Flip-Chip LED Reflector Structure for Light Loss and Spot Reduction
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Solution Overview
Problem
Flip chip type light emitting diodes experience significant light loss due to the use of metal reflection layers, which also degrade over time, leading to inefficient light emission and potential spot phenomena in display surfaces.
Innovation Solution
A light emitting diode chip design incorporating a substrate with a first and second insulating reflection layer, including a distributed Bragg reflector, that reduces light loss by reflecting light through the side surfaces without the need for diffusion plates or filters, and maintains high reflectivity by using a transparent electrode and current spreader with a distributed Bragg reflector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a metal reflection layer is used to reflect light and provide electrical connection, then both light reflection and electrical connection are achieved, but the reflectivity is not high enough resulting in significant light loss
Solution Approach 1:
The patent uses a composite structure combining a lower reflector (metal layer) and an upper reflector (insulating layer with distributed Bragg reflector pattern) to achieve high reflectivity. The lower reflector provides baseline reflection while the upper reflector with its periodic structure enhances reflectivity through constructive interference, solving the problem of insufficient reflectivity from single metal layers.
Solution Approach 2:
The patent replaces the conventional single metal reflection layer with an insulating layer containing a distributed Bragg reflector pattern. This substitution uses optical interference principles instead of relying solely on metal reflection, achieving higher and more stable reflectivity while maintaining electrical connection functionality through the underlying metal layer.
2Reliability
If a metal reflection layer is used for light reflection, then electrical connection is achieved, but the reflectivity decreases over time with extended use
Solution Approach 1:
The patent places an insulating layer with distributed Bragg reflector pattern over the metal lower reflector to protect it from degradation. This protective structure shields the metal layer from environmental factors and operational stress that cause reflectivity degradation over time, ensuring long-term reliability of the reflection function.
Solution Approach 2:
The composite structure of insulating layer with distributed Bragg reflector over the metal lower reflector creates a more durable reflection system. The insulating layer protects the metal from oxidation and degradation while the distributed Bragg reflector provides stable optical reflection, together ensuring long-term reflectivity stability.
3Illumination intensity
If light is emitted upward with a straight line from flip chip type light emitting diodes, then high efficiency light emission is achieved, but a spot phenomenon occurs on the display surface
Solution Approach 1:
The patent introduces a lower reflector extending in the lateral direction beneath the light emitting structure to reflect light that would otherwise be emitted in straight lines. This adds a lateral reflection dimension to the primarily vertical light emission, spreading light more uniformly across the display surface and eliminating the spot phenomenon while maintaining high emission efficiency.
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 effectively spreads light over a wide area, reduces light loss, and improves luminous efficacy by varying the viewing angle based on direction, while maintaining structural simplicity and reliability.
Implementation Method 1
a first and second insulating reflection layer, including a distributed Bragg reflector
Implementation Method 2
reflecting light through the side surfaces
Data Source
AI summary
A light emitting device includes a substrate; a first conductivity type semiconductor layer disposed on the substrate; a mesa; a transparent electrode; a contact electrode; a first insulating reflection layer; a first pad electrode and a second pad electrode; and a second insulating reflection layer. The first insulating reflection layer covers at least a portion of the light emitting structure, the transparent electrode and the contact electrode. The second insulating reflection layer is disposed on an opposite end of the substrate. The first and/or second insulating reflection layer have at least two regions which have different reflectivity properties.