JP2010145359A - X-ray inspection device, method of x-ray inspection, and x-ray inspection program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray inspection device, a method of X-ray inspection, and an X-ray inspection program, for automatically extracting a surface of an object suitable for inspection thereof. <P>SOLUTION: This X-ray inspection device 100 is provided with: an X-ray source 10 for applying X rays to an inspecting object 1; an X-ray detector 23 for detecting the X rays having passed through the inspecting object 1; an X-ray detector drive 22 for moving the X-ray detector 23; an inspecting-object drive mechanism 110 for moving the inspecting object 1; and an arithmetic part 70. The arithmetic part 70 controls the X-ray source 10, the X-ray detector 23, etc., images the inspecting object 1 from a plurality of directions, and generates a plurality of tomographic images of the inspecting object 1 based on an imaging result. The arithmetic part 70 determines a tomographic image with the percentage of high luminance domain being high therein out of the tomographic images, and inspects the inspecting object 1 by using a tomographic image distant from the determined tomographic image by a prescribed distance corresponding to the shape characteristic of the inspecting object 1. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an X-ray inspection apparatus, an X-ray inspection method, and an X-ray inspection program for inspecting an inspection object using X-rays. In particular, the present invention relates to an X-ray inspection apparatus, an X-ray inspection method, and an X-ray inspection program used for inspecting the quality of a bond between a printed circuit board and a circuit component.

  Conventionally, X-ray CT (Computed Tomography) is often used to inspect the quality of a soldered state on a printed circuit board (hereinafter also simply referred to as “substrate”) to which a mounted component is soldered. In X-ray CT, an object is imaged with X-rays from a plurality of directions, and a plurality of fluoroscopic images showing the distribution of the degree of X-ray absorption (attenuation) are acquired. Furthermore, reconstruction processing based on a plurality of fluoroscopic images is performed to obtain two-dimensional data or three-dimensional data of the distribution of the X-ray absorption coefficient to be inspected. An image obtained by obtaining an absorption coefficient distribution in a two-dimensional space is particularly called a tomographic image.

  In the inspection of the soldering state using the tomographic image, it is necessary to determine the height to be inspected (inspection height). Here, “height” refers to coordinates in the normal direction (hereinafter referred to as the height direction) of the tomographic image.

  One conventional method for determining the inspection height is to focus on the wiring pattern on the substrate. For example, in the conventional technique described in Patent Document 1 (Japanese Patent Application Laid-Open No. 2006-292465), the edge information of the wiring pattern is used as a feature amount, and the height at which the feature amount is the largest is determined as the inspection height.

  With reference to FIG. 17 and FIG. 18, the X-ray inspection apparatus described in Patent Document 1 will be described in more detail. FIG. 17 is a diagram showing the configuration of the X-ray inspection apparatus described in Patent Document 1. As shown in FIG. In this X-ray inspection apparatus, a plurality of fluoroscopic images of the substrate 12 are captured by the X-ray detector 13a, and a tomographic image of the substrate 12 is reconstructed at a plurality of heights. The X-ray inspection apparatus uses the coordinates of the tomographic image having the maximum edge intensity among the tomographic images as the inspection position. FIG. 18 shows a tomographic image of the inspection position disclosed in Patent Document 1. Referring to FIG. 18, a wiring pattern is observed in this tomographic image. Note that FIG. 17 and the description thereof, and the reference numerals in FIG. 18 are in accordance with Patent Document 1, and are irrelevant to the reference numerals of other parts.

Patent Document 2 (Japanese Patent No. 3665294) obtains a plurality of horizontal slice images of an object, determines a target area perpendicular to the horizontal slice image based on the acquired horizontal slice image, and sets the target area. A method for detecting defects using vertical slice images is disclosed. In the method described in Patent Document 2, the best horizontal slice image is specified to synthesize a vertical slice image based on the total value of pixel values in each horizontal slice image. Further, Patent Document 2 discloses that the best horizontal slice image is specified for analyzing a defect based on the total value.
JP 2006-292465 A Japanese Patent No. 3665294

The method described in Patent Document 1 has the following problems.
(1) In this method, the user needs to manually set the position of the wiring pattern in the tomographic image at the inspection position. Due to this set time, this method results in a long inspection time.

  (2) In this method, a human error can occur. For example, in this method, there may be a variation in the inspection position by the setter or an erroneous setting in which the setter sets a position that is not a wiring pattern.

  (3) With this method, the inspection height cannot be obtained for a substrate having no wiring pattern on the tomographic plane. For example, this method cannot be used to inspect a substrate on which wiring is realized by three-dimensional wiring such as a through hole.

  (4) In this method, when the luminance (or SN ratio) of the wiring pattern is small in the reconstruction data, the inspection height cannot be obtained. Therefore, when the wiring is thin or thin, or formed of a metal having a small absorption coefficient, the inspection by this method may not be performed.

  (5) With this method, an error may occur during the inspection of the multilayer substrate. This is because when there are wiring patterns on a plurality of layers of the substrate, it cannot be determined which wiring pattern should be used as a mark to determine the inspection height.

  (6) In this method, when the joint between the substrate and the component is separated from the wiring pattern, the inspection may not be performed correctly. This is because the substrate to be inspected is warped due to heat denaturation or the like, and the height of the joint portion may vary depending on the position in the cross section. If the joint portion is separated from the wiring pattern, the joint portion that is actually inspected may not appear in the tomographic image at the obtained inspection height.

  The method described in Patent Document 2 uses a total value of pixel values in each of a plurality of horizontal slice images in order to specify a horizontal slice image used for inspection. However, this method is susceptible to noise generated in the horizontal slice image. In this method, when the pixel value of one or a plurality of horizontal slice images is changed from a correct value due to noise, an appropriate horizontal slice image may not be specified.

  The present invention has been made paying attention to such conventional problems, and provides an X-ray inspection apparatus, an X-ray inspection method, and an X-ray inspection program capable of automatically extracting a surface suitable for inspection. Let it be an issue.

  According to one aspect of the present invention, an X-ray inspection apparatus that inspects an object using X-rays, the object includes a substrate and a component that is electrically coupled to and mounted on the substrate, The component has a high absorption member having a high X-ray absorption coefficient compared to the substrate at a predetermined position in the component, and X-ray output means for outputting X-rays toward the object, and a plurality of directions to the object X-ray detection means for picking up a fluoroscopic image that represents the intensity distribution of X-rays incident through the object and the reference plane on which the substrate is arranged based on X-ray fluoroscopic images from a plurality of directions. Reconstructing means for reconstructing a plurality of parallel tomographic images, specifying means for identifying the position of the first tomographic image having a high proportion of the high-absorbing member among the plurality of tomographic images, and the position of the first tomographic image And a position separated from the first tomographic image by a predetermined distance based on the shape information of the component. And a test position determining means to the examination position for elephants thereof.

  According to another aspect of the present invention, an X-ray inspection apparatus that inspects an object using X-rays, the object including a substrate and a component that is mounted by being electrically coupled to the substrate, The component has a high absorption member having a high X-ray absorption coefficient compared to the substrate at a predetermined position in the component, and X-ray output means for outputting X-rays toward the object, and a plurality of directions to the object X-ray detection means for picking up a fluoroscopic image that represents the intensity distribution of X-rays incident through the object and the reference plane on which the substrate is arranged based on X-ray fluoroscopic images from a plurality of directions. Reconstructing means for reconstructing a plurality of parallel tomographic images, specifying means for identifying the position of the first tomographic image having a high proportion of the high-absorbing member among the plurality of tomographic images, and the position of the first tomographic image And a second section separated from the first tomographic image by a predetermined distance based on the shape information of the part. Acquiring an image, and a test means for determining the quality of an object by using the second tomographic images.

  Preferably, the high absorption member is a member that connects the component and the substrate, and the second tomographic image corresponds to a connection portion between the component and the substrate.

More preferably, the high absorption member is solder.
More preferably, the part is a ball grid array.

  Preferably, the specifying unit obtains a variance of luminance values of each tomographic image and specifies a position of the tomographic image having the largest variance.

  Preferably, the image processing apparatus further includes a dividing unit that acquires a plurality of partial images included in each of the plurality of partial regions from each tomographic image, and the specifying unit has a ratio of the partial images of each tomographic image for each partial region. The position of the high first partial image is extracted, and the inspection position determining means is a position separated from the first partial image by a predetermined distance for each partial region based on the position and shape information of the first partial image. Is the inspection position of the object.

  Preferably, the image processing apparatus further includes a dividing unit that acquires a plurality of partial images included in each of the plurality of partial regions from each tomographic image, and the specifying unit has a ratio of the partial images of each tomographic image for each partial region. The position of the high first partial image is extracted, and for each partial region, the inspection unit determines a second distance apart from the first partial image by a predetermined distance based on the position and shape information of the first partial image. A partial image is acquired, and the quality of the object is determined using the second partial image.

  More preferably, the dividing unit extracts a bright region in which bright pixels having luminance exceeding a predetermined threshold value are extracted from the extracted tomographic image, and sets a region including a predetermined number of bright regions as a partial region.

Preferably, a moving mechanism for moving the object along the reference plane is further provided.
More preferably, the moving mechanism includes a rail that sandwiches the substrate.

  According to still another aspect of the present invention, there is provided an X-ray inspection method for inspecting an object using X-rays, the object including a substrate and a component mounted by being electrically coupled to the substrate. The component has a high-absorption member having a higher X-ray absorption coefficient than that of the substrate at a predetermined position in the component, and outputs X-rays toward the object, and enters the object from a plurality of directions. And taking a fluoroscopic image representing the intensity distribution of the X-rays transmitted through the object, and a plurality of tomograms each parallel to a reference plane on which the substrate is arranged, based on the X-ray fluoroscopic images from a plurality of directions. Based on the step of reconstructing the image, the step of identifying the position of the first tomographic image having a high proportion of the high absorption member among the plurality of tomographic images, the position of the first tomographic image and the shape information of the parts A position that is a predetermined distance away from the first tomographic image And determining as a test position.

  According to still another aspect of the present invention, there is provided an X-ray inspection method for inspecting an object using X-rays, the object including a substrate and a component mounted by being electrically coupled to the substrate. The component has a high-absorption member having a higher X-ray absorption coefficient than that of the substrate at a predetermined position in the component, and outputs X-rays toward the object, and enters the object from a plurality of directions. And taking a fluoroscopic image representing the intensity distribution of the X-rays transmitted through the object, and a plurality of tomograms each parallel to a reference plane on which the substrate is arranged, based on the X-ray fluoroscopic images from a plurality of directions. Based on the step of reconstructing the image, the step of identifying the position of the first tomographic image having a high proportion of the high absorption member among the plurality of tomographic images, the position of the first tomographic image and the shape information of the parts The second tomographic image separated from the first tomographic image by a predetermined distance Comprising obtaining, and determining the quality of the object using the second tomographic images.

  According to still another aspect of the present invention, an X-ray inspection program for causing an X-ray inspection apparatus having an X-ray source, an X-ray detector, and a calculation unit to execute an inspection of an object using X-rays, The object includes a board and a component that is electrically coupled to the board, and the component has a high-absorption member having a higher X-ray absorption coefficient than that of the board at a predetermined position in the component. The operation unit controls the X-ray source so that the X-ray source outputs X-rays toward the object; and the operation unit causes the X-ray detector to enter the object from a plurality of directions. The step of controlling the X-ray detector so as to capture a fluoroscopic image representing the intensity distribution of the X-rays transmitted through the object, and the computing unit based on the X-ray fluoroscopic images from a plurality of directions Reconstructing a plurality of tomographic images each parallel to a reference plane where The step of identifying the position of the first tomographic image in which the ratio of the high-absorbing member is high in the layer image, and the arithmetic unit from the first tomographic image based on the position of the first tomographic image and the shape information of the component Determining a position separated by a predetermined distance as the inspection position of the object.

  According to still another aspect of the present invention, an X-ray inspection program for causing an X-ray inspection apparatus having an X-ray source, an X-ray detector, and a calculation unit to execute an inspection of an object using X-rays, The object includes a board and a component that is electrically coupled to the board, and the component has a high-absorption member having a higher X-ray absorption coefficient than that of the board at a predetermined position in the component. The operation unit controls the X-ray source so that the X-ray source outputs X-rays toward the object; and the operation unit causes the X-ray detector to enter the object from a plurality of directions. The step of controlling the X-ray detector so as to capture a fluoroscopic image representing the intensity distribution of the X-rays transmitted through the object, and the computing unit based on the X-ray fluoroscopic images from a plurality of directions Reconstructing a plurality of tomographic images each parallel to a reference plane where The step of identifying the position of the first tomographic image in which the ratio of the high-absorbing member is high in the layer image, and the arithmetic unit from the first tomographic image based on the position of the first tomographic image and the shape information of the component A step of obtaining a second tomographic image separated by a predetermined distance, and a step of determining whether the object is good or bad by using the second tomographic image.

  According to the present invention, a position of a tomographic image having a high ratio of a portion in which a lot of X-rays are absorbed is extracted from a plurality of tomographic images parallel to the arrangement surface of the substrate included in the inspection target. Then, based on the position of the extracted tomographic image and the shape characteristics of the components arranged on the substrate, the substrate is inspected using the tomographic image separated from the extracted tomographic image by a predetermined distance. As a result, according to the present invention, it is possible to automatically inspect a substrate using a surface suitable for inspection.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

[First Embodiment]
(Outline of configuration)
With reference to FIG. 1, the structure of the X-ray inspection apparatus 100 which concerns on 1st Embodiment is demonstrated. FIG. 1 is a schematic block diagram of an X-ray inspection apparatus 100 according to the first embodiment.

  The X-ray inspection apparatus 100 includes an X-ray source 10 that outputs X-rays 18, an X-ray detector 23, an image acquisition control mechanism 30, and an inspection target drive mechanism 110 that moves the position of the inspection target 1. Furthermore, the X-ray inspection apparatus 100 includes an input unit 40, an output unit 50, an X-ray source control mechanism 60, an inspection target position control mechanism 120, a calculation unit 70, and a storage unit 90.

  The inspection object 1 is disposed between the X-ray source 10 and the X-ray detector 23. In this embodiment, it is assumed that the inspection target 1 is a circuit board on which components are mounted. In FIG. 1, the X-ray source 10, the inspection object 1, and the X-ray detector 23 are installed in order from the bottom, but from the viewpoint of maintainability of the X-ray source, the X-ray detector 23, These may be arranged in a line with the inspection object 1 and the X-ray source 10.

  The X-ray source 10 is controlled by the X-ray source control mechanism 60 and irradiates the examination object 1 with the X-ray 18. In the present embodiment, it is assumed that the inspection target 1 is a board on which circuit components are mounted.

  The inspection object 1 is moved by the inspection object driving mechanism 110. A specific configuration of the inspection target drive mechanism 110 will be described later. The inspection target position control mechanism 120 controls the operation of the inspection target drive mechanism 110 based on an instruction from the calculation unit 70.

  The X-ray detector 23 is a two-dimensional X-ray detector that detects and images the X-ray output from the X-ray source 10 and transmitted through the inspection object 1. As the X-ray detector 23, I.I. I. An (Image Intensifier) tube or an FPD (Flat Panel Detector) can be used. From the viewpoint of installation space, it is desirable to use FPD for the X-ray detector 23. Further, the X-ray detector 23 is preferably highly sensitive so that it can be used for in-line inspection, and is particularly preferably a direct conversion FPD using CdTe.

  The image acquisition control mechanism 30 includes a detector drive control mechanism 32 and an image data acquisition unit 34. The detector drive control mechanism 32 controls the operation of the X-ray detector drive unit 22 and moves the X-ray detector 23 based on an instruction from the calculation unit 70. The image data acquisition unit 34 acquires the image data of the X-ray detector 23 specified from the calculation unit 70.

  The input unit 40 is an operation input device for receiving an instruction input from the user. The output unit 50 is a device that outputs measurement results and the like to the outside. In the present embodiment, the output unit 50 is a display for displaying an X-ray image or the like configured by the calculation unit 70.

  That is, the user can execute various inputs via the input unit 40, and various calculation results obtained by the processing of the calculation unit 70 are displayed on the output unit 50. The image displayed on the output unit 50 may be output for visual quality judgment by the user, or may be output as a quality judgment result of a quality judgment unit 78 described later.

  The X-ray source control mechanism 60 includes an electron beam control unit 62 that controls the output of the electron beam. The electron beam control unit 62 receives an X-ray focal position and X-ray energy (tube voltage, tube current) designation from the calculation unit 70. The designated X-ray energy varies depending on the configuration of the inspection object.

  The calculation unit 70 executes a program 96 stored in the storage unit 90 to control each unit, and performs predetermined calculation processing. The calculation unit 70 includes an X-ray source control unit 72, an image acquisition control unit 74, a reconstruction unit 76, a quality determination unit 78, an inspection target position control unit 80, an X-ray focal position calculation unit 82, and an imaging. A condition setting unit 84.

  The X-ray source control unit 72 determines the X-ray focal position and X-ray energy, and sends a command to the X-ray source control mechanism 60.

  The image acquisition control unit 74 sends a command to the image acquisition control mechanism 30 so that the X-ray detector 23 acquires an image. Further, the image acquisition control unit 74 acquires image data from the image acquisition control mechanism 30.

  The reconstruction unit 76 reconstructs three-dimensional data from a plurality of image data acquired by the image acquisition control unit 74.

  The pass / fail judgment unit 78 obtains the height of the board surface (board height) on which the component is mounted, and judges pass / fail of the inspection object based on the tomographic image of the board height. In addition, since the algorithm for performing pass / fail judgment or the input information to the algorithm varies depending on the inspection object, the pass / fail judgment unit 78 obtains them from the imaging condition information 94.

  The inspection target position control unit 80 controls the inspection target drive mechanism 110 via the inspection target position control mechanism 120.

  When inspecting an inspection area where the inspection object 1 is present, the X-ray focal position calculation unit 82 calculates an X-ray focal position and an irradiation angle with respect to the inspection area.

  The imaging condition setting unit 84 sets conditions (for example, applied voltage to the X-ray source, imaging time, etc.) when outputting X-rays from the X-ray source 10 according to the inspection object 1.

  The storage unit 90 includes X-ray focal position information 92, imaging condition information 94, a program 96 for realizing each function executed by the arithmetic unit 70, and image data 98 captured by the X-ray detector 23. including. The X-ray focal position information 92 includes the X-ray focal position calculated by the X-ray focal position calculator 82. The imaging condition information 94 includes information regarding the imaging conditions set by the imaging condition setting unit 84 and an algorithm for determining pass / fail.

  The storage unit 90 only needs to be capable of storing data. The storage unit 90 includes, for example, a storage device such as a RAM (Random Access Memory), an EEPROM (Electrically Erasable and Programmable Read-Only Memory), and an HDD (Hard Disc Drive).

(Specific configuration)
A specific configuration of the X-ray inspection apparatus 100 according to the first embodiment will be described with reference to FIG. FIG. 2 is a diagram for explaining the configuration of the X-ray inspection apparatus 100 according to the first embodiment. In FIG. 2, the same parts as those in FIG. Also, in FIG. 2, among the parts shown in FIG. 1, the parts necessary for explanation are extracted and directly related to the control of the X-ray focal position, the control of the X-ray detector position, the control of the inspection target position, and the like. is doing.

  In the present embodiment, the X-ray source 10 is a scanning X-ray source capable of extending the X-ray generation position (X-ray focal position) along one direction. The X-ray source 10 generates X-rays according to a command from the calculation unit 70 that has passed through the X-ray source control mechanism 60.

  In FIG. 2, the same parts as those in FIG. Also, in FIG. 2, among the parts shown in FIG. 1, the parts necessary for explanation are extracted and directly related to the control of the X-ray focal position, the control of the X-ray detector position, the control of the inspection target position, and the like. is doing.

  The X-ray source 10 is a sealed X-ray source, and is installed on the upper or lower portion of the X-ray inspection apparatus 100. The target of the X-ray source 10 may be a transmissive type or a reflective type. The X-ray source 10 is attached to an operating part (not shown) and is movable in the vertical direction.

  The X-ray detector 23 is disposed at a position facing the X-ray source 10 so as to sandwich the inspection object 1 (substrate). The X-ray detector 23 images the X-rays emitted from the X-ray source 10. The X-ray detector 23 is attached to the X-ray detector driving unit 22. The X-ray detector driving unit 22 is a three-dimensional stage, and can move the X-ray detector 23 in the horizontal direction and the vertical direction.

  The inspection object drive mechanism 110 is installed between the X-ray source 10 and the X-ray detector 23. The inspection object driving mechanism 110 includes stages 111a and 111b and substrate rails 112a and 112b attached to the stages 111a and 111b. The stages 111a and 111b are capable of translating the inspection object 1 in the horizontal direction. The board rails 112a and 112b each fix the board by sandwiching the inspection object 1 from above and below.

  Referring to FIG. 2, the X-ray inspection apparatus 100 includes a displacement meter 114 and an optical camera 116 (these are not shown in FIG. 1). The displacement meter 114 measures the distance to the substrate. Therefore, the displacement meter 114 can measure the warpage of the substrate, which will be described in detail later. The optical camera 116 images the substrate with visible light. The optical camera 116 is used for photographing a fiducial mark for setting a position to be inspected. The displacement meter 114 and the optical camera 116 are retracted to an area where X-rays are not irradiated by a retracting mechanism (not shown) so as not to be exposed to X-rays during imaging with X-rays.

  With the above configuration, the X-ray inspection apparatus 100 can change the ratio (enlargement ratio) between the source-substrate distance and the source-detector distance. As a result, the X-ray inspection apparatus 100 can change the size (and therefore the resolution) of the inspection object 1 imaged by the X-ray detector 23.

  In addition, the X-ray inspection apparatus 100 can operate the substrate and the X-ray detector 23 so that the substrate can be imaged from various directions. In the present embodiment, three-dimensional data of the object 1 is generated using a three-dimensional data generation method called CT (Computed Tomography) based on the imaging results from various directions.

  In the present embodiment, X-ray inspection apparatus 100 is used for in-line inspection. For in-line inspection, the inspection object driving mechanism 110 further includes a mechanism for carrying in and out the substrate. However, such a substrate loading / unloading mechanism is not shown in FIG. As a substrate carry-in / out mechanism, a belt conveyor disposed on a substrate rail is generally used. Alternatively, a rod called a pusher may be used as the carry-in / out mechanism. A board | substrate can be moved by sliding a board | substrate on a rail with a pusher.

  Here, the arrangement of the inspection object 1 will be described in detail with reference to FIG. FIG. 3 is a side view of the inspection object 1 and its surroundings. Referring to FIG. 3, the printed circuit board included in inspection object 1 is fixed by a pair of rails 112. Each rail 112 sandwiches the left end or right end of the inspection object 1 from above and below, and fixes the printed circuit board.

  The rail 112 can move the inspection target in the horizontal (XY) and vertical (Z) directions according to a command from the inspection target position control unit 80. In the present embodiment, the inspection object driving mechanism 110 conveys the inspection object 1 along a conveyance surface that is substantially parallel to the horizontal plane, that is, the normal direction is substantially the Z direction. Here, “the normal direction is substantially the Z direction” means that the conveyance surface may be inclined from the horizontal plane within a range that does not hinder the inspection (for example, 0 to 5 degrees).

  As shown in FIG. 3, the printed circuit board is warped. Since mounting a component on a printed circuit board includes a heat treatment step such as reflow, the printed circuit board is generally deformed by heat and warps. In the case of a normal appearance inspection, the warpage of the substrate can be reduced by a support bar called a backup pin. However, the backup pin cannot be used in the X-ray inspection because the backup pin appears in the image. The inspection object drive mechanism 110 shown in the figure does not cover the upper and lower surfaces of the inspection object 1. Therefore, X-rays can pass through the inspection object 1. However, the configuration of the inspection target drive mechanism 110 is not limited to the above. For example, an XY stage that transmits X-rays may be used as the inspection target drive mechanism 110. However, in order to inspect many inspection objects 1, the illustrated inspection object drive mechanism 110 is suitable.

  As the calculation unit 70, a general central processing unit (CPU) can be used. The storage unit 90 includes a main storage unit 90a and an auxiliary storage unit 90b. For example, a memory can be used as the main storage unit 90a, and an HDD (hard disk drive) can be used as the auxiliary storage unit 90b. That is, a general computer can be used as the calculation unit 70 and the storage unit 90.

(Process flow)
FIG. 4 is a flowchart showing the flow of the X-ray inspection according to the first embodiment. With reference to FIG. 4, the flow of the whole X-ray inspection according to the first embodiment will be described.

  With reference to FIG. 4, first, when processing is started (step S401), the X-ray inspection apparatus 100 carries the substrate into a prescribed position inside the X-ray inspection apparatus 100 by the inspection target drive mechanism 110 (step S401). S403). The specified position is usually preferably set at the center of the X-ray inspection apparatus 100, that is, at the center of the X-ray irradiation range. However, the specified position may be a position where the X-ray detector 23 can capture an X-ray fluoroscopic image of the substrate.

  In step S <b> 405, the X-ray inspection apparatus 100 captures a fiducial mark with the optical camera 116. Further, the X-ray inspection apparatus 100 corrects the substrate position, if necessary, based on the position of the fiducial mark. Specifically, the X-ray inspection apparatus 100 moves the substrate position in the same manner as when carrying in. Through these processes, the X-ray inspection apparatus 100 can recognize the deviation of the substrate position and the inclination of the substrate that occur when the substrate is carried in, and can correct the deviation and the inclination.

  In step S407, the X-ray inspection apparatus 100 uses the displacement meter 114 to measure the height of the substrate in the reconstruction area (hereinafter also referred to as the field of view). The X-ray inspection apparatus 100 stores the measured substrate height in the main storage unit 90a. The stored height of the substrate is used at the time of CT imaging described later.

  When the inspection object 1 includes a plurality of fields of view, for example, the entire inspection object 1 cannot be imaged by one imaging, the X-ray inspection apparatus 100 measures the substrate height for all fields of view before performing CT imaging. Keep it. This is because the displacement meter needs to be retracted so as not to be exposed during CT imaging. Thus, measuring all the substrate heights in advance can reduce the entire inspection time compared to measuring the substrate height each time CT imaging of each field of view is performed.

  In step S409, the X-ray inspection apparatus 100 images one field of view from a plurality of directions within the inspection object 1. In the present embodiment, the X-ray inspection apparatus 100 moves the substrate and the X-ray detector 23 so as to draw a circular orbit in the horizontal direction, and images the visual field from a plurality of directions. The positions of the substrate and the X-ray detector 23 at the time of imaging are determined by the irradiation angle θR, the source-substrate distance (FOD), and the source-detector distance (FID). The substrate and the X-ray detector 23 are arranged so that the center of the visual field is imaged at the center of the X-ray detector 23. The trajectory of the substrate and the X-ray detector 23 may not be a circle, but may be a rectangle or a straight line.

  It is assumed that the number of captured images can be set by the user. It is preferable that the user determines the number of images to be captured based on the required accuracy of reconstruction data. The number of images is usually about 4 to 256. However, the number of captured images is not limited to this. For example, the X-ray inspection apparatus 100 may of course capture more than 256 images.

  In step S411, the X-ray inspection apparatus 100 generates reconstruction data from captured images in a plurality of directions. Various methods have been proposed for the reconstruction process. For example, the Feldkamp method can be used.

  In step S413, the X-ray inspection apparatus 100 extracts the board height, that is, the height of the board surface on which the components are arranged. Details of the processing performed in step S413 will be described later.

  In step S415, the X-ray inspection apparatus 100 acquires a tomographic image having a height away from the substrate height by a predetermined distance in the height direction as an inspection image used for the inspection. Here, the distance between the height of the inspection image and the substrate height is set by the user. This distance is preferably set according to the design data of the inspection object 1 and the inspection method. In the present embodiment, a tomographic image having a height slightly apart from the surface of the substrate on which the component is arranged to the side on which the component is arranged is set as the inspection image.

  In step S417, the X-ray inspection apparatus 100 performs visual field pass / fail determination using the inspection image. That is, the X-ray inspection apparatus 100 inspects the wettability of solder after heating, the presence or absence of solder voids and bridges, the presence or absence of foreign matter, and the like. Various quality determination methods are well known, and the X-ray inspection apparatus 100 may use a quality determination method suitable for the inspection item.

  In the present embodiment, the quality determination unit 78 determines the quality of the mounting board based on the solder area in the binarized image. Hereinafter, with reference to FIG. 5, the quality determination of the substrate in the present embodiment will be described. FIG. 5 is a diagram for explaining quality determination based on the solder area in the binarized image.

  FIG. 5A is a perspective view of a substrate on which electronic components are mounted. A first component 502 and a second component 503 are mounted on the substrate 501. The second component 503 is physically and electrically connected to the substrate 501 by a BGA (Ball Grid Array) 504 or the like.

  FIG. 5B is a cross-sectional view in which a connection portion between the substrate 501 and the second component 503 is cut along a cross section perpendicular to the surface of the substrate 501. The BGA 504 connects the second component 503 and the surface layer 505 of the substrate 501. The BGA 504 is heated and deforms into a state 506 after heating. However, a void 507 may occur in the state 506 after heating. In some cases, a plurality of solder balls are combined to form a bridge 508.

  The X-ray inspection apparatus 100 generates three-dimensional data of an area expected to include a solder ball, and creates a tomographic image by cutting out the three-dimensional data. The X-ray inspection apparatus 100 binarizes the created tomographic image, and acquires a binarized image obtained by separating the image into solder and other parts. For this binarization process, a general binarization process such as a discriminant analysis method can be used. The inspection apparatus labels the white (or 1) portion from the binarized image, and acquires a labeling image in which solder is distinguished. For this labeling process, it is possible to use a general labeling process that determines the presence or absence of connection by raster scanning.

  An example of a cross section parallel to the surface of the substrate 501 is shown in FIG. 5C. FIG. 5C is a cross-sectional view of a connection portion cut by a cross section indicated by a broken line in FIG. 5B. In FIG. 5C, the solder is indicated by white and the parts other than the solder are indicated by oblique lines. Here, three types of states, normal, void, and bridge, are shown. Referring to FIG. 5C, when there is void 507, a portion without solder is generated in the solder. When the bridge 508 is present, solder is observed in a wider area than in the normal state.

  The inspection device counts the area of each solder (the number of white or one pixel) from the labeling image to obtain the solder area. The inspection apparatus determines whether the solder joint surface is good or not by determining that the area is within a certain range and is non-defective, and otherwise. In general, the predetermined range of threshold values is set in advance by the user.

  Returning to FIG. 4, in step S <b> 418, the X-ray inspection apparatus 100 determines whether the pass / fail determination has been performed for all the visual fields. If there is a field of view for which pass / fail judgment has not been made (NO in step S418), X-ray inspection apparatus 100 repeats the processing from CT imaging (step S409). On the other hand, when the pass / fail determination is made for all the visual fields (YES in step S418), the process proceeds to step S419.

  In step S419, the X-ray inspection apparatus 100 carries the substrate out of the X-ray inspection apparatus 100. Specifically, the X-ray inspection apparatus 100 moves the substrate out of the X-ray inspection apparatus 100 by the inspection target drive mechanism 110.

  Thus, the X-ray inspection apparatus 100 ends the inspection for one inspection object 1 (step S421). The X-ray inspection apparatus 100 repeats a series of processes from step S401 to step S421 described so far when performing inline inspection on a plurality of inspection objects 1.

(Substrate height extraction)
From here, the substrate height extraction touched in FIG. 4 will be described. The X-ray inspection apparatus 100 first obtains the coordinates in the “height direction” of the component mounted on the substrate, and obtains the position in the height direction of the substrate from the relative position from the component. Here, the “height direction” is defined as the normal direction of the surface (reference surface) on which the substrate is transported and arranged. In the present embodiment, since the substrate is transported and arranged along a horizontal plane, the reference plane is a horizontal plane and the height direction is a vertical direction.

  In the present embodiment, the X-ray inspection apparatus 100 calculates the height of a component by calculating the variance of luminance values for a plurality of tomographic images having different heights and comparing the obtained variance for each height. be able to. This is due to the following reason.

  The luminance value varies depending on the degree (absorption coefficient) by which the imaged object absorbs X-rays. By the way, the component mounted on the substrate surface includes a member (solder in the case of BGA) having a higher absorption coefficient than objects (substrate or air) other than the component. For this reason, the luminance value of the region where the component exists is higher than the luminance value where an object other than the component exists. Therefore, in the tomographic image at a height where the part exists, the contrast of the brightness value is increased, and the dispersion of the brightness value is increased.

  Further, for any inspection object, the component is mounted at a substantially constant height with respect to the board. Therefore, in a tomographic image of a cross section separated from the substrate surface by a certain height, it is considered that the contrast of luminance values (pixel values) is large and the dispersion of luminance values is large. Therefore, the height of the substrate can be obtained from a cross section having a large luminance value dispersion.

  In the present embodiment, it is assumed that the inspection object 1 is a substrate and a BGA (Ball Grid Array) mounted on the substrate. The BGA includes a circuit component and a plurality of solder balls that join the circuit component to a substrate. The X-ray inspection apparatus 100 determines the substrate height from the height at which the dispersion is maximum and the height of the BGA solder balls. Here, the height of the solder ball is the distance from the substrate surface to the position where the solder ball swells most in the horizontal direction, that is, the radius of the solder ball.

  The relative height direction distance between the solder ball and the substrate is constant for the same region of the same inspection object 1. Therefore, the distance H between the solder ball and the substrate may be set once by the user in the teaching mode, for example. There is no need to reset the distance H in the inspection mode. Note that the X-ray inspection apparatus 100 may set the distance H based on the design value of the inspection object 1.

  However, the coordinates in the height direction at which the substrate and the solder ball are located at the time of inspection differ for each inspection. As already explained, the substrate has a warp. The amount of warpage of the board varies depending on the board to be inspected depending on factors such as the fixing position of the rail for fixing the board and the degree of thermal deformation of the board. Therefore, even if the substrate warpage amount is measured in advance by the displacement meter 114 in the teaching mode before in-line inspection, the measured warpage amount is different from the substrate warpage amount to be inspected thereafter. Therefore, the warpage amount of the substrate measured in advance before the inspection cannot be used in the inspection mode. Therefore, when obtaining the absolute substrate height, the X-ray inspection apparatus 100 obtains the height of the solder ball from the reconstructed data every time the inspection is performed, and calculates the absolute substrate height.

  Hereinafter, the substrate height position acquisition process will be described with reference to FIG. FIG. 6 is a flowchart showing the flow of processing performed by the X-ray inspection apparatus 100 in acquiring the substrate height position.

  When starting the substrate height position acquisition process (step S601), the X-ray inspection apparatus 100 first substitutes 0 for a parameter Z that specifies the height of the horizontal section of the object (step S603). The three-dimensional reconstruction data generated by the reconstruction process has a data structure in which a plurality of cubes called voxels are arranged, and the height of the uppermost layer (vertically above) of the reconstruction data is Z = 0. It is a cross section. The Zth layer in the reconstruction data corresponds to a tomographic image with Z = Z. The parameter Z does not represent the actual height, but in the following, for the sake of simplicity, the actual height specified by the parameter Z is referred to as the height Z.

  In step S605, the X-ray inspection apparatus 100 acquires two-dimensional data (tomographic image) of height Z from the reconstruction data.

  In step S607, the X-ray inspection apparatus 100 calculates the variance V (Z) of the tomographic image having the height Z acquired in step S603. Here, the variance of the tomographic image is calculated by the following equation (*).

_{V (Z) = Σ x Σ} y (I xy -I avg) ... (*)
Here, I _xy represents the luminance value of the pixel p (x, y) in the tomographic image, and I _avg represents the average value of all the pixels in the tomographic image.

  Further, in step S607, the X-ray inspection apparatus 100 stores the calculated variance V (Z) in the main storage unit 90a. The stored variance V (Z) is used when comparing the variances of the tomographic images.

  In step S609, the X-ray inspection apparatus 100 determines whether or not dispersion has been obtained for all height tomographic images. Specifically, the X-ray inspection apparatus 100 determines whether Z is less than the number of tomograms in the reconstruction data. When Z is less than the number of slices (YES in step S609), X-ray inspection apparatus 100 repeats the processing from step S605 after incrementing Z in step S611. On the other hand, when Z has reached the number of slices (NO in step S609), the X-ray inspection apparatus 100 proceeds to the process of step S613.

  In step S613, the X-ray inspection apparatus 100 compares the variance V (Z) of each tomographic image and obtains Z that maximizes the variance V (Z).

  In step S615, the X-ray inspection apparatus 100 acquires the solder ball height H. Here, the solder ball height H is set in advance as described above. The value of the height H may be automatically set by the X-ray inspection apparatus 100 from the design value of the solder height. Further, the user may set a value of height H in the teaching mode.

  In step S617, the X-ray inspection apparatus 100 obtains the substrate height based on Z obtained in step S613 and H obtained in step S615. When a component is mounted on the upper side of the board, the X-ray inspection apparatus 100 obtains ZH as the board height because the board is located below the solder balls. On the other hand, when a component is mounted on the lower side of the board, the X-ray inspection apparatus 100 obtains Z + H as the board height. Note that information on whether the component is mounted on the upper side or the lower side of the board is set by the user in the teaching mode, for example.

  FIG. 6 shows an example in which the X-ray inspection apparatus 100 obtains the variance in each tomographic data in order from the vertical tomographic data to the vertical tomographic data. It is not limited to. For example, the X-ray inspection apparatus 100 may obtain the variance in order from the vertical tomographic data to the vertical tomographic data.

  In the above description, although the X-ray inspection apparatus 100 generates a plurality of tomographic data from the reconstructed three-dimensional data, the X-ray inspection apparatus 100 can determine the ball height with a necessary accuracy. Thus, it is sufficient that a plurality of tomographic data can be generated. The X-ray inspection apparatus 100 does not have to reconstruct all voxel data in the field of view.

(Experimental result)
The applicant conducted an experiment for obtaining the board height by the above-described X-ray inspection method for the printed board on which the BGA was mounted. The experimental results are shown in FIGS. FIG. 7 is a diagram showing the value of the variance V (Z) at each fault height. FIG. 8 is a diagram showing a tomographic image at a fault height (fault height (A) in FIG. 7) at which the variance is greatest. FIG. 9 is a diagram showing a tomographic image (at the fault height (B) in FIG. 8) 20 layers below the fault height at which the variance becomes the largest.

  Referring to FIG. 8 in comparison with FIG. 9, in the tomographic image in which the variance is the largest, the region corresponding to the solder ball (region having a high luminance value) is large. Also, referring to FIG. 9, it can be seen that the wiring of the printed circuit board is observed in the tomographic image of height (B). That is, it can be seen that this tomographic image is a tomographic image of the substrate height.

  In addition, referring to FIG. 7, the dispersion shows a tendency that the fault height gradually increases as it approaches the center of the ball. This means that the dispersion is highly resistant to noise. For example, even when the noise is large and the variance becomes extremely large in a tomographic image at a certain height, the X-ray inspection apparatus 100 can accurately calculate the ball height by taking the average of the variances at a plurality of heights. It can be detected. Thus, since the X-ray inspection apparatus 100 can stably obtain the center of the ball, the substrate height can be obtained stably.

(Modification)
In the above description, in order to obtain the ball height, the dispersion in the tomographic image is used. This identification may be realized in other ways.

(1) Diameter of solder ball The pass / fail judgment unit 78 determines the height at which the diameter of the solder area corresponding to the solder ball (the area of white or value 1 when binarized) is maximum in the tomographic image, It may be the ball height. This utilizes the property that the solder ball has a spherical shape and the diameter near the center is maximized.

(2) Solder Ball Area The quality determining unit 78 may set the height at which the area of the solder region is maximized as the ball height. This setting method is based on the same idea as the method of regarding the diameter of the solder ball as the ball height. However, this method can avoid erroneous recognition due to the fact that the solder ball fault is not a perfect circle. In addition, this method has an advantage that since the area is the square of the length, it is less susceptible to noise than the comparison by length.

As described above, according to the X-ray inspection apparatus 100 according to the present embodiment, the substrate height can be automatically extracted during teaching or inspection. Therefore, the X-ray inspection apparatus 100 has the following advantageous effects as compared with the conventional technique for obtaining the substrate height using the wiring pattern.
(1) Reducing user's burden.
(2) Prevention of human error.
(3) The board height of a board without a wiring pattern on a plane can be extracted.
(4) The board height of the board having a small SN ratio of the wiring pattern can be accurately extracted.
(5) The substrate height of the multilayer substrate can be extracted with high accuracy.

[Second Embodiment]
The X-ray inspection apparatus 100 according to the second embodiment divides the reconstruction area (field of view) into a plurality of partial areas in the horizontal direction, and performs substrate height calculation and pass / fail judgment for each partial area. There are two reasons for dividing the reconstruction area, which is to cope with the substrate warp and to speed up the quality determination.

  A description will be given of how to deal with substrate warpage. As already described, the X-ray inspection of the printed circuit board warps the substrate. When the substrate is warped, the height of the entire substrate is changed, and the height of the substrate varies depending on the location in the substrate surface. Therefore, when it is desired to inspect the entire surface of the component (mounting package) using a bonding surface that is separated from the surface of the substrate by a certain distance, it is necessary to change the height to be inspected by the horizontal coordinates of the inspection area.

  This will be described in more detail with reference to FIGS. FIG. 10 is a diagram schematically showing a printed circuit board and a BGA inclined with respect to the tomographic plane due to warpage. FIG. 11 is a diagram schematically showing the luminance distribution of the tomographic image on the tomographic plane shown in FIG. In FIG. 11, pixel areas (bright areas) whose luminance is higher than a predetermined threshold and are determined to correspond to solder are indicated by hatching.

  When the substrate is warped as shown in FIG. 10, the bonding cannot be correctly inspected using one tomographic image. This is because the bright region at each position in the tomographic image corresponds to the solder sliced on the surface having a different height from the substrate surface. For example, the bright area in the upper left of FIG. 11 corresponds to the cross section of the ball at a height near the substrate height. On the other hand, it corresponds to the bright area in the upper right, the cross section of the ball at the ball center height. Therefore, if it is attempted to inspect the entire reconstructed data using the same cross section, it is difficult to inspect each joint portion at an appropriate height.

  Therefore, the X-ray inspection apparatus 100 according to the present embodiment divides the reconstruction data into a plurality of inspection areas in the horizontal direction, and determines and inspects the substrate height and the inspection height for each inspection area. Therefore, the X-ray inspection apparatus 100 according to the present embodiment can perform an appropriate inspection over all the joints between the substrate and the component.

  Next, speeding up of the pass / fail judgment will be described. When the field of view is not divided, the X-ray inspection apparatus needs to perform processing related to pass / fail judgment (substrate height extraction, pass / fail judgment, etc.) for the entire tomographic image of the reconstruction data. However, depending on the arrangement of the BGA solder balls, the tomographic image may include an image of an area that does not need to be judged as good or bad. When the field of view is not divided, the X-ray inspection apparatus makes an unnecessary determination for such a region, and therefore the determination time becomes long.

  Therefore, inspection time can be shortened by dividing the visual field. For example, when the ratio of the area occupied by the solder balls to the total area of the tomographic image (strictly speaking, a rectangular visual field is assumed to include the solder balls) is 50%, the visual field is divided. In this case, the pass / fail judgment time is about one-half that of the case where the entire tomographic image is inspected. In an in-line inspection in which the inspection time is desired to be as short as possible, it is very beneficial that the pass / fail judgment time is halved.

  X-ray inspection apparatus 100 according to the present embodiment divides a cross-sectional image into regions each including at least one region corresponding to a solder ball, and obtains the substrate height for each region after division. Pass / fail judgment is performed based on the inspection height. Therefore, the X-ray inspection apparatus 100 can shorten the inspection time.

  Hereinafter, the X-ray inspection apparatus 100 according to the present embodiment will be described in detail. Since the configuration of the X-ray inspection apparatus 100 is substantially the same as that of the first embodiment, the description thereof will not be repeated. However, the processing performed in the X-ray inspection is different from the processing in the first embodiment. Hereinafter, processing performed by the X-ray inspection apparatus 100 according to the second embodiment will be described.

(Process flow)
With reference to FIG. 12, the flow of the whole X-ray inspection according to the second embodiment will be described. FIG. 12 is a flowchart showing the flow of the X-ray inspection according to the second embodiment.

  The processes from the start of inspection (step S1201) to data reconstruction (step S1211) are the same as the processes from step S401 to step S411 in FIG. 4, respectively, and thus description thereof will not be repeated.

  In step S1213, the X-ray inspection apparatus 100 divides the field of view. That is, the X-ray inspection apparatus 100 sets a plurality of partial areas in the tomographic image. Details of step S1213 will be described later.

  In step S1215, the X-ray inspection apparatus 100 extracts the board height, that is, the height of the board surface on which the components are arranged, for each partial region. The X-ray inspection apparatus 100 obtains a variance of luminance values in a cross-sectional image (referred to as a partial image) in each partial region for each partial region, and is separated from the height of the partial image having the highest variance by a predetermined distance. Is determined as the height of the substrate surface in the partial region. The details of the process performed by the X-ray inspection apparatus 100 for each partial region are the same as those described with reference to FIG. 6, and the description thereof will not be repeated.

  In step S1217, the X-ray inspection apparatus 100 acquires a tomographic image having a height separated from the substrate height by a predetermined distance as an inspection image for each partial region.

  In step S1219, the X-ray inspection apparatus 100 performs visual field pass / fail determination similar to that in step S417 using the inspection image.

  In step S <b> 1220, the X-ray inspection apparatus 100 determines whether the pass / fail determination has been performed for all fields of view. If there is a field of view for which pass / fail judgment has not been performed (NO in step S1220), X-ray inspection apparatus 100 repeats the processing from CT imaging (step S1209). On the other hand, when the pass / fail determination is made for all the visual fields (YES in step S1220), the process proceeds to step S1221.

  In step S1221, the X-ray inspection apparatus 100 carries the substrate out of the X-ray inspection apparatus 100. Specifically, the X-ray inspection apparatus 100 moves the substrate out of the X-ray inspection apparatus 100 by the inspection target drive mechanism 110 as in the first embodiment.

  Thus, the X-ray inspection apparatus 100 ends the inspection for one inspection object 1 (step S1223). The X-ray inspection apparatus 100 repeats a series of processes from step S1201 to step S1223 described so far when performing inline inspection on a plurality of inspection objects 1.

(Field division)
With reference to FIG. 13, the visual field division process in step S1213 of FIG. 12 will be described. FIG. 13 is a flowchart showing the flow of processing performed by the X-ray inspection apparatus 100 in dividing the visual field.

  When the visual field division is started (step S1301), the quality determination unit 78 of the X-ray inspection apparatus 100 performs the processing from step S1303 to step S1315, and acquires a tomographic image having a height Z that maximizes the variance V (Z). . The processing from step S1303 to step S1315 is the same as the processing from step S603 to step S605 of FIG. 6, respectively, and description thereof will not be repeated.

  In step S <b> 1317, the quality determination unit 78 binarizes the tomographic image in order to divide the tomographic image with the maximum variance into a part corresponding to solder (solder part) and other parts. The threshold for binarization may be set in advance. Further, since the luminance difference between the solder and the other part (air or board) is sufficiently large, the pass / fail judgment unit 78 can also perform binarization using a known threshold setting method such as a discriminant analysis method. . In the following description, in the binarized image, it is assumed that the quality determination unit 78 has changed the luminance value equal to or higher than the threshold to 1 and the luminance value lower than the threshold to 0 by the binarization process.

  In step S <b> 1319, the pass / fail judgment unit 78 labels a region (referred to as a bright region) including a portion having a continuous luminance value of 1 so that the bright region is recognized in association with each solder. A known method can be used for labeling. For example, the pass / fail determination unit 78 may use a method using a raster scan and a lookup table, a contour tracking method, or the like. In addition, pixels in the vicinity in labeling can be set by the user. The user may set 4 neighborhoods or 8 neighborhoods from the viewpoint of accuracy and speed.

  In step S1321, the pass / fail judgment unit 78 gives a label for the partial region to a predetermined number of solder parts located in the vicinity of each other based on the image where the solder parts are labeled. That is, one solder part has two labels, a label of a solder part and a label of a partial region. In the following, the partial area is also referred to simply as “field of view” when it is considered that it does not cause misunderstanding of “field of view after division” or the field of view before division.

  The pass / fail judgment unit 78 determines the number of solder parts to be included in the same field of view based on a preset value. For example, when the set value is 1, the board height is obtained for each solder part and the inspection is performed. Since the number of solder parts included in the same field of view is usually determined by the design specifications of the board, the user may set it in advance. Further, the pass / fail judgment unit 78 may automatically set the number of solder parts having the same field of view based on the distribution of the solder parts in the tomographic image.

  In a board in which solder is arranged at equal intervals in the vertical and horizontal directions, the set values may be determined in the vertical and horizontal directions, respectively. In this case, the pass / fail judgment unit 78 gives visual field labeling to the set number of solder parts with reference to one solder part in the tomographic image. The reference solder part may be set by the X-ray inspection apparatus 100 or the user based on the design information of the object (for example, information about the position in the board on which the component is mounted). The pass / fail determination unit 78 may perform visual field labeling only on a solder portion within a predetermined distance from the reference solder portion. Thereby, inspection time can be shortened. An area for giving a visual field label, that is, a range where inspection is performed, can be set by the X-ray inspection apparatus 100 or the user from design information.

  FIG. 14 shows an example in which the field of view is divided by setting the number of solder parts in one divided visual field to 4 in the horizontal direction and 4 in the vertical direction. The hatched portion in FIG. 14 is a solder portion. In FIG. 14, the field of view is set starting from the lower left solder portion. Note that an area including a horizontal 4 × vertical 2 solder portion is set as the visual field 3 due to the limitation of the labeling range.

  When the solder is not arranged at equal intervals, the pass / fail judgment unit 78 may perform visual field labeling using the order of labeling. Alternatively, the quality determination unit 78 may perform visual field labeling based on the distance from the reference solder part.

  Returning to FIG. 13, after labeling the visual field, the quality determination unit 78 ends the visual field division processing (step S <b> 1323).

[Other embodiments]
The above description has been made on the inspection of the substrate on which the BGA is mounted. However, the objects that can be inspected by the X-ray inspection apparatus 100 according to the first embodiment or the second embodiment are limited to this. is not. For example, the X-ray inspection apparatus 100 can also inspect other parts using solder balls, for example, a board on which a CSP (Chip Size Package) is mounted. The X-ray inspection apparatus 100 can also be applied to inspection of other surface mounting substrates such as QFP (Quad Flat Package) and pin insertion type mounting substrates. In any case, the X-ray inspection apparatus 100 finds a cross section having a high ratio of the region corresponding to a portion having a high X-ray absorption coefficient (high absorption portion) in the component, and based on the shape characteristic of the component from the cross section. A cross section separated by a distance may be set as the inspection surface.

  As an example of application to other objects, it will be described below that a QFP backfillet inspection can be performed using the X-ray inspection apparatus 100.

  FIG. 15 is a side view of a substrate on which QFP is mounted. Referring to FIG. 15, QFP 1502 is mounted on the surface of substrate 1501. A lead 1503 drawn from the QFP 1502 and the substrate 1501 are joined by solder 1504.

  As described above, even when the board 1501 on which the QFP 1502 is mounted is to be inspected, the height at which the dispersion is maximum is the height of the fault (approximately the same as the component mounting surface of the board 1501) that occupies the largest area. It is. Similar to the BGA inspection, the height to be inspected can be determined based on the result of dispersion. A tomographic plane to be inspected, that is, a joint surface between the lead 1503 and the solder 1504 is indicated by a dotted line in FIG. As can be seen from FIG. 15, the inspection height is above the height at which the dispersion is maximum. Therefore, the user only needs to set the inspection height upward from the height at which the dispersion is maximum.

  FIG. 16 is a diagram schematically showing a cross section at the tomographic plane shown in FIG. Referring to FIG. 16, X-ray inspection apparatus 100 can determine whether or not the bonding is good based on the shape of solder 1504 surrounding lead 1503.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 is a schematic block diagram of an X-ray inspection apparatus 100 according to a first embodiment. It is a figure for demonstrating the structure of the X-ray inspection apparatus 100 which concerns on 1st Embodiment. It is a side view of inspection object 1 and its circumference. It is a figure which shows the flow of the X-ray inspection which concerns on 1st Embodiment in the flowchart format. It is a figure for demonstrating the quality determination based on the solder area in a binarized image. It is a figure which shows the flow of the process which the X-ray inspection apparatus 100 performs in the flowchart format in acquiring board | substrate height position. It is a figure which shows the value of dispersion | distribution V (Z) in each fault height. It is a figure which shows the tomographic image in the fault height (fault height (A) in FIG. 7) where dispersion | distribution becomes the largest. It is a figure which shows the tomographic image (at the tomographic height (B) in FIG. 8) 20 layers below the tomographic height at which the variance becomes the largest. It is the figure which showed typically the printed circuit board and BGA which inclined with respect to the tomographic plane by curvature. It is the figure which showed typically the luminance distribution of the tomographic image in the tomographic plane shown in FIG. It is a figure which shows the flow of the X-ray inspection which concerns on 2nd Embodiment in the flowchart format. It is a figure which shows the flow of the process which the X-ray inspection apparatus 100 performs in a flowchart format in dividing a visual field. It is a figure which shows the example which divided | segmented the visual field by setting the number of the solder parts in one visual field after a division | segmentation as 4 pieces in a horizontal direction, and 4 pieces in a vertical direction. It is a side view of the board | substrate with which QFP is mounted. It is the figure which showed typically the cross section in the tomographic plane shown in FIG. It is a figure which shows the structure of the X-ray inspection apparatus of patent document 1. It is a figure which shows the tomographic image of the test | inspection position shown by patent document 1. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Inspection object, 10 X-ray source, 12 board | substrate, 18 X-ray, 22 X-ray detector drive part, 23 X-ray detector, 30 Image acquisition control mechanism, 32 Detector drive control mechanism, 34 Image data acquisition part, 40 Input unit, 50 output unit, 60 X-ray source control mechanism, 62 electron beam control unit, 70 calculation unit, 72 X-ray source control unit, 74 image acquisition control unit, 76 reconstruction unit, 78 pass / fail judgment unit, 80 inspection target Position control unit, 82 X-ray focal position calculation unit, 84 imaging condition setting unit, 90 storage unit, 92 X-ray focal point position information, 94 imaging condition information, 96 program, 98 image data, 100 X-ray inspection apparatus, 110 inspection target Drive mechanism, 111a, 111b stage, 112a, 112b substrate rail, 114 displacement meter, 116 optical camera, 120 inspection object position control mechanism, 501 substrate 502 first part 503 second part, 505 a surface layer, after 506 heating condition, 507 void, 508 bridge, 1501 substrate, 1503 the lead.

Claims (15)

An X-ray inspection apparatus for inspecting an object using X-rays,
The object includes a substrate and a component that is electrically coupled to the substrate, and the component includes a high-absorption member having a higher X-ray absorption coefficient than that of the substrate. At the position of
X-ray output means for outputting the X-rays toward the object;
X-ray detection means for capturing a fluoroscopic image representing the intensity distribution of the X-rays incident on the object from a plurality of directions and transmitted through the object;
Reconstructing means for reconstructing a plurality of tomographic images each parallel to a reference plane on which the substrate is arranged based on the fluoroscopic images of the X-rays from the plurality of directions;
A specifying means for specifying a position of a first tomographic image having a high ratio of the high absorption member among the plurality of tomographic images;
X-ray comprising: an inspection position determining means for setting a position separated from the first tomographic image by a predetermined distance based on the position of the first tomographic image and the shape information of the component to the inspection position of the object. Inspection device. An X-ray inspection apparatus for inspecting an object using X-rays,
The object includes a substrate and a component that is electrically coupled to the substrate, and the component includes a high-absorption member having a higher X-ray absorption coefficient than that of the substrate. At the position of
X-ray output means for outputting the X-rays toward the object;
X-ray detection means for capturing a fluoroscopic image representing the intensity distribution of the X-rays incident on the object from a plurality of directions and transmitted through the object;
Reconstructing means for reconstructing a plurality of tomographic images each parallel to a reference plane on which the substrate is arranged based on the fluoroscopic images of the X-rays from the plurality of directions;
A specifying means for specifying a position of a first tomographic image having a high ratio of the high absorption member among the plurality of tomographic images;
Based on the position of the first tomographic image and the shape information of the component, a second tomographic image that is separated from the first tomographic image by a predetermined distance is acquired, and the target is obtained using the second tomographic image. An X-ray inspection apparatus comprising inspection means for determining the quality of an object. The high absorption member is a member that connects the component and the substrate,
The X-ray inspection apparatus according to claim 1, wherein the second tomographic image corresponds to a connection portion between the component and the substrate.   The X-ray inspection apparatus according to claim 3, wherein the high absorption member is solder.   The X-ray inspection apparatus according to claim 4, wherein the component is a ball grid array.   The X-ray examination apparatus according to claim 1, wherein the specifying unit obtains a variance of luminance values of each of the tomographic images and specifies a position of the tomographic image having the largest variance. Further comprising a dividing means for acquiring a plurality of partial images included in each of the plurality of partial regions from each of the tomographic images,
The specifying unit extracts, for each partial region, a position of a first partial image having a high ratio among the partial images of each of the tomographic images,
The inspection position determining means inspects the object with respect to each partial area at a position separated from the first partial image by the predetermined distance based on the position of the first partial image and the shape information. The X-ray inspection apparatus according to claim 1, wherein the position is a position. Further comprising a dividing means for acquiring a plurality of partial images included in each of the plurality of partial regions from each of the tomographic images,
The specifying unit extracts, for each partial region, a position of a first partial image having a high ratio among the partial images of each of the tomographic images,
The inspection means acquires a second partial image that is separated from the first partial image by the predetermined distance based on the position and the shape information of the first partial image for each partial region, The X-ray inspection apparatus according to claim 2, wherein the quality of the object is determined using the second partial image.   The dividing unit extracts a bright region in which bright pixels having luminance exceeding a predetermined threshold value are extracted from the extracted tomographic image, and sets a region including a predetermined number of the bright regions as the partial region. The X-ray inspection apparatus according to claim 7 or 8.   The X-ray inspection apparatus according to claim 1, further comprising a moving mechanism that moves the object along the reference plane.   The X-ray inspection apparatus according to claim 10, wherein the moving mechanism includes a rail that sandwiches the substrate. An X-ray inspection method for inspecting an object using X-rays,
The object includes a substrate and a component that is electrically coupled to the substrate, and the component includes a high-absorption member having a higher X-ray absorption coefficient than that of the substrate. At the position of
Outputting the X-rays toward the object;
Capturing a fluoroscopic image representing an intensity distribution of the X-rays incident on the object from a plurality of directions and transmitted through the object;
Reconstructing a plurality of tomographic images each parallel to a reference plane on which the substrate is arranged, based on the fluoroscopic images of the X-rays from the plurality of directions;
Identifying a position of a first tomographic image having a high ratio of the high absorption member among the plurality of tomographic images;
Determining a position separated from the first tomographic image by a predetermined distance as an inspection position of the object based on the position of the first tomographic image and the shape information of the component. . An X-ray inspection method for inspecting an object using X-rays,
The object includes a substrate and a component that is electrically coupled to the substrate, and the component includes a high-absorption member having a higher X-ray absorption coefficient than that of the substrate. At the position of
Outputting the X-rays toward the object;
Capturing a fluoroscopic image representing an intensity distribution of the X-rays incident on the object from a plurality of directions and transmitted through the object;
Reconstructing a plurality of tomographic images each parallel to a reference plane on which the substrate is arranged, based on the fluoroscopic images of the X-rays from the plurality of directions;
Identifying a position of a first tomographic image having a high ratio of the high absorption member among the plurality of tomographic images;
Acquiring a second tomographic image separated from the first tomographic image by a predetermined distance based on the position of the first tomographic image and the shape information of the component;
An X-ray inspection method comprising: determining whether the object is good or bad using the second tomographic image. An X-ray inspection program for causing an X-ray inspection apparatus having an X-ray source, an X-ray detector, and a calculation unit to inspect an object using X-rays,
The object includes a substrate and a component that is electrically coupled to the substrate, and the component includes a high-absorption member having a higher X-ray absorption coefficient than that of the substrate. At the position of
The arithmetic unit controlling the X-ray source so that the X-ray source outputs the X-ray toward the object;
The X-ray detector is configured so that the calculation unit captures a fluoroscopic image representing an intensity distribution of the X-rays that are incident on the object from a plurality of directions and transmitted through the object. A step of controlling
The arithmetic unit reconstructing a plurality of tomographic images each parallel to a reference plane on which the substrate is arranged, based on the fluoroscopic images of the X-rays from the plurality of directions;
The calculating unit specifying a position of a first tomographic image having a high ratio of the high-absorption member among the plurality of tomographic images;
And a step of determining a position separated from the first tomographic image by a predetermined distance as an inspection position of the object based on the position of the first tomographic image and the shape information of the component. X-ray inspection program. An X-ray inspection program for causing an X-ray inspection apparatus having an X-ray source, an X-ray detector, and a calculation unit to inspect an object using X-rays,
The object includes a substrate and a component that is electrically coupled to the substrate, and the component includes a high-absorption member having a higher X-ray absorption coefficient than that of the substrate. At the position of
The arithmetic unit controlling the X-ray source so that the X-ray source outputs the X-ray toward the object;
The X-ray detector is configured so that the calculation unit captures a fluoroscopic image representing an intensity distribution of the X-rays that are incident on the object from a plurality of directions and transmitted through the object. A step of controlling
The arithmetic unit reconstructing a plurality of tomographic images each parallel to a reference plane on which the substrate is arranged, based on the fluoroscopic images of the X-rays from the plurality of directions;
The calculating unit specifying a position of a first tomographic image having a high ratio of the high-absorption member among the plurality of tomographic images;
The arithmetic unit obtaining a second tomographic image separated from the first tomographic image by a predetermined distance based on the position of the first tomographic image and the shape information of the component;
An X-ray inspection program comprising: the arithmetic unit including: determining whether the object is good or bad using the second tomographic image.