A manufacturing method of a silicon carbide vacuum chuck with internal deep hole air channel

Abstract

This invention discloses a method for manufacturing a silicon carbide vacuum chuck with internal deep-hole air channels, relating to the field of silicon carbide ceramic technology. The method comprises five major steps: S1 preparing and fixing a deep-hole core mold; S2 mixing and degassing silicon carbide slurry, followed by injection molding and curing to obtain a green body; S3 dissolving the core mold; S4 segmented controlled-humidity drying followed by reaction sintering; and S5 machining the reference surface and precision assembly. By limiting key conditions such as core mold parameters, slurry ratio, and sintering process curves, the method solves problems such as high cost of existing split-assembly methods, easy cracking during integral pressing, and large sintering deformation. The product exhibits high density, excellent strength and rigidity, flatness ≤2μm, and small dimensional errors, making it suitable for high-precision air-floating working surfaces. Furthermore, the process is controllable and low-cost, meeting the needs of large-scale production.

Description

Technical Field

[0001] This invention relates to the field of silicon carbide ceramics technology, and specifically to a method for manufacturing a silicon carbide vacuum chuck with internal deep-hole air channels. Background Technology

[0002] In the field of silicon carbide ceramic technology, silicon carbide vacuum chucks with internal deep-hole channels are widely used in high-precision air-floating worktables, semiconductor wafer processing, and other applications requiring stringent adsorption stability and flatness due to their high density, excellent rigidity, and wear resistance. Currently, the mainstream manufacturing processes for this type of chuck are mainly divided into two categories: "split assembly molding" and "integral pressing molding." Split assembly molding requires the separate preparation of silicon carbide unit components with shallow holes, which are then assembled using high-temperature welding or adhesives to form deep-hole channels. This was a commonly used technical approach in the industry in the early days. Integral pressing molding, on the other hand, involves directly pressing a silicon carbide blank with a preliminary deep-hole shape using a mold, followed by sintering and processing to obtain the finished product. In recent years, this has gradually become the direction of process development.

[0003] However, the existing split-assembly molding process has significant shortcomings: on the one hand, the splicing process requires precise control of the docking accuracy of the components, and the welding or bonding process is prone to generating micro-gaps at the splicing points, which can lead to air leakage in the suction cup during use, reduce the vacuum pressure holding performance, and make it difficult to meet the stringent requirements of high-precision air-floating working surfaces; on the other hand, the splicing process requires additional investment in welding equipment, adhesives, and manual calibration costs, and the spliced ​​surfaces need to be processed again afterward, making the overall manufacturing cost higher than that of the integral molding process, which is not conducive to large-scale production.

[0004] Meanwhile, the existing integral pressing molding process also faces key technical bottlenecks: First, silicon carbide ceramics are brittle, and when integrally pressing a blank containing a deep hole prototype, the deep hole area is prone to cracking due to uneven stress. The blank is also prone to cracking during the mold demolding process, resulting in a low finished product qualification rate. Second, the blank is prone to deformation due to high-temperature thermal stress. In normal production, the subsequent finishing process needs to meet two requirements: on the one hand, a reasonable machining allowance must be preset, and on the other hand, the sintering deformation must be controlled to not exceed the allowance in order to correct errors and ensure accuracy through subsequent processing. However, the sintering deformation of the existing process often exceeds the preset machining allowance, which means that even after subsequent finishing, the flatness of the suction cup still cannot meet the standards of high-precision application scenarios. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a method for manufacturing a silicon carbide vacuum suction cup with internal deep-hole air channels, innovatively optimizing the existing technology by addressing the following pain points: firstly, the micro-gap and vacuum pressure difference issues in the splicing of separate parts; and secondly, the cracking and deformation issues in overall pressing. The core innovation of this invention lies in the use of an integrated process of "water-soluble polyvinyl alcohol (PVA) core mold + gel injection molding". By leveraging the low-temperature residue-free, high-precision molding, and gentle removal characteristics of the PVA core mold, combined with precise process parameters, high-quality molding of deep-hole air channels is achieved. The specific steps are as follows: S1: A deep hole core mold is manufactured using a water-soluble core mold material and a 3D printer. After surface finishing, the deep hole core mold is positioned and fixed in the lower mold cavity. S2: After ball mixing and vacuum degassing of silicon carbide slurry, the silicon carbide slurry gel is injected into the mold cavity containing a deep hole core mold under set temperature and pressure. After injection molding, the mold is covered and pressure is applied to promote the gel solidification of the slurry. The green body is then demolded. S3: Immerse the entire green body in a water bath to dissolve and remove the core mold; S4: The green blank is dried using a segmented humidity control method, embedded in a silicon powder bed and placed in a protected graphite crucible; the graphite crucible is placed in an atmosphere furnace, and reaction sintering is completed according to the set sintering process curve. After cooling in the furnace, it is taken out of the furnace to obtain a silicon carbide vacuum chuck sintered blank. S5: The sintered blank of silicon carbide vacuum chuck is machined with a reference surface, and then precision grinding, polishing, working surface preparation, and polishing are performed in sequence. The accessories are then installed to obtain a silicon carbide vacuum chuck with internal deep hole air channels.

[0006] Furthermore, the water-soluble mandrel material is polyvinyl alcohol (PVA) wire.

[0007] Furthermore, the diameter of the deep hole core mold is Φ2.5mm-Φ6mm, and the length is 80mm-320mm.

[0008] Furthermore, the printing parameters of the deep hole core mold are: nozzle diameter Φ0.4mm-0.6mm, layer height 0.2mm-0.3mm, printing speed 25mm / s-35mm / s, and filling rate 100%.

[0009] Furthermore, the degree of polymerization of the water-soluble polyvinyl alcohol (PVA) wire is 1700-1800, and the wire diameter is 1.75mm ± 0.02mm.

[0010] Further, the silicon carbide slurry, by weight, comprises 150-180 parts silicon carbide powder, 24-28 parts deionized water, 4.0-5.0 parts agarose, 1.0-1.5 parts ammonium polyacrylate, and 2.5-3.5 parts glycerol. The silicon carbide powder is composed of a mixture of fine powder with a particle size of 1μm-3μm and coarse powder with a particle size of 20μm-30μm, with the fine powder accounting for 35%-40% and the coarse powder accounting for 60%-65% by weight.

[0011] Furthermore, the ball mixing is carried out using a ball mixer for 3-5 hours, followed by vacuum degassing (vacuum degree is -0.09MPa to -0.085MPa, degassing time is 5-10 minutes).

[0012] Furthermore, the injection molding process uses an injection molding pressure of 0.25MPa-0.35MPa, and the embossing mold pressure applied after injection molding is 0.5MPa-0.7MPa. At the same time, the slurry curing temperature is maintained at 48℃-52℃, and the temperature is controlled to room temperature after gel curing.

[0013] Furthermore, the embossing mold is made of 304 stainless steel, and the working surface of the embossing mold is mirror polished, with a surface roughness Ra≤0.08μm.

[0014] Furthermore, the water bath conditions are as follows: the intact green body after demolding S2 is slowly immersed in a water bath at 35-45°C, and the core mold is dissolved by utilizing the water solubility of PVA; Furthermore, the segmented humidity-controlled drying method is as follows: first, place the product in a 90%-98% humidity environment for 20-28 hours, then place it in a 55%-65% humidity environment for 10-14 hours, and finally, in a drying oven, raise the temperature from room temperature to 68-72℃ at a rate of 0.4℃ / min-0.6℃ / min, and keep it at this temperature until constant weight is achieved.

[0015] Furthermore, the reference surface machining method is as follows: a CNC machining center or a precision grinding machine is used to machine the reference surface, and the depth of the machining of the reference surface is 0.5mm-1mm. After machining, the flatness of the reference surface is detected by a coordinate measuring machine.

[0016] Furthermore, the silicon powder in the silicon powder bed has a silicon powder particle size of 20μm-1mm.

[0017] Furthermore, the sintering process curve is as follows: from room temperature to 550℃, an argon atmosphere is used, with a heating rate of 1.2℃ / min-1.8℃ / min; the temperature is held at 550℃ for 100min-140min; from 550℃ to 1400℃, vacuum protection is switched, with a heating rate of 3.5℃ / min-4.5℃ / min; from 1400℃ to 1580℃, vacuum protection is maintained, with a heating rate of 1.8℃ / min-2.2℃ / min, and the temperature is held at 1580℃ for 160min-200min; while maintaining vacuum protection, the cooling rate is 1.2℃ / min-1.8℃ / min, and the temperature is lowered to room temperature before unloading.

[0018] The beneficial effects of this invention are:

[0019] 1. This invention overcomes the shortcomings of traditional split splicing and integral pressing. Through a combined process of "water-soluble PVA core mold (low temperature, no residue, high molding precision, no damage during demolding) + gel injection molding + green body dissolution", it can avoid micro-gaps caused by welding / bonding during split splicing, ensuring the sealing of deep hole air channels, and solve the problems of easy cracking and difficult demolding in deep hole parts during integral pressing. In the S2 green body stage, PVA core mold is dissolved in a water bath. Compared with the traditional "removal of core after sintering" process, it avoids the impact of residual ash on precision during sintering. The mild parameters are adapted to the structural characteristics of the green body, significantly reducing the cracking rate of the finished product. The diameter deviation of deep hole air channels is further reduced to ±0.14mm-±0.2mm, realizing the complete molding of internal deep hole air channels. After the deep hole air channels are formed, no secondary processing is required. Only precision grinding, polishing and polishing of the working surface are required, which greatly improves the reliability and efficiency of deep hole structure manufacturing.

[0020] 2. By relying on the segmented humidity control drying process, cracking or residual stress caused by uneven moisture evaporation in the green blank can be avoided. Combined with silicon powder bed support and vacuum protection sintering that match the thermal expansion characteristics of silicon carbide, the deformation and oxidation of the green blank during the sintering process are effectively suppressed, ensuring that the flatness, dimensional consistency and matrix density of the finished product meet the requirements of high-precision scenarios.

[0021] 3. This invention clearly defines the process parameters and operating procedures for each key step (core mold preparation, slurry treatment, sintering process curves, etc.), ensuring high parameter range compatibility. It can stably produce qualified products even under different parameter combinations, reducing the difficulty of process debugging. Furthermore, the equipment and consumables used are all standard industrial-grade products, requiring no special customization. Compared to traditional processes, it eliminates the need for post-sintering processing or welding equipment, reducing steps, shortening the cycle time, and significantly lowering manufacturing costs. It is highly adaptable to industrial mass production.

[0022] 4. The silicon carbide vacuum chuck prepared by this invention has high density, excellent rigidity and wear resistance, stable conductivity of deep-hole air channels and high flatness of working surface. It can not only meet the stringent requirements of adsorption stability and bonding accuracy in core scenarios such as semiconductor wafer processing and high-precision air-floating worktables, but also be extended to fields with high requirements for vacuum chuck performance such as optical component inspection and precision parts assembly. It solves the problem of limited application scenarios of traditional products and has stronger practicality and market adaptability. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] This invention solves the problems of cracking and sealing in deep hole molding by using "water-soluble PVA core mold + gel injection molding". It suppresses residual stress in green blanks by segmented humidity control and drying, and controls sintering deformation by using silicon powder bed support and precise sintering curve. The implementation details of each process parameter are explained in detail below through specific embodiments. Example 1

[0025] A method for manufacturing a silicon carbide vacuum chuck with internal deep-hole air channels includes the following steps: S1: Water-soluble polyvinyl alcohol filament was selected as the raw material for the core mold. The filament has a degree of polymerization of 1700 and a diameter of 1.75mm ± 0.02mm. An FDM 3D printer was used to manufacture the deep hole core mold. The printing parameters were set as follows: nozzle diameter 0.4mm, layer height 0.2mm, printing speed 25mm / s, and infill rate 100%. The deep hole core mold was printed according to the air passage requirements, with the core mold diameter controlled at Φ2.5mm and the length at 200mm. The outer surface of the core mold was circumferentially polished using 1000-grit sandpaper, and the surface roughness Ra ≤ 0.8μm was obtained. The deep hole core mold was then placed in the lower mold cavity and fixed.

[0026] S2: Accurately weigh 150 parts by weight of silicon carbide powder, 28 parts by weight of deionized water, 4.0 parts by weight of agarose, 1.0 part by weight of ammonium polyacrylate, and 2.5 parts by weight of glycerol. The silicon carbide powder has a particle size of 1μm-3μm and 20μm-30μm, with 1μm-3μm accounting for 40% and 20μm-30μm accounting for 60% by weight. Add each raw material to the mixing tank in sequence for initial mixing. Use a ball mixer to ball mix the initially mixed slurry for 3 hours. Silicon carbide balls are used as the ball mixing medium. The slurry after ball mixing was degassed under vacuum at a vacuum level of -0.09 MPa and a degassed time of 5 min. The degassed slurry was then transferred to a gel casting machine and slowly injected into the mold cavity containing a deep-hole core mold at a casting pressure of 0.25 MPa to ensure that the slurry fully filled the mold cavity. After casting, a 304 stainless steel embossing mold was immediately placed on the slurry surface with a working surface roughness Ra≤0.08μm and a pressure of 0.5 MPa was applied. At the same time, the slurry curing temperature was maintained at 48℃. After gel curing, the mold was separated at room temperature to obtain a complete green body.

[0027] S3: Slowly place the intact green blank after demolding into a 40℃ water bath to ensure that the green blank is completely submerged and the circulating water flow is parallel to the deep hole air channel; continue water bath for 2 hours, and gently shake the water bath every 30 minutes (amplitude ≤5cm) to accelerate the dissolution of PVA core mold; obtain a green blank without core mold residue.

[0028] S4: The green compact was first placed in an environment with 90% humidity for 20 hours, then transferred to an environment with 55% humidity for 10 hours, and finally placed in a drying oven. The temperature was increased from room temperature to 68℃ at a rate of 0.4℃ / min, and dried at 68℃ until constant weight. After drying, the moisture content of the green compact was verified by weighing to be ≤0.1%. The dried green compact was then embedded in a silicon powder bed with a silicon powder particle size of 20μm, and then placed in a protected graphite crucible. The crucible was then placed in an atmosphere furnace. The sintering process curve was set as follows: from room temperature to 550℃, an argon atmosphere was used with a heating rate of 1.2℃ / min; at 550℃, the temperature was held for 100min to fully remove organic matter; from 550℃ to 1400℃, vacuum protection was switched on with a heating rate of 3.5℃ / min; from 1400℃ to 1580℃, vacuum protection was maintained with a heating rate of 1.8℃ / min, and the temperature was held at 1580℃ for 160min to complete the melting and infiltration reaction; after sintering, vacuum protection was maintained, and the furnace was cooled to room temperature at a rate of 1.2℃ / min. The furnace door was then opened and the blank was removed to obtain a silicon carbide vacuum chuck sintered blank.

[0029] S5: Fix the sintered blank of the silicon carbide vacuum chuck onto the worktable of the CNC machining center, select diamond tools, set the spindle speed to 14000 rpm, perform datum surface machining, and cut to a depth of 0.5 mm. After machining, use a coordinate measuring machine to check the flatness of the datum surface, and then perform precision grinding, lapping, working surface preparation, polishing, and install accessories to obtain a silicon carbide vacuum chuck with internal deep-hole air channels. Example 2

[0030] A method for manufacturing a silicon carbide vacuum chuck with internal deep-hole air channels includes the following steps: S1: Water-soluble polyvinyl alcohol filament was selected as the raw material for the core mold. The degree of polymerization of this filament is 1750, and the filament diameter is 1.75mm ± 0.02mm. An FDM 3D printer was used to manufacture the deep-hole core mold. The printing parameters were set as follows: nozzle diameter 0.5mm, layer height 0.25mm, printing speed 30mm / s, and infill rate 100%. The deep-hole core mold was printed according to the air duct requirements, with a core mold diameter of Φ4.5mm and a length of 150mm. The outer surface of the core mold was circumferentially polished using 1000-grit sandpaper to ensure a surface roughness Ra ≤ 0.8μm, thus obtaining the deep-hole core mold. The deep-hole core mold was placed in the lower mold cavity and fixed.

[0031] S2: Accurately weigh 160 parts by weight of silicon carbide powder, 25 parts by weight of deionized water, 4.5 parts by weight of agarose, 1.25 parts by weight of ammonium polyacrylate, and 3.0 parts by weight of glycerol. The silicon carbide powder has a particle size of 1μm-3μm and 20μm-30μm, with 1μm-3μm accounting for 38% and 20μm-30μm accounting for 62% by weight. Add each raw material to a mixing tank for initial mixing. Use a ball mixer to ball mix the initially mixed slurry for 4 hours, using silicon carbide balls as the ball mixing medium. Vacuum degas the ball-mixed slurry, setting the vacuum degree to -0.0875MPa and the degassing time to 6 minutes. Transfer the vacuum-degassed slurry to a gel injection molding machine, and slowly inject the slurry into the mold cavity containing a deep-hole core mold at an injection pressure of 0.3MPa, ensuring that the slurry fully fills the mold cavity. After injection molding is completed, immediately cover the slurry surface with a 304 stainless steel embossing mold, with a working surface roughness Ra≤0.08μm, apply a pressure of 0.6MPa, and maintain the slurry curing temperature at 50℃. After gel curing, control the temperature to room temperature, separate the mold, and obtain a complete green body.

[0032] S3: Slowly place the intact green blank after demolding into a 45°C water bath to ensure that the green blank is completely submerged and that the circulating water flow is parallel to the deep hole air channel; continue soaking for 1.5 hours, during which the water bath is gently shaken every 30 minutes (amplitude ≤ 5cm) to accelerate the dissolution of the PVA core mold; obtain a green blank without core mold residue.

[0033] S4: The green compact was first placed in an environment with 94% humidity for 24 hours, then transferred to an environment with 60% humidity for 12 hours, and finally placed in a drying oven. The temperature was increased from room temperature to 70℃ at a rate of 0.5℃ / min, and dried at 70℃ until constant weight. After drying, the moisture content of the green compact was verified by weighing to be ≤0.1%. The dried green compact was then embedded in a silicon powder bed with a silicon powder particle size of 30μm, and then placed in a protected graphite crucible. The crucible was then placed in an atmosphere furnace. The sintering process curve was set as follows: From room temperature to 550℃, an argon atmosphere was used with a heating rate of 1.5℃ / min. The temperature was held at 550℃ for 120min to fully remove organic matter. From 550℃ to 1400℃, vacuum protection was switched on with a heating rate of 4℃ / min. From 1400℃ to 1580℃, vacuum protection was maintained with a heating rate of 2℃ / min. The temperature was held at 1580℃ for 180min to complete the melting and infiltration reaction. After sintering, vacuum protection was maintained, and the furnace was cooled to room temperature at a rate of 1.5℃ / min. The furnace door was then opened and the blank was removed to obtain a silicon carbide vacuum chuck sintered blank.

[0034] S5: Fix the sintered blank of the silicon carbide vacuum chuck onto the worktable of the CNC machining center, select diamond tools, set the spindle speed to 15000 rpm, perform datum surface machining, and cut to a depth of 0.8 mm. After machining, use a coordinate measuring machine to check the flatness of the datum surface, and then perform precision grinding, lapping, working surface preparation, polishing, and install accessories to obtain a silicon carbide vacuum chuck with internal deep-hole air channels. Example 3

[0035] A method for manufacturing a silicon carbide vacuum chuck with internal deep-hole air channels includes the following steps: S1: Water-soluble polyvinyl alcohol filament was selected as the raw material for the core mold. The filament has a degree of polymerization of 1800 and a diameter of 1.75mm ± 0.02mm. An FDM 3D printer was used to manufacture the deep-hole core mold. The printing parameters were set as follows: nozzle diameter 0.6mm, layer height 0.3mm, printing speed 35mm / s, and infill rate 100%. The deep-hole core mold was printed according to the air duct requirements, with a core mold diameter of Φ3.0mm and a length of 80mm. The outer surface of the core mold was circumferentially polished using 1000-grit sandpaper to ensure a surface roughness Ra ≤ 0.8μm, thus obtaining the deep-hole core mold. The deep-hole core mold was placed in the lower mold cavity and fixed.

[0036] S2: Accurately weigh 170 parts by weight of silicon carbide powder, 24 parts by weight of deionized water, 5.0 parts by weight of agarose, 1.5 parts by weight of ammonium polyacrylate, and 3.5 parts by weight of glycerol. The silicon carbide powder has particle sizes of 1μm-3μm and 20μm-30μm, with 1μm-3μm accounting for 35% and 20μm-30μm accounting for 65% by weight. Add each raw material sequentially to a mixing tank for initial mixing. Use a ball mixer to ball-mix the initially mixed slurry for 5 hours, using silicon carbide balls as the ball-mixing medium. Perform vacuum degassing on the ball-mixed slurry, setting the vacuum level to -0.085MPa and the degassing time to 8 minutes. Transfer the vacuum-degassed slurry to a gel injection molding machine and slowly inject the slurry into the mold cavity containing a deep-hole core mold at an injection pressure of 0.35MPa, ensuring the slurry fully fills the mold cavity. After injection molding is completed, immediately cover the slurry surface with a 304 stainless steel embossing mold, with a working surface roughness Ra≤0.08μm, apply a pressure of 0.7MPa, and maintain the slurry curing temperature at 52℃. After gel curing, control the temperature to room temperature, separate the mold, and obtain a complete green body.

[0037] S3: Slowly place the intact green blank after demolding into a water bath at 35°C, ensuring that the green blank is completely submerged and that the circulating water flow is parallel to the deep hole air channel; continue soaking for 3 hours, during which the water bath is gently shaken every 30 minutes (amplitude ≤ 5cm) to accelerate the dissolution of the PVA core mold and obtain a green blank without core mold residue.

[0038] S4: The green compact was first placed in an environment with 98% humidity for 28 hours, then transferred to an environment with 65% humidity for 14 hours, and finally placed in a drying oven. The temperature was increased from room temperature to 72℃ at a rate of 0.6℃ / min, and dried at 72℃ until constant weight. After drying, the moisture content of the green compact was verified by weighing to be ≤0.1%. The dried green compact was then embedded in a silicon powder bed with a silicon powder particle size of 40μm, and then placed in a protected graphite crucible. The crucible was then placed in an atmosphere furnace. The sintering process curve was set as follows: from room temperature to 550℃, an argon atmosphere was used with a heating rate of 1.8℃ / min; at 550℃, the temperature was held for 140min to fully remove organic matter; from 550℃ to 1400℃, vacuum protection was switched on with a heating rate of 4.5℃ / min; from 1400℃ to 1580℃, vacuum protection was maintained with a heating rate of 2.2℃ / min, and the temperature was held at 1580℃ for 200min to complete the melting and infiltration reaction; after sintering, vacuum protection was maintained, and the furnace was cooled to room temperature at a rate of 1.8℃ / min. The furnace door was then opened and the blank was removed to obtain a silicon carbide vacuum chuck sintered blank.

[0039] S5: Fix the sintered blank of the silicon carbide vacuum chuck onto the worktable of a precision grinding machine. Use the precision grinding machine to machine the reference surface. Due to the characteristics of the grinding machine, the spindle speed is set to 2200 rpm. The machining accuracy is consistent with that of a CNC machining center. The depth of cut on the reference surface is 1.0 mm. After machining, use a coordinate measuring machine to check the flatness of the reference surface. Then, perform precision grinding, lapping, working surface preparation, and polishing in sequence. Install the accessories to obtain a silicon carbide vacuum chuck with internal deep-hole air channels.

[0040] Comparative Example 1 Compared with Example 1, in this comparative example, paraffin wire with a diameter of 1.75 mm was used as the core mold raw material in S1. The printing parameters, size specifications, surface finishing requirements and lower mold cavity fixing method of the core mold are the same as in Example 1. The core mold is removed by an integrated dewaxing process: after demolding in S2, the green blank is embedded in a silicon powder bed as required in Example 1, placed in a protective graphite crucible and then placed in an atmosphere furnace. Argon gas is introduced and the temperature is raised to 300°C at a rate of 1°C / min. The temperature is held for 2 hours to allow the paraffin to melt, volatilize and decompose. Then, the reaction sintering is completed directly using the sintering process of Example 1. The remaining steps and parameters are the same as in Example 1. Finally, a finished silicon carbide vacuum chuck with internal deep-hole air channels is obtained.

[0041] Comparative Example 2 Compared with Example 1, this comparative example does not perform segmented humidity control drying in S4. Instead, the green blank is directly placed into the drying oven and heated from room temperature to 68°C at a heating rate of 0.4°C / min. It is then kept at 68°C and dried to constant weight. The remaining steps and parameters are the same, and will not be repeated in this comparative example. The final product is a silicon carbide vacuum chuck with internal deep-hole air channels.

[0042] Comparative Example 3 Compared with Example 1, in this comparative example, the green blank is not buried in the silicon powder bed after drying in S4, but is directly placed in the graphite crucible. The remaining steps and parameters are the same, and will not be repeated in this comparative example. Finally, a finished silicon carbide vacuum chuck with internal deep-hole air channels is obtained.

[0043] Comparative Example 4 This comparative example uses a traditional integral pressing molding process: ① A silicon carbide green blank with a deep hole prototype (hole diameter Φ2.4mm) is pressed at a pressure of 20MPa; ② After demolding, it is directly sintered (the sintering curve is the same as in Example 1); ③ After sintering, the deep hole air channel is drilled and corrected, and the other processing parameters are the same as in Example 1, finally obtaining a finished silicon carbide vacuum chuck with an internal deep hole air channel.

[0044] The performance of the silicon carbide vacuum chucks with internal deep-hole air channels prepared in Examples 1-3 and Comparative Examples 1-4 was tested using the following methods: Deep-hole airway diameter deviation: Five samples were selected for destructive testing. Using a diamond cutting wire and a tool microscope with an accuracy of ≤0.001mm, the samples were fixed, the airway was partially exposed, and the diameter of the relevant cross-section was measured using the tool microscope. The maximum deviation value was obtained by comparing it with the designed diameter.

[0045] Roughness of the inner wall of deep-hole airway: Based on the destructive sample of deep-hole airway diameter deviation detection, the complete morphology of the inner wall is directly exposed by the airway profile after half-section. The micro-contour data of the inner wall is extracted by high-precision contour measurement equipment, and the roughness Ra value is calculated to complete the roughness detection. Working surface flatness: A laser flatness tester is used to scan the entire area of ​​the suction cup working surface and record the maximum flatness deviation; Vacuum pressure holding performance: Connect the suction cup to the vacuum system, pump to -50KPa~-60KPa and hold the pressure for 15 minutes, record the pressure drop with a precision pressure gauge and calculate the percentage change in pressure.

[0046] Finished product qualification rate: At least 5 samples are prepared for each group of experiments, and the qualification rate is determined by statistically analyzing the proportion of qualified finished products to the total number of prepared products.

[0047] The performance test results are as follows: Examples 1-3 (method of the present invention): The product has excellent and stable performance, with a deep hole air channel diameter deviation of ±0.140mm-±0.200mm, a deep hole air channel inner wall Ra of 1.60μm-2.20μm, a working surface flatness of 1.7μm-1.9μm, a pressure change percentage of 2.2%-3.4%, and a finished product qualification rate of 96%-100%. There are no problems such as cracking, deformation, or poor air channel sealing.

[0048] Comparative Examples 1-4 (Comparative Schemes): All performance aspects are inferior to the Examples, specifically the following: deep hole air channel diameter deviation ±0.230mm-±0.320mm, deep hole air channel inner wall Ra 1.60μm-3.00μm, working surface flatness 3.1μm-6.5μm, pressure change percentage 5.6%-15.2%, and finished product qualification rate 55%-91%. In addition, there are defects such as insufficient deep hole dimensional accuracy, rough inner wall, out-of-tolerance flatness, poor vacuum pressure holding performance, or finished product cracking.

[0049] Based on the analysis of test data and process differences, the silicon carbide vacuum chucks prepared in Examples 1-3 of this invention are significantly superior to the comparative examples in terms of deep hole size accuracy, structural integrity, vacuum pressure holding reliability and adaptability to large-scale production, and have solved the two major pain points of traditional processes.

[0050] Compared with the traditional split-assembly process: The product in the example adopts the "PVA core mold + gel injection molding" integrated molding, and the deep hole air channel has no welding / bonding splicing seams. The pressure change percentage in Examples 1-3 is only 2.2%-3.4%, which is much lower than that in the comparative example (5.6%-15.2%), proving that the vacuum pressure holding performance is superior and completely solves the air leakage problem caused by splicing seams; at the same time, it eliminates splicing and secondary processing steps, and the finished product qualification rate reaches 96%-100%, which is suitable for large-scale production.

[0051] The shortcomings of the comparative model further confirm the advantages of the present invention: Comparative Example 1 uses paraffin wax wire to replace water-soluble PVA core mold. The accuracy of the deep hole air channel diameter deteriorates and the smoothness of the inner wall decreases. This is mainly due to the uneven volatilization of paraffin wax during burning, which forms pits and carbon traces. The flatness of the working surface is poor, and the vacuum pressure sealing performance is weakened. This is due to the superposition of thermal stress generated during the dewaxing stage and sintering deformation. Paraffin wax is prone to carbonization residue and affects the accuracy after sintering. It can easily affect vacuum adsorption during use, resulting in a decrease in the qualified rate of finished products and affecting the consistency of deep hole air channel conduction.

[0052] Compared with Examples 1-3 of this invention, Comparative Example 1 used a paraffin core mold that was removed by high-temperature burning before sintering, resulting in uneven heating of the green body and a high cracking rate. In contrast, this invention dissolves the PVA core mold during the green body stage, without thermal shock, and the green body integrity rate reaches over 98%. Furthermore, the inner wall roughness Ra of the deep-hole air channel of this invention is ≤2.2μm, and the percentage change in vacuum pressure is only 2.2%-3.4%, significantly better than Comparative Example 1 (Ra=2.8μm, pressure change percentage 5.6%). This fully demonstrates the superiority of this dissolution method in protecting the green body structure and improving the finished product qualification rate and performance, highlighting the advantages of the PVA core mold being low-temperature residue-free and having a smooth inner wall, meeting the requirements of high-precision applications.

[0053] Comparative Example 2 omitted the segmented humidity-controlled drying process and adopted a single-stage drying method, resulting in an imbalance in the evaporation rate of moisture inside and outside the green body. This induced cracks and residual stress in the green body, and these potential defects were further amplified during the subsequent high-temperature sintering process, ultimately leading to a significant deterioration in the mechanical properties and sealing reliability of the product. This result fully highlights the core value of the segmented humidity-controlled drying process of this invention—through the synergistic effect of gradient humidity control and slow temperature rise drying, it can effectively avoid cracking and residual stress caused by uneven moisture evaporation in the green body, laying a high-quality foundation for the subsequent sintering process.

[0054] Comparative Example 3 omits the crucial step of embedding the dried green body into the silicon powder bed, causing the green body to lose its support structure that is compatible with the thermal expansion characteristics of silicon carbide during the subsequent sintering process. This results in significant deformation of the green body due to thermal stress at high temperatures, ultimately leading to deterioration of the product's structural precision and a significant reduction in vacuum pressure holding performance.

[0055] Comparative Example 4: Traditional integral pressing molding process: The products in Examples 1-3 are precisely formed with PVA core molds to create deep holes, avoiding uneven stress on the deep hole area during pressing and the problem of internal deformation and damage to the surface quality during the demolding process. In Examples 1-3, the diameter deviation of the deep hole air passage is only ±0.140mm-±0.2mm, the inner wall Ra≤2.2μm, and the finished product is free of cracks. In contrast, the traditional integral pressing process is prone to cracking in the deep hole area, the finished product qualification rate is usually less than 70%, and a larger processing allowance is required to correct deformation, resulting in higher costs.

[0056] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for manufacturing a silicon carbide vacuum chuck with internal deep-hole air channels, characterized in that, Includes the following steps: S1: A deep hole core mold is manufactured using a water-soluble core mold material and a 3D printer. After surface finishing, the deep hole core mold is positioned and fixed in the lower mold cavity. S2: After ball mixing and vacuum degassing of silicon carbide slurry, the silicon carbide slurry gel is injected into the mold cavity containing a deep hole core mold under set temperature and pressure. After injection molding, pressure is applied to the mold to promote the gel solidification of the slurry and demold to obtain the green body. S3: Immerse the entire green body in a water bath to dissolve and remove the core mold; S4: The green blank is dried using a segmented humidity control method, embedded in a silicon powder bed and placed in a protected graphite crucible; the graphite crucible is placed in an atmosphere furnace, and reaction sintering is completed according to the set sintering process curve. After cooling in the furnace, it is taken out of the furnace to obtain a silicon carbide vacuum chuck sintered blank. S5: The sintered blank of silicon carbide vacuum chuck is machined with a reference surface, and then precision grinding, polishing, working surface preparation, and polishing are performed in sequence. The accessories are then installed to obtain a silicon carbide vacuum chuck with internal deep hole air channels.

2. The method for manufacturing a silicon carbide vacuum chuck with internal deep-hole air channels according to claim 1, characterized in that, The water-soluble core mold material is polyvinyl alcohol (PVA) wire; after surface finishing, the surface roughness Ra of the deep hole core mold is ≤0.8μm; the diameter of the deep hole core mold is Φ2.5mm-Φ6.0mm, and the length is 80mm-320mm.

3. The method for manufacturing a silicon carbide vacuum chuck with internal deep-hole air channels according to claim 1, characterized in that, The printing parameters for the deep hole core mold are: nozzle diameter Φ0.4mm-0.6mm, layer height 0.2mm-0.3mm, printing speed 25mm / s-35mm / s, and fill rate 100%.

4. The method for manufacturing a silicon carbide vacuum chuck with internal deep-hole air channels according to claim 1, characterized in that, The silicon carbide slurry, by weight, comprises 150-180 parts silicon carbide powder, 24-28 parts deionized water, 4.0-5.0 parts agarose, 1.0-1.5 parts ammonium polyacrylate, and 2.5-3.5 parts glycerol. The silicon carbide powder is composed of a mixture of fine powder with a particle size of 1μm-3μm and coarse powder with a particle size of 20μm-30μm, with the fine powder accounting for 35%-40% and the coarse powder accounting for 60%-65% by weight.

5. The method for manufacturing a silicon carbide vacuum chuck with internal deep-hole air channels according to claim 1, characterized in that, The injection molding process uses an injection pressure of 0.25MPa-0.35MPa, and the embossing mold pressure applied after injection is 0.5MPa-0.7MPa. At the same time, the slurry curing temperature is maintained at 48℃-52℃, and the temperature is controlled to room temperature after gel curing. The embossing mold is made of 304 stainless steel, and the surface roughness Ra of the working surface is ≤0.08μm.

6. The method for manufacturing a silicon carbide vacuum chuck with internal deep-hole air channels according to claim 1, characterized in that, The segmented humidity-controlled drying method is as follows: first, place the green body in an environment with 90%-98% humidity for 20-28 hours, then place it in an environment with 55%-65% humidity for 10-14 hours, and finally, heat it from room temperature to 68-72℃ in a drying oven at a rate of 0.4℃ / min-0.6℃ / min, and keep it at this temperature until it reaches constant weight. The moisture content of the green body after drying is ≤0.1%.

7. The method for manufacturing a silicon carbide vacuum chuck with internal deep-hole air channels according to claim 1, characterized in that, The reference surface machining method is as follows: a CNC machining center or a precision grinding machine is used to machine the reference surface. The depth of the machining of the reference surface is 0.5mm-1mm. After machining, the flatness of the reference surface is detected by a coordinate measuring machine.

8. The method for manufacturing a silicon carbide vacuum chuck with internal deep-hole air channels according to claim 1, characterized in that, The silicon powder in the silicon powder bed has a silicon powder particle size of 20μm-1mm.

9. The method for manufacturing a silicon carbide vacuum chuck with internal deep-hole air channels according to claim 1, characterized in that, The sintering process curve is as follows: From room temperature to 550℃, an argon atmosphere is used with a heating rate of 1.2℃ / min-1.8℃ / min; the temperature is held at 550℃ for 100min-140min; From 550℃ to 1400℃, vacuum protection is switched on with a heating rate of 3.5℃ / min-4.5℃ / min; From 1400℃ to 1580℃, vacuum protection is maintained with a heating rate of 1.8℃ / min-2.2℃ / min; the temperature is held at 1580℃ for 160min-200min; Vacuum protection is maintained, and the cooling rate is 1.2℃ / min-1.8℃ / min, cooling down to room temperature before unloading.