Thermally conductive addition-curable silicone composition and method for producing thermally conductive addition-curable silicone composition

Abstract

The present invention is a thermally conductive addition-curable silicone composition characterized by containing (A) an organopolysiloxane having at least one aliphatic unsaturated hydrocarbon group per molecule and having a kinematic viscosity at 25°C of 60-100,000 mm2 / s, (B) a thermally conductive filler containing amorphous aluminum nitride powder and amorphous zinc oxide powder, (C) an organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms per molecule, (D) a platinum group metal catalyst, (E) an organopolysiloxane represented by general formula (1), and (F) one or more addition curing reaction control agents selected from the group consisting of acetylene compounds, nitrogen compounds, organophosphorus compounds, oxime compounds, and organic chloro compounds. Provided thereby are: a thermally conductive addition-curable silicone composition that requires only a short time for the storage modulus G' to exceed the loss modulus G'' when heated and cured and has good storage stability at 25° C; and a method for producing the thermally conductive addition-curable silicone composition.

Description

Thermally conductive addition-curable silicone composition and method for producing the thermally conductive addition-curable silicone composition

[0001] The present invention relates to a thermally conductive addition-curable silicone composition and a method for producing the same.

[0002] A common problem with electronic component packages and power modules is the generation of heat during operation and the resulting degradation of performance. Various heat dissipation technologies have been used to solve this problem. In particular, a common technology is to dissipate heat by placing a cooling member near the heat-generating part in close contact with the cooling member and then efficiently removing heat from the cooling member.

[0003] In this case, if there is a gap between the heat-generating part and the cooling member, the air with poor thermal conductivity will get in, reducing heat transfer and preventing the temperature of the heat-generating part from dropping sufficiently. To prevent this air from getting in and improve heat conduction, heat-dissipating materials with good thermal conductivity and conformability to the surface of the part, such as thermal grease and thermal dissipation sheets, are used.

[0004] As a heat countermeasure for actual electronic component packages and power modules, thermal grease that can be compressed thin and has excellent penetration ability into the gap between the heat-generating part and the cooling member is suitable from the viewpoint of heat dissipation performance. Furthermore, addition-curing thermal grease is particularly useful because it can be compressed to the desired thickness and then heat-cured to prevent the heat-generating grease from flowing out (pumping out) due to expansion and contraction caused by the thermal history of repeated heating and cooling of the heat-generating part, thereby improving the reliability of electronic component packages and power modules (for example, Patent Document 1).

[0005] In recent years, with the increasing area and complexity of electronic component packages and power modules, electronic component packages and power modules can sometimes experience very large warpage. For electronic component packages and power modules that experience significant warpage, it is important to strictly control the curing properties of addition-curable thermal grease. Specifically, it is preferable to shorten the time required for the storage modulus G' to exceed the loss modulus G'' upon heat curing. This can generally be achieved by increasing the amount of platinum group metal catalyst, but the tradeoff is that this can result in poor shelf life at 25°C, shortening the usable life.

[0006] JP 2016-053140 A

[0007] In other words, there is a need for a thermally conductive addition-curable silicone composition that, when heat-cured, requires a short time for the storage modulus G' to exceed the loss modulus G'', and that has good storage stability at 25°C.

[0008] The present invention was made in consideration of the above problems, and has as its object to provide a thermally conductive addition-curable silicone composition that, when heat-cured, requires a short time for its storage modulus G' to exceed its loss modulus G'' and has good storage stability at 25°C, as well as a method for producing the same.

[0009] In order to solve the above problems, the present invention provides a thermally conductive addition-curable silicone composition, which comprises: (A) a silicone compound having at least one aliphatic unsaturated hydrocarbon group per molecule and having a kinematic viscosity at 25°C of 60 to 100,000 mm 2 (A) an organopolysiloxane having a molecular weight of 1.5 to 90% by mass of the entire composition; (B) a thermally conductive filler containing amorphous aluminum nitride powder and amorphous zinc oxide powder; (C) an organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms per molecule; (D) an effective amount of a platinum group metal catalyst; (E) an organopolysiloxane represented by the following general formula (1): (In the formula, R1 represents a monovalent hydrocarbon group having 1 to 18 carbon atoms, which may have a substituent and does not have an aliphatic unsaturated bond, and each R 1 may be the same or different, and m is an integer of 5 to 100.) (F) an effective amount of one or more addition curing reaction inhibitors selected from the group consisting of acetylene compounds, nitrogen compounds, organic phosphorus compounds, oxime compounds, and organic chloro compounds.

[0010] When heat-cured, such a thermally conductive addition-curable silicone composition requires a short time for the storage modulus G' to exceed the loss modulus G'', and has good storage stability at 25°C.

[0011] In this case, the thermally conductive addition-curable silicone composition of the present invention is preferably characterized in that component (C) is an organohydrogenpolysiloxane having two epoxy ring-containing organic groups per molecule.

[0012] Such a thermally conductive addition-curable silicone composition allows for good adhesion between the heat generating portion and the cooling member.

[0013] Furthermore, the thermally conductive addition-curable silicone composition of the present invention is preferably characterized in that, when the storage modulus G' and loss modulus G'' of the thermally conductive addition-curable silicone composition are measured using a viscoelasticity measuring device capable of measuring shear elasticity, while the composition is heated from 25°C to 150°C at a rate of 5°C / minute and then maintained at 150°C for 7,200 seconds, it takes 500 seconds or less for the storage modulus G' to exceed the loss modulus G''; and when the thermally conductive addition-curable silicone composition is stored at 25°C, it takes 5 days or more for the viscosity to exceed 1,000 Pa s.

[0014] Such a thermally conductive addition-curable silicone composition, when heat-cured, requires a short time for the storage modulus G' to exceed the loss modulus G'', and has good storage stability at 25°C, making it suitable for use in electronic component packages and power modules that are prone to significant warpage.

[0015] Furthermore, the present invention provides: (A) a polyisoprene having at least one aliphatic unsaturated hydrocarbon group in one molecule and having a kinematic viscosity at 25°C of 60 to 100,000 mm 2 (A) an organopolysiloxane having a molecular weight of 1.5 to 90% by mass of the entire composition; (B) a thermally conductive filler containing amorphous aluminum nitride powder and amorphous zinc oxide powder; (C) an organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms per molecule; (D) an effective amount of a platinum group metal catalyst; (E) an organopolysiloxane represented by the following general formula (1): (In the formula, R 1 represents a monovalent hydrocarbon group having 1 to 18 carbon atoms, which may have a substituent and does not have an aliphatic unsaturated bond, and each R 1 may be the same or different, and m is an integer of 5 to 100.) (F) an effective amount of one or more addition curing reaction inhibitors selected from the group consisting of acetylene compounds, nitrogen compounds, organic phosphorus compounds, oxime compounds, and organic chloro compounds; and mixing the components (A) to (F) while heating at 40 to 170°C.

[0016] This method for producing the thermally conductive addition-curable silicone composition of the present invention makes it possible to produce a thermally conductive addition-curable silicone composition of the present invention that, when heat-cured, requires a short time for the storage modulus G' to exceed the loss modulus G'', and that has good storage stability at 25°C.

[0017] Furthermore, the method for producing a thermally conductive addition-curable silicone composition of the present invention is preferably a method for producing a thermally conductive addition-curable silicone composition, characterized in that when the storage modulus G' and loss modulus G'' of the thermally conductive addition-curable silicone composition are measured using a viscoelasticity measuring device capable of measuring shear elasticity, the temperature is raised from 25°C to 150°C at a rate of 5°C / minute, and then the composition is maintained at 150°C for 7,200 seconds, the time required for the storage modulus G' to exceed the loss modulus G'' is 500 seconds or less, and the thermally conductive addition-curable silicone composition takes 5 days or more for its viscosity to exceed 1,000 Pa s when stored at 25°C.

[0018] The method for producing a thermally conductive addition-curable silicone composition of the present invention can reliably produce a thermally conductive addition-curable silicone composition that can be suitably used in electronic component packages and power modules that are prone to significant warpage.

[0019] The thermally conductive addition-curable silicone composition of the present invention, when heat-cured, requires a short time for the storage modulus G' to exceed the loss modulus G'', and has good storage stability at 25°C. As a result, it can be used favorably in electronic component packages and power modules that exhibit significant warpage. Furthermore, the method for producing the thermally conductive addition-curable silicone composition of the present invention can reliably produce a thermally conductive addition-curable silicone composition that can be used favorably in electronic component packages and power modules that exhibit significant warpage.

[0020] As described above, there has been a need for the development of a thermally conductive addition-curable silicone composition that, when heat-cured, requires a short time for its storage modulus G' to exceed its loss modulus G'' and that has good storage stability at 25°C.

[0021] As a result of extensive research into the above-mentioned problems, the present inventors have discovered that when a thermally conductive addition-curable silicone composition comprising the above-mentioned components (A) to (F) is heated from 25°C to 150°C at a rate of 5°C / minute and then maintained at 150°C for 7,200 seconds using a viscoelasticity measuring device capable of measuring shear elasticity, and the storage modulus G' and loss modulus G'' of the composition are measured, the time required for the storage modulus G' to exceed the loss modulus G'' is 500 seconds or less, and the viscosity of the thermally conductive addition-curable silicone composition when stored at 25°C is 5 days or more until it exceeds 1,000 Pa s, thereby completing the present invention.

[0022] That is, the present invention provides a thermally conductive addition-curable silicone composition, comprising: (A) a silicone compound having at least one aliphatic unsaturated hydrocarbon group per molecule and having a kinematic viscosity at 25°C of 60 to 100,000 mm 2 (A) an organopolysiloxane having a molecular weight of 1.5 to 90% by mass of the entire composition; (B) a thermally conductive filler containing amorphous aluminum nitride powder and amorphous zinc oxide powder; (C) an organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms per molecule; (D) an effective amount of a platinum group metal catalyst; (E) an organopolysiloxane represented by the following general formula (1): (In the formula, R 1 represents a monovalent hydrocarbon group having 1 to 18 carbon atoms, which may have a substituent and does not have an aliphatic unsaturated bond, and each R 1 may be the same or different, and m is an integer of 5 to 100.) (F) an effective amount of one or more addition curing reaction inhibitors selected from the group consisting of acetylene compounds, nitrogen compounds, organic phosphorus compounds, oxime compounds, and organic chloro compounds.

[0023] The present invention will be described in detail below, but the present invention is not limited thereto.

[0024] [Component (A)] Component (A) is a copolymer having at least one, preferably 1 to 100, more preferably 2 to 50 aliphatic unsaturated hydrocarbon groups per molecule, and a kinematic viscosity at 25°C of 60 to 100,000 mm 2 and organopolysiloxanes in which

[0025] The aliphatic unsaturated hydrocarbon group is preferably a monovalent hydrocarbon group having an aliphatic unsaturated bond and having 2 to 8 carbon atoms, more preferably 2 to 6 carbon atoms, and even more preferably an alkenyl group. Examples of alkenyl groups include vinyl, allyl, propenyl, isopropenyl, butenyl, hexenyl, cyclohexenyl, and octenyl groups. Vinyl groups are particularly preferred. The aliphatic unsaturated hydrocarbon group may be bonded to a silicon atom at the molecular chain terminal, a silicon atom in the molecular chain, or both.

[0026] The organic group other than an aliphatic unsaturated hydrocarbon group bonded to the silicon atom of the organopolysiloxane is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms, and more preferably 1 to 8 carbon atoms. Examples include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyl, and decyl; aryl groups such as phenyl, tolyl, xylyl, and naphthyl; aralkyl groups such as benzyl, phenylethyl, and phenylpropyl; and groups in which some or all of the hydrogen atoms of these groups have been substituted with halogen atoms such as fluorine, bromine, or chlorine, or with cyano groups, such as chloromethyl, chloropropyl, bromoethyl, trifluoropropyl, and cyanoethyl. Methyl and trifluoropropyl groups are particularly preferred.

[0027] The organopolysiloxane has a kinematic viscosity at 25°C of 60 to 100,000 mm 2 / s, preferably 100 to 30,000 mm2 / s. The kinematic viscosity is 60 mm 2 If the viscosity is less than 100,000 mm / s, the physical properties of the thermally conductive addition-curable silicone composition of the present invention will be reduced, and 2 If the viscosity exceeds 1 / s, the silicone composition will have poor extensibility.

[0028] In the present invention, the kinematic viscosity is a value measured at 25° C. using an Ubbelohde-type Ostwald viscometer (the same applies hereinafter).

[0029] The molecular structure of the organopolysiloxane is not particularly limited as long as it has the above properties, and examples thereof include a linear structure, a branched structure, and a linear structure having a partially branched or cyclic structure. A linear structure in which the main chain is composed of repeating diorganosiloxane units and both molecular chain terminals are capped with triorganosiloxy groups is particularly preferred. The linear organopolysiloxane may also have a partially branched or cyclic structure.

[0030] The blend amount of component (A) is 1.5 to 90% by weight, preferably 2 to 20% by weight, of the total composition. If it is more than 90% by weight, the thermal conductivity may be poor, while if it is less than 1.5% by weight, the viscosity of the thermally conductive addition-curable silicone composition of the present invention may increase significantly, reducing workability.

[0031] The organopolysiloxanes can be used alone or in combination of two or more.

[0032] [Component (B)] Component (B) is a thermally conductive filler containing amorphous aluminum nitride powder and amorphous zinc oxide powder, which is used to obtain a thermally conductive addition-curable silicone composition that achieves high thermal conductivity, that requires a short time for the storage modulus G' to exceed the loss modulus G'' when heat-cured, and that can achieve good storage stability at 25°C. In the present invention, the aluminum nitride powder and zinc oxide powder are amorphous, and preferably polyhedral.

[0033] The use of polyhedral aluminum nitride powder improves curability even with a small amount of platinum group metal catalyst, while also maintaining a long pot life. Furthermore, the physical entanglement of the polyhedral aluminum nitride powder improves G'. Taking thermal conductivity into consideration, irregularly shaped zinc oxide powder is also preferred as a sub-filler.

[0034] Furthermore, component (B) is preferably a combination of aluminum nitride powder as a large particle component and zinc oxide powder as a small particle component. The average particle size of the aluminum nitride powder as a large particle component is preferably in the range of 1 to 300 μm, more preferably 3 to 200 μm, even more preferably 5 to 150 μm, and even more preferably 6 to 50 μm. The average particle size of the zinc oxide powder as a small particle component is preferably in the range of 0.01 μm to 10 μm, more preferably 0.1 to 5 μm. When the average particle size of the aluminum nitride powder as a large particle component is in the range of 1 to 300 μm and the average particle size of the zinc oxide powder as a small particle component is in the range of 0.01 μm to 10 μm, the viscosity of the thermally conductive addition-curable silicone composition of the present invention is not too high, and the extensibility is excellent, and the resulting silicone composition is homogeneous. The ratio of the aluminum nitride powder as a large particle component to the zinc oxide powder as a small particle component is not particularly limited, but is preferably in the range of 9:1 to 1:9 (mass ratio). This range is preferable because it achieves both appropriate viscosity and thermal conductivity.

[0035] The average particle size can be determined, for example, as the volume-based average value (median diameter) in particle size distribution measurement by laser light diffraction method.

[0036] The blend amount of component (B) is 8 to 96% by mass, preferably 40 to 95.5% by mass, and more preferably 70 to 95% by mass, of the total composition. If it is more than 96% by mass, the thermally conductive addition-curable silicone composition of the present invention will have poor extensibility, and if it is less than 8% by mass, the thermal conductivity will be poor.

[0037] [Component (C)] Component (C) is an organohydrogenpolysiloxane having, per molecule, two or more silicon-bonded hydrogen atoms (Si—H groups), preferably 2 to 100 silicon-bonded hydrogen atoms (Si—H groups), and more preferably 2 to 50 silicon-bonded hydrogen atoms (Si—H groups). Any organohydrogenpolysiloxane may be used as long as the Si—H groups in the molecule can undergo an addition reaction with the aliphatic unsaturated hydrocarbon groups in component (A) in the presence of a platinum group metal catalyst to form a crosslinked structure.

[0038] The molecular structure of the organohydrogenpolysiloxane is not particularly limited as long as it has the above properties, and examples thereof include a linear structure, a branched structure, a cyclic structure, and a linear structure having a partially branched or cyclic structure, with linear structures and cyclic structures being preferred.

[0039] The organohydrogenpolysiloxane preferably has a kinematic viscosity at 25°C of 1 to 1,000 mm 2 / s, more preferably 10 to 300 mm 2 The kinematic viscosity is 1 to 1,000 mm 2 Within this range, the thermally conductive addition-curable silicone composition of the present invention will have good physical properties and excellent extensibility.

[0040] The organic group bonded to the silicon atom of the organohydrogenpolysiloxane may be an unsubstituted or substituted monovalent hydrocarbon group other than an aliphatic unsaturated hydrocarbon group. Particularly preferred are unsubstituted or substituted monovalent hydrocarbon groups having 1 to 12 carbon atoms, preferably 1 to 10 carbon atoms. Examples include alkyl groups such as methyl, ethyl, propyl, butyl, hexyl, and dodecyl; aryl groups such as phenyl; aralkyl groups such as 2-phenylethyl and 2-phenylpropyl; and groups in which some or all of the hydrogen atoms have been substituted with halogen atoms such as fluorine, bromine, and chlorine, cyano groups, and epoxy ring-containing organic groups (glycidyl or glycidyloxy-substituted alkyl groups), such as chloromethyl, chloropropyl, bromoethyl, trifluoropropyl, cyanoethyl, 2-glycidoxyethyl, 3-glycidoxypropyl, and 4-glycidoxybutyl. Among these, methyl and epoxy ring-containing organic groups are preferred. In particular, an epoxy ring-containing organic group is preferable because it allows for good adhesion between the heat generating portion and the cooling member.

[0041] The organohydrogenpolysiloxanes may be used singly or in combination of two or more, and it is preferred that at least one of them is an organohydrogenpolysiloxane having two epoxy ring-containing organic groups and two or more silicon-bonded hydrogen atoms in one molecule.

[0042] The amount of organohydrogenpolysiloxane in component (C) should be such that the ratio of the number of SiH groups in component (C) to the total number of aliphatic unsaturated hydrocarbon groups in component (A) is 0.5 to 10, preferably 0.7 to 7.5, and more preferably 1.0 to 5.0. If the amount of component (C) is less than 0.5, the addition reaction will not proceed sufficiently, resulting in insufficient crosslinking. If the amount of component (C) is more than 10, the crosslinked structure may become non-uniform, and the storage stability of the thermally conductive addition-curable silicone composition of the present invention may be significantly reduced.

[0043] [Component (D)] Component (D) is a platinum group metal catalyst that functions to promote the addition reaction of the above-mentioned components. Any conventionally known platinum group metal catalyst used in addition reactions can be used. Examples include platinum-based, palladium-based, and rhodium-based catalysts, with platinum or platinum compounds being preferred, as they are relatively readily available. Examples include platinum itself, platinum black, chloroplatinic acid, platinum-olefin complexes, platinum-alcohol complexes, and platinum coordination compounds. Platinum group metal catalysts may be used alone or in combination of two or more.

[0044] The amount of component (D) to be blended should be an effective amount as a catalyst, i.e., an effective amount necessary to promote the addition reaction and cure the thermally conductive addition-curable silicone composition of the present invention. The amount is preferably 0.01 to 10 ppm, more preferably 0.1 to 5 ppm, and even more preferably 0.2 to 3 ppm, calculated as platinum group metal atoms, based on the mass of the entire composition. A catalyst amount of 0.01 to 10 ppm is preferred because it provides sufficient catalytic effect, is economical, and provides good storage stability at 25°C.

[0045] Furthermore, the platinum group metal catalyst of component (D) may be diluted with an organo(poly)siloxane, toluene, or the like to improve dispersibility in the thermally conductive addition-curable silicone composition of the present invention.

[0046] [Component (E)] Component (E) is used to treat the surface of the thermally conductive filler, and plays a role in assisting in increasing the filler loading. (In the formula, R 1 represents a monovalent hydrocarbon group having 1 to 18 carbon atoms, which may have a substituent and does not have an aliphatic unsaturated bond, and each R 1 may be the same or different, and m is an integer of 5 to 100.

[0047] The above R １is a monovalent hydrocarbon group having 1 to 18 carbon atoms, which may have a substituent, preferably a monovalent saturated aliphatic hydrocarbon group which may have a substituent, or a monovalent aromatic hydrocarbon group which may have a substituent, and particularly preferably a monovalent saturated aliphatic hydrocarbon group which may have a substituent.

[0048] Specific examples of the monovalent saturated aliphatic hydrocarbon group which may have a substituent include linear alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, and decyl groups, branched alkyl groups such as isopropyl, isobutyl, tert-butyl, isopentyl, and neopentyl groups, cycloalkyl groups such as cyclopentyl, cyclohexyl, and cycloheptyl groups, and halogen-substituted alkyl groups such as chloromethyl, 3-chloropropyl, 3,3,3-trifluoropropyl, and bromopropyl groups. The number of carbon atoms is preferably 1 to 10, more preferably 1 to 8, and even more preferably 1 to 6.

[0049] Specific examples of the monovalent aromatic hydrocarbon group which may have a substituent include aryl groups such as a phenyl group or a tolyl group, aralkyl groups such as a benzyl group or a 2-phenylethyl group, and halogen-substituted aryl groups such as an α,α,α-trifluorotolyl group or a chlorobenzyl group. The number of carbon atoms is preferably 6 to 10, more preferably 6 to 8, and even more preferably 6.

[0050] The above R １ Among these, methyl, ethyl, 3,3,3-trifluoropropyl and phenyl groups are preferred, methyl, ethyl and phenyl groups are more preferred, and methyl group is particularly preferred.

[0051] The character m is an integer between 5 and 100, preferably between 5 and 80, and more preferably between 10 and 60. If the value of m is less than 5, oil bleeding from the thermally conductive addition-curable silicone composition of the present invention cannot be suppressed, resulting in poor pumping-out resistance. If the value of m is 100 or greater, the composition will not have sufficient wettability with the filler, increasing the viscosity of the silicone composition and worsening application workability.

[0052] The blending amount of component (E) is 0.5 to 10% by mass, and preferably 1.0 to 8.0% by mass, of the total composition. If the blending amount is less than 0.5% by mass or more than 10% by mass, the thermally conductive silicone composition of the present invention will not be able to achieve an appropriate viscosity range, and will have poor pumping-out resistance.

[0053] The component (E) may be used alone or in combination of two or more.

[0054] [Component (F)] Component (F) is a reaction inhibitor that suppresses the progress of the hydrosilylation reaction at room temperature and can be added to extend shelf life and pot life. This reaction inhibitor can be any of the conventional reaction inhibitors used in thermally conductive addition-curable silicone compositions. Examples of such reaction inhibitors include acetylene compounds such as acetylene alcohols (e.g., ethynylmethyldecylcarbinol, 1-ethynyl-1-cyclohexanol, 3,5-dimethyl-1-hexyn-3-ol), various nitrogen compounds such as tributylamine, tetramethylethylenediamine, and benzotriazole, organophosphorus compounds such as triphenylphosphine, oxime compounds, and organochloro compounds.

[0055] The amount of component (F) added should be an effective amount as a reaction inhibitor, i.e., an effective amount necessary to achieve the desired shelf life and pot life. It is preferably 0.05 to 5 parts by mass, and more preferably 0.1 to 2 parts by mass, per 100 parts by mass of component (A). When the amount of reaction inhibitor is 0.05 to 5 parts by mass, the desired sufficient shelf life and pot life are achieved, and there is no risk of a decrease in the curability of the thermally conductive addition-curable silicone composition.

[0056] The reaction inhibitor may be diluted with an organo(poly)siloxane, toluene, or the like to improve dispersibility in the thermally conductive addition-curable silicone composition of the present invention.

[0057] [Other Components] The thermally conductive addition-curable silicone composition of the present invention may contain a non-reactive organo(poly)siloxane, such as methylpolysiloxane, to adjust the strength and viscosity of the composition. Furthermore, a hydrolyzable organopolysiloxane, various modified silicones, or a hydrolyzable organosilane may be blended to impart adhesive properties to the silicone composition. Furthermore, a solvent may be blended to adjust the viscosity of the silicone composition. Furthermore, a conventionally known antioxidant, such as 2,6-di-tert-butyl-4-methylphenol, may be added as needed to prevent deterioration of the silicone composition. Furthermore, dyes, pigments, flame retardants, anti-settling agents, thixotropy improvers, and the like may be blended as needed.

[0058] The thermally conductive addition-curable silicone composition of the present invention, which is characterized by containing the above components (A) to (F) and, if necessary, the above other components, can be such that, when the storage modulus G' and loss modulus G'' of the thermally conductive addition-curable silicone composition are measured using a viscoelasticity measuring device capable of measuring shear elasticity while heating from 25°C to 150°C at a rate of 5°C / minute and then maintaining the temperature at 150°C for 7,200 seconds, the time required for the storage modulus G' to exceed the loss modulus G'' is 500 seconds or less, and the thermally conductive addition-curable silicone composition takes 5 days or more for its viscosity to exceed 1,000 Pa s when stored at 25°C.

[0059] Such a thermally conductive addition-curable silicone composition, when heat-cured, requires a short time for the storage modulus G' to exceed the loss modulus G'', and has good storage stability at 25°C. As a result, it can be suitably used in electronic component packages and power modules that are prone to significant warpage.

[0060] In the thermally conductive addition-curable silicone composition of the present invention, the time required for the storage modulus G' to exceed the loss modulus G" is measured by applying the thermally conductive addition-curable silicone composition of the present invention to a thickness of 2 mm between two parallel plates with a diameter of 2.5 cm, raising the temperature of the applied plates from 25°C to 150°C at a rate of 5°C / min, and then maintaining the temperature at 150°C for 7,200 seconds, creating a program and reading the time required for the storage modulus to exceed the loss modulus. A viscoelasticity measuring device (ARES-G2, manufactured by TA Instruments) is used for the measurement.

[0061] [Step of Preparing the Thermally Conductive Addition-Curable Silicone Composition] The method for producing the thermally conductive addition-curable silicone composition of the present invention will now be described. The method for producing the thermally conductive addition-curable silicone composition of the present invention is not particularly limited, but includes the steps of preparing the above-mentioned components (A) to (F) and, if necessary, other components.

[0062] The prepared components (A) to (F) described above, and any other components added as necessary, are mixed using a mixer such as Trimix, Twinmix, or Planetary Mixer (all registered trademarks of mixers manufactured by Inoue Seisakusho Co., Ltd.), Ultramix (registered trademark of mixers manufactured by Mizuho Kogyo Co., Ltd.), or Hivismix (registered trademark of mixers manufactured by Primix Corporation), for 3 minutes to 24 hours, more preferably 5 minutes to 12 hours, and particularly preferably 10 minutes to 6 hours. Degassing may be performed during mixing, and mixing is carried out while heating in the range of 40 to 170°C. Temperatures below 40°C result in poor dispersion of component (B), while temperatures above 170°C are undesirable because component (E) may be deteriorated.

[0063] In the present invention, from the viewpoint of achieving good thermal conductivity in the thermally conductive addition-curable silicone composition of the present invention, it is preferable to first mix components (A), (B), and (E) at 170°C, and then mix components (C), (D), and (F) at 25°C.

[0064] The thermally conductive addition-curable silicone composition of the present invention preferably has a viscosity measured at 25° C. of 10 to 1,000 Pa s, more preferably 20 to 700 Pa s, and even more preferably 40 to 500 Pa s. When the viscosity is in the range of 10 to 1,000 Pa s, the composition is easy to maintain its shape, the silver powder does not settle, and the composition is easy to discharge and apply, thereby facilitating workability.

[0065] The viscosity of the thermally conductive addition-curable silicone composition of the present invention is measured at 25° C. using a Malcom viscometer (Type PC-1T) (rotor A, 10 rpm, shear rate 6 [1 / s]).

[0066] Furthermore, the thermally conductive addition-curable silicone composition of the present invention typically has a thermal conductivity of 0.5 to 100 W / m K, but preferably has a thermal conductivity of 4.0 W / m K or greater in order to exhibit excellent heat dissipation performance when mounted in an electronic component package or power module.

[0067] The thermal conductivity is measured by wrapping the thermally conductive addition-curable silicone composition in kitchen wrap and measuring it with a TPS-2500S made by Kyoto Electronics Manufacturing Co., Ltd.

[0068] The curing conditions for heat curing the thermally conductive addition-curable silicone composition of the present invention are not particularly limited, but are preferably 80 to 200°C, more preferably 100 to 180°C, for 15 minutes to 4 hours, preferably 30 minutes to 2 hours.

[0069] Furthermore, the method for producing a thermally conductive addition-curable silicone composition of the present invention can produce a thermally conductive addition-curable silicone composition that, when the storage modulus G' and loss modulus G'' of the composition are measured using a viscoelasticity measuring device capable of measuring shear elasticity, the time required for the storage modulus G' to exceed the loss modulus G'' is 500 seconds or less, and the viscosity of the thermally conductive addition-curable silicone composition when stored at 25°C is 5 days or more until it exceeds 1,000 Pa s.

[0070] EXAMPLES The present invention will be specifically explained below using examples and comparative examples, but the present invention is not limited to these.

[0071] The kinematic viscosity is the value measured at 25°C using an Ubbelohde-type Ostwald viscometer.

[0072] The following components (A) to (F) were prepared to prepare the thermally conductive addition-curable silicone composition of the present invention, and an additional component (G) was also prepared. [Component (A)] A-1: ​​A copolymer having both ends capped with dimethylvinylsilyl groups and a kinematic viscosity of 30,000 mm at 25°C. 2 A-2: Dimethylpolysiloxane having a kinematic viscosity of 10,000 mm at 25°C (vinyl group amount = 0.00004 mol / g) and a dimethylvinylsilyl group at both ends. 2 A-3: Dimethylpolysiloxane having a kinematic viscosity of 5,000 mm at 25°C (vinyl group amount = 0.00005 mol / g) and a dimethylvinylsilyl group at both ends. 2 A-4: Dimethylpolysiloxane having a kinematic viscosity of 600 mmHg at 25°C (vinyl group amount = 0.00007 mol / g) and a dimethylvinylsilyl group-blocked copolymer having a kinematic viscosity of 600 mmHg at 25°C. 2 A-5: Dimethylpolysiloxane having a kinematic viscosity of 1,500 mm at 25°C (vinyl group amount = 0.00014 mol / g) and a trivinylsilyl group-blocked dimethylpolysiloxane having a kinematic viscosity of 1,500 mm at 25°C. 2 / s dimethylpolysiloxane (vinyl group amount = 0.00026 mol / g)

[0073] [Component (B)] B-1: Average particle size 20 μm, specific surface area 0.3 m ２ / g polyhedral aluminum nitride powder B-2: average particle size 8 μm, specific surface area 0.7 m ２ / g polyhedral aluminum nitride powder B-3: average particle size 0.4 μm, specific surface area 3.5 m ２ / g Polyhedral zinc oxide powder b-4: average particle size 24 μm, specific surface area 0.2 m ２ / g spherical aluminum powder b-5: average particle size 12 μm, specific surface area 0.4 m ２ / g spherical aluminum powder b-6: average particle size 30 μm, specific surface area 0.08 m ２ / g of spherical aluminum nitride powder

[0074] [Component (C)] C-1: Methylhydrogendimethylpolysiloxane represented by the following formula (2) (SiH content = 0.0043 mol / g) C-2: Methylhydrogendimethylpolysiloxane represented by the following formula (3) (SiH content = 0.0055 mol / g) C-3: Methylhydrogendimethylpolysiloxane represented by the following formula (4) (SiH content = 0.0014 mol / g) C-4: Methylhydrogendimethylpolysiloxane represented by the following formula (5) (SiH content = 0.0010 mol / g) C-5: Methylhydrogendimethylpolysiloxane represented by the following formula (6) (SiH content = 0.0013 mol / g)

[0075] [Component (D)] D-1: A solution of platinum-divinyltetramethyldisiloxane complex dissolved in the same dimethylpolysiloxane as in A-4 (platinum atom content: 1% by mass)

[0076] [Component (E)] E-1: Dimethylpolysiloxane terminated at one end with a trimethoxysilyl group, represented by the following formula (7):

[0077] [Component (F)] F-1: 1-ethynyl-1-cyclohexanol represented by the following formula (8):

[0078] [Component (G)] G-1: Organosilane represented by the following formula (9):

[0079] Examples 1 to 4, Comparative Examples 1 to 5 Preparation of Thermally Conductive Addition-Curable Silicone Compositions Thermally conductive addition-curable silicone compositions were prepared by blending the above components (A) to (G) in the amounts shown in Tables 1 and 2, using the method described below. In Tables 1 and 2, SiH / SiVi is the ratio of the total number of SiH groups in component (C) to the total number of vinyl groups in component (A).

[0080] Components (A), (B), (E), and (G) were placed in a 5-liter planetary mixer (manufactured by Inoue Seisakusho Co., Ltd.) and mixed at 170°C for 1 hour. The mixture was cooled to below 40°C, and then components (C), (D), and (F) were added and mixed until uniform, preparing a thermally conductive addition-curable silicone composition. The prepared thermally conductive addition-curable silicone composition was measured for viscosity, thermal conductivity, the time required for the storage modulus to exceed the loss modulus, and shelf life at 25°C, as shown below. The results are shown in Tables 1 and 2.

[0081] [Viscosity] The absolute viscosity of each thermally conductive addition-curable silicone composition was measured at 25°C using a Malcolm viscometer (Type PC-1T) (rotor A, 10 rpm, shear rate 6 [1 / s]). [Thermal Conductivity] Each thermally conductive addition-curable silicone composition was wrapped in kitchen wrap, and the thermal conductivity was measured using a TPS-2500S (manufactured by Kyoto Electronics Manufacturing Co., Ltd.). [Time Required for Storage Modulus to Exceed Loss Modulus] Each thermally conductive addition-curable silicone composition was applied to a thickness of 2 mm between two parallel plates with a diameter of 2.5 cm. A program was created to heat the applied plates from 25°C to 150°C at a rate of 5°C / min, and then maintain them at 150°C for 7,200 seconds, and the time required for the storage modulus to exceed the loss modulus was read. A viscoelasticity measuring device (ARES-G2: manufactured by TA Instruments) was used for the measurements. [Storage stability at 25°C] Each thermally conductive addition-curable silicone composition was sealed in a high-density polyethylene container and stored at 25°C, and the time until the viscosity exceeded 1,000 Pa·s was measured.

[0082]

[0083]

[0084] The results in Tables 1 and 2 show that, for the thermally conductive addition-curable silicone compositions of Examples 1 to 4 that satisfy the requirements of the present invention, the time required for the storage modulus G' to exceed the loss modulus G'' is 500 seconds or less, and when stored at 25°C, it takes 5 days or more for the viscosity to exceed 1,000 Pa s.

[0085] On the other hand, for the thermally conductive addition-curable silicone compositions of Comparative Examples 1, 2, and 5, it took 5 days or more for the viscosity to exceed 1,000 Pa·s when stored at 25°C, but it took 500 seconds or more for the storage modulus G' to exceed the loss modulus G". For the thermally conductive addition-curable silicone composition of Comparative Example 3, it took 500 seconds or more for the storage modulus G' to exceed the loss modulus G", and it was found that the viscosity exceeded 1,000 Pa·s in less than 5 days when stored at 25°C. Furthermore, for the thermally conductive addition-curable silicone composition of Comparative Example 4, it took 500 seconds or less for the storage modulus G' to exceed the loss modulus G", but it was found that the viscosity exceeded 1,000 Pa·s in less than 5 days when stored at 25°C.

[0086] As described above, it has been found that the present invention can provide a thermally conductive addition-curable silicone composition of the present invention, which, when measured using the above-mentioned viscoelasticity measuring device under the above-mentioned temperature conditions, requires a short time of 500 seconds or less for the storage modulus G' to exceed the loss modulus G'', and which has good storage stability, requiring 5 days or more for the viscosity to exceed 1,000 Pa s when stored at 25°C. As a result, the thermally conductive addition-curable silicone composition of the present invention can be suitably used in electronic component packages and power modules that exhibit significant warpage. It has also been found that the method for producing a thermally conductive addition-curable silicone composition of the present invention can reliably provide a thermally conductive addition-curable silicone composition that can be suitably used in electronic component packages and power modules that exhibit significant warpage.

[0087] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits similar effects is included within the technical scope of the present invention.

Claims

1. A thermally conductive addition-curable silicone composition, comprising: (A) at least one aliphatic unsaturated hydrocarbon group per molecule, and a kinetic viscosity at 25°C of 60 to 100,000 mm 2 (A) an organopolysiloxane having formula (I)-(s)-(ZnO)-containing siloxane (A) and (B) a thermally conductive filler comprising amorphous aluminum nitride powder and amorphous zinc oxide powder, the amount being 1.5 to 90 mass% of the entire composition; (B) a thermally conductive filler comprising amorphous aluminum nitride powder and amorphous zinc oxide powder, the amount being 8 to 96 mass% of the entire composition; (C) an organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms in one molecule, the amount being such that the number of Si-H groups in component (C) relative to the total number of aliphatic unsaturated hydrocarbon groups in component (A) is 0.5 to 10; (D) a platinum group metal catalyst, the amount being an effective amount; (E) an organopolysiloxane represented by the following general formula (1): the amount being 0.5 to 10 mass% of the entire composition; (In the formula, R 1 represents a monovalent hydrocarbon group having 1 to 18 carbon atoms, which may have a substituent and has no aliphatic unsaturated bonds, and each R 1 may be the same or different, and m is an integer from 5 to 100.) (F) an effective amount of one or more addition curing reaction inhibitors selected from the group consisting of acetylene compounds, nitrogen compounds, organic phosphorus compounds, oxime compounds, and organic chloro compounds.

2. The thermally conductive addition-curable silicone composition according to claim 1, wherein component (C) is an organohydrogenpolysiloxane having two epoxy ring-containing organic groups in one molecule.

3. The thermally conductive addition-curable silicone composition according to claim 1 or 2, characterized in that, when the storage modulus G' and loss modulus G'' of the thermally conductive addition-curable silicone composition are measured using a viscoelasticity measuring device capable of measuring shear elasticity, while heating the composition from 25°C to 150°C at a rate of 5°C / minute and then maintaining the composition at 150°C for 7,200 seconds, the time it takes for the storage modulus G' to exceed the loss modulus G'' is 500 seconds or less, and the thermally conductive addition-curable silicone composition takes 5 days or more for its viscosity to exceed 1,000 Pa·s when stored at 25°C.

4. (A) At least one aliphatic unsaturated hydrocarbon group per molecule, with a kinetic viscosity of 60 to 100,000 mm at 25°C. 2 (A) an organopolysiloxane having formula (I)-(s)-(ZnO)-containing siloxane (A) and (B) which is a thermally conductive filler containing amorphous aluminum nitride powder and amorphous zinc oxide powder: a quantity that is 8 to 96% by mass of the entire composition; (C) an organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms in one molecule: a quantity such that the number of Si-H groups in component (C) relative to the total number of aliphatic unsaturated hydrocarbon groups in component (A) is 0.5 to 10; (D) a platinum group metal catalyst: an effective amount; (E) an organopolysiloxane represented by the following general formula (1): a quantity that is 0.5 to 10% by mass of the entire composition; (In the formula, R 1 represents a monovalent hydrocarbon group having 1 to 18 carbon atoms, which may have a substituent and has no aliphatic unsaturated bonds, and each R 1 may be the same or different, and m is an integer of 5 to 100.) A method for producing a thermally conductive addition-curable silicone composition, comprising the steps of: preparing each of the components: (F) an effective amount of one or more addition-curing reaction inhibitors selected from the group consisting of acetylene compounds, nitrogen compounds, organic phosphorus compounds, oxime compounds, and organic chloro compounds; and mixing the components (A) to (F) while heating at 40 to 170°C.

5. A method for producing a thermally conductive addition-curable silicone composition as described in claim 4, characterized in that when the storage modulus G' and loss modulus G'' of the thermally conductive addition-curable silicone composition are measured using a viscoelasticity measuring device capable of measuring shear elasticity, while heating the composition from 25°C to 150°C at a rate of 5°C / min and then maintaining the composition at 150°C for 7,200 seconds, the time required for the storage modulus G' to exceed the loss modulus G'' is 500 seconds or less, and the thermally conductive addition-curable silicone composition requires 5 days or more for its viscosity to exceed 1,000 Pa·s when stored at 25°C.

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