JPH077868B2 - Method and apparatus for detecting reference hole position of multilayer printed circuit board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention is a method for detecting a reference hole position of a multilayer printed circuit board, in which the actual coordinate position of a reference hole processed with the reference mark of the multilayer printed circuit board as a target is obtained. And the device.

(B) Conventional Technology When manufacturing a multilayer printed circuit board, it is necessary to accurately align the electric wiring pattern provided on the inner layer board with the electric wiring pattern formed on the outer layer board. For this reason, the inner layer board is provided with a reference mark which serves as a reference position for the electric wiring pattern. A reference hole is formed at this reference mark position, and an electric wiring pattern of the outer layer board is formed with the reference hole as a reference. The fiducial marks on the inner layer plate cannot be seen from the outside. In order to make the fiducial mark visible to the naked eye, there is a method of exposing the fiducial mark by performing counterboring with an end mill etc., but the work of counterboring with an appropriate depth is troublesome and the work efficiency is low. bad. Therefore, there is a method of obtaining a reference mark from a transmission image using X-rays. For example, JP-A-56-1
26999 discloses a method for automatically detecting the position of a reference mark. That is, the video signal of the transmitted image is binarized, and the degree of coincidence between the obtained binary video pattern and the pattern of the reference mark stored in advance is obtained for the entire screen. The reference mark position is obtained by detecting the coordinate position where the degree of coincidence is maximum. Then, a reference hole is processed by using a drill with the obtained reference mark position as a target.

(C) Problem to be Solved by the Invention Since the reference hole is drilled with the reference mark position determined as described above as a target, the reference mark position and the reference hole should match, but to what extent The above publication does not show a method for confirming whether the positions match with each other. It is also possible to obtain the coordinates of the center of the reference hole by arithmetically averaging the number of pixels of the binary information corresponding to the reference hole based on the binary image obtained from the X-ray transmission image. If the binary image of the obtained reference hole is not a perfect circle due to the adhesion of powder etc., the center position may be deviated only by calculating the arithmetic mean, and the center position of the reference hole can be accurately calculated. Can not. The present invention aims to solve such problems.

(D) Means for Solving the Problem The present invention creates a point-symmetric binary image that is point-symmetric from a binary image of a reference hole, and then the binary image of the reference hole and the point-symmetric binary image of the reference hole. The above problem is solved by taking the logical sum of the image and the center of the reference hole of the binary image of the logical sum obtained thereby. That is, the method of detecting the reference hole position of the multilayer printed circuit board according to the present invention is designed to move the X position to the position around the reference hole.
Irradiating a line and obtaining a transmission image with an image receiving camera, binarizing the obtained transmission image to obtain a binary image, moving a window having a frame larger than the reference hole in the binary image, a) There is binary information corresponding to the reference hole in the center of the window, (b) There is no binary information corresponding to the reference hole on the frame of the window, and (c) Corresponding to the reference hole in the window. A step of obtaining a position where all of the conditions (a) to (c) that the number of pixels of the binary information is more than a predetermined number are satisfied, and the binary image in the window at the window position obtained as described above A step of creating a point symmetric binary image, a step of creating a logical sum binary image in a state where the degree of coincidence between the binary image in the window and the created point symmetric binary image, Of the binary information corresponding to the reference hole Y perpendicular X direction and to prime
The process comprises the steps of obtaining the arithmetic mean value in the direction, and the step of obtaining the coordinates of the reference hole center position from the center position of the window and the arithmetic mean values in the X and Y directions.

Further, the reference hole position detecting device for a multilayer printed circuit board according to the present invention for carrying out the above method includes an X-ray generator (10) capable of irradiating the multilayer printed circuit board (14) with X-rays, and an X-ray transmitted through the multilayer printed circuit board. Image receiving camera (12) that obtains a transmitted image from a line
And binarize the transmission image obtained by the image receiving camera 2
Reference value detecting means (26) and reference hole detecting means for moving a window (36) having a frame (36b) larger than the reference hole on the binary image to a position inside which the image of the reference hole is surrounded ( 50), point symmetric binary image creating means (51) for creating a point symmetric binary image of the binary image in the window at the position detected by the reference hole detecting means, and point symmetry with the binary image in the window. A logical sum means (52) for creating a logical sum binary image in a state where the degree of coincidence with the binary image is the highest;
An arithmetic mean means (54) for obtaining an arithmetic mean value of the number of pixels of the binary information corresponding to the reference hole in the logical sum binary image in the X direction and the Y direction orthogonal thereto, the center position of the window and the above. A reference hole center coordinate calculating means (56) for obtaining the coordinates of the reference hole center position from the arithmetic mean values in the X and Y directions. The reference numerals in parentheses indicate the corresponding members in the embodiments described later.

(E) Action Create a point-symmetric binary image (that is, an image that is vertically and horizontally inverted) from the binary image of the reference hole in the window,
The image of the reference hole of the logical OR binary image obtained by taking the logical OR of the two images at the position where the binary image and the point symmetric binary image are most coincident with each other is always an image symmetrical about the center thereof. That is, even if the chips generated during drilling adhere to the periphery of the reference hole and the shape of the reference hole apparently becomes non-circular, the logical OR binary value of the reference hole is obtained by taking the logical OR as described above. The image is symmetrical about its center.
The arithmetic mean value in the X and Y directions is calculated from the logical OR binary image of this symmetrical reference hole, and the center position is obtained from this, so the center of the reference hole is as accurate as when the reference hole was circular from the beginning. The coordinates of the position can be obtained. The positional accuracy of the reference hole can be evaluated from the coordinate position of the center of the reference hole and the coordinate position of the center of the reference mark thus obtained.

(F) Embodiment An embodiment of the present invention is shown as a block diagram in FIG. X-ray generator 10 and X-ray IT arranged so as to face each other
The multilayer printed circuit board 14 is installed at a predetermined position between the V cameras 12. A drill 13 for processing a reference hole is provided at a position at a constant distance from the X-ray ITV camera 12. The multilayer printed board 14 has a circular reference mark 16 on the inner layer portion. The transmitted image signal obtained by the X-ray ITV camera 12 is A
It is sent to the D converter 18, where it is converted into 6 as 256 × 256 pixels.
Digitized into 4 gradations. The digitized image information is stored in the image memory 20. In addition, the AD converter 18
The digital image information from is sent to the monitor television 24 via the DA converter 22, which allows a transparent image to be displayed on the screen of the monitor television 24. Image memory 20
The digital image information stored in is converted by the binary image converter 26 into a binary image of "1" or "0" at a predetermined threshold level. For example, an image part that is lighter than a predetermined brightness is set to "1", and a dark image part is set to "0".
It is said that Thereby, for example, a binary image as shown in FIG. 2 is obtained. The binary image thus converted is also stored in the image memory 20. Based on this binary image, the reference mark detector 28 detects the reference mark 16 and the center of gravity calculator 30 as described later.
The center of gravity of the reference mark 16 is determined by Further, the coordinates of the reference mark 16 are obtained by the reference mark center coordinate calculator 31.

A reference hole 17 is formed in the multilayer printed circuit board 14 by a drill 13 provided in a predetermined positional relationship with the X-ray ITV camera 12. With respect to the processed reference hole 17, a transmission image is obtained by the X-ray ITV camera 12, and a binary image is obtained similarly to the case of the reference mark 16, and this is stored in the image memory 20. The reference hole detector 50 detects the reference hole 17 based on this binary image, and after the image invertor 51 and the image corrector 52 correct the center of gravity of the reference hole 17 by the center of gravity calculator 54. Calculation is performed. Further, the reference hole center coordinate calculator 56 determines the coordinates of the reference hole 17, and the comparator 58 compares the coordinates of the reference mark 16 and the coordinates of the reference hole 17.

Next, the detection operation of the reference mark 16 by the reference mark detector 28, the center of gravity calculator 30, and the reference mark center coordinate calculator 31 will be described. On the screen of the monitor television 24, for example, an image as shown in FIG. 3 is displayed. In FIG. 3, the hatched portion 32 corresponds to the "0" pixel, and the other portion 34 corresponds to the "1" pixel. An octagonal window of a predetermined size is displayed on the screen of this monitor TV 24.
36 scans from the top left edge of the screen to the right. The scanning position moves from the upper part to the lower part by one pixel. When the window 36 is moved, the reference mark 16 is detected by the flow shown in FIG. That is, it is judged whether or not there is a "0" pixel (that is, binary information corresponding to the reference mark 16) at the center 36a of the window 36 (step 10).
0), the movement of the window 36 is continued until this is detected (at 140). When a "0" pixel is detected in the center 36a of the window 36, it is judged whether or not there is a "0" pixel on the frame 36b of the window 36 (at 110), and "0" is determined.
If there are pixels, continue moving window 36 (see
140). When there are no "0" pixels on the frame 36b of the window 36, it is determined whether the number of "0" pixels in the window 36 is a predetermined number or more (120). If there are no more than "0" pixels, the window 36 continues to move (140). If there are more than a certain number of "0" pixels in window 36, stop moving window 36,
The arithmetic mean value of the "0" pixel in each of the X direction (horizontal direction in FIG. 3) and the Y direction (vertical direction in FIG. 3) is calculated (13
0). As a result, the barycentric position of the “0” pixel in the window 36, that is, the center position of the reference mark 16 is obtained. Since the position of the window 36 and the center position of the reference mark 16 in the window 36 are obtained, the coordinates of the center position of the reference mark 16 can be obtained (150). The above operation can be completed in about 0.5 seconds.

The window 36 according to steps 100, 110 and 120 above.
The ability to capture the fiducial mark 16 in it is
This is apparent from Figures 5 and 6. That is, when the window 36 moves to the position shown in FIG. 4, step 100
Can pass, but cannot go through step 110. Further, even in the state shown in FIG. 5, it is not possible to proceed from step 110 to step 120. It is possible to proceed from step 110 to step 120 only in the state shown in FIG. In this case the fiducial mark in window 36
16 will be located. The determination of the number of “0” pixels in step 120 is to prevent misidentification as the reference mark 16 when there is a “0” pixel only at the center position of the window 36 due to impurities, stains and the like. This is because Therefore, the predetermined number in step 120 is set to a value slightly smaller than the value corresponding to the number of pixels of the reference mark 16.

Next, the drill 13 is moved to the position corresponding to the coordinates of the reference mark 16 detected as described above, and the reference hole 17 is formed in the multilayer printed board 14.

The coordinates of the processed reference hole 17 are obtained by the reference hole detector 50, the image inverter 51, the image corrector 52, the center of gravity calculator 54, and the reference hole center coordinate calculator 56 as follows. After the processing of the reference hole 17, an image as shown in FIG. 8 is displayed on the screen of the monitor TV 24. In FIG. 8, the hatched portion 60 corresponds to the pixel “0”, and the other portion 62
(Reference hole 17) corresponds to the pixel of "1". The screen of this monitor TV 24 has an octagonal window 36 similar to the above.
By scanning with, the position of the reference hole 17 is detected by the flow shown in FIG. The flow shown in FIG. 9 is basically the same as the flow shown in FIG. 7 because “0” and “1” are reversed. This is because the portion corresponding to the hole corresponds to "1" and the other portions correspond to "0". According to the flow shown in FIG. 9, the reference hole 17 is formed in the window 36 as shown in FIG.
Can be caught.

Next, the image of the reference hole 17 is corrected. That is, the eleventh
As shown in the figure, a point symmetric binary image 64 of the binary image in the window 36 (that is, a binary image in which the top, bottom, left and right are inverted) is created, and the center of gravity of the reference hole 17 is obtained using this. The flow for this is shown in FIG. First, the point-symmetrical binary image 64 is created as described above (step 200), and the point-symmetrical binary image 64 is moved from the upper left end to the right end in the monitor TV 24, and when the movement to the right end is completed, one pixel is displayed. Move down by a minute, and similarly move from the left end to the right end (see Figure 13). This operation is performed from the upper left end to the lower right end in the monitor television 24 (at 210). During this time, for each pixel between the binary image in the window 36 and the point-symmetrical binary image 64,
The logical product is taken and the number of pixels whose result is "1" is calculated (22
0). Next, the obtained added values are compared to obtain the position where the added value is the largest (at 230). Then
The point symmetric binary image 64 is moved to this obtained position (
(See FIG. 14), the point-symmetric binary image 64 and the binary image are ORed to each pixel, thereby creating a logical OR binary image as shown in FIG. 15 (240). . That is,
When the pixel of either one of the images is "1", this pixel is set to "1". Therefore, the image as shown in FIG. 15 is obtained. Next, an arithmetic mean value is calculated for each of the X-direction and the Y-direction of the pixel of "1" in the binary OR image thus obtained, and the center of gravity is calculated.
0). The coordinates of the center position of the reference hole 17 are obtained from the position of the center of gravity and the position of the window 36 obtained in this way (see 26
0).

Next, in the comparator 58, the coordinates of the reference mark 16 and the reference hole
By comparing with the coordinates of 17, it is possible to determine with what accuracy the actually processed reference hole 17 matches the reference mark 16.

As described above, the logical sum binary image created by taking the logical sum of the binary image of the reference hole 17 and the point-symmetrical binary image 64 of the reference hole 17 is always a symmetrical figure with respect to the center. . Therefore, even if the image of the reference hole 17 becomes a partially non-circular image due to the chips at the time of drilling the substrate, the image is corrected to a symmetrical state, and the center of gravity of this image is the image of the reference hole 17. It matches the center of gravity of a normal circle. Therefore, the center position of the reference hole 17 can be accurately detected.

In the above-described embodiment, the window 36 is moved from the upper left end to the lower right end on the monitor TV 24 to find the position where the binary image of the reference hole 17 and the point-symmetrical binary image 64 are most coincident with each other. As shown in the flow in FIG. 16, a frame 70 (see FIG. 17) larger than the window 36 at the position where the reference hole 17 is detected by a predetermined size is set (step 205), and the window is set in this frame 70. It is also possible to scan 36 and find the position with the highest degree of coincidence. The other operations are the same as those in the flow shown in FIG. As a result, it is possible to shorten the scanning time for obtaining the position where the degree of coincidence of images is highest, as compared with the above-described embodiment.

(G) Effect of the Invention As described above, according to the present invention, the two reference holes
By taking the logical sum of the value image and its point-symmetric binary image, a symmetrical figure is created with respect to the center of the reference hole, and the position of the center of gravity of this figure is determined. The coordinates of the center position of the reference hole can be obtained without being affected by. As a result, the position of the reference hole can be accurately obtained, and the degree of coincidence with the reference mark can be precisely evaluated.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG.
FIG. 3 is a diagram showing a value image, FIGS. 3, 4, 5 and 6 are diagrams showing a state in which a window is moved on a binary image, FIG. 7 is a diagram showing a flow of reference mark coordinate detection, and FIG. The figure which shows the state which is moving the window on the binary image of a reference hole, FIG. 9 is the figure which shows the flow of reference hole coordinate detection, 10th.
The figure shows the state that the reference hole is caught in the window, 11th
The figure shows a point symmetric binary image created from the binary image in the window, Fig. 12 shows the flow for obtaining the reference hole coordinates, and Fig. 13 shows the point symmetric binary image moved on the screen. Fig. 14 shows the state in which the binary image of the reference hole and the point symmetric binary image of it have the highest degree of coincidence, and Fig. 15 is created by taking the logical sum of Fig. 14. FIG. 16 is a diagram showing a logical OR binary image, FIG. 16 is a diagram showing a flow of another embodiment, and FIG. 17 is a diagram showing a frame set on the screen. 10 …… X-ray generator, 12 …… ITV camera for X-ray, 14 …… Multilayer printed circuit board, 16 …… Reference mark, 17 …… Reference hole, 20
…… Image memory, 26 …… Binary image converter, 28 …… Mark detector, 30 …… Center of gravity calculator, 31 …… Reference mark center coordinate calculator, 50 …… Reference hole detector, 51 …… Image Inverter, 52
…… Image corrector, 54 …… centroid calculator, 56 …… reference hole center coordinate calculator, 58 …… comparator.

Claims (2)

[Claims] 1. A reference hole position detection method for a multilayer printed circuit board, comprising: detecting a position of a reference hole formed by drilling a reference mark provided on an inner layer portion of the multilayer printed circuit board; X-ray is radiated to obtain a transmission image with an image receiving camera, the obtained transmission image is binarized to obtain a binary image, and a window having a frame larger than the reference hole is moved within the binary image. , (A) there is binary information corresponding to the reference hole in the center of the window, (b) there is no binary information corresponding to the reference hole on the frame of the window, and (c) the reference hole in the window. The number of pixels of the binary information corresponding to is present in a predetermined number or more, the position where all of the conditions (a) to (c) are satisfied is determined, and the window position at the window position determined as described above Binary Creating a point symmetric binary image of the image, creating a logical OR binary image in the state of the highest degree of coincidence between the binary image in the window and the created point symmetric binary image, logical OR binary Obtaining the arithmetic mean value of the number of pixels of binary information corresponding to the reference hole of the image in the X direction and the Y direction orthogonal to this, and based on the center position of the window and the arithmetic mean value in the X direction and the Y direction. A reference hole position detection method for a multilayer printed circuit board, which comprises: determining the coordinates of the hole center position. 2. An X-ray generator capable of irradiating a multilayer printed circuit board with X-rays, an image-receiving camera for obtaining a transmitted image from X-rays transmitted through the multilayer printed circuit board, and a transmitted image obtained by the image-receiving camera is binarized. Detection means for moving the window having a frame larger than the reference hole on the binary image to a position where the image of the reference hole is surrounded by the binarizing means, and the reference hole detecting means. A point symmetric binary image creating means for creating a point symmetric binary image of a binary image in a window at a specified position, and a logic in a state where the degree of coincidence between the binary image in the window and the point symmetric binary image is the highest. Sum 2
A logical sum means for creating a value image, and an arithmetic mean means for obtaining an arithmetic mean value of the number of pixels of the binary information corresponding to the reference hole in the logical sum binary image in the X direction and the Y direction orthogonal thereto. A reference hole position detecting device for a multilayer printed circuit board, which comprises a reference hole center coordinate calculating means for obtaining coordinates of the reference hole center position from the center position of the window and the arithmetic mean values in the X and Y directions.