As electric vehicle (EV) powertrains escalate in power density, electronics engineers continue to grapple with the ever-familiar foe: heat. Multiple components in EVs, such as power electronics, e-motors, and batteries require adequate thermal management as the industry is pushing for higher power, higher voltage, faster data transmission, lighter weight, and smaller size. Therefore, thermal management plays a vital role in maximizing the safety, performance, efficiency and overall longevity of electric vehicles.
Thermally conductive, but electrically insulating thermal interface materials (TIMs) with high dielectric strength and low dielectric constant are needed to meet these thermal management challenges. Since TIMs made of dielectric polymers are naturally thermally insulative, ceramic fillers need to be added to improve thermal conductivity while maintaining electrical resistance. Superior thermal and dielectric properties of the ceramic thermal fillers are key to the success of thermal management materials.
Boron Nitride Meets the Challenge:
Momentive Technologies, a specialty materials manufacturer based in Ohio, advocates for boron nitride as a solution over traditional thermal materials such as aluminum oxide (alumina), silicon dioxide (silica), and aluminum nitride.
Boron nitride possesses a hexagonal crystal structure akin to graphite, albeit with boron and nitrogen atoms instead of carbon atoms.
Within each boron nitride layer, the strong covalent bonds and rigid lattice ensure solidity and stability, enhancing phonon transfer and resulting in excellent thermal conduction, while maintaining high electrical resistivity. Between adjacent layers, the bonding is relatively weak, characterized by van der Waals forces (weak attraction between atoms), which makes boron nitride crystal an anisotropic material. The high thermal conductivity along the XY planes combined with high electrical resistivity contributes to boron nitride’s effectiveness in heat dissipation for electronics cooling applications.
Comparison of BN and other ceramic fillers:
High Thermal Conductivity:
“Boron Nitride has one of the highest thermal conductivities and electrical insulative properties of ceramic fillers. This, along with low dielectric loss characteristics, makes BN a highly desired filler in epoxies, silicones, and PU systems.” – says Dr. Xiang Liu, Director of Global Product at Momentive Technologies.
Compared to other ceramic fillers such as spherical alumina, the Momentive Technologies team says that BN enables superior thermal and electrical performance, capable of providing more than 2x thermal conductivity and improved electrical breakdown properties. This is achieved with less volume loading compared to other fillers, and less impact on mechanical properties such as hardness. Higher thermal conductivities enable higher power through the circuits.
The inherent softness of boron nitride also makes it a non-abrasive filler that will not cause damage to compounding equipment while blended into polymers to make thermal interface materials.
High Dielectric Breakdown Strength:
In high-power applications such as electric vehicles, especially when compared to consumer electronics, there is an amplified risk of dielectric breakdown. BN has one of the highest breakdown strengths (Eb) among fillers, enabling lower bond line thicknesses compared to others. The breakdown strength of BN filled system compares favorably with spherical alumina filled system at equivalent volume loadings.
Additionally, the versatility of boron nitride powders—available in various grades and forms such as platelets and agglomerates—allows engineers to optimize thermal management strategies across different applications, ensuring that crucial systems operate within safe thermal limits.
Broad Range of Boron Nitride Powders and Applications:
Boron nitride is a synthetic ceramic material. Momentive Technologies have been producing this material for almost 70 years and currently offers a portfolio with more than 50 grades of boron nitride powders, with different particle size (from 0.5-400 micrometers), morphology (both platelet and agglomerates) and purity. Momentive Technologies’ research and application engineering teams develop new boron nitride powder products specifically designed to meet customers’ particular needs in electronic and automotive applications. Many customers have formulated thermal interface materials with Momentive Technologies’ boron nitride powders to boost their compound’s performance to a new level.
Typical BN properties:
Ready to explore if boron nitride is right for your application? Reach out to the scientists at Momentive Technologies here
Special thanks to Dr. Xiang Liu, Dawn Krencisz, and Dr. Bei Xiang for the interview!
