In a study published in the Journal of Advanced Ceramics, a team led by Ji-Lin Wang from Guilin University of Technology in Guilin investigated the impact of differing the amount of toughened phase BNMR on the density, mechanical properties, dielectric constant, and thermal conductivity of BNMR/Al2O3 composite ceramics, as well as the mechanisms underlying the toughening and increased thermal conductivity of the ceramics.
The BNMR/Al2O3 composite ceramics prepared by spark plasma sintering (SPS) not only have excellent mechanical properties, but also have high thermal conductivity and low dielectric properties. Image Credit: Journal of Advanced Ceramics, Tsinghua University Press
The rising complexity of integrated devices has led to a greater need for heat dissipation from substrates and packaging materials in recent years due to the vital nature of heat buildup. In this study, spark plasma sintering (SPS) is used to create composite ceramics, including boron nitride microribbon (BNMR) and Al2O3.
Using spark plasma sintering (SPS), the boron nitride microribbon (BNMR)/Al2O3 composite ceramics were created. High temperature and pressure constantly extruded and distorted the malleable BNMRs throughout the sintering process, which even wrapped the Al2O3 grains.
The BNMRs dispersed across the Al2O3 grain boundaries lowered the atomic diffusion coefficient and hindered the possible aberrant development of Al2O3 grains. In this process, a specific nuclear shell structure is generated, and an excellent BN thermal conduction pathway is established, which better enhances the quick conduction of heat.
In this work, we prepared BNMR/Al2O3 composite ceramics, and during the sintering process, the pliable BNMRs were continuously extruded and deformed by the Al2O3 grains under high temperature and pressure, and as a result, not only did we form a special thermal conductivity pathway to enhance the thermal conductivity of the composites, but we also improved the mechanical properties of the Al2O3 ceramics.
Ji-Lin Wang, Study First Author and Associate Researcher, School of Materials Science and Engineering, Guilin University of Technology
Overall, the performance of the BNMRs/Al2O3 composite ceramics, which were made of 1-2 um BNMRs powder and 3-4 um Al2O3 powder, was good. At a 5 wt% content of BNMRs composite ceramics, the thermal conductivity and dielectric constant were 6.18±0.02 and 15.89±0.13 W/(m·K), respectively, and the relative densities, hardness, fracture toughness, and flexural strengths were 99.95%±0.025%, 34.11±1.5 Gpa, 5.42±0.21 MPa·m1/2, and 375±2.5 MPa, respectively.
When compared to the same values for pure Al2O3 ceramics, the fracture toughness, bending strength, and thermal conductivity increased by 35%, 25%, and 45.6%, respectively.
The findings of this study show potential for providing new experimental and theoretical references for increasing the overall performance of high thermal conductivity alumina-based ceramic substrates.
The next work plan is to increase the overall performance of alumina Al2O3-based composite ceramic packaging substrates by using multiphase particles, whiskers, or fibers to fulfill the demands of modern electronic information technology development.
The other contributors are Dongping Lu, Weiping Xuan, Yuchun Ji, Shaofei Li, Wenbiao Li, Shilin Tang, Guoyuan Zheng, and the corresponding author, Prof. Fei Long from Guilin University of Technology in Guilin, China; and Ruiqi Chen from the Department of Civil and Environmental Engineering at Hong Kong Polytechnic University.
National Natural Science Foundation of China (No.52262010), the Guangxi Natural Science Foundation of China (No.2023GXNSFAA026384), and the Guilin Scientific Research and Technology Development Program (No.2020011203-3) supported the study.
Journal Reference:
Wang, J., et. al. (2024) Boron nitride microribbons strengthened and toughened alumina composite ceramics with excellent mechanical, dielectric, and thermal conductivity properties. Journal of Advanced Ceramics. doi:10.26599/JAC.2024.9220872