A porous gradient distribution porous suction cup and a preparation method thereof

Abstract

The application relates to the field of suction cups, and discloses a pore gradient distribution porous suction cup and a preparation method thereof. The preparation method comprises the following steps: mixing formula powder; powder glue granulation; dry pressing preforming; secondary cold isostatic pressing forming; glue removal sintering; and finishing to obtain a final product. The pore gradient distribution porous suction cup prepared by the method has the advantages that the pore gradient is controllable and the adsorption effect is maximized. Under the same negative pressure condition, the higher the porosity and the larger the pore diameter of the material, the greater the adsorption force generated. The various formula powders are integrally formed in different regions, the content of the pore forming agent in the formula and the particle size of the low-activity alumina are gradually adjusted from the inner ring to the outer ring, the porosity and the pore diameter of each region of the sintered blank body are regulated, the porosity of the inner and outer rings of the suction cup can be regulated in a step-by-step mode in the range of 15-50%, and the pore diameter can be regulated in the range of 10-100 mu m, so that the problem that the wafer edge is easily deformed due to insufficient edge adsorption force is avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of suction cups, and more particularly to a pore gradient distribution porous suction cup and a preparation method thereof. BACKGROUND

[0002] Alumina porous ceramics is an environmentally friendly ceramic. Due to its porous microstructure, it has a large specific surface area and porosity, thereby having excellent adsorption performance and permeability. These properties make it play an important role in high-tech fields such as semiconductor manufacturing, and are of great significance to reducing production costs and improving the competitiveness of domestic manufacturing.

[0003] Although there are many production methods for alumina porous suction cups on the current market, the adsorption performance of these products is generally single and uniform. There are still some deficiencies for the needs of some specific occasions, such as the problem that wafers are easily deformed due to insufficient edge adsorption force during handling and processing. The adsorption force generated by the material is related to the pore condition of the material itself. Under the same negative pressure condition, the larger the pore size and the higher the porosity of the material, the greater the adsorption force generated. Therefore, it is urgent to find a method to control the pore rate and pore size gradient distribution of different regions of the material to meet the adsorption force requirements of different positions in actual application. SUMMARY

[0004] The purpose of the present application is to overcome the problem that the single pore suction cup cannot meet the different adsorption force requirements of different parts for some specific occasions. The present application provides a preparation method of a pore gradient distribution porous suction cup, which is simple in process, controllable in pore gradient distribution, low in cost and has a pore gradient distribution porous suction cup.

[0005] The preparation method of the pore gradient distribution porous suction cup provided by the present application comprises the following steps:

[0006] (1) Mixing of formula powder:

[0007] The low-activity alumina powder with a mass fraction of 70-90wt% (particle size of 10-60pm), the high-activity alumina powder with a mass fraction of 0-15wt% (particle size of 0.1-1.5pm), the liquid phase sintering aid with a mass fraction of 0-15wt%, and the pore former with a mass fraction of 0-30wt% are ball milled to obtain the formula powder for granulation;

[0008] The high-activity alumina powder is first solid-soluted with the aid to form a liquid phase, while inhibiting the growth of low-activity alumina grains or solid-soluted to form a liquid phase, thereby protecting the skeleton of large-grained alumina and improving the strength of the material.

[0009] The sintering activity of alumina powder is related to the particle size, specific surface area and crystal phase of the powder, and the specific surface area is usually related to the particle size of the powder to some extent, which is mainly characterized by the grain size of the powder. The alumina powder with a particle size of 10 microns or more is low-activity alumina, and the alumina powder with a particle size of tens of nanometers to several microns is active alumina.

[0010] In the formula powder of the present application, high-activity and low-activity alumina powders are used together. The purpose is to use large-particle (particle size of 10-60 μm) low-activity alumina as a skeleton to ensure uniform and interconnected pore distribution. However, it is easy to have the problem of low green strength and easy cracking and slagging by sintering between large grains to maintain the structure of the green body. Therefore, it is necessary to increase the strength of the green body by forming a liquid phase between large-particle low-activity alumina under the action of a high-activity alumina and a liquid-phase aid. In addition, the high-activity alumina has a small particle size (particle size of 0.1-1.5 μm) and a larger specific surface area, which can form a liquid phase to some extent and can play a protective role for low-activity alumina to prevent large-particle alumina from further growing under the action of the aid.

[0011] Preferably, the step (1) is specifically: first add high-activity alumina powder, liquid-phase sintering aid and spherical pore-forming agent, mix by ball milling for 4-8 hours, then add large-particle α-phase low-activity alumina powder and continue ball milling for 12-24 hours.

[0012] More preferably, the low-activity alumina powder is α-phase low-activity alumina with a particle size of 10-60 μm; the high-activity alumina has a purity of more than 99.95% and a median particle size of 0.1-1.5 μm; the liquid-phase sintering aid used is at least one of silica, titanium dioxide and zirconium oxide powder with AR-grade purity and a particle size of 1-10 μm; and the pore-forming agent used is paraffin powder and / or PMMA powder with a particle size of 7.5-50 μm.

[0013] Further preferably, the ball milling ratio in the step (1) is 1:1.5-1:2.5, and the ball milling medium is 99 alumina balls with a ball milling speed of 70-90 r / min.

[0014] The silica and titanium dioxide form a solid solution with the active alumina to promote sintering and reduce the sintering temperature at the same time, and the zirconium oxide as the other phase can inhibit the further abnormal growth of the grains and improve the dispersion uniformity of the pores. In addition, the aids used are oxides, and there is no need to additionally increase the oxygen concentration for oxidation.

[0015] (2) Powder and glue granulation:

[0016] The adhesive is added to the formula powder to obtain a slurry by ball milling, and the slurry is aged and homogenized for a period of time, then dried and dehydrated, crushed and sieved to obtain the final molding powder;

[0017] Specifically, in the step (2), the binder used is a PVA solution with a concentration of 10-15 wt%, wherein the PVA has a viscosity of 40-55 mPa·s, an alcoholysis degree of 88%, and a molecular weight of 101200-110000. Since the original formula powders used are all refractory powders, the forming performance is poor. By adding glue to the powder and granulating, the forming performance and uniformity of the powder can be improved, and the strength of the green body can be increased.

[0018] Preferably, in the step (2), the amount of PVA solution added is 10-20 wt% of the mass of the powder, and the ball ratio of the ball mill is 1:1.5-1:3, wherein the ball mill medium is zirconia ball, the particle size coarse-fine mass ratio is 1:1-2:1, the small ball diameter is 5-10 mm, and the large ball diameter is 15-30 mm.

[0019] More preferably, in the step (2), the slurry aging time is 24-48 h, the ambient temperature is 20-40℃, and the dehydration drying is carried out in a constant temperature and humidity drying box at 40-60℃ humidity and 80-95% for 3-12 h, the residual water content in the final powder is controlled to be 3-7%, the glue content is 1-3%, the powder broken particle size D50≤150μm, and D90≤200μm.

[0020] (3) Dry pressing preforming:

[0021] The two prepared powders are respectively dry pressed into green bodies with a thickness density close to a compatible disc and a ring-shaped green body by using a dry pressing mold, at this time, the internal structure of the obtained green body is relatively loose to a certain extent, and there is still space for further compression;

[0022] In the step (3), the dry pressing preforming pressure is 15-30 MPa, the thickness of the preformed body of the two powders is 15-22 mm, and the thickness difference is not more than 0.2 mm, and the green body density is 1.39-1.67 / cm 3 .

[0023] Specifically, the outer diameter of the disc-shaped dry pressing mold cavity is 150-170 mm, and the outer diameter of the ring-shaped mold cavity is 240-270 mm and the inner diameter is 150.2-170.2 mm.

[0024] (4) Secondary cold isostatic pressing forming:

[0025] The green body after dry pressing preforming is transferred into a rubber mold for assembly and sealing, and then fixed by a metal clamp plate on the upper and lower end faces, and then placed into a cold isostatic body for secondary cold isostatic forming to obtain a green body;

[0026] The secondary cold isostatic pressure in the step (4) is between 180-260 MPa, the rubber mold inner cavity outer diameter is between 240.4-270.4 mm, the metal clamp thickness used is between 20-35 mm and the material is aluminum alloy, and the green body density after cold isostatic is between 1.88-2.17 g / cm 3 .

[0027] At this time, the green body of the dry-pressed preform is further compressed and densified, and the un-compacted powder at the contact position between the preform green bodies of different raw material ratios will engage with each other in the further compression process to form a whole, and finally realize the composite molding of the green body with multiple porosity formulas. The porosity and pore size between the inner and outer rings or different regions of the green body after sintering are controlled by adjusting the porosity formula ratio of the powder used between the inner and outer rings or different regions of the green body.

[0028] The dry-pressed preforming and then cold isostatic pressing of the present application can realize the integrated molding of multiple formula powders in different regions, and the porosity and pore size of each region of the green body are adjusted by adjusting the formula ratio of the powder in each region.

[0029] (5) Debinding and sintering:

[0030] The sintering process adopted is a debinding-sintering integrated mode, the green body is placed in a sintering furnace for sintering, the sintering temperature is between 1500-1550℃, and the holding time is between 120-180 min. Compared with other sintering of alumina, the required sintering temperature is relatively low, which can save cost to a certain extent.

[0031] Specifically, the sintering temperature of the sintering curve in the step (5) is between 1500-1550℃, and the temperature rising curve is a sintering process curve: 0.25-0.5℃ / min from room temperature to 100℃, holding for 150-200 min, then 0.25-0.5℃ / min to 200℃, holding for 150-200 min, then 0.25-0.5℃ / min to 250℃, holding for 150-200 min, then 0.25-0.35℃ / min to 350℃, holding for 120-180 min, then 0.25-0.5℃ / min to 450℃, holding for 120-180 min, then 0.25-0.5℃ / min to 600℃, holding for 120-180 min, then 1-1.5℃ / min to 900℃, holding for 60-90 min, then 1-1.5℃ / min to 1200℃, holding for 60-90 min, then 1-1.5℃ / min to 1400℃, holding for 60-90 min, then 1-1.5℃ / min to 1500-1550℃, holding for 120-240 min, and then cooling with the furnace.

[0032] (6) Finishing:

[0033] The sintered ceramic green body is placed in clear, low-temperature molten paraffin to seal the pores, and then dewaxed through subsequent processing to obtain the final product.

[0034] Molten paraffin is a material with a relatively low melting point, easy to clean and remove, inert and non-corrosive, and low strength that will not damage the internal pore structure of the blank. It has a good sealing effect on the sintered ceramic green body.

[0035] A porous suction cup with a pore gradient distribution is prepared by the aforementioned method for preparing a porous suction cup with a pore gradient distribution. The porosity of the inner and outer rings of the porous suction cup is controlled in a stepwise manner within the range of 15-50% and the pore size is controlled within the range of 10-100μm.

[0036] Compared with the prior art, the beneficial effects of this application embodiment are as follows: Compared with other existing porous suction cups with single pore sizes that cannot meet the greater adsorption force required for specific areas, the porous suction cup prepared by the method of this invention has the advantages of controllable pore gradient and maximized adsorption effect. Under the same negative pressure conditions, the higher the material porosity and the larger the pore size, the greater the adsorption force generated. By integrally molding various formula powders in different regions, and gradually adjusting the content of pore-forming agent and the particle size of low-activity alumina in the formula from the inner ring to the outer ring, the porosity and pore size of each region of the sintered blank can be controlled. This allows for stepwise control of the porosity of the inner and outer rings of the suction cup within the range of 15-50% and the pore size within the range of 10-100μm, avoiding the problem of wafer edge deformation due to insufficient edge adsorption force, thus enabling it to be applicable to a wider range of applications. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a schematic flowchart illustrating a method for preparing a porous suction cup with a pore gradient distribution, as provided in an embodiment of this application.

[0039] Figure 2 Scanning electron microscope (SEM) image of a porous sample area prepared from 80g of pore-forming agent with α-phase low-activity alumina and a particle size D50 of 30μm. Detailed Implementation

[0040] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit the scope of this application. In the following embodiments, unless otherwise specified, the raw materials or processing techniques used are conventional commercially available raw materials or conventional processing techniques in the art.

[0041] Example 1

[0042] This embodiment provides a method for preparing a porous suction cup with a pore gradient distribution, including the following steps:

[0043] (1) Mixing of formula powders

[0044] Weigh out 800g of α-phase low-activity alumina with a particle size D50 of 30μm, 100g of high-activity alumina powder with a D50 of 0.4μm, and 100g of liquid-phase sintering aid (silica) according to the following mass ratio. Without adding pore-forming agent, mix the materials by ball milling with 99 alumina balls at a speed of 80r / min at a material-to-ball ratio of 1:2 for 18h to obtain the formula powder for granulation.

[0045] (2) Powder granulation with binder

[0046] Add 20% PVA solution (15wt%) by weight of the powder to the above formula powder, ball mill at 25℃ with a material-to-ball ratio of 1:2 for 24 hours (the ratio of 8mm small balls to 25mm large balls is 1:1), age at room temperature for 24 hours, and then dry in a constant temperature and humidity chamber at 48℃ and 90% humidity for 6 hours. Crush to obtain shaped powder A.

[0047] Weigh out 800g of α-phase low-activity alumina with a particle size D50 of 30μm, 100g of high-activity alumina powder with a particle size D50 of 0.4μm, 100g of liquid phase sintering aid (silica), and 40g of pore-forming agent with a D50 of 30μm according to the same granulation steps to obtain shaped powder B.

[0048] Weigh out 800g of α-phase low-activity alumina with a particle size D50 of 30μm, 100g of high-activity alumina powder with a particle size D50 of 0.4μm, 100g of liquid phase sintering aid (silica), and 80g of pore-forming agent with a D50 of 30μm according to the same granulation steps to obtain shaped powder C.

[0049] Weigh out 800g of α-phase low-activity alumina with a particle size D50 of 30μm, 100g of high-activity alumina powder with a particle size D50 of 0.4μm, 100g of liquid phase sintering aid (silica), and 120g of pore-forming agent with a particle size D50 of 30μm according to the same granulation steps to obtain shaped powder D.

[0050] Weigh out 800g of α-phase low-activity alumina with a particle size D50 of 30μm, 100g of high-activity alumina powder with a particle size D50 of 0.4μm, 100g of liquid phase sintering aid (silica), and 160g of pore-forming agent with a D50 of 30μm according to the same granulation steps to obtain shaped powder E.

[0051] The residual moisture content of powder A is 6.2%, and the glue content is 2.8%; the residual moisture content of powder B is 6.2%, and the glue content is 2.7%; the residual moisture content of powder C is 6.3%, and the glue content is 2.9%; the residual moisture content of powder D is 6.4%, and the glue content is 2.9%; and the residual moisture content of powder E is 6.4%, and the glue content is 2.7%.

[0052] (3) Dry pressing preforming

[0053] The five powders were pre-formed under a pressure of approximately 14 MPa according to the above dry pressing preforming process. The pre-formed green body A had dimensions of D100.0*16.2 mm and a density of 1.65 g / cm³. 3 The preformed green body B has dimensions of D140-D100.1*16.2 mm and a density of 1.64 g / cm³. 3 The preformed green body has dimensions C of D180-D140.2*16.2 and a density of 1.62 g / cm³. 3 The preform green body has dimensions D220-D180.2*16.2 and a density of 1.59 g / cm³. 3 The preform green body E has dimensions of D260-D220.2*16.2 mm and a density of 1.57 g / cm³. 3 .

[0054] (4) Secondary cold isostatic pressing

[0055] The preformed blanks were assembled and then subjected to a second cold forming process at 240 MPa to obtain a green blank with an overall density of 2.16 g / cm³. 3 .

[0056] (5) Debinding and sintering

[0057] A porous alumina suction cup material with a pore gradient distribution was obtained by sintering at 1550℃ through a debinding-sintering integrated process. The heating curve was as follows: room temperature 0.5℃ / min to 100℃ and hold for 200 min, then 0.5℃ / min to 200℃ and hold for 200 min, then 0.5℃ / min to 250℃ and hold for 200 min, then 0.35℃ / min to 350℃ and hold for 180 min, then 0.5℃ / min to 450℃ and hold for 120 min, then 0.5℃ / min to 600℃ and hold for 120 min, then 1℃ / min to 900℃ and hold for 60 min, then 1℃ / min to 1200℃ and hold for 60 min, then 1℃ / min to 1400℃ and hold for 60 min, then 1℃ / min to 1550℃ and hold for 180 min, and then cooled in the furnace.

[0058] (6) Finishing

[0059] The sintered ceramic green body is placed in clear molten paraffin at 58°C for sealing, and then dewaxed through subsequent processing to obtain the final product.

[0060] Measurements showed that the porosity of region A at the center of the finished product was 18%, with a pore size of 30-100 μm and a density of 3.07 g / cm³. 3 Region B has a porosity of 21%, a pore size of 40-100 μm, and a density of 2.96 g / cm³. 3 Region C has a porosity of 25%, a pore size of 40-100 μm, and a density of 2.81 g / cm³. 3 The porosity of region D is 29.5%, the pore size is 50-100 μm, and the density is 2.64 g / cm³. 3 The porosity of region D is 35%, the pore size is 50-100 μm, and the density is 2.45 g / cm³. 3 .

[0061] Example 2

[0062] This embodiment provides a method for preparing a porous suction cup with a pore gradient distribution, including the following steps:

[0063] (1) Mixing of formula powders

[0064] Weigh out 900g of α-phase low-activity alumina with a particle size D50 of 15μm, 50g of high-activity alumina powder with a D50 of 0.6μm, 50g of liquid phase sintering aid (titanium dioxide), and 40g of pore-forming agent (paraffin powder) with a D50 of 15μm according to the following mass ratio. Mix the powder with 99 alumina balls at a speed of 70r / min at a material-to-ball ratio of 1:2 for 21h to obtain the formula powder for granulation.

[0065] (2) Powder granulation with binder

[0066] Add 20% PVA solution (15wt%) by weight of the powder to the above formula powder, ball mill at 25℃ with a material-to-ball ratio of 1:2 for 36 hours (8mm small balls to 25mm large balls in a 1:1 ratio), age at room temperature for 24 hours, and then dry in a constant temperature and humidity chamber at 48℃ and 90% humidity for 6 hours. Crush to obtain shaped powder A.

[0067] Weigh out 900g of α-phase low-activity alumina with a particle size D50 of 15μm, 50g of high-activity alumina powder with a D50 of 0.6μm, 50g of liquid phase sintering aid (titanium dioxide), and 80g of pore-forming agent (PMMA micro powder) with a D50 of 15μm according to the same mass ratio, and obtain shaped powder B by the same granulation steps.

[0068] Weigh out 900g of α-phase low-activity alumina with a particle size D50 of 15μm, 50g of high-activity alumina powder with a D50 of 0.6μm, 50g of liquid phase sintering aid (titanium dioxide), and 120g of pore-forming agent (PMMA micro powder) with a D50 of 15μm according to the same mass ratio, and obtain the shaped powder C by the same granulation steps.

[0069] Weigh out 900g of α-phase low-activity alumina with a particle size D50 of 15μm, 50g of high-activity alumina powder with a D50 of 0.6μm, 50g of liquid phase sintering aid (titanium dioxide), and 160g of pore-forming agent (PMMA micro powder) with a D50 of 15μm according to the same mass ratio, and obtain the shaped powder D by the same granulation steps;

[0070] Weigh out 900g of α-phase low-activity alumina with a particle size D50 of 15μm, 50g of high-activity alumina powder with a D50 of 0.6μm, 50g of liquid phase sintering aid (titanium dioxide), and 200g of pore-forming agent (PMMA micro powder) with a D50 of 15μm according to the same mass ratio, and obtain the shaped powder E according to the same granulation steps.

[0071] Powder A has a residual moisture content of 5.9% and a glue content of 2.6%; Powder B has a residual moisture content of 5.7% and a glue content of 2.7%; Powder C has a residual moisture content of 5.8% and a glue content of 2.6%; Powder D has a residual moisture content of 5.6% and a glue content of 2.9%; and Powder E has a residual moisture content of 6.0% and a glue content of 2.8%.

[0072] (3) Dry pressing preforming

[0073] The five powders were pre-formed under a pressure of approximately 18 MPa according to the above dry pressing preforming process. The pre-formed green body A had dimensions of D100.0*16.2 mm and a density of 1.65 g / cm³. 3 The preformed green blank B has dimensions of D140-D100.1*16.2 mm and a green blank density of 1.64 g / cm³. The preformed green blank C has dimensions of D180-D140.2*16.2 mm and a green blank density of 1.62 g / cm³.3 The preform green body has dimensions D220-D180.2*16.2 and a density of 1.59 g / cm³. 3 The preform green body E has dimensions of D260-D220.2*16.2 mm and a density of 1.57 g / cm³. 3 .

[0074] (4) Secondary cold isostatic pressing

[0075] The preformed blanks were assembled and then subjected to a second cooling process at 260 MPa to obtain a green blank with an overall density of 2.16 g / cm³. 3 .

[0076] (5) Debinding and sintering

[0077] A porous alumina suction cup material with a pore gradient distribution was obtained by sintering at 1500℃ through a debinding-sintering integrated process. The heating curve was as follows: room temperature 0.5℃ / min to 100℃ and hold for 200 min, then 0.5℃ / min to 200℃ and hold for 200 min, then 0.5℃ / min to 250℃ and hold for 200 min, then 0.35℃ / min to 350℃ and hold for 180 min, then 0.5℃ / min to 450℃ and hold for 120 min, then 0.5℃ / min to 600℃ and hold for 120 min, then 1℃ / min to 900℃ and hold for 60 min, then 1℃ / min to 1200℃ and hold for 60 min, then 1℃ / min to 1400℃ and hold for 60 min, then 1℃ / min to 1500℃ and hold for 180 min, and then cooled in the furnace.

[0078] (6) Finishing

[0079] The sintered ceramic green body is placed in clear molten paraffin at 58°C for sealing, and then dewaxed through subsequent processing to obtain the final product.

[0080] Measurements showed that the porosity of region A at the center of the finished product was 19%, the pore size was 10-50 μm, and the density was 3.11 g / cm³. 3 Region B has a porosity of 22%, a pore size of 10-60 μm, and a density of 2.99 g / cm³. 3 Region C has a porosity of 27%, a pore size of 20-70 μm, and a density of 2.80 g / cm³. 3 The porosity of region D is 32%, the pore size is 20-70 μm, and the density is 2.61 g / cm³. 3 The porosity of region D is 36%, the pore size is 20-80 μm, and the density is 2.46 g / cm³. 3 .

[0081] Example 3

[0082] This embodiment provides a method for preparing a porous suction cup with a pore gradient distribution, including the following steps:

[0083] (1) Mixing of formula powders

[0084] Weigh out 750g of α-phase low-activity alumina with a particle size D50 of 60μm, 150g of high-activity alumina powder with a D50 of 1μm, and 100g of liquid phase sintering aid (silicon dioxide: titanium dioxide: zirconium oxide = 2:2:1) according to the following mass ratio, without adding pore-forming agent.

[0085] First, add high-activity alumina powder, liquid phase sintering aid, and spherical pore-forming agent. Then, use 99% alumina balls to ball mill and mix for 8 hours at a material-to-ball ratio of 1:2.5 at a speed of 90 r / min. Next, add α-phase low-activity alumina powder and continue ball milling for 16 hours to obtain the formula powder for granulation.

[0086] (2) Powder granulation with binder

[0087] Add 15% PVA solution (12wt%) by weight of the powder to the above formula powder, ball mill at 25℃ with a material-to-ball ratio of 1:2 for 30h (8mm small balls to 25mm large balls in a 1:1 ratio), age at room temperature for 24h, and then dry in a constant temperature and humidity chamber at 48℃ and 85% humidity for 5h, and crush to obtain shaped powder A;

[0088] Weigh out 750g of α-phase low-activity alumina with a particle size D50 of 60μm, 150g of high-activity alumina powder with a D50 of 1μm, 100g of liquid phase sintering aid (silicon dioxide:titanium dioxide:zirconia = 2:2:1) and 40g of pore-forming agent (PMMA micro powder) with a D50 of 15μm according to the same granulation steps to obtain shaped powder B;

[0089] Weigh out 750g of α-phase low-activity alumina with a particle size D50 of 60μm, 150g of high-activity alumina powder with a D50 of 1μm, 100g of liquid phase sintering aid (silicon dioxide:titanium dioxide:zirconia = 2:2:1) and 80g of pore-forming agent (PMMA micro powder) with a D50 of 15μm according to the same granulation steps to obtain shaped powder C;

[0090] Weigh out 750g of α-phase low-activity alumina with a particle size D50 of 60μm, 150g of high-activity alumina powder with a D50 of 1μm, 100g of liquid phase sintering aid (silicon dioxide:titanium dioxide:zirconia = 2:2:1) and 120g of pore-forming agent (PMMA micro powder) with a D50 of 15μm according to the same granulation steps to obtain shaped powder D;

[0091] Weigh out 750g of α-phase low-activity alumina with a particle size D50 of 60μm, 150g of high-activity alumina powder with a D50 of 1μm, 100g of liquid phase sintering aid (silicon dioxide:titanium dioxide:zirconia = 2:2:1) and 160g of pore-forming agent (PMMA micro powder) with a D50 of 15μm according to the same granulation steps to obtain shaped powder E;

[0092] Powder A has a residual moisture content of 6.0% and a glue content of 2.7%; Powder B has a residual moisture content of 6.1% and a glue content of 2.6%; Powder C has a residual moisture content of 6.2% and a glue content of 2.8%; Powder D has a residual moisture content of 6.3% and a glue content of 2.9%; and Powder E has a residual moisture content of 6.3% and a glue content of 2.8%.

[0093] (3) Dry pressing preforming

[0094] The five powders were pre-formed under a pressure of approximately 16 MPa according to the above dry pressing preforming process. The pre-formed green body A had dimensions of D100.0*16.2 mm and a density of 1.65 g / cm³. 3 The preformed green body B has dimensions of D140-D100.1*16.2 mm and a density of 1.63 g / cm³. 3 The preform green body has dimensions C of D180-D140.2*16.2 and a density of 1.61 g / cm³. 3 The preformed green body has dimensions D220-D180.2*16.2 and a density of 1.58 g / cm³. 3 The preformed green body E has dimensions of D260-D220.2*16.2 mm and a density of 1.56 g / cm³. 3 .

[0095] (4) Secondary cold isostatic pressing

[0096] The preformed blanks were assembled and then subjected to a second cooling process at 250 MPa to obtain a green blank with an overall density of 2.16 g / cm³. 3 .

[0097] (5) Debinding and sintering

[0098] A porous alumina suction cup material with a pore gradient distribution was obtained by sintering at 1550℃ through a debinding-sintering integrated process. The heating curve was as follows: room temperature 0.25℃ / min to 100℃ and hold for 150 min, then 0.25℃ / min to 200℃ and hold for 180 min, then 0.25℃ / min to 250℃ and hold for 150 min, then 0.35℃ / min to 350℃ and hold for 150 min, then 0.5℃ / min to 450℃ and hold for 150 min, then 0.5℃ / min to 600℃ and hold for 150 min, then 1.5℃ / min to 900℃ and hold for 90 min, then 1.5℃ / min to 1200℃ and hold for 90 min, then 1.5℃ / min to 1400℃ and hold for 90 min, then 1.5℃ / min to 1500℃ and hold for 200 min, followed by furnace cooling.

[0099] (6) Finishing

[0100] The sintered ceramic green body is placed in clear molten paraffin at 58°C for sealing, and then dewaxed through subsequent processing to obtain the final product.

[0101] Measurements showed that the porosity of region A at the center of the finished product was 19%, the pore size was 30-100 μm, and the density was 3.11 g / cm³. 3 Region B has a porosity of 21.5%, a pore size of 40-100 μm, and a density of 2.99 g / cm³. 3 Region C has a porosity of 25.5%, a pore size of 40-100 μm, and a density of 2.85 g / cm³. 3 The porosity of region D is 29.8%, the pore size is 50-100 μm, and the density is 2.66 g / cm³. 3 The porosity of region D is 35.61%, the pore size is 50-100 μm, and the density is 2.65 g / cm³. 3 .

[0102] Figure 2 This is a scanning electron microscope (SEM) image of a porous sample region prepared from α-phase low-activity alumina with a particle size D50 of 30 μm and 80 g of pore-forming agent with a D50 of 30 μm. Figure 2 As can be seen from the figure, the pores of the material are relatively uniformly distributed, and the pore size of the sample in the figure is about 20-80 μm.

[0103] The beneficial effects of the above-mentioned implementation method are that the porous suction cup with a pore gradient distribution prepared by the method of the present invention has the advantages of controllable pore gradient and maximizing adsorption effect. Under the same negative pressure conditions, the higher the porosity of the material and the larger the pore size, the greater the adsorption force generated. By integrally molding various formula powders in different regions, the content of pore-forming agent and the particle size of low-activity alumina in the formula are gradually adjusted from the inner ring to the outer ring, thereby controlling the porosity and pore size of each region of the sintered blank. It is possible to achieve step-by-step control of the porosity of the inner and outer rings of the suction cup within the range of 15-50% and the pore size within the range of 10-100μm, avoiding the problem of easy deformation of the wafer edge due to insufficient edge adsorption force.

[0104] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a porous suction cup with a pore gradient distribution, characterized in that, Includes the following steps: (1) Mixing of formula powders Weigh out 800g of α-phase low-activity alumina with a particle size D50 of 30μm, 100g of high-activity alumina powder with a D50 of 0.4μm, and 100g of silica by mass ratio. Without adding pore-forming agent, mix the powders with 99 alumina balls at a speed of 80r / min at a material-to-ball ratio of 1:2 for 18h to obtain the formula powder for granulation. (2) Powder granulation with binder Add 20% of the powder mass of the above-mentioned formula to a 15wt% PVA solution, ball mill at 25°C with a material-to-ball ratio of 1:2 for 24 hours, wherein the ratio of 8mm small balls to 25mm large balls is 1:1, age at room temperature for 24 hours, and then dry in a constant temperature and humidity chamber at 48°C and 90% humidity for 6 hours, and crush to obtain shaped powder A. Weigh out 800g of α-phase low-activity alumina with a particle size D50 of 30μm, 100g of high-activity alumina powder with a particle size D50 of 0.4μm, 100g of silica, and 40g of pore-forming agent with a particle size D50 of 30μm according to the same granulation steps to obtain shaped powder B. Weigh out 800g of α-phase low-activity alumina with a particle size D50 of 30μm, 100g of high-activity alumina powder with a particle size D50 of 0.4μm, 100g of silica, and 80g of pore-forming agent with a D50 of 30μm according to the same granulation steps to obtain shaped powder C. Weigh out 800g of α-phase low-activity alumina with a particle size D50 of 30μm, 100g of high-activity alumina powder with a particle size D50 of 0.4μm, 100g of silica, and 120g of pore-forming agent with a particle size D50 of 30μm according to the same mass ratio, and obtain the shaped powder D by the same granulation steps. Weigh out 800g of α-phase low-activity alumina with a particle size D50 of 30μm, 100g of high-activity alumina powder with a particle size D50 of 0.4μm, 100g of silica, and 160g of pore-forming agent with a particle size D50 of 30μm according to the same granulation steps to obtain shaped powder E. (3) Dry pressing preforming: The prepared molding powder AE was dry-pressed into mating disc and ring-shaped green bodies using a dry press mold. (4) Secondary cold isostatic pressing: After the dry pressing pre-formed blank is transferred into the mold for assembly and sealing, the upper and lower end faces are fixed with metal clamps, and then placed in the cold waiting cylinder for secondary cold waiting to obtain the green blank. (5) Debinding and sintering: The sintering process adopted is an integrated debinding and sintering method, in which the billet is placed in a sintering furnace for sintering at a temperature of 1500-1550℃ and held for 120-180 minutes. (6) Finishing: The sintered ceramic green body is placed in clear molten paraffin at 58°C for sealing, and then dewaxed through subsequent processing to obtain the final product.

2. The method for preparing a porous suction cup with a pore gradient distribution as described in claim 1, characterized in that, In step (2), the PVA viscosity is 40-55 mPa·s, the degree of alcoholysis is 88%, and the molecular weight is 101200-110000.

3. The method for preparing a porous suction cup with a pore gradient distribution as described in claim 1, characterized in that, In step (3), the dry pressing preforming pressure is 15-30 MPa, the thickness of the preformed blanks of the five molding powders is 15-22 mm with a thickness difference not exceeding 0.2 mm, and the green density is 1.39-1.67 g / cm³. 3 .

4. The method for preparing a porous suction cup with a pore gradient distribution as described in claim 1, characterized in that, In step (4), the secondary cooling pressure is between 180-260 MPa, and the density of the green billet after cooling is between 1.88-2.17 g / cm³. 3 .

5. The method for preparing a porous suction cup with a pore gradient distribution as described in claim 1, characterized in that, In step (5), the sintering temperature of the sintering curve is 1500-1550℃, and the heating curve is the sintering process curve: 0.25-0.5℃ / min at room temperature to 100℃, hold for 150-200min, then 0.25-0.5℃ / min to 200℃, hold for 150-200min, then 0.25-0.5℃ / min to 250℃, hold for 150-200min, then 0.25-0.35℃ / min to 350℃, hold for 120-180min, then 0.25-0.5℃ / min... Increase the temperature by ℃ / min to 450℃ and hold for 120-180 min, then increase it by 0.25-0.5℃ / min to 600℃ and hold for 120-180 min, then increase it by 1-1.5℃ / min to 900℃ and hold for 60-90 min, then increase it by 1-1.5℃ / min to 1200℃ and hold for 60-90 min, then increase it by 1-1.5℃ / min to 1400℃ and hold for 60-90 min, then increase it by 1-1.5℃ / min to 1500-1550℃ and hold for 120-240 min before cooling it in the furnace.

6. A porous suction cup with a pore gradient distribution, characterized in that, The porous suction cup is prepared by the method of any one of claims 1 to 5, wherein the porosity of the inner and outer rings of the porous suction cup is controlled in a stepwise manner within the range of 15-50% and the pore size is controlled within the range of 10-100μm.

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