JP2021103152A - Foreign matter inspection device - Google Patents

Abstract

To provide a foreign matter inspection device capable of identifying a place at which a foreign matter exists on a substrate with high accuracy by combining height information and color information.SOLUTION: A foreign matter inspection device disclosed by the present description includes a height measuring instrument, a region extractor, and a foreign matter determiner. The height measuring instrument associates a two-dimensional lattice point with each place of a substrate, irradiates light to the substrate, and measures the height of each of the lattice points on the basis of its reflection light. The region extractor extracts regions other than a specific color as a foreign matter candidate region from a photographed image of the substrate. The foreign matter determiner outputs lattice points at which height exceeds prescribed threshold height and lattice points within a foreign matter candidate region among lattice points whose height cannot be measured by the height measuring instrument as a place at which a foreign matter exists.SELECTED DRAWING: Figure 3

Description

The techniques disclosed herein relate to foreign matter inspection devices that detect foreign matter on a substrate.

Foreign matter inspection devices that detect foreign matter on the surface of an object using light are known. The foreign matter inspection device of Patent Document 1 divides a laser beam into two by a beam splitter and irradiates the surface of an object with one of the laser beams. The foreign matter is identified from the phase difference between the reflected light from the surface of the object and the other divided laser light. The phase difference between the two laser beams represents the height from the object surface at the position where the laser beams are irradiated.

Further, the foreign matter inspection device disclosed in Patent Document 2 measures the height of the object surface from an image of the object surface, and identifies a portion higher than the object surface as a foreign matter.

Japanese Unexamined Patent Publication No. 10-293100 Japanese Unexamined Patent Publication No. 2019-027947

An inspection device that measures the height of an object surface based on the reflected light from the object surface and determines foreign matter from the height information can obtain a sufficient amount of reflected light due to the inclination of the upper surface of the foreign matter and dirt on the substrate surface. It may not be possible. In places where a sufficient amount of reflected light cannot be obtained, the height cannot be measured and the presence or absence of foreign matter cannot be determined. On the other hand, there is also known a technique of extracting a specific color region from an image of the surface of an object without being based on height information and identifying the color region as a foreign substance. However, an error may occur in the determination of foreign matter by color.

The present specification provides a foreign matter inspection apparatus capable of identifying a location where a foreign matter is present with high accuracy by combining height information and color information.

The techniques disclosed herein focus on the fact that substrates such as circuit boards have a particular distinct color. The present specification provides a foreign matter inspection device for detecting a foreign matter on a substrate of a specific color. The foreign matter inspection device disclosed in the present specification includes a height measuring device, a region extractor, and a foreign body determining device. The height measuring instrument associates two-dimensional lattice points with various parts on the surface of the substrate, irradiates the substrate with light, and measures the height of each lattice point based on the reflected light. The region extractor extracts a region other than a specific color from the captured image of the substrate as a foreign matter candidate region. The foreign matter judge is a grid point whose height exceeds a predetermined threshold height and a grid point in the foreign matter candidate region among the grid points whose height could not be measured by the height measuring device, where the foreign matter exists. Output as.

By the measurement of the height measuring device, it can be naturally determined that the lattice points whose height exceeds the threshold height are foreign substances. On the other hand, the grid points whose height could not be measured may be foreign substances. However, even if the height is a lattice point whose height cannot be measured, if the color is a specific color indicating the substrate, it can be inferred that it is not a foreign substance. On the contrary, if the height is a point that cannot be measured and the lattice point is not a specific color of the substrate, that is, the lattice point in the foreign matter candidate region, there is a high possibility that the foreign matter is present. Therefore, the foreign matter determining device of the foreign matter inspection device of the present specification outputs the grid points in the foreign matter candidate region as the places where the foreign matter exists among the grid points whose height cannot be measured by the height measuring device.

The foreign matter inspection device disclosed in the present specification classifies grid points whose height cannot be measured into those having a high possibility of being foreign matter and those having no possibility of being foreign matter by using color information, and enhances the accuracy of foreign matter determination. Note that the grid points whose height is found to exceed the threshold height based on the measurement results of the height measuring device are output as locations where foreign matter exists regardless of the color information. By doing so, the uncertainty of foreign matter identification based on color information is eliminated. That is, the foreign matter inspection device disclosed in the present specification can combine height information and color information to detect a location where a foreign matter is present with high accuracy.

The foreign matter judge adopts the following algorithm as a method of simultaneously extracting the grid points whose height exceeds a predetermined threshold height and the grid points in the foreign matter candidate region among the grid points whose height cannot be measured. Is also good. That is, the foreign matter determination device assigns a predetermined height exceeding the threshold height to the grid points in the foreign matter candidate region among the grid points whose height cannot be measured by the height measuring device, and then associates them with the surface. A grid point having a height exceeding the threshold height from the two-dimensional grid point is output as a place where a foreign substance exists. In this algorithm, foreign matter can be detected by comparing the height associated with each grid point with the threshold height without distinguishing between the grid points whose height can be measured and the grid points whose height cannot be measured. ..

As a method for measuring the height of the substrate surface, in addition to a method using a laser, for example, an optical cutting method or an interferometry method is known, but if the height measuring instrument uses reflected light, it is known. Any method may be adopted. An example of a region extractor includes a camera and a computer that processes images. Further, the foreign body determination device may be realized entirely by software and a computer, or a part of the processing realized by the foreign body determination device may be realized by dedicated hardware.

Details of the techniques disclosed herein and further improvements will be described in the "Modes for Carrying Out the Invention" below.

It is a block diagram of the foreign matter inspection apparatus of an Example. It is a figure which shows the relationship between the shape of an actual foreign substance and the measurement result of a height measuring instrument. It is a flowchart of the process of detecting a foreign substance. It is a figure which shows an example of the output result of a height measuring instrument. It is a figure which shows an example of the output result of a region extractor. It is a figure which shows an example of the result which complemented the output result of a height measuring instrument. It is a figure which shows an example of the output result of the foreign matter determination device.

The foreign matter inspection device 2 of the embodiment will be described with reference to the drawings. FIG. 1 shows a schematic block diagram of the foreign matter inspection device 2. In this embodiment, the foreign matter inspection device 2 inspects whether or not foreign matter is attached on the circuit board 90. The circuit board 90 is a board before devices such as semiconductor chips and resistance chips are mounted, and has a flat surface, but foreign matter 91 such as dust may be attached to the circuit board 90. The foreign matter inspection device 2 checks for foreign matter that may cause a short circuit prior to mounting a device such as a chip on the circuit board 90. The circuit board 90 determined to contain foreign matter is sent to a cleaning device, the surface of the circuit board 90 is cleaned, and then the foreign matter inspection device 2 checks again.

A solder resist is applied to the surface of the circuit board 90. Solda resist is a protective material containing a resin and a green pigment. The surface of many circuit boards is green, but it may be in other colors (such as red or black). The foreign matter inspection device 2 of the embodiment can check the presence or absence of foreign matter on the surface of the circuit board of a specific color.

The foreign matter inspection device 2 includes a height measuring device 10, a region extractor 20, and a foreign matter determining device 30. The height measuring device 10 includes a laser irradiator 11, an optical system 12, a galvanometer mirror 13, and a first controller 14. The laser beam emitted from the laser irradiator 11 is split into two optical paths by the beam splitter of the optical system 12, and one of the laser beams is reflected by the galvanometer mirror 13 and irradiated to the circuit board 90. The first controller 14 swings the galvano mirror 13. The laser beam reflected by the oscillating galvano mirror 13 scans two-dimensionally on the surface of the circuit board 90.

The laser beam reflected by the circuit board 90 is reflected by the galvano mirror again and returned to the optical system 12. The optical system 12 outputs the phase difference between the reflected light of the laser returned from the circuit board 90 and the other laser light split by the beam splitter to the first controller 14. The first controller 14 measures the height of the surface of the circuit board 90 from the phase difference obtained by the optical system 12. The resolution of the height (distance) due to the phase difference of the laser is several [μm] to several tens [μm]. The distance resolution in the scanning direction by the galvanometer mirror is several [μm] to several hundred [μm], although it depends on the scanning angle.

Since the laser beam scans the surface of the circuit board 90 two-dimensionally, the first controller 14 can obtain the data of the height of the surface of the circuit board 90 as the data of the two-dimensional lattice points. In other words, the height measuring device 10 associates two-dimensional grid points with various parts of the surface of the circuit board 90 and measures the height of each grid point. The two-dimensional grid points are associated so as to finely cover the surface of the circuit board 90. The distance between adjacent grid points is set to be smaller than the size of foreign matter allowed on the circuit board 90.

The standard of the measured height is the position of the surface of the circuit board 90 when it is assumed that no foreign matter is present. That is, the first controller 14 outputs the phase difference when there is no foreign matter on the surface of the circuit board 90 as a height of zero. Since the technique of measuring the height by the reflected light of the laser is well known, detailed explanation is omitted, but if the amount of the reflected light of the laser is not sufficient, the height of the lattice points at that time cannot be measured. There is.

Here, an example of the cause of the height becoming unmeasurable will be described with reference to FIG. FIG. 2A is raw data of the measurement result of the height measuring device 10. The horizontal axis shows the position on the surface of the circuit board 90 along the scanning direction of the laser beam, and the vertical axis shows the measurement result of the height at each position. Zero height means the surface of the circuit board 90 that is completely free of foreign matter. In FIG. 2A, the actual shape of the foreign matter is shown by a chain double-dashed line. In the start range A and the end range C of the foreign matter in the scanning direction, the top surface of the foreign matter is greatly inclined, so that the reflected light of the laser deviates greatly from the incident direction. Since most of the reflected light of the laser does not return to the galvanometer mirror 13 (optical system 12), the height cannot be measured. At the center of the foreign matter (range B) along the scanning direction, the parietal surface of the foreign matter is substantially flat, so that most of the reflected light of the laser returns to the galvano mirror 13 (optical system 12) and the height is measured. ..

FIG. 2B shows data in which grid points (lattice points 1 to grid points 8) are assigned at equal intervals with respect to the scanning direction of FIG. 2 (A) and the height of each grid point is described. The distance between the grid points is larger than the distance resolution in the scanning direction determined by the mechanism of the optical system 12 and the galvanometer mirror 13. The first controller 14 uses the average value of the height data during the distance corresponding to the grid point interval centered on each grid point as the height of the grid points. In the case of two-dimensional scanning, the height of the grid points is the average value of the height measurement results within the range of the rectangle centered on the grid points (rectangle with the grid point spacing as one side).

Further, the "lattice point" is expressed as a variable in the program executed by the first controller 14. In other words, the "grid points" on the surface of the circuit board 90 are associated with a specific area of memory included in the first controller 14.

At grid point 1-lattice point 3, grid point 7, and grid point 8, the height is appropriately measured, and the measurement result is almost zero. Therefore, the height "0" is stored in those grid points (memory areas associated with the grid points). The grid point 5 corresponds to the center (range B) of the foreign matter along the scanning direction, and the height of approximately 500 [μm] is measured in the range B. Therefore, "500" is stored in the grid point 5 (memory area associated with the grid point 5). The grid points 4 and 6 correspond to the start range A and the end range C of the foreign matter along the scanning direction, and the height cannot be measured.

The first controller 14 measures the height of each lattice point of the two-dimensional lattice point group associated with the surface of the circuit board 90, but cannot measure the lattice point (memory area corresponding to the lattice point). Stores a special value in. A height (for example, -500) that cannot be actually measured is set for a special value attached to a grid point that cannot be measured. Considering the efficiency of the subsequent processing, a negative value having a large absolute value is preferable as a special value.

FIG. 2C shows the result of storing a special value (-500) at the unmeasurable grid points. "-500" is stored in the grid points 4 and 6 whose height cannot be measured. The first controller 14 outputs data (height data of a two-dimensional grid point group) in the format (however, two-dimensional) shown in FIG. 2C. By storing a special value in the grid points that could not be measured, the foreign matter judge 30 that received the height data of each grid point of the two-dimensional grid point group identifies the grid points that could not be measured. It will be easier. In the following, for convenience of explanation, storing a specific numerical value in a memory area corresponding to a grid point is simply expressed as storing height data in the grid point.

Returning to FIG. 1, the region extractor 20 will be described. The area extractor 20 includes a camera 21 and a second controller 22. The camera 21 acquires the surface of the circuit board 90 as a color image. The second controller 22 extracts the contour of the circuit board 90 from the color image of the surface of the circuit board 90, and specifies a color region other than the color of the surface of the circuit board 90 within the contour. As described above, since the surface of the circuit board 90 is green, the second controller 22 extracts a non-green region inside the contour of the circuit board 90. The region extractor 20 outputs a region inside the contour of the circuit board 90 that is not the color (green) of the circuit board 90 as a foreign matter candidate region. Since the technique of region identification based on the difference in color is also well known, detailed description thereof will be omitted.

The foreign matter determining device 30 includes a third controller 31 and a display device 32. The third controller 31 is a computer, and by executing a predetermined program, the output of the height measuring device 10 (height data of each lattice point of the two-dimensional lattice point group) and the output of the area extractor 20 (foreign matter). The presence or absence of foreign matter (where the foreign matter exists) is determined from the data of the candidate area).

The third controller 31 is preset with a threshold height (and an allowable area) for determining whether or not it is a foreign substance from the height data. More specifically, the height (allowable height) of foreign matter allowed in the finished product of the circuit board 90 on which the device is mounted is predetermined, and the threshold height is the allowable height plus a predetermined margin. It is set to the value. Even if the height exceeds the threshold height, if the area does not exceed the permissible area, it is not determined as a foreign substance, but the area will be mentioned at the end of the embodiment. In this embodiment, since the main purpose is to handle the grid points that could not be measured by the height measuring device 10, it is assumed that the grid points whose height data exceeds the threshold height are unacceptable foreign substances.

The third controller 31 identifies a lattice point having a height exceeding the threshold height as a place where a foreign substance exists from the height data of each lattice point of the two-dimensional lattice point group acquired from the height measuring device 10. .. Further, the third controller 31 collates the output of the height measuring device 10 with the output of the area extractor 20, and determines whether or not the grid points whose height cannot be measured correspond to the foreign matter. Specifically, the third controller 31 identifies the grid points in the foreign matter candidate region among the grid points whose height could not be measured by the height measuring device 10 as the locations where the foreign matter exists.

Finally, the third controller 31 displays the area determined to be foreign matter on the display device 32, and notifies the upper controller 40 that the circuit board 90 has a foreign matter having a height exceeding the permissible range. The host controller 40 excludes the notified circuit board 90 from the production line and issues a command to the substrate transfer device (not shown) to send it to the cleaning device (not shown).

FIG. 3 shows a flowchart of the process executed by the foreign matter inspection device 2. Steps S2 and S3 are executed by the height measuring instrument 10, and steps S4 and S5 are executed by the region extractor 20. The foreign matter inspection device 2 may execute steps S2 and S3 and steps S4 and S5 in parallel or in order. Steps S6-S8 are executed by the foreign matter determining device 30.

The height measuring device 10 irradiates the surface of the circuit board 90 with laser light while scanning it two-dimensionally, and measures the height of each portion of the surface of the circuit board 90 (step S2). Next, the height measuring instrument 10 allocates a two-dimensional grid point group to the surface of the circuit board 90, and stores the height data of the portion corresponding to each grid point from the scanning information and the measured height data. In other words, the height data of the two-dimensional grid point group is generated based on the measured height of each part of the substrate surface (step S3). That is, the height measuring instrument 10 secures a memory area representing the grid points corresponding to each location on the surface of the circuit board 90, and stores the data of the corresponding height in each memory area (that is, the grid points).

FIG. 4 shows an example of the output result of the height measuring instrument 10. In the example of FIG. 4, height data is stored in each grid of a two-dimensional grid of 8 rows × 8 columns. In the example of FIG. 4, the entire region of 8 rows × 8 columns corresponds to the entire surface of the circuit board 90. As mentioned earlier, the spacing between adjacent grids is shorter than the size of foreign matter allowed. For convenience of explanation, each row is represented by letters ah and each column is represented by a number 1-8. The upper left grid point in FIG. 4 is referred to as "lattice point a1", and the lower right grid point is represented by "lattice point h8". Is written. The same applies to FIGS. 5 to 7 below.

In the example of FIG. 4, a numerical value other than zero is stored in the grid points of the area A and the area B. The numerical value indicates the height, and the unit is [μm]. On the other hand, the grid points where zeros are stored indicate the points where the height was measured appropriately and the height was zero as a result of the measurement.

"-500" is stored in the grid points marked with black circles in the area A and the area B. That is, the grid points with black circles indicate the grid points whose height could not be measured. Numerical values other than "-500" represent appropriately measured heights. In the example of FIG. 4, some grid points cannot be measured in height in region A, and all grid points belonging to region B cannot be measured in height. The height measuring device 10 sends the data shown in FIG. 4 (height data of the two-dimensional lattice point group) to the foreign matter determining device 30.

Returning to FIG. 3, the description of the process is continued. The region extractor 20 photographs the surface of the circuit board 90 (step S4), and extracts a foreign matter candidate region from the captured image (step S5). As described above, specifically, the region extractor 20 extracts the contour of the circuit board 90 from the captured image, and the region excluding the color region of the substrate included in the contour is a foreign matter candidate. Extract as an area.

FIG. 5 shows an example of the output result of the region extractor 20. FIG. 5 corresponds to FIG. 4, and the region extractor 20 divides the region in the contour of the circuit board 90 so as to correspond to the two-dimensional grid point group set by the height measuring instrument 10. That is, 8 rows × 8 columns in FIG. 5 correspond to the entire surface of the circuit board 90. In the example of FIG. 5, the white grid points indicate a region that is the color of the substrate, and the hatched region represents a region of a color other than the substrate, that is, a foreign matter candidate region.

In the case of the example of FIG. 5, a region A and a region C are extracted as foreign matter candidate regions. Area A corresponds to area A in FIG. The region extractor 20 determined that the region C was also a foreign matter candidate region. However, referring to FIG. 4, the height measuring instrument 10 can appropriately measure the heights of the grid points b2 and the grid points b3 corresponding to the region C, and the heights of those grid points are zero. there were. On the other hand, the area B of FIG. 5 corresponds to the area B of the result measured by the height measuring device 10 shown in FIG. 4, and the area extractor 20 determines that the area B is the color of the substrate.

Returning to FIG. 3, the description of the process is continued. The foreign matter determining device 30 collates the output of the height measuring device 10 (FIG. 4) with the output of the area extractor 20 (FIG. 5), and determines the height of the grid points that the height measuring device 10 could not measure. Complement the data (step S6). In this embodiment, the threshold height described above is set to 200 [μm].

Specifically, the foreign matter determining device 30 stores a special numerical value “−500” in the grid points in the foreign matter candidate region among the grid points whose height cannot be measured by the height measuring device 10. FIG. 6 shows an example in which the result of the height measuring device 10 is complemented by using the result of the area extractor 20. As shown in FIG. 4, in the region A, the grid points e2, e4, g2, g4, and h1 are the grid points whose height cannot be measured. Since the region A is a region determined to be a foreign matter candidate region by the region extractor 20, the foreign matter determining device 30 applies a specific value (here, “900”) exceeding the threshold height to those grid points. Store. In FIG. 6, the grid points marked with stars correspond to the grid points marked with black circles in FIG. 4, and the numerical value “900” is stored in those grid points.

On the other hand, as shown in FIG. 4, the heights of all the grid points in the region B could not be measured, but according to the region extractor 20, the region B is not a foreign matter candidate region, so the data of those grid points. Does not change.

Further, the region C is a region determined by the region extractor 20 to be a foreign matter candidate region, but the grid points in the region C are grid points at which the height measuring instrument 10 can appropriately measure the height. , The data is not changed.

Returning to the description of FIG. The foreign matter determination device 30 searches the data of the complemented two-dimensional grid point group, identifies the grid points whose height exceeds the threshold height as the region where the foreign matter exists (step S7), and identifies the grid points. The result is output (step S8).

FIG. 7 shows an example of the result of identifying the foreign matter region. The foreign matter determining device 30 searches for the result of FIG. 6 (data of a two-dimensional grid point group supplemented with height data), and the grid whose height exceeds the threshold height (200 in the case of this embodiment). The point is identified as a foreign body area. From the result of FIG. 6, since only the grid points of the region A exceed the threshold height (200), the foreign matter determining device 30 identifies the region A as a region where the foreign matter exists. The range showing hatching in FIG. 7 (that is, region A) shows a group of grid points determined to be foreign matter.

The foreign matter determining device 30 displays the result of FIG. 7 on the display device 32 and sends it to the host controller 40.

The advantages of the foreign matter inspection device 2 will be described. In the example of FIG. 4, the height measuring device 10 could not measure the heights of the grid points e2, e4, g2, g4, and h1 in the region A. In addition, the heights of all the grid points belonging to the region B could not be measured. In the region B, since the region extractor 20 determined that the color of the substrate was used, the foreign matter determining device 30 determined that the height could not be measured but was not a foreign matter.

On the other hand, since the region extractor 20 determined that the region A was a foreign matter candidate region, the foreign matter determining device 30 determined that the height could not be measured but was a foreign matter.

Further, the region extractor 20 determined that the region C in FIG. 5 was a foreign matter candidate region because the color of the substrate was different from that of the substrate. However, as a result of measuring the height of the grid point of the region C by the height measuring device 10, it is found that the height is zero. Judged.

As described above, the foreign matter inspection device 2 of the embodiment can classify the lattice points whose height cannot be measured into foreign matter and non-foreign matter using color information, and can realize highly accurate foreign matter determination.

The points to be noted regarding the technique described in the examples will be described. When the permissible range is set for the area of the foreign matter, the foreign matter determining device 30 checks whether or not the area of the region specified as the foreign matter exceeds the permissible range from the result of FIG. 7. Only when the area of the region specified as a foreign matter exceeds the permissible range, the foreign matter determining device 30 determines that the region is a foreign matter and notifies the upper controller 40 that the foreign matter is present. Since the area comparison process is well known, the explanation is omitted.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of claims. The techniques described in the claims include various modifications and modifications of the specific examples illustrated above. The technical elements described herein or in the drawings exhibit their technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the techniques illustrated in the present specification or drawings can achieve a plurality of purposes at the same time, and achieving one of the purposes itself has technical usefulness.

2: Foreign matter inspection device 10: Height measuring device 11: Laser irradiator 12: Optical system 13: Galvano mirror 14: First controller 20: Area extractor 21: Camera 22: Second controller 30: Foreign matter judging device 31 : Third controller 32: Display device 40: Upper controller 90: Circuit board 91: Foreign matter

Claims (2)

It is a foreign matter inspection device that detects foreign matter on a substrate of a specific color.
A height measuring device that associates two-dimensional grid points with various parts of the surface of the substrate, irradiates the substrate with light, and measures the height of each grid point based on the reflected light.
A region extractor that extracts regions other than the specific color as foreign matter candidate regions from the captured image of the substrate, and
Of the grid points whose height exceeds a predetermined threshold height and the grid points whose height cannot be measured by the height measuring device, the grid points in the foreign matter candidate region are defined as places where foreign matter exists. Foreign matter judge to output and
Foreign matter inspection device equipped with. The foreign matter determination device gives a predetermined height exceeding the threshold height to the lattice points in the foreign matter candidate region among the lattice points whose height cannot be measured by the height measuring device, and is two-dimensional. The foreign matter inspection device according to claim 1, wherein a grid point having a height exceeding the threshold height from the grid point is output as a place where a foreign matter exists.

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