LED Electrode Structure for Accurate Display Mass Transfer Bonding

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Solution Overview

Problem

Conventional methods of transferring light-emitting diodes (LEDs) onto circuit substrates face issues with erroneously transferred or adversely affected LEDs, leading to display defects and difficulty in cleaning up conductive adhesive, which complicates repair processes.

Innovation Solution

The use of a specific electrode structure for LEDs, comprising a first conductive layer with higher adhesion to the semiconductor stack layer than the barrier layer, and a metal layer with a melting point below 260 degrees Celsius, facilitates improved bonding and reduces cracks during the transfer process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a conductive adhesive is formed on the circuit substrate in a large area for mass transfer, then the light-emitting diode can be transferred onto the circuit substrate, but it becomes difficult to clean up the conductive adhesive and complicates repair processes

Engineering Contradiction:

Improvemass transfer capabilityVSAvoidconductive adhesive cleanup difficulty

Core Design Contradiction:

Ease of manufactureVSEase of repair

Solution Approach 1:

The patent extracts the bonding function from a large-area conductive adhesive layer and concentrates it into a small-area metal layer (melting point <260°C) located only at the electrode positions. This allows the conductive adhesive to be removed from the entire substrate surface while retaining bonding capability at critical locations, enabling easy cleanup and simplified repair processes.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent applies local quality by forming the metal layer with low melting point only at specific electrode regions rather than uniformly across the entire circuit substrate. This localized approach provides bonding functionality exactly where needed (at LED electrode positions) while eliminating the need for conductive adhesive in other areas, thus solving the cleanup difficulty.

Inventive Principle:

Principle #3Local quality

2Productivity

If conventional transfer methods are used, then light-emitting diodes can be transferred onto the circuit substrate, but erroneously transferred or adversely affected LEDs occur, preventing normal operation of some pixels

Engineering Contradiction:

Improvetransfer efficiencyVSAvoidtransfer accuracy

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent changes the physical parameter of the bonding material by using a metal layer with melting point below 260°C (such as tin, indium, or their alloys). This low melting point enables precise thermal control during transfer, allowing bonding to occur only at intended locations through localized heating, thereby reducing erroneous transfers and improving transfer accuracy while maintaining high productivity.

Inventive Principle:

Principle #35Parameter changes

3Strength

If the first conductive layer has higher adhesion to the semiconductor stack layer than the barrier layer, then bonding between LED and circuit substrate is improved, but intermetallic compound formation may occur

Engineering Contradiction:

Improvebonding strengthVSAvoidintermetallic compound formation

Core Design Contradiction:

StrengthVSObject-generated harmful factors

Solution Approach 1:

The patent uses a composite electrode structure consisting of multiple layers: a first conductive layer with high adhesion to the semiconductor stack layer, a barrier layer to prevent intermetallic compound formation, and a metal layer with low melting point for bonding. This composite structure combines the advantages of each material layer to achieve strong bonding while preventing harmful intermetallic compound formation.

Inventive Principle:

Principle #40Composite materials

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach enhances the bonding between LEDs and circuit substrates, reducing defects and simplifying the repair process by minimizing intermetallic compound formation and cracks, thus improving display device performance.

Implementation Method 1

The metal layers of one of the light-emitting diodes are eutectically bonded to two of the pads

Methodology Applied

Scientific EffectEutectic bonding:

Implementation Method 2

the barrier layer is formed on the first conductive layer... An adhesion of a material selected for the first conductive layer to the semiconductor stack layer is greater than an adhesion of a material selected for the barrier layer to the semiconductor stack layer

Methodology Applied

Scientific EffectDiffusion barrier: Diffusion Barrier

Data Source

PatentUS20260006961A1Display device

Publication Date: 2026.01.01 AU OPTRONICS CORP

AI summary

A display device includes a circuit substrate and a light-emitting diode. Two electrodes of the light-emitting diode are connected to two pads of the circuit substrate. Each electrode of the light-emitting diode includes a first conductive layer, a barrier layer, and a metal layer. The first conductive layer is connected to a semiconductor stack layer of the light-emitting diode. The barrier layer is electrically connected to the semiconductor stack layer of the light-emitting diode through the first conductive layer. The adhesion of the material selected for the first conductive layer to the semiconductor stack layer is greater than the adhesion of the material selected for the barrier layer to the semiconductor stack layer. The metal layer electrically connects the barrier layer to the corresponding one of the pads. The melting point of the metal layer is lower than 260 degrees Celsius.