Thermally conductive silicone grease composition

Abstract

The present invention aims to provide a silicone grease composition that offers excellent workability and oil bleed resistance, high thermal conductivity, and is less likely to scratch the substrate surface. [Solution] A thermally conductive silicone grease composition, (A) A methylpolysiloxane having three alkoxy groups at one end, represented by the following general formula (1), [Formula 1] TIFF2026049379000009.tif2670(in the formula, R 1 (where a is an alkyl group having 1 to 6 carbon atoms, and a is an integer between 10 and 100.) (B) Thermally conductive fillers having a Mohs hardness of 4 or less. A thermally conductive silicone grease composition characterized by comprising the following.

Description

Technical Field

[0001] The present invention relates to a silicone grease composition that is excellent in workability and oil bleed resistance, has a high thermal conductivity, and is less likely to damage the surface of a substrate.

Background Art

[0002] With the progress of semiconductor technology, thermal countermeasures for elements have become increasingly important. A thermally conductive silicone grease composition that efficiently transfers the heat of an element to a cooling mechanism has been actively developed because of its high reliability (for example, Patent Documents 1 to 3).

[0003] On the other hand, the development of devices themselves equipped with cooling mechanisms has also been remarkable, and the development of small composite devices in which a cooling plate and a fan are integrated has also progressed. Many of such composite devices are designed using materials with high thermal conductivity such as aluminum and copper, and in particular, the contact portion with the element has a high flatness by polishing.

[0004] In many composite cooling devices, a cooling performance inspection is carried out before being shipped as a product. In this inspection, heat is generated by applying it to an element to confirm its cooling efficiency, and a thermally conductive grease is thinly coated on the interface between the element and the device. However, when the thermally conductive grease is removed after the inspection, scratches derived from the thermally conductive filler in the grease may remain on the plate surface. When the scratches are shallow, the scratches can be removed by re-polishing, but when the scratches are deep, there is a major problem that they cannot be removed and the device becomes a defective product due to the inspection.

[0005] As mentioned above, thermal conductive grease is applied as a thin film on a cooling plate, and then the plate is assembled with the element or metal lid for use. However, it is not assembled immediately after being applied as a thin film on the plate; in most cases, it is stored in a thin film state. When stored on a plate, a problem arises: the oil in the thermal conductive grease composition seeps out onto the plate surface (oil bleeding phenomenon). When oil bleeding occurs and the amount of oil in the thermal conductive grease composition decreases, the viscosity increases, which leads to problems such as poor conformability to the element and inability to fully exert heat dissipation performance. Furthermore, if the amount of oil bleeding increases, the surface of the composition loses its fluidity and becomes dry (dry-out state), which not only prevents it from exerting heat dissipation performance but also makes it easier to scratch the surface of the substrate. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Special Publication No. 2012-520923 [Patent Document 2] International Publication No. 2013 / 168291 [Patent Document 3] Japanese Patent Publication No. 2014-105283 [Overview of the project] [Problems that the invention aims to solve]

[0007] Conventional technology has a problem where, when thermal conductive grease is applied as a thin film, storing it in a thin film state causes an oil bleed phenomenon, preventing it from performing its heat dissipation function. Furthermore, if the amount of oil bleed is large, the surface of the composition becomes dry out, which not only prevents it from performing its heat dissipation function but also makes the substrate surface more susceptible to scratches.

[0008] The present invention has been made in view of the above circumstances, and aims to provide a thermally conductive silicone grease composition that has excellent workability and oil bleed resistance, high thermal conductivity, and is less likely to scratch the surface of the substrate. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention provides: A thermally conductive silicone grease composition, (A) A methylpolysiloxane having three alkoxy groups at one end, represented by the following general formula (1), [ka] (In the formula, R 1 (where a is an alkyl group having 1 to 6 carbon atoms, and a is an integer between 10 and 100.) (B) Thermally conductive fillers having a Mohs hardness of 4 or less. The present invention provides a thermally conductive silicone grease composition characterized by comprising the following:

[0010] Such a thermally conductive silicone grease composition is preferable because it offers excellent workability and oil blade resistance, has high thermal conductivity, and reduces damage such as scratches and abrasions to the substrate surface.

[0011] It is preferable that component (B) is present in an amount of 500 to 3000 parts by mass relative to 100 parts by mass of component (A).

[0012] If the amount of component (B) is 500 parts by mass or more, the thermal conductivity of the composition will be sufficient, and if it is 3000 parts by mass or less, the workability and printability will not be negatively affected, which is preferable. [Effects of the Invention]

[0013] As described above, the thermally conductive silicone grease composition of the present invention offers excellent workability, flexibly conforms to elements and substrates to promote heat dissipation, and reduces damage such as scratches and abrasions to the surface of elements and substrates. Furthermore, it has excellent oil bleed resistance, allowing it to maintain its grease state for a long period even after thin-film application. Therefore, the thermally conductive silicone grease composition of the present invention is suitable for inspection applications of devices equipped with cooling mechanisms and for heat dissipation applications between cooling plates and metal lids.

Mode for Carrying Out the Invention

[0014] As described above, there has been a demand for the development of a silicone grease composition that is excellent in workability and oil bleed resistance, has a high thermal conductivity, and is less likely to damage the surface of the base material.

[0015] As a result of intensive studies on the above problems, the present inventors have found that a thermal conductive silicone grease composition comprising the following components (A) and (B) is excellent in workability and oil bleed resistance, has a high thermal conductivity, and can further make it difficult to damage the surface of the base material, and thus completed the present invention.

[0016] That is, the present invention is a thermal conductive silicone grease composition comprising: (A) A methylpolysiloxane having three alkoxy groups at one end represented by the following general formula (1): [Chemical formula] (In the formula, R 1 is an alkyl group having 1 to 6 carbon atoms, and a is an integer of 10 to 100.) And (B) a thermal conductive filler having a Mohs hardness of 4 or less A thermal conductive silicone grease composition characterized by comprising the above.

[0017] Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.

[0018] The thermal conductive silicone grease composition of the present invention will be described in detail below.

[0019] -(A) Methylpolysiloxane having three alkoxy groups at one end- The component (A) is a methylpolysiloxane having three alkoxy groups at one end represented by the following general formula (1). The component (A) is a base oil component that imparts greasiness to the present composition, and at the same time increases the filling rate of the component (B) to improve the thermal conductivity and workability of the composition. [ka] (In the formula, R 1 (where a is an alkyl group having 1 to 6 carbon atoms, and a is an integer between 10 and 100.)

[0020] In the above equation (1), R 1 The group is an alkyl group having 1 to 6 carbon atoms, with 1 to 3 carbon atoms being preferred. Specifically, examples include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, etc.

[0021] a is a number between 10 and 100, with 20 to 80 being preferable. If a is less than 10, there may be a lot of oil bleeding from the composition, resulting in poor shelf life. If a is greater than 100, the wettability of component (B) may be insufficient, resulting in poor workability and printability.

[0022] This methylpolysiloxane, having three alkoxy groups at one end, may be used alone or in combination of two or more types.

[0023] In thermally conductive silicone greases, it is common to use a non-reactive organopolysiloxane, described later, as the base oil, and component (A) is used to improve the wettability between the non-reactive organopolysiloxane and the thermally conductive filler component (B). However, in the present invention, we have found that using only component (A) as the base oil results in superior oil bleed resistance compared to using a non-reactive organopolysiloxane.

[0024] -(B) Thermally conductive filler- Component (B), the thermally conductive filler, is an ingredient that imparts thermal conductivity to the composition. The thermally conductive filler used in this composition has a Mohs hardness of 4 or less. Mohs hardness is an index that indicates resistance to scratching; a higher number indicates greater resistance to scratching, while a lower number indicates greater resistance to scratching. In other words, a lower Mohs hardness value indicates greater resistance to scratching. Typical thermally conductive fillers with a Mohs hardness of 4 or less include indium, silver, aluminum, copper, zinc oxide, aluminum hydroxide, and boron nitride, with silver, aluminum, and zinc oxide being preferred.

[0025] The shape of the thermally conductive filler particles of component (B) may be spherical, rounded, or an amorphous mixture with no particular shape, but spherical is preferred from the viewpoint of filling the composition and reducing damage to the substrate. Spherical refers to particles that are commercially available in a spherical shape after processing such as melting or granulation. Rounded refers to particles with few corners and a smooth, rounded state. Rounded refers to particles with few corners and a smooth, rounded state, but does not include spherical particles. Rounded particles are clearly different from spherical in that they have corners. Irregular refers to any shape that has not been intentionally spheroidized by melting or granulation. Furthermore, the average particle size is not particularly limited, but from the viewpoint of filling, uniformity of the composition, and viscosity, it is preferably 0.1 to 150 μm, more preferably 0.2 to 100 μm. Here, the average particle size of the powder is the cumulative average diameter D in the volume-based particle size distribution by laser diffraction scattering method. 50 This is the median diameter and can be measured using a Microtrac MT3300EX from Microtrac-Bell Corporation, among others.

[0026] Preferably, the amount of component (B) is 500 to 3000 parts by mass, and more preferably 1000 to 2500 parts by mass, relative to 100 parts by mass of component (A). If the amount of component (B) is 500 parts by mass or more, the thermal conductivity of the composition will be sufficient, and if it is 3000 parts by mass or less, the workability and printability will not be negatively affected, which is preferable.

[0027] The aforementioned component (B) may be used alone or in combination of two or more types.

[0028] The thermally conductive silicone grease composition of the present invention can be manufactured by mixing predetermined amounts of components (A) and (B) using a mixer such as Trimix, Twinmix, Planetary Mixer (all registered trademarks of mixers manufactured by Inoue Seisakusho Co., Ltd.), Ultra Mixer (registered trademark of mixers manufactured by Mizuho Industries Co., Ltd.), or Hibis Disper Mix (registered trademark of mixers manufactured by Tokushu Kika Kogyo Co., Ltd.).

[0029] The viscosity of the obtained thermally conductive silicone grease composition at 25°C, as measured by a spiral viscometer, is preferably 30 to 500 Pa·s, and particularly preferably 50 to 300 Pa·s. A viscosity within the range of 30 Pa·s to 500 Pa·s is acceptable for workability and printability. Furthermore, the thermal conductivity of the thermally conductive silicone grease composition is preferably 0.8 (W / mK) or higher. [Examples]

[0030] The present invention will be specifically described below using examples and comparative examples, but the present invention is not limited to these.

[0031] [(A) component] (A-1): A methylpolysiloxane with one-terminated trimethoxysilyl group blocked off, represented by the following average composition formula. [ka]

[0032] [(B) Component] (B-1): Aluminum powder (average particle size 9 μm, Mohs hardness 2.5) (B-2): Aluminum powder (average particle size 20 μm, Mohs hardness 2.5) (B-3): Silver powder (average particle size 3 μm, Mohs hardness 3.0) (B-4): Zinc oxide powder (average particle size 0.25 μm, Mohs hardness 4.0) (b-5): Alumina powder (average particle size 10 μm, Mohs hardness 9.0) (b-6): Alumina powder (average particle size 2 μm, Mohs hardness 9.0) (b-7): Aluminum nitride powder (average particle size 20 μm, Mohs hardness 7.5)

[0033] [(C) component] (C-1): Nonreactive organopolysiloxane represented by the following average empirical formula [ka]

[0034] [Examples 1-4, Comparative Examples 1 and 2] Components (A) and (B) were placed in the amounts shown in Table 1 into a 5-liter planetary mixer (manufactured by Inoue Seisakusho Co., Ltd.), mixed at room temperature for 30 minutes, and then mixed under reduced pressure at 170°C for 1.5 hours. The mixture was cooled to room temperature (25°C) and the composition was obtained at atmospheric pressure.

[0035] [viscosity] The viscosity of the composition was measured at 25°C using a spiral viscometer, specifically a Malcolm viscometer (Type PC-10AA) manufactured by Malcolm Corporation.

[0036] [Thermal conductivity] The thermal conductivity of the compositions was measured at 25°C using the hot disk method in accordance with ISO 22007-2, with a TPS-2500S manufactured by Kyoto Electronics Manufacturing Co., Ltd.

[0037] [Damage assessment to the copper substrate] The composition was squeegee-printed onto a copper substrate (JIS H 3100: C1100P) (40 mm long, 40 mm wide, 200 μm thick), and a glass substrate was placed on top to sandwich it. A 1.5 kg weight was placed on the glass substrate and left for 3 hours. After removing the weight and glass substrate, the composition was carefully wiped off the copper substrate with gauze. The copper substrate was washed with toluene solvent and then dried. The surface of the copper substrate used had a reddish-brown mirror finish. The surface condition was observed before and after the test to check for scratches and abrasions. Maintaining the reddish-brown mirror finish was marked with ○, some whitening due to fine abrasions was observed with △, and whitening due to abrasions was present on the entire surface, or there were clear linear scratches was marked with ×. Each composition was tested three times.

[0038] [Oil bleed evaluation] 0.1 cc of the composition was applied in a dot pattern onto frosted glass (5 cm long, 5 cm wide, 5 mm thick) and left in a room at 23°C and 50% humidity for a predetermined time. After standing, the width (top, bottom, left, and right) of the oil bled from the composition was measured and the average value was calculated.

[0039] [Dryout Rating] The composition was squeegee-printed onto an aluminum substrate (JIS, H, 4000: A1050P) (40 mm long, 40 mm wide, 125 μm thick), and then left in a room at 23°C and 50% humidity for a specified period. After the period, the composition was collected with a plastic spatula, and it was confirmed whether the composition maintained its grease properties.

[0040] Table 1 shows the results of each test and measurement performed using the obtained composition. [Table 1]

[0041] In Examples 1-4, almost no damage such as scratches or abrasions were observed on the copper substrate. On the other hand, in Comparative Examples 1 and 2, whitening of the surface due to abrasion was significant across the entire surface, and linear scratches were also observed. In particular, as in Comparative Example 1, even if components (A) and (B) of the present invention were contained, scratches occurred if substances that did not meet the Mohs hardness requirements of the present invention, such as (b-5), were present.

[0042] [Comparative Example 3] Components (B) and (C) were placed in the amounts shown in Table 2 into a 5-liter planetary mixer (manufactured by Inoue Seisakusho Co., Ltd.), mixed at room temperature for 30 minutes, and then mixed under reduced pressure at 170°C for 3 hours. The mixture was cooled to room temperature (25°C) and the composition was obtained at atmospheric pressure.

[0043] Table 2 shows the results of each test and measurement performed using the obtained compositions (Example 2 and Comparative Example 3).

[0044] [Table 2]

[0045] In the composition of Example 2, the oil bleed width was small in the oil bleed evaluation, and the grease properties were maintained over the long term in the dry-out evaluation. On the other hand, in the composition of Comparative Example 3, the oil bleed width was large in the oil bleed evaluation, and it became putty-like after long-term storage in the dry-out evaluation. Furthermore, its surface was dry out. In other words, even if component (B) was used, oil bleed worsened when the non-reactive organopolysiloxane component (C) was used as the base oil without using component (A). It can be seen that the occurrence of oil bleed can be suppressed by using only components (A) and (B).

[0046] It should be noted that the present invention is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the claims of the present invention and achieves similar effects is included within the technical scope of the present invention.

Claims

1. A thermally conductive silicone grease composition, (A) A methylpolysiloxane having three alkoxy groups at one end, represented by the following general formula (1), 【Chemistry 1】 (In the formula, R １ (where a is an alkyl group having 1 to 6 carbon atoms, and a is an integer between 10 and 100.) (B) A thermally conductive filler having a Mohs hardness of 4 or less. A thermally conductive silicone grease composition characterized by comprising the following.

2. The thermally conductive silicone grease composition according to claim 1, characterized in that the amount of component (B) is 500 to 3000 parts by mass per 100 parts by mass of component (A).

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