Image acquisition device, substrate inspection device, image acquisition method, and substrate inspection method

Abstract

To acquire an image suitable for inspecting a protection layer of a substrate and a pattern by a simplified imaging optical system in a short time.SOLUTION: A visible light irradiation unit 13 and an infrared light irradiation unit 14 are provided in a substrate inspection device 1 which inspects a substrate 9 in which a protective layer transmitting infrared light is formed. An imaging unit 11 simultaneously receives visible light and infrared light from the substrate 9 and acquires an inspection image used to inspect the substrate 9. A position in an optical axis direction of an imaging surface of the imaging unit 11 is closer to a position at which an image of the visible light of the substrate 9 is formed by an imaging optical system 12 than a position at which an image of the infrared light of the substrate 9 is formed by the imaging optical system 12.SELECTED DRAWING: Figure 1

Description

【Technical Field】 【0001】 The present invention relates to a technique for inspecting a substrate having a protective layer formed on a substrate on which a pattern is formed. 【Background Art】 【0002】 Conventionally, for a printed wiring board or a printed wiring board on which electronic components are mounted (hereinafter referred to as "mounted substrate"), visible light is irradiated to obtain a visible light image, and further, infrared light is irradiated to obtain an infrared light image, and a technique for inspecting a printed wiring board or a mounted substrate using a visible light image and an infrared light image is known. 【0003】 For example, in the inspection apparatus of the first embodiment of Patent Document 1, a first CCD element for white light and a second CCD element for infrared light are provided. By irradiating a master substrate with white light and infrared light and separating the light from the master substrate with a dichroic prism, a color information image is acquired by the first CCD element, and at the same time, an infrared light image is acquired by the second CCD element. Then, the gold plating region on the printed wiring board is specified from the color information image, and the gold plating region of the infrared light image is acquired as a reference image. Thereafter, a color information image and an infrared light image are acquired for the substrate to be inspected, and the range of the gold plating region and the unevenness of the gold plating portion are inspected. 【0004】 In the second embodiment of Patent Document 2, first, near-infrared light that passes through a flux and a solder resist is irradiated onto a printed wiring board, and an image A in which conductor patterns, surface-mounted components, and external connection terminals can be seen is acquired. Next, visible light that is reflected by the flux and absorbed by the solder resist is irradiated onto the printed wiring board, and an image B obtained by binarizing an image in which only the flux can be seen is acquired. Then, by obtaining the logical product of image A and image B, an image excluding the conductor patterns covered with the solder resist is acquired. 【Prior Art Documents】 【Patent Documents】 【0005】 [Patent Document 1] Japanese Patent Publication No. 2003-172711 [Patent Document 2] Japanese Patent Publication No. 2010-91529 [Overview of the project] [Problems that the invention aims to solve] 【0006】 By the way, Patent Document 1 requires two image sensors and a complex optical system, making the inspection device expensive. In Patent Document 2, visible light images and infrared light images are acquired separately, which takes time to acquire the images. 【0007】 This invention has been made in view of the above problems, and aims to acquire images suitable for inspecting the protective layer and patterns of a substrate in a short time using a simplified imaging optical system. [Means for solving the problem] 【0008】 One aspect of the present invention is an image acquisition apparatus for acquiring an image of a substrate having a pattern formed on it and a protective layer that transmits infrared light formed on the substrate, comprising: a visible light irradiation unit for irradiating the substrate with visible light; an infrared light irradiation unit for irradiating the substrate with infrared light; an imaging unit; and an imaging optical system for guiding visible light and infrared light from the substrate to the imaging unit, wherein the position of the imaging surface of the imaging unit is closer to the position where a visible light image of the substrate is formed by the imaging optical system than to the position where an infrared light image of the substrate is formed by the imaging optical system, and the imaging unit simultaneously receives visible light and infrared light from the substrate to acquire an inspection image used for inspecting the substrate. 【0009】 Aspect 2 of the present invention is an image acquisition apparatus of aspect 1, wherein the position of the imaging surface of the imaging unit coincides with the position where the visible light image of the substrate is formed by the imaging optical system. 【0010】 A third aspect of the present invention is an image acquisition apparatus of the first or second aspect, wherein the visible light irradiation unit is turned off and infrared light is emitted from the infrared light irradiation unit at the intensity used to acquire the inspection image, and the average brightness of the image of the illumination adjustment substrate acquired by the imaging unit is 10 percent or more and 30 percent or less of the average brightness of the image of the illumination adjustment substrate acquired by the imaging unit when the infrared light irradiation unit is turned off and visible light is emitted from the visible light irradiation unit at the intensity used to acquire the inspection image. 【0012】 Embodiments of the present invention 4 is, 1 (Appearance 1 to 3 It may be any one of the following: an image acquisition device in which the visible light irradiation unit has two or more light source units and the infrared light irradiation unit has one light source unit. 【0013】 Embodiments of the present invention 5 is, 1 (Appearance 1 to 4 It may be any one of the following: an image acquisition device, wherein the substrate is a printed circuit board, the pattern is a wiring, and the protective layer is a solder resist. 【0014】 Embodiments of the present invention 6 is, 5 An image acquisition device wherein the color of the solder resist is green, blue, or black. 【0015】 Embodiments of the present invention 7 is, 1 (Appearance 1 to 6 An image acquisition device (which may be any one of the above) further comprises a substrate moving mechanism that moves the substrate relative to the imaging unit in a direction parallel to the surface of the substrate, wherein the imaging unit includes a line sensor. 【0016】 Embodiments of the present invention 8 This is a substrate inspection apparatus for inspecting a substrate on which a protective layer that transmits infrared light is formed on a substrate on which a pattern is formed, and the aspect 1 (Appearance 1 to 7It may be any one of them.) An image acquisition device, and a defect detection unit that detects defects in the protective layer and defects in the pattern of the substrate by processing the inspection image acquired by the image acquisition device. 【0017】 Aspects of the present invention 9 is an image acquisition method for acquiring an image of a substrate on which a protective layer that transmits infrared light is formed on a base material on which a pattern is formed, comprising: a) a step of irradiating the substrate with visible light by a visible light irradiation unit; b) a step of irradiating the substrate with infrared light by an infrared light irradiation unit in parallel with the step a); and c) a step of an imaging unit receiving visible light and infrared light from the substrate through an imaging optical system and acquiring an inspection image used for inspecting the substrate. In the step c), the position of the imaging surface of the imaging unit is closer to the position where the image of the substrate of visible light is formed by the imaging optical system than the position where the image of the substrate of infrared light is formed by the imaging optical system. 【0019】 Aspects of the present invention 10 is a substrate inspection method for inspecting a substrate on which a protective layer that transmits infrared light is formed on a base material on which a pattern is formed, comprising: 9 a step of acquiring the inspection image by the image acquisition method described in aspect and a step of detecting defects in the protective layer and defects in the pattern of the substrate by processing the inspection image. 【0020】 According to the present invention, an image suitable for inspecting the protective layer and pattern of a substrate can be acquired in a short time by a simplified imaging optical system. 【Brief Description of the Drawings】 【0021】 [Figure 1] It is a diagram showing the configuration of a substrate inspection device. [Figure 2] It is a diagram showing an enlarged view of a visible light irradiation unit and an infrared light irradiation unit. [Figure 3] It is a diagram showing an enlarged view of an imaging unit and an imaging optical system. [Figure 4]This is a diagram showing a magnified view of the image sensor. [Figure 5] This block shows the configuration related to the operation and inspection of the circuit board inspection equipment. [Figure 6] This diagram shows the operation flow of a circuit board inspection device. [Figure 7] This is a longitudinal cross-sectional view showing an example of the substrate structure. [Figure 8A] This figure shows an example of an image acquired when only the visible light illumination area is lit. [Figure 8B] This figure shows an example of an image acquired when only the infrared light irradiating section is illuminated. [Figure 8C] This figure shows an example of an examination image. [Modes for carrying out the invention] 【0022】 Figure 1 shows the configuration of a substrate inspection apparatus 1 according to one embodiment of the present invention. The substrate inspection apparatus 1 is a final appearance inspection apparatus for printed circuit boards. The substrate inspection apparatus 1 includes an imaging unit 11, an imaging optical system 12, a visible light irradiation unit 13, an infrared light irradiation unit 14, and a substrate transport mechanism 15. The imaging unit 11, the imaging optical system 12, the visible light irradiation unit 13, and the infrared light irradiation unit 14 are mounted on a support (not shown). 【0023】 The substrate transport mechanism 15 includes a stage 151 and a stage moving mechanism 152. The stage 151 holds a substrate 9, which is a plate-shaped printed circuit board, on its upper surface. The upper surface of the stage 151 is horizontal, and the substrate 9 is held on the stage 151 in a horizontal position. The stage 151 may, for example, have a number of suction ports, and the substrate 9 is held on the stage 151 by sucking air from the suction ports. The substrate 9 may also be held on the stage 151 by being gripped by a mechanical mechanism such as claws. The state in which the substrate 9 is simply placed on the stage 151 may be considered as the state in which the substrate 9 is held on the stage 151. 【0024】 The stage moving mechanism 152 moves the stage 151 horizontally. In the configuration shown in Figure 1, the stage moving mechanism 152 moves the stage 151 and the substrate 9 in the Y direction in Figure 1. Any mechanism capable of moving the stage 151 can be used for the stage moving mechanism 152. For example, a structure in which a ball screw is connected to a motor may be the mechanism for moving the stage 151, or a linear motor may be the mechanism for moving the stage 151. 【0025】 The visible light irradiation unit 13 irradiates the surface of the substrate 9 to be inspected with visible light. In this embodiment, the visible light is white light. White light includes light with a wavelength of 400 nm to 700 nm. Preferably, a commercially available white LED is used as the light source for the visible light irradiation unit 13. The white LED may be one that utilizes a blue LED and a phosphor, or one that uses LEDs of the three primary colors. The visible light may be light with a single wavelength of 400 nm to 700 nm. The visible light may be light with multiple wavelengths of 400 nm to 700 nm. 【0026】 In the example shown in Figure 1, the visible light irradiation unit 13 includes two light source units 131. The number of light source units 131 may be one or three or more. Each light source unit 131 is elongated in a direction perpendicular to the transport direction (Y direction) of the substrate 9 and in a direction along the substrate 9 (X direction). Each light source unit 131 irradiates visible light to a region on the substrate 9 that crosses in the X direction. Figure 2 is an enlarged view of the visible light irradiation unit 13 and the infrared light irradiation unit 14. Each light source unit 131 includes a white LED 21 and a diffuser plate 22. More precisely, a number of white LED chips are arranged in the X direction as the white LED 21. The diffuser plate 22 is provided as needed. In place of the diffuser plate 22, other optical elements that homogenize the amount of light, such as a lenticular lens, may be used. By using two or more light source units 131, the occurrence of shadows on the substrate 9 is suppressed. 【0027】 The infrared light irradiation unit 14 irradiates the surface of the substrate 9 to be inspected with infrared light. In this embodiment, the wavelength of the infrared light is 850 nm. The wavelength of the infrared light may be between 700 nm and 900 nm, and preferably between 800 nm and 900 nm. Preferably, a commercially available infrared LED is used as the light source for the infrared light irradiation unit 14. 【0028】 The infrared light irradiation unit 14 includes a light source unit 141. Preferably, the number of light source units 141 in the infrared light irradiation unit 14 is one. As will be described later, infrared light is used to observe the pattern under the solder resist, and the irradiation direction can be set so that there is one infrared light irradiation unit 14. Of course, the number of light source units 141 may be two or more. The light source unit 141 is long in a direction perpendicular to the transport direction (Y direction) of the substrate 9 and in a direction along the substrate 9 (X direction). The light source unit 141 irradiates infrared light to a region on the substrate 9 that crosses in the X direction. As shown in Figures 1 and 2, the infrared light irradiation unit 14 irradiates the substrate 9 with infrared light at a small incident angle. A number of infrared LED chips are arranged in the X direction as infrared LEDs 25. If necessary, optical elements to homogenize the light amount are used, as in the case of the white light source unit 131. 【0029】 Figure 3 is an enlarged view of the imaging unit 11 and the imaging optical system 12. The imaging unit 11 includes an image sensor 111. The image sensor 111 is a so-called color line sensor. That is, in the image sensor 111, a large number of light-receiving elements are arranged in the X direction to acquire a one-dimensional color image. The imaging optical system 12 guides visible light and infrared light from the substrate 9 to the imaging unit 11. The imaging unit 11 images a thin linear region extending in the X direction (see Figure 1) on the substrate 9 via the imaging optical system 12. The thin linear imaging region is illuminated with visible light from the visible light illumination unit 13 and infrared light from the infrared light illumination unit 14. 【0030】 Figure 4 is a magnified view of the image sensor 111. The image sensor 111 is mounted on a mounting plate 113 within the imaging unit 11. An image of the substrate 9 is formed on the imaging surface 112 of the image sensor 111 by the imaging optical system 12. Two images of the substrate 9 are formed: an image using visible light and an image using infrared light. Hereinafter, the image using visible light will be called the "visible light image," and the image using infrared light will be called the "infrared light image." The imaging optical system 12 includes multiple optical elements, including lenses. Because visible light and infrared light have different wavelengths, even if the angle of incidence to the optical element is the same, the angle of refraction when passing through the optical element will be different. As a result, the position on the optical axis 121 where the visible light image of the substrate 9 is formed by the imaging optical system 12 is different from the position on the optical axis 121 where the infrared light image is formed. 【0031】 In Figure 4, the position on the optical axis 121 where the visible light image is formed is indicated by a straight line denoted by reference numeral 122 (a straight line drawn laterally from the image sensor 111), and the position on the optical axis 121 where the infrared light image is formed is indicated by a straight line denoted by reference numeral 123 (same as above). As indicated by reference numeral 122, in the substrate inspection apparatus 1, the position on the optical axis 121 of the imaging optical system 12 on the imaging surface 112 coincides with the position on the optical axis 121 where the visible light image is formed by the imaging optical system 12. On the other hand, as indicated by reference numeral 123, the position on the optical axis 121 where the infrared light image is formed by the imaging optical system 12 is shifted inward from the position on the optical axis 121 of the imaging optical system 12 on the imaging surface 112. 【0032】 Figure 5 is a block diagram showing the components related to the operation and inspection of the substrate inspection apparatus 1. Of the components shown in Figure 5, the control unit 31, storage unit 32, and defect detection unit 33 represent functions realized by a computer system. The computer system may be a general-purpose computer with an interface connected, a dedicated computer system, or a general-purpose computer equipped with dedicated electrical circuits. Of the components of the substrate inspection apparatus 1, all components except the defect detection unit 33 are image acquisition devices that acquire images of the substrate 9. 【0033】 Figure 6 shows the operation flow of the substrate inspection apparatus 1. When imaging the substrate 9, first, the visible light irradiation unit 13 and the infrared light irradiation unit 14 are turned on under the control of the control unit 31, and visible light and infrared light are simultaneously irradiated onto the imaging area on the substrate 9 (steps S11, S12). Of course, the visible light irradiation unit 13 and the infrared light irradiation unit 14 may be turned on at the same time, or one of them may be turned on first. Under the control of the control unit 31, the substrate 9 is moved in the Y direction (for example, from left to right in Figure 1) by the substrate transport mechanism 15, and in parallel with this, the imaging unit 11 repeatedly acquires a one-dimensional image. This acquires a two-dimensional color image of the top surface of the substrate 9 (step S13). In step S13, the imaging unit 11 receives visible light and infrared light from the substrate 9 simultaneously and acquires an image of the substrate 9. Hereinafter, the two-dimensional image acquired by the imaging unit 11 will be referred to as the "acquired image". The data of the acquired image is stored in the storage unit 32 as image data 81. 【0034】 The acquired image is obtained by the output of the image sensor 111 according to the visible light image and infrared light image formed by the imaging optical system 12. In other words, the acquired image is an image obtained by the color line sensor by superimposing the visible light image and the infrared light image. As described above, since the visible light image is formed on the imaging surface 112 of the image sensor 111, the outline of the image based on visible light in the acquired image is clear and sharp. On the other hand, since the infrared light image is formed slightly offset from the imaging surface 112 of the image sensor 111, the outline of the image based on infrared light in the acquired image is blurred. 【0035】 Figure 7 is a longitudinal cross-sectional view showing an example of the structure of the substrate 9. In the substrate 9, a copper wiring pattern 92 is formed on a plate-shaped base material 91, and the area of ​​the pattern 92 that needs to be protected is covered with a solder resist 93, which is an insulating protective layer. That is, a layer of solder resist 93 is formed on the base material 91 and the pattern 92. A thin solder layer, called a solder pad 94, is formed on a part of the pattern 92. 【0036】 Figure 8A shows an example of an acquired image when the substrate 9 is transported by the substrate transport mechanism 15 while the imaging unit 11 acquires an image of the substrate 9 in the substrate inspection device 1 with the visible light irradiation unit 13 lit and the infrared light irradiation unit 14 turned off. In Figure 8A, the shaded area is the area of ​​solder resist 93. The color of the solder resist 93 is preferably green, blue, or black. In particular, the substrate inspection device 1 can perform highly accurate inspections when the solder resist 93 is green or blue. Inspection is also possible with some types of solder resist when the solder resist 93 is black. Printed characters 95 are written on the solder resist 93 in white ink. For illustrative purposes, the printed characters 95 are shown in black in Figure 8A (the same applies hereafter). Solder pads 94 also appear in the image. A pattern 92 (see Figure 7) exists beneath the solder resist 93, and slight irregularities appear on the surface of the solder resist 93 along the pattern 92, but the pattern 92 is not visible in the image. 【0037】 Figure 8B shows an example of an acquired image when the substrate 9 is transported by the substrate transport mechanism 15 while the infrared light irradiation unit 14 is lit and the visible light irradiation unit 13 is turned off in the substrate inspection apparatus 1, and an image of the substrate 9 is acquired by the imaging unit 11. In the example of Figure 8B, the image was acquired after adjusting the height of the stage 151 so that the position of the infrared light image on the optical axis coincides with the position of the imaging surface 112 of the image sensor 111. Since infrared light penetrates the solder resist 93, which is a protective layer made of resin, the pattern 92 beneath the solder resist 93 appears in the image. Solder pads 94 and printed characters 95 also appear in the image. 【0038】 Figure 8C shows an example of an acquired image when the substrate 9 is transported by the substrate transport mechanism 15 while the substrate 9 is transported by the substrate transport mechanism 15 with the visible light irradiation unit 13 and the infrared light irradiation unit 14 illuminated in the substrate inspection apparatus 1, and an image of the substrate 9 is acquired by the imaging unit 11. As previously described, this is an image acquired when the position of the visible light image on the optical axis coincides with the position of the imaging surface 112 of the image sensor 111. In Figure 8C, the contours corresponding to the visible light image, i.e., the contours of the solder resist 93, solder pads 94, and printed characters 95, are clearly visible, while the contour of the pattern 92 corresponding to the infrared light image appears slightly blurred. 【0039】 In the substrate inspection apparatus 1, the defect detection unit 33 processes the acquired image, as exemplified in Figure 8C, as an inspection image to be used for inspection, thereby detecting defects (Figure 6: Step S14). As shown in Figure 5, the defect detection result 82 is stored in the storage unit 32 and displayed on a display unit (not shown). The inspection image represents both a visible light image and an infrared light image. Therefore, by inspecting the inspection image, it is possible to perform not only an external inspection of the substrate 9 based on visible light (white light), but also an inspection of the pattern 92 under the solder resist 93 based on infrared light. Specifically, defects in the appearance of the substrate 9 include foreign matter on the solder resist, peeling of the solder resist, scratches on the solder resist, foreign matter on the pads, misaligned holes, and abnormal printed characters. In addition, defects in the pattern include short circuits in the pattern, missing pattern parts, broken patterns, abnormal pattern shapes, and foreign matter on the pattern under the solder resist. In this way, the defect detection unit 33 detects defects in the appearance of the substrate 9, including the protective layer, and defects in the pattern 92 by processing the inspection image. 【0040】 The substrate inspection device 1 is primarily intended for visual inspection of the substrate 9, and simultaneously inspects the pattern beneath the solder resist. Here, since the position of the visible light image on the optical axis coincides with the position of the imaging surface 112 of the image sensor 111, the acquired inspection image is suitable for visual inspection. Furthermore, since the infrared light image is slightly blurred, the influence of the infrared light image on the visual inspection can be reduced. In addition, in the substrate inspection device 1, both the visible light image and the infrared light image are acquired using the same imaging optical system 12 and imaging unit 11, so an image suitable for inspection can be acquired with a simplified imaging optical system 12. As a result, the configuration related to imaging can be made cheaper compared to cases where a complex optical system and imaging units dedicated to acquiring visible light images and infrared light images are provided, and the manufacturing cost of the device can be reduced. Furthermore, since an inspection image including the appearance in the visible light image and the pattern in the infrared light image can be acquired in a single imaging operation, an inspection image can be acquired from a single substrate in a shorter time compared to cases where the visible light image and infrared light image are acquired sequentially. 【0041】 Next, the intensity of visible light and infrared light irradiated onto the substrate 9 by the substrate inspection device 1 will be explained. As previously described, the substrate inspection device 1 is primarily intended for visual inspection of the substrate 9, and at the same time, it also inspects the pattern under the solder resist. Therefore, if the infrared light image appears strongly in the inspection image, the accuracy of the visual inspection may decrease. To address this, the intensity of visible light and infrared light in the substrate inspection device 1 are set in advance by the following procedure. 【0042】 First, a lighting adjustment board is held on the stage 151 in place of the substrate 9. The lighting adjustment board is, in principle, a white substrate. The lighting adjustment board is also called a "shading board." Of course, a substrate that is not white may be used as the lighting adjustment board. 【0043】 Next, under the control of the control unit 31, with only the visible light irradiation unit 13 lit, that is, with the infrared light irradiation unit 14 turned off and the visible light irradiation unit 13 lit, an image of the illumination adjustment board is acquired by the imaging unit 11. The average brightness of the image is then compared with a predetermined target value (hereinafter referred to as the "first target value"). If the brightness is lower than the first target value, the intensity of the illumination light from the visible light irradiation unit 13 is increased; if the brightness is higher than the first target value, the intensity of the illumination light from the visible light irradiation unit 13 is decreased. The acquisition of an image of the illumination adjustment board with only the visible light irradiation unit 13 lit, and the adjustment of the intensity of the illumination light from the visible light irradiation unit 13, are repeated until the difference of the average brightness of the image with respect to the first target value falls within an acceptable range. If the number of grayscale levels in the image is 256, for example, the first target value is 200, and the acceptable range is ±10. Through the above operation, the illumination intensity of the visible light from the visible light irradiation unit 13 when acquiring the inspection image is determined. 【0044】 Next, under the control of the control unit 31, with only the infrared light irradiator 14 lit, that is, with the visible light irradiator 13 turned off and the infrared light irradiator 14 lit, the imaging unit 11 acquires an image of the illumination adjustment substrate. The average brightness of the image is then compared with a predetermined target value (hereinafter referred to as the "second target value"). If the brightness is lower than the second target value, the intensity of the illumination light from the infrared light irradiator 14 is increased, and if the brightness is higher than the second target value, the intensity of the illumination light from the infrared light irradiator 14 is reduced. Here, the second target value, which is compared with the average brightness of the image acquired with only the infrared light irradiator 14 lit, is between 10 percent and 30 percent of the first target value related to visible light. 【0045】 The acquisition of an image of the illumination adjustment board with only the infrared light irradiator 14 illuminated, and the adjustment of the illumination light intensity from the infrared light irradiator 14, are repeated until the difference in the average brightness of the image relative to the second target value falls within an acceptable range. For example, if the first target value is 200, the acceptable range for the second target value is ±10. Through the above operation, the illumination intensity of the infrared light from the infrared light irradiator 14 when acquiring the inspection image is determined. 【0046】 Through the above process, Visible light irradiation section 13Turn off the lights and use the intensity when acquiring the examination image. Infrared light irradiation section 14 from infra-red When light is emitted, the average brightness of the image of the illumination adjustment board acquired by the imaging unit 11 is: Infrared light irradiation section 14 Turn off the lights and use the intensity when acquiring the examination image. Visible light irradiation section 13 from visible When light is emitted, the average brightness of the image of the illumination adjustment substrate acquired by the imaging unit 11 is between 10 percent and 30 percent. Because the intensity of visible light from the visible light irradiation unit 13 and infrared light from the infrared light irradiation unit 14 is determined in this way, the inspection image obtained by imaging the substrate 9 to be inspected shows a clearer visible light image than an infrared light image. This suppresses the reduction in accuracy of the visible light image of the substrate 9 due to the influence of the infrared light image. 【0047】 The substrate inspection apparatus 1, including the image acquisition device, is not limited to the one described above and may be modified in various ways. 【0048】 The light source of the visible light irradiation unit 13, which irradiates the substrate 9 with visible light, is not limited to an LED, and the visible light is not limited to white light. Various other structures can be used as long as visible light can be irradiated onto the substrate 9. The light source of the infrared light irradiation unit 14, which irradiates the substrate 9 with infrared light, is also not limited to an LED, and the infrared light can be any light with a wavelength that can pass through the protective layer (solder resist 93). 【0049】 The arrangement direction of the light-receiving elements in the image sensor 111 of the imaging unit 11 is not limited to a direction perpendicular to the transport direction of the substrate 9. The light-receiving elements are arranged in a direction intersecting the transport direction of the substrate 9. The substrate transport mechanism 15 does not need to include a stage 151 and a stage moving mechanism 152, as long as it is a mechanism for transporting the substrate 9. If the substrate 9 is held by a structure other than the stage 151, a mechanism is provided to move this holding structure. Note that as long as the normal to the main surface of the substrate 9 and the transport direction of the substrate 9 are perpendicular, the substrate 9 does not necessarily need to be held in a horizontal position, and the transport direction is not limited to the horizontal direction. The substrate transport mechanism 15 moves the substrate 9 relative to the imaging unit 11 in a direction parallel to its surface. The substrate 9 may be held by a structure other than the stage 151. For example, the substrate 9 may be held by a mechanism that holds the four corners of the substrate 9 without using the stage 151. 【0050】 The image sensor 111 is not limited to a line sensor, but may also be a two-dimensional image sensor. In this case, transport of the substrate 9 during imaging is generally unnecessary. When a two-dimensional image sensor is used, the visible light irradiation unit 13 irradiates the entire area where imaging is performed with visible light, and at the same time, the infrared light irradiation unit 14 irradiates the same area with infrared light. 【0051】 The imaging optical system 12, which guides visible light and infrared light from the substrate 9 to the imaging unit 11, preferably has a simple structure in order to guide visible light and infrared light equally. Specifically, it is preferable that it does not include a reflective mirror and is composed of optical elements that transmit visible light and infrared light. As described above, the imaging optical system 12 forms a visible light image from the substrate 9 using visible light and an infrared light image from the infrared light. The position of the imaging surface 112 of the imaging unit 11 (more precisely, the position in the direction of the optical axis 121) and the position of the visible light image from the imaging optical system 12 (more precisely, the position in the direction of the optical axis 121) coincide. Of course, if the visible light is multi-wavelength light, strictly speaking, the position of the image will differ slightly for each wavelength, but the above statement of "coincidence" is an expression that ignores the slight positional shift of the image that depends on the wavelength and the surface irregularities of the substrate 9. 【0052】 From the perspective of acquiring inspection images with greater importance given to the visible light image than the infrared light image, the position of the imaging surface 112 and the position of the visible light image produced by the imaging optical system 12 do not need to coincide. It is sufficient that the position of the imaging surface 112 is closer to the position of the visible light image produced by the imaging optical system 12 than to the position of the infrared light image produced by the imaging optical system 12. Here, "closer" means closer in the direction of the optical axis 121, as described above. 【0053】 In the substrate inspection apparatus 1, the imaging unit 11 acquires an inspection image by simultaneously receiving visible light and infrared light from the substrate 9. "Simultaneously receiving" visible light and infrared light means that the photodetector corresponding to each pixel of the image sensor 111 reacts simultaneously to both visible light and infrared light and outputs information corresponding to the pixel value. Each photodetector may be a CCD (Charge Coupled Device), a CMOS (Complementary Metal Oxide Semiconductor), or any other type of photodetector. 【0054】 As previously mentioned, Infrared light irradiation section 14 The average brightness of the image of the lighting adjustment board obtained by turning on only that light is, Visible light irradiation section 13 The output of the visible light irradiation unit 13 and the infrared light irradiation unit 14 is adjusted so that the average brightness of the image of the illumination adjustment board, obtained by illuminating only the visible light and infrared light irradiation unit 14 is between 10 percent and 30 percent. The "illumination adjustment board" refers to the board used in the board inspection device 1 when correcting the intensity of the illumination light. Such boards are prepared in advance in the board inspection device 1. There does not need to be only one type of illumination adjustment board; different types may be prepared depending on the type of board 9 to be inspected. 【0055】 The technique of making the intensity of visible light illumination different from the intensity of infrared light illumination may be applied to the substrate inspection apparatus 1 independently of the technique of making the formation position of the visible light image closer to the imaging surface than the formation position of the infrared light image. 【0056】 The substrate inspection device 1 is preferably a final appearance inspection device for printed circuit boards. The substrate inspection device 1 may also be an appearance inspection device for printed circuit boards that is not the final one. It may also be used to inspect substrates other than printed circuit boards. The technique of acquiring an inspection image by superimposing a visible light image and an infrared light image can be applied to acquiring images used for inspecting various substrates on which a protective layer that transmits infrared light is formed on a substrate on which a pattern is formed. The pattern is not limited to wiring, and the protective layer is not limited to solder resist as long as it transmits infrared light. The appearance defects and pattern defects that are detected are not limited to those described above. The image sensor 111 is not limited to a color sensor. 【0057】 The configurations in the above embodiments and each modified example may be combined as appropriate, as long as they do not contradict each other. [Explanation of symbols] 【0058】 1. Circuit board inspection equipment 9 circuit boards 11 Imaging Unit 12 Imaging optical system 13 Visible light irradiation section 14 Infrared light irradiation section 15. Substrate moving mechanism 33 Defect detection unit 91 Base material 92 patterns 93 Solder Resist (Protective Layer) 111 Image sensor (line sensor) 112 Imaging surface 131,141 Light source units S11~S14 Step

Claims

[Claim 1] An image acquisition device for acquiring an image of a substrate on which a pattern is formed, wherein a protective layer that transmits infrared light is formed on the substrate, A visible light irradiation unit that irradiates the substrate with visible light, An infrared light irradiation unit that irradiates the substrate with infrared light, Imaging unit, An imaging optical system that guides visible light and infrared light from the substrate to the imaging unit, Equipped with, The position of the imaging surface of the imaging unit is closer to the position where the visible light image of the substrate is formed by the imaging optical system than to the position where the infrared light image of the substrate is formed by the imaging optical system. An image acquisition device characterized in that the imaging unit simultaneously receives visible light and infrared light from the substrate to acquire an inspection image used for inspecting the substrate. [Claim 2] An image acquisition device according to claim 1, An image acquisition device characterized in that the position of the imaging surface of the imaging unit coincides with the position where a visible light image of the substrate is formed by the imaging optical system. [Claim 3] An image acquisition device according to claim 1 or 2, An image acquisition device characterized in that, when the visible light irradiation unit is turned off and infrared light is emitted from the infrared light irradiation unit at the intensity used to acquire the inspection image, the average brightness of the image of the illumination adjustment board acquired by the imaging unit is 10 percent or more and 30 percent or less of the average brightness of the image of the illumination adjustment board acquired by the imaging unit when the infrared light irradiation unit is turned off and visible light is emitted from the visible light irradiation unit at the intensity used to acquire the inspection image. [Claim 4] An image acquisition device according to claim 1, The number of light source units in the visible light irradiation unit is two or more. An image acquisition device characterized in that the infrared light irradiation unit has one light source unit. [Claim 5] An image acquisition device according to claim 1, An image acquisition device characterized in that the substrate is a printed circuit board, the pattern is a wiring, and the protective layer is a solder resist. [Claim 6] An image acquisition device according to claim 5, An image acquisition apparatus characterized in that the color of the solder resist is green, blue, or black. [Claim 7] An image acquisition device according to claim 1, The system further comprises a substrate moving mechanism that moves the substrate relative to the imaging unit in a direction parallel to the surface of the substrate, An image acquisition device characterized in that the imaging unit includes a line sensor. [Claim 8] A substrate inspection apparatus for inspecting a substrate on which a pattern has been formed, wherein a protective layer that transmits infrared light has been formed on the substrate, The image acquisition device according to claim 1, A defect detection unit that processes the inspection image acquired by the image acquisition device to detect defects in the protective layer and the pattern of the substrate, A substrate inspection apparatus characterized by comprising the following features. [Claim 9] An image acquisition method for acquiring an image of a substrate on which a pattern has been formed, wherein a protective layer that transmits infrared light has been formed on the substrate, a) A step in which the visible light irradiation unit irradiates the substrate with visible light, b) A step in which the infrared light irradiation unit irradiates the substrate with infrared light in parallel with step a), c) The imaging unit simultaneously receives visible light and infrared light from the substrate via the imaging optical system to acquire an inspection image used for inspecting the substrate, Equipped with, An image acquisition method characterized in that, in step c) above, the position of the imaging surface of the imaging unit is closer to the position where the imaging optical system forms an image of the substrate in visible light than the position where the imaging optical system forms an image of the substrate in infrared light. [Claim 10] A substrate inspection method for inspecting a substrate on which a pattern has been formed, wherein a protective layer that transmits infrared light has been formed on the substrate, A step of acquiring the inspection image using the image acquisition method described in claim 9, The process of detecting defects in the protective layer and the pattern of the substrate by processing the inspection image, A substrate inspection method characterized by comprising the following:

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