Silicon UV LED Package With Index-Matched Cavity Reflector
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Solution Overview
Problem
Flip-chip UV LED packages face significant light loss due to scattering and Fresnel losses at the rough laser-cut surfaces of sapphire substrates, which limits the extraction efficiency and beam divergence of UV light.
Innovation Solution
The use of an index-matching material around the laser-cut sapphire area and a silicon reflector with an aluminum coating minimizes scattering and Fresnel losses by reducing the refractive index difference and filling the cavity between the sapphire substrate and the silicon reflector, optimizing the placement of the reflector to enhance light transmission and emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If laser scribing is used to cut sapphire substrate, then manufacturing process is simplified, but scattering loss and Fresnel loss increase significantly
Solution Approach 1:
The patent introduces an index-matching material as an intermediary substance between the rough laser-cut sapphire surfaces. This material has a refractive index that matches both sapphire surfaces, eliminating the optical interface and preventing light scattering and Fresnel losses while maintaining the simplicity of the laser scribing manufacturing process
Solution Approach 2:
The patent changes the optical parameter (refractive index) by filling the cavity with index-matching material. This parameter change eliminates the refractive index mismatch at the rough surfaces, thereby reducing scattering and Fresnel losses without requiring additional manufacturing steps
2Manufacturing precision
If separation gap between cover and light source is increased, then assembly tolerance is improved, but beam divergence increases and light extraction efficiency decreases
Solution Approach 1:
The patent changes the optical parameter by introducing index-matching material in the separation gap. This allows the gap to serve dual purposes: providing mechanical assembly tolerance while simultaneously maintaining optimal optical coupling to prevent beam divergence and preserve light extraction efficiency
3Productivity
If flip-chip configuration is used, then production yield is improved and process is simplified, but scattering loss at base substrate interface increases
Solution Approach 1:
The patent uses index-matching material as an intermediary to eliminate the rough interface between the flip-chip LED and the base substrate. This mediator removes the scattering problem inherent in the flip-chip configuration while preserving its manufacturing advantages
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
This approach increases UV light extraction by 30 to 40% and improves beam divergence from 120 degrees to 80 degrees, significantly reducing thermal heating and absorption losses, while maintaining a cost-effective manufacturing process.
Implementation Method 1
The use of an index-matching material around the laser-cut sapphire area and a silicon reflector with an aluminum coating minimizes scattering and Fresnel losses by reducing the refractive index difference
Implementation Method 2
a silicon reflector with an aluminum coating minimizes scattering and Fresnel losses by reducing the refractive index difference and filling the cavity between the sapphire substrate and the silicon reflector, optimizing the placement of the reflector to enhance light transmission and emission
Data Source
AI summary
A flip-chip package includes a light source, a silicon base plate, a silicon reflector, and a cover. The light source includes a piece of Light-Emitting Diode (LED) in flip-chip configuration. The silicon base plate includes a piece of silicon with electrical pads to bond the light source, two etched, square, via-holes to provide electrical connection to the bottom of the silicon base plate, and filling port for liquid epoxy. The silicon reflector includes a chemically etched silicon piece to form an angled reflector where the light radiation from the light source reflects on the surface of the angled reflector and a recess forms on the top surface of the silicon reflector. The cover includes a piece of window material that transmits the light radiation of the light source.