JP4491722B2 - Film inspection equipment - Google Patents

Description

  The present invention relates to a film inspection apparatus. In particular, the present invention relates to a film inspection apparatus capable of accurately inspecting a dispersed state of particles in a film in which a large number of particles are dispersed, such as an anisotropic conductive adhesive film.

  Anisotropic conductive adhesive films are used for connection between electrodes of electronic components and circuit boards, and for connection of electrodes between circuit boards. This film is a tape-like film in which conductive particles are dispersed in an insulating binder such as an epoxy resin. The film is placed between the electrodes to be connected and connected without being damaged by heating and pressure bonding. Do.

  In such a film, the conductive particles must be almost uniformly dispersed at a predetermined density so that the conductive particles are interposed between the electrodes to be connected. For this reason, in manufacture of an anisotropically conductive adhesive film, inspection of the dispersion state of the conductive particles in the film is performed before product shipment.

  As such a film inspection technique, the technique described in Patent Document 1 is known. In this technique, the image sensor of a CCD camera receives light that has passed through a film, and converts the light signal of the image sensor into lightness. On the other hand, the relationship (correlation graph, relational expression, etc.) between the number of particles and the brightness in a predetermined region in the film is obtained in advance by experiments or the like. Then, the number of fine particles existing in a predetermined area of the film is determined by substituting the brightness measured by the image sensor into the relational expression or comparing the correlation graph with the measured brightness. According to this technique, the number of particles can be measured in a short time by computer processing based on the correlation between the brightness and the number of particles obtained in advance by directly photographing the film with a CCD camera.

Japanese Patent Laid-Open No. 2003-222584

  However, the above inspection technique has the following problems.

(1) It is difficult to accurately recognize individual particles in the film.
In the above prior art, the average brightness per unit region is obtained, and the number of particles is estimated by calculation from the relationship between the average brightness and the number of particles and the brightness obtained in advance. For this reason, individual particles are not recognized, and the number of particles obtained is merely an estimated value obtained by calculation, so that accuracy is lacking.

  On the other hand, it is also conceivable to make individual particles appear by applying a binarization process to a transmission image of a film. However, it is difficult to set the binarization threshold appropriately, and for example, fine particles may be overlooked. In particular, in the case of an anisotropic conductive adhesive film, there are cases where elongated particles having a large aspect ratio are used as the conductive particles. At that time, if the long diameter of the long and narrow particle is oriented along the optical axis of the camera that shoots the film, the particle is displayed only as an extremely fine particle in the image, so that it is distinguished from the noise in the image. It is very difficult.

(2) Characteristics other than the number of particles, particularly the orientation state of the particles cannot be detected.
As described above, in the case of the anisotropic conductive adhesive film, there are cases where elongated particles having a large aspect ratio are used as the conductive particles. At that time, it is also an important characteristic which direction of the film the long diameter of the elongated particles is oriented. Although the number of conductive particles can be estimated in the above prior art, since the number of particles does not change regardless of the orientation state, it is impossible to inspect the orientation state at all. In particular, as described above, since it is difficult to accurately grasp individual particles, it cannot be expected to accurately measure the size of conductive particles.

(3) It is difficult to obtain a clear image when the film thickness varies.
The distance between the CCD camera and the film used in the prior art is kept constant. Therefore, when inspecting products with different film thicknesses, the CCD camera cannot be accurately focused on the film, and an appropriate transmission image of the film cannot be obtained.

  Accordingly, a main object of the present invention is to provide a film inspection apparatus capable of accurately inspecting various dispersion characteristics of particles dispersed in a film.

  The present invention obtains a transmission image of a film in which particles are dispersed, creates two types of images in which fine particles and coarse particles are manifested from the image, and uses both images to create individual images. The above-mentioned purpose is achieved by enabling accurate grasp of particles.

  The inspection apparatus according to the present invention includes a light source disposed on one side of a light transmissive film in which particles are dispersed, an image receiving unit disposed on the other side of the film, and acquiring a transmission image of the film, and an image receiving unit. Fine particle revealing means for creating fine particle manifestation images by revealing fine particles from the obtained original image, and coarse particle revealing means for creating coarse particle revealing images by revealing coarse particles from the original image, It has inspection image creation means for creating an inspection image from a fine particle exposure image and a coarse particle exposure image, and characteristic calculation means for calculating the characteristics of the particles in the inspection image.

  In this inspection apparatus, a transmission image of a film in which particles are dispersed is subjected to image processing using a computer to create two types of images in which fine particles and coarse particles are manifested. By using both of these images, an inspection image in which not only coarse particles but also fine particles are clarified is created, and the characteristics of the particles are calculated from the inspection images. Therefore, the individual particles in the film can be accurately grasped, and various characteristics of each particle can be calculated.

  Hereinafter, the device of the present invention will be described in more detail.

  In the apparatus of the present invention, a film to be inspected is arranged between the light source and the image receiving means. A transmission image of the film can be obtained by the arrangement of the light source and the image receiving means.

  The film is preferably run between the light source and the image receiving means. By running the film and sequentially performing inspections at different positions in the longitudinal direction of the film, it is possible to perform inspections at arbitrary positions such as a part, main part, or all of the film in a short time.

  The light source may be any light source that has sufficient brightness to allow the image receiving means to obtain a transmission image of the film.

  The image receiving means captures a transmission image of the film. Typically, a CCD camera having a large number of image sensors and converting and outputting the intensity of light received by each element to an electrical signal can be suitably used. An original image of the film is obtained by this image receiving means.

The fine particle revealing means may be any means that can remove coarse particles from the transmission image and reveal the fine particles so that the fine particles can be accurately grasped. For example, an expansion / contraction unit that performs expansion / contraction processing on an original image to obtain an expansion / contraction image, a difference image generation unit that generates a difference image between the original image and the expansion / contraction image, and binarization processing of the difference image What has a binarization means for obtaining a binarized difference image is mentioned. When an expansion and contraction process is performed on an original image including coarse particles and fine particles, the coarse particles are enlarged and the fine particles are substantially removed. In general, expansion processing is processing for setting a pixel to 1 if there is even one (for example, white) in the vicinity of a pixel (for example, 4 or 8), and contraction processing is performed in the vicinity of a certain pixel. If there is even one 0 (for example, black), this is a process for setting the image to 0. For example, in the case of an original image in which substantially black particles are dispersed in an almost white insulating binder, when the expansion process is performed on the original image, fine particles are removed, and by performing a contraction process on the expanded image, An expansion / contraction image in which the remaining coarse particles are clear is generated.

  After the expansion / contraction image is created, the difference image is obtained by dividing the expansion / contraction image from the original image. By this process, coarse particles are removed from the original image, and a difference image in which fine particles are represented is created. Then, by binarizing the difference image, it is possible to obtain a binarized difference image in which fine particles are revealed and coarse particles are removed.

  On the other hand, the coarse particle revealing means can remove the fine particles or noise that is difficult to distinguish from the fine particles from the transmission image so that the coarse particles can be accurately grasped, so long as the coarse particles can be revealed. Good. For example, there may be mentioned one having binarization means for binarizing the original image to obtain a binarized original image. By this binarization process, pixels brighter than the threshold to be binarized are white and pixels darker than the threshold are black, so fine particles and noise are removed and coarse particles are removed. Can be revealed.

  The inspection image creation means includes, for example, creating an inspection image by adding the binarized original image and the binarized difference image. The above-mentioned binarized original image and binarized difference image are an image in which coarse particles are manifested and an image in which fine particles are manifested. By adding both images, all the particles are not leaked. I can grasp it. Therefore, if the particle property is detected based on the inspection image, a more accurate film inspection can be realized.

  The characteristic calculation means calculates the properties of the particles from the inspection image. Specific examples of the particle properties include at least one of aspect ratio, area, particle size, particle density, particle pitch, number of particles present in a certain region, and area where particles are absent in a certain region. By accurately obtaining these many particle characteristics, it is possible to measure not only the number of particles in the film but also items that could not be accurately detected in the past, such as orientation.

  In the apparatus of the present invention, it is also desirable to have a drive mechanism that makes the distance between the film and the image receiving means variable. The driving mechanism may drive either the film side or the image receiving means side. However, the driving mechanism can be simplified by driving the image receiving means rather than driving the traveling film side. As a specific example of the drive mechanism, there is an elevating mechanism that moves the image receiving means up and down with respect to the film. In that case, the image receiving means acquires a preliminary image at each position where the distance between the film and the image receiving means is different, and selects an image with the most accurate focus of the image receiving means as an original image from the plurality of preliminary images. Can do.

  In other words, each preliminary image is subjected to differential processing, differential processing means for calculating the differential value of the brightness of the particle contour in the preliminary image, area calculating means for calculating the area of the particles in the preliminary image, and each preliminary image. It is preferable to have a focus determination unit that obtains a ratio “derivative value / particle area” between the obtained differential value and the particle area as a focus value and determines a preliminary image having the maximum focus value as an original image.

  When the focus of the image receiving means, for example, the camera, is poor, the particles are expressed in a blurred manner on the preliminary image and larger than the particles on the image with the proper focus. On the other hand, when the focus is appropriate, the particles are clearly expressed on the preliminary image and are expressed smaller than the particles on the sweet image. Therefore, if the differential value of the luminance of the particle contour portion in the preliminary image is calculated, the differential value becomes small in the preliminary image with poor focus (the luminance change rate in the contour portion becomes small), and the preliminary image with the appropriate focus is obtained. In, the differential value increases (the luminance change rate at the contour increases). Further, if the area of the particles in the preliminary image is measured, the particle area increases in the preliminary image with poor focus, and the particle area decreases in the preliminary image with appropriate focus. Then, by determining the ratio of the differential value obtained from each preliminary image and the particle area “differential value / particle area” as the focus value, the influence of the original size of the particle is eliminated and the appropriate degree of focus is determined. Can do. That is, it can be determined that the preliminary image from which the maximum point of the focus value is obtained is the most focused image.

  A film in which particles are dispersed is suitable for the inspection target of the apparatus of the present invention. In order to obtain a transmission image, a transparent or translucent film is used. A typical example is an anisotropic conductive adhesive film in which a large number of conductive particles are dispersed in an insulating binder.

  According to the apparatus of the present invention, an inspection image is created not only by binarizing an original image but also by combining both an image in which fine particles are manifested and an image in which coarse particles are manifested. Therefore, it is possible to accurately grasp fine particles to coarse particles without omission. Therefore, an inspection image in which individual particles are clearly displayed can be obtained, and various particle properties can be obtained from the inspection image by image processing.

  Hereinafter, an embodiment of the present invention will be described by taking as an example the case of inspecting an anisotropic conductive film.

(Device configuration)
FIG. 1 is a schematic configuration diagram of the apparatus of the present invention, and FIG. 2 is a functional block diagram of the apparatus.

  The apparatus of the present invention includes a camera 100 disposed above an anisotropic conductive film 500 traveling in one direction on a horizontal plane, an illumination 200 disposed below the film 500, and an image captured by the camera 100. An image processing apparatus (computer 300) that performs image processing on the display and a monitor 400 that displays inspection results and the like are included.

  Here, the film 500 is a transparent insulating binder in which a large number of conductive particles are dispersed. The film 500 is supplied from a supply reel (not shown), runs on a transparent glass plate 600, and is also wound up (not shown). It is wound up on a reel. The transport mechanism for the film 500 is provided with an encoder 610, and the traveling position in the longitudinal direction of the film 500 can be grasped from the number of rotations of the reel detected by the encoder 610.

  The camera 100 is a CCD camera. The light emitted from the illumination 200 passes through the film 500, and the transmitted light is captured by the camera 100, and the transmitted light is converted into image data and output. This data is amplified by the camera amplifier 110 and stored in the image memory 310 as a preliminary image or original image to be described later.

  The camera 100 is supported by an X-Z stage 120, and is configured to move up and down and slide in the film width direction. The operation of the X-Z stage 120 is controlled via the motor driver 320 in accordance with a command from the computer 300. The raising / lowering operation of the camera 100 is used when the camera 100 is focused on the film 500, as will be described later. Therefore, the camera 100 of this example uses a fixed focus type.

  As the illumination 200, strobe illumination emitted by a command from the computer 300 was used. The strobe illumination light is irradiated from a condenser lens disposed at a position facing the camera 100 via an optical fiber.

  A synchronization signal is output from the synchronization signal generation unit 330 to the camera 100 and the illumination 200 in response to the signal of the encoder 610, and the camera 100 acquires a transmission image of the film 500 in response to light emission from the strobe illumination. This makes it possible to recognize which position in the longitudinal direction of the film 500 is acquired. Further, it can be determined from the command signal from the motor driver 320 to the X-Z stage 120 which position in the width direction of the film 500 is acquired.

  On the other hand, the image data stored in the image memory 310 is used for determining the appropriateness of the focus of the camera 100 and creating an inspection image. The focus suitability is determined by using a preliminary image acquired in the image memory 310, obtaining a differential value of luminance at the contour of the conductive particle by the differential processing means 341, and calculating the area of the particle by the area calculating means 342. Then, the focus determination means 343 selects the preliminary image with the best focus as the original image from the ratio between the differential value and the area.

  The selected original image is processed by the fine particle revealing means 350 that reveals fine particles among the conductive particles and the coarse particle revealing means 360 that reveals coarse particles, and each fine particle reveals. Create images and coarse particle manifestation images. Subsequently, an inspection image is created by the inspection image creation means 370 by using these two manifest images.

  The characteristic calculation means 380 evaluates the characteristics of the film 500 with respect to the obtained inspection image. Here, the aspect ratio, area, particle size, particle density, particle pitch, number of particles present in a certain region, and particle non-existing area within the certain region are obtained by calculation.

  These evaluation results are displayed on the monitor 400. Monitor 400, if necessary, each image acquired and generated at each stage of inspection, that is, preliminary image, original image, fine particle manifestation image, coarse particle manifestation image, difference image, binarized original image, A binary difference image is also displayed.

(Processing procedure)
FIG. 3 is a flowchart showing the processing procedure of the apparatus of the present invention. In the following description, refer to FIG. 1 and FIG. 2 for each component of the apparatus.

<Focus and selection of original image>
In order to obtain an accurately focused transmission image, first, the camera 100 is moved up and down by the XZ stage 120, the vertical position of the camera 100 with respect to the film 500 is changed, and a preliminary image at each position is acquired (step S1). . The preliminary image is a group of original image candidates from which an inspection image is created, and is composed of a transmission image of the film 500 taken at each camera position.

  The obtained luminance data of each preliminary image is differentiated by the differentiation processing means 341 (step S2). From this differential result, the differential value of the contour part of any conductive particle is acquired (step S3). This differential value indicates the rate of change in luminance at the contour of the particle. The higher the value, the more clearly the particle is shown on the image and the image is in focus. Indicates that the subject is out of focus.

  Next, the area calculation means 342 calculates the area of the target particle for which the differential value has been obtained (step S4). In general, an image out of focus of a camera shows a particle outline that is blurred, so that the particle area is large. In an image that is in focus, the particle outline is clear and the particle area is small.

  The differential value and the particle area are obtained for each preliminary image, and the ratio “differential value / particle area” is obtained as the focus value for each preliminary image (step S5). By determining the ratio “differential value / particle area”, it is possible to determine the appropriate degree of focus while eliminating the influence of the original size of the particles. This determination is made by obtaining the maximum point of the ratio “differential value / particle area” by the focus determination means 343.

  An example of the relationship between the vertical distance between the film and the camera and the focus value is shown in the graph of FIG. As shown in this graph, it can be seen that the focus value is small and the maximum point exists in the middle if the vertical distance between the film and the camera is too small or too large. The preliminary image from which the maximum point is obtained is the preliminary image with the best focus, and the preliminary image may be selected as the original image (step S6).

<Realization of fine particles>
Next, when an original image is selected, the original image is temporarily stored in the image memory (step S7). Although this original image is a transmission image of the film, it is difficult to accurately recognize the conductive particles as it is, so the image processing described below is performed to create an optimal inspection image for determining the properties of the conductive particles. To use.

  To create an inspection image, first, the fine particles in the original image are made obvious. In this processing, the original image is subjected to expansion / contraction processing by the expansion / contraction means 351, once fine particles are removed, and an expansion / contraction image showing only coarse particles is obtained (step S8).

  Subsequently, the difference image creating means 352 subtracts the expansion / contraction image from the original image to create a difference image (step S9). Since only the coarse particles are represented in the expansion / contraction image, if the expansion / contraction image is subtracted from the original image, a differential image in which only fine particles remain is obtained. Then, the difference image is binarized by the binarization means 353, thereby creating a fine particle manifestation image (binarization difference image) in which fine particles are manifested (step S10). That is, by combining the expansion / contraction process, the difference process, and the binarization process, a fine particle manifestation image can be created.

<Appearance of coarse particles>
On the other hand, a coarse particle manifestation image in which coarse particles are manifested is created from the original image. This actualized image is created by reading the original image from the image memory 310, binarizing the original image by the binarization processing means 361, and obtaining the binarized original image (step S11). ). In other words, by binarizing the original image, some fine particles are substantially removed, and as a result, coarse particles become apparent.

<Creation and evaluation of inspection images>
Next, an inspection image is created by the inspection image creating means 370 using the binarized difference image and the binarized original image. Here, an inspection image is created by adding the binarized difference image and the binarized original image (step S12). By adding these two images, it is possible to obtain an image that clearly shows not only coarse particles but also fine particles.

  The characteristics of the particles are obtained by calculation from the inspection image in which conductive particles of all sizes are clearly represented (step S13). FIG. 5 schematically shows the state of the particles in the inspection image. In this figure, in addition to the plan view observed by the camera, the arrangement state of the particles viewed from the side surface of the film that is not actually observed by the camera is also shown as an estimation diagram. Figure (A) shows the case where the long diameter of the elongated particles is oriented along the film thickness direction, and Figure (B) shows the case where the long diameter and the film thickness direction are random. . As is clear from this plan view, the oriented particles (hatched display) have an aspect ratio of approximately 1, and the particles with varying orientations vary in aspect ratio. The orientation can be inspected.

  In this example, the number of particles, the particle size, the particle area, and the aspect ratio are obtained from the inspection image by the characteristic calculation means 380. The calculation method for each item is as follows.

Number of particles: Count the number of particles present in one field of view.
Particle size: The maximum diameter of each particle is defined as the particle size of the particle. The maximum diameter is the maximum that occurs when particles (hatched display) are projected onto the XY axis as shown in FIG. 6 (A) and the XY axis is rotated as shown in FIG. 6 (B). The projection length.
Particle area: Calculated from the number of pixels in the region constituting the particle.
Aspect ratio: Calculated from particle size / particle width. This particle diameter is the maximum diameter, and the short diameter shown in FIG. 6 (B) is used as the particle width.

  Then, the characteristic evaluation results of these particles are displayed on the monitor 400 (step S14).

  Thus, if the device of the present invention is used, individual particles can be clearly grasped on the image, and the properties of the conductive particles of the anisotropic conductive film can be accurately grasped.

  The present invention can be used for inspection of a light-transmitting film in which particles are dispersed. In particular, it can be effectively used for inspection of anisotropic conductive films used in the field of electronic component manufacturing.

It is a schematic block diagram of this invention apparatus. It is a functional block diagram of this invention apparatus. It is a flowchart which shows the process sequence of this invention apparatus. It is a graph which shows the relationship between the vertical distance of a camera from a film, and a focus value. It is a schematic diagram which shows the state of the particle | grains in a film. It is explanatory drawing of the method of calculating the characteristic of the particle | grains in a film.

Explanation of symbols

100 Camera 110 Camera amplifier 120 XZ stage
200 Lighting 300 Computer 310 Image memory 320 Motor driver
330 Synchronization signal generator 341 Differential processing means 342 Area calculation means
343 Focus determination means 350 Fine particle manifestation means 360 Coarse particle manifestation means
351 Expansion / contraction means 352 Difference image creation means 353, 361 Binarization means
370 Inspection image creation means 380 Characteristic calculation means
400 monitor 500 film (anisotropic conductive film) 600 glass plate
610 encoder

Claims (5)

A light source disposed on one side of a light transmissive film in which particles are dispersed;
An image receiving means arranged on the other side of the film to obtain a transmission image of the film;
Fine particle revealing means for creating fine particle manifestation images by revealing fine particles from the original image obtained by the image receiving means;
Coarse particle manifestation means for creating coarse particle manifestation images by revealing coarse particles from an original image,
Inspection image creation means for creating an inspection image from a fine particle manifestation image and a coarse particle manifestation image,
And a characteristic calculation means for calculating the characteristics of the particles in the inspection image ,
The fine particle revealing means includes
Expansion / contraction means for performing expansion / contraction processing on the original image to obtain an expansion / contraction image;
Differential image creating means for creating a differential image between the original image and the expansion / contraction image;
Binarizing means for binarizing the difference image to obtain a binarized difference image;
The coarse particle revealing means includes:
A binarization means for binarizing the original image to obtain a binarized original image;
The inspection image creation means creates an inspection image by adding the binarized original image and the binarized difference image,
The said characteristic calculating means calculates | requires an aspect ratio as a parameter | index of the orientation of particle | grains, The inspection apparatus of the film characterized by the above-mentioned. Characteristic calculation means further area, particle size, according to claim 1 particle density, characterized by determining at least one particle pitch, particle absence area of a particle present number and constant region in constant domain Film inspection equipment. A drive mechanism for changing the distance between the film and the image receiving means;
The image receiving means acquires a preliminary image at each position where the distance between the film and the image receiving means is different;
Further, differential processing means for differentiating each preliminary image, and calculating a differential value of the luminance of the particle contour portion in the preliminary image,
Area calculating means for calculating the area of the particles in the preliminary image;
It has a focus determination means for determining a ratio “differential value / particle area” between a differential value and a particle area obtained from each preliminary image as a focus value, and determining a preliminary image having the maximum focus value as an original image. The film inspection apparatus according to claim 1 or 2 .   The film inspection apparatus according to claim 1, wherein the film is an anisotropic conductive adhesive film in which a large number of conductive particles are dispersed in an insulating binder.   The aspect ratio of the particle is determined by projecting the particle of the inspection image on the XY axis and setting the maximum projected length of the particle on one axis generated when the XY axis is rotated as the maximum diameter. 5. The film inspection apparatus according to claim 1, wherein the projection length of the particles onto the surface is determined from a “maximum diameter / short diameter” as a short diameter.

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