JP7632143B2 - Silicone resin composition - Google Patents

Description

The present invention relates to a silicone resin composition that maintains fluidity and is easy to handle, even when highly filled with a thermally conductive filler to impart thermal conductivity.

Many electronic components generate heat during use, and heat removal is necessary to maintain their functionality. In particular, the amount of heat generated by recent electronic components increases with the increasing integration and power output of circuit boards, making heat countermeasures an important issue.

As a means of removing heat from electronic components, a method has been proposed in which a thermally conductive material such as thermally conductive grease or sheet is placed between the electronic component and a cooling member such as a heat sink to allow heat to escape from the electronic component. One such thermally conductive material is a silicone resin composition made of organopolysiloxane and a thermally conductive filler such as aluminum oxide powder or zinc oxide powder (see Patent Document 1, Patent Document 2, or Patent Document 3).

In the above thermally conductive materials, the Brugman model is known as a formula for predicting thermal conductivity. This formula shows that when the filling rate of the thermally conductive filler is low, the thermal conductivity hardly changes regardless of the filling rate, but when the filling rate exceeds a certain level, it increases rapidly. In other words, in order to increase the thermal conductivity of a thermally conductive material, it is important to fill it with as much thermally conductive filler as possible.

On the other hand, increasing the filling rate of the thermally conductive filler significantly reduces the fluidity of the resin composition used in the thermally conductive material, making it difficult to eject or apply the resin composition, and it also becomes unable to conform to the fine irregularities on the surfaces of electronic components and heat sinks, resulting in increased contact thermal resistance. A known method of solving this problem is to use an additive in the resin composition to improve the dispersibility of the thermally conductive filler.

JP 2005-054099 A JP 2004-091743 A JP 2000-063873 A

The objective of the present invention is to provide a silicone resin composition that not only maintains fluidity and is easy to work with even when highly filled with a thermally conductive filler, but also conforms to the surface irregularities of electronic components and the like to reduce contact thermal resistance, thereby providing high heat dissipation performance.

As a result of intensive research conducted by the inventors to solve the above problems, they discovered that a combination of a polyorganosiloxane having a specific structure and a molecular weight distribution (Mw/Mn) of 1.20 or less and a silicone resin composition containing a thermally conductive filler is useful, and thus completed the present invention.

（式（１）中、Ｒ^１は独立して、一価飽和炭化水素基、または一価芳香族炭化水素基であり、Ｘは末端に水酸基を有する、式（２）または式（３）で表される基であり、ｎは１以上の整数である。）

で表される、分子量分布（Ｍｗ／Ｍｎ）が、１．２０以下であるオルガノポリシロキサンと
（Ｂ）熱伝導性充填剤
を含有するシリコーン樹脂組成物。 That is, according to the present invention, there is provided the following silicone resin composition.
Item 1. (A) Formula (1):

(In formula (1), R ¹ is independently a monovalent saturated hydrocarbon group or a monovalent aromatic hydrocarbon group, X is a group having a hydroxyl group at its terminal and represented by formula (2) or (3), and n is an integer of 1 or more.)

and (B) a thermally conductive filler.

The silicone resin composition of the present invention has excellent workability because it maintains its fluidity even when highly filled with thermally conductive filler. In addition, it conforms to the irregularities on the surfaces of electronic components and heat sinks, providing high heat dissipation performance.

The following describes an embodiment of the present invention, but the present invention is not limited to the following embodiment.

[Component (A)]
Component (A) is an organopolysiloxane having a hydroxyl group at one terminal, as represented by formula (1).

（式（１）中、Ｒ^１は独立して、一価飽和炭化水素基、または一価芳香族炭化水素基であり、Ｘは末端に水酸基を二つ有する式（２）で表される基、または末端に水酸基を一つ有する式（３）で表される基であり、ｎは１以上の整数である。）

(In formula (1), ^R1 is independently a monovalent saturated hydrocarbon group or a monovalent aromatic hydrocarbon group, X is a group represented by formula (2) having two terminal hydroxyl groups or a group represented by formula (3) having one terminal hydroxyl group, and n is an integer of 1 or more.)

Examples of monovalent saturated hydrocarbon groups include linear alkyl, branched alkyl, and cyclic alkyl. Examples of linear alkyl groups include methyl, ethyl, propyl, and n-butyl. Examples of branched alkyl groups include isopropyl, isobutyl, tert-butyl, and 2-ethylhexyl. Examples of cyclic alkyl groups include cyclopentyl and cyclohexyl. Examples of monovalent aromatic hydrocarbon groups include phenyl and tolyl.

Specific examples of component (A) include FM-DA11, FM-DA21, FM-DA25, FM-DA26, FM-0411, FM-0421, FM-0425, and FM-0426 (each of which is a product name) manufactured by JNC Corporation.

When the ratio of the weight average molecular weight (Mw) and number average molecular weight (Mn) of the component (A) in terms of polystyrene, measured by gel permeation chromatography (GPC), is taken as the molecular weight distribution (Mw/Mn), Mw/Mn must be 1.20 or less. If the molecular weight distribution (Mw/Mn) is within this range, the content of high molecular weight and low molecular weight components that inhibit dispersion is reduced, and a silicone resin composition with excellent fluidity can be obtained.

[Component (B)]
The component (B) functions as a thermally conductive filler in the silicone resin composition of the present invention. The component (B) may be used alone or in combination of two or more types.

Specific examples of component (B) include aluminum oxide, aluminum nitride, boron nitride, zinc oxide, diamond, graphene, graphite, carbon nanotubes, carbon fiber, glass fiber, or a combination of two or more of these. There are no particular limitations on the crystal form, particle size, surface condition, or presence or absence of surface treatment of component (B).

[Component (C)]
The composition of the present invention may further contain an organopolysiloxane other than the above-mentioned (A) as component (C). Component (C) is used appropriately for the purpose of adjusting the viscosity of the thermally conductive silicone resin composition of the present invention, imparting curability, etc., but is not limited thereto. Component (C) may be used alone or in combination of two or more kinds, and may be non-curable or curable by heat, moisture, or active energy radiation.

Specific examples of component (C) include dimethylpolysiloxane, methylphenylpolysiloxane, methylhydrogenpolysiloxane, amino-modified polysiloxane, epoxy-modified polysiloxane, carboxy-modified polysiloxane, carbinol-modified polysiloxane, polyether-modified polysiloxane, alkyl-modified polysiloxane, fluorine-modified polysiloxane, or a combination of two or more of these.

In the silicone resin composition of the present invention, the content of component (A) is preferably 0.1 to 50 parts by mass, and more preferably 0.1 to 30 parts by mass, per 100 parts by mass of component (B). When the content of component (A) is within this range per 100 parts by mass of component (B), a dispersion in which component (B) is stably dispersed can be obtained, and the filling rate of component (B) can be sufficiently ensured, resulting in sufficient heat dissipation properties. The total content of components (A) and (C) is preferably 0.1 to 50 parts by mass, and more preferably 1.0 to 30 parts by mass, per 100 parts by mass of component (B).

The viscosity of the silicone resin composition of the present invention at 25°C is preferably 1000 Pa·s or less. If the viscosity is within this range, the composition has good fluidity and is easy to handle during dispensing, application, etc.

The silicone resin composition of the present invention can contain various additives such as other surfactants, plasticizers, defoamers, and hardeners, as long as the purpose of the composition is not impaired.

The present invention will be described in more detail below. In the examples, "parts" and "%" are all based on mass (parts by mass, % by mass) unless otherwise specified. The present invention is not limited in any way by these examples.

<Measurement of molecular weight>
The molecular weight of the organopolysiloxane was measured by gel permeation chromatography (GPC), and the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) was taken as the molecular weight distribution (Mw/Mn). Polystyrene was used as a standard sample to measure the molecular weight in terms of polystyrene. The measurement of the molecular weight in terms of polystyrene by the GPC method was carried out under the following measurement conditions.
a) Measuring instrument: JASCO HPLC LC-2000Plus series
b) Column: Shodex KF-804L x 2 c) Oven temperature: 40°C
d) Eluent: toluene 0.7 mL/min
e) Standard sample: polystyrene f) Injection volume: 20 μL
g) Concentration: 0.05g/10mL
h) Sample preparation: Toluene was used as a solvent and the sample was dissolved by stirring at room temperature.

<Preparation of Samples for Fluidity Evaluation>
As the component (A), polydimethylsiloxanes (A-1) to (A-4) represented by formula (4) and polydimethylsiloxanes (A-5) to (A-8) represented by formula (5) were used.

（式（４）中、ｎは表１に示す数平均分子量になるように任意に選択される整数である）
表１

(In formula (4), n is an integer arbitrarily selected so as to obtain the number average molecular weight shown in Table 1.)
Table 1

（式（５）中、ｎは表２に示す数平均分子量になるように任意に選択される整数である）
表２

(In formula (5), n is an integer arbitrarily selected so as to obtain the number average molecular weight shown in Table 2.)
Table 2

The compositions of Examples 1-2 and Comparative Examples 1-6 were obtained by mixing components (A)-(C) in the composition ratios shown in Tables 3 and 4. That is, components (A)-(C) were weighed into an ointment jar container, stirred with a spatula, and then kneaded at 2000 rpm for 1 minute under normal pressure and at 2000 rpm for 1 minute under reduced pressure using a Thinky Corporation Vacuum Type Awatori Rentaro (Model: ARV-310) to prepare a composition for evaluating fluidity.

<Liquidity assessment>
The fluidity of the composition prepared as described above was evaluated by visual observation. The shear viscosity was measured under the following conditions using a rheometer (MCR302, manufactured by Anton Paar).
a) Plate shape: circular flat plate 25 mm diameter
b) Sample thickness: 1 mm
c) Temperature: 25±1° C.
d) Shear rate: 0.01 ^s

表４

＊１ 平均径１３μｍの球形アルミナ（デンカ株式会社製ＤＡＷ－１０）
＊２ ポリジメチルシロキサン（信越化学工業株式会社製ＫＦ－９６－３００ＣＳ）
Table 3

Table 4

*1 Spherical alumina with an average diameter of 13 μm (DAW-10 manufactured by Denka Co., Ltd.)
*2 Polydimethylsiloxane (KF-96-300CS manufactured by Shin-Etsu Chemical Co., Ltd.)

The composition (Example 1) to which the component (A) having a molecular weight distribution (Mw/Mn) of 1.20 or less is added has a lower composition viscosity than the compositions (Comparative Examples 1 to 3) to which the component (A) having a molecular weight distribution (Mw/Mn) of more than 1.20 is added. Also, the composition (Example 2) to which the component (A) having a molecular weight distribution (Mw/Mn) of 1.20 or less is added has a lower composition viscosity than the compositions (Comparative Examples 4 to 6) to which the component (A) having a molecular weight distribution (Mw/Mn) of more than 1.20 is added. By comparing the compositions, the composition to which the component (A) having a molecular weight distribution (Mw/Mn) of 1.20 or less is added has a good result in terms of fluidity. From the above, it can be concluded that the silicone resin composition of the present invention has excellent properties.

The silicone resin composition of the present invention can be used as a thermally conductive material to be interposed between heat-generating electronic components such as transistors, IC chips, and memory elements and cooling members such as heat sinks.

Claims (1)

(A) Formula (1):

(In formula (1), R ¹ is independently a monovalent saturated hydrocarbon group or a monovalent aromatic hydrocarbon group, X is a group having a hydroxyl group at its terminal and represented by formula (2) or (3), and n is an integer of 1 or more.)

and (B) a thermally conductive filler.