A rapid detection method for the minimum allowable range between elements in PCB board AOI

Abstract

The present invention discloses a rapid detection method for the minimum allowable range between elements in PCB board AOI, comprising the following steps: S1, obtaining all line segments and circle elements in the PCB board graphics; S2, using a method to calculate the difference between the expanded contour of the element pair and the minimum allowable range to roughly screen the element pairs, and determine whether the element pairs need further detection; S3, framing a suspected area of ​​the element pairs on the image based on the minimum allowable range, and finely screening the element pairs within the area. The present invention uses a method to calculate the difference between the expanded contour of the element pair and the minimum allowable range to roughly screen the element pairs, and then finely screens the suspected point set, thereby improving the speed of whole-board detection.

Description

Technical Field

[0001] The invention belongs to the field of PCB board defect detection and relates to a method for quickly detecting the minimum allowable range between elements in PCB board AOI. Background Art

[0002] Printed circuit boards (PCBs), also known as printed circuit boards (PCBs), are important electronic components that support electronic components and serve as the electrical interconnections between them. During PCB AOI (automated optical inspection), due to inevitable errors in the PCB manufacturing process, areas with close proximity between graphic elements are prone to misalignment, necessitating inspection. Traditional minimum tolerance calculations are performed between copper-attached surfaces. Even for negative surfaces, the minimum tolerance determination is not comprehensive. Traditional minimum tolerance detection methods use a fixed minimum tolerance for the entire PCB and fail to screen for areas where misalignment may occur. This leads to two issues: the minimum tolerance cannot be customized, and the lack of area-by-area screening results in slower full-board inspection speeds. With the increasing complexity of PCBs, traditional minimum distance misalignment detection methods are no longer suitable for future PCB inspection systems. Summary of the Invention

[0003] To solve the above problems, the technical solution of the present invention is a method for quickly detecting the minimum allowable range between elements in PCB board AOI, comprising the following steps:

[0004] S1, obtain all line segments and circle elements in the PCB board graphics;

[0005] S2, using a method to calculate the difference between the expansion profile of the element pair and the minimum allowable range to roughly screen the element pairs and determine whether the element pairs need further testing;

[0006] S3, based on the minimum allowable range, a suspected area of ​​the element pair is framed on the image, and the element pairs in the area are finely screened.

[0007] Preferably, the S1 specifically includes the following steps:

[0008] S11, parsing the PCB board graphic data to obtain all line segments and circle elements;

[0009] S12, calculating the slopes of all line segment elements, and grouping the line segment elements whose slopes are consistent within the error range into line segment element pairs;

[0010] S13, calculating the perpendicular line of the line segment element, and forming an element pair from the circle element and the line segment element whose center can be projected onto the line segment in the direction of the perpendicular line;

[0011] S14, calculating the line connecting the centers of two circle elements, and forming an element pair from two circle elements whose centers can be projected onto another circle according to the direction of the line connecting the two circle centers.

[0012] Preferably, the step S2 specifically includes the following steps:

[0013] S21, calculating the minimum allowable range based on the percentage of the line width of the line segment element or the radius of the circle element;

[0014] S22, calculating the difference between the minimum allowable range and the actual distance between the element pair's expanded contours, and checking whether the difference is greater than 0;

[0015] S23: If yes, then the element pair does not need to be tested for the minimum allowable range between elements;

[0016] S24: No, it is necessary to perform minimum allowable range detection between elements.

[0017] Preferably, the step S3 specifically includes the following steps:

[0018] S31, calculating the distance between element pairs, and according to the obtained minimum allowable range, taking the area where the graphic elements whose distance is less than the given minimum allowable range are located as a suspected area, and framing the corresponding suspected area on the image;

[0019] S32, screening out point sets corresponding to two elements based on the suspected area on the image, and determining whether the distance between the two element point sets in the same direction is less than a given minimum allowable range;

[0020] S33, if yes, then this is considered as a wrong point;

[0021] S34: No, the element pair is considered to be a correct element pair.

[0022] The beneficial effects of the present invention are as follows:

[0023] This method extracts all line segments and circle elements from a PCB pattern, selects element pairs based on their positional relationships, then performs a preliminary screening based on the difference between the expanded contour spacing and the minimum tolerance. Finally, a finer screening of point pairs within the suspected area is performed on the image. This method uses a method that calculates the difference between the expanded contour of the element pair and the minimum allowable range to perform a coarse screening of the element pairs, followed by a finer screening of the suspected point set, thus improving the speed of whole-board inspection. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a flowchart of a method for quickly detecting the minimum allowable range between elements in PCB board AOI according to a specific embodiment of the present invention;

[0025] Figure 2A flowchart of a PCB automatic optical inspection method for quickly detecting the minimum allowable range between elements in PCB board AOI according to the present invention;

[0026] Figure 3 A flowchart of the calculation of the suspected negative area of ​​a graphic in a method for quickly detecting the minimum allowable range between elements in PCB board AOI according to a specific embodiment of the present invention;

[0027] Figure 4 This is a flowchart of an image misalignment detection method for a rapid detection method of the minimum allowable range between elements in PCB board AOI according to an embodiment of the present invention;

[0028] Figure 5 This is a graphical parameter explanation diagram of a method for quickly detecting the minimum allowable range between elements in PCB board AOI according to an embodiment of the present invention. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0030] On the contrary, the present invention covers any alternatives, modifications, equivalents, and solutions that fall within the spirit and scope of the present invention as defined by the claims. Furthermore, to facilitate a better understanding of the present invention, certain specific details are described in detail below in the detailed description of the present invention. Those skilled in the art will be able to fully understand the present invention without these details.

[0031] See also Figure 1 , which is a flowchart of a method for quickly detecting the minimum allowable range between elements in PCB board AOI according to an embodiment of the present invention, comprising the following steps:

[0032] S1, obtain all line segments and circle elements in the PCB board graphics;

[0033] S2, using a method to calculate the difference between the expansion profile of the element pair and the minimum allowable range to roughly screen the element pairs and determine whether the element pairs need further testing;

[0034] S3, based on the minimum allowable range, a suspected area of ​​the element pair is framed on the image, and the element pairs in the area are finely screened.

[0035] S1 specifically includes the following steps:

[0036] S11, parsing the PCB board graphic data to obtain all line segments and circle elements;

[0037] S12, calculating the slopes of all line segment elements, and grouping the line segment elements whose slopes are consistent within the error range into line segment element pairs;

[0038] S13, calculating the perpendicular line of the line segment element, and forming an element pair from the circle element and the line segment element whose center can be projected onto the line segment in the direction of the perpendicular line;

[0039] S14, calculating the line connecting the centers of two circle elements, and forming an element pair from two circle elements whose centers can be projected onto another circle according to the direction of the line connecting the two circle centers.

[0040] S2 specifically includes the following steps:

[0041] S21, calculating the minimum allowable range based on the percentage of the line width of the line segment element or the radius of the circle element;

[0042] S22, calculating the difference between the minimum allowable range and the actual distance between the element pair's expanded contours, and checking whether the difference is greater than 0;

[0043] S23: If yes, then the element pair does not need to be tested for the minimum allowable range between elements;

[0044] S24: No, it is necessary to perform minimum allowable range detection between elements.

[0045] S3 specifically includes the following steps:

[0046] S31, calculating the distance between element pairs, and according to the obtained minimum allowable range, taking the area where the graphic elements whose distance is less than the given minimum allowable range are located as a suspected area, and framing the corresponding suspected area on the image;

[0047] S32, screening out point sets corresponding to two elements based on the suspected area on the image, and determining whether the distance between the two element point sets in the same direction is less than a given minimum allowable range;

[0048] S33, if yes, then this is considered as a wrong point;

[0049] S34: No, the element pair is considered to be a correct element pair.

[0050] In a specific embodiment, Figure 2In order to apply the PCB automatic optical inspection system provided by the embodiment of the present invention, the PCB board can generate an image under the CCD imaging system. The hardware designer uses CAD software to design the PCB circuit diagram, which is called a graphic. Since the generated image is bound to have errors, the suspected area can be found on the graphic by calculating the distance of the shadow surface of the graphic, and the distance of the pixel points in the suspected area is calculated to determine the wrong point. In the optical inspection system of the PCB circuit board, the present invention implements the customized minimum distance wrong point detection method, which includes two parts: graphic suspected area calculation and image wrong point detection.

[0051] The calculation process of suspected area of ​​graphics can be found in Figure 3 The system reads all line elements and circles in the PCB graphics and performs a preliminary screening based on their line width and circle radius. Further inspection is performed on line elements with a line width less than 4 mil or any circle with a radius less than 4 mil. The minimum allowable range of the element is customized based on the line width and radius. The element to be inspected is comprehensively screened based on the distance difference between the minimum allowable range and the element's expansion profile, reducing unnecessary inspection time. The suspected area is framed based on the calculated Δ value.

[0052] The image error point judgment process can be found in Figure 4 , on the image, the point sets corresponding to the two elements are screened out according to the suspected area, and it is judged whether the distance between the two element point sets in the same direction is less than the given minimum allowable range. If it is less than the minimum allowable range, it is considered to be a wrong point. If it is greater than the minimum allowable range, the point pair is considered to be a correct point pair.

[0053] Take any two parallel line elements as an example. The parameters used in the calculation of the suspected area of ​​the figure are shown in Figure 5 Line segment element 1 is represented by a solid green box with a line width of w. Expansion contour 11 is line segment element 1 expanded according to a certain expansion coefficient. The rectangular box width of suspected region 2 is 2Δ (Δ = minimum distance - actual distance), and the domain width of the given minimum allowable range 3 is d. In the calculation method for suspected region 2, the PCB CAD graphics are read in and, after a certain screening process, the distances of all mutually parallel line segment elements 1 are calculated. The calculation process is divided into three cases: horizontal, vertical, and other tilt angles. For line segment elements whose distance between expansion contours 11 is less than the minimum allowable range 3, the width 2Δ of suspected region 2 is calculated. The height of suspected region 2 is determined by the parallel overlap of the two line segment elements 1. To determine if a point is misidentified in the image, the corresponding set of suspected points within suspected region 2 is identified. The distance between two points in this set that are in the same direction is calculated and compared with the minimum allowable range 3. Points with distances less than the minimum allowable range 3 are marked as misidentified.

[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for quickly detecting the minimum allowable range between elements in PCB board AOI, characterized in that: The following steps are involved: S1, obtain all line segments and circle elements in the PCB board graphics; S2, using a method to calculate the difference between the expansion profile of the element pair and the minimum allowable range to roughly screen the element pairs and determine whether the element pairs need further testing; S3, based on the minimum allowable range, the suspected area of ​​the element pair is framed on the image, and the element pairs in the area are finely screened; The S1 specifically includes the following steps: S11, parsing the PCB board graphic data to obtain all line segments and circle elements; S12, calculating the slopes of all line segment elements, and grouping the line segment elements whose slopes are consistent within the error range into line segment element pairs; S13, calculating the perpendicular line of the line segment element, and forming an element pair from the circle element and the line segment element whose center can be projected onto the line segment in the direction of the perpendicular line; S14, calculating a line connecting the centers of two circle elements, and forming an element pair from two circle elements whose centers can be projected onto another circle along the direction of the line connecting the two circle centers; The S2 specifically includes the following steps: S21, calculating the minimum allowable range based on the percentage of the line width of the line segment element or the radius of the circle element; S22, calculating the difference between the minimum allowable range and the actual distance between the element pair's expanded contours, and checking whether the difference is greater than 0; S23: If yes, then the element pair does not need to be tested for the minimum allowable range between elements; S24: No, it is necessary to perform minimum allowable range detection between elements.

2. The method according to claim 1, characterized in that The S3 specifically includes the following steps: S31, calculating the distance between element pairs, and according to the obtained minimum allowable range, taking the area where the graphic elements whose distance is less than the given minimum allowable range are located as a suspected area, and framing the corresponding suspected area on the image; S32, screening out point sets corresponding to two elements based on the suspected area on the image, and determining whether the distance between the two element point sets in the same direction is less than a given minimum allowable range; S33, if yes, then this is considered as a wrong point; S34: No, the element pair is considered to be a correct element pair.

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