A heat-conducting filler for anti-cracking and anti-sagging gels and a method for preparing the same

Abstract

The present invention provides a thermally conductive filler for anti-cracking and anti-sagging gel, comprising the following components in the following weight proportions: 110-200 parts of boron nitride powder No. 1, 140-230 parts of boron nitride powder No. 2, 320-410 parts of alumina powder No. 1, 200-290 parts of alumina powder No. 2, 60-150 parts of alumina powder No. 3, 170-260 parts of zinc oxide powder No. 1, and 5-8 parts of surface treatment agent. The particle size of boron nitride powder No. 1 is 110-130 μm, the particle size of boron nitride powder No. 2 is 90-110 μm, the particle size of alumina powder No. 1 is 40-50 μm, the particle size of alumina powder No. 2 is 5-10 μm, the particle size of alumina powder No. 3 is 1-5 μm, and the particle size of zinc oxide powder No. 1 is 0.8-1.1 μm. This application discloses a thermally conductive filler for anti-cracking and anti-sagging gel, which is made by mixing boron nitride with two-stage particle size, alumina with three-stage particle size, and ultrafine zinc oxide. Through reasonable filler gradation and selection, high thermal conductivity and low specific gravity are achieved with low filler content.

Description

Technical Field

[0001] This invention relates to the field of thermally conductive filler technology, specifically a thermally conductive filler for anti-cracking and anti-sagging gel and its preparation method. Background Technology

[0002] With the rapid development of new energy vehicles, 5G communications, consumer electronics, and industrial power supplies, the requirements for the insulation, lightweight, high-temperature reliability, and deformation resistance of heat dissipation materials in terminal devices are constantly being upgraded. High-conductivity thermally insulating gels have become the mainstream heat dissipation materials, but existing technologies have the following core defects:

[0003] First, the proportion of products with the same thermal conductivity level is too high, making it unsuitable for lightweight requirements: Existing... Thermally conductive gel fillers typically use alumina (density 3.95 g / cm3) and zinc oxide (density 5.6 g / cm3) as the main fillers, but due to their high density, they have certain limitations in use in lightweight electronic devices.

[0004] Second, it is difficult to balance thermal conductivity and reliability, and the crack resistance and anti-sagging performance are insufficient: In the existing technology, if a single alumina filler system is used, even if the filler content is increased, failure phenomena such as through cracks and sagging will still easily occur under high temperature conditions (140℃×60h); if the filler content is reduced to reduce the specific gravity, the thermal conductivity will be greatly reduced, and the flowability of the rubber compound will be out of control, which will not meet the reliability requirements of practical applications.

[0005] Third, the compatibility between insulation performance and filler ratio is poor: In existing technologies, adding high thermal conductivity fillers to improve thermal conductivity easily leads to a decrease in insulation performance; if the amount of thermal conductivity fillers is reduced simply to pursue high insulation, it will not achieve the desired effect. The high thermal conductivity requirement, coupled with the lack of a synergistic optimization solution for "thermal conductivity-insulation-lightweighting", makes it difficult to adapt to demanding application scenarios requiring high insulation and high thermal conductivity. Summary of the Invention

[0006] The purpose of this invention is to provide a thermally conductive filler for anti-cracking and anti-sagging gels to solve the technical problems in the prior art.

[0007] To achieve the aforementioned objectives, the present invention provides the following technical solution:

[0008] A thermally conductive filler for anti-cracking and anti-sagging gel comprises the following components in the following weight proportions: 110-200 parts of boron nitride powder No. 1, 140-230 parts of boron nitride powder No. 2, 320-410 parts of alumina powder No. 1, 200-290 parts of alumina powder No. 2, 60-150 parts of alumina powder No. 3, 170-260 parts of zinc oxide powder No. 1, and 5-8 parts of surface treatment agent. The particle size of the boron nitride powder No. 1 is 110-130 μm, the particle size of the boron nitride powder No. 2 is 90-110 μm, the particle size of the alumina powder No. 1 is 40-50 μm, the particle size of the alumina powder No. 2 is 5-10 μm, the particle size of the alumina powder No. 3 is 1-5 μm, and the particle size of the zinc oxide powder No. 1 is 0.8-1.1 μm.

[0009] The surface treatment agent is any one of a silane coupling agent, a titanate coupling agent, or an aluminate coupling agent.

[0010] It comprises the following components by weight: 110 parts of boron nitride No. 1 powder, 140 parts of boron nitride No. 2 powder, 320 parts of alumina No. 1 powder, 200 parts of alumina No. 2 powder, 60 parts of alumina No. 3 powder, 170 parts of zinc oxide No. 1 powder, and 5 parts of surface treatment agent, wherein the surface treatment agent is a silane coupling agent.

[0011] A method for preparing a thermally conductive filler for a crack-resistant and anti-sagging gel includes the following steps:

[0012] S1. Weigh out No. 2 alumina powder, No. 3 alumina powder and No. 1 zinc oxide powder according to the formula ratio, put them into a high-speed mixer, and stir at 50Hz for 5-10 minutes to make the powder fully mixed and uniform; add 0.4% of the formula amount of silane coupling agent into the high-speed mixer, and stir at 50Hz for 10-20 minutes to obtain powder filler A;

[0013] S2. Based on filler A, weigh boron nitride powder No. 1, boron nitride powder No. 2, and alumina powder No. 1 according to the formula ratio, and put them into a high-speed mixer. Stir at 15Hz for 5-10 minutes to ensure that the powders are fully mixed and uniform. Add 0.1% of the formula amount of silane coupling agent to the high-speed mixer and stir at 35Hz for 10-20 minutes to ensure that the coupling agent is uniformly coated on the surface of the filler and completes the in-situ chemical bonding modification, thus obtaining the modified composite thermally conductive filler.

[0014] The boron nitride powder No. 1 has a particle size of 120 μm, the boron nitride powder No. 2 has a particle size of 100 μm, the alumina powder No. 1 has a particle size of 45 μm, the alumina powder No. 2 has a particle size of 7 μm, the alumina powder No. 3 has a particle size of 2 μm, and the zinc oxide powder No. 1 has a particle size of 1 μm.

[0015] Compared with existing technologies, the thermally conductive filler for anti-cracking and anti-sagging gel of this application is made by mixing boron nitride with two-stage particle size, alumina with three-stage particle size, and ultrafine zinc oxide. Through reasonable filler gradation and selection, it achieves low-filling-weighted filling. With high thermal conductivity and a finished product specific gravity as low as 2.235 g / cm³, it balances lightweight and high thermal conductivity, achieving both high thermal conductivity and low specific gravity with low filler content. At the same time, this application uses a step-by-step modification process of "treating small-particle-size fillers first and integrating coarse-particle-size fillers later" to ensure that the coupling agent uniformly coats the surface of various fillers, constructing a stable "filler-coupling agent-matrix" chemical bonding interface, reducing interface debonding and crack propagation at high temperatures, ensuring stable interface bonding, and preventing cracking at high temperatures. Attached Figure Description

[0016] Figure 1 The data in Example 2 is used in this application as a line graph. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0018] Specific Embodiment 1: In this embodiment of the invention, a thermally conductive filler for anti-cracking and anti-sagging gel comprises the following components in the following weight proportions: 110-200 parts of boron nitride powder No. 1, 140-230 parts of boron nitride powder No. 2, 320-410 parts of alumina powder No. 1, 200-290 parts of alumina powder No. 2, 60-150 parts of alumina powder No. 3, 170-260 parts of zinc oxide powder No. 1, and 5-8 parts of surface treatment agent. The particle size of boron nitride powder No. 1 is 110-130 μm, that of boron nitride powder No. 2 is 90-110 μm, that of alumina powder No. 1 is 40-50 μm, that of alumina powder No. 2 is 5-10 μm, that of alumina powder No. 3 is 1-5 μm, and that of zinc oxide powder No. 1 is 0.8-1.1 μm. In this embodiment, the specific filler formulation and proportions are as follows:

[0019] Boron nitride powder No. 1 (110-130μm): 110 parts;

[0020] Boron nitride No. 2 powder (90-110μm): 140 parts;

[0021] Alumina powder No. 1 (40-50μm): 320 parts;

[0022] Alumina No. 2 powder (5-10μm): 200 parts;

[0023] Alumina powder No. 3 (1-5μm): 60 parts;

[0024] Zinc oxide powder (0.8-1.1μm): 170 parts;

[0025] Surface treatment agent (silane coupling agent): 5 parts.

[0026] A method for preparing a thermally conductive filler for a crack-resistant and anti-sagging gel includes the following processing steps:

[0027] S1. Weigh out No. 2 alumina powder, No. 3 alumina powder and No. 1 zinc oxide powder according to the formula ratio, put them into a high-speed mixer, and stir at 50Hz for 5-10 minutes to make the powder fully mixed and uniform; add 0.4% of the formula amount of silane coupling agent into the high-speed mixer (i.e., four parts of silane coupling agent), and stir at 50Hz for 10-20 minutes to obtain powder filler A;

[0028] S2. Based on filler A, weigh boron nitride powder No. 1, boron nitride powder No. 2, and alumina powder No. 1 according to the formula ratio, and put them into a high-speed mixer. Stir at 15Hz for 5-10 minutes to ensure that the powders are fully mixed and uniform. Add 0.1% of the formula amount of silane coupling agent to the high-speed mixer (i.e., one part of silane coupling agent), and stir at 35Hz for 10-20 minutes to ensure that the coupling agent is uniformly coated on the surface of the filler and completes in-situ chemical bonding modification, thus obtaining the modified composite thermally conductive filler.

[0029] In the above preparation method, the particle size of boron nitride No. 1 powder is 120 μm, the particle size of boron nitride No. 2 powder is 100 μm, the particle size of alumina No. 1 powder is 45 μm, the particle size of alumina No. 2 powder is 7 μm, the particle size of alumina No. 3 powder is 2 μm, and the particle size of zinc oxide No. 1 powder is 1 μm.

[0030] The particle size and physicochemical properties of each raw material in the formulation of this application are as follows:

[0031] Boron nitride powder No. 1 (110-130μm): conductivity ≤100μS / cm, pH value: 7-10;

[0032] Boron nitride No. 2 powder (90-110μm): conductivity ≤100μS / cm, pH value: 7-10;

[0033] Alumina powder No. 1 (40-50μm): conductivity ≤100μS / cm, pH value: 7.5-9.5;

[0034] Alumina No. 2 powder (5-10μm): conductivity ≤100μS / cm, pH value: 7.5-9.5;

[0035] Alumina powder No. 3 (1-5μm): conductivity ≤100μS / cm, pH value: 7.5-9.5;

[0036] Zinc oxide powder (0.8-1.1μm): conductivity ≤100μS / cm, pH: 7.5-9.5;

[0037] The aforementioned silane coupling agent is an epoxy-based silane coupling agent with the molecular formula RSiX3, where R represents an organic functional group and X represents a hydrolyzable group. This silane coupling agent can link inorganic materials and organic compounds, forming stable chemical bonds with hydroxyl groups on the surface of inorganic materials and interacting with long molecular chains in organic polymers.

[0038] The thermally conductive filler was prepared and tested according to the above method. The test cases include Implementation Case 1, Implementation Case 2, Implementation Case 3, and Implementation Case 4. The specific data are as follows:

[0039]

[0040] According to the formulas shown in the table, four different thermally conductive fillers were prepared, namely, the first thermally conductive filler, the second thermally conductive filler, the third thermally conductive filler, and the fourth thermally conductive filler. The first thermally conductive filler is consistent with the formula requirements of this application. The application implementation test analysis of these four thermally conductive fillers is as follows:

[0041] Application Example 1: The fillers from the above four examples were used to prepare thermally conductive gel products according to the following formulations, the specific formulations of which include:

[0042] 200 mPa·s vinyl silicone oil: 100 parts;

[0043] Hydrogen-containing silicone oil: 1.5 parts;

[0044] Platinum catalyst: 1.2 parts;

[0045] Inhibitor: 0.4 parts;

[0046] Thermally conductive filler for low-density gels: 440 parts;

[0047] The preparation method of the gel product is as follows: Weigh vinyl silicone oil, hydrogen-containing silicone oil, reaction inhibitor, and platinum catalyst according to the formula ratio, and put them together with the modified composite thermally conductive filler prepared in the above four examples into a double planetary stirrer. Under the conditions of vacuum degree ≥ -0.095MPa and temperature 150℃, stir at a stirring rate of 10~50r / min for 0.5~1h to make the components fully mixed and uniform, and simultaneously complete the low molecular weight removal, bubble removal and pre-crosslinking reaction to obtain the single-component thermally conductive gel product.

[0048] The performance of the thermally conductive gel products obtained from Implementation Case 1, Implementation Case 2, Implementation Case 3, and Implementation Case 4 was tested, and the specific performance data is shown in the table below:

[0049]

[0050] It can be seen from the above table:

[0051] (1) The overall effect of Implementation Case 1 meets the product performance requirements, and its comprehensive performance is superior to other implementation cases; Example 1 is the preferred ratio of the present invention, with multi-size boron nitride, alumina, and zinc oxide working synergistically to achieve a thermal conductivity of With a specific gravity controlled to 2.235 g / cm³, it exhibits no cracking or sagging at high temperatures, excellent breakdown insulation performance, and optimal overall performance.

[0052] (2) Compared with implementation case 1, implementation case 2 cancels the addition of boron nitride and relies only on alumina + zinc oxide as filler. Although it does not crack or sag at high temperature and has high extrusion, it has very low thermal conductivity and high specific gravity under low filler conditions.

[0053] (3) Compared with Case 1, Case 3 eliminated the addition of zinc oxide and retained boron nitride + multi-stage alumina. At high temperature, it showed fine cracking, 2mm sag, reduced thermal conductivity and extrusion, and high specific gravity. This proves that zinc oxide has significant key roles in interface toughening, crack resistance and anti-sag.

[0054] (4) Compared with Case 1, Case 4 eliminates boron nitride and zinc oxide, and uses a pure alumina system. The adhesive is non-thixotropic, has strong fluidity, penetrates cracks at high temperatures, flows out vertically, has very low thermal conductivity under low filler, and has a high specific gravity.

[0055] Based on the experimental data above, it can be seen that boron nitride is the core of a high thermal conductivity and high insulation framework, while zinc oxide is the core with anti-cracking and anti-sagging functions.

[0056] Application Example 2: Fabrication of thermally conductive pads, specifically including the following formula:

[0057] 500-1000 mPa·s vinyl silicone oil: 100 parts;

[0058] Hydrogen-containing silicone oil: 3.5 parts;

[0059] Platinum catalyst: 1 part;

[0060] Inhibitor: 0.5 parts;

[0061] Thermally conductive filler for low specific gravity gel: 440 parts.

[0062] The preparation method includes: taking 440 parts by mass of the modified thermally conductive composite powder described in the four examples above, 100 parts by mass of 500 mPa·s vinyl silicone oil, hydrogen-containing silicone oil, platinum catalyst, and inhibitor, and placing them in a stirring device. Mixing is carried out at room temperature and a stirring speed of 10-50 r / min for 5-10 minutes, ensuring the device is under vacuum during stirring. The resulting compound is then pressed into a 1 mm thin sheet and baked at 130°C for 15-30 minutes to obtain the thermally conductive pad. The electrical insulation performance of the pads in Examples 1, 2, 3, and 4 is tested using a breakdown voltage tester. The tester is set to AC power, with a voltage ramp rate of 1000 V / s. The actual thickness of the sheet is input to start the test. The voltage strength data at which the sheet is just broken down is obtained. The test results are attached. Figure 1 As shown.

[0063] The higher the breakdown voltage, the better the electrical insulation performance of the material; conversely, the lower the breakdown voltage, the worse the electrical insulation performance. Figure 1 It can be seen that the electrical insulation performance is low without the addition of boron nitride, slightly worse with the addition of zinc oxide, and the electrical insulation performance is the best with the addition of boron nitride, that is, the electrical insulation performance is excellent with a low filler ratio. Even with the addition of zinc oxide along with boron nitride, the material still exhibits excellent dielectric properties. The breakdown voltage of Example 1 is 13.32 kV / mm, which is slightly lower than that of Example 3, but this value still exceeds the performance level of current mainstream commercially available thermal conductive gel products. The ultrafine zinc oxide contained in the formulation of Example 1 plays a key role in interfacial toughening. Combined with the segmented modification process, the interface between the filler and the matrix is ​​more firmly bonded, which can effectively release thermal stress and avoid crack initiation and flow at high temperatures. In contrast, the system of Example 3 (without zinc oxide) has insufficient structural stability at long-term high temperatures and is at risk of failure. Moreover, the specific gravity of Example 1 is only 2.235 g / cm³, which is the lowest among all formulations. That is, the formulation of Example 1 achieves a perfect balance of core properties such as high thermal conductivity, low specific gravity, high insulation, high temperature resistance, crack resistance, and anti-sagging, and is the optimal solution. Example 3 only has a slight advantage in the single insulation index.

[0064] Compared with existing technologies, the thermally conductive filler for anti-cracking and anti-sagging gel of this application is made by mixing boron nitride with two-stage particle size, alumina with three-stage particle size, and ultrafine zinc oxide. Through reasonable filler gradation and selection, it achieves low-filling-weighted filling. High thermal conductivity, with a finished product specific gravity as low as 2.235 g / cm³, achieving both lightweight and high thermal conductivity, i.e., high thermal conductivity and low specific gravity with low filler content; simultaneously, this application employs a step-by-step modification process of "treating small-particle-size fillers first and then integrating coarse-particle-size fillers later" to ensure that the coupling agent uniformly coats the surface of various fillers, constructing a stable "filler-coupling agent-matrix" chemical bonding interface, reducing interface debonding and crack propagation at high temperatures, ensuring stable interface bonding, and preventing cracking at high temperatures.

[0065] It will be apparent to those skilled in the art that the present invention is not limited to the details of the foregoing exemplary embodiments, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0066] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A thermally conductive filler for use in crack-resistant and anti-sagging gels, characterized in that: The powder comprises the following components by weight: 110-200 parts of boron nitride powder No. 1, 140-230 parts of boron nitride powder No. 2, 320-410 parts of alumina powder No. 1, 200-290 parts of alumina powder No. 2, 60-150 parts of alumina powder No. 3, 170-260 parts of zinc oxide powder No. 1, and 5-8 parts of surface treatment agent. The particle size of the boron nitride powder No. 1 is 110-130 μm, the particle size of the boron nitride powder No. 2 is 90-110 μm, the particle size of the alumina powder No. 1 is 40-50 μm, the particle size of the alumina powder No. 2 is 5-10 μm, the particle size of the alumina powder No. 3 is 1-5 μm, and the particle size of the zinc oxide powder No. 1 is 0.8-1.1 μm.

2. The thermally conductive filler for an anti-cracking and anti-sagging gel according to claim 1, characterized in that: The surface treatment agent is any one of a silane coupling agent, a titanate coupling agent, or an aluminate coupling agent.

3. The thermally conductive filler for an anti-cracking and anti-sagging gel according to claim 2, characterized in that: It comprises the following components by weight: 110 parts of boron nitride No. 1 powder, 140 parts of boron nitride No. 2 powder, 320 parts of alumina No. 1 powder, 200 parts of alumina No. 2 powder, 60 parts of alumina No. 3 powder, 170 parts of zinc oxide No. 1 powder, and 5 parts of surface treatment agent, wherein the surface treatment agent is a silane coupling agent.

4. The thermally conductive filler for an anti-cracking and anti-sagging gel according to claim 3, characterized in that: Its preparation method includes the following steps: S1. Weigh out No. 2 alumina powder, No. 3 alumina powder and No. 1 zinc oxide powder according to the formula ratio, put them into a high-speed mixer, and stir at 50Hz for 5-10 minutes to make the powder fully mixed and uniform; add 0.4% of the formula amount of silane coupling agent into the high-speed mixer, and stir at 50Hz for 10-20 minutes to obtain powder filler A; S2. Based on filler A, weigh boron nitride powder No. 1, boron nitride powder No. 2, and alumina powder No. 1 according to the formula ratio, and put them into a high-speed mixer. Stir at 15Hz for 5-10 minutes to ensure that the powders are fully mixed and uniform. Add 0.1% of the formula amount of silane coupling agent to the high-speed mixer and stir at 35Hz for 10-20 minutes to ensure that the coupling agent is uniformly coated on the surface of the filler and completes the in-situ chemical bonding modification, thus obtaining the modified composite thermally conductive filler.

5. The method for preparing a thermally conductive filler for an anti-cracking and anti-sagging gel according to claim 4, characterized in that: The boron nitride powder No. 1 has a particle size of 120 μm, the boron nitride powder No. 2 has a particle size of 100 μm, the alumina powder No. 1 has a particle size of 45 μm, the alumina powder No. 2 has a particle size of 7 μm, the alumina powder No. 3 has a particle size of 2 μm, and the zinc oxide powder No. 1 has a particle size of 1 μm.

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