Detection method for mounting missing material on flexible circuit board strips

Abstract

The present invention discloses a method for detecting material shortage during placement of a flexible circuit board strip, comprising the following steps: S1, acquiring a first image template and a second image template of the flexible circuit board; S2, using an area array camera to capture a real-time image of the strip, and identifying whether there is a material shortage area in the strip based on the real-time image; if the material shortage area is identified, obtaining the coordinate position of the material shortage area; S3, using a suction head to absorb the flexible circuit board to be placed, using a flying camera to capture a real-time image of the suction head, and identifying whether there is a flexible circuit board on the suction head based on the real-time image; if the flexible circuit board is identified, converting the coordinate position of the material shortage area into physical coordinates of the suction head movement, and using a suction head drive mechanism to place the flexible circuit board on the material shortage area based on the physical coordinates; S4, detecting the position of the flexible circuit board within the material shortage area after placement. The present invention not only ensures the accuracy of calculating the material shortage position, but also improves the detection efficiency of the placement process.

Description

Technical Field

[0001] The present invention relates to the field of detection technology, and in particular to a method for detecting material shortage placement of flexible circuit board strips. Background Art

[0002] Flexible printed circuits (FPCs), due to their high bendability, lightweight design, and space-saving advantages, have been widely used in consumer electronics, automotive electronics, medical devices, and other fields, becoming a crucial component in the high-density assembly of electronic products. During FPC manufacturing, carrier tape is typically used for transport and packaging to enable automated mass production. During the FPC loading process, factors such as production processes, equipment precision, and material control can lead to some defective FPCs being loaded into the tape. These defects may include broken wires, exposed copper, stains, indentations, and foreign matter contamination, seriously impacting product quality and the reliability of end devices.

[0003] To ensure production quality, production lines are typically equipped with automated optical inspection (AOI) systems to inspect FPCs in the material strip and remove defective products that do not meet quality standards. As high-precision electronic components, FPCs are expensive to produce. If defects in the material strip are removed due to defective removal, it will not only affect the subsequent placement process but may also reduce overall production efficiency. Therefore, after AOI inspection, gaps in the removed locations need to be compensated to ensure the integrity and continuity of the material strip, thereby improving production stability.

[0004] The existing material shortage subsidy is mainly through manual subsidy, which is not only inefficient but also easy to introduce new position errors, affecting the subsequent placement process. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that the manual subsidization method not only has low work efficiency, but also easily introduces new position errors, affecting the subsequent mounting process.

[0006] To this end, the present invention provides a method for detecting material shortage placement of flexible circuit board strips, which on the one hand ensures the accuracy of calculating the material shortage position, and on the other hand improves the detection efficiency of the filling process.

[0007] The technical solution adopted by the present invention to solve its technical problem is:

[0008] A method for detecting a shortage of flexible circuit board strips for mounting, comprising the following steps:

[0009] S1. Acquire a first image template and a second image template of a flexible circuit board;

[0010] S2. Using an area array camera to capture a real-time image of the material strip, and identifying whether there is a material-deficient area in the material strip based on the real-time image; if a material-deficient area is identified in the material strip, obtaining the coordinate position of the material-deficient area;

[0011] S3, sucking the flexible circuit board to be mounted with a suction head, capturing a real-time image of the suction head with a flying camera, and identifying whether there is a flexible circuit board on the suction head based on the real-time image. If a flexible circuit board is identified on the suction head, converting the coordinate position of the material-deficient area into physical coordinates of the suction head movement, and the suction head driving mechanism mounts the flexible circuit board to the material-deficient area according to the physical coordinates;

[0012] S4. Perform position detection on the flexible circuit board in the material shortage area after placement.

[0013] Furthermore, step S2 specifically includes:

[0014] S21, create multiple rectangular frames that can contain flexible circuit boards, the coordinates of the upper left corner vertex of the rectangular frame are , the coordinates of the lower right vertex are ;

[0015] S22, sequentially adjusting the center coordinates of the plurality of rectangular frames to the center position of the first row of flexible circuit boards in the real-time image of the material strip; and after each adjustment, matching the first image template with the region of interest framed by the rectangular frames, retaining the rectangular frame with the highest matching degree as the detection frame;

[0016] S23, using the detection frame to detect the real-time image of the material strip, and matching the area framed by the detection frame with the first image template. If the match is successful, it is determined that there is a flexible circuit board in the area; if the match fails, it is determined that there is a material shortage in the area, and the area is recorded as a material shortage area;

[0017] S24, performing grayscale feature analysis on the material-deficient area. If the grayscale feature Gavg ≥ grayscale threshold Tgray, it is determined that there is foreign matter in the material-deficient area and filling and mounting are prohibited; if the grayscale feature Gavg < grayscale threshold Tgray, it is determined that the material-deficient area can be filled and mounted.

[0018] Furthermore, the flexible circuit boards on the material strip are arranged in two columns and multiple rows;

[0019] In step S2, the coordinate position of the material shortage area is obtained, including:

[0020] S25, first row of feeding,

[0021] If the material shortage area is located in the first row, and there is no flexible circuit board in the first row and two columns of the real-time image of the material strip, the first row will be skipped for material replenishment;

[0022] If the material shortage area is located in the first row, and there is a flexible circuit board in one column of the first row of the real-time image of the material strip, the first row replenishment and placement strategy is executed;

[0023] The first-line material replenishment and placement strategy includes:

[0024] (i) When there is material in the left column of the first row but no material in the right column:

[0025] Extract the coordinates of the feature points of the left column of flexible circuit board ,

[0026] Left edge line equation based on the strip , a, b, c represent the coefficients of the equation, calculate the coordinates of the feature point Coordinates of the foot point of the perpendicular to the left edge line :

[0027] , ,

[0028] Get the distance between the right column of flexible circuit board and the left edge line according to the strip drawing definition , then the key point coordinates of the flexible circuit board to be filled in the first row and right column are :

[0029] , ;

[0030] (ii) When there is material in the right column of the first row but not in the left column, swap the left and right parameters and perform the symmetric operation.

[0031] Furthermore, in step S2, obtaining the coordinate position of the material-deficient area further includes:

[0032] S26, non-first row feed,

[0033] Extract the coordinates of the feature points of the previous row of flexible circuit boards in the same column as the material shortage area The inclination angle of the edge of the strip , as the feature point coordinates Perpendicular to the edge of the strip The coordinates of the foot point are , get the perpendicular line Angle And the distance between the upper and lower rows of flexible circuit boards ;

[0034] Calculate temporary coordinates :

[0035] , ;

[0036] According to the temporary coordinates , the distance between the flexible circuit board in the column where the material shortage area is located and the edge line ,perpendicular The tilt angle , calculate the key point coordinates of the flexible circuit board to be filled :

[0037] , .

[0038] Furthermore, the feature point coordinates of the flexible circuit board The calculation process includes:

[0039] Define the lower right corner of the flexible circuit board as the feature point, generate N scan lines at equal intervals on the right and lower edges of the flexible circuit board image, and perform the following operations on each scan line:

[0040] (i) Grayscale gradient calculation:

[0041] , =1 pixel, pixel gradient, Represents pixel points Pixel value of

[0042] (ii) On each scan line, extract the points with the largest grayscale gradient amplitude to form the edge point set and the lower edge point set. The extreme point extraction formula is: ;

[0043] The right edge point set and the lower edge point set are fitted using weighted least squares method, with the weight being the grayscale gradient amplitude of the corresponding pixel point, to obtain two fitting lines:

[0044] Fitting a straight line to the lower edge of the flexible circuit board image : ,

[0045] Fitted straight line to the right edge of the flexible circuit board image : ,

[0046] in, 、 Represent the slopes of the lower edge fitting line and the right edge fitting line, 、 They represent the intercepts of the corresponding straight lines respectively;

[0047] Lower edge fitting straight line Fit a straight line to the right edge The intersection point is the feature point, and the coordinates of the feature point are:

[0048] , .

[0049] Furthermore, obtaining the first image template includes:

[0050] Use an area scan camera to capture images of qualified material strips and frame the area of ​​interest containing the flexible circuit board from the image;

[0051] The Canny operator and Sobel gradient operator are used to extract the edge information of the flexible circuit board in the region of interest, retaining the contour features, position features, and angle features of the flexible circuit board;

[0052] The template is trained using the region of interest and its features, and a qualified template is used as the first image template; that is, the first image template is an image template of the flexible circuit board in the qualified material strip;

[0053] Acquiring the second image template includes:

[0054] Use a flying camera to capture an image of the flexible circuit board after the suction head picks up the flexible circuit board, and frame the area of ​​interest containing the flexible circuit board from the image;

[0055] The Canny operator and Sobel gradient operator are used to extract the edge information of the flexible circuit board in the area of ​​interest, retaining the contour features, position features, and angle features of the flexible circuit board;

[0056] The template is trained using the region of interest and its features, and a qualified template is used as the second image template; that is, the second image template is an image template of the suction head sucking up the flexible circuit board.

[0057] Furthermore, identifying whether there is a flexible circuit board on the suction head includes:

[0058] Matching the real-time image of the suction tip with the second image template, and sending the matching result to the PLC in the form of a status code;

[0059] Status code 0X01: Indicates that the nozzle has a flexible circuit board;

[0060] Status code 0X02: Indicates that the suction head has no flexible circuit board or recognition fails.

[0061] Furthermore, step S4 specifically includes:

[0062] S41, using the first image template to scan the flexible circuit board after the patching and placement of the patched material line by line, and locate the position areas of all flexible circuit boards;

[0063] S42: Extracting the coordinates of feature points of the flexible circuit board within the location area of ​​the flexible circuit board ,

[0064] For the flexible circuit board in the left column, calculate the horizontal distance between its feature point coordinates and the feature point coordinates of the adjacent flexible circuit board in the right column , the vertical spacing between the feature points of the adjacent flexible circuit board in the previous row ;

[0065] For the right column of flexible circuit boards, calculate the horizontal distance between the coordinates of its feature points and the coordinates of the feature points of the adjacent flexible circuit boards in the left column , the vertical spacing between the feature points of the adjacent flexible circuit board in the previous row ;

[0066] like or If the absolute value of the difference between the standard value and the standard value is ≤0.1mm, the spacing is considered qualified;

[0067] like or If the absolute value of the difference between the standard value and the standard value is ≤0.1mm, the spacing is considered qualified;

[0068] S43. When both the horizontal spacing and the vertical spacing of the subsidized flexible circuit board are qualified, it is determined that the current flexible circuit board subsidy is qualified; otherwise, it is determined that the subsidy is unqualified.

[0069] The beneficial effects of the present invention are:

[0070] In terms of accuracy: through testing, the accuracy of the present invention in calculating the position of material shortage is as high as 99.3%, which is a huge improvement in accuracy compared with traditional manual compensation methods and general image processing automatic recognition methods.

[0071] Identification efficiency: By recording the time required for image detection, this method can complete over 1,000 missing pieces per hour, significantly improving production efficiency. Compared to traditional manual counting methods, this method significantly improves both identification speed and accuracy, fully demonstrating the significant advantages of the detection system in efficient identification and automated production.

[0072] The present invention improves the problems of material feeding deviation and misalignment that are prone to occur in manual operation, forming an industrial-grade solution that integrates high-precision detection and rapid response, and significantly improves the yield stability and automation level of the FPC production line. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] The present invention will be further described below with reference to the accompanying drawings and examples.

[0074] Figure 1 The present invention is a flow chart of a method for detecting a shortage of flexible circuit board strips for mounting.

[0075] Figure 2 It is a schematic diagram of a real-time image of a material strip captured by the area array camera of the present invention.

[0076] Figure 3 is a schematic diagram of the first image template of the present invention.

[0077] Figure 4 is a schematic diagram of the second image template of the present invention.

[0078] Figure 5 It is a schematic diagram of a detection frame outlining a region of interest according to the present invention.

[0079] Figure 6 It is a schematic diagram of matching the first image template of the present invention with the region of interest within the detection frame.

[0080] Figure 7 It is a schematic diagram of the material strip edge line fitting and the flexible circuit board edge line fitting of the present invention.

[0081] Figure 8 It is a schematic diagram of the first row of feed coordinate calculation of the present invention.

[0082] Figure 9 It is a schematic diagram of the calculation of the non-first row feed coordinates of the present invention. DETAILED DESCRIPTION

[0083] The present invention will now be described in further detail with reference to the accompanying drawings, which are simplified schematic diagrams that illustrate the basic structure of the present invention in a schematic manner.

[0084] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, features defined as "first" or "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0085] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0086] like Figure 1 and Figure 2 As shown, the detection method for the short-stack placement of a flexible circuit board strip in this embodiment includes the following steps: S1. Acquire a first image template and a second image template of the flexible circuit board. S2. Use an area array camera to capture a real-time image of the strip, and identify whether there is a short-stack area in the strip based on the real-time image; if it is identified that there is a short-stack area in the strip, obtain the coordinate position of the short-stack area. S3. Use a suction head to suck up the flexible circuit board to be mounted, use a flying camera to capture a real-time image of the suction head, and identify whether there is a flexible circuit board on the suction head based on the real-time image; if it is identified that there is a flexible circuit board on the suction head, convert the coordinate position of the short-stack area into the physical coordinates of the suction head movement, and the suction head drive mechanism mounts the flexible circuit board to the short-stack area based on the physical coordinates. S4. Perform position detection on the flexible circuit board in the short-stack area after mounting.

[0087] This embodiment can realize automatic material replenishment and placement in the material-deficient area of ​​the material strip, which can improve the precision and accuracy of the material replenishment and placement on the one hand, and on the other hand, improve the work efficiency of the material strip quality inspection.

[0088] It should be noted that when the material strip is conveyed to the inspection station, an area array camera is used to capture the strip image and identify whether there is a material-deficient area in the current real-time image. If not, the strip continues to be conveyed forward, and the area array camera continues to image the next area of ​​the strip. If it is, the coordinates of the material-deficient area are identified based on the real-time image, and the material replenishment and placement process is carried out. The suction head used in this embodiment is a dual suction head equipped with a motion control mechanism. The suction head is used to pick up the flexible circuit board to be placed. The flying camera captures the suction head from bottom to top to identify whether there is material on the suction head.

[0089] In this embodiment, if Figure 3 As shown, the first image template is an image template of the flexible circuit board in the qualified material strip; Figure 4As shown, the second image template is an image template of the flexible circuit board sucked by the suction head. For example, obtaining the first image template includes: using an area array camera to capture an image of a qualified material strip, and framing the region of interest containing the flexible circuit board from the image; using the Canny operator and the Sobel gradient operator to extract the edge information of the flexible circuit board in the region of interest, and retaining the contour features, position features, and angle features of the flexible circuit board; using the region of interest and its features to train the template, and using the trained qualified template as the first image template. Obtaining the second image template includes: using a flying camera to capture an image after the suction head sucks the flexible circuit board, and framing the region of interest containing the flexible circuit board from the image; using the Canny operator and the Sobel gradient operator to extract the edge information of the flexible circuit board in the region of interest, and retaining the contour features, position features, and angle features of the flexible circuit board; using the region of interest and its features to train the template, and using the trained qualified template as the second image template. For example, during the template training process, the template can be verified. When the error of using the current template for image matching for 10 consecutive times is ≤ When the pixel value is 0.5, the template is judged to be qualified.

[0090] In other words, the feature extraction process for the region of interest is similar during the acquisition of the first and second image templates. The reason for preparing two image templates in this embodiment is that the images of the flexible circuit board mounted on the strip and captured by the suction head differ. Using the first image template to match the flexible circuit board in the strip image and the second image template to match the flexible circuit board in the suction head image improves image recognition accuracy, thereby improving the precision of the patching.

[0091] In this embodiment, the flexible circuit boards on the strip are arranged in two columns and multiple rows. That is, two flexible circuit boards are mounted in each row. In actual applications, the real-time image of the strip captured by the area array camera generally contains four complete flexible circuit boards. The first row in the image is recorded as the first row, and the second row is recorded as a non-first row. Missing areas may appear in the first row or a non-first row, so the coordinates of the missing areas need to be considered separately when calculating their locations.

[0092] In step S2, the process of identifying the material shortage area includes:

[0093] S21. Create multiple rectangular boxes that can contain flexible circuit boards. The coordinates of the upper left corner of the rectangular box are , the coordinates of the lower right vertex are .

[0094] It should be noted that the rectangular frame is used to frame the region of interest containing a complete flexible circuit board in the real-time image of the outfeed tape.

[0095] S22. Adjust the center coordinates of the multiple rectangular frames in sequence to the center position of the first row of flexible circuit boards in the real-time image of the material strip; and after each adjustment, use the first image template to match the area of ​​interest framed by the rectangular frames, and retain the rectangular frame with the highest matching degree as the detection frame.

[0096] Since the area of ​​interest outlined by the rectangular frame is closely related to the subsequent detection results, the generated rectangular frames must be screened and the optimal rectangular frame must be selected as the detection frame. The center coordinates of the rectangular frame are , then move the center coordinates of the rectangular frame to the center of the first row of flexible circuit boards in the image. At this time, use the first image template to perform image matching on the area of ​​interest framed by the rectangular frame. "Matching" can be understood as performing normalized product correlation calculation (NCC) on the gradient amplitude and direction of the flexible circuit board in the first image template and the flexible circuit board in the area of ​​interest. The calculation formula is: , NCC value represents the matching degree (range 0 to 1), represents the normalized gradient value of the first image template, It represents the normalized gradient value of the region of interest. The matching threshold can be set to 0.6, and the rectangular box with the highest matching degree exceeding the matching threshold is selected as the detection box.

[0097] S23, using the detection frame to detect the real-time image of the material strip (such as Figure 5 and Figure 6 As shown), the area framed by the detection box is matched with the first image template. If the match is successful, it is determined that there is a flexible circuit board in the area. If the match fails, it is determined that there is a material shortage in the area, and the area is recorded as a material shortage area.

[0098] It should be noted that during the detection process, the detection frame is dynamically offset in the real-time image of the material strip to detect the first and non-first rows in the real-time image in sequence. The offset rules are: , , , , Indicates the horizontal expansion value, Indicates the vertical length of the flexible circuit, Indicates the preset vertical spacing. That is, during the inspection process, the inspection frame is movable, and each movement frames a region of interest. The region of interest is then matched with the first image template. If the match is successful, it indicates that a flexible circuit board is present in the region of interest. If the match fails, it indicates that there is no flexible circuit board in the region of interest, and the region of interest is recorded as a material-deficient area.

[0099] S24. Perform grayscale feature analysis on the material-deficient area. If the grayscale feature Gavg ≥ grayscale threshold Tgray, it is determined that there are foreign objects in the material-deficient area and filling and mounting are prohibited. If the grayscale feature Gavg < grayscale threshold Tgray, it is determined that the material-deficient area can be filled and mounted.

[0100] It's important to note that once an area is identified as a material-shortage area, the refill placement process doesn't immediately begin. Instead, the area is first analyzed to determine if it's suitable for refilling. Generally speaking, the tape itself is transparent, so the grayscale values ​​of the tape image are essentially the same. Grayscale analysis can be used to determine if the material-shortage area is suitable for refilling. First, the average grayscale value (Gavg) of the material-shortage area is calculated. If there's foreign matter in the area, the average grayscale value will significantly increase. Therefore, by analyzing the grayscale characteristics of the material-shortage area, it's possible to determine if there's foreign matter interfering with the area. If there is, refill placement is unsuitable, as this will affect the placement results.

[0101] To place additional material in a missing area, you need to calculate the placement coordinates. The calculation of the coordinates is divided into two cases: the first row and the non-first row.

[0102] Case 1: S25, first row feeding,

[0103] If the missing material area is located in the first row and there are no FPCs in either of the first row and columns of the strip's real-time image, the first row replenishment strategy is skipped. If the missing material area is located in the first row and there is an FPC in one of the first rows of the strip's real-time image, the first row replenishment strategy is executed.

[0104] like Figure 7 and Figure 8 As shown, the first-line replenishment and placement strategy includes:

[0105] (i) When there is material in the left column of the first row but no material in the right column:

[0106] Extract the coordinates of the feature points of the left column of flexible circuit board , based on the left edge line equation of the strip , a, b, c represent the coefficients of the equation, calculate the coordinates of the feature points Coordinates of the foot point of the perpendicular to the left edge line : , , according to the strip drawing definition, get the distance between the right column flexible circuit board and the left edge line , then the key point coordinates of the flexible circuit board to be filled in the first row and right column are : , .

[0107] (ii) When there is material in the right column of the first row but not in the left column, swap the left and right parameters and perform the symmetric operation.

[0108] It should be noted that when there are no flexible circuit boards in the first row and the second column in the real-time image of the material strip, the material replenishment and placement procedure will not be performed and will be skipped directly. When there is a flexible circuit board in the first row and the second column in the real-time image of the material strip (either in the left column or the right column), the material replenishment and placement of the first row can be performed. In this embodiment, when there is material in the left column of the first row and there is no material in the right column, the key point coordinates of the flexible circuit board to be replenished in the right column are calculated based on the characteristic points of the flexible circuit board in the left column and the left edge line of the material strip. So why not calculate the key point coordinates of the replenishment based directly on the characteristic points and the mounting spacing of the flexible circuit board in the right column? This is because when the flexible circuit board is being mounted, sometimes there will be a certain deviation between the mounting spacing between the left and right columns and the standard spacing. The coordinates calculated by the deviated reference point will also be deviated. Coupled with the errors of the mechanical components themselves, the superposition of multiple errors will cause the coordinates of the key points of the replenishment to be inaccurate. This embodiment adopts a fixed distance between the material strip line, the mounted product in the right column and the edge line of the material strip. The coordinates of the key points of the products to be replenished in the right column are calculated based on the coordinates of the characteristic points of the mounted products in the left column, which can reduce the superposition of errors and help improve the accuracy of the calculation of the key point coordinates.

[0109] Case 2: S26, non-first row feeding,

[0110] like Figure 9 As shown, extract the coordinates of the feature points of the previous row of flexible circuit boards in the same column as the material shortage area The inclination angle of the edge of the strip , as the feature point coordinates Perpendicular to the edge of the strip The coordinates of the foot point are , get the perpendicular line The tilt angle And the distance between the upper and lower rows of flexible circuit boards ; Calculate temporary coordinates : , ; According to the temporary coordinates , the distance between the flexible circuit board in the column where the material shortage area is located and the edge line ,perpendicular Angle , calculate the key point coordinates of the flexible circuit board to be filled : , .

[0111] It should be noted that the first-row patching strategy cannot be used when patching non-first rows. This is because products already exist in the row above the non-first row in the image. In this case, patching requires considering the vertical spacing between the products in the previous row and the horizontal spacing between products in the same row. Therefore, the position of the patched product must be calculated based on the products in the previous row. However, a concern is that if the products in the previous row are slightly tilted, the position of the patched product will also deviate, and this deviation will be propagated row by row. Therefore, when patching non-first rows, this embodiment cannot rely solely on the position of the products in the previous row. Instead, this embodiment calculates key point coordinates based on the coordinates of the feature points of the products in the previous row and the characteristics of the strip edge. Another consideration is that while the strip edge appears vertical overall, it can sometimes have a slight tilt angle. Therefore, when patching non-first rows, this embodiment establishes a targeted geometric reference to eliminate the impact of the previous row's product offset, ensuring that the patch coordinates are strictly aligned with the strip direction, thereby improving placement accuracy and consistency.

[0112] In this embodiment, the feature point coordinates of the flexible circuit board The calculation process includes:

[0113] Define the lower right corner of the flexible circuit board as the feature point, generate N scan lines at equal intervals on the right and lower edges of the flexible circuit board image, and perform the following operations on each scan line:

[0114] (i) Grayscale gradient calculation:

[0115] , =1 pixel, pixel gradient, Represents pixel points Pixel value of

[0116] (ii) On each scan line, extract the points with the largest grayscale gradient amplitude to form the right edge point set and the lower edge point set. The extreme point extraction formula is: ;

[0117] Perform weighted least squares linear fitting on the right edge point set and the lower edge point set respectively, with the weight being the grayscale gradient amplitude of the corresponding pixel point, and obtain two fitting lines:

[0118] Fitting a straight line to the lower edge of the flexible circuit board image : ,

[0119] Fitted straight line to the right edge of the flexible circuit board image : ,

[0120] in, 、 Represent the slopes of the lower edge fitting line and the right edge fitting line, 、 They represent the intercepts of the corresponding straight lines respectively;

[0121] Lower edge fitting straight line Fit a straight line to the right edge The intersection point is the feature point, and the coordinates of the feature point are: , .

[0122] It should be noted that the reason for selecting the lower right corner of the flexible circuit board as the feature point in this embodiment is that the flexible circuit board in this embodiment is roughly L-shaped. When performing contour fitting on the flexible circuit board, it is necessary to collect multiple feature points on the edge line of the flexible circuit board. The more feature points collected, the better the fitting effect. The lower and right edge lines of the flexible circuit board in this embodiment can collect more feature points, and the straight line fitting will be more accurate, which is conducive to improving the coordinates of the feature points of the flexible circuit board. The accuracy of the data can be further improved to further improve the accuracy of subsequent material shortage subsidies.

[0123] After calculating the key point coordinates of the flexible circuit board that needs to be patched, the flexible circuit board can be picked up by the suction head and mounted to the corresponding coordinate position. The movement of the suction head is realized by a motion control mechanism (such as a robot). It can be understood that the calculated key point coordinates It is pixel coordinates, while the movement of the suction head is world coordinates (ie physical coordinates). Coordinate conversion is required before placement.

[0124] In this embodiment, the coordinate conversion process includes:

[0125] S31, Rotation Center Coordinate Correction

[0126] Based on the pre-calibrated dual-head parameters, the rotation center of the heads is calculated in real time through the mapping relationship between the robot coordinate system and the camera coordinate system. The rotation center coordinates of the head 1 / head 2 positioning point are: the x / y translation of the robot coordinates plus the pre-stored rotation reference point coordinates.

[0127] S32, pixel-level coordinate space conversion

[0128] Sub-pixel coordinates of the feature points of the flexible circuit board , the affine transformation matrix generated by calibration is converted into the physical coordinates in the world coordinate system of the manipulator , the conversion relationship satisfies: , , 、 Indicates the pixel-to-physical size scaling factor.

[0129] S33, Motion control mechanism inherent error compensation

[0130] The calculated physical coordinates Overlay the pre-stored fixed compensation values ​​in X / Y direction , to eliminate mechanical errors, the coordinates after compensation are:

[0131] , , 、 Indicates the set compensation parameters.

[0132] In this embodiment, identifying whether a flexible circuit board is present on a suction head includes matching a real-time image of the suction head using a second image template and transmitting the matching result to the PLC as a status code. Status code 0X01 indicates that the suction head has a flexible circuit board; status code 0X02 indicates that the suction head does not have a flexible circuit board or that the identification failed. For example, using a dual suction head as an example, {0X01, 0X01} indicates that suction head one and suction head two have material; {0X01, 0X02} indicates that suction head one has material, suction head two has no material, or that the identification failed; {0X02, 0X02} indicates that suction head one has no material, or that the identification failed, suction head two has no material, or that the identification failed; {0X02, 0X01} indicates that suction head one has no material, or that the identification failed, suction head two has no material, or that the identification failed; and {0X02, 0X01} indicates that suction head one has no material, or that the identification failed, and suction head two has material.

[0133] In this embodiment, testing the subsidized flexible printed circuit board includes:

[0134] S41 , using the first image template to scan the flexible circuit board after the patching and placement of the materials line by line, and locate the position areas of all the flexible circuit boards.

[0135] S42: Extracting the coordinates of feature points of the flexible circuit board within the location area of ​​the flexible circuit board ; For the left column of flexible circuit boards, calculate the horizontal distance between the coordinates of its feature points and the coordinates of the feature points of the adjacent flexible circuit boards in the right column , the vertical spacing between the feature points of the adjacent flexible circuit board in the previous row ; For the right column of flexible circuit boards, calculate the horizontal distance between the coordinates of its feature points and the coordinates of the feature points of the adjacent flexible circuit boards in the left column , the vertical spacing between the feature points of the adjacent flexible circuit board in the previous row ;

[0136] like or If the absolute value of the difference between the standard value and the standard value is ≤0.1mm, the spacing is considered qualified;

[0137] like or If the absolute value of the difference with the standard value is ≤0.1mm, the spacing is judged to be qualified.

[0138] S43. When both the horizontal spacing and the vertical spacing of the subsidized flexible circuit board are qualified, it is determined that the current flexible circuit board subsidy is qualified; otherwise, it is determined that the subsidy is unqualified.

[0139] When the subsidy is judged to be unqualified, an NG signal is triggered and recorded. The record content includes: type of deviation (horizontal spacing or vertical spacing) and deviation amount (unit: mm).

[0140] By improving the calculation method of the key point coordinates of the material shortage area, this embodiment can significantly improve the accuracy of the material shortage location calculation and the detection efficiency. The advantages of this method compared with the existing method are shown in Table 1.

[0141] Table 1

[0142]

[0143] In summary, the method for detecting the shortage of flexible circuit board strips of the present invention has the following advantages:

[0144] In terms of accuracy: Through the test results of the present invention in an actual factory, the accuracy of the present invention in calculating the position of material shortages reached 99.3%, which has achieved a huge improvement in accuracy compared with traditional manual compensation methods and general image processing automatic recognition methods.

[0145] Identification efficiency: By recording the time required for image detection, this method can complete over 1,000 missing pieces per hour, significantly improving production efficiency. Compared to traditional manual counting methods, this method significantly improves both identification speed and accuracy, fully demonstrating the significant advantages of the detection system in efficient identification and automated production.

[0146] The present invention improves the problems of material feeding deviation and misalignment that are prone to occur in manual operation, forming an industrial-grade solution that integrates high-precision detection and rapid response, and significantly improves the yield stability and automation level of the FPC production line.

[0147] With the above-described preferred embodiments of the present invention as a guide, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical spirit of this invention. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for detecting the lack of material in flexible circuit board strip placement, characterized in that: The following steps are involved: S1. Acquire a first image template and a second image template of a flexible circuit board; The first image template is an image template of the flexible circuit board in the qualified material strip, and the second image template is an image template of the flexible circuit board picked up by the suction head; S2. Using an area array camera to capture a real-time image of the material strip, and identifying whether there is a material shortage area in the material strip based on the real-time image; If it is identified that there is a material shortage area in the material strip, the coordinate position of the material shortage area is obtained; Step S2 specifically includes: S21, create multiple rectangular frames that can contain flexible circuit boards, the coordinates of the upper left corner vertex of the rectangular frame are , the coordinates of the lower right vertex are ; S22, sequentially adjusting the center coordinates of the plurality of rectangular frames to the center position of the first row of flexible circuit boards in the real-time image of the material strip; and after each adjustment, matching the first image template with the region of interest framed by the rectangular frames, retaining the rectangular frame with the highest matching degree as the detection frame; S23, using the detection frame to detect the real-time image of the material strip, and matching the area framed by the detection frame with the first image template. If the match is successful, it is determined that there is a flexible circuit board in the area; if the match fails, it is determined that there is a material shortage in the area, and the area is recorded as a material shortage area; S3, sucking the flexible circuit board to be mounted with a suction head, capturing a real-time image of the suction head with a flying camera, and identifying whether there is a flexible circuit board on the suction head based on the real-time image. If a flexible circuit board is identified on the suction head, converting the coordinate position of the material-deficient area into physical coordinates of the suction head movement, and the suction head driving mechanism mounts the flexible circuit board to the material-deficient area according to the physical coordinates; Identifying whether there is a flexible circuit board on the suction head includes: Matching the real-time image of the suction tip using the second image template, and sending the matching result to the PLC as a status code; Status code 0X01: Indicates that the nozzle has a flexible circuit board; Status code 0X02: Indicates that the nozzle has no flexible circuit board or the recognition fails; S4. Perform position detection on the flexible circuit board in the material shortage area after placement.

2. The method for detecting the shortage of flexible circuit board strips according to claim 1, wherein: Step S2 further includes: S24, performing grayscale feature analysis on the material-deficient area. If the grayscale feature Gavg ≥ grayscale threshold Tgray, it is determined that there is foreign matter in the material-deficient area and filling and mounting are prohibited; if the grayscale feature Gavg < grayscale threshold Tgray, it is determined that the material-deficient area can be filled and mounted.

3. The method for detecting the shortage of flexible circuit board strips according to claim 2, wherein: The flexible circuit boards on the material strip are arranged in two columns and multiple rows; In step S2, the coordinate position of the material shortage area is obtained, including: S25, first row of feeding, If the material shortage area is located in the first row, and there is no flexible circuit board in the first row and two columns of the real-time image of the material strip, the first row will be skipped for material replenishment; If the material shortage area is located in the first row, and there is a flexible circuit board in one column of the first row of the real-time image of the material strip, the first row replenishment and placement strategy is executed; The first-line material replenishment and placement strategy includes: (i) When there is material in the left column of the first row but no material in the right column: Extract the coordinates of the feature points of the left column of flexible circuit board , Left edge line equation based on the strip , a, b, c represent the coefficients of the equation, calculate the coordinates of the feature point Coordinates of the foot point of the perpendicular to the left edge line : ， ， Get the distance between the right column of flexible circuit board and the left edge line according to the strip drawing definition , then the key point coordinates of the flexible circuit board to be filled in the first row and right column are : ， ； (ii) When there is material in the right column of the first row but not in the left column, swap the left and right parameters and perform the symmetric operation.

4. The method for detecting the shortage of flexible circuit board strips according to claim 3, wherein: In step S2, the coordinate position of the material shortage area is obtained, which also includes: S26, non-first row feed, Extract the coordinates of the feature points of the previous row of flexible circuit boards in the same column as the material shortage area The inclination angle of the edge of the strip , as the feature point coordinates Perpendicular to the edge of the strip The coordinates of the foot point are , get the perpendicular line Angle And the distance between the upper and lower rows of flexible circuit boards ; Calculate temporary coordinates : ， ； According to the temporary coordinates , the distance between the flexible circuit board in the column where the material shortage area is located and the edge line ,perpendicular The tilt angle , calculate the key point coordinates of the flexible circuit board to be filled : ， 。 5. The method for detecting the shortage of flexible circuit board strips according to claim 3 or 4, characterized in that: Feature point coordinates of flexible circuit board The calculation process includes: Define the lower right corner of the flexible circuit board as the feature point, generate N scan lines at equal intervals on the right and lower edges of the flexible circuit board image, and perform the following operations on each scan line: (i) Grayscale gradient calculation: , =1 pixel, pixel gradient, Represents pixel points Pixel value of (ii) On each scan line, extract the points with the largest grayscale gradient amplitude to form the right edge point set and the lower edge point set. The extreme point extraction formula is: ; Perform weighted least squares linear fitting on the right edge point set and the lower edge point set respectively, with the weight being the grayscale gradient amplitude of the corresponding pixel point, and obtain two fitting lines: Fitting a straight line to the lower edge of the flexible circuit board image : , Fitted straight line to the right edge of the flexible circuit board image : , in, 、 They represent the slopes of the lower edge fitting line and the right edge fitting line, 、 They represent the intercepts of the corresponding straight lines respectively; Lower edge fitting straight line Fit a straight line to the right edge The intersection point is the feature point, and the coordinates of the feature point are: ， 。 6. The method for detecting the shortage of flexible circuit board strips according to claim 1, wherein: Acquiring the first image template includes: Use an area scan camera to capture images of qualified material strips and frame the area of ​​interest containing the flexible circuit board from the image; The Canny operator and Sobel gradient operator are used to extract the edge information of the flexible circuit board in the region of interest, retaining the contour features, position features, and angle features of the flexible circuit board; The template is trained using the region of interest and its features, and the qualified template is used as the first image template; Acquiring the second image template includes: Use a flying camera to capture an image of the flexible circuit board after the suction head picks up the flexible circuit board, and frame the area of ​​interest containing the flexible circuit board from the image; The Canny operator and Sobel gradient operator are used to extract the edge information of the flexible circuit board in the region of interest, retaining the contour features, position features, and angle features of the flexible circuit board; The template is trained using the region of interest and its features, and the qualified template is used as the second image template.

7. The method for detecting the shortage of flexible circuit board strips according to claim 1, wherein: Step S4 specifically includes: S41, using the first image template to scan the flexible circuit board after the patching and placement of the patched material line by line, and locate the position areas of all flexible circuit boards; S42: Extracting the coordinates of feature points of the flexible circuit board within the location area of ​​the flexible circuit board , For the flexible circuit board in the left column, calculate the horizontal distance between its feature point coordinates and the feature point coordinates of the adjacent flexible circuit board in the right column , the vertical spacing between the feature points of the adjacent flexible circuit board in the previous row ; For the right column of flexible circuit boards, calculate the horizontal distance between the coordinates of its feature points and the coordinates of the feature points of the adjacent flexible circuit boards in the left column , the vertical spacing between the feature points of the adjacent flexible circuit board in the previous row ; like or If the absolute value of the difference between the standard value and the standard value is ≤0.1mm, the spacing is considered qualified; like or If the absolute value of the difference between the standard value and the standard value is ≤0.1mm, the spacing is considered qualified; S43. When both the horizontal spacing and the vertical spacing of the subsidized flexible circuit board are qualified, it is determined that the current flexible circuit board subsidy is qualified; otherwise, it is determined that the subsidy is unqualified.

Images