Flip-Chip LED With Gradient Refractive Index Substrate
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Solution Overview
Problem
Conventional flip-chip light emitting diodes have limited beam angles, which restrict their application in wide-area lighting applications like backlight units and sheet-lighting apparatuses, requiring additional lenses or molding members to enhance beam angle, and they also face challenges in heat dissipation and current spreading efficiency.
Innovation Solution
A flip-chip type light emitting diode with a transparent substrate and a conformal coating layer, featuring a beam angle of 140° or more without the need for additional lenses, improved current spreading performance, and enhanced light extraction efficiency through reflective electrodes and current spreading layers, allowing for direct use in various applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a conventional flip-chip type light emitting diode is used, then heat dissipation efficiency is improved, but beam angle is limited to about 120°
Solution Approach 1:
The patent changes the physical parameters of the semiconductor layer by introducing a specific refractive index gradient structure. The semiconductor layer has a refractive index that varies from 2.0 at the light-emitting interface to 2.4 at the opposite interface, creating optical parameter variation that widens the beam angle to 140° or more while preserving the flip-chip heat dissipation architecture
Solution Approach 2:
The patent employs a composite structure combining the flip-chip LED architecture with a specially engineered semiconductor layer having gradient optical properties. This composite approach integrates the thermal management benefits of flip-chip mounting with the optical beam control of gradient-index materials, achieving both wide beam angle and efficient heat dissipation
2Loss of energy
If surface texturing is applied to improve light extraction efficiency, then light loss due to total internal reflection is reduced, but beam angle becomes smaller than 120°
Solution Approach 1:
Instead of using surface texturing, the patent changes the bulk optical parameters of the semiconductor layer by creating a refractive index gradient. This parameter change approach achieves light extraction enhancement while maintaining beam angle control, producing a beam angle of 140° or more unlike conventional textured surfaces
3Shape
If a molding member or secondary lens is added to increase beam angle, then beam angle is improved, but device complexity and packaging requirements increase
Solution Approach 1:
The patent merges the beam angle control function directly into the semiconductor layer structure itself, eliminating the need for separate molding members or secondary lenses. The refractive index gradient semiconductor layer performs both light extraction and beam shaping functions, simplifying the overall device structure and packaging requirements
Solution Approach 2:
The semiconductor layer provides self-service by inherently controlling the beam angle through its gradient refractive index structure. The material structure itself performs the beam shaping function that would otherwise require external optical components, making the LED self-sufficient for wide-area illumination applications
4Manufacturing precision
If current spreading performance is improved through additional layers, then current distribution is enhanced, but device complexity increases
Solution Approach 1:
The gradient refractive index semiconductor layer serves multiple functions simultaneously: it provides the primary semiconductor functionality, enhances light extraction through refractive index matching, controls beam angle, and improves current spreading. This multi-functionality reduces the need for separate current spreading layers, simplifying the overall device structure while achieving excellent current distribution
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 solution provides a flip-chip type light emitting diode with a wide beam angle, improved light extraction efficiency, and enhanced current spreading performance, enabling efficient illumination of wide areas without additional packaging or lenses, suitable for backlight units and sheet-lighting apparatuses.
Implementation Method 1
the transparent substrate is configured to discharge light generated in the active layer through the second surface of the transparent substrate. Further, the light emitting diode has a beam angle of 140° or more
Data Source
AI summary
A light-emitting diode is provided to include: a transparent substrate having a first surface, a second surface, and a side surface; a first conductive semiconductor layer positioned on the first surface of the transparent substrate; a second conductive semiconductor layer positioned on the first conductive semiconductor layer; an active layer positioned between the first conductive semiconductor layer and the second conductive semiconductor layer; a first pad electrically connected to the first conductive semiconductor layer; and a second pad electrically connected to the second conductive semiconductor layer, wherein the transparent substrate is configured to discharge light generated by the active layer through the second surface of the transparent substrate, and the light-emitting diode has a beam angle of at least 140 degrees or more. Accordingly, a light-emitting diode suitable for a backlight unit or a surface lighting apparatus can be provided.