Self-rebound tubular composite thermal pad based on metal aerogel, its preparation method and application

Abstract

This invention relates to the field of thermal interface materials technology, and particularly to a self-rebound tubular composite thermal pad based on metal aerogel, its preparation method, and its application. The self-rebound tubular composite thermal pad prepared by this invention is a key material for ensuring stable heat dissipation in electronic systems in the semiconductor field. It features a single material composition, low bonding region thickness (30μm), excellent resilience, no flowability, and anti-aging properties. During the encapsulation process, it avoids phenomena such as liquid pumping out and flux evaporation, thus solving the problems of traditional thermal grease such as pumping out, aging, and delamination, high thermal resistance due to high thermal pad thickness, and flux evaporation during indium wafer use. Therefore, it exhibits better production stability and performance reliability.

Description

Technical Field

[0001] This invention relates to the field of thermal interface materials technology, and in particular to a self-rebound tubular composite thermal pad based on metal aerogel, its preparation method, and its application. Background Technology

[0002] Thermal interface materials (TIMs) play a crucial role in chip packaging, especially in high-performance and high-power-density electronic devices. When a chip is operating, it generates a significant amount of heat. If this heat is not dissipated promptly, it can lead to overheating, affecting performance and lifespan, and even causing damage. Thermal interface materials are essential for effectively transferring heat from the chip to the heatsink or cooling system.

[0003] The primary function of thermal interface materials is to provide a low-thermal-resistance bonding layer between a chip (typically an integrated circuit made of silicon or other semiconductor materials) and a heat sink or heat plate. Since the chip surface and the heat sink surface cannot be perfectly flat, microscopic irregularities and voids exist. These voids form air layers, and air, with its very low thermal conductivity, significantly increases thermal resistance. Thermal interface materials fill these voids, reducing the presence of air and thus significantly improving heat transfer efficiency. Common thermal interface materials include thermal grease, thermal gel, silicone-free thermal pads, thermally conductive phase change materials, thermally conductive elastomers, thermally conductive silicone cloth, and carbon fiber thermal pads.

[0004] While thermal interface materials (TIMs) offer crucial thermal management solutions in chip packaging, they are not without their technical drawbacks. Here are some common issues and challenges: (1) Thermal Resistance: Although TIMs are designed to reduce thermal resistance, they themselves introduce additional thermal resistance. This is because TIMs are generally less thermally conductive than direct-contact materials such as metals, and they may form bubbles due to drying, aging, or insufficient pressure, further increasing thermal resistance. (2) Volatility and Curing: Some types of TIMs, such as thermal pastes, may contain volatile components that may evaporate during long-term use, leading to material drying and increased thermal resistance. Furthermore, some liquid TIMs require curing to achieve optimal performance, and the curing process may be affected by environmental conditions such as temperature and humidity. (3) Mechanical Resilience: TIMs must be able to withstand the thermal expansion and contraction of the chip during operation, as well as prolonged thermal cycling. TIMs with poor mechanical resilience may crack or lose adhesion after multiple thermal cycles, delaminating between the TIM and the chip or heat exchanger, affecting thermal management effectiveness. (4) Electrical insulation: For applications requiring electrical isolation, TIMs must have sufficient electrical insulation properties. However, some high-performance TIMs, such as liquid metals, may not have good electrical insulation properties, limiting their application in specific scenarios. (5) Process compatibility: Some TIMs may be difficult to be compatible with existing packaging processes. For example, liquid metals may corrode surrounding components, or some materials may decompose at high temperatures, releasing harmful gases. (6) Interface compatibility: Differences in the coefficients of thermal expansion between chips and heat sinks made of different materials may cause interface stress. Inappropriately selected TIMs may not be able to adequately alleviate this stress, thus affecting reliability. (7) Long-term stability: Under long-term use, the performance of TIMs may degrade, such as reduced thermal conductivity and changes in viscosity, which may require regular inspection and maintenance.

[0005] To address these technical shortcomings, researchers and manufacturers are continuously working to develop new materials and technologies to improve the performance, stability, and reliability of thermal interface materials (TIMs), while reducing costs and environmental impact. Therefore, a novel thermal interface material is needed that can comprehensively solve these problems. Summary of the Invention

[0006] The first aspect of the present invention provides a method for preparing a self-resilient tubular composite thermal conductive pad based on metal aerogel, comprising the following steps:

[0007] S1. Prepare metal hydrogels by washing and drying them to obtain metal aerogels;

[0008] S2. Disperse liquid metal in an ethanol solution of citric acid to obtain a mixture, blend the mixture with metal aerogel and let it stand for soaking, then reset it with an ethanol solution to obtain a metal hydrogel-based composite material;

[0009] S3. Dry the metal hydrogel-based composite material to obtain a metal aerogel-based composite material;

[0010] S4. The metal aerogel-based composite material is immersed in an ethanol solution of acetic acid for 5-20 minutes, and then reset by the ethanol solution. The product is dried, mechanically cut, and laser processed to obtain the self-rebound tubular composite thermal pad.

[0011] The liquid metal occupies 60-80% of the volume in the self-rebound tubular composite thermal pad.

[0012] Furthermore, the metal aerogel is prepared by: mixing PVP and AgNO3. 3、 FeCl3 was dissolved in ethylene glycol and stirred until homogeneous. Then, it was placed in a drying oven and heated to react, yielding silver nanogels. The silver nanogels were then soaked in NaBH4 aqueous solution, with fresh NaBH4 solution used for each soak. They were then soaked in alcohol. After washing, the mixture was supercritically dried to obtain silver nanowire aerogels.

[0013] The metal aerogel obtained by chemical method is a three-dimensional network structure composed of nanowires. Liquid metal particles are immersed in the three-dimensional network structure and adhere to the surface of the nanowires. The particles are in contact with each other and with the nanowires. Liquid metal has strong oxidizing properties and has an oxide shell on its surface. The presence of the oxide shell will hinder heat conduction. Therefore, immersion in acetic acid breaks down the oxide shell of the liquid metal, allowing the liquid metal particles to aggregate and wrap around the surface of the nanowires, ultimately forming a tubular structure of liquid metal wrapping nanowires, resulting in a self-rebound tubular composite thermal pad.

[0014] In some embodiments, the metal aerogel is made of at least one of silver, copper, nickel, gold, and tin.

[0015] In some embodiments, the liquid metal is selected from at least one of gallium indium, gallium indium tin, and gallium indium zinc.

[0016] In some embodiments, the melting point of the liquid metal is 3-40°C.

[0017] The fluidity of liquid metal at room temperature can facilitate the coating of liquid metal onto the surface of nanowires, forming tubular structures. This improves the resilience of the aerogel, compensates for the volume shrinkage deformation that occurs during the operation of the new power chip, ensures effective heat conduction, and extends the chip's lifespan.

[0018] In some embodiments, the particle size of the liquid metal is 500 nm to 3 μm.

[0019] In some embodiments, the concentration of the citric acid ethanol solution is 0.05-0.5 g / L.

[0020] In some embodiments, the concentration of the ethanol solution of acetic acid is 1-8 vol%.

[0021] In some embodiments, the drying time in S3 is 0.5-5 hours.

[0022] In some embodiments, the mass ratio of the liquid metal composite is 30% to 80%.

[0023] A second aspect of the present invention provides a self-rebound tubular composite thermal pad based on metal aerogel, which is obtained by the preparation method described above.

[0024] In some embodiments, the thermal resistance of the self-rebound tubular composite thermal pad is 0.15 °C·cm. 2 / W, with a springback rate of 70%.

[0025] In some embodiments, the interior of the self-rebound tubular composite thermal pad is a three-dimensional network structure composed of nanowires, which are tubular structures encapsulated in liquid metal.

[0026] A third aspect of the present invention provides the application of the above-described self-rebound tubular composite thermal pad in the semiconductor field.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The self-rebound tubular composite thermal pad prepared by this invention is a key material for ensuring stable heat dissipation of electronic systems in the semiconductor field. Unlike the paste-like thermal grease and traditional thermal pads with high modulus and large thickness (0.5mm) in the prior art, the novel thermal pad of this invention has a single composition, low bonding area thickness (30μm), no flowability, and anti-aging properties. There are no phenomena such as liquid pumping out or flux volatilization during the packaging process. It can solve the pain points of traditional thermal grease such as paste pumping out, aging and delamination, high thermal resistance due to high thickness of thermal pads, and flux volatilization during the use of indium wafers. Therefore, it has better production stability and performance reliability.

[0029] 2. The self-rebound tubular composite thermal pad prepared in this invention exhibits excellent resilience. The liquid metal coating on the nanowires enhances their mechanical strength, thereby giving the aerosolizer composed of nanowires a certain degree of resilience. During power chip operation, temperature changes cause the device to shrink and expand, and the thermal interface material with high deformability and resilience can compensate for this deformation, improving the packaging's adaptability. By controlling the amount of liquid metal coating, the resilience can be adjusted from 2% to 70%. Attached Figure Description

[0030] Figure 1 The image shows the internal microstructure of the silver nanowire aerogel prepared in Example 1 before it is combined with the second phase.

[0031] Figure 2 This is a schematic diagram of the internal structure of the self-rebound tubular composite thermal pad prepared in Example 1.

[0032] Figure 3 The images show the overall macroscopic view and a partial internal microscopic view of the self-rebound tubular composite thermal pad prepared in Example 1. Detailed Implementation

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Example 1

[0035] This embodiment provides a self-rebound tubular composite thermal pad based on metal aerogel, the preparation method of which includes the following steps:

[0036] S1. Preparation of nano-silver aerogel by chemical in-situ reduction method: 0.2g PVP, 0.5g AgNO3 3、 0.2 g FeCl3 was dissolved in 50 mL ethylene glycol and stirred until homogeneous. The solution was then placed in a drying oven and reacted at 130 °C for 4 h to obtain a silver nanogel. The silver nanogel was then soaked five times in a 0.002 M NaBH4 aqueous solution for 10 min each time, with a fresh NaBH4 solution used for each soak. It was then soaked in alcohol for 10 min each time. After washing, it was supercritically dried to obtain a silver nanowire aerogel. The silver nanowire aerogel is a three-dimensional network structure composed of silver nanowires. A 25 mm * 25 mm * 5 mm silver aerogel preform was obtained by laser cutting. The internal microstructure of the aerogel is shown in the figure below. Figure 1 As shown.

[0037] S2. Dissolve 0.03g of citric acid in 30ml of ethanol and stir thoroughly to obtain a citric acid-ethanol solution. Then add 2g of liquid metal GaInSn into the citric acid-ethanol solution and sonicate for 10min at 200W to obtain a suspension of liquid metal GaInSn nanoparticles with a particle size range of 500nm-3um.

[0038] S3. The nano-silver aerogel obtained in S1 is immersed in the liquid metal nanoparticle suspension obtained in S2. The mass ratio of GaInSn nanoparticles in the nano-silver hydrogel-based composite material is adjusted by controlling the standing time. When the standing time is 2h, the composite ratio is as high as 80%.

[0039] S4. The liquid metal suspension was then displaced by immersion in an ethanol solution to obtain a nano-silver hydrogel-based composite material; the nano-silver hydrogel-based composite material was then dried by supercritical carbon dioxide for 1 hour to obtain a nano-silver aerogel-based composite material.

[0040] S5. The nano-silver hydrogel-based composite material was immersed in an ethanol solution of acetic acid (5 vol%) for 10 min, then reset with an ethanol solution, and the product was dried to obtain a self-rebound tubular composite thermal conductive pad. A schematic diagram of the self-rebound tubular composite thermal conductive pad is shown below. Figure 2 As shown, the overall macroscopic view of the thermal pad is as follows. Figure 3 As shown in (a), the microscopic image of the internal tubular structure is as follows. Figure 3 As shown in (b).

[0041] Example 2

[0042] This embodiment provides a self-rebound tubular composite thermal conductive pad based on metal aerogel. The specific implementation method is the same as that in Embodiment 1, except that:

[0043] S4. The composite hydrogel obtained in S3 is placed in an ethanol solution and subjected to ultrasound (30W power, 20kHz frequency). Under the ultrasonic vibration, the oxide shell on the surface of the liquid metal particles is broken, and the liquid metals fuse together to wrap the silver nanowires to form a tubular structure. The remaining liquid metal suspension is then replaced with an ethanol solution.

[0044] S5. The material obtained in S4 is subjected to supercritical carbon dioxide drying to finally obtain a self-rebound tubular composite thermal pad.

[0045] In addition to the comparison with Example 1, the ultrasonic breaking of liquid metal used in this embodiment can improve the convenience of operation and avoid the possibility of acetic acid causing invisible damage to silver nanowires.

[0046] Comparative Example 1

[0047] The specific implementation method of this comparative example is the same as that of Example 1, except that the liquid metal particles in S2 are GaIn, the ultrasonic power is 150W, the concentration of the acetic acid ethanol solution in S5 is 2 vol%, and the soaking time is 10 min.

[0048] Comparative Example 2

[0049] The specific implementation method of this comparative example is the same as that of Example 1, except that the liquid metal particles in S2 are GaIn, the ultrasonic power is 250W, the concentration of the acetic acid ethanol solution in S5 is 7 vol%, and the soaking time is 20 min.

[0050] Comparative Example 3

[0051] The specific implementation method of this comparative example is the same as that of Example 1, except that the ultrasonic power in S2 is 100W, the concentration of the acetic acid ethanol solution in S5 is 10 vol%, and the soaking time is 5 min.

[0052] Comparative Example 4

[0053] The specific implementation method of this comparative example is the same as that of Example 1, except that the liquid metal particles in S2 are Ga, the ultrasonic power is 100W, the concentration of the acetic acid ethanol solution in S5 is 10 vol%, and the soaking time is 5 min.

[0054] Performance testing

[0055] The composite materials prepared in the above examples and comparative examples were subjected to the following tests, and the results are shown in Table 1:

[0056] Thermal resistance: The thermal resistance of the material was measured using the LW-9389 (LongWin Co., Ltd., China) interface material thermal conductivity and thermal resistance measurement device designed based on the ASTM-D5470 standard test method, which was used to test the total thermal resistance of the sample by steady-state method.

[0057] Resilience: Tested using a mechanical testing machine, 5mm material is compressed to 30μm and allowed to stand for 10 seconds. The rebound distance is measured using vernier calipers. The rebound distance / compression distance × 100% is calibrated as the rebound amount.

[0058] Table 1

[0059] thermal resistance Resilience (%) Example 1 <![CDATA[0.15℃·cm 2 / W]]> 70 Example 2 <![CDATA[0.16℃·cm 2 / W]]> 72 Comparative Example 1 <![CDATA[0.4℃·cm 2 / W]]> 60 Comparative Example 2 <![CDATA[0.3℃·cm 2 / W]]> 65 Comparative Example 3 <![CDATA[0.25℃·cm 2 / W]]> 55 Comparative Example 4 <![CDATA[0.5℃·cm 2 / W]]> 45

[0060] As can be seen from the above performance test results, the self-rebound tubular composite thermal pad of Example 1 has excellent resilience and thermal conductivity. This is mainly because the three-dimensional thermal conductive network formed by the metal aerogel greatly improves the deformability of the composite thermal interface material, enabling it to exert excellent thermal conductivity. The liquid metal wrapped in silver nanowires improves the mechanical strength of the material, thereby improving the resilience of the thermal pad.

[0061] The comparative examples, however, did not employ the necessary technical solutions, resulting in significantly inferior performance compared to the examples. In comparative examples 1-4, the type of composite liquid metal, ultrasonic power, acetic acid-ethanol concentration, and immersion time were changed, and it can be seen that the conductivity and rebound effects decreased to varying degrees, proving that the scheme of example 1 had a significant impact on the effectiveness of the present invention.

[0062] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a self-rebound tubular composite thermal conductive pad based on metal aerogel, characterized in that, Includes the following steps: S1. Prepare metal hydrogel: Wash and dry the metal hydrogel to obtain metal aerogel; The method for preparing metal aerogels is as follows: PVP, AgNO3, and other components are mixed. 3、 FeCl3 was dissolved in ethylene glycol and stirred until homogeneous. Then, it was placed in a drying oven and heated to react, yielding silver nanogel. The silver nanogel was then soaked in NaBH4 aqueous solution, with a fresh NaBH4 aqueous solution used for each soak. It was then soaked in alcohol. After washing, it was supercritically dried to obtain silver nanowire aerogel, i.e., metal aerogel. S2. Disperse liquid metal in an ethanol solution of citric acid to obtain a mixture, blend the mixture with metal aerogel and let it stand for soaking, and then reset it with an ethanol solution to obtain a metal hydrogel-based composite material; S3. Dry the metal hydrogel-based composite material to obtain a metal aerogel-based composite material; S4. The metal aerogel-based composite material is immersed in an ethanol solution of acetic acid for 5-20 minutes, and then reset by the ethanol solution. The product is dried, mechanically cut, and laser processed to obtain the self-rebound tubular composite thermal pad. The liquid metal occupies 60-80% of the volume in the self-rebound tubular composite thermal pad.

2. The preparation method according to claim 1, characterized in that, The liquid metal has a particle size of 500 nm to 3 μm.

3. The preparation method according to claim 2, characterized in that, The concentration of the citric acid ethanol solution is 0.05-0.5 g / L.

4. The preparation method according to claim 3, characterized in that, The concentration of the ethanol solution of acetic acid is 1-8 vol%.

5. The preparation method according to claim 4, characterized in that, The drying time in S3 is 0.5-5 hours.

6. A self-rebound tubular composite thermal conductive pad based on metal aerogel, characterized in that, The preparation method according to any one of claims 1-5 is obtained.

7. The self-rebound tubular composite thermal pad according to claim 6, characterized in that, The thermal resistance of the self-rebound tubular composite thermal pad is 0.15℃·cm. 2 / W, with a springback rate of 70%.

8. The application of the self-rebound tubular composite thermal pad according to claim 6 in the semiconductor field.

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