Light irradiation device

Abstract

This invention provides a light irradiation device that allows for high irradiance settings on the irradiated surface of a workpiece without changing the device size, suppresses variations in irradiance for each direction viewed from the workpiece, facilitates circuit design, and allows for easy adjustment of the declination angle and collimation half-angle. [Solution] The light irradiation device comprises a flat plate-shaped mounting substrate with an observation hole formed in the center that penetrates in the thickness direction, a plurality of light sources mounted on the mounting substrate so as to surround the observation hole, and a reflective member positioned in front of the light emission direction of the plurality of light sources, which reflects the light emitted from the plurality of light sources toward an observation axis passing through the center of the observation hole, wherein the reflective member is composed of a plurality of flat plate-shaped reflectors arranged to form a regular polygon shape surrounding the observation hole when viewed from the direction of the observation axis.

Description

Technical Field

[0001] The present invention relates to a light irradiation device that irradiates light onto a workpiece.

Background Art

[0002] For example, in an appearance inspection system that extracts the edges and scratches of a workpiece such as a semiconductor chip from a captured image, a light irradiation device that irradiates low-angle light onto the workpiece is used so that the extraction target becomes clear in the image (Patent Document 1). This device forms a light-emitting surface in the shape of an inwardly truncated conical surface by bending an annular flexible substrate with a plurality of LEDs attached, and irradiates low-angle light from the light-emitting surface onto the workpiece. Then, through a circular observation hole surrounded by the light-emitting surface, the surface of the workpiece irradiated with light can be observed by an imaging means.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the aforementioned visual inspection system, in order to obtain high-contrast images of workpieces by irradiating them with low-angle light, it is desirable to set the declination angle of the irradiated light and the collimation half-angle on the irradiated surface of the workpiece according to the type of workpiece. However, in conventional light irradiation devices as described above, the orientation of the light-emitting surface created by bending the flexible substrate is predetermined, and it is not possible to adjust the declination angle or collimation half-angle of the irradiated light. Furthermore, when a flexible substrate is used, a small gap is created between the flexible substrate and the housing. This makes it difficult to reduce the thermal resistance from the LED to the housing and prevents the flow of large currents, making it difficult to increase the irradiance on the irradiated surface of the workpiece.

[0005] Therefore, for example, one could prepare multiple mounting boards on which light sources are mounted and combine them to form an inwardly oriented truncated pyramidal surface that emits light. In this way, the declination angle and collimation half-angle of the irradiated light can be adjusted by changing the tilt of each mounting board and the distance from each mounting board to the workpiece. However, in this case, changing the tilt of each mounting board and the distance from each mounting board to the workpiece will change the size of the device as viewed from the observation axis. In addition, due to variations in the contact thermal resistance between the housing and heat dissipation material that the back surface of each mounting board abuts, differences in heat dissipation performance will occur for each mounting board, resulting in variations in irradiance for each mounting board on the irradiated surface of the workpiece. Furthermore, having multiple mounting boards complicates the circuit design.

[0006] The present invention aims to solve these problems all at once, and its main objective is to provide a light irradiation device that can set a high irradiance on the irradiated surface of a workpiece without changing the size of the device, suppress variations in irradiance for each direction viewed from the workpiece, and allow for easy adjustment of the declination angle and collimation half-angle, while also facilitating circuit design. [Means for solving the problem]

[0007] In other words, the light irradiation device according to the present invention comprises a flat plate-shaped mounting substrate having an observation hole formed in the center that penetrates in the thickness direction, a plurality of light sources mounted on the mounting substrate so as to surround the observation hole, and a reflective member positioned in front of the light emission direction of the plurality of light sources, which reflects the light emitted from the plurality of light sources toward an observation axis passing through the center of the observation hole, wherein the reflective member is composed of a plurality of flat plate-shaped reflectors arranged to form a regular polygon shape surrounding the observation hole when viewed from the direction of the observation axis.

[0008] With this design, the light emitted from the light source is reflected towards the observation axis by a reflective member placed in front of the direction of emission, allowing the mounting substrate on which the light source is mounted to be a single flat plate perpendicular to the observation axis. This eliminates the need to arrange multiple divided mounting substrates, thereby reducing variations in irradiance on the illuminated surface of the workpiece in different directions as viewed from the workpiece, which are caused by differences in the heat dissipation performance of each mounting substrate, and also simplifies circuit design. Furthermore, by using a flat plate-shaped mounting substrate, it can be brought into closer contact with the housing compared to a flexible substrate, thus reducing the thermal resistance from the light source to the housing. This allows for the flow of a large current, and the irradiance on the irradiated surface of the workpiece can be made as high as possible. Furthermore, since the reflective element is composed of multiple reflectors, the declination angle of the light emitted from the light source can be adjusted by adjusting the tilt of each reflector without changing the tilt of the mounting substrate. Additionally, the collimation half-angle on the illuminated surface of the workpiece can be adjusted by adjusting the distance of each reflector from the mounting substrate. This allows for the illumination of various workpieces with appropriate light, resulting in high-contrast images, without changing the size of the device as viewed from the observation axis. While increasing the distance of each reflector from the mounting substrate increases the size of the device as viewed from the direction perpendicular to the observation axis, the overall size of the inspection system can be kept from increasing by utilizing the surplus space around the imaging device.

[0009] Furthermore, if the reflector constituting the reflective element has a curvatured reflective surface, then when manufacturing equipment to set the declination angle, collimation half-angle, and lighting system size to match various workpieces, it becomes necessary to manufacture a new reflector with a different curvature each time. However, by using a flat plate-shaped reflector, this necessity is eliminated. That is, since the curvature of the reflective surface of a flat plate-shaped reflector is 0 regardless of size, it is sufficient to simply cut one large flat plate-shaped reflector to the required size. This reduces manufacturing costs. In addition, there is no need to worry about interference between the mounting board and the workpiece, and by placing the reflector as close to the workpiece as possible, the declination angle can be set to be larger (i.e., a lower angle).

[0010] The light irradiation device is preferably configured such that the reflective member is composed of an even number of reflectors. If the reflective element consists of an odd number of reflectors (for example, three), some of the inspection light reflected by the reflectors and reaching the workpiece may be specularly reflected on the workpiece surface and reach the inner wall of the housing. The light diffusely reflected by this inner wall may then travel towards the workpiece, reducing inspection accuracy, or travel to the lens of the imaging device, causing flare and ghosting, which further reduces inspection accuracy. Therefore, when the reflective element is composed of an even number of reflectors (for example, four), the inspection light that has been reflected by the reflectors and reached the workpiece, and then specularly reflected on the workpiece surface, can be further reflected by the opposite reflector in its pair, allowing it to be directed towards the light source without being directed towards the workpiece or the imaging device, thereby suppressing a decrease in inspection accuracy.

[0011] In the light irradiation device, the plurality of light sources are arranged so as to be rotationally symmetric with respect to the observation axis, and it is preferable that the plurality of reflectors and the plurality of light sources are arranged so as to be lineally symmetric when viewed from the direction of the observation axis. In this way, multiple reflectors and multiple light sources are arranged in a manner that is both rotationally symmetrical and lineally symmetrical, thus eliminating the problem of asymmetrical detection accuracy depending on the direction of the scratches on the workpiece surface. For example, if the reflective element consists of four reflectors, then for a rectangular workpiece, as long as the side directions are aligned, the same inspection result can be obtained even if the workpiece is rotated ±90° or 180° when set.

[0012] Preferably, the light irradiation device has the plurality of light sources arranged to form a regular polygon surrounding the observation hole, and the reflectors are individually arranged to correspond to each side of the regular polygon formed by the plurality of light sources. In a configuration where multiple light sources correspond to a single reflector, and there are multiple distances from the plane containing the normal to the reflector surface and the observation axis to each light source, if the multiple light sources are arranged in a circular shape, when viewed from a direction perpendicular to both the normal to the reflector surface and the observation axis, the position of the light sources will shift towards the observation axis as the distance increases. As a result, when comparing those with small and large distances, the light sources with larger distances will have larger declination angles (i.e., lower angles), and the declination angles will vary from light source to light source, negatively impacting inspection accuracy. On the other hand, by arranging the multiple light sources to form a regular polygon surrounding the observation hole, and individually arranging the reflector to correspond to each side of the regular polygon formed by the multiple light sources, the positional shift between each light source is eliminated when viewed from a direction perpendicular to both the normal to the reflector surface and the observation axis, thus reducing the variation in the declination angle of light from each light source.

[0013] However, even in this case, when we consider the optical path from the center of the multiple light sources arranged along each side of the regular polygon to the illuminated surface of the workpiece in three dimensions, the declination angle becomes slightly larger for the light source with a larger distance compared to the light source with a smaller distance. Therefore, it is preferable that the multiple light sources surround the observation hole, forming a regular polygon shape, with each side being curved and convex inward. In this way, the light sources are positioned such that, when viewed from the observation axis, the distance increases gradually, making it possible to make the declination angle from each light source more constant.

[0014] The light irradiation device preferably uses a surface-mount LED as its light source. For example, when using a light source with a narrow beam pattern, such as a bullet-shaped LED, if multiple light sources are arranged correspondingly on a single flat reflector, some light may not reach the workpiece depending on the light source arrangement. By using a surface-mount LED with a wide beam pattern as the light source, it becomes possible to ensure that light from each light source reaches the workpiece even when multiple light sources are arranged on a single flat reflector. This increases the flexibility in the number and arrangement of light sources and reflectors.

[0015] In the aforementioned light irradiation device, the plurality of light sources are arranged in accordance with each of the plurality of reflectors when viewed from the observation axis direction, and it is preferable that the light distribution characteristics of each light source are set such that the difference in luminous intensity between the plurality of light sources corresponding to each reflector is within approximately 50% of the difference in luminous intensity of the light emitted from the center of the light source, reflected by the reflector, and reaching the observation axis. In this way, inspection light of sufficient intensity can be irradiated onto the workpiece from any light source, ensuring the necessary inspection accuracy.

[0016] The light irradiation device preferably further includes a heat dissipation member located on the back side of the mounting substrate. In this configuration, the heat dissipation component is positioned on the back of the mounting board, allowing for improved heat dissipation performance without changing the device size when viewed from the observation axis. Furthermore, because the heat dissipation component is on the opposite side of the workpiece, the workpiece is less affected by the heat emitted from the light source.

[0017] As a specific aspect of the light irradiation device that significantly exhibits the effects of the present invention, there is one in which the angles of the plurality of reflecting plates are set so as to irradiate a workpiece arranged on the observation axis with low-angle light. Note that the low-angle light referred to in this specification means that the declination angle of the inspection light is 60° or more and 90° or less.

Effects of the Invention

[0018] According to the present invention configured as described above, it becomes possible to provide a light irradiation device that can set a high irradiance on the irradiated surface of the workpiece without changing the device size, suppress variations in irradiance in each direction viewed from the workpiece, is easy to circuit-design, and can easily adjust the declination angle and the collimation half-angle.

Brief Description of the Drawings

[0019] [Figure 1] A diagram showing the configuration of an inspection system using the light irradiation device according to an embodiment of the present invention. [Figure 2] A plan view showing the positional relationship between the light source and the reflecting member in the light irradiation device of the same embodiment. [Figure 3] A cross-sectional view taken along line A - A' schematically showing the configuration of the light irradiation device of the same embodiment. [Figure 4] A diagram for explaining the declination angle and the collimation half-angle of the light irradiation device of the same embodiment. [Figure 5] A plan view showing the positional relationship between the light source and the reflecting member in the light irradiation device of another embodiment. [Figure 6] A plan view showing the positional relationship between the light source and the reflecting member in the light irradiation device of another embodiment. [Figure 7] A plan view showing the positional relationship between the light source and the reflecting member in the light irradiation device of another embodiment. [Figure 8] A plan view showing the positional relationship between the light source and the reflecting member in the light irradiation device of another embodiment.

Modes for Carrying Out the Invention

[0020] Hereinafter, a light irradiation device 100 according to one embodiment of the present invention will be described with reference to the drawings.

[0021] The light irradiation device 100 of this embodiment is used in an appearance inspection system S that extracts edges, scratches, and dust on a workpiece W, such as a semiconductor chip, from an image captured by the system. It irradiates the workpiece W, such as a CMOS sensor, that is being transported with low-angle inspection light. The light irradiation device 100 has observation holes H that pass through in the thickness direction, and the workpiece W being irradiated with inspection light can be observed and inspected by an observation means C such as a camera through these observation holes H.

[0022] Specifically, as shown in Figures 1-3, the light irradiation device 100 comprises a mounting substrate 1 with an observation hole H formed in the center that penetrates in the thickness direction, a plurality of light sources 2 mounted on the mounting substrate 1, and a reflective member 3 positioned in front of the light emission direction of the light sources 2. The mounting substrate 1 and the reflective member 3 are housed and held in a housing (not shown).

[0023] The mounting substrate 1 is a single flat plate, and one of its surfaces forms a flat mounting surface on which multiple light sources 2 are mounted. The observation hole H is formed in the center of the mounting substrate 1 so as to be circular when viewed from above. The observation axis A passing through the center of the observation hole H is oriented perpendicular to the mounting surface. Note that the observation hole H is not limited to a circular shape, but may also be polygonal or other shapes.

[0024] Light source 2 is a surface-mount type LED mounted on the mounting surface of the mounting substrate 1 so as to surround the observation hole H. The light sources 2 are arranged so as to be rotationally and linearly symmetrical with respect to each other around the observation axis A when viewed from the direction of the observation axis A, and more specifically, they are arranged to form a regular polygon. More specifically, the same number of light sources 2 (three in this case) are arranged on each side of the regular polygon (in this case, a regular octagon). In this embodiment, the multiple light sources 2 surround the observation hole to form a regular polygon, and are arranged so that each side is a straight line.

[0025] The reflective member 3 has a reflective surface that is inclined with respect to the observation axis A, and the orientation of its reflective surface is set so as to reflect light emitted from multiple light sources 2 toward the observation axis A.

[0026] This reflective member 3 is composed of a plurality of reflectors 31 arranged so as to be rotationally and linearly symmetrical with respect to each other around the observation axis A when viewed from the direction of the observation axis A. All of the plurality of reflectors 31 are flat plates (in this case, rectangular plates) and are identical in shape and size to each other. In this embodiment, the reflective member 3 is composed of an even number (specifically eight) of reflectors 31.

[0027] In this embodiment, the multiple reflectors 31 are arranged to surround the observation hole H and form a regular polygon, more specifically, one reflector 31 is placed on each side of the regular polygon. The multiple reflectors 31 and the multiple light sources 2 are arranged to have line symmetry (i.e., they share the same axis of symmetry) when viewed from the direction of the observation axis A. More specifically, the reflectors 31 are individually arranged to correspond to each side of the regular polygon formed by the multiple light sources 2.

[0028] Multiple reflectors 31 are arranged so as to be tilted at the same angle relative to the observation axis A. In this embodiment, the angle of each reflector 31 is set so that the declination angle of the inspection light emitted from each light source 2 is between 60° and 90°. The declination angle is the angle between the light ray emitted from the center of the light source 2, reflected by the reflector 31 and reaching the observation axis A, and the observation axis A, as shown in Figure 4.

[0029] In this embodiment, the light distribution characteristics of each light source 2 are set so that the emitted light reaches the illuminated surface of the workpiece W with sufficient luminosity. Specifically, the light distribution characteristics of each light source 2 are set so that the difference in luminosity of the light emitted from the center of the light source, reflected by the reflector 31 and reaching the observation axis A is within approximately 50% among the multiple light sources 2 corresponding to each reflector 31.

[0030] Furthermore, the light irradiation device 100 of this embodiment is equipped with a heat dissipation member 4 for dissipating heat from the light source 2. The heat dissipation member 4 is positioned in contact with the back surface of the mounting substrate 1. The aforementioned observation holes H are formed to continuously penetrate the heat dissipation member 4 and the mounting substrate 1. The size and shape of the observation holes H may be the same or different for the layers of the heat dissipation member 4 and the layers of the mounting substrate 1.

[0031] With the light irradiation device 100 of this embodiment configured in this way, the light emitted from the light source 2 is reflected toward the observation axis A by a reflecting member 3 positioned in front of the direction of emission, so that the mounting substrate 1 on which the light source 2 is mounted can be made of a single flat plate that is perpendicular to the observation axis A. As a result, it is possible to use a single mounting substrate 1 without arranging multiple divided mounting substrates 1, so that variations in irradiance on the irradiated surface of the workpiece W caused by differences in the heat dissipation performance of each mounting substrate 1 can be reduced, and circuit design can be simplified. Furthermore, since the reflective member 3 is composed of multiple reflectors 31, the declination angle of the light emitted from the light source 2 can be adjusted by adjusting the tilt of each reflector 31 without changing the tilt of the mounting substrate 1. In addition, the collimation half-angle on the illuminated surface of the workpiece W can be adjusted by adjusting the distance of each reflector 31 from the mounting substrate 1. As a result, without changing the size of the device as viewed from the observation axis A, appropriate light can be irradiated onto various workpieces W, and high-contrast images can be obtained. The collimation half-angle is the apparent size of the light-emitting surface as viewed from the illuminated surface of the workpiece W, expressed as an angle, as shown in Figure 4.

[0032] Furthermore, if the reflector 31 constituting the reflective member 3 has a curvatured reflective surface, then when manufacturing the device by setting the declination angle, collimation half-angle, and lighting system size to match various workpieces W, it would be necessary to manufacture a new reflector 31 with a different curvature each time. However, by making the reflector 31 a flat plate, this necessity is eliminated. That is, since a flat plate reflector 31 has zero curvature regardless of size, it is sufficient to simply cut one large flat plate reflector to the required size. This reduces manufacturing costs.

[0033] However, the present invention is not limited to the embodiments described above. For example, the light irradiation device 100 of the above embodiment was composed of an even number of reflectors 31 as the reflective member 3, but is not limited to this. In other embodiments of the light irradiation device 100, as shown in Figure 5, the reflective member 3 may be composed of an odd number of reflectors 31.

[0034] Furthermore, while the light irradiation device 100 of the above embodiment had rectangular plate shapes for each reflector 31 constituting the reflector member 3, it is not limited to this. In other embodiments of the light irradiation device 100, as shown in Figure 6, the reflectors may be trapezoidal plates of the same shape. By shaping the reflectors 31 in this way, the gaps between adjacent reflectors 31 can be narrowed, allowing the light emitted from the light source 2 to reach the workpiece W efficiently.

[0035] Furthermore, in the above embodiment of the light irradiation device 100, the multiple light sources 2 are arranged in a regular polygon shape, and the reflectors 31 are individually arranged to correspond to each side of the regular polygon formed by the arrangement of the multiple light sources 2, but the device is not limited to this. In other embodiments of the light irradiation device 100, as shown in Figure 7, the multiple reflectors 31 are arranged to form a regular polygon shape, while the multiple light sources 2 are arranged to form a circle, or to form any other shape.

[0036] Furthermore, in the above embodiment, the multiple light sources 2 were arranged to form a regular polygon shape with each side being a straight line, but the embodiment is not limited to this. In the light irradiation device 100 of other embodiments, as shown in Figure 8, the multiple light sources 2 may be arranged to form a regular polygon shape with each side being curved so as to be convex inward.

[0037] In other embodiments of the light irradiation device 100, the multiple light sources 2 may be of a different type, such as bullet-shaped LEDs, instead of surface-mount LEDs.

[0038] Furthermore, while the light irradiation device 100 in the above embodiment had the angles of each reflector 31 set so that low-angle light was irradiated onto the workpiece W, it is not limited to this.

[0039] Furthermore, the reflective member 3 may not be composed of one reflector 31 placed on each side of the regular polygon, but rather of multiple reflectors 31 placed on each side of the regular polygon.

[0040] Furthermore, it goes without saying that the present invention is not limited to the embodiments described above, and various modifications are possible without departing from its spirit. [Explanation of Symbols]

[0041] 100...Light irradiation device 1 ··· Implemented circuit board 2...Light source 3. Reflective material 31...reflector H ··· Observation hole A... Observation axis W ···Work

Claims

1. A flat plate-shaped mounting substrate with an observation hole formed in the center that penetrates in the thickness direction, Multiple light sources mounted on the substrate so as to surround the observation hole, The system includes a reflective member positioned in front of the light emission direction of the plurality of light sources, which reflects the light emitted from the plurality of light sources toward an observation axis passing through the center of the observation hole, The light irradiation device comprises a plurality of flat plate-shaped reflectors arranged to form a regular polygonal shape surrounding the observation hole when viewed from the direction of the observation axis.

2. The light irradiation device according to claim 1, wherein the reflective member is composed of an even number of reflectors.

3. The plurality of light sources are arranged so as to be rotationally symmetrical with respect to each other around the observation axis. The light irradiation device according to claim 1, wherein the plurality of reflectors and the plurality of light sources are arranged to have line symmetry when viewed from the direction of the observation axis.

4. The plurality of light sources are arranged to surround the observation hole in a regular polygonal shape. The light irradiation device according to claim 3, wherein the reflectors are individually arranged to correspond to each side of the regular polygon formed by the plurality of light sources.

5. The light irradiation device according to claim 4, wherein the plurality of light sources are arranged to surround the observation hole in a regular polygonal shape, with each side being curved and convex inward.

6. The light irradiation device according to claim 1, wherein the light source is a surface-mount LED.

7. Viewed from the observation axis direction, the multiple light sources are arranged corresponding to each of the multiple reflectors. The light irradiation device according to claim 1, wherein the light distribution characteristics of each light source are set such that, among the plurality of light sources corresponding to each reflector, the difference in luminous intensity of the light emitted from the center of the light source, reflected by the reflector, and reaching the observation axis is within approximately 50%.

8. The light irradiation device according to claim 1, further comprising a heat dissipation member disposed on the back side of the mounting substrate.

9. The light irradiation device according to claim 1, wherein the angles of the plurality of reflectors are set so as to irradiate a workpiece placed on the observation axis with low-angle light.

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