JP2011209296A - Appearance inspection method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology for cutting down resources required for processing.SOLUTION: An amplification control unit 62 adjusts the amplification factor of image signals by an amplifier 60, according to the lighted state of a lighting unit 30 to balance the light quantity of a plurality of inspection images. Image processing for the plurality of inspection images can thereby be smoothly carried out.

Description

  The present invention relates to an appearance inspection technique. In particular, the present invention relates to an appearance inspection method and apparatus for scanning an object to be inspected to acquire an image and inspecting the appearance of the object to be inspected.

  Hardware that supports the IT boom can be broadly divided into the Internet as infrastructure and information devices such as PCs, PDAs, and mobile phones as terminals. The latter, that is, the background of the explosive spread of various terminals, largely contributes to the downsizing and cost reduction of products due to technological innovation, which is supported by high integration design.

  In addition to the enhancement of various design tools and the advancement of semiconductor technology, high-density mounting technology can be cited as factors that realize high integration design. The point of high-density mounting lies in manufacturing technology and inspection technology. Recently, due to the high mounting density, the demand for a non-contact type, in particular, an appearance inspection apparatus using an image recognition technology is increasing.

  The idea of using image recognition technology for appearance inspection has been known for a long time. However, the resolution required for inspection images is very high under the present situation in which hundreds to thousands of parts are often mounted even on a compact board. For example, when considering a resolution of around 20 microns, the time required for inspection is much longer than the mounting of components, which is becoming a huge drag in the intense product development competition.

  Under such circumstances, the present applicant has previously proposed an appearance inspection apparatus equipped with a line sensor in Japanese Patent Application Laid-Open No. 8-254500. This apparatus is provided with an epi-illumination source in addition to the side illumination source that was common at that time, and switches between these in accordance with the test items. The purpose is as follows.

  Now, let FIG. 1 be the board | substrate 1 which is a to-be-inspected object. 2 (a) and 2 (b) show the effects of the side light 6a and the incident light 6b, respectively. As shown in FIG. 2 (a), the reflected light 8a of the side light 6a is directed obliquely upward with respect to the horizontal plane of the component 2, and a part thereof is directed vertically upward with respect to the inclined portion where the solder 4 is correctly stacked. On the other hand, as shown in FIG. 2B, the reflected light 8b of the incident light 6b is substantially totally reflected on the horizontal surface of the component 2 and goes vertically upward, but this is not the case with the inclined portion.

  FIGS. 3A and 3B show images obtained by a CCD sensor provided vertically above the substrate 1 by side light 6a and incident light 6b, respectively. According to the side light 6a as shown in FIG. 3 (a), an image like a copy machine is obtained, and a bridge of a lead portion of a component, that is, determination of a mounting defect or a component polarity mark in which a solder shorts a plurality of leads. Is relatively easy. On the other hand, according to the incident light 6b as shown in FIG. 3B, a strong contrast image is obtained, and the contour portion of the three-dimensional object and the inclined portion of the solder appear black. Therefore, it becomes relatively easy to determine whether the solder is correctly attached to the electrode or lead of the component, in addition to the positional deviation of the component and the missing part.

  In recent years, the number of parts and other letters and numbers (hereinafter simply referred to as “model numbers”) are marked on a component with a laser. The model number engraved with a laser has almost no irregularities in the portion, and it is generally difficult to confirm the model number with a conventional appearance inspection apparatus. Therefore, in addition to specifying the mounted component itself, it tends to be difficult to inspect the attribute of the component, that is, resistance value, capacity, polarity, and the like. Also in the experiment by the present inventor, it was found that the confirmation of the laser marking is very difficult even in the inspection using the side light described above.

  The present invention has been made in view of such a situation, and an object thereof is to provide an appearance inspection technique capable of appropriately confirming the marking of a part. At this time, consideration is also given to the improvement of the processing speed, which is a general problem described above.

  One embodiment of the present invention relates to an appearance inspection method. In this method, by switching the lighting state of the illumination source, the object to be inspected under different lighting conditions and acquiring a plurality of inspection images, the image is acquired according to the lighting state of the illumination source. Alternatively, the light amounts of the plurality of inspection images are balanced by adjusting the amplification factor of the signal in the processing step. Here, “balance the light quantity” means that the light quantity falls within a predetermined range. Therefore, image processing for a plurality of inspection images, for example, edge detection processing in an image, determination processing for a bright and dark portion in an image, and the like can be shared or facilitated.

  When taking an inspection image under an illumination condition in which light is projected at the shallowest angle with respect to the upper surface of the object to be inspected, the amplification factor may be maximized. Here, “shallow angle” indicates that the incident angle with respect to the upper surface of the object to be inspected is close to 90 degrees. Thereby, the light quantity with the other image for an inspection can be appropriately balanced.

  Another embodiment of the present invention also relates to an appearance inspection method. In this method, by switching the lighting state of the illumination source, the inspected object is photographed under different illumination conditions, and a plurality of inspection images are acquired. In addition, the light amount is adjusted by providing an off time with a predetermined duty ratio in the on state, and the light amounts of a plurality of inspection images are balanced.

  By sequentially switching the lighting state of the illumination source in units of scanning lines while relatively moving the one-dimensional sensor and the object to be inspected in a direction perpendicular to the scanning direction of the one-dimensional sensor, the image for the inspecting object is scanned in the scanning line. The processing may be performed by sequentially switching the process of balancing the light amounts of a plurality of inspection images for each scanning line. Here, an image obtained by a plurality of scanning line units in the same illumination source lighting state is referred to as one “inspection image”. Therefore, when the lighting state of the illumination source is sequentially switched in units of scanning lines, “a plurality of inspection images” are obtained. According to this aspect, in addition to facilitating the processing due to the balance of the amount of light, the inspection time can be shortened by simultaneously acquiring a plurality of inspection images.

  Another aspect of this invention is related with an external appearance inspection apparatus. This device captures a plurality of images for inspection under different illumination conditions by switching the lighting state of an illumination source, and includes an epi-illumination source and a side illumination source as illumination sources. The lighting state of the side illumination source can be set to the first mode for normal side testing and the second mode in which only the lower part is lit so that only light from a shallower angle is cast. It is characterized by comprising. As a result, it is possible to acquire an image that makes it easy to grasp the fine uneven portions on the object to be inspected, for example, the marking of the mounted component.

  The surface of the object to be inspected is engraved. Based on the inspection image taken in the second mode, the surface of the object to be inspected (hereinafter, the imprinted characters and marks are simply “marked”). And an analysis unit for determining whether or not it matches a predetermined mark. Accordingly, it is possible to appropriately inspect whether or not a legitimate component is mounted on the inspected object based on the marking on the component mounted on the inspected object.

  It should be noted that any combination of the above-described constituent elements and those expressing the present invention as a method, system, computer program, etc. are also effective as an aspect of the present invention.

  According to the present invention, the number of items that can be inspected by the appearance inspection apparatus can be increased.

It is an external view of the board | substrate which is an example of a to-be-inspected object. FIG. 2A and FIG. 2B are diagrams showing the side light in the side test, the incident light in the incident test, and the direction of the reflected light, respectively. FIGS. 3A and 3B are diagrams showing examples of images obtained in the side test and the epi-illumination test, respectively. 1 is an overall configuration diagram of an appearance inspection apparatus according to a first embodiment. It is a detailed perspective view of the test unit which concerns on 1st Embodiment. It is a side view of the scanning unit containing an illumination unit. FIG. 7A, FIG. 7B, and FIG. 7C are diagrams showing lighting on and off states during the epi-illumination test, the side test, and the low side test, respectively. It is a figure which shows the state in which the illumination of the low side test was irradiated to the components mounted in the board | substrate. It is a figure explaining the content of control by an amplification control unit. It is a flowchart which shows the procedure performed by interleaving an incident test and a side test. It is a whole block diagram of the external appearance inspection apparatus which concerns on 2nd Embodiment. It is a figure explaining the lighting state which concerns on 2nd Embodiment.

  FIG. 4 shows a configuration of the appearance inspection apparatus 10 according to the embodiment. In this apparatus, an inspection surface of an object to be inspected is scanned with a line sensor to form an image, and pass / fail of a component mounting state is determined by image recognition. An image for each line is sequentially obtained by flowing the object to be inspected perpendicularly to the scanning direction by the line sensor.

  As shown in FIG. 4, the appearance inspection apparatus 10 includes a main unit 12 and a test unit 14. A conveyor 22 is provided in the lower part of the test unit 14 and flows at a constant speed from another process, for example, in a state where the substrate 1 that is an object to be inspected is gripped. A scanning head 16 is provided above the test unit 14.

  The scanning head 16 has an illumination unit 30, a lens 32, and a line sensor 34. These members are fixed on the frame 36. The illumination unit 30 incorporates an epi-illumination source, a side illumination source, a half mirror and the like which will be described later. The reflected light vertically upward from the substrate 1 is guided to the lens 32 by the half mirror, and after passing through the lens 32, is input to the line sensor 34 which is a one-dimensional CCD sensor. The line sensor 34 scans the substrate 1 line by line and outputs the image data 54.

  The main unit 12 controls the entire apparatus as a whole. The main unit 12 can be realized by a CPU, memory, or other LSI of any computer in terms of hardware, and an appearance inspection loaded into the memory in terms of software. It is realized by a functional program or the like, but here, functional blocks realized by their cooperation are depicted. Accordingly, those skilled in the art will understand that these functional blocks can be realized in various forms by hardware only, software only, or a combination thereof.

  First, the head control unit 40 of the main unit 12 outputs an illumination control signal 50 to the illumination unit 30 to realize different lighting states depending on the contents of the test. The head control unit 40 further outputs an amplification control signal 66 to the amplification control unit 62 and a test start signal 56 to the memory control unit 42, respectively. The amplification control unit 62 amplifies the image data 54 by the amplifier 60 so that the light amounts of images obtained in a plurality of tests are balanced as will be described later. The image data amplified by the amplifier 60 is converted into a digital format by an analog / digital converter 64 (A / D converter) and supplied to the memory 44. Even if the tests are different, the amount of light is adjusted to be balanced, so that each can be appropriately digitally converted. On the other hand, referring to the test start signal 56, the memory control unit 42 controls the writing of the digital image data to the memory 44, and thereafter the image data is recorded in line units.

  The analysis unit 46 reads the image data from the memory 44 in parallel with the scan or after the scan is completed, and determines pass / fail for each inspection item in light of the determination criterion recorded in the determination criterion storage unit 48 in advance. In the present embodiment, since the light amounts of the images obtained by the plurality of tests are balanced, for example, edge detection, light / dark determination in the image, and the like can be determined by the same or similar processing. Here, the presence or absence of solder bridges in tests that use side lighting (referred to as side tests), such as part misalignment, missing parts, and solder dullness determined by tests using epi-illumination (referred to as epi-illumination tests) There is an error determination of a mounted component by a test using a lower illumination of the side illumination (referred to as a low side test), such as a determination of a mounting component error or polarity reversal. In the judgment reference storage unit 48, judgment criteria or reference images relating to acceptance / rejection are recorded in advance for component mounting of the board 1 to be inspected, and these criteria or images are applied to the images actually acquired by the line sensor 34 to pass / fail. A determination is made.

  FIG. 5 is a perspective view of the test unit 14, and FIG. 6 is a schematic view of the test unit 14 viewed from the scanning direction 110. The illumination unit 30 has an epi-illumination source 100 and a side illumination source 102 that surround the half mirror 108. A lenticular sheet 106 is inserted between the epi-illumination source 100 and the half mirror 108, and the epi-illumination light passes through the lenticular sheet 106 and the half mirror 108 and is incident on the inspection surface of the substrate 1 with an incident angle of substantially zero. An acrylic sheet 104 is provided below the side illumination source 102. In this embodiment, the epi-illumination source 100 is given a width so that an epi-illumination component is present so that the incident angle becomes zero even when the substrate 1 is warped.

  As shown in FIG. 6, the epi-illumination source 100 is divided into two sub-boards 100 a and 100 b from the center, and each has an LED (light emitting diode) group in the scanning direction 110. These sub-boards 100a and 100b are connected so as to be slightly inwardly directed, and each LED group is arranged to efficiently project incident light onto the line 112 under inspection.

  On the other hand, the two side illumination sources 102 include a high side illumination source 102a having three rows of LED groups and a low side illumination source 102b having one row of LED groups. The line 112 is inclined so that side light is efficiently cast. The reflected light from the line 112 is reflected by the half mirror 108 and directed to the lens 32. If this is shown in FIG. 5, the incident light L1 from a certain point P in the incident illumination source 100 is reflected near the point Q on the substrate 1, and the reflected light L2 is reflected again by the half mirror 108, and the reflected light L3. Enters the lens 32. It should be noted that a power supply (not shown) is a separate system so that two rows of LED groups close to the center of the epi-illumination source 100 and the other four rows of LED groups can be controlled independently. The high side illumination source 102a and the low side illumination source 102b have separate power sources (not shown) so that the lighting control can be performed independently.

  The acrylic sheet 104 diffuses side light from the side illumination source 102. Since the side illumination source 102 is an aggregate of LEDs that are point light sources, if there is no diffusing action, there is a concern that spot-like light is reflected in image data and adversely affects inspection accuracy. On the other hand, the lenticular sheet 106 acts to narrow incident light to a component perpendicular to the substrate 1 in the scanning direction 110. The diffusing action related to the incident light is realized by the lenticular sheet 106.

  FIG. 7A, FIG. 7B, and FIG. 7C indicate the LED groups that are turned on during the epi-illumination test, the side test, and the low side test, by hatching. First, during the epi-illumination test, the epi-illumination source 100 as a whole is turned on, and the epi-illumination light 160 is projected from vertically above the substrate 1. The epi-illumination source 100 has a width in the driving direction to cope with warpage or deflection of the substrate 1.

  During the side test, which is the first mode, the entire side illumination source 102 is turned on and the side light 162 is cast. At the same time, the LED group outside the epi-illumination source 100 is turned on and the auxiliary light 164 is cast. Yes. As can be seen from FIGS. 2A and 2B, when the incident illumination source 100 and the side illumination source 102 have the same brightness, the reflected light 8a from the side light 6a detected by the line sensor 34 is obtained. Is darker than the reflected light 8b from the incident light 6b. Therefore, in order to compensate for this, an area outside the epi-illumination source 100 is turned on as shown in FIG. Even in this case, the light quantity is often not balanced, so the light quantity balancing process according to the present invention is useful. Note that since the auxiliary light 164 is emitted from an angle different from that of the side light 162, it approaches a state that is originally desirable in the side test, that is, a state in which light is uniformly irradiated from the entire periphery of the photographing unit.

  In the low side test which is the second mode, the low side illumination source 102b of the side illumination source 102 is turned on and the low side light 166 is emitted. Thereby, it is possible to project light at a shallower angle with respect to the substrate 1.

  FIG. 8 is a diagram illustrating a state where the illumination of the low side test is applied to the component mounted on the substrate. Here, a part of the surface of the component 2 is engraved with a mark 3 by a laser, for example. As shown in FIG. 8, most of the reflected light 166a of the low side light 166 is directed obliquely upward in the part 2 other than the mark 3 of the component 2. In the present embodiment, the side light 166 is cast at a shallow angle with respect to the substrate, so that the reflected light is hardly guided to the line sensor 34. On the other hand, part of the reflected light 166 b of the low side light 166 at the part 3 of the component 2 is directed vertically upward and guided to the line sensor 34. Therefore, it has been confirmed in experiments that the image of the mark 3 of the component 2 can be captured more appropriately.

  FIG. 9 is a diagram for explaining the contents of control by the amplification control unit 62. The amplification control unit 62 changes the amplification factor of the image data by the amplifier 60 for each test, and balances the light amount of the obtained image data. In this embodiment, according to the notification from the head control unit 40, the gain by the amplifier 60 is set to “100” in the case of the epi-illumination test, and is set to “70” in the case of the side test. In the case of the direction test, since the amount of light reflected is the smallest, the gain by the amplifier 60 is set to the maximum “250”. Although these numerical values are relative values, for example, “100” may be considered as the standard gain. Note that, when the amplification factor is high, noise components are visible, so here, the offset is set as a voltage value as an example.

  FIG. 10 is a flowchart showing processing operations performed by interleaving the epi-illumination test, the side test, and the low side test. Here, the lighting of the incident light, the lighting of the side light and the auxiliary light, and the lighting of the low side light are performed by interleaving, and for the incident light test while the substrate 1 passes under the scanning head 16, Test and low side test images are created individually and at once. For this reason, it is assumed that the image resolution of the appearance inspection apparatus 10 is sufficiently high, and even if the image is acquired every several lines, it sufficiently withstands the inspection purpose.

  First, it waits until the board | substrate 1 which flows on the conveyor 22 arrives at a predetermined position (S10), and when it comes to a predetermined position, scanning of 1 line is implemented under incident light (S12), and the image data Is amplified, A / D converted, and written to the memory 44 (S14). Then, it is determined whether or not the end position of the substrate 1 is to be inspected (S16). If it is not the end position (N in S16), the epi-illumination test mode is switched to the next side test mode in the next order (S18), the next one line scan under the side light and the auxiliary light, and the memory 44. Is written to (S12, S14), and it is again determined whether or not the end position is reached (S16). If it is not the end position (N in S16), switching from the side test mode to the next lower side test mode is performed (S18), and scanning of the next line under the low side light, the memory 44 is performed. Writing to (S12, S14) is performed. As described above, the processes from S12 to S18 are repeated until the substrate 1 comes to the end position, and a plurality of images are formed by each test. The 3N + 1-th (N = 0,1,2,...) Line image is an image of the epi-illumination test formed by epi-illumination, and the 3N + 2 (N = 0, 1, 2,...) Line image. The image is an image of a side test formed by side light and auxiliary light, and the image of the 3N-th (N = 1, 2,...) Line is a low side formed by low side light. It is an image of a test.

  If the board | substrate 1 comes to an end position, a process will progress to S20 from Y of S16, and the test | inspection regarding each item will be performed. The analysis unit 46 reads out the image obtained in the epi-illumination test mode from the memory 44 and inspects the epi-illumination test item, subsequently reads out the image obtained in the side-examination test mode and inspects the side test item. The image obtained in the side test mode is read to inspect the low side test item. Criteria and other information for pass / fail judgment are read from the judgment criteria storage unit 48 and used. The result is displayed when the test is finished. According to this interleave method, a plurality of test images can be acquired by passing the substrate 1 once under the scanning head, and the inspection time can be shortened.

  Next, it is determined whether or not to end the inspection process (S22). When the inspection process is ended (Y in S22), the series of processing is exited. On the other hand, when the inspection processing for the subsequent substrate 1 flowing on the conveyor 22 is continued (N in S22), the processing from S10 to S20 is performed on the substrate 1. In this way, the inspection process can be continuously performed on the substrate 1 that flows sequentially.

  FIG. 11 is an overall configuration diagram of an appearance inspection apparatus according to the second embodiment. Note that. In the figure, the same components as those in the appearance inspection apparatus shown in FIG. The head control unit 70 outputs an illumination control signal 50 to the illumination unit 30, and realizes different lighting states depending on the content of the test. In the present embodiment, not only the on / off steady state is set as the lighting state of the illumination source of the illumination unit 30, but also the light amount is adjusted by providing an off time with a predetermined duty ratio in the on state. . Thereby, the light quantity of each inspection image obtained by the plurality of tests obtained from the line sensor 34 is balanced.

FIG. 12 is a diagram illustrating a lighting state according to the second embodiment.
In the present embodiment, the head control unit 70 performs the epi-illumination shown in FIG. 7 (a) every 250 μs (microseconds) from when the line to be inspected of the substrate 1 comes under the scanning head 16, FIG. Control is performed so that illumination is possible in the order of side illumination shown in b) and low side illumination shown in FIG. Here, 250 μs is an example of the time required to move by one line by the conveyor 22.

  The head control unit 70 lights it for 100 μs when it is in a state where epi-illumination is possible, lights it for 70 μs when it can be side-illuminated, and lights it fully for 250 μs when low-side illumination is possible. In this way, by changing the lighting time so that the intensity of the reflected light is extinguished, the image light amounts of a plurality of tests taken into the line sensor 34 are balanced.

  The present invention has been described based on some embodiments. It is understood by those skilled in the art that these embodiments are exemplifications, and that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are also within the scope of the present invention. By the way.

  For example, in the embodiment, the conveyor 22 may be configured to be set on the substrate 1 from the production line.

  In the embodiment, when the image is stored in the memory 44, that is, in the image acquisition process, the signal amplification factor is adjusted. However, the present invention is not limited to this, and the amplification factor is used in the process of processing the data stored in the memory 44. May be adjusted.

  In the embodiment, the image is acquired by moving the substrate 1 without moving the scanning head 16, but the present invention is not limited to this, and the scanning head 16 is moved without moving the substrate 1. An image may be acquired. In short, the image may be acquired by relatively moving the scanning head 16 and the substrate 1.

  In the embodiment, the substrate 1 is considered as the object to be inspected, but the application of the appearance inspection apparatus 10 is not limited thereto. For example, the present invention can be widely applied to inspections that are meaningful for combinations of epi-illumination tests, side tests, and low side tests, as well as BGA (Ball Grid Array) type LSI pin inspections.

  In the embodiment, the epi-illumination source 100 and the side illumination source 102 are separately configured, but may be integrated. There is no need for a gap between the epi-illumination source 100 and the side illumination source 102, and various designs are possible as long as an optical path from the half mirror 108 to the lens 32 can be secured.

  1 substrate, 10 visual inspection device, 12 main unit, 14 test unit, 16 scanning head, 30 illumination unit, 34 line sensor, 40 head control unit, 42 memory control unit, 44 memory, 46 analysis unit, 60 amplifier, 62 amplification Control unit, 64 A / D converter, 100 epi-illumination source, 102 lateral illumination source, 110 scanning direction, 160 epi-illumination light, 162 lateral light, 164 auxiliary light, 166 low lateral light.

Claims (2)

In a method of photographing a test object under different illumination conditions by switching the lighting state of the illumination source and acquiring a plurality of inspection images,
In addition to setting a steady state of on and off as the lighting state of the illumination source, the light amount is adjusted by providing an off time with a predetermined duty ratio in the on state, and the plurality of inspection images An appearance inspection method characterized by balancing the amount of light. The visual inspection method is
By sequentially switching the lighting state of the illumination source in units of scanning lines while relatively moving the one-dimensional sensor and the object to be inspected in a direction perpendicular to the scanning direction of the one-dimensional sensor, the image for the inspecting object is scanned in the scanning line. Is obtained in units,
The appearance inspection method according to claim 1, wherein the process of balancing the light amounts of the plurality of inspection images is sequentially switched for each scanning line.

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