A centering device for the fixed plate of a silicon carbide precision double-sided grinding machine

Abstract

The present invention provides an upper fixed plate centering device for a silicon carbide precision double-sided grinding machine, comprising an upper fixed plate, which is also connected to a centering mechanism. The centering mechanism is a cylindrical structure and is installed on the lower side of an upper hanging plate. A central shaft is provided in the center of the centering mechanism, which is connected to a connecting shaft sleeve. The centering outer ring of the centering mechanism is connected to the upper hanging plate by screws. The centering outer ring and the centering inner ring of the centering mechanism are connected by two circumferentially symmetrically distributed centering outer ring pins. One end of the centering outer ring pin is fixed on the centering outer ring, and the other end of the centering outer ring pin is inserted into the inner hole of the centering inner ring roller bearing and is axially fixed to the inner ring of the centering outer ring bearing through a pin step. There is a gap between the centering outer ring and the centering inner ring; the centering inner ring and the centering inner ring of the centering mechanism are connected by two circumferentially symmetrically distributed centering inner ring pins, and the axes of the two centering inner ring pins are perpendicular to the axis of the centering outer ring pin.

Description

Technical Field

[0001] The invention relates to the field of grinding and polishing machines, and in particular to a fixed plate centering device on a silicon carbide precision double-sided grinding machine. Background Art

[0002] Compared to traditional semiconductors, silicon carbide, as a third-generation semiconductor material, has the characteristics of a large bandgap, high breakdown electric field, high saturated electron drift rate, and high thermal conductivity. These characteristics are very consistent with the needs of high-frequency and high-power electronic devices and cannot be replaced by traditional semiconductors. Therefore, the replacement of traditional semiconductor materials by silicon carbide in power electronic devices is an inevitable trend in future development. As the reliability and durability of electronic devices increase, the surface quality requirements for silicon carbide single crystal substrates are becoming increasingly stringent. The processing technology of silicon carbide wafers is the basis of device manufacturing. The key to its widespread use in electronic components is to produce silicon carbide single crystals into silicon carbide wafers that meet the requirements.

[0003] The Mohs hardness of single-crystal silicon carbide is as high as 9.5, second only to diamond, and the compressive strength of single-crystal silicon carbide is much higher than its bending strength. The material as a whole exhibits great hardness and brittleness. These factors make silicon carbide wafer processing extremely difficult.

[0004] The working principle of a precision double-sided silicon carbide grinding machine is to double-side grind the surface of a silicon carbide wafer using abrasive fluid, using upper and lower grinding discs that rotate around a center. When grinding a silicon carbide wafer, the upper platen, driven by a pneumatic cylinder, descends into contact with the wafer. Pressure is applied to the wafer surface, and the lapping fluid removes the surface. During the pressurization process of the upper platen cylinder, if the upper and lower plates of the equipment do not fit properly with the wafer, the quality of the silicon carbide wafer will be significantly affected, resulting in uneven grinding of the upper and lower surfaces of the wafer, inconsistent material removal, and a low product yield, as well as the generation of broken pieces and debris. Using a rigid connection between the upper and lower plates results in high processing costs, and flatness and parallelism cannot be guaranteed. Therefore, the connection between the upper platen and the cylinder must utilize an automatic centering system to ensure flexible contact between the upper and lower plates, achieving precise control of the fit and parallelism of the two working surfaces.

[0005] In traditional double-sided grinding machines, the upper fixed plate is usually aligned in the form of a spherical plain bearing + rolling bearing, or directly in the form of a spherical roller bearing, but both have certain shortcomings.

[0006] (1) The self-aligning spherical plain bearing + rolling bearing method is adopted. The spherical plain bearing is used for self-alignment and the rolling bearing is used for rotation. When the weight of the upper fixed plate is large, the spherical plain bearing will be deformed due to its limited bearing capacity. The inner and outer spherical surfaces of the spherical plain bearing are no longer in surface contact, but in line contact or point contact. This will cause the self-alignment to be inflexible and shorten the service life of the spherical plain bearing.

[0007] (2) Directly using the form of spherical roller bearings, its load-bearing capacity is greatly improved, but due to its structural reasons, it can only withstand unidirectional force and cannot well meet the use requirements of grinding equipment. Secondly, the simultaneous realization of the two functions of rotation and spherical roller bearings by one bearing will have a certain impact on the running accuracy, stability and bearing life of the grinding equipment.

[0008] (3) Using self-aligning spherical bearings, there is no space opening in the middle of the upper fixed plate, and the sensor for measuring the thickness of the chip is difficult to install.

[0009] (4) The self-aligning spherical plain bearing + rolling bearing method is adopted. Since the structure adopts a series method, the height dimension of the upper fixed plate is relatively large, resulting in the overall height of the grinding equipment being too high, causing difficulties in transportation and installation.

[0010] In order to meet the market demand for silicon carbide precision double-sided grinding machines, this patent designs a fixed plate centering device for silicon carbide precision double-sided grinding machines to meet the market demand for silicon carbide wafer grinding. Summary of the Invention

[0011] In view of the problems existing in the prior art, the present invention provides a fixed plate centering device for a silicon carbide precision double-sided grinding machine to solve at least one of the above technical problems.

[0012] The technical solution of the present invention is: a centering device for an upper fixed plate of a precision double-sided grinding machine of silicon carbide, comprising an upper fixed plate, characterized in that the upper fixed plate is connected to an upper fixed plate lifting cylinder via a connecting shaft sleeve, and the upper fixed plate lifting cylinder is fixed to the bed of the precision double-sided grinding machine via a supporting structure;

[0013] The upper fixed plate is also connected to a centering mechanism, which has a cylindrical structure and is installed on the lower side of the upper hanging plate. A central shaft is provided in the center of the centering mechanism, which is connected to the connecting sleeve. The centering outer ring of the centering mechanism is connected to the upper hanging plate by screws. The centering outer ring and the centering ring of the centering mechanism are connected by two centering outer ring pins symmetrically distributed around the circumference. One end of the centering outer ring pin is fixed on the centering outer ring, and the other end of the centering outer ring pin is inserted into the inner hole of the centering ring roller bearing. The axial direction is fixed to the inner ring of the centering outer ring bearing through the pin step, and there is a gap between the centering outer ring and the centering ring.

[0014] The centering ring and the centering inner ring of the centering mechanism are connected by two centering ring pins symmetrically distributed around the circumference, and the axes of the two centering ring pins are perpendicular to the axis of the centering outer ring pin and are in the same plane. One end of the centering ring pin is fixed to the centering ring, and the other end of the centering ring pin is inserted into the inner hole of the centering inner ring roller bearing and is axially fixed to the inner ring of the centering ring bearing through a pin step. There is a gap between the centering ring and the centering inner ring.

[0015] The spindle located at the center-aligning outer ring and the spindle located at the center-aligning inner ring together form a cross hinge mechanism.

[0016] A gap exists between the outer and middle centering rings, and between the inner and middle centering rings, allowing them to swing in a circular motion along the axis of the pin. The cross-hinged joint mechanism can withstand both axial and radial loads, ensuring the upper platen's centering ability and uniform force distribution. The upper platen can withstand both radial and axial loads and flexibly adjust for unevenness between the upper platen surface and the crystal processing surface, preventing damage to the crystal from impact with the platen surface.

[0017] Further preferably, lubrication holes are provided on the centering outer ring pin and the centering inner ring pin, and the bearings therein are lubricated through the lubrication oil nozzle on the centering mechanism.

[0018] Further preferably, the upper hanging plate is connected to the upper fixed plate mounting plate through four upper fixed plate connecting columns evenly distributed around the circumference, the upper fixed plate is fixed to the upper fixed plate mounting plate by screws, each connecting column is provided with an adjusting round nut, and a counterweight block is installed on each connecting column.

[0019] By coordinating the centering mechanism to level the entire lower fixed plate, a stable contact between the upper fixed plate surface and the wafer processing surface can be achieved, preventing damage to the wafer caused by contact impact.

[0020] Further preferably, a thickness sensor is mounted on the spindle, and the thickness sensor is mounted on the spindle via a thickness sensor mounting block. The thickness sensor is used to detect the thickness of the ground wafer in real time, so as to better detect and control the grinding process.

[0021] Further preferably, a through hole is formed in the middle of the connecting sleeve to facilitate the lead-out of the wires of the thickness sensor installed in the middle.

[0022] Further preferably, the threaded connection of the connecting sleeve is fixed by a set screw to prevent the connecting thread from loosening.

[0023] Further preferably, three upper fixed plate driving connection blocks evenly distributed around the circumference are mounted on the upper fixed plate mounting plate to drive the upper fixed plate to perform circular motion.

[0024] Further preferably, the outer ring pin and the inner ring pin are fixed in the mounting holes of the outer ring and the inner ring, respectively, and the outer ring bearing and the inner ring bearing are also mounted in the mounting holes of the inner ring and the inner ring, respectively, thereby improving the compactness of the overall structure.

[0025] Further preferably, the self-aligning inner ring and the spindle are connected by two tapered roller bearings mounted face to face, the spindle is fixed, and the self-aligning inner ring rotates with the upper fixed plate. When the cylinder moves up and down, the spindle drives the self-aligning inner ring and the upper fixed plate mechanism to move up and down together.

[0026] Further preferably, the spindle and the inner ring are sealed by a skeleton oil seal; the outer ring and the inner ring are sealed by a gland and a V-ring; and the outer ring pin and the outer ring are sealed by an O-ring. To prevent grinding fluid from entering the aligning mechanism and corroding the aligning bearing, the aligning mechanism is sealed.

[0027] More preferably, a liquid baffle is installed on the upper portion of the centering mechanism to block most of the grinding liquid outside the spindle of the centering mechanism to prevent the grinding liquid from entering the centering mechanism and corroding the centering bearing.

[0028] Beneficial effects:

[0029] (1) In order to reduce the overall height of the upper fixed plate, the lifting cylinder and the lower fixed plate mechanism are directly connected by a connecting sleeve. At the same time, the original series cross hinge structure and support bearing structure are changed to a parallel structure, and the entire self-aligning structure is placed under the upper hanging plate, thereby reducing the overall height of the upper fixed plate mechanism.

[0030] (2) The cross hinge structure is formed by the centering inner ring, the centering middle ring, the centering inner ring and the centering spindle, so that the centering mechanism can withstand both axial force and radial force, and can flexibly adjust the contact surface between the disk surface and the crystal surface.

[0031] (3) The centering mechanism is hollow in the middle, which provides space for installing a thickness sensor to facilitate real-time monitoring of the thickness of the polished wafer.

[0032] (4) In order to prevent the grinding fluid from corroding the internal bearings of the self-aligning mechanism, it is necessary to set appropriate sealing devices at each connection position to improve the service life of the self-aligning mechanism.

[0033] (5) The upper fixed plate connecting column is equipped with a counterweight block. According to the center of gravity offset after the upper fixed plate is assembled, the center of gravity is fine-tuned by the counterweight block to improve the stability of the upper fixed plate grinding. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of the upper fixed plate of the precision double-sided grinding machine of the present invention;

[0035] Figure 2 This is a schematic diagram of the centering structure of the precision double-sided grinding machine of the present invention;

[0036] Figure 3 It is a schematic cross-sectional view of the centering structure of the precision double-sided grinding machine of the present invention.

[0037] In the figure: 1. Upper fixed plate lifting cylinder 2. Cylinder mounting plate 3. Connecting sleeve 4. Counterweight 5. Upper hanging plate 6. Upper fixed plate connecting column 7. Upper fixed plate mounting plate 8. Upper fixed plate drive connecting block 9. Upper fixed plate 10. Liquid baffle 11. Aligning outer ring 12. Aligning middle ring 13. Aligning inner ring 14. Round nut 15. Skeleton oil seal 16. V-ring 17. Tapered roller bearing 18. Cover plate 19. Spindle 22. Thickness sensor mounting block 23. Thickness sensor 24. Bearing cover plate 25 Aligning inner ring roller bearing 26. Aligning middle ring pin 27. Lubrication nipple 28. Aligning outer ring pin 29. Aligning middle ring roller bearing 30. O-ring DETAILED DESCRIPTION

[0038] The present invention will be further described below with reference to the accompanying drawings.

[0039] Reference Figure 1-Figure 3 As shown, a centering device for an upper fixed plate of a silicon carbide precision double-sided grinding machine includes an upper fixed plate 9, which is connected to an upper fixed plate lifting cylinder 1 through a connecting shaft sleeve 3, and a cylinder mounting plate 2 is provided at the lower end of the upper fixed plate lifting cylinder, and the upper fixed plate lifting cylinder is fixed to the bed of the precision double-sided grinding machine through a supporting structure; the upper fixed plate is also connected to a centering mechanism, which is a cylindrical structure and is installed on the lower side of the upper hanging plate 5, and a spindle 19 is provided in the center of the centering mechanism, which is connected to the connecting shaft sleeve, and the centering outer ring 11 of the centering mechanism is connected to the upper hanging plate by screws, and the centering outer ring and the centering middle ring 12 of the centering mechanism are connected by two centering outer ring pins 28 symmetrically distributed on the circumference, and one end of the centering outer ring pin is fixed on the centering outer ring, and the centering outer ring The other end of the pin is inserted into the inner hole of the centering inner ring roller bearing 29, and is axially fixed to the inner ring of the centering outer ring bearing through the pin step, and there is a gap between the centering outer ring and the centering inner ring; the centering ring and the centering inner ring 13 of the centering mechanism are connected through two centering ring pins 26 that are circumferentially symmetrically distributed, and the axes of the two centering ring pins are perpendicular to the axis of the centering outer ring pin, and in the same plane, one end of the centering ring pin is fixed on the centering ring, and the other end of the centering ring pin is inserted into the inner hole of the centering inner ring roller bearing 25, and is axially fixed to the inner ring of the centering ring bearing through the pin step, and there is a gap between the centering ring and the centering inner ring; the spindle located at the centering outer ring and the spindle located at the centering inner ring together constitute a cross hinge mechanism.

[0040] A gap exists between the outer and middle centering rings, and between the inner and middle centering rings, allowing them to swing in a circular motion along the axis of the pin. The cross-hinged joint mechanism can withstand both axial and radial loads, ensuring the upper platen's centering ability and uniform force distribution. The upper platen can withstand both radial and axial loads and flexibly adjust for unevenness between the upper platen surface and the crystal processing surface, preventing damage to the crystal from impact with the platen surface.

[0041] Further preferably, lubrication holes are provided on the outer aligning ring pin and the inner aligning ring pin, and the bearings therein are lubricated through the lubrication oil nozzle 27 on the aligning mechanism.

[0042] Further preferably, the upper hanging plate is connected to the upper fixed plate mounting plate via four upper fixed plate connecting posts 6 evenly spaced around the circumference. The upper fixed plate is fixed to the upper fixed plate mounting plate 7 via screws. Each connecting post is equipped with an adjustment nut 14, and each connecting post is mounted with a counterweight 4. By coordinating the centering mechanism to level the entire lower fixed plate structure, stable contact between the upper fixed plate surface and the wafer processing surface can be achieved, preventing damage to the wafer caused by contact impact.

[0043] Further preferably, a thickness sensor 23 is mounted on the spindle, and the thickness sensor is mounted on the spindle via a thickness sensor mounting block 22. The thickness sensor is used to detect the thickness of the ground wafer in real time, so as to better detect and control the grinding process.

[0044] Further preferably, a through hole is provided in the middle of the connecting sleeve to facilitate the lead-out of the wires of the thickness sensor installed in the middle.

[0045] Further preferably, the threaded connection of the connecting sleeve is fixed by a set screw to prevent the connecting thread from loosening.

[0046] Further preferably, three upper fixed disk drive connecting blocks 8 evenly distributed around the circumference are installed on the upper fixed disk mounting plate to drive the upper fixed disk to perform circular motion.

[0047] Further preferably, the outer ring pin and the inner ring pin are fixed in the mounting holes of the outer ring and the inner ring, respectively, and the outer ring bearing and the inner ring bearing are also mounted in the mounting holes of the inner ring and the inner ring, respectively, thereby improving the compactness of the overall structure.

[0048] More preferably, the self-aligning inner ring and the spindle are connected by two tapered roller bearings 17 mounted face to face. The spindle is fixed, while the self-aligning inner ring rotates along with the upper fixed plate. When the cylinder moves up and down, the spindle drives the self-aligning inner ring and the upper fixed plate mechanism to move up and down together.

[0049] More preferably, the spindle and the self-aligning inner ring are sealed by a skeleton oil seal 15; the self-aligning outer ring and the self-aligning inner ring are sealed by a gland and a V-ring 16; and the self-aligning outer ring pin and the self-aligning outer ring are sealed by an O-ring 30. In order to prevent grinding fluid from entering the self-aligning mechanism and corroding the self-aligning bearing, the self-aligning mechanism is sealed.

[0050] More preferably, a liquid baffle 10 is installed on the upper part of the centering mechanism to block most of the grinding liquid outside the spindle of the centering mechanism to prevent the grinding liquid from entering the centering mechanism and corroding the centering bearing.

[0051] Further preferably, a bearing cover plate 24 is provided at the lower end of the centering mechanism, the bearing cover plate covers the bottom of the centering inner ring and is arranged around the spindle, and a cover plate 18 is provided around the outer side of the bearing cover plate, thereby further improving the overall sealing effect.

[0052] The above are only preferred embodiments of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A centering device for an upper platen of a silicon carbide precision double-sided grinding machine, comprising an upper platen, characterized in that: The upper fixed plate is connected to an upper fixed plate lifting cylinder via a connecting shaft sleeve, and the upper fixed plate lifting cylinder is fixed to the bed of the precision double-sided grinding machine via a supporting structure; The upper fixed plate is also connected to a centering mechanism, which has a cylindrical structure and is installed on the lower side of the upper hanging plate. A central shaft is provided in the center of the centering mechanism, which is connected to the connecting sleeve. The centering outer ring of the centering mechanism is connected to the upper hanging plate by screws. The centering outer ring and the centering ring of the centering mechanism are connected by two centering outer ring pins symmetrically distributed around the circumference. One end of the centering outer ring pin is fixed on the centering outer ring, and the other end of the centering outer ring pin is inserted into the inner hole of the centering ring roller bearing. The axial direction is fixed to the inner ring of the centering outer ring bearing through the pin step, and there is a gap between the centering outer ring and the centering ring. The centering ring and the centering inner ring of the centering mechanism are connected by two centering ring pins symmetrically distributed around the circumference, and the axes of the two centering ring pins are perpendicular to the axis of the centering outer ring pin and are in the same plane. One end of the centering ring pin is fixed to the centering ring, and the other end of the centering ring pin is inserted into the inner hole of the centering inner ring roller bearing and is axially fixed to the inner ring of the centering ring bearing through a pin step. There is a gap between the centering ring and the centering inner ring. The spindle located at the center-aligning outer ring and the spindle located at the center-aligning inner ring together form a cross hinge mechanism.

2. The centering device for a fixed plate of a silicon carbide precision double-sided grinding machine according to claim 1, characterized in that: Lubrication holes are provided on the outer aligning ring pin and the inner aligning ring pin, and the bearings therein are lubricated through the lubricating oil nozzle on the aligning mechanism.

3. The centering device for a fixed plate of a silicon carbide precision double-sided grinding machine according to claim 1, characterized in that: The upper hanging plate is connected to the upper fixed plate mounting plate through four upper fixed plate connecting columns evenly distributed around the circumference. The upper fixed plate is fixed to the upper fixed plate mounting plate by screws. Each connecting column is provided with an adjusting round nut, and a counterweight is installed on each connecting column.

4. The centering device for a fixed plate of a silicon carbide precision double-sided grinding machine according to claim 1, characterized in that: A thickness sensor is installed on the spindle, and the thickness sensor is installed on the spindle through a thickness sensor installation block.

5. The centering device for a fixed plate of a silicon carbide precision double-sided grinding machine according to claim 4, characterized in that: A through hole is provided in the middle of the connecting sleeve, and the through hole facilitates the lead-out of the wires of the thickness measuring sensor.

6. The centering device for a fixed plate of a silicon carbide precision double-sided grinding machine according to claim 3, characterized in that: The upper fixed disc mounting plate is provided with three upper fixed disc drive connecting blocks which are evenly distributed around the circumference.

7. The upper plate centering device of a silicon carbide precision double-sided grinding machine according to claim 1, characterized in that: The outer ring pin and the centering ring pin are respectively fixed in the mounting hole of the outer ring and the mounting hole of the centering ring, and the outer ring bearing and the centering ring bearing are also respectively installed in the mounting hole of the centering ring and the mounting hole of the inner ring.

8. The centering device for a fixed plate of a silicon carbide precision double-sided grinding machine according to claim 1, characterized in that: The self-aligning inner ring and the spindle are connected through two tapered roller bearings installed face to face. The spindle is fixed, while the self-aligning inner ring rotates along with the upper fixed plate.

9. The upper plate centering device of a silicon carbide precision double-sided grinding machine according to claim 1, characterized in that: The core shaft and the center-aligning inner ring are sealed by a skeleton oil seal; the center-aligning outer ring and the center-aligning inner ring are sealed by a pressure cover and a V-shaped sealing ring; the center-aligning outer ring pin shaft and the center-aligning outer ring are sealed by an O-ring.

10. The upper plate centering device of a silicon carbide precision double-sided grinding machine according to claim 1, characterized in that: A liquid baffle is installed on the upper part of the centering mechanism.

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