JPS5839933A - Inspection method of packaging printed circuit substrate - Google Patents

Abstract

PURPOSE:To detect errors and positions of parts on a printed circuit substrate, by making a light and darkness boundary line by a projector on the surface of the printed circuit substrate and obtaining the data of a profile line by photographing the parts on the substrate which is passing the boundary line by a video camera. CONSTITUTION:A printed circuit substrate 1 which is transported is arranged so that the right side of a light and darkness boundary surface Z including an optical axis which is vertical to the substrate 1 is projected by a slit 21 of a projector 2 and the left-side light is shielded. A television camera 3 is arranged so that the optical axis forms 90 deg.-theta angle to an irradiated area Za side against the boundary surface Z, and a scanning direction is arranged so that a horizontal amplitude direction forms right angles to the direction of a boundary line Y between an irradiated area Za and a light shielded area Zb made on the substrate 1. By operating the profile line data of the Y axial direction obtained from a length of the light and darkness part of the Y axial direction, an outer profile in a width direction is decided. Then, the substrate 1 is moved to a prescribed distance and the profile line data in an X axial direction is obtained and the outer profile of a part 13 in the thickness direction is decided. The shape of the part 13 is specified from these data.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to an automatic inspection method for inspecting the correctness or incorrectness of the types and mounting positions of components on a mounted printed circuit board.

This inventor uses a projector to form a bright and dark boundary line on a mounted printed circuit board that is being transported at a constant speed, and a video camera images the parts passing through this bright and dark boundary line from diagonally above. Y-axis direction specifying data for specifying the link line in the Y-axis direction of the part obtained by connecting the lightness change points is obtained at predetermined intervals in the constant speed conveyance direction based on the dark part of the scanning line, Shape data and position data for characterizing the three-dimensional envelope mi obtained by combining these Y-axis direction specific data are compared with pre-stored reference shape data and position data of the part, respectively. It is an object of the present invention to provide a method for inspecting a mounted printed circuit board that can automatically and quickly determine whether the type of component and the mounting position on the printed circuit board are correct or incorrect.

An embodiment of the present invention will be described below with reference to the drawings.

In Fig. 1, 1 is a width WO mounting printed circuit board, 11~
Reference numeral 14 denotes a portion such as a semiconductor integrated circuit element.

The printed circuit board 1 is transported in the direction of the arrow shown in the figure. Reference numeral 2 denotes a light projector, which emits light to the right side in the figure of 2, a vertical light-dark boundary surface (hereinafter referred to as the boundary surface) including an optical axis perpendicular to the printed circuit board 1, and has a slit so that the left side is 11 points. 21 is attached, therefore, the right side of the boundary liz is the irradiation area Zas, and the left side is the irradiation area zb. 3a TV camera, the optical axis is 9a''-#O to the boundary mz to the irradiation area 2 @ 2, no angle within 9a''-#O, the scanning direction of scan-8, and the horizontal line middle direction is on the printed circuit board 1. Make the irradiation area z1 perpendicular to the direction of the boundary line Y of the light area zb,
The composition of FIG. 2 is set so that the screen 30 of the JR map 3 can be obtained. In this screen, the boundary lIy corresponds to the boundary My, and is the boundary line y running on the part 13.

Part understanding #! (hereinafter referred to as the Y-axis direction link line *) corresponds to yl. Point A on this link line yl is
Boundary on part 13! Corresponding to point A at the highest position across the printed circuit board 1 of Iy, the dark side of the scanning line S that scans the point A, scanning II that scans the boundary line y on the surface of the printed circuit board 1
The dark length of S is shorter than Lmax by t, and L is proportional to h. That is, H-k= (H/tan#)
tan (#-ψ)・・・・・・・-(1) k=H(t
-tan (e-91) ] -・------
-・-・-”' (2) Since ψ is extremely small, if Iff and a=45, b can be found by a simple proportional calculation.

Accordingly, [, boundary line yt on section #113 - scanning line 8 to be scanned]
Y-axis direction link line 1 obtained by connecting the brightness change points of
Since a corresponds to the cross-sectional profile in the width direction of the part 13 cut at the boundary surface 2, in this embodiment, specific data for characterizing the Y-axis direction linkage <mya is calculated from the dark part of the scanning line. Specify the cross-sectional shape in the width direction. 41 As constant data, the forest, maximum weight, □ maximum height, presence or absence of the top horizontal part, its length, and center coordinates are sufficient for that. Then, the heights of the respective center coordinates - are successively connected to obtain constant data in the X-axis direction <axoq#. This X-axis direction flesh-grain line corresponds to the cross-sectional profile in the thickness direction of the part 130 cut on the vertical plane perpendicular to the boundary 1iiz, so the specific data (maximum thickness Da height h
, the length (dim) of the horizontal apex (center coordinate Xs), and the cross-sectional shape in the thickness direction is specified. Feature data extraction point Xs of this sink〈-,! +, Horizontal top O start point and end point, center -
Superimpose the corresponding Y-axis direction coordinates (maximum weight obtained for liya - 1 horizontal top length x 1 center coordinate Ym) on the coordinates, and calculate the link line γa at the start and end points of the X-axis direction line. The position of the component 13 on the printed circuit board 1 is determined by calculating the positions X and Y of the starting point and end point, the position of the horizontal top, and the position of the center, and the maximum width, maximum thickness, and horizontal top length are calculated.
, dm, the maximum height of 11 m (hereinafter collectively referred to as shape data) and the center position Xm, Ym are compared with the standard shape data of part 130 and the standard mounting position on the printed circuit board, and it is determined that part O was inserted incorrectly). Automatically checks for forgotten insertion, misalignment, etc.

Next, a method for specifying parts and their mounting positions will be explained.

1) If a part of the specific data boundary line 1 in the Y-axis direction has a height with respect to the printed circuit board 10 surface, a link line ya in the Y-axis direction is created, so 1EalO
When the dark part of the scanning line 8nO first becomes shorter than Ln+ax, the scanning line gn becomes the starting point of the thinning line ya. The dark length of subsequent scanning lines decreases sequentially, reaches the shortest length, and then increases sequentially to 1jnax. Scanning II at this time
CI! qth) is 9 (the end point of line y1).Also, when parts overlap and the length L decreases and then suddenly increases, it is the time when the next part changes. be.

Therefore, a) the maximum inside of the component 13 can be calculated from the number of scanning lines from the starting point to the ending point.

Ex) The maximum height of the part 13 included in the boundary surface 2 can be calculated from the shortest dark part.

c) When the component 13 has a horizontal top, the dark lines of the scanning lines that scan this horizontal top are the same, so the first scanning line and the last O scanning line among these scanning lines are the starting points of the horizontal top, respectively. and the end point), and the length of the horizontal top of the part 13 can be calculated from the number of scanning lines from the start point to the end point. Of course, if the dark area does not change over a predetermined number of scanning lines, this may be characterized as a horizontal apex, and numerical processing will be easier if this is done.

2) Set the center between the starting point and the ending point of the horizontal peak as the center coordinate -.

2) About the X-axis direction synchronization line obtained by plotting the height at the center coordinate Ym of the specific data in the X-axis direction and the specific data in the Y-axis direction, a) Maximum thickness Y-axis direction specific data extraction point m, Xl, Xt,...
・) and the extraction interval (predetermined movement interval).

Ex) Horizontal top length: Calculated based on the number of Y-axis specific data extraction points whose height is constant in the adjacent Y-axis direction, particularly at the center coordinate Ym of the data extraction points.

c) Center coordinates - Calculate the coordinates of the center of the pixel from the coordinates of the Y-axis direction specific data extraction point that gives the starting point and ending point of the horizontal apex.

Next, an example of a method for processing a video signal sent from the control circuit of the television camera 3 will be described with reference to FIG. In the figure, 5 is a binarization circuit, and the television camera 30
It receives the video signal 41 from the control circuit 4, and sends the video signal binarized into the black level and its own level to the scanning line dark length measuring circuit @.

The threshold value for binarization is set to a level that makes the dark part of the image slightly brighter than the dark part of the image lim@0. The scanning line dark length measuring circuit 6 is a flip circuit that is set at the brightness change point where the binarized video signal 41m changes from black level to white level, and reset at the end of one pulse of the horizontal synchronizing signal 42.・
It has a flop 6a and a counter 6b energized by the output of the 7-lip flop 6a, and receives the binary video signal 4.
1. Count clock pulses from oscillator 1 only while a is at black level. Therefore, the scanning line dark length measuring circuit 6 counts the dark length of the scanning line, and the counting data 6
1 is input to an electronic computer (hereinafter referred to as a computer) s through an interface $. In the interface, an interrupt signal 421.4$1 is generated by the beginning of the pulse of the horizontal synchronizing signal 42 and the vertical synchronizing signal 43, respectively. The computer S Hiro reads the count data 61 using the interrupt signal 421, calculates the shape data and position data described above, compares them with the reference shape data and position data written in advance, and determines the degree of discrepancy. If the deviation exceeds a permissible limit value predetermined depending on the type of component and stored in the computer, the comparison result is sent to a display device 10 such as a television monitor, and an alarm signal is issued.

In the above explanation, we have explained the case where the shape and position of the part 13 are identified and matched based on six features, but if you want to further improve the matching accuracy, you can increase the number of data, and the following is explained below. , a case will be described in which the shape of the horizontal top, which is extremely effective in characterizing a part, is described in more detail and newly incorporated into the shape data. 1ILs Figures 0) and ←) are a top view and a side view of a certain part, in which the direction of the solid arrow indicates the direction of movement, and the direction of the dashed line arrow indicates the vertical oscillation direction of the scanning line. Further, F is a link line at the bottom of the part, G is a sink line at the horizontal top, Gs and Gy are center coordinates at the starting and ending points of the horizontal top, and Gm is the center of the part. This link line G is the point GB, Ga, G where the rate of change in length in the vertical width direction with respect to the moving distance of the component reaches a predetermined value.
m and am are newly extracted as feature points, and the point G@,01
The length between the points G and G, the length between the points G, , G, between the points G@s and G1 and between the points Gl and c.

When calculating the length between points, etc., the 0 points Gi and Gs can be specified in more detail than in the case of the above explanation.
u This is the point where the above rate of change becomes 1.

In the above embodiment, the printed circuit board 1 is moved at a constant speed, but the printed circuit board 1 may be fixed and the projector 2 and the television camera 3 may be moved together.

As described above, according to the present invention, a light-dark boundary line is projected onto the surface of a printed circuit board using a projector, and parts on the printed circuit board that pass through this bright-dark boundary line are photographed from diagonally above by a video camera. The feature of the external shape of the mounting cross-section cut in the width direction of the part on a surface containing The characteristics of the above-mentioned external shape can be expressed only with specific data, and this specific data is used for scanning #A to scan the part because the intersection line is two-dimensional.

It can be easily calculated based on the number of lines and dark part, and
The features of the link lines obtained by sequentially connecting the corresponding points of the above-mentioned link lines also directly represent the features of the outer shape of the cutting surface in the thickness direction of the part, so calculation of specific data featuring this link line is performed. Since this can be easily performed, it is possible to determine whether the parts 011 class and the mounting position are correct or incorrect quickly enough using a low-grade computer.

In addition, since the features of the two-dimensional external shape in the width direction are extracted at every predetermined interval in the thickness direction of the part, and the features of the two-dimensional external shape in the thickness direction are also extracted, features that are effective for identifying the type of part can be extracted. It is easy to specify the mounting position, and it is possible to accurately determine whether the type of component on the printed circuit board is correct, whether the mounting position is misaligned, etc. using a small number of feature points.

[Brief explanation of the drawing]

fllLx Zusha, Layout diagram showing the optical system of an embodiment of the automatic inspection method for a mounted printed circuit board according to the present invention, Figures 2 and 3, Sha, Diagram for explaining the operation of the above embodiment, Iris Zusha , a block diagram of the control system of the embodiment described above, and FIGS. In the figure, 1... Printed circuit board, 2... Floodlight, 3... Television camera, 4... Control circuit, 5... -binarization circuit, 6... Scanning line dark section II length circuit, DESCRIPTION OF SYMBOLS 1... Oscillator, 8--Interface, 9... Computer, 10... Display device, etc.-1 In the drawings, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] a projector that directly faces the surface of a printed circuit board that is transported at a constant speed after mounting the components and divides the surface of the printed circuit board into a light-shielding part and an irradiation part by a bright and dark boundary line perpendicular to the transport direction, and a predetermined vertical angle with the surface of the printed circuit board; A television camera that scans the light area and the irradiation area including the bright/dark boundary line in a direction orthogonal to the bright/dark boundary line, a scanning line dark area edge determining circuit that measures the dark area of a scanning line of a video signal, and A computer is provided to read the output of the adjustment circuit, and the computer specifies, based on the dark part of the scanning line, the two-dimensional shape of the Y-axis direction synchronization line created by the brightness change points of the scanning line. T of
The X-axis direction link line 0 is obtained by calculating the axial direction specific data for each predetermined movement distance of the printed circuit board and connecting the corresponding points of the Y-axis direction determination data in the X-axis direction.
X-axis direction specifying data for specifying the two-dimensional shape is calculated based on the T-axis direction specifying data, and shape data for specifying the three-dimensional envelope obtained by combining both of the above specifying data. An implementation characterized in that position data is calculated based on both of the specific data, and the shape data and position data are compared with reference shape data and reference position data for the component stored in advance in the computer, respectively. How to inspect printed circuit boards.