LED Bonding Pad Structure for Precise Stretchable Display Transfer

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing display devices face issues with misalignment and defects during the transfer and bonding of light emitting diodes (LEDs) due to non-uniform adhesive layers and conductive balls, leading to tearing, short circuits, and reduced transfer efficiency.

Innovation Solution

A stretchable display device design featuring a multilayer structure for connection pads and an adhesive layer covering the entire upper surface of a planarization layer, with conductive balls spaced apart to prevent short circuits and ensure proper LED placement, simplifying the manufacturing process and reducing defects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If a conventional bonding process is used to transfer and bond LEDs to a pixel substrate, then the manufacturing process is simple, but misalignment and defects occur due to non-uniform adhesive layers and conductive balls

Engineering Contradiction:

ImproveLED alignment precisionVSAvoidbonding process complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The adhesive layer is applied to the entire upper surface of the planarization layer before LED transfer, creating a uniform bonding surface in advance. This preliminary action ensures consistent adhesive distribution and prevents misalignment during the bonding process, directly improving manufacturing precision without significantly increasing process complexity

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the physical state and distribution parameters of the adhesive layer from non-uniform to uniform coverage across the entire planarization layer. This parameter change ensures consistent bonding force distribution, preventing LED misalignment and defects while maintaining a relatively simple bonding process

Inventive Principle:

Principle #35Parameter changes

2Reliability

If adhesive layer is applied only at specific locations, then the manufacturing process is simpler, but non-uniform distribution causes misalignment and defects

Engineering Contradiction:

Improvebonding reliabilityVSAvoidmanufacturing complexity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The adhesive layer serves multiple functions simultaneously: it provides bonding force, ensures uniform distribution across the entire planarization layer, and prevents misalignment. This multi-functional approach improves bonding reliability while the standardized application process keeps manufacturing complexity manageable

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The adhesive layer is applied uniformly across the entire upper surface of the planarization layer, ensuring homogeneous distribution. This homogeneity prevents localized bonding issues, misalignment, and defects, significantly improving bonding reliability while using a straightforward application method

Inventive Principle:

Principle #33Homogeneity

3Reliability

If conductive balls are densely packed in adhesive layer, then electrical connection is improved, but short circuits occur due to non-uniform distribution

Engineering Contradiction:

Improveelectrical connection reliabilityVSAvoidconductive ball placement precision

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent applies local quality by spacing conductive balls at specific intervals within the adhesive layer rather than dense packing. This localized distribution ensures adequate electrical connection while preventing short circuits, improving both electrical connection reliability and placement precision through controlled spacing

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The adhesive layer acts as an intermediary medium that distributes conductive balls at controlled intervals. This intermediary role ensures uniform spacing, prevents direct contact between conductive balls (avoiding short circuits), while maintaining reliable electrical connections through the adhesive matrix

Inventive Principle:

Principle #24Intermediary (Mediator)

4Productivity

If adhesive layer is applied selectively at specific positions, then material usage is reduced, but transfer efficiency decreases due to non-uniform placement

Engineering Contradiction:

ImproveLED transfer efficiencyVSAvoidadhesive material quantity

Core Design Contradiction:

ProductivityVSQuantity of substance

Solution Approach 1:

The adhesive layer is applied preliminarily to the entire planarization layer before LED transfer, ensuring uniform availability of bonding material. This preliminary uniform application improves transfer efficiency by preventing misalignment, while the thin-layer approach minimizes adhesive material usage

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS20240405183A1Display device

Publication Date: 2024.12.05 LG DISPLAY CO LTD

AI summary

According to an aspect of the present disclosure, the display device includes a lower substrate and a plurality of pixel substrates disposed on the lower substrate. The display device also includes a plurality of transistors disposed on the plurality of pixel substrates and a planarization layer disposed on the plurality of pixel substrates to cover upper portions of the plurality of transistors. The display device further includes a plurality of individual connection pads and a common connection pad disposed on the planarization layer. The display device also includes a plurality of light emitting diodes disposed on the plurality of individual connection pads and the common connection pad. At least one of the plurality of individual connection pads and the common connection pad may have a multilayer structure.