Method for manufacturing diamond copper heat sink with labyrinth CNT film and heat sink

Abstract

A diamond copper heat sink with a labyrinth CNT film and a preparation method thereof, first, the carbon nanotube film is combined on the surface of the diamond-copper composite material substrate, then the carbon nanotube film layer is laser scanned and etched according to the preset labyrinth pattern, forming continuous and tortuous grooves, and obtaining a diamond copper heat sink with a labyrinth CNT film. The design constructs a labyrinth groove structure on the surface of the carbon nanotube film, significantly increases the heat dissipation area, induces turbulent flow of air and destroys the thermal boundary layer, greatly improves the convective heat transfer efficiency; At the same time, the integrated structure of the heat sink is realized, the interface thermal resistance is low, the process is flexible and adjustable, and the diversified heat dissipation demand of high power density chip in different scenes can be met.

Description

Technical Field

[0001] This invention relates to a method for preparing a heat sink and the heat sink itself, belonging to the field of heat dissipation technology for electronic devices, and particularly to a method for preparing a diamond copper heat sink with a labyrinth CNT film and the heat sink itself. Background Technology

[0002] With the continuous increase in chip power density, some high-power chips have exceeded 2000W / cm². Traditional copper and aluminum heat dissipation materials, due to their limited thermal conductivity and mismatched coefficients of thermal expansion with chip materials, are no longer sufficient to meet heat dissipation requirements. Diamond-copper composite materials combine the ultra-high thermal conductivity of diamond (approximately 2000W / m·K) with the good processability and low cost of copper. By adjusting the ratio, the coefficient of thermal expansion can be matched with that of chip materials such as silicon and gallium nitride. Therefore, it is considered an ideal next-generation heat dissipation substrate material.

[0003] However, existing diamond-copper composite heat sinks still suffer from poor convective heat transfer efficiency in practical applications. The main reason for this defect is that the surface structure of existing heat sinks is relatively simple, mostly flat or traditional fins, with limited contact area with cooling air, and they cannot effectively disturb airflow, making it difficult for heat to be quickly dissipated from the surface into the environment.

[0004] Chinese patent application CN202421827019.9, filed on July 30, 2024, discloses a copper-diamond heat dissipation substrate. This substrate includes a copper-diamond composite layer, a first metal layer, and a second metal layer. The copper-diamond composite layer is composed of copper-diamond material and a metal frame. The copper-diamond material is disposed in through-holes in the metal frame. The first metal layer is fixedly connected to the upper side of the copper-diamond composite layer via a first solder layer, and the second metal layer is fixedly connected to the lower side of the copper-diamond composite layer via a second solder layer, forming a metallurgically bonded sandwich structure, thereby improving the bonding strength and reliability between the layers. However, the heat dissipation surface of this copper-diamond heat dissipation substrate is the upper surface of the first metal layer, which is a planar metal film layer. When heat is conducted from the chip to the surface of the metal layer, heat dissipation relies solely on natural or forced convection between the planar surface and the air. The effective heat exchange area with the cooling air is limited, and the airflow cannot be effectively disturbed, making it difficult for heat to dissipate quickly from the heat dissipation surface to the environment. It still has the following drawbacks:

[0005] The convective heat transfer efficiency is poor.

[0006] The information disclosed in this background section is intended only to enhance understanding of the overall background of this application and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of existing diamond-copper composite heat sinks with poor convective heat transfer efficiency, and to provide a method for preparing a diamond-copper heat sink with a labyrinth CNT film and a heat sink with excellent convective heat transfer efficiency.

[0008] To achieve the above objectives, the technical solution of the present invention is:

[0009] A method for preparing a diamond copper heat sink with a labyrinth CNT film, the method comprising the following steps:

[0010] The first step is to bond a carbon nanotube film onto the upper surface of a pre-fabricated diamond-copper composite substrate to obtain a composite substrate with an integrated carbon nanotube film layer.

[0011] The second step involves laser scanning etching the carbon nanotube film on the composite substrate according to the preset maze pattern, forming a series of continuous and tortuous grooves on the surface of the carbon nanotube film to obtain a diamond copper heat sink with a maze CNT film.

[0012] The first step of the preparation of the diamond-copper composite material substrate includes: firstly, depositing an active metal layer on the surface of diamond particles to obtain surface-modified diamond particles; then, mixing the surface-modified diamond particles with copper powder at a predetermined volume ratio to obtain a mixed powder; and then sintering the mixed powder to obtain the diamond-copper composite material substrate.

[0013] In the predetermined volume ratio, the volume fraction of diamond particles is 50%-70%, and the volume fraction of copper powder is 30%-50%.

[0014] The diamond particles have a particle size of 300-350 μm, and the copper powder has a particle size of no more than 25 μm.

[0015] The active metal layer is any one of Cr, W, and Ti.

[0016] The thickness of the active metal layer is 1-2 μm.

[0017] In the first step, the carbon nanotube membrane is a pure carbon nanotube membrane with a thickness of 190-210 μm.

[0018] In the second step, the width of the trench is 10-200 μm and the depth of the trench is 5-100 μm.

[0019] In the second step, by controlling the laser scanning path, the turning points of the groove are made to form an arc transition.

[0020] A method for preparing a diamond-copper heat sink with a labyrinth CNT film is described above. The heat sink has a plate-like structure, including a diamond-copper composite substrate and a carbon nanotube film layer. The carbon nanotube film layer is fixedly covered on the upper surface of the diamond-copper composite substrate, and the upper surface of the carbon nanotube film layer has a number of continuous and tortuous grooves.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] 1. The present invention discloses a method for preparing a diamond-copper heat sink with a labyrinth CNT film. First, a carbon nanotube film is bonded to the upper surface of a pre-fabricated diamond-copper composite substrate to obtain a composite substrate integrated with a carbon nanotube film layer. Then, according to a preset labyrinth pattern, laser scanning etching is performed on the carbon nanotube film layer on the composite substrate to form a series of continuous, tortuous grooves on the surface of the carbon nanotube film layer, thus obtaining a diamond-copper heat sink with a labyrinth CNT film. The advantages of the present invention are:

[0023] First, laser etching technology creates numerous continuous, tortuous microgrooves on the originally flat surface of the carbon nanotube film, expanding the original planar surface into a three-dimensional structure containing "groove bottoms" and "sidewalls." Geometric calculations show that the total area of ​​the etched sidewalls far exceeds the original planar area, directly breaking the physical limitations of projected area. Simultaneously, the laser cuts through the dense carbon nanotube array while slicing the grooves, exposing numerous end faces and sidewalls of the carbon nanotubes. Carbon nanotubes themselves possess extremely high aspect ratios and specific surface areas; this microscopic "section activation" further increases the material's effective heat dissipation area, providing a structural basis for efficient heat dissipation.

[0024] Secondly, the constructed continuous, tortuous labyrinthine flow channel forces the airflow to constantly change direction. Whenever the airflow passes through a bend or turn in the channel, the fluid collides and separates from the wall, forcibly stripping and interrupting the original thermal boundary layer. The boundary layer needs to regenerate in each new flow segment, thus maintaining a consistently thin thermal boundary layer thickness and significantly reducing thermal resistance. Simultaneously, the high-speed turns of the airflow within the labyrinthine channel generate centrifugal force, inducing a "secondary flow" perpendicular to the mainstream direction. This "throws" the cooler mainstream fluid at the channel center towards the heated wall, while simultaneously "entraining" the heated fluid near the wall into the center of the mainstream, breaking down the stratification of hot and cold fluids and allowing heat to be rapidly transferred from the carbon nanotube membrane surface to the cooling air.

[0025] Therefore, this invention achieves a significant improvement in convective heat transfer efficiency by laser etching a continuous, tortuous labyrinthine groove structure on the surface of a carbon nanotube film, resulting in excellent convective heat transfer efficiency.

[0026] 2. The present invention provides a method for preparing a diamond-copper heat sink with a labyrinth CNT film and the preparation steps of the diamond-copper composite material substrate in the heat sink include: firstly, depositing an active metal layer on the surface of diamond particles to obtain surface-modified diamond particles; then mixing the surface-modified diamond particles with copper powder at a predetermined volume ratio to obtain a mixed powder; and then sintering the mixed powder to obtain a diamond-copper composite material substrate. During sintering, the active metal reacts with diamond to form carbides, which are firmly bonded to the diamond surface and simultaneously form a good metallurgical bond with the copper matrix. This creates a continuous atomic-scale transition interface between diamond and copper, eliminating micropores and air layers, and fundamentally reducing interfacial thermal resistance. Meanwhile, the carbon nanotube film is firmly bonded to the substrate surface through brazing or pressure sintering, forming an integrated structure without the need for additional adhesive layers, thus avoiding the introduction of new interfacial thermal resistance. Throughout the heat sink, from the diamond particles to the copper matrix and then to the carbon nanotube film layer, all interfaces are tightly bonded by metallurgy or welding, resulting in a robust structure resistant to thermal shock and maintaining stable heat dissipation performance even under high-power cycling conditions. Therefore, this invention achieves an integrated structure with significantly reduced interfacial thermal resistance between layers within the heat sink, inheriting the excellent thermophysical properties of diamond-copper composite materials and laying a solid foundation for efficient heat dissipation.

[0027] 3. In the preparation method and heat sink of the diamond copper heat sink with a maze CNT film of the present invention, a laser scanning etching method is used to process the carbon nanotube film layer, forming a series of continuous and tortuous grooves on the surface of the film layer according to a preset maze pattern. Laser etching is a non-contact processing method, which does not generate mechanical stress and will not damage the carbon nanotube film layer or the underlying substrate. At the same time, the focal spot diameter of the laser beam can be controlled at the micrometer level. With the help of a high-precision displacement platform, it is possible to achieve fine processing control of the width and depth of the grooves, and the processing accuracy is far higher than that of traditional mechanical engraving. More importantly, the laser etching system is controlled by a computer program. By simply changing the preset pattern, maze patterns of different densities, directions and complexities can be quickly switched on the same machine without remaking molds or adjusting the mechanical structure. Therefore, the present invention has both high precision and high flexibility, and can be adapted to various heat dissipation scenarios of high power density chips at low cost and high efficiency. Attached Figure Description

[0028] Figure 1 This is a flowchart of the preparation process of the present invention.

[0029] Figure 2 This is a schematic diagram of the structure of the carbon nanotube film and the labyrinth groove in Embodiment 1 of the present invention.

[0030] Figure 3 This is a schematic diagram of the maze groove structure in Embodiment 1 of the present invention.

[0031] Figure 4 This is a schematic diagram of the maze groove structure in Embodiment 1 of the present invention.

[0032] Figure 5 This is a schematic diagram of the maze groove structure in Embodiment 1 of the present invention. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0034] See Figure 1 — Figure 5 A method for preparing a diamond copper heat sink with a labyrinth CNT film, the method comprising the following steps:

[0035] The first step is to bond a carbon nanotube film onto the upper surface of a pre-fabricated diamond-copper composite substrate to obtain a composite substrate with an integrated carbon nanotube film layer.

[0036] The second step involves laser scanning etching the carbon nanotube film on the composite substrate according to the preset maze pattern, forming a series of continuous and tortuous grooves on the surface of the carbon nanotube film to obtain a diamond copper heat sink with a maze CNT film.

[0037] The first step of the preparation of the diamond-copper composite material substrate includes: firstly, depositing an active metal layer on the surface of diamond particles to obtain surface-modified diamond particles; then, mixing the surface-modified diamond particles with copper powder at a predetermined volume ratio to obtain a mixed powder; and then sintering the mixed powder to obtain the diamond-copper composite material substrate.

[0038] In the predetermined volume ratio, the volume fraction of diamond particles is 50%-70%, and the volume fraction of copper powder is 30%-50%.

[0039] The diamond particles have a particle size of 300-350 μm, and the copper powder has a particle size of no more than 25 μm.

[0040] The active metal layer is any one of Cr, W, and Ti.

[0041] The thickness of the active metal layer is 1-2 μm.

[0042] In the first step, the carbon nanotube membrane is a pure carbon nanotube membrane with a thickness of 190-210 μm.

[0043] In the second step, the width of the trench is 10-200 μm and the depth of the trench is 5-100 μm.

[0044] In the second step, by controlling the laser scanning path, the turning points of the groove are made to form an arc transition.

[0045] A method for preparing a diamond-copper heat sink with a labyrinth CNT film is described above. The heat sink has a plate-like structure, including a diamond-copper composite substrate and a carbon nanotube film layer. The carbon nanotube film layer is fixedly covered on the upper surface of the diamond-copper composite substrate, and the upper surface of the carbon nanotube film layer has a number of continuous and tortuous grooves.

[0046] The supplementary technical features of this invention are as follows:

[0047] In this invention, the trench width is limited to 10-200 μm, which is based on a comprehensive consideration of heat dissipation performance and processing feasibility. If the trench width is less than 10 μm, the trench is too narrow, making it difficult for airflow to enter smoothly, and laser processing becomes extremely difficult, which can easily lead to structural closure. If the trench width is greater than 200 μm, the flow channel length per unit area is reduced, the effect of disrupting the air boundary layer is weakened, and the heat dissipation gain exhibits marginal decrease.

[0048] In this invention, the trench depth is limited to 5-100 μm to balance heat dissipation and structural reliability. If the trench depth is less than 5 μm, the etching is too shallow and cannot effectively disturb the airflow, making it difficult to destroy the thermal boundary layer; if the trench depth is greater than 100 μm, the excessively deep trenches can easily cause the carbon nanotube film to crack or fall off during processing, and will significantly increase processing costs.

[0049] In this invention, the preferred particle size of the diamond particles is 300-350 μm, and its Raman spectrum shows a particle size of approximately 1332 cm⁻¹. －1 The full width at half maximum (FWHM) of the peak is preferably less than 2 cm. －1 To ensure the high crystallinity of the diamond, the purity of the copper powder must reach 99.9% or higher (preferably 99.99%), with a particle size range of 0-25μm, and the maximum particle size must be controlled to not exceed 30-40μm to avoid process safety hazards caused by large particles. The morphology of the copper powder can be spherical or irregular as needed, and its thermal conductivity should be close to that of pure copper, generally not less than 380W / (m·K), to ensure the overall high thermal conductivity of the substrate.

[0050] Example 1:

[0051] See Figure 1 — Figure 5 A method for preparing a diamond copper heat sink with a labyrinth CNT film, the method comprising the following steps:

[0052] Diamond particles with a particle size of 300 μm were selected, and a Cr active metal layer was deposited on the surface of the diamond particles using a magnetron sputtering process. The coating thickness was 1 μm, resulting in surface-modified diamond particles.

[0053] Select copper powder with a purity of not less than 99.9% and a particle size not exceeding 25μm, in accordance with conventional requirements; mix surface-modified diamond particles with copper powder at a volume ratio of 60:40 to obtain a mixed powder.

[0054] The mixed powder was loaded into a graphite mold and sintered using a spark plasma sintering (SPS) process. The sintering process was carried out under conventional SPS conditions, such as a sintering temperature of 800℃, a pressure of 40MPa, a holding time of 5min, and a vacuum degree ≤10Pa. After furnace cooling, a densified diamond-copper composite substrate was obtained.

[0055] A pre-fabricated pure carbon nanotube film with a thickness of 200 μm is selected. The carbon nanotube film is cut into a shape matching the substrate size and placed on the upper surface of a diamond-copper composite substrate. A brazing process is used for bonding: a brazing filler metal (e.g., Ag-Cu-Ti alloy) is uniformly coated between the carbon nanotube film and the substrate. The substrate is then placed in a vacuum brazing furnace and heated to the brazing temperature (e.g., 800-850°C) using conventional brazing techniques. The temperature is held for an appropriate time (e.g., 10-20 min) to allow the brazing filler metal to melt and fully wet the substrate surface and the carbon nanotube film. The substrate is then slowly cooled to room temperature to form a strong metallurgical bond. Alternatively, a pressure sintering process can be used: the carbon nanotube film is placed on the upper surface of the substrate, a pressure of 5-10 MPa is applied, and the substrate is heated to 700-800°C in a protective atmosphere (argon) and held for 30-60 min to directly bond the carbon nanotube film to the substrate. Both methods can yield composite substrates integrated with carbon nanotube film layers. This embodiment preferably uses the brazing process.

[0056] Based on a pre-defined maze pattern (e.g., a serpentine, continuous, tortuous path), a laser scanning path is designed. An ultraviolet or femtosecond pulsed laser is used, and standard laser etching parameters are set (e.g., laser power 2-5W, scanning speed 100-500mm / s, repetition frequency 100-500kHz, spot diameter 20-30μm). The carbon nanotube film is then scanned and etched along the pre-defined path. The laser precisely removes a portion of the material from the surface of the carbon nanotube film, forming several continuous, tortuous trenches on the surface (e.g.,...). Figure 2 - Figure 5As shown, each trench has an opening for airflow to exit the trench. These openings are distributed on each side and top surface of the carbon nanotube film, allowing airflow to travel in multiple directions and ultimately exit the trench in multiple directions, further improving heat dissipation. The width of the trench is controlled within the range of 10-200 μm (preferably 100 μm in this embodiment), and the depth is controlled within the range of 5-100 μm (preferably 50 μm in this embodiment). Simultaneously, by controlling the radius of the arc at the turning points of the laser scanning path, an arc transition is formed at the turning points of the trench to reduce airflow resistance. After etching, the etched substrate is obtained.

[0057] The etched substrate is placed in an ultrasonic cleaner, using anhydrous ethanol as the cleaning solvent, and cleaned according to a conventional ultrasonic cleaning process (e.g., ultrasonic power 200W, cleaning time 10-15min) to remove carbon nanotube debris and residues generated by laser etching. Then it is rinsed 2-3 times with deionized water, and finally the surface is dried with high-purity nitrogen gas to obtain a diamond copper heat sink with a labyrinth CNT film.

[0058] The above description is only a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. Any equivalent modifications or changes made by those skilled in the art based on the content disclosed in the present invention should be included within the scope of protection set forth in the claims.

Claims

1. A method for preparing a diamond copper heat sink with a labyrinth CNT film, characterized in that: The preparation method includes the following steps: The first step is to bond a carbon nanotube film onto the upper surface of a pre-fabricated diamond-copper composite substrate to obtain a composite substrate with an integrated carbon nanotube film layer. The second step involves laser scanning etching the carbon nanotube film on the composite substrate according to the preset maze pattern, forming a series of continuous and tortuous grooves on the surface of the carbon nanotube film to obtain a diamond copper heat sink with a maze CNT film.

2. The method for preparing a diamond copper heat sink with a labyrinth CNT film according to claim 1, characterized in that: The first step of the preparation of the diamond-copper composite material substrate includes: firstly, depositing an active metal layer on the surface of diamond particles to obtain surface-modified diamond particles; then, mixing the surface-modified diamond particles with copper powder at a predetermined volume ratio to obtain a mixed powder; and then sintering the mixed powder to obtain the diamond-copper composite material substrate.

3. The method for preparing a diamond copper heat sink with a labyrinth CNT film according to claim 2, characterized in that: In the predetermined volume ratio, the volume fraction of diamond particles is 50%-70%, and the volume fraction of copper powder is 30%-50%.

4. The method for preparing a diamond copper heat sink with a labyrinth CNT film according to claim 2, characterized in that: The diamond particles have a particle size of 300-350 μm, and the copper powder has a particle size of no more than 25 μm.

5. The method for preparing a diamond copper heat sink with a labyrinth CNT film according to claim 2, characterized in that: The active metal layer is any one of Cr, W, and Ti.

6. The method for preparing a diamond copper heat sink with a labyrinth CNT film according to claim 2, characterized in that: The thickness of the active metal layer is 1-2 μm.

7. A method for preparing a diamond copper heat sink with a labyrinth CNT film according to claims 1-6, characterized in that: In the first step, the carbon nanotube membrane is a pure carbon nanotube membrane with a thickness of 190-210 μm.

8. A method for preparing a diamond copper heat sink with a labyrinth CNT film according to claims 1-6, characterized in that: In the second step, the width of the trench is 10-200 μm and the depth of the trench is 5-100 μm.

9. A method for preparing a diamond copper heat sink with a labyrinth CNT film according to claims 1-6, characterized in that: In the second step, by controlling the laser scanning path, the turning points of the groove are made to form an arc transition.

10. A heat sink prepared by the method for preparing a diamond copper heat sink with a labyrinth CNT film as described in claims 1-6, characterized in that: The heat sink has a plate-like structure, including a diamond-copper composite substrate and a carbon nanotube film layer; the carbon nanotube film layer is fixedly covered on the upper surface of the diamond-copper composite substrate, and the upper surface of the carbon nanotube film layer has several continuous and tortuous grooves.

Images