JP4760072B2 - X-ray inspection apparatus and X-ray inspection method - Google Patents

Description

  The present invention relates to an X-ray inspection apparatus and an inspection method, and more particularly to a method for correcting measured dimension data in order to perform a high-accuracy inspection of a component mounting state on a mounted printed board.

In a conventional X-ray inspection apparatus, as a method for measuring a dimension of a measurement target whose imaging magnification is unknown, as shown in FIG. 6, an X-ray irradiation unit 601 and an X-ray imaging unit 602 are arranged to face each other, and On the optical path of the X-ray light 603 irradiated from the irradiation unit 601, the measurement object 604 and the reference block 605 whose dimensions are known are arranged at the same distance from the X-ray imaging unit 602, and the measurement object 604 and the reference block are arranged. An X-ray transmission image 605 is taken on the same screen. Next, the photographed X-ray transmission image is subjected to image processing such as contour extraction using the image processing unit 606, and then the transmission unit of the reference block 605 subjected to image processing using the dimension measurement unit 607. Count the number of pixels in the known size range, divide the known size of the reference block 605 by the counted number of pixels to calculate the size per pixel on the X-ray transmission image, and calculate one pixel Dimension measurement is performed by integrating the per-dimension and the number of pixels between two points for distance measurement on the X-ray transmission image, and the photographed X-ray transmission image and the dimension measurement result are displayed on the image display means 608. By doing so, high-accuracy dimension measurement of a measurement object whose shooting magnification is unknown is performed. (See Patent Document 1).
JP-A 63-173907

  However, in the conventional configuration, as shown in FIG. 7, the measurement object 703 disposed on the optical path of the X-ray light 702 emitted from the X-ray irradiation means 701 is, for example, a printed board curved by component mounting. In the case of having the curved region 704, even if the reference block 705 and the measurement target 703 whose dimensions are known are arranged at the same height from the X-ray imaging unit 706, the curved region 704 and the reference block 705 of the measurement target 703 Since the heights are different, there is a difference in imaging magnification between the curved region image 709 of the measurement target image 708 on the captured X-ray transmission image 707 and the reference block image 710, which is calculated from the known dimensions of the reference block 705. When the dimension measurement of the curved region image 709 of the measurement target image 708 is performed using the dimension data per pixel, an error due to a difference in photographing magnification occurs. And, there is a problem that highly accurate dimension measurement can not be performed.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an X-ray inspection apparatus capable of measuring a dimension with high accuracy in the entire measurement target region even in a measurement target having a curved region.

In order to solve the conventional problems, an X-ray inspection apparatus according to the present invention is arranged with an X-ray irradiation means for irradiating a measurement object with cone-beam X-rays, and a known distance from the X-ray irradiation means. is an X-ray imaging means having a flat receiving surface for capturing the transmitted X-ray of the measurement object, a moving means for moving parallel to the measurement object with respect to the light-receiving surface of the X-ray imaging means, and moving distance calculating means for calculating the movement distance on the transmission image of the set reference region with the travel distance between the measurement object of the moving means, the moving distance of the moving means which is calculated by the moving distance calculating unit And a photographing magnification calculating means for calculating a photographing magnification for each unit pixel of the transmission image of the measurement object based on a moving distance of the reference region on the transmission image, and the height of the measurement object is different. The distance on the transparent image of two points Correction is performed using the calculated imaging magnification for each unit pixel, and the distances on the measurement object at two points having different heights that form an image on the light receiving surface of the X-ray imaging unit are obtained. It is what.

  According to the X-ray inspection apparatus and X-ray inspection method of the present invention, even when the measurement target is imaged at different magnifications for each measurement region due to curvature or the like, the imaging magnification of those regions is measured and the captured X By calculating the imaging magnification for each unit pixel of the line transmission image and correcting the dimension data to be measured based on the imaging magnification for each unit pixel, highly accurate dimension measurement can be performed.

  Embodiments of the X-ray inspection apparatus of the present invention will be described below in detail with reference to the drawings.

  FIG. 1 shows a configuration diagram of an X-ray inspection apparatus according to Embodiment 1 of the present invention.

  In FIG. 1, an X-ray inspection apparatus according to the present invention includes an X-ray irradiation means 102 for irradiating cone-beam X-ray light 101, and X-ray light 101 transmitted through a measurement object 103 and incident on a light receiving surface. X-ray imaging means 104 for converting to an image, moving means 105 for moving the measuring object 103 in parallel with the light receiving surface of the X-ray imaging means 104, coordinates for searching for the reference region 106 on the measuring object 103 in advance, The search area setting means 107 for setting shape information and the like, the reference area extraction means 108 for extracting the reference area 106 from the photographed X-ray transmission image, and the coordinates of the reference area 106 extracted by the reference area extraction means 108 Reference area coordinate calculation means 109 to be calculated, movement control means 110 for moving the measurement object 103 using the movement means 105, and measurement object moved by the movement means 105 A moving distance calculating unit 111 that calculates a moving distance of 03 and a moving distance of the reference region 106 in the X-ray imaging unit, and an imaging magnification calculating unit 112 that calculates an imaging magnification of the reference region 106 based on the moving distance of the reference region 106. And a dimension measuring means 113 for measuring the dimension of the measuring object 103 using the calculated imaging magnification, and an image display means 114 for displaying the dimension measurement result and the X-ray transmission image.

  Then, the imaging magnification of each unit pixel of the X-ray transmission image is calculated from the imaging magnification of the reference region 106 on the measurement object 103 from a plurality of X-ray transmission images acquired by moving the measurement object 103. The X-ray inspection apparatus performs highly accurate dimension measurement by correcting the dimension of the X-ray transmission image using the imaging magnification.

  Note that, by moving the X-ray irradiation apparatus 102 and the X-ray imaging apparatus 104 in the moving apparatus 105 of the present embodiment, the same effect as the movement of the measurement target 103 can be obtained.

  Next, a method for calculating the imaging magnification of the measurement object will be described with reference to FIG.

In FIG. 2, cone beam-shaped X-ray light irradiated in the direction of the X-ray imaging unit 201 from the light emitting point 204 of the X-ray irradiation unit 203 located at a distance L2 from the light receiving surface 202 of the X-ray imaging unit 201. 205 is transmitted through the measuring object 206 at a distance L1 from the light receiving surface 202 of the X-ray imaging means 201 and then enters the light receiving surface 202, and the X-ray imaging apparatus 201 captures an X-ray transmission image 207. At this time, if a region formed of a material having a different X-ray transmittance from the peripheral region, such as a printed circuit board wiring pattern, on the measurement target 206 is defined as a reference region 208, the reference region 208 is defined as the peripheral region and the X-ray. Since the transmittance is different, the X-ray transmission image 207 is imaged as a region having a different image brightness like the reference region image 209. Therefore, by processing the X-ray transmission image 207 and extracting the reference region image 209, The coordinates of the reference area image 209 on the X-ray transmission image 207 are measured. Next, when the measurement object 206 is moved by a distance D1 parallel to the light receiving surface 202 and an X-ray transmission image is taken, the reference area image 210 taken after the movement is separated from the position of the reference area image 209 before the movement by a distance D2. Since the image is taken at the position, the distance L1 from the light receiving surface 202 to the measuring object 206, the distance L2 from the light receiving surface 202 to the light emitting point 204, the moving distance D1 of the measuring object 206, the reference region image on the X-ray transmission image The relationship of the movement distance D2 from 209 to 210 is expressed by Equation 1.
(L2−L1): L2 = D1: D2 (Equation 1)
From Equation 1, the distance L1 from the light receiving surface 202 to the measurement object 206 is calculated by Equation 2.

L1 = L2 (1-D1 / D2) (Formula 2)
Therefore, even when the measurement target has a curved region such as a printed circuit board, the distance L1 to the reference region 208 on the measurement target 206 can be calculated by measuring the distances L2, D1, and D2. Thus, the photographing magnification M of the reference area 208 is expressed by Equation 3.

M = L2 / (L2-L1) = D2 / D1 (Formula 3)
In addition, in the height measurement method of the measurement target of this example, the measurement target was irradiated with a laser beam and the height was measured based on the principle of triangulation, or the image was taken using an external imaging means such as a camera. Measure the height of the object to be measured using a method of measuring the height by stereoscopic viewing using appearance images from multiple directions, and determine the imaging magnification of the X-ray transmission image from the measured height data. It is possible to calculate.

  Next, the reference region set on the measurement target will be described with reference to FIG. 3 using the case where the measurement target is a mounted printed board as an example.

  In FIG. 3, chip components 302 such as resistors and capacitors, and IC components such as a QFP (Quad Flat Package) 303 are mounted on a printed circuit board 301, and circuit connection of these components is performed on the printed circuit board 301. The wiring pattern 304 for performing and the correction mark 305 for mounting IC components, such as QFP303, with high precision are formed with copper foil. Since the wiring pattern 304 and the correction mark 305 formed of these copper foils have an X-ray transmittance of 1 to 10% lower than the glass fiber constituting the base material of the printed board 301, the X-ray transmission of the printed board 301 is reduced. When the image 306 is photographed, the wiring pattern 304 and the correction mark 305 on the printed circuit board 301 are photographed on the X-ray transmission image 306 with lower brightness than the surrounding area like the wiring pattern image 307 and the correction mark image 308. The As described above, an area where the luminance distribution changes on the X-ray transmission image 306 is set as a reference area, and coordinates and shape information of the surrounding area are set as the search area 309 in advance, and the X-ray transmission image 306 is captured. By searching the search area 309 and image-processing the reference areas such as the wiring pattern 304 and the correction mark 305 in the area, the coordinates of the reference area can be calculated.

  For the search area 309 set in this embodiment, for example, an area made of a material other than copper foil, such as the IC lead 310 of the QFP 303, can also be set to calculate the coordinates of the reference area. Become.

  The setting of the search area 309 of the printed circuit board 301 can be performed by using the design data of the printed circuit board 301 and the coordinate and shape information of the printed circuit board 301 acquired by performing dimension measurement in advance. When performing dimension measurement, the search area 309 can also be set by setting an area on the photographed X-ray transmission image.

  Next, the operation of the X-ray inspection apparatus will be described with reference to FIG.

  FIG. 4 shows a flowchart of the X-ray inspection apparatus in Embodiment 1 of the present invention.

In FIG. 4, first, in order to extract the wiring pattern serving as a reference area on the printed circuit board to be measured and the coordinates and shape of the reference area such as correction marks, a search area is set in step 401 and the set print is set. In step 402, the printed circuit board is moved so that the board search area is within the field of view, and in step 403, the first X-ray transmission image is taken. Next, the printed circuit board is moved on the XY plane parallel to the light receiving surface of the X-ray imaging means using Step 402 so that the search area falls within the imaging field of view. In Step 403, the second X-ray transmission image is scanned. Take a picture. Next, after confirming the completion of the second imaging in step 404, the images of the first and second X-ray transmission images that have been acquired, such as edge extraction and binarization processing in step 405, are obtained. In step 406, the XY coordinates of the wiring pattern, the edge portion of the reference region such as the correction mark, or the center are calculated. Next, from the XY coordinates of the reference area calculated from the first and second X-ray transmission images, the movement distance D2 is calculated from the relative position on the X-ray transmission image for each reference area in Step 407, By substituting the movement distance D1 of the printed circuit board when photographing the second X-ray transmission image and this movement distance D2 into Equation 3, the imaging magnification of each reference region set in step 408 is calculated. . Next, in step 409, data interpolation processing such as linear interpolation, quadratic spline interpolation, and cubic spline interpolation is performed using the XY coordinate data of each reference region and the calculated imaging magnification, and an X-ray transmission image is obtained. The photographing magnification of each unit pixel on the entire surface is calculated. Next, in step 410, dimension correction processing is performed on the dimension between any two points on the X-ray transmission image on which the dimension measurement is performed using the calculated imaging magnification data of the X-ray transmission image. By displaying the obtained X-ray transmission image and the dimension measurement result corrected in step 410 in step 411, the X-ray inspection apparatus according to the present invention enables highly accurate dimension measurement.

  Next, a dimensional measurement correction method using an X-ray transmission image whose imaging magnification is calculated will be described with reference to FIG.

次に、測定対象はそれぞれの単位画素ごとに撮影倍率で拡大され、Ｘ線撮像手段の受光面上に像を形成しているため、Ｘ線透過画像上で計測された２点間の寸法を撮影倍率で除算することにより、測定対象における２点間距離が求まるので、（数式５）のように、各画素を通過する直線の寸法を、直線が通過する領域の各単位画素の撮影倍率Ｍ_ｘｙで除算する。

そして、単位画素ごとに補正されたそれらの距離の値を加算することで、撮影倍率Ｍ_ｘｙで補正されたａ，ｂ間の寸法が算出され、プリント基板のような湾曲領域を有する測定対象についても、撮影倍率により寸法補正することで測定誤差の小さい高精度な寸法計測が可能になる。 When the measurement target has a curved region such as a printed circuit board, the distance from the light receiving surface of the curved printed circuit board varies depending on the position of the surface. Therefore, for each unit pixel of the X-ray transmission image of the photographed printed circuit board In order to measure the dimension between two points with different heights on the X-ray transmission image of the printed circuit board with high accuracy, calculate the shooting magnification of the unit pixel through which the straight line connecting these two points passes. It is necessary to perform dimension correction processing. Therefore, regarding the imaging magnification of the entire X-ray transmission image calculated in step 409 of FIG. 4, assuming that the imaging magnification for each unit pixel in the XY direction of the X-ray transmission image is M _xy , these X-rays The imaging magnification M _xy of each pixel of the transmission image is set as a magnification correction table 501 for performing magnification correction, and the captured X-ray transmission image pixel size 502 is assumed to be equal to the pixel size of the X-ray imaging unit. When measuring the dimension between the coordinate (x ₁ , y ₁ ) of the designated dimension measurement start position 503: a and the coordinate (x ₅ , y ₅ ) of the dimension measurement end position 504: b, two points a and b , And the boundary of the X-ray transmission image pixel, the intersection coordinates 505: (x ₂ , y ₂ ) and the intersection coordinates 506: (x ₃ , y ₃ ) in order from the distance measurement start position 503: a. ), Intersection coordinates 5 7: (x 4, _{y 4)} as to calculate the coordinates, to calculate the size of the straight line passing through each pixel of the X-ray transmission image by using the (Equation 4).

Next, since the measurement object is magnified by the photographing magnification for each unit pixel and an image is formed on the light receiving surface of the X-ray imaging means, the dimension between the two points measured on the X-ray transmission image is set. By dividing by the shooting magnification, the distance between the two points in the measurement object is obtained, so that the size of the straight line passing through each pixel is set as the shooting magnification M of each unit pixel in the area through which the straight line passes as shown in (Formula 5). Divide by _xy .

Then, by adding the distance values corrected for each unit pixel, the dimension between a and b corrected with the photographing magnification M _xy is calculated, and the measurement target having a curved region such as a printed circuit board is calculated. In addition, it is possible to perform highly accurate dimension measurement with a small measurement error by correcting the dimension according to the photographing magnification.

  The X-ray inspection apparatus and X-ray inspection method according to the present invention measure the imaging magnification of each region and measure the X-ray transmission of the image even when the measurement object has different imaging magnifications for each measurement region due to curvature or the like. By calculating the shooting magnification for each unit pixel of the image and performing dimension correction based on the shooting magnification, high-accuracy dimension measurement with small measurement error is possible. In order to perform an accurate inspection, it is useful as a method for correcting measured dimension data.

1 is an overall configuration diagram of an X-ray inspection apparatus according to Embodiment 1 of the present invention. The figure for demonstrating the imaging magnification calculation method of the X-ray inspection apparatus in Example 1 of this invention The figure for demonstrating the setting method of the reference | standard area | region and search area | region on the printed circuit board with which the X-ray inspection apparatus in Example 1 of this invention was mounted. The flowchart for demonstrating operation | movement of the X-ray inspection apparatus in Example 1 of this invention. The figure for demonstrating the dimension correction method of the X-ray inspection apparatus in Example 1 of this invention Configuration diagram of a conventional X-ray inspection device for measuring dimensions The figure for demonstrating the subject of the X-ray inspection apparatus which performs the conventional dimension measurement

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 X-ray light 102 X-ray irradiation means 103 Measurement object 104 X-ray imaging means 105 Movement means 106 Reference area 107 Search area setting means 108 Reference area extraction means 109 Reference area coordinate calculation means 110 Movement control means 111 Movement distance calculation means 112 Imaging | photography Magnification calculation means 113 Dimension measurement means 114 Image display means 201 X-ray imaging means 202 Light receiving surface 203 X-ray irradiation means 204 Light emitting point 205 X-ray light 206 Measurement object 207 X-ray transmission image 208 Reference area 209, 210 Reference area image 301 Print Substrate 302 Chip component 303 QFP
304 Wiring pattern 305 Correction mark 306 X-ray transmission image 307 Wiring pattern image 308 Correction mark image 309 Search area 310 IC lead 401 Search area setting 402 Measurement object movement 403 X-ray transmission image imaging 404 Imaging completion 405 Image processing 406 Reference area coordinate calculation 407 Reference area moving distance calculation 408 Reference area imaging magnification calculation 409 Image whole area imaging magnification calculation 410 Dimension correction processing 411 Measurement result display 501 Magnification correction table 502 X-ray transmission image pixel size 503 Dimension measurement start position 504 Dimension measurement end position 505 Intersection coordinates 1
506 Intersection coordinates 2
507 Intersection coordinates 3
601 X-ray irradiation means 602 X-ray imaging means 603 X-ray light 604 Measurement object 605 Reference block 606 Image processing means 607 Dimension measurement means 608 Image display means 701 X-ray irradiation means 702 X-ray light 703 Measurement object 704 Curved area 705 Reference block 706 X-ray imaging means 707 X-ray transmission image 708 Measurement target image 709 Curved region image 710 Reference block image

Claims (4)

X-ray irradiation means for irradiating a measurement object with cone-beam X-rays;
An X-ray imaging unit that is arranged at a known distance from the X-ray irradiation unit and includes a flat light receiving surface that images the transmitted X-rays of the measurement object;
Moving means for moving the measurement object parallel to the light receiving surface of the X-ray imaging means;
A moving distance calculating means for calculating a moving distance of the moving means and a moving distance on the transmission image of a reference area set for the measurement object;
An imaging magnification for calculating an imaging magnification for each unit pixel of the transmission image of the measurement object based on the movement distance of the movement unit calculated by the movement distance calculation unit and the movement distance on the transmission image of the reference region A calculation means;
With
An image was formed on the light-receiving surface of the X-ray imaging unit by correcting the distance on the transmission image at two points with different heights of the measurement object using the calculated imaging magnification for each unit pixel. An X-ray inspection apparatus characterized in that a distance on a measurement object at two points having different heights is obtained. 2. The imaging magnification M is represented by M = D2 / D1, where D1 is a moving distance of the moving means of the reference area and D2 is a moving distance of the reference area on the transmission image. X-ray inspection apparatus described in 1. A cone beam-shaped X-ray is irradiated onto the measurement object, and a transmission image of the measurement object is imaged by an X-ray imaging means having a flat light receiving surface,
Moving the measurement object parallel to the light receiving surface of the X-ray imaging means by a moving means to capture a transmission image of the measurement object;
The movement distance measuring means measures the movement distance of the movement means and the movement distance on the transmission image of the reference region set in the measurement object,
Based on the movement distance of the movement means measured by the movement distance measurement means and the movement distance on the transmission image of the reference region, the imaging magnification for each unit pixel of the transmission image of the measurement object is calculated, The distance formed on the transmission image at two points having different heights of the measurement object is corrected using the calculated imaging magnification for each unit pixel, and the image is formed on the light receiving surface of the X-ray imaging unit. An X-ray inspection method characterized by obtaining a distance on a measurement object at two points having different heights. 4. The imaging magnification M is expressed by M = D2 / D1, where D1 is a moving distance of the moving means of the reference area and D2 is a moving distance of the reference area on the transmission image. X-ray inspection method described in 1.

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