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: and a second treatment agent of Formula 2: wherein R, R1, R2, Y, x and n are as defined herein. The composition disclosed by the invention can be used as heat-conducting grease, and can realize the combination of high heat conductivity and heat stability.

Description

Background Art

[0001] The present invention relates to a non-curable thermal grease composition comprising an ester-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 thermal stability. 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 stability of the thermal grease compared to greases without this component.

[0004] There remains a need to achieve even better thermal stability; 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 decrease in thermal stability. 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 15 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% to 2% by weight of an ester-functional trialkoxysilane of Formula 2:

[0009]

[0010] where R 2 C1-C 16 Alkyl or C2-C 16 alkenyl; each R 1 are independently C1-C6 alkyl; and n is 1 or 2; 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 15 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% to 2% by weight of an ester-functional trialkoxysilane of Formula 2:

[0017]

[0018] where R 2 C1-C 16 Alkyl or C2-C 16 alkenyl; each R 1 are independently C1-C6 alkyl; and n is 1 or 2; 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 50smaller 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 50 Larger 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 I is in the range of 0.2 wt % or 1 wt % or 3 wt % or 5 wt % to 15 wt % or to 10 wt % based on the weight of the composition. Y is preferably O, and R and R 1 Each is preferably methyl; x is 20 or 50 to 200 or to 250.

[0023] The concentration of the ester-functional trialkoxysilane is in the range of 0.5 wt % or 0.1 wt % to 2 wt % or to 1 wt % or to 0.5 wt % based on the weight of the composition. 16 Alkyl or C1-C 10 Alkyl or C1-C6 alkyl or C2-C 16 Alkenyl or C2-C 10 alkenyl; R is preferably methyl; each R 1 is independently a C1-C6 alkyl group, preferably a methyl group; and n is 1 or 2.

[0024] Ester-functionalized trialkoxysilanes of formula 2 can be prepared, for example, by condensation of a salt of a carboxylic acid with a trialkoxysilyl alcohol, as described in WO 2011 / 101278 A1. Compounds of formula 1 can also be prepared by base-catalyzed reaction of a salt of a carboxylic acid with a chloroalkyltrialkoxysilane:

[0025]

[0026] Or by hydrosilylation of an allyl ester with trichlorosilane followed by alkanolysis:

[0027]

[0028] 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 50 Particle 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.

[0029] The composition of the present invention provides a non-curable grease that can achieve high thermal conductivity at a dispensable and workable viscosity.

[0030] Example

[0031] 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.

[0032] General procedure for preparing thermally conductive materials

[0033] The first filler treating agent of Formula 1 (TA1, 7.09 pbw, each of R and R 1=CH3; R=O; and x=110, prepared as described in U.S. Patent Publication No. 2006 / 0100336), a second filler treatment (TA-2 to TA-6, 0.2 pbw), and Zoco 102 ZnO particles (ZnO, 17.38 pbw, 0.12 μm) were added to a MAX100 cup and mixed for 15 seconds. The first aluminum particles (Al-1, 24.12 pbw, 2.0 μm, equivalent to TCP-2Al powder) were then added to the mixer, and the contents were mixed for 15 seconds. TCP-9Al powder (Al-2, 48.24 pbw, 9.9 μm) was then added to the mixer and mixed for a further 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 mixed for a further 15 seconds. The formulated composition was transferred to an aluminum pan and heated at 150°C under vacuum (23 Torr) for 1 hour.

[0034] 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:

[0035]

[0036] Table 1 - Thermal Grease Composition

[0037] Material Comparative Example 1(g) Comparative Example 2(g) Example 1(g) Example 2(g) Example 3(g) Al-1 24.12 24.12 24.12 24.12 24.12 Al-2 48.24 48.24 48.24 48.24 48.24 ZnO 17.38 17.38 17.38 17.38 17.38 BN 3.00 3.00 3.00 3.00 3.00 TA-1 7.26 7.09 7.09 7.09 7.09 TA-2 - 0.17 - - - TA-3 - - 0.17 - - TA-4 - - - 0.17 - TA-5 - - - - 0.17

[0038] Viscosity measurement

[0039] The complex viscosity at the dilatant point is measured using ASTM D4440-15 (Standard Test Method for Plastics: Dynamic Mechanical Properties - Melt Rheology) using a TA Instruments ARES-G2 instrument equipped with 25 mm parallel plates (serrated steel). The test conditions are based on a strain scan performed at 25°C with a gap of 2.0 mm. Care is taken to avoid air being trapped in the sample when the sample is loaded. Excess material is trimmed from the edge of the fixture with the flat edge of a scraper. The measurement is performed using a standard procedure with an oscillation frequency of 10 rad / s, scanning with a strain amplitude of 0.01% to 300%, and 20 sampling points per decade. The dilatant point is defined as the strain at which the complex viscosity begins to increase.

[0040] Thermal conductivity measurement

[0041] Thermal conductivity was measured using a Hot Disk Instrument TPS2500S Hot Disk Instrument and a C5501 sensor according to ISO 22007-2:2015 (Test method for determination of thermal conductivity). Each sample was placed in two cups, with the flat sensor held between them. Analysis conditions included fine-tuning analysis, temperature drift compensation, and time correction, with calculations performed using selected points between points 50 and 150.

[0042] The viscosity and thermal conductivity results of the samples are shown in Table 2. The viscosity refers to the viscosity at the dilatant point.

[0043] Table 2 - Sample viscosity and thermal conductivity properties

[0044]

[0045] The results show that the viscosity of Comparative Example 3 of the present invention is significantly improved.

[0046] Sample stability measurement

[0047] Thickness measurement of samples before aging

[0048] The sample (1 g) was dispensed onto a Q-Panel-AL-35 chromate pretreated substrate (0.65 mm x 75 mm x 125 mm). Aluminum spacers (1 mm thick) were placed on either side of the dispensed sample, and a glass slide (50 mm x 75 mm) was placed over the spacers and sample. The spacers were removed, and a texture analyzer probe (13 mm diameter) was guided toward the slide at a rate of 0.5 mm / s until the probe touched the slide, at which point a force of 5 kg was applied to the slide for 30 seconds. The thickness of the sample was then measured (thickness o ) to indicate its fluidity before aging after subtracting the thickness of the substrate and slide.

[0049] Thickness measurement of aged samples

[0050] The sample was dispensed and the aluminum spacer (1 mm thick) and glass slide were positioned as described above. The stability of the sample was determined as follows: the assembly was heated to 125°C for 21 days. The spacer was removed and the probe was guided toward the glass slide at a rate of 0.5 mm / s until the probe contacted the slide, at which point a force of 5 kg was applied to the slide for 30 seconds. The thickness of the sample was then measured as described above (thickness f ) to indicate its fluidity after aging.

[0051] Table 3 summarizes the initial pre-aging thickness of the samples and the thickness of the aged samples. o is the initial thickness of the sample, and the thickness fRefers to the thickness of the aged sample after being subjected to an applied force.

[0052] Table 3 - Stability study of aged samples

[0053] <![CDATA[Thickness o (mm)]]> <![CDATA[Thickness f (mm)]]> CE-1 0.29 1.00 CE-2 0.27 0.87 IE-1 0.25 0.49 IE-2 0.24 0.47 IE-3 0.24 0.47

[0054] The comparative examples did not show a significant decrease in thickness, indicating that the samples had hardened; in contrast, the examples containing the ester treating agent of Formula 2 all exhibited fluidity, which is a sign of the relative stability of the samples.

Claims

1. A composition comprising a) 80 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, silicon carbide, graphite, and zinc oxide, based on the weight of the composition; b) 0.2 wt% to 15 wt% 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% to 2% by weight of an ester-functional trialkoxysilane of Formula 2: where R 2 C1-C 16 Alkyl or C2-C 16 alkenyl; each R 1 are independently C1-C6 alkyl; and n is 1 or 2; 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; and each of R and R 1 It 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 3 wt % to 10 wt % based on the weight of the composition; and the concentration of the ester-functionalized trialkoxysilane 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 5 wt % to 10 wt %; and wherein x is in the range of 50 to 150.

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.

9. The composition according to claim 7, wherein the second treating agent of Formula 2 is: 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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