A method for preparing an ultra-thin vapor chamber wick with high heat transfer performance and an ultra-thin vapor chamber wick

Abstract

The present disclosure relates to a method for preparing an ultra-thin vapor chamber wick with high heat transfer performance and a ultra-thin vapor chamber wick with a hierarchical structure. The method comprises: S1, pre-treating a metal substrate; S2, placing the pre-treated metal substrate on a work platform, setting laser processing parameters and focusing the laser spot so that the laser spot is focused on the surface of the metal substrate; S3, processing a first groove on the metal substrate along a first direction of the metal substrate; S4, processing a second groove on the metal substrate along a second direction of the metal substrate; wherein the first direction is perpendicular to the second direction; the depth of the first groove is greater than the depth of the second groove; the ultra-thin vapor chamber wick is prepared by the above method; the wick prepared by the above method has good heat transfer performance, simple process and low manufacturing cost, and the liquid transport capacity and working medium phase change capacity of the wick are processed in a hierarchical manner, so as to have both high liquid transport capacity and high-efficiency working medium phase change capacity.

Description

Technical Field

[0001] The present invention relates to the technical field of vapor chamber wick preparation technology, and in particular to a method for preparing an ultra-thin vapor chamber wick with a hierarchical structure and high heat transfer performance, and an ultra-thin vapor chamber wick. Background Art

[0002] With the rapid development of the electronic information industry, high performance and miniaturization of electronic equipment have become the mainstream. In order to meet the performance of the product, the transistor density of electronic chips is getting higher and higher. The increase in power consumption causes electronic equipment to generate extremely high heat flux density in a small space, causing the equipment to fail to operate normally. The heat spreader phase change latent heat with the working fluid phase change heat transfer as the core to remove heat is the most potential thermal management method to solve the heat dissipation problem of electronic equipment. Therefore, in order to meet the heat dissipation technology of modern miniaturized electronic equipment, achieving high performance and thinness of the heat spreader is the current focus of the industry.

[0003] As the core component of the vapor chamber, the wick plays a vital role in the performance of the vapor chamber. The wick affects the performance of the vapor chamber mainly in two aspects. On the one hand, the working fluid on the evaporation end of the wick can quickly undergo liquid-gas conversion and carry a large amount of heat to the condensation end. On the other hand, the working fluid at the condensation end can quickly liquefy and flow back to the evaporation end, and can be transferred from the wetted area of ​​the evaporation end to the dry area to achieve a long-term liquid-vapor-liquid cycle, which is specifically manifested in the performance of the wick in transporting liquid to maintain wettability.

[0004] Powder sintering is currently one of the mainstream methods for preparing vapor chamber wicks. This type of wick has high capillary force and is the most commonly used method in previous vapor chamber research. However, powder sintering has a low permeability, and to achieve ultra-thin vapor chambers, powders with smaller particles need to be used, further reducing the permeability. Similarly, wire mesh sintering, as one of the mainstream methods, adjusts the size of the capillary force by changing the wire diameter. It has the characteristics of high permeability, but its capillary force is relatively small. Importantly, as the vapor chamber becomes ultra-thin, the wicks made by powder sintering and wire mesh sintering are prone to wick shedding because there are only a few layers of powder or wire mesh combined, and the bonding force is relatively small. These two methods are prone to wick shedding.

[0005] At present, in order to solve the problem of easy detachment of the wick, an alloy with a capillary structure is also provided to serve as the wick. The difference is that by performing hydrogenation heat treatment in the copper alloy, this process forms grooves with a connected network structure at the grain boundary, realizing the "integrated" design of the capillary channel network and the alloy metal itself. Although the above method prepares an "integrated" wick, achieves ultra-thinness, and can effectively solve the problem of powder and screen detachment under the ultra-thin heat spreader, its process is complicated and the production cost is high. In addition, the wick prepared by the above method is completely "integrated" and the steam cavity is extremely small. Under the size effect, a liquid plug is formed in the steam channel, which hinders the flow of steam and inhibits the process of liquid phase change. The liquid transportation capacity and phase change capacity are relatively poor, which affects the heat transfer performance of the ultra-thin heat spreader. Summary of the invention

[0006] In order to solve the problems existing in the above-mentioned prior art, the present invention aims to provide a method for preparing an ultra-thin vapor chamber wick with high heat transfer performance having a hierarchical structure, so as to solve the technical problems of the prior art such as complex process, high production cost and relatively poor liquid transport capacity and phase change ability.

[0007] A method for preparing an ultra-thin vapor chamber wick with a hierarchical structure and high heat transfer performance disclosed in the present invention comprises the following steps:

[0008] S1. Pre-treating the metal substrate;

[0009] S2, placing the pre-treated metal substrate on the work platform, setting the laser processing parameters and focusing the laser spot on the surface of the metal substrate;

[0010] S3, machining a first groove on the metal substrate along a first direction of the metal substrate;

[0011] S4: machining a second groove on the metal substrate along a second direction of the metal substrate;

[0012] wherein the first direction is perpendicular to the second direction;

[0013] The depth of the first groove is greater than the depth of the second groove.

[0014] Preferably, the step S1 comprises:

[0015] Place the metal substrate in an ultrasonic cleaning machine, pour solvent and metal degreasing and degreasing cleaning agent into the ultrasonic cleaning machine until the metal degreasing and degreasing cleaning agent exceeds the surface of the metal substrate, ultrasonicate for 3 to 10 minutes, pour out the liquid in the ultrasonic cleaning machine, pour deionized water until the liquid level exceeds the surface of the metal substrate, continue ultrasonicate for 3 to 10 minutes to complete the pretreatment.

[0016] Preferably, the step S3 comprises:

[0017] By setting the following parameters, a first groove is processed on the metal substrate along a first direction of the metal substrate:

[0018] The laser pulse width is 3 to 15 ps, the basic repetition frequency of laser scanning is 2000 kHz, the division frequency is 500 kHz, the laser scanning speed is 1000 to 3000 mm / s, the number of scans is 70 to 90 times, the laser energy is 4 to 6 μJ, and the scanning interval is 0.005 mm.

[0019] Preferably, the laser pulse width is 9 ps, the laser scanning speed is 2000 mm / s, the number of scans is 80 times, and the laser energy is 5.8 μJ.

[0020] Preferably, the step S4 comprises:

[0021] By setting the following parameters, a second groove is processed on the metal substrate along the second direction of the metal substrate:

[0022] The laser pulse width is 3 to 15 ps, the basic repetition frequency of laser scanning is 500 kHz, the laser scanning speed is 500 to 600 mm / s, the number of scans is 8 to 14 times, the laser energy is 9 to 14 μJ, and the scanning interval is 0.008 mm.

[0023] Preferably, the laser pulse width is 9 ps, the laser scanning speed is 550 mm / s, the number of scans is 12 times, and the laser energy is 10.8 μJ.

[0024] Preferably, the material of the metal substrate may be brass, copper or aluminum.

[0025] Preferably, the thickness of the metal substrate is 0.5-1 mm.

[0026] The present disclosure also provides an ultra-thin vapor chamber wick, which is prepared by the above method.

[0027] The advantages of the method for preparing a high heat transfer ultra-thin vapor chamber wick with a hierarchical structure disclosed in the present invention are:

[0028] The present invention arranges the first groove and the second groove, and the scanning interval is arranged, so that the surface of the first groove is smooth, and the smooth surface can reduce bubble nucleation points, and prevent the working fluid from vaporizing at the bottom of the groove to form an air film, and isolate the heat exchange between the hot surface and the working fluid, causing the deterioration of the heat transfer performance of the liquid wick; and the surface of the second groove is formed with a micro-nano structure, which increases its surface area, can provide a large number of bubble nucleation sites, promote the large amount of vaporization of the working fluid to form bubbles to carry heat away, and enhance the phase change ability of the working fluid;

[0029] At the same time, since the parameter settings for forming the first groove and the parameter settings for forming the second groove are different, the depth of the first groove is greater than the depth of the second groove, and the width of the widest part of the first groove is the same as the width of the widest part of the second groove, so that the aspect ratio of the first groove is greater than the aspect ratio of the second groove, and thus the first groove can provide high capillary force to maintain the liquid transport performance; and the second groove is conducive to the rapid escape of nucleated bubbles, and can quickly take heat away from the hot surface; the combination of the two makes the ultra-thin heat spreader wick prepared by the method for preparing an ultra-thin heat spreader wick with high heat transfer performance with a hierarchical structure described in the present disclosure have both high liquid transport capacity and high-efficiency working fluid phase change capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a flow chart of a method for preparing an ultra-thin vapor chamber wick with high heat transfer performance having a hierarchical structure as disclosed in the present invention;

[0031] Figure 2 is a schematic diagram of an operating device corresponding to the preparation method;

[0032] Figure 3 From left to right are respectively a schematic diagram of the metal substrate after being processed in step S3 and a schematic diagram of the metal substrate after being processed in step S4;

[0033] Figure 4 is a surface morphology image of the ultra-thin vapor chamber wick;

[0034] Figure 5 It is an evaporation experiment diagram of the ultra-thin vapor chamber wick prepared by the method and the ordinary vapor chamber wick.

[0035] Explanation of the reference numerals: 1-PC control terminal, 2-fiber nanosecond laser, 3-beam expander, 4-galvanometer, 5-field mirror, 6-working platform, 7-copper sheet, 8-vacuum cleaner. DETAILED DESCRIPTION

[0036] like Figure 1 to Figure 3 As shown, the method for preparing a high heat transfer ultra-thin vapor chamber wick with a hierarchical structure disclosed in the present invention comprises the following steps:

[0037] S1. Pre-treating the metal substrate;

[0038] S2, placing the pre-treated metal substrate on the work platform, setting the laser processing parameters and focusing the laser spot on the surface of the metal substrate;

[0039] S3, machining a first groove on the metal substrate along a first direction of the metal substrate;

[0040] S4: machining a second groove on the metal substrate along a second direction of the metal substrate.

[0041] The first direction is perpendicular to the second direction; and the depth of the first groove is greater than the depth of the second groove.

[0042] Specifically, in the method for preparing a high heat transfer ultra-thin vapor chamber wick with a hierarchical structure disclosed in the present invention, steps S2 to S4 are as follows: Figure 2 The operating device shown in the figure is operated, and the device includes:

[0043] The laser equipment includes a PC control terminal, a green light picosecond laser, a beam expander, a galvanometer, a field lens, and a work platform; the coaxial CCD work platform is used to fix the copper sheet, the laser beam emitted by the green light picosecond laser is focused on the surface of the copper sheet through the beam expander, the galvanometer, and the field lens, the PC control terminal is electrically connected to the green light picosecond laser and the galvanometer, the laser parameters and the laser scanning trajectory can be adjusted through the PC control terminal to form the first groove and the second groove on the surface of the copper sheet, and the coaxial CCD is used to observe the laser processing process in real time. In order to absorb the dust generated by the copper sheet during the processing, a vacuum cleaner is generally set on one side of the work platform to absorb the dust in time to avoid excessive dust at the processing site and affect the operation.

[0044] More specifically, the diameter of the laser spot is preferably 18 μm.

[0045] Furthermore, step S1 specifically includes: placing the metal substrate in an ultrasonic cleaning machine, pouring a solvent and a metal degreasing and degreasing cleaning agent into the ultrasonic cleaning machine until the metal degreasing and degreasing cleaning agent exceeds the surface of the metal substrate, ultrasonicating for 3 to 10 minutes, pouring out the liquid in the ultrasonic cleaning machine, pouring deionized water until the liquid level exceeds the surface of the metal substrate, and continuing ultrasonicating for 3 to 10 minutes to complete the pretreatment.

[0046] The ultrasonic cleaning machine can be any conventional model sold on the market.

[0047] When performing ultrasonic cleaning, the ratio of the metal degreasing and degreasing cleaning agent to the solvent is selected according to actual conditions. Preferably, in one embodiment of the present disclosure, the ratio of the metal degreasing and degreasing cleaning agent to the solvent can be 15:85, that is, the metal degreasing and degreasing cleaning agent poured into the ultrasonic cleaning machine accounts for 15% of the solution; in another embodiment of the present disclosure, the ratio of the metal degreasing and degreasing cleaning agent to the solvent is 1:1, that is, the metal degreasing and degreasing cleaning agent poured into the ultrasonic cleaning machine accounts for 50% of the solution.

[0048] Furthermore, step S3 specifically includes:

[0049] By setting the following parameters, a first groove is processed on the metal substrate along a first direction of the metal substrate:

[0050] The laser pulse width is 3 to 15 ps, the basic repetition frequency of laser scanning is 2000 kHz, the division frequency is 500 kHz, the laser scanning speed is 1000 to 3000 mm / s, the number of scans is 70 to 90 times, the laser energy is 4 to 6 μJ, and the scanning interval is 0.005 mm.

[0051] Preferably, the laser pulse width is 9 ps, the laser scanning speed is 2000 mm / s, the number of scans is 80 times, and the laser energy is 5.8 μJ.

[0052] Through the above parameter settings, a first groove is formed on the metal substrate along its first direction. Due to the settings of the laser parameters and the scanning interval, the surface of the first groove is smooth. The smooth surface can reduce the bubble nucleation points, prevent the working fluid from vaporizing at the bottom of the groove to form an air film, isolate the heat exchange between the hot surface and the working fluid, and cause the deterioration of the heat transfer performance of the wick.

[0053] Furthermore, step S4 specifically includes:

[0054] By setting the following parameters, a second groove is processed on the metal substrate along the second direction of the metal substrate:

[0055] The laser pulse width is 3 to 15 ps, the basic repetition frequency of laser scanning is 500 kHz, the laser scanning speed is 500 to 600 mm / s, the number of scans is 8 to 14 times, the laser energy is 9 to 14 μJ, and the scanning interval is 0.008 mm.

[0056] Preferably, the laser pulse width is 9 ps, the laser scanning speed is 550 mm / s, the number of scans is 12 times, and the laser energy is 10.8 μJ.

[0057] Through the above parameter settings, a second groove is formed on the metal substrate along its second direction. Due to the settings of the laser parameters and the scanning interval, a micro-nano structure is formed on the surface of the second groove to increase its surface area, that is, the surface of the second groove is rougher than the surface of the first groove, which can provide a large number of bubble nucleation sites, promote the vaporization of the working fluid in large quantities to form bubbles that carry heat and detach, and enhance the phase change ability of the working fluid.

[0058] At the same time, due to the difference between the parameter setting in step S3 and the parameter setting in the above step S4, there is a difference in the depth of the first groove and the second groove. The first groove is deeper and the second groove is shallower, and the width of the widest part of the first groove is the same as the width of the widest part of the second groove, so that the depth-to-width ratio of the first groove is greater than the depth-to-width ratio of the second groove, and thus the first groove can provide high capillary force to maintain the liquid transport performance; and the second groove is conducive to the rapid escape of nucleated bubbles, and can quickly take away heat from the hot surface; the combination of the two makes the ultra-thin heat spreader wick prepared by the method for preparing an ultra-thin heat spreader wick with high heat transfer performance with a hierarchical structure described in the present disclosure have both high liquid transport capacity and high-efficiency working fluid phase change capacity.

[0059] Furthermore, the material of the metal substrate may be brass, copper or aluminum.

[0060] Furthermore, the thickness of the metal substrate is 0.5-1 mm.

[0061] The present disclosure also provides an ultra-thin vapor chamber wick, the ultra-thin vapor chamber wick is prepared by the above-mentioned preparation method, and its surface morphology is as follows: Figure 4 shown.

[0062] According to the above method, an embodiment and a control example are set. The embodiment is obtained by the above method, and the embodiment is called a graded groove structure; the control example is only completed to step S3, that is, there is only the first groove on the metal substrate of the control example, and the control example is called a single-stage groove structure. The evaporation performance of the embodiment and the control example is tested as follows:

[0063] 50 μL of deionized water was injected into the two grooves of the embodiment and the two grooves of the control example at the same time, and the wick sample was heated by the heating platform, and the evaporation of the embodiment and the control example was observed. The evaporation time of the embodiment and the control example was measured to obtain the time required for evaporating the same volume of deionized water in the embodiment and the control example, and then the working fluid phase change ability of the embodiment and the control example was judged.

[0064] The experimental results are as follows Figure 5 As shown, after evaporation for 45 seconds, the deionized water on the two grooves of the embodiment is completely evaporated, while the deionized water on the two grooves of the control example needs to evaporate for 55 seconds before completely evaporating. In summary, the embodiment has a higher working fluid phase change capability, that is, the ultra-thin vapor chamber wick prepared by the method for preparing an ultra-thin vapor chamber wick with high heat transfer performance having a hierarchical structure disclosed in the present invention has a higher working fluid phase change capability.

[0065] In the description of the present disclosure, it is necessary to understand that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present disclosure and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the scope of protection of the present disclosure.

[0066] For those skilled in the art, various other corresponding changes and deformations can be made according to the technical solutions and concepts described above, and all of these changes and deformations should fall within the protection scope of the claims of the present disclosure.

Claims

1. A method for preparing an ultra-thin vapor chamber wick with high heat transfer performance having a hierarchical structure, characterized in that: The following steps are involved: S1. Pre-treating the metal substrate; S2, placing the pre-treated metal substrate on the work platform, setting the laser processing parameters and focusing the laser spot on the surface of the metal substrate; S3, processing a plurality of first grooves on the metal substrate along a first direction of the metal substrate, wherein surfaces of the plurality of first grooves are smooth; The step S3 comprises: machining a first groove on the metal substrate along a first direction of the metal substrate by setting the following parameters: The laser pulse width is 3 to 15 ps, the basic repetition frequency of laser scanning is 2000 kHz, the frequency division is 500 kHz, the laser scanning speed is 1000 to 3000 mm / s, the number of scans is 70 to 90 times, the laser energy is 4 to 6 μJ, and the scanning interval is 0.005 mm; S4, machining second grooves on the plurality of first grooves along the second direction of the metal substrate, and forming micro-nano structures on the surfaces of the plurality of second grooves; The step S4 comprises: By setting the following parameters, a second groove is processed on the metal substrate along the second direction of the metal substrate: The laser pulse width is 3 to 15 ps, the basic repetition frequency of laser scanning is 500 kHz, the laser scanning speed is 500 to 600 mm / s, the number of scans is 8 to 14 times, the laser energy is 9 to 14 μJ, and the scanning interval is 0.008 mm; Wherein, the first direction is perpendicular to the second direction, and the plurality of the first grooves respectively intersect the plurality of the second grooves perpendicularly; The depth of the first groove is greater than the depth of the second groove, and the aspect ratio of the first groove is greater than the aspect ratio of the second groove; The thickness of the metal substrate is 0.5-1 mm.

2. The method for preparing a high heat transfer ultra-thin vapor chamber wick with a hierarchical structure according to claim 1, wherein: The step S1 comprises: Place the metal substrate in an ultrasonic cleaning machine, pour solvent and metal degreasing and degreasing cleaning agent into the ultrasonic cleaning machine until the metal degreasing and degreasing cleaning agent exceeds the surface of the metal substrate, perform ultrasonic cleaning for 3 to 10 minutes, pour out the solvent and metal degreasing and degreasing cleaning agent in the ultrasonic cleaning machine, pour deionized water until the liquid level exceeds the surface of the metal substrate, continue ultrasonic cleaning for 3 to 10 minutes to complete the pretreatment.

3. The method for preparing an ultra-thin vapor chamber wick with high heat transfer performance having a hierarchical structure according to claim 1, characterized in that: The step S3 comprises: The laser pulse width is 9 ps, the laser scanning speed is 2000 mm / s, the number of scans is 80 times, and the laser energy is 5.8 μJ.

4. The method for preparing a high heat transfer ultra-thin vapor chamber wick with a hierarchical structure according to claim 1, wherein: The step S4 comprises: The laser pulse width is 9 ps, the laser scanning speed is 550 mm / s, the number of scans is 12 times, and the laser energy is 10.8 μJ.

5. The method for preparing a high heat transfer ultra-thin vapor chamber wick with a hierarchical structure according to claim 1, wherein: The material of the metal substrate is brass, copper or aluminum.

6. An ultra-thin vapor chamber wick, characterized in that: The invention is prepared by the method for preparing an ultra-thin vapor chamber wick with high heat transfer performance and a hierarchical structure as claimed in any one of claims 1 to 5.

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