CN109545815B - Mass transfer method of micro light-emitting diode - Google Patents

Abstract

The invention discloses a method for mass transfer of miniature light-emitting diodes, and relates to the field of light-emitting display. Cut the micro light-emitting diode array with a conductive adhesive layer; make the conductive adhesive layer electrostatically charged; make an oscillating insulating platform, and apply an electric field above the oscillating insulating platform to make the charged micro-light emitting diode components the same. Orientation; move the platform of the arranged micro light-emitting diodes into the optical tweezers array, and use the optical tweezers array to capture the micro-light-emitting diode components; move the optical tweezers array to make the micro-light-emitting diode components correspond to the positions of the driving circuit one-to-one; The heating and bonding methods make the P and N poles of the miniature light-emitting diode components and the driving circuit electrically connected through the conductive adhesive layer, and each miniature light-emitting diode component obtains address control and individual driving.

Description

A Mass Transfer Method for Micro-Light Emitting Diodes

technical field

The invention relates to the field of light-emitting display, in particular to a method for mass transfer of miniature light-emitting diodes by using optical tweezers.

Background technique

Miniature light-emitting diode is a display technology that miniaturizes and matrixes the traditional light-emitting diode structure, and uses CMOS integrated circuit technology to make a driving circuit to realize the address control and individual driving of each pixel. Because the brightness, life, contrast, response time, energy consumption, viewing angle and resolution of micro light-emitting diode technology are stronger than LCD and OLED technology, plus it is self-luminous, simple in structure, small in size and energy-saving The advantages of it have been regarded by many manufacturers as the next generation of display technology and have begun to actively deploy. One of the core technical problems faced in the process of industrialization of micro-LEDs is the mass transfer technology of micro-LED components. Because mass transfer technology requires very high efficiency, yield and transfer accuracy, mass transfer technology has become the biggest challenge in the research and development process of micro LEDs, hindering the promotion and use of micro LED technology.

In the prior art, laser-induced forward transfer technology is used to solve the unique challenges of assembling high-resolution displays containing millions of tiny light-emitting diode chips. Ideal for precise peeling of the original carrier. As a result of the laser irradiation, the nitrogen gas generated by the decomposition of the gallium nitride expands and creates mechanical forces on the miniature light-emitting diode structure, which push the chip from the original carrier to the receiving substrate. By using a combination of large cross-section beams, masks and projection optics, up to a thousand chips can be delivered in parallel with just one laser shot. There is an alternative to the process, using polymer adhesives to pre-assemble the micro LEDs on a temporary carrier wafer or tape. These adhesives are extremely UV-absorbing. When irradiated by excimer laser light, the adhesive undergoes a photochemical decomposition reaction, which separates from the miniature light-emitting diode chip and generates a force that pushes the chip toward the receiving substrate. The energy required to irradiate polymer tapes or adhesives can be one-twentieth to one-fifth of the energy required for laser lift-off technology, which means that very high treatments can be achieved with only moderate laser intensity speed. However, since the intensity of the excimer laser is difficult to control, the equipment for which the intensity can be precisely controlled is very expensive, and the speed and degree of the photochemical decomposition reaction directly affect the process yield and efficiency.

Therefore, those skilled in the art are devoted to developing a method for mass transfer of miniature light-emitting diodes, which is simple and practical, has good economy, high efficiency, high yield and high transfer precision.

SUMMARY OF THE INVENTION

In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is how to design a complete set of mass transfer technology that is simple, practical, economical, efficient, high yield and transfer precision.

In order to achieve the above object, the present invention provides a method for mass transfer of miniature light-emitting diodes, comprising the following steps:

Step 1. Make a miniature light-emitting diode array;

Step 2, coating a conductive adhesive layer on the surface of the micro light-emitting diode array with P and N poles, and making the conductive adhesive layer electrostatically charged;

Step 3, cutting the micro LED array with the conductive adhesive layer;

Step 4, making the conductive adhesive layer electrostatically charged;

Step 5. Make an oscillating insulating platform, and apply an electric field above the oscillating insulating platform to make the charged miniature light-emitting diode components align in the same direction; finally, let the conductive adhesive layer face downward. , in order to facilitate the subsequent bonding process.

Step 6. Move the platform of the arranged micro-LEDs into the optical tweezers array, and use the optical tweezers array to capture the micro-LED components;

Step 7, moving the optical tweezers array so that the positions of the miniature light-emitting diode components and the driving circuit correspond one-to-one;

Step 8. Using heating and bonding methods, the P and N poles of the miniature light-emitting diode components and the driving circuit are electrically connected through the conductive adhesive layer, and each of the miniature light-emitting diode components obtains addressing control and control. Drive alone.

Preferably, the P and N poles of each micro light emitting diode element in the micro light emitting diode array are on the same side.

Preferably, the P poles of the miniature light-emitting diode components are arranged around, and the N poles are arranged on the inside, or the N poles of the miniature light-emitting diode components are arranged around, and the P poles are arranged inside.

Preferably, the miniature light emitting diode components have a symmetrical structure.

Preferably, the top view shape of the miniature light emitting diode component is square or rectangle.

Preferably, the following steps are added after the step 2: Step 2.1, after drying the conductive adhesive layer, the conductive adhesive layer is charged.

Preferably, the optical tweezers array is formed by converting the laser light into parallel light through a collimator, and then using a microlens array.

Preferably, the collimator and microlens array are used for laser expansion, control and focusing.

Preferably, the following steps are added before the step 7: step 7.0, the position of the same type of miniature light-emitting diodes to be filled is covered with a mold.

Preferably, the oscillating platform in the step 5 is replaced with an insulating liquid.

The method for mass transfer of miniature light-emitting diodes of the present invention adopts optical tweezers (laser passes through a collimator and a lens array to form optical traps) to pick up and place the miniature light-emitting diodes, which is simple, practical, economical, efficient, and yields high yields. High and high transfer accuracy features.

The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings, so as to fully understand the purpose, characteristics and effects of the present invention.

Description of drawings

FIG. 1 is a micro-LED component array fabricated on a substrate according to a preferred embodiment of the present invention;

FIG. 2 is a schematic diagram of a miniature light-emitting diode component according to a preferred embodiment of the present invention;

Fig. 3 is a preferred embodiment of the present invention, the surface of the micro-LED component array is coated with a conductive adhesive layer;

Fig. 4 is a preferred embodiment of the present invention, the single particle miniature light-emitting diode component after cutting has a charged conductive adhesive layer on the surface;

5 is an electric field and an oscillating insulating platform for making the charged micro-LED components aligned in the same direction according to a preferred embodiment of the present invention;

Fig. 6 is a preferred embodiment of the present invention where the platform of the arranged micro light-emitting diodes is moved into the optical tweezers array.

Detailed ways

The following describes several preferred embodiments of the present invention with reference to the accompanying drawings, so as to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the protection scope of the present invention is not limited to the embodiments mentioned herein.

In the drawings, structurally identical components are denoted by the same numerals, and structurally or functionally similar components are denoted by like numerals throughout. The size and thickness of each component shown in the drawings are arbitrarily shown, and the present invention does not limit the size and thickness of each component. In order to make the illustration clearer, the thicknesses of components are appropriately exaggerated in some places in the drawings.

The method for mass transfer of miniature light-emitting diodes according to the present invention includes the following steps, as shown in FIG. 1 , fabricating an array of micro-LED components on a substrate, and making the P-pole and N-pole of the micro-LED components in the same side (as shown in Figure 2); at the same time, the miniature light emitting diode components have a symmetrical structure (the top view shape is a square or a rectangle), which is conducive to efficient cutting of the miniature light emitting diode components. The P poles of the miniature light-emitting diode components are arranged around, and the N poles are on the inside (as shown in Figure 2), or the N poles of the miniature light-emitting diode components are arranged around, and the P poles are on the inside, that is, the positions of the P and N poles can be mutually Change.

As shown in FIG. 3 , a conductive adhesive layer is coated on the surface of the array of miniature light-emitting diode elements with P and N electrodes. After the conductive adhesive layer is properly dried, the micro-LED array is cut, and then the conductive adhesive layer is charged (electrostatic charge).

As shown in Fig. 4, after cutting, there is a charged conductive adhesive layer on the surface of the single micro-LED component.

As shown in FIG. 5 , an insulating platform that can be oscillated is fabricated, and an electric field can be applied above the oscillating insulating platform to align the charged micro-LED components in the same direction.

As shown in FIG. 6 , the platform of the arranged micro-LEDs is moved into the optical tweezers array, and the micro-LED components are captured by the optical tweezers array. The optical tweezers array is formed by converting the laser light into parallel light through a collimator, and then forming it through a microlens array, so that one by one light traps can be formed to capture the miniature light-emitting diode components. Collimators and microlens arrays are used for laser expansion, control and focusing.

Move the optical tweezers array so that the positions of the driving circuits of the miniature light-emitting diode components correspond one-to-one.

By means of heating and bonding, the P and N electrodes of the miniature light-emitting diode components and the driving circuit are electrically connected through the conductive adhesive layer, so as to realize the addressing control and individual driving of each miniature light-emitting diode component.

In addition, the micro light-emitting diode components have three colors of RGB, and the micro light-emitting diode components can be transferred to the driving circuit by using the optical tweezers array three times.

In order to improve the operation efficiency, when transferring a certain color of micro-LED components to the driving circuit, the position of the same type of micro-LED to be filled can be covered with a mold, and the RGB three-type micro-LED components can be transferred in steps. to the drive circuit. The conductive adhesive layer of the miniature light-emitting diode can also be charged after cutting.

In another preferred embodiment of the present invention, due to the limited "grip force" of the optical tweezers, the bulk transfer corresponding to the relatively heavy components is placed in an insulating liquid. The purpose of using insulating liquid is to reduce the influence of gravity, so that the mass transfer of the optical tweezers array can be carried out. Of course, the oscillating platform can also be placed in an insulating liquid to achieve a comprehensive effect.

The preferred embodiments of the present invention have been described in detail above. It should be understood that many modifications and changes can be made according to the concept of the present invention by those skilled in the art without creative efforts. Therefore, all technical solutions that can be obtained by those skilled in the art through logical analysis, reasoning or limited experiments on the basis of the prior art according to the concept of the present invention shall fall within the protection scope determined by the claims.

Claims (9)

1. A mass transfer method of a micro light-emitting diode is characterized by comprising the following steps:

step 1, manufacturing a micro light-emitting diode array;

step 2, coating a conductive adhesive layer on the surface of the micro light-emitting diode array with the P, N poles;

step 3, cutting the micro light-emitting diode array with the conductive adhesive layer to obtain a plurality of micro light-emitting diode components;

step 4, enabling the conductive adhesive layer to be charged with static electricity;

step 5, manufacturing a vibratile insulating platform, and applying an electric field above the vibratile insulating platform for enabling the electrified micro light-emitting diode components to be arranged in the same direction;

step 6, moving the arranged platform of the micro light-emitting diode into an optical tweezers array, and capturing the micro light-emitting diode component in insulating liquid by using the optical tweezers array, wherein the optical tweezers array is formed by converting laser into parallel light through a collimator and then passing through a micro lens array;

step 7, moving the optical tweezers array to enable the positions of the miniature light-emitting diode components and the driving circuit to correspond one to one;

and 8, adopting a heating and bonding mode to electrically connect the P, N electrode of the miniature light-emitting diode component with the driving circuit through the conductive adhesive layer, wherein each miniature light-emitting diode component is subjected to addressing control and independent driving.

2. The mass transfer method of micro-leds as claimed in claim 1, wherein P, N poles of each micro-led device in the micro-led array are on the same plane.

3. The mass transfer method for micro light-emitting diodes according to claim 1, wherein the P poles of the micro light-emitting diode devices are disposed at the periphery and the N poles are at the inner side, or the N poles of the micro light-emitting diode devices are disposed at the periphery and the P poles are at the inner side.

4. The mass transfer method of micro-leds as claimed in claim 1, wherein the micro-leds are symmetrical.

5. The mass transfer method of micro-leds as claimed in claim 1, wherein the top view of the micro-leds is square or rectangular.

6. The method of claim 1, wherein the step 2 is followed by the following step

And 2.1, drying the conductive adhesive layer to electrify the conductive adhesive layer.

7. The mass transfer method of micro-leds of claim 1, wherein the collimator and microlens array are used for laser expansion, control and focusing.

8. The method of claim 1, wherein the following steps are added before step 7:

and 7.0, covering the positions of the micro light-emitting diodes of the same type to be filled with a mould.

9. The method according to claim 1, wherein said step 5 of co-aligning is performed with all of said micro light-emitting diodes with their conductive paste layers facing down.

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