JP2004340632A - Substrate inspection device, and substrate inspection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To optimally inspect a component or the like incapable of discriminating a solder from the component by an X-ray image only, by combining the X-ray image with an optical image in response to an inspection object to inspect the component, when inspecting a substrate using, for example, the X-ray image. <P>SOLUTION: This substrate inspection device provided with an X-ray image pick-up part 3 for picking up a transmission X-ray image of an X-ray emitted from an X-ray source 1 toward the inspected object 5 mounting the component, and a visible light image pick-up part 2 for picking up the inspected object 5, to inspect the inspected object 5 by the X-ray image and the optical image, is provided with an image processing means 13 for composing the X-ray image obtained by the X-ray image pick-up part 3 and the optical image obtained by the visible light image pick-up part 2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a board inspection apparatus and a board inspection method which are suitable for application to an inspection of a printed board on which components such as an IC (Integrated Circuit) chip are mounted.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an X-ray substrate inspection apparatus using X-rays has been used, for example, for the purpose of inspecting a solder state inside a BGA (Ball Grid Array) of an IC package used for high-density substrate mounting. Inspection of a mounting substrate is not completed by itself, and component polarity, positional deviation, and product type difference of a component chip to be mounted are performed by an optical substrate inspection device using an optical image using visible light (for example, see Patent Document 1). .).
[0003]
[Patent Document 1]
JP-A-11-295242
[Problems to be solved by the invention]
However, if all of the solder fillets, which are difficult to see in the optical image, are to be viewed with X-rays, there is a problem that the components and the solder cannot be distinguished, and there are some that cannot be inspected. Further, when the optical board inspection apparatus and the X-ray board inspection apparatus are arranged in a series of two units, it is very disadvantageous in cost and space.
[0005]
In view of such a point, the present invention, for example, when performing a board inspection using an X-ray image, an X-ray image and an optical image such as a component that cannot be distinguished from a solder and a component in the X-ray image are inspected. It is an object of the present invention to propose a board inspection apparatus and a board inspection method for performing an optimum inspection by performing inspections in accordance with each other.
[0006]
[Means for Solving the Problems]
A substrate inspection apparatus according to the present invention includes an X-ray imaging unit that captures a transmitted X-ray image of an X-ray radiated from an X-ray source to an inspection target on which components are mounted, and a visible image that captures the inspection target object. An X-ray image obtained by the X-ray imaging unit and an optical image obtained by the visible light imaging unit in a board inspection apparatus that includes an optical imaging unit and inspects the inspection target object using the X-ray image and the optical image Is provided with image processing means for synthesizing.
[0007]
According to the present invention, the optical image and the X-ray image are combined and processed, and the processed composite image is used to determine, for example, a solder or a component that cannot be distinguished from a solder or a component in the X-ray image.
[0008]
Further, according to the present invention, the image processing means calculates the presence / absence of solder of the component and the shape of the solder based on a luminance distribution according to the X-ray transmittance of the X-ray image.
[0009]
According to the present invention, a wide-range luminance distribution on a substrate is obtained at once by X-ray irradiation, and the quality of soldering is determined based on a solder state calculated from the luminance distribution.
[0010]
According to the present invention, the image processing means creates a three-dimensional view of the solder portion from the luminance distribution of the X-ray image.
[0011]
According to the present invention, a solder state can be visually confirmed by adding a three-dimensional view of a solder portion to the solder state based on the above-described luminance distribution.
[0012]
Further, the present invention includes a selection unit that selects an inspection based on an X-ray image, an optical image, or a combination of an X-ray image and an optical image, according to a component mounted on the inspection object.
[0013]
According to the present invention, the selection unit selects an optimum inspection based on an X-ray image, an optical image, a composite image, or a combination thereof, depending on the type of the component mounted on the board.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an example of an embodiment of a substrate inspection apparatus of the present invention and a substrate inspection method applied to this example will be described with reference to FIGS.
[0015]
FIG. 1 is a schematic device configuration diagram of the board inspection apparatus of the present embodiment. Reference numeral 1 denotes a data collection device that collects image data of an inspection object and supplies the data to a data processing device. An X-ray source 6 from which X-rays are emitted is arranged below an inspection target substrate (hereinafter, simply referred to as a substrate) 5 on which components such as an IC chip are mounted. An optical CCD camera 2 as an optical imaging unit and an X-ray receiving CCD camera 3 as an X-ray imaging unit are arranged above the inspection target substrate 5. It is assumed that the optical CCD camera 2 and the X-ray receiving CCD camera 3 include, for example, a mechanism unit 4 and move on a plane perpendicular to the plane of the paper and positioning is performed automatically or by a user's operation. Alternatively, the substrate 5 may be placed on an XY stage (not shown) movable on a plane perpendicular to the plane of the drawing, and the XY stage may be moved to position the substrate 5. Further, the X-ray source 6 may be provided with a mechanism so as to be movable.
[0016]
Since the device using X-rays is housed in a sealed case to prevent leaking radiation, the inside of the case is completely dark. Therefore, normal illumination is required as a means for obtaining visible light, but the description is omitted here. ing.
[0017]
Reference numeral 10 denotes a data processing device, which processes and processes image data imaged and transmitted by the data collection device 1, analyzes data, controls irradiation X-rays of the X-ray source 1 via a GUI as an operation means, The control of the mechanical unit 4 and the like, or the control of selecting an appropriate inspection method according to the type of components mounted on the board 5 is performed. Various types of the data processing device 10 such as a personal computer can be considered.
[0018]
Reference numeral 11 denotes a CPU for controlling and calculating the data collection device; 12, a main memory including a ROM storing a control program of the CPU 11 and a RAM functioning as a work area; 13, an optical CCD camera 2 and an X-ray receiving CCD camera 3; An image board as image processing means for processing and processing image data to be transmitted, 14 is an I / O board for performing input / output required for the apparatus, and 15 is a motor board for controlling positioning of the mechanical unit 4 and the like. . Reference numeral 16 denotes a GUI (Graphical User Interface) including display means such as an LCD and operation means such as a keyboard, a mouse, and a touch panel. These devices are connected by a system bus 17 to transmit and receive data. Note that the representation of wiring from each device of the data collection device 1 to each board of the data processing device 10 is omitted.
[0019]
When an X-ray image of the inspection target substrate 5 is obtained in the substrate inspection apparatus having the above-described configuration, the mechanism unit 4 is controlled so that the X-ray source 1, the inspection target substrate 5, and the X-ray receiving CCD camera 3 are aligned. Deploy. When X-rays are emitted from the X-ray source 6 to the substrate 5, the X-rays pass through the substrate 5, and the X-ray receiving CCD 3 provided above the substrate 5 captures the transmitted X-rays. Then, image data captured by the X-ray receiving CCD camera 3 is transmitted to the image board 13, image processing is performed, and an X-ray image is displayed on the display screen of the GUI 16.
[0020]
On the other hand, when obtaining an optical image of the substrate 5 to be inspected, the mechanism unit 4 is controlled to arrange the optical CCD camera 2 and the substrate 5 to be inspected in an appropriate positional relationship. Then, the substrate 5 is imaged by the optical CCD camera 2, the image data captured by the optical CCD camera 2 is transmitted to the image board 13, image processing is performed, and an optical image is displayed on the display screen of the GUI 16.
[0021]
The image board 13 also functions as image processing means for synthesizing the X-ray image and the optical image, and uses the X-ray image and the optical image held in the main memory 12 or the like by a command from the CPU 11 as necessary. Then, the combining process is performed, and the created combined image can be displayed on the display screen of the GUI 16.
[0022]
Hereinafter, a method for judging the quality of soldering by inspecting the solder shape for inspecting the soldering state of the chip component mounted on the substrate using the above-described substrate inspection apparatus will be described.
[0023]
A description will be given of a solder shape inspection using an X-ray image of a chip component on a substrate, for example, a chip resistor. FIG. 2 shows an example of an optical image of a part of the substrate on which the chip components are mounted. In the figure, it appears that there are four components, but there are chip components on both sides, and the central part is in a state where the chip components are missing. FIG. 3 is an X-ray image of the same part as in FIG. 2 taken by X-ray.
[0024]
FIG. 4 shows an X-ray image threshold display based on the X-ray image of FIG. The X-ray image threshold display represents the luminance distribution of the X-ray image shown in FIG. 2, and specifically, is an 8-bit, 256-gradation luminance display that is color-coded for every 10 gradations. The portion having a high luminance is a portion having a low X-ray transmittance, that is, a solder portion, and is displayed in yellow or green in this example.
[0025]
For example, assuming that the color of pink or more is the portion where the solder is located, the position of the center of gravity (+ portion) 20a of the entire solder in the portion where the solder is located and the position of the center of gravity (+ portion) 20b of the high-brightness portion of yellow or more are determined. By calculating the difference, the solder shape can be inspected. For example, the center of gravity can be calculated by calculating the area of the target portion from the luminance distribution and calculating the center thereof, for example, by using a function of an image processing software engine. In addition, since the height of the cross section of the solder portion beside the chip component and the degree of rise of the solder can be known from the luminance distribution of the X-ray image, the volume (solder amount) of the solder fillet can be calculated.
[0026]
A method of measuring the height of the solder part by irradiating the solder part with the laser light and measuring the reflected laser light is known. However, in this conventional method, the solder part is measured in units of a laser spot having an extremely small area. It took time to measure the height. According to the method using the luminance distribution of X-rays in this example, the entire board is irradiated with X-rays, and the solder height measurement processing of each component can be performed at a time, so that the efficiency is high and the measurement time is short. There are advantages.
[0027]
The distance between the position of the center of gravity 20a where the solder of the chip component shown in FIG. 4 is located and the position of the opposite center of gravity on this component is A, and the distance between the position of the center of gravity 20b of the high luminance portion and the position of the opposite center of gravity on this component is B. For example, the presence or absence of a component can be inspected by measuring the distance between the highest points in each pad. For example, in the normal solder fillet a portion, the uppermost point 20b exists on the outer side of the image, but in the portion b where the chip floats or is missing, the uppermost point 20b exists near the center, that is, near the center of gravity 20a.
[0028]
FIG. 5A is a schematic view of a cross section of a solder fillet of the chip part of the part a in FIG. 4. This shows a state in which a normal solder fillet 22 is formed for the chip component 21 placed on the substrate 5. FIG. 5B is a schematic view of a cross section of a solder fillet of the chip part of the part b in FIG. The figure shows a state in which a solder fillet 23 in which defective soldering is performed is formed on the chip component 21 placed on the substrate 5 and the chip component 21 is floating. As described above, the quality of the soldering is determined not only by the area and the volume but also by the shape of the solder, so that more accurate judgment can be made.
[0029]
FIG. 6 is a three-dimensional view (3D view) of a solder part of a certain chip component. The height of the cross section of the solder part is detected from the difference in the luminance of the X-ray image, and a three-dimensional view displayed in a mesh shape is created, and the plan views shown in FIGS. Visualize the shape. For example, when it is difficult to perform inspection according to the above plan view, a command is issued from the CPU 11 or automatically by the user via the GUI 16 to create a three-dimensional view, and the user can visually check the solder shape. The solder shape can be easily confirmed by using the three-dimensional view together when checking the shape.
[0030]
Next, a description will be given of a solder inspection based on a combination of an X-ray image and an optical image, taking a chip component as an example of a chip component. 8 is an image of the same chip condenser as the X-ray image and the optical image in FIG. 7. As can be seen from the X-ray image, there is a component such as a chip capacitor which is in a so-called black state and indistinguishable from solder and component. In such a case, the X-ray image cannot accurately inspect the solder portion. Therefore, by using the optical image, combining the X-ray image and the optical image on the image board 13 and cutting out the part corresponding part from the X-ray image to create a processed image, the exact position of the solder part is known. Can be. In the figure, an enclosing portion 20 represents a solder portion of the processed image.
[0031]
FIG. 8 shows the processed image shown in FIG. 7 processed to a level that can be used for actual inspection. In the drawing, an enclosure 20 indicates a solder part. 7 shows the basic processing (which is easy for humans to see), but in an actual inspection, finally, the image data is binarized and only two types of luminance levels, Hi and Lo, exist. Do not let it. Therefore, from the luminance including the solder and the component detected by the X-ray, the part of the component obtained by the optics is erased and processed only by the X-ray solder.
In formula,
X-ray (component / solder)-optics (component) = X-ray (solder)
It is expressed as
[0032]
Next, a case in which, for example, a BGA (Ball Grid Array) is inspected as a chip component will be described as an example. FIG. 9 shows an optical image of the BGA mounted on the board and its peripheral portion. As the inspection items here, positional deviation, polarity, and type difference are checked. In the displacement check, a so-called fiducial mark provided on the substrate as a reference position is detected and corrected. These checks are applied to various other components such as tantalum capacitors, electrolytic capacitors, various ICs such as QFP (Quad Flat Package) and SOP (Small Outline Package).
[0033]
FIG. 10 shows an X-ray image of BGA, in which the presence or absence of solder and the shape of solder are checked.
[0034]
FIG. 11 shows a flowchart of the inspection by the board inspection apparatus of this example. First, the optical CCD camera 2 is set so that an optical image of a substrate to be inspected or an inspection region of the substrate can be captured, and an optical image is captured (step S1). The inspection described with reference is performed (step S2). Here, non-defective / defective products are discriminated by inspecting the presence / absence, component polarity, misalignment, and the like of various components, such as BGA, which are targets of the optical image inspection (step S3). If the inspection results in NG, the corresponding component on the board is determined to be defective.
[0035]
In the determination processing in step S3, if the inspection result is OK, the process proceeds to the next X-ray image inspection step. The X-ray source 6 and the X-ray receiving CCD camera 3 are set so that an X-ray image of the substrate to be inspected or the inspection site of the substrate can be captured, and an X-ray image is captured (step S4). The inspection described with reference to FIGS. 4 to 6 and 10 is performed on the image (step S5). Here, for example, the amount of solder in the BGA, the shape of the solder, the amount of solder for general components, and the like, which are the targets of the X-ray image inspection, are inspected to determine non-defective / defective products (step S6). If the inspection results in NG, the corresponding component on the board is determined to be defective.
[0036]
In the determination processing in step S6, if the result of the inspection is OK, the processing shifts to processing of an X-ray image and an optical image. The optical image and the X-ray image of the substrate to be inspected are read out from a storage unit such as the main memory 12, and the images are processed by combining the images as shown in FIG. 7 (step S7). Then, the inspection described with reference to FIGS. 7 and 8 is performed using the obtained processed image (step S8). Here, the amount of soldering of, for example, capacitors and other components, which are the inspection targets of the processed image of the X-ray image and the optical image, is inspected to determine non-defective / defective products (step S9). If the inspection results in NG, the corresponding component on the board is determined to be defective.
[0037]
In the determination processing in step S7, if the inspection result is OK, the inspected substrate is regarded as a non-defective product, and the substrate inspection ends.
[0038]
This inspection flowchart is based on the fact that the CPU 11 as a selection unit is provided with an X-ray image and an optical image according to the type of components mounted on the board by providing the X-ray system and the optical system inspection unit in the same apparatus. Inspection can be performed efficiently while selecting the most appropriate one or the inspection method using the processed image. For example, depending on the part, if the X-ray image inspection is not necessary after performing the optical image inspection in steps S1 to S3, the process skips to step S7 to perform the inspection using the processed image of the X-ray image and the optical image. . Alternatively, if the component cannot be inspected by the optical image inspection and the X-ray image inspection and needs to be inspected by the processed image, an inspection flow based on various combinations such as starting from the inspection by the processed image in step S7 can be considered.
[0039]
In the above selection of the CPU 11, for example, components to be mounted as finished products are registered in the main memory 12 in advance, and an inspection method is selected according to the registered contents. Alternatively, it is conceivable to first take in an optical image, determine what components are mounted from the optical image, and select an inspection method.
[0040]
As described above, according to the present example, in the component mounting board inspection, by combining the X-ray image inspection and the optical image inspection, it is possible to inspect a component that has been conventionally difficult.
[0041]
In addition, the X-ray inspection apparatus and the optical inspection apparatus are simply arranged in series by the board inspection apparatus of the present embodiment, and by processing both images, an effect equivalent to two or more of these inspection apparatuses is obtained. Is obtained. In other words, the inspection involves the use of an optical inspection device based on an optical image to determine the presence / absence of components, component polarity, positional deviation, and the like, and the inspection performed by an X-ray inspection device using an X-ray image for solder fillets and solder in a BGA There is. If two units are arranged in a series, the functions of both units are added as they are to provide the functions for two units. However, when checking the solder fillet, there is a case in which the component and the solder cannot be distinguished, and this cannot be inspected by the above-described respective inspection apparatuses alone. In this board inspection apparatus, inspection can be realized by combining and processing each image of the optical image and the X-ray image.
[0042]
The present invention is not limited to the example of the above-described embodiment, but also includes X-rays emitted from the X-ray source to the inspection target substrate and light reflected from the inspection target substrate from light or the like. The present invention can also be applied to a case where they are on the same axis.
[0043]
Further, the present invention is not limited to the above-described embodiment, and it goes without saying that various other configurations can be adopted without departing from the gist of the present invention.
[0044]
【The invention's effect】
According to the present invention, the optical image and the X-ray image are combined and processed, and the processed composite image is used, for example, to discriminate the solder or the component even if the component is indistinguishable from the solder or the component in the X-ray image. This has the effect that the inspection of parts, which has been difficult in the past, can be realized.
[0045]
In addition, the quality of the soldering is determined not only by the area and volume, but also by a single-step brightness distribution over a wide area on the board by X-ray irradiation. There is an effect that the pass / fail can be more accurately determined.
[0046]
In addition, by creating a solder part three-dimensional diagram based on the luminance distribution of the X-ray image, the solder state can be visually checked by adding the solder part three-dimensional figure to the solder state calculated based on the luminance distribution, so that more accurate soldering can be performed. There is an effect that a good pass / fail judgment can be made.
[0047]
In addition, since an optimum inspection based on an X-ray image, an optical image, a composite image, or a combination thereof is selected according to the type of a component mounted on the board, the inspection can be performed efficiently. .
[Brief description of the drawings]
FIG. 1 is an apparatus configuration diagram showing an example of an embodiment of a substrate inspection apparatus of the present invention.
FIG. 2 is an optical image used for describing an example of an embodiment of the present invention.
FIG. 3 is an X-ray image for explaining an example of an embodiment of the present invention.
FIG. 4 is an X-ray image threshold display for explaining an example of an embodiment of the present invention.
FIG. 5 is a diagram showing an example of a solder fillet used for describing an example of an embodiment of the present invention.
FIG. 6 is an X-ray image 3D diagram for describing an example of an embodiment of the present invention.
FIG. 7 is a processed image used for describing an example of an embodiment of the present invention.
FIG. 8 is another processed image used for describing an example of an embodiment of the present invention.
FIG. 9 is a BGA optical image for explaining an example of an embodiment of the present invention.
FIG. 10 is a BG X-ray image for describing an example of an embodiment of the present invention.
FIG. 11 is a flowchart for explaining a substrate inspection method according to the present invention;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Data collection device, 2 ... Optical camera, 3 ... X-ray camera, 4 ... Mechanical part, 5 ... Inspection object board, 6 ... X-ray source, 10 ... Data processing device, 11 ... CPU, 12 ... Main memory, 13 ... Image board, 14 ... I / O board, 15 ... Motor board, 16 ... GUI, 17 ... System bus, 20 ... Solder part, 20a ... Solder part center of gravity, 20b ... High brightness part center of gravity, 21 ... Parts chip, 22, 23 ... solder fillet

Claims (8)

An X-ray imaging unit configured to capture a transmitted X-ray image of X-rays emitted from an X-ray source to an inspection target on which components are mounted; and a visible light imaging unit configured to image the inspection target. In a board inspection apparatus for inspecting the object to be inspected by a line image and an optical image,
A board inspection apparatus comprising: an image processing unit that combines an X-ray image obtained by the X-ray imaging unit and an optical image obtained by the visible light imaging unit. The board inspection apparatus according to claim 1,
The board inspection apparatus according to claim 1, wherein the image processing means calculates presence / absence of solder and a solder shape of the component based on a luminance distribution according to an X-ray transmittance of the X-ray image. The board inspection apparatus according to claim 2,
The board inspection apparatus according to claim 1, wherein the image processing means creates a three-dimensional view of the solder portion from the luminance distribution of the X-ray image. The board inspection apparatus according to claim 1,
According to a component to be mounted on the inspection object, the X-ray image, or the optical image, or a combination of the X-ray image and the optical image, the selection means for selecting an inspection, characterized by comprising Substrate inspection method. An X-ray imaging unit configured to capture a transmitted X-ray image of X-rays emitted from an X-ray source to an inspection target on which components are mounted; and a visible light imaging unit configured to image the inspection target. In a board inspection method for inspecting the object to be inspected by a line image and an optical image,
A method of inspecting a substrate, comprising combining an X-ray image obtained by the X-ray imaging unit and an optical image obtained by the visible light imaging unit. The board inspection method according to claim 5,
A board inspection method, wherein the presence or absence of solder and the solder shape of the component are calculated based on a luminance distribution according to an X-ray transmittance of the X-ray image. The board inspection method according to claim 6,
Further, a board inspection method, wherein a three-dimensional view of a solder portion is created from the luminance distribution of the X-ray image. The board inspection method according to claim 5,
A board inspection method, wherein an inspection based on the X-ray image, the optical image, or a composite image of the X-ray image and the optical image is selected according to a component mounted on the inspection object. .

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