Method for preparing silicon nitride ceramic substrate by tape casting

Abstract

The present invention relates to a method for preparing a silicon nitride ceramic substrate by a tape casting method, comprising the following steps: A. adding silicon nitride powder, yttrium oxide, aluminum oxide, and sodium polyacrylate to deionized water, and mixing them by ball milling in a ball mill to obtain a mixed slurry; B. adding polyvinyl alcohol and glycerol to the mixed slurry, and continuing ball milling to obtain a stable water-based tape casting slurry; C. injecting the water-based tape casting slurry into the material trough of the tape casting machine, controlling the thickness of the slurry to 450 μm by a scraper, forming a uniform wet film on the tape casting belt, and drying the wet film to obtain a green film with a certain strength. The present invention relates to a method for preparing a silicon nitride ceramic substrate by a tape casting method, which can prepare a silicon nitride ceramic substrate with better performance by a tape casting method without using an organic solvent, and removing the use of organic solvents to reduce costs, reduce safety hazards and environmental pollution, and make the manufactured silicon nitride ceramic substrate have better performance.

Description

Technical Field

[0001] The invention belongs to the technical field of silicon nitride ceramic substrate manufacturing, and in particular relates to a method for preparing a silicon nitride ceramic substrate by a tape casting method. Background Art

[0002] At present, silicon nitride ceramic substrates have broad application prospects in the field of electronic packaging due to their excellent thermal conductivity, mechanical strength, electrical insulation and other properties. However, the traditional preparation method has problems such as complex process, high cost and environmental pollution. Although the commonly used organic solvent casting method can produce silicon nitride ceramic substrates with good performance, the use of organic solvents not only increases the cost, but also poses safety hazards and environmental pollution. Summary of the invention

[0003] In view of the deficiencies in the prior art, the technical problem to be solved by the present invention is to provide a method for preparing a silicon nitride ceramic substrate by a tape casting method, which can make the silicon nitride ceramic substrate have excellent thermal conductivity, mechanical strength, electrical insulation and other properties without adding organic solvents.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing a silicon nitride ceramic substrate by a tape casting method, comprising the following steps: A. adding silicon nitride powder, yttrium oxide, aluminum oxide and sodium polyacrylate into deionized water, and mixing them by ball milling in a ball mill to obtain a mixed slurry; B. adding polyvinyl alcohol and glycerol to the mixed slurry, and continuing ball milling to obtain a stable water-based casting slurry; C. Inject the water-based casting slurry into the material tank of the casting machine, control the thickness of the slurry to 450 μm by a scraper, form a uniform wet film on the casting belt, and dry the wet film to obtain a green film with a certain strength; D. stacking the green film in the required number of layers and making each layer tightly bonded by hot pressing; E. The pressed green body is placed in a debinding furnace for debinding; F. The debinding green body is placed in a sintering furnace for calcination, and then cooled in the furnace to obtain a silicon nitride ceramic substrate.

[0005] In step A, the silicon nitride powder is selected to have an average particle size of 0.5-1 μm and a purity greater than 99.5%. The added amounts of yttrium oxide and aluminum oxide are 3% and 2% of the mass of the silicon nitride powder respectively, and the added amount of sodium polyacrylate is 0.5% of the mass of the silicon nitride powder.

[0006] In step B, the amount of polyvinyl alcohol added is 10% of the mass of the silicon nitride powder, and the amount of glycerol added is 5% of the mass of the silicon nitride powder.

[0007] In steps A and B, the ball mill is used for ball milling at a rotation speed of 30 revolutions per minute for 20 hours, and then after adding polyvinyl alcohol and glycerol, the ball milling is continued for 24 hours to obtain a stable water-based casting slurry.

[0008] In step D, 5 layers of green sheets were stacked and then hot-pressed at a pressure of 20 MPa and a temperature of 60° C. for 1 hour.

[0009] In step E, the pressed green body is subjected to a debinding treatment in a debinding furnace at 500° C. for 3-5 hours.

[0010] In step F, the sintering furnace is filled with nitrogen, and the temperature of the sintering furnace is increased to 1750-1850° C. at a heating rate of 5° C. per minute, kept at this temperature for 2-4 hours, and then cooled with the furnace to obtain a silicon nitride ceramic substrate.

[0011] In step A, the ball mill includes a receiving barrel, a turntable, a plurality of locking fixing frames and a plurality of ball milling barrels. The turntable is rotatably installed in the receiving barrel. A driving assembly for driving the turntable to rotate is provided in the receiving barrel. The plurality of locking fixing frames are rotatably installed on the turntable. The plurality of ball milling barrels are respectively placed in the plurality of locking fixing frames.

[0012] The locking and fixing frame comprises a rotating disk, a locking cover and three supporting columns, the rotating disk comprises an inner rotating disk and an outer fixing ring, the inner rotating disk is rotatably located inside the outer fixing ring, the inner rotating disk is transmission-connected with a driving assembly, the rotating disk is rotatably mounted on the inner rotating disk, a transmission gear coaxially connected to the rotating disk is rotationally mounted below the inner rotating disk at a position corresponding to the rotating disk, an outer gear ring meshing with the transmission gear is mounted below the inner rotating disk, an inner ring of the outer fixing ring is mounted with an inner gear ring meshing with the transmission gear, three supporting columns are equidistantly mounted on the rotating disk around the rotating axis of the transmission gear, and the locking cover is provided with three through holes for the supporting columns to pass through; The locking cover includes a fixed plate, a clamping screw, three driving gears and three abutting racks. The clamping screw is threaded and rotatably installed in the middle part of the fixed plate. The three driving gears are equidistantly rotatably arranged in the fixed plate around the clamping screw, and the three driving gears are all meshed with the clamping screw. The fixed plate is provided with three sliding grooves respectively connected to the three through holes. The three abutting racks are respectively slidably placed in the three sliding grooves, and the three abutting racks are respectively meshed with the three driving gears.

[0013] The upper and lower parts of the ball mill barrel are both provided with a first opening and a second opening, the first opening is threadedly connected to a first sealing cover, the second opening is fixedly connected to an extension tube, a screen is installed in the extension tube, the extension tube is threadedly connected to a second sealing cover, and the holes on the screen are chamfered at one end facing the ball mill barrel.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention discloses a method for preparing a silicon nitride ceramic substrate by a tape casting method. The tape casting method can prepare a silicon nitride ceramic substrate with better performance without using an organic solvent. Eliminating the use of organic solvents reduces costs, reduces safety hazards and environmental pollution, and makes the manufactured silicon nitride ceramic substrate have better performance.

[0015] 2. The present invention provides a method for preparing a silicon nitride ceramic substrate by a tape casting method. After the ball milling is completed, the second sealing cover can be opened first, and then the output port of the extension tube is directed toward the collecting tank, and then the first sealing cover is opened to leak out the first port, and the output end of the external high-pressure blowing device is aligned with the first port and then blown, so that the ball-milled raw material flows out through the second port with the help of high-pressure gas, and the ball of the ball mill barrel will be intercepted by the screen, and the raw material sticking to the ball can also be blown off by the high-pressure gas, so that the raw material can be stably discharged from the ball mill barrel and will not remain in the ball mill barrel. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of the ball mill of the present invention; Figure 2 It is a structural schematic diagram of the turntable of the present invention; Figure 3 It is a schematic diagram of the internal structure of the turntable of the present invention; Figure 4 It is a structural schematic diagram of the locking and fixing frame of the present invention; Figure 5 This is a schematic diagram of the structure of the compression screw and the driving gear transmission of the present invention; Figure 6 It is a schematic diagram of the explosion structure of the ball mill barrel of the present invention; Figure 7 It is a schematic structural diagram of the ball mill barrel of the present invention.

[0017] Markings in the figure: 1. Supporting barrel; 2. Turntable; 3. Locking bracket; 4. Ball mill barrel; 5. Rotating disk; 6. Locking cover; 7. Support column; 8. Transmission gear; 9. External gear ring; 10. Internal gear ring; 11. Fixed plate; 12. Pressing screw; 13. Driving gear; 14. Top rack; 15. First sealing cover; 16. Extension tube; 17. Screen; 18. Second sealing cover. DETAILED DESCRIPTION

[0018] In order to make the above features and advantages of the present invention more obvious and easy to understand, embodiments are given below with reference to the accompanying drawings for detailed description as follows.

[0019] like Figure 1-Figure 7 As shown, this embodiment provides a method for preparing a silicon nitride ceramic substrate by a tape casting method, comprising the following steps: A. adding silicon nitride powder, yttrium oxide, aluminum oxide and sodium polyacrylate into deionized water, and mixing them by ball milling in a ball mill to obtain a mixed slurry; B. adding polyvinyl alcohol and glycerol to the mixed slurry, and continuing ball milling to obtain a stable water-based casting slurry; C. Inject the water-based casting slurry into the material tank of the casting machine, control the thickness of the slurry to 450 μm by a scraper, form a uniform wet film on the casting belt, and dry the wet film to obtain a green film with a certain strength; D. stacking the green film in the required number of layers and making each layer tightly bonded by hot pressing; E. The pressed green body is placed in a debinding furnace for debinding; F. The debinding green body is placed in a sintering furnace for calcination, and then cooled in the furnace to obtain a silicon nitride ceramic substrate.

[0020] Silicon nitride ceramic substrates with better performance can be prepared by the tape casting method without using organic solvents. Eliminating the use of organic solvents reduces costs, reduces safety hazards and environmental pollution, and makes the manufactured silicon nitride ceramic substrates have better performance.

[0021] In step A, the silicon nitride powder is selected to have an average particle size of 0.5-1 μm and a purity greater than 99.5%. The added amounts of yttrium oxide and aluminum oxide are 3% and 2% of the mass of the silicon nitride powder respectively, and the added amount of sodium polyacrylate is 0.5% of the mass of the silicon nitride powder.

[0022] In step B, the amount of polyvinyl alcohol added is 10% of the mass of the silicon nitride powder, and the amount of glycerol added is 5% of the mass of the silicon nitride powder.

[0023] In steps A and B, the ball mill is used for ball milling at a rotation speed of 30 revolutions per minute for 20 hours, and then after adding polyvinyl alcohol and glycerol, the ball milling is continued for 24 hours to obtain a stable water-based casting slurry.

[0024] In step D, five layers of green sheets were stacked and then hot-pressed at a pressure of 20 MPa and a temperature of 60° C. for 1 hour to make the layers closely bonded.

[0025] In step E, the pressed green body is subjected to a debinding treatment in a debinding furnace at 500° C. for 3-5 hours.

[0026] In step F, the sintering furnace is filled with nitrogen, and the temperature of the sintering furnace is increased to 1750-1850° C. at a heating rate of 5° C. per minute, kept at this temperature for 2-4 hours, and then cooled with the furnace to obtain a silicon nitride ceramic substrate.

[0027] In step A, the ball mill includes a holding barrel 1, a turntable 2, a plurality of locking and fixing frames 3 and a plurality of ball milling barrels 4. The turntable 2 is rotatably mounted in the holding barrel 1. A driving assembly for driving the turntable 2 to rotate is provided in the holding barrel 1. The plurality of locking and fixing frames 3 are rotatably mounted on the turntable 2. The plurality of ball milling barrels 4 are respectively placed in the plurality of locking and fixing frames 3. By preparing the raw materials, putting them in the ball milling barrel 4, and fixing the ball milling barrel 4 on the locking and fixing frames 3, and then driving the turntable 2 to rotate through the driving assembly, the turntable 2 drives the plurality of locking and fixing frames 3 to rotate, so that the plurality of ball milling barrels 4 can be ball milled simultaneously, thereby increasing the ball milling amount.

[0028] Furthermore, the locking and fixing frame 3 includes a rotating disk 5, a locking cover 6 and three supporting columns 7. The rotating disk 2 includes an inner rotating disk 2 and an outer fixing ring. The inner rotating disk 2 is rotatably located in the outer fixing ring. The inner rotating disk 2 is connected to the driving assembly in a transmission manner. The rotating disk 5 is rotatably installed on the inner rotating disk 2. A transmission gear 8 coaxially connected to the rotating disk 5 is rotatably installed below the inner rotating disk 2 corresponding to the position of the rotating disk 5. An outer toothed ring 9 meshing with the transmission gear 8 is installed under the inner rotating disk 2. An inner toothed ring 10 meshing with the transmission gear 8 is installed on the inner ring of the outer fixing ring. The three supporting columns 7 surround the rotating disk 2. The rotating shaft of the transmission gear 8 is equidistantly installed on the rotating disk 5, and the locking cover 6 is provided with three through holes for the support columns 7 to pass through; the ball mill barrel 4 is placed on the rotating disk 5 and is located between the three support columns 7, and the ball mill barrel 4 is fixed by the three support columns 7, and the outer gear ring 9 is driven to rotate by the rotation of the inner turntable 2, so that the outer gear ring 9 cooperates with the inner gear ring 10 to drive the transmission gear 8 to rotate, so that the transmission gear 8 drives the rotating disk 5 to rotate, so that the turntable 2 drives the rotating disk 5 to rotate, and the rotating disk 5 can also rotate on its own to make the ball milling more stable. Specifically, the locking cover 6 includes a fixed plate 11, a clamping screw 12, three driving gears 13 and three abutting racks 14. The clamping screw 12 is threadedly rotatably installed in the middle part of the fixed plate 11. The three driving gears 13 are equidistantly rotatably arranged in the fixed plate 11 around the clamping screw 12, and the three driving gears 13 are all meshed with the clamping screw 12. The fixed plate 11 is provided with three sliding grooves respectively connected to the three through holes. The three abutting racks 14 are respectively slidably placed in the three sliding grooves, and the three abutting racks 14 are respectively meshed with the three driving gears 13. When the ball mill barrel 4 is fixed, the through hole of the fixing plate 11 is aligned with the supporting column 7 and placed on the ball mill barrel 4, and the pressing screw 12 is rotated to move the pressing screw 12 toward the ball mill barrel 4. At the same time, the pressing screw 12 drives the three driving gears 13 to rotate, so that the three driving gears 13 respectively drive the three abutting racks 14 to move toward the sliding groove, so that the three abutting racks 14 respectively abut the three supporting columns 7, and the pressing screw 12 presses the ball mill barrel 4 to fix it, so that the ball mill barrel 4 is stably fixed between the three supporting columns 7.

[0029] Furthermore, the upper and lower parts of the ball mill barrel 4 are provided with a first opening and a second opening, the first opening is threadedly connected with a first sealing cover 15, the second opening is fixedly connected with an extension tube 16, a screen 17 is installed in the extension tube 16, a second sealing cover 18 is threadedly connected with the extension tube 16, and a chamfer is provided at one end of the hole on the screen 17 facing the ball mill barrel 4. After the ball milling is completed, the second sealing cover 18 can be opened first, and then the output port of the extension tube 16 is directed toward the collection tank, and then the first sealing cover 15 is opened to leak out the first opening, and the output end of the external high-pressure blowing device is aligned with the first opening and then blown, so that the ball-milled raw materials flow out through the second opening with the help of high-pressure gas, and the balls of the ball mill barrel 4 will be intercepted by the screen 17, and the raw materials sticking to the balls can also be blown off by the high-pressure gas, so that the raw materials can be stably discharged from the ball mill barrel 4 and will not remain in the ball mill barrel 4.

[0030] The performance of the silicon nitride ceramic substrate prepared by the method of the present invention and the silicon nitride ceramic substrate prepared by the comparative example were tested, and the results are shown in the following table: In the appeal table, comparative example 1: a silicon nitride ceramic substrate is prepared by a conventional organic solvent casting method, the solvent used is toluene, and the other raw materials and process parameters are the same as the process parameters of the present invention; Comparative Example 2: In the raw material formula of the present invention, yttrium oxide is not added as a sintering aid, and the remaining steps and parameters are the same as the process parameters of the present invention; Comparative Example 3: In the tape casting step, the drying time was shortened to 1.5 hours, and the remaining steps and parameters were the same as the process parameters of the present invention; Example 1 is a preparation method of the present invention. Specifically, in the preparation of raw materials, the addition amount of yttrium oxide is 3% of the mass of silicon nitride powder, and the addition amount of aluminum oxide is 2%, and the preparation is carried out according to the above process parameters. The prepared silicon nitride ceramic substrate is tested for performance, and its thermal conductivity reaches 85W / (m·K), the bending strength reaches 800MPa, and the volume resistivity is greater than 10-14Ω·cm.

[0031] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for illustrating the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which shall fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for preparing a silicon nitride ceramic substrate by tape casting, characterized in that: The steps include: A. adding silicon nitride powder, yttrium oxide, aluminum oxide and sodium polyacrylate into deionized water, and mixing them by ball milling in a ball mill to obtain a mixed slurry; B. adding polyvinyl alcohol and glycerol to the mixed slurry, and continuing ball milling to obtain a stable water-based casting slurry; C. Inject the water-based casting slurry into the material tank of the casting machine, control the thickness of the slurry to 450 μm by a scraper, form a uniform wet film on the casting belt, and dry the wet film to obtain a green film with a certain strength; D. stacking the green film in the required number of layers and making each layer tightly bonded by hot pressing; E. The pressed green body is placed in a debinding furnace for debinding; F. The debinding green body is placed in a sintering furnace for calcination, and then cooled in the furnace to obtain a silicon nitride ceramic substrate.

2. The method for preparing a silicon nitride ceramic substrate by tape casting according to claim 1, characterized in that: In step A, the silicon nitride powder is selected to have an average particle size of 0.5-1 μm and a purity greater than 99.5%. The added amounts of yttrium oxide and aluminum oxide are 3% and 2% of the mass of the silicon nitride powder respectively, and the added amount of sodium polyacrylate is 0.5% of the mass of the silicon nitride powder.

3. The method for preparing a silicon nitride ceramic substrate by tape casting according to claim 1, characterized in that: In step B, the amount of polyvinyl alcohol added is 10% of the mass of the silicon nitride powder, and the amount of glycerol added is 5% of the mass of the silicon nitride powder.

4. The method for preparing a silicon nitride ceramic substrate by tape casting according to claim 1, characterized in that: In steps A and B, the ball mill is used for ball milling at a rotation speed of 30 revolutions per minute for 20 hours, and then after adding polyvinyl alcohol and glycerol, the ball milling is continued for 24 hours to obtain a stable water-based casting slurry.

5. The method for preparing a silicon nitride ceramic substrate by tape casting according to claim 1, characterized in that: In step D, 5 layers of green sheets were stacked and then hot-pressed at a pressure of 20 MPa and a temperature of 60° C. for 1 hour.

6. The method for preparing a silicon nitride ceramic substrate by tape casting according to claim 1, characterized in that: In step E, the pressed green body is subjected to a debinding treatment in a debinding furnace at 500° C. for 3-5 hours.

7. The method for preparing a silicon nitride ceramic substrate by tape casting according to claim 1, characterized in that: In step F, the sintering furnace is filled with nitrogen, and the temperature of the sintering furnace is increased to 1750-1850° C. at a heating rate of 5° C. per minute, kept at this temperature for 2-4 hours, and then cooled with the furnace to obtain a silicon nitride ceramic substrate.

8. The method for preparing a silicon nitride ceramic substrate by tape casting according to claim 1, characterized in that: In step A, the ball mill includes a receiving barrel, a turntable, a plurality of locking fixing frames and a plurality of ball milling barrels. The turntable is rotatably installed in the receiving barrel. A driving assembly for driving the turntable to rotate is provided in the receiving barrel. The plurality of locking fixing frames are rotatably installed on the turntable. The plurality of ball milling barrels are respectively placed in the plurality of locking fixing frames.

9. The method for preparing a silicon nitride ceramic substrate by tape casting according to claim 8, characterized in that: The locking and fixing frame comprises a rotating disk, a locking cover and three supporting columns, the rotating disk comprises an inner rotating disk and an outer fixing ring, the inner rotating disk is rotatably located inside the outer fixing ring, the inner rotating disk is transmission-connected with a driving assembly, the rotating disk is rotatably mounted on the inner rotating disk, a transmission gear coaxially connected to the rotating disk is rotationally mounted below the inner rotating disk at a position corresponding to the rotating disk, an outer gear ring meshing with the transmission gear is mounted below the inner rotating disk, an inner ring of the outer fixing ring is mounted with an inner gear ring meshing with the transmission gear, three supporting columns are equidistantly mounted on the rotating disk around the rotating axis of the transmission gear, and the locking cover is provided with three through holes for the supporting columns to pass through; The locking cover includes a fixed plate, a clamping screw, three driving gears and three abutting racks. The clamping screw is threaded and rotatably installed in the middle part of the fixed plate. The three driving gears are equidistantly rotatably arranged in the fixed plate around the clamping screw, and the three driving gears are all meshed with the clamping screw. The fixed plate is provided with three sliding grooves respectively connected to the three through holes. The three abutting racks are respectively slidably placed in the three sliding grooves, and the three abutting racks are respectively meshed with the three driving gears.

10. The method for preparing a silicon nitride ceramic substrate by tape casting according to claim 8, characterized in that: The upper and lower parts of the ball mill barrel are both provided with a first opening and a second opening, the first opening is threadedly connected to a first sealing cover, the second opening is fixedly connected to an extension tube, a screen is installed in the extension tube, the extension tube is threadedly connected to a second sealing cover, and the holes on the screen are chamfered at one end facing the ball mill barrel.

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