Micro-led module and method for fabricating the same

Patent metadata

Field	Value
Publication number	US-2020388596-A1
Application number	US-201916524790-A
Country	US
Kind code	A1
Filing date	Jul 29, 2019
Priority date	Dec 23, 2016
Publication date	Dec 10, 2020
Grant date	—

Abstract

A micro-LED module is disclosed. The micro-LED module includes: a micro-LED including a plurality of LED cells, each of which includes a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer; a submount substrate mounted with the micro-LED; a plurality of electrode pads formed on the micro-LED cells; a plurality of electrodes formed corresponding to the plurality of electrode pads on the submount substrate; a plurality of connection members through which the plurality of electrode pads are connected to the corresponding plurality of electrodes; and a gap fill layer formed in the gap between the micro-LED and the submount substrate and having a bonding strength to the micro-LED and the submount substrate.

First claim

What is claimed is:

1 . A method for fabricating a micro-LED module, comprising:
forming a plurality of pillar bumps, each of which comprises a pillar and a hemispherical solder cap formed on one end of the pillar, on an active matrix substrate; preparing a micro-LED comprising a plurality of LED cells corresponding to the plurality of pillar bumps; and flip-bonding the micro-LED to the active matrix substrate, wherein the flip-bonding comprises reducing the interval between the pillar and an electrode pad of the LED cell to a first distance such that the solder cap is compressed in a semi-molten state and increasing the interval between the pillar and the electrode pad from the first distance to a second distance larger than the first distance such that the solder cap is extended in a semi-molten state.

2 . The method according to claim 1 , wherein the solder cap is compressed such that the first distance is reduced to less than half of the height of the solder cap.

3 . The method according to claim 1 , wherein the solder cap is extended such that the second distance is larger than half of the height of the solder cap.

4 . The method according to claim 1 , wherein the formation of pillar bumps comprises:
preparing an active matrix substrate comprising a substrate material, a plurality of electrode pads formed on the substrate material, and an insulating layer having openings through which the individual electrode pads are exposed; forming a UBM on the active matrix substrate to cover the insulating layer and the electrode pads; forming pillars on the UBM by plating; forming solder caps with a predetermined thickness on the pillars; and heating and melting the solder caps by reflow such that the solder caps are made hemispherical.

5 . The method according to claim 4 , wherein the formation of pillar bumps comprises forming a photosensitive PR to cover the UBM, placing a mask pattern on the PR, and applying light to form openings through which only areas of the UBM formed directly on the electrode pads are exposed (photolithography) between the UBM formation and the pillar plating; and the pillars are formed by plating through the openings.

6 . The method according to claim 5 , wherein the formation of pillar bumps further comprises removing the PR to expose the side surfaces of the pillars and the solder caps and removing portions of the UBM other than the portions of the UBM located directly under the pillars by etching after formation of the solder caps.

7 . The method according to claim 6 , wherein the method comprises washing the active matrix substrate before the UBM formation (first washing), washing the active matrix substrate between the UBM etching and the reflow (second washing), and washing the active matrix substrate after the reflow (third washing).

8 . The method according to claim 1 , wherein the pillar bumps are formed such that the intervals between the plurality of pillars in the widthwise and lengthwise directions are the same as the diameter of the pillars.

9 . The method according to claim 1 , wherein the pillar bumps are formed such that the height of the pillars exceeds 1.5 times that of the solder caps.

10 . The method according to claim 1 , wherein each of the plurality of LED cells of the micro-LED comprises an n-type semiconductor layer, an active layer, and a p-type semiconductor layer, the electrode pad is a p-type electrode pad formed on the p-type semiconductor layer, an exposed area of the n-type semiconductor layer is formed at the periphery surrounding the plurality of LED cells, and an n-type electrode pad is formed in the exposed area of the n-type semiconductor layer.

11 . A micro-LED module, comprising:
electrode pads formed in a micro-LED; pillars formed corresponding to the electrode pads on an active matrix substrate; and solder bonding portions bonding the pillars to the corresponding electrode pads, wherein the maximum cross-sectional diameter of each of the solder bonding portions is larger than the diameter of the corresponding Cu pillar and the minimum cross-sectional diameter of the solder bonding portion is larger by 80-100% than the diameter of the Cu pillar.

12 . The micro-LED module according to claim 11 , wherein the portion having the maximum cross-sectional diameter is located at a contact position with the side surface of the end of the pillar or the corresponding electrode pad.

13 . The micro-LED module according to claim 11 , wherein the portion having the minimum cross-sectional diameter is located at the midpoint of the height of the solder bonding portion.

14 . The micro-LED module according to claim 11 , wherein the solder bonding portions are formed by compressing solder caps, each of which is formed at one end of the corresponding pillar, in a semi-molten state between the pillars and the electrode pads to a first distance, followed by extension to a second distance larger than the first distance.

15 . The micro-LED module according to claim 14 , wherein each of the solder caps is compressed such that the first distance is reduced to less than half of the height of the solder cap.

16 . The micro-LED module according to claim 14 , wherein each of the solder caps is extended such that the second distance is larger than half of the height of the solder cap.

17 . The micro-LED module according to claim 14 , wherein the height of the pillars is at least 1.5 times larger than the height of the solder caps.

18 . A micro-LED module, comprising:
electrode pads formed in a micro-LED; pillars formed corresponding to the electrode pads on an active matrix substrate; and solder bonding portions bonding the pillars to the corresponding electrode pads, wherein the solder bonding portions are formed by compressing solder caps in a semi-molten state, followed by extension, each of the solder bonding portions comprises a first portion adjacent to the micro-LED, a second portion adjacent to the active matrix substrate, and a third portion formed between the first portion and the second portion and whose cross-sectional area is smaller than those of the first and second portions, and the third portion is more dilute than the first and second portions.

19 . The micro-LED module according to claim 18 , wherein each of the solder caps is compressed to less than half its original height.

20 . The micro-LED module according to claim 18 , wherein each of the solder caps is extended to more than half its original height.

Assignees

• Lumens Co Ltd

Inventors

• Kim Daewon
• Shin Eunsung
• Moon Myungji
• Chang Hanbeet
• Kim Yongpil
• Park Jaesoon

Classifications

• H10P14/40

  of conductive or resistive materials · CPC title

• H10W72/077

  Connecting of TAB connectors · CPC title

• H10W72/222

  Multilayered bumps, e.g. a coating on top and side surfaces of a bump core · CPC title

• H10W72/012

  of bump connectors, dummy bumps or thermal bumps · CPC title

• H10W90/00 Primary

  Package configurations · CPC title