JP2006266941A - Surface inspection method and surface inspection device for conductive particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface inspection method for rapidly and accurately detecting defects in a surface coating of conductive particles formed by coating the surfaces of spherical bodies formed of a nonconductive material, with conductive films. <P>SOLUTION: The method of inspecting defects in the surfaces of the conductive particles 3 formed by coating the surfaces of the spherical bodies formed of the nonconductive material, with the conductive films, comprises processes of arranging a plurality of conductive particles 3 not to overlap one another, photographing the plurality of conductive particles 3 with an X-ray camera 6 to acquire an image by X-rays, and detecting defects in the surface of the conductive particles based on the density of the conductive particles 3 in the photographed image of the plurality of conductive particles 3. In the process of detecting the defects in the surface coating, the presence of surface defects is detected by comparing image data of the conductive particles photographed with the X-ray camera, with reference data corresponding to the image of the conductive particles in the case of no defects existing in the surface coating. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a surface inspection method and a surface inspection apparatus for detecting defects in the surface coating of conductive particles formed by coating the surface of a non-conductive sphere made of, for example, synthetic resin or ceramics with a conductive film such as metal. More specifically, the present invention relates to a surface inspection method and a surface inspection apparatus including a step of inspecting the surface of conductive particles using an X-ray camera.

  Conventionally, spherical conductive particles have been produced by forming a metal plating layer on the surface of a sphere made of synthetic resin. This conductive particle is used for the purpose of electrically connecting an electronic component element such as a semiconductor element to an electrode on a mounting substrate. Therefore, if there are missing portions or scratches on the metal plating layer on the surface of the conductive particles, there is a possibility that conduction between the electronic component element and the electrode of the mounting substrate may not be ensured.

  Therefore, after producing the conductive particles, it was necessary to inspect whether or not there are missing portions or scratches on the metal plating layer on the surface, and to eliminate defective products. In detecting such surface defects, conventionally, spherical conductive particles are placed in a hemispherical depression, the surface of the conductive particles is photographed with a camera, and the conductive particles are rotated in the depression, A surface defect was detected by photographing a surface portion and inspecting a two-dimensional image obtained by photographing.

  However, in the above method, in order to eliminate the surface portion that is not photographed, the conductive particles have to be rotated so that the surface portions to be photographed overlap. Therefore, it is difficult to inspect the entire surface of the spherical conductive particles quickly and easily.

On the other hand, in Patent Document 1 described below, as a solution to such a problem, a pair of rollers that are arranged in parallel to each other and are driven to rotate in the same direction, and a line that captures an area between the rollers A sphere inspection device including a sensor is disclosed. Here, in a portion where a pair of cylindrical rollers are adjacent to each other, a moving path of the sphere is configured, and the sphere inserted into the moving path advances while rolling on the moving path. Further, since the pair of rollers are rotated in the same direction, the sphere rotates in a direction opposite to the rotation direction of the rollers. Therefore, if the sphere surface is imaged by a line sensor arranged so that the imaging area is parallel to the movement path while traveling along the movement path, the entire surface of the sphere can be easily and reliably inspected.
JP 2003-294642 A

  As described above, in the conventional surface inspection apparatus using a two-dimensional camera, it has been difficult to reliably and quickly inspect the entire surface of the sphere.

  On the other hand, in the sphere inspection device described in Patent Literature 1, as described above, the sphere that is rotating in the direction opposite to the roller further rolls along the movement path while traveling along the movement path between adjacent rollers. Since it progresses, the entire surface of the sphere can be reliably inspected by the line sensor. However, in this method, the sphere has to be rolled along the movement path, and therefore, it takes a considerable time to photograph the entire surface of the sphere. In addition, since the image obtained by the line sensor is linear, an image of the surface of the sphere has been obtained by scanning the linear image in a direction orthogonal to the movement path. Therefore, the processing of the signal obtained from the line sensor has to be complicated.

  An object of the present invention is to provide a surface inspection method for conductive particles, which makes it possible to more quickly and more reliably inspect defects in surface coating by a conductive film in spherical conductive particles in view of the above-described conventional state of the art. And providing a surface inspection apparatus.

  The method for inspecting the surface of conductive particles according to the present invention is a method for inspecting the surface defect of spherical conductive particles formed by coating the surface of a sphere made of a non-conductive material with a conductive film. A step of arranging the conductive particles so as not to overlap, a step of photographing the plurality of conductive particles with an X-ray camera to obtain an image of the plurality of conductive particles by X-ray, and a step of photographing the plurality of conductive particles And a step of detecting defects in the surface coating of the conductive particles based on the concentration of the conductive particle portion in the obtained image, and the step of detecting defects in the surface coating in the step of detecting defects in the surface coating The presence or absence of surface defects is detected by comparing the reference data corresponding to the image of the particles with the image data of the conductive particles photographed by the X-ray camera.

  In a specific aspect of the surface inspection method for conductive particles according to the present invention, a difference between the reference data and the captured image data is compared with the reference data and the captured image data of the conductive particles. An image is obtained, and the presence or absence of a surface defect is detected based on the difference image.

  In still another specific aspect of the method for inspecting the surface of conductive particles according to the present invention, the concentration of the peripheral portion of the image of the conductive particles photographed with an X-ray camera is set to the concentration when no surface defect exists, and the surface There is further provided a step of detecting the presence / absence of a surface defect in the peripheral portion by discriminating based on a threshold density between the density and the density when a defect exists.

  In yet another specific aspect of the conductive particle surface inspection method according to the present invention, it is determined whether the shape of the peripheral portion in the image of the conductive particles photographed by the X-ray camera is a shape other than a circle, A step of determining a defective product having a surface defect when the shape is other than a circle is further provided.

  In still another specific aspect of the surface inspection method for conductive particles according to the present invention, the plurality of conductive particles are arranged in a plurality of groups, and the plurality of conductive particles are included in one group. When it is determined that conductive particles having surface defects are present, a step of removing a plurality of conductive particles belonging to the group to which the conductive particles belong as a defective product is further provided.

  A surface inspection apparatus according to the present invention is a surface defect inspection apparatus used in the surface defect inspection method for conductive particles according to claim 1, wherein a tray on which a plurality of conductive particles are placed; An X-ray camera that images a plurality of conductive particles placed on a tray from above, and an image of the plurality of conductive particles that are connected to the X-ray camera and obtained from the X-ray camera have surface defects. The image processing apparatus corresponds to an image of conductive particles in the case of non-existence, and includes detection means for detecting the presence or absence of surface defects in the conductive particles in comparison with predetermined reference data.

  In a specific aspect of the surface inspection apparatus according to the present invention, in the detection unit, a difference image between the predetermined reference data and a photographed image of the conductive particles is created, and based on the difference image The presence or absence of surface defects is detected.

  In still another specific aspect of the surface inspection apparatus according to the present invention, the difference image is obtained by subtracting the concentration in the image of the captured conductive particles from the concentration in the reference data.

  In still another specific aspect of the surface inspection apparatus according to the present invention, the density of the outer peripheral edge of the image of the conductive particles is a density corresponding to a density when there is no surface defect, and when a surface defect exists. There is further provided a second detection means for binarizing based on a threshold density between the density and determining that there is a surface defect when the density at the peripheral edge is lower than the threshold density.

  In yet another specific aspect of the surface inspection apparatus according to the present invention, it is determined whether or not the shape of the outer peripheral edge of the image of the conductive particles photographed by the X-ray camera is a circle, and the shape other than the circle is determined. In this case, a third detection means for determining that there is a surface defect is further provided.

  In the conductive particle surface inspection method and inspection apparatus according to the present invention, the spherical conductive particles coated with the conductive film are arranged so that the surface of the sphere made of the nonconductive material does not overlap. Then, images of the plurality of conductive particles arranged in this way are taken with an X-ray camera. The plurality of conductive particles have a conductive layer on the surface, and the inside is a spherical non-conductive material. Therefore, as an image of conductive particles photographed by an X-ray camera, a circular image having a substantially uniform density is obtained when there is no defect in the conductive film on the surface according to the density of the portion caused by the conductive film. Will be obtained.

  On the other hand, when a missing part or a flaw exists in the conductive film on the surface, the image density is reduced in a region corresponding to the part where such a defect exists. In this case, since X-rays pass through materials other than the conductive material, defects are generated not only on the surface on the X-ray camera side but also on the surface opposite to the X-ray camera in the coating made of the conductive material. Even in such a case, the above-described decrease in density occurs. Therefore, according to the present invention, since an image obtained by an X-ray camera is used, it is possible to obtain the presence or absence of defects in the conductive film on the surface of the spherical conductive particles simply by photographing the spherical conductive particles from one side. Detection can be performed easily and reliably based on the density of the image.

  That is, when a two-dimensional camera is used in the conventional method for inspecting surface defects of spherical conductive particles, the conductive particles have to be rotated in order to detect defects on the entire surface. Also, in the inspection method described in Patent Document 1 using a line sensor, it is necessary to roll the spherical conductive particles while advancing the movement path and to rotate them by adjacent rollers. That is, in any of the conventional surface inspection methods, it has been necessary to photograph the entire surface by rotating spherical conductive particles.

  On the other hand, in the surface inspection method and the surface inspection apparatus of the present invention, since X-rays are used, surface defects can be easily and quickly obtained by photographing from one side without rotating spherical conductive particles. It becomes possible to detect from the obtained image. Therefore, the presence or absence of surface defects on the spherical conductive particles can be detected quickly and with high accuracy without requiring any work for rotating the conductive particles.

  Hereinafter, the present invention will be clarified by describing specific embodiments of the present invention with reference to the drawings.

  FIG. 1 is a schematic configuration diagram for explaining a surface inspection apparatus for conductive particles according to an embodiment of the present invention. The surface inspection apparatus 1 of the present embodiment is used to detect a surface coating defect between a plurality of conductive particles arranged on a tray 2. As shown in FIG. 2, the conductive particles 3 include a nonconductive sphere 4 and a conductive film 5 provided so as to cover the outer surface of the sphere 4.

  The sphere 4 is made of an appropriate nonconductive material such as synthetic resin or insulating ceramics. Preferably, when the sphere 4 is made of a synthetic resin having flexibility, the conductive particles 3 are suitably used for applications where flexibility is required.

  The conductive film 5 is made of an appropriate conductive material such as a metal film. The conductive particles 3 are used for the purpose of electrically connecting an electronic component such as an IC to an electrode on a mounting substrate, for example. In the surface inspection apparatus 1 according to the present embodiment, surface defects such as missing or scratches on the conductive film 5 covering the surface of the sphere 4 are detected using X-rays.

  FIG. 3 is a perspective view schematically showing the tray 2 shown in FIG. As shown in FIG. 3, it has the some storage recessed part 2a separated by the partition wall. Although not particularly limited, in the present embodiment, the plurality of storage recesses 2a are arranged in a matrix. As shown in FIG. 4, the size of the storage recess 2a is determined so that the plurality of conductive particles 3 are placed in one storage recess 2a.

  In the present embodiment, the size of the one storage recess 2a is about 10 mm × 10 mm, but this size can be appropriately changed depending on the size and number of conductive particles to be stored. However, in this embodiment, for example, by storing the conductive particles 3 having a particle size of about 300 μm in the storage recess, about 1000 to 2000 conductive particles 3 are arranged in one storage recess 2a, It is possible to determine defective products. Therefore, the surface defects of the conductive particles 3 can be detected at high speed and with high accuracy.

  The tray 2 can be formed of an appropriate non-conductive material such as a synthetic resin.

  Returning to FIG. 1, the X-ray camera 6 is disposed above one storage recess 2 a. The X-ray camera 6 is disposed so as to photograph the one storage recess 2a with X-rays. Further, a drive device 7 including a motor M is connected to the tray 2. By means of the driving device 7, the tray 2 can be moved in the vertical and horizontal directions of the matrix in which the storage recesses 2a are arranged. In other words, the tray 2 is driven by the driving device 7 so that the region captured by the X-ray camera 6 is changed by the driving device 7 from one storage recess 2a to another storage recess 2a.

  Further, in the present embodiment, the control device 8 as detection means is electrically connected to the X-ray camera and the driving device 7, and the control device 8 performs imaging by the X-ray camera 6 and the tray by the driving device 7. The movement of 2 is controlled.

  On the other hand, a suction head 9 is disposed above the tray 2. The suction head 9 is connected to the driving device 10. The suction head 9 has a plurality of suction holes 9a opened on the lower surface, and is configured to suck and hold one conductive particle 3 in each suction hole. Therefore, the suction head 9 is connected to a suction source (not shown). Further, the lower surface of the suction head 9 is configured to suck and hold a plurality of conductive particles 3 in a region corresponding to one storage recess 2a. Then, the drive device 10 moves the plurality of conductive particles 3 held by the suction head 9 to above the one storage recess 2a, and releases the suction to the one storage recess 2a. It is comprised so that the particle | grains 3 can be mounted.

  In addition, the suction head 9 is moved to a conductive particle supply unit (not shown) at a position away from the upper side of the tray 2 by the drive device 10, and a plurality of prepared in the conductive particle supply unit. The conductive particles 3 are configured to be adsorbed and held on the lower surface.

  The suction head 9 is configured such that one conductive particle 3 can be sucked and held in one suction hole 9a, and the suction head 9 is moved above one storage recess 2a. The electroconductive particle 3 is mounted in the accommodation recessed part 2a by canceling | releasing the said adsorption | suction. The area of the suction holding region for the conductive particles 3 on the lower surface of the suction head 9 is defined so that the conductive particles 3 are arranged so as not to overlap each other in one storage recess 2a. Therefore, when a plurality of conductive particles 3 are placed from the suction head 9 to one storage recess 2a, the plurality of conductive particles 3 are arranged so as not to overlap in one storage recess 2a.

  Further, the control device 8 detects defects in the surface coating of the plurality of conductive particles 3 based on the image taken by the X-ray camera 6. This will be clarified by describing the surface inspection method of the present embodiment with reference to FIGS. 5 and 6 together with FIG.

  In the conductive particle surface inspection method of the present embodiment, first, the conductive particles 3 are sucked and held in the above-described conductive particle supply section by sucking the suction head 9 from the suction holes 9a. Then, the drive device 10 is driven by the control device 8, the suction head 9 is moved above the one storage recess 2 a, and the suction is released, so that the plurality of conductive particles 3 are placed in one storage recess 2 a. Stored. As shown in FIG. 4, the plurality of conductive particles 3 are thus arranged in one storage recess 2 of the tray 2. In this case, since the area of the lower surface of the suction head 9 and the space between the suction holes 9a and 9a are determined as described above, the plurality of conductive particles 3 are placed so as not to overlap in the storage recess 2a. Will be.

  Next, the control device 8 is driven, and the suction head 9 is moved away from above the storage recess 2a on which the conductive particles 3 are placed.

  Thereafter, the storage recess 2a in which the plurality of conductive particles 3 are placed is photographed by the X-ray camera 6. In this case, if necessary, the drive device 7 is driven by the control device 8, and the X-ray camera 6 is moved above the storage recess 2a in which the conductive particles 3 are stored.

  Imaging by the X-ray camera 6 is instructed by the control device 8, and a signal captured by the X-ray camera 6 is given to the control device 8.

  The outer surface of the conductive particles 3 is covered with the conductive film 4. On the other hand, in the image photographed by the X-ray camera, the conductive film portion is photographed so as to have a certain density, and X-rays are transmitted through the spherical body 4 made of the non-conductive material inside. Accordingly, when the entire outer surface of the sphere 4 is completely covered with the conductive film 5, an image 11 shown in FIG. 5A is obtained. The image 11 has a uniform density. This is due to the presence of both the conductive film in the upper half of the conductive particles 3 and the lower half of the conductive film which is shaded from the X-ray camera 6 side when taken from the X-ray camera 6, that is, from above. A density image is obtained as the image 11.

  On the other hand, if there is a missing part in which the conductive film 4 is partially missing in half of the conductive particles 3, an image 12 shown in FIG. 5B is obtained. In the image 12, the density of the missing portion 12a is lower than that of the remaining portion. This is due to the absence of a conductive film in the missing portion 12a.

  Since X-rays pass through the sphere 4 made of a non-conductive material, the missing portion shown in FIG. 5B is present even when the missing portion exists in the lower half instead of the upper half of the conductive particles 3. Similar to 12a, the absence of the conductive film causes the missing portion to be identified as a portion having a low concentration.

  That is, in the surface inspection method of the present embodiment, the presence or absence of a surface defect is detected from an image photographed using X-rays. However, since X-rays are used, the spherical conductive particles 3 are not rotated. That is, it is possible to easily and quickly detect a coating defect on the entire surface while the conductive particles 3 are fixedly placed.

  In the present embodiment, more specifically, in the control device 8, reference data corresponding to the image 11 shown in FIG. 5A is stored in the control device 8 in advance as described above. This reference data corresponds to the image data when no defects occur in the coating of the conductive film 5 on the surface of the conductive particles 3, that is, the circular image 11 having a uniform density as shown in FIG. 5A. It is data.

  On the other hand, in the control device 8, the reference data is compared with the data of the image 12 of one conductive particle 3 photographed by the X-ray camera 6, and due to the difference, a surface defect such as the missing portion 12a is obtained. The presence of is detected. In this case, in this embodiment, a difference image between the reference data and the captured image data is obtained, and the presence or absence of a surface defect is detected based on the difference image. However, in addition to the method for obtaining the difference image, the presence or absence of a missing portion may be determined by comparing the densities of the images 11 and 12 at each coordinate position while scanning the images 11 and 12 in a certain coordinate direction.

  As described above, in the surface inspection apparatus described in Patent Document 1, since the surface of spherical conductive particles is captured using normal visible light instead of X-rays, all of the spherical conductive particles are captured. In order to photograph the surface, the conductive particles themselves had to be rotated. Therefore, the apparatus and operation have to be complicated. On the other hand, in this embodiment, since the defect of the coating with the conductive film 5 on the surface of the spherical conductive particle 3 is detected by using X-rays, it is necessary to rotate the spherical conductive particle 3. There is no. Therefore, the coating defect on the surface of the conductive particle 3 can be detected quickly and with high accuracy.

  In FIG. 5B, the partial missing portion 12a is shown, but the present invention can also detect a slight scratch on the surface of the conductive particle 3 such as a scratch. That is, the surface defect inspected by the surface inspection apparatus according to the present invention includes not only a missing portion where the conductive film is completely missing, but also a scratch on the conductive film such as a scratch. In other words, even when the scratch is provided and the conductive film is partially thin, the density is reduced in the portion where the scratch exists in the image taken with the X-ray camera as described above. Therefore, the presence or absence of a defect can be detected in the same manner as described above.

  In the above embodiment, the presence or absence of a defect was detected by comparing the entire image of the conductive particles 3 with reference data in the case where no defect exists. In addition to the inspection method, the control device 8 may further perform the following detection process. That is, in the image obtained by the X-ray camera 6 of the spherical conductive particles 3, actually, when the adjacent conductive particles 3 and 3 are close to each other or are in contact, one conductive property In some cases, the peripheral portion of the image of the particle 3 cannot be accurately captured. For example, the conductive particles 3A and 3B shown in FIG. 4 are almost in contact with each other, and when such a conductive particle 3A is photographed by the X-ray camera 6, the conductive particles 3A are electrically conductive in the peripheral portion of the conductive particle 3A. The portion in contact with the conductive particles 3B may not be photographed with high accuracy.

  Therefore, preferably, the density of the annular region having a predetermined width from the peripheral edge of the conductive particle 3A, that is, the outer peripheral edge, is binarized by comparing with the predetermined threshold density, thereby You may perform discrimination | determination of the quality goods and inferior goods in a peripheral part.

  More specifically, similarly to the reference data, the control device 8 previously sets a threshold concentration between the density of the annular region when there is no defect on the surface and the concentration when there is no coating in the annular region. The binarized data 14 shown in FIG. 7 may be obtained depending on whether the density of the annular region in the photographed image is higher or lower than the threshold density. Here, as shown by the arrow X in the missing portion, the annular region is divided, and therefore, it is determined as a defective product. That is, the control device 8 may constitute second detection means for carrying out the second detection method by binarization in such an annular region near the outer periphery.

  As described above, the annular portion is binarized, and a non-defective product or a defective product is determined depending on whether or not the annular portion is continuous, that is, whether or not the threshold concentration is exceeded in all regions of the annular portion. It is preferable to combine detection methods.

  In the present invention, the control device 8 takes out a third detection method for taking out only the contour of the image signal photographed by the X-ray camera 6 and discriminating a non-defective product or a defective product depending on whether the contour is circular. You may use it in combination. That is, there may be a large missing portion 13a on the side as in the image 13 of the conductive particle 3 shown in FIG. 6A. In such a case, as indicated by an arrow A in FIG. 6A. In addition, when the image is taken from the side instead of the upper side, an image 14 shown in FIG. 6B is obtained. As described above, when a large missing portion is present on the side surface, the camera imaged by the X-ray camera 6 can obtain an image 13 having a shape greatly damaged from a circle as shown in FIG. Therefore, when the image 13 shown in FIG. 6A is obtained, it is possible to easily determine whether the image is a good product or a defective product depending on whether the contour of the image data is circular. In the case where adjacent conductive particles are in contact with each other, the accuracy of discriminating between non-defective products and defective products can be improved when the outer peripheral edge portion cannot be accurately inspected.

  Therefore, it is desirable to combine the second and / or third detection method with the first detection method.

  In the surface inspection method of the present embodiment, a plurality of conductive particles 3 arranged in one storage recess are photographed by the X-ray camera 6, and the surface covering defects in the plurality of conductive particles 3 are detected by the control device 8. Is detected. In this case, when at least one conductive particle 3 is determined as a defective product, all the conductive particles 3 stored in the storage recess 2a are removed as defective products for easy selection. preferable. Therefore, preferably, when surface coating is detected in at least one conductive particle 3 in one storage recess 2a, all the conductive particles 3 stored in the storage recess 2a may be removed. In addition, when there is no surface defect in all the conductive particles 3 stored in one storage recess 2a, an appropriate take-out jig such as the suction head 9 described above is used to store the inside of the storage recess 2a. What is necessary is just to take out the electroconductive particle 3 as a good article.

1 is a schematic configuration diagram of a surface inspection apparatus according to an embodiment of the present invention. The front sectional view of the electroconductive particle in which the surface is inspected in one embodiment of the present invention. The perspective view which shows the tray which has a some recessed part in which several electroconductive particle is accommodated used by one Embodiment of this invention. The partial notch front sectional drawing which shows the electroconductive particle 3 accommodated in one accommodation recessed part 2a of a tray. (A) is a schematic diagram for demonstrating the image as reference | standard data, (b) is a figure which shows typically image data in case a missing part exists in the surface. (A) is a schematic diagram which shows image data in case a big missing part exists in the side of an electroconductive particle, (b) is an electroconductive particle from which the image shown to (a) is obtained laterally. The schematic diagram which shows the image obtained when it is assumed that it image | photographs from. The schematic diagram which shows an example of the data obtained by binarizing the cyclic | annular area | region of the outer periphery vicinity of electroconductive particle.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Surface inspection apparatus 2 ... Tray 2a ... Storage recessed part 3, 3A, 3B ... Conductive particle 4 ... Sphere 5 ... Conductive film 6 ... X-ray camera 7 ... Drive apparatus 8 ... Control apparatus 9 ... Suction head 9a ... Suction hole 10 ... Driving device 11... Image according to reference data 12. Captured image 12 a. Missing portion 13. Captured image 13 a.

Claims (10)

A method for inspecting surface defects of conductive particles formed by coating the surface of a sphere made of a nonconductive material with a conductive film,
Arranging a plurality of the conductive particles so as not to overlap; and
Photographing the plurality of conductive particles with an X-ray camera and obtaining images of the plurality of conductive particles by X-rays;
A step of detecting defects in the surface coating of the conductive particles based on the concentration of the conductive particle portion in the image obtained by photographing the plurality of conductive particles,
In the step of detecting defects in the surface coating, the reference data corresponding to the image of the conductive particles when there is no defect in the surface coating is compared with the image data of the conductive particles photographed by the X-ray camera. A method for inspecting the surface of conductive particles, wherein the presence or absence of surface defects is detected.   When comparing the reference data with the captured image data of the conductive particles, a difference image between the reference data and the captured image data is obtained, and the presence or absence of a surface defect is detected based on the difference image. The surface inspection method for conductive particles according to claim 1.   The density of the peripheral portion of the image of the conductive particles photographed by the X-ray camera is determined by the threshold density between the density when the surface defect does not exist and the density when the surface defect exists, The surface inspection method for conductive particles according to claim 1, further comprising a step of detecting the presence or absence of a surface defect in the peripheral portion.   A step of determining whether the shape of the peripheral portion in the image of the conductive particles photographed by the X-ray camera is a shape other than a circle, and determining a defective product having a surface defect when the shape is a shape other than a circle. The surface inspection method for conductive particles according to claim 1, further comprising:   The plurality of conductive particles are arranged in a plurality of groups, and when it is determined that there are conductive particles having surface defects in the plurality of conductive particles included in one group, the conductivity The surface inspection method for conductive particles according to claim 1, further comprising a step of removing a plurality of conductive particles of a group to which the particles belong as defective products. A surface defect inspection apparatus used in the surface defect inspection method for conductive particles according to claim 1,
A tray on which a plurality of conductive particles are placed;
An X-ray camera for photographing a plurality of conductive particles placed on the tray from above the tray;
A plurality of conductive particle images connected to the X-ray camera correspond to the conductive particle images when no surface defects exist, and predetermined reference data. A surface inspection apparatus comprising: detecting means for detecting the presence or absence of surface defects in the conductive particles as compared with the above.   In the detection unit, a difference image between the predetermined reference data and a photographed image of conductive particles is produced, and the presence or absence of a surface defect is detected based on the difference image. The surface inspection apparatus described.   The surface inspection apparatus according to claim 7, wherein the difference image is obtained by subtracting a density in an image of conductive particles photographed from a density in the reference data.   The density of the outer peripheral edge of the image of the conductive particles is binarized based on a threshold density between a density corresponding to a density when no surface defect exists and a density when a surface defect exists, The surface inspection apparatus according to claim 6, further comprising a second detection unit that determines that there is a surface defect when the density of the peripheral edge is lower than the threshold density.   Third detection means for determining whether or not the shape of the outer peripheral edge of the image of the conductive particles photographed by the X-ray camera is circular, and determining that there is a surface defect when the shape is other than circular, is further provided. The surface inspection apparatus of any one of Claims 6-9 provided.

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