Spherical Alumina Powder Production via Controlled Flame Spheroidization
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Solution Overview
Problem
Existing methods for producing spherical alumina powder face challenges in achieving high productivity while maintaining a small specific surface area and low uranium content, which are essential for semiconductor applications, as they often require excessive heat and can result in agglomerated particles or complex two-step processes.
Innovation Solution
A method involving the spray-feeding of aluminum hydroxide powder with specific physical properties into flames, where the powder has a controlled specific surface area, particle diameter distribution, and crystal form, to produce spherical alumina with a low uranium content and improved thermal conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a generally-used aluminum hydroxide or water is used as a medium, then the spheroidization process can be performed, but a great deal of amount of heat is necessary and particle agglomeration occurs
Solution Approach 1:
The invention changes the physical parameters of the aluminum hydroxide raw material, specifically controlling the specific surface area to 0.3-3.0 m²/g and the D50/Dbet ratio to 10 or less. These parameter changes enable the spheroidization process to proceed with reduced heat input and prevent particle agglomeration, resolving the contradiction between ease of manufacture and energy consumption.
2Ease of manufacture
If aggregated aluminum hydroxide is used as a raw material, then the spheroidization can be performed, but the obtained spherical alumina may be in the form where several particles agglomerate each other
Solution Approach 1:
The invention specifies precise parameter ranges for the aluminum hydroxide raw material: specific surface area of 0.3-3.0 m²/g and D50/Dbet ratio of 10 or less. These parameter controls ensure that the spheroidization process produces well-dispersed spherical alumina particles without agglomeration, maintaining both manufacturing ease and particle dispersion quality.
3Reliability
If high-purity aluminum is molten and then atomized to produce aluminum powder, then the uranium content can be decreased to an extremely low level, but the productivity decreases due to the two-step process
Solution Approach 1:
The invention merges the powder preparation and spheroidization steps into a single integrated process. By using pre-prepared aluminum hydroxide powder with controlled properties (specific surface area 0.3-3.0 m²/g, D50/Dbet ≤ 10) as direct feedstock, the process eliminates the separate atomization step while maintaining low uranium content (10 ppb or less), thereby improving productivity without sacrificing reliability.
4Reliability
If the specific surface area of aluminum hydroxide is increased, then the reactivity may be improved, but the thermal conductivity of the resulting resin composition decreases
Solution Approach 1:
The invention optimizes the specific surface area parameter to a specific range (0.3-3.0 m²/g) that balances reactivity and thermal conductivity. This controlled parameter change ensures sufficient reactivity for complete spheroidization while maintaining the thermal conductivity required for semiconductor encapsulation applications, resolving the contradiction between these two requirements.
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
This method efficiently produces spherical alumina powder with a small specific surface area, low uranium content, and high thermal conductivity, suitable for semiconductor encapsulation materials, while enhancing productivity and preventing particle agglomeration.
Implementation Method 1
spraying an aluminum hydroxide powder having a specific surface area measured by a nitrogen adsorption method of 0.3 m2/g or more and 3 m2/g or less; a ratio of an average particle diameter D50, which is a particle diameter at which 50% by weight of particles from the finest particle side are accumulated in a particle diameter distribution measured by a laser diffraction scattering method, to a sphere conversion particle diameter Dbet calculated from a specific surface area, D50/Dbet, of 10 or less; and the average particle diameter D50 of 2 μm or more and 100 μm or less, into flames
Implementation Method 2
spraying an aluminum hydroxide powder into flames
Data Source
AI summary
A production method comprising the steps of: spraying an aluminum hydroxide powder having a specific surface area measured by a nitrogen adsorption method of 0.3 m2/g or more and 3 m2/g or less; a ratio of an average particle diameter D50, which is a particle diameter at which 50% by weight of particles from the finest particle side are accumulated in a particle diameter distribution measured by a laser diffraction scattering method, to a sphere conversion particle diameter Dbet calculated from a specific surface area, of 10 or less; and the average particle diameter D50 of 2 μm or more and 100 μm or less, into flames, and then collecting it in the form of a powder to give a spherical alumina powder having a small specific surface area and a low uranium content, and capable of providing high thermal conductivity to resin compositions.