Conformable Pickup Head for Micro-LED Transfer

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Solution Overview

Problem

The challenge in semiconductor device fabrication, specifically in LED display manufacturing, is the difficulty in picking and placing micro-LEDs of varying colors onto target substrates without damaging them, due to their decreasing form factor and the need for precise alignment and bonding.

Innovation Solution

A pickup assembly with a conformable layer on its pickup head, made of material with a coefficient of thermal expansion matching that of the LED, is used to attach, move, and bond micro-LEDs from a temporary substrate to a target substrate, utilizing thermal expansion to align and secure the LEDs onto the target substrate.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If a rigid pickup head is used to pick and place micro-LEDs, then the structural stability is improved, but the risk of damaging the micro-LEDs increases due to mismatched thermal expansion

Engineering Contradiction:

Improvestructural stabilityVSAvoidrisk of damaging micro-LEDs

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

A conformable layer is applied to the pickup head, allowing it to adapt to the micro-LED surface while maintaining structural integrity. This flexible interface reduces stress concentration and prevents damage during pick and place operations.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The pickup head is constructed with materials having matched coefficients of thermal expansion to the micro-LEDs. This homogeneity in thermal response prevents differential expansion/contraction that would otherwise cause mechanical stress and potential damage to the fragile micro-LED structures.

Inventive Principle:

Principle #33Homogeneity

2Manufacturing precision

If the form factor of LEDs is decreased to achieve higher display resolution, then the display quality is improved, but the difficulty of picking and placing without damage increases

Engineering Contradiction:

Improvedisplay resolutionVSAvoiddifficulty of picking and placing

Core Design Contradiction:

Manufacturing precisionVSEase of operation

Solution Approach 1:

The conformable layer on the pickup head provides a compliant interface that can adapt to the reduced form factor of micro-LEDs, enabling reliable grasping and transfer of these increasingly small and fragile components without causing mechanical damage.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The pickup head material composition is specifically selected to match the thermal expansion characteristics of micro-LEDs. This parameter matching ensures that during temperature variations in the manufacturing process, the pickup head and micro-LED expand and contract together, preventing damage to the smaller, more vulnerable micro-LED structures.

Inventive Principle:

Principle #35Parameter changes

3Strength

If thermal expansion is used for bonding LEDs to the target substrate, then the bonding strength is improved, but the alignment precision may deteriorate due to thermal distortion

Engineering Contradiction:

Improvebonding strengthVSAvoidalignment precision

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

By using materials with matched thermal expansion coefficients throughout the pickup head assembly, the system minimizes differential thermal distortion during the heating process. This homogeneity allows thermal bonding to proceed with maintained alignment precision, as all components expand uniformly rather than distorting relative to each other.

Inventive Principle:

Principle #33Homogeneity

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 precise placement and bonding of micro-LEDs onto target substrates with reduced risk of damage, ensuring accurate alignment and efficient transfer, facilitating the assembly of electronic displays.

Implementation Method 1

The pickup head is made of a material having a coefficient of thermal expansion substantially identical to a coefficient of thermal expansion of a body of the LED

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

The conformable layer is placed at an end of a pickup head on a top surface of a light emitting diode (LED) placed on a temporary substrate. The LED attaches to the conformable layer.

Methodology Applied

Scientific EffectAdhesion: Adhesive

Implementation Method 3

An electrode of the LED is bonded to a corresponding electrical contact pad of the target substrate by increasing the temperature of the electrode and the corresponding pad

Methodology Applied

Scientific EffectThermal bonding: Diffusion Welding

Data Source

PatentUS10818643B1Rigid pickup head with conformable layer

Publication Date: 2020.10.27 META PLATFORMS TECHNOLOGIES LLC

AI summary

Embodiments relate to using a pickup assembly to place light emitting diodes (LEDs) onto an electronic display substrate after fabrication of the LEDs. An LED assembly system places LEDs on a temporary substrate after fabrication. Pickup heads of the pickup assembly are coated with a conformable material to enable attachment of each LED to a pickup head. The pickup head removes the LEDs away from the temporary substrate and aligns the LEDs onto a target substrate. The LED assembly system provides heat to an electrode of the LEDs and a corresponding electrical contact pad of the target substrate. The pickup assembly applies force to the LED on the target substrate, such that with the heat, the electrode of the LED and the electrical contact pad are bonded. The pickup assembly releases the LED onto the target substrate.