Textured LED Encapsulant Surface for Light Extraction
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Solution Overview
Problem
Conventional LED packages face challenges in achieving uniform color temperature and efficient light extraction due to total internal reflection (TIR) and non-uniform color distribution, especially in multi-chip configurations, where the refractive index difference between the LED substrate and encapsulant materials limits light escape and results in poor color mixing.
Innovation Solution
A textured encapsulant surface is introduced to reduce TIR and enhance light extraction, achieved through modifying the encapsulant surface with irregular features such as pyramids, spheres, or trenches, which randomize the emission angle and improve color uniformity, using methods like etching, machining, or molding processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a flat encapsulant surface is used, then the manufacturing process is simple, but light extraction efficiency is limited due to total internal reflection
Solution Approach 1:
The patent applies surface curvature by forming hemispherical protrusions on the encapsulant surface. This curvature changes the angle at which light rays strike the encapsulant-air interface, reducing total internal reflection and improving light extraction efficiency. The hemispherical shape is particularly effective as it creates multiple internal reflections that increase the probability of light escape.
Solution Approach 2:
The encapsulant surface is segmented into multiple discrete hemispherical protrusions rather than being flat or continuously curved. This segmentation allows different regions of the surface to handle light at different angles, collectively improving overall light extraction while maintaining manufacturing feasibility through mold-based formation.
2Quantity of substance
If phosphor containing material extends above the cup rim, then the cup can be fully filled, but color uniformity deteriorates due to predominant sideways emitted light
Solution Approach 1:
The hemispherical protrusions on the encapsulant surface redirect light paths, reducing the predominance of sideways emitted light. The curved surfaces refract and reflect light at multiple angles, distributing the emitted light more uniformly across different viewing angles and improving color temperature consistency.
Solution Approach 2:
The encapsulant surface is modified locally with hemispherical protrusions in specific regions rather than being uniformly flat. This local modification creates zones of enhanced light extraction that compensate for the non-uniform light distribution caused by the phosphor material extending above the cup rim.
3Adaptability or versatility
If multiple LED chips are used in a package, then the desired color output can be achieved, but color mixing becomes poor due to non-uniform light distribution
Solution Approach 1:
The hemispherical protrusions create multiple internal reflection paths that mix light from different LED chips more effectively. The curved surfaces refract light at varying angles, causing light rays from multiple chips to overlap and mix more uniformly in the far field, improving overall color consistency.
Solution Approach 2:
The invention adds a vertical dimension to light extraction by creating three-dimensional hemispherical protrusions on the encapsulant surface. This vertical structuring creates additional light paths and reflection angles that enhance color mixing from multiple chips, transforming a two-dimensional light distribution problem into a three-dimensional solution.
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 textured encapsulant surface significantly reduces TIR, enhances light extraction efficiency, and maintains uniform color temperature and mixing in the output profile, even in multi-chip configurations, by redirecting and scattering light effectively.
Implementation Method 1
the refractive index difference between the LED substrate and encapsulant materials limits light escape and results in poor color mixing
Implementation Method 2
A textured encapsulant surface is introduced to reduce TIR and enhance light extraction, achieved through modifying the encapsulant surface with irregular features such as pyramids, spheres, or trenches, which randomize the emission angle and improve color uniformity
Data Source
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AI summary
A packaged LED device having a textured encapsulant (102) that is conformal with a mount surface on which at least one LED chip is (104) disposed. The textured encapsulant, which can be textured using an additive or subtractive process, is applied to the LED either prior to or during packaging. The encapsulant includes at least one textured surface (108) from which light is emitted. The textured surface (108) helps to reduce total internal reflection within the encapsulant, improving the extraction efficiency and the color temperature uniformity of the output profile. Several chips (104) can be mounted beneath a single textured encapsulant (102). A mold having irregular surfaces can be used to form multiple encapsulants over many LEDs simultaneously.