Chip flexible laminating mechanism based on series connection of positive stiffness and negative stiffness and control method

Abstract

The invention relates to the technical field of precision mechanical design and automatic control, and aims to solve the problems that a chip is easy to break and the laminating pressure is difficult to master in the laminating process. The invention discloses a chip flexible laminating mechanism based on positive and negative stiffness series connection and a control method. The chip flexible laminating mechanism comprises a control device, a laminating platform, and a driving motor, an execution mechanism, a position detection device, a positive and negative stiffness series connection mechanism, a sucker head and a chip placement base which are arranged on the laminating platform. The executing mechanism is movably arranged in the Z-axis direction and is connected with the driving motor; the position detection device is used for detecting and feeding back position information of the execution mechanism; the positive and negative stiffness series mechanism is connected with the execution mechanism; the suction cup head is arranged on the positive and negative stiffness series connection mechanism and located above the chip containing base, and the control device is connected with the driving motor and the position detection device. According to the invention, the soft contact of the chip can be realized, the stable fitting pressure can be provided, and an additional force sensor is not needed.

Description

Technical Field

[0001] The present invention relates to the technical field of precision machinery design and automation control, and specifically to a chip flexible bonding mechanism and control method based on the series connection of positive and negative stiffnesses. Background Art

[0002] Chip flexible bonding is one of the core technologies of chip packaging, which affects the quality, stability, and reliability of chip production and is crucial for producing high-quality chip packaging products. Because the chip material has the characteristic of being easily broken, it is necessary to precisely control the impact force and bonding force generated by the mechanism during the chip mounting process. Otherwise, it may cause adverse phenomena such as cracks, chipping, and hidden damage to the chip.

[0003] A mounting pressure correction method based on a high-precision die bonder for chips disclosed by Chen Shubin et al. in the Chinese invention patent CN117594491A mainly relies on a complex control algorithm to achieve bonding pressure control. It determines the pressure error compensation value according to the distance difference between the actual distance and the preset distance, and corrects the current control current value to adjust the actuator position in real time to achieve the soft landing of the suction cup head and constant force pressure holding. Its control is complex, and the algorithm is sensitive to mechanical parameters. If the parameters change, it is necessary to readjust the algorithm to give appropriate control compensation, which is not conducive to modular production. Summary of the Invention

[0004] In order to at least solve one of the problems existing in the prior art, the present invention provides a chip flexible bonding mechanism and control method based on the series connection of positive and negative stiffnesses, which has high reliability and strong anti-interference ability, can achieve soft contact between the suction cup head and the chip and output a constant bonding pressure, ensure chip flexible bonding, and can solve the problems of easy chip breakage and difficult bonding pressure control during the bonding process.

[0005] To achieve the object of the present invention, a chip flexible bonding mechanism based on the series connection of positive and negative stiffnesses provided by the present invention includes a control device, a bonding platform, and a driving motor, an actuator, a position detection device, a positive and negative stiffness series mechanism, a suction cup head, and a chip placement base arranged on the bonding platform;

[0006] The actuator is movably arranged in the Z-axis direction and is connected to the driving motor. The mover of the driving motor drives the actuator to move in the Z-axis direction;

[0007] The position detection device is used to detect and feedback the position information of the actuator;

[0008] The positive and negative stiffness series mechanism is connected to the actuator;

[0009] The suction cup head is arranged on the positive and negative stiffness series mechanism, and the suction cup head is located above the chip placement base.

[0010] The control device is connected to both the drive motor and the position detection device.

[0011] Furthermore, it also includes a drive board which is connected to the drive motor and the control device to drive the drive motor to drive the actuator to move.

[0012] The control device controls the drive board to drive the drive motor to drive the actuator to move, and according to the set control strategy, accurate position control is achieved.

[0013] Furthermore, the drive board is also connected to an external power supply.

[0014] According to the detected position information of the actuator, a control signal is input to the drive board, and the actuator is driven to move to a preset height, and then slowly descends a fixed distance (working distance). The positive and negative stiffness series mechanism drives the suction cup head to achieve soft contact with the chip and provide a stable output of the bonding pressure. After moving the fixed downward displacement and maintaining for a certain time, it returns to complete the chip bonding movement.

[0015] Furthermore, it also includes a spring which is arranged along the Z-axis direction, and both ends of the spring are respectively connected to the bonding platform and the actuator. The spring is used to compensate for the gravity of the actuator. When the actuator is stationary, the gravity and the elastic force cancel each other out, and the actuator stays within the stroke range.

[0016] Furthermore, both between the positive and negative stiffness series mechanism and the actuator, and between the suction cup head and the positive and negative stiffness series mechanism are connected by threads.

[0017] The upper threaded interface of the positive and negative stiffness series mechanism is connected to the actuator, and the lower threaded interface is connected to the suction cup head.

[0018] Furthermore, the position detection device adopts an open linear grating scale, which is installed in the Z-axis direction, and the displacement of the actuator detected is the displacement at the end of the actuator.

[0019] The control device uses a single-chip microcomputer, the drive motor is a linear voice coil motor, and the drive board is PWM-driven. The way to obtain the displacement of the actuator is that the position signal acquisition circuit on the drive board processes the pulse signal fed back by the open linear grating scale, and then inputs it to the single-chip microcomputer. The counting module of the single-chip microcomputer counts the pulses, calculates the required control quantity, and the single-chip microcomputer changes the duty cycle of the output PWM to control the movement of the drive motor.

[0020] Furthermore, through the upper computer burning the corresponding algorithm into the single-chip microcomputer to calculate the required control quantity, the single-chip microcomputer controls the drive board to drive the drive motor to drive the actuator to move, and accurate position control is achieved.

[0021] Further, the actuator includes a motor and a connector. The connector is connected to the output end of the motor, and the connector is connected to the positive and negative stiffness series mechanism.

[0022] Further, the positive and negative stiffness series mechanism includes a straight beam mechanism and a curved beam mechanism. The straight beam mechanism and the curved beam mechanism are superposed on each other to provide a buffering effect and a constant bonding force when the suction cup head contacts the chip. Among them, the straight beam mechanism is closer to the suction cup head, and the curved beam mechanism is closer to the actuator.

[0023] Further, the stiffness of the positive and negative stiffness series mechanism changes with displacement. When considering the curved beam mechanism alone, when the positive and negative stiffness series mechanism moves downward, the positive stiffness of the overall mechanism can be realized; when considering the straight beam mechanism alone, when the positive and negative stiffness series mechanism moves downward, the stiffness of the overall mechanism first becomes positive and then negative.

[0024] Further, the straight beam mechanism of the positive and negative stiffness series mechanism is used to realize that the slope of the force-displacement relationship curve is first positive and then negative, and the curved beam mechanism of the positive and negative stiffness series mechanism is used to realize that the slope of the force-displacement relationship curve is positive. The two are connected in series and superposed to provide a constant force output under certain displacement conditions.

[0025] The present invention also provides a control method for a chip flexible bonding mechanism based on a positive and negative stiffness series, including the steps of:

[0026] The control device receives the position pulse data fed back by the position detection device to obtain the position information of the actuator;

[0027] Compare the position information of the actuator with the preset descent height to obtain a control quantity;

[0028] The control device controls the driving motor to move based on the control quantity, so that the actuator quickly moves to the preset descent height;

[0029] The control device slowly controls the actuator to descend to the working height through the driving motor, and the positive and negative stiffness series mechanism drives the suction cup head to realize soft contact with the chip and provide a stable output of the bonding pressure.

[0030] Compared with the prior art, the present invention has the following advantages:

[0031] The chip flexible bonding device based on the positive and negative stiffness series mechanism of the present invention obtains the end displacement of the actuator through the position detection device. After the control device controls the actuator to descend to the preset height, it slowly descends a certain displacement, realizes soft contact with the chip based on the positive and negative stiffness series mechanism, and realizes continuous and stable output of the bonding pressure. Without an additional force sensor, it realizes flexible contact between the suction cup head and the chip and continuously and stably outputs the bonding pressure to ensure chip flexible bonding. Description of the Drawings

[0032] Figure 1It is a schematic diagram of a chip flexible bonding mechanism based on series connection of positive and negative stiffness provided by an embodiment of the present invention.

[0033] Figure 2 It is a schematic diagram of the actuator provided by an embodiment of the present invention.

[0034] Figure 3 It is a schematic diagram of a positive and negative stiffness series mechanism proposed by an embodiment of the present invention.

[0035] In the figure, 1 - base; 2 - driving motor; 3 - chip placement base; 4 - positive and negative stiffness series mechanism; 5 - actuator; 6 - slide rail device; 7 - L-shaped fixing bracket; 8 - position detection device; 9 - suction cup head; 10 - spring; 11 - mounting base; 41 - upper threaded interface; 42 - curved beam mechanism; 43 - straight beam mechanism; 44 - lower threaded interface; 51 - hollow motor; 52 - L-shaped slide rail device; 53 - connector. Detailed implementation manners

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts are within the scope of protection of the present invention.

[0037] Please refer to Figures 1 to 3 , a chip flexible bonding mechanism based on series connection of positive and negative stiffness provided by the present invention includes a bonding platform, a driving motor 2, an actuator 5, a driving plate, a chip placement base 3, a positive and negative stiffness series mechanism 4, a suction cup head 9, and a control device.

[0038] The bonding platform includes a base 1 and a chip placement base 3 and a mounting base 11 provided on the base 1. In some embodiments of the present invention, please refer to Figure 1 , the mounting base is a vertical plate seat in a T shape.

[0039] The driving plate is connected to the driving motor 2, the actuator 5 is connected to the driving motor 2, the driving plate drives the driving motor 2, and further drives the actuator 5 to move; the upper end of the positive and negative stiffness series mechanism 4 is connected to the actuator 5, and the lower end is connected to the suction cup head 9, which is used to provide a buffering effect and a constant bonding force when the suction cup head 9 contacts the chip.

[0040] Please refer to Figure 1, the driving motor 2 is arranged on the mounting base through an L-shaped fixing bracket 7; a slide rail device 6 is arranged on the mounting base, the actuator 5 is slidably arranged on the slide rail device 6, and a position detection device 8 is installed on the side of the slide rail device 6. The position detection device 8 is used to detect and feedback the position information of the actuator 5; the actuator 5 is connected to the mover of the driving motor 2, the lower end of the actuator 5 is connected to the positive and negative stiffness series mechanism 4, and the positive and negative stiffness series mechanism 4 is connected to the suction cup head 9. The suction cup head 9 is located directly above the chip placement base 3.

[0041] The control device is connected to the driving motor 2, the driving board, the position detection device 8 and the host computer. According to the position information of the actuator 5 detected and collected by the position detection device 8, a control signal is input to the driving board to drive the actuator 5 to move to a preset height, and then slowly descend. The positive and negative stiffness series mechanism 4 drives the suction cup head 9 to achieve soft contact with the chip and provide a stable output of the fitting pressure. After moving a fixed downward displacement and maintaining for a certain period of time, it returns to complete the chip fitting movement. To prevent overshoot caused by inaccurate point-to-point control and impact on the chip by the suction cup head 9, the distance in the rapid descent stage is preset in advance, leaving sufficient safety redundancy, and slowly descending after reaching the preset height.

[0042] In some embodiments of the present invention, the driving motor 2 adopts a servo voice coil linear motor, the driving board is PWM-driven, and the control device adopts an STM32H723 single-chip microcomputer. The STM32H723 single-chip microcomputer is connected to the host computer, the driving board and the position detection device 8, and the driving board is connected to the driving motor 2, the STM32H723 single-chip microcomputer and an external power supply.

[0043] In some embodiments of the present invention, the position detection device 8 adopts an open linear grating scale and is installed on the side of the slide rail device 6. The reading head of the open linear grating scale is fixed, and the open grating scale installed on the side of the slide rail device 6 moves up and down with the driving motor 2 driving the actuator 5. The position signal feedback by the reading head is the displacement output by the actuator 5.

[0044] In some embodiments of the present invention, a spring 10 is further provided. One end of the spring 10 is connected to the mounting base 11, and the other end is connected to the actuator 5 along one end in the Z-axis direction.

[0045] When the driving motor 2 stops driving and remains stationary, the spring deformation force is equal to the weight of the actuator 5. The spring 10 pulls the actuator 5 to the equilibrium position, and the position of the actuator 5 is in the middle of the displacement range. During operation, if the driving motor 2 has an abnormal power failure, the spring 10 can prevent the actuator 5 from continuing to move along the Z-axis and damaging the workpiece, thus playing a role in protecting the workpiece.

[0046] The actuator 5 includes a hollow motor 51, an L-shaped slide rail device 52, and a connector 53. A hollow shaft is provided at the center of the hollow motor 51, allowing air pipes, cables, etc. to pass through, which is responsible for reducing external wiring and simplifying the system complexity; the L-shaped slide rail device 52 mounts the actuator 5 on the slide rail device 6 to keep it moving along the Z-axis; the connector 53 is connected to the hollow motor 51, and the connector 53 is connected to the positive and negative stiffness series mechanism 4. If chip angle alignment is required during the bonding process (such as rotational mounting), the hollow motor 51 can drive the positive and negative stiffness series mechanism 4, and then drive the suction cup head 9 to drive the chip to rotate around the Z-axis.

[0047] The positive and negative stiffness series mechanism 4 includes four parts: an upper threaded interface 41, a curved beam mechanism 42, a straight beam mechanism 43, and a lower threaded interface 44. The upper threaded interface 41 is connected to the end of the actuator 5, that is, the connector 53, the lower threaded interface 44 is connected to the suction cup head 9, and the curved beam mechanism 42 and the straight beam mechanism 43 are connected in series and superimposed to provide buffering for the suction cup head 9 to contact the chip and a constant bonding force.

[0048] In some embodiments of the present invention, such as Figure 3 shown, the curved beam mechanism 42 includes 3 curved beams, the straight beam mechanism 43 includes 3 straight beams, and each curved beam is correspondingly located above a straight beam.

[0049] According to the characteristics of the mechanism, from the perspective of input and output, a single straight beam and a single curved beam are connected in parallel to form a unit. This unit is realized through a 120° circumferential array to obtain a mechanism composed of 3 units. However, during the loading process of the 3 units, the radial forces at the two ends of the unit cancel each other out due to the circumferential array, leaving only the axial force.

[0050] The axial direction has a constant force characteristic. Considering the straight beam mechanism 43 in the upper half of the positive and negative stiffness series mechanism 4 alone, the straight beam mechanism 43 includes a vertical elastic beam. In the initial stage, the stiffness of the straight beam mechanism 43 is positive, that is, the stiffness k1 of the straight beam mechanism 43 > 0. At this time, as the displacement increases, the force output by the straight beam mechanism 43 is positive. When the displacement exceeds the designed critical value of the mechanism, the straight beam mechanism 43 bends, and the stiffness turns negative and gradually increases, that is, the stiffness k1 of the straight beam mechanism 43 < 0. Considering the curved beam mechanism 42 in the lower half of the positive and negative stiffness series mechanism 4 alone, when the curved beam mechanism 42 is compressed, the arc-shaped elastic beam gradually unfolds and transmits the force to the straight beam mechanism 43 in the upper half. At this time, the stiffness of the curved beam mechanism 42 increases linearly, that is, the stiffness k2 of the curved beam mechanism 4 gradually increases from a lower value until the upper limit.

[0051] When the positive-negative stiffness series mechanism 4 drives the suction cup head 9 to just come into contact with the chip placement base 3, the stiffness k = k1 + k2 of the positive-negative stiffness series mechanism 4 is at a relatively small value, realizing the soft landing of chip bonding. As the suction cup head 9 continues to descend, the reaction force of the chip on the suction cup head 9 is transmitted to the positive-negative stiffness series mechanism 4. The stiffness of the curved beam mechanism 42 increases linearly, and the stiffness of the straight beam mechanism 43 changes from positive to negative, that is, the straight beam mechanism 43 exhibits negative stiffness characteristics after the displacement exceeds the critical value, and the negative stiffness offsets the curved beam stiffness through the buckling effect; until the negative stiffness of the straight beam mechanism 43 is equal to the positive stiffness of the curved beam mechanism 42, the overall stiffness approaches 0. At this time, the resultant force is a constant value, keeping the stiffness of the positive-negative stiffness series mechanism 4 at 0 for a certain displacement, then the force output by the positive-negative stiffness series mechanism 4 is a constant value.

[0052] A control method for a chip flexible bonding mechanism based on positive-negative stiffness series includes:

[0053] The control device receives the position pulse data feedback by the position detection device 8 to obtain the position information of the actuator 5, compares it with the preset descent height, and calculates the control amount; according to the control amount, the control device changes the duty cycle of the output PWM, and the drive board controls the movement of the drive motor 2 to realize the position update until the actuator 5 reaches the preset height; subsequently, the control device changes the control strategy, changing from the fast descent mode to the slow and uniform descent mode, and remains stationary for a certain time after moving the set displacement distance and then returns.

[0054] In some embodiments of the present invention, first, the upper computer burns the set position information of each stage to the STM32H723 single-chip microcomputer. The position detection device 8 obtains the position information of the actuator 5 in real time, and transmits the obtained position pulse signal data of the current actuator 5 to the counting module of the STM32H723 single-chip microcomputer for pulse counting. According to the current-velocity-position three-closed-loop PID control algorithm burned by the upper computer to the single-chip microcomputer, the control quantity is calculated in the position mode. The STM32H723 single-chip microcomputer changes the duty cycle of the output PWM to control the movement of the driving motor 2 to achieve position update; when the actuator 5 reaches the preset height, it stops moving and slowly descends. The positive and negative stiffness series mechanism 4 provides the soft contact and bonding force required for chip bonding; the displacement of the slow descent is a preset fixed value. When the positive and negative stiffness series mechanism 4 drives the suction cup head 9 to just contact the chip, the stiffness of the curved beam mechanism 42 and the straight beam mechanism 43 is positive, reflecting the dynamic performance of the spring and ensuring the soft contact between the suction cup head 9 and the chip. When continuing to descend, the straight beam mechanism 43 is distorted and the stiffness becomes negative. The straight beam mechanism 43 and the curved beam mechanism 42 are connected in series and superimposed to provide a constant force output for a certain displacement, that is, the stiffness characteristics of the straight beam mechanism 43 and the curved beam mechanism 42 are complementary, and a constant force is synthesized within a specific displacement interval. The displacement value range of the slow descent of the actuator 5 during the contact stage is always smaller than the constant force output displacement value of the positive and negative stiffness series mechanism 4. After the fixed descent value is completed and stays for a certain time, it rises to achieve the pressure holding and bonding effect of the chip.

[0055] The main functions of the embodiments of the present invention: The chip flexible bonding mechanism based on the positive and negative stiffness series mechanism in the embodiments of the present invention obtains the displacement of the actuator 5 through the position detection device 8. After the control device controls the actuator 5 to descend to the preset height, it slowly descends by a certain displacement. The chip flexible bonding mechanism based on the positive and negative stiffness series mechanism realizes the soft contact with the chip and outputs a stable bonding pressure, and can realize the flexible contact between the suction cup head 9 and the chip without additional force sensors and precise motion control algorithms, and continuously and stably outputs the bonding pressure to ensure the flexible bonding of the chip.

[0056] The above embodiments are the preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and shall be included in the protection scope of the present invention.

Claims

1. A chip flexible bonding mechanism based on the series connection of positive and negative stiffness, characterized in that It includes a control device, a bonding platform, a driving motor, an actuator, a position detection device, a positive and negative stiffness series mechanism, a suction cup head and a chip placement base arranged on the bonding platform; The actuator is movably arranged in the Z-axis direction and is connected to the driving motor; The position detection device is used to detect and feedback the position information of the actuator; The positive and negative stiffness series mechanism is connected to the actuator; The suction cup head is arranged on the positive and negative stiffness series mechanism, and the suction cup head is located above the chip placement base. The control device is connected to both the driving motor and the position detection device.

2. The chip flexible bonding mechanism based on the series connection of positive and negative stiffnesses according to claim 1, wherein It also includes a driving board, which is connected to the driving motor and the control device and is used to drive the driving motor to drive the actuator to move.

3. The chip flexible bonding mechanism based on the series connection of positive and negative stiffness according to claim 1, characterized in that, It also includes a spring, which is arranged along the Z-axis direction, and both ends of the spring are respectively connected to the bonding platform and the actuator.

4. A chip flexible bonding mechanism based on the series connection of positive and negative stiffnesses according to claim 1, characterized in that, Both between the positive and negative stiffness series mechanism and the actuator, and between the suction cup head and the positive and negative stiffness series mechanism are connected by threads.

5. A chip flexible bonding mechanism based on the series connection of positive and negative stiffnesses according to claim 1, characterized in that, The position detection device adopts an open linear grating scale, which is installed in the Z-axis direction, and the displacement of the actuator detected is the displacement of the end of the actuator.

6. The chip flexible bonding mechanism based on the series connection of positive and negative stiffness according to claim 1, characterized in that, The actuator includes a motor and a connecting head, the connecting head is connected to the output end of the motor, and the connecting head is connected to the positive and negative stiffness series mechanism.

7. A chip flexible bonding mechanism based on the series connection of positive and negative stiffnesses according to any one of claims 1-6, characterized in that, The positive and negative stiffness series mechanism includes a straight beam mechanism and a curved beam mechanism. The straight beam mechanism and the curved beam mechanism are superposed on each other to provide a buffering effect and a constant bonding force when the suction cup head contacts the chip. Among them, the straight beam mechanism is closer to the suction cup head, and the curved beam mechanism is closer to the actuator.

8. A chip flexible bonding mechanism based on series connection of positive and negative stiffnesses according to claim 7, characterized in that, The stiffness of the positive and negative stiffness series mechanism changes with displacement. When considering the curved beam mechanism alone, when the positive and negative stiffness series mechanism moves downward, the positive stiffness of the overall mechanism can be achieved; when considering the straight beam mechanism alone, when the positive and negative stiffness series mechanism moves downward, the stiffness of the overall mechanism first becomes positive and then negative.

9. A chip flexible bonding mechanism based on series connection of positive and negative stiffness according to claim 7, characterized in that, The straight beam mechanism of the positive and negative stiffness series mechanism is used to achieve that the slope of the force-displacement relationship curve is first positive and then negative, and the curved beam mechanism of the positive and negative stiffness series mechanism is used to achieve that the slope of the force-displacement relationship curve is positive. The two are connected in series and superposed to provide a constant force output under certain displacement conditions.

10. A control method for a chip flexible bonding mechanism based on series connection of positive and negative stiffness, characterized in that, It includes steps: The control device receives the position pulse data feedback by the position detection device (8) to obtain the position information of the actuator (5); Compare the position information of the actuator (5) with the preset descent height to obtain a control quantity; The control device controls the movement of the driving motor (2) based on the control quantity to make the actuator (5) quickly move to the preset descent height; The control device slowly controls the actuator (5) to descend to the working height through the driving motor (2), and the positive and negative stiffness series mechanism (4) drives the suction cup head (9) to achieve soft contact with the chip and provide a stable output of the bonding pressure.

Images