Fluid-Encapsulated DUV LED Package for Heat and Light Extraction
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Solution Overview
Problem
Deep ultraviolet (DUV) light-emitting diode (LED) packages face challenges with heat extraction and light trapping due to high-Al-content AlGaN materials, leading to reliability issues and inefficient light extraction, particularly in the UV-C range where TM mode light is trapped within the chip.
Innovation Solution
A DUV LED package design featuring a fluid encapsulate and a rigid lens with a cavity, where the encapsulate is partially or fully filled with a perfluoropolyether (PFPE) oil, providing improved thermal and light extraction efficiency and enhanced reliability by accommodating thermal expansion and reducing the effects of DUV radiation on the encapsulant materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If UV transparent cured polymers (PMMA or PDMS) are used as encapsulates/adhesives for DUV LEDs, then light extraction efficiency is improved, but reliability deteriorates due to decay under DUV radiation
Solution Approach 1:
The patent changes the material parameter from organic UV-transparent polymers (PMMA, PDMS) to inorganic fluoride-based materials (magnesium fluoride, calcium fluoride). This material substitution maintains optical transparency in the DUV range while providing radiation stability, thereby resolving the contradiction between light extraction efficiency and reliability under DUV radiation.
2Illumination intensity
If high-Al-content AlGaN materials are used for DUV LEDs (wavelength < 350 nm), then desired wavelength performance is achieved, but thermal management deteriorates due to severe heat generation
Solution Approach 1:
The patent introduces fluoride-based encapsulate materials (magnesium fluoride, calcium fluoride) as an intermediary between the high-Al-content AlGaN LED chip and the external environment. These materials provide both optical transparency for DUV emission and thermal management capabilities, mediating between the high heat generation of the LED and the need for wavelength performance.
3Illumination intensity
If dome shaped lenses are attached onto LED chips to enhance light extraction, then light extraction efficiency improves, but device complexity increases due to additional components and assembly steps
Solution Approach 1:
The patent merges the lens function with the encapsulate material by forming a dome-shaped fluoride-based encapsulate directly over the LED chip. This integration combines the light extraction enhancement function of the lens with the protective and thermal management functions of the encapsulate, eliminating the need for separate lens components and reducing assembly complexity.
4Illumination intensity
If high-Al-content AlGaN heterostructures are used for DUV LEDs, then desired optical properties are achieved, but electrical performance deteriorates due to large electrical resistivity and strong polarization field
Solution Approach 1:
The fluoride-based encapsulate materials serve as an intermediary that does not interfere with the electrical characteristics of the high-Al-content AlGaN heterostructures. By providing optical transparency and physical protection without electrical interference, these materials enable the LED to achieve desired optical emission properties while managing the inherent electrical resistivity issues through proper material selection and device design.
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 package achieves a light output gain of 1.46 to 1.54 times compared to unpackaged LEDs, with minimal decay over 1008 hours under strong DUV radiation, demonstrating improved reliability and efficiency in light and heat extraction.
Implementation Method 1
improved thermal and light extraction efficiency
Implementation Method 2
light extraction efficiency of DUV LEDs
Data Source
AI summary
An UV or DUV light-emitting diode package includes: a foundation; a first metal layer, a second metal layer, and third metal layer formed on a top surface of the foundation, wherein the first metal layer and the second metal layer are electrically isolated by a first gap, the third metal layer surrounds the first and second metal layers and is electrically isolated from the first and second metal layers by a second gap; a lens attached to the top surface of the foundation, wherein a cavity is formed between the foundation and the lens; a chip disposed in the cavity, wherein an anode of the chip is electrically connected to the first metal layer and a cathode of the chip is electrically connected to the second metal layer; and a fluid encapsulate, wherein the cavity is fully or partially filled with the fluid encapsulate.