SiAlON Sintered Body Densification for Flat, Joinable Substrates
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Solution Overview
Problem
Existing methods for producing SiAlON sintered bodies face issues with inhomogeneous composition, high porosity, and insufficient surface flatness due to the use of sintering aids or difficulties in densification without them, leading to problems in polishability and joinability of substrates.
Innovation Solution
A SiAlON sintered body with a composition of Si6-zAlzOzN8-z (0<z≤4.2) is produced using high-purity silicon nitride, aluminum nitride, and alumina powders, with a hot-press firing method at 1725° C. to 1900° C. and press pressure of 100 to 300 kgf/cm2 to achieve low open porosity and high relative density, ensuring enhanced surface flatness and joinability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a sintering aid is used in producing SiAlON, then sintering can be facilitated, but the composition becomes inhomogeneous and large quantities of different phase components occur
Solution Approach 1:
The invention extracts and removes sintering aids from the production process entirely. By using high-purity raw materials (purity 99.9% or higher) and optimizing hot-press firing conditions (1700-1900°C for 1-10 hours at 100-300 atm), the patent achieves successful sintering without any sintering aids, thereby eliminating composition inhomogeneity and unwanted phase components while maintaining manufacturing feasibility
Solution Approach 2:
The invention changes the physical and chemical parameters of the sintering process by using high-purity raw materials with controlled particle size distributions and optimizing the hot-press firing conditions (temperature range 1700-1900°C, pressure 100-300 atm, time 1-10 hours). These parameter changes enable sintering to proceed without sintering aids, resolving the contradiction between ease of manufacture and composition stability
2Stability of the object's composition
If normal-pressure firing is conducted without sintering aid, then composition inhomogeneity is avoided, but pores are not completely discharged and relative density is insufficient
Solution Approach 1:
The invention transitions from normal-pressure firing to hot-press firing, adding the dimension of applied pressure (100-300 atm) to the sintering process. This dimensional change enables complete pore discharge and achieves high relative density (99.5% or higher) while maintaining composition homogeneity, as the pressure facilitates densification without requiring sintering aids that would compromise compositional stability
3Ease of manufacture
If different phase components are present, then sintering can proceed, but surface flatness becomes insufficient due to different polishabilities
Solution Approach 1:
The invention extracts and eliminates different phase components from the SiAlON sintered body by using high-purity raw materials and optimizing hot-press firing conditions. This removal of unwanted phases ensures uniform polishability across the entire material, achieving excellent surface flatness (Ra ≤ 0.5 μm) while maintaining sintering feasibility through the optimized hot-press process
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 SiAlON sintered body exhibits high surface flatness, low porosity, and improved joinability, with a thermal expansion coefficient of 3.0 ppm/K or less, enhancing the performance of composite substrates in electronic devices by improving frequency temperature dependence and filtering performance.
Implementation Method 1
the raw material powder is hot-press fired in a nitrogen atmosphere at 1725° C. to 1900° C. and a press pressure of 100 to 300 kgf/cm2 for 1 to 10 hours to obtain the SiAlON sintered body
Implementation Method 2
densification can proceed while discharging the pores by pressure in this method
Implementation Method 3
the thermal expansion coefficient of the SiAlON sintered body constituting the supporting substrate is 3.0 ppm/K (40° C. to 400° C.) or less; thus, when a surface acoustic wave device is prepared, the frequency temperature dependence and the filtering performance are notably improved
Data Source
AI summary
A SiAlON sintered body according to the present invention is represented by Si6-zAlzOzN8-z (0<z≤4.2) and has an open porosity of 0.1% or less and a relative density of 99.9% or more. A ratio of a total of intensities of maximum peaks of components other than SiAlON to an intensity of a maximum peak of the SiAlON in an X-ray diffraction diagram is 0.005 or less.