TWI588499B - Method and apparatus for testing light-emitting device - Google Patents

Description

Test method and device for illuminating device

The present invention relates to a method and apparatus for testing a light emitting device.

With the development of light-emitting diode (LED) technology, the application of light-emitting diodes has become more widespread. Light-emitting devices of today's light-emitting diodes typically include more than one light-emitting diode. For example, a high-voltage light-emitting diode (HVLED), an alternating current light-emitting diode (ACLED), or an array of light-emitting devices, which are commonly used in displays, traffic signs, and lamps, etc., include a plurality of light-emitting diodes. Taking a high-voltage light-emitting diode as an example, a single light-emitting diode operates at a low voltage, and a plurality of light-emitting diodes are connected in series to form a high-voltage light-emitting diode. Figure 1 shows a high voltage LED. The externally supplied AC voltage 11 is reduced in voltage via the converter 12 and converted to a corresponding DC voltage. The converted DC voltage is then supplied to a plurality of light emitting diodes. As shown in FIG. 1, in order to form a high voltage light emitting diode, one light emitting diode is connected in series with another light emitting diode. Each series unit is then connected in parallel with another series unit. The bonding method can form a plurality of light emitting diodes through a layout on a single die, or enclose a plurality of light emitting diodes in a single package at the package end. However, some of the failures caused by manufacturing processes or material defects, such as local leakage current or surface stress/damage, cannot be detected in conventional electrical tests. For a light-emitting diode device including a plurality of light-emitting diodes, when connected in series and/or in parallel, if only a few light-emitting diodes fail, it is difficult to detect by conventional electrical tests. . In addition, if a plurality of light-emitting diodes have inconsistent luminous intensity at the application end, they cannot be detected by a conventional electrical test.

The invention discloses a method for testing a light-emitting device, comprising the steps of: providing an integrating sphere comprising an inlet port and a first outlet; arranging the light-emitting device close to the inlet of the integrating sphere; providing a current source for driving the light-emitting device An image is formed in a driving state; an image receiving device is provided to receive an image of the light emitting device, wherein the image receiving device is connected to the first outlet of the integrating sphere; and the light emitting intensity of the light emitting device is determined according to the image. The invention also discloses an apparatus for testing a light-emitting device, comprising: an integrating sphere comprising an inlet port and a first outlet, wherein the light-emitting device is close to the inlet of the integrating sphere; an image receiving device, and the first outlet of the integrating sphere Connecting and receiving an image of the light emitting device; and a processing unit coupled to the image receiving device to determine the luminous intensity of the light emitting device.

11‧‧‧External AC voltage

12‧‧‧ converter

200‧‧‧ equipment

201, 501‧‧‧Test objects

210, 510‧‧‧ current source

220, 520‧‧‧ image receiving device

221, 521‧‧‧ image sensor

222‧‧‧ Eyepiece

223‧‧‧filter

230, 530‧‧‧Image Processing Unit

231, 531‧‧‧ comparison unit

240, 540‧‧‧Automation equipment

511a, 511b‧‧ ‧ probe

550‧‧ Score the ball

550e1‧‧‧ first exit

550e2‧‧‧ second exit

550i‧‧‧ entrance

551‧‧‧Light barrier

552‧‧‧ fiber optic

560‧‧‧Detector

561, 561'‧‧‧ signal processor

1 is a circuit diagram of a conventional high-voltage light-emitting diode; and FIG. 2 is a test device capable of testing a light-emitting device including a plurality of light-emitting diodes according to an embodiment of the present invention; In order to capture an actual image of a light-emitting device by a CCD according to an embodiment of the present invention; FIG. 4A is a view showing a method of testing a light-emitting device including a plurality of light-emitting diodes according to another embodiment of the present invention; FIG. 4B is as shown in FIG. Figure 4A illustrates the steps of a method for testing a test light-emitting device comprising a plurality of light-emitting diodes in accordance with another embodiment of the present invention; and Figure 5 illustrates a test comprising a plurality of light-emitting levels in accordance with another embodiment of the present invention. Test equipment for the body of the light-emitting device.

The light-emitting device to be tested in the present invention comprises a plurality of light-emitting diodes. A plurality of light emitting diodes may be connected in series, in parallel, or in series and in parallel. The illuminating device can take a variety of forms. For example, the light emitting device to be tested may be in the form of a die (or wafer) or a package. Luminescence in the form of grains In the device, the light-emitting device may have a light-emitting diode of a crystal grain, or a plurality of light-emitting diodes integrally formed by a single crystal grain. In the case of a light-emitting device in the form of a wafer, the light-emitting device has a plurality of light-emitting diodes on a wafer, and the wafer can be subsequently cut and separated to form a plurality of crystal grains including one or more light-emitting diodes. In the case of a packaged light-emitting device, the light-emitting device may comprise one or more die electrically connected to each other, or may be electrically connected to a plurality of individual packages to form a light-emitting device.

2 is a test apparatus capable of testing a light-emitting device including a plurality of light-emitting diodes according to an embodiment of the present invention. The device 200 includes a current source 210, a video receiving device 220, and an image processing unit 230. The illuminating device to be tested (hereinafter referred to as the object to be tested 201) is placed under the image receiving device 220, and the current source 210 supplies the current of the object to be tested 201 to drive a plurality of illuminating diodes. Each of the plurality of light-emitting diodes emits light in a driving state. The image receiving device 220 receives an image of the object to be tested 201 in a driving state, and the image processing unit 230 confirms the luminous intensity of each of the light emitting diodes according to the image received by the image receiving device 220.

The image receiving device 220 can include a microscope that can magnify the image when receiving the image of the object to be tested 201. The image receiving device 220 further includes an image sensor 221, such as a charge coupled device (CCD) or a CMOS image sensor, for capturing an image of the object to be tested 201. The image sensor 221 can be placed side by side with the eyepiece 222 of the image receiving device 220, so that the operator can view the image through the eyepiece 222 of the image receiving device 220, and/or simultaneously capture the image by the image sensor 221, and the image signal It is transmitted to the image processing unit 230 for further processing or confirmation. When the operator observes the image through the eyepiece 222 of the image receiving device 220, the operator can confirm the luminous intensity of the light-emitting diode. When the image sensor 221 captures the image, the image signal is transmitted to the image processor 230. After the image processing unit 230 performs further processing, for example, the image processing unit 230 performs analog-to-digital conversion (ADC), and the gray scale value of the luminous intensity of each of the light-emitting diodes is obtained to determine the luminous intensity of each of the light-emitting diodes. The grayscale value is usually a hierarchical number and is 2 ⁿ . In general, 256 (= 2 ⁸ ) orders are usually used to represent gray scales. The device 200 further includes a comparing unit 231, which can compare the luminous intensity represented by the grayscale value of each of the light emitting diodes with a predetermined luminous intensity to determine whether the light emitting diode is defective. The predetermined illuminance can be pre-confirmed by certain statistics, such as the average of the illuminance of the good LED, which is represented by the gray scale value. The image receiving device 220 further includes a filter 223 that filters out a specific range of wavelengths in the light. When the difference between the illuminating intensity of the defective illuminating diode and the illuminating intensity of the good illuminating diode is small or indistinguishable, the filter 223 is used to filter out the wavelength of the specific range of the light, so that the detected illuminating diode can be detected. The difference between the luminous intensity and the luminous intensity of a good light-emitting diode is large to facilitate discrimination. The filter 223 can be placed between the object to be tested 201 and the image receiving device 220 or between the image receiving device 220, the image sensor 221 and the eyepiece 222. In addition, the image processing unit 230 and the comparison unit 231 can be assembled together in an automation device 240 such as a computer. Moreover, the current source 210 can be combined in the same automation device 240, so the image processing unit 230, the comparison unit 231, and the current source 210 can be controlled or coordinated by a computer program to operate.

The current source 210 provides a current to the object to be tested 201 to drive a plurality of light emitting diodes, and the magnitude of the current supplied may be a constant value or a variable value. Each of the plurality of light emitting diodes can emit light in a driving state. FIG. 3 is a view showing an actual image taken by the image sensor 221 when the object 201 is a light-emitting device. In this example, the object to be tested 201 includes 16 light-emitting diodes arranged in two rows, each row having eight light-emitting diodes. These 16 light-emitting diodes are all connected in series. In one embodiment, the magnitude of the current supplied by current source 210 increases from a small value to a larger value over time, for example, from 1 mA to 15 mA. As shown in the figure, as the supply current increases, the luminous intensity of each of the light-emitting diodes becomes large. It should be noted that the second (indicated by ellipse) light-emitting diode in the left row has a lower luminous intensity than other LEDs, especially when the current is about 6 mA to 11 mA. . This shows that the darker light-emitting diode is a defective light-emitting diode due to leakage current. However, when the current is greater than 11 mA, such as 12 mA to 15 mA, the difference between the luminous intensity of the defective light-emitting diode and the luminous intensity of the other light-emitting diodes is not sufficiently distinguishable. This is due to local leakage current. When the supply current increases, the leakage current and the operating current also increase, but the rate of increase of the leakage current is smaller than the rate of increase of the operating current. For example, when the supply current is large enough, the current is from 12 mA to 15 mA, and the leakage current is only a small proportion of the operating current, so the difference between the luminous intensity of the defective light-emitting diode and the other light-emitting diodes becomes small and difficult to distinguish. . In the above embodiments, the current sufficient to discern the defective light-emitting diode is about 6 mA to 10 mA. Taking 10 mA as an example, if the area of the object to be tested 201 is about 1 mm ² , the current density of each of the light-emitting diodes in the light-emitting device is about 160 mA/mm ² (that is, 10 mA/(1 mm ² /16)). For most light-emitting diodes, a current density of less than or equal to about 300 mA/mm ² is small enough to distinguish between defective light-emitting diodes. In other embodiments, the current can be substantially a constant value and the current density is less than or equal to about 300 mA/mm ² sufficient to screen for defects. In the conventional electrical test, the current supplied to the light-emitting device is usually the operating current of the light-emitting diode, and the leakage current is usually not detected. In addition, even in the conventional electrical test, the supply current supplied to the light-emitting device is set to a small current so that the current density of each of the light-emitting diodes is smaller than the operating current density, because the leakage current usually occurs in a local region without causing an open circuit. Therefore, defects such as leakage current are generally not easily detected. In contrast, with the image of the luminous intensity of each of the light-emitting diodes, the leakage current is easily detected.

Figure 4A is a diagram showing a method of testing a light-emitting device comprising a plurality of light-emitting diodes in accordance with another embodiment of the present invention. The illuminating device to be tested comprises a plurality of illuminating diodes as described above.

This method can be carried out via a device as described above. The method includes: providing a current to drive a plurality of light emitting diodes (step 401); providing an image receiving device (step 402); the image receiving device receiving an image of the light emitting device in a driving state (step 403); The luminous intensity of each of the light-emitting diodes is determined (step 404). In step 401, a current is supplied to the light emitting device to drive a plurality of light emitting diodes, wherein the current magnitude may be a constant value or a varying value. Each of the plurality of light-emitting diodes emits light in a driving state. In one embodiment, the supply current is a varying value and the current increases over time. In other alternative embodiments, the current is a constant value and the current increases with time. In the foregoing two embodiments, the current density of each of the light emitting diodes is less than or equal to about 300 mA/mm ² .

In step 402, the image processing device may be a microscope, and may further include a filter that filters out a specific wavelength range of the light. In step 403, the image receiving device can receive the image of the light emitting device in the driving state. In step 404, the intensity of illumination of each of the light-emitting diodes in the illumination device can be determined by eye observation, for example, by an operator from an eyepiece of the image receiving device. In an embodiment, the image receiving device further includes an image sensor, such as a CCD or CMOS image sensor, for capturing an image of the light emitting device. The image sensor can be arranged side by side with the eyepiece of the image receiving device, so that the image sensor can capture the image at the same time, and the image signal is transmitted to an image processor for further processing or decision. That is, the image processing unit can be combined in an automated device, such as a personal computer, and in step 404, the illumination intensity of each of the light-emitting diodes is determined based on the image and is also performed by an automated device. The image processing unit further processes the image, such as an analog digital conversion (ADC), to obtain a gray scale value representative of the luminous intensity of each of the light emitting diodes to determine the luminous intensity of each of the light emitting diodes. By implementing this method with an automated device, it is easy to provide a current with a varying value from a small increase over time to confirm the luminous intensity. This method is easy to operate with an automated device that has a computer program that includes loops, since the control currents can have different current values at different loops.

As shown in Figure 4B, this method can include additional steps. For example, the grayscale value of each light-emitting diode can be selectively applied to generate an intensity profile to display each hair The position of the photodiode and the corresponding luminous intensity are as shown in step 405. The intensity map can also be output by the computer screen to enable the operator to compare the luminous intensity displayed by the grayscale value with the predetermined luminous intensity, and whether the LED is a defective LED, as in step 406. Shown. Alternatively, in another optional method, in step 406, the automation device further includes a comparing unit, and comparing each of the light-emitting diodes with a grayscale value indicating a luminous intensity and a predetermined grayscale value to determine a Whether the light-emitting diode is a defective light-emitting diode. The predetermined luminous intensity can be obtained by collecting statistics such as the average value of the luminous intensity displayed by the gray scale value of the good light emitting diode.

The method can then further include the step 407 of comparing the number of defective light-emitting diodes with a predetermined amount to confirm compliance. For example, a light-emitting diode having one or two defects in a light-emitting device is generally acceptable. In this case, the predetermined number is set to 3. Similarly, step 407 can be performed by an operator or by using a computer program with an automated device. When the light emitting device is in the form of a wafer, the entire wafer can be loaded for inspection. After the test, the method further includes an optional step 408 to generate a verification state map to display the area under test of the wafer and the corresponding verification status, wherein the verification status includes a pass and fail status.

The method further includes a step 409 for indicating a failed illumination device. When the luminous intensity is automatically confirmed by the automation device in steps 404, 406, and 407, the operator can visually reconfirm the program by the eyepiece of the image receiving device. The reconfirmation procedure can also be performed simultaneously with the detection of the automated device. When the automated device detects an unqualified illumination device, the automation device will issue a warning and suspend operation, wait for the operator's instruction, or wait for the entire wafer to complete the detection. Then, confirm again. Similarly, in step 406, when the automation device (comparison unit) performs the comparison procedure, the defective light-emitting diode is detected, and the operator can perform the re-confirmation procedure as described above. Additionally, the intensity profile generated in step 405 and the verification state map generated in step 408 can be stored in an automated device for use in future quality control or engineering analysis. In addition, the uniformity of the luminous intensity of a plurality of light-emitting diodes is generally considered in general applications, but can not be measured by conventional electrical tests, and this method can obtain this data. The intensity profile generated in step 405 clearly shows the position of each of the light-emitting diodes and its corresponding luminous intensity expressed in grayscale values, from which uniformity can be calculated and monitored.

Figure 5 is a diagram showing a test apparatus for testing a light-emitting device comprising a plurality of light-emitting diodes in accordance with another embodiment of the present invention. It should be noted that some of the elements in Figure 5 are substantially identical to those of Figure 2. The corresponding elements in Fig. 5 and Fig. 2 are denoted by the same component number, but the first code is changed from 2 to 5. For example, element 510 in FIG. 5 is a current source corresponding to current source 210 in FIG. The device includes a current source 510, an image receiving device 520, an image processing unit 530, and an integrating sphere 550. The integrating sphere 550 includes an inlet port 550i; a first outlet 550e1 and a second outlet 550e2. The light-emitting device to be tested (hereinafter referred to as the object to be tested 501) is placed near the entrance port 550i of the integrating sphere 550, and the light emitted from the object to be tested 501 enters and is collected by the integrating sphere 550. The image receiving device 520 is connected to the first outlet 550e1 of the integrating sphere 550 for receiving an image of the object to be tested 501 when the object to be tested 501 is driven by the current source 510. As shown in the figure, the current source 510 is in contact with the electrodes of the object to be tested 501 through probes 511a and 511b to provide a current to the object to be tested 501. As illustrated in FIG. 2, the image receiving device 520 can include a microscope for magnifying the image of the object 501 to be tested. The image receiving device 520 can be further connected to an image sensor 521, such as a charge coupled device (CCD) or a CMOS image sensor, to capture an image of the object to be tested 501. The image signal is transmitted to image processing unit 530 for further processing or decision. After further processing by the image processing unit 530, for example, a digital analog conversion (ADC), a grayscale value of an image of the object 501 can be obtained to represent and determine the luminous intensity of the object 501. The device further includes a comparing unit 531 for comparing the luminous intensity of the object 501 represented by the grayscale value with a predetermined luminous intensity to determine whether the object to be tested 501 is a defective LED. For example, the predetermined luminous intensity can be determined in advance by, for example, a plurality of good light-emitting diodes, such as an average value of the luminous intensity of the grayscale value. As shown in FIG. 2, the image receiving device 520 further includes a filter (not shown) for filtering out light of a certain range of wavelengths emitted by the object 501. The filter may be disposed above or below the first air outlet 550e1 of the integrating sphere 550 or between the image receiving device 520 and the image sensor 521. Further, in some embodiments, the image processing unit 530 and the comparison unit 531 together with the signal processor 561' of the detector 560 (described later) can be combined together in an automation device 540 such as a computer. In addition, the current source 510 can also be combined in the same automation device 540 to enable the image processing unit 530, the comparison unit 531, and the current source 510 to be controlled and coordinated for operation by, for example, a computer program.

The light emitted from the object to be tested 501 is incident on one point on the inner surface of the integrating sphere 550, and is evenly distributed to all other points after multiple scattering reflections. With this feature, the detector 560 can be coupled to the second outlet 550e2 of the integrating sphere 550 to measure the optical characteristics of the object 501 to be tested. A baffle 551 can be used to prevent light entering the integrating sphere 550 from directly illuminating the second outlet 550e2. In other words, the light barrier 551 can be used to prevent light from directly illuminating the detector 560. In this embodiment, detector 560 is coupled to second outlet 550e2 of integrating sphere 550 via fiber 552. For example, the detector 560 can be a photometer, a radiometer, a spectroradiometer, or a colorimeter. The photometer measures the energy of the light perceived by the human eye. A radiometer is a device that measures the energy of light. A spectroradiometer is a device that measures the energy per wavelength interval as the energy is expressed as a function of wavelength. The colorimeter measures and quantifies the color of the light. The detector 560 further includes a signal processor 561 for calculating or further processing the signal detected by the detector 560. Taking a colorimeter as an example, the colorimeter consists of three or four filtered detection elements. These detection components are used to simulate , and CIE function. Signals from these detection elements are used by signal processor 561 to calculate chromaticity coordinates -x and y. As shown in the figure and as described above, in some embodiments, the signal processor 561 internal to the detector 560 can be arranged or combined within the automation device 540, such as the signal processor 561'.

It should be noted that although the object to be tested 501 is shown as a single crystal having a light-emitting diode in the figure, the object to be tested 501 can be presented in various forms. For example, the object to be tested 501 may be in the form of a crystal (in the form of a wafer) or a package. In the case of the object 501 in the form of a crystal grain, the object to be tested 501 may also be a plurality of light-emitting diodes in which a single crystal grain is integrally formed. It should also be noted that, by the above apparatus, the optical characteristics of the image to be tested 501 and the measurement object 501 can be performed substantially simultaneously. That is, when the object to be tested 501 is placed close to the inlet port 550i of the integrating sphere 550, the light emitted by the object to be tested 501 enters the integrating sphere 550, and the image receiving device 520 receives the image of the object to be tested 501. At the same time, the integrating sphere 550 collects the light emitted by the object 501 and uniformly distributes all the points on the inner surface of the integrating sphere 550, so that the detector 560 connected to the second outlet 550e2 of the integrating sphere 550 is used to measure the measured Optical properties of object 501. As a result, the test for determining the defect of the object to be tested 501 and the optical characteristic of the object to be tested 501 by using the apparatus of the embodiment can be completed substantially simultaneously.

The embodiments of the invention are merely illustrative of the invention and are not intended to be limiting The scope of the invention. Any changes or modifications of the present invention to those skilled in the art will be made without departing from the spirit and scope of the invention.

200‧‧‧ equipment

201‧‧‧Test object

210‧‧‧current source

220‧‧‧Image receiving device

221‧‧‧Image sensor

222‧‧‧ Eyepiece

223‧‧‧filter

230‧‧‧Image Processing Unit

231‧‧‧Comparative unit

240‧‧‧Automation equipment

Claims (10)

An apparatus for testing a light-emitting device comprising a plurality of light-emitting diodes, comprising: an integrating sphere, the integrating sphere comprising an inlet port and a first outlet, wherein the light-emitting device is adjacent to the inlet port of the integrating sphere; a receiving device, the image receiving device is connected to the first outlet of the integrating sphere, and can receive an image of the lighting device; and a processing unit, the processing unit is connected to the image receiving device for analog digital conversion, and obtains the a luminous intensity gray scale value of each of the light emitting diodes of the light emitting device. The device of claim 1, further comprising an intensity distribution map generating device for generating an intensity distribution map showing the position of each of the light emitting diodes and the corresponding luminous intensity Grayscale value. The device of claim 1, further comprising an image sensor coupled to the microscope to capture an image of the illumination device. The device of claim 3, wherein the image sensor comprises a charge coupled device (CCD) or a CMOS image sensor. The device of claim 1, wherein the image receiving device further comprises a filter that filters out a specific range of wavelengths of light emitted by the illuminating device. The device of claim 1, wherein the integrating sphere further comprises a second outlet, and the apparatus further comprises a detector coupled to the second outlet to measure optical characteristics of the illumination device. The device of claim 6, wherein the detector can be a photometer, a radiometer, a spectroradiometer or a colorimeter. The device of claim 1, further comprising a comparison unit connected to the processing unit, wherein the comparison unit is configured to compare a grayscale value of each of the light emitting diodes of the light emitting device with a predetermined luminous intensity The gray scale value determines whether each of the light emitting diodes of the light emitting device is defective. The device of claim 1, further comprising a current source coupled to the illumination device. The device of claim 1, wherein the illuminating device is a die comprising the plurality of illuminating diodes integrally formed together.