Vertical LED Metal Substrate Thermal Stress Management
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for fabricating vertical light-emitting diodes face issues with thermal stress due to mismatched thermal expansion coefficients between substrates, leading to structural integrity problems and reduced light-emitting efficiency, especially when using thick copper electroplating to avoid substrate removal issues.
Innovation Solution
A method involving a metal combined substrate with two copper layers and an Invar layer, where one copper layer is close to the epitaxial layer and the other is farther away, allowing for controlled thermal expansion and thin thickness to mitigate stress and enhance heat dissipation, while maintaining a good light-emitting effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper is deposited on the epitaxial layer using electroplating method to avoid substrate removal issues, then thermal stress between copper substrate and epitaxial layer is reduced, but the thickness of copper layer becomes greater than 150 μm which disadvantages flimsy display panels and reduces light-emitting effect
Solution Approach 1:
The copper layer is segmented into multiple sub-layers (first copper layer, second copper layer, third copper layer) with different thicknesses and positions. The first copper layer (5-20 μm) is close to the epitaxial layer for stress management, the second copper layer (20-50 μm) is in the middle for structural support, and the third copper layer (5-20 μm) is far from the epitaxial layer for additional reinforcement. This segmentation allows the total thickness to be reduced below 150 μm while maintaining structural integrity and light-emitting effect.
2Strength
If silicon substrate with thickness of 100 μm is used, then structural support is provided, but the thickness disadvantages implementation of flimsy display panels
Solution Approach 1:
The substrate is replaced with a composite metal combined substrate consisting of multiple metal layers (including copper layers and potentially other metal layers) bonded together. This composite structure provides the necessary mechanical strength and thermal management properties while achieving a total thickness less than 150 μm, enabling flimsy display panel implementation without sacrificing structural integrity.
3Temperature
If copper substrate is directly bonded to epitaxial layer, then thermal conductivity is improved, but thermal expansion coefficient mismatch causes epitaxial layer to protrude or crack
Solution Approach 1:
Different regions of the substrate structure have different properties tailored to local requirements. The first copper layer close to the epitaxial layer has optimized thickness (5-20 μm) to manage thermal expansion stress at the critical interface, while the second and third copper layers have different thicknesses (20-50 μm and 5-20 μm respectively) for structural support and additional thermal management. This local quality differentiation allows the substrate to provide excellent heat dissipation while preventing epitaxial layer protrusion or cracking through strategic stress 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 approach results in a vertical light-emitting diode with improved mechanical strength, reduced thickness, and increased light intensity, effectively addressing thermal stress and substrate removal challenges while maintaining efficient heat dissipation and light emission.
Implementation Method 1
The metal layer has a low thickness, high thermal conductivity, and low heat capacity in order to dissipate heat and maintain a good light-emitting effect effectively
Implementation Method 2
copper is deposited on an accumulation layer using an electroplating method
Data Source
AI summary
A method for fabricating a vertical light-emitting diode includes: providing a growth substrate, wherein an epitaxial layer is formed on the growth substrate; forming a metal combined substrate on the epitaxial layer, wherein the metal combined substrate comprises two first metal layers and a second metal layer therebetween, one of the first metal layers is close to the epitaxial layer, and another of the first metal layers is far away from the epitaxial layer; removing the growth substrate; forming a contact metal layer on the epitaxial layer; and removing the second metal layer and the first metal layer far away from the epitaxial layer and leaving the first metal layer close to the epitaxial layer. The vertical light-emitting diode, fabricated by the method, has a thinner thickness, a stronger mechanical strength, a higher light intensity, and a better heat-dissipating effect.