LED Encapsulant Composition with High Refractive Index
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Solution Overview
Problem
Conventional encapsulant materials for LEDs face challenges such as low total light extraction efficiency due to refractive index differences between LED chips and encapsulants, poor thermal stress dispersion, and inadequate mechanical properties, leading to reliability issues like wire breaking and delamination, especially in high-powered LEDs.
Innovation Solution
A transparent encapsulant composition comprising a liquid bi-functional epoxy resin with aromatic rings, a bi-functional thiol curing agent containing aromatic rings, and an aliphatic tetra-functional thiol curing agent, along with a catalyst, is developed to enhance refractive index and mechanical properties, balancing hardness between epoxy and silicone resin levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional epoxy resin encapsulant is used, then mechanical strength and hardness are improved, but thermal stress dispersion capability deteriorates
Solution Approach 1:
The patent employs a composite encapsulant material combining epoxy resin with silicone resin or rubber particles. This composite structure integrates the high mechanical strength of epoxy resin with the excellent thermal stress dispersion and flexibility of silicone resin, achieving both hardness and reliability simultaneously without requiring multi-layered packaging structures.
2Reliability
If silicone resin encapsulant is used, then thermal stress dispersion is improved, but refractive index deteriorates
Solution Approach 1:
The patent creates a composite encapsulant where epoxy resin provides high refractive index (1.5-1.7) for efficient light extraction, while dispersed silicone resin or rubber particles provide thermal stress dispersion capability. This composite approach achieves both high refractive index and excellent thermal stress dispersion without requiring multi-layered structures.
3Strength
If high hardness encapsulant is used, then mechanical protection is improved, but stress dispersion deteriorates
Solution Approach 1:
The patent formulates a composite encapsulant with hard epoxy resin matrix providing mechanical protection and soft silicone resin or rubber particles providing stress dispersion. The synergistic combination allows the encapsulant to maintain high hardness for chip protection while simultaneously dispersing thermal and mechanical stresses to prevent wire breaking and delamination.
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 encapsulant composition achieves a refractive index above 1.60, improved thermal stress dispersion, enhanced light extraction efficiency, resistance to yellowing under thermal aging, and passes soldering tests, addressing the limitations of existing materials while maintaining transparency and mechanical integrity.
Implementation Method 1
The encapsulant composition comprises: (a) about 100 parts by weight of at least one liquid bi-functional epoxy resin containing about 40～50 weight % of aromatic ring; (b) about 55～120 parts by weight of a curing agent comprising at least one bi-functional thiol curing agent containing aromatic ring and at least one aliphatic tetra-functional thiol curing agent
Implementation Method 2
The encapsulant composition comprises: (c) about 0.05～0.5 parts by weight of a catalyst
Data Source
AI summary
An encapsulant composition for a light-emitting diode is provided. One embodiment of the encapsulant composition comprises: (a) about 100 parts by weight of at least one liquid bi-functional epoxy resin containing about 40˜50 weight % of aromatic ring; (b) about 55˜120 parts by weight of a curing agent comprising at least one bi-functional thiol curing agent containing aromatic ring and at least one aliphatic tetra-functional thiol curing agent, wherein the curing agent contains about 10˜50 weight % of aromatic ring and about 20˜35 weight % of sulfur; and (c) about 0.05˜0.5 parts by weight of a catalyst. The encapsulant composition having a high refractive index can be used for a solid state light emitting device to enhance light extraction efficiency.