Metal Composite Substrate for LED Thermal Management
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Solution Overview
Problem
Current light-emitting diodes (LEDs) face challenges with thermal management due to thermal expansion coefficient mismatch between high thermal conductivity materials and the LED device, leading to reliability issues under high current density and long thermal cycles.
Innovation Solution
A method of fabricating high power LEDs using an electrolessly or electrolytically plated metal composite heat dissipation substrate with excellent thermal conductivity and matching thermal expansion coefficient, which is applied to reflector and contact layers on p-type or n-type compound semiconductors, and grown using techniques like MOCVD, HVPE, or MBE, with optional surface roughening for enhanced light extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If high thermal conductivity materials (CVD diamond, Cu, Al, Ni, CuW alloy) are used as sub-mounts for LED thermal management, then thermal management performance is improved, but thermal expansion coefficient mismatch increases leading to device reliability degradation
Solution Approach 1:
The patent applies composite materials by creating a metal matrix composite sub-mount consisting of metal particles (Cu, Al, Ni, or their alloys) embedded in a ceramic matrix (Al2O3, AlN, or Si3N4). This composite structure combines the high thermal conductivity of metal particles with the matched thermal expansion coefficient and mechanical strength of the ceramic matrix, thereby achieving both improved thermal management and enhanced device reliability under thermal cycling conditions.
2Temperature
If CVD diamond is used as sub-mount material, then thermal management is excellent, but CTE matching with LEDs is less satisfactory
Solution Approach 1:
The patent creates a composite sub-mount where metal particles providing high thermal conductivity are embedded in a ceramic matrix that provides matched CTE. By selecting appropriate ceramic materials (Al2O3, AlN, Si3N4) and metal particles (Cu, Al, Ni, CuW alloy) and optimizing their volume ratios, the composite achieves both excellent thermal management and satisfactory CTE matching with LED chips, resolving the contradiction between these two properties.
3Reliability
If AlN is used as sub-mount material, then CTE matching is improved, but thermal management becomes less satisfactory
Solution Approach 1:
The patent enhances the thermal management capability of AlN-based sub-mounts by incorporating high thermal conductivity metal particles (Cu, Al, Ni, CuW alloy) into the AlN ceramic matrix. The metal particles act as thermal conduits, creating efficient heat dissipation pathways within the AlN sub-mount, thereby improving thermal management while maintaining the excellent CTE matching property of AlN.
4Ease of manufacture
If conventional wafer bonding methods are used for mounting LEDs on sub-mounts, then device assembly is achieved, but manufacturing cost increases due to complex and lengthy processes
Solution Approach 1:
The patent integrates the LED chip directly onto the metal matrix composite sub-mount during the epitaxial growth process, eliminating the need for separate wafer bonding steps. The composite sub-mount's unique structure with metal particles in ceramic matrix enables direct mounting with good thermal contact and mechanical bonding, simplifying the manufacturing process while maintaining excellent thermal management and device reliability.
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
This approach improves the thermal properties and reliability of LEDs by reducing the cost of wafer bonding and enhancing light extraction, while maintaining efficient thermal management and matching thermal expansion coefficients, thus addressing the limitations of existing materials.
Implementation Method 1
CVD diamond provides excellent thermal management for LEDs... Copper (Cu), aluminium (Al), nickel (Ni), and CuW alloy are commonly used metal and metal alloy sub-mounts for LEDs
Implementation Method 2
the metal composite can be formed on reflector and contact layers by electroless or electrolytic plating
Implementation Method 3
the metal composite can be formed on reflector and contact layers by electroless or electrolytic plating
Implementation Method 4
the device structure can be grown by MOCVD (Metal organic chemical vapour deposition)
Implementation Method 5
the device structure can be grown by... HVPE (Hydride vapour phase epitaxy)
Implementation Method 6
the device structure can be grown by... MBE (Molecular beam epitaxy)
Implementation Method 7
a sapphire, silicon carbide, LiAlO2, ZnO or silicon substrate can be removed using laser lift-off (LLO)
Data Source
AI summary
The present invention relates to a method of fabricating a high power light-emitting device using an electrolessly or electrolytically plated metal composite heat dissipation substrate having a high thermal conductivity and a thermal expansion coefficient matching with the device.