The present invention relates to a display and, more particularly, to an LED display.
A light-emitting diode (“LED”) display includes light-emitting diodes attached to a substrate by glue. Each of the light-emitting diodes is in the form of a die cut from a wafer. The attachment of the light-emitting diodes to the substrate is called “die bonding.”
A light-emitting diode in the form of a flip chip includes a positive electrode P and a negative electrode N on a same side, and each of the positive and negative electrodes is covered by a block of solder. The light-emitting diode in the form of a flip chip is cut and bonded before it can be electrically connected to a circuit board.
Pixels-per-inch (“PPI”) is often used to describe the resolution of a display. However, the size of a micro light-emitting diode is smaller than 100 μm, about 1% of the size of a regular light-emitting diode. In the making of micro light-emitting diodes, problems are encountered.
For example, millions of micro light-emitting diodes are transferred to a glass substrate of a thin film transistor (“TFT”) or a circuit board from an original substrate made of sapphire or gallium arsenide for example. Transfer of such a large amount of micro light-emitting diodes is too difficult for conventional machines that are suitable for making average light-emitting diodes.
Moreover, an even larger amount of contact points have to be handled to attach such a large amount of micro light-emitting diodes to a circuit board. A display needs complicated wiring to connect micro light-emitting diodes at a high resolution. Such complicated wiring required a precise and expansive process and are not good for the transfer of such a large amount of micro light-emitting diodes. Hence, the rate of defects in the making of the displays equipped with micro light-emitting diodes is high.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in the prior art.
It is the primary objective of the present invention to provide an inexpensive and high-solution display.
To achieve the foregoing objective, the display includes micro light-emitting diodes connected to a color conversion layer and driver integrated circuits connected to the micro light-emitting diodes via an electrically connecting layer. Each of the micro light-emitting diodes includes an N pad and a P pad. The micro light-emitting diodes emit light beams of a same color. The color conversion layer converts the light beams into various colors. The electrically connecting layer includes elongated negative electrodes connected to the N pads and elongated positive electrodes connected to the P pads. Each of the driver integrated circuits includes a first group of bonding pads on a face, a second group of bonding pads on an opposite face, and conductors for connecting the first group of bonding pads to the second group of bonding pads. Some of the bonding pads in the first group are connected to the elongated negative electrodes. The remaining ones of the bonding pads in the first group are connected to the elongated positive electrodes. The circuit board is connected to the second group of bonding pads of each of the driver integrated circuits.
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 the preferred embodiment referring to the drawings wherein:
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The light-emitting units 33 are electrically connected to the electrically connecting layer 28 by various etching techniques such as mask techniques or reticle techniques. A so-called etching technique is a technique that produces or deposits layers of different materials and etches each of the layers into a circuit.
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The micro light-emitting diodes 39 are formed in the extensive layer 32, which is grown on the crystal layer 31. The extensive layer 32 is supported on the driver IC 11.
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The circuit board 20 is a printed circuit board (“PCB”), a printed wiring board (“PWB”), a polyimide (“PI”) board or a glass substrate. At least one cable 21 is used to electrically connect the circuit board 20 to at least one controller 22. The controller 22 is programmable to turn on and off the driver IC 11 through the electrically connecting layer 28.
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A color conversion layer 40 is laid on the micro light-emitting diodes 39. The color conversion layer 40 is preferably a quantum dot color filter (“QDCF”).
The micro light-emitting diodes 39 emit light beams to the color conversion layer 40 as indicated by an arrow head 41 when the circuit board 20 is turned on. The color conversion layer 40 turns the light beams of a color into light beams of red, green and blue. The light beams of red, green and blue then go out of the display 10. The controller 22 is used to correct brightness of the micro light-emitting diodes 39 so that the display shows desired colors and brightness.
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For example, multiple light-emitting units 33 are used together to provide a value of PPI of 180×180 and each driver IC 11 provides a value of PPI of 30×30. Thus, it takes only six driver ICs 11 that are arranged along a diagonal line of the array of light-emitting units 33 to control all the micro light-emitting diodes 39 of the display equipped 10.
In another embodiment, the display 10 does not include any color conversion layer 40, i.e., QDCF. Instead, each driver IC 11 of the display 10 is electrically connected to three groups of micro light-emitting diodes. The micro light-emitting diodes in the first group emit red light. The micro light-emitting diodes in the second group emit green light. The micro light-emitting diodes in the third group emit blue light. Each driver IC 11 is electrically connected to the circuit board 20. The color conversion layer 40 is not essential when techniques for massive transfer of micro light-emitting diodes mature. The display 10 is reduced by omitting the color conversion layer 40.
As discussed above, the display 10 is advantageous in several aspects. Firstly, the light-emitting units 33, each of which includes multiple micro light-emitting diodes 39, are cut from the wafer. There is no need to cut the micro light-emitting diodes 39, one by one, from the wafer. There is no need to transfer a very large number of separated micro light-emitting diodes 39. There is no need to precisely locate the micro light-emitting diodes 39, one by one.
Secondly, the process for electrically connecting the driver ICs 11 to the micro light-emitting diodes 39 is simplified. The related cost is reduced.
Thirdly, the precision of connecting the micro light-emitting diodes 39 to the electrode strips 24 and 25 is improved. The yield of the making of displays is increased.
The present invention has been described via the illustration of the preferred embodiment. Those skilled in the art can derive variations from the preferred embodiment without departing from the scope of the present invention. Therefore, the preferred embodiment shall not limit the scope of the present invention defined in the claims.
This application is a divisional of U.S. Non-Provisional patent application Ser. No. 17/151,685 filed on Jan. 19, 2021, and titled “LED DISPLAY” the entire contents of which are incorporated herein by reference.
Number | Date | Country | |
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Parent | 17151685 | Jan 2021 | US |
Child | 18486175 | US |