A tool hole self-adaptive adjusting device of a high-precision circuit board alignment system

Abstract

This invention discloses an adaptive adjustment device and method for tool holes in a high-precision circuit board alignment system. The device includes an upper camera group, a lower camera group, and multiple PIN adjustment units. The upper camera group acquires images of a target on film, while the lower camera group acquires images of the tool holes on the circuit board. The theoretical coordinates of the current part number are loaded, and the dual cameras are simultaneously triggered to acquire images and calculate the actual offset vector of each tool hole. When the offset exceeds a preset threshold, the theoretical position of the tool hole is used as the control point. A nonlinear deformation field is reconstructed using the radial basis function of a thin-plate spline, and the displacement compensation amount of each PIN adjustment unit is calculated based on the deformation field, driving each PIN unit to move to the target position. The flexible conical PIN head is coated with a PEEK coating and, in conjunction with a force sensor, achieves adaptive force-controlled insertion, automatically correcting the center offset. This method can accurately compensate for the nonlinear deformation and temperature drift of the circuit board, reduce tool hole wear, and improve changeover efficiency and alignment accuracy.

Description

Technical Field

[0001] This invention relates to circuit board manufacturing technology, and more particularly to a tool hole adaptive adjustment device for a high-precision circuit board alignment system. Background Technology

[0002] Currently, high-precision printed circuit board (PCB) exposure processes commonly employ fixed alignment pins and manual / CCD overall alignment. This method has the following technical drawbacks: During processes such as lamination, etching, and baking, circuit boards undergo thermal expansion and contraction or release of internal stress, resulting in non-uniform and non-linear deformations (such as stretching at one corner, shrinking at one corner, or twisting in the middle). Traditional fixed pin or integrally movable alignment platforms can only achieve linear compensation such as translation, rotation, and scaling, and cannot effectively handle complex non-linear deformations, leading to the accumulation of alignment errors, which in severe cases can cause short circuits or open circuits.

[0003] The film and PCB materials exhibit significant differences in their response to temperature and humidity, leading to inconsistent dimensional changes. Current processes primarily rely on manual movement of the film to align the target, which cannot track the film's own deformation in real time. This results in misalignment reappearing within minutes of alignment, affecting the alignment stability of high-density circuitry.

[0004] High-precision circuit boards require multiple exposures. Repeated insertion and removal of the fixing pins wears down the inner wall of the tool hole, leading to increased alignment gaps and decreased accuracy. Furthermore, the tool hole positions, diameters, and quantities vary between different part numbers, necessitating manual pin re-insertion and removal for frequent changes, which is inefficient and prone to errors. While existing CCD exposure machines can automatically identify targets, the initial positioning of the film and fixture still requires manual visual alignment, introducing a random error of approximately 50–100 μm, becoming a bottleneck for production line accuracy. Summary of the Invention

[0005] To address the shortcomings of the existing technology, this invention proposes an adaptive adjustment device for tool holes in a high-precision circuit board alignment system.

[0006] The technical solution of this invention is implemented as follows: A tool hole adaptive adjustment device for a high-precision circuit board alignment system, characterized in that it comprises: The upper camera assembly is mounted above the circuit board and the film negative to acquire images of the film negative target; The lower camera assembly is installed below the circuit board and is used to capture actual images of the tool holes on the circuit board. Multiple pin adjustment units, each of which includes a flexible conical pin head and a Z-axis lifting motor; The tool hole adaptive adjustment device performs the following operations: Load the theoretical coordinates of the tool hole and the film target for the current part number, and move each PIN adjustment unit to the theoretical position; Simultaneously trigger the upper and lower camera groups to acquire images of the film target and tool holes, and calculate the actual offset vector of each tool hole; If the offset vector exceeds the preset threshold, the nonlinear deformation field is reconstructed using the theoretical position of the tool hole as the control point and the radial basis function of the thin plate spline TPS. The displacement compensation of each PIN adjustment unit is calculated based on the deformation field function, and the target position coordinates are generated. Drive each PIN adjustment unit to move to the target position, and control the Z-axis lifting motor to drive the flexible conical PIN head to insert into the tool hole.

[0007] In this invention, the tool hole adaptive adjustment device includes a temperature sensor for real-time acquisition of ambient temperature changes; Among them, the tool hole adaptive adjustment device calculates the thermal compensation amount based on the difference in thermal expansion coefficients between the circuit board and the film, and dynamically updates the deformation field function.

[0008] In this invention, the surface of the flexible tapered PIN head is coated with a PEEK coating to guide the center offset to ±0.1mm.

[0009] In this invention, a force sensor is installed at the end of the Z-axis lifting motor to monitor the axial contact force in real time; wherein, the tool hole adaptive adjustment device adjusts the descent speed according to the magnitude of the contact force.

[0010] In this invention, the tool hole adaptive adjustment device synchronously sends the target position to each servo driver via EtherCAT industrial Ethernet in a distributed clock mode.

[0011] In this invention, the upper camera group and the lower camera group are synchronously triggered to achieve simultaneous acquisition from both sides; the acquired images are sequentially subjected to grayscale conversion, Gaussian filtering, histogram equalization, edge extraction and sub-pixel center fitting, and the positioning accuracy reaches the level of 0.1 pixels.

[0012] In this invention, the Z-axis lifting motor controls the speed in segments during the descent process. Specifically, when descending from the initial position to a certain height above the plate surface, the speed is 10-20 mm / s; after entering the tool hole detection area, the speed is 0.5-1 mm / s. The system monitors the contact force value in real time and compares the detected contact force value with a threshold, thereby readjusting the descent speed.

[0013] In this invention, the Z-axis lifting motor moves with a fixed step size, cooperates with the lower camera group to acquire images and obtain the actual focus height, compares the actual focus height with the theoretical focus height to obtain the warp amount, and when the warp amount exceeds the threshold, the deformation field is extended to three-dimensional space.

[0014] In this invention, the warpage threshold is a preset allowable out-of-plane deformation amount based on the circuit board thickness and process requirements.

[0015] In this invention, the radial basis function of the thin plate spline TPS at any point is equal to the product of the linear transformation vector and the coordinates of that point, plus the translation vector, plus the sum of the products of the weight coefficients of all control points and the radial basis function value; wherein the independent variable of the radial basis function is the Euclidean distance from the current point to the control point.

[0016] The tool hole adaptive adjustment device of the high-precision circuit board alignment system of the present invention has the following beneficial effects: By reconstructing the nonlinear deformation field using the radial basis function of thin plate spline TPS and combining it with the actual offset vector of tool hole, the local nonlinear deformation of PCB can be accurately described, such as corner stretching, corner shrinkage, and center twisting, realizing independent displacement compensation for each PIN unit and significantly improving alignment accuracy.

[0017] By collecting ambient temperature changes in real time through temperature sensors and combining the difference in thermal expansion coefficients between the PCB and the substrate, the thermal compensation amount is calculated and the deformation field function is dynamically updated to effectively compensate for alignment errors caused by temperature drift and improve the system's adaptability to the thermal environment.

[0018] Load the theoretical coordinates of the tool hole and the film target for the current part number, and automatically identify the target position of each tool hole. No manual re-insertion of PINs is required, which greatly reduces changeover time and human error, and improves the flexibility and efficiency of the production line.

[0019] The flexible tapered PIN is coated with PEEK, which has low friction and high wear resistance. It can automatically correct the center offset to ±0.1mm. When used with a Z-axis force sensor, it decelerates when the contact force is >3N and accelerates when it is <0.5N, avoiding overstress insertion or jamming, protecting the inner wall of the tool hole and extending its service life. Attached Figure Description

[0020] Figure 1 This is a structural block diagram of the tool hole adaptive adjustment device of the present invention; Figure 2 This is a schematic diagram of the tool hole adaptive adjustment device of the present invention; Figure 3 This is another structural schematic diagram of the tool hole adaptive adjustment device of the present invention; Figure 4This is a logic block diagram of the tool hole adaptive adjustment device of the present invention.

[0021] The reference numerals in the attached figures are as follows: 1-Upper camera group; 2-Lower camera group; 3-Temperature sensor; 4-EtherCAT industrial Ethernet; 5-Multiple servo drives; 6-XY axis servo motors; 61-X-axis translation assembly; 62-Y-axis translation assembly; 7-Z-axis lifting motor; 8-Multiple PIN adjustment units; 9-Multiple flexible conical PIN heads; 10-Force sensor. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0023] Example 1 Reference Figures 1 to 3 As shown, this embodiment proposes a tool hole adaptive adjustment device for a high-precision circuit board alignment system, including an upper camera group 1, a lower camera group 2, a temperature sensor 3, an EtherCAT industrial Ethernet 4, multiple servo drivers 5, XY axis servo motors 6, a Z axis lifting motor 7, multiple PIN adjustment units 8, multiple flexible conical PIN heads 9, and a force sensor 10.

[0024] The XY-axis servo motor 6 includes an X-axis translation component 61 and a Y-axis translation component 62. The Z-axis lifting motor 7 is mounted on the Y-axis translation component 62 via the X-axis translation component 61, or the Z-axis lifting motor 7 is mounted on the X-axis translation component 61 via the Y-axis translation component 62. That is, the X-axis translation component 61 and the Y-axis translation component 62 can drive the Z-axis lifting motor 7 along... Figure 3 Move in the XY direction.

[0025] Furthermore, the individual PIN adjustment unit 8, the multiple flexible conical PIN heads 9, and the force sensor 10 are all mounted on the Z-axis lifting motor 7 and will move together with the Z-axis lifting motor 7.

[0026] The upper camera group 1 is installed above the PCB board and the film negative to acquire images of the film negative target; the lower camera group 2 is installed below the PCB board to acquire actual images of the PCB tool holes; the upper camera group 1 and the lower camera group 2 achieve simultaneous acquisition on both sides through a synchronous triggering mechanism to ensure the spatiotemporal consistency of the film and board surface deformation data.

[0027] First, the theoretical coordinates of the tool hole and the film target for the current part number are loaded. Each PIN adjustment unit 8 is moved to its theoretical position and raised to complete initialization. Then, the upper camera group 1 and the lower camera group 2 are triggered synchronously to acquire images of the film target and the PCB tool hole, respectively. After sub-pixel edge extraction and center coordinate calculation, the actual offset vector of each tool hole is obtained. If the offset exceeds a preset threshold, the theoretical position of the tool hole is used as the control point, and the nonlinear deformation field is reconstructed using the thin-plate spline TPS radial basis function. Simultaneously, the temperature sensor 3 collects real-time ambient temperature changes, calculates the thermal compensation amount based on the difference in thermal expansion coefficients between the PCB and the film, and dynamically updates the deformation field function. Then, the displacement compensation amount at the theoretical position of each PIN adjustment unit 8 is calculated based on the deformation field function, resulting in... The final target position coordinates are synchronously transmitted to each servo drive 5 via EtherCAT industrial Ethernet 4 in a distributed clock mode. The servo drive 5 drives the corresponding XY axis servo motor 6 to precisely move the PIN adjustment unit 8 to the target position. After the XY plane is adjusted into place, the Z axis lifting motor 7 drives the entire PIN assembly to descend at a low speed, allowing the flexible conical PIN head 9 to enter the tool hole. The surface of the PIN head is coated with PEEK, which can automatically correct the center offset to ±0.1mm. During the descent, the force sensor 10 installed at the end of the Z axis monitors the axial contact force in real time. When the contact force is greater than 3N, the descent speed is reduced, and when it is less than 0.5N, the descent speed is increased. With the help of the force control algorithm, over-stress insertion or jamming is avoided, and finally, high-precision alignment is completed.

[0028] Example 2 Based on the above embodiments, referring to Figure 4 As shown in the figure, the specific working principle of the tool hole adaptive adjustment device of the high-precision circuit board alignment system proposed in this embodiment includes the following steps: Step 1: Load theoretical coordinates and initialize adjustment units; Different PCB parts have varying tool hole positions, diameters, and numbers, making traditional fixed pin methods unsuitable for diverse tooling requirements. Load the theoretical coordinate set of tool holes for the current part number. Theoretical coordinate set of film target It can automatically identify the target position of each tool hole, avoiding manual PIN re-insertion and removal, reducing changeover time and human error. During initialization, the PIN is moved to the theoretical position and raised to establish a benchmark for subsequent visual acquisition and deformation compensation.

[0029] Step 2: Simultaneous acquisition of images from both sides; Film and PCB board will undergo non-linear deformation under different temperature and humidity environments, and the deformation of the two is inconsistent. Traditional single-sided vision or manual alignment cannot capture this difference.

[0030] By synchronously triggering the upper and lower dual camera groups, images of the film target and PCB tool holes are acquired simultaneously, ensuring the spatiotemporal consistency of the alignment data of the two sides, providing accurate raw data for calculating the relative deformation between the two, and avoiding additional errors caused by asynchronous acquisition time.

[0031] Step 3: Subpixel edge extraction and center coordinate calculation; The edges of the tool hole and the target may be blurred due to factors such as lighting, material reflection, and wear. Traditional pixel-level positioning accuracy is insufficient to meet the requirements of high-precision alignment. By using sub-pixel algorithms, such as circle fitting and Canny edge detection + interpolation, the positioning accuracy is improved to the 0.1 pixel level. Combined with a telecentric lens and optimized light source, the extraction accuracy of the tool hole center coordinates is improved, providing higher-quality input data for deformation field reconstruction.

[0032] The acquired images are processed sequentially as follows: Step 301: Convert the color image to grayscale to reduce computation; use Gaussian filtering to smooth noise; enhance edge contrast through histogram equalization or contrast stretching. Step 302: Use the Canny operator, double threshold to suppress false edges, or the SUSAN operator, based on local gray-level similarity, to extract the contour points of the target / hole, which is robust to noise. Step 303: For the circular target, perform least-squares circle fitting using edge points to obtain the center coordinates; for the cross target, find the intersection point through line fitting. To improve accuracy, perform grayscale interpolation in the edge normal direction, such as parabolic interpolation, to achieve a sub-pixel resolution of 0.1 pixels for the center coordinates.

[0033] Finally, output the actual coordinates of the film target. actual coordinates of tool hole .

[0034] Step 4: Calculate the tool hole offset vector; PCBs undergo nonlinear deformation during manufacturing, such as corner stretching, corner shrinkage, and central twisting. Traditional overall translation / rotation / scaling methods cannot describe such complex deformations. By calculating the difference between the actual and theoretical positions of each tool hole, a discrete offset vector is obtained. This offset vector serves as the basis for subsequent deformation field reconstruction and can reflect the deformation characteristics of various local areas of the PCB.

[0035] For each tool hole i, its theoretical design coordinates are known. Then the offset vector for: ; For offset vector Make a judgment if the offset vectors of all tool holes If all values ​​are less than the preset threshold T, it indicates that all are accurately aligned, and the process proceeds directly to Step 7; otherwise, the process continues to the next step for correction. The preset threshold T is typically 5µm.

[0036] Step 5: Based on the offset vector Nonlinear deformation field reconstruction correction is performed; based on the theoretical position of the tool hole. Given the control points, their offset vectors are known. Solve for a smooth and accurate deformation function. The linear combination coefficients yield a nonlinear mapping that precisely or approximately satisfies the given offset at the control points while being smooth globally.

[0037] Since discrete offset vectors cannot be directly used to drive individual PIN units, they need to be transformed into a continuous and smooth deformation field for the entire PCB.

[0038] Furthermore, for points in two-dimensional space The TPS deformation function is expressed as: ; In the formula, Denotes the linear transformation vector, where, The 1×2 row vectors are merged into a 2×2 matrix M; simplified form Indicates the linear part. Let be the translation vector, where is the translation vector. Depend on as well as composition. This represents the weight vector of the i-th control point. Include as well as Each control point corresponds to two component weights. Indicate control points; Represents the radial basis function of TPS. ,in, Represents the Euclidean distance, which varies with p. N is the total number of control points. Linear transformation vector. Translation vector Weighting coefficients All of these are values ​​to be solved.

[0039] Subsequently, the fitting accuracy and surface smoothness are balanced by minimizing the following energy functional, representing the dimension: ; ; ; In the formula, To fit the error term, the deformation field is forced to approximate the true offset vector at the control points. ; It represents the bending energy term, measures the square integral of the second derivative of the surface, and indicates the degree of bending of the surface; For regularization parameters, regularization parameters The value range of is [0, 1]. When At this time, a certain degree of fitting deviation is allowed in exchange for smoother deformation. The time is a strict interpolation. Represents the domain of the deformation field, a continuous region of an image or mesh.

[0040] Then Substitute the expression into the function and add the orthogonality condition. and This forms a system of linear equations, from which the linear transformation vector is obtained. Translation vector Weighting coefficients Specifically, how to calculate the linear transformation vector of the value to be solved? Translation vector Weighting coefficients Among them, control points That is, the theoretical position of the tool hole is known, and the offset vector at the control point is... Also known is the control point offset vector. That is, actual position - theoretical position.

[0041] The parameters to be solved are: the weight vector of each control point. Linear transformation matrix Translation vector .

[0042] Construct a matrix form and define a block matrix. , as well as .in, , and Indicates two adjacent control points. .

[0043] The parameters to be solved are the matrix sum matrix For example, suppose a circuit board has 3 tool holes, and the theoretical position and actual offset are as follows:

[0044] Tool Hole 1, Theoretical Coordinates The actual offset is (10,10). (15,10); Tool hole 2, theoretical coordinates The actual offset is (110, 10). (12, -5); Tool hole 3, theoretical coordinates The actual offset is (60, 90). The coordinates are (-8, 20); where the theoretical coordinates are in mm and the actual offsets are in um.

[0045] The computation matrix K is represented as: ; ; ; ; ; ;

[0046] Based on the above, matrix , matrix ,matrix .

[0047] Solve the matrix based on the actual offsets of tool hole 1, tool hole 2, and tool hole 3. sum matrix Among them, matrix The right-hand vector Solve the system of linear equations ,get: ; ; ; .

[0048] Similarly, matrix The right-hand vector Solve the system of linear equations ,get: ; ; ; .

[0049] This allows us to obtain the theoretical offset at any point, thereby driving each PIN unit to independently compensate for the actual deformation and achieve precise alignment.

[0050] Furthermore, the film and PCB materials have different coefficients of thermal expansion, and temperature changes can cause dynamic dimensional drift. (This addresses the issue of temperature fluctuations during exposure causing continuous relative dimensional drift between the film and PCB due to their different coefficients of thermal expansion.) Step 6: Read the temperature sensor Calculate the predicted deformation of thermal expansion Update the deformation field function Among them, when the temperature changes At this time, the two materials have different lengths due to their different coefficients of thermal expansion. The relative deformation caused by thermal expansion is: ; In the formula, This is expressed as the coefficient of thermal expansion of the PCB board. This refers to the coefficient of thermal expansion of the film. The coefficient of thermal expansion can be found in the material handbook, and a typical value can be directly obtained from the TDS (Total Displacement Data Sheet) provided by the selected film type or the film material supplier. The unit of the coefficient of thermal expansion is 1 / ℃.

[0051] This indicates the change in ambient temperature, i.e., the reading of the temperature sensor; Indicates the initial dimensions, such as the spacing between alignment marks or the nominal length of the workpiece.

[0052] Deformation field function Describes arbitrary coordinates on the workpiece plane The combined displacement vector at the location. The initial deformation field is obtained through calibration, and then, in each control cycle, it is calculated based on the fused deformation field. The deformation field can be updated locally or globally.

[0053] Step 7: Let the theoretical design position of each PIN adjustment unit be... In actual assembly, due to factors such as thermal expansion and mechanical deformation, this position will deviate from the theoretical value. This is achieved through the reconstructed continuous deformation field function. It provides a displacement compensation vector for any spatial location.

[0054] The target command position for each PIN adjustment unit is calculated as follows: ; in, Represents the theoretical coordinates of the i-th PIN; Represents the reconstructed continuous deformation field function, outputting two-dimensional or three-dimensional displacement compensation; This indicates the final target position coordinates of the PIN adjustment unit.

[0055] Local compensation values ​​at the theoretical positions are used to correct the theoretical coordinates, enabling the PIN adjustment unit to move to the target pose after actual deformation, thereby offsetting alignment errors caused by thermal expansion and contraction or deformation due to stress. All target positions are synchronously transmitted to each servo drive via EtherCAT real-time industrial Ethernet in a distributed clock mode. EtherCAT's low jitter ensures strict time synchronization of multi-axis movements, avoiding relative displacement errors caused by time differences in command arrival.

[0056] Step 8: After all the PIN adjustment units are in the correct XY plane position, the Z-axis lifting mechanism drives the entire PIN assembly to descend at a low speed, allowing the flexible tapered PIN head to gradually enter the tool hole. Meanwhile, a force sensor (range 0–5N, resolution 0.01N) installed at the end of the Z-axis monitors the axial contact force F in real time.

[0057] It should be noted that when the PIN component descends from its initial position to a certain height above the board surface, such as 2-5mm, it uses a speed of 10-20mm / s, and this stage does not rely on contact force feedback.

[0058] After entering the tool hole detection area, the PIN assembly descends at a speed of 0.5-1 mm / s, and the contact force value F is monitored in real time. The detected contact force value F is compared with a threshold, and the descent speed of the PIN assembly is adjusted accordingly. Specifically, if the contact force F > 3 N, the descent speed of the PIN assembly is reduced to prevent over-stress insertion; if the contact force < 0.5 N, the descent speed of the PIN assembly is increased to maintain insertion efficiency.

[0059] The PIN head is designed with a flexible tapered structure and coated with a PEEK coating. This PEEK coating has a low coefficient of friction (μ≈0.2) and high wear resistance. The tapered geometry can automatically correct the hole diameter deviation with a center offset of ±0.1mm, and the force control algorithm prevents jamming.

[0060] The specific details of this technical solution are as follows: Load the theoretical coordinate set of the tool hole and the theoretical coordinate set of the film target corresponding to the current processing part number of the PCB, automatically identify the target position of each tool hole, move each PIN adjustment unit to the theoretical position and raise it to complete the initialization, and establish a benchmark for subsequent visual acquisition and deformation compensation.

[0061] Next, by synchronously triggering the upper and lower dual-camera groups, images of the film target and PCB tool holes are simultaneously acquired to ensure the spatiotemporal consistency of the alignment data on both sides. The acquired images undergo preprocessing such as grayscale conversion, Gaussian filtering smoothing, histogram equalization, or contrast stretching. Subsequently, the edge contours of the target or holes are extracted using Canny or SUSAN operators. Through sub-pixel algorithms, the actual coordinates of the film target and the actual center coordinates of each tool hole are calculated, achieving a positioning accuracy of 0.1 pixels. Then, the offset vector between the actual position of each tool hole and its theoretical design position is calculated. If all offset vectors are less than the preset threshold T, it is determined to be accurately aligned, and the process directly proceeds to the PIN unit position adjustment stage; otherwise, the process proceeds to the nonlinear deformation field reconstruction and correction step.

[0062] In the deformation field reconstruction stage, using the theoretical position of the tool hole as the control point, a continuous and smooth nonlinear deformation field is constructed using the radial basis function of the thin-plate spline TPS. By minimizing the fitting error and bending energy functional, the linear transformation vector, translation vector, and weighting coefficients are solved to obtain the theoretical offset of any point on the entire PCB. In addition, temperature sensor data is read in real time, and combined with the difference in thermal expansion coefficients between the circuit board and the substrate, the relative deformation caused by thermal expansion is calculated, and the deformation field function is dynamically updated to compensate for the alignment error caused by temperature drift.

[0063] Based on the reconstructed continuous deformation field function, the displacement compensation corresponding to the theoretical design position of each PIN adjustment unit is calculated to obtain the final target position coordinates. All target positions are synchronously transmitted to each servo drive via EtherCAT industrial Ethernet in a distributed clock mode to ensure strict synchronization of multi-axis motion.

[0064] Once all PIN units are aligned in the XY plane, the Z-axis lifting mechanism lowers the entire PIN assembly at a low speed, allowing the flexible tapered PIN head to gradually enter the tool hole. A force sensor mounted at the end of the Z-axis monitors the axial contact force in real time: if the contact force exceeds 3N, the descent speed is reduced to prevent overstress insertion; if the contact force is below 0.5N, the descent speed is increased to maintain efficiency. The flexible tapered structure can automatically correct hole diameter deviations of up to ±0.1mm, and combined with a force control algorithm, it avoids jamming, ultimately achieving precise alignment.

[0065] Example 3 Based on one or more of the above embodiments, this embodiment further discloses that when significant out-of-plane warping is detected, such as bending of a thin plate in the thickness direction, it is necessary to extend the deformation field to three-dimensional space. The three-dimensional TPS deformation function is: ; in, Represents three-dimensional spatial coordinates; The translation amount, A linear transformation vector is equivalent to a translation vector in two-dimensional space. and linear transformation vector . Represents the radial basis function of TPS. It represents the Euclidean distance. It should be noted that in three-dimensional space, this function is still the radial basis with the minimum bending energy.

[0066] In three-dimensional space, the solution process is similar to that in two-dimensional space, requiring the establishment of a system of linear equations with N+4 unknowns and the application of orthogonality conditions. , , and Once the continuous deformation field is obtained, warpage compensation can be performed on any voxel or mesh point.

[0067] Furthermore, the Z-axis lifting motor 7 is controlled to move upward or downward in fixed steps, starting from the initial height, with each fixed step being 10 μm. For each fixed step, the lower camera group 2 acquires one frame of image, and the actual focusing height of the lower camera group 2 during image acquisition is obtained. .

[0068] Actual focus height Altitude of focus with theoretical focus By comparison, the warping amount at that point can be obtained. Warpage When the warping exceeds the threshold, the deformation field is extended to three-dimensional space.

[0069] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A tool hole adaptive adjustment device for a high-precision circuit board alignment system, characterized in that, include: The upper camera assembly is mounted above the circuit board and the film negative to acquire images of the film negative target; The lower camera assembly is installed below the circuit board and is used to capture actual images of the tool holes on the circuit board. Multiple pin adjustment units, each of which includes a flexible conical pin head and a Z-axis lifting motor; The tool hole adaptive adjustment device performs the following operations: Load the theoretical coordinates of the tool hole and the film target for the current part number, and move each PIN adjustment unit to the theoretical position; Simultaneously trigger the upper and lower camera groups to acquire images of the film target and tool holes, and calculate the actual offset vector of each tool hole; If the offset vector exceeds the preset threshold, the nonlinear deformation field is reconstructed using the theoretical position of the tool hole as the control point and the radial basis function of the thin plate spline TPS. The displacement compensation of each PIN adjustment unit is calculated based on the deformation field function, and the target position coordinates are generated. Drive each PIN adjustment unit to move to the target position, and control the Z-axis lifting motor to drive the flexible conical PIN head to insert into the tool hole.

2. The tool hole adaptive adjustment device according to claim 1, characterized in that, The tool hole adaptive adjustment device includes a temperature sensor for real-time acquisition of ambient temperature changes; Among them, the tool hole adaptive adjustment device calculates the thermal compensation amount based on the difference in thermal expansion coefficients between the circuit board and the film, and dynamically updates the deformation field function.

3. The tool hole adaptive adjustment device according to claim 1, characterized in that, The flexible tapered PIN head is coated with a PEEK coating to correct center offset to ±0.1mm.

4. The tool hole adaptive adjustment device according to claim 1, characterized in that, A force sensor is installed at the end of the Z-axis lifting motor to monitor the axial contact force in real time; the tool hole adaptive adjustment device adjusts the descent speed according to the magnitude of the contact force.

5. The tool hole adaptive adjustment device according to claim 1, characterized in that, The tool hole adaptive adjustment device synchronously sends the target position to each servo drive via EtherCAT industrial Ethernet in a distributed clock mode.

6. The tool hole adaptive adjustment device according to claim 1, characterized in that, The upper and lower camera groups are synchronously triggered to achieve simultaneous acquisition from both sides; the acquired images are sequentially subjected to grayscale conversion, Gaussian filtering, histogram equalization, edge extraction and sub-pixel center fitting, with a positioning accuracy of 0.1 pixel level.

7. The tool hole adaptive adjustment device according to claim 1, characterized in that, The Z-axis lifting motor controls its descent speed in segments. When descending from the initial position to a certain height above the plate surface, it uses a speed of 10-20 mm / s. After entering the tool hole detection area, it descends at a speed of 0.5-1 mm / s. The system monitors the contact force value in real time and compares the detected contact force value with a threshold, thereby readjusting the descent speed.

8. The tool hole adaptive adjustment device according to claim 1, characterized in that, The Z-axis lifting motor moves in fixed steps, and cooperates with the lower camera group to acquire images and obtain the actual focus height. The actual focus height is compared with the theoretical focus height to obtain the warp amount. When the warp amount exceeds the threshold, the deformation field is extended to three-dimensional space.

9. The tool hole adaptive adjustment device according to claim 8, characterized in that, The warpage threshold is a preset allowable out-of-plane deformation amount based on the circuit board thickness and process requirements.

10. The tool hole adaptive adjustment device according to claim 1, characterized in that, The radial basis function of the thin plate spline TPS at any point is equal to the product of the linear transformation vector and the coordinates of that point, plus the translation vector, plus the sum of the products of the weight coefficients of all control points and the radial basis function value; The independent variable of the radial basis function is the Euclidean distance from the current point to the control point.

Images