Non-curable heat-conducting grease with boron nitride
By introducing boron nitride sheet particles and specific proportions of aluminum, zinc oxide particles and silicone compositions into the thermal grease, the pumping problem of non-curable thermal grease during the power cycle is solved, and the resistance and thermal conductivity of the thermal interface material are improved.
Patent Information
- Application Number
- CN202380085533.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-01-13
- Publication Date
- 2025-08-01
AI Technical Summary
The pumping phenomenon caused by the warping of the die during the power cycle of the existing non-curable thermal grease will result in loss of thermal interface materials and affect thermal performance.
The non-curable thermal grease composition containing boron nitride sheet particles, aluminum and zinc oxide particles is used to combine a specific concentration of trialkoxylated polydimethylsiloxane and polydimethylsiloxane carrier fluid to optimize the viscosity and printability of the composition to improve pumping resistance.
While maintaining printability, the pumping resistance and thermal conductivity of thermal grease are significantly improved, and the formation of hot spots is reduced.
Smart Images
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Abstract
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a composition comprising a non-curable thermal grease containing boron nitride. The non-curable thermal grease can be used as a thermal interface material in microelectronic devices to transfer heat generated by a heat source to a heat sink.
[0002] Non-curable thermal greases contain a large amount of one or more thermal fillers such as zinc oxide, aluminum oxide (i.e., Al2O3), and aluminum dispersed in a non-curable polyorganosiloxane matrix. They have high thermal conductivity, low thermal resistance, and low disassembly force. For applications with a bare die chip architecture where the thermal grease is directly applied as the thermal interface material between the die and the heat sink, die warpage during power cycling causes repeated movement of the die, which tends to squeeze the thermal grease out of the interface. This loss of thermal grease (also known as pump-out) results in the formation of hot spots on the die, which impairs its performance. Therefore, it would be desirable to prepare a non-curable thermal grease with improved pump-out resistance while maintaining acceptable printability and thermal conductivity. SUMMARY OF THE INVENTION
[0003] The present invention solves the need in the art by providing a non-curable thermal grease composition which, based on the weight of the composition, comprises: a) 80 wt% to 95 wt% of one or more filler particles selected from the group consisting of aluminum, aluminum oxide, and zinc oxide; b) 0.2 wt% to 8 wt% of boron nitride flake particles; and c) 0.2 wt% to 10 wt% of a trialkoxylated polydimethylsiloxane of Structure 1:
[0004]
[0005] wherein R and R 1 are each independently a C1-C6-alkyl group, Y is O or CH2-CH2; and x is from 30 to 200; wherein the non-curable thermal grease composition comprises d) up to 10 wt% of a polydimethylsiloxane or poly(phenylmethylsiloxane-co-dimethylsiloxane) carrier fluid having a viscosity in the range of 30 cSt to 200 cSt. The non-curable thermal grease of the present invention provides excellent pump-out resistance while maintaining acceptable printability, thermal conductivity, and viscosity. DETAILED DESCRIPTION
[0006] The present invention is a non-curable thermal conductive grease composition, which, based on the weight of the composition, comprises: a) 80% to 95% by weight of one or more filler particles selected from the group consisting of aluminum, aluminum oxide, and zinc oxide; b) 0.2% to 8% by weight of boron nitride flake particles; and c) 0.2% to 10% by weight of a trialkoxylated polydimethylsiloxane of Structure 1:
[0007]
[0008] wherein R and R 1 are each independently a C1-C6-alkyl group, Y is O or CH2-CH2; and x is from 30 to 200; and wherein the non-curable thermal conductive grease composition comprises d) at most 10% by weight of a polydimethylsiloxane or poly(phenylmethylsiloxane-co-dimethylsiloxane) carrier fluid having a viscosity in the range of 30 cSt to 200 cSt.
[0009] Based on the weight of the composition, the composition preferably comprises aluminum and zinc oxide and / or aluminum oxide filler particles at a concentration in the range of 85% or 90% to 95% by weight. The aluminum particles advantageously exist as a multimodal distribution, preferably a bimodal distribution, of spherical aluminum particles. The D 50 volume average particle size of the larger spherical aluminum particles is preferably in the range of 5 μm, or 7 μm, or 8 μm to 25 μm or to 10 μm; the D 99 volume average particle size of these larger particles is preferably ≤50 μm or ≤30 μm. Based on the weight of the composition, the concentration of the larger spherical aluminum particles is preferably in the range of 40% or 45% or 48% to 60% or to 55% or to 52% by weight.
[0010] The D 50 volume average particle size of the smaller spherical aluminum particles is preferably in the range of 1 μm to 5 μm. Based on the weight of the composition, the concentration of the smaller spherical aluminum particles is preferably in the range of 15% or 20% or 23% to 35% or to 30% or to 27% by weight.
[0011] The D 50 volume average particle size of the zinc oxide (ZnO) particles and / or aluminum oxide particles is preferably in the range of 50 nm or 100 nm to 500 nm or to 200 nm or to 150 nm. Based on the weight of the composition, the concentration of the ZnO particles and / or aluminum oxide particles is preferably in the range of 10% or 15% to 25% or to 20% by weight. The D 50 and D 99 volume average particle size refers to the D measured by laser refraction method50 Volume average particle size.
[0012] The boron nitride flake particles have a thickness preferably in the range of 750 nm to 5 μm as measured by scanning electron microscopy (SEM), and a D 50 particle size diameter preferably in the range of 3 μm to 40 μm as measured by dynamic light scattering. The diameter-thickness aspect ratio of the boron nitride flake 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 flake particles have a hexagonal crystal structure. During assembly, after the flake particles are applied between the substrates, the boron nitride flake particles are arranged substantially along the same direction as the substrates. Therefore, the D 50 particle size of the boron nitride flake particles does not affect the final adhesive layer thickness. Commercially available examples of the boron nitride flake particles include CarboTherm PCTP30 boron nitride from Saint-Gobain Group and PolarTherm PT110 from Momentive Performance Materials. Based on the weight of the composition, the concentration of the boron nitride flake particles is preferably in the range of 0.5 wt% or 1 wt% or 2 wt% to preferably 6 wt% or to 5 wt% or to 4 wt%.
[0013] C1-C 20 -alkyltri-C1-C6-alkoxysilane is preferably C6-C 16 -alkyltrimethoxysilane or C8-C 12 -alkyltrimethoxysilane. An example of a suitable C1-C 20 -alkyltri-C1-C6-alkoxysilane is n-decyltrimethoxysilane. Based on the weight of the composition, the concentration of the C1-C 20 -alkyltri-C1-C6-alkoxysilane is preferably in the range of 0.1 wt% to 2 wt% or to 1 wt%.
[0014] Based on the weight of the composition, the concentration of the polydimethylsiloxane of Structure 1 is preferably in the range of 1 wt% or 3 wt% to 8 wt%. R and R 1 are each preferably methyl; and x is preferably in the range of 50 or 80 or 100 to preferably 180 or to 150 or to 130.
[0015] The composition may also comprise up to 10% by weight of a carrier fluid which is a polydimethylsiloxane or a poly(phenylmethylsiloxane-co-dimethylsiloxane) fluid having a viscosity in the range of preferably 50 cSt or 80 cSt to preferably 150 cSt or to 120 cSt. In one aspect, based on the weight of the composition, the non-curable thermal grease comprises from 1% or 2% or 4% to 10% or to 8% or to 6% by weight of a polydimethylsiloxane or poly(phenylmethylsiloxane-co-dimethylsiloxane) carrier fluid.
[0016] The non-curable grease composition contains a substoichiometric concentration of crosslinkable functional groups (such as a combination of vinyl groups and Si-H groups) to cause the grease to cure. Preferably, the non-curable grease contains neither vinyl groups nor Si-H groups.
[0017] The compositions of the present invention provide excellent pump-out resistance as well as desirable printability, viscosity, and thermal conductivity. Thus, in another aspect, the present invention is a microelectronic device comprising a non-curable thermal grease composition embedded therein as a thermal interface material.
[0018] Examples
[0019] In the following examples, unless otherwise stated, all samples were mixed using a Flacktek mixer at 1500 rpm; pbw refers to parts by weight.
[0020] Comparative Example 1 - Preparation of Non-Curable Thermal Conductive Grease without Boron Nitride : Phenylmethylsiloxane-dimethylsiloxane copolymer (100 cSt, 5.10 pbw, product code PMM-1021 from Gelest), structure 1 polydimethylsiloxane (each R and R 1 =CH3, x = 110, Y = O, 1.99 pbw), n-decyltrimethoxysilane (0.17 pbw) and Zoco102 ZnO (approx. 0.12 μm, 17.37 pbw) were added to a MAX100 cup and mixed for 15 s. Then TCP-2 aluminum powder (Toyo Aluminum K.K., particle size of about 2 μm, 25.12 pbw) was added to the mixer and the components were mixed for 15 s. Then TCP-9 aluminum powder (Toyo Aluminum K.K., particle size of about 9 μm, 50.25 pbw) was added to the mixer and the components were mixed for an additional 40 s. The components were manually mixed using a spatula and then mixed in the mixer for 40 s. The preparation was then transferred to an aluminum pan and vacuum heated at 150 °C for 1 h.
[0021] Example 1 - Preparation of Non-Curable Thermal Conductive Grease with Boron Nitride
[0022] Repeat the steps for preparing the non-curable thermal grease of Comparative Example 1, except that PCTP30 boron nitride (Saint-Gobain Group, 3.0 pbw) is added to the mixer, and the components are mixed for 15 s after adding and mixing TCP-9 aluminum powder (47.25 pbw). Manually mix the components using a spatula and then mix in the mixer for 40 s. Then transfer the preparation to an aluminum tray and heat it under vacuum at 150 °C for 1 h.
[0023] Example 2 - Preparation of Non-Curable Thermal Conductive Grease with Boron Nitride
[0024] Repeat the steps for preparing the non-curable thermal grease of Comparative Example 1, except that phenylmethylsiloxane-dimethylsiloxane is not added, the amount of Structure 1 polydimethylsiloxane is 7.09 pbw, and PCTP30 boron nitride (Saint-Gobain Group, 1.0 pbw) is added to the mixer, and the components are mixed for 15 s after adding and mixing TCP-9 aluminum powder (49.25 pbw). Manually mix the components using a spatula and then mix in the mixer for 40 s. Then transfer the preparation to an aluminum tray and heat it under vacuum at 150 °C for 1 h.
[0025] Example 3 - Preparation of Non-Curable Thermal Conductive Grease with Boron Nitride : Add Structure 1 polydimethylsiloxane (each R and R 1 =CH3, x = 110, 354.5 g, 7.09 pbw), n-decyltrimethoxysilane (8.5 g, 0.17 pbw) and Zoco102 ZnO (approx. 0.12 μm, 869 g, 17.37 pbw) to a 1 g Baker Perkins crank mixer and mix the components for 30 min. Then add TCP-2 aluminum powder (1206 g, 25.12 pbw) and TCP-9 aluminum powder (2412 g, 47.25 pbw) to the mixer and remix the components for 55 min. Add BN (150 g, 3.00 pbw) to the mixer and remix the components for 15 min. Vacuum dry the mixture under mixing (25 Torr, 45 min), then heat to 150 °C for 60 min, then remove the heat and allow the mixture to cool to room temperature.
[0026] Example 4 - Preparation of Non-Curable Thermal Conductive Grease with Boron Nitride
[0027] Repeat the preparation as described in Example 2, except that 5.0 pbw boron nitride and 45.25 pbw TCP-9 are used.
[0028] Viscosity Measurement
[0029] The complex viscosity at the dilatancy point was measured using an ARES-G2 instrument from TA Instruments equipped with 25 mm parallel plates (serrated steel) by ASTM D4440-15 (Standard Test Method for Plastics: Dynamic Mechanical Properties - Melt Rheology). The test conditions were based on a strain sweep conducted at a 2.0 mm gap at 25 °C. Measurements were made using a standard procedure with an oscillation frequency of 10 rad / s, scanning from 0.01% to 200% strain amplitude with 20 sampling points per decade of time. The dilatancy point was defined as the strain at which the complex viscosity began to increase.
[0030] Thermal Conductivity Measurement
[0031] The thermal conductivity was measured using a C5501 sensor and a Hot Disk Instrument TPS2500S from Hot Disk AB in Gothenburg, Sweden by ISO 22007-2:2015 (Test Method for Determining Thermal Conductivity). The grease material was filled into two cups with the planar sensor held between the cups. Analysis conditions: fine-tuning analysis, temperature drift compensation, and time correction, calculations were made using the selected points between point 50 and point 150.
[0032] Printability Test
[0033] The printability of the sample was measured by screen-printing a 25 cm × 25 cm pattern with a thickness of 200 μm using a 60-mesh metal screen. The screen was held above the radiator and 5 g of the sample was applied on top of the screen. The sample was transferred through the screen onto the radiator using a squeegee held at a 45° angle and applying a constant force and a constant draw rate. If the grease could be deposited on the radiator, the printability was considered good.
[0034] Pumping Resistance
[0035] The sample was applied to an MSI GeForce RTX 2070 TRIFROZR graphics card (die size: 24.0 mm × 18.5 = 445 mm) through a template 2) on the radiator. Then the graphics card is assembled and installed in the computer. The following computer components are used for testing: CPU: AMD Ryzen 7 2700X 8-core; Motherboard: ASUS TUF X470-PLIS GAMING; Memory: KINSTONDDR4 266 8GB; Graphics card: MSI GeForce RTX 2080TRI FROZR (8GB GDDR6, Nvidia Turing chip architecture); Solid state drive: Intel SSD 760P series (256GB, M.2 80mm PCle 3.0x4, 3D2, TLC); Monitor: Del U2417H; Keyboard: Dell; Mouse: Dell; Computer case: Antec P8 ATX; Power supply: Antec NEO750W; KVM: MT-viki HK05.
[0036] The thermal cycling test is carried out by running the FurMark GPU stress test software developed by Geeks3D, which is available from https: / / geeks3d.com / furmark / . The script (in AutoIt) includes steps to open and close the Furmark software and steps to change the fan speed to control the temperature of the GPU card. Use MSIAfterburner available from Afterburner(msi.com) to control the fan speed.
[0037] The AutoIt script includes the following steps: (1) Open the Furmark program; (2) Start the Furmark stress test routine; (3) During the 140,000-millisecond heating cycle, adjust the fan speed to 30% of its maximum speed; (4) Stop the stress test routine; (5) Close the Furmark program; (6) During the 180,000-millisecond cooling cycle, adjust the fan speed to 90% of its maximum speed; (7) Repeat the sequence. This process is used to cycle the temperature on the GPU card from 35 °C to 85 °C and back to 35 °C. After running 5000 cycles, turn off the computer and remove the graphics card.
[0038] Open the graphics card and record the radiator and die images. Measure the areas (bare spots) on the radiator and die without sample material due to pumping during the cycle test. Use the readily available software "sketchandclac" to calculate the quantitative area of the bare spots. Divide the total bare spot area due to grease pumping by the total GPU die area (495mm 2 ) to determine the bare spot area percentage on the die. The results are classified as follows: Excellent = less than 5% bare spot area on the die; Medium = 5% to 15% bare spot area on the die; and Poor = greater than 15% bare spot area on the die.
[0039] Table 3 summarizes the thermal conductivity in W / m·K (TC), the complex viscosity (viscosity) at the dilatant point in Pa·s, and the pump-out resistance as measured by the bare point area. Good printability was found for all samples.
[0040] Table 3 - Summary of the Properties of Non-Curable Thermal Conductive Grease
[0041]
[0042]
[0043] The data show a significant positive effect of boron nitride on the pump-out resistance. Surprisingly, the improved pump-out resistance is not correlated with an increase in viscosity.
Claims
1. An uncured thermal grease composition, based on the weight of the composition, the uncured thermal grease composition comprising: a) 80% to 95% by weight of one or more filler particles selected from the group consisting of aluminum, aluminum oxide, and zinc oxide; b) 0.2% to 8% by weight of flaky boron nitride particles; and c) 0.2% to 10% by weight of a trialkoxylated polydimethylsiloxane of Structure 1: wherein R and R 1 are each independently C1-C6-alkyl, Y is O or CH2-CH2; and x is from 30 to 200; wherein the uncured thermal grease composition optionally comprises d) up to 10% by weight of a polydimethylsiloxane or poly(phenylmethylsiloxane-dimethylsiloxane) carrier fluid having a viscosity in the range of 30 cSt to 200 cSt.
2. The composition according to claim 1, wherein the composition further comprises (e) 0.05% to 1% by weight of a C1-C 20 -alkyltri-C1-C6-alkoxysilane.
3. The composition according to any one of claims 1 or 2, based on the weight of the composition, the composition comprises 85% to 95% by weight of aluminum and zinc oxide particles and / or alumina particles, wherein the aluminum particles are a bimodal distribution of larger and smaller spherical aluminum particles, wherein the D 50 volume average particle size of the larger spherical aluminum particles is in the range of 5 μm to 15 μm, and wherein the D 99 volume average particle size of the larger spherical aluminum particles is ≤ 30 μm; wherein the D 50 volume average particle size of the smaller spherical aluminum particles is in the range of 1 μm to 5 μm; wherein the D 50 volume average particle size of the zinc oxide particles and / or the alumina particles is in the range of 50 nm to 200 nm.
4. The composition according to claim 3, wherein, Based on the weight of the composition, the concentration of the larger spherical aluminum particles is in the range of 40% to 60% by weight; the concentration of the smaller spherical aluminum particles is in the range of 15% to 35% by weight; and wherein the concentration of the zinc oxide particles and / or the aluminum oxide particles is in the range of 10% to 25% by weight.
5. The composition according to any one of claims 1 to 4, wherein, based on the weight of the composition, the concentration of the boron nitride flaky particles is in the range of 0.5 wt% to 6 wt%, and the D 50 particle size diameter of the boron nitride flaky particles is in the range of 3 μm to 40 μm; and the thickness of the boron nitride flaky particles is in the range of 750 nm to 5 μm.
6. The composition according to claim 5, wherein the C1-C 20 -alkyltri-C1-C6-alkoxysilane is a C6-C 16 -alkyltrimethoxysilane, and wherein, based on the weight of the composition, the concentration of the C6-C 16 -alkyltrimethoxysilane is in the range of 0.1% by weight to 2% by weight; wherein the boron nitride flake particles have a diameter:thickness aspect ratio in the range of 3:1 to 30:
1.
7. The composition according to claim 6, wherein the C6-C 16 -alkyltrimethoxysilane is a C8-C 12 -alkyltrimethoxysilane; wherein the polydimethylsiloxane of Structure 1 is represented by the following structure: where each R and R 1 is methyl, x is from 50 to 180, and Y is O; wherein based on the weight of the composition, the concentration of the polydimethylsiloxane of Structure 1 is in the range of 1% to 10% by weight; wherein the boron nitride flaky particles have a diameter:thickness aspect ratio in the range of 3:1 to 20:
1.
8. The composition according to claim 7, based on the weight of the uncured thermal grease, the composition comprising 1% to 10% by weight of a polydimethylsiloxane or poly(phenylmethylsiloxane-co-dimethylsiloxane) carrier fluid; wherein the viscosity of the carrier fluid is in the range of 30 cSt to 150 cSt.
9. The composition according to claim 8, wherein based on the weight of the composition, the concentration of the boron nitride flaky particles is in the range of 1% to 5% by weight.
10. The composition according to claim 7, wherein, based on the weight of the composition, the concentration of the boron nitride flaky particles is in the range of 2% to 4% by weight; wherein the C8-C 12 -alkyltrimethoxysilane is n-decyltrimethoxysilane; wherein x is from 80 to 130; wherein the boron nitride flaky particles have a diameter:thickness aspect ratio in the range of 4:1 to 10:
1.
11. The composition according to claim 7, based on the weight of the non-curable composition, the composition comprises 90 wt% to 95 wt% of aluminum and zinc oxide particles, wherein the D 50 volume average particle size of the larger spherical aluminum particles is in the range of 7 μm to 25 μm; and wherein the D 50 volume average particle size of the zinc oxide particles is in the range of 100 nm to 200 nm; Among them, Based on the weight of the composition, the concentration of the larger spherical aluminum particles is in the range of 45% to 55% by weight; the concentration of the smaller spherical aluminum particles is in the range of 20% to 30% by weight; and the concentration of the zinc oxide particles is in the range of 15% to 20% by weight.
12. The composition according to claim 8, based on the weight of the composition, the composition comprising 2% to 8% by weight of the polydimethylsiloxane or phenylmethylsiloxane-co-dimethylsiloxane carrier fluid; wherein the viscosity of the carrier fluid is in the range of 30 cSt to 120 cSt.
13. A microelectronic device, the microelectronic device comprising the uncured thermal grease composition according to any one of claims 1 to 12 embedded therein as a thermal interface material.