Organic Buffer Pads for LED Thermal Stress Absorption

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Solution Overview

Problem

The mismatch in thermal expansion coefficients between light emitting chip materials and circuit boards leads to significant thermal and internal stresses, causing dislocation between the epitaxial structure and the circuit board, which compromises the structural reliability of light emitting devices.

Innovation Solution

Incorporating organic buffer pads with a Young's modulus of 2-10 GPa between the light emitting diode chips and the receiving substrate, which absorb internal stresses and reduce movement when high stress is applied, thereby preventing dislocation and enhancing structural reliability during thermal bonding.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If light emitting chip is directly bonded to circuit board, then manufacturing process is simple, but thermal stress and internal stress cause dislocation and reduce structural reliability

Engineering Contradiction:

Improvemanufacturing process simplicityVSAvoidstructural reliability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent introduces a buffer pad as an intermediary layer between the light emitting chip and the circuit board. This buffer pad absorbs thermal stress and internal stress generated during thermal bonding, preventing dislocation of the epitaxial structure while maintaining manufacturing simplicity. The buffer pad acts as a mediator that resolves the stress mismatch between the chip and substrate.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The buffer pad is designed with specific mechanical properties (Young's modulus of 2-10 GPa) to provide beforehand cushioning against thermal stress and internal stress. By pre-positioning this stress-absorbing layer before thermal bonding, the patent prevents dislocation from occurring in the first place, thereby improving structural reliability without complicating the manufacturing process.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

2Reliability

If buffer pad with low Young's modulus is used, then stress absorption is improved, but mechanical strength decreases

Engineering Contradiction:

Improvestress absorption capabilityVSAvoidmechanical strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent optimizes the Young's modulus parameter of the buffer pad material to a specific range (2-10 GPa). This parameter change balances the conflicting requirements: the material is soft enough to absorb thermal stress and internal stress effectively, yet maintains sufficient mechanical strength to support the light emitting chip during bonding and operation.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If organic material is used for buffer pad, then stress absorption is enhanced, but thermal conductivity decreases

Engineering Contradiction:

Improvestress absorption capabilityVSAvoidthermal conductivity

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The patent converts the typically harmful effect of low thermal conductivity in organic materials into a beneficial feature. The organic buffer pad material (such as epoxy resin or polyimide) with low thermal conductivity reduces heat transfer to the substrate, minimizing thermal stress generation while maintaining excellent stress absorption capability. This transforms the material's thermal insulation property from a disadvantage into an advantage for stress management.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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

The use of organic buffer pads effectively absorbs internal stresses and reduces dislocation between the epitaxial structure and the receiving substrate, improving the structural reliability and reliability of the light emitting device during thermal bonding processes.

Implementation Method 1

the buffer pads are with Young's modulus of 2 ̃10 GPa... absorb internal stresses and reduce movement when high stress is applied

Methodology Applied

Scientific EffectStress absorption: Absorption (physical)

Implementation Method 2

absorb internal stresses and reduce movement when high stress is applied, thereby preventing dislocation

Methodology Applied

Scientific EffectMechanical constraint:

Data Source

PatentUS10593658B2Light emitting device and method of forming the same

Publication Date: 2020.03.17 PLAYNITRIDE DISPLAY CO LTD

AI summary

A method of forming a light emitting device is provided. A carrier with a plurality of buffer pads and a plurality of light emitting diode chips is provided, wherein the buffer pads are disposed between the carrier and the light emitting diode chips and are with Young's modulus of 2˜10 GPa. The carrier is positioned over a receiving substrate. A thermal bonding process is performed to electrically connect the light emitting diode chips to the receiving substrate, and wherein the buffer pads and the receiving substrate are located at opposite sides of each light emitting diode chip.