Smooth gluing device of gluing developing machine

Abstract

The invention provides a flat gluing device of a gluing developing machine, and relates to the technical field of wafer processing, the flat gluing device comprises a photoetching glue coating table, a glue coating motor is installed below the photoetching glue coating table, a photoresist dripping device is installed on the side edge of the upper portion of the photoetching glue coating table, after a wafer is placed through a mechanical arm or manual work, the position of the wafer can be accurately adjusted, and the position of the wafer can be accurately adjusted. The circle center of the wafer is kept concentric with the axis of the spin-coating table, the situation that the wafer deviates from the spin-coating table due to centrifugal force caused by eccentricity in the high-speed rotation spin-coating process of the wafer is avoided, efficient spin-coating and high-quality spin-coating of photoresist are guaranteed, and the problem that in existing wafer spin-coating work, the spin-coating efficiency is high is solved. The problems that wafers in part of the gluing devices are placed through a mechanical arm or manually, and if the placement position deviates, the wafers and a photoresist uniformizing table are eccentric, centrifugal force is generated due to the eccentricity of the wafers in the high-speed rotation photoresist uniformizing process of the wafers, the wafers deviate from the photoresist uniformizing table, and the photoresist uniformizing uniformity is affected are solved.

Description

Technical Field

[0001] The invention relates to the technical field of wafer processing, and in particular to a device for smoothing glue coating in a glue coating and developing machine. Background Art

[0002] The smooth coating of the coating and developing machine has an important impact on subsequent processes such as exposure, development, etching, etc. The uniformity of the coating and the thickness control are directly related to the quality and accuracy of the photolithography pattern, which in turn affects the performance and reliability of the final product. Therefore, achieving smooth coating of the coating and developing machine is a key step to ensure product quality. Glue spreading is one of the basic steps in the photolithography process. Liquid photoresist is applied by spin coating. Spin coating includes four steps: glue dripping, low-speed spreading, high-speed spinning, and volume volatilization.

[0003] In the existing wafer coating work, the wafers in some coating devices are placed by robots or manually. If there is a deviation in the placement position, resulting in eccentricity between the wafer and the coating table, centrifugal force will be generated during the high-speed rotation of the wafer for coating, causing the wafer to deviate from the coating table and affecting the uniformity of the photoresist coating. Summary of the invention

[0004] The disclosed embodiments relate to a device for smoothing glue coating in a glue coating and developing machine, so as to solve the problem in existing wafer coating work that in some coating devices, the wafers are placed by robots or manually, and if there is a deviation in the placement position, resulting in eccentricity between the wafer and the glue spreading table, centrifugal force will be generated during the high-speed rotation of the wafer for glue spreading, causing the wafer to deviate from the glue spreading table, and also affecting the uniformity of the photoresist coating.

[0005] The first aspect of the present disclosure provides a device for smoothing glue coating in a glue coating and developing machine, specifically comprising: a photolithography glue coating table, a glue coating motor is installed below the photolithography glue coating table, a photoresist glue dropper is installed on the upper side of the photolithography glue coating table, a rotating glue coating table is movably connected to the center of the top of the photolithography glue coating table, the center of the lower surface of the rotating glue coating table is fixedly connected to the upper end of the rotating shaft of the glue coating motor, a wafer outer carrier is fixedly connected inside the rotating glue coating table, a wafer center carrier is fixedly connected to the center of the wafer outer carrier, a wafer lifting push rod is slidably connected inside the wafer center carrier, and the wafer lifting push rod A push rod cylinder (10) is installed below the rod, and the push rod cylinder (10) is fixedly connected to the lower surface of the wafer center carrier. A floating frame cylinder (11) is fixedly connected to the bottom of the rotating glue-splitting platform. The push rod of the floating frame cylinder (11) is connected to the centering floating frame. The centering floating frame is located above the wafer outer carrier. Two wafer centering frames are movably connected inside the centering floating frame. A lifting float rod is slidably connected to the center of the centering floating frame. The bottom of the lifting float rod is movably connected to the inner end of the wafer centering frame through a centering connecting rod. A centering clamp is fixedly connected above the outer end of the wafer centering frame.

[0006] In at least some embodiments, a clamping rod storage groove is formed on the upper surface of the outer wafer carrier table, the centering floating frame is located in the clamping rod storage groove, and clamping plate storage openings are formed at both ends of the clamping rod storage groove on the upper surface of the outer wafer carrier table, and the centering clamping plates are located in the clamping plate storage openings.

[0007] In at least some embodiments, a central storage groove is formed at the center of the central wafer carrier table, and the centering floating frame is movably arranged inside the central storage groove.

[0008] In at least some embodiments, the centering floating frame is a pipe structure with a rectangular cross-section, and a lower guide opening is formed through the center of the lower surface of the centering floating frame.

[0009] In at least some embodiments, two floating connecting rods are vertically connected to the lower surface of the centering floating frame by welding, and the lower ends of the floating connecting rods are fixedly connected to the upper ends of the push rods of the floating frame push cylinder (11).

[0010] In at least some embodiments, centering clamping plates are fixedly connected to the outer ends of the upper surface of the wafer centering frame. The centering clamping plates are in an "L" shape, and the openings of the centering clamping plates face the center of the central wafer carrier table.

[0011] In at least some embodiments, a hinge connecting block is connected to the inner end of the lower surface of the wafer centering frame by welding, and the hinge connecting block is hinged to the centering connecting rod.

[0012] In at least some embodiments, a vertical push plate is fixedly connected to the lower end of the lifting floating rod, and the vertical push plate is hinged to the other end of the centering connecting rod.

[0013] In at least some embodiments, a central floating plate is fixedly connected to the upper end of the lifting floating rod. A floating plate top spring is sleeved on the lifting floating rod. The upper end of the floating plate top spring is fixedly connected to the central floating plate, and the lower end of the floating plate top spring is fixedly connected to the upper surface of the centering floating frame.

[0014] The present invention provides a device for flat coating in a coating and developing machine, which has the following beneficial effects: In the coating and developing machine of the present invention, the coating device for the wafer is improved. After the wafer is placed by a manipulator or manually, the position of the wafer can be accurately adjusted to horizontally adjust the position of the wafer, so as to keep the center of the wafer concentric with the axis of the spin coater table, and avoid the situation that the wafer deviates from the spin coater table due to the centrifugal force caused by eccentricity during the high-speed rotation and spin coating of the wafer, thus ensuring the efficient and high-quality spin coating of the photoresist.

[0015] In addition, in the wafer centering function of the present invention, the descending action of the wafer cooperates with the gravity of the wafer itself to trigger the wafer centering function. The gravity of the wafer applies pressure to the center floating plate downward, causing the lifting floating rod to descend, and through a series of precise transmission structures, the wafer centering frames on both sides are pushed towards the center of the wafer outer stage. The position of the circular wafer is adjusted by the contact between the centering clamping plate and the edge of the wafer, so that the center of the wafer is coaxial with the wafer outer stage. The clamping force is light and will not cause wear and damage to the wafer edge.

[0016] In addition, in the present invention, when the wafer completes high-precision centering, during the process of controlling the centering floating frame and the wafer centering frame to descend by the floating frame push cylinder (11), due to the downward movement of the centering floating frame, the two wafer centering frames automatically move outwards, releasing the clamping of the wafer edge, and settling into the clamping rod placement groove and the center placement groove, avoiding affecting the spin coating and avoiding friction during the process of the wafer descending to the wafer center stage along with the wafer lifting ejector rod. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments will be briefly introduced below.

[0018] The drawings in the following description only relate to some embodiments of the present invention and do not limit the present invention.

[0019] In the drawings: Figure 1 A schematic diagram showing the overall structure of the present application is shown; Figure 2 A schematic diagram showing the internal structure of the spin coating table of the present application is shown; Figure 3 A schematic diagram showing the state where the two centering clamping plates contract and push the wafer for centering of the present application is shown; Figure 4 A schematic diagram showing the hidden state of the centering floating frame and the wafer centering frame of the present application is shown; Figure 5 Shows the present application Figure 4 front view structure schematic diagram; Figure 6 A schematic diagram showing the structure of the spin coating table of the present application is shown; Figure 7 Shows the present application Figure 6 top view structure schematic diagram; Figure 8 A schematic diagram showing the structure of the lifting floating rod of the present application is shown; Figure 9 Shows the Figure 2 partial enlarged structure schematic diagram at position A in the present application; Figure 10 Shows theFigure 3 Schematic diagram of the locally enlarged structure at position B in the middle.

[0020] List of reference numerals 1. Photolithography coating and leveling stage; 2. Leveling motor; 3. Photoresist dropper; 4. Rotary leveling stage; 5. Wafer outer carrier stage; 501. Clamping rod storage groove; 502. Clamping plate storage opening; 6. Wafer center carrier stage; 601. Center storage groove; 7. Wafer lifting ejector rod; 8. Centering floating frame; 801. Lower guide port; 802. Floating connecting rod; 9. Wafer centering frame; 901. Centering clamping plate; 902. Hinge connecting block; 903. Lifting floating rod; 904. Vertical push plate; 905. Centering connecting rod; 906. Center floating plate; 907. Floating plate top spring; 10. Ejector rod push cylinder; 11. Floating frame push cylinder. Detailed implementation manners

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the described embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0022] Embodiment 1: Please refer to Figures 1 to 10 : The present invention provides a device for evenly coating glue on a spin coater and developer, comprising: a photolithography glue coating table 1, a glue spreading motor 2 is installed below the photolithography glue coating table 1, a photoresist dropper 3 is installed on the upper side of the photolithography glue coating table 1, a rotating glue spreading table 4 is movably connected to the center of the upper part of the photolithography glue coating table 1, the upper end of the rotating shaft of the glue spreading motor 2 is fixedly connected to the center of the lower surface of the rotating glue spreading table 4, a wafer outer carrier 5 is fixedly connected inside the rotating glue spreading table 4, a wafer center carrier 6 is fixedly connected to the center of the wafer outer carrier 5, a wafer lifting ejector rod 7 is slidably connected inside the wafer center carrier 6, a push cylinder 10 for the ejector rod is installed below the wafer lifting ejector rod 7, the push cylinder 10 for the ejector rod is fixedly connected to the lower surface of the wafer center carrier 6, a floating frame push cylinder 11 is fixedly connected to the bottom inside the rotating glue spreading table 4, the push rod of the floating frame push cylinder 11 is connected to a centering floating frame 8, the centering floating frame 8 is located above the wafer outer carrier 5, two wafer centering frames 9 are movably connected inside the centering floating frame 8, a lifting floating rod 903 is slidably connected to the center of the centering floating frame 8, the bottom of the lifting floating rod 903 is movably connected to the inner end of the wafer centering frame 9 through a centering connecting rod 905, and centering clamping plates 901 are fixedly connected above the outer ends of the wafer centering frames 9; when placing the wafer, the push cylinder 10 for the ejector rod contracts, so that the upper end of the wafer lifting ejector rod 7 protrudes from the upper surface of the wafer center carrier 6, and the wafer to be coated with photoresist is placed through the wafer lifting ejector rod 7. After the wafer is placed, the push cylinder 10 for the ejector rod is controlled to drive the wafer lifting ejector rod 7 to slowly drop, so that the lower surface of the wafer fits with the upper surface of the center floating plate 906. As the wafer lifting ejector rod 7 slowly drops, under the action of the self-gravity of the wafer, the center floating plate 906 is pushed downward, so that the floating plate top spring 907 is compressed, the lifting floating rod 903 moves downward, and the hinge connecting block 902 is pulled in the direction close to the center of the wafer center carrier 6 through the centering connecting rod 905, so that the wafer centering frame 9 and the centering clamping plate 901 move closer to the center direction. The two inner surfaces of the centering clamping plate 901 are attached to the edge of the circular wafer and push the wafer in the direction of the center of the wafer center carrier 6, so that the circular wafer is aligned in the direction of the center of the wafer center carrier 6, and the deviation between the center of the wafer and the center of the wafer center carrier 6 is reduced, and the concentricity of the wafer and the wafer center carrier 6 is improved. In this process, the movement of the wafer centering frame 9 is triggered by the self-gravity of the wafer as the power, and the thrust is slight, which can effectively avoid the wear caused by the excessive thrust of the centering clamping plate 901 on the wafer, and avoid the situation that the wafer deviates from the glue coating table due to the centrifugal force caused by eccentricity during the high-speed rotation and glue spreading of the wafer, providing a guarantee for the high-quality glue spreading of the photoresist.

[0023] In the embodiments of the present disclosure, a clamping rod storage groove 501 is formed on the upper surface of the wafer external carrier 5. The centering floating frame 8 is located in the clamping rod storage groove 501. Clamping plate storage openings 502 are formed at both ends of the clamping rod storage groove 501 on the upper surface of the wafer external carrier 5. The centering clamping plates 901 are located in the clamping plate storage openings 502. The settled centering floating frame 8 is hidden through the clamping rod storage groove 501, and the settled centering clamping plates 901 are hidden through the clamping plate storage openings 502, so as to avoid affecting the rotation and spin coating of the wafer.

[0024] In the embodiments of the present disclosure, a central storage groove 601 is formed at the center of the wafer central carrier 6. The centering floating frame 8 is movably arranged inside the central storage groove 601. The centering floating frame 8 in the settled state is hidden through the central storage groove 601, so that the centering floating frame 8 and the wafer centering frame 9 can be further deeply hidden inside the wafer external carrier 5 and the wafer central carrier 6. The wafer is carried by the upper surface of the wafer central carrier 6 being attached to the lower surface of the wafer.

[0025] In the embodiments of the present disclosure, the centering floating frame 8 is a pipe structure with a rectangular cross-section. A lower guide opening 801 is formed through the center of the lower surface of the centering floating frame 8. The hinge connecting block 902 is slidably connected inside the lower guide opening 801. The sliding connection between the centering floating frame 8 and the wafer centering frame 9 plays a guiding role to avoid rotation and deviation during the telescopic process of the wafer centering frame 9.

[0026] In the embodiments of the present disclosure, two floating connecting rods 802 are vertically connected to the lower surface of the centering floating frame 8 by welding. The lower ends of the floating connecting rods 802 are fixedly connected to the upper ends of the push rods of the floating frame push cylinder 11. The height of the centering floating frame 8 is controlled by the telescopic movement of the floating frame push cylinder 11, and the ascending and descending movements of the centering floating frame 8 are controlled.

[0027] In the embodiments of the present disclosure, centering clamping plates 901 are fixedly connected to the outer ends of the upper surface of the wafer centering frame 9. The centering clamping plates 901 are in an "L" shape structure, and the openings of the centering clamping plates 901 face the center direction of the wafer central carrier 6. When the two wafer centering frames 9 move synchronously towards the center direction of the wafer central carrier 6, the two centering clamping plates 901 follow and move towards the center direction of the wafer central carrier 6. During this process, the inner surfaces of the centering clamping plates 901 are attached to the edges of the wafer. The four planes of the two centering clamping plates 901 respectively push the wafer from four directions, so that the wafer moves to the center of the wafer central carrier 6, and the center of the wafer is located on the axis of the wafer central carrier 6, avoiding the situation that the wafer deviates from the spin coating table due to the centrifugal force caused by eccentricity during the high-speed rotation and spin coating of the wafer.

[0028] Embodiment 2, on the basis of Embodiment 1, a hinge connecting block 902 is connected to the inner end of the lower surface of the wafer centering frame 9 by welding, and the hinge connecting block 902 is hinged to the centering connecting rod 905; a vertical push plate 904 is fixedly connected to the lower end of the lifting floating rod 903, and the vertical push plate 904 is hinged to the other end of the centering connecting rod 905; a central floating plate 906 is fixedly connected to the upper end of the lifting floating rod 903, a floating plate top spring 907 is sleeved on the lifting floating rod 903, the upper end of the floating plate top spring 907 is fixedly connected to the central floating plate 906, and the lower end of the floating plate top spring 907 is fixedly connected to the upper surface of the centering floating frame 8; when placing the wafer above the wafer lifting ejector rod 7, the wafer lifting ejector rod 7 is controlled to descend by the ejector rod push cylinder 10, so that the wafer moves downward following the wafer lifting ejector rod 7. At this time, the centering floating frame 8 and the wafer centering frame 9 are located outside the wafer central stage 6, and the floating frame push cylinder 11 remains fixed. The lower surface of the wafer is attached to the upper surface of the central floating plate 906. As the wafer lifting ejector rod 7 continues to descend, as the wafer lifting ejector rod 7 slowly drops, under the action of the self-gravity of the wafer, the central floating plate 906 is pushed downward, so that the floating plate top spring 907 is compressed, the lifting floating rod 903 moves downward, and the hinge connecting block 902 is pulled toward the center of the wafer central stage 6 through the centering connecting rod 905, so that the wafer centering frame 9 and the centering clamping plate 901 move closer to the center. The two inner surfaces of the centering clamping plate 901 are attached to the edge of the circular wafer and push the wafer toward the center of the wafer central stage 6, so that the circular wafer is aligned toward the center of the wafer central stage 6, and the deviation between the center of the wafer and the center of the wafer central stage 6 is reduced, improving the concentricity between the wafer and the wafer central stage 6; when the position of the wafer is adjusted, the floating frame push cylinder 11 is controlled to contract, pulling the centering floating frame 8 downward, so that the centering floating frame 8 and the wafer centering frame 9 move downward synchronously. When the wafer is attached to the upper surface of the wafer central stage 6, as the centering floating frame 8 descends, the compressed floating plate top spring 907 is reset, pushing the central floating plate 906 upward, so that the lifting floating rod 903 rises. Through the action of the centering connecting rod 905, the two hinge connecting blocks 902 are pushed outward, so that the two centering clamping plates 901 move outward and disengage from the wafer, realizing the function of automatic release and avoiding affecting the rotation and spin coating of the wafer.

[0029] The working principle of this embodiment is as follows: first, the wafer is placed above the wafer lifting push rod 7 by a robot or manually, and the wafer lifting push rod 7 is controlled to descend by the push rod pushing cylinder 10, so that the wafer moves downward with the wafer lifting push rod 7. At this time, the centering floating frame 8 and the wafer centering frame 9 are located outside the wafer center carrier 6, and the floating frame pushing cylinder 11 remains fixed, and the lower surface of the wafer is in contact with the upper surface of the center floating plate 906. As the wafer lifting push rod 7 continues to descend, as the wafer lifting push rod 7 slowly falls, the center floating plate 906 is pushed downward under the action of the wafer's own gravity, so that the floating plate top spring 907 is compressed, the lifting float rod 903 moves downward, and the hinged connecting block 902 is pulled toward the center of the wafer center carrier 6 through the centering connecting rod 905, so that the wafer centering frame 9 and the centering clamping plate 901 are close to the center direction, and the two inner surfaces of the centering clamping plate 901 are in contact with the edge of the circular wafer and push the wafer toward the center direction of the wafer center carrier 6, so that the circular structure of the wafer The center of the wafer is aligned with the center direction of the wafer center carrier 6, and the deviation between the center of the wafer and the center of the wafer center carrier 6 is reduced, thereby improving the concentricity of the wafer and the wafer center carrier 6; and when the wafer position adjustment is completed, the floating frame push cylinder 11 is controlled to contract, and the centering floating frame 8 is pulled downward, so that the centering floating frame 8 and the wafer centering frame 9 move downward synchronously. When the wafer fits the upper surface of the wafer center carrier 6, as the centering floating frame 8 descends, the compressed floating plate top spring 907 is reset, and the wafer is The central floating plate 906 is pushed upward to raise the lifting floating rod 903. Through the action of the centering connecting rod 905, the hinged connecting blocks 902 on both sides are pushed outward to make the centering clamps 901 on both sides move outward and detach from the wafer, realizing the function of automatic release to avoid affecting the rotation and coating of the wafer. A certain amount of photoresist is dripped on the center of the wafer through the photoresist dropper 3, and the coating motor 2 is started. The rotating coating table 4 is driven by the coating motor 2 to rotate so that the photoresist is evenly spread on the surface of the wafer.

[0030] In this article, there are a few points to note: 1. The drawings of the embodiments of the present disclosure only involve structures related to the embodiments of the present disclosure, and other structures may refer to general designs.

[0031] 2. In the absence of conflict, the embodiments of the present disclosure and the features therein may be combined with each other to obtain new embodiments.

[0032] The above are only specific embodiments of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present disclosure, which should be included in the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be based on the protection scope of the claims.

Claims

1. An apparatus for planar coating of a spin coater and developer, comprising: Photolithography glue spreading table (1), a glue spreading motor (2) is installed below the photolithography glue spreading table (1), and a photoresist dropper (3) is installed on the upper side of the photolithography glue spreading table (1). It is characterized in that a rotating glue spreading table (4) is movably connected to the center above the photolithography glue spreading table (1). The center of the lower surface of the rotating glue spreading table (4) is fixedly connected to the upper end of the rotating shaft of the glue spreading motor (2). A wafer outer carrier (5) is fixedly connected inside the rotating glue spreading table (4), and a wafer center carrier (6) is fixedly connected to the center of the wafer outer carrier (5). A wafer lifting ejector rod (7) is slidably connected inside the wafer center carrier (6). A push cylinder (10) for the ejector rod is installed below the wafer lifting ejector rod (7), and the push cylinder (10) for the ejector rod is fixedly connected to the lower surface of the wafer center carrier (6). A floating frame push cylinder (11) is fixedly connected to the bottom inside the rotating glue spreading table (4). The push rod of the floating frame push cylinder (11) is connected to an alignment floating frame (8). The alignment floating frame (8) is located above the wafer outer carrier (5). Two wafer alignment frames (9) are movably connected inside the alignment floating frame (8). A lifting floating rod (903) is slidably connected to the center of the alignment floating frame (8). The bottom of the lifting floating rod (903) is movably connected to the inner end of the wafer alignment frame (9) through an alignment connecting rod (905). An alignment clamping plate (901) is fixedly connected above the outer end of the wafer alignment frame (9).

2. The device for flat glue spreading of a glue coating and developing machine according to claim 1, characterized in that A clamping rod storage groove (501) is formed on the upper surface of the wafer outer carrier (5). The alignment floating frame (8) is located inside the clamping rod storage groove (501). Clamping plate storage openings (502) are formed at both ends of the clamping rod storage groove (501) on the upper surface of the wafer outer carrier (5). The alignment clamping plate (901) is located inside the clamping plate storage openings (502).

3. The device for flat glue spreading of a glue coating and developing machine according to claim 1, characterized in that A central storage groove (601) is formed at the center of the wafer center carrier (6). The alignment floating frame (8) is movably arranged inside the central storage groove (601).

4. The device for flat glue spreading of a glue coating and developing machine according to claim 1, characterized in that The alignment floating frame (8) is a pipe structure with a rectangular cross-section. A lower guide opening (801) is formed through the center of the lower surface of the alignment floating frame (8).

5. The device for flat glue spreading of a glue coating and developing machine according to claim 1, characterized in that Two floating connecting rods (802) are vertically connected to the lower surface of the alignment floating frame (8) by welding. The lower ends of the floating connecting rods (802) are fixedly connected to the upper end of the push rod of the floating frame push cylinder (11).

6. The device for flat glue spreading of a glue coating and developing machine according to claim 1, characterized in that An alignment clamping plate (901) is fixedly connected to the outer end of the upper surface of the wafer alignment frame (9). The alignment clamping plate (901) is in an "L" shape structure, and the opening of the alignment clamping plate (901) faces the center direction of the wafer center carrier (6).

7. The device for flat coating of a coating and developing machine according to claim 1, characterized in that the inner end of the lower surface of the wafer centering frame (9) is connected by welding with a hinge connecting block (902), and the hinge connecting block (902) is hinged with the centering connecting rod (905).

8. The device for flat coating of a coating and developing machine according to claim 7, characterized in that a vertical push plate (904) is fixedly connected to the lower end of the lifting floating rod (903), and the vertical push plate (904) is hinged with the other end of the centering connecting rod (905).

9. The device for flat coating of a coating and developing machine according to claim 8, characterized in that a central floating plate (906) is fixedly connected to the upper end of the lifting floating rod (903), a floating plate top spring (907) is sleeved on the lifting floating rod (903), the upper end of the floating plate top spring (907) is fixedly connected to the central floating plate (906), and the lower end of the floating plate top spring (907) is fixedly connected to the upper surface of the centering floating frame (8).

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