JPH04319649A - Through hole inspecting device - Google Patents

Abstract

PURPOSE:To make through hole inspections possible even when a through hole picture formed to a striped pattern by transmissive modulated light does not become circular as the picture of a thick or wide printed board. CONSTITUTION:The reflected light picture and transmissive light picture of a printed wiring pattern are taken with one image pickup device 103 and an edge detecting means 107 detects an edge after a through hole picture formed to a striped pattern is binarized. Then an ANDing means 114 performs an ANDing process on a through hole picture obtained by means of expansion/ contraction processing means 109-110 and another through hole picture obtained by means of expansion/contraction processing means 111-113 from the inverted picture of the striped pattern. Therefore, a circular through hole picture which faithfully reflects the land shape of a through hole section can be detected and various kinds of inspections, such as width inspection, land shape inspection, etc., can be easily performed on a through hole pattern.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a through-hole inspection apparatus in pattern inspection for inspecting defects in wiring patterns on printed circuit boards, photomasks, etc.

0002

2. Description of the Related Art As the density of mounting electronic components on printed circuit boards increases, wiring patterns are becoming increasingly finer. Conventionally,
Visual inspection by humans has been used to inspect defects in printed circuit boards, etc., but as wiring patterns become more detailed, it has become difficult to continue inspection work over long periods of time while maintaining inspection accuracy. is requested.

A conventional through-hole image pattern inspection apparatus will be described below with reference to the drawings. FIG. 3 is a block diagram of a conventional wiring pattern inspection device. In FIG. 3, 301 is a printed circuit board, 302 is a diffused illumination device such as a ring-shaped light guide 304, and C is 303.
an image input unit equipped with an imaging device such as a CD sensor camera;
305 is a modulated light generation unit that modulates transmitted light and generates modulated light; 306 is a binarization processing unit that binarizes the grayscale image; 307
308 is an edge detection unit that detects edges of a pattern in a binary image; 308 is an expansion processing unit (1) that expands an edge image;
09 is a contraction processing unit that contracts the output image of the expansion processing unit (1) 308; 310 is an expansion processing unit (2) that expands the output image of the contraction processing unit 309; and 311 is a binary value from the binarization processing unit 306. Defect detection units for detecting defects such as lands from the image and the binary image from the expansion processing unit (2) are shown.

The operation of the through-hole inspection apparatus constructed as described above will be explained below. From above the wiring pattern formed on the printed circuit board 301,
The wiring pattern is illuminated by a diffuse illumination device 304 such as a ring-shaped light guide, and is read as a grayscale image by an image input unit 302 equipped with an imaging device 303 such as a CCD sensor camera. At this time, light modulated at a predetermined period by the modulated light generating section 305 is simultaneously emitted from below the printed circuit board and inputted to the image input section 302 . This modulated light generating section 3
02 blinks every cycle in synchronization with the horizontal synchronization signal of a one-dimensional CCD sensor camera, etc., and modulates the amplitude of the transmitted light. Since the printed circuit board 301 is placed on a moving table (not shown) and scanned by the CCD sensor camera, the image signal level of the grayscale image obtained from the imaging device 303 is modulated line by line in the sub-scanning direction in the through-hole area. The resulting image will be The binarization processing unit 306 compares the grayscale image from the imaging device 303 with a predetermined threshold value and converts it into a binary image in which the wiring pattern part is set to 1 and the base material part is set to 0. Therefore, the through hole area is set in the sub-scanning direction. The result is an image with a striped pattern of alternating 1's and 0's. FIG. 4 shows a schematic diagram of the through-hole image after this binarization, and shows that the through-hole portion has a striped pattern. The edge detection section converts the binary image from the binarization processing section 306 into a contour image. The expansion processing unit (1) 308 thickens the outline image by a predetermined number of pixels and fills in the through-hole area. According to this method, since the outline of the through-hole area is spaced at intervals of one pixel, the through-hole area can be filled in by expanding one pixel. The contraction processing unit 309 contracts the binary image from the expansion processing unit 308 to a predetermined size, and erases the contour image other than the through-hole area. Expansion processing section (1
) 308, the outline is expanded by one pixel to have a width of three pixels, so if, for example, the pattern is contracted by two pixels from both sides, the outline other than the through-hole area will be erased and only the through-hole area will be separated. The expansion processing unit (2) 310 expands the binary image from the contraction processing unit 309 to a predetermined size and returns the through hole to its original size. Furthermore, since the through-hole area has shrunk by one pixel in the series of processes up to the shrinkage processing unit 309, the through-hole returns to its original size by expanding by one pixel. The defect detection unit 311 uses the binary image from the binarization processing unit 306 and the through-hole image from the expansion processing unit (2) 310 to separate the land portion and the conductor portion and detect defects. be.

[0005]

[Problems to be Solved by the Invention] However, the above-mentioned through-hole image pattern inspection apparatus has the disadvantage that when the thickness of the printed circuit board is thick, the through-hole portion cannot be obtained as a uniform striped pattern over the entire land portion. It has
In the conventional configuration, even if the wiring pattern portion and the through hole region are separated, the shape of the through hole portion may not be properly circular. The reason for this is as follows. For example, a one-dimensional CCD with 5000 elements is used as an imaging device.
When reading wiring patterns using a camera, the pixel width of a commonly used CCD sensor is 7 microns, so if the wiring pattern is read at an imaging magnification of 1:2, the pixel resolution is 1 pixel 14. Micron becomes CCD
The width that can be read by the sensor is 70 mm. Therefore, there is no problem if the printed circuit board is thin, but if the board is thick, the transmitted modulated light is influenced by the depth direction of the through-hole portion, and the transmitted modulated light that reaches the imaging device is eclipsed. This effect becomes more pronounced as the diameter of the through-hole becomes smaller, and especially at the ends of the wide wiring pattern as described above, and the through-hole striped pattern becomes crescent-shaped. FIG. 5 shows an example under the above imaging conditions. As shown in the figure, it is clearly seen that this effect is noticeable at the left and right ends of the wiring pattern. In this state, correct defect detection could not be performed even if the land portion and the conductor portion were separated as described above.

The present invention has been made in view of the above-mentioned conventional problems, and it is possible to satisfactorily separate the wiring pattern and the through-hole portion when inspecting the through-hole portion of a printed circuit board, even if the striped pattern by transmitted modulated light is not necessarily circular. The present invention provides a through-hole inspection device that can inspect for breakage of the land portion of a through-hole.

[0007]

[Means for Solving the Problems] The technical solution of the present invention for solving the above problems includes an image input means for optically detecting and photoelectrically converting a wiring pattern formed on a printed circuit board, and a modulated light generating means for irradiating the substrate with light modulated at a predetermined period by a transmitted light source; a binarizing means for converting the grayscale image from the image inputting means into a binary image; and a binary image from the binarizing means. an edge detection means for detecting an edge of a value pattern; a first expansion means for expanding an edge image from the edge detection means; and a first contraction means for contracting a binary image from the first expansion means. , a binary image obtained by a second expansion means for expanding the binary image from the first contraction means is converted into a binary image from the binarization means.
a binary image obtained by a third expansion means that inverts the value image and expands the inverted binary image; and a second contraction means that contracts the binary image from the third expansion means. , separating the land portion and the conductor portion by extracting the central part of the through-hole image by a logical product means, and detecting the binary image obtained by the logical product means as a through-hole image by a fourth expansion device; It is composed of defect detection means for detecting defects in lands.

[0008]

[Operation] The present invention first converts the reflected light from the wiring pattern on the printed circuit board and the modulated light transmitted through the through hole into a binary image that is read by photoelectrically converting it into a binary image, so that the reflected light image and the transmitted light image are mixed. A through-hole image obtained by dilation/contraction processing from a binary image, and another through-hole image obtained by dilation/contraction processing from an inverted image of the binary image are centered by logical product processing. Since the through-hole area is completely separated and a circular through-hole image is obtained, various inspections such as pattern width inspection and cut-out inspection of the through-hole area are possible. Second, by superimposing the separated through-hole image with the original image to generate an image in which the through-hole area is filled in, it is possible to obtain the same image as the board before through-hole processing with a simple configuration. Wiring patterns can be inspected without generating false alarms in the area.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a through-hole inspection apparatus according to an embodiment of the present invention. In Figure 1,
101 is a printed circuit board; 102 is an image input means including a diffuse illumination device such as a ring-shaped light guide 104; and an imaging device such as a CCD sensor camera 103; and 105 is a modulated light generator that modulates transmitted light to generate modulated light. means, 106
107 is a binarization means for binarizing the grayscale image; 107 is an edge detection means for detecting edges of the pattern of the binary image; 108
109 is a first expansion means for expanding the edge image, and 109 is a first contraction means for contracting the output image of the first expansion means 108, which has the same structure as the conventional example. 110 is a second expansion means for expanding the output image of the contraction means 109;
1 is an inverter for inverting the binary image from the binarizing means;
112 is a third expansion means for expanding the binary image from the inverter, 113 is a second contraction means for compressing the binary image from the third expansion means, and 114 is the second expansion means 110. The obtained binary image and the second shrinking means 1
115 is a fourth expansion means for expanding the central part of the through-hole image obtained by the logical product means 114;
indicates defect detection means for detecting defects such as lands from the binary image from the binarization means 106 and the binary image from the expansion means 115.

The operation of the through-hole inspection apparatus constructed as described above will be explained below. From above the wiring pattern formed on the printed circuit board 101,
The light is illuminated by a diffuse illumination device 104 such as a ring-shaped light guide, and input as a grayscale image by an image input means 102 equipped with an imaging device 103 such as a CCD sensor camera. At this time, the modulated light generating means 1 is simultaneously transmitted from below the printed circuit board.
05 emits light modulated at a predetermined period and inputs it to the image input means 102. In this embodiment, the imaging device 103
An example using a one-dimensional CCD sensor camera is shown below. Furthermore, methods for separating the wiring pattern and the through-hole portion can be roughly divided into two methods: a method of separating the illumination irradiated by two sensors into two wavelengths, and a method of separating the through-hole from image data. In this embodiment, explanation will be given using a method of separating the image data from the image data, in which illumination from below is modulated with the horizontal period of the CCD camera, and the through-hole portion can be easily separated as a striped pattern. The printed circuit board 101 is placed on a moving table (not shown), and by driving a CCD camera in synchronization with the moving table, the grayscale image obtained from the imaging device 103 is imaged line by line in the sub-scanning direction in the through-hole area. The resulting image has a modulated signal level. In the binarization means 106, the imaging device 103
The grayscale image from is compared with a predetermined threshold value and converted into a binary image in which the wiring pattern part is set to 1 and the base material part is set to 0. By binarizing, an image of a striped pattern in which 1 and 0 are alternated in the sub-scanning direction is obtained in the through-hole area. The edge detection means converts the binary image from the binarization means 106 into a contour image. The first expansion means 108 thickens the outline image by a predetermined number of pixels and fills in the through-hole area. In this embodiment, the outlines of the through-hole area are lined up at intervals of one pixel, so that the through-hole area can be filled in by expanding one pixel. The first shrinking means 109 shrinks the binary image from the first expanding means 108 to a predetermined size and erases the contour image outside the through-hole area. Since the outline is expanded by one pixel to a width of three pixels by the first expansion means 108, for example, if the pattern is contracted by two pixels from both sides, the outline other than the through-hole area will be erased, and the through-hole area will be separated. Ru. The operations up to this point are performed in the same manner as before. However, as mentioned above, as the thickness of the wiring pattern board increases and the reading width increases, the transmitted modulated light is influenced by the depth direction of the through-hole section, and the transmitted modulated light that reaches the imaging device is vignetted. As a result, the obtained through-hole image becomes crescent-shaped and does not accurately reflect the land shape of the through-hole portion. This effect is particularly noticeable at the ends of the wiring pattern where the diameter of the through hole is smaller and the width thereof is wider. Therefore, if a negative image obtained by inverting the binary image obtained by the binarizing means 106 by the inverter 111 is used and the third expanding means 112 expands it by one pixel, the land in the through-hole portion becomes completely circular. Since it is obtained as an image that accurately reflects the shape, it can be referenced as the accurate center position of the through-hole portion. Therefore, if this binary image is shrunk by a predetermined pixel by the second shrinking means 113 and the through-hole image is expanded by a predetermined pixel by the second dilating means 110, by the AND means 114, a binary negative is obtained. The wiring pattern other than the through-hole area included in the image is erased, and the obtained through-hole image becomes circular reflecting the center position of the land portion. In this case, the expansion pixel size of the second expansion means 110,
The contracted pixel size of the second contracting means 113 is determined by the size, circularity, and deviation from the center of the through-hole image obtained by the first contracting means 109. The through-hole image obtained by the AND means 114 is expanded to a predetermined size by the fourth expansion means 115,
Return the through hole to its original size. Defect detection means 11
6 uses the binary image from the binarization means 106 and the through-hole image from the fourth expansion means 115 to separate the land portion and the conductor portion and detect defects. FIG. 2 shows an overview of the above processing flow. The effect of this embodiment can be clearly understood from this figure.

0012

As described above, the present invention detects a reflected light image and a transmitted light image of a printed wiring pattern with a single imaging device, obtains a through-hole image with a striped pattern, and after binarizing it. Edges are detected, and the through-hole image obtained by dilation/contraction processing is center-aligned with the other through-hole image obtained by dilation/contraction processing from the inverted image of the striped pattern. Since the hole area can be separated and detected as a circular through-hole image, through-hole areas can be extracted faithfully and with a simple configuration even when reading thick printed circuit boards or wide images, which was previously difficult. , width inspection of through-hole patterns, breakage inspection, and various other inspections are possible.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a through-hole inspection device according to an embodiment of the present invention.

[Fig. 2] A diagram showing an outline of the processing flow of the through-hole inspection device according to the same embodiment.

[Figure 3] Block wiring diagram of conventional through-hole inspection equipment

[Figure 4] Diagram showing a binary image showing a striped pattern of through holes

[Figure 5] Diagram showing an example of imaging a through-hole striped pattern

[Explanation of symbols]

101 Printed circuit board 102 Image input means 103 CCD sensor camera 104 Ring-shaped light guide 105 Modulated light generation means 106 Binarization means 107 Edge detection means 108 First expansion means 109 First contraction means 110 Second expansion means 111 Inverter 112 Third expansion means 113 Second contraction means 114 Logical product means 115 Fourth expansion means 116 Defect detection means

Claims (1)

[Claims] 1. An image input means for optically detecting and photoelectrically converting a wiring pattern formed on a printed circuit board; and a modulated light generating means for irradiating the printed circuit board with light modulated at a predetermined period by a transmitted light source. , binarization means for converting the grayscale image from the image input means into a binary image;
edge detection means for detecting edges of the binary pattern from the digitization means; first expansion means for expanding the edge image from the edge detection means;
A binary image obtained by a first contraction means for compressing a value image and a second expansion means for expanding a binary image from the first contraction means is converted into a binary image from the binarization means. A binary image obtained by a third expansion means for inverting the inverted binary image and a second contraction means for contracting the binary image from the third expansion means is logically The central part of the through-hole image is extracted by the product means, and the binary image obtained by the logical product means is detected as the through-hole image by the fourth expansion means, thereby separating the land portion and the conductor portion. A through-hole inspection device comprising a defect detection means for detecting defects.