Boron Nitride Powder Aggregation for Heat Dissipation
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Solution Overview
Problem
Conventional methods fail to produce boron nitride powders with particle sizes of 20 μm or less and high compressive strength, leading to inadequate heat dissipation in electronic components due to orientation issues and poor resin fluidity.
Innovation Solution
A boron nitride powder is produced by aggregating scaly primary particles to form bulky particles with a particle strength of 5.0 MPa or more and an average size of 2 μm to 20 μm, using a pressure nitriding baking step and decarbonizing crystallization process, or through vapor phase reaction, resulting in reduced anisotropy and enhanced heat conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hexagonal boron nitride powder with scaly shape is used to fill resin, then heat conductivity in a-axis direction is high (400 W/(m·K)), but the particles orient in one direction causing poor resin fluidity and making high filling difficult
Solution Approach 1:
The patent applies sphericalization by aggregating scaly primary particles into spherical secondary particles. This transformation maintains the high heat conductivity of the scaly primary particles while the spherical secondary particle shape prevents orientation in resin, thereby improving resin fluidity and enabling high filling without compromising thermal performance
2Reliability
If oriented sheets are laminated to utilize high heat conductivity in a-axis direction, then heat dissipation is improved, but production steps become complicated and dimension precision of thickness is difficult to ensure
Solution Approach 1:
The patent extracts the orientation problem by creating spherical secondary particles that do not require lamination. The high heat conductivity is achieved within individual spherical particles through their aggregated internal structure, eliminating the need for complex multi-step lamination processes and enabling direct molding with precise thickness control
3Stability of the object's composition
If conventional methods are used to produce aggregated boron nitride, then particle aggregation is achieved, but only bulky powder with particle size more than 20 μm can be produced
Solution Approach 1:
The patent changes the aggregation parameters by controlling sintering temperature (1000-2000°C) and time to produce spherical secondary particles with specific size ranges (2-20 μm). This parameter optimization enables production of finely divided aggregated powder that maintains both aggregation stability and small particle size, unlike conventional methods that only produce bulky powder
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 boron nitride powder exhibits excellent heat conductivity and high particle strength, suitable for use in heat-dissipating electronic components with improved resin fillability and reduced orientation index, enabling effective heat dissipation in thin film applications.
Implementation Method 1
a pressure nitriding baking step of baking boron carbide having a carbon content of 18% or more and 21% or less and an average particle size of 5 μm or more and 15 m or less in a pressurized nitrogen atmosphere at 1800° C. or more and 0.6 MPa or more
Implementation Method 2
a decarbonizing crystallization step of mixing a baked product obtained by the pressure nitriding baking step with a boron source, and heating the resulting mixture to a temperature capable of initiating decarbonization, then heating the mixture to a retention temperature of 1800° C. or more at a temperature rising rate of 5° C./min or less, and retaining the mixture in a nitrogen atmosphere at the retention temperature to obtain bulky boron nitride
Implementation Method 3
a decarbonizing crystallization step of mixing a baked product obtained by the pressure nitriding baking step with a boron source, and heating the resulting mixture to a temperature capable of initiating decarbonization, then heating the mixture to a retention temperature of 1800° C. or more
Implementation Method 4
a vapor phase reaction step of subjecting alkoxide borate gas and ammonia gas to vapor phase reaction at 750° C. or more
Implementation Method 5
a crystallization step of heating an intermediate obtained by the vapor phase reaction step until a baking temperature of 1500° C. or more is reached under conditions of an atmosphere containing 20 vol % or less of ammonia up to 1000° C. and an atmosphere containing 50 vol % or more of ammonia at 1000° C. or more, and baking the intermediate at the baking temperature to obtain bulky boron nitride
Data Source
AI summary
To provide a boron nitride powder having excellent heat conductivity and high particle strength. Provided is a boron nitride powder which comprises bulky boron nitride formed such that scaly primary particles of hexagonal boron nitride are aggregated to form bulky particles, and which has the following characteristics (A) to (C):(A) a particle strength of the bulky particles at a cumulative breakdown rate of 63.2% is 5.0 MPa or more;(B) an average particle size of the boron nitride powder is 2 μm or more and 20 μm or less; and(C) an orientation index of the boron nitride powder as determined from X-ray diffraction is 20 or less.