Beveled Reflector for CSP LED Light Extraction
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Solution Overview
Problem
Chip-scale packaging (CSP) LEDs face issues with light extraction efficiency, spatial color uniformity, heat dissipation, and tunable viewing angles due to their compact size and vertically flat reflector design, leading to optical energy loss and limited application flexibility.
Innovation Solution
A light emitting device with a photoluminescent structure having a beveled edge surface and a reflective material surrounding the vertical and beveled edges, forming a beveled reflector to enhance light extraction and adjust the viewing angle, while maintaining a compact size and improving heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a vertically flat reflector design is used in CSP LEDs, then the package size is reduced and manufacturing is simplified, but light extraction efficiency decreases due to total internal reflection trapping light within the photoluminescent structure
Solution Approach 1:
The reflector surface is changed from a vertically flat symmetric design to an asymmetric design with specific angled surfaces. The reflector includes a first reflective surface with a first angle and a second reflective surface with a second angle, creating asymmetric light redirection paths that prevent total internal reflection and improve light extraction efficiency while maintaining compact packaging
Solution Approach 2:
The reflector geometry parameters are optimized by specifying precise angle ranges (first angle between 30-60 degrees, second angle between 60-85 degrees). These parameter changes transform the light propagation characteristics within the photoluminescent structure, enabling efficient light extraction without increasing package volume
2Ease of manufacture
If a vertically flat reflector design is used in CSP LEDs, then manufacturing is simplified, but spatial color uniformity deteriorates due to variations in optical path lengths
Solution Approach 1:
The asymmetric reflector configuration with specifically angled surfaces creates more uniform optical path lengths for different light emitting angles. This asymmetry compensates for the variations that would otherwise cause color non-uniformity, while the manufacturing process remains relatively simple through conventional semiconductor fabrication techniques
Solution Approach 2:
Different regions of the reflector are designed with different angles (first angle vs. second angle) to locally optimize light extraction for specific angular ranges. This local quality variation ensures uniform color distribution across the emitted light while maintaining manufacturing feasibility
3Device complexity
If a vertically flat reflector design is used in CSP LEDs, then the structure is simplified, but viewing angle control is limited and cannot be tuned for different applications
Solution Approach 1:
The reflector design enables dynamic control of viewing angles through adjustable angle parameters. By varying the first angle (30-60 degrees) and second angle (60-85 degrees), the light extraction characteristics and viewing cone can be tuned for different applications without changing the fundamental device structure or adding complex components
Solution Approach 2:
The viewing angle is controlled by changing the geometric parameters of the reflector surfaces. Specific angle ranges are specified to achieve different viewing angle characteristics, allowing the same device structure to be adapted for various applications by simply adjusting these fabrication parameters
4Volume of moving object
If light is reflected back into the photoluminescent structure by vertically flat side-reflector, then the package structure is compact, but optical energy is lost through absorption by the LED semiconductor die
Solution Approach 1:
The asymmetric reflector design with angled surfaces redirects light away from the LED semiconductor die, preventing absorption losses. The specific angle configuration ensures that reflected light exits the photoluminescent structure efficiently rather than being trapped and absorbed, maintaining compact packaging while reducing energy loss
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 beveled reflector design improves light extraction efficiency by 5-20% and achieves better spatial color uniformity, reduces thermal resistance, and allows for tunable viewing angles, making the CSP-type LEDs more efficient and versatile for various applications.
Implementation Method 1
A reflective material is disposed surrounding the vertical edge surfaces of the LED semiconductor die and the beveled edge surfaces of the photoluminescent structure, forming a beveled reflector
Implementation Method 2
a photoluminescent structure disposed on top of the LED semiconductor die
Data Source
AI summary
A light emitting device, including an LED semiconductor die, a photoluminescent structure and a reflector, is disclosed. The photoluminescent structure with a beveled edge surface is disposed on top of the LED semiconductor die, wherein a lower surface of the photoluminescent structure adheres to an upper surface of the LED semiconductor die. A reflective resin material is disposed surrounding edge surfaces of the LED semiconductor die and the photoluminescent structure forming a beveled reflector. A method to manufacture the above light emitting device is also disclosed. Advantages of this light emitting device with beveled reflector include increasing the light extraction efficiency, making the viewing angle tunable, improving spatial color uniformity and reducing the light source etendue realized in a compact form-factor size.