Microstructured LED Encapsulant Surface for Light Extraction
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Solution Overview
Problem
Current LED packaging methods using silicone resin encapsulants result in significant light trapping due to high refractive index and total internal reflection, reducing optical efficiency and LED lifespan by generating excess heat.
Innovation Solution
A patterned release film with microstructures is used in the LED packaging process, forming a microstructured surface on the encapsulant that acts as an optical diffuser, allowing for improved light extraction and shaping, reducing reflections and enhancing optical efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silicone resin encapsulant is used for HB-LED packaging, then the LED chip is protected and encapsulated, but light is significantly trapped due to high refractive index and total internal reflection, reducing optical efficiency
Solution Approach 1:
The patent modifies the optical parameters of the encapsulant surface by introducing a microstructure layer with specific refractive index properties and geometric configurations. This layer changes the light propagation parameters at the encapsulant-air interface, reducing total internal reflection and improving light extraction efficiency while maintaining the protective function of the silicone resin encapsulant.
Solution Approach 2:
The patent creates a composite structure consisting of the silicone resin encapsulant combined with a microstructure layer having different optical properties. This composite material system leverages the protective qualities of silicone resin while the microstructure layer component addresses the light trapping issue through its engineered optical characteristics and geometric features.
2Reliability
If silicone resin encapsulant is used for HB-LED packaging, then the LED chip is encapsulated, but excess heat is generated by trapped light, reducing overall LED lifespan
Solution Approach 1:
By introducing the microstructure layer with optimized optical parameters, the system changes the light extraction efficiency, thereby reducing the conversion of trapped light into heat. This parameter modification directly addresses the thermal management issue and extends LED operational lifespan while preserving the encapsulation function.
3Loss of energy
If a patterned release film with microstructures is used, then light extraction is improved by approximately 2.5%, but the manufacturing process becomes more complex
Solution Approach 1:
The microstructure pattern is pre-formed on the release film before the encapsulation process. This preliminary preparation allows the microstructured surface to be transferred to the cured encapsulant without adding complex post-processing steps, thereby improving light extraction while minimizing manufacturing process complexity.
Solution Approach 2:
The release film serves as an intermediary tool that carries the microstructure pattern and transfers it to the encapsulant during the molding process. This intermediary approach simplifies the overall manufacturing by using the release film as a template rather than requiring direct formation of microstructures on the encapsulant itself.
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 microstructured surface increases light extraction by approximately 2.5% and allows for better light distribution, reducing color temperature and extending LED lifespan by minimizing heat generation from trapped light.
Implementation Method 1
the patterned release film forms an optical diffuser on the surface of the cured resin
Implementation Method 2
The trapped light reduces the LED package's optical efficiency as well as its overall life because of the excess heat generated by the undesirably trapped light
Implementation Method 3
The resin is cured in the space between the LED chip and the patterned release film in the cavity
Data Source
AI summary
Encapsulated LEDs can be made by taking a mold tool defining a cavity that defines a lens shape and providing a patterned release film defining the inverse of a microstructure in a surface of the film. The patterned release film is conformed to the cavity of the mold tool. An LED chip is placed in a spaced relationship from the patterned release film in the cavity. A resin is then introduced into the space between the LED chip and the patterned release film in the cavity. The resin is cured in the space between the LED chip and the patterned release film in the cavity while contact is maintained between the patterned release film and the curing resin. The encapsulated LED is then freed from the mold tool and the patterned release film.