TW201839872A - Testing method for micro-led wafer - Google Patents

Abstract

A testing method for micro-LED wafer includes providing a wafer not yet packaged, the wafer having a plurality of micro-LEDs thereon; applying a current to the micro-LEDs such that a first exposing surface of each of the micro-LEDs illuminates simultaneously, an illuminating area of each of the first exposing surfaces occupies 70%-90% of its total area; detecting the illuminated micro-LEDs to form an image; and comparing corresponding illuminating conditions of the micro-LEDs in the image and determining a functional status of each of the micro-LEDs.

Description

 Test method for micro-lighting diode wafer  

The invention relates to a test method for a micro-light emitting diode wafer.

In order to ensure the production quality of electronic components such as light-emitting diodes, in the development of light-emitting diodes, tests for photoelectric properties are usually involved. Generally, before the light emitting diode is fabricated on the wafer and the wafer is not cut, the user first makes electrical contact with the light emitting diode on the wafer by the probe to perform the light emitting diode. Testing of photoelectric properties.

With the rapid development of technology, the light-emitting diodes have also become micro-shaped, that is, the development of micro-light emitting diodes (micro-LEDs). However, even if the light-emitting diode becomes micro-shaped, the test of its photoelectric characteristics is still an important part of the production process.

Therefore, one of the objects of the present invention is to provide a test method for a micro-light-emitting diode wafer, which enables a user to effectively judge the functional status of the micro-light-emitting diode.

According to an embodiment of the invention, a method for testing a micro-light emitting diode wafer includes providing a wafer that is not packaged, the wafer having a plurality of micro-light emitting diodes thereon; applying a current to the micro-light emitting diode, The first exposed surface of the micro-light emitting diode is simultaneously illuminated, and the bright area of the first exposed surface occupies 70%-90% of the total area; sensing the illuminated micro-light emitting body to form an image; The function of the micro-light-emitting diode is judged by the lighting condition corresponding to the micro-light-emitting diode in the image.

100‧‧‧ wafer

110‧‧‧Substrate

111‧‧‧ side

120‧‧‧microluminescent diode

121‧‧‧First exposed surface

130‧‧‧ positive electrode

131‧‧‧Second exposed surface

140‧‧‧negative electrode

141‧‧‧ Third exposed surface

200‧‧‧ probe

300‧‧‧ camera

310‧‧‧Charge-coupled components

320‧‧‧Filter

C‧‧‧Lighting area

S1~S4‧‧‧ steps

X‧‧‧ range

1 is a partial cross-sectional view showing a test process of a wafer in accordance with an embodiment of the present invention.

Fig. 2 is a top view showing the wafer of Fig. 1.

Fig. 3 is a partially enlarged top plan view showing a range X of Fig. 2.

Figure 4 is a flow chart showing the test method of the wafer of Figure 1.

Fig. 5 is a partially enlarged top plan view showing the micro-light emitting diode of Fig. 1.

The embodiments of the present invention are disclosed in the following drawings, and the details of However, it should be understood that these practical details are not intended to limit the invention. That is, in some embodiments of the invention, these practical details are not necessary. In addition, some of the conventional structures and elements are shown in the drawings in a simplified schematic manner in order to simplify the drawings. And if implementation is possible, the features of different embodiments can be applied interactively.

Please refer to pictures 1~3. 1 is a partial cross-sectional view showing a test process of a wafer 100 in accordance with an embodiment of the present invention. 2 is a top view of the wafer 100 of FIG. Fig. 3 is a partially enlarged top plan view showing a range X of Fig. 2. As shown in FIGS. 1 to 3, the wafer 100 includes a substrate 110, a plurality of micro-light emitting diodes 120, a positive electrode 130, and a negative electrode 140. The micro-light emitting diode 120 is disposed on the side 111 of the substrate 110, and the micro-light emitting diode 120 has a first exposed surface 121. The positive electrode 130 is disposed on the side 111 of the substrate 110, the micro-light emitting diode 120 is electrically connected to the positive electrode 130, the positive electrode 130 has a second exposed surface 131, and the second exposed surface 131 is larger than the first exposed surface 121, and the area thereof is The size is sufficient for the probe 200 to be in contact. The negative electrode 140 is disposed on the same side 111 of the substrate 110, the micro-light emitting diode 120 is electrically connected to the negative electrode 140, the negative electrode 140 has a third exposed surface 141, and the third exposed surface 141 is larger than the first exposed surface 121, and The size of the area is also sufficient for the probe 200 to be in contact. In other words, the positive electrode 130 and the negative electrode 140 are common positive and negative electrodes of the plurality of micro-light-emitting diodes 120.

Furthermore, the imaging device 300 is at least partially facing the side 111 of the substrate 110, that is, toward the micro-light-emitting diode 120, and the imaging device 300 has a charge-coupled device (CCD) 310 to simultaneously sense a plurality of The brightness of the micro-light emitting diode 120. In the present embodiment, the first exposed surface 121 of the micro-light-emitting diode 120 is a light-emitting surface, but the invention is not limited thereto.

Please refer to FIG. 4 , which is a flow chart showing a test method of the wafer 100 of FIG. 1 . As shown in FIG. 4, the test method of the wafer 100 includes the following steps (it should be understood that the steps mentioned in some embodiments can be adjusted according to actual needs, unless otherwise specified. , even at the same time or in part):

(1) Providing a wafer 100 that has not been packaged, the wafer 100 having a plurality of micro-light emitting diodes 120 on its side 111 (step S1). Further, step S1 is to provide the uncut wafer 100.

(2) Applying a current to the micro-light-emitting diode 120, so that the first exposed surface 121 of the micro-light-emitting diode 120 is simultaneously illuminated, and the bright area C of the first exposed surface 120 accounts for 70%-90% of the total area thereof. (Step S2). Please refer to FIG. 5 , which is a partially enlarged top view of the micro-light emitting diode 120 of FIG. 1 . For example, the bright area C may be a rectangular area, but the invention is not limited thereto.

(3) The lit micro-light emitting diode 120 is sensed to form an image (step S3). It should be noted that in the present embodiment, the micro-light-emitting diode 120 is a bare crystal that is not coated with a colloid, so that the imaging device 300 can sense the brightness emitted by the micro-light-emitting diode 120 without being blocked.

(4) The lighting condition corresponding to the micro-light-emitting diode 120 in the image is compared to determine the functional status of the micro-light-emitting diode 120 (step S4). More specifically, in step S4, an image of the micro-light-emitting diode 120 is first provided, and then the actual image of the micro-light-emitting diode 120 is actually used by the imaging device 300 to form a grayscale value, and then borrowed. Whether the micro-light-emitting diode 120 conforms to the test specifications is judged by the gray-scale value.

Further, since the bright area C only occupies about 70% to about 90% of the corresponding first exposed surface 121, the brightness emitted by each of the micro-light-emitting diodes 120 does not interfere with adjacent micro-- Light emitting diode 120. In other words, the camera 300 can clearly sense the brightness emitted by each of the micro-light-emitting diodes 120 and form an image, so that the user can effectively compare the lighting conditions corresponding to the micro-light-emitting diodes 120 in the image. In order to determine the functional status of the micro-light-emitting diode 120, it is determined whether or not to package. For example, if the micro-light-emitting diode 120 is not emitted in the image, the micro-light-emitting diode 120 can be judged as having a function that does not meet the specifications, and the micro-light-emitting diode is cut in the wafer 100. After the 120 separation, the light-emitting diode 120 that does not meet the specifications does not need to be packaged later to save packaging costs. In practical applications, for example, the micro-light-emitting diode 120 that is determined to have a non-compliant function may be marked on its first exposed surface 121 as an imprint or recorded in a computer for subsequent use. The package process is easy to identify without packaging.

More specifically, since the user can gradually increase the current flowing through the micro-light-emitting diode 120 when the electrical connection 120 is electrically connected, the brightness emitted from the micro-light-emitting diode 120 can be gradually increased, so that the imaging device can be maintained. The images formed by 300 are clearly defined. In the present embodiment, the current applied to the micro-light-emitting diode 120 can be initially set to be slightly larger than 10% of the rated current of the micro-light-emitting diode 120, and then gradually increased. For example, if the rated current of the micro-light-emitting diode 120 is 2 amps (A), the positive electrode 130 and the negative electrode 140 can be electrically connected first with a current of 0.2 amps, and then gradually increased according to actual conditions until at least The brightened area C of the first exposed surface 121 of the micro-light emitting diode 120 occupies 70% to 90% of its total area.

On the other hand, in order to improve the sharpness of the image formed by the imaging device 300, the imaging device 300 may further have a filter 320, and the filter 320 is located between the imaging device 300 having the charge coupled device 310 and the wafer 100. The brightness emitted by the micro-light emitting diode 120 is filtered to remove stray light. For example, the filter 320 can be a polarizer or a black card, etc., but the invention is not limited thereto.

Furthermore, when the photoelectric characteristics of the micro-light-emitting diode 120 are tested, since the second exposed surface 131 of the positive electrode 130 and the third exposed surface 141 of the negative electrode 140 are respectively larger than the second light-emitting diode 120 An exposed surface 121, therefore, even if the first exposed surface 121 of the micro-light-emitting diode 120 is too small, the user can directly contact the second exposed portion of the positive electrode 130 electrically connected to the micro-light-emitting diode 120, respectively. The surface 131 and the third exposed surface 141 of the negative electrode 140 are not in direct contact with the first exposed surface 121 of the micro-light emitting diode 120. In this way, the user can electrically connect the probe 200 to the micro-light-emitting diode 120 through the positive electrode 130 and the negative electrode 140 and apply a current to energize and illuminate the micro-light-emitting diode 120, thereby allowing the camera to be illuminated. 300 can sense the micro-light emitting diode 120. Furthermore, in the present embodiment, the area of the second exposed surface 131 and the area of the third exposed surface 141 may be substantially the same, but the invention is not limited thereto.

Please return to Figure 1. In the present embodiment, as shown in FIG. 1 , the second exposed surface 131 of the positive electrode 130 is higher than the first exposed surface 121 of the micro-light emitting diode 120 . That is, when the user touches the second exposed surface 131 of the positive electrode 130 with the probe 200, and the probe 200 slides relative to the substrate 110 in a direction parallel to the substrate 110, since the second exposed surface 131 is higher than the first exposed surface The surface 121 is, for example, about 10 microns or more, but the invention is not limited thereto, so even if the probe 200 slides out of the second exposed surface 131 of the positive electrode 130, the distance or force of pressing down will not be The first exposed surface 121 of the micro-light emitting diode 120 is touched or less susceptible to damage.

Similarly, in the present embodiment, as shown in FIG. 1, the third exposed surface 141 of the negative electrode 140 is higher than the first exposed surface 121 of the micro-light emitting diode 120. That is, when the user contacts the third exposed surface 141 of the negative electrode 140 with the probe 200, and the probe 200 slides relative to the substrate 110 in a direction parallel to the substrate 110, since the third exposed surface 141 is higher than the first exposed surface The surface 121 is, for example, about 10 microns or more, but the invention is not limited thereto, so even if the probe 200 slides out of the third exposed surface 141 of the negative electrode 140, the distance or force of pressing down will not be The first exposed surface 121 of the micro-light emitting diode 120 is touched or less susceptible to damage.

In summary, the technical solution disclosed in the foregoing embodiments of the present invention has at least the following advantages:

(1) Since the brightened area only accounts for about 70% to about 90% of the corresponding first exposed surface, the brightness emitted by each of the micro-light emitting diodes does not interfere with the adjacent micro-light emitting diodes. . That is to say, the camera device can clearly sense the brightness emitted by each of the micro-light-emitting diodes and form an image, so that the user can effectively compare the lighting conditions corresponding to the micro-light-emitting diodes in the image, thereby judging The functional status of the micro-light-emitting diode determines whether or not to package.

(2) Since the user can gradually increase the current flowing through the micro-light-emitting diode when the micro-light-emitting diode is electrically connected, the brightness emitted from the micro-light-emitting diode can be gradually increased, so that the image pickup device can be maintained. The resulting image is clearly defined.

(3) Since the micro-light-emitting diode is a bare crystal which is not coated with a colloid, the image pickup device can sense the brightness emitted by the micro-light-emitting diode without being blocked.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and the present invention can be modified and modified without departing from the spirit and scope of the present invention. The scope is subject to the definition of the scope of the patent application attached.

Claims (10)

 A method for testing a micro-light-emitting diode wafer, comprising: providing an un-packaged wafer having a plurality of micro-light-emitting diodes thereon; applying current to the micro-light-emitting diodes to make the micro-light-emitting diodes The first exposed surface of the light emitting diode is simultaneously illuminated, and the bright area of the first exposed surface occupies 70% to 90% of the total area; the light emitting diodes are sensed to form an image; And determining, according to the lighting condition corresponding to each of the micro-light emitting diodes in the image, the functional status of each of the micro-light emitting diodes.    The test method of claim 1, wherein the applied current is slightly greater than 10% of the rated current of one of the micro-light emitting diodes.    The test method of claim 2, further comprising: increasing the applied current until at least one of the light-emitting regions of the first exposed surface of the micro-light-emitting diodes accounts for 70% to 90% of the total area.    The test method of claim 1, wherein the step of applying a current to the micro-light-emitting diodes further comprises: contacting a positive electrode and a negative electrode of the wafer with a probe to apply a current, wherein the positive and negative electrodes are The common positive and negative electrodes of the micro-light emitting diodes.    The test method of claim 4, wherein the positive electrode has a second exposed surface, the negative electrode has a third exposed surface, and the second exposed surface and the third exposed surface are respectively larger than the first exposed surface.    The test method of claim 5, wherein the second exposed surface and the third exposed surface are respectively higher than the first exposed surface.    The test method of claim 6, wherein the second exposed surface and the third exposed surface are respectively about 10 microns higher than the first exposed surface.    The test method of claim 1, further comprising: determining that the functions of the micro-light-emitting diodes do not conform to the specifications, and marking the ink on the first exposed surface to indicate that no packaging is required.    The test method of claim 1, wherein the step of sensing the illuminated micro-light emitting diodes to form an image is performed by an image pickup device having a charge coupled device.    The test method of claim 9, wherein the step of sensing the light-emitting diodes to form an image further comprises: placing a filter on the image pickup device having the charge-coupled component and the wafer between.