in Inventive Examples and Comparative Examples
Table 2: (cont. )
Test parameters are listed in the following Table 3, and results are listed in the following Table 4:
Table 3. Test Properties and Performance Criteria
Table 4: Test Properties of Inventive Examples and Comparative Examples
Table 4: (cont. )
＊＊Many bubbles inside durometer puck and not able to measure the hardness
The hardness changes of Inventive Examples IE1, IE2, IE3 and IE4 under 175℃ and 200℃ aging were shown in Fig. 1 and 2, respectively, together with Comparative Examples CE1, CE2, CE3, CE4, CE5, CE6, CE7, CE8, CE9 and CE10 as a control.
It was obvious that with prolonged aging time, the sole effect of A-1 (copper-containing phthalocyanine) and A-2 (low molecule one functionality pendant SiH containing polyorganosiloxane) to slow down the hardening was limited, see for sample CE1 and CE2. While with synergy of A-1 and A-2, the hardness was more stable. After exposure at 175℃ and 200℃ for 42 days (1000h) , the hardness of sample IE4 was 25 Shore A and 39 Shore A, respectively. Upon further optimizing the ratio of A-1 and A-2 by increasing the amount of A-1, similar synergetic effect worked for IE1 and IE2, with a hardness of 20 Shore A and 18 Shore A after aging at 175℃ for 42 days, and 35 Shore A and 25 Shore A after aging at 200℃ for 42 days. While outside the optimized ratio of A-1 and A-2, relatively poor high temperature stability was found for CE6, CE7, CE8 and CE9.
Compared with the low molecule one functionality terminal SiH containing polyorganosiloxane used in JP6243567B1, the low molecule one functionality pendant SiH containing polyorganosiloxane disclosed herein had innovation towards the synergetic effect with copper-containing phthalocyanine to enable high temperature 175-200℃ stability. CE4, CE5 and CE10 showed dsistinct hardness change with a durometer of 28 Shore A, 52 Shore A and 55 Shore A, and 29 Shore A, 47 Shore A and 36 Shore A after aging at 175℃ and 200℃ for 42 days. With the sole role of with the low molecule one functionality terminal SiH containing polyorganosiloxane, much severe hardening can be found for sample CE3. Similar result with the low molecule one functionality pendant SiH containing polyorganosiloxane.
Without treating agent D-3, IE3 showed stable thermal performance at ultra-high temperature with a well maintained softness of Shore A 3 after aging at 175℃ for 42 days and the hardness was Shore A 35 which was less than Shore A 40 after aging at 200℃ for 42 days.

Claims

A thermally conductive composition, which comprises:

(A1) a metal-containing phthalocyanine; and

(A2) a SiH polyorganosiloxane comprising a structural formula:

R₃-Si- (OSiR₂) _m- (OSiRH) _n-SiR₃, where R is independently selected from hydrocarbon groups, and on average n=1 and m=0 to 10;

(B) a SiH crosslinker containing on average 2 or more SiH groups per molecule;

(C) a polyorganosiloxane containing 2 or more alkenyl groups per molecule;

(D) a filler treating agent;

(E) a thermally conductive filler; and

(F) a hydrosilylation reaction catalyst.
The thermally conductive composition according to claim 1, wherein (A1) metal-containing phthalocyanine has an amount of 0.25-0.40 wt%, based on the total weight of the composition.
The thermally conductive composition according to claim 1, wherein (A2) SiH polyorganosiloxane has a SiH content in range of 0.05%to 0.8%.
The thermally conductive composition according to claim 1, wherein (B) SiH crosslinker containing on average 2 or more SiH groups per molecule has a SiH content in range of 0.01%to 0.2%.
The thermally conductive composition according to claim 1, wherein (C) polyorganosiloxane containing 2 or more alkenyl groups per molecule has an amount such that SiH/Vi ratio is in range of 1.07-1.26, based on the total SiH of components A2 and B in the composition.
The thermally conductive composition according to claim 1, wherein (D) filler treating agent comprises at least one of the following:

(D1) mono-trialkoxysiloxy terminated dimethylpolysiloxane;

(D2) alkyl trialkoxysilane; and

(D3) mono-dimethylvinylsiloxy and mono-trimethoxysiloxy terminated dimethylsiloxane.
The thermally conductive composition according to claim 1, wherein (E) thermally conductive filler comprises at least one of the following:

(E1) spherical Al₂O₃ having an average particle size of 10-100μm; and

(E2) irregular Al₂O₃ having an average particle size of 0.1 to 5 μm.
The thermally conductive composition according to claim 1, further comprises at least one of the following:

(G) an inhibitor;

(H) a thixotropic agent-surface treated fumed silica; and

(I) a spacer.
A cured silicone prepared by curing the thermally conductive composition of claim 1.
A thermal interface material comprising the cured silicone according to claim 9.
The thermal interface material according to claim 10, wherein the material comprises a support coated with the cured silicone.
The thermal interface material according to claim 11, wherein the thermal interface material dissipates heat.
A method of increasing high temperature stability of a thermally conductive polyorganosiloxane composition comprising the step of adding components A1 and A2 to the thermally conductive polyorganosiloxane composition:

(A1) a metal-containing phthalocyanine; and

(A2) a SiH polyorganosiloxane comprising a structural formula:

R₃-Si- (OSiR₂) _m- (OSiRH) _n-SiR₃, where R is independently selected from hydrocarbon groups, and on average n=1 and m=0 to 10.
A method of conducting heat from a first component to a second component wherein the first component has a higher temperature than the second component and the thermal interface material according to claim 10 is in contact with the first component and with the second component.
A method of dissipating heat from a first component wherein the thermal interface material according to claim 10 is in contact with the first component.