DIE BONDING METHOD FOR MICRO-LED

Abstract

A die bonding method for a micro-LED. The method includes plating tin at a die bonding position of a printed circuit board (PCB) to obtain a tin-plated layer; adding a protective layer and a flux layer on the tin-plated layer in sequence to obtain a pretreated PCB; and transferring a flip-chip micro-LED to the pretreated PCB, reflowing and die bonding to complete die bonding of the micro-LED.

Claims

1. A die bonding method for a micro-LED, comprising: plating tin at a die bonding position of a printed circuit board (PCB) to obtain a tin-plated layer; adding a protective layer and a flux layer on the tin-plated layer in sequence to obtain a pretreated PCB; and transferring a flip-chip micro-LED to the pretreated PCB, reflowing and die bonding to complete die bonding of the micro-LED.

2. The method according to claim 1, wherein the tin-plated layer has a thickness of 5-30 .Math.m.

3. The method according to claim 1, wherein adding the protective layer comprises one of sticking a protective film or an organic solderability preservative (OSP) process.

4. The method according to claim 1 , wherein a flux comprises at least one of the following organic no-clean fluxes: ketones, alcohols or esters.

5. The method according to claim 1 , wherein the flux layer has a thickness of 1-5 .Math.m.

6. The method according to claim 1 , wherein the flip-chip micro-LED is a flip-chip micro-LED with tin.

7. The method according to claim 1 , further comprising adjusting a reflow profile before the reflowing and the die bonding.

8. The method according to claim 1 , wherein the reflowing and the die bonding comprise evacuating and filling with nitrogen to correct a negative pressure, wherein the nitrogen has a concentration greater than 99.99%.

9. The method according to claim 1 , wherein the tin-plated layer has a thickness of 530 .Math.m; wherein the flux layer has a thickness of 1-5 .Math.m, and the method for adding the protective layer comprises any one of sticking the protective film or the OSP process.

10. The method according to claim 2, wherein adding the protective layer comprises one of sticking a protective film or an organic solderability preservative (OSP) process.

11. The method according to claim 2, wherein a flux comprises at least one of the following organic no-clean fluxes: ketones, alcohols or esters.

12. The method according to claim 3, wherein a flux comprises at least one of the following organic no-clean fluxes: ketones, alcohols or esters.

13. The method according to 2, wherein the flux layer has a thickness of 1-5 .Math.m.

14. The method according to 3, wherein the flux layer has a thickness of 1-5 .Math.m.

15. The method according to 4, wherein the flux layer has a thickness of 1-5 .Math.m.

16. The method according to claim 2, wherein the flip-chip micro-LED is a flip-chip micro-LED with tin.

17. The method according to claim 3, wherein the flip-chip micro-LED is a flip-chip micro-LED with tin.

18. The method according to claim 4, wherein the flip-chip micro-LED is a flip-chip micro-LED with tin.

19. The method according to claim 5, wherein the flip-chip micro-LED is a flip-chip micro-LED with tin.

20. The method according to claim 2, further comprising adjusting a reflow profile before the reflowing and the die bonding.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0012] FIG. 1 is a structure diagram of a die bonding method for a micro-LED according to a specific embodiment of the present application.

[0013] FIG. 2 is a structure diagram of a PCB used in a specific embodiment of the present application.

DETAILED DESCRIPTION

[0014] As shown in FIGS. 1 and 2, FIG. 1 is a structure diagram of a die bonding method for a micro-LED according to an embodiment of the present application, and FIG. 2 is a structure diagram of a PCB used in an embodiment of the present application.

Embodiment One

[0015] The present embodiment provides a die bonding method for a micro-LED. The method includes the steps below. [0016] (1) Tin is plated at a die bonding position of a PCB to obtain a tin-plated layer having a thickness of 15 .Math.m. [0017] (2) A protective layer and a flux layer are added on the tin-plated layer obtained in step (1) in sequence, where the flux layer has a thickness of 1 .Math.m. A method for adding the protective layer is to stick a protective film, and the flux layer uses a spraying process to obtain a pretreated PCB. [0018] (3) A flip-chip micro-LED with tin is transferred to the pretreated PCB obtained in step (2), a reflow profile is adjusted, and then reflowed and die bonded to complete die bonding of the micro-LED.

Embodiment Two

[0019] The present embodiment provides a die bonding method for a micro-LED. The method includes the steps below. [0020] (1) Tin is plated at a die bonding position of a PCB to obtain a tin-plated layer having a thickness of 30 .Math.m. [0021] (2) A protective layer and a flux layer are added on the tin-plated layer obtained in step (1) in sequence, where the flux layer has a thickness of 5 .Math.m. A method for adding the protective layer is to stick a protective film, and the flux layer uses a spraying process to obtain a pretreated PCB. [0022] (3) A flip-chip micro-LED with tin is transferred to the pretreated PCB obtained in step (2), a reflow profile is adjusted, and then reflowed and die bonded to complete die bonding of the micro-LED.

Embodiment Three

[0023] The present embodiment provides a die bonding method for a micro-LED. The method includes the steps below. [0024] (1) Tin is plated at a die bonding position of a PCB to obtain a tin-plated layer having a thickness of 20 .Math.m. [0025] (2) A protective layer and a flux layer are added on the tin-plated layer obtained in step (1) in sequence, where the flux layer has a thickness of 2 .Math.m. A method for adding the protective layer is an organic solderability preservative (OSP) process, and the flux layer uses a spraying process to obtain a pretreated PCB. [0026] (3) A flip-chip micro-LED with tin is transferred to the pretreated PCB obtained in step (2), a reflow profile is adjusted, and then reflowed and die bonded to complete die bonding of the micro-LED.

Embodiment Four

[0027] The present embodiment provides a die bonding method for a micro-LED. The method includes the steps below. [0028] (1) Tin is plated at a die bonding position of a PCB to obtain a tin-plated layer having a thickness of 25 .Math.m. [0029] (2) A protective layer and a flux layer are added on the tin-plated layer obtained in step (1) in sequence, where the flux layer has a thickness of 3 .Math.m. A method for adding the protective layer is an OSP process, and the flux layer uses a spraying process to obtain a pretreated PCB. [0030] (3) A flip-chip micro-LED with tin is transferred to the pretreated PCB obtained in step (2), a reflow profile is adjusted, and then reflowed and die bonded to complete die bonding of the micro-LED.

[0031] The tin plating method used in embodiments one to four of the present application is an electroless tin plating method. Under the action of a reductant, metal ions in a plating solution are deposited on an active surface of a matrix. A tin layer formed through the electroless tin plating has a uniform thickness, and no external power supply is required.

[0032] The reflowing and die bonding process used in embodiments one to four of the present application includes evacuating and filling with nitrogen to correct a negative pressure, where the nitrogen has a concentration greater than 99.99%.

[0033] The protective film used in embodiments one and two is a ultraviolet (UV) curable film. A material type of the OSP process in embodiments three and four includes rosins, active resins and azoles, and the azole OSP is selected in the present embodiment. The protective film requires to be torn off when in use, and the die bonding and the reflowing are completed within an operable time limit.

[0034] Compared with the gold plating method in the related art, the die bonding method for a micro-LED used in embodiments one to four of the present application can save a cost by 20% to 30%.

[0035] Compared with the related technical solution, the present application has at least the beneficial effects described below.

[0036] In the present application, the process of tin plating and an anti-oxidation layer is used instead of the gold plating and reduces the cost of the PCB by 20% to 30%. In cooperation with a flip chip which has an electrode with tin, the process can reduce a process flow of printing a solder paste with no need of using a solder paste printer and manufacturing a steel mesh, thereby improving efficiency.