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Why is a boron nitride ceramic crucible suitable for sintering silicon nitride and aluminum nitride substrates


Crucible is a container or vessel commonly used in high-temperature sintering and melting processes. It is typically made of high-temperature resistant materials such as ceramics, metals, and graphite. The main function of a crucible is to contain and hold materials at high temperatures for sintering, melting, or other heat treatment processes. The selection of a crucible material and size is crucial, considering factors such as the sintering temperature, sample size, thermal expansion compatibility, wettability, and other specific application requirements.


In the sintering process of aluminum nitride (AlN) and silicon nitride (Si3N4) ceramic substrates, using boron nitride (BN) ceramic as a crucible offers several advantages:boron nitride ceramic crucible


1.High-temperature stability: The highest sintering temperature for AlN substrates is around 2000°C, and for Si3N4 substrates, it is around 1850°C. Both processes involve thermal shock at different temperature ranges. BN crucibles can withstand high temperatures up to 2100°C and exhibit similar thermal expansion coefficients to AlN and Si3N4, ensuring stability under high-temperature conditions. This is crucial for sintering high-temperature ceramic materials like AlN and Si3N4.  Boron nitride crucibles can endure the high-temperature environment and maintain their structural integrity, ensuring stability and consistency during the sintering process.


2.Low wettability: BN ceramic has low wettability, meaning that molten materials are less likely to spread extensively on its surface and instead tend to form small spherical shapes. This reduces the contact area between the substrate material and the Boron nitride crucible during sintering, minimizing adhesion and difficulties in removing the sintered substrates from the crucible.


3.Chemical stability: BN ceramic exhibits high chemical stability and does not react with or contaminate many materials. When sintering AlN and Si3N4 substrates, using BN crucibles allows direct contact with the substrate material without introducing impurities or altering the composition and properties of the substrates.


4.Good thermal conductivity: BN crucible have high thermal conductivity, facilitating efficient heat transfer. This helps achieve uniform heating and temperature distribution during the sintering process, enhancing sintering uniformity and quality. It also contributes to the uniformity of substrate density, structure, composition, and dimensional shape, resulting in improved electrical performance, durability, and precision dimensions for AlN and Si3N4 substrates.


In conclusion, compared to other crucible materials, boron nitride (BN) crucible offers advantages of low wettability, chemical stability, high-temperature stability, and good thermal conductivity in the sintering of aluminum nitride (AlN) and silicon nitride (Si3N4) substrates. These advantages provide a reliable, clean, and high-quality sintering environment, ensuring the substrates are sintered in optimal conditions and maintain the desired performance.

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