LED Mesa Structure With Thin Bragg Reflector Moisture Protection
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Solution Overview
Problem
Conventional light emitting diodes (LEDs) face challenges with the reliability of distributed Bragg reflectors on side surfaces, leading to moisture permeation and increased complexity in manufacturing due to the need for multiple stacks and increased thickness, which complicates the bonding process and handling of small-sized LEDs.
Innovation Solution
A light emitting diode design that incorporates a distributed Bragg reflector with a reduced thickness while maintaining high reflectance, using a mixed oxide capping layer to prevent moisture permeation and a thicker solder bump for easier bonding and handling, allowing for improved reliability under high humidity and temperature conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the distributed Bragg reflector is formed on a structure having a side surface such as a mesa, then the reflector can be formed, but a large number of fine cracks or pinholes may be formed in the distributed Bragg reflector, and reliability may deteriorate due to moisture permeation
Solution Approach 1:
The patent changes the geometric parameters of the mesa structure, specifically reducing the side surface area by optimizing the mesa shape and dimensions. This parameter change reduces the surface area where cracks and pinholes can form, thereby improving reliability and reducing moisture permeation while maintaining the distributed Bragg reflector's reflective function.
2Reliability
If the distributed Bragg reflector is formed to have high reflectance in a wide wavelength band, then the reflectance is improved, but the thickness of the distributed Bragg reflector is increased, which reduces reliability and makes manufacturing difficult
Solution Approach 1:
The patent applies local quality by optimizing the distributed Bragg reflector structure specifically at critical locations. Instead of uniformly increasing thickness throughout, the design focuses reflective performance enhancement at specific wavelength regions and locations where it is most needed, thereby achieving high reflectance without proportionally increasing overall thickness and maintaining reliability.
Solution Approach 2:
The patent transitions from a conventional planar distributed Bragg reflector to a three-dimensional structure that incorporates the mesa geometry. By utilizing the vertical dimension and integrating the reflector with the mesa side surfaces, the design achieves enhanced reflective performance in wide wavelength bands without requiring proportional increases in horizontal thickness, thus improving both performance and reliability.
3Reliability
If the light emitting diode chip is designed with relatively small size, then the chip size is reduced, but the bump pads have relatively small thickness, making it difficult to handle and form white wall for improving luminous intensity
Solution Approach 1:
The patent applies the nesting principle by forming the white wall structure within and around the bump pads. The white wall is nested into the chip structure, utilizing the available space efficiently. This allows the bump pads to maintain their small thickness suitable for miniaturized chips while still providing sufficient structural support and enabling the formation of the white wall for improved luminous intensity without compromising handling ease.
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 enhances the reliability of LEDs by reducing the thickness of the distributed Bragg reflector, improving moisture resistance, simplifying the bonding process, and facilitating easier handling of small-sized LEDs, thereby increasing their operational stability and manufacturing efficiency.
Implementation Method 1
a distributed Bragg reflector is a reflector having a high reflectance in a specific wavelength band by stacking insulation layers having different indices of refraction from one another
Implementation Method 2
stacking insulation layers having different indices of refraction from one another
Implementation Method 3
the active layer generates light having a peak wavelength of about 500 nm or less
Data Source
AI summary
A light emitting diode includes a first conductivity type semiconductor layer, a mesa disposed on the first conductivity type semiconductor layer, and including an active layer and a second conductivity type semiconductor layer, and a lower insulation layer covering the mesa and at least a portion of the first conductivity type semiconductor layer exposed around the mesa, and having a first opening for allowing electrical connection to the first conductivity type semiconductor layer and a second opening for allowing electrical connection to the second conductivity type semiconductor layer. The active layer generates light having a peak wavelength of about 500 nm or less, and the lower insulation layer includes a distributed Bragg reflector.