Silicone Resin Composition for LED Encapsulation
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Solution Overview
Problem
Conventional phenyl-containing silicone resins used for encapsulating LEDs exhibit unsatisfactory resistance to discoloration due to high gas permeability, which can lead to blackening of the lead frame and reduced brightness, and increasing cross-linking density to improve gas permeability results in issues like wire breakage and chip detachment.
Innovation Solution
A silicone resin composition comprising an organopolysiloxane with alkenyl and aryl groups, an organohydrogenpolysiloxane, and an addition reaction catalyst, which forms a cured product with low gas permeability and a small elastic modulus, preventing discoloration and enhancing durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gas permeability of the silicone encapsulating material is high, then the material provides good flexibility and adhesion, but silver sulfide is produced at the silver surface over time causing blackening and reduced LED brightness
Solution Approach 1:
The patent changes the chemical composition parameters of the silicone resin by incorporating specific amounts of phenyl-containing silicone resin (5-50 parts by mass per 100 parts by mass of base silicone resin) and linear phenyl-containing hydrogen oligosiloxane (5-50 parts by mass per 100 parts by mass of base silicone resin). This compositional parameter adjustment reduces gas permeability and improves resistance to discoloration while maintaining the encapsulating material's flexibility and adhesion properties.
Solution Approach 2:
The patent creates a composite silicone resin system by combining multiple components: base silicone resin, phenyl-containing silicone resin, linear phenyl-containing hydrogen oligosiloxane, and crosslinking agents. This composite material approach achieves synergistic effects where the combination provides both low gas permeability (preventing silver sulfide formation) and maintained mechanical flexibility, resolving the contradiction between reliability and harmful gas permeability.
2Reliability
If the cross-linking density of the silicone resin is increased to improve gas permeability resistance, then gas permeability decreases, but the hardness of the cured product becomes too high causing wire breakage or chip detachment
Solution Approach 1:
The patent precisely controls the cross-linking density by limiting the combined content of phenyl-containing silicone resin and linear phenyl-containing hydrogen oligosiloxane to specific ranges (5-50 parts by mass each per 100 parts by mass of base silicone resin). This parameter control achieves sufficient gas permeability resistance while preventing excessive cross-linking that would cause high hardness and mechanical failure. The balanced composition ensures the cured product maintains appropriate flexibility to prevent wire breakage and chip detachment.
Solution Approach 2:
The patent introduces local quality variation through the use of linear phenyl-containing hydrogen oligosiloxane with specific structural characteristics (average degree of polymerization 2-10). This creates localized regions with optimal cross-linking density that provide gas permeability resistance without creating uniformly high hardness throughout the cured product, thereby preventing mechanical damage while maintaining protective function.
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 composition provides a reliable encapsulating material for LEDs with excellent resistance to discoloration and impact, maintaining durability and preventing damage from heat and light loads, while ensuring the LED's brightness is maintained.
Implementation Method 1
a silicone resin composition comprising: (A) 100 parts by mass of an organopolysiloxane containing two or more alkenyl groups within each molecule... (B) 0.4 to 4.0 mols of silicon atom-bonded hydrogen atoms per 1 mol of silicon atom-bonded alkenyl groups... (C) an addition reaction catalyst
Data Source
AI summary
A silicone resin composition that exhibits low gas permeability and is suitable for encapsulating optical semiconductors. The composition includes: (A) an organopolysiloxane having a specific structure containing two or more alkenyl groups, (B) an organohydrogenpolysiloxane composed of two organohydrogenpolysiloxanes having specific structures, in which the mass ratio between the two organohydrogenpolysiloxanes is within a range from 10:90 to 90:10, in an amount that provides 0.4 to 4.0 mols of silicon atom-bonded hydrogen atoms within the component (B) per 1 mol of alkenyl groups within the component (A), and (C) an addition reaction catalyst.