Steel mesh and PCB size matching dynamic mapping method and device

Abstract

The invention relates to the technical field of high-precision assembly of an LED die bonding process, in particular to a steel mesh and PCB size matching dynamic mapping method and device, and solves the problem of matching failure caused by size change of a steel mesh. The method comprises the following steps of: selecting a PCB (Printed Circuit Board) product of which the stability meets a preset condition after solder paste printing is completed from the current production, and calculating by extracting solder paste images at four corners of the PCB product to obtain the actual size data of the current screen; matching a to-be-matched PCB with the screen plate based on the actual size data of the current screen plate; and when a preset screen data updating condition is met, re-selecting the printed PCB product meeting the preset condition from the current production, extracting the solder paste images at the four corners of the PCB product to update the actual size data of the screen, and continuing to match the subsequent to-be-matched PCB with the screen based on the updated actual size data.

Description

TECHNICAL FIELD

[0001] The present application relates to the high-precision assembly technical 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 size matching precision of the steel mesh and the PCB (Printed Circuit Board) is very high in the COB (Chip On Board) die bonding link. The PCB may be affected by factors such as temperature fluctuations and external forces during processing, transportation and storage, and may expand or shrink by microns. Since the size of the COB single pad is in the micron level, the expansion or shrinkage 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 may 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: 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 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 accuracy of image recognition and the accuracy of machinery, and the accuracy can only reach ± 5 μm.

[0003] 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 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.

[0004] 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 after a certain number of printing processes due to continuous stress and extrusion during printing, which will cause the matching relationship between the original steel mesh and the PCB to fail, 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 improve the production efficiency and welding quality. SUMMARY

[0005] The present application relates to the high-precision assembly, die bonding technical field of LED die bonding process, and provides a steel mesh and PCB size matching dynamic mapping method and device to solve the technical problem of matching failure caused by the size change of the steel mesh in the traditional scheme.

[0006] A steel mesh and PCB size matching dynamic mapping method, the steel mesh is a screen plate for PCB solder paste printing, the method comprises: Selecting a PCB product with stable performance after solder paste printing from current production, and calculating the actual size data of the current screen plate by extracting the solder paste image of the four corners of the PCB product; Matching the PCB to be matched with the screen plate based on the actual size data of the current screen plate; When the preset screen plate data updating condition is met, reselecting the PCB product with preset conditions after printing from current production and extracting the solder paste image of the four corners thereof 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; Further, the actual size data of the current screen plate is calculated by extracting the solder paste image of the four corners of the PCB product, comprising: When extracting the solder paste image of the four corners of the PCB product, 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.

[0007] 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: Extracting the solder paste points of the solder paste image of the four corners of the PCB to be matched to obtain the actual size features of the PCB; 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 features of the PCB; The center points of the screen plate and the PCB are coincided to form a coincident center point, which is used as the reference origin point of coordinate conversion; 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 the new screen plate four corner coordinates and the PCB four corner pad coordinates in the unified coordinate system; 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 point completely covers the effective soldering area of the corresponding pad and the edge has no overlap, and the perpendicular distance between the solder paste and the four edges of the pad meets the preset process safety condition; When the double-dimension constraint mechanism condition is met, the PCB is marked as having size adaptability with the current screen plate, and when any condition fails to pass the verification, it is determined that the matching is not matched and an alarm prompt is triggered and recorded.

[0008] Further, the preset screen data updating condition comprises at least one of the following: the number of times of using the actual size data of the screen reaches a preset number threshold, and the number of matched PCB products corresponding to the screen reaches a preset quantity threshold.

[0009] Further, the system comprises a plurality of production lines, each of which is configured to acquire actual size data of a screen of each line, match and classify the to-be-matched PCBs based on the actual size data of the screens, and separately classify the PCBs that do not satisfy any screen matching condition.

[0010] Further, the coordinate conversion comprises: translating the coordinates of the vertices of the screen quadrilateral and the vertices of the PCB quadrangular pads to a temporary coordinate system with the coincidence center point as the origin to obtain temporary coordinates; applying a rotation matrix to the temporary coordinates in the temporary coordinate system to rotate the screen to be parallel to the X axis; translating the rotated temporary coordinates back to the original coordinate system to obtain new screen quadrangular coordinates and PCB quadrangular pad coordinates unified to the same coordinate system.

[0011] A steel mesh and PCB size matching dynamic mapping device, the steel mesh is a screen for PCB solder paste printing; the device comprises an image acquisition module, a data processing module and a control module; The image acquisition module is configured to acquire solder paste images of the four corners of a PCB product that has completed printing and has a stable quality meeting a preset condition; The data processing module is configured to calculate actual size data of a current screen based on the solder paste images of the four corners of the PCB product acquired by the image acquisition module, and match a to-be-matched PCB with the screen based on the actual size data of the current screen; The control module is configured to trigger the image acquisition module to re-acquire solder paste images of the four corners of a PCB product that has completed printing and has a stable quality meeting a preset condition from the current production when a preset screen data updating condition is met, so as to update the actual size data of the screen by the data processing module, and control the matching of a subsequent to-be-matched PCB with the screen based on the updated actual size data.

[0012] Further, when acquiring the solder paste images of the four corners of the product, the image acquisition module identifies a plurality of pads for each corner and forms a face, and calculates the actual size data of the current screen based on the face information of the four corners.

[0013] Further, when matching the to-be-matched PCB with the screen, the data processing module is specifically configured to: extract solder paste points of the solder paste images of the four corners of the to-be-matched PCB to obtain actual size features of the PCB; Calculate the center point of the screen plate based on the actual size data of the current screen plate, and calculate the center point of the PCB based on the actual size characteristics of the PCB; Align the center point of the screen plate with the center point of the PCB to form an aligned center point, which serves as the reference origin point for coordinate conversion; Convert the coordinates of the four corners of the screen plate and the coordinates of the four corner pads of the PCB 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; Determine the matching of the double-dimension constraint mechanism based on the unified new screen plate four-corner coordinates and 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 meets the preset process safety condition; When the double-dimension constraint mechanism conditions are met at the same time, mark that the PCB and the current screen plate have size adaptability, and when any condition fails to pass the verification, determine that it does not match and trigger an alarm prompt and record it.

[0014] A PCB printing system includes a printing execution mechanism and a screen plate and PCB size matching dynamic mapping device as described in any of the preceding embodiments; the printing execution mechanism is used to perform solder paste printing on the PCB using the screen plate; the screen plate and PCB size matching dynamic mapping device is used to realize the size matching dynamic mapping of the screen plate and the PCB, and provide matching information for the printing execution mechanism.

[0015] In one of the schemes provided in the present application, 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. 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 that meets 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 LED lamp panel production, and is conducive to improving production efficiency and welding quality. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the description of the embodiments of the present application. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creating labor intensity on the premise of the drawings.

[0017] Figure 1 is a flowchart of a steel mesh and PCB size matching dynamic mapping method in an embodiment of the present application; Figure 2 is a schematic diagram of a position relationship between a solder paste dot and a pad in a steel mesh and PCB size matching dynamic mapping method in an embodiment of the present application; Figure 3 is a schematic diagram of an arrangement relationship of four cameras in a steel mesh and PCB size matching dynamic mapping method in an embodiment of the present application; Figure 4 is a coordinate schematic diagram of a mesh plate size calculation in a steel mesh and PCB size matching dynamic mapping method in an embodiment of the present application; Figure 5 is a schematic diagram of mesh plate and PCB matching determination in a steel mesh and PCB size matching dynamic mapping method in an embodiment of the present application; Figure 6 is a working process schematic diagram of a PCB printing system in an embodiment of the present application. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0019] In the embodiments of the present application, a steel mesh and PCB size matching dynamic mapping method is provided, the steel mesh is a mesh plate for PCB solder paste printing, and the method comprises the following steps: S101, selecting a PCB product with stable solder paste printing after completion and meeting a preset condition from current production, and calculating actual size data of a current mesh plate by extracting solder paste images of four corners of the PCB product; S102, matching a PCB to be matched with the mesh plate based on the actual size data of the current mesh plate; S103, when a preset mesh plate data updating condition is met, selecting a PCB product with stable printing after completion and meeting a preset condition from current production again, extracting solder paste images of four corners of the PCB product to update actual size data of the mesh plate, and continuing to match the PCB to be matched with the mesh plate based on the updated actual size data.

[0020] The mesh plate refers to a mesh 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 a preset condition refers to a qualified PCB product with no defects such as offset and overflow after solder paste printing, and a high pad solder paste coverage, that is, a PCB product with good stability.

[0021] In this embodiment, a high-precision camera can be used to capture an image of the solder paste distribution of a PCB product whose stability meets preset conditions after solder paste printing is completed, and then the actual size data of the stencil can be calculated. Specifically, the current actual aperture size and overall geometric parameters of the stencil (such as four-corner coordinates, side lengths, etc.) are calculated based on the solder paste image features (such as the solder paste outline and the relative position of the pads). Preset stencil data update conditions include the following: the number of comparisons of the actual stencil size data reaches a preset threshold (for example, 500 times) or the number of corresponding PCB products reaches a preset threshold (for example, 500), which triggers the re-extraction of the actual stencil size data.

[0022] To facilitate understanding of the processing of this embodiment, this embodiment uses the COB die bonding process of LED light board production as an example to illustrate the application scenario. In the LED light board production line of an electronics factory, the COB pad size is 50μm×50μm, and the matching accuracy of the steel mesh (screen) and the PCB is required to be ±2μm. However, after about 500 printings, the steel mesh increases in size due to continuous force, causing the original matching relationship to fail, and the problem of solder paste overflowing the pad frequently occurs during printing. Through the dynamic matching mapping method of this embodiment, the steel mesh size data can be dynamically and real-time updated to achieve dynamic and precise matching with the PCB, thereby reducing printing defects.

[0023] Taking the matching of steel mesh and PCB of this LED production line as an example, three PCB products with satisfactory stability (no offset in solder paste printing and high pad coverage) are selected from the currently produced LED light boards and placed on the carrier of the matching mapping device. Figure 3 As shown, four cameras (Camera 1, Camera 2, Camera 3, and Camera 4) capture solder paste images at the four corners of the PCB. The cameras are adjustable, corresponding to the four corners of the PCB. The cameras clearly identify the pads at the four corners, extract clear images, and calculate the spacing between the four pads.

[0024] The data processing module extracts features (such as solder paste edge coordinates, pad center distance) of the solder paste images of the four faces, and obtains actual size data (such as hole edge length 52 μm, four-corner diagonal distance 120.3 mm) of the current steel mesh through multi-face geometric operation. For the PCB to be matched newly entering the production line, the image acquisition module obtains solder paste point images of the four corners of the PCB, and extracts size features (such as pad spacing, 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 two-dimensional constraint mechanism (solder paste covers the pad and the edge does not overlap, solder paste and pad edge distance ≥ 3 μm), it is determined whether the PCB to be matched matches the current steel mesh. Example: the diagonal distance of the pads of a certain PCB is 120.1 mm, and the diagonal distance of the steel mesh is 120.3 mm, which meets the two-dimensional constraint after calculation, and is marked as “matched” and enters the next die bonding process. The comparison times of the actual size data of the steel mesh are recorded in real time (1 time for each matched PCB). When the comparison times reach a preset threshold of 500 times, the motion control module triggers a reminder (flashing indicator light + screen prompt “Please update the steel mesh data”). The operator or the device selects a new PCB (solder paste printing qualified) with stable performance meeting the preset conditions, repeats the image extraction and operation, and obtains the updated actual size data of the steel mesh. Based on the updated actual size data, the subsequent PCBs are matched (such as a certain PCB pad diagonal distance 120.4 mm, which matches the updated steel mesh and is determined as “adapted”).

[0025] In this embodiment, by extracting the actual size data of the steel mesh in real time and dynamically updating, the problem of matching failure of the traditional scheme due to the size increase of the steel mesh caused by the increase of the printing times is solved. For example, the size of the steel mesh changes by 30 μm after being used for 500 times, and the continuous and accurate matching with the PCB can be ensured through data updating. Moreover, by taking the PCB product with stable performance as a 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, and adapt to the complex environment in the production of LED lamp panels.

[0026] In addition, in an embodiment, the actual size data (such as hole size, diagonal distance) of the steel mesh obtained each time is automatically stored in a local database, including a time stamp and a corresponding PCB batch number, records the size change history of the mesh plate, and is used for traceability and wear analysis. A “steel mesh size-use times” trend chart can be generated, and when the slope is greater than a set condition (wear acceleration), a warning is automatically pushed to the administrator terminal.

[0027] In an embodiment, the actual size data of the current mesh plate obtained by extracting the solder paste images of the four corners of the PCB product comprises: when the solder paste images of the four corners of the PCB product are extracted, a plurality of pads are identified at each corner to form a face, and the actual size data of the current mesh plate is obtained based on the face information of the four corners.

[0028] As shown in Figure 4 , multiple pads constitute a plane. Select multiple pads at each corner of the PCB product. A geometric plane is formed by the relative positional relationship of the pads, rather than point information of a single pad. Based on the plane formed by multiple pads at each corner, the geometric parameters of the plane (such as flatness, pad spacing, diagonal length, etc.) are calculated, and the actual size data of the steel mesh is calculated based on the face information of the four corners, rather than only through single pad or mark point data.

[0029] 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 plate produced by the production line is 160 μm x 120 μm. The traditional steel mesh size measurement only calculates the overall size based on single corner or single pad data, which is easy to cause overall matching deviation due to local error. Through the embodiment of the present application, the actual size of the steel mesh used for subsequent matching is dynamically calculated based on the face information of multiple pads, which can improve the processing precision.

[0030] Taking the actual size calculation of the steel mesh of the production line as an example, 3 pieces of PCB product 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 4 , the solder paste images of the four corners of the PCB product are captured by four high-precision cameras respectively. The capture area of each corner contains 6 adjacent pads (such as pads A1-A6 of the upper left corner, B1-B6 of 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 6 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 6 pads: including the distance between adjacent pads (such as the distance d1 between A1 and A2), the flatness deviation, the diagonal length (the distance d2 between A1 and A6); integrate these parameters into the "face information" of the upper left corner to reflect the steel mesh opening characteristics of the region. The right upper corner, the left lower corner and the right lower corner of the PCB are calculated respectively to obtain the face information of each corner (such as the spacing, flatness, etc. of the 6 pads of the upper right corner). 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); 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, the opening size 120. μm * 80 μm.

[0031] In this embodiment, multiple pads are identified at each corner to form a surface, avoiding the occasional errors associated with single-pad measurement. Local errors can be averaged, improving the accuracy of the overall actual dimensional data. Furthermore, because surface information includes multi-dimensional parameters such as plane flatness and pad spacing, it can better reflect the overall deformation of the stencil (such as local warping caused by stress) than a single mark point. For example, if a corner of the stencil has tilted 0.5° due to compression, the surface information's normal vector deviation can accurately identify this deformation, whereas single-pad data cannot reflect this type of deformation.

[0032] It is also worth mentioning that if one of the six pads in a corner has an invalid image due to missing solder paste (for example, the solder paste coverage of pad A3 is less than 50%), the pad will be automatically removed and the surface information will be recalculated using the remaining five pads. In other words, a maximum of one invalid pad can be removed from a single corner to ensure the continuity of the surface information.

[0033] In one embodiment, matching the PCB to be matched with the stencil based on the actual size data of the current stencil includes: Extract the solder paste dots 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; The center point of the stencil is aligned with the center point of the PCB to form a coincident center point, which is used as the reference origin for coordinate transformation; The coordinates of the four corners of the stencil and the four corner pads of the PCB are unified into the same coordinate system through coordinate conversion, so as to obtain the new coordinates of the four corners of the stencil and the four corner pads of the PCB in the unified coordinate system; Based on the unified coordinates of the new stencil's four corners and the PCB pad's four corners, a two-dimensional constraint mechanism is determined to ensure compatibility. This constraint mechanism ensures that the geometric center of the solder paste dot completely covers the effective soldering area of ​​the corresponding pad without any overlap, and that the vertical distances between the solder paste and the four edges of the pad meet pre-set process safety conditions. When the dual-dimensional constraint mechanism conditions are met at the same time, the PCB is marked as size compatible with the current stencil. If any of the conditions fails to pass the verification, it is determined to be mismatched and an alarm is triggered and recorded.

[0034] In one embodiment, the coordinate conversion includes: Translate the coordinates of the vertices of the stencil quadrilateral and the vertices 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, the temporary coordinates are rotated by applying a rotation matrix, which is a two-dimensional rotation matrix: , where the rotation angle Based on the angle between the target edge of the stencil and the X-axis, the stencil is rotated to be parallel to the X-axis. The rotated temporary coordinates are translated back to the original coordinate system to obtain the new stencil four corner coordinates and PCB four corner pad coordinates that are unified to the same coordinate system.

[0035] In this embodiment, the PCBs to be matched are sorted based on the actual size data of the current stencil obtained: Extract the solder paste dots from the four corners of the PCB solder paste image, selecting six solder paste dots in each corner; extract a set of data with the area closest to the true value to calculate the center point of the stencil.

[0036] Coordinate transformation principle and process: Coordinate system and point representation: In the two-dimensional plane rectangular coordinate system, the four vertices of the quadrilateral formed by the steel mesh can be expressed as , where each vertex is a two-dimensional coordinate vector, which can be expressed as a column matrix: Rotation matrix principle: In a two-dimensional plane, a point rotates around the origin The transformation matrix for angles (positive counterclockwise) is: Among them, the role of the matrix is ​​to transform the original coordinate vector Transformed into a rotated coordinate vector ,Right now: .

[0037] The calculation steps for the directional rotation of a quadrilateral: Center point coordinate calculation: geometric center point of the quadrilateral is the arithmetic mean of the four vertex coordinates, and the calculation formula is as follows: .

[0038] The matrix of the center point is represented as: .

[0039] Determine the rotation angle: Set the target edge to , it needs to be rotated to be parallel to the X axis (that is, the y coordinates of the two points are equal after rotation). The direction vector is: in, The angle between this direction vector and the X axis is (radians) can be calculated using the inverse tangent function: .

[0040] To make the edge Parallel to the X-axis, it needs to be rotated until the angle with the X-axis is 0, so the required rotation angle is Coordinate transformation process: To ensure that the center point position remains unchanged, a composite transformation process of "translation-rotation-translation back" is adopted: ① Translate the coordinates of each vertex to a temporary coordinate system with the center point C as the origin to obtain the temporary coordinates ② In the temporary coordinate system, the temporary coordinates Applying a rotation matrix , get the temporary coordinates after rotation : Expand to component form: ③ The temporary coordinates after rotation Translate back to the original coordinate system to get the final coordinates : The coordinates of the four new points after transformation are: In this embodiment, the coordinate calculation and processing of the stencil and the coordinate calculation and processing of the PCB to be matched are both processed in the above manner.

[0041] The actual size characteristics of the PCB refer to the extraction of the coordinates, spacing, shape and other features of the solder paste dots at the four corners of the PCB to reflect the current actual geometric dimensions of the PCB to be matched. The geometric center point of the stencil and the PCB (the arithmetic mean of the coordinates of each vertex) is used as the basis for coordinate transformation. Through the composite transformation of translation-rotation-translation back, the coordinates of the four corners of the stencil and the PCB are unified into the same coordinate system to eliminate the influence of angle deviation. Figure 5 As shown in Figure 2, a two-dimensional constraint mechanism is used for matching judgment: ① The geometric center of the solder paste completely covers the effective area of ​​the pad and there is no overlap at the edges, as shown in Figure 2. Figure 1As shown, check whether the geometric center of the solder paste completely covers the pad and that there is no overlap between the edge of the solder paste and the edge of the pad. The solder paste width (Wtin) and the pad width (Wsolder) satisfy W=Wtin-Wsolder>0, and the solder paste height (Htin) and the pad height (Hsolder) satisfy H=Htin-Hsolder>0, with both W and H greater than 0), ensuring that the solder paste completely covers the pad and has no size. ② The vertical 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 for FR4 PCBs is set to 8μm, and the threshold for ceramic substrate PCBs is set to 10μm due to their higher brittleness. It can be dynamically adjusted according to the PCB material. For example, the threshold for aluminum substrate material is dynamically adjusted to 10μm.

[0042] Here, an automotive electronics COB module production line is used as an example application scenario. The PCB pads on this production line are a 40μm x 40μm rectangular array, and the stencil openings must precisely match the pads. Because the PCB expands and contracts due to temperature fluctuations during storage, and the stencil deforms slightly after use, traditional direct size comparison methods are prone to matching errors, resulting in offset solder paste printing. This embodiment achieves high-precision matching through coordinate transformation and two-dimensional constraints, controlling deviations and reducing printing defects.

[0043] For example, taking the matching of a batch of PCBs and steel meshes on this production line as an example, based on the actual size data of the steel mesh obtained in the above steps, the coordinates of its four corner vertices are (10.000,5.000), (30.000,5.000), (30.000,25.000), (10.000, 25.000) (unit: mm), calculate the center point C of the stencil 网板 : =(10+30+30+10) / 4=20.000, =(5+5+25+25) / 4=15.000, which is C 网板 =(20.000, 15.000).

[0044] Collect the solder paste dot images at the four corners of the PCB to be matched, select 6 solder paste dots at each corner, and extract the vertex coordinates of the pads. (10.002,5.001), (30.003,5.002), (30.001,25.003), (10.003, 25.001), calculate the PCB center point C PCB : = (10.002 + 30.003 + 30.001 + 10.003) / 4 = 20.002, = (5.001 + 5.002 + 25.003 + 25.001) / 4 = 15.002, i.e. C PCB = (20.002, 15.002).

[0045] Coordinate conversion (unified to the same coordinate system): C 网板 is coincided with C PCB (treated as the reference origin), at this time the deviation of the center point of the stencil and the PCB to be matched is corrected by translation. Calculate the coordinates of the vertices of the stencil in the temporary coordinate system (with the coincided center point as the origin): = C 网板 = (-10.000, -10.000) = (10.000, -10.000), = (10.000, 10.000), = (-10.000, 10.000); the temporary coordinates of the vertices of the PCB are calculated in the same way = (-9.999, -9.999), = (9.999, -9.999), = (9.999, 9.999), = (-9.999, 9.999).

[0046] The direction vector of the target edge of the stencil is (0, 20.000) (parallel to the X axis), and the corresponding edge of the PCB has a 0.1° inclination, so the two are made consistent in direction by the rotation matrix . Translate the temporary coordinates after rotation back to the original coordinate system to obtain the unified new stencil four-corner coordinates and the PCB four-corner pad coordinates .

[0047] After the converted coordinates, perform a two-dimensional constraint matching determination: Dimension one (coverage and edge): as shown in Figure 2 , check whether the geometric center of the solder paste completely covers the pad and whether the edge of the solder paste overlaps with the edge of the pad. The solder paste width (W_solder) and the pad width (W_pad) satisfy W = W_solder - W_pad > 0, the solder paste height (H_solder) and the pad height (H_pad) satisfy H = H_solder - H_pad > 0, and both W and H are greater than 0, to ensure that the solder paste completely covers the pad without size. In the example, the edge coordinates of the solder paste of a certain pad of the PCB are all within the range of the pad (without overflow), satisfying the condition.​​​

[0048] Dimension two (distance threshold): measure the vertical distance of the solder paste from the upper, lower, left and right edges of the pad, which are 9 μm, 9.5 μm, 9.2 μm and 9.8 μm respectively, all of which are greater than or equal to the preset threshold value of 8 μm, satisfying the distance constraint.

[0049] Both two-dimensional constraints are satisfied, indicating that the PCB is "size-fitted" with the current steel mesh, allowing it to enter the printing process. If the distance between the solder paste and one edge of the pad is 6.5 μm (<3 μm), it is determined that "it does not match", triggering an alarm (light + screen prompt) and recording the data.

[0050] In this embodiment, the screen plate and the PCB are unified to the same coordinate system through coordinate transformation, solving the misjudgment caused by angle and position deviation in traditional direct comparison. The angle deviation and center point deviation are eliminated through transformation, improving the matching accuracy. Moreover, the double constraints of non-overlapping coverage edge and threshold determination not only avoid solder paste overflow from the pad, but also ensure the reliability of welding. It can greatly reduce the printing defects.

[0051] In addition, in the aforementioned "translation-rotation-translation back" process, the position deviation is first eliminated through the temporary coordinate system, and then 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 steel mesh and the PCB, effectively reducing the matching error, and also effectively avoiding the measurement error caused by the non-uniformity of the coordinate system.

[0052] 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.

[0053] 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 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.

[0054] Taking the steel mesh 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 comparison number of screen plate size data); preset quantity threshold = 500 (maximum number of PCB products that can be matched by a single screen plate).

[0055] The actual size data of the steel mesh (open hole size 120 pm) is obtained. After the system completes matching of 1 PCB, the actual size data usage times are automatically recorded (cumulative +1). When the usage times reach 500 times, the control module triggers an update reminder (the display module pops up “steel mesh data has reached 500 times, needs to be updated”, accompanied by a beeping prompt). The operator or equipment selects a new PCB product that meets the stability requirements (solder paste printing is qualified), reextracts the solder paste image and calculates the actual size data of the steel mesh (at this time, the steel mesh has been used for 500 times, and the open hole size has increased to 135 pm), and completes data updating.

[0056] The number of PCB products that have been matched and passed quality inspection corresponding to the current steel mesh is recorded synchronously (cumulative +1 for each production of 1 qualified product). When the number of qualified products corresponding to a certain mesh reaches 500, even if the usage times have not reached 500 times, the control module still triggers an update reminder (displaying “the steel mesh has matched 500 products, it is suggested to update the data”). After reextracting the actual size data of the steel mesh, it is found that the size has increased to 138.5 pm due to long-term use, and the updated data is used for subsequent matching, avoiding defective products caused by size deviation.

[0057] In this embodiment, through the double-threshold triggering mechanism, the usage times of the actual size data of the steel mesh (500 times) and the corresponding product quantity (500) are restricted, covering the size changes of the steel mesh caused by usage frequency and cumulative load. The size deviation of the steel mesh is always within the range, and the printing defect rate of the PCB product is reduced. 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 updating, while ensuring the timeliness of the data. The production continuity is improved.

[0058] It should be noted that if the comparison times do not reach 500 times, but consecutive multiple PCBs fail to match (both dimensions do not meet the requirements), an emergency updating mechanism can be triggered to forcibly reextract the size data of the steel mesh. The updating process is immediately executed.

[0059] In an embodiment, a plurality of production lines are included, each production line adopts a device for obtaining the actual size data of the mesh of each line, and the PCBs to be matched are respectively matched with the meshes of each line based on the actual size data thereof, and the PCBs that do not meet the matching conditions of any mesh are separately classified.

[0060] Multiple production lines refer to multiple independent lines (such as A, B, and C lines) that produce the same type of PCB product in parallel, and each line 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, the corresponding matching mapping device extracts the solder paste image, and the calculated current actual size data (such as hole size, diagonal distance, etc.) needs to be stored and managed separately. Compare the PCB to be matched with the actual size data of each line steel mesh, and determine the adaptability according to the two-dimensional constraint results (the processing process can be seen in the previous embodiment, which is not repeated here). Assign to the corresponding line. For PCBs that do not match all line steel meshes, mark them as to-be-processed, record and analyze the reasons separately.

[0061] For example, taking the matching classification of a batch of 100 PCBs as an example, the specific steps are as follows: Each line selects the PCB produced by this line that meets the stability requirements (solder paste printing is qualified) through its matching mapping device, extracts the four-corner solder paste image (6 pads per corner), and calculates the actual size data of each steel mesh, for example: A line steel mesh: hole size 120 μm, four-corner coordinates PA1-PA4, diagonal distance 100.000 mm; B line steel mesh: hole size 121 μm, four-corner coordinates PB1-PB4, diagonal distance 100.003 mm; C line steel mesh: hole size 122 μm, four-corner coordinates PC1-PC4, diagonal distance 100.005 mm.

[0062] For this batch of 100 PCBs, the four-corner solder paste point image is 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, match and determine with the actual size data of A, B, and C line steel meshes: 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 μm), and is assigned to the A line production; 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 (the edge distance is only 2 μm when matched with the A line, which does not meet the requirements), and is assigned to the B line production; 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 assigned to the C line production; Separate classification: 3 PCBs have excessive expansion (diagonal distance 100.010 mm), and solder paste overflow occurs when matched with A, B, and C line steel meshes (not meeting the two-dimensional constraints), which are marked as to-be-processed and can be separately sent to the manual review station.

[0063] Finally, 97 pieces of adaptive PCBs are assigned to corresponding lines according to the classification results, and 3 pieces of PCBs to be processed are detected manually to confirm that they are caused by storage deformation and are re-participated in matching after being corrected by secondary processing.

[0064] In this embodiment, multi-line matching classification enables the same batch of PCBs to be adapted to different states of the steel mesh (such as a new mesh plate or a half-old mesh plate), thereby avoiding PCB waste caused by the mismatch of a single line steel mesh. In this embodiment, the PCB utilization is effectively improved. Moreover, it is worth noting that the PCBs that do not meet any mesh matching conditions are classified separately, which facilitates the analysis of defect causes (such as storage deformation and batch differences) and is conducive to targeted process optimization (such as adjusting the storage environment), thereby enhancing the production flexibility.

[0065] 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 embodiments of the present application.

[0066] 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. The image acquisition module is configured to acquire solder paste images of four corners of a PCB product that has been printed and has stability meeting a preset condition. 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. The control module is configured to trigger the image acquisition module to re-acquire solder paste images of four corners of a PCB product that has been printed and has stability meeting a 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 a subsequent PCB to be matched with the mesh plate based on the updated actual size data.

[0067] In an embodiment, when the image acquisition module acquires solder paste images of four corners of a 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.

[0068] In an embodiment, when the data processing module matches the PCB to be matched with the mesh plate, it is specifically configured to: extract solder paste points of four corners of a solder paste image of the PCB to be matched to obtain 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 characteristics of the PCB; aligning the center point of the stencil with the center point of the PCB to form an aligned center point, which serves as a reference origin point for coordinate conversion; unifying the coordinates of the four corners of the stencil and the coordinates of the four corner pads of the PCB to the same coordinate system through coordinate conversion, to obtain new stencil four-corner coordinates and PCB four-corner pad coordinates in the unified coordinate system; performing a matching determination of a two-dimensional constraint mechanism based on the unified new stencil four-corner coordinates and PCB four-corner pad coordinates; the two-dimensional 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 meets the preset process safety condition; When the conditions of the two-dimensional constraint mechanism are met at the same time, it is determined that the PCB and the current stencil 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.

[0069] It should be noted that more details about the steel mesh and PCB size matching dynamic mapping device, including implementation principle, process and technical effect, can be referred to the relevant description of the foregoing embodiments, which will not be described here.

[0070] In an embodiment, a PCB printing system is provided, which includes a printing execution mechanism and a stencil and PCB size matching mapping device as described in any of the foregoing embodiments; the printing execution mechanism is used for performing solder paste printing on the PCB using the stencil; the matching mapping device is used to implement the size matching dynamic mapping process of the stencil and the PCB (see the method embodiment described above), and provides matching information for the printing execution mechanism.

[0071] PCB printing system: composed of a printing execution mechanism and a stencil 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 mesh fixing assembly, a PCB conveying platform, a servo blade system, and a vacuum suction device, which are used to complete the solder paste printing according to the instructions of the matching device.

[0072] Matching mapping device: including an image acquisition module (such as Figure 3 As shown, four cameras (camera 1, camera 2, camera 3, and camera 4) corresponding to the four corners of the PCB, 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 mesh in real time and determine the matching with the PCB.

[0073] 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.

[0074] The printing executive mechanism conveys the PCB to be printed to the positioning platform and fixes it by vacuum adsorption.

[0075] 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.

[0076] 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.

[0077] 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 the doctor blade parameters according to the information, solving the problem of printing deviation caused by the change of the steel mesh size 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 the batch defects. It improves the production continuity, improves the production efficiency, and reduces the product defect rate.

[0078] As a whole working scene, as shown in Figure 6 , it includes: 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] Those skilled 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.

[0084] 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.

[0085] 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 skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements for part of the 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 steel mesh and PCB size, characterized in that: The steel mesh is a stencil for printing solder paste on a PCB, and the method comprises: Select a PCB product from the current production whose stability meets the preset conditions after solder paste printing, and calculate the actual size data of the current stencil by extracting the solder paste images at the four corners of the PCB product; Matching the PCB to be matched with the stencil based on actual size data of the current stencil; When the preset stencil data update conditions are met, a PCB product that meets the preset conditions after printing is selected from the current production and the solder paste images of its four corners are extracted to update the actual size data of the stencil, and the subsequent matching of the PCB to be matched with the stencil is continued based on the updated actual size data.

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

3. The method according to claim 1, characterized in that The matching of the PCB to be matched with the stencil based on the actual size data of the current stencil includes: Extract the solder paste dots 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; The center point of the stencil is aligned with the center point of the PCB to form a coincident center point, which is used as the reference origin for coordinate transformation; The coordinates of the four corners of the stencil and the four corner pads of the PCB are unified into the same coordinate system through coordinate conversion, so as to obtain the new coordinates of the four corners of the stencil and the four corner pads of the PCB in the unified coordinate system; Based on the unified coordinates of the new stencil's four corners and the PCB pad's four corners, a two-dimensional constraint mechanism is determined to ensure compatibility. This constraint mechanism ensures that the geometric center of the solder paste dot completely covers the effective soldering area of ​​the corresponding pad without any overlap, and that the vertical distances between the solder paste and the four edges of the pad meet pre-set process safety conditions. When the dual-dimensional constraint mechanism conditions are met at the same time, the PCB is marked as size compatible with the current stencil. If any of the conditions fails to pass the verification, it is determined to be mismatched and an alarm is triggered and recorded.

4. The method according to claim 1, wherein The preset stencil data update condition includes at least one of the following: the number of times the actual size data of the stencil is used reaches a preset number threshold, and the number of matched PCB products corresponding to the stencil reaches a preset number threshold.

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

6. The method according to claim 3, characterized in that The coordinate conversion includes: Translate the coordinates of the vertices of the stencil quadrilateral and the vertices 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, apply the rotation matrix to the temporary coordinates to rotate them so that the stencil is parallel to the X-axis. The rotated temporary coordinates are translated back to the original coordinate system to obtain the new stencil four corner coordinates and PCB four corner pad coordinates that are unified to the same coordinate system.

7. A dynamic mapping device for matching steel mesh and PCB size, 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 capture solder paste images at the four corners of the PCB product after printing, whose stability meets the preset conditions; 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 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 is completed from the current production when the preset stencil data update conditions are met, so as to update the actual size data of the stencil through the data processing module, and control the subsequent matching of the PCB to be matched with the stencil based on the updated actual size data.

8. The device according to claim 7, 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, and calculates the actual size data of the current stencil based on the surface information of the four corners.

9. The device according to claim 7, characterized in that When matching the PCB to be matched with the stencil, the data processing module is specifically used to: Extract the solder paste dots 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; The center point of the stencil is aligned with the center point of the PCB to form a coincident center point, which is used as the reference origin for coordinate transformation; The coordinates of the four corners of the stencil and the four corner pads of the PCB are unified into the same coordinate system through coordinate conversion, so as to obtain the new coordinates of the four corners of the stencil and the four corner pads of the PCB in the unified coordinate system; Based on the unified coordinates of the new stencil's four corners and the PCB pad's four corners, a two-dimensional constraint mechanism is determined to ensure compatibility. This constraint mechanism ensures that the geometric center of the solder paste dot completely covers the effective soldering area of ​​the corresponding pad without any overlap, and that the vertical distances between the solder paste and the four edges of the pad meet pre-set process safety conditions. When the dual-dimensional constraint mechanism conditions are met at the same time, the PCB is marked as size compatible with the current stencil. If any of the conditions fails to pass the verification, it is determined to be mismatched and an alarm is triggered and recorded.

10. The device according to claim 7, characterized in that The preset stencil data update condition includes at least one of the following: the number of times the actual size data of the stencil is used reaches a preset number threshold, and the number of matched PCB products corresponding to the stencil reaches a preset number threshold.

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