Thermally conductive silicone composition

Abstract

The present invention provides a thermally conductive silicone composition that provides a cured product which has low thermal resistance and excellent reliability.　Provided is a thermally conductive silicone composition comprising components (A), (B), (C), (D), (E), and (F). (A) is an organopolysiloxane which has at least two alkenyl groups at a molecular chain end, and which has a kinematic viscosity of 100-500,000 mm2 / s at 25°C. (B) is a hydrolyzable methyl polysiloxane which is represented by general formula (1) and which has three functional groups at one end (in formula (1), R1 is a C1-6 alkyl group and a is a number of 5 to 100). (C) is a bismuth-tin-based alloy powder which has a melting point of not higher than 220°C. (D) is a thermally conductive filler other than component (C) which has a melting point of not lower than 280°C and which has an average particle size of not less than 3 μm. (E) is an organohydrogen polysiloxane which, per molecule, has a hydrogen atom directly bonded to at least two silicon atoms (Si-H group). (F) is a catalyst selected from among platinum and platinum compounds.

Description

Thermally conductive silicone composition

[0001] The present invention relates to a thermally conductive silicone composition that has high heat dissipation performance and excellent reliability.

[0002] It is widely known that electronic components such as LSIs and IC chips generate heat during use, resulting in a decline in performance. Various heat dissipation technologies have been used to address this issue. For example, a known method involves placing a cooling component, such as a heat sink, near a heat-generating component and closely contacting the two to promote efficient heat transfer to the cooling component, thereby cooling the cooling component and thereby efficiently dissipating heat from the heat-generating component. In this case, if there is a gap between the heat-generating component and the cooling component, the presence of air with low thermal conductivity can result in inefficient heat transfer, preventing the temperature of the heat-generating component from sufficiently decreasing. To prevent this phenomenon, heat-dissipating materials, such as heat-dissipating sheets and heat-dissipating greases, that have good thermal conductivity and conform to the surface of the components are used to prevent air from entering between the heat-generating component and the cooling component (see Japanese Patent Nos. 2938428, 2938429, and 3952184: Patent Documents 1 to 3). Among these, heat-dissipating greases exhibit high performance in terms of thermal resistance because they can be used in a thin package.

[0003] Some thermal greases are sandwiched between components and then heated and cured before use. Many materials have been designed to increase thermal conductivity and improve heat dissipation performance by incorporating a large amount of solid filler. However, to reduce contact thermal resistance with heat-generating and cooling components, it is preferable for the thermally conductive filler to be in a fluid state when in contact. From this perspective, various thermal greases incorporating low-melting-point metals have been reported (see JP 2021-169582 A, JP 4551074 A, and JP 4860229 A: Patent Documents 4 to 6). However, because these greases contain gallium or alloys containing gallium, exposure of the gallium due to stress during device operation poses a risk of corrosion to metal components. Furthermore, gallium is a rare metal, making it expensive. On the other hand, Japanese Patent Laid-Open Publication No. 2014-003152 (Patent Document 7) proposes a thermal interface material containing a thermally conductive filler made of a bismuth-tin alloy, but the filler content is insufficient, and it is difficult to say that the thermal resistance is sufficiently reduced. Also, because the particle size of the filler added as a spacer is small, the BLT (material thickness) decreases after a heat cycle test, and as a result, the material is unable to conform to warpage, and there is a risk of delamination from the substrate, resulting in a deterioration in thermal resistance.

[0004] Japanese Patent No. 2938428 Japanese Patent No. 2938429 Japanese Patent No. 3952184 Japanese Patent Publication No. 2021-169582 Japanese Patent No. 4551074 Japanese Patent No. 4860229 Japanese Patent Publication No. 2014-003152

[0005] Therefore, an object of the present invention is to provide a thermally conductive silicone composition that provides a cured product that has low thermal resistance and excellent reliability.

[0006] As a result of extensive research to achieve the above object, the inventors discovered that the following thermally conductive silicone composition could achieve the object, and thus completed the present invention. That is, the present invention provides the following thermally conductive silicone composition, etc.

[0007] [1] A thermally conductive silicone composition containing the following components (A), (B), (C), (D), (E), and (F): (A) a silicone oil having at least two alkenyl groups per molecule and a kinematic viscosity at 25°C of 100 to 500,000 mm 2 / s organopolysiloxane: 100 parts by mass; (B) one-terminal trifunctional hydrolyzable methylpolysiloxane represented by the following general formula (1): 50 to 500 parts by mass per 100 parts by mass of component (A): (In formula (1), R 1 is an alkyl group having 1 to 6 carbon atoms, and a is a number from 5 to 100. (C) Bismuth-tin alloy powder having a melting point of 220°C or less: 1,000 to 3,000 parts by mass per 100 parts by mass of the total of component (A) and component (B). (D) A thermally conductive filler other than component (C) having a melting point of 280°C or more and an average particle size of 3 μm or more: 200 to 1,500 parts by mass per 100 parts by mass of the total of component (A) and component (B). The total of component (C) and component (D) is 2,300 to 3,500 parts by mass per 100 parts by mass of the total of component (A) and component (B). (E) An organohydrogenpolysiloxane having at least two hydrogen atoms directly bonded to silicon atoms (Si—H groups) per molecule: an amount such that {the number of Si—H groups in component (E)} / {the number of alkenyl groups in component (A)} is 0.1 to 5.0. (F) a catalyst selected from platinum and platinum compounds: in an amount of 0.1 to 500 ppm in terms of platinum atoms relative to the mass of component (A) [2] The thermally conductive silicone composition according to item (1), further comprising the following component (G): (G) one or more compounds selected from the group consisting of acetylene compounds, nitrogen compounds, organic phosphorus compounds, oxime compounds, and organic chloro compounds: in an amount of 0.1 to 5% by mass relative to the mass of component (A).

[0008] The thermally conductive silicone composition of the present invention contains a bismuth-tin alloy and a filler other than the bismuth-tin alloy that has a specific average particle size, making it possible to provide a cured product that has low thermal resistance and excellent reliability.The thermally conductive silicone composition of the present invention is therefore useful as a heat-dissipating material for electronic components.

[0009] The present invention will be described in detail below.

[0010] Component (A) The organopolysiloxane used in the composition of the present invention, component (A), has at least two alkenyl groups directly bonded to silicon atoms per molecule. These may be linear or branched, or may be a mixture of two or more of these with different viscosities. It is preferable that at least one alkenyl group directly bonded to a silicon atom is located at each end of the molecular chain. Examples of alkenyl groups include vinyl, allyl, 1-butenyl, and 1-hexenyl, with vinyl being preferred from the standpoints of ease of synthesis and cost. Examples of organic groups other than alkenyl groups bonded to silicon atoms include alkyl groups such as methyl, ethyl, propyl, butyl, hexyl, and dodecyl, aryl groups such as phenyl, and aralkyl groups such as 2-phenylethyl and 2-phenylpropyl. Further examples include substituted hydrocarbon groups such as chloromethyl and 3,3,3-trifluoropropyl. Of these, methyl groups are preferred from the standpoint of ease of synthesis and cost. The alkenyl groups bonded to silicon atoms are preferably present at the terminals of the molecular chains of the organopolysiloxane.

[0011] The organopolysiloxane of component (A) has a kinematic viscosity at 25°C of 100 to 500,000 mm 2 / s, preferably in the range of 400 to 100,000 mm 2 The kinematic viscosity of the organopolysiloxane is a value measured at 25°C using an Ostwald viscometer.

[0012] The content of component (A) in the thermally conductive silicone composition of the present invention is preferably 0.1 to 8.0 mass%, more preferably 0.1 to 6.0 mass%, and even more preferably 0.1 to 5.0 mass%. Note that component (A) may be used alone, or two or more types may be used in combination.

[0013] Component (B) The component (B) used in the composition of the present invention is a hydrolyzable methylpolysiloxane having trifunctional groups at one end, which is represented by the following general formula (1). (In formula (1), R 1 is an alkyl group having 1 to 6 carbon atoms, and a is a number from 5 to 100.

[0014] In the above formula (1), R 1 represents an alkyl group having 1 to 6 carbon atoms, preferably a methyl group, an ethyl group, or a propyl group, and particularly preferably a methyl group or an ethyl group.

[0015] In the above formula (1), a is in the range of 5 to 100, and preferably in the range of 10 to 60. If the above a is less than 5, oil bleeding of the composition may become severe, resulting in poor reliability, whereas if it is more than 100, wettability may become insufficient.

[0016] The amount of component (B) blended is in the range of 50 to 500 parts by mass, preferably 100 to 500 parts by mass, per 100 parts by mass of component (A). If the amount of component (B) blended is less than 50 parts by mass, sufficient wettability may not be exhibited, and if it is more than 500 parts by mass, oil bleeding may become severe, resulting in poor reliability. Note that component (B) may be used alone or in combination of two or more types.

[0017] Component (C) The component (C) used in the composition of the present invention is a bismuth-tin alloy powder having a melting point of 220°C or less. The melting point of component (C) is 220°C or less, preferably 200°C or less, more preferably 190°C or less, and particularly preferably 180°C or less. If the melting point is higher than 220°C, the alloy may not melt sufficiently in a typical heating process, making it difficult to achieve low thermal resistance. The average particle size of component (C) is preferably in the range of 0.1 to 80 μm, more preferably 0.1 to 70 μm, and particularly preferably 0.1 to 60 μm. If the average particle size is less than 0.1 μm, the composition may have poor extensibility, while if it is greater than 80 μm, it may be difficult to achieve low thermal resistance. In this specification, the average particle size can be measured using a Microtrac MT3300EX manufactured by Nikkiso Co., Ltd. and is the volume-based volume average diameter (hereinafter the same). The shape of component (C) may be any shape, including amorphous and spherical.

[0018] The amount of component (C) blended is in the range of 1,000 to 3,000 parts by mass, preferably 1,000 to 2,700 parts by mass, and more preferably 1,200 to 2,700 parts by mass, per 100 parts by mass of the total of components (A) and (B). If the blending amount is less than 1,000 parts by mass, the substrates may not be sufficiently bonded when heated, and low thermal resistance may not be obtained. If the blending amount is more than 3,000 parts by mass, the spreadability of the composition may be poor. Note that component (C) may be used alone or in combination of two or more types.

[0019] Component (D) The component (D) used in the composition of the present invention is a thermally conductive filler other than component (C) that has a melting point of 280°C or higher and an average particle size of 3 μm or higher. Component (D) preferably has a thermal conductivity of 10 W / m°C or higher. If the thermal conductivity is lower than 10 W / m°C, the thermal conductivity of the thermally conductive silicone composition itself may be reduced. Examples of component (D) include aluminum powder, copper powder, silver powder, iron powder, nickel powder, gold powder, metal silicon powder, aluminum nitride powder, boron nitride powder, alumina powder, diamond powder, carbon powder, zinc oxide powder, and aluminum hydroxide powder. However, any filler having a conductivity of 10 W / m°C or higher may be used, and one or a mixture of two or more fillers may be used. The melting point of component (D) is 280°C or higher, preferably 300°C or higher. If the temperature is lower than 280°C, when the composition is exposed to heating at 260°C, which is typical for lead solder reflow conditions, the thermally conductive filler of component (D) will melt, causing the composition to become thinner and less reliable.

[0020] The average particle size of component (D) is 3 μm or more, preferably in the range of 3 to 100 μm, more preferably in the range of 3 to 80 μm, and particularly preferably in the range of 3 to 70 μm. If the average particle size is smaller than 3 μm, the composition may not maintain a sufficient thickness when component (C) is heated and dissolved, resulting in poor reliability after a heat cycle test. If the average particle size is larger than 100 μm, the thermal resistance of the composition may increase, resulting in reduced performance. The shape of component (D) may be any shape, including amorphous and spherical.

[0021] The amount of component (D) is in the range of 200 to 1,500 parts by mass, preferably 200 to 1,200 parts by mass, and more preferably 250 to 1,200 parts by mass per 100 parts by mass of the total of components (A) and (B). If the amount of component (D) is less than 200 parts by mass, the thermal conductivity of the composition may be reduced, while if it is more than 1,500 parts by mass, the dissolution of component (C) may be inhibited. Note that component (D) may be used alone or in combination of two or more types.

[0022] The total amount of components (C) and (D) is in the range of 2,300 to 3,500 parts by mass, preferably 2,300 to 3,300 parts by mass, and more preferably 2,300 to 3,200 parts by mass, per 100 parts by mass of the total of components (A) and (B). If the amount is less than 2,300 parts by mass, the thermal conductivity of the composition may be low, and if it is more than 3,500 parts by mass, the spreadability of the composition may be poor.

[0023] Component (E) Component (E) used in the composition of the present invention is an organohydrogenpolysiloxane having at least two hydrogen atoms directly bonded to silicon atoms (Si—H groups) per molecule. Examples of organic groups other than Si—H groups bonded to silicon atoms 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; substituted hydrocarbon groups such as chloromethyl and 3,3,3-trifluoropropyl; and epoxy ring-containing organic groups such as 2-glycidoxyethyl, 3-glycidoxypropyl, and 4-glycidoxybutyl. The organohydrogenpolysiloxane of component (E) may be linear, branched, or cyclic, or may be a mixture of these.

[0024] The amount of component (E) blended, {the number of Si-H groups in component (E)} / {the number of alkenyl groups in components (A) and (B)}, is in the range of 0.1 to 5.0, preferably 0.5 to 4.5, and more preferably 0.5 to 2.5. If the ratio {the number of Si-H groups in component (E)} / {the number of alkenyl groups in components (A) and (B)} is less than 0.1, the composition may not be sufficiently reticulated, and the grease may not cure sufficiently. If it is more than 5.0, the crosslink density may be too high, resulting in poor reliability. One type of component (E) may be used alone, or two or more types may be used in combination.

[0025] Component (F) used in the composition of the present invention is a catalyst selected from platinum and platinum compounds, and promotes the addition reaction between the alkenyl groups of component (A) and component (B) and the Si—H groups of component (E). Examples of component (F) include platinum alone, chloroplatinic acid, platinum-olefin complexes, platinum-alcohol complexes, and platinum coordination compounds. The amount of component (F) to be added is in the range of 0.1 to 500 ppm, preferably 0.1 to 400 ppm, of platinum atoms relative to the mass of component (A). If the amount of component (F) is less than 0.1 ppm of platinum atoms, the catalytic effect is ineffective, and if it is more than 500 ppm, the effect is not enhanced and it is uneconomical. Component (F) may be used alone or in combination of two or more types.

[0026] Component (G) Component (G) used in the composition of the present invention is a regulator that suppresses the catalytic activity of optional component (F), inhibiting the progress of the hydrosilylation reaction at room temperature and extending shelf life and pot life. Known reaction regulators can be used, including, for example, acetylene compounds, nitrogen compounds, organic phosphorus compounds, oxime compounds, and organic chloro compounds. The amount of component (G) is preferably 0.1 to 5 mass% relative to the mass of component (A), more preferably 0.1 to 4 mass%. A blend amount of component (G) less than 0.1% may not provide sufficient shelf life and pot life extension, while a blend amount greater than 5% may result in a reduced curing rate. Component (G) may be used alone or in combination with two or more types. Component (G) may also be diluted with toluene or the like to improve dispersibility in the thermally conductive silicone composition.

[0027] Other Components In addition to the above components (A) to (G), the composition of the present invention may contain, if necessary, an antioxidant or the like to prevent deterioration.

[0028] Production Method The composition of the present invention can be produced by mixing components (A) to (F), and, if necessary, component (G) and / or other components in predetermined amounts using a mixer such as Trimix, Twinmix, or Planetary Mixer (all of which are registered trademarks of mixers manufactured by Inoue Seisakusho Co., Ltd.), Ultramixer (registered trademark of mixers manufactured by Mizuho Kogyo Co., Ltd.), or Hivismix (registered trademark of mixers manufactured by Primix Corporation).

[0029] The present invention will be described in more detail below with reference to examples and comparative examples in order to clarify the effects of the present invention, but the present invention is not limited thereto. Tests regarding the effects of the present invention were carried out as follows.

[0030] [Viscosity] The absolute viscosity of the composition was measured at 25°C using a Malcom viscometer (type PC-10).

[0031] [BLT (material thickness), thermal resistance] A thermally conductive silicone composition was sandwiched between a 15 mm x 15 mm x 1 mm thick Si chip and a 15 mm x 15 mm x 1 mm thick Ni plate. The composition was then heated and cured by placing the composition in a 170°C oven for 90 minutes while maintaining a pressure of 0.18 (MPa). A test piece for measuring thermal resistance was then prepared, and the initial BLT and thermal resistance were measured. Furthermore, a heat cycle test (HC test) was performed 1,000 times, alternating between 30 minutes at -40°C and 30 minutes at 125°C. The BLT and thermal resistance after the test were measured. The BLT was calculated by measuring the thickness of the Si chip and Ni plate with a microgauge and subtracting this from the overall thickness of the test piece. Thermal resistance measurements were performed using a Nanoflash (NETZSCH, LFA467).

[0032] The following components constituting the composition of the present invention were prepared.

[0033] Component (A) A-1: ​​Both ends are capped with dimethylvinylsilyl groups, and the kinematic viscosity at 25°C is 600 mm 2 A-2: Dimethylpolysiloxane having a kinematic viscosity of 30,000 mm at 25°C (vinyl value: 0.015 mol / 100 g) and a vinyl value of 0.015 mol / 100 g. A-3: Dimethylpolysiloxane having a kinematic viscosity of 30,000 mm at 25°C and a vinyl value of 0.015 mol / 100 g. 2 A-3: Dimethylpolysiloxane having a kinematic viscosity of 1,500 mm at 25°C (vinyl value: 0.0036 mol / 100 g) and a vinyl value of 0.0036 mol / 100 g. A-4: Dimethylpolysiloxane having a kinematic viscosity of 1,500 mm at 25°C and a vinyl value of 0.0036 mol / 100 g. 2 / s dimethylpolysiloxane (vinyl value: 0.026 mol / 100 g)

[0034] Component (B) B-1: ((CH3)3SiO 1 / 2 )((CH3)2SiO) 30 ((OCH3)3SiO 1 / 2 ) B-2: ((CH3)3SiO 1 / 2 )((CH3)2SiO) 20 ((OCH3)3SiO 1 / 2 )

[0035] Component (C) C-1: Bi 57 Sn 43 Powder Melting point 144°C Average particle size 19 μm C-2: Bi 40 Sn60 Powder, melting point 142°C, average particle size 25 μm

[0036] Component (D) d-1: Aluminum powder with an average particle size of 10 μm d-2: Aluminum powder with an average particle size of 2 μm d-3: Copper powder with an average particle size of 10 μm d-4: Copper powder with an average particle size of 2 μm d-5: Zinc oxide powder with an average particle size of 0.6 μm Components d-1 to d-5 were mixed in the parts shown in Table 1 below to obtain components D-1 to D-5. The results of measuring the average particle sizes of D-1 to D-5 are also shown below. The average particle sizes are values ​​measured as volume-based volume average diameters using a Microtrac MT3300EX manufactured by Nikkiso Co., Ltd.

[0037]

[0038] Component (E) E-1: Organohydrogenpolysiloxane represented by the following formula: Si—H content: 0.088 mol / 100 g E-2: Organohydrogenpolysiloxane represented by the following formula Si—H content: 0.137 mol / 100 g E-3: Organohydrogenpolysiloxane represented by the following formula Si-H content: 0.500mol / 100g

[0039] Component (F) F-1: A-1 solution of platinum-divinyltetramethyldisiloxane complex, containing 1 wt% platinum atoms

[0040] Component (G) G-1: 1-ethynyl-1-cyclohexanol

[0041] Examples 1 to 8 and Comparative Examples 1 to 6 Components (A) to (G) were mixed as follows to obtain Examples 1 to 8 and Comparative Examples 1 to 6. That is, component (A) was placed in 1 liter of Hibismix (manufactured by Primix Corporation), and components (B), (C), and (D) were added in the amounts shown in Tables 2 and 3, and mixed for 1 hour. Next, components (E), (F), and (G) were added in the amounts shown in Tables 2 and 3, and mixed until uniform.

[0042]

[0043]

Claims

1. A thermally conductive silicone composition containing the following components (A), (B), (C), (D), (E) and (F): (A) a silicone rubber having at least two alkenyl groups per molecule and a kinetic viscosity at 25°C of 100 to 500,000 mm 2 / s organopolysiloxane: 100 parts by mass; (B) a hydrolyzable methylpolysiloxane having three functional groups at one end and represented by the following general formula (1): 50 to 500 parts by mass per 100 parts by mass of component (A); (In formula (1), R 1 is an alkyl group having 1 to 6 carbon atoms, and a is a number from 5 to 100. (C) Bismuth-tin alloy powder having a melting point of 220° C. or less: 1,000 to 3,000 parts by mass per 100 parts by mass of the total of components (A) and (B). (D) A thermally conductive filler other than component (C) having a melting point of 280° C. or more and an average particle size of 3 μm or more: 200 to 1,500 parts by mass per 100 parts by mass of the total of components (A) and (B). The total of components (C) and (D) is 2,300 to 3,500 parts by mass per 100 parts by mass of the total of components (A) and (B). (E) An organohydrogenpolysiloxane having at least two hydrogen atoms directly bonded to silicon atoms (Si—H groups) per molecule: an amount such that {the number of Si—H groups in component (E)} / {the number of alkenyl groups in component (A)} is 0.1 to 5.

0. (F) a catalyst selected from platinum and platinum compounds: an amount of 0.1 to 500 ppm in terms of platinum atoms relative to the mass of component (A) 2. The thermally conductive silicone composition according to claim 1, further comprising the following component (G): (G) one or more compounds selected from the group consisting of acetylene compounds, nitrogen compounds, organic phosphorus compounds, oxime compounds, and organic chloro compounds: in an amount of 0.1% to 5% by mass relative to the mass of component (A).

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