LED Package Multilayer Insulation Mitigates Thermal Stress

Solution Overview

Problem

Conventional light emitting device packages face destruction due to differences in coefficients of thermal expansion between stacked layers, leading to residual stress and potential layer destruction during flip-chip bonding.

Innovation Solution

A light emitting device package design featuring a multilayer insulation structure with alternating layers of different thermal expansion materials, including a Distributed Bragg Reflector (DBR), to mitigate thermal stress and enhance adhesion between layers, while also incorporating a reflective contact layer to improve light reflectance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If multiple layers with different coefficients of thermal expansion are stacked together, then the device can achieve required functional performance, but thermal stress causes layer destruction and reliability degradation

Engineering Contradiction:

Improvepackage reliabilityVSAvoidlayer adhesion strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent changes the material parameters of the insulation layer by selecting a material whose coefficient of thermal expansion is specifically matched to be between those of the substrate and the upper layer. This parameter matching resolves the thermal expansion mismatch problem, reducing thermal stress and preventing layer destruction while maintaining package reliability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs a composite layer structure consisting of substrate, light emitting device, insulation layer, and upper layer. The insulation layer acts as an intermediate composite material that bridges the thermal expansion properties between the substrate and upper layer, reducing interfacial stress and improving overall package reliability

Inventive Principle:

Principle #40Composite materials

2Device complexity

If a single-layer insulation structure is used, then the device complexity is reduced, but thermal stress concentration leads to layer destruction

Engineering Contradiction:

Improveinsulation structure complexityVSAvoidlayer stability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

Rather than complicating the structure with multiple insulation layers, the patent simplifies the design by using a single insulation layer with specifically selected material parameters. The coefficient of thermal expansion of this single layer is chosen to be intermediate between the substrate and upper layer, effectively distributing thermal stress without requiring complex multilayer insulation structures

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If layers with large coefficient of thermal expansion difference are stacked, then manufacturing flexibility is improved, but residual stress causes layer destruction during flip-chip bonding

Engineering Contradiction:

Improvemanufacturing flexibilityVSAvoidlayer integrity during bonding

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent addresses the manufacturing issue by changing the thermal expansion parameter of the insulation layer. By selecting a material with intermediate thermal expansion properties, the patent reduces residual stress during thermal processing and flip-chip bonding operations, ensuring layer integrity while maintaining manufacturing flexibility

Inventive Principle:

Principle #35Parameter changes

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 multilayer insulation structure reduces the risk of layer destruction from thermal stress, enhances adhesion, and increases reflectance, resulting in improved reliability and performance of the light emitting device package.

Implementation Method 1

A light emitting device package design featuring a multilayer insulation structure with alternating layers of different thermal expansion materials, including a Distributed Bragg Reflector (DBR), to mitigate thermal stress and enhance adhesion between layers

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

A light emitting device package design featuring a multilayer insulation structure with alternating layers of different thermal expansion materials, including a Distributed Bragg Reflector (DBR), to mitigate thermal stress and enhance adhesion between layers, while also incorporating a reflective contact layer to improve light reflectance

Methodology Applied

Scientific EffectBragg diffraction: Bragg Diffraction

Data Source

PatentUS9559264B2Light emitting device package and light emitting apparatus including the package

Publication Date: 2017.01.31 SUZHOU LEKIN SEMICON CO LTD

AI summary

A light emitting device may include a substrate, a light emitting structure disposed under the substrate, the light emitting structure including a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer, a first electrode configured to penetrate the second conductive semiconductor layer and the active layer, so as to come into contact with the first conductive semiconductor layer, a contact layer configured to come into contact with the second conductive semiconductor layer, a first insulation layer disposed between the second conductive semiconductor layer and the first electrode and between the active layer and the first electrode, the first insulation layer being provided for capping of a side portion and an upper portion of the contact layer, and a second electrode configured to penetrate the first insulation layer, so as to come into contact with the contact layer.