Mass transfer method for micro-LEDs with a temperature-controlled adhesive layer

Abstract

A mass transfer method for Micro-LEDs with a temperature-controlled adhesive layer, including: configuring a self-assembling structure based on Micro-LED dies and a transfer substrate having a self-receiving structure coated on its surface with a temperature-controlled adhesive layer; distributing the Micro-LED dies in water, soaking the transfer substrate in water and heating water to perform self-assembling; carrying out transferring and removing the transfer substrate to separate Micro-LED dies from a transfer substrate then onto a target substrate.

Claims

1. A mass transfer method for Micro-LEDs with a temperature-controlled adhesive layer, comprising: a) configuration of a self-assembling structure by providing an anode pin and a cathode pin on a side of Micro-LED dies; providing a self-assembling microstructure on the other side of the Micro-LED dies; providing a self-receiving microstructure on a transfer substrate; and coating a surface of the self-receiving microstructure with a temperature-controlled adhesive layer; wherein the self-assembling microstructure and the self-receiving microstructure are fitted with each other; and the temperature-controlled adhesive layer is sticky at a temperature higher than 40 C. and loses a sticky property at a temperature below 25 C., and a switch of the sticky property of the temperature-controlled adhesive layer is reversible and repeatable; b) self-assembling by distributing the Micro-LED dies in a container with water; soaking the transfer substrate in the water to allow the temperature-controlled adhesive layer on the surface of the self-receiving microstructure of the transfer substrate to become sticky; and at the same time, stirring, by a stirrer, the water to allow the Micro-LED dies to fit with the self-receiving microstructure, wherein the Micro-LED dies are fixed to the self-receiving microstructure due to the temperature-controlled adhesive layer; c) transferring by stopping heating and stirring the water; taking out the transfer substrate; soaking a target substrate into the water; putting the transfer substrate into the water to align with the target substrate; and cooling the water to allow the temperature-controlled adhesive layer on the self-receiving microstructure of the transfer substrate to lose the sticky property, so that the Micro-LED dies are separated from the transfer substrate and transferred to the target substrate; and d) taking out the transfer substrate; wherein the transfer substrate is applied to the Micro-LED dies having a geometrical size of 1-10 m.

2. The mass transfer method of claim 1, wherein the self-assembling microstructure and the self-receiving microstructure are of a stepped structure, and a height difference of two steps of the stepped structure is 1-10 m.

3. The mass transfer method of claim 1, wherein in step a), the temperature-controlled adhesive layer is made of pHIPAM-CD and has a thickness of 10-100 m.

4. The mass transfer method of claim 1, wherein in step b), after the heating, the water has a temperature of 40 C.; in step c), after the heating, the water has a temperature of 40 C., and after the cooling, the water has a temperature of 25 C.

5. The mass transfer method of claim 1, wherein the transfer substrate is taken out by lifting at a directional movement speed of 1-10 mm/s.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a flow chart of a mass transfer method for Micro-LEDs with temperature-controlled adhesive layer according to an embodiment of the present invention;

(2) FIG. 2 is a schematic diagram showing a picking process of the mass transfer method for Micro-LEDs according to an embodiment of the present invention;

(3) FIG. 3 is an enlarged view showing a Micro-LED die and a self-receiving microstructure according to an embodiment of the present invention; and

(4) FIG. 4 is a schematic diagram showing the releasing process in the mass transfer method for Micro-LEDs according to an embodiment of the present invention;

REFERENCE NUMERALS

(5) 102: container; 103: water; 104: transfer substrate; 106: Micro-LED die; 107: self-receiving microstructure; 201: anode pin; 202: cathode pin; 204: temperature-controlled adhesive layer; 304: target substrate; 305: heating stage.

DETAILED DESCRIPTION OF EMBODIMENTS

(6) The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

(7) As shown in FIGS. 1-4, illustrated is a mass transfer method for Micro-LEDs with temperature-controlled adhesive layer, comprising:

(8) A) configuration of a self-assembling structure

(9) an anode pin 201 and a cathode pin 202 are provided on a side of Micro-LED dies 106, and a self-assembling microstructure is provided on the other side of the Micro-LED dies 106; a self-receiving microstructure 107 is provided on a transfer substrate 104; the self-assembling microstructure and the self-receiving microstructure are fitted with each other; and a temperature-controlled adhesive layer 204 is coated on the surface of the self-receiving microstructure, and is sticky at a temperature higher than 40 C. and loses the sticky property at a temperature below 25 C., and the switch of the sticky property of the temperature-controlled adhesive layer is reversible and repeatable;

(10) B) self-assembling

(11) water 103 is filled in a container 102, in which the Micro-LED dies are distributed; the transfer substrate 104 is soaked in the water; the water is heated by a heating device, such that the temperature-controlled adhesive layer 204 on the surface of the self-receiving microstructure 107 becomes sticky; at the same time, the water is stirred by a stirrer to allow the Micro-LED dies 106 to fit with the self-receiving microstructure 107, and since the temperature-controlled adhesive layer 204 is sticky, the Micro-LED dies 106 are fixed to the self-receiving microstructure 107;

(12) C) transferring

(13) the transfer substrate 104 is taken out from the water after the heating and stirring for the water are stopped; a target substrate 304 is soaked in high-temperature water; the transfer substrate 104 is then put into the high-temperature water to align with the target substrate 304; and the temperature-controlled adhesive layer 204 on the surface of the self-receiving microstructure 107 of the transfer substrate 104 loses the sticky property by cooling the water, such that the Micro-LED dies 106 separate from the transfer substrate 104 and are transferred to the target substrate 304;

(14) D) the transfer substrate 104 is taken out after the transferring.

(15) In the present invention, the Micro-LED dies 106 can be orderly picked up by the self-receiving microstructure 107 and the temperature-controlled adhesive layer 204, improving the efficiency of the mass transfer of the Micro-LEDs; the transfer substrate 104 of the present invention is reusable and the whole process is simple and requires little manual operation; and the heating device is usually a heating stage 305, on which the container is placed and heated.

(16) The transfer substrate 104 is applied to the Micro-LED dies 106 having a geometrical size of 1-10 m, which means the transfer substrate 104 is suitable for all existing Micro-LED dies.

(17) The self-assembling microstructure and the self-receiving microstructure 107 both are of a stepped structure, and a height difference of two steps of the stepped structure is 1-10 m.

(18) The stepped self-assembling microstructure has a slot-like structure, and by mounting with the dies of the same type, a die with a reversed anode and cathode cannot be attached to the self-receiving microstructure 107, such that the dies can be properly attached.

(19) In addition, the temperature-controlled adhesive layer 204 in the step A is made of pHIPAM-CD and has a thickness of 10-100 m. The pHIPAM-CD is an existing adhesive material that has different stickiness at different temperatures. The pHIPAM-CD may have or lose the sticky property under different temperatures.

(20) In addition, in step B, after the heating, the water has a temperature of 40 C.; in step C, after the heating, the water has a temperature of 40 C., and after the cooling, the water has a temperature of 25 C.

(21) In step D, the transfer substrate 104 is taken out by lifting with a directional movement speed of 1-10 mm/s.

(22) The speed of the water flow ensures that the Micro-LED dies 106 are reliably attached to the self-receiving microstructure 107. A die, if not reliably attached, may be separated from the self-receiving microstructure 107 by the water, and finally the die is repeated to be reattached to the self-receiving microstructure 107.

(23) The present invention has been described above in conjunction with the embodiment. The descriptions are merely illustrative of the spirit of the present invention and are not intended to limit the scope of the present invention. Any embodiments obtained by those skilled in the art based on the invention without any creative work shall fall within the scope of the invention.