Boron Nitride Ceramics

It has good heat resistance, thermal stability, thermal conductivity, high temperature dielectric strength, and is an ideal heat dissipation material and high temperature insulating material. Boron nitride has good chemical stability and can resist the leaching of most molten metals. It also has good self-lubricating properties. Boron nitride products have low hardness and can be machined with an accuracy of 0.005mm.

Performance parameter of PBN

Boron Nitride Ceramics

Properties of boron nitride.

Excellent thermal shock resistance
High resistivity-excluding aerosols, coatings and ZSBN
Low density
High thermal conductivity
Corrosion resistant
Good chemical inertness
High temperature material
High dielectric breakdown strength
Low dielectric constant
Excellent processability

Uses of boron nitride.

Fracture rings for continuous casting of metals
Heat treatment jigs
High temperature lubricants
Mold release agents
Molten metal and glass castings
Nozzles for transfer or atomization
Laser nozzles
Induction heating coil holders
High temperature and high voltage electrical insulators
Furnace supports requiring resistivity
Crucibles and containers for high purity molten metals
Radar assemblies and antenna windows
Ion thruster discharge channels

Characteristics of pyrolytic boron nitride ceramics

Pyrolytic boron nitride (PBN) belongs to the hexagonal crystal system and can reach 99.999% purity, acid and alkali resistance, oxidation resistance, good thermal conductivity, dense, and processable. It is made by chemical vapor deposition (CVD) of ammonia and boron halides under high temperature and high vacuum conditions, and can be used to prepare both PBN sheets and PBN end products such as crucibles, boats and coatings directly.

Pyrolytic boron nitride differs from ordinary hot pressed boron nitride (HBN) in that it does not have to go through the traditional hot press sintering process without adding any sintering agent, so the products obtained have the following remarkable features.
1, non-toxic and tasteless.
2、 High purity, reaching more than 99.999%.
3、It does not react with acids, alkalis, salts and organic reagents at room temperature, and slightly corrodes in molten salts and alkaline liquids, but can resist the corrosion of various acids at high temperatures.
4, and most molten metals, semiconductors and their compounds do not react.
5、Good antioxidant properties below 1000℃.
5, good thermal shock resistance, 2000 ℃ into the water did not see cracks.
6、high operating temperature, no sublimation point, decomposing directly into B and N above 3000℃.
7, high resistance, good electrical insulation properties.
8, smooth surface, no air holes, and most of the semiconductor melt does not wet.

Applications of pyrolytic boron nitride

Due to the nature of the CVD process, pyrolytic boron nitride parts typically require a wall thickness of no more than 3 mm. However, the CVD process gives pyrolytic boron nitride a nearly perfect layered structure, resulting in anisotropic thermal conductivity that makes it ideal for making crystal growth crucibles.

Product applications.

1、OLED evaporation units.
2、Semiconductor single crystal growth (VGF, LEC) crucibles.
3、Molecular beam epitaxy (MBE) evaporation crucible.
4、MOCVD heater.
5、Polycrystalline synthesis boat.
6、PBN infrared window.
7、Microwave tube for satellite communication.
8、PBN coating carrier plate.
9, high temperature, high vacuum equipment insulation board.

Pyrolytic boron nitride ceramic clamping rod

A spiral line traveling wave tube as the main high-power microwave amplifier parts, is the key components of radar, electronic countermeasures, relay communications, satellite communications, television live satellite, navigation, remote sensing, remote control and telemetry and other electronic equipment, in the national defense equipment such as millimeter wave radar, satellite, airborne communications and electronic countermeasures and other fields have an important role and broad application prospects.

Clamping rod as a spiral Traveling-wave tube in the off-weight parts mainly plays four roles, one is in the shell of the clamping spiral line, the second is to provide a thin film attenuator “carrier”, the third is to play a role in thermal conductivity, the heat generated in the tube to the outer surface of the shell in a timely manner, the fourth is the performance of the clamping rod related to the spiral Traveling-wave tube high-frequency characteristics, such as standing wave, phase velocity, etc. The high working frequency and small size of the spiral Traveling-wave tube put forward extremely high requirements for the clamping rod, mainly in the straightness of the product up to 0.01mm, surface roughness Ra ≤ 0.6μm, high dimensional accuracy to ± 0.005mm, and complex shape. Clamping rod material dielectric loss angle tangent value is low, low dielectric constant, high-temperature thermal conductivity and other aspects, the commonly used aluminum oxide and beryllium oxide can no longer meet the technical requirements.

Pyrolytic boron nitride code PBN ceramic material is a kind of boron nitride ceramic plate prepared by a vapor deposition method, because of non-toxic, high-temperature thermal conductivity decay is small (within 300 ° C almost no decay), low dielectric constant and other characteristics to become one of the preferred materials for ultra-high power traveling wave tube clamping rod. Size, because the plate thickness is more fixed usually only 0.8mm, 1mm, 1.2mm, 1.5mm a few specifications, and are much larger than the size of the clamping rod products, so the surface processing area of the boron nitride substrate up to 100%. During processing, considering the thermal conductivity of PBN material in the direction of deposition, i.e. thickness and length or width, there is a big difference in heat conduction.

Meanwhile, due to the low bulk density of the boron nitride clamping rod, the elasticity of the material itself, the complexity of repeated positioning during product processing, the randomness of the size, shape, and abrasive distribution of the processed grinding wheel, and the complexity of the grinding motion law, it brings great difficulties to the research of the grinding mechanism of boron nitride clamping rod. However, the current backwardness of high-precision boron nitride ceramic clamping rod precision processing capability cannot meet the high-precision requirements of this product, and the domestic must import high-performance PBN clamping rod through abnormal channels. 

Therefore, to carry out research on high-precision boron nitride clamping rod processing technology, designing a reasonable processing process and control method to ensure the performance of the boron nitride clamping rod substrate and improve the dimensional accuracy of the product has become an urgent technical problem for technicians in this field.

Clamping rod performance 

Width tolerance ±0.005mm  

Height tolerance ±0.005mm  

Symmetry 0.01mm

Surface roughness Ra<0.6μm  

Perpendicularity 0.01mm  

Straightness 0.01mm  

Pyrolytic boron nitride ceramic clamping rod
PBN disk