Preparation method of lightweight high-power heat dissipation aluminum-based bidirectional carbon network composite heat sink plate
By optimizing the connection between aluminum alloy and carbon nanotube-reinforced aluminum foam composite materials through brazing technology, the heat dissipation efficiency problem of traditional heat dissipation materials under lightweight and high power density conditions is solved, achieving efficient heat conduction and temperature control.
Patent Information
- Application Number
- CN202610003161.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-05
- Publication Date
- 2026-02-24
AI Technical Summary
Traditional heat dissipation materials have limitations in terms of weight and heat dissipation efficiency in terms of lightweighting and high power density. Riveting and bonding methods have problems such as increased mass or poor high temperature resistance when joining dissimilar materials. Brazing technology has not been fully explored when joining aluminum alloys and carbon nanotube reinforced aluminum foam composite materials.
Brazing technology is used in a vacuum environment to control the brazing temperature and holding time. The material surface is treated by mechanical grinding and ultrasonic cleaning to form a connecting component of aluminum alloy plate-brazing seam-porous composite material, which optimizes the generation of interfacial reaction phases and improves the interfacial connection strength and thermal conductivity.
This achievement enables efficient heat dissipation for lightweight high-power devices. The thermal conductivity of the aluminum-based bidirectional carbon network composite heat sink plate has been increased to 34.3 W·m⁻¹·K⁻¹, and the surface steady-state temperature has been reduced by 19.1 ℃, providing theoretical and technical support.
Smart Images
Figure CN121551732A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of brazing technology. Background Technology
[0002] Heat sinks, as a core component of thermal management systems for modern electronic devices and high-power devices, are functional structural components specifically designed to absorb, diffuse, and ultimately dissipate heat. Their core function is to rapidly transfer Joule heat or operating heat generated by the heat source to the surrounding environment through efficient heat conduction and convection, thereby preventing performance degradation or equipment failure caused by temperature buildup. An ideal heat sink typically requires high thermal conductivity, low density, good structural strength, and excellent heat dissipation surface area. However, with the rapid development of electronic devices towards lightweight, miniaturized, and high-power-density designs, the limitations of traditional heat dissipation materials (such as pure aluminum or copper) in terms of weight and heat dissipation efficiency are becoming increasingly apparent. Therefore, developing novel lightweight, high-conductivity composite materials and effectively integrating them into reliable heat sink components has become a key research focus and cutting-edge direction in the field of thermal management.
[0003] In recent years, aluminum foam has attracted widespread attention from researchers in the field of thermal management. Its porous structure gives it excellent convective heat transfer performance, enabling rapid reduction of heat source temperature in air-cooled or liquid-cooled environments. Furthermore, its low density makes it a promising candidate for lightweight heat dissipation. However, aluminum foam itself has low thermal conductivity, typically less than 8 W / m². -1 ·K -1 However, heat dissipation capabilities remain insufficient in the face of severe heat accumulation in high-power devices. In our previous research, we successfully fabricated a two-dimensional carbon hierarchical structure composed of a high-crystalline carbon layer (HCC) and a carbon nanotube (carbon nanotube) reinforced aluminum foam (AF) composite material. The effective thermal conductivity of the composite material is 43.17 W·m. -1 ·K -1 This is 5.6 times faster than pure autofocus. The instantaneous cooling rate is 16.1 Ks. -1The 34.6% cooling efficiency demonstrates the superior heat dissipation performance of the composite material compared to other similar carbon-reinforced radiators, showing positive potential in heat dissipation applications. Aluminum alloys, with their lightweight and high mechanical strength, are widely used as ideal materials for lightweight heat dissipation structures. This characteristic makes the effective combination of aluminum alloys with bidirectional carbon hierarchical structures crucial for manufacturing practical heat sink components. Various techniques exist for joining these dissimilar materials, including adhesive bonding, riveting, and brazing. However, riveting significantly increases structural mass while inducing localized stress concentration, while adhesive bonding suffers from poor high-temperature resistance and low joint strength. In contrast, brazing offers superior joint strength and excellent high-temperature resistance, and eliminates mechanical stress concentration, making it a promising and ideal method for joining dissimilar materials. This study investigated the influence of brazing temperature and holding time on the joint microstructure, analyzed the mechanism by which phase composition and interface structure affect the overall thermal conductivity and heat dissipation performance of the heat sink component, and determined the optimal brazing process parameters. The differences in thermal conductivity and heat dissipation performance of heat sink components made with different heat sink materials were then compared, highlighting the advantages of forming heat sink components by brazing MGS-CNTs / foamed aluminum porous composite materials, which provides important theoretical and technical support for efficient heat dissipation of lightweight high-power devices.
[0004] I. Pre-treatment of experimental materials:
[0005] An aluminum plate, brazing filler metal, and porous composite material are stacked sequentially to form a sandwich structure, with a pressure of 2N~4N consistently applied above the porous composite material during brazing. The contact surfaces of the aluminum plate, porous composite material, and brazing filler metal are mechanically ground, with the surface roughness Ra value controlled within the range of 0.1-0.4μm. The surfaces of the aluminum plate, brazing filler metal, and porous composite material are then cleaned using an ultrasonic cleaning solution to remove oil, oxides, and other impurities. The cleaning process lasts 20~40 minutes, with the temperature controlled between 20~70℃.
[0006] II. Brazing:
[0007] In the brazing experiment, the obtained assembly was placed in a vacuum brazing furnace and evacuated to a vacuum level of 1×10⁻⁶. -4 Pa~5×10 -3 Pa is held at a temperature of 360℃~480℃, heated to 360℃~480℃ at a heating rate of 10℃ / min~15℃ / min, held at 360℃~480℃ for 5~20℃ / min, and then cooled to room temperature at a cooling rate of 2℃ / min~10℃ / min. After cooling, a brazed connection component of aluminum alloy plate-brazed seam-porous composite material is formed.
[0008] The aluminum-based bidirectional carbon network composite heat sink plate prepared by this invention provides important theoretical and technical support for efficient heat dissipation of lightweight high-power devices. Summary of the Invention
[0009] This invention proposes a method for preparing a lightweight, high-power aluminum-based two-way carbon network composite heat sink. It explores the influence of brazing temperature and holding time on the microstructure of the joint, analyzes the mechanism by which phase composition and interface structure affect the overall thermal conductivity and heat dissipation performance of the heat sink component, and determines the optimal brazing process parameters. Then, it compares the differences in thermal conductivity and heat dissipation performance of heat sink components prepared using different heat sink materials, highlighting the advantages of brazing MGS-CNTs / foamed aluminum porous composite materials to form heat sink components. This provides important theoretical and technical support for efficient heat dissipation of lightweight, high-power devices. The method for preparing a lightweight, high-power aluminum-based two-way carbon network composite heat sink is completed according to the following steps:
[0010] I. Pre-treatment of experimental materials:
[0011] An aluminum plate, brazing filler metal, and porous composite material are stacked sequentially to form a sandwich structure, with a pressure of 2N~4N consistently applied above the porous composite material during brazing. The contact surfaces of the aluminum plate, porous composite material, and brazing filler metal are mechanically ground, with the surface roughness Ra value controlled within the range of 0.1-0.4μm. The surfaces of the aluminum plate, brazing filler metal, and porous composite material are then cleaned using an ultrasonic cleaning solution to remove oil, oxides, and other impurities. The cleaning process lasts 20~40 minutes, with the temperature controlled between 20~70℃.
[0012] II. Brazing:
[0013] In the brazing experiment, the obtained assembly was placed in a vacuum brazing furnace and evacuated to a vacuum level of 1×10⁻⁶. -4 Pa~5×10 -3 Pa is held at a temperature of 360℃~480℃, heated to 360℃~480℃ at a heating rate of 10℃ / min~15℃ / min, held at 360℃~480℃ for 5~20℃ / min, and then cooled to room temperature at a cooling rate of 2℃ / min~10℃ / min. After cooling, a brazed connection component of aluminum alloy plate-brazed seam-porous composite material is formed.
[0014] The beneficial effects of this invention are:
[0015] (1) Increased brazing temperature promotes the dissolution of the base material and the diffusion of elements, which is beneficial for enhancing interfacial bonding and promoting the formation of reactive phases. When the brazing temperature is 330 ℃ and the holding time is 10 min, a continuous reactive layer is formed at the aluminum plate / brazed joint interface, which enhances the heat conduction capacity of the brazed joint to the surrounding area. The thermal conductivity of the brazed heat sink component is 29.7 W·m. -1 ·K -1 At a constant heat flux density of 130 W·cm -2 Below, the steady-state temperature of the surface is 80.1 ℃.
[0016] (2) Increasing the holding time enhances the degree of elemental reaction, further increasing the content of the reactive phase. When the brazing temperature is 330 ℃ and the holding time is 15 min, a straight and continuous reaction layer forms inside the brazed seam, further enhancing the heat conduction ability to diffuse to the surroundings. The density of the heat sink component is 1.24 g·cm³. -3 The thermal conductivity further increased to 34.3 W·m. -1 ·K -1 At a constant heat flux density of 130 W·cm -2 Under these conditions, the steady-state temperature of the surface drops to 74.2 ℃.
[0017] (3) Heat sink components with different structures were prepared using different heat sink materials, highlighting the advantages of the MGS-CNTs / aluminum foam porous composite brazed heat sink component. The thermal conductivity of this heat sink component is 34.3 W·m. -1 ·K -1 It is the original aluminum foam heat sink component with a capacity of 4.8 W·m. -1 ·K -1 Seven times that at a constant heat flux density of 130 W·cm⁻¹. -2 The steady-state temperature of the original foamed aluminum heat sink component was 93.3 ℃, while the temperature of the porous composite brazed heat sink component decreased by 19.1 ℃. The brazed heat sink component prepared in this paper provides important theoretical and technical support for efficient heat dissipation of lightweight high-power devices. Attached Figure Description
[0018] Figure 1 Schematic diagram of brazing aluminum alloy plate and porous composite material
[0019] Figure 2 SEM morphology of brazed joints
[0020] Figure 3 Transmission electron microscopy images
[0021] Figure 4(a) Density test, (b) Specific heat capacity test, (c) Thermal diffusivity test, (d) Thermal conductivity test, (e) Global temperature profile, (f) Statistical results of steady-state temperature and arrival time, (g) Heating phase, (h) Cooling phase
[0022] Figure 5 Schematic diagrams of brazing mechanism and heat transfer mechanism in samples of aluminum alloy plate and porous composite material: (a) Brazing mechanism; (b) Heat transfer mechanism. Detailed Implementation
[0023] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments. Specific implementation method one:
[0025] I. Pre-treatment of experimental materials:
[0026] An aluminum plate, brazing filler metal, and porous composite material are stacked sequentially to form a sandwich structure, with a pressure of 2N~4N consistently applied above the porous composite material during brazing. The contact surfaces of the aluminum plate, porous composite material, and brazing filler metal are mechanically ground, with the surface roughness Ra value controlled within the range of 0.1-0.4μm. The surfaces of the aluminum plate, brazing filler metal, and porous composite material are then cleaned using an ultrasonic cleaning solution to remove oil, oxides, and other impurities. The cleaning process lasts 20~40 minutes, with the temperature controlled between 20~70℃.
[0027] II. Brazing:
[0028] In the brazing experiment, the obtained assembly was placed in a vacuum brazing furnace and evacuated to a vacuum level of 1×10⁻⁶. -4 Pa~5×10 -3 Pa is held at a temperature of 360℃~480℃, heated to 360℃~480℃ at a heating rate of 10℃ / min~15℃ / min, held at 360℃~480℃ for 5~20℃ / min, and then cooled to room temperature at a cooling rate of 2℃ / min~10℃ / min. After cooling, a brazed connection component of aluminum alloy plate-brazed seam-porous composite material is formed.
[0029] The beneficial effects of this embodiment are:
[0030] (1) Increased brazing temperature promotes the dissolution of the base material and the diffusion of elements, which is beneficial for enhancing interfacial bonding and promoting the formation of reactive phases. When the brazing temperature is 330 ℃ and the holding time is 10 min, a continuous reactive layer is formed at the aluminum plate / brazed joint interface, which enhances the heat conduction capacity of the brazed joint to the surrounding area. The thermal conductivity of the brazed heat sink component is 29.7 W·m. -1 ·K-1 At a constant heat flux density of 130 W·cm -2 Below, the steady-state temperature of the surface is 80.1 ℃.
[0031] (2) Increasing the holding time enhances the degree of elemental reaction, further increasing the content of the reactive phase. When the brazing temperature is 330 ℃ and the holding time is 15 min, a straight and continuous reaction layer forms inside the brazed seam, further enhancing the heat conduction ability to diffuse to the surroundings. The density of the heat sink component is 1.24 g·cm³. -3 The thermal conductivity further increased to 34.3 W·m. -1 ·K -1 At a constant heat flux density of 130 W·cm -2 Under these conditions, the steady-state temperature of the surface drops to 74.2 ℃.
[0032] (3) Heat sink components with different structures were prepared using different heat sink materials, highlighting the advantages of the MGS-CNTs / aluminum foam porous composite brazed heat sink component. The thermal conductivity of this heat sink component is 34.3 W·m. -1 ·K -1 It is the original aluminum foam heat sink component with a capacity of 4.8 W·m. -1 ·K -1 Seven times that at a constant heat flux density of 130 W·cm⁻¹. -2 The steady-state temperature of the original foamed aluminum heat sink component was 93.3 ℃, while the temperature of the porous composite brazed heat sink component decreased by 19.1 ℃. The brazed heat sink component prepared in this paper provides important theoretical and technical support for efficient heat dissipation of lightweight high-power devices.
[0033] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the thickness of the aluminum alloy plate, brazing filler metal sheet, and porous composite material is 2mm~8mm, and a pressure of 4N~8N is consistently applied above the porous composite material during the brazing process. Everything else is the same as in Specific Implementation Method One.
[0034] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that: in step one, the contact surfaces of the aluminum alloy plate, porous composite material, and brazing filler metal are mechanically ground. The surface roughness Ra value after grinding should be controlled within the range of 0.4~0.6μm. Everything else is the same as in Specific Implementation Methods One and Two.
[0035] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the cleaning process in Step One lasts for 20 to 40 minutes, and the temperature is controlled between 70 and 90°C. Everything else is the same as in Specific Implementation Methods One to Three.
[0036] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One through Four in that: a vacuum is drawn to 1×10⁻⁶. -5 Pa~5×10 -4 Pa. The rest is the same as in specific embodiments one through four.
[0037] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the solder used in step two is SAC-15. Everything else is the same as in Specific Implementation Methods One to Five.
[0038] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that, in the brazing experiment, the temperature is increased to 360℃~480℃ at a heating rate of 5℃ / min~10℃ / min. Everything else is the same as Specific Implementation Methods One to Six.
[0039] The beneficial effects of the present invention are verified using the following embodiments:
[0040] Example 1:
[0041] A method for preparing a lightweight, high-power heat dissipation aluminum-based two-way carbon network composite heat sink plate, which is completed according to the following steps:
[0042] I. Pre-treatment of experimental materials:
[0043] An aluminum plate, brazing filler metal, and porous composite material are stacked sequentially to form a sandwich structure, with a pressure of 2N~4N consistently applied above the porous composite material during brazing. The contact surfaces of the aluminum plate, porous composite material, and brazing filler metal are mechanically ground, with the surface roughness Ra value controlled within the range of 0.1-0.4μm. The surfaces of the aluminum plate, brazing filler metal, and porous composite material are then cleaned using an ultrasonic cleaning solution to remove oil, oxides, and other impurities. The cleaning process lasts 20~40 minutes, with the temperature controlled between 20~70℃.
[0044] II. Brazing:
[0045] In the brazing experiment, the obtained assembly was placed in a vacuum brazing furnace and evacuated to a vacuum level of 1×10⁻⁶. -4 Pa~5×10 -3 Pa is held at a temperature of 360℃~480℃, heated to 360℃~480℃ at a heating rate of 10℃ / min~15℃ / min, held at 360℃~480℃ for 5~20℃ / min, and then cooled to room temperature at a cooling rate of 2℃ / min~10℃ / min. After cooling, a brazed connection component of aluminum alloy plate-brazed seam-porous composite material is formed.
[0046] Figure 1The SEM morphology of the brazed joint is shown below. The SEM morphology of the brazed joint at low magnification is shown below. Figure 2 As shown in (a), from left to right are the aluminum alloy base material, the brazing seam, and the porous composite material base material. A magnified view of the dashed box area in the figure reveals the following morphology: Figure 2 As shown in (b), the aluminum skeleton is embedded in the brazing seam, and backscatter imaging shows that there is also brazing filler metal on the surface of the aluminum skeleton near the brazing seam. This is because the aluminum skeleton was partially embedded in the brazing filler metal during the brazing process. As the temperature cooled, the structure was preserved. The embedded structure is conducive to forming a high-quality and reliable connection between the porous composite material and the aluminum alloy plate. Figure 2 (c) shows the XRD pattern of the brazing filler metal before brazing. As can be seen from the figure, the filler metal is mainly composed of Sn phase, followed by Cu and Ag phases, with a small amount of Ag4Sn alloy phase also present. To compare the differences in phase composition before and after brazing, XRD tests were also performed on the brazed joint, and the patterns are shown below. Figure 2 As shown in (d), the phases in the brazed joint mainly include Sn, Cu, and Ag phases from the brazing filler metal, Al phase from the aluminum alloy plate and aluminum skeleton, C phase of carbonaceous reinforcement phase on the surface of the aluminum skeleton, and compounds generated by inter-element reactions such as Al2Cu and Cu6Sn5 phases.
[0047] SEM morphology of brazed joints in samples at different brazing temperatures is as follows Figure 2 As shown in (e), sample N1 shows that at lower brazing temperatures, the interface between the aluminum plate and the brazing seam is relatively flat, the reaction between the two is not strong, a small amount of filler metal penetrates into the aluminum plate side, and black granular phases are diffusely distributed inside the brazing seam. As the brazing temperature increases, the degree of interface reaction between the aluminum plate and the filler metal in sample N2 increases, more filler metal penetrates into the aluminum plate side, and the size and number of island-like black phases inside the brazing seam increase significantly. When the brazing temperature is further increased, sample N3 shows a strong reaction between the aluminum plate and the filler metal, a large amount of filler metal penetrates into the aluminum plate side, and continuous strip-shaped reaction phases appear near the interface. When the brazing temperature continues to rise, sample N4 shows that the reaction between the aluminum plate and the filler metal is too violent, and the interface exhibits wavy bending. Surface deformation of the aluminum plate base material may adversely affect the mechanical properties of the base material itself, and the discontinuous distribution of the black reaction phase is not conducive to heat diffusion inside the brazing seam, resulting in a large heat flow and thermal resistance.
[0048] The interface morphology between the aluminum skeleton surface and the brazing seam is as follows: Figure 2 As shown in (f), a relatively slender aluminum skeleton is inserted into the brazing seam. Due to the immersion of the skeleton and the rise of the brazing filler metal during brazing, a reactive phase of the brazing filler metal also exists on the surface of the aluminum skeleton, with the same morphology as the white matrix phase of the Sn solid solution in the brazing seam. At the same time, it can be noted that a bright white phase is clearly present at the interface, which should be the carbonaceous reinforcing phase of MGS and CNTs on the surface of the aluminum skeleton. Meanwhile, a discontinuous dark gray phase of Al-Cu compounds is formed near the interface.
[0049] A line scan analysis was performed on the route indicated by the yellow dashed arrow in the figure, and the results are as follows: Figure 2 As shown in (g), in the range of 0 μm–2 μm, the Al content is relatively high, corresponding to the aluminum skeleton, and the Sn content is also relatively high, corresponding to the Sn solid solution phase coating the surface of the aluminum skeleton; in the range of 3 μm–6 μm, the Al and Sn contents decrease significantly, while the C content increases significantly, corresponding to the carbonaceous reinforcing phases such as MGS and CNTs at the interface, while the Cu content increases slightly, corresponding to the Al-Cu compound phase near the interface; in the range of 6 μm–8 μm, the Sn and Al contents increase again, possibly because some of the Al in the aluminum skeleton dissolves and diffuses into the brazing seam.
[0050] Figure 2 These are transmission electron microscopy (TEM) images. The nanoscale phase and structure characterization of the material was performed using transmission electron microscopy (TEM). Figure 3 (a) shows a thin transition layer between the aluminum substrate and the carbon layer. Figure 3 (b) demonstrated Figure 3 (a) The (002) crystal plane of the aluminum matrix in region A. For example... Figure 3 As shown in (c), the bright-field image of the aluminum substrate shows that its framework structure consists of polycrystalline grains with an average grain size ranging from approximately 170 nm to 250 nm. Figure 3 (d) shows the selected area electron diffraction (SAED) pattern of the aluminum phase, which exhibits single-crystal diffraction characteristics under the prominent
[110] zone axis. Figure 3 As shown in (e), the interface between the aluminum substrate and the carbon layer, as well as the distribution of aluminum and carbon elements, can be observed in STEM-HAADF mode. Figure 3 Images (f)-(g) show bright-field imaging results, revealing that the aluminum matrix is encapsulated by a carbon layer. Elemental distribution analysis shows that aluminum is located at the center, surrounded by carbon, thus demonstrating an effective bond between the aluminum alloy and the bidirectional carbon hierarchical structure. Meanwhile, as... Figure 3 As shown in (h), Figure 3 (a) The Fast Fourier Transform (FFT) image of region A reflects the orientation information of the {002} crystal plane family. Figure 3 (i) shows a TEM image of carbon nanotubes. Figure 3 (j) presents a high-magnification image of the characteristic diffraction lattice plane of carbon nanotubes. Figure 3 (k) shows Figure 3 (j) The (200) crystal plane of the A region of the carbon nanotube. Figure 3 (l) corresponds to the FFT diffraction pattern of the main (111) crystal plane of the nickel phase.
[0051] Figure 3 The following tests were conducted: (a) density test, (b) specific heat capacity test, (c) thermal diffusivity test, (d) thermal conductivity test, (e) global temperature profile, (f) statistical results of steady-state temperature and arrival time, (g) heating stage, and (h) cooling stage. The density, specific heat capacity, and thermal conductivity of samples prepared at different brazing temperatures were tested, and the results are as follows: Figure 3 As shown in Figure 3(a), the test results for different sample densities are basically the same, around 1.24 g·cm³. -3 Similarly, 3(b) shows that different samples have almost the same specific heat capacity, at 0.62 J·g. -1 ·K -1 The surrounding area. This indicates that different brazing temperatures did not significantly affect the overall phase composition and content of the sample.
[0052] but Figure 3 (c) The thermal diffusivity results show that the thermal diffusivity of the samples first increases and then decreases with increasing brazing temperature. Sample N1 has the lowest thermal diffusivity, at 33.6 mm²·s⁻¹. -1 Sample N3 exhibited the highest thermal diffusivity, reaching 38.7 mm²·s⁻¹. -1 The thermal conductivity of sample N4 increased significantly by 15% compared to sample N1, while the thermal conductivity of sample N4 decreased to 35.2 mm²·s⁻¹. -1 Similarly, Figure 3 (d) The calculated thermal conductivity results show that sample N1 has the lowest thermal conductivity, while sample N3 has the highest thermal conductivity, reaching 29.7 W·m. -1 ·K -1 However, the thermal conductivity of sample N4 decreased to 26.9 W·m. -1 ·K -1 .
[0053] The above phenomenon occurs because, at lower brazing temperatures, the reaction between the base material and the filler metal is weak, element interdiffusion is minimal, and the interfacial bonding strength is low. Furthermore, the brazing seam is primarily composed of the Sn solid solution phase. Therefore, when heat flows from the aluminum plate to the porous composite material, the interfacial thermal resistance is high, resulting in a low overall equivalent thermal conductivity. As the brazing temperature increases, element diffusion intensifies, the interfacial bonding strength increases, and the continuous phase formed by Al and Cu elements at the interface facilitates heat flow to the surrounding areas, achieving a uniform heat dissipation effect, thus increasing thermal conductivity. However, when the brazing temperature is too high, the interfacial reaction becomes excessively vigorous, forming a wavy, curved interface. Simultaneously, the excessively high temperature makes the filler metal flow unstable, and the continuous phase in the brazing seam transforms into a blocky, localized phase. These factors make heat flow more tortuous, increasing the heat conduction path and significantly increasing the total interfacial thermal resistance. Therefore, the thermal conductivity of sample N4 actually decreases. The heating and cooling processes of different samples were tested and compared, and the results are as follows: Figure 3 As shown in (e)-(h).
[0054] Figure 4 The brazing mechanism diagram and the heat transfer mechanism diagram in the sample are shown in (a) Brazing mechanism diagram; (b) Heat transfer mechanism diagram. In stage one, the brazing temperature gradually increases, and Al atoms in the aluminum skeleton of the aluminum plate and the porous composite material diffuse into the brazing filler metal, while Cu and Sn atoms in the brazing filler metal diffuse to both sides of the interface and to each other. The higher the brazing temperature, the longer the diffusion distance of the atoms and the stronger the mutual reaction. In stage two, the brazing temperature exceeds the melting point of the brazing filler metal, and Sn atoms diffuse into the aluminum base material side to form a discontinuous Sn solid solution. Near the interface on both sides, Al atoms and Cu atoms react with each other to form a diffusely distributed island-shaped Al-Cu compound, while inside the brazing seam, Sn solid solution and a small amount of island-shaped Cu-Sn compound are mainly formed. In stage three, as the holding time increases, different atoms continue to diffuse and react with each other. The Sn solid solution that penetrates into the aluminum substrate forms a continuous reaction layer, while the Al-Cu compounds near the interface change from a dispersed island-like distribution to a straight and continuous reaction layer. At the same time, the Cu-Sn compounds in the brazing seam also change from a dispersed island-like distribution to a continuous strip-like distribution. On the porous composite material side, due to the blocking effect of MGS and CNTs on the skeleton, the diffusion of Al atoms from the aluminum skeleton into the brazing seam is weaker. Therefore, the continuous growth of Al-Cu compounds is also weaker, and the Al-Cu phase still exists in the form of dispersed islands near the interface.
[0055] Figure 5To understand the heat conduction mechanism of the straight and continuous reaction layer in the brazed joint of sample ACB, the heat source at the bottom is first conducted to the aluminum plate. The isotropic aluminum plate conducts heat vertically and horizontally, reducing the heat density of the bottom heat source. The straight and continuous strip-shaped Sn solid solution reaction layer, Al-Cu compound reaction layer, and Cu-Sn compound reaction layer on the aluminum plate side and in the brazed joint effectively dissipate heat horizontally, evenly distributing it to each contact surface, further reducing heat flux density. Furthermore, the straight structural shape minimizes the heat flow path, reducing thermal resistance and improving heat conduction efficiency. Therefore, compared to samples prepared with other process parameters, sample ACB exhibits higher thermal conductivity and superior heat dissipation performance.
Claims
1. A method for preparing a lightweight, high-power heat dissipation aluminum-based two-way carbon network composite heat sink, characterized in that... It was completed in the following aspects:
1. Pre-treatment of experimental materials: Aluminum plates, brazing filler metal sheets, and porous composite materials were stacked together to form a sandwich structure, and a pressure of 2N~4N was applied to the porous composite material throughout the brazing process. The contact surfaces of the aluminum alloy plate, porous composite material, and brazing filler metal were mechanically ground, and the surface roughness Ra value after grinding should be controlled within the range of 0.1-0.4μm. The surfaces of the aluminum plate, brazing filler metal sheets, and porous composite material were cleaned with ultrasonic cleaning fluid to remove oil, oxides, and other impurities. The cleaning process lasted for 20~40 minutes, and the temperature was controlled between 20~70℃.
2. Brazing: In the brazing experiment, the obtained assembly was placed in a vacuum brazing furnace, and a vacuum of 1×10⁻⁶ was drawn. -4 Pa~5×10 -3 Pa is held at a temperature of 360℃~480℃, heated to 360℃~480℃ at a heating rate of 10℃ / min~15℃ / min, held at 360℃~480℃ for 5~20℃ / min, and then cooled to room temperature at a cooling rate of 2℃ / min~10℃ / min. After cooling, a brazed connection component of aluminum alloy plate-brazed seam-porous composite material is formed.
2. The method for preparing a lightweight, high-power heat dissipation aluminum-based two-way carbon network composite heat sink according to claim 1, characterized in that: In step one, the material dimensions are prepared as follows: the thickness of the aluminum alloy plate, the brazing filler metal sheet, and the porous composite material is 2mm~8mm, and a pressure of 2N~4N is always applied above the porous composite material during the brazing process. The contact surfaces of the aluminum alloy plate, the porous composite material, and the brazing filler metal are mechanically polished, and the surface roughness Ra value after polishing should be controlled within the range of 0.1~0.4μm.
3. The method for preparing a lightweight, high-power heat dissipation aluminum-based two-way carbon network composite heat sink according to claim 1, characterized in that: The cleaning process in step one lasts for 20 to 40 minutes, with the temperature controlled between 20 and 70 degrees Celsius.
4. A method for preparing a lightweight, high-power heat dissipation aluminum-based two-way carbon network composite heat sink, characterized in that: Step 1 involves stacking aluminum plates, brazing filler metal sheets, and porous composite materials together in sequence to form a sandwich structure, thus obtaining the workpiece to be welded.
5. The method for preparing a lightweight, high-power heat dissipation aluminum-based two-way carbon network composite heat sink according to claim 1, characterized in that: The obtained assembly was placed in a vacuum brazing furnace and evacuated to a vacuum level of 1×10⁻⁶. -4 Pa~5×10 -3 Pa, the solder mentioned in step two is AgCuInTi, AgCuTi, or SnAgCuTi.
6. The method for preparing a lightweight, high-power heat dissipation aluminum-based two-way carbon network composite heat sink according to claim 1, characterized in that: In the brazing experiment, the temperature was increased to 360℃~480℃ at a heating rate of 10℃ / min~15℃ / min.
7. The method for preparing a lightweight, high-power heat dissipation aluminum-based two-way carbon network composite heat sink according to claim 1, characterized in that: Step 2: Maintain the temperature at 360℃~480℃ for 5~20℃ / min.
8. The method for preparing a lightweight, high-power heat dissipation aluminum-based two-way carbon network composite heat sink according to claim 1, characterized in that: Cool down to room temperature at a rate of 2℃ / min to 10℃ / min.