Patent Application
20250092259
The present invention relates to a thermally conductive silicone composition.
Recently, as electronic parts, such as a power module and a CPU, are increasingly improved in performance and reduced in size, thermal management is needed. The thermal management uses a thermally conductive grease and a radiator sheet. The thermally conductive grease has problems in that a so-called pumping out occurs in which a heat generating element and a heat exchanger suffer thermal expansion and shrinkage to push the thermally conductive grease out of the portion to which the grease is applied, and in that separation of the filler and oil in the grease is caused due to a change of them with the passage of time, and thus the thermally conductive grease must be further improved in view of the reliability and function. On the other hand, the radiator sheet is a formed article and hence does not have the above-mentioned problems, but there is a concern about radiator properties of the radiator sheet having an increased thickness from the viewpoint of the heat resistance and contact resistance.
As a method for solving the problems, there has been proposed a technique using a large particle-diameter inorganic filler or two or more types of inorganic fillers in a composition containing a thermally conductive filler and silicone in order to improve the thermal conductivity. For example, patent document 1 discloses a thermally conductive polysiloxane composition using silicon carbide having at least two peaks of the particle size distribution.
With respect to the radiator material, taking the heat resistance into consideration, applying the material with a reduced thickness is an important factor. BLT (Bond-Line-Thickness) is a thinness index for the material applied. The thickness of the radiator material largely affects the radiator properties, and a reduction of the thickness contributes to a lowering of the heat resistance of the radiator material, and therefore the BLT properties are important to achieve a high radiator material.
Further, the present inventors have found that the thermally conductive polysiloxane composition described in patent document 1 can be further improved with respect to the electrical insulating properties, BLT properties, discharge properties, and radiator properties.
An object of the present invention is to provide a thermally conductive silicone composition which not only has excellent electrical insulating properties, discharge properties, and radiator properties but also has low BLT.
The present invention is directed to the following [1] to [6].
In the present invention, there can be provided a thermally conductive silicone composition which not only has excellent electrical insulating properties, discharge properties, and radiator properties but also has low BLT.
The structural units of a siloxane compound are frequently indicated using the abbreviations shown below (hereinafter, these structural units are frequently respectively referred to as, for example, “M unit” and “DH unit”)
In the present specification, specific examples of groups (substituents) are as described below.
Examples of monovalent hydrocarbon groups include an alkyl group, a cycloalkyl group, an aryl group, an aralkyl group, and an alkenyl group. Examples of monovalent hydrocarbon groups having no aliphatic unsaturated bond include the above-mentioned monovalent hydrocarbon groups except the alkenyl group.
An alkenyl group is a linear or branched group having 2 to 6 carbon atoms, and examples include a vinyl group, an allyl group, a 3-butenyl group, and a 5-hexenyl group.
An alkyl group is a linear or branched group having 1 to 18 carbon atoms, and examples include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, an octyl group, a decyl group, a dodecyl group, a hexadecyl group, and an octadecyl group.
A cycloalkyl group is a monocyclic or polycyclic group having 3 to 20 carbon atoms, and examples include a cyclopentyl group and a cyclohexyl group.
An aryl group is an aromatic group containing a monocyclic or polycyclic group having 6 to 20 carbon atoms, and examples include a phenyl group and a naphthyl group.
An aralkyl group is an alkyl group substituted with an aryl group, and examples include a 2-phenylethyl group and a 2-phenylpropyl group.
An alkylene group is a linear or branched group having 1 to 18 carbon atoms, and examples include a methylene group, an ethylene group, a trimethylene group, a 2-methylethylene group, and a tetramethylene group.
The alkenyl group, alkyl group, cycloalkyl group, aryl group, aralkyl group, and alkylene group may be substituted with a halogen, such as chlorine, fluorine, or bromine; or a cyano group. Examples of the above groups substituted with a halogen include a chloromethyl group, a chlorophenyl group, and a 3,3,3-trifluoropropyl group, and examples of the above groups substituted with a cyano group include a 2-cyanoethyl group.
In the present specification, “(A) polyorganosiloxane having an alkenyl group bonded to a silicon atom” is frequently referred to as “component (A)”. This applies to “(C) Pt catalyst” and other components.
The thermally conductive silicone composition (hereinafter, frequently referred to simply as “the composition”) is a thermally conductive silicone composition which comprises:
Polyorganosiloxane (A) having an alkenyl group bonded to a silicon atom is a component that serves as a base polymer in the composition. Component (A) comprises (A-1) a polyorganosiloxane having in the molecule thereof two or more alkenyl groups bonded to a silicon atom.
Component (A-1) is a polyorganosiloxane having in the molecule thereof two or more alkenyl groups bonded to a silicon atom. The alkenyl group of component (A-1) and the hydrosilyl group (Si—H group) of component (B-1) undergo an addition reaction to form a network structure in a cured product of the composition.
With respect to component (A-1), there is no particular limitation as long as component (A-1) and component (B-1) can together form the above-mentioned network structure. Component (A-1) typically has in the molecule thereof two or more alkenyl group-containing siloxane units represented by the following general formula (I):
(R11)a1(R12)b1SiO(4-a1-b1)/2 (I)
R11 is preferably a vinyl group in view of easy synthesis of the compound and no adverse effect on the fluidity of the composition before being cured and heat resistance of the composition after cured. a is preferably 1 in view of easy synthesis of the compound. In view of easy synthesis of the compound and excellent balance between properties, such as mechanical strength and fluidity of the composition before being cured, R12 is preferably a methyl group or a phenyl group, especially preferably a methyl group.
As an example of an organic group bonded to the silicon atom of another siloxane unit in component (A-1), there can be mentioned a monovalent hydrocarbon group having no aliphatic unsaturated bond. For the same reasons as those for R12, the organic group is preferably a methyl group or a phenyl group, especially preferably a methyl group.
R11 may be present either at an end of or in the molecular chain of component (A-1), and may be present both at an end of and in the molecular chain.
The siloxane skeleton of component (A-1) can be linear or branched. Specifically, component (A-1) can be linear polyorganosiloxane (A-1-1) or branched polyorganosiloxane (A-1-2).
As an example of linear polyorganosiloxane (A-1-1), there can be mentioned a linear polyorganosiloxane having both ends capped by an R3SiO1/2 unit and having an intermediate unit comprised only of an R22SiO2/2 unit, wherein R is R11 or R12, wherein R11 is an alkenyl group, and R12 is a monovalent hydrocarbon group having no aliphatic unsaturated bond, and two or more R11's are contained in the molecule. The R3SiO1/2 unit in component (A-1-1) is preferably an R11R122SiO1/2 unit, an R11R122SiO1/2 unit, or an R113SiO1/2 unit, especially preferably an R11R122SiO1/2 unit.
Component (A-1) is more preferably a linear polyorganosiloxane having both ends capped by an R11R122SiO1/2 unit and having an intermediate unit comprised only of an R122SiO2/2 unit. Component (A-1-1) is especially preferably a linear polyorganosiloxane represented by MviDnMvi (i.e., a linear polyorganosiloxane having both ends capped by an Mvi unit (dimethylvinylsiloxane unit) and having an intermediate unit comprised only of a D unit (dimethylsiloxane unit)). In the present specification, the “Dn” means that the intermediate unit is comprised only of a D unit, and the “n” means the degree of polymerization of the D unit, and is a value which varies depending on the viscosity of the corresponding polyorganosiloxane.
As an example of branched polyorganosiloxane (A-1-2), there can be mentioned a branched polyorganosiloxane comprising a SiO4/2 unit and an R3SiO1/2 unit as essential units and an R2SiO2/2 unit and/or an RSiO3/2 unit as an optional unit. In the units, R is R11 or R12, and, among R's, two or more R's are R11 per molecule. For forming a crosslinking point in a curing reaction, it is preferred that, among R's, at least three R's are R11 per molecule and the remaining R is R12. From the viewpoint of obtaining a cured product of the composition having excellent mechanical strength, branched polyorganosiloxane (A-1-2) is preferably in such a solid or viscous semisolid resin form at ordinary room temperature that the ratio of the R3SiO1/2 unit and the SiO4/2 unit, in terms of a molar ratio, is in the range of from 1:0.8 to 1:3.
In component (A-1-2), R11 may be present as R for the R3SiO1/2 unit, and may be present as R for the R2SiO unit or RSiO3/2 unit. From the viewpoint of achieving rapid curing at room temperature, it is preferred that part of or all of the R3SiO1/2 unit is an R11R122SiO1/2 unit.
«Component (A) Other than Component (A-1)»
Component (A) can contain component (A) other than component (A-1) (hereinafter, referred to also as “component (A-2)”). Examples of component (A-2) include a polyorganosiloxane having in the molecule thereof one alkenyl group bonded to a silicon atom. The siloxane skeleton of component (A-2) as well as a preferred aspect thereof are as mentioned above in connection with component (A-1).
Component (A-2) is preferably a linear polyorganosiloxane having in the molecule thereof one alkenyl group bonded to a silicon atom. Component (A-2) is more preferably a linear polyorganosiloxane having one end capped by an R11R122SiO1/2 unit and another end capped by an R123SiO1/2 unit and having an intermediate unit comprised only of an R122SiO2/2 unit. Further, component (A-2) is especially preferably a linear polyorganosiloxane represented by MviDnM.
Component (A) preferably has a viscosity at 23° C. of 0.01 to 500 Pa·s, more preferably 0.05 to 300 Pa·s, especially preferably 0.1 to 100 Pa·s. When the viscosity of component (A) is in the above range, the filler and polymer can be easily kneaded in the production process, so that the resultant composition is advantageous in that a final product obtained from the composition has excellent electrical insulating properties, BLT properties, discharge properties, and radiator properties. Further, when the viscosity of component (A) at 23° C. is 0.01 Pa·s or more, volatilization of low molecular-weight components is suppressed in the production process, making it possible to efficiently satisfy the properties of the thermally conductive silicone composition. On the other hand, when the viscosity of component (A) at 23° C. is 500 Pa·s or less, component (E) and the polymer components (component (A) and component (B)) are well miscible with each other. When component (A) is a combination of two or more types of components, the viscosity of component (A) means the viscosity of the mixed alkenyl group-containing polyorganosiloxanes. In the present specification, the viscosity is a value as measured in accordance with JIS K 6249 using a rotational viscometer under conditions at 23° C. such that the spindle number and the speed of rotation are appropriately selected.
Component (A) may be one type of component or a combination of two or more types of components. For example, component (A) may be comprised only of two or more types of components (A-1), and may be a mixture of one or more types of components (A-1) and one or more types of components (A-2).
(B) Polyorganohydrogensiloxane having a hydrogen atom bonded to a silicon atom comprises (B-1) a polyorganohydrogensiloxane having in the molecule thereof two or more hydrogen atoms bonded to a silicon atom. With respect to component (B), there is no particular limitation as long as component (B) and component (A) can together form the above-mentioned network structure.
Component (B-1) serves as a crosslinking agent for component (A). Component (B-1) typically has in the molecule thereof two or more units represented by the following general formula (II):
(R13)cHdSiO(4-c1-d1)/2 (II)
In view of easy synthesis of the compound, R13 is preferably a methyl group. In view of easy synthesis of the compound, d1 is preferably 1.
In view of easy synthesis of the compound, component (B-1) preferably has three or more siloxane units. Further, in view of an advantage that the component does not volatilize even when heated to the curing temperature and has such excellent fluidity that the component is easily mixed with component (A), the number of the siloxane units of component (B-1) is preferably 6 to 200, especially preferably 10 to 150. From the viewpoint of efficiently serving as a crosslinking agent for component (A), component (B-1) preferably has in the molecule thereof three or more units represented by the general formula (II).
The siloxane skeleton in component (B-1) may be linear, branched, or cyclic, and is preferably linear. In component (B-1), the hydrogen atom bonded to a silicon atom may be present either at an end or in an intermediate unit, but is preferably present in an intermediate unit.
Component (B-1) is preferably (B-1-1) a linear polyorganohydrogensiloxane having both ends independently capped by an R143SiO1/2 unit and having an intermediate unit comprised only of an R142SiO2/2 unit, and (B-1-2) a polyorganohydrogensiloxane comprised only of an R143SiO1/2 unit and a SiO4/2 unit (wherein each R14 is independently a hydrogen atom or a monovalent hydrocarbon group having no aliphatic unsaturated bond, with the proviso that at least three of R14's are a hydrogen atom).
In component (B-1-1) and component (B-1-2), examples of R143SiO1/2 units include an HR152SiO1/2 unit and an R153SiO1/2 unit, and examples of R142SiO2/2 units include an HR15SiO2/2 unit and an R152SiO2/2 unit (wherein R15 is a monovalent hydrocarbon group having no aliphatic unsaturated bond).
Component (B-1) is especially preferably a linear polyorganohydrogensiloxane having both ends capped by an MH unit (dimethylhydrogensiloxane unit) and having an intermediate unit comprised only of a D unit (dimethylsiloxane unit) and a DH unit (dimethylsiloxane unit), and a linear polyorganohydrogensiloxane having both ends capped by an MH unit (dimethylhydrogensiloxane unit) and having an intermediate unit comprised only of a D unit (dimethylsiloxane unit).
«Polyorganohydrogensiloxane Other than Component (B-1)»
Component (B) can contain component (B) other than component (B-1) (hereinafter, referred to also as “component (B-2)”). As an example of component (B-2), there can be mentioned a polyorganohydrogensiloxane having in the molecule thereof one hydrogen atom bonded to a silicon atom. The siloxane skeleton in component (B-2) may be linear, branched, or cyclic, and is preferably linear. Further, in component (B-2), the hydrogen atom bonded to a silicon atom may be present either at an end or in an intermediate unit.
Component (B-2) is especially preferably a linear polyorganohydrogensiloxane represented by MHDnM.
«Preferred aspect of component (B)»
Component (B) preferably has a viscosity at 23° C. of 0.01 to 500 mPa·s, more preferably 1 to 300 mPa·s, especially preferably 5 to 100 mPa·s. When the viscosity of component (B) is in the above range, component (E) and the polymer components (component (A) and component (B)) can be easily kneaded in the production process, so that the composition having more excellent electrical insulating properties, BLT properties, discharge properties, and radiator properties can be obtained. The viscosity is as mentioned above in connection with component (A).
Component (B) may be one type of component or a combination of two or more types of components. For example, component (B) may be comprised only of two or more types of components (B-1), and may be a mixture of one or more types of components (B-1) and one or more types of components (B-2).
From the viewpoint of the curing properties and heat resistance and from the viewpoint of controlling the hardness of the material, it is preferred that the thermally conductive silicone composition further comprises at least one member selected from the group consisting of (A-2) a polyorganosiloxane having in the molecule thereof one alkenyl group bonded to a silicon atom and (B-2) a polyorganohydrogensiloxane having in the molecule thereof one hydrogen atom bonded to a silicon atom.
(C) Pt catalyst is a catalyst for accelerating an addition reaction of the alkenyl group in component (A) and the hydrosilyl group in component (B).
Examples of component (C) include platinum compounds, such as hexachloroplatinic(IV) acid, a reaction product of hexachloroplatinic(IV) acid and an alcohol, a platinum-olefin complex, a platinum-vinylsiloxane complex, a platinum-ketone complex, and a platinum-phosphine complex. Of these, in view of excellent catalytic activity, a platinum-vinylsiloxane complex is preferred, and, in view of achieving curing at room temperature in a short time, especially preferred is a Karstedt's complex, a platinum-1,1,3,3-tetramethyl-1,3-divinyldisiloxane complex (platinum-methylvinylsiloxane dimer complex), an Ashley complex, or a platinum-2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane complex (platinum-methylvinylsiloxane tetramer complex).
Component (C) may be one type of component or a combination of two or more types of components.
Component (D) is represented by the following general formula (1):
In component (D), the unit containing R1, the unit containing R2, and the unit represented by SiR32O are not necessarily arranged as shown in the general formula (1) above, and, for example, the unit represented by SiR32O may be present between the unit containing R1 and the unit containing R2.
The siloxane compound having the cyclic structure represented by the general formula (1) can have introduced a large number of hydrolysable groups into the cyclic structure, and further has the hydrolysable groups concentrated in the position of the structure, and therefore is considered to have an increased treatment efficiency for component (E), enabling higher filling. In addition, the siloxane compound per se has high heat resistance, and therefore can cause the thermally conductive silicone composition to have high heat resistance. Further, the siloxane compound represented by the general formula (1) has an advantage in that the compound can be easily obtained by subjecting to addition reaction, for example, a cyclic siloxane containing a hydrogen group, a siloxane having a vinyl group at one end, and a silane compound containing a vinyl group and a hydrolysable group.
R1 is a group having an alkoxysilyl group having 1 to 4 carbon atoms, which is a hydrolysable functional group. R1 may be directly bonded to X with silicon, but may be bonded through a linking group, such as an ester linkage. R1 is preferably a group having the following structure.
In view of a tendency toward a further improvement of the treatment efficiency for the thermally conductive filler, R1 is preferably a group of a structure having two or more alkoxysilyl groups, especially having three or more alkoxysilyl groups. Further, in view of easy availability of the raw material, R1 preferably contains a methoxysilyl group.
R2 is a linear organosiloxy group represented by the general formula (2). In the general formula (2), d is an integer of 2 to 60. d is 2 to 60, and therefore the effect on the fluidity is improved, enabling high incorporation, so that the viscosity of the siloxane compound per se can be reduced. Each R4 is independently a monovalent hydrocarbon group having 1 to 12 carbon atoms, and examples of R4's include linear or branched C1-12 alkyl groups, and aryl groups, such as phenyl and naphthyl. Further, the hydrocarbon group may be substituted with a halogen, such as chlorine, fluorine, or bromine, and examples of such groups include perfluoroalkyl groups, such as a trifluoromethyl group. In view of easy synthesis of the compound, R4 is preferably a methyl group. Y is a group selected from the group consisting of R4, and an aliphatic unsaturated group. The aliphatic unsaturated group preferably has 2 to 10 carbon atoms, more preferably 2 to 6 carbon atoms. Further, from the viewpoint of facilitating the curing reaction, the aliphatic unsaturated group preferably has a double bond at the end thereof. In view of easy synthesis of the compound, Y is preferably a methyl group or a vinyl group.
R1 and R2 are individually bonded through group X to the cyclic siloxane portion of the siloxane represented by the general formula (1). Group X is a divalent hydrocarbon group having 2 to 10 carbon atoms, and examples of such groups include alkylene groups, such as —CH2CH2—, —CH2CH2CH2—, —CH2CH2CH2CH2CH2CH2—, —CH2CH(CH3)—, and —CH2CH(CH3)CH2—. In view of easy synthesis of the compound, X is preferably —CH2CH2— or —CH2CH(CH3)—.
Each R3 is independently a monovalent hydrocarbon group having 1 to 6 carbon atoms or a hydrogen atom. R3's may be the same or different. R3 is preferably a methyl group or a hydrogen atom in view of easy synthesis of the compound.
a is an integer of 1 or more, preferably 1. b is an integer of 1 or more, preferably 1 or 2. c is an integer of 0 or more, preferably 0 to 2. Further, the total of a+b+c is an integer of 4 or more, and is preferably 4 in view of easy synthesis of the compound.
As specific examples of the siloxane compounds, there can be mentioned compounds represented by the following structural formulae.
Component (D) may be one type of component or a combination of two or more types of components.
Component (E-1) is a silicon carbide having a peak of the particle size distribution in the range of from 10 to 40 μm. With respect to the silicon carbide, there is no particular limitation, and any commercially available silicon carbide can be used as long as it is of a grade that can be used as a thermally conductive filler. Examples of commercially available products of silicon carbide include black silicon carbide and green silicon carbide, manufactured by Pacific Rundum Co., Ltd. Further, one which is obtained by very finely pulverizing the above silicon carbide can be used.
When component (E-1) has a monodisperse particle size distribution, the peak of the particle size distribution of the silicon carbide and the average particle diameter have the same meaning. The average particle diameter can be determined, for example, as a weight average value (or median diameter) using a particle size distribution measurement apparatus, for example, by a laser diffraction method.
Component (E-1) preferably has a monodisperse particle size distribution. Further, component (E-1) preferably has a peak of the particle size distribution in the range of from 15 to 35 μm, especially preferably a peak of the particle size distribution in the range of from 20 to 30 μm. Further, from the viewpoint of the electrical insulating properties, BLT properties, discharge properties, and radiator properties, component (E-1) preferably has a BET specific surface area of 0.01 to 5.0 m2/g, especially preferably 0.5 to 3.0 m2/g. Component (E-1) may be one type of component or a combination of two or more types of components.
Silicon carbide can be used as the below-mentioned component (E-2) and/or component (E-3). When silicon carbide is used as component (E-2) and/or component (E-3), the silicon carbide contained in the composition can have at least two peaks of the particle size distribution, that is, the silicon carbide can have a polydisperse particle size distribution. Specifically, the thermally conductive silicone composition can contain, as component (E-1), a silicon carbide having a peak of the particle size distribution in the range of from 10 to 40 μm, and, as component (E-2), a silicon carbide having a peak of the particle size distribution in the range of from 0.1 to 1.0 μm, and/or, as component (E-3), a silicon carbide having a peak of the particle size distribution in the range of from more than 1.0 to less than 10 μm.
«(E-2) First Thermally Conductive Filler Having a Thermal Conductivity of 10 to 300 W/mK and Having a Peak of the Particle Size Distribution in the Range of from 0.1 to 1.0 μm»
With respect to component (E-2), the thermal conductivity is a value as measured by a laser flash method. Further, the peak of the particle size distribution is as mentioned above in connection with component (E-1).
With respect to component (E-2), there is no particular limitation, and component (E-2) can be appropriately selected from conventionally known components. Component (E-2) is preferably alumina (thermal conductivity: 30 W/mK), aluminum nitride (thermal conductivity: 180 W/mK), aluminum hydroxide (thermal conductivity: 11 W/mK), magnesium oxide (thermal conductivity: 60 W/mK), zinc oxide (thermal conductivity: 25 W/mK), crystalline silica (thermal conductivity: 10 W/mK), aluminum (thermal conductivity: 250 W/mK), boron nitride (thermal conductivity: 60 to 200 W/mK), or graphitized carbon (thermal conductivity: 100 to 250 W/mK).
Further, from the viewpoint of the electrical insulating properties, BLT properties, discharge properties, and radiator properties, component (E-2) preferably has a BET specific surface area of 0.01 to 5 m2/g, especially preferably 0.1 to 1 m2/g.
Component (E-2) may be one type of component or a combination of two or more types of components.
«(E-3) Second Thermally Conductive Filler Having a Thermal Conductivity of 10 to 300 W/mK and Having a Peak of the Particle Size Distribution in the Range of from More than 1.0 to Less than 10 μm»
With respect to component (E-3), the thermal conductivity is as mentioned above in connection with component (E-2). Further, the peak of the particle size distribution is as mentioned above in connection with component (E-1).
With respect to component (E-3), there is no particular limitation, and component (E-3) can be appropriately selected from conventionally known components. Component (E-3) is preferably alumina, aluminum nitride, aluminum hydroxide, magnesium oxide, zinc oxide, crystalline silica, aluminum, boron nitride, or graphitized carbon.
Further, from the viewpoint of the electrical insulating properties, BLT properties, discharge properties, and radiator properties, component (E-3) preferably has a BET specific surface area of 0.1 to 3.0 m2/g, especially preferably 0.5 to 2.0 m2/g.
Component (E-3) may be one type of component or a combination of two or more types of components.
«(E-4) Third Thermally Conductive Filler (Exclusive of Silicon Carbide) Having a Thermal Conductivity of 60 to 300 W/mK and Having a Peak of the Particle Size Distribution in the Range of from 10 to 40 μm»
With respect to component (E-4), the thermal conductivity is as mentioned above in connection with component (E-2). Further, the peak of the particle size distribution is as mentioned above in connection with component (E-1).
With respect to component (E-4), there is no particular limitation, and component (E-4) can be appropriately selected from conventionally known components. Component (E-4) is preferably aluminum nitride, boron nitride, or graphitized carbon.
Further, from the viewpoint of the electrical insulating properties, BLT properties, discharge properties, and radiator properties, component (E-4) preferably has a BET specific surface area of 0.01 to 1.0 m2/g, especially preferably 0.1 to 0.5 m2/g.
Component (E-4) may be one type of component or a combination of two or more types of components.
Component (E) can contain (E-5) additional thermally conductive filler other than components (E-1) to (E-4).
Examples of component (E-5) include a thermally conductive filler having a thermal conductivity of 10 to 300 W/mK and having a peak of the particle size distribution in the range of more than 40 μm (for example, silicon carbide and aluminum nitride); and a thermally conductive filler having a thermal conductivity of 10 to less than 60 W/mK and having a peak of the particle size distribution in the range of from 10 to 40 μm. From the viewpoint of the electrical insulating properties, BLT properties, discharge properties, and radiator properties, component (E-5) preferably has a BET specific surface area of 0.1 to 3.0 m2/g, especially preferably 0.5 to 2.0 m2/g.
Component (E-5) may be one type of component or a combination of two or more types of components.
The composition can contain (F) additional component, such as a reaction inhibitor, an organic solvent, a tackifier, an inorganic pigment, an organic pigment, a thixotropic agent, a viscosity modifier, a mildewproofing agent, a heat resistance improving agent, or a flame retardant, in such an amount that the effects of the present invention are not sacrificed. Each component (F) may be one type of component or a combination of two or more types of components.
Examples of reaction inhibitors include organic compounds having a polar group in the molecule thereof, such as diallyl maleate; and organic compounds having an unsaturated bond, such as an acetylene alcohol and a derivative thereof. The reaction inhibitor suppresses the curing reaction rate of the composition and contributes to an improvement of the handling operation properties and the balance between the development of adhesive properties and the curing rate.
An organic solvent is a component that is capable of dissolving or dispersing therein the components contained in the composition. Examples of organic solvents include aromatic organic solvents, such as toluene and xylene.
Component (F) other than the reaction inhibitor and organic solvent can be appropriately selected from components used in the thermally conductive silicone composition.
The amounts of the individual components contained in the thermally conductive silicone composition are as described below.
The total amount of the components (A) to (D) is 1.0 to 10.0 parts by mass, based on 100 parts by mass of component (E). When the total amount of the components (A) to (D) is less than 1.0 part by mass, based on 100 parts by mass of component (E), the thermal conductivity likely becomes high, but the amount of the polymer is extremely small, as compared to the amount of component (E), and thus there is a concern that the resultant composition cannot be obtained in a paste form. When the total amount of the components (A) to (D) is more than 10.0 parts by mass, based on 100 parts by mass of component (E), excellent discharge properties can be obtained, but the thermal conductivity is reduced. The total amount of the components (A) to (D) is preferably 2.0 to 8.0 parts by mass, especially preferably 3.0 to 7.0 parts by mass, based on 100 parts by mass of component (E). Further, the total amount of the components (A) to (D) may be 6.0 to 8.0 parts by mass, based on 100 parts by mass of component (E).
The amount of the component (E-2) is 28.0 parts by mass or less, based on 100 parts by mass of component (E). When the amount of the component (E-2) is more than 28.0 parts by mass, based on 100 parts by mass of component (E), the resultant mixture cannot be obtained in the form of a composition. From the viewpoint of the electrical insulating properties, BLT properties, discharge properties, and radiator properties, the amount of the component (E-2) is preferably 10.0 to 28.0 parts by mass, especially preferably 15.0 to 25.0 parts by mass, based on 100 parts by mass of component (E).
The amounts of the individual components contained in the thermally conductive silicone composition are preferably as described below.
From the viewpoint of the electrical insulating properties, BLT properties, discharge properties, and radiator properties, the amount of the component (E-1) is preferably 5.0 to 30.0 parts by mass, more preferably 10.0 to 30.0 parts by mass, especially preferably 10.0 to 25.0 parts by mass, based on 100 parts by mass of component (E).
From the viewpoint of the electrical insulating properties, BLT properties, discharge properties, and radiator properties, the amount of the component (E-3) is preferably 15.0 to 40.0 parts by mass, especially preferably 20.0 to 35.0 parts by mass, based on 100 parts by mass of component (E).
From the viewpoint of the electrical insulating properties, BLT properties, discharge properties, and radiator properties, the amount of the component (E-4) is preferably 5.0 to 40.0 parts by mass, especially preferably 20.0 to 35.0 parts by mass, based on 100 parts by mass of component (E).
Thus, it is preferred that, based on 100 parts by mass of component (E), the amount of the component (E-1) is 5.0 to 30.0 parts by mass, the amount of the component (E-2) is 10.0 to 28.0 parts by mass, the amount of the component (E-3) is 15.0 to 40.0 parts by mass, and the amount of the component (E-4) is 5.0 to 40.0 parts by mass.
From the viewpoint of the discharge properties and curing properties, based on 100 parts by mass of the total of components (A), (B), (C), (D), and (F), the amount of the component (A) is preferably 55.0 to 95.0 parts by mass, more preferably 60.0 to 90.0 parts by mass, especially preferably 65.0 to 85.0 parts by mass.
With respect to the amount of the component (B), there is no particular limitation as long as a network structure can be formed in a cured product of the thermally conductive silicone composition. The amount of the component (B) is preferably such an amount that the ratio (H/Vi) of the number H of the hydrogen atom bonded to a silicon atom of component (B) to the number Vi of the alkenyl group of component (A) is 0.1 to less than 3.5, more preferably such an amount that the ratio (H/Vi) is 0.2 to 2.5, especially preferably such an amount that the ratio (H/Vi) is 0.3 to 2.0.
The amount of the component (C) is a catalytic amount, based on the amount of the thermally conductive silicone composition. Specifically, from the viewpoint of the curing properties, based on 100 parts by mass of the total of components (A), (B), (C), (D), and (F), the amount of the component (C) is preferably 0.1 to 1,000 ppm by weight, especially preferably 0.5 to 200 ppm by weight, in terms of a platinum atom.
With respect to the amount of the component (F), there is no particular limitation as long as the purpose of use of the thermally conductive silicone composition can be achieved.
The thermally conductive silicone composition can be produced by uniformly kneading components (A) to (E), which are essential components, and component (F), which is an optional component, by a mixing means, such as a universal kneading machine or a kneader.
The cured product of the thermally conductive silicone composition can be obtained by curing the thermally conductive silicone composition. The curing conditions (i.e., the heating temperature and heating time) can be appropriately controlled according to the heat resistance temperature of the member to which the thermally conductive silicone composition is applied. From the viewpoint of the heat resistance of the member and operation properties, the heating temperature is preferably 20 to 150° C., especially preferably higher than 23 to 100° C. The heating time varies depending on the amount of the material to be cured or the heating output of the apparatus used for curing, but, from the viewpoint of the simple and easy curing step, the heating time is preferably 15 minutes to 3 hours, especially preferably 30 minutes to 2 hours.
The cured product obtained by curing the thermally conductive silicone composition can be used as a radiator part of an electronic part for, for example, an electronic device or an integrated circuit element. Therefore, an electronic part comprising the thermally conductive silicone composition is also the subject for the present invention.
Hereinbelow, the present invention will be described in more detail with reference to the following Examples and Comparative Examples. In the following Examples, the “part(s)” indicates part(s) by mass, and the “viscosity” means a viscosity measured at 23° C. The following Examples should not be construed as limiting the scope of the present invention.
The components used in the Examples and Comparative Examples are as follows.
The thermally conductive fillers used in the Examples are of a monodisperse type and therefore, in the thermally conductive fillers used in the Examples, the peak diameter of particle size distribution has the same meaning as that of the “average particle diameter”. Further, the “Particle diameter” shown in the tables below indicates “peak diameter of particle size distribution”.
With respect to the base polymer to be mixed in the Examples and Comparative Examples, the base polymer having the formulation shown in Table 1 was kneaded using a planetary mixer to prepare base polymer (1).
Base polymer (2) having the formulation shown in Table 2 was prepared by the same method as that for base polymer (1).
The components for thermally conductive filler and base polymer were mixed in the formulation shown in Tables 3 to 13, and kneaded using a planetary mixer to prepare a thermally conductive silicone composition.
Using a thermal conductivity meter (TPS 1500) (manufactured by Kyoto Electronics Manufacturing Co., Ltd.), a container made of a plastic having an inner diameter of 30 mm and a depth of 10 mm was filled with the composition, and allowed to stand at 70° C. for one hour to cure the composition, producing a sample. A sensor of the thermal conductivity meter was placed between the obtained two samples, and a thermal conductivity was measured. The radiator properties were evaluated in accordance with the following criterion. The composition having a thermal conductivity of 7.0 W/(m·K) or more was judged to have excellent radiator properties.
A flow rate (g/min) of the composition was measured as described below, and used for evaluation of discharge properties.
The composition having a flow rate of 20 g/min or more was judged to have excellent discharge properties.
The measurement of a BLT, i.e., a bond line thickness of a radiator material was conducted as described below. Two silicon chips having a size of 10 mm×10 mm were prepared, and a thickness of each chip was preliminarily measured. 0.01 ml of the composition was applied to the one silicon chip, which had been measured with respect to the thickness, and then another silicon chip was stacked on the composition applied to the chip, and a load of 100 N was applied to the resultant stacked material, and then the stacked material was allowed to stand at 70° C. for one hour. Using a micrometer, a thickness of the stacked material was measured. A BLT thickness was determined by subtracting the total thickness of the two silicon chips from the measured thickness of the stacked material.
The composition having a BLT of 60 μm or less was judged to have low BLT.
A dielectric breakdown voltage was measured in accordance with JIS K 6249. Using an electrically insulating oil dielectric breakdown voltage testing machine Portatest A-2 (manufactured by Soken Electric Co., Ltd.), a dielectric breakdown voltage was measured. The composition was cured at 70° C. for one hour, and controlled to have a thickness of 1 mm to obtain a test specimen, and a voltage was applied to the test specimen at a voltage increase rate of 2 kV/sec, and a voltage measured at a time when electrical conduction of the test specimen was made so that electrical insulating properties disappeared was determined as a dielectric breakdown voltage. The composition having a dielectric breakdown voltage of 1.0 kV/mm or more was judged to have excellent electrical insulating properties.
A volume resistivity was measured in accordance with JIS K 6249. Specifically, using Advantest R8340 digital ultrahigh resistance/microammeter (manufactured by Advantest Corporation), a volume resistance was measured. The composition was cured at 70° C. for one hour, and controlled to have a thickness of 1 mm to obtain a test specimen, and a voltage of 500 V was applied to the test specimen, and, from a current value obtained as a response value of the voltage, a volume resistivity was determined by making a calculation. The composition having a volume resistivity of 1.00×1012 Ω·cm or more was judged to have excellent electrical insulating properties.
As apparent from the tables above, the thermally conductive silicone compositions in the Examples had low BLT and excellent electrical insulating properties, discharge properties, and radiator properties. Specifically, the amount of the component (E), based on the total amount of the components (A) to (D), and the amount of the component (E-2), based on the amount of the component (E), were in their respective predetermined ranges, and therefore the thermal conductivity and discharge properties were able to be appropriately controlled while maintaining the BLT properties.
Particularly, from a comparison between Example 1 and Example 10, it was found that when the amount of the “silicone composition containing no filler” was large (that is, when the total amount of the components (A) to (D) was 6.0 parts by mass or more, based on 100 parts by mass of component (E)), a lower BLT and more excellent discharge properties and radiator properties were obtained.
From a comparison between Examples 1 to 3, it was found that when the amount of component (E-1) was large, more excellent radiator properties were obtained.
From a comparison between Examples 1 and 2, it was found that when the amount of component (E-1) was small, more excellent electrical insulating properties were obtained. Further, as compared to Example 3, in Examples 1 and 2, a lower BLT and more excellent discharge properties were obtained.
From a comparison between Examples 1, 4, and 7, it was found that when the particle diameter of component (E-1) was large, more excellent thermal conductivity was obtained. Among Examples 1 to 9, in Examples 1, 4, and 7, a lower BLT and more excellent discharge properties were obtained.
The composition in Comparative Example 1 does not contain component (E-4). Therefore, the composition in Comparative Example 1 had poor discharge properties and electrical insulating properties, as compared to the compositions in Examples 1 to 3.
The composition in Comparative Example 2 does not contain component (E-4). In addition, the composition in Comparative Example 2 contains a thermally conductive filler having a large peak of the particle size distribution, as compared to component (E-4). Therefore, the composition in Comparative Example 2 had poor discharge properties, as compared to the composition in Example 1.
The relationship between Examples 4 to 6 and Comparative Example 3 and the relationship between Examples 7 to 9 and Comparative Example 5 are similar to the relationship between Examples 1 to 3 and Comparative Example 1. Further, the relationship between Example 4 and Comparative Example 4 and the relationship between Example 7 and Comparative Example 6 are similar to the relationship between Example 1 and Comparative Example 2.
The composition in Comparative Example 7 does not contain component (E-1) and component (E-4). Therefore, the composition in Comparative Example 7 could not be obtained in the form of an appropriate composition.
The composition in Comparative Example 8 does not contain component (E-1) and component (E-4). In addition, the composition in Comparative Example 8 contains silicon carbide having a large peak of the particle size distribution, as compared to component (E-1). Therefore, the composition in Comparative Example 8 had poor discharge properties and electrical insulating properties, as compared to the composition in Example 1.
The composition in Comparative Example 9 contains a thermally conductive filler having a low thermal conductivity, as compared to component (E-4). Therefore, the composition in Comparative Example 9 had poor thermal conductivity.
The composition in Comparative Example 10 does not contain component (E-4). Therefore, the composition in Comparative Example 10 had poor discharge properties and electrical insulating properties, as compared to the composition in Example 10.
The composition in Comparative Example 11 does not contain component (E-4). Therefore, the composition in Comparative Example 11 had poor discharge properties and electrical insulating properties, as compared to the composition in Example 11.
In the compositions in Comparative Examples 12 and 13, the amount of the component (E-2) is more than 28.0 parts by mass, based on 100 parts by mass of the thermally conductive filler. Therefore, the compositions in Comparative Examples 12 and 13 could not be obtained in the form of an appropriate composition.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-153110 | Sep 2023 | JP | national |
| 2024-073852 | Apr 2024 | JP | national |
