Hexagonal Boron Nitride Powder for Thermal Conductive Resin Sheets
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Solution Overview
Problem
Conventional hexagonal boron nitride (hBN) powders face challenges in achieving high thermal conductive properties and electric insulation due to orientation anisotropy and slow reaction rates in production methods, leading to insufficient filling rates and thermal conductive properties in thermally conductive sheets.
Innovation Solution
A high-purity hBN powder with a specific particle size distribution, tap density, and BET specific surface area is developed, comprising an aggregate of primary particles with a large ratio of average longer diameter to average thickness, which maintains random orientation and enhances thermal conductive properties and electric insulation when used in resin compositions and sheets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the filling rate of hBN powder with large aspect ratio primary particles is increased, then thermal conductive properties are improved, but orientation anisotropy occurs in the molded article
Solution Approach 1:
The hBN powder is segmented into primary particles with large aspect ratios (L1/d1 ≥ 10) that are aggregated into secondary particles. This segmentation allows the primary particles to maintain random orientation while the aggregate structure facilitates better packing and thermal conduction pathways in the molded article.
Solution Approach 2:
The hBN powder undergoes preliminary classification to achieve a specific particle size distribution (bimodal distribution with D10≥0.5μm, D50≥2.0μm, D90≤10μm) before molding. This preliminary action ensures that the particles are pre-positioned in size ranges that prevent orientation anisotropy while maximizing thermal conductive properties.
2Ease of manufacture
If conventional production methods are used to obtain hBN powder, then production cost is reduced, but thermal conductive properties and electric insulation are insufficient
Solution Approach 1:
The production method parameters are changed to fire the hBN powder at temperatures of 1500-2200°C for 1-24 hours under nitrogen atmosphere. These parameter changes produce high-purity hBN with superior thermal conductive properties (≥10 W/mK) and electric insulation, while maintaining reasonable production costs through optimized firing conditions.
3Ease of operation
If the aggregate strength is insufficient, then mixing with resin is easier, but the aggregate disintegrates during composite formation
Solution Approach 1:
The hBN powder is processed to form aggregate structures with controlled morphology that balance strength and processability. The aggregate structure maintains sufficient internal bonding strength to prevent disintegration during composite formation, while the external surface characteristics facilitate easy mixing with resin materials.
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 hBN powder achieves superior thermal conductive properties and electric insulation by maintaining a dense granular shape and random particle orientation, improving the thermal conductivity and insulation of resin compositions and sheets.
Implementation Method 1
maintaining random orientation and enhances thermal conductive properties and electric insulation
Implementation Method 2
has excellent properties such as thermal conductive properties
Implementation Method 3
has excellent properties such as thermal conductive properties, electric insulation
Data Source
AI summary
An hBN powder containing an aggregate of primary particles of hBN, the hBN powder having a ratio of an average longer diameter (L1) to an average thickness (d1) of the primary particles, [L1/d1], of 10 to 25, a tap density of 0.80 g/cm3 or more, and a BET specific surface area of less than 5.0 m2/g, in which a particle size distribution curve showing a frequency distribution based on volume of the hBN powder is a bimodal distribution curve having a first peak and a second peak in a range of a particle size of 500 μm or less and having a peak height ratio of a second peak height (HB) to a first peak height (HA), [(HB)/(HA)], of 0.90 or less, a method for producing the same, and a resin composition and a resin sheet each comprising the hBN powder.