JP2006177847A - Visual inspection device and visual inspection method of substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To select and provide a substrate equipped with a highly-reliable conduction through-hole by detecting an abnormality such as deficiency or a state close to disconnection by performing not only conduction inspection using electricity but also visual inspection using image processing in order to secure reliability of the conduction through-hole on the substrate. <P>SOLUTION: The visual inspection of the through-hole such as a through-hole is performed by using this visual inspection device equipped with an illumination means for irradiating light into the through-hole from a prescribed angle with respect to the forming direction of the through-hole on the substrate, an imaging means installed at a prescribed angle with respect to the forming direction of the through-hole on the opposite side of the illumination means, and an image processing means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an appearance inspection method for an appearance inspection apparatus substrate that performs a predetermined inspection on an inspection object by performing image processing on image data obtained by imaging the inspection object.

  Conventional continuity tests for printed wiring boards are provided with test pads at both ends of the printed circuit board, with test probes in contact with these pads, and a current is passed while sequentially switching the locations to be inspected, resulting in disconnection or short circuit. Was inspecting.

  However, in the above method, a defect can be found in the case where the wire is completely disconnected and short-circuited in the inspection stage. However, as shown in FIG. When the conductor 22 is approaching or when the conductor 22 is about to be disconnected as shown in FIG. 5, it is difficult to find and remove it, and there is a possibility that the electronic device may be disconnected or short-circuited during use.

  Accordingly, the appearance inspection apparatus detects the conductors as shown in FIGS. 4 and 5 and selects them.

As prior art document information related to the invention of this application, for example, Patent Document 1 is known.
Japanese Patent Laid-Open No. 4-136747

  In the appearance inspection of the conductor pattern formed on the insulating substrate, it is possible to cope with the conventional method, but the appearance inspection of the through hole 17 shown in FIG. 6 is difficult to cope with with the conventional inspection apparatus. Met.

  Therefore, conventionally, the through hole of the printed circuit board is guaranteed only for continuity / insulation by electrical inspection, and in the visual inspection, there is only a method for performing the visual inspection for each hole artificially.

  However, in the conventional appearance inspection, the inspection of the inner wall is difficult because the inspection is performed with the substrate inclined, and it is difficult for the operator to perform the inspection by lifting a plate-shaped object of about 1 kg. It was in a state where a burden was imposed.

  In addition, it is difficult for an artificial visual inspection to completely grasp a defect in the state of a through hole, and an inspection method using an appearance inspection apparatus has been desired.

  That is, in the electrical inspection, the through hole conduction inspection is possible, but when the through hole is about to be disconnected, the defect cannot be detected in the electrical inspection.

  In particular, in a printed circuit board that requires high reliability, it is necessary to reliably detect through-hole defects by an inspection method using image processing in order to reliably detect these defects.

  Therefore, conventionally, as an appearance inspection of the through hole 17, as shown in FIG. 7A, the illumination light source 14 is set at an angle at which the incident light L can enter the inner wall of the through hole 17, and the reflected light R is captured by the imaging means 15. There was a method of capturing an image.

  However, in the case of an appearance inspection with such an appearance inspection apparatus, not only the reflected light R from the through hole 17 but also the reflected light R from the land 19 is displayed. As shown in FIG. The land 19 occupies most of the area. In this case, the ratio of the area of the defect in the through hole 17 is a small ratio, and considering the variation in the finished dimension of the land 19, the size of the defect is absorbed in the variation, and the presence or absence of the defect is determined. There was a problem that it was not possible to do the inspection.

  The present invention solves the above-described conventional problems, and in order to ensure the reliability of the conductive through hole (through hole) of the substrate, not only the continuity inspection using electricity but also the appearance inspection using image processing is performed. Accordingly, it is an object to detect abnormalities such as chipping or disconnection, and to select and provide a substrate having a highly reliable through-hole.

  In order to achieve the above object, the present invention has the following configuration.

  According to the first aspect of the present invention, there is provided a conveying means for conveying a substrate having a through-hole to an inspection unit, and the through-hole from a predetermined angle with respect to a forming direction of the through-hole of the substrate conveyed to the inspection unit. Illuminating means for irradiating light, imaging means on the opposite side of the illuminating means via the substrate conveyed to the inspection section, and image processing means, the imaging means with respect to the through-hole formation direction It is an appearance inspection device that is installed at a position to image the reflected light from the through-hole at a predetermined angle, and provides an appearance inspection device that can fully grasp defects in the through-hole state Thus, the image data obtained by imaging the inner wall of the through hole can be determined as a good product or a defective product.

  The invention according to claim 2 of the present invention is the appearance inspection apparatus according to claim 1, wherein the light emitted from the illumination means is white light. The three primary colors of blue light are included and can be reflected to the imaging means as reflected light in any state in the through hole. Thus, not only the copper plating film in the through-hole but also the abnormality such as preflux application, solder leveler treatment, solder resist ink, etc. can be grasped.

  The invention according to claim 3 of the present invention is the appearance inspection apparatus according to claim 1, wherein the illumination means is a linear parallel light source, and the imaging means is a line sensor camera. A plurality of through-holes positioned perpendicular to the substrate transport direction can be inspected at the same time, and the productivity can be improved.

  In the invention according to claim 4 of the present invention, the predetermined angle at which the light of the illumination means is irradiated is in the range of 35 to 37 °, and the predetermined angle at which the imaging means images the reflected light is in the range of 7 to 10 °. The appearance inspection apparatus according to claim 1 is characterized in that the detection of the through-hole state can be reliably performed without variation.

  According to a fifth aspect of the present invention, the predetermined angle at which the light of the illumination unit is irradiated is 36 °, and the predetermined angle at which the imaging unit images the reflected light is 9 °. Is an appearance inspection apparatus described in the above, which provides the setting conditions most suitable for detecting the through-hole state, and thus has an effect that the inspection can be reliably performed without variation.

  According to a sixth aspect of the present invention, the image processing means comprises means for comparing the image data obtained by imaging the inner wall of the through hole and the image data of the other inner wall of the through hole stored in advance. The external appearance inspection apparatus according to claim 1, wherein the image data obtained by imaging the through-hole inner wall is stored in advance as image data of other through-hole inner walls ( (Non-defective product data) is compared with the non-defective product or defective product.

  The invention according to claim 7 of the present invention is such that the image data of the other inner wall of the through hole is image data of the inner wall of the through hole in a state that is judged to be a non-defective product. It is an apparatus, and has an effect that it is possible to easily determine a non-defective product or a defective product by using, as comparison data, an inner wall of a through hole that is determined to be a non-defective product.

  The invention according to claim 8 of the present invention is characterized in that the transport means transports the substrate horizontally, the illumination means is provided below the transport means, and the imaging means is provided above the transport means. The visual inspection apparatus described in 1) has an effect of improving productivity by enabling in-line operation by horizontally transporting the substrate.

  According to a ninth aspect of the present invention, there is provided a step of irradiating light from the illumination means into the through hole at a predetermined angle with respect to the formation direction of the through hole of the substrate having a circuit pattern and the through hole; And imaging the reflected light from the through-hole with an imaging means installed at a predetermined angle with respect to the direction of formation of the through-hole on the opposite side of the illumination means, and obtained by imaging the inner wall of the through-hole And a step of comparing the image data of the other through-hole inner wall stored in advance with the step of determining whether the image data obtained by imaging the inner wall of the through-hole is good or defective. This is an appearance inspection method. By comparing the image data obtained by imaging the inner wall of the through hole with the image data (non-defective product data) of the other inner wall of the through hole stored in advance, it becomes a non-defective product or a defective product. Judgment, The detection of defects in Ruhoru can be carried out with high probability.

  The invention described in claim 10 of the present invention is the substrate visual inspection method according to claim 9, wherein the through hole is a through hole subjected to electroplating or electroless plating. It has the effect of providing an appearance inspection method suitable for detecting the through-hole state of the conductive through hole subjected to electroplating or electroless plating, and detecting abnormalities such as the occurrence of disconnection and pinholes.

  Invention of Claim 11 of this invention is a board | substrate external appearance inspection method of Claim 9 characterized by the above-mentioned. The through-hole is a long hole which gave electroplating or electroless plating, In addition to the circular shape, it is possible to detect the through hole state of elongated holes such as screws for electroplating or electroless plating, and it is also possible to detect abnormalities such as wire breaks and pin holes. Have.

  The invention described in claim 12 of the present invention is the substrate visual inspection method according to claim 9, wherein the substrate is formed with a solder resist or a component layout drawing, and only the conductive through hole is provided. In addition, it has an effect that it is possible to detect the filling condition of the solder resist ink or the component arrangement drawing ink in the through hole and the application state to the wall surface of the through hole.

  The invention according to claim 13 of the present invention is characterized in that the substrate is subjected to surface treatment, preflux coating, or solder leveler treatment on the through hole. In this way, it is possible to detect not only the conductive through hole but also the abnormality of the wall surface of the through hole after the surface treatment or preflux coating or solder leveler treatment into the through hole.

  The invention described in claim 14 of the present invention is the substrate visual inspection method according to claim 9, wherein the substrate is subjected to external punching, and the external appearance after completion of external punching It is suitable for inspection, and it is possible to detect abnormalities such as clogging of through-holes of substrate scraps after the external punching process, and products such as surface treatment or preflux coating on through-holes into through-holes It can also be used as a final inspection before shipment.

  The invention according to claim 15 of the present invention is the substrate visual inspection method according to claim 9, wherein the light emitted from the illumination means is white light, and the emitted light is white light. As a result, it is possible to reflect the reflected light as reflected light to any state in the through hole. As a result, not only the conductive through-hole, but also the solder resist ink or component layout ink embedded in the through-hole and the state of application to the wall surface of the through-hole, and the surface treatment or preflux coating or solder leveler treatment to the through-hole It has an effect that it is possible to detect an abnormality in the wall surface of the subsequent through-hole.

  The invention according to claim 16 of the present invention is characterized in that the step of irradiating light from the illumination means and the step of imaging the reflected light from the through-hole by the imaging means are both performed on the substrate being transported. The method for inspecting the appearance of a substrate according to claim 9 has the effect that the productivity of appearance inspection can be improved by grasping the image data as the substrate is transported and moved.

  According to a seventeenth aspect of the present invention, there is provided a step of performing an electrical continuity test on the through-conduction hole of the substrate provided with the circuit pattern and the through-conduction hole, and a forming direction of the through-conduction hole of the substrate. Irradiating light from the illuminating means into the through-conduction hole at a predetermined angle; and passing through the imaging means disposed on the opposite side of the illuminating means through the substrate and at a predetermined angle with respect to the formation direction of the through-conduction hole Imaging reflected light from the conduction hole, comparing image data obtained by imaging the inner wall of the through-conduction hole with image data of other through-conduction hole inner walls stored in advance, and penetration conduction This is a method for inspecting the appearance of a substrate, comprising the step of determining whether the image data obtained by imaging the inner wall of the hole is a non-defective product or a defective product. A visual inspection that determines whether the inspection is a non-defective product or a defective product by comparing image data obtained by imaging the inner wall of the through hole with image data (non-defective product data) of other through hole inner walls stored in advance. By combining these, it is possible to detect a defect in the through hole with a high probability.

  With the above configuration, the present invention solves the conventional problem that an abnormality in a through hole cannot be detected only by an electrical continuity test, and provides an appearance inspection apparatus capable of completely grasping a defect in a through hole state. Can do. As a result, it is possible to determine whether the image data obtained by imaging the inner wall of the through-hole is a non-defective product or a defective product. By adopting this appearance inspection method, it is possible to detect defects in a substrate that requires high reliability. This has the effect that only good substrates can be provided.

  Hereinafter, embodiments of the present invention will be described.

(Embodiment)
FIG. 1 is a schematic diagram of an appearance inspection apparatus according to an embodiment of the present invention.

  First, the configuration of the appearance inspection apparatus of the present invention will be described.

  The appearance inspection apparatus 1 includes an inspection unit 2, a conveyance unit 3, an illumination unit 4, an imaging unit 5, and an image processing unit 6, and the conveyance unit 3 conveys a substrate 8 provided with a through hole 7 to the inspection unit 2, thereby penetrating. In this configuration, the state of the inner wall of the hole 7 is inspected.

  Moreover, the illumination means 4 which irradiates the light L with the predetermined angle (alpha) from the downward direction with respect to the formation direction of the through-hole 7 of the board | substrate 8 conveyed horizontally to the test | inspection part 2 is installed.

  Furthermore, the imaging means 5 is located above the opposite side of the illumination means 4 through the substrate, and the imaging means 5 images the reflected light R from the through hole 7 at a predetermined angle θ with respect to the direction in which the through hole 7 is formed. In place.

  The image data obtained by imaging the inner wall of the through-hole 7 by the appearance inspection apparatus having this configuration is determined as a non-defective product or a defective product.

  The light L emitted from the illumination unit 4 is preferably white light. White light consists of the three primary colors of red light (wavelength: about 0.7 μm), green light (wavelength: about 0.5 μm), and blue light (wavelength: about 0.4 μm), and includes light with different refraction and scattering. This is because the reflected light R can be reflected to the image pickup means 5 in any state in the through hole. In particular, red light (having a wavelength of about 0.7 μm) is excellent in entering and reflecting through the through-hole 7 which tends to be dark. From this, not only the copper plating film in the through hole but also abnormalities such as preflux application, solder leveler treatment, solder resist ink, etc. can be grasped.

  In addition, the transport unit 3 can transport the substrate vertically, but by transporting the substrate horizontally, in-line connection with other devices is facilitated, and productivity can be improved.

  Further, it is desirable that the illumination unit 4 is a linear parallel light source, and the imaging unit 5 is a line sensor camera. As a result, a plurality of through-holes positioned perpendicular to the conveyance direction of the substrate 8 can be inspected simultaneously, and productivity can be improved.

  Next, a substrate visual inspection method using the visual inspection apparatus of the present invention will be described below including the operation of the visual inspection apparatus.

  As shown in FIG. 1, a substrate 8 having a through hole 7 as a through hole subjected to a circuit pattern and electroplating or electroless plating is transported by the transport means 3 to the inspection unit 2 of the appearance inspection apparatus 1.

  Simultaneously with the conveyance, white light L is irradiated from the illumination means 4 into the through hole 7 at a predetermined angle α. The white light is reflected in the through hole 7 and the reflected light R is imaged by the imaging means 5 installed at a predetermined angle θ.

  The captured image is converted into image data by the image processing means 6 and is determined by a determination means for comparing with prestored image data having a good through hole inner wall state, and has a good through hole inner wall state. When it is different from the image data and exceeds the allowable range, it is output as defective product information by the defect output means.

  The image data of the inner wall of the through-hole that is judged to be a good product can be stored in advance in several stages of image data from the best product to the limit of the allowable range, thereby determining whether the product is good or defective. Can be easily performed.

  When the through-hole 7 is a through hole subjected to electroplating or electroless plating as in the present embodiment, the image data is stored in advance from the best product such as a broken wire or a pinhole to the allowable range limit. By detecting the through-hole state, it is possible to easily detect abnormalities such as wire breakage, pinholes and discoloration, and clogging of the inner wall roughness of the through-holes.

  In addition, while the substrate 8 is transported to the inspection unit 2 and unloaded, it is configured as a system in which the image data is grasped and the determination of a non-defective product is completed, whereby the appearance inspection is performed on the substrate being transported. be able to. Thereby, the productivity of appearance inspection can be improved.

  Next, the detail of the structure of the external appearance inspection apparatus for detecting reliably the defect | deletion of through-holes, such as a through hole, is demonstrated below.

  The appearance inspection apparatus 1 described above employs a structure for preventing light from reflecting from the land 19, which has been a conventional problem. That is, an illuminating means 4 that irradiates light L at a predetermined angle α from below with respect to the formation direction of the through-hole 7 of the substrate 8 conveyed horizontally to the inspection unit 2 is installed, and is opposite to the illuminating means 4 through the substrate. The image pickup means 5 is located at a position corresponding to the upper side of the side, and the image pickup means 5 is installed at a position for picking up the reflected light R from the through hole 7 at a predetermined angle θ with respect to the formation direction of the through hole 7.

  An important point in this structure is that, as shown in FIG. 2A, a part of the light L emitted from the illumination unit 4 enters the insulating base material 10 of the substrate 1 and the reflected light R is imaged by the imaging unit 5. Then, the part other than the through hole 7 is reflected, and the boundary between the through hole 7 and the insulating base material 10 as shown in FIG. It cannot be detected.

  In particular, as described above, white light is used for the illumination means of the appearance inspection apparatus according to the present embodiment. Normally, red light is used for detecting a copper foil and green light is used for detecting a solder resist, which is suitable for detecting defects such as printed wiring boards. However, the green light is a straight light, and excessively reacts with a solder resist or the like, so that a fine flaw may be determined as a defect even though it is a good product. Therefore, in the appearance inspection apparatus of the present invention, by adopting white light including blue light that is easily scattered, it was possible to suppress an excessive determination with respect to fine scratches and realize an appearance inspection apparatus that can cope with mass production.

  However, since white light also includes scattered light, it is necessary to set the installation conditions of the illumination unit 4 and the imaging unit 5 so as not to be in the state shown in FIG.

  Therefore, the inventor arranges the illumination means 4 at an angle at which the incident light L can enter the inner wall of the through hole 7, and the reflected light R can enter the reflected light from the insulating substrate 10. The importance of arranging the image pickup means 5 at a position where R does not enter and image is grasped, and the following confirmation was performed.

  That is, whether or not the inner wall of the through hole 7 can be imaged was verified while changing the predetermined angle θ of the imaging unit 5 and the predetermined angle α of the illumination unit 4 as shown in FIG.

  In the verification, whether or not imaging and inspection can be performed was confirmed in a range where the predetermined angle θ of the imaging unit 5 is 5 to 12 ° and a predetermined angle α of the illumination unit 4 is 20 to 40 °.

  The results are shown in (Table 1). In addition, when the predetermined angle α of the illumination unit 4 is 20 to 34 ° and 38 to 40 °, the imaging is not possible and the description is omitted.

  In addition, the focus distance of the camera of the imaging unit 5 is 400 mm, the resolution is 30 μm, and the illumination linear distance from the illumination unit 4 is 50 mm.

  In addition, as to the result of whether or not imaging is possible, “x” indicates that imaging is not possible, “Δ” indicates that imaging is possible, and “◯” indicates the case where imaging is most suitable.

  From the results of (Table 1), when the range of the predetermined angle θ of the camera of the imaging unit 5 is 7 to 10 °, and when the range of the predetermined angle α of the illumination unit 4 is 35 to 37 °, the insulation that is a non-inspection region The part of the base material 10 was not imaged, and only the through hole 7 necessary for the inspection was imaged so that the inspection was possible.

  In particular, the best results were obtained when the predetermined angle θ of the imaging means 5 was 9 ° and the predetermined angle α of the illumination means 4 was 36 °.

  In the appearance inspection apparatus of the present invention, the predetermined angle for irradiating the light L of the illumination unit 4 is set in the range of 35 to 37 °, preferably 36 °, and the predetermined angle at which the imaging unit 5 images the reflected light R is By setting the angle within the range of 7 to 10 °, preferably 9 °, the setting condition is most suitable for detecting the state of the inner wall of the through hole. As a result, the inspection can be reliably performed without variation.

  As another embodiment of the present invention described above, a circuit pattern and a through-conduction hole of a substrate provided with a through-conduction hole are subjected to an electrical continuity inspection, and then a combination of the appearance inspection methods described above may be employed. it can. In this case, the defect in the through hole can be detected with high probability by the electrical continuity inspection and the appearance inspection.

  In the present embodiment, the detection of defects or abnormalities in through-holes subjected to electroplating or electroless plating as through-holes has been described. However, not only circular shapes but also screws subjected to electroplating or electroless plating have been described. It is also possible to detect a through-hole state of a long hole for stopping, etc., and detect an abnormality such as a break or pin hole.

  In addition, when a solder resist or component layout is formed on the substrate 1, not only the conductive through hole but also the solder resist ink or component layout ink embedded in the through hole and the state of application to the wall surface of the through hole It is also possible to detect an abnormality.

  Further, when surface treatment or preflux coating or solder leveler treatment is applied to the through-hole 7 of the substrate 1, the through-hole wall surface after surface treatment or preflux coating or solder leveler treatment to the through-hole into the through-hole It is also possible to detect abnormalities.

  Furthermore, when the substrate 1 has been subjected to outer shape punching, it is possible to detect abnormalities such as clogging of through-holes of base material scraps after the outer shape punching process.

  As described above, according to the configuration of the present invention, not only electrical through-hole continuity inspection, but also visual inspection using image processing can be performed to detect a level that is missing or disconnected. It is possible to supply a printed wiring board having a highly reliable through hole, and the industrial applicability is great.

Schematic of an appearance inspection apparatus in an embodiment of the present invention Schematic for demonstrating the external appearance inspection method in embodiment of this invention Schematic for demonstrating the external appearance inspection method in embodiment of this invention The figure which shows the subject in the conventional appearance inspection method The figure which shows the subject in the conventional appearance inspection method The figure which shows the subject in the conventional appearance inspection method The figure which shows the subject in the conventional appearance inspection method

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Appearance inspection apparatus 2 Inspection | inspection part 3 Conveyance means 4 Illumination means 5 Imaging means 6 Image processing means 7 Through-hole 8 Substrate 10 Insulating base material

Claims (17)

A transport means for transporting a substrate having a through hole to an inspection unit;
Illuminating means for irradiating light to the through hole from a predetermined angle with respect to the formation direction of the through hole of the substrate conveyed to the inspection unit;
Imaging means on the opposite side of the illumination means through the substrate conveyed to the inspection unit,
Image processing means,
The visual inspection apparatus, wherein the imaging means is installed at a position for imaging reflected light from the through hole at a predetermined angle with respect to the formation direction of the through hole. The appearance inspection apparatus according to claim 1, wherein the light emitted from the illumination unit is white light. 2. The appearance inspection apparatus according to claim 1, wherein the illumination unit is a linear parallel light source, and the imaging unit is a line sensor camera. 2. The external appearance according to claim 1, wherein the predetermined angle at which the illumination unit emits light is in a range of 35 to 37 °, and the predetermined angle at which the imaging unit images reflected light is in a range of 7 to 10 °. Inspection device. The appearance inspection apparatus according to claim 1, wherein the predetermined angle at which the illumination unit emits light is 36 °, and the predetermined angle at which the imaging unit images reflected light is 9 °. The image processing means includes means for comparing image data obtained by imaging the inner wall of the through hole and image data of another inner wall of the through hole stored in advance. Appearance inspection device. 6. The appearance inspection apparatus according to claim 5, wherein the image data of the other inner wall of the through hole is image data of the inner wall of the through hole in a state that is determined to be a non-defective product. The appearance inspection apparatus according to claim 1, wherein the transport unit transports the substrate horizontally, the illumination unit is provided below the transport unit, and the imaging unit is provided above the transport unit. Irradiating light from the illumination means into the through hole at a predetermined angle with respect to the formation direction of the through hole of the circuit pattern and the substrate provided with the through hole;
Imaging reflected light from the through-hole with an imaging means installed at a predetermined angle with respect to the formation direction of the through-hole on the opposite side of the illumination means through the substrate;
Comparing image data obtained by imaging the inner wall of the through hole with image data of other through hole inner walls stored in advance;
A method for inspecting the appearance of a substrate, comprising: determining whether image data obtained by imaging an inner wall of a through hole is a good product or a defective product. 10. The method of inspecting a substrate according to claim 9, wherein the through hole is a through hole subjected to electroplating or electroless plating. The method for inspecting the appearance of a substrate according to claim 9, wherein the through hole is a long hole subjected to electroplating or electroless plating. 10. The method for inspecting the appearance of a substrate according to claim 9, wherein a solder resist or a component layout is formed on the substrate. The substrate visual inspection method according to claim 9, wherein the substrate is subjected to surface treatment, preflux coating, or solder leveler treatment on the through hole. The method for inspecting the appearance of a substrate according to claim 9, wherein the substrate is subjected to external punching. The substrate visual inspection method according to claim 9, wherein the light emitted from the illumination unit is white light. The substrate visual inspection method according to claim 9, wherein the step of irradiating light from the illumination unit and the step of imaging the reflected light from the through-hole by the imaging unit are both performed on the substrate being transported. . Performing an electrical continuity test on the through-conduction hole of the substrate having a circuit pattern and a through-conduction hole; and
Irradiating light from the illumination means into the through-conduction hole at a predetermined angle with respect to the formation direction of the through-conduction hole of the substrate;
Imaging reflected light from the through-conduction hole with an imaging means installed at a predetermined angle with respect to the formation direction of the through-conduction hole on the side opposite to the illumination means via the substrate;
Comparing the image data obtained by imaging the inner wall of the through hole and the image data of the other inner wall of the through hole stored in advance;
A substrate visual inspection method comprising a step of determining image data obtained by imaging an inner wall of a through-conduction hole as a good product or a defective product.

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