Copper-Molybdenum Clad Material for LED Substrates
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Solution Overview
Problem
Existing LED technologies face challenges in growing high-quality group III-V semiconductor crystals on substrates due to lattice constant and thermal expansion mismatches, leading to warping and poor thermal conductivity, which affects light-emitting efficiency and device life, especially in high-power LEDs.
Innovation Solution
A clad material with a coefficient of linear thermal expansion of 14×10−6/K or less and thermal conductivity of 200 W/mK or more is developed by laminating copper and molybdenum layers, bonded to the semiconductor crystal surface via a metal layer, allowing for efficient heat dissipation and reduced substrate warping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a single-crystal sapphire substrate is used for growing group III-V semiconductor crystals, then the substrate provides good mechanical stability, but the poor thermal conductivity (about 40 W/mK) leads to insufficient heat dissipation and reduced device life in high-power LEDs
Solution Approach 1:
The patent applies composite material principle by creating a clad structure consisting of a sapphire substrate layer and a copper layer bonded together. The sapphire substrate provides mechanical stability and lattice matching for crystal growth, while the copper layer provides high thermal conductivity (about 380 W/mK) for efficient heat dissipation. This composite structure resolves the contradiction between mechanical stability and thermal management in high-power LED substrates.
2Temperature
If a copper substrate with high thermal conductivity is used, then heat dissipation is improved, but the significant difference in coefficient of thermal expansion from group III-V semiconductor crystals causes warping and cracking
Solution Approach 1:
The clad structure combines sapphire and copper layers, where sapphire has a coefficient of thermal expansion (about 5.0×10^-6/K) close to group III-V semiconductor crystals, while copper provides high thermal conductivity. The layered composite allows the copper layer to handle thermal conduction while the sapphire layer maintains dimensional stability during thermal cycling, preventing warping and cracking.
Solution Approach 2:
The sapphire substrate acts as an intermediary between the copper heat sink layer and the group III-V semiconductor crystal. It provides a thermal expansion-matched interface for crystal growth while conducting heat to the copper layer, mediating between the thermal management requirements and the mechanical stability requirements.
3Manufacturing precision
If a buffer layer is formed on sapphire substrate to enable epitaxial growth, then crystal growth is improved, but the difference in coefficient of linear thermal expansion between sapphire and GaN still causes substrate warping after epitaxial growth
Solution Approach 1:
The patent maintains the sapphire substrate for its crystal growth properties but adds a copper layer to compensate for the thermal expansion mismatch issue. The composite structure allows the sapphire substrate to continue providing good epitaxial growth conditions while the copper layer absorbs thermal stress, preventing warping.
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 light-emitting efficiency and extends the life of high-power LEDs by improving thermal management and reducing substrate-related issues, while also enabling the formation of electrodes on both surfaces for improved manufacturing processes.
Implementation Method 1
a thermal conductivity of 200 W/mK or more
Implementation Method 2
bonded to a group III-V semiconductor crystal surface via a metal layer
Data Source
AI summary
Disclosed is a clad material for an LED light-emitting element holding substrate in which a plurality of layers composed of different materials are stacked and bonded via a metal layer to a III-V group semiconductor crystal surface, the linear expansion coefficient being 14×10−6/K or less and the thermal conductivity at a temperature of 25° C. being 200 W/mK or greater. The clad material is composed of three alternately stacked layers: two copper layers and a molybdenum layer, the molybdenum layer being 10 to 60 vol % and the difference in thickness between the copper layers being 5% or less; or a clad material composed of three copper layers alternately stacked with molybdenum layers to make five layers, the molybdenum layers being 20 to 70 vol % and the difference in thickness between the top and bottom two copper layers and the molybdenum layers being 5% or less.