Flip-Chip LED with Polygonal Substrate for Wide Beam Angle
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Solution Overview
Problem
Conventional flip-chip type light emitting diodes have limited beam angles, which restrict their application in lighting applications requiring wide area irradiation, such as backlight units and sheet-lighting apparatuses, and they often require additional lenses or molding members to enhance beam angle, which complicates packaging and increases light loss.
Innovation Solution
A flip-chip type light emitting diode design with a substrate thickness of 225 μm to 400 μm and a polygonal shape including acute angles, featuring a current spreading layer and reflective electrodes, allows for improved light extraction efficiency and adjustable beam angles without the need for external lenses, enabling wider beam angles of 140° or more.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a conventional flip-chip type LED is used, then heat dissipation efficiency is improved, but beam angle is limited to about 120°
Solution Approach 1:
The patent applies asymmetry by creating different beam angles in different directions through the polygonal substrate shape with acute angles. The LED emits light with different beam angles depending on the direction, achieving asymmetric beam distribution without requiring additional optical components. This resolves the contradiction by maintaining the flip-chip heat dissipation structure while achieving wider effective beam angles through directional light emission patterns.
Solution Approach 2:
The patent changes the physical parameter of substrate thickness to 225-400 μm, which is thicker than conventional LEDs. This parameter change affects light extraction and beam angle characteristics, enabling wider beam angles while maintaining the flip-chip configuration for improved heat dissipation. The thickness parameter optimization allows the device to achieve both good thermal management and wider light distribution.
2Shape
If a molding member or secondary lens is added to increase beam angle, then beam angle is improved, but device complexity and light loss increase
Solution Approach 1:
The patent extracts and eliminates the need for external molding members or secondary lenses by achieving the desired beam angle characteristics through the LED structure itself. The polygonal substrate with acute angles and optimized thickness directly produces wide beam angles, removing the requirement for additional optical components and simplifying the overall device packaging.
Solution Approach 2:
The LED structure serves itself by using the polygonal substrate geometry to control light emission patterns. The substrate shape with acute angles inherently provides the beam angle control function that would otherwise require separate optical components, making the device self-sufficient and reducing overall complexity.
3Illumination intensity
If surface texturing is applied to improve light extraction, then light extraction efficiency is improved, but beam angle decreases below 120°
Solution Approach 1:
The patent changes the substrate thickness parameter to 225-400 μm and uses the polygonal shape with acute angles instead of surface texturing. This alternative approach achieves both improved light extraction efficiency and wider beam angles by controlling light emission through the substrate geometry and thickness rather than through surface texturing methods that limit beam angle.
4Illumination intensity
If vertical type LED structure is used, then light extraction efficiency is improved by removing substrate, but heat dissipation efficiency decreases
Solution Approach 1:
The patent merges the advantages of both vertical and flip-chip structures by maintaining the substrate (unlike vertical type) for heat dissipation while achieving improved light extraction through optimized substrate thickness and polygonal shape. This combination allows simultaneous achievement of good thermal management and light extraction efficiency without sacrificing either performance metric.
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 design enhances light extraction efficiency, improves current spreading performance, and allows for different beam angles according to directions, reducing light loss and simplifying packaging, making it suitable for wide-area illumination applications.
Implementation Method 1
a reflective electrode placed over the second conductivity type semiconductor layer and reflecting light generated in the active layer
Implementation Method 2
an active layer placed between the first conductivity type semiconductor layer and the second conductivity type semiconductor layer
Data Source
AI summary
A light emitting diode apparatus includes a substrate, a first conductive type semiconductor layer, a second conductive type semiconductor layer, a mesa, a lower insulating layer, a first pad and a second pad. The substrate has a first surface and a second surface opposite to the first surface. The first conductivity type semiconductor layer is disposed on the first surface of the substrate. The mesa is disposed on the first conductive semiconductor layer and has an active layer and the second conductive semiconductor layer. A peripheral edge of the first conductive semiconductor layer is exposed. The lower insulating layer covers the mesa and the first conductive semiconductor layer and has a plurality of first openings exposing the first conductive semiconductor layer along a peripheral edge of the substrate.