Measuring device and measuring method

Abstract

Provided is a measuring device capable of accurately measuring the positions of LED chips arranged on a substrate, regardless of the material of the substrate surface.　Specifically, the measuring device subjects a plurality of LED chips on a substrate to position measurement and light emission measurement, and comprises an imaging unit that images the substrate and the LED chips, a first light source that illuminates the substrate and the LED chips with visible light, a second light source that illuminates the substrate and the LED chips with excitation light that causes the LED chips to emit fluorescence, a position recognition unit that recognizes the positions of the substrate and the LED chips from the captured images, and a control unit that controls the imaging unit, the first light source, the second light source, and the position recognition unit, wherein, under the control of the control unit: alignment marks provided on the substrate are imaged using the first light source to measure the position of the substrate, and the position of the substrate is recognized by the position recognition unit; the LED chips are imaged using the second light source; and the position of each LED chip and the presence or absence of light emission are measured by the position recognition unit.

Description

Measuring Apparatus and Measuring Method

[0001] The present invention relates to a measuring apparatus and a measuring method.

[0002] In a manufacturing process of semiconductor devices, electronic devices and the like, there is a step of arranging (for example, mounting) chip components on a substrate such as a semiconductor wafer, glass or resin. After that, there are steps of performing a quality inspection to check whether the chip components are arranged with predetermined accuracy, position measurement to check at which position the chip components are held, and inspection of the quality of the appearance and shape of the chip components (Patent Document 1). There is also a step of inspecting the quality of characteristics of chip components, for example, inspecting the quality of light emission for chip LEDs.

[0003] Japanese Unexamined Patent Publication No. 2019-163956

[0004] However, when measuring the position and arrangement accuracy of chip components on a substrate with a conventional imaging apparatus, if there is no clear difference in the degree of light reflection between the substrate surface and the chip components, only an image with an unclear boundary between the substrate and the chip components can be obtained, which causes a problem that position measurement and quality inspection cannot be performed accurately.

[0005] The present invention has been made in view of the above point, and an object of the present invention is to provide a measuring apparatus capable of accurately measuring the position of an LED chip arranged on a substrate without being influenced by the material of the substrate surface.

[0006] The measuring device of the present invention is a measuring device that performs position measurement and light emission measurement on a substrate for a plurality of LED chips arranged on a substrate, and comprises an imaging unit that images the substrate and the LED chips, a first light source that irradiates the substrate and the LED chips with visible light, a second light source that irradiates the substrate and the LED chips with excitation light that causes the LED chips to emit fluorescence, a position recognition unit that recognizes the positions of the substrate and the LED chips from the image captured by the imaging unit, and a control unit that controls the imaging unit, the first light source, the second light source and the position recognition unit, and under the control of the control unit, the alignment marks provided on the substrate are imaged using the first light source to measure the position of the substrate and the position of the substrate is recognized by the position recognition unit, the LED chips are imaged using the second light source and the position and presence or absence of light emission of each LED chip are measured by the position recognition unit. Light emission measurement is the measurement of the degree of light emission, and the quality of the light emission of the LED chips can be determined by the degree.

[0007] Furthermore, the system may include a position assignment unit, in which the position recognition unit recognizes the position of the LED chip that has emitted light due to the excitation light, and the position assignment unit uses the position of the LED chip that has emitted light to assign the position of the LED chip that has not emitted light.

[0008] The position recognition unit may use the data from the position assignment unit to measure the position of the LED chip that did not emit light and whether it was not emitting light.

[0009] Furthermore, a visual inspection of the LED chip may also be performed.

[0010] The substrate may be a display substrate, and may be electrically connected to the LED chip by an anisotropic conductive film.

[0011] The present invention provides a measurement method for performing position measurement and light emission measurement on a substrate for a plurality of LED chip components arranged on a substrate, comprising: a first measurement step of irradiating the substrate with visible light and measuring the position of alignment marks provided on the substrate; a second measurement step of irradiating the LED chips with excitation light that causes fluorescence emission and measuring the position and presence or absence of light emission for each LED chip; and a position coordinate determination step of determining the position coordinates of each LED chip based on the position of the alignment marks, wherein in the position coordinate determination step, the position coordinates of the LED chips that did not emit light are estimated and assigned from the position coordinates of the LED chips that emitted light in the vicinity.

[0012] By using two light sources to capture images and perform measurements from each, the position of the LED chip can be accurately measured regardless of the reflectivity of the substrate surface.

[0013] This is a schematic diagram of the measuring device according to the embodiment. The images show the substrate and LED chip captured by irradiating them with visible light. The images also show the substrate and LED chip captured by irradiating them with excitation light.

[0014] Embodiments of the present invention will be described in detail below with reference to the drawings. The following description of preferred embodiments is essentially illustrative and is not intended to limit the present invention, its applications, or its uses.

[0015] (Embodiment 1) Figure 1 shows a measuring device according to Embodiment 1. The measuring device 100 of this embodiment measures the position of each LED chip 12 on the substrate 10 and the degree of light emission of each LED chip 12, which is mounted on the substrate 10. The degree of light emission of an LED chip 12 refers to the degree of light emission of the LED chip 12. For example, when an LED chip 12 is used in an LED display, it serves as an indicator for determining whether or not a state called a dead dot occurs where the LED does not emit light as specified (in terms of light intensity and color) (normal light emission as specified).

[0016] The measuring device 100 of this embodiment is equipped with a first light source (coaxial light source) 30 that emits visible light, and illuminates the substrate 10 and LED chips 12 with visible light L1 via the illumination unit 72. The reflected light enters the imaging unit 20 from the objective lens 70 via the illumination unit 72, and imaging is performed. Since the area in which imaging can be performed is narrower than the entire surface of the substrate 10, the stage 90 on which the substrate 10 is placed moves, so that the portion of the substrate 10 to be imaged is sequentially moved relative to the objective lens 70, allowing all LED chips 12 to be imaged.

[0017] The measuring device 100 is equipped with a second light source (excitation light source) 40 that emits excitation light. This second light source 40 irradiates the substrate 10 and the LED chip 12 with excitation light L2 from diagonally above the substrate 10. The excitation light L2 is light with a wavelength that generates fluorescence in the LED chip 12, and light with a wavelength of approximately 385 nm to 525 nm can be used. The fluorescence generated from the LED chip 12 is incident on the imaging unit 20 via the objective lens 70 and illumination unit 72, and imaging is performed.

[0018] Furthermore, alignment marks A are provided on the surface of the substrate 10 on which the LED chips 12 are placed. One or more alignment marks are provided in areas where the LED chips 12 are not placed, for example, at the edges of the substrate 10, and their position and shape can be determined by irradiating them with visible light L1.

[0019] Next, we will explain the method for measuring the position of each LED chip 12 on the substrate 10 and the degree of light emission.

[0020] First, the position of the alignment marks is measured using the first light source 30. Specifically, the imaging unit 20 captures an image of the alignment marks by moving the stage 90. Then, the computer 50 identifies the position of the alignment marks on the XY coordinate system. This can be rephrased as the position recognition unit built into the computer 50 measuring and recognizing the position of the alignment marks. Subsequently, the position of each LED chip 12 is measured based on the position of these alignment marks, and their XY coordinates are determined. Before explaining the measurement of the position of the LED chips 12 in this embodiment, we will explain a conventional measurement method (reference example) and its problems.

[0021] <LED Chip Position Measurement Using Visible Light: Reference Example> In conventional methods for measuring the position of an LED chip 12 on a substrate 10, imaging was performed by irradiating it with visible light L1. In this case, if the degree of visible light reflection on the LED chip mounting surface of the substrate 10 is sufficiently large and the difference with the visible light reflection of the LED chip 12 is large, the difference between the substrate 10 and the LED chip 12 can be determined by image recognition by the computer 50 from the image captured by the imaging unit 20. However, depending on the type of LED chip mounting surface of the substrate 10, the degree of visible light reflection may be small, and as shown in Figure 2, the alignment mark A may be clear in the captured image, but the boundary with the LED chip 12 may be unclear.

[0022] In such cases, the boundary could be distinguished by devising image processing techniques using the computer 50. However, when a certain type of anisotropic conductive film was attached to the LED chip mounting surface, the reflectivity of the anisotropic conductive film was low, making it difficult to distinguish the boundary by image processing techniques alone. Similarly, when the reflectivity of the surface of the substrate 10 using visible light L1 was close to the reflectivity of the surface of the LED chip 12, boundary discrimination was also difficult.

[0023] <Position and emission measurement of LED chips using excitation light> In this embodiment, the position of the LED chip 12 is measured using excitation light irradiation from the second light source 40. Since this excitation light L2 is light of a wavelength that cannot be detected by the imaging unit 20, the image of an object that simply reflects the excitation light L2 will be a completely dark image. However, when the LED chip 12 is irradiated with excitation light L2, as shown in Figure 3, the LED chip 12 emits fluorescence, so it can be clearly distinguished in the captured image from the LED chip mounting surface of the substrate 10 which does not emit fluorescence. In particular, when an anisotropic conductive film with low light reflectivity is attached to the substrate 10 and the LED chip 12 is mounted on it, the chip and the substrate surface can be clearly distinguished in the image, unlike when visible light is irradiated. For this reason, this is a particularly preferred position measurement method when an anisotropic conductive film is attached to the surface of the substrate 10.

[0024] In this embodiment, after measuring the position of the alignment marks, the light source irradiating the substrate 10 is switched from the first light source 30 to the second light source 40. The imaging unit 20 captures an image (Figure 3) of the excitation light L2 irradiated by the second light source 40 and sends the image data to the computer 50. In the computer 50, the position recognition unit analyzes the image data to recognize the position of the fluorescently emitting LED chip 12, measures the position of the LED chip 12 based on the position of the alignment marks, and positions it in coordinates.

[0025] Furthermore, the position recognition unit measures and recognizes the degree of fluorescence emission (e.g., brightness), and if the degree of emission is above a predetermined threshold, it is determined that emission is present. For example, in Figure 3, when a high-brightness LED chip 12a, a medium-brightness LED chip 12b, and a low-brightness LED chip 12c are present, their degrees of emission (brightness) are recognized by image processing. Then, they are compared with a predetermined threshold for the degree of emission, and if they are above the threshold, it is determined that emission is present. In this way, the position measurement of the LED chip 12 and the measurement of whether or not emission is present can be performed simultaneously by irradiation with excitation light from the second light source 40. In addition, by performing image processing on the image of the LED chip 12 due to fluorescence emission to obtain the shape of the LED chip (more precisely, the emission shape), and comparing this shape with the shape of a normally emitting LED chip 12 that has been stored in advance, the appearance of the LED chip 12 can be inspected.

[0026] In this case, the LED chip 12 that does not emit light even when irradiated with excitation light L2 appears as a completely dark image, just like the substrate 10, and its position cannot be recognized or measured from the image data. In such a case, the position assignment unit in the computer 50 uses the arrangement and placement information of all the LED chips 12 on the substrate 10, which is stored in the computer 50 beforehand, to assign coordinates to the position of the LED chip 12 whose position cannot be recognized or measured from the image data because it does not emit light.

[0027] Specifically, if LED chips 12 are arranged on a substrate 10 at equal intervals in, for example, n rows and m columns, the distance X1 between two adjacent LED chips 12, 12 is stored in the computer 50. If one LED chip 12 in row a does not emit light due to excitation light L2, the positions of the LED chips 12, 12 before and after it are measured and recognized, but the non-emitting LED chip 12 cannot be measured and is not recognized. Therefore, the distance X2 between the LED chips 12, 12 before and after the non-emitting chip is greater than the distance X1 between adjacent LED chips 12, 12. The position assignment unit estimates from X2 > X1 and the information of the row a arrangement that there is a non-emitting LED chip 12 between two emitting LED chips 12, 12, estimates the position of the non-emitting LED chip 12 and assigns its coordinates. The position assignment unit sends the coordinate data of the non-emitting LED chip 12 to the position recognition unit, which recognizes (measures) that the LED chip 12 is not emitting light and also recognizes (measures) its position.

[0028] As described above, the position recognition unit works in cooperation with the position assignment unit to measure the position of all LED chips 12 and to measure whether each LED chip 12 is emitting light or not. The computer 50 includes an imaging unit 20, a first light source 30, a second light source 40, a position recognition unit, and a control unit that controls the measurement of the position and the presence or absence of light emission of the LED chips 12 as described above.

[0029] In this embodiment, by using the first light source 30 and the second light source 40 interchangeably, the position of all LED chips 12 can be recognized and measured regardless of the state of light reflection on the LED chip mounting surface of the substrate 10, and the presence or absence of light emission from all LED chips 12 can also be measured. Therefore, the position of the LED chips 12 can be measured accurately in a short time, and the presence or absence of light emission can also be measured in a short time.

[0030] (Embodiment 2) In Embodiment 2, the same measuring device 100 as in Embodiment 1 is used to further inspect the appearance of the LED chip 12. Since the same measuring device 100 as in Embodiment 1 is used, the parts that have already been described in Embodiment 1 will be omitted from the following description.

[0031] Visual inspection of the LED chip 12 is performed by irradiating it with excitation light L2 from the second light source 40. When the LED chip 12 is irradiated with excitation light L2, as shown in Figure 3, the LED chip 12 emits fluorescence, and the LED chip 12 is captured as a clear image by the imaging unit 20 against the background of the substrate 10, which does not emit fluorescence. Visual inspection of the LED chip 12 is performed using this image.

[0032] Specifically, a comparison target image is created first. The creation method involves preparing several good LED chips and irradiating them with excitation light L2 to capture images of the resulting fluorescence emission. Next, these multiple image data are statistically processed to create an average image data of a good product. This average image data of a good product is used as a comparison target and compared with the image of the LED chip 12 that was actually captured to determine whether the appearance is good or bad. It is preferable to perform the determination of the appearance quality in parallel with the measurement of the position of the LED chip 12 and the measurement of whether or not it emits light. The appearance determination unit that performs the determination by comparing with the comparison target is built into the computer 50. The content of the appearance inspection can appropriately adopt known inspection content such as the shape of the LED chip 12 itself and the unevenness of light emission within the chip.

[0033] In Embodiment 2, in addition to the effects of Embodiment 1, visual inspection of the LED chip can also be easily performed. Furthermore, the position measurement, the measurement of the presence or absence of light emission, and the visual inspection of the LED chip can be performed simultaneously, reducing the time and cost of measurement and inspection.

[0034] (Other Embodiments) The embodiments described above are illustrative examples of the present invention, and the present invention is not limited to these examples. These examples may be combined with or partially replaced with well-known technologies, conventional technologies, or prior art. Modified inventions that can be easily conceived by a person skilled in the art are also included in the present invention.

[0035] When measuring and determining the degree of fluorescence emission of LED chips, it is acceptable to measure and determine not only whether or not light is emitted, but also differences in color at the same time.

[0036] 10 Substrate 12 LED chip 20 Imaging unit 30 First light source 40 Second light source 50 Computer 100 Measuring device A Alignment mark L1 Visible light L2 Excitation light

Claims

1. A measuring device for performing position measurement and light emission measurement on a substrate for a plurality of LED chips arranged on a substrate, comprising: an imaging unit for imaging the substrate and the LED chips; a first light source for irradiating the substrate and the LED chips with visible light; a second light source for irradiating the substrate and the LED chips with excitation light to cause the LED chips to emit fluorescence; a position recognition unit for recognizing the positions of the substrate and the LED chips from an image captured by the imaging unit; and a control unit for controlling the imaging unit, the first light source, the second light source, and the position recognition unit, wherein, under control by the control unit, alignment marks provided on the substrate are imaged using the first light source to measure the position of the substrate and the position of the substrate is recognized by the position recognition unit, and the LED chips are imaged using the second light source, and the position and presence or absence of light emission of each LED chip are measured by the position recognition unit.

2. The measuring device according to claim 1, further comprising a position assignment unit, wherein the position recognition unit recognizes the position of the LED chip that has emitted light due to the excitation light, and the position assignment unit assigns the position of the LED chip that has not emitted light using the position of the LED chip that has emitted light.

3. The measuring device according to claim 2, wherein the position recognition unit measures the position of the LED chip that did not emit light and the fact that it was not emitting light using the data from the position assignment unit.

4. The measuring apparatus according to claim 1, further comprising performing an external inspection of the LED chip.

5. The measuring device according to claim 1, wherein the substrate is a display substrate and is electrically connected to the LED chip by an anisotropic conductive film.

6. A measurement method for performing position measurement and light emission measurement on a substrate for a plurality of LED chip components arranged on a substrate, comprising: a first measurement step of irradiating visible light and measuring the position of alignment marks provided on the substrate; a second measurement step of irradiating the LED chips with excitation light that causes fluorescence emission and measuring the position and presence or absence of light emission of each LED chip; and a position coordinate determination step of determining the position coordinates of each LED chip based on the position of the alignment marks, wherein in the position coordinate determination step, the position coordinates of the LED chips that did not emit light are estimated and assigned from the position coordinates of the LED chips that emitted light in the vicinity.

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