Micro-LED array transfer method, manufacturing method and display device

Abstract

A micro-LED transfer method, manufacturing method and display device are provided. The micro-LED transfer method comprises: bonding the micro-LED array on a first substrate onto a receiving substrate through micro-bumps, wherein the first substrate is laser transparent; applying underfill into a gap between the first substrate and the receiving substrate; irradiating laser onto the micro-LED array from a side of the first substrate to lift-off the micro-LED array from the first substrate; and removing the underfill.

Claims

1. A method for transferring a micro-LED array, comprising: bonding the micro-LED array on a first substrate onto a receiving substrate through a plurality of micro-bumps, wherein the first substrate is laser transparent; applying an underfill into a gap between the first substrate and the receiving substrate; irradiating the micro-LED array with a laser from a side of the first substrate to lift-off the micro-LED array from the first substrate; and removing the underfill.

2. The method according to claim 1, further comprising: separating the first substrate from the receiving substrate.

3. The method according to claim 1, wherein the first substrate is a sapphire substrate.

4. The method according to claim 1, wherein the micro-bumps are of low temperature bonding material.

5. The method according to claim 1, wherein the underfill is selected from the group consisting of a low viscosity liquid, solvent, resist, glue, polymer, silicone and grease.

6. The method according to claim 1, wherein the underfill is solidified or a viscosity of the underfill is increased during the irradiating.

7. The method according to claim 1, wherein the underfill is applied in a low atmospheric pressure environment or in a vacuum.

8. The method according to claim 1, wherein the underfill is removed by one or more of a chemical, solvent, undercutting or phase change.

9. A method for manufacturing a display device, comprising transferring a micro-LED array from a first substrate to a receiving substrate of the display device by using the method according to claim 1.

10. A display device manufactured by using the method for manufacturing a display device according to claim 9.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description thereof, serve to explain the principles of the invention.

(2) FIG. 1 shows a schematic diagram of a prior art example of transferring a micro-LED array through laser lifting-off.

(3) FIGS. 2-5 shows a schematic diagram of a process of transferring a micro-LED array from a first substrate to a receiving substrate according to an embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(4) Various exemplary embodiments of the present invention will now be described in detail with reference to the drawings. It should be noted that the relative arrangement of the components and steps, the numerical expressions, and numerical values set forth in these embodiments do not limit the scope of the present invention unless it is specifically stated otherwise.

(5) The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.

(6) Techniques, methods and apparatus as known by one of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate.

(7) In all of the examples illustrated and discussed herein, any specific values should be interpreted to be illustrative only and non-limiting. Thus, other examples of the exemplary embodiments could have different values.

(8) Notice that similar reference numerals and letters refer to similar items in the following figures, and thus once an item is defined in one figure, it is possible that it need not be further discussed for following figures.

(9) In an embodiment, it is proposed to apply an underfill during a LLO transfer of a micro-LED array to improve the bonding strength between the micro-LED array. The underfill can be removed after the transfer.

(10) FIGS. 2-5 shows a schematic diagram of a process of transferring a micro-LED array from a first substrate to a receiving substrate according to an embodiment.

(11) As shown in FIG. 2, the micro-LED array 204 on a first substrate 201 is bonded onto a receiving substrate 202 through micro-bumps 206. The first substrate 201 is laser transparent. For example, it is a sapphire substrate.

(12) The micro bumps 206 may be anodes on top of the circuitry 203 such as a TFT circuitry in the receiving substrate 202. For example, the micro-LEDs 204 are bonded on the micro-bumps 206 through solder 205.

(13) For example, the micro-bumps 206 are of low temperature bonding material, such as In, Sn or other low temperature metals/alloys. It can also be electrical conductive adhesives or resists.

(14) As shown in FIG. 3, underfill 208 is applied into a gap between the first substrate 201 and the receiving substrate 202. For example, the underfill is applied by capillary. The underfill can act as a protection layer for the micro-LEDs 204 and the receiving substrate 202 during the laser lifting-off.

(15) For example, the underfill 208 can be at least one of is a low viscosity liquid, solvent, resist, glue, polymer, silicone and grease.

(16) In an example, the underfill 208 is applied in a low atmospheric pressure environment or in vacuum. In this way, the bubbles or air in the underfill can be gotten rid of.

(17) As shown in FIG. 4, laser 207 is irradiated onto the micro-LED array from a side of the first substrate to lift-off the micro-LED array from the first substrate.

(18) In FIG. 4, the laser 207 is irradiated onto selected micro-LEDs 204. The selected micro-LEDs constitute the micro-LED array 204 which is to be transferred to the receiving substrate 202.

(19) In an example, the underfill is applied in an elevated temperature. The elevated temperature is not as high as that causing a significant thermal mismatch. Then, the underfill is solidified or the viscosity of the underfill is increased during the micro-LED array is lifted-off.

(20) Alternatively, the underfill will not be solidified or the viscosity thereof will not be increased. This will simplify the processing.

(21) Here, a temporary underfill 208 is added into gap between the first substrate 201 and the receiving substrate 202. The underfill will mechanically enhance the bonding between the two substrates. Thus, the yield will significantly be improved LLO yield.

(22) In addition, the underfill can also function as a protection layer for the receiving substrate during the laser lifting-off. For example, it prevents the laser from irradiating onto the receiving substrate 202, which may damage the circuitry 203 in the receiving substrate 202.

(23) Here, the underfill will reinforce the bonding strength between the micro-LEDs and the receiving substrate, without a high temperature/high strength bonding. This will reduce the negative influence caused by a thermal mismatch between the micro-LEDs and the receiving substrate.

(24) The underfill can be low viscosity resist, polymer, silicone, glue or grease, or it can even be liquid, such as water, solvent. The underfill can be applied into the gap by capillary force due to surface tension.

(25) As shown in FIG. 5, the underfill 208 is removed. For example the underfill is removed by chemical, solvent, undercutting or phase change. Then, it is rinsed and dried.

(26) Next, the first substrate 201 is separated from the receiving substrate 202.

(27) In another embodiment, an embodiment includes a method for manufacturing a display device. The manufacturing method comprises transferring a micro-LED array from a first substrate to a receiving substrate of the display device by using the method for transferring a micro-LED array according to an embodiment as above. The display device can be a display panel, a display screen and so on.

(28) In another embodiment, another embodiment includes a display device manufactured by using the method for manufacturing a display device according to an embodiment as above.

(29) In comparison with the prior art, since the underfill can improve the bonding strength during the laser lifting-off and/or can be a protection layer for the receiving substrate, the display device will show a better performance than one of the prior art under a similar condition.

(30) In another embodiment, another embodiment can further include an electronic apparatus. The electronic apparatus contains a display device as above. For example, the electronic apparatus can be a mobile phone, a pad computer and so on.

(31) Although some specific embodiments of the present invention have been demonstrated in detail with examples, it should be understood by a person skilled in the art that the above examples are only intended to be illustrative but not to limit the scope of the present invention.