Multi-layer circuit board drilling defect automatic detection method and system

Abstract

The invention discloses an automatic detection method and system for drilling defects of a multilayer circuit board, relates to the field of circuit board detection, and solves the problem that the drilling defects of the multilayer circuit board cannot be accurately judged. The method comprises the following steps: acquiring an outer surface image of the multilayer circuit board, and preprocessing the outer surface image to obtain an edge profile diagram of a first circuit board and an Nth circuit board; analyzing the edge contours of the first circuit board and the Nth circuit board to obtain an expression and a direction vector of a corresponding drilling linear equation; measuring a second circuit board to an (N-1) th circuit board in the multilayer circuit board to obtain a corresponding X-ray image and an ultrasonic model, and analyzing the X-ray image and the ultrasonic model of the multilayer circuit board to obtain a drill hole deviation level of a drill hole corresponding to any circuit board; and receiving an abnormal signal or a drilling offset level corresponding to the multilayer circuit board, and reading the abnormal signal or the drilling offset level to obtain the drilling defect condition of the multilayer circuit board, so that accurate judgment of the drilling defect of the multilayer circuit board is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of circuit board detection, and specifically relates to an automatic detection method and system for drilling defects of multi-layer circuit boards. Background Art

[0002] A circuit board, also known as a printed circuit board, is an important electronic component, a support for electronic components, and a carrier for electrical connections of electronic components; a multi-layer circuit board is formed by stacking at least three copper foil layers and two insulating layers, and connections are formed between the layers through a pore electroplating process. Its structure usually consists of 3 to 16, or even more, copper foil layers stacked together and contains pores for connection. Each copper foil layer has its own circuit pattern, and these circuit patterns are connected to each other through conductive holes. In order to avoid misalignment of blind holes, the inner wall of the holes is often coated with conductive metal, which increases the complexity of the process; However, at the present stage, when monitoring the drilling of multi-layer circuit boards, the detection accuracy is relatively low. Traditional methods are difficult to judge the defect conditions of the internal drilling of multi-layer circuit boards, such as the offset situation and the drilling size of the internal drilling, and thus it is impossible to accurately know the quality of the corresponding multi-layer circuit board; Therefore, the present invention proposes an automatic detection method and system for drilling defects of multi-layer circuit boards. Summary of the Invention

[0003] The purpose of the present invention is to propose an automatic detection method and system for drilling defects of multi-layer circuit boards to solve the problems raised in the above background art.

[0004] To achieve the above purpose, the present invention adopts the following technical solutions: An automatic detection method for drilling defects of multi-layer circuit boards, the method comprising: Step S1, collecting the outer surface image of the multi-layer circuit board, and then preprocessing the outer surface image to obtain the edge contour diagrams of the first circuit board and the Nth circuit board; Step S2, analyzing the edge contours of the first circuit board and the Nth circuit board to obtain the expression of the corresponding drilling straight line equation and the direction vector; Step S3, measuring the second circuit board to the N-1th circuit board in the multi-layer circuit board to obtain the corresponding X-ray image and ultrasonic model; Step S4, analyzing the X-ray image and ultrasonic model of the multi-layer circuit board to obtain the drilling offset grade of the corresponding drilling of any circuit board; Step S5, receiving the abnormal signal or drilling offset grade corresponding to the multi-layer circuit board, and reading the abnormal signal or drilling offset grade to know the drilling defect situation of the multi-layer circuit board.

[0005] Further, the step S1 includes the following sub-steps: Step S11: Divide the multi-layer circuit board into the first circuit board to the Nth circuit board in sequence, where N is the number of layers of the circuit board; Step S12: Adjust the multi-layer circuit board so that the first circuit board faces upward and is placed within the shooting range of the camera, and capture the outer surface image of the first circuit board through the camera; Step S13: Adjust the multi-layer circuit board so that the Nth circuit board faces upward and is placed within the shooting range of the camera, and then capture the outer surface image of the Nth circuit board through the camera; Step S14: Analyze the outer surface image of the first circuit board to obtain the edge contour of the first circuit board; Step S15: Similarly, extract the edge contour of the Nth circuit board.

[0006] Further, the step S14 includes the following sub-steps: Step S141: Obtain the outer surface image of the first circuit board, extract the pixel values of multiple pixel points in the first circuit board, and obtain the R value component RZx, G value component GZx, and B value component BZx of each pixel point; where x is the number of the pixel point, x = 1, 2,..., z, and z is a positive integer; Step S142: Calculate the grayscale value HDx of each pixel point in the first circuit board through the formula. The specific formula is as follows: HDx = (A1 × RZx + A2 × GZx + A3 × BZx) / 3; In the formula, A1, A2, and A3 are proportionality coefficients with fixed values, A1 < A2 < A3 and A1 + A2 + A3 = 1; Step S143: Obtain the Gaussian grayscale value GHDx of the corresponding pixel point by passing the grayscale value of the pixel point through the Gaussian filtering function. The Gaussian filtering function is specifically: ; In the formula, σ is a constant, and exp is the power function with e as the base.

[0007] Further, the step S14 also includes: Step S144: Denote any pixel point as the selected pixel point, denote the pixel points adjacent to the selected pixel point as adjacent pixel points, and calculate the difference in Gaussian grayscale values between the adjacent pixel points and the selected pixel point and denote it as the grayscale difference; Step S145: Compare the grayscale difference of the selected pixel point with the grayscale difference threshold. If any grayscale difference corresponding to the selected pixel point is greater than or equal to the grayscale difference threshold, then denote the selected pixel point as an edge pixel point. If all grayscale differences corresponding to the selected pixel point are less than the grayscale difference threshold, then do not perform any operation; Step S146: Connect the adjacent edge pixel points to obtain the edge contour of the first circuit board.

[0008] Further, the step S2 includes the following sub-steps: Step S21, obtain the edge contour of the first circuit board and the edge contour of the Nth circuit board; Step S22, match the edge contour of the first circuit board and the edge contour of the Nth circuit board with the drilling schematic diagram. If the match is successful, record the successfully matched edge contour as the drilling contour; if the match fails, it is determined that there is a drilling defect on the circuit board and an abnormal signal is generated; Step S23, take any two mutually perpendicular lines in the plane where the Nth circuit board is located as the X-axis and the Y-axis, and draw a line perpendicular to the plane where the Nth circuit board is located as the Z-axis to construct a space rectangular coordinate system; Step S24, record the first center coordinate of the first circuit board corresponding to the drilling contour as (X1, Y1, Z1); record the Nth center coordinate of the Nth circuit board corresponding to the drilling contour as (X2, Y2, 0).

[0009] Further, the step S2 also includes the following sub-steps: Step S25, calculate the offset distance PY of the projection between the first center coordinate and the Nth center coordinate through the formula. The specific formula is as follows: ; Step S26, compare the offset distance with the deviation distance threshold. If the offset distance is greater than or equal to the deviation distance threshold, it is determined that there is a drilling defect on the circuit board and an abnormal signal is generated; if the offset distance is less than the deviation distance threshold, obtain the expression of the drilling straight line equation corresponding to the drilling. The specific expression of the drilling straight line equation is: ; Step S27, further, obtain the direction vector XL = (X2 - X1, Y2 - Y1, -Z1) of the corresponding drilling straight line equation.

[0010] Further, the step S4 includes the following sub-steps: Step S41, obtain the X-ray images of the multi-layer circuit board, and synthesize the multiple X-ray images corresponding to the multi-layer circuit board to obtain a three-dimensional X-ray model of the multi-layer circuit board; Step S42, obtain the standard thickness of the circuit board, segment the three-dimensional X-ray model according to the standard thickness of the circuit board, and then remove the topmost circuit board and the bottommost circuit board to obtain a three-dimensional X-ray model of the second circuit board to the (N - 1)th circuit board; Step S43, for the second circuit board to the (N - 1)th circuit board, select the three-dimensional X-ray model of any circuit board to match with the drilling model. If the match is successful, read the geometric center coordinates (Xi, Yi, Zi) at the position where the match is successful; where i is the circuit board number, i = 2, 3,..., N - 1; If the matching fails, it is determined that there is a drilling defect in the corresponding circuit board, and an abnormal signal is generated. Step S44: Calculate the shortest distance JLi between the geometric center coordinates corresponding to any circuit board and the drilling straight-line equation.

[0011] Furthermore, step S4 further includes the following sub-steps: Step S45: Compare the shortest distance between the geometric center coordinates and the drilling straight-line equation with the distance threshold. If the shortest distance is less than or equal to the first distance threshold, record the drilling offset level of the corresponding circuit board as a first-level offset; if the shortest distance is greater than the first distance threshold and less than or equal to the second distance threshold, record the drilling offset level of the corresponding circuit board as a second-level offset; if the shortest distance is greater than the second distance threshold, it is determined that there is a drilling defect in the corresponding circuit board, and an abnormal signal is generated. Among them, the drilling corresponding to the first-level offset is better than that corresponding to the second-level offset, and the first distance threshold is less than the second distance threshold. Step S46: Obtain the ultrasonic model of the multi-layer circuit board, sequentially obtain the ultrasonic models of the second circuit board to the (N - 1)-th circuit board, and obtain the drilling model of the drilling in the ultrasonic model of the corresponding circuit board according to the geometric center coordinates. Step S47: Read the maximum width and the minimum width of the drilling model, and compare the maximum width and the minimum width of the drilling model with the width threshold interval; if both the maximum width and the minimum width of the drilling model are within the width threshold interval, proceed to the subsequent steps; if any one of the maximum width and the minimum width of the drilling model is outside the width threshold interval, it is determined that there is a drilling defect in the corresponding circuit board, and an abnormal signal is generated.

[0012] Furthermore, the specific calculation process of the shortest distance in step S44 is as follows: Step S441: Obtain the drilling straight-line equation, and set the drilling straight-line equation as t, that is: ; Step S442: Further, obtain x = (X2 - X1)t + X1; y = (Y2 - Y1)t + Y1, Z = -Z1t + Z1; Step S443: Set the geometric center coordinates Q(Xi, Yi, Zi), and any point P(x, y, z) on the straight line; Step S444: Then the vector PQ is expressed as: PQ = ((Xi - (X2 - X1)t - X1), (Yi - (Y2 - Y1)t - Y1), (Zi + Z1t - Z1)); Step S445: Obtain the direction vector XL = (X2 - X1, Y2 - Y1, -Z1) of the drilling straight-line equation; Step S446: Use the projection of the vector to obtain the shortest distance JLi: ; where × represents the cross product of vectors, and |XL| represents the modulus of the calculated vector XL.

[0013] An automatic detection system for drilling defects of multi-layer circuit boards, comprising: A first acquisition module, configured to acquire an outer surface image of a multi-layer circuit board and send it to an image processing module; An image processing module, configured to process the outer surface image of the multi-layer circuit board to obtain edge contour maps of the first circuit board and the Nth circuit board in the multi-layer circuit board and send them to an image analysis module; An image analysis module, configured to analyze the edge contour maps of the first circuit board and the Nth circuit board, and send the expression and direction vector of the straight line equation corresponding to the drilling of the multi-layer circuit board to a comprehensive analysis module, or send an abnormal signal to a user terminal; A second acquisition module, configured to acquire X-ray images and ultrasonic models corresponding to the second circuit board to the (N-1)th circuit board in the multi-layer circuit board and send them to the comprehensive analysis module; A comprehensive analysis module, configured to analyze the X-ray images and ultrasonic models of the multi-layer circuit board to obtain the drilling offset level or abnormal signal corresponding to the drilling of any circuit board and send it to the user terminal; A user terminal, configured to receive the abnormal signal or drilling offset level corresponding to the multi-layer circuit board, and the user reads the abnormal signal or drilling offset level to know the drilling defect situation of the multi-layer circuit board.

[0014] In summary, due to the adoption of the above technical solutions, the beneficial effects of the present invention are: 1. The present invention first acquires the outer surface image of the multi-layer circuit board, then preprocesses the outer surface image to obtain the edge contour maps of the first circuit board and the Nth circuit board, and then analyzes the edge contours of the first circuit board and the Nth circuit board to obtain the expression and direction vector of the corresponding drilling straight line equation, and the present invention realizes the accurate determination of the drilling defects on the outer surface of the multi-layer circuit board.

[0015] 2. The present invention measures the second circuit board to the (N-1)th circuit board in the multi-layer circuit board to obtain the corresponding X-ray images and ultrasonic models, and then analyzes the X-ray images and ultrasonic models of the multi-layer circuit board to obtain the drilling offset level corresponding to the drilling of any circuit board. Finally, it receives the abnormal signal or drilling offset level corresponding to the multi-layer circuit board, and reads the abnormal signal or drilling offset level to know the drilling defect situation of the multi-layer circuit board. The present invention realizes the accurate determination of the drilling defects inside the multi-layer circuit board. Description of the Drawings

[0016] For the convenience of those skilled in the art to understand, the present invention will be further described below with reference to the accompanying drawings.

[0017] Figure 1 This is the flowchart of the method of the present invention; Figure 2 This is the schematic diagram of the drilling straight-line equation in the present invention; Figure 3 This is the side view of the multi-layer circuit board in the present invention; Figure 4 This is the system framework diagram related to the present invention. Specific embodiments

[0018] Next, the technical solution of the present invention will be clearly and completely described in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0019] Embodiment 1, please refer to Figures 1-3 As shown, the technical solution provided by the present invention is: an automatic detection method for drilling defects of multi-layer circuit boards, which is used to perform external drilling detection and internal drilling detection on multi-layer circuit boards respectively, so as to accurately identify the drilling defects of multi-layer circuit boards; In this embodiment, the method includes: Step S1, collect the outer surface image of the multi-layer circuit board, and then preprocess the outer surface image to obtain the edge contour maps of the first circuit board and the Nth circuit board; specifically, when collecting the outer surface image of the multi-layer circuit board, place the multi-layer circuit board in a well-lit position to ensure that the camera can clearly capture the multi-layer circuit board; In the present invention, the step S1 includes the following sub-steps: Step S11, divide the multi-layer circuit board into the first circuit board to the Nth circuit board in sequence, where N is the number of layers of the circuit board; Step S12, adjust the multi-layer circuit board so that the first circuit board faces upward and is placed within the shooting range of the camera, and shoot the outer surface image of the first circuit board through the camera; Step S13, adjust the multi-layer circuit board so that the Nth circuit board faces upward and is placed within the shooting range of the camera, and then shoot the outer surface image of the Nth circuit board through the camera; Step S14, analyze the outer surface image of the first circuit board to obtain the edge contour of the first circuit board; In the present invention, the step S14 includes the following sub-steps: Step S141, obtain the outer surface image of the first circuit board, extract the pixel values of multiple pixel points in the first circuit board, and obtain the R value component RZx, G value component GZx, and B value component BZx of each pixel point; where x is the number of the pixel point, x = 1, 2,..., z, and z is a positive integer; Step S142: Calculate the gray value HDx of each pixel point on the first circuit board through the formula. The specific formula is as follows: HDx = (A1 × RZx + A2 × GZx + A3 × BZx) / 3; where A1, A2, and A3 are proportional coefficients with fixed values, A1 < A2 < A3 and A1 + A2 + A3 = 1; Step S143: Obtain the Gaussian gray value GHDx of the corresponding pixel point by passing the gray value of the pixel point through the Gaussian filtering function. The Gaussian filtering function is specifically: ; where σ is a constant, and exp is the power function with base e; Step S144: Denote any pixel point as the selected pixel point, denote the pixel points adjacent to the selected pixel point as adjacent pixel points, and calculate the difference in Gaussian gray values between the adjacent pixel points and the selected pixel point, which is denoted as the gray difference. Step S145: Compare the gray difference of the selected pixel point with the gray difference threshold. If any gray difference corresponding to the selected pixel point is greater than or equal to the gray difference threshold, then denote the selected pixel point as an edge pixel point. If all gray differences corresponding to the selected pixel point are less than the gray difference threshold, then no operation is performed. Step S146: Connect adjacent edge pixel points to obtain the edge contour of the first circuit board. Step S15: Similarly, extract the edge contour of the Nth circuit board.

[0020] Step S2: Analyze the edge contours of the first circuit board and the Nth circuit board to obtain the expression of the corresponding drilling straight line equation and the direction vector. In the present invention, the step S2 includes the following sub-steps: Step S21: Obtain the edge contour of the first circuit board and the edge contour of the Nth circuit board. Step S22: Match the edge contour of the first circuit board and the edge contour of the Nth circuit board with the drilling schematic diagram. If the match is successful, then denote the successfully matched edge contour as the drilling contour. If the match fails, then it is determined that there is a drilling defect on the circuit board, and an abnormal signal is generated. Step S23: As Figure 2 shown, take any two mutually perpendicular lines in the plane of the Nth circuit board as the X-axis and the Y-axis, draw a line perpendicular to the plane of the Nth circuit board as the Z-axis, and construct a spatial rectangular coordinate system. Step S24: Denote the first center coordinate of the corresponding drilling contour of the first circuit board as (X1, Y1, Z1); denote the Nth center coordinate of the corresponding drilling contour of the Nth circuit board as (X2, Y2, 0); Specifically, due to various factors, the drilling profile may not be a standard circle. In this case, when selecting the center of the circle, select the center of the minimum circumscribed circle corresponding to the drilling profile. Step S25, calculate the offset distance PY of the projection between the first center coordinate and the Nth center coordinate through the formula. The specific formula is as follows: ; Step S26, compare the offset distance with the deviation distance threshold. If the offset distance is greater than or equal to the deviation distance threshold, it is determined that there is a drilling defect on the circuit board, and an abnormal signal is generated. If the offset distance is less than the deviation distance threshold, the drilling straight line equation expression corresponding to the drilling is obtained. The specific expression of the drilling straight line equation is: ; In the formula, (x, y, z) is a variable describing the position coordinates of different points in the drilling straight line equation. For the convenience of writing, the point-direction equation of the drilling straight line equation is shown in the present invention. When specifically calculating, the general equation of the straight line should be selected. The format of the general equation of the straight line is: Ax + By + Cz + D = 0, where A, B, C, and D are all constants. Step S27, further, obtain the direction vector XL = (X2 - X1, Y2 - Y1, -Z1) of the corresponding drilling straight line equation.

[0021] Step S3, measure the second circuit board to the (N - 1)th circuit board in the multilayer circuit board to obtain the corresponding X-ray image and ultrasonic model. In the present invention, the step S3 includes the following sub-steps: Step S31, place the multilayer circuit board on the detection platform to ensure that the multilayer circuit board is located in the path of the X-ray. Step S32, rotate the multilayer circuit board at a constant speed. Take an X-ray image every 0.5° to 1° of rotation until a full circle is rotated to obtain multiple X-ray images of the multilayer circuit board. Step S33, place the multilayer circuit board on the ultrasonic detection platform, and send ultrasonic waves to the multilayer circuit board at a specific frequency to obtain the corresponding ultrasonic image, which is recorded as the ultrasonic model of the multilayer circuit board. It should be noted that the ultrasonic model is a three-dimensional model of the multilayer circuit board.

[0022] Step S4, analyze the X-ray image and ultrasonic model of the multilayer circuit board to obtain the drilling offset grade corresponding to any circuit board. In the present invention, the step S4 includes the following sub-steps: Step S41, obtain the X-ray image of the multilayer circuit board, and synthesize the multiple X-ray images corresponding to the multilayer circuit board to obtain the three-dimensional X-ray model of the multilayer circuit board. Specifically, it can be obtained by importing multiple X-ray images into 3D reconstruction software or tools. Optionally, such as Autodesk ReCap and MeshLab, etc. Step S42: Obtain the standard thickness of the circuit board, segment the 3D X-ray model according to the standard thickness of the circuit board, and then remove the top circuit board and the bottom circuit board to obtain the 3D X-ray model of the second to the (N - 1)th circuit boards. Step S43: For the second to the (N - 1)th circuit boards, select the 3D X-ray model of any circuit board to match with the drilling model. If the match is successful, read the geometric center coordinates (Xi, Yi, Zi) at the position where the match is successful; where i is the circuit board number, i = 2, 3, ……, N - 1. If the match fails, it is determined that there is a drilling defect in the corresponding circuit board, and an abnormal signal is generated. Step S44: Calculate the shortest distance JLi between the geometric center coordinates of any circuit board and the drilling straight-line equation. The calculation process of the shortest distance in step S44 is as follows: Step S441: Obtain the drilling straight-line equation and set the drilling straight-line equation as t, that is: ; Step S442: Further, obtain x = (X2 - X1)t + X1; y = (Y2 - Y1)t + Y1, Z = -Z1t + Z1; Step S443: Set the geometric center coordinates Q(Xi, Yi, Zi), and any point P(x, y, z) on the straight line. Step S444: Then the vector PQ is expressed as: PQ = ((Xi - (X2 - X1)t - X1), (Yi - (Y2 - Y1)t - Y1), (Zi + Z1t - Z1)). Step S445: Obtain the direction vector XL of the drilling straight-line equation: XL = (X2 - X1, Y2 - Y1, -Z1). Step S446: Use the projection of the vector to obtain the shortest distance JLi: ; where × represents the cross product of vectors, and |XL| represents calculating the modulus of the vector XL. Step S45: Compare the shortest distance between the geometric center coordinates and the drilling straight-line equation with the distance threshold. If the shortest distance is less than or equal to the first distance threshold, record the drilling offset level of the corresponding circuit board as a first-level offset; if the shortest distance is greater than the first distance threshold and less than or equal to the first distance threshold (it should be noted that there may be an error in the description here, assuming it means greater than the first and less than or equal to the second), record the drilling offset level of the corresponding circuit board as a second-level offset; if the shortest distance is greater than the second distance threshold, it is determined that there is a drilling defect in the corresponding circuit board, and an abnormal signal is generated. Among them, the drill holes corresponding to the first-level offset are superior to the drill holes corresponding to the second-level offset, and the first distance threshold is smaller than the second distance threshold; Step S46: Obtain the ultrasonic models of the multi-layer circuit boards, sequentially obtain the ultrasonic models of the second circuit board to the (N-1)th circuit board, and obtain the drill hole models of the drill holes in the corresponding circuit board ultrasonic models according to the geometric center coordinates; Step S47: Read the maximum width and minimum width of the drill hole model, and compare the maximum width and minimum width of the drill hole model with the width threshold range; if both the maximum width and minimum width of the drill hole model are within the width threshold range, proceed to the subsequent steps; if any one of the maximum width and minimum width of the drill hole model is outside the width threshold range, it is determined that there is a drill hole defect in the corresponding circuit board, and an abnormal signal is generated.

[0023] Step S5: Receive the abnormal signal or drill hole offset level corresponding to the multi-layer circuit board, and read the abnormal signal or drill hole offset level to know the drill hole defect situation of the multi-layer circuit board.

[0024] In this application, if there are corresponding calculation formulas, the above calculation formulas are all dimensionless and take their numerical values for calculation. The weight coefficients, proportionality coefficients, and other coefficients in the formulas are set to obtain a result value by quantifying each parameter. Regarding the magnitudes of the weight coefficients and proportionality coefficients, as long as the proportional relationship between the parameters and the result value is not affected.

[0025] Embodiment 2, please refer to Figure 4 As shown, based on another concept of the same invention, a multi-layer circuit board drill hole defect automatic detection system is proposed, including a first acquisition module, a second acquisition module, an image processing module, an image analysis module, a comprehensive analysis module, and a user terminal; The first acquisition module is used to acquire the outer surface image of the multi-layer circuit board and send it to the image processing module; The image processing module is used to process the outer surface image of the multi-layer circuit board to obtain the edge contour maps of the first circuit board and the Nth circuit board in the multi-layer circuit board and send them to the image analysis module; The image analysis module is used to analyze the edge contour maps of the first circuit board and the Nth circuit board, analyze and obtain the expression and direction vector of the straight line equation of the drill holes corresponding to the multi-layer circuit board and send them to the comprehensive analysis module, or analyze and obtain an abnormal signal and send it to the user terminal; The second acquisition module is used to acquire the X-ray images and ultrasonic models corresponding to the second circuit board to the (N-1)th circuit board in the multi-layer circuit board and send them to the comprehensive analysis module; The comprehensive analysis module is used to analyze the X-ray images and ultrasonic models of the multi-layer circuit board, obtain the drill hole offset level or abnormal signal corresponding to any circuit board and send it to the user terminal; The user terminal is used to receive the abnormal signal or the drilling offset level corresponding to the multi-layer circuit board, and the user reads the abnormal signal or the drilling offset level to know the drilling defect situation of the multi-layer circuit board.

[0026] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only the specific embodiments. Obviously, many modifications and variations can be made according to the content of this specification. These embodiments are selected and specifically described in this specification in order to better explain the principle and practical application of the present invention, so that those skilled in the relevant technical field can well understand and utilize the present invention. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A method for automatically detecting drilling defects in multi-layer circuit boards, characterized in that: include: Step S1, collecting an outer surface image of a multilayer circuit board, and then preprocessing the outer surface image to obtain edge contour images of a first circuit board and an Nth circuit board; Step S2, analyzing the edge contours of the first circuit board and the Nth circuit board to obtain the expression and direction vector of the corresponding drilling line equation; Step S3, measuring the second circuit board to the N-1th circuit board in the multilayer circuit board to obtain corresponding X-ray images and ultrasonic models; Step S4, analyzing the X-ray image and ultrasonic model of the multilayer circuit board to obtain the drilling offset level of the corresponding drilling hole of any circuit board; Step S5, receiving an abnormal signal or a drilling deviation level corresponding to the multi-layer circuit board, and reading the abnormal signal or the drilling deviation level to obtain a drilling defect condition of the multi-layer circuit board.

2. The method for automatically detecting drilling defects in a multi-layer circuit board according to claim 1, characterized in that: The step S1 includes the following sub-steps: Step S11, dividing the multilayer circuit board into a first circuit board to an Nth circuit board in sequence, where N is the number of layers of the circuit board; Step S12, adjusting the multilayer circuit board so that the first circuit board faces upward and is placed within the camera shooting range, and capturing an image of the outer surface of the first circuit board through the camera; Step S13, adjusting the multilayer circuit board so that the Nth circuit board faces upward and is placed within the camera shooting range, and then using the camera to shoot an image of the outer surface of the Nth circuit board; Step S14, analyzing the outer surface image of the first circuit board to obtain an edge profile of the first circuit board; Step S15: similarly, extract the edge contour of the Nth circuit board.

3. The method for automatically detecting drilling defects of a multi-layer circuit board according to claim 2, characterized in that: The step S14 includes the following sub-steps: Step S141, obtaining an outer surface image of the first circuit board, extracting pixel values ​​of multiple pixels in the first circuit board, and obtaining an R value component RZx, a G value component GZx, and a B value component BZx of each pixel; wherein x is the number of the pixel, x=1, 2, ..., z, and z is a positive integer; Step S142, calculating the gray value HDx of each pixel in the first circuit board by a formula, the specific formula is as follows: HDx=(A1×RZx+A2×GZx+A3×BZx) / 3; where A1, A2 and A3 are fixed proportional coefficients, A1<A2<A3 and A1+A2+A3=1; Step S143, the grayscale value of the pixel point is passed through a Gaussian filter function to obtain a Gaussian grayscale value GHDx of the corresponding pixel point. The Gaussian filter function is specifically: ; In the formula, σ is a constant and exp is a power function with e as the base.

4. The method for automatically detecting drilling defects in a multi-layer circuit board according to claim 3, characterized in that: The step S14 further includes: Step S144, record any pixel point as a selected pixel point, record the pixel points adjacent to the selected pixel point as adjacent pixel points, calculate the difference in Gaussian grayscale values ​​between the adjacent pixel point and the selected pixel point and record it as a grayscale difference; Step S145, comparing the grayscale difference of the selected pixel with the grayscale difference threshold. If any grayscale difference corresponding to the selected pixel is greater than or equal to the grayscale difference threshold, the selected pixel is recorded as an edge pixel. If all grayscale differences corresponding to the selected pixel are less than the grayscale difference threshold, no operation is performed. Step S146, connecting adjacent edge pixel points to obtain an edge contour of the first circuit board.

5. The method for automatically detecting drilling defects of a multi-layer circuit board according to claim 1, characterized in that: The step S2 includes the following sub-steps: Step S21, obtaining edge contours of the first circuit board and the Nth circuit board; Step S22, matching the edge contour of the first circuit board and the edge contour of the Nth circuit board with the drilling schematic diagram, if the matching is successful, recording the successfully matched edge contour as the drilling contour; if the matching fails, it is determined that the circuit board has a drilling defect, and an abnormal signal is generated; Step S23, taking any two mutually perpendicular straight lines in the plane where the Nth circuit board is located as the X-axis and the Y-axis, and taking the straight line perpendicular to the plane where the Nth circuit board is located as the Z-axis, to construct a spatial rectangular coordinate system; Step S24, marking the first center coordinate of the first circuit board corresponding to the drilling contour as (X1, Y1, Z1); marking the Nth center coordinate of the Nth circuit board corresponding to the drilling contour as (X2, Y2, 0).

6. The method for automatically detecting drilling defects in a multi-layer circuit board according to claim 5, characterized in that: The step S2 further comprises the following sub-steps: Step S25, calculating the offset distance PY of the projection between the first circle center coordinate and the Nth circle center coordinate by a formula, the specific formula is as follows: ； Step S26, compare the offset distance with the deviation distance threshold. If the offset distance is greater than or equal to the deviation distance threshold, it is determined that there is a drilling defect in the circuit board and an abnormal signal is generated; if the offset distance is less than the deviation distance threshold, the drilling line equation expression of the corresponding drilling hole is obtained, and the drilling line equation expression is specifically: ； Step S27, further, obtain the direction vector XL=(X2-X1, Y2-Y1, -Z1) corresponding to the drilling straight line equation.

7. The method for automatically detecting drilling defects in a multi-layer circuit board according to claim 1, characterized in that: The step S4 includes the following sub-steps: Step S41, obtaining an X-ray image of the multi-layer circuit board, and synthesizing a plurality of X-ray images corresponding to the multi-layer circuit board to obtain a three-dimensional X-ray model of the multi-layer circuit board; Step S42, obtaining a standard thickness of the circuit board, segmenting the three-dimensional X-ray model according to the standard thickness of the circuit board, and then removing the uppermost circuit board and the lowermost circuit board to obtain the three-dimensional X-ray models of the second circuit board to the N-1th circuit board; Step S43, for the second circuit board to the N-1th circuit board, select the 3D X-ray model of any circuit board and match it with the drilling model. If the match is successful, read the geometric center coordinates (Xi, Yi, Zi) of the position where the match is successful; where i is the number of the circuit board, i=2, 3, ..., N-1; If the match fails, it is determined that the corresponding circuit board has a drilling defect and an abnormal signal is generated; Step S44, calculating the shortest distance JLi between the corresponding geometric center coordinates of any circuit board and the drilling straight line equation.

8. The method for automatically detecting drilling defects in a multi-layer circuit board according to claim 7, characterized in that: The step S4 further comprises the following sub-steps: Step S45, comparing the shortest distance between the geometric center coordinates and the drilling line equation with the distance threshold, if the shortest distance is less than or equal to the first distance threshold, the drilling offset level of the corresponding circuit board is recorded as a first-level offset; if the shortest distance is greater than the first distance threshold and the shortest distance is less than or equal to the first distance threshold, the drilling offset level of the corresponding circuit board is recorded as a second-level offset; if the shortest distance is greater than the second distance threshold, it is determined that the corresponding circuit board has a drilling defect, and an abnormal signal is generated; Among them, the borehole corresponding to the first-level offset is better than the borehole corresponding to the second-level offset, and the first distance threshold is less than the second distance threshold; Step S46, obtaining an ultrasonic model of the multilayer circuit board, obtaining ultrasonic models of the second circuit board to the N-1th circuit board in sequence, and obtaining a drilling model of a hole drilled in the ultrasonic model of the corresponding circuit board according to the geometric center coordinates; Step S47, read the maximum width and the minimum width of the drilling model, and compare the maximum width and the minimum width of the drilling model with the width threshold interval; if the maximum width and the minimum width of the drilling model are both between the width threshold interval, proceed to the subsequent steps; if any one of the maximum width and the minimum width of the drilling model is outside the width threshold interval, it is determined that the corresponding circuit board has a drilling defect and an abnormal signal is generated.

9. The method for automatically detecting drilling defects in a multi-layer circuit board according to claim 8, characterized in that: The calculation process of the shortest distance in step S44 is specifically as follows: Step S441, obtain the equation of the drilling line, and set the equation of the drilling line to t, that is: ； Step S442, further, obtain x=(X2-X1)t+X1; y=(Y2-Y1)t+Y1, Z=-Z1t+Z1; Step S443, set the geometric center coordinates Q(Xi, Yi, Zi), any point P(x, y, z) on the straight line; Step S444, the vector PQ is expressed as: PQ=((Xi-(X2-X1)t-X1), (Yi-(Y2-Y1)t-Y1), (Zi+Z1t-Z1)); Step S445, obtaining the direction vector XL=(X2-X1, Y2-Y1, -Z1) of the drilling line equation; Step S446, using the projection of the vector to obtain the shortest distance JLi: ; In the formula, × represents the cross product of the vectors, and |XL| represents the modulus length of the calculated vector XL.

10. The automatic detection system for drilling defects in multi-layer circuit boards is characterized by: The method for automatically detecting drilling defects of a multilayer circuit board according to any one of claims 1 to 9 comprises: A first acquisition module, used for acquiring an outer surface image of the multi-layer circuit board and sending the image to the image processing module; An image processing module, used for processing the outer surface image of the multilayer circuit board, obtaining edge contour images of the first circuit board and the Nth circuit board in the multilayer circuit board and sending the edge contour images to the image analysis module; An image analysis module is used to analyze the edge contours of the first circuit board and the Nth circuit board, obtain the expression and direction vector of the drilling line equation corresponding to the multi-layer circuit board through analysis and send them to the comprehensive analysis module, or obtain an abnormal signal through analysis and send it to the user terminal; A second acquisition module is used to acquire X-ray images and ultrasonic models corresponding to the second circuit board to the N-1th circuit board in the multi-layer circuit board and send them to the comprehensive analysis module; A comprehensive analysis module is used to analyze the X-ray image and ultrasonic model of the multi-layer circuit board, obtain the drilling deviation level or abnormal signal of the corresponding drilling hole of any circuit board and send it to the user terminal; The user terminal is used to receive the abnormal signal or drilling deviation level corresponding to the multi-layer circuit board. The user reads the abnormal signal or drilling deviation level to learn the drilling defect situation of the multi-layer circuit board.

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