AlN Substrate Grain Boundary Hardness for Heat Transfer
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Solution Overview
Problem
Conventional AlN substrates face limitations in achieving low surface roughness, which impairs heat transfer efficiency for high-output light emitting devices, leading to inadequate heat dissipation and instability in device operation.
Innovation Solution
An AlN sintered compact with AlN crystal grains and a grain boundary phase of lower Vickers hardness, produced using Yb2O3 and Nd2O3 as sintering additives, is polished to achieve a surface roughness of 0.015 µm or less, reducing thermal contact resistance and enhancing heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional AlN sintered compacts with yttria sintering additive are used, then the substrate provides adequate structural support, but the surface roughness remains above 0.015 µm resulting in insufficient heat transfer efficiency
Solution Approach 1:
The invention changes the chemical composition parameters of the sintering additive system by replacing conventional yttria (Y2O3) with a dual-oxide system of ytterbium oxide (Yb2O3) and neodymium oxide (Nd2O3) in specific proportions. This parameter change in the additive composition fundamentally alters the grain boundary phase properties, enabling surface roughness reduction to 0.015 µm or less while maintaining structural integrity and achieving excellent heat transfer efficiency.
Solution Approach 2:
The invention employs a composite sintering additive system combining Yb2O3 and Nd2O3 oxides with AlN powder, creating a multi-phase sintered compact structure. The composite nature of the additive system produces a grain boundary phase with optimized properties that simultaneously achieve ultra-smooth surfaces and high thermal conductivity, resolving the contradiction between surface precision and heat transfer reliability.
2Reliability
If the surface roughness is reduced to improve heat transfer, then thermal contact resistance decreases, but the grain boundary phase hardness may increase making polishing more difficult
Solution Approach 1:
The invention changes the physical and chemical parameters of the grain boundary phase by using Yb2O3-Nd2O3 dual-oxide additives, which create a softer grain boundary phase compared to conventional yttria-based systems. This parameter change in the grain boundary characteristics enables effective polishing to achieve surface roughness of 0.015 µm or less, simultaneously improving heat transfer efficiency without excessive manufacturing difficulty.
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 an AlN substrate with excellent heat transfer efficiency, supporting reliable operation of light emitting devices by minimizing surface roughness and thermal contact resistance.
Implementation Method 1
subjecting the compact to a heat treatment to obtain an AlN sintered compact
Implementation Method 2
polishing a surface of the AlN sintered compact to obtain a main surface having a surface roughness Ra of 0.015 µm or less
Implementation Method 3
An AlN substrate composed of an aluminum nitride (AlN) sintered compact has a significantly high thermal conductivity, and accordingly, it is utilized as a substrate to mount thereon a semiconductor device required to provide heat dissipation
Data Source
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AI summary
An AlN sintered compact includes AlN crystal grains and a grain boundary phase, and the grain boundary phase is lower in Vickers hardness than the AlN crystal grains.