A steel mesh and PCB size matching dynamic mapping method and device

Abstract

The application relates to the high-precision assembly technical field of an LED die bonding process, in particular to a steel mesh and PCB size matching dynamic mapping method and device, which solve the matching failure problem caused by the size change of a steel mesh. The method part comprises the following steps: selecting a PCB product with stable tin paste printing and meeting preset conditions from current production, calculating the actual size data of a current screen plate through tin paste images of four corners of the PCB product; matching a PCB to be matched with the screen plate based on the actual size data of the current screen plate; when preset screen plate data updating conditions are met, selecting a PCB product with printing meeting preset conditions from current production again, extracting tin paste images of four corners of the PCB product to update the actual size data of the screen plate, and continuing the matching of the PCB to be matched with the screen plate based on the updated actual size data.

Description

TECHNICAL FIELD

[0001] The present application relates to the high-precision assembly technology field of LED die bonding process, and particularly relates to a steel mesh and PCB size matching dynamic mapping method and device. BACKGROUND

[0002] In the production process of LED lamp panels, the COB (Chip On Board) die bonding link has very high requirements for the size matching accuracy of the steel mesh and the PCB (Printed Circuit Board). During the processing, transportation and storage of the PCB, the PCB will expand or shrink by microns due to factors such as temperature fluctuations and external forces. Since the size of the COB single pad is in the micron level, the expansion and contraction of the PCB will directly cause the offset of the coincidence degree with the pad during the printing of the solder paste, and then the solder paste will overflow the pad area or be printed into the positive and negative channels. The traditional scheme generally uses the following scheme to solve the coincidence degree offset problem:

[0003] Single-camera acquisition and identification scheme: The mark points of the PCB board are dynamically acquired by a single camera, the distance between the four mark points is calculated to obtain the actual size of the PCB, and then the PCB is divided into multiple size categories according to the preset size difference (such as 20 μm for one category), and different categories are matched with different steel meshes for printing. The accuracy of this scheme is affected by the superposition of the accuracy of the equipment moving parts, the image recognition accuracy and the mechanical accuracy, and the accuracy can only reach ± 5 μm.

[0004] 4-camera fixed identification scheme: Four cameras are fixed at the mark point positions of the four corners of the PCB, the actual size of the PCB is obtained by image recognition of the mark points, and then the steel mesh is matched according to the set classification difference size. This scheme avoids the influence of the accuracy of the mechanical moving parts, and the accuracy is improved to ± 3 μm, but only solves the classification accuracy problem caused by mechanical movement.

[0005] As can be seen, although the above two schemes can realize the size classification of the PCB, they have the common limitation that the steel mesh will increase in size by microns during the printing process due to continuous stress and compression, which will cause the matching relationship between the original steel mesh and the PCB to fail after a certain number of printing times, and the matching needs to be re-matched through secondary metrology or printing experiments. The re-matching process is tedious and time-consuming, which seriously affects the production efficiency, and it is difficult to ensure the real-time and accuracy of the matching. Therefore, there is an urgent need for a technical scheme that can realize real-time dynamic matching of the size of the steel mesh and the PCB to solve the matching failure problem caused by the size change of the steel mesh, and to improve the production efficiency and welding quality. SUMMARY

[0006] The application relates to the high-precision assembly and die bonding technology field of an LED die bonding process, and provides a steel mesh and PCB size matching dynamic mapping method and device, which are used for solving the matching failure problem caused by the size change of a steel mesh in a traditional scheme.

[0007] A steel mesh and PCB size matching dynamic mapping method, the steel mesh being a screen plate for PCB solder paste printing, the method comprising:

[0008] PCB products with stable performance meeting preset conditions after solder paste printing are selected from current production, and actual size data of the current screen plate is calculated by extracting solder paste images of four corners of the PCB products;

[0009] The PCB to be matched is matched with the screen plate based on the actual size data of the current screen plate;

[0010] When a preset screen plate data updating condition is met, the PCB products meeting preset conditions after printing are selected from current production again, solder paste images of four corners of the PCB products are extracted to update the actual size data of the screen plate, and the matching of the PCB to be matched with the screen plate is continued based on the updated actual size data;

[0011] Further, the actual size data of the current screen plate is calculated by extracting solder paste images of four corners of the PCB products, comprising:

[0012] When the solder paste images of four corners of the PCB products are extracted, a plurality of pads are identified at each corner to form a face, and the actual size data of the current screen plate is calculated based on the face information of the four corners.

[0013] Further, the matching of the PCB to be matched with the screen plate based on the actual size data of the current screen plate comprises:

[0014] Solder paste points of four corners of the solder paste images of the PCB to be matched are extracted to obtain actual size features of the PCB;

[0015] The center point of the screen plate is calculated based on the actual size data of the current screen plate, and the center point of the PCB is calculated based on the actual size features of the PCB;

[0016] The center point of the screen plate is coincided with the center point of the PCB to form a coincided center point, and the coincided center point is used as a reference origin point of coordinate conversion;

[0017] The four-corner coordinates of the screen plate and the four-corner pad coordinates of the PCB are unified to the same coordinate system through coordinate conversion, so as to obtain new screen plate four-corner coordinates and PCB four-corner pad coordinates in the unified coordinate system;

[0018] The matching of the double-dimension constraint mechanism is determined based on the unified new screen plate four-corner coordinates and the PCB four-corner pad coordinates; the double-dimension constraint mechanism includes that the geometric center of the solder paste completely covers the effective soldering area of the corresponding pad and there is no overlap on the edge, and the vertical distance between the solder paste and the four edges of the pad satisfies the preset process safety condition;

[0019] When the double-dimension constraint mechanism conditions are met at the same time, it is marked that the PCB and the current screen plate have size adaptability, and when any condition fails to pass the verification, it is determined that there is no match and an alarm prompt is triggered and recorded.

[0020] Further, the preset screen plate data update condition includes at least one of the following: the number of times of using the actual size data of the screen plate reaches a preset number threshold, and the number of matched PCB products corresponding to the screen plate reaches a preset number threshold.

[0021] Further, a plurality of production lines are included, each production line uses an actual size data acquisition device for acquiring the actual size data of the screen plate of each line body, and the PCB to be matched is matched and classified based on the actual size data of each line body screen plate, and the PCB that does not meet any screen plate matching condition is classified separately.

[0022] Further, the coordinate conversion includes:

[0023] Translate the vertex coordinates of the screen plate quadrilateral and the vertex coordinates of the PCB four-corner pad to a temporary coordinate system with the coincidence center point as the origin, to obtain temporary coordinates;

[0024] In the temporary coordinate system, the temporary coordinates are rotated by applying a rotation matrix, and the screen plate is made parallel to the X-axis by rotation;

[0025] Translate the rotated temporary coordinates back to the original coordinate system to obtain the new screen plate four-corner coordinates and the PCB four-corner pad coordinates unified to the same coordinate system.

[0026] A steel mesh and PCB size matching dynamic mapping device, the steel mesh is a screen plate for PCB solder paste printing; the device includes an image acquisition module, a data processing module and a control module;

[0027] The image acquisition module is used to acquire the solder paste image of the four corners of the PCB product after printing, which meets the preset condition of stability;

[0028] The data processing module is used to calculate the actual size data of the current screen plate based on the solder paste image of the four corners of the PCB product acquired by the image acquisition module, and to match the PCB to be matched with the screen plate based on the actual size data of the current screen plate;

[0029] The control module is configured to trigger the image acquisition module to re-acquire the solder paste images of the four corners of the PCB product with stable post-printing stability meeting the preset condition from the current production when the preset stencil data updating condition is met, to update the actual size data of the stencil through the data processing module, and to control the matching of the subsequent to-be-matched PCB and the stencil based on the updated actual size data.

[0030] Further, when the image acquisition module acquires the solder paste images of the four corners of the product, a plurality of pads are identified at each corner to form a face, and the actual size data of the current stencil is calculated based on the face information of the four corners.

[0031] Further, the data processing module is configured to, when matching the to-be-matched PCB and the stencil, specifically:

[0032] extracting solder paste points of the four corners of the solder paste image of the to-be-matched PCB to obtain actual size features of the PCB;

[0033] calculating a center point of the stencil based on the actual size data of the current stencil and calculating a center point of the PCB based on the actual size features of the PCB;

[0034] aligning the center point of the stencil and the center point of the PCB to form an aligned center point, which serves as a reference origin point for coordinate conversion;

[0035] unifying the four-corner coordinates of the stencil and the four-corner pad coordinates of the PCB to the same coordinate system through coordinate conversion to obtain new four-corner coordinates of the stencil and new four-corner pad coordinates of the PCB in the unified coordinate system;

[0036] performing matching determination based on the unified new four-corner coordinates of the stencil and the new four-corner pad coordinates of the PCB through a two-dimension constraint mechanism; the two-dimension constraint mechanism includes that the geometric center of the solder paste points completely covers the effective soldering area of the corresponding pad and the edges do not overlap, and the perpendicular distance between the solder paste and the four edges of the pad meets the preset process safety condition;

[0037] when the two-dimension constraint mechanism conditions are met at the same time, marking that the PCB and the current stencil have size adaptability, and when any condition fails to pass the verification, determining that the matching fails and triggering an alarm prompt and recording.

[0038] A PCB printing system includes a printing execution mechanism and a stencil and PCB size matching dynamic mapping device as claimed in any one of the preceding claims; the printing execution mechanism is configured to perform solder paste printing on the PCB using the stencil; and the stencil and PCB size matching dynamic mapping device is configured to realize dynamic mapping of the size matching between the stencil and the PCB and provide matching information for the printing execution mechanism.

[0039] In one of the schemes provided in the application, the actual size data of the steel mesh is extracted in real time and dynamically updated, solving the problem of matching failure of the steel mesh due to size increase caused by increased printing times in the traditional scheme. By updating the data, the continuous and accurate matching with the PCB can be ensured, and the matching implementation problem is solved. Moreover, by taking the PCB product meeting the stability condition as the reference, the accuracy of the actual size data of the steel mesh is ensured, which can cover the expansion (micron level) of the PCB caused by temperature and external force and the stress deformation of the steel mesh, adapt to the complex environment in the production of LED lamp panels, and is conducive to improving the production efficiency and welding quality. BRIEF DESCRIPTION OF DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the application, the drawings needed to be used in the description of the embodiments of the application will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0041] Figure 1 is a flowchart of a steel mesh and PCB size matching dynamic mapping method in an embodiment of the application;

[0042] Figure 2 is a positional relationship diagram of a tin paste point and a pad in a steel mesh and PCB size matching dynamic mapping method in an embodiment of the application;

[0043] Figure 3 is a layout relationship diagram of four cameras in a steel mesh and PCB size matching dynamic mapping method in an embodiment of the application;

[0044] Figure 4 is a coordinate diagram of a screen plate size calculation in a steel mesh and PCB size matching dynamic mapping method in an embodiment of the application;

[0045] Figure 5 is a schematic diagram of a screen plate and PCB matching determination in a steel mesh and PCB size matching dynamic mapping method in an embodiment of the application;

[0046] Figure 6 is a working process diagram of a PCB printing system in an embodiment of the application. DETAILED DESCRIPTION

[0047] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only some of the embodiments of the present application, but not all of the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present application.

[0048] In the embodiments of the present application, a steel mesh and PCB size matching dynamic mapping method are provided, the steel mesh is a screen plate for PCB solder paste printing, and the method comprises the following steps:

[0049] S101, selecting a PCB product with stable solder paste printing after completion and meeting preset conditions from current production, and calculating actual size data of a current screen plate by extracting solder paste images of four corners of the PCB product;

[0050] S102, matching a PCB to be matched with the screen plate based on the actual size data of the current screen plate;

[0051] S103, when a preset screen plate data updating condition is met, reselecting a PCB product with stable printing after completion and meeting preset conditions from current production and extracting solder paste images of four corners thereof to update actual size data of the screen plate, and continuing to match the PCB to be matched with the screen plate based on the updated actual size data.

[0052] The screen plate refers to a screen plate for PCB solder paste printing, for example, a steel mesh, the opening size of which is matched with a PCB pad, and which is used for solder paste printing in a COB fixed crystal link. The PCB product with stable solder paste printing after completion and meeting preset conditions refers to a qualified PCB product with no defects such as offset and overflow after solder paste printing, and high solder paste coverage of the pad, that is, a PCB product with good stability.

[0053] In the embodiments, solder paste distribution images of a PCB product with stable solder paste printing after completion and meeting preset conditions can be collected by a high-precision camera, and then actual size data of the screen plate is calculated. The current actual opening size and overall geometric parameters (such as four corner coordinates, side length, etc.) of the screen plate are calculated by solder paste image features (such as solder paste contour, pad relative position). The preset screen plate data updating condition: the actual size data of the screen plate is compared for a preset threshold (for example, 500 times) or the number of corresponding PCB products reaches a preset threshold (for example, 500), and then the actual size data of the screen plate is reextracted.

[0054] To facilitate understanding of the processing procedure of this embodiment, this embodiment takes the COB die bonding link of LED lamp panel production as an application scenario for illustration. In the LED lamp panel production line of an electronic factory, the COB pad size is 50 pm x 50 pm, and the matching precision requirement of the steel mesh (screen plate) and the PCB reaches ±2 pm. However, the steel mesh size increases after about 500 times of printing due to continuous stress, resulting in invalidation of the original matching relationship, and frequent overflow of the pads during solder paste printing. Through the dynamic matching mapping method of this embodiment, the steel mesh size data can be dynamically and real-timely updated, the dynamic and accurate matching with the PCB is realized, and the printing defects are reduced.

[0055] Taking the matching of the steel mesh and the PCB of the LED production line as an example, 3 PCB products (solder paste printing without deviation, and higher pad coverage) with stable conditions are selected from the currently produced LED lamp panels and placed on the stage of the matching mapping device. As shown in FIG. 1, 4 cameras (camera 1, camera 2, camera 3, and camera 4) corresponding to the four corners of the PCB product shoot the solder paste images. The positions of the cameras can be adjusted, and the positions correspond to the four corners of the PCB respectively. The cameras can clearly identify the pads of the four corners of the PCB and can extract clear images to calculate the distances of the four pads. Figure 3

[0056] The data processing module extracts features (such as solder paste edge coordinates and pad center distance) from the solder paste images of the four sides, and obtains the actual size data (such as the opening side length 52 pm and the diagonal distance of the four corners 120.3 mm) of the current steel mesh through multi-surface geometric operations. For the PCB to be matched newly entering the production line, the image acquisition module obtains the solder paste point images of the four corners thereof, and extracts size features (such as pad distance and diagonal distance). Based on the actual size data of the steel mesh obtained in the foregoing steps, through coordinate conversion (unified to the same coordinate system) and a double-dimension constraint mechanism (solder paste covers the pad and the edge does not overlap, and the solder paste and the pad edge distance is greater than or equal to 3 pm), it is determined whether the PCB to be matched matches the current steel mesh. Example: the pad diagonal distance of a certain PCB is 120.1 mm, and the steel mesh diagonal distance is 120.3 mm. After calculation, it is determined that the double-dimension constraint is satisfied, and the PCB is marked as “matched” and enters the next die bonding process. The comparison times of the actual size data of the steel mesh (1 time for each matched PCB) are recorded in real time. When the comparison times reach the preset threshold value 500 times, the motion control module triggers a reminder (flashing of the indicator light + screen prompt “Please update the steel mesh data”). The operator or the device selects a new PCB with stable conditions (solder paste printing qualified) that meets the preset conditions, repeats the image extraction and operation, and obtains the actual size data of the updated steel mesh. Based on the updated actual size data, the subsequent PCBs are continuously matched (for example, a certain PCB pad diagonal distance 120.4 mm matches the updated steel mesh, and is determined as “adapted”).

[0057] ​In this embodiment, by extracting the actual size data of the steel mesh in real time and dynamically updating, the problem of matching failure caused by the increase in size of the steel mesh due to the increase in printing times in the traditional scheme is solved. For example, the size of the steel mesh changes by 30 μm after being used 500 times, and the data can be updated to ensure continuous and accurate matching with the PCB. Moreover, by taking the PCB product that meets the stability condition as a reference, the accuracy of the actual size data of the steel mesh is ensured, which can cover the expansion and contraction (micron level) of the PCB caused by temperature and external force and the stress deformation of the steel mesh, and adapt to the complex environment in the production of LED lamp panels.

[0058] In addition, in an embodiment, the actual size data (such as the opening size and the diagonal distance) of the steel mesh calculated each time is automatically stored in a local database, including a time stamp and a corresponding PCB batch number, to record the size change history of the mesh plate for traceability and wear analysis. A trend chart of “steel mesh size-use times” can be generated, and when the slope is greater than a set condition (wear acceleration), a warning is automatically pushed to the administrator terminal.

[0059] In an embodiment, the actual size data of the current mesh plate calculated by extracting the solder paste image of the four corners of the PCB product includes: when the solder paste image of the four corners of the PCB product is extracted, a plurality of pads are identified at each corner to form a plane, and the actual size data of the current mesh plate is calculated based on the plane information of the four corners.

[0060] As shown in Figure 4 , a plurality of pads form a plane, which means that a plurality of pads are selected at each corner of the PCB product, and a geometric plane is formed by the relative position relationship of the pads, rather than the point information of a single pad. Based on the plane formed by the plurality of pads at each corner, the geometric parameters (such as the flatness of the plane, the pad spacing, and the diagonal line length) of the plane are calculated, and the overall actual size data of the steel mesh is calculated by integrating the plane information of the four corners, rather than by using only single pad or mark point data.

[0061] For ease of understanding, the COB die bonding production line of a certain LED packaging factory is taken as an application scenario. The pad size of the MiniLED lamp panel produced by the production line is 160 μm x 120 μm. The traditional steel mesh size measurement only calculates the overall size by using single corner or single pad data, which is prone to cause overall matching deviation due to local error. By using the embodiments of the present application, the actual size of the steel mesh used for subsequent matching is dynamically calculated based on the plane information formed by multiple pads, which can improve the processing accuracy.

[0062] Taking the calculation of the actual size of the steel mesh of the production line as an example, three PCB products with stable solder paste printing are selected from the current production and placed on the stage of the matching mapping device. As shown in Figure 4As shown, the solder paste images of the four corners of the PCB product are captured by four high-precision cameras respectively, and the capture area of each corner contains six adjacent pads (such as pads A1-A6 at the upper left corner, B1-B6 at the upper right corner, etc.). Taking the upper left corner of the PCB as an example, the data processing module processes the solder paste images of the six pads: identifies the geometric center coordinates of each pad (such as A1: (x1, y1), A2: (x2, y2)... A6: (x6, y6)); calculates the plane parameters formed by the six pads: including the distance between adjacent pads (such as the distance d1 between A1 and A2), the flatness deviation of the plane, and the diagonal length (the distance d2 between A1 and A6); integrates these parameters into the "face information" of the upper left corner, reflecting the steel mesh opening characteristics of the area. The right upper corner, the left lower corner, and the right lower corner of the PCB are calculated respectively to obtain their respective face information (such as the distance between the six pads at the upper right corner, the flatness, etc.). The data processing module performs the following operations based on the face information of the four corners: calculates the parallelism of the overall plane of the steel mesh; calculates the opening coordinates of the four corners of the steel mesh (based on the diagonal length and relative position of the face information of each corner); and integrates to obtain the actual size data of the steel mesh: such as the overall length L = 150.234 mm, the width W = 80.121 mm, and the opening size 120.μm*80μm.

[0063] In this embodiment, the plane formed by multiple pads is identified at each corner, avoiding accidental errors of single-pad measurement. Local errors can be averaged to improve the calculation accuracy of the overall actual size data. In addition, since the face information contains multiple parameters such as plane flatness and pad spacing, it can better reflect the overall deformation of the steel mesh (such as local warping caused by stress) than a single mark point. For example, if a corner of the steel mesh is tilted by 0.5° due to extrusion, the normal vector deviation of the face information can accurately identify it, while single-pad data cannot reflect such deformation.

[0064] It is also worth mentioning that if one of the six pads at a corner has no valid image due to missing solder paste (such as A3 pad with solder paste coverage < 50%), the pad will be automatically excluded, and the face information will be recalculated using the remaining five pads. That is, up to one invalid pad can be excluded at a single corner to ensure the continuity of the face information.

[0065] In an embodiment, the matching of the PCB to be matched with the current screen plate based on the actual size data of the current screen plate comprises:

[0066] Extracting the solder paste points of the four corners of the solder paste image of the PCB to be matched to obtain the actual size characteristics of the PCB;

[0067] Calculating the center point of the screen plate based on the actual size data of the current screen plate, and calculating the center point of the PCB based on the actual size characteristics of the PCB;

[0068] The center point of the screen plate is coincided with the center point of the PCB to form a coincided center point, which is used as a reference origin point for coordinate conversion;

[0069] The four corner coordinates of the screen plate and the four corner pad coordinates of the PCB are unified to the same coordinate system through coordinate conversion to obtain new screen plate four corner coordinates and PCB four corner pad coordinates in the unified coordinate system;

[0070] Based on the unified new screen plate four corner coordinates and the PCB four corner pad coordinates, a double-dimension constraint mechanism is matched to determine the matching; the double-dimension constraint mechanism includes that the geometric center of the solder paste completely covers the effective soldering area of the corresponding pad and the edge has no overlap, and the vertical distance between the solder paste and the four edges of the pad meets the preset process safety condition;

[0071] When the double-dimension constraint mechanism conditions are met at the same time, it is marked that the PCB and the current screen plate have size adaptability, and when any condition fails to pass the verification, it is determined that it does not match and triggers an alarm prompt and records.

[0072] In an embodiment, the coordinate conversion includes:

[0073] The coordinates of the vertices of the screen plate quadrilateral and the vertices of the PCB four corner pads are translated to a temporary coordinate system with the coincided center point as the origin to obtain temporary coordinates;

[0074] In the temporary coordinate system, a rotation matrix is applied to the temporary coordinates for rotation, and the rotation matrix is a two-dimensional rotation matrix:

[0075] , wherein the rotation angle Based on the included angle between the target edge of the screen plate and the X-axis, the screen plate is rotated to be parallel to the X-axis;

[0076] The rotated temporary coordinates are translated back to the original coordinate system to obtain the new screen plate four corner coordinates and the PCB four corner pad coordinates unified to the same coordinate system.

[0077] In this embodiment, the PCB to be matched is sorted based on the actual size data of the current steel mesh obtained:

[0078] The solder paste points of the four corners of the PCB solder paste image are extracted, and 6 solder paste points are selected for each corner; a set of data closest to the true value is extracted to calculate the center point of the steel mesh.

[0079] Coordinate conversion principle and process: coordinate system and point representation: in a two-dimensional rectangular coordinate system, the four vertices of the quadrilateral formed by the steel mesh can be represented as , wherein each vertex is a two-dimensional coordinate vector, which can be represented in the form of a column matrix:

[0080]

[0081] Rotation matrix principle: in two-dimensional plane, point rotates around the origin The transformation matrix of angle (counterclockwise positive) is:

[0082]

[0083] Where the role of the matrix is to transform the original coordinate vector Into the coordinate vector after rotation That is: .

[0084] Calculation steps of quadrilateral directional rotation:

[0085] Center point coordinate calculation: the geometric center point of the quadrilateral Is the arithmetic mean of the coordinates of the four vertices, and the calculation formula is as follows: .

[0086] The matrix representation of the center point is: .

[0087] Rotation angle determination: let the target side be , which needs to be rotated to be parallel to the X axis (that is, the y coordinates of the two points after rotation are equal). The direction vector of side is:

[0088]

[0089] Where, . The angle between the direction vector and the X axis (radian) can be calculated by the inverse tangent function: .

[0090] In order to make side parallel to the X axis, it needs to be rotated to the angle of 0 with the X axis, so the required rotation angle is

[0091]

[0092] Coordinate transformation process: in order to ensure that the center point position does not change, the composite transformation process of "translation-rotation-translation back" is adopted:

[0093] ① Translate each vertex coordinate to the temporary coordinate system with the center point C as the origin, and get the temporary coordinate

[0094] ② In the temporary coordinate system, apply the rotation matrix to the temporary coordinate , and get the rotated temporary coordinate :

[0095]

[0096] Unfolded into component form:

[0097]

[0098] ③ Rotate the temporary coordinates of the four corners of the PCB to the coordinate system of the steel mesh Translate back to the original coordinate system to get the final coordinates :

[0099]

[0100] The new coordinates of the four points after conversion are:

[0101]

[0102]

[0103]

[0104]

[0105] In this embodiment, the coordinate calculation and processing of the steel mesh and the coordinate calculation and processing of the PCB to be matched are processed in the above manner.

[0106] The actual size feature of the PCB reflects the current actual geometric size of the PCB to be matched by extracting the coordinates, spacing, shape, and other features of the four corner solder paste points of the PCB. The geometric center points (the arithmetic mean of the coordinates of each vertex) of the screen plate and the PCB are used as the reference for coordinate conversion. Through the composite transformation of translation-rotation-translation back, the coordinates of the four corners of the screen plate and the PCB are unified to the same coordinate system, eliminating the influence of angle deviation. As shown in Figure 5 , a two-dimensional constraint mechanism is used for matching judgment: ① The solder paste geometric center completely covers the pad effective area and the edge has no overlap, as shown in Figure 1 , check whether the solder paste geometric center completely covers the pad, and the solder paste edge and the pad edge have no overlap. The solder paste width (Wtin) and the pad width (Wpad) satisfy W=Wtin-Wpad>0, the solder paste height (Htin) and the pad height (Hpad) satisfy H=Htin-Hpad>0, W and H are both greater than 0), to ensure that the solder paste completely covers the pad and has no size. ② The perpendicular distance between the solder paste and the four sides of the pad is ≥ the preset process safety threshold. The process safety threshold can be dynamically adjusted according to the PCB material: for example, the threshold of FR4 material PCB is set to 8μm, and the threshold of ceramic substrate PCB is set to 10μm due to higher brittleness, which can be dynamically adjusted according to the PCB material, and for example, the aluminum substrate material is dynamically adjusted to 10μm.

[0107] Here, a certain automotive electronic COB module production line is taken as an application scenario. The PCB pads of this production line are rectangular arrays with a size of 40 pm x 40 pm, and the steel mesh openings need to be accurately matched with the pads. Since the PCB expands and shrinks due to temperature changes during storage, and the steel mesh deforms slightly after use, the traditional direct comparison method is prone to matching errors, leading to offset of the solder paste printing. Through this embodiment, high-precision matching can be achieved through coordinate transformation and two-dimensional constraints, and the deviation can be controlled to reduce printing defects.

[0108] For example, taking the matching of a certain batch of PCBs and steel meshes of this production line as an example, based on the actual size data of the steel mesh obtained in the foregoing steps, the coordinates of the four corner points are (10.000, 5.000), (30.000, 5.000), (30.000, 25.000), (10.000, 25.000) (unit: mm), and the center point C 网板 of the mesh plate is calculated as = (10 + 30 + 30 + 10) / 4 = 20.000, = (5 + 5 + 25 + 25) / 4 = 15.000, that is, C 网板 = (20.000, 15.000).

[0109] The solder paste point images of the four corners of the PCB to be matched are collected, and 6 solder paste points are selected for each corner, and the pad vertex coordinates are extracted as (10.002, 5.001), (30.003, 5.002), (30.001, 25.003), (10.003, 25.001), and the center point C PCB of the PCB is calculated as = (10.002 + 30.003 + 30.001 + 10.003) / 4 ≈ 20.002, = (5.001 + 5.002 + 25.003 + 25.001) / 4 ≈ 15.002, that is, C PCB = (20.002, 15.002).

[0110] Coordinate transformation (unified to the same coordinate system): C 网板 is coincided with C PCB (taken as the reference origin), and at this time the center point deviation of the mesh plate and the PCB to be matched is corrected by translation. The coordinates of the mesh plate vertices in the temporary coordinate system (with the coincided center point as the origin) are calculated as = -C 网板=(-10.000,-10.000) =(10.000,−10.000), =(10.000,10.000), =(−10.000,10.000); The temporary coordinates of the PCB vertices are calculated similarly. ≈(-9.999, -9.999), ≈(9.999, -9.999), ≈(9.999,9.999), ≈(-9.999,9.999).

[0111] Target edge of the mesh panel The direction vector is (0, 20.000) (parallel to the X-axis), and the corresponding edge of the PCB... There is a 0.1° tilt, which can be addressed using a rotation matrix. To align the directions of both, the temporary coordinates after rotation are translated back to the original coordinate system to obtain the unified coordinates of the four corners of the new mesh. ~ PCB corner pad coordinates ~ .

[0112] After the coordinates are transformed, a two-dimensional constraint matching judgment is performed:

[0113] Dimension 1 (Coverage and Edge): such as Figure 2 As shown, check whether the geometric center of the solder paste completely covers the pad, and whether the edges of the solder paste and the pad overlap. The solder paste width (W_solder) and the pad width (W_pad) satisfy W = W_solder - W_pad > 0, and the solder paste height (H_solder) and the pad height (H_pad) satisfy H = H_solder - H_pad > 0 (both W and H are greater than 0), ensuring that the solder paste completely covers the pad and has no dimensional constraints. In the example, the coordinates of the solder paste edge of a certain pad on the PCB are all within the pad range (no overflow), which meets the conditions.

[0114] Dimension 2 (Distance Threshold): The vertical distances between the solder paste and the four sides of the pad (top, bottom, left, and right) are measured and are 9μm, 9.5μm, 9.2μm, and 9.8μm respectively. All of these distances are ≥ the preset threshold of 8μm, thus satisfying the distance constraint.

[0115] If both constraints are met, the PCB is marked as "size-fits-all" with the current stencil, allowing it to proceed to the printing process. If the distance between the solder paste and one side of a PCB pad is 6.5μm (<3μm), it is determined to be "mismatched," triggering an alarm (light + screen prompt) and recording the data.

[0116] In this embodiment, the screen plate and the PCB are unified to the same coordinate system through coordinate conversion, solving the misjudgment caused by angle and position deviation in traditional direct comparison. The angle deviation and the center point deviation are eliminated through conversion, improving the matching accuracy. Moreover, the double constraints of non-overlapping of the coverage edge and threshold determination avoid solder paste overflow from the pad and ensure the welding reliability. The printing defects can be greatly reduced.

[0117] In addition, in the aforementioned "translation-rotation-translation back" process, the position deviation is eliminated through the temporary coordinate system, and the angle deviation is corrected through the rotation matrix, finally unifying the screen plate and the PCB coordinates, accurately aligning the geometric positions of the screen plate and the PCB, effectively reducing the matching error, and also effectively avoiding the measurement error caused by the non-uniform coordinate system.

[0118] In an embodiment, the preset screen plate data update condition includes at least one of the following: the number of times of using the actual size data of the screen plate reaches a preset number threshold, and the number of matched PCB products corresponding to the screen plate reaches a preset quantity threshold.

[0119] In this embodiment, the preset number threshold refers to the upper limit of the number of times of using the actual size data of the screen plate for matching PCB (such as preferably 500 times), and the actual size data of the screen plate is updated when the number of times reaches the threshold. The preset quantity threshold refers to the upper limit of the number of matched and produced PCB products corresponding to a screen plate (such as preferably 500), and the actual size data of the screen plate is updated when the number of products exceeds the threshold. The actual size data of the screen plate is updated when any of the above thresholds is met, ensuring that the actual size data of the screen plate is synchronized with the actual state, and realizing real-time dynamic matching.

[0120] Taking the screen plate data updating mechanism of the production line as an example, based on the production process requirements, the control module of the matching mapping device is set as: preset number threshold = 500 times (maximum number of times of comparing the size data of the screen plate); preset quantity threshold = 500 (maximum number of PCB products that can be matched by a single screen plate).

[0121] After the actual size data (aperture size 120 pm) of the screen plate is obtained and put into use, the system automatically records the "number of times of using the actual size data" (cumulative +1) every time a PCB is matched. When the number of times reaches 500, the control module triggers an update reminder (the display module pops up "the screen plate data has reached 500 times, and needs to be updated", accompanied by a beeping prompt). The operator or the device selects a new PCB product (solder paste printing qualified) that meets the stability requirements, reextracts the solder paste image and calculates the actual size data of the screen plate (at this time, the aperture size of the screen plate increases to 135 pm due to 500 times of use), and completes the data update.

[0122] Synchronous record the number of matched and passed PCB products corresponding to the current steel mesh (each production of 1 qualified product, cumulative +1). When the number of qualified products corresponding to a certain mesh reaches 500, even if the number of uses does not reach 500 times, the control module still triggers an update reminder (displaying "the steel mesh has matched 500 products, it is recommended to update the data"). After re-extracting the actual size data of the steel mesh, it is found that its size has increased to 138.5μm due to long-term use. The updated data is used for subsequent matching to avoid defective products caused by size deviation.

[0123] In this embodiment, through the double-threshold triggering mechanism, the number of uses of the actual size data of the steel mesh (500 times) is limited, and the number of corresponding products (500) is also restricted, covering the size changes of the steel mesh caused by the frequency of use and the cumulative load. The size deviation of the steel mesh is always within the range, reducing the printing defect rate of the PCB product. Moreover, the preset threshold (such as 500 times / 500) is set based on the wear law of the steel mesh, avoiding production interruption caused by frequent data updates, while ensuring the timeliness of the data. The continuity of production is improved.

[0124] It should be noted that if the number of comparisons does not reach 500 times, but a large number of PCBs fail to match in succession (both dimensions do not meet the requirements), an emergency update mechanism can be triggered to forcibly re-extract the size data of the steel mesh. The update process is immediately executed.

[0125] In an embodiment, multiple production lines are included, each production line uses a device for obtaining the actual size data of the mesh of each line body, and the PCBs to be matched are respectively matched with the mesh of each line body based on the actual size data thereof, and the PCBs that do not meet the matching conditions of any mesh are separately classified.

[0126] The multiple production lines refer to multiple independent line bodies (such as A, B, and C lines) that produce the same type of PCB product in parallel, and each line body is equipped with an independent steel mesh and a matching mapping device (such as A, B, and C line bodies). For the steel mesh of each line body, the tin paste image is extracted by the corresponding matching mapping device, and the current actual size data (such as the opening size and the diagonal distance) calculated thereby need to be stored and managed separately. The PCBs to be matched are respectively compared with the actual size data of the steel mesh of each line body, and the adaptability is determined according to the double-dimension constraint results (the processing process can be seen in the previous embodiment, which is not repeated here). The PCBs that do not match with the steel mesh of all line bodies are marked as to-be-processed, and the reasons are recorded and analyzed separately.

[0127] For example, taking the matching and classification of a batch of 100 PCBs as an example, the specific steps are as follows:

[0128] Each line body selects the PCB (solder paste printing qualified) produced by the line body through its matching mapping device, extracts the four-corner solder paste image (6 pads per corner), and calculates the actual size data of the respective steel mesh, for example:

[0129] A line steel mesh: hole size 120 pm, four-corner coordinates PA1-PA4, diagonal distance 100.000 mm;

[0130] B line steel mesh: hole size 121 pm, four-corner coordinates PB1-PB4, diagonal distance 100.003 mm;

[0131] C line steel mesh: hole size 122 pm, four-corner coordinates PC1-PC4, diagonal distance 100.005 mm.

[0132] For the batch of 100 PCBs, the four-corner solder paste point images are obtained one by one through the image acquisition module, the size features (such as pad spacing, diagonal distance) are extracted, and the center point and four-corner coordinates of each PCB are calculated. For each PCB, the actual size data of the A, B, and C line steel meshes are matched and determined:

[0133] Adapt to A line: the diagonal distance of a certain PCB is 100.000 mm, which matches the A line steel mesh (solder paste coverage without overflow, edge distance ≥ 3 pm), and is allocated to A line production;

[0134] Adapt to B line: a certain PCB has slight expansion, and the diagonal distance is 100.003 mm, which matches the B line steel mesh (when matched with the A line, the edge distance is only 2 pm, which does not meet the requirements), and is allocated to B line production;

[0135] Adapt to C line: the diagonal distance of a certain PCB is 100.005 mm, which only matches the C line steel mesh, and is allocated to C line production;

[0136] Separate classification: 3 PCBs have excessive expansion (diagonal distance 100.010 mm), and when matched with the A, B, and C line steel meshes, solder paste overflow occurs (which does not meet the two-dimensional constraints), and are marked as to-be-processed, and can be separately sent to the artificial re-inspection station.

[0137] Finally, 97 adapted PCBs are allocated to the corresponding line body according to the classification results, and 3 to-be-processed PCBs are detected by artificial detection, and it is confirmed that the storage deformation causes, and after secondary processing correction, they are re-participated in matching.

[0138] In the embodiment, the multi-line body matching classification can adapt the same batch of PCBs to different states of the steel mesh (such as a new mesh plate and a half-old mesh plate), so as to avoid PCB waste caused by the mismatch of a single line body steel mesh. In the embodiment, the utilization rate of the PCB is effectively improved. Moreover, it is worth mentioning that the PCBs that do not meet any mesh plate matching condition are classified separately, which facilitates the centralized analysis of defect causes (such as storage deformation and batch difference), is beneficial to targeted optimization of the process (such as adjustment of the storage environment), and enhances the production flexibility.

[0139] It should be understood that the size of the serial number of each step in the above embodiment does not mean the order of execution, and the execution order of each process should be determined according to its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present application.

[0140] In an embodiment, a steel mesh and PCB size matching dynamic mapping device is provided, and the steel mesh is a mesh plate used for PCB solder paste printing. The device comprises an image acquisition module, a data processing module and a control module.

[0141] The image acquisition module is configured to acquire solder paste images of four corners of a PCB product after printing is completed and the stability meets a preset condition.

[0142] The data processing module is configured to calculate actual size data of a current mesh plate based on the solder paste images of the four corners of the PCB product acquired by the image acquisition module, and match a PCB to be matched with the mesh plate based on the actual size data of the current mesh plate.

[0143] The control module is configured to trigger the image acquisition module to reacquire the solder paste images of the four corners of the PCB product after printing is completed and the stability meets the preset condition from the current production when a preset mesh plate data updating condition is met, so as to update the actual size data of the mesh plate by the data processing module, and control the matching of the subsequent PCB to be matched with the mesh plate based on the updated actual size data.

[0144] In an embodiment, when the image acquisition module acquires the solder paste images of the four corners of the product, a plurality of pads are identified at each corner to form a face, and the actual size data of the current mesh plate is calculated based on the face information of the four corners.

[0145] In an embodiment, when the data processing module matches the PCB to be matched with the mesh plate, the data processing module is specifically configured to:

[0146] extract solder paste points of the four corners of the solder paste image of the PCB to be matched to obtain actual size features of the PCB;

[0147] calculate a center point of the mesh plate based on the actual size data of the current mesh plate, and calculate a center point of the PCB based on the actual size features of the PCB;

[0148] The center point of the screen plate is coincided with the center point of the PCB to form a coincided center point, which is taken as a reference origin point of coordinate conversion;

[0149] The four corner coordinates of the screen plate and the four corner pad coordinates of the PCB are unified to the same coordinate system through coordinate conversion to obtain new screen plate four corner coordinates and PCB four corner pad coordinates in the unified coordinate system;

[0150] Based on the unified new screen plate four corner coordinates and the PCB four corner pad coordinates, a two-dimension constraint mechanism is matched to determine the matching; the two-dimension constraint mechanism includes that the geometric center of the solder paste completely covers the corresponding pad effective welding area and the edge has no overlap, and the vertical distance between the solder paste and the four edges of the pad all meet the preset process safety condition;

[0151] When the two-dimension constraint mechanism conditions are met at the same time, it is marked that the PCB and the current screen plate have size adaptability, and when any condition fails to pass the verification, it is determined that there is no matching and an alarm prompt is triggered and recorded.

[0152] It should be noted that more details about the steel screen and PCB size matching dynamic mapping device, including the implementation principle, process and technical effect, can be referred to the relevant description of the foregoing embodiments, which will not be described here.

[0153] In an embodiment, a PCB printing system is provided, which includes a printing execution mechanism and a screen plate and PCB size matching mapping device as described in any of the foregoing; the printing execution mechanism is used for performing solder paste printing on the PCB by using the screen plate; the matching mapping device is used for realizing the size matching dynamic mapping process of the screen plate and the PCB (see the method embodiment described above), and providing matching information for the printing execution mechanism.

[0154] PCB printing system: composed of a printing execution mechanism and a screen plate and PCB size matching mapping device, the former is responsible for actual solder paste printing, and the latter provides real-time matching information to guide the adjustment of printing parameters. For example, the printing execution mechanism can include a steel screen fixing assembly, a PCB conveying platform, a servo doctor system and a vacuum suction device, which are used to complete the solder paste printing according to the instructions of the matching device.

[0155] Matching mapping device: including an image acquisition module (such as Figure 3 As shown, four cameras (camera 1, camera 2, camera 3, camera 4) corresponding to the four corners of the PCB product, a data processing module (such as an I7 industrial computer), a motion control module (such as a PLC controller) and a display module (such as a 27-inch display) are used to calculate the size of the steel screen in real time and determine the matching with the PCB.

[0156] This embodiment takes the COB lamp panel full-automatic printing production line of a certain LED packaging factory as an application scenario to illustrate the working process of the system.

[0157] The printing executive mechanism conveys the PCB to be printed to the positioning platform and fixes it by vacuum adsorption.

[0158] The image acquisition module (4 cameras respectively aligned with the four corners of the PCB) of the matching mapping device takes the PCB pad image and extracts the solder paste point features (6 pads at each corner, constituting 4 sides). The data processing module calculates the actual size data of the current PCB (such as the coordinates of the four corners and the diagonal distance) based on the image and calls the pre-stored actual size data of the steel mesh. Through coordinate conversion, the steel mesh and PCB coordinates are unified to the same coordinate system, and through double-dimensional constraint judgment, the matching of the current steel mesh and PCB is confirmed. The motion control module sends the matching result to the control system of the printing executive mechanism.

[0159] The printing executive mechanism adjusts the parameters according to the matching information: the steel mesh fixing assembly calibrates the position to ensure alignment with the center point of the PCB to complete the solder paste printing. During the printing process, when the system accumulates the printing to meet the preset number threshold (such as 500 times) or the product quantity threshold (such as 500), the matching mapping device triggers the steel mesh size re-extraction, and calculates the current actual size data of the steel mesh through the newly printed qualified PCB. The printing executive mechanism receives the updated actual size data of the steel mesh and automatically adjusts the steel mesh positioning compensation value to ensure continuous adaptation of subsequent printing.

[0160] In this embodiment, the system obtains the size matching information of the steel mesh and the PCB in real time through the matching mapping device, and the printing executive mechanism dynamically adjusts the positioning accuracy and squeegee parameters according to the information, solving the problem of printing deviation caused by the size change of the steel mesh in the traditional system, improving the printing accuracy. The matching mapping device automatically and dynamically completes the steel mesh data update and PCB classification matching; at the same time, real-time abnormal alarm reduces batch defects. It improves production continuity, improves production efficiency, and reduces product defect rate.

[0161] As a whole working scene, as shown in Figure 6 , it includes:

[0162] Board feeding and product positioning: the PCB conveying platform of the printing executive mechanism starts the board feeding action to transport the product to be printed to the designated position, completes the "product positioning" state confirmation, and prepares for the subsequent printing process.

[0163] Lifting and vacuum adsorption: the motion control module drives the lifting mechanism to lift the product and position it, and then starts the vacuum system, adsorbs and vacuums the product to the preset value, ensuring the product to be flat and fixed, providing a stable reference for camera image acquisition and printing.

[0164] Image acquisition and data processing: the image acquisition module performs camera sampling to obtain image information of the product and the steel mesh; the data processing module calculates product data based on the collected images, including key parameters such as size and position, to provide data support for matching.

[0165] Matching and print count: the matching device matches the product data with the steel mesh and outputs the result, and after matching, the system performs the current steel mesh print count + 1 operation to record the frequency of use of the steel mesh.

[0166] Threshold judgment and process branching: determine whether to reach the preset value (the preset value can be set based on the steel mesh wear characteristics, product accuracy requirements, etc., such as print count threshold, product quantity threshold): if not: perform vacuum breaking, release product vacuum adsorption; then lift down to the preset position, return to the initial position; finally, the plate is out, completing the current product printing process and entering the next product cycle. If yes: trigger an alarm to relearn the steel mesh, prompt the operator that the steel mesh state needs to be updated, and reacquire the actual size data of the steel mesh to ensure the accuracy of subsequent printing.

[0167] A person of ordinary skill in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by a computer program instructing related hardware, and the computer program can be stored in a non-volatile computer readable storage medium. When the computer program is executed, it can include the processes of the above-mentioned embodiments of each method.

[0168] Those skilled in the art can clearly understand that, for the convenience and brevity of description, only the division of the above-mentioned functional units and modules is exemplified, and in actual application, the above-mentioned functions can be completed by different functional units and modules according to needs, that is, the internal structure of the device is divided into different functional units or modules to complete all or part of the functions described above.

[0169] The above-described embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements for some technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. A dynamic mapping method for matching the dimensions of a stencil and a PCB, characterized in that, The stencil is a stencil used for PCB solder paste printing, and the method includes: Select PCB products whose stability meets preset conditions after solder paste printing from the current production, and calculate the actual size data of the current stencil by extracting the solder paste images from the four corners of the PCB product; The PCB to be matched is matched with the stencil based on the actual size data of the current stencil. When the preset stencil data update conditions are met, the PCB products that meet the preset conditions after printing are selected from the current production and the solder paste images of the four corners are extracted to update the actual size data of the stencil. The matching of subsequent PCBs and stencils is then carried out based on the updated actual size data. The process of matching the PCB to be matched with the stencil based on the actual size data of the current stencil includes: extracting solder paste points at the four corners of the solder paste image of the PCB to be matched to obtain the actual size features of the PCB; calculating the center point of the stencil based on the actual size data of the current stencil, and calculating the center point of the PCB based on the actual size features of the PCB; aligning the center point of the stencil with the center point of the PCB to form a coincident center point, which serves as the origin for coordinate transformation; and unifying the coordinates of the four corners of the stencil and the four corner pads of the PCB to the same coordinate system through coordinate transformation to obtain... The coordinates of the four corners of the new stencil and the four corner pads of the PCB are unified in a coordinate system. A matching determination of the two-dimensional constraint mechanism is performed based on the unified coordinates of the four corners of the new stencil and the four corner pads of the PCB. The two-dimensional constraint mechanism includes the solder paste point's geometric center completely covering the effective soldering area of ​​the corresponding pad with no edge overlap, and the vertical distance between the solder paste and the four sides of the pad meeting preset process safety conditions. When both conditions of the two-dimensional constraint mechanism are met simultaneously, the PCB is marked as having dimensional compatibility with the current stencil. If any condition fails verification, a mismatch is determined, an alarm is triggered, and the information is recorded. The coordinate transformation includes: translating the coordinates of each vertex of the quadrilateral of the stencil and each vertex of the four corner pads of the PCB to a temporary coordinate system with the coincident center point as the origin to obtain temporary coordinates; in the temporary coordinate system, applying a rotation matrix to rotate the temporary coordinates to make the stencil parallel to the X-axis. The rotated temporary coordinates are translated back to the original coordinate system to obtain the new coordinates of the four corners of the stencil and the four corner pads of the PCB, which are unified to the same coordinate system.

2. The method according to claim 1, characterized in that, The step of calculating the actual size data of the current stencil by extracting solder paste images from the four corners of the PCB product includes: When extracting solder paste images from the four corners of the PCB product, multiple pads are identified at each corner and they form a surface. The actual size data of the current stencil is calculated based on the surface information of the four corners.

3. The method according to claim 1, characterized in that, The preset stencil data update conditions include at least one of the following: the actual size data of the stencil is used a preset number of times, or the number of matched PCB products corresponding to the stencil is a preset number of times.

4. The method according to any one of claims 1-3, characterized in that, It includes multiple production lines, each of which uses data to obtain the actual size of the stencils of each line. The PCBs to be matched are matched and classified with the stencils of each line based on their actual size data, and PCBs that do not meet the matching conditions of any stencil are classified separately.

5. A dynamic mapping device for matching the dimensions of a stencil and a PCB, characterized in that, The stencil is a stencil used for PCB solder paste printing; the device includes an image acquisition module, a data processing module, and a control module; The image acquisition module is used to acquire solder paste images of the four corners of a PCB product whose stability meets preset conditions after printing. The data processing module is used to calculate the actual size data of the current stencil based on the solder paste images of the four corners of the PCB product acquired by the image acquisition module, and to match the PCB to be matched with the stencil based on the actual size data of the current stencil. The control module is used to trigger the image acquisition module to re-acquire solder paste images of the four corners of the PCB product whose stability meets the preset conditions after printing when the preset stencil data update conditions are met. This allows the data processing module to update the actual size data of the stencil and control the subsequent matching of the PCB and stencil based on the updated actual size data. When matching the PCB to be matched with the stencil, the data processing module specifically performs the following steps: extracting solder paste points at the four corners of the solder paste image of the PCB to be matched to obtain the actual size characteristics of the PCB; calculating the center point of the stencil based on the actual size data of the current stencil, and calculating the center point of the PCB based on the actual size characteristics of the PCB; aligning the center point of the stencil with the center point of the PCB to form a coincident center point, which serves as the reference origin for coordinate transformation; and unifying the coordinates of the four corners of the stencil and the four corner pads of the PCB to the same coordinate system through coordinate transformation to obtain a unified coordinate system. The coordinates of the four corners of the new stencil and the four corner pads of the PCB are defined under the new standard system. A matching determination of the two-dimensional constraint mechanism is performed based on the unified coordinates of the four corners of the new stencil and the four corner pads of the PCB. The two-dimensional constraint mechanism includes the solder paste point's geometric center completely covering the effective soldering area of ​​the corresponding pad with no edge overlap, and the vertical distance between the solder paste and the four sides of the pad meeting preset process safety conditions. When both conditions of the two-dimensional constraint mechanism are met simultaneously, the PCB is marked as having dimensional compatibility with the current stencil. If any condition fails verification, a mismatch is determined, an alarm is triggered, and the information is recorded. The coordinate transformation includes: translating the coordinates of each vertex of the quadrilateral of the stencil and each vertex of the four corner pads of the PCB to a temporary coordinate system with the coincident center point as the origin to obtain temporary coordinates; in the temporary coordinate system, applying a rotation matrix to rotate the temporary coordinates to make the stencil parallel to the X-axis. The rotated temporary coordinates are translated back to the original coordinate system to obtain the new coordinates of the four corners of the stencil and the four corner pads of the PCB, which are unified to the same coordinate system.

6. The apparatus according to claim 5, characterized in that, When the image acquisition module acquires solder paste images at the four corners of the product, it identifies multiple pads at each corner and forms a surface. Based on the surface information of the four corners, it calculates the actual size data of the current stencil.

7. The apparatus according to claim 5, characterized in that, The preset stencil data update conditions include at least one of the following: the actual size data of the stencil is used a preset number of times, or the number of matched PCB products corresponding to the stencil is a preset number of times.

Images