Partial Laser Liftoff for High-Yield LED Transfer

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Solution Overview

Problem

It is challenging to attach different color LEDs to the same backplane of a display device with high yield, as existing methods face difficulties in efficiently transferring and bonding LEDs with minimal damage to the fragile components.

Innovation Solution

A method employing partial laser liftoff and bonding, where gallium-rich material portions are created on the LEDs, allowing for selective transfer and bonding to a backplane using localized laser irradiation, reducing mechanical shock and enabling efficient attachment of multiple color LEDs without damaging the backplane.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional mechanical transfer methods are used to attach LEDs to the backplane, then the bonding process is simple and direct, but the mechanical stress damages the fragile LED components and reduces yield

Engineering Contradiction:

ImproveLED attachment yieldVSAvoidmechanical stress on LED

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent replaces traditional mechanical transfer methods with a laser-based transfer system. A laser beam is used to locally melt and evaporate material at the LED bonding interface, enabling stress-free attachment of fragile LED components to the backplane without mechanical contact or stress

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent utilizes phase transitions of material (solid to liquid to vapor) through controlled laser heating. The laser beam locally melts and evaporates bonding material or substrate material at the LED interface, enabling transfer and attachment while avoiding mechanical stress that would damage the LED

Inventive Principle:

Principle #36Phase transitions

2Manufacturing precision

If selective laser liftoff is performed to enable precise LED transfer, then transfer precision is improved, but the process complexity increases

Engineering Contradiction:

ImproveLED transfer precisionVSAvoidtransfer process complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent extracts only the necessary LED portions for transfer by using laser liftoff to selectively remove and transfer specific LED regions to the backplane. This enables precise placement while avoiding the need to handle or transfer entire LED structures, simplifying the overall transfer process despite the added laser step

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent performs preliminary laser liftoff processing on the LED structure before transfer, preparing the LED for precise attachment to the backplane. This preliminary action creates a ready-to-transfer state that simplifies the subsequent bonding process and improves overall transfer precision

Inventive Principle:

Principle #10Preliminary action

3Manufacturing precision

If laser bonding is used to attach LEDs to the backplane, then bonding precision is improved, but the energy consumption and process time increase

Engineering Contradiction:

Improvebonding precisionVSAvoidbonding process time

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The patent uses periodic or pulsed laser action for bonding LEDs to the backplane. By delivering laser energy in controlled pulses rather than continuous exposure, the process achieves precise bonding while minimizing total energy input and process time, balancing precision with efficiency

Inventive Principle:

Principle #19Periodic action

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 method enables high-yield attachment of different color LEDs to a backplane with reduced mechanical stress on the components, ensuring efficient bonding and minimizing damage to the backplane, thereby improving the manufacturing process for display devices.

Implementation Method 1

performing a partial laser liftoff of the first light emitting diode from the first substrate, laser bonding the first light emitting diode to the backplane

Methodology Applied

Scientific EffectLaser heating: Laser

Implementation Method 2

a gallium-rich material portion located on a surface of the first conductivity type semiconductor layer and including gallium at an atomic concentration greater than 55%

Methodology Applied

Scientific EffectMelting: Melting

Data Source

PatentUS11605754B2Partial laser liftoff process during die transfer and structures formed by the same

Publication Date: 2023.03.14 SAMSUNG ELECTRONICS CO LTD

AI summary

A transfer method includes providing a first light emitting diode on a first substrate, performing a partial laser liftoff of the first light emitting diode from the first substrate, laser bonding the first light emitting diode to the backplane after performing the partial laser liftoff, and separating the first substrate from the first light emitting diode after the laser bonding.