A method for online control of surface mount height based on laser sensing data

Abstract

This invention relates to an online surface mount height control method based on laser sensor data, belonging to the field of electronic assembly process optimization technology, specifically involving an online surface mount height control method based on laser sensor data. The purpose of this invention is to solve the problem that existing surface mount height control strategies struggle to balance warp adaptive compensation and production efficiency. This invention employs a circuit board warp modeling method that integrates the circuit board surface height calculated by an upward-looking laser sensor with the calibrated height of sampling points at the circuit board surface track edge. It only requires collecting single-point height data at the center of each circuit board, combining it with pre-calibrated sampling point heights and the known circuit board thickness to reconstruct the overall board warp distribution, providing Z-axis height compensation model support for each mounting point. This invention calibrates the laser sensor position and the warp-free height, and uses a pressure sensor on the mounting head to calibrate the height of the sampling points at the circuit board surface track edge.

Description

Technical Field

[0001] This invention belongs to the field of electronic assembly process optimization technology, specifically relating to an online control method for surface mount height based on laser sensing data. Background Technology

[0002] With the rapid development of Industry 4.0 and intelligent manufacturing, the integration of electronic products is constantly increasing, and surface mount technology (SMT) is evolving towards high speed, high precision, and high flexibility. In SMT production lines, the pick-and-place machine is the core equipment, and the stability of its placement process directly determines the placement quality and the overall production capacity of the line.

[0003] The placement process of a pick-and-place machine can be summarized as follows: After the nozzle picks up a component from the feeder, the vision system identifies the component's offset relative to the nozzle center and the component's own angle. Based on this, the pick-and-place machine calculates the compensation amounts in the X, Y, and R directions. Subsequently, the placement head rotates the component to the target angle and moves it directly above the target position. It then descends along the Z-axis to press the component into the solder paste, relying on the adhesiveness of the solder paste for temporary fixation. The stable execution of the above process depends on the precise control of the relative distance between the placement head and the circuit board.

[0004] Existing height control strategies generally use preset placement heights, without taking into account the warpage of the circuit board. When the board surface is convex, the actual downward travel of the placement head is too large, and the placement force applied to the components increases accordingly, which can easily cause component damage, lead deformation, or solder paste splatter. When the board surface is concave, the actual downward travel is insufficient, and the placement force is too small, which will weaken the wetting effect between the solder paste and the pads, thereby affecting the reliability of soldering.

[0005] Recent research has proposed a strategy of adding a laser sensor to the placement head to measure the placement height in real time. This approach typically involves the laser sensor emitting a laser beam towards the circuit board. The distance between the sensor and the circuit board is calculated based on the propagation time of the reflected beam and the speed of light. Combined with the sensor's calibration parameters, the actual distance between the placement head and the circuit board is calculated, and the Z-axis downward travel is dynamically adjusted to adapt to local warping. However, this approach requires independent laser ranging before the placement action, leading to decreased production efficiency and making it difficult to balance placement quality and production efficiency.

[0006] Currently, existing technologies lack effective solutions to the aforementioned problems. On the one hand, control strategies based on fixed preset heights do not take circuit board warping into account, making it difficult to adapt to the dynamic changes of actual circuit boards. On the other hand, while real-time measurement strategies based on laser sensors can detect warping, they introduce additional detection steps, sacrificing production efficiency. How to achieve adaptive compensation for circuit board warping without increasing detection time remains a critical problem that urgently needs to be solved. Summary of the Invention

[0007] The purpose of this invention is to solve the problem that existing surface mount height control strategies cannot simultaneously achieve warpage adaptive compensation and production efficiency, and to propose an online surface mount height control method based on laser sensor data.

[0008] The specific process of an online surface mounting height control method based on laser sensing data is as follows:

[0009] Step 1: Fix the laser sensor in an upward viewing position below the circuit board transmission track;

[0010] Step 2: During the machine preparation stage or fixed maintenance cycle, obtain the coordinates of the laser sensor in the calibrated equipment coordinate system, the position and height data of the upper surface of the circuit board at the edge of the track, the height data from the position of the laser sensor to the warp-free fixture, and the height data of the warp-free fixture.

[0011] Step 3: During production, after each circuit board is delivered to its position, the height of the calibrated warp-free fixture is obtained. Based on the measurement value of the current warped circuit board obtained by the laser sensor and the known thickness of the circuit board, the height of the upper surface of the circuit board at the laser sensor position is calculated.

[0012] The height of the upper surface of the circuit board refers to the height from the mounting head 1 to the upper surface of the circuit board.

[0013] Step 4: Based on the height of the upper surface of the circuit board at the location of the laser sensor and the height of the two edges of the upper surface of the circuit board, model the warping distribution of the upper surface of the circuit board.

[0014] Step 5: Based on the warpage distribution model of the current circuit board surface, obtain the height compensation value of each mounting point through coordinate system transformation;

[0015] Step 6: Use the height compensation value to adjust the placement height online and complete the placement head placement.

[0016] The beneficial effects of this invention are as follows:

[0017] Unlike traditional methods that involve mounting a laser sensor on the placement head, this invention fixes the laser sensor in an upward-looking position below the circuit board transport track. Once the circuit board is in place along the conveyor belt, a lifting platform rises to clamp it (in the mechanical design, this upward clamping ensures a fixed height of the circuit board's upper surface, unaffected by board thickness, and the placement height is based on the position of the placement head returning to its origin, with downwards being positive). The laser sensor collects data at its current position below the circuit board. This data, combined with the known circuit board thickness and calibration parameters, is used to calculate the true height of the circuit board's upper surface at that point. Based on this, and combined with the pre-calibrated height of the sampling points on the circuit board's upper surface at the track edge, a warpage distribution model of the entire circuit board can be reconstructed through surface fitting, providing a basis for Z-axis height compensation at subsequent placement points. Since single-point measurement is extremely time-efficient and the computational load required for warpage model fitting is small, the above process can be completed within the interval between the circuit board's arrival and the placement of the first component, without occupying placement time and effectively avoiding production capacity loss. In addition, to ensure the accuracy of the above-mentioned height measurement data and the reliability of the warping model, this invention proposes a calibration scheme for the parameters of the upward-looking laser sensor for the above-mentioned system.

[0018] This invention aims to address the challenge of existing surface mount height control strategies in balancing warpage adaptive compensation and production efficiency, thereby further improving the placement quality and overall line capacity stability of pick-and-place machines when circuit boards are warped. Unlike existing solutions that mount laser sensors on the placement head, this invention fixes the laser sensor in an upward-looking orientation below the circuit board transport track. Height measurement and warpage fitting of the circuit board's upper surface are completed within the interval between the circuit board's arrival and the placement of the first component, thus achieving online height control without interrupting placement time.

[0019] Specifically, this invention has the following two innovative aspects:

[0020] This invention proposes a circuit board warpage modeling method that integrates the height of the circuit board's upper surface calculated by an upward-looking laser sensor with the calibrated height of the sampling points at the track edge of the circuit board's upper surface. It only requires collecting the height data of a single point in the middle of each circuit board, and combining the pre-calibrated sampling point heights with the known circuit board thickness. The warpage distribution of the entire board is reconstructed through surface fitting, providing Z-axis height compensation model support for each mounting point.

[0021] This invention uses a dedicated calibration tool to calibrate the position and warp-free height of the laser sensor, and uses a pressure sensor on the mounting head to calibrate the height of the sampling points on the track edge of the upper surface of the circuit board. Attached Figure Description

[0022] Figure 1 This is a flowchart of the present invention;

[0023] Figure 2 This is a schematic diagram of the mechanical structure of the present invention;

[0024] Figure 3 This is a schematic diagram of the system architecture of the present invention. Detailed Implementation

[0025] Specific Implementation Method 1: The specific process of this implementation method for online control of surface mount height based on laser sensing data is as follows:

[0026] Step 1: Fix the laser sensor in an upward viewing position below the circuit board transmission track for laser sensing data acquisition with online control of surface mount height;

[0027] Step 2: During machine preparation or fixed maintenance cycles, obtain the laser sensor coordinates in the calibrated equipment coordinate system. Position and height data of the upper surface of the circuit board at the edge of the track. The height data from the position of the laser sensor to the warp-free fixture (lower surface). and height data of the warp-free fixture ;

[0028] Step 3: During production, after each circuit board is delivered to its designated position, the height of the calibrated warp-free fixture is obtained. Based on the measured values ​​of the current warped circuit board obtained by the laser sensor. Given the circuit board thickness, calculate the height of the upper surface of the circuit board at the location of the laser sensor. ;

[0029] The height of the upper surface of the circuit board refers to the height from the mounting head 1 to the upper surface of the circuit board.

[0030] Step 4: Based on the height of the upper surface of the circuit board at the location of the laser sensor. Based on the height of the two edges of the upper surface of the circuit board, a warpage distribution model is created for the upper surface of the circuit board.

[0031] Step 5: Based on the warpage distribution model of the current circuit board surface, obtain the height compensation value of each mounting point through coordinate system transformation;

[0032] Step 6: Use the height compensation value to adjust the placement height online and complete the placement head placement.

[0033] Combination Figure 2This embodiment illustrates that the pick-and-place machine has a gantry structure, and the placement head on the cantilever can move along the X, Y, and Z directions within the placement area. The circuit board is conveyed to the placement area of ​​the pick-and-place machine and fixed via a conveyor. Then, a calibrated laser sensor calculates the placement height at the current position. Combined with pre-calibrated height data of sampling points on the upper surface of the circuit board, a warpage plane model is fitted. Simultaneously, a reference camera on the placement head scans the circuit board's mark points to calibrate the board's tilt and recalculates the new placement point coordinates. Finally, based on the warpage fitting model, the online adjustment value of the placement height for each placement point is calculated.

[0034] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that, in step two, during the machine preparation stage or a fixed maintenance cycle, the laser sensor coordinates in the calibrated equipment coordinate system are obtained. Position and height data of the upper surface of the circuit board at the edge of the track. The height data from the position of the laser sensor to the warp-free fixture (lower surface). and height data of the warp-free fixture The specific process is as follows:

[0035] Step 21: Set the fuzzy position of the laser sensor This allows the laser sensor's emitted light to hit approximately the center of the nozzle of the placement head 1 of the pick-and-place machine;

[0036] Step 22: Prepare the calibration disc; the calibration disc contains a positioning circle with a central hole (the calibration circle, positioning circle, and hole are integrated into one piece).

[0037] The positioning circle and the round hole are concentric circles;

[0038] After the placement head 1 of the pick-and-place machine picks up the calibration disc, it moves to the blurred position of the laser sensor. Then, the position is blurred by the laser sensor. Centered on the center, the mounting head moves in four directions (front, back, left, and right) with a variable step size. When the return value of the laser sensor changes, the mounting head moves in four directions (front, back, left, and right) with a smaller step size near the change. When the return value of the laser sensor does not change after the movement, it is determined that the laser beam of the laser sensor hit the circular hole in the center of the calibration disc during the last change.

[0039] For example, if the return value of the laser sensor changes abruptly at 10cm, check if the return value of the laser sensor changes abruptly at 9cm. If it does, check if the return value of the laser sensor changes abruptly at 8cm. If no change occurs at 8cm, then the laser beam of the laser sensor will hit the circular hole in the center of the calibration disc at 9cm.

[0040] Record the position coordinates of the placement head 1 of the pick-and-place machine in the equipment coordinate system when the laser beam enters the circular hole at the center of the calibration disc. ;

[0041] The device coordinate system is a three-dimensional coordinate system, and the coordinate system orientation is as follows: Figure 2 As shown, The shaft is parallel to the guide rail of the pick-and-place machine. The shaft is parallel to the crossbeam of the pick-and-place machine. Axis perpendicular flat;

[0042] Steps 2 and 3: Placement head 1 of the pick-and-place machine The axis is moved upwards to the shooting height of the flying camera (built into the pick-and-place machine), the swing mirror of the flying camera is opened, and the flying camera takes an image of the calibration disc picked up by the placement head 1 of the pick-and-place machine. The image is processed by the OpenCV algorithm to identify the coordinates of the center of the positioning circle on the calibration disc in the coordinate system of the flying camera. ;

[0043] The coordinate system of the flying camera is a two-dimensional coordinate system, with the right side of the captured image as the coordinate system. Axis, and The axis is vertically downward. axis;

[0044] Step 24: Position coordinates of the placement head 1 of the pick-and-place machine in the equipment coordinate system based on the information obtained in Step 22. The coordinates of the center of the circular hole on the calibration disc in steps two and three, in the flight camera coordinate system. Calculate the coordinates of the laser sensor in the calibrated equipment coordinate system; expressed as:

[0045]

[0046]

[0047] in,

[0048] The angle of the flying camera 1 in the equipment coordinate system (counterclockwise is positive) (the placement head 1 of the pick and place machine is photographed by the flying camera 1);

[0049] The offset of flight camera 1 in the known equipment coordinate system of the machine;

[0050] The fixed offset of the flying camera 1 in the known equipment coordinate system of the machine;

[0051] As an intermediate variable;

[0052] The coordinates of the laser sensor in the calibrated equipment coordinate system;

[0053] Step 25: The placement head 1 of the pick-and-place machine lowers the calibration disc to complete the position calibration of the laser sensor in the equipment coordinate system;

[0054] Step 26: Remove the circuit board from the conveyor belt, adjust the conveyor belt width, and transfer it to the warp-free fixture (thickness). The placement head 1 of the pick-and-place machine moves to the preset positions of the two edges of the warp-free fixture parallel to the track. (e.g., 2n symmetrical sampling points on two edges parallel to the track without warping fixture, and n sampling points on one edge) symmetrical sampling points In the equipment coordinate system, the placement head 1 of the pick-and-place machine moves along... The axis descends while simultaneously monitoring the air pressure sensor mounted on the placement head 1 of the pick-and-place machine. When the air pressure value detected by the air pressure sensor changes abruptly, the placement head 1 moves along... The distance the axis descends is from the placement head 1 of the pick-and-place machine to the sampling points at the two edges of the warp-free fixture parallel to the track. height ; sampling points The coordinates are , ;

[0055] For example, along the mounting head 1 When the axis descends 10cm, the air pressure sensor reading jumps. This 10cm mark corresponds to the sampling point between the placement head 1 of the pick-and-place machine and the two edges of the non-warping fixture parallel to the track. height ; sampling points The coordinates are ;

[0056] Step 27: Using the position coordinates of the laser sensor in the equipment coordinate system calibrated in Step 24, obtain the height value of the laser sensor position from the warp-free fixture (lower surface). (The return value of the laser emitted by the laser sensor to the warp-free fixture (lower surface);

[0057] Simultaneously, the placement head 1 of the pick-and-place machine moves to the laser sensor coordinate position in the equipment coordinate system calibrated in step two or four. Pick and place machine along Axially downward, the air pressure sensor mounted on the placement head 1 of the pick-and-place machine is monitored. When the air pressure value detected by the air pressure sensor changes abruptly, the placement head 1 moves along... The distance the axis descends is the height from the placement head 1 of the pick-and-place machine to the warp-free fixture. ;

[0058] Remove the warp-free fixture from the conveyor belt.

[0059] The other steps and parameters are the same as in Specific Implementation Method 1.

[0060] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that, in step three, during production, after each circuit board is delivered to its designated position, the height of the calibrated warp-free fixture is obtained. Based on the measured values ​​of the current warped circuit board obtained by the laser sensor. and known circuit board thickness Calculate the height of the upper surface of the circuit board at the location of the laser sensor. ;

[0061] The height of the upper surface of the circuit board refers to the height from the mounting head 1 to the upper surface of the circuit board.

[0062] The specific process is as follows:

[0063] Step 3: During production, after each circuit board is conveyed to the stop position, the lifting platform rises to fix the circuit board. The laser sensor, calibrated in Step 2:4, then activates to acquire the laser sensor's position. Measurements to the circuit board (bottom surface) ;

[0064] Step 3.2: Based on the height of the placement head 1 of the pick-and-place machine to the warp-free fixture. The height value from the laser sensor position to the warp-free fixture (lower surface) The measured value of the current warped circuit board obtained by the laser sensor. Calculate the position from mounting head 1 to the laser sensor The height of the upper surface of the circuit board is expressed as:

[0065]

[0066] in, Indicates the position of the placement head 1 to the laser sensor. The height of the upper surface of the circuit board. This indicates that the thickness of the circuit board may have been warped during manufacturing. This indicates the thickness of the non-warped circuit board.

[0067] Other steps and parameters are the same as in specific implementation method one or two.

[0068] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that, in step four, the height of the upper surface of the circuit board at the location of the laser sensor is used as the reference. Based on the height of the two edges of the upper surface of the circuit board, a warpage distribution model is created for the upper surface of the circuit board; the specific process is as follows:

[0069] Step 41: According to the pre-marked mounting head 1 in Step 26, place it onto the two edges of the non-warping fixture parallel to the track. Coordinates and height data of each sampling point Obtain the area of ​​the two edge regions on both sides of the circuit board. The coordinates and height data of a symmetrical sampling point are denoted as follows: ,in ; ;

[0070] Step 4.2: Extract the laser sensor position coordinates in the device coordinate system calibrated in Step 2.4. and the height of the upper surface of the circuit board at the location of the laser sensor obtained in step three. , recorded as ;

[0071] Step 4.3. Considering the continuous and smooth variation of circuit board warpage across the entire board in actual production, a quadratic surface model is used to fit the warpage distribution on the upper surface of the circuit board. The expression for the quadratic surface model is as follows:

[0072]

[0073] in, These are the coordinates of any point on the circuit board in the device coordinate system.

[0074] To place the placement head 1 of the pick-and-place machine onto the circuit board. Height;

[0075] , , , , , These are the fitting coefficients for the six surfaces to be determined;

[0076] Step 44: Combine the results obtained in Step 41 and Step 42. Substituting the coordinates of each sampling point into the quadratic surface model expression from step four-three, we obtain the following overdetermined linear equation system:

[0077]

[0078] in, for dimensional matrix, matrix of dimension 1 The row elements are as follows: , ; Sampling points coordinate, ;

[0079] Let be the column vector of the fitting coefficients to be determined;

[0080] for The height column vector of each sampling point; the superscript T indicates transpose;

[0081] Steps four and five: Due to the number of sampling points The number of coefficients to be determined is greater than the number of equations in the system, which is an overdetermined system. The least squares method is used to solve the overdetermined linear system of equations. This yields a column vector of fitting coefficients, represented as:

[0082]

[0083] Step 46: Apply the fitting coefficients obtained in Step 45. , , , , , Substituting back into the quadratic surface model expression from step four-three, we obtain the warping distribution model of the current circuit board surface.

[0084] This model describes any coordinate point within the entire circuit board mounting area in the device coordinate system. The height distribution at each location is used to calculate the Z-axis height compensation value for each mounting point in step five.

[0085] The other steps and parameters are the same as those in one of the specific implementation methods one to three.

[0086] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that, in step five, the height compensation value of each mounting point is obtained through coordinate system transformation based on the warp distribution model of the current circuit board surface; the specific process is as follows:

[0087] Step 51: Before the placement operation begins, the reference camera on the placement head is moved to the theoretical mark point of the circuit board in the equipment coordinate system. coordinates (Pre-programmed) Identifies the actual mark points on the circuit board in the reference camera coordinate system. The coordinates of the center are , ;

[0088] The reference camera coordinate system is a two-dimensional coordinate system, with the right side of the captured image as the reference coordinate system. Axis, and The axis is vertically downward. axis;

[0089] Step 52: Place the actual mark points on the circuit board in the reference camera coordinate system. center coordinates Transform to the device coordinate system to obtain the actual mark points of the circuit board in the device coordinate system. coordinates ;

[0090] Step 53: Based on the actual mark points of the circuit board in the device coordinate system coordinates Compared with the known theoretical mark points of the circuit board in the device coordinate system coordinates , Obtain the current circuit board angle in the device coordinate system. ;

[0091] Current circuit board angle in device coordinate system Calculate the first The connection angle between the sticker point and the mark point 0 ;

[0092] Step 54: Record the first... The theoretical coordinates of each mounting point in the circuit board coordinate system Transform to the device coordinate system to obtain the first... The actual coordinates of each mounting point

[0093] Step 55: Transfer the equipment coordinates obtained in Step 54 to the [missing information - likely a coordinate system or coordinate system]. The actual coordinates of each mounting point Substituting the warping distribution model obtained in step four, calculate the warping distribution in the device coordinate system. The actual height of the upper surface of the circuit board corresponding to each placement point coordinate (from placement head 1 to the upper surface of the circuit board) (height of each mounting point coordinate)

[0094] Step 56: Repeat steps 54 to 55 for all mounting points on the circuit board to obtain the actual height of the upper surface of the circuit board corresponding to the coordinates of all mounting points. The actual height of the upper surface of the circuit board corresponding to the coordinates of all mounting points is used as the height compensation sequence.

[0095] The other steps and parameters are the same as those in one of the specific implementation methods one to four.

[0096] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that, in step five-two, the actual mark points on the circuit board in the reference camera coordinate system will be used. center coordinates Transform to the device coordinate system to obtain the actual mark points of the circuit board in the device coordinate system. coordinates The formula is as follows:

[0097]

[0098]

[0099] in, These are the coordinates of the origin of the circuit board in the device coordinate system.

[0100] Here is the orientation coefficient of the circuit board coordinate system, where , At that time, the circuit board coordinate system is based on the right side. Axis, and The axis is vertically upward. axis; , At that time, the circuit board coordinate system is based on the left side. Axis, and The axis is vertically downward. axis;

[0101] The theoretical mark point of the circuit board in the known device coordinate system The coordinates;

[0102] The reference camera's angle in the device coordinate system is shown on the right. Axis, and The axis is vertically downward. axis;

[0103] The theoretical mark points of the circuit board in the circuit board coordinate system recorded in the production data. The coordinates;

[0104] For the actual mark points of the circuit board in the device coordinate system The coordinates; .

[0105] The other steps and parameters are the same as those in one of the specific implementation methods one to five.

[0106] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One through Six in that, in step five-three, the actual mark points of the circuit board in the device coordinate system are used. coordinates Compared with the known theoretical mark points of the circuit board in the device coordinate system coordinates , Obtain the current circuit board angle in the device coordinate system. ;

[0107] Current circuit board angle in device coordinate system Calculate the first The connection angle between the sticker point and the mark point 0 ;

[0108] The calculation formula is as follows:

[0109]

[0110] in, The current angle of the circuit board in the device coordinate system;

[0111] .

[0112] The other steps and parameters are the same as those in one of the specific implementation methods one to six.

[0113] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that, in step five-four, the number of records in the production data... The theoretical coordinates of each mounting point in the circuit board coordinate system Transform to the device coordinate system to obtain the first... The actual coordinates of each mounting point The conversion formula is as follows:

[0114]

[0115] in, , This represents the total number of components to be mounted on this circuit board.

[0116] The actual mark points of the circuit board in the device coordinate system identified in step 52. The actual coordinates;

[0117] The theoretical mark points of the circuit board in the circuit board coordinate system recorded in the production data. The coordinates;

[0118] The current circuit board angle in the device coordinate system obtained in step 53;

[0119] For the first The angle between the sticker point and the mark point 0;

[0120] The time is marked by the mark point As a reference point, the first The theoretical coordinates of each placement point can be transformed from the circuit board coordinate system to the device coordinate system by rotation and translation, thus obtaining the actual placement coordinates of the j-th placement point in the device coordinate system.

[0121] The other steps and parameters are the same as those in any of the specific implementation methods one to seven.

[0122] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One through Eight in that, in step five-five, the device coordinate system obtained in step five-four is... The actual coordinates of each mounting point Substituting the warping distribution model obtained in step four, calculate the warping distribution in the device coordinate system. The actual height of the upper surface of the circuit board corresponding to each placement point coordinate (from placement head 1 to the upper surface of the circuit board) The height of each mounting point's coordinates); is represented as:

[0123] .

[0124] The other steps and parameters are the same as those in one of the specific implementation methods one to eight.

[0125] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One to Nine in that step six uses a height compensation value to adjust the mounting height online, completing the mounting head placement; the specific process is as follows:

[0126] Step 61: The placement head picks up the first [item] according to the placement sequence. The first component to be mounted (programmed), the flight camera identifies the first... The X and Y offsets of the component to be mounted relative to the center of the nozzle and the first The pick-and-place machine compensates for the angle R of the component to be placed in the X, Y, and R directions. After compensation, the center of the component is moved to the device coordinate system obtained in step 5.2. The actual coordinates of each mounting point Directly above;

[0127] Step 62, based on the device coordinate system The actual coordinates of each mounting point Read the device coordinate system obtained in step 53 beforehand. The actual height of the circuit board surface corresponding to each mounting point coordinate. ;

[0128] Step 63: The mounting head descends along the Z-axis. The components are pressed in and temporarily fixed by the adhesive properties of the solder paste, completing the first step. The placement action of the component to be placed; then the placement head rises along the Z-axis to a safe height, ready for the placement of the next component;

[0129] Step 64: Repeat steps 61 to 63 for all mounting points on this circuit board until the entire board is mounted; after the next circuit board is delivered, repeat steps 3 to 6 to achieve real-time adaptive online control of mounting height to circuit board warping.

[0130] The other steps and parameters are the same as those in any of the specific implementation methods one to nine.

[0131] This invention may have other embodiments. Without departing from the spirit and essence of this invention, those skilled in the art can make various corresponding changes and modifications according to this invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.

Claims

1. A method for online control of surface mounting height based on laser sensing data, characterized in that: The specific process of the method is as follows: Step 1: Fix the laser sensor in an upward viewing position below the circuit board transmission track; Step 2: During the machine preparation stage or fixed maintenance cycle, obtain the coordinates of the laser sensor in the calibrated equipment coordinate system, the position and height data of the upper surface of the circuit board at the edge of the track, the height data from the position of the laser sensor to the warp-free fixture, and the height data of the warp-free fixture. Step 3: During production, after each circuit board is delivered to its position, the height of the calibrated warp-free fixture is obtained. Based on the measurement value of the current warped circuit board obtained by the laser sensor and the known thickness of the circuit board, the height of the upper surface of the circuit board at the laser sensor position is calculated. The height of the upper surface of the circuit board refers to the height from the mounting head 1 to the upper surface of the circuit board. Step 4: Based on the height of the upper surface of the circuit board at the location of the laser sensor and the height of the two edges of the upper surface of the circuit board, model the warping distribution of the upper surface of the circuit board. Step 5: Based on the warpage distribution model of the current circuit board surface, obtain the height compensation value of each mounting point through coordinate system transformation; Step 6: Use the height compensation value to adjust the placement height online and complete the placement head placement.

2. The method for online control of surface mount height based on laser sensing data according to claim 1, characterized in that: In step two, during the machine preparation stage or fixed maintenance cycle, the coordinates of the laser sensor in the calibrated equipment coordinate system, the position and height data of the upper surface of the circuit board at the edge of the track, the height data from the position of the laser sensor to the warp-free fixture, and the height data of the warp-free fixture are obtained. The specific process is as follows: Step 21: Set the fuzzy position of the laser sensor This causes the laser sensor's emitted light to hit the center of the nozzle of the placement head 1 of the pick-and-place machine; Step 22: Prepare the calibration disc; the calibration disc contains a positioning circle with a central hole. The positioning circle and the round hole are concentric circles; After the placement head 1 of the pick-and-place machine picks up the calibration disc, it moves to the blurred position of the laser sensor. Then, the position is blurred by the laser sensor. Centered on the center, the mounting head moves in four directions (front, back, left, and right) with a variable step size. When the return value of the laser sensor changes, the mounting head moves in four directions (front, back, left, and right) with a smaller step size near the change. When the return value of the laser sensor does not change after the movement, it is determined that the laser beam of the laser sensor hit the circular hole in the center of the calibration disc during the last change. Record the position coordinates of the placement head 1 of the pick-and-place machine in the equipment coordinate system when the laser beam enters the circular hole at the center of the calibration disc. ; The equipment coordinate system is a three-dimensional coordinate system. The shaft is parallel to the guide rail of the pick-and-place machine. The shaft is parallel to the crossbeam of the pick-and-place machine. Axis perpendicular flat; Steps 2 and 3: Placement head 1 of the pick-and-place machine The axis is moved upwards to the flight camera's imaging height, the flight camera's tilting mirror is opened, and the flight camera picks up and takes an image of the calibration disc from the placement head 1 of the pick-and-place machine. The image is then processed using the OpenCV algorithm to identify the coordinates of the center of the positioning circle on the calibration disc in the flight camera's coordinate system. ; The aerial camera uses a two-dimensional coordinate system, with the right side of the captured image as the coordinate system. Axis, and The axis is vertically downward. axis; Step 24: Position coordinates of the placement head 1 of the pick-and-place machine in the equipment coordinate system based on the information obtained in Step 22. The coordinates of the center of the circular hole on the calibration disc in steps two and three, in the flight camera coordinate system. Calculate the coordinates of the laser sensor in the calibrated equipment coordinate system; expressed as: in, The angle of flight camera 1 in the device coordinate system; The offset of flight camera 1 in the known device coordinate system; The fixed offset of the flying camera 1 in the known device coordinate system; As an intermediate variable; The coordinates of the laser sensor in the calibrated equipment coordinate system; Step 25: The placement head 1 of the pick-and-place machine lowers the calibration disc to complete the position calibration of the laser sensor in the equipment coordinate system; Step 26: Remove the circuit board from the conveyor belt, adjust the conveyor belt width, and transfer it to the warp-free fixture. The placement head 1 of the pick-and-place machine moves to the preset positions on the two edges of the warp-free fixture parallel to the track. Symmetric sampling points In the equipment coordinate system, the placement head 1 of the pick-and-place machine moves along... The axis descends while simultaneously monitoring the air pressure sensor mounted on the placement head 1 of the pick-and-place machine. When the air pressure value detected by the air pressure sensor changes abruptly, the placement head 1 moves along... The distance the axis descends is from the placement head 1 of the pick-and-place machine to the sampling points at the two edges of the warp-free fixture parallel to the track. height ; Sampling points The coordinates are , ; Step 27: Using the position coordinates of the laser sensor in the equipment coordinate system calibrated in Step 24, obtain the height value from the position of the laser sensor to the warp-free fixture. ; Simultaneously, the placement head 1 of the pick-and-place machine moves to the laser sensor coordinate position in the equipment coordinate system calibrated in step two or four. Pick and place machine along Axially downward, the air pressure sensor mounted on the placement head 1 of the pick-and-place machine is monitored. When the air pressure value detected by the air pressure sensor changes abruptly, the placement head 1 moves along... The distance the axis descends is the height from the placement head 1 of the pick-and-place machine to the warp-free fixture. ; Remove the warp-free fixture from the conveyor belt.

3. The method for online control of surface mount height based on laser sensing data according to claim 2, characterized in that: In step three of the production process, after each circuit board is delivered to its position, the height of the calibrated non-warping fixture is obtained. Based on the measured value of the current warped circuit board obtained by the laser sensor and the known thickness of the circuit board, the height of the upper surface of the circuit board at the location of the laser sensor is calculated. The height of the upper surface of the circuit board refers to the height from the mounting head 1 to the upper surface of the circuit board. The specific process is as follows: Step 3: During production, after each circuit board is conveyed to the stop position, the lifting platform rises to fix the circuit board. The laser sensor, calibrated in Step 2:4, then activates to acquire the laser sensor's position. Measurements to the circuit board ; Step 3.2: Based on the height of the placement head 1 of the pick-and-place machine to the warp-free fixture. The height value from the position of the laser sensor to the warp-free fixture The measured value of the current warped circuit board obtained by the laser sensor. Calculate the position of the mounting head 1 to the laser sensor The height of the upper surface of the circuit board is expressed as: in, Indicates the position of the placement head 1 to the laser sensor. The height of the upper surface of the circuit board. This indicates that the thickness of the circuit board may have warped during manufacturing. This indicates the thickness of the non-warped circuit board.

4. The method for online control of surface mount height based on laser sensing data according to claim 3, characterized in that: In step four, a warping distribution model is created on the upper surface of the circuit board based on the height of the upper surface of the circuit board at the location of the laser sensor and the heights of the two edges on both sides of the upper surface of the circuit board; the specific process is as follows: Step 41: According to the pre-marked mounting head 1 in Step 26, place it onto the two edges of the non-warping fixture parallel to the track. Coordinates and height data of each sampling point Obtain the area of ​​the two edge regions on both sides of the circuit board. The coordinates and height data of a symmetrical sampling point are denoted as follows: ,in ; ; Step 4.2: Extract the laser sensor position coordinates in the device coordinate system calibrated in Step 2.

4. and the height of the upper surface of the circuit board at the location of the laser sensor obtained in step three. , recorded as ; Step 4.3: Fit the warpage distribution on the upper surface of the circuit board using a quadratic surface model. The expression for the quadratic surface model is as follows: in, These are the coordinates of any point on the circuit board in the device coordinate system. To place the placement head 1 of the pick-and-place machine onto the circuit board. Height; , , , , , These are the fitting coefficients for the six surfaces to be determined; Step 44: Combine the results obtained in Step 41 and Step 42. Substituting the coordinates of each sampling point into the quadratic surface model expression from step four-three, we obtain the following overdetermined linear equation system: in, for dimensional matrix, matrix of dimension 1 The row elements are as follows: , ; Sampling points coordinate, ; Let be the column vector of the fitting coefficients to be determined; for The height column vector of each sampling point; the superscript T indicates transpose; Steps four and five: Solve the overdetermined linear equation system using the least squares method. This yields a column vector of fitting coefficients, represented as: Step 46: Apply the fitting coefficients obtained in Step 45. , , , , , Substituting back into the quadratic surface model expression from step four-three, we obtain the warping distribution model of the current circuit board surface.

5. The method for online control of surface mount height based on laser sensing data according to claim 4, characterized in that: In step five, the height compensation value of each mounting point is obtained through coordinate system transformation based on the warpage distribution model of the current circuit board surface; the specific process is as follows: Step 51: Before the placement operation begins, the reference camera on the placement head is moved to the theoretical mark point of the circuit board in the equipment coordinate system. coordinates Identify the actual mark points on the circuit board in the reference camera coordinate system. The coordinates of the center are , ; The reference camera coordinate system is a two-dimensional coordinate system, with the right side of the captured image as the reference coordinate system. Axis, and The axis is vertically downward. axis; Step 52: Place the actual mark points on the circuit board in the reference camera coordinate system. center coordinates Transform to the device coordinate system to obtain the actual mark points of the circuit board in the device coordinate system. coordinates ; Step 53: Based on the actual mark points of the circuit board in the device coordinate system coordinates Theoretical mark points of the circuit board in the device coordinate system coordinates , Obtain the current circuit board angle in the device coordinate system. ; Current circuit board angle in device coordinate system Calculate the first The connection angle between the sticker point and the mark point 0 ; Step 54: Record the first... The theoretical coordinates of each mounting point in the circuit board coordinate system Transform to the device coordinate system to obtain the first... The actual coordinates of each mounting point ; Step 55: Transfer the equipment coordinates obtained in Step 54 to the [missing information - likely a coordinate system or coordinate system]. The actual coordinates of each mounting point Substituting the warping distribution model obtained in step four, calculate the warping distribution in the device coordinate system. The actual height of the upper surface of the circuit board corresponding to the coordinates of each mounting point; Step 56: Repeat steps 54 to 55 for all mounting points on the circuit board to obtain the actual height of the upper surface of the circuit board corresponding to the coordinates of all mounting points. The actual height of the upper surface of the circuit board corresponding to the coordinates of all mounting points is used as the height compensation sequence.

6. The method for online control of surface mount height based on laser sensing data according to claim 5, characterized in that: In step five two, the actual mark points of the circuit board will be located in the reference camera coordinate system. center coordinates Transform to the device coordinate system to obtain the actual mark points of the circuit board in the device coordinate system. coordinates The formula is as follows: in, These are the coordinates of the origin of the circuit board in the device coordinate system. Here is the orientation coefficient of the circuit board coordinate system, where , At that time, the circuit board coordinate system is based on the right side. Axis, and The axis is vertically upward. axis; , At that time, the circuit board coordinate system is based on the left side. Axis, and The axis is vertically downward. axis; The theoretical mark point of the circuit board in the device coordinate system The coordinates; The reference camera's angle in the device coordinate system is shown on the right. Axis, and The axis is vertically downward. axis; The theoretical mark points of the circuit board in the circuit board coordinate system recorded in the production data. The coordinates; For the actual mark points of the circuit board in the device coordinate system The coordinates; .

7. The method for online control of surface mount height based on laser sensing data according to claim 6, characterized in that: In step five-three, the actual mark points of the circuit board in the device coordinate system are used. coordinates Theoretical mark points of the circuit board in the device coordinate system coordinates , Obtain the current circuit board angle in the device coordinate system. ; Current circuit board angle in device coordinate system Calculate the first The connection angle between the sticker point and the mark point 0 ; The calculation formula is as follows: in, The current angle of the circuit board in the device coordinate system; 。 8. The method for online control of surface mount height based on laser sensing data according to claim 7, characterized in that: In step five-four, the first record in the production data is... The theoretical coordinates of each mounting point in the circuit board coordinate system Transform to the device coordinate system to obtain the first... The actual coordinates of each mounting point The conversion formula is as follows: in, , This represents the total number of components to be mounted on this circuit board. The actual mark points of the circuit board in the device coordinate system identified in step 52. The actual coordinates; The theoretical mark points of the circuit board in the circuit board coordinate system recorded in the production data. The coordinates; The current circuit board angle in the device coordinate system obtained in step 53; For the first The angle between the sticker point and the mark point 0 is [0].

9. The method for online control of surface mount height based on laser sensing data according to claim 8, characterized in that: In step 55, the device coordinate system obtained in step 54 is used to... The actual coordinates of each mounting point Substituting the warping distribution model obtained in step four, calculate the warping distribution in the device coordinate system. The actual height of the upper surface of the circuit board corresponding to each mounting point coordinate is represented as: 。 10. The method for online control of surface mount height based on laser sensing data according to claim 9, characterized in that: In step six, the placement height is adjusted online using a height compensation value to complete the placement head placement; the specific process is as follows: Step 61: The placement head picks up the first [item] according to the placement sequence. The first component to be mounted, identified by the flight camera. The X and Y offsets of the component to be mounted relative to the center of the nozzle and the first The pick-and-place machine compensates for the angle R of the component to be placed in the X, Y, and R directions. After compensation, the center of the component is moved to the device coordinate system obtained in step 5.

2. The actual coordinates of each mounting point Directly above; Step 62, based on the device coordinate system The actual coordinates of each mounting point Read the device coordinate system obtained in step 53 beforehand The actual height of the circuit board surface corresponding to each mounting point coordinate. ; Step 63: The mounting head descends along the Z-axis. The components are pressed in and temporarily fixed by the adhesive properties of the solder paste, completing the first step. The placement action of the component to be placed; then the placement head rises along the Z-axis to a safe height, ready for the placement of the next component; Step 64: Repeat steps 61 to 63 for all mounting points on this circuit board until the entire board is mounted; after the next circuit board is delivered, repeat steps 3 to 6 to achieve real-time adaptive online control of mounting height to circuit board warping.

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