Electronic component mounting pressure self-adaptive control method

Abstract

The application provides an electronic component mounting pressure self-adaptive control method, and relates to the technical field of electronic manufacturing equipment, and comprises the following steps: preparing mounting pressure control tools and equipment, and providing a mounting pressure control hardware platform; calibrating a down pressure sensor with a standard weight, and mutually calibrating an up pressure sensor based on the calibrated down pressure sensor; driving a mounting head assembly to make a suction nozzle contact a pressure correction platform at different down pressure depths, recording pressure values corresponding to each down pressure depth, establishing and storing a pressure-position curve; obtaining material characteristic information of a current batch of components to be mounted, and obtaining an initial mounting pressure target value of the current batch based on similarity matching calculation of the material characteristic information and historical batches; and the mounting head assembly is driven to move to a substrate direction under a motion control instruction generated by a monitoring system according to the initial mounting pressure target value, and is switched from position control to pressure control after contacting the substrate surface.

Description

Technical Field

[0001] This invention relates to the field of electronic manufacturing equipment technology, and more specifically, to an adaptive control method for mounting pressure of electronic components. Background Technology

[0002] In the field of electronic manufacturing equipment technology, mounting pressure control is a core process that determines the mounting quality and reliability of components. Existing mounting equipment generally adopts a closed-loop control strategy based on pressure sensor feedback. This involves integrating a force sensor at the Z-axis end of the mounting head, collecting contact force signals in real time, comparing them with the target pressure, and then driving the actuator to perform position corrections to achieve constant mounting pressure control. Furthermore, to address the inertial impact of moving parts during high-speed mounting, some solutions employ constant-force spring assemblies for gravity balancing to reduce the impact force at the moment the nozzle contacts the substrate, preventing damage to the workpiece or solder pads. These solutions have been widely used in conventional mounting scenarios.

[0003] Existing technical solutions still have several limitations when facing the flexible placement needs of multiple varieties and varying working conditions. On the one hand, feedback control based on pressure sensors is constrained by factors such as sensor sampling frequency, signal transmission delay, and actuator response lag. In high-speed placement scenarios, it is difficult to respond to sudden changes in contact state in a timely manner, which can easily lead to overpressure, causing chip microcracks or solder paste extrusion. On the other hand, for the differentiated placement pressure required by different materials in the multi-variety, small-batch production mode, traditional methods rely on manual experience or simple gear switching to set parameters. There is a lack of intelligent means to automatically recommend the initial pressure based on historical data, which leads to repeated trial and error of parameters when producing new batches.

[0004] The thermal position drift caused by the heat generated by the drive motor and friction during long-term continuous operation of the placement head has not been effectively incorporated into the pressure compensation model. The Z-axis zero point offset caused by temperature changes directly affects the accuracy and stability of pressure control. This invention solves the technical problems of existing solutions in terms of initial parameter setting relying on human experience, delayed response to pressure changes, and lack of compensation for thermal drift by constructing an intelligent initial pressure recommendation mechanism based on historical data similarity matching, a dynamic displacement compensation strategy based on pressure-position curve calibration, and thermal drift predictive feedforward compensation based on temperature field perception. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention is proposed. A first aspect of this invention provides an adaptive control method for mounting pressure of electronic components, comprising the following specific steps: preparing tools and equipment for mounting pressure control, and providing a hardware platform for mounting pressure control; The lower pressure sensor is calibrated with standard weights, and the upper pressure sensor is cross-calibrated based on the calibrated lower pressure sensor. The drive placement head assembly causes the nozzle to contact the pressure calibration platform at different pressure depths, records the pressure value corresponding to each pressure depth, and establishes and stores the pressure-position curve. Obtain the material characteristic information of the components to be mounted in the current batch, and calculate the initial mounting pressure target value of the current batch based on the similarity matching between the material characteristic information and historical batches. Driven by motion control commands generated by the monitoring system based on the initial mounting pressure target value, the mounting head assembly moves toward the substrate. After contacting the substrate surface, it switches from position control to pressure control. Based on the pressure-position curve, the displacement of the mounting head assembly is adjusted in real time to make the actual mounting pressure approach the target pressure value. When a pressure change is detected, the internal air pressure of the control cylinder assembly changes, causing the piston to apply compensating pressure to the force transmission component or release pressure to buffer the pressure change. During the placement process, temperature data of key components of the placement head assembly are collected in real time. Thermal drift compensation is calculated based on the temperature data and superimposed on the motion control command. The placement pressure is feedforward corrected based on the temperature change trend prediction. After the mounting is completed, the mounting process data and mounting quality inspection results are stored in the historical database.

[0006] Preferably, preparing tools and equipment for mounting pressure control, and providing a hardware platform for mounting pressure control includes the following steps: The mounting head assembly includes a mounting plate, a mounting cylinder fixed below the mounting plate, a motor fixed above the mounting plate, a diaphragm support driven by the motor to rotate, an elastic diaphragm fixedly mounted on the diaphragm support, a connecting rod with its top hanging at the center of the elastic diaphragm, a cylinder assembly installed inside the mounting cylinder and surrounding the connecting rod, a rotating mounting shaft located below the cylinder assembly and fixedly connected to the bottom of the connecting rod, an air-bearing bushing installed inside the mounting cylinder and surrounding the rotating mounting shaft, a force transmission component located above the air-bearing bushing and fixed on the rotating mounting shaft, and a micro-pressure sensing module fixed on the mounting cylinder and monitoring the axial pressure and axial displacement of the force transmission component. A suction nozzle is provided at the end of the rotating mounting shaft. The cylinder assembly includes a cylinder barrel and a piston that is vertically movable inside the cylinder barrel, with the lower surface of the piston pressing down on a force transmission component. The pressure calibration platform is located below the placement head assembly. The upper pressure sensor is installed on the upper part of the placement head assembly, and the lower pressure sensor is installed on the lower part of the pressure calibration platform. The monitoring system is connected to the drive motor signals of the upper pressure sensor, lower pressure sensor, micro-pressure sensing module, and placement head assembly, respectively, to obtain a placement pressure control hardware platform that is assembled and ready for use and whose monitoring system is connected.

[0007] Preferably, the lower pressure sensor is calibrated with standard weights, and the upper pressure sensor is cross-calibrated based on the calibrated lower pressure sensor, including the following steps; Place a standard 100-gram weight on the pressure calibration platform to apply force to the platform. The pressure sensor then reads the pressure value and compares it with the weight of the standard weight. If there is a deviation, adjust the zero point and gain coefficient of the pressure sensor until the reading of the pressure sensor matches the weight of the standard weight, thus obtaining a calibrated pressure sensor. The drive placement head assembly descends, causing the nozzle at the end of the rotating placement shaft of the placement head assembly to press against the upper surface of the pressure calibration platform. At this time, the upper pressure sensor and the lower pressure sensor read the pressure value simultaneously. Compare the reading of the upper pressure sensor with the reading of the calibrated lower pressure sensor obtained in step one. If there is a discrepancy, adjust the parameters of the upper pressure sensor until the reading of the upper pressure sensor is consistent with the reading of the calibrated lower pressure sensor, thus obtaining an upper pressure sensor and a calibrated lower pressure sensor that have been cross-calibrated and have consistency.

[0008] Preferably, driving the placement head assembly to make the nozzle contact the pressure calibration platform at different pressure depths, recording the pressure value corresponding to each pressure depth, and establishing and storing the pressure-position curve includes the following steps; Drive the placement head assembly to move downward from the initial position to the pressure calibration platform, so that the nozzle at the end of the rotating placement shaft of the placement head assembly gradually increases the downward pressure depth to contact the pressure calibration platform in stroke increments of 0.1 mm each time; Record the current pressure value of the pressure sensor and the current Z-axis position value of the mounting head assembly at each pressure depth position until the recorded pressure value covers 1.2 times the upper limit of the actual mounting pressure range of 5 Newtons, i.e., 6 Newtons, to obtain multiple sets of recorded data for different pressure depths and corresponding pressure values. The pressure-position curves are plotted from multiple sets of recorded data for different pressing depths and corresponding pressure values. The pressure-position curves are stored in the monitoring system to obtain pressure-position curves that describe the quantitative mapping relationship between the pressing displacement of the mounting head assembly and the contact pressure.

[0009] Preferably, the process of obtaining the material characteristic information of the components to be mounted in the current batch and calculating the initial mounting pressure target value of the current batch based on the similarity matching between the material characteristic information and historical batches includes the following steps: The substrate type, substrate thickness, substrate flexibility characteristics, chip size, and package type information of the components to be mounted in the current batch are obtained as the material feature information of the current batch, and the material feature information of the current batch is constructed into the feature vector of the current batch. The cosine similarity algorithm is used to calculate the similarity score between the feature vector of the current batch and the feature vectors of each historical batch; Historical batches of data with similarity scores higher than a preset threshold are used as reference datasets to obtain similarity scores for the reference datasets and feature vectors of each historical batch. The similarity scores corresponding to the feature vectors of each historical batch in the reference dataset are summed to obtain the total similarity score. The weighted average method is then used to calculate the recommended initial mounting pressure value for the current batch. The recommended initial placement pressure value is automatically set as the target initial placement pressure value for this placement, thus obtaining the target initial placement pressure value for the current batch.

[0010] Preferably, the placement head assembly moves towards the substrate under the drive of motion control commands generated by the monitoring system based on the initial placement pressure target value, and after contacting the substrate surface, the control switches from position control to pressure control, including the following steps: Driven by the initial mounting pressure target value, the mounting head moves towards the substrate at a rapid approach speed. The monitoring system of the mounting head assembly reads the axial pressure value of the force transmission component and the axial displacement of the rotating mounting axis in real time from the micro pressure sensing module of the mounting head assembly. Based on the axial displacement of the rotary mounting axis, when the mounting head assembly approaches the substrate surface, the descent speed of the mounting head assembly is switched to low speed to obtain a state in which the mounting head assembly approaches the substrate surface at low speed. After the nozzle at the end of the rotating mounting shaft of the mounting head assembly contacts the substrate surface, the axial pressure of the force transmission component detected by the micro-pressure sensing module of the mounting head assembly begins to rise from zero. After the monitoring system of the mounting head assembly detects the pressure inflection point of the axial pressure of the force transmission component rising from zero, it switches the control strategy of the mounting head assembly from position control to pressure control, thereby obtaining the mounting state in which the mounting head assembly operates in pressure control mode.

[0011] Preferably, the displacement of the placement head assembly is adjusted in real time based on the pressure-position curve to make the actual placement pressure approach the target pressure value. When a pressure change is detected, the internal air pressure of the control cylinder assembly changes, causing the piston to apply compensating pressure to the force transmission component or release pressure to buffer the pressure change. This includes the following steps: The monitoring system of the placement head assembly obtains the current pressure value of the upper pressure sensor and compares the current pressure value of the upper pressure sensor with the initial placement pressure target value. If the current pressure value of the upper pressure sensor is less than the initial placement pressure target value; Substitute the current pressure value and the initial mounting pressure target value of the upper pressure sensor into the pressure-position curve to obtain the corresponding current pressing position value and target pressing position value, and calculate the difference as the descent displacement. If the current pressure value of the upper pressure sensor is greater than the initial mounting pressure target value, the upward displacement is calculated. The monitoring system of the mounting head assembly controls the mounting head assembly to move by this displacement and repeats the comparison and adjustment until the deviation between the current pressure value of the upper pressure sensor and the initial mounting pressure target value is within the preset allowable range. The pressure change rate of the axial pressure of the force transmission component fed back by the micro pressure sensing module is calculated during the pressure control process. If the pressure change rate exceeds the preset switching threshold, the system switches to the cylinder assembly intervention mode. By adjusting the internal air pressure of the cylinder assembly, the piston applies pressure to or releases pressure to the force transmission component. After the pressure change rate returns to normal, the monitoring system of the mounting head assembly switches back to the fine pressure control mode dominated by the micro pressure sensing module.

[0012] Preferably, the temperature data of each key component of the placement head assembly is collected in real time during the placement process, the thermal drift compensation is calculated based on the temperature data and superimposed on the motion control command, and the placement pressure is feedforward corrected based on the temperature change trend prediction, including the following steps. The monitoring system of the placement head assembly acquires temperature data collected by temperature sensing units located at key components of the placement head assembly, and reconstructs the three-dimensional temperature field distribution of the placement head assembly based on the temperature data of each temperature sensing unit and the heat transfer path between components. The displacement compensation amount in the Z-axis direction and the torsional compensation amount in the radial direction of the mounting head assembly are obtained by dynamically calculating the thermal expansion amount of each key component based on the three-dimensional temperature field distribution of the mounting head assembly. The displacement compensation and torsional compensation are added to the position control amount of the next motion command of the mounting head assembly; The temperature data collected at multiple consecutive time points at the current moment will be used to predict the thermal expansion trend of each key component of the mounting head assembly within a preset time period in the future. If the prediction results show that the future thermal drift will exceed the preset threshold, the monitoring system of the mounting head assembly will output a feedforward compensation command to the Z-axis drive module of the mounting head assembly in advance before the actual occurrence of the future thermal drift. The thickness expansion of the substrate is generated by combining the change of ambient temperature with the coefficient of thermal expansion of the substrate. The thickness expansion or contraction factor is combined with the thermal drift prediction value of the mounting head assembly and then a feedforward correction is added to the initial mounting pressure target value based on the judgment result.

[0013] Preferably, after the mounting is completed, storing the mounting process data and mounting quality inspection results in the historical database includes the following steps: The material type, material size, batch information, pressure-time-displacement curve, final mounting pressure value, and temperature drift during this mounting process are recorded as the process data for this mounting. The mounting quality inspection results fed back by the AOI inspection equipment are combined with the process data of this mounting to form the complete data of this mounting. The complete data of this mounting is then stored in the historical database of the monitoring system.

[0014] Preferably, if the mounting quality inspection result fed back by the AOI inspection equipment is that the material feature vector and the final mounting pressure value of the current batch are stored as positive samples in the historical database of the monitoring system through the monitoring system of the mounting head assembly; If the AOI inspection equipment reports a failure in the placement quality inspection and the reason for the failure is related to the placement pressure, the monitoring system of the placement head assembly will record the failure case and reduce the recommendation weight of the batch feature vector in subsequent similarity matching.

[0015] Compared with existing technologies, the adaptive control method for electronic component mounting pressure provided by this invention automatically recommends the initial mounting pressure target value by matching historical data based on cosine similarity, avoiding repeated manual parameter adjustments and improving the process switching efficiency in multi-variety, small-batch production scenarios. By calibrating the pressure-position curve of the quantitative mapping relationship between the pressing displacement of the mounting head assembly and the contact pressure, and combining it with real-time pressure feedback to dynamically adjust the displacement, the mounting pressure continuously approaches the target value during the stable contact stage, ensuring the consistency of the mounting pressure. By automatically activating the cylinder assembly to intervene and buffer during pressure changes, the pressure overshoot at the moment of contact and under abnormal operating conditions is effectively suppressed, reducing the risk of impact damage to the mounted components and substrate. By reconstructing the three-dimensional temperature field distribution of the mounting head assembly and calculating the displacement compensation and torsional compensation caused by thermal expansion and superimposing them into the motion control command, and combining temperature change trend prediction to perform feedforward correction of the mounting pressure, the influence of thermal drift on pressure control accuracy is eliminated. Thus, adaptive and precise control of electronic component mounting pressure is achieved under all operating conditions, improving the consistency of mounting quality and production yield. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings: Figure 1 This is a flowchart of an adaptive control method for mounting pressure of electronic components according to an embodiment of the present invention. Detailed Implementation

[0017] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It is obvious that the described embodiments are merely some embodiments of the present invention, and not all embodiments of the present invention, and it should be understood that the present invention is not limited to the exemplary embodiments described herein.

[0018] As mentioned in the background section, existing technical solutions still have several limitations when facing the flexible mounting needs of multiple varieties and varying working conditions. On the one hand, feedback control based on pressure sensors is constrained by factors such as sensor sampling frequency, signal transmission delay, and actuator response lag. In high-speed mounting scenarios, it is difficult to respond to sudden changes in contact state in a timely manner, which can easily lead to overpressure, causing chip microcracks or solder paste extrusion. On the other hand, for the differentiated mounting pressure required by different materials in multi-variety, small-batch production modes, traditional methods rely on manual experience or simple gear switching to set parameters. There is a lack of intelligent means to automatically recommend the initial pressure based on historical data, which leads to repeated trial and error of parameters when producing new batches.

[0019] Figure 1 A flowchart of an adaptive control method for mounting pressure of electronic components according to an embodiment of the present invention is shown, including the following specific steps: S1: Prepare tools and equipment for mounting pressure control, and provide a hardware platform for mounting pressure control.

[0020] In step S1, the mounting head assembly includes a mounting plate, a mounting cylinder fixed below the mounting plate, a motor fixed above the mounting plate, a diaphragm support driven by the motor to rotate, an elastic diaphragm fixedly mounted on the diaphragm support, a connecting rod with its top hanging at the center of the elastic diaphragm, a cylinder assembly installed inside the mounting cylinder and surrounding the connecting rod, a rotating mounting shaft located below the cylinder assembly and fixedly connected to the bottom of the connecting rod, an air-bearing bushing installed inside the mounting cylinder and surrounding the rotating mounting shaft, a force transmission component located above the air-bearing bushing and fixed on the rotating mounting shaft, and a micro-pressure sensing module fixed on the mounting cylinder and monitoring the axial pressure and axial displacement of the force transmission component. A suction nozzle is provided at the end of the rotating mounting shaft.

[0021] The cylinder assembly includes a cylinder barrel and a piston that moves vertically within the cylinder barrel, with the lower surface of the piston pressing down on a force transmission component.

[0022] Furthermore, the cylinder assembly is assembled inside the mounting sleeve of the placement head assembly. The cylinder is fixed in a predetermined position on the mounting sleeve, and the piston is constrained inside the cylinder and has the freedom to move up and down along the cylinder's axial direction. In the initial assembly state, the lower surface of the piston remains in contact with the upper surface of the force transmission component, allowing the piston to transmit the pressure generated by the cylinder assembly to the rotary placement shaft via the force transmission component. When the cylinder assembly is not driven by air pressure, the piston maintains contact with the force transmission component due to its own weight. When compressed air is filled into the cylinder assembly, the air pressure pushes the piston downward, and the lower surface of the piston presses down on the force transmission component, thereby adjusting the axial pressure of the rotary placement shaft. By controlling the air pressure inside the cylinder assembly, the pressure applied by the piston to the force transmission component can be controlled, thereby controlling the placement pressure of the suction nozzle at the end of the rotary placement shaft on the substrate.

[0023] The pressure calibration platform is located below the placement head assembly. The upper pressure sensor is installed on the upper part of the placement head assembly, and the lower pressure sensor is installed on the lower part of the pressure calibration platform. Furthermore, the pressure calibration platform is fixed within the working stroke range of the placement head assembly and located directly below it. The upper surface of the pressure calibration platform provides a flat force reference surface for pressure calibration of the placement head assembly. An upper pressure sensor is fixed in the upper structure of the placement head assembly. When the placement head assembly moves downwards and the nozzle at the end of the rotating placement shaft presses against the upper surface of the pressure calibration platform, the upper pressure sensor senses the reaction force on the placement head assembly and outputs a corresponding pressure signal. A lower pressure sensor is fixed in the lower part of the pressure calibration platform. When the upper surface of the pressure calibration platform is subjected to pressure from the placement head assembly, the lower pressure sensor senses the pressure on the pressure calibration platform and outputs a corresponding pressure signal. Both the upper and lower pressure sensors simultaneously measure the same pressure value during the downward pressing process of the placement head assembly. Mutual calibration verification of the pressure sensors is achieved by comparing their readings.

[0024] The monitoring system is connected to the drive motor signals of the upper pressure sensor, lower pressure sensor, micro-pressure sensing module, and placement head assembly, respectively, to obtain a placement pressure control hardware platform that is assembled and ready for use and whose monitoring system is connected.

[0025] Furthermore, signal cables are connected to the signal output terminals of the upper pressure sensor, lower pressure sensor, micro-pressure sensing module, and the control terminal of the drive motor of the placement head assembly. The system acquires pressure signals sensed at the top of the placement head assembly from the upper pressure sensor, pressure signals sensed at the bottom of the pressure calibration platform from the lower pressure sensor, and axial pressure and axial displacement signals from the force transmission component from the micro-pressure sensing module. Motion control signals are then output to the drive motor of the placement head assembly. The monitoring system has a pre-installed signal acquisition and processing circuit that converts the analog signals output by each sensor into digital signals and performs filtering and amplification. Once the upper pressure sensor, lower pressure sensor, micro-pressure sensing module, and drive motor of the placement head assembly are all connected to the monitoring system and communication is normal, the monitoring system confirms that the placement pressure control hardware platform is assembled and connected, at which point the placement pressure control hardware platform enters the operational state.

[0026] S2: Perform standard weight calibration on the lower pressure sensor, and perform mutual calibration on the upper pressure sensor based on the calibrated lower pressure sensor.

[0027] In step S2, a standard weight of 100 grams is placed on the pressure calibration platform to apply force to the platform. At this time, the pressure sensor reads the pressure value and compares it with the weight value of the standard weight. If there is a deviation, the zero point and gain coefficient of the pressure sensor are adjusted until the reading of the pressure sensor matches the weight value of the standard weight, thus obtaining a calibrated pressure sensor.

[0028] Furthermore, a standard 100-gram weight is placed at the center of the upper surface of the pressure calibration platform. The weight's gravity causes a downward force on the platform. The pressure sensor, fixed to the bottom of the platform, senses this force and outputs a corresponding pressure reading. The monitoring system acquires the pressure value output by the sensor and compares it with the standard pressure value corresponding to the 100-gram weight. If there is a deviation between the sensor reading and the standard pressure value, the system adjusts the sensor's zero-point voltage and gain amplification factor to gradually bring the sensor's output reading closer to the standard pressure value. This process is repeated until the sensor reading matches the weight of the standard weight. At this point, the system confirms that the pressure sensor has been calibrated.

[0029] The drive placement head assembly descends, causing the nozzle at the end of the rotating placement shaft of the placement head assembly to press against the upper surface of the pressure calibration platform. At this time, the upper pressure sensor and the lower pressure sensor simultaneously read the pressure value.

[0030] Furthermore, a descent command is sent to the drive motor of the placement head assembly. The drive motor drives the rotating placement shaft to move downward along the Z-axis until the nozzle at the end of the rotating placement shaft contacts and presses against the upper surface of the pressure calibration platform. The placement head assembly continues to apply downward pressure to form a stable contact pressure between the nozzle and the upper surface of the pressure calibration platform. In this state, the upper pressure sensor fixed to the upper part of the placement head assembly senses the reaction force on the placement head assembly and outputs a pressure reading. At the same time, the lower pressure sensor fixed to the lower part of the pressure calibration platform senses the pressure on the pressure calibration platform and outputs a pressure reading. The monitoring system collects the readings of the upper pressure sensor and the lower pressure sensor at the same time to obtain the synchronous measurement value of the same contact pressure by the two sensors.

[0031] Compare the reading of the upper pressure sensor with the reading of the calibrated lower pressure sensor obtained in step one. If there is a discrepancy, adjust the parameters of the upper pressure sensor until the reading of the upper pressure sensor is consistent with the reading of the calibrated lower pressure sensor, thus obtaining an upper pressure sensor and a calibrated lower pressure sensor that have been cross-calibrated and have consistency.

[0032] Furthermore, the reading of the lower pressure sensor is used as a reference value, and the reading of the upper pressure sensor is compared with this reference value. If there is a deviation between the readings of the upper and lower pressure sensors, the zero offset and gain coefficient of the upper pressure sensor are adjusted. During the adjustment process, the monitoring system continuously reads the real-time reading of the upper pressure sensor and compares it with the reading of the lower pressure sensor. The output value of the upper pressure sensor is consistent with the output value of the calibrated lower pressure sensor. The monitoring system confirms that the upper pressure sensor has passed the mutual calibration verification, and obtains a mutually calibrated and consistent upper pressure sensor and a calibrated lower pressure sensor.

[0033] S3: Drive the placement head assembly to make the nozzle contact the pressure calibration platform at different pressure depths, record the pressure value corresponding to each pressure depth, and establish and store the pressure-position curve.

[0034] In step S3, the drive placement head assembly moves downward from its initial position to the pressure calibration platform, so that the nozzle at the end of the rotating placement shaft of the placement head assembly gradually increases the downward pressure depth to contact the pressure calibration platform in stroke increments of 0.1 mm each time.

[0035] Furthermore, a position control command is sent to the drive motor of the placement head assembly. The drive motor drives the rotary placement axis to move downwards along the Z-axis from the initial position until the nozzle at the end of the rotary placement axis just contacts the upper surface of the pressure calibration platform. This position is recorded as the zero point position. Then, the placement head assembly is controlled to continue moving downwards from the zero point position, with each downward pressure increasing by 0.1 mm. At each pressure increment position, the nozzle is made to stably contact the upper surface of the pressure calibration platform at that pressure depth. After completing the contact at one pressure depth position, the monitoring system controls the placement head assembly to continue moving downwards by the next 0.1 mm pressure increment.

[0036] Record the current pressure value of the pressure sensor and the current Z-axis position value of the mounting head assembly at each pressure depth position until the recorded pressure value covers 1.2 times (6 Newtons) of the upper limit of the actual mounting pressure range required, obtaining multiple sets of recorded data for different pressure depths and corresponding pressure values.

[0037] Furthermore, at each of the pressure depth positions described in the first paragraph, the movement of the mounting head assembly is paused. The current pressure value output by the upper pressure sensor at that pressure depth position is read, and the current Z-axis position value of the mounting head assembly at that position is also read. The current pressure value and the current Z-axis position value are recorded as a set of corresponding data in the monitoring storage medium. After completing the data recording for one position, the mounting head assembly is controlled to continue moving to the next pressure depth position and recording is performed. The above reading and recording operations are repeated until the current pressure value output by the upper pressure sensor reaches 6 Newtons, at which point the pressure action is stopped. At this time, the monitoring system has obtained multiple sets of corresponding recorded data of pressure depth and pressure value for each 0.1 mm stroke increment position within the range from zero contact pressure to 6 Newtons.

[0038] The pressure-position curves are plotted from multiple sets of recorded data for different pressing depths and corresponding pressure values. The pressure-position curves are stored in the monitoring system to obtain pressure-position curves that describe the quantitative mapping relationship between the pressing displacement of the mounting head assembly and the contact pressure.

[0039] Furthermore, pressure-position curves are plotted from multiple sets of recorded data for different pressing depths and corresponding pressure values. These pressure-position curves are stored in the monitoring system. The pressure range covered by these curves extends from 0 to an upper limit pressure value that is 1.2 times the upper limit of the actual mounting pressure range. These pressure-position curves serve as a standard curve for querying during the actual mounting process. If the current pressure value of the upper pressure sensor during the actual mounting process does not exceed the upper limit of the pressure range covered by the pressure-position curve, the corresponding pressing position value is directly queried from the pressure-position curve. If the current pressure value of the upper pressure sensor during the actual mounting process exceeds the upper limit of the pressure range covered by the pressure-position curve, the monitoring system issues an alarm signal and stops the mounting action. This yields a pressure-position curve that describes the quantitative mapping relationship between the pressing displacement of the mounting head assembly and the contact pressure, and has upper limit query protection.

[0040] S4: Obtain the material characteristic information of the components to be mounted in the current batch, and calculate the initial mounting pressure target value of the current batch based on the similarity matching between the material characteristic information and historical batches.

[0041] In step S4, the substrate type, substrate thickness, substrate flexibility characteristics, chip size and package type information of the components to be mounted in the current batch are obtained as the material feature information of the current batch, and the material feature information of the current batch is constructed into the feature vector of the current batch.

[0042] Furthermore, the substrate type, substrate thickness, substrate flexibility characteristics, chip size, and package type information of the components to be mounted in the current batch are read from the mounting task list. The substrate type is converted into numerical data according to a preset encoding rule, the substrate thickness is converted into a numerical value in millimeters, the substrate flexibility characteristics are converted into numerical data according to the flexibility level, the chip size is the product of length and width, and the package type is converted into numerical data according to a preset encoding rule. The converted values ​​are arranged in a fixed order to form a multidimensional array, and this multidimensional array is used as the feature vector of the current batch.

[0043] The cosine similarity algorithm is used to calculate the similarity score between the feature vector of the current batch and the feature vectors of each historical batch.

[0044] Let the feature vector of the current batch be A, and the feature vector of the historical batch be B. The cosine similarity score S between the two is calculated using the following formula: ; Parameter explanation: A is the feature vector of the current batch, B is the feature vector of the historical batch, n is the total number of dimensions of the feature vector, Aᵢ is the feature value of the current batch feature vector in the i-th dimension, Bᵢ is the feature value of the historical batch feature vector in the i-th dimension, and S is the cosine similarity score.

[0045] Historical batches of data with similarity scores higher than a preset threshold are used as reference datasets to obtain similarity scores for the reference dataset and the feature vectors of each historical batch.

[0046] Furthermore, the cosine similarity score corresponding to each historical batch is compared with a preset threshold, which is a value between -1 and 1. If the cosine similarity score of a certain historical batch is greater than the preset threshold, the monitoring system stores the historical batch feature vector, the historical mounting pressure value corresponding to the historical batch, and the cosine similarity score of the historical batch into the reference dataset. After traversing all historical batches, the reference dataset contains all historical batch data with similarity scores higher than the preset threshold.

[0047] The similarity scores corresponding to the feature vectors of each historical batch in the reference dataset are summed to obtain the total similarity score. A weighted average method is then used to calculate the recommended initial mounting pressure for the current batch. For the j-th historical batch in the reference dataset, its weight Wⱼ is calculated as follows: ; Parameter explanation: Sⱼ is the cosine similarity score between the feature vector of the j-th historical batch and the feature vector of the current batch; M is the total number of historical batches in the reference dataset. For the reference dataset, the historical batch index is used, where Wⱼ is the weight of the j-th historical batch and j is the feature index of the historical batch. Recommended initial placement pressure for the current batch Calculate using the following formula: ; Parameter explanation: P represents the recommended initial mounting pressure for the current batch, and Pⱼ represents the mounting pressure value that was ultimately successfully used in actual production for the j-th historical batch.

[0048] The recommended initial placement pressure value is automatically set as the target initial placement pressure value for this placement, thus obtaining the target initial placement pressure value for the current batch.

[0049] Furthermore, the recommended initial placement pressure value is written into the placement pressure setting field of the placement task control parameter table. This recommended initial placement pressure value is used as the target initial placement pressure value for this placement process. The monitoring system stores the target initial placement pressure value in the monitoring storage medium for the placement execution steps to call. Thus, the monitoring system obtains the target initial placement pressure value for the current batch.

[0050] S5: The mounting head assembly moves toward the substrate under the motion control command generated by the monitoring system according to the initial mounting pressure target value. After contacting the substrate surface, the position control switches to pressure control. The displacement of the mounting head assembly is adjusted in real time based on the pressure-position curve to make the actual mounting pressure approach the target pressure value. When a pressure change is detected, the internal air pressure of the control cylinder assembly changes, so that the piston applies compensating pressure to the force transmission component or releases pressure to buffer the pressure change.

[0051] In step S5, driven by the initial mounting pressure target value, the device moves towards the substrate at a rapid approach speed. The monitoring system of the mounting head assembly reads in real time the axial pressure value of the force transmission component and the axial displacement of the rotating mounting shaft fed back by the micro pressure sensing module of the mounting head assembly.

[0052] Furthermore, the initial mounting pressure target value is extracted from the monitoring storage medium and a control command is sent to the drive motor of the mounting head assembly to move at a rapidly approaching speed. The drive motor drives the rotating mounting axis of the mounting head assembly to move from the initial position toward the substrate. The axial pressure value of the force transmission component and the axial displacement of the rotating mounting axis are continuously read from the micro pressure sensing module at a fixed sampling period.

[0053] Based on the axial displacement of the rotary mounting axis, when the mounting head assembly approaches the substrate surface, the descent speed of the mounting head assembly is switched to low speed to obtain a state where the mounting head assembly approaches the substrate surface at low speed.

[0054] Furthermore, the axial displacement of the rotary mounting axis is compared with the substrate surface position value pre-stored in the monitoring storage medium. The axial displacement of the rotary mounting axis reflects the distance between the current position and the initial position of the mounting head assembly. The substrate surface position value is the axial position of the rotary mounting axis when the nozzle at the end of the rotary mounting axis of the mounting head assembly just contacts the substrate surface. When it is determined that the axial displacement of the rotary mounting axis has reached a predetermined distance range before the substrate surface position value, a speed switching command is sent to the drive motor of the mounting head assembly. The drive motor switches the descent speed of the mounting head assembly from a fast approach speed to a low speed. The mounting head assembly continues to move towards the substrate at a low speed until it is ready to contact the substrate surface.

[0055] After the nozzle at the end of the rotating mounting shaft of the mounting head assembly contacts the substrate surface, the axial pressure of the force transmission component detected by the micro-pressure sensing module of the mounting head assembly begins to rise from zero. After the monitoring system of the mounting head assembly detects the pressure inflection point of the axial pressure of the force transmission component rising from zero, it switches the control strategy of the mounting head assembly from position control to pressure control, thereby obtaining the mounting state in which the mounting head assembly operates in pressure control mode.

[0056] Furthermore, the force is transmitted to the force transmitter via the rotating mounting shaft and connecting rod. The micro-pressure sensing module detects that the axial pressure of the force transmitter gradually increases from zero. It continuously compares the axial pressure value of the force transmitter read at the current moment with the axial pressure value read at the previous moment. When the axial pressure value of the force transmitter changes from zero to a positive value and continues to increase, it is determined that a pressure inflection point has been detected. After the pressure inflection point is detected, the control strategy of the mounting head assembly is switched from position control to pressure control.

[0057] The monitoring system of the placement head assembly obtains the current pressure value of the upper pressure sensor and compares the current pressure value of the upper pressure sensor with the initial placement pressure target value. If the current pressure value of the upper pressure sensor is less than the initial placement pressure target value...

[0058] Furthermore, the initial mounting pressure target value is extracted from the monitoring storage medium. The current pressure value of the upper pressure sensor is compared with the initial mounting pressure target value. If the comparison result shows that the current pressure value of the upper pressure sensor is less than the initial mounting pressure target value, the current pressure value of the upper pressure sensor is used as the query key to search in the pressure-position curve data table. The downward pressure position value that matches the current pressure value of the upper pressure sensor is taken as the current downward pressure position value. Then, the initial mounting pressure target value is used as the query key to search in the pressure-position curve data table. The downward pressure position value that matches the initial mounting pressure target value is taken as the target downward pressure position value. The downward displacement is output to the drive motor of the mounting head assembly to execute the downward action.

[0059] Substitute the current pressure value of the upper pressure sensor and the initial mounting pressure target value into the pressure-position curve to obtain the corresponding current downward pressure position value and target downward pressure position value, and calculate the difference as the downward displacement.

[0060] Downward displacement: ; Parameter explanation To reduce the displacement, This is the initial placement pressure target value. This is the current pressure value of the upper pressure sensor.

[0061] If the current pressure value of the upper pressure sensor is greater than the initial mounting pressure target value, the upward displacement is calculated, the mounting head assembly is controlled to move by that displacement, and the comparison and adjustment are repeated until the deviation between the current pressure value of the upper pressure sensor and the initial mounting pressure target value is within the preset allowable range.

[0062] Upward displacement: ; in, This represents the upward displacement.

[0063] The pressure change rate of the axial pressure of the force transmission component fed back by the micro pressure sensing module is calculated during the pressure control process.

[0064] ; Parameter explanation The rate of change of axial pressure in the force transmission component. The value of the axial pressure transmitted by the force transmission component is given by the micro-pressure sensing module, where t is time. For at any time The axial pressure value of the force transmission component is fed back by the micro-pressure sensing module. At any moment The axial pressure value of the force transmission component fed back by the micro pressure sensing module - The time interval between two samples. The instantaneous rate of change of axial pressure with respect to time in a force transmission component.

[0065] If the pressure change rate exceeds the preset switching threshold, the system switches to the cylinder assembly intervention mode. By adjusting the internal air pressure of the cylinder assembly, the piston applies pressure to or releases pressure to the force transmission component. After the pressure change rate returns to normal, the monitoring system of the mounting head assembly switches back to the fine pressure control mode dominated by the micro pressure sensing module.

[0066] Furthermore, the pressure change rate is compared with a preset switching threshold stored in the monitoring storage medium. The preset switching threshold represents the maximum allowable rate of change of axial pressure in the force transmission component during normal placement of the placement head assembly. When the pressure change rate exceeds the preset switching threshold, the control logic of the placement head assembly is switched from the fine pressure control mode dominated by the micro-pressure sensing module to the cylinder assembly intervention mode. A pressure adjustment command is sent to the air pressure regulating valve of the cylinder assembly. By increasing or decreasing the air pressure value inside the cylinder assembly, the piston of the cylinder assembly moves up or down in the cylinder. When the piston moves down, it applies additional pressure to the force transmission component. When the piston moves up, it releases the pressure on the force transmission component, thereby buffering the pressure shock caused by the sudden change in contact state. During the cylinder assembly intervention mode, the pressure change rate of the axial pressure of the force transmission component is continuously monitored. When the pressure change rate of the axial pressure of the force transmission component has dropped below the preset switching threshold, the control logic of the placement head assembly is switched back from the cylinder assembly intervention mode to the fine pressure control mode dominated by the micro-pressure sensing module, restoring the control state of real-time adjustment of placement pressure by the micro-pressure sensing module.

[0067] S6: During the placement process, the temperature data of each key component of the placement head assembly is collected in real time. The thermal drift compensation is calculated based on the temperature data and superimposed on the motion control command. The placement pressure is feedforward corrected based on the temperature change trend prediction.

[0068] In step S6, the monitoring system of the placement head assembly acquires the temperature data collected by the temperature sensing units arranged at each key component of the placement head assembly, and reconstructs the three-dimensional temperature field distribution of the placement head assembly based on the temperature data of each temperature sensing unit and the heat transfer path between each component.

[0069] Furthermore, a spatial coordinate system is established with the geometric center of the placement head assembly as the origin. The installation position coordinates of each temperature sensing unit on the placement head assembly are associated with the temperature value collected by the temperature sensing unit as temperature field node data. Based on the thermal conductivity and specific heat capacity parameters of each component material of the placement head assembly and the contact thermal resistance parameters between each component, the heat transfer path between each node is determined. The temperature distribution between adjacent temperature sensing units is estimated by interpolation algorithm, so that each coordinate position in the internal space of the placement head assembly corresponds to a temperature value, and the three-dimensional temperature field distribution of the placement head assembly is obtained.

[0070] Based on the dynamic calculation of the thermal expansion of each key component according to the three-dimensional temperature field distribution of the mounting head assembly, the displacement compensation amount in the Z-axis direction and the torsional compensation amount in the radial direction of the mounting head assembly are obtained.

[0071] The thermal expansion of the i-th critical component of the placement head assembly in the Z-axis direction is calculated using the following formula: ; Parameter explanation: i is the serial number of the key component of the mounting head assembly. The key components include the Z-axis drive module, bearing housing, sensor bracket, and nozzle connection.

[0072] Let be the amount of thermal expansion of the i-th critical component in the Z-axis direction. Let be the linear thermal expansion coefficient of the material of the i-th critical component in the Z-axis direction. Let be the original dimension of the i-th critical component in the Z-axis direction. Let be the current temperature value of the i-th critical component. This is a reference temperature.

[0073] The displacement compensation and torsional compensation are added to the position control amount of the next motion command of the mounting head assembly.

[0074] Furthermore, the raw position control quantity of the next movement command of the placement head assembly is read from the monitoring storage medium. The raw position control quantity includes the target position coordinates in the Z-axis direction and the target rotation angle around the Z-axis. The displacement compensation amount of the placement head assembly in the Z-axis direction is added to the target position coordinates in the Z-axis direction of the raw position control quantity to obtain the corrected Z-axis position coordinates. The torsional compensation amount of the placement head assembly in the radial direction is added to the target rotation angle around the Z-axis of the raw position control quantity to obtain the corrected rotation angle around the Z-axis. The corrected Z-axis position coordinates and the corrected rotation angle around the Z-axis are combined to form the corrected position control quantity. The corrected position control quantity is sent to the drive motor of the placement head assembly to execute the next movement.

[0075] The temperature data collected at multiple consecutive time points at the current moment can be used to predict the thermal expansion trend of key components of the mounting head assembly within a preset time period in the future.

[0076] Furthermore, the temperature data of each temperature sensing unit at multiple consecutive time points are arranged in chronological order to form the temperature time series of that temperature sensing unit. Linear regression analysis is performed on the temperature time series of each temperature sensing unit, and the temperature is fitted with time as the independent variable and temperature as the dependent variable to obtain the predicted temperature value of that temperature sensing unit at a future preset time point.

[0077] If the prediction results indicate that the future thermal drift will exceed the preset threshold, the monitoring system of the placement head assembly will output a feedforward compensation command to the Z-axis drive module of the placement head assembly in advance before the actual occurrence of the future thermal drift.

[0078] Furthermore, if the predicted displacement compensation amount is greater than the preset displacement drift threshold, it is determined that the future thermal drift amount will exceed the preset threshold. At the current moment, a feedforward compensation command is immediately generated and sent to the Z-axis drive module of the mounting head assembly. The feedforward compensation command contains the displacement compensation value and torsional compensation value that the mounting head assembly needs to execute in advance within a preset time period in the future. Under the control of the feedforward compensation command, the Z-axis drive module of the mounting head assembly completes the position correction action in advance.

[0079] The thickness expansion of the substrate is generated by combining the change of ambient temperature with the coefficient of thermal expansion of the substrate. The thickness expansion or contraction factor is combined with the thermal drift prediction value of the mounting head assembly and then a feedforward correction is added to the initial mounting pressure target value based on the judgment result.

[0080] Furthermore, the ambient temperature value collected by the ambient temperature sensing unit in the external environment of the placement head assembly is used to read the thermal expansion coefficient of the substrate and the original thickness value of the substrate at room temperature from the monitoring storage medium. The thermal drift prediction value of the placement head assembly is extracted from the monitoring storage medium. The thickness expansion value of the substrate is added to the thermal drift prediction value of the placement head assembly to obtain the comprehensive deviation. The comprehensive deviation is divided by the slope of the pressure-position curve at the current placement pressure value to obtain the feedforward correction. The initial placement pressure target value is extracted from the monitoring storage medium and the feedforward correction is superimposed on the initial placement pressure target value to obtain the corrected target placement pressure value. The corrected target placement pressure value is used as the pressure target value for the next placement action of the placement head assembly.

[0081] S7: After the mounting is completed, the mounting process data and mounting quality inspection results will be stored in the historical database.

[0082] In step S7, the material type, material size, batch information, pressure-time-displacement curve, final mounting pressure value, and temperature drift of this mounting process are recorded as the process data of this mounting. The mounting quality inspection results fed back by the AOI inspection equipment are merged with the process data of this mounting to form the complete data of this mounting. The complete data of this mounting is then stored in the historical database of the monitoring system.

[0083] Furthermore, the material type, material size, and batch information for this placement are read from the placement task list. The pressure-time-displacement curve, final placement pressure value, and temperature drift recorded during this placement process are extracted from the monitoring storage medium. The material type, material size, batch information, pressure-time-displacement curve, final placement pressure value, and temperature drift are combined to form the process data for this placement. The placement quality inspection results fed back by the AOI inspection equipment after placement are received through the signal interface. The placement quality inspection results include the judgment of placement as qualified or unqualified, as well as the defect type when placement is unqualified. The placement quality inspection results fed back by the AOI inspection equipment are added to the process data for this placement to form the complete data for this placement. The complete data for this placement is then stored in the historical database in the monitoring storage medium.

[0084] If the AOI inspection equipment returns a pass rating for the placement quality, the monitoring system of the placement head assembly will store the material feature vector and the final placement pressure value of the current batch as positive samples in the historical database of the monitoring system.

[0085] Furthermore, the current batch feature vector is extracted from the monitoring storage medium, and the final mounting pressure value is extracted from the complete data of this mounting. A correspondence is established between the current batch feature vector and the final mounting pressure value, and this correspondence is stored as a positive sample data in the historical database of the monitoring storage medium.

[0086] If the AOI inspection equipment reports a failure in the placement quality inspection and the reason for the failure is related to the placement pressure, the monitoring system of the placement head assembly will record the failure case and reduce the recommendation weight of the batch feature vector in subsequent similarity matching.

[0087] Furthermore, defect types are extracted from the placement quality inspection results. If the defect type is any one of component misalignment, solder paste bridging, or cold solder joint related to placement pressure, the failure reason is determined to be related to placement pressure. The current batch feature vector, the final placement pressure value, and the placement quality inspection results are combined to form failure case data and stored in the historical database of the monitoring storage medium. In the historical database, a recommended weight reduction mark is added to the current batch feature vector.

[0088] Example 2

[0089] like Figure 1 As shown, this embodiment provides an adaptive control method for electronic component mounting pressure, including: To verify the effectiveness of the adaptive pressure control method for electronic component mounting provided by this invention, comparative experiments were conducted on a surface mount production line using the same model of mounting equipment, the same mounting objects, and the same environmental conditions. The traditional mounting pressure control method and the method of this invention were used respectively. The mounting objects were 0201 type ceramic capacitors, and the substrate was an FR-4 epoxy resin board. Each experiment mounted 1000 components, and the pressure overshoot, pressure steady-state deviation, and final mounting yield were recorded during the mounting process.

[0090] I. Comparison of Pressure Overshoot Pressure overshoot is the difference between the maximum peak pressure that occurs when the placement head contacts the substrate and the target pressure value, reflecting the system's ability to respond to sudden contact changes. In traditional methods, the peak pressure value of the pressure overshoot is... With target pressure value The difference is the pressure overshoot. : In the method of this invention, the cylinder assembly is activated to buffer the pressure surge during a sudden pressure change, thus reducing the pressure overshoot. Peak pressure value when using the method of the present invention With target pressure value Difference: Pressure overshoot suppression rate Calculate using the following formula: % In the comparative experiment, the target pressure value The value is set at 1.5 Newtons. When using the traditional method, the peak pressure value at the moment of contact... The measured value is 2.25 Newtons, and the pressure overshoot is: Newton.

[0091] When using the method of this invention, the cylinder assembly intervenes in a timely manner to buffer the sudden pressure change, thus mitigating the peak pressure value at the moment of contact. The measured value is 1.68 Newtons, and the pressure overshoot is: Newton.

[0092] The pressure overshoot suppression rate is calculated accordingly. This indicates that the method of the present invention can effectively suppress pressure overshoot at the moment of mounting contact.

[0093] II. Comparison of Pressure Steady-State Deviation The pressure steady-state deviation is the range of fluctuation of the actual pressure value relative to the target pressure value after the mounting enters the stable pressure holding stage, reflecting the system's ability to resist external disturbances and maintain constant pressure.

[0094] In traditional methods, pressure steady-state deviation The actual pressure value during the pressure holding stage using traditional methods. Relative to target pressure value Maximum absolute deviation: ; In the method of this invention, thermal drift feedforward compensation is performed through temperature field sensing, thus reducing the pressure steady-state deviation. The actual pressure value during the pressure holding stage of the method of the present invention. Relative to target pressure value Maximum absolute deviation: ; Steady-state deviation reduction rate Calculate using the following formula: ; In the comparative experiment, the target pressure value The pressure is set at 1.5 Newtons. The actual pressure value during the holding phase using the traditional method is... The fluctuation range is 1.38 to 1.62 Newtons, and the steady-state pressure deviation is... Newton.

[0095] When using the method of the present invention, due to the temperature compensation amount The actual pressure value during the pressure holding phase is superimposed in real time onto the motion control command and the feedforward correction is superimposed onto the target pressure value. The fluctuation range is 1.46 to 1.54 Newtons, and the steady-state pressure deviation is: Newton.

[0096] Therefore, the steady-state deviation reduction rate is calculated. This indicates that the method of the present invention can effectively reduce pressure fluctuations during the mounting and holding pressure stage.

[0097] III. Comparison of Surface Mount Yield Surface mount yield Number of qualified components to be mounted Total number of mounted components The ratio: %; In the comparative experiment, each group was equipped with 1000 0201 type ceramic capacitors. When using the traditional method, the number of qualified components mounted was [missing information]. Unit, mounting yield The main defects include component misalignment and solder paste bridging. When using the method of this invention, because the initial placement pressure target value is obtained through historical data similarity matching, pressure overshoot is effectively suppressed, and thermal drift is compensated for, the number of qualified placement components is increased. Unit, mounting yield .

[0098] Improved assembly yield Calculate using the following formula: ; The experimental data above show that the adaptive control method for electronic component mounting pressure provided by the present invention is significantly better than the traditional method in terms of pressure overshoot suppression, pressure steady-state accuracy, and mounting yield, thus verifying the effectiveness of the technical solution of the present invention.

[0099] It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A method for adaptive control of mounting pressure for electronic components, characterized in that, The specific steps include: preparing tools and equipment for mounting pressure control, and providing a hardware platform for mounting pressure control; The lower pressure sensor is calibrated with standard weights, and the upper pressure sensor is cross-calibrated based on the calibrated lower pressure sensor. The drive placement head assembly causes the nozzle to contact the pressure calibration platform at different pressure depths, records the pressure value corresponding to each pressure depth, and establishes and stores the pressure-position curve. Obtain the material characteristic information of the components to be mounted in the current batch, and calculate the initial mounting pressure target value of the current batch based on the similarity matching between the material characteristic information and historical batches. Driven by motion control commands generated by the monitoring system based on the initial mounting pressure target value, the mounting head assembly moves toward the substrate. After contacting the substrate surface, it switches from position control to pressure control. Based on the pressure-position curve, the displacement of the mounting head assembly is adjusted in real time to make the actual mounting pressure approach the target pressure value. When a pressure change is detected, the internal air pressure of the control cylinder assembly changes, causing the piston to apply compensating pressure to the force transmission component or release pressure to buffer the pressure change. During the placement process, temperature data of key components of the placement head assembly are collected in real time. Thermal drift compensation is calculated based on the temperature data and superimposed on the motion control command. The placement pressure is feedforward corrected based on the temperature change trend prediction. After the mounting is completed, the mounting process data and mounting quality inspection results are stored in the historical database.

2. The adaptive control method for electronic component mounting pressure according to claim 1, characterized in that, Preparing tools and equipment for placement pressure control, and providing a hardware platform for placement pressure control, includes the following steps: The mounting head assembly includes a mounting plate, a mounting cylinder fixed below the mounting plate, a motor fixed above the mounting plate, a diaphragm support driven by the motor to rotate, an elastic diaphragm fixedly mounted on the diaphragm support, a connecting rod with its top hanging at the center of the elastic diaphragm, a cylinder assembly installed inside the mounting cylinder and surrounding the connecting rod, a rotating mounting shaft located below the cylinder assembly and fixedly connected to the bottom of the connecting rod, an air-bearing bushing installed inside the mounting cylinder and surrounding the rotating mounting shaft, a force transmission component located above the air-bearing bushing and fixed on the rotating mounting shaft, and a micro-pressure sensing module fixed on the mounting cylinder and monitoring the axial pressure and axial displacement of the force transmission component. A suction nozzle is provided at the end of the rotating mounting shaft. The cylinder assembly includes a cylinder barrel and a piston that is vertically movable inside the cylinder barrel, with the lower surface of the piston pressing down on a force transmission component. The pressure calibration platform is located below the placement head assembly. The upper pressure sensor is installed on the upper part of the placement head assembly, and the lower pressure sensor is installed on the lower part of the pressure calibration platform. The monitoring system is connected to the drive motor signals of the upper pressure sensor, lower pressure sensor, micro-pressure sensing module, and placement head assembly, respectively, to obtain a placement pressure control hardware platform that is assembled and ready for use and whose monitoring system is connected.

3. The adaptive control method for electronic component mounting pressure according to claim 1, characterized in that, The process of calibrating the lower pressure sensor with standard weights and then cross-calibrating the upper pressure sensor based on the calibrated lower pressure sensor includes the following steps: Place a standard 100-gram weight on the pressure calibration platform to apply force to the platform. The pressure sensor then reads the pressure value and compares it with the weight of the standard weight. If there is a deviation, adjust the zero point and gain coefficient of the pressure sensor until the reading of the pressure sensor matches the weight of the standard weight, thus obtaining a calibrated pressure sensor. The drive placement head assembly descends, causing the nozzle at the end of the rotating placement shaft of the placement head assembly to press against the upper surface of the pressure calibration platform. At this time, the upper pressure sensor and the lower pressure sensor read the pressure value simultaneously. Compare the reading of the upper pressure sensor with the reading of the calibrated lower pressure sensor obtained in step one. If there is a discrepancy, adjust the parameters of the upper pressure sensor until the reading of the upper pressure sensor is consistent with the reading of the calibrated lower pressure sensor, thus obtaining an upper pressure sensor and a calibrated lower pressure sensor that have been cross-calibrated and have consistency.

4. The adaptive control method for electronic component mounting pressure according to claim 1, characterized in that, The process of driving the placement head assembly to make the nozzle contact the pressure calibration platform at different pressure depths, recording the pressure value corresponding to each pressure depth, and establishing and storing the pressure-position curve includes the following steps: Drive the placement head assembly to move downward from the initial position to the pressure calibration platform, so that the nozzle at the end of the rotating placement shaft of the placement head assembly gradually increases the downward pressure depth to contact the pressure calibration platform in stroke increments of 0.1 mm each time; Record the current pressure value of the pressure sensor and the current Z-axis position value of the mounting head assembly at each pressure depth position until the recorded pressure value covers 1.2 times the upper limit of the actual mounting pressure range of 5 Newtons, i.e., 6 Newtons, to obtain multiple sets of recorded data for different pressure depths and corresponding pressure values. The pressure-position curves are plotted from multiple sets of recorded data for different pressing depths and corresponding pressure values. The pressure-position curves are stored in the monitoring system to obtain pressure-position curves that describe the quantitative mapping relationship between the pressing displacement of the mounting head assembly and the contact pressure.

5. The adaptive control method for electronic component mounting pressure according to claim 1, characterized in that, Obtaining the material characteristic information of the components to be mounted in the current batch, and calculating the initial mounting pressure target value of the current batch based on the similarity matching between the material characteristic information and historical batches, includes the following steps; The substrate type, substrate thickness, substrate flexibility characteristics, chip size, and package type information of the components to be mounted in the current batch are obtained as the material feature information of the current batch, and the material feature information of the current batch is constructed into the feature vector of the current batch. The cosine similarity algorithm is used to calculate the similarity score between the feature vector of the current batch and the feature vectors of each historical batch; Historical batches of data with similarity scores higher than a preset threshold are used as reference datasets to obtain similarity scores for the reference datasets and feature vectors of each historical batch. The similarity scores corresponding to the feature vectors of each historical batch in the reference dataset are summed to obtain the total similarity score. The weighted average method is then used to calculate the recommended initial mounting pressure value for the current batch. The recommended initial placement pressure value is automatically set as the target initial placement pressure value for this placement, thus obtaining the target initial placement pressure value for the current batch.

6. The adaptive control method for electronic component mounting pressure according to claim 1, characterized in that, The placement head assembly moves towards the substrate under the drive of motion control commands generated by the monitoring system based on the initial placement pressure target value. After contacting the substrate surface, the control switches from position control to pressure control, including the following steps: Driven by the initial mounting pressure target value, the mounting head moves towards the substrate at a rapid approach speed. The monitoring system of the mounting head assembly reads the axial pressure value of the force transmission component and the axial displacement of the rotating mounting axis in real time from the micro pressure sensing module of the mounting head assembly. Based on the axial displacement of the rotary mounting axis, when the mounting head assembly approaches the substrate surface, the descent speed of the mounting head assembly is switched to low speed to obtain a state in which the mounting head assembly approaches the substrate surface at low speed. After the nozzle at the end of the rotating mounting shaft of the mounting head assembly contacts the substrate surface, the axial pressure of the force transmission component detected by the micro-pressure sensing module of the mounting head assembly begins to rise from zero. After the monitoring system of the mounting head assembly detects the pressure inflection point of the axial pressure of the force transmission component rising from zero, it switches the control strategy of the mounting head assembly from position control to pressure control, thereby obtaining the mounting state in which the mounting head assembly operates in pressure control mode.

7. The adaptive control method for electronic component mounting pressure according to claim 1, characterized in that, The displacement of the placement head assembly is adjusted in real time based on the pressure-position curve to make the actual placement pressure approach the target pressure value. When a pressure change is detected, the internal air pressure of the control cylinder assembly changes, causing the piston to apply compensating pressure to the force transmission component or release pressure to buffer the pressure change. The steps include: The monitoring system of the placement head assembly obtains the current pressure value of the upper pressure sensor and compares the current pressure value of the upper pressure sensor with the initial placement pressure target value. If the current pressure value of the upper pressure sensor is less than the initial placement pressure target value; Substitute the current pressure value and the initial mounting pressure target value of the upper pressure sensor into the pressure-position curve to obtain the corresponding current pressing position value and target pressing position value, and calculate the difference as the descent displacement. If the current pressure value of the upper pressure sensor is greater than the initial mounting pressure target value, the upward displacement is calculated. The monitoring system of the mounting head assembly controls the mounting head assembly to move by this displacement and repeats the comparison and adjustment until the deviation between the current pressure value of the upper pressure sensor and the initial mounting pressure target value is within the preset allowable range. The pressure change rate of the axial pressure of the force transmission component fed back by the micro pressure sensing module is calculated during the pressure control process. If the pressure change rate exceeds the preset switching threshold, the system switches to the cylinder assembly intervention mode. By adjusting the internal air pressure of the cylinder assembly, the piston applies pressure to or releases pressure to the force transmission component. After the pressure change rate returns to normal, the monitoring system of the mounting head assembly switches back to the fine pressure control mode dominated by the micro pressure sensing module.

8. The adaptive control method for electronic component mounting pressure according to claim 1, characterized in that, During the placement process, the temperature data of each key component of the placement head assembly is collected in real time. The thermal drift compensation is calculated based on the temperature data and superimposed on the motion control command. The placement pressure is feedforward corrected based on the temperature change trend prediction, including the following steps. The monitoring system of the placement head assembly acquires temperature data collected by temperature sensing units located at key components of the placement head assembly, and reconstructs the three-dimensional temperature field distribution of the placement head assembly based on the temperature data of each temperature sensing unit and the heat transfer path between components. The displacement compensation amount in the Z-axis direction and the torsional compensation amount in the radial direction of the mounting head assembly are obtained by dynamically calculating the thermal expansion amount of each key component based on the three-dimensional temperature field distribution of the mounting head assembly. The displacement compensation and torsional compensation are added to the position control amount of the next motion command of the mounting head assembly; The temperature data collected at multiple consecutive time points at the current moment will be used to predict the thermal expansion trend of each key component of the mounting head assembly within a preset time period in the future. If the prediction results show that the future thermal drift will exceed the preset threshold, the monitoring system of the mounting head assembly will output a feedforward compensation command to the Z-axis drive module of the mounting head assembly in advance before the actual occurrence of the future thermal drift. The thickness expansion of the substrate is generated by combining the change of ambient temperature with the coefficient of thermal expansion of the substrate. The thickness expansion or contraction factor is combined with the thermal drift prediction value of the mounting head assembly and then a feedforward correction is added to the initial mounting pressure target value based on the judgment result.

9. The adaptive control method for electronic component mounting pressure according to claim 1, characterized in that, After the mounting is completed, the mounting process data and mounting quality inspection results are stored in the historical database, including the following steps: The material type, material size, batch information, pressure-time-displacement curve, final mounting pressure value, and temperature drift during this mounting process are recorded as the process data for this mounting. The mounting quality inspection results fed back by the AOI inspection equipment are combined with the process data of this mounting to form the complete data of this mounting. The complete data of this mounting is then stored in the historical database of the monitoring system.

10. The adaptive control method for electronic component mounting pressure according to claim 9, characterized in that, If the mounting quality inspection result fed back by the AOI inspection equipment is that the material feature vector and the final mounting pressure value of the current batch are stored as positive samples in the historical database of the monitoring system through the monitoring system of the mounting head assembly; If the AOI inspection equipment reports a failure in the placement quality inspection and the reason for the failure is related to the placement pressure, the monitoring system of the placement head assembly will record the failure case and reduce the recommendation weight of the batch feature vector in subsequent similarity matching.

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