Online monitoring method for expansion and shrinkage of PCB (Printed Circuit Board)

Abstract

The invention discloses an on-line monitoring method for the expansion and contraction of a PCB, and the method comprises the steps: scanning the PCB, collecting a PCB image, and importing a PCB design drawing; setting a plurality of calibration measurement points on the PCB design drawing; obtaining calibration coordinate group data corresponding to each calibration measurement point; collecting actual coordinate group data corresponding to each calibration measurement point of the actual PCB; and the numerical value difference between each piece of calibration coordinate group data and the corresponding actual coordinate group data in the X direction and the Y direction is used for judging the expansion and contraction amplitude of the actual PCB. On-line monitoring of the expansion and shrinkage of the PCB is realized by adopting a PCB design drawing and a mode of calculating the expansion and shrinkage value of the actual PCB, the actual expansion and shrinkage condition of the PCB in production can be efficiently and continuously supervised, the production scrap loss is effectively reduced, the error rate of the expansion and shrinkage value is further reduced, and the expansion and shrinkage value can adapt to actual production requirements.

Description

Technical Field

[0001] This invention relates to the field of PCB circuit board expansion and contraction monitoring technology, and in particular to an online monitoring method for PCB circuit board expansion and contraction. Background Technology

[0002] As PCBs evolve towards multi-layer, high-density designs, expansion and contraction have become critical indicators, constantly challenging product stability, hindering quality control of high-end products, and even leading to product scrap. Different PCB materials possess varying physical and chemical properties, resulting in residual thermal stress and deformation after lamination. How to effectively control abnormal expansion and contraction at different temperatures has become one of the most complex problems facing PCB manufacturers.

[0003] The current control method in the industry is manual intermittent sampling measurement. Specifically, at certain intervals or at certain quantities, a circuit board sample is drawn from the production line and measured manually with the assistance of a special instrument. The existing manual intermittent sampling measurement has the disadvantages of low efficiency and high cost. Therefore, if we want to achieve continuous monitoring, improve efficiency, and not increase production costs, we need a more ideal way to monitor the expansion and contraction of PCB boards. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] To address the shortcomings of existing technologies, this invention uses PCB design drawings to define standard position coordinates. The expansion / contraction ratio is calculated from the position coordinates obtained by the acquisition device, which can continuously monitor the actual expansion / contraction of the PCB board during production and effectively reduce production scrap and waste.

[0006] (II) Technical Solution

[0007] To achieve the above objectives, the present invention provides the following technical solution: an online monitoring method for the expansion and contraction of a PCB circuit board, comprising the following steps:

[0008] Scan the PCB, acquire PCB images, and import PCB design drawings;

[0009] Multiple calibration measurement points are set on the PCB design drawing;

[0010] Obtain the calibration coordinate set data corresponding to each calibration measurement point;

[0011] Collect the actual coordinate set data of the actual PCB circuit board at each of the calibration measurement points;

[0012] The numerical differences in the X and Y directions between each set of calibrated coordinate data and the corresponding actual coordinate data are used to determine the expansion and contraction range of the actual PCB circuit board.

[0013] As a preferred embodiment, two measurement points on the actual PCB circuit board are selected as the reference for establishing the coordinate system. Measurement point one is selected as the origin, and measurement point two is selected as the reference point in the +X direction. A perpendicular line is drawn through the origin as the Y direction to obtain the abscissa and ordinate of the actual coordinate set to obtain the expansion and contraction value of the actual PCB circuit board. All calibration measurement points are found on the PCB design drawing. The reference point of the calibration measurement point is the center point of the expansion and contraction hole. Every two sets of calibration measurement points form a target measurement unit, and the original +X direction coordinates and original Y direction coordinates of the target measurement unit are obtained.

[0014] As a preferred embodiment, the actual PCB circuit board is divided into NxM discrete micro-elements (N and M are large positive integers). With any point P as the center of the micro-element, two concentric circles C1 and C2 are drawn with point P as the center. The coordinates of the center of the two concentric circles are obtained by using a camera calibration algorithm with a concentric double-ring target.

[0015] As a preferred embodiment, the expansion / contraction ratio is calculated based on the center coordinates and the target measurement unit, and the coordinates of point P are adjusted according to the expansion / contraction ratio, and the standard position coordinate data is output.

[0016] As a preferred embodiment, standard position coordinates are defined by the PCB design drawing, and the acquisition device obtains the coordinates corresponding to the standard positions. The expansion / contraction ratio is calculated from the position coordinates obtained by the acquisition device, and the expansion / contraction ratio is the ratio of the actual hole spacing to the standard hole spacing.

[0017] As a preferred embodiment, the selection of calibration measurement points includes: selecting three PCB pattern points on the upper edge of the PCB design drawing, such that the selected pattern points can form a triangle zoy, and extracting the center coordinate values ​​(ax1, ay1), (ax2, ay2) and (ax3, ay3) of these three pattern points respectively as group a.

[0018] As a preferred embodiment, the acquisition of the coordinate group data of the calibration measurement points specifically includes: using an image sensor to collect three pattern points at corresponding positions on the actual PCB board, and extracting their center coordinate values ​​(bx1, by1), (bx2, by2), and (bx3, by3) respectively as group b.

[0019] As a preferred approach, the two largest differences in x and y coordinates are extracted from the coordinates of group a and group b respectively to obtain max, may, mbx, and mby; max is compared with mbx to obtain the expansion / contraction value in the x-direction, and may is compared with mby to obtain the expansion / contraction value in the y-direction, wherein:

[0020] The expansion / contraction value in the x-direction is X = max - mbx

[0021] The expansion / contraction value in the y-direction is Y = may - mby

[0022] X and Y are the expansion and contraction values ​​in the x and y directions, respectively. A positive value indicates contraction, a negative value indicates expansion, and a zero value indicates no expansion or contraction.

[0023] (III) Beneficial Effects

[0024] Compared with the prior art, the present invention provides an online monitoring method for the expansion and contraction of PCB circuit boards, which has the following beneficial effects:

[0025] This invention uses PCB design drawings and actual PCB circuit board calculations to achieve online monitoring of PCB circuit board expansion and contraction. It can efficiently and continuously monitor the actual expansion and contraction of PCB boards during production, effectively reducing production scrap and waste, providing quality control departments with detailed process parameters for production control, and providing directional guidance for subsequent production process optimization. At the same time, this invention further reduces the error rate of expansion and contraction values ​​by using target measurement units and drawing concentric circles to calculate the center coordinates, making it adaptable to actual production needs. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the method steps of the present invention;

[0027] Figure 2 This is a schematic diagram showing the correspondence between the PCB circuit board design drawing and the actual board of this invention;

[0028] Figure 3 This is a schematic diagram of the coordinate system of measurement points on the PCB circuit board of the present invention;

[0029] Figure 4 This is a schematic diagram of the triangular zoy distribution on the PCB circuit board of the present invention. Detailed Implementation

[0030] To better understand the purpose, structure, and function of this invention, the following will further explain the online monitoring method for expansion and contraction of a PCB circuit board in conjunction with the accompanying drawings and specific embodiments.

[0031] This invention is applied to the field of intelligent manufacturing and involves a combination of technologies such as high-precision imaging, mechanical motion control, programmable control, image pixel calibration, and high-performance computing servers. It mainly addresses the quality and cost control issues in single-layer and multi-layer PCB manufacturing by providing an effective means to eliminate factors that cause scrap as early as possible.

[0032] Example 1

[0033] refer to Figure 1-2 The present invention provides an online monitoring method for the expansion and contraction of a PCB circuit board, comprising the following steps:

[0034] Scan the PCB, acquire PCB images, and import PCB design drawings;

[0035] Set multiple calibration measurement points on the PCB design drawing;

[0036] Obtain the calibration coordinate set data corresponding to each calibration measurement point;

[0037] Collect actual coordinate data of the actual PCB circuit board at each calibration measurement point;

[0038] The numerical differences in the X and Y directions between each calibrated coordinate set and the corresponding actual coordinate set are used to determine the actual expansion and contraction range of the PCB circuit board.

[0039] Specifically, the actual PCB circuit board is first removed from the target device, and its surface is cleaned to ensure it is free of dirt or debris. An optical scanner is then used to scan the PCB surface, generating a high-resolution PCB image. Multiple calibration measurement points are then set on the PCB design drawing. These calibration measurement points are specific small dots on the circuit board used to provide the probe contact path during automated testing, thereby avoiding direct contact with electronic components on the circuit board, protecting components from damage, and improving test reliability. The PCB coordinate file records the precise position of each electronic component on the printed circuit board (PCB), which is the PCB design drawing mentioned in this invention. The server, in conjunction with software, calculates the coordinate set data of the calibration measurement points. Simultaneously, image sensors acquire the coordinate set data of the corresponding measurement points on the actual PCB circuit board. The PCB design software then uses its functions to generate the coordinate information of the actual PCB circuit board, which generally includes the X-axis and Y-axis coordinates of the components and their rotation angles.

[0040] Furthermore, to better characterize the quantitative values ​​related to expansion and contraction, two measurement points on the actual PCB circuit board are selected as the reference for establishing the coordinate system. Measurement point one is chosen as the origin, and measurement point two is chosen as the reference point in the +X direction. A perpendicular line is drawn through the origin as the Y direction, obtaining the x and y coordinates of the actual coordinate set to obtain the expansion and contraction values ​​of the actual PCB circuit board. All calibration measurement points are found on the PCB design, with the reference point of each calibration measurement point being the center point of the expansion and contraction via. Every two sets of calibration measurement points form a target measurement unit, and the original +X and original Y coordinates of the target measurement unit are obtained. First, the size of the PCB design is determined, then the lower left corner of the PCB design is set as the coordinate origin. Then, all calibration measurement points are found on the PCB design, with the reference point of each calibration measurement point being the center point of the expansion and contraction via. Every two sets of calibration measurement points form a target measurement unit, and the original +X and original Y coordinates of the target measurement unit are obtained. The pixel distance between the reference points of two calibration measurement points in the target measurement unit is calculated. Based on the pixel distance between the reference points of the two calibration measurement points and the millimeter-pixel ratio of the surface image of the PCB design, the actual distance between the reference points of the two sets of calibration measurement points is calculated. The design distance between the reference points of the two sets of calibration measurement points is subtracted from the actual distance to obtain the error distance. The error distance is divided by the design distance to obtain the expansion / contraction ratio of the reference point direction of the two sets of calibration measurement points in a target measurement unit of the PCB design. Specifically, the actual coordinate set data can be obtained from the actual PCB circuit board, and the calibration coordinate set data can be obtained from the calibration on the PCB design. The expansion / contraction situation is determined by comparing the actual coordinate set data with the calibration coordinate set data.

[0041] Example 2

[0042] refer to Figure 3-4 As shown, the actual PCB circuit board is divided into N×M discrete micro-elements (N and M are large positive integers). With any point P as the center of the micro-element, two concentric circles C1 and C2 are drawn with point P as the center. C1 and C2 are two concentric circles with the center of the circle being o. L is the straight line at infinity on the supporting plane. Triangle zoy is a self-polar triangle. All common self-polar triangles of the two concentric circles have a common vertex. The opposite side of this vertex is on the same line. This line is the straight line between the center of the circle and the infinity on the supporting plane. The self-polar triangles of the two concentric circles are both right triangles. The camera calibration algorithm of concentric double-ring target is used to obtain the coordinates of the center of the two concentric circles.

[0043] Specifically, suppose the coordinates of the centers of the two concentric circles are [x0y0]. TGiven radii r1 and r2, the center coordinates of two concentric circles C1 and C2 are determined using a feature extraction algorithm for a double-ring target: First, the camera captures images of the double-ring target. Then, all the circles are extracted and the ellipse equation C is fitted. For the concentric circles, the equations are combined sequentially and solved. Eigenvalues ​​and eigenvectors, and based on the distance between eigenvalues. The center of the circle is calculated by selecting the combination with the smallest distance.

[0044] Furthermore, the expansion / contraction ratio is calculated using the center coordinates and the target measurement unit, and the coordinates of point P are adjusted according to the expansion / contraction ratio. The standard position coordinate data is then output. Finally, the standard position coordinates are defined by the PCB design drawing, and the acquisition device obtains the coordinates corresponding to the standard position. The expansion / contraction ratio is calculated from the coordinates obtained by the acquisition device, which is the ratio of the actual hole spacing to the standard hole spacing. The selection of calibration measurement points includes: selecting three PCB pattern points on the upper edge of the PCB design drawing, such that the selected pattern points can form a triangle zoy, and extracting the center coordinate values ​​(ax1, ay1), (ax2, ay2), and (ax3, ay3) of these three pattern points as group a. Obtaining the coordinate group data of the calibration measurement points specifically includes: using an image sensor to acquire three pattern points at the corresponding positions on the actual PCB board, and extracting their center coordinate values ​​(bx1, by1), (bx2, by2), and (bx3, by3) as group b.

[0045] Furthermore, from each of the three sets of coordinates a and b, the two largest differences in x and y coordinates are extracted to obtain max, may, mbx, and mby; max is compared with mbx to obtain the x-direction expansion / contraction value, and may is compared with mby to obtain the y-direction expansion / contraction value, where:

[0046] The expansion / contraction value in the x-direction is X = max - mbx

[0047] The expansion / contraction value in the y-direction is Y = may - mby

[0048] X and Y are the expansion and contraction values ​​in the x and y directions, respectively. A positive value indicates contraction, a negative value indicates expansion, and a zero value indicates no expansion or contraction.

[0049] For example, as can be seen from the above embodiments, the present invention defines standard position coordinates based on the PCB design drawing. Three PCB pattern points on the upper edge of the PCB design drawing are selected so that the selected pattern points can form a triangle. The coordinates of point 1 are (10, 10), point 2 is (590, 250), and point 3 is (300, 490). After obtaining the coordinates of the design drawing, the acquisition device obtains the actual coordinates corresponding to these three coordinates, i.e., the actual coordinates of point 1 are (10.01, 10.01), point 2 are (590.59, 250.25), and point 3 are (300.3, 490.49). Therefore, the following can be obtained:

[0050] max = 590.59 - 10.01 = 580.58

[0051] may = 490.49 - 10.01 = 480.48

[0052] mbx = 590 - 10 = 580

[0053] Mby = 490 - 10 = 480

[0054] Furthermore, its expansion / contraction value in the X direction is X = max - mbx = 580.58 - 580 = 0.58

[0055] Its expansion / contraction value in the Y direction is Y = may - mby = 480.48 - 480 = 0.48

[0056] Thus, it can be seen that the PCB circuit board shrinks in the X and Y directions, and similarly, if it is negative, it expands. This allows monitoring of the expansion and contraction of the PCB circuit board during the production process. Each step in the PCB production process affects the expansion and contraction of the circuit board's shape. The reason is that the circuit board, which is composed of flexible copper-clad laminate, epoxy resin prepreg, polyimide, and polyimide reinforcing film, requires the material temperature to be raised to above 170℃ during the lamination process. After cooling, internal stress occurs due to the difference in the expansion and contraction coefficients of copper and polyimide, which disrupts the material balance force, causes the substrate to shrink and deform, and distorts the circuit pattern of the substrate, resulting in uneven expansion and contraction of the PCB circuit board.

[0057] Furthermore, the method of this invention is applied to an assembly line to achieve online continuous monitoring. The above-described actions and all calculations are run on a computer server to support high-speed production in the assembly line. Specifically, the PCB circuit board is transported to the loading position by the loading machine, and then the PCB circuit board is sent to the scanning position and the measurement position by the circulating conveyor belt. The PCB is automatically scanned by the array CCD camera to acquire the PCB image, and the measurement is performed in conjunction with the method of this invention. After the measurement is completed, it is sent to the unloading position, where the double suction cup clamp picks up the PCB circuit board and the release paper at the same time. Finally, the sorting robot arm stacks the products into the corresponding sorting boxes. It should be noted that during product inspection, the pressing cylinder drives the transparent pressing fixture to flatten the product to prevent product warping and measurement errors.

[0058] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. An online monitoring method for the expansion and contraction of a PCB circuit board, characterized in that, Includes the following steps: Scan the PCB, acquire PCB images, and import PCB design drawings; Multiple calibration measurement points are set on the PCB design drawing; Obtain the calibration coordinate set data corresponding to each calibration measurement point; Collect the actual coordinate set data of the actual PCB circuit board at each of the calibration measurement points; The numerical differences in the X and Y directions between each set of calibrated coordinate data and the corresponding actual coordinate data are used to determine the expansion and contraction range of the actual PCB circuit board.

2. The online monitoring method for expansion and contraction of a PCB circuit board according to claim 1, characterized in that, Two measurement points on the actual PCB circuit board are selected as the reference for establishing a coordinate system. Measurement point one is selected as the origin, and measurement point two is selected as the reference point in the +X direction. A perpendicular line is drawn through the origin as the Y direction to obtain the abscissa and ordinate of the actual coordinate set to obtain the expansion and contraction value of the actual PCB circuit board. All calibration measurement points are located on the PCB design drawing. The reference point of the calibration measurement point is the center point of the expansion and contraction hole. Every two sets of calibration measurement points form a target measurement unit. The original +X direction coordinates and the original Y direction coordinates of the target measurement unit are obtained.

3. The online monitoring method for expansion and contraction of a PCB circuit board according to claim 2, characterized in that, The actual PCB circuit board is divided into NxM discrete micro-elements (N and M are large positive integers). With any point P as the center of the micro-element, two concentric circles C1 and C2 are drawn with point P as the center. The coordinates of the center of the two concentric circles are obtained by using the camera calibration algorithm of concentric double-ring target.

4. The online monitoring method for expansion and contraction of a PCB circuit board according to claim 3, characterized in that... The expansion / contraction ratio is calculated based on the center coordinates and the target measurement unit, and the coordinates of point P are adjusted according to the expansion / contraction ratio. The standard position coordinate data is then output.

5. The online monitoring method for expansion and contraction of a PCB circuit board according to claim 4, characterized in that, The standard position coordinates are defined by the PCB design drawing. The acquisition device obtains the coordinates corresponding to the standard positions. The expansion / contraction ratio is calculated from the position coordinates obtained by the acquisition device. The expansion / contraction ratio is the ratio of the actual hole spacing to the standard hole spacing.

6. The online monitoring method for expansion and contraction of a PCB circuit board according to claim 2, characterized in that, The selection of calibration measurement points includes: selecting three pattern points on the upper edge of the PCB design drawing, such that the selected pattern points can form a triangle. zoy The center coordinates (ax1, ay1), (ax2, ay2), and (ax3, ay3) of these three pattern points are extracted respectively and used as group a.

7. The online monitoring method for expansion and contraction of a PCB circuit board according to claim 6, characterized in that, The acquisition of the coordinate group data of the calibration measurement points specifically includes: using an image sensor to collect three pattern points at corresponding positions on the actual PCB board, and extracting their center coordinate values ​​(bx1, by1), (bx2, by2), and (bx3, by3) respectively as group b.

8. The online monitoring method for expansion and contraction of a PCB circuit board according to claim 7, characterized in that, Extract the two largest differences in x and y coordinates from the coordinates of group a and group b respectively to obtain max, may and mbx, mby; The expansion / contraction value in the x-direction is obtained by comparing max with mbx, and the expansion / contraction value in the y-direction is obtained by comparing may with mby, where: The expansion / contraction value in the x-direction is X = max - mbx The expansion / contraction value in the y-direction is Y = may - mby X and Y are the expansion and contraction values ​​in the x and y directions, respectively. A positive value indicates contraction, a negative value indicates expansion, and a zero value indicates no expansion or contraction.

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