LED Conductive Pillar Layout for Uniform Brightness and Lower Thermal Stress
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Solution Overview
Problem
Vertical and flip-chip light emitting devices face issues with uneven brightness due to high current density and thermal expansion coefficient mismatches between the patterned current blocking layer and semiconductor/reflective layers, leading to reliability problems during manufacturing and testing.
Innovation Solution
A light emitting device design featuring a die-bonding substrate, a light emitting semiconductor structure with conductive pillars, an insulating layer with a trench and openings, and electrodes, where the trench surrounds the edge of the light emitting area and the openings disperse current to optimize current density distribution, and a metal layer fills the trench and openings to enhance adhesion and stress resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a patterned current blocking layer is added to improve luminous efficiency, then luminous efficiency is improved, but current density becomes concentrated and brightness becomes uneven
Solution Approach 1:
The current blocking layer is divided into multiple isolated blocking regions rather than a continuous layer. These segmented blocking regions are distributed across the light emitting area, allowing current to flow through multiple paths and preventing concentration at single points, thereby maintaining brightness uniformity while preserving current blocking functionality
Solution Approach 2:
The current blocking layer has spatially varying properties - it is positioned specifically in regions where current concentration occurs, with different blocking densities in different areas. This local optimization allows current to be redirected to under-utilized regions, improving overall current distribution uniformity while maintaining high luminous efficiency
2Use of energy by moving object
If a patterned current blocking layer is added to improve luminous efficiency, then luminous efficiency is improved, but thermal expansion coefficient mismatch causes poor product yield and reliability
Solution Approach 1:
An intermediate buffer layer is introduced between the current blocking layer and the semiconductor layer. This buffer layer has thermal expansion properties that gradually transition between the two layers, reducing the thermal expansion coefficient mismatch and preventing gap formation during temperature cycling, thereby improving product yield and reliability
Solution Approach 2:
The current blocking structure uses composite material design combining multiple layers with different thermal expansion coefficients. The layered composite structure distributes thermal stress more evenly, reducing the harmful effects of thermal expansion mismatch while maintaining the electrical current blocking function for improved luminous efficiency
3Use of energy by moving object
If current is concentrated on n-type conductive pillar and opening area to improve luminous efficiency, then luminous efficiency is improved, but epitaxial recombination efficiency deteriorates
Solution Approach 1:
The current blocking function is segmented into multiple distributed regions rather than concentrated at the conductive pillar openings. This segmentation spreads current flow across multiple pathways, preventing excessive current density at any single location, thereby maintaining epitaxial recombination efficiency while achieving high luminous efficiency through improved 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 design improves luminous efficiency, brightness uniformity, and product reliability by evenly distributing current and reducing thermal stress, resulting in increased process yield and reliability.
Implementation Method 1
Each conductive pillar is in direct contact with the second-type semiconductor layer and electrically connected to the die-bonding substrate
Implementation Method 2
The second portion electrically insulates the first-type semiconductor layer and the light emitting layer from the conductive pillars
Implementation Method 3
The combination of electron-hole pairs when the element acts on causes emission of photons
Implementation Method 4
a metal layer fills the trench and openings to enhance adhesion and stress resistance
Data Source
AI summary
The light emitting device includes a growth substrate, a light-emitting semiconductor structure, conductive pillars, an insulating layer, and first and second electrodes. The light-emitting semiconductor structure includes a first-type semiconductor layer, a light-emitting layer and a second-type semiconductor layer disposed on the growth substrate from top to bottom. The conductive pillars are disposed in the light-emitting semiconductor structure. The conductive pillars penetrates is in contact with the second-type semiconductor layer and electrically connected to the substrate. A first portion of the insulating layer is disposed between the first-type semiconductor layer and the substrate, and a second portion of the insulating layer electrically insulates the first-type semiconductor layer and the light emitting-layer from the conductive pillars. The first electrode is electrically connected to the first-type semiconductor layer and electrically insulated from the conductive pillars. The second electrode is electrically connected to the conductive pillar.