RU2519005C1 - Method of prestart check of printboards - Google Patents

Abstract

FIELD: printing.

SUBSTANCE: method of prestart check of printboards is proposed, in which from the matrix of the original image the additional matrix is formed, in which the fields of the related image elements correspond to the image fragments which size is larger than the minimum allowable value set by the coefficients of isotropic compression and defocusing, by logical deduction of indications of the additional matrix from the matrix of the original image the matrix of defects is obtained, in which the areas of related elements are marked, corresponding to the defects, and the defective areas adjacent to the areas of the related elements of the additional matrix, from these defective areas the doubly-linked defective areas are selected that are marked and the coordinates of centres of gravity are defined for them, at that the shells of printed conductors are identified, which have adjacent doubly-linked defects, through the centre of gravity of each of these shells and the centre of gravity of each adjacent to it doubly-linked defect the rectilinear cross-section of the printed conductor is made, the total width of the printed conductor in the shell area is defined as the difference between the length of this section and the total length of its segments crossing the shells, if the total width of the printed conductor in the shell area is less than the minimum allowable width of the printed conductor, it is concluded that in the area of this shell the unallowable narrowing of the printed conductor is detected.

EFFECT: enhanced functional capabilities due to locating the shells of printed conductors, resulting in unallowable narrowing.

1 dwg

Description

The invention relates to automation and computer technology and can be used in systems with technical vision in the control of printed circuit boards.

Known methods of control of printed circuit boards based on comparison with standards (Automatic PCI Inspection Algoritms / M. Moganti, F. Ercal, C. Dagli [etc.] // A Survey, Computer Vision and Image Understanding. - 1996. - No. 63. - P.287-313; Automatic Visual Inspection of Printed Circuit Boards: An Experimental System / B. Benhabib, CR Charette, KC Smith, AM Yip // International Journal of Robotic and Automation. - 1990. - No. 5 (2)) .

Despite the apparent simplicity, the methods are sensitive to the quality of alignment of the image and the standard, in particular, to mutual rotation, parallel displacement and to a slight change in scale and do not allow differentiation to determine actual and false narrowings.

Known methods for controlling printed circuit boards based on the use of structural-linguistic methods of image recognition (A. L. Drzhevecki, V. N. Kontishev. “Methods and means of monitoring the topological characteristics of many objects in systems with technical vision.” Devices and control systems. 1993 , No. 3), allowing to control the acceptable values of the width of the conductors and the permissible distances between the conductors, regardless of their orientation. The disadvantages of these methods are: reduced accuracy in determining the narrowing of conductors in the presence of shells located on the periphery of the printed conductors, and the inability to classify the causes of narrowing.

Closest to the proposed one is a method of optical tolerance control (A.L.Drzhevetsky, A.V. Grigoriev. “Automated system of optical tolerance control of printed circuit boards and photo masks.” Metrology, monthly supplement to the scientific and technical journal “Measuring equipment.” 1995, No. 4), which allows controlling almost the entire wide class of defects in printed circuit boards with an indication of their location and quantitative characteristics, including unacceptable narrowing of printed conductors, for the detection of which using complex algorithms are introduced that reduce the control performance and do not exclude the selection of false defects due to the presence of shells located on the periphery of the printed conductors, as well as the difficulty of unambiguously specifying the causes of narrowing, which can be caused by a natural decrease in the cross section of the conductors due to the influence of shells in the conductor body, which is an important characteristic of defects, simplifying the analysis of the technological process and the choice of direction of its correction.

The technical result of the proposed method of tolerance control of printed circuit boards is the expansion of functionality by determining the location of shells of printed conductors, leading to unacceptable narrowing.

The proposed method of tolerance control of printed circuit boards is based on the fact that sections of the conductors of printed circuit boards are made that have a cross section that exceeds the permissible value. In the body of the conductor there are shells that reduce its cross section and form biconnected defects, which is a necessary but not sufficient sign of narrowing. The narrowing of conductors in the absence of shells also forms a doubly connected defect, and the presence of such a defect is a necessary and sufficient sign of narrowing.

For the correct diagnosis of narrowing, it is important to determine the nature of the formation of doubly connected defects, namely, to find out: they are caused by physical narrowing of the conductor or by shells inside the conductor.

The problem is solved by identifying the relationship between the shells and biconnected defects. If these bonds are present, sections are drawn through the centers of gravity of the shells and biconnected defects. Find the coordinates of the intersection points of the secant lines with the boundaries of the given printed conductor, find the coordinates of the intersection points of the secant lines with the boundaries of the shells, which calculate the width of the conductors in this section, the cross section of the shells, the location of the center of gravity of the shells relative to the boundaries of the printed conductors. The difference between the width of the conductors and the cross-sectional value of the shells determines the admissibility or not tolerance of the narrowing of the conductors due to the shells with a certain area value, determines their weight during the ranking of defects, makes it possible to classify shells as defects. Biconnected defects that do not have a connection with the sinks determine the location of unacceptable narrowing of the printed conductors.

As a result, the accuracy of tolerance control of printed circuit boards is increased. Improving the accuracy of tolerance control of printed circuit boards during selection of defects is achieved due to the fact that reveal the actual narrowing of the printed conductors and determine the area and location of the shells in the conductors relative to their boundaries. The proposed method allows us to answer the question of the admissibility or not admissibility of the influence of shells on the magnitude of the narrowing of the conductors. In addition, the proposed method allows to determine the actual unacceptable narrowing not associated with the formation of shells and to classify such narrowing as defects. This method can be part of other methods, significantly improving their characteristics or used independently.

The proposed method of tolerance control of printed circuit boards is focused on the use of television-type readers that convert the image of a section of a printed circuit board into a video signal, which, after quantizing it into two levels, forms samples of a binary image of a section of a printed circuit board corresponding to the matrix of the original image in which the level “1” corresponds to the sections metallization, and "0" - the dielectric.

Then four matrices are formed, obtained from the matrix of the original image, one of which corresponds to the external boundaries of the printed conductors, the second to the sections of the shells, and the third to the boundaries of the shells. Sink sections are marked, and the areas and coordinates of the centers of gravity are determined for them. The fourth matrix is formed from the original one by means of the isotropic compression and defocus operation, in which the related elements correspond to image sections whose size exceeds the minimum allowable value specified by the isotropic compression and defocus coefficients.

The principle of performing compression and defocus operations and the implementation of digital filters are described in the article (A. L. Drzhevetsky. “Methods for constructing non-linear spatial filters with controllable characteristics”, Penza, 1991). Methods for obtaining matrices of the outer boundaries of printed conductors, shell sections, shell boundaries, as well as marking and determining the areas and coordinates of centers of gravity are known. A method and apparatus for determining the coordinates of the centers of gravity of images of many objects that are maximally adapted for use in this invention are discussed in (Patent of the Russian Federation RU No. 2032218 C1, CL G06K 9/00 of 03/27/95, Bull. No. 9).

To establish relations between the shell regions and the regions of defects, a defect matrix is first formed by logically subtracting the matrix samples obtained as a result of the isotropic compression and defocus operation from the matrix of the original image, based on which the connected image sections corresponding to the matrix of defective sections adjacent to the compressed and defocused areas.

Since biconnected defects are a sign of unacceptable narrowing, from the matrix of defective sections adjacent to the compressed and defocused areas, only biconnected defective sections are marked, which are marked, and the coordinates of the centers of gravity are determined for them.

To identify unacceptable narrowing based on the analysis of doubly connected defects, it is first necessary to find out the reasons for the formation of doubly connected defects. One of them is the physical unacceptable narrowing of the conductor, and the presence of shells does not matter here, and the second is the presence of shells, which can lead to narrowing, but may not lead.

In the second case, it is also important to determine the location of the sink in relation to the boundary of the printed conductor, and this parameter is an important characteristic of the admissibility of defects of this kind.

For example, the presence of a puncture or shell of the same area, but located on the periphery of the printed conductor, is not taken for a defect, however, a puncture or shell already in the middle of the printed conductor refers to defects with the same effective width of the conductor. It is also important in determining the admissibility of defects of this type and the ratio of the width of the conductor to the effective width of the conductor and so on.

, $$Y_{р}^0$$

) и ( $$X_{д}^0$$

, $$Y_{д}^0$$

) двухсвязных дефектных участков.To find out the effect of a doubly connected defect on the narrowing of the conductor due to shells, it is necessary to establish its connection with the shells. For this, a connection is established between the marked sections of the shells and doubly connected defective sections, provided that they are adjacent to each other. Then sections in the matrices of the outer boundaries of the printed conductors and the boundaries of the shells are drawn through points corresponding to the coordinates of the centers of gravity of the shells connected together ( $$X_R^0$$

, $$Y_R^0$$

) and ( $$X_d^0$$

, $$Y_d^0$$

) doubly connected defective areas.

Figure 1 shows an illustration of a method for determining the location of shells relative to the boundaries of printed circuit boards of conductors. The calculation of the coordinates of the intersection points of the secant lines with the nearest elements of the matrix of the outer borders of the printed conductors is as follows. The slope of the secant lines originating from the centers of gravity of the shells is calculated:

$$tg\varphi =\frac{Y_{d\mathrm{one}}^0-Y_p^0}{X_{d\mathrm{one}}^0-X_p^0}\left(\mathrm{one}\right)$$

, $$Y_{г}^1$$

), затем направление изменяют на 180° (направление по стрелке А) и определяют координаты точек пересечения секущих прямых также с ближайшими элементами матрицы внешних границ ( $$X_{г}^2$$

, $$Y_{г}^2$$

) и вычисляют ширину проводника.First, in the direction to the center of gravity of the doubly connected defects (direction along arrow B (Fig. 1)), the coordinates of the intersection points of the secant lines with the nearest elementary matrices of the outer boundaries ( $$X_g^{\mathrm{one}}$$

, $$Y_g^{\mathrm{one}}$$

), then the direction is changed by 180 ° (direction along arrow A) and the coordinates of the intersection points of the secant lines are also determined with the nearest elements of the matrix of external boundaries ( $$X_g^2$$

, $$Y_g^2$$

) and calculate the width of the conductor.

$$h=\sqrt{{\left(X_g^{\mathrm{one}}-X_g^2\right)}^2+\left(Y_g^{\mathrm{one}}-Y_g^2\right)}\left(2\right)$$

, $$Y_{р}^2$$

, $$X_{р}^1$$

, $$Y_{р}^1$$

), по которым вычисляют поперечное сечение раковин:Similarly, the coordinates of the intersection points of the secant lines with the nearest elements of the shell boundary matrix are determined ( $$X_R^2$$

, $$Y_R^2$$

, $$X_R^{\mathrm{one}}$$

, $$Y_R^{\mathrm{one}}$$

), which calculate the cross section of the shells:

$$l=\sqrt{{\left(X_p^2-X_p^{\mathrm{one}}\right)}^2+{\left(Y_p^2-Y_p^{\mathrm{one}}\right)}^2}\left(3\right)$$

The equivalent width of the conductor is calculated:

, $$h_{\mathrm{uh}}=h-l\left(\mathrm{four}\right)$$

,

which is compared with the permissible value and decide on the presence or absence of defects.

The location of the shells relative to the boundaries of the printed conductor is determined as the distance from the centers of gravity of the shells to the boundaries of the printed conductors and calculated on the basis of the relations:

$$l_g^{\mathrm{one}}=\sqrt{{\left(X_g^{\mathrm{one}}-X_p^0\right)}^2+{\left(Y_g^{\mathrm{one}}-Y_p^0\right)}^2},l_g^2=h-l_g^{\mathrm{one}}\left(5\right)$$

, $$Y_{д2}^0$$

) недопустимых заужений печатных проводников. Таким образом, предложенный метод повышает точность допускового контроля при селекции дефектов.The equivalent width of the conductors, the location of the shells and their area allow us to make a conclusion about the suitability of the product and adjust the process to reduce the number of defects. Marked doubly connected defective areas that do not have a connection with the marked areas of the sinks determine the location ( $$X_{d2}^0$$

, $$Y_{d2}^0$$

) unacceptable narrowing of printed conductors. Thus, the proposed method improves the accuracy of tolerance control during selection of defects.

Claims (1)

The method of tolerance control of printed circuit boards according to their binary images, which consists in the fact that from the matrix of the original image, by isotropic compression and defocusing, an additional matrix is formed in which the areas of the connected image elements correspond to image fragments whose size exceeds the minimum allowable value specified by the isotropic coefficients compression and defocusing, by logically subtracting the samples of the additional matrix from the matrix of the original image, a matrix of defects is obtained in which the regions of connected elements corresponding to defects and the defective regions adjacent to the regions of the connected elements of the additional matrix are distinguished, from these defective regions biconnected defective regions are selected that mark and determine the coordinates of the centers of gravity for them, characterized in that they reveal shells of printed conductors having adjacent doubly connected defects, a rectilinear section is printed through the center of gravity of each such shell and the center of gravity of each adjacent doubly connected defect o of the conductor, the total width of the printed conductor in the sink area is defined as the difference between the length of this section and the total length of its segments crossing the sinks, if the total width of the printed conductor in the shell area is less than the minimum allowable width of the printed conductor, then we conclude that in the region This shell has detected an unacceptable narrowing of the printed conductor.