Fiber liquid absorption core, preparation method thereof and application of fiber liquid absorption core on chip phase change heat dissipation substrate

Abstract

The invention belongs to the field of liquid absorption core manufacturing, and particularly relates to a fiber liquid absorption core, a preparation method thereof and application of the fiber liquid absorption core to a chip phase change heat dissipation substrate. The preparation method of the fiber wick comprises the following steps: S1, preparing a plurality of spiral short fibers by a turning method; the diameter of the spiral short fiber is 50-200 [mu] m, and the length of the spiral short fiber is 1-4 mm; and S2, sintering the plurality of spiral short fibers on the substrate through a high-temperature solid-phase sintering process to prepare the fiber wick. The fiber liquid absorption core has the high capillary pressure of a powder sintering liquid absorption core and the good permeability and stability of the fiber sintering liquid absorption core, and the molybdenum-copper chip phase change heat dissipation substrate prepared from the fiber liquid absorption core has the high heat dissipation capacity and can meet the heat dissipation requirement of a gallium nitride chip.

Description

Technical Field

[0001] This invention belongs to the field of liquid absorbent core manufacturing, specifically relating to a fiber liquid absorbent core, its preparation method, and its application on a chip phase change heat dissipation substrate. Background Technology

[0002] Gallium nitride (GaN) chips are evolving towards miniaturization and high power density, resulting in a dramatic increase in heat flux density during operation. If the heat generated during operation cannot be efficiently dissipated, the chip's performance will be limited. Therefore, effective thermal management is crucial for fully realizing the chip's performance potential.

[0003] Currently, copper heat sinks are commonly used for thermal management of gallium nitride chips, but due to the coefficient of thermal expansion of copper (approximately 16.5 × 10⁻⁶), this method is problematic. -6 / °C) and gallium nitride chip (approximately 5.6 × 10⁻⁶) -6 The temperature difference between the copper heat sink and the chip is significant. The heat generated during chip operation causes a rise in temperature, resulting in a large difference in thermal strain between the two. This leads to substantial thermal stress at the interface, which can easily damage the interface structure and cause the heat sink to fail. Adding a transition layer between the chip and the copper substrate can reduce the risk of structural damage, but it increases thermal resistance, preventing rapid heat dissipation. The coefficient of thermal expansion of molybdenum-copper (70% molybdenum, 30% copper) is approximately 7.6 × 10⁻⁶. -6 At / °C, compared to copper, molybdenum-copper has a thermal expansion coefficient closer to that of gallium nitride (GaN) chips. Therefore, using molybdenum-copper as a heat sink material can reduce thermal stress at the interface during chip operation, effectively reducing the risk of structural damage at the interface. However, the thermal conductivity of molybdenum-copper heat sinks (approximately 180 W / m·K) is low, making it difficult to efficiently dissipate the heat generated by the chip. Currently, neither of the above two methods can solve the problem of efficient heat dissipation for chips.

[0004] Existing technology CN111673086A discloses a porous fiber liquid-absorbing core with in-situ surface growth of carbon nanotubes and its preparation method. The method involves using a multi-toothed lathe tool to cut continuous long fibers from a stainless steel rod; cutting the long fibers into short fibers and pressing them into a mold; placing the mold in a vacuum sintering furnace for solid-state sintering; removing the sintered porous material from the stainless steel fibers after the furnace cools to room temperature; cleaning and acid-washing the surface of the porous fiber liquid-absorbing core; placing the porous fiber liquid-absorbing core in an atmosphere sintering furnace for in-situ thermal CVD growth of carbon nanotubes; and removing the composite porous fiber liquid-absorbing core after cooling to room temperature. This core possesses a three-dimensional network porous structure with high thermal conductivity carbon nanotubes attached to its surface, exhibiting advantages such as high specific surface area, good boiling heat transfer performance, simple manufacturing process, and low cost. However, this existing technology prepares continuous, linear fibers, requiring additional cutting processes to separate the long fibers into short fibers, and the prepared liquid-absorbing core fibers are prone to separation. Summary of the Invention

[0005] The purpose of this invention is to provide a fiber liquid-absorbing core with both high structural strength and capillary pressure, its preparation method, and its application on a chip phase change heat dissipation substrate.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a fiber absorbent core includes the following steps: S1. Multiple helical short fibers are prepared by turning; the diameter of the helical short fibers is 50-200μm and the length is 1-4mm; S2. Multiple helical short fibers are sintered onto a substrate using a high-temperature solid-state sintering process to prepare a fiber liquid-absorbing core.

[0007] In one preferred embodiment, the helical short fibers are made of molybdenum copper.

[0008] The molybdenum-copper material used in this embodiment of the invention was purchased from Shenzhen Anteng Metal Technology Co., Ltd.

[0009] In one preferred embodiment, the spiral short fiber has a spiral diameter of 100-400 μm, a pitch of 300-600 μm, and 2-6 turns.

[0010] If the fiber diameter is too small, its strength is low and it is prone to breakage. If the fiber diameter is too large, its strength is high during processing and it is not easy to break into short fibers on its own. If the fiber length is too short, the number of fiber helical turns will be limited, reducing the entanglement between fibers, making the fibers relatively easy to separate, resulting in a decrease in the strength of the absorbent core structure. On the other hand, the metal material used in this invention is a brittle powder metallurgy material. During the fiber preparation process, the fiber generates internal stress. If the fiber length is too long, the fiber is prone to breakage, so its length needs to be controlled within 4 mm. If the fiber helical diameter is too small, the helical entanglement effect between fibers is limited. If the fiber helical diameter is too large, its strength is low and it is prone to breakage. If the fiber pitch is too small or too large, the helical entanglement effect between fibers is limited. If the number of fiber turns is too small, the helical entanglement effect between fibers is limited; if the number of fiber turns is too large, the fiber length is long, the strength is low, and it is prone to breakage.

[0011] In one preferred embodiment, during the turning process, the tool parameters are: tooth height of 0.2-0.4 mm, tooth width of 0.3-0.6 mm, cutting speed of 50-180 r / min, cutting depth of 0.05-0.2 mm, and feed rate of 0.05-0.2 mm / r.

[0012] If the tooth height is too low (<0.2 mm), it is difficult to break the chips; if the tooth height is too high (>0.4 mm), it is easy to chip; if the tooth width is too small (<0.3 mm), it is difficult to break the chips; if the tooth width is too large (>0.6 mm), it is difficult to produce spiral fibers.

[0013] In one preferred embodiment, the solid-state sintering temperature is 1100℃~1300℃, and the sintering process adopts a segmented heating method: when the temperature inside the sintering furnace is below 800℃, the heating rate is 5℃ / min; when the temperature inside the furnace reaches 800℃, the heating rate is 3℃ / min; and the sintering time is 60min~120min.

[0014] Based on the same inventive concept, the present invention also claims protection for the fiber absorbent core prepared by the said preparation method.

[0015] In one preferred embodiment, the fiber absorbent core has a thickness of 0.2-0.5 mm and a porosity of 70%-90%.

[0016] If the wick thickness is too small, the fibers will not spread evenly, which will reduce the capillary performance of the wick. If the wick thickness is too large, the thickness of the chip phase change heat dissipation substrate will also increase, limiting its application in microelectronic devices.

[0017] A porosity below 70% reduces its permeability to liquid working fluids, while a porosity above 90% reduces its capillary pressure.

[0018] Based on the same inventive concept, the present invention also claims a chip phase change heat dissipation substrate, the chip phase change heat dissipation substrate including the fiber liquid-absorbing core.

[0019] In one preferred embodiment, the chip is a gallium nitride chip.

[0020] In one preferred embodiment, the chip phase change heat dissipation substrate includes an upper substrate, a lower substrate, and a fiber absorbent core disposed on the inner surface of the lower substrate; a support post is provided on the inner side of the lower substrate, the fiber absorbent core is located in the cavity formed by the upper substrate and the lower substrate, the fiber absorbent core is provided with a through hole corresponding to the support post, and the upper end of the support post passes through the through hole on the fiber absorbent core and connects to the inner surface of the upper substrate.

[0021] In one preferred embodiment, the upper substrate and the lower substrate are made of molybdenum copper.

[0022] The molybdenum-copper material used in this embodiment of the invention was purchased from Shenzhen Anteng Metal Technology Co., Ltd.

[0023] In one preferred embodiment, the thickness of the lower substrate is 0.5-1.2 mm, and the thickness of the upper substrate is 0.1-0.2 mm.

[0024] Based on the same inventive concept, this invention also claims a method for preparing the chip phase change heat dissipation substrate, comprising the following steps: S1. A cavity and a support column are prepared on the inner side of the lower substrate, and the fiber liquid-absorbing core is fixed on the inner surface of the lower substrate to obtain a lower substrate with a fiber liquid-absorbing core. S2. Prepare the upper substrate, connect the upper substrate and the lower substrate, then vacuum, inject liquid working fluid, and seal to obtain the chip phase change heat dissipation substrate.

[0025] In one preferred embodiment, the cavity thickness is two times or more the thickness of the wick.

[0026] In one preferred embodiment, the connection is welding.

[0027] The beneficial effects of this invention are as follows: (1) Compared with traditional heat sinks, the molybdenum-copper chip phase change heat sink of the present invention has a higher heat dissipation capacity. Since the present invention adopts the most efficient phase change heat transfer technology, the thermal conductivity of the prepared chip phase change heat sink is expected to exceed 10,000 W / m·K, which is more than 50 times that of the thermal conductivity of molybdenum-copper material itself (200 W / m·K). Therefore, the heat dissipation capacity of the chip phase change heat transfer substrate is significantly higher than that of traditional heat sinks.

[0028] (2) Compared with long-fiber sintered liquid absorbent cores, short-fiber sintered liquid absorbent cores have higher capillary pressure. The specific reason is that the fibers in long-fiber sintered liquid absorbent cores are usually arranged parallel to each other along their length, and the microchannels formed between the fibers are long-channel structures with a larger equivalent pore size. In contrast, the fibers in short-fiber sintered liquid absorbent cores are randomly distributed, and the microchannels formed between the fibers have varying pore sizes, achieving the effect of powder sintered liquid absorbent cores and increasing the capillary pressure of the liquid absorbent core.

[0029] (3) Compared with traditional powder sintered liquid absorbers, molybdenum-copper short fiber sintered liquid absorbers have higher stability and are less prone to cracking and detachment during use. The specific reasons are as follows: ① Powder sintered liquid absorbers are formed by sintering powder, and the powders are only connected by point contact. In contrast, the fibers in short fiber sintered liquid absorbers are connected by line contact or surface contact, which can form more sintered neck structures during the sintering process, thereby improving the structural strength of the liquid absorber; ② Molybdenum-copper short fibers have a spiral shape, and the fibers are intertwined and not easily separated; ③ The surface of the short fibers has a serrated microstructure. During the sintering process, the serrated microstructures interlock with each other, further preventing the fibers from falling off.

[0030] In summary, the molybdenum-copper short fiber sintered liquid wick combines the high capillary pressure of powder sintered liquid wick with the good permeability and stability of fiber sintered liquid wick. The chip phase change heat dissipation substrate prepared from it has high heat dissipation capacity and can meet the heat dissipation requirements of gallium nitride chips. Attached Figure Description

[0031] Figure 1 This is an overall diagram of the helical fiber; Figure 2 This is a detailed diagram of the surface structure of the helical fiber; Figure 3 This is an overall view of the fiber absorbent core; Figure 4 A magnified view of the fiber absorbent core details; Figure 5 This is a schematic diagram of the overall packaging structure of the chip phase change heat dissipation substrate; Figure 6 A schematic diagram of the disassembled chip phase change heat dissipation substrate; Figure 7 This is a schematic cross-sectional view of the chip phase change heat dissipation substrate; In the figure, 1-upper substrate; 2-fiber absorbent core; 3-lower substrate; 4-support column. Detailed Implementation

[0032] This invention is not limited to the specific embodiments listed below. Those skilled in the art can implement this invention using various other specific embodiments based on the content disclosed herein. Any modifications or alterations made to the design structure and concept of this invention fall within the protection scope of this invention. It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other.

[0033] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," "outer," "front," and "rear," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and 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 should not be construed as a limitation of this invention. Furthermore, unless otherwise explicitly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0034] Example 1

[0035] The processing steps of the chip phase change heat dissipation substrate of the present invention are as follows: (1) Preparation of molybdenum-copper cutting fibers Using a multi-tooth cutting tool with a tooth height of 0.2-0.4 mm and a tooth width of 0.3-0.6 mm, molybdenum-copper rods were machined on a lathe. By adjusting the cutting parameters (cutting speed 130-180 r / min, depth of cut 0.05 mm, feed rate 0.05 mm / r), short helical fibers with a diameter of 50 μm, a length of 3-4 mm, a helix diameter of 100-200 μm, a pitch of 300-600 μm, and 4-6 turns were prepared. The fiber surface has a "serrated" microstructure, which can improve the structural strength and capillary pressure of the liquid-absorbing core during subsequent sintering. The prepared short fibers were collected, cleaned, and dried for subsequent use. Figure 1 The fibers are in a spiral shape; Figure 2 It has a "serrated" microstructure.

[0036] (2) Substrate preparation of chip phase change heat dissipation substrate The lower substrate is prepared by using a 20 mm × 20 mm × 0.9 mm molybdenum copper plate and processing it by milling or chemical etching to create an inner cavity of 18 mm × 18 mm × 0.8 mm and a support column structure with a diameter of 1 mm and a height of 0.8 mm.

[0037] (3) Solid-phase sintering of molybdenum-copper fiber liquid-absorbing core The prepared molybdenum-copper diced short fibers were randomly arranged and laid onto the inner surface of the lower substrate, and then molded using a custom mold. High-temperature solid-state sintering was then performed at a temperature of 1200±5°C. A segmented heating method was used: when the furnace temperature was below 800°C, the heating rate was 5°C / min; when the furnace temperature reached 800°C, the heating rate was 3°C / min, and the sintering time was 60 minutes, producing a lower substrate with a liquid-absorbing core. During sintering, the copper component in the fibers began to melt at approximately 1083°C and accumulated on the fiber surface, promoting adhesion between the fibers and the lower substrate. The fibers intertwined and spiraled, forming a large number of interconnected and interwoven microchannel networks inside the liquid-absorbing core, which facilitated rapid reflux of the liquid working fluid. The liquid-absorbing core structure is as follows: Figure 3 As shown, the microstructure of the spiral winding is as follows Figure 4 As shown, the prepared fiber absorbent core has a thickness of 0.4 mm and a porosity of 70%.

[0038] (4) Welding of the upper and lower substrates of the chip phase change heat dissipation substrate A solder (Sn99.3Cu0.7) was uniformly coated onto a raised surface with a width of 2 mm on the edge of the lower substrate, covering it with an upper substrate with a thickness of 0.1 mm. The substrate was then positioned and fixed by applying pressure using a mold. Finally, the substrate was sintered using a high-temperature solid-state sintering process at a temperature of 700±5°C for 60 minutes to prepare a complete component.

[0039] (5) Chip phase change heat dissipation substrate packaging A series of processes, including vacuuming, filling with liquid working fluid (deionized water), and sealing, are performed on the components to ultimately prepare the chip phase change heat dissipation substrate. The chip phase change heat dissipation substrate includes an upper substrate 1, a lower substrate 3, and a fiber absorbent core 2 disposed on the inner surface of the lower substrate. A support pillar 4 is provided on the inner side of the lower substrate 3. The fiber absorbent core 2 is located within the cavity formed by the upper substrate 1 and the lower substrate 3, and the cavity thickness is twice the thickness of the absorbent core. The fiber absorbent core 2 has through holes corresponding to the support pillars 4, and the upper end of the support pillar 4 passes through the through holes in the fiber absorbent core 2 and connects to the inner surface of the upper substrate. A schematic diagram of the overall packaging structure of the chip phase change heat dissipation substrate is shown below. Figure 5 As shown in the diagram. A schematic diagram of the disassembled chip phase-change heat dissipation substrate is shown below. Figure 6 As shown, a cross-sectional schematic diagram of the chip phase change heat dissipation substrate is as follows. Figure 7 As shown, 1 is the upper substrate, 2 is the fiber absorbent core, 3 is the lower substrate, and 4 is the support column.

[0040] Example 2

[0041] The difference from Example 1 is that the cutting depth was adjusted to 0.2 mm and the feed rate to 0.2 mm / r, resulting in short helical fibers with a diameter of 200 μm, a length of 3-4 mm, a helical diameter of 200-400 μm, a pitch of 300-600 μm, and 4-6 turns, and the fiber surface has a "serrated" microstructure. Everything else is the same as in Example 1.

[0042] Example 3

[0043] The difference from Example 1 is that the porosity of the liquid-absorbing core is adjusted to 90%. Everything else is the same as in Example 1.

[0044] Example 4

[0045] The difference from Example 1 is that the cutting speed was adjusted to 50-105 r / min to prepare short helical fibers with a diameter of 50 μm, a length of 1-2 mm, a helical diameter of 100-200 μm, a pitch of 300-600 μm, and 2-3 turns, and the fiber surface has a "serrated" microstructure. Everything else is the same as in Example 1.

[0046] Comparative Example 1 The liquid-absorbing core is made of cut copper fiber, and the upper and lower substrates are molybdenum-copper chip phase change heat dissipation substrates. The absorbent core material in Comparative Example 1 was copper fiber. Using the same cutting parameters as in Example 1, continuous fibers with a diameter of 50 μm were prepared, and then the continuous copper fibers were cut to a length of 3-4 mm. The fiber was generally straight, with a wrinkled structure on its free surface. All other processes and parameters remained consistent with those in Example 1.

[0047] Comparative Example 2 The liquid-absorbing core is made of cut beryllium copper fiber, and the upper and lower substrates are molybdenum copper, forming a chip phase change heat dissipation substrate. The absorbent core material in Comparative Example 2 was beryllium copper fiber. Using the same cutting parameters as in Example 1, continuous fibers with a diameter of 50 μm were prepared, and then the continuous beryllium copper fibers were cut to a length of 3-4 mm. The fiber was straight, and its free surface had a wing-like microstructure. All other processes and parameters remained consistent with those in Example 1.

[0048] Comparative Example 3 The liquid-absorbing core is made of diced stainless steel fiber, and the upper and lower substrates are molybdenum-copper chip phase change heat dissipation substrates. The absorbent core material in Comparative Example 3 was stainless steel fiber. Using the same cutting parameters as in Example 1, continuous fibers with a diameter of 50 μm were prepared, and then the continuous stainless steel fibers were cut to a length of 3-4 mm. The fibers were straight, and their free surfaces showed no obvious microstructure. All other processes and parameters remained consistent with those in Example 1.

[0049] Comparative Example 4 The liquid absorption core and the upper and lower substrates are all made of molybdenum-copper chip phase change heat dissipation substrate. The absorbent core material in Comparative Example 4 was molybdenum-copper fiber. The porosity of the absorbent core was adjusted to 60%. All other processes and parameters remained the same as in Example 1.

[0050] Comparative Example 5 The liquid absorption core and the upper and lower substrates are all made of molybdenum-copper chip phase change heat dissipation substrate. The absorbent core material in Comparative Example 5 was molybdenum-copper fiber. The porosity of the absorbent core was adjusted to 95%. All other processes and parameters remained the same as in Example 1.

[0051] Comparative Example 6 The liquid absorption core and the upper and lower substrates are all made of molybdenum-copper chip phase change heat dissipation substrate. The liquid-absorbing core material in Comparative Example 6 was molybdenum-copper fiber. By adjusting the cutting depth to 0.04 mm and the feed rate to 0.04 mm / r, short helical fibers with a diameter of 40 μm, a length of 3-4 mm, a helix diameter of 100-200 μm, a pitch of 300-600 μm, and 4-6 turns were prepared, with a serrated microstructure on the fiber surface. All other process procedures and parameters remained consistent with those in Example 1.

[0052] Comparative Example 7 The liquid absorption core and the upper and lower substrates are all made of molybdenum-copper chip phase change heat dissipation substrate. The liquid-absorbing core material in Comparative Example 7 was molybdenum-copper fiber. A multi-tooth cutting tool with a tooth height of 0.3-0.4 mm and a tooth width of 0.3-0.6 mm was used to cut the molybdenum-copper rod on a lathe. The cutting depth was adjusted to 0.25 mm, and the feed rate was 0.25 mm / r. This produced short helical fibers with a diameter of 250 μm, a length of 3-4 mm, a helix diameter of 300-400 μm, a pitch of 300-600 μm, and 4-6 turns. The fiber surface exhibited a serrated microstructure. All other process procedures and parameters remained consistent with those in Example 1.

[0053] Comparative Example 8 The chip phase change heat dissipation substrate, with the liquid suction core and upper and lower substrates made of molybdenum-copper, is used. The liquid-absorbing core material in Comparative Example 8 was molybdenum-copper fiber. By adjusting the cutting speed to 210-260 r / min, short helical fibers with a diameter of 50 μm, a length of 6-8 mm, a helical diameter of 100-200 μm, a pitch of 300-600 μm, and 8-10 turns were prepared, with the fiber surface exhibiting a serrated microstructure. All other process procedures and parameters remained consistent with those in Example 1.

[0054] Comparative Example 9 The liquid absorption core and the upper and lower substrates are all made of molybdenum-copper chip phase change heat dissipation substrate. The liquid-absorbing core material of Comparative Example 9 was molybdenum-copper fiber. By adjusting the cutting speed to 25 r / min, short helical fibers with a diameter of 50 μm, a length of 0.5-0.8 mm, a helical diameter of 100-200 μm, a pitch of 300-600 μm, and 1-2 turns were prepared, with a "serrated" microstructure on the fiber surface. All other processes and parameters remained consistent with those of Example 1.

[0055] Comparative Example 10 The liquid absorption core and the upper and lower substrates are all made of molybdenum-copper chip phase change heat dissipation substrate. The absorbent core material in Comparative Example 10 was molybdenum-copper fiber. Short helical fibers with a diameter of 50 μm, a length of 3-4 mm, a helical diameter of 100-200 μm, a pitch of 300-600 μm, and 4-6 turns were prepared using a multi-toothed cutter with a tooth height of 0.1-0.15 mm and a tooth width of 0.3-0.6 mm. The fiber surface had no "serrated" microstructure. All other processes and parameters remained consistent with those in Example 1.

[0056] Comparative Example 11 The liquid absorption core and the upper and lower substrates are all made of molybdenum-copper chip phase change heat dissipation substrate. The absorbent core material in Comparative Example 11 was molybdenum-copper fiber. Short, straight fibers with a diameter of 50 μm and a length of 3-4 mm were prepared using a multi-toothed cutter with a tooth height of 0.2-0.4 mm and a tooth width of 0.7-0.9 mm. The fiber surface had a serrated microstructure. All other processes and parameters remained consistent with those in Example 1.

[0057] Performance tests (steady-state test method) were performed on the chip phase change heat dissipation substrates of each embodiment and comparative example, and the results are shown in the table below.

[0058] Table 1. Performance test results of the chip phase change heat dissipation substrate for each embodiment and comparative example. The comparison reveals that the copper fiber bonding strength in Comparative Example 1 is lower, and the coefficient of thermal expansion of copper is also lower (17.6 × 10⁻⁶). -6 / K) and molybdenum copper (7.6 ×10 -6 The difference in heat transfer performance ( / K) is significant. During the thermal cycling test, some fibers separated from each other, and some liquid-absorbing cores peeled off from the substrate, resulting in a decrease in the heat transfer performance of the phase change heat transfer substrate. Therefore, the heat transfer performance of Comparative Example 1 is significantly lower than that of Example 1.

[0059] The beryllium copper fibers in Comparative Example 2 showed lower interfiber bonding strength, and the coefficient of thermal expansion of beryllium copper was 17 × 10⁻⁶. -6 / K) and molybdenum copper (7.6 ×10 -6 The difference in heat transfer performance ( / K) is significant. During the thermal cycling test, some fibers separated from each other, and some liquid-absorbing cores peeled off from the substrate, resulting in a decrease in the heat transfer performance of the phase change heat transfer substrate. Therefore, the heat transfer performance of Comparative Example 2 is significantly lower than that of Example 1.

[0060] Comparative Example 3 showed lower interfiber bond strength in the stainless steel and a lower coefficient of thermal expansion (20×10). -6 / K) and molybdenum copper (7.6 ×10 -6The difference in thermal conductivity (W / m·K) is significant. During the thermal cycling test, some fibers separated from each other, and some wicks peeled off from the substrate, resulting in a decrease in the heat transfer performance of the phase change heat transfer substrate. In addition, the thermal conductivity of stainless steel fibers (22 W / m·K) is much lower than that of molybdenum copper (200 W / m·K). Therefore, the heat transfer performance of Comparative Example 3 is significantly lower than that of Example 1.

[0061] The wick porosity of Comparative Example 4 was too low (60%), resulting in insufficient working fluid permeability and thus reducing the heat transfer performance of the phase change heat transfer substrate. Therefore, the heat transfer performance of Comparative Example 4 was significantly lower than that of Example 1.

[0062] The high porosity (95%) of the wick in Comparative Example 5 resulted in low capillary pressure, thereby reducing the heat transfer performance of the phase change heat transfer substrate. Therefore, the heat transfer performance of Comparative Example 5 was significantly lower than that of Example 1.

[0063] In Comparative Example 6, the diameter of the molybdenum-copper fibers constituting the liquid-absorbing core was too small (40 μm), and molybdenum-copper is a brittle powder metallurgy material with low strength. During the thermal cycling test, some fibers broke, thereby reducing the heat transfer performance of the phase change heat transfer substrate. Therefore, the heat transfer performance of Comparative Example 6 was significantly lower than that of Example 1.

[0064] In Comparative Example 7, the molybdenum-copper fibers constituting the liquid-absorbing core have an excessively large diameter (250 μm) and a small specific surface area, resulting in low capillary pressure in the fiber liquid-absorbing core and thus reducing the heat transfer performance of the phase change heat transfer substrate. Therefore, the heat transfer performance of Comparative Example 7 is significantly lower than that of Example 1.

[0065] In Comparative Example 8, the molybdenum-copper fibers constituting the liquid-absorbing core were too long (6-8 mm), and molybdenum-copper is a brittle powder metallurgy material with low strength. During the thermal cycling test, some fibers broke, thereby reducing the heat transfer performance of the phase change heat transfer substrate. Therefore, the heat transfer performance of Comparative Example 8 was significantly lower than that of Example 1.

[0066] In Comparative Example 9, the molybdenum-copper fibers constituting the liquid-absorbing core were too short (0.5-0.8 mm), resulting in fewer spiral turns between the fibers and lower inter-fiber bonding strength. Consequently, during the thermal cycling test, some fibers separated, thus reducing the heat transfer performance of the phase change heat transfer substrate. Therefore, the heat transfer performance of Comparative Example 9 was significantly lower than that of Example 1.

[0067] In Comparative Example 10, the blade tooth height is too low (0.1-0.15 mm), which easily damages the "serrated" microstructure of the fibers, resulting in lower inter-fiber bonding strength and capillary pressure. Consequently, during thermal cycling tests, some fibers separate, thus reducing the heat transfer performance of the phase change heat transfer substrate. Therefore, the heat transfer performance of Comparative Example 10 is significantly lower than that of Example 1.

[0068] In Comparative Example 11, the cutter tooth width was too large (0.7-0.9 mm), making it difficult to cut helical fibers. This resulted in low inter-fiber bonding strength, causing some fibers to separate during thermal cycling tests, thereby reducing the heat transfer performance of the phase change heat transfer substrate. Therefore, the heat transfer performance of Comparative Example 11 was significantly lower than that of Example 1.

[0069] It should be noted that the above embodiments are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is impossible to exhaustively list all possible implementations here. All obvious variations or modifications derived from the technical solutions of this invention are still within the scope of protection of this invention.

Claims

1. A method for preparing a fiber absorbent core, characterized in that, Includes the following steps: S1. Multiple helical short fibers are prepared by turning; the diameter of the helical short fibers is 50-200 μm and the length is 1-4 mm; S2. Multiple helical short fibers are sintered onto a substrate using a high-temperature solid-state sintering process to prepare a fiber liquid-absorbing core.

2. The preparation method according to claim 1, characterized in that, The spiral short fiber is made of molybdenum copper.

3. The preparation method according to claim 1, characterized in that, The spiral short fibers have a spiral diameter of 100-400μm, a pitch of 300-600μm, and 2-6 turns.

4. The preparation method according to claim 1, characterized in that, During the turning process, the tool parameters are as follows: tooth height is 0.2-0.4 mm, tooth width is 0.3-0.6 mm, cutting speed is 50-180 r / min, cutting depth is 0.05-0.2 mm, and feed rate is 0.05-0.2 mm / r.

5. The preparation method according to claim 1, characterized in that, The solid-state sintering temperature is 1100℃~1300℃. The sintering process adopts a segmented heating method: when the temperature inside the sintering furnace is below 800℃, the heating rate is 5℃ / min; when the temperature inside the furnace reaches 800℃, the heating rate is 3℃ / min; and the sintering time is 60min~120min.

6. The fiber absorbent core prepared by the preparation method according to any one of claims 1-5.

7. The fiber absorbent core according to claim 6, characterized in that, The thickness of the fiber absorbent core is 0.2-0.5 mm, and the porosity is 70%-90%.

8. A chip phase-change heat dissipation substrate, characterized in that, The chip phase change heat dissipation substrate includes the fiber liquid-absorbing core according to claim 6.

9. The chip phase change heat dissipation substrate according to claim 8, characterized in that, The chip phase change heat dissipation substrate includes an upper substrate, a lower substrate, and a fiber liquid-absorbing core disposed on the inner surface of the lower substrate; a support column is provided on the inner side of the lower substrate, and the fiber liquid-absorbing core is located in the cavity formed by the upper substrate and the lower substrate. The fiber liquid-absorbing core is provided with a through hole corresponding to the support column, and the upper end of the support column passes through the through hole on the fiber liquid-absorbing core and connects to the inner surface of the upper substrate.

10. The chip phase-change heat dissipation substrate according to claim 8, characterized in that, The upper and lower substrates are made of molybdenum copper, with the lower substrate having a thickness of 0.5-1.2 mm and the upper substrate having a thickness of 0.1-0.2 mm.

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