LED Package Recess Geometry for Light Extraction
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Solution Overview
Problem
Conventional light emitting diode (LED) packages suffer from reduced external light output due to internal reflection and absorption, as they are typically designed with assumptions that the white plastic material is a true Lambertian reflector, which is not accurate, leading to inefficient light emission.
Innovation Solution
The design of the LED package is modified to include a recess with specific geometry, such as angles greater than 3° between side walls and 40° between end walls, which enhances light output by reducing multiple reflections and optimizing the emission profile, and using a resin package with a reflective structure that complements the emission field of the chip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional LED packages use white plastic material assumed to be a true Lambertian reflector, then manufacturing is simplified, but light output efficiency deteriorates due to inaccurate reflection assumptions causing internal reflection and absorption
Solution Approach 1:
The patent changes the geometric parameters of the package cavity, specifically setting the sidewall angle between 85-95 degrees and endwall angle between 30-60 degrees, to optimize light extraction efficiency while maintaining manufacturing feasibility
Solution Approach 2:
Instead of assuming the package material is a perfect Lambertian reflector and designing around that assumption, the patent inverts the approach by designing the cavity geometry to compensate for the non-ideal reflection characteristics of white plastic material, thereby improving light output
2Loss of energy
If the package cavity has steep sidewalls and narrow angles, then light extraction efficiency improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies optimized angle ranges (sidewall: 85-95 degrees, endwall: 30-60 degrees) that balance light extraction efficiency with manufacturability, avoiding excessively narrow angles that would be difficult to produce while still improving performance
3Loss of energy
If multiple reflections occur within the package cavity, then light is trapped internally, but increasing cavity size to reduce reflections increases package volume
Solution Approach 1:
The patent employs curved reflective surfaces on the cavity walls, specifically with the sidewalls having a radius of curvature between 0.5-2.0 mm and endwalls with 0.3-1.5 mm, to redirect light efficiently toward the exit without requiring a large cavity volume
Solution Approach 2:
The patent uses curved surfaces that operate in multiple dimensions to redirect light paths, effectively reducing the number of reflections needed to extract light without increasing the linear dimensions of the package
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 the overall light output of the LED lamp by directing light more effectively outside the package, improving the efficiency of light emission and reducing dark spots, while also allowing for easier chip placement and alignment during manufacturing.
Implementation Method 1
Conventional light emitting diode (LED) packages suffer from reduced external light output due to internal reflection and absorption
Data Source
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AI summary
A light emitting diode lamp is disclosed that includes a resin package that defines a recess in the shape of a solid polygon or another three-dimensional solid. The recess includes a floor, two side walls along the respective longer sides of the floor, and two end walls along the respective shorter sides of the floor. The two side walls define an angle therebetween greater than 3°, and the two end walls define an angle therebetween greater than 40°. A light emitting diode chip is positioned on the rectangular floor of the package.