JPH05877B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for automatically detecting a mark position in an internal layer of a multilayer printed circuit board or the like.

Generally, a multilayer printed circuit board (consisting of a copper plate 1, an interior copper plate 2, and a transparent paper 4) for interior shipping is provided with a hole-drilling reference guide that indicates the reference position of the pattern on the interior copper plate 2, as shown in Figure 1. Mark 3 (tape) is embedded, and at the time of shipment, holes are drilled from the top of the multilayer printed circuit board at the position of this guide mark to serve as a reference. As shown in FIG. 2, the machining process involves an operator estimating and visually observing the marker pattern embedded in the inner layer from the upper layer, placing a counterbore at the position of the guide mark, and drilling the hole.

According to this method, the operator needs to counterbore in order to find the guide mark for drilling, and it takes some time to counterbore one to several times and change the drill etc. after counterboring, which reduces work efficiency. There was a problem that caused it to deteriorate easily.

The object of the present invention has been made in view of the above-mentioned prior art, and the object of the present invention is to provide a multilayer printed circuit board that can automatically and precisely recognize the pattern position of an internal layer that cannot be accurately detected visually, thereby improving the efficiency of drilling work. An object of the present invention is to provide a method for automatically detecting the position of a reference pattern in an internal layer.

To achieve this objective, the present invention
The ITV camera is used to enhance the X-ray image,
The present invention is characterized by accurately recognizing the inner layer reference pattern position and outputting the coordinates of the reference pattern position.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The method for detecting the position of a pattern on a multilayer printed circuit board or the like according to the present invention will be described below with reference to the drawings.

FIG. 3 is a block diagram showing an embodiment of an apparatus for carrying out the method of the present invention. Fig. 4a shows an example of a reference guide mark for drilling attached to an internal printed circuit board, and Fig. 4b shows an example of a guide mark in a multilayer printed board attached to an X-ray ITV shown in Fig. 3. 2 is a scanning waveform of the horizontal center portion of the video signal as seen by the camera. In Figure 5, a to c are the third
Figure 6a is a diagram showing an example of the output of the position coordinates of a reference guide mark, and Figure 6b is a diagram showing a reference pattern used when determining the reference coordinates. This is an example. FIG. 7 is a diagram specifically showing the image cutout memory reference pattern memory and comparison circuit of FIG. 3. By the way, 7 is an X-ray generator that irradiates the multilayer printed circuit board 8 with X-rays, 9 is an X-ray ITV camera that captures a pattern image of transmitted light that has passed through the guide mark 3 of the multilayer printed circuit board 8, and 10 is an X-ray Protective cover, 1
1 is the video signal 2 obtained from the X-ray ITV camera
3 (shown in Figure 5a);
12 is a video signal 2 output from the video amplifier 11
A clipper circuit 13 clips the video signal 24 outputted from the clipper circuit 12 and the video signal 23 outputted from the video amplifier 11 by analog clipping the video signal 24 shown in FIG. Analog multiplier that performs multiplication and emphasis processing, 1
Reference numeral 4 denotes a clipper circuit which clips the signal output from the analog multiplier 13 using a predetermined threshold value and outputs the video signal 25 shown in FIG. A binarization circuit 16 converts the binary pixel signal outputted from the binarization circuit into pixels by sampling it with a clock pulse signal.
An image cutting memory consisting of a shift register group 16a for storing raster data and a memory 16b for cutting out the signal output from the shift register into 8 x 8 bits; 17 is a memory for storing a reference pattern serving as a dictionary in 8 x 8 bits; reference pattern memory, 1
8 is an image cutting memory 16 and a reference pattern memory 1
A comparison circuit 19 compares picture elements No. 7 with exclusive OR; an addition circuit 19 adds the signals (matched signals) output from the comparison circuit 18; and an addition circuit 20 that counts clock signals and outputs a horizontal synchronization signal Hsync. The counter 21 counts the horizontal synchronization signal Hsync and outputs the x-coordinate value.
A counter that is reset by Hsync and outputs the y-coordinate value, 22 is the above-mentioned x-coordinate value xc and y-coordinate value indicating the maximum value among the values output from the adding circuit 19.
This is a maximum value detection circuit that outputs yc.

However, in FIG. 3, X-rays are irradiated from the top of the multilayer printed circuit board 8, a pattern image of the transmitted light transmitted through the guide mark 3 is detected by the X-ray ITV camera 9, and the image amplified signal is As shown in Figure 3, the contrast and S/N are poor and it is difficult to obtain a recognizable binarized image in this state, so the signal is clipped with a freely variable threshold using the clipper circuit 12, and the resulting image in Figure 5b is The video waveform 24 shown in FIG. 5A and the original video waveform 23 shown in FIG. Furthermore, a clip circuit 14 whose threshold value can be independently varied is provided at the next stage to form a video signal 25 shown in FIG. 5c.

Next, this pattern image is converted into two parts by the binarization circuit 15.
The value picture elements are converted into reference pattern memory 17 in advance.
For example, the reference pattern of the reference guide mark stored in the 8 x 8 bit reference pattern as shown in FIG. The correspondence is determined for each bit and the degree of coincidence is determined by the exclusive OR that constitutes the comparison circuit 18, and the results are added in the addition circuit 19. This outputs the center position coordinates (xc, yc) of the pattern of high picture elements.

In addition, the coordinate position (xc,
yc), for example, one picture element (1
From bit) = 5μm, it is determined by Xc = 5xc and Yc = 5yc.

As described above, by using the pattern position detection method for a multilayer printed circuit board according to the present invention, it is possible to completely eliminate the counterboring work that conventional workers had to do, relying mostly on their intuition. Further, since the positional information of the reference guide mark detected by the detection method of the present invention can be fed back to a drilling power tool or the like for NC control, it is possible to process the board quickly and accurately.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the configuration of a multilayer printed circuit board,
FIG. 2 shows a hole-drilling process that is performed to expose guide marks formed on a conventional multilayer printed circuit board. Fig. 3 is a schematic configuration diagram showing an embodiment of a device to which the method of automatically detecting the position of a reference pattern in an internal layer of a multilayer printed circuit board, etc. of the present invention is applied, and Fig. 4a shows a reference guide mark formed on an internal copper plate. Figure 4b is a diagram showing the waveform of the video signal of the central horizontal scanning line obtained by detecting the reference guide mark with an X-ray ITV camera through X-rays, and Figure 5 is a diagram showing the waveform of the video signal of the central horizontal scanning line. A diagram showing a video signal obtained from the circuit shown in the figure, FIG. 6a shows the center position coordinates (xc, yc) of the reference guide mark obtained by the present invention.
Figure 6b shows the reference pattern stored in the reference memory in advance.
Image cutting memory, reference pattern memory shown in the figure,
FIG. 3 is a diagram specifically showing a comparison circuit. Explanation of symbols, 3...Reference guide mark, 7...
X-ray generator, 8...Multilayer printed circuit board, 9...X
Line ITV camera, 15...binarization circuit, 16...
...Image cutting memory, 17...Reference pattern memory, 18...Comparison circuit, 22...Maximum value detection circuit.

Claims (1)

[Claims] 1. A standard guide mark for drilling attached to an internal layer of a multilayer printed circuit board, etc. is imaged by an X-ray ITV camera through X-rays, the imaged video signal is clipped, and the image signal is combined with the video signal. The video signal is emphasized by integrating the clipped signal, the emphasized video signal is binarized, and the position of a reference guide mark for drilling attached to the inside of the multilayer printed circuit board, etc. is determined. A method for detecting a pattern position on a multilayer printed circuit board, etc.