Optical Semiconductor Encapsulant Composition Reducing Surface Tack
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Solution Overview
Problem
Addition-curable silicone rubber compositions used as encapsulants for LEDs suffer from surface tack, leading to issues like dust adhesion and unintended bonding, while hard silicone resins improve shock resistance but are prone to cracking under thermal shock, and existing solutions either inadequately suppress tack or require complex two-layer structures.
Innovation Solution
A composition combining specific linear, branched, and resin organopolysiloxanes with controlled alkenyl and silanol groups, along with a platinum group catalyst and functional organopolysiloxanes, to create a cured product with reduced surface tack and improved adhesion, eliminating the need for a two-layer structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If addition-curable silicone rubber composition is used as encapsulant, then weather resistance and rubber-like properties are improved, but surface tack increases causing dust adhesion and unintended bonding
Solution Approach 1:
The patent changes the chemical composition parameters of the silicone rubber by incorporating specific ratios of linear organopolysiloxane (A1), resin organopolysiloxane (A2), branched organohydrogenpolysiloxane (B1), and cyclic organohydrogenpolysiloxane (B2). This parameter optimization reduces surface tack while preserving weather resistance and rubber-like properties through controlled molecular structure and crosslinking density.
Solution Approach 2:
The patent creates a composite encapsulant material combining multiple types of organopolysiloxanes with different molecular structures (linear, branched, cyclic) and functional groups. This composite approach allows simultaneous achievement of low surface tack, good adhesion, and excellent weather resistance by leveraging the complementary properties of each component.
2Object-generated harmful factors
If hard silicone resin is used to prevent surface tack, then surface tack is reduced, but shock resistance deteriorates and cracking occurs under thermal shock
Solution Approach 1:
The patent optimizes the compositional parameters by controlling the mass ratios of different polysiloxane components, specifically setting A1/A2 within 50/50 to 95/5 and B1/B2 within 50/50 to 90/10. This parameter control ensures the cured product has appropriate hardness to prevent tack while maintaining sufficient flexibility for shock and thermal shock resistance.
Solution Approach 2:
The patent develops a composite system combining rigid resin organopolysiloxane (A2) with flexible linear (A1), branched (B1), and cyclic (B2) organohydrogenpolysiloxanes. This composite structure provides the rigidity needed for tack suppression while the flexible components maintain shock resistance and prevent thermal shock cracking.
3Object-generated harmful factors
If resin is coated onto cured product to suppress tack, then surface tack is reduced, but production process complexity increases and component seepage occurs
Solution Approach 1:
The patent merges the tack suppression function with the base encapsulant material by incorporating resin organopolysiloxane (A2) directly into the silicone rubber composition during the single encapsulation step. This eliminates the need for separate coating processes and multi-layer structures, simplifying production while achieving effective tack suppression.
Solution Approach 2:
The patent creates a universal encapsulant composition that simultaneously provides structural encapsulation, tack suppression, and adhesion enhancement in a single material system. The resin-containing composition serves multiple functions that would otherwise require separate layers or coatings, reducing process complexity.
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 significantly reduces surface tack, enhances thermal shock resistance, and ensures reliable adhesion to silver pads, improving production yield and productivity while withstanding extreme reliability tests.
Implementation Method 1
a platinum group catalyst and functional organopolysiloxanes
Data Source
Figure 1~2
Figure 3~4
AI summary
A composition for encapsulating optical semiconductors. The composition comprises (A) a mixture of a linear alkenyl group-containing organopolysiloxane and an alkenyl group-containing organopolysiloxane resin containing at least one SiO2 unit, (B) a mixture of a linear organohydrogenpolysiloxane containing two or more SiH groups and a branched organohydrogenpolysiloxane that is liquid at 25°C, (C) a platinum group metal catalyst, and (D) a linear or cyclic organopolysiloxane having at least two functional groups selected from the group consisting of alkenyl groups, alkoxysilyl groups and epoxy groups bonded to silicon atoms. A cured product of the composition exhibits dramatically reduced surface tack, and therefore using the composition for encapsulating optical semiconductor elements improves the optical semiconductor device yield.