Graphite film low-temperature connection method based on core-shell nano transition layer

Abstract

The application relates to a graphite film low-temperature connecting method based on a core-shell nano transition layer, which comprises the following steps: raising the temperature of a graphite film / nano transition layer / graphite film laminated structure to 80-350 DEG C and keeping for 100-120 s, realizing low-temperature bonding of the graphite film, and realizing reliable connection of the graphite film through the synergistic effect of low-temperature bonding, self-adaptive matching and gradient conduction; the nano transition layer system is prepared from core-shell structure nanoparticles, liquid crystal state dispersion medium and directional arrangement aid, the core-shell structure nanoparticles are composed of 30-50 nm boron nitride wrapped graphene quantum dots, the liquid crystal state dispersion medium is fluorine-containing benzocyclobutene resin, and the directional arrangement aid is a magnetic field response type carbon nanotube. The application provides the nano transition layer system with temperature and stress double response characteristics, and realizes efficient and reliable connection of the graphite film through the synergistic effect of low-temperature bonding, self-adaptive matching and gradient conduction.

Description

Technical Field

[0001] This invention relates to graphite film bonding technology for high-performance heat dissipation in the field of thermal interface materials, specifically a low-temperature bonding method for graphite films based on a core-shell nano-transition layer. Background Technology

[0002] In modern electronic devices, heat dissipation performance directly affects the stability and lifespan of the equipment. Graphite film, as a high-performance thermally conductive material, is widely used in the heat dissipation systems of electronic devices due to its high thermal conductivity, low coefficient of thermal expansion, and good mechanical properties. However, the bonding technology of graphite film has always been a key bottleneck restricting its application. Currently, the bonding methods for graphite film mainly include traditional welding, adhesive bonding, and mechanical pressing, but these methods all have significant drawbacks. Traditional welding processes require high temperatures (>300 ℃), which causes distortion of the lattice structure of the graphite film, resulting in a 40%~60% decrease in the thermal conductivity of the heat-affected zone. This high-temperature treatment not only damages the original properties of the graphite film but may also introduce additional thermal stress, affecting its mechanical stability.

[0003] While adhesive bonding is convenient, it suffers from poor thermal conductivity; typical epoxy resins have a thermal conductivity of only 0.2–1.5 W / mK. This low thermal conductivity introduces significant interfacial thermal resistance at the graphite film bonding interface, severely impacting heat dissipation.

[0004] While mechanical crimping avoids high temperatures and the use of adhesives, micro-gaps still exist after crimping due to the slight unevenness on the graphite film surface. These micro-gaps significantly increase contact thermal resistance, accounting for more than 65% of the total thermal resistance, thereby reducing heat dissipation efficiency.

[0005] With the increasing performance and miniaturization of electronic devices, heat dissipation has become a key factor restricting their performance. Graphite films, due to their excellent thermal conductivity and mechanical properties, have been widely used in the field of electronic device heat dissipation. However, existing graphite film bonding technologies still have many bottlenecks, limiting their application in high-performance heat dissipation systems. Therefore, developing an efficient and reliable graphite film bonding method is of significant practical importance.

[0006] In summary, existing graphite film bonding technologies cannot meet all the requirements of high-performance heat dissipation systems for low thermal resistance, high thermal conductivity, and mechanical reliability. Therefore, developing a novel graphite film bonding method to overcome the shortcomings of existing technologies is a pressing technical challenge. There is an urgent need in this field for a novel bonding method that can achieve bonding at low temperatures, adaptively fill microscopic irregularities at the interface, and construct efficient three-dimensional thermal conduction pathways, thereby simultaneously addressing the problems of high-temperature damage, high interface thermal resistance, and poor mechanical reliability. Summary of the Invention The purpose of this invention is to provide a low-temperature graphite film bonding method based on a core-shell nano-transition layer. This method addresses the problems of high-temperature damage, high interfacial thermal resistance, and poor mechanical reliability in existing graphite film bonding technologies.

[0007] The technical solution adopted by this invention to solve its technical problem is as follows: This low-temperature bonding method for graphite films based on a core-shell nano-transition layer involves heating the graphite film / nano-transition layer / graphite film stacked structure to 80-350 ℃ at a heating rate of 1-3 ℃ / s and holding it for 100-120 s. The active components in the nano-transition layer are activated, achieving low-temperature bonding of the graphite film. Through the synergistic effect of low-temperature bonding, adaptive matching, and gradient conduction, reliable bonding of the graphite film is achieved. The nano-transition layer system is prepared from core-shell structured nanoparticles, a liquid crystal dispersion medium, and an orientation accelerator, possessing dual temperature and stress response characteristics. The core-shell structured nanoparticles consist of 30-50 nm boron nitride-encapsulated graphene quantum dots, with a BET specific surface area of ​​50-300 m². 2 / g, the liquid crystal dispersion medium is fluorinated benzocyclobutene resin, and the orientation accelerator is magnetic field responsive carbon nanotubes.

[0008] The low-temperature bonding method for graphite films based on core-shell nano-transition layers in the above scheme includes the following steps: a) Prepare a nano-transition layer; b) Pre-treat the surface of the graphite film; c) Stack the graphite film with the nano-transition layer, and then enter the pre-compression stage. Apply a contact pressure of 0.5~1.5 MPa and maintain it for 30~60 s to ensure that the surface of the graphite film and the nano-transition layer are in full contact. d) Bonding stage: The temperature of the laminated structure is raised to 80~350 ℃ at a heating rate of 1~3 ℃ / s and held for 100~120 s. The laminated structure is bonded and cured under low temperature conditions to form covalent bond networks such as BCN, and achieve chemical locking and corrugated interlocking micromorphology. e) Stabilization stage: Apply an alternating magnetic field of 0.1~1.5 T and 50~100 kHz to the bonded and solidified multilayer structure to induce the directional alignment of carbon nanotubes. The action time is 100~120 s. Cool to room temperature at a cooling rate of 2~10℃ / min to complete the low-temperature bonding of graphite film.

[0009] The method for preparing the nano-transition layer in the above scheme is as follows: Step 1: Add the core-shell structured nanoparticles to the liquid crystal dispersion medium and ultrasonically disperse them for 10-40 min to ensure that the nanoparticles are uniformly dispersed in the liquid crystal dispersion medium, thus obtaining a uniformly dispersed system. Step 2: Add magnetic field responsive carbon nanotubes to the uniformly dispersed system obtained in Step 1, apply an alternating magnetic field with a frequency of 50~100 kHz and an intensity of 0.1~1.5 T for 15~25 min to orient the carbon nanotubes and form thermally conductive channels to obtain a mixed system. Step 3: Mixing and curing; Place the mixture in a water bath at 55~65 ℃ and stir at a stirring speed of 100~200 r / min for 15~20 min. Then cure the mixture at a low temperature of 80~120 ℃ for 60~90 min to form a stable nano-transition layer.

[0010] The method for pretreating the graphite film surface in the above scheme is as follows: the graphite film is subjected to plasma treatment with a treatment power of 100~200 W and a treatment time of 5~10 min.

[0011] In the above scheme, the specific microstructure of the corrugated interlocking is that the peak spacing is 5~8 μm and the height difference is 1.2~2.5 μm.

[0012] In the above schemes, covalent networks such as BCN have a length of 1360 cm⁻¹. -1 Characteristic peaks.

[0013] In the above scheme, adaptive matching enables the nano-transition layer to dynamically compensate for assembly tolerances of ±15 μm, thereby improving the reliability, adaptability, and thermal contact of the connection.

[0014] In the above scheme, gradient conduction is achieved by forming a three-dimensional heat conduction network through directional arrangement, constructing a network from sp 2 Hybridization to sp 3 Hybridized electron migration channels enable gradient optimization of heat conduction, improve heat dissipation performance, and enhance the mechanical stability of the interface.

[0015] Beneficial effects: 1. This invention provides a nano-transition layer system with dual temperature and stress response characteristics, and through the synergistic effect of low-temperature bonding, adaptive matching and gradient conduction, it successfully achieves efficient and reliable connection of graphite films.

[0016] 2. This invention utilizes a nano-transition layer system constructed from core-shell structured nanoparticles, liquid crystal dispersion medium, and directional alignment aids, and optimizes the interface structure through a three-stage welding process to achieve efficient and reliable connection of graphite films, significantly reducing interfacial thermal resistance and improving heat dissipation performance and connection reliability.

[0017] Low-temperature bonding: A stable covalent bond network is formed at a low activation temperature, avoiding the damage to the graphite film lattice structure caused by high temperatures, while significantly reducing interfacial thermal resistance. During this process, the boron nitride shell reacts with the plasma-treated graphite film surface and resin medium to form covalent bond networks such as BCN, achieving chemical locking and corrugated interlocking microstructures.

[0018] 3. Adaptive matching: The nano-transition layer can dynamically compensate for assembly tolerances of ±15 μm, improving the reliability and adaptability of the connection and ensuring good thermal contact under different assembly conditions.

[0019] 4. Gradient propagation: Constructing gradients from sp 2 Hybridization to sp 3 The hybrid electron migration channels enable gradient optimization of heat conduction, further improving heat dissipation performance. This gradient structure not only optimizes the heat flow path but also enhances the mechanical stability of the interface.

[0020] 5. Microstructure: A corrugated interlocking morphology is formed, with a peak spacing of 5–8 μm and a height difference of 1.2–2.5 μm. This unique morphology significantly increases the interfacial contact area and reduces micro-gap, thereby lowering contact thermal resistance. Simultaneously, the corrugated interlocking structure exhibits good self-adaptability under mechanical stress, further improving the reliability of the connection.

[0021] 6. Chemical bonding: A BCN ternary covalent bond is formed, which is detected at 1360 cm⁻¹ by Raman spectroscopy. -1 The characteristic peaks indicate that a stable chemical bond has been achieved between the nano-transition layer and the graphite film, significantly enhancing the interfacial bonding strength.

[0022] 7. Thermal Conductive Network: This oriented arrangement constructs a continuous thermal conduction path from the in-plane to the vertical direction, significantly reducing the anisotropy ratio of the transition layer and forming a highly efficient three-dimensional thermal conductive network. This optimized three-dimensional thermal conductive network enables rapid heat transfer, significantly improving heat dissipation performance. Simultaneously, the three-dimensional network structure also enhances the mechanical stability of the interface, allowing it to withstand greater mechanical stress.

[0023] 8. This invention is applicable to ultra-thin and efficient heat dissipation systems in fields such as communication equipment, power battery packs, and high-power LEDs.

[0024] Instruction manual illustrations: Figure 1 This is a diagram of a graphite film connector. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings: This low-temperature bonding method for graphite films based on core-shell nano-transition layers involves utilizing a nano-transition layer system with dual temperature and stress response characteristics to achieve efficient and reliable bonding of graphite films through the synergistic effects of low-temperature bonding, adaptive matching, and gradient conduction.

[0026] Key components of the nano-transition layer material system: The nano-transition layer material system consists of the following key components: core-shell structured nanoparticles, liquid crystal dispersion medium, and orientation accelerator.

[0027] The core-shell structured nanoparticles consist of graphene quantum dots encapsulated in boron nitride at a density of 30–50 nm, and have a BET specific surface area of ​​50–300 m². 2 / g. The boron nitride shell provides abundant bonding active sites, while the highly thermally conductive graphene quantum dot core ensures the continuity of the heat conduction pathway. This core-shell structure design ensures both low-temperature bonding and optimized thermal conductivity.

[0028] Fluorinated benzocyclobutene resin was selected as the liquid crystal dispersion medium, with a viscosity controllable between 500 and 1000 mPa·s. This resin exhibits good flowability and film-forming properties, enabling uniform dispersion of nanoparticles during the bonding process to form a stable nano-transition layer. Furthermore, its liquid crystal properties facilitate rapid curing at low temperatures, further optimizing the interface structure.

[0029] The directional alignment aid is magnetic field-responsive carbon nanotubes with an aspect ratio of 100–1000. While the system is still in a well-fluid mixing stage, an alternating magnetic field with a frequency of 50–100 kHz and an intensity of 0.1–1.5 T is applied to directionally align the carbon nanotubes, forming highly efficient heat-conducting channels. This directional alignment not only optimizes the heat flow path but also significantly improves the mechanical properties of the nano-transition layer.

[0030] The low-temperature bonding method for graphite films based on core-shell nano-transition layers of this invention is as follows: a) Prepare a nano-transition layer; b) Pre-treat the surface of the graphite film. The graphite film needs to be treated with plasma before bonding. The treatment power is 100~200 W and the treatment time is 5~10 min.

[0031] c) The graphite film is laminated with the nano-transition layer to form a graphite film / nano-transition layer / graphite film stacked structure. Then, a pre-compression stage is initiated, applying a contact pressure of 0.5–1.5 MPa and maintaining it for 30–60 s to ensure sufficient contact between the graphite film surface and the nano-transition layer, providing favorable initial conditions for subsequent bonding processes. The main objective of this stage is to achieve a uniform distribution of the nano-transition layer on the graphite film surface by applying appropriate pressure, thereby reducing contact thermal resistance.

[0032] d) Bonding Stage: The temperature of the laminated structure is raised to 80-350 ℃ at a heating rate of 1-3 ℃ / s and held for 100-120 s. Bonding and curing of the laminated structure are carried out under low-temperature conditions, forming a covalent bond network such as BCN, achieving a chemically locked and corrugated interlocking microstructure. During this process, the active components in the nano-transition layer are activated, achieving low-temperature bonding of the graphite film. The key to this stage is precise control of temperature and time to ensure the uniform formation of the covalent bond network.

[0033] e) Stabilization Stage: During the thermal insulation stage of the above process, an alternating magnetic field of 0.1–1.5 T and 50–100 kHz is applied to induce the directional alignment of carbon nanotubes. The action time is 100–120 s, followed by cooling to room temperature at a cooling rate of 2–10 °C / min to complete the connection. In this stage, the magnetic field further optimizes the microstructure of the nano-transition layer, improving its thermal conductivity and mechanical properties. The use of the alternating magnetic field not only promotes the directional alignment of carbon nanotubes but also reduces interfacial stress caused by uneven thermal expansion.

[0034] The mixing preparation steps of the nano-transition layer in this invention are as follows: 1. Dispersed core-shell structured nanoparticles: Take an appropriate amount of liquid crystal dispersion medium and add core-shell structured nanoparticles into it. Use ultrasonic dispersion, and control the reaction time to 10-40 min to ensure that the nanoparticles are uniformly dispersed in the liquid crystal dispersion medium.

[0035] 2. Add and orient the additives: Magnetic field-responsive carbon nanotubes were added to the pre-dispersed system. An alternating magnetic field with a frequency of 50–100 kHz and an intensity of 0.1–1.5 T was applied for 15–25 min to orient the carbon nanotubes and form efficient heat-conducting channels.

[0036] 3. Mixing and curing: The mixture was placed in a water bath at 55–65 °C and stirred at 100–200 r / min for 15–20 min to ensure thorough mixing of all components. Based on the characteristics of the liquid crystal dispersion medium, the mixture was cured at a low temperature of 80–120 °C for 60–90 min to form a stable nano-transition layer.

Claims

1. A low-temperature bonding method for graphite films based on a core-shell nano-transition layer, characterized in that: This low-temperature bonding method for graphite films based on a core-shell nano-transition layer involves heating a graphite film / nano-transition layer / graphite film stacked structure to 80-350℃ at a heating rate of 1-3℃ / s and holding it for 100-120 s. The active components in the nano-transition layer are activated, achieving low-temperature bonding of the graphite film. Reliable bonding of the graphite films is achieved through the synergistic effects of low-temperature bonding, adaptive matching, and gradient conduction. The nano-transition layer system is prepared from core-shell structured nanoparticles, a liquid crystal dispersion medium, and an orientation accelerator, exhibiting dual temperature and stress response characteristics. The core-shell structured nanoparticles consist of 30-50 nm boron nitride-encapsulated graphene quantum dots, with a BET specific surface area of ​​50-300 m². 2 / g, the liquid crystal dispersion medium is fluorinated benzocyclobutene resin, and the orientation accelerator is magnetic field responsive carbon nanotubes.

2. The low-temperature bonding method for graphite films based on a core-shell nano-transition layer according to claim 1, characterized in that... Includes the following steps: a) Prepare a nano-transition layer; b) Pre-treat the surface of the graphite film; c) Stack the graphite film with the nano-transition layer, and then enter the pre-compression stage. Apply a contact pressure of 0.5~1.5 MPa and maintain it for 30~60 s to ensure that the surface of the graphite film and the nano-transition layer are in full contact. d) Bonding stage: The temperature of the laminated structure is raised to 80~350℃ at a heating rate of 1~3℃ / s and held for 100~120s. The laminated structure is bonded and cured under low temperature conditions to form covalent bond networks such as BCN, and to achieve chemical locking and corrugated interlocking microstructure. e) Stabilization stage: Apply an alternating magnetic field of 0.1~1.5 T and 50~100 kHz to the bonded and solidified multilayer structure to induce the directional alignment of carbon nanotubes. The action time is 100~120 s. Cool to room temperature at a cooling rate of 2~10℃ / min to complete the low-temperature bonding of graphite film.

3. The low-temperature bonding method for graphite films based on a core-shell nano-transition layer according to claim 2, characterized in that: The method for preparing the nano-transition layer is as follows: Step 1: Add the core-shell structured nanoparticles to the liquid crystal dispersion medium and ultrasonically disperse them for 10-40 min to ensure that the nanoparticles are uniformly dispersed in the liquid crystal dispersion medium, thus obtaining a uniformly dispersed system. Step 2: Add magnetic field responsive carbon nanotubes to the uniformly dispersed system obtained in Step 1, apply an alternating magnetic field with a frequency of 50~100 kHz and an intensity of 0.1~1.5 T for 15~25 min to orient the carbon nanotubes and form thermally conductive channels to obtain a mixed system. Step 3: Mixing and curing; The mixture was placed in a water bath at 55-65°C and stirred at 100-200 r / min for 15-20 min. The mixture was then cured at a low temperature of 80-120°C for 60-90 min to form a stable nano-transition layer.

4. The low-temperature bonding method for graphite films based on a core-shell nano-transition layer according to claim 3, characterized in that: The method for pretreating the graphite film surface is as follows: the graphite film is subjected to plasma treatment with a treatment power of 100~200W and a treatment time of 5~10 min.

5. The low-temperature bonding method for graphite films based on a core-shell nano-transition layer according to claim 4, characterized in that: The specific microstructure of the corrugated interlocking is characterized by a peak spacing of 5-8 μm and a height difference of 1.2-2.5 μm.

6. The low-temperature bonding method for graphite films based on a core-shell nano-transition layer according to claim 5, characterized in that: The BCN and other covalent bond networks have a length of 1360 cm⁻¹ -1 Characteristic peaks.

7. The low-temperature bonding method for graphite films based on a core-shell nano-transition layer according to claim 6, characterized in that: The adaptive matching is that the nano-transition layer can dynamically compensate for assembly tolerances of ±15 μm, improving the reliability, adaptability and thermal contact of the connection.

8. The low-temperature bonding method for graphite films based on a core-shell nano-transition layer according to claim 7, characterized in that: The gradient conduction is achieved by forming a three-dimensional heat-conducting network through directional arrangement, constructing a structure from sp 2 Hybridization to sp 3 Hybridized electron migration channels enable gradient optimization of heat conduction, improve heat dissipation performance, and enhance the mechanical stability of the interface.

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