Patent Application
20220059605
The present invention relates to displays and, more particularly, to a pixel unit with a driver IC, a light-emitting device with such pixel units and a method for making such pixel units and the light-emitting device.
A conventional display includes multiple light-emitting elements or pixels controlled by a circuit array (or “active array”). The circuit array includes one transistor or more, drivers to control the pixels, and one capacitor or more to maintain biases of the pixels of the display that are updated many times.
The development of liquid crystal displays and plasma displays makes large and durable displays possible. However, there are problems with power efficiency and directionality, and there are problems with power consumption and screen burn-in.
There have been attempts to use organic light-emitting diodes (“OLED”s) in displays. However, the results have not been satisfying. Displays based on OLEDs are less durable and flash. These problems cause manufacturers hesitate about using OLEDs in displays of electronic devices such as smart phones.
Moreover, to manufacture LCD displays, plasma displays and OLED displays, thin-film deposition techniques are used to make control circuits that include thin-film transistors (“TFT”s). In the making of an LCD, the thin-film deposition is used to form 5 to 9 via areas electrically connected to transistors, capacitors and circuits. Control circuits made by TFT techniques are extremely expansive. In addition, TFT deposition techniques require large machines to make large deposition films for large circuit arrays, and hence involve high costs of manufacturing. Hence, only a limited number of manufacturers with huge capitals dare attempt to use TFT techniques.
The present invention is therefore 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 simple method for making an inexpensive and highly integrated light-emitting device at a low cost.
It is another objective of the present invention to provide a light-emitting device with pixel units that occupy a minimized total area of a face of a display substrate to provide an excellent fill ratio. That is, a total area of transparent portions of the display substrate is maximized. Hence, the light-emitting device is an ideal transparent display that is less expensive than TFT and performs better than LCDs, plasma display and OLED displays.
It is another objective of the present invention to provide a light-emitting device with tiny light-emitting diodes stacked on driver integrated circuits to minimize a distance of electric connection. Surface mount technology is used to attach the driver integrated circuits to a display substrate, and a simple circuit is used to connect the driver integrated circuits to each other to operate the tiny light-emitting diodes. Integration of the tiny light-emitting diodes is better than LCDs, plasma displays and OLED displays.
To achieve the foregoing objectives, the method includes providing a driver IC wafer with control circuits. Groups of tiny light-emitting diodes are stacked on the driver IC wafer and electrically connected to the control circuits. Each of the groups includes a tiny light-emitting diode for emitting red light, a tiny light-emitting diode for emitting green light and a tiny light-emitting diode for emitting blue light. The groups of tiny light-emitting diodes on the driver IC wafer are packaged. The driver IC wafer is cut into driver integrated circuits. Each of the driver integrated circuits includes one of the control circuits electrically connected to one of the groups of tiny light-emitting diodes. Thus, pixel units are provided. The pixel units are transferred to a display substrate and the control circuits of the pixel units are connected to a circuit of the display substrate. Thus, a single light-emitting device is provided.
In another aspect, the method includes the step of providing a combinative light-emitting device by connecting display substrates to one another.
In another aspect, the display substrate is selected from the group consisting of a flexible transparent substrate, a flexible non-transparent substrate, a glass substrate and a printed circuit board.
In another aspect, each of the pixel units includes a driver integrated circuit, a group of three tiny light-emitting diodes and a transparent molding. The driver integrated circuit includes a control circuit. The tiny light-emitting diodes emit red light, green light and blue light respectively. The group of tiny light-emitting diodes is stacked on a face of the driver integrated circuit and electrically connected to the control circuit. The transparent resin molding covers the group of tiny light-emitting diodes and a visible face of the driver integrated circuit.
In another aspect, the control circuit includes a first pin, a second pin, a third pin, a fourth pin, a fifth pin, a pulse width modulator and data lock and a constant current driver. The fourth pin detects and prevents bad-node blocking. The second and fifth pins form a clock data recovery.
In another aspect, the control circuit includes upper bond pads formed on a face of the driver integrated circuit and lower bond pads formed on another face of the driver integrated circuit. Each of upper bond pads is electrically connected to a corresponding one of the lower bond pads by a silicon via.
In another aspect, each of the tiny light-emitting diodes includes an N-electrode and a P-electrode formed on a lower face. The N-electrode and the P-electrode are electrically connected to the upper bond pads of the driver integrated circuit.
In an alternative aspect, each of the tiny light-emitting diodes includes a N-electrode formed on an upper face of the tiny light-emitting diode, a P-electrode formed on a lower face of the tiny light-emitting diode and electrically connected to the control circuit, and a metal wire including an end electrically connected to the control circuit and another end electrically connected to the N-electrode.
In an alternative aspect, each of the tiny light-emitting diodes includes an N-electrode formed on an upper face, a P-electrode formed on a lower face and electrically connected to the control circuit, an ITO transparent conductive film electrically connected to the N-electrode, and a tiny metal rod located next to the tiny light-emitting diodes. The tiny metal rod an end electrically connected to the ITO transparent conductive film and another end electrically connected to the control circuit. The N-electrode, the P-electrode and the tiny metal rod are wrapped by the resin molding.
In another aspect, the light-emitting device includes driver integrated circuits, pixel units and a display substrate. Each of the driver integrated circuits includes a control circuit. Each of the pixel units includes a group of tiny light-emitting diodes and a transparent resin molding. In the group, the tiny light-emitting diodes emit red light, green light and blue light respectively. The group of tiny light-emitting diodes is stacked on a corresponding one of the driver integrated circuits and electrically connected to the control circuit of the corresponding driver integrated circuit. The transparent resin molding covers the group of tiny light-emitting diodes and a visible face of the corresponding driver integrated circuit. The display substrate including a modular connector and a circuit for connecting the modular connector to the multiple pixel units.
In another aspect, a combinative light-emitting device includes light-emitting devices as described above and a controller for electrically connected to the modular connectors of the display substrates.
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 three embodiments referring to the drawings wherein:
Referring to
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The process shown in
At 10, a driver IC wafer 24 is provided. The driver IC wafer 24 includes multiple areas corresponding to multiple driver integrated circuits 26 (
At 12, the tiny light-emitting diodes 22 are sorted into groups. Each of the groups includes an LED 22 for emitting red light, an LED 22 for emitting green light and an LED 22 for emitting blue light. The groups of tiny light-emitting diodes 22 are located on the driver IC wafer 24. Each of the groups of tiny light-emitting diodes 22 is electrically connected to a corresponding one of the driver integrated circuits 26 before packaging. Then, the tiny light-emitting diodes 22 and the driver IC wafer 24 are packaged by a 3D integration-through-stacked-die packaging technique. Chip scale packaging (“CSP”) is executed on the tiny light-emitting diodes 22 in the form of a flip chip.
At 14, laser is used to cut the driver IC wafer 24 into the driver integrated circuits 26 after the packaging. The control circuit 40 of each of the driver integrated circuits 26 is electrically connected to a corresponding one of the tiny light-emitting diodes 22 to provide a pixel unit 30 (
At 16, the pixel units 30, 50 or 70 are transferred to a display substrate and electrically connected to one another by a circuit of the display substrate to provide a single light-emitting device. The circuits of multiple display substrates can be electrically connected to one another to provide a combinative light-emitting device.
Referring to
The driver integrated circuit 26 of the pixel unit 30 includes five pins 21, 23, 25, 27 and 29, upper bond pads 31, lower bond pads 33 and silicon vias 38. The upper bond pads 31 are formed on an upper face of each of the driver integrated circuits 26 of the driver IC wafer 24. The lower bond pads 33 are formed on a lower face of each of the driver integrated circuits 26 of the driver IC wafer 24.
The silicon vias 38 are made in the driver IC wafer 24 in a through-silicon-via (“TSV”) process. Each of the silicon vias 38 allows vertical connection of a corresponding one of the upper bond pads 31 to a corresponding one of the lower bond pads 33. The upper bond pads 31 and the lower bond pads 33 provide pins for the control circuit 40.
Each of the pins 21, 23, 25, 27 and 29 is electrically connected to a corresponding one of the lower bond pads 33 by a corresponding one of the silicon vias 38.
A transparent resin molding 32 is used to cover the group of tiny light-emitting diodes 22 and a visible face of the driver IC 26 after the group of tiny light-emitting diodes 22 is electrically connected to the control circuit 40 of the driver IC 26.
Each of the tiny light-emitting diodes 22 includes an N-electrode 34 and a P-electrode 36 formed on a same face. The N-electrode 34 and the P-electrode 36 are electrically connected to the upper bond pads 31 of the corresponding driver IC 26 to form a simple loop. Hence, the control circuit 40 of the driver IC 26 (
Referring to
The control circuit 40 of the driver IC 26 includes a pulse width modulator and data lock 42 and a constant current driver 44. The constant current driver 44 is electrically connected to the corresponding group of tiny light-emitting diodes 22 to overcome problems of changed wavelengths in analog dimming and uneven brightness.
Referring to
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The area of an upper face of the display substrate 52 occupied by the pixel units 30 is minimized to provide an excellent fill ratio so that the area of transparent portions of the display substrate 52 is maximized. Therefore, the light-emitting device 50 is an ideal transparent display.
The display substrate 52 is a flexible transparent substrate, a flexible non-transparent substrate, glass substrate or a PCB.
The step represented by “12” can be executed to make the light-emitting elements 30 according to the first embodiment of the present invention. To this end, the step represented by “12” includes several steps to be described.
Firstly, conductive silver or tin paste is provided on the areas of the driver IC wafer 24 corresponding to the tiny light-emitting diodes 22.
Secondly, the groups of tiny light-emitting diodes 22 are transferred onto the areas of the driver IC wafer 24 wherein the conductive silver or tin paste is provided.
Thirdly, a bonding operation based on heating and curing is executed to connect a N-electrode 34 and a P-electrode 36 of each tiny LED 22 to the upper bond pads 31 of the control circuit 40 of the corresponding driver IC 26 by soldering.
Fourthly, the resin molding 32 is heated to attach the tiny light-emitting diodes 22 to the upper face of the driver IC wafer 24.
Then, the step represented by “14” is taken to cut the driver IC wafer 24 into the pixel units 30.
Referring to
The step represented by “12” can be taken to make pixel units 60 according to the second embodiment. A chip-on-board (“COB”) technique is executed on the tiny light-emitting diodes 22 for packaging. Accordingly, the step represented by “12” includes several steps to be described.
Firstly, conductive silver or tin paste is provided on the areas of the driver IC wafer 24 corresponding to the tiny light-emitting diodes 22.
Secondly, the groups of tiny light-emitting diodes 22 are transferred onto the areas of the driver IC wafer 24 wherein the conductive silver or tin paste is provided.
Thirdly, a bonding operation based on heating and curing is executed to connect the P-electrode 66 of each tiny LED 22 to a pin (not numbered) of the control circuit 40 of the corresponding driver IC 26 by soldering.
Fourthly, conductive silver or tin paste is provided on the N-electrode 64 of the tiny LED 22 and a pin of the control circuit 40 of the corresponding driver IC 26.
Fifthly, an end of the metal wire 62 is connected to the N-electrode 64 of each tiny LED 22 by conductive silver or tin paste, and the other end of the metal wire 62 is connected to the pin of the control circuit 40 of the corresponding driver IC 26 by conductive silver or tin paste.
Sixthly, resin molding is heated and cured to secure each tiny LED 22 to the upper face of the driver IC wafer 24.
Then, the step represented by “14” is taken to use laser to cut the driver IC wafer 24 into the pixel units 60.
Referring to
The step represented by “12” can be taken to make the light-emitting elements according to the third embodiment. A transparent conductive film technique such as an ITO technique is executed on the tiny light-emitting diodes 22. To this end, the step represented by “12” includes several steps to be described.
Firstly, conductive silver or tin paste is provided on the areas of the driver IC wafer 24 corresponding to the tiny light-emitting diodes 22.
Secondly, the groups of tiny light-emitting diodes 22 and multiple tiny metal rods 78 are transferred onto the driver IC wafer 24.
Thirdly, a bonding operation based on heating and curing is executed to connect the P-electrode 76 of each tiny LED 22 to a pin (not numbered) of the control circuit 40 of the corresponding driver IC 26 by soldering. The tiny metal rod 78 of each pixel unit 70 is located next to the tiny LED 22 and connected to the upper bond pads 31 of the control circuit 40 of the corresponding driver IC 26.
Fourthly, the ITO transparent conductive film 72 is attached to an upper face of the resin molding 32. In a common-cathode method, the N-electrode 74 of the tiny LED 22 is connected to the tiny metal rod 78.
Then, the step represented by “14” is taken to use laser to cut the driver IC wafer 24 into the pixel units 70.
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.
