Heat-conducting grease composition

Abstract

The present invention relates to a composition comprising one or more filler particles and a first treatment agent of Formula 1: # imgabs 0 # and a second treatment agent of Formula 2: # imgabs 1 # wherein R, R1, R2, R3, Y, x, y and z are as defined herein. The composition of the present invention can be used as a non-curable thermally conductive grease which can achieve high thermal conductivity at distributable and processable viscosities.

Description

Background Art

[0001] The present invention relates to a non-curable thermal grease composition comprising an ether-functional trialkoxysilane.

[0002] Non-curable thermal greases are widely used as thermal interface materials to transfer heat from heat-generating electronic components to heat sinks. Available thermal greases are characterized by high bulk thermal conductivity, low thermal resistance, low bondline thickness, good flowability, and reworkability. Greater than 90% by weight of the components that make up the thermal grease are a combination of thermally conductive fillers (such as zinc oxide, aluminum oxide, aluminum, boron nitride, and aluminum nitride) dispersed in a silicone-based fluid. The rapid increase in power and power density of electronic components has led to increased heat generation, necessitating the use of thermal greases with higher thermal conductivity.

[0003] Thermal conductivity can be increased by increasing the loading of thermally conductive fillers used in the preparation of thermal greases. Unfortunately, however, higher filler loadings result in higher thermal grease viscosity, which reduces key properties such as printability and processability. To address this problem, US 2008 / 0213578A1 (Endo) discloses a thermal grease composition comprising, inter alia, a trialkylsilyl-trialkoxysilyl-terminated polysiloxane (component B, paragraph

[0034] ) and an alkoxysilane (component C, paragraph

[0035] ); the inclusion of component C provides a composition with a lower viscosity and, therefore, improved thermal grease flowability compared to greases without this component.

[0004] There remains a need to achieve even better thermal grease viscosities; therefore, it would be an advantage in the art of non-curable thermal greases to discover a thermal grease that can achieve higher thermal conductivity without an accompanying increase in viscosity. Summary of the Invention

[0005] The present invention addresses the need in the field of non-curable thermal greases by providing a composition comprising: a) 80 wt% to 95 wt% of one or more filler particles selected from the group consisting of aluminum, aluminum oxide, silicon, silicon dioxide, magnesium oxide, aluminum nitride, graphite, silicon carbide, and zinc oxide, based on the weight of the composition; and b) 0.2 wt% to 10 wt% of a first treating agent of Formula 1:

[0006]

[0007] Where R and R 1 Each is independently a C1-C6 alkyl group; Y is O or CH2-CH2; x is 20 to 200;

[0008] c) 0.05 wt % to 2 wt % of a second treating agent of Formula 2:

[0009]

[0010] where R 2 C1-C 10 -alkyl; each R 3 are independently C1-C6 alkyl; y is 0 to 8; and z is 1 to 10; and

[0011] d) up to 8% by weight of boron nitride platelet-shaped particles.

[0012] The composition of the present invention can be used as a non-curable thermal grease. DETAILED DESCRIPTION

[0013] The present invention is a composition comprising: a) 80 to 95 weight percent of one or more filler particles selected from the group consisting of aluminum, aluminum oxide, silicon, silicon dioxide, magnesium oxide, aluminum nitride, silicon carbide, graphite, and zinc oxide, based on the weight of the composition; and b) 0.2 to 10 weight percent of a first treating agent of Formula 1:

[0014]

[0015] Where R and R 1 Each is independently a C1-C6 alkyl group; Y is O or CH2-CH2; x is 20 to 200;

[0016] c) 0.05 wt % to 2 wt % of a second treating agent of Formula 2:

[0017]

[0018] where R 2 C1-C 10 -alkyl; each R 3 are independently C1-C6 alkyl; y is 0 to 8; and z is 1 to 10; and

[0019] d) up to 8% by weight of boron nitride platelet-shaped particles.

[0020] The composition preferably comprises aluminum and zinc oxide filler particles in a combined concentration in the range of 85 wt % or 90 wt % to 95 wt % based on the weight of the composition. The concentration of the aluminum particles is preferably in the range of 65 wt % or 68 wt % or 70 wt % to 80 wt % or to 78 wt % or to 75 wt % of the composition. The aluminum particles are advantageously a bimodal distribution of particles: a) having a D in the range of 0.5 μm or 1 μm to 5 μm or to 3 μm 50 smaller particles of a volume average particle size and b) having a D in the range of 7 μm to 20 μm or to 15 μm or to 12 μm 50Larger particles with a volume average particle size.

[0021] The concentration of the ZnO particles is preferably in the range of 10 wt % or 15 wt % to 25 wt % or to 20 wt %, based on the weight of the composition. The ZnO particles preferably have a D in the range of 50 nm or 80 nm to 500 nm or to 200 nm or to 150 nm. 50 Volume average particle size. D of aluminum, zinc oxide and aluminum oxide particles 50 and D 99 The volume average particle size is the D as measured using laser refractometry. 50 Volume average particle size.

[0022] The concentration of the first treating agent of Formula 1 is in the range of 0.2 wt % or 1 wt % or 3 wt % to 8 wt % based on the weight of the composition. 1 Each is preferably methyl, more preferably methyl; x is in the range of 20 or 200 or to 150 or to 100 or to 50.

[0023] The concentration of the second treating agent of Formula 2 is in the range of 0.05 wt % or 0.1 wt % to 2 wt % or to 1 wt % or to 0.5 wt % based on the weight of the composition. 2 and R 3 each is independently ethyl or methyl, more preferably methyl; y is 0 to 8 or to 6 or to 5; and z is 1 to 10 or to 8 or to 6.

[0024] The composition optionally comprises boron nitride platelet particles, which increase thermal conductivity at the expense of viscosity. The platelet particles have a thickness preferably in the range of 750 nm to 5 μm as measured by scanning electron microscopy (SEM), and a D preferably in the range of 3 μm to 40 μm as measured by dynamic light scattering. 50 Particle size diameter. The diameter-thickness aspect ratio of the boron nitride platelet particles is preferably in the range of 2:1 or 3:1 or 4:1 to 50:1 or to 30:1 or to 20:1 or to 10:1. The boron nitride platelet particles have a hexagonal crystal structure. During assembly, after the platelet particles are applied between the substrates, the boron nitride platelet particles are aligned substantially in the same direction as the substrates. Therefore, the D of the boron nitride platelet particles is 50Particle size does not affect the final bondline thickness. Commercially available examples of boron nitride flake particles include CarboTherm PCTP30 boron nitride from Saint-Gobain and PolarTherm PT110 from Momentive Performance Materials. The concentration of the boron nitride flake particles is preferably in the range of 0 wt %, 0.5 wt %, 1 wt %, 2 wt %, to 8 wt %, 6 wt %, 5 wt %, or 4 wt %, based on the weight of the composition.

[0025] The composition of the present invention provides a non-curable grease that can achieve high thermal conductivity at a dispensable and workable viscosity.

[0026] Example

[0027] In each of the following examples, pbw means parts by weight. Unless otherwise indicated, all mixing was performed using a Flacktek high speed mixer at 1500 rpm.

[0028] General procedure for preparing thermally conductive materials

[0029] The first filler treating agent of Formula 1 (TA1, 6.01 pbw, each of R and R 1 =CH3; R=O; and x=30, prepared as described in U.S. Patent Publication No. 2006 / 0100336), a second filler treatment (TA-2 to TA-6, 0.2 pbw), Zoco 102 ZnO particles (ZnO-1, 11.76 pbw, 0.12 μm); and Zoco 104 ZnO particles (ZnO-2, 5.88 pbw, 0.20 μm) were added to a MAX100 cup and mixed for 15 seconds. First, aluminum particles (Al-1, 24.38 pbw, 2.0 μm, equivalent to TCP-2Al powder) were added to the mixer and the contents mixed for 15 seconds. TCP-9Al powder (Al-2, 48.77 pbw, 9.9 μm) was then added to the mixer and mixing continued for 40 seconds. The mixture was then mixed manually with a spatula and then further mixed in the mixer for 40 seconds. Boron nitride (BN, 3 pbw) was then added to the mixer and mixing was continued for 15 seconds. The formulated composition was transferred to an aluminum pan and heated at 150° C. under vacuum (23 Torr) for 1 hour.

[0030] Table 1 summarizes the materials and amounts used to prepare the examples and comparative examples. TA-2, TA-3, TA-4, TA-5, and TA-6 have the following structures:

[0031]

[0032] Table 1 - Thermal Grease Composition

[0033] Material Comparative Example 1(g) Comparative Example 2(g) Example 1(g) Example 2(g) Example 3(g) Al-1 24.38 24.38 24.38 24.38 24.38 Al-2 48.77 48.77 48.77 48.77 48.77 ZnO-1 11.76 11.76 11.76 11.76 11.76 ZnO-2 5.88 5.88 5.88 5.88 5.88 BN 3.00 3.00 3.00 3.00 3.00 TA-1 6.01 6.01 6.01 6.01 6.01 TA-2 0.20 - - - - TA-3 - 0.20 - - - TA-4 - - 0.20 - - TA-5 - - - 0.20 - TA-6 - - - - 0.20

[0034] Viscosity measurement

[0035] Complex viscosity at the dilatant point was measured using ASTM D4440-15 (Standard Test Methods for Plastics: Dynamic Mechanical Properties - Melt Rheology) using a TA Instruments ARES-G2 equipped with 25 mm parallel plates (serrated steel). The test conditions were based on a strain sweep at 25°C with a 2.0 mm gap. The measurement was performed using a standard procedure with an oscillation frequency of 10 rad / s, sweeping from 0.01% to 200% strain amplitude at 20 sampling points per decade. The dilatant point was defined as the strain at which the complex viscosity began to increase.

[0036] Table 2 summarizes the viscosity (viscosity) of the samples at the dilatant point in Pa·s.

[0037] Table 2 - Viscosity of samples at dilatant point

[0038] Example No. Second filler treating agent Viscosity (Pa·s) Comparative Example 1 TA-2 89 Comparative Example 2 TA-3 106 Example 1 TA-4 53 Example 2 TA-5 23 Example 3 TA-6 40

[0039] The data shows that samples prepared with ether-functionalized trimethoxysilane filler treatments exhibited significantly lower viscosities compared to samples prepared with alkyltrimethoxysilanes. Lower viscosity formulations offer formulators a path to optimize viscosity and thermal conductivity. For example, when the formulation of Example 2 was modified to increase the BN concentration to 5 pbw and reduce the Al-2 concentration to 46.77 pbw, the measured thermal conductivity was 7.9 W / m·K, and the viscosity was found to increase to 68 Pa·s. In contrast, the thermal conductivity of Comparative Example 1 was measured to be 7.9 W / m·K, but the viscosity was 89 Pa·s.

Claims

1. A composition comprising: a) 80 to 95 weight percent of one or more filler particles selected from the group consisting of aluminum, aluminum oxide, silicon, silicon dioxide, magnesium oxide, aluminum nitride, silicon carbide, graphite, and zinc oxide, based on the weight of the composition; and b) 0.2 to 10 weight percent of a first treating agent of Formula 1: Where R and R 1 Each is independently a C1-C6 alkyl group; Y is O or CH2-CH2; x is 20 to 200; c) 0.05 wt % to 2 wt % of a second treating agent of Formula 2: where R 2 C1-C 10 -alkyl; each R 3 are independently C1-C6 alkyl; y is 0 to 8; and z is 1 to 10; and d) up to 8% by weight of boron nitride platelet-shaped particles.

2. The composition of claim 1, wherein the filler particles are selected from the group consisting of aluminum, aluminum oxide, and zinc oxide.

3. The composition of claim 2 comprising a) aluminum and zinc oxide filler particles at a combined concentration in the range of 85% to 95% by weight, based on the weight of the composition, and b) boron nitride flake particles at a concentration in the range of 0.5% to 8% by weight, based on the weight of the composition.

4. The composition of claim 3, wherein Y is O; x is 20 to 100; y is 0 to 6; z is 1 to 8; and R, R 1 、R 2 and R 3 Each is a methyl group.

5. The composition of claim 2, wherein the concentration of the first treating agent of Formula 1 is in a range of 1 wt % to 8 wt % based on the weight of the composition; and the concentration of the second treating agent of Formula 2 is in a range of 0.1 wt % to 1 wt % based on the weight of the composition.

6. The composition of claim 3, wherein the concentration of the aluminum particles is in the range of 65 wt % to 80 wt % based on the weight of the composition; and the concentration of the zinc oxide particles is in the range of 10 wt % to 25 wt % based on the weight of the composition; wherein The aluminum particles are a bimodal distribution of particles having a D in the range of 0.5 μm to 5 μm. 50 smaller particles having a volume average particle size; and b) having a D in the range of 7 μm to 20 μm 50 and wherein the zinc oxide particles have a D in the range of 50 nm to 200 nm. 50 Volume average particle size.

7. The composition of claim 5, wherein the concentration of the aluminum particles is in the range of 70% to 78% by weight, based on the weight of the composition; and the concentration of the zinc oxide particles is in the range of 15% to 20% by weight, based on the weight of the composition; wherein the aluminum particles are a bimodal distribution of particles that: a) have a D in the range of 1 μm to 3 μm; 50 smaller particles having a volume average particle size; and b) having a D in the range of 7 μm to 15 μm 50 and wherein the zinc oxide particles have a volume average particle size D in the range of 80 nm to 150 nm. 50 Volume average particle size; wherein the concentration of the first treating agent of Formula I is in the range of 3 wt % to 8 wt %; wherein x is in the range of 20 to 50.

8. The composition according to claim 7, wherein the second treating agent of Formula 2 is selected from: And the concentration of the second treating agent of Formula 2 is in the range of 0.1 wt % to 0.5 wt % based on the weight of the composition.

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