Patent Publication Number: US-2019170808-A1

Title: Testing system for micro lighting device and related testing method

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority of Taiwan Application No. 106142656 filed on 2017 Dec. 6. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is related to a testing system for micro lighting device and related testing method, and more particularly, to a testing system for micro LED and related testing method. 
     2. Description of the Prior Art 
     Compared to traditional incandescent bulbs, light-emitting diodes (LEDs) are advantageous in low power consumption, long lifetime, small size, no warm-up time, fast reaction speed, and the ability to be manufactured as small or array devices. In addition to outdoor displays, traffic signs, and liquid crystal display (LCD) backlight for various electronic devices such as mobile phones, notebook computers or personal digital assistants (PDAs), LEDs are also widely used as indoor/outdoor lighting devices in place of fluorescent of incandescent lamps. 
     The size of traditional LED arrays is the dimension of millimeters (mm). The size of micro LED arrays may be reduced to the dimension of micrometers (μm) while inheriting the same good performances regarding power consumption, brightness, resolution, color saturation, reaction speed, life time and efficiency. In a micro LED manufacturing process, a thin-film, miniaturized and array design is adopted so that multiple micro LEDs are fabricated in the dimension of merely 1-300 μm. Next, these micro LEDs are mass transferred to be disposed on another circuit board. Protection layers and upper electrodes may be formed in a physical deposition process before packaging the upper substrate. Since the manufacturing process of micro LEDs is very complicated, there is a need for a testing system and related testing method in order filter flawed micro LEDs. 
     SUMMARY OF THE INVENTION 
     The present invention provides a testing system for use in a micro lighting device. The testing system includes a test electrode, a carrier, a power supply, an optical receiver, and a judging unit. The carrier is configured to hold the test electrode and adjust a distance between the test electrode and a first electrode of a luminance device in the micro lighting device. The power supply is configured to apply a first voltage to the first test electrode and apply a second voltage to a second electrode of the luminance device. The optical receiver is configured to detect an optical signal of the luminance device. The judging unit is configured to determine whether the luminance device is able to light up according to a detecting result of the optical receiver. 
     The present invention also provides a testing system for use in a micro lighting device. The testing system includes a power supply and a testing material layer. The power supply is configured to apply a first voltage to a first electrode of a luminance device in the micro lighting device and apply a second voltage to a second electrode of the luminance device. The testing material layer is disposed on the micro lighting device, wherein a color of the testing material layer is associated with at least one of luminous energy and thermal energy provided by the luminance device in the micro lighting device. 
     The present invention also provides a method of testing a micro lighting device. The method includes applying a first voltage to a first test electrode, applying a second voltage to a first electrode of a luminance device in the micro lighting device, adjusting a distance between the first test electrode and the luminance device until a second electrode of the luminance device is able to sense the first voltage, and determining whether the luminance device is lit up by detecting an optical signal from the luminance device. 
     The present invention also provides a method of testing a micro lighting device. The method includes applying a first voltage to a first test electrode, applying a second voltage to a second test electrode, adjusting a distance between the first test electrode and a luminance device in the micro lighting device until a first electrode of the luminance device is able to sense the first voltage, adjusting a distance between the second test electrode and the luminance device until a second electrode of the luminance device is able to sense the second voltage, and determining whether the luminance device is lit up by detecting an optical signal from the luminance device. 
     The present invention also provides a method of testing a micro lighting device. The method includes fabricating a plurality of luminance devices and then transferring the plurality of luminance devices to be disposed on a substrate, disposing a testing material layer on the plurality of luminance devices, wherein a color exhibited by the testing material layer on a region is associated with at least one of luminous energy and thermal energy received in the region, applying a first voltage to a first electrode of each luminance device and applying a second voltage to a second electrode of each luminance device, and determining whether each luminance device is lit up according to the color of each region corresponding to each luminance device. 
     These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A-1B  are diagrams illustrating a testing system for micro lighting device according to an embodiment of the present invention. 
         FIGS. 2A-2B  are diagrams illustrating a testing system for micro lighting device according to another embodiment of the present invention. 
         FIG. 3  and  FIG. 4  are diagrams illustrating a testing system for micro lighting device according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1A-1B and 2A-2B  are diagrams illustrating testing system for micro lighting device according to embodiments of the present invention. The test system  100  depicted in  FIGS. 1A-1B  and the test system  200  depicted in  FIGS. 2A-2B  may be apply to a micro lighting device  500  in order to detect anomalies such as defects, contamination or missing materials in devices. 
     The micro lighting device  500  with a thin-film, miniaturized and array design includes a plurality of luminescent devices (only two luminescent devices  10  are depicted for illustrative purpose). The luminescent devices  10  are fabricated by combining P-type and N-type semiconductor materials before being mass transferred to be disposed on a substrate  20 . Under normal condition, when a positive voltage is applied to the P-electrode and a negative voltage is applied to the N-electrode, electrons flow from the N-region towards the P-region and holes flow from the P-region towards the N-region due to the forward-bias voltage. These electrons and holes then combine in the PN junction of the luminescent layer, thereby emitting photons of light. In an embodiment of the present invention, each luminescent device  10  may be a micro LED device which includes a P-type semiconductor layer  12 , an N-type semiconductor layer  14 , a P-electrode  16 , an N-electrode  18 , and a luminescent layer  15 . 
     In the embodiment illustrated in  FIGS. 1A-1B , the test system  100  includes a carrier  30 , a test electrode  40 , a plurality of optical receivers  50 , a power supply  60 , and a judging unit  70 . The carrier  30  is configured to hold the test electrode  40  and adjust the distance between the test electrode  40  and the luminance device  10 . The power supply  60 , coupled between the test electrode  40  and the N-electrode  18  of the luminance device  10 , is configured to apply a first voltage to the test electrode  40  and apply a second voltage to the N-electrode  18 , thereby establishing a voltage difference V BIAS  between the test electrode  40  and the N-electrode  18 . 
     In the embodiment illustrated in  FIGS. 2A-2B , the test system  200  includes a carrier  30 , two test electrodes  41  and  42 , a plurality of optical receivers  50 , a power supply  60 , and a judging unit  70 . The test electrodes  41  and  42  with a pattern design are disposed on the carrier  30  at locations corresponding to the P-electrode  16  and the N-electrode  18 , respectively. In other words, the distance between the test electrode  41  and the P-electrode  16  and the distance between the test electrode  42  and the N-electrode  18  may be adjusted by moving the carrier  30 . The power supply  60 , coupled between the test electrodes  41  and  42 , is configured to apply a first voltage to the test electrode  41  and apply a second voltage to the test electrode  42 , thereby establishing a voltage difference V BIAS  between the test electrodes  41  and  42 . 
     The amount of the optical receivers  50  is related to the amount of the luminescent devices  10 . Each optical receiver  50  is configured to detect the optical signals from one or multiple corresponding luminescent devices  10  when lit up. The judging unit  70  is configured to determine whether the luminescent devices  10  function normally according to the detecting result of each optical receiver  50  for subsequent repair process. In an embodiment, each luminescent device  10  may be accurately monitored by a corresponding optical receiver  50 . In another embodiment, each optical receiver  50  is configured to monitor the status of multiple luminescent devices  10  within a specific region. However, the amount of the optical receivers  50  does not limit the scope of the present invention. 
     In an embodiment when the test system  100  is used to run a test flow, the power supply  60  is first turned on to establish the voltage difference V BIAS  between the test electrode  40  and the N-electrode  18  of the luminescent device  10 . Next, the carrier  30  is moved in a way so that the test electrode  40  gradually approaches the P-electrode  16  of the luminescent device  10 . Once the distance d between the test electrode  40  and the P-electrode  16  is reduced to a specific value ( FIG. 1B  depicts the case of d=0 in which the test electrode  40  is in contact with the P-electrode  16 ), the P-electrode  16  is able to sense the first voltage on the test electrode  40 , and the voltage difference V BIAS  established between the P-electrode  16  and the N-electrode  18  may conduct the luminescent device  10 . Under normal condition, the luminescent device  10  can be successfully lit up and emit optical signals which may be detected by the corresponding optical receiver  50 . If the luminescent device  10  is flawed (such as due to defects, contamination or missing materials in devices) and cannot be lit up, the corresponding optical receiver  50  is unable to detect any optical signal. Therefore, the judging unit  70  may determine whether the luminescent devices  10  can function normally according to the detecting result of each optical receiver  50  for subsequent repair process. 
     In another embodiment when the test system  100  is used to run a test flow, the carrier  30  is first moved in a way so that the distance d between the test electrode  40  and the P-electrode  16  of the luminescent device  10  is reduced to a specific value ( FIG. 1B  depicts the case of d=0 in which the test electrode  40  is in contact with the P-electrode  16 ). Next, the power supply  60  is turned on to establish the voltage difference V BIAS  between the test electrode  40  and the N-electrode  18  of the luminescent device  10 . Once the P-electrode  16  senses the first voltage on the test electrode  40 , the voltage difference V BIAS  established between the P-electrode  16  and the N-electrode  18  may conduct the luminescent device  10 . Under normal condition, the luminescent device  10  can be successfully lit up and emit optical signals which may be detected by the corresponding optical receiver  50 . If the luminescent device  10  is flawed (such as due to defects, contamination or missing materials in devices) and cannot be lit up, the corresponding optical receiver  50  is unable to detect any optical signal. Therefore, the judging unit  70  may determine whether the luminescent devices  10  can function normally according to the detecting result of each optical receiver  50  for subsequent repair process. 
     In an embodiment when the test system  200  is used to run a test flow, the power supply  60  is first turned on to establish the voltage difference V BIAS  between the test electrodes  41  and  42 . Next, the carrier  30  is moved in a way so that the test electrodes  41  and  42  gradually approach the P-electrode  16  and the N-electrode  18  of the luminescent device  10 , respectively. Once the distance d 1  between the test electrode  41  and the P-electrode  16  and the distance d 2  between the test electrode  42  and the N-electrode  18  are reduced to a specific value ( FIG. 2B  depicts the case of d 1 =d 2 =0 in which the test electrode  41  is in contact with the P-electrode  16  and the test electrode  42  is in contact with the N-electrode  18 ), the P-electrode  16  is able to sense the first voltage on the test electrode  41  and the N-electrode  18  is able to sense the second voltage on the test electrode  42 . The voltage difference V BIAS  established between the P-electrode  16  and the N-electrode  18  may thus conduct the luminescent device  10 . Under normal condition, the luminescent device  10  can be successfully lit up and emit optical signals which may be detected by the corresponding optical receiver  50 . If the luminescent device  10  is flawed (such as due to defects, contamination or missing materials in devices) and cannot be lit up, the corresponding optical receiver  50  is unable to detect any optical signal. Therefore, the judging unit  70  may determine whether the luminescent devices  10  can function normally according to the detecting result of each optical receiver  50  for subsequent repair process. 
     In another embodiment when the test system  200  is used to run a test flow, the carrier  30  is first moved in a way so that the distance d 1  between the test electrode  41  and the P-electrode  16  and the distance d 2  between the test electrode  42  and the N-electrode  18  are reduced to a specific value ( FIG. 2B  depicts the case of d 1 =d 2 =0 in which the test electrode  41  is in contact with the P-electrode  16  and the test electrode  42  is in contact with the N-electrode  18 ). Next, the power supply  60  is turned on to establish the voltage difference V BIAS  between the test electrodes  41  and  42 . Once the P-electrode  16  senses the first voltage on the test electrode  41  and the N-electrode  18  senses the second voltage on the test electrode  42 , the voltage difference V BIAS  established between the P-electrode  16  and the N-electrode  18  may thus conduct the luminescent device  10 . Under normal condition, the luminescent device  10  can be successfully lit up and emit optical signals which may be detected by the corresponding optical receiver  50 . If the luminescent device  10  is flawed (such as due to defects, contamination or missing materials in devices) and cannot be lit up, the corresponding optical receiver  50  is unable to detect any optical signal. Therefore, the judging unit  70  may determine whether the luminescent devices  10  can function normally according to the detecting result of each optical receiver  50  for subsequent repair process. 
       FIG. 3  and  FIG. 4  are diagrams illustrating a testing system  300  for micro lighting device according to another embodiment of the present invention. The test system  300  may be apply to a micro lighting device  600  in order to detect anomalies such as defects, contamination or missing materials in devices. 
     The micro lighting device  600  with a thin-film, miniaturized and array design includes a plurality of luminescent devices (only two luminescent devices  10  are depicted for illustrative purpose), a drain line  22 , and a ground line  24 . The luminescent devices  10  are fabricated by combining P-type and N-type semiconductor materials before being mass transferred to be disposed on a substrate  20 . Under normal condition, when a positive voltage is applied to the P-electrode and a negative voltage is applied to the N-electrode, electrons flow from the N-region towards the P-region and holes flow from the P-region towards the N-region due to the forward-bias voltage. These electrons and holes then combine in the PN junction of the luminescent layer, thereby emitting photons of light. In an embodiment of the present invention, each luminescent device  10  may be a micro LED device which includes a P-type semiconductor layer  12 , an N-type semiconductor layer  14 , a P-electrode  16 , an N-electrode  18 , and a luminescent layer  15 , wherein the P-electrode  16  is electrically connected to the drain line  22  and the N-electrode  18  is electrically connected to the ground line  24 . 
     In the embodiments illustrated in  FIG. 3  and  FIG. 4 , the test system  300  includes a power supply  60  and a testing material layer  80 . The power supply  60 , coupled between the drains line  22  and the ground line  24 , is configured to apply a first voltage to the P-electrode  16  and apply a second voltage to the N-electrode  18 , thereby establishing a voltage difference V BIAS  between the P-electrode  16  and the N-electrode  18 . The testing material layer  80  may be connected to the drain line  22  and the ground line  24  in a deposition, coating or attachment process. The color exhibited by the testing material layer  80  is associated with the luminous energy and the thermal energy provided by the corresponding luminance device  10 . 
     In an embodiment, the testing material layer  80  may include thermochromatic materials including, but not limited to cholesteric liquid crystal, smectic liquid crystal, bismuth vanadate (Bivo4), iodide or Ni/SiO2 compound. In another embodiment, the testing material layer  80  may include photochromic materials including, but not limited to, photocatalysis chemical compounds (such as ZnO, WO3, CdS, Fe2O3 or TiO2), high molecular materials (such as spiropyran, fulgide, or diarylethene), or silver halide (AgX). However, the type of the thermochromatic/photochromic materials included in the testing material layer  80  does not limit the scope of the present invention. 
     After turning on the power supply  60 , the voltage difference V BIAS  established between the P-electrodes  16  and the N-electrodes  18  may conduct the luminescent device  10 . For illustrative purpose, it is assumed that the luminescent device  10  depicted on the left side of  FIG. 3  and  FIG. 4  can function normally, while the luminescent device  10  depicted on the right side of  FIG. 3  and  FIG. 4  is flawed (such as due to defects, contamination or missing materials in devices). When the normal luminescent device  10  on the left side is successfully lit up, it emits luminous energy and thermal energy which changes the color of the testing material layer  80  in a corresponding region, as depicted by the colored region  90  in  FIG. 4 . When the flawed luminescent device  10  on the right side is unable to light up, the color of the testing material layer  80  in a corresponding region remains unchanged. Therefore, the present invention may determine whether the luminescent devices  10  can function normally according to the color of the testing material layer  80  in the corresponding region for subsequent repair process. 
     In conclusion, the present invention provides a micro lighting device with repair mechanism in which flawed luminescent devices may be detected for subsequent repair process. 
     Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.