A copper-liquid metal composite thermal interface material and a method of making the same

Abstract

The application relates to the field of thermal interface materials, in particular to a copper-liquid metal composite thermal interface material and a preparation method thereof. The preparation method comprises the following steps: edge sealing of a copper foil, then coating liquid metal on the surface of the copper foil to obtain a copper foil coated with liquid metal; then layer-by-layer stacking of the copper foil coated with liquid metal, and fixing to obtain copper-liquid metal; high-temperature treatment or high-low temperature cycle treatment of the copper-liquid metal to obtain the copper-liquid metal composite thermal interface material. The high-thermal-conductivity copper-liquid metal composite thermal interface material provided by the application is different from common thermal interface materials, does not have overall phase change, cannot be washed away by cooling liquid, and the liquid metal does not leak and does not corrode. Moreover, the thermal interface material has good filling property and high thermal conductivity.

Description

Technical Field

[0001] This invention relates to the field of thermal interface materials, specifically to a copper-liquid metal composite thermal interface material and its preparation method. Background Technology

[0002] With the increasing demand for computing power in recent years, the heat generated by chips is also rapidly increasing. Server cooling methods are gradually shifting from air cooling to immersion liquid cooling. Traditional polymer thermally conductive interface materials are prone to swelling and dissolving in coolants. Research shows that 55% of electronic device failures are temperature-related, and for every 2°C increase in the temperature of electronic components, reliability decreases by 10%, leading to problems such as breakdown, stress mismatch, and solder joint cracking. Therefore, with the growing demand for immersion liquid cooling, there is a need for a thermally conductive material compatible with all coolants and suitable for the application environment of immersion liquid cooling.

[0003] Existing liquid metal thermal interface materials are prone to flow and leakage, resulting in poor material filling and affecting their performance. Furthermore, these materials are susceptible to corrosion, leading to device aging and reduced lifespan.

[0004] There is an urgent need to provide a novel method for preparing liquid metal composite thermal interface materials to address issues such as the easy swelling and dissolution of traditional polymer thermally conductive interface materials in coolants; the tendency of existing liquid metal thermal interface materials to flow and leak, affecting their performance; and the susceptibility of liquid metal thermal interface materials to corrosion, leading to device corrosion and aging, and affecting their service life. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a copper-liquid metal composite thermal interface material and its preparation method. The copper-liquid metal composite thermal interface material provided by this invention differs from common thermal interface materials in that it does not undergo an overall phase change, is not washed away by the coolant, the liquid metal does not leak or corrode, and the material exhibits good filling properties and high thermal conductivity.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows.

[0007] In a first aspect, the present invention provides a method for preparing a copper-liquid metal composite thermal interface material, comprising: sealing the edges of a copper foil, then coating the surface of the copper foil with liquid metal to obtain a copper foil coated with liquid metal; then stacking the copper foil coated with liquid metal layer by layer and fixing them to obtain copper-liquid metal; and subjecting the copper-liquid metal to high-temperature treatment or high-low temperature cycling treatment to obtain a copper-liquid metal composite thermal interface material. The copper-liquid metal composite thermal interface material preparation process provided by the present invention, through sealing the copper foil edges, coating with liquid metal, stacking, and specific treatments, effectively ensures the material's high thermal conductivity and structural stability. By reacting liquid metal with copper under high-temperature or high-low-temperature cycling conditions, a high thermal conductivity copper-liquid metal composite thermal interface material is obtained, which serves as an effective heat dissipation component and solves the existing technical problems of thermal interface materials. Combining copper with liquid metal can improve the thermal conductivity and stability of the composite thermal interface material. Compared with traditional polymer thermally conductive interface materials, it has a high thermal conductivity and will not decompose in the coolant, solving the problems of easy swelling and dissolution of traditional polymer thermally conductive interface materials in immersion liquid cooling, as well as the resulting breakdown, stress mismatch, and solder joint cracking. The reaction between liquid metal and copper forms an alloy, which improves the material's filling capacity and solves the problems of easy leakage and corrosion of liquid metal in existing liquid metal thermal interface materials.

[0008] Preferably, the edges of the copper foil are sealed with high-temperature resistant double-sided adhesive.

[0009] Preferably, layers of copper foil coated with liquid metal are stacked to obtain a sandwich stacked structure. A layer of copper foil without liquid metal coating is then placed over the upper and lower surfaces of the sandwich stacked structure and fixed to obtain a copper-liquid metal mixture. This sandwich stacked structure, formed by stacking copper foil coated with liquid metal and covering the upper and lower surfaces with copper foil without liquid metal coating, further enhances the overall strength and stability of the material while improving its thermal conductivity, ensuring the material's integrity during high-temperature processing.

[0010] Further preferably, the preparation method of the copper-liquid metal composite thermal interface material includes the following steps.

[0011] 1) Preparation of liquid metal.

[0012] 2) Seal the edges of the copper foil with high-temperature resistant double-sided adhesive, then coat the inside of the sealed copper foil with liquid metal, and stack the copper foil coated with liquid metal layer by layer to obtain a sandwich stacked structure.

[0013] 3) Cover the upper and lower surfaces of the sandwich stacked structure with a layer of copper foil without liquid metal coating, and fix it with a clamp to obtain copper-liquid metal.

[0014] 4) The copper-liquid metal is subjected to high-temperature treatment or high-low temperature cycling treatment to obtain a copper-liquid metal composite thermal interface material. The above preparation steps can improve the quality of the final product.

[0015] Preferably, the liquid metal comprises the following components in mass percentage: gallium 50-100%, indium 0-50%, and tin 0-50%. This invention uses liquid metal with specific component ratios to ensure the characteristics and performance of the liquid metal, optimize its thermal conductivity and physical properties, better meet application requirements, and improve the applicability and flexibility of the material.

[0016] Further preferably, the liquid metal is selected from one or more of Ga, GaIn, GaSn, and GaInSn. In this invention, using a preferred liquid metal ensures high thermal conductivity and chemical stability.

[0017] Preferably, the thickness of the copper foil is 0.03~1mm.

[0018] Preferably, the thickness of the liquid metal (single layer) coating is 0.005~0.3mm.

[0019] This invention, by controlling the optimal thickness of the copper foil (0.03~1mm), ensures that the copper foil is not easily deformed during the coating of liquid metal and high-temperature treatment, thereby improving the overall performance and service life of the composite material and guaranteeing its strength and thermal conductivity. Reasonable control of the coating thickness prevents excessive flow of the liquid metal during the stacking process, maintains material consistency, and optimizes the material's thermal conductivity and stability. By optimizing the copper foil thickness and the liquid metal coating thickness, the structural balance and thermal conductivity of the material are ensured, optimizing its mechanical properties and thermal conductivity, and preventing various problems caused by excessively thick or thin coatings.

[0020] Further preferably, the copper foil coated with liquid metal has 3 to 25 layers, more preferably 4 to 8 layers. This invention limits the preferred number of layers, ensuring the stability of the composite material's thickness and performance. By rationally controlling the number of layers, both the material's efficient thermal conductivity and its mechanical strength and durability can be guaranteed, resulting in superior performance in practical applications.

[0021] Preferably, the high-temperature treatment is performed at a temperature of 100~500℃ for a duration of 72~1000h.

[0022] Preferably, the low temperature of the high and low temperature cycling treatment is -40 to -30°C, the high temperature is 60 to 250°C, and the time is 100 to 1200 hours.

[0023] Further preferably, the high and low temperature cycling treatment includes: constant temperature treatment at -40~-30℃ for 0.5~1h, and then constant temperature treatment at 60~250℃ for 0.5~1h, repeating the operation 100~600 times.

[0024] In this invention, by employing high-temperature treatment and high-low temperature cycling treatment under specific conditions, the material properties can be significantly improved. This effectively eliminates internal stress, enhances heat resistance and thermal conductivity, and optimizes the material's stability and durability under extreme temperature changes. This ensures the material can withstand frequent temperature fluctuations and maintain stable physical and chemical properties in practical applications. These treatment steps endow the material with not only excellent thermal conductivity but also long-term stability and reliability under extreme environmental conditions, making it suitable for various high-tech fields.

[0025] The second invention provides a copper-liquid metal composite thermal interface material, which is obtained by the above-mentioned method for preparing copper-liquid metal composite thermal interface material.

[0026] Preferably, the copper-liquid metal composite thermal interface material has a thermal conductivity greater than 67 W / (m·K) and a contact thermal resistance less than 0.06 K / cm. 2 / W.

[0027] Further preferably, the copper-liquid metal composite thermal interface material has a thermal conductivity of 80~156.5 W / (m·K) and a contact thermal resistance of less than 0.045 K·cm. 2 / W.

[0028] The beneficial effects of this invention are at least as follows: The high thermal conductivity copper-liquid metal composite thermal interface material and its preparation method provided by this invention, by reacting liquid metal with copper under high temperature or high and low temperature cycling conditions, obtains a high thermal conductivity copper-liquid metal composite thermal interface material as an effective heat dissipation component, solving the existing technical problems of thermal interface materials; the combination of copper and liquid metal can improve the thermal conductivity and stability of the composite thermal interface material, and compared with traditional polymer thermally conductive interface materials, it has a high thermal conductivity coefficient and will not be decomposed in the coolant, solving the problems of easy swelling and dissolution of traditional polymer thermally conductive interface materials in immersion liquid cooling, as well as the problems of breakdown, stress mismatch, and solder joint cracking; the reaction of liquid metal with copper to form an alloy improves the material filling capacity and solves the problems of easy leakage and corrosion of liquid metal in existing liquid metal thermal interface materials. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0030] Figure 1 This is a microstructure diagram of the high thermal conductivity copper-liquid metal composite thermal interface material in Example 2. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0032] In this embodiment of the invention, the thermal conductivity test adopts the GB / T22588-2008 standard and is conducted at an environmental temperature of 25±1℃. In this embodiment of the invention, the fixture is fixed by using a 2-5mm thick stainless steel (or carbon steel) metal plate with dimensions not smaller than that of copper foil. In this embodiment of the invention, the liquid metal is uniformly coated inside the cavity enclosed by double-sided adhesive, with a single layer thickness of 0.05-0.2mm.

[0033] Example 1

[0034] This embodiment provides a method for preparing a high thermal conductivity copper-liquid metal composite thermal interface material, including the following steps.

[0035] 1) Prepare liquid metal by heating 76 parts Ga, 15 parts In and 9 parts Sn to 100°C and melting to obtain the liquid metal alloy. The melting time is 30~60 min. After melting, cool to room temperature for later use.

[0036] 2) Apply double-sided adhesive with a temperature resistance of 300℃ to the edge of a copper foil with a thickness of 0.1mm and a length and width of 15cm, seal the edge, and evenly coat the liquid metal inside. Stack 5 copper foils coated with the liquid metal to form a sandwich stacked structure.

[0037] 3) Cover the upper and lower surfaces of the sandwich stacked structure with a layer of copper foil without liquid metal coating, and use a fixture to fix it to prepare copper-liquid metal.

[0038] 4) The copper-liquid metal is reacted at a high temperature of 250°C for 720 hours to obtain a high thermal conductivity copper-liquid metal composite thermal interface material.

[0039] The final high thermal conductivity copper-liquid metal composite thermal interface material has a thermal conductivity of 89 W / (m·K) and a contact thermal resistance of 0.032 K·cm. 2 / W.

[0040] Example 2

[0041] This embodiment provides a method for preparing a high thermal conductivity copper-liquid metal composite thermal interface material, including the following steps.

[0042] 1) Prepare liquid metal by heating 100 parts of Ga to 35°C and melting to obtain the liquid metal alloy. The melting time is 30~60 minutes. The alloy is then ready for use.

[0043] 2) Apply double-sided adhesive with a temperature resistance of 300℃ to the edge of a copper foil with a thickness of 0.05mm and a length and width of 15cm, seal the edge, and evenly coat the liquid metal inside. Stack 8 copper foils coated with the liquid metal to form a sandwich stacked structure.

[0044] 3) Cover the upper and lower surfaces of the sandwich stacked structure with a layer of copper foil without liquid metal coating, and use a fixture to fix it to prepare copper-liquid metal.

[0045] 4) The copper-liquid metal is placed in a high and low temperature cycling chamber at -40~125℃. The environment is kept at -40℃ for 30 minutes, and then rapidly switched (each switching time is 5 seconds) to the environment at 125℃ for 30 minutes. This cycle is repeated 500 times to obtain a high thermal conductivity copper-liquid metal composite thermal interface material.

[0046] The final high thermal conductivity copper-liquid metal composite thermal interface material has a thermal conductivity of 96 W / (m·K) and a contact thermal resistance of 0.026 K·cm. 2 / W. The microstructure of the high thermal conductivity copper-liquid metal composite thermal interface material provided in this embodiment is as follows: Figure 1 As shown.

[0047] Example 3

[0048] This embodiment provides a method for preparing a high thermal conductivity copper-liquid metal composite thermal interface material, including the following steps.

[0049] 1) Prepare liquid metal by heating 80 parts of Ga and 20 parts of In to 100°C and melting to obtain the liquid metal alloy. The melting time is 30-60 minutes. After melting, cool to room temperature for later use.

[0050] 2) Apply double-sided adhesive with a temperature resistance of 300℃ to the edge of a copper foil with a thickness of 0.2mm and a length and width of 15cm, seal the edge, and evenly coat the liquid metal inside. Stack the four copper foils coated with the liquid metal to form a sandwich stacked structure.

[0051] 3) Cover the upper and lower surfaces of the sandwich stacked structure with a layer of copper foil without liquid metal coating, and use a fixture to fix it to prepare copper-liquid metal.

[0052] 4) The copper-liquid metal is placed in a high-temperature environment of 300℃ for 680h to prepare a high thermal conductivity copper-liquid metal composite thermal interface material.

[0053] The final high thermal conductivity copper-liquid metal composite thermal interface material has a thermal conductivity of 91 W / (m·K) and a contact thermal resistance of 0.027 K·cm. 2 / W.

[0054] Example 4

[0055] This embodiment provides a method for preparing a high thermal conductivity copper-liquid metal composite thermal interface material, including the following steps.

[0056] 1) Prepare liquid metal by heating 85 parts of Ga and 15 parts of Sn to 100°C to obtain the liquid metal alloy. The melting time is 30~60 min. After melting, cool to room temperature for later use.

[0057] 2) Apply double-sided adhesive with a temperature resistance of 300℃ to the edge of a copper foil with a thickness of 0.2mm and a length and width of 15cm, seal the edge, and evenly coat the liquid metal inside. Stack 5 copper foils coated with the liquid metal to form a sandwich stacked structure.

[0058] 3) Cover the upper and lower surfaces of the sandwich stacked structure with a layer of copper foil without liquid metal coating, and use a fixture to fix it to prepare copper-liquid metal.

[0059] 4) The copper-liquid metal is placed in a high and low temperature cycling chamber at -40~125℃. The environment is kept at -40℃ for 45 minutes, and then rapidly switched (each switching time is 5 seconds) to the environment at 125℃ for 45 minutes. This cycle is repeated 400 times to obtain a high thermal conductivity copper-liquid metal composite thermal interface material.

[0060] The final high thermal conductivity copper-liquid metal composite thermal interface material has a thermal conductivity of 88 W / (m·K) and a contact thermal resistance of 0.028 K·cm. 2 / W.

[0061] Example 5

[0062] This embodiment provides a method for preparing a high thermal conductivity copper-liquid metal composite thermal interface material, including the following steps.

[0063] 1) Prepare liquid metal by heating 65 parts Ga, 25 parts In and 10 parts Sn to 100°C and melting to obtain the liquid metal alloy. The melting time is 30~60 min. After melting, cool to room temperature for later use.

[0064] 2) Apply double-sided adhesive with a temperature resistance of 300℃ to the edge of a copper foil with a thickness of 0.05mm and a length and width of 15cm, seal the edge, and evenly coat the liquid metal inward. Stack 6 copper foils coated with the liquid metal to form a sandwich stacked structure.

[0065] 3) Cover the upper and lower surfaces of the sandwich stacked structure with a layer of copper foil without liquid metal coating, and use a fixture to fix it to prepare copper-liquid metal.

[0066] 4) The copper-liquid metal is placed in a high and low temperature cycling chamber of -40~125℃, kept at -40℃ for 60 minutes, and then rapidly switched (each switching time is 5 seconds) to keep at 125℃ for 60 minutes. This cycle is repeated 200 times to obtain a high thermal conductivity copper-liquid metal composite thermal interface material.

[0067] The final high thermal conductivity copper-liquid metal composite thermal interface material has a thermal conductivity of 83 W / (m·K) and a contact thermal resistance of 0.024 K·cm. 2 / W.

[0068] Comparative Example 1

[0069] This comparative example provides a method for preparing a high thermal conductivity copper-liquid metal composite thermal interface material, including the following steps.

[0070] 1) Prepare liquid metal by heating 65 parts Ga, 25 parts In and 10 parts Sn to 100°C and melting to obtain the liquid metal alloy. The melting time is 30~60 min. After melting, cool to room temperature for later use.

[0071] 2) Apply double-sided adhesive with a temperature resistance of 300℃ to the edge of a copper foil with a thickness of 0.05mm and a length and width of 15cm, seal the edge, and evenly coat the liquid metal inward. Stack 6 copper foils coated with the liquid metal to form a sandwich stacked structure.

[0072] 3) Cover the upper and lower surfaces of the sandwich stacked structure with a layer of copper foil without liquid metal coating, and use a fixture to fix it to prepare copper-liquid metal.

[0073] 4) The copper-liquid metal is placed in a high and low temperature cycling chamber at -40~125℃. The environment is kept at -40℃ for 30 minutes, and then rapidly switched (each switching time is 5 seconds) to the environment at 125℃ for 30 minutes. This cycle is repeated 80 times to obtain a high thermal conductivity copper-liquid metal composite thermal interface material.

[0074] The resulting high thermal conductivity copper-liquid metal composite thermal interface material has a thermal conductivity of 95 W / (m·K) and a contact thermal resistance of 0.12 K·cm. 2 / W. This comparative example differs from Example 5 only in the cycle time. Although the thermal conductivity is also within the range of this invention, the contact thermal resistance is 5 times that of Example 5, which cannot meet the usage requirements and does not achieve the effect of traditional thermal interface materials.

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a copper-liquid metal composite thermal interface material, characterized in that, include: The edges of the copper foil are sealed with high-temperature resistant double-sided tape, and then liquid metal is coated on the surface of the copper foil to obtain copper foil coated with liquid metal. Then, the copper foil coated with liquid metal is stacked layer by layer to obtain a sandwich stacked structure. A layer of copper foil without liquid metal is covered on the upper and lower surfaces of the sandwich stacked structure and fixed to obtain copper-liquid metal. The copper-liquid metal was subjected to high and low temperature cycling treatment to obtain a copper-liquid metal composite thermal interface material; The high and low temperature cycling treatment includes: constant temperature treatment at -40~-30℃ for 0.5~1h, and then constant temperature treatment at 60~250℃ for 0.5~1h, repeating the operation 100~600 times.

2. The method for preparing the copper-liquid metal composite thermal interface material according to claim 1, characterized in that, Includes the following steps: 1) Preparation of liquid metal; 2) Seal the edges of the copper foil with high-temperature resistant double-sided adhesive, then coat the inside of the sealed copper foil with liquid metal, and stack the copper foil coated with liquid metal layer by layer to obtain a sandwich stacked structure. 3) Cover the upper and lower surfaces of the sandwich stacked structure with a layer of copper foil without liquid metal coating, and fix it with a clamp to obtain copper-liquid metal; 4) The copper-liquid metal is subjected to high and low temperature cycling treatment to obtain a copper-liquid metal composite thermal interface material.

3. The method for preparing the copper-liquid metal composite thermal interface material according to claim 1, characterized in that, The liquid metal comprises the following components by mass percentage: gallium 50-100%, indium 0-50%, and tin 0-50%.

4. The method for preparing the copper-liquid metal composite thermal interface material according to claim 3, characterized in that, The liquid metal is selected from one or more of Ga, GaIn, GaSn, and GaInSn.

5. The method for preparing the copper-liquid metal composite thermal interface material according to any one of claims 1-4, characterized in that, The thickness of the copper foil is 0.03~1mm; And / or, the thickness of the single layer of liquid metal coating is 0.005~0.3mm.

6. A copper-liquid metal composite thermal interface material, characterized in that, It is obtained by the preparation method of the copper-liquid metal composite thermal interface material according to any one of claims 1-5.

7. The copper-liquid metal composite thermal interface material according to claim 6, characterized in that, The copper-liquid metal composite thermal interface material has a thermal conductivity greater than 67 W / (m·K) and a contact thermal resistance less than 0.06 K / cm. 2 / W.

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