Rigidity measuring device and method of wafer thinning machine

Abstract

The invention discloses a rigidity measuring device and method for a wafer thinning machine. The rigidity measuring device comprises a force application module, a displacement measuring module, a visual auxiliary module and a signal processing module. A composite structure of an arc-shaped force application plate, a piezoelectric ceramic piece and a belleville spring is adopted as a core force application unit, the piezoelectric ceramic piece loads and simulates real grinding force, and the belleville spring provides force application buffering; in the data processing process, the instantaneous rigidity value is calculated in real time, the curvature change of the acting force-displacement curve is dynamically analyzed, and when the rigidity sudden change condition is met or the curvature changes remarkably, abnormity is recognized in time, and testing is stopped. According to the invention, the problem that the rigidity of the whole machine cannot be measured in a narrow space of the thinning machine due to geometric mismatch and overlarge thickness is solved, the integrated overload protection mechanism ensures the safety, the innovative data processing method can capture rigidity mutation in real time, and the accuracy and reliability of rigidity evaluation of equipment in a stable working interval are remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of mechanical measurement, and in particular relates to a device and method for measuring the stiffness of a wafer thinning machine. Background Art

[0002] Wafer thinning, a key process in semiconductor power device manufacturing, is directly impacted by the performance of the thinning machine's grinding system (turntable-bed-column-spindle). During the thinning process, the arc-shaped contact interface between the grinding wheel spindle and the turntable is subjected to continuous offset grinding forces. The resulting nonlinear elastic deformation of the thinning machine has become a key bottleneck restricting improved machining accuracy. As a core performance indicator for resisting offset grinding forces, the precise measurement of grinding system stiffness is the core technical foundation for quantitatively evaluating machine tool dynamic performance and guiding the optimization of the turntable-bed-column-spindle stiffness chain structure. It is also a prerequisite for achieving stable processing of large wafers.

[0003] Existing stiffness measurement devices primarily focus on key functional components (such as the spindle) in lathes and CNC machine tools. These devices typically employ force-applying modules such as pneumatic, electric, or hydraulic cylinders. A rigid loading head fixed to a worktable applies load to these individual components, and displacement sensors are used to record displacement to determine their stiffness. Currently, no device exists that can simulate the grinding process within this compact space and measure the overall stiffness of a grinding system.

[0004] There are three significant defects in the existing stiffness measurement device: First, the point / line contact loading mode is geometrically mismatched with the actual arc contact mode between the thinning machine spindle and the turntable, resulting in a serious deviation of the load distribution state from the actual grinding working conditions; second, the overall thickness of the force module significantly exceeds the actual working distance between the grinding wheel spindle and the turntable, and an external air compressor, hydraulic station and other additional power units are required, which basically loses the installation feasibility in the stiffness measurement of the thinning machine grinding system and greatly increases the measurement cost; third, the existing measurement device does not integrate the overload protection module with the machine tool control system. When the applied force increases abnormally or exceeds the tolerance of the machine tool, the Z-axis feed system cannot be linked to emergency braking, and there is an uncontrollable risk of structural damage.

[0005] In addition, existing stiffness data processing methods mainly obtain stiffness curves by fitting discrete load-displacement points. Such methods have essential limitations: their data processing process completely relies on the final overall differential algorithm and lacks real-time piecewise linear fitting capabilities, resulting in the inability to timely identify abnormal data such as stiffness mutations, ultimately causing the stiffness assessment value in the system's stable working area to deviate from the true value. Summary of the Invention

[0006] In order to overcome the defects and shortcomings of the existing stiffness measurement technology, the present invention aims to provide a stiffness measurement device and method for a wafer thinning machine, which can realize the stiffness measurement of the wafer thinning machine in a narrow grinding space.

[0007] In order to achieve the above-mentioned purpose, the technical solution of the present invention is as follows: a stiffness measuring device for a wafer thinning machine, wherein the wafer thinning machine includes a bed, a worktable, a turntable, a vacuum suction cup, a spindle seat, a grinding wheel spindle, a Z-axis slide, a Z-axis motor, a Z-axis screw, a Z-axis guide rail and a CNC system.

[0008] The stiffness measuring device of the wafer thinning machine is hereinafter referred to as the stiffness measuring device, and includes a force application module, a displacement measurement module, a visual assistance module and a signal processing module.

[0009] The force application module is fixedly installed on the turntable, the displacement measurement module is fixedly installed on the grinding wheel spindle, and the visual assistance module is fixed on the spindle seat; the signal processing module is installed on the bed and is connected to the force sensor, displacement sensor and CNC system respectively through data cables.

[0010] Furthermore, the force module includes an arc-shaped force plate on the turntable side, a piezoelectric ceramic sheet, an adapter plate I, a butterfly spring, an adapter plate II, a micro piezoelectric actuator, a force sensor, an arc-shaped force plate on the grinding wheel spindle side, a force plate radius adjustment ring I, a force plate radius adjustment ring II and a guide column: the arc-shaped force plate on the turntable side is installed on the turntable, and a plurality of piezoelectric ceramic sheets are installed on the upper surface of the arc-shaped force plate on the turntable side. The adapter plate I is fixed on the top of the piezoelectric ceramic sheet, and butterfly springs are evenly distributed on the upper surface of the adapter plate I in the circumferential direction. The top of the butterfly spring abuts the adapter plate II, and a force sensor is installed on the upper surface of the adapter plate II, and the top of the force sensor is equipped with an arc-shaped force plate on the grinding wheel spindle side.

[0011] The outer coaxial sleeve of the arc-shaped force plate on the grinding wheel spindle side is provided with a force plate radius adjustment ring I and a force plate radius adjustment ring II. Micro piezoelectric actuators are evenly distributed on the lower surfaces of the force plate radius adjustment ring I and the force plate radius adjustment ring II, which are used to adjust the height of the force plate radius adjustment ring I and the force plate radius adjustment ring II; the arc-shaped force plate on the turntable side and the arc-shaped force plate on the grinding wheel spindle side are relative to each other through a vertically penetrating guide column.

[0012] Furthermore, the number of the piezoelectric ceramic sheets is determined according to the following formula: n × F single ≥ C × F max Where, n is the number of piezoelectric ceramic sheets, F single is the allowable thrust of a single piezoelectric ceramic piece, C is the safety factor, F maxThe maximum predetermined load required for wafer thinner stiffness measurement.

[0013] Furthermore, the displacement measurement module includes a fixed plate, a displacement sensor and a sensor support frame, the fixed plate is fixed on the grinding wheel spindle flange, the sensor support frame is installed below the fixed plate, and a plurality of displacement sensors are evenly distributed on the sensor support frame along the circumferential direction.

[0014] Furthermore, the visual assistance module includes a camera, a connecting plate and a magnetic base, the magnetic base is fixed on the spindle base, the connecting plate is installed at the end of the magnetic base, the camera is fixed under the connecting plate, and the lens of the camera is adjusted to the side of the grinding wheel spindle and the grinding wheel spindle side force plate to observe the contact state of the grinding wheel spindle and the grinding wheel spindle side force plate.

[0015] Furthermore, the signal processing module is connected to the force sensor, the displacement sensor and the numerical control system respectively, and is used to process the measured force and displacement data.

[0016] A method for measuring the stiffness of a wafer thinning machine, using a stiffness measuring device of the wafer thinning machine for measurement, comprises the following steps: H. Initialization Drive the Z-axis motor to drive the Z-axis slide through the Z-axis screw to raise the grinding wheel spindle to the upper limit of the Z-axis travel; fix the force module on the turntable and install the displacement measurement module on the end flange of the grinding wheel spindle; turn on the power supply of the piezoelectric ceramic piece, micro piezoelectric actuator, force sensor, displacement sensor and signal processing module.

[0017] I. Calibrate the force application surface posture According to the actual working conditions, the micro piezoelectric actuator is controlled to adjust the height of the force plate radius adjustment ring I and the force plate radius adjustment ring II so that their upper surfaces are coplanar with the force plate on the grinding wheel spindle side.

[0018] J. Establish a measurement benchmark Drive the Z-axis motor to move the grinding wheel spindle downward until the force plate on the grinding wheel spindle side contacts the grinding wheel spindle, then lock the Z-axis screw; adjust the installation height of the displacement sensor so that the distance between its measuring end and the upper surface of the vacuum suction cup is within the calibrated range, and record the initial displacement value. H 0; K. Hierarchical loading and data collection Control the piezoelectric ceramic piece to apply force to the grinding wheel spindle in a step-by-step load mode, with each load increment Δ F is the preset value, the constant load holding time ≥ T Seconds; real-time acquisition of load values ​​output by force sensors F i and the relative displacement measured by the displacement sensor Hi , i is the current measurement sequence number; L. Overload protection response When the conditions are met F ≥ F max or | H i – H 0| ≥ Δ H max When the overload protection program is triggered: the loading is stopped immediately and the grinding wheel spindle is driven to the upper limit of the Z axis; the power supply of the stiffness measuring device is cut off; M. Real-time data processing and stiffness calculation when F < F max and| H i – H 0|<Δ H max Continuously collect force-displacement data and calculate stiffness values ​​in real time K =Δ F / Δ H =( F i – F i–1 ) / | H i – H i–1 |, generate stiffness change curve; N. End of measurement: Complete the maximum predetermined load F max After the test or overload protection is triggered, the measurement ends.

[0019] Furthermore, the data processing method in step F includes the following steps: F1. Calculate real-time stiffness During the graded loading process, when the real-time load value F When the fluctuation amplitude is ≤C1%, the displacement value is collected H i ; Based on the adjacent two-level load increment Δ F = F i - F i-1 and displacement change Δ H =| H i - H i-1 |, calculate the instantaneous stiffness value K =Δ F / ΔH =( F i – F i–1 ) / | H i – H i–1 |;. F2. Judgment of curve mutation Real-time analysis of the curvature change rate of the force-displacement curve. When the curvature suddenly changes, segmented processing is performed: cubic spline interpolation fitting is used for the preload stage data; in the linear deformation stage, a segmented linear regression analysis is performed every time N measurement data points are accumulated; F3. Determine stiffness mutation If satisfied | K i – K i-1 | / K i-1 >C2%, the stiffness is judged to have a sudden change and the test is terminated.

[0020] F4. Calculate the comprehensive stiffness value of the stable working range Extract all stiffness values ​​calculated by piecewise linear regression K 1. K 2. ... K m , perform arithmetic averaging on all the above stiffness values ​​to obtain the comprehensive stiffness value in the stable working range: ∑ .

[0021] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention uses a force module composed of an arc-shaped force plate on the turntable side and an arc-shaped force plate on the grinding wheel spindle side, combined with a micro piezoelectric actuator to drive the axial lifting and lowering of the force plate radius adjustment ring, to adjust the contact area of ​​the effective arc surface of the force plate, and accurately reproduce the offset grinding force distribution state between the spindle and the turntable under thinning conditions, as well as the stiffness measurement requirements under different grinding wheel tooth widths.

[0022] 2. The present invention uses a composite structure of piezoelectric ceramic sheets and butterfly springs to achieve force loading. Piezoelectric ceramic sheets can generate hundreds to thousands of Newtons of force between the grinding wheel spindle and the turntable. To meet higher force requirements, multiple piezoelectric ceramic sheets can be stacked and used. At the same time, the butterfly spring group uses its nonlinear deformation characteristics to provide a flexible buffer for the force application process, effectively avoiding damage to the spindle system due to instantaneous overload. Compared with traditional cylinder, electric cylinder or hydraulic cylinder force modules, the force module of the present invention has a compact structure and can effectively compress the thickness of the device to the limited space of grinding.

[0023] 3. The present invention realizes the force during loading by establishing real-time communication between the signal processing module and the numerical control system. F ) and relative displacement ( H ) real-time monitoring. When an overload risk is detected ( F ≥ F max or | H – H 0| ≥ Δ H max ), the system immediately stops loading and drives the grinding wheel spindle to a safe position (the upper limit of the Z-axis travel). This invention overcomes the lack of an active overload protection mechanism in traditional measurement methods, effectively preventing damage or even destruction of the grinding wheel spindle due to overload during testing, significantly improving the safety of the measurement process and the protection capabilities of the equipment.

[0024] 4. The stiffness data processing method proposed in this invention can not only calculate the instantaneous stiffness value in real time ( K = Δ F / Δ H ), and can analyze the curvature change of the force-displacement curve when a sudden change in stiffness value is detected (satisfying | K i – K i-1 | / K i-1 When the curve curvature changes significantly (>C2%) or the system promptly identifies and determines that the stiffness is abnormal or the structure has entered a nonlinear phase. Compared with traditional offline data processing methods, real-time stiffness calculation and analysis improves the accuracy and reliability of the wafer thinning machine's stiffness performance assessment within the stable operating range. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural schematic diagram of the wafer thinning machine stiffness measurement device of the present invention; Figure 2 yes Figure 1 A partial enlarged view of point A in the middle; Figure 3 It is a structural schematic diagram of the force application module of the present invention; Figure 4 yes Figure 3 Partial cross-sectional view along BB direction; Figure 5 This is an exploded view of the force application module of the present invention; Figure 6 This is a schematic diagram of adjusting the radius of the force applying plate in the force applying module of the present invention; Figure 7 Schematic diagram of the displacement measurement module structure of the present invention; Figure 8This is a schematic diagram of the stiffness measurement principle of the wafer thinning machine of the present invention; Figure 9 It is a flow chart of the stiffness measurement of the wafer thinning machine of the present invention; Figure 10 It is a method for processing the stiffness data of a wafer thinning machine of the present invention; Figure 11 Schematic diagram of the static stiffness curve of the grinding system provided by an embodiment of the present invention.

[0026] Figure: 1. Bed; 2. Workbench; 3. Turntable; 4. Vacuum suction cup; 5. Visual assistance module; 501. Camera; 502. Connecting plate; 503. Magnetic table base; 6. Spindle seat; 7. Grinding wheel spindle; 8. Z-axis slide; 9. Z-axis motor; 10. Z-axis lead screw; 11. Z-axis guide rail; 12. Column; 13. Displacement measurement module; 1301. Fixing plate; 1302. Displacement sensor; 1303. Sensor support frame ; 14. Force-applying module; 1401. Arc-shaped force-applying plate on the turntable side; 1402. Piezoelectric ceramic sheet; 1403. Adapter plate I; 1404. Butterfly spring; 1405. Adapter plate II; 1406. Micro piezoelectric actuator; 1407. Force sensor; 1408. Arc-shaped force-applying plate on the grinding wheel spindle side; 1409. Force-applying plate radius adjustment ring I; 1410. Force-applying plate radius adjustment ring II; 1411. Guide column; 15. Signal processing module. DETAILED DESCRIPTION

[0027] The present invention is described in detail below with reference to the accompanying drawings and embodiments: The overall structure of an embodiment of the wafer thinning machine stiffness measuring device of the present invention is as follows: Figure 1 The wafer thinning machine includes, but is not limited to, a bed 1, a worktable 2, a turntable 3, a vacuum chuck 4, a spindle seat 6, a grinding wheel spindle 7, a Z-axis slide 8, a Z-axis motor 9, a Z-axis lead screw 10, a Z-axis guide rail 11, a column 12, and a numerical control system. The stiffness measurement device includes a visual assistance module 5, a displacement measurement module 13, a force application module 14, and a signal processing module 15.

[0028] In this embodiment, the displacement measurement module 13 is installed at the lower end of the grinding wheel spindle 7 near the grinding area, such as its flange end face; the force module 14 is arranged on the turntable 3; the visual assistance module 5 is installed at the lateral observation position of the contact interface between the grinding wheel spindle 7 and the force module 14, so as to observe the contact state, such as Figure 2 shown.

[0029] The specific implementation of each part is described as follows in conjunction with the accompanying drawings: The structure of the force application module 14 is as follows Figure 3-6It mainly consists of a turntable-side arc-shaped force-applying plate 1401, a piezoelectric ceramic sheet 1402, an adapter plate I 1403, a butterfly spring assembly 1404, an adapter plate II 1405, a micro piezoelectric actuator 1406, a force sensor 1407, a grinding wheel spindle-side arc-shaped force-applying plate 1408, a force-applying plate radius adjustment ring I 1409, a force-applying plate radius adjustment ring II 1410, and a guide post 1411.

[0030] A turntable-side arc-shaped force-applying plate 1401 is fixedly mounted on turntable 3, with its outer edge preferably tangent to the central rotation axis of turntable 3. The number of piezoelectric ceramic sheets 1402 is determined based on the required force and stacked above the turntable-side arc-shaped force-applying plate 1401 (for example, by adhesive bonding). An adapter plate I 1403 is mounted above the piezoelectric ceramic sheets 1402. Disc springs 1404 are evenly distributed along the circumference of the top surface of adapter plate I 1403. The radial position of the disc springs 1404 is constrained by positioning structures (for example, positioning grooves) provided on adapter plate I 1403. An adapter plate II 1405 is mounted above the disc springs 1404. Corresponding positioning structures (for example, positioning grooves) can be provided on the bottom surface of adapter plate II 1405 to constrain the position of the top ends of the disc springs 1404. A force sensor 1407 is fixedly mounted on the top surface of adapter plate II 1405. The force sensor 1407 can be a thin film pressure sensor, a resistance strain gauge sensor, or other sensor type capable of measuring pressure. The grinding wheel spindle side curved force application plate 1408 is fixedly mounted on the upper surface of the force sensor 1407. The guide post 1411 vertically passes through the turntable side curved force application plate 1401 and the grinding wheel spindle side curved force application plate 1408, and is used to guide the movement trajectory of the grinding wheel spindle side curved force application plate 1408 relative to the turntable side curved force application plate 1401, so that it can only move along the Z-axis direction.

[0031] In order to adapt to different grinding wheel structural sizes, the force module 14 of the present invention can achieve the adjustment of the force surface area: at least one force plate radius adjustment ring is provided on the outside of the arc-shaped force plate 1408 on the grinding wheel spindle side (such as the force plate radius adjustment ring I 1409 and the force plate radius adjustment ring II 1410 shown in the figure). The width of the force plate radius adjustment ring 1409 or the force plate radius adjustment ring 1410 is usually smaller than the width of the arc-shaped force plate 1408 on the grinding wheel spindle side, and the bottom thereof abuts against the micro piezoelectric actuator 1406. Several micro piezoelectric actuators 1406 are evenly distributed along the circumferential direction, and their radial arrangement positions need to be adapted to the size structure of the supported force plate radius adjustment ring I 1409 and the force plate radius adjustment ring II 1410 (for example, refer to Figure 6(See the arrangement and related dimensional parameters shown in the figure). The lower end of the micro-piezoelectric actuator 1406 is fixed to the adapter plate II 1405 (for example, by threading, bonding, or other fixing methods). Before measurement, according to the required force application surface area, the corresponding micro-piezoelectric actuator 1406 is driven to push the corresponding force application plate radius adjustment ring I 1409 or force application plate radius adjustment ring II 1410 axially until its upper end surface is substantially coplanar with the upper surface of the curved force application plate 1408 on the grinding wheel spindle side. This operation can adjust the actual contact area involved in force application.

[0032] The structure of the displacement measurement module 13 is as follows: Figure 7 It mainly consists of a fixing plate 1301, a displacement sensor 1302 and a sensor support frame 1303.

[0033] The fixed plate 1301 is fixedly mounted on the lower mounting surface (such as the flange end face) of the grinding wheel spindle 7. Below the fixed plate 1301, a sensor support frame 1303 with an arc structure is fixedly set. On the sensor support frame 1303, multiple mounting positions (such as the three mounting holes shown in the figure) are evenly distributed along the circumferential direction, and multiple displacement sensors 1302 are respectively installed in the mounting positions. The displacement sensor 1302 can be a contact type (such as inductive, capacitive) or a non-contact type (such as laser, eddy current) displacement sensor. Adjust the measuring end position of each displacement sensor 1302 so that it corresponds to the displacement of the selected point on the upper surface of the vacuum suction cup 4. Preferably, as Figure 2 As shown, these selected points include but are not limited to points passing through the center of the circle (such as point O ) and points symmetrically distributed on both sides of it (such as point M 、 N ).

[0034] The measuring principle of the stiffness measuring device is as follows Figure 8 The core of the method is: for machine tools with a C-shaped frame structure (such as wafer thinning machines), by applying a force between the grinding wheel spindle 7 and the turntable 3 and accurately measuring the relative displacement change between the two. The stiffness value (K) of the grinding system at the grinding position can be calculated by the load increment (Δ F ) and the corresponding relative displacement change (Δ H ) is calculated, that is, K = Δ F / Δ H .

[0035] The wafer thinning machine stiffness measurement process proposed by the present invention is as follows: Figure 9 The specific measurement steps are as follows: Step 1. Device Initialization: Start the wafer thinning machine's CNC system, drive the Z-axis motor 9 via the Z-axis leadscrew 10, and drive the Z-axis slide 8, raising the grinding wheel spindle 7 to its upper Z-axis travel limit. Secure the force application module 14 to the turntable 3, and install the displacement measurement module 13 on the end flange of the grinding wheel spindle 7. Turn on the power to the piezoelectric ceramic 1402, micro piezoelectric actuator 1406, force sensor 1407, displacement sensor 1302, and signal processing module 15.

[0036] Step 2: Calibrate the force surface posture: Based on the actual working conditions, control the micro piezoelectric actuator 1406 to adjust the height of the force plate radius adjustment ring I 1409 or the force plate radius adjustment ring II 1410 so that its upper surface is coplanar with the force plate 1408 on the grinding wheel spindle side.

[0037] Step 3: Establish the measurement reference: Drive the Z-axis motor 9 to move the grinding wheel spindle 7 downward until the grinding wheel spindle side force plate 1408 contacts the grinding wheel spindle 7, then lock the Z-axis position (for example, by tightening the Z-axis screw 10). Adjust the installation height of the displacement sensor 1302 so that the distance between its measuring end and the upper surface of the vacuum suction cup 4 is within the calibration range, and record the initial displacement reference value. H 0.

[0038] Step 4: Gradual loading and data acquisition: Control the piezoelectric ceramic 1402 to load the piezoelectric ceramic 1402 with a predetermined load increment (Δ F ) Carry out step-by-step load increase, and the constant load holding time after each level of loading shall not be less than the set time T . Real-time acquisition of the real-time load value output by the force sensor 1407 F i and the relative displacement measured by the displacement sensor 1302 H i (i is the current measurement number).

[0039] Step 5: Overload protection response: When the conditions are met F ≥ F max or | H i – H 0| ≥ Δ H max When the load plate and the grinding wheel spindle 7 are in contact, the overload protection program is triggered: loading is immediately stopped, the grinding wheel spindle 7 is driven to the upper limit of the Z axis, and the power supply to all measuring devices is cut off. In addition, during the force application process, when the loading force fluctuates momentarily, the butterfly spring 1404 uses its nonlinear deformation characteristics to produce flexible compression deformation. This deformation effectively absorbs impact energy, significantly reducing the peak impact load at the moment of contact between the force application plate and the grinding wheel spindle 7, and buffering force fluctuations during the loading process, thereby preventing micro-damage to the grinding wheel spindle system due to momentary overload or impact.

[0040] Step 6: Real-time data processing and stiffness calculation: F < F max and| H i – H 0|<Δ H max Continuously collect force-displacement data and calculate stiffness values ​​in real time K =Δ F / Δ H =( F i – F i–1 ) / | H i – H i–1 |, generate stiffness change curve.

[0041] Step 7, measurement end: complete the maximum predetermined load ( F max ) test or triggering the overload protection, the measurement process ends.

[0042] The wafer thinning machine stiffness data processing method of the present invention is as follows Figure 10 The specific measurement steps are as follows: Step 61: Real-time stiffness calculation During the graded loading process, when the real-time load value F When the fluctuation amplitude is ≤1%, the displacement value is collected H i ; Based on the adjacent two-level load increment Δ F = F i - F i-1 and displacement change Δ H =| H i - H i-1 |, calculate the instantaneous stiffness value K =Δ F / Δ H =( F i – F i–1 ) / | H i – H i–1 |;. Step 62: Determine the curve mutation Real-time analysis of the curvature change rate of the force-displacement curve. When the curvature suddenly changes, segmented processing is performed: cubic spline interpolation fitting is used for the preload stage data; in the linear deformation stage, a segmented linear regression analysis is performed every time N measurement data points are accumulated; Step 63: Determine stiffness mutation If satisfied | K i – K i-1 | / K i-1 >C2%, the stiffness is judged to have a sudden change and the test is terminated.

[0043] Step 64: Calculate the comprehensive stiffness value in the stable working range Based on the results of the segmented regression analysis of the linear deformation stage, the stiffness value of the grinding system of the wafer thinning machine under stable working conditions is determined. Figure 11 The stiffness curve measured in this embodiment is given.

[0044] Although the implementation example of the stiffness measurement device designed by the present invention is applied in the context of a single-axis wafer thinning machine, it is also applicable to the stiffness measurement of the grinding system of a multi-axis and multi-station fully automatic wafer thinning machine.

[0045] The above embodiment only expresses one embodiment of the present invention and should not be construed as limiting the scope of the present invention. All other embodiments obtained by a person skilled in the art without creative work fall within the scope of protection of the present invention.

Claims

1. A device for measuring the stiffness of a wafer thinning machine, the wafer thinning machine comprising a bed (1), a worktable (2), a turntable (3), a vacuum suction cup (4), a spindle seat (6), a grinding wheel spindle (7), a Z-axis slide (8), a Z-axis motor (9), a Z-axis lead screw (10), a Z-axis guide rail (11) and a numerical control system; Its characteristics are: The stiffness measuring device of the wafer thinning machine is hereinafter referred to as the stiffness measuring device, comprising a force application module (14), a displacement measurement module (13), a visual assistance module (5) and a signal processing module (15); The force application module (14) is fixedly mounted on the turntable (3), the displacement measurement module (13) is fixedly mounted on the grinding wheel spindle (7), and the visual assistance module (5) is fixed on the spindle seat (6); the signal processing module (15) is mounted on the bed (1) and is connected to the force sensor (1407), the displacement sensor (1302) and the numerical control system respectively through data cables.

2. The device for measuring the stiffness of a wafer thinning machine according to claim 1, wherein: The force application module (14) comprises a turntable side arc-shaped force application plate (1401), a piezoelectric ceramic sheet (1402), an adapter plate I (1403), a butterfly spring (1404), an adapter plate II (1405), a micro piezoelectric actuator (1406), a force sensor (1407), a grinding wheel spindle side arc-shaped force application plate (1408), a force application plate radius adjustment ring I (1409), a force application plate radius adjustment ring II (1410) and a guide column (1411): the turntable side arc-shaped force application plate (1401) is installed on the turntable (3), A plurality of piezoelectric ceramic sheets (1402) are mounted on the upper surface of the arc-shaped force-applying plate (1401) on the turntable side; an adapter plate I (1403) is fixed on the top of the piezoelectric ceramic sheet (1402); butterfly springs (1404) are evenly distributed along the circumferential direction on the upper surface of the adapter plate I (1403); the top of the butterfly spring (1404) abuts against the adapter plate II (1405); a force sensor (1407) is mounted on the upper surface of the adapter plate II (1405); and a grinding wheel spindle-side arc-shaped force-applying plate (1408) is mounted on the top of the force sensor (1407); A force plate radius adjustment ring I (1409) and a force plate radius adjustment ring II (1410) are coaxially sleeved on the outer side of the arc-shaped force plate (1408) on the grinding wheel spindle side. Micro piezoelectric actuators (1406) are evenly distributed on the lower surfaces of the force plate radius adjustment ring I (1409) and the force plate radius adjustment ring II (1410) for adjusting the height of the force plate radius adjustment ring I (1409) and the force plate radius adjustment ring II (1410). Relative displacement guidance is achieved between the turntable side arc-shaped force plate (1401) and the grinding wheel spindle side arc-shaped force plate (1408) via a vertically penetrating guide column (1411).

3. The stiffness measurement device for a wafer thinning machine according to claim 1, characterized in that: The number of the piezoelectric ceramic sheets (1402) is determined according to the following formula: n × F single ≥ C × F max Where, n is the number of piezoelectric ceramic sheets (1402), F single is the allowable thrust of a single piezoelectric ceramic piece (1402), C is the safety factor, F max The maximum predetermined load required for wafer thinner stiffness measurement.

4. The stiffness measurement device for a wafer thinning machine according to claim 1, characterized in that: The displacement measurement module (13) comprises a fixed plate (1301), a displacement sensor (1302) and a sensor support frame (1303), wherein the fixed plate (1301) is fixed to a flange of a grinding wheel spindle (7), the sensor support frame (1303) is installed below the fixed plate (1301), and a plurality of displacement sensors (1302) are evenly distributed on the sensor support frame (1303) along a circumferential direction.

5. The stiffness measurement device for a wafer thinning machine according to claim 1, characterized in that: The visual assistance module (5) includes a camera (501), a connecting plate (502) and a magnetic base (503), wherein the magnetic base (503) is fixed on the spindle base (6), the connecting plate (502) is installed at the end of the magnetic base (503), the camera (501) is fixed below the connecting plate (502), and the lens of the camera (501) is adjusted to the side of the grinding wheel spindle (7) and the side force plate of the grinding wheel spindle (7) so as to observe the contact state of the grinding wheel spindle (7) and the side force plate of the grinding wheel spindle (7).

6. The stiffness measurement device for a wafer thinning machine according to claim 1, characterized in that: The signal processing module (15) is connected to the force sensor (1407), the displacement sensor (1302) and the numerical control system respectively, and is used to process the measured force and displacement data.

7. A method for measuring the stiffness of a wafer thinning machine, comprising: The following steps are involved: A. Initialization The Z-axis motor (9) is driven to drive the Z-axis slide (8) through the Z-axis lead screw (10), so that the grinding wheel spindle (7) is raised to the upper limit of the Z-axis travel; the force application module (14) is fixed on the turntable (3), and the displacement measurement module (13) is installed on the end flange of the grinding wheel spindle (7); the power supply of the piezoelectric ceramic piece (1402), the micro piezoelectric actuator (1406), the force sensor (1407), the displacement sensor (1302) and the signal processing module (15) is turned on; B. Calibrate the force application surface posture According to actual working conditions, the micro piezoelectric actuator (1406) is controlled to adjust the height of the force plate radius adjustment ring I (1409) and the force plate radius adjustment ring II (1410) so that their upper surfaces are coplanar with the force plate on the grinding wheel spindle (7) side; C. Establish a measurement benchmark Drive the Z-axis motor (9) to move the grinding wheel spindle (7) downward until the side force plate of the grinding wheel spindle (7) contacts the grinding wheel spindle (7), and then lock the Z-axis screw (10); adjust the installation height of the displacement sensor (1302) so that the distance between its measuring end and the upper surface of the vacuum suction cup (4) is within the calibration range, and record the initial displacement value H 0; D. Load and collect data in stages The piezoelectric ceramic piece (1402) is controlled to apply a force to the grinding wheel spindle (7) in a step-by-step load increment mode, with each load increment Δ F is the preset value, the constant load holding time ≥ T Second; Real-time acquisition of load values ​​output by the force sensor (1407) F i and the relative displacement measured by the displacement sensor (1302) H i , i is the current measurement sequence number; E. Overload protection response When the conditions are met F ≥ F max or | H i – H 0| ≥ Δ H max When the overload protection program is triggered: the loading is stopped immediately and the grinding wheel spindle (7) is driven to the upper limit of the Z axis; the power supply of the stiffness measuring device is cut off; F. Real-time data processing and stiffness calculation when F < F max and| H i – H 0| < Δ H max Continuously collect force-displacement data and calculate stiffness values ​​in real time K =Δ F / Δ H =( F i – F i–1 ) / | H i – H i–1 |, generate stiffness change curve; G. End of measurement: Complete the maximum predetermined load F max After the test or overload protection is triggered, the measurement ends.

8. The method for measuring the stiffness of a wafer thinning machine according to claim 7, wherein: The data processing method in step F comprises the following steps: F1. Calculate real-time stiffness During the graded loading process, when the real-time load value F When the fluctuation amplitude is ≤C1%, the displacement value is collected H i ; Based on the adjacent two-level load increment Δ F = F i - F i-1 and displacement change Δ H =| H i - H i-1 |, calculate the instantaneous stiffness value K =Δ F / Δ H =( F i – F i–1 ) / | H i – H i–1 |;. F2. Judgment of curve mutation Real-time analysis of the curvature change rate of the force-displacement curve. When the curvature suddenly changes, segmented processing is performed: cubic spline interpolation fitting is used for the preload stage data; in the linear deformation stage, a segmented linear regression analysis is performed every time N measurement data points are accumulated; F3. Determine stiffness mutation If satisfied | K i – K i-1 | / K i-1 >C2%, it is determined that the stiffness has a sudden change and the test is terminated; F4. Calculate the comprehensive stiffness value of the stable working range Extract all stiffness values ​​calculated by piecewise linear regression K 1. K 2. ... K m , perform arithmetic averaging on all the above stiffness values ​​to obtain the comprehensive stiffness value in the stable working range: ∑ .

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