JPH0322498A - Method and apparatus for detecting position of guide hole of multilayer printed circuit board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention provides a method for detecting the position of a reference hole in a multilayer printed circuit board, which determines the actual coordinate position of a reference hole machined in the multilayer printed circuit board with the reference mark thereof as a target. and devices.

(B) Prior Art When manufacturing a multilayer printed circuit board, it is necessary to accurately align the electrical wiring pattern provided on the inner layer board with the electrical wiring pattern formed on the outer layer board. For this reason, the inner layer board is provided with a reference mark that serves as a reference position for the electrical wiring diagram. A reference hole is drilled at the position of this reference mark, and the electrical wiring pattern of the outer layer board is formed using the reference hole as a reference. The fiducial mark on the inner layer plate is not visible from the outside. In order to make the fiducial mark visible to the naked eye, there is a method of counterboring it with an end mill or the like to expose the fiducial mark, but counterboring the appropriate depth is troublesome and reduces work efficiency. bad.

For this reason, there is a method of obtaining a reference mark from a transmitted image using Xi. For example, Japanese Patent Laid-Open No. 561-26999 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 resulting binary video pattern and the pre-stored reference mark pattern is determined for the entire screen.

The reference mark position is determined by detecting the coordinate position where the degree of coincidence is maximum. Next, a drill is used to drill a reference hole using the obtained reference mark position as a target.

(c) Problems to be Solved by the Invention Since the drilling of the reference hole is performed with the reference mark position determined as described above as the target, the reference mark position and the reference hole should match, but to what extent? The above-mentioned publication does not disclose a method for confirming whether the positions match with an accuracy of . It is also possible to find the coordinates of the center of the reference hole by arithmetic averaging the number of pixels of binary information corresponding to the reference hole based on the binary image obtained from the X-ray transmission image, but If the resulting binary image of the reference hole is not a perfect circle due to the adhesion of powder, etc., the center position may shift just by calculating the arithmetic average, and it is difficult to accurately determine the center position of the reference hole. Can not. The present invention aims to solve these problems.

(2) Means for Solving the Problems The present invention creates a point-symmetric binary image that is point-symmetrical from a binary image of a reference hole, and creates a point-symmetric binary image of the reference hole and a point-symmetric binary image of the reference hole. The above problem is solved by calculating the logical sum with the image and finding the center of the reference hole of the logical sum binary image obtained thereby.

That is, the method for detecting the position of a reference hole in a multilayer printed circuit board according to the present invention includes the steps of irradiating X-rays to the peripheral position of the reference hole, obtaining a transmitted image using an image receiving camera, and binarizing the obtained transmitted image to create a binary image. , by moving a window with a frame larger than the reference hole within the binary image, (a) that 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) There is no binary information corresponding to the reference hole within the window.
(a) to (c) that the number of pixels of value information is greater than or equal to a predetermined value
), a step of creating a point-symmetric binary image of the binary image within the window at the window position determined as above, and a step of creating a point-symmetric binary image of the binary image within the window. A step of creating a logical sum binary image in a state where the degree of coincidence with the point-symmetric binary image is highest, the X direction of the number of pixels of binary information corresponding to the reference hole of the logical sum binary image, and the direction orthogonal to this The method is comprised of the steps of determining the arithmetic mean value in the Y direction, and determining the coordinates of the reference hole center position from the window center position and the arithmetic mean values in the X and Y directions.

Further, the reference hole position detection device for a multilayer printed circuit board according to the present invention that implements the above method includes a multilayer printed circuit board (14).
an X-ray generator (10) that can irradiate X-rays to
2), a binarization means (26) for binarizing the transmitted image obtained by the image receiving camera, and a window (36) having a frame (36b) larger than the reference hole on the binary image. a reference hole detection means (50) for moving the image of the reference hole to a position where it is surrounded; and point symmetry 2 of the binary image within the window at the position detected by the reference hole detection means.
point-symmetric binary image creation means (51) for creating a value image;
a disjunction means (52) for creating a disjunction binary image in a state where the degree of coincidence between the binary image in the window and the point-symmetric binary image is highest; an arithmetic mean means (54) for calculating the arithmetic mean value of the number of pixels of the value information in the X direction and the Y direction perpendicular thereto; It consists of a reference hole center coordinate calculation means (56) for calculating the coordinates of the center position. Note that the symbols in parentheses indicate corresponding members in the embodiments described later.

(e) Create a point-symmetric binary image (i.e., an image with the top 1 left and right reversed) from the binary image of the reference hole in the action window,
The image of the reference hole of the logical sum binary image obtained by taking the logical sum of the binary image and the point-symmetric binary image at the position where the two images most match is always a symmetrical image with respect to its center.

In other words, even if chips generated during drilling become attached to the periphery of the reference hole and the shape of the reference hole becomes non-circular in appearance,
By calculating the logical sum as described above, the logical sum binary image of the reference hole becomes symmetrical with respect to its center. The arithmetic mean value in the X and Y directions is calculated from this logical sum binary image of the symmetrical reference hole, and the center position is determined from this, so the center of the reference hole can be centered with the same precision as when the reference hole is circular from the beginning. You can also find the coordinates of a location. The positional accuracy of the reference hole can be evaluated from the thus determined coordinate position of the center of the reference hole and the coordinate position of the center of the reference mark.

(F) Embodiment FIG. 1 shows an embodiment of the present invention as a block diagram. A multilayer printed circuit board 14 is installed at a predetermined position between the X-ray generator 10 and the X-ray ITV camera 12, which are arranged to face each other. Note that a drill 13 for drilling a reference hole is provided at a position a certain distance from the ITV camera 12 for X-rays. The multilayer printed circuit board 14 has a circular reference mark 16 on the inner layer. The transmission image signal obtained by the X-ray ITV camera 12 is sent to the AD converter 18,
Here, 256×256 pixels are digitized into 64 gradations. Digitized image information is stored in image memory 2
Stored as 0. Further, the digital image information from the AD converter 18 is sent to the monitor television 24 via the DA converter 22, so that a transmitted image can be displayed on the screen of the monitor television 24. Image memory 20
The digital image information stored in the binary image converter 26
2 of “1” or “0” at a predetermined threshold level by
converted to a value image. For example, an image part that is brighter than a predetermined brightness is set to "1", and a dark image part is set to rQ.
It is considered to be J. As a result, for example, two
A value image will be obtained. The binary image converted in this way is also stored in the image memory 20. Based on this binary image, the reference mark 16 is detected by the reference mark detector 28 as will be described later, and the center of gravity of the reference mark 16 is determined by the center of gravity calculator 30. Furthermore, the coordinates of the reference mark 16 are determined by the reference mark center coordinate calculator 31.

A reference hole 17 is formed in the multilayer printed circuit board 14 using a drill 13 provided in a predetermined positional relationship with the X-ray ITV camera 12 . X also for the machined reference hole 17
A transmission image is obtained by the line ITV camera 12, and a binary image is obtained as in the case of the fiducial mark 16, which is stored in the image memory 20. The reference hole 17 is detected by the reference hole detector 50 based on this binary image,
After correction is performed by the image inverter 51 and the image corrector 52, the center of gravity of the reference hole 17 is calculated by the center of gravity calculator 54. Furthermore, the coordinates of the reference hole 17 are determined by the reference hole center coordinate calculator 56, and the coordinates of the reference mark 16 and the reference hole 17 are compared in the comparator 58.

Next, the detection operation of the reference mark 16 in the reference mark detector 28, the center of gravity calculator 30, and the reference mark center coordinate calculator 31 will be described. For example, an image as shown in FIG. 3 is displayed on the screen of the monitor television 24. In FIG. 3, the hatched portion 32 corresponds to the "O" pixel, and the other portion 34 corresponds to the "1" pixel. An octagonal window 36 of a predetermined size scans the screen of the monitor television 24 from the left edge -E of the screen to the right. The scanning position moves one pixel at a time from the top to the bottom. When the window 36 is moved, the reference mark 16 is detected according to the flow shown in FIG. That is, it is determined whether there is a "0" pixel (that is, binary information corresponding to the reference mark 16) at the center 36a of the window 36 (step 100), and the movement of the window 36 is continued until this is detected. (ibid. 140).

If a "0" pixel is detected at the center 36a of the window 36, it is determined whether or not there is a "0" pixel on the frame 36b of the window 36. If there is a "0" pixel, the window Continue moving 36 (140)
.

If there is no "0" pixel on the frame 36b of the window 36, it is determined whether the number of "0" pixels within the window 36 is greater than or equal to a predetermined value 11 1 2 (120). If there are no more than a predetermined number of "O" pixels,
The movement of the window 36 is continued (140). If there are more than a predetermined 10" pixels in the window 36, the movement of the window 36 is stopped, and the rQJ pixels are moved in the X direction (horizontal direction in FIG. 3) and Y direction (vertical direction in FIG. 3), respectively. Find the arithmetic mean value (130). As a result, the position of the center of gravity of the "0" pixel within the window 36, that is, the center position of the reference mark 16 is determined. Since the position of the window 36 and the center position of the reference mark 16 within the window 36 have been determined, it is possible to obtain the coordinates of the center position of the reference mark 16 (see 15).
0).

The above operation can be completed in about 0.5 seconds.

It is clear from FIGS. 4, 5 and 6 that the steps Zoo, 110 and 120 described above make it possible to capture the fiducial mark 16 within the window 36. That is,
When the window 36 is moved to the position shown in FIG. 4, step 100 is passed, but step 110 cannot be passed. Also, in the state shown in FIG. 5, it is not possible to proceed from step 110 to step 120. Step 11 begins in the state shown in FIG.
0, it is possible to proceed to step 120. In this case, the fire mark 16 is located within the window 36. Note that the reason for determining the number of "0" pixels in step 120 is to prevent misidentification as the reference mark 16 when "O" pixels exist only at the center position of the window 36 due to impurities, dirt, etc. This is to do so. 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 a position corresponding to the coordinates of the reference mark 16 detected as described above, and a reference hole 17 is formed in the multilayer printed circuit board 14.

The coordinates of the processed reference hole 17 are determined by the reference hole detector 50, image inverter 51, image corrector 52, center of gravity calculator 54, and reference hole center coordinate calculator 56 as follows. After the reference hole 17 is machined, an image as shown in FIG. 8, for example, is displayed on the screen of the monitor television 24. The hatched portion 60 in FIG. 8 corresponds to the rOJ pixel, and the other portion 62 (reference hole 17) corresponds to the "1" pixel. By scanning the screen of the monitor television 24 with the same octagonal window 36 as described above, the position of the reference hole 17 is detected according to the flow shown in FIG. Note that the flow shown in FIG. 9 is basically the same as the flow shown in FIG. 7, except that "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 can be captured within the window 36 as shown in FIG. 10.

Next, the image of the reference hole 17 is corrected. That is, as shown in FIG. 11, 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 sides are reversed) is created, and this is used to determine the center of gravity of the reference hole 17. demand. The flow for this purpose is shown in FIG. First, a point-symmetric binary image 64 is created as described above (step 200).
, this point-symmetric binary image 64 is moved from the upper left end to the right side in the monitor television 24, and when the movement to the right end is completed, 1
It is moved downward by the amount of pixels, and similarly moved from the left end to the right end (see FIG. 13). This operation is performed from the upper left edge to the lower right edge of the monitor television 24 (210)
. During this time, a logical product is performed for each pixel between the binary image in the window 36 and the point-symmetric binary image 64, and the result is r.
The number of pixels of "l" is determined (220). Next, the obtained added values are compared and the position where the added value is the largest is determined (230). Next, the point-symmetric binary image 64 is moved to the determined position (see FIG. 14), and the logical sum is calculated for each pixel of the point-symmetric binary image 64 and the binary image. Logical sum 2 as shown in Figure 15
A value image is created (240). That is, if a pixel in one of the 1 5 1 6 images is "1", this pixel is set to "1". Therefore, an image as shown in FIG. 15 is obtained. Next, the arithmetic mean values of the "1" pixels in the X direction and the Y direction are obtained for the logical sum binary image thus obtained, and the center of gravity is calculated (250). The coordinates of the center position of the reference hole 17 are determined from the center of gravity position obtained in this way and the position of the window 36 (260)
.

Next, the comparator 58 compares the coordinates of the reference mark 16 and the reference hole 17 to determine how accurately the actually machined reference hole 17 matches the reference mark 16. be able to.

As mentioned above, the binary image of the reference hole 17 and its point symmetry 2
A logical sum binary image created by performing a logical sum in a state where the value image 64 most closely matches the value image 64 always becomes a symmetrical figure with respect to the center. Therefore, even if the image of the reference hole 17 becomes partially non-circular due to, for example, chips from drilling holes in the board, the image is corrected to a symmetrical state, and the center of gravity of this image is determined by the image of the reference hole 17. This is the center of gravity for a normal circular shape. Therefore, the center position of the reference hole 17 can be detected accurately.

In the embodiment described above, the window 36 is connected to the monitor television 2.
4, move it from the upper left end to the lower end, and insert the reference hole 17-2.
The position where the value image and the point-symmetric binary image 64 most match is determined, but as shown in the flow shown in FIG. Set the frame 70 (see Figure 17) (
Step 205), within this frame 70, window 3
It is also possible to scan 6 and find the position with the highest degree of accuracy. Other operations are the same as the flow shown in FIG. 12 described above. This makes it possible to shorten the scanning time for finding the position with the highest degree of image accuracy compared to the above-described embodiments.

(g) Effects of the invention As explained above, according to the present invention, two of the reference holes
By taking the logical sum of the value image and its point-symmetric binary image, we created a symmetrical figure with respect to the center of the reference hole, and found the center of gravity of this figure, so image defects caused by chips on the board etc. The coordinates of the center position of the reference hole can be determined without being affected by the Thereby, the position of the reference hole can be accurately determined, and the degree of coincidence with the reference mark can be precisely evaluated.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing an embodiment of the present invention.
Figures 3, 4, 5, and 6 are diagrams showing the value image, respectively, are diagrams showing the state of moving the window on the binary image, Figure 7 is a diagram showing the flow of reference mark coordinate detection, and Figure 8 is a diagram showing the flow of detecting reference mark coordinates. Figure 9 shows the state in which the window is moved on the binary image of the reference hole. Figure 9 is a diagram showing the flow of reference hole coordinate detection.
Figure 0 shows the reference hole captured in the window, and Figure 11 shows the point symmetry z created from the binary image in the window.
Figure 12 is a diagram showing the flow of determining the reference hole coordinates, Figure 13 is a diagram showing a point-symmetric binary image being moved on the screen, and Figure 14 is a diagram showing the 2-value image of the reference hole. A diagram showing the highest degree of coincidence between a value image and its point-symmetric binary image, FIG. 15 is a diagram showing a logical sum binary image created by taking the logical sum of FIG. 14, and FIG. FIG. 17, which is a diagram showing the flow of another embodiment, is a diagram showing frames set on the screen. DESCRIPTION OF SYMBOLS 10... X-ray generator, 12... ITV camera for X-rays, 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, 3l... Reference mark center coordinate calculator, 50... Reference hole detector, 51... Image inverter, 5
2... Image corrector, 54... Center of gravity calculator, 56...
- Reference hole center coordinate calculator, 58... comparator.

Claims (2)

[Claims] 1. In a multilayer printed circuit board reference hole position detection method that detects the position of a reference hole formed by drilling targeting a reference mark provided on the inner layer of a multilayer printed circuit board, X-rays are irradiated to the surrounding position of the reference hole. (a) Obtaining a transmitted image using an image receiving camera; Binarizing the obtained transmitted image to obtain a binary image; moving a window with a frame larger than the reference hole within the binary image; (a) (b) there is no binary information corresponding to the reference hole on the frame of the window, and (c) there is binary information corresponding to the reference hole in the window. The number of pixels in the window is greater than a predetermined value, the position where all conditions (a) to (c) are satisfied is found, and the point symmetry of the binary image within the window at the window position found as above is determined. Creating a binary image; 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 is highest; and a reference hole for the logical sum binary image. The arithmetic mean value of the number of pixels of the binary information corresponding to the X direction and the Y direction orthogonal thereto is determined, and the reference hole center position is determined from the center position of the window and the arithmetic mean value in the X direction and Y direction. A method for detecting the position of a reference hole in a multilayer printed circuit board, comprising: determining coordinates. 2. An X-ray generator capable of irradiating X-rays to a multilayer printed circuit board, an image receiving camera that obtains a transmitted image from the X-rays transmitted through the multilayer printed circuit board, and a binarization means that binarizes the transmitted image obtained by the image receiving camera. a reference hole detection means for moving a 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 window; and a window at the position detected by the reference hole detection means. a point-symmetric binary image creating means for creating a point-symmetric binary image of a binary image within a window; and a logical sum binary image in a state where the degree of coincidence between the binary image within the window and the point-symmetric binary image is highest. an arithmetic mean means for calculating the arithmetic mean value of the number of pixels of the binary information corresponding to the reference hole in the disjunctive binary image in the X direction and in the Y direction perpendicular thereto; A reference hole position detecting device for a multilayer printed circuit board, comprising a center position and a reference hole center coordinate calculating means for determining the coordinates of the reference hole center position from the arithmetic mean value in the X direction and the Y direction.