Vacuum thermocompression bonding device and method thereof

Abstract

The invention relates to the field of precision manufacturing equipment and automatic control, in particular to a vacuum thermocompression bonding device and method. The device comprises a base part, a pressing heating part, a servo driving part, a transmission force measuring part, a floating leveling part and an industrial personal computer, the system combines servo driving and force measurement feedback to accurately control the pressing process; the core is that a floating leveling part utilizes a universal ball head and a high-temperature-resistant disc spring to adaptively incline to absorb impact energy at the moment of contacting with a glass substrate, and meanwhile, a transmission push rod penetrates through a vacuum cavity in a corrugated pipe dynamic sealing manner; traditional rigid contact is abandoned, base material breakage caused by local stress concentration is effectively avoided, tiny particles generated by friction are eliminated through dynamic sealing, high cleanliness of a vacuum environment is guaranteed, and then the quality of a bonding interface is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of precision manufacturing equipment and automation control, specifically to a vacuum hot pressing bonding device and method. Background Technology

[0002] In the current semiconductor device packaging and MEMS manufacturing environment, vacuum thermocompression bonding of glass substrates is a necessary process for achieving chip hermeticity protection and wafer-level packaging. In this process, the substrate needs to be softened by heating in a vacuum clean chamber and subjected to continuous and uniform downward pressure to achieve high-quality bonding. To perform vacuum thermocompression bonding of glass substrates, existing equipment usually relies on cables, pulleys and mechanical counterweights to provide continuous downward pressure. Although this solution has a certain pressing capability under conventional constant force application scenarios, such structures will generate particles due to friction during long-term operation, which will seriously damage the cleanliness of the vacuum chamber. Moreover, the flexible force transmission relationship changes with the elongation of the cable, resulting in the lack of positioning accuracy and force feedback that meet the preset tolerance requirements of the force transmission path, making it difficult to stably adapt to the thickness changes of the glass substrate during the heating process. At the same time, when the glass substrate has thickness tolerance or wedge error, the rigid indenter will be unbalanced in the initial contact with the substrate, causing local stress concentration, which significantly increases the risk of breakage when pressing brittle materials.

[0003] Therefore, how to eliminate particulate contamination generated by mechanical transmission and apply a measurable, adjustable, and passively tolerant continuous pressing force to a glass substrate in a vacuum environment has become an urgent technical problem to be solved. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention provides a vacuum hot-press bonding apparatus and method. Specifically, the technical solution of the present invention is as follows: On one hand, the present invention provides a vacuum hot-press bonding apparatus, comprising: A base component, including a base and a vacuum chamber fixed to its top; The pressing and heating section is located in the cavity and includes a lower heating platform fixed to the bottom surface of the cavity and an upper pressing head located above it. The top surface of the lower heating platform is for placing the glass substrate, and the bottom surface of the upper pressing head is parallel to and opposite to the top surface of the lower heating platform. A servo drive unit is located on the top outer side of the cavity, including a motor bracket and an AC servo motor fixed thereon; The transmission force measuring unit connects the motor and the upper pressure head, including a transmission push rod and a strain gauge force gauge. The motor drives the push rod, which passes through the cavity and its bottom end is connected to the force receiving end of the force gauge. The floating leveling part is matched between the output end of the force gauge and the upper pressure head, and includes an upper connecting seat, a lower connecting plate, a universal ball joint and a high-temperature resistant disc spring. The universal ball joint is clamped between the upper connecting seat and the lower connecting plate, and the two ends of the high-temperature resistant disc spring respectively abut against the bottom surface of the connecting seat and the top surface of the connecting plate. The industrial computer connects and controls the pressing and heating unit, servo drive unit, transmission force measuring unit, and floating leveling unit.

[0005] Furthermore, the transmission force measuring unit also includes a ball screw, the output shaft of the AC servo motor is connected to the screw shaft of the ball screw, and the nut flange of the ball screw is threadedly connected to the transmission push rod. When the AC servo motor is working, it drives the transmission push rod to move in the vertical direction.

[0006] Furthermore, the output shaft of the AC servo motor is directly connected to the lead screw shaft of the ball screw via a plum blossom-shaped flexible coupling.

[0007] Furthermore, a bellows dynamic sealing ring is provided at the top of the vacuum chamber, and the transmission push rod extends vertically downward through the bellows dynamic sealing ring into the interior of the vacuum chamber.

[0008] Furthermore, a hemispherical groove is machined at the center of the bottom surface of the upper connecting seat, and a lower hemispherical groove is machined at the center of the top surface of the lower connecting plate. The universal ball joint is matched and disposed between the hemispherical groove and the lower hemispherical groove to form a spherical rotating pair.

[0009] Furthermore, the floating leveling part also includes four guide posts evenly distributed around the periphery of the universal ball head. The top end of the guide post is fixed to the upper connecting seat, and the bottom end of the guide post passes through the gap hole of the lower connecting plate. Each guide post is fitted with a high-temperature resistant disc spring.

[0010] Furthermore, the servo drive unit also includes an incremental photoelectric encoder, which is connected to the AC servo motor to obtain rotor position information and transmit it to the industrial control computer.

[0011] On the other hand, the present invention provides a vacuum hot-press bonding control method, comprising: S1. Control the servo drive unit to work, and drive the upper pressing head to move downward and approach the glass substrate placed on the lower heating platform through the transmission push rod; S2. Control the industrial control computer to continuously read the force value data of the strain gauge force gauge and calculate the force value change rate. When the force value change rate is less than or equal to the preset contact threshold, control the AC servo motor to maintain the current speed and decrease; when the force value change rate exceeds the preset contact threshold, control the AC servo motor to reduce the speed to micro-stepping mode. S3. The floating leveling part absorbs the impact energy and tilts until the force value output by the strain gauge reaches the preset leveling confirmation threshold, and then the AC servo motor is controlled to stop rotating to complete the passive leveling. S4. Control the lower heating platform to heat up, read the current contact force in real time, and calculate the force deviation by subtracting the target bonding force from the current contact force. S5. Multiply the force deviation by the virtual compliance coefficient that represents the displacement compensation amount corresponding to the unit force deviation to calculate the downward displacement amount, and control the AC servo motor to perform micro-motion compensation to complete the constant force application. S6. Control the lower heating platform to stop heating, divide the time axis of the cooling process into multiple intervals, and calculate the descent gradient of the force value in each interval; S7. Multiply the descent gradient by the pre-calibrated thermal stress release coefficient to obtain the lower limit of the safe contact force, and control the AC servo motor to reverse and retract, so that the real-time contact force dynamically approaches and does not fall below the lower limit of the safe contact force to attenuate, thereby completing the thermal stress unloading. S8. When the temperature drops to the preset safe room temperature range and the real-time contact force decays to the zero-point error allowable range, control the AC servo motor to quickly reverse to lift the upper pressure head; repeat steps S1 to S8 above.

[0012] Furthermore, the transmission push rod is configured for vertical extension and retraction drive within the vacuum cavity; the step S1 includes the following prior to: S0. Control the robotic arm to place the two aligned glass substrates on the top surface of the lower heating stage, and control the vacuum pump to start to evacuate the vacuum chamber to the target vacuum level.

[0013] Furthermore, in step S5: when the force deviation is positive, the industrial control computer is controlled to convert the downward displacement into a target pulse number, driving the AC servo motor to perform micro-motion downward pressure; When the force deviation is negative, the industrial control computer is controlled to drive the AC servo motor to retract after conversion. When the absolute value of the force deviation falls within the preset error dead zone range, the industrial control computer is controlled to keep the current position of the AC servo motor unchanged.

[0014] The present invention has the following beneficial effects: 1. This invention adopts a structural design that combines a servo drive unit, a transmission force measuring unit, and a floating leveling unit. The floating leveling unit utilizes a universal ball joint and a high-temperature resistant disc spring to absorb impact energy and tilt when it approaches the glass substrate placed on the lower heating stage, thus avoiding local stress concentration and substrate breakage. At the same time, a bellows dynamic sealing ring is provided at the top of the vacuum chamber, and the transmission push rod extends vertically downward through the bellows dynamic sealing ring into the vacuum chamber, avoiding the generation of tiny particles from friction, effectively ensuring the high cleanliness of the vacuum environment, and thus improving the bonding interface quality. 2. This invention continuously reads the force data from the force gauge using an industrial control computer and controls the displacement. When the heating platform heats up under control, the force deviation is multiplied by a virtual compliance coefficient representing the displacement compensation per unit force deviation to calculate the downward displacement. This drives an AC servo motor for micro-motion compensation, achieving stable constant force application. During the cooling process after the heating platform stops heating under control, the lower limit of the safe contact force is obtained by calculating the descent gradient within multiple intervals and multiplying it by a thermal stress release coefficient. The AC servo motor is then controlled to reverse and retract, causing the real-time contact force to dynamically approach and attenuate to a level not lower than the lower limit of the safe contact force, thus completing thermal stress unloading. This method effectively avoids residual stress retention and stress instability, improving the overall bonding pass rate of the process. Attached Figure Description

[0015] The following drawings, illustrating embodiments of this application, are incorporated herein by reference and are used to understand this application. The drawings illustrate embodiments of this application and their descriptions, serving to explain the principles of this application. In the drawings, Figure 1 This is a schematic diagram of the overall structure of the device; Figure 2 This is a schematic diagram of the internal structure of the vacuum chamber of the device; Figure 3 This is a schematic diagram of the ball screw structure of the device; Figure 4 This is a schematic diagram of the upper connecting seat and lower connecting plate of the device; Figure 5 This is a flowchart of the method of the present invention.

[0016] In the diagram: 101, base; 102, vacuum chamber; 103, bellows dynamic seal ring; 201, lower heating platform; 202, upper pressing head; 301, motor bracket; 302, AC servo motor; 303, incremental photoelectric encoder; 401, transmission push rod; 402, strain gauge force gauge; 403, ball screw; 404, screw shaft; 405, nut flange; 406, plum blossom-shaped flexible coupling; 501, upper connecting seat; 502, lower connecting plate; 503, universal ball joint; 504, high-temperature resistant disc spring; 505, hemispherical groove; 506, lower hemispherical groove; 507, guide column; 601, glass substrate. Detailed Implementation

[0017] In the following description, numerous specific details are set forth to provide a more thorough understanding of this application. However, it will be apparent to those skilled in the art that embodiments of this application may be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described to avoid confusion with embodiments of this application.

[0018] Example 1: A vacuum hot-press bonding apparatus, comprising: Base components, such as Figure 1 As shown, it includes a base 101 and a vacuum chamber 102 fixed to its top; Pressing heating section, such as Figure 2 As shown, the cavity 102 includes a lower heating platform 201 fixed to the bottom surface of the cavity and an upper pressing head 202 disposed above it. The top surface of the lower heating platform 201 is used to place the glass substrate 601, and the bottom surface of the upper pressing head 202 is parallel to and opposite to the top surface of the lower heating platform 201. The servo drive unit is located on the top outer side of the cavity 102 and includes a motor bracket 301 and an AC servo motor 302 fixed thereon. Transmission force measuring unit, such as Figure 3 As shown, the connection between the motor 302 and the upper pressure head 202 includes a transmission push rod 401 and a strain gauge force gauge 402. The motor 302 drives the push rod 401, which passes through the cavity 102 and is connected at its bottom end to the force-receiving end of the force gauge 402. Floating leveling section, such as Figure 4 As shown, the matching device is located between the output end of the force gauge 402 and the upper pressure head 202, including an upper connecting seat 501, a lower connecting plate 502, a universal ball joint 503 and a high-temperature resistant disc spring 504. The universal ball joint 503 is clamped between the upper connecting seat 501 and the lower connecting plate 502, and the two ends of the high-temperature resistant disc spring 504 abut against the bottom surface of the connecting seat 501 and the top surface of the connecting plate 502, respectively. The industrial computer connects and controls the pressing and heating unit, the servo drive unit, the transmission force measuring unit, and the floating leveling unit. When performing vacuum hot pressing bonding on glass substrate 601, existing equipment usually relies on cables, pulleys and mechanical counterweights to provide continuous downward pressure. Such structures will generate particles due to friction during long-term operation, and the flexible force transmission relationship will change with the elongation of the cable, making it difficult to stably adapt to the thickness changes of glass substrate 601 during the heating process. To address this problem, this embodiment provides a vacuum hot-press bonding device that utilizes the coordinated operation of an AC servo motor 302, a transmission force measuring unit, a floating leveling unit, and an industrial control computer to apply a measurable, adjustable, and posture-tolerant pressing force to a glass substrate 601 in a vacuum environment. The base 101 component is used to support the entire machine and maintain the installation rigidity of the vacuum chamber 102. The base 101 can be a welded steel structure platform or an integral cast frame. The vacuum chamber 102 is fixed to the top of the base 101 to provide a low-pressure processing environment and isolate external particles. The lower heating platform 201 in the pressing and heating section is fixed to the bottom surface of the vacuum chamber 102, and its top surface is processed into a plane to serve as the bearing surface of the glass substrate 601; the upper pressing head 202 is set above the lower heating platform 201, and its bottom surface is parallel to the top surface of the lower heating platform 201 to ensure that the pressing direction is transmitted along the vertical direction of the chamber; the servo drive section is arranged on the top outer side of the vacuum chamber 102, and the motor bracket 301 is used to provide the installation and positioning reference for the AC servo motor 302, and the AC servo motor 302 outputs controlled displacement; The transmission force measuring unit is located between the servo drive unit and the upper pressing head 202. The transmission push rod 401 is responsible for axial displacement transmission. The strain gauge force gauge 402 is set in the force transmission path to convert the force during the pressing process into an electrical signal for the industrial control computer to read in real time. The floating leveling part is located between the strain gauge force gauge 402 and the upper pressure head 202. The upper connecting seat 501 is connected to the output end of the force gauge, and the lower connecting plate 502 is connected to the upper pressure head 202. The universal ball head 503 is located between the two to form a support center that can be slightly deflected. The high-temperature resistant disc spring 504 provides axial preload and attitude recovery force around the support center. When the glass substrate 601 has thickness tolerance or wedge error, the upper pressing head 202 will be under eccentric load in the initial contact with the substrate. The floating leveling part will tilt at a small angle under the action of eccentric load. The high temperature resistant disc spring 504 absorbs the contact impact and makes the bottom surface of the pressing head gradually fit the substrate surface, thereby reducing local stress concentration. The industrial control computer simultaneously connects to the relevant signals of the pressing and heating section, the servo drive section, the transmission force measurement section, and the floating leveling section. The pressing and heating section provides the temperature control object, the servo drive section provides the displacement execution object, the transmission force measurement section provides the force value sampling object, and the floating leveling section provides the passive attitude adaptation basis. This device combines mechanical compliance with force feedback, so that the force transmission path has both preset positioning accuracy and buffering capacity suitable for pressing brittle materials, which can meet the implementation requirements of hot pressing bonding of glass substrate 601 in a clean environment. The floating leveling section itself is a passive mechanical leveling structure without an independent actuator. Its posture change is determined by the off-center load, contact reaction force and elastic restoring force of the high-temperature resistant disc spring 504 generated during the pressing contact process. The industrial control computer controls the floating leveling unit by controlling the descent speed, stopping timing and compensation displacement of the servo drive unit, and simultaneously reading the force value signal output by the transmission force measuring unit and the position feedback of the servo drive unit, thereby indirectly limiting the force boundary and displacement boundary of the floating leveling unit. In other words, the industrial control computer does not send action commands to the universal ball joint 503, the upper connecting seat 501, the lower connecting plate 502 or the high-temperature resistant disc spring 504 individually. Instead, it uses a closed-loop control method of displacement input, force value monitoring and action correction to enable the floating leveling part to complete passive leveling within the allowable mechanical degrees of freedom. From the perspective of signal flow and causality, the inputs received by the industrial control computer include at least the temperature signal of the lower heating platform 201, the force signal of the strain gauge 402, and the position or speed feedback signal of the AC servo motor 302; the outputs generated by the industrial control computer include at least the commands for the AC servo motor 302 to descend, stop, micro-motion compensation, and retraction, as well as the commands for the lower heating platform 201 to heat up, maintain temperature, and stop heating. Since the floating leveling part is located between the force measuring path and the pressure head, when the industrial control computer changes the approach speed or stop position of the pressure head, the actual axial load growth rate and off-center load duration of the floating leveling part change accordingly. Therefore, its tilt amount, recovery process and buffering effect are also indirectly constrained. Through this relationship, the device as a whole forms a closed-loop feedback mechanism: temperature changes cause material state changes—force signals reflect contact state changes—the industrial control computer adjusts displacement—the floating leveling unit completes attitude adaptation, thus making the functional division and interaction between the various structural components clearer; The transmission force measuring unit also includes a ball screw 403. The output shaft of the AC servo motor 302 is connected to the screw shaft 404 of the ball screw 403. The nut flange 405 of the ball screw 403 is connected to the transmission push rod 401 by a thread. When the AC servo motor 302 is working, it drives the transmission push rod 401 to move in the vertical direction. In order to convert the rotary output of the AC servo motor 302 into linear displacement suitable for the pressing process, this embodiment provides a ball screw 403 in the transmission force measuring part; the ball screw 403 is a mechanical element that converts the angular displacement of the motor into axial linear displacement, and its screw shaft 404 is connected to the output shaft of the AC servo motor 302, and the nut flange 405 is connected to the transmission push rod 401 by threads. When the AC servo motor 302 is working, it drives the lead screw shaft 404 to rotate, and the balls roll between the lead screw shaft 404 and the nut, thereby causing the nut flange 405 to move axially along the lead screw shaft 404, driving the transmission push rod 401 to rise and fall in the vertical direction. Compared to ordinary trapezoidal screws, the 403 ball screw has a frictional resistance lower than the preset resistance threshold and a displacement resolution that meets fine control tolerances, making it suitable for converting minute control commands output by industrial control computers into repeatable axial displacements. In this embodiment, the lead of the ball screw 403 can be selected as 5mm / r or 10mm / r; when higher displacement resolution is required, a lead of 5mm / r is selected, and when higher motion efficiency is required, a lead of 10mm / r is selected. The transmission push rod 401 is connected to the nut flange 405 by thread, which facilitates disassembly and maintenance, and also facilitates the alignment of the push rod axis with the screw shaft 404 during assembly. Since the upper pressing head 202 needs to approach quickly during the contact identification stage and move slowly during the leveling and constant force control stages, the ball screw 403 can simultaneously meet the requirements of both large stroke and small displacement compensation. This structure enables the displacement control of the transmission chain to be based on a clear lead relationship. The industrial control computer can directly calculate the motor rotation angle or pulse number based on the target displacement, and combine the real-time data of the strain gauge force gauge 402 to realize the corresponding adjustment between displacement and force value. Among them, virtual compliance coefficient The determination logic is as follows: The industrial control computer has pre-stored calibration tables for glass substrate 601 of different materials and thicknesses; for elastic modulus of... Thickness is The initial coefficient of the substrate is given by the formula: It is confirmed that, among them, For the area under pressure, This is the stiffness correction factor for the equipment's transmission chain; when executing S5, the industrial control computer retrieves and applies the corresponding value from the preset step value based on the currently detected temperature range. Values ​​to achieve displacement: The precise conversion, among which, For force deviation, The downward displacement is represented by the output shaft of the AC servo motor 302, which is directly connected to the screw shaft 404 of the ball screw 403 via a plum blossom-shaped flexible coupling 406. To reduce the additional load caused by assembly errors between the output shaft of the AC servo motor 302 and the ball screw 403 and screw shaft 404, this embodiment provides a plum blossom-shaped flexible coupling 406 between the two. The plum blossom-shaped flexible coupling 406 consists of two metal claw discs and an elastic body located in the middle, which can compensate for radial deviation, angular deviation and axial deviation within a preset tolerance range while transmitting torque. The output shaft of the AC servo motor 302 is fixedly connected to the upper claw plate of the coupling, and the screw shaft 404 of the ball screw 403 is fixedly connected to the lower claw plate of the coupling, forming a direct drive path. The term "direct drive" here means that the power is directly transmitted from the AC servo motor 302 to the ball screw 403 without the need for pulleys, sprockets, or gear reduction mechanisms, thereby reducing transmission clearance and additional particulate sources. Since the transmission push rod 401 in the vacuum hot pressing bonding device needs to pass through the vacuum cavity 102 and accurately transmit the displacement to the strain gauge force gauge 402 and the upper pressing head 202, if there is an assembly deviation between the motor shaft and the lead screw shaft 404 that exceeds the coaxiality tolerance, the ball screw 403 will be subjected to eccentric force, which may cause bearing wear, displacement fluctuation or increased force measurement noise after long-term operation. The plum blossom-shaped flexible coupling 406 absorbs this type of error through the shear deformation of its intermediate elastic body, so that the lead screw shaft 404 maintains a rotational state that meets the preset coaxiality tolerance. The coupling material can be selected from polyurethane elastomer with metal claw disc, or engineering elastomer with higher temperature resistance to adapt to the temperature environment near the motor bracket 301; this design helps to maintain the axial force purity of the transmission force measuring part and reduce the impact of lateral disturbance on the output of strain gauge force gauge 402. A bellows dynamic seal ring 103 is provided at the top of the vacuum chamber 102, and the transmission push rod 401 extends vertically downward through the bellows dynamic seal ring 103 into the vacuum chamber 102. In this embodiment, a bellows dynamic sealing ring 103 is provided at the top of the vacuum cavity 102 to solve the vacuum sealing problem when the transmission push rod 401 passes through the cavity wall; the bellows dynamic sealing ring 103 is a flexible sealing component that allows the rod to make axial reciprocating motion while maintaining pressure isolation between the inside and outside of the cavity, and can be made of stainless steel welded bellows structure. The transmission push rod 401 passes vertically downward through the bellows dynamic seal ring 103 and extends into the vacuum chamber 102. The outer wall of the push rod is sealed to one end of the bellows, and the other end of the bellows is sealed to the top wall of the vacuum chamber 102. When the transmission push rod 401 rises and falls, the bellows adapts to the displacement change through its own axial expansion and contraction deformation, without relying on the relative friction between the traditional sliding seal ring and the outer wall of the push rod, thereby reducing the amount of particles generated. Since the device is used for hot pressing bonding of glass substrate 601, particle control and vacuum leakage control in the vacuum environment directly affect the bonding interface quality. The use of bellows dynamic sealing ring 103 can avoid the friction and wear problem of conventional dynamic sealing structure under high cleanliness requirements. The effective stroke of the bellows is determined by the maximum pressing stroke of the upper pressing head 202, and can be set from 20mm to 80mm; the material can be selected from 304 stainless steel, 316 ultra-low carbon stainless steel or nickel-based corrosion-resistant alloy. To ensure that the bellows does not become unstable during repeated expansion and contraction, the transmission push rod 401 is coaxially arranged with the ball screw 403 and the strain gauge force gauge 402. A guide mounting surface can be provided on the top of the vacuum chamber 102 to limit the eccentricity of the bellows installation. This structure allows the servo drive unit to be arranged outside the vacuum chamber 102, while the upper pressing head 202 is located inside the vacuum chamber 102, thus taking into account vacuum isolation, maintainability, and force transmission accuracy. The bottom center of the upper connecting seat 501 is machined with a hemispherical groove 505, and the top center of the lower connecting plate 502 is machined with a lower hemispherical groove 506. The universal ball head 503 is matched and disposed between the hemispherical groove 505 and the lower hemispherical groove 506 to form a spherical rotating pair. In this embodiment, the floating leveling part adopts a spherical rotating pair to achieve micro-adaptive attitude of the upper pressing head 202; a hemispherical groove 505 is machined at the center of the bottom surface of the upper connecting seat 501, and a lower hemispherical groove 506 is machined at the center of the top surface of the lower connecting plate 502; the universal ball head 503 is matched and disposed between the two grooves; the radius of curvature of the hemispherical groove 505 and the lower hemispherical groove 506 matches the outer spherical surface of the universal ball head 503 to form a stable surface contact support; The spherical revolute joint referred to here means that the lower connecting plate 502 can rotate at a small angle relative to the upper connecting seat 501 around the center of the universal ball head 503, while retaining limited axial displacement under the constraint of the high-temperature resistant disc spring 504; for the hot pressing bonding process of glass substrate 601, if the glass sheet has thickness tolerance, surface micro-wedge or placement error, if the upper pressing head 202 maintains absolute rigidity, it will generate high contact stress in the local first contact area; This embodiment utilizes a spherical rotating pair to enable the lower connecting plate 502 to tilt at a small angle when it first contacts one side. The tilt center is located near the center of the universal ball joint 503. Therefore, the attitude adjustment process has a clear geometric reference, and the edge of the pressing head will not generate additional impact due to random swinging. The 503 universal ball joint can be made of high-hardness stainless steel, tool steel or surface-hardened alloy steel, with a surface roughness controlled between Ra0.4μm and Ra0.8μm. The groove surface is matched to it to reduce rotational resistance and local wear. To adapt to vacuum and heated environments, the spherical contact area can be coated with a solid lubricant or treated with vacuum-compatible lubrication. The spherical rotating pair is connected in series with the strain gauge force gauge 402, so that the leveling action occurs in the force measurement path. The industrial control computer can simultaneously observe the force value change process caused by the off-center load contact, thus providing a stable data basis for contact identification and leveling confirmation. The floating leveling part also includes four guide posts 507 evenly distributed around the universal ball head 503. The top of the guide post 507 is fixed to the upper connecting seat 501, and the bottom of the guide post 507 passes through the gap hole of the lower connecting plate 502. Each guide post 507 is fitted with a high temperature resistant disc spring 504. Based on the spherical rotating pair, this embodiment forms an attitude constraint and elastic recovery structure through four guide posts 507 and corresponding high-temperature resistant disc springs 504; the four guide posts 507 are evenly distributed around the universal ball head 503, preferably at 90-degree intervals, with the top ends fixed to the upper connecting seat 501 and the bottom ends passing through the gap holes of the lower connecting plate 502; the diameter of the hole in the lower connecting plate 502 is larger than the outer diameter of the guide posts 507 to provide the clearance required for tilting and axial micro-movement; Each guide post 507 is fitted with a high-temperature resistant disc spring 504, with the two ends of the high-temperature resistant disc spring 504 respectively abutting against the bottom surface of the upper connecting seat 501 and the top surface of the lower connecting plate 502; the disc spring is a sheet-shaped elastic element with axial elasticity, and the high-temperature resistant disc spring 504 can be made of spring steel, high-temperature alloy steel or nickel-based elastic material, suitable for bearing the heat conducted from the upper pressing head 202 during the heating process of the lower heating platform 201; The guide post 507 is used to limit the lateral displacement and excessive tilt of the lower connecting plate 502, so that it can deflect in a controlled manner around the universal ball head 503; the high temperature resistant disc spring 504 is used to apply axial preload to the lower connecting plate 502 and provide differential elastic compression when it is under pressure on one side. In this way, when one side of the upper pressing head 202 contacts the glass substrate 601 first, the compression of the high-temperature resistant disc spring 504 on the corresponding side increases, while the compression on the other side decreases relatively. The lower connecting plate 502 tilts due to its poor elasticity until the bottom surface of the upper pressing head 202 and the surface of the glass substrate 601 reach the preset bonding area threshold. The evenly distributed arrangement of the four guide posts 507 makes the restoring force distribution more balanced, which can avoid the instability problem that occurs when only a single central spring is used; the guide posts 507 can be fixed to the upper connecting seat 501 by interference fit, threaded connection or pin connection. The single-sided gap between the gap hole and the guide post 507 can be set to 0.5mm to 1.5mm to balance tilting freedom and guiding stability. Through this structure, the floating leveling part not only provides attitude adaptability, but also buffers the impact load at the moment of contact, which helps to reduce the risk of local breakage of the brittle glass substrate 601. The servo drive unit also includes an incremental photoelectric encoder 303, which is connected to the AC servo motor 302 to obtain rotor position information and transmit it to the industrial control computer. In order to enable the industrial control computer to obtain the actual rotation information of the AC servo motor 302, this embodiment provides an incremental photoelectric encoder 303 in the servo drive unit; the incremental photoelectric encoder 303 generates pulse signals by detecting the changes in light transmission and shading on the rotating encoder disk, the number of output pulses corresponds to the motor rotation angle, the pulse frequency corresponds to the motor speed, and the phase relationship between the A-phase and B-phase signals can be used to determine the rotation direction. The encoder is connected to the AC servo motor 302. It can be built into the motor tail end or installed externally on the coaxial side. After the encoder output signal is transmitted to the industrial control computer, the industrial control computer can combine the lead parameters of the ball screw 403 to convert the motor rotation angle into the theoretical axial displacement of the transmission push rod 401. For example, when the encoder resolution is 2500 lines per revolution, after using quadruple frequency sampling, 10000 counts per revolution can be obtained. Combined with the 5mm / r ball screw 403 lead, the theoretical displacement resolution can reach 0.5μm / count. This position information and the force value information provided by the strain gauge 402 together constitute the input quantity for control calculation. During the contact recognition phase, the industrial control computer confirms that the motor descends continuously at the set speed based on encoder feedback, preventing the actual speed from deviating from the set value due to load changes; during the constant force application phase, the industrial control computer calculates the target compensation displacement based on the force value deviation and uses encoder feedback to confirm whether the compensation displacement is in place. During the thermal stress unloading stage, the industrial control computer controls the AC servo motor 302 to reverse and retract at a first preset low speed based on encoder feedback, so that the contact force decays according to the set law; the introduction of the incremental photoelectric encoder 303 makes the displacement execution process measurable and verifiable, thereby improving the implementation accuracy of displacement calculation during force adjustment.

[0019] Example 2: like Figure 5 As shown, the vacuum thermocompression bonding control method includes: S1. Control the servo drive unit to work, and drive the upper pressing head 202 to move downward and approach the glass substrate 601 placed on the lower heating stage 201 through the transmission push rod 401; S2. Control the industrial control computer to continuously read the force value data of the strain gauge force gauge 402 and calculate the force value change rate. When the force value change rate is less than or equal to the preset contact threshold, control the AC servo motor 302 to maintain the current speed and decrease; when the force value change rate exceeds the preset contact threshold, control the AC servo motor 302 to reduce the speed and switch to micro-stepping mode. S3. The floating leveling part absorbs the impact energy and tilts until the force value output by the strain gauge 402 reaches the preset leveling confirmation threshold, and the AC servo motor 302 is controlled to stop rotating to complete the passive leveling. S4. Control the heating stage 201 to heat up, read the current contact force in real time, and calculate the force deviation by subtracting the target bonding force from the current contact force. S5. Multiply the force deviation by the virtual compliance coefficient that represents the displacement compensation amount corresponding to the unit force deviation to calculate the downward displacement amount, and control the AC servo motor 302 to perform micro-motion compensation to complete the constant force application. S6. Control the lower heating stage 201 to stop heating, divide the time axis of the cooling process into multiple intervals, and calculate the decreasing gradient of the force value in each interval; S7. Multiply the descent gradient by the pre-calibrated thermal stress release coefficient to obtain the lower limit of the safe contact force, and control the AC servo motor 302 to reverse and retract, so that the real-time contact force dynamically approaches and does not fall below the lower limit of the safe contact force to attenuate, thereby completing the thermal stress unloading. S8. When the temperature drops to the preset safe room temperature range and the real-time contact force decays to the zero-point error allowable range, control the AC servo motor 302 to quickly reverse to lift the upper pressure head 202; repeat the above steps S1 to S8. This embodiment provides a control method for the aforementioned vacuum hot-press bonding device, the purpose of which is to convert the constant downward pressure generated by the traditional mechanical counterweight into a calculable displacement compensation logic, and to achieve hot-press bonding of the brittle glass substrate 601 by combining the passive mechanical adaptability of the floating leveling part. In S1, the industrial control computer sends a running command to the servo drive unit. The AC servo motor 302 drives the ball screw 403 to rotate, and through the transmission push rod 401, the upper pressing head 202 moves downward in the vertical direction, gradually approaching the glass substrate 601 on the lower heating table 201. The descent speed in this stage can be set from 50 mm / min to 200 mm / min according to the process cycle, so as to balance approach efficiency and contact safety. In S2, the industrial control computer continuously reads the force data of the strain gauge force gauge 402. The sampling period can be set from 1ms to 10ms. The force change rate is obtained by subtracting the previous sampling value from the current sampling value and dividing by the sampling period. It is used to reflect the rate at which the force value rises at the moment of contact. When the rate of change of force exceeds the preset contact threshold, it indicates that the upper pressing head 202 has contacted the glass substrate 601. The industrial control computer then controls the AC servo motor 302 to switch from the approach speed to the micro-stepping mode. This contact threshold can be calibrated based on the no-load noise, the sensitivity of the force gauge and the mass of the pressing head, for example, set to 0.5N / ms to 5N / ms. In S3, the floating leveling part tilts under eccentric loading. The high-temperature resistant disc spring 504 absorbs the contact impact and allows the bottom surface of the upper pressing head 202 to make minor posture corrections relative to the substrate surface. The industrial control computer continuously reads the output of the strain gauge force gauge 402. When the force value reaches the leveling confirmation threshold, it controls the AC servo motor 302 to stop, indicating that the upper pressing head 202 and the glass substrate 601 have established a surface contact relationship with the force fluctuation within the preset range. The leveling confirmation threshold can be set to 5% to 20% of the target bonding force. In S4, the lower heating platform 201 heats up according to the set heating curve. The industrial control computer reads the current contact force in real time and calculates the force deviation by subtracting the target bonding force input by the operator from the current contact force. In S5, the industrial control computer multiplies the force deviation by the virtual compliance coefficient to obtain the downward displacement. Here, the virtual compliance coefficient represents the displacement compensation amount corresponding to a unit force deviation, and its unit can be μm / N, with a typical range of 0.1μm / N to 20μm / N. If the substrate softens due to heat, resulting in a decrease in thickness and a drop in current contact force, the force deviation is positive, and the industrial control computer controls the AC servo motor 302 to press down. If the substrate expands locally, causing the contact force to increase, the force deviation is negative, and the industrial control computer controls the AC servo motor 302 to retract. In this way, the rigid transmission mechanism exhibits flexible pressure characteristics that can be adjusted according to changes in thickness through continuous micro-motion. In S6, the lower heating stage 201 stops heating and enters the cooling stage. The industrial control computer divides the cooling time into multiple intervals, such as 0.5s, 1s or 2s per interval, and calculates the force value decrease gradient in each interval. This gradient is obtained by dividing the difference between the force value at the end of the interval and the force value at the beginning of the interval by the interval duration, and is used to characterize the trend of contact force release of the substrate during cooling. In S7, the industrial control computer multiplies the descent gradient by the pre-calibrated thermal stress release coefficient to obtain the lower limit of the safe contact force in the current range, and controls the AC servo motor 302 to reverse and retract, so that the real-time contact force is close to the lower limit and not lower than the lower limit. The thermal stress relief coefficient can be obtained by experimental calibration based on different glass materials, substrate thicknesses and indenter materials; the control objective at this stage is not to maintain a constant force, but to make the contact force decay at a controlled rate in order to reduce the residual stress caused by the difference in thermal expansion coefficients. In S8, when the temperature drops to the preset safe room temperature range and the real-time contact force decays to the zero-point error allowable range, the industrial control computer controls the AC servo motor 302 to quickly reverse and lift the upper pressure head 202 to prepare for the next cycle. In this method, there is a clear data transfer relationship between contact identification, passive leveling, virtual flexibility constant force application and thermal stress unloading. The force value collected by the force gauge is used for both contact judgment and displacement compensation and unloading follow-up. The position information collected by the encoder is used to perform displacement verification. Therefore, the whole method has an implementable control basis. The data sources and decision-making roles of the aforementioned contact threshold, leveling confirmation threshold, virtual flexibility coefficient, descent gradient, thermal stress release coefficient, and lower limit of safe contact force are as follows; The contact threshold represents the threshold at which the contact force rises per unit time when the upper pressure head 202 transitions from idle motion to actual contact state, and can be clearly distinguished from no-load noise. It is not simply an empirical constant, but is determined by both no-load sampling results and pressure test calibration results. When the glass substrate 601 is not placed in the equipment and the upper pressure head 202 is suspended, the industrial control computer first continuously collects a segment of no-load force value change rate data to obtain the upper limit of no-load fluctuation. The force change rate range during the first stable contact was recorded by contacting the standard test piece at low speed. The industrial control computer then wrote the contact threshold after leaving a safety margin between the two, so as to ensure that the threshold is both higher than the noise and lower than the typical rise rate during normal contact. The leveling confirmation threshold represents the minimum confirmation force value corresponding to the stable surface contact formed between the pressure head and the glass substrate 601 after the floating leveling part completes the initial posture adaptation. Its function is to avoid stopping too early when there is only point contact or line contact. This threshold can be given first according to a fixed ratio of the target bonding force, and then corrected by observing the uniformity of the indentation, the stability time of the force value, and the number of subsequent constant force compensations through multiple test presses. If the force value continues to drift rapidly after reaching this threshold, it indicates that the fit is not yet sufficient. The industrial control computer can continue to maintain micro-step descent until the force value enters a stable fluctuation range. The above calculation logic can be broken down into the following process according to the data processing order: The first step involves the industrial control computer acquiring the original force value sampling sequence from the strain gauge 402 and performing moving average or amplitude limiting filtering on several consecutive sampling points to remove electrical noise and occasional spikes. Taking moving average filtering as an example, let the current sampling time be... The original force value sampling sequence is The set sliding window size is , The filtered force value is obtained by using the index of the historical sampling time within the sliding window. The calculation logic is as follows: The second step is to divide the difference in filtered force values ​​between two adjacent time points by the sampling time interval to obtain the force change rate, which is used to perform the contact judgment in S2. The third step is that after the contact is confirmed, the industrial control computer continues to read the current contact force and compares it with the preset target bonding force to obtain the force value deviation. The sign of the force value deviation directly indicates whether to press down or back down. The fourth step is to input the force deviation into the virtual compliance conversion step to obtain the displacement compensation amount that needs to be performed in this cycle. The fifth step involves the industrial control computer combining encoder feedback and lead screw lead to convert the displacement compensation into a motor micro-motion command, and then reading the force value again in the next sampling cycle to form a closed-loop correction. The output of the above process includes contact state determination result, leveling completion determination result, displacement compensation amount, and unloading stage retraction amount. These results flow to the speed switching control, stop control, constant force compensation control, and thermal stress unloading control of the servo drive unit, respectively. The physical meaning of the virtual compliance coefficient is to make the originally rigid screw drive system exhibit equivalent elasticity in the control logic, that is, to map the force value deviation into the compensation displacement; its determination process can be carried out by step-by-step calibration: first, at room temperature, use a standard test block to test the range of contact force change caused by unit displacement to obtain the basic stiffness range of the device; Then, a short-time heating test was conducted near the target process temperature to observe the change in force value per unit displacement after the glass substrate 601 softened due to heat; the compensation sensitivity was set to a range that could correct the force value deviation in a timely manner without causing dynamic oscillation of the force value. For example, the same batch of glass may cause a first force change when pressed down by 1μm at room temperature, while the force change caused by the same displacement at high temperature is a second force change, and the second force change is less than the first force change. At this time, the industrial control computer can call the pre-stored temperature zone parameter table and use different virtual compliance coefficients in different temperature zones. Therefore, the virtual compliance coefficient is no longer an isolated parameter, but a control intermediate quantity connecting the current temperature, material state and displacement compensation amount; The descending gradient represents the rate of change of contact force over time during the cooling phase. The larger its absolute value, the more significant the thermal contraction or stress release within the current temperature range. The thermal stress release coefficient represents the proportional factor used to convert this release trend into a safe pressure holding lower limit. It can be determined through repeated cooling tests of glass of the same material and thickness. Specifically, multiple rounds of tests can be conducted using a low-speed retraction method below the set threshold. The force attenuation curves of each temperature zone when no cracks, warping, or bonding failures occur can be recorded. Then, the appropriate thermal stress release coefficient for each temperature zone can be derived. The lower limit of the safe contact force is the minimum non-zero contact force that can be maintained during the unloading stage. Its function is to prevent the pressure head from detaching too early and causing interface instability, while also preventing excessive contact force from causing residual thermal stress to remain. The industrial control computer first calculates the force descent gradient in each cooling range, then calls the thermal stress release coefficient of the corresponding temperature range to generate the lower limit of the safe contact force in that range, and uses it as a comparison benchmark for the servo motor back-off control in real time. When the real-time contact force is higher than the lower limit, continued retraction is allowed; when the real-time contact force is close to the lower limit, the retraction amount is reduced or retraction is paused. Through the above hierarchical definition, each parameter and threshold has a clear physical meaning, source path, and control purpose, thus making the implementation logic of this method more complete. In this embodiment, the micro-stepping mode refers to the AC servo motor 302 switching to a fine position control state with small displacement increments, low speed, and repeatable verification after contact recognition. In this state, the industrial control computer no longer controls the AC servo motor 302 according to the continuous large displacement command of the rapid approach phase. Instead, it breaks down the total displacement into multiple preset displacement increments and outputs them one by one. After each increment is executed, it rereads the strain gauge force gauge 402 signal and encoder feedback and then decides whether to continue pressing down, hold or stop. Therefore, this mode focuses on control granularity and feedback closed loop, rather than requiring the AC servo motor 302 to have a current subdivision drive structure in the sense of a stepper motor. S2 to S7 can be understood as being composed of three logical sub-processes connected in sequence. The first sub-process is the contact identification and leveling sub-process. Its input is the force value sampling sequence and position feedback, and its output is two state quantities: contact completed and leveling completed. These are used to determine the switch from rapid approach to fine pressing and when to stop the initial descent. The second subprocess is the constant force compensation subprocess. Its inputs are the target bonding force, the current contact force, the current temperature range, and the virtual compliance coefficient. Its output is the compensation displacement command, which is used to offset the contact force drift caused by thickness changes, softening, and thermal expansion during the heating process. The third subprocess is the thermal stress unloading subprocess. Its inputs are the cooling range, the force value descent gradient, the thermal stress release coefficient, and the real-time contact force. Its output is the lower limit of the safe contact force and the corresponding retreat command, which is used to make the contact force decay according to the controlled law. The causal relationship between the three sub-processes is as follows: because the first sub-process establishes a stable contact and attitude basis, the second sub-process can perform constant force compensation under real surface contact conditions; because the second sub-process avoids significant loss of control of contact force during the heating phase, the third sub-process can implement thermal stress release control based on the continuous force value change trend. Multiplying the descent gradient by a pre-calibrated thermal stress release coefficient to obtain the lower limit of the safe contact force can be understood as a temperature-dependent unloading decision model. The purpose of this model is not to obtain the theoretical absolute value of the internal stress of the material, but to provide a minimum holding pressure reference value for servo backoff that will not lose pressure too early, based on the contact force release trend measured during the cooling stage. The model logically includes at least a temperature zone identification unit, a gradient calculation unit, a parameter calling unit, and a lower limit generation unit; among which, the temperature zone identification unit receives the temperature or cooling time interval information of the lower heating stage 201 to determine the current temperature zone; The gradient calculation unit receives force value data from adjacent time periods to generate the force value descent gradient for the current interval; the parameter calling unit retrieves the corresponding thermal stress release coefficient based on the current temperature zone; and the lower limit generation unit forms a safe contact force lower limit based on the descent gradient and the corresponding coefficient. The model as a whole represents the causal relationship of the gradual decrease in contact force caused by the difference in thermal shrinkage, release of interfacial stress and elastic recovery of materials during the cooling process of glass substrate 601 and indenter system; through the above explanation, the model purpose, logical structure, data flow and physical relationship represented in S7 are all clarified. To ensure that the calculation processes in S6 and S7 have clearly defined rules for programmable implementation, this implementation method supplements the following quantization derivation examples and calculation rules; let the first... The starting point for each cooling interval is... The end point of the time is The contact force corresponding to the starting point of time is The contact force corresponding to the end of the time is ,in, The integer is positive; the industrial control computer calculates the force descent gradient within this interval. : Call the thermal stress relief coefficient corresponding to the current temperature range Calculate the lower limit of safe contact force : For example, in a certain cooling range, the duration is set to 2 seconds, the contact force at the beginning of the range is 100N, and the contact force at the end of the range decreases to 90N. Then the industrial control computer calculates the descent gradient. It is 5 N / s; if the thermal stress relief coefficient for this temperature range is pre-calibrated. If the time is 4 seconds, then the lower limit of safe contact force can be calculated. It is 20N; The industrial control computer then uses this 20N as the lower limit reference for the pressure holding of the servo motor back-off control; through the above specific mathematical rules and quantitative deduction, the abstract control logic of thermal stress unloading is transformed into algebraic operations that can be directly encoded inside the industrial control computer, which can be achieved without excessive experimentation; The transmission push rod 401 is configured to extend and retract in the vertical direction of the vacuum chamber 102; the steps prior to S1 include: S0. Control the robotic arm to place the two aligned glass substrates 601 on the top surface of the lower heating stage 201, and control the vacuum pump to start to evacuate the vacuum chamber 102 to the target vacuum level. Based on the control method, this embodiment further defines the process preparation process and the movement mode of the transmission push rod 401; The design of the transmission push rod 401 to extend and retract along the vertical direction of the vacuum chamber 102 means that the motion axis of the transmission push rod 401 is consistent with the vertical direction of the vacuum chamber 102, and the lifting displacement is achieved through the ball screw 403 or the equivalent axial actuator, so that the pressing path between the upper pressing head 202 and the lower heating table 201 is kept along the normal direction of force transmission. This arrangement helps to reduce the impact of lateral force on the edge of the glass substrate 601, and also facilitates the axial expansion and contraction of the bellows dynamic sealing ring 103. In S0, the robot places two aligned glass substrates 601 on the top surface of the lower heating stage 201; the two aligned glass substrates 601 here can be an upper glass sheet and a lower glass sheet to be bonded, or a glass sheet with a microstructure and a flat glass sheet. The robotic arm can use a vacuum adsorption end effector to clean and confirm the top surface of the lower heating stage 201 before placing the glass, and ensure that the two pieces of glass achieve the predetermined alignment accuracy in the plane through a vision positioning module or a mechanical limit module. After placement, the vacuum pump is started to evacuate the vacuum chamber 102 to the target vacuum level. The target vacuum level can be set to below 1000 Pa, below 100 Pa, or even lower according to the bonding process to reduce residual gas at the bonding interface. The industrial control computer can be connected to a vacuum gauge to detect the vacuum level. Only when the vacuum level reaches the set value and stabilizes for a period of time is the pressure head descent action in S1 allowed to be executed. By introducing step S0 before S1, the method implementation process has complete pre-processing conditions, avoiding direct pressing in a state of misalignment or vacuum; this limitation, together with the vertical extension and retraction setting of the transmission push rod 401, ensures that the subsequent contact identification, leveling and pressurization processes are established on stable initial boundary conditions. In step S0, the two aligned glass substrates 601 refer to the placement state of the two glass substrates within the predetermined reference coordinate system on the top surface of the lower heating stage 201, which meets the positional error range. The judgment basis can come from the visual positioning result, the contact state of the mechanical positioning pin, or a combination of the two. If a vision positioning module is used, the industrial control computer first reads the edge or marker point image captured by the camera to obtain the planar offset and angular deviation of the upper and lower glass sheets relative to the lower heating stage 201 reference. If the offset or angular deviation exceeds the allowable range of the process, the robot arm performs repositioning or fine-tuning until the allowable conditions are met. If a mechanical limit module is used, the contact state between the glass edge and the limit surface is used as the input for judging whether the alignment is completed. This alignment state is a prerequisite for initiating vacuuming and pressure head descent. Its purpose is to avoid local suspension, edge cracking, or bonding area displacement caused by initial misalignment during subsequent hot pressing. In the data flow process using the above-mentioned vision positioning module, in order to clarify the details of data interaction and processing between devices, the industrial camera transmits the acquired image frames to the industrial control computer in real time through the gigabit Ethernet vision standard or USB 3.0 vision standard interface. The industrial control computer calls the machine vision algorithm library to extract the pixel coordinates of the reference marker points in the image, and uses the pre-calibrated affine transformation matrix to convert them into the actual coordinates in the physical coordinate system of the lower heating platform 201, and calculates the plane offset and angle deviation. Specifically, let the extracted reference marker pixel coordinates be ( , The actual coordinates of the lower heating platform in the 201 physical coordinate system are ( , The pre-calibrated affine transformation matrix is: To satisfy the matrix multiplication dimension and achieve translation transformation, the coordinates are extended to a homogeneous coordinate vector form with an additional constant of 1. The calculation logic of the coordinate transformation then satisfies: Among them, the column vectors of the matrix Let be a constant of the homogeneous coordinate system, and let be a matrix. It includes translation, rotation, and scaling parameters for the current vision system; the industrial computer then converts the actual coordinates... With the preset standard reference coordinates Compare and calculate the planar offset. , and angle deviation ; If fine-tuning is required, the industrial control computer sends specific pose compensation instructions to the robot controller via the TCP / IP industrial Ethernet protocol, and the robot performs closed-loop fine-tuning actions accordingly. This clear data interaction protocol and coordinate transformation rules ensure the programmability of the glass substrate 601 alignment process. The target vacuum level represents the upper limit of the cavity pressure allowed to enter the pressing stage. Its physical meaning is to control the residual gas at the bonding interface within the allowable range of the process. This parameter is not simply the reading at the end of the evacuation, but also includes stability assessment. The specific process can be as follows: The first step is that after the vacuum pump is started, the industrial control computer periodically reads the pressure value of the vacuum gauge; The second step is that when the pressure value first falls below the preset target vacuum level, the industrial control computer does not immediately enter S1, but continues to maintain the vacuum and time the process. The third step is to determine that the vacuum condition is qualified if the pressure remains below the target vacuum level or only changes within the allowable fluctuation range within the preset stable time. Fourth, if the pressure rises beyond the allowable range, restart the timing or perform a leak check. Therefore, the target vacuum level is both a numerical threshold and a process permitting condition, and its output flows to S1 as a permitting signal to start the pressure head descent action. A state interlock relationship can be set between S0 and S1; the industrial control computer only sends a descent command to the servo drive unit after receiving status signals such as the glass substrate 601 being aligned, the vacuum degree being up to standard and stable, the lower heating stage 201 being within the standby temperature range, and the upper pressing head 202 being in the initial lifting position. Among them, the standby temperature range of the lower heating stage 201 is used to avoid the stage temperature from becoming too high and causing thermal shock before the glass is placed stably; the initial lifting position of the upper pressing head 202 can be confirmed by the encoder zero position or the origin switch; by connecting these input conditions in series, S0 is no longer just a simple feeding and vacuuming step, but forms the boundary condition establishment process for the subsequent control flow, thereby improving the feasibility and repeatability of the whole method. In step S5: When the force deviation is positive, the control computer converts the downward displacement into the target pulse number and drives the AC servo motor 302 to press down. When the force deviation is negative, the control computer will drive the AC servo motor 302 to retract after conversion. When the absolute value of the force deviation falls into the preset error dead zone range, the control computer keeps the current position of the AC servo motor 302 unchanged. This embodiment clarifies the displacement execution method of step S5; In S5, the industrial control computer obtains the force deviation based on the difference between the target bonding force and the current contact force, and calculates the downward displacement using the virtual compliance coefficient. In order to realize the specific action of the AC servo motor 302, the industrial control computer needs to perform conversion based on the lead of the ball screw 403 and the motor encoding resolution. When the force deviation is positive, it means that the current contact force is less than the target bonding force, and the clamping amount needs to be increased. The industrial control computer divides the downward displacement by the lead of the ball screw 403 to obtain the number of revolutions that the AC servo motor 302 should increase. Then, it converts the number of revolutions into the target number of pulses according to the encoder resolution or the driver pulse equivalent, and outputs the corresponding pulse command to the AC servo motor 302 driver to make the motor micro-motion press down. For example, if the virtual compliance coefficient is 2μm / N and the force deviation is 10N, then the downward displacement is 20μm; if the ball screw 403 has a lead of 5mm / r and the driver is set to 10,000 pulses per revolution, then the corresponding target pulse number is 40 pulses. After the industrial computer sends the pulse, the transmission push rod 401 moves down about 20μm, and the clamping force of the upper pressing head 202 on the glass substrate 601 increases accordingly. When the force deviation is negative, it means that the current contact force is greater than the target bonding force, and the clamping amount needs to be reduced. The industrial computer uses the same conversion relationship to obtain the number of pulses required for retraction and drives the AC servo motor 302 to reverse the micro-motion retraction. To avoid force oscillations caused by excessive single compensation, the industrial control computer can set an upper limit for the maximum number of pulses per compensation, such as 10 to 200 pulses, and read the output of the strain gauge 402 again in the next sampling cycle, and continue to recalculate according to the new force deviation; this method makes a clear mathematical correspondence between the force deviation and the executed displacement, avoiding the need to adjust the motor rotation based solely on experience. By corresponding the positive and negative deviations to the pressing and retraction actions respectively, the device can continuously correct the contact force fluctuations caused by the softening of the glass substrate 601 due to heat, local expansion or material flow during the heating and holding pressure stage, thereby maintaining the target bonding force within the set range. The conversion logic in S5 is as follows: The industrial control computer reads the current contact force output by the strain gauge force gauge 402 in the current sampling period and retrieves the target bonding force from the process formula; the industrial control computer subtracts the current contact force from the target bonding force to obtain the signed force deviation, where a positive sign indicates insufficient contact force and a negative sign indicates excessive contact force; The industrial control computer multiplies the force deviation with the virtual compliance coefficient corresponding to the current temperature zone to obtain the theoretical compensation displacement for this cycle. The industrial control computer determines whether the theoretical compensation displacement exceeds the upper limit of the allowable displacement for a single cycle. If it exceeds, it is truncated to the upper limit value. If it does not exceed, it is directly adopted. The industrial control computer outputs a positive or negative micro-pulse according to the compensation direction and re-enters the next sampling cycle after execution. Therefore, the input source, processing sequence, and output destination of S5 are clearly corresponding, forming a repeatable control flow; the conversion of the target pulse number can be achieved using the following relationship: in, The target number of pulses, This is the downward displacement. For the lead of ball screw 403, This represents the number of pulses or equivalent count value corresponding to each revolution of the motor. The industrial control computer uses this relationship to convert the displacement command into a pulse command that the servo driver can execute, and verifies whether the actual executed pulses have reached the target value through encoder feedback. If the deviation between the actual executed value and the target value exceeds the allowable range, the industrial control computer can record it as an execution error and correct it in the next cycle, or trigger deceleration, shutdown or alarm logic to avoid continuing to force the pressing under mechanical jamming conditions; The boundary conditions for micro-motion pressing down and micro-motion retraction are as follows: when the force deviation is positive and the absolute value is outside the dead zone, the industrial control computer performs pressing down compensation; when the force deviation is negative and the absolute value is outside the dead zone, the industrial control computer performs retraction compensation; when the absolute value of the force deviation falls into the dead zone, the industrial control computer maintains its current position. The dead zone range represents the allowable small fluctuations in force value, and its function is to avoid frequent back-and-forth corrections caused by measurement noise, thermal disturbances, or mechanical micro-vibrations. This dead zone range can be set according to the force gauge resolution and the allowable fluctuations in the process, for example, set to ±0.5% to ±3% of the target bonding force. In this way, the industrial control computer does not immediately respond to every tiny error, but only performs compensation when the error has practical technological significance, thereby improving the stability of constant force control. The virtual compliance coefficient is selected in S5 as follows: the industrial computer can pre-store one or more sets of virtual compliance coefficient parameter tables corresponding to glass material, thickness, and target temperature range; When executing S5, the industrial control computer first confirms the parameters of the glass to be processed based on the current process formula, and then calls the corresponding virtual compliance coefficient according to the temperature range fed back by the lower heating stage 201. If the current temperature is between two calibrated temperature zones, the adjacent temperature zone coefficient can be selected or the transition coefficient can be obtained by piecewise interpolation. In this way, when the same device processes glass substrates 601 with different thicknesses or different softening properties, it can complete the displacement compensation logic by switching through the parameter table without changing the limited structural composition. Through the above additional explanation, a clear causal chain is formed between displacement conversion, pulse execution, error dead zone and parameter calling in S5. The control boundary and feedback verification relationship in S5 is as follows: Before outputting the micro-pulse, the industrial control computer first checks whether the current position, the maximum allowable downward stroke, the minimum allowable clearance position, and the current force value are within the compensable range; only when all the above conditions are met is the output of the compensation command allowed. After the micro-motion command is executed, the industrial control computer does not directly assume that the compensation has taken effect. Instead, it first reads the encoder feedback to confirm that the AC servo motor 302 has actually completed the corresponding rotation, and then reads the updated force value of the strain gauge force gauge 402 to determine whether the compensation has reduced the force value deviation. If the encoder feedback indicates that the displacement has not been executed, it is first determined to be a transmission abnormality or load abnormality; if the displacement is executed but the force deviation does not decrease as expected, it is first determined to be a change in material state, redistribution of contact surface, or that the current temperature parameters need to be iteratively compensated; based on this, the industrial control computer then decides to proceed to the next micro-motion pressing down, micro-motion retraction, or to remain stationary. S5 can be understood as a conversion control model that takes force deviation as input and displacement compensation as output. The purpose of this model is to approximate the target bond force with executable displacement increments, rather than directly applying an unverifiable abstract constant force command to the system. The model logically includes at least a deviation acquisition unit, a compliance mapping unit, a limiting determination unit, a pulse conversion unit, and an execution verification unit; wherein, the deviation acquisition unit receives the target bonding force and the current contact force to form a signed force value deviation; the compliance mapping unit receives the force value deviation and the virtual compliance coefficient corresponding to the current temperature zone to generate the theoretical compensation displacement; The amplitude limiting determination unit is used to constrain the theoretical compensation displacement within the allowable range of a single cycle; the pulse conversion unit is used to convert the adopted compensation displacement into the target number of positive or negative pulses of the AC servo motor 302; the execution verification unit receives the encoder feedback and updated force value data to determine whether the compensation in this cycle is effective. The model as a whole represents the approximate correspondence between changes in contact force and changes in indenter displacement, as well as the causal relationship that requires dynamic correction as temperature and material state change. Through the above decomposition, the functional objectives, data flow and meaning in S5 are clearer. The communication interface and data transmission method between the modules in the above micro-motion pressing and retraction control model are as follows: The industrial computer is connected to the transmitter of the strain gauge force gauge 402 via an RS-485 bus or an analog input module. The transmitter converts the microvolt-level strain signal into a standard digital signal or a 4 to 20mA analog signal and transmits it to the industrial computer. The industrial computer is connected to the driver of the AC servo motor 302 via an industrial Ethernet bus for control automation technology. The industrial control computer encapsulates the calculated target pulse number into a process data object, sends position commands to the driver with a synchronization period of milliseconds, and simultaneously obtains the real-time position feedback of the encoder by receiving the process data object. This explicit data interaction protocol and underlying communication link design ensure that the data transmission in the closed-loop control has a definite timing sequence, thereby meeting the real-time requirements of constant force application on brittle materials.

[0020] This application has been described through the above embodiments; however, it should be understood that the above embodiments are for illustrative purposes only and are not intended to limit this application to the described embodiments. Those skilled in the art will understand that many more variations and modifications can be made based on the teachings of this application, and all such variations and modifications fall within the scope of protection claimed in this application.

Claims

1. A vacuum hot-press bonding apparatus, characterized in that, include: The base component includes a base (101) and a vacuum chamber (102) fixed to its top. The pressing and heating section is located inside the cavity (102) and includes a lower heating platform (201) fixed to the bottom surface of the cavity and an upper pressing head (202) located above it. The top surface of the lower heating platform (201) is used to place the glass substrate (601), and the bottom surface of the upper pressing head (202) is parallel to and opposite to the top surface of the lower heating platform (201). The servo drive unit is located on the top outer side of the cavity (102) and includes a motor bracket (301) and an AC servo motor (302) fixed thereon. The transmission force measuring unit connects the motor (302) and the upper pressure head (202), including a transmission push rod (401) and a strain gauge force gauge (402). The motor (302) drives the push rod (401), which passes through the cavity (102) and its bottom end is connected to the force receiving end of the force gauge (402). The floating leveling part is matched between the output end of the force gauge (402) and the upper pressure head (202), including an upper connecting seat (501), a lower connecting plate (502), a universal ball head (503) and a high-temperature resistant disc spring (504). The universal ball head (503) is clamped between the upper connecting seat (501) and the lower connecting plate (502), and the two ends of the high-temperature resistant disc spring (504) are respectively pressed against the bottom surface of the connecting seat (501) and the top surface of the connecting plate (502); The industrial computer connects and controls the pressing and heating unit, servo drive unit, transmission force measuring unit, and floating leveling unit.

2. The vacuum hot-press bonding apparatus according to claim 1, characterized in that, The transmission force measuring unit also includes a ball screw (403), the output shaft of the AC servo motor (302) is connected to the screw shaft (404) of the ball screw (403), and the nut flange (405) of the ball screw (403) is threadedly connected to the transmission push rod (401). When the AC servo motor (302) is working, it drives the transmission push rod (401) to move in the vertical direction.

3. The vacuum hot-press bonding apparatus according to claim 2, characterized in that, The output shaft of the AC servo motor (302) is directly connected to the screw shaft (404) of the ball screw (403) via a plum blossom-shaped flexible coupling (406).

4. The vacuum hot-press bonding apparatus according to claim 1, characterized in that, The top of the vacuum chamber (102) is provided with a bellows dynamic seal ring (103), and the transmission push rod (401) extends vertically downward through the bellows dynamic seal ring (103) into the vacuum chamber (102).

5. The vacuum hot-press bonding apparatus according to claim 1, characterized in that, The bottom center of the upper connecting seat (501) is machined with a hemispherical groove (505), and the top center of the lower connecting plate (502) is machined with a lower hemispherical groove (506). The universal ball head (503) is matched and disposed between the hemispherical groove (505) and the lower hemispherical groove (506) to form a spherical rotating pair.

6. The vacuum hot-press bonding apparatus according to claim 5, characterized in that, The floating leveling part also includes four guide posts (507) evenly distributed around the universal ball head (503). The top of the guide post (507) is fixed to the upper connecting seat (501), and the bottom of the guide post (507) passes through the gap hole of the lower connecting plate (502). Each guide post (507) is fitted with a high-temperature resistant disc spring (504).

7. The vacuum hot-press bonding apparatus according to claim 1, characterized in that, The servo drive unit also includes an incremental photoelectric encoder (303), which is connected to the AC servo motor (302) to obtain rotor position information and transmit it to the industrial control computer.

8. A control method applied to the vacuum hot-press bonding apparatus according to any one of claims 1 to 7, characterized in that, include: S1. Control the servo drive unit to work, and drive the upper pressing head (202) to move downward and approach the glass substrate (601) placed on the lower heating stage (201) through the transmission push rod (401). S2. Control the industrial control computer to continuously read the force value data of the strain gauge force gauge (402) and calculate the force value change rate. When the force value change rate is less than or equal to the preset contact threshold, control the AC servo motor (302) to maintain the current speed and decrease. When the force value change rate exceeds the preset contact threshold, control the AC servo motor (302) to reduce the speed to micro-stepping mode. S3. The floating leveling part absorbs the impact energy and tilts until the force value output by the strain gauge force gauge (402) reaches the preset leveling confirmation threshold, and the AC servo motor (302) is controlled to stop rotating to complete the passive leveling. S4. Control the lower heating stage (201) to heat up, read the current contact force in real time, and calculate the force deviation by subtracting the target bonding force from the current contact force. S5. Multiply the force deviation by the virtual compliance coefficient that represents the displacement compensation amount corresponding to the unit force deviation to calculate the downward displacement amount, and control the AC servo motor (302) to perform micro-motion compensation to complete the constant force application. S6. Control the lower heating platform (201) to stop heating, divide the time axis of the cooling process into multiple intervals, and calculate the descent gradient of the force value in each interval; S7. Multiply the descent gradient by the pre-calibrated thermal stress release coefficient to obtain the lower limit of the safe contact force, and control the AC servo motor (302) to reverse and retract, so that the real-time contact force dynamically approaches and is not lower than the lower limit of the safe contact force to attenuate, thereby completing the thermal stress unloading. S8. When the temperature drops to the preset safe room temperature range and the real-time contact force decays to the zero-point error allowable range, control the AC servo motor (302) to quickly reverse to lift the upper pressure head (202); repeat the steps S1 to S8 above.

9. The control method according to claim 8, characterized in that, The transmission push rod (401) is driven to extend and retract in the vertical direction of the vacuum chamber (102); before step S1, the following steps are included: S0, controlling the robot to place the two aligned glass substrates (601) on the top surface of the lower heating stage (201), and controlling the vacuum pump to start to evacuate the vacuum chamber (102) to the target vacuum level.

10. The control method according to claim 8, characterized in that, In step S5: when the force deviation is positive, the industrial control computer is controlled to convert the downward displacement into a target pulse number and drive the AC servo motor (302) to move downward; when the force deviation is negative, the industrial control computer is controlled to drive the AC servo motor (302) to move backward after conversion. When the absolute value of the force deviation falls into the preset error dead zone range, the industrial control computer is controlled to keep the current position of the AC servo motor (302) unchanged.

Images