A vapor chamber with high heat dissipation efficiency and its manufacturing method

Abstract

The present invention provides a vapor chamber with efficient heat dissipation and a manufacturing method thereof, which is divided into four parts: an upper plate, a gradient hydrophobic layer, a gradient hydrophilic layer, and a lower plate. The lower plate uses sintering-electroplating technology to construct the gradient hydrophilic layer. The gradient hydrophilic layer enables the liquid at the cold end to rapidly flow towards the hot end through the action of Laplace force. After the vapor chamber absorbs heat, the working fluid will quickly vaporize into steam. The upper plate is provided with a gradient hydrophobic layer. Under the action of the Laplace force of the gradient hydrophobic layer and the pressure difference between the hot and cold ends, the formed liquid droplets can be quickly transferred to the cold end. The liquid film or liquid droplets form a liquid pool at the cold end. Under the dual action of hydrophobicity and gravity, the liquid droplets quickly fall, reducing the thermal resistance between the wall surface and the steam, and enabling the gradient hydrophobic layer to fully exchange heat with the steam. The beneficial effects are as follows: Based on the bionic principle, a gradient structure is established on the lower surface of the upper plate and the upper surface of the lower plate, accelerating the movement rate of the liquid phase towards the hot end and the vapor phase towards the cold end, enhancing heat transfer, improving the heat transfer efficiency, and forming an efficient cyclic heat transfer system.

Description

Technical Field

[0001] The present invention relates to the technical field of heat dissipation devices, and particularly relates to a heat pipe with high heat dissipation efficiency and a manufacturing method thereof. Background Art

[0002] As a main component for heat energy transfer, heat pipes are widely used in different fields such as new energy vehicles, household appliances, and industrial production. Optimizing the structural process of heat pipes, enhancing the heat energy transfer efficiency, and reducing the loss of heat exchange equipment are important means to improve the overall performance of the system.

[0003] In recent years, with the development of electronic components towards high performance, integration, and miniaturization, the heat dissipation problem of electronic chips has become increasingly prominent. At present, the traditional heat pipe structure can no longer meet the heat dissipation requirements of electronic chips under the increasing high heat flux density. Heat transfer devices are facing more and more difficulties and challenges, especially in mobile terminals such as smart phones and tablet computers, where thermal management design is very difficult.

[0004] In a heat pipe, due to the large accumulation of bubbles, a gas film is formed on the boiling surface, the heat transfer surface deteriorates, and the heat transfer process increases, resulting in a sharp drop in the heat transfer coefficient; on the condensation surface, due to the condensation of steam, a liquid film and liquid droplets are formed on the condensation surface, increasing the heat transfer path between the steam and the wall surface and reducing the heat transfer efficiency. Summary of the Invention

[0005] In order to overcome the deficiencies of the prior art, the purpose of the present invention is to provide a heat pipe with high heat dissipation efficiency and a manufacturing method thereof, which can improve the heat dissipation efficiency and meet the heat dissipation requirements of electronic chips.

[0006] To solve the above problems, the technical solutions adopted by the present invention are as follows:

[0007] A heat pipe with high heat dissipation efficiency includes an upper plate (1), a gradient hydrophobic layer (2), a gradient hydrophilic layer (3), and a lower plate (4). Both ends of the upper plate (1) and the lower plate (4) are provided with connecting parts (5). A gap is left in the middle of the upper plate (1) and the lower plate (4). The connecting parts (5) are connected, fixed, and sealed by welding. The gradient hydrophobic layer (2) is attached below the upper plate (1), and the gradient hydrophilic layer (3) is attached above the lower plate (4). The gradient hydrophobic layer (2) is a nano-rippled structure with several different depths on the upper plate (1), and the gradient hydrophilic layer (3) is an area on the upper surface of the lower plate (4) where copper powder particles with different mesh numbers are sintered.

[0008] Preferably, a femtosecond laser method is used to fabricate the nano-rippled structure of the gradient hydrophobic layer (2). According to the magnitude of the pulse energy, several segments of the nano-rippled structure are divided into four sections: a 50 μJ section (201), an 80 μJ section (202), a 120 μJ section (203), and a 155 μJ section (204). The above four sections are connected in sequence from small to large.

[0009] Preferably, the gradient hydrophilic layer (3) is fabricated by a sintering-electroplating method. Above the lower plate (4) are, in sequence, a 50-mesh section (301), a 100-mesh section (302), a 150-mesh section (303), a 200-mesh section (304), and a 250-mesh section (305). The above five sections are connected in sequence from small to large.

[0010] Preferably, the upper plate (1) and the lower plate (4) are preferably copper plates.

[0011] For the manufacturing method of a heat pipe for high-efficiency heat dissipation as described in claims 1 to 4, the steps include:

[0012] S1. Use a femtosecond laser method to fabricate the nano-rippled structure of the gradient hydrophobic layer (2). Fix the scanning pitch at 50 μm, the lens focal length at 200 mm, and scan the lower side of the upper plate (1) at a scanning speed of 0.5 mm / s. The pulse energy of the femtosecond laser is sequentially selected as 50 μJ, 80 μJ, 120 μJ, and 155 μJ on the upper plate (1). In the case where the pulse power of the femtosecond pulsed laser exceeds the ablation threshold, a nano-rippled structure with different depths is formed under the repeated action of different pulses.

[0013] S2. After femtosecond laser processing, place it in a 1% fluoroalkylsilane ethanol solution, soak it statically for 3 to 5 hours, then take it out and put it into a forced-air drying oven with the temperature set at 120 °C. After baking for 4 hours, let it stand and cool to obtain the upper plate (1) with the gradient hydrophobic layer (2).

[0014] S3. First, divide the area above the lower plate (4) into five equal parts, namely, a 50-mesh section (301), a 100-mesh section (302), a 150-mesh section (303), a 200-mesh section (304), and a 250-mesh section (305). Apply an adhesive in this area, and bond 50-mesh copper powder particles, 100-mesh copper powder particles, 150-mesh copper powder particles, 200-mesh copper powder particles, and 250-mesh copper powder particles to the five areas of the 50-mesh section (301), 100-mesh section (302), 150-mesh section (303), 200-mesh section (304), and 250-mesh section (305) respectively.

[0015] S4, placing the lower plate (4) treated in step S3 into a tube furnace, first raising the temperature in the furnace to 600°C at a rate of 5°C / min, and maintaining it for 10 minutes to remove the adhesive, then heating it to 850°C at the same rate, and maintaining it for 2 hours;

[0016] S5, the lower plate (4) after sintering in step S4 is placed in an electroplating device for electroplating. In the electroplating tank of the electroplating device, the copper sheet serves as an anode and the sintered lower plate (4) serves as a cathode. The electrolyzed copper element adheres to the sintered lower plate (4) to form a gradient hydrophilic layer (3) with a micro-nano particle structure on the surface;

[0017] S6. The upper plate (1) and the lower plate (4) manufactured in step S2 and step S4 are aligned and welded together through the connection portion thereof. At this time, the gradient hydrophobic layer (2) on the lower surface of the upper plate (1) and the gradient hydrophilic layer (3) on the upper surface of the lower plate (4) are aligned, and a gap is left between the gradient hydrophobic layer (2) and the gradient hydrophilic layer (3).

[0018] Preferably, during the entire sintering process of step S4, nitrogen is continuously introduced to isolate oxygen.

[0019] Preferably, in step S5, the plating solution of the electroplating device is preferably a mixture of 0.8 mol / L CuSO4, 1.5 mol / L H2SO4 and 0.2 mol / L HCl.

[0020] Preferably, the electroplating device uses an electroplating time of 40 minutes and a current density of 0.4 mA / mm 2 .

[0021] The beneficial effects of the present invention are:

[0022] 1. The present invention is based on a bionic structure, and a gradient hydrophobic layer is established on the upper plate. After the droplets and liquid films are condensed on the wall, the Laplace force generated by the gradient surface on the droplets causes the droplets to be spontaneously transported in a directional manner, pushing the droplets to the cold end quickly, reducing the heat transfer path between the wall and the steam, and improving the heat exchange efficiency;

[0023] 2. The hydrophobic structure of the upper plate can make the wall droplets drip quickly, speed up the replenishment rate of the bottom liquid pool in the heat plate, improve the deterioration of heat exchange, and improve the boiling heat transfer coefficient;

[0024] 3. The sintering-electroplating coupling method adopted in the present invention manufactures a gradient hydrophilic layer, and utilizes the wettability of different roughness to make the liquid pool move spontaneously from the bottom to the hot end, thereby increasing the migration speed of the liquid on the lower plate;

[0025] 4. The lower plate of the present invention has a micron-scale surface formed by sintering, which increases the contact area between the surface and the liquid, improves the heat transfer efficiency, and provides more capillary core force with the nanometer particle layer formed by electroplating, enabling the formation of more vaporization nuclei and further enhancing the boiling heat transfer coefficient. Brief Description of the Drawings

[0026] Figure 1 is a schematic cross-sectional view of the structure of the present invention;

[0027] Figure 2 is a schematic diagram of gas migration in the gradient hydrophobic layer;

[0028] Figure 3 is a schematic diagram of liquid migration in the gradient hydrophilic layer. Detailed Description of the Invention

[0029] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0030] As Figures 1-3 shown, a heat pipe for efficient heat dissipation includes an upper plate 1, a gradient hydrophobic layer 2, a gradient hydrophilic layer 3, and a lower plate 4. The upper plate 1 and the lower plate 4 are preferably copper plates. Both ends of the upper plate 1 and the lower plate 4 are provided with connecting parts 5. There is a gap in the middle of the upper plate 1 and the lower plate 4. The connecting parts 5 are connected, fixed, and sealed by welding. This connection method can also achieve the seal between the upper plate 1 and the lower plate 4 by pressing. The gradient hydrophobic layer 2 is attached below the upper plate 1, and the gradient hydrophilic layer 3 is attached above the lower plate 4. There is a gap between the gradient hydrophobic layer 2 and the gradient hydrophilic layer 3, and there is a working medium in the gap. The gradient hydrophobic layer 2 is a nano-rippled structure with several different depths on the upper plate 1, and the gradient hydrophilic layer 3 is an area on the lower plate 4 where copper powder particles with different mesh numbers are sintered.

[0031] The nano-rippled structure of the gradient hydrophobic layer 2 is fabricated by using the femtosecond laser method. According to the magnitude of the pulse energy, the several nano-rippled structures are divided into four sections: a 50 μJ region 201, an 80 μJ region 202, a 120 μJ region 203, and a 155 μJ region 204. The above four sections are connected in sequence from small to large.

[0032] The gradient hydrophilic layer 3 is fabricated by using the sintering-electroplating method. Above the lower plate 4 are, in sequence, a 50-mesh region 301, a 100-mesh region 302, a 150-mesh region 303, a 200-mesh region 304, and a 250-mesh region 305. The above five regions are connected in sequence from small to large.

[0033] After the working fluid is heated, water vapor will be generated. Droplets will form on the gradient hydrophobic layer 2. Due to the gradient nano-ripple structure on the gradient hydrophobic layer 2, the droplets will spontaneously move towards the 155 μJ area. The 155 μJ area is close to the cold end, so the droplets will quickly drip onto the lower plate 4 at the cold end.

[0034] On the upper surface of the lower plate (4), by using hydrophilic regions with different gradients, namely the 50-mesh region 301, 100-mesh region 302, 150-mesh region 303, 200-mesh region 304, and 250-mesh region 305, the liquid moves spontaneously from the cold end (the 250-mesh region 305 is close to the cold end) to the hot end (the 50-mesh region 301 is close to the hot end), which improves the migration speed of the liquid on the lower plate (4).

[0035] A method for manufacturing a heat pipe with high heat dissipation as described in claims 1 to 4, the steps of which include:

[0036] S1. Use the method of femtosecond laser to fabricate the nano-ripple structure of the gradient hydrophobic layer 2. Fix the scanning pitch at 50 μm, the lens focal length at 200 mm, and scan below the upper plate 1 at a scanning speed of 0.5 mm / s. The pulse energy of the femtosecond laser is sequentially selected as 50 μJ, 80 μJ, 120 μJ, and 155 μJ on the upper plate 1. In the case where the pulse power of the femtosecond pulsed laser exceeds the ablation threshold, different pulses act repeatedly to form a nano-ripple structure with different depths.

[0037] S2. After femtosecond laser processing, place it in a 1% fluorosilane ethanol solution, soak it statically for 3 to 5 hours, then take it out and put it into a forced-air drying oven with a temperature set at 120 °C. After baking for 4 hours, let it stand and cool to obtain the upper plate 1 with the gradient hydrophobic layer 2.

[0038] S3. First, evenly divide the area above the lower plate 4 into five equal parts, namely the 50-mesh region 301, 100-mesh region 302, 150-mesh region 303, 200-mesh region 304, and 250-mesh region 305, and apply an adhesive in this area. Bond the 50-mesh copper powder particles, 100-mesh copper powder particles, 150-mesh copper powder particles, 200-mesh copper powder particles, and 250-mesh copper powder particles to the five regions of the 50-mesh region 301, 100-mesh region 302, 150-mesh region 303, 200-mesh region 304, and 250-mesh region 305 respectively.

[0039] S4. Put the lower plate 4 processed in step S3 into a tube furnace. First, raise the furnace temperature to 600 °C at a rate of 5 °C / min and keep it for 10 min to remove the adhesive, then heat it to 850 °C at the same rate and keep it for 2 hours. During the whole sintering process, continuously introduce nitrogen to isolate oxygen.

[0040] S5. After the sintering in step S4, the lower plate 4 is placed in an electroplating device for electroplating. The electroplating solution of the electroplating device is preferably a mixture of 0.8 mol / L CuSO4, 1.5 mol / L H2SO4 and 0.2 mol / L HCl. The electroplating time is 40 min and the current density is 0.4 mA / mm 2 In the electroplating tank of the electroplating device, the copper sheet is used as the anode, and the sintered lower plate 4 is used as the cathode. The electrolyzed copper element adheres to the sintered lower plate 4, forming a gradient hydrophilic layer 3 with a nano-particle structure on the surface;

[0041] S6. The upper plate 1 and the lower plate 4 manufactured in step S2 and step S4 are aligned and welded together through the connecting parts thereof. At this time, the gradient hydrophobic layer 2 on the lower surface of the upper plate 1 and the gradient hydrophilic layer 3 on the upper surface of the lower plate 4 are opposite to each other, and a gap is left between the gradient hydrophobic layer 2 and the gradient hydrophilic layer 3.

[0042] Working principle: The heat generated by the operation of the processor is conducted to the evaporation end of the heat spreader, and the working fluid inside absorbs the heat and vaporizes into steam. At this time, the upper plate 1 forms a gradient nano-scale corrugated hydrophobic structure after femtosecond laser processing. The Laplace force formed by the internal air pressure and the wall of the upper plate 1 causes the droplets to quickly reach the cold end and fall quickly. The droplets formed on the upper plate 1 will fall onto the gradient hydrophilic layer 3 of the lower plate 2 constructed by sintering electroplating technology. The liquid at the cold end can quickly flow to the hot end under the capillary action of the inner wall of the cavity, and evaporate and absorb heat again.

Claims

1. A vapor chamber with high-efficiency heat dissipation, characterized in that, It includes an upper plate (1), a gradient hydrophobic layer (2), a gradient hydrophilic layer (3), and a lower plate (4). The upper plate (1) and the lower plate (4) are copper plates. Both ends of the upper plate (1) and the lower plate (4) are provided with connecting parts (5). There is a gap in the middle of the upper plate (1) and the lower plate (4). The connecting parts (5) are connected, fixed, and sealed by welding. The gradient hydrophobic layer (2) is attached below the upper plate (1), and the gradient hydrophilic layer (3) is attached above the lower plate (4). The gradient hydrophobic layer (2) is a nano-rippled structure with several different depths on the upper plate (1), and the gradient hydrophilic layer (3) is an area where copper powder particles with different mesh numbers are sintered on the upper surface of the lower plate (4); The nano-rippled structure of the gradient hydrophobic layer (2) is fabricated by using the femtosecond laser method. According to the magnitude of the pulse energy, several segments of the nano-rippled structure are divided into four sections: a 50 μJ region (201), an 80 μJ region (202), a 120 μJ region (203), and a 155 μJ region (204). The above four sections are connected in sequence from small to large; The gradient hydrophilic layer (3) is fabricated by using the sintering-electroplating method. Above the lower plate (4) are, in sequence, a 50-mesh region (301), a 100-mesh region (302), a 150-mesh region (303), a 200-mesh region (304), and a 250-mesh region (305). The above five regions are connected in sequence from small to large.

2. The manufacturing method of a heat pipe for high-efficiency heat dissipation according to claim 1, the steps of which include: S1. Use the femtosecond laser method to fabricate the nano-rippled structure of the gradient hydrophobic layer (2). Fix the scanning pitch at 50 μm, the lens focal length at 200 mm, and scan the lower part of the upper plate (1) at a scanning speed of 0.5 mm / s. The pulse energy of the femtosecond laser is sequentially selected as 50 μJ, 80 μJ, 120 μJ, and 155 μJ on the upper plate (1). In the case where the pulse power of the femtosecond pulsed laser exceeds the ablation threshold, a nano-rippled structure with different depths is formed under the repeated action of different pulses; S2. After the femtosecond laser processing, place it in a 1% fluoroalkylsilane ethanol solution, soak it statically for 3 to 5 hours, then take it out and put it into a forced-air drying oven with a temperature set at 120 °C. After baking for 4 hours, let it stand and cool to obtain the upper plate (1) with the gradient hydrophobic layer (2); S3. First, evenly divide the area above the lower plate (4) into five equal parts, namely a 50-mesh region (301), a 100-mesh region (302), a 150-mesh region (303), a 200-mesh region (304), and a 250-mesh region (305), and apply an adhesive in this area. Bond 50-mesh copper powder particles, 100-mesh copper powder particles, 150-mesh copper powder particles, 200-mesh copper powder particles, and 250-mesh copper powder particles to the five regions of the 50-mesh region (301), the 100-mesh region (302), the 150-mesh region (303), the 200-mesh region (304), and the 250-mesh region (305) respectively; S4, placing the lower plate (4) treated in step S3 into a tube furnace, first raising the temperature in the furnace to 600°C at a rate of 5°C / min, and maintaining it for 10 minutes to remove the adhesive, and then heating it to 850°C at the same rate and maintaining it for 2 hours; S5, the lower plate (4) after sintering in step S4 is placed in an electroplating device for electroplating. In the electroplating tank of the electroplating device, the copper sheet serves as an anode and the sintered lower plate (4) serves as a cathode. The electrolyzed copper element adheres to the sintered lower plate (4) to form a gradient hydrophilic layer (3) with a micro-nano particle structure on the surface; S6. The upper plate (1) and the lower plate (4) manufactured in step S2 and step S4 are aligned and welded together through the connection portion thereof. At this time, the gradient hydrophobic layer (2) on the lower surface of the upper plate (1) and the gradient hydrophilic layer (3) on the upper surface of the lower plate (4) are directly opposite, and a gap is left between the gradient hydrophobic layer (2) and the gradient hydrophilic layer (3).

3. The manufacturing method of the heat pipe with high-efficiency heat dissipation according to claim 2, wherein During the entire sintering process of step S4, nitrogen is continuously introduced to isolate oxygen.

4. The manufacturing method of the heat pipe with high heat dissipation according to claim 2, characterized in that In step S5, the electroplating solution of the electroplating device is a mixed solution consisting of 0.8 mol / L CuSO4, 1.5 mol / L H2SO4 and 0.2 mol / L HCl.

5. The manufacturing method of the heat pipe with high heat dissipation according to claim 2, characterized in that, The electroplating time adopted by the electroplating device is 40 min, and the current density is 0.4 mA / mm 2 .

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