Boron Nitride is gaining significant attention due to the next gen advancements in wireless communication. The lower value of dielectric constants and the corresponding least loss makes them excel in high frequency electronics engineering. Here we are trying to explore the various aspects of BN- composites and the dielectric performances.
A generic understanding on Boron Nitride
Boron Nitride is a nontoxic refractory that is basically colourless offering great thermal resistance and low density. Since their structure is almost like diamond or graphene they are generally known in the name of “white graphene”. The advanced properties of Boron nitride make them an ideal fit in electronics and radar communications. They are either found in the form of crystals that are colourless or in the form of white powder.
Boron Nitride Properties
As the name indicates Boron Nitride has Boron and Nitrogen atoms in their every essential structure. The different lattice is the reason of distinct Boron Nitride properties. H-BN exhibits blanketing structure. Hence , this advanced ceramic is generally suitable as insulators and lubricants.
On contrary cubic Boron Nitride, c-BN is harder and possesses diamond like structure. They are extremely resistant to oxidation. c-BN is the second hardest material followed by that of diamond. Wurtzite is another structural form of BN which is harder than that of cubic Boron Nitride.
Boron Nitride also holds other relevant key properties. Due to their high thermal conductivity, they are majorly used in heat dissipation components in electronic installations. They stay inert to acids, alkalis or molten components. The density value h-BN and c-BN are around 2.1 g/cm3 and 3.5 g/cm3.
Since their dielectric constant is in appreciable range , they excel as electrical insulators. Boron Nitride also holds high melting points in the range of 2900 degC or more and stays intact in extreme temperature conditions.
Boron Nitride Composites formed through strategic manufacturing
Modern science has resulted in the invention of several Boron Nitride Composites. Some of them are ZS- Boron Nitride, ALN- Boron Nitride and BO – Boron Nitride. Each composite is curated for distinct applications subject to their property and functionality. A detailed information of the different Boron Nitride composites and their applications are given below.
ZS-BN composite
As the name suggests, ZSBN is BN composite a combination of Silicon Carbide and Zirconia with Boron Nitride. The addition of Both Zirconia and SiC has essentially improved the hardness and the wear resistance of the conventional BN. The additional merit of ZSBN is its chemical and thermal stability that makes it ideal for electronic or high-power applications. The BN composite made of Zirconia and SiC can also act as heat sink.
BN – ALN composites
BN-ALN is a BN composite made up of Boron Nitride and Aluminum Nitride. This composite has high thermal stability, resistance and conductivity. These composites are basically used in semiconductor accessory manufacture, insulation parts and to make gears and bearings. The mechanical properties include extreme hardness and rigidity.
BN – BO composite
BN-BO composite has BN mixed with Oxide of Boron. The major constituent in the BN composite is BN holding 98% majority of the material. The BN-BO possesses high thermal stability, shock resistance and offers high chemical stability. It is used to manufacture materials withstanding high temperature and works in harsh environments such as nozzles.
Grades of Boron Nitride Ceramic
The BN ceramic composite types are given below for understanding.
|
Grade Name |
BN – BO |
BN – ALN |
ZSBN |
BN 99 |
|
Constitution |
H-BN>98% |
BN +ALN |
h-BN – 45%
ZrO2 – 45% Borosilicate – 10% |
h-BN > 99% |
|
Характеристики |
|
|
|
|
|
Приложение |
Metal casts | Semiconductors and insulation materials | Nozzles and high wear and tear components | Crucible and other machinable materials |
The dielectric constant of Boron Nitride
Диэлектрическая проницаемость is also known as relative permittivity which is something that determine the materials behaviour in electric fields. Диэлектрическая проницаемость tells us about the extend a material can store energy subject to the electric field applied. Generally, the dielectric constant value of Boron Nitride falls in the range of 3 to 5. This property helps it to perform as better insulators in electronic applications.
What is a dielectric material?
A dielectric material has weak thermal conductivity. It lacks free moving electronics aiding in electricity transmission. But a dielectric material for sure can store the electrical charge which helps them function as electrical insulators.
The BN is suitable as dielectric material in electronic components such as capacitors as it’s able to resist electric currents. Boron Nitride are also insulators that can deal with high temperature environments. The structure of Boron Nitride has its impact in varying dielectric properties due to the configuration it possesses. Generally, the engineers use several technologies to modify the dielectric properties to fit Boron Nitride in desired applications.
Tuning Dielectric properties of bn composites
Method of tuning dielectric properties
As explained the dielectric properties of the BN composites is generally a function of its microstructure and composition. In the essential micro composition of a composite the uniformity in dispersing BN decreases the dielectric loss. The other fillers such as SiC and AlN will enhance the property effect in the main lattice. The prominent tuning factors are as follows:
- The nanosheet alignment in the composite helps reduce the tan values. This is attributed to the variation in morphology.
- The filler constitution helps in varying the thermal conductivity and electrical insulating properties
- Polarization and enduing losses can be minimized by controlling the porosity or defects at the interface.
- The BN composite of better dielectric values has dielectric constants around 1.3 – 3.6 and dielectric losses of around below 0.01 GHz
High frequency systems and the dielectric tuning
- The low tan values are favourable for electronic 5G PCB to ensure signal integrity
- High thermal conductivity, lesser dielectric losses and superior shock resistance helps in wireless or radar-based communication systems
- Stable dielectric constant and thermal dissipation behaviour is important when it comes to electronic packing.
Benefits of tuning dielectric properties – structural or morphological alterations
- The fillers used in the BN composites can alter the particle size and geometry of BN composite. The altered orientation and shape improve heat flow and limit dielectric loss.
- The method of synthesising continues thermal paths in network engineering helps in the insulating behaviour of the BN composites
- The performance and the stability of the material is generally influenced by minimising the voids and discontinuities at the interface
Dielectric properties and trade-offs in BN composite systems
- BN-ALN composite ensures a thermal conductivity of around 320 W/ Mk and dielectric constant value is less than 4
- BN – SiC based composite offers good insulation and better mechanical strength
- BN – Zirconia as a composite offers good thermal shock resistance. It also controls the dielectric property and its related performance
- The alignment methodology adopted in Polymer based BN composites ensures low permittivity. It offers thermal conduction through the anisotropic lattice geometry.
Заключение
The invention of BN composites has escalated the functionality of the ceramic making it suit many applications. The tuning of the composites is very much required for the essential property alteration to suit the applications in electronics. Dielectric tuning is a subject to increase the efficiency of the conventional composite.