Liquid absorption core with concave-convex structure, preparation method of liquid absorption core and vapor chamber

Abstract

The invention belongs to the technical field of vapor chambers, and particularly relates to a liquid absorption core with a concave-convex structure, a preparation method of the liquid absorption core and a vapor chamber. According to the wick with the concave-convex structure, the upper surface of the wick is provided with a plurality of convex parts and concave parts which are arranged at intervals, the height h of the concave parts is 30-50 microns, the height H of the convex parts is 150-250 microns, and the ratio of the total volume V1 of the concave parts to the volume V of the wick is 1-3. According to the vapor chamber manufactured by the liquid absorption core with the concave-convex structure, the heat transfer power Qmax can be maximized, and the evaporation efficiency of an evaporation area can be maximized, so that the comprehensive performance of the vapor chamber is integrally improved. A multi-steam-channel and multi-liquid-backflow-channel structure meets the use requirement of a large-area vapor chamber and an ultra-thin vapor chamber when the heat source power is 5-8 W, and the temperature difference between the upper surface of a heat source of the vapor chamber and the cold end of the upper surface can be controlled within 5 DEG C.

Description

Technical Field

[0001] The invention belongs to the technical field of vapor chambers, and in particular relates to a liquid wick with a concave-convex structure, a preparation method thereof, and a vapor chamber. Background Art

[0002] With the advancement of 5G network construction, the functions of 5G terminal equipment have become more diversified. Chips need to cope with complex environmental conditions, and their high-speed operation will bring high heat problems. While meeting the requirements of high integration, lightness and thinness of terminal equipment and maximization of space utilization, higher performance heat spreaders must be considered. Since the internal structure of the heat spreader is delicate and changeable, and the phase change heat transfer mechanism is very complex, there are many factors that affect the heat transfer performance. As the heat spreader develops towards small temperature difference and high power, many design problems must be considered comprehensively. The present invention designs a wick structure with a wavy structure to achieve the design problem of effective evaporation and continuous working fluid supply, and effectively solves the problem of local high heat flux heat dissipation of microelectronic devices in confined spaces.

[0003] For existing technologies, on the one hand, the heat transfer performance of the vapor chamber must be met and the heat transfer power must be improved, and on the other hand, effective evaporation must be achieved. Studies have shown that increasing the volume of the wick can increase the amount of evaporated water and the heat transfer Qmax, but too much water in the evaporation zone will form a liquid film that increases the evaporation resistance and reduces the vapor chamber's heat dissipation performance. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a liquid wick with a concave-convex structure and a preparation method thereof, and a vapor chamber. The present invention can maximize the heat transfer power Qmax and the evaporation efficiency of the evaporation zone by using a liquid wick with a concave-convex structure in the vapor chamber, thereby improving the overall performance of the vapor chamber.

[0005] In order to achieve the above technical objectives, the technical solution adopted by the embodiment of the present invention is: In the first aspect, an embodiment of the present invention provides a liquid absorbent core having a concave-convex structure, wherein the upper surface of the liquid absorbent core is provided with a plurality of convex portions and concave portions arranged at intervals, the height h of the concave portion is 30-50 μm, the height H of the convex portion is 150-250 μm, and the total volume V1 of the concave portion: the volume V of the liquid absorbent core=1-3.

[0006] Furthermore, the liquid absorbent core is integrally formed and is made of one or more of foam metal, two-dimensional metal wire mesh, metal spiral braided wire and sintered metal powder; the porosity of the liquid absorbent core is 60%-80%, and the pore size is 10-25μm.

[0007] Furthermore, the material of the liquid wick is metal copper or stainless steel.

[0008] Furthermore, the cross section of the lower concave portion is square or arc-shaped, and the upper surfaces of the convex portions are located on the same horizontal plane; When the cross section of the concave portion is an arc, the minimum height h of the bottom of the concave portion from the lower surface of the absorbent core is 30-50 μm, the maximum width b of the concave portion is 2-8 mm, the width of the convex portion in the middle part is 2a, and the width of the convex portions at both ends is a, where a=0.5-4 mm; When the cross section of the concave portion is square, the height h of the bottom of the concave portion from the lower surface of the absorbent core is 30-50 μm, the width of the concave portion is b=2-8 mm, the width of the convex portion in the middle part is 2a, and the width of the convex portions at both ends is a, where a=0.5-4 mm.

[0009] Furthermore, the liquid absorbent core is formed by forming a copper slurry mold and then sintering it as a whole, or is formed by compositely stacking liquid absorbent cores of different shapes and thicknesses.

[0010] In a second aspect, an embodiment of the present invention provides a method for preparing the liquid absorbent core having a concave-convex structure as described in the first aspect, using a mold forming method, comprising the following steps: (1) preparing a stepped or wavy wet film by screen printing, using cold isostatically pressed graphite as a mold substrate for forming a stepped or wavy wet film with copper slurry, and the shape and size of the mold are opposite to the shape and size of the finished product of the liquid absorbent core to be obtained; (2) The stepped or wavy wet film formed by the copper slurry is sent into a sintering furnace together with a graphite substrate to sinter the porous copper foam. The sintering temperature is 900-1000°C, the sintering time is 1-3 hours, and the atmosphere is a hydrogen-nitrogen mixed gas, in which the volume fraction of hydrogen is 10%-20%; (3) The obtained porous copper foam metal sheet is cut and processed to obtain a liquid absorbent core with a concave-convex structure.

[0011] Furthermore, the preparation method of the copper slurry comprises the following steps: The copper powder and the solvent are uniformly mixed in a dispersing mixer at a stirring speed of 1000-5000 rpm for 30-60 min and the temperature is controlled below 35° C. to obtain a copper slurry; a pore-forming agent is added to the copper slurry and dispersed at a speed of 6000-10000 rpm for 5-10 min until the slurry is uniformly dispersed; The copper slurry comprises, by mass fraction, 60%-80% copper powder, 20%-35% solvent and 0-5% pore-forming agent, and the particle size of the copper powder is 200-400 mesh; Calculated by mass fraction, the solvent includes: 0.5%-5% of a binder PVA, 2%-6% of a wetting agent PEG wet material, 3%-9% of a thixotropic agent, and the remainder is one or more of water, ethanol and glycerol; The thixotropic agent is one or more of polyamide wax, ethyl cellulose and bentonite; The pore-forming agent is PMMA microspheres and / or PS microspheres.

[0012] In a third aspect, an embodiment of the present invention provides a method for preparing the liquid absorbent core having a concave-convex structure according to the first aspect, which adopts a stacking method and comprises the following steps: a. Prepare several flat copper foams of different thicknesses by screen printing and sinter them; b. Using a thin copper foam as the base, a thick copper foam is partially superimposed on the copper foam base according to the shape and size of the stepped or wavy wick. The two components are clamped by a graphite flat mold and sintered as a whole to obtain a wick with a concave-convex structure.

[0013] In a fourth aspect, an embodiment of the present invention provides a heat spreader, the heat spreader comprising an upper shell plate and a lower shell plate, the upper shell plate and the lower shell plate are sealed and connected at their peripheries to form a sealed working medium chamber, the sealed working medium chamber is in a vacuum state, and is filled with a liquid working medium, a liquid wick is further provided in the sealed working medium chamber, the upper surface of the liquid wick is tightly fitted with the lower surface of the upper shell plate, and the lower surface of the liquid wick is tightly fitted with the upper surface of the lower shell plate; The liquid absorbent core adopts the liquid absorbent core with a concave-convex structure described in the first aspect.

[0014] The technical solution provided by the embodiment of the present invention has the following beneficial effects: (1) The liquid absorbent core with a concave-convex structure of the present invention has a convex portion and a concave portion. Since the liquid absorbent core material is thin in the concave portion, the resistance encountered by the liquid in the evaporation process is small, and it is easy to form steam, and the steam is transmitted in the channel formed by adjacent wave peaks; the convex portion has a larger volume and can store a larger amount of working fluid, and can continuously replenish the working fluid in the evaporation area; and the steam pressure is very large in the concave portion and smaller in the convex portion, thereby constructing a certain pressure gradient, realizing rapid steam transmission, and improving the steam transmission rate, which is beneficial to improving the temperature uniformity of the overall heat spreader.

[0015] (2) The wick with a concave-convex structure of the present invention is actually a wick with a coplanar structure design (the steam channel and the liquid reflux channel are in the same plane) of multiple steam channels and multiple liquid reflux channels. It has an effective steam outlet gate, and steam can be released at the bottom of the trough arc and quickly enter the multiple steam channels. At the same time, the circulation rate of steam and liquid in the entire heat spreader is increased, which is beneficial to improving the overall temperature uniformity of the heat spreader.

[0016] (3) The heat spreader made of the liquid wick with a concave-convex structure of the present invention can maximize the heat transfer power Qmax and the evaporation efficiency of the evaporation zone, thereby improving the overall performance of the heat spreader. In a multi-steam channel and multi-liquid reflux channel structure that meets the requirements of a large-area heat spreader (such as a width of 60mm×length of 100mm×height of 0.3mm) and a heat source power of 5-8W, the temperature difference between the upper surface of the heat source of the heat spreader and the cold end of the upper surface can be controlled within 5°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the cross-sectional structure of the wavy liquid absorbent core in Example 1.

[0018] Figure 2 Schematic diagram of the cross-sectional structure of the stepped liquid absorbent core in Example 2.

[0019] Figure 3 It is a schematic diagram of the cross-sectional structure of the heat spreader in Example 1.

[0020] Figure 4 It is a schematic diagram of the cross-sectional structure of the heat spreader in Example 2.

[0021] Figure 5 It is a schematic diagram of the cross-sectional structure of the heat spreader in the comparative example.

[0022] Explanation of the reference numerals: 1- raised portion; 2- recessed portion; 3- heat sink; 31- upper shell plate; 32- lower shell plate; 4- liquid absorption core; 5- solder paste; 6- support column. DETAILED DESCRIPTION

[0023] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by directional words such as "inside, outside", "up, down", "left, right", etc. are usually based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention 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 direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention.

[0024] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0025] Example 1 like Figure 1As shown, a liquid absorbent core with a concave-convex structure is provided on the upper surface of the liquid absorbent core with a plurality of convex portions 1 and concave portions 2 arranged at intervals, the minimum height h of the concave portion 2 is 30 μm, the height H of the convex portion 1 is 200 μm, and the total volume V1 of the concave portion 2: the volume V of the liquid absorbent core=1.5.

[0026] The absorbent core body 1 is made of foamed copper, and the cross section of the lower concave portion 2 is arc-shaped. In this case, the absorbent core is a wavy absorbent core; the porosity of the absorbent core is 70%, and the pore size is 15 μm.

[0027] From top to bottom, the lower concave portion 2 is a groove with a gradually decreasing opening, and the maximum width of the lower concave portion 2 is b=6mm. The width of the raised portion 1 in the middle part is 2a, and the width of the raised portions 1 at both ends is a, where a=0.5mm.

[0028] The method for preparing the wavy liquid-absorbing core comprises the following steps: (1) Preparation of copper slurry: Copper powder and solvent were mixed uniformly in a disperser at a stirring speed of 1000 rpm for 30 min at a temperature of 25°C to obtain copper slurry; a pore-forming agent was added to the copper slurry, and the mixture was dispersed at a high speed of 6000 rpm for 5 min and stirred until uniform.

[0029] The copper slurry includes the following components by mass fraction: 70% copper powder, 29% solvent and 1% pore-forming agent PMMA microspheres, and the particle size of the copper powder is 300 meshes; Calculated by mass fraction, the solvent ratio is: 1% by mass of the binder PVA, 3% by mass of the wetting agent PEG wet material, 7% by mass of the thixotropic agent, and the remainder is solvent water; the thixotropic agent is polyamide wax.

[0030] (2) Preparation of wavy liquid-absorbing core: a. First, a wavy wet film is prepared by screen printing, the size of which is 100 mm × 200 mm, and cold isostatic graphite is selected as a mold substrate for forming a wavy wet film with copper slurry. The shape and size of the mold are opposite to the shape and size of the finished liquid-absorbing core to be obtained; b. The wavy wet film formed by the copper slurry and the graphite substrate are sent into a sintering furnace to sinter the porous copper foam. The sintering temperature is 950°C, the sintering time is 2 hours, and the atmosphere is a hydrogen-nitrogen mixed gas, in which the volume fraction of hydrogen is 10%; c. The obtained porous copper foam metal sheet is cut and processed to obtain a wavy liquid absorbent core.

[0031] (3) Preparation of a heat spreader: A heat spreader of 60 mm (width) × 100 mm (length) × 0.3 mm (height) is prepared. The heat spreader 3 includes an upper shell plate 31 and a lower shell plate 32. The upper shell plate 31 and the lower shell plate 32 are sealed and connected at their peripheries to form a sealed working medium cavity. The sealed working medium cavity is in a vacuum state and is filled with a liquid working medium. A liquid wick 4 is also placed in the sealed working medium cavity. The upper surface of the liquid wick 4 is tightly fitted with the lower surface of the upper shell plate 31, and the lower surface of the liquid wick 4 is tightly fitted with the upper surface of the lower shell plate 32. Figure 3 shown.

[0032] The absorbent core 4 is the wavy absorbent core obtained in step (2), the absorbent core thickness is 200 μm, the absorbent core porosity is 70%, and the pore size is 15 μm. The upper shell plate 31 and the lower shell plate 32 are both made of copper plates, and the thickness of the upper shell plate 31 and the lower shell plate 32 are both 50 μm. The above-mentioned heat spreader can meet the temperature uniformity of the heat source power of 5-8W, and the temperature difference between the upper surface of the heat source of the heat spreader and the cold end of the upper surface can be controlled within 3°C.

[0033] Example 2 like Figure 2 As shown, a liquid absorbent core with a concave-convex structure is provided on the upper surface of the liquid absorbent core with a plurality of convex portions 1 and concave portions 2 arranged at intervals, the height h of the concave portion 2 is 50 μm, the height H of the convex portion 1 is 200 μm, and the total volume V1 of the concave portion 2: the volume V of the liquid absorbent core=2.

[0034] The liquid wick is made of foam copper, and the cross section of the lower concave portion 2 is square. At this time, the liquid wick is a stepped liquid wick, and the porosity of the liquid wick is 75%, and the pore size is 20 μm.

[0035] The width of the lower concave portion 2 is b=6mm, the width of the raised portion 1 in the middle is 2a, and the width of the raised portions 1 at both ends is a, where a=0.5mm.

[0036] The preparation method of the stepped liquid-absorbing core comprises the following steps: (1) Preparation of copper slurry: Copper powder and solvent were mixed uniformly in a disperser at a stirring speed of 5000 rpm for 30 min at a temperature of 25°C to obtain copper slurry; a pore-forming agent was added to the copper slurry, and the mixture was dispersed at a high speed of 10000 rpm for 5 min and stirred until uniform.

[0037] The copper slurry includes the following components by mass fraction: 77% copper powder, 22% solvent and 1% pore-forming agent; the particle size of the copper powder is 300 mesh; The solvent ratio is calculated by mass fraction as follows: the mass percentage of the binder PVA is 1%, the percentage of the wetting agent PEG wet material is 3%, the percentage of the thixotropic agent is 7%, the balance is the solvent water, the pore-forming agent is PMMA microspheres, and the thixotropic agent is bentonite; (2) Preparation of stepped wick: a. First, a wavy wet film with a size of 100 mm × 200 mm is prepared by screen printing, and cold isostatic graphite is used as a mold substrate for forming a stepped wet film with copper slurry. The shape and size of the mold are opposite to the shape and size of the finished wick to be obtained; b. The stepped wet film formed by the copper slurry and the graphite substrate are sent into a sintering furnace to sinter the porous copper foam at a temperature of 980°C for 2 hours in a hydrogen-nitrogen mixed gas atmosphere, wherein the volume fraction of hydrogen is 10%; c. The obtained porous copper foam metal sheet is cut and processed to obtain a stepped liquid wick.

[0038] (3) Preparation of a heat spreader: A heat spreader of 60 mm (width) × 100 mm (length) × 0.3 mm (height) is prepared. The heat spreader 3 includes an upper shell plate 31 and a lower shell plate 32. The upper shell plate 31 and the lower shell plate 32 are sealed and connected at their peripheries to form a sealed working medium cavity. The sealed working medium cavity is in a vacuum state and is filled with a liquid working medium. A liquid wick 4 is also provided in the sealed working medium cavity. The upper surface of the liquid wick 4 is tightly fitted with the lower surface of the upper shell plate 31, and the lower surface of the liquid wick 4 is tightly fitted with the upper surface of the lower shell plate 32. Figure 4 shown.

[0039] The absorbent core 4 is a stepped absorbent core obtained in step (2), the absorbent core thickness is 200 μm, the absorbent core porosity is 75%, and the pore size is 20 μm. The upper shell plate 31 and the lower shell plate 32 are both made of copper plates, and the thickness of the upper shell plate 31 and the lower shell plate 32 are both 50 μm. The above-mentioned heat spreader can meet the temperature uniformity of the heat source power of 5-8W, and the temperature difference between the upper surface of the heat source of the heat spreader and the cold end of the upper surface can be controlled within 5°C.

[0040] Example 3 The stepped liquid-absorbing core in Example 2 is prepared by stacking, and the preparation method comprises the following steps: a. Prepare two kinds of planar copper foams with different thicknesses by screen printing and sinter them to obtain copper foams with a thickness of 50 μm and copper foams with a thickness of 200 μm; b. Using 50 μm thick copper foam as the base, according to the shape and size of the stepped liquid absorbent core, partially superimpose 200 μm thick copper foam on the 50 μm thick copper foam base, clamp these two components with a graphite flat mold and sinter them as a whole to obtain the stepped liquid absorbent core.

[0041] Preparation of a heat spreader: Prepare a heat spreader of 60 mm (width) × 100 mm (length) × 0.3 mm (height). The heat spreader 3 includes an upper shell plate 31 and a lower shell plate 32. The upper shell plate 31 and the lower shell plate 32 are sealed and connected at their peripheries to form a sealed working fluid cavity. The sealed working fluid cavity is in a vacuum state and is filled with liquid working fluid. A liquid wick 4 is also provided in the sealed working fluid cavity. The upper surface of the liquid wick 4 is tightly fitted with the lower surface of the upper shell plate 31, and the lower surface of the liquid wick 4 is tightly fitted with the upper surface of the lower shell plate 32.

[0042] The absorbent core 4 is a stepped absorbent core obtained by stacking, with a thickness of 200 μm, a porosity of 75%, and a pore size of 20 μm. The upper shell plate 31 and the lower shell plate 32 are both made of copper plates, and the thickness of the upper shell plate 31 and the lower shell plate 32 are both 50 μm. The above-mentioned heat spreader can meet the temperature uniformity of the heat source power of 5-8W, and the temperature difference between the upper surface of the heat source of the heat spreader and the cold end of the upper surface can be controlled within 5°C.

[0043] Example 4 A liquid absorbent core with a concave-convex structure, wherein a plurality of convex portions 1 and concave portions 2 are arranged at intervals on the upper surface of the liquid absorbent core, the height h of the concave portions 2 is 30 μm, the height H of the convex portions 1 is 200 μm, and the total volume V1 of the concave portions 2: the volume V of the liquid absorbent core=2.

[0044] The liquid absorbent core is made of foam copper, and the cross section of the lower concave portion 2 is arc-shaped. At this time, the liquid absorbent core is a wavy liquid absorbent core, and the porosity of the liquid absorbent core is 65%, and the pore size is 15 μm.

[0045] From top to bottom, the lower concave portion 2 is a groove with a gradually decreasing opening, and the maximum width of the lower concave portion 2 is b=6mm. The width of the raised portion 1 in the middle part is 2a, and the width of the raised portions 1 at both ends is a, where a=0.5mm.

[0046] The method for preparing the wavy liquid-absorbing core comprises the following steps: (1) Preparation of copper slurry: Copper powder and solvent were mixed uniformly in a disperser at a stirring speed of 3000 rpm for 30 min at a temperature of 25°C to obtain copper slurry; a pore-forming agent was added to the copper slurry, and the mixture was dispersed at a high speed of 8000 rpm for 5 min and stirred until uniform.

[0047] The copper slurry includes the following components by mass fraction: 75% copper powder, 24.5% solvent and 0.5% pore-forming agent PMMA microspheres; the particle size of the copper powder is 300 mesh; Calculated by mass fraction, the solvent ratio is: 1% by mass of the binder PVA, 3% by mass of the wetting agent PEG wet material, 5% by mass of the thixotropic agent, and the remainder is solvent water; the thixotropic agent is polyamide wax.

[0048] (2) Preparation of wavy liquid-absorbing core: a. First, a wavy wet film is prepared by screen printing, the size of which is 100 mm × 200 mm, and cold isostatic graphite is selected as a mold substrate for forming a wavy wet film with copper slurry. The shape and size of the mold are opposite to the shape and size of the finished liquid-absorbing core to be obtained; b. The wavy wet film formed by the copper slurry and the graphite substrate are sent into a sintering furnace to sinter the porous copper foam. The sintering temperature is 950°C, the sintering time is 1h, and the atmosphere is a hydrogen-nitrogen mixed gas, in which the volume fraction of hydrogen is 10%; c. The obtained porous copper foam metal sheet is cut and processed to obtain a wavy liquid absorbent core.

[0049] (3) Preparation of a heat spreader: A heat spreader of 60 mm (width) × 100 mm (length) × 0.3 mm (height) is prepared. The heat spreader 3 includes an upper shell plate 31 and a lower shell plate 32. The upper shell plate 31 and the lower shell plate 32 are sealed and connected at their peripheries to form a sealed working fluid chamber. The sealed working fluid chamber is in a vacuum state and is filled with a liquid working fluid. A liquid wick 4 is also provided in the sealed working fluid chamber. The upper surface of the liquid wick 4 is tightly fitted with the lower surface of the upper shell plate 31, and the lower surface of the liquid wick 4 is tightly fitted with the upper surface of the lower shell plate 32.

[0050] The absorbent core 4 is the wavy absorbent core obtained in step (2), the absorbent core thickness is 200 μm, the absorbent core porosity is 65%, and the pore size is 15 μm. The upper shell plate 31 and the lower shell plate 32 are both made of copper plates, and the thickness of the upper shell plate 31 and the lower shell plate 32 are both 50 μm. The above-mentioned heat spreader can meet the temperature uniformity of the heat source power of 5-8W, and the temperature difference between the upper surface of the heat source of the heat spreader and the cold end of the upper surface can be controlled within 3°C.

[0051] Example 5 A liquid absorbent core with a concave-convex structure, wherein a plurality of convex portions 1 and concave portions 2 are arranged at intervals on the upper surface of the liquid absorbent core, the height h of the concave portions 2 is 50 μm, the height H of the convex portions 1 is 200 μm, and the total volume V1 of the concave portions 2 is 5 / 3 of the volume V of the liquid absorbent core.

[0052] The liquid wick is made of foam copper, and the cross section of the lower concave portion 2 is square. At this time, the liquid wick is a stepped liquid wick, and the porosity of the liquid wick is 70%, and the pore size is 12 μm.

[0053] The width of the lower concave portion 2 is b=5mm, the width of the raised portion 1 in the middle is 2a, and the width of the raised portions 1 at both ends is a, where a=0.5mm.

[0054] The preparation method of the stepped liquid-absorbing core comprises the following steps: (1) Preparation of copper slurry: Copper powder and solvent were mixed uniformly in a disperser at a stirring speed of 2000 rpm for 30 min at a temperature of 25°C to obtain copper slurry; a pore-forming agent was added to the copper slurry, and the mixture was dispersed at a high speed of 7500 rpm for 5 min and stirred until uniform.

[0055] The copper slurry includes the following components by mass fraction: 78% copper powder, 21.5% solvent and 0.5% pore-forming agent; the particle size of the copper powder is 300 mesh; Calculated by mass fraction, the solvent ratio is: 1% by mass of the binder PVA, 3.5% by mass of the wetting agent PEG wet material, 6% by mass of the thixotropic agent, the remainder is solvent water, the pore-forming agent is PMMA microspheres, and the thixotropic agent is polyamide wax.

[0056] (2) Preparation of stepped wick: a. First, a wavy wet film with a size of 100 mm × 200 mm is prepared by screen printing, and cold isostatic graphite is used as a mold substrate for forming a stepped wet film with copper slurry. The shape and size of the mold are opposite to the shape and size of the finished wick to be obtained; b. The stepped wet film formed by the copper slurry and the graphite substrate are sent into a sintering furnace to sinter the porous copper foam at a sintering temperature of 950°C for 2 hours in a hydrogen-nitrogen mixed gas atmosphere, wherein the volume fraction of hydrogen is 10%; c. The obtained porous copper foam metal sheet is cut and processed to obtain a stepped liquid wick.

[0057] (3) Preparation of a heat spreader: A heat spreader of 60 mm (width) × 100 mm (length) × 0.3 mm (height) is prepared. The heat spreader 3 includes an upper shell plate 31 and a lower shell plate 32. The upper shell plate 31 and the lower shell plate 32 are sealed and connected at their peripheries to form a sealed working fluid chamber. The sealed working fluid chamber is in a vacuum state and is filled with a liquid working fluid. A liquid wick 4 is also provided in the sealed working fluid chamber. The upper surface of the liquid wick 4 is tightly fitted with the lower surface of the upper shell plate 31, and the lower surface of the liquid wick 4 is tightly fitted with the upper surface of the lower shell plate 32.

[0058] The absorbent core 4 is a stepped absorbent core obtained in step (2), the absorbent core thickness is 200 μm, the absorbent core porosity is 70%, and the pore size is 12 μm. The upper shell plate 31 and the lower shell plate 32 are both made of copper plates, and the thickness of the upper shell plate 31 and the lower shell plate 32 are both 50 μm. The above-mentioned heat spreader can meet the temperature uniformity of the heat source power of 5-8W, and the temperature difference between the upper surface of the heat source of the heat spreader and the cold end of the upper surface can be controlled within 3°C.

[0059] Comparative Example Prepare a heat spreader: prepare a heat spreader of 60 mm (width) × 100 mm (length) × 0.3 mm (height). The heat spreader 3 includes an upper shell plate 31 and a lower shell plate 32. The upper shell plate 31 and the lower shell plate 32 are sealed and connected at their peripheries to form a sealed working medium cavity. The sealed working medium cavity is in a vacuum state and is filled with a liquid working medium. The inner surface of the upper shell plate 31 is a concave surface. The inner surface of the upper shell plate 31 is provided with regularly arranged support columns 6. A liquid wick 4 is placed in the sealed working medium cavity. The upper surface of the liquid wick 4 is tightly fitted with the lower surface of the support column 6, and the lower surface of the liquid wick 4 is tightly fitted with the upper surface of the lower shell plate 32. Figure 5 shown.

[0060] The liquid wick 4 is a two-dimensional metal copper mesh with a mesh size of 250 meshes, a wire diameter of 0.04 mm, a copper mesh thickness of 70 μm, a porosity of 52%, and a pore size of 60 μm.

[0061] The upper shell plate 31 and the lower shell plate 32 are both made of copper plates, and the upper shell plate 31 and the lower shell plate 32 are welded with solder paste 5. The thickness of the upper shell plate 31 and the lower shell plate 32 are both 50μm, and the height of the steam channel is 130μm. When the heat source power is 5W, the temperature difference between the upper surface of the heat source of the above-mentioned heat spreader and the cold end of the upper surface is more than 10°C, which cannot achieve the requirement of 5°C temperature difference on the upper surface.

[0062] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A liquid-absorbing core having a concave-convex structure, characterized in that: The upper surface of the liquid absorbent core is provided with a plurality of convex portions (1) and concave portions (2) arranged at intervals, the height h of the concave portions (2) is 30-50 μm, the height H of the convex portions (1) is 150-250 μm, and the total volume V1 of the concave portions (2): the volume V of the liquid absorbent core = 1-3.

2. The wavy structure liquid absorbent core according to claim 1, characterized in that: The liquid absorbing core is integrally formed and is made of one or more of foam metal, two-dimensional metal wire mesh, metal spiral braided wire and sintered metal powder; the porosity of the liquid absorbing core is 60%-80%, and the pore size is 10-25μm.

3. The wavy structure liquid absorbent core according to claim 2, characterized in that: The material of the liquid absorbing core is metal copper or stainless steel.

4. The wavy structure liquid absorbent core according to claim 1, characterized in that: The cross section of the concave portion (2) is square or arc-shaped, and the upper surfaces of the convex portions (1) are located on the same horizontal plane; When the cross section of the concave portion (2) is an arc, the minimum height h of the bottom of the concave portion (2) from the lower surface of the liquid absorbent core is 30-50 μm, the maximum width b of the concave portion (2) is 2-8 mm, the width of the convex portion (1) in the middle is 2a, and the width of the convex portions (1) at both ends is a, wherein a=0.5-4 mm; When the cross section of the concave portion (2) is square, the height h of the bottom of the concave portion (2) from the lower surface of the liquid absorbent core is 30-50 μm, the width b of the concave portion (2) is 2-8 mm, the width of the convex portion (1) in the middle is 2a, and the width of the convex portions (1) at both ends is a, wherein a=0.5-4 mm.

5. The wavy structure liquid absorbent core according to claim 1, characterized in that: The liquid wick is formed by forming a copper slurry mold and then sintering it as a whole, or is formed by compound stacking liquid wicks of different shapes and thicknesses.

6. The method for preparing the liquid-absorbing core having a concave-convex structure according to any one of claims 1 to 5, characterized in that: The mold forming method includes the following steps: (1) preparing a stepped or wavy wet film by screen printing, using cold isostatically pressed graphite as a mold substrate for forming a stepped or wavy wet film with copper slurry, and the shape and size of the mold are opposite to the shape and size of the finished product of the liquid absorbent core to be obtained; (2) The stepped or wavy wet film formed by the copper slurry is sent into a sintering furnace together with a graphite substrate to sinter the porous copper foam. The sintering temperature is 900-1000°C, the sintering time is 1-3 hours, and the atmosphere is a hydrogen-nitrogen mixed gas, in which the volume fraction of hydrogen is 10%-20%; (3) The obtained porous copper foam metal sheet is cut and processed to obtain a liquid absorbent core with a concave-convex structure.

7. The method for preparing the liquid-absorbing core with a concave-convex structure according to claim 6, characterized in that: The preparation method of the copper slurry comprises the following steps: The copper powder and the solvent are uniformly mixed in a dispersing mixer at a stirring speed of 1000-5000 rpm for 30-60 min and the temperature is controlled below 35° C. to obtain a copper slurry; a pore-forming agent is added to the copper slurry and dispersed at a speed of 6000-10000 rpm for 5-10 min until the slurry is uniformly dispersed; The copper slurry comprises, by mass fraction, 60%-80% copper powder, 20%-35% solvent and 0-5% pore-forming agent, and the particle size of the copper powder is 200-400 mesh; Calculated by mass fraction, the solvent includes: 0.5%-5% of a binder PVA, 2%-6% of a wetting agent PEG wet material, 3%-9% of a thixotropic agent, and the remainder is one or more of water, ethanol and glycerol; The thixotropic agent is one or more of polyamide wax, ethyl cellulose and bentonite; The pore-forming agent is PMMA microspheres and / or PS microspheres.

8. The method for preparing the liquid absorbent core with a concave-convex structure according to any one of claims 1 to 5, in a stacking manner, comprising the following steps: a. Prepare several flat copper foams of different thicknesses by screen printing and sinter them; b. Using a thin copper foam as the base, a thick copper foam is partially superimposed on the copper foam base according to the shape and size of the stepped or wavy wick. The two components are clamped by a graphite flat mold and sintered as a whole to obtain a wick with a concave-convex structure.

9. A heat spreader, characterized in that: The heat spreader (3) comprises an upper shell plate (31) and a lower shell plate (32); the upper shell plate (31) and the lower shell plate (32) are sealed and connected at their peripheries to form a sealed working medium cavity; the sealed working medium cavity is in a vacuum state and is filled with a liquid working medium; a liquid wick (4) is also provided in the sealed working medium cavity; the upper surface of the liquid wick (4) is in close contact with the lower surface of the upper shell plate (31); and the lower surface of the liquid wick (4) is in close contact with the upper surface of the lower shell plate (32); The liquid absorbent core (4) is the liquid absorbent core with a concave-convex structure as described in any one of claims 1 to 5.

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