Silicon Nitride Powder Oxygen Control for Thermal Conductivity
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Solution Overview
Problem
Silicon nitride substrates require high thermal conductivity for effective heat dissipation, which is influenced by the amount of defects in the sintered body, and the physical properties of the silicon nitride powder used, particularly the oxygen content.
Innovation Solution
A silicon nitride powder with an internal oxygen content of 0.6 mass% or less is used, produced through a method involving firing under a nitrogen and hydrogen or ammonia atmosphere and treated with hydrofluoric acid to control surface oxygen levels, resulting in a sintered body with reduced defects and enhanced thermal conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the total amount of oxygen in silicon nitride powder is reduced to improve high temperature characteristics, then high temperature strength and creep resistance are improved, but the manufacturing complexity increases due to stricter control requirements
Solution Approach 1:
The patent applies preliminary action by controlling the oxygen content in the silicon nitride powder before sintering. By specifying that the total oxygen amount is 1.5 mass% or less (with internal oxygen at 0.6 mass% or less), the powder is pre-prepared with optimized properties, eliminating the need for complex post-sintering treatments and simplifying the overall manufacturing process while maintaining high temperature strength
Solution Approach 2:
The patent applies parameter changes by precisely controlling the oxygen concentration parameters in the silicon nitride powder. By setting specific thresholds for total oxygen (1.5 mass% or less) and internal oxygen (0.6 mass% or less), the invention transforms the manufacturing approach from complex process control to simple parameter specification, reducing manufacturing complexity while improving high temperature characteristics
2Temperature
If the internal oxygen content in silicon nitride powder is reduced to increase thermal conductivity, then heat dissipation performance is improved, but the production difficulty increases due to stricter raw material requirements
Solution Approach 1:
The patent applies parameter changes by establishing a specific threshold for internal oxygen content (0.6 mass% or less) to optimize thermal conductivity. This clear parameter specification guides raw material selection and processing, making it easier to control thermal properties without excessive production difficulty
Solution Approach 2:
The patent uses the internal oxygen content as an intermediary parameter to connect raw material quality with final product performance. By controlling this intermediate parameter during powder production and characterization, the invention achieves high thermal conductivity (100 W/mK or more) while maintaining manageable production requirements through standardized measurement and control
3Strength
If the surface oxygen content in silicon nitride powder is increased to improve strength through liquid phase formation during sintering, then bending strength is improved, but thermal conductivity decreases
Solution Approach 1:
The patent applies local quality by differentiating between surface oxygen and internal oxygen roles. Surface oxygen (up to 1.0 mass%) is allowed to form liquid phase at grain boundaries to improve strength, while internal oxygen is strictly controlled (0.6 mass% or less) to maintain high thermal conductivity. This spatial differentiation of oxygen functions resolves the contradiction between strength and thermal conductivity
Solution Approach 2:
The patent resolves the contradiction by establishing distinct parameter thresholds for surface oxygen (1.0 mass% or less) and internal oxygen (0.6 mass% or less). This dual-parameter control strategy enables simultaneous optimization of strength (through controlled surface oxygen forming liquid phase) and thermal conductivity (through restricted internal oxygen), achieving both 500 MPa bending strength and 100 W/mK thermal conductivity
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 enables the production of silicon nitride sintered bodies with high thermal conductivity and improved strength, achieving thermal conductivity of 100 W/mK or more and 3-point bending strength of 500 MPa or more at room temperature.
Implementation Method 1
a silicon powder having an oxygen concentration of 0.4 mass% or less is fired under a mixed atmosphere containing nitrogen and at least one selected from the group consisting of hydrogen and ammonia to obtain a fired product
Implementation Method 2
the fired product is treated with hydrofluoric acid having a hydrogen fluoride concentration of 10 to 40 mass%
Implementation Method 3
when it is used as a raw material for sintering, it is possible to obtain a silicon nitride sintered body having high thermal conductivity
Data Source
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AI summary
There is provided a silicon nitride powder having an amount of internal oxygen of 0.6 mass% or less. There is provided a method for producing a silicon nitride powder including a step in which a silicon powder having an oxygen concentration of 0.4 mass% or less is fired under a mixed atmosphere containing nitrogen and hydrogen to obtain a fired product and a step in which the fired product is treated with hydrofluoric acid having a hydrogen fluoride concentration of 10 to 40 mass%.