Patent Application
20210398837
The present invention relates to light emitting diodes in the order of micron (1×10−3 mm) and, more particularly, to a system and method for aligning grains of micro light-emitting diodes to facilitate mass transfer.
A micro light-emitting diode is different from an ordinary light-emitting diode in the size of grain. The size of a grain of an ordinary light-emitting diode is 100 to 1000 μm, with thickness of 100 to 500 μm. The size of a grain of a micro light-emitting diode is smaller than 100 μm, with thickness of 4 to 5 μm.
Ingentec Corporation has developed a method for making grains of vertical-type light-emitting diodes. An epitaxial layer is grown on a growth substrate. The epitaxial layer is connected to a metallic laminate. Multiple electrode units are provided on the epitaxial layer after the growth substrate is removed. Then, the combination of the electrode units with the epitaxial layer is cut into grains of micro light-emitting diodes. Each micro light-emitting diode includes an epitaxial grain. The epitaxial grain includes a metallic laminate on a side and an electrode unit layer on another side. The metallic laminate exhibits magnetic permeability to facilitate mass transfer of micro light-emitting diodes. The so called mass transfer of light-emitting diodes is a process of transferring a large amount of grains of micro light-emitting diodes to a single display substrate after the completion of the production of the epitaxial grains.
In commercial application, an objective is to precisely transfer a large amount of micro light-emitting diodes to a display substrate from an epitaxial substrate in a reasonable period of time. For example, a display (or “4K television set”) that exhibits a horizontal resolution of 4000 pixels and a vertical resolution of 2000 pixels needs about 24 million grains of RGB micro light-emitting diodes. It takes about 2400 rounds of transfer if 10000 grains are transferred in each round. It requires precision to pick up, transfer and lay down a large amount of grains of micro light-emitting diodes in the mass transfer of the micro light-emitting diodes.
Many techniques have been developed for mass transfer such as electrostatic transfer techniques and adhesive transfer techniques.
In an electrostatic transfer technique, multiple electrostatic transfer heads are arranged in an array. Electrostatic attraction is used to pick up micro light-emitting diodes so that they can be moved. After reaching a destination, the electrostatic attraction is turned off to lay down the micro light-emitting diodes.
In an adhesive transfer technique, there is provided an array of stabilizing chambers. Each of the stabilizing chambers includes walls extending from a lower portion. The walls are tilted to define an opening larger than an opening in the lower portion of each of the stabilizing chambers. Stabilizing axles extend from the stabilizing chambers. Micro light-emitting diodes are adhered to free ends of the stabilizing axles and kept in the stabilizing chambers. Thus, the micro light-emitting diodes are picked up.
Alternatively, in a transfer technique, an impression element is made of elastomer and used to capture an array of micro light-emitting diodes. Speed of movement of the impression element is changed to adjust a force (Van der Waals force) for adhesion of the impression element to the micro light-emitting diodes to release the micro light-emitting diodes.
Moreover, the applicant of the present application has devised a method for transferring a batch of micro elements such as micro light-emitting diodes. A transportation tool is equipped with an array of needles. The needles stick out of a lower portion of the transportation tool. The transportation tool includes a temperature-controlling channel to change the temperature of the needles so that the micro elements can be attracted to the tips of the needles.
However, none of these techniques addresses how to align the micro light-emitting diodes. Therefore, the present invention is intended to obviate or at least alleviate the problems encountered in the prior art.
It is an objective of the present invention to provide a method for aligning magnetic micro light-emitting diodes.
To achieve the foregoing objective, the method is provided for aligning micro light-emitting diodes. A platform is provided with arrays. Each of the arrays includes grooves. The platform is used to receive magnetic micro light-emitting diodes. Magnetic attraction and vibration are alternately exerted on the platform to cause the magnetic micro light-emitting diodes to fall into the grooves in a correct orientation. It is determined whether the magnetic micro light-emitting diodes fill the platform. Mass transfer is executed if the magnetic micro light-emitting diodes fill the platform.
It is another objective of the present invention to provide a system for aligning magnetic micro light-emitting diodes.
To achieve the foregoing objective, the system includes a table, a platform, a camera, operative rods, magnets and two vibrators. The platform is supported on the table and includes grooves corresponding to the micro light-emitting diodes. The camera is supported on the table above the platform and operable to take photographs of the grooves and send the photographs to a computer. The operative rods are supported on the table and operable to tilt the platform. The operative rods are alternately actuated to move the platform along a z-axis to flip over the micro light-emitting diodes if so desired. The magnets are supported on the table corresponding to the grooves of the platform. The vibrators are supported on the table and operable to vibrate the platform in an x-axis and a y-axis, respectively.
Other objectives, advantages and features of the present invention will be apparent from the following description referring to the attached drawings.
The present invention will be described via detailed illustration of two embodiments referring to the drawings wherein:
Referring to
In addition, the table 21 is equipped with an adjustor 30. The adjustor 30 includes two operative rods 32 extending parallel to each other. The operative rods 32 extend toward the vehicle 23 for a certain distance. Each of the operative rods 32 is in contact with or pivotally connected to a corresponding portion of the platform 34.
Referring to
Two vibrators 36 are supported on the table 21. One of the vibrators 36 is located between the operative rods 32 to vibrate the platform 34 along the y-axis. The other vibrator 36 is actuated to vibrate the platform 34 along the x-axis.
Each of the vibrators 36 is a mandrel of a pneumatic cylinder or a cam operatively connected to a motor. The amplitude of the vibration of the platform 34 by the vibrators 36 is under control mechanically.
Referring to
Any two adjacent ones of the ridges 42 are used to restrain one of the micro light-emitting diodes 50 from two sides. Thus, each of the micro light-emitting diodes 50 is only movable along a corresponding one of the passages 44 on the platform 34.
Referring to
Such a magnetostatic element exerts a magnetic force without having to consume any electricity. The location of such a magnetostatic element can be changed to change the intensity of its magnetic force.
Such an electromagnet is energized by electricity to exert a magnetic force. A current for energizing such an electromagnet can be changed to change the intensity of its magnetic force.
Referring to
At 10, the platform 34 receives a batch of magnetic micro light-emitting diodes 50. A transporting tool (not shown) can be used to transport the entire batch of micro light-emitting diodes 50 onto platform 34.
A grain of each of the micro light-emitting diodes 50 is connected to a metallic laminate on a side and connected to an electrode unit on another side. The metallic laminate is magnetically permeable. Thus, the micro light-emitting diodes 50 are magnetically permeable.
The transporting tool includes at least one vibrating tray (not shown) for vibrating the micro light-emitting diodes 50, thereby moving the micro light-emitting diodes 50 onto the platform 34. Thus, piling of the micro light-emitting diodes 50 is avoided. Inevitably, some of the micro light-emitting diodes 50 are defective. Such a vibrating tray can disperse such defective ones among the micro light-emitting diodes 50.
At 11, the platform 34 is vibrated to translate or orient the entire batch of micro light-emitting diodes 50.
About the translation of the micro light-emitting diodes 50, one of the vibrators 36 vibrates the platform 34 along the x-axis and hence moves the micro light-emitting diodes 50 along the passages 44. The other vibrator 36 vibrates the platform 34 along the y-axis to move the micro light-emitting diodes 50 perpendicular to the passages 44. If necessary, the operative rods 32 can change the tilting of the platform 34 and hence speed up movement of the micro light-emitting diodes 50 on the platform 34.
Regarding the orientation of the micro light-emitting diodes 50, when the micro light-emitting diodes 50 are upside down or disoriented, the operative rods 32 are alternately actuated to move the platform 34 along the z-axis. Thus, the micro light-emitting diodes 50 are flipped over or moved to a correct orientation on the platform 34.
That is, the foregoing process is executed to vibrate and move the micro light-emitting diodes 50 to the correct location and orientation on the platform 34, which is horizontal or tilted.
At 12, the correctly oriented micro light-emitting diodes 50 fall into the grooves 46 in the platform 34. A reduced lower portion of each of the micro light-emitting diodes 50 reaches a reduced lower portion of the corresponding groove 46. The arrays 40 enable the platform 34 to receive a large amount of micro light-emitting diodes 50.
At 13, magnetic attraction is exerted on the micro light-emitting diodes 50 in the grooves 46 via the platform 34. The magnets 27 magnetically attract the micro light-emitting diodes 50 in the grooves 46, thereby keeping the micro light-emitting diodes 50 in the grooves 46 against the vibration that could otherwise cause the micro light-emitting diodes 50 to jump back onto the upper face of the platform 34 from the grooves 46.
At 14, it is determined whether the micro light-emitting diodes 50 are well aligned on the platform 34. The camera 25 is used to take photographs of the platform 34 and transmit the photographs to the computer. The computer compares the photographs with a default to determine whether the micro light-emitting diodes 50 are well aligned.
The process goes to 16 if the micro light-emitting diodes 50 fill 99% of the grooves 46 of the platform 34. Then, the process goes to 15.
The process goes to 17 if otherwise, i.e., the micro light-emitting diodes 50 fail to fill 99% of the grooves 46 of the platform 34. Then, the process will be repeated. The process will be executed once and again until the process finally goes to 16, i.e., the micro light-emitting diodes 50 fill 99% of the grooves 46 of the platform 34.
At 15, mass transfer is executed. The transfer unit equipped with probes (not shown) corresponding to the array 40 is used to transfer the micro light-emitting diodes 50 to a predetermined location from the arrays 40. Thus, the micro-aligning system 20 executes the micro-aligning method for successful mass production and mass transfer.
It should be noted that the steps represented by “11”, “12” and “13” are combined with one another to provide a subroutine of alternate magnetic attraction and vibration to cause the grooves 46 of the platform 34 to capture correctly located and oriented micro light-emitting diodes 50. These steps can be arranged in any other proper order.
The subroutine is executed for only once if the grooves 46 of the platform 34 are used to capture micro light-emitting diodes 50 of one color. However, the subroutine is executed for three times if the grooves 46 of the platform 34 are used to capture micro light-emitting diodes 50 of three colors, i.e., RGB.
For example, the micro light-emitting diodes 50 are of red. At 10, the vibrating tray is used to disperse defective micro light-emitting diodes 50 among the micro light-emitting diodes 50 and then transport the micro light-emitting diodes 50 onto the platform 34. At 11, vibration is imposed on the platform 34 to correctly locate and orient the micro light-emitting diodes 50 on the platform 34. At 12, the correctly located and oriented micro light-emitting diodes 50 are inserted into the grooves 46 of the platform 34. At 13, magnetic attraction is used to keep the micro light-emitting diodes 50 in the grooves 46 of the platform 34.
At 14, it is determined whether the micro light-emitting diodes 50 are well aligned on the platform 34. The process goes to 16 if the micro light-emitting diodes 50 fill 99% of the grooves 46 of the platform 34. Then, the process goes to 15. The process goes to 17 if otherwise. Then, the subroutine will be repeated. The process will be executed once and again until the process finally goes to 16. At 15, mass transfer is executed.
To capture micro light-emitting diodes 50 of red, green and blue, the subroutines is executed for three rounds. Firstly, the magnets 27 are used to move the micro light-emitting diodes 50 of red into first one-third of the grooves 46 of the platform 34. The micro light-emitting diodes 50 that are not captured in the first one third of the grooves 46 are swept.
Secondly, the magnets 27 are used to move the micro light-emitting diodes 50 of green into second one-third of the grooves 46 of the platform 34. The micro light-emitting diodes 50 that are not captured in the two thirds of the grooves 46 are swept.
Thirdly, the magnets 27 are used to move the micro light-emitting diodes 50 of blue into third one-third of the grooves 46 of the platform 34. The micro light-emitting diodes 50 that are not captured in the grooves 46 are swept.
Finally, mass transfer is executed for only once.
The present invention has been described via the illustration of the embodiments. Those skilled in the art can derive variations from the embodiments without departing from the scope of the present invention. Therefore, the embodiments shall not limit the scope of the present invention defined in the claims.
