JPH0851131A - X-ray inspecting method - Google Patents

Abstract

PURPOSE:To accurately detect the positional coordinates and the deviation of the rotating direction of a material to be inspected by obtaining a binary image of the material to be inspected by thresholding the X-ray transmission image of the material to be inspected, detecting the coordinates of the center of the gravity and the inclination of the centerline of a component based on the binary image, and comparing it with a preset reference value. CONSTITUTION:The X-ray transmission distribution image data of a mounting board 3 is input to a computer 5. The data of the board 3 on which the components are mounted at proper locations is previously stored in the computer 5. The inspecting area of the component to be inspected is set from the data, and a binary image is so formed by using a threshold value to threshold the entire component for the region. The center of the gravity of the component and the inclination of the straight line in which the sum of squares of the distances to the pixels becomes minimum are calculated from the binary image, compared, and the absolute value of the difference is calculated as the deviation of the component. This deviation is compared with the allowable value of the preset deviation, and the propriety of the position of the component is decided according to whether it falls within the allowable range or not. Thus, the deviation of the rotating direction can be accuraately detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is to inspect an object to be inspected for X-rays and detect the transmitted X-rays to inspect the quality of the position of the object to be inspected. The present invention relates to an X-ray inspection method used for inspecting the quality of the mounting position of the mounted component.

[0002]

2. Description of the Related Art As a means for inspecting the mounting position of a component mounted on a board, the mounting board is imaged by a video camera,
A method is known in which an edge of a component is detected from the image data, the coordinate value of each corner of the component is obtained from the obtained edge data, and the coordinate value is compared with a preset reference value. Also, in order to inspect the soldering state of the mounting board, X
When the state of the soldering portion is detected from the X-ray transmission amount distribution by irradiating the X-ray, it is necessary to specify the inspection position. As a method of specifying the inspection position, a method of obtaining from the mounter data of the mounting board and a method of detecting the soldered portion from the X-ray transmission image are known.

[0003]

However, in the detection of the mounting position in the above-mentioned prior art, when the corner portion of the component is rounded or the image is picked up under an unfavorable condition and the contour is unclear. In addition, since it is difficult to detect the edge, there is a high possibility that the corner portion will be erroneously detected, and in particular, the misregistration amount of the rotational direction tends to be erroneously determined. (First Problem) Further, in the method of specifying the inspection position of the soldering inspection from the X-ray transmission image, an error occurs in the inspection position when the mounting position of the component is deviated or there is a soldering failure. There was a point (the second task). In view of the first problem, therefore, the object of the present invention is to accurately detect the positional coordinates of the object to be inspected and the deviation in the rotation direction from the image data by X-ray transmission, and further to detect the second problem. In view of the problem, an object of the present invention is to provide an X-ray inspection method that detects accurate component position data that specifies an inspection position.

[0004]

According to a first aspect of the present invention, an object to be inspected is irradiated with X-rays, and the position of the object to be inspected is determined from an X-ray transmission image transmitted through the object. In the X-ray inspection method for inspecting the quality of the object, the X-ray transmission image is binarized to obtain a binary image of the inspection object, and the barycentric coordinates of the inspection object are calculated from the binary image. The center line of the object to be inspected is calculated, the inclination thereof is obtained, the barycentric coordinates and the inclination of the center line are compared with a set reference value, and the quality of the position of the object to be inspected is judged from the difference. Is configured as an X-ray inspection method. When the object to be inspected is a component arranged on a mounting board, the X-ray transmission image is binarized to obtain a binary image by a threshold value that can detect a part that is a characteristic point of the inspection target component. The center coordinates of the feature points are obtained from the image, the barycentric coordinates of the component are calculated from the respective center coordinates, the inclination of the center line of the component is obtained from the center of gravity coordinates, and the barycentric coordinates and the inclination of the center line are set as a reference. It can be configured as an X-ray inspection method characterized by comparing the value with the value and judging the quality of the mounting position of the component from the difference. In a second aspect of the present invention, an X-ray is applied to a board before the part is mounted on a printed board, and the mounting position of the part is detected from a transmission image of the X-ray transmitted through the board.
In the line inspection method, the X-ray transmission image is binarized to obtain a binary image of the soldering land formed on the substrate, the center coordinates of each soldering land are obtained from the binary image, and the component placement data is obtained. Based on the above, the center of gravity coordinates of the part are calculated from the above center coordinates, the inclination of the center line of the part is obtained from the above center of gravity coordinates, the above center of gravity coordinates are the mounting position of the part, and the inclination of the center line is the mounting angle of the part. It can be configured as an X-ray inspection method characterized by creating mounting position data of the component. The center line in each of the inspection methods is made by detecting a straight line that minimizes the sum of squares of the distance from each pixel of the binary image.

[0005]

According to the first invention, the X-ray transmission image of the inspection object is binarized to obtain the binary image of the inspection object, and the center of gravity of the inspection object is calculated from the pixels forming the binary image. At the same time, by calculating a straight line that minimizes the sum of squares of the distance to each pixel, the barycentric coordinates of the component and the inclination of the center line are detected. By comparing this with a preset reference value, the quality of the position of the inspection object can be determined. Claim 1 corresponds to this. When the object to be inspected is a component mounted on the mounting board and having a high X-ray transmittance, it is difficult to obtain a binary image of the object to be inspected, and therefore it is characterized in that the soldered portion of the component has a low X-ray transmittance. Set as a point. From the binary image of the characteristic points, the barycentric coordinates of the component and the inclination of the center line can be detected. Claim 2 corresponds to this. Further, according to the second invention, a binary image of the soldering land formed on the substrate is obtained from the X-ray transmission image of the substrate on which no component is mounted, and the center coordinates of each soldering land are obtained. From the center coordinates, the barycentric coordinates of the parts attached to the soldering land are calculated. Calculate the inclination of the center line from the above center coordinates,
The center of gravity coordinates are detected as the mounting position of the component, and the inclination of the center line is detected as the mounting angle of the component. Claim 3 corresponds to this.

[0006]

Embodiments of the present invention will be described below with reference to the accompanying drawings for the understanding of the present invention. The following embodiments are examples embodying the present invention and do not limit the technical scope of the present invention. In the present embodiment, the quality of the mounting position of the component on the mounting substrate on which the component is mounted by soldering is inspected. here,
FIG. 1 is a flow chart showing the procedure of the X-ray inspection method according to the first embodiment of the present invention, and FIG. 2 is a block diagram showing the configuration of an X-ray inspection apparatus for executing the X-ray inspection method according to the embodiment. . As shown in FIG. 2, the mounting substrate 3 is irradiated with X-rays from the X-ray source 2, the transmitted X-rays are detected by the imaging plate 4, and the image reading device 7 creates an X-ray transmission amount distribution image. . This image data is A / D
After being converted, it is input to the computer 5. The computer 5 controls the X-ray control unit 6 to operate the X-ray irradiation position from the X-ray source 2 to obtain a transmission image of the entire surface of the mounting board 3 and also from the image data based on the input teaching data and the like. The quality of the mounting position of the component is determined. The procedure of the inspection method executed by the computer 5 will be described with reference to the flowchart shown in FIG. This inspection method is an inspection method of the mounting position of a component having a low X-ray transmittance such as a capacitor chip. Note that S1, S2, ... Shown in the figure are step numbers indicating the processing procedure, and coincide with the reference numerals in the text.

First, the X-ray transmission amount distribution image data of the mounting board 3 is input to the computer 5 (S1). Since the data of the mounting board 3 in a state where the components are mounted in the normal positions are stored in the computer 5 in advance as teaching data, the inspection area of the component to be inspected is set from this teaching data (S2). . The inspection area is binarized using a threshold value such that the entire component is binarized (S3). The barycentric coordinates (x _g , y _g ) of the component are calculated from the binary image by the following equation (1) (S4). In equation (1),
(X _i , y _i ) is the coordinate of each pixel of the binary image, and N is the total number of pixels of the binary image. x _g = Σx _i / N, y _g = Σy _i / N (1)

Next, the coordinates of each pixel of the binary image are coordinate-converted into a coordinate system having the center of gravity as the origin (S5). The coordinates of each pixel converted here are defined as (X _i , Y _i ).
The slope a of the straight line that minimizes the sum of squares of the distance from the coordinates of each pixel is calculated from the following equation (2) (S6). aΣX _i ² −aΣY _i ² + (a ² −1) ΣX _i Y _i = 0 (2) Equation (2) is the sum of squares of the distance between the straight line y = ax and the point (X _i , Y _i ). Is a modified expression of the least-squares method for deriving the slope a that minimizes, and is derived as follows. Straight line y =
The sum of squares Σl _i ² of the distance between ax and the point (X _i , Y _i ) is
It is expressed as the following formula (3). Σl _i ² = Σ {(aX _i −Y _i ) ² / (a ² +1)} (3) When the expression (3) is differentiated with respect to a, it is expressed as the following expression (4). ∂Σl _i ² / ∂a = 2 {aΣX _i ² −aΣY _i ² + (a ² −1) ΣX _i Y _i } / (a ² +1) ² (4) The sum of squares Σl _i ² represents the minimum value. The inclination a to be taken is given by the equation (4)
Since ∂Σl _i ² / ∂a = 0, the above equation (2) is derived. Since the coordinates of each pixel are converted into the coordinate system based on the barycentric coordinates in S5, the linear equation passing through the barycenter can be set as y = ax, which is the center line of the component. The barycentric coordinates and center line detected by the above processing are compared with the barycentric coordinates and center line inclination of the parts of the teaching data stored in the computer 5, and the absolute value of the difference is calculated as the deviation amount of the parts ( S7). The calculated deviation amount is compared with the tolerance value of the deviation amount preset by the operator (S8), and the quality of the component position is determined by whether or not it is within the tolerance range (S9). The above is the position detection of the parts with low X-ray transmittance such as chip parts.
The inspection method for the case of a component having a high X-ray transmittance such as an IC component will be described below as a second embodiment.

FIG. 3 is a flow chart showing the procedure of the component position inspection according to the second embodiment, FIG. 4 is a side view showing an example of a soldering part of an IC component, and FIG. It is a schematic diagram which shows the example of a value image. The inspection procedure according to the second embodiment will be described with reference to the flowchart shown in FIG. Note that S1, S2, ... Shown in the figure are step numbers indicating the processing procedure, and coincide with the reference numerals in the text. First, the X-ray transmission amount distribution image data is input to the computer 5 (S1). An area in which the feature points of the component to be inspected are easily obtained from the teaching data for this image is set as the inspection area (S2).
As a characteristic point, in the case of an IC component having high X-ray transmittance, it is difficult to obtain an image of the component body, but as shown in FIG. 4, the solder portion 9 at the position where the lead 8 rises from the soldering land 10 becomes thick. Therefore, the X-ray transmittance is low and it is detected as a clear image. This lead rising position can be used as a characteristic point. Therefore, the inspection area image is binarized with a threshold value such that the rising position of the lead 8 can be binarized using the rising position of the lead 8 (S3). Since the leads 8 of the IC component are symmetrically arranged on both sides of the component, the binary image is as shown in FIG. The hatched portion shown in FIG. 5 is the rising position of the lead, that is, the feature point 11. The center coordinates of the feature point 11 are detected from the binary image (S4). This is performed for all feature points 11 (S5). The barycentric coordinates (x _g , y _g ) of the component are calculated from the obtained center coordinates (S6). Each center coordinate (x _c , y _c ) is converted into a coordinate system with the barycentric coordinate as the origin (S7). Let each transformed center coordinate be (X _i , Y _i ). The slope a of the straight line that minimizes the sum of squares of the distances from the center coordinates (X _i , Y _i ) is calculated by the above equation (2) (S8). This straight line becomes the center line 12 of the mounted components as shown in FIG. The barycentric coordinates and center line detected by the above processing are compared with the barycentric coordinates and center line inclination of the parts of the teaching data stored in the computer 5, and the absolute value of the difference is calculated as the deviation amount of the parts ( S9). The calculated deviation amount is compared with the allowable value of the deviation amount set in advance by the operator (S10), and the quality of the component position is determined by whether the deviation amount is within the allowable range (S11). In the above inspection method, it is also possible to detect the apex of the solder portion 9 formed at the rising position of the lead 8 and replace this point (x _p , y _p ) with the central coordinate, and execute the processing from S5 onward. .

Next, an example of creating teaching data stored in the computer 5 for executing the above-described inspection method or teaching data indicating a component position for soldering inspection by X-ray transmission will be described as a third embodiment. To do. Here, FIG. 6 is a schematic diagram showing the configuration of the X-ray inspection teaching data creation device, and FIG. 7 is a flowchart showing the procedure of teaching data creation. In FIG. 6, a substrate 13 on which no component is mounted is arranged in the X-ray inspection apparatus 1 shown in FIG. 2, and X-rays are emitted from the X-ray source 2 and detected by the imaging plate 4. The transmitted X-ray is input to the image reading device 7. This board 1
Teaching data is created by the teaching data creating device 19 using the X-ray transmission image of No. 3. The procedure for creating this teaching data will be described below with reference to the flowchart in FIG. The X-ray inspection apparatus 1 obtains an X-ray transmission image of the substrate 13 (S1), and this is input to the teaching data creation apparatus 19. The image data is once stored in the board image storage unit 15,
The land image extracting unit 14 binarizes the soldering lands formed on the substrate 13 by a threshold value that can be extracted,
A binary image is created (S2). By displaying this binary image on the display 17 and designating a soldering land by the input device 18 such as a mouse (S3), the center coordinates of the soldering land designated by the arithmetic processing unit 16 are calculated ( S4). From the data (number of electrodes and leads) of the component attached to the soldering land, the center of gravity coordinate of the component is calculated using each center coordinate (S5). The center coordinates of each soldering land are converted into a coordinate system with the barycentric coordinates as the origin (S6). Further, the slope of the straight line that minimizes the sum of squares of the distances to the respective transformed center coordinates is calculated by the above-described equation (2) (S7). Teaching data is created with the barycentric coordinates obtained here as the mounting position of the component and the inclination of the straight line as the mounting angle of the component. This teaching data is input to the computer 5 and used for inspection of the component mounting position of the mounting board using the board 13 or for soldering inspection.

[0011]

As described above, according to the first invention of the present application, the X-ray transmission image of the inspection object is binarized to obtain the binary image of the inspection object, and the pixels forming the binary image are obtained. By calculating the center of gravity of the object to be inspected and the straight line that minimizes the sum of squares of the distances from the respective pixels, the barycentric coordinates of the component and the inclination of the center line are detected. By comparing this with a preset reference value, the quality of the position of the inspection object can be determined. Not only uncertain edge information that depends on the threshold of binarization but also the information of the entire object, which mostly consists of the confirmed information, is used to detect the amount of deviation in the rotation direction even from images where corner detection is difficult. be able to.
(Claim 1) When the object to be inspected is a component mounted on a mounting board and having a high X-ray transmittance, it is difficult to obtain a binary image of the object to be inspected. The low point of is set as the feature point. From the binary image of the characteristic points, the barycentric coordinates of the component and the inclination of the center line can be detected. Since the barycentric coordinates of the component and the inclination of the center line can be detected from the feature points where a binary image can be easily obtained, it is possible to detect the amount of positional deviation even from an unclear image that is difficult to binarize. (Claim 2)

According to the second invention of the present application, the binary image of the soldering land formed on the substrate is obtained from the X-ray transmission image of the substrate on which no component is mounted, and the center of each soldering land is obtained. The coordinates are obtained, and the barycentric coordinates of the component attached to the soldering land are calculated from each center coordinate. The inclination of the center line is calculated from the respective center coordinates, the barycentric coordinate is detected as the mounting position of the component, and the inclination of the center line is detected as the mounting angle of the component, and this is used as the reference value. Since the reference value is detected from the original board of the mounting board to be inspected, the quality of the mounting position can be accurately determined. (Claim 3)

[Brief description of drawings]

FIG. 1 is a flowchart showing an inspection procedure according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of an X-ray inspection apparatus according to an embodiment.

FIG. 3 is a flowchart showing an inspection procedure according to the second embodiment.

FIG. 4 is a side view of a soldering portion which is a characteristic point according to the second embodiment.

FIG. 5 is a schematic diagram showing distribution of feature points according to the second embodiment.

FIG. 6 is a block diagram showing the configuration of a teaching data creation device according to a third embodiment.

FIG. 7 is a flowchart showing an inspection procedure according to the third embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... X-ray inspection apparatus 2 ... X-ray source 3 ... Mounting board 4 ... Imaging plate 5 ... Calculator 11 ... Characteristic point 12 ... Center line 13 ... Board 19 ... Teaching data creation apparatus

Claims (4)

[Claims] 1. An X-ray inspection method for irradiating an object to be inspected with X-rays and inspecting the quality of the position of the object to be inspected from the X-ray image transmitted through the object to be inspected. The binary image of the inspection object is obtained by binarization, the barycentric coordinates of the inspection object are calculated from the binary image, the center line of the inspection object is calculated from the barycentric coordinates, and the inclination thereof is calculated. An X-ray inspection method characterized in that the barycentric coordinates and the inclination of the center line are compared with a set reference value, and the quality of the position of the inspection object is judged from the difference. 2. An X-ray for inspecting the mounting position of the component from a transmission image of the X-ray transmitted through the mounting substrate by irradiating the mounting substrate on which the component is mounted on the printed circuit board by soldering. In the inspection method, a binary image is obtained by binarizing the X-ray transmission image with a threshold value capable of detecting a plurality of feature points symmetrically arranged on the component, and each of the feature points is obtained from the binary image. The center coordinates of the part are calculated, the barycentric coordinates of the part are calculated from the respective center coordinates, the centerline of the part is calculated from the barycentric coordinates, the inclination thereof is calculated, and the barycenter coordinates and the inclination of the centerline are set as a reference. An X-ray inspection method characterized by comparing the value with a value and judging the quality of the mounting position of the component from the difference. 3. An X-ray inspection method for irradiating a board before mounting a component on a printed board with X-rays and detecting a mounting position of the component from a transmission image of the X-rays transmitted through the board. The X-ray transmission image is binarized to obtain the binary image of the soldering land formed on the board, the center coordinates of each soldering land are obtained from the binary image, and the above-mentioned each is obtained based on the component arrangement data. The center of gravity of the part is calculated from the center coordinates, the center line of the part is calculated from the center of gravity coordinates, and the inclination is obtained. The center of gravity coordinates are the mounting position of the part, and the inclination of the center line is the mounting angle of the part. An X-ray inspection method comprising detecting the mounting position of the. 4. The X-ray inspection method according to claim 1, 2, or 3, wherein the center line is calculated by detecting a straight line having a minimum sum of squares of distances from pixels of a binary image.