CN112018218B - Micro light emitting diode transfer method and display panel manufacturing method - Google Patents

Micro light emitting diode transfer method and display panel manufacturing method Download PDF

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Publication number
CN112018218B
CN112018218B CN201910470274.XA CN201910470274A CN112018218B CN 112018218 B CN112018218 B CN 112018218B CN 201910470274 A CN201910470274 A CN 201910470274A CN 112018218 B CN112018218 B CN 112018218B
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emitting diode
micro light
diode chip
transfer head
substrate
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CN112018218A (en
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王岩
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Chengdu Vistar Optoelectronics Co Ltd
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Chengdu Vistar Optoelectronics Co Ltd
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Priority to PCT/CN2019/120948 priority patent/WO2020238099A1/en
Priority to KR1020217035346A priority patent/KR20210137219A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/005—Processes
    • H01L33/0095—Post-treatment of devices, e.g. annealing, recrystallisation or short-circuit elimination
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/50—Assembly of semiconductor devices using processes or apparatus not provided for in a single one of the subgroups H01L21/06 - H01L21/326, e.g. sealing of a cap to a base of a container
    • H01L21/52—Mounting semiconductor bodies in containers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L25/00—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof
    • H01L25/03—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes
    • H01L25/04—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes the devices not having separate containers
    • H01L25/075—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes the devices not having separate containers the devices being of a type provided for in group H01L33/00
    • H01L25/0753—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes the devices not having separate containers the devices being of a type provided for in group H01L33/00 the devices being arranged next to each other
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/15—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components having potential barriers, specially adapted for light emission
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/15—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components having potential barriers, specially adapted for light emission
    • H01L27/153—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components having potential barriers, specially adapted for light emission in a repetitive configuration, e.g. LED bars
    • H01L27/156—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components having potential barriers, specially adapted for light emission in a repetitive configuration, e.g. LED bars two-dimensional arrays
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/48—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor body packages
    • H01L33/62—Arrangements for conducting electric current to or from the semiconductor body, e.g. lead-frames, wire-bonds or solder balls

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Computer Hardware Design (AREA)
  • Manufacturing & Machinery (AREA)
  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Led Device Packages (AREA)

Abstract

The invention provides a micro light emitting diode transfer method and a display panel manufacturing method. The transfer method of the micro light-emitting diode comprises the following steps: picking up the micro light-emitting diode chip by adopting a flexible transfer head arranged on a rigid substrate; aligning the micro light-emitting diode chip with the circuit substrate to enable an electrode on the micro light-emitting diode chip to correspond to an electrode on the circuit substrate; applying pressure to the rigid substrate to enable the micro light-emitting diode chip to be extruded into the flexible transfer head, wherein the pressure is transmitted to the micro light-emitting diode chip through the rigid substrate and the flexible transfer head, and the electrode on the micro light-emitting diode chip is bonded with the electrode on the circuit substrate; the flexible transfer head is separated from the micro light emitting diode chip. The transfer method provided by the invention can effectively fix the micro light-emitting diode chip on the circuit substrate, and ensures that the electrode of the micro light-emitting diode chip is electrically connected with the electrode on the circuit substrate well, thereby improving the quality and the yield of the display panel.

Description

Micro light emitting diode transfer method and display panel manufacturing method
Technical Field
The present invention relates to display technologies, and in particular, to a method for transferring micro light emitting diodes and a method for manufacturing a display panel.
Background
A Micro Light Emitting Diode (Micro LED) is a device with a size of several micrometers to several hundred micrometers, and since the size of the Micro LED is much smaller than that of a common LED, it is possible to use a single Micro LED as a pixel for display. The Micro LED display is a display for displaying images by using a high-density Micro LED array as a display pixel array, each pixel is addressable and can be independently driven to Light, so the Micro LED display and an Organic Light-Emitting Diode (OLED) display belong to self-luminous displays, but the Micro LED display has the advantages of better material stability, longer service life, no image burn-in and the like compared with the OLED display, and is considered as the biggest competitor of the OLED display.
In the prior art, when the micro light emitting diode chip is bonded with the receiving substrate, the micro light emitting diode chip cannot be effectively fixed on the circuit substrate, and the electrode of the micro light emitting diode chip cannot be well electrically connected with the electrode on the circuit substrate, so that the quality and yield of the micro light emitting diode display panel are reduced.
Disclosure of Invention
In view of the above-mentioned drawbacks, the present invention provides a method for transferring micro leds, which can effectively fix a micro led chip on a circuit board and ensure that the electrodes of the micro led chip and the electrodes on the circuit board are electrically connected well.
The invention also provides a manufacturing method of the display panel, which comprises the transfer method of the micro light-emitting diode and can improve the quality and yield of the micro light-emitting diode display panel.
In order to achieve the above object, an aspect of the present invention provides a method for transferring a micro light emitting diode, including: picking up the micro light-emitting diode chip by adopting a flexible transfer head arranged on a rigid substrate; aligning the micro light-emitting diode chip picked up by the rigid substrate with the circuit substrate to enable the electrode on the micro light-emitting diode chip to correspond to the electrode on the circuit substrate; applying pressure to the rigid substrate to enable the micro light-emitting diode chip to be extruded into the flexible transfer head, transmitting the pressure to the micro light-emitting diode chip through the rigid substrate and the flexible transfer head, and enabling an electrode on the micro light-emitting diode chip to be bonded with an electrode on the circuit substrate; and separating the flexible transfer head from the micro light-emitting diode chip.
Further, the flexible transfer head picks up the micro-led chip by van der waals forces.
Further, the flexible transfer head is a transfer head having polydimethylsiloxane PDMS as a base component.
Furthermore, the thickness of the flexible transfer head does not exceed the thickness of the micro light-emitting diode chip.
Further, the rigid substrate is a hard glass substrate, a hard plastic substrate, or a metal substrate.
Further, adjacent flexible transfer heads are not in contact with each other during the process of pressing the micro light emitting diode chips into the flexible transfer heads.
Furthermore, the electrode layer of the circuit substrate is provided with solder, and the solder and the electrode of the micro light-emitting diode chip are welded to realize the bonding.
Further, the bonding temperature between the solder and the electrodes of the micro light emitting diode chip does not exceed the maximum withstand temperature of the flexible transfer head when bonding is performed. Specifically, the solder is selected from low temperature solders, including but not limited to indium, indium-tin alloy, bismuth-lead-tin alloy.
Further, the step of picking up the micro light emitting diode chip by using the flexible transfer head disposed on the rigid substrate further includes: the micro-light emitting diode chip formed on the substrate is transferred from the substrate onto a temporary base plate.
Another aspect of the present invention provides a method for manufacturing a display panel, including: forming a micro light emitting diode chip on a substrate; according to the transfer method of the first aspect, the micro light emitting diode chips are transferred onto the circuit substrate to form a micro light emitting diode display array for constituting a display; and packaging the micro light-emitting diode display array to obtain the micro light-emitting diode display panel.
According to the micro light-emitting diode transfer method provided by the invention, the flexible transfer head is arranged on the rigid substrate, so that the micro light-emitting diode chip can be extruded into the flexible transfer head during pressing, the pressing force applied to the rigid substrate can be effectively transferred to the micro light-emitting diode chip and the circuit substrate through the rigid substrate, the electrode of the micro light-emitting diode chip and the electrode on the circuit substrate are ensured to realize effective bonding and electric connection, and the performance of the micro light-emitting diode device is improved.
In addition, in the pressing process, the flexible transfer head is extruded and deformed to form a groove for accommodating the micro light-emitting diode chip, the groove not only increases the contact area and the bonding force between the flexible transfer head and the micro light-emitting diode chip, but also has a limiting effect, so that the micro light-emitting diode chip can be prevented from deviating relative to the circuit substrate, and the effective bonding and the electric connection between the micro light-emitting diode chip and the circuit substrate are further ensured.
In addition, the transfer method realizes batch transfer of the micro light-emitting diode chips, and the whole process flow is simple, thereby being very beneficial to practical production, application and popularization.
According to the manufacturing method of the display panel, due to the fact that the transfer method is adopted for batch transfer of the micro light-emitting diodes, the manufacturing method has the same advantages as the transfer method, and the quality and the yield of the micro light-emitting diode display panel are improved.
Drawings
FIG. 1 is a schematic diagram of a transfer method of micro light emitting diodes provided in an embodiment of the present invention;
fig. 2 is a schematic diagram of step S1 of a transfer method of micro light emitting diodes according to an embodiment of the invention;
fig. 3 is a schematic diagram of step S2 of a transfer method of micro light emitting diodes according to an embodiment of the invention;
fig. 4 is a schematic diagram illustrating a step S3 of a micro led transferring method according to an embodiment of the invention;
fig. 5 is a schematic diagram illustrating a step S4 of a transfer method of micro light emitting diodes according to an embodiment of the invention;
fig. 6 is a schematic diagram illustrating a step S0 of a micro led transferring method according to an embodiment of the invention;
fig. 7 is a schematic flow chart illustrating a transfer method of micro leds according to another embodiment of the present invention.
Description of the reference numerals:
10-a rigid substrate; 20-a flexible transfer head;
30-micro light emitting diode chip; 31-an electrode;
40-a circuit substrate; 41-an electrode;
42-solder; 50-a temporary substrate;
51-temporary bonding glue; 60-substrate.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the preparation of the Micro LED display panel at the present stage, a Micro LED is obtained by epitaxy on a sapphire substrate, then a Micro light emitting diode chip is separated from the substrate by a Laser lift-off (Laser lift-off) technology, then the Micro light emitting diode chip is transferred to a circuit substrate which is prepared in advance and provided with an electrode pattern by a Micro Transfer Print (Micro Transfer Print) technology to form a Micro LED array, and finally the Micro LED display panel is prepared by processes such as packaging and the like. The principle of micro-transfer printing technology is roughly as follows: the micro led chip is picked up by a Transfer head (Transfer head) with a certain viscosity, such as Polydimethylsiloxane (PDMS), and then the PDMS Transfer head is aligned with the circuit substrate. The circuit substrate is provided with welding spots corresponding to the electrodes of the Micro light-emitting diode chips, the surfaces of the welding spots are provided with welding fluxes, and the welding flux layers are welded and fixed with the electrodes of the Micro light-emitting diode chips at high temperature, so that the electrodes of the Micro light-emitting diode chips are electrically connected with the electrodes on the circuit substrate, and finally the PDMS transfer heads are peeled off from the circuit substrate, so that batch transfer of the Micro light-emitting diode chips can be completed, and the Micro LED array is formed.
However, the inventor has found that, when the micro led chip is bonded on the receiving substrate by using the prior art, the material of the transfer head commonly used at present is soft, and thus sufficient pressing force cannot be provided for the micro led chip, so that the micro led chip cannot be effectively fixed on the circuit substrate, and the electrodes of the micro led chip cannot be well electrically connected with the electrodes on the circuit substrate, thereby reducing the quality and yield of the micro led display panel. In order to solve the above problems, the inventors propose a transfer method of micro light emitting diodes.
Example one
The present embodiment provides a method for transferring a micro light emitting diode, please refer to fig. 1 in combination with fig. 2 to 5, which specifically includes the following steps:
s1, picking up a micro light-emitting diode chip 30 by using a flexible transfer head 20 arranged on a rigid substrate 10;
s2, aligning the micro light-emitting diode chip 30 picked up by the rigid substrate 10 with the circuit substrate 40, and enabling the electrode 31 on the micro light-emitting diode chip 30 to correspond to the electrode 41 on the circuit substrate 40;
s3, applying pressure to the rigid substrate 10 to enable the micro light-emitting diode chip 30 to be extruded into the flexible transfer head 20, transmitting the pressure to the micro light-emitting diode chip 30 through the rigid substrate 10 and the flexible transfer head 20, and enabling the electrode 31 on the micro light-emitting diode chip 30 to be bonded with the electrode 41 on the circuit substrate 40;
and S4, separating the flexible transfer head 20 from the micro light-emitting diode chip 30.
In the method for transferring a micro light emitting diode provided in this embodiment, the flexible transfer head 20 is disposed on the rigid substrate 10, and when the micro light emitting diode chip 30 is pressed against the circuit substrate 40, the micro light emitting diode chip 30 presses the flexible transfer head 20 and is not continuously close to the rigid substrate 10, so that the pressing force applied to the rigid substrate 10 can be effectively transmitted to the micro light emitting diode chip 30 and the circuit substrate 40, and the electrode 31 of the micro light emitting diode chip 30 and the electrode 41 on the circuit substrate 40 are ensured to be effectively bonded and electrically connected, thereby improving the performance of the micro light emitting diode device.
In addition, in the pressing process, the micro led chip 30 is pressed into the flexible transfer head 20, that is, the flexible transfer head 20 is pressed and deformed to form a groove for accommodating the micro led chip 30, the groove increases the contact area and the adhesive force between the flexible transfer head 20 and the micro led chip 30, and the groove can also play a certain limiting role, so that the micro led chip 30 and the circuit substrate 40 can be prevented from deviating, and effective bonding and electrical connection between the micro led chip 30 and the circuit substrate 40 can be further ensured.
Moreover, the transfer method increases the functionality of the micro light-emitting diode transfer printing technology, has a simpler process flow, and improves the batch transfer efficiency of the micro light-emitting diode chips 30.
The structure of the micro light emitting diode chip 30 and the electrode 31 thereof is not particularly limited in this embodiment, as long as at least one of the n-type electrode and the p-type electrode of the micro light emitting diode chip 30 faces the circuit substrate 40 and is used for soldering with the circuit substrate 40 at the time of bonding. For example, the micro light emitting diode chip 30 is a flip chip, and when bonding, both the n-type electrode and the p-type electrode face the circuit substrate 40 and are used for welding with the circuit substrate 40; alternatively, the micro light emitting diode chip 30 may be a vertical chip, and one of the n-type electrode and the p-type electrode faces the circuit board 40 and is used for connection with the circuit board 40, and the other faces away from the circuit board 40 during bonding.
For convenience of illustration, fig. 2 to 6 illustrate the transfer method of the present embodiment by using a flip chip as an example, but it should be understood by those skilled in the art that the transfer method of the micro light emitting diode provided by the present embodiment is not limited to the flip chip, and can be applied to a vertical chip as well, as long as at least one electrode 31 is connected to the circuit substrate 40 by soldering.
Referring further to fig. 1, before the micro led chips 30 are picked up by the flexible transfer head 20, the micro led chips 30 may be disposed on the temporary substrate 50, i.e. the flexible transfer head 20 disposed on the rigid substrate 10 picks up the micro led chips 30 from the temporary substrate 50.
Referring to fig. 1 and fig. 2 in combination with fig. 6, the method for transferring a micro light emitting diode provided in this embodiment may further include the following step S0 before the step S1 is implemented:
the micro light emitting diode chip 30 formed on the substrate 60 is transferred from the substrate 60 onto the temporary substrate 50.
In this embodiment, the material of the substrate 60 is not particularly limited, and may be selected reasonably according to the requirements of the processing equipment and the micro light emitting diode device, for example, the substrate may be a sapphire substrate, a silicon carbide substrate, a silicon substrate, etc. commonly used in the field of the micro light emitting diode device. The formation method of the micro led chip 30 on the substrate 60 is not particularly limited in this embodiment, and the micro led chip may be formed on a C-plane sapphire substrate by epitaxial growth, for example.
In this embodiment, a specific implementation manner of transferring the micro led chip 30 from the substrate 60 to the temporary substrate 50 is not particularly limited, for example, a laser lift-off technology may be used, and as shown in fig. 6, the micro led chip 30 may be firstly adhered to the temporary substrate 50 by using the temporary bonding adhesive 51, and then the substrate 60 is removed by laser lift-off, so that the micro led chip 30 is transferred from the substrate 60 to the temporary substrate 50.
Specifically, before the micro led chip 30 is picked up from the temporary substrate 50 by the flexible transfer head 20 disposed on the rigid substrate 10, the bonding may be optionally performed, for example, the temporary bonding adhesive 51 is heated or subjected to UV irradiation according to the material of the temporary bonding adhesive 51, so as to reduce the acting force between the temporary bonding adhesive 51 and the micro led chip 30, and facilitate the flexible transfer head 20 to pick up the micro led chip 30 from the temporary substrate 50. Alternatively, if the adhesion between the temporary bonding paste 51 and the micro led chip 30 is smaller than the adhesion between the flexible transfer head 20 and the micro led chip 30, the step of debonding may not be performed.
Specifically, in step S1, the flexible transfer head 20 disposed on the rigid substrate 10 may pick up the micro light emitting diode chip 30 by van der waals force.
In this embodiment, the material of the flexible transfer head 20 is not particularly limited, as long as it has enough adhesive force with the micro led chip 30 to overcome the acting force between the temporary bonding adhesive 51 and the micro led chip 30, and can be easily pressed and deformed by the micro led chip 30 during the bonding process, for example, the transfer head may be a transfer head using polydimethylsiloxane PDMS as a base component. That is, the flexible transfer head 20 may be made of PDMS material, or other materials may be doped into the PDMS material to improve the physical and chemical properties such as viscosity, hardness, temperature tolerance, etc., so as to further improve the effect of the PDMS transfer head in picking up the micro led chip 30, bonding the micro led chip 30 with the circuit substrate 40, and separating the PDMS transfer head from the micro led chip 30 after bonding. For convenience of explanation, the transfer head having polydimethylsiloxane PDMS as a base component is collectively referred to as a PDMS transfer head in this embodiment.
Referring further to fig. 1 and 3, in step S2, the micro led chip 30 picked up by the rigid substrate 10 and the circuit substrate 40 are aligned, so that the electrode 31 on the micro led chip 30 and the electrode 41 on the circuit substrate 40 are disposed opposite to each other and aligned with each other.
In this embodiment, the circuit substrate 40 is used for carrying and driving the micro led chip 30, so that the micro led chip 30 is driven to emit light. The circuit substrate 40 may be a circuit substrate 40 commonly used in a current micro light emitting diode display panel, including but not limited to a printed backplane, a TFT backplane, a PM wiring backplane, a CMOS transistor backplane, and the like.
Referring to fig. 1 and 4, in step S3, a pressure is applied to the rigid substrate 10 (the direction of the dotted arrow in fig. 4 represents the direction of the gauge pressure force), and since the material of the flexible transfer head 20 is soft, the micro led chip 30 moves relative to the rigid substrate 10 in the direction away from the pressure force and presses the flexible transfer head 20; with the continuous extrusion deformation of the flexible transfer head 20, the distance between the micro led chip 30 and the rigid substrate 10 is continuously reduced or even infinitely approached, so that the rigid substrate 10 can provide the hardness required in the pressing process, and the pressure applied to the rigid substrate 10 can be fully transmitted to the micro led chip 30 and the circuit substrate 40, which is also beneficial to realizing the bonding between the electrode 31 on the micro led chip 30 and the electrode 41 on the circuit substrate 40 and forming good electrical connection.
As previously mentioned, the rigid substrate 10 should be capable of providing sufficient stiffness during the bonding process so that the bonding force is sufficiently transmitted through the rigid substrate 10 to the micro-led chips 30 and the circuit substrate 40. The rigid substrate 10 may be a hard glass substrate, a hard plastic substrate, or a metal substrate, wherein the hard glass substrate may be a borosilicate glass plate, the hard plastic substrate may be a polyvinyl chloride plate, a polyurethane plate, or the like, and the metal substrate may be a steel plate, a copper plate, or the like.
It can be understood that, during the process of applying pressure to the rigid substrate 10, the flexible transfer head 20 is pressed to be deformed due to the micro light emitting diode chip 30 being pressed into the flexible transfer head 20. It is apparent that the portion of the flexible transfer head 20 in direct contact with the micro led chip 30 is compressed and has a reduced thickness and extends in a direction parallel to the rigid substrate 10, so that the portion of the flexible transfer head 20 not in contact with the micro led chip 30 also extends, and the thickness may be slightly increased.
In order to avoid the micro led chips 30 being completely wrapped by the increased thickness of the flexible transfer head 20 and affecting the bonding connection with the circuit substrate 40, the thickness of the flexible transfer head 20 is preferably not more than the thickness (or height) of the micro led chips 30. In addition, the thickness of the flexible transfer head 20 should also take into consideration the material characteristics such as viscosity and hardness of the flexible transfer head 20 itself, so that the pressing force applied to the rigid substrate 10 can be sufficiently transferred to the micro led chips 30 during bonding, and sufficient van der waals force can be ensured between the flexible transfer head 20 and the micro led chips 30 during the picking up process, and the flexible transfer head 20 can be easily separated from the micro led chips 30 after the bonding is completed. In consideration of the above factors, the thickness of the micro led chip 30 is typically 5 to 7 μm, so that the thickness of the flexible transfer head 20 can be controlled to be not more than 7 μm, such as 1 to 7 μm, and further such as 3 to 5 μm.
The ultra-thin film-thick flexible transfer head 20 can prevent the micro light-emitting diode chip 30 from being completely wrapped, and in the pressing process, the thickness of the flexible transfer head 20 can be further reduced on the basis, so that infinite approach between the micro light-emitting diode chip 30 and the rigid substrate 10 is facilitated, and the pressing force is ensured to be transmitted to the micro light-emitting diode chip 30 and the circuit substrate 40 through the rigid substrate 10. In addition, the flexible transfer head 20 with the above thickness can easily realize the separation from the micro light emitting diode chip 30 in the subsequent step S4.
Referring further to fig. 4, it is preferable that adjacent flexible transfer heads 20 do not contact each other during the process of pressing the micro light emitting diode chips 30 into the flexible transfer heads 20. Or, the adjacent flexible transfer heads 20 have a sufficient distance therebetween, so that during the process of applying pressure to the rigid substrate 10, although the flexible transfer heads 20 are pressed to extend in a direction parallel to the rigid substrate 10, the flexible transfer heads 20 are still spaced apart from each other, thereby preventing the flexible transfer heads 20 from being designed as a whole layer or the adjacent flexible transfer heads 20 from contacting each other during the bonding process, which may cause the micro-led chips 30 and the circuit substrate 40 to be misaligned.
In addition, because the adjacent flexible transfer heads 20 are arranged at intervals, when the bonding between the micro light emitting diode chip 30 and the circuit substrate 40 is realized through subsequent welding, especially heating welding, even if the flexible transfer heads 20 expand due to heating, each flexible transfer head 20 also expands with the position of the flexible transfer head as the center, so that the micro light emitting diode chip 30 is prevented from being integrally deviated relative to the circuit substrate 40 due to the fact that the flexible transfer heads 20 are designed in a whole layer or the adjacent flexible transfer heads 20 are contacted with each other in the pressing process.
In the present embodiment, the specific manner of bonding between the micro light emitting diode chip 30 and the circuit substrate 40 is not particularly limited, and as mentioned above, the bonding may be achieved by soldering. Specifically, the solder 42 may be provided on the electrode 41 of the circuit board 40 in advance. During the pressing process, the solder 42 is bonded to the electrodes 31 of the micro led chips 30 by soldering. Specifically, in the pressing process, the solder 42 is heated and then cooled to melt and resolidify the solder 42, thereby completing the bonding between the micro led chip 30 and the circuit substrate 40.
Furthermore, when the solder 42 is bonded to the electrodes 31 of the micro led chips 30, the bonding temperature is preferably not higher than the maximum temperature (or called as the maximum temperature tolerance) of the flexible transfer head 20, so as to avoid damage to the flexible transfer head 20 and damage to the micro led chips 30. Specifically, the selected solder 42 is a low temperature solder, and the actual soldering temperature does not exceed the maximum withstand temperature of the flexible transfer head 20. For example, the maximum temperature of the PDMS transfer heads currently used in the industry may be about 120 ℃, and the solder 42 may be selected from indium, indium-tin alloy, bismuth-lead-tin alloy, and the like. In the case of indium, the melting point is approximately 156.6 ℃, and in practice, a metal bond can be formed by soldering indium at about 100 ℃. Indium tin alloy, bismuth lead tin alloy, etc. are generally considered to have melting points 120 degrees below the maximum withstanding temperature of PDMS.
With further reference to fig. 1 and 5, after the bonding between the micro led chip 30 and the circuit substrate 40 is completed, the flexible transfer head 20 and the micro led chip 30 are separated. In this embodiment, the separating means between the flexible transfer head 20 and the micro led chip 30 is not particularly limited, and an appropriate separating means may be selected according to the specific material of the flexible transfer head 20, for example, the rigid substrate 10 and the flexible transfer head 20 may be separated first, and then the flexible transfer head 20 may be peeled off from the micro led chip 30, or the rigid substrate 10 and the flexible transfer head 20 may be separated from the micro led chip 30 together, so as to complete the transfer of the micro led chip 30 to the circuit substrate 40.
Example two
The present embodiment provides a method for transferring a micro light emitting diode, as shown in fig. 1, 6 and 7, the method is different from the first embodiment in that: in step S1, the micro light emitting diode chips 30 are selectively picked up from the temporary substrate 50 using the flexible transfer head 20 provided on the rigid substrate 10.
It is understood that in actual industrial production, the arrangement of the micro led chips 30 on the substrate 60 and the circuit substrate 40 is often different. The former mainly depends on the formation process of the micro light emitting diode chip 30, and the latter mainly depends on the pixel arrangement of the micro light emitting diode display panel. The flexible transfer head 20 can thus selectively pick up the flexible transfer head 20 from the temporary substrate 50 when performing batch transfer of the micro light emitting diode chips 30.
As shown in fig. 7, for example, the distance between two adjacent micro led chips 30 on the circuit substrate 40 is 2 times the distance between two adjacent micro led chips 30 on the substrate 60, the flexible transfer head 20 disposed on the rigid substrate 10 can pick up the # 1 micro led chip 30 and the # 3 micro led chip 30 first, and then pick up the # 2 micro led chips 30 and the # 4 micro led chips 30.
EXAMPLE III
The present embodiment provides a method for manufacturing a display panel, please refer to fig. 1 to 7, which includes:
forming a micro light emitting diode chip 30 on a substrate 60;
according to the transfer method in the first or second embodiment, the micro light emitting diode chips 30 are transferred onto the circuit substrate 40 to form a micro light emitting diode display array for constituting a display;
and packaging the micro light-emitting diode display array to obtain the micro light-emitting diode display panel.
As described above, in the present embodiment, the material of the substrate 60 is not particularly limited, and includes, but is not limited to, a sapphire substrate, a silicon carbide substrate, and a silicon substrate. The formation method of the micro light emitting diode chip 30 is not particularly limited in the present embodiment, and the micro light emitting diode chip 30 may be formed by epitaxial growth on a C-plane sapphire substrate, for example.
The structure of the Micro LED chip 30 is not limited in this embodiment, for example, a typical GaN-based Micro LED chip structure includes an n-GaN layer on a substrate 60, an n-type electrode on a portion of the n-GaN layer, a multi-quantum well active layer on another portion of the n-GaN layer, a p-GaN layer on the multi-quantum well active layer, and a p-type electrode on the p-GaN layer. In the present embodiment, for convenience of description, the n-type electrode and the p-type electrode are collectively referred to as the electrode 31.
In this embodiment, the packaging method of the micro led display array is not particularly limited, and for example, a physical deposition process may be adopted to complete the passivation layer and the upper electrode, thereby completing the packaging and obtaining the micro led display panel.
The manufacturing method of the display panel provided by this embodiment includes the transferring method in the first embodiment to form the micro led display array for forming the display, so that the manufacturing method also has the same advantages as the first embodiment, and since the effective bonding and electrical connection are formed between the electrode 31 of the micro led chip 30 and the electrode 41 on the circuit substrate 40, the performance and yield of the micro led display panel are both significantly improved.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims (3)

1. A method for transferring micro light emitting diodes, comprising:
picking up the micro light-emitting diode chip by adopting a flexible transfer head arranged on a rigid substrate;
aligning the micro light-emitting diode chip picked up by the rigid substrate with the circuit substrate to enable the electrode on the micro light-emitting diode chip to correspond to the electrode on the circuit substrate;
applying pressure to the rigid substrate to enable the micro light-emitting diode chip to be extruded into the flexible transfer head, wherein the pressure is transmitted to the micro light-emitting diode chip through the rigid substrate and the flexible transfer head, and the electrode on the micro light-emitting diode chip is bonded with the electrode on the circuit substrate;
separating the flexible transfer head from the micro light emitting diode chip;
the flexible transfer head picks up the micro light-emitting diode chip through Van der Waals force;
the flexible transfer head is a transfer head taking polydimethylsiloxane as a basic component;
in the process that the micro light-emitting diode chip is extruded into the flexible transfer heads, adjacent flexible transfer heads are not contacted with each other;
the thickness of the flexible transfer head is not more than that of the micro light-emitting diode chip, and the thickness of the flexible transfer head is 3-5 microns;
the rigid substrate comprises at least one of a polyvinyl chloride plate and a polyurethane plate;
the electrodes of the circuit substrate are provided with solder, and the solder and the electrodes of the micro light-emitting diode chip are welded to realize the bonding;
during the bonding, the welding temperature between the solder and the electrode of the micro light-emitting diode chip does not exceed the maximum bearing temperature of the flexible transfer head.
2. The transfer method of claim 1, wherein the step of picking up the micro-led chip using a flexible transfer head disposed on a rigid substrate further comprises: the micro-light emitting diode chip formed on the substrate is transferred from the substrate onto a temporary base plate.
3. A method for manufacturing a display panel is characterized by comprising the following steps:
forming a micro light emitting diode chip on a substrate;
the transfer method according to any one of claims 1 to 2, transferring the micro light emitting diode chips onto a circuit substrate to form a micro light emitting diode display array for constituting a display;
and packaging the micro light-emitting diode display array to obtain the micro light-emitting diode display panel.
CN201910470274.XA 2019-05-31 2019-05-31 Micro light emitting diode transfer method and display panel manufacturing method Active CN112018218B (en)

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