| Processing and properties of nano‑hBN‑added glass/ceramic composites for low‑temperature co‑fired ceramic applications |
Oğuzhan Bilaç, Gülsüm Meryem Dursun, Cihangir Duran
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| Metallurgical and Materials Engineering Department, Ankara Yıldırım Beyazıt University, Etlik, Ankara 06010, Turkey |
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Received: September 24, 2021; Revised: December 13, 2021 Accepted: December 29, 2021. Published online: May 31, 2022. |
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| ABSTRACT |
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LTCC applications require densification at temperatures lower than 950 °C to allow co-firing with metal electrodes, lower dielectric constant to increase signal transmission speed, a thermal expansion coefficient matched to Si for reliability and higher thermal conductivity to dissipate heat. For this purpose, ( SiO2–Al2O3–CaO)-based glass (50–60 wt%)/ceramic ( Al2O3 or mullite) composites with nano-hBN (0–10 wt%) addition were investigated. Al2O3 was replaced by mullite to decrease dielectric constant and to match thermal expansion coefficient to Si, and hBN was incorporated to increase thermal conductivity and to decrease dielectric constant. Densification at temperatures ≤ 900 °C was easily achieved for all compositions due to viscous sintering of the glass matrix. hBN did not react chemically with crystalline and amorphous phases, which effectively decreased dielectric constant and increased thermal conductivity. Hence, both mullite and nano-hBN strongly improved dielectric and thermal properties required for the LTCC applications. Dense mullite/glass (55 wt%) base composite with 10 wt% hBN addition was successfully engineered and had comparable dielectric and thermal properties (i.e., 2.3 gcm−3 after sintering at 900 °C, dielectric constant (loss) = 5.13 (0.003) at 5 MHz, thermal conductivity = 1.91 Wm−1 K−1 at 25 °C, and thermal expansion coefficient for the base composite = 4.75 ppm°C-1) with respect to the commercial LTCC products. |
| Key words:
Glass/ceramic composites · Hexagonal boron nitride · Low-temperature co-fired ceramics · Dielectric properties · Thermal properties |
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