JP2008157749A - Inspection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve low-cost three-dimensional automatic inspection and three-dimensional measurement for cream solder printing. <P>SOLUTION: A three-dimensional imaging geometrical-optical arrangement includes a one-dimensional color image sensor camera for imaging a board at an oblique imaging angle, a first hue light source that lights a cream solder upper surface substantially from just above, and a second hue light source that lights a cream solder side surface at an oblique angle smaller than the imaging angle. A three-dimensional image on the whole surface of the board is acquired by moving the board in a direction orthogonal to the pixel arrangement of the camera. A differential image processing is performed between a three-dimensional image on a specimen cream solder printed board and a three-dimensional image on a reference cream solder printed board. Pixels having differences exceeding a set threshold are detected as dissimilar pixels. As to the reference board image and the specimen board image in a domain where the dissimilar pixels are detected, three-dimensional measurement values of cream solder are calculated from first and second hue light reflection domains. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an inspection apparatus that performs appearance inspection by three-dimensionally imaging a cream solder printed board with a one-dimensional image sensor camera in an electronics factory or the like.

The recent method of assembling parts on a printed circuit board is almost surface-mounting, and cream solder is printed on the base board in a photocopied form, then the parts are automatically mounted, and the cream solder is heated and melted in a reflow oven. Complete the soldering of the parts. Component mounting defects in this method can occur in the cream solder printing process, component mounting process, and solder melting process, so the need to inspect and confirm quality in each process has been generally recognized. .
In particular, printing defects in the cream solder printing process are the largest cause of soldering defects, and therefore, inspection apparatuses that automatically inspect the solder printing quality are used. These conventional inspection apparatuses are roughly classified into a two-dimensional detection method and a three-dimensional measurement method. The former detects a defect in the plane direction of printing from a plane image taken from a direction perpendicular to the substrate. The latter measures the height of printed solder by three-dimensional measurement.
The three-dimensional measurement method can be calculated from the amount of deformation by projecting laser light from an oblique direction onto the solder and calculating the position change amount of the reflected spot depending on the height, or projecting structured light with a known pattern. And the like are disclosed (see Patent Documents 1 and 2).
JP 2000-097631 A JP-A-2005-337943

  The inspection apparatus of the three-dimensional measurement method based on these principles has a high cost for a mechanism for performing three-dimensional measurement, and has been an obstacle to the spread of inspection automation.

On the other hand, the present applicant has devised and disclosed a mounting inspection technique that does not require conventional teaching work by imaging the entire surface of the printed circuit board and performing an appearance inspection based on the image (see FIG. (See Patent Documents 3 and 4;
JP 2003-037342 A JP 2004-354265 A

  These disclosed technologies are for inspecting a substrate after soldering by a one-dimensional image sensor camera installed in a direction directly above the substrate, and are generally technologies for performing difference image processing of a two-dimensional image. Three-dimensional measurement of cream solder was not possible.

  The problem to be solved is that the two-dimensional image method cannot detect an abnormal cream solder height, while the three-dimensional measurement method cannot avoid a high-cost structure.

According to the present invention, a one-dimensional color image sensor camera having an oblique imaging angle with respect to a substrate illuminates the first hue light source from almost directly above and the second hue light source illuminates at an oblique angle shallower than the imaging angle. The substrate is imaged, and a three-dimensional image of the entire surface of the solder paste printed board that is simultaneously double-illuminated with the first hue light and the second hue light is obtained. The main feature is to detect and perform three-dimensional image measurement of the cream solder on the abnormal part.
The present invention also provides a substrate in which a one-dimensional image sensor camera having an oblique imaging angle with respect to a substrate flashes and illuminates the first light source from substantially above and the second light source blinks at an oblique angle shallower than the imaging angle. The main feature is that images are alternately captured in accordance with electronic scanning, a first light source reflection image and a second light source reflection image are acquired, and a three-dimensional measurement value of cream solder is calculated to determine whether it is good or bad.

  The inspection apparatus according to the present invention generates a three-dimensional image of a cream solder printed circuit board by a one-dimensional image sensor camera having an oblique imaging angle, a three-dimensional imaging geometric optical arrangement including illumination from directly above and illumination at an angle shallower than the imaging angle. Since the acquisition and the defect detection of the three-dimensional image of the cream solder are performed, there is an advantage that an inexpensive three-dimensional cream solder printing inspection apparatus that does not require an expensive three-dimensional measurement structure is realized.

  For the purpose of realizing an inexpensive and popular automatic inspection apparatus for cream solder printing, it is composed of a one-dimensional image sensor camera with an oblique imaging angle, an illumination light source from almost above, and an illumination light source with a shallower angle than the imaging angle. This was realized by acquiring a three-dimensional image of the cream solder printed board by three-dimensional imaging geometric optical arrangement, measuring the three-dimensional image, and detecting defects.

  FIG. 1 is an overall configuration diagram of a first embodiment of an inspection apparatus according to the present invention, in which cream solder 2 is printed on a substrate 1, and the substrate 1 is held in a horizontal posture on a one-dimensional table 3.

  Above the substrate 1, a one-dimensional color image sensor camera 4, a first hue light source 5-1 and a second hue light source 5-2 of an illumination device are arranged. The one-dimensional color image sensor camera 4 is a color line CCD camera, and is installed in an inclined posture so that its visual axis is inclined with respect to the substrate 1. Although not shown, a telecentric lens is provided in front of the one-dimensional color image sensor camera 4 so that incident light from the substrate is parallel light.

As shown in the schematic diagram of the optical arrangement in FIG. 2A, the configuration of the illumination / imaging system is as follows:
The first hue light source 5-1 is installed almost directly above the substrate, and projects the first hue light, for example, a green light beam, onto the substrate, thereby coloring the upper surface of the cream solder in green. On the other hand, the second hue light source 5-2 is installed below the one-dimensional color image sensor camera 4, and colors the side surface of the cream solder in red by projecting the second hue light, for example, a red light flux, onto the substrate.
When the one-dimensional color image sensor camera 4 in an oblique posture installed between the first hue light source 5-1 and the second hue light source 5-2 captures the substrate in this geometric optical arrangement, the image of FIG. As shown in the schematic diagram, a three-dimensional image of cream solder is obtained, and the upper surface of the solder becomes a green image region, and the side surface becomes a red image region.
The depth of the red area (corresponding to the width in FIG. 2) is the depth of the side image of the cream solder, and is proportional to the height of the cream solder. Proportional. The actual height and area can be estimated from the tilt angle of the camera visual axis and the number of pixels, and the volume of the cream solder is calculated from the height and area.
In the pass / fail judgment, a difference image process between the images of the reference substrate and the sample substrate is performed, and when a difference equal to or greater than a threshold value is detected, it is determined as defective (see FIG. 2C).

  The above calculation is performed by (1) making the electronic scanning axis of the one-dimensional image sensor camera and the relative movement axis of the substrate perpendicular, and (2) making the incident light to the camera parallel light by the telecentric lens. It is very easy. Since the cream solder side surface is often an inclined surface, the correction calculation is performed using the red luminance value of the side surface region pixel that changes according to the angle of the incident angle of the second hue light source beam.

  The protrusion or bridge of cream solder is detected as an abnormal spread of the green region.

  In FIG. 1, a one-dimensional color image sensor camera 4 is connected to a control device 6, and the control device 6 controls a one-dimensional sensor imaging unit 7, an image data storage unit 8, an image processing arithmetic unit 9, and the entire system. It has an integrated system control unit 10, and each unit 7, 8, 9, and 10 exchanges data through a bus 15.

  The control device 6 also includes an input unit 11 for inputting teaching data, an output unit 12 for printing inspection results, a communication unit 13 for transmitting / receiving data to / from an external device, and images and inspection results. A display unit 14 for displaying the above is connected.

    Next, the teaching steps of this embodiment inspection apparatus will be described with reference to the flowchart of FIG. First, the reference substrate 1 (FIG. 1) is loaded on the table (ST1), the ID data of the substrate is taught (ST2), and then the reference substrate is moved by the one-dimensional table 3 and the one-dimensional color image sensor camera 4 is used. Scan imaging is performed (ST3). The acquired three-dimensional whole image of the reference substrate is displayed on the display unit 14, and an inspection area is set (ST4).

The inspection area setting is set so as to surround each of the component mounting location or the soldering location. When the area teaching is completed, the reference substrate is removed (ST5).

Next, a test substrate is loaded (ST6), moved by the one-dimensional table 3, and scanned by the one-dimensional color image sensor camera 4 (ST7). The three-dimensional whole image of the reference substrate and the three-dimensional whole image of the test substrate are displayed on the display unit 14, and the difference image processing between them is tried under the conditions of default image accuracy and default detection sensitivity (ST8).
At this time, if there is an oversight of a defect on the test board, the default image accuracy or detection sensitivity of the inspection area is increased. Adjust to image accuracy and detection sensitivity.
In this embodiment, the image accuracy and detection sensitivity of the inspection area can be individually adjusted. Therefore, over-detection and non-detection, which were difficult with the entire uniform level method, can be achieved by adjusting according to the image condition of each inspection area. The possibility of occurrence is greatly reduced.
When the adjustment of the image accuracy and detection sensitivity of all inspection areas is completed, the test substrate is removed (ST9).

As for the image accuracy, it is possible to select whether all pixels in the inspection area are compared or thinned out. When all the pixels are targeted, the inspection accuracy is naturally improved, but the image processing time becomes long. Therefore, a necessary pixel density is applied depending on the type of substrate and the type of defect so that the inspection time can be shortened.
The detection sensitivity of the inspection region is roughly classified into difference sensitivity that raises and lowers the threshold value of the difference image processing, and sensitivity that limits the range of pixel expansion and movement exceeding the threshold value. By detecting the range of different pixels, it is possible to detect not only the protrusion or deficiency of the cream solder printed on the substrate in the planar direction, but also the height defect.

Next, the automatic inspection operation in this embodiment will be described with reference to the flowchart of FIG.
First, in FIG. 1, the sample substrate 1 is loaded on the one-dimensional table 3 (ST11), and when the ID data of the sample substrate is input or read (ST12), the sample substrate 1 is moved one-dimensionally according to a command from the control device 6. The one-dimensional color image sensor camera 4 scans and captures the entire surface of the sample substrate 1 under the control of the one-dimensional sensor imaging unit 7 (ST13).

  Therefore, the image processing arithmetic unit 9 performs differential image processing for each inspection region of the reference substrate 3D image and the sample substrate 3D image (ST14), and based on the image accuracy and detection sensitivity taught from the difference image data, the defective region Is detected.

  Next, regarding the cream solder in the defective area, the area is calculated from the first hue light area, the height is calculated from the second hue light area, the volume is calculated (ST15), and the inspection result is reported (ST16). ), The specimen substrate is removed (ST17).

  The overall configuration of the second embodiment of the inspection apparatus of the present invention is shown in FIG. Cream solder 2 is printed on the substrate 1, and the substrate 1 is held in a horizontal posture on the one-dimensional table 3.

  Above the substrate 1, a one-dimensional image sensor camera 4, a first light source 5-1 and a second light source 5-2 of an illumination device are arranged. The one-dimensional image sensor camera 4 is a line CCD camera, and is installed in an inclined posture so that its visual axis is inclined with respect to the substrate 1. Although not shown, a telecentric lens is provided in front of the one-dimensional image sensor camera 4 so that incident light from the substrate is parallel light.

As shown in the schematic diagram of the optical arrangement in FIG. 5A, the configuration of the illumination / imaging system is as follows:
The first light source 5-1 is installed almost directly above the substrate, and illuminates the upper surface of the cream solder by projecting a light beam onto the substrate. On the other hand, the second light source 5-2 is installed below the one-dimensional image sensor camera 4, and illuminates the side surface of the cream solder by projecting a light beam onto the substrate.
With this geometric optical arrangement, the first light source 5-1 is turned on in synchronization with the odd-numbered electronic scanning of the one-dimensional image sensor camera 4, and the one-dimensional image sensor camera 4 acquires the first light source reflected image of the substrate. Further, the second light source 5-2 is turned on in synchronization with the even-numbered electronic scanning of the one-dimensional image sensor camera 4 to acquire a second light source reflected image of the substrate. As a result, as shown in the schematic image of FIG. 5B, a three-dimensional image of the cream solder on the two surfaces is obtained, the upper surface of the solder is the first light source reflective region, and the side surface is the second light source reflective region. Become.
Since the depth of the second light source reflection area (corresponding to the horizontal width in FIG. 5) is the depth of the side image of the cream solder, it is proportional to the height of the cream solder, and the first light source reflection area is the top image of the cream solder. , Proportional to the area of cream solder. The actual height and area can be estimated from the tilt angle of the camera visual axis and the pixel size, and the volume of the cream solder is calculated from the height and area.
In the pass / fail judgment, the measured values of the cream solders of the reference board and the specimen board are compared, and when a difference equal to or greater than the threshold value is detected, it is judged as defective.

  The above calculation is performed by (1) making the electronic scanning axis of the one-dimensional image sensor camera and the relative movement axis of the substrate perpendicular, and (2) making the incident light to the camera parallel light by the telecentric lens. It is very easy. Since the cream solder side surface is often an inclined surface, the correction calculation is performed using the luminance value of the side surface region pixel that changes according to the angle of the second light source beam with respect to the incident angle.

  The protrusion or bridge of the cream solder is detected as an abnormal spread of the first light source reflection region.

  In FIG. 4, the one-dimensional image sensor camera 4 is connected to a control device 6, and the control device 6 controls the one-dimensional sensor imaging unit 7, the image data storage unit 8, the image processing arithmetic unit 9, and the entire system. A system control unit 10 is provided, and the units 7, 8, 9, and 10 exchange data through a bus 15.

  The control device 6 also includes an input unit 11 for inputting teaching data, an output unit 12 for printing inspection results, a communication unit 13 for transmitting / receiving data to / from an external device, and images and inspection results. A display unit 14 for displaying the above is connected.

  Next, the teaching steps of this embodiment inspection apparatus will be described with reference to the flowchart of FIG. First, the reference substrate 1 (FIG. 4) is loaded on the table (ST21), the ID data of the substrate is taught (ST22), and then the reference substrate is moved by the one-dimensional table 3 and scanned by the one-dimensional image sensor camera 4. An image is taken (ST23). The acquired first light source image of the reference substrate is displayed on the display unit 14, and an inspection area is set (ST24).

The inspection area setting is set so as to surround each soldered portion. In this case, it is possible to use computer design data. When the area teaching is completed, the image processing arithmetic unit 9 calculates the solder area from the first light source image (ST25), calculates the solder height from the second light source image, and calculates the volume from the area and height. The data is saved (ST26).

  Next, the first light source image and the second light source image of the reference substrate are stored (ST27), and the reference substrate is removed (ST28).

Next, the automatic inspection operation in this embodiment will be described with reference to the flowchart of FIG.
First, in FIG. 4, the sample substrate 1 is loaded on the one-dimensional table 3 (ST31), and when the ID data of the sample substrate is input or read (ST32), the sample substrate 1 is moved one-dimensionally according to the command of the control device 6. The one-dimensional image sensor camera 4 scans and images the entire surface of the sample substrate 1 under the control of the one-dimensional sensor imaging unit 7 (ST33).

  Therefore, the image processing arithmetic unit 9 calculates the solder area from the first light source image (ST34), calculates the solder height from the second light source image, and calculates the volume from the area and height (ST35).

  Next, the reference board data stored in the teaching step ST26 and the specimen board data are compared (ST36), the quality of the printed solder is judged from the comparison value (ST37), and the test result is reported (ST38). The substrate is removed from the one-dimensional table 3 (ST39).

  A three-dimensional imaging geometric optical arrangement is configured by a one-dimensional image sensor camera with an oblique imaging angle, a light source that illuminates from almost right above, and a light source that illuminates at an angle shallower than the imaging angle. The present invention can be applied to an inspection apparatus that performs automatic three-dimensional image measurement and inspection.

It is explanatory drawing which showed the whole structure of the inspection apparatus. (Example 1) It is a figure explaining the geometric optical arrangement | positioning and image processing of imaging in a test | inspection apparatus. (Example 1) It is the flowchart which showed the operation | movement of the teaching and automatic test | inspection in a test | inspection apparatus. (Example 1) It is explanatory drawing which showed the whole structure of the inspection apparatus. (Example 2) It is a figure explaining the geometric optical arrangement | positioning and image processing of imaging in a test | inspection apparatus. (Example 2) It is the flowchart which showed the operation | movement of the teaching and automatic test | inspection in a test | inspection apparatus. (Example 2)

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Board | substrate 2 Cream solder 4 One-dimensional color image sensor camera 5 Illumination device 6 Control apparatus

Claims (3)

An inspection apparatus for inspecting and measuring the print quality of a cream solder printed circuit board using a three-dimensional image,
A one-dimensional color image sensor camera that images the substrate at an oblique imaging angle, a first hue light source that illuminates the cream solder top surface from almost right above, and a second that illuminates the cream solder side surface at an oblique angle shallower than the imaging angle. An image pickup means that includes a hue light source and acquires a three-dimensional image of the entire surface of the substrate that is simultaneously double-illuminated with the first hue light and the second hue light by relatively moving the substrate in a direction orthogonal to the pixel arrangement of the camera. When,
Image processing means for performing difference image processing between the three-dimensional image of the specimen substrate acquired by the imaging means and the three-dimensional image of the reference board, and detecting pixels having a difference exceeding a set threshold as different pixels;
Image measurement means for calculating a three-dimensional measurement value of cream solder from the first hue light reflection region and the second hue light reflection region with respect to the reference substrate image and the specimen substrate image in the region where the different pixels are detected by the difference image processing; ,
An inspection apparatus comprising reporting means for reporting different pixels and three-dimensional measurement values. An inspection device that measures and inspects the print quality of a cream solder printed circuit board using a three-dimensional image,
A one-dimensional image sensor camera that images the substrate at an oblique imaging angle, a first light source that illuminates the top surface of the cream solder from almost right above, and a second light source that illuminates the cream solder side surface at an oblique angle shallower than the imaging angle. And by relatively moving the substrate in a direction orthogonal to the pixel arrangement of the camera, turning on the first light source during odd-numbered electronic scanning of the one-dimensional image sensor camera, and turning on the second light source during even-numbered electronic scanning Imaging means for acquiring a first light source reflected image of the substrate and a second light source reflected image of the substrate;
Image measuring means for calculating a three-dimensional measurement value of the cream solder from the first light source reflected image and the second light source reflected image;
An inspection apparatus comprising determination means for comparing the three-dimensional measurement values of the cream solder on the reference substrate and the sample substrate to determine whether or not the solder paste is good.   The inspection apparatus according to claim 1, further comprising a telecentric lens in front of the one-dimensional color image sensor camera of the imaging unit, or a telecentric lens in front of the one-dimensional image sensor camera of the imaging unit. The inspection apparatus according to claim 2.

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