Mullite Composite Substrate Thermal Expansion Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Mullite sintered bodies with low thermal expansion coefficients and high rigidity are not known, and those with high surface smoothness are also lacking, which can lead to warping in composite substrates due to temperature differences.
Innovation Solution
A mullite-containing sintered body is developed by mixing mullite with silicon nitride, silicon oxynitride, or sialon, achieving a thermal expansion coefficient of less than 4.3 ppm/°C and high rigidity, with a manufacturing method involving hot press firing at specific temperatures and pressures to ensure high surface smoothness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a large amount of another component is added to mullite to increase thermal expansion coefficient, then thermal expansion coefficient is improved, but material purity deteriorates
Solution Approach 1:
The invention changes the chemical composition parameters by introducing silicon nitride, silicon oxynitride, or sialon components in controlled amounts (1-50 mass%) to adjust the thermal expansion coefficient while maintaining sintered body integrity and achieving the desired thermal-mechanical properties
Solution Approach 2:
The invention creates a composite material system combining mullite with silicon nitride, silicon oxynitride, or sialon phases. This composite approach allows simultaneous achievement of low thermal expansion (4.0-5.5 ppm/°C), high rigidity (Young's modulus ≥200 GPa), and high strength (bending strength ≥300 MPa) that cannot be obtained with pure mullite alone
2Stability of the object's composition
If mullite sintered body with low thermal expansion is used as support substrate, then thermal stability is improved, but surface smoothness deteriorates leading to warping
Solution Approach 1:
The invention optimizes sintering parameters including temperature (1500-1700°C), pressure (10-300 MPa), and atmosphere control to achieve dense microstructure with minimal pores and fine grain size (0.5-5 μm), resulting in Ra ≤ 1.0 nm surface smoothness while maintaining low thermal expansion
Solution Approach 2:
The invention creates different microstructural zones within the sintered body, with a dense, fine-grained surface layer for smoothness and bonding, and an optimized bulk structure for low thermal expansion and high mechanical strength, achieving both surface quality and bulk performance
3Strength
If mullite sintered body with high rigidity is used, then structural stability is improved, but thermal expansion coefficient increases
Solution Approach 1:
The invention employs composite materials combining mullite with silicon nitride, silicon oxynitride, or sialon phases. The silicon nitride-based components contribute to high rigidity (Young's modulus ≥200 GPa) while the overall composite structure maintains low thermal expansion (4.0-5.5 ppm/°C) through phase composition control
Solution Approach 2:
The invention adjusts the composition ratio of mullite to silicon nitride-based components (99-50 mass% mullite, 1-50 mass% silicon nitride-based component) to optimize the balance between rigidity and thermal expansion, achieving Young's modulus ≥200 GPa while maintaining thermal expansion coefficient of 4.0-5.5 ppm/°C
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 resulting mullite-containing sintered body exhibits improved thermal stability, rigidity, and surface smoothness, enhancing the performance of composite substrates in devices like acoustic wave devices by reducing temperature-dependent frequency variations.
Implementation Method 1
the mullite-containing sintered body has a thermal expansion coefficient of less than 4.3 ppm/°C at 40°C to 400°C
Implementation Method 2
producing the mullite-containing sintered body by forming the mixed raw material powder into a compact having a predetermined shape and subjecting the compact to hot press firing
Implementation Method 3
an average grain size (average grain size of sintered particles) of 1.5 μm or less
Data Source
AI summary
A mullite-containing sintered body according to the present invention contains mullite and at least one selected from the group consisting of silicon nitride, silicon oxynitride, and sialon. It is preferable that the mullite-containing sintered body have a thermal expansion coefficient of less than 4.3 ppm/° C. at 40° C. to 400° C., an open porosity of 0.5% or less, and an average grain size of 1.5 μm or less.